Permeability of the porous Al2O3 ceramic with bimodal pore size distribution

Porous Al₂O₃ ceramics with bimodal pore size distribution were fabricated by partial sintering with monodispersed PMMA micro balls as pore agent. The porosity of the fabricated porous Al₂O₃ is increased with content of the pore agent increase, the bulk density and bending strength are decreased, accordingly. Relations between pressure drop and flow velocity of the air through the porous Al₂O₃ fit the Forchheimer's equation well for compressible fluid. Due to pores introduced by the pore agent, the Darcy permeability and inertial permeability of the porous Al₂O₃ are increased obviously. For given flow velocity, with increase of the PMMA content, the Forchheimer's number of the fluid through the porous Al₂O₃ is decreased, which results in decrease of the inertial resistance ratio to the total pressure drop. The porous Al₂O₃ ceramics with pores introduced by the monodispersed PMMA micro balls show higher permeability while the filtration selectivity is not deteriorated.     

Filtration performance of ceramic membrane for the recovery of volatile fatty acids from liquid organic sludge

This research focused on the filtration performance of a membrane-coupled fermenter system for dissolved organics recovery from liquid organic sludge. Over the range 0.1-5 μm, the magnitude of total membrane resistance (R₁) is ranged as follows in the order: 0.1 μm>0.2 μm>0.5 μm>1 μm>2 μm>5 μm. The cake layer resistance (R_c) occupied about 68-88% of total resistance. The decline of permeation flux was mainly attributed to R_c, which was formed by a strong deposition from physicochemical interactions of solids on the membrane surface. Higher suspended solids concentration of suspension caused lower permeation flux. However, there was not a proportional relation beyond a certain SS concentration. The cross-flow velocity on the membrane surface was faster, which resulted in higher permeation flux and also more efficiency with low transmembrane pressure. The appropriate pH of suspension was in the range of 5.0 to 6.0 for dissolved organics recovery as well as permeation flux. It is possible for bacteria to be separated perfectly with 0.1 μm and 0.2 μm membrane pore sizes. Based on experimental results, optimal membrane pore size for the recovery is believed to be around 1 μm.     

Investigation of the impact of simulated commercial centrifugation and microfiltration conditions on levels of Mycobacterium avium ssp. paratuberculosis in milk

The potential for physical removal of Mycobacterium avium ssp. paratuberculosis (M. paratuberculosis ) from milk by centrifugation and microfiltration was investigated by simulating commercial processing conditions in the laboratory by means of a microcentrifuge and syringe filters, respectively. Results indicated that both centrifugation of preheated milk (60°C) at 7000 × g for 10 s, and microfiltration through a filter of pore size 1.2 µm, were capable of removing up to 95–99.9% of M. paratuberculosis cells from spiked whole milk and Middlebrook 7H9 broth suspensions, respectively. Centrifugation and microfiltration may therefore have potential application within the dairy industry as pretreatments to reduce M. paratuberculosis contamination of raw milk.     

The concept and theory of material flow

This paper, for the first time, presents seven main theories under the Material Flow (MF) Theory, namely “Material flow theory”, “Comprehensive MF theory”, “MF element theory”, “MF nature theory”, “MF science and technology theory”, “MF engineering theory” and “MF industry theory”. The paper points out that the MF is the collective term for the flow of macroscopic goods and that of microcosmic substances. The material flow is not only an economic phenomenon, but also social and natural ones. There is not only economic MF, but also social and natural ones. The economic MF is the core for the MF, and the social and natural MF is the basis for the MF; no matter whether in nature, society or economic circles, the MF comprises of five basic elements: Material, Flow, Owner, Region and Time, among which Material is the core one; the MF is divided into intrinsic and extrinsic ones by nature. Its intrinsic natures include Material, Flow, Owner, Region and Time; its extrinsic natures include Party, Service, Management, Technology and Economy. The MF science and technology is a scientific and technological field with very strong comprehensibility, dealing with subjects including natural science, engineering technology and science, and human and social studies; the MF engineering is a syntheses comprising of six MF elements or six MF forces. The MF’s hard science and technology and its soft science and technology can be applied to national economy in the most efficient way, with the fundamental purpose to benefit the mankind; the MF is not only an industry, but also a backbone industry, and even a backbone industry group. The paper provides some insights into future enterprise integration in a global supply chain environment.

一种应用高性能电源模块研制的新型中频电源

本文介绍了一种新型中频电源。在电源中采用日本公司DC/DC电源模块取代传统的分离元件组成PWM稳压单元,对逆变单元中的全桥开关、LC谐振回路采取了优化设计,使该电源的电性能指标及可靠性大大提高。     

利用微结构光纤进行全光再生的实验研究

利用自相位调制(SPM)效应和窄带滤波器,在高非线性微结构光纤(MF)中实现了全光2R再生,获得了无波长变换的再生信号。实验中,再生前的信号由经过一段普通单模光纤(SMF)和衰减器的10Gb/s脉冲信号获得,两段MF的非线性系数均为36W-1·km-1。通过两级2R再生后,获得了与初波长相同的再生信号,再生效果良好。实验结果表明,高非线性MF在全光再生方面有很大的应用潜力。     

基于STR71X+MF RC500架构的射频识别系统设计

本设计采用STR710FZ2T6作为微处理器,充分利用RFID的非接触身份认证特性,将设备信息储存在标签(Tag)中,并通过RS232在PC机上显示出来.整个系统由STR710FZ2T6微处理器、MF RC500射频芯片、主机管理系统等部分构成.该系统实现了智能化的产品监控和管理,提高了设备管理的效率及其准确可靠性.     

小型化定向中波天线阵的设计

为了实现定向中波天线阵的小型化,采用现代专业电磁仿真软件FEKO,对常规的中波T型天线进行改进和优化设计使其达到小型化,并以此为天线单元,进行三单元组阵,采用不等幅、不同相馈电技术,从而实现定向中波天线阵的小型化设计,具有一定的工程应用前景。     

DVB-RCS协议研究

DVB-RCS通信系统是基于交互式应用的卫星通信系统,目前已受到业界的广泛关注。首先介绍了DVB-RCS系统的模型和协议结构,然后分别对前向信道和反向信道协议进行了分析,最后对所存在的问题进行了说明。     

Network-Level QoS Assurances Through Adaptive Allocation of CDMA Resources

In a Code Division Multiple Access (CDMA) network, multiple Mobile Hosts (MHs) can simultaneously transmit over the wireless channel by using different codes. To assure an acceptable Quality of Service (QoS) for all MHs' flows, the network usually tunes the transmit powers of all MHs to achieve a certain level of signal strength as compared to the noise and the interference (SINR) for each MH. The traditional assumption in power control schemes is that the SINR requirement is statically determined for each MH's flow. In contrast, in this paper, we propose a scheme that dynamically adapts the SINR requirements of MH's flow based on its QoS requirements and the conditions of the wireless channel between the MHs and the base station. As a result of this adaptation, we show that network-level QoS measures such as fraction of packets meeting their delay requirements and energy consumed per packet transmission are significantly better than in a scheme that statically fixes the SINR requirements. We show that the adaptation approach works well for the Matched Filter (MF) and the Minimum Mean Squared Error (MMSE) receivers. Our scheme uses a simple table-driven approach for optimally selecting the target SINR requirement for each MH at run time. The entries in the table are computed off-line using a dynamic programming algorithm with the objective of maximizing a profit function that balances the need for meeting the network-level QoS requirements and the cost of using a particular target SINR for a given transmission. Moncef Elaoud (M'97) received his B.Sc. (1988) his M.Sc. (1990) and his Ph.D. (2000) in electrical an computer engineering from the University of Wisconsin-Madison. He is currently a senior research Scientist at Telcordia Technologies' Applied Research organization. His main research interests are in the areas of quality of service, self-forming and self healing networks, auto-configuration, and mobility management in wireless and ad-hoc networks. Bechir Hamdaoui received the B.S. degrees in both electrical and mechanical engineering, and the M.S. degree in mechanical engineering from the National School of Engineering in Tunis (BAC+6+DEA, ENIT), Tunisia, in 1997 and 1998, respectively. He also received the M.S. degree in electrical and computer engineering from the University of Wiconsin, Madison, WI, in 2002, where he is currently working toward the Ph.D. degree. From 1998 to 1999, he worked as a quality control and planning engineer on power generation plant project under the supervision of FIAT Avio. His research focuses on various aspects in the area of computer networking including mobile networks, wireless communication systems, and ad hoc networks. Parameswaran Ramanathan received the B. Tech degree from the Indian Institute of Technology, Bombay, India, in 1984, and the M. S. E. and Ph. D. degrees from the University of Michigan, Ann Arbor, in 1986 and 1989, respectively. Since 1989, Dr. Ramanathan has been faculty member in the Department of Electrical & Computer Engineering, University of Wisconsin, Madison, where is presently a Full Professor. He leads research projects in the areas of sensor networks and next generation cellular technology. In 1997–98, he took a sabbatical leave to visit research groups at AT&T Laboratories and Telcordia Technologies. Dr. Ramanathan's research interests include wireless and wireline networking, real-time systems, fault-tolerant computing, and distributed systems. He is presently an Associate Editor for IEEE Transactions on Mobile Computing and Elsevier AdHoc Networks Journal. He served as an Associate Editor for IEEE Transactions on Parallel and Distributed Computing from 1996–1999. He has also served on program committees of conferences such as Mobicom, Mobihoc, International Conferences on Distributed Systems and Networks, Distributed Computing Systems, Fault-tolerant Computing Symposium, Real-time Systems Symposium, Conference on Local Computer Networks, and International Conference on Engineering Complex Computer Systems. He was the Finance and Registration Chair for the 1999 Fault-tolerant Computing Symposium. He was the program chairman of the Workshop on Architectures for Real-time Applications, 1994 and the program vice-chair for the International Workshop on Parallel and Distributed Real-time Systems, 1996. He is a member of Association of Computing Machinery and a senior member of IEEE.