Showing papers by "Shanghai Jiao Tong University published in 1985"

An approximate approach for the calculation ofM s in iron-base alloys

Abstract: Having estimated the critical driving force associated with martensitic transformation,ΔG α→M, as $$\Delta G^{\alpha \to M} = 2.1 \sigma + 900$$ whereσ is the yield strength of austenite atM s, in MN m−2, we can directly deduce theM s by the following equation: $$\Delta G^{\gamma \to {\rm M}} |_{M_S } = \Delta G^{\gamma \to \alpha } + \Delta G^{\alpha \to M} = 0.$$ The calculatedM s are in good agreement with the experimental results in Fe-C, Fe-Ni-C and Fe-Cr-C, and are consistent with part of the data in Fe-Ni, Fe-Cr and Fe-Mn alloys. Some higher “M s” determined in previous works may be identified asM a,M s of surface martensite or bainitic temperature. TheM s of pure iron is about 800 K. TheM s in Fe-C can be approximately expressed as $$M_S (^\circ {\text{C}}) = 520 {\text{--- }}\left[ {{\text{\% C}}} \right]{\text{ }}x 320.$$ In Fe-X, the effect of the alloying element onM s depends on its effect onT 0 and on the strengthening of austenite. An approach for calculation of ΔG γ→α in Fe-X-C is suggested. Thus dM s/dx c in Fe-X-C is found to increase with the decrease of the activity coefficient of carbon in austenite.

A “Hydrogen partitioning” model for hydrogen assisted crack growth

Abstract: A “hydrogen partitioning” model has been developed to account for the pressure and temperature dependence for hydrogen-assisted crack growth. The model gives explicit recognition to the role of hydr en-microstructure interactions in determining the distribution (or partitioning) of hydrogen among the various microstructural elements (principally between the prior-austenite grain boundaries and the matrix) and the rate of crack growth along the elements. It also takes into account the role of various rate controlling processes in determining the rate that hydrogen is being supplied to the fracture process (or embrittlement) zone. Quantitative assessment of the model indicates very good agreements between the model predictions and the observed crack growth responses for AISI 4340 and 4130 steels tested in hydrogen and for AISI 4340 steel tested in hydrogen sulfide. This model accurately characterizes the reduction in crack growth rate and the concomitant change in fracture mode at “high” temperatures. Through its integration with the earlier models, based on rate controlling processes, the model predicts the pressure and temperature dependence for K-independent crack growth over the entire range of environmental conditions.

Bad Data Suppression in Power System State Estimation with a Variable Quadratic-Constant Criterion

Abstract: This paper reports numerical results on tests of a new bad data suppression strategy for power system state estimation. A transformation-decoupled state estimator [1] is used in conjunction with a variable quadratic-constant criterion whose break even point is designed to track the upper bound of normalized residues of good measurements. Numerical simulations with a 6-bus test system and the IEEE 30-bus system show that the new bad data suppression strategy, is very effective for different systems under many uncertainties in the sizes and numbers of bad data with a moderate measurement redundancy.

Measuring the birefringence of single-mode fibers with short beat length or nonuniformity: a new method.

Abstract: A three-section fiber model has been used to derive the formula for measuring the birefringence of single-mode optical fibers. This analysis relieves the problems associated with measurements of the birefringence of optical fibers with very short beat length. The distortion of the measured curves for fibers with nonuniform birefringence is discussed. A newly developed nulling scheme makes the measurement accurate and stable.

A generalized statistical N-level J-C model

Abstract: A quantum statistical model for the interaction of an N -level atom with N −1-mode radiation field is presented. The mean photon numbers and the average values of the atomic level occupations are studied by means of the operator equation of motion. It is found that decays and revivals exist. Application of this model to the investigation of ab N − 1-mode laser is also discussed.

Automatic Description of the Venation of Mosquito Wings from Digitized Images

Abstract: -Methods are described for the automatic measurement of morphological features of mosquito wings (wing outline and venation) from TV images of specimens mounted on microscope slides. The digitized images were preprocessed to locate the "ridge points" in the gray-scale image surface and the digitized images were thinned so that veins could be represented by curves only a single pixel wide. The image was then segmented into the wing outline and the 10 longitudinal wing veins. Polynomial functions were fitted to each vein. The coordinates of the end points of each vein and the coefficients of the polynomials could then be used as descriptors of each wing for subsequent multivariate analyses. Comparisons are made with other algorithms and the results are shown. [Feature extraction; orthogonal polynomials; image analysis; tracing.] Now that inexpensive hardware is available for the attachment of TV cameras and other imaging devices to computers (even microcomputers), there is an immediate interest in practical applications of image analysis. Most applications in biology have been related to the field of medicine, but there are many potential applications in systematics and areas of population biology. While the methods described in the present paper were developed specifically for the veins and outlines of mosquito wings, the general approach has applicability to many other types of images in which the features of interest consist of a set of lines. Mosquito wings are especially challenging because the veins vary in density and are partly obscured by scales, and are seen against a cluttered background. In this paper we describe a method for locating the veins of mosquito wings (using image-segmentation techniques) and fitting the coefficients of polynomials to each vein. The coefficients may be difficult to interpret biologically, but they are convenient descriptors for subsequent multivariate analyses. They also permit one to reconstruct the image of the veins from the coefficients (the importance of which was discussed by Rohlf and Archie, 1984). Our procedures are: (1) digitizing an image of a mosquito wing (mounted on a microscope slide) using a TV camera and digitizer; (2) enhancing the original image to reduce the effects of imperfections in the image; (3) tracing the lines corresponding to the wing outline and the veins in order to obtain sets of coordinates; and (4) computing the coefficients of polynomial functions fitted to the coordinates to serve as the final descriptive features of the wings. The present report describes in detail steps 2 and 3 (preprocessing of the image) and step 4 (feature extraction). Many methods exist to describe the features of objects in an image (Pratt, 1978; Rohlf and Ferson, 1983). Methods include Fourier descriptors (Kuhl, 1982; Chellappa and Bajdajian, 1984; Rohlf and Archie, 1984), moments (Gonzalez and Wintz, 1977), and topological descriptors (Gonzalez and Wintz, 1977). This study is an extension of that of Rohlf and Archie (1984), who considered only outline shape of mosquito wings and used coordinates produced by tracing the outline of a wing manually with a coordinate digitizer. Ferson et al. (1985) reported on methods for automatically obtaining the outline trace of mussel shells (which have images with distinct edges).

A new method for the solution of three dimensional magnetostatic fields, using a scalar potential

Abstract: A new method "Equivalent Magnetized Region Solution" based on scalar potential for solving 3D magnetostatic fields is presented. The current distribution is transformed into a region of magnetic dipoles and only one scalar potential is used to calculate the field. A program "CMF3D" has been developed by finite element method, equipped with program "MESH" for subdividing field region into elements. Three examples by the solution are presented and compared with results from analytical method or experiment.

An analytic solution for interlaminar stresses in a fiber- reinforced double-layer cylindrical shell

Abstract: The present paper investigates the basic characteristics of the interlaminar stresses in a double-layer cylindrical shell with both ends simply-supported under uniform external or internal pressure. The double layer shell is composed of a 0° fiber-reinforced composite layer and an isotropic layer. In this paper, this axisymmetric problem is solved exactly with the three-dimensional theory of elasticity. Both the displacement field and the stress field of each layer of the shell are expressed in Fourier series and Fourier-Bessel series. Then we illustrate the effects of the various parameters, such as geometry, material constants, loading conditions and stacking sequence, on the interlaminar stresses.

The numerical computation of aircraft response to arbitrary verticalgust distributions

Abstract: The partial results of a subsonic longitudinal response that has been used in some practical design work are summarized. The aircraft gust response consists of three modes: dynamic, control and elastic structure. In the control response mode, the responses of both the pilot and the gust alleviator have been considered. The type of gust may be either discrete or continuous with an arbitrary velocity distribution. The aircraft are also arbitrary and include conventional and canard configurations. The method of time history is the mainstay of this computing program. The disturbed flight path is divided into several thousand time intervals; during each interval, the aerodynamic, flight dynamic, structural elastic, and control equations are solved in succession. The resulting parameters are used as the input of the next interval. The method of finite elementary solutions is arranged to calculate the unsteady aerodynamic loadings over the wing and tail surfaces. A new parallelogrammic paneling is suggested to minimize the number of influence coefficients. Some comparisons of the results obtained here with those of analytical methods have been made and it is found that they agree quite well.

A Transformation-Decoupled Estimator for Power System State Estimation

Abstract: This paper presents a new decoupled power system state estmator The decoupling is achieved via simple linear transformations on power measurements in contrast with the fast decoupled state (FDS) estimators which assume decoupling by direct negligence of the off- diagonal blocks of the Jacobian of the observation functions The new estimator is compared with the conventional weighted least-squares (WLS) estimator and the fast decoupled state estimator against test systems ranging from 6-bus to 30-bus in size and different system loading conditions, network parameters, measurement types and redundancies

Three-dimensional holographic reconstruction of two-dimensional image information from serial sections and its applications in biomedicine

Abstract: An experimental study to synthesize holographically two-dimensional projections of serial sections at various depths into three-dimensional images is described. The effects caused by the position, size and resolution of virtual images during reconstruction are analysed, and the advantages and limitations of this method are discussed. An application of this experimental method — the three-dimensional reconstruction of serial sections of a newt embryo — is presented.

Some properties of efficient solutions for vector optimization

Abstract: In this paper, we discuss the optimality conditions for vector optimization problems. Properties of efficient and weakly efficient solutions are studied, and some new necessary conditions are obtained. Most of them are related to the mapping properties of the derivative operatorf′(x) of the objective functionf. Almost all of our results are based on the methods of functional analysis and the theory of degree.

Program synthesis based on Boyer-Moore theorem proving techniques

Abstract: Program synthesis based on theorem proving usually relies on resolution theorem proving techniques. We develop a deductive approach to program synthesis based on non-resolution theorem proving techniques -- Boyer-Moore techniques. It combines knowledge base, theorem proving, and program synthesis in a systematic way of knowledge development, and can be used in program construction, program verification, and program optimization.

Equilibrium copolymerization, 2. Effect of ultimate unit

Abstract: In this paper, three cases of equilibrium copolymerization with the effect of ultimate unit are studied. The two-dimensional molecular size distribution functions and other molecular parameters of the copolymer generated are derived. Then, with the aid of this theory, the values of all molecular parameters of the copolymer can be calculated from the comonomer feed composition and equilibrium constants of initiation and propagation.

Equilibrium copolymerization, 1. Random model

Abstract: Three cases of equilibrium copolymerization are re-treated theoretically. The expression of the molecular weight distribution of the copolymer is a two-dimensional distribution function with two random variables m and n, where m and n are the numbers of two different monomeric units, respectively. The molecular parameters of the copolymer, such as the number- and weight-average molecular weights, number-average degree of polymerization, copolymer composition and equilibrium conversions of comonomers, are derived. The relation between the parametric variables in the formulae and the equilibrium copolymerization conditions are determined from two binary cubic equations.

An example of applications of the elementary catastrophe theory in Hamiltonian systems

Abstract: The convection in atmosphere discussed in ref. [1] is rigorously treated by considering the variation of environmental temperature\(\bar T\left( z \right)\) with the height. This represents an example of applications of the elementary catastrophe theory in Hamiltonian systems.

Prospects of office automation in China

Abstract: At the present time, interest in Office Automation is evident at every level from the central government down to the local government. It can be said that there is an \"OA Heat\" uprising. The Shanghai City government is the first which announced its office automation plan and invited companies, universities and research institutes to attend. The Shanghai City government makes arrangements for all kinds of activities, economic, political as well as foreign affairs in a city with a population of 10 million people.

Equilibrium polymerization with a multifunctional initiator

Abstract: The equilibrium polymerization with a multifunctional initiator is re-treated theoretically The expressions for the molecular weight distribution function, the number- and weight-average degrees of polymerization, the distribution of the degree of branching and the average degree of branching of the polymer formed are rigorously derived All the formulae given are much simpler than those reported by Baur and Eisenberg A theoretical method is established by which all the molecular parameters of the polymer can be calculated from polymerization conditions, such as the equilibrium constants, the functionality of the initiator and the initial concentrations of initiator and monomer

Perturbation solution of axisymmetric plastic problem I—Necking of a bar

Abstract: In this paper, basing on the general equations of axisymmetric plastic problems deduced in ref. [11], and employing perturbation technique, the asymptotic analysis for the necking problem is given. The result will provide knowledge of distribution of stress and strain in whole plastic region, thus, it will lead to a better understanding of the necking phenomena in a tension specimen, such as the cup-cone type fracture. I. Introduction The question of the stress and strain distribution in the neck formed under tension is complicated and it has not been fully solved. Since it is important to know the magnitudes of the flow stresses at the instant preceding rupture, this question attracts many investigators. Bridgman (1944) [~l, basing on the experimental data, assumed that the deformation was uniform across the minimum section, i.e. the radial velocity is proportional to r; hence the radial strain-rate ~, is equal to the circumferential strain-rate ~ 0 in the minimum section. It follows that ~,-~o there. Since the shape of the neck is unknown and can only be determined by tracing its gradual development, Bridgman supposed the profile of neck was circular arc, i.e. and assumed the radius of the curvature of the neck profile was

Transition Region Effect in the SiO2-SiOx-Si System on the Si Two-Dimensional Electron Gas

Abstract: The energy levels of the Si two-dimensional electron gas (2 DEG) subband is theoretically investigated, considering a graded composition in a transition region of the SiO2–SiOx–Si system. An expression is found of an effective atomic potential of the transition, varying continually along the space coordinate, and variational calculations are performed with trial wave functions to obtain the subband energy of the 2 DEG. The theoretical results coincide satisfactorily with some known FIR experimental results about Si-2DEG. It is shown that the properties of the Si-2DEG are quite sensitive to the transition and, further, that if the transition width is above a certain critical value, there is no 2DEG in the SiO2–SiOx–Si system. Die Energieniveaus des zweidimensionalen Elektronengas (2DEG)-Subbands von Si werden theoretisch untersucht, wobei eine graduelle Zusammensetzung im Ubergangsbereich des SiO2–SiOx–Si-Systems betrachtet wird. Ein Ausdruck fur ein effektives atomares Potential des Ubergangs wird gefunden, der sich in Richtung der Raumkoordinate kontinuierlich andert, und es werden Variationsrechnungen mit Testwellenfunktionen durchgefuhrt, um die Subbandenergien des 2DEG zu erhalten. Die theoretischen Ergebnisse stimmen befriedigend mit einigen bekannten experimentellen FIR-Ergebnissen am Si-2DEG uberein. Es wird gezeigt, das die Eigenschaften des Si-2DEG gegenuber dem Ubergang empfindlich sind und weiter wird gezeigt, das kein 2DEG im SiO2–SiOx–Si-System existiert, wenn die Ubergangsbreite uber einem gewissen kritischen Wert ansteigt.

Unsteady theory of the hydrofoil of finite span

Abstract: A three-dimensional unsteady flow around the hydrofoil has been dealt with in this paper. Under the assumption of infinitesimal wave and thin hydrofoil, analytic solution of perturbation velocity potential induced by the unsteady flow of a hydrofoil which is simplified as a series of rectangular vortex rings is achieved and then the unsteady forces can be evaluated.