4. Dynamic loading tests of bridges and monitoring

In situ dynamic testing of bridges gives very useful information for numerical modeling and assessment of real bridge dynamic parameters and service conditions. In many countries, the requirement of putting the bridges into operation is the execution of bridge static and dynamic loading tests, which aim is to prove and confirm the projected parameters (standards criteria, serviceability, safety limit states, etc.) of tested bridge structures according to technical standards, e.g., in Slovakia by standard STN—Slovak Technical Standards [28]. Results from static or dynamic test enable to calibrate a bridge analytical model and can be utilized as basic data for a bridge health monitoring program and for other sophisticated calculations of the bridge dynamic response (seismic, fatigue, etc.).

#### 4.1. Test procedures

In this section, bridges dynamic test procedure is shortly described. Bridges are tested according to the rules of the dynamic loading test (DLT) [28]. Excitation of highway bridges are commonly due to the passage of single, fully loaded, multi-axles lorries. The testing vehicles' gross weight usually lies near the legal limit which is defined by standards and regulations. In the case of railway bridges, locomotives are used. Also normal traffic flow is used for both highway and railway bridges.

δ calculated by designer and dynamic amplification factor (DAF—from DLT), greater than 1 (the amount by which the static effects are increased by bridge-vehicle interaction contribution).

Bridges Subjected to Dynamic Loading http://dx.doi.org/10.5772/intechopen.73193 127

Note 1 In relevant standards of many countries, it is defined how to obtain coefficient DLA (= δ) in a normalized way (e.g., Canada, France, Germany, India, Spain, Switzerland-UK, USA, and

Note 2 Nowadays for Slovak Republic (CEN member), from 1.5.2006, it is mandatory to applying new European Standard. For the chapter content, it is actual Eurocode 1—Action on

Note 3 In this EN, for road bridges, the dynamic amplification was included into the load models (fatigue accepted), although established for a medium pavement quality and pneumatic vehicle suspension, which depends on various parameters and on the action effect under consideration. Therefore, it cannot be represented by a unique factor. For example, in former Slovak Standard (till 2006)—STN 73 6203, Load actions on bridges for calculation of δ = DLA

Note 4 For railway bridges, the dynamic amplification was accepted and dynamic factor Φ (= DLA = δ) is possible to calculate according to the given algorithm (EN 1991–2, Section 6).

In this section, data acquisition and recording (DAR) processes during a bridge DLT are shortly described. More detailed DAR processes descriptions are in [23, 26, 29]. Dynamic deflections are measured by pick-ups at the characteristic points of the bridge, which is normally at the mid-span. The bridge structure dynamic response at these points, in the horizontal and vertical directions, is then recorded in the form of time histories signal. Deflections w(t) are also measured at additional points along the super-structure. Except for dynamic deflections, other relevant parameters are measured: speed of the loading vehicles, magnitude and time history

Instrumentation: During standard dynamic tests of bridges (Figure 10(a)), inductive displacement transducers—IDT are mounted at the bridge parapet or bottom of the bridge structure, which are used to monitor displacement amplitudes time histories. In these cases, recorded displacement amplitudes time histories contains both static and dynamic components of the bridge dynamic response. The measured baseline is given by an invar wire (max 30 m), strained between the measuring points of the structure and a fixed reference point under the bridge structure. The application IDT enables extracting the static component from displacement time histories w(t) by using filtering techniques. This procedure is applied for DAF calculation. When the measured structure cross section is situated over water (e.g., river, lake, bay, etc.), the IDT are usually replaced by accelerometers or velocity-type transducers, Figure 10(b), or strain gauges, Figure 10(c), (measuring of strain amplitudes time history contains both static and dynamic components of the bridge response due to moving load) with relevant hardware

of excitation forces, temperature of the structure and ambient air, wind velocity, etc.

former Czechoslovakia, etc.).

Structures, Part 2: Traffic loads on bridges (EN 1991–2).

was used a formula in unnumbered format

4.2. DLT data acquisition and recording

For the expected dynamic bridge response caused by well-defined individual testing vehicles, dynamic calculations are carried out before the bridge dynamic tests. The testing vehicle is driven with a constant speed (in each measurement travel) along the bridge and respectively in the same direction or in both directions. The tests begin with a vehicle speed of c = 5 km/h, which is increased after each passage in steps of 5 km/h, up to the maximum achievable speed [22, 26]. If a static test with the used testing vehicle is not performed before the dynamic tests, the bridge deflection caused by vehicle traveling at a speed c = 5 km/h can be considered to present the static deflection ws with sufficient accuracy (e.g., via filtering signals).

In the case of highway bridges, the tests on the undisturbed bridges pavement are also repeated with a plank or standard obstacles placed across highway pavement, Figure 9(a). The cross section of the standard obstacle (length 5000 mm) is a cylindrical sector of height 60 mm and chord length 500 mm [28]. During the tests of highway bridges pay load, tires and tire pressure are kept the same; it means that the vehicle dynamic properties remain approximately constant.

Pulse forces produced by the ignition of pulse rocket engines (PRE) during DLT are also used mainly on large bridge structures. Harmonically variable forces produced by vibration exciters and the free vibrations of the bridge are also applied.

This type of the DLT so-called proof-loading test is performed for checking if the construction of the bridge has been constructed according to the design project. These tests (DLT) comprise the evaluation of the dynamic loading allowance (DLA) ! from standard = dynamic coefficients

Figure 9. Testing load: (a) lorries traveling over the obstacles; (b) the PRE applied mainly on large bridge structure.

δ calculated by designer and dynamic amplification factor (DAF—from DLT), greater than 1 (the amount by which the static effects are increased by bridge-vehicle interaction contribution).

Note 1 In relevant standards of many countries, it is defined how to obtain coefficient DLA (= δ) in a normalized way (e.g., Canada, France, Germany, India, Spain, Switzerland-UK, USA, and former Czechoslovakia, etc.).

Note 2 Nowadays for Slovak Republic (CEN member), from 1.5.2006, it is mandatory to applying new European Standard. For the chapter content, it is actual Eurocode 1—Action on Structures, Part 2: Traffic loads on bridges (EN 1991–2).

Note 3 In this EN, for road bridges, the dynamic amplification was included into the load models (fatigue accepted), although established for a medium pavement quality and pneumatic vehicle suspension, which depends on various parameters and on the action effect under consideration. Therefore, it cannot be represented by a unique factor. For example, in former Slovak Standard (till 2006)—STN 73 6203, Load actions on bridges for calculation of δ = DLA was used a formula in unnumbered format

$$s = \frac{1}{\mathbf{0.9S} - (1.4l)^{-0.6}}$$

Note 4 For railway bridges, the dynamic amplification was accepted and dynamic factor Φ (= DLA = δ) is possible to calculate according to the given algorithm (EN 1991–2, Section 6).

#### 4.2. DLT data acquisition and recording

4.1. Test procedures

126 Bridge Engineering

constant.

highway and railway bridges.

In this section, bridges dynamic test procedure is shortly described. Bridges are tested according to the rules of the dynamic loading test (DLT) [28]. Excitation of highway bridges are commonly due to the passage of single, fully loaded, multi-axles lorries. The testing vehicles' gross weight usually lies near the legal limit which is defined by standards and regulations. In the case of railway bridges, locomotives are used. Also normal traffic flow is used for both

For the expected dynamic bridge response caused by well-defined individual testing vehicles, dynamic calculations are carried out before the bridge dynamic tests. The testing vehicle is driven with a constant speed (in each measurement travel) along the bridge and respectively in the same direction or in both directions. The tests begin with a vehicle speed of c = 5 km/h, which is increased after each passage in steps of 5 km/h, up to the maximum achievable speed [22, 26]. If a static test with the used testing vehicle is not performed before the dynamic tests, the bridge deflection caused by vehicle traveling at a speed c = 5 km/h can be considered to present

In the case of highway bridges, the tests on the undisturbed bridges pavement are also repeated with a plank or standard obstacles placed across highway pavement, Figure 9(a). The cross section of the standard obstacle (length 5000 mm) is a cylindrical sector of height 60 mm and chord length 500 mm [28]. During the tests of highway bridges pay load, tires and tire pressure are kept the same; it means that the vehicle dynamic properties remain approximately

Pulse forces produced by the ignition of pulse rocket engines (PRE) during DLT are also used mainly on large bridge structures. Harmonically variable forces produced by vibration exciters and

This type of the DLT so-called proof-loading test is performed for checking if the construction of the bridge has been constructed according to the design project. These tests (DLT) comprise the evaluation of the dynamic loading allowance (DLA) ! from standard = dynamic coefficients

Figure 9. Testing load: (a) lorries traveling over the obstacles; (b) the PRE applied mainly on large bridge structure.

the static deflection ws with sufficient accuracy (e.g., via filtering signals).

the free vibrations of the bridge are also applied.

In this section, data acquisition and recording (DAR) processes during a bridge DLT are shortly described. More detailed DAR processes descriptions are in [23, 26, 29]. Dynamic deflections are measured by pick-ups at the characteristic points of the bridge, which is normally at the mid-span. The bridge structure dynamic response at these points, in the horizontal and vertical directions, is then recorded in the form of time histories signal. Deflections w(t) are also measured at additional points along the super-structure. Except for dynamic deflections, other relevant parameters are measured: speed of the loading vehicles, magnitude and time history of excitation forces, temperature of the structure and ambient air, wind velocity, etc.

Instrumentation: During standard dynamic tests of bridges (Figure 10(a)), inductive displacement transducers—IDT are mounted at the bridge parapet or bottom of the bridge structure, which are used to monitor displacement amplitudes time histories. In these cases, recorded displacement amplitudes time histories contains both static and dynamic components of the bridge dynamic response. The measured baseline is given by an invar wire (max 30 m), strained between the measuring points of the structure and a fixed reference point under the bridge structure. The application IDT enables extracting the static component from displacement time histories w(t) by using filtering techniques. This procedure is applied for DAF calculation. When the measured structure cross section is situated over water (e.g., river, lake, bay, etc.), the IDT are usually replaced by accelerometers or velocity-type transducers, Figure 10(b), or strain gauges, Figure 10(c), (measuring of strain amplitudes time history contains both static and dynamic components of the bridge response due to moving load) with relevant hardware

devices to the recording technique at the MS by special low noise cables were usually used. The application of the wireless sensor network (WSN) platform for DLT or distributed measurement application, e.g., bridge structural health monitoring, is possible to eliminate the need for costly and work-intensive wiring measuring technique. The WSN platform simplifies remote monitoring applications and delivers low-power, reliable measurement nodes that feature

Bridges Subjected to Dynamic Loading http://dx.doi.org/10.5772/intechopen.73193 129

The application of the quick-setup WSN enables to implement a stand-alone remote monitoring system or easily connect with measuring PC and control systems (e.g., NI WSN, BK PULSE WSN). Figure 12 shows examples of equipment set for experimental measurement data wire-

The final experimental analysis is usually carried out in the laboratory. The bridge vibrations induced by the lorries crossing the bridge during the DLT with different velocities are analyzed in order to quantify and compare the different dynamic effects on the bridge structure. The analysis of the time histories of vibration recorded, when lorries crossed the viaduct

• double integration of the accelerations to displacements and evaluation of their maxima and RMS values. The displacements maximum value is used for DAF calculations;

• digital filtering with a low-pass Butterworth filter with a cut frequency, e.g., of 150 Hz and

Also from the bridge dynamic response and free vibration measured time histories, can be

Figure 12. The experimental measurement data wireless transmissions by NI WSN modules with portable PC layout and

with a high-pass Butterworth filter with a cut frequency of 0.5 Hz; and

• frequencies of one or more vibration modes of the loaded and unloaded bridge;

• maximum and RMS values of acceleration amplitudes evaluation.

• the natural vibration damping parameters, dominant in free decay;

less transmissions by NI WSN modules with portable PC layout and scheme.

bridge, is processed with the following operations:

• offset and linear trends removal;

obtained:

scheme.

local control capabilities.

Figure 10. Examples of bridge DLT instrumentation: (a) inductive displacement transducers (IDT); (b) accelerometers set up; (c) strain sensor (d) charge amplifiers devices; (e) accelerometer installation process to bridge bottom for DLT.

components (amplifiers, cables, wireless technique, etc.), Figure 10(d). The view of accelerometers installation on bridge bottom for DLT is showed in Figure 10(e).

The signals from the used pick-ups are amplified and filtered by the signal amplifiers and lowband pass filters, and then recorded by portable notebook with relevant software and hardware facilities in test measuring station (MS). Scheme and view of the equipment in MS used in situ tests are plotted in Figure 11. During DLT, the signals transmission from measurement

Figure 11. View of the equipment in MS with its scheme mounting used during the bridge dynamic tests.

devices to the recording technique at the MS by special low noise cables were usually used. The application of the wireless sensor network (WSN) platform for DLT or distributed measurement application, e.g., bridge structural health monitoring, is possible to eliminate the need for costly and work-intensive wiring measuring technique. The WSN platform simplifies remote monitoring applications and delivers low-power, reliable measurement nodes that feature local control capabilities.

The application of the quick-setup WSN enables to implement a stand-alone remote monitoring system or easily connect with measuring PC and control systems (e.g., NI WSN, BK PULSE WSN). Figure 12 shows examples of equipment set for experimental measurement data wireless transmissions by NI WSN modules with portable PC layout and scheme.

The final experimental analysis is usually carried out in the laboratory. The bridge vibrations induced by the lorries crossing the bridge during the DLT with different velocities are analyzed in order to quantify and compare the different dynamic effects on the bridge structure. The analysis of the time histories of vibration recorded, when lorries crossed the viaduct bridge, is processed with the following operations:

components (amplifiers, cables, wireless technique, etc.), Figure 10(d). The view of accelerom-

Figure 10. Examples of bridge DLT instrumentation: (a) inductive displacement transducers (IDT); (b) accelerometers set up; (c) strain sensor (d) charge amplifiers devices; (e) accelerometer installation process to bridge bottom for DLT.

The signals from the used pick-ups are amplified and filtered by the signal amplifiers and lowband pass filters, and then recorded by portable notebook with relevant software and hardware facilities in test measuring station (MS). Scheme and view of the equipment in MS used in situ tests are plotted in Figure 11. During DLT, the signals transmission from measurement

Figure 11. View of the equipment in MS with its scheme mounting used during the bridge dynamic tests.

eters installation on bridge bottom for DLT is showed in Figure 10(e).

128 Bridge Engineering

Also from the bridge dynamic response and free vibration measured time histories, can be obtained:

Figure 12. The experimental measurement data wireless transmissions by NI WSN modules with portable PC layout and scheme.

• percentage of vibration critical damping via the 3 dB band with method and curve fitting techniques;

5. Case study

The dynamic loading test and the following dynamic monitoring of the Lafranconi bridge over the Danube in Bratislava (Slovakia) are shortly described in this section [38–40]. The dynamic response behavior of a prestressed concrete, seven span highway bridge (761.0 m long) was examined via DLT according to standard [24] in 1990. Excitations of bridge structure were induced by the passage of two fully loaded, multi-axles lorries as well as by the rocket engines. Applied structural measurement technique was developed for in situ testing of the bridges. The DLT results enabled to identify bridge global dynamic characteristics of the bridge, e.g., maximum and RMS of displacements amplitude, natural frequencies f(j), mode shapes, DAF ! δOBS (δOBS = wmax/ws) and the structure amplitude damping parameter (ϑ). The obtained dynamic characteristics were compared with the numerical computed data [29] and standard prescriptions. For maximum and RMS displacements amplitude, and so on, see technical report [2].

Bridges Subjected to Dynamic Loading http://dx.doi.org/10.5772/intechopen.73193 131

The main bridge structure is composed of seven span continuous beams with one bridge frame pier (P3). The total length of the bridge was 761.0 m with spans 83.0 m + 174.0 m + 172.0 m + 4 � 83.0 m. The highway bridge consists of two independent bridges (left and right bridge) with three traffic lanes each (i.e., three in each bridge for one direction only) and sidewalks on both sides. The bridge's longitudinal section is shown in Figure 14. The bridge structure including multispan junctions, the test program, field measurements, and applied instrumentation are fully described in [29]. The vibration amplitudes were measured and recorded in 18 selected points. The measuring station for recording accelerometer signals (DSM-1) was situated on the top of the pier P3, Figure 14. The time history of vertical as well as horizontal vibration amplitudes have been registered by accelerometers in the second and the third span of the bridge. In the other bridge spans were applied inductive displacement transducer with working

5.1. Dynamic loading test of Lafranconi highway bridge over the Danube

Figure 14. Longitudinal section of the Lafranconi highway bridge over the Danube in Bratislava.

#### 4.3. Bridges' dynamic parameters monitoring

Long-term bridges observation is discussed in literature, e.g., [29–37]. Some dynamic methods used by other authors [33], were applied to correlate relative changes of material, frequencies, and damping with carrying capacity. It was found that used monitoring techniques gave an early indication of incipient deterioration. The main scope of monitoring tests was to evaluate mainly the relative change of well-defined natural frequencies or the corresponding damping and the RMS value of the displacements amplitude of the bridge vibration due to traffic loading. The monitoring technique based on measurement of the bridge vibration time history due to regular traffic is not focused to give detailed bridge information but for making decision if more detailed bridge assessment methods should be used. The sophisticated bridge monitoring was introduced e.g. on the Akhashi Kaikyo bridge in Japan, (Figure 13) completed 1998. At that time, it was the largest and longest suspension bridge in the world. Bridge is a 3-span 2 hinged bridge with steel-truss-stiffened girders located near Kobe City.

Bridge has a impressive 1991-m center span between two main towers that rise 300.0 m above the sea level. The Akashi Kaikyo bridge, being easily affected by natural conditions and traffic means, requires high level of disaster prevention and bridge structure functionality with projected structure parameters. Therefore, to provide centralized control, traffic control and bridge structure and facility monitoring have been integrated into the Traffic Control Center. There, information acquisition and processing are performed continuously 24 h a day, providing vital traffic and bridge structure information.

Figure 13. Akashi Kaikyo bridge: (a) look-out on the bridge; (b) 24 h a day monitoring center (source: Kobe—Awaji— Naruto Expressway. Honshu—Shikoku Bridge Authority 1998, advertising material).


**3. Computational fluid dynamics**

Computational fluid dynamics (CFD) is the analysis of systems involving fluid flow, heat transfer, and associated phenomena such as chemical reactions by means of computer-based simulation. This methodology is very powerful and may be used in a wide range of industrial and nonindustrial application areas. For hydrodynamic simulations, CFD is the proper methodology that may be used during reactor design procedures.

### **3.1 CFD methodology**

CFD codes may be considered a series of numerical algorithms that can resolve fluid flow problems. Commercial CFD packages include sophisticated user interfaces to facilitate the process of input problem parameters and to examine the results, and our interest within this chapter is the code ANSYS® [6, 7]. Most codes contain three main elements: (a) a preprocessor, (b) a solver, and (c) a postprocessor. There are external functions that can be coded as additional or complementary functions that can add up to the calculations and results; for ANSYS Fluent® these functions are known as user-defined functions (UDFs) [8]. Briefly, the function of each of these elements within a CFD code is mentioned [1–5].

## *3.1.1 Preprocessing*

Preprocessing consists of the input of a flow problem to a CFD program by means of an interface and the subsequent transformation of this input into a data ready to use by the solver. The user activities at the preprocessing stage involve geometry definition (domain), grid generation (mesh), physical and chemical phenomena to be modeled, fluid properties, and boundary conditions.

#### *3.1.2 Processing*

There are three different schemes for numerical solution techniques: finite difference, finite element, and spectral methods. In this work only finite volume method will be considered, a special finite difference formulation that is central to the most well-established CFD codes including the program used in our case of study ANSYS Fluent®. The numerical algorithm to resolve the problem at hand consists of the following steps: governing equations, discretization, and solution of algebraic equations.

#### *3.1.3 Postprocessing*

In this step, results are available, and thanks to the visualization code tools, the data may be presented in different ways to facilitate the results analysis. The leading CFD packages are equipped with versatile data visualization tools. These may include domain geometry and grid display, vector plots, line and shaded contour plots, 2D and 3D surface plots, particle tracking, and view in perspective (translation, rotation, scaling, etc.), and more recently, animation has been included.

**89**

Pressure field:

Velocity field:

*Hydrodynamic Analysis on a Photocatalytic Reactor Using ANSYS Fluent®*

Most codes produce trusty alphanumeric output and have data export facilities for further manipulation external to the code which also represents a possibility to enhance the result analysis and solution presentation/explanation procedures.

The governing equations of fluid flow represent mathematical statements of the conservation laws of physics: (a) mass conservation, (b) momentum conservation,

The fluid will be subject to the theory of the continuum. For the analysis of fluid flows at macroscopic length scales (around 1 μm and larger), the molecular structure of matter and molecular motions may be ignored. The behavior of the fluid is described in terms of macroscopic properties, such as velocity, pressure, density and temperature, and their space and time derivatives. These may be thought of as averages over a suitable large number of molecules. We will save the mathematical development because it is beyond the scope of this chapter and recommend the

As mentioned in prior sections, the design of a chemical reactor involves several steps and disciplines, and simulation hydrodynamic calculations are the first to be carried on. Fluid kinematics deals with describing the motion of fluids without necessarily considering the forces and moments that cause the motion. In this section, we introduce fundamental kinematic concepts related to flowing fluids. We discuss briefly the material derivative and its role in transforming the conservation equations from the Lagrangian description of fluid flow (following a fluid particle)

The kinematics of experiments under the Lagrangian description involves keeping track of the position vector of each object, xA, xB,. …, and the velocity vector of each object, *VA*, *VB*, …, as functions of time. When this method is applied to a flowing fluid, we call it the Lagrangian description of fluid motion. From a microscopic point of view, a fluid is composed of billions of molecules that are subject to continuous collisions into one another, somewhat like billiard balls, but the task of following even a subset of these molecules is quite difficult, even for our biggest computers. A more common method of describing fluid flow is the Eulerian description of fluid motion. In the Eulerian description of fluid flow, a finite volume called a control volume is defined, through single piece of volume fluid flows in and out. We do not need to keep track of the position and velocity of a mass of fluid particles of fixed identity. Instead, we define field variable functions of space and time, within the control volume [3–5]. For example, the pressure field is a scalar field variable for

to the Eulerian description of fluid flow (pertaining to a flow field).

general unsteady tridimensional fluid flow in Cartesian coordinates:

→ *P*=*P*( → *x*, → *y*, →

→ *V* = *V*( → *x*, → *y*, →

Likewise, the acceleration field is also a vector field variable:

We define the velocity field as a vector field variable in a similar fashion:

*z*,*t*) (1)

*z*,*t*) (2)

*DOI: http://dx.doi.org/10.5772/intechopen.89782*

reader to consult CFD textbooks for such purpose.

**3.2 Governing equations**

and (c) energy conservation.

**4. Hydrodynamic calculations**

Most codes produce trusty alphanumeric output and have data export facilities for further manipulation external to the code which also represents a possibility to enhance the result analysis and solution presentation/explanation procedures.


**6. Toxicity**

The clinical application of proteasome inhibitors might be limited due to potential side effects of available compounds following chronic administration. Toxic affects might result from the accumulation of ubiquitinated proteins after inhibition of the 26S proteasome. The proteasome inhibitor bortezomib (PS-341) induced mild-to-moderate neurotoxic effects in rats [Cavaletti et al., 2007] and peripheral sensory neuropathy in cancer patients when given this compound chronically [Cata et al., 2006]. The features of bortezomib neuropathy are characteristic for a small fiber neuropathy and are characterized by a more sensory than motor neuropathy. Several observations, however, argue against these possibilities. First, in rats, the neurotoxic effects were observed when bortezomib was administered at maximum tolerated, sub-lethal doses in rats [Cavaletti et al., 2007]. Bortezomib might have induced neurotoxic effects because of the presence of a component in its activity that is blocked by the polyhydroxyl compound Tiron, this component is not involved in MG132 activity [Fernandez et al., 2006]. No effects of MG132 toxicity were apparent on motor performance during rotarod, posture, gait, exploratory and locomotor activity, or on cell death in the spinal cord, when MG132 was administered at higher doses [Ossipov et al., 2006]. Moreover, MG132 treated animals gained significantly more body weight than the vehicle treated arthritic controls [Ahmed et al., 2010]. These results indicate that proteasome inhibitor MG132 given at therapeutically relevant doses was well tolerated. This is a significant finding as the proteasome plays a central role in many intracellular functions and its inhibition might theoretically be expected to induce numerous side effects.


*Edited by Isam AL-Zwaini*

Thalassemia is a very common disease first described by pediatrician Thomas Benton Cooley in 1925 who described it in a patient of Italian origin. At that time, it was designated as Cooley's anemia. George Hoyt Whipple, a Nobel prize winner, and W. L. Bradford, a professor of pediatrics at the University of Rochester, coined the term thalassemia in 1936, which in Greek means anemia of the sea (Thalassa means "sea", and *emia* means "blood"), due to the fact that it is very common in the area of the Mediterranean Sea. This name is actually misleading because it can occur everywhere in the world. Thalassemia is not a single disease; it is rather a group of hereditary disorders of the production of globulin chain of the hemoglobin. Throughout the world, thalassemia affects approximately 4.4 of every 10,000 live births. It represents a major social and emotional impact on the patient and his family and a major burden on health services where the prevalence is high.

ISBN 978-1-78923-366-7

Thalassemia and Other Hemolytic Anemias

Published in London, UK © 2018 IntechOpen © toeytoey2530 / iStock


**Abstract**

Finely dispersed (СeO2)1-x(Sm2O3)x (x = 0.02; 0.05; 0.10); La1-xSrxNiO3, La1-xSrxCoO3 and La1-xSrxFe0.7Ni0.3O3 (x = 0.30; 0.40) mesoporous xerogel powders are synthesized by co-crystallization of the corresponding nitrates with ultrasonic processing and used to obtain nanoscale ceramic materials with cubic fluorite-like, orthorhombic, and perovskite-like tetragonal crystal structure, respectively, with CSR 64–81 nm (1300°C). Physicochemical characterization of the obtained ceramics revealed that (СeO2)1-x(Sm2O3)x features with open porosity 2–6%, while for La1-xSrxNiO3, La1-xSrxCoO3, and La1-xSrxFe0.7Ni0.3O3, this value is about 21–29%. Ceria-based materials possess a predominantly ionic conductivity (ion transport numbers *ti* = 0.82–0.71 in the temperature range 300–700°C, σ700°С = 1.3102 S/cm) determined by the formation of mobile oxygen vacancies upon heterovalent substitution of Sm3+ for Се4+. For solid solutions based on lanthanum nickelate and cobaltite, a mixed electronic-ionic conductivity (σ700°С = 0.80101 S/cm) with ion transport numbers (*te* = 0.98–0.90, ti = 0.02–0.10) was obtained. The obtained ceramic materials are shown to be promising as solid oxide electrolytes and electrodes for medium-temperature fuel cells.

**Keywords:** co-crystallization of salts, oxides, finely dispersed powders, fuel cells, nanoceramics, electrolytes, electrode materials


**4.4. FET design and gate coupling**

contamination and scattering sites, while the hot electron and barrier lowering effects affect graphene due to the pinchoff formation needed to have the large Ion/Ioff ratio required for typical electronics applications and to create large enough voltage and power gains for RF

Graphene is a self-contained electronic sheet showing no classical band bending interactions when coupled to a metallic contact as shown in Figure 18. This creates an abrupt transition in the vacuum level, creating a barrier that any carrier would have to tunnel through, creating

**Figure 18.** Classical band diagrams for a metal-silicon interface, a metal-metal interface, and a metal graphene inter‐

In conjunction to this challenge is the relative inertness of a graphene sheet, making good electrical contacts difficult to realize and mainly occurring at grain edges. [56] This creates a situation where the bulk of the contact sits over the graphene electrostatically doping it, while also trying to realize good adhesion creating a search for a metals with good adhesion to graphene along with the correct Fermi level. [56] To achieve this goal, a double or triple metal stack is commonly used with an oxygen scavenger interfacing the graphene (normally Ti), followed by one or a couple of Fermi level contacts (Au, Pd, Ni). [56] The metallic doping effect, however, can be utilized for some interesting devices such as one using asymmetric contacts to create an internal electric field making an IR detector through the photothermoelectric effect, or using large gap superconducting contacts to confine electrons and holes in a graphene sheet

As stated in Section 1 and Section 3, graphene is a self-contained layer without any dangling bonds, thus adhesion and interfaces with graphene are a challenge. Multiple groups have been

**4.2. Metallic doping by source drain contacts in graphene**

charge buildup at the band edges and large contact resistances. [56]

applications.

74 Graphene - New Trends and Developments

face.

to enhance bolometric response. [45, 57]

**4.3. Dielectric deposition and trap states**

To overcome some of the short channel issues and problems with graphene integration into common process flows, a wafer bonding type of integration has been suggested as shown in Figure 19. [59] This allows for the separation of the drain and gate contacts, which reduces coupling and alleviates some of the issues with drain induced barrier lowering. [60]

**Figure 19.** Wafer bonding with subsequent source drain contact deposition [59].

Gate coupling is a significant issue with graphene FETs due to the large gate voltages needed to create sufficient barriers for high Ion/Ioff ratios, the metallic characteristic of the graphene layer, the thin gate oxide needed to ensure good gate control and reduced gate potential for smaller electrical field propagation, and finally the dielectric breakdown strength. [60] All of these needs show that a thin high-k gate with opposing gate and source drain contact geometry is desired as shown in Figure 19.

Graphene devices have a very thin cross section where the active electric field can affect one another. It has been shown that by using tapered contacts as shown in Figure 20, the amount of source drain coupling is reduced due to electric field reduction. [60] This is especially effective if utilizing a back gate design as shown later in Figure 21, or a large gate that could overlap the source and drain contacts on the opposing side of the devices channel. [55, 60]

**Figure 20.** Tapered contacts used on opposing sides of the gate to reduce [60].


*3.3. CEO Turnover, Capital Structure, Dividend Policy, and Sector Homogeneity*

The agency conflict between CEO and shareholders can also be mitigated using capital structure and dividend policy. The creditors have the concern and appropriate skills to monitor the firms, and the shareholders benefit from their financial expertise (Ross 1977). In the meantime, the CEO is less willing to undertake excessive risks and is more disciplined, which eventually leads to a lower probability of being forced to quit his/her position. On the other hand, capital structure is considered in the literature as a reflection of the financial risk undertaken by the company (Hazarika et al. 2012; Hu and Leung 2012; Cronqvist et al. 2012). Hence, the leverage is expected to be positively associated with CEO turnover (forced or voluntary), especially in economies based on capital markets. Hazarika et al. (2012) for the US, and Hu and Leung (2012) for China provide weak evidence of a positive correlation between leverage and CEO turnover (forced and voluntary). On the other hand, Lin and Liu (2004) found a negative relation between leverage and forced CEO turnover in Taiwan.

In recent decades, financial theory has offered several explanations for dividend policy, based on signaling theories, or taking into consideration the agency conflicts between corporate insiders and outside shareholders. The dividend signaling hypothesis predicts that dividends convey information to shareholders/investors regarding the firm's future prospects, and only good-quality firms can use it (Bhattacharya 1979). Even when managers are not sure whether their company has the ability to generate cash flows in the future, they may keep dividends constant, or even gradually increase payments in order to avoid sending a negative signal to the market (Zwiebel 1996). Myers (2000) created a link between maintaining leading positions in the companies and the trustworthy perspective of dividend payments. Moreover, other studies argue that top-executive managers protect minority shareholders through dividend policy to create a reputation for treating outside shareholders well (Gomes 2000). Parrino et al. (2003) provide evidence that firms experience dividend cuts prior to forced CEO turnover.

Based on these arguments, we expect a company that pays dividends to have a lower probability of forced CEO turnover. High dividend yields increase the demand for the company's shares, which is expected to mitigate the potential conflict between managers and shareholders.

Parrino (1997) introduced sector homogeneity as a determinant of CEO turnover. He measured sector homogeneity through a volatility indicator of the company's stock return related to industry return. The intuition behind this assumption refers to the fact that in more homogeneous industries, the managerial skills required are similar, and managers can be easily replaced by others from the same industry. The low liquidity of the Romanian capital market did not allow us to follow the same methodology, but we indirectly studied the role of sector homogeneity on CEO turnover.