Algorithms for Data Migration

The data migration problem is the problem of computing a plan for moving data objects stored on devices in a network from one configuration to another. Load balancing or changing usage patterns might necessitate such a rearrangement of data. In this paper, we consider the case where the objects are fixed-size and the network is complete. Our results are both theoretical and empirical. Our main theoretical results are (1) a polynomial time algorithm for finding a near-optimal migration plan in the presence of space constraints when a certain number of additional nodes is available as temporary storage, and (2) a 3/2-approximation algorithm for the case where data must be migrated directly to its destination. We also run extensive experiments on several algorithms for various data migration problems and show that empirically, many algorithms perform better in practice than their theoretical bounds suggest. We conclude that many of the algorithms we present are both practical and effective for data migration.     

Nonmetric calibration of wide-angle lenses and polycameras

Images taken with wide-angle cameras tend to have severe distortions which pull points towards the optical center. This paper proposes a simple method for recovering the distortion parameters without the use of any calibration objects. Since distortions cause straight lines in the scene to appear as curves in the image, our algorithm seeks to find the distortion parameters that map the image curves to straight lines. The user selects a small set of points along the image curves. Recovery of the distortion parameters is formulated as the minimization of an objective function which is designed to explicitly account for noise in the selected image points. Experimental results are presented for synthetic data as well as real images. We also present the idea of a polycamera which is defined as a tightly packed camera cluster. Possible configurations are proposed to capture very large fields of view. Such camera clusters tend to have a nonsingle viewpoint. We therefore provide analysis of what we call the minimum working distance for such clusters. Finally, we present results for a polycamera consisting of four wide-angle sensors having a minimum working distance of about 4 m. On undistorting the acquired images using our proposed technique, we create real-time high resolution panoramas.     

Password-authenticated key exchange based on RSA

There have been many proposals in recent years for password-authenticated key exchange protocols, i.e., protocols in which two parties who share only a short secret password perform a key exchange authenticated with the password. However, the only ones that have been proven secured against offline dictionary attacks were based on Diffie–Hellman key exchange. We examine how to design a secure password-authenticated key exchange protocol based on RSA. In this paper, we first look at the OKE and protected-OKE protocols (both RSA-based) and show that they are insecure. Then we show how to modify the OKE protocol to obtain a password-authenticated key exchange protocol that can be proven secure (in the random oracle model). This protocol is very practical; in fact, it requires about the same amount of computation as the Diffie–Hellman-based protocols. Finally, we present an augmented protocol that is resilient to server compromise, meaning (informally) that an attacker who compromises a server would not be able to impersonate a client, at least not without running an offline dictionary attack against that client’s password.     

A hybrid policy for fault tolerant load balancing in grid computing environments

Due to the emergence of grid computing over the Internet, there is a need for a hybrid load balancing algorithm which takes into account the various characteristics of the grid computing environment. Hence, this research proposes a fault tolerant hybrid load balancing strategy namely AlgHybrid_LB, which takes into account grid architecture, computer heterogeneity, communication delay, network bandwidth, resource availability, resource unpredictability and job characteristics. AlgHybrid_LB juxtaposes the strong points of neighbor-based and cluster based load balancing algorithms. Our main objective is to arrive at job assignments that could achieve minimum response time and optimal computing node utilization. Major achievements include low complexity of proposed approach and drastic reduction of number of additional communications induced due to load balancing. A simulation of the proposed approach using Grid Simulation Toolkit (GridSim) is conducted. Experimental results show that the proposed algorithm performs very well in a large grid environment.     

Nano‐hydroxyapatite (HAp) and hydroxyapatite/platinum (HAp/Pt) core shell nanorods: Development,structural study,and their catalytic activity

The development of a new kind of material that is a nanostructured catalytic material with an environmentally benign nature that can be used for alternative energy has acquired significance in recent years. In this context, the use of heterogeneous catalysts for the transesterification of vegetable oils has gained prominence due to their eco‐friendly and reusable nature. Hence in the present study, pure hydroxyapatite (HAp) and hydroxyapatite/platinum (HAp/Pt) nanostructured particles have been prepared successfully through a facile chemical method without templates and surfactants and their catalytic activity investigated for transesterification of natural vegetable oil to bioenergy (biodiesel). The textural and structural features of pure HAp and HAp/Pt were investigated using various characterization techniques such as x‐ray diffraction, Fourier transform infrared (FTIR) and Raman spectroscopy, field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). The elements present in the prepared nanostructures were confirmed through energy dispersive spectroscopy (EDS) and x‐ray photoelectron spectroscopy (XPS) techniques. The XPS analysis also confirms the metallic nature of the platinum in HAp/Pt. The specific surface area and porous nature of the prepared nanostructured catalysts were studied using the N₂ physisorption Brunauer‐Emmett‐Teller‐Barrett‐Joyner‐Halenda (BET‐BJH) method. The catalytic activity of the pure HAp nanoparticles and HAp/Pt core shell nanorods with the Simarouba glauca plant seed oil was investigated. The obtained results indicate that the pristine HAp nanoparticles and HAp/Pt core shell nanorods (NRs) show 91.4% and 87.1% fatty acid methyl ester (FAME) conversion, respectively, potentially offering environmental benign biocatalysts for biofuel production from natural feed stock.     

Morphology characterization of high‐impact resistant polypropylene using AFM and SALS

Atomic force microscopy and small angle light scattering have been used to characterize the morphology of high‐impact polypropylene. Because of sample preparation requirements, both techniques are relatively simple compared with conventional electron microscopy approaches. Using atomic force microscopy the spatial distribution of the impact‐modifying ethylene‐propylene rubber (EPR) domains could be readily identified whereas small angle light scattering was used to quantify overall domain size distribution. EPR domains from a few hundred nanometers to a few microns in size were observed with average sizes that vary from the edge to the center of the polypropylene particle. In addition, it has been observed that the morphology shifts from discrete domains to bicontinuous as the EPR content is increased. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 452–457, 2000     

Compatibilizing effect of poly(styrene)‐block‐poly(isoprene) copolymers in heterogeneous poly(styrene)/natural rubber blends

Compatibility of poly(styrene) (PS)/natural rubber (NR) blend is improved by the addition of diblock copolymer of poly(styrene) and cis‐poly(isoprene) (PS‐b‐PI). The compatibilizing effect has been investigated as a function of block copolymer molecular weight, composition and concentration. The effect of homopolymer molecular weight, processing conditions and mode of addition on the morphology of the dispersed phase have also been investigated by means of optical microscopy and scanning electron microscopy. A sharp decrease in phase dimensions is observed with the addition of a few percent of block copolymers. The effect levels off at higher concentrations. The leveling off could be an indication of interfacial saturation. For concentrations below the critical value, the particle size reduction is linear with copolymer volume fraction and agrees well with the prediction of Noolandi and Hong. The addition of the block copolymer improves the mechanical properties of the blend. An attempt is made to correlate the mechanical properties with the morphology of the blends. © 2001 Society of Chemical Industry     

Burning Rate Evaluation of Composite Solid Propellants. A simplified approach

One of the principal parameters associated with a solid propellant is its linear burning rate. Many attempts have been made in the past to determine theoretically the burning rates of solid propellants by the use of appropriate combustion models. The object of the present paper is to propose a simplified theory of burning rate suitable for composite solid propellants. While the paper follows basically the scheme suggested for this purpose by Beckstead, Derr and Price using multiple flamelets, certain simplifying assumptions have been introduced with a view to make the model easier to operate. An attempt is also made in the paper to extend it to the case of aluminized solid propellants as well on the basis of a specific hypothesis regarding the role of aluminium. The relevant transcendental equations of combustion were solved on a digital computer. The burning rates and related characteristics were evaluated by this technique for two specific ammonium perchlorate-based solid propellants, one aluminized and the other non-aluminized, and the results obtained agree reasonably with the reported experimental trends.     

Highly solar active Fe(III) immobilised alumina for the degradation of Acid Violet 7

The hetero-Fenton catalyst Fe(III)-Al₂O₃ was prepared and characterised by ICP-AES, FT-IR and SEM-EDX. A detailed investigation of photocatalytic degradation of Acid Violet 7 (AV 7) using this Fenton immobilised Al₂O₃ catalyst was carried out. The optimal reaction conditions for the photodegradation of AV 7 with this catalyst are reported. Higher efficiency of the catalyst in solar light than in UV light makes this heterophoto-Fenton degradation, a green technological process. The catalyst is found to be stable and reusable. The completion of degradation has also been confirmed by chemical oxygen demand (COD) measurements.