首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   20篇
  免费   0篇
化学工业   1篇
无线电   1篇
一般工业技术   4篇
冶金工业   6篇
自动化技术   8篇
  2011年   1篇
  2006年   1篇
  2005年   1篇
  2003年   1篇
  2000年   1篇
  1999年   1篇
  1998年   3篇
  1997年   1篇
  1989年   1篇
  1982年   1篇
  1981年   1篇
  1978年   1篇
  1977年   1篇
  1976年   3篇
  1975年   2篇
排序方式: 共有20条查询结果,搜索用时 15 毫秒
1.
2.
BACKGROUND/AIMS: To determine if the use of Intraoperative choliangiography (IOC) should be routinely performed and, if not, which criteria should be used to select patients requiring IOC during open or laparoscopic cholecystectomy. METHODOLOGY: 495 Patients with 1 or more gallstones were included in a two-year study. Twelve clinical, laboratory, ultrasonographic and intraoperative factors were chosen and evaluated in all cases. Prior to cholecystectomy, IOC was performed after having identified the common bile duct (CBD) and cystic duct. The majority of the patients were operated on by the same surgeon to avoid differences in criteria and techniques. Statistical evaluation made use of the exact Fisher test and chi square test and, a p-value less than 0.05 was considered as significant. RESULTS: IOC could be performed in 479 out of the 495 cases. IOC resulted in a normal CBD in 76.0%, had a false positive in 2.7%, a false negative in 0.48%, and a presence of 1 or more stones in the CBD in 20.9%. The study revealed that when none of the 12 risk factors were present, there were no cases with CBD stones. As the number of risk factors increased, so did the number of cases presenting with CBD stones. CONCLUSION: Not all 12 risk factors show the same index of predictability; only 5 in particular (jaundice, ultrasound diameter CBD 7 mm, bilirubin over 26 umol/it, cystic duct > 4 mm and CBI, diameter over 9 mm) showed a high rate of predictability. However, when careful measurement and evaluation of risk factors for CBD stones are undertaken, it is possible to avoid the routine use of IOC.  相似文献   
3.
Finite element analysis of the skin effect in current carrying conductors   总被引:2,自引:0,他引:2  
The current density distribution in a conductor of finite size is affected by the presence of eddy currents in the conductor. This phenomenon, generally known as skin effect, causes ohmic losses in the conductors and alters their magnetic induction. This paper presents an analysis of skin effect phenomena using the triangular finite element method. The results obtained by this method are compared with those of classical one-dimensional analysis for (i) a conductor in free space and (ii) a conductor in the presence of an iron boundary.  相似文献   
4.
5.
A finite element method is developed by which it is possible to obtain the general solution of an ordinary differential equation directly. The procedure consists of approximating the differential equation with a rectangular matrix equation and of solving the latter equation by using generalized matrix inversion. It is shown in the paper that the homogeneous and inhomogeneous solutions of the two systems correspond and that the approximate solutions produced form the complete general solution of the original differential equation.  相似文献   
6.
Csendes  Tibor 《Reliable Computing》2003,9(2):109-125
The convergence properties are studied for interval global optimization algorithms that select the next subinterval to be subdivided with the largest value of the indicator pf(f k, X) = . In contrast to previous work, here the more general case is investigated, when the global minimum value is unknown, and thus its estimation f k in the iteration k has an important role.Extensive numerical tests on 40 problems confirm that substantial improvements can be achieved both on simple and sophisticated algorithms by the new method (not utilizing the minimum value).  相似文献   
7.
A finite element method is presented for solving boundary value problems for ordinary differential equations in which the general solution of the differential equation is computed first, followed by a selection procedure for the particular solution of the boundary value problem from the general solution. In this method, the discrete representation of the differential equation is a singular matrix equation, which is solved by using generalized matrix inversion. The technique is applied to both linear and nonlinear boundary value problems and to boundary value problems requiring eigenvalue evaluation. The solution of several examples involving different types of two-point boundary value problems is presented.  相似文献   
8.
9.
10.
This paper deals with the empirical convergence speed of inclusion functions applied in interval methods for global optimization. According to our experience the natural interval extension of a given function can be as good as a usual quadratically convergent inclusion function, and although centered forms are in general only of second-order, they can perform as one of larger convergence order. These facts indicate that the theoretical convergence order should not be the only indicator of the quality of an inclusion function, it would be better to know which inclusion function can be used most efficiently in concrete instances. For this reason we have investigated the empirical convergence speed of the usual inclusion functions on some test functions.This work has been supported by the Grants OTKA T 034350 and T 032118, OMFB D–30/2000, and OMFB E–24/2001.The authors are grateful for the anonymous referees for their suggestions.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号