Grounding and ground fault protection of multiple generator installations on medium-voltage industrial and commercial power systems - Part 3: Protection Methods Working Group Report

This paper discusses typical grounding practices and ground fault protection methods for medium-voltage generator stators, highlighting their merits and drawbacks. Particular attention is given to applications of multiple generators connected to a single bus. The paper also provides an overview of the generator damage mechanism during stator ground faults. Problem areas associated with each type of grounding are identified and solutions are discussed. The paper also provides a list of references on the topic. The paper is intended as a guide to aid engineers in selecting adequate grounding and ground fault protection schemes for medium-voltage industrial and commercial generators for new installations, for evaluating existing systems, and for future expansion of facilities, to minimize generator damage from stator ground faults. These topics are presented in four separate parts, Parts 1-4. Part 1 covers scope, introduction, user examples of stator ground failure, and theoretical basis for the problem. Part 2 discusses various grounding methods used in industrial applications. Part 3 describes protection methods for the various types of grounding and Part 4 provides a conclusion and bibliography of additional resource material.     

A branch and bound algorithm for numerical Max-CSP

The Constraint Satisfaction Problem (CSP) framework allows users to define problems in a declarative way, quite independently from the solving process. However, when the problem is over-constrained, the answer “no solution” is generally unsatisfactory. A Max-CSP \(\mathcal{P}_m = \langle V, \textbf{D}, C \rangle\) is a triple defining a constraint problem whose solutions maximize the number of satisfied constraints. In this paper, we focus on numerical CSPs, which are defined on real variables represented as floating point intervals and which constraints are numerical relations defined in intension. Solving such a problem (i.e., exactly characterizing its solution set) is generally undecidable and thus consists in providing approximations. We propose a Branch and Bound algorithm that provides under and over approximations of a solution set that maximize the maximum number \({m_{\mathcal P}}\) of satisfied constraints. The technique is applied on three numeric applications and provides promising results.     

基于树型结构网格矢量量化的点云渲染算法

针对3D模型海量点云数据存在的空间冗余问题,提出一种基于TSLVQ(tree structure lattice vector quantization)的静态点云有损渲染算法。算法旨在利用层级嵌套网格的集合,解决渲染低效的问题。首先对整个点云进行包围盒封装,多层量化,把数个较小尺度的截断包围盒嵌入到一个较高尺度的截断包围盒单元中,每一步量化过程采用8叉树方法将包围盒分割为八个最佳尺寸的空或非空小包围盒;最后在最高深度的层级里,用包围盒来代替整个小包围盒中全部的点。同时,算法可自行设定8叉树的深度,从而任意控制编码的复杂度和精度,满足渲染的实时性要求。实验结果表明,与现有的网格有损压缩算法相比,提出的算法能在保证模型重建精度的基础上具有较好的空间分解优势,实现实时渲染效果。     

A Novel Application-specific Instruction-set Processor Design Approach for Video Processing Acceleration

Application-specific instruction-set processors (ASIPs) provide a good alternative for video processing acceleration, but the productivity gap implied by such a new technology may prevent leveraging it fully. Video processing SoCs need flexibility that is not available in pure hardware architectures, while pure software solutions do not meet video processing performance constraints. Thus, ASIP design could offer a good tradeoff between performance and flexibility. Video processing algorithms are often characterized by intrinsic parallelism that can be accelerated by ASIP specialized instructions. In this paper, we propose a new approach for exploiting sequences of tightly coupled specialized instructions in ASIP design applicable to video processing. Our approach, which avoids costly data communications by applying data grouping and data reuse, consists of accelerating an algorithm’s critical loops by transforming them according to a new intermediate representation. This representation is optimized and loop parallelism possibilities are also explored. This approach has been applied to video processing algorithms such as the ELA deinterlacer and the 2D-DCT. Experimental results show speedups up to 18 (on the considered applications, while the hardware overhead in terms of additional logic gates was found to be between 18 and 59%.     

Comparison of the Acoustic and Mechanical Signatures of Two Cellular Crunchy Cereal Foods at Various Water Activity Levels

Cheese balls and croutons at various water activity levels (0·11–0·75) were compressed between parallel metal plates using a Universal testing machine and their acoustic emissions were recorded at compact disc quality (sampling rate of 44·1 kHz). The sound wave record (up to about 2 MB) had high intensity bursts at irregular intervals. These records were compressed after the background noise had been filtered out to produce files of less than 48 kB. The compressed signatures were characterised by their mean and peak amplitude, two measures of the sound emission intensity, and by the amplitude's standard deviation and the mean magnitude of the power spectrum, two measures of the acoustic signature complexity. All four parameters could be used to monitor the plasticisation effect of water. Although their magnitudes were correlated, they did not always change in unison upon moisture sorption. The standard deviation and mean magnitude of the power spectrum of the compressed acoustic signatures were only broadly correlated with their correspondents in the normalised mechanical signatures primarily because they were not determined from the same particles and because the latter, for technical reasons, were sampled at the low rate of 6 Hz.     

Energy and water metabolism, body composition, and hormonal changes induced by 42 days of enforced inactivity and simulated weightlessness

Inactivity causes profound deleterious changes. We investigated in eight healthy men the impact of a 42-day head-down bed rest (HDBR) on energy and water metabolism and their interrelationships with body composition (BC) and catabolic and anabolic hormones. Total energy expenditure (TEE), total body water, water turnover, and metabolic water formation were assessed by the doubly labeled water method 15 days before and for the last 15 days of HDBR. Resting energy expenditure was determined by indirect calorimetry, and BC was determined by dual energy x-ray absorptiometry. Urinary excretion of cortisol, GH, normetanephrine, metanephrine, urea, and creatinine were measured daily. HDBR resulted in significant reductions in body weight (2%), total body water (5%), metabolic water (17%), and lean body mass (LBM; 4%), but fat mass and water turnover did not change. Segmental BC showed a decreased LBM in legs and trunk, whereas fat mass increased, no significant changes were noted in the arms. The hydration of LBM was unchanged. TEE and energy intake decreased significantly (20% and 13%), whereas resting energy expenditure was maintained. Expenditure for physical activity dropped by 39%. Subjects were in energy balance during HDBR, whereas it was negative during the control period (-1.5 MJ/day). There were decreases in urinary normetanephrine (23%) and metanephrine (23%), but urinary cortisol (28%; weeks 2 and 3), GH (75%; weeks 2-4), and urea (15%; weeks 3 and 4) increased. It was concluded that during prolonged HDBR no relevant modifications in water metabolism were triggered. BC changes occurred in the nonexercised body segments, and the reduction in TEE was due to inactivity, not to LBM loss. Moreover, body weight alone does not accurately reflect the subject's energy state, and energy balance alone could not explain the body weight loss, which involves a transient metabolic stress.     

Vérification expérimentale de l'épaisseur du film pour des liquides non-newtoniens s'écoulant par gravité sur un plan incliné

The film thickness of twelve different polymeric solutions in a stable, laminar flow on a plane of known inclination has been measured as a function of the volumetric flow rates of the fluid. The theoretical value of the film thickness has been calculated using the Ostwald-de Waele model, neglecting any apparent slip at the wall. The results obtained from over 250 experimental determinations show that the film thickness can be predicted within 4% by using the Ostwald-de Waele model. However evaluation of the film thickness based on a Newtonian behavior with viscosity determined at the wall clearly indicates that the thickness is not much influenced by any variation of viscosity across the film. Hence the gravity flow along inclined plane surfaces is not a severe test of a rheological equation.     

Adaptive averaging for improved SNR in real-time coronary artery MRI

A technique has been developed for combining a series of low signal-to-noise ratio (SNR) real-time magnetic resonance (MR) images to produce composite images with high SNR and minimal artifact in the presence of motion. The main challenge is identifying a set of real-time images with sufficiently small systematic differences to avoid introducing significant artifact into the composite image. To accomplish this task, one must: 1) identify images identical within the limits of noise; 2) detect systematic errors within such images with sufficient sensitivity. These steps are achieved by evaluating the correlation coefficient (CC) between regions in prospective images and a template containing the anatomy of interest. Images identical within noise are selected by comparing the measured CC values to the theoretical distribution expected due to noise. Sensitivity for systematic error depends on the SNR of the CC (=SNR(CCmax)), which in turn depends on the noise, and the template size and structure. By varying the template size, SNR(CCmax) may be altered. Experiments on phantoms and coronary artery images demonstrate that the SNR(CCmax) necessary to avoid introducing significant artifact varies with the target composite SNR. The future potential of this technique is demonstrated on high-resolution (approximately 0.9 mm), reduced field-of-view real-time coronary images.     

Effect of tocopherols on the frying stability of regular and modified canola oils

A study was conducted to compare the relationship between frying stability and levels and degradation rates of tocopherols in regular and three modified canola oils. Oils were heated at 175 ± 2°C for a total of 72 h, with french fries fried intermittently. Frying stability was compared based on the rates of formation of free fatty acids (FFA) and total polar compounds (TPC). Significant differences (P<0.05) were identified between oils using analysis of covariance and t-tests for multiple comparisons. No significant differences were observed in the rates of FFA formation among the canola oils during frying. Nevertheless, regular canola (RCO) and high-oleic, low-linolenic acid canola (HOLLCO) oils produced less FFA compared to higholeic LLCO and HOCO both had significantly (P<0.05) faster rates of TPC formation compared to HOLLCO or RCO. HOLLCO with the highest level of tocopherols (893 mg/kg) exhibited a slow rate of degradation which accounted for a halflife of 48–60 h of frying. RCO, with a lower level of tocopherols (565 mg/kg), however, had the slowest degradation rate with a half-liofe of >72 h. In contrast, HOCO and LLCO with 601 and 468 mg/kg tocopherols, respectively, both exhibited a half-life for tocopherols of 3–6 h of frying. An inverse relatioship was observed between TPC formation and the reduction of tocopherol. Thus, the greater frying stability of RCO and HOLLCO appears to be affected far more by the rate of tocopherol degradation than by any changes in fatty acid composition.