A Projected Extrapolated Gradient Method with Larger Step Size for Monotone Variational Inequalities

Journal of Optimization Theory and Applications - A projected extrapolated gradient method is designed for solving monotone variational inequality in Hilbert space. Requiring local Lipschitz...     

A Feature-Based Stochastic Permeability of Shale: Part 1—Validation and Two-Phase Permeability in a Utica Shale Sample

Transport in Porous Media - Estimate of permeability plays a crucial role in flow-based studies of fractured tight-rocks. It is well known that most of the flow through tight-rocks (e.g., shales)...     

Prediction of new vortices in single-phase nanofluid due to dipole interaction

Journal of Thermal Analysis and Calorimetry - Magnetic field effects are encountered in many engineering applications which include but are not limited to metal casting, nuclear reactor coolers,...     

Dynamics Modeling and Experimental Investigation of Gear Mechanism with Coupled Small Clearances

Internal gear mechanism is widely used in micro-nano satellites due to its compact structure and high precision transmission. However, the vibration coupling caused by the small clearance coupling is more obvious and cannot be ignored under low speed, light load and zero gravity conditions. Based on the geometric relationship between radial clearance and backlash, a coupled model between dynamic backlash and radial clearance of internal meshing gear is established. Based on the conformal contact theory, the radial collision force model of the gear shaft and shaft sleeve considering the small clearances is established. Additionally, a multi-clearance gear rotor system test device is built to measure the vibration acceleration of the internal gear rotor system by an acceleration sensor and transmitted to the industrial computer through a signal collector for data processing. Through the comparison of simulation and experiment, the accuracy of the gear dynamics model is verified. The analysis results show that, compared with the traditional model, the calculation results of the gear mechanism model considering the small clearance coupling is closer to the experimental data.     

Visible light photopolymerization of nitro‐stilbenzene photosensitive initiating systems

In this paper, we presented four novel visible light photoinitiating systems, which employed nitro‐stilbenzene derivatives as photoinitiators. Visible light photopolymerization of these systems was studied completely. The results showed that the chemical structures of the photoinitiators, photoinduced electron transfer approach, solvent polarity, and monomers played significant effects on the visible light photopolymerization. The electrochemistry of nitro‐stilbenzene was dramatically influenced by the linking benzophenone moiety. The cyclic voltammograms of four photoinitiators were determined and discussed. We further estimated the thermodriving force for electron transfer between nitro‐stilbenzene and benzophenone. Thermal stabilities of new photoinitators were determined by the analysis of differential scanning calorimetry (DSC) and thermogravimetry (TG) in this paper. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis and properties of novel α‐(1,2,4‐triazolo[1,5‐a]pyrimidine‐2‐oxyl)phosphonate derivatives

In an attempt to discover novel compounds with high activity and low toxicity, a series of new phosphonate derivatives containing triazolo[1,5‐a]pyrimidine moieties have been designed and synthesized by a nucleophilic substitution between α‐hydroxyphosphonates and 2‐methanesulfonyl‐1,2,4‐triazolo[1,5‐a]pyrimidines. The structures of all compounds prepared were confirmed by elemental analyses and by NMR and MS spectroscopy. The results of preliminary bioassay indicate that the title compounds possess certain selective herbicidal activity against rape and also, to some extent, inhibit of acetolactase synthase activity. © 2000 John Wiley & Sons, Inc. Heteroatom Chem 11:313–316, 2000     

PVT法钨坩埚系统中自发生长自支撑AlN单晶及其表征分析

采用物理气相传输(PVT)法在AlN原料表面自发生长出大量毫米级尺寸的AlN单晶.本文对该工艺下AlN单晶的自然形貌、极性、杂质含量等进行了分析.实验及分析结果表明,在实验工艺条件下,原料表面生长的AlN晶粒具有规则的六方外形,晶粒沿C向择优生长且具有高的生长速率(约200～ 250 μm/h),但径向生长受限于{10-10}(m面).不同颜色的AlN晶粒经机械切割及化学机械抛光(CMP)后,形成高表面质量的C轴取向抛光片.通过化学湿法腐蚀和SEM表征发现,淡黄色晶粒为Al极性晶体,暗棕色晶粒为N极性晶体,淡黄-暗棕混合色晶粒为Al/N混合极性晶体,其内部可以观察到清晰的两种极性分界.通过GDMS与EGA对不同颜色晶粒内部的主要杂质元素含量进行了分析,结果表明,淡黄色晶粒内氧元素的含量相比暗棕色晶粒的含量低,而碳含量则相反.     

PVT法AlN单晶生长技术研究进展及其面临挑战

氮化铝(AlN)具有超宽禁带宽度(6.2 eV)、高热导率(340 W/(m·℃))、高击穿场强(11.7 MV/cm)、良好的紫外透过率、高化学和热稳定性等优异性能,是氮化镓基(GaN)高温、高频、高功率电子器件以及高Al组分深紫外光电器件的理想衬底材料.物理气相传输(PVT)法是制备大尺寸高质量AlN单晶最有前途的方法.本文介绍了AlN单晶的晶体结构、基本性质及PVT法生长AlN晶体的原理与生长习性.基于AlN单晶PVT生长策略,综述了自发形核工艺、同质外延工艺及异质外延工艺的研究历程,各生长策略的优缺点及其最新进展.最后对PVT法生长AlN单晶的发展趋势及其面临的挑战进行了简要展望.     

A Mathematical Model for Determining Oil Migration Characteristics in Low-Permeability Porous Media Based on Fractal Theory

Shale reservoirs are characterized by very low permeability in the scale of nano-Darcy. This is due to the nanometer scale of pores and throats in shale reservoirs, which causes a difference in flow behavior from conventional reservoirs. Slip flow is considered to be one of the main flow regimes affecting the flow behavior in shale gas reservoirs and has been widely studied in the literature. However, the important mechanism of gas desorption or adsorption that happens in shale reservoirs has not been investigated thoroughly in the literature. This paper aims to study slip flow together with gas desorption in shale gas reservoirs using pore network modeling. To do so, the compressible Stokes equation with proper boundary conditions was applied to model gas flow in a pore network that properly represents the pore size distribution of typical shale reservoirs. A pore network model was created using the digitized image of a thin section of a Berea sandstone and scaled down to represent the pore size range of shale reservoirs. Based on the size of pores in the network and the pore pressure applied, the Knudsen number which controls the flow regimes was within the slip flow regime range. Compressible Stokes equation with proper boundary conditions at the pore’s walls was applied to model the gas flow. The desorption mechanism was also included through a boundary condition by deriving a velocity term using Langmuir-type isotherm. It was observed that when the slip flow was activated together with desorption in the model, their contributions were not summative. That, is the slippage effect limited the desorption mechanism through a reduction of pressure drop. Eagle Ford and Barnett shale samples were investigated in this study when the measured adsorption isotherm data from the literature were used. Barnett sample showed larger contribution of gas desorption toward gas recovery as compared to Eagle Ford sample. This paper has produced a pore network model to further understand the gas desorption and the slip flow effects in recovery of shale gas reservoirs.

     

纳米纤维素/MnO2自支撑锌离子电池正极的制备及其电化学性能研究

以羟基纳米纤维素为原料,利用其表面丰富的羟基还原KMnO 4,在纳米纤维表面原位生成MnO₂纳米颗粒,并与Super P混合,通过简单抽滤的方式获得CNF@MnO₂/Super P自支撑正极。结果表明:无粘结剂的CNF@MnO₂/Super P自支撑正极具有较高的循环稳定性,在0.5 A·g^-1的电流密度下,循环800圈后,容量仍能达到247 mAh·g^-1;均匀分布的纳米MnO₂与Super P能够有效缩短离子和电子扩散路径,大大降低材料的电阻,使正极具有良好的倍率性能,在2 A·g^-1的电流密度下,循环300圈之后,电池容量仍保持在175 mAh·g^-1,库仑效率~99%;利用该正极良好的延展性,制备了软包电池,并表现出了较高的循环稳定性和容量保持率,该工作为柔性无粘结剂的水系Zn-MnO₂二次电池的设计开发提供了新的研究思路。