Simulation of free-surface flow using a boundless grid

Physically based fluid simulation in recent years has been successful for small-scale fluids such as liquid in a cubic cavity.However,for boundless free-surface flow of large scale and irregular area,there is a critical trade-off between simulation efficiency and accuracy because of the restriction of the traditional regular computational grids.This paper introduces boundless computational grids based on hierarchical runlength encoding to simulate large-scale free-surface flow.We first modeled the free-surface flow with a lattice Boltzmann method,and calculated the surface curvature in the update process.We then introduced an effective method with which to calculate the surface curvature according to the surface tension so that the surface detail was enhanced,and obtained the curvature of each surface effectively as it was extracted.Furthermore,we dynamically compressed and indexed the computational cells with the improved hierarchical run-length encoding algorithm,so that the grid expands dynamically according to the fluid flow and the computational resources used were proportional to the volume of the fluid.Finally fluids in different situations were simulated realistically.The proposed method makes the best of the computational resources to perform the simulation with high resolution,and dynamically allocates resources so that the fluid can expand in random directions without boundaries,which is suited to the simulation of large-scale visual scenes.     

Engineering practice of seismic isolation and energy dissipation structures in China

The concepts of seismic isolation and energy dissipation structures emerged in the early 1970s.In China,the first seismic isolation structure was finished in 1993,and the first energy dissipation structure was built at about the same time.Up to 2007,China had more than 600 seismic isolation and about 100 energy dissipation building structures.In 2008,the huge Wenchuan earthquake hit the southwest of China,which triggered a bloom of new seismic isolation and energy dissipation structures.This paper presents the development history and representative applications of seismic isolation and energy dissipation structures in China,reviews the state-of-the-practice of Chinese design,and discusses the challenges in the future applications.Major findings are as follows:Basic design procedures are becoming standardized after more than ten years of experiences,which mainly involve determination of design earthquake forces,selection of ground motions,modeling and time-history analyses,and performance criteria.Nonlinear time-history analyses using multiple ground motions are the characteristic of the design of seismic isolation and energy dissipation structures.Regulations,standardization and quality control of devices,balance between performance and cost,comparison with real responses,and regular inspection are identified as the issues that should be improved to further promote the application of seismic isolation and energy dissipation structures in China.     

控制注入/压降试井测试时间因素分析

为了减少注入/压降试井对整个煤层气井施工进度的影响,基于对煤层气注入/压降试井测试理论及实际操作的研究,提出控制试井测试时间长短的几个因素,应用实例说明其解决方案,结果表明在煤层气井况、设备等基本固定的情况下,对于中高渗煤层,通过提高地面注入压力增大注入量是缩短试井测试时间的重要手段。     

PIPENET软件用于海上平台消防水系统的水力分析

在介绍PIPENET水力分析软件的基础上,以某一海上无人驻守平台为例,重点论述了PIPENET软件在消防水系统水力分析方面的应用,分析结果表明,此海上平台的消防水系统在正常和故障状态下都能满足设计要求,验证了消防水系统设计的正确性。文章最后对PIPENET水力分析软件在平台消防水系统上的进一步应用提出了建议。     

Effect of surface passivation on optical and electronic properties of ultrathin silicon nanosheets

The binding energy,electronic structure and optical properties of H-,H 3 C-,and HS-cluster-passivated ultrathin silicon (single-layer and double-layer) nanosheets were calculated using density functional theory based on the plane-wave ultra-soft pseudopotential.Firstly,the most stable configuration was selected from passivated configurations according to the principle of lowest energy after calculating their total energies.Then the density of state and the band structure of the different passivated systems were calculated.It was found that different passivation clusters could affect the forbidden band,theremore the passivated cluster with sulfur could greatly decrease the width of the forbidden band through electron transfer.Lastly,the light absorption and reflection properties were also investigated.All results were conducive to the development of silicon-based optoelectronic devices.     

Reliability of flip-chip bonded RFID die using anisotropic conductive paste hybrid material

A reliability of flip-chip bonded die as a function of anisotropic conductive paste (ACP) hybrid materials, bonding conditions, and antenna pattern materials was investigated during the assembly of radio frequency identification(RFID) inlay. The optimization condition for flip-chip bonding was determined from the behavior of bonding strength. Under the optimized condition, the shear strength for the antenna printed with paste-type Ag ink was larger than that for Cu antenna. Furthermore, an identification distance was varied from the antenna materials. Comparing with the Ag antenna pattern, the as-bonded die on Cu antenna showed a larger distance of identification. However, the long-term reliability of inlay using the Cu antenna was decreased significantly as a function of aging time at room temperature because of the bended shape of Cu antenna formed during the flip-chip bonding process.     

热轧变形对AZ40Mg合金晶粒细化与力学性能的影响(英文)

以热挤压材为坯料,经多道次热轧制备AZ40Mg合金板材。研究热轧变形对合金组织、力学性能与断裂行为的影响。结果表明:随着热轧道次的增加,通过动态再结晶,材料的组织均匀性得到逐步改善,晶粒尺寸持续细化。相应地,热轧板材的力学性能与挤压态坯料相比得到显著改善。经过5道次以上热轧制备的AZ40Mg合金板材,其平均晶粒尺寸细化到10μm以下,轧向及横向的室温拉伸屈服强度与伸长率均可分别达到175MPa和20%以上。     

室温剧烈冷变形和细化AZ31镁合金的加工硬化行为(英文)

在室温下,挤压态镁合金丝材最大累计面积减少61%,并对所得材料进行退火处理以细化晶粒。在室温下以恒定的应变速率对拉拔态和退火态试样进行拉伸试验,分析每个试样的拉拔面积减少量和平均晶粒尺寸与整个应力—应变曲线的关系。结果表明:冷变形试样具有恒定的弹性模量,但应力明显依赖变形程度。相应的θ—σ曲线(θ代表加工硬化速率,dσ/dε)表现为加工硬化扩展阶段Ⅱ和抑制阶段Ⅳ。再结晶试样随着晶粒的细化屈服应力增高且表现出典型的多晶材料加工硬化阶段:Ⅱ,Ⅲ,Ⅳ和Ⅴ。此外,随着晶粒的细化,由于晶界滑移的作用,第Ⅳ阶段出现下降。在冷拉和再结晶材料中,不同的硬化行为显示出不同的硬化机理。     

矿仓硫精矿自燃的表观活化能(英文)

为了判定储存在矿仓内的硫精矿是否存在自燃危险性,从冬瓜山铜矿矿仓采集了不同类型的3种矿样(高硫精矿、硫铁精矿、硫铜精矿)。利用同步TG-DTG-DSC分析技术对3种矿样在升温速率分别为5、10、15、20和25℃/min的条件下,在空气气氛中的化学反应过程进行深入研究。利用DTG曲线上的峰值温度,将每种矿样的反应过程划分为不同阶段,基于Ozawa-Flynn-Wall方法求得相应区间的表观活化能。结果表明:每种矿样的反应过程相当复杂,求得的表观活化能随着反应温度区间的不同而发生改变,从室温到800℃,3种矿样在各个反应阶段的活化能为36～160kJ/mol;高硫精矿与硫铁精矿在150℃以下的表观活化能较铜精矿的低,因此在室温条件下高硫精矿与硫铁精矿更容易引发自燃。     

Ti/Al扩散偶中间相长大过程的数值模拟(英文)

为研究固态Ti/Al扩散偶的扩散反应,将Ti/Al箔构成的扩散偶分别在525,550,575和600°C退火1～40h。实验结果表明TiAl3是Ti/Al界面处生成的唯一相。TiAl3的优先长大是界面热力学作用的结果。TiAl3相主要向Al箔一侧长大,其长大过程符合抛物线规律。在晶界扩散的基础上,用有限差分方法模拟TiAl3相的长大过程,模拟结果和实验结果吻合较好。