Comparing German and Taiwanese secondary school students’ knowledge in solving mathematical modelling tasks requiring their assumptions

Mathematization is critical in providing students with challenges for solving modelling tasks. Inadequate assumptions in a modelling task lead to an inadequate situational model, and to an inadequate mathematical model for the problem situation. However, the role of assumptions in solving modelling problems has been investigated only rarely. In this study, we intentionally designed two types of assumptions in two modelling tasks, namely, one task that requires non-numerical assumptions only and another that requires both non-numerical and numerical assumptions. Moreover, conceptual knowledge and procedural knowledge are also two factors influencing students’ modelling performance. However, current studies comparing modelling performance between Western and non-Western students do not consider the differences in students’ knowledge. This gap in research intrigued us and prompted us to investigate whether Taiwanese students can still perform better than German students if students’ mathematical knowledge in solving modelling tasks is differentiated. The results of our study showed that the Taiwanese students had significantly higher mathematical knowledge than did the German students with regard to either conceptual knowledge or procedural knowledge. However, if students of both countries were on the same level of mathematical knowledge, the German students were found to have higher modelling performance compared to the Taiwanese students in solving the same modelling tasks, whether such tasks required non-numerical assumptions only, or both non-numerical and numerical assumptions. This study provides evidence that making assumptions is a strength of German students compared to Taiwanese students. Our findings imply that Western mathematics education may be more effective in improving students’ ability to solve holistic modelling problems.     

A critique of fractional age assumptions

Published mortality tables are usually calibrated to show the survival function of the age at death distribution at exact integer ages. Actuaries make fractional age assumptions when valuing payments that are not restricted to integer ages. A fractional age assumption is essentially an interpolation between integer age values which are accepted as given.Three fractional age assumptions have been widely used by actuaries. These are the uniform distribution of death (UDD) assumption, the constant force assumption and the hyperbolic or Balducci assumption. Under all three assumptions, the interpolated values of the survival function between two consecutive ages depend only on the survival function at those ages. While this has the advantage of simplicity, all three assumptions result in force of mortality and probability density functions with implausible discontinuities at integer ages.In this paper, we examine some families of fractional age assumptions that can be used to correct this problem. To help in choosing specific fractional age assumptions and in comparing different sets of assumptions, we present an optimality criterion based on the length of the probability density function over the range of the mortality table.     

Solutions of evolution inclusions generated by a difference of subdifferentials

An evolution inclusion with the right-hand side containing the difference of subdifferentials of proper convex lower semicontinuous functions and a multivalued perturbation whose values are nonconvex closed sets is considered in a separable Hilbert space. In addition to the original inclusion, we consider an inclusion with convexified perturbation and a perturbation whose values are extremal points of the convexified perturbation that also belong to the values of the original perturbation. Questions of the existence of solutions under various perturbations are studied and relations between solutions are established. The primary focus is on the weakening of assumptions on the perturbation as compared to the known assumptions under which existence and relaxation theorems are valid. All our assumptions, in contrast to the known assumptions, concern the convexified rather than original perturbation.     

最小二乘法回归中的一些问题

最小二乘法估计通常基于：线性、独立、正态和方差齐性四个基本假定．在实际工作中，这些假定常很难满足，偏离时往往对估计结果带来影响．本文对偏离假定的情况予以讨论并给出发现和处理这些问题的方法；同时结合实例对回归中的影响点和异常点、共线性等问题予以说明．这将对我们实际工作中的数据分析具有指导性意义．     

GENERAL DECAY OF SOLUTIONS FOR A VISCOELASTIC EQUATION WITH BALAKRISHNAN-TAYLOR DAMPING AND NONLINEAR BOUNDARY DAMPING-SOURCE INTERACTIONS

A viscoelastic equation with Balakrishnan-Taylor damping and nonlinear boundary/interior sources is considered in a bounded domain. Under appropriate assumptions imposed on the source and the damping, we establish uniform decay rate of the solution energy in terms of the behavior of the nonlinear feedback and the relaxation function, without setting any restrictive growth assumptions on the damping at the origin and weakening the usual assumptions on the relaxation function.     

MISUNDERSTANDING MODELLING IN MECHANICS: A REVIEW OF THE A-LEVEL TEXTBOOK LITERATURE

All A-level boards have included a modelling approach in the syllabus of their respective mechanics modules and the plethora of textbooks during the past decade is structured according to this approach. This review will attempt to show that these books have confused modelling that is specific to mechanics with mathematical modelling in general. To place the recent textbooks in perspective, this review outlines the logical structure of mechanics, how this relates to the specificity of modelling in mechanics, the philosophical assumptions underlying the traditional textbook, how these assumptions have influenced the modern textbook and how history has been rewritten to justify these assumptions. The conclusion drawn is that the modular scheme has made this confusion unsustainable.     

Forecasting travel demand: a comparison of logit and artificial neural network methods

This paper describes the use of backpropagation artificial neural networks to forecast travel demand from disaggregate discrete choice data and compares them with logit models. Three data sets are used; synthetic data which fulfils the underlying logit assumptions, snythetic data which breaches the underlying logit assumptions and real data. It is found that neural networks with no hidden layers exhibit almost identical performance to logit models in all three cases. For the synthetic data which breaches the underlying logit assumptions and with real data, backpropagation neural networks with a hidden layer can achieve a better fit than logit. However, careful choice of the number of hidden units and training iterations is needed to avoid overfitting and consequent degradation of performance.     

求解结构型单调变分不等式的改进的邻近类分解方法

邻近类分解方法首先是由Chen和Teboulle（Math. Programming,1994,64(1):81-101）提出用来求解凸的极小化问题．在此基础上,该文提出一种新方法求解具有分离结构的单调变分不等式．其主要优点在于放松了算法中对某些参数的限制,使得新方法更加便于计算．在和原分解方法相同的假设下,可以证明新方法是全局收敛的．     

On the asymptotics of fault probability in least‐recently‐used caching with Zipf‐type request distribution

We consider the least‐recently‐used cache replacement rule with a Zipf‐type page request distribution and investigate an asymptotic property of the fault probability with respect to an increase of cache size. We first derive the asymptotics of the fault probability for the independent‐request model and then extend this derivation to a general dependent‐request model, where our result shows that under some weak assumptions the fault probability is asymptotically invariant with regard to dependence in the page request process. In a previous study, a similar result was derived by applying a Poisson embedding technique, where a continuous‐time proof was given through some assumptions based on a continuous‐time modeling. The Poisson embedding, however, is just a technique used for the proof and the problem is essentially on a discrete‐time basis; thus, it is preferable to make assumptions, if any, directly in the discrete‐time setting. We consider a general dependent‐request model and give a direct discrete‐time proof under different assumptions. A key to the proof is that the numbers of requests for respective pages represent conditionally negatively associated random variables. © 2005 Wiley Periodicals, Inc. Random Struct. Alg., 2006     

ON SOLUTION OF A KIND OF RIEMANN BOUNDARY VALUE PROBLEM WITH SQUARE ROOTS

IIntroductlonIn[11。we formulated the Rlemann boundary、lue problem with square roots:/U7ii二G(t)Jn7iT十g(t),t〔L,(l·l)where L Is a smooth closed contour In the complex plane,oriented counter－clockwisely,boundingregion S＋and S－In its Interior。d exterior respectlvelyt G(t)ajnd g(t)are gi、n functionsHolder continuous on L;and the unknown W(。)Is a sectionally holomorphic function withJumping curve L,h。lug a finite order at z二 co(for definition;of．【2]or [3]);and gare continuous …     

Adaptive full-order and reduced-order observers for the Lur’e differential inclusion system

This paper deals with the observer design for the Lur’e differential inclusion system with unknown parameters. The set-valued mapping in the differential inclusion is upper semi-continuous, closed, convex, bounded and monotone. First, under some assumptions an adaptive full-order observer is designed for the system. Then, under the same assumptions, a reduced-order observer is proved to exist. An example is provided to show the validation of the designed observers.     

Performance measurement in nonprofit governance: an empirical study of the Minnesota independent school districts

Linearity and input separability assumptions are pervasive in most nonprofit cost and performance measurement systems. In this paper, we employ both parametric and nonparametric econometric methodologies to test the linearity and input separability assumptions using data collected from the Minnesota independent school districts. Our test results reject both the assumptions for the Minnesota independent school districts. These findings suggest a need to develop alternative procedures that do not rely on these two pervasive assumptions if the information provided by not-for-profit performance measurement systems is to be relevant for decision making and performance evaluation.     

Discretization orders and efficient computation of cartesian coordinates for distance geometry

Distance geometry is a class of problems where the position of points in space is to be identified by using information about some relative distances between these points. Although continuous approaches are usually employed, problems belonging to this class can be discretized when some particular assumptions are satisfied. These assumptions strongly depend on the order in which the points to be positioned are considered. We discuss new discretization assumptions that are weaker than previously proposed ones, and present a greedy algorithm for an automatic identification of discretization orders. The use of these weaker assumptions motivates the development of a new method for computing point coordinates. Computational experiments show the effectiveness and efficiency of the proposed approaches when applied to protein instances.     

Equality of proofs for linear equality

This paper is about equality of proofs in which a binary predicate formalizing properties of equality occurs, besides conjunction and the constant true proposition. The properties of equality in question are those of a preordering relation, those of an equivalence relation, and other properties appropriate for an equality relation in linear logic. The guiding idea is that equality of proofs is induced by coherence, understood as the existence of a faithful functor from a syntactical category into a category whose arrows correspond to diagrams. Edges in these diagrams join occurrences of variables that must remain the same in every generalization of the proof. It is found that assumptions about equality of proofs for equality are parallel to standard assumptions about equality of arrows in categories. They reproduce standard categorial assumptions on a different level. It is also found that assumptions for a preordering relation involve an adjoint situation.      

Feasibility principles for Downstream Demand Inference in supply chains

Many companies are adopting strategies that enable Demand Information Sharing (DIS) between the supply chain links. Recently, a steady stream of research has identified mathematical relationships between demands and orders at any link in the supply chain. Based on these relationships and strict model assumptions, it has been suggested that the upstream member can infer the demand at the downstream member from their orders. If this is so, DIS will be of no value. In this paper, we argue that real-world modelling requires less restrictive assumptions. We present Feasibility Principles to show that it is not possible for an upstream member to accurately infer consumer demand under more realistic model assumptions. Thus, we conclude that DIS has value in supply chains. We then move our focus to the supply chain model assumptions in the papers arguing that there is value in sharing demand information. Using a simulation experiment, we show that the value of sharing demand information in terms of inventory reductions will increase under more realistic supply chain model assumptions.     

Single-path routing of stochastic flows in networks

The paper revisits a very simple network routing and dimensioning model, with two specific assumptions: the traffic amounts to be routed are Gaussian random variables, and each commodity must use one single route in the network. The need to control congestion leads naturally to probabilistic constraints. The impact of stochastic assumptions on solution algorithms is investigated, when compared to the usual deterministic case.     

Lagrange identity method for microstretch thermoelastic materials

Our paper is concerned with some basic theorems for microstretch thermoelastic materials. By using the Lagrange identity, we prove the uniqueness theorem and some continuous dependence theorems without recourse to any energy conservation law, or to any boundedness assumptions on the thermoelastic coefficients. Moreover, we avoid the use of positive definiteness assumptions on the thermoelastic coefficients.     

Zeno Product Formula Revisited

We introduce a new product formula which combines an orthogonal projection with a complex function of a non-negative operator. Under certain assumptions on the complex function the strong convergence of the product formula is shown. Under more restrictive assumptions even operator-norm convergence is verified. The mentioned formula can be used to describe Zeno dynamics in the situation when the usual non-decay measurement is replaced by a particular generalized observables in the sense of Davies.     

Introducing Young Children to the Role of Assumptions in Proving

The notion of assumptions permeates school mathematics, but instruction tends to highlight this notion only in the advanced grades. In this article, I argue that it is important for even young children to develop a sense of the role of assumptions in proving, and I investigate what it might mean and look like for instruction to promote this goal. Toward this end, I study an episode from third grade that describes the first time that the students in the class were introduced in a deliberate and explicit way to the role of assumptions in proving. The central role of the mathematical task in the episode is identified, and features of mathematical tasks that can generate rich mathematical activity in the intersection of assumptions and proving are discussed. In addition, issues of the role of teachers in fostering productive interactions between students and mathematical tasks that have those features are considered.     

Using Operational Analysis in Simulation: A Queueing Network Example

The calculation of certain performance measures in queueing network simulation using operational analysis is presented. A systematic approach to the gathering of output and calculation of performance measures for quantitative system-performance analysis is demonstrated. The assumptions used in operational analysis to derive performance-measure relationships are verifiable by examining the output generated by the simulation. Any errors in assumptions revealed by the output may be measured, and these error measures used to determine correction terms. The performance-measure relations may still be used, even when the assumptions upon which they are based are in error, by adding these correction terms to the performance-measure values obtained. The results will be exact values for the performance measures over the period of the simulation. Calculations of performance measures, error measures and correction terms are illustrated with an example queueing network simulation.