990 resultados para 149-897A


Relevância:

10.00% 10.00%

Publicador:

Resumo:

庆贺林同骅教授八十寿辰:汇集了国内塑性力学和细观力学两个领域内的一些学者和专家撰写的20余篇学术论文。

目录

・塑性力学部分・积分型理论中的内时和后继屈服面&匡震邦

单晶体弹塑性变形的Lagrange描述&黄筑平

一个三维弹粘塑性本构模型&徐 桢 梁乃刚

蠕变-塑性交互作用的微观机理及其一维本构模型&钱正芳 段祝平 范镜泓

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The status of the Gulf menhaden, Brevoortia patronus, fishery was assessed with purse-seine landings data from 1946 to 1997 and port sampling data from 1964 to 1997. These data were analyzed to determine growth rates, biological reference points for fi shing mortality from yield per recruit and maximum spawning potential analyses, spawner-recruit relationships, and maximum sustainable yield (MSY). The separable virtual population approach was used for the period 1976–97 (augmented by earlier analyses for 1964–75) to obtain point estimates of stock size, recruits to age 1, spawning stock size, and fishing mortality rates. Exploitation rates for age-1 fi sh ranged between 11% and 45%, for age-2 fi sh between 32% and 72%, and for age-3 fi sh between 32% and 76%. Biological reference points from yield per recruit (F0.1: 1.5–2.5/yr) and spawning potential ratio (F20: 1.3–1.9/yr and F30: 0.8–1.2/yr) were obtained for comparison with recent estimates of F (0.6–0.8/yr). Recent spawning stock estimates (as biomass or eggs) are above the long-term average, while recent recruits to age 1 are comparable to the long-term average. Parameters from Ricker-type spawner-recruit relations were estimated, although considerable unexplained variability remained. Recent survival to age-1 recruitment has generally been below that expected based on the Ricker spawner-recruit relation. Estimates of long-term MSY from PRODFIT and ASPIC estimation of production model ranged between 717,000 t and 753,000 t, respectively. Declines in landings between 1988 and 1992 raised concerns about the status of the Gulf menhaden stock. Landings have fl uctuated without trend since 1992, averaging about 571,000 t. However, Gulf menhaden are short lived and highly fecund. Thus, variation in recruitment to age 1, largely mediated by environmental conditions, infl uences fi shing success over the next two years (as age-1 and age-2 fi sh). Comparisons of recent estimates of fi shing mortality to biological reference points do not suggest overfishing. (PDF file contains 22 pages.)

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Sets and catches of Atlantic menhaden, Brevoortia tyrannus, made in 1985-96 by purse-seine vessels from Virginia and North Carolina were studied by digitizing and analyzing Captain's Daily Fishing Reports (CDFR's), daily logs of fishing activities completed by captains of menhaden vessels. 33,674 CDFR's were processed, representing 125,858 purse-seine sets. On average, the fleet made 10,488 sets annually. Virginia vessels made at least one purse-seine set on 67%-83% of available fishing days between May and December. In most years, five was the median number of sets attempted each fishing day. Mean set duration ranged from 34 to 43 minutes, and median catch per set ranged from 15 to 30 metric tons (t). Spotter aircraft assisted in over 83% of sets overall. Average annual catch in Chesapeake Bay (149,500 t) surpassed all other fishing areas, and accounted for 52% of the fleet's catch. Annual catch from North Carolina waters (49,100 t) ranked a distant second. Fishing activity in ocean waters clustered off the Mid-Atlantic states in June-September, and off North Carolina in November-January. Delaware Bay and the New Jersey coast were important alternate fishing grounds during summer. Across all ocean fishing areas, most sets and catch occurred within 3 mi. of shore, but in Chesapeake Bay about half of all fishing activity occurred farther offshore. In Virginia, areas adjacent to fish factories tended to be heavily fished. Recent regulatory initiatives in various coastal states threaten the Atlantic menhaden fleet's access to traditional nearshore fishing grounds. (PDF file contains 26 pages.)

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Enpresa bateko tekniko informatikoak bi motako lanak egiten ditu enpresa batean: langileek beren ordenagailuetan dituzten arazoak konpondu eta enpresako web orria kudeatu. Langillek planteatzen dituzten arazoen kopurua Poisson-en banakuntzaren araberakoa da, batazbestekoa 4 izanik. Hala ere, teknikoak k muga ezartzen du konpontzen dituen arazoetarako, web orriak gutxieneko denbora bat behar duelako.

Relevância:

10.00% 10.00%

Publicador:

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Overexpression of the mammalian homolog of the unc-18 gene (munc18-1) has been described in the brain of subjects with schizophrenia. Munc18-1 protein is involved in membrane fusion processes, exocytosis and neurotransmitter release. A transgenic mouse strain that overexpresses the protein isoform munc18-1a in the brain was characterized. This animal displays several schizophrenia-related behaviors, supersensitivity to hallucinogenic drugs and deficits in prepulse inhibition that reverse after antipsychotic treatment. Relevant brain areas (that is, cortex and striatum) exhibit reduced expression of dopamine D-1 receptors and dopamine transporters together with enhanced amphetamine-induced in vivo dopamine release. Magnetic resonance imaging demonstrates decreased gray matter volume in the transgenic animal. In conclusion, the mouse overexpressing brain munc18-1a represents a new valid animal model that resembles functional and structural abnormalities in patients with schizophrenia.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Monografia (especialização) – Curso de Parlamento e Direito, Câmara dos Deputados, Centro de Formação, Treinamento e Aperfeiçoamento (Cefor), 2015