Randomized Assignment of Jobs to Servers in Heterogeneous Clusters of Shared Servers for Low Delay

We consider the job assignment problem in a multi-server system consisting of $N$ parallel processor sharing servers, categorized into $M$ ($\ll N$) different types according to their processing capacity or speed. Jobs of random sizes arrive at the system according to a Poisson process with rate $N \lambda$. Upon each arrival, a small number of servers from each type is sampled uniformly at random. The job is then assigned to one of the sampled servers based on a selection rule. We propose two schemes, each corresponding to a specific selection rule that aims at reducing the mean sojourn time of jobs in the system. We first show that both methods achieve the maximal stability region. We then analyze the system operating under the proposed schemes as $N \to \infty$ which corresponds to the mean field. Our results show that asymptotic independence among servers holds even when $M$ is finite and exchangeability holds only within servers of the same type. We further establish the existence and uniqueness of stationary solution of the mean field and show that the tail distribution of server occupancy decays doubly exponentially for each server type. When the estimates of arrival rates are not available, the proposed schemes offer simpler alternatives to achieving lower mean sojourn time of jobs, as shown by our numerical studies

Raman spectroscopy in electrochermistry

Raman spectroscopy is a particularly useful technique for studying electrochemical surface reactions because it is a visible wavelength spectroscopy and permits in situ investigations. Most electrochemical systems can be studied by Surface Enhanced Raman Spectroscopy ISERS) which involves surface selection and preparation. The techniques involved in the preparation and observation of SERS signals have been highlighted in this review. Recent developments in the observation of SERS on non-SERS active substrates have also been rrported. Studies on the various material - substrate systems have been listed. The application of SERS to various electrochemical systems is also reviewe

A 9/7 -Approximation Algorithm for Graphic TSP in Cubic Bipartite Graphs

We prove new results for approximating Graphic TSP. Specifically, we provide a polynomial-time 9/7-approximation algorithm for cubic bipartite graphs and a (9/7+1/(21(k-2)))-approximation algorithm for k-regular bipartite graphs, both of which are improved approximation factors compared to previous results. Our approach involves finding a cycle cover with relatively few cycles, which we are able to do by leveraging the fact that all cycles in bipartite graphs are of even length along with our knowledge of the structure of cubic graphs

Pharmaceutico-Analytical Study of Agnikumara Rasa - A Kupipakwa Kalpana

Agnikumara Rasa is a Sagandha, Sagni, Kantastha Bahirdhuma Kupipakwa Rasayana mentioned in Rasakamadhenu under Sangrahani Chikitsa Adhikara. It is prepared under Kramagni Tapa for 18 hours as per classics. The core ingredients are Shuddha Parada, Shuddha Gandhaka, Shuddha Vatsanabha and Hamsapadi Swarasa. It is indicated in conditions like Sannipata Kasa, Shwasa, Kshaya, Panduroga and Mandagni. Even though a total of 50 formulations have been explained in classics under the name of Agnikumara Rasa, no research work has been done till date on this particular yoga explained in Rasakamadhenu

Linear Differential Constraints for Photo-polarimetric Height Estimation

In this paper we present a differential approach to photo-polarimetric shape estimation. We propose several alternative differential constraints based on polarisation and photometric shading information and show how to express them in a unified partial differential system. Our method uses the image ratios technique to combine shading and polarisation information in order to directly reconstruct surface height, without first computing surface normal vectors. Moreover, we are able to remove the non-linearities so that the problem reduces to solving a linear differential problem. We also introduce a new method for estimating a polarisation image from multichannel data and, finally, we show it is possible to estimate the illumination directions in a two source setup, extending the method into an uncalibrated scenario. From a numerical point of view, we use a least-squares formulation of the discrete version of the problem. To the best of our knowledge, this is the first work to consider a unified differential approach to solve photo-polarimetric shape estimation directly for height. Numerical results on synthetic and real-world data confirm the effectiveness of our proposed method.Comment: To appear at International Conference on Computer Vision (ICCV), Venice, Italy, October 22-29, 201

Crystal growth and properties of the non-centrosymmetric superconductor, Ru7B3

We describe the crystal growth of high quality single crystals of the non-centrosymmetric superconductor, Ru7B3 by the floating zone technique, using an optical furnace equipped with xenon arc lamps. The crystals obtained are large and suitable for detailed measurements, and have been examined using x-ray Laue patterns. The superconducting properties of the crystals obtained have been investigated by magnetisation and resistivity measurements. Crystals have also been grown starting with enriched 11B isotope, making them suitable for neutron scattering experiments.Comment: 4 pages, 5 figures. Accepted for publication in Journal of Crystal Growt

Synthesis of Colloidal Mn2+:ZnO Quantum Dots and High-TC Ferromagnetic Nanocrystalline Thin Films

We report the synthesis of colloidal Mn2+-doped ZnO (Mn2+:ZnO) quantum dots and the preparation of room-temperature ferromagnetic nanocrystalline thin films. Mn2+:ZnO nanocrystals were prepared by a hydrolysis and condensation reaction in DMSO under atmospheric conditions. Synthesis was monitored by electronic absorption and electron paramagnetic resonance (EPR) spectroscopies. Zn(OAc)2 was found to strongly inhibit oxidation of Mn2+ by O2, allowing the synthesis of Mn2+:ZnO to be performed aerobically. Mn2+ ions were removed from the surfaces of as-prepared nanocrystals using dodecylamine to yield high-quality internally doped Mn2+:ZnO colloids of nearly spherical shape and uniform diameter (6.1 +/- 0.7 nm). Simulations of the highly resolved X- and Q-band nanocrystal EPR spectra, combined with quantitative analysis of magnetic susceptibilities, confirmed that the manganese is substitutionally incorporated into the ZnO nanocrystals as Mn2+ with very homogeneous speciation, differing from bulk Mn2+:ZnO only in the magnitude of D-strain. Robust ferromagnetism was observed in spin-coated thin films of the nanocrystals, with 300 K saturation moments as large as 1.35 Bohr magneton/Mn2+ and TC > 350 K. A distinct ferromagnetic resonance signal was observed in the EPR spectra of the ferromagnetic films. The occurrence of ferromagnetism in Mn2+:ZnO and its dependence on synthetic variables are discussed in the context of these and previous theoretical and experimental results.Comment: To be published in the Journal of the American Chemical Society Web on July 14, 2004 (http://dx.doi.org/10.1021/ja048427j

HST-FOS Observations of M87: Ly-a Emission from the Active Galactic Nucleus

The Faint Object Spectrograph on the Hubble Space Telescope was used to obtain spectra of the central region of M87. These spectra cover the wavelength range 1140 - 1606 Angstrom and have a resolution of about 1 Angstrom. The nuclear continuum is clearly visible in the spectra. The only strong line that is observed is Ly-alpha, which has a velocity width of about 3000 km/sec. There is also a marginal detection of C IV 1549. The ratio of Ly-alpha to C IV in the nuclear spectrum is at least a factor of 2 higher than in a spectrum taken at a position on the disk about 0.6" away from the nucleus by Dopita et al. This enhancement of Ly-alpha at the nucleus could point to significant differences in the properties of the emitting gas and/or the excitation mechanism between the outer and inner disk regions. The strength of the observed Ly-alpha places limits on the properties of the absorbing gas present within M87. For instance, if the hydrogen column at the systemic velocity of M87 is greater than about 10^18 cm^{-2} then it can cover only a small fraction of the line emitting region. Spectra separated by 5 days show a 60% difference in the Ly-alpha flux, but the same continuum level. This could be due to either a displacement between the aperture positions for the two sets of observations, or it could be due to intrinsic variability of the source. The current observations do not strongly favor either of these alternatives. The observations do show, however, that the Ly-alpha line is a useful tracer of kinematics in the M87 nucleus.Comment: 14 pages + 5 figures. LaTeX uses aaspp4.sty. Accepted for publication in the Astrophysical Journa

Choosing among heterogeneous server clouds

This paper considers a model of interest in cloud computing applications. We consider a multiserver system consisting of N heterogeneous servers. The servers are categorized into M( ≪N ) different types according to their service capabilities. Jobs having specific resource requirements arrive at the system according to a Poisson process with rate Nλ . Upon each arrival, a small number of servers are sampled uniformly at random from each server type. The job is then routed to the sampled server with maximum vacancy per server capacity. If a job cannot obtain the required amount of resources from the server to which it is assigned, then the job is discarded. We analyze the system in the limit as N→∞ . This gives rise to a mean field, which we show has a unique fixed point and is globally attractive. Furthermore, as N→∞ , the servers behave independently. The stationary tail probabilities of server occupancies are obtained from the stationary solution of the mean field. Numerical results suggest that the proposed scheme significantly reduces the average blocking probability compared to static schemes that probabilistically route jobs to servers in proportion to the number of servers of each type. Moreover, the reduction in blocking holds even for systems at high load. For the limiting system in statistical equilibrium, our simulation results indicate that the occupancy distribution is insensitive to the holding time distribution and only depends on its mean