Separating psychological momentum from strategic momentum: Evidence from men’s professional tennis

In dynamic contests, strategic momentum and psychological momentum potentially coexist, which makes it difficult to distinguish between the two. We employ the setting of professional tennis, which allows us to separate psychological from strategic momentum. In tennis, converting a break point potentially triggers both strategic momentum—due to a change in the relative position of the players—and psychological momentum—due to a change in the perception of the players. To distinguish between these two momentum types, we employ exogenously given interruptions. Interruptions are predicted to affect psychological momentum negatively, while leaving strategic momentum unaffected. Using 4930 game-by-game observations from 141 Grand Slam men’s single matches, we show that the breaking players’ probability of winning a game increases after converting a break point, which provides evidence for momentum. Moreover, we show that this momentum effect is negatively affected by an interruption. Thus, psychological momentum seems to be the main trigger leading to a performance increase after a converted break point.     

Estimation of system reliability for exponential distributions based on L ranked set sampling

Abstract

In the case where strength and stress both follow exponential distributions, this paper considers the maximum likelihood estimator (MLE) of the system reliability based on L ranked set sampling (LRSS). The proposed MLE is shown to have existence, uniqueness and asymptotic normality, and its asymptotic variance is obtained by the Fisher information matrix of LRSS. The values of asymptotic relative efficiencies show that the proposed MLE is always more efficient than the MLE using simple random sampling (SRS). However, the MLE using LRSS cannot be written in closed form. Therefore, the modified MLE is proposed using the technique replaced some terms in the maximum likelihood equations by their expectations. The newly modified MLE using LRSS is shown to be superior to the MLE using SRS. Finally, the proposed method is applied to a real data set on metastatic renal carcinoma study.     

Sensitivity Analysis for Critical Control Points Determination and Uncertainty Analysis to Link FSO and Process Criteria: Application to Listeria monocytogenes in Soft Cheese Made from Pasteurized Milk

Microbiological food safety is an important economic and health issue in the context of globalization and presents food business operators with new challenges in providing safe foods. The hazard analysis and critical control point approach involve identifying the main steps in food processing and the physical and chemical parameters that have an impact on the safety of foods. In the risk‐based approach, as defined in the Codex Alimentarius, controlling these parameters in such a way that the final products meet a food safety objective (FSO), fixed by the competent authorities, is a big challenge and of great interest to the food business operators. Process risk models, issued from the quantitative microbiological risk assessment framework, provide useful tools in this respect. We propose a methodology, called multivariate factor mapping (MFM), for establishing a link between process parameters and compliance with a FSO. For a stochastic and dynamic process risk model of in soft cheese made from pasteurized milk with many uncertain inputs, multivariate sensitivity analysis and MFM are combined to (i) identify the critical control points (CCPs) for throughout the food chain and (ii) compute the critical limits of the most influential process parameters, located at the CCPs, with regard to the specific process implemented in the model. Due to certain forms of interaction among parameters, the results show some new possibilities for the management of microbiological hazards when a FSO is specified.     

SALES AND COLLUSION IN A MARKET WITH STORAGE

Sales are a widespread and well‐known phenomenon documented in several product markets. This paper presents a novel rationale for sales that does not rely on consumer heterogeneity, or on any form of randomness to explain such periodic price fluctuations. The analysis is carried out in the context of a simple repeated price competition model, and establishes that firms must periodically reduce prices in order to sustain collusion when goods are storable and the market is large. The largest equilibrium profits are characterized at any market size. A trade‐off between the size of the industry and its profits arises. Sales foster collusion, by magnifying the inter‐temporal links in consumers' decisions.     

TRADE QUOTAS AND BUYER POWER,WITH AN APPLICATION TO THE E.U. NATURAL GAS MARKET

We consider a market in which domestic buyers negotiate contracts with foreign sellers, and explore how trade quotas can help to increase the buyers' countervailing power. We use the Shapley value to describe bargaining power and the distribution of the trade surplus in such a bilateral oligopoly. By exploiting strategic externalities among the buyers, bilateral trade quotas can improve the buyers' bargaining positions. In contrast, aggregate trade restrictions on all buyers' trade never improve buyer surplus. Minimum quotas on imports from fringe suppliers can benefit nonaffected buyers, as these enjoy positive externalities. We apply these insights to the E.U. market for natural gas and show that the effects of trade quotas on E.U. gas importers' power can be significant.     

基于股价预测的泛证券投资组合策略

本文基于期望效用最大化和L₁-中位数估计研究了在线投资组合选择问题。与EG（Exponential Gradient）策略仅利用单期价格信息估计价格趋势不同,本文将利用多期价格信息估计价格趋势,以提高在线策略的性能。首先,基于多期价格数据,利用L₁-中位数估计得到预期价格趋势。然后,通过期望效用最大化,提出一个新的具有线型时间复杂度的在线策略,EGLM（Exponential Gradient via L₁-Median）。并通过相对熵函数定义资产权重向量的距离,进而证明了EGLM策略具有泛证券投资组合性质。最后,利用国内外6个证券市场的历史数据进行实证分析,结果表明相较于UP（Universal Portfolio）策略和EG策略,EGLM策略有更好的竞争性能。     

Critical success factors in managing modular production design: Six company case studies in Hong Kong, China, and Singapore

Many researchers have explored the advantages of modular product design, its design methods and its effects on product performance. Modular design is, for example, required for product platform, mass customization and postponement in order to achieve greater product variety and differentiation. However, a few empirical studies explicitly examine how to coordinate modular product design in a managerial way. This paper addresses it by conducting multiple case studies with six companies which have successfully adopted modular product design for five years. Seven critical factors are explored in the management of modular product design. These are pre-defined product advantage, selectively used design rules, module definition, system integration, technological newness, internal communication, and supplier and customer involvement. While most of the literature studies the technical dimension of modular design within a firm, this study focuses on the managerial side across the supply chain. It gives new insights on how to manage modular product design and proposes future research opportunities.     

Output-Flexibilität in der Dienstleistungsproduktion

Zusammenfassung  Den Ausgangspunkt der überlegungen bildet die Interpretation von Dienstleistungen als Probleml?sungen, die eine M?glichkeit zur formalen Analyse der Output-Flexibilit?t er?ffnet. Im vorliegenden Beitrag werden in einer eigenschaftsorientierten Betrachtung zun?chst die Komponenten der Output-Flexibilit?t identifiziert, um dann darauf aufbauend ein Kalkül zur Gestaltung der Output-Flexibilit?t von Dienstleistungsunternehmungen abzuleiten.

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Summary  Output flexibility enables the service provider to cope with both uncertainties in demand and the external production factor. This paper aims at formulating a calculus for the design of output flexibility based on production theory. The interpretation of services as specific problem solutions serves as a basis for a feature-oriented modelling of service production.

Die Autoren danken zwei anonymen Gutachtern für wertvolle Verbesserungsvorschl?ge.     

Comparison of computer programs for simple linear L 1 regression

A number of efficient computer codes are available for the simple linear L ₁ regression problem. However, a number of these codes can be made more efficient by utilizing the least squares solution. In fact, a couple of available computer programs already do so.

We report the results of a computational study comparing several openly available computer programs for solving the simple linear L ₁ regression problem with and without computing and utilizing a least squares solution.     

近三十年新疆高校少数民族汉语教学研究述评

文章对1979年以来发表在新疆主要刊物和区外核心刊物中的423篇高校少数民族汉语教学研究论文进行了统计分析。在30年的发展中其成绩主要表现在研究基础不断扩大、研究论题走向广泛与细化、研究方法有一定的改进。而存在的主要缺憾是研究内容不深入、研究方法单一,定量和定性研究重视不够等问题。目前新疆高校少数民族汉语教育虽然有较大发展,但在教学上过度依赖对外汉语教学,在研究层次上仍处于相对较低的水平。