Photoablation and lens damage from fractional Talbot images of Dammann gratings

UV photoablation of materials is recorded for both the near and far fields after transmission through a Dammann grating. The fused silica Fourier lens used for far-field imaging was damaged by a near-field intensity pattern with the same periodicity as the Dammann grating. The lens was located inadvertently at one eighth of the Talbot distance Z (T) behind the Dammann grating. Patterns recorded in copper film at the even-fractional Talbot planes compare qualitatively with calculated intensities. On the basis of these findings, a near-field intensity pattern was used to ablate vias in copper and polyimide films. The pattern at a distance of Z(T)/8 was used for via ablation because it is the pattern with the most fluence per spot.     

水溶液中电沉积非晶态Ni-RE-P（RE=Ce，Nd）稀土合金

报道了从水溶液中电沉积稀上含量高于30％的Ni-RE-P(RE=Ce，Nd)合金，其中Ni-P，Ni-Ce-P及Ni-Nd-P合金镀层均为非晶态结构，玻璃化温度约为385℃；用DTA测定了3种合金的晶化活化能分别为：523．3kJ／mol，574．4kJ／mol，558．9kJ／mol；利用二维Miedema坐标(△φ^*和△nws^-1.3)以及加入尺寸因素(△R/RA)构成的三维化学坐标分析了合金的非晶形成规律，探讨了实现稀土合金电沉积的途径，具体为：选择适当的络合剂、合适的电极材料及合适的共沉积元素。     

Small-scale resistance spot welding of austenitic stainless steels

Small-scale resistance spot welding (SSRSW) was carried out for austenitic stainless steels. A weld lobe that shows the process window for making sound joints was obtained for type 304 stainless steel thin sheets, and the effects of welding current, force and weld time on joint strength and nugget size were investigated. The cooling rate that was estimated from the solidification cell size was approximately 2.4 × 10⁵ K/s which is almost similar to that produced by laser beam welding. The microstructures of weld zones were almost fully austenitic due to the rapid solidification rate. Despite the fully austenitic microstructure, no hot cracking was found in types 302, 304, 316L, 310S and 347 austenitic stainless steels by SSRSW. Rapid cooling rate in SSRSW made it difficult to predict the microstructures from the conventional Schaeffler diagram.     

Quantitative hydrogen analysis of zircaloy-4 using low-pressure laser plasma technique

It is found in this work that variation of laser power density in low-pressure plasma spectrochemical analysis of hydrogen affects sensitively the hydrogen emission intensity from the unwanted and yet ubiquitous presence of ambient water. A special experimental setup has been devised to allow the simple condition of focusing/defocusing the laser beam on the sample surface. When applied to zircaloy-4 samples prepared with various hydrogen impurity concentrations using low-pressure helium surrounding gas, good-quality hydrogen emission lines of very high signal to background ratios were obtained with high reproducibility under weakly focused or largely defocused laser irradiation. These measurements resulted in a linear calibration line with nonzero intercept representing the residual contribution from the recalcitrant water molecules. It was further shown that this can be evaluated and taken into account by means of the measured intensity ratio between the oxygen and zirconium emission lines. We have demonstrated the applicability of this experimental approach for quantitative determination of hydrogen impurity concentrations in the samples considered.     

Improvement in the tribological properties of imidazolium‐derived ionic liquids by additive technology

Molecular design of wear‐preventing and friction‐reducing additives for ionic liquids is described. The tribological properties of carboxylic acid‐derived additives were evaluated by a ball‐on‐flat type tribotest under reciprocating motion. Tetraalkylammonium and tetraalkylphosphonium salts of N‐benzyl‐protected aspartic acid were dissolved in 1‐alkyl‐3‐methylimidazolium‐derived ionic liquids. They prevented wear remarkably and reduced friction fairly. Influences of alkyl group in imidazolium molecule on additive response were observed. In tetraalkylammonium‐derived ionic liquids, the additive reduced wear but did not reduce friction under these conditions. The salt of N‐acetyl‐protected glutamic acid prevented wear, but did not reduce friction. Copyright © 2008 John Wiley & Sons, Ltd.     

Mechanical and thermal properties of ZrSiO4

In order to conduct defueling operations for the decommissioning of the reactor at the Fukushima Daiichi nuclear power plant, an understanding of the physical properties of ZrSiO₄ is of extreme importance. ZrSiO₄ appears to have formed in the molten core–concrete interaction products at the Fukushima Daiichi nuclear disaster site through a reaction between Zircaloy cladding materials and concrete. Since ZrSiO₄ has a high melting point of 2550 K, together with chemical inertness, the material has been widely studied as a refractory material. Various studies on the physical properties of ZrSiO₄ have been performed; however, significant differences exist in the data, possibly due to the porosity within the studied samples. In the present study, we have prepared a ZrSiO₄ bulk sample with 97.4% of the theoretical density by spark plasma sintering of the ZrSiO₄ powder and heat treatment. We have evaluated the thermal and mechanical properties of ZrSiO₄ by the measurement of sound velocities, thermal diffusivity, Vickers hardness, and fracture toughness. The Vickers hardness and fracture toughness were found to be 17 ± 3 GPa and 2.1 ± 0.5 MPa m^1/2, respectively.     

Assessment of cervical lymph node metastasis in esophageal carcinoma using ultrasonography

Cadherins are Ca2+-dependent cell-cell adhesion molecules, and are involved in the formation and maintenance of the organocellular architecture. Using a combination of molecular biologic and biochemical methods, we analyzed cadherins expressed on cultured human malignant lymphoma cell lines (adult T cell lymphomas, human T cell leukemia virus type 1-negative T cell lines, and thymus-derived lymphoma cell lines), and obtained evidence that N-cadherin is the major cadherin expressed on these cells. These cells were found to form cell aggregates in a Ca2+-dependent manner, and more importantly to coaggregate and adhere with cells expressing N-cadherin, suggesting that N-cadherin on lymphoma cells is functionally active. Therefore, N-cadherin expressed on lymphoma cells could underlie the frequent invasion of these cells into the mesenchymal tissue in the skin and the central nervous system.     

Tunable external-cavity semiconductor laser using monolithicallyintegrated tapered amplifier and grating coupler for collimation

A novel lensless tunable external-cavity laser using monolithically integrated tapered amplifier, grating coupler (GC) and an external half mirror is proposed and demonstrated. It can be fabricated by a simple process and emits a collimated output beam. By making use of wavelength dispersion of the GC, the lasing wavelength can be angle tuned. Wavelength tuning over a wide range of 21.5 nm by 4.5° device rotation and an 84-mW output power were achieved under continuous-wave operation. A well-collimated output beam with a divergence angle as small as 0.3° was maintained over the entire tuning range     

Effects of fiber compression and length distribution on the flexural properties of short kenaf fiber‐reinforced biodegradable composites

The effects of the fiber compression and the length distribution on the flexural properties of short kenaf fiber‐reinforced biodegradable composites were investigated. Two types of kenaf (KU and KT) that were different in the density and the length distribution were used as reinforcements. These fibers were mixed with a corn–starch‐based resin, and the composite specimens were fabricated by a hot press forming. The flexural modulus in the KU specimens was not different from that in the KT, despite the difference of the fiber Young's modulus (KU 14.5 GPa and KT 22.1 GPa). This was because the KU was compressed more than the KT in the composite specimen because of the lower density structure. However, in the longest fiber (10.5 mm), the flexural strength in the KT specimens was considerably higher by 67% than that in the KU. The reason was that the KT did not include the fibers below the critical length (4.2 mm) because of the narrower fiber distribution than the KU. In fact, the flexural strength in the KT specimen significantly decreased with decrease in the average fiber length, which included the fibers below the critical length. Moreover, the flexural modulus agreed well with the calculated values by Cox's model that incorporated the effect of the fiber compression. POLYM. COMPOS. 27:170–176, 2006. © 2006 Society of Plastics Engineers     

粒子扁平现象研究现状及发展

热喷涂过程中熔滴在与基材撞击后的扁平及固化行为是形成涂层过程中的一个基本现象,因此,关于单个粒子扁平化行为的研究不可或缺.从等离子喷涂过程中基材预热温度、喷涂压强环境、材料润湿能力、基材的表面粗糙度、固化能力、脱附吸附能力等因素对粒子扁平化转变的影响,以及研究过程中自由下落试验和数值模拟方法的应用,概述了关于粒子扁平现象的研究现状.指出了未来关于粒子扁平化研究的发展趋势在于结合数值模拟和喷涂试验,以期找出粒子扁平化的控制因素.并解释了基材在较高的预热温度和低压条件下,盘状沉积为何更容易出现.