冻结肉类食品远红外辐射加热解冻的可行性研究

低温冻藏食品在利用之前必须经过解冻。解冻方法和装置的研究是食品冻藏技术的难题，各国都在不断地研究开发。本文介绍了肉类食品解冻的要求，进行了红外辐射加热解冻的模拟实验后，初步得出单独应用远红外辐射加热技术解冻实用价值不大的结论，指出一般红外烤箱不宜用作冻结食品的解冻。     

Multihour engineering and traffic routing optimization in hierarchical telephone networks

Classical hierarchical routing in telephone networks is extended to a wider class called out-of-chain routing in such a way that some useful properties of hierarchical routing are retained. This new routing pattern offers more potential paths than the fixed hierarchical one and can be introduced as a dynamic routing where the fixed alternate sequences change at some predetermined instants during the day. The effect of this new routing pattern on the network performances is examined. The main topic of this paper is to present heuristic methods used to optimise such routings in large networks. We show on artificial networks that the throughput of a given network can be significantly improved by suitable routing choices. We demonstrate that the integration of routing changes within a multihour dimensioning process is possible but the lack of realistic data does not permit at this time to quantify the value of routing optimization on real networks.     

Hot Corrosion of Silica

The high-temperature corrosion of bulk silica glass was studied in pure oxygen and in SO₃-containing oxygen atmospheres in the presence of liquid sulfate deposits at temperatures of 700° and 1000°C. No reaction and devitrification were observed without Na₂SO₄ on the surface. The wetting of the silica by the sulfate, the tendency toward basic fluxing, and the crystallization of the silica incrased with the activity of Na₂O. The most extensive degradation of vitreous silica occurred by crystallization, and the resulting spalling under basic conditions and thermal cycling at basic conditions were parabolic. This behavior is explained by a model in which the crystallization is controlled by sodium at the glass-crystal interface and its diffusion into the glass. This sodium diffuses into the glass before crystallization and is swept ahead of the crystallization front.     

Application of the percolation model to gelation of an epoxy resin

The percolation model has been applied to the study of gelation of the TGDDM-DDS system (tetraglycidyldiaminodiphenylmethane–diaminodiphenylsulfone) at a mass concentration of 100–30. For each temperature the experimental viscosity curves are satisfactorily described by a percolation law. Using the degree of chemical reactions, X, as a variable, a very clear change in the reaction mechanism with temperature can be shown. Then a rate of advancement of effective reactions, Y, is defined. This value only takes intermolecular-type reactions into account, and is probably the only variable on which viscosity depends in a percolation law: η = B(1 ? Y/Y_c)^?p. We obtain Y_c= 0.45 and p= 2.0. Comparing X_c and Y_c at the gel point, we obtain information on the proportion of intramolecular reactions with temperature. It is also demonstrated that the critical percolation threshold agrees closely with the gel point determined experimentally on log G″= f(t) curves.     

MC-CDMA with exponential power profile in Nakagami fading channel

A refined study of multi-carrier code division multiple access transmission over a Nakagami fading channel is proposed. The channel power is modeled with an exponential power profile rather than the uniform profile prevalent in other papers. An expression for the bit error rate (BER) is then derived. Numerical results show that MC-CDMA performances depend on the power dispersion of interferers around the desired user power.     

A New CMOS Current-Mode Multiplexer for l0 Gbps Serial Links

This paper presents an in-depth study of the pros and cons of voltage-mode multiplexers for Gbps serial links and exploits the advantages of multiplexing in current domain. In addition, it proposes a new fully differential CMOS current-mode multiplexer where a high multiplexing speed is achieved by multiplexing at a low-impedance node. Multiplexing speed is further improved by inductive shunt peaking with active inductors. The differential configuration of the multiplexer minimizes the effect of common-mode disturbances, particularly those coupled from the power and ground rails. The flow of the output currents in the opposite directions minimizes the effect of electro-magnetic interference from channels, making the multiplexer particularly attractive for high-speed data transmission over long interconnects and printed-circuit-board (PCB) traces. The proposed multiplexer draws a constant current from the supply voltage, thereby minimizing both switching noise and noise injected to the substrate. A fully differential CMOS current-mode 8-to-l multiplexer has been implemented in TSMC’s 1.8 V 0.18 μm CMOS technology and analyzed using Spectre from Cadence Design Systems with BSIM3.3v device models. Simulation results demonstrate that the multiplexer offers sufficiently large eye-opening when multiplexed at 10 Gbps.Jean Jiang received the B.Eng. degree in Electrical Engineering from Wuhan University of Technology, Wuhan, China in 1995. From 1999 to 2001, she worked for Ericsson Global IT Services where she was a technical staff to maintain computer networks. Since 2002, she has been a research assistant with the System-on-Chip research lab of Ryerson University. She is currently a M.A.Sc candidate under the supervision of Dr. Fei Yuan in the Department of Electrical and Computer Engineering, Ryerson University, Toronto, Canada. Her research interests are in analog CMOS circuit design for high-speed data communications. She was awarded the Ontario Graduate Scholarship (OGS) in 2003–2005 for academic excellence.Fei Yuan received the B.Eng. degree in electrical engineering from Shandong University, Jinan, China in 1985, the MASc. degree in chemical engineering and PhD. degree in electrical engineering from University of Waterloo, Waterloo, Ontario, Canada in 1995 and 1999, respectively.During 1985–1989, he was a Lecturer in the Department of Electrical Engineering, Changzhou Institute of Technology, Jiangsu, China. In 1989 he was a Visiting Professor at Humber College of Applied Arts and Technology, Toronto, Canada. During 1989–1994, he worked for Paton Controls Limited, Sarnia, Ontario, Canada as a Controls Engineer. Since July 1999 he has been with the Department of Electrical and Computer Engineering, Ryerson University, Toronto, Ontario, Canada, where he is currently an Associate Professor and the Associate Chair for Undergraduate Studies and Faculty Affairs. He is the co-author of the book “Computer Methods for Analysis of Mixed-Mode Switching Circuits” (Kluwer Academic Publishers, 2004, with Ajoy Opal). Dr. Yuan received an “Excellence of Teaching” award from Changzhou Institute of Technology in 1988, a post-graduate scholarship from Natural Science and Engineering Research Council (NSERC) of Canada during 1997–1998. He is a senior member of IEEE and a registered professional engineer in the province of Ontario, Canada.     

Ester-functionalized poly(3-alkylthiophene) copolymers: Synthesis,physicochemical characterization and performance in bulk heterojunction organic solar cells

The introduction of functional moieties in the donor polymer (side chains) offers a potential pathway toward selective modification of the nanomorphology of conjugated polymer:fullerene active layer blends applied in bulk heterojunction organic photovoltaics, pursuing morphology control and solar cell stability. For this purpose, two types of poly(3-alkylthiophene) random copolymers, incorporating different amounts (10/30/50%) of ester-functionalized side chains, were efficiently synthesized using the Rieke method. The solar cell performance of the functionalized copolymers was evaluated and compared to the pristine P3HT:PCBM system. It was observed that the physicochemical and opto-electronic characteristics of the polythiophene donor material can be modified to a certain extent via copolymerization without (too much) jeopardizing the OPV efficiency, as far as the functionalized side chains are introduced in a moderate ratio (<30%) and that preference is given to side chains with a small molar volume. A range of complementary techniques – UV–Vis spectroscopy, (modulated temperature) differential scanning calorimetry, transmission electron microscopy and X-ray diffraction analysis – indicated that variations in polymer crystallinity, while maintaining a high level of regioregularity, are probably the main factor responsible for the observed differences.     

Electrical characterization of HfO2 films obtained by UV assisted injection MOCVD

HfO₂ films were deposited at low temperature (400 °C) by UV assisted injection metal-organic chemical vapor deposition (UVI-MOCVD). A three-step process was used for this study, consisting of (A) Pre-deposition anneal for nitridation; (B) Deposition step; (C) Post-deposition annealing in oxygen. Special attention was paid to the effect of UV exposure during these steps. Films were characterized by physical, optical and electrical techniques. Thickness was determined by different methods (X-ray Reflectrometry (XRR), spectroscopic ellipsometry and transmission electron microscopy) and a good agreement was found for all samples. The HfO₂ permittivity, equivalent oxide thickness (E_OT), flat-band voltage (V_fb) and total charge (Q_t) were extracted from the CV response at high frequency taking into account the HfO₂ and SiO₂ thicknesses obtained by XRR. The calculated permittivity values were in the range 7–13, i.e. lower than theoretical values for the monoclinic phase. Explanations are suggested in the context of the other characterizations. JE_eff characteristics were constructed taking into account the E_OT values (E_eff = V/E_OT). Effective breakdown fields range between 8.7 and 16.9 MV/cm. No dependence of E_eff with UV exposure was found.     

Microwave filters-applications and technology

This paper describes the development of microwave filter technology from an applications perspective. Military applications required wide-band and tunable devices for electronic support measures receivers, which led to the development of highly selective wide-band waveguide filters, coaxial resonator and suspended-substrate multiplexers, and electronically tunable filters. The satellite communications industry created demand for low-mass narrow-band low-loss filters with severe specifications on amplitude selectivity and phase linearity. These requirements resulted in the development of dual-mode waveguide and dielectric-resonator filters, and advances in the design of contiguous multiplexers. Cellular communications base-stations demanded low-loss high power-handling selective filters with small physical size, capable of being manufactured in tens of thousands at a reasonable cost. These demands led to advances in coaxial resonator, dielectric resonator, and superconducting filters, and also to methods of cost-reduction, including computer-aided alignment. Cellular radio handsets have required the manufacture of hundreds of millions of extremely small very low-cost filters, still with reasonably low loss and high selectivity. This has driven significant advances in integrated ceramic, surface, and bulk acoustic-wave active filters and filters using micromachined electromechanical systems