激光遥测甲烷气体最低可探测浓度

对一种使用单一激光源遥感检测甲烷方案的最低可探测的路径-积分浓度进行了理论分析和实验研究,该方案主要采用了频率调制及谐波探测技术。通过理论计算得出了最低可探测甲烷的路径-积分浓度大约为8.7×10-8m。实验中测得该探测系统的探测灵敏度为8.43×10-6m/mV,甲烷最低可探测路径-积分浓度为4.2×10-7m。结果表明该探测系统具有较高的探测灵敏度,完全满足对矿井瓦斯的实时监测要求。     

Design and Characterization of Fabry–Pérot MEMS-Based Short-Wave Infrared Microspectrometers

Microspectrometers based on the monolithic integration of a microelectromechanical system (MEMS) Fabry–Pérot filter and a Hg _x Cd_1–x Te-based infrared detector are discussed and measured results presented. The microspectrometers are designed to operate in the 1.5 μm to 2.6 μm wavelength range. Design equations are presented which account for the mechanical and optical characteristics of the device. Measurements indicate linewidths as narrow as 55 nm, switching times of 40 μs, and a tuning range of 380 nm, which is limited by snap-down. Optical characterization of the distributed Bragg mirrors and the Fabry–Pérot filter are presented, and these are shown to be in good agreement with simple first-order analytical models. Bowing of the movable Fabry–Pérot mirror due to stress gradients is identified as the dominant source of linewidth broadening.     

Interaction of α radiation with iron-doped n-type silicon

Deep-level transient spectroscopy (DLTS) measurements were carried out on low-doped n-silicon before and after irradiation with 5.48 MeV α particles at room temperature with a fluence of 10¹⁰ α particles/cm². The DLTS measurements on the samples identified three electron levels E₁, E₂ and E₃ before irradiation. The deep-levels characteristic studies include emission rate signatures, activation energies, defect concentrations and capture cross sections. It was found that all pre-existing defects decreased their amplitudes during irradiation. The decrease in activation energy of level E₃ and noticeable suppression of level E₁ was also observed after irradiation. It was clearly seen that the composite peak E₃ (combination of E₂ and E₃) was successfully resolved after irradiating with α particles. α-irradiation is seen to lead a significant suppression of the iron interstitial defect, and without causing any change in its room temperature annealing characteristics.     

A Realistic Timing Test Model and Its Applications in High-Speed Interconnect Devices

This paper extends the timing test model in [5] to be more realistic by including the effects of the test fixtures between a device under test and a tester. The paper enables analyzing the trade-offs that arise between the predicted yield and the required overall test environment timing accuracy (OTETA) which involves the tester overall timing accuracy (OTA) and the test fixtures' impacts. We specifically focus on the application of the extended model to predict the test yield of standard high-speed interconnects, such as PCI Express, Parallel/Serial RapidIO, and HyperTransport. The extended model reveals that achieving an actual yield of 80% with a test escape of 300 DPM (Defects Per Million) requires an equivalent OTETA that is about half the acceptable absolute limit of the tested parameter. Baosheng Wang received his B.S. degree from Beijing University of Aeronautics and Astronautics (BUAA), Beijing, P.R. China, in 1997 and M.S. degree from Precision Instrument & Mechanical Engineering from the Tsinghua University, Beijing, P. R. China in 2000. In 2005, he received his Ph.D. degree in Electrical Engineering from the University of British Columbia (UBC), Vancouver, BC, Canada. During his Master study, he was doing MEMS, Micro Sensors and Digital Signal processing. From 2000 to 2001, he worked in Beijing Gaohong Telecommunications Company as a hardware engineer in ATM technology. Currently, he is a Design-for-Test (DFT) engineer at ATI Technologies Inc., Markham, Ontario, Canada. He publishes widely at international conferences and journals. His primary research interests are time-driven or timing-oriented testing methodologies for System on-a-Chip (SoC). These fields include test time reduction for SRAMs, accelerated reliability test for non-volatile memories, yield analysis for SoC timing tests, SoC path delay timing characterization and embedded timing measurements. Andy Kuo is currently a Ph.D student of System on a Chip (SoC) Research Lab at the Department of Electrical and Computer Engineering, University of British Columbia. He received his M.A.Sc. and B.A.Sc in electrical and computer engineering from University of British Columbia and University of Toronto in 2004 and 2002 respectively. His research interests include high-speed signal integrity issues, jitter measurement, serial communications. Touraj Farahmand received the B.Sc. degree in Electrical Engineering from Esfahan University of Technology, Esfahan, Iran in 1989 and the M.Sc. in Control Engineering from Sharif university of Technology, Tehran, Iran in 1992. After graduation, he joined the Electrical and Computer Research center of Esfahan University of Technology where he was involved in the DSP algorithm development and design and implementation of the control and automation systems. Since October 2001, he has been working in the area of high-speed signal timing measurement at SoC (System-on-a-Chip) lab of UBC (University of British Columbia) as a research engineer. His research interests are signal processing, jitter measurement, serial communication and control. André Ivanov is Professor in the Department of Electrical and Computer Engineering, at the University of British Columbia. Prior to joining UBC in 1989, he received his B.Eng. (Hon.), M. Eng., and Ph.D. degrees in Electrical Engineering from McGill University. In 1995–96, he spent a sabbatical leave at PMC-Sierra, Vancouver, BC. He has held invited Professor positions at the University of Montpellier II, the University of Bordeaux I, and Edith Cowan University, in Perth, Australia. His primary research interests lie in the area of integrated circuit testing, design for testability and built-in self-test, for digital, analog and mixed-signal circuits, and systems on a chip (SoCs). He has published widely in these areas and holds several patents in IC design and test. Besides testing, Ivanov has interests in the design and design methodologies of large and complex integrated circuits and SoCs. Dr. Ivanov has served and continues to serve on numerous national and international steering, program, and/or organization committees in various capacities. Recently, he was the Program Chair of the 2002 VLSI Test Symposium (VTS'02) and the General Chair for VTS'03 and VTS'04. In 2001, Ivanov co-founded Vector 12, a semiconductor IP company. He has published over 100 papers in conference and journals and holds 4 US patents. Ivanov serves on the Editorial Board of the IEEE Design and Test Magazine, and Kluwer's Journal of Electronic Testing: Theory and Applications. Ivanov is currently the Chair of the IEEE Computer Society's Test Technology Technical Council (TTTC). He is a Golden Core Member of the IEEE Computer Society, a Senior Member of the IEEE, a Fellow of the British Columbia Advanced Systems Institute and a Professional Engineer of British Columbia. Yong Cho received the B.S. degree from Kyung Pook National Unviersity, Korea, in 1981 and the M.S. degree from in electrical and computer engineering from the University of South Carolina, Columbia, S.C., in 1988 and the Ph.D. degree in electrical engineering and applied physics from Case Western Reserve University, Cleveland, OH, in 1992. He is currently a Professor with the Department of Electronics Engineering, Konkuk University, Seoul, Korea. His recent research interests include SoC Design and Verification, H/W and S/W co-design, and embedded programming on SoC. Sassan Tabatabaei received his PHD in Electrical Engineering from the University of British Columbia, Vancouver, Canada in 2000. Since then, he has held several senior technical positions at Vector12 Corp, Guide Technology, and Virage Logic. His professional and research interests include mixed-signal design and test, and signal integrity and jitter test methodologies for high-speed circuits and multi-Gbps serial interfaces. He has published several papers and holds a US patent in the area of timing and jitter measurement. Currently, he holds the position of the director for embedded test at Virage Logic Corporation.     

Biomass equations and estimation for Gmelina arborea and Nauclea diderrichii stands in Akure forest reserve

Biomass estimation was carried out for even-aged stands of Gmelina arborea and Nauclea diderrichii in Akure forest reserve. Linear and allometric regression equations for biomass prediction were developed for trees of both species. The yield of each species and total above-ground biomass (TAGB) were estimated and compared. The various equations developed were assessed based on high coefficient of determination (R²), significant F-ratio, and small Furnival index (FI) to select appropriate equation for prediction. The t-test shows a significant difference when the total volume and total dry weight of both species were compared, Gmelina arborea having a greater value than Nauclea diderrichii in both cases. The total volume of Gmelina arborea per hectare was 721.40 m³ and 265.18 m³ for Nauclea diderrichii. The TAGB for Gmelina arborea was 264,762 kg/ha and 88,293 kg/ha for Nauclea diderrichii.     

Sol–gel derived CuCoMnOx spinel coatings for solar absorbers: Structural and optical properties

A novel black coloured coating with the composition CuCoMnO_x was prepared using sol–gel synthesis. The coatings were deposited using the dip-coating technique from alcoholic sols based on Mn-acetate and Co- and Cu-chloride precursors. Thermogravimetric analysis showed that xerogels become crystalline at 316°C while X-ray diffraction analysis revealed that the coatings and powders correspond predominantly to CuCoMnO_x spinels. Rutherford back scattering (RBS) and transmission electron microscopic (TEM) studies combined with energy dispersive X-ray spectroscopy (EDXS) measurements confirmed that Cu, Mn and Co are present in the films in stoichiometric ratios close to that in the initial sols. IR spectroscopy has been employed to study the formation of sols by following the changes in the vibrational bands of the acetate groups during both thermal hydrolysis and the ageing of sols to xerogels. It was found that ageing of xerogels was accompanied by the formation of −COO⁻ bridging units, which at 250°C are no longer visible in the IR spectra but substituted by the vibrational modes characteristic for CuCoMnO_x. The solar absorptance (a_s) and thermal emittance (e_T) of the coatings when deposited on an Al-substrate are a_s=0.9 and e_T=0.05, which rank deposited black sol–gel CuCoMnO_x spinels among the promising candidates for spectrally selective absorber coatings for solar collectors and solar facades.     

Synthesis of large-area single-walled carbon nanotube films on glass substrate and their field electron emission properties

Large-area and homogeneous single-walled carbon nanotube (SWCNT) films have been deposited via arc discharge directly on glass substrate coated with a layer of indium tin oxide film. The characterization, by means of electron microscopy and Raman spectroscopy, shows that the as-grown films are uniformly woven and consist of SWCNT with diameters ranging from 0.82 to 1.15 nm. As a cathode material, the field emission test indicates the films have low turn-on field of ∼1.2 V/μm at 10 μA/cm² emission current, and high emission intensity causing luminance of about 7000 cd/cm² with fine uniformity. The best performing sample exhibits a constant degradation of less than 3% per hour at an emission current of around 1 mA. Measuring with the high voltage (2000 V) on the films for 2.0 h increased the field enhancement factor from 4500 to 5400 at the high field region. The results are of significance to the development of field emission display using nanoemitters.     

NiMn2−xFexO4 prepared by a reverse micelles method as conversion anode materials for Li-ion batteries

Synthesis by reverse micelles was used to produce NiMn_2−xFe_xO₄ with nanometric particle sizes for their use as conversion anode materials for lithium ion batteries. The hydroxide precursor was characterized by infrared spectroscopy and the decomposition was followed by thermal analysis. Cation distribution in the spinel structure of pristine samples was evaluated by Mössbauer spectroscopy evidencing that octahedral Fe³⁺ is substituted by Mn³⁺ ions in NiMnFeO₄. Capacity values of 750 mA h g⁻¹ were retained for 50 cycles for NiMnFeO₄ and NiFe₂O₄, respectively. A good kinetic response was observed in NiMnFeO₄ at 2C.