As Doping in (Hg,Cd)Te: An Alternative Point of View

Acceptor doping of many II–VI compound semiconductors has proved problematic and doping of epitaxial mercury cadmium telluride (MCT, Hg_1−x Cd _x Te) with arsenic is no exception. High-temperature (>400°C) anneals followed by a lower temperature mercury-rich vacancy-filling anneal are frequently required to activate the dopant. The model frequently used to explain p-type doping with arsenic invokes an amphoteric nature of group V atoms in the II–VI lattice. This requires that group VI substitution with arsenic only occurs under mercury-rich conditions either during growth or the subsequent annealing and involves site switching of the As. However, there are inconsistencies in the amphoteric model and unexplained experimental observations, including arsenic which is 100% active as grown by metalorganic vapor-phase epitaxy (MOVPE). A new model, based on hydrogen passivation of the arsenic, is therefore proposed.     

Cooperative localization techniques for wireless sensor networks: free,signal and angle based techniques

This paper addresses the problem of localization in sensor networks where, initially, a certain number of sensors are aware of their positions (either by using GPS or by being hand‐placed) and are referred to as anchors. Our goal is to localize all sensors with high accuracy, while using a limited number of anchors. Sensors can be equipped with different technologies for signal and angle measurements. These measures can be altered by some errors because of the network environment that induces position inaccuracies. In this paper, we propose a family (AT‐Family) of three new distributed localization techniques in wireless sensor networks: free‐measurement (AT‐Free) where sensors have no capability of measure, signal‐measurement (AT‐Dist) where sensors can calculate distances, and angle‐measurement (AT‐Angle) where sensors can calculate angles. These methods determine the position of each sensor while indicating the accuracy of its position. They have two important properties: first, a sensor node can deduce if its estimated position is close to its real position and contribute to the positioning of others nodes; second, a sensor can eliminate wrong information received about its position. This last property allows to manage measure errors that are the main drawback of measure‐based methods such as AT‐Dist and AT‐Angle techniques. By varying the density and the error rate, simulations show that the three proposed techniques achieve good performances in term of high accuracy of localized nodes and less energy consuming while assuming presence of measure errors and considering low number of anchors. Copyright © 2012 John Wiley & Sons, Ltd.     

将RF信号转换为数字信号的CMOS转换器

从频率计数与合成到传感器信号调整等很多应用都需要将RF信号转换为数字逻辑电平。在这些情况下,设计者一般采用一个高速电压比较器完成RF到数字信号的转换工作。由于电压比较器具有高增益,它们一般有很好的灵敏度,但也会带来一些问题。高速比较器价格高,很难找到现成的商品,并且易于被快速淘汰。     

New CMOS Class AB Transmitter for 10 Gb/s Serial Links

This paper presents a new fully differential CMOS class AB transmitter for 10 Gb/s serial links. The transmitter consists of a fully differential multiplexer, a rail-to-rail configured pre-amplification stage, and a push-pull output stage. The multiplexer achieves a high multiplexing speed by using modified pseudo-NMOS logic where pull-up networks are replaced with self-biased active inductors. The rail-to-rail configured pre-amplification stage with active inductors amplifies the signals from the multiplexer. The fully differential output current is generated by a class AB output stage operated in a push-pull mode. High data rates of the transmitter are obtained by ensuring that the transistors in both the pre-amplification and output stages are always in saturation and the voltage swing of all critical nodes is small. The fully differential configuration of the transmitter effectively suppresses common-mode disturbances, particularly those coupled from the power and ground rails, the electro-magnetic interference exerted from channels to neighboring devices is also minimized. The transmitter minimizes switching noise by drawing a constant current from the supply voltage. The transmitter has been implemented in TSMC 0.18 μm 1.8 V 6-metal CMOS technology and analyzed using Spectre from Cadence Design Systems with BSIM3.3 device models. Simulation results demonstrate that the transmitter provides a 5 mA peak-to-peak differential output current with 100 ps eye-width and >5 mA eye-height at 10 Gb/s. The transmitter consumes 18 mW with a total transistor area of 100 μm² approximately. Jean Jiang received the B.Eng. degree in Electrical Engineering from Wuhan University of Technology, Wuhan, China in 1995, and the M.A.Sc. degree in Electrical and Computer Engineering from Ryerson University, Toronto, Ontario, Canada in 2004. From 1999 to 2001, she worked for Ericsson Global IT Services where she was a technical staff to maintain computer networks. From 2002 to 2004, she was a research assistant and a M.A.Sc. student with the Microsystem Research Laboratory in the Department of Electrical and Computer Engineering at Ryerson University. She is now with Intel Corp., CA. as an IC design engineer. Her research interests are in analog CMOS circuit design for high-speed data communications. Jean Jiang was awarded the Ontario Graduate Scholarship in 2003–2005 for academic excellence. Fei Yuan received the B.Eng. degree in electrical engineering from Shandong University, Jinan, China in 1985, the M.A.Sc. degree in chemical engineering and Ph.D. 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, Ontario, Canada, and Lambton College of Applied Arts and Technology, Sarnia, Ontario, Canada. He was with Paton Controls Limited, Sarnia, Ontario, Canada as a Controls Engineer during 1989–1994. Since 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 (Springer-Verlag, 2004, with Ajoy Opal). Dr. Yuan received the Ryerson Research Chair award from Ryerson University in Jan. 2005, the Research Excellence Award from the Faculty of Engineering and Applied Science of Ryerson University in 2004, the post-graduate scholarship from Natural Science and Engineering Research Council of Canada during 1997–1998, and the Teaching Excellence Award from Changzhou Institute of Technology in 1988. Dr. Yuan is a senior member of IEEE and a registered professional engineer in the province of Ontario, Canada.     

Can the dietary element content of virgin argan oils really be used for adulteration detection?

Levels of eight dietary elements were assessed by ICP-AES in virgin edible and beauty argan oil samples prepared from four remote locations of the argan forest, and over a three-year period. The data showed sufficiently little variability to assess that all argan oil samples present, in terms of dietary elements, a similar composition, independently from the tree location within the argan forest. Therefore, adulteration detection by trace element analysis in edible and beauty argan oil is a method that can be generalised.     

Biobased packaging for improving preservation of fresh common mushrooms (Agaricus bisporus L.)

Freshness of common mushrooms was related to the internal atmosphere composition during modified atmosphere packaging (MAP) experiments at 20 °C and 80% RH with stretchable polyvinylchloride (PVC) film, paper, and the same paper coated with a wheat gluten solution. MAP with the stretchable film led to a detrimental deterioration of mushrooms after only one day of storage: dark brown blotches appeared and almost 30% of mushrooms exhibited open veil. This was due to the formation of condensed water at the inner surface of the material and onto mushrooms combined to a high O₂ partial pressure (16 kPa) in the headspace. Wheat gluten (WG) coated paper was the most effective to improve the shelf-life of mushrooms since it allowed the preservation of a fair colour, unbroken veils, and an acceptable texture during 3 days. This beneficial effect was attributed to the combination of a medium CO₂ (9.5 kPa) and low O₂ (2.5 kPa) partial pressure, without condensation. The main drawback of using WG-coated paper was its high water vapour permeability that led to an important weight loss (3.8 wt.% on day 3). However it did not affect the overall quality of mushrooms within the storage duration.

Industrial relevance

Even with the development of micro-perforated materials that provide the largest range of O₂ and CO₂ permeability values, several limitations are still encountered for synthetic MAP applications such as

– an insufficient perm-selectivity ratio that remains lower than 6 (value of 1 for micro-perforated material): generated atmosphere cannot reach both low O₂ and low CO₂ partial pressures and then are not adapted to CO₂-sensitive fresh produces.

– unattractive water condensation at the inner surface of the packaging that might occur due to a low water vapour permeability, favouring the development of microorganisms.

– their non biodegradability.

Previous studies reported a high selectivity ratio and a high water vapour permeability for biodegradable materials made from crops proteins (wheat gluten, for instance) that appeared well adapted for fresh fruits and vegetables preservation. However, despite low cost and such interesting functional properties, these materials exhibited poor mechanical properties and cannot be used as packaging material. Combination with other materials, such as cellulosic fibres, appeared to one way to get round this major drawback without losing its biodegradability. Indeed paper exhibits an environmental-friendliness potential (recyclability, sustainability, biodegradability, and compostability) and a high versatility in food packaging.By choosing common mushrooms, known to be sensitive to high CO₂ content, and a stretchable PVC film, commonly used to over-wrap mushrooms in tray (on European market), we demonstrate that this material was greatly less effective than a new biobased material (wheat gluten film coated onto paper) developed in collaboration with Smurfit Worldwide Research Center. This work confirms the interest in developing functionalised paper based packaging material with agro-based polymers adapted to the storage of fresh fruits and vegetable storage in ambient temperature.