基于MATHEMATICA的因次分析程序

因次分析是一种重要的数学建模方法,广泛应用于化工原理中与湍流有关的物理现象的无因次数群关联式的建立。经典化工原理在因次分析过程中采用手算法进行符号运算,非常烦琐；本文基于MATHEMATICA软件强大的符号运算功能,给出了一个因次分析程序,用来进行因次分析中的这些烦琐而重复的计算。本文还给出了该程序的若干应用实例。     

A fast computer program for conformational analysis

We describe a program, called SOBALCAN, that enables us to compute very quickly the rotation hypersurface of a flexible molecule in the “ soft-sphere” approximation. Only those conformations in which the overlap of spheres associated to all pairs of non-bonded atoms is less than a prefixed threshold are computed.     

A computer program for thin walled frame analysis

The paper presents a general purpose computer program capable of analysing any planar frame made up of members which can be categorised as thin-walled members. The approach is based on Vlasov's theory which accunts for coupling between torsion and bending actions. The topic is gaining importance due to the improved techniques of producing cold-formed steel sections which have much higher strength than normal steels. The program is in the form of single-array storage which makes its application easy even by a practicing engineer who cannot go into the details of Vlasov's theory. The program is illustrated by means of an example with complete information about input and output for the particular problem.     

基于MATHEMATICA(R)的因次分析程序

因次分析是一种重要的数学建模方法,广泛应用于化工原理中与湍流有关的物理现象的无因次数群关联式的建立.经典化工原理在因次分析过程中采用手算法进行符号运算,非常烦琐;本文基于MATHEMATICA(R)软件强大的符号运算功能,给出了一个因次分析程序,用来进行因次分析中的这些烦琐而重复的计算.本文还给出了该程序的若干应用实例.     

A computer program for the analysis of matched case-control studies

The use of regression methods for matched epidemiologic studies is discussed. A computer program is given for use in analysis of 1-1 and 1-R matched case-control data as well as the more general stratified analysis, where m cases are matched with n controls in each of K strata. The program permits variable matching ratios. An illustration is given.     

A new computer program for the analysis of pediatric scalar electrocardiograms

The authors report the development and evaluation of a computer program for analysis of pediatric scalar electrocardiograms. The program is an extension of the existing IBM 5890 ECG Analysis Program. It includes extensive age-dependent criteria and tables of limits for ECG parameters. Special pediatric correlative statements are incorporated to direct physician attention to combinations of electrocardiographic findings which may indicate congenital abnormality. The program permits the use of alternate precordial leads V_4R, V_3R, and V₇ in addition to the standard V₁ to V₆. The evaluation shows the program to be 96.8% sensitive and 88.3% specific in detecting abnormal rhythms; a sensitivity of 99.8% and specificity of 96.0% were obtained for detection of abnormalities affecting ECG contour. Program performance is apparently insensitive to choice of precordial leads, but dependent on patient age, improving as age increases.     

A computer program for kinematic analysis of three-dimensional cascaded linkage chains

The KIN program analyses the motion of three-dimensional cascaded linkage chains consisting of combinations of four-bar linkage units, axial translation units, and sliders (units confined to motion along a fixed line). Motion can be simulated for any combination of geometrical parameters. The model, the program, input-output features and an application are described. The program is written in PL/1, and can be run in either batch or conversational mode.     

A FORTRAN program for multivariate survival analysis on the personal computer

In this paper a FORTRAN program is presented for multivariate survival or life table regression analysis in a competing risks' situation. The relevant failure rate (for example, a particular disease or mortality rate) is modelled as a log-linear function of a vector of (possibly time-dependent) explanatory variables. The explanatory variables may also include the variable time itself, which is useful for parameterizing piecewise exponential time-to-failure distributions in a Gompertz-like or Weibull-like way as a more efficient alternative to Cox's proportional hazards model. Maximum likelihood estimates of the coefficients of the log-linear relationship are obtained from the iterative Newton-Raphson method. The program runs on a personal computer under DOS; running time is quite acceptable, even for large samples.     

A computer program for calculating ratio estimates

A computer program is described to calculate ratio estimates for an endpoint measured on patient subunits, such as progression of disease in coronary arteries and extent of dental caries. The program calculates ratio estimates for levels of stratification factors measured in the patient as a unit, e.g. age and sex. Test statistics are computed to evaluate differences in ratio estimates for factors with two levels. A method for making pairwise comparisons for factors with more than two levels is also described, but is not computed by the program. Data from the Veterans Administration Study of Bypass Surgery (Am. J. Cardiol. 40 (1977) 212-225) are used to illustrate the features of the program.     

A computer program for non-linear curve fitting

Recently several techniques for non-linear curve fitting have been developed. The implementation of a non-linear curve fitting procedure is treated for mathematical models in which the linear and the nonlinear parameters are separable. The technique of Golub and Pereyra is used so that a minimization algorithm only for the non-linear parameters is needed. The minimization algorithm of Marquardt has been completed with an eigenvalue analysis. In order to reduce the computation steps the inverses of matrices of the form A + λI are calculated with the eigenvalues and eigenvectors of the matrix A. Of particular interest is the obtained convergence speed and the ease with which the method can be applied.     

A computer program for the statistical analysis of cancer inhibition/promotion experiments

The computer program discussed and presented in this paper is designed for the statistical analysis of data from cancer inhibition/promotion experiments that involve Type I censoring. The theoretical derivation of the method is described in Biometrics 43 (1987) 525-534 and Appl. Math. Lett. 1 (1988) 197-201. Turbo Pascal is used to compute maximum likelihood estimates of the parameters of interest: the mean number of induced tumors per animal, and the mean time to tumor detection. The program conducts a likelihood ratio test to determine if there is an overall experiment effect, and allows the user to select options to isolate the pair(s) of groups contributing to the experiments effect, to isolate group differences in terms of tumor number and growth rate, and to graph 95% confidence regions for the vector parameter of interest.     

The analysis of nonlinear three dimensional frames

The problems involved in the analysis of three dimensional frames of non-prismatic members, made of nonlinearly elastic material are investigated. The sources of nonlinearity considered are material behavior and interaction of loads and small deformations. The material response is expressed in the form of a table of uniaxial stress and related strain with monotonically increasing values. This table is used to create a table of bending moment-curvature relationships for beams at a discrete number of cross-sections along their length and also a table of the axial load-biaxial moments-biaxial curvatures relationships for eccentrically loaded columns. These tables are then used to obtain the responses of structural members to different loadings. Length effects in the columns and sidesway in the frame are both considered. The Displacement Method of structural analysis is used with an incremental loading approach to analyze three dimensional frames made of materials whose stress-strain curves were assumed to be of circular or parabolic form, at different load patterns and magnitudes. It was found that the combination of three dimensional and nonlinear material effects on the magnitudes of the frame moments is important when compared to the moments obtained by linear, plane frame analysis, and that the assumption of linear behavior may give results which are in error by more than 30 per cent for high axial loads on columns.

It appears that the method, developed herein, of representing material and member behavior in tabular form, offers a very direct and versatile approach to the problem of analyzing structures made of several different and/or nonlinearly elastic materials.