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排序方式: 共有8800条查询结果,搜索用时 46 毫秒
71.
针对具有多变量、非线性、强耦合和不确定性的可逆冷带轧机速度张力系统,提出了一种基于扩张状态观测器(extended state observer,ESO)的全局积分滑模自适应反步分散控制方法.首先,采用机理建模方法,建立了相对完备的可逆冷带轧机速度张力多变量耦合系统的数学模型.其次,将各子系统的耦合项和不确定项看成外扰,通过构造的ESO对其进行动态观测,并分别引入所设计的全局积分滑模自适应反步控制器中进行补偿,速度张力系统实现了有效的动态解耦和协调控制.理论分析表明,所提出的控制方法能够保证滑模面的渐近稳定和闭环系统的渐近跟踪性能.最后,基于某1422mm可逆冷带轧机速度张力系统的实际数据进行仿真,结果验证了所提方法的有效性. 相似文献
72.
T. Watanabe P. Chairoj H. Tsuruta W. Masarngsan C. Wongwiwatchai S. Wonprasaid W. Cholitkul K. Minami 《Nutrient Cycling in Agroecosystems》2000,57(1):55-65
Nitrous oxide (N2O) emission from fertilized maize fields was measured using a closed chamber at four experimental sites in Thailand. The average measured N2O flux from unfertilized plots through crop season was 4.16 ± 1.52, 5.05 ± 1.65, 5.25 ± 1.68 and 6.74 ± 2.95 g N2O-N m-2 h-1, at Nakhon Sawan, Phra Phutthabat, Khon Kaen and Chiang Mai, respectively. Increased N2O emissions by the application of nitrogen fertilizer were 0.22–0.44, 0.19–0.38%, 0.12–0.24 and 0.08–0.15% of the applied N, respectively. Compared to other data, N2O emission rate to applied nitrogen was not significantly different between the data of Thailand and the Temperate Zone. 相似文献
73.
Carsten Dachsbacher Jaroslav Křivánek Miloš Hašan Adam Arbree Bruce Walter Jan Novák 《Computer Graphics Forum》2014,33(1):88-104
Recent years have seen increasing attention and significant progress in many‐light rendering, a class of methods for efficient computation of global illumination. The many‐light formulation offers a unified mathematical framework for the problem reducing the full lighting transport simulation to the calculation of the direct illumination from many virtual light sources. These methods are unrivaled in their scalability: they are able to produce plausible images in a fraction of a second but also converge to the full solution over time. In this state‐of‐the‐art report, we give an easy‐to‐follow, introductory tutorial of the many‐light theory; provide a comprehensive, unified survey of the topic with a comparison of the main algorithms; discuss limitations regarding materials and light transport phenomena and present a vision to motivate and guide future research. We will cover both the fundamental concepts as well as improvements, extensions and applications of many‐light rendering. 相似文献
74.
The novel distributed mobility management trend is a promising direction to cope with the increasing mobile data traffic and flatten network architectures. Most of the novel mobility approaches distribute the mobility anchors through the access level, as opposed to the centralized mobility anchoring model. Other recent approaches argue that mobility anchors closer to the content servers may be the solution to optimize the mobility performance. However, none of the mobility anchoring models is ideal for all scenarios, since it depends on the user, the session and the network. Hence, we propose an IP mobility approach driven by the context of the user, sessions and the network, where the mobility anchors for IP address allocation and for routing/forwarding are distributed through the network nodes, while the mobility context is managed by the mobile devices. Although each session is properly anchored in the establishment phase, the routing/forwarding is adapted over time, according to the user, the session and the network context: the proposed approach is able to signal different mobility anchors to optimize the routing path to new and ongoing sessions of the user. The outcome of the evaluation shows that the proposed approach overall reduces the data cost, the data delay, the tunneled packets and the tunnel length, when compared with other anchoring models. 相似文献
75.
随着经济的飞速发展,我国的环境状况在不断恶化。就目前的环境现状、环境污染问题和环境保护工作现状进行了详细分析和阐述,并对环境保护工作提出参考和建议。 相似文献
76.
J. N. Armor 《Catalysis Letters》2007,114(3-4):115-121
Perspectives are offered for reducing the impact of huge amounts of CO2 produced today from power generation and transportation vehicles. The origins of the dilemma between the world’s increasing
use of hydrocarbons as an energy source and the cogeneration of CO2 which results as a co-product are discussed. Hydrocarbons will provide much of the fuel needs for these major, global industries
for the next 20 years and meet 60% of the world’s energy demand. With the growth of both power generation and transportation
vehicles around the world, CO2 levels will continue to increase in the atmosphere. Renewables such as wind, dams, and biomass will not be able to handle
all the energy demand. Technology breakthroughs are needed to reduce the world’s dependence on fossil fuels, which will be
aggravated by the drive to use more coal. Current approaches for removing CO2 are discussed as well as near term and future options with particular focus on how catalysis can offer some solutions. In
particular, solar photocatalysis based approaches offer a potentially viable energy solution. 相似文献
77.
针对基本粒子群优化算法(PSO)容易陷入局部最优点和收敛速度较慢的缺点,提出在PSO更新过程中加入两类基于正态分布投点的变异操作。一类变异用来增强局部搜索能力,另一类变异用来提高发现全局最优点的能力,避免所有粒子陷入到一个局部最优点的邻域内。数值结果表明,所提出算法的全局搜索能力有显著提高,并且收敛速度更快。 相似文献
78.
针对量子粒子群优化(QPSO)算法迭代后期种群多样性下降、收敛速度慢、易陷入局部最优的缺点,提出一种自适应收缩-扩张系数的双中心协作最子粒子群优化算法。该算法从2个方面进行改进:(1)自适应调节收缩-扩张系数,其目的是帮助粒子跳出局部最优点,提高粒子的全局搜索能力;(2)双重更新全局最优位置,即在每次迭代中,先后分别采用2种不同的方式更新全局最优位置。第1种方式与QPSO算法一致,第2种方式则引入双中心粒子,使其和当前全局最优位置在相应维度上合作,从而达到更新全局最优位置的目的。从固定迭代次数和固定精度角度分析算法性能,仿真结果表明,相比于QPSO算法,该算法在保证复杂度较低的情况下,可提高收敛速度,增强全局和局部搜索能力。 相似文献
79.
微分进化算法(DE)是模仿生物进化“优胜劣汰、适者生存”的一种随机优化算法,具有简单、快速、鲁棒性好等特点,已经得到广泛应用.通过运用微分进化算法的整数编码方法,在整数空间中求解,并在实数空间中计算解的适应度.使用测试函数对程序进行测试,证明了整数编码解对空间个体中寻优的快速性、准确性. 相似文献
80.