Properties of a-C:H films deposited from a methane electron cyclotron wave resonant plasma

An electron cyclotron wave resonant methane plasma discharge was used for the high rate deposition of hydrogenated amorphous carbon (a-C:H). Deposition rates of up to ∼400 Å/min were obtained over substrates up to 2.5 in. in diameter with a film thickness uniformity of ∼±10%. The deposited films were characterised in terms of their mass density, sp3 and hydrogen contents, C-H bonding, intrinsic stress, scratch resistance and friction properties. The deposited films possessed an average sp3 content, mass density and refractive index of ∼58%, 1.76 g/cm3 and 2.035 respectively.Mechanical characterisation indicated that the films possessed very low steady-state coefficients of friction (ca. 0.06) and a moderate shear strength of ∼141 MPa. Nano-indentation measurements also indicated a hardness and elastic modulus of ∼16.1 and 160 GPa respectively. The critical loads required to induce coating failure were also observed to increase with ion energy as a consequence of the increase in degree of ion mixing at the interface. Furthermore, coating failure under scratch test conditions was observed to take place via fracture within the silicon substrate itself, rather than either in the coating or at the film/substrate interface. © 2003 Elsevier B.V. All rights reserved.

Low Temperature Properties of PI/SiO_2 Nanocomposite Films

In this paper, the mechanical properties of PI/Si_O, nanocomposite hybrid films with different silica doping levels are experimentally studied at low temperature. Experimental results show that the coefficient of thermal expansion (CTE) of the PI/Si_O, nanocomposite hybrid films gradually reduces when the ambiance temperature is decreased. At the liquid nitrogen temperature (77 K), the CTE value is about five times less than that at room temperature (287 K). The measured CTEs of hybrid films greatly decrease when doped with inorganic silica, especially when the silica doping level is more than 1 wt.%. However, too high silica contents (more than 10 wt.%) can cause problem to disperse effectively and the specimens become quite opaque. Experimental results also show that the effects of the pre-applied stress levels can be neglected on the CTE testing. When the ambient temperature changes from 287 to 77 K, the measured average values of the films' ultimate tensile strength (UTS) and Young's modulus increase about 60 and 90%, respectively, while the breaking elongation decreases about 42%.

Elastodynamic erosion of thermal barrier coatings

The finite element method is used to analyze the elastodynamic response of a columnar thermal barrier coating due to normal impact and oblique impact by an erosive particle. An assessment is made of the erosion by crack growth from preexisting flaws at the edge of each column: it is demonstrated that particle impacts can be sufficiently severe to give rise to columnar cracking. First, the transient stress state induced by the normal impact of a circular cylinder or a sphere is calculated in order to assess whether a 2D calculation adequately captures the more realistic 3D behavior. It is found that the transient stress states for the plane strain and axisymmetric models are similar. The sensitivity of response to particle diameter and to impact velocity is determined for both the cylinder and the sphere. Second, the transient stress state is explored for 2D oblique impact by a circular cylindrical particle and by an angular cylindrical particle. The sensitivity of transient tensile stress within the columns to particle shape (circular and angular), impact angle, impact location, orientation of the angular particle, and to the level of friction is explored in turn. The paper concludes with an evaluation of the effect of inclining the thermal barrier coating columns upon their erosion resistance. © 2011 The American Ceramic Society.

Characteristics Of Energy Dissipation In Hyperconcentrated Flows

An equilibrium equation for the turbulence energy in sediment-laden flows was derived on the basis of solid-liquid two-phase flow theory. The equation was simplified for two-dimensional, uniform, steady and fully developed turbulent hyperconcentrated flows. An energy efficiency coefficient of suspended-load motion was obtained from the turbulence energy equation, which is defined as the ratio of the sediment suspension energy to the turbulence energy of the sediment-laden flows. Laboratory experiments were conducted to investigate the characteristics of energy dissipation in hyperconcentrated flows. A total of 115 experimental runs were carried out, comprising 70 runs with natural sediments and 45 runs with cinder powder. Effects of sediment concentration on sediment suspension energy and flow resistance were analyzed and the relation between the energy efficiency coefficient of suspended-load motion and sediment concentration was established on the basis of experimental data. Furthermore, the characteristics of energy dissipation in hyperconcentrated flows were identified and described. It was found that the high sediment concentration does not increase the energy dissipation; on the contrary, it decreases flow resistance.

Designing Of Partial Similarity Models And Evaluation Method In Polymer Flooding Experiment

Based on the scaling criteria of polymer flooding reservoir obtained in our previous work in which the gravity and capillary forces, compressibility, non-Newtonian behavior, absorption, dispersion, and diffusion are considered, eight partial similarity models are designed. A new numerical approach of sensitivity analysis is suggested to quantify the dominance degree of relaxed dimensionless parameters for partial similarity model. The sensitivity factor quantifying the dominance degree of relaxed dimensionless parameter is defined. By solving the dimensionless governing equations including all dimensionless parameters, the sensitivity factor of each relaxed dimensionless parameter is calculated for each partial similarity model; thus, the dominance degree of the relaxed one is quantitatively determined. Based on the sensitivity analysis, the effect coefficient of partial similarity model is defined as the summation of product of sensitivity factor of relaxed dimensionless parameter and its relative relaxation quantity. The effect coefficient is used as a criterion to evaluate each partial similarity model. Then the partial similarity model with the smallest effect coefficient can be singled out to approximate to the prototype. Results show that the precision of partial similarity model is not only determined by the number of satisfied dimensionless parameters but also the relative relaxation quantity of the relaxed ones.

Notch sensitivity of circular rings subjected to impact loading

'Notch-sensitive regions' have been observed during a series of experimental investigations into the dynamic plastic behaviour and failure of thin-walled metallic radially notched circular rings with are-shaped supports subjected to concentrated impact loads. The experimental results show that the exterior notches at some regions have no effect on the deformation of the rings, but do have effect at the remaining regions. The notch-sensitive region is theoretically determined by using the equivalent structures technique; fairly good agreement has been reached between the simple theory and the experimental results. Both dimensional and theoretical analyses prove that whether a plastic hinge formed or not at the notched section does not depend on the mean radius of the ring and the input kinetic energy. It depends on the weak coefficient of the notched section and the angle of the support. Generally speaking, there are mainly three failure modes for a notched circular ring with are-shaped support under impact loading: Mode I, large inelastic deformation when the notch is outside the sensitive region, in this case the ring deforms as a normal one; Mode II, large inelastic deformation only at some part of the ring and tearing occurred at the notched sections; Mode III, large inelastic deformation and total rupture occurred at the notched sections. It is believed that the present study could assist the understanding of the dynamic behaviour and failure of other kinds of nonstraight components with macroscopic imperfections under impulsive loading.

Influence of convections on dopant segregation in floating-zone crystal-growth system

The steady and axisymmetric crystal growth process of floating zone model was studied numerically to concern with the influence of convection and phase change on effective segregation. An iteration method of numerical simulation considering both thermocapillary and buoyancy effects for GaAs crystal growth gave the effective segregation coefficient, which was compared with the space experiment of GaAs on board the Chinese recoverable satellite. The calculated segregation coefficient of a two-dimensional model was found to be smaller than the one suggested by space experiment with the simplified assumption of an one-dimensional model.

The concentration-jump coefficient in a rarefied binary gas-mixture

The problem of the concentration jump of a vapour in the vicinity of a plane wall, which consists of the condensed phase of the vapour, in a rarefied gas mixture of that vapour (A) and another 'inert' gas (B), is considered. The general formulation of the problem of determining the concentration-jump coefficient for dA is given. In the Knudsen layer the simplest model of Boley-Yip theory is used to simplify the Boltzmann equations for the binary gas mixture. The numerical calculation of the concentration jump coefficient for dA for various values of evaporation coefficient of A is illustrated for the case of the equilibrium concentration of B being much greater than that of A, for which experimental data are available.

Microscopic theory of chemical-reaction rate

In this paper we deduce the formulae for rate-constant of microreaction with high resolving power of energy from the time-dependent Schrdinger equation for the general case when there is a depression on the reaetional potential surface (when the depression is zero in depth, the case is reduced to that of Eyring). Based on the assumption that Bolzmann distribution is appropriate to the description of reactants, the formula for the constant of macrorate in a form similar to Eyring's is deduced and the expression for the coefficient of transmission is given. When there is no depression on the reactional potential surface and the coefficient of transmission does not seriously depend upon temperature, it is reduced to Eyring's. Thus Eyring's is a special case of the present work.

含尘大气近地层流底层流动特性及其摩阻系数

采用双向耦合的双流体模型，了大气悬浮沙尘的存在对大气边界层中流底层流动特性及摩阻系数的影响，计算并讨论了不同沙尘含量下含尘大气相对于无尘大气摩阻系数的变化，结果表明，摩阻系数的变化取决于悬浮沙尘的初始运动状态和质量载荷率。

Precision of age determination of northern offshore spotted dolphins.

We investigated within- and between-reader precision in estimating age for northern offshore spotted dolphins and possible effects on precision from the sex and age-class of specimens. Age was estimated from patterns of growth layer groups i n the dentine and cementum of the dolphins' teeth. Each specimen was aged at least three times by each of two persons. Two data samples were studied. The first comprised 800 of each sex from animals collected during 1973-78. The second included 45 females collected during 1981. There were significant, generally downward trends through time in the estimates from multiple readings of the 1973-78 data. These trends were slight, and age distributions from last readings and mean estimates per specimen appeared to be homogeneous. The largest factor affecting precision in the 1973-78 data set was between-reader variation. In light of the relatively high within-reader precision (trends considered), the consistent between-reader differences suggest a problem of accuracy rather than precision for this series. Within-reader coefficients of variation averaged approximately 7% and 11%. Pooling the data resulted i n an average coefficient of variation near 16%. Within- and between-reader precision were higher for the 1981 sample, and the data homogeneous over both factors. CVs averaged near 5% and 6% for the two readers. These results point to further refinements in reading the 1981 series. Properties of the 1981 sample may be partly responsible for greater precision: by chance there were proportionately fewer older dolphins included, and preparation and selection criteria were probably more stringent. (PDF contains 35 pages.)

Role of G protein coupled inwardly rectifier K+ channels (GIRK) on the neurobiology depression

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Estimates of the rates of mortality of yellowfin tuna in the Eastern Pacific Ocean derived from tagging experiments

ENGLISH: Tag release and return data for the Baja California and Gulf of Guayaquil areas were selected for this study because substantial numbers of returns resulted from these releases and because the effects of emigration are small in these areas. The returns of tags per unit of fishing effort for several experiments in each area were used to estimate the coefficients of total mortality and shedding. The coefficient of annual natural mortality was estimated to be less than 2.0, which is in agreement with a previous estimate of 0.8, but does not improve upon it. The estimates for the average coefficients of catchability are 2.02 X 10-3 for the Baja California area and 0.67 X 10-3 for the Gulf of Guayaquil area. SPANISH: Se seleccionaron para este estudio algunos da tos de liberación y retorno de marcas en las áreas de Baja California y el Golfo de Guayaquil debido a que cantidades substanciales de retornos resultaron de estas liberaciones y porque los efectos de migración son pequeños en estas áreas. Los retornos de marcas por unidad de esfuerzo de pesca de varios experimentos en cada área fueron empleados para estimar los coeficientes de mortalidad total y desprendimiento. Se estimó que el coeficiente de mortalidad natural anual fue inferior a 2.0, lo que está de acuerdo con una estimación anterior de 0.8, pero no la mejora. Las estimaciones de los coeficientes promedios de capturabilidad son 2.02 X 10-3 en el área de Baja California y 0.67 X 10-3 en el área del Golfo de Guayaquil. (PDF contains 58 pages.)

Growth, movement, and attrition of northern bluefin tuna, Thunnus thynnus, in the Pacific Ocean, as determined by tagging

ENGLISH: The growth of northern bluefin tuna is described by a two-stanza model. For fish between 191 and 564 mm in length the Gompertz curve, with values of 581 mm and 4.32 for Loo and K (annual), respectively, is used. The fish between 564 and 1530 mm grow linearly, at the rate of 0.709 mm per day. Age-O fish tagged and released in the western Pacific Ocean have been recaptured in the western, central, and eastern Pacific. The minimum time between release in the western Pacific and recapture in the eastern Pacific is 215 days. Older fish, mostly Land 2-year olds, tagged and released in the eastern Pacific have been recaptured in the eastern and western Pacific. The minimum time between release in eastern Pacific and recapture in the western Pacific is 674 days. The coefficient of natural mortality is estimated from data on growth and ambient temperature to be 0.276 on an annual basis, with 90-percent confidence limits of 0.161 and 0.47L Spawning of northern bluefin takes place only in the western Pacific. Some of the juveniles migrate to the eastern Pacific, where they reside for several months to several years before returning to the western Pacific. The portion of fish which migrate to the eastern Pacific varies among years, and this appears to be an important cause of the annual variation in the catches in the eastern Pacific Ocean. SPANISH: El crecimiento del atún aleta azul del norte es descrito por un modelo de dos estadios. Para los peces de entre 191 y 564 mm de talla se usa la curva de Gompertz, con valores de 581 mm y 4.32 para Loo y K (anual), respectivamente. Los peces de entre 564 y 1530 mm crecen de forma lineal, a 0.709 mm por día. Peces de edad Omarcados y liberados en el Pacífico occidental han sido recapturados en el Pacífico occidental, central, y oriental. La demora mínima entre la liberación en el Pacífico occidental y la recaptura en el Pacífico oriental es de 215 días. Peces mayores, principalmente de 1 ó 2 años de edad, marcados y liberados en el Pacífico oriental han sido re capturados en el Pacífico occidental y oriental. La demora mínima entre la liberación en el Pacífico oriental y la recaptura en el Pacífico occidental es de 674 días. Se estima el coeficiente de mortalidad natural a partir de los datos de crecimiento y temperatura ambiental en un 0.276 anual, con límites de confianza al 90% de 0.161 y 0.471. El aleta azul del norte desova únicamente en el Pacífico occidental. Algunos de los juveniles migran al Pacífico oriental, donde permanecen entre varios meses y varios años antes de regresar al Pacífico occidental. La porción de los peces que migran al Pacífico oriental varía entre años, y ésto parece ser una causa importante de la variación anual en las capturas en el Océano Pacífico oriental. (PDF contains 94 pages.)

Measurements Of In Situ Stress And Mining-Induced Stress In Beiminghe Iron Mine Of China

In order to obtain the distribution rules of in situ stress and mining-induced stress of Beiminghe Iron Mine, the stress relief method by overcoring was used to measure the in situ stress, and the MC type bore-hole stress gauge was adopted to measure the mining-induced stress. In the in situ stress measuring, the technique of improved hollow inclusion cells was adopted, which can realize complete temperature compensation. Based on the measuring results, the distribution model of in situ stress was established and analyzed. The in situ stress measuring result shows that the maximum horizontal stress is 1.75-2.45 times of vertical stress and almost 1.83 times of the minimum horizontal stress in this mineral field. And the mining-induced stress measuring result shows that, according to the magnitude of front abutment pressure the stress region can be separated into stress-relaxed area, stress-concentrated area and initial stress area. At the -50 m mining level of this mine, the range of stress-relaxed area is 0-3 m before mining face; the range of stress-concentrated area is 3-55 m before mining face, and the maximum mining-induced stress is 16.5-17.5 MPa, which is 15-20 m from the mining face. The coefficient of stress concentration is 1.85.