Analytic Solution for Axial Point Load Strength Test on Solid Circular Cylinders

This paper presents a new analytic solution for the stresses within an elastic solid finite cylinder subjected to the axial point load strength test (PLST). The “displacement potential approach” is used to uncouple the equations of equilibrium; then the contact stresses on the end surfaces induced by the point load indentors are expanded in terms of a Fourier-Bessel expansion to yield the unknown constants of the appropriate form of the displacement potential. Our solution shows that a zone of higher tensile stress is developed in the vicinity of the applied point loads, compared with the roughly uniform tensile stress in the central portion of the line between the two point loads. This peak tensile stress within the cylinder decreases with increasing Poisson's ratio and the size of the loading area, and it increases with increasing Young's modulus. The tensile stress distributions along the axis of symmetry in a cylinder under the axial PLST are remarkably similar to that observed in a sphere under the diametral PLST. Our solution also demonstrates both size and shape effects on the point load strength index (PLSI) that we observed in our experiments. In particular, for a fixed length-to-diameter ratio, the larger the specimen, the smaller the PLSI, whereas for a fixed diameter, the longer the specimen the smaller the PLSI.     

Activation of c-Jun NH2-terminal kinase and subsequent CPP32/Yama during topoisomerase inhibitor beta-lapachone-induced apoptosis through an oxidation-dependent pathway

PKR is an interferon-inducible, double-stranded (ds) RNA-activated serine/threonine protein kinase, and has been shown to play roles in viral pathogenesis, cell growth and apoptosis. We expressed PKR as a fusion protein with enhanced jellyfish green fluorescence protein (EGFP) in human embryonic kidney 293 cells to visualize the effect of PKR transfection. The EGFP-fusion construct with wild-type PKR showed both auto- and substrate-phosphorylation activities independent of dsRNA, indicating EGFP-PKR is constitutively active. The EGFP-construct with a mutant PKR with the first RNA binding domain deleted still possessed kinase activities. On the other hand, the EGFP-fusion with a catalytically inactive mutant of PKR with the substitution of K at 296 with R, which has been shown to have tumorigenic properties, did not possess kinase activities. Transfection of the constitutive active forms of EGFP-PKR constructs induced apoptosis in 293 cells without dsRNA, whereas the EGFP-fusion with the catalytically inactive mutant did not cause apoptosis but rather protected cells from Fas-induced cell death. In addition, Fas-stimulation increased endogenous PKR activities. These results constitute evidence that PKR is sufficient to induce apoptosis, and plays a role in Fas-mediated apoptosis.     

Clarification of viscous poly tetramethylene ether glycol (PTMEG) containing solid suspension by dead‐end flow microfiltration under constant pressure

In this study, the microfiltration of polyester fluid containing solid suspension has been investigated under constant pressure. A membrane module, which consists of a microfilter paper of surface area of 19.4 cm² and a SS‐316 net support (160 mesh), was used. It was found that the homogeneous sodium acetate suspension in polymer can be completely removed by the membrane filter paper to yield a very clear polymer product. The property and rheology of polyester fluid with suspending solids have been studied. The polymer fluid can be viewed as a Newtonian fluid in this work. The filtration behavior in the membrane system was simulated by the blocking filtration law. Satisfactory fit between experimental data and theoretical calculations was demonstrated. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 2303–2312, 1999     

An empirical investigation on factors affecting the acceptance of CASE by systems developers

This paper presents the findings of an empirical study of factors affecting the acceptance of CASE by systems developers. Based on two research models (technology acceptance and personal computer utilization) recently published in IS literature, an integrated model which consists of six variables and incorporates key elements of both models was developed to examine determinants of CASE acceptance. The findings indicate that ease of use has the largest influence on CASE acceptance, followed by long-term consequences. Both transitional support and near-term usefulness do not have a significant direct effect on the acceptance but exhibit their indirect influence through ease of use and/or long-term consequences. The implementation gap was found to have a relatively small and negative effect on CASE acceptance through its influence on ease of use, near-term usefulness, and long-term consequences. Implications of the findings, from both a research and a managerial perspective are discussed in this paper.     

The effect of surface chemistry in lubrication on the tribological behaviour of steel rollers under rolling-sliding contacts

Experiments were carried out on a wear test machine utilising a gearcam adapter to simulate line-contact lubrication. Due to the formation of a surface adsorption layer on the steel substrate, the tribological performance was detected by measuring the voltage for a lubricant with various additive concentrations. The roller wear rate was found to be strongly dependent upon both the rising rate of voltage in the wear process and the time period needed to create a positive voltage. The antiwear effect of differing additive concentrations was evaluated using the measurements of voltage for various operating conditions. An increase in rotational speed, with a lubricating oil with a low additive concentration, decreases the wear rate. A lubricating oil with a high additive concentration does little to decrease the wear rate at low rotational speeds.     

Upconversion luminescence of Gd2O3:Er3+ and Gd2O3:Er3+/silica nanophosphors fabricated by EDTA combustion method

Gd_2O_3:Er~(3+) nanophosphors were fabricated by the combustion method in presence of Na_2 ethylene diamine tetra acetic acid(EDTA-Na_2) as fuel at not high temperature(≤350℃) within a very short time of 5 min.The added concentration of Er~(3+)ions in Gd_2O_3 matrix was changed from 0.5 mol% to 5.0 mol%.The X-ray diffraction pattern of samples indicates the monoclinic structure of Gd_2O_3:Er3+.The morphology and chemical composition analysis of the Gd_2O_3:Er~(3+) samples are characterized by a field emission scanning electron microscope(FESEM) and a Fourier-transform infrared spectrometer(FTIR).The photoluminescence(PL),photo luminescence excitation(PLE) and upconversion(UC) at room temperature of the prepared materials with different concentrations of Er~(3+) were investigated.The PL of Gd_2O_3:Er~(3+)nanomaterials are shown in visible at 545,594,623,648,688 nm under excitation at 275 nm.The emission bands from transitions of Er~(3+) from ~2P_(3/2) to ~4F_(9/2) are observed,UC luminescent spectra of the Gd_2O_3:Er~(3+)/silica nanocomposites under 976 nm excitation show the bands at 548 and 670 nm.The influence of excitation power at 980 nm for transitions were measured and calculated.The results indicate that the upconversion process of Gd_2O_3:Er~(3+)/silica is two photons absorption mechanism.The low temperature dependence of UC luminescent intensities of the main bands of Gd_2O_3:Er~(3+)was investigated towards development of a nanotemperature sensor in the range of 10-300 K.     

Soft lithography replication based on PDMS partial curing

In this paper, a partial curing technique is presented. Its aim is to enable the soft lithography replication process for the case requiring usage of PDMS mold. Through controlling the curing time during molding step, the liquid PDMS prepolymer in original status, which will later constitute the device substrate, can be partially polymerized as well as solidified. As a result, not only can the structural pattern in the mold be successfully transferred into the device layer, but also the spontaneous adhesive interaction between these two PDMS parts happening during curing can be effectively limited within very low level, thus largely facilitating the demoulding process. Based on this process, several devices have been successfully developed and high fidelity pattern transfer capability has also been demonstrated. Comparing with the most commonly used treatments such as silanization, the presented method demonstrates easier operation and better user-friendly interface advantages.     

An efficient numerical approach to studying impact ionization in sub-micrometer devices

A positive feedback model is introduced to facilitate numerical calculations of the impact-ionization current gain in sub-micrometer devices. Demonstrations of this model’s applicability are done through Monte Carlo simulations to fit the experimental data of short p-i-n diodes. It is shown from the simulations’ results that the phonon-collision broadening effect and the intra-collisional field effect play an important role in the II process in deep sub-micrometer devices. It is also shown, for the first time, that the impact-ionization rates at very low energies can be extracted from the measured current gain in short p-i-n diodes.