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231.
介绍了四参数正弦波最小二乘法评价通道间延迟时间差指标及不确定度分析和评价过程,同时给出了一个分析评价实例。该过程及结论可应用在对于测量标准进行相应指标的不确定度分析上,也可用于估计指标本身的不确定度。 相似文献
232.
我国城乡居民消费差异比较研究 总被引:5,自引:0,他引:5
张伟 《郑州航空工业管理学院学报(管理科学版)》2004,22(1):24-26
分析了我国近20年来城乡居民在消费行为中的差异,然后以西方经济理论中关于消费函数的理论模型为依据,根据城乡居民1981~2000年实际消费和收入的变化情况,通过回归模型,比较分析了城乡居民消费函数和边际消费倾向的差别.最后根据城乡居民消费的不同特点,提出了相应的政策建议. 相似文献
233.
相关分析技术在工程测量中的应用分析与研究 总被引:3,自引:1,他引:2
刘利秋 《沈阳航空工业学院学报》2004,21(5):67-69
相关分析法是信号分析和工程测量中重要的技术方法。通过理论分析和数学仿真研究了两种相关法测量——相差法相关测量和时差法相关测量的理论基础和适用条件。相位差法相关测量要求源信号为单一频率的简谐信号,适宜测量较小的时差。时差法相关测量要求源信号为非单一频率的宽频带信号,适宜测量较大的时差。源信号的带宽越宽,互相关函数的峰值点的峰值优势越大,其测量的抗干扰性能越好。 相似文献
234.
235.
对计算板坯连铸结晶器内三维速度场时常用的连续性方程的处理方法进行讨论,用有限差分法评述了处理此方程的新途径。 相似文献
236.
This paper investigates the problem of target position estimation with a single-observer passive coherent location(PCL) system. An approach that combines angle with time difference of arrival(ATDOA) is used to estimate the location of a target. Compared with the TDOA-only method which needs two steps, the proposed method estimates the target position more directly. The constrained total least squares(CTLS) technique is applied in this approach. It achieves the Cramer–Rao lower bound(CRLB) when the parameter measurements are subject to small Gaussian-distributed errors. Performance analysis and the CRLB of this approach are also studied. Theory verifies that the ATDOA method gets a lower CRLB than the TDOA-only method with the same TDOA measuring error. It can also be seen that the position of the target affects estimating precision.At the same time, the locations of transmitters affect the precision and its gradient direction.Compared with the TDOA, the ATDOA method can obtain more precise target position estimation.Furthermore, the proposed method accomplishes target position estimation with a single transmitter,while the TDOA-only method needs at least four transmitters to get the target position. Furthermore,the transmitters' position errors also affect precision of estimation regularly. 相似文献
237.
湖北省生态文明建设区域差异分析 总被引:1,自引:0,他引:1
自党的“十七大”明确提出建设生态文明是实现全面建设小康社会奋斗目标的新要求以来,全国掀起了生态文明建设理论研究和实践活动的热潮.但是我国幅员辽阔,各地区之间资源环境的区域差异明显,这严重制约了生态文明建设的整体推进.以湖北省生态文明建设的区域差异为研究对象,首先分析了湖北省生态文明建设区域差异的分布特征、结构特征和数量特征;其次从自然地理条件、历史基础、产业结构、政策倾斜等方面分析了区域差异形成的原因;最后利用最近几年的统计数据分析了湖北省生态文明建设区域差异的走向.研究发现,最近几年来,湖北省各地区资源条件、经济效率和人文发展水平的绝对差异在不断扩大,生态环境质量的相对差异也在不断扩大.但是根据不平衡增长理论可以判断,不久的将来湖北生态文明建设的区域差异将逐渐缩小,最终出现生态文明建设区域协调发展的趋势. 相似文献
238.
在运动目标无源定位系统中,许多算法的前提是精确已知传感器的位置以及速度,但实际情况下可利用的传感器的参数均会存在一些噪声扰动。针对这一问题,提出一种改进的两步加权最小二乘(TSWLS)时差(TDOA)与频差(FDOA)定位算法。该算法是一种闭式算法并且分为2步。第1步与经典的两步加权最小二乘算法相同,第2步进一步研究了额外变量与目标参数之间的关系并且建立了新的矩阵方程。随后,利用加权最小二乘技术给出了最终解。理论分析证明了在测量噪声较小时该算法能够达到克拉美罗界(CRLB)。所提算法具有计算复杂度低,实时性高的优点;另外,经过适当的维度调整,该算法同样适用于对多非相交源进行定位求解。计算机仿真进一步证明了理论分析的正确性。 相似文献
239.
A novel predictive algorithm for double difference observations of obstructed BeiDou geostationary earth orbit (GEO) satellites 总被引:1,自引:0,他引:1
Yuan Du Guanwen Huang Qin Zhang Rui Tu Junqiang Han Xingyuan Yan Xiaolei Wang 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2019,63(5):1554-1565
Transmission link disturbances and device failure cause global navigation satellite system (GNSS) receivers to miss observations, leading to poor accuracy in real-time kinematic (RTK) positioning. Previously described solutions for this problem are influenced by the length of the prediction period, or are unable to account for changes in receiver state because they use information from previous epochs to make predictions. We propose an algorithm for predicting double difference (DD) observations of obstructed BeiDou navigation system (BDS) GEO satellites. Our approach adopts the first-degree polynomial function for predicting missing observations. We introduce a Douglas-Peucker algorithm to judge the state of the rover receiver to reduce the impact of predictive biases. Static and kinematic experiments were carried out on BDS observations to evaluate the proposed algorithm. The results of our navigation experiment demonstrate that RTK positioning accuracy is improved from meter to decimeter level with fixed ambiguity (horizontal?<?2?cm, vertical?<?18?cm). Horizontal accuracy is improved by over 50%, and the vertical accuracies of the results of the static and kinematic experiments are increased by 47% and 27% respectively, compared with the results produced by the classical approach. Though as the baseline becomes longer, the accuracy is weakened, our predictive algorithm is an improvement over existing approaches to overcome the issue of missing data. 相似文献
240.
《中国航空学报》2020,33(12):3460-3468
The YSZ coatings are prepared by the plasma spray-physical vapor deposition (PS-PVD) technology based on a specific experimental design. The structure, thickness and growth angle of YSZ coatings on the entire circumferential surface of the cylindrical sample are studied. The results indicated that the structure, thickness and deflection growth angle of YSZ coatings are related to the orientation of deposition location. The numerical simulation of the multiphase mixed fluid near the substrate is carried out and the deposition regularity and mechanism of YSZ coatings prepared by PS-PVD is deduced. The growth rate is related to the local characteristics of the plasma flow field, and is directly proportional to the field pressure and inversely proportional to the field velocity. The growth angle of the coating is generally affected by the flow direction of the plasma jet. Especially, the normal component of velocity vector, Vnorm, mainly affects the speed at which the coating grows vertically upwards. The tangential component of velocity vector, Vtan, determines the degree that the coating growth direction deviates from the vertical direction. When Vtan ≠ 0, the coating forms a fine column with a certain deflection angle and finally develops into an oblique columnar structure. 相似文献