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21.
小杂粮是山西省的特色农业产品,早以质量优、营养丰富而闻名全国。但就山西省而言,由于市场化、组织化程度较低,产品营销一直是钳制生产发展的瓶颈因素。因此,在发展小杂粮生产的问题上,我们首先要考虑的是;如何使小杂粮产品适应市场需求,顺利实现其价值。也就是先要有一个明确的营销思路,以避免生产决策的失误。只有选择适宜的目标市场、准确地进行市场定位、建立通畅的分销渠道等,才能促进小杂粮生产健康发展。  相似文献   
22.
Conservation biology aims at assessing the status of a population, based on information which is often incomplete. Integrated population modelling based on state‐space models appears to be a powerful and relevant way of combining into a single likelihood several types of information such as capture‐recapture data and population surveys. In this paper, the authors describe the principles of integrated population modelling and they evaluate its performance for conservation biology based on a case study, that of the black‐footed albatross, a northern Pacific albatross species suspected to be impacted by longline fishing  相似文献   
23.
Parameter design or robust parameter design (RPD) is an engineering methodology intended as a cost-effective approach for improving the quality of products and processes. The goal of parameter design is to choose the levels of the control variables that optimize a defined quality characteristic. An essential component of RPD involves the assumption of well estimated models for the process mean and variance. Traditionally, the modeling of the mean and variance has been done parametrically. It is often the case, particularly when modeling the variance, that nonparametric techniques are more appropriate due to the nature of the curvature in the underlying function. Most response surface experiments involve sparse data. In sparse data situations with unusual curvature in the underlying function, nonparametric techniques often result in estimates with problematic variation whereas their parametric counterparts may result in estimates with problematic bias. We propose the use of semi-parametric modeling within the robust design setting, combining parametric and nonparametric functions to improve the quality of both mean and variance model estimation. The proposed method will be illustrated with an example and simulations.  相似文献   
24.
曲流河、辫状河、网状河和若干三角洲的沉积模式目前已成为对比和解释古河流岩石层序的标准框架。但是,近来的野外资料和钻井资料证明,应该把末端扇模式加入上述沉积模式表中。末端扇的作用、地貌、有关的沉积物及沉积学特征相比河流体系及三角洲体系差距较大。通过大量的岩芯观察和描述,结合测井资料、区域地质资料及各项分析鉴定资料等进行综合分析,对东濮凹陷濮城油田沙二上亚段1砂组的沉积特征与沉积相进行了较全面的分析,认为该地区主要为末端扇沉积体系,在对末端扇的岩性、沉积相序、沉积微相特征分析的基础上,研究了末端扇的识别标志并建立了末端扇的沉积模式。  相似文献   
25.
There is an emerging consensus in empirical finance that realized volatility series typically display long range dependence with a memory parameter (d) around 0.4 (Andersen et al., 2001; Martens et al., 2004). The present article provides some illustrative analysis of how long memory may arise from the accumulative process underlying realized volatility. The article also uses results in Lieberman and Phillips (2004, 2005) to refine statistical inference about d by higher order theory. Standard asymptotic theory has an O(n-1/2) error rate for error rejection probabilities, and the theory used here refines the approximation to an error rate of o(n-1/2). The new formula is independent of unknown parameters, is simple to calculate and user-friendly. The method is applied to test whether the reported long memory parameter estimates of Andersen et al. (2001) and Martens et al. (2004) differ significantly from the lower boundary (d = 0.5) of nonstationary long memory, and generally confirms earlier findings.  相似文献   
26.
The Coase theorem maintains that where free-market precepts exist, the allocation of property rights does not impact the distribution of resources. An application to Major League Baseball suggests that institutions such as free agency and the reverse-order amateur draft would not impact player distributions and therefore would not impact competitive balance. The present study finds that the distribution of wins is generally consistent with the precepts of the Coase theorem and therefore suggests a course for those who wish to alter the level of competitive balance: Major League Baseball should increase its focus on expanding the size of its labor pool. (JEL O15 , L83 , C22 )  相似文献   
27.
目的 :回顾气囊扩张治疗贲门失弛缓症的近、远期疗效及治疗过程中的经验。方法 :对经食管吞钡X线拍片确诊的 16例贲门失弛缓症患者 ,采用内镜下气囊扩张治疗并评价其近、远期疗效。结果 :近期疗效 :16例患者中 ,12例 (75 % )显效 ,4例 (2 5 % )有效 ,总有效率为 10 0 % ;远期疗效 :16例患者中 ,1例 2周后复发经再次扩张治疗后未复发 ,另有 1例在治疗后的半年内复发扩张治疗后 ,半年再次复发 ,经直径 4 .0cm气囊扩张后 4年未复发。结论 :气囊扩张治疗贲门失弛缓症有效、易操作、安全、并发症少及复发率低 ,但有较多的细小经验及体会值得总结 ,以便更完善和更成熟。  相似文献   
28.
UNDERSTANDING THE DECISION TO PARTICIPATE IN A SURVEY   总被引:18,自引:1,他引:17  
The lack of full participation in sample surveys threatens theinferential value of the survey method. We review a set of conceptualdevelopments and experimental findings that appear to be informativeabout causes of survey participation; offer an integration ofthat work with findings from the more traditional statisticaland survey methodological literature on nonresponse; and, giventhe theoretical structure, deduce potentially promising pathsof research toward the understanding of survey participation.  相似文献   
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30.
This study examines the influence of the socialization of aggression among different gender and social class groupings and the influence of psychosocial stage on cognitive developmental play preferences among groups of school aged children. Observations of 143 play groups were coded for play preference (symbolic play, practice play, games with rules) and play performance (cooperative or competitive). Findings of the log-linear data analysis suggest a middle class and masculine bias in Piaget's cognitive model (i.e., that as age increases children prefer more games with rules). This model held only for middle class and affluent boys. Girls (both latency and prepubertal) and lower socioeconomic groups tended to prefer practice play. Girls were more likely to play cooperatively; boys more likely to play competitively. Implications for theory development and clinical practice are explored.  相似文献   
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