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排序方式: 共有178条查询结果,搜索用时 15 毫秒
1.
The selection of which requirements should be implemented in the next software release is an important and complex task in the software development process, considering the presence of budget constraints and other conflicting aspects. In this context, search based software engineering, has the main objective of applying automatic search methods to solve complex software engineering problems. However, most of these methods do not consider human expertise during the search, especially due to the difficulty in mathematically modeling the user's preferences. Consequently, the user can present some resistance or place little confidence in the final results, given that his/her knowledge and domain expertise was not properly considered in the solution construction. This paper aims at proposing an interactive model for the next release problem using ant colony optimization, where the user can define which requirements he/she would like to include or not in the next release. Employing humans and a simulator, an empirical study was performed that considers real-world and artificial instances. The achieved results demonstrate that the loss of score was, on average, 12% when it was compared with a solution with no human intervention. On the other hand, the algorithm generates solutions that have more than 80% of the met preferences, as defined by the users. Furthermore, the results showed that ACO can be an interesting choice as an interactive search engine, given the low quantity of interactions that are required to reach good solutions.  相似文献   
2.
A model for multiaxial high-cycle fatigue life evaluation of notched structural components is proposed, which considers the impact of the stress field on fatigue life by utilizing the Theory of Critical Distances (TCD) and Finite Element Method (FEM). The maximum shear stress range plane is defined as the critical plane, and the damage parameters are the maximum effective shear stress amplitude and the maximum effective normal stress, which are obtained by averaging the stress in the hemisphere volume around the maximum stress point. To validate the accuracy of the model, multiaxial fatigue tests are carried out for both smooth and notched specimens of Aluminum–Silicon alloy. The results indicate that the evaluated life and experimental life have a good agreement.  相似文献   
3.
Similar alarm sequence alignment algorithms have been used to find similar alarm floods in the historical database for the prediction and prevention of alarm floods. However, the existing modified Smith–Waterman (SW) algorithm has a high computation complexity, preventing its online applications within a tolerable computation time period. This paper proposes a new local alignment algorithm, based on the basic local alignment search tool (BLAST). The novelty of the proposed algorithm is three-fold. First, a priority-based similarity scoring strategy makes the proposed algorithm more sensitive to alarms having higher alarm priorities. Second, a set-based pre-matching mechanism avoids unnecessary computations by excluding all irrelevant alarm floods and alarm tags. Third, the seeding and extending steps of the conventional BLAST are adapted for alarm floods, which reduce the searching space significantly. Owing to the novelties, the proposed algorithm is much faster in computation and provides a higher alignment accuracy than the SW algorithm. The efficiency of the proposed algorithm is demonstrated by industrial case studies based on the historical alarm floods from an oil conversion plant.  相似文献   
4.
Temperature regulation is an important control challenge in open-cathode fuel cell systems. In this paper, a feedback controller, combined with a novel output-injection observer, is designed and implemented for fuel cell stack temperature control. The first functionality of the observer is to smooth the noisy temperature measurements. To this end, the observer gain is calculated based on Kalman filter theory which, in turn, results in a robust temperature estimation despite temperature model uncertainties and measurement noise. Furthermore, the observer is capable of estimating the output voltage model uncertainties. It is shown that temperature control not only ensures the fuel cell temperature reference is properly tracked, but, along with the uncertainty estimator, can also be used to stabilize the output voltage. Voltage regulation is of great importance for open-cathode fuel cells, which typically suffer from gradual voltage decay over time due to their dead-end anode operation. Moreover, voltage control ensures predictable and fixed fuel cell output voltages for given current values, even in the presence of disturbances. The observer stability is proved using Lyapunov theory, and the observer's effectiveness in combination with the controller is validated experimentally. The results show promising controller performances in regulating fuel cell temperature and voltage in the presence of model uncertainties and disturbances.  相似文献   
5.
砂堆雪崩幂律分布现象的解释   总被引:2,自引:2,他引:0  
自组织临界性的提出者Per Bak认为,处于临界状态砂堆雪崩呈现幂律分布,可作为广延耗散动力系统自组织临界性存在的证据。采用真实砂堆试验和元胞自动机砂堆模拟两种方法进行研究,提出处于亚临界状态的砂堆,在向临界状态演化的过程中,砂堆在亚临界状态发生众多小规模的雪崩,越接近临界状态,系统的波动越强,大规模的雪崩也时而发生,因此在从亚临界状态向临界状态演化的过程之中,大规模雪崩的发生次数少,小规模雪崩发生的次数多,雪崩发生的规模也呈现幂律分布,并认为这种情况更具普适性。  相似文献   
6.
张茜  余乐 《电气技术》2011,(1):10-12,47
讨论基于瞬时无功理论的各种谐波和无功检测方法在电网电压畸变情况下的适用性,独立设计有源电力滤波器对三相电力系统进行无功谐波综合补偿,并基于Matlab/Simulink仿真平台对系统进行建模仿真,仿真结果表明,所设计的并联型有源电力滤波器对系统的谐波无功综合补偿效果显著,验证了理论的正确性与可行性.  相似文献   
7.
一类超混沌系统电路实现及其动力学分析   总被引:5,自引:1,他引:4  
针对如何生成超混沌信号问题,通过在一个3维混沌Lü系统的电路中简单地加载一个积分电路,实现了一类超混沌系统电路.电路仿真获得了这类系统的超混沌吸引子及混沌、周期和准周期吸引子.并对实验电路所对应的四维连续自治耗散系统方程进行了分析和数值仿真,论证了这些系统电路的超混沌现象及其动力学特性.提出的超混沌系统电路实现简单,具有工程应用价值.  相似文献   
8.
We point out that a simpler expression could be derived for the outage probability considered by Chalise and Vandendorpe (2008). As a result, the computation of confluent hypergeometric function of two variables is not needed and the required computational effort is significantly reduced.  相似文献   
9.
粘弹性板热机耦合非线性振动(Ⅰ)——动力学模型   总被引:1,自引:1,他引:0  
建立了横向周期荷载、面内均布荷载和温度场作用下,考虑热传导效应的粘弹性矩形板的热机耦合非线性动力学模型.基于薄板大挠度Karman理论和用Boltzmann叠加原理描述的粘弹性材料本构方程、动力学平衡方程和热粘弹能量原理建立了考虑热传导效应的粘弹性矩形板的热机耦合非线性动力学模型,并用Galerkin方法将该热机耦合非线性动力学模型转化为非线性微分-积分动力系统.研究表明:1)在热传导系数和热膨胀都为0时,该热机耦合非线性动力学模型退化为粘弹性板动力学模型;2)在热传导系数为0而热膨胀不为0时,该热机耦合动力学模型简化为仅考虑热膨胀时的粘弹性板动力学模型;3) 当材料的粘性项为0时,即动力学模型中积分项为0时,该热机耦合动力学模型退化为热机耦合弹性板动力学模型.  相似文献   
10.
考虑了一类具有对称刚性约束的三自由度碰撞振动系统.建立了系统的Poincaré映射,并导出了Poincaré映射的对称性.把映射不动点的稳定性与分岔理论应用于该系统,分析表明Poincaré映射的对称性完全抑制了对称周期n-2运动的周期倍化分岔,Hopf-flip分岔和pitchfork-flip分岔,并证明了两个反对称的周期n-2运动具有相同的稳定性.数值模拟得到了对称周期n-2运动的音叉分岔,Hopf分岔和Hopf-Hopf分岔.此外,通过Poincaré截面投影相图的形式研究了由音叉分岔通向混沌的路径.  相似文献   
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