基于影响系数法的激光切割机床主体机构运动学研究

将3-PUU并联机构作为激光切割机床的主体机构,以对3-PUU并联机构的运动学分析为目的,构建3-PUU并联机构的位置方程,采用虚设机构法建立并联机构的影响系数矩阵,包括Jacobian矩阵和Hessian矩阵。采用影响系数矩阵和对位置方程微分的方式分别求得并联机构的驱动副与动平台间速度和加速度的映射关系,将影响系数法和微分法所得驱动副速度和加速度图谱与ADAMS仿真结果对比。通过对比3种分析方法所得曲线的一致性,验证运动学理论研究的正确性、仿真验证的可靠性以及作为激光切割机床主体机构的适用性。影响系数矩阵的正确建立也为激光切割机床主体机构的动力学分析、性能指标的建立以及优化设计提供了基础。     

Strengthening molecular replacement with maximum likelihood in Beast

In molecular replacement we test a series of hypotheses about the position and/or orientation of molecules in the crystal. Likelihood is the natural score for hypothesis testing, and applications to experimental phasing and structure refinement have already demonstrated the value of likelihood in crystallography. A new likelihood function is required for rotation searches, because hypotheses about orientations leave the relative phases of structure factor contributions from symmetry-related molecules undefined. This function can also make good use of information from partial molecular replacement solutions. When multiple choices of model are available, multivariate statistics can be used to generate an ensemble average model, which is particularly powerful in solving structures with NMR models. The likelihood-based approach to molecular replacement will become even more powerful when the targets become more sophisticated, taking account of factors such as anisotropy of diffraction or the presence of non-crystallographic symmetry.     

影响增强聚丙烯雾化测试结果的因素

雾化重量法是衡量汽车内饰材料挥发物中的有害成分对人体健康的影响程度的测试.因此,为了合理控制挥发性物质的产生,降低车内环境污染,对用于汽车内饰的材料进行雾化测试是十分必要的.通过控制变量研究样品状态、加工工艺、测试温度、测试时间、平衡时间对雾化重量法进行测试,分别测试了内饰材料增强聚丙烯系列的长玻璃纤维增强材料和短玻璃...     

九龙江北溪水电站建设对下游干流枯水径流影响

九龙江是福建省第二大河流,北溪是龙岩、漳州和厦门三市的重要水源地,北溪下游干流的枯水流量大小不仅影响干流河道的生态用水和纳污能力,而且直接影响到漳州市和厦门市的饮用水安全。本文通过北溪主要水电站工程对干流的枯水期平均流量、最小月平均流量及最小日平均流量的影响原因和影响程度分析,为北溪枯水期水量调度提供参考。     

Analysis on influence factors of China's CO2 emissions based on Path–STIRPAT model

With the intensification of global warming and continued growth in energy consumption, China is facing increasing pressure to cut its CO₂ (carbon dioxide) emissions down. This paper discusses the driving forces influencing China's CO₂ emissions based on Path–STIRPAT model—a method combining Path analysis with STIRPAT (stochastic impacts by regression on population, affluence and technology) model. The analysis shows that GDP per capita (A), industrial structure (IS), population (P), urbanization level (R) and technology level (T) are the main factors influencing China's CO₂ emissions, which exert an influence interactively and collaboratively. The sequence of the size of factors' direct influence on China's CO₂ emission is A>T>P>R>IS, while that of factors' total influence is A>R>P>T>IS. One percent increase in A, IS, P, R and T leads to 0.44, 1.58, 1.31, 1.12 and −1.09 percentage change in CO₂ emission totally, where their direct contribution is 0.45, 0.07, 0.63, 0.08, 0.92, respectively. Improving T is the most important way for CO₂ reduction in China.     

用广义影响系数法对600 MW汽轮发电机模拟轴系转子的设计计算

在应用影响系数法对简支梁进行计算的基础上推出广义影响系数法，在考虑支承与集中质量相距为任意长度以及轴系在弹性支承的工况下，编制相应的广义影响系数法的计算机程序，对自行设计的“多功能模拟轴系试验台”(已申请专利)的各转子进行设计计算，并用有限元法、传递矩阵法进行计算验证和模态试验验证。     

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在对MDEA溶液中各种杂质组分的分析基础上，通过发泡实验考察了操作条件及各种杂质组分对溶液发泡性能的影响。随着MDEA浓度、MDEA溶液温度的逐渐降低，发泡高度及消泡时间逐渐增大；另外随着通气流率和溶液中CO₂负荷的增大，MDEA溶液发泡高度及消泡时间也逐渐增大。考察了NaCl、CaCl₂、FeSO₄无机盐对MDEA溶液发泡性能的影响。MDEA溶液中有机杂质甲醇、三甘醇、重烃对MDEA溶液则具有一定的消泡作用，而气井缓蚀剂无疑是强的发泡剂。残液的加入使纯净的MDEA溶液发泡性能大幅度地增加，验证了MDEA溶液受到了污染是造成溶液发泡的主要原因。最后对MDEA溶液发泡提出了相应的处理措施和建议。     

页岩气扩散实验与数学模型

在地层条件下,页岩气流动状态受多尺度效应影响,包含黏性流、扩散流以及滑脱流等,气体的产出是多种机制协同作用的结果,前人提出的扩散模型已不能准确地描述页岩气在基质中的扩散行为。为了定量表征页岩气扩散能力的影响因素,揭示气井在全生命周期开发过程中的流动规律以及对产能的影响,利用自主研发的高温高压近平衡态实验系统,开展了页岩气在0~1 MPa微压差条件下的流动实验,并提出一种综合考虑渗透率、温度与压力的扩散系数计算方法,成功地运用于川南地区五峰组-龙马溪组页岩中,指出该地区优质储层扩散产量成为主控因素时临界开发压力为4.5 MPa,对于页岩气井产能评价以及扩散能力的表征有重要的意义。通过实验结果与理论分析表明,扩散在高温、低渗、低压力条件下会有更高的分配系数,考虑了基质渗流能力的扩散系数模型能更好地运用在实际流动中,忽略扩散的影响将对产能计算带来较大误差。     

非加剂柴油十六烷值对柴油机性能影响的研究

本文研究了非加剂柴油十六烷值对其低热值、柴油机热效率、燃油消耗率、排气温度和排气烟度等的影响,给出了相应的试验曲线,分析了十六烷值与这些性能之间的内在关系     

Compliance Based Assessment of Stress Intensity Factor in Cracked Plates with Finite Boundary Restraint: Application to Thermal Shock Part II

A Compliance Adjusted Weight Function (CAWF) approach has been recently developed to enable the estimation of stress intensity factor in thermal shocked cracked plates with finite boundary restraint. In this article the CAWF approach is used to analyse three case studies that collectively encompass the plate configurations, crack configurations and load configurations with which the CAWF is currently formulated. The results of these analyses highlight that the CAWF approach is suitable for estimates within 5–10% of benchmark fracture mechanics finite element values for a wide range of targeted cracked plate configurations and boundary restraint. An exception occurs for the semi-elliptical surface cracked plates where a free boundary effect can be observed at a free or near free boundary restraint condition.