Influence of analysis and design models on minimum weight design

The results of numerical experiments designed to illustrate how the minimum weight design, accuracy, and cost can be influenced by: (1) refinement of the finite element analysis model and associated load path problems, and (2) refinement of the design variable linking model are examined. The numerical experiments range from simple structures where the modelling decisions are relatively obvious and less costly to the more complex structures where such decisions are less obvious and more costly. All numerical experiments used employ the dual formulation in ACCESS-3 computer program. Guidelines are suggested for creating analysis and design models that predict a minimum weight structure with greater accuracy and less cost. These guidelines can be useful in an interactive optimization environment and in the design of heuristic rules for the development of knowledge-based expert optimization systems

Equivalent widths of atomic lines in sunspot spectra

Equivalent widths of 82 Cr I lines, 70 Fe 1 lines, and 74 Ti I lines are measured in the spectra of four sunspots of average area 55 millionths of the visible hemisphere of the sun. Separate curves of growth for Cr I, Fe t, and Ti I are constructed. Excitation temperatures of 4030° ± 80° , 4200° ± 150° , and 3800° ± 100° are obtained for Cr I, Fe I, and Ti I, respectively

On semistable principal bundles over a complex projective manifold, II

Let (X, \omega) be a compact connected Kaehler manifold of complex dimension d and E_G a holomorphic principal G-bundle on X, where G is a connected reductive linear algebraic group defined over C. Let Z (G) denote the center of G. We prove that the following three statements are equivalent: (1) There is a parabolic subgroup P of G and a holomorphic reduction of the structure group of E_G to P (say, E_P) such that the bundle obtained by extending the structure group of E_P to L(P)/Z(G) (where L(P) is the Levi quotient of P) admits a flat connection; (2) The adjoint vector bundle ad(E_G) is numerically flat; (3) The principal G-bundle E_G is pseudostable, and the degree of the charateristic class c_2(ad(E_G) is zero.Comment: 15 page

Observation of a 2D Bose-gas: from thermal to quasi-condensate to superfluid

We present experimental results on a Bose gas in a quasi-2D geometry near the Berezinskii, Kosterlitz and Thouless (BKT) transition temperature. By measuring the density profile, \textit{in situ} and after time of flight, and the coherence length, we identify different states of the gas. In particular, we observe that the gas develops a bimodal distribution without long range order. In this state, the gas presents a longer coherence length than the thermal cloud; it is quasi-condensed but is not superfluid. Experimental evidence indicates that we observe the superfluid transition (BKT transition).Comment: 5 pages, 6 figure

Mechanical Properties of Randomly Oriented Calotropis Gigantea Fiber-Reinforced Phenol Formaldehyde Biocomposites

Mechanical properties such as tensile, flexural and impact, of randomly oriented Calotropis Gigantea Fiber (CGF) -reinforced Phenol Formaldehyde (PF) biocomposites were studied based on the five different fiber loadings (10, 20, 30, 40, and 50 vol%) and three different fiber lengths (3, 9, and 15 mm). The critical fiber length and optimum fiber loading were identified with the maximum level of mechanical properties in this composite. The fractured surfaces of composites after testing were studied by scanning electron microscope (SEM). The results revealed that the addition of CGFs is improving the mechanical properties of the PF composite. The properties of composites reach the properties of the neat resin sample at 20 vol% of all the cases. The critical fiber length and the optimum fiber loading to obtain the maximum mechanical properties were identified as 9 mm and 40 vol% respectively. Experimental tensile property values were compared with theoretical values and found to be in good agreement

Effects of Addition of Prosopis Juliflora Fiber on the Physical and Mechanical Properties of Wood Dust and Coir Pith Particle Reinforced Phenol Formaldehyde Hybrid Composite

In this study, Wood Dust (WD)/Phenol Formaldehyde (PF) and Coir Pith (CP)/PF composites were hybridized with the Prosopis Juliflora Fiber (PJF) to obtain the hybrid composites. Composites were prepared by hand moulding technique. The weight percentage of particles and fibers are fixed in the ratio of 1:1. Mechanical properties such as tensile, flexural and impact strengths were evaluated as a function of the particle and fiber loadings. The results show that the properties of both the WD and CP composites obviously improved by the addition of the PJF. The improvement in WD/PF composites was obviously higher than the CP/PF composites for all loadings. The WD/PJF/PF hybrid composites exhibited better tensile (strength of 48.9 MPA and modulus of 1262.1 MPa, respectively), flexural (strength of 55.4 MPa and modulus of 1344.3 MPa, respectively), and impact properties (1.32 KJ/m2).Â

Application of the Continuous Variation Method to Systems Involving Stable Stepwise Complexes: Ni(II)-1,10-Phenanthroline & Cu(II)-Ethylenediamine Systems

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Towards a Better Understanding of the Local Attractor in Particle Swarm Optimization: Speed and Solution Quality

Particle Swarm Optimization (PSO) is a popular nature-inspired meta-heuristic for solving continuous optimization problems. Although this technique is widely used, the understanding of the mechanisms that make swarms so successful is still limited. We present the first substantial experimental investigation of the influence of the local attractor on the quality of exploration and exploitation. We compare in detail classical PSO with the social-only variant where local attractors are ignored. To measure the exploration capabilities, we determine how frequently both variants return results in the neighborhood of the global optimum. We measure the quality of exploitation by considering only function values from runs that reached a search point sufficiently close to the global optimum and then comparing in how many digits such values still deviate from the global minimum value. It turns out that the local attractor significantly improves the exploration, but sometimes reduces the quality of the exploitation. As a compromise, we propose and evaluate a hybrid PSO which switches off its local attractors at a certain point in time. The effects mentioned can also be observed by measuring the potential of the swarm

Latitude gradient in aerosol properties across the Inter Tropical Convergence Zone: results from the joint Indo-US study onboard Sagar Kanya

As part of the Indian Ocean Experiment (INDOEX) Intensive Field Phase (IFP), a cruise by ORV Sagar Kanya was conducted in the Arabian Sea and the Indian Ocean from 20 January to 12 March 1999. Measurements on aerosol properties such as optical depth, mass concentration, size distribution, scattering and absorption coefficients were measured using instruments such as sun-photometer, quartz crystal microbalance, nephelometer and particle-soot absorption photometer. One of the important findings is the large north-south asymmetry in the aerosol characteristics. Aerosol optical depth values were very high, exceeding 0.4, close to the west coast of India and the Arabian Sea, which is greater than by a factor of 4 or more, compared to the values south of the ITCZ. The wavelength exponent α, is found to be in the range of 1.3 to 1.7 in the high optical depth region and is in the range of 0.5 to 0.7 over the pristine region. Aerosol mass concentration data show that the nucleation mode aerosols (radius < 0.1 µm) are systematically higher over the Arabian Sea, with values ranging from 20 to 50 µg/m3. Correlating the aerosol mass with the scattering coefficient, we get a scattering to mass concentration ratio of 2.27 m2/g, for the Arabian Sea region, which is in between the values reported by other workers, 3.3 m2/g for the continent and 1.67 m2/g for the marine regions, elsewhere in the world. The single scattering albedo, ω derived from the scattering and absorption data, is around 0.9 for aerosols found over the Arabian Sea, while near the coastal regions the values are as low as 0.8. Low ω and high optical depth found in the coastal region and Arabian Sea indicate large absorption by aerosols. The results undoubtedly show a large spatial difference in aerosol characteristics between north and south of the ITCZ which could lead to a large asymmetry in aerosol radiative forcing between the two regions