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排序方式: 共有672条查询结果,搜索用时 18 毫秒
41.
提出能够鉴别损伤位置和截面损伤严重程度的钢框架非比例破坏监测方法。所提出的方法由两部分组成,一是损伤识别,二是损伤严重程度分析。损伤识别和严重程度分析均以结构动力性质的变化作为损伤的判据,以此来确定损伤位置和严重程度。所提方法中损伤判别的重要特点是能够在损伤严重程度分析之前,精确地区分不同的损伤区域。与整个结构尺寸相比,损伤区域相对较小,因此,确定损伤严重程度的计算量更小。检测方法的另一个特点是有些特征值或振型对噪声相对不敏感。采用所提检测方法对几个框架进行验证,结果表明,该方法能够成功地检测及量化截面的损伤。 相似文献
42.
大蒜精油对食用油脂的抗氧化特性 总被引:35,自引:3,他引:35
以过氧化值(POV)为指标研究了大蒜精油对花生油的抗氧化性能。结果表明:大蒜精油对花生油具有较强的抗氧化作用,且具有剂量效应关系;添加了大蒜精油的花生油应尽量贮存于低温条件下;VC、柠檬酸、酒石酸对大蒜精油的抗氧化作用均有协同增效作用;大蒜精油与合成抗氧化剂混合使用时,其抗氧化能力均好于只添加单一抗氧化剂的效果;使用0.2%大蒜精油和0.04%大蒜精油+0.005%PG为花生油的抗氧化剂时,可使花生油在20℃下的贷架寿命由4.2个月延长至24.3个月和14.1个月。 相似文献
43.
J. Ross Beveridge Geof H. Givens P. Jonathon Phillips Bruce A. Draper David S. Bolme Yui Man Lui 《Image and vision computing》2010
A study is presented showing how three state-of-the-art algorithms from the Face Recognition Vendor Test 2006 (FRVT 2006) are effected by factors related to face images and people. The recognition scenario compares highly controlled images to images taken of people as they stand before a camera in settings such as hallways and outdoors in front of buildings. A Generalized Linear Mixed Model (GLMM) is used to estimate the probability an algorithm successfully verifies a person conditioned upon the factors included in the study. The factors associated with people are: Gender, Race, Age and whether they wear Glasses. The factors associated with images are: the size of the face, edge density and region density. The setting, indoors versus outdoors, is also a factor. Edge density can change the estimated probability of verification dramatically, for example from about 0.15 to 0.85. However, this effect is not consistent across algorithm or setting. This finding shows that simple measurable factors are capable of characterizing face quality; however, these factors typically interact with both algorithm and setting. 相似文献
44.
Hot-rolled Al–3Mg alloy processed by various cold-rolled reductions exhibited excellent vibration fracture resistance, however subsequent friction stirring did not endow better vibration fracture resistance than cold-rolled samples in spite of possessing microstructural refinement and homogenization. The D–N curve under a constant initial deflection amplitude (6.5 mm) also showed that the vibration fracture resistance of cold-rolled specimens increased as a result of the slower crack propagation rate. All samples used in this investigation showed a work hardening feature from the initial stage of the D–N curve, and the deflection amplitude tended to increase as the number of vibration cycles increased. During this ascending stage, slip band cracking and strain hardening in the vicinity of the main crack could be recognized. The D–N curve feature of the cold-rolled samples depicted a longer plateau region while the deflection amplitude was at its maximum. It is suggested that the dislocation tangles introduced by cold rolling can strengthen the matrix. As a result, the deflection amplitude drops could be associated with increasing the dislocation tangles due to prior cold rolling while the main crack achieved a critical crack length. 相似文献
45.
冰淇淋生产中老化条件的确定 总被引:6,自引:0,他引:6
冰淇淋生产中老化条件的确定是冰淇淋质量好坏的重要因素之一。根据冰淇淋的实际生产配方、加工工艺与条件,测定料液在老化时粘度的增长情况。通过凝冻操作鉴定冰淇淋质量,最终确定料液所需老化时间。 相似文献
46.
47.
Epidemiological research during the past 40 years has demonstrated with increasing clarity that amphibole asbestos fibres--crocidolite, amosite and tremolite--are more carcinogenic than chrysotile. A smaller number of well-controlled studies using lung burden analyses, while adding to the specificity of this conclusion, have shown that amphibole fibres also differ from chrysotile in being far more durable and biopersistent in lung tissue. Analyses of mesothelioma and lung cancer in a large cohort of Canadian chrysotile miners and millers have recently shown that the low-level presence of fibrous tremolite in these mines, rather than the chrysotile, may well be responsible. The high risk of lung cancer, but not of mesothelioma, in the chrysotile textile industry remains anomalous and cannot be explained in this way. These various findings are directly relevant to the choice of the experimental methods which should be used for screening man-made fibres for industrial use. Although it is clear that biopersistence is a major determinant of cancer risk in animals, and perhaps also in man, other factors affecting the biological activity of mineral fibres may also be important. 相似文献
48.
49.
A frequency notched ultra-wideband (UWB) microstrip slot antenna with a fractal tuning stub is proposed. The antenna is similar to a conventional microstrip slot antenna, and by introducing a fractal tuning stub, frequency notched function is achieved. The antenna was studied experimentally regarding impedance bandwidth, radiation patterns and gain. The operation bandwidth of the antenna is from 2.66 to 10.76 GHz, in which a frequency notched band from 4.95 to 5.85 GHz was achieved, along with good radiation performance over the entire frequency range. 相似文献
50.
KJ Lui 《Canadian Metallurgical Quarterly》1997,16(15):1777-1786
When data are dichotomous, this paper notes the utility of inverse sampling in establishing equivalence with respect to the risk ratio. This paper develops an exact equivalence test that accounts for the risk ratio under inverse sampling and further discusses the relationship between the exact equivalence test and the exact conditional confidence limits. Also included are an exact and two asymptotic procedures for calculation of the minimum required number of index subjects for a desired power 1--beta at a given alpha-level. Finally, this paper provides a table that summarizes the minimum required number of index subjects for powers equal to 0.90 and 0.80 in application of the proposed exact equivalence test at 0.05-level in a variety of situations. 相似文献