首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 125 毫秒
1.
文中从硫酸亚铁铵标准溶液浓度、空白和水样消耗硫酸亚铁铵标准溶液体积、水样体积、重复性评定用重铬酸盐法测定水中化学需氧量时产生的不确定度,最后计算相对合成不确定度和相对扩展不确定度,并报告化学需氧量测定结果。  相似文献   

2.
论述了采用重铬酸钾法测定水中化学需氧量(COD)的不确定度的评定方法。分析了各不确定分量的来源,确定了评估方法并建立了COD不确定度计算方法的数学模型,并以2007年参加北京中实国金国际实验室能力验证研究中心组织实施的COD能力验证样品为实例,对标准不确定的分量进行了详尽的分析和计算,得出测定COD扩展不确定度的结果。  相似文献   

3.
通过对色织氨纶弹力布经向断裂强力进行重复测试,建立了条样法断裂强力不确定度评估的数学模型,分析了各不确定度分量对合成不确定度的影响,来评价其不确定度,并给出了不确定度报告。  相似文献   

4.
本文对测量不确定度的有关概念,给出了准确的定义 和必要的解释,并对标准不确定度的A分量、B分量和合成标准不确定度,给出了一般估算方法。  相似文献   

5.
按照检测和校准实验室认可准则的要求,以亚甲基蓝分光光度法测定硫化物为例,分析了不确定度分量的来源,通过试验和计算确定了各不确定度分量值,最终给出了水质中硫化物测定结果的扩展不确定度。  相似文献   

6.
依据GB 24330-2009《家用卫生杀虫用品安全通用技术条件》附录E对蚊香烟尘量进行测定,基于JJF 1059.1-2012《测量不确定度评定及表示》对影响蚊香的烟尘量测量不确定度的各分量进行分析,并对各分量的标准不确定度进行计算和合成。通过比较各分量的标准不确定度,得出了影响蚊香的烟尘量测量不确定度的主要因素。  相似文献   

7.
全面介绍了采用红外吸收法对煤中氢的不确定度评定方法,应用统计学理论对其不确定度的产生原因进行分析,包括由各种随机因素产生的不确定度分量、天平引起的不确定度、煤有证标准物质的标准值不确定度引起的不确定度、工作曲线回归方程引入的标准不确定度、检测设备引入的不确定度、Mad重复测定引起的不确定度。分析测量过程各不确定度分量对总不确定度的影响,确定测定结果的置信区间。给出煤中氢的含量及其置信区间为4.10%±0.014%。  相似文献   

8.
为评定抽油杆抗拉强度的测量不确定度,以H级抽油杆为例,建立不确定度计算的数学模型,确定影响试验结果的各项因素,计算各因素所带来的不确定度分量,求出合成标准不确定度。从而得出扩展不确定度,最终给出抽油杆抗拉强度测量结果的表达式。  相似文献   

9.
当前对于输变电工程不确定因素的研究集中于不确定因素识别,对其预测研究较少。不确定因素变化呈现出明显的非周期性及非平稳性,常规模型的预测精度较低。鉴于此,本文建立了EEMD-BP模型,将历史数据序列分解为随机分量和呈现明显波动周期的若干趋势分量。对各趋势分量采用BP算法预测,将各分量预测值叠加后得到趋势分量预测结果。对随机分量通过分析其相对于趋势分量的离散度得到其波动范围。综合考虑趋势分量预测值和波动区间得到最终的预测结果。选取PPI的历史数据进行算例分析,验证了方法的有效性,并对未来两个时点进行预测。采用同样方法对包括铜材价格、导线价格在内的其他不确定因素进行了预测。  相似文献   

10.
本文依据《中华人民共和国国家计量技术规范》JJF1059.1-2012《测量不确定度评定与表示》对离子色谱仪测量加标水样中的碘化物的不确定度进行分析,如实反映测量的置信度和准确性。通过建立评估的数学模型,分析不确定度的主要来源,计算出不确定度的各主要分量,得出合成不确定度和扩展不确定度。结果表明:影响结果不确定的主要因素是曲线拟合过程带来的不确定度,其次是仪器本身带来的不确定度,溶液的稀释对结果影响不大。该评估可为离子色谱法测定碘化物的不确定度评估提供参考。  相似文献   

11.
建立了16个风向下的三维多箱模式,该模式充分考虑了污染源的空间变化、气象条件和周围环境对污染扩散的影响,以及干沉积和化学转化等物理化学机理对SO2的去除作用,根据质量守恒定律,得到了箱体方程,最后将该模式用于石家庄市区SO2质量浓度的预测,并对其进行了验证,结果表明多箱模型是预测市区和经济开发区的大气质量最佳方法之一。  相似文献   

12.
本文通过综合运用VAR模型和MVGARCH-BEKK模型,在“8.11汇改”前后对样本进行分段,分析了经济政策不确定性和人民币汇率间均值溢出效应和波动溢出效应。结果表明:(1)在全样本期间,人民币汇率对经济政策不确定性同时产生均值溢出效应和波动溢出效应,而经济政策不确定性对汇率不产生溢出效应;(2)“8.11汇改”后,经济政策不确定和人民币汇率的联动关系发生了改变。汇改前经济政策不确定性对汇率不产生溢出效应,汇改后出现了波动溢出效应;汇改前汇率变化对经济政策不确定性产生正均值溢出,汇改后人民币汇率对经济政策不确定性产生负均值溢出;(3)汇改后汇率市场化程度提高,中国经济政策不确定性和外汇市场的联动性增强。  相似文献   

13.
A note by Milliken (1973) suggests the usage of programme trend charts will help managers estimate the total duration of the project slippage. Whilst his sample graphs are informative they are of little use in evaluating two aspects of the problem: (a) The uncertainty inherent in the project–known to the Shop Floor, but unknown to the management. (b) The expected completion date–until sufficient data has been collected to yield reliable regression extrapolations. It is postulated that the assessment of suitably encoded subjective probability distributions be used to satisfy points (a) and (b) above. These distributions, when evaluated by a scoring rule, will also give the management, and the assessor, a true statement of the quality of the assessments. Furthermore, the underlying theory of subjective probability scoring rules suggests that assessors should become ‘better’ when being scored than when given no incentive, other than the usual behavioural guidance of most hierarchic organizations.  相似文献   

14.
This paper applies measures of risk to capacity expansion decisions made under uncertainty. Eight different decision making rules are constructed by varying both the frequency of the forecast updates and the hedge against uncertainty in a rolling horizon heuristic procedure. Using demand, capacity, and cost data from the utility division of a manufacturing company, the risk characteristics of each decision making rule are evaluated by simulation. The results indicate that annual forecast revisions hedged by ninety percent prediction limits are preferred over decision rules with less frequent forecast revisions or fixed-width hedges.  相似文献   

15.
We find support for the role of experiential learning in the international expansion process by extending the stages model of internationalization to incorporate a sophisticated consideration of temporal and cross‐national variation in the credibility of the policy environment. Using a sample of 3857 international expansions of 665 Japanese manufacturing firms, we build on the concepts of uncertainty and experiential learning, to show that firms that had gathered relevant types of international experience were less sensitive to the deterring effect of uncertain policy environments on investment. One implication of our results is that research on international strategy should emphasize understanding the political institutions that constrain or enable political actors, just as entry mode research has done. A second implication is that research in the stages model of internationalization should give the same weight to the policy environment as a source of uncertainty to a firm, as it has given to cultural, social and market institutions. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

16.
使用气相色谱/质谱测定汽油中元素硫含量,采用样品直接进样和外标法定量,该分析方法简单、快速、灵敏,且无干扰。根据不确定度的传播规律,对所用标准曲线、有证标准样品、称重、合格的玻璃器皿、测量重复性等不确定度来源进行分析评定,其中由标准曲线上求元素硫含量时所产生的不确定度分量最大,其次是测量重复性,这两项是该法测定结果不确定度的重要来源,标准溶液浓度所产生的不确定度分量较小。置信度为95%时,高、低浓度样品元素硫含量的扩展相对不确定度分别为6.4%和4.2%。  相似文献   

17.
This paper examines the effect of product market uncertainty and government research and development (R&D) subsidies on firm-level R&D investment. Using a sample of German manufacturing firms, we find that product market uncertainty reduces R&D investment and government R&D subsidies increase R&D investment. Moreover, our results indicate that R&D subsidies mitigate the effect of product market uncertainty on R&D investment. These findings suggest that public policies aimed at increasing business R&D investment can achieve this objective by reducing the degree of uncertainty in the product market.   相似文献   

18.
We explore transaction cost economics (TCE) and real option (RO) rationales for alliance governance and find the predictive power of each depends upon the type of uncertainty confronted. Our review of alliance activity from 1995 through 2000 for 642 alliances confirms that governance is influenced directly by partner, task, and technological uncertainty and by interactions among asset co‐specialization, partner uncertainty, and task uncertainty. Consistent with TCE, co‐specialized assets increased the likelihood of hierarchical governance. Partner and task uncertainty increased this effect. Consistent with RO, we find technological uncertainty decreased the likelihood of hierarchical governance. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

19.
Five hypotheses were formulated regarding the exogamic nature of Sino-foreign joint ventures and two propositions regarding incentives for technology transfers and protection against imitation. Research relied on a questionnaire-based investigation in 67 joint ventures and case studies in various industries. Three lessons were drawn. (1) Each partner contributes with a differentiated set of idiosyncratic and non-substitutable set of resources; technology is the core contribution of foreign companies no matter which aspect is examined. There is an almost perfect symmetry between the pooled resources and the learning objectives of each partner. (2) Chinese respondents give a strong competitive value to technology transfers. (3) Beyond traditional technical and legal protection, foreign companies slow down imitation with three strategies: taking advantage of time lag; keeping the most creative value added stages at home; playing, not on the technology itself, but on inherent financial or commercial obstacles.  相似文献   

20.
This empirical study examines the influence of environmental uncertainty on industrial product innovation. The present study addresses what is believed to be a shortcoming in the new product development literature and explores potential effects of environmental uncertainty on the development process, project organization, and on project timeliness with a sample of development projects in two countries, Canada and Australia. When looking at the combined sample of 182 completed projects, this study finds that the perceived market‐related project environment has a direct and positive impact on time efficiency. Further, this research finds that a higher degree of technological uncertainty moderates the relationship between development process, project organization and time efficiency. Consequently, innovating companies may benefit by adapting some of their development approaches to different environmental conditions and to varying degrees of uncertainty. However, when examining country‐specific effects, the results change quite significantly. In particular, the findings indicate that environmental uncertainty in the Canadian sample neither directly impacts time efficiency, nor does it have any moderating effect. Instead, technical proficiency in the development process, project team organization, and process compression appear to be viable strategies to increase time‐efficient development. In contrast, the results of the Australian study suggest that perceived market and technological uncertainty impact time efficiency. In particular, under conditions of technological unpredictability, project team organization increases time efficiency, whereas process compression appears to decrease time‐efficient product development. However, process compression seems to be a viable strategy in environments characterized by lower technological uncertainty. The results also point to the importance of disaggregating data when studying product development processes across countries.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号