全文获取类型
收费全文 | 95篇 |
免费 | 1篇 |
专业分类
电工技术 | 5篇 |
化学工业 | 12篇 |
机械仪表 | 1篇 |
建筑科学 | 2篇 |
能源动力 | 2篇 |
轻工业 | 7篇 |
无线电 | 3篇 |
一般工业技术 | 27篇 |
冶金工业 | 9篇 |
原子能技术 | 2篇 |
自动化技术 | 26篇 |
出版年
2022年 | 2篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 3篇 |
2016年 | 1篇 |
2015年 | 1篇 |
2014年 | 3篇 |
2013年 | 2篇 |
2012年 | 7篇 |
2011年 | 8篇 |
2010年 | 5篇 |
2009年 | 7篇 |
2007年 | 2篇 |
2006年 | 4篇 |
2005年 | 3篇 |
2004年 | 2篇 |
2002年 | 2篇 |
2001年 | 1篇 |
2000年 | 6篇 |
1998年 | 2篇 |
1997年 | 5篇 |
1996年 | 2篇 |
1995年 | 4篇 |
1994年 | 1篇 |
1992年 | 2篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有96条查询结果,搜索用时 31 毫秒
1.
Nutritional requirements and economics of lowering feed costs 总被引:1,自引:0,他引:1
D L Bath 《Journal of dairy science》1985,68(6):1579-1584
Feed costs are, and will continue to be, the largest single expense for milk production. Gross efficiency of milk production is greater for high-producing cows because a lower proportion of total feed intake is used for maintenance of the cow. High milk production and high feed intake are positively correlated. The challenge for the future is to continue the remarkable progress in milk yield potential and increased feed efficiency realized in the recent past. Some areas of research that show promise for improving our knowledge and ability to feed cows for even greater efficiency include studies of energy metabolism, protein metabolism, voluntary feed intake, ruminal fermentation and fiber requirements, effects of growth hormone on milk production and animal metabolism, mineral nutrition, buffers, and vitamins. Practical studies on treatment and utilization of by-product feeds, manipulation of milk composition through nutrition, and continued development of better computer models for feeding and management decisions will have a significant effect on the efficiency and profitability of the dairy enterprise. 相似文献
2.
A new methodology, called hybrid predictive dynamics (HPD), is introduced in this work to simulate human motion. HPD is defined as an optimization-based motion prediction approach in which the joint angle control points are unknowns in the equations of motion. Some of these control points are bounded by the experimental data. The joint torque and ground reaction forces are calculated by an inverse algorithm in the optimization procedure. Therefore, the proposed method is able to incorporate motion capture data into the formulation to predict natural and subject-specific human motions. Hybrid predictive dynamics includes three procedures, and each is a sub-optimization problem. First, the motion capture data are transferred from Cartesian space into joint space by using optimization-based inverse kinematics (IK) methodology. Secondly, joint profiles obtained from IK are interpolated by B-spline control points by using an error-minimization algorithm. Third, boundaries are built on the control points to represent specific joint profiles from experiments, and these boundaries are used to guide the predicted human motion. To predict more accurate motion, the boundaries can also be built on the kinetic variables if the experimental data are available. The efficiency of the method is demonstrated by simulating a box-lifting motion. The proposed method takes advantage of both prediction and tracking capabilities simultaneously, so that HPD has more applications in human motion prediction, especially towards clinical applications. 相似文献
3.
Predictive simulation of human walking transitions using an optimization formulation 总被引:1,自引:1,他引:0
Yujiang Xiang Jasbir S. Arora Hyun-Joon Chung Hyun-Jung Kwon Salam Rahmatalla Rajankumar Bhatt Karim Abdel-Malek 《Structural and Multidisciplinary Optimization》2012,45(5):759-772
A general optimization formulation for transition walking prediction using 3D skeletal model is presented. The formulation
is based on a previously presented one-step walking formulation (Xiang et al., Int J Numer Methods Eng 79:667–695, 2009b). Two basic transitions are studied: walk-to-stand and slow-to-fast walk. The slow-to-fast transition is used to connect
slow walk to fast walk by using a step-to-step transition formulation. In addition, the speed effects on the walk-to-stand
motion are investigated. The joint torques and ground reaction forces (GRF) are recovered and analyzed from the simulation.
For slow-to-fast walk transition, the predicted ground reaction forces in step transition is even larger than that of the
fast walk. The model shows good correlation with the experimental data for the lower extremities except for the standing ankle
profile. The optimal solution of transition simulation is obtained in a few minutes by using predictive dynamics method. 相似文献
4.
5.
Strategic alignment between an organization's business strategy/capabilities and those of its information technology (IT) unit is an extensively researched subject that addresses the issue of fit between business and technology strategies. A key gap in the literature is lack of recognition that underlying this macro level of alignment are other, more granular levels of alignment involving the interdependent subunits within the corporate IT unit. Given the critical interdependencies between development and testing subunits in software engineering, this paper focuses on an alignment model for ensuring that these two functions work together effectively. A development-testing alignment (DTA) model is described, and a case study investigating its value and application is presented. This DTA is decomposed into distinct components for the purposes of theoretical clarity and pragmatic application. The case study analysis uses the model to understand and interpret development-testing alignment in a Fortune 500 company. We found that the development and testing functions were significantly misaligned, and our model identified close to twenty specific aspects that needed to be considered to enhance alignment. These included changes in specificity of scope, governance, resource availability, competencies, and processes. Our analysis shows that the DTA model can be usefully applied for the purpose of understanding tactical alignment between subunits within a corporate IT unit. It also demonstrates that there is value in considering alignment as a dynamic, context-driven, social phenomenon as well as a useful interpretative lens for exploring organizational interactions and interdependencies. 相似文献
6.
Summary An overview ofvariational inequality andvariational equality formulations for frictionless contact and frictional contact problems is provided. The aim is to discuss the state-of-the-art
in these two formulations and clearly point out their advantages and disadvantages in terms of mathematical completeness and
practicality. Various terms required to describe the contact configuration are defined.Unilateral contact law and classical Coulomb’s friction law are given.Elastostatic frictional contact boundary value problem is defined. General two-dimensional frictionless and frictional contact formulations for elastostatic
problems are investigated. An example problem of a two bar truss-rigid wall frictionless contact system is formulated as an
optimization problem based on the variational inequality approach. The problem is solved in a closed form using the Karush-Kuhn-Tucker
(KKT) optimality conditions. The example problem is also formulated as a frictional contact system. It is solved in the closed
form using a new two-phase analytical procedure. The procedure avoids use of the incremental/iterative techniques and user
defined parameters required in a typical implementation based on the variational equality formulation. Numerical solutions
for the frictionless and frictional contact problems are compared with the results obtained by using a general-purpose finite
element program ANSYS (that uses variational equality formulation). ANSYS results match reasonably well with the solutions
of KKT optimality conditions for the frictionless contact problem and the two-phase procedure for the frictional contact problem.
The validity of the analytical formulation for frictional contact problems (with one contacting node) is verified. Thevariational equality formulation for frictionless and frictional, contact problems is also studied in detail. The incremental/iterative Newton-Raphson
scheme incorporating the penalty approach is utilized. Studies are conducted to provide insights for the numerical solution
techniques. Based on the present study it is concluded that alternate formulations and computational procedures need to be
developed for analysis of frictional contact problems. 相似文献
7.
M. Bath 《Power Engineer (see also Power Engineering Journal)》2005,19(3):26-31
Power systems for military aircraft must tolerate extreme conditions: temperatures as low as -40/spl deg/C or as high as 70/spl deg/C, as well as short-term fluctuations from -55/spl deg/C to 180/spl deg/C; relative humidity as high as 100%; impacts reaching 60G. Difficult conditions can be tackled by using suitable materials and enclosure designs, but a system or unit's weight, size and shape are often governed by its location. These challenges are just the beginning. System reliability and availability are paramount as failures must be minimised at all times. To provide a reliable and safe power system for today's military aviators, many design teams are needed to tackle the architectural, electrical, mechanical and chemical parameters of power units. Exploiting emerging technical innovations, such as high-performance FETs, can only make life easier for designers of the future. 相似文献
8.
Bath BD Michael DJ Trafton BJ Joseph JD Runnels PL Wightman RM 《Analytical chemistry》2000,72(24):5994-6002
High-repetition fast-scan cyclic voltammetry and chronoamperometry were used to quantify and characterize the kinetics of dopamine and dopamine-o-quinone adsorption and desorption at carbon-fiber microelectrodes. A flow injection analysis system was used for the precise introduction and removal of a bolus of electroactive substance on a sub-second time scale to the disk-shaped surface of a microelectrode that was fabricated from a single carbon fiber (Thornel type T650 or P55). Pretreatment of the electrode surfaces consisted of soaking them in purified isopropyl alcohol for a minimum of 10 min, which resulted in S/N increasing by 200-400% for dopamine above that for those that were soaked in reagent grade solvent. Because of adsorption, high scan rates (2,000 V/s) are shown to exhibit equivalent S/N ratios as compared to slower, more traditional scan rates. In addition, the steady-state response to a concentration bolus is shown to occur more rapidly when cyclic voltammetric scans are repeated at short intervals (4 ms). The new methodologies allow for more accurate determinations of the kinetics of neurotransmitter release events (10-500 ms) in biological systems. Brain slice and in vivo experiments using T650 cylinder microelectrodes show that voltammetrically measured uptake kinetics in the caudate are faster using 2,000 V/s and 240 Hz measurements, as compared to 300 V/s and 10 Hz. 相似文献
9.
Sharad V. Belsare Jasbir S. Arora 《International journal for numerical methods in engineering》1983,19(6):841-858
In this paper a new concept for development of algorithms for optimal design of engineering systems is presented. The basic idea is to use upper and lower bounds on optimum cost to develop iterative search strategies. The main feature of the concept is that it does not rely on one-dimensional search to compute a step size at any design iteration. Implication of the feature is that the algorithms based on this concept require evaluation of constraint functions only once at any design iteration. This is highly desirable for optimal design of engineering systems because evaluation of functions for such systems is very expensive due to their implicit dependence on design variables. An algorithm based on the new concept is derived in the paper. Several new step sizes are introduced and their relation to proper reduced optimal design problems are presented. A new step size based on the constant cost requirement at some design iterations is introduced. Numerical aspects for the algorithm are also presented. Based on the new algorithm, a general-purpose computer code GRP2 is developed. The code is used to solve several problems to gain experience and insight for the algorithm. Numerical experience with examples is discussed. It is concluded that algorithms based on bounding optimum cost have substantial potential for applications in optimal design of engineering systems. 相似文献
10.
Qian Wang Jasbir S. Arora 《International journal for numerical methods in engineering》2007,69(2):390-407
Sparsity features of simultaneous analysis and design (SAND) formulations are studied and exploited for optimization of large‐scale truss structures. Three formulations are described and implemented with an existing analysis code. SAND formulations have large number of variables; however, gradients of the functions and Hessian of the Lagrangian are quite sparsely populated. Therefore, this structure of the problem is exploited and an optimization algorithm with sparse matrix capability is used to solve large‐scale problems. An existing analysis software is integrated with an optimizer based on a sparse sequential quadratic programming (SQP) algorithm to solve sample problems. The formulations and algorithms work quite well for the sample problems, and their performances are compared and discussed. For all the cases considered, the SAND formulations out perform the conventional formulation except one case. Further research is suggested to fully study and utilize sparse features of the alternative SAND formulations and to develop more efficient sparse solvers for large‐scale and more complex applications. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献