Simplification of z -transfer functions by continued fractions †

A computer-oriented procedure for the simplification of a z -transfer function is presented. The method consists of (1) transformation of the z-transfer function into the w domain by the bilinear transformation, w=(z? l)/)z+ 1), (2) continued fraction expansion of the w -transfer function into the Cauer second form, (3) keeping the first several quotients and discarding others, (4) converting the truncated continued fraction into z-transfer function of low order. An example is used to illustrate the rapid rate of convergence.     

Visual search strategies and eye movements when searching Chinese character screens

Most visual search studies have been restricted to alphanumeric stimulus materials. Research related to scanning patterns of Chinese characters is sparse. This study is an attempt to understand the differences and similarities in visual search of Chinese characters having a varying degree of complexity among Hong Kong Chinese, Mainland Chinese and Chinese reading non-Chinese people. Eighteen participants were tested on Chinese character screens with three layouts (row, column, and uniform separation) and two word complexities (high and low). The 18 participants comprised six Hong Kong Chinese, six Mainland Chinese and six non-native Chinese readers. Performance data and eye movement data were recorded. The percent correct and search time were the two performance measures. A new measure, called HV-ratio was developed to characterize eye movements. The results show that Hong Kong Chinese use predominantly horizontal search patterns while the Mainland Chinese change their search pattern depending on the layout presented. Non-native Chinese readers, on the other hand, do not seem to show any preference on scanning strategy for a given layout. Word complexity did not show any significant effect on search time. Potential reasons for these differences and design implications are discussed.     

OXIDATION OF RIMMING STEEL INGOT DURING TEEMING AND SOLIDIFICATION

本文定量地研究了在不同性质的气氛下凝固的小沸腾钢锭遭受氧化的程度;并研究了在大气中和隔绝大气凝固的大型沸腾钢锭,在浇铸和模内沸腾过程中的沸腾情况,母液成分的变化及钢坏中杂质含量和偏析等。结果指出:在浇铸和模内沸腾过程中,钢液的二次氧化对沸腾起着主要作用;用限制锭模内钢液与大气接触的办法来控制沸腾,可以减轻钢锭的偏析。     

渗铝、渗铬工业纯铁的耐低温热腐蚀性能

分别采用热浸法和固渗法在工业纯铁上制备了铝的扩散涂层;工业纯铁上铬的扩散涂层是用固渗法获得的。对渗铝和渗铬的工业纯铁在有K_2SO_4-Na_2SO_4 盐膜存在时的低温热腐蚀行为进行了研究。结果表明,渗铝的工业纯铁仍遭受低温热腐蚀,这一热腐蚀的发生归因于K-Na-Al-Fe 四元低熔点复合硫酸盐的形成。而渗铬的工业纯铁表现出优异的耐蚀性能,这归因于涂层表面完整的富Cr_2O_3 氧化膜的快速形成。据此有理由认为,渗铬是铁基合金低温热腐蚀防护的一个有效途径。     

Applying the digital-image-correlation technique to measure the deformation of an old building’s column retrofitted with steel plate in an in situ pushover test

An in situ pushover test is carried out on an old building of Guan-Miao elementary school in south Taiwan. Columns of this building are seismically retrofitted with steel plate. The DIC (digital-image-correlation) technique is used to measure the deformation of the retrofitted column. The result shows that the DIC technique can be successfully applied to measure the relative displacement of the column. Additionally, this method leads to the measurement of relative displacements for many points on the column simultaneously. Hence, the column deformation curve, rotation and curvature can be determined using interpolation method. The resulting curvature-diagram reveals that the phenomenon of plastic hinge occurs at about 2% storey drift ratio, and that the DIC technique can be applied to measure column deformation in a full scale in situ test.     

完善验证的凝聚力测量方法以提升软件品质

无适当使用软件测量将可能引起软件低品质且高成本的窘态.凝聚力是软件品质重要因子之一如同维护度,可靠度和再利用度.软件模组品质的优劣必影响整体系统之品质的优劣.为了设计和维护高品质软件,软件专案经理人和软件工程师无可避免需引用软件凝聚力测量以衡量和产生高品质软件.提出以活路跃变量及视觉化变量纵距为分析基础之功能导向凝聚力测量方法.进而,以一系列实际案例来作实验验证,并以一组性质来作理论辩证所提的测量方法.因此一经完善定义,完善实验和完善辩证之凝聚力测量方法被提出用于当软件凝聚力强度的指标和因此增进软件品质.这凝聚力测量方法能容易嵌入CASE以帮助软件工程师确保软件品质.     

AN INVESTIGATION ON AN AUSTENITIC Fe-Mn-Al HEAT-RESISTING STEEL

根据本文作者以前的结果,对一种成分为29.4％Mn,3.8％Al,1.9％Mo,0.5％V,0.4％W,0.015％B,0.03％N,0.1％C的奥氏体耐热钢进行了下述研究: (1)热加工塑性:Fe-Mn-Al奥氏体耐热钢的高温可塑性类似于1Cr18Ni9Ti。 (2)持久强度:在600—700℃,数千小时的持久强度接近于ЭИ257T(14％Cr,14％Ni,2.15％W,0.5％Mo,0.5％Ti,0.1％C)的水平。 (3)时效过程的变化:观察并测定了在600—750℃,保温长达9500小时时效过程中的金相组织变化、沉淀相的类型、冲击功及硬度的变化。在时效过程中顺序沉淀出V_4C_3,M_6C及Laves相,时效变脆的倾向不很大。 各种实验结果表明,为节约铬与镍,Fe-Mn-Al奥氏体耐热钢有研究发展的前途,但最大弱点是抗电化学腐蚀能力差,这有待进一步寻求解决途径。 同时,指出由Fe-Mn-Al系发展出在630℃左右使用的奥氏体耐热钢是可能的。     

热腐蚀的电化学机理初探

简要叙述至今仍普遍接受的热腐蚀的盐熔模型,以实验事实为依据较系统地阐述这一机理模型的局限性。根据热腐蚀的特点,吸收盐熔模型的合理成分,并考虑到热腐蚀与高温气体腐蚀的共性,提出热腐蚀的电化学模型。用这一新的模型描述金属和合金的热腐蚀历程。     

SYNTHESIS AND REACTIONS OF POLY[(4-CHLOROBUTYL)THIIRANE]: EVIDENCE FOR BACKBONE-ASSISTED SOLVOLYSIS†‡

(4-Chlorobutyl)thiirane is prepared in 80% yield in a single step from (4-chlorobutyl)oxirane. Homopolymerization of (4-chlorobutyl)thiirane with ZnEt₂—CH₃OH or CdCO₃ initiator systems provides poly[(4-chlorobutyl)thiirane] as a soft elastomer with inherent viscosity 0.2dL/g. Reaction of poly[(4-chlorobutyl)thiirane] with tetra-n-butylammonium benzoate in N,N-dimethylacetamide proceeds by direct displacement, without involvement of the backbone sulfur atom. Solvolysis under more strongly ionizing conditions (acetic acid/chloroform) occurs with repeating unit isomerization, most probably via a cyclic intermediate formed by attack of the backbone sulfur atom on the chloromethyl group at the side chain terminus.