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21.
This paper analyses the thermal moist characteristics of the hull layer beside an air layer at lower temperature in an envelope for a cold storage and presents a new method of waterproof by air layer. With test data from engineering practice, the theory on the barrier of self moisture proof at the surface sublayer of the hull layer in an attic on a cold storage is proven. The dried zone about three phase point is confirmed. It is a new knowledge for thermophysics on thermal design of a cold storage with an optimum thermal performance.  相似文献   
22.
海湾及潮汐河口的冷却水工程研究近年来受到人们的重视,由于受到潮汐的影响,其冷却水布置及热污染特性比河道及水库型更为复杂。采用数值模拟的方法,首先对电厂附近的潮流特性及冷却水输移扩散进行模拟计算,研究了电厂近海水域的水动力结构及其对冷却水排放的影响,给出电厂取水温升及热污染范围,为电厂取水设计工作提供依据。  相似文献   
23.
浇筑温度对碾压混凝土重力坝温度应力的影响   总被引:3,自引:0,他引:3  
采用三维有限元浮动网格法模拟碾压混凝土重力坝薄层施工过程,对百色碾压混凝土重力坝施工期和运行期的温度场、温度徐变应力场进行了全过程仿真计算,分析了按旬平均气温浇筑和设计浇筑温度浇筑两种不同浇筑温度对坝体温度应力分布的影响.  相似文献   
24.
25.
温度对微小花蝽实验种群增长的影响   总被引:2,自引:0,他引:2  
实验室饲养观察结果表明,在15-35℃温度范围内,随温度升高,微小花蝽的发育速率加快,成虫寿命缩短,在25℃下的世代存活率最高。根据实验数据计算出该虫的卵期发育起点温度为13.6℃,有效积温为1=55.15日.度;若虫期发育起点温度为8.0℃,有效积温为270.1日.度。组建了25℃和30℃两种温度下的该虫的实验种群生命表。  相似文献   
26.
Atlantic salmon become thermally stressed when water temperatures exceed 23 °C. To alleviate this stress, they behaviourally thermoregulate by moving to patches of cold water, often forming large aggregations. These patches are known as thermal refuges. Given the consensus that climate change will increase temperatures in Atlantic salmon catchments, thermal refuges will become increasingly important in minimising summer mortalities. While the behaviour of salmonids within thermal refuges is fairly well understood, less is known about their main stem movement in search of thermal refuges or its thermal and temporal cues. We detail the results of a PIT telemetry study to investigate the main stem movement behaviour of thermally stressed Atlantic salmon parr in a temperature‐impacted river. PIT antennas placed around two thermal refuges and at the upstream and downstream limits of their surrounding reach were used to record the movement of salmonids during a heatwave. We observed parr movement at the upstream and downstream antennas 135 min prior to the occurrence of the midpoint of aggregations in the thermal refuges, indicating that Atlantic salmon parr make reach‐scale movements in search of cool water prior to aggregating. Logistic regression showed that the number of degree hours >28 °C predicted the occurrence of main stem movement with a good degree of accuracy, indicating that this temperature represents a fundamental threshold causing Atlantic salmon parr to move towards cool water. Such data could be instrumental in allowing river managers to place limits on human activity within rivers, allowing salmon populations time to recover following heat stress events.  相似文献   
27.
Based on the sequence of a novel expressed sequence tag (EST), the full-length cDNA of 1 017 nucleotides was cloned from Brassica napus cv. Xiangyou 15 through rapid amplification of cDNA ends (RACE). The gene was designated as Bnhol34 (HQ585980), encoding a protein of 338 amino acids. BLAST analysis showed no high degree of sequence identity to any known gene. The calculated molecular weight of the Bnhol34 protein was 36.23 kDa, and the theoretical isoelectric point was 8.74. The Bnhol34 was also cloned from a high oleic acid mutant 854-1 through homologous cloning. There was no difference between the two Bnhol34 genes. Bnhol34 was localized in a tissue-specific manner in B. napus, and its expression level was about eight-fold greater in Xiangyou 15 seeds than in 854-1. The promoter region sequences of Bnhol34 were then isolated from Xiangyou 15 and 854-1, and a 93-bp deletion was found to occur in the Bnhol34 promoter region of 854-1. Three abscisic acid-responsive cis-elements (ABRE) were identified in the promoter region of Xiangyou 15. Real-time PCR analyses revealed that exogenous abscisic acid increased Bnhol34 expression by about four-fold in Xiangyou 15 seeds, yet did not change Bnhol34 expression in 854-1. It appeared that Bnhol34 might be abscisic acid insensitive in 854-1.  相似文献   
28.
Abstract – The persistent effects of embryonic temperature stress and individual parentage on fry swimming performance were examined in a cross‐fertilisation experiment using sockeye salmon (Oncorhynchus nerka). A fixed‐velocity test of burst swimming was used to assess the endurance capacity and behavioural performance of individual fry from 10 offspring families incubated at 12, 14 or 16 °C to hatch and then reared through yolk absorption and exogenous feeding stages in a common posthatch environment (average 6.9 °C). Fry burst swim time (BST) was influenced by an interaction between incubation temperature and family identity. Average BST was longer for fry from the 12 °C prehatch treatment compared to 14 and 16 °C, although differences were largely attributable to temperature effects on average fry size. Behavioural observations revealed that fish incubated at 16 °C performed more poorly, having a larger proportion of individuals that required stimulation to swim, fatigued more frequently or were classified as ‘nonswimmers’. Within all three incubation temperature treatments, mean BST varied significantly among offspring families, independent of fry mass and length. An interesting relationship was observed within the 16 °C treatment, whereby families with higher survivorship were characterised with lower mean BSTs. Collectively, these findings demonstrate that exposure to high temperatures in early sockeye salmon development can result in persistent, parentally mediated effects on fry performance. As such, these results provide important insight into how elevated temperature events during egg incubation may affect early life history selection processes and survival in stages beyond when the stressor is experienced.  相似文献   
29.
In order to study forest fragmentation in the Virginia, USA Piedmont, a series of Landsat images from 1973, 1987, and 1999 covering a rapidly developing area (Loudoun County) was used to classify forest from non-forest. The classified images were analyzed using a geographic information system (GIS) to determine the spatial and temporal patterns of fragmentation, and to relate these patterns to infrared radiance provided by Landsat Enhanced Thematic Mapper Plus (ETM+) band 6. The analysis was concentrated on eleven major watersheds of Loudoun County. The relationship between urbanized area per watershed and mean fragment size showed a strong negative decay form (r 2=0.757, p<0.0001). Analysis of four landscape metrics showed increasing fragmentation of forest cover, particularly from 1987 to 1999, as well as an increase in forest edge and shape complexity. Of the landscape metrics used, the perimeter-to-area (P/A) ratio showed the strongest relationship with mean radiance of forest patches. In addition, there was a negative, linear relationship between distance from major roads and band 6 radiance of forested pixels. Overall, the study shows that landscape metrics can convey meaningful information on biophysical changes associated with forest fragmentation at broad scales. These changes suggest that ambient temperature increases associated with urban sprawl may have important, long-term implications for ecophysiological processes.  相似文献   
30.
在玉米光热生产潜力的基础上,进一步讨论沈阳地区水分对玉米生产潜力发挥的限制作用,结果表明:水分的限制率为18.5%,使玉米经济产量降低395.01kg/mu。  相似文献   
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