This paper mainly introduces the longitudinal transmission mechanism of urban vegetable prices in Chongqing area. On the basis of the supply chain theory,the " farm price- wholesale price- retail price" of v...This paper mainly introduces the longitudinal transmission mechanism of urban vegetable prices in Chongqing area. On the basis of the supply chain theory,the " farm price- wholesale price- retail price" of vegetables in Chongqing has been identified as the research object. Through statistical analysis,it is found that the above three types of price show a modest annual fluctuation of 7- 12% from 2008 to2013. Later,the paper focuses on the empirical research on the weekly price data in 2013 applying the co-integration theory,which reveals that the farm price of vegetables is largely influenced by themselves; the wholesale price of vegetables is mainly affected by their own price,the production price and the retail price of the earlier stage without the current influence of the production price; and the retail price of vegetables is also affected by their own price,but is not affected by the their current local price and the wholesale price. Vegetable prices have shown an obvious positive transmission mechanism in the links from production to retail,but the feedback effect of retail on production is not brought into play.展开更多
崇启大桥主桥为六跨双幅钢箱连续梁桥,其跨径布置为:102m+4×185m+102m=944m。风洞试验识别出大桥有发生竖向涡激振动的可能,为制止运营期可能发生的涡激振动,对比主动控制和被动控制技术方案,综合比选采用TMD(Tuned Mass Damper,...崇启大桥主桥为六跨双幅钢箱连续梁桥,其跨径布置为:102m+4×185m+102m=944m。风洞试验识别出大桥有发生竖向涡激振动的可能,为制止运营期可能发生的涡激振动,对比主动控制和被动控制技术方案,综合比选采用TMD(Tuned Mass Damper,调谐质量阻尼器)制振措施。计算主桥动力特性并进行实桥风洞试验,对试验结果进行频谱分析后确定一阶竖向反对称是涡激振动的主振型,基于该振型特点初步确定TMD布置位置。根据理论和数值计算初步确定了TMD频率、质量、阻尼比、行程等参数,利用谐响应和时程两种方法对TMD减振效果进行设计验证,指出低频TMD设计的主要难点和解决思路;为指导TMD安装施工,进行频率、质量、阻尼比的参数敏感性分析,明确TMD主要设计参数安装容许偏差,提出安装完成后验收指标。崇启大桥是国内首座采用TMD控制涡激振动的特大型桥梁,研究对类似结构的风致涡激振动控制积累了工程经验,对TMD设计、检验评定、制造验收等相关规范的编制具有一定的参考价值。展开更多
基金Supported by Western Project of Ministry of Education(13XJC630006)Young Scholar Project of National Social Science Foundation"Cooperative Path for Evolution of Social Network and Advance of Farmers Starting an Undertaking in Transformation Period"(14CGL029)
文摘This paper mainly introduces the longitudinal transmission mechanism of urban vegetable prices in Chongqing area. On the basis of the supply chain theory,the " farm price- wholesale price- retail price" of vegetables in Chongqing has been identified as the research object. Through statistical analysis,it is found that the above three types of price show a modest annual fluctuation of 7- 12% from 2008 to2013. Later,the paper focuses on the empirical research on the weekly price data in 2013 applying the co-integration theory,which reveals that the farm price of vegetables is largely influenced by themselves; the wholesale price of vegetables is mainly affected by their own price,the production price and the retail price of the earlier stage without the current influence of the production price; and the retail price of vegetables is also affected by their own price,but is not affected by the their current local price and the wholesale price. Vegetable prices have shown an obvious positive transmission mechanism in the links from production to retail,but the feedback effect of retail on production is not brought into play.
文摘崇启大桥主桥为六跨双幅钢箱连续梁桥,其跨径布置为:102m+4×185m+102m=944m。风洞试验识别出大桥有发生竖向涡激振动的可能,为制止运营期可能发生的涡激振动,对比主动控制和被动控制技术方案,综合比选采用TMD(Tuned Mass Damper,调谐质量阻尼器)制振措施。计算主桥动力特性并进行实桥风洞试验,对试验结果进行频谱分析后确定一阶竖向反对称是涡激振动的主振型,基于该振型特点初步确定TMD布置位置。根据理论和数值计算初步确定了TMD频率、质量、阻尼比、行程等参数,利用谐响应和时程两种方法对TMD减振效果进行设计验证,指出低频TMD设计的主要难点和解决思路;为指导TMD安装施工,进行频率、质量、阻尼比的参数敏感性分析,明确TMD主要设计参数安装容许偏差,提出安装完成后验收指标。崇启大桥是国内首座采用TMD控制涡激振动的特大型桥梁,研究对类似结构的风致涡激振动控制积累了工程经验,对TMD设计、检验评定、制造验收等相关规范的编制具有一定的参考价值。
