共查询到10条相似文献，搜索用时 31 毫秒
1.
2.
NIU Yingxuan 《六安师专学报》2013,(5):26-30
I.et （X,d） be a metric space and fn ： X→X be a sequence of continuous maps that converges uniformly to a map f. In this paper, we investigate the conditions that the uniform map f has transitivity and sensitivity from the viewpoint of family. We obtain that a equivalence condition for the uniform map f to be -transitive, and a equivalence condition for the uniform map f to be .P-sensitive when X is a compact metric space, where is a collection of subsets of Z＋ that is hereditary upward. Our results improve and extend the existing results. Moreover, we give a example which shows that the several results in [8] are all wrong. 相似文献
3.
This paper attempts to give an interpretation of communicative competence by a comparative approach,internally and externally.It first examines the internal components of communication competence as formulated by Hymes and Canale & Swain,and then explores the possible relationship between linguistic competence and communication competence by comparing and constrasting the two.Our conclusion is that linguistic competence is the foundation for communicative competence and the latter is a further development of the former. 相似文献
4.
This paper deals with design and analysis of user scheduling and power allocation for multi-antenna OFDM systems with DPC, ZF-DPC, ZF-BF and TDMA transmit strategies. We consider the general multi-user downlink scheduling problem and power minimization with multi-user rate constraints. According to the channel state, it is shown that there is a power optimal policy which selects a subset of users in each scheduling interval. We present user selection algorithms for DPC, ZF-DPC, ZF-BF and TDMA for multi-antenna OFDM system in broadcast channels, and we also present the practical water-filling solution in this paper. By the selected users with the consideration of fairness, we derive the power optimization algorithm with multi-user rate constraints. We also analyze the power duality of uplink-downlink for the transmit strategies of DPC, ZF-DPC and ZF-BF. Simulation results show that the present user-scheduling algorithm and power minimization algorithm can achieve good power performance, and that the scheduling algorithm can guarantee fairness. 相似文献
5.
《初中生学习》2008,(4)
Official site:http://www.sonymusic.co.jp/Animation/hagaren/ The legend tells of a mystical artifact that when it used its possessor's power will increase a thousand fold.Anyone possessing this artifact could in theory produce an elixir of extraordinary power that would heal all injuries,and give them everlasting life.It is rumored to be red;a brilliant,sparkling crimson rivaling the most precious jewel in any museum.The stone's power is equal to the greatest of Nature's fury and beauty alike. 相似文献
6.
This paper studies the modelling and simulation for all forms of hcaters.The assumption of former days that the temperature of condensation is the saturationtemperature corresponding to heater pressure in steam side is no longer used.On the basisof the laws of conservation of mass,energy and momentum,the mathematical model ofheaters is established and the simulation calculation of a 125MW unit is made.The rcsultshows that the model is applicable for various kinds of steam-water heater in power plant. 相似文献
7.
ZHANG Wei-chen 《重庆大学学报(英文版)》2015,14(3):101-108
Nowadays renewable energy has become a trend for energy production but its variable nature has made balancing of demand and supply of the power grid difficult. Dynamic demand management using smart appliances is proposed to serve as a way that part of the regulation burden of balancing demand and supply is shifted to the demand side. However, if all appliances respond to the same frequency deviation, they may start to synchronize, causing large power overshoots and instability of the power grid. Therefore, the idea of implementing randomness into the frequency control of the appliances is proposed and this is what we call a stochastic approach. Simulators are built from scratch to model both scenarios. The effect of synchronization is analyzed and the parameters that can affect the synchronization are investigated. It has been found that the larger the contribution from the smart appliances to the power grid, the easier and faster the synchronization takes place. The stochastic approach solves the problem of synchronization and averages out the large power overshoot. However, the overall performance of stochastic operations is unacceptable due to the randomness in the operation though the mean and variance are as expected. More advanced feedback policies and schemes may be designed to achieve a better performance. 相似文献
8.
The musicality of poetry is a project that has been in great need of scholars’attentions and studies due to its charming typicality,which has been a rarely-visited for a long time.To get away with this intellectual sterility and poverty,and highlight the aesthetic universality of the musicality in poetic texts,this paper aims to give a preliminary exploration of the metrical musicality in A Red,Red Rose. 相似文献
9.
This paper develops a new mathematical model of electrical power system,in which the transient saliency effect of synchronous machine is taken into account.Thecomputation results show that the new model has higher precision and less computationlabor.So it is suitable for the analysis and controller design of transient power system. 相似文献
10.
HUANG Biao YAN Guo-zheng LI Qian-ru 《浙江大学学报(A卷英文版)》2007,8(10):1560-1567
Antenna is very crucial to radiotelemetry capsules which can measure the physiological parameters of the gastroin- testinal (GI) tract. The objective of this paper is to design a novel spiral slots microstrip patch antenna for the radiotelemetry capsules communicating with external recorder at 915 MHz located in ISM (Industry, Science, and Medical) bands. The microstrip patch antenna is designed and evaluated using the finite-difference time-domain (FDTD) method. Return loss characteristics and the effect of the human body on resonant frequency are analyzed, and the performances of radiation patterns at different positions of the human alimentary tract are also estimated. Finally, specific absorption rate (SAR) computations are performed, and the peak 1-g and 10-g SAR values are calculated. According to the peak SAR values, the maximum delivered power for the designed antenna was found so that the SAR values of the antenna satisfy the ANSI (American National Standards Institute) limitations. 相似文献