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61.
文章分析了锅炉水位控制系统的基本原理及结构,针对传统PID控制器的不足之处设计了基于遗传算法的新型锅炉水位控制器,在此基础上搭建了锅炉水位控制系统。最后,通过仿真验证了该水位控制器在改善水位系统稳态误差及动态超调方面均具有较好的作用。 相似文献
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63.
Inmaculada Beltrán‐Martín Juan Carlos Bou‐Llusar Vicente Roca‐Puig Ana Belén Escrig‐Tena 《Human Resource Management Journal》2017,27(3):403-422
Drawing on the contextual perspective, this study provides novel empirical evidence on how the organisational context (specifically, the firm's human resource strategy) has an effect on employee proactivity. We use matched data from managers and employees in 102 Spanish professional service firms to examine how high performance work systems contribute to enhance employee proactive behaviours through two motivational variables: role breadth self‐efficacy and flexible role orientation. Results of a multilevel study demonstrate that role breadth self‐efficacy mediates between HPWS and employee proactivity, but flexible role orientation does not mediate this relationship. 相似文献
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65.
E. Bárcena‐Martín B. Lacomba A. I. Moro‐Egido S. Pérez‐Moreno 《Review of Income and Wealth》2014,60(4):802-820
This paper assesses to what extent differences in the characteristics of individuals (micro‐level perspective) and country‐specific factors (macro‐level perspective) can explain country differences with respect to material deprivation levels. Thus, our work aims to simultaneously consider the macro dimension and the predominantly individually‐oriented study field of material deprivation using multilevel techniques. We make use of the European Union Statistics on Income and Living Conditions. Our results show that country‐specific factors seem to be much more relevant than individual effects in explaining country differences in material deprivation. We estimate that the introduction of country‐specific factors reduces the proportion of total variance due to between‐country differences in deprivation by 72.7 percent, while individual‐level variables reduce this proportion by only 9.4 percent. We also show, through interaction variables, that the effect of sociodemographic characteristics can be shaped by institutional and structural factors, especially by the level of GDP. 相似文献
66.
The westernization of Asian countries has led to the rapid expansion of Western-style fast-food restaurants, which are believed to be fueling an unprecedented rise in body mass in these countries. This study tests this belief using longitudinal data from China. Exploiting the opening of a Western-style fast-food restaurant in a particular community, we conduct a transition analysis to make a more convincing causal interpretation than the standard cross-sectional or fixed-effects approach. Considering several measures of fatness, we find no robust evidence of Western fast food having a substantial effect overall, but there is some indication of effect heterogeneity. 相似文献
67.
In the Ming and Qing Dynasties (1368–1911), China saw rapid development in industrial and commercial sectors. Over this period, a group of merchants originating from the inland province of Shanxi gradually built a multilevel financial system and became leaders in China’s banking sector. The system of financial institutions they established (pawnshops, seal shops, money shops, loan banks, and draft banks) each had a unique business model, with specific target client group and carefully designed risk management. They were also interconnected to allow for flexible capital flows, contributing to the fast economic growth in this period. Nevertheless, the traditional system also had limitations, leading to its replacement by modern banks eventually. 相似文献
68.
Jaeyoung Jung R. Jayakrishnan 《International Journal of Sustainable Transportation》2017,11(8):567-581
Electric vehicles (EVs) are energy efficient and often presented as a zero-emission transport mode to achieve long-term decarbonization visions in the transport sector. The implementation of a sustainable transportation environment through EV utilization, however, requires the addressing of certain cost and environmental concerns such as limited driving range and battery-charging issues before its full potential can be realized. Nevertheless, a specific type of use of EVs, namely in taxi services, may elicit positive public opinion, as it promises a commitment toward sustainability in urban life. In light of this, this study proposes an integrated approach that combines EV operation with a conceptual design for shared-ride taxi services. As some productivity loss may be naturally expected due to the time spent in charging, it is important to look at whether such performance loss from the passenger and system standpoints can be offset with ingenuity in operational design. In this study, an EV taxi charge-replenishing scheme that can be coupled with a real-time taxi-dispatch algorithm is designed. The proposed EV charging schemes for taxi services are studied via simulations and the effects of the limited driving range and battery-charging details are examined from a system performance viewpoint. The simulation study also reveals illustrative results on the impact of the EV taxi fleet's operation on the charging system. Next, a real-time shared-taxi operation scheme that allows ride sharing with other passengers is proposed to maximize the operational efficiency. The simulation results suggest that the shared-taxi concept can be a viable option to improve on the limitations caused by EV operation. In addition, the importance of projected charging demands and queue delays at different charging locations are also addressed. Some limitations and a future research agenda are also discussed. 相似文献
69.
由于BOT项目本身的长期性和复杂性,所以在BOT项目实施前需要准确科学的预测出所面临的风险大小。针对BOT项目风险影响因素众多的问题,先利用主成分分析法进行降维,然后利用遗传算法找出BP神经网络的最优全值阈值,建立了PCAGA-BP BOT项目风险预测模型。同时将以往的BOT项目数据作为学习样本,对BOT项目风险进行预测,并利用某地污水厂的例子进行验证,说明此模型对实际工程的科学指导性。 相似文献
70.
将K-means聚类算法应用到无线局域网(WLAN)位置指纹定位中,虽然可以缩短定位时间,但是容易降低定位精度。为了解决此问题,提出了基于改进指纹聚类的WLAN定位优化方法。首先根据接收信号强度标准差来优化初始聚类中心的选取,然后对指纹数据进行聚类处理,最后进行在线定位。实验结果表明,与传统的WLAN位置指纹定位方法和K-means聚类定位方法相比,基于改进指纹聚类的定位优化方法不仅缩短了定位时间,还能有效提高定位精度。 相似文献