Influence of initial imperfection and coupling between bending and extension on vibration, buckling and nonlinear dynamic stability of laminated plates

ＩｎｔｒｏｄｕｃｔｉｏｎＣｏｕｐｌｉｎｇｂｅｔｗｅｎｂｅｎｄｉｎｇ＿ｅｘｔｅｎｓｉｏｎｃａｕｓｅｄｂｙｌａｍｉｎａｔｅｍａｔｅｒｉａｌａｎｄ／ｏｒｇｅｏｍｅｔｒｉｃａｌａｓｙｍｍｅｔｒｙａｂｏｕｔｌａｍｉｎａｔｅｍｉｄｄｌｅｓｕｒｆａｃｅｉｓｋｎｏｗ...     

Analysis of the Singularity for the Vertical Contact Problem of Line Crack-Inclusion

ＩｎｔｒｏｄｕｃｔｉｏｎＵｐｔｏｎｏｗ ,ｔｈｅｔｅｃｈｎｉｃａｌｌｉｔｅｒａｔｕｒｅｏｎｓｅｐａｒａｔｅｃｒａｃｋｓ,ｖｏｉｄｓ,ｉｎｃｌｕｓｉｏｎｓａｎｄｔｈｅｉｎｔｅｒａｃｔｉｏｎｓｂｅｔｗｅｅｎｃｒａｃｋｓａｎｄｉｎｃｌｕｓｉｏｎｓｈａｖｅｂｅｅｎｑｕｉｔｅｅｘｔｅｎｓｉｖｅ.Ｈｏｗｅｖｅｒ,ｔｈｅｃｏｎｔａｃｔｐｒｏｂｌｅｍｓｏｆｃｒａｃｋ＿ｉｎｃｌｕｓｉｏｎｄｏｎｏｔｓｅｅｍｔｏｂｅａｓｗｉｄｅｌｙｓｔｕｄｉｅｄ .Ｔｈｉｓｐａｐｅｒｃａｎｂｅｒｅｇａｒｄｅｄａｓｔｈｅｆｕｒｔｈｅｒｒｅｓｅ…     

Coupled fields of two-dimensional anisotropic magneto-electro-elastic solids with an elliptical inclusion

ＩｎｔｒｏｄｕｃｔｉｏｎＤｅｔｅｒｍｉｎａｔｉｏｎｏｆｐｅｒｔｕｒｂｅｄｆｉｅｌｄｓｉｎｄｕｃｅｄｂｙｉｎｃｌｕｓｉｏｎｓｈａｓｂｅｅｎａｎｉｍｐｏｒｔａｎｔｔｏｐｉｃｆｏｒｓｔｕｄｙｉｎｇｔｈｅｐｈｙｓｉｃａｌｂｅｈａｖｉｏｒｓｏｆａｄｖａｎｃｅｄｃｏｍｐｏｓｉｔｅｍａｔｅｒｉａｌｓ.Ｆｒｏｍｔｈｅｐｏｉｎｔｏｆｖｉｅｗｏｆａｐｐｌｉｃａｔｉｏｎｓ,ｔｈｅａｄｖａｎｃｅｄｃｏｍｐｏｓｉｔｅｍａｔｅｒｉａｌｓｃａｎｂｅｄｉｖｉｄｅｄｉｎｔｏｔｗｏｃａｔｅｇｏｒｉｅｓ:ｏｎｅｉｓｔｈｅｓｔｒｕｃｔｕ…     

UNILATERAL CONTACT PROBLEMS USING QUASI-ACTIVE SET STRATEGY

ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｒｅａｒｅｏｆｔｅｎｓｏｍｅｓｔｒｕｃｔｕｒｅｓｏｒｃｏｍｐｏｎｅｎｔｓｗｈｉｃｈｃａｎｏｎｌｙｔｒａｎｓｆｅｒｏｎｅｓｐｅｃｉａｌｆｏｒｍｏｆｓｔｒｅｓｓ,ｓｕｃｈａｓｔｈｅｃａｂｌｅｗｈｉｃｈｃａｎｏｎｌｙｂｅｕｓｅｄｔｏｔｒａｎｓｆｅｒｔｈｅｔｅｎｓｉｏｎｓｔｒｅｓｓａｎｄｔｈｅｃｏｎｔａｃｔｃｏｍｐｏｎｅｎｔｗｈｉｃｈｃａｎｏｎｌｙｔｒａｎｓｆｅｒｔｈｅｐｒｅｓｓｕｒｅ.Ｉｎｇｅｎｅｒａｌ,ｓｕｃｈｐｒｏｂｌｅｍｓａｒｅｏｆｔｅｎｃａｌｌｅｄｔｈｅｕｎｉｌａｔ…     

BIFURCATION ANALYSIS OF A MITOTIC MODEL OF FROG EGGS

ＩｎｔｒｏｄｕｃｔｉｏｎＷｉｔｈｔｈｅｒａｐｉｄｄｅｖｅｌｏｐｍｅｎｔｏｆｂｉｏｌｏｇｙｓｃｉｅｎｃｅｓ,ｃｅｌｌｓｉｇｎａｌｔｒａｎｓｄｕｃｔｉｏｎ ,ｃｅｌｌｅｐｏｐｔｏｓｉｓ,ｇｅｎｏｍｅａｎｄｐｏｓｔ＿ｇｅｎｏｍｉｃａｎａｌｙｓｉｓｈａｖｅａｔｔｒａｃｔｅｄｉｎｃｒｅａｓｉｎｇａｔｔｅｎｔｉｏｎ[1- 6 ].Ｔｈｅｃｅｌｌｄｉｖｉｓｉｏｎｃｙｃｌｅｉｓｔｈｅｓｅｑｕｅｎｃｅｏｆｅｖｅｎｔｓｂｙｗｈｉｃｈａｇｒｏｗｉｎｇｃｅｌｌｄｕｐｌｉｃａｔｅｓａｌｌｉｔｓｃｏｍｐｏｎｅｎｔｓａｎｄｔｈｅｎｄｉｖ…     

The loss of stability of laminar flow in open channel and the mechanism of sand ripple formation

ＩｎｔｒｏｄｕｃｔｉｏｎＤｕｒｉｎｇｔｈｅｔｉｍｅｏｆｂｅｄｓｕｒｆａｃｅｓｅｄｉｍｅｎｔｔｒａｎｓｐｏｒｔａｔｉｏｎ,ｓｅｄｉｍｅｎｔｐａｒｔｉｃｌｅｓｏｆｂｅｄｌｏａｄｍａｋｅｔｈｅｃｏｌｌｅｃｔｉｖｅｍｏｔｉｏｎｏｆｖａｒｉｏｕｓｄｉｆｆｅｒｅｎｔｆｏｒｍｓｏｎｔｈｅｒｉｖｅｒｂｅｄｓｕｒｆａｃｅ,ｔｈｕｓｔｈｅｆｏｒｍｏｆｂｅｄｓｕｒｆａｃｅｃｈａｎｇｅｓｃｏｎｓｔａｎｔｌｙ .Ｔｈｉｓｋｉｎｄｏｆｃｏｌｌｅｃｔｉｖｅｍｏｔｉｏｎｏｆｓｅｄｉｍｅｎｔｐａｒｔｉｃｌｅｓｏｎｔｈｅｂｅｄｓｕｒｆ…     

On the Resonant Generation of Weakly Nonlinear Stokes Waves in Regions with Fast Varying Topography and Free Surface Current

ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｉｎｔｅｒａｃｔｉｏｎｏｆｓｕｒｆａｃｅｗａｔｅｒｗａｖｅｓｗｉｔｈａｍｂｉｅｎｔｃｕｒｒｅｎｔｓａｎｄｕｎｄｕｌａｔｉｎｇｓｅａｂｅｄｔｏｐｏｇｒａｐｈｙｉｓｏｆｆｕｎｄａｍｅｎｔａｌｉｍｐｏｒｔａｎｃｅｔｏｃｏａｓｔａｌｅｎｇｉｎｅｅｒｓａｎｄｓｅｄｉｍｅｎｔｏｌｏｇｉｓｔｓ.Ｆｏｒｅｘａｍｐｌｅ,ｔｈｅｒｅｓｏｎａｎｔｇｅｎｅｒａｔｉｏｎｏｆｓｕｒｆａｃｅｗａｖｅｓｉｎａｃｕｒｒｅｎｔｏｖｅｒｏｔｈｅｒｔｉｄａｌｌｙｏｒｗａｖｅｉｎｄｕｃｅｄｂｅｄｆｏｒｍｓ,ｓ…     

A discrete algorithm for complex frequency-domain convolutions

ＩｎｔｒｏｄｕｃｔｉｏｎＩｔｉｓｗｅｌｌ＿ｋｎｏｗｎｔｈａｔｔｈｅＬａｐｌａｃｅｔｒａｎｓｆｏｒｍｏｆｔｈｅｐｒｏｄｕｃｔｏｆｔｗｏｔｉｍｅ＿ｄｏｍａｉｎｓｉｇｎａｌｓｅｑｕａｌｓｔｈｅｃｏｍｐｌｅｘｆｒｅｑｕｅｎｃｙ＿ｄｏｍａｉｎｃｏｎｖｏｌｕｔｉｏｎｏｆｉｎｄｉｖｉｄｕａｌＬａｐｌａｃｅｔｒａｎｓｆｏｒｍｓｏｆｔｗｏｓｉｇｎａｌｓ.Ｇｅｎｅｒａｌｌｙ,ｔｈｅｃｏｎｖｏｌｕｔｉｏｎｏｆｔｗｏｃｏｍｐｌｅｘｆｒｅｑｕｅｎｃｙ＿ｄｏｍａｉｎａｎａｌｙｔｉｃａｌｆｕｎｃｔｉｏｎｓｉｓｃａｌｃｕｌａｔｅ…     

A form function method for form finding of tension structure

ＩｎｔｒｏｄｕｃｔｉｏｎＩｎｅｎｇｉｎｅｅｒｉｎｇ ,ｉｔｉｓｏｆｔｅｎｒｅｑｕｉｒｅｄｔｏｅｘｔｅｎｄａｔｅｎｓｉｏｎｓｔｒｕｃｔｕｒｅｏｎａｇｉｖｅｎｂｏｕｎｄａｒｙ ,ｓｕｃｈａｓｃａｂｌｅｎｅｔｏｒｍｅｍｂｒａｎｅ.Ｔｏａｎａｌｙｚｅｔｈｅｓｔｒｕｃｔｕｒｅ ,ｉｔｉｓｎｅｃｅｓｓａｒｙｔｏｋｎｏｗｔｈｅｉｎｉｔｉａｌｆｏｒｍｏｆｉｔ.Ｂｕｔｉｔｉｓｎｏｔｅａｓｙｔｏｇｅｔａｎａｃｃｕｒａｔｅｏｎｅｏｎａｎａｖｅｒａｇｅｂｏｕｎｄａｒｙ .Ｔｈｅｆｏｒｍｏｆｔｅｎｓｉｏｎｓｔｒｕｃｔｕｒｅｕｎｄｅ…     

Global composite element iteration for analysis of seepage free surface

ＩｎｔｒｏｄｕｃｔｉｏｎＳｅｅｐａｇｅｆｒｅｅｓｕｒｆａｃｅｉｓｏｆｔｅｎｅｎｃｏｕｎｔｅｒｅｄｉｎｔｈｅｃｏｕｒｓｅｏｆｓｅｅｐａｇｅｐｒｏｂｌｅｍｔｈｒｏｕｇｈｍｅｄｉａｏｆｓｌｏｐｅ,ｅａｒｔｈｄａｍａｎｄｔｕｎｎｅｌｅｎｇｉｎｅｅｒｉｎｇ．Ｔｈｅｐｈｅｎｏｍｅｎａｏｆｓｅｅｐａｇｅｆｒｅｅｓｕｒｆａｃｅｉｓｏｎｅｏｆｔｈｅｉｍｐｏｒｔａｎｔａｎｄｄｉｆｆｉｃｕｌｔｔｏｐｉｃｓｏｆｒｏｃｋｍａｓｓｈｙｄｒｏｍｅｃｈａｎｉｃｓ［１～３］,ａｎｄｑｕｉｔｅａｎｉｍｐｏｒｔａｎｔｒｅｓｅａｒｃｈ…     

Application of dispersion theory to time domain reflectometry in soils

With time domain reflectometry (TDR) two dispersive parameters, the dielectric constant, , and the electrical conductivity, can be measured. Both parameters are nonlinear functions of the volume fractions in soil. Because the volume function of water ( _w) can change widely in the same soil, empirical equations have been derived to describe these relations. In this paper, a theoretical model is proposed based upon the theory of dispersive behaviour. This is compared with the empirical equations. The agreement between the empirical and theoretical aproaches was highly significant: the ( _w) relation of Topp et al. had a coefficient of determination r ² = 0.996 and the (_u) relation of Smith and Tice, for the unfrozen water content, _u, at temperatures below 0°C, had an r ² = 0.997. To obtain ( _w) relations, calibration measurements were performed on two soils: Caledon sand and Guelph silt loam. For both soils, an r ² = 0.983 was obtained between the theoretical model and the measured values. The correct relations are especially important at low water contents, where the interaction between water molecules and soil particles is strong.     

坡面流及土壤侵蚀动力学（II）——————土壤侵蚀

介绍了坡面土壤侵蚀的基本特征和主要类型, 综述了坡面土壤侵蚀动力学过程和预报模型等方面的研究进展, 包括土壤表层结皮、雨滴溅蚀、片流侵蚀、细沟侵蚀、坡面流输沙、土壤侵蚀界限坡度, 以及土壤侵蚀预报模型等. 并简要讨论了土壤侵蚀动力学研究的发展趋势.     

Activation energy of viscoelastic flow emulsion inks as a function of shear rate

The plastic viscosities of five production batches of a nonthixotropic pseudoplasticGestetner 217 type emulsion duplicating ink were determined at 40 RPM (700 sec^–1) using aFerranti-Shirley cone-plate viscometer. The activation energiesE were determined from the slope of anArrhenius plot over the range of 1/2 °C to 40 °C. The value ofE was not affected by batch-to-batch variations.Working with one ink only, the same procedure was then applied to shear rates from 5 to 220 RPM (87.5 to 3850 sec^–1) over the same temperature range.E was found to be constant below about 60 RPM (1000 sec^–1) but dropped rapidly with increasing shear rate above that threshold. A plot ofE vs. In shear rate gave a straight line parallel to the shear rate axis, intersected by a second straight line with a negative slope. The value ofE corresponding to the point of intersection is denotedE _L , the limiting activation energy of viscoelastic flow in a rotational shear field.It is suggested that the rate of shear corresponding toE _L is that necessary to eliminate the last traces of slippage flow in the system and to convert it to 100% laminar flow. The theoretical implications of this suggestion are discussed.Presented at the Joint Meeting of the British Society of Rheology and Research Association of British Paint, Colour and Varnish Manufacturers at Teddington, April 29, 1964.     

Thermohaline instability with thermal diffusion and horizontal gradients

The effect of thermal diffusion on an unbounded vertically stratified thermohaline fluid with compensating horizontal thermal and salinity gradients (i.e., with no horizontal density gradient) is investigated in this analysis. It is observed that the maximum growth rate of instability, the slope of the wave front and the wave number depend on the Soret parameter, S. For 1+S= ^–1, the system is stable for any value of the horizontal gradient where is the ratio of mass diffusivity to thermal diffusivity. For 1+S<0, there is convective instability when both vertical gradients are stable even in the absence of the horizontal gradient. When 1+S> ^–1, the slopes of the wave fronts tilt such that there is a diffusive set-up when stationary convection sets in and finger formation when there is oscillatory convection.     

A method for measuring recompression shock unsteadiness applied to two supersonic wakes

The recompression shock system in blunt-base cylinder wakes at 0° and 10° angles-of-attack to an M=2.46 freestream is visualized by planar laser scattering, allowing the instantaneous position of the shock to be determined over a wide region of the flow. The recompression shock at =0° is highly branched and appears to be quite weak. The shock appears to be stronger at =10°, with far less branching. Correlation analysis for the =10° wake indicates that fluctuations in the shock position tend to be correlated over relatively long streamwise distances. Analysis of the shock angle for the angle-of-attack wake shows a significant variation in the local angle of the shock, with trends similar to those seen for the unsteadiness in the shock position.     

Determination of normal stress differences in steady shear flow

Summary Using the cone- and-plate apparatus ofAdams andLodge, values of pressure gradient,r-d¯p/dr in a range 300 to 3000 dyn/cm², have been measured to an accuracy of 1% at shear rates near 10 sec^–1 in liquids of viscosity less than 200 poise. Using the constancy of pressure gradient at a given shear rate as an indicator of liquid stability, it was found that a polyisobutene liquid containing 2% of Oppanol B 200 in Oppanol B I, when stored at rest at 25 °C, was stable during a certain 7-day period after dissolution and unstable during the subsequent 30 days.     

Heat,Water, and Solution Transfer in Unsaturated Porous Media: I -- Theory Development and Transport Coefficient Evaluation

A detailed theory describing the simultaneous transfer of heat, water, and solute in unsaturated porous mediais developed. The theory includes three fully-coupledpartial differential equations. Heat, water, andsolute move in the presence of temperature, T; matricpressure head, _m ; solution osmotic pressure head _o ; and solute concentration C gradients. Thetheory can be applied to describe the mass and energyin radioactive waste repositories, food processing,underground energy storage sites, buried electriccables positions, waste disposal sites, and inagricultural soil. Several transport coefficients forheat, water, and solute are included in the theory. The coefficients are evaluated for a silty clay loamsoil to clarify their dependence on water content (),T, and C. The thermal vapor diffusivity D _Tv first increased as increased to0.22 m³/m³ then decreased with furtherincreases in . D _Tv was 3 orders of magnitudegreater than either isothermal vapor D _mv orosmotic vapor D _ov , diffusivities at of0.20~m³/m³, T of 50°C, and C of 0.001mol/kg. All of the liquid and vapor water transport coefficients increased with increasing T. D _Tv decreased with increasing C to a greater extent thanD _mv and D _ov . The effective thermalconductivity decreased slightly with increasing C. Thesolute diffusion coefficient D _d was 6 to 7orders of magnitude greater than the thermal soluteand salt sieving diffusion coefficients at of0.20~m³/m³, T of 50°C, and C of 0.001 mol/kg.     

Thermal Conductivity of Soils at Very Low Moisture Content and Moderate Temperatures

An analysis of soil thermal conductivity data shows that, at very low moisture content, this property first varies insignificantly and then begins to increase from a certain critical moisture content, whose value tends to depend on clay mass fraction. Two simple models evaluating the critical moisture content were developed; the first one is a fraction of the permanent wilting point; the second one is a simple linear function dependent on clay mass fraction. An insignificant variation of soil thermal conductivity is observed at 20°C, within a water pressure head ranging from 1×10³ to 1×10³m, while for higher temperatures (45–50°C) from 5000 to 100000m. Three extensions of the enhanced thermal conductivity model by Sundberg, namely SUN-1, SUN-2 and SUN-3, were proposed and tested. They produce an average root mean square error of 27%, 24% and 30%, respectively, with respect to experimental data. SUN-1and SUN-2 predictions could be further improved if better estimates of thermal conductivity at the dry state and the permanent wilting point were provided. SUN-3 is a simple model which does not require information about the PWP and critical moisture content. All SUN models have a potential for implementing the latent heat transfer component.     

Drag measurements on planar riblet surfaces at high subsonic speeds

This paper presents the results of an investigation of riblet performance at high subsonic Mach numbers, and Reynolds numbers of about 20 000 based on the momentum thickness, in both zero and adverse pressure gradient boundary layers. The maximum length Reynolds number of the ribbed section was 3.4×10⁷ so the results were directly relevant to flight applications on the engine nacelles of civil airliners. Seven different sizes of riblets with heights h (equal to spacing s) ranging from 0.0007 (0.0178mm) to 0.006 (0.1524 mm) have been studied, covering a range of h+, s+ from 10 to 106. The maximum percentage skin friction reduction, as deduced from velocity profiles measured at the downstream end of the riblet surfaces, under nominally zero pressure gradient conditions was 5.5±1; rather less than that recorded in low speed studies, but consistent with a recent theoretical analysis of the effect of Reynolds number. The values of h+ required for maximum and zero skin friction reduction agreed closely with other data. In addition subsequent floating element drag balance measurements revealed little effect of yaw angles up to 15°, again in line with other findings, and also suggested that the extent of the initial development length on, and recovery length behind, the riblets was approximately 5. The adverse pressure gradient studies indicated that riblet performance was essentially unaffected by mild gradients (=0.25), but diminished to zero in a more severe gradient (=0.5).     

A permeameter for unsaturated soil

A permeameter for unsaturated soil was developed by observing the way in which pore water recovers hydrostatic equilibrium. It works like an hour glass that is turned upside-down everytime the state of reference (or hydrostatic equilibrium) is reached. The hydraulic conductivity is deduced from the curves of evolution of pore-water pressure and from the distribution of partial density of water at hydrostatic equilibrium. Roman Letters a is defined by (10), kg m^–3 - A _n coefficients of the analytic solution, kgm^–3 - C ₁, C ₂, C ₃, C ₄ constants and constants of integration - D diffusivity, m² s^-1 - g gravity constant, m s^-2 - g gravity vector field - K hydraulic conductivity defined by (2), m⁵ s^-1 J^-1 - K _w hydraulic conductivity defined by (5), m ^-1 - k permeability - L length of soil sample, m - n integer in (22) - n porosity - p absolute pore water pressure, Pa - p ₀ absolute pore water pressure, Pa - p _a absolute air pressure, Pa - q volume flux or Darcy's velocity, m s^-1 - r exponent defined by (13) - S _w degree of saturation, % - t time variable, sec - u _n , v _n are defined by (22b), (22c) - x(x, y, z) space variable Greek Letters , are defined by (11), (13) - _w dynamic viscosity - water partial density, kg m^–3. It is the ratio of the mass of water to total volume of a representative elementary volume - ₀, _l water partial densities, kgm^–3 - _w density of water, kgm^–3 - _s density of solid particles, kgm^–3 - differences of partial density, kgm^–3 - p differences of water pressure, Pa - pi - , · gradient operator, divergence operator - Laplacian operator - volumetric water content, % - piezometric head, m