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数据加密是保护数据安全的一种有效的方法,它是将一段明文按某种算法进行处理,使其成为密文,以保护数据不被非法人窃取、阅读。数据加密技术常分为"对称式"加密与"非对称式"加密两类。多步加密算法属对称式加密,由于安全性高得到广泛应用。 相似文献
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证明了k次Fibonacci数列{Fnk}n∞=1中连续的k+2个数的线性恒等式并给出具体公式。 相似文献
85.
Timing is everything: A meta-analysis of the relationships between organizational performance and innovation 总被引:1,自引:0,他引:1
The relationship between innovation and firm performance has been uncertain. In previous empirical tests of both causal directions of the organizational performance and innovation relationship, the temporal sequence of research designs has often been flawed. We meta-analytically test both temporal sequences of this relationship using 158 effect sizes from 55 empirical studies. We find that many empirical studies hypothesized one temporal sequence (e.g. innovation and future performance), but used data based on the opposite temporal sequence (e.g. past performance and innovation). Correcting the studies based on the actual temporal sequence used reveals that while the relationship between innovation and future performance is positive (based on economic rent-seeking), the relationship between past performance and innovation is less clear, especially when the study's framing is taken into account. Focusing on temporal sequencing suggests new research avenues on the organizational performance and innovation relationship. 相似文献
86.
Paloma Lopez-Garcia Jose Manuel Montero 《Economics of Innovation and New Technology》2013,22(7):589-612
This paper investigates whether the existence of knowledge spillovers and the capacity of firms to assimilate them, which we relate with R&D intensity and some human resource management practices, are associated with the decision to innovate of Spanish firms. In order to do this, we employ data from the ‘Central de Balances’ database, which covers both manufacturing and services firms during the period 2003–2007, and use an estimator proposed by Wooldridge [2005. Simple solutions to the initial conditions problem in dynamic nonlinear panel data models with unobserved heterogeneity. Journal of Applied Econometrics 20, no. 1: 39–54] for dynamic random effects discrete choice models. The empirical exercise provides evidence on the positive link between spillovers and the innovative behaviour of companies, not just for the knowledge generated in the same industry, but also for that generated in the same region or by the public sector. Moreover, this link is stronger for those firms with a higher capacity to absorb those spillovers. This ability not only works through firms’ R&D capabilities, but also through factors such as the quality of the labour force, the share of temporary employment and the amount of resources spent in training. In addition to these factors, we find that innovation performance exhibits a high degree of inertia. Further, some other observed firm characteristics, such as size, sales growth, export behaviour, sector capital intensity or financial structure variables, are also found to be relevant determinants of the likelihood of innovation. 相似文献
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为探讨如何有效地预防和控制危险化学品泄漏事故,运用混沌理论方法对焦作市某化工厂泄漏事故统计数据进行了时间序列分析和R/S分析,指出危险化学品泄漏事故具有明显的混沌特性。分析和讨论了危险化学品泄漏事故的混沌特性,并对后续短期内可能发生的事故进行了预测。 相似文献
88.
We develop real rainbow option models to value an operating asset with the flexibility to choose between two commodity outputs. We provide a quasi-analytical solution and a numerical lattice solution to a model with continuous switching opportunities between two commodity outputs, taking into account operating and switching costs. The models are applied to an illustrative case, demonstrating that the quasi-analytical solution and the lattice approach provide near identical results for the asset valuation and optimal switching boundaries. We find that the switching boundaries generally narrow as prices decline. In the presence of operating costs and temporary suspension, however, the thresholds diverge for low enough prices. A fertilizer plant with flexibility between selling ammonia and urea is valued in an empirical section using our real option models. Despite the high correlation between the two alternative commodities, ammonia and urea, there is significant value in the flexibility to choose between the two. Both strategic and policy implications for stakeholders in flexible assets are discussed, with some generalisations outside the fertilizer industry. 相似文献
89.
应用层序地层学的理论和方法,针对研究区的地质概况,综合分析地震、测井、岩心等资料,对莺山地区的层序界面进行识别,共识别出5个三级层序界面(SB1-SB5)。研究区的登娄库组是一套完整的超层序,共发育三个体系域,自下而上为低水位体系域、水进体系域、高水位体系域。在层序格架内,总体以冲击扇、扇三角洲、辫状河三角洲、泛滥平原等相配的沉积体系为主。研究区由下而上共发育3套生储盖组合,表明该区具有一定勘探潜力。 相似文献
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