**1. Introduction**

Coronavirus disease (COVID-19), which started in Wuhan, China, in December 2019, became a pandemic in a few months, leading to extraordinary risks to human beings [1]. Despite the majority of infected subjects having a moderate illness and about 10–15% of

Briguglio, G.; Mento, C.; Muscatello, M.R.A.; Alibrandi, A.; Larese Filon, F.; Spatari, G.; Teodoro, M.; Fenga, C. Quality of Life, Insomnia and Coping Strategies during COVID-19 Pandemic in Hospital Workers. A Cross-Sectional Study. *Int. J. Environ. Res. Public Health* **2021**, *18*, 12466.

**Citation:** Italia, S.; Costa, C.;

Academic Editors: Paolo Roma, Merylin Monaro and Cristina Mazza

https://doi.org/10.3390/ijerph182312466

Received: 22 October 2021 Accepted: 25 November 2021 Published: 26 November 2021

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**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

patients developing grave complications [2], until 21 October 2021, about 4.9 million deaths were declared, with over 241 million cases confirmed globally [3].

In Italy, the epidemiological situation during the first wave, since February 2020, differently concerned the country with a significant burden of disease in the North rather than the South; in particular, Lombardy, Piedmont, Emilia Romagna, and Veneto were the most affected northern regions [4]. The Italian government handled this critical situation by implementing preventive measures and adopting a national lockdown on 10 March 2020 [5]. Consequently, Italians lived in social isolation for about two months; only indispensable activities were allowed and leaving home was consented to only for health reasons, purchasing vital products, and reaching the workplace, when permitted [6]. The pandemic altered everybody's lives and work behaviors, particularly those healthcare workers (HCWs) who were involved on the frontline with increased exposure to SARS-CoV-2 infection, lack of validated guidelines, and shortage of resources including personal protective equipment [7]. In addition, these workers have often decided to live far from their loved ones to keep them safe from an additional risk of contagion [8].

In previous research, outbreaks of other contagious diseases led to adverse health outcomes in HCWs impacting physical, social, emotional, or spiritual wellbeing, globally reducing the quality of life [9–11]. Despite life quality being a broad-range concept, the WHO defines it as the subjective perception of own position in life in the specific cultural context and in relation to personal expectations, standards, and concerns [12]. The literature describes five dimensions that define life quality in terms of mobility, self-care, usual activities, pain/discomfort, and anxiety/depression [13]. The current COVID-19 pandemic has created circumstances with overwhelming stressors on HCWs, through increased working loads, high risk of exposure to SARS-CoV-2, and overall disruptions of daily life, leading to increased anxiety, stress, depression, burnout and sleep disorders [14], especially insomnia [15], and to a drastic reduction in the perceived quality of life [16,17].

The considerable psychological impact of the COVID-19 pandemic has undoubtedly influenced feelings and behaviors [18,19], requiring the adoption of coping strategies to play a buffering role on stress and have a preventive effect on mental health [20]. Different coping strategies are used depending on external factors (such as cultural and workplace context or geographical area) [21] and individual components (e.g., rage, terror, or sadness) [22].

Though it has been demonstrated that the trend of contagion has differently affected the mental health status of HCWs working in areas with dissimilar incidences of COVID-19 cases [23,24], it is also true that regional differences in stress perception and coping strategies also depend on cultural factors, home/work interface, social support, and economic environment [25,26]. In a Chinese study, comparing subjects coming from Hubei and from non-endemic provinces, health workers in the endemic region showed lower anxiety levels about the COVID-19 epidemic [23]. In a multicentre prospective cohort epidemiological study, the regional origin explained a small fraction of differences in perceived job stress [27], while other factors seem to play major roles in affecting this aspect. For example, family is a fundamental source of support, particularly in developing areas where social services are scarce [28]. Under these premises, we mainly aimed to assess the quality of life, insomnia, and analyze the different coping strategies adopted among hospital personnel during the first wave of the COVID-19 pandemic in Italy. More specifically, we examined the differences in sociodemographic characteristics and work-related factors in two different Italian metropolitan areas with similar epidemiological trends, located in the North and in the South of Italy, respectively. We intended to identify eventual work-related and sociodemographic predictors of worse outcomes, suggesting insights on the best tailored preventive and organizational measures in the workplace.


Robust Guidance Algorithm against Hypersonic Targets

Jian Chen, Yu Han and Yuan Ren

## Abstract

This chapter presents a robust guidance algorithm for intercepting hypersonic targets. Since the differential of the line-of-sight rate is more sensitive to the target maneuver, a nonlinear proportional and differential guidance law (NPDG) is given by employing the differential of the line-of-sight rate produced by a nonlinear tracking differentiator. Based on the NPDG, a fractional calculus guidance law (FCG) is presented by utilizing the differential definition of fractional order. On the basis of interceptor-target relative motions, the stability criteria of the guidance system of the FCG are deduced. In different target maneuver and noisy cases, simulation results verify that the proposed guidance laws have small miss distances and the FCG has a stronger robustness.

Keywords: hypersonic target, target maneuver, fractional order control, guidance law, stability criteria


**Water Resource Management through the Lens of Planetary Health Approach**

Editors **Pankaj Kumar Ram Avtar**

MDPI ' Basel ' Beijing ' Wuhan ' Barcelona ' Belgrade ' Manchester ' Tokyo ' Cluj ' Tianjin

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Ram Avtar Faculty of Environmental Earth Science Hokkaido University Sapporo Japan

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**Abstract**

DG presents with three main presentations: hyperthyroidism with diffuse goiter, infiltrative ophthalmopathy and pre-tibial myxedema. Patients with Graves' Disease can rarely develop severe hyperthyroidism. The hyperthyroidism of Graves' Disease is characterized immunologically by the lymphocytic infiltration of the thyroid gland and by the activation of the immune system with elevation of the circulating T lymphocytes. In GD, goiter is characteristically diffuse. May have asymmetric or lobular character, with variable volume. The clinical manifestations of hyperthyroidism are due to the stimulatory effect of thyroid hormones on metabolism and tissues. Nervousness, eye complaints, insomnia, weight loss, tachycardia, palpitations, heat intolerance, damp and hot skin with excessive sweating, tremors, hyperdefecation and muscle weakness are the main characteristics. In the laboratory diagnosis, biochemical and hormonal exams will be done to assess thyroid hormones and the antithyroid antibodies. Additionally, imaging tests may be performed, such as radioactive iodine capture in 24 hours, ultrasonography, thyroid scintigraphy and fine needle aspiration. It is necessary to make the differential diagnosis of Graves' Disease for thyrotoxicosis, subacute lymphocytic thyroiditis and toxic nodular goiter. The treatment of DG aims to stop the production of thyroid hormones and inhibit the effect of thyroid hormones on the body. Hyperthyroidism caused by DG can be treated in the following ways: it may be the use of synthetic antithyroid medicines, thionamides, MMI being a long-term medicine, it allows a single daily dose, and adherence to treatment occurs, a disadvantage is that it cannot be used in pregnant women; beta-blockers, preferably used in the initial phase of DG with thionamides; radioactive iodine therapy (RAI), being the best cost–benefit and preventing DG recurrence; finally the total thyroidectomy, causing the withdrawal of the thyroid gland. Therefore, it should be discussed with the patient what is the best treatment for your case, with a view to the post and against each approach. If the patient develops Graves ophthalmopathy, in lighter cases the artificial tears should be used, and in more severe cases can be used as treatment, corticosteroids, orbital decompression surgery, prisms and orbital radiotherapy. In addition, the patient should keep their body healthy, doing exercise and healthy eating, following the guidance of their doctor.

**Keywords:** Graves' Disease, Hyperthyroidism, Goiter, Thyroid hormones

## **1. Introduction**

GD presents with three main presentations: hyperthyroidism with diffuse goiter, infiltrative ophthalmopathy and dermopathy (pretibial myxedema). Patients with Graves' Disease rarely may develop severe hyperthyroidism (thyroid storm or thyrotoxic crisis) [1]. Consider tests for thyroid dysfunction for people if there is a clinical suspicion of thyroid disease, but bear in mind that only an isolated symptom may not be associated with this disease [2].

## **2. Hyperthyroidism**

Graves' Disease hyperthyroidism is characterized immunologically by lymphocytic infiltration of the thyroid gland and by activation of the immune system with elevation of circulating T lymphocytes, appearance of autoantibodies that bind to the TSH receptor (TRAb) and that stimulate glandular growth and function [3–5]. The reasons for triggering this autoimmune process have not yet been fully understood, but factors such as susceptibility genetics, constitutional factors such as sex hormones and changes in immune function, and factors environmental factors (stress, iodine intake and the action of infectious agents) [6, 7].

From a clinical point of view, the hyperthyroidism of Graves' Disease is characterized by diffuse enlargement and hyperactivity of the gland thyroid, associated or not with infiltrative ophthalmopathy and, more rarely, localized myxedema. Excess thyroid hormones can lead to the development of serious complications such as congestive heart failure, cardiomyopathy and arrhythmias, mainly atrial fibrillation (10–30%). It is also associated with increased bone resorption, increased calcium and phosphorus excretion in urine and faeces, with a consequent decrease in bone mineral density and risk of fractures in women elderly [1, 3].

### **3. Dermopathy (pretibial myxedema)**

It affects only 5 to 10% of patients with GD and is almost associated with ophthalmopathy (usually severe) and high levels of TRAb [8]. Exceptionally, it has seen in euthyroid patients with GD [1] or with Hashimoto's thyroiditis [9]. It consists of within the thickening of the skin, particularly within the pretibial area, because of the buildup of the glycosaminoglycans. The evidence is shown in plaques and on them; the skin is type of thickened, with the looks of orange rind and violet color. Sometimes a Dermopathy involves the entire lower leg and should reach the feet. Rarely (less than 1% of cases), it can be seen in other places (hands or shoulders), especially after prolonged trauma [8, 10]. Very rarely, pretibial myxedema is the initial manifestation of GD [1, 11].

*Graves' Disease: Hyperthyroidism, Symptoms, Causes and Treatment DOI: http://dx.doi.org/10.5772/intechopen.97578*


Author details

Ali Hadi Abdulwahid1,2\* and Adnan A. Ateeq2

1 School of Electrical and Electronic Engineering, Huazhong University of Science and Technology, Wuhan, Hubei, China

2 Department of Engineering Electrical Power, Engineering Technical College, Southern Technical University, Basra, Iraq

\*Address all correspondence to<EMAIL_ADDRESS>
© 2019 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.

Innovative Differential Protection Scheme for Microgrids Based on RC Current Sensor DOI: http://dx.doi.org/10.5772/intechopen.85473


**2. Literature review**

Even though creativity studies have been oriented toward the creative process and understanding its dynamic and evolving momentum [12], children's everyday experiences with their significant others may influence their motivation, perseverance, competence, and so on, required for the fine elements in children's thinking [13]. Having said that, the casual relationship between mother's personality and children's creativity may be more complicated than one might assume. For example, it may be possible, depending on the conditions, that children's creativity has some effects on parent's personality, and there may be other factors such as socio-economic status which affect children's creativity [14, 15].

### **2.1 Maternal personality and children's creativity in Chinese societies**

Studies of the relationship between parents' personalities and children's creativity have conflicting results. On the one hand, studies showed mothers have an effect on children's creativity. Kwaśniewska and Lebuda [16] conducted 27 qualitative interviews with mothers and found that creative mothers foster a climate conducive to children's creativity. Kwaśniewska et al. [2]'s study showed that mothers who possess openness and extraversion traits more may show higher creative potential, while highly neuroticism parents may have less creative potential. And mothers with openness traits have a positive attitude to creativity, as well as are willing to provide the "climate" for creativity in a parent-child relationship. Since mothers are usually the primary caregivers who have been shown to play a key role in children's development, more studies are needed to examine the parentchild relationship in terms of mother's personality and children's, especially young children, creativity performance as it will shed light on creativity development in the early years, an issue that has drawn people's attention in recent years. On the other hand, Fu et al. [17]'s research showed that there was no indication of any significant relationship between maternal personality and preschoolers' creativity. The conflicting results may be due to the limitation of samples, or the measurements applied to measuring creative abilities.

From above, the relationship between maternal personality and children's creativity could be further discussed. Furthermore, considering the cultural factor, assessment of Chinese personality indicated that neuroticism, extraversion, agreeableness, and conscientiousness factors were jointly listed in the widely used Big Five inventory, but openness factor was not [18]. The openness factor was more identifiable in individualist cultures but was negatively correlated with collectivism [19]. Chinese society is more inclined to collectivism. However, previous studies showed that the openness factor was highly correlated to creativity [20]. Even the compatibility between cultural personality and creative personality in China was discussed (e.g., [21, 22]), the impacts of mother's personality on children's creativity require further investigations.

More importantly, it may be difficult to measure children's creativity as young children's manifestations of creativity are subtle and nonverbal. Therefore, the Thinking

#### *Indirect Effects of Parenting Style on the Relationship between Maternal Personality… DOI: http://dx.doi.org/10.5772/intechopen.102378*

Creatively in Action and Movement (TCAM) measure [23], which takes around 30 minutes for each child, is used in this study. Details will be given in the Section 3. This paper aims at finding the direct and indirect effects of maternal personality on children's creativity. For indirect effects, we conjecture that parenting style may be one of the possible mediators. So, we shall look at previous studies on the relationship between parental personality and parenting style.

### **2.2 Parental personality and parenting style**

Parents play an important role in children's development [24, 25]. Clark et al. [26] and van Aken et al. [27] study showed that parents' personality relates to their parenting behaviors, and in turn children's behaviors generally. Smith et al. [28] found that mothers with higher levels of agreeableness showed more warmth and support toward their children. Mothers with higher extraversion showed more maternal warmth and, thus, were more likely to support their children's autonomy, but such mothers also exercised higher power assertion over their children [28, 29]. Furthermore, mothers with high conscientiousness levels displayed support toward their children's autonomy, yet these mothers were more controlling and restrictive; but at the same time, less forcefully disciplinarian [26, 30]. Such mothers provided more rational, structured, and less forceful parenting to their children [30]. Coplan et al. [31] concluded that maternal neuroticism may lead to an overprotective parenting style, while higher agreeableness in mothers represented a low, harsh parenting style.

There are possible relationships between maternal personality and maternal parenting style. According to Baumrind [32] research on parenting authority, there were three categories: authoritarian (high in control and maturity demands, low in responsiveness and communication), authoritative (high in control, maturity demands, responsiveness, and communication), and permissive (high in communication and responsiveness, but low in control and maturity demands). In China, Xu et al. [33]'s research showed that Chinese mothers prefer authoritarian and authoritative parenting. Results showed that authoritative parenting could increase children's creativity while authoritarian parenting plays a negative role in children's creativity in high-school students [34]. The relationship between parenting style and children's creativity is worth studying, given the importance of the early years which are known to set the foundation for later development.

#### **2.3 Parenting style and creativity**

Maternal parenting style is one of the factors that influence children's development [35]. Feldman and Klein [36] found that mothers who give warm and sensitive feedback to their children's needs may lead to positive and effective interactions between mother and child. Also, children who accept their parents' advice may be more willing to correct misbehavior [37]. In contrast, negative interactions between parents and children, or even worse, punishment, may intensify children's misbehavior [38, 39]. Few studies have focused on the relationship between parenting and creativity, but some are described as follows.

Fan and Zhang [40] found that perceived parental involvement is positively related to a creativity-generating thinking style. Siegelman [7] found that students who perceive lower parental attention show higher creative potential than those who perceive parental love, and we will return to this with our results in the Section 5. Both studies focused on university students and not on young children. Fearon et al. [13]

investigated the inter-relationship among parents' creativity, parenting styles, and children's creativity for primary school students, and the Torrance Tests of Creative Thinking (TTCT) were used. Results showed that there were significant effects of parents' creativity and parenting styles on children's creativity. In this study, the importance of maternal personality in affecting young children's creativity, instead of children's creativity level or performance, is emphasized.

### **2.4 Research objectives**

Some previous studies have shown the relationships between two variables, namely parents' personality and parenting style, or between parenting style and children's creativity for primary school students. Meanwhile, the cultural issues that were highlighted in previous studies are still contested. This study, therefore, investigates the direct and indirect effects of maternal personality on 4- to 8-year-old children's creativity under the Chinese context. For indirect effects, parenting style is treated as a mediator. And before we do that, we explore the interrelationships among maternal personality, maternal parenting style, and children's creativity.


*4.5. Collected Samples (Protocorm and Seedling) and Sample Processing*

Water agar (0.65% w/v) was used as media and relocated into the glass bottles for the coculturing experiments. No additional nutriments were added into the media; only twofold distilled water and agar were used. *D. nobile* and *D. o*ffi*cinale* (both protocorms aged 4 months) and seedlings (aged 8 months) were obtained from the Bioresource Institute for Healthy Utilization (BIHU), Zunyi Medical University (ZMU; Zunyi, Guizhou, China) for experiments and authenticated per previous work [29–32]. After the sterilization of the media bottles, the protocorms of the *D. nobile* and *D. o*ffi*cinale* were inoculated into separate bottles under aseptic conditions. For seedlings, we cut marks into the top leaf of the seedlings where it joined then stem using a sterilized scalpel blade over sterilized paper, as shown in Figure 8. Three seedlings were transferred into each bottle under aseptic conditions for pathogenicity and symptoms evaluation.

**Figure 8.** Different phases of coculturing experiment for pathogenicity evaluation. (**a**) Healthy seedlings; (**b**) cut marks at the top leaf and inoculation of mycelial plug of endophytic fungi; (**c**) symptoms developed for pathogenicity evaluation; and (**d**) histopathological examination of infected tissues.

### *4.6. In Vitro Inoculation for Seedling Pathogenicity Assay*

For pathogenicity experiments, the identified endophytic fungal mycelium was used for the pathogenicity evaluation. For protocorms, 0.5-cm fungal discs were transferred into the protocorm bottles of *D. nobile* and *D. o*ffi*cinale*. The control was set in triplicates under the same conditions without added any endophytic fungal cultures. After the inoculation, the test co-culturing bottles were transferred into the plant growth chamber instrument and maintained at 25 ◦C along with a 14/10 h light/dark cycle with 2000 lux light intensity. All the test bottles were examined in 7-day intervals up to 21 days. For *D. nobile* and *D. o*ffi*cinale* seedlings, the contents of endophytic fungal flask cultures were filtered to separate the mycelium suspension. The mycelium was concentrated and injected onto cut marks at terminal leaves at the link to the stem. The sterilized cotton plug served as a control for seedlings co-culturing pathogenicity and symptoms evaluation experiments. The disease index was measured using the disease scale and disease index formula. The scale of the disease index is described as follows: 0 indicates no disease (non-pathogens), 1 indicates small spots < 1% (pin brown spots: fewest pathogens), 3 indicates spots (1–11%: least pathogens), 5 indicates spots with 12–25% coverage (moderate pathogens), 7 indicates circular spots (26–55% coverage: moderate pathogens), and 9 indicates circular to irregular spots (>75% coverage: highly pathogenic) [33].

*Disease index percentage* = *Sum o f disease rating Total number o f rating* × *Maximum disease grade* × 100%


**7. Diagnosis of functional swalloving disorders**

Conventional radiology, computed tomography, ultrasound scans, and magnetic resonance imaging facilitate visualization of gastrointestinal tract organ morphology, but these scans cannot precisely quantify their function. In the diagnosis of esophagus disease, fluoroscopy has been used with non-physiological contrast materials, and this is not a quantitative evaluation either. The use of endoscopy or manometry is an invasive way of investigating the organ condition. The use of nuclear medicine can quantify gastrointestinal organ function assessment by measuring the passage of isotope-labeled material (Russel et al., 1981). At the investigation of patients with dysphagia and normal manometric and endoscopic findings, 50% of them presented dysmotility when dynamic scintigraphy was used (Kjellen et al., 1984). A positive diagnoses of functional gastrointestinal disorders are a result of an expert gastroenterologist´s work. Usually, this diagnosis is determined after exclusion of all other potential causes of dysfunction.

However, it is necessary to take into account the importance of psychological factors that may be the cause of motility disorders of the esophagus. Studies using sophisticated psychometric instruments, dealing with the importance of psychological factors in patients with painful esophageal motility disorders, identified a number of mutual relations. Groups of patients with esophageal spasm, with irritable colon, with benign abnormalities of the impaired esophagus were compared with a control set of healthy persons. Patients with esophageal motility and irritable colon had significantly higher scores than other groups with somatic anxiety and gastrointestinal susceptibility. This shows that certain patients tend to have a significant interest in the somatic function and have more frequent and severe gastrointestinal symptoms due to stress (Waterman et al., 1989).

When 50 referred patients with pathogenic esophageal manometry underwent a psychiatric examination, abnormalities were detected in 21 out of 25 patients with motility disorders of the distal esophagus. On the contrary, abnormalities were found in only 4 out of 13 patients with normal manometric findings. The most common findings were somatization disorders, anxiety, and depression. (Clouse & Lustman, 1983).


*3.2. Results of the between-Method Correlations for n-Butanol Thresholds*

The correlation between the Sniffin' Sticks- and olfactometer-based threshold (see Figure 2) was significant (*r* = −0.47; *p* = 0.004, Bonferroni-adjusted *p* = 0.012).

**Figure 2.** Scatter plot depicting the association between n-butanol Sniffin' Sticks- and olfactometer-derived thresholds. Note that in the Sniffin' Sticks test, a higher pen number corresponds to a higher n-butanol dilution and thus a lower threshold (higher sensitivity). Vertical and horizontal lines depict the respective cut-off values for high vs. low sensitivity groups (for details see text).

When applying the cut-off values for the Sniffin' Sticks- (≥9) and olfactometer-based (≤1.9 log ppb) thresholds, nine participants (25.7%; lower right quadrant) were classified as individuals with high olfactory sensitivity in both standardized n-butanol threshold assessments (cf. Figure 2). Three of these participants were males (three out of 12; 25%) and the other six were females (six out of 23; 26%). However, the statistical analysis of the 2 × 2 contingency table yielded a non-significant Pearson chi-square value of 0.94 (*p* = 0.49). Thus, there was no significant overlap of the two olfactory sensitivity classification approaches.

Both thresholds for n-butanol (olfactometer and Sniffin' Sticks) were correlated with the exposure lab-based threshold for n-butanol (Figure 3). Due to repeated computation of correlations with the same participants, a Bonferroni adjustment of *p*-values was conducted, resulting in a significant correlation between the olfactometer-based threshold and the exposure-lab based threshold (*r* = 0.41, *p* = 0.015, Bonferroni-adjusted *p* = 0.045, see Figure 3a). However, the Bonferroni-adjusted correlation between the Sniffin' Sticks-based threshold and the exposure lab-based threshold was non-significant (*r* = −0.34, *p* = 0.048, Bonferroni-adjusted *p* = 0.144, see Figure 3b).

**Figure 3.** Scatter plots depicting the associations between the n-butanol thresholds derived with the exposure lab and the investigated methods, (**a**) Sniffin' Sticks and (**b**) olfactometer. Note that in the Sniffin' Sticks test, a higher pen number corresponds to a higher n-butanol dilution and thus a lower threshold (higher sensitivity).

In a second step, it was investigated whether subgrouping the participants into more and less sensitive individuals based on detection thresholds was associated with odor effects for the compound ammonia. As only the olfactometry-derived thresholds showed a significant association with the exposure lab n-butanol detection threshold, a cut-off score of 80 ppb in the olfactometer-based assessment was used in the following analyses to indicate individuals more and less sensitive to n-butanol.


**3.5 Metallographic examination and EDS analysis**

Microstructures for not H2SO4-immersed alloys C-0, C-0.25, C-0.50, and C-1.00 are with single FCC, single FCC, duplex FCC-BCC, and BCC-ordered BCC phases, respectively [6]. Table 6 lists the EDS composition for each phase in different alloys.

Table 6. EDS analyses (at %) for alloys C-0, C-0.25, C-0.50, and C-1.00.

Electrochemical Passive Properties of AlxCoCrFeNi

(x = 0, 0.25, 0.50, 1.00) High-Entropy Alloys in Sulfuric Acids 147

microstructure. The composition of BCC phase after alloy immersion is close to the overall alloy composition before immersion, indicating that the BCC phase is a corrosion-resistant phase. Moreover, the change in overall composition after immersion is attributed to the

selective dissolution of Al and Ni in the ordered BCC phase of this alloy (Table 6).

Fig. 12. Metallograph of alloy C-0.50. (a), before; (b) & (c), after immersion; and

containing this bonding readily react with (OH)-

procedure.

passive film.

(d), EDS line-scan results of the location indicated in (c). Retained holes were from cast

This selective corrosion in Al and Ni-rich phase in C-0.50 and C-1.00, which results in the corrosion attack on Al and Ni, is due to the large bonding in Al and Ni [37]. Alloys

and dissolve in a sulfuric solution. Accordingly, after immersion, the remaining compound in the less corrosive-resistant Al and Ni-rich phase is an oxide, rich in Cr, in the residual

and (SO4)2- to form Al and Ni complexes

Figs. 11(a)-(b) show the microstructure of C-0 before and after 3-d immersion in 0.5 M H2SO4, respectively. Figs. 11(c)-(d) show the microstructure of C-0.25 before and after 3-d immersion in 0.5 M H2SO4, respectively. General corrosion occurs for both C-0 and C-0.25, as revealed by EDS analyses (Table 6).

Fig. 11. Metallograph of alloys C-0 ((a) & (b)) and C-0.25 ((c) & (d)). (a) & (c), before; and (b) & (d), after immersion. Retained holes were from cast procedure, and Al2O3 residuals were from polishing procedure.

Figs. 12(a)-(b) show the microstructure of C-0.50 before and after 3-d immersion in 0.5 M H2SO4, respectively. According to these figures, after immersion the FCC phase remains smooth while the BCC phase shows a rough morphology. Fig. 12(c) shows a line-scanned area across the FCC and BCC phases for an immersed sample. Fig. 12(d) summarizes the line-scanned results, indicating that the BCC phase of C-0.50 before immersion is rich in Al and Ni. However, after immersion, it is poor in Al and Ni and rich in Cr.

Fig. 13 shows the microstructure and line-scan analysis of C-1.00 before and after immersion. Before immersion, BCC and ordered BCC phases cannot be resolved from the

Figs. 11(a)-(b) show the microstructure of C-0 before and after 3-d immersion in 0.5 M H2SO4, respectively. Figs. 11(c)-(d) show the microstructure of C-0.25 before and after 3-d immersion in 0.5 M H2SO4, respectively. General corrosion occurs for both C-0 and C-0.25,

Fig. 11. Metallograph of alloys C-0 ((a) & (b)) and C-0.25 ((c) & (d)). (a) & (c), before; and (b) & (d), after immersion. Retained holes were from cast procedure, and Al2O3 residuals were

Figs. 12(a)-(b) show the microstructure of C-0.50 before and after 3-d immersion in 0.5 M H2SO4, respectively. According to these figures, after immersion the FCC phase remains smooth while the BCC phase shows a rough morphology. Fig. 12(c) shows a line-scanned area across the FCC and BCC phases for an immersed sample. Fig. 12(d) summarizes the line-scanned results, indicating that the BCC phase of C-0.50 before immersion is rich in Al

Fig. 13 shows the microstructure and line-scan analysis of C-1.00 before and after immersion. Before immersion, BCC and ordered BCC phases cannot be resolved from the

and Ni. However, after immersion, it is poor in Al and Ni and rich in Cr.

as revealed by EDS analyses (Table 6).

from polishing procedure.

microstructure. The composition of BCC phase after alloy immersion is close to the overall alloy composition before immersion, indicating that the BCC phase is a corrosion-resistant phase. Moreover, the change in overall composition after immersion is attributed to the selective dissolution of Al and Ni in the ordered BCC phase of this alloy (Table 6).

Fig. 12. Metallograph of alloy C-0.50. (a), before; (b) & (c), after immersion; and (d), EDS line-scan results of the location indicated in (c). Retained holes were from cast procedure.

This selective corrosion in Al and Ni-rich phase in C-0.50 and C-1.00, which results in the corrosion attack on Al and Ni, is due to the large bonding in Al and Ni [37]. Alloys containing this bonding readily react with (OH) and (SO4)2- to form Al and Ni complexes and dissolve in a sulfuric solution. Accordingly, after immersion, the remaining compound in the less corrosive-resistant Al and Ni-rich phase is an oxide, rich in Cr, in the residual passive film.

Electrochemical Passive Properties of AlxCoCrFeNi

including Icri, Ipass, Wloss, and Rf, for AlxCoCrFeNi in H2SO4.

Fig. 14. (a) Icri, (b) Ipass, (c) Wloss, (d) Qf, (e) Rf, and (i) Icorr values vs. Al content x plots.

(x = 0, 0.25, 0.50, 1.00) High-Entropy Alloys in Sulfuric Acids 149

Ipass locate at the passive region of polarization curve. The same tendency for Icri, Ipass, and Wloss here indicates that the spontaneous passivation occurs for AlxCoCrFeNi, i.e., the open circuit potential (OCP) is readily in the passive region of polarization curve. The above phenomenon can be attributed to the spontaneous passivation of pure Al in H2SO4 [24]. EIS equivalent circuits reveal that the passive layers of AlxCoCrFeNi consist of an oxide layer and an adsorption layer mentioned in Section 3.3. Here, only parameters associated with the oxide layer, i.e., Qf and Rf, are discussed. The oxide layer thickness is evaluated by using the Helmholtz model mentioned above and denoted by d, as d =0S/Qf, where denotes the permittivity of free space (8.85 x 10-14 F/cm), denotes the dielectric constant of the medium, and S denotes the surface area of the electrode. Assuming that and S for oxide layers of alloys are the same allows us to compare relative values of d for all samples by 1/Qf. Figs. 14(d)-(e), whose data were listed in Table 5, show the Qf and Rf vs. x plot, respectively. Both Qf and Rf decreases with x. This represents that d increases with Al content x, and a thicker oxide layer implies a smaller value of impedance. Therefore, one can explain this phenomenon by considering both the thickness and the density of oxide layer. Related study reported Al oxide easily forms a porous structure [25]. Hence, it is easily understood that in addition to causing a thicker oxide layer, Al promotes the dispersive and porous oxide layer. In summary, Al has a negative effect to the passive parameters,

Fig. 13. Metallograph of alloy C-1.00. (a), before; (b) & (c), after immersion; and (d), EDS line-scan results of the location indicated in (c).

#### **3.6 Comparison among potentiodynamic polarization, electrochemical impedance spectroscopy, and weight-loss immersion tests**

As discussed above, the corrosion current density (Icorr), the critical current density (Icri), and the passive current density (Ipass) were obtained from potentiodynamic polarization. The capacitance (Qf) and the resistance (Rf) of oxide layer were obtained from electrochemical impedance spectroscopy (EIS) equivalent circuits. And the weight-loss rate (Wloss) was obtained from weight-loss immersion test. All these data were taken from experiments at ambient temperature (25oC) in 0.5 M H2SO4.

Figs. 14(a)-(b), whose data were listed in Table 2, show Icri and Ipass vs. Al content x plots, respectively. One can easily see that both Icri and Ipass increase with x. This implies that the passive corrosion property of AlxCoCrFeNi decreases with Al content x. Fig. 14(c) shows Wloss vs. x plot. Like Icri and Ipass, Wloss also increases with x. Notice that, unlike potentiodynamic polarization, immersion weight-loss test is a natural electrochemical reaction, i.e., without applying any voltage on the test sample. On the other hand, Icri and

Fig. 13. Metallograph of alloy C-1.00. (a), before; (b) & (c), after immersion; and (d), EDS

**3.6 Comparison among potentiodynamic polarization, electrochemical impedance**

As discussed above, the corrosion current density (Icorr), the critical current density (Icri), and the passive current density (Ipass) were obtained from potentiodynamic polarization. The capacitance (Qf) and the resistance (Rf) of oxide layer were obtained from electrochemical impedance spectroscopy (EIS) equivalent circuits. And the weight-loss rate (Wloss) was obtained from weight-loss immersion test. All these data were taken from experiments at

Figs. 14(a)-(b), whose data were listed in Table 2, show Icri and Ipass vs. Al content x plots, respectively. One can easily see that both Icri and Ipass increase with x. This implies that the passive corrosion property of AlxCoCrFeNi decreases with Al content x. Fig. 14(c) shows Wloss vs. x plot. Like Icri and Ipass, Wloss also increases with x. Notice that, unlike potentiodynamic polarization, immersion weight-loss test is a natural electrochemical reaction, i.e., without applying any voltage on the test sample. On the other hand, Icri and

line-scan results of the location indicated in (c).

ambient temperature (25oC) in 0.5 M H2SO4.

**spectroscopy, and weight-loss immersion tests**

Ipass locate at the passive region of polarization curve. The same tendency for Icri, Ipass, and Wloss here indicates that the spontaneous passivation occurs for AlxCoCrFeNi, i.e., the open circuit potential (OCP) is readily in the passive region of polarization curve. The above phenomenon can be attributed to the spontaneous passivation of pure Al in H2SO4 [24]. EIS equivalent circuits reveal that the passive layers of AlxCoCrFeNi consist of an oxide layer and an adsorption layer mentioned in Section 3.3. Here, only parameters associated with the oxide layer, i.e., Qf and Rf, are discussed. The oxide layer thickness is evaluated by using the Helmholtz model mentioned above and denoted by d, as d =0S/Qf, where denotes the permittivity of free space (8.85 x 10-14 F/cm), denotes the dielectric constant of the medium, and S denotes the surface area of the electrode. Assuming that and S for oxide layers of alloys are the same allows us to compare relative values of d for all samples by 1/Qf. Figs. 14(d)-(e), whose data were listed in Table 5, show the Qf and Rf vs. x plot, respectively. Both Qf and Rf decreases with x. This represents that d increases with Al content x, and a thicker oxide layer implies a smaller value of impedance. Therefore, one can explain this phenomenon by considering both the thickness and the density of oxide layer. Related study reported Al oxide easily forms a porous structure [25]. Hence, it is easily understood that in addition to causing a thicker oxide layer, Al promotes the dispersive and porous oxide layer. In summary, Al has a negative effect to the passive parameters, including Icri, Ipass, Wloss, and Rf, for AlxCoCrFeNi in H2SO4.

Fig. 14. (a) Icri, (b) Ipass, (c) Wloss, (d) Qf, (e) Rf, and (i) Icorr values vs. Al content x plots.

Electrochemical Passive Properties of AlxCoCrFeNi

a very small amount of Ni(OH)2 appears in our case.

\*General corrosion, \*\*Selective dissolution in Al and Ni

C-1.00.

with the results of EIS.

(x = 0, 0.25, 0.50, 1.00) High-Entropy Alloys in Sulfuric Acids 151

A value for the identified sputter rate for SiO2 in this AES device is 7.5 nm per min. Because the immersion for the samples is in the same 1-h period of time, the oxide layers of C-0, C-0.25, C-0.50, and C-1.00 can be distinguished from the terminals of the negative slope shown in each of the profiles. Look at the vertical red-dashed line, i.e., the end-terminal of each profile. It represents the interface between the oxide layer and the intrinsic metal. One can see that the thickness of the oxide layer increases with Al content x that is in accordance

XPS analyses attempt to investigate the binding energy profile of 2psub<3/2>sub for Al, Co, Cr, Fe, and Ni. Compared to Co, Cr, Fe, and Ni, Al reveals relatively low atomic sensitivity factor [38]. The signals of Al for alloys C-0 to C-0.50 are too small to identify. Hence, only C-1.00 was used for XPS analysis. Figs. 16(a)-(b) show the Al(2psub<3/2>sub) spectra of C-1.00 after the sputter times of 20 and 35 s, respectively. The raw profile revealing two main peaks represents the exhibition of the selective dissolution. The oxides consists of Al2O3, Al(OH)3, and Al25Ni75Ox. Al tends to form oxides in H2SO4 [24] can explain the formation of Al2O3 and Al(OH)3. The existence of Al25Ni75Ox results from the relatively negative enthalpy of Al and Ni. Corresponding to the ICP-AES analysis in the next section, Al-Ni selective dissolution undoubtedly exists for C-1.00. Figs. 16(c)-(d) show the Co(2psub<3/2>sub) spectra of C-1.00 after the sputter times of 20 and 35 s, respectively. The binding types of Co2+ and Co3+ can be seen. Compare Fig. 16(c) with Fig. 16(d), one can see that the peak intensity of Co2O3 is very small in the deep region of the oxide layer. Figs. 16(e)-(f) show the Cr(2psub<3/2>sub) spectra of C-1.00 after the sputter times of 20 and 35 s, respectively. Three kinds of oxide, including Cr2O3, Cr(OH)3, and CrO3, exist for Cr [39]. However, CrO3 merely forms at high temperatures. Hence, only Cr2O3 and Cr(OH)3 are revealed in the profile. One can see that the deep region of oxide layer remains in relatively small amount Cr2O3. Figs. 16(g)-(h) show the Fe(2psub<3/2>sub) spectra of C-1.00 after the sputter times of 20 and 35 s, respectively. Similar to references [23,40] Fe3O4 and Fe2O3 oxides can be found. Figs. 16(i)-(j) show the Ni(2psub<3/2>sub) spectra of C-1.00 after the sputter times of 20 and 35 s, respectively. In resemblance with reference [41], NiO and Ni(OH)2 can be observed. However,

Table 7 lists the results of ICP-AES of immersion solutions for C-x. To trace the ions resulting from the intrinsic metal, one can study the selective dissolution of the alloy elements. Compared with C-0 and C-0.25, C-0.50 and C-1.00 reveal relatively greater Al-Ni

Alloys Al Co Cr Fe Ni Remarks

selective dissolution. This event is consistent with the results of the XPS analysis.

C-0 alloy 0 25.93 25.73 24.21 24.13 solution 0 24.91 24.89 25.17 25.01 \*

C-0.25 alloy 6.16 23.27 23.58 23.59 23.40

C-0.50 alloy 11.01 22.77 22.61 21.70 21.92

C-1.00 alloy 18.88 20.55 20.63 20.01 19.93

solution 7.90 23.01 23.07 23.20 22.80 \*

solution 14.92 21.90 16.51 19.96 26.70 \*\*

solution 31.52 20.98 4.86 14.92 27.71 \*\*

Table 7. ICP-AES composition (at%) of immersion solution for alloys C-0, C-0.25, C-0.50, and

Interestingly, Al makes a different effect on general corrosion. Fig. 14(f) shows Icorr vs. x plot. One can see that Icorr decreases with x. This implies that Al promotes the general corrosion resistance, but degrades the passive one.

#### **3.7 AES, XPS, and ICP-AES analyses of oxide layers**

Figs. 15(a)-(d) show the AES results for C-0, C-0.25, C-0.50, and C-1.00, respectively. Owing to the slight difference of atomic number, the signals of Fe, Co, and Ni overlap in AES analysis. Hence, one can see the signals of Co are higher than that of Fe or Ni even for the equal-mole nominal chemical composition of Fe, Co, and Ni. What mentioned above, only the longitudinal composition profiles of O are discussed. A negative and a near-zero slopes are revealed in the relative concentration vs. sputter time profiles in Figs. 15(a)-(d).

Fig. 15. AES analyses for (a) C-0, (b) C-0.25, (c) C-0.50, and (d) C-1.00.

Interestingly, Al makes a different effect on general corrosion. Fig. 14(f) shows Icorr vs. x plot. One can see that Icorr decreases with x. This implies that Al promotes the general corrosion

Figs. 15(a)-(d) show the AES results for C-0, C-0.25, C-0.50, and C-1.00, respectively. Owing to the slight difference of atomic number, the signals of Fe, Co, and Ni overlap in AES analysis. Hence, one can see the signals of Co are higher than that of Fe or Ni even for the equal-mole nominal chemical composition of Fe, Co, and Ni. What mentioned above, only the longitudinal composition profiles of O are discussed. A negative and a near-zero slopes are revealed in the relative concentration vs. sputter time profiles in Figs. 15(a)-(d).

resistance, but degrades the passive one.

**3.7 AES, XPS, and ICP-AES analyses of oxide layers**

Fig. 15. AES analyses for (a) C-0, (b) C-0.25, (c) C-0.50, and (d) C-1.00.

A value for the identified sputter rate for SiO2 in this AES device is 7.5 nm per min. Because the immersion for the samples is in the same 1-h period of time, the oxide layers of C-0, C-0.25, C-0.50, and C-1.00 can be distinguished from the terminals of the negative slope shown in each of the profiles. Look at the vertical red-dashed line, i.e., the end-terminal of each profile. It represents the interface between the oxide layer and the intrinsic metal. One can see that the thickness of the oxide layer increases with Al content x that is in accordance with the results of EIS.

XPS analyses attempt to investigate the binding energy profile of 2psub<3/2>sub for Al, Co, Cr, Fe, and Ni. Compared to Co, Cr, Fe, and Ni, Al reveals relatively low atomic sensitivity factor [38]. The signals of Al for alloys C-0 to C-0.50 are too small to identify. Hence, only C-1.00 was used for XPS analysis. Figs. 16(a)-(b) show the Al(2psub<3/2>sub) spectra of C-1.00 after the sputter times of 20 and 35 s, respectively. The raw profile revealing two main peaks represents the exhibition of the selective dissolution. The oxides consists of Al2O3, Al(OH)3, and Al25Ni75Ox. Al tends to form oxides in H2SO4 [24] can explain the formation of Al2O3 and Al(OH)3. The existence of Al25Ni75Ox results from the relatively negative enthalpy of Al and Ni. Corresponding to the ICP-AES analysis in the next section, Al-Ni selective dissolution undoubtedly exists for C-1.00. Figs. 16(c)-(d) show the Co(2psub<3/2>sub) spectra of C-1.00 after the sputter times of 20 and 35 s, respectively. The binding types of Co2+ and Co3+ can be seen. Compare Fig. 16(c) with Fig. 16(d), one can see that the peak intensity of Co2O3 is very small in the deep region of the oxide layer. Figs. 16(e)-(f) show the Cr(2psub<3/2>sub) spectra of C-1.00 after the sputter times of 20 and 35 s, respectively. Three kinds of oxide, including Cr2O3, Cr(OH)3, and CrO3, exist for Cr [39]. However, CrO3 merely forms at high temperatures. Hence, only Cr2O3 and Cr(OH)3 are revealed in the profile. One can see that the deep region of oxide layer remains in relatively small amount Cr2O3. Figs. 16(g)-(h) show the Fe(2psub<3/2>sub) spectra of C-1.00 after the sputter times of 20 and 35 s, respectively. Similar to references [23,40] Fe3O4 and Fe2O3 oxides can be found. Figs. 16(i)-(j) show the Ni(2psub<3/2>sub) spectra of C-1.00 after the sputter times of 20 and 35 s, respectively. In resemblance with reference [41], NiO and Ni(OH)2 can be observed. However, a very small amount of Ni(OH)2 appears in our case.

Table 7 lists the results of ICP-AES of immersion solutions for C-x. To trace the ions resulting from the intrinsic metal, one can study the selective dissolution of the alloy elements. Compared with C-0 and C-0.25, C-0.50 and C-1.00 reveal relatively greater Al-Ni selective dissolution. This event is consistent with the results of the XPS analysis.

\*General corrosion, \*\*Selective dissolution in Al and Ni

Table 7. ICP-AES composition (at%) of immersion solution for alloys C-0, C-0.25, C-0.50, and C-1.00.

Electrochemical Passive Properties of AlxCoCrFeNi

**3.8 Corrosion current density (Icorr) at various temperatures**

dispersive oxide dominates. Therefore, this special phenomenon occurs.

Fig. 17. Icorr values for alloys C-x (Alx) at various temperatures.

**4. Conclusions**

long-term dipping.

(x = 0, 0.25, 0.50, 1.00) High-Entropy Alloys in Sulfuric Acids 153

As mentioned in Section 3.1, Icorr decreases with Al content at 25oC. However, this differs from temperatures to temperatures. Fig. 17 shows the Icorr values of C-x at various temperatures. One can see that Icorr decreases with Al content x at low temperatures (< 27oC), and, conversely, at high temperatures (> 27oC). The EIS results (Section 3.1) indicate that more Al content x makes the oxide layers thicker and more dispersive. At low temperatures, the thicker oxide is the dominator for Icorr; whereas, at high temperatures, the

Owing to the spontaneous passivation of Al element in H2SO4, the variation of Al reveals a more apparent effect in a passive region rather than in an active one. Therefore, in contrast with Ipass, which increases with x, no obvious trends occur for Ecorr and Icorr vs. x variation. In particular, the weight loss experiment indicates that Ipass is a proper index to evaluate the weight loss of samples since AlxCoCrFeNi alloys are found to have passive behaviour in

EIS results indicate that the passive films of AlxCoCrFeNi alloys become increasingly thicker and more dispersive with an increasing x. Therefore, Ipass increases with x. As x value increases to 1.00, the inductance effect appears in the equivalent circuit for severe dissolution of Al and Ni-rich phase. As for the effect of chloride on the anti-corrosion property, chloride eases the passive layer to form metastable ion complexes and further dissolve into H2SO4. With an increasing chloride concentration and Al content, the metastable ion complexes easily form, allowing Epit to shift to a more active region. Additionally, the microstructure of both C-0 and C-0.25 is single FCC phase, while those of C-0.50 and C-1.00 are duplex FCC-BCC and complex BCC-ordered BCC phase, respectively.

Fig. 16. XPS analyses after pre-sputtering for (a) Al-20 s, (b) Al-35 s, (c) Co-20 s, (d) Co-35 s, (e) Cr-20 s, (f) Cr-35 s, (g) Fe-20 s, (h) Fe-35 s, (i) Ni-20 s, and (j) Ni-35 s.

Fig. 16. XPS analyses after pre-sputtering for (a) Al-20 s, (b) Al-35 s, (c) Co-20 s, (d) Co-35 s,

(e) Cr-20 s, (f) Cr-35 s, (g) Fe-20 s, (h) Fe-35 s, (i) Ni-20 s, and (j) Ni-35 s.

### **3.8 Corrosion current density (Icorr) at various temperatures**

As mentioned in Section 3.1, Icorr decreases with Al content at 25oC. However, this differs from temperatures to temperatures. Fig. 17 shows the Icorr values of C-x at various temperatures. One can see that Icorr decreases with Al content x at low temperatures (< 27oC), and, conversely, at high temperatures (> 27oC). The EIS results (Section 3.1) indicate that more Al content x makes the oxide layers thicker and more dispersive. At low temperatures, the thicker oxide is the dominator for Icorr; whereas, at high temperatures, the dispersive oxide dominates. Therefore, this special phenomenon occurs.

Fig. 17. Icorr values for alloys C-x (Alx) at various temperatures.


**3. New innovation method in seaweed cultivation**

Floating cage is a technological design that functions as a seaweed cultivation tool. This cultivation tool can protect seaweed from pests while reducing the potential for ice–ice disease [16, 29, 30]. Various sizes and shapes were developed as tools that can be used for seaweed cultivation. The basic materials of floating cages include PVC pipes, nets equipped with buoys as markers, and weights attached to the raft to facilitate the laying of the raft in the desired area. The shape of the tool is designed like a rectangular box with varied sizes. The surface of the raft is left

**Figure 2.** *Illustration of floating cage that was used during research (a). Thallus of* K. alvarezii *inside the floating cage (B).*

open, while the bottom and all sides are covered using a multifilament net with a mesh size of 1 cm [31]. The process of seaweed cultivation in floating cages is done by spreading seaweed directly in floating cage without binding. In the harvesting process, floating cage can be directly drawn to the shallower parts of the coast so that the harvesting process can be more easily done (**Figure 2**).