An archiving model for a hierarchical information storage environment

Cataloged from PDF version of article.We consider an archiving model for a database consisting of secondary and tertiary storage devices in which the query rate for a record declines as it ages. We propose a `dynamic' archiving policy based on the number of records and the age of the records in the secondary device. We analyze the cases when the number of new records inserted in the system over time are either constant or follow a Poisson process. For both scenarios, we characterize the properties of the policy parameters and provide optimization results when the objective is to minimize the average record retrieval times. Furthermore, we propose a simple heuristic method for obtaining near-optimal policies in large databases when the record query rate declines exponentially with time. The e ectiveness of the heuristic is tested via a numerical experiment. Finally, we examine the behavior of performance measures such as the average record retrieval time and the hit rate as system parameters are varied. Ó 2000 Elsevier Science B.V. All rights reserved

Dynamic Voltage Scaling Techniques for Energy Efficient Synchronized Sensor Network Design

Building energy-efficient systems is one of the principal challenges in wireless sensor networks. Dynamic voltage scaling (DVS), a technique to reduce energy consumption by varying the CPU frequency on the fly, has been widely used in other settings to accomplish this goal. In this paper, we show that changing the CPU frequency can affect timekeeping functionality of some sensor platforms. This phenomenon can cause an unacceptable loss of time synchronization in networks that require tight synchrony over extended periods, thus preventing all existing DVS techniques from being applied. We present a method for reducing energy consumption in sensor networks via DVS, while minimizing the impact of CPU frequency switching on time synchronization. The system is implemented and evaluated on a network of 11 Imote2 sensors mounted on a truss bridge and running a high-fidelity continuous structural health monitoring application. Experimental measurements confirm that the algorithm significantly reduces network energy consumption over the same network that does not use DVS, while requiring significantly fewer re-synchronization actions than a classic DVS algorithm.unpublishedis peer reviewe

Extending the life of nuclear power plants : technical and institutional issues

Managing nuclear power plant aging is one of the important technical issues which needs to be addressed by utilities in order to extend the operating life of some of the early LWR power stations. Plant managers must understand complex aging phenomena, identify aging effects, anticipate failure, and mitigate the aging process. Typically, the age-related design limits of crucial components are not known, and this information usually does not appear to be easily available from the equipment vendor. Electrical cables, insulation and instrumentation are most susceptible to age-related degradation. material degradation due to corrosion is the main costly problem affecting a small but important portion of piping and major equipment. Upgrading the plant, replacing aging equipment, and implementing good maintenance, surveillance and spare parts inventory control programs are actions a utility can take to extend the life of operating nuclear plants. Considerable institutional uncertainties are associated with nuclear plant life extension. These spring mainly from the absence of clearly defined policies by the U.S. Nuclear Regulatory Commission stating the technical and procedural requirements for plant life extension. From precedents established to-date, it is reasonable to expect plant operation to be permitted for most plants for a total of 40 years after start of commerical operation. As a large share of the net discounted benefits of extended life operation may be derived from the first decade of additional life, the basis for utility investments for life extension is thus assured.Northeast Utilities Service Compan

A Study of Form and Content of Private Speech Used by Iranian EFL Learners

From the sociocultural point of view, the investigation of private speech is important in seeing how the mind works. Yet, not much is known about the form and content of private speech. A group of English language learners were required to talk about some topics of their reading courses. Their voices were recorded and the private speech used by them were identified. It was found that the main role of the loud and silent forms of the private speech in the data is to help learners manage the interaction. Private speech is embedded within the speech context and it needs to be explained in the context in which it happens

The Challenge of Terminographic Gaps in Translation: A Text-based Approach Put to Practice

The issue of terminographic gaps in specialized discourses has always concerned the researchers and readers alike. However, due to the interlingual nature of such a technical issue, the need for interdisciplinary collaboration between translation and terminography seems to be in prospect. For such a reciprocation scheme to come into practical effect, the present study has aimed to conduct a translational-terminographic concerto by putting a specialized English text to the test of Persian translation. This has been done to answer the question if a translator is required to provide for any terminological gap once all attempts at finding the corresponding terminological items have failed. In this pursuit, certain workable criteria for terminographic proposition via translation have been discussed. As such, the practical phase of this study concerns itself with addressing the issue of Persian terminological gaps in a language-related metadiscoursal field and consequently detecting the problem zones of non-equivalence in a specialised text carefully selected for translation. Ultimately, a list of Persian terminological items constructed on the basis of the proposed translational-cum-terminographical scheme is compiled to address the identified terminological gaps in the target metadiscourse under study

Registries in systemic sclerosis: a worldwide experience

SSc is a multisystem disease characterized by an unpredictable course, high mortality and resistance to therapy. The complexity and severity of SSc is a growing burden on the health-care systems. As a result, researchers are seeking new therapeutic strategies for effectively managing these patients. Disease registries are used to support care management efforts for groups of patients with chronic diseases and are meaningful to capture and track key patient information to assist the physicians in managing patients. For these reasons, SSc surveys, research associations and consortiums are pivotal to conduct ongoing research and data collection to enhance disease knowledge and support research projects. Currently, there are several national SSc registries in the UK, Germany, USA, Canada, Brazil and Australia. There is also an international registry established by the European League Against Rheumatism scleroderma trial and research (EUSTAR) called minimal essential data set (MEDS) Online, which collects data from over 8000 patients from 92 centres worldwide, including 21 European centres and 9 centres outside Europe. By collecting, analysing and disseminating data on disease progression and patient responses to long-term disease management strategies, registries help to improve understanding of the disease and keep medical professionals up to date on the latest advance

The Efficacy of Teaching English as a Foreign Language to Iranian Students with Autism Spectrum Disorderon Their Social Skills and Willingness to Communicate

AbstractObjectivesThis applied research is the first practical study of teaching English as a foreign language (EFL) to students with autism spectrum disorder (ASD) in Iran. We examined the effect of a well-designed foreign language learning setting in facilitation of social skills and willingness to communicate in children with ASD.Materials & MethodsA mixed-method research design was used. Using stratified sampling, a limited sample of 18 students were chosen from Kerman Province, southeastern Iran in 2014 categorized in three levels of ASD for each group of experimental and control; matched pairs were used to ensure homogeneity of participants in two groups. Each participant received 15 sessions with totaling 67 h of language learning. First 10 sessions were in the form of tutorials and the last 5 sessions were held in the form of paired classes with a peer. Before and after the sessions, caregivers and parents completed a questionnaire on students' social skills; the English instructor also rated participants' willingness to communicate.ResultsTeaching a foreign language had a positive main effect on social skills from caregivers’ and parents’ view compared to those of controls, significantly (P<0.05). From the instructor's view, there was additionally a significant improvement in the students with ASD’s willingness to communicate in classroom settings compared to the control group (P<0.05).ConclusionOptimum foreign language pedagogy for students with ASD is applied as an effective context enhancing children’s capabilities in social skills and willingness to communicate, provoked through a motivational foreign setting modulation in a novel environment. Suggestions on enhancing joint attention during the curriculum are provided

Interpersonal Behavior: More vs. Less Favorable Teachers

Classrooms can be regarded as dynamic systems in which behaviors of teachers and students affect each other mutually and in a spiral manner. In this study it was intended to investigate differences in interpersonal behaviors of a more vs. a less favorable teacher at micro- and macro-levels. To analyze classroom interaction dynamically and in real-time, State Space Grid technique was applied. On the macro-level, teacher profiles were determined based on vector method. 211 students of six classes rated the behavior of their own teacher and an imaginary ideal one. One teacher who was closest to and one farthest from that ideal were identified and their classes were video-taped. Two raters coded behaviors with a joystick and then content and structure of interaction were analyzed. Differences on the micro-level were especially noticeable in the strength of attractors, not in their position. Structurally, the behavior of the more favorable teacher had higher variability and less predictability. On the macro-level, the more favorable teacher had Authoritative, and the less favorable one had Directive profiles. The results of this study can be used in promoting interactive ground of the class and in teacher education programs

Analysis of maintenance policies for M machines with deteriorating performance

In this paper, we consider the maintenance scheduling of a group of M identical machines, the performance of which deteriorates with usage. Examples of such situations are frequently found in the heavy machine tooling, petro-chemical and semi-conductor industries among others. Assuming a limited maintenance resource and that the maintenance times are i.i.d., we propose a dynamic maintenance policy which utilities the information about the number of operating machines and their ages. We analyze the system for the special cases of constant and exponentially distributed maintenance times. We investigate the impact of maintenance time variability on system performance and evaluate the performance of various maintenance policies within the proposed policy class when the expected profit rate is maximized