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941.
Al-Li alloys being developed as lighter, substitutes for conventional high strength Al alloys are to be processed by routine
methods. During extrusion of a 8090 Al-Li alloy, the extrusion die container failed causing some alarm. This failed die container
was analysed to examine if the failure was caused by interaction of Li diffusing out of Al-Li alloy with the carbides of die
steel. The evidence, although not conclusive, is sufficient to exercise caution during such processing. 相似文献
942.
943.
944.
945.
946.
Agnesi A. Dell'Acqua S. Piccinini E. Reali G. Piccinno G. 《Quantum Electronics, IEEE Journal of》1998,34(8):1480-1484
Powerful CW diode-pumped Nd:YAG and Nd:YVO4 lasers Q-switched by Cr:YAG saturable absorbers demonstrate efficient (30%-60%) harmonic and parametric conversion, generating hundreds of milliwatts from ultraviolet to mid-infrared 相似文献
947.
Prediction error method for second-order blind identification 总被引:7,自引:0,他引:7
Blind channel identification methods based on the oversampled channel output are a problem of current theoretical and practical interest. In this paper, we introduce a second-order blind identification technique based on a linear prediction approach. In contrast to eigenstructure-based methods, it will be shown that the linear prediction error method is “robust” to order overdetermination. An asymptotic performance analysis of the proposed estimation method is carried out, consistency and asymptotic normality of the estimates is established. A closed-form expression for the asymptotic covariance of the estimates is given. Numerical simulations and investigations are finally presented to demonstrate the potential and the “robustness” of the proposed method 相似文献
948.
K Bj?ro JP Blomhoff E Schrumpf F Brosstad A Bergan T Egge 《Canadian Metallurgical Quarterly》1997,117(9):1274-1276
Budd Chiari syndrome (liver vein thrombosis) may be a diagnostic and therapeutic problem. On the basis of four different cases we review the major diagnostic and therapeutic principles involved. Imaging techniques are necessary in order to establish the diagnosis. Ultrasound examination with Duplex doppler is usually sufficient, but MR angiography is also useful. Treatment options are thrombolysis, surgery or liver transplantation. What treatment is selected will depend on the clinical situation and the prognosis. 相似文献
949.
M Pan J Suárez de Lezo A Medina M Romero E Hernández J Segura F Melian F Wangüemert M Landin F Benítez M Amat F Velasco A Torres 《Canadian Metallurgical Quarterly》1997,80(10):1336-1338
Two hundred twenty-eight patients with successful coronary stent implantation were randomized either to protamine administration and femoral sheath removal (group I, n = 117) or no heparin neutralization and delayed sheath removal (group II, n = 111). The hospital stay after treatment was shorter in patients receiving protamine; therefore, protamine use for neutralizing circulating heparin may be safely administered immediately after stent implantation. 相似文献
950.
SW D'Souza E Rivlin J Cadman B Richards P Buck BA Lieberman 《Canadian Metallurgical Quarterly》1997,76(2):F70-F74
AIMS: To compare the outcome in in vitro fertilisation (IVF) children (after fresh embryo transfer) from multiple and singleton births with one another, and with normally conceived control children. METHODS: A cohort of 278 children (150 singletons, 100 twins, 24 triplets and four quadruplets), conceived by IVF after three fresh embryos had been transferred, born between October 1984 and December 1991, and 278 normally conceived control children (all singletons), were followed up for four years after birth. They were assessed for neonatal conditions, minor congenital anomalies, major congenital malformations, cerebral palsy and other disabilities. Control children, all born at term, were matched for age, sex and social class. RESULTS: The ratio of male:female births was 1.03. Forty six per cent of IVF children were from multiple births; 34.9% were from preterm deliveries; and 43.2% weighed less than 2500 g at birth. The IVF singletons were on average born one week earlier than the controls, weighed 400 g less, and had a threefold greater chance of being born by caesarean section. The higher percentage of preterm deliveries was largely due to multiple births and they contributed to neonatal conditions in 45.0% of all IVF children. The types of congenital abnormalities varied: 3.6% of IVF children and 2.5% of controls had minor congenital anomalies, and 2.5% of IVF children and none of the controls had major congenital malformations. The numbers of each specific type of congenital abnormality were small and were not significantly related to multiple births. IVF children (2.1%) and 0.4% of the controls had mild/moderate disabilities. They were all from multiple births, including two children with cerebral palsy who were triplets. CONCLUSIONS: The outcome of IVF treatment leading to multiple births is less satisfactory than that in singletons because of neonatal conditions associated with preterm delivery and disabilities in later childhood. A reduction of multiple pregnancies by limiting the transfer of embryos to two instead of three remains a high priority. 相似文献