Arbeitszufriedenheit und Energie

Focussing on energy as a highly activated affective state offers new opportunities to promote well-being at work and job performance. In this paper, I will describe current research on recovery, affective work events and characteristics of work tasks linked to energy. The practical implications for promoting energy at work are discussed.     

Organisation of new product development in Asia and Europe: results from Western multinationals R&D sites in Germany,India, and China

From research on Western new product development (NPD) practices a rich body of literature has emerged. However, the impact of country specific and cultural influences has not been examined in this context yet. This study is a first attempt to identify differences in NPD practices between Research and Development (R&D) subsidiaries in Germany, China and India within multinational companies. Data has been generated by qualitative interviews with R&D executives in those countries across multiple cases. The study samples strategic, organizational and operational aspects indicates definite differences in process coordination, rewarding systems, market orientation and the average age of NPD teams. Other aspects like strategic targets, the management involvement, etc. show rather slight differences across the countries. Hence, findings suggest that while some aspects are universally applicable across cultural frontiers, Western companies have to understand different expectations regarding NPD in India and China by adjusting practices accordingly.     

Influential factors and performance of logistics outsourcing practices: an evidence of malaysian companies

Despite the growing trend of logistics outsourcing, there are very limited sources of literature on logistics outsourcing, especially in determining the relationship between factors influencing outsourcing and the extent of logistics outsourcing practices. In this study, we tap into the field of strategic management to help clarify the mechanisms underlying the links between factors influencing, logistics outsourcing practices and outsourcing performance. A model based on the resource based view illustrates the hypothetical connections among these variables. The data gathered from the survey were analysed using SmartPLS software. A response rate of 21 % out of the 486 firms selected was achieved and fixed as the empirical data for this study. The results of this study provide support that superior performance is correlated to the resources of the firm. The analysis shows that lack of human and physical asset capabilities, as well as transaction uncertainty influence the extent of different logistics outsourcing practices. The four logistics outsourcing practices under study were found to have a positive relationship with logistics outsourcing performance, particularly strategic focus. This study shows that although theoretically firms aim at cost reduction by employing a logistics outsourcing strategy but not proven in this study because the financial benefit was only positively contributed by one of the four logistics outsourcing practices under study. Besides that, the results from this study also support that most firms outsource their non-core activities of the logistics practices to respond to the transaction uncertainty that their business experiences.     

<Emphasis Type="BoldItalic">MAD-STEC</Emphasis>: a method for multiple automatic detection of space-time emerging clusters

Crime or disease surveillance commonly rely in space-time clustering methods to identify emerging patterns. The goal is to detect spatial-temporal clusters as soon as possible after its occurrence and to control the rate of false alarms. With this in mind, a spatio-temporal multiple cluster detection method was developed as an extension of a previous proposal based on a spatial version of the Shiryaev–Roberts statistic. Besides the capability of multiple cluster detection, the method have less input parameter than the previous proposal making its use more intuitive to practitioners. To evaluate the new methodology a simulation study is performed in several scenarios and enlighten many advantages of the proposed method. Finally, we present a case study to a crime data-set in Belo Horizonte, Brazil.     

An adaptive-to-model test for partially parametric single-index models

Residual marked empirical process-based tests are commonly used in regression models. However, they suffer from data sparseness in high-dimensional space when there are many covariates. This paper has three purposes. First, we suggest a partial dimension reduction adaptive-to-model testing procedure that can be omnibus against general global alternative models although it fully use the dimension reduction structure under the null hypothesis. This feature is because that the procedure can automatically adapt to the null and alternative models, and thus greatly overcomes the dimensionality problem. Second, to achieve the above goal, we propose a ridge-type eigenvalue ratio estimate to automatically determine the number of linear combinations of the covariates under the null and alternative hypotheses. Third, a Monte-Carlo approximation to the sampling null distribution is suggested. Unlike existing bootstrap approximation methods, this gives an approximation as close to the sampling null distribution as possible by fully utilising the dimension reduction model structure under the null model. Simulation studies and real data analysis are then conducted to illustrate the performance of the new test and compare it with existing tests.     

Fast parallel $$\alpha $$-stable distribution function evaluation and parameter estimation using OpenCL in GPGPUs

\(\alpha \)-Stable distributions are a family of probability distributions found to be suitable to model many complex processes and phenomena in several research fields, such as medicine, physics, finance and networking, among others. However, the lack of closed expressions makes their evaluation analytically intractable, and alternative approaches are computationally expensive. Existing numerical programs are not fast enough for certain applications and do not make use of the parallel power of general purpose graphic processing units. In this paper, we develop novel parallel algorithms for the probability density function and cumulative distribution function—including a parallel Gauss–Kronrod quadrature—, quantile function, random number generator and maximum likelihood estimation of \(\alpha \)-stable distributions using OpenCL, achieving significant speedups and precision in all cases. Thanks to the use of OpenCL, we also evaluate the results of our library with different GPU architectures.     

Joint modeling of longitudinal and survival data with the Cox model and two-phase sampling

A common objective of cohort studies and clinical trials is to assess time-varying longitudinal continuous biomarkers as correlates of the instantaneous hazard of a study endpoint. We consider the setting where the biomarkers are measured in a designed sub-sample (i.e., case-cohort or two-phase sampling design), as is normative for prevention trials. We address this problem via joint models, with underlying biomarker trajectories characterized by a random effects model and their relationship with instantaneous risk characterized by a Cox model. For estimation and inference we extend the conditional score method of Tsiatis and Davidian (Biometrika 88(2):447–458, 2001) to accommodate the two-phase biomarker sampling design using augmented inverse probability weighting with nonparametric kernel regression. We present theoretical properties of the proposed estimators and finite-sample properties derived through simulations, and illustrate the methods with application to the AIDS Clinical Trials Group 175 antiretroviral therapy trial. We discuss how the methods are useful for evaluating a Prentice surrogate endpoint, mediation, and for generating hypotheses about biological mechanisms of treatment efficacy.     

Additive mixed effect model for recurrent gap time data

Gap times between recurrent events are often of primary interest in medical and observational studies. The additive hazards model, focusing on risk differences rather than risk ratios, has been widely used in practice. However, the marginal additive hazards model does not take the dependence among gap times into account. In this paper, we propose an additive mixed effect model to analyze gap time data, and the proposed model includes a subject-specific random effect to account for the dependence among the gap times. Estimating equation approaches are developed for parameter estimation, and the asymptotic properties of the resulting estimators are established. In addition, some graphical and numerical procedures are presented for model checking. The finite sample behavior of the proposed methods is evaluated through simulation studies, and an application to a data set from a clinic study on chronic granulomatous disease is provided.     

Variable selection in discrete survival models including heterogeneity

Several variable selection procedures are available for continuous time-to-event data. However, if time is measured in a discrete way and therefore many ties occur models for continuous time are inadequate. We propose penalized likelihood methods that perform efficient variable selection in discrete survival modeling with explicit modeling of the heterogeneity in the population. The method is based on a combination of ridge and lasso type penalties that are tailored to the case of discrete survival. The performance is studied in simulation studies and an application to the birth of the first child.