Reinforcement learning models for scheduling in wireless networks

The dynamicity of available resources and network conditions, such as channel capacity and traffic characteristics, have posed major challenges to scheduling in wireless networks. Reinforcement learning (RL) enables wireless nodes to observe their respective operating environment, learn, and make optimal or near-optimal scheduling decisions. Learning, which is the main intrinsic characteristic of RL, enables wireless nodes to adapt to most forms of dynamicity in the operating environment as time goes by. This paper presents an extensive review on the application of the traditional and enhanced RL approaches to various types of scheduling schemes, namely packet, sleep-wake and task schedulers, in wireless networks, as well as the advantages and performance enhancements brought about by RL. Additionally, it presents how various challenges associated with scheduling schemes have been approached using RL. Finally, we discuss various open issues related to RL-based scheduling schemes in wireless networks in order to explore new research directions in this area. Discussions in this paper are presented in a tutorial manner in order to establish a foundation for further research in this field.     

Family, school, and neighborhood: Links to Chinese American adolescent perceptions of racial/ethnic discrimination.

The purpose of the study was to examine how family, school, and neighborhood factors contributed to Chinese American adolescent perceptions of discrimination. The sample included 185 Chinese American adolescents (mean age = 16.8 years, SD = .81; 58% female; 70% U.S.-born) and their parents. As hypothesized, the results showed that greater parent perceptions of discrimination, more negative school environment, and less availability of cultural resources were related to greater adolescent perceptions of discrimination. Contrary to the hypothesis, parent/adolescent subjective perceptions of ethnic density were related to greater adolescent perceptions of discrimination. The findings suggest that adolescent perceptions of discrimination are related to both within and outside family factors, supporting an ecological approach to understanding racial/ethnic discrimination. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Increasing the efficiency of single walled carbon nanotube amplification by Fe-Co catalysts through the optimization of CH4/H2 partial pressures

Single walled carbon nanotubes (SWNTs) seeds are grown using Fe-Co nanoparticles on spin-on-glass. The relative efficiency of nucleation and amplification (versus etching) was investigated as a function of the CH(4)/H(2) feedstock ratio and growth temperature. At 900 °C, maximum amplification is obtained with CH(4)/H(2) ratio of 80:20 but 60:40 for nucleation. Amplification is further enhanced at 800 °C, compared with etching dominating at 1000 °C. Amplification of SWNTs is in equilibrium with etching; higher carbon feedstock pressure and decreased temperature increase the rate of amplification; the converse increases etching.     

Infectivity of Trichinella nativa in traditional northern (country) foods prepared with meat from experimentally infected seals

The infectivity of Trichinella nativa larvae in three traditional northern (country) foods was assessed. Foods were prepared with meat from seals experimentally infected with Trichinella nativa and evaluated over a 317-day period during which this food was fed directly to cats while mice were orally inoculated with larvae recovered following the digestion of the food in a solution containing 1% pepsin and 1% HCl at 37 degrees C. Foods examined were igunaq (meat and blubber placed in a seal skin bag and allowed to ferment), nikku (air-dried meat), and sausage (meat, fillers, salt, and spices). Sausage was examined both in a raw state and after partial cooking. Infective T. nativa larvae survived in igunaq, nikku, raw frozen sausage, and poorly cooked sausage for at least 5 months under controlled laboratory conditions. Core temperatures of partially cooked sausage never exceeded 50 degrees C. Caution should be exercised in using these data to establish guidelines for the consumption of raw products, since the survival of infective larvae could be unpredictably extended under field conditions. These data indicate significant food safety risks associated with igunaq, nikku, and sausage prepared with Trichinella-infected meat and provide information for use in risk management and in directing future research.     

Pulsed field gel electrophoresis typing of human and retail foodstuff Campylobacters: an Irish perspective

Campylobacter enteritis is a zoonosis, an infectious disease transmissible under normal conditions from vertebrate animals to man, presenting a major global public health burden. In this study, Pulsed Field Gel Electrophoresis (PFGE) was employed to identify common genotypes in a collection of 600 Campylobacter isolates in order to investigate if profiles obtained from retail samples of foodstuffs matched genotypes causing illness in the community in Ireland. The Campylobacters were isolated from retail foodstuffs, and cases of gastroenteritis, over the same 20-month period in three population centres in Ireland. The major observation made was of a high level of PFGE-genotype heterogeneity; 236 SmaI discrete genotypes were found in 507 strains successfully analysed. Analysis of the PFGE profiles revealed 22 common profiles amongst food isolates and those causing enteritis in humans. These cojoint PFGE genotypes indicate that 56 (38%) of the human clinical isolates are genetically related to 129 (36%) of the food isolates. The identification of these recurrent PFGE types, in the sampled Campylobacter coli and Campylobacter jejuni populations, indicates that a high proportion of Campylobacter isolates found in foods of animal origin also occur in patients with symptoms of enteritis. This data adds weight to the epidemiological hypothesis that a high proportion of human Campylobacter cases are contracted via the handling and consumption of contaminated foodstuffs, in particular poultry.     

Genetic variation of lodgepole pine, Pinus contorta var. latifolia, chemical and physical defenses that affect mountain pine beetle, Dendroctonus ponderosae, attack and tree mortality

Plant secondary chemistry is determined by both genetic and environmental factors, and while large intraspecific variation in secondary chemistry has been reported frequently, the levels of genetic variation of many secondary metabolites in forest trees in the context of potential resistance against pests have been rarely investigated. We examined the effect of tree genotype and environment/site on the variation in defensive secondary chemistry of lodgepole pine, Pinus contorta var. latifolia, against the fungus, Grosmannia clavigera (formerly known as Ophiostoma clavigerum), associated with the mountain pine beetle, Dendroctonus ponderosae. Terpenoids were analyzed in phloem samples from 887, 20-yr-old trees originating from 45 half-sibling families planted at two sites. Samples were collected both pre- and post-inoculation with G. clavigera. Significant variation in constitutive and induced terpenoid compounds was attributed to differences among families. The response to the challenge inoculation with G. clavigera was strong for some individual compounds, but primarily for monoterpenoids. Environment (site) also had a significant effect on the accumulation of some compounds, whereas for others, no significant environmental effect occurred. However, for a few compounds significant family x environment interactions were found. These results suggest that P. c. latifolia secondary chemistry is under strong genetic control, but the effects depend on the individual compounds and whether or not they are expressed constitutively or following induction.     

Routing in Distributed Cognitive Radio Networks: A Survey

Cognitive Radio Networks (CRNs) have been receiving significant research attention recently due to their ability to solve issues associated with spectrum congestion and underutilization. In a CRN, unlicensed users (or Secondary Users, SUs) are able to exploit and use underutilized licensed channels, but they must evacuate the channels if any interference is caused to the licensed users (or Primary Users, PUs) who own the channels. Due to the dynamicity of spectrum availability in CRNs, design of protocols and schemes at different layers of the SU’s network stack has been challenging. In this article, we focus on routing and discuss the challenges and characteristics associated with it. Subsequently, we provide an extensive survey on existing routing schemes in CRNs. Generally speaking, there are three categories of challenges, namely channel-based, host-based, and network-based. The channel-based challenges are associated with the operating environment, the host-based with the SUs, and the network-based with the network-wide SUs. Furthermore, the existing routing schemes in the literature are segregated into three broad categories based on the relationship between PUs and SUs in their investigation, namely intra-system, inter-system, and hybrid-system; and within each category, they are further categorized based on their types, namely Proactive, Reactive, Hybrid, and Adaptive Per-hop. Additionally, we present performance enhancements achieved by the existing routing schemes in CRNs. Finally, we discuss various open issues related to routing in CRNs in order to establish a foundation and to spark new interests in this research area.     

The effect of increased interrogation zone,reader antenna polarization and application factors in the performance of UHF RFID tag detection on modified atmosphere packaged meat

The effect of conveyor speed, test sample size, antenna to sample distance, antenna polarization and ideal tag location in relation to the coupling capabilities of ultra‐high frequency radio frequency identification on optimal reader antenna placement were studied. The influence of each individual factor and its interaction was determined using the general linear model analysis of variance. In decreasing order of significance of the variables tested were sample type (F = 4174.40, p < 0.0005), smaller samples preferred for coupling; distance (F = 863.83, p < 0.0005), where distance between sample and antenna should be kept to a minimum; inlay design (F = 167.82, p < 0.0005), where AD‐612 preformed best due to its large antenna area; and reader antenna polarization (F = 149.64, p < 0.0005), where circular polarization preformed better yet comparative advantage decreased with distance. A reader antenna offset of 95 mm, while not significant, (F = 1.73, p = 0.188) tended to decrease coupling capabilities of the system despite increasing the zone of influence. Ideal tag location on sample was found to be on the right, back and front face with y‐orientation proving superior than either x or z. A 190‐mm centre–to‐centre reader antenna offset resulted in a decrease in the average tag detection rate from 62 to 49% highlighting the importance of optimal reader antenna placement which needs to be confirmed if a similar result is to be obtained when a large number of tags are interrogated simultaneously. Copyright © 2010 John Wiley & Sons, Ltd.     

Characteristics of students who enroll and succeed in psychology Web-based classes.

This study compared the cognitive-motivational and demographic characteristics of students enrolled in 3 Web-based sections of Psychological Statistics with their counterparts in 3 conventional (face-to-face) sections of this course. No demographic differences were found, however, cyberstudents exhibited a greater external locus of control than conventional students. The authors also investigated whether there were any predictors of student performance in Web courses. Measures of on-line course activity (e.g., homepage hit rate), a high need for cognition, and an internal locus of control were predictive of cyberstudent success. The authors discuss the implications of these results for instructors who are considering the design and implementation of Web-based classes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)