Trust Model for Optimized Cloud Services

Cloud computing with its inherent advantages draws attention for business critical applications, but concurrently expects high level of trust in cloud service providers. Reputation-based trust is emerging as a good choice to model trust of cloud service providers based on available evidence. Many existing reputation based systems either ignore or give less importance to uncertainty linked with the evidence. In this paper, we propose an uncertainty model and define our approach to compute opinion for cloud service providers. Using subjective logic operators along with the computed opinion values, we propose mechanisms to calculate the reputation of cloud service providers. We evaluate and compare our proposed model with existing reputation models

Explicit Space-Time Codes Achieving The Diversity-Multiplexing Gain Tradeoff

A recent result of Zheng and Tse states that over a quasi-static channel, there exists a fundamental tradeoff, referred to as the diversity-multiplexing gain (D-MG) tradeoff, between the spatial multiplexing gain and the diversity gain that can be simultaneously achieved by a space-time (ST) block code. This tradeoff is precisely known in the case of i.i.d. Rayleigh-fading, for T>= n_t+n_r-1 where T is the number of time slots over which coding takes place and n_t,n_r are the number of transmit and receive antennas respectively. For T < n_t+n_r-1, only upper and lower bounds on the D-MG tradeoff are available. In this paper, we present a complete solution to the problem of explicitly constructing D-MG optimal ST codes, i.e., codes that achieve the D-MG tradeoff for any number of receive antennas. We do this by showing that for the square minimum-delay case when T=n_t=n, cyclic-division-algebra (CDA) based ST codes having the non-vanishing determinant property are D-MG optimal. While constructions of such codes were previously known for restricted values of n, we provide here a construction for such codes that is valid for all n. For the rectangular, T > n_t case, we present two general techniques for building D-MG-optimal rectangular ST codes from their square counterparts. A byproduct of our results establishes that the D-MG tradeoff for all T>= n_t is the same as that previously known to hold for T >= n_t + n_r -1.Comment: Revised submission to IEEE Transactions on Information Theor

Size-distribution of submicron aerosol particles over the Indian Ocean during IFP-99 of INDOEX

Measurements of the size-distribution of submicron aerosol particles of diameter from 0.003 to 1 &#956;m are made over the Indian Ocean during the IFP-99 of the Indian Ocean Experiment (INDOEX). Measurements are made during the onward journey from Goa to Port Louis, Mauritius from 20 January to 11 February 1999 onboard ORV Sagar Kanya and during the return journey from Port Louis to Male from 22 February to 1 March 1999 onboard Ronald H. Brown. Observations show large concentrations in the range of 2-6 &#215; 103 particles/cm3 over the Indian Ocean in the northern hemisphere and these drop down to about 500 particles/cm3 in the southern hemisphere. However, the aerosol concentrations show a peak of about 3 &#215; 103 particles/cm3 at 13&#176;S. In the northern hemisphere, the concentration of particles of diameter &lt; 0.0749 &#956;m increases from 14&#176;N to 1&#176;N and then steeply falls. On the other hand, the concentration of particles of diameter &gt; 0.0749 &#956;m keeps decreasing up to 6&#176;S. Size distributions of particles at open sea in the northern hemisphere show a maximum at 0.133 &#956;m and minimum at 0.0422 &#956;m and are generally openended at the smaller size end. The size-distributions of particles are sometimes relatively flat from 0.0133 to 0.237 &#956;m when the particle concentrations are low in the southern hemisphere. The transport and accumulation of aerosol particles in the Inter-Tropical Convergence Zone is discussed. The relative abundance of large versus small particles is examined with respect to the variation of surface atmospheric pressure along the route

Effect of anthropogenic disturbances on biomass and carbon storage potential of a dry tropical forest in India

The forests of Chhattisgarh are very well known for its species richness, diversity, biomass, carbon stock and productivity. The present study was carried out at Katghora forest division under Bilaspur circle of Korba district, Chhattisgarh considering three sites viz., least, moderately and highly disturbed site to estimate biomass and carbon storage in relation to anthropogenic disturbances. For collection of data quadrats were selected under stratified random sampling design. For enumeration of tree and saplings ten quadrats of 10 m × 10 m were laid and each species counted separately. The tree density varies from 100-510 stems ha-1 across study sites. Total biomass in the present study was between 127.69 t ha-1 and 227.71 t ha-1. Total above ground biomass was between 111.20 t ha-1 and 199.42 t ha-1, whereas total below ground biomass varied from 16.49-28.29 t ha-1, respectively. The total carbon storage across the sites were ranged from 55.125 to 98.548 t C ha-1 found higher under least disturbed site and lowest under medium disturbed site. Carbon storage pattern according to girth class followed the similar trend of distribution as was in the case of biomass. It has least proportion in small girth class and maximum storage under the higher girth class. It is evident from the study that disturbances have significant impact on density, vegetation diversity, biomass accumulation and carbon storage pattern. Conservation affords are required to control on disturbances and for the natural recovery of forest ecosystem