A coupled finite element/one-dimensional wave model of stress wave propagation in a shock tube

A finite element model coupled to a numerical representation of one-dimensional wave propagation is used to model stress wave propagation in the structure of a large shock tunnel. Modelling difficulties and the method of coupling the two types of model are described. Results are presented which indicate that stress wave damper rods, attached to the tunnel, are effective as a means of controlling stress levels.     

Satellite and ground-based microclimate and hydrologic analyses coupled with a regional urban growth model

Urban development is shown to induce predictable changes in satellite-based measures of radiant surface temperature and evapotranspiration fraction—as long as certain features of the development are known. Specifically, the vegetation changes that accompany the development and the initial climatic state of the land parcel must be noted. Techniques are also developed for quantifying the effects of urbanization on the surface hydrology at a watershed scale. Streamflow and precipitation data are related graphically in order to determine a watershed's general ratio of stormwater runoff to rainfall, along with any changes in the ratio over time. Four distinct runoff responses, separated by season and antecedent moisture conditions, are distinguishable for a particular basin, with the response during the non-summer months under typical antecedent moisture conditions the most representative of and responsive to land-use patterns. This particular runoff response can be estimated from satellite-derived land cover patterns and certain physical attributes of a basin. These satellite-based microclimate and hydrologic analyses are coupled with an existing urban growth model (SLEUTH). The SLEUTH urban growth model simulates future development scenarios for a region of interest. The resulting changes in urban land use lead to the evolution of site-specific climate and hydrology based on the scheme that is presented in this paper. This study, as well as related tools and bodies of knowledge, can be used to broaden the scientific basis behind land-use management decisions.     

High-purity control of internal thermally coupled distillation columns based on nonlinear wave model

Internal thermally coupled distillation column (ITCDIC) is a frontier of energy saving distillation researches, which is a great improvement on conventional distillation column (CDIC). However its high degree thermal coupling makes the control design a bottleneck problem, where data-driven model leads to obvious mismatch with the real plant in the high-purity control processes, and a first-principle model which is comprised of complex mass balance relations and thermally coupled relations could not be directly used as control model for the bad online computing efficiency. In the present work, wave theory is extended to the control design of ITCDIC with variable molar flow rates, where a general nonlinear wave model of ITCDIC processes based on the profile trial function of the component concentration distribution is proposed firstly; combined with the thermally coupled relations, a novel wave model based generic model controller (WGMC) of ITCDIC processes is developed. The benzene-toluene system for ITCDIC is studied as illustration, where WGMC is compared with another generic model controller based on a data-driven model (TGMC) and an internal model controller (IMC). In the servo control and regulatory control, WGMC exhibits the greatest performances. Detailed research results confirm the efficiency of the proposed wave model and the advantage of the proposed WGMC control strategy.     

Sedtrans05: An improved sediment-transport model for continental shelves and coastal waters with a new algorithm for cohesive sediments

The one-dimensional (vertical) sediment-transport model SEDTRANS96 has been upgraded to predict more accurately both cohesive and non-cohesive sediment transport. Sedtrans05 computes the bed shear stress for a given set of flow and seabed conditions using combined wave-current bottom boundary layer theory. Sediment transport (bedload and total load) is evaluated using one of five methods. The main modifications to the original version of the model are: (1) a reorganization of the code so that the computation routines can be easily accessed from different user interfaces, or may be called from other programs; (2) the addition of the Van Rijn method to the options for non-cohesive sediment transport; (3) the computation of density and viscosity of water from temperature and salinity inputs; and (4) the addition of a new cohesive sediment algorithm. This latter algorithm introduces variations of sediment properties with depth, represents the suspended sediment as a spectrum of settling velocities (i.e. size classes), includes the flocculation process, and models multiple erosion–deposition cycles. The new model matches slightly better the field measurements of non-cohesive sediment transport, than does the predictions by SEDTRANS96. The sand-transport calibration has been extended to high transport rates. The cohesive sediment algorithm reproduced well experimental data from annular flume experiments.     

Development and application of a three-dimensional artificial visual system

A three-dimensional artificial visual system has been developed to aid in the analysis of 3-D fluorescence images of smooth muscle cells. The system consists of three sets of 3-D spatial filters that decompose the image to enable a simple recombination algorithm to locate the discrete bodies of protein concentration in a cell, classify the concentration bodies as globular or oval, and determine the 3-D orientation of the oval bodies. A graphic model of the protein concentration is created from the data provided by the artificial visual system. Patterns of organization in the distribution of the protein bodies are investigated using an interactive graphics system.     

Integration of a GIS and a complex three-dimensional hydrodynamic,sediment and heavy metal transport numerical model

The paper presents an integration of a geographic information system (GIS) and a complex three-dimensional hydrodynamic sediment and heavy metal transport numerical model. The integration overcomes the two-dimensional constraint of conventional GIS by supplementing advance tools for three-dimensional, dynamic visualization. The application of a GIS-based interface module together with the three-dimensional, dynamic display tools enhances communication of relationships and trends of hydrodynamic and pollutant transport simulation in both spatial and temporal context, and thus promotes better coastal water quality planning and management. Model functionality includes input data viewing and editing, mesh grid configuration, and result interpretation. The functionality of the GIS-model integrated system is illustrated through a case study on the Pearl River Estuary (PRE).     

On a model of three-dimensional bursting and its parallel implementation

A mathematical model for the simulation of three-dimensional bursting phenomena and its parallel implementation are presented. The model consists of four nonlinearly coupled partial differential equations that include fast and slow variables, and exhibits bursting in the absence of diffusion. The differential equations have been discretized by means of a second-order accurate in both space and time, linearly-implicit finite difference method in equally-spaced grids. The resulting system of linear algebraic equations at each time level has been solved by means of the Preconditioned Conjugate Gradient (PCG) method. Three different parallel implementations of the proposed mathematical model have been developed; two of these implementations, i.e., the MPI and the PETSc codes, are based on a message passing paradigm, while the third one, i.e., the OpenMP code, is based on a shared space address paradigm. These three implementations are evaluated on two current high performance parallel architectures, i.e., a dual-processor cluster and a Shared Distributed Memory (SDM) system. A novel representation of the results that emphasizes the most relevant factors that affect the performance of the paralled implementations, is proposed. The comparative analysis of the computational results shows that the MPI and the OpenMP implementations are about twice more efficient than the PETSc code on the SDM system. It is also shown that, for the conditions reported here, the nonlinear dynamics of the three-dimensional bursting phenomena exhibits three stages characterized by asynchronous, synchronous and then asynchronous oscillations, before a quiescent state is reached. It is also shown that the fast system reaches steady state in much less time than the slow variables.     

Numerical analysis of coupled hydromagnetic wave equations with a finite difference scheme

A finite difference scheme offering second-order accuracy is introduced to solve numerically a system of two mixed-type coupled partial differential equations with variable coefficients. The stability conditions of the scheme have been examined by both the Fourier method and the matrix method. The Fourier method via the local transform is first used to investigate parametrically the stability conditions of the proposed scheme. The stability conditions are checked point by point for the entire domain of interest without involving the convolution of the Fourier transform. These conditions are further verified by the matrix method. Since two different methods are employed, one can ensure that the stability conditions are achieved consistently. Moreover, the optimum parameters increasing the accuracy of the numerical solutions can be determined during the stability analysis. The proposed numerical algorithm has been demonstrated by a boundary value problem which considers the coupling and propagation of hydromagnetic waves in the magnetosphere.     

Geometrical and statistical foundations of a three-dimensional model of software performance

This work presents the geometrical and statistical foundations of a three-dimensional model of a software project performance model called (Quality factor+Economic, Social and Technical dimensions). In this model, the three dimensions taken into consideration are combined through the use of a regular tetrahedron geometrical representation of a pyramid, the sides of which represent the normalised values of each of the project dimensions being measured and the apex represents the normalised optimal target value of each project dimension. This paper presents the three geometrical concepts used for assessing project performance progress using geometrical concepts of distance, area and volume, and describes how the corresponding geometrical formulae are derived. The relative merit of each is also discussed and an analysis is included of the multiple combinations of values along the three axes which can be used to assess the respective adequacy of each in order to convey maximum information in the greatest number of instances along all the axes.     

Kinetic analysis of manual lifting activities: Part I—Development of a three-dimensional computer model

This paper, the first of a series of two papers, presents the development of a three-dimensional dynamic biomechanical model for analyzing spinal stresses generated in individuals while lifting materials manually. A comparison between model predicted and actual measured ground reaction forces indicates that the proposed model represents significant improvements over existing biomechanical models developed to date for this purpose.     

Finite element simulation of polymer behaviour using a three-dimensional, finite deformation constitutive model

This paper presents a phenomenological three-dimensional viscoelastic–plastic constitutive model for polymers. The model is based on the assumption that stress can be decomposed into two parts, namely viscoelastic and elastic–plastic. The proposed rate-dependent nonlinear model is then implemented in a finite element program. The validity of the code is assessed by the data from experiments on a specific polymer. The data from three types of tests, namely uniaxial compression, creep, and relaxation, are used to evaluate the validity of the model. Comparisons show that the proposed constitutive model could satisfactorily represent the time-dependent mechanical behaviour of polymers. The model is then used to study the effect of friction in the compression test and the behaviour of polymers under cyclic loading.     

一种新型光电电流互感器的研制

提出了一种基于激光供能的新型电流互感器的整体方案 ,并系统介绍了系统整体结构和工作原理     

WB法在声固耦合分析中的应用

描叙了耦合振动声系统建模技术的基本概念.根据WB法的基本原理,将结构位移和声压展开成波函数和特解函数的叠加.应用加权余量法将结构和声学边界条件以及结构与声耦合界面上的连续性条件转换成近似积分,推导出一组由代数方程表示的耦合模型.求解方程的未知系数,再代入展开式得到耦合结构与声系统的响应预报.通过分析二维的算例表明这种预报技术计算量小而精度高,因此可应用到中频的分析.     

脉搏波分析用多路正弦恒流源设计

介绍了一种用于脉搏波分析的多路正弦恒流源系统设计方案。该系统主要由PC机用户接口程序、单片机控制电路、DDS正弦波生成电路、滤波器、数字幅度控制电路以及电压-电流转换电路组成。PC机用户程序通过RS232接口与总控AVR单片机通信;总控AVR单片机通过TWI(Two Wire Interface)总线与下位单片机通信。该系统实现了多路正弦恒流源的生成与控制。     

Self-consistent compensated microfield model for a strongly coupled plasma

A compensated microfield model of plasma nonideality is proposed as an improvement of the traditional microfield models. In this model, a double contribution of a microfield to the truncation of statistical sums removed. The new method of truncation of the statistical sums of atoms or ions is compared with the results of experiments and computations performed by well-known Debye-type and other models. It is shown that only the microfield model correctly describes experiments. Ionization of Li and Hg atoms is calculated. The effect of metallization of plasma—an abrupt increase of ionization from zero to a single ionization at low temperatures and nearly normal densities—is qualitatively described. The results of calculation of Hg vapor ionization qualitatively agree with known experimental results on the measurement of electric conductivity of this vapor.     

Entrainment in a disaggregated economic long wave model

This paper investigates how mode-locking and other nonlinear dynamic phenomena arise through the interaction of two capital-producing sectors in a disaggregated economic long wave model. Each sector in isolation produces a self-sustained oscillation with a period and amplitude determined by the characteristics of that sector. However, the sectors interact through their mutual dependence on each other's output for their own production. When this coupling is accounted for, the two sectors tend to synchronize or lock together with a rational proportion between the periods. While keeping the aggregate equilibrium characteristics of the system constant, we study how this locking occurs as a function of the difference in capital lifetimes and as a function of the strength of the coupling between the sectors. Besides mode-locking and quasi-periodic behavior, the observed phenomena include cascades of period-doubling bifurcations, chaos, and intermittency. When the difference in capital lifetimes is very large, the coupled system tends to behave like a one-sector model with a reduced capital content of production.     

Computational methods for a three-dimensional model of the petroleum-discovery process

A discovery-process model devised by Drew, Schuenemeyer, and Root can be used to predict the amount of petroleum to be discovered in a basin from some future level of exploratory effort: the predictions are based on historical drilling and discovery data. Because marginal costs of discovery and production are a function of field size, the model can be used to make estimates of future discoveries within deposit size classes. The modeling approach is a geometric one in which the area searched is a function of the size and shape of the targets being sought. A high correlation is assumed between the surface-projection area of the fields and the volume of petroleum. To predict how much oil remains to be found, the area searched must be computed, and the basin size and discovery efficiency must be estimated. The basin is assumed to be explored randomly rather than by pattern drilling. The model may be used to compute independent estimates of future oil at different depth intervals for a play involving multiple producing horizons. We have written FORTRAN computer programs that are used with Drew, Schuenemeyer, and Root's model to merge the discovery and drilling information and perform the necessary computations to estimate undiscovered petroleum. These program may be modified easily for the estimation of remaining quantities of commodities other than petroleum.     

Mathematical model of reconstructing a three-dimensional image from plane projections

Images are a finite sets of points in two-dimensional or in three-dimensional Euclidean space. Restoration of the three-dimensional image from any affine transformed projection is considered. Point-to-conformity between projections a priori is not set.     

Development of a new three-phase triangular wave oscillator

The present paper is another one in a series of papers on the development of models of precisely stabilized three-phase ocillators. A new model of a three-phase triangular wave oscillator is developed by considering its expected analogy to previously suggested models of sinusoidal and triangular wave oscillators in two and three phases. The development is validated by solving the nonlinear model equations on a digital computer. The expected advantages of the new model and its envisaged applications are considered in the conclusion section.The paper possesses a further value in serving as a tutorial review in the field of precisely stabilized oscillators. The review is carried out with the aid of a relatively new concept of. ‘invariants’ associated with the damping stabilization forces in the oscillator systems.