装填设备载荷影响因素分析及动力学仿真

大型货物的装填过程中影响载荷的因素较多,其中对中精度对装填载荷影响较为明显。通过动力学仿真软件ADAMS对装填过程中载荷进行模拟,并对各影响因素进行定量分析,得到对中偏差与装填载荷的关系。将仿真结果与试验数据进行对比,验证该仿真方法的正确性,可作为后续研究装填载荷的一种方法,为结构设计提供指导。     

多泥沙河流水电站水轮机转轮内部流动数值模拟

针对多泥沙水电站水轮机转轮的泥沙磨损问题,以HLA351-LJ-275水轮机为模型,对水轮机在设计工况下,运用N-S方程和标准κ-ε湍流模型,利用CFX求解器进行仿真流动模拟。水轮机转轮进口沿叶高20%、50%、80%流面的压力、泥沙速度及泥沙体积分数分布的数值结果表明,水轮机转轮叶片工作面压力大于背面且最小压力高于气化压力。泥沙速度在叶片进水边和出水口位置普遍较高。水轮机转轮叶片工作面的泥沙体积分数大于背面,叶片工作面的泥沙体积分数在叶片出水口普遍较高,叶片背面的泥沙体积分数在叶片进水边普遍较高。研究结果对多泥沙河流水轮机转轮叶片的泥沙磨损评估及维修具有指导意义。     

锅炉二次风道流动特性的模拟优化

以武汉武锅能源工程有限公司设计的二次风道为对象,运用数值模拟的方法考查了改造前后二次风道各出口空气的速度分布和质量流量分配情况。结果表明,通过布置弧形挡板,风道出口速度的均匀性显著提升,最大变异系数Cv由29%下降到9%,而且还避免了因风速不均引起的烧边现象。此外,改进后风道各出口空气的流量分配非常接近理想工况,与理想工况的偏差从9.9%缩小到2.1%。     

CFD modeling of thermal contact resistance between solid contacting surfaces

Heat transfer has considerable applications in different industries such as designing of heat exchanger, nuclear reactor cooling, control system for spacecraft, and designing of microelectronics cooling. As the surfaces of two metals contact each other, this issue becomes so crucial. Thermal contact resistance (TCR) is one of the key physical parameters in heat transfer of mentioned surfaces. Measuring the experimental value of TCR in laboratory is highly expensive and difficult. As an alternative, numerical modeling methods could be engaged. In this study, inverse problem method solution is utilized as a proper method for estimation of TCR value. In this order, three different configurations (flat-flat, flat-cylinder, and cylinder-cylinder) were utilized in two steady and unsteady state conditions to predict the value of TCR. A comparison between the measured values and obtained values from the simulation show the errors for flat-flat, flat-cylinder, and cylinder-cylinder configuration after 10 min from starting the experiment are 4.6074%, 0.1662%, and 0.5622%, respectively. And in steady-state condition, the corresponding errors are 6.06e-3%, 1.506%, and 0.846%, respectively. In conclusion, the final results establish the fact that the inverse problem method solution can predict TCR values between contacting surfaces.     

改性淀粉抑制赤铁矿反浮选石英的作用机理研究

通过矿物浮选试验、动电位测定以及吸附量测试,考察了4种淀粉抑制剂对赤铁矿和石英浮选性能的影响,并探讨了其作用机理。在碱性条件下,改性淀粉抑制剂对赤铁矿抑制效果明显,且以改性玉米淀粉效果最佳,改性磷酸酯淀粉、改性羧甲基淀粉的抑制效果次之,而普通淀粉抑制作用一般。同时4种淀粉抑制剂对主要脉石矿物石英的抑制效果均不明显。pH=10~12.5条件下,改性玉米淀粉因其羟基氧和裸露在赤铁矿表面的铁元素发生了化学键合,因而选择性抑制能力最佳。分子动力学模拟表明,改性玉米淀粉片段与赤铁矿作用更为紧密,验证了改性淀粉能更好地抑制赤铁矿。     

Outcome‐based ventilation: A framework for assessing performance,health, and energy impacts to inform office building ventilation decisions

This article presents an outcome‐based ventilation (OBV) framework, which combines competing ventilation impacts into a monetized loss function ($/occ/h) used to inform ventilation rate decisions. The OBV framework, developed for U.S. offices, considers six outcomes of increasing ventilation: profitable outcomes realized from improvements in occupant work performance and sick leave absenteeism; health outcomes from occupant exposure to outdoor fine particles and ozone; and energy outcomes from electricity and natural gas usage. We used the literature to set low, medium, and high reference values for OBV loss function parameters, and evaluated the framework and outcome‐based ventilation rates using a simulated U.S. office stock dataset and a case study in New York City. With parameters for all outcomes set at medium values derived from literature‐based central estimates, higher ventilation rates’ profitable benefits dominated negative health and energy impacts, and the OBV framework suggested ventilation should be ≥45 L/s/occ, much higher than the baseline ~8.5 L/s/occ rate prescribed by ASHRAE 62.1. Only when combining very low parameter estimates for profitable impacts with very high ones for health and energy impacts were all outcomes on the same order. Even then, however, outcome‐based ventilation rates were often twice the baseline rate or more.     

浮法玻璃熔窑火焰空间石油焦部分替代重油燃烧的数值模拟

针对浮法玻璃熔窑火焰空间建立模型并进行了数值模拟，在保证热值相同的前提下，对比研究了重油燃烧及将石油焦部分替代重油燃烧时的流场分布特征。结果表明，石油焦部分代替重油燃烧后，两种燃料可很好地混合燃烧，窑炉内温度制度基本不受影响；石油焦着火时间比重油长，两种燃料混合燃烧时平均着火点滞后于仅使用重油时，且燃烧路径更长，燃烧时产生了大量CO，整个火焰空间及烟气出口处NOx的平均排放量与仅使用重油相比降低了30.02%，NOx减排效果明显。     

Sequence-Dependent Nanofiber Structures of Phenylalanine and Isoleucine Tripeptides

The molecular design of short peptides to achieve a tailor-made functional architecture has attracted attention during the past decade but remains challenging as a result of insufficient understanding of the relationship between peptide sequence and assembled supramolecular structures. We report a hybrid-resolution model to computationally explore the sequence–structure relationship of self-assembly for tripeptides containing only phenylalanine and isoleucine. We found that all these tripeptides have a tendency to assemble into nanofibers composed of laterally associated filaments. Molecular arrangements within the assemblies are diverse and vary depending on the sequences. This structural diversity originates from (1) distinct conformations of peptide building blocks that lead to different surface geometries of the filaments and (2) unique sidechain arrangements at the filament interfaces for each sequence. Many conformations are available for tripeptides in solution, but only an extended β-strand and another resembling a right-handed turn are observed in assemblies. It was found that the sequence dependence of these conformations and the packing of resulting filaments are determined by multiple competing noncovalent forces, with hydrophobic interactions involving Phe being particularly important. The sequence pattern for each type of assembly conformation and packing has been identified. These results highlight the importance of the interplay between conformation, molecular packing, and sequences for determining detailed nanostructures of peptides and provide a detailed insight to support a more precise design of peptide-based nanomaterials.     

桁架式火星探测器的着陆缓冲特性分析

着陆缓冲机构是着陆器实现行星探测软着陆的关键部位之一,它的缓冲性能直接关系到着陆器是否能安全地在行星表面实现软着陆。根据某院提供的火星着陆器模型,在三维建模软件中建立着陆器的合理简化模型,为了提高分析着陆器软着陆过程冲击响应的准确性,采用MSC公司的Patran/Dytran有限元软件,用瞬态动力学的方法对着陆器的缓冲性能进行分析。仿真结果与试验数据十分吻合,着陆器的缓冲和传力性能良好。因此,采用拉杆缓冲的桁架式火星着陆器是可行的,仿真结果与试验数据也为今后的火星探测提供了参考。     

A Practical Method for Animating Anisotropic Elastoplastic Materials

This paper introduces a simple method for simulating highly anisotropic elastoplastic material behaviors like the dissolution of fibrous phenomena (splintering wood, shredding bales of hay) and materials composed of large numbers of irregularly-shaped bodies (piles of twigs, pencils, or cards). We introduce a simple transformation of the anisotropic problem into an equivalent isotropic one, and we solve this new “fictitious” isotropic problem using an existing simulator based on the material point method. Our approach results in minimal changes to existing simulators, and it allows us to re-use popular isotropic plasticity models like the Drucker-Prager yield criterion instead of inventing new anisotropic plasticity models for every phenomenon we wish to simulate.