Training sequence design and channel estimation of OFDM-CDMA broadband wireless access networks with diversity techniques

In this paper, an OFDM-CDMA system employing various diversity schemes is considered for a possible candidate of broadband wireless access networks and broadcasting applications. With an emphasis on a preamble design for multi-channel separation, we address a channel estimation based on the time-domain windowing and its imperfectness in OFDM-based multiple-antenna transmission systems. By properly designing each preamble for multiple antennas to be orthogonal in the time domain, the channel estimation can be applied to the HIPERLAN/2 and IEEE 802.11a standards in the case of more than two transmit antennas. Also, the effect of diversity techniques on the performance of OFDM-CDMA based broadband wireless access networks is investigated and the maximum achievable diversity gain for a two-path Rayleigh fading environment is evaluated. Simulation results show that the OFDM-CDMA system applying a space-time-frequency diversity with a full-rate full diversity code can give the diversity of D=4 and D=8 for both multi-user cases of maximum user and half user capacities, respectively.     

非接触型光外差轮廓仪

本文介绍一种纳米级非接触型高精度光外差轮廓仪,它是基于普通光路的光外差干涉仪。工件表面被两束有微小频差的激光束所照射,其中一束经聚焦后用作测量光探针来扫描工件表面,另一束则用作参考光束。两束光经表面反射后产生干涉。测量信号和参考信号的相位差与表面的微不平值成正比。仪器的横向分辨率为2μm,高度分辨率为1 nm,它不需要对试样作大范围的调整,且可用试样自身作参考面。信号经光电转换后由微型计算机进行处理,它能快速完成测量、计算、显示及打印出各种参数和曲线。     

烧结机双层插板式卸灰阀的研制

烧结机双层卸灰阀由蘑菇头式改为电液推杆插板式，有效地解决了系统卸料及漏风问题，实现了控制自动化，提高了设备作业率，改善了岗位环境。     

丰满流域可能最大暴雨与可能最大洪水分析研究

依据丰满漉域的水文气象资料,计算丰满流域可能最大暴雨,推求白丰区间的可能最大洪水并进行成果合理性分析.     

Multistage amplifier topologies with nested Gm-Ccompensation

This paper presents a multistage amplifier for low-voltage applications (<2 V). The amplifier consists of simple (noncascode) low gain stages and is stabilized using a nested transconductance-capacitance compensation (NGCC) scheme. The resulting topology is similar to the well known nested Miller compensation (NMC) multistage amplifier, except that the proposed topology contains extra G _m feedforward stages which are used to enhance the amplifier performance. The NGCC simplifies the transfer function of the proposed multistage amplifier which, in turn, simplifies its stability conditions. A comparison between the NGCC and NMC shows that the NGCC has wider bandwidth and is easier to stabilize. A four-stage NGCC amplifier has been fabricated using a 2-μm CMOS process and is tested using a ±1.0 V power supply. A dc gain of 100 dB has been measured. A gain bandwidth product of 1 MHz with 58° of phase margin and power of 1.4 mW can be achieved. The op amp occupies an active area of 0.22 mm². Step response shows that the op amp is stable     

Boundary Constrained Swept Surfaces for Modelling and Animation

Due to their simplicity and intuitiveness, swept surfaces are widely used in many surface modelling applications. In this paper, we present a versatile swept surface technique called the boundary constrained swept surfaces. The most distinct feature is its ability to satisfy boundary constraints, including the shape and tangent conditions at the boundaries of a swept surface. This permits significantly varying surfaces to be both modelled and smoothly assembled, leading to the construction of complex objects. The representation, similar to an ordinary swept surface, is analytical in nature and thus it is light in storage cost and numerically very stable to compute. We also introduce a number of useful shape manipulation tools, such as sculpting forces, to deform a surface both locally and globally. In addition to being a complementary method to the mainstream surface modelling and deformation techniques, we have found it very effective in automatically rebuilding existing complex models. Model reconstruction is arguably one of the most laborious and expensive tasks in modelling complex animated characters. We demonstrate how our technique can be used to automate this process.     

在3．39μm波段甲烷吸收特性的测量与应用研究

报道了甲烷气体在３．３９μｍ波段吸收特性的研究结果，及其在３．３９μｍ波段多波长干涉测量中的应用。通过改变甲烷吸收室的充气参数，使激光器工作在双等光强工作点，并完成了绝对距离的干涉测量。     

Testing of the multi-application small light water reactor (MASLWR) passive safety systems

Experimental thermal hydraulic research has been conducted at Oregon State University for the purpose of assessing the performance of a new reactor design concept, the multi-application small light water reactor (MASLWR). The MASLWR is a pressurized light water reactor design with a net output of 35 MWe that uses natural circulation in both normal and transient operation. Due to its small size, portability and modularity, the MASLWR design is well suited to help fill the potential need for grid appropriate reactor designs for smaller electricity grids as may be found in developing or remote regions. The purpose of the OSU MASLWR test facility is to assess the operation of the MASLWR under normal full operating pressure and full temperature conditions and to assess the passive safety systems under transient conditions. The data generated by the testing program will be used to assess computer code calculations and to provide a better understanding of the thermal-hydraulic phenomena in the design of the MASLWR NSSS. During this testing program, four tests were conducted at the OSU MASLWR test facility. These tests included one design basis accident and one beyond design basis accident. During the performance of these tests, plant operations to include start up, normal operation and shut down evolutions were demonstrated successfully.