Development of discharge-stage curves affected by hysteresis using time varying models,model trees and neural networks

Flow data forms the base on which much of the edifice of water management is raised. However, flow measurements are expensive and difficult to conduct. Therefore, the more accessible stage measurements are employed in combination with stage–discharge relationships. Setting up such relationships is often infeasible using traditional regression techniques. Two case studies are examined that show hystereses using various approaches, namely (1) single rating curves, (2) rating curves with dynamic correction, (3) artificial neural networks (ANN) and (4) M5′ model trees. All methods outperform the traditional rating curve. The presented approach that uses a dynamically corrected rating curve delivers accurate results and allows for physical interpretation. The ANNs mimic the calibration data precisely, but suffer from overfitting when a small amount of data is applied for training. The rarely used M5′ model tree's architecture is easier to interpret than that of neural networks and delivers more accurate results.     

The influence of flywheel weight and pedalling frequency on the biomechanics and physiological responses to bicycle exercise†

The physiological, subjective and biomechanical effects of altering flywheel weight and pedalling rate on a Quinton Model 870 bicycle ergometer were studied. Steel plates were added to the flywheel to increase its weight to 35·9 kg with a moment of inertia of 1·65 kg m². A 1·5 kg spoked wheel with a moment of inertia of 0·1 kg m² was used as the light flywheel. Eight subjects pedalled on two separate occasions for 6 min at 40, 50, 60, 70, 80 and 90 r.p.m. with workload levels representing 30 and 60% of their [Vdot]O₂max with each flywheel. Force plate pedals were used to measure the total resultant force on the pedals (F_R ) and the component perpendicular to the crank arm (F_T). A force effectiveness index (FEI) was denned as the average of F_T/F_R over a crank cycle. The result showed no statistically significant change (p<0·05) in [Vdot]O₂, heart rate and rating of perceived exertion of the FEI as a function of flywheel weight except for the [Vdot]O₂ at 50 r.p.m. for the light workload. As the r.p.m. increased from 40 to 90 r.p.m., the FEI decreased from 0·5 to 0·35 with the heavy load and from 0·36 to 0·22 with the light load. Measured physiological, subjective and biomechanical indices did not change significantly with flywheel weight. Increasing the pedalling rate caused a significantly less effective application of forces to the crank arm with only a small change in [Vdot]O₂.     

低压断路器电流参数选择的四要素

开关参数的选择是建筑供配电系统设计的重头工作,对低压断路器作参数选择时,要考虑繁杂的选择、设置、整定问题,往往使设计人员的操作很不顺手.本文以建筑供配电系统中用得最多,需要考虑的选择事项也最多的低压断路器为代表,将其选择理顺为四个方面,使得选择工作有序可循,不会漏项.     

Reliability and validity of Women's Health Initiative Insomnia Rating Scale.

The reliability and construct validity of the 5-item Women's Health Initiative Insomnia Rating Scale (WHIIRS) were evaluated in 2 studies. In Study 1, using a sample of 66,269 postmenopausal women, validity of the WHIIRS was assessed by examining its relationship to other measures known to be related to sleep quality. Reliability of the WHIIRS was estimated using a resampling approach; the mean alpha coefficient was .78. Test-retest reliability coefficients were .96 for same-day administration and .66 after a year or more. Correlations of the WHIIRS with the other measures were in the predicted directions. Study 2 used a sample of 459 women and compared the WHIIRS with objective indicators of sleep quality. Results showed that differences in the objective indicators could be detected by the WHIIRS. Findings suggest that a between-group mean difference of approximately 0.50 of a standard deviation on the WHIIRS may be clinically meaningful. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Environmental risk index: A tool to assess the safety of dams for leachate

Dams for leachate store very toxic substances that contain a large amount of organic material and, probably, heavy metals; they therefore constitute an important threat to the environment. Existing models of environmental risk assessment for landfills do not take into consideration the specific risk that leachate dams may represent for the environment. In this paper a methodology to improve the environmental safety is presented according to the parameters used in their construction and management. In order to do that, the following characteristics of the dam must be known: (1) geotechnical stability, (2) erosion of downstream slope, (3) type of sealing of the dam, (4) overtopping probability, (5) volume of leachate stored inside the dam and (6) pollution load of leachate. Once these parameters have been calculated, they are transformed by means of rating curves into homogeneous units, so as to make it possible to operate between them. From the study and analysis of these parameters an environmental risk index for a dam for leachate can be calculated. If the environmental risk index exceeds an established value then it involves a dam for leachate with high environmental risk, therefore preventive measures in its design, construction and management would be necessary.     

échelle d'évaluation des dimensions du comportement destinée aux parents: Sensibilité diagnostique en contexte scolaire.

Studied the diagnostic sensitivity of the French-Canadian version of the Behavior Dimensions Rating Scale--Parent form (BDRS-PF; M. Poirier et al, 1999) in the elementary school setting. The BDRS-PF, which is designed to support the screening and assessment of behavior problems in elementary school children, was administered to a clinical sample of 77 mainly male Ss (aged 5-13 yrs) with behavior problems who were screened in the school setting and to 1,175 normal male and female elementary school students in Canada. Sensitivity and specificity analyses and discriminant function analysis were performed. The results indicate that the BDRS-PF can adequately classify normal children and most children with behavior problems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

现有铁路钢桥的评估

对现有铁路钢桥进行一系列的动力试验、加速度测量、评估、有限元模拟和安全指数计算。采用专门列车进行动力试验,并获取动力参数。这些参数还可用于建立桥梁的有限元模型。如果模型能够反映实际工况,就能用于计算每种工况下桥梁结构的安全指数。这些安全指数可用于计算杆件的破坏可能性,因此可采用本模型评估桥梁的可靠性。通过了解现有桥梁结构的实际工况,本研究可为新的货运列车重级荷载研究提供可靠依据。     

探讨高校体育教学的改革和发展

通过对高校体育教学的现状分析,从适应社会发展的需要出发,探讨高校体育课的改革和发展。提出为加大高校体育课的改革力度,应该从教学指导思想、课程设置、教学模式以及教学评价几方面切实做好。     

基于Cortex-M4的电梯能耗综合测试仪研制

针对电梯能效评估现场作业实际需求及特点,研制了便携式电梯能耗综合测试仪。采用钳式电流互感器和电阻分压网络感测电参数,利用高性能计量芯片采集电梯电量参数,选用DGUS触摸屏实现人机交互,基于32位Cortex-M4和DSP内核架构,应用多任务处理机制,实现电梯能耗数据的采集与处理、人机交互控制、数据存储记录和能效智能评定。该测试仪具有集成度高、操作简便和功能多等优点,有利于提高能效测试准确性及效率,具有推广价值。     

构造移动P2P环境下的分布式信任模型

基于固定网络的信任模型缺乏对网络高度动态性的考虑,不能直接应用于移动P2P网络。本文利用节点的报文转发能力,提出了一种移动P2P环境下的分布式信任模型MobTrust。该模型通过分布式存储机制,将节点转发的评价数据备份于K桶中,扩充了评价数据的存储范围。同时,鉴于移动设备有限的计算能力,设计双反馈机制提高评价数据的可靠性,然后以轻量级的方式计算信任度。仿真结果表明,MobTrust能有效降低系统开销,并拥有较高的评价数据利用率和交易成功率。