物流业发展对产业结构优化的实证分析 ——基于空间面板杜宾模型     

高秀丽  孟飞荣 《热带地理》2013,33(6):703-710

目前,我国正处于产业结构优化升级和实现经济发展方式转变的关键时期。物流业作为第三产业的重要组成部分,具有有效降低经济运行成本、提高运作效率和促进产业结构升级的作用。文章首先对省域产业结构合理化和产业结构高级化空间依赖性进行了检验。然后,基于我国1997―2010年30个省级面板数据,通过引入因变量空间滞后项和自变量空间滞后项,构建空间面板杜宾模型,从产业结构合理化和产业结构高级化2个方面分析物流业发展对产业结构优化的影响。研究结果表明：我国产业结构合理化和产业结构高级化存在着显著为正的空间溢出效应,东部、中部和西部地区存在着明显的空间差异;物流业的发展不仅能够显著促进当地产业结构合理化和产业结构高级化进程,而且对邻近地区产业结构优化具有正向的空间溢出效应。最后,文章有针对性地提出了政策建议。  相似文献   

Bedload transport measurements with impact plate geophones: comparison of sensor calibration in different gravel‐bed streams          下载免费PDF全文

Dieter Rickenmann  Jens M. Turowski  Bruno Fritschi  Carlos Wyss  Jonathan Laronne  Ronel Barzilai  Ian Reid  Andrea Kreisler  Johann Aigner  Hugo Seitz  Helmut Habersack 《地球表面变化过程与地形》2014,39(7):928-942

Indirect bedload transport measurements have been made with the Swiss plate geophone system in five gravel‐bed mountain streams. These geophone sensors record the motion of bedload particles transported over a steel plate mounted flush with the channel bed. To calibrate the geophone system, direct bedload transport measurements were undertaken simultaneously. At the Erlenbach in Switzerland, a moving‐basket sampler was used. At the Fischbach and Ruetz streams in Austria, a Helley–Smith type bedload sampler provided the calibration measurements. A Bunte‐type bedload trap was used at the Rofenache stream in Austria. At the Nahal Eshtemoa in Israel, Reid‐type slot bedload samplers were used. To characterize the response of the geophone signal to bedload particles impacting on the plate, geophone summary values were calculated from the raw signal and stored at one second intervals. The number of impulses, i.e. the number of peaks above a pre‐defined threshold value of the geophone output signal, correlated well with field measured gravel transport loads and was found to be a robust parameter. The relations of impulses to gravel transport loads were generally near‐linear, but the steepness of the calibration relations differed from site to site. By comparing the calibration measurements from the different field sites and utilizing insights gained during preliminary flume experiments, it has been possible to identify the main factors that are responsible for site specific differences in the calibration coefficient. The analysis of these calibration measurements indicates that the geophone signal also contains some information about the grain size distribution of bedload. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Bedload hysteresis in a glacier‐fed mountain river          下载免费PDF全文

Luca Mao  Andrea Dell'Agnese  Carolina Huincache  Michal Engel  Georg Niedrist  Francesco Comiti 《地球表面变化过程与地形》2014,39(7):964-976

Sediment transport during flood events often reveals hysteretic patterns because flow discharge can peak before (counterclockwise hysteresis) or after (clockwise hysteresis) the peak of bedload. Hysteresis in sediment transport has been used in the literature to infer the degree of sediment availability. Counterclockwise and clockwise hysteresis have been in fact interpreted as limited and unlimited sediment supply conditions, respectively. Hysteresis has been mainly explored for the case of suspended sediment transport, but it was rarely reported for bedload transport in mountain streams. This work focuses on the temporal variability of bedload transport in an alpine catchment (Saldur basin, 18.6 km², Italian Alps) where bedload transport was monitored by means of an acoustic pipe sensor which detects the acoustic vibrations induced by particles hitting a 0.5m‐long steel pipe. Runoff dynamics are dominated by snowmelt in late spring/early summer, mostly by glacier melt in late summer/early autumn, and by a combination of the snow and glacier melt in mid‐summer. The results indicate that hysteretic patterns during daily discharge fluctuations are predominantly clockwise during the snowmelt period, likely due to the ready availability of unpacked sediments within the channel or through bank erosion in the lower part of the basin. On the contrary, counterclockwise hysteresis tend to be more frequent during late glacier melting period, possibly due to the time lag needed for sediment provided by the glacial and peri‐glacial area to be transported to the monitoring section. However, intense rainfall events occurring during the glacier melt period generated predominantly clockwise hysteresis, thus indicating the activation of different sediment sources. These results indicate that runoff generation processes play a crucial role on sediment supply and temporal availability in mountain streams. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

测角网间接平差中近似坐标自动概算算法设计     

郭辉 《地理空间信息》2012,10(6):158-160,16

在对测角网进行平差计算时,网中未知点平面坐标的概算是一个关键问题。针对测角网的特点,设计了测角网近似坐标自动概算的算法,用实例验证了算法的正确性及可靠性,避免了繁琐的手工近似计算过程,提高了数据处理的效率。  相似文献   

Defense by association: Sponge‐eating fishes alter the small‐scale distribution of Caribbean reef sponges          下载免费PDF全文

Michael K. Wooster  Micah J. Marty  Joseph R. Pawlik 《Marine Ecology》2017,38(2)

Recent studies have demonstrated that sponge‐eating fishes alter the community of sponges on coral reefs across the Caribbean. Sponge species that lack chemical defenses but grow or reproduce faster than defended species are more abundant on reefs where sponge‐eating fishes have been removed by overfishing. Does predator‐removal have an effect on the distribution of sponges at smaller spatial scales? We conducted transect surveys of sponge species that are palatable to sponge predators in proximity to refuge organisms that are chemically or physically defended (fire coral, gorgonians, hard corals) on the heavily overfished reefs of Bocas del Toro, Panama, and a reef in the Florida Keys where sponge‐eating fishes are abundant. In Panama, palatable sponge species were not distributed in close association with refuge organisms, while in the Florida Keys, palatable sponge species were strongly associated with refuge organisms. The presence of fish predators alters the meter‐scale pattern of sponge distribution, and defense by association enhances biodiversity by allowing palatable sponges to persist on reefs where sponge‐eating fishes are abundant.  相似文献   

基于投入产出模型的大型活动对举办地的经济影响——以广交会为例   总被引：8，自引：1，他引：7  

罗秋菊  庞嘉文  靳文敏 《地理学报》2011,66(4):487-503

事件活动的经济影响评估是国外近20 年来的研究热点,然而近年来遭到很多质疑和争论,国内在该领域的理论和实证研究仍处于起步阶段。一年两届的广交会对举办城市具有持续的深远影响,是城市大型活动的典范。本研究以104 与105 届广交会为案例,采用问卷调查及深度访谈法收集广交会所有参与者的消费支出与结构,并运用投入产出模型评估广交会对广州市间接经济影响。结论表明城市定期举办的大型商务活动对举办地的许多产业部门具有很强的拉动效应,对当地经济产生明显的持续性的经济效应;一届广交会对广州市的直接与间接效应合计163.24 亿元,其中直接经济效应55.26 亿元,间接经济效应为107.98 亿元,直接与间接效应之比为1:1.95;2008 年104 届广交会的直接与间接效应总和占广州市全年GDP的1.98%;参与者对广州的经济拉动作用依次为采购商、参展企业、参展个人、承办方、交易团。此外,本文还特别就研究结论存有高估或低估倾向进行了探究。  相似文献   

Comparing Landslide Hazard Maps   总被引：18，自引：1，他引：17  

Van Westen  C. J.  Seijmonsbergen  A. C.  Mantovani  F. 《Natural Hazards》1999,20(2-3):137-158

The objective of the method explained in this paper isto obtain a better insight in the decision rulesapplied by geomorphologists in the direct mapping oflandslide hazard. This can be obtained by forcinggeomorphologists to specify for each unit (polygon) intheir hazard map the criteria that they used toclassify the unit as high, medium or low hazard. Whenthis is done systemically for an entire area, it ispossible to analyze those criteria statistically, andto evaluate whether they can be grouped into generaldecision rules, or whether these criteria arecompletely site specific. The same area in the Alpagoregion in Italy was mapped at 1 : 5000 scale by threeteams of experts individually. The different methodsare presented and the results are compared.  相似文献   

自然灾害的影响及间接经济损失评估方法   总被引：4，自引：2，他引：4  

吴吉东  李宁  温玉婷  胡爱军  崔维佳  张鹏 《地理科学进展》2009,28(6):877-885

灾害的损失受灾前经济发展水平、灾种差异、灾后恢复重建策略、灾害管理水平和灾害保险体系完善程度等复杂因素的影响,加上基础数据精度、获取难度和校验的不确定性,目前还没有有效的灾害间接经济损失评估方法。而已有间接经济损失评估方法存在不足：首先,评估对灾害间接经济损失的构成、时空维界定模糊;其次,评估模型假设太多往往偏离灾后实际经济状况;最后,模型对灾害扰动的动态影响机制考虑不足,往往忽视灾后经济系统的弹性和部门生产容量的动态变化特征。因此,在进行灾害损失评估时应注意灾害对经济影响的动态机理,结合不同灾害类型对经济影响的特点和当地的经济发展状况,合理设置相关参数,使模型更切合实际,从而更合理有效的评估灾害造成的间接损失。  相似文献   

产河豚毒素菌株的筛选、鉴定及透析培养          下载免费PDF全文

张宏宇  林涛  武斌  李增鹏  郭文斌  陈明谅 《应用海洋学学报》2023,42(2):210-217

河豚毒素(Tetrodotoxin, TTX)在镇静、镇痛、麻醉、戒毒等神经性疾病治疗方面效果显著且无致瘾性,因此具有极好的应用前景,但由于其从河豚体内提取的成本过高,所以难以大量推广应用。越来越多的证据表明TTX来源于河豚体内共生的微生物。我们从野生横纹东方鲀(Takifugu oblongus)肝脏中分离得到了一株产TTX较高的芽孢杆菌3G2(Bacillus sp. 3G2),通过ELISA和胶体金的方法检测到其发酵液TTX含量为35 ng/mL。将该菌株接种于专用透析培养器中,不断流加新鲜培养基实现连续培养,同时实现简化分离工艺,对发酵液进行小鼠生物活性检测、TTX试纸条检测,并通过河豚毒素抗体免疫共沉淀纯化得到TTX粗品后进行高效液相色谱鉴定均表明发酵液中含有TTX且含量较高。本研究通过筛选产TTX的优质菌株进一步了证实河豚毒素外源性假说,并初步验证了透析法生产河豚毒素的优越性,为后续商业应用提供实践性基础。  相似文献   

红笛鲷弧菌病血清流行病学研究方法的建立     

简贺君  简纪常  吴灶和  鲁义善  张丽敏 《广东海洋大学学报》2007,27(4):45-48

以红笛鲷Lutjanus sanguineus弧菌病的主要病原菌——溶藻弧菌Vibrio alginolyticus为抗原制备兔抗血清,以辣根过氧化酶标记的羊抗兔血清为酶标二抗,建立了酶联免疫吸附试验检测技术。通过棋盘滴定法测定,得出溶藻弧菌菌悬液的最佳工作浓度为5×108mL-1,兔抗溶藻弧菌血清的最佳稀释度为1∶16000,酶标羊抗兔抗体的最佳稀释度为1∶2000。应用本实验建立的间接双抗体夹心法对红笛鲷进行现场检测,患病红笛鲷特异性抗体的检出率为70%,外观健康红笛鲷的检出率为20%。结果表明,本实验所建立的酶联免疫吸附试验(ELISA)检测法可以用于红笛鲷弧菌病的血清流行病学研究,而且可以检测出隐性感染状态下的红笛鲷。  相似文献