Nonlinear Three-Wave Interaction among Barotropic Rossby Waves in a Large-scale Forced Barotropic Flow

In this paper. the coupling equations describing nonlinear three-wave interaction amongRossby waves including the forcing of an external vorticity source are obtained. Under certainconditions, the coupling equations with a constant amplitude forcing, the stability analysis indicates that when the amplitude of the external forcing increases to a certain extent, a pitchforkbifurcation occurs. Also. it is shown fi-o m numerical results that the bifurcation can lead to chaoticbehavior of' strange' attractor. For the obtained three-variable equation, when the amplitude ofmodulated external forcing gradually increases, a Period-doubling bifurcation is found to lead tochaotic behavior. Thus, in a nonlinear three-wave coupling model in the large-scale forcedbarotropic atmospheric flow, chaotic behavior can be observed. This chaotic behavior can explainin part 30-60-day low-flequency oscillations observed in mid-high latitudes.

EPON+低频EOC在乡镇广电网双向改造中的应用

EPON+低频EOC技术接入模式比较适合有线电视双向改造,阐述了EPON+低频EOC的工作特性,认为完全可以做到灵活、快捷、经济地改造现有有线电视网络,介绍了设计、调试、监测直至应用一套组合网络的过程、方法。

康特低频有源EOC在漳州广电的应用

介绍康特低频有源EOC在漳州广电的应用情况,包括主要设备局端EM40、EOC模块和终端ES11等,对其在广电上的设计优缺点提出了自己的看法,此外还结合实际工作情况,给出了一些实际操作方法与故障排除方法,供同行参考。

ZONALLY SYMMETRICAL EKMAN-CISK MECHANISM AND 30—60-DAY LOW FREQUENCY OSCILLATION NEAR THE EQUATOR

Based on the baroclinic semi-geostrophic model,the effects of zonally symmetrical Ekman- CISK mechanism on the characteristics of 30—60-day low frequency oscillation(LFO)near the equator are investigated.It is found that the theoretical results are in good agreement with the observational features of LFO.Besides,the planetary-scale LFO with the period of 30—60 d could be triggered by the Ekman-CISK mechanism,and the growth rate of perturbation with wave number 1 is in order of O (10^(-6)s^(-1)).The zonal propagation of LFO and the corresponding longitudinal-height structure of physical quantities are also discussed in detail.

低频调制EoC信号在有线电视网络中衰减值分析

通过对东港开发区有线电视网络组网结构的介绍,分析网络中分支分配器件、双向辅助器件和同轴电缆对低频调制EoC信号的损耗,得出低频调制EoC信号在东港开发区有线电视网络中的衰减值满足要求的结论。

PROPAGATION OF 30—60 DAY LOW FREQUENCY OSCILLATIONS AND THEIR INFLUENCE UPON THE SUBTROPICAL WESTERLIES JET STREAM DURING NORTHERN HEMISPHERE WINTER

Based on daily ECMWF gridpoint data of two winters during 1981—1983 including an ENSO year,propagation of low frequency oscillations(LFO)during Northern Hemisphere winters and their influences upon 30—60 day oscillations of the subtropical jet stream are studied with the sta- tistical methods as complex empirical orthogonal function(CEOF)and so on.Results show that in the winter of a normal year(1981—1982),30—60 day oscillations in the subtropical zone are mainly in the northern and southern flanks of exit region of jet stream.In the ENSO year(1982— 1983),they are mainly in the vicinity of entrance and exit regions of jet stream.Intraseasonal changes of subtropical jet stream manifested themselves as latitudinal fluctuation or longitudinal progression or regression of about 40 day period.There are marked differences between propagat- ing passages of low frequency modes responsible for changes of subtropical jet stream in the normal year(1981—1982)and in the ENSO year(1982—1983).Changes of oscillation amplitude show obvious phases.In general,the one in late winter is stronger than that in early winter,strongest one occurs in February.

Heart Rate Variability, Standard of Measurement, Physiological Interpretation and Clinical Use in Mountain Marathon Runners during Sleep and after Acclimatization at 3480 m

Fluctuations in autonomic cardiovascular regulation during exposure to high altitude may increase the risk of heart attack during waking and sleep. This study compared heart rate variability (HVR) and its components during sleep at low altitude and after 30 - 41 hours of acclimatization at high altitude (3480 m) in five mountain marathon runners controlled for diet, drugs, light-dark cycle and jet lag. In comparison to sea level, RR-intervals during sleep at high altitude decreased significantly (P 0.001). The significant increase in sympathetic autonomic cardiovascular modulation at high altitude protects against excessive oxygen deprivation during sleep. Increases in R-R intervals can require longer periods of acclimatization at3480 m to mitigate the effects of altitude/hypoxia on sympathetic tone, thus reducing cardiovascular distress at rest during waking and sleep and probably before during and after athletic performance at altitude.

怎样用SDA5000型数字电视分析仪测试双向放大器的反向插入损耗

介绍了SDA5000数字电视分析仪和漳州广电双向网络的改造方案,并简单地阐述了双向放大器的概念。介绍了SDA5000数字电视分析仪3个接口的作用,结合实际案例说明怎样用SDA5000数字电视分析仪测试双向放大器的插入损耗。

Brain activity in Parkinson's disease patients with mild cognitive impairment

Mild cognitive impairment （MCI） is common in patients with Parkinson＇s disease （PD）, yet the underlying neural mechanisms of this disease state remain unclear. We investigated alterations in the spontaneous brain activity of PD patients with MCI （PD-MCI） relative to cognitively normal PD patients （PD-CN） and healthy control （HC） subjects. In this work, 13 PD-MCI patients, 16 PD-CN patients, and 16 HC subjects completed resting state functional MRI. Spontaneous brain activity was measured by calculating amplitude of low frequency fluctuation （ALFF） values across the whole brain. Between-group differences and correlations between ALFF values and cognitive test scores were analyzed. ALFF values decreased in the right superior temporal gyrus and increased in the left middle temporal gyrus and left superior frontal gyms of PD-MCI patients compared with PD-CN patients. In the PD-MCI group, ALFF values in the left middle temporal gyrus were negatively correlated with Montreal Cognitive Assessment and vocabulary test scores, and the ALFF values in the left superior frontal gyms were negatively correlated with vocabulary test scores. Our study demonstrates that PD-MCI is associated with abnormal spontaneous brain activity in the temporal and frontal lobes. These findings inform the underlying neural mechanism of cognitive impairment in PD.