A Unified Approach to Submicron DC MOS Transistor Modeling for Low-Voltage ICs

A unified single-equation approach for the MOS transistordrain current modeling for energy-efficient submicron MOS circuitsis presented. Instead of three sets of separate equations forthe triode, saturation, and weak inversion regions, only a continuousexpression which is valid to describe the behavior of drain currentand the derivatives in all operation regions can be realizedby using a combination of hyperbola, sigmoid, and interpolationmethods. The model expression can predict accurate results forthe current, output conductance, and transconductance with continuousand smooth characteristics. The simulation results agree wellwith experimental data.     

Differentiated Service Provision in Optical CDMA Network Using Power Control

A simple scheme to use power control for differentiated service provision is proposed for the optical code-division multiple-access network. The main advantages of this scheme are: 1) Interference from other users can be eliminated theoretically. 2) The decoder with simple configuration can be used as compared to that in a previous power control scheme. 3) The design procedure of various service requirements in one network is simplified.      

A location‐aware peer‐to‐peer overlay network

This work describes a novel location‐aware, self‐organizing, fault‐tolerant peer‐to‐peer (P2P) overlay network, referred to as Laptop. Network locality‐aware considerations are a very important metric for designing a P2P overlay network. Several network proximity schemes have been proposed to enhance the routing efficiency of existing DHT‐based overlay networks. However, these schemes have some drawbacks such as high overlay network and routing table maintenance overhead, or not being completely self‐organizing. As a result, they may result in poor scalability as the number of nodes in the system grows. Laptop constructs a location‐aware overlay network without pre‐determined landmarks and adopts a routing cache scheme to avoid maintaining the routing table periodically. In addition, Laptop significantly reduces the overlay maintenance overhead by making each node maintain only the connectivity between parent and itself. Mathematical analysis and simulations are conducted to evaluate the efficiency, scalability, and robustness of Laptop. Our mathematical analysis shows that the routing path length is bounded by log_d N, and the joining and leaving overhead is bounded by d log_d N, where N is the number of nodes in the system, and d is the maximum degree of each node on the overlay tree. Our simulation results show that the average latency stretch is 1.6 and the average routing path length is only about three in 10 000 Laptop nodes, and the maximum degree of a node is bounded by 32. Copyright © 2006 John Wiley & Sons, Ltd.     

Properties of PVA-AA cross-linked HEMA-based hydrogels

Poly(HEMA) hydrogel is usually prepared by using 1,1,1-trimethylol propane trimethacrylate and ethylene glycol dimethacrylate as the crosslinkers. Another method using PVA-AA (polyvinyl alcohol partially esterified with acryloyl chloride) as the cross linker is reported here. Two hydrogels, co-A1H9 and co-A2H8, were prepared by the polymerization of HEMA in the presence of 10% and 20% PVA-AA, respectively. The presence of PVA-AA reduced the water content from 32% to 25% in the resultant copolymer, whereas T_g did not change significantly. Co-A1H9 had an elastic modulus of 6.3 Mpa, which is much higher than 3.9 MPa and 3.7 MPa for poly(HEMA) and co-A2H8, respectively. The interfacial energies of poly(HEMA), co-A1H9 and co-A2H8 were calculated to be 0.52, 0.65 and 0.71 dyne/cm², respectively, whereas the fractional polarities of these three hydrogels were all about 0.74. Thus a HEMA-based hydrogel with surface properties similar to poly(HEMA) but with stronger mechanical strength was successfully prepared. This copolymeric hydrogel could provide a choice other than the conventionally cross linked poly(HEMA) for various applications.     

Synthesis,characterization, and application of PVP/chitosan blended polymers

The purpose of this study was to research the compatibility and application of polyvinylpyrrolidone (PVP)/chitosan blended polymers. The polymers were synthesized at different weight ratios and tested using techniques such as Fourier transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis to evaluate the compatibility of the blended materials. Incompatibility occurred when the quantity of chitosan exceeded 75%. The addition of PVP was beneficial for the thermal stability of chitosan, but resulted in inferior strength performance. Furthermore, the blended polymers did not show a color‐enhancement effect, but did show elevated water absorption, chlorine resistance, and colorfastness. In addition, the treated fabrics with a higher chitosan ratio in the blended polymer had antimicrobial properties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 885–891, 2006     

A module‐integrated isolated solar micro‐inverter without electrolytic capacitors

This paper presents a module‐integrated isolated solar micro‐inverter. The studied grid‐tied micro‐inverters can individually extract the maximum solar power from each photovoltaic (PV) panel and transfer to the AC utility system. A harmonic suppression technique is used to reduce the DC‐bus capacitance. Electrolytic capacitors are not needed in the studied solar micro‐inverter. High conversion efficiency, high maximum power point tracking accuracy and long lifespan can be achieved. The operation principles and design considerations of the studied PV inverter are analyzed and discussed. A laboratory prototype is implemented and tested to verify its feasibility. Copyright © 2012 John Wiley & Sons, Ltd.     

Design and implementation of a contact‐less power charger for robot applications

In this paper, a contact‐less power charger for robot applications is studied and developed. Contact‐less charging can be achieved by a separable transformer design. The transformer primary core is in the charger unit, and the secondary core is in the robots. The transformer air‐gap is equal to the distance between these two parts. By theoretical analysis, software simulations, and circuit implementation, the relationship among the transformer's coupling coefficient, the core geometry, and gap are formulated. In addition, a high‐efficiency circuit topology for the studied contact‐less charger is fulfilled. It is anticipated that the research results of this paper can contribute to the development of the contact‐less charging techniques for robot systems. Copyright © 2012 John Wiley & Sons, Ltd.     

Design and implementation of a high‐efficiency LiFePO4 battery charger for electric vehicle applications

This letter studies and implements a high‐efficiency LiFePO₄ battery charger. The modular design can satisfy the requirements of series/parallel charging for electric vehicle applications. A CC‐CC‐CV charging scheme is also realized to meet the characteristics of LiFePO₄ battery stacks. A 2 kW laboratory prototype is built and tested. The experimental results are shown to verify the feasibility of the proposed scheme. Copyright © 2012 John Wiley & Sons, Ltd.     

Design and implementation of a high‐efficiency bidirectional DC‐DC Converter for DC micro‐grid system applications

This paper studies the design and implementation of a non‐isolated dual‐half‐bridge bidirectional DC‐DC converter for DC micro‐grid system applications. High efficiency can be achieved under wide‐range load variations by the zero‐voltage‐switching features and an adaptive phase‐shift control method. A three‐stage charging scheme is designed to meet the fast‐charging demand and prolong the lifetime of LiFePO₄ batteries. A digital‐signal‐processing control IC is used to realize the power flow control, DC‐bus voltage regulation, and battery charging/ discharging of the studied bidirectional DC‐DC converter. Finally, a 10 kW prototype converter with Enhanced Controller Area Network communication function is built and tested for micro‐grid system applications. A light‐load efficiency over 96% and a rated‐load efficiency over 98% can be achieved. Copyright © 2013 John Wiley & Sons, Ltd.