Nanomechanical analyses of porous SiO2 low-dielectric-constant films for evaluation of interconnect structure reliability

Porous SiO₂ low-dielectric-constant films containing different porosities and sizes of uniformly distributed pores were prepared in this study. Their nanomechanical properties including true flow stress and fracture toughness were analyzed by a nanoindentation test. The hardness and elastic modulus of the films prepared with an ethanol molar ratio of 3 and an aging time of 16 h reached maximum values of 2.4 and 40 GPa, respectively. With increasing ethanol molar ratio, the porosity increased, and the mechanical properties consequently decreased. With increasing aging time, the mechanical properties increased and then dropped due to enlarged pore sizes. From converted true flow stress, the porous SiO₂ films were found to yield at an ultimate stress of 3.1 GPa, and the maximum fracture energy release rate was calculated as 3.4 J/m². The plastic deformation and fracture behavior of the porous films was observed through crack initiation and propagation along the large amount of pores.     

设计文件标准化审查工作初探

介绍了设计文件标准化审查的内容，指出了存在的问题，并提出了解决的措施。     

空间的塑造--厦门海湾公园设计

海湾公园利用植物、地形、大海与湖泊的周边环境等景观要素,运用隐喻、对比的手法,创造丰富、神秘、变化的空间,注重空间灵活的使用功能及其良好的人性化.     

Credibility and applicability of virtual reality models in design and construction

In this paper, we present the findings from an extensive study of the use of virtual reality (VR) models in large construction projects. The study includes two parts: The first part presents a quantitative questionnaire designed to investigate how VR models are experienced and assessed by the workforce at a building site. The second part includes a qualitative field survey of how VR models can be applied and accepted by professionals in the design and planning process of a large pelletizing plant. Through mainly studying persons who had little or no experience with advanced information technology (IT), we hoped to reveal the attitudes of the average person working at a construction site rather than of an IT expert. In summary, the study shows that the VR models in both projects have been very useful and well accepted by the users. Today’s information flow is, from a general point of view, considered to be insufficient and the hypothesis is that using VR models in the construction process have the potential to minimize waste of resources and improve the final result.     

Numerical modelling of the structural behaviour of thin-walled cast magnesium components using a through-process approach

A through-process methodology for numerical simulations of the structural behaviour of thin-walled cast magnesium components is presented. The methodology consists of casting process simulations using MAGMAsoft, mapping of data from the process simulation onto a FE-mesh (shell elements) and numerical simulations using the explicit FE-code LS-DYNA. In this work, generic High Pressure Die Cast (HPDC) AM60 components have been studied using axial crushing, 3-point bending and 4-point bending tests. The experimental data are applied to obtain a validated methodology for finite element modelling of thin-walled cast components subjected to quasi-static loading. The cast magnesium alloy is modelled using a user-defined material model consisting of an elastic–plastic model based on a modified J2-flow theory and the Cockcroft–Latham fracture criterion. The fracture criterion is coupled with an element erosion algorithm available in LS-DYNA. The constitutive model and fracture criterion are calibrated both with data from material tests and data from the process simulation using MAGMAsoft.     

Study of the effective parameters on mechanical and electrical properties of carbon black filled PP/PA6 microfibrillar composites

In this study the electrical and mechanical properties of microfibrillar polypropylene (PP)/polyamide6 (PA6) blend filled with super conductive carbon black (CB) have been investigated. In situ microfibrillar PP/PA6 composites filled with CB are produced using a single screw extruder equipped with a spinneret. Glycidyl methacrylate (GMA) grafted polypropylene (PP-g-GMA) is used as the compatibilizer. To investigate the effects of extensional flow on the microstructure, electrical and mechanical properties, three adaptors with various convergence angles were designed, prepared and applied between the extruder and the spinneret. To optimize the effects of processing and material parameters on the electrical and mechanical properties, the Taguchi method of experimental design is used. Material and processing factors which are studied include: concentration of PA6, compatibilizer level, CB concentration, drawing speed of melt spinning line, adaptor angle, order of mixing and temperature profile along the extruder. The results show an increase in DC conductivity of up to 10¹¹ times in comparison with pure PA6, by increasing the concentration of CB, drawing speed, adaptor angle and optimizing other parameters. By optimizing processing and material factors studied here, strength of microfibrillar structured composites is increased of up to 80% in comparison to pure PP.     

Multiresolution Representation of 2D CSG Models

Multiresolution is currently one of the main schemes used in CAD modeling for representing objects, particularly when large-scale geometric data must be transferred interactively over a network, as in the case of collaborative design. Increasingly complex products and growing competition have turned design into a collaborative team effort. Furthermore, the widespread development of Internet viewers has also necessitated the transfer and display of large-scale CAD models over networks. In order to reduce the volume of transferred data, efforts have been made to transfer CSG (Constructive Solid Geometry) models rather than those based on B_rep (Boundary Representation). This paper presents an original new method for speeding up data transfer by using multiresolution CSG models at different levels of details (LOD). The multiresolution CSG algorithm generates a hierarchy of multiresolution CSG trees; at each level, the shape is further approximated and represented by a smaller number of CSG primitives. The paper analyzes the proposed algorithm, and demonstrates its feasibility.     

Young’s modulus of crystalline C60 nanotubes studied by in situ transmission electron microscopy

Bending tests of crystalline nanotubes composed of fullerene C₆₀ molecules are performed inside a high-resolution transmission electron microscope. We fixed one side of a C₆₀ nanotube with a body-centered tetragonal structure with typical inner and outer diameters, i.e., 180 nm and 510 nm, respectively, and then applied concentrated forces on the other side using piezomanipulation of a silicon nanotip. The bending process was observed in situ by transmission electron microscopy with simultaneous measurements of the forces by an optical deflection method. It was found that the Young’s modulus of the nanotube was estimated to be 62–107 GPa, which was 1.1–3.3 times larger than that of C₆₀ nanowhiskers. The result concerning the increase in the Young’s modulus of the C₆₀ nanotube provided an experimental evidence for the structural model composed of an inner core and a surface shell for C₆₀ nanowhiskers.     

凯萨·布隆斯泰德和沃迪·凯威设计事务所

本文通过对主要设计成员凯萨·布隆斯泰德和沃迪·凯威的背景,以及对私人住宅、餐馆、办公楼、图书馆、精品屋等案例的阐释,向读者介绍了这家十分活跃的芬兰设计事务所,同时展现了北欧的室内设计风格。