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Levi McNeil,Heshim Song 한국외국어교육학회 2016 Foreign languages education Vol.23 No.2
This study investigated peer-to-peer interaction during collaborative, computer-mediated reading tasks. Fourteen university EFL students in Korea worked in pairs to complete three gapfill tasks. The transcript data from these tasks were analyzed to determine: (1) how often collaboration occurs during collaborative reading tasks, (2) the ways in which peers help each other, and (3) how successful peers are in resolving the problems they collaboratively pursue. The results showed that each of these aspects of interaction varied among sets of pairs. On average, however, the participants collaborated to jointly solve 75% of the problems they encountered. They also used a range of helping behaviors during collaboration. While the participants correctly resolved nearly half of the problems they attempted, half were incorrectly answered or unresolved. Based on these findings, pedagogical implications are offered, in addition to suggestions for future research into collaborative reading tasks.
Levi, F.,Shirley, J.H.,Heavner, T.P.,Yu, Dai-Hyuk,Jefferts, S.R. IEEE 2006 and Frequency Control Vol.53 No.9
The presence of spurious spectral components in the microwave excitation may induce frequency shifts in an atomic fountain frequency standard. We discuss how such shifts behave as a function of power variations of the excitation carrier and in the spur-to-carrier ratio. The discussion here is limited to the case of single-sideband spurs, which are generally much more troublesome due to their ability to cause frequency shifts. We find an extremely rich and unintuitive behavior of these frequency shifts. We also discuss how pulsed operation, typical of today's fountain frequency standards, relates to frequency shifts caused by spurs in the microwave spectrum. The conclusion of these investigations is that it is, at best, difficult to use elevated power microwaves in fountain frequency standards to test for the presence of spurs in the microwave spectrum.
Levy, Richard H.,Dunbar, Gavin B.,Vandergoes, Marcus J.,Howarth, Jamie D.,Kingan, Tony,Pyne, Alex R.,Brotherston, Grant,Clarke, Michael,Dagg, Bob,Hill, Matthew,Kenton, Evan,Little, Steve,Mandeno, Darc Copernicus GmbH 2018 Scientific drilling Vol.24 No.-
<P><p><strong>Abstract.</strong> A new annually resolved sedimentary record of Southern Hemisphere mid-latitude hydroclimate was recovered from Lake Ohau, South Island, New Zealand, in March 2016. The Lake Ohau Climate History (LOCH) project acquired cores from two sites (LOCH-1 and -2) that preserve sequences of laminated mud that accumulated since the lake formed <span class='inline-formula'>∼</span><span class='thinspace'></span>17<span class='thinspace'></span>000 years ago. Cores were recovered using a purpose-built barge and drilling system designed to recover soft sediment from thick sedimentary sequences in lake systems up to 150<span class='thinspace'></span>m deep. This system can be transported in two to three 40<span class='thinspace'></span>ft long shipping containers and is suitable for use in a range of geographic locations. A comprehensive suite of data has been collected from the sedimentary sequence using state-of-the-art analytical equipment and techniques. These new observations of past environmental variability augment the historical instrumental record and are currently being integrated with regional climate and hydrological modelling studies to explore causes of variability in extreme/flood events over the past several millennia.</p> </P>
Rayleigh-Ritz optimal design of orthotropic plates for buckling
Levy, Robert Techno-Press 1996 Structural Engineering and Mechanics, An Int'l Jou Vol.4 No.5
This paper is concerned with the structural optimization problem of maximizing the compressive buckling load of orthotropic rectangular plates for a given volume of material. The optimality condition is first derived via variational calculus. It states that the thickness distribution is proportional to the strain energy density contrary to popular claims of constant strain energy density at the optimum. An engineers physical meaning of the optimality condition would be to make the average strain energy density with respect to the depth a constant. A double cosine thickness varying plate and a double sine thickness varying plate are then fine tuned in a one parameter optimization using the Rayleigh-Ritz method of analysis. Results for simply supported square plates indicate an increase of 89% in capacity for an orthotropic plate having 100% of its fibers in $0^{\circ}$ direction.
Thermal Characterization of Alkali Treated Kenaf Fibers and Kenaf-Epoxy Composites
Levi Gardner,Troy Munro,Ezekiel Villarreal,Kurt Harris,Thomas Fronk,Heng Ban 한국섬유공학회 2018 Fibers and polymers Vol.19 No.2
Chemical treatment of natural fibers is a well-defined means of mechanical property improvement in natural fiberreinforced composites. An understanding of mechanical and thermal properties in these media is essential for evaluating heat transfer, thermal degradation, and overall performance of these composites over their product lifetime. However, very little information is available illustrating the effect of such treatment on the thermal properties of kenaf composites. Also, no study to date has reported the thermal conductivity of individual kenaf fibers. This study reports the effects of fiber treatment (in 6 % NaOH) on thermal transport in unidirectionally oriented kenaf-epoxy composites and individual kenaf fibers. The effective thermal conductivities and thermal diffusivities of chemically treated fiber composites show a general increase over untreated fiber composites (0.210 to 0.232 W/m/K at 28 ℃, 0.206 to 0.234 W/m/K at 200 ℃). This improvement may be attributed to improved interfacial contact between the fibers and epoxy matrix shown in microstructural images after chemical treatment. The thermal conductivity of individual fibers was evaluated at room temperature using two techniques. Results from both techniques showed slight increases after chemical treatment (0.58±0.53 to 1.0±0.13 W/m/K and 1.2±0.54 to 1.6±0.28 W/m/K) but lacked statistical significance. Any improvement in surface crystallinity after chemical treatmentdoes not appear to affect overall fiber thermal conductivity. A better understanding of thermal transport in kenaf fibers and composites enables better estimation of the performance of these composites in different applications. Moreover, the thermal conductivities of individual fibers are useful in understanding the fiber’s contribution to conduction in different fiber reinforcement configurations.
Mixed Adenoneuroendocrine Gastric Carcinoma: A Case Report and Review of the Literature
Levi Sandri, Giovanni Battista,Carboni, Fabio,Valle, Mario,Visca, Paolo,Garofalo, Alfredo The Korean Gastric Cancer Association 2014 Journal of gastric cancer Vol.14 No.1
We present a rare case of a gastric mixed adenoneuroendocrine tumor and review the related English literature. A 77-year-old Caucasian woman was admitted to our department with nausea, anorexia, weight loss, and anemia. Esophagogastroduodenoscopy showed a large (>7 cm) ulcerative mass in the greater curvature of the stomach. Biopsy showed the presence of an adenocarcinoma with moderate differentiation. The patient underwent D2 subtotal gastrectomy. Histopathological analysis revealed a diagnosis of mixed gastric adenoneuroendocrine carcinoma. The post-operative course was uneventful, and at the 6-month follow-up, the patient was alive without evidence of recurrence. Our review of the English literature suggested that such cases are most often reported from eastern countries. Multimodal treatment should be the aim for these patients because of the neuroendocrine component of the tumor.