A bootstrapped robust data envelopment analysis model for efficiency estimating of telecommunication companies in Iran

One of the primary concerns in measuring the relative efficiency of a telecommunication unit compared with other similar units is the uncertainty on input/output data. In this paper, a bootstrapped robust data envelopment analysis (BRDEA) model is proposed to measure the efficiency of telecommunication companies. The proposed method is capable of handling different issues such as the uncertainty in data or sampling errors. The model is examined using some real data from a telecommunication company. First, the data from 24 telecommunication companies are assumed with uncertainty and the efficiency of telecommunication companies are estimated using a robust DEA model. Then, the results of the efficiencies are corrected by a bootstrapping technique. The results indicate that the BRDEA method considers the perturbation in data and sampling error with an adaptation of bootstrapped robust data envelopment analysis and could be more reliable for efficiency estimating strategies.     

On the Use of Spline Smoothing in Estimating Hedonic Housing Price Models: Empirical Evidence Using Hong Kong Data

Traditionally in estimating hedonic housing price functions, investigators use parametric models involving specific functional forms and a finite number of unknown parameters. Some investigators have questioned whether the underlying theory is capable of conveying sufficient information to enable a correct and successful specification of parametric models and have instead proposed the less restrictive semiparametric approach to the problem. In this paper, we illustrate how the technique of smoothing splines can be used to estimate hedonic housing price models. Smoothing splines are a powerful approach to the analysis of housing data as they are exceptionally flexible in their functional forms and provide a computationally tractable method even with a large number of explanatory variables. Our illustration takes the form of a rather limited, but very promising, application with Hong Kong data. In the forecasting comparison, the spline smoothing procedure outperforms the traditional parametric Box–Cox model in mean square error terms for out-of-sample predictions. Our results also suggest that the distortion caused by underfitting the model is smaller for spline smoothing than for the kernel and k-nearest-neighbor semiparametric procedures.     

Statistical precision of productivity change: A bootstrap application to Taiwan’s telecommunications industry

This study investigates the impacts of telecommunications policy on productivity change of the Chunghwa Telecom Company (CHT) from pre- to post-privatization. A three-stage method is employed to measure the productivity scores of CHT during the period 1966–2008. The Malmquist productivity index (MPI) is used in the first stage to assess the productivity of CHT. In the second stage, the statistical confidence intervals of productivity scores of CHT were obtained using the bootstrapping algorithm. Finally, the Chow test and multiple regression models were also utilized to investigate the impact of telecommunications policy on productivity change of CHT. Results of empirical examination indicate that on average TFP scores obtained by the bootstrapping technique are smaller than those obtained by the MPI technique. In addition, there is no difference in productivity change of CHT between pre- and post-privatization according to the MPI and bootstrapping MPI. The results show that the effect of privatization on productivity change is insignificant. Instead, the operational efficiency of CHT is affected by the government involvement in decision-making under its private/public joint ownership, which causes CHT to be a firm with little managerial profit orientation.     

Counterfeit, imitation, reverse engineering and learning: reflections from Chinese manufacturing firms

In a previous paper, we developed an alternative perspective on product imitation and innovation. In this paper, we explore some of our research questions using empirical data gathered in China. While we do not condone counterfeit activities, we explore the role of counterfeiting, imitation and learning from the perspective of Chinese manufacturers and provide insight from a small number of key informants about the motives and incentives for non-consensual acquisition of technology and their views on what Western firms should be doing to counteract the threat to their technological advantage. In this paper, we argue that where companies use the technology property of others to develop their own technology capability without the consent of the other party (non-consensual acquisition of technology), firms should consider whether there are opportunities for collaboration before resorting immediately to the legal tools at their disposal to enforce intellectual property rights and seek financial recompense from infringers without due consideration of the learning, new product development and innovation context. We believe that the findings from our case studies can make a significant contribution towards a better understanding of non-consensual acquisition of technology in an innovation context. In particular, the information gained from the key informants provides their perspective on the causes of non-consensual acquisition of technology and their views and recommendations of how companies affected by this behaviour might be able to better handle this problem.     

The telecommunications divide among Indian states

Using data for 16 major states in India from 2001 to 2015, this paper examines the patterns, distribution dynamics, and the drivers of telecommunications (telecom) services across different states. We apply both parametric and nonparametric econometric techniques to study the distribution dynamics of telecom services across the states. Further, we employ the generalised method of moment (GMM) to examine the determinants of telecommunications services in India. Our results indicate that the interstate gap in telecommunications services has been declining over time and there is a tendency for convergence in teledensity towards the national average. The regression analysis suggests that per capita income and network externality are significant determinants of teledensity across states in India. Furthermore, literacy rate and relative size of the service sector are independently significant predictors of teledensity. If we consider rural and urban areas separately, there are some important differences. For example, while the interstate gaps in telecom services in rural areas seem to have declined, there is little evidence of such a tendency in urban areas. However, the regression results with respect to the importance of per capita income and network externality for telecom services are robust to the rural-urban divide and to the inclusion of additional explanatory variables. The findings of this study have important policy implications.     

A note on constructive heuristics for the flowshop problem with blocking

This paper analyzes the minimization of the makespan criterion for the flowshop problem with blocking. In this environment, there are no buffers between successive machines, and therefore intermediate queues of jobs waiting in the system for their next operations are not allowed. As the problem is NP-hard, a constructive heuristic that explores specific characteristics of the problem is developed. The small computational effort of such strategy, which is valuable in practical applications, is one of the reasons that motivated this study. The performance of a combination of the proposed method with existing ones is examined through a comparative study. The new methods outperform the NEH algorithm, currently the best constructive heuristic for this problem, in problems with up to 500 jobs and 20 machines.     

Considering stochastic lead times in a manufacturing/remanufacturing system with deterministic demands and returns

In this paper we study a manufacturing/remanufacturing system with stochastic lead times and a constant demand. We base our approach on previous research in which we have developed models to describe an inventory system with stochastic lead times. In this paper, we first adopt this method to manufacturing/remanufacturing situations, where there are essentially two supply sources for replenishing serviceable inventory. We then provide a solution procedure when a cycle ordering policy is used. Secondly, we investigate the possibility to use a dual sourcing ordering policy in which each order is split between a manufacturing and a remanufacturing process. Finally, we compare the two ordering policies and illustrate how the lead-time patterns influence the economic consequences.     

ROBUSTNESS OF PRODUCTIVITY ESTIMATES*

Researchers interested in estimating productivity can choose from an array of methodologies, each with its strengths and weaknesses. We compare the robustness of five widely used techniques, two non‐parametric and three parametric: in order, (a) index numbers, (b) data envelopment analysis (DEA), (c) stochastic frontiers, (d) instrumental variables (GMM) and (e) semiparametric estimation. Using simulated samples of firms, we analyze the sensitivity of alternative methods to the way randomness is introduced in the data generating process. Three experiments are considered, introducing randomness via factor price heterogeneity, measurement error and differences in production technology respectively. When measurement error is small, index numbers are excellent for estimating productivity growth and are among the best for estimating productivity levels. DEA excels when technology is heterogeneous and returns to scale are not constant. When measurement or optimization errors are nonnegligible, parametric approaches are preferred. Ranked by the persistence of the productivity differentials between firms (in decreasing order), one should prefer the stochastic frontiers, GMM, or semiparametric estimation methods. The practical relevance of each experiment for applied researchers is discussed explicitly.     

A Comparison of Nonparametric Methods to Measure Efficiency in the Savings and Loan Industry

Using data on 1,360 savings and loan (S&L) institutions, we compare two non-parametric methods for measuring efficiency: data envelopment analysis (DEA) and algebraic methods based on Varian (1984). We show that both methods are vulnerable to measurement error, although both theoretically and empirically we find the Varian-style measures to be less vulnerable. Because we have data on the future insolvency of our S&Ls, we can directly compare the two methods by seeing which does a better job of predicting insolvency (working under the hypothesis that efficiency and insolvency should be negatively correlated). We find that various measures perform very similarly, except for the technical efficiency measure in DEA. Importantly, this last measure frequently yields the implausible result that efficiency and insolvency are positively correlated, possibly because it does not account for factor prices.     

Gender Differences in Sorting

In this paper, we investigate gender differences in workers’ career development within and outside the firm to explain the existence of gender wage gaps. Using Danish employer–employee matched data, we find that good female workers are more likely to move to better firms than men but are less likely to be promoted. Furthermore, these differences in career advancement widen after the first child is born. Our findings suggest that career impediments in certain firms cause the most productive female workers to seek better jobs in firms in which there is less gender bias.     

Bootstrapping the Malmquist indexes for Italian airports

This paper uses data envelopment analysis to assess the operational performance of 28 Italian airports during the period of 2000 through 2006. Recent developments in bootstrapping techniques are used to correct total factor productivity estimates for bias and to assess the uncertainty surrounding such estimates. This study found that the Italian airport industry experienced a significant technological regress, with few airports achieving an increase in productivity led by improvements in efficiency. Moreover, the paper shows that the form of ownership (public majority vs. private majority) of an airport management company does not significantly affect performance. In contrast, this type of the concession agreement has positive and significant effects on airport productivity. Finally, the paper highlights the existence of a productivity gap between airports located in the North-Central part of the country and those located in the south.     

湿球温度计算方法研究

电力设计中冷却塔的设计经常需要用到湿球温度这一参数,但是气象部门提供的气象数据缺少湿球温度参数,影响了工业冷却塔的设计优化。为了提高冷却塔设计的准确性以及计算效率,采用非线性曲面拟合方法以及二分法求解湿球温度,提供了拟合方法的详细公式以及二分法求解的源代码。在标准大气压下,两种计算方法的误差最小,气压越低,误差越大;相对湿度越高,两种计算方法的误差越小。计算结果表明,拟合法求得的湿球温度稍差,但能满足工程设计要求;二分法求解方法简便,精度高,计算源代码的可移植性高。研究结果可为相关工程设计提供参考,具有一定的实践意义。     

A COMPARISON BETWEEN TWO MULTIATTRIBUTE DECISION METHODOLOGIES USED IN CAPITAL INVESTMENT DECISION ANALYSIS

Two multicriteria decision methodologies applied to evaluating capital investments are the Analytic Hierarchy Process (AHP) and the Non-Traditional Capital Investment Criteria (NCIC) model. In this paper we demonstrate that a mathematical relationship exists between these two models. In-particular, a data set obtained by one method can be mapped into an equivalent data set obtained using the other method. It is suggested that this offers an opportunity of empirically assessing decision makers judgmental capabilities under varying data collection methods. An example problem illustrates the manner in which such comparisons can be made.     

普通圆柱蜗杆减速器的概率优化设计

本文对机械工程中最常用的普通圆柱蜗杆减速器,设计中所追求的目标:效率最大与润滑条件最佳(最大油膜厚度)和体积最小,提出了供优化设计用的数学模型。对三目标的非线性优化设计问题,采用了线性加权和的方法,其中加权因子系用像集方法算出。本方法特点是以主要传动零件的工作可靠性作为基本的设计原则     

基于百度指数的碳交易市场波动率的实证研究

碳交易市场波动率研究主要基于成交量数据对收益率GARCH效应的解释作用。在互联网时代可以有更新更为有效的方法来衡量碳交易市场的波动性。基于“碳交易”词条的百度指数,以湖北碳交易市场中的收益率为样本,本文通过对比使用引入成交量和搜索量的IGARCH（1,1）模型,实证研究发现传统的量价方程的确没有解释力,而百度指数可以对收益率的GARCH效应做出部分合理的解释,这可以在某种程度上反映湖北碳交易市场的交易信息流。     

两步法快速复原噪声模糊图像

本文提出了一种两步复原法,以用于复原被脉冲噪声干扰的模糊图像。第一步,对离群点进行识别,即那些疑似被脉冲噪声损坏的像素,并将剩余的像素视为基本非离群点。第二步,基于非离群像素,利用变分法对图像进行去模糊和去噪声。实验结果显示,使用该方法复原后图像的峰值信噪比dB值较采用典型变分法有所提高。     

From complexity to transparency: managing the interplay between theory, method and empirical phenomena in IMM case studies

Theory, method and empirical phenomena are the three cornerstones of research. In this paper we contemplate the interplay between them when case research in industrial marketing is concerned. Developments in research depend on what empirical phenomena we are able to capture, how theories are developed to understand and explain these phenomena and what methods we use and/or develop in the process. While the emphasis is often put on one of these aspects alone, this paper focuses on the links and interplay between theory, case method and empirical phenomena in the development of research in industrial marketing. Specifically, we seek to provide common ground between orthodox (deductive) and unorthodox (abductive) approaches to managing the interplay by making a pragmatic call for transparency in research procedures. In this endeavour we use the papers included in this special issue as examples of various aspects of this interplay. We conclude by suggesting that there is a gamut of approaches possible to case research in industrial marketing, each with its specific links to theory and empirical phenomena, and that this is promising for the development of research in the field, as long as it helps reduce, rather than increase, the complexity of the case studied.     

Supplier segmentation using fuzzy logic

Supplier segmentation means that the suppliers of a specific firm are categorized on the basis of their similarities. This supply-side business-to-business (B2B) segmentation is of special importance to companies with many suppliers. Supplier segmentation yields a manageable number of segments, each of which requires a separate strategy. Standard supplier segmentation methods have serious shortcomings, for instance because they fail to make a proper connection between supplier segmentation and other supplier-related activities such as supplier selection and development. Moreover, these standard methods typically use a limited number of segmentation criteria and different sets of criteria are suggested for each method. It is unclear for practitioners how to choose a particular method. The purpose of this paper is to form a practical tool for supplier segmentation taking into account all suggested segmentation criteria. The principal result of this paper is the design of a rule-based method to segment the suppliers of a firm based on two overarching dimensions: supplier capabilities and supplier willingness. The method is applied to a real-world situation to show how the results can be used in practice. A general sensitivity analysis procedure for fuzzy rule-based systems is proposed and then implemented, to identify the most important supplier capabilities and willingness criteria and to formulate better supplier development strategies. A major conclusion of the paper is that the fuzzy logic approach to supplier segmentation is simple to apply in practice, yet considers all available segmentation criteria and their inherent fuzziness in a way that is easily adaptable to a specific industrial context.     

A multiple ant colony optimization algorithm for the capacitated location routing problem

The success of a logistics system may depend on the decisions of the depot locations and vehicle routings. The location routing problem (LRP) simultaneously tackles both location and routing decisions to minimize the total system cost. In this paper a multiple ant colony optimization algorithm (MACO) is developed to solve the LRP with capacity constraints (CLRP) on depots and routes. We decompose the CLRP into facility location problem (FLP) and multiple depot vehicle routing problem (MDVRP), where the latter one is treated as a sub problem within the first problem. The MACO algorithm applies a hierarchical ant colony structure that is designed to optimize different subproblems: location selection, customer assignment, and vehicle routing problem, in which the last two are the decisions for the MDVRP. Cooperation between colonies is performed by exchanging information through pheromone updating between the location selection and customer assignment. The proposed algorithm is evaluated on four different sets of benchmark instances and compared with other algorithms from the literature. The computational results indicate that MACO is competitive with other well-known algorithms, being able to obtain numerous new best solutions.