Application of nonperiodic phase structures in optical systems

Wide, nonperiodic stepped phase structures are studied to correct various parameter-dependent wave-front aberrations in optical systems. The wide nature of these phase structures makes them easy to manufacture with sufficient compensation of the wave-front aberrations. Wave-front aberration correction for both continuous and discrete parameter variations are studied. An analytical method is derived for the discrete parameter variations to find the optimal phase structure. Both theoretical and experimental results show that these nonperiodic phase structures can be used to make (1) lenses athermal (defocus and spherical aberration compensated), (2) lenses achromatic, (3) lenses with a large field of view, (4) lenses with a reduced field curvature, and (5) digital versatile disk objective lenses for optical recording that are compatible with compact disk readout.     

Experimental set-up for measuring diffusive and advective transport of radon through building materials

This study describes an approach for measuring and modelling diffusive and advective transport of radon through building materials. The goal of these measurements and model calculations is to improve our understanding concerning the factors influencing the transport of radon through building materials. To reach this goal, a number of experiments have to be conducted. These experiments, including measurements in a large cylinder for creating diffusive and advective transport of radon under controlled, 'dwelling-like' conditions, are described here and the initial results are presented. A better understanding about the transport of radon through building materials will lead to more effective ways to decrease or to prevent the entrance of radon into dwellings.     

An MMSE Estimator for Speech Enhancement Under a Combined Stochastic–Deterministic Speech Model

Although many discrete Fourier transform (DFT) domain-based speech enhancement methods rely on stochastic models to derive clean speech estimators, like the Gaussian and Laplace distribution, certain speech sounds clearly show a more deterministic character. In this paper, we study the use of a deterministic model in combination with the well-known stochastic models for speech enhancement. We derive a minimum mean-square error (MMSE) estimator under a combined stochastic-deterministic speech model with speech presence uncertainty and show that for different distributions of the DFT coefficients the combined stochastic-deterministic speech model leads to improved performance of approximately 0.8 dB segmental signal-to-noise ratio (SNR) over the use of a stochastic model alone. Evaluation with perceptual evaluation of speech quality (PESQ) shows performance improvements of approximately 0.15 on an MOS scale     

MAP Estimators for Speech Enhancement Under Normal and Rayleigh Inverse Gaussian Distributions

This paper presents a new class of estimators for speech enhancement in the discrete Fourier transform (DFT) domain, where we consider a multidimensional normal inverse Gaussian (MNIG) distribution for the speech DFT coefficients. The MNIG distribution can model a wide range of processes, from heavy-tailed to less heavy-tailed processes. Under the MNIG distribution complex DFT and amplitude estimators are derived. In contrast to other estimators, the suppression characteristics of the MNIG-based estimators can be adapted online to the underlying distribution of the speech DFT coefficients. Compared to noise suppression algorithms based on preselected super-Gaussian distributions, the MNIG-based complex DFT and amplitude estimators lead to a performance improvement in terms of segmental signal-to-noise ratio (SNR) in the order of 0.3 to 0.6 dB and 0.2 to 0.6 dB, respectively     

Can the distress-signal and arousal-reduction views of crying be reconciled? Evidence from the cardiovascular system.

Theorists have staked out two ostensibly opposing views of human crying as either an arousing behavior that signals distress or a soothing behavior that reduces arousal after distress. The present study examined whether these views of crying might be reconciled by attending to physiological changes that unfold over crying episodes. Sixty female students watched neutral and cry-eliciting films while autonomic physiology, including respiratory sinus arrhythmia and pre-ejection period, was assessed. Crying participants exhibited heart rate increases that rapidly subsided after crying onset. Crying onset was also associated with increases in respiratory sinus arrhythmia and slowed breathing. All crying effects subsided by 4 minutes after onset. It is possible that crying is both an arousing distress signal and a means to restore psychological and physiological balance, depending on how and when this complex behavior is interrogated. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Flow-Based Network Management: A Report from the IRTF NMRG Workshop

This is the report on the Workshop on Flow-Based Network Management, held within the 37th IRTF NMRG meeting, during IETF 93, on 24th July 2015, in Prague, Czech Republic. Following the tradition of the IRTF NMRG, the workshop focused on technologies, developments, and challenges of using flow-level traffic measurements for network management.     

On Taylor vortices and Ekman layers in flow-induced vibration of hard disk drives

This paper is about flow-induced vibration (FIV) of disks in hard disk drives (HDD) influenced by two classical flow structures in fluid dynamics, Taylor Couette vortices (TCV) and Ekman layers. FIV is computed with a fully coupled commercial aerodynamics/structural code. The emphasis is on FIV of disks and geometries under conditions typical for high speed, server HDDs. In typical server drives computational fluid dynamic (CFD) analysis predicts the occurrence of TCVs in the disk to shroud clearance. TCVs typically do not occur in mobile and desktop drives. The main controlling non-dimensional parameters are the Reynolds number, the Taylor number and the aspect ratio of the disk to shroud clearance. The existence of Ekman layers on the disk surfaces is persistent. The Ekman layers and their radial return flow interact in a complex manner with the flow in the disk to shroud clearance. The turbulent viscosity between shrouded disks results from “bursting” phenomena that are typical for the flow field near the disk rims and shroud. The details of a turbulent burst are presented together with its momentary disk excitation effect. The benchmark case used is a fully shrouded set of two disks with a disk to shroud clearance and a disk thickness to shroud aspect ratio such that TCVs occur in the disk to shroud clearance. The TCVs interact with the Ekman layers such that the outer TCVs are continuously destroyed and recreated. An example is presented of fully coupled FIV of a two-disk axi-symmetric benchmark case. The two co-rotating shrouded disks attract aerodynamically: they deflect statically inward. The results also show the dynamic disk deformation dominated by the disk (0,0) “umbrella” mode. In addition, there is random disk deflection caused by the turbulent bursting. At server drive conditions and a 70 mm diameter disk the peak to peak deflection is approximately 20% of the mean deflection. Three dimensional effects are also presented such as wavy TCVs. In another benchmark with a cavity the flow near unshrouded disk edges is shown. In that case the pressure fluctuations can be an order of magnitude greater than in shrouded regions.     

Games to Create Awareness and Design Policies for Transboundary Cooperation in River Basins: Lessons from the Shariva Game of the Mekong River Commission

International river basins cover a vast majority of the land surface, international cooperation is therefore important for the proper management, and to assure equitable and effective use in the basins. Key elements to improve international cooperation are common understanding of the issues in the basin, understanding upstream-downstream impacts and sharing a common vision for the future. This article focuses on the role of games in international basin cooperation to create awareness and to support policy development. The paper analysed the effects of the game in creating awareness and upgrading knowledge amongst water and related professionals and in designing procedures for cooperation in transboundary river basins. This was analysed during the implementation of the game with 28 participants from the four Lower Mekong countries. The impact on creating awareness and upgrading knowledge was evaluated through the use of questionnaires and pre- and post evaluation questions and for the design of policies, a SWOT analysis was used to evaluate the usefulness of the policies and frameworks as well as to identify possible improvements to the framework. The game implementation proved to be an appropriate tool to provide a practical way for stakeholders to become acquainted with the administrative and technical tools available in the Lower Mekong Basin. Pre- and post test shows that participants gained substantial knowledge on transboundary cooperation and use of tools. The game was part of a longer training programme addressing all the issues, however, the participants gained additional knowledge and insight by playing the game, well above what they had learned during the earlier training workshops. Playing the game proved an important aspect in training and education of such complex systems. The study also shows the role games can play in policy analysis, in particular the way the game provided insight in the design of the policy and the development of procedures, and their function to review and update policies and procedures. A number of recommendations have been made to strengthen the role in both training and education as well as in design of procedures.