Bayesian model averaging and model selection: two sides of the same coin when identifying the determinants of trade union density?

One of the main problems in empirical sciences is the uncertainty about the relevance of variables. In the debate on the variables that provide a systematic and robust explanation of the share of employees that are members of trade unions, i.e. of trade union density, the problem of variable uncertainty is striking. In regression analyses there is the problem of having to select variables. One problem in the union density discussion is that depending on the chosen combination of regressors different results in the identification of relevant variables are achieved. To systematically analyze which variables are relevant the literature suggests model averaging and selection strategies. While the two strategies have advantages and disadvantages, the aim of this paper is to apply both. Based on a characteristic cross-country panel data set we find differences and similarities based on our evaluation and ask whether a methodological triangulation is possible.     

Generalised Cumulative Arrays in Secret Sharing

Cumulative arrays have played an important role in the early development of the secret sharing theory. They have not been subject to extensive study so far, as the secret sharing schemes built on them generally result in much larger sizes of shares, when compared with other conventional approaches. Recent works in threshold cryptography show that cumulative arrays may be the appropriate building blocks in non-homomorphic threshold cryptosystems where the conventional secret sharing methods are generally of no use. In this paper we study several extensions of cumulative arrays and show that some of these extensions significantly improve the performance of conventional cumulative arrays. In particular, we derive bounds on generalised cumulative arrays and show that the constructions based on perfect hash families are asymptotically optimal. We also introduce the concept of ramp perfect hash families as a generalisation of perfect hash families for the study of ramp secret sharing schemes and ramp cumulative arrays.     

Delineating store trade areas through morphological analysis

The precise knowledge of trade area limits is of importance for companies that want to accurately fit their marketing strategy to local features. Many methods have been already proposed in the literature but either they are too simple or often are at the same time approximate and expensive in computer times. This paper develops the framework of a new method based on mathematical morphology, a science usually used in image processing but not yet applied on data resulting from management sources. This method applied to the delineation of a trade area breaks up the acquisition of the data, filtering, segmentation and regularization of the area boundaries.     

A secret sharing scheme based on cellular automata

A new secret sharing scheme based on a particular type of discrete delay dynamical systems: memory cellular automata, is proposed. Specifically, such scheme consists of a (k, n)-threshold scheme where the text to be shared is considered as one of the k initial conditions of the memory cellular automata and the n shares to be distributed are n consecutive configurations of the evolution of such cellular automata. It is also proved to be perfect and ideal.     

FDI与中国对外贸易的向量误差修正模型

本文以中国的经济数据对外国直接投资(FDI)与对外贸易的联系做了实证检验,根据协整理论建立向量误差修正模型对此问题予以分析,得出结论是在长期和短期内进入中国的外国直接投资与中国的出口都是互补联系,同时在短期外国直接投资与中国的进口也是互补,而在长期外国直接投资与中国的进口却是替代联系。     

On an EPQ model for deteriorating items under permissible delay in payments

This paper derives a production model for the lot-size inventory system with finite production rate, taking into consideration the effect of decay and the condition of permissible delay in payments, in which the restrictive assumption of a permissible delay is relaxed to that at the end of the credit period, the retailer will make a partial payment on total purchasing cost to the supplier and pay off the remaining balance by loan from the bank. At first, this paper shows that there exists a unique optimal cycle time to minimize the total variable cost per unit time. Then, a theorem is developed to determine the optimal ordering policies and bounds for the optimal cycle time are provided to develop an algorithm. Numerical examples reveal that our optimization procedure is very accurate and rapid. Finally, it is shown that the model developed by Huang [1] can be treated as a special case of this paper.     

Properties and constraints of cheating-immune secret sharing schemes

A secret sharing scheme is a cryptographic protocol by means of which a dealer shares a secret among a set of participants in such a way that it can be subsequently reconstructed by certain qualified subsets. The setting we consider is the following: in a first phase, the dealer gives in a secure way a piece of information, called a share, to each participant. Then, participants belonging to a qualified subset send in a secure way their shares to a trusted party, referred to as a combiner, who computes the secret and sends it back to the participants.Cheating-immune secret sharing schemes are secret sharing schemes in the above setting where dishonest participants, during the reconstruction phase, have no advantage in sending incorrect shares to the combiner (i.e., cheating) as compared to honest participants. More precisely, a coalition of dishonest participants, by using their correct shares and the incorrect secret supplied by the combiner, have no better chance in determining the true secret (that would have been reconstructed if they submitted correct shares) than an honest participant.In this paper we study properties and constraints of cheating-immune secret sharing schemes. We show that a perfect secret sharing scheme cannot be cheating-immune. Then, we prove an upper bound on the number of cheaters tolerated in such schemes. We also repair a previously proposed construction to realize cheating-immune secret sharing schemes. Finally, we discuss some open problems.     

Strongly ideal secret sharing schemes

We define strongly ideal secret sharing schemes to be ideal secret sharing schemes in which certain natural requirements are placed on the decoder. We prove an information-theoretic characterization of perfect schemes, and use it to determine which access structures can be encoded by strongly ideal schemes. We also discuss a hierarchy of secret sharing schemes that are more powerful than strongly ideal schemes.     

Graph decompositions and secret sharing schemes

In this paper we continue a study of secret sharing schemes for-access structures based on graphs. Given a graph G, we require that a subset of participants can compute a secret key if they contain an edge of G; otherwise, they can obtain no information regarding the key. We study the information rate of such schemes, which measures how much information in being distributed as shares compared with the size of the secret key, and the average information rate, which is the ratio between the secret size and the arithmetic mean of the size of the shares. We give both upper and lower bounds on the optimal information rate and average information rate that can be obtained. Upper bounds arise by applying entropy arguments due to Capocelli et al. [15]. Lower bounds come from constructions that are based on graph decompositions. Application of these constructions requires solving a particular linear programming problem. We prove some general results concerning the information rate and average information rate for paths, cycles, and trees. Also, we study the 30 (connected) graphs on at most five vertices, obtaining exact values for the optimal information rate in 26 of the 30 cases, and for the optimal average information rate in 28 of the 30 cases.The research of C. Blundo, A. De Santis, and U. Vaccaro was partially supported by the Italian Ministry of University and Research (M.U.R.S.T.) and by the National Council for Research (C.N.R.) under Grant 91.02326.CT12. The research of D. R. Stinson was supported by NSF Grant CCR-9121051.     

我国PCB行业跨境贸易使用人民币结算的现状分析及路径选择

随着我国跨境人民币结算业务的推广,境内外企业对人民币的接受度不断提升,跨境贸易使用人民币结算的规模不断扩大,跨境贸易人民币结算实实在在给企业带来了便利。PCB行业的产能主要集中在亚洲地区,这为PCB行业使用人民币结算提供了极为有利的前提条件。本文将基于PCB行业使用人民币结算的现状,分析PCB行业使用人民币结算的优势何在？障碍何在？探究我国PCB行业跨境贸易使用人民币结算的路径选择。