检索结果-南通市图书馆

Shape phase transitions in nuclei:Effective order parameters and trajectories

在线全文

学校读者我要写书评

暂无评论

Science china(Physics,Mechanics & Astronomy) 2011年第S1期54卷 88-97页

作者： ZHANG Yu1,2, HOU ZhanFeng2 & LIU YuXin2,3 1Department of Physics, Liaoning Normal University, Dalian 116029, china 2Department of Physics and the State key laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871, china 3Center of Theoretical Nuclear Physics, National laboratory of Heavy Ion Accelerator, Lanzhou 720000, china 1. Department of Physics Liaoning Normal University Dalian 116029 China2. Department of Physics and the State Key Laboratory of Nuclear Physics and Technology Peking University Beijing 100871 China3. Center of Theoretical Nuclear Physics National Laboratory of Heavy Ion Accelerator Lanzhou 720000 China

We analyze systematically the effective order parameters in nuclear shape phase transition both in experiments and in the interacting boson model. We find that energy ratios and B(E2) ratios can distinguish the first from the second-order phase transition in theory above a certain boson number N (about 50), but in experiments, only those quantities, such as E(L1+)/E(02+) and B(E2; (L+2)1 → L1)/B(E2; 21 → 01), etc., of which the monotonous transitional behavior in the second-order phase transition is broken in the first order phase transition independent of N, are qualified as the effective order parameters. By implementing the originally proposed effective order parameters and the new ones, we find that the isotones with neutron number Nn = 62 are a trajectory of the second order phase transition. In addition, we predict that the transitional behavior of isomer shifts of Xe, Ba isotopes and Nn = 62 isotones is approximately monotonous due to the finiteness of nuclear system.

关键词： nuclear shape phase transition interacting boson model effective order parameter finite particle number effect transition trajectory

CO_2 Mitigation in Coal Gasification Cogeneration Systems with Integration of the Shift Reaction, CO_2 Absorption and Methanol Production

在线全文

学校读者我要写书评

暂无评论

Journal of Thermal Science 2004年第3期13卷 193-198页

作者： Yuanyuan DUAN Jin ZHANG key laboratory of Thermal Science and Power Engineering, Department of Thermal Engineering, Tsinghua University, Beijing 100084, china key laboratory of Thermal Science and Power Engineering Department of Thermal Engineering Tsinghua University Beijing China

Cogeneration of electricity and liquid fuel can achieve higher efficiencies than electricity generation alone in Integrated Gasification Combined Cycle (IGCC), and cogeneration systems are also expected to mitigate CO2 emissions. A proposed methanol-electricity cogeneration system was analyzed in this paper using exergy method to evaluate the specified system. A simple cogeneration scheme and a complicated scheme including the shift reaction and CO2 removal were compared. The results show that the complicated scheme consumes more energy, but has a higher methanol synthesis ratio with partial capture of *** those methanol and electricity cogeneration systems, the CO2 mitigation is not merely an additional process that consumes energy and reduces the overall efficiency, but is integrated into the methanol production.

关键词： cogeneration system methanol synthesis CO2 mitigation exergy analysis

A Creep Equation Based on Thermal Activation

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 1998年第1期12卷 44-46页

作者： Jiyue Sun Guoliang Chen (State key laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083, china) State key laboratory for Advanced Metals and Materials University of Science and Technology Beijing Beijing 100083 China

The creep equation proposed in so called θ projection concept is developed in the concept of thermal activation of creep. The measured creep curves of A286 alloy are fitted by the equation. The activation energy in theequation is evaluated, and creep rupture lives are predicted. The results are confirmed by creep tests of up to 13years.

关键词： creep creep curve equation creep rupture life A286 superalloy

Interdecadal trend turning of global terrestrial temperature and precipitation during 1951-2002

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2008年第11期18卷 1383-1393页

作者： Xiaohui Shi Xiangde Xu State key laboratory of Severe Weather,Chinese Academy of Meteorological Sciences,Beijing 100081,china State key laboratory of Severe Weather Chinese Academy of Meteorological Sciences Beijing 100081 China

A grid-by-grid counting of interdecadal trend turning(ITT)of annual mean surface air temperature(SAT)and total precipitation at 67,359 terrestrial grids in the period 1951-2002 is *** analysis of the last ITTs of SAT and total precipitation in the period,in the context of both occurrence time and linear trends after the breakpoint,indicates that a warming trend has become highly significant across most reagent of the world in the late 20th *** terrestrial grids have recorded an ITT of total precipitation in either the 1970s or 1980s,and 45.7% of the terrestrial grids in the study have seen a decreasing trend in total annual precipitation after the break- point,with the remaining 54.3% having experienced an increasing ***,global terrestrial regions have experienced either an increasingly warm and dry climate or an increasingly warm and wet *** analysis of ITT of regional mean SAT and total pre- cipitation in 22 regions shows that the Northern American continent has become increasingly warm and dry after the last interdecadal ***,the African continent has become increasingly warm and wet,with both Europe and most of Asia having the same *** South America and the West of Australia have experienced an opposite trend in climate,becoming increasingly cold and wet.

关键词： Global terrene Surface air temperature Precipitation Interdecadal trend turning

Effect of streambed sediment on benthic ecology

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

International Journal of Sediment Research 2009年第3期24卷 325-338页

作者： Xuehua DUAN1, Zhao-Yin WANG2, Mengzhen XU3, and Kang ZHANG41 Ph.D., Jiangyin Environmental Monitoring Station, Jiangyin 214431, china, Dept. of Hydraulic Engineering, Tsinghua University,2 Prof., State key laboratory of Hydroscience and Engineering, Tsinghua University, Beijing 100084, china, 3 Doctoral candidate, State key laboratory of Hydroscience and Engineering, Tsinghua University, Beijing 100084, china,4 Doctoral candidate, State key laboratory of Hydroscience and Engineering, Tsinghua University, Beijing 100084, china [a] Ph.D. Jiangyin Environmental Monitoring Station Jiangyin 214431 china Dept. of Hydraulic Engineering Tsinghua University [b] Prof. State key laboratory of Hydroscience and Engineering Tsinghua University Beijing 100084 china Tel: 86-10-62773448(O) [c] Doctoral candidate State key laboratory of Hydroscience and Engineering Tsinghua University Beijing 100084 china [d] Doctoral candidate State key laboratory of Hydroscience and Engineering Tsinghua University Beijing 100084 china

Benthic macroinvertebrates have been commonly used as indicator species for assessment of aquatic ecology. Streambed sediment, or substrate, plays an important role in habitat conditions for macroinvertebrate communities. Field investigations were done to study the benthic diversity and macroinvertebrate compositions in various stream substrata. Sampling sites with different bed sediment, latitude, and climate were selected along the Yangtze River, the Yellow River, the East River, and the Juma River, in china. The results show that benthic community structures found in different substrata clearly differ, while those found in substrata of similar composition and flow conditions but in different macroclimates are similar. The study, thus, demonstrates that the benthic macroinvertebrate community is mainly affected by substrate composition and flow conditions, but is generally unaffected by latitudinal position and macroclimate. Taxa richness of the macroinvertebrate community was found to be the highest on hydrophyte-covered cobbles, high on moss-covered bedrock, and low on clay beds and cobble beds devoid of plant biomass. Sandy beds are compact and unstable, thus, no benthic macroinvertebrates were found colonizing such substrata. Aquatic insects account for most of the macroinvertebrates collected in these rivers. Different insects dominate in different types of substrata: mainly EPT species (Ephemeroptera, Plecoptera, Trichoptera) in cobble, gravel, and moss-covered bedrock; and Chironomidae larvae in clay beds. The relation between the number of species in the samples and the size of the sampling area fits a power function of the species area. One square meter (1m2) is suggested as the minimum sampling area. A substrate suitability index is proposed by integrating the suitability of sediment, periphyton, and benthic organic materials for macroinvertebrates. The biodiversity of macroinvertebrates increases linearly with the substrate suitability index. Benthic ta

关键词： Streambed sediment Macroinvertebrates Benthic ecology Substrate suitability Biodiversity

Progress and review of the studies on the end-Triassic mass extinction event

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 Earth Sciences 2005年第12期48卷 2049-2060页

作者： DENG Shenghui1,2, LU Yuanzheng1,2,3 & XU Daoyi4 1. Research Institute of Petroleum Exploration and Development, Beijing 100083, china 2. key laboratory of Oil and Gas Reservoir of Petrochina, Beijing 100083, china 3. china University of Geosciences, Beijing 100083, china 4. Institute of Geology, china Earthquake Administration, Beijing 100029, china 1. Research Institute of Petroleum Exploration and Development 100083 Beijing China 2. key laboratory of Oil and Gas Reservoir of Petrochina 100083 Beijing China 3. china University of Geosciences 100083 Beijing China 4. Institute of Geology China Earthquake Administration 100029 Beijing China

The mass extinction at the end-Triassic is one of the five biggest in the Phanerozoic. However,it is the least well understood among these five events, and only till last decade it became a great academic interesting subject to geologists. The evidences for this event come obviously from bivalves, brachiopods, ammonites, corals, radiolaria, ostracods and foraminifera of marine habitats, and plants and tetrapods of terrestrial realm. By contrast, for some of other groups, such as marine gastropods and marine vertebrates, no mass extinction has been recog-nized yet. The extinction event is strongly marked at specific level but shown a complicated situa-tion at generic and family levels. Dramatic changing of the environment, such as the temperature raise due to the greenhouse effect, the marine anoxic habitats caused by a sudden transgression after the regression at the end of Triassic, has been claimed to be the main cause of the extinction. Many hypotheses have been suggested to demonstrate the mechanisms of the environment changing, among which two popular ones are the bolide impact and volcanic eruption. The Triassic-Jurassic (Tr-J) boundary mass extinction event is still poorly understood because no enough data have been obtained from the Tr-J boundary successional sections of both marine and terrestrial sediments, and most of these studies were regionally restricted. The basic aspects of the event and its associated environmental conditions remain poorly characterized and the causal mechanism or mechanisms are equivocal. Some authors even doubt its occurrence. china has many successionally developed terrestrial and marine Tr-J sections. Detailed studies of these sections may be important and significant for well understanding of the event.

关键词： progress, review, end-Triassic, mass extinction, mechanism, Tr-J boundary.

A NEW GENERALIZED ASYNCHRONOUS PARALLELMULTISPLITTING ITERATION METHOD

在线全文

学校读者我要写书评

暂无评论

Journal of Computational Mathematics 1999年第5期17卷 449-456页

作者： Zhong-zhi Bai(State key laboratory of Scientific and Engineering Computing, ICMSEC, Chinese Academyof Sciences, Beijing 100080, china) Chinese Acad Sci ICMSEC State Key Lab Sci & Engn Comp Beijing 100080 Peoples R China

For the large sparse systems of linear and nonlinear equations, a new class of generalized asynchronous parallel multisplitting iterative method is presented, and its convergence theory is established under suitable conditions. This method not only unifies the discussions of various existing asynchronous multisplitting iterations, but also affords new algorithmic and theoretical results for the parallel solution of large sparse system of linear equations. Besides its generality, this method is also much more suitable for implementing on the MIMD multiprocessor systems.

关键词： systems of linear and nonlinear equations asynchronous multisplitting iteration relaxed method convergence theory

Exsolution of ilmenite and Cr-Ti magnetite from olivine of garnet-wehrlite

在线全文

学校读者我要写书评

暂无评论

Science china Earth Sciences 2005年第9期48卷 1368-1376页

作者： LIU Xiangwen1,2, JIN Zhenmin1,3, QU Jing2 & WANG Lu2 1. State key laboratory of Geological Processes and Mineral Resources, china University of Geosciences, Wuhan 430074, china 2. Graduate School of china University of Geosciences, Wuhan 430074, china 3. Faculty of Earth Sciences, china University of Geosciences, Wuhan 430074, china 1. State key laboratory of Geological Processes and Mineral Resources China University of Geosciences 430074 Wuhan China 2. Graduate School of china University of Geosciences 430074 Wuhan China 3. Faculty of Earth Sciences China University of Geosciences 430074 Wuhan China

Exsolution of rod-like ilmenite (Ilm) and Cr-Ti magnetite (Mt) have been found in olivine of garnet-wehrlite from the core of Chinese Continental Sciences Drilling (CCSD). Their composition, morphology, crystal structure and their topotaxies with host olivine have been studied in detail by the transmission electron microscopy (TEM) and electron probe microanaly- sis (EPMA) technique. It shows that rod-like Ilm exsolution reported in this paper has similar characteristic with that of Alpe Arami olivine, while Cr-Ti magnetite exsolution mentioned in this paper has large discrepancy with chromite exsolution in Alpe Arami olivine. These observations suggest that both of the exsolutions found in this paper should be solid solution phases in β-olivine at their first period, then experiencing decomposition of solid solution and therefore forming Ilm and Cr-Ti magnetite exsolution with the pressure decreasing. So, this garnet-wehrlite perhaps had been ever located in mantle transition zone with a minimum depth of 300 km.

关键词： garnet-wehrlite, ilmenite, magnetite, exsolution, CCSD.

Performance analysis of a noise-normalized FFH/MFSK receiver over Rayleigh fading channels with partial-band noise jamming

在线全文

学校读者我要写书评

暂无评论

Science china(Information Sciences) 2011年第1期54卷 129-135页

作者： ZHOU ZhiQiang,LI ShaoQian & CHENG YuFan National key laboratory of Science and Technology on Communications,University of Electronic Science and Technology of china,Chengdu 610054,china 1. National key laboratory of Science and Technology on Communications University of Electronic Science and Technology of China Chengdu 610054 China

Fast frequency hopping can reduce the degradation caused by *** performance of noise-normalized fast frequency-hopped M-ary orthogonal frequency-shift-keying(FFH/MFSK)receivers over frequency nonselective Rayleigh fading channels with partial-band noise jamming is *** of numerical evaluation,a closed-form error probability expression is given based on the theory of complex variables. The simulation results validate the analytical *** is shown that there is an optimum diversity order and the system performance gets better with an increase in the modulation order.

关键词： anti-jamming fast frequency hopping noise normalization combining Rayleigh fading