参数线性规划及应用讨论     

龚强 《东北测绘》1999,22(3):7-9

本文介绍了测绘运筹学参数线性规划的实用意义,并就如何应用参数线性规划为测绘生产管理提供量化决策依据进行了讨论。  相似文献   

多种权函数固定临界值与可变临界值抗差估计的比较     

吴富梅 《测绘工程》2006,15(3):19-22

抗差估计等价权函数中临界值一般定为常数。若基于学生化分布构造标准化残差,其临界值可由观测自由度以及给定的显著性水平确定。首先对几种权函数进行了分析和比较,然后讨论了各个权函数抗差性与误差显著性水平以及由之确定的临界值的关系。利用模拟数据详细分析和比较了不同的权函数在不同显著性水平下的抗差性,针对不同的权函数给出了合适的显著性水平;并将其与经验确定的常数临界值所对应的抗差估计进行比较,发现这种基于合适的显著性水平下的权函数不仅具有较严格的理论基础,而且计算也是行之有效的。  相似文献   

利用MODIS监测2008年初广西甘蔗的寒害冻害   总被引：3，自引：0，他引：3  

谭宗琨  丁美花  杨鑫  欧钊荣  何燕  匡昭敏 《气象》2010,36(4):116-119

在获取广西甘蔗种植空间分布遥感信息及结合大量田间调查的基础上,应用EOS/MODIS遥感数据资料对2008年初寒害冻害发生前、后及2007年同期的广西区域甘蔗NDVI值变化进行比较、分析,结果表明:应用EOS/MODIS遥感数据资料开展甘蔗寒害冻害监测具有重要意义。  相似文献   

两种类型的低温对冬季免耕马铃薯的影响     

陈国保  夏小曼  李永平 《气象研究与应用》2010,31(Z2)

通过实况调查并根据玉林市的气候规律进行对比分析后发现:2008初的寒害虽然是玉林有气象记录以来最强的一次,但对冬季免耕马铃薯的影响并不是很大,因为这种平流型寒害天气的最大特点就是北方较强的冷空气不断补充南下而使玉林长期处于大范围冷气团的控制之下,各地的温度比较均匀,因此灾情的地域分布比较一致,各种地形地貌和不同栽培方式之间也没有明显差别。而2009初的霜冻天气虽然只达到了中等强度的级别,却对冬季免耕马铃薯产生了严重的危害,并且不同的地形地貌和栽培方式之间灾情明显不同,地域差异也很大。要最大限度地避免或减轻寒害和霜冻天气对冬种马铃薯的影响,首先要注意选择在避寒环境良好,又不利于霜冻形成的地方种植,其次是栽培技术的灵活运用,另外还要注意收看收听当地的天气预报,提前做好防寒防霜的准备工作。  相似文献   

On critical values concerning the evolution of the long period families     

Xi-Yun Hou 《中国天文和天体物理学报》2009,9(4)

In a previous paper, we proposed another special critical value concerning the evolution of the long period family around the equilateral equilibrium points, besides the two values given by Henrard. Are there any other special critical values? After studying the stability curves of the long period family carefully, we gave a negative answer. During the study, we found an interesting family of periodic orbits which we called the homo family. We studied the evolution of this family following the increase of μ. With these findings, we were able to explain the origin of the four branches of periodic families emanating from L4 and the stability results of the equilateral equilibrium points.  相似文献   

清远市冬季气温和寒害的变化特征   总被引：2，自引：2，他引：0  

宋艳华  杨伟民  陈洁雯  谢玉宏 《广东气象》2012,34(1):15-18

据清远国家气象观测站1957～2010年逐日的气温观测资料,采用趋势分析、Mann-Kendall突变检验和多项式拟合等方法,对清远市的气温和寒害变化特征进行了研究。结果表明,清远市年平均气温升温速率为0.018℃/年,在1998～1999年发生了向暖的突变。冬季气温的升温速率为0.023℃/年,冬季气温变化不稳定性加剧,可能是引发寒害的原因之一。寒害频次和强度在总体变化(线性趋势)上均呈明显减少趋势,主要集中在20世纪60和80年代,寒害强度以中度型为主。  相似文献   

张掖城市湿地保护区生态需水量分析与计算          下载免费PDF全文

巴建文  马小全  秦晓燕 《甘肃地质》2009,(3):67-71

浅埋的地下水位以及泉水溢出是张掖城市湿地形成的主要原因。在充分考虑保持湿地现状的同时,顾及到湿地区内农耕区不至于因地下水位变化而产生负茴环境地质影响。将2005年8月份湿地保护区水位埋深,确定为保持湿地现状的地下水位埋深临界值。按照张掖城市湿地保护区的基本特征、表现、生态保护目标,生态需水量主要包括湿地植被蒸腾量、湿地土壤蒸发量、灌溉需水量以及景观建设需水量等。计算得生态需水量为3053．87×10^4m^3/a。湿地生态需水量的分析与计算对于制定合理的湿地保护措施具有重要意义。  相似文献   

钦州红树林寒害调查及无瓣海桑耐寒性初探   总被引：7，自引：4，他引：3  

蒋礼珍  黄汝红 《气象研究与应用》2008,29(3):35-38

介绍钦州市2008年初红树林的受灾情况及其成灾的原因分析,并根据近年引种的无瓣海桑造林成败,通过其越冬条件及几个极限温度的进一步对比分析,对无瓣海桑的耐寒性进行了初步的探讨,为保护和改善钦州市沿海红树林生态环境提供了科学依据.  相似文献   

Examination of Silicate Limitation of Primary Production in Jiaozhou Bay,China Ⅱ.Critical Value and Time of Silicate Limitation and Satisfaction of the Phytoplankton Growth   总被引：2，自引：0，他引：2  

Yang Dongfang  Zhang Jing  Gao Zhenhui  Chen Yu  Sun Peiyan 《中国海洋湖沼学报》2003,21(1):46-63

Analysis and comparison of Jiaozhou Bay data collected from May 1991 to February 1994 revealed the spatiotemporal variations of the ambient Si(OH)₄:NO₃ (Si:N) concentration rations and the seasonal variations of (Si:N) ratios in Jiaozhou Bay and showed that the Si:N ratios were <1 throughout Jiaozhou Bay in spring, autumn, and winter. These results provide further evidence that silicate limits the growth of phytoplankton (i.e. diatoms) in spring, autumn and winter. Moreover, comparison of the spatiotemporal variations of the Si:N ratio and primary production in Jiaozhou Bay suggested their close relationship. The spatiotemporal pattern of dissolved silicate matched well that of primary production in Jiaozhou Bay. Along with the environmental change of Jiaozhou Bay in the last thirty years, the N and P concentrations tended to rise, whereas Si concentration showed cyclic seasonal variations. With the variation of nutrient Si limiting the primary production in mind, the authors found that the range of values of primary production is divided into three parts: the basic value of Si limited primary production, the extent of Si limited primary production and the critical value of Si limited primary production, which can be calculated for Jiaozhou Bay by Equations (1), (2) and (3), showing that the time of the critical value of Si limitation of phytoplankton growth in Jiaozhou Bay is around November 3 to November 13 in autumn; and that the time of the critical value of Si satisfaction of phytoplankton growth in Jiaozhou Bay is around May 22 to June 7 in spring. Moreover, the calculated critical value of Si satisfactory for phytoplankton growth is 2.15–0.76 μmol/L and the critical value of Si limitation of phytoplankton growth is 1.42–0.36 μmol/L; so that the time period of Si limitation of phytoplankton growth is around November 13 to May 22 in the next year; the time period of Si satisfactory for phytoplankton growth is around June 7 to November 3. This result also explains why critical values of nutrient silicon affect phytoplankton growth in spring and autumn are different in different waters of Jiaozhou Bay and also indicates how the silicate concentration affects the phytoplankton assemblage structure. The dilution of silicate concentration by seawater exchange affects the growth of phytoplankton so that the primary production of phytoplankton declines outside Jiaozhou Bay earlier than inside Jiaozhou Bay by one and half months. This study showed that Jiaozhou Bay phytoplankton badly need silicon and respond very sensitively and rapidly to the variation of silicon. This study was funded by NSFC (No. 40036010) and subsidized by Special Funds from National Key Basic Research Program of P. R. China (G19990437), the Postdoctoral Foundation of Ocean University of Qingdao, the Director's Foundation of the Beihai Monitoring Center of the State Oceanic Administration and the Foundation of Shanghai Fisheries University.  相似文献   

液化判别的简化计算法     

李兴祥 《浙江国土资源》2002,18(1):45-47

针对国家标准《建筑抗震设计规范》规定的地震液化判别规则 ,本文提出一种简化的判别计算方法  相似文献