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以太网技术在中国石油化工集团公司安庆石油化工总厂、中国石油化工股份有限公司安庆分公司(以下合称安庆石化)计算机网络系统中的应用已有较长的时间。早在上个世纪90年代初期,安庆石化就开始建设基于以太网技术的企业计算机网络系统,对以太网技术的应用已有广泛的网络基础和长期的运行经验。在建设安庆石化宽带接入网时,以太网技术又作为宽带接入网的骨干接入技术。 相似文献
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本文首先分析了以太网的应用技术,然后结合PLC的运用,给出了某水电站监控与自动控制综合系统的构成。重点分析了系统的架构,以及PLC程序的设计,然后给出了系统的测试。该开发可以对同类开发起到良好的借鉴作用。 相似文献
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介绍了基于Vx Works系统的多个快速以太网PCI控制器驱动的编程方法,给出了硬件框图和程序流程图,并说明了该驱动与上层程序的接口。 相似文献
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阐述SCADA系统中PLC时钟控制的误差及S7-300以太网与PLC间时钟同步的设置和校正。 相似文献
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安钢焦炉煤气脱硫项目中应用西门子PCS7系统。系统采用双冗余CPU414H,现场通信由PROFIBUS-DP与ET200M构成;工程师站和操作员站是利用1613网卡和光纤通信模块OSM构成冗余环形工业以太网。 相似文献
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针对棒材生产线上冷床下卸钢系统机械效率低、运行周期长,不能适应快节奏生产的现状,采用以工业以太网为主、DP网为辅的网络通讯,应用西门子FM350-2高速计数器,通过有效的数学计算模型,结合变频器和液压传动控制技术,实现网络自动化控制。 相似文献
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电力负控系统主要采用辐射的分散用户集中管理方式,由前置机、操作机和用电信息分析处理三个分系统组成。网络结构采用标准以太网形式,内部以星形方式连接,使整个网络结构稳定,便于扩充,并且功能划分清楚,便于使用和操作。 相似文献
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Organizational research has revealed ample evidence of self-serving attributional patterns in managerial sensemaking, but has not yet resolved whether actor–observer attributional effects also influence managers’ sensemaking tendencies. The primary purpose of this study was to investigate whether such actor–observer effects can be detected in managers’ interpretation of equivocal information. Results indicate that managers receiving equivocal information about the performance of an organization described as their own credited positive outcomes to organizational strengths and blamed negative outcomes on environmental threats. In contrast, managers receiving equivocal information about an organization described as managed by others associated positive outcomes with environmental opportunities and linked negative outcomes to organizational weaknesses. Both self-serving and actor–observer attributional patterns were thus detected. © 1997 by John Wiley & Sons, Ltd 相似文献
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《Telecommunications Policy》2022,46(5):102296
The objectives of this paper are to investigate the effect of ICT on sustainable development and the mechanisms through which the effect is modulated. The focus is on a sample of 140 countries around the globe for the period 2000–2019. The methodology involves the: (i) Fixed Effects estimator to control for individual heterogeneity, (ii) Driscoll and Kraay estimator to control for cross-section dependence between panels, (iii) the Mean Group estimator to take into account the averages between panel groups, (iv) the system GMM to correct for unobserved heterogeneity and simultaneity bias and (v) the instrumental variable Fixed Effects Tobit to take in to account the limited range in our dependent variable. The results show that ICT has a positive and significant effect on sustainable development. Whereas overall net effects are positive, the findings are contingent on the choice of the ICT measurement, the geographical location of the economy and the income group category. The study recommends policy makers to take into account ICT and the advantages it offers in the elaboration of measures for the sustainable development agenda. 相似文献
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Generalizing the OLS and Grid Estimators 总被引:2,自引:0,他引:2
The vast majority of market valuations employ either some formal estimator such as ordinary least squares (OLS) or rely upon an informal set of rules defining the grid adjustment estimator. The success of the grid adjustment estimator suggests the data do not obey the ideal assumptions underlying OLS. However, the grid adjustment estimator's lack of a formal statistical foundation makes it difficult to use for inference and other purposes. This article demonstrates how to generalize the grid estimator and OLS to potentially obtain the best features of both. Interestingly, the generalization defines a spatial autoregression. On an empirical example the spatial autoregression outperforms the grid estimator which in turn outperforms OLS. 相似文献
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Daniel P. McMillen 《Real Estate Economics》2012,40(4):745-773
The most common approaches for constructing house price indices—hedonic price functions and the repeat sales estimator—focus on changes over time in mean prices. Though the hedonic approach is less wasteful of data than the repeat sales estimator, it relies on an accurate specification of the underlying econometric model. I suggest using a matching estimator as an alternative to the hedonic and repeat sales approaches. Like the repeat sales approach, a matching estimator uses pairs of sales from different dates to estimate the mean difference in sales prices over time. The matching approach preserves much larger sample sizes than the repeat sales estimator while requiring less preimposed structure than the hedonic approach. The matching approach makes it easy to characterize changes in the full distribution of house prices. 相似文献
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The adjustment-grid method and the multiple-regression method are the two most frequently used techniques in the sales comparison approach. This paper demonstrates that although both techniques provide unbiased estimators, the minimum-variance grid estimator should result in a smaller standard deviation than the multiple-regression estimator. A technique is also derived to estimate the confidence interval or to perform hypothesis tests for the minimum-variance grid estimator. 相似文献
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The rapid introduction of new products in high‐tech industries is a key competence for firms wanting to benefit from the first‐mover advantage (FMA). Prior studies call for forging links between FMA and the resource‐based view, as the resources at the disposal of a firm tend to influence the likelihood and timing of market entry. Analysing the way firms orchestrate internal and external resources enables a better understanding of this link. More precisely, synchronising the combination of internal and external resources is important in determining the development time of new products. This issue becomes vital when the NPD process regroups competitors due to the short age of the acquired knowledge. An in‐depth case study of the product development strategies of four competitors that collaborated to develop Ethernet solutions identifies three different product introduction strategies based on different resource orchestrations and timing: pioneer, wise and slow. The firms that structured their resources early to make them available for bundling during coopetition were able to introduce products faster than firms that structured their resources during coopetition. Furthermore, our results show that only prepared firms are able to reap benefits from knowledge gained through coopetitive NPD. 相似文献