Research Trends and Challenges in Physical Science Vol. 5

The general scheme of heat-to-electric power conversion in closed thermally inhomogeneous heterogeneous flow with constantly renewable local imbalance is considered. Conversion system comprises high-speed motor-generator rigidly coupled with propulsor. Propulsor has the form of rotating vessel containing liquid phase of working substance. Nozzles are installed on it to discharge liquid into closed volume filled with gas. The jet of working substance leaving the propulsor under the action of high pressure due to centrifugal forces is directed in the opposite direction of rotation of the generator, but its phase composition and other thermodynamic parameters are not determined. The transition of the working substance from the propulsor to the closed volume goes beyond equilibrium thermodynamics. Motion energy of each element of working substance mass leaving the propulsor is supplied to electric power generation. The rapid transition of the accelerated compressed liquid to the low gas pressure region and its shutdown lead to "self-cooling" of the working substance.

This paper addresses the issues of nonlinearity and coupling between anode pressure and cathode pressure in proton exchange membrane fuel cell (PEMFC) gas supply systems. A fuzzy adaptive PI decoupling control strategy with an improved advanced genetic algorithm (AGA) is proposed. This AGA s utilized to optimize the PI parameters offline, and the fuzzy adaptive algorithm s used to adjust the PI parameters dynamically online to achieve the approximate decoupling control of the PEMFC gas supply system. According to the proposed dynamic model, the PEMFC gas supply system with the fuzzy–AGA–PI decoupling control method was simulated for comparison. The simulation results demonstrate that the proposed control system can reduce the pressure difference more efficiently with the classical control method under different load changes.

A simple empirical relationship has been proposed to estimate the bulk modulus (B) of ternary chalcopyrite structure solids of I-II-VI, II-IV-V type from the electronegativities of the constituent atoms and the principal quantum number of the compounds. The current relationship is based on a model of chemical bonding. The chemical bonding of constituent atoms of compounds is determined by electronegativity and principal quantum number. Chemical bonding is the beginning point for a compound's stability, which is based on the minimal energy principle. The nature of material bonding was correlated with ground state properties such as bulk modulus in this study. The bonding of ternary chalcopyrite structure solids is well explained by the combination of electronegativity and main quantum number. These two metrics are a good indicator of chalcopyrite structure solids' structural stability. The computed bulk modulus values are found to be in good agreement with known values, and a comparison of our current results to those in the literature is also provided. In the present study, it is found that electronegativity and average principal quantum number which expresses the nature of bonding in chalcopyrites.

The simplest model of a metal is considered: a homogeneous, positively charged background and an electron liquid filling the same volume with the same average charge density. This article examines the response of an e-liquid to large-scale inhomogeneity’s created by external causes. Using two inhomogeneity’s as an example: the outer boundary of a positive background and a uniform magnetic field throughout the volume, it is shown that the electron liquid screens the inhomogeneity, transforming it into an exponential potential at the boundary. The exponential parameter is determined by the average charge density and is significantly less than the sample size. Some properties of the energy spectrum of the exponential well are proved. This made it possible to explain the laws of the photoelectric effect, to determine the energy dependence of the density of states of elementary excitations of an electron liquid in a magnetic field. The electric field created by the inhomogeneous density distribution of the electron liquid should affect the phenomena in the ionic lattice.

The multiple-resonator (MR) filter structure has been proposed in previous works as a convenient approach to the dynamic harmonic analysis.  This method, by using a parallel structure with common feedback, is very robust and, in addition, allows a reduction of the computational burden. The objective of this article is to determine the design algorithms which simultaneously assure: i) the quasi-equiripple minimax frequency response in stopband(s), ii) the wide flat-top amplitude response in the passband, and iii) the reduced group delay, which is often requested in standards. In this article, an optimized postprocessing compensation filters are applied to obtain the desired frequency responses convenient for fast measurements in the dynamic conditions. A linear-programming-based optimization design method is applied. This way, both the flatness in the passband and the attenuation in the stopband are significantly improved simultaneously. Three different optimization criteria are formulated, and design examples with obtained results are presented. The proposed method has been investigated for up to 64 harmonics, under different conditions, and confirmed to be valuable and efficient tool for harmonic components estimation.

Earlier we concluded, that RSA (reverse saturable absorption) is the main mechanism of optical limiting in CdSe/ZnS QDs by nanosecond pulses acting, which is accompanied by " light quenching " simultaneously . The reduction of the pulse duration fundamentally changes the limiting kinetics and OL mechanisms [1,2,3]. Free carriers absorption became significant in the case of ps-pulses and intense light. We present, that in the case of picosecond durations, the limitation efficiency of laser radiation and absorption kinetics in CdSe/ZnS colloidal solutions are determined by the Auger relaxation through the 1S(e) states. A "delayed limitation" effect has been identified in the measured kinetics of a probe-pulse transmission. The competition between the following two relaxation processes of highly excited states, relaxing through size quantization levels and phononless relaxation through traps states, has been identified using numerical modelling.

When there is a temporary disturbance of earth’s magnetosphere, then a geomagnetic storm (or solar storm) has occurred. It is caused by a solar wind shock wave and/or cloud of a magnetic field that interacts with the Earth's magnetic fields. The interaction of Interplanetary Magnetic Fields (IMF) of the sun with the earth’s magnetic fields in opposite directions is known as magnetic reconnection (Yousif, 2014). Magnetic reconnection (often referred as "reconnection") is the breaking and reconnecting of oppositely directed magnetic field lines in plasma at a neutral point which leads to converting the magnetic field energy into plasma kinetic and thermal energy. It occurs either in the day-time (day reconnection) where the sunward convection near the polar cusps allows energised particles to be transmitted earthward or night-time (tail reconnection) where particles injected into the magnetosphere are saturated, thus releasing stored energy in the form of auroral substorms. Sokolov (2011) suggested that a geomagnetic storm can be determined by changes in the Disturbed-storm time (Dst). However, not all geomagnetic storms have an initial phase and not all sudden increase in Dst or SYM-H are followed by a geomagnetic storm. This paper attempts to determine what are responsible for magnetic reconnections in the solar cycle 24 considering a low solar activity year 2009 and a high solar activity year 2012. We have to classify the geomagnetic storms using the Dst indices and rearrange the IMF Bz according to its negative, neutral and positive values. We measured the correlation between Bz and solar wind using a 1-min resolution OMNIweb dataset. Thereafter, establish the factors responsible for magnetic reconnections. We analysed 39 and 202 geomagnetic storms in 2009 and 2012 respectively considering the Dst indices and IMF Bz values of each month obtained from the OMNIWeb Database. Our results showed that geomagnetic storms occurred in 10% and 45% of days in the year 2009 and 2012 respectively which implies they were frequent and intense due to high solar activity caused by the frequent occurrence of coronal mass ejections (CMEs) and interplanetary coronal mass ejections (ICMEs) in the year 2012 than in the year 2009. This study also revealed that negative Bz occurrences were 47.54% and 52.18% in 2009 and 2012 respectively. Thus, the more intense the geomagnetic storms, the more Bz would go south and the more magnetic reconnections and subsequently auroral substorms which can increase radiation doses for occupants of transpolar flights, disruption of shortwave radio communications, distortion of compass readings in polar regions, failure of electrical transmission lines, increased corrosion in long pipelines, anomalies in the operations of communications satellites, and potentially lethal dosages of radiation for astronauts in interplanetary spacecraft.

One of the compounds that can be developed as raw material for drugs or excipients is carrageenan which can be obtained from the red algae Kappaphycus alvarezii. This species of red algae was chosen as the object of research because in addition to its high carrageenan content, this species is easily found in the waters of South Sulawesi Indonesia. This research was started with collecting, washing and processing the red algae, then carrageenan extraction was carried out using the modified extraction method. The calculation results repeatability and reproducibility show that the %RSD of both does not exceed 3%, therefore the carrageenan extraction method using technical ethanol precipitator and pro-analytical ethanol meets the requirements repeatability and reproducibility precision because it meets the Horwitz standard, which is a maximum RSD of 3%. The extracted products were separated, purified and dried to obtain carrageenan raw materials. Then, the products were analyzed physically and chemically, and also using spectrophotometry and chromatography to ensure that carrageenan obtained meets the quality standards as excipient raw materials in pharmaceutical preparations. The results obtained were that Kappaphycus alvarezii red algae raw material fulfil the quality of the Indonesian National Standard (SNI) and carrageenan produced meet the quality standards of carrageenan according to Food Agriculture Organization (FAO), Food Chemicals Codex (FCC) and European Economic Community (EEC).

During last couple of decades, a number of researchers have been involved in discovering advanced oxide materials that possess multiferroic properties at room temperature for multifunctional applications. In this book chapter, our objective is to review the growth and characterization of palladium doped PbPd_0.3Ti_0.7O₃ (PT-Pd) single phase room temperature multiferroic thin films. Earlier Pd-doped Pb (Zr_0.20Ti_0.80)_0.70O₃ materials were first investigated in ceramic forms in our laboratory at the university of Puerto Rico by Shalini et. al. [1]. Thin films were grown, employing pulse laser deposition technique, and were characterized for their structure, magnetization, and ferroelectric properties. Highly (001) oriented PT-Pd thin films were deposited on (LaAlO₃)_0.3(Sr₂AlTaO₆)_0.7 (LSAT) substrates with or without thin bottom layer of La_0.7Sr_0.3MnO₃ (LSMO) utilizing laser ablation processes in oxygen atmosphere. For magnetic measurements, PT-Pd deposited on LSAT substrate was used to avoid any contribution from LSMO. However, for piezo force microscopy and ferroelectric measurements, PT-Pd thin films deposited on LSMO/LSAT were chosen with LSMO as bottom electrode. Saturated magnetization M-H loops with remanent magnetization of 3.4 emu.cm^-3 and coercive field Hc of 114.5 Oe were obtained at 300 K, and PT-Pd retained the ferromagnetic ordering in the entire temperature range from 5-500 K. The origin of magnetization in the films were ascribed to Pd²⁺ and Pd⁴⁺ cations dispersed in polar PbTiO₃ ferroelectric matrix. Ferroelectric ordering in the thin films was inferred from the strong domain switching responses in its phase and amplitude image contrasts. Experimentally, our results showed that PT-Pd thin films were ferroelectric and ferromagnetic (multiferroic) at room temperature.

Density fluctuations in the early universe provide the initial seeds for the structures we see today. These small initial density fluctuations lead to galaxy clusters up to about 10¹⁵h-¹M_\(\odot\) at present. Knowledge of both the shape and amplitude of the fluctuation spectrum is needed before critical cosmological implications can be derived. The mass function of galaxy clusters is a powerful tool to determine the cosmological parameters, e.g., the mass fluctuation on the scale of 8h^-1Mpc (denoted by \(\sigma\)₈) . The determination of modern cosmological parameters dates back to Hubble’s discovery of the expansion of the Universe (1929). But their number increased during the late 1980s with the introduction of what is often referred to as the Standard Cosmological Model. These parameters also allow us to track the history of the Universe, back to an epoch of interchanges between the densities of the different species, believed to have last happened at neutrino decoupling, before Big-Bang Nucleosynthesis. This paper presents a new analytical method to determine amplitude of density fluctuations of 152 nearby clusters (Z\(\le\)0.15). We investigate the rms linear fluctuation in the mass distribution on scales of 8h^-1Mpc i.e.\(\sigma\)₈ , by using Press-Shechter mass function. The mass function is estimated for masses larger than M_lim=4X10¹⁴h^-1M_{\(\curvearrowright\)} . We find rms density fluctuation equal to 0.52 for the critical density universe. The results found are consistent with those, obtained with alternative models for the high density universe. The results agree with the previous papers obtained from different models and considerations. It is interesting to note that the recent results by Planck Collaboration have also shown that the cosmological parameters derived from cluster number counts prefer lower values of the matter density parameter \(\omega\)_m and power spectrum amplitude \(\sigma\)₈ This takes us to introduce a new approach to estimate the cosmological parameters. For critical density, the slight variation in results may be due to the fact that there are observational uncertainties in estimates of cluster masses, which are in general not negligible.

The objective is to study the health implication of using graphene which may be either good or bad. This study will review of risk-related information on graphene with the purpose of outlining potential environmental and health risks. It is a guide to future risk-related research on graphene. The study will be based on the emissions, environmental fate, and toxicity of graphene. It shows that graphene could exert a considerable toxicity, emission of graphene from electronic devices and composites are possible in the future. It is known that graphene is both persistent and hydrophobic. Although these results indicate that graphene may cause adverse environmental and health effects, and that there are many risk-related knowledges gaps to be filled with the environment. Graphene can bind the cell surface and cause physical and chemical damage to the cell membrane. It is known that graphene may interact with protein and nucleic acids, altering their structure and function on the other hand, graphene may regenerate reactive oxygen species (ROS) which can also cause disruption of membrane, lipids, proteins and nucleic acids. The toxicity of graphene should be further studied.

The series of the glasses with general formula (40-x)Li₂O:30B₂O₃:30Bi₂O₃:xV₂O_5, with x = 0, 0.5, 1.0, 1.5 and 2.0 mol%  was prepared using conventional quenching technique. The glass transition temperature T_g for these samples were determined from Differential Thermal Analysis. The glass transition temperature increases beyond 0.5 mol%. It was found that the glasses under study consist of randomly connected BO₃ & BO₄ structural units. The density and molar volume of glasses were found to depend on V₂O₅ content. Initially the density increases, molar volume and glass transition temperature decrease with the addition of V₂O_5. This suggests that when V₂O₅ is added to the glass initially up to 0.5 mol% it may be entering as a modifier. Beyond 0.5 mol% density decreases and molar volume increases as V₂O₅ goes as former. This reveals the role of V₂O₅ as a glass network former beyond 0.5 mol%. Optical band gap energy decreases and cut off wavelength increases with increase in V₂O₅ content. Author wish to study the effect of transition metals on the optical properties of the lithium bismuth borate glasses

The aim of the study is the motion dynamics analysis of a parametrically excited micromechanical gyroscope and exploration of the possibility of its use as a ground-based precision device for orienting mobile objects. A mathematical model of the microelectromechanical system (MEMS) has obtained, which performs the task of orienting mobile objects. A distinctive feature of the construction of such MEMS is its parametric excitation by modulating the static stiffness of the suspension of the sensitive element. Based on the analysis of model equations, the possibility of determining the direction of the true meridian with the required accuracy has shown. The results of numerical calculations have presented that allow not only to illustrate the operation of the device as a high-speed gyrocompass, but also to determine the conditions that ensure the stable operation of the device in the incoherent mode of its excitation.