Ductility of FRP plated flexural members

The design of reinforced concrete (RC) flexural members such as beams, slabs and columns is intrinsically based on the inherent ductility of the member. In reinforced concrete beams and slabs, ductility is generally achieved by using ‘under-reinforced’ sections and generally governed by the neutral axis depth parameter k_u which requires ultimate failure by concrete crushing at a specified strain ε_c. As the plates of fibre reinforced polymer (FRP) plated RC beams can fracture or debond before the concrete crushes at ε_c, the k_u approach is not directly applicable. Hence, new fundamental approaches and a deeper understanding of ductility are required which are the subjects of this paper.     

Effect of fiber orientation on the structural behavior of FRP wrapped concrete cylinders

In this study, 27 concrete cylinders with a diameter of 152.4 and a height of 304.8 mm were prepared. Among them, 18 cylinders were wrapped using two layers of fiber reinforced polymer (FRP) with six fiber orientations; six cylinders were wrapped using four layers of FRP with fibers in axial or hoop direction only; the remaining three cylinders were used as control. The FRP used was E-glass fiber reinforced ultraviolet (UV) curing vinyl ester. Fifteen coupon specimens were prepared to experimentally determine the tensile strength of the FRP with fibers oriented at 0°, 45°, and 90° from the loading direction. Co-axial compression tests were conducted on the wrapped cylinders and control cylinders. The test results were compared with existing confinement models. It is found that the strength, ductility, and failure mode of FRP wrapped concrete cylinders depend on the fiber orientation and wall thickness. Fibers oriented at a certain angle in between the hoop direction and axial direction may result in strength lower than fibers along hoop or axial direction. A larger database is desired in order to refine the existing design-oriented confinement models.     

Mixed mode fracture toughness of GFRP composites

Glass fibre reinforced polymer (GFRP) composites are used in a wide range of applications as a structural material. They have high specific mechanical properties but are prone to delamination as a result of manufacturing defects and impact/shock loading. The ability of the structure to continue to carry load after damage and the subsequent propensity of the damage to propagate are important considerations for the design of damage tolerant composite structures. In order to accurately predict the stability of damage under load, relevant mechanical properties of the material must be accurately determined. In particular, mixed mode fracture toughness data is required in order to study the damage criticality in such structures. This paper describes an experimental study to determine Mixed Mode fracture toughness for thick glass/vinylester specimens. The test methodology used for the experiments and its difficulties will be discussed. Mixed mode fracture toughness results are presented, as are Mode I and Mode II fracture toughness results obtained via Double Cantilever Beam (DCB) and End Notch Flexure (ENF) tests, respectively.     

Porous methacrylate tissue engineering scaffolds: using carbon dioxide to control porosity and interconnectivity

Porous scaffold structures are used in tissue engineering to provide structural guidance for regenerating tissues. The use of carbon dioxide (CO₂) to create such scaffolds has received some attention in the past but many researchers believe that although CO₂ processing of polymers can lead to porous scaffolds there is limited interconnectivity between the pores. In this study, highly porous (greater than 85%) and well interconnected scaffolds were obtained in which the size, distribution and number of pores could be controlled. This control was achieved by altering the rate of venting from polymer discs saturated with CO₂ under modest temperature and pressure. The polymer used is a blend of poly (ethyl methacrylate) and tetrahydrofurfuryl methacrylate (PEMA/THFMA). This polymer system has shown promise for potential applications in cartilage repair.     

Time-domain simulation of nonlinear transformers displaying hysteresis

This paper introduces a novel technique for modeling, in the time domain, a power transformer with nonlinear and hysteretic behavior. The model is particularly suitable for harmonic or protection studies where the transformer is driven into the nonlinear regime. The technique uses a single-phase two-winding transformer model based on the Jiles-Atherton model of ferromagnetic hysteresis. It includes eddy-current loss by adding an extra single-turn winding so that the transients are modeled as fully as possible.     

Hemocompatibility of lanthanum oxide films fabricated by dual plasma deposition

Lanthanum oxide films were fabricated using dual plasma deposition. X-ray photoelectron spectroscopy (XPS) showed that La existed in the + 3 oxidation state. X-ray diffraction (XRD) revealed a (101) oriented hexagonal structure. Blood platelet adhesion tests and endothelial cell cultures were used to evaluate the hemocompatibility of the as-deposited films. Scanning electron microscopy (SEM) and optical microscopy were employed to evaluate the surface morphology of the blood platelets and endothelial cells on the films. The results showed that the number of adhered, aggregated and morphologically changed platelets was reduced compared to that observed on low-temperature isotropic carbon (LTIC). Endothelial cells culture tests indicated good adhesion and proliferation of human umbilical vein endothelial (HUVE) cells in vitro. Our study suggests that lanthanum oxide films are potential blood-contacting biomedical materials.     

纳米技术使太阳能领域的未来充满阳光

随着对能源问题和环境问题的日益重视，各种可替代传统石化能源方式的新能源方式纷纷涌现。其中，太阳能是一种资源最丰富的可再生清洁能源，而且可以认为是一种用之不竭的能源方式。近年来，太阳能发电技术也进入快速发展的时期。而且与新兴的纳米技术相结合，有望为绿色能源的发展带来革命性的变化。     

ArcFVS: An integration of a Geographic Information System and Forest Vegetation Simulator

This paper presents the design and implementation of an integrated application program called ArcFVS that links the Forest Vegetation Simulator (FVS) and a Geographic Information System (GIS) to realize spatial selection of input files and graphic display of modeling output. Data for testing and running the model came from the U.S. Forest Service’s Forest Inventory and Analysis (FIA) Database and were also collected in field surveys in north-central Indiana. ArcFVS 1.0 is designed using the ArcGIS software from the Environmental Systems Research Institute (ESRI) and the Visual Basic for Applications (VBA) programming environment to manipulate ESRI’s ArcObjects. The resulting product offers custom functions as commands in a new menu or as tools on a new toolbar. They are used to: select spatially or by attribute the forest plots to be projected by FVS, create the FVS input files for the selected plots and display in a geospatial environment different types of FVS output (text output files, tables with variables of interest and visualization image files). Advantages of ArcFVS 1.0 include the new GIS capabilities, enhanced format translation functions and the standardized programming environment.     

Scenario-oriented design for single-chip heterogeneous multiprocessors

Single-chip heterogeneous multiprocessors (SCHMs) are arising to meet the computational demands of portable and handheld devices. These computing systems are not fully custom designs traditionally targeted by the design automation community, general-purpose designs traditionally targeted by the computer architecture community, nor pure embedded designs traditionally targeted by the real-time community. An entirely new design philosophy will be needed for this hybrid class of computing. The programming of the device will be drawn from a narrower set of applications with execution that persists in the system over a longer period of time than for general-purpose programming. However, the devices will still be programmable, not only at the level of the individual processing element, but across multiple processing elements and even the entire chip. The design of other programmable single chip computers has enjoyed an era where the design tradeoffs could be captured in simulators such as SimpleScalar and performance could be evaluated to the SPEC benchmarks. Motivated by this, we describe new benchmark-based design strategies for SCHMs which we refer to as scenario-oriented design. We include an example and results.