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801.
主要讨论了技术创新条件下产业系统的演化行为及过程,并利用我国能源产业系统进行了实证分析。研究结果表明,产业系统的整体演化过程遵循Logistic方程曲线。由于技术创新模型的参数是时变的,因而使得产业系统的实际演化过程具有多样性和复杂性。 相似文献
802.
803.
研究三角形取样鉴相数字合成器锁相环中的混沌现象。其方法是先对三角形取样鉴相数字合成器锁相环系统作离散化处理,得到相应的离散化系统模型;系统中的环路滤波器采用RC积分滤波器,鉴相器采用三角形鉴相特性;通过验证离散化系统相应的低维系统存在快返反射点,证明了当系统方程满足一定条件时,原系统有混沌输出。最后导出了混沌与系统参数间的关系式。 相似文献
804.
张洪德 《西华师范大学学报(自然科学版)》1988,(3)
本文对相当广泛的一类一阶微分方程研究奇解的存在问题,提出一种不借助几何直观,而是用分析方法寻求一阶微分方程的奇解. 相似文献
805.
采用分层介质方法处理非均匀等离子体层,研究了电磁波射向覆盖磁化等离子体层的金属平板时电磁波的衰减特性。着重讨论Epstein密度分布的等离子体层,分析了等离子体电子密度、电子碰撞频率、外加磁场和入射角度等因素对电磁波衰减的影响,得出在一定等离子体密度和电子碰撞频率下,等离子体对电磁波的吸收特性。 相似文献
806.
沈尚达 《上海理工大学学报(社会科学版)》1988,(2)
本文研究了二阶非线性微分方程x″+f(x,x′)=0全局渐近稳定的充要条件,并推广了文[5](8][9]中的定理。 相似文献
807.
808.
Few studies have examined the role of managerial support in the adaptation of entrants to healthcare. The purpose of this study was to identify the job characteristic and role-related variables that mediate the effects of managerial support and personality on the mental and physical health and sickness absence in two independent groups of new recruits to a healthcare organization. Entrants to a healthcare environment (student nurses) were surveyed 25 weeks after entry. Latent variables represented neuroticism, demand, control, role clarity and affective outcome variables in a simplified version of the Michigan model of work stress (House, 1981). This study used a two-stage approach to structural equation modelling, exploring hypothesized structural models on an initial data set (N=195) prior to confirmation on an independent replication data set (N=239) using multi-sample methods. Finally the confirmed model of choice was evaluated using the combined data (N=434). Emotional distress reported at 6 months was found to be associated with dispositional characteristics of the entrant and indirectly, via job satisfaction, with managerial support from academic and clinical sources. Managerial support from academic and clinical sources had an indirect influence on job satisfaction, but by differing mechanisms involving role clarity and control. The demands perceived by the entrants arose from neuroticism and were independent of any other variable. Emotional distress had its deleterious association with sickness absence via somatic health. This study details a series of mechanisms that will subsequently be tested longitudinally. 相似文献
809.
研制了一种连续可调的基波Gunn振荡器,频率可从65GHz调到82GHz.在大部分工作频段内输出功率大于10mW.最大功率达到30mW.并与美国millitcch公司最新产品做了比较,在频带宽度上远超过GDM-12,在输出功率上大致相当. 相似文献
810.
Katsumi Togashi 《Researches on Population Ecology》1991,33(2):245-256
Summary To understand the mechanism of spread of pine wilt disease caused by the pinewood nematode,Bursaphelenchus xylophilus, which is vectored by a cerambycid,Monochamus alternatus, the spatial distribution of trees weakened by the nematode was examined within aPinus thunbergii stand from June to October for 4 years. The weakened trees were distributed in a clumped pattern in 1980 and 1981, at an
early stage of infestation. In many cases, they showed a double-clumped pattern. The degree of aggregation was higher in June
or July than after August. They were uniformly distributed in June or July 1982 and in June 1983 whereas they showed a double-clumped
pattern after August. The trees were frequently weakened in June or July when they were near the trees weakened during the
previous year. At quadrat sizes of more than 25 m2, spatial overlapping was pronounced between trees weakened during June–July of the current year and those weakened in the
previous year. The seasonal changes in spatial distribution of weakened trees were explained by the interaction amongM. alternatus, B. xylophilus andPinus trees. 相似文献