基于时差分析的时标网络图探究

鉴于已有时差概念并不能充分反映CPM网络紧前和紧后工序时差的内在联系，文中引入三个新时差（前共后单时差，前单后共时差，双共时差）概念。针对目前工程项目管理中通用的时标网络图一早时标网络图和迟时标网络图，在路长定理的基础上，给出其理论依据，并在时差分析的基础上，随机绘出时标网络图，三个新时差的引入将有助于今后时标网络图的绘制，使网络技术的应用更具灵活性和实用性。     

时标动力方程的稳定性分析

近来，一种称之为时标动力系统的新理论得到了蓬勃的发展. 该文给出并建立了时标动力系统的各种稳定性概念和Lyapunov稳定性准则(稳定, 一致稳定, 渐近稳定, 指数渐近稳定等等).     

小波标架的稳定性

在小波分析理论中,标架起着十分重要的作用．对(∈Ｌ~２（Ｒ）和ａ＞１．ｂ＞０,Ｉ．Ｄａｕｂｅｃｈｉｅｓ给出了｛ａ~（ｊ／２）(（ａ~ｊｘ—ｋｂ）：ｊ,ｋ ∈Ｚ｝构成Ｌ~２（Ｒ）的标架的充分条件．近年来,人们对小波标架的稳定性进行了大量研究．首先把Ｋａｄｅｃ定理推广到高维情形,然后研究当(,｛ａ~ｊ｝,｛ｋ｝同时变化时标架的稳定性．特别地,我们给出｛ａ~ｊ｝扰动时标架的稳定性．     

实数集到时标上的概念推广的若干原则

从时标的定义出发,通过研究时标上的全局指数稳定性,给出了将实数集上的概念推广到时标上应遵循的两个原则.利用这两个原则,考虑了定义在实数集上的函数的四种几何性质,得出了单调性与有界性能被时标继承下来,而奇偶性与周期性不一定能被时标继承下来的结论.     

时标上的一类二元神经网络模型的渐进性

在基于时标的稳定性理论基础上,考虑了时标上的一类二元神经网络动力系统的收敛性的充分条件,所得结论统一了已有连续和离散形式.通过讨论时标上一类带有McCulloch-pitts型信号函数的二元神经网络模型的渐进行为.将动力模型转化为时标上的几个方程来考虑,并应用时标中的微分学理论以及基本的不等式放缩传递方法,通过对建立的一维映射的迭代规律进行分析,得到神经网络模型的收敛性.     

时标上矩阵指数函数的计算

本文利用时标上指数函数的性质,系统的讨论了时标矩阵指数函数eA(t,t0),t,t0∈T的计算问题,把实数和整数空间中传统的计算指数函数的方法推广到任意时标,得到了两种多项式形式的算法,并举例说明现有三种算法的特点;最后比较分析了几种算法之间的内在等价关系.     

时标上右端函数为两项和的集值微分方程解的平方收敛性

本文讨论了一类时标上右端函数为两项和的集值微分方程解的收敛性问题.首先引入时标上集值函数的Hukuhara导数意义下的Δ偏导数概念,并给出了时标上集值微分系统的比较原理.对于所构造的迭代序列,通过利用广义拟线性化方法和分析技巧,得到了上述问题近似解的平方收敛结果.     

时标上具有变时滞的推广的Gronwall型积分不等式

研究具有变时滞推广的Gronwall型积分不等式,并考虑在时标上的情况.基于时标定义、时标上的性质、时标上的Gronwall不等式判据等方法研究了 Gronwall型积分不等式的上界问题,并把研究区间分成三部分,然后采用在区间上分类讨论的方法,得到了三种情况下的推广的Gronwall型积分不等式.     

用上下解方法证明时标上四阶四点边值问题解的存在性

考虑时标上四阶四点边值问题,通过运用上下解方法来证明时标上四阶四点边值问题解的存在性.     

关于时标上的适应Nabla分数阶导数

本文研究了时标上的适应Nabla分数阶导数的问题.利用时标理论,获得了关于适应Nabla分数阶导数的若干重要性质.这些结果推广并改进了文献[9,10]中的有关结论以及一般Nabla导数的性质.     

The application of a mathematical model of sustainability to the results of a semi-quantitative Environmental Impact Assessment of two iron ore opencast mines in Iran

The paper outlines the application of a mathematical model of sustainability to an Environmental Impact Assessment (EIA) of two opencast iron ore mines in Iran. The model’s application to the EIA, which used the Folchi method, was undertaken for the purpose of indicating the potential level and nature of sustainability (if appropriate) of the two mines.The results indicated that both Chogart and Gol-e-Gohar iron ore mine were deemed to be potentially unsustainable. The results suggests the delicate balance and failure of achieving some form of sustainability in regards to mining in Iran, due to the impacts it has upon the local environment and community affected. The paper concludes as to the potential significance of the model’s application in the attainment of the goal of sustainable mining.     

内窥镜中Walter B流体的蠕动流

研究内窥镜中Walter B流体的蠕动流,在圆柱坐标系中建立问题的模型,目的是研究内窥镜对Walter B流体蠕动流的影响.以delta为摄动参数,使用正规的摄动法求出解析解.利用数值积分,求得压力增量和摩擦力的近似解析解.用图形给出了Walter B流体所显现参数的影响.     

An approach to modelling industrial unit processes: application to a spiral concentrator for minerals

A suite of computer models which simulate process operations in common use in the minerals processing industry is being developed. Application of the models is described with reference to a particular process device, the spiral concentrator. The paper sets out to explain the basic strategy behind the unit process modelling approach and discusses in detail the overall model structure adopted. The model aims to provide a set of equations, with sufficient physical significance to give a reasonable fit to any specific data set, and which can be systematically adjusted (through auxiliary models, user judgement and experience) to provide meaningful performance predictions over a broad range of operating conditions. The approach is thought to be applicable to a wide variety of processes. The model has been tested using a variety of ores, separated on plant-scale equipment and practical examples are given. The scope and limitations of the method are reported, drawing on the results of parallel experimental work. The extent to which this kind of approach can be used as a predictive tool in process design applications and in the day-to-day running of mineral processing plant is discussed.     

The use of the fractal model to complex resistivity in the interpretation of induced polarization data

Several researchers demonstrated that spectral parameters in induced polarization can be applied to discriminate different IP sources. In this paper it was applied an inversion procedure using the Gauss–Newton method to recover the spectral parameters of fractal model to complex resistivity. The finite element method was applied to carry out the forward modeling. The procedure was applied in synthetic data and simulations were carried out in five different frequencies. The inversion of the data were carried out in each frequency, further the inversion was applied also to each cell of the finite element mesh to recover the fractal parameter in order to analyze the possibility of using the fractal model parameters in the interpretation of the induced polarization response to this geological geometry. The results showed that the anomalies are well detected by the image of the fractal model parameters.     

Analytical modeling of active magnetic bearing geometry

The aim of this paper is to present a new graphical approach to the shape design of the active magnetic bearing (AMB) stator. The AMB is a tool to levitate the rotor without contact. The standard design method uses a computer-aided design (CAD) software in the modeling process. Therefore the designed AMB shape consists of graphical primitives like lines and arcs with fixed properties. For the advanced interdisciplinary analysis of the AMB construction the shape generation and modifications ought to be done automatically. The proposed method is based on mathematical analysis and representation of the AMB stator by curves. Second and third order Bézier curves given in polynomial and rational form are compared to the circle and arc based arcs. The fitting quality is considered for the selection of the appropriate arc representation. The obtained shapes are ready to be used in the magnetic field analysis and optimization procedures to find an optimal form of the AMB construction. The author’s experience in modeling and vector graphics was a motivation to look at the AMB construction from mathematical and programming point of view. The AMB components are modeled with parametric curves under constraints defined by the AMB static and dynamic properties. Such a described 2D or 3D model can be generated automatically in a programming way for a wide range of AMB configurations in further research. Selected configurations are presented to show features of the proposed method and realized algorithm. The selected features of the proposed solution as well as feedback from industry are discussed.     

Modelación del funcionamiento hidráulico de los dispositivos de aireación de desagües de fondo de presas mediante el método de partículas y elementos finitos

Dam bottom are key elements to control the water surface elevation below the spillway crest level. As a consequence, they are essential in reservoir management, and play a vital role in dam safety.The convenience of installing an aeration system in dam bottom outlets is well known nowadays. Otherwise, damages due to cavitation and vibration are frequently serious, as could be observed in several dams built in the beginning of the 20th century.The intrinsic features of the phenomenon make it hard to analyze either in situ or in full scaled experimental facilities. As a consequence, most of the previous studies have been carried out in small-scale physical models. The results of these works have been used to develop empirical formulas which provide an estimation of the maximum air demand of the aeration system.The progress in the development of numerical methods allows addressing this problem using numerical modeling. The Particle Finite Element Method (PFEM) had been previously applied and validated for the analysis of the performance of other hydraulic structures. In this work, it has been used to simulate air-water interaction in free-flowing gated conduits. The objective is to avoid the scale effects of physical modeling and to study in detail the key parameters. The results clarify the behaviour of the involved fluids (air and water) and provide information about the influence of the main variables that affect their circulation.     

The role of mathematics in engineering education: an engineer's view

Students of mathematics in the first term studied calculus in two parallel courses. One course was in the standard approach, while the other was based on the non‐standard (Robinson) approach. The students participated in tests of the brain's hemispheres. The scores of both mathematical courses and the results of the hemispheric tests were correlated. The results show that the standard approach is positively correlated to both hemispheres. The n.s. approach is positively correlated to the right hemisphere and negatively correlated to the left hemisphere. It is possible to predict relative success in the two approaches to calculus.

     

SOLVING A CROP PROBLEM BY AN OPTIMAL CONTROL METHOD

ABSTRACT. A system of ordinary differential equations coupled with a parabolic partial differential equation is studied in order to understand an interaction between two crops and a pathogen. Two different types of crops are planted in same field in some pattern so that the spread of pathogen can be controlled. The pathogen prefers to eat one crop. The other crop, which is not preferred by the pathogen, is introduced to control the spread of pathogen in the farming land. The “optimal” initial planting pattern is sought to maximize plant yields while minimizing the variation in the planting pattern. The optimal pattern is characterized by a variation inequality involving the solutions of the optimality system. Numerical examples are given to illustrate the results.     

Stochastic optimal control of internal hierarchical labor markets

This paper develops an optimal control model for a graded manpower system where the demand for manpower is uncertain. The organization's objective is to minimize the discounted costs of operating the manpower system, including excess demand costs. The stock of workers in various grades can be adjusted in two ways. The first method is outside hiring flows, which is the usual control variable used in previous research. The second method is to control the transition rates between grades of the hierarchy, an instrument not previously studied. Incorporating the transition rates into the control variables creates time lags in the control process. The resulting problem is solved numerically using an approximation for the time-lagged control variables. The numerical example is based on the Air Force officer hierarchy. The model is used to examine such issues as the desirability of granting tenure to workers who are not promoted to the highest grade and the effects of length-of-service and demand uncertainty on manpower policy.     

Integrating design problems in mathematics curriculum: an architecture college case study

This paper reports an attempt to improve results in the mathematics course in one of the architecture colleges in Israel through practise in applications. The effect of integrating structure design problems in the calculus curriculum on students' achievements and attitudes was examined. The applied topics in the curriculum were connected to calculus topics and studied through problembased learning activities. The integrated curriculum was implemented and the learning results in experimental and control groups were assessed by means of achievement tests, attitude questionnaires and student interviews. The learning achievements in the experimental group proved to be significantly higher than in the control group. The positive impact of learning applications on motivation, understanding, creativity and interest in mathematics is indicated.