How (Not) to design strong-RSA signatures

This paper considers strong-RSA signature schemes built from the scheme of Cramer and Shoup. We present a basic scheme encompassing the main features of the Cramer-Shoup scheme. We analyze its security in both the random oracle model and the standard model. This helps us to spot potential security flaws. As a result, we show that a seemingly secure signature scheme (Tan in Int J Security Netw 1(3/4): 237?C242, 2006) is universally forgeable under a known-message attack. In a second step, we discuss how to turn the basic scheme into a fully secure signature scheme. Doing so, we rediscover several known schemes (or slight variants thereof).     

如何在教学中让学生觉得《抽象代数》不再"抽象"

主要从近世代数的一些定义和定理的导入着手,讨论了如何在教学中让学生觉得它的内容不再抽象,从而激发学生学习该课程的积极性,进而更好地学习它.     

How to Solve Nonlinear Equations When a Third Order Method is Not Applicable

In this paper, we use a one-parametric family of second-order iterations to solve a nonlinear operator equation in a Banach space. A Kantorovich-type convergence theorem is proved, so that the first Fréchet derivative of the operator satisfies a Lipschitz condition. We also give an explicit error bound.Supported in part by the University of La Rioja (grants: API-98/A25 and API-98/B12)and DGES (grant: PB96-0120-C03-02).     

会议筹备中如何合理筛选宾馆及挑选房间

本文利用层次分析法对与会代表入住哪些宾馆进行筛选,然后在所挑选的宾馆中挑选房间,再根据所选的房间分布情况合理安排会议室,最后根据会议室的分布的地点租用客车的问题进行分析.通过建立两个多目标规划模型找出实现花费的费用最少、使用的宾馆数量最少以及各个宾馆之间距离相对较近的最优方案.     

如何不用复数讲解常系数线性微分方程

在高等数学课程中,复指数函数及其导数知识的严格讲解,通常要比微分方程知识的讲解晚很多.这使得微分方程的教学在逻辑上有些不足.用复值函数解的复系数线性组合推导出实值函数解,在教学实践中,学生经常感到迷惑.不以复数的任何知识作为前提,给出了常系数微分方程的一种自然的讲解方法.     

How Airlines and Airports Recover from Schedule Perturbations: A Survey

The explosive growth in air traffic as well as the widespread adoption of Operations Research techniques in airline scheduling has given rise to tight flight schedules at major airports. An undesirable consequence of this is that a minor incident such as a delay in the arrival of a small number of flights can result in a chain reaction of events involving several flights and airports, causing disruption throughout the system. This paper reviews recent literature in the area of recovery from schedule disruptions. First we review how disturbances at a given airport could be handled, including the effects of runways and fixes. Then we study the papers on recovery from airline schedule perturbations, which involve adjustments in flight schedules, aircraft, and crew. The mathematical programming techniques used in ground holding are covered in some detail. We conclude the review with suggestions on how singular perturbation theory could play a role in analyzing disruptions to such highly sensitive schedules as those in the civil aviation industry.     

Concepts and Perceptual Belief: How (Not) to Defend Recognitional Concepts

Recognitional concepts have the following characteristic property: thinkers are disposed to apply them to objects merely on the basis of undergoing certain perceptual experiences. I argue that a prominent strategy for defending the existence of constitutive connections among concepts, which appeals to thinkers’ semantic-cum-conceptual intuitions, cannot be used to defend the existence of recognitional concepts. I then outline and defend an alternative argument for the existence of recognitional concepts, which appeals to certain psychological laws.     

Mixed Integer Programming to Schedule a Single-Shift Workforce under Annualized Hours

Nowadays flexibility is a strategic concept for firms. Indeed workload has to follow, as close as possible, the development of demand throughout the year. However, firms cannot engage and dismiss employees according to production requirements. Thus, workforce scheduling becomes a delicate task. In this paper, four mixed integer programming models are developed to solve the workforce schedule problem for a single-shift. The annualized hour scenario is considered with respect to a set of Swiss legal constrains. Furthermore, the minimal required workforce is guaranteed and it is assumed that each employee is able to perform each task within the team. All employees are full-time workers.     

How to build a barricade

Given a packing of congruent copies of a strictly convex planar setC in a parallel stripS of widthw and a straight linel, let |l| denote the sum of the lengths of the segmentslC _i over alliI It is proved that Where (C) is the density of the densest packing of congruent copies ofC in the plane. Some generalizations are also considered.     

How to build a hypercomputer

We claim that the theoretical hypercomputation problem has already been solved, and that what remains is an engineering problem. We review our construction of the Halting Function (the function that settles the Halting Problem) and then sketch possible blueprints for an actual hypercomputer.     

How to select a loser

N people select a loser by flipping coins. Recursively, the 0-party continues until the loser is found. Among other things, it is shown that this process stops on the average after about log₂ N steps. Nevertheless, this very plausible result requires rather advanced methods.     

Optimizing a Production System with a Fixed Delivery Schedule

This note considers a model in which a manufacturing company purchases a raw material, manufactures a product (at a finite rate) and ships a fixed quantity of the product to a single customer at fixed and regular intervals of time, as specified by the customer. In general there are several shipments made during each production run. The objective is to determine a purchasing and production schedule which minimises the total cost of purchasing, manufacturing and stockholding. It extends previously published work by considering the possibility that a single raw material purchase provides stock for several production runs or that several raw material purchases provide stock for a single production run.     

Not every pseudoalgebra is equivalent to a strict one

We describe a finitary 2-monad on a locally finitely presentable 2-category for which not every pseudoalgebra is equivalent to a strict one. This shows that having rank is not a sufficient condition on a 2-monad for every pseudoalgebra to be strictifiable. Our counterexample comes from higher category theory: the strict algebras are strict 3-categories, and the pseudoalgebras are a type of semi-strict 3-category lying in between Gray-categories and tricategories. Thus, the result follows from the fact that not every Gray-category is equivalent to a strict 3-category, connecting 2-categorical and higher-categorical coherence theory. In particular, any nontrivially braided monoidal category gives an example of a pseudoalgebra that is not equivalent to a strict one.     

How Publishing Can be More Than Not Perishing: Writing Relationships

Abstract

From time to time, the editors of Change will be spotlighting interesting research in progress. The following report by Barbara Burn, coordinator of U.S. participation in the Study Abroad Evaluation Project, is one of this series.     

Heuristics to Schedule Service Engineers within Time Windows

This paper describes the development of a set of heuristics for tackling vehicle routeing problems with time windows (VRPTW) subject to uncertain demand where schedules are prepared interactively. Many public utility companies, e.g. gas, water, electricity, are now having to quote very specific times for visits to customers, both for regular service and emergency call-outs. The heuristics developed produce good tours by sequencing visits on the basis of closeness to existing visits. Tours are developed as and when demand occurs so that the customer is given an immediate appointment time, rather than waiting for a number of requests for service to be received. Simple methods to construct time windows will also be discussed.     

How to best fold a triangle

We fold a triangle once along a straight line and study how small the area of the folded figure can be. It can always be as small as the fraction \(2-\sqrt{2}\) of the area of the original triangle.This is best possible: For every positive number \(\varepsilon\) there are triangles that cannot be folded better than \(2-\sqrt{2}-\varepsilon\).