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101.
102.
TUJian-jun 《武汉大学学报:自然科学英文版》2005,10(4):641-646
On the basis of the ecological footprint (EF) model, this paper studied the ecological security in the Upper Min River Basin ecosystem. The result shows that with 2. 038 2hm^2 per capita ecological capacity (0.422 2hm^2 higher than per capita EF), and 165 825hm^2 ecology surplus, the ecosystem in Upper Min River is generally secure at present. But the arable land is overweighed and omens an ecosecurity crisis. Meanwhile, problems such as low forest coverage rate, severe loss of water and soil, enlargement of aridvalley area, frequent occurrence of mountain hazards and degradation of pastures have been major threats to the eco-security of this region. The calculation result of ten thousand-yuan (RMB) GDP shows that the use of natural resources is extensive, and there will be a rapid increase tendency of EF in the future. In order to maintain the present eco-security, the ways of use natural resources must be improved in the Upper Min River Basin. 相似文献
103.
集值映射的Ky Fan不等式 总被引:2,自引:1,他引:1
本文得到一个集值映射的KyFan不等式,它以通常的KyFan不等式及似变分不等式为特例。其中在非紧情况下,使用了escaping序列的概念。 相似文献
104.
The Cambrian explosion was coined to describe the geologically sudden appearance of numerous bilaterian body plans(Phyla)around the Ediacaran-Cambrian transition,around 565-520million years ago.Many explanations and conjectures have been postulated in order to explain the pattern and duration of this explosive radiation of many different phyla of early metazoans.Here,we focus on the evolution of a phylum of marine suspension-feeding animals—the brachiopods,as exemplified by the exceptionally preserved taxa from the celebrated Chengjiang Konservat Lagerst(a|¨)tte(Yunnan,China).The abundant soft-bodied preservation at these fossil quarries gives us the only firm insights into what brachiopods looked like and how they functioned and lived when they first appeared on the Earth.Studies of Chengjiang brachiopods demonstrate that the early animals developed a remarkably varied organization of tissues and organs shortly after the onset of Cambrian explosion.In the marine suspension-feeding brachiopods,most importantly the tentaculate feeding structure of early brachiopods is already differentiated into two shapes of lophophore,anteriorly coiled(spiralled)and posteriorly arching tentacle crowns and the unique latter type was previously not documented from fossil and living brachiopods.Also unlike any known Recent brachiopod,all the known Cambrian brachiopods from Chengjiang have an open digestive tract that was disposed either as a Ushaped gut in linguliform and stem group brachiopods,or straight gut with a posterior anus in some calcareous-shelled stocks.Moreover,in contrast toliving lingulids,all the Cambrian brachiopods have an epibenthic lifestyle either cemented by a ventral valve or attached by variable pedicles to establish complex ecological community encompassing primary tierers and variable secondary tierers.It is therefore assumed that brachiopods were the first benthic metazoan that achieved their success in ecological stratification and tiering complexity by late Atdabanian.The setae are also important for the brachiopod suspension-feeding life style,and in the Chengjiang braehiopods they include two types cilia-like and spine-like setae.The mantle canals of different braehiopod species are also distinctly variable in arrangement,mainly disposed in pinnate,baeulate and peripheral conditions.Of these,the peripheral disposition of mantle canals is for the first time proposed here so as to differentiate from the bifurcate condition in recent lingulids in that the former is devoid of posteriorly extending main trunks of sinus,but possesses a diverging dorsal vascula media in dichotomy. 相似文献
105.
四川盆地上震旦统灯影组风化壳古岩溶特征及模式分析 总被引:1,自引:1,他引:0
风化壳古岩溶的发育是四川盆地上震旦统灯影组获得新突破的重要因素。基于大量野外剖面、钻井岩心及薄片观察、地震、测井及地球化学分析,在论证灯影组两套风化壳古岩溶发育的基础上,进行古岩溶相带特征研究及差异分析,进而建立相应的风化壳古岩溶发育模式。结果表明,灯影组两套风化壳古岩溶均符合缓坡模式,但受古地貌坡降差异的影响,灯四段不整合面附近岩溶作用强烈,发育大洞穴及角砾、泥岩充填物,垂向分带结构以水平潜流带和深部缓流带为主;灯二段不整合面附近岩溶作用相对和缓,溶洞充填物主要由小粒径的角砾云岩、白云岩组成,盆地范围内其垂向分带结构以垂向渗流带、水平潜流带及深部缓流带为主。 相似文献
106.
江西修武盆地下寒武统黑色页岩矿物成分特征及意义 总被引:3,自引:0,他引:3
以江西修武盆地下寒武统王音铺组、观音堂组黑色页岩为研究对象,通过对野外剖面样品和钻井取心样品定性和定量分析,研究修武盆地下寒武统页岩气储层矿物成分特征,结果表明,王音铺组、观音堂组黑色页岩矿物成分以黏土矿物和石英为主,石英的平均质量分数为58.63%,黏土矿物平均为25.4%。其次为方解石,平均为51.46%,另外还含有较高的长石和黄铁矿,平均质量分数分别为2.5%和4.68%。其余矿物如方解石、白云石、(硬)石膏等含量较少,平均质量分数5%。这种矿物成分组成与Barnett页岩及龙马溪组页岩既有相似性,又有差异性。修武盆地下寒武统页岩矿物组分所反映的沉积环境、有机质演化及黑色页岩储集意义表明,该套页岩石英的质量分数50%的泥(页)岩厚度接近50m,是理想的页岩气勘探开发层位。 相似文献
107.
仇芒仙 《山西师范大学学报:自然科学版》1996,10(2):59-62
本文对86系列微机内存空间进行了分析,根据DOS提供的内存管理命令,总结了如何充分利用DOS内存空间的实用经验,提出几条使DOS突破640KB的限制,增大用户程序空间的方法与技巧. 相似文献
108.
利用上下解方法研究了某一类四阶非线性微分方程的Robin过值问题X(4)=f(t,x,x′,x″,x),x(0)=A,x(1)=B,a0x″(0)-a1x″(0)=C,box″/(1)+b1x″/(1)=D得到了其解的存在性结果. 相似文献
109.
文章讨论了早寒武世早期小壳动物的生存条件及几类常见软舌螺(Microcornus, Actinotheca, Neogloborilus, Paragloborilus, Adyshevitheca, Sulcavitus等)的生活环境及生存方式,并在古生态分析的基础上,对扬子地台早寒武世早期小壳动物的地理分区进行了探讨,提出扬子地台自西向东可分为三个不同的生物地理区,即底栖生物区;浮游、游泳、底栖生物混生区;浮游、游泳动物区。其分区界线大致与三叶虫的分区界线相吻合。 相似文献
110.
CHENZhe HUJie ZHOUChuanming XlAOShuhai YUANXunlai 《科学通报(英文版)》2004,49(15):1625-1628
Abundant well-preserved large articulated sponge fossils and isolated spicules have been reported from the Early Cambrian Hetang Formation, southern Anhui Province. This unique epifaunal fossil assemblage dominated by articulated sponge fossils is called the Xidi Sponge Fauna. The sponge fauna lived in a quiet oxygenic environment below the storm wave base. Bloom of phytoplankton and rapid sedimentation rate resulted in the deposition of the black shales. Sufficient food supply, lack of other competitors, abundant ecological niches, and demand for oxygen during early Cambrian were in favor of the diversification and evolution of large sponges in the Early Cambrian. 相似文献