TRANSFER FUNCTION MODEL ORDER AND PARAMETER ESTIMATION

Abstract. A distributed lag model with a rational transfer function is considered. We have demonstrated that the C -table can be used to determine the orders of the rational transfer function and the Padé table can be used to estimate the parameters of an identifiable transfer function. In case the model is not uniquely identified, the C -table reduces possible competing models to only a few for further examination. Padé approximant gives consistent initial values for possibly more efficient iterative procedures to estimate the coefficients of the identified model. Some asymptotic results on the estimation of the C -table and the Padé table are given. A few examples are presented to demonstrate the effectiveness of the method.     

Wide-band guided-wave acoustooptic Bragg cells in GaAs-GaAlAs waveguide

One of the key components in future GaAs-based monolithic integrated acoustooptic modules or circuits is an efficient and wide-band acoustooptic Bragg cell. In this paper, design, fabrication, and performance characteristics of compact miniaturized GaAs-GaAlAs waveguide acoustooptic Bragg cells that operate at the acoustic frequency from 190 to 625 MHz are reported. A 201 MHz bandwidth has been obtained with the Bragg cell that employs a single tilted-finger chirp transducer centering at 360 MHz. The acoustic propagation losses in the GaAs-GaAlAs waveguides that were measured using acoustooptic Bragg diffraction as a probe are also presented.     

白藜芦醇磺酸酯的合成及抗氧化、抗肿瘤活性的研究

以白藜芦醇和2, 4-二硝基苯磺酰氯为原料,通过酯化法得到白藜芦醇磺酸酯,通过NMR和LC-MS确定了该化合物结构。以维生素C为阳性对照,研究白藜芦醇磺酸酯对2, 2-联苯基-1-苦基肼(DPPH)自由基和2, 2′-联氮-双-3-乙基苯并噻唑啉-6-磺酸(ABTS)自由基的清除活性和抗氧化活性;噻唑蓝(MTT)法研究其对人肺癌细胞A549的增殖活性。实验结果表明,目标产物收率为33.1%。同时,目标产物在浓度为1.0 mg/mL时,对DPPH自由基和ABTS自由基的清除率分别为31.6%和42.7%,抗氧化活性均高于白藜芦醇,但低于维生素C;目标产物对人肺癌细胞A549具有较好抑制作用,IC50值为(10.2±0.37)μg/mL。     

典型的高效混凝与沉淀工艺

由于我国饮用水水质标准的提高,典型高效混凝沉淀工艺近年来被广泛应用于水处理领域。该文着重对利用该工艺研发出来的、具有典型特点的三种国外典型沉淀池的工艺流程及技术特点进行了说明,并针对已有给水处理工艺需要进行提标改造的现状,提出了将典型高效混凝沉淀工艺应用到已有常规工艺升级改造的初步方案,为今后我国常规水处理工艺的升级改造,达到新版饮用水国标提供了技术和工艺方面的支持。     

Processing and physical properties of Al2O3/aluminum alloy composites

Porous aluminum oxide (Al₂O₃) preforms were formed by sintering in air at 1200 °C for 2 h. A356, 6061, and 1050 aluminum alloys were infiltrated into the preforms by squeeze casting in order to fabricate Al₂O₃/A356, Al₂O₃/6061, and Al₂O₃/1050 composites, respectively, with different volumes of aluminum alloy content. The content of aluminum alloy in the composites was 10–40% by volume. The resistivity of Al₂O₃/A356, Al₂O₃/6061, and Al₂O₃/1050 composites decreased dramatically from 6.41 × 10¹² to 9.77 × 10⁻⁴, 7.28 × 10⁻⁴, and 6.24 × 10⁻⁴ Ω m, respectively, the four-points bending strength increased from 397 to 443, 435.1, 407.2 MPa, respectively, and the deviations were smaller than 2%. From SEM microstructural analysis and TEM bright field images, the pore volume fraction and the relative density of the composites were the most important factors that affected the physical and mechanical properties. The ceramic phase and alloy phase in Al₂O₃/aluminum alloy composites were found to be homogenized and uniformly distributed using electrical and mechanical properties analysis, microstructure analysis, and image analysis.     

Methionine restriction up‐regulates the expression of the pi class of glutathione S‐transferase partially via the extracellular signal‐regulated kinase‐activator protein‐1 signaling pathway initiated by glutathione depletion

Understanding the molecular events underlying gene regulation by amino acids has attracted increasing attention. Here, we explored whether the mechanism by which methionine restriction affects the expression of the π class of glutathione S‐transferase (GSTP) is related to oxidative stress initiated by glutathione (GSH) depletion. Rat primary hepatocytes were cultured in an L‐15‐based medium in the absence or presence of 200 μM L ‐buthionine sulfoximine (BSO) or in a methionine‐restricted L‐15 medium supplemented with 20 μM L ‐methionine up to 72 h. BSO and methionine restriction time‐dependently induced GSTP mRNA and protein expression in a similar pattern accompanied by a decrease in the cellular GSH level. The phosphorylation of extracellular signal‐regulated kinase (ERK), but not of c‐Jun NH₂‐terminal kinase and p38, was stimulated by methionine restriction and BSO. Electromobility gel shift assay showed that the DNA‐binding activity of nuclear activator protein‐1 (AP‐1) increased in cells exposed to methionine restriction or BSO. With the ERK inhibitor FR180204, AP‐1 activation and GSTP expression were abolished. Moreover, the induction of GSTP by methionine restriction and BSO was reversed by GSH monoethyl ester and N‐acetylcysteine. Our results suggest that methionine restriction up‐regulates GSTP gene expression, which appears to be initiated by the ERK‐AP‐1 signaling pathway through GSH depletion in rat hepatocytes.     

一体化智能抢修指挥系统在电网调度中的应用

介绍了一体化智能抢修指挥系统（TCM）的内涵,在分析TCM的技术亮点的基础上,解析了TCM在浦东电网调度工作中的应用案例,阐述了将TCM结合智能电表及用电信息采集系统、配电自动化系统建设的应用前景,用以优化电网故障处理流程,提高电网故障响应能力,提升对客户的服务水平.分析认为：TCM取得了创新性的实用化科研成果,对电网运行过程中出现的各种故障信息能够自动接入并提示,辅助热线支持组人员通过故障登记、工单合并,提高了工作效率和故障抢修速度,在优化抢修资源后进一步提高了供电可靠性,实现了电网与客户的互动服务,具有推广应用价值.     

利用L1范数求取道间时差技术进行地震道插值

本文采用L1范数求取道间时差技术求出剖面上每一样点的时间倾角，然后逐道进行倾角插值。当出现较多空道时，利用L1范数极小准则找出差值道集中绝对值最小点对应的移动时间，求出时间倾角进行插值。此法既能适应线性同相轴插值、非线性同相轴插值，又能适应等道距、非等道距插值。通过对合成记录及实际记录的处理表明，此法具有比常规道内插方法速度快、精度高、适应性强等优点。     

Reliability design of distribution systems using modified genetic algorithms

This investigation presents an evolutionary algorithm to reliably design a distribution system. Adopted reliability indices include failure rate and interruption duration, which are both commonly used in distribution systems. The total cost including the apparatus investment cost and the system interruption cost, is the objective function to be minimized. Reliability constraints on a load point are addressed to ensure the adequacy of the power supply of the load point. The evolutionary optimization algorithm is a modified genetic algorithm (GA), which uses binary and floating-point representations. The proposed GA is compared with the conventional generalized reduced gradient (GRG) method. A secondary substation of the Taiwan Power Company is used in an example of the method's application. The discussed method is simple and effective and is useful for expanding the existing systems and constructing new systems.     

Investigation of substrate bias effects on the reactively sputtered ZrN diffusion barrier films

ZrN diffusion barrier films were prepared by DC reactive magnetron sputtering under different negative substrate bias. The composition, microstructure, resistivity and diffusion barrier properties of ZrN films, with respect to substrate bias, were studied by means of X-ray diffraction, electron probe microanalyzer, Auger electron spectroscopy, and four point probe method. Results showed that the deposition rate and impurity oxygen content of ZrN films were substantially influenced by the resputtering effects due to the ion bombardment on the film surface. The competition between surface energy and strain energy made the preferred orientation of ZrN films change from (1 1 1) to (2 0 0) and then back to highly (1 1 1) preferred orientation as a function of substrate bias. The application of negative substrate bias could effectively decrease the electrical resistivity due to the decrease of impurity oxygen content and the densification of films, resulting from the moderate-energy ion irradiation. The biased ZrN films could successfully be used as a diffusion barrier layer, between Cu and SiO₂, even up to the high temperature of 800 °C for 30 min.