利用模板阴影体算法实现矢量数据在三维场景中的绘制

提出了一种基于模板阴影体算法的矢量数据绘制方法,实现了矢量数据在三维场景中的高质量实时叠加显示。由于该方法基于屏幕空间,所以具有像素级的精度,不会出现传统的基于纹理方法所产生的绘制走样现象;而且不受地形几何数据的约束,其执行效率与地形数据的复杂度无关,仅取决于矢量数据本身的复杂度。详细论述了基于模板阴影体算法矢量数据绘制的关键技术,并通过试验验证了该方法的有效性。     

网络测试中新方法的探讨

吞吐量是网络测试非常重要的测试指标。文中探讨吞吐量测试的1个新方法,该方法仅用2个端口便可实现对被测设备大量端口的吞吐量测试。此法不仅可以用于2层网络流量的测试,还可以用于3层IP网的测试,具有很好的现实意义。在第3层测试中需要通过VPN来实现IP包转发,测试可以实现跨接口卡的流量测试;应用证明,该方法不仅能测试吞吐量,而且能更好地实现多项综合测试,得到更真实可靠的数据。同时,该方法可以大量节约测试成本,具备多种优点,是1种值得在高校推广的测试方法。     

Closed-loop randomized kinodynamic path planning for an autonomous underwater vehicle

A randomized kinodynamic path planning algorithm based on the incremental sampling-based method is proposed here as the state-of-the-art in this field applicable in an autonomous underwater vehicle. Designing a feasible path for this vehicle from an initial position and velocity to a target position and velocity in three-dimensional spaces by considering the kinematic constraints such as obstacles avoidance and dynamic constraints such as hard bounds and non-holonomic characteristic of AUV are the main motivation of this research. For this purpose, a closed-loop rapidly-exploring random tree (CL-RRT) algorithm is presented. This CL-RRT consists of three tightly coupled components: a RRT algorithm, three fuzzy proportional-derivative controllers for heading and diving control and a six degree-of-freedom nonlinear AUV model. The branches of CL-RRT are expanded in the configuration space by considering the kinodynamic constraints of AUV. The feasibility of each branch and random offspring vertex in the CL-RRT is checked against the mentioned constraints of AUV. Next, if the planned branch is feasible by the AUV, then the control signals and related vertex are recorded through the path planner to design the final path. This proposed algorithm is implemented on a single board computer (SBC) through the xPC Target and then four test-cases are designed in 3D space. The results of the processor-in-the-loop tests are compared by the conventional RRT and indicate that the proposed CL-RRT not only in a rapid manner plans an initial path, but also the planned path is feasible by the AUV.     

Axial friction response of full-scale pipes in soft clays

The axial friction response of subsea pipelines in soft clays is a very important aspect for designers of subsea pipelines but the response is not well understood so far. There is a pressing need for the comprehension of the response. In this paper, model tests are performed using full-scale pipes coated with polyethylene (PE) to study the effects of the set-up period, the pipe diameter, the buried depth of the pipe, the shear strength of soft clays and the loading rate on the axial friction response of pipelines in soft clays. The variations of the axial friction coefficient are analyzed using the effective stress method based on model test results. The results show that the axial friction resistance increases with the increasing pipe diameter but the effect of the pipe diameter on the axial friction coefficient can be neglected. The ultimate axial resistance also increases with the increase of the buried depth of pipelines, the undrained shear strength of soft clays and the loading rate. The axial friction coefficient increases with the increasing loading rate. However, the axial friction coefficient decreases with the increasing buried depth. The method to determine the axial friction coefficient is developed by analyzing model test results, which considers the effects of the diameter, the buried depth, the undrained shear strength of soft clays and the loading rate. The study results not only extend the industry data base but also supply a basis to determine the axial friction coefficient of PE-coated pipes in soft clays for ocean engineering geological investigations.     

基于LabVIEW的自升沉式潜标模拟测试系统设计

自升沉式潜标正式布放使用前应进行大量的测试试验工作。为了能够在岸边或实验室对潜标的各项性能进行验证和调试工作,开发了基于LabVIEW的潜标模拟测试系统。该系统充分利用虚拟仪器的特点,采用模块化编程技术,利用软件模拟潜标在水下的各种运动状态及传感器感应的测量参数变化,或通过对现场测量数据的回放查找分析潜标系统本身存在的缺陷,实现潜标不下水或少下水就可以进行全面测试的目的。实验结果表明,利用模拟测试系统可以进行固定值、极值和连续变化值模拟,能够缩短设备开发周期,优化系统控制方案,对提高产品质量具有非常重要的作用。     

Impact Compressive Creep Characteristics of Simulative Soil for Deep-Sea Sediment

The impact load (equivalent impact height) applied to deep-sea sediment by a walking mining machine was first deduced by the energy conservation principle, and the simulative soil was prepared based on the deep-sea sediment collected from the Pacific C-C mining area. The self-designed impact compressive creep tests of the simulative soil were conducted under different ground stresses and impact heights, in order to determine impact compressive creep parameters using a K-H rheological model. Test results show that the impact compressive creep curves have three similar creep stages (transient creep, unstable creep, and stable creep) to static compressive creep curves, where the transient creep deformation and total deformation at the unstable creep stage decrease with the impact load. Among the three impact compressive creep parameters (K₁, K₂, β) of the simulative soil, K₁ is first increased with impact height and finally fluctuated to a certain stable value, while K₂ and β are approximately linearly increased with impact height. The maximum subsidence of the mining machine under a specific designed ground stress and walking velocity predicted by the impact compressive creep constitutive equation can be used for safety assessment of the mining machine.     

Geotechnical Hybrid Simulation to Investigate the Effects of the Hydraulic Conductivity on One-Dimensional Consolidation Settlement

Difficulties in the prediction of time-distribution of consolidation settlement will be introduced by using the Murayama test embankment case of Japan. In particular, it will be discussed why the prediction of consolidation rate is difficult in multi-layered soil with complex and variable mechanical properties like organic soil or peat. It can be inferred that uncertainties, which are embedded intricately in the consolidation problem as well as given ground condition, would be major causes for consolidation settlement. After that, the author focused on the movement of pore water under the various conditions of hydraulic conductivity in the soils, and how it can affect the time-distribution of the consolidation settlement. For the applied key methodology on the consolidation settlement problem, we propose the hybrid consolidation simulation controlling the movement of pore water with high accuracy and, finally, the aim of this article is to discuss the methodological approaches obtained by the study, including the basic concept and accurate movement of pore water under various conditions of soil layers and hydraulic conductivity.     

黄骅电厂取水河段取水特性的数模与物模研究

本文采用数值模拟与物模试验相结合的研究方法，详细地研究了黄骅电厂一、二、三期工程的取水特性。结果表明，现有河道只能满足电厂一期工程的取水需求；若将现有河道进行适当开挖，可以满足电厂三期取水需要。     

三传感器波浪水槽二次反射主动吸收方法

三传感器波浪水槽二次反射主动吸收方法是加拿大科学院水力中心最近开发的一种水槽反射波控制技术。该法在造波板前 1～ 2倍波长处布置 3个传感器 ,通过入反射波分离方法得到准确的入反射波参数 ,以此调整造波信号 ,有效地吸收由建筑物反射回到造波板的二次反射波。文中在分析波浪水槽二次反射吸收方法研究现状的基础上 ,介绍了加拿大水力中心对现有方法的改进及其效果     

FPSO甲板上浪研究现状

浮式生产储油轮（FPSO）是当今海洋石油开发的主流设施。FPSO通常采用单点系泊系统,船首暴露在波浪作用下,定位于特定海域进行长达数年的长期作业,上浪的风险很大。甲板上浪及其产生的载荷已是当前国际FPSO工程和研究领域的热点之一。介绍了国内外在试验研究和理论研究两方面对FPSO甲板上浪研究的进展情况,并建议我国开展这方面的研究。