The planar quadratic system with an invariant cubic curve has at most one limit cycle 類(lèi)方程的極限環(huán)存在性的注記
The cubic curve is constructed from the first point to the fourth point by using the second and third points as control points 立方曲線以第二個(gè)點(diǎn)和第三個(gè)點(diǎn)為控制點(diǎn),從第一個(gè)點(diǎn)到第四個(gè)點(diǎn)來(lái)構(gòu)造。
If there is a previous line or curve segment in the figure , a line is added to connect the endpoint of the previous segment to the starting point of the cubic curve 如果圖形中已有一段直線段或曲線段,則添加一段直線連接已有線段的終結(jié)點(diǎn)和立方曲線的起始點(diǎn)。
If there are previous lines or curves in the figure , a line is added to connect the endpoint of the previous segment to the starting point of the first cubic curve in the sequence 如果圖形中已有直線或曲線,則將添加一段直線連接已有線段的終結(jié)點(diǎn)和序列中第一段立方曲線的起始點(diǎn)。
In order to verify the feasibility of ann , adopting same training sample the author establishes quadratic curve model and index model of tourism foreign exchange income and cubic curve model and index model of total inbound tourist quantity 為了驗(yàn)證人工神經(jīng)網(wǎng)絡(luò)模型的可行性,筆者用同樣的訓(xùn)練樣本分別建立了旅游外匯收入二次曲線模型、指數(shù)曲線模型和入境游客三次曲線模型、指數(shù)曲線模型。
During interpolation , the original frequency of seismic signal is kept very well without negative effect to the subsequent processing . 5 . cubic curves are used to geologic structure model input , and the formation boundary becomes smooth , which is good to the forward modeling . this method could hold true to various background 成功地將樣條曲線應(yīng)用于地質(zhì)模型輸入環(huán)節(jié),保證了地質(zhì)模型界面的光滑連續(xù),并能夠廣泛適應(yīng)于各種質(zhì)量的模型底圖,為正演模擬取得良好的效果奠定了基礎(chǔ)。
This research is based on a group of countries in deferent developing phase in the same period . then , by using spss statistic software , from the regressive model , we made a conclusion that a cubic curve is found to describe the law of the housing ratio that change with economic development . we hereby divide the cubic curve into three phases : rising , falling , and re - rising , then we analysis the character of each phase 本文采用橫向數(shù)據(jù)分析法,研究了同一時(shí)期處于不同經(jīng)濟(jì)發(fā)展水平的一系列國(guó)家住宅產(chǎn)業(yè)增加值在gdp中所占的比率,然后借助spss統(tǒng)計(jì)軟件進(jìn)行回歸分析,得出了住宅比率隨經(jīng)濟(jì)發(fā)展呈現(xiàn)三次曲線的變化規(guī)律的結(jié)論,并據(jù)此劃分了住宅產(chǎn)業(yè)發(fā)展軌跡的三個(gè)階段,即上升階段、下降階段、再上升階段,分析了每個(gè)階段的基本特征。