The impact of CCT on driving safety in the normal and accident situation: A VR-based experimental study

Correlated color temperature (CCT) of the light source inside the road tunnel plays a crucial role in ensuring driving safety, which is demonstrated by previous studies that CCT influences not only visual effects but also non-visual effects. Although conventional laboratory experiments could simulate the CCT environment inside the tunnel to some extent, they fail to restore driving experience, let alone simulate driving behavior in the accident situation. It has largely remained unclear whether and how CCT would influence visual/non-visual performance of the subjects who are performing driving tasks, especially in the accident situation. Motivated by this gap, a virtual-reality-based framework for assessing the influence of CCT on the visual and non/visual performance in normal driving situation and in accident situation was proposed. In this study, tunnel models under seven different CCTs were created and a rear-end accident was designed in the tunnel. By integrating analog driving equipment, all participants were required to perform virtual driving tasks both in the normal situation and in the accident situation. The non-visual performance (driving fatigue) and the visual performance (reaction time) of the participants were collected and analyzed. Results show that the CCT of light source inside the tunnel was significant on the driving fatigue of the driver who was performing driving task, and it also had a significant impact on the visual performance when the driver was faced with a rear-end accident. Detailed experimental methodology, behavioral explanations underlying these findings, validity of results and practical implications are also discussed in the paper.     

Teaching and Learning Crystal structures through Virtual Reality based systems

Teaching and learning through Virtual Reality(VR) is an emerging technology in the last few years. In this article, the development and use of a VR based teaching–learning system for crystal structures are discussed. The VR system is designed as a lab environment where a user can do experiments related to crystal structures. The VR system is designed in Unity,¹ and Oculus Rift S² is used as a VR headset. Currently, the system consists of three phases; in the first phase user can visualize the crystal lattice structures, wherein the second one a user can visualize the light interaction with the crystal lattice structure using a virtual torch ray. The third phase is the X-ray Diffraction (XRD) experiment. In this phase, users can perform the XRD experiment in the lab environment by taking a random crystal from a crystal dispenser machine and placing it in the X-ray machine which identifies the chosen crystalline material and analyses the unit cell. The incident ray colour changes when there is a peak found in the crystal for a better understanding of the user. There is also an interactive display where users can increase/decrease the angles of the radiation and also lock and unlock the experiment to view the diffraction plot for the crystal structure. In many cases, it was found that XRD and the crystal structure is available in the course syllabus but there are no experiments to enhance their learning. Therefore an experiment with 39 participants was performed where the maximum participants are new to crystallography. The study was conducted in two phases; in the first phase, participants are asked to watch video tutorials of the topic followed by questionnaires; in the second phase participants are asked to do the VR based experiment and followed by questionnaires related to overall study and experiment. From the analysis of the study we found that everyone found VR based teaching methods are better than traditional book/video studies. Study results give an average score of 56.74% in comparison to VR based learning approach with an average score of 93.81%. Participants who took part in the experiment found the experience interactive and motivating and found it helpful to learn elusive concepts, which can be learned when simulated. For example, one participant wrote: “The VR experience was surreal and was easy to control. Lucid user experience. Got a view of XRD like never seen before”.     

基于向量地址的数据中心网络数据面模型的研究

软件定义网络（Software Defined Network, SDN）是目前构建数据中心网络的一个研究热点,SDN可满足数据中心的集中管控、虚拟机部署与迁移等需求。但实现SDN优势的最大难题在于流量超大规模的优化问题,采用三态内容寻找存储器（TCAM）存储和查找流表带来了数据中心扩展性、成本和能耗的问题。为此,提出一种基于向量交换的数据中心数据面模型,即VADC(Vector Address Data Center),以一种源路由地址——向量地址（Vector Address,VA）作为数据包交换标签,VA定义了完整的通信路径。根据VA即可完成数据转发操作。VADC具有如下优点：（1）数据转发过程不再需要查表操作,交换机不必引入TCAM进行流表操作,解决了数据中心扩展性问题,交换机的复杂度和成本大幅度降低;（2）VADC简化了流的建立过程,新数据流建立时,无需下载流表至交换机,其消耗的控制信令数量约减少73%;（3）设计并实现了基于NetFPGA平台的VADC交换机,实验结果表明VADC交换机的硬件资源消耗约是OpenFlow交换机的28%。     

基于二分内包围盒的玉米光照逆光线跟踪算法

为了在玉米仿真中构建逼真有效的光环境,提出一种基于二分内包围盒的玉米光照逆光线跟踪算法。首先,在玉米表面建立二分内包围盒进行预处理,减少光线与玉米相交运算量;其次,引入遮挡因子简化光能计算的复杂度;最后,通过调整光能阈值达到光环境逼真度和算法效率的统一。为了验证算法的快速有效性,建立玉米模型,对比不同包围盒求交运算的速率,得出二分内包围盒的求交速度最快,逆光线跟踪算法模拟出的玉米生长效果较为逼真。     

Virtual network embedding based on real-time topological attributes

As a great challenge of network virtualization, virtual network embedding/mapping is increasingly important. It aims to successfully and efficiently assign the nodes and links of a virtual network (VN)...     

惯性矩二次变化变截面梁柱几何非线性分析

为研究考虑剪切变形的变截面梁杆结构几何非线性问题,应用Timoshenko梁理论,采用位移、转角独立插值的方法,获取考虑剪切影响的惯性矩二次变化变截面梁单元的形函数;从严格的虚功增量方程出发,建立同时考虑轴力、剪切、弯曲效应及其耦合项的平面变截面梁柱单元几何非线性增量平衡方程,得到惯性矩二次变化变截面梁单元大位移切线刚度阵;与经典算例进行对比,验证了本文方法的精确性与有效性．     

并联机床的历史、现状及展望

本文介绍了并联机床的基本概念、分类方法及其基本特性，详细地阐述了并联机床在国内外的发展历史、研究状况以及关键基础零部件的发展状况，在此基础上，分析了并联机床结构上的优缺点，表明了并联机床走向实用化所面临的一些问题，本文的最后对并联机床的发展趋势作了展望。     

基于Pro/E的原子滑车底盘虚拟设计技术研究

原子滑车作为一种大型的高空翻滚滑行游艺机，是一种吸引入的、冒险的、令人兴奋的娱乐形式，其设计是一个很庞大的系统工程。探讨了基于虚拟样机技术的原子滑车设计技术，介绍了用Pro/E软件对原子滑车底盘进行虚拟设计，构建产品的数字化模型，进行虚拟装配过程仿真。该技术的应用，缩短了产品的开发周期，提高了生产效率。     

Surface Reconstruction for Interactive Modeling of Freeform Solids by Virtual Sculpting

This paper presents a new method for surface reconstruction from dexel data for virtual sculpting. This is part of our research efforts to develop a dexel model based sculpting system with the capability of interactive solid modeling with haptics interface. Dexel data are converted to a series of planar contours in parallel slices (i.e. cross sections). Then triangular meshes are created by connecting the contour points in adjacent slices. Examples are given to demonstrate the ability of the described method to convert from dexel data to triangular meshes for the viewing of a sculpted model in different directions.     

虚拟样机技术在轴向柱塞泵仿真分析中的应用

固液耦合效果对柱塞泵运动学与动力学特性影响很大。利用有限元分析软件,建立柱塞泵刚柔耦合模型,在此基础上建立其固液耦合虚拟样机模型。仿真研究斜盘倾角、主轴转速对柱塞泵运动学和动力学特性的影响,以及柱塞腔内压力变化规律。结果表明:泵的出口流量及压力脉动幅值随斜盘倾角的增大而增大;柱塞加速度与主轴转速的平方呈正比,造成柱塞泵受到的液压冲击力急剧增大。研究结果为柱塞泵性能的深入分析提供了参考。