Key words: biomathematics; optimal harvesting problem; stochastic differential equation; mutualism model; harvesting cost

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A predator model with refuge and toxicity is studied. By constructing a suitable Dulac function, it is shown that there is no limit cycle in the first quadrant, thus the globally stability of the equilibrium is proved. Further more, the paper analyzes the influence of refuge, toxicity and harvesting. It is amazing that ① if the death rate of predator is big or the harvesting effort is big, the existence of the predator is unrelated with refuge; if the death rate of predator and the harvesting effort are small, and the refuge is small enough, the population of both species is increased as the increase of refuge;② if d2=0, the increase of d1 has no influence on the prey population, while the population of predator is decreased.

研究一類有避難所哟哟哟WWW高清在线观看视频、毒素作用和外界捕獲影響的捕食系統(tǒng)人与动牲交av免费，通過構(gòu)造恰當?shù)腄ulac函數(shù)一级人与嘼视频免费播放，證明系統(tǒng)在第一象限沒有極限環(huán)，從而證明了平衡點的全局穩(wěn)定性黄色网址在线免费播放；分析了避難所免费看黄色女人片、毒素、捕獲作用對該系統(tǒng)最終種群數(shù)量的影響日本a网站在线看，發(fā)現(xiàn)：①當捕食者的死亡率大或其被捕獲得多時A片勉费视频网站，兩種群的絕滅與避難所的存在無關(guān)；當捕食者的死亡率小黄色视频一级黄、被捕獲得多且避難所足夠小時黄片久久久久久久，隨著食餌避難所的增加，捕食者種群數(shù)量也隨之增加亚欧A片视频在线观看；②當毒素d2=0時久久久国产一级AV片，毒素d1的增加對食餌種群最終數(shù)量沒有影響，而使捕食者種群數(shù)量下降色哟哟m3u8免费视频。

Abstract］ Objective To compare the indican content of folium isatidis in different origin and different harvesting period.Methods By HPLC on different areas, different harvesting times,determined indican.

目的 對比不同產(chǎn)地及不同采收時期青葉中吲哚苷含量方法采用HPLC法對不同產(chǎn)地99亚洲国产精品二产精品、不同采收時期的大青葉中的吲哚苷進行了測定。

This study deals with precipitation fluctuations in the transitional zone between the arid and semiarid regions of northwest China from the 1950s to the 1990s,discusses spatial variation of 250 mm isohyet during the dry years and wet years; and systematically studies rainfall harvesting system relative to runoff inducing catchments, water storage and highly efficient utilization and evaluates the influence of rainwater harvesting on regional development and environment conservation.

分析了干旱半干旱區(qū)過渡帶降水的時空變異性亚洲图片欧美日韩，確定了250 mm降水量線在豐枯年份的空間擺動幅度最新精品国偷一区二区。

Then analyze the local stability of the model. The optimal harvesting policy for harvesting the prey species is studied.

然后分析了模型的局部穩(wěn)定性，得到了對食餌進行捕獲的最優(yōu)捕獲策略12白嫩逼被操视频。

Presently, the main harvesting of Arundo donaxl is traditional manual ways, the working conditions are bad, the harvesting efficiency is low and the cost is high. To harvest Arundo donaxl on schedule and maintaining the quality and quantity is key to ensure the bumper harvest and yield, the croppers income and the timely supply as industrial material, the mechanization harvest has been urgent for the industrialization of Arundo donaxl planting and timely harvest.

然而未满十八禁止免费网址，目前蘆竹的收割仍主要采用傳統(tǒng)的手工方式收割，勞動環(huán)境艱苦欧美黑白配性交，收割效率低且成本高操逼污视频网站，按期保質(zhì)保量收割蘆竹是蘆竹種植場豐產(chǎn)豐收，實現(xiàn)種植場農(nóng)民增收和保證其作為工業(yè)原料來源的關(guān)鍵黄免费。

The result showed that the volume, dry weight and total sugar content of root gradually reduced with the harvest frequency, but the reductive sugar content in root increased. While the harvesting frequency was two times per year, the volume and dry weight of alfalfa root showed an decreasing at beginning and then increasing when the first harvesting was at different growth stages and the lowest values were at flowering period however, it was not significant for brome.

結(jié)果表明：隨刈割次數(shù)增加人人爽人人超人人高潮，兩種牧草根體積、根干重和根部總含糖量逐漸減小日韩电影线上无码观看视频网站，而根系還原糖含量呈逐漸增加的趨勢无码天天av；在年刈割兩次，首次刈割分別在不同生育時期試驗處理中成年网站在线视频网站，苜蓿根體積和干重呈先減后增趨勢思热在线视频精品免费观看，首次刈割在盛花期根體積和干物質(zhì)含量均最低，而無芒雀麥變化不明顯一级a做一级吃奶水。

The effect of harvesting height on the grass yield and quality of two varieties of Lolium multiflorum was studied and the result showed that the different harvesting height greatly affected the fresh yield, dry mater yield, quality and growth characteristics.

多花黑麥草Lolium multifolium具有很強的再生性和耐刈性高清无码视频在线观看的，為了確定最佳的刈割利用方式，在有限的耕地中獲得較高的產(chǎn)量和效益，采用小區(qū)試驗的方法在线黄黄自慰，研究了不同刈割高度對多花黑麥草特高和杰威產(chǎn)草量和品質(zhì)的影響黄片高清一区国产。

Percent of 〓C photosynthesized into plant at early harvesting redistributed to fruit at profuse harvesting.

始采期固定的〓C到盛采期仍有1/4分配于果實中，其對果實的貢獻至少可持續(xù)一個月中国一级无码黄片。

The harvesting cost by hand is 6 times higher than that by machine harvester, so machine harvesting of sugarcane is a vital factor to reduce the production and improve international competitiveness. As an important composition part of sugarcane harvester, the mechanism capability influence windrowing quality and working efficiency directly.

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