基于GPGPU的Lattice-Boltzmann数值模拟算法

对Lattice Boltzmann方法(LBM)在GPGPU下的建模和算法进行了一系列研究,使得该方法在GPU下的计算加速比提升,大大缩短计算过程的时间消耗.重新设计了GPU的计算流程,在舍弃pixel buffer离屏渲染的同时,采用最新的帧缓存对象,多重纹理、多通道渲染和乒乓技术来设计一套基于方腔的LBM数值模拟程序,最终使GPU的计算时间缩短到CPU计算时间的六分之一.     

一种索穹顶结构初始预应力分布确定的新方法—预载回弹法

对索穹顶结构初始预应力分布的确定进行了研究,提出一种新方法—预载回弹法。该方法首先对索穹顶施加一个预设荷载,提取有利于抵抗预设荷载的内力分布。将该组内力作为预应力施加至结构上,并撤除预载,使结构回弹,通过两阶段变弹性模量迭代计算,收敛后可获得索穹顶结构的整体可行预应力分布。该方法通过施加对称荷载,即可自动实现单元的分组,便于整体可行预应力的判定,并可直接获得多自应力模态结构的优化初始预应力分布。通过算例证明预载回弹法具有很高的精度、较快的收敛速度,求得的整体可行预应力分布直接适用于实际工程应用。     

双缓冲腔环形间隙对凿岩机缓冲系统动态特性的影响

分析了液压凿岩机双缓冲系统的结构特点,应用孔口节流理论确定了缓冲活塞的静平衡位置,基于应力波传递原理得到了缓冲活塞的回弹速度,考虑油液的压缩特性推导出一级缓冲腔压力公式,由间隙流量公式得到了二级缓冲腔压力,在此基础上建立了缓冲活塞的运动微分方程.应用Matlab工具对双缓冲系统的动态特性进行了仿真,分析了不同环形间隙下缓冲活塞的运动规律,探讨了环形间隙对一级和二级缓冲腔压力的影响.提出与环形间隙和活塞最大行程的比值相关的间隙行程系数η.仿真结果表明,间隙行程系数与双缓冲系统的特性密切相关,存在最优范围.搭建了实验台,通过实验对缓冲系统的数学模型进行了验证.     

工程检测中回弹法测强不确定性影响因素分析

 建筑施工领域中,常采用回弹法对混凝土进行无损检测,以确定其强度指标。但近几年来,越来越多地出现关于回弹法检测混凝土强度不确定性的争议。在研究利用回弹法测定混凝土结构实体强度的基础上 , 从混凝土强度与硬度的关系、用碳化深度修正回弹值换算强度的偏差、养护条件的影响及 JGJ/T23 2001 规程有关规定方面,对现行工程检测中回弹法测定混凝土强度不确定性影响因素进行了分析,旨在不断完善回弹法在混凝土构件强度检测中的应用。     

执行《回弹法规程》提高检测精度

回弹法检测混凝土强度,在实际应用中存在着许多易出现偏差的环节,如仪器、碳化、检测面试件或芯样修正等。结合《回弹法规程》及工作实践,对这些问题,进行剖析总结,强调对新仪器、钢砧率定以及回弹仪的检定、保养,细化碳化测量,注意试件或芯样修正,加深对检测面与回弹法检测混凝土强度的正确认识,以提高回弹法检测精度。     

Numerical study on dynamic behaviours of a micro-droplet impacting on a vertical wall in PEMFC

The droplet/wall interaction in the gas channel (GC) of proton exchange membrane fuel cells (PEMFCs) has significant influence on water management, which may affect the performance and durability of the cell. In this paper, a coupled level-set and volume-of-fluid (CLSVOF) method is used to simulate the dynamic behaviours of a micro-droplet impacting on a vertical wall in the GC. The effects of impact velocity (expressed by the Weber number, We), and impact angle on the spreading dynamics are evaluated. Next, the critical conditions for the transition from spreading to rebound are further discussed. For 0 < We < 80, only the spreading, retracting, and rebound are observed, and the phenomenon of air bubble entrapment is captured on different wettable walls. With an increment of We, the maximum total spreading factor l1 tot and corresponding normalised time t1 will increase, as well as the normalised time difference Δτ₂ between the maximum spreading length and minimum height. Moreover, when increasing the impact angle, the maximum front spreading factor depending on the tangential velocity component will decrease, while the absolute value of maximum back spreading factor squeezed by the normal velocity component will increase. For the oblique downward impact, the front liquid led by the tangential velocity component plays a more important role in dominating the spreading process. The results also indicate that both the wall wettability and We can affect the transition threshold. When the static contact angle is between 90° and 150°, the effect of We on the rebound is inversely proportional to the hydrophobicity of the wall.     

Unified model of short- and long-term HIV viral rebound for clinical trial planning

Antiretroviral therapy (ART) effectively controls HIV infection, suppressing HIV viral loads. Typically suspension of therapy is rapidly followed by rebound of viral loads to high, pre-therapy levels. Indeed, a recent study showed that approximately 90% of treatment interruption study participants show viral rebound within at most a few months of therapy suspension, but the remaining 10%, showed viral rebound some months, or years, after ART suspension. Some may even never rebound. We investigate and compare branching process models aimed at gaining insight into these viral dynamics. Specifically, we provide a theory that explains both short- and long-term viral rebounds, and post-treatment control, via a multitype branching process with time-inhomogeneous rates, validated with data from Li et al. (Li et al. 2016 AIDS 30, 343–353. (doi:10.1097/QAD.0000000000000953)). We discuss the associated biological interpretation and implications of our best-fit model. To test the effectiveness of an experimental intervention in delaying or preventing rebound, the standard practice is to suspend therapy and monitor the study participants for rebound. We close with a discussion of an important application of our modelling in the design of such clinical trials.     

对三分远投篮板球落点规律的初探

篮板球是篮球技战术的重要组成部分。篮球规则实行了“远投得三分”的规定后,三分球普遍受到各队重视,由于三分球命中率比中近距记命中率低,争夺三分蓝板球机会必将增加。本文通过实验得出三分远投反弹距离和反弹方向的规律,将会给篮板球技术与战术的教学和训练工作提供理论依据。     

戈壁地区不同养护方式下混凝土桥墩回弹强度与试块强度试验研究

为了研究戈壁地区不同养护方式下混凝土桥墩的回弹强度与试块强度的变化规律,首先对原材料的各项性能进行了检测与分析,然后通过对戈壁地区不同养护方式(标准养护、大气养护、土工布包裹养护、橡塑板包裹养护)下混凝土桥墩及同条件试块在不同龄期(3,5,7,14,28,56 d)时的强度进行了测试和分析,将所得的混凝土桥墩回弹强度及试块强度的发展规律进行了公式拟合和验证。结果表明:①按照大气养护、土工布包裹养护、橡塑板包裹养护、标准养护的顺序,混凝土抗压强度、抗拉强度、拉压比逐渐增大;②戈壁地区不同养护方式下,混凝土桥墩的回弹强度小于试块强度,两者的差值在3~9 MPa之间,随着龄期的增加两者的差值逐渐减小;③戈壁地区混凝土养护方式保温保湿效果越好,回弹强度与试块强度之间的差值就越小;④提出了戈壁地区不同养护方式下混凝土回弹强度及试块强度的计算公式,所得公式经验证误差较小,可以作为强度计算的参考。     

对结构实体混凝土强度检验的理解

对结构实体混凝土强度检验的验收规范进行了探讨，就结构混凝土强度实体检验的具体实施方法进行了介绍，并指出了现行实体混凝土强度回弹报告的不妥之处，以达到控制工程质量的目的。