城市区位条件与企业区位动态研究

随着新新经济地理理论的发展,企业异质性的研究逐渐受到重视,不同效率企业的区位选择被认为是造成城市生产效率差异的重要原因。验证企业区位选择对城市生产效率的影响,以及探讨企业区位选择的城市影响要素是研究的关键问题。沿用Baldwin和Melitz等学者的研究思路,从企业区位主动选择与被动选择的视角,理解中国城市生产效率的差异及其变化,分析企业区位自选择效应的空间差异。在此基础上,采用2002-2007年的规模以上工业企业面板数据,通过建立基于企业进入、退出区位动态的回归模型,揭示企业区位自选择效应的作用机制和城市影响因素。研究发现：企业区位自选择效应确实存在,不同效率企业的主动选择和被动选择都会影响城市的生产效率。生产率较高的工业企业倾向于选择科技研发水平高、市场潜力大、产业相对集聚的城市,生产率较低的工业企业更容易因城市高昂的要素成本和激烈的行业竞争,尤其是同行企业竞争而被挤出。此外,政府的政策优惠可以吸引高效率企业进入,但这种政策倾斜也会加剧其他企业的退出。因此,提高科技水平、扩大市场规模、促进产业集聚、合理运用政策调控是提高城市竞争力的关键。     

Sources of uncertainty in estimating stream solute export from headwater catchments at three sites

Uncertainty in the estimation of hydrologic export of solutes has never been fully evaluated at the scale of a small‐watershed ecosystem. We used data from the Gomadansan Experimental Forest, Japan, Hubbard Brook Experimental Forest, USA, and Coweeta Hydrologic Laboratory, USA, to evaluate many sources of uncertainty, including the precision and accuracy of measurements, selection of models, and spatial and temporal variation. Uncertainty in the analysis of stream chemistry samples was generally small but could be large in relative terms for solutes near detection limits, as is common for ammonium and phosphate in forested catchments. Instantaneous flow deviated from the theoretical curve relating height to discharge by up to 10% at Hubbard Brook, but the resulting corrections to the theoretical curve generally amounted to <0.5% of annual flows. Calibrations were limited to low flows; uncertainties at high flows were not evaluated because of the difficulties in performing calibrations during events. However, high flows likely contribute more uncertainty to annual flows because of the greater volume of water that is exported during these events. Uncertainty in catchment area was as much as 5%, based on a comparison of digital elevation maps with ground surveys. Three different interpolation methods are used at the three sites to combine periodic chemistry samples with streamflow to calculate fluxes. The three methods differed by <5% in annual export calculations for calcium, but up to 12% for nitrate exports, when applied to a stream at Hubbard Brook for 1997–2008; nitrate has higher weekly variation at this site. Natural variation was larger than most other sources of uncertainty. Specifically, coefficients of variation across streams or across years, within site, for runoff and weighted annual concentrations of calcium, magnesium, potassium, sodium, sulphate, chloride, and silicate ranged from 5 to 50% and were even higher for nitrate. Uncertainty analysis can be used to guide efforts to improve confidence in estimated stream fluxes and also to optimize design of monitoring programmes. © 2014 The Authors. Hydrological Processes published John Wiley & Sons, Ltd.     

云南省地震应急短波通信系统建设及应用

介绍了云南省地震应急短波通信系统的建设情况、实际工作频率的选择依据,并以景谷6.6级地震为例详细说明了该系统的应用模式。地震应急短波通信系统经历了多次地震应急的考验,在震区通信中断时确实能够提供最后的通信保障,达到了预期的设计目标。     

McMurdo sound hydrological observations, 1972–73

Hydrological data, including current observations, from a line of five stations across seasonal ice in McMurdo Sound, Antarctica, are presented. The observations, which were made during the 1972–73 summer, gave evidence for a net flux of approximately 0.4 × 10⁶m³.s^‐1 flowing towards the south to pass under the Ross Ice Shelf. There was a small northward flux (0.04 × 10⁶m³.s^‐1) on the western side of the sound, but over most of the width the flow was to the south.

Diurnal tidal currents, which were analysed in terms of K1, P1, and O1 components, were superposed on the drift currents.

Temperature and salinity measurements revealed signs of surface water dilution and warming down to 200 m in the region of southerly drift. Temperatures associated with the northerly drift on the western side of the section were close to freezing at all depths. This water can be identified as coming from under the Ross Ice Shelf.     

精密单点定位的一种低动态解法

采用自适应选权滤波法,对低动态精密单点定位的解算方法进行研究,并编写了精密单点定位程序。通过合理选择自适应因子参数,对船载动态GPS测量数据进行了事后精密单点定位处理。结果表明:相对于经典卡尔曼滤波方法,采用自适应选权滤波法可大大提高低动态精密单点定位解的精度,X、Y、Z三个方向的RMS分别提高了79.9%、69.7%和92.0%。     

Assessing multiple mating and reproductive skew in three species of clinid fishes (Blenniiformes: Clinidae: Clinini), in reference to multiple mating in viviparous teleosts

This study investigated multiple mating in three species of intertidal klipfishes (family Clinidae): super klipfish Clinus superciliosus, bluntnose klipfish Clinus cottoides, and nosestripe klipfish Muraenoclinus dorsalis. These species display the rare reproductive mode of female vivipary with superfetation, a phenomenon where offspring at various stages of development are found within the female. Three or four microsatellite loci were used to genotype 25–30 adults of each species, as well as embryos of 131 C. superciliosus from six broods, 103 C. cottoides from six broods, and 63 M. dorsalis from five broods. The presence of multiple mating by females was assessed by maximum-likelihood sibship reconstruction implemented in the program COLONY, and the non-random distribution of reproductive success among individuals (reproductive skew) within broods was tested using the binomial skew index. Multiple mating by females was pervasive and observed in 83%, 100% and 80% of the broods of C. superciliosus, C. cottoides and M. dorsalis, respectively. The mean number of sires per brood was 4.3, 3.0 and 3.2, and, correspondingly, 5/5, 5/6 and 1/4 of multiply-sired broods showed significant reproductive skew in C. superciliosus, C. cottoides and M. dorsalis, respectively. The presence of pronounced reproductive skew may indicate post-copulatory processes taking place that bias paternity. We compared our results on multiple mating within the klipfish family, and with four other fish families that have vivipary with superfetation, and found the klipfish patterns were among those of live-bearing vertebrate groups with the highest average numbers of sires per brood.     

单视影像下的人脸快速三维重建

提出了一种单视影像下的人脸快速三维重建方案,能够对非可控条件下获取的单幅人脸图像进行有效、快速的三维重建。在三维人脸重建阶段,提出了一种特征动态选择策略,针对待重建人脸图像动态选择合适的2D-3D特征变换子空间,在保证执行效率的同时能显著提高三维人脸模型的重建精度。实验证明,本方法不仅简洁高效,而且对人脸姿态和光照变化具较好的鲁棒性,在WHU-3DFaceData数据库上取得了理想的重建效果。     

直升机应急机降模糊叠置选址模型

直升机凭借着其灵活的机动性能,在反恐演习,社会治安和抗震救灾等方面得到了广泛的应用。直升机的机动除了受地形制约外,受气象要素影响较大。分析了影响直升机机降的相关因素和多因子下的模糊叠置分析模型,并在Visual Studio 2008和ArcGIS Engine环境中对直升机应急机降选址原型系统进行了实现,分别对地形与风力、地形与能见度以及三者共同影响下的直升机应急机降选址进行了分析。该实验对顾及气象环境要素情况下的选址分析进行了探索,使分析结果更加准确、实用。     

Firewood consumption amongst poor inhabitants in a semiarid tropical forest: A case study from Piura,northern Peru

Semiarid forests are disappearing on a large scale and are considered to be the most endangered ecosystems in the lowland tropics. The deforestation rate in Peru is among the highest in Latin America and the Caribbean. Poor people are often more dependent on forest resources than those who are well off. However, little is known about poor people's use of forest resources or the effect of logging in semiarid forests. The article deals with household energy use and the source of firewood (bought or collected, either locally or over some distance) in two semiarid forests in Piura, northern Peru. The most used tree species and the vulnerability of the species are also examined in order to understand deforestation. Peru has introduced regulations on the use of forest resources and the article focuses on how these regulations are locally understood. The methodology includes questionnaires, recording local household practices, and in-depth interviews with local informants and both governmental and non-governmental organizations. The daily wood consumption rates per person were measured. The findings reveal that household economy is not the only factor affecting daily firewood consumption rate, but also climate, ecology, access to firewood, and traditions are contributing factors.