Using the past to indicate the possible presence of relics in the present-day landscape: the Western Front of the Great War in Belgium

The First World War (WWI) had a notable influence on the landscape at the former Western Front in Belgium. Research on a landscape scale is necessary to understand the destructive and constructive impact of the war and its consequences for the post-war landscape in a holistic manner. This paper focuses on the trajectory and impact analysis of three study areas with contrasting landscape types and aims to indicate possible preserved military relics today. Therefore, landscape changes are studied using historical aerial photographs (WWI and WWII) and contemporary orthophotos. A military landscape characterisation is made based on land use/land cover and linear structures that were mapped throughout time. Specific landscape trajectories could be designated as areas with a possible preservation of WWI heritage, with a related impact degree. The results are useful for sustainable heritage management and for further interdisciplinary research on WWI-heritage, by providing a broad knowledge of the area.     

Environmental and food applications of LC-tandem mass spectrometry in pesticide-residue analysis: an overview

An overview is given on pesticide-residue determination in environmental and food samples by liquid chromatography/mass spectrometry/mass spectrometry (LC/MS/MS). Pesticides comprise a large number of substances that belong to many completely different chemical groups, the only common characteristic is that they are effective against pests. They still constitute a challenge in MS because there is no collective pathway for fragmentation. A brief introduction to the theory of tandem MS permits a discussion of which parameters influence the ionization efficiency when the ions are subjected to different actions. Emphasis is placed on the different tandem MS instruments: triple and ion-trap quadrupoles, and hybrid quadrupole time-of-flight (Q-TOF), including advantages and drawbacks, typical detection limits, and ion signals at low concentrations. The instrumental setup, as well as LC and mass spectrometric experimental conditions, must be carefully selected to increase the performance of the analytical system. The capacity of each instrument to provide useful data for the identification of pesticides, and the possibility to obtain structural information for the identification of target and non-target compounds, are discussed. Finally, sample preparation techniques and examples of applications are debated to reveal the potential of the current state-of-the-art technology, and to further promote the usefulness of tandem MS.     

广州新白云机场货运站大面积特殊地坪施工

介绍了库区超大面积钢纤维混凝土结构层、骨料耐磨面层一次成型的特殊地坪综合施工技术以及施工中为防止地坪沉陷而采取的相应技术措施。     

Distributed fiber optic monitoring of a CFA pile with a central reinforcement bar bundle

In this paper, we present an application of distributed fiber optic sensor (DFOS) technology to measure the strain of a continuous flight auger (CFA) test pile with a central reinforcement bar bundle, during a static load test carried out in London. Being distributed in nature, DFOS gives much more information about the pile performance as compared to traditional point sensors, such as identifying cross-sectional irregularities or other anomalies. The strain profiles recorded along the depth of the piles from the DFOS were used to calculate pile deformation (contraction), shaft friction, and tip resistance under various loads. Based on this pile load test, a finite element (FE) analysis was performed using a one-dimensional nonlinear load-transfer model. Calibrated by the shaft friction and tip resistance derived from the monitored data, the FE model was able to simulate the pile and soil performance during the load testing with good accuracy. The effect of the reinforcement cage and central reinforcement bar bundle were investigated, and it was found that the addition of a reinforcement cage would reduce the pile settlement by up to 20%.     

Simulation of oil spills near environmentally sensitive areas in Egyptian coastal waters

Oil spills in Egyptian coastal waters have a direct impact on the national economy because of the potential environmental damage, and the corresponding negative effect on tourism. Computer simulations of oil spills were performed for four environmentally sensitive areas along Egyptian coasts using an existing oil spill model that incorporates the important variables and processes affecting oil transport in seawater. The expected slick trajectory and variation of oil properties with time were calculated for a proposed spill scenario at each site. Water current maps, the most critical model input parameter with respect to spill trajectory, were developed for each location. The simulations demonstrated that the most important oil property affecting spill response decisions and operations is the emulsion viscosity, in that it indicates when, where, and how responders can intervene for cleanup.     

四足机器人腿部运动空间和足端运动轨迹研究

机器人的单腿的运动空间及足端点运动轨迹决定了所设计的机器人的应用范围。为了研究四足步行机器人摆动腿在一定参数条件下的运动空间大小及足端的运动轨迹,通过对机器人摆动腿正运动学方程,足端点轨迹在y、z轴上对时间的函数进行计算,并将计算结果运用MATLAB软件进行仿真,不仅直观地观测到机器人的运动情况,还得到所需的数据,且以图形的形式显示出来,达到了预期目的。     

一种用于控制工业机器人运动轨迹误差的观测控制策略研究

为了提高工业机器人运动轨迹的控制准确度,提出一种运动误差观测控制策略。分析机器人的组成结构,明确其工作原理。建立工业机器人的坐标系,并在该坐标系上求取机器人连杆间坐标系的变换矩阵;利用连杆间坐标系的变换矩阵,得到机器人末端执行器的运动学模型。以机器人的测量运动误差为依据,联合工业机器人的标称正向运动学模型,求取传感器架以及标称架与底座之间的变换模型;通过该变换模型,计算传感器架相对于标称架之间的位置向量及动态误差变换矩阵,得到测量运动误差值;通过测量运动误差值,构造运动误差观测器,用于获取机器人的估计运动误差,并将估计运动误差联合神经网络控制器,以实现对机器人运动轨迹的准确控制。利用此方法和滑模控制策略对平面和空间标定运动轨迹进行追踪,结果显示：此方法能准确地对平面和空间标定运动轨迹进行追踪,而且与滑模控制策略相比,此方法的追踪精度提高了34.25%。说明此方法能对工业机器人的运动轨迹进行精确的控制。     

3自由度柔索并联机构的运动轨迹规划

首先基于3自由度柔索并联机构模型,通过对索端重物进行正、逆运动学分析找到重物位置坐标与索长输入的相互关系。在此基础上,运用达朗贝尔原理推导出各柔索索端拉力与重物位置及柔索长度之间的关系。此过程中建立的非齐次线性方程组,证明了其具有无穷多组解,并采用广义逆矩阵的相关理论求解获得该方程组的最小范数解,即任意一时刻索端拉力的最优解;然后,在满足约束条件的前提下,寻找该并联机构的工作空间,即重物运动轨迹的范围。最后,对重物实现空间螺旋线轨迹进行了仿真,结果表明该机构能使重物的运动满足轨迹要求并具有较好的平稳性。仿真结果也为后续的对实现重物按规划轨迹运动的机构控制提供了理论基础。     

承压设备的超声检测技术

系统介绍了承压设备的超声检测技术的发展概况。较全面地展示了传统超声检测技术的应用领域,综述了超声衍射时差技术、空气耦合技术和超声导波技术等超声检测新技术的最新研究成果。最后,讨论了承压设备的超声检测技术的发展方向。     

选区电化学沉积快速成型轨迹规划

数控选区电化学沉积快速成型是将快速成型技术与电化学沉积技术相结合的一种新型快速成型方法。为保证数控选区电化学沉积快速成型的零件精度,提出了一种基于电化学沉积技术的快速成型工艺的路径生成算法。结合该成型工艺的特点,分析了快速成型领域常用的几种扫描方式,轨迹规划方案分为STL切片处理、轮廓偏置、轮廓填充、数控加工代码生成四个过程,提出了平行交错往复间隙填充法。实验表明该轨迹规划能够达到选区电化学沉积快速成型的要求,制造出高精度、高表明光洁度的零件。