Stability estimation method for compartmental models with delay

The paper proposes a method to construct exponential estimates for solutions of compartmental models with time delay. Constructing estimates for such systems is important since much attention in medical system study is paid to problems described by compartmental models.     

A comparison of traditional geometrical models and mass triangle model in calculating the surface tensions of ternary sulphide melts

Surface tension of the Ni₃S₂–FeS–Cu₂S ternary mattes has been calculated using a mass triangle model as well as six traditional geometrical models based on the same calculation data to investigate the difference between mass triangle model and other kinds of geometrical models. From the calculated results, it might be seen that, the mass triangle model, irrespective of the method of selection of the binary data, would give the best results compared with other traditional geometrical models. The mean square root errors of the mass triangle method only range from 1.09% to 2.8%, which are almost within the experimental error of 2.5%.     

A comparison of different geometrical models in calculating physicochemical properties of quaternary systems

In this paper, the geometric model has been extended to estimate the physicochemical properties of quarternary systems based on the data of its six sub-binary systems. It has been pointed out that the asymmetrical model is not suitable for the calculation of the systems higher than three components due to the difficulty of selecting the asymmetrical component. Though this difficulty will disappear in the symmetrical model, another trouble will be introduced instead. When two of “n$n$” components are identical, this symmetrical model cannot be reduced to a “n−1$n-1$” component system, of course, which is unreasonable. Based on these facts, Chou et al. have proposed a “new generation geometric model” that can overcome all these defects mentioned above. The correctness of this new generation geometric model has already been proved through a theoretical analysis and partially demonstrated by some ternary examples. However, it has never been tested in high order practical systems due to the lack of data. Recently, some volume and viscosity data in the Propan-2-ol + methylacetate + dichloromethane +n$n$-pentane quaternary system have been found that can be used to judge which model would be better. The calculation results show that in the viscosity calculation our model is the best, while in the volume calculation our model is still good, when the calculation error is considered. These facts prove that the new generation geometrical model can work well in a higher order system.     

A feedback oscillator model for circulatory autoregulation

Circulatory autregulation is the phenomenon whereby an isolated organ can maintain a constant or almost-constant blood flow rate over a range of perfusion pressures. A mathematical model is developed, based on work reported in the physiological literature, and tuned to show that autoregulation can be accomplished by pressure-induced oscillations in arteriolar radius. Various features known lo be exhibited by skeletal muscle and by stretch receptors are incorporated in the model of smooth muscle surrounding the arterioles.     

Simulation of compartmental models for kinetic data from a positron emission tomograph.

Linear compartmental models are used to describe the disposition of radio-labelled compounds in regions of interest in the mammalian body, based on a time sequence of measurements from a positron emission tomograph (PET). In this paper we show how closed form solutions for the model equations have been incorporated into a computer program for simulation and parameter estimation. A typical PET data example is included to illustrate the implementation and compare the closed form method with a numerical ode solution method.     

A circulatory model for the estimation of insulin sensitivity

Insulin sensitivity is commonly assessed by analysing intravenous glucose tests with a simple model, called the minimal model. However, the physiological meaning of the insulin sensitivity indices estimated using this model is not transparent. To overcome this problem, a circulatory model was developed to analyse intravenous glucose tests in which a tracer was injected together with glucose. Physiological parameters, such as glucose volume, clearance and production, were estimated. Insulin sensitivity was defined in terms of glucose clearance. The parameter values estimated in 5 normal subjects were in good agreement with the values reported in previous independent studies.     

A system for compartmental modelling and simulation

The paper describes a software package for modelling and simulating compartmental systems based upon a generalisation of the equations of compartmental systems. The aim is a versatile package which can be used for rapid model development. Its use is first illustrated in a number of simple classical examples. The power of the software--and more generally the methodology--is demonstrated by showing its application in developing a model-based system for insulin planning for diabetic patients. The software has been written in Pascal and runs on IBM PC and compatible computers.     

A constrained machine model for calculating effective production capacity

The objective of this paper is to provide procedures to aid in the capacity planning effort at the strategic level. A general model is formulated which allows the computation of machine requirements at the end product level and a procedure for elimination of non-key machines from further analysis is developed. A procedure for determining the effective production capacity based on the remaining key machines is then presented. An example of the application of these procedures is provided followed by general comments regarding implementation.     

A comparison of semantic models for noninterference

The literature on definitions of security based on causality-like notions such as noninterference has used several distinct semantic models for systems. Early work was based on state machine and trace-set definitions; more recent work has dealt with definitions of security in two distinct process algebraic settings. Comparisons between the definitions has been carried out mainly within semantic frameworks. This paper studies the relationship between semantic frameworks, by defining mappings between a number of semantic models and studying the relationship between notions of noninterference under these mappings.     

A microcomputer program for simulation of linear compartmental physiological models: computation on Apple IIe

The microcomputer program presented here allows the simulation of linear compartmental physiological models whose structure is known. The method used is the 4th order Runge-Kutta method. Implemented on the Apple IIe, this program is fully interactive and presents the possibility of changing model parameters or initial values from run to run.     

认知行为计算模型结合DM的教学质量提升

为了根据认知及行为表现区分不同类别的学生以更好地提升教师教学质量,提出了基于认知行为计算模型的数据挖掘模型。基于各种重要的认知、行为输入参数,提出了认知、行为指数因子计算模型;依据所搜集的六个认知参数及三个行为参数,运用人工神经网络、灵敏度分析、数据挖掘及分类回归树算法对数据进行分类;将学生划分成三种不同的类别,从而更好地针对不同类别的学生实施不同的教学策略。实验结果表明,学生分类问题中,行为参数远比认知参数重要,分析结果表明了所提模型在教育系统教师工作支持领域的可行性。     

A comparison of finite-difference and finite-element methods for calculating free edge stresses in composites

This study considers the accuracy of the finite difference method in the solution of linear elasticity problems that involve either a stress discontinuity or a stress singularity. Solutions to three elasticity problems are discussed in detail: a semi-infinite plane subjected to a uniform load over a portion of its boundary; a bimetallic plate under uniform tensile stress; and a long, midplane symmetric, fiber-reinforced laminate subjected to uniform axial strain. Finite difference solutions to the three problems are compared with finite element solutions to corresponding problems. For the first problem a comparison with the exact solution is also made. The finite difference formulations for the three problems are based on second order finite difference formulas that provide for variable spacings in two perpendicular directions. Forward and backward difference formulas are used near boundaries where their use eliminates the need for fictitious grid points. Moreover, forward and backward finite difference formulas are used to enforced continuity of interlaminar stress components for the third problem. The study shows that the finite difference method employed in this investigation provides solutions to the three elasticity problems considered that are as accurate as the corresponding finite element solutions. Furthermore, the finite difference method appears to give a solution for the laminate problem that characterizes the stress distributions near an interface corner in a more realistic manner than the finite element method.     

Dynamic estimations of metabolic fluxes with constraint-based models and possibility theory

Living cells can be modelled by successively imposing known constraints that limit their behaviour, such as mass balances, thermodynamic laws or enzyme capacities. The resulting constraint-based models enclose all the functional states that the modelled cells may exhibit. Then, predictions can be obtained from the models in two main ways: adding experimental data to determine the state of cells at given conditions (MFA) or invoking an assumption of evolved optimal behaviour (FBA). Both MFA and FBA predictions are typically performed at steady state. However, it is easy to take extracellular dynamics into account. This work explores the benefits of using possibility theory to get these dynamic predictions. It will be shown that the possibilistic methods (a) provide rich estimates for time-varying fluxes and metabolite concentrations, (b) account for uncertainty and data scarcity, and (c) give predictions relaxing the optimality assumption of FBA. On the other hand, these methods could serve as basis for monitoring and fault detection systems in industrial bioprocesses.     

A mathematical model and image analysis technique for calculating regional cerebral blood flow

This paper discusses the theory and implementation of a modular data analysis system for the calculation and imaging of regional cerebral blood flow. The program may be generalized to any system requiring instantaneous and controllable visual data display, and we have set it up for compartmental analysis as described by the Fick equation with certain correction factors. We have included flow charts of the program source code and data paths for the various modules. We also describe the functional hardware components necessary for the execution of these algorithms. Finally, analyzed data are represented from a set of experiments employing differential visual stimulation. The results obtained using our methods are comparable to those in the existing literature; they are more accurately and easily obtained, and have the added power of manipulable digitization of the original image without loss of data.     

Sequential architecture models for Prolog: A performance comparison

In this paper we investigate the relation between architectural support for Prolog and performance. We will show that partial support for tags does perform as well as full support, but it only reduces the execution time by approximately 10%. With respect to special addressing modes, auto address modification (post/pre increment, decrement on loads and stores) only yields a cycle reduction of approximately 6% and the introduction of a single shadow register set yields around 8%. Combining these optimizations, a performance gain of 20 to 25% can be achieved, depending on the memory system. Usingvliw techniques, which exploit instruction-level parallelism, the performance can be doubled, using three processing elements. Two processing elements already provide a significant speedup, but the use of four processing elements is not justified if we compare the gain in performance with the cost of the extra hardware. In general we observe only a small performance improvement (around 20%) when moving fromrisc to special-purposerisc architectures, an improvement which can also be achieved by applying advanced compiler technology, such as compiler optimization, optimizations forwam, and optimal scheduling techniques forvliw architectures. Unfortunately these hardware and software effects do not add up, as a better compiler reduces the effect of hardware support. Finally, the cycle time is essential for comparing the performance of different (micro)-architectures, but it is not always clear what the effects of the different tradeoffs are on the maximum achievable cycle time.     

A comparison of time domains for software reliability models

A comparison of time domains (i.e., execution time vs. calendar time) is made for software reliability models, with the purpose of reaching some general conclusions about their relative desirability. The comparison is made by using a generic failure intensity function that represents a large majority of the principal models. The comparison is based on how well the function fits the estimated failure intensity, where the failure intensity is estimated with respect to both kinds of time. The failure intensity in each time domain is examined for trends. Failure intensity estimates are calculated from carefully collected data. The execution time domain is found to be highly superior to the calendar time domain.     

A quality evaluation model for calculating block and blur effects generated by H.264 and MPEG2 codecs

Many factors can affect and/or compromise the quality of visual media. Most video compression standards use motion compensation and block-based encoding scheme for compression. As a result, the decoded video is altered by one or more compression artifacts, such as block effect, blur, color bleeds, buzzing, false edges, jagged motion and flickering chrominance. In this framework, we present in this paper a quality prediction model for video encoders. Our model is designed to calculate the distortions of blocking and blurring effects, which appeared from the coding operation. We also give an overall score of the two distortions. The validation of our model is done using the subjective video database “LIVE” to correlate with the judgment of the observers. Correlation indicators such as the Spearman rank correlation coefficient (SROCC) and the Pearson linear correlation coefficient (PLCC) indicate that our model gives good performance.     

BoltzTraP. A code for calculating band-structure dependent quantities

A program for calculating the semi-classic transport coefficients is described. It is based on a smoothed Fourier interpolation of the bands. From this analytical representation we calculate the derivatives necessary for the transport distributions. The method is compared to earlier calculations, which in principle should be exact within Boltzmann theory, and a very convincing agreement is found.

Program summary

Title of program:BoltzTraPCatalogue identifier:ADXU_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADXU_v1_0Program obtainable from: CPC Program Library, Queen's University of Belfast, N. IrelandLicensing provisions:noneProgramming language used:Fortran 90Computer:The program should work on any system with a F90 compiler. The code has been tested with the Intel Fortran compilerOperating system:Unix/LinuxRAM:bytes up to 2 GB for low symmetry, small unit cell structuresNo. of lines in distributed program, including test data, etc.:1 534 213No. of bytes in distributed program, including test data, etc.:27 473 227Distribution format:tar.gzExternal routines:The LaPack and Blas libraries are neededNature of problem:Analytic expansion of energy-bands. Calculation of semi-classic integrals.Solution method:Smoothed Fourier expansion of bands.Running time:Up to 3 hours for low symmetry, small unit cell structures.     

A dedicated algorithm for calculating ground states for the triangular random bond Ising model

In the presented article we present an algorithm for the computation of ground state spin configurations for the 2d random bond Ising model on planar triangular lattice graphs. Therefore, it is explained how the respective ground state problem can be mapped to an auxiliary minimum-weight perfect matching problem, solvable in polynomial time. Consequently, the ground state properties as well as minimum-energy domain wall (MEDW) excitations for very large 2d systems, e.g. lattice graphs with up to N=384×384 spins, can be analyzed very fast.Here, we investigate the critical behavior of the corresponding T=0 ferromagnet to spin-glass transition, signaled by a breakdown of the magnetization, using finite-size scaling analyses of the magnetization and MEDW excitation energy and we contrast our numerical results with previous simulations and presumably exact results.