检索结果-南通市图书馆

DISTRIBUTION OF THE (0,∞) ACCUMULATIVE LINES OF MEROMORPHHIC FUNCTIONS

在线全文

学校读者我要写书评

暂无评论

Chinese Annals of mathematics,Series B 1994年第4期15卷 453-462页

作者： wu shengjian(department of mathematics, beijing university,beijing 100871, china.) 北京大学数学系北京 100871

Suppose that f(z) is a meromorphic function of order and of lower order μin the plane. Let ρ be a positive number such that .(1) If f(l)(z) () has ρ() finite nonzero deficient values ai (i =1,…,p) with deficiencies δ(ai, f(l)), then f(z) has a (0, ∝) accumulative line of order inany angular domain whose vertex is at the origin and whose magnitude is larger than(2) If f(z) has only p ()(0, ∝) accumulative lines of order : arg z = θk (θ1<θ2…<θp<2π, θp+1 = θ1 + 2π), then , where , providedthat has a finite noasero deficient value.

关键词： Meromorphic function Accumulative line Order.

Recursive equations for compound distribution with the severity distribution of the mixed type

在线全文

学校读者我要写书评

暂无评论

Science china mathematics 2005年第5期48卷 594-609页

作者： YANG Jingping, CHENG Shihong & wu Qin LMAM, department of Financial mathematics, peking university, beijing 100871, china LMAM Department of Financial Mathematics Peking University Beijing China

In this paper, recursive equations are obtained for compound distribution with the number of claims belonging to (a, b)-family and the severity distribution of the mixed type. Numerical methods to solve these equation... 详细信息

关键词： recursive equation compound distribution (a b)-family severity distribution of the mixed type.

VARIABILITY SETS AND HAMILTON SEQUENCES

在线全文

学校读者我要写书评

暂无评论

Chinese Annals of mathematics,Series B 2005年第4期26卷 543-550页

作者： SUN NA wu shengjian Key Laboratory of Pure and Applied mathematics School of Mathematical Sciences Peking University Beijing 100871 China.

This paper studies extremal quasiconformal mappings. Some properties of the variability set are obtained and the Hamilton sequences which are induced by point shift differentials are also discussed.

关键词： Quasiconformal mapping Point shift differentials Hamilton sequence Extremal mapping

On Catastrophe and Cavitation for SphericalCavity

在线全文

学校读者我要写书评

暂无评论

Communications in Nonlinear Science and Numerical Simulation 1999年第4期4卷 249-254页

作者： Ming JIN Kefu HUANG Jike wu(department of Mechanics and Engineering Science, peking university, beijing 100871,china) department of Mechanics and Engineering Science Peking University Beijing 100871 China

IntroductionInrecelltyears,theresearchesoncavitationandcatastropheofacavitysu***therwithbifllrcationtheory... 详细信息

IntroductionInrecelltyears,theresearchesoncavitationandcatastropheofacavitysu***therwithbifllrcationtheory...

关键词： nonlinearity bifurcation Hooke material

Composition of sandstone and heavy minerals implies the provenance of Kuqa Depression in Jurassic, Tarim basin, china

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2005年第7期15卷 633-640页

作者： wu Chaodong, LIN Changsong, SHEN Yanping and FENG Xue ( Key Laboratory of Orogenic Belts and Crustal Evolution, Ministry of Education, peking university, beijing 100871, china department of Resources, china university of Geosciences, beijing 100083, china) Key Laboratory of Orogenic Belts and Crustal Evolution Ministry of Education Peking University Beijing 100871 China department of Resources China University of Geosciences Beijing 100083 China

The petrological characteristics and heavy mineral assembly of the Jurassic System in Kuqa Basin are consistent with the tectonic evolution, which is the major factor controlling the filling process of Kuqa Basin. Controlled by the source areas at the both sides of the Basin, the matrixes are dominated by sedimentary rock, high-grade metamorphic rock, acid magmatic rock, and the highest heavy mineral assemblage of zircon-garnet-magnetite in the content. According to heavy mineral indexes, the Jurassic strata can be classified into three rhythmic units of heavy mineral. The lower sequence contains abundant heavy minerals and relatively high content of detritus and its matrixes primarily came form the recycling orogen. The assemblage of "zircon-garnet-magnetite" indicates that the sedimentary area in the early evolution period of the basin is relatively near the provenance. The middle sequence is different from the lower sequence in the heavy mineral assemblage and has the different characteristics from that of source rock. The heavy mineral assemblage is "garnet-zircon" with the highest content of garnet and its main matrices are the high-grade metamorphic rock, acid magmatic rock and hydrothermal vein at the northeastern edge of the basin. The middle and upper sequences are characterized by the clast provenance, which is primarily from the recycling orogen at the northern edge of the basin and secondarily from the southern uplift. As a result of the two provenances, the strata with apparent changes of heavy mineral assemblage and index better coincides with the interfaces of the secondary strata sequences, which reflects the denudation history and the filling process of the orogen at the northern edge of the basin.

关键词： sandstone components provenance analysis filling sequence tectonic evolution.

User-experience-based availability analysis model and its application in P2P storage systems

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science china(Information Sciences) 2011年第8期54卷 1585-1595页

作者： wu Yu, YANG Zhi,QU Zhi, XIAO Zhen & DAI YaFei department of Computer Science,peking university,beijing 100871,china department of Computer Science Peking University Beijing China

Data availability is one of the most important properties of peer-to-peer (P2P) storage *** analysis model and data placement are two key design *** in P2P storage system are both providers and *** characteristic determines that the availability analysis must be user-centric,and thereby enhance the quality of service and decrease the system *** popular approach in recent studies is simple random placement with steady-state model,which has the following drawbacks:1) It ignores the up/down patterns of nodes,whose availability is over-estimated or under-estimated at different periods of time.2) It ignores the access patterns of users,so the availability perceived by users is hard to evaluate precisely.3) It ignores the huge difference of nodes’ availability, thus leading to the absence of incentive. This paper proposes a novel user-experience-based availability model, which evaluates the availability of P2P storage system in terms of user experience,which can degenerate to traditional availability analysis model. Based on the new model,this paper proposes decentralized data placement algorithms for two typical P2P storage applications:"data sharing"and"personal backup".By the trace-driven simulation, we prove that our methods can enhance the availability perceived by users greatly,reduce the variance of the availability dramatically and eliminate the nodes with low availability in data-sharing applications;meanwhile,it can provide different-level service to encourage users according to their contributions.

关键词： P2P storage user experience availability data replacement

A submillimeter observation and study of star-forming regions

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Chinese Science Bulletin 2002年第1期47卷 16-21页

作者： JIANG Linhua, wu Yuefang & M. Millerdepartment of Astronomy, peking university, beijing 100871, china Chinese Academy of Sciences-peking university Joint beijing Astrophysics Center, beijing 100871, china I. Physikalisches Institut, Zulpicher Str department of Astronomy Peking University Beijing China Chinese Academy of Sciences-peking university Joint beijing Astrophysics Center Beijing China I. Physikalisches Institut Koeln 41 Germany

Using the 3-m radio telescope of KOSMA, we mapped 12CO (J = 3-2) lines for three molecular clouds, B35, S146 and TMC-2A. High-velocity molecular outflows are found in all these regions. The physical and dynamical pa-rameters of the outflows are derived, and their shapes and driving sources are analyzed. Contour maps of center veloci-ties show that the large scale systematic gradients exist in the three clouds. These observed motions are best explained by rotation after excluding the cause of outflows. Furthermore, in the core region of TMC-2A there is a velocity gradient in opposite direction from that of the large scale. It may be caused by magnetic braking. Finally, angular velocities of the clouds are calculated, and the effects of rotation against gravity and lowering the star-formation rate are also ana-lyzed.

关键词： dynamics of interstellar medium jets and outflows star formation.

Study of spatial distribution of sandy desertification in North china in recent 10 years

在线全文

学校读者我要写书评

暂无评论

Science china Earth Sciences 2004年第Z1期47卷 78-88页

作者： WANG Tao, wu Wei, XUE Xian, SUN Qingwei & CHEN GuangtingKey Laboratory of Desert and Desertification, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000, china department of Environment Engineering, peking university, beijing 100871, china Key Laboratory of Desert and Desertification Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences Lanzhou China department of Environment Engineering Peking University Beijing China

Sandy desertification is a land degradation characterized by wind erosion, mainly resulted from the excessive human activities in arid, semiarid and part of sub-humid regions in North china. It is one of main kinds of desertification/land degradation as well as water-soil erosion and salinization in china. Rapid and continuous spread of sandy desertification during last 50 years has created a major environmental and socio-economic problem in North china. Remote sensing monitored results in 2000 showed that the sandy desertified land area has been 38.57× 104 km2. The area of potential to slightly sandy desertified land is 13.93× 104 km2, moderately land 9.977×104 km2, severely land 7.909 ×104 km2 and very severely land 6.756×104 km2. Sandy desertification mainly occurs in the semi-arid mixed farming-grazing zone and its northern rangeland zone, semi-arid dryland rainfed cropping zone and arid oasis-desert margin zone. The average annually developmental rate of sandy desertified land increased from 2,100 km2 ·a-1 in 1976-1988 to 3,600 km2 · a-1 in 1988-2000. The basic status of sandy desertification in North china is 'overall deterioration, while local rehabilitation'. Already achieved rehabilitation results and monitoring assessment show that about 60% of desertified land in North china can be restored under the conditions of rational land-use ways and intensity.

关键词： sandy desertified land, spatial distribution, remote sensing monitoring, last 10 years, North china.

A preliminary analysis of arcuate structures-relationship of the island arc and deep-sea trench to the dip angle of Benioff zone

在线全文

学校读者我要写书评

暂无评论

Acta Oceanologica Sinica 1989年第1期8卷 125-136页

作者： wu Lun, Liang Haihua, Ren Fuhu and Li Maosong The department of Geography, peking university, beijing, china The department of Geology, peking university, beijing, china Dept of Geography Peking Univ. Beijing China China

The origin of arcuate islands and deep-sea trenches has been studied for a long time and various interpretations have been proposed. In this paper, some analytical models are put forward from a geometrical viewpoint and then the theoretical dip angles of the underthrusting slabs of circum-Pacific island arcs are computed and compared with those of the Benioff zone. As a result, it is found that the dip angle of the underthrusting slab is one of the main factors determining the curvature of the arcuate structure. The authors consider that this result may contribute to the plate theory.

关键词： A preliminary analysis of arcuate structures-relationship of the island arc and deep-sea trench to the dip angle of Benioff zone deep