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排序方式： 共有274条查询结果，搜索用时 46 毫秒
91.
Himanshu Sharma karthikeyan Rajagopal G. Gugapriya Rajneesh Pareek Arun Kumar Haya Mesfer Alshahrani Mohamed K. Nour Hany Mahgoub Mohamed Mousa Anwer Mustafa Hilal 《计算机系统科学与工程》2023,45(2):1199-1210
Multicarrier Waveform (MCW) has several advantages and plays a very important role in cellular systems. Fifth generation (5G) MCW such as Non-Orthogonal Multiple Access (NOMA) and Filter Bank Multicarrier (FBMC) are thought to be important in 5G implementation. High Peak to Average Power Ratio (PAPR) is seen as a serious concern in MCW since it reduces the efficiency of amplifier use in the user devices. The paper presents a novel Divergence Selective Mapping (DSLM) and Divergence Partial Transmission Sequence (D-PTS) for 5G waveforms. It is seen that the proposed D-SLM and PTS lower PAPR with low computational complexity. The work highlighted a combination of multi-data block partial transmit schemes along with tone reservation. In this, an overlapping factor is used to determine the number of data blocks for every group. Here, considering only those data blocks that have minimum signal power, the use of DSLM and DPTS are required to eliminate the segment’s peaks. Simulation results reveal that the suggested hybrid technique proves to be better than the conventional PTS scheme. Furthermore, the power saving performance of FBMC and NOMA is compared with the Orthogonal Frequency Division Multiplexing (OFDM) waveform. 相似文献
92.
93.
AbstractThe new Caputo Fabrizio fractional differential operator is used to investigate a problem in the fractional order theory of thermoelasticity. The problem concerns an infinite elastic space under the effect of a continuous line source of heat. The problem is solved using asymptotic expansions valid for short times. Laplace and Hankel transforms are used to solve the problem. A brief study to the nature of propagation of waves is introduced. Graphical results are presented and discussed. 相似文献
94.
I/V polarization curves of proton‐exchange membrane fuel cells (PEMFCs) are used to characterize the performance of single cells and stacks. Numerous semi‐empirical models are presented to predict such polarization curves by determining the unknown parameters of mathematical model of the PEMFCs stack. In this paper, a novel optimization approach, namely neural network algorithm (NNA) is applied for an estimation of the unknown PEMFC model parameters. The NNA is employed to minimize adopted objective function, which is formulated as the sum of squared deviations (SSD) between the actual data and estimated voltage points subjects to set of inequality constraints are satisfied. Three commercial types of PEMFCs stack namely Ballard Mark V, BCS‐500 W, and Nedstack PS6 are numerically simulated to show the effectiveness of the proposed NNA‐based tool for parameter identification. The minimum values of SSD are 0.8536 V 2 for Ballard Mark V, 0.011698 V 2 for BCS‐500 W stack, and 2.14487 V 2 for Nedstack PS6, respectively. The obtained results of the NNA are compared with other optimizers recently published in the literature such as flower pollination algorithm, slap swarm optimizer, grey wolf algorithm, grasshopper optimization algorithm, and shark smell algorithm under the same conditions. The comparisons and other performance tests indicate the robustness and the competition of the adopted NNA‐based method for producing accurate I/V polarization curves under different operating scenarios. 相似文献
95.
Maximilian Bernt Alexandra Hartig-Weiß Mohammad Fathi Tovini Hany A. El-Sayed Carina Schramm Jonas Schröter Christian Gebauer Hubert A. Gasteiger 《化学，工程师，技术》2020,92(1-2):31-39
This work addresses current challenges in catalyst development for proton exchange membrane water electrolyzers (PEM-WEs). To reduce the amount of iridium at the oxygen anode to levels commensurate with large-scale application of PEM-WEs, high-structured catalysts with a low packing density are required. To allow an efficient development of such catalysts, activity and durability screening tests are essential. Rotating disk electrode measurements are suitable to determine catalyst activity, while accelerated stress tests on the MEA level are required to evaluate catalyst stability. 相似文献
96.
Peng Qin Paek Sanghyun M. Ibrahim Dar Kasparas Rakstys Hany ElBatal Shaheen A. Al‐Muhtaseb Christian Ludwig Mohammad Khaja Nazeeruddin 《Advanced functional materials》2016,26(30):5550-5559
Molecularly engineered weakly conjugated hybrid porphyrin systems are presented as efficient sensitizers for solid‐state dye‐sensitized solar cells. By incorporating the quinolizino acridine and triazatruxene based unit as the secondary light‐harvester as well as electron‐donating group at the meso‐position of the porphyrin core, the power conversion efficiencies of 4.5% and 5.1% are demonstrated in the solid‐state devices containing 2,2′,7,7′‐tetrakis (N,N‐di‐p‐methoxyphenylamine)‐9,9′‐spiro bifluorene as hole transporting material. The photovoltaic performance of the triazatruxene donor based porphyrin sensitizer is better than that of the previously published porphyrin molecules exhibiting strongly conjugated push–pull structure. The effect of molecular structure on the optical and electrochemical properties, the dynamics of charge extraction, as well as the photovoltaic performance are systematically investigated, which offers a new design strategy for further refinement of porphyrin molecules. 相似文献
97.
Mourad S. Semary Hany N. Hassan Ahmed G. Radwan 《Chemical Engineering Communications》2017,204(6):635-647
This paper discusses the diffusion and reaction behaviors of catalyst pellets in the fractional-order domain as well as the case of nth-order reactions. Two generic models are studied to calculate the concentration of reactant in a porous catalyst in the case of a spherical geometric pellet and a flat-plate particle with different examples. A controlled Picard analytical method is introduced to obtain an approximated solution for these systems in both linear and nonlinear cases. This method can cover a wider range of problems due to the extra auxiliary parameter, which enhances the convergence and is suitable for higher-order differential equations. Moreover, the exact solution in the linear fractional-order system is obtained using the Mittag–Leffler function where the conventional solution is a special case. For nonlinear models, the proposed method gives matched responses with the homotopy analysis method (HAM) solutions for different fractional orders. The effect of fractional-order parameter on the dimensionless concentration of the reactant in a porous catalyst is analyzed graphically for different cases of order reactions and Thiele moduli. Moreover, the proposed method has been applied numerically for different cases to predict and calculate the dual solutions of a nonlinear fractional model when the reaction order n?=??1. 相似文献
98.
Jian Liu Hany Hassanin Zhenyu Ni Yi Yang Gang Yang 《Materials and Manufacturing Processes》2017,32(12):1325-1330
In this study, nickel (Ni) micro components with high precision were produced by electroforming using a soft mold produced by soft lithography and photolithography techniques. The effects of current densities on the microstructures and mechanical properties of the fabricated micro components were studied. It is found that a high-precision soft mold was successfully fabricated and micro Ni gears with sharp walls and fine features were produced. A feature size as small as approximately 70?µm, a height of 380?µm, and a pitch diameter of 3?mm were achieved for the gear. The densities of the gears electroformed are found to be within the range of 5.24–2.95?g/cm3 when current densities utilized vary between 50 and 10?mA/cm2. A lower current density leads to a finer microstructure and a larger value of microhardness. Meanwhile, by changing the current density from 50 to 10?mA/cm2, the grain size decreases from around 50 to 30?nm while the microhardness increases from 220 to 410. In addition, the preferred orientation of the Ni matrix changes from (111) to (200) or (220) with the decreasing current density. 相似文献
99.
100.