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41.
This note reconsiders the marginal density of a threshold moving average process and proposes a simple yet effective numerical algorithm to implement that by solving an associated integral equation. This algorithm can also be applied to calculate stationary probability density or distribution functions of a few other types of nonlinear stationary stochastic processes numerically. 相似文献
42.
《International Journal of Hydrogen Energy》2021,46(75):37333-37339
Water electrolysis is an efficient approach for high-purity hydrogen production. However, the anodic sluggish oxygen evolution reaction (OER) always needs high overpotential and thus brings about superfluous electricity cost of water electrolysis. Therefore, exploiting highly efficient OER electrocatalysts with small overpotential especially at high current density will undoubtedly boost the development of industrial water electrolysis. Herein, we used a simple hydrothermal method to prepare a novel FeOOH–CoS nanocomposite on nickel foam (NF). The as-prepared FeOOH–CoS/NF catalyst displays an excellent OER performance with extremely low overpotentials of 306 and 329 mV at 500 and 1000 mA cm−2 in 1.0 M KOH, respectively. In addition, the FeOOH–CoS/NF catalyst can maintain excellent catalytic stability for more than 50 h, and the OER catalytic activity shows almost no attenuation no matter after 1000 repeated CV cycles or 50 h of stability test. The high catalytic activity and stability have exceeded most non-noble metal electrocatalysts reported in literature, which makes the FeOOH–CoS/NF composite catalyst have promising applications in the industrial water electrolysis. 相似文献
43.
ABSTRACTThe RF output power dissipated per unit area is calculated using Runge-Kutta method for the high-moderate-moderate-high (n+-n-p-p+) doping profile of double drift region (DDR)-based impact avalanche transit time (IMPATT) diode by taking different substrate at Ka band. Those substrates are silicon, gallium arsenide, germanium, wurtzite gallium nitride, indium phosphide and 4H-silicon carbide. A comparative study regarding power dissipation ability by the IMPATT using different material is being presented thereby modelling the DDR IMPATT diode in a one-dimensional structure. The IMPATT based on 4H-SiC element has highest power density in the order of 1010 Wm?2 and the Si-based counterpart has lowest power density of order 106 Wm?2 throughout the Ka band. So, 4H-SiC-based IMPATT should be preferable over others for the power density preference based application. This result will be helpful to estimate the power density of the IMPATT for any doping profile and to select the proper element for the optimum design of the IMPATT as far as power density is concerned in the Ka band. Also, we have focused on variation of power density with different junction temperatures and modelled the heat sink with analysis of thermal resistances. 相似文献
44.
In this study, the decomposition of methanol into the CO and H species on the Pd/tungsten carbide (WC)(0001) surface is systematically investigated using periodic density functional theory (DFT) calculations. The possible reaction pathways and intermediates are determined. The results reveal that saturated molecules, i.e., methanol and formaldehyde, adsorb weakly on the Pd/ WC(0001) surface. Both CO and H prefer three-fold sites, with adsorption energies of −1.51 and −2.67 eV, respectively. On the other hand, CH3O stably binds at three-fold and bridge sites, with an adsorption energy of −2.58 eV. However, most of the other intermediates tend to adsorb to the surface with the carbon and oxygen atoms in their sp3 and hydroxyl-like configurations, respectively. Hence, the C atom of CH2OH preferentially attaches to the top sites, CHOH and CH2O adsorb at the bridge sites, while COH and CHO occupy the three-fold sites. The DFT calculations indicate that the rupture of the initial C–H bond promotes the decomposition of CH3OH and CH2OH, whereas in the case of CHOH, O–H bond scission is favored over the C–H bond rupture. Thus, the most probable methanol decomposition pathway on the Pd/WC(0001) surface is CH3OH → CH2OH → trans-CHOH → CHO → CO. The present study demonstrates that the synergistic effect of WC (as carrier) and Pd (as catalyst) alters the CH3OH decomposition pathway and reduces the noble metal utilization. 相似文献
45.
46.
The influence of network density on the strain hardening behaviour of amorphous polymers is studied. The network density of polystyrene is altered by blending with poly(2,6-dimethyl-1,4-phenylene-oxide) and by cross-linking during polymerisation. The network density is derived from the rubber-plateau modulus determined by dynamic mechanical thermal analysis. Subsequently uniaxial compression tests are performed to obtain the intrinsic deformation behaviour and, in particular, the strain hardening modulus. At room temperature, the strain hardening modulus proves to be proportional to the network density, irrespective of the nature of the network, i.e. physical entanglements or chemical cross-links. With increasing temperature, the strain hardening modulus is observed to decrease. This decrease appears to be related to the influence of thermal mobility of the chains, determined by the distance to the glass-transition temperature (T−Tg). 相似文献
47.
48.
针对车用柴油酸度等性质测定过程繁琐,采用衰减全反射样品池测定车用柴油的红外光谱,用偏最小二乘法(PLS)建立红外光谱测定车用柴油酸度、密度、闪点和凝点的4个校正模型,验证标准误差分别为0.46 mg/(100 mL),0.77kg/m3,2.60 ℃,2.77 ℃,该方法符合标准方法再现性要求。与标准方法相比,该方法具有无需预处理、操作简单、测量快速、重复性好等优点。 相似文献
49.
低阻VDMOSFET的优化设计与制造 总被引:1,自引:1,他引:0
文章对9926型双N沟增强型VDMOSFET进行了结构和版图的优化设计。给出了该器件的纵横向结构参数,材料的物理参数和版图总体结构。单胞结构的优化设计使单胞密度达到204万个/cm2,比国际市场现有产品的单胞密度(156万个/cm2)提高了30%。这种设计采用浅n+注入工艺可使器件生产成本下降31%。最后对研制结果进行了分析讨论。 相似文献
50.
用方位密度成像测井资料计算水平井钻遇地层倾角的方法 总被引:1,自引:0,他引:1
Schlumberger公司的随钻方位密度测井(ADN)可以提供井周16个方位的密度成像资料,为过井眼的地质界面产状的计算提供了方便.对于垂直井或大斜井,当井眼穿过一个有明显电测响应变化的地质界面时,利用井壁成像资料可以方便地描述地质界面的产状;对于水平井,由于井眼轨迹基本与地层平行,井眼轨迹常常只能穿越地层界面.传统的对界面产状的描述方法已不再适用.提出了一种利用方位密度成像测井计算水平井井旁地层产状的方法.希望随着测井新技术的出现不断完善新的解释方法,以提高随钻方位密度测井的使用范围和精度. 相似文献