Simpler and more accurate throughput analysis of a DS CDMA/unslotted ALOHA system with two user classes based on M/M/infinity queueing model

We propose that the throughput performance of the DS CDMA unslotted ALOHA system with two user classes is analyzed by the M/M/infinity queueing model without the death rate approximation. The previous scheme uses the M/D/infinity queueing model with the death rate approximation. The new analysis method is simpler than the previous one because four‐dimensional summation is replaced by two‐dimensional summation in the packet success probability calculation. The speed of new analysis program is 250 times faster than that of the previous one. In the numerical results, we consider the cases when the message arrival rates of the two classes are equal or not equal, and the access control is present or not. It shows that the proposed scheme has more accurate analyzed throughput than the previous one does. Copyright © 2009 John Wiley & Sons, Ltd.     

Improving the performance of blue phosphorescent organic light-emitting devices using a composite emitter

A composite emitter is constructed by doping a carrier-transporting material into a conventional emitter composing of only host and dopant. The transport of carriers from either hole- or electron-transporting layer into the emitter can be promoted through the carrier-transporting material, in particular, when a wide-band-gap host material is used. A blue phosphorescent OLED based on iridium(III)bis((4,6-difluorophenyl)-pyridinate-N,C^2′)-picolinate (FIrpic) as dopant in the composite emitter achieved a power efficiency of 20 lm/W and a low driving voltage of 4.2 V at 1000 cd/m², whose current efficiency at 20 mA/cm² was 2.5 times better than that of device using the conventional emitter.     

Differentiation and identification of Shigella spp. and enteroinvasive Escherichia coli in environmental waters by a molecular method and biochemical test

Both Shigella spp. and enteroinvasive Escherichia coli (EIEC) are important human pathogens that are responsible for the majority of cases of endemic bacillary dysentery. However, they are difficult to identify and differentiate by biochemical tests or molecular methods alone. In this study, we developed a procedure to detect Shigella spp. and EIEC from environmental water samples using membrane filtration followed by nutrient broth enrichment, isolation using selective culture plates, and identification of the invasion plasmid antigen H (ipaH) gene by PCR amplification and DNA sequencing. Finally, we used a biochemical test and a serological assay to differentiate between Shigella and EIEC. Among the 93 water samples from nine reservoirs and one watershed, 76 (81.7%) water samples of culture plates had candidate colonies of Shigella and EIEC and 5 water samples were positive (5.4%) for a Shigella- and EIEC-specific polymerase chain reaction targeting the ipaH gene. Guided by the molecular method, the biochemical test, and the serological assay, 11 ipaH gene-positive isolates from 5 water samples were all identified as EIEC.     

Retracted: The Relationship between Personality Traits and Sales Force Automation Usage: A Preliminary Study

Sales force automation (SFA) came to cognition and officially gained momentum in the 1990s (Taylor, 1993). SFA provides salespeople with speedy information access, diminishing the time needed to prepare for calls and cutting down on the number of follow‐ups, particularly for urgent need of further information support (Taylor, 1993). This study attempts to look specifically at the “utilization–individual impact” link. In particular, the close link of the personality type of the sales representative to the individual performance usage of the sales forces automation systems in the pharmaceutical industry in Taiwan. This study provides insight into how the personality traits of the individual medical representatives of pharmaceutical companies in Taiwan could influence the adoption of innovative technology, the sales force automation system. © 2012 Wiley Periodicals, Inc.     

Cobalt selenide electrocatalyst supported by nitrogen-doped carbon and its stable activity toward oxygen reduction reaction

We have prepared durable catalysts of CoSe₂/N-carbon using low-cost raw materials, measured their activities, peroxide yields, stabilities in reducing molecular oxygen, and characterized their crystalline phases and morphology. CoSe₂/N-carbon is featured with an active support, N-carbon, which by itself shows high stability as evidenced in its small activity decay. After 1000 CV cycles, the half-wave potential (E_1/2) of N-carbon decreases from 0.667 V to 0.636 V in 0.5 M H₂SO₄. Loading of CoSe₂ enhances the activity of N-carbon, when the samples were synthesized above 385 °C and formulated with the Se/Co ratio higher than 10. The higher activity is attributed to the pyrite phase of CoSe₂. But the stability of pyrite CoSe₂ is less than that of N-carbon. Corrosion during the stability test exposes the active sites of underlying N-carbon, which sustains the catalyst activity. Consequently the E_1/2 value of the active CoSe₂/N-carbon decreases moderately, from 0.711 V to 0.644 V after 1000 CV cycles. In contrast, the E_1/2 value of CoSe₂/C descends much more, from 0.681 V to 0.475 V.     

A hybrid scheme for energy-efficient object tracking in sensor networks

Energy saving is a critical issue in many sensor-network-based applications. Among the existing sensor-network-based applications, the surveillance application has attracted extensive attention. Object tracking in sensor networks (OTSNs) is a typical surveillance application. Previous studies on energy saving for OTSNs can be divided into two main approaches: (1) improvements in hardware design to lower the energy consumption of attached components and (2) improvements in software to predict the movement of objects. In this paper, we propose a novel scheme, namely hybrid tracking scheme (HTS), for tracking objects with energy efficiency. The scheme consists of the two parts: (1) adaptive schedule monitoring and (2) a recovery mechanism integrated with seamless temporal movement patterns and seeding-based flooding to relocate missing objects with the purpose of saving energy. Furthermore, we also propose a frequently visited periods mining algorithm, which discovers the corresponding frequently visited periods for adaptive schedule monitoring efficiently from the visitation information of sensor nodes. To decrease the number of sensor nodes activated in flooding, a seeding-based flooding mechanism is first proposed in our work. Empirical evaluations of various simulation conditions and real datasets show that the proposed HTS delivers excellent performance in terms of energy efficiency and low missing rates.     

A novel approach for assisting teachers in analyzing student web-searching behaviors

Although previous research has demonstrated the benefits of applying the Internet facilities to the learning process, problems with this strategy have also been identified. One of the major difficulties is owing to the lack of an online learning environment that can record the learning portfolio of using the Internet facilities in education, such that the teacher can analyze and evaluate the learning performance of students, and hence the teaching strategies can be adjusted accordingly. In this paper, we propose a web-search learning environment, called Meta-Analyzer, which is able to assist the teachers in analyzing student learning behaviors of using search engines for problem solving. Two-hundred and twenty students and 54 teachers contributed to the trial of the system. The results have shown that the novel approach is able to gain a better understanding about students’ learning processes and searching strategies in technology-enhanced environments, as well as to assist the teachers to acquire more about the learning status of students, and hence more constructive suggestions can be given accordingly.     

Reversible Data Hiding for Medical Images in Cloud Computing Environments Based on Chaotic Hénon Map

Reversible data hiding techniques are capable of reconstructing the original cover image from stego-images. Recently, many researchers have focused on reversible data hiding to protect intellectual property rights. In this paper, we combine reversible data hiding with the chaotic Hénon map as an encryption technique to achieve an acceptable level of confidentiality in cloud computing environments. And, Haar digital wavelet transformation (HDWT) is also applied to convert an image from a spatial domain into a frequency domain. And then the decimal of coefficients and integer of high frequency band are modified for hiding secret bits. Finally, the modified coefficients are inversely transformed to stego-images.     

Preparation and characterization of PPSU/PBNPI blend membrane for hydrogen separation

Novel polymer blend membranes of poly(bisphenol A-co-4-nitrophthalic anhydride-co-1,3-phenylenediamine) (PBNPI) and polyphenylsulfone (PPSU) in different weight ratios were prepared by a solution casting technique with N-methyl-2-pyrrolidone (NMP) as solvent. The effects of blend polymer composition on the membrane structure and the H₂, CO₂ and CH₄ separation performance were investigated. The membranes appear macroscopically miscible but microscopically immiscible based on thin-film X-ray diffraction investigations. A remarkably and continuously enhanced permeability has been achieved for these gases with increasing PPSU content from 0 to 50%. The highest pure H₂, CO₂ and CH₄ permeability are, respectively, equal to 40.4, 34.1 and 8.0 barrer.     

Implementation of physical optics analysis of spiral antenna radiations in the presence of Bor radome structure for the application of direction finding

Abstract

A practical physical optics (PO) implementation procedure is employed to study the radiations of multi‐arm spiral antennas in the presence of a body of revolution (BOR) radome structure in direction finding applications. This procedure potentially simplifies the geometrical optics ray tracing procedure based on characteristics of spiral antennas, which is required to define the equivalent currents of PO, and provides efficient formulations to compute the radiation fields due to PO currents that are equivalent to the radiation of spiral antennas in the presence of the same type radome structure.