IBM

About: IBM is a company organization based out in Armonk, New York, United States. It is known for research contribution in the topics: Layer (electronics) & Signal. The organization has 134567 authors who have published 253905 publications receiving 7458795 citations. The organization is also known as: International Business Machines Corporation & Big Blue.

Restful web services vs. "big"' web services: making the right architectural decision

Abstract: Recent technology trends in the Web Services (WS) domain indicate that a solution eliminating the presumed complexity of the WS-* standards may be in sight: advocates of REpresentational State Transfer (REST) have come to believe that their ideas explaining why the World Wide Web works are just as applicable to solve enterprise application integration problems and to simplify the plumbing required to build service-oriented architectures. In this paper we objectify the WS-* vs. REST debate by giving a quantitative technical comparison based on architectural principles and decisions. We show that the two approaches differ in the number of architectural decisions that must be made and in the number of available alternatives. This discrepancy between freedom-from-choice and freedom-of-choice explains the complexity difference perceived. However, we also show that there are significant differences in the consequences of certain decisions in terms of resulting development and maintenance costs. Our comparison helps technical decision makers to assess the two integration styles and technologies more objectively and select the one that best fits their needs: REST is well suited for basic, ad hoc integration scenarios, WS-* is more flexible and addresses advanced quality of service requirements commonly occurring in enterprise computing.

Materials interface engineering for solution-processed photovoltaics

Abstract: Advances in solar photovoltaics are urgently needed to increase the performance and reduce the cost of harvesting solar power. Solution-processed photovoltaics are cost-effective to manufacture and offer the potential for physical flexibility. Rapid progress in their development has increased their solar-power conversion efficiencies. The nanometre (electron) and micrometre (photon) scale interfaces between the crystalline domains that make up solution-processed solar cells are crucial for efficient charge transport. These interfaces include large surface area junctions between photoelectron donors and acceptors, the intralayer grain boundaries within the absorber, and the interfaces between photoactive layers and the top and bottom contacts. Controlling the collection and minimizing the trapping of charge carriers at these boundaries is crucial to efficiency.

Losses in single-mode silicon-on-insulator strip waveguides and bends.

Abstract: We report the fabrication and accurate measurement of propagation and bending losses in single-mode silicon waveguides with submicron dimensions fabricated on silicon-on-insulator wafers. Owing to the small sidewall surface roughness achieved by processing on a standard 200mm CMOS fabrication line, minimal propagation losses of 3.6+/-0.1dB/cm for the TE polarization were measured at the telecommunications wavelength of 1.5microm. Losses per 90 masculine bend are measured to be 0.086+/-0.005dB for a bending radius of 1microm and as low as 0.013+/-0.005dB for a bend radius of 2microm. These record low numbers can be used as a benchmark for further development of silicon microphotonic components and circuits.

Twin Problems of Interfacial Carbonate Formation in Nonaqueous Li-O2 Batteries.

Abstract: We use XPS and isotope labeling coupled with differential electrochemical mass spectrometry (DEMS) to show that small amounts of carbonates formed during discharge and charge of Li–O2 cells in ether electrolytes originate from reaction of Li2O2 (or LiO2) both with the electrolyte and with the C cathode. Reaction with the cathode forms approximately a monolayer of Li2CO3 at the C–Li2O2 interface, while reaction with the electrolyte forms approximately a monolayer of carbonate at the Li2O2–electrolyte interface during charge. A simple electrochemical model suggests that the carbonate at the electrolyte–Li2O2 interface is responsible for the large potential increase during charging (and hence indirectly for the poor rechargeability). A theoretical charge-transport model suggests that the carbonate layer at the C–Li2O2 interface causes a 10–100 fold decrease in the exchange current density. These twin “interfacial carbonate problems” are likely general and will ultimately have to be overcome to produce a high...

Approximating the Kullback Leibler Divergence Between Gaussian Mixture Models

Abstract: The Kullback Leibler (KL) divergence is a widely used tool in statistics and pattern recognition. The KL divergence between two Gaussian mixture models (GMMs) is frequently needed in the fields of speech and image recognition. Unfortunately the KL divergence between two GMMs is not analytically tractable, nor does any efficient computational algorithm exist. Some techniques cope with this problem by replacing the KL divergence with other functions that can be computed efficiently. We introduce two new methods, the variational approximation and the variational upper bound, and compare them to existing methods. We discuss seven different techniques in total and weigh the benefits of each one against the others. To conclude we evaluate the performance of each one through numerical experiments.