Angle Φ0 Research Articles

Interaction of structural and acoustical waves at a wedge‐shaped junction of two fluid‐loaded plates.

Two semi‐infinite elastic plates are joined along a line forming a wedge structure with unilateral fluid loading in the sector of angle 2Φ. The structure is modeled using thin plate theory, allowing freely propagating flexural and longitudinal waves. The junction is mechanically connected with an applied force and moment acting there to simulate a possible internal connection. The general 2‐D solution is described for incidence of time harmonic structural or acoustical waves. The method of Osipov is used to express the total pressure as a Sommerfeld integral, the integrand comprising Malyuzhinets functions and particular solutions of certain difference equations. The junction conditions reduce to a system of eight linear equations. Numerical examples indicate the coupling between the modes for different wedge angles, specifically Φ=112.5°, 135°, and 157.5°, for steel plates in water. Acoustic plane wave incidence on the flatter junction (112.5°) is converted almost equally, in terms of energy, among diffracted flexural and longitudinal waves. The coupling to flexural energy increases with the wedge angle, at the expense of the longitudinal energy which vanishes as Φ→180°. An incident longitudinal wave generates relatively little acoustic sound for all values of Φ considered, with most of its energy redistributed among structural modes. The acoustical diffraction is generally greater for flexural incidence. [Work supported by ONR.]

Study on Damage Stability with Water on Deck of a RO-RO Passenger Ship in Waves

RO-RO passenger vessel has a wide non-separated car deck. Once free flooded water is piled up on it, the large heel moment could be the cause of capsize because of this feature.The stability standard of RO-RO passenger vessels was deliberated at IMO commission from 1994 to 1995 in order to prevent capsizing disaster like the one of ESTONIA in 1994. The authors, one of which was a member of the IMO expert panel, conducted an experiment on the stability of this type of ship because few papers have been published on this problem. The experiment was carried out in beam seas using a model ship with a side damage hole which is prescribed by the SOLAS regulation.After the duration time of the experiment (30 minutes in ship scale) in irregular waves the ship survived with a constant mean heel angle φ0 and a mean water volume on deck w in most test conditions, but capsized in a few ones. The variation of these constant values with CG height, existence of center casing, height of freeboard and initial heel was discussed. It was clarified that φ0 tends to decrease and w tends to increase as GMd (GM in damaged condition) have a larger value, and that ship can survive even with w of 40% of intact ship displacement if she has a large (not extraordinary) GMd value.The effect of resonance of roll motion on this problem was also studied based on the test result in regular waves. φ0, w and some other data often have a peak near the resonant frequency, so the stability test of RO-RO passenger vessel should be carried out including resonant conditions.The height of water on deck above the calm sea surface Hd was proposed as an index which settles the balancing condition. It was clarified that Hd keeps a certain value above calm outer surface when wave hight is not so low and mean heel angle is not so large to lee side. The equilibrium curve for each GMd can be calculated from GZ-curves with a constant volume of water on deck, fully static calculation, and figured on Hd-φ0 diagram. It is concluded that the possibility of capsize can be judged by this equilibrium curve.

Three-Dimensional Vibration Analysis of Rotating Laminated Composite Blades

This work offers the first known three-dimensional continuum vibration analysis for rotating, laminated composite blades. A cornerstone of this work is that the dynamic energies of the rotating blade are derived from a three-dimensional elasticity-based, truncated quadrangular pyramid model incorporating laminated orthotropicity, full geometric nonlinearity using an updated Lagrangian formulation and Coriolis acceleration terms. These analysis sophistications are included to accommodate the nonclassical directions of modern blade designs comprising thin, wide chord-lifting surfaces of laminated composite construction. The Ritz method is used to minimize the dynamic energies with displacements approximated by mathematically complete polynomials satisfying the vanishing displacement conditions at the blade root section exactly. Several tables and graphs are presented that describe numerical convergence studies showing the validity of the assumed displacement polynomials used herein. Nondimensional frequency data are presented for various rotating, truncated quadrangular pyramids, serving as first approximations of practical blades employed in aircraft engines and fans. A wide scope of results explain the influence of a number of parameters coined to rotating, laminated composite blade dynamics, namely aspect ratio (a/b), chord ratio (c/b), thickness ratio (b/h), variable thickness distribution (h1/ht), blade pretwist angle (φ0), composite fiber orientation angle (θ), and angular velocity (Ω). Additional examples are given that elucidate the significance of the linear and nonlinear kinematics used in the present three-dimensional formulation along with the importance of the Coriolis acceleration terms included in the analysis.

Conformational Analysis of a 139 Base-pair DNA Fragment Containing a Single-stranded Break and Its Interaction with Human Poly(ADP-ribose) Polymerase

The conformational changes induced by the introduction of a central and unique single-stranded break in a 139 base-pair DNA duplex have been analysed by means of polyacrylamide gel electrophoresis, HPLC and dark-field electron microscopy. Compared to the control DNA, the disruption of the covalent sugar-phosphate backbone induces a retardation detected both by gel electrophoresis and anion exchange based HPLC. Electron microscopic visualization of the DNA molecules reveals that most, of them present a central fracture at the position of the nick. Measures of the angle at the apex were very well fitted by a simple model of isotropic flexible junction assuming spatial Hooke's law and simple basic Boltzmann statistics. This amounts to using a folded Gaussian distribution. The fit yields an angle equilibrium value ϕ0 = 122° for the nicked fragment. The angle distribution could also result from an equilibrium between two forms of the molecule with isotropic flexibility at the nicked site: a stacked and a very flexible unstacked form. The majority of bound poly(ADP-ribose) polymerase, a zinc-finger enzyme involved in DNA break detection, was localized at the apex of the V-shaped DNA duplex, with an accentuation of its general V -shaped conformation (ϕ0 = 102°).

Grazing incidence diffraction of X-rays in semiconductor heterostructures: Application of the integral mode

The grazing incidence diffraction (GID) of X-rays enables to characterize thin subsurface layers in semiconductor heterostructures having a thickness smaller than 100 nm. The dynamical theory of X-ray diffraction is extended for the case of identical in plane lattice parameters at the heterointerface. Especially the variation in the specular diffracted (220) Bragg intensity measured with open detector (integral mode) is evaluated in dependence on the grazing angle Φ0 of the primary beam with respect to the (001) surface. Using a parallel beam an oscillation behaviour occurs at the high angle side Θc < Φ0≦0.50(Θc is the angle of total external reflection) of the diffraction curveI(Φ0) which can be related to the thickness of the perfect crystalline part of the epilayertK. Having an incident beam divergence and a small difference in the effective refractive indices of the layer and the substrate the oscillations are almost leveled. They are further visible in case of a minute inclination of the (220) lattice plane with respect to the surface normal. In the interval 0 < Φ0<Θc the slope of the integral curve depends on the thickness of the subsurface layertAwhich does not contribute to the Bragg diffraction. The integral mode is sensitive for layers of about 0<tA<15 nm and 15<tK<80 nm. The proposed theory working principally for multilayer structures is presently suplicated to interpret GID curves ofAIIIBvheterostructures.

QNS investigation of restricted molecular reorientation in the nematic phase. I. The incoherent scattering law for MBBA

Abstract On the basis of the solution of the random flight problem of a particle between two perfectly reflecting potential barriers the incoherent scattering law for the model of the uniaxial, molecular stochastic reorientation within an arbitrary apex angle Ф0 has been calculated. In conjunction with the published NMR results evidence is presented, that the along the long axis uniaxial rotation, can be described in terms of the model with an apex angle φ0 of 57°. The model of the restricted uniaxial reorientation, which is expected to be of interest in nematic phases of biaxial molecules, has been applied to the investigation, by quasi elastic incoherent cold neutron scattering, of the rotational dynamics of the rigid benzylidene central part of a magnetically oriented MBBA sample in the nematic phase at 303 K.

Design of Quick-Returning R-S-S-R Mechanisms

An algebraic method is presented to synthesize quick-returning R-S-S-R mechanisms which satisfy the given time-ratio and follower oscillation angle requirements. In these designs, the three parameters, which define the follower spheric joint, satisfy a quadratic condition. When the shaft angle between the input and output shafts is zero, this quadratic condition reduces to the equation of a circle which is a familiar classical result for the planar case. The solution space for the quick-returning R-S-S-R linkage is such that, for each set of choices for crank length a2, follower axial distance S4, and initial follower angle φ0, there are four sets of follower length a4, initial crank angle θ0, crank axial distance S2, and coupler length a3. These designs are screened so that they do not have branch defect, have transmission angle values in a given range, and have reasonable link length proportions.

Prediction of a large polar Kerr angle in NiUSn

An ab initio calculation of the magneto-optic Kerr effect is reported for ferromagnetic NiUSn. The double polar Kerr angle 2Φ is predicted to be about 10° in the infrared and about 4° in the visible spectrum. It is concluded that substitutional alloys involving Clb phase materials and uranium atoms are important candidates for device applications.

Discussion of thn linking and cracking processes of two neighboring holes in a thin sheet metal and their fracture ductility under tension.

The linking and cracking processes of two neighboring holes in a thin sheet metal were investigated in detail to get quantitative information about the deformation behavior of voids in a ductile fracture. The holes deform into elliptical holes and crack with come intruding and/or protruding under tension, depending on the experimental variables of the inter-hole distance ξo/2ro (ro: radius), the two-hole arrangement angle φ0 and the plastic strain. The complicated shape of the deformed hole is qualitatively measured and analyzed. The deformation of two holes having various arrangements of ξo/2ro and φ0 has also been analyzed by an elastic-plastic FEM, and the results are in qualitative agreement with the experimental data. Fracture ductility for the linking or cracking of two holes is approximately expressed by applying McClintock's fracture model for each volume which contains a hole at its center. The values of linking strain eZ, cal. and fracture strain ef, cal. by the equations are consistent with the experimental linking strain eZ, exp. and cracking strain eC, exp. where cracking strain is, of course, a few percentages smaller than the fracture strain in a ductile fracture.

Cavitation Phenomena and Performance of Oil Hydraulic Poppet Valve : 5th Report, Influence of Dimensions of Valve on the Thrust Force Characteristics

The thrust force characteristics of oil hydraulic poppet valves are studied experimentally. The thrust force is measured by using two apparatus ; a half cut model and a full shaped model of a poppet valve, with the valve lift X, the seat chamfer length S and the poppet angle 2φ changed. The influence of the change in these three valve factors on the thrust characteristics is made clear by comparison of the thrust coefficients, and the mechanism of the change in the thrust characteristics is also made clear by studying the pressure distributions and the thrust force components within three different region along the poppet surface; the upstream region, the restricted part and the downstream region.

A simple model of the mutual interaction of parallel flow and cellular motion in a shear layer applied to the finite amplitude instability of plane Couette flow

The disturbing motion of plane Couette and Poiseuille flow is described using three parameters: two amplitudes corresponding to the disturbance of the parallel flow and the cellular motion, respectively, and the angle ϕ0 which defines the orientation of the vortex blobs with respect to the parallel flow. Equations of motion for these parameters are obtained using a Ritz-Galerkin method. For Reynolds numbers above a critical value sufficiently big disturbances will grow until a steady finite amplitude state is achieved. The energy of the disturbance remains finite, in spite of the highly truncated field representation using only three parameters. This is possible because of the nonlinear dependence of the field functions on ϕ0. The critical values of Reynolds number, above which finite amplitude states exist, are computed for the plane Couette flow and the Poiseuille channel flow.

Cross polarization of EM waves scattered by an isotropic inhomogeneous moving plasma column

Interaction of obliquely incident linearly polarized plane electromagnetic waves with a radially inhomogeneous plasma column of infinite length moving uniformly in the axial direction is treated analytically. It is found that the cross-polarized field components disappear at the incident angle Φ0=sin−1(vz/c) (vz is the velocity of the moving plasma column and c is the free-space velocity of light) for the case of an inhomogeneous plasma column with an arbitrary electron density profile. Numerical results for the differential scattering cross sections are obtained for a range of plasma velocities by using the two-point boundary-value method.

Shear Angle Relationship With Variable Undeformed Chip Thickness

Effect of surface slope of the workpiece on shear angle has been considered by applying Hill’s [1] deformation criteria to the triangular shear zone in orthogonal metal-cutting process with variable undeformed chip thickness. It is shown that the variation of the shear angle with the surface slope δ can be written in the form φ = φ0 + Cδ where “C” is not a constant but depends upon steady state shear angle φ0, surface slope δ, and rake angle α. It is also shown that the present theory is in good agreement with the experimental results of Boothroyd [2].

Analysis of the stem in the servomotor of the hydraulic drive of a radial (Segemental) gate under a compressive load

1. In the analysis of stems of the servomotors of hydraulic drives of radial (Tainter) gates, an important role is played by the frictional moments at the highes, which must be taken into consideration in order to design correctly the hinged connections. 2. It is necessary to determine experimentally the limits of variation of the angle ϕ0 between the axes of the stem. 3. As a result of the nonlinearity of the problem when the stem acts under compession, the quantities Mmax and Ymax do not increase proportionally to the load, but much faster.