Application of numerical simulation for wear analysis of warm forging die

Warm forging process has better forming precision than hot forging process and has better formability than cold forging. But warm forging die sustains higher temperature and working pressure, the die wear is faster than those of hot forging and cold forging. The purpose of this research is to combine the experimental techniques, wear model and numerical simulation method to predict the wear of warm forging die. The non-isothermal ring compression test was adopted to estimate the friction coefficient in different temperatures and the on-line temperature recording system was setup to correct the heat transfer coefficient of the interface. The wear coefficients in different temperatures were acquired from high temperature wear experiment. Finally, the Archard wear theory and DEFORM, a FEM code, were used to analyze the warm forging of automotive transmission outer-race and predict the die wear condition.     

(Al/sub 0.5/Ga/sub 0.5/)/sub 0.65/In/sub 0.35/P/Ga/sub 0.65/In/sub 0.35/P double-heterostructure orange light-emitting diodes

Visible light-emitting diodes (LEDs) emitting at 615 nm and employing the AlGaInP/GaInP double heterostructure (DH) grown on a lattice-matched GaAs/sub 0.7/P/sub 0.3/ substrate have been fabricated for the first. The external quantum efficiency of 0.156% for the orange LEDs can be achieved by introducing the GaP material as the current spreader and window layer for the DH LEDs.<>     

Enhancing the output power of GaN-based LEDs grown on wet-etched patterned sapphire substrates

GaN-based light-emitting diodes (LEDs) with emitting wavelength of 450 nm were grown on patterned sapphire substrates (PSSs) fabricated by chemical wet etching. The crystallography-etched facet was {1-102} R-plane with a 57/spl deg/ against {0001} C-axis and had superior capability for enhancing light extraction efficiency. The light output power of the PSS LED was 1.15 times higher than that of the conventional LED at an injection current of 20 mA. The output power and external quantum efficiency were estimated to be 9 mW and 16.4%, respectively. The improvement was attributed not only to geometrical shapes of {1-102} crystallography-etched facets that efficiently scatter the guided light to find escape cones, but also to dislocation density reduction by adopting the PSS growth scheme.     

Transient response of a peak voltage detector for sinusoidalsignals

A fast peak detector for constant frequency sinusoidal signals is proposed. This detector is based on the concept of the orthogonal function set. The theoretical response time of this detector is less than one-fourth of a cycle. When this detector is used, the transient response of the output voltage is different under different inception angles. The mathematical equations to describe transient phenomena are derived and simulated. Because its transient response performance is superior to the conventional sinusoidal amplitude detector used in an analog controller, it can improve the transient response performance of the controller. For practical applications, the effects of harmonics and frequency variation are also discussed, simulated, and tested     

A novel structure of woven continuous-carbon fiber composites with high electromagnetic shielding

A novel structure employing the woven continuous-carbon fiber (CCF) epoxy composite with high electromagnetic (EM) shielding is presented experimentally and theoretically. The influences of weave type, number, and angle of overlapped plates upon the shielding effectiveness (SE) of the woven CCF-epoxy composite are investigated. The minimum SE of the single, double, and triple-plain or balanced-twill woven CCF-composite plates was measured to be as high as 50 dB, 60 dB, and 70 dB, respectively. More than 100 dB in SE was obtained for the triple-overlapped, plain-weave CCF composite at a frequency of 0.9 GHz. The weight percentage of the single CCF-composite plate required for electronic application is 4.8% only, which is less than one quarter of the CF content, and the performance in SE is 10 dB higher in comparison with long, CF-filled, liquid-crystal polymer (LCP) composites. The SE calculated theoretically is consistent with that measured by the experiment.     

Lattice parameter determination of mullite by energy-filtered needle-texture electron diffraction pattern

The thermal transformations of pyrophyllite to mullite by heating were re-examined using mainly energy-filtering transmission electron microscopy and, for the first time, the texture electron diffraction pattern of the mullite was completely interpreted. Through a temperature range in which pyrophyllite dehydroxylate maintained a long-range order with a fluctuation of approximately 1% in d-spacings of (100) and (010) planes at 1000 degrees C, without prominent exothermic feature, pyrophyllite dehydroxylate was gradually decomposed and transformed into mullite through topotaxy. Pyrophyllite dehydroxylate did not collapse completely until 1100 degrees C, which promoted the rapid growth of mullite in random orientation at 1200 degrees C and the crystallization of amorphous silica to cristobalite at 1300 degrees C. The mullite needles, having their c-axis (texture axis) parallel to the elongation direction, lined up along the b(*)-axis of the pyrophyllite dehydroxylate in the needle-texture electron diffraction patterns. The mullite needles had monoclinic symmetry with lattice parameters of 7.27 A (a), 7.75 A (b), 2.90 A (c), 90 degrees (alpha), 90 degrees (beta) and 88.41 degrees (gamma), which, because of the structural affiliation to the parent pyrophyllite dehydroxylate, differ to the orthorhombic 3/2-mullite.     

Bibliometric Analysis of Physics in Catalonia: Towards Quality Consolidation?

This paper studies the main bibliometric figures in order to analyse the "states of the art" and the evolution of research in physics in Catalonia (Spain) between 1981 and 1998 via the National Citation Report (NCR) for Catalonia elaborated by ISI (Institute for Scientific Information). The main indicators and parameters used are: bibliometric size, rate of citation, citedness of papers, concentration of scientific categories, journals and types of paper, index of immediacy, international collaboration, and papers and citation distribution by research centres and universities.     

ALTO: an iterative area/performance tradeoff algorithm forLUT-based FPGA technology mapping

In this paper, we propose an iterative area/performance tradeoff algorithm for look-up table (LUT)-based field programmable gate array (FPGA) technology mapping. First, it finds an area-optimized, performance-considered initial network by a modified area optimization technique. Then, an iterative algorithm consisting of several resynthesizing techniques is applied to trade the area for the performance in the network gracefully. Experimental results show that this approach can efficiently provide a complete set of mapping solutions from the area-optimized one to the performance-optimized one for the given design. Furthermore, these two extreme solutions produced by our algorithm outperform the results provided by most existing algorithms. Therefore, our algorithm is very useful for the timing-driven, LUT-based FPGA synthesis     

Effect of immobilization of poly(γ-glutamic acid) on the biocompatibility of electrospun poly (L-lactide) mats

In this study, poly(L-lactide) (PLLA) non-woven mats were prepared by electrospinning technique, followed by treating with oxygen plasma and grafting with 3-aminopropyl triethoxysilane (APTES), then immersed in poly(γ-glutamic acid) (γ-PGA) solution to form a layer of γ-PGA on the surface. In so doing, hydrophobic PLLA would become highly hydrophilic. Through characterization of hydrophilicity and biocompatibility, the feasibility of these modified mats for wound dressing was evaluated. The results show that after the grafting of γ-PGA, the swelling ratio increased greatly from 7% for pristine PLLA mat to 321% for γ-PGA-grafted PLLA mat, and the contact angle decreased from 112° to 25°. In vitro cytocompatibility tests against L929 fibroblast show that γ-PGA-grafted PLLA was non-cytotoxic. In addition, the proliferation of fibroblasts was higher on γ-PGA-grafted PLLA than on pristine PLLA.     

Reduction of greenhouse gas emission on a medium-pressure boiler using hydrogen-rich fuel control

The increasing emission of greenhouse gases from the combustion of fossil fuel is believed to be responsible for global warming. A study was carried out to probe the influence of replacing fuel gas with hydrogen-rich refinery gas (R.G.) on the reduction of gas emission (CO₂ and NO_x) and energy saving. Test results show that the emission of CO₂ can be reduced by 16.4% annually (or 21,500 tons per year). The NO_x emission can be 8.2% lower, or 75 tons less per year. Furthermore, the use of refinery gas leads to a saving of NT$57 million (approximately US$1.73 million) on fuel costs each year. There are no CO₂, CO, SO_x, unburned hydrocarbon, or particles generated from the combustion of added hydrogen. The hydrogen content in R.G. employed in this study was between 50 and 80 mol%, so the C/H ratio of the feeding fuel was reduced. Therefore, the use of hydrogen-rich fuel has practical benefits for both energy saving and the reduction of greenhouse gas emission.