Mechanical properties of some high-entropy alloys [8].
\r\n\tHydrogen gas is the key energy source for hydrogen-based society. Ozone dissolved water is expected as the sterilization and cleaning agent that can comply with the new law enacted by the US Food and Drug Administration (FDA). The law “FDA Food Safety Modernization Act” requires sterilization and washing of foods to prevent food poisoning and has a strict provision that vegetables, meat, and fish must be washed with non-chlorine cleaning agents to make E. coli adhering to food down to “zero”. If ozone dissolved water could be successively applied in this field, electrochemistry would make a significant contribution to society.
\r\n\r\n\t
\r\n\tOxygen-enriched water is said to promote the growth of farmed fish. Hydrogen dissolved water is said to be able to efficiently remove minute dust on the silicon wafer when used in combination with ultrasonic irradiation.
\r\n\tAt present researches on direct water electrolysis have shown significant progress. For example, boron-doped diamonds and complex metal oxides are widely used as an electrode, and the interposing polymer electrolyte membrane (PEM) between electrodes has become one of the major processes of water electrolysis.
\r\n\t
\r\n\tThe purpose of this book is to show the latest water electrolysis technology and the future of society applying it.
High-entropy alloys (HEAs) are known for their special mechanical properties: high tensile strength resistance even at high temperature, high hardness, toughness exceeding that of most pure metals and alloys, comparable strength to that of structural ceramics and some metallic glasses, exceptional ductility and fracture toughness at cryogenic temperatures, and corrosion resistance. These specific properties were mainly attributed to complex concentrated solid solutions formed by the suppression of fragile intermetallic compounds as a result of high mixing entropy and enthalpy values [1]. HEAs generally tend to form single-phase solid solutions in the case of low mixing enthalpy and atomic size difference. Generally speaking, the formation of a single-phase solid solution corresponds to the mixing enthalpy values (DHmix) situated in domain of −15 kJ/mol < DHmix <5 kJ/ml and 0 < δ < 5 [2].
\nAs a result of these special features, HEA is currently an alternative to use as material for a number of special areas, such as structural applications; aerospace engineering and civil transportations; superconducting electromagnets such as magnetic resonance imaging, scanners, nuclear magnetic resonance machines, and particle accelerators; high-temperature applications such as gas turbines, rocket nozzles, and nuclear construction; cryogenic applications such as rocket casings, pipework, and liquid O2 or N2 equipment; refractory elements such as Nb, Mo, and Ta that can maintain their high strength even above 1200°C, superior to traditional super alloys such as Inconel 718 and Haynes 230; hardfacing applications; and military applications.
\nThe specifications on the security of collective protection equipment and structures in the military field set forth enhanced requirements for the resistance of the protection panels/floors/elements against the penetration by various types of projectiles, due to the diversification of the types of interventions in the military activities.
\nThe main characteristics of the materials intended for the manufacture of protection components are as follows: the highest possible breaking and yield strength values, the highest possible hardness and impact resistance, and the highest possible elongation at break and energy absorbed by a notched specimen while breaking under an impact load (the Charpy test) at temperatures down to minus 40°C. The current military specifications recommend hardness values of at least 540–600 BHN (Brinell hardness) or 55–60 HRC (Rockwell hardness) and, for strength characteristics, such as the yield strength, values above 1500 and 1700 MPa for the breaking strength. In the case of the impact fracture energy using the Charpy test, the values must be of approximately 13 J at −40°C, with elongations of at least 6% [3].
\nSuch requirements have been met by designing metallic alloys of various compositions; the most widely used is the high-strength microalloyed steels, used to produce reinforcement elements of thicknesses between 8.5 and 30 mm. Some research papers in the military field [4] have shown that the hardness of the plating material is not a sufficient factor to provide maximum resistance against penetration by projectiles, considering that the values of the mechanical strengths (yield and breaking) are much more important in the behavior process under dynamic stress.
\nAccurate measurements of dynamic stresses during impact stress have detected mechanical stress values of 28 GPa in the case of bainitic microstructure steels, while in the case of static stress, the measured stresses were of no more than 2 GPa [5].
\nA ballistic performance index (BPI) [6, 7] was also proposed to estimate the ballistic strength of armored plates, containing data on steel density, the elastic modulus, yield and tensile strength, Poisson’s coefficient, and the constriction or elongation during impact tests. There are terms that contain elastic and plastic deformation components, as well as terms that take into account the kinetic energy of the target-projectile system after impact. Therefore, the main characteristics that metallic materials used in special military applications need to feature for the best impact behavior are as follows:
The highest possible hardness, as a measurement of the solid material’s resistance against the penetration of its surface by various types of penetrators, with permanent shape changes, when a static or dynamic force is applied to them; the macroscopic hardness is generally characterized by the nature and strength of the intermolecular bonds, and the behavior of the solid material under the action of force is complex.
Toughness, which describes the capacity of a metallic material to absorb the breaking energy, the strength of its metallic matrix when various cracks occur and propagate, and the energy of forming the breaking surfaces, considering that the breaking occurs by consuming the impact stress energy, with local plastic deformation.
Impact strength, which is the relative susceptibility to breaking by the action of forces applied at high velocity.
High-entropy alloys from the AlCrFeCoNi system feature very good mechanical properties for military applications, as shown in Table 1. Thus, the yield stress, the compressive strength, and the plastic deformation of these alloys reach unexpected values [8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20], making them usable as composite structures, resistant to dynamic stresses with high deformation velocity, applicable in the field of collective protection [9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20].
\nAlloy | \nYield strength, MPa | \nCompressive strength, MPa | \nPlastic deformation, % | \n
---|---|---|---|
AlCrFeCoNi | \n1250.96 | \n2004.23 | \n32.7 | \n
CrFeCoNiCuTi | \n1272 | \n1272 | \n1.6 | \n
AlCrMnFeCoNiCuTiV | \n1862 | \n2431 | \n0.95 | \n
CrFeCoNiCuTi0.5\n | \n700 | \n1650 | \n21.26 | \n
Mechanical properties of some high-entropy alloys [8].
The most commonly used method for successfully producing high-entropy alloys is the electric arc melting of the load materials in a vacuum arc remelting equipment (with current values of up to 500 A) in controlled atmosphere. The main technological operations pursued in this case are presented below.
\nSpecial type of materials chosen for making the ballistic target is experimental alloys AlCrFeCoNi, obtained in vacuum arc remelting equipment (MRF ABJ 900, in ERAMET Laboratory, University Politehnica of Bucharest, Romania). For calculating the metallic load, the theoretical degrees of assimilation of the elements in the melt and of the possible vaporization losses during the metallurgical process in vacuum or in argon-controlled atmosphere must be taken into account (Figure 1).
\nVacuum arc remelting equipment MRF ABJ 900 and working chamber, in ERAMET Laboratory, University Politehnica of Bucharest, Romania.
Mass losses are estimated on the basis of the literature data thereon, the degree of oxidation of the metallic load materials, the characteristics of the elements in the load, their positioning in the series of electrochemical potentials, the characteristics of the preparation aggregate, and the experience in the preparation process. It should be noted that the metallic load used to obtain high-entropy alloys must be of high quality, low in phosphorus and sulfur, and degreased and properly machined (in terms of granulometry). The degree of purity of the elements the alloy is over 99%. The elements dosed in equimolecular or quasi-equimolecular proportions are introduced following an order determined according to the type of alloy to be prepared, into the crucibles in the copper plate, water-cooled throughout the metallurgical process.
\nIn order to produce high-entropy alloys under high-purity conditions, the working chamber must be suitably prepared by successive vacuuming and argon purging operations performed at least three times. The vacuuming is performed using preliminary vacuum systems and diffusion pumps, which can provide pressure levels of about 3.5–4 × 10−4 mbar. Pure argon (Ar 5.3, 99.99%) is used for purging and melting. These operations provide a maximum oxygen content of 40–60 ppm in the working chamber. The final stage of the process is the argon purging of the working chamber and the setting of a working pressure level slightly above the atmospheric pressure.
\nThe process of producing high-entropy alloys consists in melting the load materials, followed by the remelting of the samples for five to seven times, turning them on opposite sides to ensure a fully alloyed state and to improve the chemical homogenization of the mini-ingots. The entire preparation process is carried out by electric arc remelting in argon-controlled atmosphere.
\nThe melting mode of the vacuum arc remelting furnace must be adapted to the type of alloy being prepared. These parameters vary during the preparation process, depending on the stages and the activities being carried out. The thorium tungsten electrode must be shifted during melting so that it is approximately 1/4” away from the copper plate electrode, and the electric arc formed sweeps the entire surface of the load for complete homogenization. Following melting and solidification, mini-ingots of weights almost constant compared to that of the load introduced into the VAR are produced.
\nUsing this method, experimental high-entropy alloys have been instantaneously cooled by forced cooling of the water pumped at the base of the copper plate (the crystallizer of the furnace).
\nThe melted material solidifies ultrafast in the water-cooled copper shell. The mini-ingots produced can have different shapes, depending on the shape of the cavity in the copper plate of the furnace. The samples were analyzed, according to the chemical composition, in order to define their physical, chemical, mechanical, etc. properties.
\nThe chemical compositions of the metallic materials used are as follows:
Extra soft steel, MK3 grade: C = 0.02 wt%; Si = 0.04 wt%; Mn = 0.21 wt%; S = 0.02 wt%; P = 0.015 wt%; Ni = 0.2 wt%; Cr = 0.15 wt%; Mo = 0.07 wt%; Cu = 0.14 wt%; Al = 0.12 wt%; Fe = ballance wt%
Metallic chromium with 99 wt% Cr
Electrolytic aluminum with 98.5 wt% Al
Metallic cobalt with 99.5 wt% Co
Electrolytic nickel with 99.5 wt% Ni
A vacuum induction melting-vacuum arc remelting (VIM-VAR) duplex technology was selected to produce the high-entropy alloy AlCrFeCoNi in order to increase the purity of the alloy and to improve its mechanical properties. The experimental batches were prepared in the vacuum induction melting furnace Balzers, HU-40-25-40-04 type, with a capacity of 12 kg and in the MRF ABJ 900 vacuum arc remelting equipment, both from the ERAMET Laboratory, Bucharest.
\nThe high-entropy alloy used to make the ballistic protection plates in the vacuum induction furnace was produced according to a classical preparation technology, using highly pure materials, and metallic molds made of iron Fc 250 (Figure 2) were used for casting to ensure the production of 150 × 100 × 10 mm rectangular plates.
\nMetallic molds for casting Al0.8CrFeCoNi alloy.
The load calculation (based on the molar mass of the chemical elements, Mmol) for obtaining the Al0.8CrFeCoNi alloy, taking into account the estimated elemental losses, is as follows (Eq. (1)):
\nThe concentration (% weight) of the alloying elements in the alloy was Al = 8.72 wt%; Cr = 21 wt%; Fe = 22.62 wt%; Co = 23.83 wt%; and Ni = 23.83 wt%. The alloy mass calculated based on the volume and density of the alloy cast in a plate and related network was 1.111 and 0.574 kg, respectively, resulting in an alloy quantity of approx. 1.6855 kg per ingot.
\nSince alloy losses occur due to oxidation, due to the interaction with the furnace walls and to the casting ladle, a quantity of 8 kg of prepared alloy is considered per batch.
\nThe quantities of materials used for each batch, also taking into account the oxidation losses, are as follows: Al = 0.74 kg; Cr = 1.70 kg; Fe = 1.85 kg; Co = 1.95 kg; and Ni = 1.93 kg. The total weight of the batch was of 8.17 kg. The Al0.8CrFeCoNi alloy plates obtained by casting are shown in Figure 3.
\nHEA Al0.8CrFeCoNi alloy plates obtained by VIM-VAR technology. (a) As-cast HEA samples obtained by VIM technology; (b) HEA sample positioned in copper plate of VAR equipment to be remelted; (c) sample after remelting procedure in VAR equipment.
The production of the HEA Al0.8CrFeCoNi plates was completed by refining in the vacuum arc remelting furnace, for which, based on the requirements of the military field, a special copper plate was made, according to Figure 2b.
\nThe working procedure in the VAR furnace was classical, seeking the most efficient homogenization of the alloy to ensure the best possible mechanical properties, by remelting each sample three times on each side (Figure 3c).
\nThe impact fracture tests were performed using a Charpy pendulum, to measure the energy absorbed in the process of dynamic fracture of standardized (notched) specimens. The values resulting from the impact fracture test for some AlCrFeCoNi alloys are shown in Table 2.
\nTest no. | \nImpact energy, J | \n||||
---|---|---|---|---|---|
HEA 1 | \nHEA 5 | \nHEA 6 | \nHEA 12 | \nHEA 14 | \n|
1 | \n62.1 | \n67.1 | \n67.0 | \n66.0 | \n62.4 | \n
2 | \n62.7 | \n67.2 | \n66.9 | \n65.8 | \n62.3 | \n
3 | \n62.1 | \n67.0 | \n67.1 | \n65.9 | \n62.1 | \n
4 | \n62.2 | \n67.3 | \n68.9 | \n66.1 | \n62.1 | \n
Impact fracture energy values for some experimental HEAs.
As can be seen from the values of the breaking energy shown in the table, the experimental materials have a tenacity corresponding to structural steels, while the hardness values are similar to those of tool steels.
\nThe hardness of the experimental materials was determined using the Shimadzu HMV2T microhardness apparatus in Lamet Laboratories from Politehnica University of Bucharest. The measurements were made in line, with mark distances of about 500 μm, using the fingerprint force of 0.1 N and pressing time of 10 seconds [9, 10, 11, 12]. For the AlxCryFezCovNiw system, the entire spectrum of microhardness values in the x = y = z = v = w = 0.2 … 2 at% range was analyzed, as shown in Figure 4.
\nMicrohardness HV0.1 values for experimental HEA 1 to HEA 10.
The coding of the samples in Figure 4 was based on the atomic proportions of the chemical elements; thus, HEA 1 = AlCrFeCoNi; HEA 2 = Al1.5CrFeCoNi; HEA 3 = Al2CrFeCoNi; HEA 5 = Al0.8CrFeCoNi; HEA 6 = Al0.6CrFeCoNi; HEA 7 = Al0.4CrFeCoNi; HEA 8 = Al0.2CrFeCoNi; HEA 9 = Al1.2CrFeCoNi; and HEA 10 = Al1.4CrFeCoNi. The maximum hardness value was obtained for the sample HEA 3, with maximum concentration of aluminum.
\nThe coding of the samples in Figure 5 was based on the atomic proportions of the chemical elements; thus, HEA 11 = AlCrFeCoNi1.2; HEA 12 = AlCrFeCoNi1.4; HEA 13 = AlCrFeCoNi1.6; HEA 14 = AlCrFeCoNi1.8; HEA 15 = AlCrFeCoNi2; HEA 16 = AlCrFeCoNi0.8; HEA 17 = AlCrFeCoNi0.6; HEA 18 = AlCrFeCoNi0.4; and HEA 19 = AlCrFeCoNi0.2. The maximum hardness value was obtained for the sample HEA 11.
\nMicrohardness HV0.1 values for experimental HEA 11 to HEA 19.
The coding of the samples in Figure 6 was based on the atomic proportions of the chemical elements; thus, HEA 20 = AlCrFeCo0.8Ni; HEA 21 = AlCrFeCo0.6Ni; HEA 22 = AlCrFeCo0.4Ni; HEA 23 = AlCrFeCo0.2Ni; HEA 24 = AlCrFeCo1.2Ni; HEA 25 = AlCrFeCo1.4Ni; HEA 26 = AlCrFeCo1.6Ni; HEA 27 = AlCrFeCo1.8Ni; and HEA 28 = AlCrFeCo2Ni. The maximum hardness value was obtained for the sample HEA 26.
\nMicrohardness HV0.1 values for experimental HEA 20 to HEA 28.
The coding of the samples in Figure 7 was based on the atomic proportions of the chemical elements; thus, HEA 29 = AlCr0.2FeCoNi; HEA 30 = AlCr0.4FeCoNi; HEA 31 = AlCr0.6FeCoNi; HEA 32 = AlCr0.8FeCoNi; HEA 33 = AlCr1.2FeCoNi; HEA 34 = AlCr1.4FeCoNi; HEA 35 = AlCr1.6FeCoNi; HEA 36 = AlCr1.8FeCoNi; and HEA 37 = AlCr2FeCoNi. The maximum hardness value was obtained for the sample HEA 36.
\nMicrohardness HV0.1 values for experimental HEA 29 to HEA 37.
The coding of the samples in Figure 8 was based on the atomic proportions of the chemical elements; thus, HEA 38 = AlCrFe0.2CoNi; HEA 39 = AlCrFe0.4CoNi; HEA 40 = AlCrFe0.6CoNi; HEA 41 = AlCrFe0.8CoNi; HEA 42 = AlCrFe1.2CoNi; HEA 43 = AlCrFe1.4CoNi; HEA 44 = AlCrFe1.6CoNi; HEA 45 = AlCrFe1.8CoNi; and HEA 46 = AlCrFe2CoNi. The maximum hardness value was obtained for the sample HEA 38, for minimum concentration of iron.
\nMicrohardness HV0.1 values for experimental HEA 38 to HEA 46.
The microstructure of experimental high-entropy alloys was performed selectively by optical microscopy (Olympus GX51 reversed optical microscope) and scanning electron microscopy (Inspect SEM, FEI Company, scanning electron microscope equipped with EDAX Z2e detector) [9, 13, 14, 15, 16]. The microstructural aspect of some experimental alloys is shown in Figures 9–14.
\nExperimental as-cast AlxCrFeCoNi alloys.
Experimental as-cast AlCrFeCoNix alloys.
Experimental as-cast AlCrFeCoxNi alloys.
Experimental as-cast AlCrxFeCoNi alloys.
SEM images of AlxCrFeCoNi alloys.
SEM images of AlCrFeCoNix alloys.
All materials show dendritic formations and interdendritic precipitations in experimental as-cast HEAs. Some of them (HEA 5) shows polyhedral grains and acicular phase growth from the grain boundary (Figure 9). The images have been performed for the same magnification (scale of 200 μm). The sample HEA 15 with the highest nickel concentration has the orientation and sequence of the alpha and gamma phases, in the form of parallel or perpendicular planes (Figure 10).
\nChanging the Co content does not make changes to the microstructure, which has a dendritic appearance (Figure 11). The increase in chromium content resulted in an increased finishing of dendritic microstructure granulation for HEA 36 sample, which also led to an increase in hardness (Figure 12).
\nScanning electron microscopy images revealed the fine and nanostructured microstructure with polyhedral grains and the layout of phases in quasi-parallel planes (Figure 13) [15].
\nIn the case of high-Ni samples, higher magnification powers can be seen in phase configurations, in acicular or polymorphic form (Figure 14).
\nSeveral ballistic packages (Figure 15) were made for the testing of composite structures at high-velocity perforation, explosion, and high-velocity deformation. The packages have a sandwich structure, containing aluminum, steel, or ceramic plates or polymer HEA plate and, finally, aluminum plate again. The images from the firing room and the testing configuration are shown in Figure 16, and the experimental stand scheme for dynamic test is shown in Figure 17.
\nBallistic packages prepared for dynamic tests.
Firing room and experimental stand for dynamic test.
HEA-steel ballistic package during dynamic tests (a) after the first firing and (b) after the second firing.
The ballistic packages undergoing tests for checking the bullet impact behavior were fastened to a wooden stand at a distance of 5 m from the machine-gun barrel’s muzzle. The amount of powder in the cartridge shell was varied in order to obtain the desired initial velocity [15, 16, 17, 18, 19].
\nTwo 7.62 × 39 mm incendiary armor-piercing bullets with initial velocities of 660 and 728 m/s, respectively, were fired at the targets. The ballistic package resisted punching for the first fire (Figure 17a) and then perforated at the second firing (Figure 17b).
\nThe same procedure of dynamic testing, using 7.62 × 39 mm incendiary armor-piercing bullets at initial velocities of 723 and 728 m/s, respectively, was applied at the HEA-ceramic ballistic package. This type of ballistic package was perforated both at the first and second cases (Figure 18).
\nHEA-ceramic ballistic package during dynamic tests (a) after the first firing (b) and after the second firing (c).
The last procedure was applied using 7.62 × 39 mm incendiary armor-piercing bullets at initial velocities of 720 and 725 m/s, respectively, for dynamic testing of HEA-ceramic ballistic package. This type of ballistic package was entirely perforated, in both cases (Figure 19).
\nHEA-polymer ballistic package during dynamic tests. (a) after the first firing and (b) after the second firing.
High-entropy alloys are well suited for production in vacuum arc remelting furnaces due to low material losses and to obtaining high purity by working in vacuum and argon. Moreover, they can also be produced in induction furnaces, for superior purity, using the VIM-VAR duplex process.
\nThe hardness decrease of the AlCrFeCoNi class high-entropy alloys is proportional to the aluminum content decrease, from 500 HV1 for HEA 1 (AlCrFeCoNi) at 400 HV1 for HEA 5 (Al0.8CrFeCoNi) and 224 HV1 for HEA 6 (Al0.6CrFeCoNi). The hardness decrease can be explained by the reduction in the quantity and number of hard precipitates (Fe-Al compounds) in the metallic matrix.
\nThe hardness further decreases by increasing the nickel content, which allows the formation of face-centered cubic (FCC) solid solutions of low hardness and high tenacity. In this type of solid solution the chemical elements have a good solubility, with a low tendency of separation of hard and brittle compounds.
\nThe fracture energy values are in the range of 62–67 J for all five types of alloys, as the hardness oscillates in the range 200–500 HV0.1. As a result, the hardening effect is not manifested by decreasing the metal matrix toughness in the case of high-entropy alloys in the analyzed alloy class.
\nThe microstructure of high-entropy alloys is virtually “frozen” at the melt, with the solution retaining a conglomerate of chemical elements which are oftentimes very different (iron-related elements such as Cr, Ni, and Co, which together form solid solutions along with aluminum, a transition metal whose solubility greatly differs from that of Fe, Cr, Ni, and Co). The cooling condition creates entropy with very high values and explains the obtaining of completely different characteristics compared to the alloy cooled at usual rates.
\nDepending on the share of the alloying elements, one or two types of solid solutions are formed, partially embedding the other alloying elements. The dendritic microstructure predominates, separating into acicular compounds or globular precipitates, depending on the chemical composition and the cooling rate.
\nThe tests on the behavior of high-entropy alloys at strong impacts were conducted under identical conditions. In the case of ballistic packages resistant at high-velocity penetration impacts, the best option is the HEA-steel system. High-entropy alloys, according to their composition, can be used in various sectors: medical engineering, earthwork equipment, and ballistic packages for individual and collective protection.
\nThis paper was supported by the Romanian National Authority for Scientific Research CNDI-UEFISCDI, project number PN-III-P1-1.2-PCCDI-2017-0875 – PCCDI 20-2018 (HEAPROTECT).
\nThe authors want to thank the team of researchers coordinated by Professor PhD Tudor Cherecheş for collaborating in the dynamic tests and the processing of experimental data.
\nThe knowledge of electrical properties of soils in physics and electrical engineering are important for many applications. The long-distance electromagnetic telegraph systems from 1820 are used, with two or more wires to carry the signal and the return currents. It was discovered that the earth could be used as a return path to complete the circuit, making the return wire unnecessary [1]. However, during dry weather, the earth connection often developed a high resistance, requiring water on the earth electrode to enable the telegraph to ring [1].
\nAn important radio propagation and engineering problem has been solved in 1909 by A. Sommerfeld. He has solved the general problem of the effect of the finite conductivity of the ground on the radiation from a short vertical antenna at the surface of a plane earth. The surface wave propagation is produced over real ground for the medium frequency AM radio service, where the attenuation of the electric field depends on the dielectric properties of the soil, mainly of the dielectric losses [2]. Considering the word “Soil” means the uppermost layer of the earth’s crust, it contains the organic as well as mineral matter. From 1936 up to 1941, Norton, Van der Pol, and Bremmer made the computation of the field strengths at distant points on the flat and spherical Earth’s surface [3, 4].
\nIn agriculture applications, the electrical resistivity methods have been introduced by Conrad Schlumberger in France and Frank Wenner in the United States, for the evaluation of ground electrical resistivity. In saline soils, the electric conductivity measured is high, and the effects of salinity are manifested in the loss of stand, reduced rates of plant growth, reduced yields, and in severe cases, total crop failure [5].
\nThe applications like the protection of electrical generating plant are necessary to provide earth connections with low electrical resistance. The radio transmitting and receiving stations for broadcasting is generally covered by radiation transmitted directly along the ground [6]. In electrical engineering, “ground” is the reference point in an electrical circuit from which voltages are measured.
\nFor archeology, geophysics, engineering, and military applications, the so-called ground-penetrating radar (GPR) is a technique widely used. The radar signal is an electromagnetic wave that propagates through the earth, and its signal is reflected when an object appears or there is a change in the properties of the earth. In order to determine the depth of an object under the ground, it is necessary to know the electrical properties of the soil [7].
\nThe equations that relate the electric field (E) and magnetic field (H) are based on the electromagnetic theory formulated by James Clerk Maxwell in 1864, whose validity has allowed great advances in diverse areas, such as telecommunications, electricity, electronics, and materials [8].
\nRegarding the behavior of the materials under the action of an electric field, in the conductive materials, the charges can move freely, meaning that the electrons are not associated with an atomic nucleus. In the case of dielectric materials, the charges are associated with an atom or specific molecule [9]. There are two main mechanisms where the electric field distorts the distribution of charge in a dielectric, stretching and rotation. The relationship between the electric dipole moment inducted under the action of an applied electric field is called atomic electric polarizability \n
In a material with an applied electric field, a convenient definition is to consider the contributions of the dipole moment per unit volume; this parameter is called polarization, which is a macroscopic definition instead of a molecular or atomic definition [9, 10]:
\nIt is evident that the contributions of the electric dipole moment in a volume element \n
And the polarization
\nIn Figure 1, the external electric field applied to a dielectric material and the resulting polarization can be observed.
\nPolarization applying external electric field E, to a dielectric material.
From the macroscopic point of view in most of the dielectric material, when the electric field is canceled, the polarization in the material will be nullified. In addition, the polarization of the material will vary as the electric field varies, i.e., \n
It is convenient to define the electric displacement, because it allows to relate by means of the Gaussian law with the free charges; therefore
\nThen
\nThe electrical permittivity is defined as the relationship between the electric displacement vector \n
Result
\nIt is convenient to define [11]:
\nResult
\nThe electric properties of the material are completely defined by means of \n
In problems with electromagnetic fields, four vectors are defined: E and B; D and H. These vectors are assumed to be finite throughout the entire field, and at all ordinary points to be continuous functions of position and time, with continuous derivatives [12]. The constitutive relations link the vectors of the fields \n
For the electromagnetic propagation in soils, the parameters \n
The electrical resistivity obtained by soil mapping exhibits a large range of values from \n
Table of electric resistivity \n\n\n\nΩ\n/\nm\n\n\n\n and electric conductivity \n\n\n\nσ\n/\nm\n\n\n\n of soils (Ref. Samoulian et al.) [13].
There are evidences that for compacted soils of clay, it exhibits an anisotropic behavior in the resistivity measured in the horizontal and vertical directions [14].
\nThe literature contains the measurement of the dielectric properties of soils at different frequencies with slotted lines and time-domain reflectometry (TDR) methods [15].
\nThe measured variations of the electric permittivity of soils with fractions of sand, silt, and clay and with volumetric moisture content have been studied for frequency of 440 MHz used by the radar observations [16].
\nThe coaxial probe technique terminated in the material under test has been used to measure the dielectric properties of the vegetation. The dielectric data reported are based on measurements of the amplitude and phase of the reflection coefficient of a coaxial probe [17, 18].
\nThe transmission line method has been used to measure the dielectric properties [19, 20]. These transmission lines are coaxial, quasi-coaxial, and two-wire transmission lines. Consider a transmission line with a homogenous dielectric material inside, and the propagation is transverse electromagnetic mode (TEM), where the electric and magnetic field are perpendicular to the propagation direction; this can be observed in Figures 3 and 4.
\nSection of the two-wire transmission line with the electric and magnetic fields.
Section of coaxial transmission lines and the electric and magnetic fields.
The separation between the conductive cylinders that form the coax transmission line should be much lower than the wavelength of the signal that propagates, so the transmission line will not be affected by the propagation modes of high orders, such as the TE\n11 [19].
\nCoaxial transmission lines are widely used for the transmission of radiofrequency signals and its application in radiocommunications and for broadcasting [21]. The transmission lines allow the connection between a generator or emitter and a load or antenna. The air coaxial transmission line consists of two cylindrical conductors, with air between both conductors. These metallic conductors are those that impose the boarder conditions that must comply with the electric and magnetic fields of the electromagnetic wave that travel inside the line. The coaxial transmission lines are used to measure the electrical properties of a dielectric material located inside the coaxial transmission line, as shown in Figure 4.
\nBy analyzing the circuit model of a transmission line, the currents and voltages that propagate along it can be determined, using the circuit theory [22]. The equivalent circuit model of a transmission line can be seen in Figure 5. According to the equivalent circuit model of a transmission line, the characteristic impedance \n
Distributed parameters of the transmission line.
where R is the series resistance per unit length \n
If the transmission line has no losses, it means that R = 0 and G = 0; then the characteristic impedance can be reduced as follows:
\nThe input impedance of a transmission line, with a material inside considering the material with dielectric losses, can be expressed thus [23]:
\nwhere \n
The time-domain reflectometry (TDR) is a well-known technique used to find the interruption point of the transmission lines in a CATV installation and is also useful to determine the dielectric permittivity (see Figure 6).
\nSetup of the dielectric measurement by the TDR method [24].
The time-domain reflectometry uses a step generator and an oscilloscope; a fast edge is launched into the transmission line under investigation, where the incident and reflected voltage waves on the transmission line are monitored by the oscilloscope. This method shows the losses and the characteristic impedance of the line: resistive, inductive, or capacitive [25]. The TDR method is based on the velocity of the electromagnetic wave that propagates through the soil, and the velocity of the wave depends on the water content of the soil. If a pulse is applied to a no-loss transmission line, the time domain graphic can be shown like in Figure 7. Considering the soil like a nonmagnetic media with low dielectric loss is [26, 27]:
\nPropagation of the pulses in the time domain graphic with dielectric air [24].
where \n
The time interval \n
Picture of the voltage as a function of time for the probe is in the soil [26].
where \n
Then
\nUsually the transmission line probes have a minimum length of 15 cm, because the incident electromagnetic wave takes a time of 1 ns in air in order to return to the input of the line. This time is too short to be measured.
\nThe conductivity of the soil can be determined computing the reflected pulses in the probe in the time domain graphic (see Figure 8) [26, 28]. Numerous methods have been proposed by researchers; one of these is the procedure of Dalton et al. (1984) [26]:
\nwhere \n
Also the conductivity can expressed thus [29]:
\nwhere:
\n\n\n
\n\n
Temperature correction \n
This method is based on the measurement of the reflection coefficient by means of the vector network analyzer (VNA) on the frequency domain of a coaxial transmission line in the soil; this can be observed in Figure 9 [30, 31, 32].
\nDielectric measurement by the coaxial transmission line method. (a) Setup of the measurement experiment; (b) section of the transmission line and the material under test [33].
The vector network analyzer can measure the scattering coefficient of a two-port passive network where the reflection coefficient in voltage \n
where \n
The impedance of the probe can be calculated thus:
\nwhere \n
Then the complex electric permittivity for frequencies lower than 50 MHz can be approximated thus [31]:
\nSome references of these measurement methods by means of characteristic impedance have been developed [35, 36]. This methods is shown in Figure 10.
\nInput impedance of the transmission line for \n\n\nZ\nL\n\n=\n0\n\n and \n\n\nZ\nL\n\n→\n∞\n\n.
The input impedance can be computed by Eq. (17) for two different loads’ impedance:
(a) Open circuit in the load \n
\n
(b) Short circuit in the load \n
where, in general, the material inside the transmission line could be a dielectric loss; the propagation constant can be written thus:
\nwhere \n
Using the relation between \n
The argument of the ln
\nReplacing the Ln
\nThen the propagation constant can be written thus:
\nBy these last equations, the attenuation constant and the phase constant can be calculated with \n
The propagation constant \n
Equating real and imaginary parts of \n
\n\n
Another expression of \n
Equating real and imaginary part of Eq. (43)\n
\nResults
\nThe series resistance of the conductor of the coaxial transmission line used is \n
\n
The input impedances are measured for a load impedance at short circuit \n
The attenuation constant \n
The electric permittivity \n
In this way, a practical method of measurement is available to determine the parameters of dielectric materials, using coaxial transmission lines, in the frequency range from 1 to 1000 MHz. A problem that appears when measuring dielectric materials is the connector that establishes the link between the coaxial transmission line and the vector impedance meter. A systematic error in the impedance measured is introduced.
\nTherefore, the study and correction of the mentioned error in the section will be carried out.
\nThree coaxial transmission lines of General Radio (GR) Type 874, with air dielectric, have been used with a length of 100, 200, and 300 mm. The main characteristics of the General Radio coaxial transmission lines, type 874, are the following:
\nCharacteristic impedance \n
Input and output connector GR874
\nIt is important to perform the correction of the impedance introduced by the connector of the transmission line used. This connector is shown in Figure 11, and it is composed by a dielectric of very low dielectric losses and has a length of 10 mm (Figure 12). The characteristic impedance of the connector is practically \n
N connector and its equivalent of a transmission line with dielectric of air.
Equivalent length of the transmission line of the connector GR874.
The input impedance to the connector can be written thus:
\nwhere \n
The electric permittivity of the dielectric of the connector is unknown; then it is easy to assume a transmission line with air equivalent to the connector with \n
Considering the connector with no losses
\nThen the input impedance of the connector with \n
where \n
The length \n
The experimental results of the electric conductivity and the dielectric permittivity measurement of the dry sand can be observed in Figures 13 and 14. In Figure 13, the electric conductivity as a function of the frequency, by means of the capacitive method, and the three types of transmission line lengths have been measured: L = 100, 200, and 300 mm; the convergence of all measurements are evident.
\nElectric conductivity as a function of the frequency for dry sand samples, using a capacitive method and three transmission lines: 100, 200, and 300 mm.
The relative dielectric permittivity as a function of the frequency for dry sand samples has been measured, using a capacitive method and three transmission lines: 100, 200, and 300 mm.
In Figure 14, the relative electric permittivity as a function of the frequency, by means of the capacitive method, and the three types of transmission line lengths have been measured: L = 100, 200, and 300 mm; there is a convergence of all measurements. It is important to note that the shorter transmission line has a wider bandwidth of measurement. The transmission line length of \n
The expected value of the dielectric permittivity measured for the dry sand by means of a parallel plate capacitor and the three transmission lines used are shown in Table 1. The standard deviation of the three measurements shows a good agreement up to the vicinity of the resonant frequency of each transmission line. In Table 2, the electric conductivity of the dry sand can be observed. These curves have the same slope and show a good convergence.
\nfreq.(MHz) | \nCapacitor | \nT. line 100 mm | \nT. line 200 mm | \nT. line 300 mm | \nExpected value | \nStd. dev | \n
---|---|---|---|---|---|---|
1 | \n2.80 | \n2.86 | \n2.65 | \n2.65 | \n2.74 | \n0.034 | \n
2 | \n2.60 | \n2.76 | \n2.62 | \n2.75 | \n2.68 | \n0.021 | \n
3 | \n2.60 | \n2.70 | \n2.60 | \n2.70 | \n2.65 | \n0.010 | \n
5 | \n2.50 | \n2.61 | \n2.57 | \n2.65 | \n2.58 | \n0.012 | \n
7 | \n2.50 | \n2.54 | \n2.55 | \n2.62 | \n2.55 | \n0.0075 | \n
10 | \n2.50 | \n2.51 | \n2.50 | \n2.60 | \n2.52 | \n0.0073 | \n
20 | \n2.40 | \n2.45 | \n2.47 | \n2.57 | \n2.47 | \n0.0153 | \n
30 | \n2.40 | \n2.42 | \n2.46 | \n2.57 | \n2.46 | \n0.0173 | \n
50 | \n2.40 | \n2.40 | \n2.46 | \n— | \n2.41 | \n0.0028 | \n
70 | \n— | \n2.37 | \n— | \n— | \n— | \n— | \n
100 | \n— | \n2.35 | \n— | \n— | \n— | \n— | \n
Relative electric permittivity of dry sand.
freq.(MHz) | \nCapacitor | \nT. line 100 mm | \nT. line 200 mm | \nT. line 300 mm | \nExpected value | \nStd. dev | \n
---|---|---|---|---|---|---|
1 | \n1 | \n1.1 | \n1.3 | \n1.2 | \n1.15 | \n0.13 | \n
2 | \n1.6 | \n2.0 | \n1.7 | \n1.7 | \n1.75 | \n0.17 | \n
3 | \n2.1 | \n2.6 | \n2.3 | \n2.2 | \n2.30 | \n0.22 | \n
5 | \n3.2 | \n3.1 | \n3.3 | \n3.1 | \n3.20 | \n0.096 | \n
7 | \n4.4 | \n5 | \n4.3 | \n4 | \n4.40 | \n0.42 | \n
10 | \n6.0 | \n6.5 | \n5.5 | \n5.1 | \n5.80 | \n0.6 | \n
20 | \n10 | \n11 | \n9.4 | \n8.4 | \n9.70 | \n1.08 | \n
30 | \n14.4 | \n14.6 | \n12.7 | \n11.1 | \n13.20 | \n1.60 | \n
50 | \n21.9 | \n21.5 | \n20.8 | \n16 | \n20.00 | \n2.7 | \n
Electric conductivity of dry sand \n
The values of the electrical conductivity and the electrical permittivity are very useful to evaluate the propagation of surface waves in real ground, where the attenuation depends mostly on the conductivity of the soil. Such is the case that AM transmitters include radials, which consist of metallic conductors, placed at the base of the monopole antenna to increase conductivity, and in this way the losses due to Joule effect on the earth’s surface are reduced. When the conductivity of the soil is perfect, the electric field vector that propagates will be perpendicular to the earth’s surface; however, in real soils the electric field vector tilts and partly spreads into the earth, which dissipates power and transforms into heat [2]. This constitutes losses on earth.
\nApparent soil electrical conductivity (ECa) to agriculture has its origin in the measurement of soil salinity, in arid-zone problem, which is associated with irrigated agricultural land. ECa is a quick, reliable, easy-to-take soil measurement that often relates to crop yield. For these reasons, the measurement of ECa is among the most frequently used tools in precision agriculture research for the spatiotemporal characterization of edaphic and anthropogenic properties that influence crop yield [37]. There are portable instruments for measuring the electrical conductivity of the soil by the method of electromagnetic induction and by the method of the four conductors, which are installed in the agricultural machinery to obtain a map of the soil, before carrying out the work of tilling the earth.
\nFor geophysics applications, the solar disturbances (flares, coronal mass ejections) create variations of the Earth’s magnetic field. These geomagnetic variations induce a geoelectric field at the Earth’s surface and interior. The geoelectric field in turn drives geomagnetically induced currents, also called telluric currents along electrically conductive technological networks, such as power transmission lines, railways, and pipelines [38]. This geomagnetically induced currents create conditions where enhanced corrosion may occur. Earth conductivity can create geomagnetically induced current variations, in particular where a pipeline crosses a highly resistive intrusive rock. It is important to make pipeline surveys once a year to measure the voltage at test posts to ensure that pipe-to-soil potential variations are within the safe range, impressed by cathodic protection systems [38].
\nAuthors are listed below with their open access chapters linked via author name:
",metaTitle:"IntechOpen authors on the Global Highly Cited Researchers 2018 list",metaDescription:null,metaKeywords:null,canonicalURL:null,contentRaw:'[{"type":"htmlEditorComponent","content":"New for 2018 (alphabetically by surname).
\\n\\n\\n\\n\\n\\n\\n\\n\\n\\nJocelyn Chanussot (chapter to be published soon...)
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\\n\\nKhalil Amine 2017, 2018
\\n\\nEwan Birney 2015-18
\\n\\nFrede Blaabjerg 2015-18
\\n\\nGang Chen 2016-18
\\n\\nJunhong Chen 2017, 2018
\\n\\nZhigang Chen 2016, 2018
\\n\\nMyung-Haing Cho 2016, 2018
\\n\\nMark Connors 2015-18
\\n\\nCyrus Cooper 2017, 2018
\\n\\nLiming Dai 2015-18
\\n\\nWeihua Deng 2017, 2018
\\n\\nVincenzo Fogliano 2017, 2018
\\n\\nRon de Graaf 2014-18
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\\n\\nFrancisco Herrera 2017, 2018
\\n\\nJaakko Kangasjärvi 2015-18
\\n\\nHamid Reza Karimi 2016-18
\\n\\nJunji Kido 2014-18
\\n\\nJose Luiszamorano 2015-18
\\n\\nYiqi Luo 2016-18
\\n\\nJoachim Maier 2014-18
\\n\\nAndrea Natale 2017, 2018
\\n\\nAlberto Mantovani 2014-18
\\n\\nMarjan Mernik 2017, 2018
\\n\\nSandra Orchard 2014, 2016-18
\\n\\nMohamed Oukka 2016-18
\\n\\nBiswajeet Pradhan 2016-18
\\n\\nDirk Raes 2017, 2018
\\n\\nUlrike Ravens-Sieberer 2016-18
\\n\\nYexiang Tong 2017, 2018
\\n\\nJim Van Os 2015-18
\\n\\nLong Wang 2017, 2018
\\n\\nFei Wei 2016-18
\\n\\nIoannis Xenarios 2017, 2018
\\n\\nQi Xie 2016-18
\\n\\nXin-She Yang 2017, 2018
\\n\\nYulong Yin 2015, 2017, 2018
\\n"}]'},components:[{type:"htmlEditorComponent",content:'New for 2018 (alphabetically by surname).
\n\n\n\n\n\n\n\n\n\nJocelyn Chanussot (chapter to be published soon...)
\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\nYuekun Lai
\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\nPrevious years (alphabetically by surname)
\n\nAbdul Latif Ahmad 2016-18
\n\nKhalil Amine 2017, 2018
\n\nEwan Birney 2015-18
\n\nFrede Blaabjerg 2015-18
\n\nGang Chen 2016-18
\n\nJunhong Chen 2017, 2018
\n\nZhigang Chen 2016, 2018
\n\nMyung-Haing Cho 2016, 2018
\n\nMark Connors 2015-18
\n\nCyrus Cooper 2017, 2018
\n\nLiming Dai 2015-18
\n\nWeihua Deng 2017, 2018
\n\nVincenzo Fogliano 2017, 2018
\n\nRon de Graaf 2014-18
\n\nHarald Haas 2017, 2018
\n\nFrancisco Herrera 2017, 2018
\n\nJaakko Kangasjärvi 2015-18
\n\nHamid Reza Karimi 2016-18
\n\nJunji Kido 2014-18
\n\nJose Luiszamorano 2015-18
\n\nYiqi Luo 2016-18
\n\nJoachim Maier 2014-18
\n\nAndrea Natale 2017, 2018
\n\nAlberto Mantovani 2014-18
\n\nMarjan Mernik 2017, 2018
\n\nSandra Orchard 2014, 2016-18
\n\nMohamed Oukka 2016-18
\n\nBiswajeet Pradhan 2016-18
\n\nDirk Raes 2017, 2018
\n\nUlrike Ravens-Sieberer 2016-18
\n\nYexiang Tong 2017, 2018
\n\nJim Van Os 2015-18
\n\nLong Wang 2017, 2018
\n\nFei Wei 2016-18
\n\nIoannis Xenarios 2017, 2018
\n\nQi Xie 2016-18
\n\nXin-She Yang 2017, 2018
\n\nYulong Yin 2015, 2017, 2018
\n'}]},successStories:{items:[]},authorsAndEditors:{filterParams:{sort:"featured,name"},profiles:[{id:"289905",title:"Dr.",name:null,middleName:null,surname:"Inamuddin",slug:"inamuddin",fullName:"Inamuddin",position:null,profilePictureURL:"https://mts.intechopen.com/storage/users/289905/images/system/289905.jpeg",biography:"Dr. Inamuddin is currently working as an assistant professor in the Chemistry Department, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia. He has extensive research experience in multidisciplinary fields of analytical chemistry, materials chemistry, electrochemistry, and more specifically, renewable energy and the environment. He has published 127 research articles in international journals of repute and 18 book chapters in knowledge-based book editions published by renowned international publishers. He has published 39 edited books with Springer, United Kingdom, Elsevier, Nova Science Publishers, Inc. USA, CRC Press Taylor & Francis, Asia Pacific, Trans Tech Publications Ltd., Switzerland, and Materials Science Forum, USA. He is a member of various editorial boards serving as associate editor for journals such as Environmental Chemistry Letter, Applied Water Science, Euro-Mediterranean Journal for Environmental Integration, Springer-Nature, Scientific Reports-Nature, and the editor of Eurasian Journal of Analytical Chemistry.",institutionString:"King Abdulaziz University",institution:{name:"King Abdulaziz University",country:{name:"Saudi Arabia"}}},{id:"99002",title:"Dr.",name:null,middleName:null,surname:"Koontongkaew",slug:"koontongkaew",fullName:"Koontongkaew",position:null,profilePictureURL:"//cdnintech.com/web/frontend/www/assets/author.svg",biography:null,institutionString:null,institution:{name:"Thammasat University",country:{name:"Thailand"}}},{id:"156647",title:"Dr.",name:"A K M Mamunur",middleName:null,surname:"Rashid",slug:"a-k-m-mamunur-rashid",fullName:"A K M Mamunur Rashid",position:null,profilePictureURL:"//cdnintech.com/web/frontend/www/assets/author.svg",biography:"MBBS, DCH, MD(Paed.), Grad. Cert. P. Rheum.(UWA, Australia), FRCP(Edin.)",institutionString:null,institution:{name:"Khulna Medical College",country:{name:"Bangladesh"}}},{id:"234696",title:"Prof.",name:"A K M Mominul",middleName:null,surname:"Islam",slug:"a-k-m-mominul-islam",fullName:"A K M Mominul Islam",position:null,profilePictureURL:"https://intech-files.s3.amazonaws.com/a043Y00000cA8dpQAC/Co2_Profile_Picture-1588761796759",biography:"Prof. Dr. A. K. M. Mominul Islam received both of his bachelor's and Master’s degree from Bangladesh Agricultural University. After that, he joined as Lecturer of Agronomy at Bangladesh Agricultural University (BAU), Mymensingh, Bangladesh, and became Professor in the same department of the university. Dr. Islam did his second Master’s in Physical Land Resources from Ghent University, Belgium. He is currently serving as a postdoctoral researcher at the Department of Horticulture & Landscape Architecture at Purdue University, USA. Dr. Islam has obtained his Ph.D. degree in Plant Allelopathy from The United Graduate School of Agricultural Sciences, Ehime University, Japan. The dissertation title of Dr. Islam was “Allelopathy of five Lamiaceae medicinal plant species”. Dr. Islam is the author of 38 articles published in nationally and internationally reputed journals, 1 book chapter, and 3 books. He is a member of the editorial board and referee of several national and international journals. He is supervising the research of MS and Ph.D. students in areas of Agronomy. Prof. Islam is conducting research on crop management, bio-herbicides, and allelopathy.",institutionString:"Bangladesh Agricultural University",institution:{name:"Bangladesh Agricultural University",country:{name:"Bangladesh"}}},{id:"214531",title:"Mr.",name:"A T M Sakiur",middleName:null,surname:"Rahman",slug:"a-t-m-sakiur-rahman",fullName:"A T M Sakiur Rahman",position:null,profilePictureURL:"//cdnintech.com/web/frontend/www/assets/author.svg",biography:null,institutionString:null,institution:{name:"University of Rajshahi",country:{name:"Bangladesh"}}},{id:"66545",title:"Dr.",name:"A. F.",middleName:null,surname:"Omar",slug:"a.-f.-omar",fullName:"A. F. Omar",position:null,profilePictureURL:"//cdnintech.com/web/frontend/www/assets/author.svg",biography:"Dr. A. F. Omar obtained\nhis Bachelor degree in electrical and\nelectronics engineering from Universiti\nSains Malaysia in 2002, Master of Science in electronics\nengineering from Open University\nMalaysia in 2008 and PhD in optical physics from Universiti\nSains Malaysia in 2012. His research mainly\nfocuses on the development of optical\nand electronics systems for spectroscopy\napplication in environmental monitoring,\nagriculture and dermatology. He has\nmore than 10 years of teaching\nexperience in subjects related to\nelectronics, mathematics and applied optics for\nuniversity students and industrial engineers.",institutionString:null,institution:{name:"Universiti Sains Malaysia",country:{name:"Malaysia"}}},{id:"191072",title:"Prof.",name:"A. K. M. Aminul",middleName:null,surname:"Islam",slug:"a.-k.-m.-aminul-islam",fullName:"A. K. M. Aminul Islam",position:null,profilePictureURL:"https://mts.intechopen.com/storage/users/191072/images/system/191072.jpg",biography:"Prof. Dr. A. K. M. Aminul Islam received both of his bachelor and Master’s degree from Bangladesh Agricultural University. After that he joined as Lecturer of Genetics and Plant Breeding at Bangabandhu Sheikh Mujibur Rahman Agricultural University (BSMRAU), Gazipur, Bangladesh and became Professor in the same department of the university. He is currently serving as Director (Research) of Bangabandhu Sheikh Mujibur Rahman Agricultural University (BSMRAU), Gazipur, Bangladesh. Dr. Islam has obtained his Ph D degree in Chemical and Process Engineering from Universiti Kebangsaan Malaysia. The dissertation title of Dr. Islam was “Improvement of Biodiesel Production through Genetic Studies of Jatropha (Jatropha curcas L.)”. Dr. Islam is the author of 98 articles published in nationally and internationally reputed journals, 11 book chapters and 3 books. He is a member of editorial board and referee of several national and international journals. He is also serving as the General Secretary of Plant Breeding and Genetics Society of Bangladesh, Seminar and research Secretary of JICA Alumni Association of Bangladesh and member of several professional societies. Prof. Islam acted as Principal Breeder in the releasing system of BU Hybrid Lau 1, BU Lau 1, BU Capsicum 1, BU Lalshak 1, BU Baromashi Seem 1, BU Sheem 1, BU Sheem 2, BU Sheem 3 and BU Sheem 4. He supervised 50 MS and 3 Ph D students. Prof. Islam currently supervising research of 5 MS and 3 Ph D students in areas Plant Breeding & Seed Technologies. Conducting research on development of hybrid vegetables, hybrid Brassica napus using CMS system, renewable energy research with Jatropha curcas.",institutionString:"Bangabandhu Sheikh Mujibur Rahman Agricultural University",institution:{name:"Bangabandhu Sheikh Mujibur Rahman Agricultural University",country:{name:"Bangladesh"}}},{id:"322225",title:"Dr.",name:"A. K. M. Aminul",middleName:null,surname:"Islam",slug:"a.-k.-m.-aminul-islam",fullName:"A. K. M. Aminul Islam",position:null,profilePictureURL:"https://mts.intechopen.com/storage/users/no_image.jpg",biography:"Prof. Dr. A. K. M. Aminul Islam received both of his bachelor's and Master’s degree from Bangladesh Agricultural University. After that he joined as Lecturer of Genetics and Plant Breeding at Bangabandhu Sheikh Mujibur Rahman Agricultural University (BSMRAU), Gazipur, Bangladesh, and became Professor in the same department of the university. He is currently serving as Director (Research) of Bangabandhu Sheikh Mujibur Rahman Agricultural University (BSMRAU), Gazipur, Bangladesh. Dr. Islam has obtained his Ph.D. degree in Chemical and Process Engineering from Universiti Kebangsaan Malaysia. The dissertation title of Dr. Islam was 'Improvement of Biodiesel Production through Genetic Studies of Jatropha (Jatropha curcas L.)”. Dr. Islam is the author of 99 articles published in nationally and internationally reputed journals, 11 book chapters, 3 books, and 20 proceedings and conference paper. He is a member of the editorial board and referee of several national and international journals. He is also serving as the General Secretary of Plant Breeding and Genetics Society of Bangladesh, Seminar, and research Secretary of JICA Alumni Association of Bangladesh and a member of several professional societies. Prof. Islam acted as Principal Breeder in the releasing system of BU Hybrid Lau 1, BU Lau 1, BU Capsicum 1, BU Lalshak 1, BU Baromashi Seem 1, BU Sheem 1, BU Sheem 2, BU Sheem 3 and BU Sheem 4. He supervised 50 MS and 3 PhD students. Prof. Islam currently supervising the research of 5 MS and 3 PhD students in areas Plant Breeding & Seed Technologies. Conducting research on the development of hybrid vegetables, hybrid Brassica napus using CMS system, renewable energy research with Jatropha curcas.",institutionString:"Bangabandhu Sheikh Mujibur Rahman Agricultural University",institution:{name:"Bangabandhu Sheikh Mujibur Rahman Agricultural University",country:{name:"Bangladesh"}}},{id:"91977",title:"Dr.",name:"A.B.M. Sharif",middleName:null,surname:"Hossain",slug:"a.b.m.-sharif-hossain",fullName:"A.B.M. Sharif Hossain",position:null,profilePictureURL:"//cdnintech.com/web/frontend/www/assets/author.svg",biography:null,institutionString:null,institution:{name:"University of Malaya",country:{name:"Malaysia"}}},{id:"97123",title:"Prof.",name:"A.M.M.",middleName:null,surname:"Sharif Ullah",slug:"a.m.m.-sharif-ullah",fullName:"A.M.M. Sharif Ullah",position:null,profilePictureURL:"https://mts.intechopen.com/storage/users/97123/images/4209_n.jpg",biography:"AMM Sharif Ullah is currently an Associate Professor of Design and Manufacturing in Department of Mechanical Engineering at Kitami Institute of Technology, Japan. He received the Bachelor of Science Degree in Mechanical Engineering in 1992 from the Bangladesh University of Engineering and Technology, Dhaka, Bangladesh. In 1993, he moved to Japan for graduate studies. He received the Master of Engineering degree in 1996 from the Kansai University Graduate School of Engineering in Mechanical Engineering (Major: Manufacturing Engineering). He also received the Doctor of Engineering degree from the same institute in the same field in 1999. He began his academic career in 2000 as an Assistant Professor in the Industrial Systems Engineering Program at the Asian Institute of Technology, Thailand, as an Assistant Professor in the Industrial Systems Engineering Program. 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