INDIRECT INPUT IDENTIFICATION BY MODAL FILTER TECHNIQUE

This paper is a study on modal model method in estimating system inputs from vibration responses, which is one of the indirect input identification methods in frequency domain. The method has advantages over the direct inverse method especially when points of operational inputs are inaccessible for artificial excitation but accessible for response measurement. Systematic procedures of an extended modal model method are proposed and checked by numerical experiments. Mechanisms of error propagation, i.e. how errors in modal parameters such as poles and mode shape vectors affect estimation of the input forces, are illustrated. Then, in order to counteract the error propagation, discrete modal filter approach is used in this paper to compute the inversion of modal matrix in which most serious errors seem to be generated. Further, a reduced form of modified reciprocal modal vector (MRMV) is proposed to estimate multiple inputs, which is shown to have orthogonality errors smaller than by the MRMV filter.     

电镀锌钢材表面物理气相沉积Zn-Mg合金镀层的电化学性能(英文)

锌合金镀层由于具有较强的耐腐蚀性能而得到广泛的关注,特别是Zn-Mg合金镀层,其耐腐蚀性能能得到显著提高。采用气相沉积方法制备不同镁含量的Zn-Mg合金镀层,研究Zn-Mg合金镀层中镁含量对其耐腐蚀性能的影响。在3%NaCl溶液中进行浸泡试验、动电位测试和电偶腐蚀试验,研究不同Mg含量镀层的耐腐蚀性能。结果表明,Zn-Mg合金镀层的耐腐蚀性能与Mg含量显著相关,镀层的腐蚀电位随着Mg含量的增加而降低,但是腐蚀电流密度却升高,直至15%Mg含量;在Zn-Mg合金镀层中存在钝化区。     

一等奖和平墙,首尔,韩国

韩国有一道坚固的防御工事用以抵御朝鲜的入侵,它的名字叫做“防御坦克的墙”。这座20世纪70年代在韩国首都首尔建起的防御墙成为冷战时期的纪念碑,也勾起韩国民众对朝鲜战争的痛苦回忆。     

Thermal shock behaviour of Al2O3-SiC composites made by directed melt oxidation of Al-alloy

Abstracts are not published in this journal This revised version was published online in November 2006 with corrections to the Cover Date.     

Effect of Oxide Assisted Metal Nanoparticles on Microstructure and Morphology of Gallium oxide Nanowires

Several researches have been reported about the characteristic of β-Ga2O3 nanowires which was synthesized on nickel oxide particle. But indeed, recent researches about synthesis of β-Ga2O3 nanowires on oxide-assisted transition metal are limited to nickel or cobalt oxide catalyst. In this work, Gallium oxide (β-Ga2O3 ) nanowires were synthesized by a simple thermal evaporation method from gallium powder in the range of 700 - 1000℃ using the iron, nickel, copper, cobalt and zinc oxide as a catalyst, respectively. The β-Ga2O3 nanowires with single crystalline without defects were successfully synthesized at the reaction temperature of 850, 900 and 950℃ in all the catalysts. But optimum experimental condition in synthesis of nanowires varied with the kind of catalyst. As increasing synthesis temperature,the morphology of gallium oxide nanowires changed from nanowires to nanorods, and its diameter increased. From these results, we could be proposed that the growth mechanism of β-Ga2O3 nanowires was changed with synthesis temperature of nanowires. Microstructure and morphology of Synthesized nanowire was characterized by HR-TEM, FE-SEM, EDX and XRD.     

Effects of Ti thickness on epitaxial CoSi2 growth from Co/Ti bilayer

Abstracts are not published in this journal This revised version was published online in November 2006 with corrections to the Cover Date.     

Effect of chromium on the phase evolution and microstructure of ZnO doped with bismuth and antimony

Crystalline phase formation and microstructure of ZnO varistors with a basic composition ZnO–Bi₂O₃–Sb₂O₃ were examined. Addition of chromium oxide to this basic varistor resulted in an α-spinel (α-Zn₇Sb₂O₁₂) phase dissolving a significant amount of Cr, while the β-spinel did not. β-spinel transformed to pyrochlore during cooling, whereas α-spinel hardly transformed to pyrochlore irrespective of the cooling conditions. When Sb₂O₃ was completely replaced by Cr₂O₃, ZnCr₂O₄ was formed instead of spinel. α-spinel particles were 1–2 μm in size and intra- as well as intergranular. ZnCr₂O₄ particles, smaller than 1 μm in size, however, were present as aggregates in the bismuth-rich matrix phase at the grain boundaries. This revised version was published online in November 2006 with corrections to the Cover Date.     

Structural damage assessment of building structures using dynamic experimental data

Detection of damage to structures has recently received considerable attention from the viewpoint of maintenance and safety assessment. In this respect, the vibration characteristics of buildings have been applied consistently to obtain a damage index of the whole building, but it has not been established as a practical method until now. It is reasoned that this is perhaps due to restrictions on the experiment, use of improper method, and lack of inspection opportunity for the structures. In addition, in the case of large‐scale structures such as buildings, many variables to be considered for the analysis contribute to a large number of degrees of freedom, and this can also be a considerable problem for the analysis. A practical method for the detection of structural damage using the first natural frequency and mode shape of building is proposed in this paper. The effectiveness of the proposed method is verified by numerical analysis and experimental tests. From the results, it is observed that the severity and location of the damage can be estimated with a relatively small error by using modal properties of building. Copyright © 2004 John Wiley & Sons, Ltd.     

Investigation of the drying temperature dependence of the orientation in sol–gel processed PZT thin films

The crystal orientations of lead zirconate titanate (PZT) thin films have been investigated by using various drying temperatures in the sol–gel process. The films were dried at different temperatures between 310 and 350°C for pyrolysis and then were heat treated at 650°C using rapid thermal annealing (RTA). TG/DTA and FTIR spectroscopy were used to detect the remnants of organic materials in the thin films prior to the final heat treatment. In order to examine the relationship between the film orientation and the remaining organic materials for the prior and final heat treatment, the films were fabricated with different coating cycles and dried for different holding times and then annealed at 650°C. The preferred orientations were investigated using X-ray diffraction. This revised version was published online in November 2006 with corrections to the Cover Date.