合理进行多元分析——定性资料对应分析和Shannon信息量分析

本文目的是介绍与定性资料对应分析和Shannon信息量分析有关的基本概念、计算方法、两个实例以及SAS实现。基本概念包括列联表与Burt表、边缘概率、行剖面与列剖面、信息和信息量、熵;计算方法涉及定性资料对应分析和Shannon信息量分析;两个实例分别为“某医院3年间不同季节4种甲状腺疾病的检出情况”和“不同专业学生的4种气质类型分布”;借助SAS软件,对两个实例中的数据分别进行了定性资料对应分析和Shannon信息量分析,并对SAS输出结果做出了解释。

对应分析理论探究

日常生活中可经常遇到某一现象变化所引起的其他现象的变化,对应分析是探讨这种对应变化关系的常用分析方法,是市场细分、产品定位常用的分析方法。如果能够深刻掌握对应分析的理论而不是机械套用对应分析方法,则能使研究者对分析对象的结果分析与预测更加深入。本文阐述了对应分析的基本思想、基本理论与方法。

Matched-field inversion of sound speed profile in shallow water using a parallel genetic algorithm

A sound speed profile plays an important role in shallow water sound propagation.Concurrent with in-situ measurements,many inversion methods,such as matched-field inversion,have been put forward to invert the sound speed profile from acoustic signals.However,the time cost of matched-field inversion may be very high in replica field calculations.We studied the feasibility and robustness of an acoustic tomography scheme with matched-field processing in shallow water,and described the sound speed profile by empirical orthogonal functions.We analyzed the acoustic signals from a vertical line array in ASIAEX2001 in the East China Sea to invert sound speed profiles with estimated empirical orthogonal functions and a parallel genetic algorithm to speed up the inversion.The results show that the inverted sound speed profiles are in good agreement with conductivity-temperature-depth measurements.Moreover,a posteriori probability analysis is carried out to verify the inversion results.

Mission overview and key technologies of the first Mars probe of China

The first Chinese Mars exploration will fulfill the goals of ＂orbiting, landing and roving＂ in one mission. This paper briefly describes the process of international Mars exploration and analyzes the development of Chinese Mars exploration. It focuses on introducing the scientific significance and engineering difficulties of Mars exploration, and provides an overview of the system design of the probe, including the flight profile, the preliminary selection of the landing site, the entry, descent and landing （also known as EDL） process. Four types of key technologies, including telecommunications, autonomous control, the EDL process, and its structure and mechanism, are detailed in this paper. Finally, the paper highlights the expected scientific and engineering results of the mission.

Prediction of recent bank retreat processes at typical sections in the Jingjiang Reach

The Jingjiang Reach is experiencing continuous channel degradation owing to operation of the Three Gorges Project （TGP） in 2003. Significant retreat processes at composite riverbanks have occurred at local sites of this reach, which may influence the stability of the fiver regime and the effect of existing river training works. Therefore, bank retreat plays a key role in fluvial processes of the Jingjiang Reach, and it is necessary to predict the long-term processes of bank retreat at typical sections in the reach. In this study, various factors influencing bank retreat in the Jingjiang Reach are investigated, based on bank erosion processes at four sections and the corresponding flow and sediment conditions. It is discovered that fluvial erosion intensity is a dominant factor in controlling the processes of bank retreat in the reach, although other factors, such as bank soil properties, can also influence bank retreat. The bankfull width at a section with severe bank erosion since 2002 is defined as being equal to the sum of the bankfull width in 2002 and the accumulated bank retreat distance after 2002. The magnitude of the bankfull width can be expressed as an exponential function of the previous 5-year average fluvial erosion intensity during flood seasons. The accumulated distances of bank retreat at four sections over the period 2002-2012 are predicted using the proposed empirical relationships, with the calculated bank retreat processes agreeing well with observed data.

Differences in lithospheric structures between two sides of Taihang Mountain obtained from the Zhucheng-Yichuan deep seismic sounding profile

A 2-D model of lithospheric velocity structures in the southern part of the North China Craton was obtained using data from the Zhucheng-Yichuan deep seismic sounding profile.Results show that there are great differences in lithospheric structures between two sides of Taihang Mountain.In the eastern region,the lithosphere is thinner,with a thickness of about 70-80 km,while in the western region,the thickness is 85-120 km.There is a jump of the lithospheric thickness across Taihang Mountain gravity anomaly belt with a magnitude of about 30 km.P wave velocities of the lithospheric mantle and lower crust are lower in the eastern region and higher in the western region.In the eastern region,there are low velocity bodies in the middle and lower crust,while none were found in the western region.These differences indicate that the Taihang Mountain gravity anomaly belt is a belt with a abrupt change of lithospheric thickness and lithological composition.According to the Pm waveform,it can be deduced that the Moho in the eastern region is not a sharp discontinuity,but a complex transitional zone.From a preliminary analysis,it is found that the geothermal mechanical-chemical erosion could be the main mechanism causing the thinning and destruction of the lithosphere beneath the eastern side of Taihang Mountain.In addition,subduction of the Pacific Plate is an important factor which changes the properties of the lithospheric mantle of the North China Craton.

Pipe Flow and Wall Turbulence Using a Modified Navier-Stokes Equation

We use a derived incompressible modified Navier-Stokes equation to model pipe flow and wall turbulence. We reproduce the observed flattened paraboloid velocity profiles of turbulence that cannot be obtained directly using standard incompressible Navier-Stokes equation. The solutions found are in harmony with multi-valued velocity fields as a definition of turbulence. Repeating the procedure for the flow of turbulent fluid between two parallel flat plates we find similar flattened velocity profiles. We extend the analysis to the turbulent flow along a single wall and compare the results with experimental data and the established controversial yon Karman logarithmic law of the wall.