LAS词法及语法分析器自动生成工具

LAS是在VAX/VMS操作系统上用Ada语言开发的词法分析器和语法分析器的自动生成工具。词法分析器由词法执行程序和LAS根据词法规则说明文件生成的词法树组成,语法分析器由语法执行程序和LAS根据语法规则说明BNF范式生成的状态序列集组成,在BNF范式中插入语义标志,就可以在语法分析器分析到该语义标志时,使控制转入用户提供的语义处理程序。     

故障诊断神经网络系统的专家知识表达方法

通过介绍其它故障诊断技术存在的问题，研究了故障诊断神经网络系统，提出了两种故障诊断神经网络的专家知识表达方法，并将其应用于飞行器液压动力系统的故障诊断，仿真结果表明：提出的方法是正确可行的，并且专家知识表达方法对诊断结果有很大影响，该方法可推广应用于其它动力系统的故障诊断     

SketchMapia: Qualitative Representations for the Alignment of Sketch and Metric Maps

More and more private citizens collect and publish environmental data via web-based geographic information systems. These systems face two challenges: The user interface must be intuitive and the processing of geographic information must account for cognitive impact. We propose to use sketch maps as the medium for interaction, because they reflect a person's spatial knowledge. Information from sketch maps is distorted, schematized, incomplete, and generalized and metric maps are not. This article employs qualitative representations for the alignment of sketch and metric maps. We suggest a set of cognitively oriented aspects in sketch maps stably computed by people and evaluate qualitative representations to formalize these aspects. This allows us to align and integrate geographic information from sketch maps.     

Wavelet modelling in support of IRI

The slant total electron content (STEC) of the ionosphere is defined as the integral of the electron density along the ray-path of the signal between the transmitter and the receiver. So-called geometry free GPS measurements provide information on the electron density, which is basically a four-dimensional function depending on spatial position and time. Since ground-based measurements are not very sensitive to the vertical structure within the atmosphere, the ionosphere is often represented by a spherical layer, where all electrons are concentrated. Then the STEC is transformed into the vertical total electron content (VTEC), which is a three-dimensional function depending on longitude, latitude and time.In our approach, we decompose an ionospheric function, i.e. the electron density or the VTEC, into a reference part computed from a given model like the International Reference Ionosphere (IRI) and an unknown correction term expanded in a multi-dimensional series in terms of localizing base functions. The corresponding series coefficients are calculable from GPS measurements applying parameter estimation procedures. Since the GPS receivers are located rather unbalanced, finer structures are modelable just in regions with a sufficient number of observation sites. Due to the localizing feature of B-spline functions we apply a tensor product spline expansion to model the correction term regionally. Furthermore, the multi-resolution representation derived from wavelet analysis allows monitoring the ionosphere at different resolutions levels. We demonstrate the advantages of this procedure by representing a simulated VTEC data set over South America.     

The Influence of Geometrical and Nongeometrical Features on the Use of the Lexical Concepts NEAR and FAR in English and Finnish

Abstract

This paper investigates the impact of geometrical and nongeometrical features on the use of the lexical concepts NEAR and FAR in English and Finnish. Participants' acceptability ratings for these concepts demonstrate that a bar in between a Figure and a Ground acts as a scale-setting object but not as a distance enhancing barrier, shows that the influence of the geometrical feature Figure–Ground distance exceeds the influence of several nongeometrical features, but most of all reveals that language specific lexical properties associated with NEAR and FAR predict language dependent effects for functional relatedness in interaction with Figure–Ground distance and bar presence.     

Regional 4-D modeling of the ionospheric electron density

The knowledge of the electron density is the key point in correcting ionospheric delays of electromagnetic measurements and in studying the ionosphere. During the last decade GNSS, in particular GPS, has become a promising tool for monitoring the total electron content (TEC), i.e., the integral of the electron density along the ray-path between the transmitting satellite and the receiver. Hence, geometry-free GNSS measurements provide informations on the electron density, which is basically a four-dimensional function depending on spatial position and time. In addition, these GNSS measurements can be combined with other available data including nadir, over-ocean TEC observations from dual-frequency radar altimetry (T/P, JASON, ENVISAT), and TECs from GPS-LEO occultation systems (e.g., FORMOSAT-3/COSMIC, CHAMP) with heterogeneous sampling and accuracy.     

基于匹配追踪算法的波达方向估计方法

利用辐射源到达方向的稀疏特性,结合最大似然原理提出了一种基于匹配追踪的波达方向估计算法,该算法具有比常用的波束成形和子空间类波达方向估计算法更优越的性能:在给出辐射源到达方向的同时给出对应的幅度输出;不要求辐射源数目的先验知识,无需预处理,且不受来自不同辐射源的信号相关性的影响;在低信噪比和小快拍数下仍具有较好的分辨特性。仿真结果验证了该算法的有效性。     

飞行器参数化几何建模方法研究

高超声速飞行器的概念设计阶段通常要综合考虑气动力、气动热、飞行弹道、推进系统、结构和控制等多个学科的设计因素,希望通过权衡各个学科得到一个综合性能最佳的设计,即多学科设计优化结果.参数化几何建模是优化设计的基础,本文开展飞行器参数化几何建模的方法研究,利用二次曲线方法与基于类型函数和形状函数的方法,分别进行了两种飞行器几何外形的建模,并进行了初步的气动力计算.通过分析两种建模方法的特点,比较了两种方法在不同情况下的优缺点,提出了在飞行器概念设计阶段几何建模方法的一般选取建议.通过等弧度、等弧长的划分原则,完善了基于类型函数和形状函数方法所生成的表面网格质量.     

表面触觉再现技术现状和评估方法

表面触觉再现技术可通过裸指触摸屏幕来感知物体特性,在多媒体终端实现高效自然的交互,具有巨大的研究价值,因而得到国内外研究学者的广泛关注。然而,现有研究多集中于力觉交互设备,未对表面触觉再现设备进行系统分析,且对设备的各项性能评价过于主观,未给出客观可信的表面触觉再现技术评估标准。首先,在充分研究现有表面触觉再现技术的基础上,重点对近十年表面触觉再现技术进行补充和完善。将表面触觉再现设备分为振动式、压力式、压膜式、静电力式和电刺激式,重点从工作原理、装置构成和性能指标等方面对典型设备进行详细分析和介绍,总结设备在触觉表达方面存在的优缺点。然后,针对现有评价方式过于粗糙和主观的问题,提出一种表面触觉再现技术的评估方法。通过制造难度、工作区间等7种评价指标全面评价设备的性能,采用专家打分法和层次分析法获得振动式、压力式、压膜式、静电力式4种设备在每种评价指标下的权重,并对4种设备在多媒体终端应用中的性能优劣进行排序,为不同领域下选择和评价表面触觉再现设备提供参考。最后,总结现有设备的不足,讨论其未来的研究和改进方向。