Search results for: successive approximation register analog-to-digital converter

Authors: Fatima Muhammad Shitu

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This study seeks to investigate the effect of the keyword strategy on lexico–semantic acquisition, recognition, retention and comprehension in an ESL context. The aim of the study is to determine whether the keyword strategy can be used to enhance acquisition. As a quasi- experimental research, the objectives of the study include: To determine the extent to which the scores obtained by the subjects, who were trained on the use of the keyword strategy for acquisition, differ at the pre-tests and the post–tests and also to find out the relationship in the scores obtained at these tests levels. The sample for the study consists of 300 hundred undergraduate ESL Students in the Federal College of Education, Kano. The seventy-five lexical items for acquisition belong to the lexical field category known as register, and they include Medical, Agriculture and Photography registers (MAP). These were divided in the ratio twenty-five (25) lexical items in each lexical field. The testing technique was used to collect the data while the descriptive and inferential statistics were employed for data analysis. For the purpose of testing, the two kinds of tests administered at each test level include the WARRT (Word Acquisition, Recognition, and Retention Test) and the CCPT (Cloze Comprehension Passage Test). The results of the study revealed that there are significant differences in the scores obtained between the pre-tests, and the post–tests and there are no correlations in the scores obtained as well. This implies that the keyword strategy has effectively enhanced the acquisition of the lexical items studied.

Keywords: keyword, lexical, semantics, strategy

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Authors: Samah Said, Muhsin Elie Rahhal

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Due to the COVID-19 pandemic, disposable plastic-based face masks were excessively used worldwide. Therefore, the production and consumption rates of these masks were significantly brought up, which led to severe environmental problems. The main purpose of this research is to test the possibility of reinforcing soil deposits with mask fibers to reuse pandemic-generated waste materials. When testing the compaction properties, the sand was reinforced with a fiber content that increased from 0% to 0.5%, with successive small increments of 0.1%. The optimum content of 0.1% remarkably increased the maximum dry density of the soil and dropped its optimum moisture content. Add to that, it was noticed that 15 mm and rectangular chips were, respectively, the optimum fiber length and shape to maximize the improvement of the sand compaction properties. Regarding the shear strength, fiber contents of 0.1%, 0.25%, and 0.5% were adopted. The direct shear tests have shown that the highest enhancement was observed for the optimum fiber content of 0.25%. Similarly to compaction tests, 15 mm and rectangular chips were respectively the optimum fiber length and shape to extremely enhance the shear resistance of the tested sand.

Keywords: COVID-19, mask fibers, compaction properties, soil reinforcement, shear resistance

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Authors: Venkata Reddy Kota

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These days, the industrial trend is moving away from heavy and bulky passive components to power converter systems that use more and more semiconductor elements. Also, it is difficult to connect the traditional converters to the high and medium voltage. For these reasons, a new family of multilevel inverters has appeared as a solution for working with higher voltage levels. Different modulation topologies like Sinusoidal Pulse Width Modulation (SPWM), Selective Harmonic Elimination Pulse Width Modulation (SHE-PWM) are available for multilevel inverters. In this work, different hybrid modulation techniques which are combination of fundamental frequency modulation and multilevel sinusoidal-modulation are compared. The main characteristic of these modulations are reduction of switching losses with good harmonic performance and balanced power loss dissipation among the device. The proposed hybrid modulation schemes are developed and simulated in Matlab/Simulink for cascaded H-bridge inverter. The results validate the applicability of the proposed schemes for cascaded multilevel inverter.

Keywords: hybrid PWM techniques, cascaded multilevel inverters, switching loss minimization

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Authors: Kadda Amara, Mohammed Elkeurti, Mostefa Zemouli, Yassine Benallou

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In this work, we present a study of the structural, elastic and electronic properties of the cubic antiperovskites XNMg3 (X=P, As, Sb and Bi) using the full-potential augmented plane wave plus local orbital (FP-LAPW+lo) within the Generalized Gradient Approximation based on PBEsol, Perdew 2008 functional. We determined the lattice parameters, the bulk modulus B and their pressure derivative B'. In addition, the elastic properties such as elastic constants (C11, C12 and C44), the shear modulus G, the Young modulus E, the Poisson's ratio ν and the B/G ratio are also given. For the band structure, density of states and charge density the exchange and correlation effects were treated by the Tran-Blaha modified Becke-Johnson potential to prevent the shortcoming of the underestimation of the energy gaps in both LDA and GGA approximations. The obtained results are compared to available experimental data and to other theoretical calculations.

Keywords: XNMg3 compounds, GGA-PBEsol, TB-mBJ, elastic properties, electronic properties

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Authors: Jamal Hussain Al-Smail

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Hydrogen fuel cells (HFCs) are environmentally friendly, energy converter devices that convert the chemical energy of the reactants (oxygen and hydrogen) to electricity through electrochemical reactions. The level of the electricity production of HFCs mainly increases depending on the oxygen distribution in the HFC’s cathode gas diffusion layer (GDL). With a constant porosity of the GDL, the electrochemical reaction can have a great variation that reduces the cell’s productivity and stability. Our findings bring a methodology in finding porosity designs of the diffusion layer to improve the oxygen distribution such that it results in a stable oxygen-hydrogen reaction. We first introduce a mathematical model involving the mass and momentum transport equations, in which a porosity function of the GDL is incorporated as a control for the fluid flow. We then derive numerical methods for solving the mathematical model. In conclusion, we present our numerical results to show how to design the GDL porosity to result in a uniform oxygen distribution.

Keywords: fuel cells, material porosity design, mathematical modeling, porous media

Procedia PDF Downloads 138

Authors: N. R. Mohamad, H. Ono, H. Haroon, A. Salleh, N. M. Z. Hashim

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In this research, we have studied and analyzed the modulation of light and liquid crystal in HPDLCs using Finite Domain Time Difference (FDTD) method. HPDLCs are modeled as a mixture of polymer and liquid crystals (LCs) that categorized as an anisotropic medium. FDTD method is directly solves Maxwell’s equation with less approximation, so this method can analyze more flexible and general approach for the arbitrary anisotropic media. As the results from FDTD simulation, the highest diffraction efficiency occurred at ±19 degrees (Bragg angle) using p polarization incident beam to Bragg grating, Q > 10 when the pitch is 1µm. Therefore, the liquid crystal is assumed to be aligned parallel to the grating constant vector during these parameters.

Keywords: birefringence, diffraction efficiency, finite domain time difference, nematic liquid crystals

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Authors: Hicham Salhi

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This research project focuses on the numerical investigation of the mixed convection of Hybrid nanofluids in a round bottom flask commonly used in organic chemistry synthesis. The aim of this study is to improve the thermal properties of the reaction medium and enhance the rate of chemical reactions by using hybrid nanofluids. The flat bottom wall of the flask is maintained at a constant high temperature, while the top, left, and right walls are kept at a low temperature. The nanofluids used in this study contain suspended Cu and Al2O3 nanoparticles in pure water. The governing equations are solved numerically using the finite-volume approach and the Boussinesq approximation. The effects of the volume fraction of nanoparticles (φ) ranging from 0% to 5%, the Rayleigh number from 103 to 106, and the type of nanofluid (Cu and Al2O3) on the flow streamlines, isotherm distribution, and Nusselt number are examined in the simulation. The results indicate that the addition of Cu and Al2O3 nanoparticles increases the mean Nusselt number, which improves heat transfer and significantly alters the flow pattern. Moreover, the mean Nusselt number increases with increasing Rayleigh number and volume fraction, with Cu- Al2O3 hybrid nanofluid producing the best results. This research project focuses on the numerical investigation of the mixed convection of Hybrid nanofluids in a round bottom flask commonly used in organic chemistry synthesis. The aim of this study is to improve the thermal properties of the reaction medium and enhance the rate of chemical reactions by using hybrid nanofluids. The flat bottom wall of the flask is maintained at a constant high temperature, while the top, left, and right walls are kept at a low temperature. The nanofluids used in this study contain suspended Cu and Al2O3 nanoparticles in pure water. The governing equations are solved numerically using the finite-volume approach and the Boussinesq approximation. The effects of the volume fraction of nanoparticles (φ) ranging from 0% to 5%, the Rayleigh number from 103 to 106, and the type of nanofluid (Cu and Al2O3) on the flow streamlines, isotherm distribution, and Nusselt number are examined in the simulation. The results indicate that the addition of Cu and Al2O3 nanoparticles increases the mean Nusselt number, which improves heat transfer and significantly alters the flow pattern. Moreover, the mean Nusselt number increases with increasing Rayleigh number and volume fraction, with Cu- Al2O3 hybrid nanofluid producing the best results.

Keywords: bottom flask, mixed convection, hybrid nanofluids, numerical simulation

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Authors: Maxim A. Kadatskiy, Konstantin V. Khishchenko

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Iron alloys are widespread components in various types of structural materials which are exposed to intensive thermal and mechanical loads. Various quantum-statistical cell models with the approximation of self-consistent field can be used for the prediction of the behavior of these materials under extreme conditions. The application of these models is even more valid, the higher the temperature and the density of matter. Results of Hugoniot calculation for iron alloys in the framework of three quantum-statistical (the Thomas–Fermi, the Thomas–Fermi with quantum and exchange corrections and the Hartree–Fock–Slater) models are presented. Results of quantum-statistical calculations are compared with results from other reliable models and available experimental data. It is revealed a good agreement between results of calculation and experimental data for terra pascal pressures. Advantages and disadvantages of this approach are shown.

Keywords: alloy, Hugoniot, iron, terapascal pressure

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Authors: A.Zitouni, S.Bentata, B.Bouadjemi, T.Lantri, W. Benstaali, Z.Aziz, S.Cherid, A. Sefir

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Using the first-principles method, we investigate the structural, electronic, and magnetic properties of the diluted magnetic semiconductors CdCoTe and CdMnTe in the zinc blende phase with 12.5% of Cr. The calculations are performed by a developed full potential augmented plane wave (FP-L/APW) method within the spin density functional theory (DFT). As exchange–correlation potential, we used the new generalized gradient approximation GGA. Structural properties are determined from the total energy calculations and we found that these compounds are stable in the ferromagnetic phase. We discuss the electronic structures, total and partial densities of states and local moments. Finally, CdCoTe and CdMnTe in the zinc-blend phase show the half-metallic ferromagnetic nature and are expected to be potential materials for spintronic devices.

Keywords: DFT, GGA, band structures, half-metallic, spintronics

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Authors: Rafal Sochaczewski, Grzegorz Baranski, Adam Majczak

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This paper presents the bench research results on a CNG injector at steady state. The quantities measured included voltage and current in a solenoid, pressure of gas behind an injector and injector’s flow rate. Accordingly, injector’s operation parameters were determined according to needle’s lift and injection pressure. The discrepancies between the theoretical (electric) and actual time of injection were defined to specify injector’s opening and closing lag times and the uniqueness of these values in successive cycles of gas injection. It has been demonstrated that needle’s lift has got a stronger impact on injector’s operating parameters than injection pressure. With increasing injection pressure, the force increases and closes an injection valve, which adversely affects uniqueness of injector’s operation. The paper also describes the concept of an injector dedicated to direct CNG injection into a combustion chamber in a dual-fuel engine. The injector’s design enables us to replace 80% of diesel fuel in a dual-fuel engine with a maximum power of 85 kW. Minimum injection pressure is 1,4 MPa then. Simultaneously, injector’s characteristics for varied needle’s lifts and injector’s nonlinear operating points were developed. Acknowledgement: This work has been financed by the Polish National Centre for Research and Development, under Grant Agreement No. PBS1/A6/4/2012.

Keywords: CNG injector, diesel engine, direct injection, dual fuel

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Authors: Silvana Caglieri

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Theoretical study of acetylation of p-methylaniline catalyzed by Cu2+ ions from the analysis of intermediate of the reaction was carried out. The study of acetylation of amines is of great interest by the utility of its products of reaction and is one of the most frequently used transformations in organic synthesis as it provides an efficient and inexpensive means for protecting amino groups in a multistep synthetic process. Acetylation of amine is a nucleophilic substitution reaction. This reaction can be catalyzed by Lewis acid, metallic ion. In reaction mechanism, the metallic ion formed a complex with the oxygen of the acetic anhydride carbonyl, facilitating the polarization of the same and the successive addition of amine at the position to form a tetrahedral intermediate, determining step of the rate of the reaction. Experimental work agreed that this reaction takes place with the formation of a tetrahedral intermediate. In the present theoretical work were investigated the structure and energy of the tetrahedral intermediate of the reaction catalyzed by Cu2+ ions. Geometries of all species involved in the acetylation were made and identified. All of the geometry optimizations were performed by the method at the DFT/B3LYP level of theory and the method MP2. Were adopted the 6-31+G* basis sets. Energies were calculated using the Mechanics-UFF method. Following the same procedure it was identified the geometric parameters and energy of reaction intermediate. The calculations show 61.35 kcal/mol of energy for the tetrahedral intermediate and the energy of activation for the reaction was 15.55 kcal/mol.

Keywords: amides, amines, DFT, MP2

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Authors: Ali Akbar Attari, Ali Asghar Beheshti Shirazi

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In this paper, we propose a blind and robust audio watermarking scheme based on spread spectrum in Discrete Wavelet Transform (DWT) domain. Watermarks are embedded in the low-frequency coefficients, which is less audible. The key idea is dividing the audio signal into small frames, and magnitude of the 6^th level of DWT approximation coefficients is modifying based upon the Direct Sequence Spread Spectrum (DSSS) technique. Also, the psychoacoustic model for enhancing in imperceptibility, as well as Savitsky-Golay filter for increasing accuracy in extraction, is used. The experimental results illustrate high robustness against most common attacks, i.e. Gaussian noise addition, Low pass filter, Resampling, Requantizing, MP3 compression, without significant perceptual distortion (ODG is higher than -1). The proposed scheme has about 83 bps data payload.

Keywords: audio watermarking, spread spectrum, discrete wavelet transform, psychoacoustic, Savitsky-Golay filter

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Authors: Nathalia Florencia Barros Azeredo, Josué Martins Gonçalves, Pamela De Oliveira Rossini, Koiti Araki, Lucio Angnes

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This work demonstrates the electroanalysis of uric acid (UA) at very low working potential (0 V vs Ag/AgCl) directly in body fluids such as saliva and sweat using electrodes modified with mixed -Ni0.75Zn0.25(OH)2 nanoparticles exhibiting stable electrocatalytic responses from alkaline down to weakly acidic media (pH 14 to 3 range). These materials were prepared for the first time and fully characterized by TEM, XRD, and spectroscopic techniques. The electrochemical properties of the modified electrodes were evaluated in a fast and simple procedure for uric acid analyses based on cyclic voltammetry and chronoamperometry, pushing down the detection and quantification limits (respectively of 2.3*10-8 and 7.6*10-8 mol L-1) with good repeatability (RSD = 3.2% for 30 successive analyses pH 14). Finally, the possibility of real application was demonstrated upon realization of unexpectedly robust and sensitive modified FTO (fluorine doped tin oxide) glass and screen-printed sensors for measurement of uric acid directly in real saliva and sweat samples, with no significant interference of usual concentrations of ascorbic acid, acetaminophen, lactate and glucose present in those body fluids (Fig. 1).

Keywords: nickel hydroxide, mixed catalyst, uric acid sensors, biofluids

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Authors: Alirıza Kaleli, M. Akif Ceviz, Erdoğan Güner, Köksal Erentürk

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The cyclic variations in spark ignition engines occurring especially under specific engine operating conditions make the maximum pressure variable for successive in-cylinder pressure cycles. Minimization of cyclic variations has a great importance in effectively operating near to lean limit, or at low speed and load. The cyclic variations may reduce the power output of the engine, lead to operational instabilities, and result in undesirable engine vibrations and noise. In this study, spark timing is controlled in order to reduce the cyclic variations in spark ignition engines. Firstly, an ARMAX model has developed between spark timing and maximum pressure using system identification techniques. By using this model, the maximum pressure of the next cycle has been predicted. Then, self-tuning minimum variance controller has been designed to change the spark timing for consecutive cycles of the first cylinder of test engine to regulate the in-cylinder maximum pressure. The performance of the proposed controller is illustrated in real time and experimental results show that the controller has a reliable effect on cycle to cycle variations of maximum cylinder pressure when the engine works under low speed conditions.

Keywords: cyclic variations, cylinder pressure, SI engines, self tuning controller

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Authors: O. Arbouche, Y. Benallou, K. Amara

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We report a first-principles study of structural, electronic and magnetic properties of ternary plumbides (rare earth-transition metal-Plumb) Dy2Ni2Pb crystallizes with the orthorhombic structure of the Mn2AlB2 type (space group Cmmm), were studied by means of the full-relativistic version of the full-potential augmented plane wave plus local orbital method within the frame work of spin-polarized density functional theory (SP-DFT). The electronic exchange-correlation energy is described by generalized gradient approximation (GGA). We have calculated the lattice parameters, bulk modulii and the first pressure derivatives of the bulk modulii, total densities of states and magnetic properties. The calculated total magnetic moment is found to be equal to 9.52 μB.

Keywords: spin-polarized, magnetic properties, Dy2Ni2Pb, Density functional theory

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Authors: Ivan Samokhin

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A new two-factor model of school students’ capacity levels is proposed. It considers the academic productivity and emotional condition of children taking part in the study process. Each basic level reflects the correlation of these two factors. The teacher decides whether the required result is achieved or not and write down the grade (from 'A' to 'F') in the register. During the term, the teacher can estimate the students’ progress with any intervals, but it is not desirable to exceed a two-week period (with primary school being an exception). Each boy or girl should have a special notebook to record the emotions which they feel studying a subject. The children can make their notes the way they like it – for example, using a ten-point scale or a short verbal description. It is recommended to record the emotions twice a day: after the lesson and after doing the homework. Before the students start doing this, they should be instructed by a school psychologist, who has to emphasize that an attitude to the subject – not to a person in charge of it – is relevant. At the end of the term, the notebooks are given to the teacher, who is now able to make preliminary conclusions about academic results and psychological comfort of each student. If necessary, some pedagogical measures can be taken. The data about a supposed capacity level is available for the teacher and the school administration. In certain cases, this information can be also revealed to the student’s parents, while the student learns it only after receiving a school-leaving certificate (until this moment, the results are not considered ultimate). Then a person may take these data into consideration when choosing his/her future area of higher education. We single out four main capacity levels: 'nominally low', 'inclination', 'ability' and 'gift'.

Keywords: academic productivity, capacity level, emotional condition, school students

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Authors: Hichem Boulechfar, Mahfoud Djezzar

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Two-dimensional double diffusive natural convection in an annular elliptical space filled with fluid-saturated porous medium, is analyzed by solving numerically the mass balance, momentum, energy and concentration equations, using Darcy's law and Boussinesq approximation. Both walls delimiting the annular space are maintained at two uniform different temperatures and concentrations. The external parameter considered is the Lewis number. For the present work, the heat and mass transfer for natural convection is studied for the case of aiding buoyancies, where the flow is generated in a cooperative mode by both temperature and solutal gradients. The local Nusselt and Sherwood numbers are presented in term of the external parameter.

Keywords: double diffusive, natural convection, porous media, elliptical annulus

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Authors: Mounir Adal, Baalal Azeddine, Afifi Moulay Larbi

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Numerical analysis is a branch of mathematics devoted to the development of iterative matrix calculation techniques. We are searching for operations optimization as objective to calculate and solve systems of equations of order n with time and energy saving for computers that are conducted to calculate and analyze big data by solving matrix equations. Furthermore, this scientific discipline is producing results with a margin of error of approximation called rates. Thus, the results obtained from the numerical analysis techniques that are held on computer software such as MATLAB or Simulink offers a preliminary diagnosis of the situation of the environment or space targets. By this we can offer technical procedures needed for engineering or scientific studies exploitable by engineers for water.

Keywords: numerical analysis methods, obstacles solving, engineering, simulation, numerical modeling, iteration, computer, MATLAB, water, underground, velocity

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Authors: Nasser A. M. Barakat

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Membrane technology is the most promising process for oil-water separation operation if the hydrophilicity, fouling and reusability properties could be improved. In this study, novel effective and reusable membrane for oil-water separation process is introduced based on modification of polysulfone (PSF) electrospun nanofiber mats. The modification process was achieved by incorporation of NaOH nanoparticles inside the PSF nanofibers, and formation of a thin layer from a polyamide polymer on the surface of the electrospun mat. Typically, solutions composed of PSF and NaOH (twelve solutions were prepared based on different PSF concentrations; 15, 18 and 20 wt%, and various NaOH content; 1.5, 1.7 and 2.5 wt%) have been electrospun, then the dried nanofiber mats were treated by m-phenylenediamine and 1,3,5-benzenetricarbonyl chloride to form polyamide thin layer on the surface of the mats. The results indicated that incorporation of NaOH and the formed polyamide could decrease the water contact angle from ~ 130˚ to 13˚ for the nanofiber mats obtained from 20 wt% PSF solutions containing 1.7 wt% sodium hydroxide powders. Interestingly, the membrane having the lowest contact angle could separate oil-water mixture for three successive cycles and 100% removal of the oil with relatively high water flux; 5.5 m3/m2.day. Overall, simplicity of the manufacturing technique, and effectiveness and reusability of the produced nanofiber mats open new avenue for the introduced as promising membranes for the oil-water separation process.

Keywords: electrospinning, oil-water separation, hydrophilic membrane, nanofibers

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Authors: Rohin Sharma, Sumantu Chaulagain

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This paper presents calculations of total energy of InGaN alloy carried out in a disordered quasirandom structure for a triclinic super cell. This structure replicates the disorder and composition effect in the alloy. First principle calculations within the density functional theory with the local density approximation approach is employed to accurately determine total energy of the system. Lattice constants and band gaps associated with the ground states are then estimated for different concentration ratios of the alloy. We provide precise results of quasirandom structures of the alloy and their lattice constants with the total energy and band gap energy of the system for the range of seven different composition ratios and their respective lattice parameters.

Keywords: DFT, ground state, LDA, quasicrystal, triclinic super cell

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Authors: Ali Gheshmi

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The highest rate of death, after World War II, is due to the Coronavirus epidemic and more than 2 million people have died since the epidemic outbreak in December 2019, so the word “death” is one of the highest frequency words in social media; moreover, the use of social media has grown due to quarantine and successive restrictions and lockdowns. The most important aspects of the approach used by this study include the analysis of Iranian social media users’ reactions to the images of those who died due to Coronavirus, investigating if seeing such images via social media is effective on the users’ perception of the closeness of death, and evaluating the extent to which the fear of Coronavirus death is instrumental in persuading users to observe health protocols or causing mental problems in social media users. Since the goal of this study is to discover how social media users perceive and react to the images of people who died of Coronavirus, the cultural studies approach is used Receipt analysis method and in-depth interviews will be used for collecting data from Iranian users; also, snowball sampling is used in this study. The probable results would show that cyberspace users experience the closeness of “death” more than any time else and to cope with these annoying images, avoid viewing them or if they view, it will lead them to suffer from mental problems.

Keywords: death, receipt analysis method, mental health, social media, Covid-19

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Authors: Moumen Souad, Melizi Mohamed

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In order to characterize rabbits does of an Aures local population raised in Algeria, a study of their milk yield was realized in the experimental rabbitry of El Hadj Lakhdhar University. Milk production of does was measured every day during the days following 215 parturitions. It was estimated by weighing the female before and after the single daily suckling (10–15 min between the two weighing operations). The various calculated parameters were the quantity of milk produced per day, per week and the total quantity produced in 21 days, as well as the intake of milk by young rabbits. The analysis concerned the effects of the number of successive litters (3 classes: 1 to 3 and more) and of the average number of the number of young rabbits suckled per litter (6 classes: from 1-2 kits to more than 6). During the 21 days of controlled lactation, the average litter size was 6±3. The rabbits of the Aures area produced on average 2544.34±747 g in 21 days that is 121 g of milk/day or 21 g of milk/kit/day. The milk yield increased from 526, 1035, 1240 and 2801 g to 760, 1365, 1715 and 3840 for week 1, 2, 3 and the total period of lactation, respectively. Nevertheless, milk production available per kit and per day decreased linearly with kits number in the litter for each of the 3 weeks considered. On the other hand the milk yield was not affected by the weight at birth of kits.

Keywords: milk production, litter size, rabbit, Aures area, Algeria

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Authors: Deepak Choudhary

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COEP-Microgrid, a project by the students of College of Engineering Pune aims at establishing a micro grid in the college campus serving as a living laboratory for research and development of novel grid technologies. Proposed micro grid has an AC-bus and DC-bus, interconnected together with a tie line DC-AC converter. In grid-connected mode AC bus of microgrid is synchronized with utility grid. Synchronization with utility grid requires grid and AC bus to have synchronism in frequency, phase sequence and voltage. Power flow requires phase difference between grid and AC bus. Control System is required to effectively regulate power flow between the grid and AC bus. The grid synchronizing control system is composed of frequency and phase control for regulated power flow and voltage control system for reduction of reactive power flow. The control system involves automatic active power flow control. It takes the feedback of DC link Capacitor and changes the power angle accordingly. Control system incorporating voltage, phase and power control was developed for grid-tie inverter. This paper discusses the design, simulation and practical implementation of control system described in various micro grid scenarios.

Keywords: microgrid, Grid-tie inverter, voltage control, automatic power control

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Authors: Sahriye Sonmez, Sedat Citak

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The objective of this study was to evaluate the effects of different organic manures on antioxidant activity, vitamin C and nitrate concentrations of broccoli (Brassica oleracea L. var italica) plants. For this purpose, broccoli plants were grown on open field conditions in 2 successive years (2011-2013) including 4 different seasons [(Spring 1 (March-June, 2011), Autumn 1 (September 2011-January 2012), Spring 2 (March-June, 2012), Autumn 2 (September 2012-January 2013)]. Organic manures (Farm manure (FM), vermicompost (VC) and leonardite (L) and its mixture (50 % FM+50% L, 50 % VC+50% FM, 50% L+50% VC and 33% FM+33% VC+33% L), one chemical fertilizer and one control, collectively 9 applications was investigated. The results indicated that the vitamin C concentrations of broccoli plants ranged from 31.4-55.8 mg/100 g, 43-631 mg/kg in nitrate concentrations and 11.0-56.7 mg/ml as IC50 inhibition values in antioxidant activities of broccoli plants. Also, it was determined that the effective applications were at the 50 % VC+50% FM for vitamin C concentrations, at the chemical fertilizer for nitrate concentrations and at the 100 % FM for antioxidant activities.

Keywords: broccoli, chemical fertilizer, farm manure, leonardite, vermicompost

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Authors: Rim Khemiri, Mariam Dammak

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The aim of this study is to trace the historical evolution of Tunisian higher accounting education and to understand and highlight the circumstances of its birth and its development. A documentary study (archival documents, official documents, public speeches, etc.), as well as semi-directive interviews with key actors, were carried out as part of this research work. These interviews aim to fill a lack of information on this subject and to confirm events addressed by other sources, but for which it lacks the elements necessary for a good understanding. After having put forward the specificities of the Tunisian context, we will, first of all, proceed to a review of the literature related to our theme in various contexts of the world. Then, we will present the evolution of the accounting curriculum by highlighting the circumstances of its birth and those of the successive reforms led by the Tunisian government. The study of higher accounting education in Tunisia and its evolution has several interests. The first lies in understanding the circumstances of its birth and its evolution in relation to the historical, socio-economic, and political context of the country. The second is to propose a reading grid that allows an understanding of the reforms that led to the university accountancy accounting course as we know it today. And, the third, aims to complete the literature on the processes of evolution of higher education accounting, by treating a different context, in order to provide additional knowledge necessary to compare experiences in this area around the world.

Keywords: accounting history, higher accounting education, socio-economic and political context, Tunisian context

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Authors: Arvind Dhingra, Tejinder Singh Saggu

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As the energy demands rise and the pollution levels grow, it becomes imperative for us to save energy in all the fields in which it is used. The industrial sector is the major commercial energy consuming sector in India, where electrical energy is the most common and widely used type of energy. As the demand and price of energy are increasing day by day, therefore, the subject of energy conservation is a concern for most energy users particularly industry. Judicious use of energy becomes imperative for third world developing country being presence of energy crisis. This paper provides some measure for energy saving that can be commonly recommended for a rolling unit of steel industry. A case of hot rolling unit in JSL Stainless Ltd., Hisar for energy conservation is given. Overall improvement in energy consumption in light of the stated recommendation is illustrated along with the proposed utilization of the techniques and their applications. Energy conservation in conventional motor with replacement or use of star delta star converter, reduction in cable losses, replacement of filament of LED lamps, replacement of conventional transformer with cast resin dry type transformer and provision of energy management system for energy conservation and per unit production cost reduction are elaborated in this paper.

Keywords: energy audit, energy conservation, energy efficient motors

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Authors: Stojan Kravanja, Andrej Ivanič, Tomaž Žula

Abstract:

This contribution focuses on structural optimization in civil engineering using mixed integer non-linear programming (MINLP). MINLP is characterized as a versatile method that can handle both continuous and discrete optimization variables simultaneously. Continuous variables are used to optimize parameters such as dimensions, stresses, masses, or costs, while discrete variables represent binary decisions to determine the presence or absence of structural elements within a structure while also calculating discrete materials and standard sections. The optimization process is divided into three main steps. First, a mechanical superstructure with a variety of different topology-, material- and dimensional alternatives. Next, a MINLP model is formulated to encapsulate the optimization problem. Finally, an optimal solution is searched in the direction of the defined objective function while respecting the structural constraints. The economic or mass objective function of the material and labor costs of a structure is subjected to the constraints known from structural analysis. These constraints include equations for the calculation of internal forces and deflections, as well as equations for the dimensioning of structural components (in accordance with the Eurocode standards). Given the complex, non-convex and highly non-linear nature of optimization problems in civil engineering, the Modified Outer-Approximation/Equality-Relaxation (OA/ER) algorithm is applied. This algorithm alternately solves subproblems of non-linear programming (NLP) and main problems of mixed-integer linear programming (MILP), in this way gradually refines the solution space up to the optimal solution. The NLP corresponds to the continuous optimization of parameters (with fixed topology, discrete materials and standard dimensions, all determined in the previous MILP), while the MILP involves a global approximation to the superstructure of alternatives, where a new topology, materials, standard dimensions are determined. The optimization of a convex problem is stopped when the MILP solution becomes better than the best NLP solution. Otherwise, it is terminated when the NLP solution can no longer be improved. While the OA/ER algorithm, like all other algorithms, does not guarantee global optimality due to the presence of non-convex functions, various modifications, including convexity tests, are implemented in OA/ER to mitigate these difficulties. The effectiveness of the proposed MINLP approach is demonstrated by its application to various structural optimization tasks, such as mass optimization of steel buildings, cost optimization of timber halls, composite floor systems, etc. Special optimization models have been developed for the optimization of these structures. The MINLP optimizations, facilitated by the user-friendly software package MIPSYN, provide insights into a mass or cost-optimal solutions, optimal structural topologies, optimal material and standard cross-section choices, confirming MINLP as a valuable method for the optimization of structures in civil engineering.

Keywords: MINLP, mixed-integer non-linear programming, optimization, structures

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Authors: Matineh Sadat Hosseini Gheidari, Vahid Reza Yazdanpanah

Abstract:

In this paper, we used the empirical tight-binding method (ETBM) with sp3s* approximation and considering the first nearest neighbor with spin-orbit interactions in order to model superlattice structure (SLS) of (AlₓGa₁₋ₓAs)ₘ/(GaAs)ₙ grown on GaAs (100) substrate at 300K. In the next step, we investigated the behavior of the energy gap and wavelength of this superlattice in terms of different thicknesses of core materials and Al mole fractions. As a result of this survey, we found out that as the Al composition increases, the energy gap of this superlattice has an upward trend and ranges from 1.42-1.63 eV. Also, according to the wavelength range that we gained from this superlattice in different Al mole fractions and various thicknesses, we can find a suitable semiconductor for a special light-emitting diode (LED) application.

Keywords: energy gap, empirical tight-binding method, light-emitting diode, superlattice, wavelength

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Authors: Kajingulu Malandala, Ranganai Edmore

Abstract:

The asymmetric Laplace distribution (ADL) is commonly used as the likelihood function of the Bayesian quantile regression, and it offers different families of likelihood method for quantile regression. Notwithstanding their popularity and practicality, ADL is not smooth and thus making it difficult to maximize its likelihood. Furthermore, Bayesian inference is time consuming and the selection of likelihood may mislead the inference, as the Bayes theorem does not automatically establish the posterior inference. Furthermore, ADL does not account for greater skewness and Kurtosis. This paper develops a new aspect of quantile regression approach for count data based on inverse of the cumulative density function of the Poisson, binomial and Delaporte distributions using the integrated nested Laplace Approximations. Our result validates the benefit of using the integrated nested Laplace Approximations and support the approach for count data.

Keywords: quantile regression, Delaporte distribution, count data, integrated nested Laplace approximation

Procedia PDF Downloads 145

Authors: R. K. Chaurasiya, N. D. Londhe, S. Ghosh

Abstract:

The study of the electrical signals produced by neural activities of human brain is called Electroencephalography. In this paper, we propose an automatic and efficient EEG signal classification approach. The proposed approach is used to classify the EEG signal into two classes: epileptic seizure or not. In the proposed approach, we start with extracting the features by applying Discrete Wavelet Transform (DWT) in order to decompose the EEG signals into sub-bands. These features, extracted from details and approximation coefficients of DWT sub-bands, are used as input to Principal Component Analysis (PCA). The classification is based on reducing the feature dimension using PCA and deriving the support-vectors using Support Vector Machine (SVM). The experimental are performed on real and standard dataset. A very high level of classification accuracy is obtained in the result of classification.

Keywords: discrete wavelet transform, electroencephalogram, pattern recognition, principal component analysis, support vector machine

Procedia PDF Downloads 618