Showing papers by "Tongji University published in 1992"

A method for direct evaluation of singular integral in direct boundary element method

Abstract: A new method is presented for evaluating the Cauchy principal value integral and the free term in the three-dimensional elastic boundary element method. This method expresses the singular integral as the sum of a weakly singular integral and an integrable Cauchy principal value integral. The former can be computed by means of the usual standard Gaussian quadrature after a transformation suggested by Lachat and Watson,10 who correctly limited its use only to weakly singular integral. The latter can be calculated by direct integration in the Cauchy principal value sense. This paper also points out some limitations in the use of triangle polar co-ordinate suggested by Li et al.11 and later extended by Zhang and Xu.16 The general expression of the free term for a boundary point with arbitrary characteristic surface is also presented. Simple numerical examples which verify the efficiency and accuracy of the present method are given.

A free rectangular plate on elastic foundation

Abstract: This article will discuss the bending problems of the rectangular plates with free boundaries on elastic foundations. We talk over the two cases, that is, the plate acted on its center by a concentrated force and the plate subjected to by a concentrated force equally at four corner points respectively. We select a flexural function which satisfies not only all the geometric boundary conditions on free edges wholly but also the boundary conditions of the total internal forces. We apply the variational method meanwhile and then obtain better approximate solutions.

Correspondence analysis for regional tracking in coronary arteriograms

Abstract: A new method of correspondence analysis on the basis of geometrical similarity in tracking the region of interest (ROI) of coronary arteriograms is described. The method is insensitive to scaling, rotation, and gray-level variation. Experiments also show that the algorithm is valid even when large deformations exist. It is an important step toward a new approach to regional myocardial dysfunction analysis. >

Lettuce seed meal tissue-based membrane electrode with high biocatalytic activity for hydrogen peroxide

Abstract: A newly developed hydrogen peroxide selective membrane electrode using lettuce seed meal as source biocatalyst is described. This amperometric-based probe exhibits high biocatalytic activity, long lifetime and favorable selectivity for the measurement of hydrogen peroxide.

Charge dynamics in Mylar films corona-charged at various temperatures

Abstract: The discharging behavior of Mylar polyethyleneterephthalate (PETP) films is investigated and discussed in terms of dipole relaxation at 85 degrees C as well as conductivity and trap dynamics at higher temperatures. For comparison, the low-temperature peak due to positive real charge in nonpolar fluoropolymer Teflon FEP is also described. The shift of the mean charge depth in PETP samples charged at elevated temperatures, the transport of detrapped real charge in the bulk of PETP, and the compensation of detrapped charge in the bulk during thermally stimulated discharge are studied by means of heat-pulse experiments as well as measurements of the steady-state conduction current and the bulk conductivity glow curve. >

Interaction of elastic waves with a periodic array of collinear inplane cracks

Abstract: A boundary integral equation method is applied to the study of the interaction of plane elastic waves with a periodic array of collinear inplane cracks. Numerical results are presented for the dynamic stress intensity factors. The effects of the wave type, wave frequency, wave incidence angle, and crack spacing on the dynamic stress intensity factors are analyzed in detail.

Dynamic interaction analysis of a circular cylindrical shell of finite length in a half‐space

Abstract: A study on the transient response of a circular cylindrical shell of finite length embedded in a homogeneous, isotropic and linear elastic half-space is presented. The soil-structure system is subjected to suddenly applied explosion waves. The numerical method employed is a combination of the time domain semi-analytical boundary element method used for the semi-infinite soil medium and the finite strip method used for the circular cylindrical shell. The two methods are combined through equilibrium and compatibility conditions at the soil-structure interface. The dynamic responses at the interface between the soil medium and the structure for every time step are obtained. Numerical examples are presented in detail to demonstrate the use and versatility of the proposed method. The following parameters are found to affect the response: (1) the slenderness ratio of the length over the diameter of the shell, L/D; (2) the relative wall thickness, h/a; (3) the relative stiffness ratio between the shell and the medium, Es/Em; and (4) the incidence angle of the explosion wave, α.

Development of the ultrasonic high temperature bolt stress monitor

Abstract: A high temperature bolt stress monitor, based on the testing of the Transit Time of Longitudinal wave and Shear Wave (TTLSW for short) and on the calculation of the stress through the established stress vs TTLSW equation, has been developed and tested. Lithium Niobate was used for piezoelectric material, gold or silver films were used for coupling material and clamping together method was used to install the transducer. Time interval averaging, zero crossing detect and several other techniques were used to improve the accuracy of TTLSW measurement. Using this method within the range of 30-360'C, and 0-443MPa the accuracy of stress is better than 9.8MPa. Nous avons develop6 et 6ssaiye un moniteur 5 haute temperature de contrainte dans boulon. Son principe est la mesure du temps de transmission des ondes longitudinal et transversale (breivement TTLSW) et la calculation de contrainte par I'equation itablie entre contrainte et TTLSW. Niobate de Lithium est utilise comme material piezoelectrique, feuille de l'or ou de l'argent sont utilise' comme mate'rial couplant, et le transducteur est instalk par la method de "pressis en ensemble". Moyenne des lintervales du temps, dktection par le zero croissant et certains autres techniques sont utilisges pour am6liorer la precision measure du TTLSW. Dans la region de 30 a 360C, cette methode a une precision de contrainte meilleur que 9.8MPa. The integrity behavior and life of a bolted joint depend a great deal upon the clamping force exerted by the bolts on that joint. Too high or little clamping force can lead to fatigue failure, damage or leaks, vibration loosening, slipping and cramping. As a result many efforts have been made to solve the problem [1],[2],[3]. We have developed a system that tests the TTLSW and then calculates the stress from it. The influence of temperature within the range of 20-360C is automatically compensated. This equipment not only can monitor the stress during its assembling, but also at high temperature and will alarm when the bolt stress has serious changes. This alarm can win some time for us to take emergency measures to avoid disasters. Basically when temperature or stress changes, the length and velocity of that bolt would change, causing the changement of T~LSW. If we suppose that the change of transit time vs stress coefficient k,, k, and the Young's modulus E are functions of temperature, and that the coefficient of velocity vs temperature h,, h, and thermoexpansion coefficients are functions of Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jp4:19921202 C1-924 JOURNAL DE PHYSIQUE IV stress h,(P), h,(P) and f(P).Then changement of TTLSW vs temperature and stress can be written

Charge Transport in Polyimide Electret During and After Corona Charging

Abstract: The influence of bulk conductivity at elevated temperature on injected charge depth along the thickness of polyimide foil was investigated by means of heat pulse technique and a three terminal-electrode system. The transport rule of detrapped real charge after corona charging and the main reason causing the decay of the charge in the bulk of the sample during thermally stimulated discharge were studied by measuring mean charge depths, steady-state conduction current-temperature curve and effective surface charge density.

Direct determination of antimony in human urine by graphite furnace atomic absorption spectrometry with the l'vov platform

Abstract: In this paper a method for direct determination of Sb in human urine by GFAAS with L'vov platform has been developed. The best result was obtained by using a pyrocoated graphite tube with a L'vov platform and modifying the matrix with 20μg of Ni. Proposed method is simple and rapid without any chemical pretreatment. The sensitivity for determination of Sb is 0.0067μg/ml. Mean recovery is 99.6～102.0%. Variation coefficient is less than 5.6%.

Effect of skin friction on the directional stability of driven piles during driving

Abstract: In this paper, the driving forces at a pile top are considered as a periodic load during driving and the Mathieu equation is derived. From the stability charts of this equation, we can obtain the critical length of the pile, and the effect of skin friction upon the critical length is discussed.

Vibration characteristics of offshore cylindrical tanks

Abstract: The vibration characteristics of offshore cylindrical tanks are studied in this paper. This is a typical topic of liquid-shell interaction system. In this paper, a general analytical method is presented by which the axial modal functions of liquid and shell are represented as the same complete orthogonal series for uncoupling the mode of liquid and shell. Simultaneously, the mode functions are expanded into a uniform convergence series and a linear polynomial, so that the problem of convergence and differentiation of mode series is solved. Therefore, the rather exact natural frequency and its corresponding mode of offshore cylindrical tank with different liquid depths, with arbitrary boundary conditions and with intermediate constraints can be obtained.

Application of pixe to cancer research

Abstract: Photodynamic therapy (PDT) is a promising approach to the local destruction of malignant tumours. This method is based on the partially selective retension in tumor tissue of the photosensitizers which have photodynamic effect. It is important for PDT to determine the photosentizer concentration in tumor and in normal tissue. We quantitatively analysed the concentration of the metallic phthalocyanines, a class of photosensitizers now recognized as “second generation” PDT drugs and studied its action in different time by PIXE technique. The paper shows also the correlation between trace elements and cancer.

Solid state high resolution 13 c nmr study of chinese mudstone kerogens

Abstract: Using ~(13)C CP MAS TOSS DD NMR, some rules governing the variations of structure parameter and fractional contents for various aliphatic carbon in the mudstone kerogens buried in different depths in China are first reported in this paper, and the preliminary studies on their natural evolution as well for the formation of oil and gas have been made. The influence of T_(CP), T_(CH), f_(rsc) on quantity measurement of CP in kerogens is discussed.

The vibration and stability analysis of moderate thick plates by the method of lines

Abstract: The method of lines based on Hu Hai-chang's theory for the vibration and stability of moderate thick plates is developed. The standard nonlinear ordinary differential equation (ODE) system for natural frequencies and critical load is given by use of ODE techniques, and then any indicated eigenvalue could be obtained directly from ODE solver by employing the so-called initial eigenfunction technique instead of the mode orthogonality condition. Numerical examples show that the present method is very effective and reliable.

Reflection of Electrons from a Fibonacci Coupled Quantum Dots System

Abstract: The reflectivity of electrons from a kind of quasi-period one-dimensional system is investigated. This system consists of a sequence of Fibonacci coupled quantum dots. Using the transfer-matrix method, and taking account of the experimental technique, we proposed the formalism of the electron reflection rate for the chain of quantum dots. From the numerical results, we analyzed the influences of the generation number, the transmission rate of single quantum dot and the phase for reflection amplitude, and we found that the reflection spectra of the system have a rich structure of self-similarity.

Coordination compounds of uranium and thorium with a novel double β-diketone

Abstract: A novel double β-diketone 1,6-bis(1′-phenyl-3′-methyl-5′-oxo-pyrazol-4′-yl) hexanedione-[1,6] (BPMOPH) was further studied on its coordination compounds with uranium and thorium, respectively. The IR, UV, and1H-NMR spectra were examined, and the proposed structure is discussed.