Requirements-driven database systems benchmark method

Benchmarks are the vital tools in the performance measurement, evaluation, and comparison of relational database management systems (RDBMS). Standard benchmarks such as the TP1, TPC-A, TPC-B, TPC-C, TPC-D, TPC-H, TPC-R, TPC-W, Wisconsin, and AS³AP benchmarks have been used to assess the performance of relational database management systems. These benchmarks are synthetic and domain-specific. Test results from these benchmarks are estimates of possible system performance for certain pre-determined application types. Database system performance on actual database domain may vary significantly from those in the standard benchmarks. In this paper, we describe a new benchmark method that is computer-assisted and developed from the perspective of the user's requirements.     

Anisotropy of volume-backscattered light

In many measurements used for the determination of optical properties of biological tissues, a detector with a small cone of acceptance is used. Therefore a small part of the anisotropically distributed backscattered light is detected. We present the results of Monte Carlo calculations and study the anisotropy of the direction distribution of volume-backscattered photons. Close to the source it is impossible to give a general correction factor to relate the measurements to theoretical results. Far from the source, the measured radiation divided by the square of the sine of the accepting angle of the detector is a relatively good approximation of the radiant exitance at the surface of the sample under investigation. We recommend the use of a detector with a large angle of acceptance for these kinds of measurements.     

Adaptive Neuro-fuzzy Control System by RBF and GRNN Neural Networks

Recently, adaptive control systems utilizing artificial intelligent techniques are being actively investigated in many applications. Neural networks with their powerful learning capability are being sought as the basis for many adaptive control systems where on-line adaptation can be implemented. Fuzzy logic, on the other hand, has proved to be rather popular in many control system applications due to providing a rule-base like structure. In this paper, an adaptive neuro-fuzzy control system is proposed in which the Radial Basis Function neural network (RBF) is implemented as a neuro-fuzzy controller (NFC) and the General Regression neural network (GRNN) as a predictor. The adaptation of the system involves the following three procedures: (1) tuning of the control actions or rules, (2) trimming of the control actions, and (3) adjustment of the controller output gain. The tuning method is a non-gradient descent method based on the predicted system response which is able to self-organize the control actions from the initial stage. The trimming scheme can help to reduce the aggressiveness of the particular control rules such that the response is stabilized to the set-points more effectively, while the controller gain adjustment scheme can be applied in the cases where the appropriate controller output gain is difficult to determine heuristically. To show the effectiveness of this methodology, its performance is compared with the well known Generalized Predictive Control (GPC) technique which is a combination of both adaptive and predictive control schemes. Comparisons are made with respect to the transient response, disturbance rejection and changes in plant dynamics. The proposed control system is also applied in controlling a single link manipulator. The results show that it exhibits robustness and good adaptation capability which can be practically implemented.     

建立POWERBUILDER独立应用的基本方法

本文讨论了在微机上利用ＰＯＷＥＲＢＵＩＬＤＥＲ建立独立平台应用的基本方法及程序设计的有关概念。     

Photosynthesis of hydrogen and methane as key components for clean energy system

While researchers are trying to solve the world’s energy woes, hydrogen is becoming the key component in sustainable energy systems. Hydrogen could be produced through photocatalytic water-splitting technology. It has also been found that hydrogen and methane could be produced through photocatalytic reduction of carbon dioxide with water. In this exploratory study, instead of coating catalysts on a substrate, pellet form of catalyst, which has better adsorption capacity, was used in the photo-reduction of carbon dioxide with water. In the experiment, some water was first absorbed into titanium dioxide pellets. Highly purified carbon dioxide gas was then discharged into a reactor containing these wet pellets, which were then illuminated continuously using UVC lamps. Gaseous samples accumulated in the reactor were extracted at different intervals to analyze the product yields. The results confirmed that methane and hydrogen were photosynthesized using pellet form of TiO₂ catalysts. Hydrogen was formed at a rate as high as 0.16 micromoles per hourμmol h^–1). The maximum formation rate of CH₄ was achieved at 0.25 μmol h^–1 after 24 h of irradiation. CO was also detected.     

测试3G手机的DigRF

DigRF准备替换RF与基带半导体器件之间的两种主要形式的数据通信路径：模拟信令，以及针对具体设计的私有数字信令（并行或串行）。MIPI（移动业处理器接口）联盟正在致力于采用DigRF（数字射频）标准，用一种基于分组的公共数字串行接口代替各种类型的I／Q（同相位／正交相位）信令接口。一个MIPI联盟工作小组已开发了用于2．5G和3G手机标准的DigRF规范，预计其后版本会增加支持4G标准的数据流量。     

MaxSim: performance and effects of translation fluency

This paper evaluates the performance of our recently proposed automatic machine translation evaluation metric MaxSim and examines the impact of translation fluency on the metric. MaxSim calculates a similarity score between a pair of English system-reference sentences by comparing information items such as n-grams across the sentence pair. Unlike most metrics which perform binary matching, MaxSim also computes similarity scores between items and models them as nodes in a bipartite graph to select a maximum weight matching. Our experiments show that MaxSim is competitive with state-of-the-art metrics on benchmark datasets.     

Writing of Long-Period Gratings in Conventional and Photonic-Crystal Polarization-Maintaining Fibers by CO2-Laser Pulses

We report the writing of long-period gratings in conventional and photonic-crystal (PC) polarization-maintaining (PM) fibers by high-frequency CO-laser pulses. We find that the writing efficiency depends on the irradiation direction of the writing beam with respect to the principal axes of the fiber, with the highest efficiency obtained when the irradiation direction is along the slow axis of the fiber. Such orientation dependence is much stronger for a conventional PM fiber than for a PC PM fiber. Using a conventional PM fiber, we demonstrate a grating that shows two clean polarization-splitting rejection bands with a separation of 33.4 nm and a contrast higher than 30 dB.     

Ultracompact multimode interference 3-dB coupler with stronglateral confinement by deep dry etching

Extremely short InP-InGaAsP MMI 3-dB couplers (L~15-50 μm) with conventional structure have been successfully fabricated. The significant size reduction was achieved by deep dry etching and tapered access waveguide with large S-bend design. Optical transmission measurements on these devices have been performed. An optical bandwidth about 80 nm with a limit of 2-dB excess loss was obtained for most of the couplers. During the whole tunable wavelength range (λ~1485-1580 nm), the imbalance is within ±0.5 dB. Fabrication tolerance and polarization independence are also investigated and the results demonstrated the applicability of these ultracompact devices in high-density photonic integrated circuit