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1.
Diane Hope Weixing Zhu Corinna Gries Jacob Oleson Jason Kaye Nancy B. Grimm Lawrence A. Baker 《Urban Ecosystems》2005,8(3-4):251-273
We explored variations in inorganic soil nitrogen (N) concentrations across metropolitan Phoenix, Arizona, and the surrounding
desert using a probability-based synoptic survey. Data were examined using spatial statistics on the entire region, as well
as for the desert and urban sites separately. Concentrations of both NO3-N and NH4-N were markedly higher and more heterogeneous amongst urban compared to desert soils. Regional variation in soil NO3-N concentration was best explained by latitude, land use history, population density, along with percent cover of impervious
surfaces and lawn, whereas soil NH4-N concentrations were related to only latitude and population density. Within the urban area, patterns in both soil NO3-N and NH4-N were best predicted by elevation, population density and type of irrigation in the surrounding neighborhood. Spatial autocorrelation
of soil NO3-N concentrations explained 49% of variation among desert sites but was absent between urban sites. We suggest that inorganic
soil N concentrations are controlled by a number of ‘local’ or ‘neighborhood’ human-related drivers in the city, rather than
factors related to an urban-rural gradient. 相似文献
2.
贾坤鑫 《长春理工大学学报(高教版)》2006,(2)
本文主要分析了HEIDENHAIN TNC 310数控铣床系统中圆弧铣削指令及螺纹铣削指令,对螺纹铣削功能进行延伸,扩展到圆弧三轴联动,并对螺纹铣削指令格式进行了修改,从而具有圆弧三轴联动铣削功能。 相似文献
3.
Lee Friedman Edwin A. Fleishman Jennifer Mikulka Fletcher 《Journal of Engineering and Technology Management》1992,9(3-4)
This study attempted to identify the primary activities performed by R&D managers at different supervisory levels, and the cognitive and interpersonal ability requirements that underlie these activities. A task inventory containing 244 managerial tasks was completed by 117 R&D managers in nine organizations. The 48 tasks which managers rated as having spent the most time were factor analyzed, resulting in the identification of three primary activities: project management, personnel supervision, and strategic planning. Furthermore, these activities varied with supervisory level, with R&D managers performing a wider range of these activities with the progression from first-line to upper-level management.Thirty R&D managers later rated the degree to which 19 cognitive and interpersonal abilities were required for performing these primary activities. Strategic planning was rated as requiring significantly higher levels of oral expression, logical reasoning, originality, fluency of ideas, oral defense, and resistance to premature judgement than was required for the other two primary activities. Personnel supervision required a higher level of social sensitivity than was required for the other two activities. Project management required high levels of information ordering, oral fact- finding ability, problem sensitivity, and oral and written comprehension. Implications of the findings for understanding R&D managerial performance and personnel staffing functions are discussed. 相似文献
4.
The authors extend the block external bootstrap to partially linear regression models with strongly mixing, nonstationary error terms. In addition to providing an approximate distribution for the semiparametric least square estimator of the parametric component, they propose a consistent estimator of the co‐variance matrix of this estimator. 相似文献
5.
6.
Petter Osmundsen Guttorm Schjelderup Kåre Petter Hagen 《Journal of population economics》2000,13(4):623-637
This paper analyses how governments should tax labour income accruing to a group of highly skilled and geographically mobile
individuals who divide their time or career between several jurisdictions. The analysis differs from previous models on migration
and taxation by addressing optimal regulation when agents work for several principals. Optimal taxation is developed for social
welfare functions with exogenous and endogenous welfare weights. Marginal income taxes are applied for screening purposes,
and the rates are lower with endogenous than with exogenous welfare weights.
Received: 22 January 1998/Accepted: 3 July 1999) 相似文献
7.
François Bourguignon 《Journal of population economics》1999,12(4):503-521
The collective approach to household consumption behavior tries to infer from variables supposed to affect the general bargaining
position of household members information on the allocation of consumptions goods and tasks among them. This paper investigates
the extension of previous work to the case where children may be considered as a public consumption good by the two adult
members of a household. The main question being asked is whether it is possible to retrieve from the aggregate consumption
behaviour of the household and the relative earnings of the parents information on the allocation of goods between them and
children. This alternative approach to the estimation of the ‘cost of children’ is contrasted with the conventional approach
based on a ‘unitary’ representation of and demographic separability assumptions on household consumption behaviour.
Received: 29 August 1997/Accepted: 26 November 1998 相似文献
8.
Rosa Arboretti Riccardo Ceccato Luca Pegoraro Luigi Salmaso Chris Housmekerides Luca Spadoni Elisabetta Pierangelo Sara Quaggia Catherine Tveit Sebastiano Vianello 《Journal of applied statistics》2022,49(10):2674
Industrial statistics plays a major role in the areas of both quality management and innovation. However, existing methodologies must be integrated with the latest tools from the field of Artificial Intelligence. To this end, a background on the joint application of Design of Experiments (DOE) and Machine Learning (ML) methodologies in industrial settings is presented here, along with a case study from the chemical industry. A DOE study is used to collect data, and two ML models are applied to predict responses which performance show an advantage over the traditional modeling approach. Emphasis is placed on causal investigation and quantification of prediction uncertainty, as these are crucial for an assessment of the goodness and robustness of the models developed. Within the scope of the case study, the models learned can be implemented in a semi-automatic system that can assist practitioners who are inexperienced in data analysis in the process of new product development. 相似文献
9.
基于 0-3 岁婴幼儿亲子阅读互动现状调查发现的家长互动经验缺乏、形式单一等问题,开展“计划—行动—观察—反思—再计划”三轮亲子阅读互动循环提升的行动研究。实践表明,创设情境多元互动、拓展经验促成互动、审美体验美化互动是提升阅读互动质量的有效策略;家长对婴幼儿身心发展特点和教育规律的认知、对美的鉴赏与表达能力是影响互动策略实施的重要因素;专家的精心指导和及时评价、家庭间的作品展示和体会交流是营造阅读互动氛围提升互动效果的良好举措。建议家长自主学习、积极实践、主动交流来推进有效互动策略的实施。 相似文献
10.
Aaron Childs 《Statistical Papers》2006,47(2):299-310
In this paper we present analogues of Balakrishnan's (1989) relations that relate the triple and quadruple moments of order
statistics from independent and nonidentically distributed (I.NI.D.) random variables from a symmetric distribution to those
of the folded distribution. We then apply these results, along with the corresponding recurrence relations for the exponential
distribution derived recently by Childs (2003), to study the robustness of the Winsorized variance. 相似文献