Dynamic scaling and ultrasonic attenuation in 4He near the superfluid transition point

Attenuation of first sound has been measured in ⁴He under saturated vapor pressure near the lambda temperature T at frequencies /2 ranging from 10.2 to 271 MHz. The frequency dependence of the critical part of the attenuation is determined and the dynamic scaling hypothesis is examined. Above the lambda point, it is found that the critical attenuation is described by a scaling function (, ) = ^1+y F(), where = ₀^–x and = T/T – 1, with the results x = 1.02±0.05 and y = 0.33±0.03. The characteristic frequency of the order-parameter fluctuation with the wave number k equal to the inverse correlation length is then proportional to ^x , which is in an excellent agreement with the prediction of dynamic scaling. Below the lambda point, a characteristic relaxation time or times shorter than previously expected at lower frequencies appears to exist in the present frequency range.Based on a Ph.D dissertation submitted by K. Tozaki to the University of Tokyo (1977).     

Formation of layer-like voids in irradiated polytrioxane

The formation of voids and defects is investigated by X-ray diffraction methods, by weight loss measurement and by electron microscopy, for an irradiated polytrioxane (PTOX) obtained by the-ray-induced polymerization of trioxane in the solid state. The main reasons for the formation of the layer-like voids are transverse decomposition at a selective point accessible to the radiation in the micro-fibrils, and the subsequent extensible depolymerization which may occur from the unstable chain end with increase of the radiation dose. The analysis of the SAXS curve for the irradiated PTOX, according to Tsvankin's method gives reasonable results for the void structure, where the reduction of the sub-crystal fraction and also the weight loss of the sample by irradiation are taken into account.     

Oxidative Decomposition of N,N'-Dimethylformamide over Pt Catalysts with H2 Addition to the Feed

Catalysis of decomposition of dilute N, N'-dimethylformamide was explored. Among the catalysts investigated, Pt displayed the highest activity at low temperatures (~200 °C) and DMF conversion was promoted by H₂ addition to the feed. As the Pt support material, H-ZSM-5 exhibited the best performance at around 200 °C in terms of harmless decomposition.     

Development of an electroless CoNiZnP solution for high coercivity films

This paper describes the development of an electrolessly deposited CoNiZnP film for use in magnetic storage devices. A low temperature type solution, which can be operated at 310 K, has been developed. High coercivity films, which have a coercivity of 135 kA m^–1 (1700 Oe) at a film thickness of 80 nm, are deposited from the solution     

New carbon composites containing ultrafine Fe,Co, or Ni particles. 1. Facile synthesis by pyrolysis of organometallic polymers

Uniformly dispersed, air-stable carbon composites containing ultrafine α-Fe, Co, or Ni particles were obtained by a careful two-step thermal degradation of a copolymer of acrylonitrile (AN) and 2,4-hexadienyl-[tri(carbonyl)iron] acrylate. Carbonization yields were 45–55% and metal particle size ranged from 80 to 120 nm. Analogous degradation of the acrylonitrile copolymer with CoCl₂(AN)₂, CoCl₂(4-vinylpyridine)₂, or Ni(bis-styrene carboxylate) gave similar composites containing β-Co (18 nm), β-Co (55 nm), or cubic Ni (52 nm) particles, respectively, with lower carbonization yields. Other salient features noted for the metal-containing composites are progressive graphitization promoted by catalysis of nascent metal species at low temperature, microporous structures with surface areas of 75 and 55 m² g^?1 for Co and Ni composites, respectively, high electrical conductivities (10–10² S cm^?1), ferromagnetism, and catalysis in the decomposition of H₂O₂.     

Peeling Behavior and Spalling Resistance of Bonded Bidirectional Fiber Reinforced Polymer Sheets

This paper presents the peeling behavior and spalling resistant effect of bidirectional fiber reinforced polymer (FRP) sheets externally bonded to concrete surfaces. Experimental investigations are carried out through a series of newly designed punching-peeling tests. A wide range of variables, such as FRP sheet layers and fiber direction, plate constraint, concrete strength, adhesives, bond length of FRP sheets, diameter of indenter, and types of fibers, are considered in the experimental investigation. Theoretical study is also conducted for the specimens. Interfacial fracture energy is calculated analytically using a membrane-peeling method. It is realized that only two material parameters, i.e., the interfacial fracture energy of the FRP-concrete interface and the tensile stiffness of FRP sheets, are necessary to represent the interfacial spalling resistant behavior. Finally, the theoretical results are validated by comparing with experimental results. Comparison of theoretical to experimental results shows that the proposed theoretical model is satisfactory in reasonably and accurately predicting the peeling behavior and spalling resistant capacity of bidirectional FRP sheets bonded to concrete surface.     

Thermal management with self-rewetting fluids

The present paper describes the results of a series of microgravity experiments on thermal management device, actually wickless heat pipes, with using the so-called “self t-rewetting fluids” (dilute aqueous solutions of high carbon alcohols) as a working fluid. Although most of liquids show a decrease in the surface tension with increasing temperature, self-rewetting fluids show exceptionally an increase in the surface tension with increasing temperature. This particular characteristic allows for a spontaneous liquid supply to hotter interface by the thermocapillary flow. When liquid/vapor phase change takes place, furthermore, additional Marangoni effect due to concentration gradient by the preferential evaporation of alcohol-rich composition in the aqueous solutions is induced. A considerably strong liquid inflow to dry patch or thin film is therefore expected at three-phase interline or liquid/vapor interface. One of the most promising applications of the self-rewetting fluids in space is wickless heat pipes in which condensate spontaneously returns to evaporation region by enhanced Marangoni effect. Demonstrational experiments on the fluid behavior in a transparent glass tube wickless heat pipe were conducted in JAMIC, and spontaneous liquid return velocities were measured. The present authors then performed parabolic flight experiments on heat transfer characteristics of prototype wickless copper heat pipes, and the performance was compared with ordinary heat pipe having wick structure and with other working fluid.     

Motion error correction for non-contact ultrasonic motor driven by multi-layered piezoelectric actuators

An active non-contact ultrasonic motor with the micro positioning abilities of a rotor was proposed and performances were tested. The stator had a simple cylindrical form, which enabled low manufacturing costs. A resonant frequency of 22.2 kHz at eighth flexural mode of vibration was observed. With appropriate assembly and operation of piezoelectric actuators, the flexure vibration of the stator travels in the circumferential direction. The component of the stator deformation in radial direction creates an air film pressure higher than ambient thereby suspending the rotor. Simultaneously, the component that propagates in the circumferential direction rotates the rotor based on acoustic viscous flow. It was experimentally confirmed by electrical conduction test that the rotor rotated with levitation from stator. In addition, piezoelectric actuators around the stator exciting the deflective vibration could make contact-free micro positioning abilities of the rotor with a minimum step width of 0.15 μm.     

在点线接触条件下钢/钢摩擦副的干摩擦高温减摩抗磨性能的研究

用多功能SRV实验机评价了钢/钢摩擦副在干摩擦条件下的的高温减摩抗磨性能,并对高温磨损机理进行了探讨.结果表明,钢/钢摩擦副的高温摩擦系数随着实验负荷的增加呈下降趋势,而随着实验时间的延长呈增长趋势.钢/钢摩擦副的线接触高温摩擦系数明显比点接触时的高温摩擦系数大,SPHC/GCr15摩擦副的高温摩擦系数明显高于GCr15/GCr15摩擦副的高温摩擦系数.钢球在点接触条件下的磨损随实验负荷的增加呈线性增长趋势,而钢柱在线接触条件下的磨损随实验负荷的增加呈线性降低趋势.在相同负荷下,SPHC/GCr15摩擦副的磨损要较GCr15/GCr15摩擦副的磨损略微大.钢/钢摩擦副在高速度下的磨损机理主要是磨粒磨损,而在较低速度下主要是磨粒磨损和粘着磨损.     

Surface Magnetism of Liquid 3He on 4He Pre-plated Graphite

No Heading The nuclear susceptibility of liquid ³He in Grafoil pre-plated by 2.5 and 3.5 layers of ⁴He has been studied with a cw NMR method at temperatures between 0.7 and 100 mK under various liquid pressures. The 3.5 layers of ⁴He pre-plating suppresses a formation of the first and second solid ³He layer, eliminating most of surface magnetization at saturated vapor pressure. However, with increasing liquid pressure, a magnetization obeying a Curie Weiss law gradually grows in the same way as in the previous experiment for pure liquid ³He. This magnetization, induced by pressurization, is attributable to the formation of solid ³He layer above the pre-plated ⁴He.PACS numbers: 67.80.Jd, 75.70 Cn, 67.70.+n.