Towards a responsive-sustainable-resilient tea supply chain network design under uncertainty using big data

Nowadays, issues such as limited natural resources, environmental problems, social matters, and significance of resilience in agricultural supply chain (ASC) have dragged considerable attention worldwide. In this research, a five-level multi-objective stochastic mixed-integer linear programming model is designed for tea supply chain (TSC) in Iran. The objective functions of the suggested network are minimizing total costs of the supply chain (SC), the total water consumption, and non-resilience measures, and maximizing job opportunities of facilities. Literally, considering uncertainty for SC networks is extremely beneficial due to the existence of some variations in different parameters like demand. As a consequence, a robust possibilistic optimization (RPO) is implemented to manage the uncertainty. Due to the nature of the multi-objective optimization problem, the weighted-normalized-extended goal programming (WNEGP) approach is employed to solve the model. In order to credit the model, real data is collected from the tea organization of Iran. It is worth mentioning that parameters are gathered according to three aspects of big data: volume, velocity, and variety. The results validated the functionality of the model regarding planning strategy. In addition, it showed applying more costs on SC triggers an effective sustainable-resilient-responsive network. In terms of managerial insights, this study offers a far-reaching perspective to managers especially in ASC to develop their industries. Finally, some sensitivity analyses are discussed on key parameters such as demand, robustness coefficients, and also the value of the objective functions in various states. It is worth mentioning that sensitivity analyses on different states of the problem show how sustainability and resiliency affect the supply chain efficiency.     

A network of options: Evaluating complex interdependent decisions under uncertainty

The present article provides a novel framework for analyzing option network problems, which is a general class of compound real option problems with an arbitrary combination of reversible and irreversible decisions. The present framework represents the interdependent structure of decisions by using a directed graph. In this framework, the option network problem is formulated as a singular stochastic control problem, whose optimality condition is then obtained as a dynamical system of generalized linear complementarity problems (GLCPs). This enables us to develop a systematic and efficient numerical method for evaluating the option value and the optimal decision policy.     

Identification of peer effects through social networks

We provide new results regarding the identification of peer effects. We consider an extended version of the linear-in-means model where interactions are structured through a social network. We assume that correlated unobservables are either absent, or treated as network fixed effects. We provide easy-to-check necessary and sufficient conditions for identification. We show that endogenous and exogenous effects are generally identified under network interaction, although identification may fail for some particular structures. We use data from the Add Health survey to provide an empirical application of our results on the consumption of recreational services (e.g., participation in artistic, sports and social activities) by secondary school students. Monte Carlo simulations calibrated on this application provide an analysis of the effects of some crucial characteristics of a network (i.e., density, intransitivity) on the estimates of peer effects. Our approach generalizes a number of previous results due to Manski [Manski, C., 1993. Identification of endogenous social effects: The reflection problem. Review of Economic Studies 60 (3), 531–542], Moffitt [Moffitt, R., 2001. Policy interventions low-level equilibria, and social interactions. In: Durlauf, Steven, Young, Peyton (Eds.), Social Dynamics. MIT Press] and Lee [Lee, L.F., 2007. Identification and estimation of econometric models with group interactions, contextual factors and fixed effects. Journal of Econometrics 140 (2), 333–374].     

The airport problem with capacity constraints

The original airport problem is concerned with the cost sharing of an airstrip among airplanes assuming that one airstrip is sufficient to serve all airplanes. In this paper, we generalize the original airport problem by imposing capacity constraints to consider the situation when one airstrip cannot serve all airplanes and investigate how to share the cost among airplanes. We introduce the sequential equal contributions rule for our problem and show that it coincides with the Shapley value of the corresponding airport game when the worth of a coalition is defined to be the minimum cost of serving all members of the coalition. The sequential equal contributions rule requires each airplane to contribute equally to the cost of a given section of any airstrip as long as the length of the section is less than or equal to its desired length even though the airplane cannot use the airstrip. Each airplane’s contribution is the sum of terms, one for each section of the airstrip whose length is less than or equal to its desired length. We also present an axiomatic characterization of the rule by imposing the axioms of efficiency, the equal share lower bound, smaller-cost monotonicity, and population fairness.     

Network design in games with spillovers

How should an organization be designed in order to provide its members with minimal incentives to defect? And how does the optimal design depend on the type of strategic interaction between defectors and remaining organizational members? This paper addresses such issues in a game theoretic model of cooperation, in which an organization is formally represented by a connected network, and where gains from cooperation are given by a partition function. We show that critical structural features of the organization depend in a clear-cut way on the sign of spillovers. In particular, positive spillovers favor the adoption of dispersed and centralized forms, while negative spillovers favor cohesive and horizontal ones. Moreover, if the organizational form determines all the communication possibilities of members, a highly centralized organization—the star—emerges under positive spillovers, whereas two horizontal architectures—the circle and the complete—emerge under negative spillovers.     

Bilateral redistribution

We explore the implications of three basic and intuitive axioms for income redistribution problems: continuity, no transfer paradox and stability. The combination of the three axioms characterizes in the two-agent case a large family of rules, which we call threshold rules. For each level of total income in society, a threshold is considered for each agent. It is impossible for both agents to be below their respective thresholds. If an agent’s income is below the threshold, the difference is redistributed from the other agent; otherwise, the rule imposes laissez-faire.     

Identification and Estimation Issues in Exponential Smooth Transition Autoregressive Models

Exponential smooth transition autoregressive (ESTAR) models are widely used in the international finance literature, particularly for the modelling of real exchange rates. We show that the exponential function is ill‐suited as a regime weighting function because of two undesirable properties. Firstly, it can be well approximated by a quadratic function in the threshold variable whenever the transition function parameter γ, which governs the shape of the function, is ‘small’. This leads to an identification problem with respect to the transition function parameter and the slope vector, as both enter as a product into the conditional mean of the model. Secondly, the exponential regime weighting function can behave like an indicator function (or dummy variable) for very large values of γ. This has the effect of ‘spuriously overfitting’ a small number of observations around the location parameter μ. We show that both of these effects lead to estimation problems in ESTAR models. We illustrate this by means of an empirical replication of a widely cited study, as well as a simulation exercise.     

Post local forms of repair: The (extended) situation of virtualised technical support

We address the seemingly implausible project of moving the technical support of complex organisational technologies online. We say ‘implausible’ because from the point of view of micro-sociological analysis and the influential work of Orr (1996) there is a consensus that the diagnosis and resolution of technical failures is an intrinsically ‘localised affair’ (i.e., rooted within a specific place and time). Notwithstanding this view, technology producers have been pushing in the recent period to develop online forms of support. Today, and particularly in the area of organisational software, many technical failures are now repaired at a distance. How is this possible given the consensus amongst sociologists? Drawing on ethnographic fieldwork conducted at a major software producer we show how repair work has been recast and inserted in a new geographical and temporal regime. This has implications for how sociologists of technology conceptualise the nature and practice of technical failure but also the time and situation in which it occurs. We attempt to refocus understandings of technical problems from a preoccupation with their rootedness onto how they are lifted out of local contexts and passed around globally distributed offices in search of requisite specialist expertise. Importantly, whilst virtualisation appears a seemingly effective means to resolve failures it also has negative consequences. Whereas in more traditional types of technical support place-based social relations are seen to bear the burden of controlling and regulating support, in online forms other means have to be found. Our conceptual aim is to move away from a view of repair revolving exclusively around the situation conceived of as a ‘small place’. Rather, since support work is increasingly ‘stretched out’ across a global network of labs connected up by technologies, it now takes place across an extended situation. We work up this notion first to highlight how aspects once seen as central to localist forms of analysis are no longer the only organising features as technical work moves online and second to demonstrate the various ways in which the locales for this work are now mediated by technology.     

Bayesian forecasting and portfolio decisions using dynamic dependent sparse factor models

We extend the recently introduced latent threshold dynamic models to include dependencies among the dynamic latent factors which underlie multivariate volatility. With an ability to induce time-varying sparsity in factor loadings, these models now also allow time-varying correlations among factors, which may be exploited in order to improve volatility forecasts. We couple multi-period, out-of-sample forecasting with portfolio analysis using standard and novel benchmark neutral portfolios. Detailed studies of stock index and FX time series include: multi-period, out-of-sample forecasting, statistical model comparisons, and portfolio performance testing using raw returns, risk-adjusted returns and portfolio volatility. We find uniform improvements on all measures relative to standard dynamic factor models. This is due to the parsimony of latent threshold models and their ability to exploit between-factor correlations so as to improve the characterization and prediction of volatility. These advances will be of interest to financial analysts, investors and practitioners, as well as to modeling researchers.     

Crossing the bridge from network training to development: A guide to move trainees from classroom insights to effective networks

Professional networks help employees accomplish work tasks, progress in their careers, and thrive personally. Decades of research suggest that achieving these outcomes requires more than simply amassing 'more' network contacts. Instead, networks with certain characteristics (e.g., networks that are open, diverse, and deep) enhance effectiveness. Network training teaches trainees about effective networks and helps trainees identify their network development needs by providing feedback on their current network. Once back on the job, trainees are assumed to take appropriate actions to develop their networks. However, our research and experience training MBA students, executives, and employees at all levels suggest that trainees often struggle to develop their networks after training. We studied 119 trainees engaged in network training and development to understand why. Our investigation revealed that many trainees fail to set network development goals that match their personalized feedback, identify strategies that match their goals, and take actions to develop networks that match their strategies. These mismatches create gaps in the bridge that trainees build to take themselves from network training to development. Further, even after building strong bridges by aligning their feedback, goals, strategies, and actions, many trainees encounter on-the-job barriers that prevent them from improving the effectiveness of their network. We offer a guide to help address translational gaps and mitigate on-the-job barriers, thereby enhancing the translation of network training insights into network development.     

Good neighbors are hard to find: computational complexity of network formation

We investigate the computational complexity of several decision problems in a simple strategic game of network formation. We find that deciding if a player has a strategy that guarantees him a certain payoff against a given strategy profile of the other players is an NP-complete problem. Deciding if there exists a strategy profile that guarantees a certain aggregate payoff is also NP-complete. Deciding if there is a Nash equilibrium in pure strategies which guarantees a certain payoff to each player is NP-hard. The problem of deciding if a given strategy profile is a Nash equilibrium is investigated as well. We would like to thank both referees for valuable corrections and suggestions and one referee in particular for a very detailed and beneficial critique. We thank Colin de la Higuera for fruitful discussions. Support by the French Ministry for Youth, Education and Research, through project SCSHS-2004-04 is gratefully acknowledged.     

Weighted majoritarian rules for the location of multiple public facilities

We consider collective decision problems given by a profile of single-peaked preferences defined over the real line and a set of pure public facilities to be located on the line. In this context, Bochet and Gordon (2012) provide a large class of priority rules based on efficiency, object-population monotonicity and sovereignty. Each such rule is described by a fixed priority ordering among interest groups. We show that any priority rule which treats agents symmetrically — anonymity — respects some form of coherence across collective decision problems — reinforcement — and only depends on peak information — peak-only — is a weighted majoritarian rule. Each such rule defines priorities based on the relative size of the interest groups and specific weights attached to locations. We give an explicit account of the richness of this class of rules.     

A new statistic and practical guidelines for nonparametric Granger causality testing

In this paper we introduce a new nonparametric test for Granger non-causality which avoids the over-rejection observed in the frequently used test proposed by Hiemstra and Jones [1994. Testing for linear and nonlinear Granger causality in the stock price-volume relation. Journal of Finance 49, 1639–1664]. After illustrating the problem by showing that rejection probabilities under the null hypothesis may tend to one as the sample size increases, we study the reason behind this phenomenon analytically. It turns out that the Hiemstra–Jones test for the null of Granger non-causality, which can be rephrased in terms of conditional independence of two vectors X and Z given a third vector Y, is sensitive to variations in the conditional distributions of X and Z that may be present under the null. To overcome this problem we replace the global test statistic by an average of local conditional dependence measures. By letting the bandwidth tend to zero at appropriate rates, the variations in the conditional distributions are accounted for automatically. Based on asymptotic theory we formulate practical guidelines for choosing the bandwidth depending on the sample size. We conclude with an application to historical returns and trading volumes of the Standard and Poor's index which indicates that the evidence for volume Granger-causing returns is weaker than suggested by the Hiemstra–Jones test.     

Steiner minimal trees and urban service networks

The optimal configuration of urban service networks has recently been shown to be a computationally difficult problem. However, there are efficient and effective techniques by which this optimal configuration of urban service networks can be approximated. In this paper, we analyze the L_p Steiner Network problem in the plane R² and demonstrate its applicability to the urban service network problem. We present a simple algorithm for estimating the L_p metric parameter for random points in the plane, then utilize it to find the L_p values for four different American cities. Finally, we apply the L_pSMT algorithm described within the text to one of the cities in order to demonstrate the effectiveness of our algorithm for determining optimal network configurations.     

On a simple characterisation of threshold graphs

In their very interesting paper “Set-packing problems and threshold graphs” [1] V. Chvatal and P. L. Hammer have shown that the constraints $$\begin{gathered} \sum\limits_{j = 1}^n {a_{ij} x_j \leqslant 1(i = 1,2, . . . , m)} \hfill \\ x_j \in (0,1)(j = 1,2, . . . , n) \hfill \\ \end{gathered} $$ are equivalent to the only inequality $$\begin{gathered} \sum\limits_{j - 1}^n {c_j x_j \leqslant d} \hfill \\ x_j \in (0,1)(j = 1,2, . . . , n) \hfill \\ \end{gathered} $$ if and only if the intersection graph associated with the matrix (a _ij ) — see § 1 — is a threshold graph i.e. a graph none of whose induced subgraphs are isomorphic to 2K ₂,P ₄,C ₄: As Chvatal and Hammer have shown [1], threshold graphs can be characterised in many different ways; the main result of this paper is to give a new, very simple characterisation which will enable us to test whether a graph is a threshold by a simple inspection of its incidence matrix.     

Crossing the Threshold from Founder Management to Professional Management: A Governance Perspective

ABSTRACT We argue that the challenges faced by threshold firms are deeply rooted in governance characteristics (i.e. the incentives, authority and legitimacy) which imbue them with characteristic capabilities, disabilities and path dependencies. Whereas Zahra and Filatotchev (2004 ) reason the principal problem facing threshold firms relates to organizational learning and knowledge management, we posit resource acquisition and utilization to be equally important. Moreover, we argue governance theory is more able than a knowledge‐based perspective to explain the root causes of the learning and resource issues faced by threshold firms as well as the complex set of processes involved in their effective management.     

No-envy,solidarity, and strategy-proofness in the queueing problem

Given a group of agents, the queueing problem is concerned with finding the order to serve agents and the monetary transfers they should receive. In this paper, we characterize interesting subfamilies of the VCG mechanisms by investigating the implications of either no-envy or solidarity requirements. First, we present a characterization of the strategy-proofand envy-freemechanisms. Next, we present characterizations of VCG mechanisms satisfying one of two different formulations of cost monotonicity or population monotonicity. Finally, we show that among the envy-free and strategy-proof mechanisms, the only ones that satisfy one of two formulations of cost monotonicity or population monotonicity are extensions of the pivotal or the reward-based pivotal mechanisms.     

Consistent likelihood-based estimation of a star-shaped distribution

We consider the classical problem of nonparametrically estimating a star-shaped distribution, i.e., a distribution function F on [0,∞) with the property that F(u)/u is nondecreasing on the set {u : F(u) < 1}. This problem is intriguing because of the fact that a well defined maximum likelihood estimator (MLE) exists, but this MLE is inconsistent. In this paper, we argue that the likelihood that is commonly used in this context is somewhat unnatural and propose another, so called ‘smoothed likelihood’. However, also the resulting MLE turns out to be inconsistent. We show that more serious smoothing of the likelihood yields consistent estimators in this model.