Towards an Organizational Model of Attitude Change

Building on the growing literature that views organizations as complex adaptive systems, this paper proposes a general model to analyze the relationship between organizational context and attitudes. In particular, we focus on how the system of formal and informal communication channels that characterize an organization and the timing of information flows affect the dynamic process of attitude change. We also use a stylized version of the model to illustrate how the general framework is able to generate insights that are relevant to particular situations.     

Towards an Erlang formula for multiclass networks

Consider a multiclass stochastic network with state-dependent service rates and arrival rates describing bandwidth-sharing mechanisms as well as admission control and/or load balancing schemes. Given Poisson arrival and exponential service requirements, the number of customers in the network evolves as a multi-dimensional birth-and-death process on a finite subset of ℕ ^k . We assume that the death (i.e., service) rates and the birth rates depending on the whole state of the system satisfy a local balance condition. This makes the resulting network a Whittle network, and the stochastic process describing the state of the network is reversible with an explicit stationary distribution that is in fact insensitive to the service time distribution. Given routing constraints, we are interested in the optimal performance of such networks. We first construct bounds for generic performance criteria that can be evaluated using recursive procedures, these bounds being attained in the case of a unique arrival process. We then study the case of several arrival processes, focusing in particular on the instance with admission control only. Building on convexity properties, we characterize the optimal policy, and give criteria on the service rates for which our bounds are again attained.     

基于DEA的信用担保运行效率求解方法

针对基于DEA模型的Charnes-Cooper变换需引入阿基米德无穷小量这一主观因素影响效率评价结果,提出基于DEA模型的PSO效率评价方法.通过与Charnes-Cooper变换求解方法的实证比较,发现由于基于DEA的PSO效率评价方法对DEA模型直接求解,最大限度的避免主观因素的影响,使得投入产出指标的选择几乎不会影响信用担保运行效率的评价结果.从而使得效率评价结果更可靠、更符合客观实际.     

一类具有治疗的禽流感模型分析

考虑医疗机构容纳病人的有限性和治疗药物的有限性,建立和研究了一类具有治疗的禽流感传播的数学模型.给出了与禽类系统和人类系统对应的基本再生数的表达式;证明了当病人数量在治疗能力范围内时,禽类系统的基本再生数的大小决定了禽流感是否在禽类和人类中传播;当病人数量超出治疗能力范围时,禽类系统和人类系统对应的两个再生数的大小共同决定禽流感是否在禽类系统和人类系统中传播.     

带接种和抗病毒治疗的流感传播模型

疫苗注射和抗病毒治疗是两种控制流感传播的重要途径,然而随着耐药菌株即抗药毒株的产生使得抗生素失效.2013年在中国新出现的人感染H7N9病例说明了病毒变异对人类造成的潜在威胁.建立数学模型,研究了抗病毒治疗和疫苗注射对流感传播的动力学行为的影响.模型中包括药物敏感感染群体和抗药性群体.通过分析传染性和抗药性个体的再生数Rsc和RRc得到了决定两者竞争结果的阈值.通过对各平衡点的稳定性分析,由Matlab模拟得到结论:高水平的抗病毒治疗有可能导致患病者的增加,增加程度要受到其他因素包括疫苗接种速率和抗药性的发展,所以抗病毒治疗应该适可而止.     

Towards an Account of Epistemic Luck for Necessary Truths

Modal epistemologists parse modal conditions on knowledge in terms of metaphysical possibilities or ways the world might have been. This is problematic. Understanding modal conditions on knowledge this way has made modal epistemology, as currently worked out, unable to account for epistemic luck in the case of necessary truths, and unable to characterise widely discussed issues such as the problem of religious diversity and the perceived epistemological problem with knowledge of abstract objects. Moreover, there is reason to think that this is a congenital defect of orthodox modal epistemology. This way of characterising modal epistemology is however optional. It is shown that one can non-circularly characterise modal conditions on knowledge in terms of epistemic possibilities, or ways the world might be for the target agent. Characterising the anti-luck condition in terms of epistemic possibilities removes the impediment to understanding epistemic luck in the case of necessary truths and opens the door to using these conditions to shed new light on some longstanding epistemological problems.     

Forces of Infection Allowing for Backward Bifurcation in an Epidemic Model with Vaccination and Treatment

We consider an epidemic model for the dynamics of a vaccine-preventable disease, which incorporates the treatment and an imperfect vaccine given to susceptible individuals. We show that in spite of the simple structure of the model, a backward bifurcation may always occur if the treatment rate is above a threshold value. This occurs regardless of the specific form of the force of infection, which is only required to be infinitesimal of the same order of the size of the infectious compartment I, as I→0. This includes many commonly used functionals, as the linear, the monotone saturating Michaelis-Menten and the non-monotone force of infection used to represent the ‘psychological effect’.     

Towards an axiomatization of orderings

A set of six axioms for sets of relations is introduced. All well-known sets of specific orderings, such as linear and weak orderings, satisfy these axioms. These axioms impose criteria of closedness with respect to several operations, such as concatenation, substitution and restriction. For operational reasons and in order to link our results with the literature, it is shown that specific generalizations of the transitivity condition give rise to sets of relations which satisfy these axioms. Next we study minimal extensions of a given set of relations which satisfy the axioms. By this study we come to the fundamentals of orderings: They appear to be special arrangements of several types of disorder. Finally we notice that in this framework many new sets of relations have to be regarded as a set of orderings and that it is not evident how to minimize the number of these new sets of orderings.Symbol Table U universe (infinite countable) - D set of possible domains (finite and non-empty subsets of U) - R set of all considered relations - A empty relation on A - Id A identity relation on A - All A all relation on A - c complement operator (see Definition 2.1) - v converse operator (see Definition 2.1) - s symmetric part (see Definition 2.1) - asymmetric part (see Definition 2.1) - n non-diagonal part (see Definition 2.1) - r reflexive closure (see Definition 2.1) We gratefully acknowledge the support by the Co-operation Centre of Tilburg and Eindhoven Universities.     

Towards Bounding Complexity of a Minimal Model

We give some effectivity results in birational geometry. We provide an upper bound on the rational constant in Rationality Theorem in terms of certain intersection numbers, under an additional condition on the variety that it admits a divisorial contraction. One consequence is an explicit bound on the number of certain extremal rays. Our main result tries to construct from a given set of ample divisors H _j on X with their intersection numbers b _i , a certain set of ample divisors L _j on X' or X ⁺ where X' or X ⁺ arises from a contraction or a flip,such that the corresponding intersection numbers of L _j are uniformly bounded in terms of b _i and the index of X. This gives a bound on the projective degree of a minimal model in special case.     

The Paucity of Model Validation in Operational Research Projects

Validation as a concept is not well defined in the methodology of model building, although it is generally considered to be an important part of the modelling process. This paper considers the amount and type of validation carried out in a series of projects, and establishes contrasts between the expected and observed modes of validation.     

一个高效基于证书聚合签名方案的两种攻击方法及改进

对刘云芳等人新近发表在《计算机应用》上的高效可证明安全的基于证书聚合签名方案进行了安全性分析,指出CA可以对任何消息成功伪造签名,给出了两种攻击方法并分析了存在该攻击的具体原因.最后,为了克服上述攻击,给出了具体的改进方法.     

Towards an inverse scattering theory for two-dimensional nondecaying potentials

The inverse scattering method is considered for the nonstationary Schrödinger equation with the potentialu (x ₁,x ₂) nondecaying in a finite number of directions in thex plane. The general resolvent approach, which is particularly convenient for this problem, is tested using a potential that is the Bäcklund transformation of an arbitrary decaying potential and that describes a soliton superimposed on an arbitrary background. In this example, the resolvent, Jost solutions, and spectral data are explicitly constructed, and their properties are analyzed. The characterization equations satisfied by the spectral data are derived, and the unique solution of the inverse problem is obtained. The asymptotic potential behavior at large distances is also studied in detail. The obtained resolvent is used in a dressing procedure to show that with more general nondecaying potentials, the Jost solutions may have an additional cut in the spectral-parameter complex domain. The necessary and sufficient condition for the absence of this additional cut is formulated.     

具有饱和治疗的禽流感动力学模型的研究

提出了一类带有治疗的禽流感动力学模型,用来分析禽流感从禽类向人类传播的过程.由于治疗禽流感的药物十分有限,提出一个带有饱和治疗的模型.通过讨论得知当禽流感疫情已经发生时,通过控制染病的禽类就可抑制禽流感在人类的传播.     

Towards an Intelligent and Dynamic Geometry Book

The pursuit of an Intelligent and Dynamic Geometry Book should involve the study of how currently developing methodologies and technologies of geometry knowledge representation, management, deduction and discovery can be incorporated effectively into future education. Just as Doron Zeilberger pointed out in the Plane Geometry: An Elementary Textbook By Shalosh B. Ekhad (Circa 2050), a geometry book from the future would be a computer program, in which all the theorems can be automatically discovered (and of course proved) by computer and beautiful illustrations can be automatically generated and dynamically modified. Such a prospect motivates studies on how to represent and manage digitised geometric knowledge on computer. The geometry book of the future (the \(\mathcal {I}\)nt\(\mathcal {D}\)yn\(\mathcal {G}\)eo\(\mathcal {B}\)ook) should be adaptive, collaborative, visual and intelligent. Adaptive because the contents should adapt itself to the curricula and readers. It will allow collaborative work and its contents would be collaboratively formed using a knowledge base open to contributions. Statements and proofs should be en-lighted by dynamic geometry sketches and diagrams, and the correctness of the proofs should be ensured by computer checking. The book will be intelligent, the reader should be able to ask closed or open questions, and can also for proof hints. The book should also provide interactive exercises with automatic correction. Such a cloud platform, freely available in all standard computational platforms and devices, collaborative, adaptive to each and every user’s profiles, should bring together a whole new generation of mathematical tools with impact in all levels of education. To realise such a book, a network of experts must be built, increasing the connections between several research communities, such as: mathematical knowledge management; computer theorem proving and discovery; education, aggregating expertise in areas such as Proofs in a Learning Context; Interfaces and Searching; Tools Integration; Learning Environments in the Cloud. In this paper the author tries to make the case for such an endeavour.     

Towards an axiomatization of the core-center

The core-center is an allocation rule introduced in González-Díaz and Sánchez-Rodríguez (González-Díaz, J., Sánchez-Rodríguez, E., 2007. A natural selection from the core of a TU game: The core-center. International Journal of Game Theory 36, 27–46. doi: 10.1007/s00182-007-0074-5) for the class of games with a non-empty core. In this paper we present a weighted additivity axiom, which we call trade-off property, and use it to obtain two characterizations of the core-center.     

Towards an Axiomatization of Interval Arithmetic

In this paper intervals are viewed as approximate real numbers. A revised formula for interval multiplication of generalized intervals is given. This formula will be useful for further axiomatization of interval arithmetic and relevant implementations within computer algebra systems. Relations between multiplication of numbers and multiplication of errors are discussed. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Towards an Ontology of Scientific Models

Scientific models occupy centre stage in scientific practice. Correspondingly, in recent literature in the philosophy of science, scientific models have been a focus of research. However, little attention has been paid so far to the ontology of scientific models. In this essay, I attempt to clarify the issues involved in formulating an informatively rich ontology of scientific models. Although no full-blown theory—containing all ontological issues involved—is provided, I make several distinctions and point to several characteristic properties exhibited by scientific models that are relevant for individuating scientific models.     

Towards an analysis of linguistic modelling

In this paper an alternative to the numerical modelling approach, namely the linguistic modelling approach, will be analysed. Apart from a brief presentation of the main elements of the approach, the major part of the paper is devoted to the analysis of thedynamic behaviour of the linguistic model. The most important issue in this analysis is the problem of convergency of the model to some stable state. This convergency problem is treated from the point of view of a fuzzy relation matrix. Analytical results concerning the powers of a fuzzy matrix and fuzzy eigenvectors are discussed.     

具有一般接触率和治疗的SIS传染病模型的后向分支

建立了具有一般传染率函数和治疗的SIS模型并分析了其动力学性态.通过分析得到,当基本再生数小于1时,系统存在无病平衡点,并且无病平衡点是局部渐近稳定的,当染病者数量较少,发现系统在基本再生数大于1时,系统存在惟一的正平衡点且是局部渐近稳定的;当染病者数量超过医院的最大承受能力时,当基本再生数小于1时,系统可能存在两个正平衡点或无正平衡点.当存在两个正平衡点时,其中染病者数量较小的是鞍点,染病者数量较大的为结点或焦点,且是局部渐近稳定的.当治疗能力较弱时,模型会出现后向分支.