常德市降水酸度时间序列谱分析

利用谱分析方法研究了常德市10年降水酸度月均值的周期变化。将加窗周期图谱估计与三角函数拟合相结合，分别确定各主要周期长度并以所得数据对数据序列进行三角函数叠加拟合。结果表明，降水酸度月均值具有12、7、4、18、3、6个月的周期变化，以7个主要周期分量可以很好地模拟降水酸度月均值的变化。     

混沌时间序列单变量和多变量重构的预测比较

提出了多变量混沌时间序列相空间延迟重构中延迟时间间隔和嵌入维数的选取方法，给出了多变量混沌时间序列的局部平均预测法，局部线性预测法和BP神经网络预测法等3种非线性预测方法．通过Lorenz系统的仿真计算表明，无论用3种非线性预测方法中的哪一种，多变量混沌时间序列要比单变量混沌时间序列的预测误差小得多，即使前的数据长度只有后的一半，前的预测误差也要小很多．另外从预测误差最小的角度验证了多变量混沌时间序列相空间延迟重构中延迟时间间隔和嵌入维数选取方法的有效性．     

下喷自吸环流反应器内局部混沌特性(英文)

应用确定性混沌分析技术,初步研究了下喷自吸环流反应器内气－液两相流动的时序压力波动的局部混沌特性．结果发现,在本文实验条件下,该反应器内局部最大李雅普诺夫指数值均大于零,并且呈现出与局部分形维数类似的分布规律．这些结果表明,该反应器内的流动行为呈现混沌特性,可以应用诸如局部最大李雅普诺夫指数和局部分形维数等局部非线性特征参数从更深层上揭示多相反应器内的流动特性,例如流区过渡及流动结构等．     

混沌投资时间序列的分形维数谱

不同文献对沪指和深指的分形维数的计算结果相差甚大，究其原因，除计算方法，计算误差外，更深层次的原因是混沌投资时间序列分形维数谱的存在，本文对混沌投资时间序列分形维数的信息谱，奇异谱，动熵谱等问题进行探索，并简介其应用。     

基于Volterra级数的RLS自适应算法的混沌时间序列预测

根据混沌序列产生的确定性和非线性机制,基于Volterra级数和RLS算法,提出了一种少参数二阶非线性滤波算法用于混沌时间序列的自适应预测。仿真结果表明,这种非线性自适应滤波器能有效地预测一些超混沌序列,而且该滤波器的一步均方误差性能明显高于其他基于Volterra级数的NLMS算法,表明该算法具有良好的收敛性能。     

逻辑斯蒂映像混沌区的几个非线性特征量

运用非线性动力学的方法分析了逻辑斯蒂(Logiotic)映像混沌区的几个非线性特征量。采用重现图形(Recurrence plot analysis,RPA)和重现定量(Recurrence quantification analysis,RQA)分析法得出系统存在确定性的规律;计算了序列的关联维数、最大Lyapunov指数和近似熵(Approximate entropy,ApEn)。结果表明:关联维数介于1～2之间,系统的最大Lyapunov指数大于0,ApEn的值为0.676 460。     

混沌数字水印信号研究

探讨了使用M序列作为数字信号方法的优缺点,分析了混沌映射和混沌水印序列的统计特性,在此基础上,对混沌序列数字水印信号与M序列数字水印的性能进行了分析比较,指出混沌序列是最适合作为数字水印信号的序列.     

酸雨从哪里来？

所谓酸雨是指园空气污染而造成的酸性降水。通常认为大气降水与二氧化碳气体平衡时的酸度PH5．6为阵水天然酸度，并将其用作降水是否酸化的判别标准，当阵水曲PH低于5．6时，降水即为酸雨。     

都匀市区酸雨现状及成因浅析

对都匀市区2001～2003年酸雨降水数据进行统计分析，结果表明，近年来都匀市降水 pH 均值＜5．6，酸雨出现频率高。降水中化学成分以 SO_4~(2-)为主。酸雨出现的频率季节变化规律为：一、四季度＞二季度＞三季度，与 SO_2在不同季节质量浓度变化规律一致。酸雨主要是局地污染造成。同时，2001～2003年都匀市降水酸度和酸雨频率逐年有了较大改善。只有通过调整能源结构，对用煤总量进行控制，采取措施控制 SO_2污染，就能改善都匀市酸雨状况。     

混沌定义的研究进展

混洗定义从Li—Yorke提出的“周期3混沌”走向R．L．Devaney的严格化定义后，近几年又经过J．Banks等人以及M—Velllekoop andR．Berglund进一步的研究和讨论，取得较大的进展。并指出其中的关键点是使得一维区间上，只需要连续映射是拓扑可递的这一个条件，即得到区间上“拓扑传递性即混沌”这又一名论断。而对n≥2维区域上的混沌，只要拓扑可递性与周期点稠密这两个条件即可。使混沌的定义朝严格化、简单化前进了一大步。对于混沌的研究有重要的参考价值。     

卡思卡特城堡

It is worthy of noting that, whilst Crookston Castle witnessed the earlier and happier portion of Mary's variegated life,     

不同的吃喝玩乐

一、吃和喝吃苹果 eat an apple, 吃药 take medicine,吃糖 have some sweets,吃饭 have one's meals,吃馆子 dine out,吃惊 be surprised/     

漏洞百出的教育

Many college freshmen arrive woefully unprepared to do college work, and as disadvantaged populations continue to grow, the share of the American work force that has made it through college is expected to plummet. Many experts blame that educational failure not just on high schools but also on colleges. School & College, a special report by The Chronicle, looks at efforts to fix the system. What reforms would better prepare students for college? What should schools and colleges be doing differently? How should state and federal officials help?     

只要努力,不要后悔

There are numbers of crossroads on our long and unpredictable life journey where we totally have no idea about which direction to choose. No matter what our decision is, we should not turn back, but face the music and go ahead instead. I am this kind of girl who always does try without regretting, one example is how I dealt with my love.     

浅谈移民问题

Migration occurs behind a variety of reasons and has a great effect on the whole world. People may migrate in order to improve their economic situation, or in order to escape civil strife, persecution, and environmental disasters. The impact of migration is complex, bringing both benefits anddisadvantages. This paper briefly talks about the causes of migration, the allocation of benefits, and the ways in which individual countries and the international community deal with this important subject.     

Sister Carrie, an Adherent of Desires

Sister Carrie is one of the most controversial characters in American literature.Thought as a "fallen woman" firstly,she was defined as a "new woman" by some critics later. However, by digging into the motivaton behind the whole process of Carrie's "success", the relationship between Carrie and her creator (the author), the social conditions of then American, it can be found that Carrie has never been free-standing on her thought and she has never found her real-sdf even after becoming a famous actress. In a society dominated by mass consumerism Carrie is only an adherent of her own desires. She also is a representative of all those country girls flooded into cities, a symbol and a sacrifice of the urbanization of America in a time countryside was overcome by cities.     

Improvement of one-cycle controller by use of proportional integral differential controller

1.IntroductionOne-cyclecontrolmethod,whichwasproposedaboutonedecadeago[1],hasbecomeanattractivemethodinspecialfieldssuchaspowerfactorcorrection[2-6],switchingamplifiers[7,8],etc.Themainideaofthiscontrollerisbasedonintegrationofdiodevoltageinone-cycleandforcesittobeexactlyequaltothereferencevalue.Themainadvantageofthiscontrollerisitsrealtimeabilitytorejectthevariationofinputvoltage[1].Despitethisgreatability,ithasnogoodperformancesinrejectingofloaddisturbanceandfollowingreferencecommands.Espec…     

库克斯顿城堡

城堡, 是欧洲典型的建筑之一, 每个城堡都有一个美丽的传说或是一段历史。从本期开始, 我们将推出“城堡之旅”, 带各位读者去浏览、观赏欧洲各地的城堡, 开始一段文化与历史的旅途!     

胡主席在印度,我却在中国

Today, Sunday morning, I sit thinking and typing at my computer. My thoughts are in my homeland, India and my body is in China. The body is here and mind there for a good reason. Mr. Hu is president and I am resident and both are in each other's countries (what a difference the absence of one small letter makes!). Mr. Hu will return in a few days and I will stay on longer.