Academic literature on the topic 'Reverse symmetrical current'
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Journal articles on the topic "Reverse symmetrical current"
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Azizov, �. �., V. G. Babaev, and V. A. Mashtakova. "Voltage-current curves for a planar symmetrical diode with reverse bias." Radiophysics and Quantum Electronics 31, no. 1 (January 1988): 83–89. http://dx.doi.org/10.1007/bf01034576.
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Su, Xuebing, Yang Wang, Xiangliang Jin, and Hongjiao Yang. "Design of high voltage electrostatic protection device for CAN bus." Journal of Physics: Conference Series 2221, no. 1 (May 1, 2022): 012014. http://dx.doi.org/10.1088/1742-6596/2221/1/012014.
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Abstract The Dual-Direction Silicon Controlled Rectifier (DDSCR) device has dual-direction electrostatic protection function and strong current discharging ability, which is widely used in ESD on-chip protection. In this paper, a high performance symmetric high voltage Dual-Direction Silicon Controlled Rectifier with floating P+ (HVDDSCR_FP+) is designed for CAN bus under 0.18 μm BCD process. In order to predict and verify the ESD performance of the device, TCAD two-dimensional device simulation and Transmission Line Pulse (TLP) test system were used. The experimental results show that the HVDDSCR_FP + structure has not only symmetrical positive and reverse I-V curves, but also the characteristics of high holding voltage and high failure current. Compared with the traditional HVDDSCR, HVDDSCR_FP+, at 25V forward and reverse trigger voltages (Vt), has increased its holding voltage (Vh) from 12V to 20V, failure current (It2) from 5A to 35A. In the actual tape-out process, it is found that the width of the N-well has a great influence on the performance of the device. After analyzing the reason and improving it, the leakage current of the device is reduced from μA level to nA level.
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Guo, Bin, Dazheng Wang, Xu Zhou, Weichao Shi, and Fengmei Jing. "Performance Evaluation of a Tidal Current Turbine with Bidirectional Symmetrical Foils." Water 12, no. 1 (December 19, 2019): 22. http://dx.doi.org/10.3390/w12010022.
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As one might expect, tidal currents in terms of ebb and flood tides are approximately bidirectional. A Horizontal Axial Tidal Turbine (HATT) with unidirectional foils has to be able to face the current directions in order to maximize current energy harvesting. There are two regular solutions to keep a HATT always facing the direction of the flow, which are transferred from wind turbine applications. One is to yaw the turbine around the supporting structure with a yaw mechanism. The other is to reverse the blade pitch angle through 180° with a pitch-adjusting mechanism. The above solutions are not cost-effective in marine applications due to the harsh marine environment and high cost of installation and maintenance. In order to avoid the above disadvantages, a turbine with bidirectional foils is presented in this paper. A bare turbine with bidirectional foils is characterized in that it has nearly the same energy conversion capability in both tidal current directions without using the yaw or pitch mechanism. Considering the working conditions of the bidirectional turbine in which the turbine is installed on a mono-pile, the effect of the mono-pile on the turbine’s performance is evaluated in this paper, especially when the turbine is downstream of the mono-pile. The paper was focused on the evaluation of the hydrodynamic performance of the bidirectional turbine. The hydrodynamic performance of the bare bidirectional turbine without any supporting structure was evaluated based on a steady-state computational fluid dynamics (CFD) model and model tests. Performance comparison has been made between the turbine with bidirectional foils and the turbine with NACA foils. The effect of the mono-pile on the performance of the bidirectional turbine was studied by using the steady-state and the transient CFD model. The steady-state CFD model was used to evaluate the effect of the mono-pile clearance, which is the distance between the mono-pile and the turbine on the performance of the turbine. The transient CFD model was used to determine the time-dependent characteristics of the turbine, such as time-dependent power and drag coefficients. The results show that the bare bidirectional turbine has nearly the same energy conversion capability in both tidal current directions. The performance of the bidirectional turbine is inferior to the turbine with NACA foils. At the designed tip speed ratio, the power coefficient of the turbine with NACA foils is 0.4498, which increases by 1.6% compared to the 0.4338 of the bidirectional turbine. The turbine’s performance decreases due to the introduction of the mono-pile, and the closer the turbine is to the mono-pile, the greater effect on the turbine’s performance the mono-pile has. At the designed clearance of 1.5 DS, the presence of a mono-pile decreases the peak Cp value by 1.82% and 3.17% to a value of 0.4156 and 0.4004 for the turbine located in the mono-pile upstream and downstream, respectively. The mono-pile can result in the fluctuation of the turbine’s performance. This fluctuation will detrimentally harm the life of the turbine as it will lead to increased wear and fatigue issues.
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Iioka, Daisuke, Takahiro Fujii, Toshio Tanaka, Tsuyoshi Harimoto, Junpei Motoyama, and Daisuke Nagae. "Improvement of Voltage Unbalance by Current Injection Based on Unbalanced Line Impedance in Distribution Network with PV System." Energies 14, no. 23 (December 3, 2021): 8126. http://dx.doi.org/10.3390/en14238126.
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In this study, we have proposed a novel current injection determination method that improves the voltage unbalance based on the unbalanced line impedance in a distribution network with a large-capacity PV system. An increase in the unbalance of the distribution line voltage was observed owing to a large-scale reverse power flow. To visualize this phenomenon, the P-V curves were derived for each phase to indicate the increase in the voltage unbalance with respect to the reverse power flow. Based on the derived P-V curves, the effect of a current unbalance on the voltage unbalance was investigated. It was clarified that there is a current unbalance that can improve the voltage unbalance even if the line impedance is unbalanced. In other words, the current unbalance that can theoretically make the voltage unbalance zero could be expressed in terms of the symmetrical components of unbalanced line impedance. As an application of the proposed method, the effect of the mitigation of voltage unbalance was demonstrated by controlling single-phase reactors, whose numbers were determined by using the relationship between the unbalanced line current and unbalanced line impedance.
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Lef, M. R., K. F. Yarn, C. C. Chen, and W. R. Chang. "GaAs Triac-like Triangular Barrier Switch Prepared by Molecular Beam Epitaxy." Active and Passive Electronic Components 24, no. 1 (2001): 1–11. http://dx.doi.org/10.1155/2001/29392.
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A new S-shaped negative differential resistance (NDR) switching device, prepared by molecular beam epitaxy (MBE), has been successfully developed in a GaAs double triangular barrier structure. Symmetrical bidirectional S-shaped NDR characteristics are observed experimentally. The bidirectional current-voltage (I–V) characteristics exhibit a new type of NDR caused by an avalanche multiplication process in reverse biased base-collector region and barrier redistribution. Under a base current injection with respect to the cathode, the device exhibits a conventional transistor with a current gain of 1.2 at room temperature. The experimentally electrical results can be easily understood by an equivalent circuit. In addition, a new optoelectronic switching device is also proposed which may have the potential for bidirectional wave length emission.
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Overholt, J. L., A. Saulino, M. L. Drumm, and R. D. Harvey. "Rectification of whole cell cystic fibrosis transmembrane conductance regulator chloride current." American Journal of Physiology-Cell Physiology 268, no. 3 (March 1, 1995): C636—C646. http://dx.doi.org/10.1152/ajpcell.1995.268.3.c636.
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Whole cell epithelial cystic fibrosis transmembrane conductance regulator (CFTR) Cl- currents exhibited a linear current-voltage (I-V) relationship with high symmetrical transmembrane Cl- concentrations. However, when intracellular Cl- (Cli-) was reduced by replacement with glutamate, I-V relationships were outwardly rectifying. Rectification was not affected by reducing extracellular Cl- to eliminate or reverse the gradient, indicating that rectification is not a function of the Cl- gradient. Rectification was affected by Cli- in a concentration-dependent manner, and it was weaker when Cli- was reduced by replacement with sucrose. These characteristics are identical to those of the cardiac isoform of CFTR, and the experimental data could be simulated by an Eyring rate theory model assuming that permeating anions interact at a single binding site within the channel pore. No evidence was found for multiple binding sites. These results indicate that rectification is a function of the concentration and permeability of the anions inside the cell. It is concluded that rectification of CFTR Cl- current is a property of ion channel permeation that would occur under physiological conditions and that permeation of the epithelial and cardiac isoforms of CFTR is identical.
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Brzezinska, Anna K., Nicole Lohr, and William M. Chilian. "Electrophysiological effects of O2−· on the plasma membrane in vascular endothelial cells." American Journal of Physiology-Heart and Circulatory Physiology 289, no. 6 (December 2005): H2379—H2386. http://dx.doi.org/10.1152/ajpheart.00132.2005.
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Vascular dysfunction is a hallmark of many diseases, including coronary heart disease, stroke, and diabetes. The underlying mechanisms of these disorders are intimately associated with an increase in oxidative stress and excess generation of reactive oxygen species. Here, we report that the anionic free radical, superoxide (O2−·), directly affects the function of ion channels in vascular endothelial cells. Vascular endothelial cells were exposed to O2−· under physiological, symmetrical chloride and chloride-free conditions. Superoxide was generated from the reaction of xanthine (0.2 mM) and xanthine oxidase (0.1, 1, and 10 mU/ml) while its effects were determined with the whole cell mode of the patch-clamp technique. Inhibitors of K+ and Cl− channels were used to determine the role of these ion channels in mediating the electrophysiological effects of superoxide. The addition of O2−· caused a dose-dependent depolarization of endothelial cells and activation of the whole cell current. Activation of superoxide-dependent current was observed in the presence of inhibitors of K+ channels, Ba2+ (100 μM) or iberiotoxin (100 nM), and was not affected by inhibitors of nonselective cation channels, La3+, or by inhibition of the Cl−/HCO3− transporter by bumetanide. The inhibitors of the Cl− channel, NPPB (0.1 mM) or DIDS (100 μM), partially prevented activation of superoxide-dependent current but were unable to reverse it. The effects of superoxide on the amplitude of whole cell current were prevented and reversed by superoxide dismutase. Taken together, these results suggest that superoxide directly affects the function of ion channels in vascular endothelium but the mechanisms of its modulatory effects remain unresolved.
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Ding, Meng, Fan Yang, Qingquan Lv, and Qiongfang Liu. "Two coordination polymers: Crystal structures, prevention and nursing values on postoperative infection." Progress in Reaction Kinetics and Mechanism 47 (January 2022): 146867832210903. http://dx.doi.org/10.1177/14686783221090376.
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In this current work, two fresh transition metal coordination polymers (CPs) have been created with the reaction between terphenyl-3,3″,5,5″-tetracarboxylic acid (H4L), the symmetrical rigid carboxylic acid ligand and the relevant metal salts under the reaction conditions of solvothermal, and the chemical compositions of the compounds respectively are {[Cu2(TPTC) (DMF)2(H2O)]·2DMF·2H2O} (2) and {[Zn (TPTC) (1,2-bimb)2]·4(H2O)}n (1, bimb = 1,2-bis((1H-imidazol-1-yl)methyl)benzene). Moreover, the prevention and nursing values of the compound on postoperative infection was explored and their corresponding mechanism also was investigated. Firstly, enzyme linked immunosorbent assay kit (ELISA) was employed to detect the release of inflammatory cytokines into plasma. Additionally, the expression of the bacterial survival genes was determined via exploiting the real time reverse transcription-polymerase chain reaction (RT-PCR) after treated with the compound.
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Dero, Dr Sumera, Ghulam Hyder Talpur, Abbas Ali Ghoto, and Shokat Ali. "Mathematical Analysis of Magnetized Rotating Nanofluid Flow Over nonlinear shrinking surface: Duality and Stability." Sukkur IBA Journal of Computing and Mathematical Sciences 5, no. 2 (December 28, 2021): 1–13. http://dx.doi.org/10.30537/sjcms.v5i2.880.
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In this study, the MHD effect on boundary layer rotating flow of a nanofluid is investigated for the multiple branches case. The main focus of current research is to examine flow characteristics on a nonlinear permeable shrinking sheet. Moreover, the governing partial differential equations (PDEs) of the problem considered are reduced into coupled nonlinear ordinary differential equations (ODEs) with the appropriate similarity transformation. Numerical results based on the plotted graphs are gotten by solving ODEs with help of the three-stage Labatto IIIA method in bvp4c solver in MATLAB. To confirm numerical outcomes, current results are compared with previously available outcomes and found in good agreement. Skin friction coefficients, Nusselt and Sherwood numbers, velocity profiles, temperature profiles, and concentration profiles are examined. The results show that dual (no) branches exist in certain ranges of the suction parameter i.e., SSc (SSc). Further, profiles of velocity decrease for rising values of Hartmann number in the upper branch, while reverse trend has been noticed in a lower branch. Profiles of temperature and concentration enhance for the increasing values of thermophoresis in both branches. stability analysis of the branches is also done and noticed that upper branch is a stable branch from both branches. Finally, it is noted that the stable branch has symmetrical behavior with regard to the parameter of rotation.
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Freudenberg, J., H. Boriss, and D. Hasenclever. "Comparison of Preprocessing Procedures for Oligo-nucleotide Micro-arrays by Parametric Bootstrap Simulation of Spike-in Experiments." Methods of Information in Medicine 43, no. 05 (2004): 434–38. http://dx.doi.org/10.1055/s-0038-1633893.
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Summary Objective: Due to scarcity of calibration data for micro-array experiments, simulation methods are employed to assess preprocessing procedures. Here we analyze several procedures’ robustness against increasing numbers of differentially expressed genes and varying proportions of up-regulation. Methods: Raw probe data from oligo-nucleotide micro-arrays are assumed to be approximately multivariate normally distributed on the log scale. Chips can be simulated from a multivariate normal distribution with mean and variance-covariance matrix estimated from a real raw data set.A chip effect induces strong positive correlations. In reverse, sampling from a normal distribution with strong correlation variance-covariance matrix generates data exhibiting a chip effect. No explicit model of chip-effect is needed. Differences can be artificially spiked-in according to a given distribution of effect sizes.Thirty preprocessing procedures combining background correction, normalization, perfect match correction and summarization methods available from the BioConductor project were compared. Results: In the symmetrical setting “50% differentially expressed genes, 50% of which up-regulated” background correction reduces bias, but inflates low intensity probe variance as well as the mean squared error of the estimates. Any normalization reduces variance and increases sensitivity with no clear winner. Asymmetry between up and down regulation causes bias in the effect-size estimate of non-differentially expressed genes. This markedly inflates the false positive discovery rates. Variance stabilizing normalization (VSN) behaved best. Conclusion: A simple parametric bootstrap was used to simulate oligo-nucleotide micro-array raw data. Current normalization methods inflate the false positive rate when many genes show an effect in the same direction.
Dissertations / Theses on the topic "Reverse symmetrical current"
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Івашків, Василь Романович. "Теоретичні основи і технологічні засади електрохімічного перероблення псевдосплаву WC-Ni." Thesis, НТУ "ХПІ", 2016. http://repository.kpi.kharkov.ua/handle/KhPI-Press/21962.
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Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.17.03 – технічна електрохімія. – Національний університет "Львівська політехніка", Львів, 2016.
Дисертація присвячена розробленню теоретичних основ і технологічних засад електрохімічного окисного розчинення вторинної вольфрамвмісної сировини карбідного типу (псевдосплавів WC-Ni) з одержанням оксидів Вольфраму та ніколу (ІІ) сульфату кристалогідрату. У дисертації висвітлено результати електрохімічної поведінки псевдосплаву WC-Ni у розчинах кислот (HCl, HNO₃, H₂SO₄); NaOH та аміакатних електролітах (NH₄OH, NH₄OH + NH₄Cl); диметилформамідних розчинах літію та ніколу (ІІ) хлоридів, за різних температур (20…80⁰ С) та потенціалів електрода (-0,2…2 В). Вибрано найкращий за технологічними показниками процес перероблення псевдосплавів WC-Ni, а саме окиснення вольфраму (IV) карбіду до його оксидів з одночасним розчиненням нікелю, та електроліт для здійснення цього процесу, а саме сульфатну кислоту. Згідно з планом комбінаційних квадратів, проведено дослідження електрохімічного окисного розчинення вищенаведених псевдосплавів у розчинах H₂SO₄ + Ni₂SO₄, за різних концентрацій компонентів (С₁, С₂), температур (Т) та потенціалів електрода (Е). Одержано математичні моделі залежності густини струму (іₐ) та виходу за струмом (ВС) від чотирьох факторів (С₁, С₂, Т, Е). На основі розрахунків за вказаними моделями визначено оптимальні умови електролізу. Проведено дослідження електрохімічного окисного розчинення WC-Ni в 1М H₂SO₄ за симетричного реверсного струму. Показано, що таке здійснення процесу електролізу немає суттєвих переваг, порівняно із процесом за постійного струму. Запропоновано схему вузла пілотного електролізера та принципову технологічну схему перероблення псевдосплаву WC-Ni у WO₃. Виконано техніко-економічний аналіз запропонованої технології, показано її економічну доцільність та ефективність.The thesis for the degree of candidate of technical sciences, specialty 05.17.03 – technical electrochemistry. – National University "Lviv Polytechnic", Lviv, 2016. The thesis is devoted to development of theoretical basis and technological foundations electrochemical oxidative dissolution of secondary tungsten raw materials carbide type (pseudoalloys WC-Ni) to form tungsten oxide and Nicol (II) sulphate crystalline. The thesis highlights the results of the electrochemical behavior pseudoalloys WCNi in solutions of various acids (HCl, HNO₃, H₂SO₄), alkali NaOH and ammoniac electrolytes (NH₄OH, NH₄OH + NH₄Cl); dymetylformamids solutions of lithium and nicol (II) chloride, at different temperatures (20 – 80° C) and electrode potentials (-0.2 – 2 V). Selected best at technological indicators process of recycling pseudoalloys WC-Ni, namely oxidation of tungsten (IV) carbide to him oxide, while dissolving nickel, and electrolyte for this process, namely sulfuric acid. According to the plan, combination squares, studied electrochemical oxidation dissolution above pseudoalloys in solutions H₂SO₄ + Ni₂SO₄, at different concentrations of the components (С₁, С₂), temperature (T) and electrode potential (E). Obtained mathematical models depending on current density (Ia) and exit at current (AC) of the four factors (С₁, С₂, T, E). Based on the calculation at the above models, defined optimum (favorable) conditions of electrolysis. Research electrochemical oxidative dissolution of WC-Ni in 1M H₂SO₄ for symmetric reverse current. It is shown that such realization electrolysis no significant advantages compared with the process for DC. The scheme of the experimental electrolyzer and fundamental technological scheme of recycling pseudoalloys WC-Ni to WO₃ it was suggested. Completed feasibility study of the proposed technology, displayed its economic feasibility and efficiency.
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Івашків, Василь Романович. "Теоретичні основи і технологічні засади електрохімічного перероблення псевдосплаву WC-Ni." Thesis, НТУ "ХПІ", 2016. http://repository.kpi.kharkov.ua/handle/KhPI-Press/21963.
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Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.17.03 – технічна електрохімія. – Національний університет "Львівська політехніка", Львів, 2016.
Дисертація присвячена розробленню теоретичних основ і технологічних засад електрохімічного окисного розчинення вторинної вольфрамвмісної сировини карбідного типу (псевдосплавів WC-Ni) з одержанням оксидів Вольфраму та ніколу (ІІ) сульфату кристалогідрату. У дисертації висвітлено результати електрохімічної поведінки псевдосплаву WC-Ni у розчинах кислот (HCl, HNO₃, H₂SO₄); NaOH та аміакатних електролітах (NH₄OH, NH₄OH + NH₄Cl); диметилформамідних розчинах літію та ніколу (ІІ) хлоридів, за різних температур (20…80⁰ С) та потенціалів електрода (-0,2…2 В). Вибрано найкращий за технологічними показниками процес перероблення псевдосплавів WC-Ni, а саме окиснення вольфраму (IV) карбіду до його оксидів з одночасним розчиненням нікелю, та електроліт для здійснення цього процесу, а саме сульфатну кислоту. Згідно з планом комбінаційних квадратів, проведено дослідження електрохімічного окисного розчинення вищенаведених псевдосплавів у розчинах H₂SO₄ + Ni₂SO₄, за різних концентрацій компонентів (С₁, С₂), температур (Т) та потенціалів електрода (Е). Одержано математичні моделі залежності густини струму (іₐ) та виходу за струмом (ВС) від чотирьох факторів (С₁, С₂, Т, Е). На основі розрахунків за вказаними моделями визначено оптимальні умови електролізу. Проведено дослідження електрохімічного окисного розчинення WC-Ni в 1М H₂SO₄ за симетричного реверсного струму. Показано, що таке здійснення процесу електролізу немає суттєвих переваг, порівняно із процесом за постійного струму. Запропоновано схему вузла пілотного електролізера та принципову технологічну схему перероблення псевдосплаву WC-Ni у WO₃. Виконано техніко-економічний аналіз запропонованої технології, показано її економічну доцільність та ефективність.The thesis for the degree of candidate of technical sciences, specialty 05.17.03 – technical electrochemistry. – National University "Lviv Polytechnic", Lviv, 2016. The thesis is devoted to development of theoretical basis and technological foundations electrochemical oxidative dissolution of secondary tungsten raw materials carbide type (pseudoalloys WC-Ni) to form tungsten oxide and Nicol (II) sulphate crystalline. The thesis highlights the results of the electrochemical behavior pseudoalloys WCNi in solutions of various acids (HCl, HNO₃, H₂SO₄), alkali NaOH and ammoniac electrolytes (NH₄OH, NH₄OH + NH₄Cl); dymetylformamids solutions of lithium and nicol (II) chloride, at different temperatures (20 – 80° C) and electrode potentials (-0.2 – 2 V). Selected best at technological indicators process of recycling pseudoalloys WC-Ni, namely oxidation of tungsten (IV) carbide to him oxide, while dissolving nickel, and electrolyte for this process, namely sulfuric acid. According to the plan, combination squares, studied electrochemical oxidation dissolution above pseudoalloys in solutions H₂SO₄ + Ni₂SO₄, at different concentrations of the components (С₁, С₂), temperature (T) and electrode potential (E). Obtained mathematical models depending on current density (Ia) and exit at current (AC) of the four factors (С₁, С₂, T, E). Based on the calculation at the above models, defined optimum (favorable) conditions of electrolysis. Research electrochemical oxidative dissolution of WC-Ni in 1M H₂SO₄ for symmetric reverse current. It is shown that such realization electrolysis no significant advantages compared with the process for DC. The scheme of the experimental electrolyzer and fundamental technological scheme of recycling pseudoalloys WC-Ni to WO₃ it was suggested. Completed feasibility study of the proposed technology, displayed its economic feasibility and efficiency.
Book chapters on the topic "Reverse symmetrical current"
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Pisani-Ferry, Jean. "The Return of Global Asymmetries." In Europe's Transformations, 195–210. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780192895820.003.0013.
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`The last three decades have witnessed the reversal of the ‘great divergence’ between the centre and the periphery that characterized the nineteenth century and most of the twentieth. The promise of this ‘great convergence’ was a much more symmetric world where prosperity and power would be much more equally distributed, where nations would abide by a rules-based international order and where effective global institutions would help ensure an adequate provision of global public goods. Economic analysis helped foresee how such a world would function. In contrast to those in vogue in the early post-war decades, the workhorse models for international trade, money, and finance of the late twentieth century all emphasized symmetry in international relations. Countries could be big or small, developed or poor, capital exporters or importers, but the same mechanisms and rules applied to them. It was only a matter of time before they would converge, or possibly trade places. More recent models, however, have started to challenge this benign view. Asymmetries between centre and periphery do matter in the network-based models of trade, investment, and finance that have been developed to account for emerging patterns of interaction. This is even truer of data flows and the networks that structure them. Meanwhile, the centrality of the dominant global currency and the asymmetries that it entails in exchange-rate adjustment are being rediscovered. Today’s world is much more asymmetric than we thought. This change of perspectives has significant implications for international economic relations and for global governance.
Conference papers on the topic "Reverse symmetrical current"
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Sun, Xinxing, Giorgio Adamo, Mustafa Eginligil, Harish N. S. Krishnamoorthy, Nikolay I. Zheludev, and Cesare Soci. "Mirror-Symmetric Patterning of Topological Insulator Reverses Photogalvanic Currents." In CLEO: Applications and Technology. Washington, D.C.: OSA, 2021. http://dx.doi.org/10.1364/cleo_at.2021.jw1a.56.
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Elyasi, M., C. S. Bhatia, and H. Yang. "Individual site reversal in centro-symmetric matrices by common current excitation." In 2015 IEEE International Magnetics Conference (INTERMAG). IEEE, 2015. http://dx.doi.org/10.1109/intmag.2015.7156655.
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Osman, Sameer, and Esraa Mansour. "Performance of Bio-Inspired Oscillating Hydrofoil Turbine; a Computational Fluid Dynamics Study." In ASME 2021 15th International Conference on Energy Sustainability collocated with the ASME 2021 Heat Transfer Summer Conference. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/es2021-63383.
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Abstract Renewable energy has seen significant growth in the past decades because it is sustainable, has no pollution effects, and not subject to oil or gas reserves. Hydroelectric power is the cheapest type of renewable energy worldwide, even though it had limited growth in the past decades. Oscillating-hydrofoil turbine is a new type of hydroelectric turbines operating in continuous streams of water currents. In this study, a two-dimensional, unsteady computational model was developed to predict the oscillating-hydrofoil turbine’s performance using different foil sections. This model was validated with the existing experimental data in the literature. Standard symmetric foil and non-standard foils that are bio-inspired from hummingbird wings were investigated for their impact on the turbine’s performance. Results for the lift, drag, and power coefficients for these foils were compared throughout the cycle to the NACA symmetric foil used previously. Results of the vorticity contours show that the leading-edge curvature of the foil has a significant effect on the formation of the leading-edge vortex, therefore, affecting the dynamic lift force. Furthermore, using bio-inspired foils with a slight camber, the unit’s power density and efficiency increased significantly during the upward lift stroke. However, the downward lift stroke was adversely affected, which introduced the suggestion of using two reversed foils in tandem operation to obtain maximum efficiency. The largest power coefficient was obtained for the NACA0015 foil, which was equal to 0.37, and the second-best was for the RAF-19 foil with a value of 0.368.
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Gandini, Martina, and Suela Ruffa. "A DOE Approach for Sensitivity Analysis of a Shape Partitioning Algorithm." In ASME 2008 9th Biennial Conference on Engineering Systems Design and Analysis. ASMEDC, 2008. http://dx.doi.org/10.1115/esda2008-59175.
Full textAbstract:
In the field of geometrical product specification and verification, one of the main problems is classification and segmentation of 3D shapes. Shape recognition and segmentation is a widespread research area with different application fields (image processing, shape searching, pattern recognition, reverse engineering, etc.). Many methodologies and algorithms have been developed within such different fields, each one exhibiting optimized performances with respect to the set of objects and targets in each application [1, 11, 12]. Nevertheless, for manufactured parts a unique description of shape during the whole product lifecycle is still envisaged, and GPS (“Geometrical Product Specification and Verification”) project seems to be the most promising approach, but it should be stated that the partitioning process is still to be improved both theoretically and operationally. The ISO Technical Committee 213 (TC213), entrusted to develop the GPS project, founded the partitioning process on the classification of shapes based on symmetrical properties of surfaces [5, 6]. The aim of this paper is to describe the method proposed by Gelfand and Guibas [4] and analyze its performances on sampled surfaces by varying parameters of the method that basically affect its efficiency. In fact, the ISO research is currently devoted to identify a segmentation method characterized by efficiency, reliability, robustness and applicability with the aim to standardize the methodology for the verification phase of the manufacturing process. In this paper, a DOE analysis has been performed, in order to search an optimal parameter configuration, necessary to consider the method as a standard for shape partitioning.