Theory and examples of partial approximation in the finite element method

This paper presents theory and examples of partial approximation as a modification of the displacement method in the finite element analysis. This method requires different shape functions for different terms in the potential energy expression to curtail the processes in the standard displacement method. Explanation of the theory is given by use of a simple example for Poisson's equation. It can also be effectively utilized to give mathematical foundation to some finite element models based on physical reasonings, such as Melosh's rectangular element for plate bending and beam element approximation of circular arches.     

Microcomputer-Controlled Liquid Crystal Display for Automobiles

This paper presents a microcomputer-controlled liquid crystal display (LCD) speedometer with a digital seven-segment display here the response time is improved by a new driving technique employing phase control.     

Field response and gas-liquid chromatograph separation of optically active synthetic and natural pheromones in two sympatric diprionid sawflies,Neodiprion nanulus nanulus andNeodiprion sertifer (Hymenoptera: Diprionidae)

The male red pine sawflyNeodiprion nanulus nanulus Schedl responds mainly to the (2S,3S,7S)-3,7-dimethylpentadecan-2-yl acetate (2S,3S,7S-A) in the field. No other isomer is as effective by itself or syner-gizes 2S,3S, 7S-A in this species. ForNeodiprion sertifer (Geoffroy), however, we confirmed our earlier report that males responded significantly to a 50.003 mixture of 2S,3S,7S-A and either 2S,3R,7R-A or 2S,3R,7R/S-A. The 2S,3S,7S-A isomer was separated from 2S,3R,7R-A by capillary gas-liquid chromatographic (GLC) analysis using Carbowax 20 M and DB-5 columns. The latter column also separated 2S,3S,7S-A from 2S,3R,7S-A. Only 2S,3S,7S-A was found in the natural pheromones ofN. n. nanulus andN. sertifer by GLC analysis.     

Accuracy of some finite element models for arch problems

This paper presents a theoretical accuracy study of some finite element models for thin arches. As is well known, the selection of finite elements for curved members is quite a delicate problem. We obtain order estimates of errors of finite element solutions by means of the perturbation theory of mixed models and the technique of asymptotic expansion. In particular, we theoretically show that certain finite element models may suffer from the so-called locking phenomenon. Numerical results are also given to be compared with the theoretical error estimates.     

Microstructure of wood charcoal prepared by flash heating

Carbonized wood prepared by flash heating at 800 °C for 1 h shows a different microstructure and surface chemical structure than char formed after slow heating at 4 °C/min to 800 °C for 1 h. Flash heating produces pores that are surrounded by aggregates of carbon structures 25 to 100 nm in cross section. The carbon structures are built up of clearly visible graphene layers that are often curved and overlap each other in a disordered manner. The layers consist of a considerable number of oxygen-containing functional groups. The results suggest that the formation mechanism of the microstructure in wood carbonized by the flash heating process seems to originate from fragmented and oxygen-containing pyrolysis compounds in contrast to conventional heating.     

Effects of serrated grain boundaries on the crack growth in austenitic heat-resisting steels during high-temperature creep

The effect of serrated grain boundaries on creep crack growth is investigated using an austenitic 21Cr-4Ni-9Mn steel principally at 700° C. The relationship between the microstructure of specimens and the crack growth behaviour is discussed. The creep crack growth rate in the specimens with a surface notch is relatively reduced by serrated grain boundaries especially in the early stage of crack growth. The life of crack propagation in the specimens with serrated grain boundaries is longer compared with that of the specimens with straight grain boundaries. It is confirmed in the surface crack growth of smooth round bar specimens crept at 700° C that serrated grain boundaries are effective in retarding the growth of a grain-boundary crack less than about 4×10^–4 m long, and that this effect decreases with increasing crack length. It is suggested that crack deflection due to serrated grain boundaries caused a decrease in the stress intensity factor of the grain-boundary crack and resulted in a decrease of the crack growth rate in the steel. The crack arrest at the deflection points and the circumvention of crack path on the serrated grain-boundaries may also contribute to the retardation of the grain-boundary crack growth during creep. Further, it is deduced from the experimental results on the notched specimens that the creep fracture is caused by the linkage of the main crack to many microcracks and voids on the grain-boundary at 900°C.     

配筋形式对框架顶层角节点抗震性能影响试验研究

框架顶层角节点在低周反复荷载作用下梁柱交角将增大或减小。通过6个钢筋混凝土框架顶层角节点在低周反复荷载作用下的受力性能试验，分析了梁上层筋在节点内弯曲锚固长度、节点配箍量、柱筋端部锚固形式及节点内角斜拉筋量等试验参数对角节点的破坏类型、变形特征及强度等抗震性能的影响。试验结果表明：与框架中间层中节点及中间层边节点不同，框架最上层角节点的受力变形不但有剪切变形而且包含弯曲变形成分；梁柱交角增大或减小时，角节点受弯破坏特性表现迥异且节点强度有很大差异；在梁筋锚固充分的前提下，梁柱交角减小时的节点破坏为弯剪破坏，节点强度由柱筋锚固形式、节点配箍量等参数决定；梁柱交角增大时，节点破坏表现为弯曲破坏特征，节点强度受节点箍筋量、节点内角斜拉筋量的影响很大。文中还对中日两国规范节点强度设计值与试验值进行了比较。     

MOSFET Converter-Fed Position Servo System with Sliding Mode Control

Sliding mode control is an effective means to keep a system insensitive to parametric variations and disturbances. In the conventional sliding mode control applied to position servo systems, the sliding mode regime is restricted near the origin, and, therefore, insensitivity cannot be ensured throughout an entire response. This paper presents a new method in which a sliding curve is used instead of a straight line. The sliding curve is defined in such a way that in general the system responds following a max acceleration curve, then a max speed curve, and finally a max deceleration curve. Experimental results confirm that the new method can keep the system robust completely throughout a transient response, which demonstrates the advantage of the proposed sliding curve over the conventional sliding mode strategy.