16,278 research outputs found
Influence of large deflection and transverse shear on random response of rectangular symmetric composite laminates to acoustic loads
Nonlinear equations of motion of symmetrically laminated anisotropic plates are derived accounting for von Karman strains. The effect of transverse shear is included in the formulation and the rotatory inertia effect is ignored. Using a single-mode Galerkin procedure the nonlinear modal equation is obtained. Direct equivalent linearization is employed. The response of acoustic excitation on moderately thick composite panels is studied. Further, the effects of transverse shear on large deflection vibration of laminates under random excitation are studied. Mean-square deflection and mean-square inplane stresses are obtained for some symmetric graphite-epoxy laminates. Using equilibrium equations and the continuity requirements, the mean-square transverse shear stresses are calculated. The results obtained will be useful in the sonic fatigue design of composite aircraft panels. The analysis is presented in detail for simply supported plate. The analogous equations for a clamped case are given in the appendix
Application of optimization techniques to vehicle design: A review
The work that has been done in the last decade or so in the application of optimization techniques to vehicle design is discussed. Much of the work reviewed deals with the design of body or suspension (chassis) components for reduced weight. Also reviewed are studies dealing with system optimization problems for improved functional performance, such as ride or handling. In reviewing the work on the use of optimization techniques, one notes the transition from the rare mention of the methods in the 70's to an increased effort in the early 80's. Efficient and convenient optimization and analysis tools still need to be developed so that they can be regularly applied in the early design stage of the vehicle development cycle to be most effective. Based on the reported applications, an attempt is made to assess the potential for automotive application of optimization techniques. The major issue involved remains the creation of quantifiable means of analysis to be used in vehicle design. The conventional process of vehicle design still contains much experience-based input because it has not yet proven possible to quantify all important constraints. This restraint on the part of the analysis will continue to be a major limiting factor in application of optimization to vehicle design
Itinerant and local-moment magnetism in EuCr2As2 single crystals
We report on the crystal structure, physical properties, and electronic
structure calculations for the ternary pnictide compound EuCr2As2. X-ray
diffraction studies confirmed that EuCr2As2 crystalizes in the ThCr2Si2-type
tetragonal structure (space group I4/mmm). The Eu ions are in a stable divalent
state in this compound. Eu moments in EuCr2As2 order magnetically below Tm = 21
K. A sharp increase in the magnetic susceptibility below Tm and the positive
value of the paramagnetic Curie temperature obtained from the Curie-Weiss fit
suggest dominant ferromagnetic interactions. The heat capacity exhibits a sharp
{\lambda}-shape anomaly at Tm, confirming the bulk nature of the magnetic
transition. The extracted magnetic entropy at the magnetic transition
temperature is consistent with the theoretical value Rln(2S+1) for S = 7/2 of
the Eu2+ ion. The temperature dependence of the electrical resistivity
\r{ho}(T) shows metallic behavior along with an anomaly at 21 K. In addition,
we observe a reasonably large negative magneto-resistance (~ -24%) at lower
temperature. Electronic structure calculations for EuCr2As2 reveal a moderately
high density of states of Cr-3d orbitals at the Fermi energy, indicating that
the nonmagnetic state of Cr is unstable against magnetic order. Our density
functional calculations for EuCr2As2 predict a G-type AFM order in the Cr
sublattice. The electronic structure calculations suggest a weak interlayer
coupling of the Eu moments.Comment: 9 pages, 7 figure
The Effects of Life Expectancy on Fiji's Output: A Time Series Approach from 1970 to 2002
Compared to several cross-country studies on the determinants of growth, time series approaches are relatively few and limited in scope. However, time series studies are useful for country-specific policies. But in the recent time series works, with a few exceptions, ad hoc specifications of output and growth equations are used. This paper examines the specification and estimation issues in the time series approach to the determinants of output. Our approach is used to measure the effects of health on the output of Fiji for the period 1970 to 2002.The Solow Growth Model, Production Function, General to Specific Approach, Effects of Health on Output.
Instability of Rotationally Tuned Dipolar Bose-Einstein Condensates
The possibility of effectively inverting the sign of the dipole-dipole
interaction, by fast rotation of the dipole polarization, is examined within a
harmonically trapped dipolar Bose-Einstein condensate. Our analysis is based on
the stationary states in the Thomas-Fermi limit, in the corotating frame, as
well as direct numerical simulations in the Thomas-Fermi regime, explicitly
accounting for the rotating polarization. The condensate is found to be
inherently unstable due to the dynamical instability of collective modes. This
ultimately prevents the realization of robust and long-lived rotationally tuned
states. Our findings have major implications for experimentally accessing this
regime.Comment: 9 pages with 5 figure
Valence Fluctuation in CeMo2Si2C
We report on the valence fluctuation of Ce in CeMoSiC as studied
by means of magnetic susceptibility , specific heat , electrical
resistivity and x-ray absorption spectroscopy. Powder x-ray
diffraction revealed that CeMoSiC crystallizes in
CeCrSiC-type layered tetragonal crystal structure (space group
\textit{P4/mmm}). The unit cell volume of CeMoSiC deviates from the
expected lanthanide contraction, indicating non-trivalent state of Ce ions in
this compound. The observed weak temperature dependence of the magnetic
susceptibility and its low value indicate that Ce ions are in valence
fluctuating state. The formal Ce valence in CeMoSiC
= 3.11 as determined from x-ray absorption spectroscopy
measurement is well bellow the value 3.4 in
tetravalent Ce compound CeO. The temperature dependence of specific heat
does not show any anomaly down to 1.8 K which rules out any magnetic ordering
in the system. The Sommerfeld coefficient obtained from the specific heat data
is = 23.4 mJ/mol\,K. The electrical resistivity follows the
behavior in the low temperature range below 35 K confirming a Fermi
liquid behavior. Accordingly both the Kadowaki Wood ratio and
the Sommerfeld Wilson ratio are in the range expected for
Fermi-liquid systems. In order to get some information on the electronic
states, we calculated the band structure within the density functional theory,
eventhough this approach is not able to treat 4f electrons accurately. The
non- electron states crossing the Fermi level have mostly Mo 4d character.
They provide the states with which the 4f sates are strongly hybridized,
leading to the intermediate valent state.Comment: 18 pages, 10 figures Submitted to Journal of Alloys and Compound
Load-Settlement Response of Square Footing on Geogrid Reinforced Layered Granular Beds
Experimental studies were carried out to obtain the load-settlement response of a model square footing resting on unreinforced and reinforced granular beds. The response was obtained for two cases: (a) geogrid-reinforced sand layer, and (b) geogrid-reinforced layered system consisting of aggregate layer overlying a sand layer. The parameters considered in the experimental study include the thickness of the aggregate layer, the depth of geogrid reinforcement placed in sand layer and in aggregate layer, width of the reinforcement, and relative density of bed. Plate vibrator was used to compact uniform sand beds to relative densities equal to 50 % and 70 % inside large-size test chamber of dimensions equal to 1 m × 1 m × 1 m (in length, in width, and in depth). Load was applied on square footing using a 100 kN capacity actuator in displacement-controlled mode, and the improvement in the load carrying capacity of the footing resting on reinforced sand layer and layered system was quantified in terms of load improvement factors. In addition, the optimum embedment depth and width of reinforcements were proposed for various cases considered in the study. The optimum depth of reinforcement for the case of aggregate layer overlying sand layer decreased to 0.30 times the width of the footing from 0.45 times the width of the footing for sand only case
CYLINDRICAL PISTON PROBLEM IN WATER
A study of compression waves produced in water by thsnon-uniform expansion of a cylindrical piston of non-zero initial radius is made by the artificial viscosity method of von Neumann & Richtmyer. It is found that the damping dect introduced by the cylindrical geometry is much less pronounced than that of the spherical geometry
A Monopole-Antimonopole Solution of the SU(2) Yang-Mills-Higgs Model
As shown by Taubes, in the Bogomol'nyi-Prasad-Sommerfield limit the SU(2)
Yang-Mills-Higgs model possesses smooth finite energy solutions, which do not
satisfy the first order Bogomol'nyi equations. We construct numerically such a
non-Bogomol'nyi solution, corresponding to a monopole-antimonopole pair, and
extend the construction to finite Higgs potential.Comment: 11 pages, including 4 eps figures, LaTex format using RevTe
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