马尼希基海底高原重力均衡及其构造意义研究

采用三维导纳分析技术,联合海底地形和重力异常数据,对马尼希基海底高原重力均衡状况进行了分析研究,并结合地震学等研究成果,分析其构造意义。马尼希基海底高原海底地形与重力异常相干性在长波部分(大于100 km)相对较小,说明高原地壳底部存在低密度异常,并且,根据Airy均衡分析,这种低密度异常并非完全由洋壳对海底地形的均衡调整引起,推测高原地壳底部存在由岩装“板垫作用”(crustal under-plating)形成的低密度异常体,即“底部载荷”。马尼希基海底高原短波海底地形符合Airy均衡,据此分析获得高原地区洋壳厚度为22. 7 km,与地震研究结果一致。岩石圈挠曲均衡分析表明,马尼希基海底高原岩石圈有效弹性厚度为2.5-5.5 km,较优拟合值为3.5km,可能意味着高原形成时岩石圈年龄较小。根据顾及底部载荷的挠曲均衡模型进行分析,定量计算了底部载荷规模,约为地形载荷的30%,其体积约为9.3 X 105km3,平均深度为18 km,是整个高原洋壳的重要组成部分,表明洋壳底部板垫作用在马尼希基海底高原形成和演化过程中产生过重要影响。     

Lunar capture in the planar restricted three-body problem

The capture dynamics is an important field in Astronomy and Astronautics. In this paper, the near-optimal lunar capture in the Earth–Moon transfer is investigated under the frame of the planar circular restricted three-body problem. We try to work out how to achieve the permanent lunar capture with the minimum maneuver consumption. This problem is decomposed into two parts: the pre-maneuver part and the post-maneuver part. In the pre-maneuver part, considering the criteria of the gravitational capture, we obtain the minimum pre-maneuver velocity via the numerical backward integration. In the post-maneuver part, using the Poincaré section and the KAM theory, we find the maximum post-maneuver velocity to achieve the permanent capture. Synthesized the results of the two parts, a new method is presented to find the near-optimal maneuver position and the minimum maneuver consumption. The method presented is simple and visible, and can provide abundant capture orbits for the design of low energy Earth–Moon transfers.     

台湾西南海域地震数据处理及天然气水合物地震属性

对台湾西南海域增生楔部位长排列多道地震数据进行地震成像、速度分析、AVO分析、AVO反演处理,获得了天然气水合物多属性地震特征.在偏移剖面上,BSR与海底近似平行,极性与海底相反,穿越沉积层.AVO分析显示,强BSR振幅部位,BSR振幅随偏移距增大而增大.精细速度分析表明强BSR振幅下方存在纵波低速层.对应于强BSR振幅部位,AVO反演的P波、G波为相对高负值区,位于P、G交会图的第三象限,该部位泊松比变化率为负值,横波反射系数接近于零.以上多属性地震特征均预示着该区域可能存在天然气水合物层,且天然气水合物层下方可能存在游离甲烷气层.     

Comparison of Three Tropical Cyclone Intensity Datasets

Analyzed in this paper are the 16-yr (1988-2003) tropical cyclone (TC) intensity data from three major forecast centers of the western North Pacific, i.e., China Meteorological Administration (CMA), Regional Specialized Meteorological Center Tokyo (RSMC Tokyo), and Joint Typhoon Warning Center (JTWC) of the United States. Results show that there are significant discrepancies (at 1% significance level) in the intensity of TCs among the three centers, with a maximum difference for the same TC over 30 m s-1. The flight reconnaissance over TC can minish the discrepancy to some extent. A climatic and persistent prediction model is set up to study the impact of initial data from different forecast centers on the prediction of TC intensity. It is obtained that the root mean square error (RMSE) of a 4-yr independent test is the largest using data from JTWC, while the smallest using data from RSMC Tokyo. Average absolute deviation in 24-h intensity prediction is 2.5 m s-1 between CMA and RSMC Tokyo data, and 4.0 m s-1 between CMA and JTWC data, with a maximum deviation reaching 21 m s-1. Such a problem in the initial value increases the difficulty in intensity prediction of TCs over the western North Pacific.     

基于逆重复m序列信号的岩矿石电性参数采集方法研究

归纳总结了岩矿石电性参数实验过程中激励场源性质与实验装置类型,提出基于伪随机逆重复m序列信号为激励场源的实验方案,进而设计了新的观测装置.发送机产生的伪随机信号序列采用恒流源形式输出,频带宽度为1.0×10-3～1.0×104 Hz;接收机采用FGPA+ARM架构进行数据记录,在对比变频法、2n 伪随机序列与逆重复m序...     

Study on electric variations of media in epicentral area by geomagnetic transfer functions

ＳｔｕｄｙｏｎｅｌｅｃｔｒｉｃｖａｒｉａｔｉｏｎｓｏｆｍｅｄｉａｉｎｅｐｉｃｅｎｔｒａｌａｒｅａｂｙｇｅｏｍａｇｎｅｔｉｃｒａｎｓｆｅｒｆｕｎｃｔｉｏｎｓＸｉａｏ－ＰｉｎｇＺＥＮＧ；（曾小苹）Ｙｕｎ－ＦａｎｇＬＩＮＩ；（林云芳）Ｚｈｏｎｇ－ＪｉｅＺＨ...     

Prediction of tropical cyclone frequency with a wavelet neural network model incorporating natural orthogonal expansion and combined weights

A nonlinear wavelet neural network (WNN) model with natural orthogonal expansion (NOE) and combined weights is constructed to predict the annual frequency of tropical cyclones (TCF) occurring over the coastal regions of Southern China. Combined weights are obtained by calculating categorical weights, based on the particle swarm projection pursuit, and ranking weights, based on fuzzy mathematics, followed by optimization. The global monthly mean heights at 500?hPa and sea-surface temperature fields are used as two predictors. The linear and nonlinear information of the predictors with reduced dimensions is gathered through the NOE and combined weights, respectively, and treated as the input into the WNN model. This model is first trained with the 55-year (i.e., 1950?C2004) TCF data and then used to predict annual TCFs for the subsequent 5?years (i.e., 2005?C2009). Results show that the mean absolute and relative errors are 0.6175 and 9.34?%, respectively. The impacts of the combined weights, NOE and WNN as well as the traditional multi-regression approach on the TCF prediction are examined. Results show superior performance of the WNN-based model in the annual TCF prediction.     

Assessment of the Pacific decadal oscillation’s contribution to the occurrence of local torrential rainfall in north China

On 21–22 July 2012, torrential rains hit North China, with the daily precipitation record at Beijing station reaching 160.6 mm; this event is named the Beijing 7–21 case. This paper assesses the likelihood of the occurrence of local torrential rains, such as the Beijing 7–21 case, from the perspective of climate variability. In particular, the influence of the Pacific Decadal Oscillation (PDO) is assessed. There were five extreme events, with daily precipitation records equal to or larger than 160.6 mm, at Beijing station during the period 1951–2012; all of these events happened during negative phases of the PDO. The present analysis indicates that precipitation events more extreme than the Beijing 7–21 case should happen more than once per decade during negative phases of the PDO, but only about once every four decades during positive PDO phases. The negative phase of the PDO is found to be associated with a much greater probability of daily records of southerly winds in North China during summer. Strong southerly summer monsoons are deemed favorable for increasing the occurrence of local extreme rainfall over North China.     

Position-domain integrity risk-based ambiguity validation for the integer bootstrap estimator

Integrity monitoring for ambiguity resolution is of significance for utilizing the high-precision carrier phase differential positioning for safety–critical navigational applications. The integer bootstrap estimator can provide an analytical probability density function, which enables the precise evaluation of the integrity risk for ambiguity validation. In order to monitor the effect of unknown ambiguity bias on the integer bootstrap estimator, the position-domain integrity risk of the integer bootstrapped baseline is evaluated under the complete failure modes by using the worst-case protection principle. Furthermore, a partial ambiguity resolution method is developed in order to satisfy the predefined integrity risk requirement. Static and kinematic experiments are carried out to test the proposed method by comparing with the traditional ratio test method and the protection level-based method. The static experimental result has shown that the proposed method can achieve a significant global availability improvement by 51% at most. The kinematic result reveals that the proposed method obtains the best balance between the positioning accuracy and the continuity performance.