Buoyancy-driven heat transfer enhancement in a two-dimensional enclosure utilizing nanofluids

Heat transfer enhancement in a two-dimensional enclosure utilizing nanofluids is investigated for various pertinent parameters. A model is developed to analyze heat transfer performance of nanofluids inside an enclosure taking into account the solid particle dispersion. The transport equations are solved numerically using the finite-volume approach along with the alternating direct implicit procedure. Comparisons with previously published work on the basis of special cases are performed and found to be in excellent agreement. The effect of suspended ultrafine metallic nanoparticles on the fluid flow and heat transfer processes within the enclosure is analyzed and effective thermal conductivity enhancement maps are developed for various controlling parameters. In addition, an analysis of variants based on the thermophysical properties of nanofluid is developed and presented. It is shown that the variances within different models have substantial effects on the results. Finally, a heat transfer correlation of the average Nusselt number for various Grashof numbers and volume fractions is presented.     

Energy-efficiency skeptics and advocates: the debate heats up as the stakes rise

Energy efficiency (EE) is rapidly growing in many markets today, but its its cost-effectiveness and potential for growth are being hotly debated. These controversies impede public and private investment in efficiency programs, products, and services. As the stakes rise, the debate has heated up and the need grows to clarify the disagreements and disputes. We review the arguments of skeptics and advocates on 10 key questions concerning energy efficiency, attempting to answer three overriding questions: does an EE gap exist, how big is the gap, and how can the gap be shrunk? We tackle 10 areas of contention: the significance of market failures, the efficiency of investment levels, energy intensity as a measure of efficiency, the treatment of naturally occurring EE, the application of discount rates, accounting for transaction costs, treatment of the rebound effect, the practice of EE delivery, the integration of EE into utility business models, and opportunities for EE growth. Research needs in each of these areas are also described. By examining the divergent views of skeptics and advocates and by addressing the limitations of current knowledge, policymakers and stakeholders can make better-informed decisions supported by more defensible analysis.     

Polyethylene crystallization nucleated by carbon nanotubes under shear

Polyethylene crystallization under shear has been studied in the presence of single-wall, few-wall, and multiwall carbon nanotubes (SWNT, FWNT, and MWNT). Polyethylene crystal d-spacings for (110) and (200) planes in polyethylene/carbon nanotubes (CNT) are smaller than in the control polyethylene without CNT and the polymer chain is oriented along the CNT axis. The single-wall carbon nanotube templated polyethylene crystals do not redissolve in boiling xylenes; instead, the chain morphology transforms to an amorphous conformation but remains oriented along the nanotube axis. SWNT crystal peaks were also observed in polyethylene/SWNT fibers.     

Training the word recognition skills of reading disabled children: Treatment and transfer effects.

54 disabled readers were randomly assigned to 1 of 2 word recognition and spelling training programs or to a problem solving and study skills training program. One word-training program taught orthographically regular words by whole word methods alone; the other trained constituent grapheme–phoneme correspondences. The word-training groups made significant gains in word recognition accuracy and speed and in spelling. Significant transfer was observed on uninstructed spelling content but not on uninstructed reading vocabulary. In general, the word-training programs were equally effective for instructed content, but the whole-word group was superior on some transfer measures at posttest. Although the results demonstrate that dyslexic readers can be instructed successfully, the children did not profit differentially from letter-sound over whole-word training in the present context. We speculate that severely disabled readers may require either a more extended period of letter–sound instruction to reliably adopt an alphabetic decoding strategy or additional specific training in phonological awareness and subsyllabic segmentation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Models of visual word recognition: When obscuring the stimulus yields a clearer view.

It is well known that visual word recognition is influenced by context, word frequency, and stimulus quality. A processing account is outlined in which stimulus quality affects the orthographic input lexicon, whereas context influences both the orthographic input lexicon and the semantic system. Word frequency exerts its primary effects on the pathways that link lexical systems with each other and with the semantic system. Previous findings that are problematic for alternative models along with the results of 2 new experiments are consistent with this account. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Wundt's American doctoral students.

Using the student records in the archives at Karl Marx University in Leipzig, Germany, 33 American students have been identified who took their doctoral degrees with Wilhelm Wundt. Wundt served as major reader (Erstgutachter) for 16 students and as secondary reader (Zweitgutachter) for another 17. Many of these students are unknown to psychologists, even among historians of psychology. This article provides the 1st comprehensive catalog of these students and includes information on their dissertation work and subsequent careers. Wundt's effect on his American students is also discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Influence of sex stereotypes on children's exploration and memory: A competence versus performance distinction.

25 girls and 31 boys (aged 4–9 yrs) were presented with novel objects in 3 sex-labeled boxes and were given 6 min to explore the objects. Memory for information about the objects was tested 1 wk later. Results show that Ss tactually explored novel objects labeled for their own sex more than similar objects labeled for the other sex and remembered more detailed information about own-sex than other-sex objects. Furthermore, regardless of labeling condition, Ss recalled the sex-typed label applied by the experimenter to each object. As expected from the C. L. Martin and C. F. Halverson, Jr. (see record 1982-05576-001) schematic processing model, an incentive to remember did not improve recall in any labeling condition. The sex-typed labeling effects on exploration occurred primarily among the older children, whereas the effects on recall appeared among the younger and older boys and the younger girls. The results suggest that sex stereotypes restrict children's behavior by limiting their competence rather than their performance. Findings are discussed in relation to an earlier study by the 1st author and R. C. Endsley (see record 1983-32397-001). (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adjustment to occupational stress: The relationship of perceived control to effectiveness of coping strategies.

A sample of 187 medical center nurses described 2 stressful occupational episodes varying in perceived controllability and provided information regarding the coping strategies used. Outcome measures assessed effectiveness of coping across 3 dimensions: perceived coping effectiveness, job affect, and psychological adjustment. Negative affectivity was measured to control for its tendency to inflate stress-adjustment relationships. Use of problem-solving strategies was related to perceived coping effectiveness only for high-control episodes. However, differential use of coping across levels of controllability was not related to job affect or psychological adjustment. Avoidant coping was strongly associated with negative affect at work. In contrast, problem-reappraisal and problem-solving strategies were related to positive affect at work. Implications for theory and practice are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Microlesions of the ventromedial nucleus of the hypothalamus: Effects on sociosexual behaviors in male rats.

Electrolytic microlesions aimed at the dorsomedial portion of the ventromedial nucleus (VMN) of the hypothalamus were generated, and effects on copulation, 50-kHz vocalizations, scent marking, and sexual motivation were measured. Male rats were tested before and after lesions, after castration, and after testosterone replacement. Three control groups were used: One received sham surgery, another received no surgery or testosterone replacement, and a 3rd received lesions primarily outside the VMN. VMN lesions produced impairments in testosterone's ability to restore ultrasonic vocalizations and scent marking, assessed with 2 different test methods. Copulation, sexual motivation, and weight gain were largely unaffected, although some differences were observed in copulatory efficiency. The authors conclude that the integrity of the VMN is important for full expression of sociosexual behaviors in male rats. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dielectrc Polarization of Animal Lung at Radio Frequencies

Dielectric properties of the inflated and deflated fceline lung in vivo were investigated at frequencies from 10 kHz to 100 MHz. A computer-controlled network analyzer and a multiring capacitive sensor were employed. It was found that in the frequency range investigated, both the dielectric constant and the conductivity of the deflated lung were higher than those of the inflated one. The analysis of the experimental data was performed using two approaches: the loss-tangent method and the curve-fitting computer program called STEPIT. It was found that in the middle band of frequencies for both inflated and deflated states of the lung, the dielectric response mainly reflects the membrane polarization of the capillary erythrocytes with possible contributions of other components, e.g., the pulmonary microphages. The dielectric relaxation time for the capillary erythrocytes in the lung is similar to that for the packed cells, which is much longer than for the erythrocytes at physiological concentrations. The dielectric parameters at low frequencies obtained using the STEPIT program differ significantly between the inflated and deflated lung. The observed dielectric data reflect at least two overlapping dispersions: of lung capillary erythrocytes and of cellular structures forming the alveoli.