Search

The search model suggested in this study uses a unit-speed nanosensor to track the fluid's randomly linear flow particle, starting at the real line's origin. The nanosensor oscillates passing through the origin point (towards right and left) in the presence of a sequence of random points, and the particle's position is always changing with a random waiting time that varies with the Gaussian jump length. We may be able to consider the search distance as a function of a discounted effort-reward parameter (factor) because of this uncertainty. We demonstrate analytically how this parameter affects proving the existence of this model and reducing the expected value of the first collision time before the nanosensor returns a particle to the origin. To demonstrate the effectiveness of this model, a numerical example is provided. [ABSTRACT FROM AUTHOR]

We model the effect of online information search across mobile (smartphone and tablet) and nonmobile (personal computer [PC], both desktop and laptop) platforms on frequency of purchasing per online shopping session. Using clickstream data from a multinational retailer, we find that device modality drives purchase frequency, likely due to the differential ease of use of PCs, tablets, and smartphones. In particular, frequency of completed orders is highest when information search and purchase completion are highly convenient, such as when shopping via tablet. We also determine that information search in the form of reading online product reviews has no effect on mobile platforms, while it does on other platforms. These findings contribute to information search theory, suggesting that information search increases purchase likelihood when it is goal directed, extensive, and easy to conduct. Thus, the broad role of digital advertising should be to make the information search process easier and more convenient for consumers to stimulate purchases. These findings help digital advertisers understand information search patterns across device modalities. Implications for digital advertisers on electronic commerce (e-commerce) platforms are offered. [ABSTRACT FROM AUTHOR]

Despite the fast growth in the Estonian economy, unemployment has remained high for extended periods of time. This paper analyses and quantifies the mismatch between registered unemployment and vacancies and how it has contributed to unemployment in the Estonian labour market at the (county) regional, occupational, and industrial levels for the time span 2011-2021. We apply the search and matching theory and the mismatch index framework, and our findings show that around 4–5 per cent of potential hires have been lost in the Estonian labour market because of mismatch. The contribution of mismatch to the level of unemployment is roughly 5–8 per cent, meaning that if the match between unemployed individuals and vacancies was efficient, unemployment would have been 5–8 per cent lower. Mismatch has the smallest impact at the regional level and the largest at the industrial level. [ABSTRACT FROM AUTHOR]

This article advances extant research that has audited search algorithms for misinformation in four respects. Firstly, this is the first misinformation audit not to implement a national but a cross-national research design. Secondly, it retrieves results not in response to the most popular query terms. Instead, it theorizes two semantic dimensions of search terms and illustrates how they impact the number of misinformative results returned. Furthermore, the analysis not only captures the mere presence of misinformative content but in addition whether the source websites are affiliated with a key misinformation actor (Russia's ruling elites) and whom the conspiracy narratives cast as the malicious plotters. Empirically, the audit compares Covid-19 conspiracy theories in Google search results across 5 key target countries of Russia's foreign communication (Belarus, Estonia, Germany, Ukraine, and the US) and Russia as of November 2020 (N = 5280 search results). It finds that, across all countries, primarily content published by mass media organizations rendered conspiracy theories visible in search results. Conspiratorial content published on websites affiliated with Russia's ruling elites was retrieved in the Belarusian, German and Russian contexts. Across all countries, the majority of conspiracy narratives suspected plotters from China. Malicious actors from the US were insinuated exclusively by sources affiliated with Russia's elites. Overall, conspiracy narratives did not primarily deepen divides within but between national communities, since – across all countries – only plotters from beyond the national borders were blamed. To conclude, the article discusses methodological advice and promising paths of research for future cross-national search engine audits. [ABSTRACT FROM AUTHOR]

This paper examines 'The Natures of Conceptual Change', the Notre Dame lectures given by Kuhn in 1980. In particular, I aim to examine the content of these lectures which was not published before. This exegetical task will shed light on the sources of the notion of taxonomy used in these lectures for the first time with the explicit philosophical purposes. It also will shed new light on Kuhn's position regarding the causal theory of reference. Reviewing these archival materials paves the way for intertextual comparisons, as Kuhn included part of these lectures in the texts published later and in the book Plurality of Worlds: an Evolutionary Theory of Scientific Development. In recent years, the publication of Kuhn's archival material and the research on these texts increased in quantity and quality. Faced with this encouraging landscape, a comparative examination of the different unpublished texts is crucial to refining both our research tools on Kuhn's intellectual biography and the philosophical work inspired by his proposal. [ABSTRACT FROM AUTHOR]

This article summarises a laboratory program involving over 100 tests that were performed to study the influence of soil type, temperature, water content and salinity on the strength and creep of frozen soils under uniaxial compression and shear tests. Analyses of experimental data allowed to get equations for predicting strength and creep parameters depending on the temperature and salinity using generalising parameters for frozen soils (freezing point and the concentration of pore solution). These parameters reflect the total impact of all factors (soil type, salinity and water content) in forming a single pattern for all types of soil. The developed theory of searching for generalised dependencies showed a good convergence for predicting the strength and creep characteristics of frozen soils. [ABSTRACT FROM AUTHOR]

This paper focuses on the recursive parameter estimation problem of the exponential autoregressive (ExpAR) model. Applying the Newton search and multi-innovation theory, a multi-innovation Newton recursive algorithm is presented for identifying the ExpAR model. In order to improve the computational efficiency, the hierarchical identification principle is employed to decompose an ExpAR model into two sub-models, and to derive a hierarchical multi-innovation Newton recursive algorithm. A simulation example is provided to demonstrate the effectiveness of the proposed algorithms. [ABSTRACT FROM AUTHOR]

Public value continues to capture the attention of policy theorists as it provides unique insights into the accommodations public managers do and do not make when considering citizen perspectives. However, the concept is currently constrained by its emphasis on the consideration of a single public and the need to find consensus on values. This article considers the search for a unified theory of public value in complex and pluralistic settings against the inherent tensions exemplified in three policy areas – Indigenous policy, gambling policy and school education. It argues that rather than seeking a unified conception, a more productive approach is to accommodate alternative positions, including the notion of multiple publics by embracing agonistic ideas of difference. [ABSTRACT FROM AUTHOR]

Instead of using performance data to help improve organizational performance, many public officials have responded to the implementation of performance measurement (PM) systems in their organizations by gaming these systems. While research on the dysfunctional effects of PM is growing, we are still in search of frameworks and theories that are capable of explaining the causes of PM gaming by public organizations and officials. This research proposes that PM gaming is a product of the motivation of the officials and the opportunity presented by the context. It articulates specific propositions and presents a causal model that aims to provide a more systematic explanation about the main causes of PM gaming. [ABSTRACT FROM AUTHOR]

In this paper, we set up a two-sided random search model to study the trading behaviour between buyers and sellers in the commercial real estate market. Our model shows that the interaction between search and bargaining has a profound influence on the role played by the market search friction regarding the equilibrium transaction price of commercial property and the well-being of both buyers and sellers. Against the traditional view that the existence of search friction always plays a negative role in the commercial real estate market, we find that under some conditions the market search friction can increase the equilibrium transaction price of commercial property and thus benefit sellers, which is considered the most valuable especially during the downturn of a business cycle. [ABSTRACT FROM AUTHOR]

While research on the dysfunctional uses of performance data is growing, we are still in search of theories that go beyond system-specific explanations and address data manipulation behavior at the level of the employee. In this article, we conceptualize different gaming responses to performance systems and test a model of performance cheating that emphasizes the critical role of employees' prosocial impact, their job stress, and organizations' red tape. We screen through a sample of almost 10,000 potential subjects and identify 964 public employees who work with performance data. Conducting a list experiment, a technique known to yield unbiased ratings of sensitive behaviors, we find that all three factors tend to reinforce performance cheating among public employees. The article contributes to the extension of causal chains in performance gaming theory via the inclusion of factors that have proven to be influential in behavioral research. [ABSTRACT FROM AUTHOR]

This paper considers a new model in search theory to find a randomly located target in the 3-dimensional space. An approximation algorithm that facilitates searching procedures for searchers or robots is presented. The expected time to detect the target is also proved. The statistical analysis by calculating the optimal search strategy which minimizes the time to detect the target, assuming trivariate standard normal distribution is provided, and the technique by flowcharts is designed as well. The effectiveness of this strategy is illustrated by introducing an application from real world. [ABSTRACT FROM AUTHOR]

This introduction to 'Orthodox Kaleidoscope: Heterogeneity, Complexity, and Dynamics in the Russian Orthodox Church' sheds light on its contributions from a methodological-theoretical angle. Six of the seven contributions to this issue spring from an interdisciplinary academic network established in 2015 by scholars of 15 institutions in search of approaches and theories that would do justice to the multifaceted and fluid return of the Russian Orthodox Church (Moscow Patriarchate) to society and (geo-)politics after perestroika. One of the challenges this Orthodox revival presents to scholarship is an extreme heterogeneity of groups, worldviews, and teachings, each claiming to represent 'true' Orthodoxy by virtue of their belonging to Orthodox Tradition. Such belonging grants the right to exist and exercise sacral authority on micro-, meso- and macro-levels, but also involves a non-belonging, a simultaneous insider and outsider perspective of Orthodoxy/Orthodox Tradition. Since this problem arises in each situation when such an overreaching position (sub specie aeternitatis) is claimed, it is common to each religious tradition and is therefore pertinent to religious studies more broadly. In the Introduction I discuss this variation of Russell's paradox and the ways to overcome this conceptual problem. [ABSTRACT FROM AUTHOR]

A new search technique is developed to locate the hidden target (object) in one of the N-disjoint regions that are not identical. The lost object follows a bivariate distribution. Minimizing the search effort with discount reward has been applied instead of reducing the expected search time. Moreover, the minimum number of searchers is determined in order to minimize the total expected cost. Assuming the object's position has a Circular Normal distribution, the Kuhn–Tucker necessary conditions are implemented to get the optimum search plan. [ABSTRACT FROM AUTHOR]

In most realistic situations, machines may be unavailable due to maintenance, pre-schedules and so on. The availability constraints are non-fixed in that the completion time of the maintenance task is not fixed and has to be determined during the scheduling procedure. In this paper a greedy randomised adaptive search procedure (GRASP) algorithm is presented to solve the flexible job-shop scheduling problem with non-fixed availability constraints (FJSSP-nfa). The GRASP algorithm is a metaheuristic algorithm which is characterised by multiple initialisations. Basically, it operates in the following manner: first a feasible solution is obtained, which is then further improved by a local search technique. The main objective is to repeat these two phases in an iterative manner and to preserve the best found solution. Representative FJSSP-nfa benchmark problems are solved in order to test the effectiveness and efficiency of the proposed algorithm. [ABSTRACT FROM AUTHOR]

Tour splitting heuristics for capacitated vehicle routing problems build one giant tour visiting all customers and split this tour into capacity-feasible vehicle trips. They are seldom used alone because of a reputation of limited performance. This paper describes how to improve them to obtain better solutions or tackle additional constraints. Numerical tests on the capacitated arc routing problem (CARP) and the capacitated vehicle routing problem (CVRP) show that randomized versions outperform classical constructive heuristics. A greedy randomized adaptive search procedure (GRASP) and an iterated local search (ILS) based on these principles even compete with published metaheuristics, while being faster and simpler. [ABSTRACT FROM AUTHOR]

In this study we attempt to deal with process planning, scheduling and preventive maintenance (PM) decisions, simultaneously. The objective is to minimize the total completion time of a set of jobs on a CNC machine. During the process planning, we decide on the processing times of the jobs which are controllable (i.e. they can be easily changed) on CNC machines. Using shorter processing times (higher production rates) would result in greater deterioration of the machine, and we would need to plan more frequent PM visits to the machine, during which it would not be available. Therefore, the selected processing times determine not only the completion times but also the PM visit times. We first provide optimality properties for the joint problem. We propose a new heuristic search algorithm to determine simultaneously the processing times of the jobs, their sequence and the PM schedule. [ABSTRACT FROM AUTHOR]

This paper discusses Jacobinism and the French/Haitian revolution in its unity and diversity. It shows that the main imaginary and institutional elements of modernity – including further anti-colonial struggles – can be seen in this large and radical movement in both sides of the Atlantic. In dialogue with Fehér's account of the metropolitan process and with interpretations of the colonial side, this paper rejects methodological nationalism as well as the downplaying of differentiations in the development of political modernity. Normative and epistemological issues are treated in the course of the argument, in the search for a critical theory of global modernity. [ABSTRACT FROM AUTHOR]

In this paper, we present a facility layout planning method based on AI search techniques and on a set of rules and criteria called AILAY. This method may be classified as a combined constructive and improvement layout planning method, and the development and selection of its search rules and criteria are based on problemspecific knowledge. We also present the main test results and conclusions about the performance and robustness of ALLAY and each of its search rules. [ABSTRACT FROM AUTHOR]

Search theory is concerned with the problem of locating a hidden object or target (a military target, a mineral deposit, a failed component in an equipment, etc.) with minimal cost or maximal probability subject to various practical constraints. The problem solution results in a plan or strategy of search, indicating where and in what sequence to look for the target.
Koopman (1956) who pioneered the basis of the search theory states that ' search problems are more general than the problems of linear programming, since the expression to be optimized is non-linear and involves integration '. However, despite its generality and practical usefulness, almost all published material in the area emphasizes the theory which gives a false impression of the relevance of the available work to application.
In this paper it has been shown that search models can be used for the solution of testing and inspection problems arising in industrial maintenance and quality control. Search models which can be used for this purpose have been introduced, for the first, time, with a unified terminology and notation and classified in groups corresponding to problem constraints. As an application a real-life case problem and its computer solution have been provided. To encourage further applications the computer programme of the search model used for the solution of the case problem bas been included. [ABSTRACT FROM AUTHOR]

This article examines on a regional level whether active labour market policies (ALMP) improve the matching process. To take the fact of heterogeneous search effectiveness during programme participation into account, we distinguish between current and former programme participants. Our findings based on a regional augmented matching function show that higher search effectiveness due to ALMP is not outweighed by indirect effects on nonparticipants. The total number of matches in a region increases with a higher share of former programme participants among the jobseekers. However, these effects largely differ between programme types. Abbreviation OECD (Organisation for Economic Co-operation and Development)ALMP (active labour market policy) [ABSTRACT FROM AUTHOR]

This study investigates how to design sensor systems in a way that responds to certain factors in the environment. This decision analysis problem focuses on sensor placement: how to place sensors to find an intruder that is affected by environmental elements. The sensors we use are of two types: the first type detects targets, and the second type detects elements in the environment. Techniques from the learning automata literature are used to develop a detection mechanism. The approach proposed in this study is dynamic, and can adjust to environmental variations. And its rate of detection exceeds static approaches, such as evenly spread sensor configuration. This work has implications for the design of any sensor system in which the physical environment shapes the probability of events occurring. [ABSTRACT FROM AUTHOR]

With advances in personalization technologies, websites are increasingly able to customize Web content and provide users with a unique experience. Prior research has focused more on the appeal of the personalized recommendations themselves and examined user behavior toward the personalized recommendations. However, prior research has not compared the total volume of users’ sampling activity on websites that offer personalization, compared to those that do not. This motivates our interest in an extended study ofthe totality of users’ sampling behavioron the website when personalized recommendations are present. Where prior work has focused on the amount of sampling of the personalized items themselves, we define two additional indicators that characterize a consumer’s sampling behavior on a website that has both stock and personalized items: (1) the total volume of sampling to include both stock and personalized items, and (2) the pattern of sampling between personalized and stock items. Based on consumer search theory (CST) and a simulation analysis, we propose hypotheses about consumers’ behavior on these expanded outcomes, and test them in a longitudinal field study. We find that subjects sample personalized items before stock items, and sample fewer items in total when personalized recommendations are available. In addition, subjects engage in less sampling as time goes on, across sessions. Theoretically, this research brings the CST perspective to the literature on website personalization. Practically, this research sheds light on the precise nature of the benefit and possible drawbacks of personalization from the merchant’s perspective. [ABSTRACT FROM PUBLISHER]

This paper uses a unique dataset about unemployment benefit recipients and their exits to employment in Estonia to investigate the effects of benefits on unemployment duration. Both nonparametric and parametric estimations show that unemployment benefits have a strong and significant disincentive effect on hazard rates to exit into employment, just as search theory predicts. The effects of benefits are stronger and more homogeneous when the maximum duration of unemployment insurance benefit is longer. The unemployed eligible for shorter unemployment insurance benefits are influenced more by the size of benefits and changes in the benefit replacement rate. Also, both for the unemployed with shorter benefit periods and for the unemployed with longer benefit periods a rise in hazard rates occurs during the benefit period and a sharp drop straight after. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to provide an analysis of the impact the Unemployment-Vacancy (UV) curve (or Beveridge curve) had on economic theory and to provide an account of the subsequent radical changes in its place and role over the decades since its first appearance in 1958. The paper traces the historical development of the UV curve and argues that the role of the UV curve has changed from that of a measuring device, to a graphical representation of full employment, to an axiom necessary for matching models of unemployment to a diagnostic tool. This changing role is best understood in the light of the paradigmatic change from Keynesianism to neoclassical search theory. [ABSTRACT FROM AUTHOR]

Search and Rescue (SAR) comprises the search for and provision of aid to persons who are, or who are feared to be, in distress or in imminent danger of loss of life. Time is a crucial factor for survivors who must be found quickly and search planning may get complex in the case of a large search area and multiple search resources. The problem we address in this paper is that of defining and assigning multiple non-overlapping rectangular sub-areas to search units (search aircraft) such that the search plan is operationally feasible and the total probability of success is maximized. We present algorithms we developed for the search resources allocation problem for aeronautical SAR incidents when multiple indivisible searchers are present. These algorithms are based on classical search theory and on constraint programming. We assume that the search effort is continuous and measured by track length, that the search object is stationary and that search is conducted in discrete space. We present experimental results for a realistic SAR case overland. [ABSTRACT FROM AUTHOR]

This article presents a formulation of information acquisition that uses search theory to evaluate the value of information. The value of information is the added utility from being able to choose from the available travel alternatives after having received the information. There are three main advantages to the formulation: first, it results in a parsimonious model of information acquisition and travel choice. Second, it enables the use of observed information acquisition behavior for the estimation of travel related parameters (e.g., value of time). Third, its parameters are easily interpretable. The formulation is tested using data from a multimodal travel simulator with information provision. Estimation results provide face validity to the formulation. Results indicate that travelers on non-business trips attach particular importance to mean travel times, whereas during business trips travel time variability also plays an important role. Also, it is found that travelers prefer information that adds previously unknown alternatives to their choice set over information that provides estimates for uncertain attributes of known alternatives. A substantial heterogeneity exists with respect to travelers' valuation of the costs and benefits of travel information. [ABSTRACT FROM AUTHOR]

The article presents comments on the sections published within the 2008 issue of "Journal of the Operational Research Society," which includes topic on economic optimization of off-line inspection procedures with inspection errors, a more general formulation of off-line inspection errors and an ordering policy for deteriorating items with allowable shortage and permissible delay in payment. It presents sets of mathematical propositions, proofs and explanations concerning the issues discussed in the journal.

A variable neighbourhood search algorithm that employs new neighbourhoods is proposed for solving a task allocation problem whose main characteristics are: (i) each task requires a certain amount of resources and each processor has a capacity constraint which limits the total resource of the tasks that are assigned to it; (ii) the cost of solution includes fixed costs when using processors, task assignment costs, and communication costs between tasks assigned to different processors. A computational study shows that the algorithm performs well in terms of time and solution quality relative to other local search procedures that have been proposed. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the location of several transfer points to serve as collector points for customers who need the services of a facility. For example, demand for emergency services by patients is generated at a set of demand points that need the services of a central facility (such as a hospital). Patients are transferred to a helicopter pad (transfer point) at normal speed, and from there they are transferred to the facility at increased speed. The general model involves the location of multiple transfer points and one facility. Locating one transfer point when the set of demand points and the location of the facility are known was investigated in a previous paper by the authors. In this paper, we apply the results of that paper to solve the problem when the location of the facility is known. Both minisum and minimax versions of the models are investigated both in the plane and on the network. [ABSTRACT FROM AUTHOR]

Human performance in a visual search task is generally measured by a cumulative probability distribution of locating a target in a given time period. In this paper, this cumulative probability function has been derived for two systematic search strategies, non-overlapping and overlapping; with both infinitesimal and finite defect length. Moreover, for the infinitesimal defect size case, economic models are derived under the assumption that the number of defects on the search line follows a one-dimensional Spatial Poisson distribution to determine the best inspection stopping time. This research first extends the typical infinitesimal defect size assumption to a finite defect length assumption. Then, it extends the single infinitesimal defect case to the case of random number of infinitesimal defects and develops economic models for two extreme systematic search strategies. [ABSTRACT FROM AUTHOR]

A search-theoretic model of housing demand is presented and evidence is found in its support based upon the 1995 records of 260 000 New Zealand (NZ) tenants eligible to have received an unrestricted housing subsidy. In the model, a unit increase in search costs is predicted to increase the optimal rent according to a factor proportion less than one while a unit increase in moving cost is predicted to decrease the rent. The factor-proportion increase in the rent, also a marginal propensity to rent, is around 21 NZ cents for every NZ dollar increase in search costs. The moving-cost decrease is supported by the rent effects of some indicative characteristics. The empirical findings are found to be stable across a range of applicable estimators including those that may have been needed to correct for censoring and reverse-causality. [ABSTRACT FROM AUTHOR]

In the capacitated p-median problem with single source constraint, also known as the capacitated clustering problem, a given set of n weighted points is to be partitioned into p clusters such that the total weight of the points in each cluster does not exceed a given cluster capacity. The objective is to find a set of p centres that minimizes the total scatter of points allocated to these clusters. In this paper, a (λ, μ)-interchange neighbourhood based on the concept of λ-interchange of points restricted to μ-adjacent clusters is proposed. Structural properties of centres are identified and exploited to derive special data structures for their efficient evaluations. Different search and selection strategies including the variable neighbourhood search descent with respect to p-nearest points are investigated. The most efficient strategies are then embedded in a guided construction search metaheuristic framework based either on a periodic local search procedure or a greedy random adaptive search procedure to solve the problem. Computational experience is reported on a standard set of benchmarks. The computational experience demonstrates the competitive performance of the proposed algorithms when compared to the best-known procedures in the literature in terms of solution quality and computational requirement. [ABSTRACT FROM AUTHOR]

This paper investigates the resource allocation problem of maximizing a strictly concave objective function under nested constraints on a weighted amount of resources. The resources are distributed in a multi-dimensional space and the distribution gives a planner some reward. The constraints on the resources are set in such a way that a weighted amount of resources is limited in each level of subspace as well as in the whole space. We call such constraints nested. The purpose of this paper is to devise efficient methods for an optimal distribution of resources under the constraints. For the concave maximization problem, first we derive necessary and sufficient conditions for an optimal solution and, secondly, propose two methods to solve the problem. Both methods manipulate the so-called Lagrangian multipliers and make a sequence of feasible solutions so as to satisfy all the necessary and sufficient conditions. Numerical examination confirms that the proposed methods perform better than some well-known methods of nonlinear programming in terms of computational time. [ABSTRACT FROM AUTHOR]

An essential component of the history of Operational Research (OR) in Britain is the institutional development of the discipline. In this respect, a defining element is the debate on the issue of professionalism, which took place within the Operational Research Society (ORS) in the later 1960s and 1970s. For the historian, the debate provides major insights into the composition of the OR community at a critical stage in its development following on the sustained expansion of ORS membership in the 1960s. As this article reveals, the proposed movement of the ORS from ‘learned society’ to ‘professional’ status proved to be a deeply divisive issue, with a hard core of ORS members, both academics and practitioners, combining to resist the recommendations of the contemporary ORS Council and the leading officers of the Society. The article focuses on the debates on what one protagonist viewed as ‘a festering sore’ in the history of the ORS. In this respect, it provides a prologue to a second article commenting on the origins and results of the recent decision of the ORS Council to establish a professional membership grade—‘Fellow of the Operational Research Society’. [ABSTRACT FROM AUTHOR]

This article analyzes the price dispersion for products observed on the Internet and reaffirms the existence of substantial price dispersion across e-tailers. Comparison of advertised vs. unadvertised products reveals that predictions of search theory on advertising effect are generally not confirmed in the Internet market. Comparison of multi-channel vs. pure-play e-tailers reveals that multi-channel retailers with established brands in physical stores command price premiums in most on-line markets but not in very competitive markets like books, CDs, and flight tickets. A model is developed that uses cross-site and in-site search as search cost variables, and range of product options, product description, and product demonstration as Web site service feature variables. It is used to test when search cost variables are more salient than service feature variables, and vice versa. The results show that whether a variable accounts for variance in prices differs from product to product. Some service features enable e-retailers to charge higher prices without losing competitiveness; others do not offer price advantage because they represent lower cost structures that allow e-tailers to charge lower prices to become more competitive. [ABSTRACT FROM AUTHOR]

A direct search method for unconstrained optimization is described. The method makes use of any partial separability structure that the objective function may have. The method uses successively finer nested grids, and minimizes the objective function over each grid in turn. All grids are aligned with the coordinate directions, which allows the partial separability structure of the objective function to be exploited. This has two advantages: it reduces the work needed to calculate function values at the points required and it provides function values at other points as a free by-product. Numerical results show that using partial separability can dramatically reduce the number of function evaluations needed to minimize a function, in some cases allowing problems with thousands of variables to be solved. Results show that the algorithm is effective on strictly C 1 problems and on a class of non-smooth problems. [ABSTRACT FROM AUTHOR]

In many real-world applications, the cost associate with maintenance could be very significant since the maintenance work is subcontract or repairmen have to make a special trip from some central place to carry out the work. The focus of this study is to optimally coordinate the maintenance schedule of machines to save the maintenance cost incurred, which is named as the maintenance scheduling problem for a family of machines (MSPFM). Before presenting our solution approach, we first review Goyal and Kusy's [Goyal, S.K. and Kusy, M.I., 1985, Determining economic maintenance frequency for a family of machines. Journal of the Operational Research Society , 36(12), 1125–1128.] model and their heuristic for solving the MSPFM. In this study, we conduct full analysis on the mathematical model for the MSPFM. By utilizing our theoretical results, we propose a new search algorithm that solves the optimal solution for the MSPFM very efficiently. Using 36,000 instances randomly generated, we show that our new search algorithm obtains better solutions than Goyal and Kusy's heuristic. [ABSTRACT FROM AUTHOR]

Modifications in the trial point generation scheme are suggested to the differential evolution (de) and the controlled random search (crs) algorithm to improve their performances. Each of the modified de and the crs algorithm uses two different point generation schemes. A probabilistic adaptation of point generation schemes in each of the algorithms is proposed. Localizations in acceptance rule and in trial point generation schemes are also suggested in the resulting de and the crs algorithm, respectively. Numerical experiments indicate that the resulting algorithms are considerably better than their original counterparts. Therefore, they offer a reasonable alternative to many currently available stochastic algorithms, especially for problems requiring ‘direct search type’ methods. [ABSTRACT FROM AUTHOR]

Nancy Cartwright views models as blueprints for nomological machines – machines that, if properly shielded, generate law‐like behaviour or regularities. Marcel Boumans has argued that we can look for devices inside models, which enable us to measure aspects of these regularities. Therefore, if models do produce regular behaviour (Cartwright), they might perhaps generate numbers about phenomena in the world, provided we can locate a good measuring device in the model (Boumans). How do they do this? Models are often understood to consist of internal principles and bridge principles. Both of these play a role in the measuring process. This paper suggests that we can understand the internal principles to be responsible for generating the regularities displayed by the model – and for many users of the model, this is sufficient use. The bridge principles (following Cartwright – ‘the real bridge principles’) are a matter of picking the right mathematical representation to make the model work with respect to some real world case at hand. These ‘real’ bridge principles may enable the model to generate numbers and so serve to make the model into a measuring device. This paper explores this construction of a measuring device of duration dependence of unemployment. Since search theory cannot be made operational for this purpose duration models, which model of the outflow process of unemployment with a Weibull function, are taken as a representation of reservation wage setting in search models. As I show, this Weibull function serves as a bridge principle to make a measure of the elasticity of response between unemployment benefit and duration of unemployment. It enables measurement to take place by modelling behaviour according to some assumptions, which operate as constraints. While this Weibull function serves this purpose, its assumptions are arbitrary rather than connected to theory, and measurements generated with this bridge principle turn out to be highly sensitive to its specification. The Weibull function does enable the model to function as a measuring device, but the lack of ability to make newly invoked unobservable variables operational makes it of dubious worth. [ABSTRACT FROM AUTHOR]

We investigate a two-sided, multi-stage search problem where a continuous search effort is made by one or more search units to detect a moving target in a continuous target space, under noisy detection conditions. A specific example of this problem is hunting for an enemy submarine by naval forces. So far, this problem has not been solved, because of the difficulty of predicting the target's behaviour. In finding promising routes for the search units, a heuristic has been developed. To obtain these routes, at every decision moment in time an optimal point to go to must be determined. This amounts to finding at every decision moment an optimum of a function that changes over time. [ABSTRACT FROM AUTHOR]

Presents information on a study that developed variants of a tabu search meta-heuristic for the Mix Fleet Vehicle Routing Problem. Effect of data management structure; Implementation of the tabu search algorithm; Comparison of the computational results.

Presents information on a study that proposed a probabilistic greedy search algorithm for combinatorial optimization problems. Evaluation of the approach for the set covering problem; Experimental results; Conclusion.

In a series of papers Andrew Oswald has suggested that since home owners are relatively less mobile across geographic locations than renters, regional home ownership rates are positively correlated with regional unemployment rates. This paper examines this hypothesis at the individual level. Search theory suggests that when a subset of the population is less mobile than others, this less mobile group (that is, owners) will have lower probability of employment, longer spells of unemployment and lower wages than more mobile renters. These hypotheses on inferior labour market outcomes for owners were tested using US Current Population Survey data as well as data from the Panel Survey of Income Dynamics. The empirical model suggests that these hypotheses are not supported by any of the tests. Home owners, conditionally or unconditionally, have better labour market outcomes than renters. [ABSTRACT FROM AUTHOR]

This study proposes two search models for multiple targets (random search and systematic search) in an unstructured search field, derived by generalizing search models for single target search. Whilst the probability of locating a single target in the random search model is typically exponentially distributed, the probability of locating multiple targets was found to be distributed hypo-exponentially. The systematic search model was extended from a piecewise-linear function for a single target to a piecewise-curve function for multiple targets. To test whether these search models could predict human search performance, first, visibility area in a fixation, a main component of search models, was investigated at various fixation durations. Sensitivity analysis of this data indicated that using short fixation duration and a small fixation overlap would produce better search performance. Next, the visibility area data was combined with the search models and compared to human performance on a free search field with three targets. The systematic and random models provided upper and lower boundaries of actual human search performance. Additionally, at the start of the search task for multiple targets, search performance was close to the systematic search model, while for late targets, performance approached the random search model. Observers may have changed their search strategy during this multiple-target visual search task. [ABSTRACT FROM AUTHOR]

This article analyses firms' efforts to find a suitable partner for a technology co-operation. Although more theoretical studies acknowledge that search costs are an essential part of transaction costs, empirical research on interfirm co-operation neglects searching. This paper explicitly addresses this lacuna. Hypotheses on the search behavior of firms are derived by applying considerations of transaction cost economics and arguments concerning the social embeddedness of firms to a search model widely used in economics. It is argued that on the one hand the problem potential of co-operation, which is determined by the co-operations volume and the involved relation-specific investments and uncertainty, affects the benefits a firm can gain from searching. On the other hand, the social embeddedness of a firm influences the costs of searching. Further, I consider the size and homogeneity of the pool of potential partners in the analysis. The derived hypotheses are tested on a dataset of 94 technology co-operations within five Dutch multinationals. The results clearly show that transaction cost economics does explain the search efforts of firms. In addition, I find evidence that the social embeddedness also affects searching. [ABSTRACT FROM AUTHOR]

This study was conducted to generalize from models of human performance in single target search to multiple target search. The specific issue was exhaustive search for the complete set of targets on a search field, extending the work of Chan and Chan from a two-target exhaustive search. Mathematical modelling was based on earlier derivations of search for the first of a set of targets. Model and simulation results showed three quite different relationships between mean search time and the number of targets remaining in a search field. The human search strategy for multiple targets was close to the systematic strategy for the first few targets and was close to the random strategy for the last few targets. Plotting mean search time for multiple targets against the number of targets remaining would be a useful and unique way to show human use of systematic search strategy. [ABSTRACT FROM AUTHOR]

A random visual search model was fit to 2980 search times obtained from a double-target search task. The overall adequacy and prediction accuracy of the model for various search time parameters like mean and median search times, and response times for both individual and pooled data show that subjects' search strategy may reasonably be inferred from search time distributions. The results also suggest the general applicability of the random search model for describing the search behaviour of a large number of subjects performing the type of search task used here, and the practical feasibility of its application for determination of stopping policy in optimization of inspection system design. Notwithstanding the general conformity of the data with the model, some extremely long search times were found, and this was accounted for by the characteristics of visual lobes, nonoptimum interfixation distances and inappropriate overlapping of lobes previously reported. An interpretation of temporal changes of subjects' search strategies during target detection was made by considering the cross-over phenomenon exhibited by the two cumulative detection percentage curves. [ABSTRACT FROM AUTHOR]

Focuses on a study that addressed the problem of minimizing makespan in a flow shop by using tabu search procedure. Information on flow shop scheduling problem; Tabu search technique; Alternative procedures for flow shop sequencing; Conclusions.