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991.
T. Nagamitsu Kuniyasu Momose Tamiji Inoue David W. Roubik 《Researches on Population Ecology》1999,41(2):195-202
Floral resource partitioning among stingless bees (Trigona, Meliponini, Apidae) in a lowland rain forest in Sarawak, Malaysia, was investigated using tree towers and walkways in a
4-year study that included a general flowering period. We obtained 100 collections of insect visitors to flowers of varying
floral location and shape representing 81 plant species. The tendency of 11 species of stingless bees to visit specific flowers
with a particular floral location and shape was analyzed by logistic regression analysis. This analysis showed that the proportion
of flower visitor collections containing Trigona fuscobalteata and T. melanocephala differed according to floral location. The former was frequently collected at canopy and gap flowers, whereas the latter
was most often collected at understory flowers. The analysis also suggested that T. erythrogastra was more rarely collected at shallow flowers than at deep flowers. Analysis of the pollen diets of T. collina, T. fuscobalteata, T. melanocephala, and T. melina revealed that similarity of pollen sources differed among the six permutated pairs of the four species. The lowest mean rank
of similarity found was between T. fuscobalteata and T. melanocephala. This result supports the hypothesis that preference in visiting flowers in different locations leads to pollen resource
partitioning.
Received: May 14, 1997 / Accepted: April 23, 1999 相似文献
992.
本文论述美国1997年后对华新政策。文章综述90年代起美国历届政府的对华的检讨,到1997年克林顿政府采取对华新政策,主要是稳定亚洲、中国大陆、台湾,以确保美国在亚洲战略地位和经济利益 相似文献
993.
994.
A definition of reproducibility in Guttman Scaling and two chance measures of reproducibility are suggested. The first measure assumes that the items are independent. The second method assumes nonindependent items and fits respondent and item margins by an iterative method used in fitting log-linear models. Chance reproducibility is conceptualized in terms of assumptions about respondent variability. 相似文献
995.
996.
997.
David Prideaux 《The Australian journal of social issues》1975,10(4):315-321
The effectiveness of the South Australian Prohibition of Discrimination Act is examined with respect to its effect on individual and institutional racism. It is concluded that the act only deals with individual racism and not the less overt aspects of institutional racism; for example the latter still exists in poor standards of health, housing, and education. For a significant improvement in race relations in Australia there needs to be a wider guarantee against discrimination to cover both individual and institutional racism. It is suggested that the Australian government's Bill of Rights and Racial Discrimination Bill be examined in this light. 相似文献
998.
There are numerous variable selection rules in classical discriminant analysis. These rules enable a researcher to distinguish significant variables from nonsignificant ones and thus provide a parsimonious classification model based solely on significant variables. Prominent among such rules are the forward and backward stepwise variable selection criteria employed in statistical software packages such as Statistical Package for the Social Sciences and BMDP Statistical Software. No such criterion currently exists for linear programming (LP) approaches to discriminant analysis. In this paper, a criterion is developed to distinguish significant from nonsignificant variables for use in LP models. This criterion is based on the “jackknife” methodology. Examples are presented to illustrate implementation of the proposed criterion. 相似文献
999.
This paper addresses the problem of open order rescheduling in a job shop. Results are reported of experiments conducted in a simulation model of an 8-machine job shop. Four different order updating policies are examined. The due-date process is modeled to include several realistic features about the pattern of due-date variability. These features are parameterized and tested at several levels. Tardiness results indicate that open order rescheduling is beneficial only when allowances are loosely set. The results indicate that inventory performance is improved by order rescheduling, particularly in cases when due dates are revised to earlier times than originally forecast. 相似文献
1000.
To provide effective managerial support for decisions related to production planning and scheduling processes, it is useful to partition the set of decisions into a hierarchical framework. In the resulting system, higher level decisions impose constraints on lower level actions, and lower level decisions provide the necessary feed-back to reevaluate higher level actions. The purpose of this paper is to suggest optimum procedures to deal with the resulting subproblems and to analyze the interaction mechanisms among the different hierarchical levels. Computational results are given. 相似文献