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.     

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.     

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.     

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.     

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.     

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.     

On sequential comparisons of means of first-order autoregressive models

The problem of estimating a linear combination,μ, of means ofp-independent, first-order autoregressive models is considered. Sequential procedures are derived (i) to estimateμ pointwise using the linear combination of sample means, subject to a loss function (squared error plus cost per observation), and (ii) to arrive at a fixed-width confidence interval forμ. It is observed that in the case of point estimation we do not require a sampling scheme, where as in the case of interval estimation we do require a sampling scheme and a scheme similar to the one given in Mukhopadhyay and Liberman (1989) is proposed. All the first order efficiency properties of the sequential procedures involved here are derived. This paper is an extension of results of Sriram (1987) involving one time series to multiple time series. Research supported by AFOSR Grant number 89-0225.     

Decomposition of cost efficiency and its application to Japanese-US electric utility comparisons

This paper presents a new formula for decomposing cost efficiency into technical, price, and allocative efficiencies in an environment marked by the fact that unit input prices differ among certain enterprises. We employed this formula in comparing cost efficiency between Japanese and US electric power companies, and found a significant difference in the price-based efficiency. However, negligible differences were found in the technical and allocative efficiencies.     

Global networks of trade and bits

Considerable efforts have been made in recent years to produce detailed topologies of the Internet, but so far these data have been overlooked by economists. In this paper, we suggest that such information could be used to characterize both the size of the digital economy and outsourcing at country level. We analyse the topological structure of the network of trade in digital services (trade in bits) and compare it with the more traditional flow of manufactured goods across countries. To perform meaningful comparisons across networks with different characteristics, we define a stochastic benchmark for the number of connections among each country-pair, based on hypergeometric distribution. Original data are filtered so that we only focus on the strongest, i.e. statistically significant, links. We find that trade in bits displays a sparser and less hierarchical network structure, which is more similar to trade in high-skill manufactured goods than total trade. Moreover, distance plays a more prominent role in shaping the network of international trade in physical goods than trade in digital services.     

Health status and disability comparisons between CATI calendar and conventional questionnaire instruments

In comparison to conventional questionnaires, calendar interviews produce higher quality retrospective reports of factual information. This study sought to examine whether calendar interviews would also be advantageous in collecting retrospective reports of subjective assessment information. Respondents in a panel study were randomly assigned to either a calendar or conventional questionnaire method; both methods asked for retrospective reports on years in which disability was present and annual health status since young childhood. Panel data served as a source of validation for the retrospective reports. Both methods tended to underreport the number of years disabled and yielded mean levels of better annual health status in comparison to the panel reports. Calendar interviews demonstrated higher quality retrospective reports for disability in yielding a significantly stronger correlation in the frequency of years being disabled and in providing a greater number of years of higher annual correspondence with the panel data in comparison to the conventional questionnaire. Calendar interviews also demonstrated the ability to preserve the slope of change associated with aging as seen in the panel data, whereas the conventional questionnaire led to a significantly shallower slope of change. This latter finding could not be explained by the presence of an acquiescence bias.     

Empirical comparisons of some tests of separate families of hypotheses

Summary This paper is devoted to a comparison of the asymptotic tests of separate families of hypotheses proposed byCox [1961, 1962] and byAtkinson [1970]. The adequacy of the asymptotic results for finite samples is investigated and some conclusions reached. An examination of the terms which differentiate the two procedures is made. Empirical simulated results are discussed for cases involving the exponential, the lognormal and the Weibull distributions.

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Zusammenfassung In dieser Arbeit wird ein Vergleich angestellt zwischen den Vorschlägen vonCox [1961, 1962] undAtkinson [1970] über asymptotische Tests separierter Familien von Hypothesen. Die Angemessenheit der asymptotischen Resultate für endliche Proben wird untersucht und einige Folgerungen gezogen. Eine Prüfung der Terme, die die beiden Verfahren differenzieren, wird vorgenommen. Empirisch simultierte Resultate werden distribuiert für Fälle mit exponential, lognormal und Weibull Verteilungen.