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Hydrophobic polyethersulfone porous membranes for membrane distillation

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Frontiers of Chemical Science and Engineering 2015年第1期9卷 84-93页

作者： Heba ABDALLAH Ayman EL-GENDI Maaly KHEDR Elham EL-ZANATI Chemical Engineering & Pilot Plant Department Engineering Research Division National Research Center 33 Bohouth st. Dokki Giza Egypt

Membrane distillation （MD） is a thermal, vapor-driven transportation process through micro porous hydrophobic membranes that is increasingly being applied to seawater and brine desalination processes. Two types of hydrophobic microporous polyethersulfone fiat sheet membranes, namely, annealed polyethersulfone and a polyethersulfone/tetraethoxysilane （PES/TEOS） blend were prepared by a phase inversion process. The membranes were characterized and their performances were investigated using the vacuum membrane distillation of an aqueous NaCI solution. The performances of the prepared membranes were also compared with two commercially available hydrophobic membranes, polyte- trafluorethylene and polyvinylidene fluoride. The influence of operational parameters such as feed temperature （25-65 ℃）, permeate vacuum pressure （200 800 mbar）, feed flow rate （8-22 mL/s） and feed salt concentration （3000 to 35000 mg/L） on the MD permeation flux were investigated for the four membranes. The hydrophobic PES/TEOS membrane had the highest salt rejection （99.7%） and permeate flux （86 kg/（m^2 -h）） at 65 ℃, with a feed of 7000 ppm and a pressure of 200 mbar.

关键词： membrane distillation hydrophobic membrane salt rejection permeate flux

Jam Formation of Traffic Flow in Harbor Tunnel

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Communications in Theoretical Physics 2011年第12期56卷 1140-1144页

作者：何红弟卢伟真董力耘 Logistics research center & Shanghai Engineering research center of Shipping Logistics Information Shanghai Maritime University Department of Civil and Architectural Engineering City University of Hong Kong Shanghai Institute of Applied Mathematics and Mechanics Shanghai University

This paper reports a study concerning occurrence and growth of traffic jam in a harbor tunnel. The single-lane with three sections （downgrade, fiat, and upgrade） is taken into account and they are characterized with different velocity limit. At the low density, the traffic current increases linearly with density and saturates at some values of immediately density. As the density increases, the traffic jam appears firstly before the upgrade section and then extends to the downgrade section. Additionally, the relationships of the velocity and headway against position in different densities are obta/ned from simulation. These results clearly clarify where and when the traffic jam appears. Finally, the critical densities are derived via the theoretical analysis before and after the discontinuous fronts and the theoretical results are consistent with the critical values of simulation results.

关键词： traffic jam critical densities harbor tunnel slope

Semi-polar GaN LEDs on Si substrate

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Science China(Technological Sciences) 2011年第1期54卷 38-41页

作者： Nobuhiko SAWAKI Yoshio HONDA Department of Electrical and Electronic Engineering Aichi Institute of Technology Department of Electronics and Akasaki research center Nagoya University

Growth of semi-polar （1-101）GaN has been attempted on a patterned （001） silicon substrate adopting selective area MOVPE. The growth was initiated on （111） facets of the Si, which had been prepared by anisotropy etching in a KOH solution. A uni- form semi-polar layer was achieved by coalescence of stripes. Since the growth was performed on facets, the surface was atomically fiat in AFM surface analyses. By using a high temperature grown A1N nucleation layer, we achieved low threading dislocation density at the top most surface. Moreover, by tilting the c-axis of the GaN on the Si substrate, the effect of the thermal expansion coefficient mismatch was much reduced. As the result, we achieved a crack free （1-101）GaN template on （001）Si. On the thus prepared （1-101）GaN, a GalnN/GaN LED was fabricated, which showed excellent performance with weak quantum confined Stark effect.

关键词： GaN selective epitaxy semi-polar GaN MOVPE LED

Effects of slab geometry and obliquity on the interplate thermal regime associated with the subduction of three-dimensionally curved oceanic plates

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Geoscience Frontiers 2015年第1期6卷 61-78页

作者： Yingfeng Ji Shoichi Yoshioka research center for Urban Safety and Security Kobe University Department of Earth and Planetary Science Graduate School of ScienceKobe University

We investigated the relationships among slab geometry, obliquity, and the thermal regime associated with the subduction of oceanic plates using a three-dimensional （3D） parallelepiped thermal convection model. Various models with convex and concave slab shapes were constructed in the numerical simu- lation, and the temperature and mantle flow distributions were calculated. The results revealed that when the slab dip angle increases, or the obliquity of subduction becomes steeper, the interplate tem- perature decreases remarkably. Cooler （warmer） zones on the plate interface were identified from the modeling where there was a larger （smaller） subduction angle. Consequently, the interplate temperature distribution is partly controlled by the true subduction angle （TSA）, which is a function of the slab dip angle and the obliquity of subduction. The rate of change of the interface temperature for the TSA was 10-50 ℃ （10°〈 TSA 〈 20°） at depths ranging from （TSA 10） × 5 km to 60 ＋（TSA 10） × 5 km for a fiat slab after a subduction history of 7 Myrs. The along-arc slab curvature affects the variation in TSA. The slab radius also appeared to influence the radius of induced mantle flow.

关键词： Temperature Mantle flow Heat flow Numerical simulation Slab geometry Obliquity

Transit smart card data mining for passenger origin information extraction

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Journal of Zhejiang University-Science C(Computers and Electronics) 2012年第10期13卷 750-760页

作者： Xiao-lei MA Yin-hai WANG Feng CHEN Jian-feng LIU Department of Civil and Environmental Engineering University of Washington Seattle WA 98195-2700 USA Beijing Transportation research center Beijing 100073 China

The automated fare collection(AFC) system,also known as the transit smart card(SC) system,has gained more and more popularity among transit agencies *** with the conventional manual fare collection system,an AFC system has its inherent advantages in low labor cost and high efficiency for fare collection and transaction data *** it is possible to collect highly valuable data from transit SC transactions,substantial efforts and methodologies are needed for extracting such data because most AFC systems are not initially designed for data *** is true especially for the Beijing AFC system,where a passenger's boarding stop(origin) on a flat-rate bus is not recorded on the check-in *** extract passengers' origin data from recorded SC transaction information,a Markov chain based Bayesian decision tree algorithm is developed in this *** the time invariance property of the Markov chain,the algorithm is further optimized and simplified to have a linear computational *** algorithm is verified with transit vehicles equipped with global positioning system(GPS) data *** verification results demonstrated that the proposed algorithm is effective in extracting transit passengers' origin information from SC transactions with a relatively high *** transit origin data are highly valuable for transit system planning and route optimization.

关键词： Transit smart card Automated fare collection(AFC) Bayesian decision tree Markov chain Origin inference

Discrete element method study of effects of the impeller configuration and operating conditions on particle mixing in a cylindrical mixer

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Particuology 2020年第2期18卷 146-158页

作者： Yuyun Bao Tianchi Li Dengfei Wang Ziqi Cai Zhengming Gao State Key Laboratory of Chemical Resource Engineering School of Chemical EngineeringBeijing University of Chemical TechnologyBeijing 100029China Daqing Petrochemical research center Petrochemical Research InstituteChina National Petroleum CorporationDaqing 163714Heilongjiang ProvinceChina

We employed the discrete element method to study the effects of the impeller configuration(i.e.,blade diameter,inclination angle,and blade number),rotational speed,and fill level on the flow and mixing of particles in a cylindrical mixer equipped with flat and inclined *** coefficient of rolling friction,coefficient of static friction,and coefficient of restitution were experimentally determined before the simulation,and simulation results of the torque and surface particle distribution were validated in experiments,particularly when using a true Young's modulus in the discrete element *** performance of the mixer was assessed using the Lacey mixing *** input work per unit volume was used to represent the mixing *** circumferential velocity and axial diffusion coefficient of the particles were quantitatively analyzed to reveal the effect of particle flow on the *** was found that the mixing performance and efficiency of a three-blade mixer are better than those of two-and four-blade *** pitched blades,a three-fiat-blade mixer has better mixing performance than a three-45°-blade own-pumping or a three-45°-blade up-pumping mixer,but the mixing efficiency of the three-45°-blade up-pumping mixer is the best among these three *** the rotational speed increases,the mixing performance improves but the mixing efficiency hardly *** the fill level is 0.4 times the cylinder diameter,the 160D two-flat-blade mixer has good mixing performance with high mixing *** circumferential velocity has the greatest effect on mixing performance for side-by-side initial loading.

关键词： Cylindrical mixer Impeller configuration Discrete element method Particle Mixing behavior

Simulations of the Transient Flow Generated from a Started Flat Plate

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Chinese Journal of Mechanical Engineering 2012年第6期25卷 1190-1197页

作者： WANG Leqin MA Xudan LI Zhifeng WU Peng WU Dazhuan Institute of Process Equipment Zhejiang UniversityHangzhou 310027China Engineering research center of High Pressure Process Equipment and Safety Ministry of EducationHangzhou 310027China

Transient operations are commonly founded in fluid machineries such as the starting, stopping, and variations of rotor speeds, etc. Flow generated from a started fiat plate is of fundamental importance. Experiments have been done to observe the flow evolution in current researches. And in order to explore the flow in more detailed scale, some vortex methods with high resolution and other numerical methods were developed to solve various related problems by some researchers. But the promotion of vortex method to engineering application is rare due to its complexity and difficulty in specifying the boundary conditions. In order to build up a method of numerical study for such problems, a simplified model is built up with a flat plate. The development of two-dimensional viscous incompressible flow generated from an impulsively started and uniformly accelerated infinitesimally thin flat plate is simulated numerically. A dynamic mesh（DM） method based on the spring analogue and local remeshing is applied to realize the mesh motion caused by the started plate. researches show that the mesh quality will decline under large grid shear force during the updating process. To conquer this problem, a region near the plate is separated to guarantee the mesh quality at location of interest which is the innovation of the present paper. All computations at least cover a period during which the plate translates 6 times its length. The simulated instantaneous velocity profiles, flow structures and drag coefficients under several Reynolds numbers （20 ≤ Re ≤ 126） and accelerations （20 m/s2≤ a ≤ 152 m/s2） are presented and compared with existing results in literatures. Comparisons are found to be satisfactory, confirming the validity of the current proposed method（region separated DM）. The proposed DM method is firstly used to study the transient flow generated from a started flat plate and can be used in further study of transient characteristics during transient operations of turbo mach

关键词： numerical simulation flat plate start transient flow region separated dynamic mesh

Excitation of Whistler-Mode （Chorus） Emissions during Terrestrial Substorms

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Chinese Physics Letters 2005年第9期22卷 2451-2454页

作者：肖伏良赵华贺慧勇 center for Space Science and Applied research Chinese Academy of Sciences Beijing 100080 Department of Physics and Electronic Sciences Changsha University of Science and Technology Changsha 410076

The enhanced growth rate of whistler mode waves has been evaluated during an injection event associated with an isolated terrestrial substorm that occurred at 23：00 UT, on January 21, 1991. The electron phase space density observed by an LEPA instrument on the board of the CRRES spacecraft is modelled by using a bi-loss-cone distribution function （composed of a high anisotropic component and a quasi-isotropic component）. During the injection event, the path integrated gain may increase by a factor of 5 over a frequency range near a few tenths of the electron gyrofrequency, which is consistent with the enhancement observed in the CRRES plasma wave experiment （PWE） emissions. Scattering of electrons by the enhanced whistler mode waves causes the pitch angle distribution of resonant electrons to a quasi isotropic （fiat-top） distribution during the terrestrial substorm injection event.

关键词： COLLISIONLESS MAGNETIC RECONNECTION ACCELERATION INSTABILITY ELECTRONS PLASMA WAVES

Carrier transport via V-shaped pits in InGaN/GaN MQW solar cells

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Chinese Physics B 2017年第3期26卷 558-563页

作者：刘诗涛全知觉王立 School of Materials Science and Engineering Nanchang University Nanchang 330031 China National Engineering Technology research center for LED on Si Substrate Nanchang University Nanchang 330047 China

Carrier transport via the V-shaped pits （V-pits） in InGaN/GaN multiple-quantum-well （MQW） solar cells is numer- ically investigated. By simulations, it is found that the V-pits can act as effective escape paths for the photo-generated carriers. Due to the thin barrier thickness and low indium composition of the MQW on V-pit sidewall, the carriers entered the sidewall QWs can easily escape and contribute to the photocurrent. This forms a parallel escape route for the carries generated in the fiat quantum wells. As the barrier thickness of the fiat MQW increases, more carriers would transport via the V-pits. Furthermore, it is found that the V-pits may reduce the recombination losses of carriers due to their screening effect to the dislocations. These discoveries are not only helpful for understanding the carrier transport mechanism in the InGaN/GaN MQW, but also important in design of the structure of solar cells.

关键词： V-shaped pits InGaN/GaN multiple-quantum-well solar cells carrier transport