On the application of adaptive antennas to microcellularenvironments: radio channel characteristics and system performance

The possible application of adaptive antennas in microcellular operational environments is studied in this paper with the help of a site-specific ray-tracing propagation model. First are examined the statistics of propagation parameters that play an important role for the performance of adaptive antennas. Particular emphasis is put on the spatial characteristics of the radio channel under line-of-sight (LOS) and non-LOS conditions. For this reason, area statistics are produced for a typical small-cell environment for parameters such as the number of multipath clusters, number of rays, angular size, and excess delay of each impulse response, as well as the number of rays, angular size and power of the multipath clusters. Results show that contrary to the common belief for such environments, the signal is not "almost" uniformly distributed in the spatial domain, instead is contained in a few narrow clusters. Then the effect of the microcellular environment on the uplink performance of some well-known techniques like conventional beamforming, maximum entropy, switched beams, maximum ratio and optimum combining, and beam-space optimum combining is examined . The results show that for typical time-division multiple-access (TDMA) scenarios with one and two users, the beam space optimum combining (strongest eigenvalue version) and the switched beams methods, offer the best performance     

用注凝成型技术制备莫来石陶瓷坯体

用注凝成型技术，通过控制合成莫来石粉料的细度，调节好pH值在单体和交联剂的比例，制备出稳定性好的料浆和强度高的生坯。     

双时基频率校准电路

提供精确的时间基准是精密仪器和高精度设备计时和工作的关键技术之一。文中采用两套晶振电路，通过分频产生高频和低频两个频率信号，采用编码的方法对两个频率信号在每一个时钟周期内进行动态校核，只有两个晶振的频率在允许的精度范围内，或同时增大（缩小）相同的倍数，校核后频率信号才是正确的，且能给系统提供精确的时间基准。该方法能有效防止系统的时钟周期因意外的原因伸长或缩短。整个电路可以作为精密仪器或高精度设备的一个模块电路。     

用于千兆以太网基带铜缆接收器均衡的甚高频自适应 连续时间Gm-C 二阶带通滤波器的研究和设计

本文设计了用于千兆以太网基带铜缆接收器均衡的甚高频自适应连续时间Gm-C二阶带通滤波器。基于最陡梯度下降算法，带通滤波器的零点在57－340MHz的频率范围内可以自适应地调节，中心频率为1.278GHz。通过外接电阻伺服环路，滤波器中跨导转换器的跨导值不受工艺偏差和温度变化的影响，采用CSMC－HJ0.6μm CMOS工艺器件模型，用Cadence Spectres仿真器仿真了设计的自适应滤波器电路，仿真结果验证了设计原理和设计的电路。系统的最长学习时间为880个参考时钟周期。     

On the development of a direct method of determining the microcrack resistance curve

This report deals with direct observations of microcrack linkage at the crack tip prior to macroscopic crack initiation. It is shown that this process is directly linked to the inclusion distribution in the material and can be considered in terms of an R curve to describe microcrack development.     

Using motion from orthographic views to verify 3-D point matches

The specific problem addressed by the authors is how to detect the true match of a fourth point from among candidate matches in a situation in which three points have already been matched. The two sets of points to be matched are both subject to measurement errors. The depth error is more dominant than errors in the other two coordinates; however, the exact statistical distribution of the measurement errors is not known. The authors present a new method for solving the problem. The method is based on the technique of motion analysis using orthographic views. It discards the noisy z (depth) coordinates and uses only the x and y coordinates of the points to verify the match. The effect of depth errors on the motion estimate is completely prevented. Results show that this method is substantially more effective than previous methods that use all three coordinates     

The contact of elastic regular wavy surfaces

A complete solution in closed form to the elastic contact of a one-dimensional sinusoidal surface with a flat surface was presented by Westergaard in 1939. This paper is concerned with the elastic contact of a two-dimensional sinusoidal surface with a flat. In this case the stress distribution within the elastic solids is three-dimensional. As the load is increased the contact areas change in shape from being circular to square and finally leave a circular region of no contact when the waves are almost squashed flat. The problem is solved in general using a numerical method due to Kalker, but asymptotic solutions in closed form have been found for light loads and also for heavy loads at which contact is almost complete. The variation of the mean separation with load, which determines the volume of the space trapped between the two surfaces, is also found.     

An Investigation into Glucose as a Potential Precursor of N-Nitrosothiazolidine in Bacon

The possible involvement of glucose in the formation of N-nitrosothiazolidine (NTHZ) in bacon was investigated by pumping pork bellies with brines containing added glucose (2 and 4%). Raw bacon samples processed with glucose had significantly lower levels of N-nitrosothiazolidine-4-carboxylic acid than the smoked control bacons. When the bacon samples with glucose were fried for 6 and 12 min, no NTHZ was detected in the fried products. N-Nitrosopyrrolidine (NPYR) levels in these samples were much lower than those in the fried control samples. Results of this study demonstrate that the contribution of glucose to NTHZ formation in bacon is minimal relative to that of formaldehyde in the wood smoke.