Structural investigation of supply networks: A social network analysis approach

A system of interconnected buyers and suppliers is better modeled as a network than as a linear chain. In this paper we demonstrate how to use social network analysis to investigate the structural characteristics of supply networks. Our theoretical framework relates key social network analysis metrics to supply network constructs. We apply this framework to the three automotive supply networks reported in Choi and Hong (2002). Each of the supply networks is analyzed in terms of both materials flow and contractual relationships. We compare the social network analysis results with the case-based interpretations in Choi and Hong (2002) and conclude that our framework can both supplement and complement case-based analysis of supply networks.     

Structural VAR and financial networks: A minimum distance approach to spatial modeling

In this paper, I interpret a time series spatial model (T-SAR) as a constrained structural vector autoregressive (SVAR) model. Based on these restrictions, I propose a minimum distance approach to estimate the (row-standardized) network matrix and the overall network influence parameter of the T-SAR from the SVAR estimates. I also develop a Wald-type test to assess the distance between these two models. To implement the methodology, I discuss machine learning methods as one possible identification strategy of SVAR models. Finally, I illustrate the methodology through an application to volatility spillovers across major stock markets using daily realized volatility data for 2004–2018.     

Granger causality detection in high-dimensional systems using feedforward neural networks

This paper proposes a novel methodology to detect Granger causality on average in vector autoregressive settings using feedforward neural networks. The approach accommodates unknown dependence structures between elements of high-dimensional multivariate time series with weak and strong persistence. To do this, we propose a two-stage procedure: first, we maximize the transfer of information between input and output variables in the network in order to obtain an optimal number of nodes in the intermediate hidden layers. Second, we apply a novel sparse double group lasso penalty function in order to identify the variables that have the predictive ability and, hence, indicate that Granger causality is present in the others. The penalty function inducing sparsity is applied to the weights that characterize the nodes of the neural network. We show the correct identification of these weights so as to increase sample sizes. We apply this method to the recently created Tobalaba network of renewable energy companies and show the increase in connectivity between companies after the creation of the network using Granger causality measures to map the connections.     

Multilateral productivity comparisons and homotheticity

In this paper it is shown that a well known procedure (GEKS) of transitivizing a bilateral system of productivity comparisons is implicitly a way of imposing a homothetic structure onto the data. The main implication of this result is that deviations between the bilateral and the multilateral (GEKS) indexes can be interpreted as a measure of local deviation from the homothetic assumption. This establishes an additional link between homotheticity and transitivity.     

Stochastic comparisons of coherent systems

The study of stochastic comparisons of coherent systems with different structures is a relevant topic in reliability theory. Several results have been obtained for specific distributions. The present paper is focused on distribution-free comparisons, that is, orderings which do not depend on the component distributions. Different assumptions for the component lifetimes are considered which lead us to different comparison techniques. Thus, if the components are independent and identically distributed (IID) or exchangeable, the orderings are obtained by using signatures. If they are just ID (homogeneous components), then ordering results for distorted distributions are used. In the general case or in the case of independent (heterogeneous) components, a similar technique based on generalized distorted distributions is applied. In these cases, the ordering results may depend on the copula used to model the dependence between the component lifetimes. Some illustrative examples are included in each case.     

Robust comparisons of spatial patterns

A spatial allocation (a so-called pattern) is represented by a finite measure in two-space, and choices between alternative patterns are based on an average value over space. This paper presents rules for robust comparisons of patterns in the sense that one pattern should be uniformly better than another one with respect to all elements of a certain class of valuation functions. In particular, we investigate the optimum location of a new pattern (i) which interacts with a single given center and (ii) which interacts with several given patterns.     

An application of model-based estimation of unobserved components

The paper analyzes a real-world application of an ARIMA-based trend/seasonal/irregular estimation. The analysis illustrates two points of applied interest. First, it is seen how the decomposition of ARIMA models is sensitive to changes in the specification of the overall model. Alternative ARIMA models, which yield similar fits and forecasts, may produce remarkably different decompositions. Second, it is shown how the model-based approach provides tools for interpretation of the results. In particular, the comparison between the empirical autocorrelation of the estimated components and the theoretical autocorrelations of the model-based estimators can be used as an overall diagnostic check.     

Two representations of information structures and their comparisons

Decisions in Economics and Finance - This paper compares two representations of informativeness.     

LSPR detection of extracellular vesicles using a silver-PDMS nano-composite platform suitable for sensor networks

ABSTRACT

A novel method for the detection of exosomes in body fluids and cell cultures has been developed. The method is an optical method, based on LSPR of silver nanoparticles. The method was extended to a microfluidic environment, amenable to be integrated in a sensor network. However, for clinical applications, their isolation, detection and quantification methods in bio-fluids are challenging. Herein, we present a simple label-free technique to capture and detect EVs, by using a synthetic peptide, called Vn96. To quantify EVs, a LSPR detection technique was used. This work is an attempt to adapt a biosensing method to the future requirements of Industry 4.0.     

International comparisons of human resource management

C. Brewster and S. Tyson (eds) (1991) International Comparisons in Human Resource Management. London: Pitman.

P. J. Dowling and R. S. Schuler (1990) International Dimensions of Human Resource Management. Boston, MA: PWS-Kent.

R Pieper (ed.) (1990) Human Resource Management: An International Comparison. Berlin: Walter de Gruyter.

This review article assesses three major recent works in international human resource management. The author argues that the international character of human resource management can be said to rest on three things: (1) the increasing internationalization of business, which brings organizations into contact with different national cultures and promotes the spread of management practices across national boundaries, (2) underlying economic and technological trends, arising in part from the activity of multinational firms but mediated also by international institutions, which may produce similar patterns of adjustment in the organization and management of employment at the national, sectoral and firm level, and (3) the processes whereby businesses become progressively international. After critically reviewing the books listed above the author argues that the validation of an international model(s) would benefit from cross-national comparisons of a number of features identified in the internationalization process.     

Stochastic dominance and statistical comparisons of income distribution functions

This paper assesses the economic well being of the U.S. elderly population by applying asymptotically distribution-free statistical tests of stochastic dominance relations characterizing income distribution functions. The procedure is new and overcomes serious difficulties encountered in naive comparisons of summary statistics which are widely used in assessing economic well being. An important advantage of this approach is that it exploits all the information contained in the income distribution function. Application of the method to compare the elderly population to the entire U.S. population in the 1980's reveals evidence of a higher per capita level of economic well being among older Americans. The method can be applied to other socioeconomic groups and in other countries provided that appropriate micro data are available.     

Peer pressure and social comparisons with heterogeneous ability

When workers' efforts are not contractible, we investigate whether the display of workers' efforts to coworkers influences wage and effort decisions. We find that employers mainly increase the wages offered to the more valuable workers when they are observed that increases the difference in wages in such setting. We find evidence of peer pressure and strategic complementarity in efforts. Additionally, low‐ability workers are more sensitive to peer pressure than their more productive coworkers, and these workers exert less effort with increases in the reciprocity of their coworkers. Finally, the display of workers' efforts to coworkers is detrimental to the employer's payoff but enhances efficiency.     

Stochastic comparisons of multivariate reversed frailty model

Multivariate frailty approaches are most commonly used to define distributions of random vectors, which represent lifetimes of individuals or components and stochastically compare them in terms of various multivariate orders. In this paper, we study a multivariate shared reversed frailty model and a general multivariate reversed frailty mixture model, and derive sufficient conditions for some of the stochastic orderings to hold among the random vectors. We also consider a particular case of a general multivariate mixture model in which the baseline distribution function is represented in terms of a copula and study stochastic comparisons (stochastic and lower orthant order) among the two random vectors.     

International welfare comparisons and nonparametric testing of multivariate stochastic dominance

This paper outlines a class of statistical procedures that permit testing of a broad range of multidimensional stochastic dominance hypotheses and, more generally, welfare hypotheses that rely upon multiple stochastic dominance conditions. We apply the procedures to data on income and leisure hours for individuals in Germany, the UK, and the USA. We find that no country first‐order stochastically dominates the others in both dimensions for all years of comparison. Furthermore, while in general the USA stochastically dominates Germany and the UK with respect to income, in most periods Germany stochastically dominates with respect to leisure hours. Finally, we find evidence that bivariate poverty (which refers, for example, to the working poor, that is, those who have little leisure and low income) is lower in Germany than in either the UK or the USA. On the other hand, poverty comparisons between the UK and the USA are sensitive to the subpopulation of individuals considered. Copyright © 2007 John Wiley & Sons, Ltd.     

A general approach to intertemporal and interspatial productivity comparisons

The purpose of this paper is to introduce a general methodology for analysing the sources of intertemporal or interspatial differences in outputs and costs, general in the sense that our methodology allows the productivity analyst to ‘break out’ of the quadratic ‘straightjacket’ imposed by the class of superlative index number comparisons. Starting fromTaylor's series expansions about the two points to be compared, we develop a general growth accounting equation which can be approximated to any desired degree of accuracy, depending on the information available.The theoretical framework is applied to two recent examples of interspatial comparisons which use the Tornqvist superlative index. In the first example, we show that the biases in regional Canadian total manufacturing cost-efficiency comparisons which result from the use of this index are negligible. However, in the second example, it is shown that the Tornqvist index imparts a substantial bias in United States-Japan total domestic economy productivity comparisons. The index consistently overestimates the relative productivitylevel of the U.S. economy and misses the turning point, when the Japanese economy becomes more efficient, by two years.     

Changing the paradigm for telemedicine development and evaluation: a prospective model-based approach

Telemedicine is an application of information technology that provides the means to deliver healthcare services at a distance. Interest in telemedicine by the healthcare community has been highly variable since its beginnings in the early 1960s, in part due to the failure to quantitatively demonstrate its cost-effectiveness in delivering healthcare services. Although once again on the upswing, we argue that telemedicine will not fulfill its advertised promises unless the community adopts a new paradigm for its development and evaluation. The paper thus summarizes the prevailing approach—technology driven, retrospective evaluation, little planning—and describes a new one which is based on capability requirements and the use of models for prospective analysis and planning. A new program to develop structural models of the healthcare delivery system for this purpose is presented, including the program's modeling criteria, major components and processes of the healthcare system being considered, the development strategy being pursued, and the structure of specific models being developed.     

Projecting supply and use tables: new variants and fair comparisons

ABSTRACT

We have introduced in this paper new variants of two methods for projecting Supply and Use Tables that are based on a distance minimisation approach (SUT-RAS) and the Leontief model (SUT-EURO). We have also compared them under similar and comparable exogenous information, i.e.: with and without exogenous industry output, and with explicit consideration of taxes less subsidies on products. We have conducted an empirical assessment of all of these methods against a set of annual tables between 2000 and 2005 for Austria, Belgium, Spain and Italy. From the empirical assessment, we obtained three main conclusions: (a) the use of extra information (i.e. industry output) generally improves projected estimates in both methods; (b) whenever industry output is available, the SUT-RAS method should be used and otherwise the SUT-EURO should be used instead; and (c) the total industry output is best estimated by the SUT-EURO method when this is not available.