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排序方式: 共有523条查询结果,搜索用时 15 毫秒
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A Serrano Pascual C Merino Hernáez R Ochoa Mejías A Escolano Chamois J Golbano Ablanque I Otero Tejero M Sanz Redondo F Román Ruiz 《Canadian Metallurgical Quarterly》1997,21(6):631-635
BACKGROUND AND AIMS OF THE STUDY: Surgical treatment of functional tricuspid regurgitation associated with advanced valvular disease remains controversial, mainly due to the difficulty in choosing between valve replacement or reconstructive surgery. Failure to correct tricuspid regurgitation during valvular surgery carries a poor prognosis, as reoperation may represent a significant risk to the patient. Thus correct tricuspid valve surgery is vital to achieve improved early and long-term clinical results. METHODS: A total of 142 patients underwent concomitant tricuspid annuloplasty with mitral valve replacement and their clinical outcome was assessed. RESULTS: Overall hospital mortality rate was 11.3%. Seven patients died during follow up. The overall actuarial survival rate for 10 years was 74.1 +/- 14.2%. Postoperatively, 75.8% of the patients had no residual tricuspid insufficiency, while 24.2% had first- or second-degree tricuspid insufficiency and were treated medically. All patients were in NHYA functional class I or II postoperatively. CONCLUSION: Clinically, it is important to assess the severity of functional tricuspid insufficiency before and/or during the operation. Bicuspidalization annuloplasty for functional tricuspid insufficiency has provided good results, with a low incidence of reoperation and significant clinical improvement. The technique could be used in most patients with functional tricuspid regurgitation. 相似文献
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Figueres E. Garcera G. Benavent J.M. Pascual M. Martinez J.A. 《Industrial Electronics, IEEE Transactions on》2006,53(1):239-253
A new two-loop control scheme for voltage-mode control (VMC) of dc-dc switching converters is presented. The proposed method adds a high-gain robust loop with two controllers to the conventional VMC loop, achieving an analog "adaptive" loop in which the "equivalent voltage regulator" varies with the changing power stage parameters given as follows: 1) input voltage; 2) load; and 3) component tolerances. The loop significantly improves the disturbance rejection of the control system, i.e., closed-loop output impedance and audiosusceptibility while preserving the stability and the loop gain crossover frequency to a significant extent. Both the small-signal analysis and the experimental results carried out on a buck converter demonstrate the superiority of the proposed scheme with respect to the conventional single loop. 相似文献
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Hydroxylic and nonhydroxylic acrylates—methyl acrylate (MA), ethyl acrylate (EA), butylacrylate (BA), hydroxypropyl methacrylate (HPMA), ethylenglycol dimethacrylate (EGDMA), and mixtures of HPMA–MA, HPMA–EA, HPMA–BA in a 50/50 feed composition—were grafted onto amylopectin with different amounts of crosslinking agent, EGDMA. Percent of total conversion, percent crude grafting, and influence of pH in water content were studied. In this sense it was only at pH 10 when a real variation in the water content could be seen. It was also proved that the highest values were obtained when one of the comonomers was EGDMA with a 34 mol% of the initial feed composition. © 1994 John Wiley & Sons, Inc. 相似文献
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Hyperinsulinaemia, dyslipaemia and cardiovascular risk in girls with a history of premature pubarche
L Ibá?ez N Potau P Chacon C Pascual A Carrascosa 《Canadian Metallurgical Quarterly》1998,41(9):1057-1063
Girls with a history of premature pubarche, i.e. appearance of pubic hair before 8 years of age, show hyperinsulinism in response to an oral glucose tolerance test. As hyperinsulinaemia has a major role in dyslipaemia, and is considered an independent risk factor for cardiovascular disease, we assessed the patterns of plasma insulin concentration after a standard oral glucose tolerance test as well as fasting serum lipid, lipoprotein, and sex hormone-binding globulin concentrations in girls (n = 81) with premature pubarche compared with girls (n = 55) matched with them for stage and bone age to ascertain their metabolic states to identify those potentially at risk for the development of premature cardiovascular disease. Mean serum insulin concentrations were higher in patients at all pubertal stages, and associated with elevated serum triglyceride, very low density cholesterol and very low density triglyceride concentrations (p value range 0.04 to < 0.0001) but reduced sex hormone-binding globulin. Premature pubarche patients also displayed higher low density to high density lipoprotein cholesterol ratios compared with control subjects (p = 0.004 to 0.008). In conclusion, hyperinsulinaemia, decreased sex hormone-binding globulin concentrations and an unfavourable lipid pattern are common features in premature pubarche girls supporting the contention that atherogenic abnormalities composing the metabolic syndrome could start in childhood. To determine the clinical sequelae of such clustering of metabolic deviations, girls who were identified need to be followed up for the potential development of premature cardiovascular disease. 相似文献
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Laura Pascual 《Electrochimica acta》2006,51(16):3193-3201
Lithium-deficient LiYMn2O4 spinels (LD-LiYMn2O4) with nominal composition (0.9 ≤ Y < 1) have been synthesized by melt impregnation from Mn2O3 and LiNO3 at temperatures ranging from 700 °C to 850 °C. X-ray diffraction data show that LD-LiYMn2O4 spinels are obtained as single phases in the range Y = 0.975-1 at 700 °C and 750 °C. Morphological characterization by transmission electron microscopy shows that the particle size of LD-LiYMn2O4 spinels increases on decreasing the Li-content. The influence of the Li-content and the synthesis temperature on the thermal and electrochemical behaviours has been systematically studied. Thermal analysis studies indicate that the temperature of the first thermal effect in the differential thermal analysis (DTA)/thermogravimetric (TG) curves, TC1, linearly increases on decreasing the Li-content. The electrochemical properties of LD-LiYMn2O4 spinels, determined by galvanostatic cycling, notably change with the synthesis conditions. So, the first discharge capacity, Qdisch., at C rate increases on rising the Li-content and the synthesis temperature. The sample Li0.975Mn2O4 synthesized at 700 °C has a Qdisch. = 123 mAh g−1 and a capacity retention of 99.77% per cycle. This LD-LiYMn2O4 sample had the best electrochemical characteristics of the series. 相似文献
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Francisco P. Romero Pascual Julián-Iranzo Andrés Soto Mateus Ferreira-Satler Juan Gallardo-Casero 《Language Resources and Evaluation》2013,47(1):151-178
Web 2.0 provides user-friendly tools that allow persons to create and publish content online. User generated content often takes the form of short texts (e.g., blog posts, news feeds, snippets, etc). This has motivated an increasing interest on the analysis of short texts and, specifically, on their categorisation. Text categorisation is the task of classifying documents into a certain number of predefined categories. Traditional text classification techniques are mainly based on word frequency statistical analysis and have been proved inadequate for the classification of short texts where word occurrence is too small. On the other hand, the classic approach to text categorization is based on a learning process that requires a large number of labeled training texts to achieve an accurate performance. However labeled documents might not be available, when unlabeled documents can be easily collected. This paper presents an approach to text categorisation which does not need a pre-classified set of training documents. The proposed method only requires the category names as user input. Each one of these categories is defined by means of an ontology of terms modelled by a set of what we call proximity equations. Hence, our method is not category occurrence frequency based, but highly depends on the definition of that category and how the text fits that definition. Therefore, the proposed approach is an appropriate method for short text classification where the frequency of occurrence of a category is very small or even zero. Another feature of our method is that the classification process is based on the ability of an extension of the standard Prolog language, named Bousi~Prolog , for flexible matching and knowledge representation. This declarative approach provides a text classifier which is quick and easy to build, and a classification process which is easy for the user to understand. The results of experiments showed that the proposed method achieved a reasonably useful performance. 相似文献
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Eric Angel Evripidis Bampis Fanny Pascual Alex-Ariel Tchetgnia 《Journal of Scheduling》2009,12(5):437-445
We consider the problem of designing truthful mechanisms for scheduling n tasks on a set of m parallel related machines in order to minimize the makespan. In what follows, we consider that each task is owned by a selfish
agent. This is a variant of the KP-model introduced by Koutsoupias and Papadimitriou (Proc. of STACS 1999, pp. 404–413, 1999) (and of the CKN-model of Christodoulou et al. in Proc. of ICALP 2004, pp. 345–357, 2004) in which the agents cannot choose the machine on which their tasks will be executed. This is done by a centralized authority,
the scheduler. However, the agents may manipulate the scheduler by providing false information regarding the length of their
tasks. We introduce the notion of increasing algorithm and a simple reduction that transforms any increasing algorithm into
a truthful one. Furthermore, we show that some of the classical scheduling algorithms are indeed increasing: the LPT algorithm,
the PTAS of Graham (SIAM J. Appl. Math. 17(2):416–429, 1969) in the case of two machines, as well as a simple PTAS for the case of m machines, with m a fixed constant. Our results yield a randomized r(1+ε)-approximation algorithm where r is the ratio between the largest and the smallest speed of the related machines. Furthermore, by combining our approach with
the classical result of Shmoys et al. (SIAM J. Comput. 24(6):1313–1331, 1995), we obtain a randomized 2r(1+ε)-competitive algorithm. It has to be noticed that these results are obtained without payments, unlike most of the existing
works in the field of Mechanism Design. Finally, we show that if payments are allowed then our approach gives a (1+ε)-algorithm for the off-line case with related machines. 相似文献