A macro-micromechanics analysis of a notched metal matrix composite

A macro-micromechanics analysis was formulated to determine the matrix and fiber behavior near the notch tip in a center-notched metal matrix composite. Results are presented for a boron/aluminum monolayer. The macro-level analysis models the entire notched specimen using a three dimensional finite element program which uses the vanishing-fiber-diameter model to model the elastic-plastic behavior of the matrix and the elastic behavior of the fiber. The micro-behavior is analyzed using a Discrete Fiber-Matrix (DFM) model containing one fabric and the surrounding matrix. The dimensions of the DFM model were determined by the ply thickness and the fiber volume fraction and corresponded to the size of the notch-tip element in the macro-level analysis. The boundary conditions applied to the DFM model were determined from the macro-level analysis. Stress components within the DFM model were calculated and stress distributions are presented along selected planes and surfaces within the DFM model, including the fiber-matrix interface. Yielding in the matrix was examined at the notch tip in both the macro- and micro-level analyses. The DFM model predicted higher stresses (24 percent) in the fiber compared to the global analysis. In the notch-tip element, the interface stresses indicated that a multi-axial criterion may be required to predict interfacial failure. The DFM analysis predicted yielding to initiate in the notch-tip element at a stress level 28 percent lower than predicted by the global analysis

X-ray properties of the microquasar GRS 1915+105 during a variability class transition

We present a detailed X-ray study of the microquasar GRS 1915+105 during a variability class transition observed in 2000 June with the PPCs of the Indian X-ray Astronomy Experiment. We supplement this observation with data from the RXTE archives. The source made a transition from a steady low-hard state to a regular oscillatory behaviour in the light curve known as bursts or class `rho' (Belloni et al. 2000) between 2000 May 11 and 17 and reverted back to the low-hard state on 2000 June 27. A gradual change in the burst recurrence time from about 75 s to about 40 s was observed which then increased to about 120 s during the ~ 40 days of class `rho'. The regular bursts disappeared from the X-ray light curves and the class transition was observed to occur within 1.5 hours on 2000 June 27 with the PPCs. A correlation is found between the observed QPO frequency at 5-8 Hz in the quiescent phase and the average X-ray intensity of the source during the class `rho'. We notice a strong similarity between the properties of the source during the class `rho' and those during the oscillatory phase of the observations of class `alpha'. From the timing and spectral analysis, it is found that the observed properties of the source over tens of days during the class `rho' are identical to those over a time scale of a few hundreds of seconds in the class `alpha'. Examining the light curves from the beginning of the RXTE/PCA and RXTE/ASM observations, it is found that the change of state from radio-quiet low-hard state to high state occurs through the X-ray classes `rho' and `alpha' which appear together during the state transition. It is further inferred that the source switches from low-hard state to the class `rho' through the intermediate class `alpha'.Comment: 10 pages with 9 figures, LaTex. To be appeared in MNRA

Bragg Spectroscopy of Vortex Lattices in Bose-Einstein condensates

We have measured the velocity field of a vortex lattice within a sodium Bose-Einstein condensate using Bragg scattering. The phase gradient of the macroscopic wavefunction was mapped into the spatial structure of the diffracted atom cloud, allowing for single shot measurement of the rotation parameters. A combination of spectral and spatial information yields a complete description of the superfluid flow, coarse-grained over the lattice structure, including direct and independent measurements of the rate and sense of rotation. Signatures of the microscopic quantum rotation have also been observed.Comment: 5 pages, 5 Figures, A movie built from the CM data is available in our Webpage: http://www.physics.gatech.edu/chandra/index.htm; added Fig.5 presents new data, showing signatures of the microscopic vortex structure in the diffracted clou

Role of Government in Development of Sustainable Ecotourism in Karnataka

Ecotourism is a visit to the natural reserved areas like national parks, sanctuaries and biosphere reserves for sightseeing as tourism. The visit of reserved areas by the tourists, the entrepreneurs, the government and the host community, the major agencies or stakeholders in ecotourism, has created numerous effects in the field of ecology, socio-cultural, economic which are indefensible lots of time. Sustainability is also a sober concern. The current article inspects sustainability as an association with all its stakeholders and proposes on preserving equilibrium in the correlation which is necessary to achieve sustainability. The part of rule in attaining sustainability is surveyed and found that it helps in reinstating the essential stability in the association with the stakeholders in ecotourism.  Ecotourism in Karnataka is steadily qualified for the consideration of the tourists, the government and the entrepreneurs for clear motive. Karnataka has necessary prospective in ecotourism to cope up with the interests of the tourists, the entrepreneurs and the government but does sustainability study with  concern in the schedule of these organizations. An environmental law is one of the most effectual tools for executing sustainability; it needs plenty of provisions to institute synchronization between the stakeholders and hence the goal of sustainability in ecotourism remains unachievable