一类拟三次系统的中心条件与极限环分支

研究了一类拟三次系统的奇点量、中心焦点判定与极限环分支问题,首先通过适当的变换将系统的原点(无穷远点)转化为原点,得到了系统原点的前21个奇点量,从而导出原点为中心和最高阶细焦点(细奇点)的条件,并分别给出了原点和无穷远点分支出4个极限环的实例.     

图Cm-1UCm的优美性

证明了C4k 1UC4k 2的优美性，得到了Cm-1UCm为优美图的充要条件．     

Characteristics of U-pattern distribution of highconcentration <Superscript>210</Superscript>Pb in surface air at central Guizhou,China

A better understanding of the variation of ²¹⁰Pb concentrations in the surface air is the key to trace lake sedimentation and catchment erosion, to establish and validate the global diffusion model of contaminants, and to assess the impact of natural radiation on the ecological system. Basing on the study progresses of the sedimentation, the atmospheric model and the unique environmental background in the Yunnan-Guizhou Plateau, and starting from December 20, 2001, we made use of a 500 NE Type aerosol sampler to collect filter samples, once a week in the past consecutive two years, in the surface air at Mt. Guanfeng, Guiyang City, China. Synchronous detailed γ-energy spectrometric observations of ²¹⁰Pb concentrations at both Chinese and U.S. laboratories have shown that the average monthly ²¹⁰Pb concentration displays a regular U-patterns distribution of annual variations, with high values appearing in winter and low values in late spring and summer. The average annual ²¹⁰Pb concentrations are estimated to be 2.77±0.63 mBq/m³, about 4 times the average maximum concentrations reported from quite a number of monitoring stations throughout the world. The possible factors affecting the sources of ²¹⁰Pb in the surface air in the central part of Guizhou Province are: Release of ²²²Rn from the U-Ra series enriched in the soils; chemical weathering of carbonate rocks; the exploitation, processing and utilization of coal and phosphorous resources. The principal factor controlling the high ²¹⁰Pb concentrations in the surface air in the central Guizhou and their annual U-pattern distribution is the release of ²²²Rn. The average monthly ²¹⁰Pb concentrations show a good negative powerfunction relationship with increasing precipitation and also show a good negative linear-function relationship with the rise of air temperature in month grouping. Group No.1 (June to November) reflects a relatively low release of ²²²Rn from soils in relatively high temperature seasons; Group No.2 (December to May) mirrors a relatively high release of ²²²Rn from soils in relatively low temperature seasons. The average monthly ²¹⁰Pb concentrations simulated in terms of the precipitation and air temperature are in good consistency with the measured values, revealing that the regular U-pattern distribution characteristics of ²¹⁰Pb concentrations in the surface air in the central Guizhou are controlled predominantly by regional precipitation and air temperature. Meanwhile, it is also indicated that the magnitude of variation of air temperature and precipitation within the same year also constrains the ratio of high values over low values of average monthly ²¹⁰Pb concentrations. On a month time scale, precipitation and air temperature are a main factor affecting the release of ²²²Rn from soils (rocks). In this aspect strong evidence has been obtained.     

地球表层动力学理论研究（Ⅰ）──陆地表层系统

阐述了地球表层动力学理论的研究对象和研究内容及其理论方法；抽象出陆地表层系统，包括时空尺度范围的约定、状态变量的选择、物质循环和能量循环、人类活动及天文因素的影响等。     

Trend, seasonal and diurnal variations of atmospheric CO2 in Beijing

The concentration of atmospheric CO2 in Beijing increased rapidly at a mean growth rate of 3.7%@a?1 from 1993 to 1995. After displaying a peak of (409.7±25.9) ?mol@mol?1 in 1995, it decreased slowly. Both the almost stable anthropogenic CO2 source and increasing biotic CO2 sink contribute to the drop of CO2 concentration from 1995 to 2000. The seasonal variation of CO2 concentration exhibits a clear cycle with a maximum in winter, averaging (426.8±20.6) ?mol@mol?1, and a minimum in summer, averaging (369.1±6.1) ?mol@mol?1. The seasonal variation of CO2 concentration is mainly controlled by phenology. The mean diurnal variation of atmospheric CO2 concentration for a year in Beijing is highly clear: daily maximum CO2 concentration usually occurs at night, but daily minimum CO2 concentration does in the daytime, with a mean diurnal difference more than 34.7 ?mol@mol?1. It has been revealed that the interannual variations of atmospheric CO2 concentration in winter and autumn regulated the interannual trend of atmospheric CO2, whereas the interannual variation of CO2 concentration in summer affected the general tendency of atmospheric CO2 in a less degree.     

新疆石河子市蔬菜周年供应情况的调查与研究

本文通过对石河子市蔬菜周年供应情况的调查与研究,来探寻解决北方寒冷地区中、小城市和工矿区蔬菜周年供应问题的可行性措施.石河子市逐步缩小蔬菜供应淡旺季差别的主要方法是:1、建立蔬菜公司统管下的近郊专业化商品菜基地、保证国营菜店的货源.2、在淡季有计划地从外地调人鲜菜调节市场.3、适当发展加工、速冻菜、4、建立远郊冬菜生产基地,并实行蔬菜公司,单位和个人三结合贮存冬菜.5、严格价格管理.对个体菜贩实行最高限价.     

Using the life cycle to anticipate satisfaction at work

It was hypothesized that there are important non-linear life-cycle influences upon job and organizational satisfaction. Five common life-cycle stages were identified from the literature: the phases of ‘reality shock’, ‘socialization and growth’, ‘mid-career crisis’, ‘acceptance’, and ‘pre-retirement’. The first, third and last stages were expected to show declines in job and organizational satisfaction because of the personal and job-related disappointments and crises that typically occur during these periods of life. The second and fourth stages were expected to show increases in satisfaction because of the pleasant life experiences that often occur then. All but the first stage supported these hypotheses when we controlled for the influence of sex, education, job experience, level in the hierarchy and occupational upward mobility.     

二维递归数字滤波器不存在极限环的频域判据

以定理的形式给出了具有量化和溢出非线性的二维递归数字滤波器不存在零输入极限环的充分条件,并证明这些定理比现有的定理更具有一般性.给出的检验定理可用于检验具有多重和复合非线性的二维递归数字滤波器的极限环情况.     

The leading indicator approach to economic forecasting—retrospect and prospect

Our purpose in this paper is to explain briefly the theory and rationale underlying the leading, coincident and lagging indicators, describe the more important statistical procedures used, and review the evidence on how the indicators have performed in practice. The tests of performance concentrate on data not used in the selection of the indicators, in the United States and nine other countries. We conclude with some suggestions for future research and development, including the application of the approach to the analysis of inflation.     

关于一个发酵动力系统的多次振荡

利用微分系统的定性理论研究了一个连续发酵动力系统的多次非线性振荡问题,探讨和估计了存在多个极限环的条件.是对文献[3,12]所提出发酵模型的深化,并对发酵产物与基质浓度的非线性函数关系做了进一步的深入研究.