Combining rules using local statistics and uncertainty estimates for improved ensemble segmentation

Segmentation using an ensemble of classifiers (or committee machine) combines multiple classifiers’ results to increase the performance when compared to single classifiers. In this paper, we propose new concepts for combining rules. They are based (1) on uncertainties of the individual classifiers, (2) on combining the result of existing combining rules, (3) on combining local class probabilities with the existing segmentation probabilities at each individual segmentation, and (4) on using uncertainty-based weights for the weighted majority rule. The results show that the proposed local-statistics-aware combining rules can reduce the effect of noise in the individual segmentation result and consequently improve the performance of the final (combined) segmentation. Also, combining existing combining rules and using the proposed uncertainty- based weights can further improve the performance.     

Regulation of lower triangular and non‐triangular nonlinear systems with uncertain high‐order nonlinearities via dynamic gain control

In this paper, we consider a global regulation problem of a class of nonlinear systems that have uncertain high‐order nonlinear terms. In particular, we introduce new high‐order lower triangular and non‐triangular conditions and propose a controller with dynamic gains to regulate the system with uncertain high‐order nonlinearities. In designing our controller, the information of the growth rate is not required, and the forms of the high‐order nonlinearities are more relaxed. We verify that the proposed method is applicable to the system which cannot be regulated by the existing methods. Examples and simulation results are given for clear illustration. Copyright © 2016 John Wiley & Sons, Ltd.     

Secure proof of storage with deduplication for cloud storage systems

Explosion of multimedia content brings forth the needs of efficient resource utilization using the state of the arts cloud computing technologies such as data deduplication. In the cloud computing environments, achieving both data privacy and integrity is the challenging issue for data outsourcing service. Proof of Storage with Deduplication (POSD) is a promising solution that addresses the issue for the cloud storage systems with deduplication enabled. However, the validity of the current POSD scheme stands on the strong assumption that all clients are honest in terms of generating their keys. We present insecurity of this approach under new attack model that malicious clients exploit dishonestly manipulated keys. We also propose an improved POSD scheme to mitigate our attack.     

Integrating ICT adoption issues into (e-)leadership theory

Information and communication technologies (ICTs) are having a profound effect in society and organizations. However, the literature on ICT adoption—from selection to implementation—has not been well integrated into leadership theory. This is particularly true in terms of adoption. Leaders must adopt ICTs not only for their own competence—an antecedent condition for what is considered e-leadership, but choose, recommend, and support implementation of ICTs for their organizations/units to use. Leaders are also expected to become effective in dealing and navigating the challenges of leading within the digital space. At this moment, there are two pertinent literatures: the technology adoption literature and the enterprise resource planning literature—which can be considered an important special case of leadership change management literature—and which could provide the theoretical basis for developing a unified theoretical perspective on e-leadership. This article provides a framework and propositions to connect these literatures by focusing on the effects of individual leader characteristics on the ICT adoption process from both a personal and enterprise-wide perspective. Study limitations and future research opportunities are outlined.     

Wafer‐Scale Single‐Crystalline Ferroelectric Perovskite Nanorod Arrays

1D ferroelectric nanostructures are promising for enhanced ferroelectric and piezoelectric performance on the nanoscale, however, their synthesis at the wafer scale using industrially compatible processes is challenging. In order to advance the nanostructure‐based electronics, it is imperative to develop a silicon‐compatible growth technique yielding high volumetric density and an ordered arrangement. Here, a major breakthrough is provided in addressing this need and ordered and close‐packed single crystalline ferroelectric nanorod arrays, of composition PbZr_0.52Ti_0.48O₃ (PZT), grown on commercial grade 3 in. silicon wafer are demonstrated. PZT nanorods exhibit enhanced piezoelectric and ferroelectric performance compared to thin films of similar dimensions. Sandwich structured architecture utilizing 1D PZT nanorod arrays and 2D reduced graphene oxide thin film electrodes is fabricated to provide electrical connection. Combined, these results offer a clear pathway toward integration of ferroelectric nanodevices with commercial silicon electronics.     

Correlation between the performance of organic bulk‐heterojunction solar cells and the molecular structures of alcohol solvents

Morphology control is an important issue for boosting the performance of organic bulk‐heterojunction (BHJ) solar cells. In this study, we investigated the correlation between alcohol solvents and the morphologies of poly({4,8‐bis[(2‐ethylhexyl)oxy]benzo[1,2‐b:4,5‐b′] dithiophene‐2,6‐diyl}{3‐fluoro‐2‐[(2‐ethylhexyl)carbonyl]thieno[3,4‐b]thiophenediyl}) (PTB7) and [6,6]‐phenyl‐C₇₀‐butyric acid methyl ester (PC₇₀BM)‐based organic solar cells by spin‐casting the alcohol onto the active layers. We found that the morphologies strongly depended on the structure of the alcohol [alkyl chain length and hydroxyl (? OH) group position]. Ethanol or 2‐propanol showed the highest performance among the alcohols considered here. Atomic force microscopy images and absorption spectra demonstrated that the alcohols affected the morphologies of PC₇₀BM rather than those of PTB7. The morphologies of PC₇₀BM were dependent on the solubilities of the alcohols to the active layers and the hydrogen‐bonding strengths between the PC₇₀BM and alcohol molecules. Our results indicate that the use of alcohols for solvent annealing is a simple and efficient method for developing high‐performance organic BHJ solar cells. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133 , 44367.     

A Unifying Model for Statistical Arbitrage: Model Assumptions and Empirical Failure

Statistical arbitrage refers to a suite of quantitative investment strategies employed chiefly by hedge funds and proprietary trading firms. The arbitrageur can draw on a number of different approaches to identify and exploit an arbitrage opportunity, though the literature is broadly segmented by the canonical distance, cointegration and time series perspectives. Since the initial academic investigation of statistical arbitrage, its profitability has continued to diminish thanks largely to the increasing proportion of non-convergent opportunities. This paper surveys the existing literature, with particular emphasis given to evidence of statistical arbitrage failure, before unifying the distance, cointegration and time series perspectives under a single explicit model. The failure of statistical arbitrage opportunities is shown to be the direct consequence of implicit model assumptions that are inconsistent with the empirical literature. An alternative model is proposed, and evidence of its relative performance discussed.

     

Improved High-Temperature Strength of Silicon Nitride Toughened with Aligned Whisker Seeds

The effect of the amount of the sintering additives, i.e., yttria and alumina, on the microstructure and the high-temperature flexural strengths of silicon nitride with and without the aligned whisker seeds was examined. As the amount of the sintering additives was increased, both width and length of the grains were increased. The high-temperature strengths of silicon nitride with and without the aligned seeds were increased and decreased, respectively, according to the increase of the amount of the sintering additives. When both 4.8 wt% yttria and 2.2 wt% alumina were added to silicon nitride with the aligned whisker seeds, the experimental results indicated that it had three times the flexural strength as silicon nitride without the seeds at 1673 K. During the high-temperature flexure testing, observations did not indicate yielding present in the samples with the aligned whisker seeds, while it was present in samples without the whisker seeds. The reinforcing grains growing from the whisker seeds aligned perpendicular to the crack propagation direction acted as effective obstacles to the crack propagation and improved the fracture toughness.     

Partial Bi-Sr-Cu-O Subsolidus Diagram at 800°C with and without Lithium Carbonate

Solid-phase relationships have been determined for the Bi₂O₃–SrO–CuO system at 800°C in air with and without Li₂CO₃ mineralizer. Two ternary compounds were detected with Bi:Sr:Cu ratios of approximately 2:2:1 and a solid-solution phase 11−;x:9+x:5 with 0x0.4. The solid-solution phase is a 9 K super-conductor at x=0.4. Two additional compounds with Bi:Sr:Cu ratios of approximately 4:9:1 and 2:7:2 are apparently stabilized by the presence of Li₂CO₃, but do not form without it. X-ray crystallographic data are provided for each compound. Ramifications for quaternary Bi:Sr:Ca:Cu-O superconductors are discussed.     

Hydrothermal Synthesis for Large Barium Titanate Powders at a Low Temperature: Effect of Titania Aging in an Alkaline Solution

Monodisperse and spherical barium titanate (BaTiO₃) powders with diameters of 200–470 nm were directly prepared by a low-temperature hydrothermal method at 90°C. Spherical titania (TiO₂) powders, ranging in size from 150 to 420 nm, were initially prepared by a controlled hydrolysis and condensation reaction, aged in a highly alkaline solution for 12 h, and then hydrothermally reacted with barium hydroxide to be converted to BaTiO₃ without a morphological change. The aging step of the TiO₂, where the surface of TiO₂ was highly densified through elimination of the pores, was indispensable to retain the sizes and shapes of TiO₂ in the resulting BaTiO₃. This was due to the fact that the formation of BaTiO₃ proceeded by an in situ reaction mechanism. The resulting BaTiO₃ powders exhibited dense and nonporous structures even after calcination at 1000°C.