Search results for: temperature fluctuations

Authors: Ajay Aggarwal, Kamal Saroha, Sanju Nanda

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Niosomes or non-ionic surfactant vesicles are microscopic lamellar structures formed on admixture of non-ionic surfactant of the alkyl or dialkyl polyglycerol ether class and cholesterol with subsequent hydration in aqueous media. They are vesicular systems similar to liposomes that can be used as carriers of amphiphilic and lipophilic drugs. Entrapment efficiency was found to be higher in case of niosome prepared with span60 than niosome prepared with tween. The amount of release was found to be in order of Span20>Tween60>Tween20>Span60. As the concentration of surfactant is increased in vitro release was increased due to high entrapment. The stability study of optimized batch revealed that particle size was increased after 3months on increasing the temperature. On the other hand entrapment efficiency was decreased on increasing the temperature.

Keywords: niosomes, vesicles, span, tween, in vitro release

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Authors: Funda Ates

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Primary energy sources, such as petroleum, coal and natural gas are principle responsible of world’s energy consumption. However, the rapid worldwide increase in the depletion of these energy sources is remarkable. In addition to this, they have damaging environmentally effect. Renewable energy sources are capable of providing a considerable fraction of World energy demand in this century. Biomass is one of the most abundant and utilized sources of renewable energy in the world. It can be converted into commercial fuels, suitable to substitute for fossil fuels. A high number of biomass types can be converted through thermochemical processes into solid, liquid or gaseous fuels. Pyrolysis is the thermal decomposition of biomass in the absence of air or oxygen. In this study, barley straw has been investigated as an alternative feedstock to obtain fuels and chemicals via pyrolysis in fixed-bed reactor. The influence of pyrolysis temperature in the range 450–750 °C as well as the catalyst effects on the products was investigated and the obtained results were compared. The results indicated that a maximum oil yield of 20.4% was obtained at a moderate temperature of 550 °C. Oil yield decreased by using catalyst. Pyrolysis oils were examined by using instrumental analysis and GC/MS. Analyses revealed that the pyrolysis oils were chemically very heterogeneous at all temperatures. It was determined that the most abundant compounds composing the bio-oil were phenolics. Catalyst decreased the reaction temperature. Most of the components obtained using a catalyst at moderate temperatures was close to those obtained at high temperatures without using a catalyst. Moreover, the use of a catalyst also decreased the amount of oxygenated compounds produced.

Keywords: Barley straw, pyrolysis, catalyst, phenolics

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Authors: H. Ben Khlifa, W. Cheikhrouhou-Koubaa, A. Cheikhrouhou

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The orthorhombic Pr₀.₈Na₀.₂−ₓKₓMnO₃ (x = 0.10 and 0.15) manganites are prepared by using the solid-state reaction at high temperatures. The critical exponents (β, γ, δ) are investigated through various techniques such as modified Arrott plot, Kouvel-Fisher method, and critical isotherm analysis based on the data of the magnetic measurements recorded around the Curie temperature. The critical exponents are derived from the magnetization data using the Kouvel-Fisher method, are found to be β = 0.32(4) and γ = 1.29(2) at TC ~ 123 K for x = 0.10 and β = 0.31(1) and γ = 1.25(2) at TC ~ 133 K for x = 0.15. The critical exponent values obtained for both samples are comparable to the values predicted by the 3D-Ising model and have also been verified by the scaling equation of state. Such results demonstrate the existence of ferromagnetic short-range order in our materials. The magnetic entropy changes of polycrystalline samples with a second-order phase transition are investigated. A large magnetic entropy change deduced from isothermal magnetization curves, is observed in our samples with a peak centered on their respective Curie temperatures (TC). The field dependence of the magnetic entropy changes are analyzed, which shows power-law dependence ΔSmax ≈ a(μ0 H)n at the transition temperature. The values of n obey the Curie Weiss law above the transition temperature. It is shown that for the investigated materials, the magnetic entropy change follows a master curve behavior. The rescaled magnetic entropy change curves for different applied fields collapse onto a single curve for both samples.

Keywords: manganites, critical exponents, magnetization, magnetocaloric, master curve

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Authors: Tahar Abid, Haoues Ghouss, Abdelhamid Boubertakh

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This present work is focused on the hardening precipitation in two AlMgSi(Cu) automotive body sheets. The effect of pre-aging, aging treatment and 0.10 wt % copper addition on the hardening response was investigated using scanning calorimetry (DSC), transmission electron microscopy (TEM), and Vickers microhardness measurements (Hv). The results reveal the apparition of α-AlFeSi, α-AlFe(Mn)Si type precipitates frequently present and witch remain stable at high temperature in Al-Mg-Si alloys. Indeed, the hardening response in both sheets is certainly due to the predominance of very fine typical phases β' and β'' as rods and needles developed during aging with and without pre-aging. The effect of pre ageing just after homogenization and quenching is to correct the undesirable effect of aging at ambient temperature by making faster alloy hardening during artificial aging.The addition of 0.10 wt % copper has allowed to refine and to enhance the precipitation hardening after quenching.

Keywords: AlMgSi alloys, precipitation, hardening, activation energy

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Authors: Madhu Aneja, Sapna Sharma

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The water-based bioconvection of a nanofluid containing motile gyrotactic micro-organisms over nonlinear inclined stretching sheet has been investigated. The governing nonlinear boundary layer equations of the model are reduced to a system of ordinary differential equations via Oberbeck-Boussinesq approximation and similarity transformations. Further, the modified set of equations with associated boundary conditions are solved using Finite Element Method. The impact of various pertinent parameters on the velocity, temperature, nanoparticles concentration, density of motile micro-organisms profiles are obtained and analyzed in details. The results show that with the increase in angle of inclination δ, velocity decreases while temperature, nanoparticles concentration, a density of motile micro-organisms increases. Additionally, the skin friction coefficient, Nusselt number, Sherwood number, density number are computed for various thermophysical parameters. It is noticed that increasing Brownian motion and thermophoresis parameter leads to an increase in temperature of fluid which results in a reduction in Nusselt number. On the contrary, Sherwood number rises with an increase in Brownian motion and thermophoresis parameter. The findings have been validated by comparing the results of special cases with existing studies.

Keywords: bioconvection, finite element method, gyrotactic micro-organisms, inclined stretching sheet, nanofluid

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Authors: Moustafa Osman Mohammed

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This paper introduces Luhmann’s autopoietic social systems starting with the original concept of autopoiesis by biologists and scientists, including the modification of general systems based on socialized medicine. A specific type of autopoietic system is explained in the three existing groups of the ecological phenomena: interaction, social and medical sciences. This hypothesis model, nevertheless, has a nonlinear interaction with its natural environment ‘interactional cycle’ for the exchange of photon energy with molecular without any changes in topology. The external forces in the systems environment might be concomitant with the natural fluctuations’ influence (e.g. radioactive radiation, electromagnetic waves). The cantilever sensor deploys insights to the future chip processor for prevention of social metabolic systems. Thus, the circuits with resonant electric and optical properties are prototyped on board as an intra–chip inter–chip transmission for producing electromagnetic energy approximately ranges from 1.7 mA at 3.3 V to service the detection in locomotion with the least significant power losses. Nowadays, therapeutic systems are assimilated materials from embryonic stem cells to aggregate multiple functions of the vessels nature de-cellular structure for replenishment. While, the interior actuators deploy base-pair complementarity of nucleotides for the symmetric arrangement in particular bacterial nanonetworks of the sequence cycle creating double-stranded DNA strings. The DNA strands must be sequenced, assembled, and decoded in order to reconstruct the original source reliably. The design of exterior actuators have the ability in sensing different variations in the corresponding patterns regarding beat-to-beat heart rate variability (HRV) for spatial autocorrelation of molecular communication, which consists of human electromagnetic, piezoelectric, electrostatic and electrothermal energy to monitor and transfer the dynamic changes of all the cantilevers simultaneously in real-time workspace with high precision. A prototype-enabled dynamic energy sensor has been investigated in the laboratory for inclusion of nanoscale devices in the architecture with a fuzzy logic control for detection of thermal and electrostatic changes with optoelectronic devices to interpret uncertainty associated with signal interference. Ultimately, the controversial aspect of molecular frictional properties is adjusted to each other and forms its unique spatial structure modules for providing the environment mutual contribution in the investigation of mass temperature changes due to pathogenic archival architecture of clusters.

Keywords: autopoiesis, nanoparticles, quantum photonics, portable energy, photonic structure, photodynamic therapeutic system

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Authors: Monika Šípová, Daniela Marušáková, Claudia Aparicio

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New sources and ways of producing energy are still seeking, and one of the sustainable ways is Generation IV nuclear reactors. The supercritical water-cooled reactor is one of the six nuclear reactors of Generation IV, and as a consequence of the development of light water, reactors seem to be the most perspective. Thus, materials usually used in light water reactors are also tested under the expected operating conditions of the supercritical water-cooled reactor. Austenitic stainless steel 08Cr18Ni10Ti is widely used in the eastern types of light water nuclear power plants. Therefore, specimens of 08Cr18Ni10Ti were exposed to conditions close to the pseudo-critical point of water and high-temperature supercritical water. The description and evaluation of the corrosion behaviour of austenitic stainless steel have been done based on the results of X-ray diffraction in combination with energy dispersive spectroscopy and electron backscatter diffraction. Thus, significant differences have been found in the structure and composition of oxides formed depending on the temperature of exposure. The high temperature of supercritical water resulted in localised form of corrosion in contrast to the thin oxide layer of 1 µm present on the surface of specimens exposed close to the pseudo-critical point of water. The obtained results are important for further research as the supercritical water can be successfully used as a coolant for small modular reactors, which are currently of interest.

Keywords: localised corrosion, supercritical water, stainless steel, electron backscatter diffraction

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Authors: Firmanda Taufiq

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Turkey as a country with great political power and political dynamics that occurred in Turkey shows symptoms that make this country interesting enough to be studied. In addition, there is also Post-Islamism phenomenon that causes fluctuations and changes in Turkish politics. In this regard, Turkey carved out history by holding a referendum that changed the state system from a parliamentary system with a presidential system. This change has major implications in the life of Turkish society and politics. The condition is not only influenced by the government of Recep Tayyib Erdogan alone, but actually there is also anxiety middle class Turkish (Middle Class Anatolia). So there was a Turkish referendum held on 16 April 2017. This research using descriptive-analysis method to analyzing problems of research, that's how the post-Islamism situation in Turkey and Anatolian Middle Class impact to Turkish referendum. Actually, the political process that took place in Turkey is inseparable from Post-Islamism which became an important part in the change and transition of government system. The AKP Party as the basis of the Erdogan government movement became an important actor in the political and policy dynamics produced by the Erdogan government. It is then why the Turkish referendum took place.

Keywords: post-Islamism, Turkish politic, AKP, middle class Anatolia

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Authors: Ubani Onyedikachi, Atagana Harrison Ifeanyichukwu, Thantsha Mapitsi Silvester

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Components of oil sludge (PAHs) are known cytotoxic, mutagenic and potentially carcinogenic compounds also bacteria and fungi have been found to degrade PAHs to innocuous compounds. This study is aimed at measuring the effect of pig, cow, horse and poultry manures on the degradation in selected PAHs present in oil sludge. Soil spiked with oil sludge was co-composted differently with each manure in a ratio of 2:1 (w/w) spiked soil: manure and wood-chips in a ratio of 2:1 (w/v) spiked soil: wood-chips. Control was set up similar as the one above but without manure. The mixtures were incubated for 10 months at room temperature. Compost piles were turned weekly and moisture level was maintained at between 50% and 70%. Moisture level, pH, temperature, CO2 evolution and oxygen consumption were measured monthly and the ash content at the end of experimentation. Highest temperature reached was 27.5 °C in all compost heaps, pH ranged from 5.5 to 7.8 and CO2 evolution was highest in poultry manure at 18.78μg/dwt/day. Microbial growth and activities were enhanced; bacteria identified were Bacillus, Arthrobacter and Staphylococcus species. Percentage reduction in PAHs was measured using automated soxhlet extractor with Dichloromethane coupled with gas chromatography/mass spectrometry (GC/MS). Results from PAH measurements showed reduction between 77% and 99%. Co-composting of spiked soils with animal manures enhanced the reduction in PAHs.

Keywords: animal manures, bioremediation, co-composting, oil refinery sludge, PAHs

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Authors: Ki-Ho Nam, Haksoo Han

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Tetrapod zinc oxide whiskers (TZnO-Ws) were successfully synthesized by a thermal oxidation method. A series of transparent polyimide (PI)/TZnO-W composites were successfully synthesized via a solution-blending method. The structural and morphological features of TZnO-Ws and PI/TZnO-W composites were characterized by Fourier transform infrared spectroscopy (FT-IR), wide-angle X-Ray diffraction (WAXD), and field emission scanning electron microscope (FE-SEM). Dynamic stress behaviors were investigated in-situ during thermal imidization of the soft-baked PI/TZnO-W composite precursor and thermally cured composite films using a thin film stress analyzer (TFSA) by wafer bending technique. The PI/TZnO-W composite films exhibited an optical transparency greater than 80% at 550 nm (≤ 0.5 wt% TZnO-W content), a low coefficient of thermal expansion (CTE), and enhanced glass transition temperature. However, the thermal decomposition temperature decreased as the TZnO-W content increased. The water diffusion coefficient and water uptake of the PI/TZNO-W composite films were obtained by best fits to a Fickian diffusion model. The water resistance capacity of PI was greatly enhanced and moisture diffusion in the pure PI was retarded by incorporating the TZnO-W. The PI composite films based on TZNO-W resultantly may have potential applications in optoelectronic manufacturing processes as a flexible transparent substrate.

Keywords: polyimide (PI), tetrapod ZnO whisker (TZnO-W), transparent, dynamic stress behavior, water resistance

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Authors: Jackeline Kafie-Martinez, Peter B. Keating

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A three-dimensional finite element model is developed to capture the stress field generated in connected plates during the installation of hot-driven rivets. Clamping stress is generated when a steel rivet heated to approximately 1000 °C comes in contact with the material to be fastened at ambient temperature. As the rivet cools, thermal contraction subjects the rivet into tensile stress, while the material being fastened is subjected to compressive stress. Model characteristics and assumptions, as well as steel properties variation with respect to temperature are discussed. The thermal stresses developed around the rivet hole are assessed and reported. Results from the analysis are utilized to detect possible regions for fatigue crack propagation under cyclic loads.

Keywords: clamping stress, fatigue, finite elements, rivet, riveted railroad bridges

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Authors: Fatema Tasmia, Brishti Majumder, Atiqur Rahman

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Attaining appropriate thermal comfort conditions in a place where the climate is hot and humid can be perplexing. Especially, when it resides at a congested place like old Dhaka Bangladesh, the provision of giving cross ventilation and building with proper orientation is quite difficult. This paper aims to investigate the indoor thermal environment of a room with and without transitional space or threshold in traditional row houses adjacent to a narrow alley of old Dhaka through field measurements. Transitional spaces are the part of buildings which are used for semi-outdoor household activities, social gathering and it is also proved to provide an indoor thermal effect. The field study was conducted by collecting thermal data (temperature, humidity and airflow) respectively, among the outdoor narrow alley, transitional space and adjacent indoor. This east-west elongated alley has an average width of 2.13 meter (varies from 1.5 to 2.6 meter) holding row houses on both sides. Among different aspects of thermal environment, the study of this paper is based on the analysis of temperature of corresponding cases. Other aspects and their variables were considered as constant (especially material) for accuracy and avoidance of confusion. This study focuses on the outcome that can ultimately contribute to the configuration of row houses with transitional spaces and in its relation to the adjacent outdoor space while achieving thermal comfort.

Keywords: alley, Old-Dhaka, row houses, temperature, thermal comfort, threshold, transitional space

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Authors: Yosra Mefteh Rekik, Younes Boujelbene

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We introduce in this paper a new conceptual model representing the stock market dynamics. This model is essentially based on cognitive behavior of the intelligence investors. In order to validate our model, we build an artificial stock market simulation based on agent-oriented methodologies. The proposed simulator is composed of market supervisor agent essentially responsible for executing transactions via an order book and various kinds of investor agents depending to their profile. The purpose of this simulation is to understand the influence of psychological character of an investor and its neighborhood on its decision-making and their impact on the market in terms of price fluctuations. Therefore, the difficulty of the prediction is due to several features: the complexity, the non-linearity and the dynamism of the financial market system, as well as the investor psychology. The Artificial Neural Networks learning mechanism take on the role of traders, who from their futures return expectations and place orders based on their expectations. The results of intensive analysis indicate that the existence of agents having heterogeneous beliefs and preferences has provided a better understanding of price dynamics in the financial market.

Keywords: artificial intelligence methods, artificial stock market, behavioral modeling, multi-agent based simulation

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Authors: Farid M. Abdel-Rahim

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In this study, Se90Te7Cu3 chalcogenide glass was prepared using the melt quenching technique. The amorphous nature of the as prepared samples was confirmed by scanning electron microscope (SEM). Result of differential scanning calorimetric (DSC) under nonisothermal condition on composition bulk materials are reported and discussed. It shows that these glasses exhibit a single-stage glass transition and a single-stage crystallization on heating rates. The glass transition temperature (Tg), the onset crystallization (Tc), the crystallization temperature (Tp), were found by dependent on the composition and heating rates. Activation energy for glass transition (Et), activation energy of the amorphous –crystalline transformation (Ec), crystallization reaction rate constant (Kp), (n) and (m) are constants related to crystallization mechanism of the bulk samples have been determined by different formulations.

Keywords: chalcogenides, heat treatment, DSC, SEM, glass transition, thermal analysis

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Authors: Shahrzad Zolfagharnassab, Abdul Rashid Mohamed Shariff, Reza Ehsani, Hawa Ze Jaffar, Ishak Aris

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Ripeness estimation of oil palm fresh fruit is important processes that affect the profitableness and salability of oil palm fruits. The adulthood or ripeness of the oil palm fruits influences the quality of oil palm. Conventional procedure includes physical grading of Fresh Fruit Bunches (FFB) maturity by calculating the number of loose fruits per bunch. This physical classification of oil palm FFB is costly, time consuming and the results may have human error. Hence, many researchers try to develop the methods for ascertaining the maturity of oil palm fruits and thereby, deviously the oil content of distinct palm fruits without the need for exhausting oil extraction and analysis. This research investigates the potential of infrared images (Thermal Images) as a predictor to classify the oil palm FFB ripeness. A total of 270 oil palm fresh fruit bunches from most common cultivar of oil palm bunches Nigresens according to three maturity categories: under ripe, ripe and over ripe were collected. Each sample was scanned by the thermal imaging cameras FLIR E60 and FLIR T440. The average temperature of each bunches were calculated by using image processing in FLIR Tools and FLIR ThermaCAM researcher pro 2.10 environment software. The results show that temperature content decreased from immature to over mature oil palm FFBs. An overall analysis-of-variance (ANOVA) test was proved that this predictor gave significant difference between underripe, ripe and overripe maturity categories. This shows that the temperature as predictors can be good indicators to classify oil palm FFB. Classification analysis was performed by using the temperature of the FFB as predictors through Linear Discriminant Analysis (LDA), Mahalanobis Discriminant Analysis (MDA), Artificial Neural Network (ANN) and K- Nearest Neighbor (KNN) methods. The highest overall classification accuracy was 88.2% by using Artificial Neural Network. This research proves that thermal imaging and neural network method can be used as predictors of oil palm maturity classification.

Keywords: artificial neural network, maturity classification, oil palm FFB, thermal imaging

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Authors: Aynur Aker, Hasan Kaya

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Al-12.6wt.%Si-2wt.%Cu ternary alloy of near eutectic composition was directionally solidified upward at a constant temperature gradient in a wide range of growth rates (V=8.25-165.41 µm/s). The microstructures (λ), microhardness (HV), tensile stress (σ) and electrical resistivity (ρ) were measured from directionally solidified samples. The dependence of microstructures, microhardness and electrical resistivity on growth rate (V) was also determined by statistical analysis. According to these results, it has been found that for increasing values of V, the values of HV, σ and ρ increase. Variations of electrical resistivity for casting Al-Si-Cu alloy were also measured at the temperature in range 300-500 K. The enthalpy (ΔH) and the specific heat (Cp) for the Al-Si-Cu alloy were determined by differential scanning calorimeter (DSC) from heating trace during the transformation from solid to liquid. The results obtained in this work were compared with the similar experimental results in the literature.

Keywords: Al-Si-Cu alloy, microstructures, micro-hardness, tensile stress electrical resistivity, enthalpy

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Authors: Igor V. Kuzminov

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According to its content, the proposed article is a collection of articles with comments and additions. All articles, in one way or another, have a connection with the Second Law of Thermodynamics. The content of the articles is given in a concise form. The articles were published in different journals at different times. Main topics are presented: gravity, biography of the Earth, physics of global warming-cooling cycles, multiverse. The articles are based on the laws of classical physics. Along the way, it should be noted that the Second Law of thermodynamics can be formulated as the Law of Matter Cooling. As it cools down, the processes of condensation, separation, and changes in the aggregate states of matter occur. In accordance with these changes, a picture of the world is being formed. Also, the main driving force of these processes is the inverse temperature dependence of the forces of gravity. As matter cools, the forces of gravity increase. The actions of these phenomena in the compartment form a picture of the world.

Keywords: gravitational forces, cooling of matter, inverse temperature dependence of gravitational forces, planetary model of the atom

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Authors: Youn-Hwan Kim, Jae-Won Moon, Hae-Joong Kim

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This paper introduces the results of the study on the development of accelerated life test methods for the motor used in machine tools. In recent years, as well as efficiency for motors, there is a growing need for research on life expectancy of motors. It is considered impossible to calculate the acceleration coefficient by increasing the rotational load or temperature load as the acceleration stress in the motor system because the temperature of the copper exceeds the wire thermal class rating. This paper describes the equipment development procedure for the highly accelerated life test (HALT) of the 12kW three-phase squirrel-cage induction motors (SCIMs). After the test, the lifetime analysis was carried out, and it is compared with the life expectancy by finite element method (FEM) and bearing theory.

Keywords: acceleration coefficient, bearing, HALT, life expectancy, motor

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Authors: Narasimhulu Korrapati

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The objective of this present study is to optimize the process parameters for batch biosorption of Cr(VI) and Cu(II) ions by Bacillus subtilis using Response Surface Methodology (RSM). Batch biosorption studies were conducted under optimum pH, temperature, biomass concentration and contact time for the removal of Cr(VI) and Cu(II) ions using Bacillus subtilis. From the studies it is noticed that the maximum biosorption of Cr(VI) and Cu(II) was by Bacillus subtilis at optimum conditions of contact time of 30 minutes, pH of 4.0, biomass concentration of 2.0 mg/mL, the temperature of 32°C in batch biosorption studies. Predicted percent biosorption of the selected heavy metal ions by the design expert software is in agreement with experimental results of percent biosorption. The percent biosorption of Cr(VI) and Cu(II) in batch studies is 80% and 78.4%, respectively.

Keywords: heavy metal ions, response surface methodology, biosorption, wastewater

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Authors: Sarah Abdourraziq

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Photovoltaic (PV) water pumping system is one of the most used and important applications in the field of solar energy. However, the cost and the efficiency are still a concern, especially with continued change of solar radiation and temperature. Then, the improvement of the efficiency of the system components is a good solution to reducing the cost. The use of maximum power point tracking (MPPT) algorithms to track the output maximum power point (MPP) of the PV panel is very important to improve the efficiency of the whole system. In this paper, we will present a definition of the functioning of MPPT technique, and a detailed model of each component of PV pumping system with Matlab-Simulink, the results shows the influence of the changing of solar radiation and temperature in the output characteristics of PV panel, which influence in the efficiency of the system. Our system consists of a PV generator, a boost converter, a motor-pump set, and storage tank.

Keywords: PV panel, boost converter, MPPT, MPP, PV pumping system

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Authors: Nora Arbaoui, Rachid Tadili, Ilham Ihoume

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To improve the climatic conditions and increase production in the greenhouse during the winter season under the Mediterranean climate, this thesis project proposes a design of an integrated and autonomous solar system for heating, cooling, and conservation of production in an agricultural greenhouse. To study the effectiveness of this system, experiments are conducted in two similar agricultural greenhouses oriented north-south. The first greenhouse is equipped with an active solar system integrated into the double glazing of the greenhouse’s roof, while the second greenhouse has no system, it serves as a controlled greenhouse for comparing thermal and agronomic performance The solar system allowed for an average increase in the indoor temperature of the experimental greenhouse of 6°C compared to the outdoor environment and 4°C compared to the control greenhouse. This improvement in temperature has a favorable effect on the plants' climate and subsequently positively affects their development, quality, and production.

Keywords: solar system, agricultural greenhouse, heating, cooling, storage, drying

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Authors: Florence Chinyere Nwangwu, Rosemary Ene

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An experimental study was carried out to develop an adhesive from Prosopis africana seed endosperm. The Prosopis seeds for this work were obtained from Enugu State in the South East part of Nigeria. The Prosopis seeds were prepared by separating the Prosopis endosperm from the seed coat and cotyledon. The dry adhesive gotten from the endosperm was later dissolved to get the adhesive solution. Confirmatory tests like viscosity, density, pH, and binding strength were carried out. The effect of time, temperature, concentration on the yield and properties of the adhesive were investigated. The results obtained showed that increase in concentration, time, temperature decreases the viscosity of the Prosopis adhesive and yield of Prosopis endosperm. It was also deduced that increase in viscosity increases the binding strength of the Prosopis adhesive. The percentage of the adhesive yield from Prosopis endosperm showed that the commercialization of the seed in Nigeria will be possible and profitable.

Keywords: adhesive, Prosopis, viscosity, endosperm

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Authors: Flavia Cordeiro, Fabio Silva, Alvaro Eiras, Jose Luiz Acebal

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Aedes aegypti is present in the tropical and subtropical regions of the world and is a vector of several diseases such as dengue fever, yellow fever, chikungunya, zika etc. The growth in the number of arboviruses cases in the last decades became a matter of great concern worldwide. Meteorological factors like mean temperature and precipitation are known to influence the infestation by the species through effects on physiology and ecology, altering the fecundity, mortality, lifespan, dispersion behaviour and abundance of the vector. Models able to describe the dynamics of the vector population size should then take into account the meteorological variables. The relationship between meteorological factors and the population dynamics of Ae. aegypti adult females are studied to provide a good set of predictors to model the dynamics of the mosquito population size. The time-series data of capture of adult females of a public health surveillance program from the city of Lavras, MG, Brazil had its association with precipitation, humidity and temperature analysed through a set of statistical methods for time series analysis commonly adopted in Signal Processing, Information Theory and Neuroscience. Cross-correlation, multicollinearity test and whitened cross-correlation were applied to determine in which time lags would occur the influence of meteorological variables on the dynamics of the mosquito abundance. Among the findings, the studied case indicated strong collinearity between humidity and precipitation, and precipitation was selected to form a pair of descriptors together with temperature. In the techniques used, there were observed significant associations between infestation indicators and both temperature and precipitation in short, mid and long terms, evincing that those variables should be considered in entomological models and as public health indicators. A descriptive model used to test the results exhibits a strong correlation to data.

Keywords: Aedes aegypti, cross-correlation, multicollinearity, meteorological variables

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Authors: Thomas Paris, Vincent Bruyere, Patrick Namy

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A numerical model is developed to simulate gas blowdowns through a thin tube and a filter (porous media), separating a high pressure gas filled reservoir to low pressure ones. Based on a previous work, a one-dimensional approach is developed by using the finite element method to solve the transient compressible flow and to predict the pressure and temperature evolution in space and time. Mass, momentum, and energy conservation equations are solved in a fully coupled way in the reservoirs, the pipes and the porous media. Numerical results, such as pressure and temperature evolutions, are firstly compared with experimental data to validate the model for different configurations. Couplings between porous media and pipe flow are then validated by checking mass balance. The influence of the porous media and the nature of the gas is then studied for different initial high pressure values.

Keywords: compressible flow, fluid mechanics, heat transfer, porous media

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Authors: Sibani Bisoyi, Ute Zschieschang, Alexander Hoyer, Hagen Klauk

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Abstract— Organic thin-film transistors (TFTs) have great potential to be used for various applications such as flexible displays or sensors. For some of these applications, the TFTs must be able to withstand temperatures in excess of 100 °C, for example to permit the integration with devices or components that require high process temperatures, or to make it possible that the devices can be subjected to the standard sterilization protocols required for biomedical applications. In this work, we have investigated how the thermal stability of low-voltage small-molecule semiconductor dinaphtho[2,3-b:2’,3’-f]thieno[3,2-b]thiophene (DNTT) TFTs is affected by the encapsulation of the TFTs and by the ambient in which the thermal stress is performed. We also studied to which extent the thermal stability of the TFTs depends on the channel length. Some of the TFTs were encapsulated with a layer of vacuum-deposited Teflon, while others were left without encapsulation, and the thermal stress was performed either in nitrogen or in air. We found that the encapsulation with Teflon has virtually no effect on the thermal stability of our TFTs. In contrast, the ambient in which the thermal stress is conducted was found to have a measurable effect, but in a surprising way: When the thermal stress is carried out in nitrogen, the mobility drops to 70% of its initial value at a temperature of 160 °C and to close to zero at 170 °C, whereas when the stress is performed in air, the mobility remains at 75% of its initial value up to a temperature of 160 °C and at 60% up to 180 °C. To understand this behavior, we studied the effect of the thermal stress on the semiconductor thin-film morphology by scanning electron microscopy. While the DNTT films remain continuous and conducting when the heating is carried out in air, the semiconductor morphology undergoes a dramatic change, including the formation of large, thick crystals of DNTT and a complete loss of percolation, when the heating is conducted in nitrogen. We also found that when the TFTs are heated to a temperature of 200 °C in air, all TFTs with a channel length greater than 50 µm are destroyed, while TFTs with a channel length of less than 50 µm survive, whereas when the TFTs are heated to the same temperature (200 °C) in nitrogen, only the TFTs with a channel smaller than 8 µm survive. This result is also linked to the thermally induced changes in the semiconductor morphology.

Keywords: organic thin-film transistors, encapsulation, thermal stability, thin-film morphology

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Authors: Aida Rafat, Ramazan Kahraman, Mert Atilhan

Abstract:

The aggressive corrosion behavior of conventional amine solvents is one of main barriers against large scale commerizaliation of amine absorption process for carbon capture application. Novel CO2 absorbents that exhibit minimal corrosivity against operation conditions are essential to lower corrosion damage and control and ensure more robustness in the capture plant. This work investigated corrosion behavior of carbon steel CS1018 in various CO2 absrobent solvents. The tested solvents included the classical amines MEA, DEA and MDEA, piperazine activated solvents MEA/PZ, MDEA/PZ and MEA/MDEA/PZ as well as mixtures of MEA and Room Temperature Ionic Liquids RTIL, namely MEA/[C4MIM][BF4] and MEA/[C4MIM][Otf]. Electrochemical polarization technique was used to determine the system corrosiveness in terms of corrosion rate and polarization behavior. The process parameters of interest were CO2 loading and solution temperature. Electrochemical resulted showed corrosivity order of classical amines at 40°C is MDEA> MEA > DEA wherase at 80°C corrosivity ranking changes to MEA > DEA > MDEA. Corrosivity rankings were mainly governed by CO2 absorption capacity at the test temperature. Corrosivity ranking for activated amines at 80°C was MEA/PZ > MDEA/PZ > MEA/MDEA/PZ. Piperazine addition seemed to have a dual advanatge in terms of enhancing CO2 absorption capacity as well as nullifying corrosion. For MEA/RTIL mixtures, the preliminary results showed that the partial repalcement of aqueous phase in MEA solution by the more stable nonvolatile RTIL solvents reduced corrosion rates considerably.

Keywords: corrosion, amines, CO2 capture, piperazine, ionic liquids

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Authors: Samir Khene

Abstract:

Present and future industrial uses of high critical temperature superconductors require high critical temperatures TC and strong current densities JC. These two aims constitute the two motivations of the scientific research in this domain. The most significant feature of any superconductor, from the viewpoint of uses, is the maximum electrical transport current density that this superconductor is capable of withstanding without loss of energy. In this work, vortices pinning in conventional and high-TC superconductors will be studied. Our experiments on vortices pinning in single crystals and nanoparticles of YBa2Cu3O7- and La1.85 Sr0.15CuO will be presented. It will be given special attention to the study of the YBa2Cu3O7- nanoparticles doped by ferromagnetic nanoparticles of Y3Fe5O12. The ferromagnetism and superconductivity coexistence in this compound will be demonstrated, and the influence of these ferromagnetic nanoparticles on the variations of the critical current density JC in YBa2Cu3O7- nanoparticles as a function of applied field H and temperature T will be studied.

Keywords: ferromagnetism, superconductivity, coexistence, magnetic material

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Authors: Derya Güler Aydin, Bahar Araz Takay

Abstract:

Two different forms of competition theories can be distinguished: Those theories that emphasize the equilibrating forces created by competition, and those emphasizing the disequilibrating forces. This difference can be attributed, among other things, to the differences regarding the functioning of the market economy; that is to say, the basic problem here is whether competition should be understood as a static state or a dynamic process. This study aims to analyze the dynamic competition theories by K. Marx and J. A. Schumpeter and neo- Schumperians all of which focus on the dynamic role played by competition through creating disequilibria, endogenous structural change and social transformation as a distinguishing characteristic of the market system. With this aim, in the first section, after examining the static, neoclassical competition theory, both Marx‟s theory, which is based on profit rate differentials, and Schumpeter‟s theory, which is based on the notion of “creative destruction”, will be discussed. In the second section, the long-term fluctuations, based on creative gales of destruction, the concept will be examined under the framework of techno-economic paradigm. It is argued that the dynamic, even disequilibrium tendencies created by the competition process should be regarded in both understanding the working of capitalism and social transformation of the system.

Keywords: competition, techno-enomic paradigm, Schumpeter, social evolution

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Authors: P. B. Sob, A. A. Alugongo, T. B. Tengen

Abstract:

The activation volume of 6082T6 aluminum is investigated at different temperatures on grain size variants. The deformation activation volume was computed on the basis of the relationship between the Boltzmann’s constant k, the testing temperatures, the material strain rate sensitivity and the material yield stress of grain size variants. The material strain rate sensitivity is computed as a function of yield stress and strain rate of grain size variants. The effect of the material strain rate sensitivity and the deformation activation volume of 6082T6 aluminum at different temperatures of 3-D grain are discussed. It is shown that the strain rate sensitivities and activation volume are negative for the grain size variants during the deformation of nanostructured materials. It is also observed that the activation volume vary in different ways with the equivalent radius, semi minor axis radius, semi major axis radius and major axis radius. From the obtained results it is shown that the variation of activation volume increased and decreased with the testing temperature. It was revealed that, increased in strain rate sensitivity led to decrease in activation volume whereas increased in activation volume led to decrease in strain rate sensitivity.

Keywords: nanostructured materials, grain size variants, temperature, yield stress, strain rate sensitivity, activation volume

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Authors: H. Zou, B. Wang

Abstract:

Thermal distortion of the machine tool plays a critical role in its machining accuracy. This study investigates the thermal performance of a high-precision machine frame with future-oriented mineral casting components. A thermo-mechanical finite element model (FEM) was established to evaluate the thermal behavior of the frame under environmental thermal fluctuations. The validity of the presented FEM model was confirmed experimentally by a series of laser interferometer tests. Good agreement between numerical and experimental results demonstrates that the proposed model can accurately predict the thermal deformation of the frame with thermo-mechanical coupling effect. The results also show that keeping the workshop in thermally stable conditions is crucial for improving the machine accuracy of the system with large scale components. The goal of this paper is to investigate the feasibility of innovative mineral casting material applied in high-precision drilling machine and to provide a strategy for machine tool industry seeking a perfect substitute for classic frame materials such as cast iron and granite.

Keywords: thermo-mechanical model, finite element method, laser interferometer, mineral casting frame

Procedia PDF Downloads 303