The Marsquake Service: Securing Daily Analysis of SEIS Data and Building the Martian Seismicity Catalogue for InSight

Space Science Reviews - In recent decades, volcanic and cryovolcanic activity on moons within the Solar System has been recognised as an important source of cosmic dust. Two moons, Jupiter’s...     

Speech Data Rate Reduction Part I: Applicability of Modern Estimation Theory

Efficient coding of continuous speech signals for digital representation has attracted much interest in recent years. The underlying aim of efficient coding methods is to reduce the channel capacity required to represent a signal to meet a specific reconstruction fidelity criterion. To achieve this objective, modern speech data compression techniques rely on two very similar procedures. One procedure uses predictive deconvolution which subtracts from the current signal value that portion which can be predicted from its past and thus removes redundancy in the speech by removing sequential correlation. The signal thus requires fewer bits for equivalent quantization error. The second procedure involves identification of a complete mathematical model of the speech producing mechanism. This involves determination of the characteristics of the source that drives this transfer function. Data reduction is again achieved since the rate of change of the parameters of the speech model is much smaller than the rate of change of the speech waveform. This paper develops these data reduction procedures in terms of modern estimation theory, specifically a Kalman filter model, and illustrates the utility of this model as an analysis tool by means of an example based on a uniform tube which provides a qualitative assessment of the potential of the technique for application to real speech signals.     

金属增材制造数据处理与工艺规划研究综述

金属增材制造数据处理与工艺规划是金属增材制造软件系统的核心,涵盖了金属支撑结构设计、模型切片以及路径规划等内容,决定着最终金属零部件的产品性能.从金属增材制造模型前处理出发,较为全面地概述了与之相关的多类型支撑设计和新型支撑优化等数据处理内容,针对金属增材制造数据处理中模型切片这一关键环节,分别从平面切片、自适应切片和...     

The electrical Environment of the Earth's Atmosphere: A Review

The study of the electrical environment of the Earth's atmosphere has rapidly advanced during the past century. Great strides have been made towards the understanding of lightning and thunderstorms and in relating them to the global electric circuit. The electromagnetic fields and currents connect different parts of the Earth's environment, and any type of perturbation in one region affects another region. Starting from the traditional views in which the electrodynamics of one region has been studied in isolation from the neighboring regions, the modern theory of the global electrical circuit has been discussed briefly. Interconnection and electrodynamic coupling of various regions of the Earth's environment can be easily studied by using the global electric circuit model. Deficiencies in the model and the possibility of improvement in it have been suggested. Application of the global electric circuit model to the understanding of the Earth's changes of climate has been indicated.     

面向工程数据集导管工艺性批量审查技术研究

在飞机MBD数模中导管数量大,人工进行导管工艺性审查工作繁琐、效率低且容易出错.针对面向工程数据集导管工艺性审查问题,利用计算机批量处理的优势,通过自动检索、自动识别和数据库技术建立导管工艺性批量审查平台.实现导管数模的弯曲半径与直线段距离合理性、导管规格是否存在等工艺性检查,从而判断导管设计是否合理,预先发现导管设计存在的问题,避免对后续生产造成麻烦,降低了生产成本,提高了生产效率.该导管工艺性批量审查平台系统可以提高工艺审查效率数十倍,同时保证导管工艺性审查的准确性.     

Solar Forcing of Climate. 2: Evidence from the Past

The nature of the climatic response to solar forcing and its geographical coherence is reviewed. This information is of direct relevance for evaluating solar forcing mechanisms and validating climate models. Interpretation of Sun-climate relationships is hampered by difficulties in (1) translating proxy records into quantitative climate parameters (2) obtaining accurate age assessments (3) elucidating spatial patterns and relationships (4) separating solar forcing from other forcing mechanisms (5) lacking physical understanding of the solar forcing mechanisms. This often limits assessment of past solar forcing of climate to identification of correlations between environmental change and solar variability. The noisy character and often insufficient temporal resolution of proxy records often exclude the detection of high frequency decadal and bi-decadal cycles. However, on multi-decadal and longer time scales, notably the ∼90 years Gleisberg, and ∼200 years Suess cycles in the ¹⁰Be and ¹⁴C proxy records of solar activity are also well presented in the environmental proxy records. The additional ∼1500 years Bond cycle may result from interference between centennial-band solar cycles. Proxy evidence for Sun-climate relations is hardly present for Africa, South America and the marine realm; probably more due to a lack of information than a lack of response to solar forcing. At low latitudes, equatorward movement of the ITCZ (upward component of the Hadley cell) occurs upon a decrease in solar activity, explaining humidity changes for (1) Mesoamerica and adjacent North and South American regions and (2) East Africa and the Indian and Chinese Monsoon systems. At middle latitudes equatorward movement of the zonal circulation during solar minima probably (co-)induces wet and cool episodes in Western Europe, and Terra del Fuego as well as humidity changes in Southern Africa, Australia, New Zealand and the Mediterranean. The polar regions seem to expand during solar minima which, at least for the northern hemisphere is evident in southward extension of the Atlantic ice cover. The forcing-induced migration of climate regimes implies that solar forcing induces a non linear response at a given location. This complicates the assessment of Sun-climate relations and calls for nonlinear analysis of multiple long and high resolution records at regional scale. Unfortunately nonlinear Sun-climate analysis is still a largely barren field, despite the fact that major global climate configurations (e.g. the ENSO and AO) follow nonlinear dynamics. The strength of solar forcing relative to other forcings (e.g. volcanism, ocean circulation patterns, tides, and geomagnetism) is another source of dynamic responses. Notably the climatic effects of tides and geomagnetism are hitherto largely enigmatic. Few but well-dated studies suggest almost instantaneous, climatic deteriorations in response to rapid decreases in solar activity. Such early responses put severe limits to the solar forcing mechanisms and the extent of this phenomenon should be a key issue for future Sun-climate studies.     

Global Response of Martian Plasma Environment to an Interplanetary Structure: From Ena and Plasma Observations at Mars

As a part of the global plasma environment study of Mars and its response to the solar wind, we have analyzed a peculiar case of the subsolar energetic neutral atom (ENA) jet observed on June 7, 2004 by the Neutral Particle Detector (NPD) on board the Mars Express satellite. The “subsolar ENA jet” is generated by the interaction between the solar wind and the Martian exosphere, and is one of the most intense sources of ENA flux observed in the vicinity of Mars. On June 7, 2004 (orbit 485 of Mars Express), the NPD observed a very intense subsolar ENA jet, which then abruptly decreased within ∼10 sec followed by quasi-periodic (∼1 min) flux variations. Simultaneously, the plasma sensors detected a solar wind structure, which was most likely an interplanetary shock surface. The abrupt decrease of the ENA flux and the quasi-periodic flux variations can be understood in the framework of the global response of the Martian plasma obstacle to the interplanetary shock. The generation region of the subsolar ENA jet was pushed towards the planet by the interplanetary shock; and therefore, Mars Express went out of the ENA jet region. Associated global vibrations of the Martian plasma obstacle may have been the cause of the quasi-periodic flux variations of the ENA flux at the spacecraft location.     

Tools of Kinematics: A Crital Review

A review of the basic tools of kinematics widely used by aerospace engineers is presented. Two different approaches are discussed. One is the familiar "vectorial mechanics," while the other is called the "variational method." It is indicated that either approach should produce the same set of motion equations for the dynamical system considered.     

Sources of Solar Wind at Solar Minimum: Constraints from Composition Data

In this discussion of observational constraints on the source regions and acceleration processes of solar wind, we will focus on the ionic composition of the solar wind and the distribution of charge states of heavy elements such as oxygen and iron. We first focus on the now well-known bi-modal nature of solar wind, which dominates the heliosphere at solar minimum: Compositionally cool solar wind from polar coronal holes over-expands, filling a much larger solid angle than the coronal holes on the Sun. We use a series of remote and in-situ characteristics to derive a global geometric expansion factor of?～5. Slower, streamer-associated wind is located near the heliospheric current sheet with a width of 10–20°, but in a well-defined band with a geometrically small transition width. We then compute charge states under the assumption of thermal electron distributions and temperature, velocity, and density profiles predicted by a recent solar wind model, and conclude that the solar wind originates from a hot source at around 1 million?K, characteristic of the closed corona.     

An Alternate Approach to the Prediction of Polynomial Signals in Noise from Discrete Data

When the problem of predicting the past, present, or future value of a polynomial signal or any of its derivatives is considered, where the signal is in white Gaussian noise, the standard approach has been to minimize mean-square-error with constraints by use of Lagrange multipliers. In this paper an alternate approach is described, using results of Rao and Bhattacharyya from the statistical literature, which reduce the specified prediction problem to a simple one requiring no formal minimizations and no use of Lagrange multipliers. It further has the advantage of yielding the covariances between estimates of the polynomial and its derivates. Useful engineering formulas for smoothing and prediction are developed in the main part of the paper. These include both filter and covariance expressions. A tutorial discussion of the theory is given in two appendixes.     

应用软件中对ODBC数据源的配置

文章论述了在客户使用端开发工具开发数据库软件的过程中，使用ODBC数据接口对各种常用数据源进行操作的问题，并对此提出了两种有效的解决方法，讨论了具体的实施方案。     

A Review of Low Frequency Electromagnetic Wave Phenomena Related to Tropospheric-Ionospheric Coupling Mechanisms

Investigation of coupling mechanisms between the troposphere and the ionosphere requires a multidisciplinary approach involving several branches of atmospheric sciences, from meteorology, atmospheric chemistry, and fulminology to aeronomy, plasma physics, and space weather. In this work, we review low frequency electromagnetic wave observations in the Earth-ionosphere cavity from a troposphere-ionosphere coupling perspective. We discuss electromagnetic wave generation, propagation, and resonance phenomena, considering atmospheric, ionospheric and magnetospheric sources, from lightning and transient luminous events at low altitude to Alfvén waves and particle precipitation related to solar and magnetospheric processes. We review ionospheric processes as well as surface and space weather phenomena that drive the coupling between the troposphere and the ionosphere. Effects of aerosols, water vapor distribution, thermodynamic parameters, and cloud charge separation and electrification processes on atmospheric electricity and electromagnetic waves are reviewed. Regarding the role of the lower boundary of the cavity, we review transient surface phenomena, including seismic activity, earthquakes, volcanic processes and dust electrification. The role of surface perturbations and atmospheric gravity waves in ionospheric dynamics is also briefly addressed. We summarize analytical and numerical tools and techniques to model low frequency electromagnetic wave propagation and to solve inverse problems and outline in a final section a few challenging subjects that are important to advance our understanding of tropospheric-ionospheric coupling.     

Venus: The Atmosphere,Climate, Surface,Interior and Near-Space Environment of an Earth-Like Planet

This is a review of current knowledge about Earth’s nearest planetary neighbour and near twin, Venus. Such knowledge has recently been extended by the European Venus Express and the Japanese Akatsuki spacecraft in orbit around the planet; these missions and their achievements are concisely described in the first part of the review, along with a summary of previous Venus observations. The scientific discussions which follow are divided into three main sections: on the surface and interior; the atmosphere and climate; and the thermosphere, exosphere and magnetosphere. These reports are intended to provide an overview for the general reader, and also an introduction to the more detailed topical surveys in the following articles in this issue, where full references to original material may be found.     

应用数字滤波技术处理直升机地面靶试数据的研究

本文介绍在直升机地面靶试数据处理中应用FIR数字滤波器的设计和算术平均值滤波方法,通过合理选择滤波方法和巧妙设计有效抑制干扰信号,保证了试验数据的精度.     

国企改革:从搞活国有企业转向盘活国有资产

国有企业改革,特别是国有产权改革,是我国深化经济体制改革进程中的难点问题.文章认为,以往的改革主要注重于搞活国有企业,违背了市场经济中决定企业成活率的大数定理,因而注定无法获得较高的绩效.今后要以盘活国有资产为出发点,为此,必须厘清一些基本观念,不能将国有资产流失和国有资产缩水划等号;资本的社会化可以解决困扰国企的剩余索取权问题;资本的社会化可以有效解决国企的内部治理结构问题;公有制的实现形式应该是混合所有制;社会主义公有制的优越性,主要表现在政府保证社会福利提高的层面,政府对社会控制力的加强主要体现在税收领域.     

镍基单晶高温合金孔洞缺陷数值模拟与控制方法研究进展

镍基单晶高温合金是高性能航空发动机涡轮叶片的主要材料,其孔洞缺陷是影响涡轮叶片服役可靠性与耐久性的关键因素。常规试验分析手段往往只能获得定性规律,而多尺度数值模拟技术和三维形态表征技术的快速发展,为研究镍基单晶高温合金孔洞形成和演化机理以及精确预测孔洞缺陷的几何特征、分布方式和含量提供了条件。总结了国内外铸态孔洞、固溶孔洞和服役中孔洞缺陷形成与演化的数值模拟研究进展,评述了目前孔洞缺陷预测模型的使用条件和局限性,指出了从铸造到服役全流程孔洞演化与预测精确化、定量化研究所存在的问题,并展望了镍基单晶高温合金孔洞缺陷多尺度数值模拟技术的发展方向。