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排序方式: 共有7833条查询结果,搜索用时 125 毫秒
1.
Multimedia Systems - The preferences of Web information purchasers are changing. Cost-effectiveness (i.e., an emphasis on performance with respect to price) is becoming less regarded than... 相似文献
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AbstractBuilding thermal inertia and operation control strategies have impacted on the thermal performance of a radiant floor heating system. This study conducts a two-dimensional numerical analysis of an intermittently operated radiant floor heating system using the Re-Normalization Group model with Discrete Ordinates Radiation model. A detailed numerical simulation setups and various analyses are provided, including grid independency analysis, initial condition, time step sizes and external boundary conditions. Three different weekend day intermittent operation strategies are investigated. The results showed that Case 3 designed with pre-heating of 20?h has better performance compared to Case 1 designed with pre-heating of 8?h and Case 2 designed with pre-heating of 14?h. The average indoor air temperature differences of approximate 2.1, 1.6 and 1.2 K are observed for Case 1, Case 2 and Case 3, respectively, when comparing two-time slot at 8:00am on Friday morning and Monday morning. This significantly highlights the effect of thermal inertia and the potential of energy saving due to the utilization of intermittent operation. Therefore, the current study presents numerical simulation potential in evaluating the radiant floor heating effects on indoor thermal environment, taking into account building thermal inertia and transient external climatic conditions. 相似文献
4.
Park Sangwon Nam Hyunbin Na Youngsang Kim Hyoungseop Moon Younghoon Kang Namhyun 《Metals and Materials International》2020,26(5):641-649
Metals and Materials International - This study investigated the influence of the initial grain size on the plastic deformation and tunnel defects that occurred from friction stir welding of... 相似文献
5.
Kee S. Moon M. Levy Yong K. Hong H. Bakhru S. Bakhru 《Ferroelectrics Letters Section》2003,30(3):47-57
Advances in the fabrication of solid-solution single crystal relaxor ferroelectrics have made it possible to produce highly efficient piezoelectric crystals, and have attracted renewed interest in the use of these crystals for a new generation of piezoelectric transducers, actuators and sensors. Of particular interest is their incorporation into micro-electromechanical systems (MEMS). In this paper we report on the laser-induced wet chemical etching of lead zinc niobate-lead titanate (PZN-PT) in hydrochloric acid (HCl). Argon-ion laser radiation at power levels up to 4 W is focused to a spot diameter of about 15μm and results in the chemical etching of grooves at patterning speeds up to 5μm/sec. Crystal ion slicing, an ion-implant-based film separation technique, is used in combination with laser etching to form 5 to 10μm-thick patterned and freestanding films for incorporation into micro-electromechanical devices. 相似文献
6.
The aim of this study was to assess the association between the length of maternity leave and the quality of mother-infant interactions; 198 employed mothers of 4-month-old infants were interviewed and videotaped in their homes during a feeding time. Hierarchical multiple regression analyses indicated a direct association between shorter length of leave and more negative affect and behavior in maternal interactions with their infants. Infant and mother stressor/protective variables added significantly in predicting the quality of the mother-infant relationship. There were also significant interaction effects between the length of leave and these variables. Mothers who either reported more depressive symptoms or who perceived their infant as having a more difficult temperament and who had shorter leaves, compared with mothers who had longer leaves, were observed to express less positive affect, sensitivity, and responsiveness in interactions with their infants. The public policy implications of the relation between length of maternity leave, maternal and infant individual differences, and the quality of mother-infant interactions are discussed. 相似文献
7.
Lead content of rice collected from various areas in the world 总被引:1,自引:0,他引:1
ZW Zhang CS Moon T Watanabe S Shimbo M Ikeda 《Canadian Metallurgical Quarterly》1996,191(1-2):169-175
Rice samples consumed by local populations were collected between 1990 and 1995 in 17 areas in the world, mostly from Asia (10 areas), but also from 7 areas outside of Asia. In total, 1528 samples were obtained (about one half from Japan) and were analyzed for lead (Pb) by electrothermal atomic absorption spectrometry. When the Pb contents in rice samples were classified into 10 areas in Asia, the highest and the lowest geometric means (GMs) were for Indonesia (38 ng/g) and Australia (2 ng/g), respectively. Among 7 regions outside Asia, the GM was highest for Spain (58 ng/g) and the lowest for the USA. (3 ng/g). Moreover, inter-regional differences were significant, when more than 100 samples from one area were divided into 3-9 regions and GMs for regions were compared. There was a marked difference in Pb contents in rice by areas and regions in the world. Nevertheless, comparison by area of the present results with those reported in literature show that there has been no substantial reduction in Pb in rice in the past decade either in Japan or elsewhere in the world. 相似文献
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S Mahanty CL King V Kumaraswami J Regunathan A Maya K Jayaraman JS Abrams EA Ottesen TB Nutman 《Canadian Metallurgical Quarterly》1993,151(7):3704-3711
Helminth infections in humans and animals are associated with strong T helper 2 (Th2) responses. To determine whether parasite-derived Ag preferentially expand a Th2-like cell population, a filter immunoplaque assay was used to enumerate the frequencies (F0) of PBMC and CD4(+)-enriched PBMC from individuals with helminth infections secreting selected cytokines in response to parasite-derived (PAg) and nonparasite antigens (NPAg). In 20 individuals with lymphatic filariasis, frequency analysis of PBMC secreting IL-4 and IFN-gamma indicated that the F0 of PAg-specific IL-4-secreting cells (geometric mean F0 (GM): 1/12,100) was 57-fold higher than the corresponding F0 of NPAg-reactive cells (GM: 1/692,000; p < 0.02). In marked contrast, the F0 of IFN-gamma-secreting cells responding to PAg (GM: 1/2,700) did not differ from those of cells specific for NAPg (GM: 1/3,400; p = 0.83). In another group of helminth-infected individuals, the F0 of highly enriched CD4+ cells secreting IL-4 and IL-5 in response to PAg (GMs: 1/2,600 and 1/5,600 CD4+ cells, respectively) were also found to be significantly higher than those specific for NPAg (GMs: 1/291,000 and 1/303,000 CD4+; p < 0.05 and p < 0.01, respectively), whereas the corresponding F0 of IFN-gamma- and granulocyte-macrophage-CSF-secreting cells were equivalent for PAg and NPag. Furthermore, the proportion of PAg-specific IL-4- and IL-5-secreting CD4+ cells relative to all cells secreting the given cytokine were approximately 29-fold higher than the proportion of NPAg-specific cells secreting these cytokines. Again, the corresponding proportions of Ag-specific IFN-gamma-and GM-CSF-secreting CD4+ cells were equivalent for PAg and NPAg. Thus, in this ex vivo system, a circulating population of IL-4- and IL-5-secreting (Th2-like) cells has been shown to exist in humans; PAg appears to expand these cells preferentially. 相似文献
10.
A Meneghetti WV Cardoso JS Brody MC Williams 《Canadian Metallurgical Quarterly》1996,44(10):1173-1182
Explants of embryonic lung are often used to characterize lung growth, bronchial tree pattern, and cell differentiation. Most investigators culture lungs for 3-7 days in defined media lacking, e.g., added growth factors or hormones. If growth and differentiation are comparable to that in vivo, these cultures show considerable promise for identifying developmental regulatory molecules and target genes, and for elucidating molecular responses. We used in situ hybridization and RT-PCR to compare times and sites of expression of mRNAs of six epithelial genes in cultured and uncultured fetal rat lungs. These genes, expressed in distal lung of adult rats, are surfactant proteins (SP) A, B, and C; LAR, a receptor-type tyrosine phosphatase; Clara cell secretory protein (CC10, CCSP); and T1alpha. SP-A, SF-B, LAR, and CC10 are expressed by both Clara and Type II cells in adult animals. SP-C and T1alpha are unique markers for Type II and Type I cells, respectively. SP-C, LAR, and T1alpha are expressed before the lung is explanted (Day 13.5); SP-A, -B, and CC10 mRNAs are first detected later. The onset of expression is similar in vivo and in vitro. Although the patterns of expression differ for each mRNA, their sites of expression in culture match those in vivo relative to the bronchial tree. The explanted embryonic lung appears to be an excellent experimental model. 相似文献