A Markov Model of Referral-Based Hiring and Workplace Segregation

I construct a Markov model of referral hiring to look at two issues: inequality between groups and workplace segregation. The model differs from most models of referral hiring in that it explicitly considers a firm structure where employment opportunities arise. The model suggests that referral hiring does not directly produce inequality between groups at the population level, even though firms have a bias toward hiring workers from the same group they already employ. The result highlights a difference between outcomes of referral hiring at the population and individual levels in that individual firm biases balance out when aggregated. However, referral hiring does produce segregation of groups across firms in a given industry, and the degree of segregation monotonically increases in the amount of referral hiring.     

Balancing attainability,desirability and promotion steadiness in manpower planning systems

A Markov manpower planning model with fixed internal transition probabilities, enables assessing the feasibility to attain the most desirable personnel structure. In case the desirable personnel structure is not attainable under control by recruitment, the internal personnel flows can be modified while not disrupting the career progression expectations. This paper introduces the promotion steadiness degree to quantify the personnel policy deviation from the career progression expectations. As a result, this paper focuses on a model that balances three criteria, that is, the desirability degree, the attainability degree and the promotion steadiness degree, formulated by fuzzy membership functions. A new set of instances is introduced, and the algorithms are evidenced in a set of experiments.     

Hidden heterogeneity in manpower systems: A Markov-switching model approach

In modeling manpower systems, it is of crucial importance to deal with heterogeneity. Until recently, manpower models are dealing with heterogeneity due to observable sources, neglecting heterogeneity due to latent sources. In this paper a two-step procedure is introduced. In the first step personnel groups homogeneous with respect to the transition probabilities are determined in a classical way by taking into account the observable sources of heterogeneity. In the second step heterogeneity caused by latent sources is handled. A multinomial Markov-switching manpower model is introduced that deals with heterogeneity due to latent sources for the internal flows as well as for the wastage flows. The model incorporates the mover-stayer principle. A re-estimation algorithm is presented to estimate the parameters of the Markov-switching manpower model. The switching approach offers a methodology to build a Markov model with personnel groups as states that are more homogeneous, and therefore can contribute to a better validity of the manpower model.     

Stochastic optimal control of internal hierarchical labor markets

This paper develops an optimal control model for a graded manpower system where the demand for manpower is uncertain. The organization's objective is to minimize the discounted costs of operating the manpower system, including excess demand costs. The stock of workers in various grades can be adjusted in two ways. The first method is outside hiring flows, which is the usual control variable used in previous research. The second method is to control the transition rates between grades of the hierarchy, an instrument not previously studied. Incorporating the transition rates into the control variables creates time lags in the control process. The resulting problem is solved numerically using an approximation for the time-lagged control variables. The numerical example is based on the Air Force officer hierarchy. The model is used to examine such issues as the desirability of granting tenure to workers who are not promoted to the highest grade and the effects of length-of-service and demand uncertainty on manpower policy.     

Optimal Tax Inspection Strategy

A game-theoretical model is constructed describing the interaction of tax inspectors with taxpayers. The models allows for tax evasion and bribing of inspectors. We find the primary and secondary audit probabilities that maximize the net tax revenue for various inspector hiring strategies. The comparative revenue statics is analyzed and the optimal hiring strategy is determined as a function of the model parameters.     

Modelling recruitment training in mathematical human resource planning

This paper deals with mathematical human resource planning; more specifically, it suggests a new model for a manpower‐planning system. In general, we study a k‐classed hierarchical system where the workforce demand at each time period is satisfied through internal mobility and recruitment. The motivation for this work is based on various European Union incentives, which promote regional or local government assistance programs that could be exploited by firms not only for hiring and training newcomers, but also to improve the skills and knowledge of their existing personnel. In this respect, in our augmented mobility model we establish a new ‘training/standby’ class, which serves as a manpower inventory position for potential recruits. This class, which may very well be internal or external to the system, is incorporated into the framework of a non‐homogeneous Markov chain model. Furthermore, cost objectives are employed using the goal‐programming approach, under different operating assumptions, in order to minimize the operational cost in the presence of system's constraints and regulations. Copyright © 2002 John Wiley & Sons, Ltd.     

Strategic workforce planning for the Australian Defence Force

This paper presents a mixed integer linear programming (MILP) model to aid in planning a large, hierarchically structured workforce. The workforce (eg, all Army commissioned officers) is classified by occupational group and rank and modelled in yearly intervals. Personnel and their movements are modelled as stocks and flows, subject to constraints representing employment conditions and resource limitations. The task is to estimate personnel numbers and flows so as to minimize a composite cost function. The model’s detailed fidelity to actual conditions, and hence its value in practice, clearly exceed previous efforts in the workforce planning domain. To overcome computational challenges that arose when an MILP solver was applied directly, the authors developed an iterative solution approach, which has yielded an attractive combination of solution quality and computational performance.     

Order Quantities with Temporary Price Reductions

The temporary price-change problem is studied, in which the objective is to minimize discounted cash flows. As pointed out by Goyal in an earlier paper, only the cash transactions at purchase times (i.e. the payments for the goods and the ordering costs) were considered. The cash flows associated with `inventory maintenance' costs which occur more or less continuously over time were neglected, which changes the structure of the model. Examples of these costs include storage, insurance, record-keeping, deterioration and obsolescence costs. In this paper, these continuously generated cash flows are included in the analysis, thereby making the new model more applicable to practical situations. This model is of interest because order-quantity decisions often must be made under conditions of both temporary price reductions and/or imminent price increases. These changes occur frequently in practice.     

The Dynamics of Cultural Influence Networks

This article investigates the behavior of cultural influence networks over time, using a computer simulation based on a formal model of cultural transmission in organizations. In the formal model, every organizational member exerts some cultural influence on, and is influenced by, every other member; these influence paths constitute a dense social network and the weights of paths (ties) vary throughout the network. Over time, each organizational member's enculturation level changes in response to influence from other members, and the influence weight of each path changes in relationship to the cultural similarity of the individuals connected by the path. Virtual experiments explore the configuration and evolution of the cultural influence network under varying demographic conditions and influence principles. Demographic effects are studied by varying organizational size, hiring selectivity and turnover rates. Two principles for determining initial influence path weights are examined, cohort-based influence and random influence. The simulations show that the cultural influence network evolves over time to a robust configuration, fluctuating around a stable dynamic equilibrium as individuals enter and leave the organization. As turnover rates rise, cohort-based influence strengthens the influence network and reduces network inequality. In this model, cohort-based influence processes promote cultural stability in organizations.     

Modeling of flow separation of assist gas as applied to laser cutting of thick sheet metal

The present paper describes the results of mathematical modeling of supersonic flows of a viscous compressible gas, obtained by numerically solving three-dimensional full Navier–Stokes equations, and also the results of experiments with visualization of gas jet flows in channels geometrically similar to the laser cut. Separation of the gas flow from the cut front is predicted numerically and then validated by experiments on a model setup. The gas flow structure arising in a narrow channel behind a sonic (conical) or supersonic nozzle is described. Specific features of originating in the flow separation on a smooth surface in a narrow channel are examined, and mechanisms controlling the separation are proposed. Flow separation directly affects the changes in the shape and structure of striations and is the one of main reason for the worse quality of the laser cut surface. It is shown that the changes in the structures of striations over the thickness of the sheet being cut are closely related to aerodynamic features of jet flows of the assisting gas in the cut channel.     

Modeling mixed push and pull promotion flows in Manpower Planning

Manpower Planning is a useful tool for human resource management in large organizations. Classical Manpower Planning models are analytical time-discrete push and pull models. Push models are characterized by the same promotion and wastage probabilities for people within the same group. This assumption is suitable in organizations where for instance promotions are used for reasons of personnel motivation or employees are promoted after succeeding in an exam. In many organizations, people are only promoted when there are vacancies at other levels. In those cases, pull models can be used. Pull models only assume known wastage probabilities. In practice, both assumptions may occur simultaneously. In this paper, a mixed push-pull model is developed for organizations in which both types of flows are considered.     

The augmented semi‐Markov system and its asymptotic behaviour

This paper suggests a generalized semi‐Markov model for manpower planning, which could be adopted in cases of unavailability of candidates with the desired qualifications/experience, as well as in cases where an organization provides training opportunities to its personnel. In this context, we incorporate training classes into the framework of a non‐homogeneous semi‐Markov system and we introduce an additional, external semi‐Markov system providing the former with potential recruits. For the model above, referred to as the Augmented Semi‐Markov System, we derive the equations that reflect the expected number of persons in each grade and we also investigate its limiting population structure. An illustrative example is provided. Copyright © 2010 John Wiley & Sons, Ltd.     

Markov models of occupational mobility: Theoretical development and empirical support. Part 2: Continuously operative job systems

This paper, consisting of two parts, presents an analysis of the current state of Markov model building for intragenerational occupational mobility. Part 1 examined models of careers; Part 2 analyzes models of continuously operative job systems. In Part 2 we find considerable predictive power for the simple MC model of personnel flows and the job vacancy chain model. Major analytical work has extended in two primary directions: the theoretical conceptualization of job vacancies to further explicate the underlying causal structure of mobility and the use of control theory to shift the focus to manpower decision making and policy formulation. Moreover, the diversity of job systems in which the models have been tested points to their general applicability.     

Influence of the approximation viscosity on the numerical solution of the problem on the accretion disk in a binary star system

We study the effect of the approximation viscosity of Godunov-type difference schemes in a model problem on the accretion disk in a binary star system. Computations are carried out by schemes of the first and increased approximation order. In the higher-order scheme, we take into account the viscous stress tensor, which is used to model the influence of the approximation viscosity observed in the first-order scheme. It is noteworthy that the approximation viscosity can lead to global qualitative changes in the flows to be modeled. The numerical results given in the paper are of independent interest in that they illustrate some new specific features of gasdynamic flows in this classical problem of modern astrophysics.     

基于修正转移概率矩阵的Markov方法在企业人才结构预测中的应用

预测企业人才结构的变化;修正转移概率矩阵的Markov预测方法;用修正转移概率矩阵的Markov模型针对人才结构进行定量预测与分析,对历史数据样本数量要求不多,并且计算简便;获取的计算结果更具客观性、真实性.     

Aerodynamic Interaction of Systems of Bodies in a Supersonic Flow

Use of numerical experiment methods gives broad opportunities for studying complex flows by rather simple and inexpensive means. This work is devoted to researches on aerodynamic interference of bodies in supersonic flows. Interest to similar problems is shown in a number of areas of modern mechanics: meteoritics, movement of multiphase media, applied fields. The head shock wave before a configuration of spheres with growth of distance h monotonously breaks up to individual shock waves before spheres of forward lines. The basic conclusion of this research is the following: distortion of supersonic stream around systems of bodies as though is transferred downstream, i.e. the influence of back bodies on the flow nearby forward bodies is small. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Optimal employment and wage policies of a monopolistic firm

This paper deals with the problem of finding optimal hiring/firing and wage policies for a profit-maximizing monopolistic firm. The crucial assumptions of the model are convex shortage costs permitting shortages in output capacity, nonlinear hiring and firing costs, and the wage rate as control variable being restricted by a minimal level. Due to the nonsmoothness of the revenue function occurring in the objective functional, a generalized maximum principle is required to analyze the optimal control problem. The resulting phase-diagram analysis provides an insight into the optimal recruitment, wage, and pricing policies.The authors would like to thank R. Hartl, E. Fehr, F. Hof, S. Jørgensen, R. Leban, N. Van Long, and R. Neck for helpful suggestions and comments to this and earlier versions of the paper.     

Numerical analysis of a mathematical model of the myocardial blood-supply system

A hydraulic model of the hemodynamics of the arterial part of the myocardium is considered, and a numerical analysis of the model is conducted. Computer experiments are used to investigate the dependence of blood flows on parametric and structural changes in the system. Translated from Prikladnaya Matematika i Informatika, No. 2, pp. 56–62, 1999.     

一种各向异性多重尺度的湍流模型

本文给出了一种适用于复杂湍流流动计算的各向异性、多重尺度的湍流模型(MS/ASM).这种模型对雷诺应力进行直接的模拟,并可模拟湍流流动的多重尺度影响.对自由应力流动、旋转流动和回流的湍流流动的计算表明,它比常用的单重尺度的k-ε模型有明显的改进.由于计算机工作量增加得不多,所以它在工程计算中,具有广泛的应用前景.     

基于生态学视角的科技人才效能发展程度和产出效率研究——来自我国30个省市的数据

基于生态学视角构建了科技人才效能评价指标体系,通过运用生态位模型和Malmquist指数分析了我国30个省市的科技人才效能的发展程度和产出效率,结果表明,第一,我国东部和中西部地区之间的科技人才效能呈现较为明显的区域性差异;第二,技术进步效率对我国30个省市科技人才效能全要素生产率具有较明显的影响,应该引起重视;第三,从分区域全要素生产率指数的变动情况来看,全要素生产率最高的为中部地区,其次为东部地区和东北地区,最低为西部地区.