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241.
随机桥过程建模超宽带多径传播信道   总被引:2,自引:0,他引:2  
使用随机桥过程研究超宽带(UWB)多径传播信道。首先介绍随机桥过程的理论基础.然后引入能够建模无线信道传播特性的基本随机变量。给出随机桥过程建模UWB多径传播信道的两个假设条件,使用布朗桥过程建模UWB无线传播信道,得到有约束布朗桥信道模型,同时还给出使用随机桥过程方法建模UWB室内多径信道特性的算法和伪代码。使用该信道模型对典型室内传播环境进行仿真分析。仿真结果表明,得到的UWB信道的特性和使用一致性劈绕射理论(UTD)方法得到的信道特性结果非常相似,信道特征参量的取值与经验参数相符。  相似文献   
242.
While there is general agreement that a linear combination of forecasts can outperform the individual forecasts, there is controversy about the appropriateness of the combination method to be used in a given situation. Hence, in any given application it may be more beneficial to combine different sets of combined forecasts rather than picking one of them. This paper introduces the concept of N-step combinations of forecasts which involves combining the combined forecasts obtained from different combination procedures used at the preceding step. Using quarterly GNP data, evidence supporting the increase in the accuracy of the one-period-ahead ex-ante forecasts as the combination step increases is provided. The MSE, MAE, MAPE and their corresponding standard deviations are used to evaluate the accuracy of the forecasts obtained.  相似文献   
243.
对宇宙的起源、演化以及万物的来源问题提出了一系列个人见解,并利用这一观点对耗散结构论、相对论、宇宙学、现代科学理论和气功、周易、经络等人体与科学之谜作了简要论述。  相似文献   
244.
沥青砼连续配料微机控制系统蔡曙生,张屹(东南大学动力工程系,南京210018)南京市政公司供应分公司沥青在连续配料微机控制系统是一项具有较大难度的科研工程项目,鉴于国内同行业中尚无成熟实用的自动配料系统投入使用,故该科研工程项目对于提高沥育在质量,减...  相似文献   
245.
Based on the single sensor Kalman filtering equations, this paper presents two-level and three-level optimal centralized and distributed estimation algorithms for hierarchical multisensor systems. The solution shows that when the correlated matrix, the mean of noise, the control input, and the measurement error are all zero, the result in this paper turns out to be the standard algorithm discussed. Simulation shows that the mean of noise, the control input, and the measurement error will not change the estimation covariance and the estimation covariance fluctuates greatly when the cross-correlated matrix is similar to the covariance of process noise.  相似文献   
246.
提出了一种处理O-U关联噪声驱动双稳动力学系统的方法,并得到了相应的近似福克-普朗克方程。在此基础上,计算了双稳动力学系统的几率分布函数,进一步分析了噪声关联参数在定态几率分布单双峰结构上的影响。  相似文献   
247.
248.
A key statement of the 1965 Monod-Wyman-Changeux (MWC) model for allosteric proteins concerns the distinction between the ligand-binding function ( ) and the relevant state function ( ). Sequential models predict overlapping behavior of the two functions. In contrast, a straightforward experimental consequence of the MWC model is that for an oligomeric protein the parameters which characterize the two functions should differ significantly. Two situations, where \bar Y$$ " align="middle" border="0"> and the system ishyper-responsive or where and the system ishypo-responsive, have been encountered. Indeed, the hyper-responsive pattern was first observed for the enzyme aspartate transcarbamoylase, by comparing with monitored by a change in sedimentation. Extensions of the theory to ligand-gated channels led to the suggestion that, on the one hand, hyper-responsive properties also occur with high-affinity mutants. On the other hand, native channels of the acetylcholine neuronal7 receptor and low-affinity mutants of the glycine receptor can be interpreted in terms of the hypo-responsive pattern. For the ligand-gated channels, whereas is detected directly by ion flux, ligand binding has rarely been measured and the formation of desensitized states may complicate the analysis. However, stochastic models incorporating both binding and channel opening for single molecules predict differences that should be measurable with new experimental approaches, particularly fluorescence correlation spectroscopy.  相似文献   
249.
Summary Dispersal of the constituent cells of mammalian visceral and vascular smooth muscles has permitted recordings both of membrane currents under whole-cell voltage clamp, and of currents through single ionic channels using the patch-clamp technique. A rectangular depolarizing step applied to a single cell under voltage clamp yielded a net inward current followed by a net outward current in normal physiological solution. In isolated, inside-out patches of cell membrane a calcium- and potential-sensitive K channel (100 pS conductance) and a calcium-insensitive, potential-sensitive K+ channel (50 pS conductance) with slow kinetics have so far been identified and characterized.  相似文献   
250.
Summary Neonatal and adult rat pancreatic islet cells were maintained in dissociated cell culture for up to three weeks. The unexpected occurrence of giant (40–50 m) cells was noted, some of which reacted positively to an insulin antiserum, indicating the presence of insulin. The giant cells were amenable to study using the extracellular patch clamp technique, which was used to demonstrate a population of membrane channels gating outwardly directed current in these cells.  相似文献   
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