Charge storage behavior of isotropic and biaxially‐oriented polypropylene films containing α‐ and β‐nucleating agents

A study on the influence of the crystal modification (α and β) of isotactic polypropylene (i‐PP) films on the resulting electret properties is presented. Two commercial nucleating agents, sodium 2,2′‐methylene‐bis(4,6‐di‐tert‐butylphenyl)‐phosphate (NA11) and N,N′‐dicyclo‐hexyl‐2,6‐naphthalene‐dicarbox‐amide (NU100), were employed in this investigation. Isothermal charge decay was measured at 90°C. In hot pressed isotropic polypropylene films, no significant differences in the charge storage properties were observed for α‐ and β‐nucleated specimens. In addition, the article presents the influence of the nucleating agents at different concentrations on the PP‐film morphology of biaxially stretched films with respect to electret features. It was possible to prepare elongated cavities with the virtually insoluble NA11 additive during stretching, even at concentrations below 0.3 wt %. These films displayed slightly improved electret properties in comparison to stretched neat PP films due to generated cavities acting as barriers for the drift of charges. Various draw ratios were also studied for i‐PP films with 0.15 wt % NA11. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 650–658, 2006     

Sports analytics for professional speed skating

In elite sports, training schedules are becoming increasingly complex, and a large number of parameters of such schedules need to be tuned to the specific physique of a given athlete. In this paper, we describe how extensive analysis of historical data can help optimise these parameters, and how possible pitfalls of under- and overtraining in the past can be avoided in future schedules. We treat the series of exercises an athlete undergoes as a discrete sequence of attributed events, that can be aggregated in various ways, to capture the many ways in which an athlete can prepare for an important test event. We report on a cooperation with the elite speed skating team LottoNL-Jumbo, who have recorded detailed training data over the last 15 years. The aim of the project was to analyse this potential source of knowledge, and extract actionable and interpretable patterns that can provide input to future improvements in training. We present two alternative techniques to aggregate sequences of exercises into a combined, long-term training effect, one of which based on a sliding window, and one based on a physiological model of how the body responds to exercise. Next, we use both linear modelling and Subgroup Discovery to extract meaningful models of the data.     

Time-averaged concentration calculations in pulse electrochemical machining, spectral approach

Simulation of the species concentrations during the pulse electrochemical machining (PECM) process can provide information on system design and guidelines for practical use. In detailed numerical calculations, the concentrations will be calculated simultaneously with the temperature due to mutual dependencies. The pulses that are applied to the PECM system have to be described on a timescale that can be orders of magnitude smaller than the physical timescales in the system. If the full detail of the applied pulses has to be taken into account, the time accurate calculation of the variable distributions' evolutions in PECM can become a computationally very expensive procedure. A different approach is used by time averaging the pulses applied to the system. Performing this, the timesteps used during the calculations are no longer dictated by the pulse characteristics. Using this approach is computationally very cheap, yet satisfying results can be obtained. In the previous study of the authors (Smets et al., J Appl Electrochem 37(11):1345–1355, 2007 [8]), the hybrid calculation and the quasi-steady-state shortcut (QSSSC) were introduced. These methods introduce errors, however, which were quantified using analytical solutions and found to be acceptable. The results applied only to rectangular pulses. In this study, the more general case of arbitrary pulse forms is considered using a spectral approach. The concentration and the temperature calculation have different requirements for optimal approximated calculations, and a compromise has to be found between them. An analysis is performed on a simplified model, which provides useful guidelines during simulations.     

An application of the principle of minimal frustration to phase unwrapping

The problem of phase unwrapping (PU) and a new algorithm for the reconstruction of the absolute phase are presented. The PU problem is mapped to the problem of finding the global minimum of a non-equilibrium multistable system. A functional is introduced which consists of multiple constraints due to phase inconsistencies and the a priori knowledge on the regularization of the sampled wrapped phase signal. A self-annealing dynamics is used to find the state of minimal frustration of the system, where constraints on the phase signal are mostly satisfied. Experiments on a benchmark synthetic phase signal and on a real radar interferogram show the effectiveness of the proposed PU algorithm.     

The psychology of voice and performance capabilities in masculine and feminine cultures and contexts.

In this article, we examine the hypothesis that in masculine cultures or in other contexts that emphasize competitive achievement, those with higher performance capabilities will feel empowered to have input in decisions and, hence, will desire opportunities to voice their opinions about decisions to be made. In contrast, in more feminine cultures or in other contexts that value the importance of nurturing people with lower capability, those with lower capabilities will feel valued as important group members, will feel worthy of receiving voice and, hence, will appreciate voice opportunities. We provide evidence for these predictions in 2 studies, 1 conducted in the United States (a more masculine culture) and 1 in the Netherlands (a more feminine culture). Evidence also comes from experimental conditions in both studies, in which we made salient to participants countercultural norms and values, that is, nurturing the less capable in the United States and competitive achievement in the Netherlands. Implications for the psychology of voice and cross-cultural research are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A multilevel analysis of the demands–control model: Is stress at work determined by factors at the group level or the individual level?

This study explored the extent to which negative health-related outcomes are associated with differences between work groups and with differences between individuals within work groups using R. A. Karasek's (1979) demands–control model. The sample consisted of 260 employees in 31 working groups of a national bank in the Netherlands. Results suggest that job demands and job control should be conceptualized as having both group- and individual-level foundations. Support for Karasek's demands–control model was found only when these variables were split into the 2 parts, reflecting shared perceptions and employees' subjective assessment, respectively. One of the most appealing practical implications is that absence rates among homogeneous work groups can be reduced by enhancing actual control on the job. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of heat transfer on the sorption kinetics of complex hydride reacting systems

In this work, the effect of powder bed size on the absorption and desorption kinetics of NaAlH₄ catalyzed with TiCl₄ was studied experimentally. For this purpose, volumetric titration measurements were performed using cells of different diameters. The temperature was measured during the process at different positions inside the hydride bed, providing detailed information about the influence of heat conduction. Experimental results show that, under the applied conditions up to a critical size, larger diameters can lead to faster kinetics for the first and second absorption reactions. At larger cell diameters, however, temperatures up to 200 °C were measured during the first absorption step in the hydride bed. This leads to a significant delay in the start of the second absorption step, reducing the overall rate of the process. Reasons for the observed behaviour are discussed and measures for optimization are proposed.     

The Fundamental Neutron Physics Facilities at NIST

The program in fundamental neutron physics at the National Institute of Standards and Technology (NIST) began nearly two decades ago. The Neutron Interactions and Dosimetry Group currently maintains four neutron beam lines dedicated to studies of fundamental neutron interactions. The neutrons are provided by the NIST Center for Neutron Research, a national user facility for studies that include condensed matter physics, materials science, nuclear chemistry, and biological science. The beam lines for fundamental physics experiments include a high-intensity polychromatic beam, a 0.496 nm monochromatic beam, a 0.89 nm monochromatic beam, and a neutron interferometer and optics facility. This paper discusses some of the parameters of the beam lines along with brief presentations of some of the experiments performed at the facilities.