Behaviors of concrete-filled steel tubular members subjected to combined loading

The present study is an investigation on the behaviors of concrete-filled thin-walled steel tubular members subjected to combined loading, such as compression and torsion, bending and torsion, compression, bending and torsion. ABAQUS software is used in this paper for the finite element analysis (FEA). A comparison of results calculated using this modeling shows generally good agreement with test results. The FEA modeling is then used to investigate the influence of important parameters that determine the ultimate strength of the composite members under combined loading, such as compression and torsion, bending and torsion, compression, bending and torsion. The parametric studies provide information for the development of formulae for calculating the ultimate strength of the composite members subjected to combined loading.     

桉木硫酸盐浆不同漂白技术的评价

高白度漂白商品浆的白度已从通常的88%～90%提高到更高的水平,达到92%.这种高白度的要求导致了纸厂使用高价格光学漂白剂,以及过量使用这种添加剂的环境风险.     

On Ultra-Fine Leak Detection of Hermetic Wafer Level Packages

Theoretical and practical ranges of leak rates measurable by the helium mass spectrometer are characterized. The effect of noise due to: 1) background helium present in the spectrometer and 2) desorption of helium that attaches itself to the specimen surface during bombing is quantified experimentally. The results guide a framework to extract the true leak rate from the measured leak rate profile. An optical interferometry based hermeticity measurement technique for ultra-fine leaks is proposed. The setup to implement the technique is described and a preliminary experimental result is reported.     

Investigation of Mechanical and Electrical Characteristics for Cracked Conductive Particle in Anisotropic Conductive Adhesive (ACA) Assembly

In an anisotropic conductive adhesive (ACA) assembly, the electrical conduction is usually achieved with the conductive particles between the bumps of integrated circuit (IC) and corresponding conductive tracks on the glass substrate. Fully understanding of the mechanical and electrical characteristics of ACA particles can help to optimize the assembly process and improve the reliability of ACA interconnection. Most conductive particles used in the ACA assembly are with cracks in the metal coating of the particles after the ACA bonding. This paper introduced the fracture analysis by applying the cohesive elements in the numerical model of the nickel-coated polymer particle and further simulating the cracks initiation and propagation in the nickel coating during the ACA bonding. The simulation results showed that the stress distribution on the nickel-coated particle with cracks was significantly different from that on the nickel-coated particle without crack, indicating that the stress analysis by taking the crack into consideration is very important for the reliability assessment of the ACA interconnection. The stress analysis of cohesive elements indicated that the cracks initiated at the central area of the nickel coating and propagated to the polar area. Furthermore, by the introduction of a new parameter of the virtual resistance, a mathematical model was established to describe the electrical characteristics of the nickel-coated particle with cracks. The particle resistance of the nickel-coated particle with cracks was found to be much higher than that of the particle without crack in the optimized bonding pressure range, indicating that it is necessary to take the crack into consideration for the particle conduction analysis as well. Therefore, the fracture analysis on the conductive particle by taking the crack into consideration could accurately evaluate the reliability of ACA interconnection and avoid serious reliability issues.     

Study on the c-axis preferred orientation of ZnO film on various metal electrodes

ZnO thin film was deposited on various metal electrodes by reactive sputtering, and c-axis preferred orientation of the film has been studied. ZnO, which has high piezoelectricity, is promising for oscillators or filter devices such as surface acoustic wave (SAW) device, gas sensor, and film bulk acoustic resonator (FBAR). But, for the application of ZnO film for these devices, the film should be grown with c-axis normal to the electrode. In this study, Pt, Al, and Au were deposited on Si wafer, and the surface roughness and crystal structure of the ZnO film on the electrode were investigated using AFM, scanning electron microscopy (SEM), and X-ray diffraction (XRD). Columnar structures of ZnO films were grown with c-axis normal to all electrodes, and among them Pt electrode showed the highest preferred orientation of ZnO film.     

Effect of Thickness of the p-AlGaN Electron Blocking Layer on the Improvement of ESD Characteristics in GaN-Based LEDs

The following letter presents a study regarding GaN-based light-emitting diodes (LEDs) with p-type AlGaN electron blocking layers (EBLs) of different thicknesses. The study revealed that the LEDs could endure higher electrostatic discharge (ESD) levels as the thickness of the AlGaN EBL increased. The observed improvement in the ESD endurance ability could be attributed to the fact that the thickened p-AlGaN EBL may partly fill the dislocation-related pits that occur on the surface of the InGaN-GaN multiple-quantum well (MQW) and that are due to the strain and the low-temperature-growth process. If these dislocation-related pits are not partly suppressed, they will eventually result in numerous surface pits associated with threading dislocations that intersect the InGaN-GaN (MQW), thereby reducing the ESD endurance ability. The results of the experiment show that the ESD endurance voltages could increase from 1500 to 6000 V when the thickness of the p-AlGaN EBL in the GaN LEDs is increased from 32.5 to 130 nm, while the forward voltages and light output powers remained almost the same.     

烧结成品运输自动控制系统的改进

对烧结成品运输自控系统不稳定性因素进行了分析，提出了采取优化硬件外围工作环境，完善软件保护程序等改进措施。改进后的自控系统稳定性明显提高。     

Effects of Y and Ce on Microstructures and Properties of Nb-Si System Composites

The effects of yttrium and cerium on microstructures and properties of Nb-Si system composites were investigated by scanning electron microscopy( SEM), energy dispersive spectrum(EDS), X-ray diffraction(XRD) and high temperature oxidation experiments.It is found that the coarse primary silicide phase became finer and more homogeneous with Y and Ce addition.The results of high temperature oxidation experiments show that the oxidation rates of NbSi system composites with an appropriate amount of Y and Ce decrease compared with those of alloys without Y or Ce addition, and oxidation products mainly distribute along the phase boundaries between the Nb solid solution and silicide.     

Effect of deformation route on microstructural development in aluminum processed by equal channel angular extrusion

Aluminum has been deformed by equal channel angular extrusion (ECAE) to obtain submicron-grained structures under different deformation routes. The deformation routes were varied by rotating billets through 0, 90, and 180 deg between each extrusion pass, and were designated as route A, B_C, and C, respectively. Based on quantitative microstructural analysis, the effectiveness of the deformation route is shown to depend upon the different definition used. The order of effectiveness is (a) A > B_C > C for both 90 and 120 deg dies, in terms of the generation of high-angle grain boundaries (HAGBs); (b) B_C > C > A for both 90 and 120 deg dies, in terms of the formation of equiaxed shape of grains; and (c) B_C > A > C for 90 deg die and B_C ∼ A > C for 120 die, in terms of reducing grain size. It is suggested that the generation of HAGBs can be related to the accumulation of nonredundant strain, while the shape and orientation of grains may be linked to the shearing patterns of the deformation route.