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1.
美国选区划分的研究进展 总被引：2，自引：1，他引：1
选区划分是选举地理学的重要研究内容,选区划分是否科学合理,直接影响选举结果。本文从选区研究主题、选区划分原则等方面对美国选区划分的相关文献进行梳理与总结,发现美国选举选区划分的研究主要聚焦于以下议题：选区划分与社会分裂、选区划分与分区不公、选区划分与司法介入,以及选区划分与选票/席位转化曲线。在分区原则上,美国选区主要立足于人口、地理和政治三大原则进行划分,具体执行中采用邻近性、紧凑性、人口同等、种族平等、尊重行政边界、尊重利益社区、保护在任者/保留旧选区核心等原则。借鉴美国选区划分的研究进展,本文建议地理学者未来应在精准预测选举结果、追踪世界民主选举的动态和促进选区划分的公正性等方面进一步深入地展开理论探讨与政策研究。 相似文献
2.
In this paper a criterion is described for the construction of experimental designs for the evaluation ofcalibration models in analytical chemistry.The proposed criterion seeks a compromise between theD-optimal designs for estimating the parameters of different polynomial models.A computer algorithmis presented for a sequential construction of experimental designs using the optimality criterion.Theperformance of the optimality criterion and the computer algorithm is elaborated for the problem ofdiscrimination between a first-to a third-degree polynomial for the calibration of analytical methods.Anexperimental design consisting of replicate measurements at five distinct levels equally spaced over thecalibration range proved a good solution. 相似文献
3.
北极航线地缘政治的规范博弈机制分析 总被引：2，自引：0，他引：2
北极航线地缘政治权益博弈问题因为北冰洋的融化预期加快,而变得愈来愈重要。规范能够为解决北极航线地缘政治博弈提供一种有用的约束。在阐述北极航线地缘政治的概念、博弈与地缘政治的关系以及北极航线地缘政治权益现阶段争斗和未来趋势的基础上,描述了各种支持规范的机制,其中包括元规范、成员身份、支配、国际社会认同、威慑、内化及法律等,以期能为中国的北极航线地缘政治权益博弈提供帮助。 相似文献
4.
居民的购房选择是对居住区位进行选择的复杂过程,其实质是居住空间的个人行为决策问题。在调研工作基础上,论文分析并构建了居民购房选择决策评价指标体系,以北京市为实验区应用GIS制作居住适宜性基础准则(指标)地图。研究一种可以适应购房者差异化的购房需求与偏好的购房地理空间决策方法,通过层次分析法提取购房个体的偏好信息,确定个人准则权重。采用次序加权平均算法(Ordered Weighted Averaging,OWA)针对个人准则权重计算个人次序权重,结合二者对居住适宜性基础准则地图进行集结,计算多种决策风险下的个人居住适宜性准则地图,对意向住房进行分析评价,动态生成相应决策方案,为购房者提供购房决策支持,减少主观意愿与客观环境带来的决策风险。最后通过一个实验对以上方法进行实现。 相似文献
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陕北黄河中游淤地坝拦沙功能失效的判断标准 总被引：7，自引：0，他引：7
利用2011 年第一次全国水利普查中4157 座骨干坝数据、1989 年陕北淤地坝调查中1640座中小坝数据,分别计算了1950-2011 年期间骨干坝、1956-1989 年期间中小坝的逐年平均淤积比例,得到截至2011 年,1980 年前修建骨干坝的平均淤积比例基本稳定,平均值为0.77,1980 年后开始逐渐下降;截至1989 年,1980 年前修建中小坝的平均淤积比例基本稳定,平均值为0.88,1980 年后开始逐渐下降的变化趋势,确定平均淤积比例0.77、0.88 分别为骨干坝、中小坝拦沙能力失效的判断标准。利用陕北淤地坝调查数据计算得到的骨干坝拦沙功能失效判断一致;在无定河、延河流域,水文站输沙数据的变化趋势与淤地坝是否拦沙显著相关。最后从淤地坝工程结构的角度,剖析了排水排沙位置的改变是判断标准形成的原因。 相似文献
6.
基于遗传算法的理想区间法在洪水灾情评价中的应用 总被引：8，自引：0，他引：8
洪水灾情评价的实质就是建立各洪水灾情评价指标与洪水灾情等级之间的非线性关系,目前在实际评价过程中反映这种关系的信息来源只有洪水灾情评价标准,而后者一般是以区间形式表示的。基于此,提出了基于加速遗传算法的改进理想区间法(AGAIIM)。AGAIIM直接由洪水灾情评价标准样本数据驱动,把利用全部隶属度值信息进行计算的洪水灾情相对等级值作为洪水灾情的评价结果,可避免应用最大隶属度原则进行判断所可能造成的失真,提高了洪水灾情评价的精度。AGAIIM方法直观、简便、通用,可在具有评价标准或具有已知评价指标值及其等级值样本系列的系统综合评价中推广应用。 相似文献
7.
This work evaluates objective functions for multiresponse non-linear modeling using computersimulations.Tests are performed under a variety of signal-to-noise ratios and noise variance-covariancestructures.The standard error of prediction for the model parameters,computed from 50 trials,is usedfor performance comparisons.The full rank and rank-deficient problems are considered.For the fullrank problem one model was investigated,a first-order two-step consecutive reaction model,and twoobjective functions were considered,the total sum of squares and the determinant criterion.Nodistinction could be made between the two objective functions for this model.For the rank-deficient case two models were investigated,a first-order two-step consecutive reactionas in the full rank case,and a pH titration model described by the Henderson-Hasselbalch equation.Three objective functions were investigated for the rank-deficient case,the total sum of squares,aweighted total sum of squares and the determinant criterion.The total sum of squares was found toperform poorly under all conditions tested compared to the weighted total sum of squares and thedeterminant criterion.The determinant criterion was found to perform much better than the other twocriteria when the data have a combination of a low signal-to-noise ratio and high variance-covariancenoise structure. 相似文献
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根据区内所拥有的特点:产业结构处于初级变动阶段,自然资源丰富,以及大量处于隐蔽失业的农业剩余劳动力的优势还未发挥,提出了目前本区选择主导产业部门的三个准则,即:资源开发准则、相关效果准则和劳动就业准则。由此判定本区主导产业所得出的结论是:水力发电工业、矿产资源开发业(原材料工业)、农林土特产品加工工业,应成为区内的主导产业部门。 相似文献
10.
城市地物具有多尺度分布特点,尺度鉴别与确定是分类的前提。提出改进的面积相对差指标,根据城市植被的分布状态确定最优分割尺度。采用面向对象方法,利用对象的光谱和空间信息对高空间分辨率影像进行植被分类。与基于像元的传统光谱分类方法和单尺度分类结果比较,最优分割尺度的鉴别和面向对象的分类方法分类精度较高,6种城市植被的分类总精度达85.5%,Kappa系数为0.83;同时有效抑制了光谱数据分类中存在的地物破碎问题。 相似文献
11.
《生态环境状况评价技术规范(试行)》中若干值得商榷的问题 总被引：2，自引：0，他引：2
分析了<生态环境状况评价技术规范(试行)>(简称<规范>)中指标使用、计算方法和应用范围等值得商榷的问题.认为<规范>中的湿地除了应包括天然湿地外还应包含人工湿地,同时应将湿地作为水网的重要构成;未利用地中的部分指标在国家尺度上不具有代表性:将各类水网指标直接相加而不进行权重分配有失客观;归一化方法使用上没有统一.<规范>对于同一区域生态环境状况的动态变化评价没有意义,且不适用于城市内设区的区级行政单位生态环境状况评价.建议根据各区域生态环境特征建立分区的评价指标体系,指标应具有很强的代表性、可比性和操作性,在指数计算中应对各指数及其下设指标分别进行权重分配,各指数均应进行归一化,同一区域不同时期各指标的归一化系数应保持恒定. 相似文献
12.
盐湖沉积不仅是一种重要化工矿产沉积建造 ,还是一种重要的含油气沉积组合 ,其中常常蕴藏有十分丰富的油气资源。但是 ,此类盆地的层序地层学研究起步较晚 ,尤其是对于陆相盐湖盆地更是如此 ,其关键在于国内外的专家学者对盐湖层序的划分与特征了解较少 ,层序地层划分标准不统一。在充分吸收和消化前人研究成果的基础上 ,从当今的盐湖形成理论出发 ,以潜江古盐湖为研究对象 ,讨论了盐湖盆地沉积的层序地层划分标准 ,及层序地层单元基本特征。认为从层序地层的基本控制因素———可容纳空间 (Accommo dationSpace)出发 ,可将盐岩沉积作为盆地水体浓缩的产物———水面下降阶段的沉积代表 ,从而建立起盐湖的层序地层划分标准。 相似文献
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风沙现象的相似问题 总被引：3，自引：2，他引：1
风沙现象室内模型实验要做到与自然界的风沙现象完全相似是很难实现。第一,要做到模型与实物几何相似很困难,如气流中沙粒按模型缩尺缩小,其在与流中物理本质将完全改变;第二,满足相似的判据太复杂,技术上难以实现。如要同时满足两个最重要的判据雷诺数(Re)和福洛德数(Fr),就需要改变运动介质或改变地球的重大加速度,这在技术上实现很困难,故只能采用近似相似的方法,只考虑一个较重要的相似判据。风沙问题可以分为无沙与有沙气流两大类。无沙气流研究沙粒或其他物质在风力作用下的稳定性问题时(如沙粒起动,大风吹翻火车货车等).应主要考虑Fr数相同。而在研究固定的物体在风力作用下的绕流问题时(如防护林防风效益).应主要考虑Re数相同。研究风沙流的问题就较为复杂,在可能情况下加以简化,如只测流场,由流场中的风速大小、分布推测沙的蚀积情况;或采用不同比尺的模型实验,用系列模型法外推原型的情况。 相似文献
15.
T. B. Yanovskaya 《Geophysical Journal International》1984,79(1):293-304
Summary. The Backus-Gilbert method has been extended to the estimation of the seismic wave velocity distribution in 2-D or 3-D inhomogeneous media from a finite set of travel-time data. The method may be applied to the inversion of body wave as well as surface wave data. The problem of determining a local average of the unknown velocity corrections may be reduced to a choice of a suitable δ-ness criterion for the averaging kernel. For 2-D and 3-D inhomogeneous media the simplest criterion is to minimize a sum of 'spreads' over all the coordinates. The use of this criterion requires the solution (the averaged velocity corrections) to be represented as a sum of functions, each of which depends only on one coordinate. This is a basic restriction of the method. In practice it is possible to achieve good agreement between the solution and a real velocity distribution by a reasonable choice of the coordinate system.
Numerical tests demonstrate the efficiency of the method. Some examples of the application of the method to the inversion of real seismological data for body and surface waves are given. 相似文献
Numerical tests demonstrate the efficiency of the method. Some examples of the application of the method to the inversion of real seismological data for body and surface waves are given. 相似文献
16.
M. Itonaga 《Geophysical Journal International》1997,128(2):451-458
A smoother realized by a one-pass method with a piecewise cubic polynomial and a modified Powell criterion is termed a PCP filter. Since its action is data-adaptive, the PCP filter is non-linear. Furthermore, this filler is also non-causal and in practice causes little phase shift in the output and/or residual data as long as the input data has no dominant components with frequencies within its transition band. An average amplitude response of the PCP filter for sinusoidal inputs is determined numerically for each value of the parameter μ, which appears in the modified Powell criterion and controls the smoothness in output of the filter. An objective criterion for the selection of μ in the practical application of the PCP filter is then obtained from this response. Furthermore, the cut-off frequency of the PCP filter is defined as the first frequency at which the attenuation of the average amplitude response becomes 3 dB. It is found that the cut-off frequency is a good measure of the smoothness in output of the PCP filter. This frequency decreases with increasing μ, meaning that the output of the PCP filter becomes smoother and the oscillations with longer periods can be separated as residuals as μ grows large. As μ increases, the average number of sample points between two adjacent knots becomes larger and the computational cost increases for data processing by the PCP filter. 相似文献
17.
弹性应变能的积聚是产生岩爆的内因,但岩爆的发生往往具有外界因素的扰动．据些首先分析了动力扰动对岩爆触发的机理,然后结合某水电站引水隧洞岩爆实例,利用复反应分析原理计算了动力扰动过程对岩爆的影响． 相似文献
18.
We examine the distinguishing features and problems associated with the development of the system of regional indices for landscape diversity as the sustainable development criterion for poorly developed regions of Russia (as exemplified by Khabarovsk krai). 相似文献
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Kalyn M. Rossiter David W. S. Wong Paul L. Delamater 《The Professional geographer》2013,65(4):609-623
The process of congressional redistricting, delineating boundaries for districts in which voters elect members to the U.S. House of Representatives, has always been an expensive and controversial process. Congressional districts (CDs) are redrawn due to changes in population reflected by the decennial census to ensure equal representation. Laws and regulations literature identifies eight criteria that may be considered when determining the boundaries of CDs and this article focuses on one of those criteria, maintaining communities of interest (COIs). This criterion requires states to preserve these boundaries when delineating CDs but fails to define a COI. This research proposes and evaluates two approaches to define a COI and examines the extent to which this criterion has been adhered to. One definition uses Thiessen polygons and census designated places to delineate COIs based on known cultural places, whereas the other definition uses cluster analysis to group together people with similar sociodemographic characteristics. The results show that the two definitions are feasible for defining a COI. Furthermore, the states largely maintain the COI boundaries within their CDs by only splitting, at most, 17.1 percent of the COIs defined. Existing literature shows that maintaining COIs within CDs leads to higher voter participation and engagement, as well as better representation. The results show that if either definition was adopted, states could comply with this criterion with relative ease. Furthermore, a standard definition could help reduce the cost and controversy surrounding the redistricting process. 相似文献