Author details

Cicek Hocaoglu Recep Tayyip Erdogan University Medical School, Department of Psychiatry, Rize, Turkey

\*Address all correspondence to<EMAIL_ADDRESS>
© 2018 The Author(s). Licensee IntechOpen. This chapteris distributed underthe terms oftheCreative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Transitioning to **Sustainable Industry, Innovation and Infrastructure**

Transitioning to Sustainability Series

EDITORS Wojciech J. Cynarski Rzeszów University, Rzeszów, Poland

Bożena Gajdzik Silesian University of Technology, Gliwice, Poland

EDITORIAL OFFICE MDPI St. Alban-Anlage 66 4052 Basel, Switzerland

For citation purposes, cite each article independently as indicated below:

Author 1, and Author 2. Chapter Title. In *Transitioning to Sustainable Industry, Innovation and Infrastructure*. Edited by Wojciech J. Cynarski and Bożena Gajdzik. Transitioning to Sustainability Series 9; Basel: MDPI, Page Range.

© 2023 by the authors. Chapters in this volume are Open Access and distributed under the Creative Commons Attribution (CC BY 4.0) license, which allows users to download, copy and build upon published articles, as long as the author and publisher are properly credited, which ensures maximum dissemination and a wider impact of our publications. The book taken as a whole is distributed by MDPI under the terms and conditions of the Creative Commons license CC BY-NC-ND.

**ISBN 978-3-03897-868-8 (Hbk) ISBN 978-3-03897-869-5 (PDF) ISSN: 2624-9324 (Print) ISSN: 2624-9332 (Online) doi:10.3390/books978-3-03897-869-5**

## **Contents**

### **About the Editors**

 Wojciech J. Cynarski PhD is a Full-Professor with degrees from the University of Technology in Rzeszow (building engineering), the University of Rzeszow in Rzeszow (sociology), and doctoral studies at University of Physical Education in Warsaw (physical culture sciences). Since 2005, he has worked as a Professor at the University of Rzeszow and was appointed Head of Chair of the Socio-Cultural )RXQGDWLRQIRU3K\VLFDO(GXFDWLRQDQG6SRUWV+HKDVSXEOLVKHGRYHUVFLHQWLÀF ZRUNVLQFOXGLQJERRNVPRQRJUDSKVDQGPDQXDOV+LVPDMRUVFLHQWLÀFLQWHUHVWV concern sociology (of culture, tourism and sport), coaching and pedagogy, and martial arts.

 %RŧHQD\*DMG]LN3K' KDE(QJLVD3URIHVVRUDW WKH6LOHVLDQ8QLYHUVLW\RI Technology, Gliwice, Poland. Her interests include manufacturing, management, restructuring, sustainability, industrial transformation, digitalization, resource management, human factor, energy consumption, decarbonisation, and industrial engineering. She is an expert on the steel market in Poland and collaborates with business practices, particularly with steel companies. She has experience in the industrial transformation of the European market and ranks second place in the OLVWRIWRSJOREDOVFLHQWLVWV6KHLVWKHDXWKRUFRDXWKRURIPRUHWKDQVFLHQWLÀF publications, including 30 books and monographs. Her monographs concern the restructuring of the steel sector in Poland and the transformation of steel mills within Industry 4.0. Her writing centres on business management and organization development, as well as industry transformation to changing socioeconomic FRQGLWLRQV+HURXWSXWLQFOXGHVUDQNHGIRUHLJQDQGGRPHVWLFVFLHQWLÀFSXEOLFDWLRQV on the implementation of changes in manufacturing companies in hard and soft DUHDV RIPDQDJHPHQW 6KHLV D UHYLHZHU RI VFLHQWLÀF SXEOLFDWLRQV IRU UHFRJQLVHG publishing houses. In recent years, she has reviewed extensively on papers RI VLJQLÀFDQFH RQ JUHHQ HFRQRP\ 6KH LV D PHPEHU RI WKH (GLWRULDO %RDUGV RI UHFRJQL]HGVFLHQWLÀFMRXUQDOV+HU+LQGH[LVZLWKPRUHWKDQFLWDWLRQVRQ WoS.


*3.7. Analysis of Denaturation Spectral Measurements*

The spectral property (*F*344) plotted against the concentration of urea/GdmCl generated the transition curve. The molar concentration of urea/GdmCl were used to calculate thermodynamic properties such as stability parameters (∆*G 0 D*), slope (*m*), and Cm (=∆*G 0 D/m*) where ∆*G* 0 *D* is the Gibbs free energy change without the denaturants, *m* is

*(∂*∆*GD/∂[urea/GdmCl*]), and Cm is the transition midpoint of chemical-induced denaturation curve where ∆*GD* = 0. The analysis was done based on the least-square method to fit the denaturation curve using the following Equation (1):

$$y = \frac{yN + yD \times Exp[-(\Delta G^\circ \,\_D - m[\murea/Gdm\text{Cl}])/\text{RT}]}{(1 + Exp[-(\Delta G^\circ \,\_D - m[\murea/Gdm\text{Cl}]/\text{RT}])} \tag{1}$$

where *yN* and *yD* are the estimated optical properties of the native protein and the denatured protein, respectively, under the similar experimental condition in which y has been measured, *T* is the temperature in Kelvin, and *R* is the universal gas constant.


**1. Introduction**

Healthcare-associated infections (HCAIs) impact on millions of patients annually, and hundreds of thousands of deaths worldwide [1–4]. Current models predict that global mortality rates will approach 10 million annual deaths as a direct result of HCAIs by 2050 [5]. Approximately one-third of all such HCAIs are preventable [6], and while recent improvements in hygiene standards across the medical sector have for example significantly reduced the number of HCAIs per year in the UK, certain groups remain at very high risk of infection during hospital visits, and infection rates for some bacteria such as *Escherichia coli* have even increased [7–9].

The rise of drug-resistant bacteria which are disproportionately responsible for HCAIs, such as methicillin-resistant *Staphylococcus aureus* (MRSA) and extended-spectrum beta-lactamases (ESBL)-producing *Enterobacteriaceae* [2], has prompted a resurgence in the search for broad-spectrum antibiotics to tackle HCAIs. Silver is one such broad spectrum antibiotic, effective against Gram-positive (e.g., MRSA, *B. subtilis*) and Gram-negative bacteria (e.g., *E. coli*, *P. aeruginosa*) [10], and is consequently the subject of commercial [11] and academic interest for the treatment of existing HCAIs and drug-resistant organisms through its incorporation in surface coatings [12], nanotechnology [13–16], and pharmaceuticals [17–19].

A major advantage of nanoparticulate silver (and silver-based solid compounds) compared with salts or complexes is that oxidative dissolution is confined to exposed surfaces, offering a potential route to regulate the release of biologically active (commonly held to be Ag+) [20] species permitting the design of long lasting antimicrobial therapies [15,21–23]. Control over silver dissolution kinetics in Ag-nanoparticle-(NP) based systems has been investigated through tuning particle size [23–26], the use of inert coatings to retard release [26], or control of silver speciation in nanocomposite to accelerate dissolution and hence antibacterial activity [13,14]. Silver has also shown recent promise as a promoter of conventional antibiotic therapies [27].

Here we explore the use of high surface area and porous metal oxide frameworks to control the dispersion and subsequent dissolution of surface silver. The impact of framework porosity and oxide termination on silver speciation, dissolution, and antibacterical efficacy, was studied using ordered mesoporous and hierarchical macroporous-mesoporous SBA-15 silicas [28,29], and titania functionalized analogues. Conformal titania surface coatings, and hierarchically porous architectures promote silver NP dissolution and activity against Gram-positive (*Staphylococcus aureus*) and Gram-negative (*Pseudomonas aeruginosa*) bacteria.

#### **2. Results and Discussion**

#### *2.1. Materials Synthesis and Characterisation*

Three families of ordered porous frameworks were prepared using soft or hard-soft dual templating approaches and subsequent titania functionalization (Figure 1). Mesoporous and macroporous-mesoporous (MM) SBA-15 silicas were prepared using a Pluronic 123 (P123) surfactant either alone or in conjunction with 400 nm colloidal polystyrene nanospheres respectively, according to literature methods. Titania modified variants were subsequently prepared adapting the procedure of Landau et al. [30] to preactivate surface silanols before the self-limited grafting of titanium isopropoxide under anhydrous conditions, and calcination. Repeated grafting cycles were used to create conformal TiO2 monolayers encapsulating the silica supports. Silver nanoparticles were introduced to either the parent SBA-15, or TiO2-grafted SBA-15 and TiO2-grafted MM-SBA-15, frameworks by wet impregnation with varying silver nitrate concentrations.

**Figure 1.** Synthesis of Ag-doped mesoporous silica and titania-functionalized mesoporous and mesoporous-macroporous silica materials.

Textural properties of the parent SBA-15 and MM-SBA-15 supports, before and after titania functionalization, were first characterized by transmission electronic microscopy (TEM), N2 porosimetry, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The expected hexagonally close-packed channels of the SBA-15 mesopore network were observed in all cases, with surface areas and mesopore diameters decreasing with successive TiO2 grafting cycle (Figure 2 and Figure S1), reflecting pore narrowing and partial blockage of micropores in the silica framework [31]. Uniform mesopores of 6.3 nm diameter were in accordance with previous reports [29]. No titania crystallites were visible by TEM following grafting, indicating the formation of highly dispersed phase. Assuming a TiO2 monolayer thickness of 0.355 nm [32], mesopore shrinkage across three grafting cycles from 6.3 to 5.3 nm for SBA-15 was consistent with deposition of a 1.4 monolayer (ML) titania coating, and from 6 to 5.2 nm for MM-SBA-15 consistent with 1.1 ML titania.

**Figure 2.** Bright-field transmission electron microscopy (TEM) images of (**a**) TiO2/SBA-15 (3rd cycle grafting), and (**b**) TiO2/MM-SBA-15 (3rd cycle grafting) highlighting ordered hexagonally close-packed mesopores and uniform macropores, and the evolution of textural properties and calculated TiO2 monolayer thickness as a function of grafting cycle for (**c**) TiO2/SBA-15 and (**d**) TiO2/MM-SBA-15.

Low-angle X-ray diffraction (XRD) (Figure 3) confirmed that titania-functionalized frameworks retained the *P6mm* symmetry of the parent SBA-15 mesopore network. Wide angle XRD (Figure S2) showed no evidence for crystalline titania phases, consistent with TEM and the formation of conformal monolayers over the SBA-15 template. The surface chemical environment of Ti atoms within the monolayer coatings was examined by XPS, which reveals the presence of Ti-O-Si (associated with the silica-titania interface) and Ti-O-Ti species over both SBA-15 and MM-SBA-15 with Ti 2p5/2 binding energies of 459.9 eV and 458.5 eV respectively. The shift to higher binding energy for Ti coordinated to Si (through a bridging oxygen) reflects the higher electronegativity of the latter, and hence higher induced initial charge on the former. We attribute the small shift between the Ti-O-Ti environments in P25 and the titania monolayers to quantum size (initial and/or final state) effects.

**Figure 3.** (**a**) Low angle X-ray diffraction (XRD), and (**b**) fitted Ti 2p XP spectra of TiO2/SBA-15 and TiO2/MM-SBA-15, alongside pure silica (SBA-15) and titania (P25) references.

Silver was subsequently deposited over the unfunctionalized SBA-15, and TiO2/SBA-15 and TiO2/MM-SBA-15 at three different nominal loadings spanning 0.3–3 wt% (see the Supplementary Materials (Table S1); elemental analysis revealed almost identical bulk loadings for the mesoporous materials, but systematically lower loadings for the hierarchical material. Surface and bulk silver loadings were generally in good agreement for all materials (see the Supplementary Materials Table S1), indicating a homogenous distribution throughout the porous frameworks. Physicochemical properties of the resulting silver species were determined by TEM, XPS, XRD, and X-ray absorption near edge spectroscopy (XANES). Only fcc metallic silver (JCPDS no. 04-0783) reflections were observed by XRD, which sharpened with increasing loading (see the Supplementary Materials Figure S3), indicative of crystallite growth. Volume averaged silver NP sizes were smaller for MM-SBA-15 (3.5–6.5 nm) than SBA-15 (4.5–8.5 nm) at comparable loadings (~0.3 wt%), evidencing higher metal dispersion over the hierarchically porous framework, and indeed fell below the threshold of detection for the lowest 0.25 wt% Ag/TiO2/MM-SBA-15. Ag NPs were directly visualized by TEM (see the Supplementary Materials Figures S4–S6), which revealed a relatively broad size distribution spanning 1–20 nm over all three supports. The mean particle size increased (and size distribution narrowed) with Ag loading (see the Supplementary Materials Figure S7), with the smallest NPs observed over the hierarchical support in all cases, in accordance with XRD. Ag 3d XP spectra showed the existence of two distinct chemical environments with 3d5/2 spin-orbit split component binding energies of 368.0 eV and 370.5 eV consistent with Ag0 and possibly a surface Ag2CO3 respectively (see the Supplementary Materials Figure S8) [33].

Note that discrimination of silver oxides and carbonate by XPS alone is complicated due to their similar core-level binding energies, and anomalous negative binding energy shift of the oxides relative to the metal [14,34,35] and therefore requires careful fitting to well-defined standards (difficult to guarantee due to the tendency of Ag2O to oxidise, and of both oxides to adsorb atmospheric CO2 and form surface carbonates [36]), or Auger parameter analysis employing the Ag M4,5NN Auger transition in conjunction with 3d5/2 core-level spectra [13]. Silver speciation as metal, oxide, or carbonate was therefore examined by linear combination fitting of Ag K-edge X-ray absorption near-edge spectroscopy (XANES, see the Supplementary Materials Figures S9–S11). In all cases, good spectral fits could only be obtained using Ag and Ag2CO3 components. Nanoparticle growth is accompanied by a continuous decrease in the proportion of surface and bulk silver carbonate for all frameworks (Figure 4). This switchover from electron deficient to metallic silver with particle size likely reflects the higher surface energy of the latter [37], which is thus favoured for larger particles. The bulk Ag2CO3 content determined by XANES was systematically higher than that of the surface determined by XPS, likely reflecting the distribution of particle sizes present in all materials; XPS is expected to more sensitive to larger (more metallic) particles preferentially located on the external surface. AgO and Ag2O could not be detected by linear combination fitting of the XANES data.

**Figure 4.** Surface (XPS) and bulk (XANES) silver speciation as Ag2CO3 of Ag/SBA-15, Ag/TiO2/SBA-15, and Ag/TiO2/MM-SBA-15 as a function of Ag loading.

#### *2.2. Materials Performance Assaying*

The release rate of ionic silver (Ag+) from the preceding SBA-15 and MM-SBA-15 frameworks in a 0.5 M NaNO3 solution at 37 ◦C was subsequently determined by ICP-MS analysis (Figure 5). Dissolution rates normalised to the mass of silver were inversely proportional to particle size (loading) for all frameworks, as reported for citrate stabilized silver metal nanoparticles [23] and core-shell silver-silica nanoparticles [26] indicating that the release of ionic silver occurred by a common mechanism, being solely dependent on the geometric surface area of the silver nanoparticles. Coating of the mesoporous SBA-15 by a conformal titania monolayer slightly decreased the average particle size over the bare silica framework, and hence increased the rate of silver dissolution, a phenomenon further enhanced by the introduction of macropores. The rate constant for Ag+ dissolution was determined as 5244 μmol·h−1·nm−1·g1Ag by fitting the data (see the Supplementary Materials Figure S12) in accordance with the method of Zhang et al. [23] This is significantly higher than that found for Ag@SiO2 core-shell nanoparticles (14.7 μmol·h−1·nm−1·g−1Ag) [26], while the absolute release rate

of the 0.3 wt% Ag/TiO2/MM-SBA-15 is consistent with that previously observed for 0.05 wt% high surface area Ag-hydroxyapatite nanoparticles [14].

**Figure 5.** Ag+ dissolution rates normalized to mass of Ag determined by XANES for Ag/SBA-15, Ag/TiO2/SBA-15 and Ag/TiO2/MM-SBA-15.

Antibacterial activity was subsequently assessed against a range of bacteria (*Pseudomonas aeruginosa*, *Staphylococcus aureus*, *Clostridium difficile*, *Escherichia coli*, *Bacillus subtilis* and MRSA) by zone plate inhibition (ZoI) (Figure 6) using simulated body fluid (SBF), in which the antimicrobial efficacy is proportional to the size of the colony-free zone surrounding the silver functionalized porous frameworks. None of the parent (silver-free) materials exhibited bactericidal properties. In all cases the ZoI values normalized to the mass of silver were inversely proportional to silver loading, mirroring the ionic silver release rates, and superior to those reported for hydroxyapatite (HA) supported Ag3PO4 composites or Ag@SiO2 core-shell nanocomposites. For example, for *S. aureus* Ag/TiO2/MM-SBA-15 achieved 70 mm·gAg−1 versus 40–60 mm·gAg−1 for a high area Ag-HA [14] or 23 mm·gAg−1 for 4.5 nm Ag nanoparticles encapsulated by a 10.5 nm mesoporous silica shell) [26]. The zone size (antibacterial performance) decreased in the sequence Ag/TiO2/MM-SBA-15 > Ag/TiO2/SBA-15 > Ag/SBA-15.

The logarithmic reduction method was also employed to obtain a more quantitative evaluation of antibacterial activity for representative Gram-positive and Gram-negative bacteria (*Staphylococcus aureus* and *Pseudomonas aeruginosa* respectively). Experiments were performed in the absence of light to eliminate any possible influence from photogenerated reactive oxygen species by the semiconducting titania coating. All three frameworks were inactive in the absence of silver (see the Supplementary Materials Figure S13). Corresponding decimal reduction times (D-values), i.e., the time to kill 90% of the bacteria, normalised to the mass of silver, also evidenced an inverse relationship with silver loading for all frameworks (Figure 7) consistent with their Ag+ release rates. (Figures S14–S15). As for the ZoI assays, antibacterial activity followed the order Ag/TiO2/MM-SBA-15 > Ag/TiO2/SBA-15 > Ag/SBA-15, i.e., titania functionalization, and the introduction of macroporosity, both enhanced the potency of silver nanoparticles dispersed throughout an SBA-15 framework. Ag/MM-TiO2/SBA-15 outperformed Ag/SBA-15 by ~105% against *Staphylococcus aureus* and ~103% against *Pseudomonas aeruginosa*. The present observations are consistent with previous reports of augmented antimicrobial efficacy arising from the preferential formation of highly soluble silver carbonate versus silver metal over γ-alumina supports [13].

**Figure 6.** Zone of inhibition plots, normalized to mass of Ag, against a range of Gram-positive and Gram-negative bacteria for (**a**) Ag/SBA-15, (**b**) Ag/TiO2/SBA-15 and (**c**) Ag/TiO2/MM-SBA-15.

**Figure 7.** Decimal reduction times for Ag/TiO2/MM-SBA-15, Ag/TiO2/SBA-15 and Ag/SBA-15 against (**a**) *Staphylococcus aureus*, and (**b**) *Pseudomonas aeruginosa.*


**10. Hawaiian eruption**

Some eruptions descriptions have been subdivided into phases for the sake of clarity from the inside to outside volcano.

Phase 1: The ascent rate of the bubble-free basaltic magma is >1 m/s. The low viscosity allows the formation of large bubbles that are brought to the surface (**Figure 29**).

**Figure 26.** *Strombolian eruption schematically explained (author's collection).*

**Figure 27.**

*Paroxysistic phase of the eruption of 1944 AD (author's collection). Photo made from allied force during the second world war.*

Phase 2: The expansion of the large bubbles expels fragments of magma outward from the conduit that forms incandescent lava fountains with a speed of 10–20 m/s reaching heights of 200–500 m (**Figure 29**).  Lava fountains can also form in craters occupied by a lava lake.


2.2.5. Energy harvesting control system

Switching circuit is the crucial part of this energy harvesting system. Arduino UNO microcontroller is used in this circuit where it controls two N-type MOSFETs namely P36NF06L. For testing, LED was placed in parallel to the gate-source pin of the MOSFET. The system will continue to charge and discharge until the battery reaches up to 6 V. In the stripboard of the energy harvesting circuit, MOSFETs are placed as shown in Figure 4. Aligned with the bias voltage, two LEDs are placed to indicate the status of the circuit. When the MOSFET is turned on, the LED will glow and vice versa.

Figure 3. LCD screen of energy harvesting circuit.

Figure 4. MOSFET configurations in energy harvesting circuit.

The algorithm of the decision-making switching algorithm is illustrated in Figure 5. Here MOSFET 3 is usually turned off all the time. However, it is significant to declare that although the MOSFET does not have any role worthy of mention in the system, it is placed there if in case the battery has to be discharged manually. Therefore, unless stated otherwise, this MOSFET will be turned off all the time.

MOSFET 2 whose job is to charge the battery from supercapacitor is turned off. When Vsupercap is greater than or equal to 7.5 V, the second condition triggers which will turn off the MOSFET 1 and turn on MOSFET 2. Thus, overcharging does not occur from the wind turbine. In this time, the rechargeable battery will be charged up to rated voltage 6 V. When the supercapacitors' voltage dropped to 4 V, MOSFET 1 was switched on again. The switching circuit coding in

Supercapacitor-Based Hybrid Energy Harvesting for Low-Voltage System

http://dx.doi.org/10.5772/intechopen.71565

9

The basic working principle of this part of the code is very simple. A signal "LOW" corresponding to 0 V was sent to the Arduino digital pin assigned to "MOSFET 1." As soon as the voltage across the supercapacitor bank exceeded 7.5 V, MOSFET 1 was switched off to

Arduino is given in Figure 6.

Figure 6. Arduino control coding.

Figure 7. Developed GUI panel of Labview.

As it is seen in Figure 5, the control system has mainly two conditions. First one is the supercapacitor charging circuit which occurs when Vsupercap is less than 4 V. Under this condition, MOSFET 1 is turned on; thus, it will charge the supercapacitor bank. In the meantime,

Figure 5. Flowchart of EHC control structure.

MOSFET 2 whose job is to charge the battery from supercapacitor is turned off. When Vsupercap is greater than or equal to 7.5 V, the second condition triggers which will turn off the MOSFET 1 and turn on MOSFET 2. Thus, overcharging does not occur from the wind turbine. In this time, the rechargeable battery will be charged up to rated voltage 6 V. When the supercapacitors' voltage dropped to 4 V, MOSFET 1 was switched on again. The switching circuit coding in Arduino is given in Figure 6.

The basic working principle of this part of the code is very simple. A signal "LOW" corresponding to 0 V was sent to the Arduino digital pin assigned to "MOSFET 1." As soon as the voltage across the supercapacitor bank exceeded 7.5 V, MOSFET 1 was switched off to

Figure 6. Arduino control coding.

The algorithm of the decision-making switching algorithm is illustrated in Figure 5. Here MOSFET 3 is usually turned off all the time. However, it is significant to declare that although the MOSFET does not have any role worthy of mention in the system, it is placed there if in case the battery has to be discharged manually. Therefore, unless stated otherwise, this

As it is seen in Figure 5, the control system has mainly two conditions. First one is the supercapacitor charging circuit which occurs when Vsupercap is less than 4 V. Under this condition, MOSFET 1 is turned on; thus, it will charge the supercapacitor bank. In the meantime,

MOSFET will be turned off all the time.

8 Supercapacitors - Theoretical and Practical Solutions

Figure 5. Flowchart of EHC control structure.

Figure 7. Developed GUI panel of Labview.

prevent overcharging. A signal "HIGH" which equals to 5 V was sent to Arduino digital pin "MOSFET 2" at the same time, and the rechargeable battery then was charged by the supercapacitor bank. Now, a signal "HIGH" was sent to one of the Arduino digital pins assigned "MOSFET 1" as soon as the voltage across supercapacitor bank was lesser than 4 V. A signal "LOW" equivalent to 0 V was sent to Arduino digital pin assigned to "MOSFET 2" at the same time. This charging and discharging of supercapacitor bank algorithm repeated simultaneously until battery was fully charged.

voltage, charging current of the supercapacitor, charging current of the battery when supercapacitor discharges and finally the rotational speed of the turbine. The data gathered here can also be easily exported to the spreadsheet software (Figure 8). Therefore, this enables

Supercapacitor-Based Hybrid Energy Harvesting for Low-Voltage System

http://dx.doi.org/10.5772/intechopen.71565

11

The energy harvesting circuit built and the experimental setup are shown in Figure 9. The field testing was done in the Research Building, Block N, University of Nottingham Malaysia Campus.

This section gives a performance analysis of a Supercap (supercapacitor)-based energy harvesting battery charging device operated by the Maglev VAWT adopted to a 200 W PMSG as per the configuration discussed previously which was sent for fabrication. Upon arrival of the turbine, the system was set up in the laboratory, and field testing was performed to

This subchapter has two parts. First part includes one of the three cases in detail which has been compared for performance analysis. "Case A" showed a battery of 6 V, 3.2 AH, which was charged from 4.2 to 5 V through a DC/DC converter followed by a series of four supercapacitors (2.7 V, 35 F). "Case B" and "Case C" demonstrated the direct charging of the battery where "Case B" was experimented with the converter and "Case C" was without converter. All the three cases were experimented in low wind speed that ranges between 6 and 3 m/s. To keep it short, only results from wind speed 4 m/s will be discussed in detail. The remaining results have been given in a tabularized form to compare and find out the efficiency

The same procedure from the earlier section was followed, and results were graphically plotted for analysis. Following figures are the details of the charging process. It is noteworthy mentioning that both the Supercap discharge voltage and discharge current were the same as the previous value. This is because while Supercap bank discharged its charge to the battery, the turbine system was isolated through the MOSFET switch. Therefore, wind speed cannot make any impact on the discharging half cycle. Consequently, in all the three cases, the discharge voltage and current amount with respect to time were the same. Here, Figures 10 and 11 show the charging voltage and current graph with respect to time. For the discharging details, Section 4.5.1 may be reviewed as in both of the cases, the data will be the same.

At this point, 35 min were required to charge up the Supercap bank. Adding the discharging cycle time which was 2 min, the complete cycle duration was then 37 min. The starting current

the user to keep track of the system in real time of the system 9.

2.2.6. Experimental setup

3. Results

tabulate the data.

of the EHC.

3.1. At wind speed = 4 m/s

Case A: Energy harvesting through supercapacitor.

#### <IP_ADDRESS>. DAQ and Labview

With NI-6212 device, data acquisition was implemented. A graphical user interface (GUI) was developed using LabVIEW. This GUI enables the user to easily monitor and analyze data. The LabVIEW interface is shown in Figure 7. This GUI displays supercapacitor and battery's

Figure 8. Data exported to excel spreadsheet from LabVIEW.

Figure 9. Experimental setup for the integrated system.

voltage, charging current of the supercapacitor, charging current of the battery when supercapacitor discharges and finally the rotational speed of the turbine. The data gathered here can also be easily exported to the spreadsheet software (Figure 8). Therefore, this enables the user to keep track of the system in real time of the system 9.

#### 2.2.6. Experimental setup

The energy harvesting circuit built and the experimental setup are shown in Figure 9. The field testing was done in the Research Building, Block N, University of Nottingham Malaysia Campus.


*2.2. ELT Modification*

In the search for improving the adhesion and interaction between the cementitious matrix and the ELT rubber aggregate, three methods were applied to the surface of the ELT grains before the incorporation in the cement mortar mix.

#### 2.2.1. Treatment 1: Hydration (R1)

Treatment 1 is the simplest of the three treatments applied. The method is based on the work by Mohammadi et al. [26], and consists of soaking the rubber in water for 24 h before incorporating it into the mortar mix. This treatment reduces the amount of air trapped on the surface of the material after the hydration time, which improves the interaction with the cement paste.

#### 2.2.2. Treatment 2: Oxidation–Sulphonation (R2)

Treatment 2 is based on the work by He et al. [27]. It consists of an immersion of the rubber in a 15% sodium hydroxide solution stirring at 150 rpm for 45 h at room temperature. After washing and filtering, the sample is put in contact with a 7% KMnO4 solution. This solution is adjusted to pH 2 and stirred at 150 rpm for 2 h at 70 ◦C. The product is then transferred to a saturated NaHSO3 solution, which is reacted at 150 rpm for another 2 h at 70 ◦C. After washing and filtering, the sample is dried for 12 h at 50 ◦C. By this means, polar groups, such as carbonyl, hydroxyl, and sulfonic groups, are introduced on the surface of the rubber, which increases the hydrophilicity.

#### 2.2.3. Treatment 3: Contact with Hydrogen Peroxide (R3)

This method is based on the study by Shatanawi et al. [25] originally developed to incorporate rubber into asphalt mixes. The treatment consists of contacting the rubber with a hydrogen peroxide solution at a concentration of 50% at a temperature of 60 ◦C, for a time of 60 min, where a Fenton reaction is subsequently provoked, using a concentration of Fe2+ 12 mM and H2O2 600 mM at pH 3–4. These reactions produce homolytic cleavage of single C–C bonds to produce terminal hydroxyls.

#### *2.3. Experimental Program*

Due to the large number of combinations, and in order to reduce the uncertainty of the results, the evaluation was divided into three stages. The variables considered in each phase were the type of cement, the size of the rubber grains, the surface treatment applied to the rubber, and the test age to which the samples were subjected. Moreover, the percentage of rubber replacement varies from a range of 0% (control samples) to 12.5%, with respect to the weight of the fine aggregate.

The first stage aimed to make a fast characterization of the samples in order to take useful decisions for the next phases. For that, samples with the addition of untreated rubber, at early test ages of 7 and 14 days, with two cements, were included in the experimental analysis. Furthermore, two replacement percentages were considered, a minimum of 2.5% and a maximum of 12.5%, with respect to the weight of the fine aggregate and with three rubber grain sizes (T1, T2, and T3). Figure 1 presents the details of stage 1.

**Figure 1.** Experimental plan description of stage 1.

Based on the results obtained in the first stage, the second stage is developed (Figure 2). This phase contemplates substitution percentages with rubber of 5% and 7.5% with respect to the weight of the fine aggregate in conditions without treatment and with treatment R1, and test ages up to 28 days. This, in order to have more information on the properties of the samples studied, maintaining the two cements and the three sizes of rubber as variables.

**Figure 2.** Experimental plan description of stage 2.

Due to the technical complexity of applying the R2 and R3 treatments, stage 3 is based on the previous results in order to optimize the number of samples evaluated. Therefore, in this stage, the best results obtained in the previous stages are considered in the analysis. Figure 3 presents the details of stage 3.

**Figure 3.** Experimental plan description of stage 3.

In the three stages, the tests were conducted on specimens with dimensions 40 × 40 × 160 mm according to the Réunion Internationale des Laboratoires et Experts des Maté-riaux, systèmes de construction et ouvrages (RILEM) [36]. The workability of each mixture was evaluated according to the NCh 2257/3 standard [37], based on ISO 1920-2: 2016, using the reduced cone method. Additionally, the flexural and compressive strengths

were evaluated according to the standard NCh 158 [38], whose international equivalent corresponds to the UNE-EN 196-1: 2018 standard. In order to determine the density, the weight and size measurements of the samples were performed at the hardened state in accordance to NCh 158 [38]. In addition to the macro-characterisation of the samples, i.e., the fresh and hardened mechanical behaviour of cement mortars, a micro-level analysis of the rubber grains under the treatments was performed. The micro-characterisation consists of the measurement of the contact angle between the rubber samples and the water, in addition to the analysis of the SEM (Scanning Electron Microscopy) images. The aim of this approach is to have a better understanding of the macro behaviour of the cement mortar samples.

#### *2.4. Cement Mortar Mix Dosage*

For the mix dosage, the Mortar Manual developed by the Chilean Institute of Cement and Concrete was applied. This manual establishes generalities, properties and dosage methods for cement mortars [39]. The procedure based on compliance with workability and compressive strength, modified due to the partial replacement of the aggregate by ELT rubber, was applied.

The reference compressive strength used in this study corresponds to 300 kg/cm2, which, according to the applied design method [39], implies a design strength of 350 [kg/cm2], with a medium workability, which means a drop of between 3 and 8 cm measured by the reduced cone method. The mix dosage is presented in Table 6.

**Table 6.** Mix dosage to produce 1 m3 of mortar.

#### **3. Results**

*3.1. Stage 1*

3.1.1. Workability

The results of the reduced cone test for the samples with untreated rubber addition are presented in Figure 4. With respect to the control mortar, without rubber addition, there is an important variation in the workability of the mix with high dependence on the percentage of replacement. With larger amounts of rubber, although all the results are within the design range [38], the samples with smaller rubber size have a much lower workability compared to the others. This is explained due to the higher specific surface area of the smaller rubber particles, causing a greater friction with the rest of the mixture, resulting in a lower cone slump.

**Figure 4.** Mortar cone slump with addition of untreated rubber 2.5% and 12.5% replacement: (**a**) cement C1; (**b**) cement C2.

#### 3.1.2. Density

The results of the densities for the samples with the addition of untreated rubber are presented in Figure 5. The error bars correspond to the standard deviation for the two cements used; the measured densities are similar, with minimal differences of around 2% in the case of the control mortar, being generally higher in samples with cement C1. Due to the lower density of the ELT rubber with respect to the aggregate, an inverse relationship is observed between the amount of rubber added and the mortar density. Regarding the size of the rubber aggregate, it is not possible to establish a relationship between this and the density since the results do not show a trend in this respect.

**Figure 5.** Density of mortar with addition of untreated rubber 2.5% and 12.5% replacement: (**a**) cement C1; (**b**) cement C2.

#### 3.1.3. Flexural Strength

The results of the flexural strength for the samples with the addition of untreated rubber are presented in Figure 6. The control mortar has practically equal strengths with both cements at 7 days. This changes at 14 days, where the samples with cement C1 have higher strengths. It is observed that, as the percentage of ELT rubber increases, the strength of the samples decreases.

At a test age of 14 days, when the cement used is C1, the average strength reduction (considering the three rubber sizes) for replacement percentages of 2.5% and 12.5% is 20% and 39%, respectively, with respect to the control mortar. In the case of mortars made with C2 cement, the reduction in strength for both replacement percentages reaches 15% and 38%, respectively.

**Figure 6.** Flexural strength of mortar samples with addition of untreated rubber at 2.5% and 12.5% replacement, after 7 and 14 days: (**a**) cement C1; (**b**) cement C2.

#### 3.1.4. Compressive Strength

Figure 7 presents the results of the compressive strength tests for the samples with untreated rubber addition. Similar to the results previously shown, a strength reduction is observed as the amount of rubber added increases. In general, the strength reduction is greater than in the case of flexural strength, which is in agreement with what is found in the literature [23]. At a test age of 14 days, when the cement used is C1, the average strength reduction (considering the three rubber sizes) for replacement percentages of 2.5% and 12.5% is 18% and 45%, respectively, with respect to the control mortar. In the case of mortars made with C2 cement, the reduction in strength for both replacement percentages reaches 19% and 48%, respectively.

**Figure 7.** Compressive strength of mortar samples with untreated rubber addition at 2.5% and 12.5% replacement, after 7 days and 14 days: (**a**) cement C1; (**b**) cement C2.

From the results, is possible to conclude that the 12.5% replacement is not recommended. In the case of cement C2, for example, the reduction of compressive strength is approximately 50% with this replacement.


*Article* **Quality Control of CyGNSS Reflectivity for Robust Spatiotemporal Detection of Tropical Wetlands**

**Hironori Arai 1,2,3,4,\*, Mehrez Zribi 1, Kei Oyoshi 5, Karin Dassas 1, Mireille Huc 1, Shinichi Sobue 5 and Thuy Le Toan 1**

**Abstract:** The aim of this study was to develop a robust methodology for evaluating the spatiotemporal dynamics of the inundation status in tropical wetlands with the currently available Global Navigation Satellite System-Reflectometry (GNSS-R) data by proposing a new quality control technique called the "precision index". The methodology was applied over the Mekong Delta, one of the most important rice-production systems comprising aquaculture areas and natural wetlands (e.g., mangrove forests, peatlands). Cyclone Global Navigation Satellite System (CyGNSS) constellation data (August 2018–December 2021) were used to evaluate the spatiotemporal dynamics of the reflectivity Γ over the delta. First, the reflectivity Γ, shape and size of each specular footprint and the precision index were calibrated at each specular point and reprojected to a 0.0045◦ resolution (approximately equivalent to 500 m) grid at a daily temporal resolution (Lv. 2 product); then, the results were obtained considering bias-causing factors (e.g., the velocity/effective scattering area/incidence angle). The Lv. 2 product was temporally integrated every 15 days with a Kalman smoother (+/− 14 days temporal localization with Gaussian kernel: 1σ = 5 days). By applying the smoother, the regional-annual dynamics over the delta could be clearly visualized. The behaviors of the GNSS-R reflectivity and the Advanced Land Observing Satellite-2 Phased-Array type L-band Synthetic Aperture Radar-2 quadruple polarimetric scatter signals were compared and found to be nonlinearly correlated due to the influence of the incidence angle and the effective scattering area.

**Keywords:** CyGNSS; GNSS-R; inundation; wetland; Mekong Delta


**Author details**

Diego Incontri-Abraham and José Juan Antonio Ibarra Arias\* Health Sciences Research Center (CICSA), Universidad Anáhuac México, Campus Norte Huixquilucan, Estado de México, México

\*Address all correspondence to<EMAIL_ADDRESS>
© 2021 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


*2.2. Study Site: Kahana, Ko'olauloa, O'ahu*

The *ahupua*'*a* of Kahana is located within the *moku* (district) of Ko'olauloa on the windward side of O'ahu, Hawai'i's most developed island (Figure 1). This rural *ahupua*'*a* encompasses a single watershed (5228.7 acres) that empties into Kahana Bay, an important spawning and nursery ground for many native aquatic species. Kahana's nearshore fishery sustained a thriving Native Hawaiian population prior to Western contact [36], and continues to be important for the cultural identity and subsistence of area families. Kahana has a long history of Native Hawaiian presence, with archaeological research indicating habitation for over 800 years [37]. Historical continuity is further evidenced by Kahana's many *mo*'*olelo* (oral stories) of Hawaiian deities dating from time immemorial, and by its cultural landscapes and seascapes [38–41], including Huilua Fishpond, a stone wall enclosure traditionally used for aquaculture.

**Figure 1.** Location of the *ahupua*'*a* of Kahana within the *moku* (district) of Ko'olauloa on the island of O'ahu. Geographic Information System (GIS) boundaries and names are delineated by the "Ahupua'a" layer provided by the Office of Hawaiian Affairs and distributed by the Hawai'i Statewide GIS Program.

*Konohiki* fishing rights were officially recognized in Kahana until 1965–1969, when the State of Hawai'i acquired the *ahupua*'*a* and opened its fishery for public access. Today, the *ahupua*'*a* is established as a recreational state park offering ten beach campsites, two designated hiking trails, and interpretive programs for visitors to learn about Hawaiian culture. Kahana families, many with multigenerational and genealogical ties to the area, continue to reside in the park on long-term leases with the state. Despite nearly half a century of planning efforts, there is no master plan or shared state and community vision for managing the *ahupua*'*a* and its resources, including the nearshore fishery.

#### **3. Methods**

For this study, the lead author conducted 19 in-depth interviews, 9 with elders and fishers of Kahana and 10 with state resource management personnel, along with informal discussions and time spent between June 2015 and April 2017 participating in community events and workdays. Using a snowball sampling method [42], community members identified elders and fishers' (subsistence and commercial) extensive knowledge of the history related to Kahana's fishery. Semi-structured interviews focused on stories of place, stewardship practices, perceived changes and threats to coastal resources, and recommendations for improving management, capturing personal recollections from as early as the 1930s. State resource management personnel representing different agencies in the Department of Land and Natural Resources were identified by community members, as well as other personnel [42], based on having worked with the Kahana community or their familiarity with community concerns and caretaking efforts. Semi-structured interviews with state resource management personnel addressed management approaches in Kahana, as well as agency efforts and experiences working with community.

Secondary data include Kahana-related research publications such as scientific studies, state government documents including master plans and environmental impact statements, and transcripts from previous collections of interviews [21,43–46] with 23 community members from across the district of Ko'olauloa (Table 1). The lead author also searched archival records such as English language newspapers, correspondence by historic land owners, photos and maps from the Hawai'i State Archives, Bishop Museum, and Brigham Young University–Hawai'i. Newspaper articles were also accessed from online repositories, dating from as early as 1852. A constructivist grounded theory approach guided collection and analysis of qualitative data in this study [47]. Codes derived from interview transcripts, field notes, and secondary data were used to develop conceptual categories related to *konohiki* and community caretaking.

**Table 1.** Number of individuals interviewed (primary interviews, N = 19; secondary interviews, N = 23).

#### **4. Results**

Although Kahana formally maintained local level *konohiki* fishing rights through the mid-1960s, over half a century longer than most communities in Hawai'i, the modern *konohiki* system detailed in this case study operated within a very different context than during pre-contact times (Table 2). The *konohiki*, who are remembered by community elders, operated between the 1920s and mid-1960s within a changed system of Western land privatization, commercial use of the nearshore fishery, and the ability to lease *konohiki* fishing rights. Transition to a private property regime following the land division process of 1846–1858 brought new interpretations of the role and responsibilities of *konohiki* [26]. Once a position held by well-respected individuals appointed to oversee the well-being of *ahupua*'*a* residents and resources, *konohiki* of the late 19th and early 20th centuries enjoyed the benefits of owning particular lands while no longer accountable for ensuring their provision of abundance. According to certified deeds, purchase of Kahana's *konohiki* land came with the rights to the *konohiki* fishery (and fishponds) [48]. Thus, Kahana's *konohiki* fishing rights exchanged hands with new landowners, from Caesar Kapa'akea and Chiefess Keohoka¯lole in 1850, to three different Chinese businessmen, and finally to Ka Hui Ku'ai i Ka ' ¯ A¯ ina o Kahana (Hui of Kahana, or Hui) in 1874 [36,48]. The Hui was a group of 95 mostly Native Hawaiians from Kahana and surrounding *ahupua*'*a* who collectively purchased back the land and divided it among 115 shares [36]. However, with Hawai'i's increasingly foreign-controlled government and new laws enabling wealthy foreigners to acquire Hawaiian lands, Hui shares and other land parcels were eventually sold outside of the Kahana community. By 1903, the majority of Hui shares were owned by Mary Foster, a wealthy part Hawaiian businesswoman with no known connection to Kahana [36], and by 1930, she owned 99% of the *ahupua*'*a* [49].

Between 1905 to around 1965, Kahana's konohiki fishery appears to have operated under Mary Foster or her estate (having majority rule on Hui decisions) for commercial production, while ahupua'a residents continued to exercise their legal right to the fishery for subsistence. Court documents under the territory of Hawai'i reveal successful registration of Kahana's *konohiki* fishery in 1905, to the Hui of Kahana as vested owners [50]. Within the same year, archival records indicate that Mary Foster and her estate, acting on behalf of the Hui, began leasing the fishing rights for commercial operation [51]. Although newspaper advertisements announced lease of the fishing rights for the highest bidder, community interviews reveal that lessees were still expected to fulfill the traditional *konohiki* responsibility of leading communal fishing efforts. To invite community ability and bring people together for collective harvests, lessees still had to earn and maintain the respect of community members.

#### *4.1. Persisting Role of Konohiki to Invite Ability*

Although *konohiki* of the 19th and 20th centuries acquired their positions through new means, the role of *konohiki* remained an important aspect of life in Kahana. Community interviews recall three *konohiki* operating in Kahana, some at the same time (Table 2). The first *konohiki* people remember is Samuel Pua Ha'aheo, who held the fishing rights possibly as early as 1924, when he became the caretaker of Huilua Fishpond, through to 1946 [40]. According to interviews, Pua was not originally from Kahana but married a woman from the area. Archival records show that he rented property from Mary Foster [52]. Pua's responsibilities were to monitor the fishery, determine when it was time to collectively surround schools of fish, guide fishers from the shoreline, and oversee distribution of the catch. Interviewees expressed that Pua was beloved and well-respected because he was perceived as taking care of everyone, especially the elders.

**Table 2.** Changes in land and sea tenure in Kahana, O'ahu (1200–1969).

Following Pua, most community members remember the Kamake'ea¯ina family, and in particular, Uncle or Papa 'A¯ ina Pahumoa Kamake'ea¯ina from La¯'iemalo'o, a nearby *ahupua*'*a* within the same district (Figure 1). The Kamake'ea¯inas are considered to be the last *konohiki* of Kahana, maintaining this role through the mid-1960s. One of the eldest interviewees described how the first time the Kamake'ea¯inas surrounded *akule* (big eye scad, *Selar crumenopthalmus*) in Kahana, not a single resident went to the beach to help. However, younger interviewees only remember doing collective harvests with the Kamake'ea¯inas and recall Uncle 'A¯ ina as a person who always gave fish. Together, these varied accounts suggest the Kamake'ea¯inas were able to build their relationships with the Kahana community over time.

During both Pua's and the Kamake'ea¯inas' tenures as *konohiki*, Nicholas Peterson, who was part Hawaiian and originally from the south side of O'ahu, served as "the caretaker of Kahana". However, as one elder clarified, "Uncle Nick wasn't really the People's *konohiki*, so they say, but [he worked] for Mary Foster ... He had to make sure that he made the bucks out of the fishing and make sure that she had revenues coming in." According to newspaper articles, Peterson worked as a foreman for Mary Foster from around 1925 through to 1960 [53]. Community interviews suggest that Peterson collected rent from the residents, made sure people were taking care of upland resources, enforced Kahana's restriction on harvesting *akule*, and sold the fish surrounded from communal harvests. Whether responsible for leading the fishing effort or ensuring reliable harvests, the 20th century *konohiki* of Kahana continued to mobilize community efforts around cultivating and harvesting abundance.

#### *4.2. Managing Land-Sea Connectivity*

One way in which Kahana's *konohiki* maintained the health of the nearshore fishery was by managing the land and streams, which affect coastal resources. According to community interviews, it was Peterson, who primarily oversaw the whole *ahupua*'*a*. As one long-time resident describes, Peterson would make sure people were "keeping their yards clean, make sure they came out and did what they're supposed to, make sure the rivers were clean, the stream beds, and just [responsibilities] that belong to our people anyway." Elders remember Kahana being well cared for when there was a *konohiki*, commenting in particular on how Kahana Stream was cleared of vegetation. Many interviewees recalled how the *hau* (*Hibiscus tiliaceus*), an invasive tree that has overgrown the stream in recent decades, never used to reach the water's surface. The importance of managing land–sea connectivity is emphasized in the Hui's requirement of the Kamake'ea¯inas, as non-residents, to cultivate one *lo*'*i* (flooded-field agriculture) in Kahana in order to hold the *konohiki* fishing rights. Residents also cared for their own *lo*'*i* and home gardens, and recall how "from time to time, everyone went up the valley to clean the [irrigation ditches]. We never let the [irrigation ditches] get dirty or blocked with rubbish. We all cleaned it together" [54] (p. 13). In these various ways, Kahana's *konohiki* and the community managed the land and sea as an integrated unit, recognizing that fisheries management begins on land.

#### *4.3. Protecting Spawning Behavior*

Kahana's *konohiki* also protected natural processes to replenish the fishery, such as spawning behavior. Kahana Bay provides important spawning and nursery habitat for many of Hawai'i's native aquatic species, including hammerhead sharks, manta rays, *moi* (*Polydactylus sexfilis*; Pacific threadfin), *a*¯*holehole* (*Kuhlia xenura*; Hawaiian flagtail), and '*ama*'*ama* (striped mullet, *Mugil cephalus*). However, Kahana is most famed for the large schools of *akule* (big eye scad, *Selar crumenopthalmus*) that aggregated in the center of its bay to spawn [39]. From as early as 1852, lasting into the mid-1960s, Kahana's *konohiki* actively claimed exclusive rights to harvest *akule* [50,55]. This restriction on harvesting *akule* additionally meant that no one except the *konohiki* could even enter the center of the bay. As one elder explained, "If you want to go fishing, we got to stick to the side of the bay and then go out. They don't like us in the middle, because we're going to chase the *akule* away. Chase the fish away." *Ahupua*'*a* residents could still exercise their right to the *konohiki* fishery by accessing the edges of the bay and its fringing reefs to fish and gather for home consumption. Elders attribute a productive nearshore fishery—with schools of fish visiting the bay more frequently, in greater numbers, and with larger individuals—to *konohiki* management. Kahana Bay's establishment as a *konohiki* fishery protected it from overuse by prohibiting entry of non-residents, and the restriction on harvesting *akule* further protected replenishment of fish stocks by ensuring that spawning behaviors were not disrupted.

#### *4.4. Sharing Responsibility*

Another enduring feature of *konohiki* was the sharing of responsibility, exemplified through the continued practice of *hukilau*. *Hukilau* is a communal surround net fishing method in which *lau* (ti leaf) is intertwined with rope and used to guide schools of fish towards the shore. In modern practice, nets were also used and attached to the rope. Nearly every community member interviewed in this study, and in previous studies, discussed *hukilau* for *akule*. This Hawaiian fishing method required the help of the whole community to contribute various skills and labor including spotting the school of fish, rowing the boat, diving to check the net, pulling the net in, and loading baskets full of fish to sell at the market. Once a school of fish was surrounded, the work continued with everyone helping to clean the boats and nets, patch up holes in the nets, cut and gather wood to build racks for the nets to dry on, and store everything back in Kahana's net and boat houses, ready for the next surround. All of this shared responsibility and work was coordinated by the *konohiki*.

#### *4.5. Supporting Communal Benefit*

Only by sharing in the work, the entire community also could share in the benefits. The *konohiki* who led the fishing effort was also responsible for overseeing the distribution of catch from each surround, making sure that everyone—workers, community members, and even visitors—had fish to bring home to their families. One resident, born and raised in Kahana, shared of Pua Ha'aheo, "No matter how big the school or how small the school ... each resident had their share of fish to go home with. That's how it was. So that's how he maintained the fishing rights over here" [56]. In addition to their shared distribution of the catch, everyone who helped also received a share of the money earned from selling the fish. Kahana elders describe how Mary Foster and the *konohiki* would split the money fifty-fifty, then the *konohiki* "would split the money up so everybody got money ... [Your share] would depend on how old you were and how much work you did." Pua and the Kamake'ea¯inas kept their roles as *konohiki* through facilitating collective ability to harvest then distributing the share to see that the community, especially elders, were well provided for.

#### *4.6. Limited State Capacity to Manage Ahupua'a Resources*

Kahana's elders shared how their nearshore fishery, even as it was being used for both subsistence and commercial purposes, was well cared for and abundant under *konohiki* management. However, with the loss of *konohiki* fishing rights, interviewees began to see the fishery decline. Between 1965 and 1969, the State of Hawai'i acquired Kahana through eminent domain, establishing the *ahupua*'*a* as a recreational state park and opening its *konohiki* fishery for public access. Facing eviction, Kahana families protested and successfully lobbied the state legislature to remain on the land [49]. Today, just 28 households, many with multi-generational and genealogical ties to Kahana, have secured 65-year leases with the state [57]. Per lease terms, residents are required to provide 25 hours each month of cultural activities and interpretive services for park visitors, as part of the state's "living park" concept. Since Kahana became a state park, residents have endured decades of meetings, interviews, and surveys involved in state-funded studies, legislative reports, environmental impact assessments, at least eight master planning efforts and numerous park program proposals [49,58]. Yet there is no master plan for Kahana and the majority of State Parks and community interviewees agree the "living park" concept is no longer viable.

Community interviewees also expressed that the state has poorly addressed threats to coastal resources, including intensive commercial fishing, disruptive recreational uses such as jet skis, invasive species introductions, and habitat change. State Parks interviewees expressed they lack the capacity and expertise to manage ecological function. Though State Parks is tasked to manage Kahana's natural and cultural resources, their efforts largely focus on creating public recreational opportunities. Additionally, State Parks does not have jurisdiction over the nearshore fishery. Interviews with personnel from Aquatic Resources, Boating and Ocean Recreation, and Conservation and Resources

Enforcement highlight their responsibility to the whole archipelago, and therefore their inability to focus limited resources on any one community's concerns. Following decades of failed planning efforts, mismanagement and fishery decline, the Kahana community, including residents and fishers from across the district of Ko'olauloa, is strengthening local governance to improve coastal resource health.

#### *4.7. Reviving and Strengthening Local Fisheries Institutions*

Kahana families are finding creative ways to manage their coastal resources through reviving *ahupua*'*a* health and food systems, restoring customary harvesting practices, teaching across generations, and building community relationships and management capacity. With the help of younger residents and Ko'olauloa families, elders have restored and continue to maintain *lo*'*i* (flooded-field agriculture) that were cared for within their families for generations. These farmers also work together to maintain the traditional irrigation ditch that feeds their *lo*'*i* with stream water. These traditional food systems have become features of the park, where visitors from schools and organizations across the island visit to learn and contribute through workdays.

Huilua Fishpond, which once functioned as a community food source, also fell into disuse under state ownership. In 2015, young leaders worked with State Parks to obtain a master permit, in compliance with state and federal regulations, to begin restoring the fishpond's 1000-foot wall. Although the permit determines the extent of activities that can be performed, fishpond caretakers lead the restoration effort and design best-management practices based on traditional environmental and cultural protocol [59].

Other young community members created the community-based nonprofit organization, Kahana Kilo Kai, in 2014 to steward the bay. They formally enrolled in the "Adopt-a-Harbor" program their first year to restore area facilities long neglected by Boating and Ocean Recreation. They also worked with the agency to post signage reminding jet skiers of Hawai'i's "slow-no-wake" laws, to minimize disturbance to fish spawning behavior. Along with these efforts, three youth completed training in identifying and reporting violations of fishing regulations through the Conservation and Resources Enforcement agency's Makai Watch program. Over the course of this study, Kahana families gathered at the pier regularly to monitor recreational activities, record fish catches and spawning times, build relationships with fishers, and educate the public about both state regulations and local values for using area resources responsibly. In recognition of these collective efforts by Kahana's young leaders, one state resource manager stated, "They don't just suggest things, they don't just plan things. They're doing it. They're working in the taro patches, they're carrying [rocks] at the fishpond ... they can walk their talk." Through restoring traditional agriculture and aquaculture, and promoting responsible use of the nearshore fishery, the Kahana community is reintegrating land and sea management, while reasserting their role as caretakers.

Kahana fishing families are also reviving other customary nearshore management and fishing practices, such as *hukilau* or communal surround net fishing. Though *hukilau* ended in Kahana in the mid-1960s, community members revived the practice for '*ama*'*ama*, a native mullet, with guidance from one particular elder over the past ten years. While *hukilau* requires substantial effort, this harvesting practice, in which everyone who participates can contribute, strengthens community through relearning, reconnecting, and working together.

Community interviews also highlight potential rules for future local-level fisheries management that draw upon customary practices. The majority of community interviews expressed interest in introducing a new state law to place an island-wide seasonal restriction on harvesting *akule*, as well as placing a ban on disruptive recreational uses in Kahana, such as jet skis, to protect fish spawning behaviors. Many, including commercial fishers within the community, also share a desire to limit commercial fishing. Guided by elder knowledge and recommendations, the Kahana community is relearning harvesting and caretaking practices of *konohiki* to improve management of their nearshore fishery.

Another way in which Kahana families are strengthening local influence is through teaching across generations. Over the past several years, young community members have organized fishing camps, held for multiple days each summer, to educate area families and especially youth about ecosystem health and function, caretaking values, and responsible harvesting practices. The camps integrate Indigenous and Western knowledge systems through activities such as sewing and patching fishing nets, monitoring changing ecological conditions according to the Hawaiian moon calendar, and analyzing fish gonads to document spawning times. Many community elders and longtime fisher men and women informally teach at the camps, but also, learn. One Kahana elder shared, "A lot of the things that I've been taught today [through fishing camps and community gatherings] was never ever taught to our young ones or even to our old ones." Logistically, hosting the camps in Kahana requires Special Use permits to be filed with State Parks at least 45 days in advance. Aside from general rules for using the area, these permits secure space for families, many of whom no longer live in Kahana, to gather, teach, and learn together on the land. These camps also strengthen relationships with nonprofit and state resource management personnel, who are also invited to participate in and help conduct activities.

Kahana families are also building their capacity to manage coastal resources through participating in local and global community partnerships and knowledge sharing networks. As a member of the nonprofit organization, Kua'a¯ina Ulu 'Auamo (KUA), Kahana families are connected to more than 33 communities across Hawai'i working to protect and steward their lands and fisheries, including the restoration of 38 fishponds. In 2016, Kahana families expanded this network internationally, hosting a fishpond workday with over 100 Indigenous and community leaders, practitioners, and supporters from 35 nations. The global gathering was organized by KUA to build solidarity among individuals engaged in community grassroots efforts prior to attending the IUCN (International Union for Conservation of Nature) World Conservation Congress in Honolulu.

Although the Kahana community lacks formal government recognition of local management rights or co-management agreements, these informal efforts demonstrate community action and commitment. State resource management personnel across agencies have begun to take notice and lend their support. Within the timeframe of this study, state personnel attended fishing camp activities to give talks to the youth, helped to pull *hukilau* nets in to shore, and passed rocks at the fishpond alongside community members. These means of informal engagement are beginning to repair state–community relationships, while also building community confidence, connections, and ability. Here, informal caretaking efforts hold promise for collaborative management driven by community objectives and needs.

#### **5. Discussion**

Understanding how Indigenous and place-based institutions historically operated and adapted to social–ecological change, and how they can fit within contemporary contexts is essential for biocultural restoration [6,60,61]. We use a case study approach focused on one Hawai'i fishing community reclaiming their role as caretakers despite changes in land and sea tenure, governance, access, and use. Emerging from this research are key considerations for community-based collaborative management. These include: (1) understanding historical context for enhancing institutional fit, (2) enduring community leadership, (3) balancing rights and responsibilities, and (4) fostering community ability to manage coastal resources through both formal and informal processes.

#### *5.1. Understanding Historical Context for Enhancing Institutional Fit*

Understanding social-ecological systems from a historical perspective is critical in designing effective collaborative fisheries management institutions. Institutions are systems of rights, formal and informal rules, and decision-making procedures that guide human–environment interactions [62]. Institutional fit refers to how well institutions match a particular social–ecological system, often in terms of their spatial, temporal, and functional contexts [63–65]. Findings from this research emphasize that

design of fisheries institutions must also factor in the historical contexts of a social–ecological system, specifically the traditional and place-based institutions historically in place. *Konohiki* management was tailored to local socio–cultural contexts and ecological systems, including prime spawning habitat and the impacts of land-based activities on the nearshore fishery. The experience of coastal resource decline is not unique to Kahana, but is shared across Hawai'i [21,26], the Pacific [7,11], and other parts of the world [5,9] where Western models and concepts of resource management have replaced Indigenous and place-based institutions. Still, a wealth and diversity of traditional and place-based knowledge systems endure, and can be adapted within contemporary contexts to improve coastal resource management [3,5,11–13,66]. Rather than simply replicating specific practices of these time-tested institutions, it is important to understand their foundational principles, the key functions they fulfilled, and how they can be adapted to foster future biocultural restoration.

#### *5.2. Enduring Community Leadership*

Hawai'i's *konohiki* system is an example of a community-based collaborative management institution that endured by maintaining key features within a changing social–ecological context. One enduring feature was *konohiki* facilitation of community caretaking and harvesting efforts, which depended upon in-depth knowledge of the local ecology, exceptional fishing skills, and ability to earn and maintain the respect of the community [28,67]. Such leadership roles are increasingly recognized as important attributes contributing to sustainable fisheries [20,68–70], specifically when leadership is perceived to be legitimate and highly engaged [71]. A recent analysis of 130 co-managed fisheries worldwide identified leadership—the presence of at least one respected individual with entrepreneurial skills, who is driven by collective interests and committed to the co-management process—as the most important feature for successful co-management [68]. The Kahana case study provides an example in which leadership emerges through a community as a collective in the context of perceived government inaction and resource decline. In this case, leadership is dispersed among elders as knowledge holders and young adults who mobilize community around various caretaking activities. These collective efforts demonstrate how multiple sources of leadership can be complementary, interact through mutual support, and coexist within community, adding to a pluralistic conceptualization of environmental leadership [70].

#### *5.3. Balancing Rights and Responsibilities*

Maintaining collective benefit through balancing rights and responsibilities was another enduring feature of *konohiki* management. *Konohiki* carried unique responsibility to oversee harvests, facilitating a system in which everyone who contributed to collective work would in turn receive the benefits of reliable harvests [24,25,67]. Rights and responsibilities for all resource users need to be balanced and based upon contributions to collective efforts and caretaking [60]. One key challenge to fisheries co-management in Hawai'i is that traditional management rested upon reserving distinct rights for area residents [13,29]. Under the state, open access allows the public to use and harvest coastal resources with no expectation to care for them, cultivate their abundance, or give back in any way. This decoupling of rights and responsibility has resulted in coastal resource decline worldwide [7,14,72]. Displacement of Indigenous people throughout the world for the purpose of establishing national parks, uninhabited wilderness [9], and marine protected areas [7] violates their customary rights and prevents them from exercising their distinct responsibilities to care for their homelands. Managing natural areas for public benefit limits community ability to continually interact with, eat from, perpetuate knowledge of, and govern coastal resources for which they are responsible. Emerging literature on co-management emphasizes the need to maintain a balanced distribution of rights and responsibilities, obligations, and benefits amongst all resource users [60,61,67].

#### *5.4. Fostering Community Ability to Manage Coastal Resources through Both Formal and Informal Processes*

This case study also highlights the power of informal fisheries co-management as a means to foster community ability to lead caretaking efforts. Co-management comprises a variety of institutional arrangements shaped by different goals, partners, knowledge systems, and degrees of power sharing [15–20]. Such arrangements are negotiated and acknowledged through a formal (e.g., officially recognized by law) or informal (e.g., verbally accepted) agreement among partners [18]. In Kahana, the fishery has been minimally managed with archipelago-wide species-specific regulations administered by the state. Formal state park leases focus only on community service to educate visitors. However, within the last decade, Kahana families have been reclaiming their role as caretakers through informal means of managing coastal resources. Many of these caretaking activities require state approval (e.g., through special permits) and increasingly engage state resource management personnel, for example, to give invited talks to youth at fishing camps.

Through informal co-management, communities have the flexibility to self-organize, determine their own management objectives, and act upon them within their own time frames. By working within informal co-management systems, collective governance of fisheries, along with feelings of empowerment and shared responsibility, can be achieved and lead to effective management practices [73]. Informal caretaking efforts in Kahana also highlight the importance of creating protected spaces for families and community to spend time together and build upon generational knowledge of place and practice. Traditional activities provide not only a gathering space for renewing relationships with family, community, and place, but also a foundation for cultural resurgence and resilience [74]. Adaptive community-led management can guide progress towards more just and effective conservation solutions, restoring coastal resources along with Indigenous and place-based communities' rights and responsibilities [60].

Still, this study recognizes the need for higher levels of governance to formally complement and support community caretaking efforts [19,20,69]. Informal co-management can be limited in confronting unsustainable fishing and recreational activity, and may require legal backing [19]. Long-term sustainability requires place-specific rules, the ability of communities to recognize and respond to change, and support from higher levels of organization [12,69]. In this case, as in others, informal efforts can strengthen relationships that pave the way for more formal co-management agreements [16,67].

#### **6. Conclusions**

Understanding how Indigenous and place-based institutions historically operated and adapted to social–ecological change, and how they can be reinvigorated within contemporary contexts, is essential for biocultural restoration [6,60,61]. This study provides a historical perspective of fisheries governance within one rural Hawaiian fishing community, covering the transition from local to state level fisheries management, to an emerging collaborative arrangement led by community. This study also demonstrates how informal community initiative *ma ka hana ka* '*ike*, to learn by doing the work [75], can be more powerful than formal co-management arrangements for building community ability [67,74]. Findings also emphasize the value of understanding historical institutions that adapted to local socio-cultural and ecological contexts, building collective leadership that fulfills traditional functions, and balancing rights and responsibilities amongst all resource users. Effective fisheries governance requires true partnerships, formal and informal, that value Indigenous and place-based knowledge systems and while creating the space for communities to build enduring relationships among people, place and practice.

**Author Contributions:** Both authors were involved in the design of this research. M.M. wrote the initial draft manuscript and carried out the field research. Both authors contributed to analysis and writing the paper. Both authors read and approved the final manuscript.

**Funding:** The APC was funded by Hawai'i Community Foundation.

**Acknowledgments:** Mahalo first and foremost to the Kahana elders and fishers who shared their stories, knowledge of place, and recommendations for Kahana's people, fishery, and future. We also thank the state resource management personnel who took time to share their thoughts and efforts moving forward. A special thanks to Shaelene Kamaka'ala, who has been a tremendous support and guiding light in this work. We also thank Ho¯'ala 'A¯ ina Ku¯pono, the Ku¯'oko'a Strategic Initiative, the Hawai'i Community Foundation, Malia Akutagawa, Kirsten Oleson, Heather McMillen, and the Ko'olauloa families who continue to care for this place. Credit goes to Kalani Quiocho for the title, meaning "Through Kahana, one learns," a word play on the Hawaiian proverb, "Ma ka hana ka 'ike."

**Conflicts of Interest:** The authors declare no conflict of interest.