Simulation of the mean zero-up-crossing wave period using artificial neural networks trained with a simulated annealing algorithm

The aim of this work was to develop a predictive model to forecast the mean zero-up-crossing wave periods (T _z ) for 3-hourly sea states at a location in the Pacific using artificial neural networks (ANNs). Seven multilayer ANNs were trained with a simulated annealing algorithm. The output of each trained ANN was used to estimate each of the seven parameters of a new distribution called the hepta-parameter spline proposed for the conditional distribution of T _z , given some mean zero-up-crossing wave periods and significant wave heights. After estimating the parameters of the distribution, the model was used to simulate and predict future values of T _z . Forecasting a sea state and developing the joint distribution of sea state characteristics with the help of the simulated characteristics are also discussed in this article.     

Biochemical composition of marine sediment from the eastern Weddell Sea (Antarctica): High nutritive value in a high benthic-biomass environment

Within the SCAR's international EASIZ programme, as part of the benthic–pelagic coupling experiment, grain size and organic matter contents in marine surface sediment were measured. Samples were taken during the austral autumn of 2000 from 3 regions in the eastern Weddell Sea: Kapp Norvegia, Four Seasons Bank, and Austasen.In general, sediments were fine sand with a grain size fraction < 200 μm representing more than 40% of the total weight. The sediments from Four Seasons Bank (64 to 107 m depth) were coarser than those from Austasen and Kapp Norvegia (209 to 480 m depth), presumably due to winnowing of fine sediment at shallow depths. Organic carbon (OC) content ranged from 0.25% to 1.2% and constituted 10% to 97% of the total carbon. The samples from Kapp Norvegia presented the highest OC values. Overall, protein (PRT), lipid (LPD), and carbohydrate (CHO) contents were similar to those in sediment from cold regions (e.g., the North Atlantic and the Ross Sea) but higher than those in sediment from other Antarctic and more septentrional regions (e.g., the Ross Sea and the Mediterranean). The difference within the Antarctic is explained through the local conditions in Terra Nova Bay and Kapp Norvegia. In the Antarctic, PRT and LPD carbon were the main contributors to the biopolymeric carbon (BPC). In the eastern Weddell Sea shelf, the BPC accounted for more than 90% of the OC in most of the samples. More than 82% of the total PRT, LPD, and CHO were present in the fraction < 200 μm. This work remarks the existence of sediments with a high nutritional value persistent several weeks after the spring–summer pulse of fresh organic matter. It is also highlighted the high potential availability of these sediments (due to its grain size) for the benthic communities inhabiting this high-latitude continental shelf.     

基于车激动力响应互相关指标的桥梁基础冲刷诊断方法

针对当前桥梁基础冲刷诊断和检测方法过程复杂、成本高且受环境影响大等问题，提出一种基于车激动力响应互相关指标的桥梁基础冲刷诊断方法。该方法通过桥墩和桥跨不同测点的纵向加速度响应自由衰减段信号的互相关分析，建立基础冲刷诊断指标体系，实现冲刷定位和均匀性诊断。首先，依据互相关函数幅值向量置信度判据指标进行基础冲刷初判；然后，通过响应互相关函数幅值向量因子变化率向量进行冲刷定位，再根据横桥向互相关函数幅值变化率向量诊断冲刷均匀性；并通过统计评估方法提高诊断精度；最后，结合1座连续梁桥算例进行多种冲刷工况的数值仿真分析，对所提方法的有效性和适用性进行验证。结果表明：该方法能够很好地实现基础冲刷的定位和均匀性诊断，指标具有较高敏感性；同时具有较好的抗噪性能，通过所提出诊断指标体系的综合使用可消除噪声对诊断结果的干扰。该方法具有诊断结果精度高、过程简便易行、无需进行复杂且误差较大的模态识别、允许试验测试参数和条件适量变化等优点，可嵌入常规桥梁荷载试验同步开展，具有很好的工程应用潜力和实用价值。     

Performance Design of an Exhaust Superheater for Waste Heat Recovery of Construction Equipment

Although fuel cost has been the largest portion of annual operating costs of construction equipment, it is possible to save the energy and reduce cost using fuel economy enhancement technology. In this study, an organic Rankine cycle is applied to an excavator in order to recover waste heat, reproduce it into electrical energy, and consequently reduce the fuel consumption by 10 %. A design process was carried out to develop an exhaust gas superheater that recovers the waste heat from exhaust gas through a composite-dimensional thermal flow analysis. A one-dimensional code was developed to perform a size design for the exhaust gas superheater. The ranges for the major design parameters were determined to satisfy the target of the heat recovery, as well as the pressure drop at both fluid sides. Performance analysis was done through onedimensional design code results, which were compared with three-dimensional CFD analysis. By utilizing a 3D commercial code, the arrangement of the tubes was selected and the working fluid pressure drop was reduced through a detailed layout design. The design procedure was verified by a performance evaluation of the prototype, which yielded only a 7 % tolerance in heat recovery.     

Research on the coefficient of sound absorption in turbid water

China’s coastal waters are turbid and the properties of the seabed are complex. This negatively impacts the performance of underwater detection equipment. The properties of sound absorption in turbid water are not well understood. In this paper, the coefficient of sound absorption in turbid water was measured by the reverberation technique. All work was done in a reverberation barrel made of seamless aluminum. First, pure water was poured into the reverberation barrel and its reverberation time measured. Next, various concentrations of turbid water were poured into the barrel and their reverberation time measured. After all data had been gathered, the coefficient of sound absorption in turbid water of different concentrations was calculated. From this we determined a law of sound absorption in turbid water as summarized in the paper.     

Comparative analysis of vehicle brake data in the ministry of transport test on the roller brake tester and on flat ground

This study performs a comparison between what occurs when braking on a Ministry of Transport (MOT) brake tester and on flat ground. The tire pressure is changed, but the other parameters remain constant. The results from this research and from the in-depth comparative study conducted by the mechanical engineering staff in the mechanical laboratory at the Miguel Hernández University in Elche have led to the following main conclusions: By varying the tire pressure, false results can be obtained with the MOT brake tester, which means that, if the tires are inflated at a low pressure but the brakes are in good condition, the vehicle will not pass the MOT. Conversely, if the brakes are in poor condition but the tire pressure is higher than what is recommended by the manufacturer, a false pass is produced. This article shows that the MOT brake testing equipment is often wrong and inexact, and the data and graphs presented prove that the tire pressure is a determining factor when assessing the condition of brakes.     

机车轴悬式电机悬挂齿轮副变形的三维有限元分析

本文用三维有限元方法对东风_4型内燃机车的整个牵引电机传动系统进行了计算。其计算模型利用假想的二力杆连接齿轮副的啮合点,人为地造成了均匀传递啮合力的力学条件,从而计算出了合理的齿轮修形量。     

An investigation of passenger interchange and train standing time at LRT stations: (i) Alighting,boarding and platform distribution of passengers

The train standing-time at a station is a determinant of the line capacity and the necessary fleet-size. Its determination is usually based on the assumption that boarding and alighting is uniform at all doors of a train. Uniform boarding and alighting is conceivable if passengers distribute themselves uniformly on station platforms while waiting for trains. The validity of the uniformity assumptions is tested using data from two stations (one CBD, one suburban) of the Calgary, Alberta LRT system. It is shown that passenger distribution on the platform, alighting and boarding is not uniform and is closely related to the location of platform access points. Some strategies that will encourage uniformity are discussed. However, procedures that can estimate the standing time for non-uniform boarding and alighting need to be developed.