有氧条件下氩弧焊钨电极表面的烧蚀

研究了在有氧条件下钨极氩弧焊的钨电极表面的烧蚀.研究结果表明,有氧条件下钨电极的钨基体烧蚀大大增加,主要原因是在一定温度范围内发生了氧和钨的反应;添加氧化钍的烧蚀主要是由于氧化钍的熔化和蒸发,采用纳米尺寸氧化钍的电极,氧化钍的烧蚀明显减轻,有助于提高钨电极的使用寿命.采用纳米氧化物添加钨电极以及保证保护惰性气体的纯度和流量可以降低钨电极的烧蚀,保证焊接质量.     

Substitution effects on the electronic anomaly and superconductivity in La2−xBaxCuO4 and La2−xSrxCuO4 with x ∼ 1/8

The effects of substitution of Y or Bi on the low-temperature structural phase transition, electronic anomaly and superconductivity have been studied in La_2-y-xY_yBa_xCuO La_2-y-xBi_yBa_xCuO₄ and La_1.9-y-xTb_0.1Bi_ySr_xCuO₄ with x = 1/8. Moreover, an electronic anomaly, which is analogous to those observed in La_2–xBa_xCuO₄ and La_1.6-xNd_0.4Sr_xCuO₄ with x 1/8, has been found below about 60 K in the thermoelectric power measurements for the Zn-substituted La_2–xSr_xCu_1–yZn_yO₄ with x 0.115 and y = 0.01 – 0.02. These experimental results support the conclusions by Tranquada et al. that static order of the stripe correlations of holes and spins, owing to pinning by the low-temperature structure or impurities (Zn in this case), is the origin of the electronic anomaly, leading to the suppression of superconductivity.     

Gait motion for naturally curving variously shaped corners

Modeling the curving motion of humans in actual environment is rarely done because of the complexity and variability of the turning motion. In this study, various gait motions, including straight, round corner, and circular walks, were recorded and analyzed using factor analysis. As a result, we successfully extracted several factors that represent turning motions, such as long stride motion, turning motion led by the inner leg, and turning motion led by the outer leg. In particular, we found that the natural curving motion, which is a motion that results when turning around a round corner, is widely and continuously distributed on the factor space. Although several typical stepping strategies were reported by related studies, we found that the stepping motion changes between straight and turning gaits in the factor space during natural curving motions. Thus, the classification of curving motion into several typical distinct stepping patterns is probably insufficient to understand the natural curving motion. Furthermore, natural curving motions that comprise circular curving motions that were believed to represent typical curving motions was not validated. On the other hand, this result also suggests the possibility of generating curving motions for a physical assistant robot by combining straight gait and circler curving motion.     

Effect of strong gravitational field on oriented crystalline perovskite-type manganese oxide La<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Sr<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>MnO<Subscript>3</Subscript>

We report the effect of a strong gravitational field on oriented crystalline perovskite-type manganese oxide La_1?x Sr _x MnO₃ (LSMO). The perovskite-type manganese oxides La_1?x Sr _x MnO₃ (LSMO) have been investigated for giant magnetoresistance (GMR) by controlling the hole-doping level (x). A strong gravitational field can change in crystalline state and the enhancement of usual diffusion. We subjected oriented crystalline La_1?x Sr _x MnO₃ with different grain and grain-boundary (GBs) Sr concentrations to a strong gravitational field and investigated the resulting changes in the A-site cation diffusion and physical properties of the material. Electron probe micro-analysis (EPMA) results showed appearance of the GBs where the Sr concentration was quite high compared with in other GBs. The quantitative analysis at the grain and GBs indicated that cation diffusion was more enhanced than the annealed one. The temperature dependence of the magnetic susceptibility of the gravity samples changed with the Sr concentration in the grains. The temperature dependence of the resistivity curves of the gravity sample showed several abrupt changes, which corresponded to phase transitions at the grains and GBs, which may be caused by composition changes.     

Emission mechanism in phosphorescent and fluorescent OLED utilizing energy transfer from exciplex to emitter

This paper discusses the effectiveness of energy transfer from an exciplex to an emitter in both phosphorescent and fluorescent organic light‐emitting diodes. This energy transfer enhances the efficiency, lowers the drive voltage, and extends the lifetime. The increase in the quantum efficiency of a fluorescent organic light‐emitting diode using this mechanism is also analyzed.     

Single polymer chain rubber elasticity investigated by atomic force microscopy

A method, which is called as ‘nanofishing’, enabled us to stretch a single polymer chain adsorbed on an Au(111) substrate with picking it at its two thiol-modified termini using atomic force microscope equipped with a gold-coated probe. A force-extension curve obtained for a single polystyrene chain in a Θ solvent (cyclohexane) showed a good agreement with a so-called worm-like chain model, and thus gave microscopic information about entropic elasticity. Solvent effects on the statistical properties of single polymer chains were also investigated. For example, the second virial coefficient in cyclohexane was determined at a single polymer basis, which was almost comparable with a simple Flory's lattice model.     

Preparation and properties of a siloxane‐containing 2‐vinylpyridine–styrene–butadiene copolymer with water glass

A siloxane‐containing 2‐vinylpyridine–styrene–butadiene copolymer (PSBR/WG) was prepared from a 2‐vinylpyridine–styrene–butadiene copolymer (PSBR) latex and water glass. The water glass was added slowly, with stirring, to the PSBR latex. The latex mixture was stirred for 3 h at room temperature, and then, it was coagulated with 1N sulfuric acid producing a sulfate of PSBR with siloxane. The physical properties, such as the filling and stiffening effects of the hybrid polymer, and the vulcanizates were improved. An important advantage of this system is that it is possible to prepare the hybrid polymer simply, and the sodium ions formed in the reaction can also be easily removed. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 891–899, 2006     

Estimation of mixing index and contact number by spot sampling

Most of the available definitions of the mixing index, which specifies homogeneity or distribution of the composition in a solids mixture, are based on the variance of the concentration of a certain component among spot samples. However, for a solid—solid chemical reaction or any process involving contact between different solid phases, its rate is proportional to the contact points or area among particles of the different phases. Thus a definition of a microscopic and geometric mixing index based on the number of contact points appears to be of practical significance.The contact number is the number of contact points between two different types of particles for one key particles, a particle species which is selected as a reference. In this paper, the estimation of the mean contact number from spot samples is considered. An expression for estimating the contact number from spot samples is derived. Expressions for the expected value (population mean contact number) and the variance of this mean contact number are also derived. To verify these expression, random numbers with a uniform distribution are generated to simulate a binary component mixture in the completely mixed state. Results of the simulation are in reasonably good agreement with the derived expressions. The mixing index based on the mean contact number is able to indicate the homogeneity of a mixture with regular packing arrangement. In such a mixture, particles are packed either cubically or hexagonally in each layer, and therefore it is difficult to estimate the homogeneity of the mixture from the sample variance.     

Effect of pressure on phase behavior in polymer blends of poly(2,6-dimethyl-1,4-phenylene oxide) and poly(o-fluorostyrene-co-p-fluorostyrene) copolymers

The effect of pressure on miscibility and phase separation in blends of random copolymers of ortho- and para-fluorostyrene, P(o-FS-co-p-FS) and poly(2,6-dimethyl-1,4-phenylene oxide), PPO, has been studied by differential thermal analysis (DTA) at pressures up to 300 MPa. At 200 MPa the copolymers containing from 10 to 38 mol% p-FS are miscible with PPO below 230°C using the customary criterion of a single calorimetric glass transition temperature (T_g). Each blend undergoes phase separation upon annealing at higher temperatures at both atmospheric and elevated pressures indicating the presence of a lower critical solution temperature (LCST). When the phase behaviors of the 50/50 wt% blends are examined as a function of temperature and copolymer composition, a symmetric miscibility “window” can be observed in the resulting temperature-composition diagram with a maximum at about 22 mol% p-FS. In a complementary set of experiments, the pressure dependence of the phase boundary for the blend of PPO and P(o-FS-co-p-FS) in which the copolymer contained 29 mol% p-FS was studied. The temperature minimum of the phase boundary is at about 50 wt% PPO and is independent of pressure. The consolute temperature, T_c, increases at about 0.1₀°C/MPa up to 200 MPa and then becomes independent of pressure to reach an asymptotic value at around 270°C. Similar behavior is also observed for blends in which the copolymer composition contains either 16 or 23 mol% p-FS. In these blends the decrease of dT_c/dP at higher pressures may indicate that the negative volume of mixing approaches zero above 200 MPa. This study shows therefore, that pressure no longer plays a role in increasing the miscibility above 200 MPa.     

Amplifying shear deformation of finger pad increases tracing distances

Human sensory inputs and motor outputs mutually affect one another. We pursue the idea that a tactile interface can influence human motor outputs by intervening in sensory–motor relationships. This study focuses on the shear deformation of a finger pad while a person traces a line or circle. During these tracing movements, the finger pads were deformed using a tactile interface. The tracing distances increased when the finger pad deformations were amplified by the tactile interface, which indicates that the intervention in the haptic sensorimotor loop affected the tracing movements. Elucidation of such interaction between the tracing movements and the shear deformations of finger pads enhances the understanding of human-assistive haptic techniques.