An Efficient Web Service Discovery Architecture for Static and Mobile Environments

The widely adopted and implemented core web servicesstandards SOAP and WSDL have achieved extraordinaryinteroperability across highly disparate software systems. The serviceoriented architecture SOA has become widely recognized for itsimportant role in information technology (IT) projects. A SOA is a styleof design that guides an organization during all aspects of creating andusing business services (including conception, modeling, design,development, deployment and management). SOA has been the idealcombination of architecture and technology for consistently deliveringrobust, reusable services that support today’s business needs and that canbe easily adapted to satisfy changing business requirements. As systemsbecome more complex, the overall system structure-or architecture---becomes a central design problem. A system's architecture provides amodel of the system that suppresses implementation detail.Unfortunately, current representations of SOA architecture are informaland ad hoc. Currently many state of the art formal methods have beenapplied into the modeling, interoperability, dependability andtrustworthiness of web services and this could have a significant impacton the ongoing standardization efforts for services and cloudtechnologies. This paper presents a formal verification of proposed x-SOA based architecture for UDDI based web service discoveryframework. The paper attempts to establish the proposed architecture forlocating services in mobile computing environment as well. Potentially,extending the state of art formal method techniques could have asignificant impact on the ongoing standardization efforts for web servicesand cloud technologies for both fixed and mobile networks

A Demand Based Load Balanced Service Replication Model

Cloud computing allows service users and providers to access the applications, logical resources and files on any computer with ease. A cloud service has three distinct characteristics that differentiate it from traditional hosting. It is sold on demand, typically by the minute or the hour; it is elastic. It is a way to increase capacity or add capabilities on the fly without investing in new infrastructure, training new personnel, or licensing new software. It not only promises reliable services delivered through next-generation data centers that are built on compute and storage virtualization technologies but also addresses the key issues such as scalability, reliability, fault tolerance and file load balancing. The one way to achieve this is through service replication across different machines coupled with load balancing. Though replication potentially improves fault tolerance, it leads to the problem of ensuring consistency of replicas when certain service is updated or modified. However, fewer replicas also decrease concurrency and the level of service availability. A balanced synchronization between replication mechanism and consistency not only ensures highly reliable and fault tolerant system but also improves system performance significantly. This paper presents a load balancing based service replication model that creates a replica on other servers on the basis of number of service accesses. The simulation results indicate that the proposed model reduces the number of messages exchanged for service replication by 25-55% thus improving the overall system performance significantly. Also in case of CPU load based file replication, it is observed that file access time reduces by 5.56%-7.65%

Far-Ultraviolet Spectroscopy Of Active Galactic Nuclei With AstroSat/UVIT

\require{mediawiki-texvc} We study accretion disk emission from eight Seyfert $1 - 1.5$ active galactic nuclei (AGN) using far ultra-violet ($1300-1800$ ${\AA}$) slit-less grating spectra acquired with AstroSat/UVIT. We correct for the Galactic and intrinsic extinction, contamination from the host galaxies, narrow and broad-line regions, Fe II emission and Balmer continuum, and derive the intrinsic continua. We use HST COS/FOS spectra to account for the emission/absorption lines in the low-resolution UVIT spectra. We find generally redder power-law ($f_\nu \propto \nu^{\alpha}$) slopes ($\alpha \sim -1.1 - 0.3$) in the far UV band than predicted by the standard accretion disk model in the optical/UV band. We fit accretion disk models such as the multi-temperature disk blackbody ($\texttt{DISKBB}$) and relativistic disk ($\texttt{ZKERRBB}$, $\texttt{OPTXAGNF}$) models to the observed intrinsic continuum emission. We measure the inner disk temperatures using the $\texttt{DISKBB}$ model for seven AGN. These temperatures in the range $\sim 3.6-5.8$ eV are lower than the peak temperatures predicted for standard disks around maximally spinning super-massive black holes accreting at Eddington rates. The inner disks in two AGN, NGC 7469 and Mrk 352, appear to be truncated at $\sim 35-125r_{g}$ and $50-135r_{g}$, respectively. While our results show that the intrinsic FUV emission from the AGN are consistent with the standard disks, it is possible that UV continua may be affected by the presence of soft X-ray excess emission, X-ray reprocessing, and thermal Comptonisation in the hot corona. Joint spectral modeling of simultaneously acquired UV/X-ray data may be necessary to further investigate the nature of accretion disks in AGN.Comment: 29 pages, 12 figures, accepted for publication in Ap

Far-ultraviolet spectroscopy of active galactic nuclei with AstroSat/UVIT

We study accretion disk emission from eight Seyfert 1−1.5 active galactic nuclei (AGN) using far ultra-violet (1300−1800 Å) slit-less grating spectra acquired with AstroSat/UVIT. We correct for the Galactic and intrinsic extinction, contamination from the host galaxies, narrow and broad-line regions, Fe II emission and Balmer continuum, and derive the intrinsic continua. We use HST COS/FOS spectra to account for the emission/absorption lines in the low-resolution UVIT spectra. We find generally redder power-law (fν∝να) slopes (α∼−1.1−0.3) in the far UV band than predicted by the standard accretion disk model in the optical/UV band. We fit accretion disk models such as the multi-temperature disk blackbody (DISKBB) and relativistic disk (ZKERRBB, OPTXAGNF) models to the observed intrinsic continuum emission. We measure the inner disk temperatures using the DISKBB model for seven AGN. These temperatures in the range ∼3.6−5.8 eV are lower than the peak temperatures predicted for standard disks around maximally spinning super-massive black holes accreting at Eddington rates. The inner disks in two AGN, NGC 7469 and Mrk 352, appear to be truncated at ∼35−125rg and 50−135rg, respectively. While our results show that the intrinsic FUV emission from the AGN are consistent with the standard disks, it is possible that UV continua may be affected by the presence of soft X-ray excess emission, X-ray reprocessing, and thermal Comptonisation in the hot corona. Joint spectral modeling of simultaneously acquired UV/X-ray data may be necessary to further investigate the nature of accretion disks in AGN

Large scale validation of a new non-invasive and non-contact bilirubinometer in neonates with risk factors

Abstract The study was aimed to evaluate the performance of a newly developed non-invasive and non-contact bilirubin measurement device (AJO-Neo) as an alternative to the conventional invasive biochemical method of total serum bilirubin (TSB) estimation in preterm and term neonates suffering from hyperbilirubinemia associated with risk factors, and/or undergoing phototherapy. The safety and efficacy of the device were assessed in 1968 neonates with gestational ages ranging from 28 to 41 weeks and suffering from incidences of hyperbilirubinemia. Linear regression analysis showed a good correlation between AJO-Neo and the conventional method of TSB (Pearson’s coefficient, r = 0.79). The small bias (0.27 mg/dL) and limits of agreements (− 3.44 to 3.99 mg/dL) were within the range of clinical acceptance. The device was also precise in the measurement of bilirubin levels in all subgroups of the study. The receiver operator curve (ROC), that takes account of both sensitivity and specificity of a device showed high efficacy of the device (area under the curve, AUC = 0.83) in the detection of bilirubin. While monitoring the bilirubin level during phototherapy, the device indicated promising results showing good agreement with TSB. Specificities and sensitivities of the device indicated a much higher accuracy in neonates with associated risk factors for hyperbilirubinemia. Hence, the newly developed device (AJO-Neo) is reliable in measuring bilirubin level in preterm, and term neonates irrespective of gestational or postnatal age, sex, risk factors, feeding behavior or skin color