173581 research outputs found
Sort by
基于行人落地碰撞的车辆前部结构参数分析
Get PDF在行人-车辆碰撞事故中,行人头部损伤不仅源于行人与车辆的一次碰撞,而且还有与地面的二次碰撞.为了综合分析车辆前部结构参数对一、二次碰撞中行人运动学及头部损伤的影响,本文在MADYMO中对车辆前部结构(挡风玻璃角度(WA)、发动机罩角度(BA)、发动机罩长度(BL)、发动机罩前沿高度(BLEH)和离地间隙(GC))进行参数调整,构建一系列行人-车辆碰撞多体模型,并采用多元线性回归方法分析车辆参数对行人运动学和头部损伤的影响.结果表明,一、二次碰撞中,BLEH对行人头部HIC值(车)和行人旋转角度的影响均最为显著(p<0.01),BA对头部角加速度(车)的影响较BLEH更为显著,WA、BL和GC对行人运动学与损伤的影响均较小.较低的BLEH对一次碰撞中行人头部的保护更好,但BLEH过低易导致二次碰撞中行人头部首先与地面碰撞,这会增大头颈部的损伤风险.本文定量分析了车辆前部结构参数对行人一、二次碰撞的影响,研究结果可为车辆安全性设计提供理论参考.国家自然科学基金资助项目(31300784,51675466);;国家外专局高端团队项目(GDT20173600037);;福建省科技创新平台项目资助(2016H2003)~
基于矢量螺旋推进舵的新型主动式减摇装置的仿真研究
Get PDF本文介绍了一种基于矢量螺旋推进舵的主动式船舶减摇装置,并在分析随机海浪的波能谱和波倾角以及船舶运动受力的基础上,建立了随机海浪的仿真模型,利用Matlab对海浪波倾角及有无减摇装置的船舶横摇运动进行了建模及仿真研究,研究表明该减摇装置具有可控性强、易改装的特点,能够提高船舶的耐波性。福建省海洋高新产业发展专项资金项目[2016]13
分层架构下智能电动汽车纵向运动自适应模糊滑模控制
Get PDF针对智能电动汽车(intelligent electric vehicles,IEV)的纵向控制在不确定性干扰下存在非线性、强时变特征,提出一种分层控制架构下的智能电动汽车纵向跟车运动自适应模糊滑模控制方法.根据经典理..
高精度齿轮副侧隙自动测量技术研究
Get PDF齿轮副侧隙是齿轮机械设计和齿轮啮合时的重要参数,为了提高齿轮副侧隙的测量精度,解决由于结构所限无法实现两个齿轮上同时安装圆光栅光电码盘作为角度传感器的齿轮副侧隙的测量问题,..
中小企业创新能力影响因素模型研究
Get PDF通过对福建省厦门市企业的调研和访谈,证实驱动并影响中小企业与大企业创新的因素存在差异。在此基础上,总结归纳影响中小企业创新能力的八要素,利用解释结构模型层次化分析各要素之间的作用机制,构建中小企业创新能力影响因素模型,揭示制约中小企业创新的核心要素是企业管理者、研发人员等创新人员。福建省科技厅软科学研究项目“福建省中小型企业绿色创新能力评价与激励研究”(2017R0098
高超声速飞行器多约束再入轨迹快速优化
Get PDF针对高超声速飞行器再入过程中面临测控区和绕飞区的再入轨迹设计问题,提出了一种基于Gauss伪谱法(GPM)的分段轨迹优化策略。将轨迹优化的一般最优控制问题转换为多段最优控制问题,进而将各段轨迹按Gauss伪谱方法进行离散化,将连续多段最优控制问题转换为非线性规划问题(NLP)进行求解。所得再入轨迹能够使得飞行器在满足各种约束条件的情况下成功进入测控区并且有效规避绕飞区,最终到达指定点。此外,本文综合考虑飞行器再入飞行的快速性和工程实用性,并提出了再入时间、弹道倾角以及航向角相关指标的加权性能指标,同时保证了轨迹规划快速、再入轨迹平滑以及控制量变化平缓等实际需求,提高了计算效率。仿真结果表明,本文所提出的分段优化方案能够快速规划出适应不同飞行任务的再入轨迹
超精密飞切机床结合面虚拟材料法建模及模态优化
Get PDF在超精密飞切加工中,机床自身的动态特性是引起加工表面微波纹的主导因素。为探究超精密金刚石飞切机床的动态特性及其对加工表面微波纹的影响机理,将虚拟材料法的结合面建模方法引入整机动力学模型中。进一步地,利用有限元分析软件进行整机的模态分析及优化。结果表明:相较于传统的弹簧-阻尼模型,该模型具有更高的综合精度。同时模态分析表明,机床固有频率为268 Hz的第五阶模态对加工尤为敏感,而通过适当增加结合面的结合刚度,可优化机床模态进而消除波纹提高表面质量。科学挑战计划(JCKY2016212A506-0504
A new indicator of hypoxia tolerance in abalone, developed based on heart rate fluctuations
Get PDFAbstract(#br)China is the largest producer and consumer of abalone worldwide, harvesting nearly 140,000 tons in 2016. Due to rising temperatures, intensive culture patterns, and other factors, hypoxia has become a serious problem for Chinese abalone aquaculture, especially in Fujian Province. A hypoxia-tolerant strain is needed for the sustainable development of abalone farming. However, it is problematic to evaluate hypoxia tolerance in abalone. Usually, the traditional analyses cause severe damages to the sampled individuals, possibly including disorders in gonad development or death and these samples could hardly be used for breeding. Here, it was found that abalone heart rates characteristically exhibited a sharp decline below a certain DO threshold, which can be referred to as the breakpoint of dissolved oxygen (BPDO). The BPDOs were sensitive to temperature – the higher acclimation temperature or experimental temperature would increase BPDO. To verify the utility of BPDO as an indicator of hypoxia tolerance in abalone, an acute stress test was conducted with 32 abalone individuals under severe hypoxia (~0.5 mg/L) and significant negative correlations between BPDO and attachment duration, and between BPDO and survival time were found. The BPDO method was advantageous, as it supported individual detection and survival, which allows the selection and retention of hypoxic-tolerant individuals for further genetic breeding. BPDOs at different temperatures also provide important references for abalone aquaculture
Adaptations to the mudflat: Insights from physiological and transcriptional responses to thermal stress in a burrowing bivalve Sinonovacula constricta
Get PDFAbstract(#br)Understanding physiological adaptations of organisms to temperature changes that characterize their habitat is the first step in predicting the putative effects of global climate change on population dynamics. Mudflats are an important part of the intertidal zone and experience extreme and fluctuating temperatures. Therein, species would be potentially susceptible to global warming. The present study explored physiological adaptations of burrowing species to life in an intertidal mudflat by analyzing the potential operative temperatures in the mudflat, and assessing cardiac performance and the transcriptional response to thermal stress by a typical burrowing bivalve, the razor clam Sinonovacula constricta in different thermal environments, mimicking conditions during low tides. Clams showed higher thermal sublethal limits in mud with overlying air than in mud with overlying water, indicating an adaptation to rapidly changing ambient temperatures and thermal environments during emersion. This sublethal limit was far above the maximum operative temperature in the actual habitat site and suggests a potential buffer zone to ensure survival under unexpected high temperatures, that could occur with global warming. In response to high temperature, S . constricta exhibited the common heat stress response by up-regulating expression of the Bcl2-associated athanogene 3 ( BAG3 ) and heat shock proteins to cope with the adverse effects of high temperature on protein homeostasis. Increased expression of key genes, including molybdenum cofactor synthesis 3 ( MOCS3 ), oligoribonuclease ( REX2 ), and NFκappaB inhibitor alpha ( NFIA ) may further remit the effect of thermal stress during the emersion period and delay a situation where clams reach their thermal sublethal limit, thereby helping to endure high temperature during low tide. These results clearly illustrate significant adaptations of a burrowing bivalve to life in intertidal mudflats at both physiological and molecular levels and can provide insights into potential physiological or evolutionary responses that could aid survival of mudflat species in a changing global climate