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The Model of“Post,Course,Competition,Certificate”Integrated Education for Electronic Information Engineering Technology Major in Higher Vocational Colleges
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作者 Qinqin Jing Yun Liu Xinyu Zheng 《Journal of Contemporary Educational Research》 2024年第5期223-229,共7页
The core education function of higher vocational colleges is to train technical talents with high quality,so as to meet the needs of talents in the development stage of our society.Under the guidance of talent trainin... The core education function of higher vocational colleges is to train technical talents with high quality,so as to meet the needs of talents in the development stage of our society.Under the guidance of talent training,higher vocational colleges need to pay attention to establishing an all-round and three-dimensional education model,and promote innovation of higher vocational education on the basis of this.It is also a way to promote the innovation of higher vocational education to vigorously promote the construction of“post,course,competition,certificate”mode in the construction of education mode.Through the construction of“post,course,competition,certificate”mode,the education mode of higher vocational colleges is gradually improved,so as to strengthen the effectiveness of talent training in higher vocational colleges.Therefore,in this paper,the author puts forward some suggestions to promote the construction of the integrated education mode of the electronic information engineering technology major in higher vocational colleges,so as to help improve the talent training level of higher vocational colleges. 展开更多
关键词 Higher vocational education Electronic information engineering technology major “Post course competition certificate” Integrated education model
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Storage reliability assessment model based on competition failure of multi-components in missile 被引量:10
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作者 Yunxiang Chen Qiang Zhang +1 位作者 Zhongyi Cai Lili Wang 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2017年第3期606-616,共11页
The degradation data of multi-components in missile is derived by periodical testing. How to use these data to assess the storage reliability (SR) of the whole missile is a difficult problem in current research. An SR... The degradation data of multi-components in missile is derived by periodical testing. How to use these data to assess the storage reliability (SR) of the whole missile is a difficult problem in current research. An SR assessment model based on competition failure of multi-components in missile is proposed. By analyzing the missile life profile and its storage failure feature, the key components in missile are obtained and the characteristics voltage is assumed to be its key performance parameter. When the voltage testing data of key components in missile are available, a state space model (SSM) is applied to obtain the whole missile degradation state, which is defined as the missile degradation degree (DD). A Wiener process with the time-scale model (TSM) is applied to build the degradation failure model with individual variability and nonlinearity. The Weibull distribution and proportional risk model are applied to build an outburst failure model with performance degradation effect. Furthermore, a competition failure model with the correlation between degradation failure and outburst failure is proposed. A numerical example with a set of missiles in storage is analyzed to demonstrate the accuracy and superiority of the proposed model. 展开更多
关键词 competition failure model storage reliability (SR) missile degradation degree (DD) proportional risk model individual variability
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CRB:A new rumor blocking algorithm in online social networks based on competitive spreading model and influence maximization
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作者 董晨 徐桂琼 孟蕾 《Chinese Physics B》 SCIE EI CAS CSCD 2024年第8期588-604,共17页
The virtuality and openness of online social platforms make networks a hotbed for the rapid propagation of various rumors.In order to block the outbreak of rumor,one of the most effective containment measures is sprea... The virtuality and openness of online social platforms make networks a hotbed for the rapid propagation of various rumors.In order to block the outbreak of rumor,one of the most effective containment measures is spreading positive information to counterbalance the diffusion of rumor.The spreading mechanism of rumors and effective suppression strategies are significant and challenging research issues.Firstly,in order to simulate the dissemination of multiple types of information,we propose a competitive linear threshold model with state transition(CLTST)to describe the spreading process of rumor and anti-rumor in the same network.Subsequently,we put forward a community-based rumor blocking(CRB)algorithm based on influence maximization theory in social networks.Its crucial step is to identify a set of influential seeds that propagate anti-rumor information to other nodes,which includes community detection,selection of candidate anti-rumor seeds and generation of anti-rumor seed set.Under the CLTST model,the CRB algorithm has been compared with six state-of-the-art algorithms on nine online social networks to verify the performance.Experimental results show that the proposed model can better reflect the process of rumor propagation,and review the propagation mechanism of rumor and anti-rumor in online social networks.Moreover,the proposed CRB algorithm has better performance in weakening the rumor dissemination ability,which can select anti-rumor seeds in networks more accurately and achieve better performance in influence spread,sensitivity analysis,seeds distribution and running time. 展开更多
关键词 online social networks rumor blocking competitive linear threshold model influence maximization
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Entropy squeezing for a two-level atom in two-mode Raman coupled model with intrinsic decoherence 被引量:2
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作者 张剑 邵彬 邹健 《Chinese Physics B》 SCIE EI CAS CSCD 2009年第4期1517-1527,共11页
In this paper, we investigate the entropy squeezing for a two-level atom interacting with two quantized fields through Raman coupling. We obtain the dynamical evolution of the total system under the influence of intri... In this paper, we investigate the entropy squeezing for a two-level atom interacting with two quantized fields through Raman coupling. We obtain the dynamical evolution of the total system under the influence of intrinsic decoherence when the two quantized fields are prepared in a two-mode squeezing vacuum state initially. The effects of the field squeezing factor, the two-level atomic transition frequency, the second field frequency and the intrinsic decoherence on the entropy squeezing are discussed. Without intrinsic decoherence, the increase of field squeezing factor can break the entropy squeezing. The two-level atomic transition frequency changes only the period of oscillation but not the strength of entropy squeezing. The influence of the second field frequency is complicated. With the intrinsic decoherence taken into consideration, the results show that the stronger the intrinsic decoherence is, the more quickly the entropy squeezing will disappear. The increase of the atomic transition frequency can hasten the disappearance of entropy squeezing. 展开更多
关键词 entropy squeezing intrinsic decoherence two-mode Raman coupled model
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Analysis of Porter’s Five Forces Competitive Model in China’s Property Rights Trading Market
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作者 Weinong Wang 《Proceedings of Business and Economic Studies》 2024年第3期206-211,共6页
In recent years,China’s property rights trading market has been extremely competitive,but there are also new contradictions and challenges.This paper aims to analyze the external and internal competitive market of th... In recent years,China’s property rights trading market has been extremely competitive,but there are also new contradictions and challenges.This paper aims to analyze the external and internal competitive market of the property rights market through Porter’s five forces competition model,then find out the problems and defects in the development,thereby promoting the better development and progress of China’s property rights trading market. 展开更多
关键词 Porter’s five forces competitive model Market optimization Innovative development
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The entanglement between two isolated atoms in the double mode mode competition model
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作者 吴琴 方卯发 +1 位作者 蔡建武 胡要花 《Chinese Physics B》 SCIE EI CAS CSCD 2009年第12期5336-5341,共6页
Extending the double Jaynes Cummings model to a more complicated case where the mode-mode competition is considered, we investigate the entanglement character of two isolated atoms by means of concurrence, and discuss... Extending the double Jaynes Cummings model to a more complicated case where the mode-mode competition is considered, we investigate the entanglement character of two isolated atoms by means of concurrence, and discuss the dependence of atom atom entanglement on the different initial state and the relative coupling strength between the atom and the corresponding cavity field. The results show that the amplitude and the period of the atom atom entanglement evolution can be controlled by the choice of initial state and relative coupling strength, respectively. We find that the phenomenon of entanglement sudden death (ESD) is sensitive to the initial conditions. The length of the time interval for zero entanglement depends not only on the initial degree of entanglement between two atoms but also on the relative coupling strength of atom field interaction. The ESD effect can be weakened by enhancing the mode-mode competition between the three- and single-photon processes. 展开更多
关键词 double mode-mode competition model CONCURRENCE ENTANGLEMENT sudden death
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Research on the Competition Degree and Competition Strategy of China's Processing Industries of Agricultural Products Based on the Potter Model——Taking "LaoGanMa" as an Example
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作者 YUAN Jia-Ju Guizhou College of Finance and Economics,Guiyang 550004,China 《Asian Agricultural Research》 2011年第2期138-140,144,共4页
By using Porter's Five Forces Model,and from 5 aspects of individual farmer,purchaser,new entrant,substitute and the enterprise of the same trade,I analyze the leading enterprise in Guizhou Province-LaoGanMa,so as... By using Porter's Five Forces Model,and from 5 aspects of individual farmer,purchaser,new entrant,substitute and the enterprise of the same trade,I analyze the leading enterprise in Guizhou Province-LaoGanMa,so as to reveal the commonality and particularity reflected from the competition degree of LaoGanMa as follows:LaoGanMa has absolute dominance over material purchase;the purchasers' recognition on the quality of LaoGanMa,bearing capacity of sales price and habitual consumption allay consumers' ability to bargain;as for the problems of substitutes,the threat of new entrants and competition of the same trading,LaoGanMa has not done enough.The thesis formulates the competitive strategy conducive to development,like differentiation strategy,Cost-leadership strategy and brand strategy,in order to promote the development of processing industries of agricultural products. 展开更多
关键词 POTTER model competition DEGREE competition strate
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GPU parallel computation of dendrite growth competition in forced convection using the multi-phase-field-lattice Boltzmann model
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作者 高梓豪 朱昶胜 王苍龙 《Chinese Physics B》 SCIE EI CAS CSCD 2023年第7期530-547,共18页
A graphics-processing-unit(GPU)-parallel-based computational scheme is developed to realize the competitive growth process of converging bi-crystal in two-dimensional states in the presence of forced convection condit... A graphics-processing-unit(GPU)-parallel-based computational scheme is developed to realize the competitive growth process of converging bi-crystal in two-dimensional states in the presence of forced convection conditions by coupling a multi-phase field model and a lattice Boltzmann model.The elimination mechanism in the evolution process is analyzed for the three conformational schemes constituting converging bi-crystals under pure diffusion and forced convection conditions,respectively,expanding the research of the competitive growth of columnar dendrites under melt convection conditions.The results show that the elimination mechanism for the competitive growth of converging bi-crystals of all three configurations under pure diffusion conditions follows the conventional Walton-Chalmers model.When there is forced convection with lateral flow in the liquid phase,the anomalous elimination phenomenon of unfavorable dendrites eliminating favorable dendrites occurs in the grain boundaries.In particular,the anomalous elimination phenomenon is relatively strong in conformation 1 and conformation 2 when the orientation angle of unfavorable dendrites is small,and relatively weak in conformation 3.Moreover,the presence of convection increases the tip growth rate of both favorable and unfavorable dendrites in the grain boundary.In addition,the parallelization of the multi-phase-field-lattice Boltzmann model is achieved by designing the parallel computation of the model on the GPU platform concerning the computerunified-device-architecture parallel technique,and the results show that the parallel computation of this model based on the GPU has absolute advantages,and the parallel acceleration is more obvious as the computation area increases. 展开更多
关键词 multi-phase field model GPU grain competition growth lattice Boltzmann model
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Entanglement of two atoms in two-mode Raman coupled model with intrinsic decoherence
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作者 张剑 邵彬 邹健 《Chinese Physics B》 SCIE EI CAS CSCD 2009年第12期5179-5188,共10页
Considering intrinsic decoherence, the two-atom two-mode Raman coupled model is investigated in this paper. Utilizing the constants of motion in this model, we obtain the analytic expressions of the density operator o... Considering intrinsic decoherence, the two-atom two-mode Raman coupled model is investigated in this paper. Utilizing the constants of motion in this model, we obtain the analytic expressions of the density operator of the system for investigating the entanglement of two atoms. The speed of entanglement decay increases with the increasing of the coupling coefficient of one atom. The difference between the oscillation periods when the initial state parameter of atomic subsystem belongs to two intervals becomes smaller with the increasing of the coupling coefficient of one atom. The increasing of the initial photon number of the second field can hasten the vanishing of entanglement of atomic subsystem. The robustness of atomic entanglement against decoherence depends on the interval of the initial state parameter of atomic subsystem. 展开更多
关键词 ENTANGLEMENT intrinsic decoherence two-atom two-mode Raman coupled model
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Revisit Language Modeling Competition and Extinction: A Data-Driven Validation
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作者 Chosila Sutantawibul Pengcheng Xiao +1 位作者 Sarah Richie Daniela Fuentes-Rivero 《Journal of Applied Mathematics and Physics》 2018年第7期1558-1570,共13页
Understanding language competition and extinction is an interdisciplinary challenge, and math models provide a tool for interpreting linguistic census data and possibly predict the language shift trend at the populati... Understanding language competition and extinction is an interdisciplinary challenge, and math models provide a tool for interpreting linguistic census data and possibly predict the language shift trend at the population scale. In this study, new data from previously examined areas were modeled, specifically Catalan and Spanish in Catalonia, Spanish and English in Houston, Texas, Dutch and French in Brussels, Euskera and Spanish in Spain and French and English in Canada. Three mathematical models of the language competition have been validated. The first is the Abrams-Strogatz model, which treats populations as having two monolingual groups. The second is the Castelló model, which considers bilingual speakers. The third is the Mira model, which considers language competition when the two languages have high similarities. It was found that the some of the data matched Abrams-Strogatz original model, but some divergences could still be addressed. It was also found that the Mira model needs some improvement in how it treats the differences between languages. 展开更多
关键词 LANGUAGE competition model PARAMETER Estimation Nonlinear Regression
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Ground-state phase diagram,symmetries,excitation spectra and finite-frequency scaling of the two-mode quantum Rabi model
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作者 陈越 刘卯鑫 陈晓松 《Chinese Physics B》 SCIE EI CAS CSCD 2023年第10期509-521,共13页
We investigate the two-mode quantum Rabi model(QRM)describing the interaction between a two-level atom and a two-mode cavity field.The quantum phase transitions are found when the ratioηof transition frequency of ato... We investigate the two-mode quantum Rabi model(QRM)describing the interaction between a two-level atom and a two-mode cavity field.The quantum phase transitions are found when the ratioηof transition frequency of atom to frequency of cavity field approaches infinity.We apply the Schrieffer–Wolff(SW)transformation to derive the low-energy effective Hamiltonian of the two-mode QRM,thus yielding the critical point and rich phase diagram of quantum phase transitions.The phase diagram consists of four regions:a normal phase,an electric superradiant phase,a magnetic superradiant phase and an electromagnetic superradiant phase.The quantum phase transition between the normal phase and the electric(magnetic)superradiant phase is of second order and associates with the breaking of the discrete Z_(2) symmetry.On the other hand,the phase transition between the electric superradiant phase and the magnetic superradiant phase is of first order and relates to the breaking of the continuous U(1)symmetry.Several important physical quantities,for example the excitation energy and average photon number in the four phases,are derived.We find that the excitation spectra exhibit the Nambu–Goldstone mode.We calculate analytically the higher-order correction and finite-frequency exponents of relevant quantities.To confirm the validity of the low-energy effective Hamiltonians analytically derived by us,the finite-frequency scaling relation of the averaged photon numbers is calculated by numerically diagonalizing the two-mode quantum Rabi Hamiltonian. 展开更多
关键词 two-mode quantum Rabi model superradiant phase transition Nambu–Goldstone mode finite-frequency scaling Schrieffer–Wolff(SW)transformation
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Competition of Quantum Anomalous Hall States and Charge Density Wave in a Correlated Topological Model
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作者 Xin Gao Jian Sun +1 位作者 Xiangang Wan Gang Li 《Chinese Physics Letters》 SCIE EI CAS CSCD 2022年第7期63-68,共6页
We investigate the topological phase transition driven by non-local electronic correlations in a realistic quantum anomalous Hall model consisting of d_(xy)–d_(x^(2)-y^(2)) orbitals. Three topologically distinct phas... We investigate the topological phase transition driven by non-local electronic correlations in a realistic quantum anomalous Hall model consisting of d_(xy)–d_(x^(2)-y^(2)) orbitals. Three topologically distinct phases defined in the noninteracting limit evolve to different charge density wave phases under correlations. Two conspicuous conclusions were obtained: The topological phase transition does not involve gap-closing and the dynamical fluctuations significantly suppress the charge order favored by the next nearest neighbor interaction. Our study sheds light on the stability of topological phase under electronic correlations, and we demonstrate a positive role played by dynamical fluctuations that is distinct to all previous studies on correlated topological states. 展开更多
关键词 QUANTUM competition of Quantum Anomalous Hall States and Charge Density Wave in a Correlated Topological model
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Application and Practice of the Teaching Model of “Promoting Teaching by Competition” in Tourism Management Specialty
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作者 LI Xiu LV Chen +1 位作者 ZHENG Mingjing LI Weimei 《Journal of Landscape Research》 2022年第1期129-132,共4页
The fundamental task of applied universities is to cultivate high-level applied talents facing the needs of economic and social development, and "promoting teaching by competition" is the booster for the con... The fundamental task of applied universities is to cultivate high-level applied talents facing the needs of economic and social development, and "promoting teaching by competition" is the booster for the construction of applied universities and the reform of talent training mode in colleges and universities.Taking tourism management specialty as an example, the needs of subject skill competition for students’personality ability are analyzed, and the teaching mode of "promoting teaching by competition" is constructed, and the implementation of teaching process and classroom teaching design are analyzed.Moreover, the supporting conditions of the teaching mode of "promoting teaching by competition" are put forward, such as building and perfecting the practice and training base, deepening the integration of industry and education and the cooperation of work and study, and strengthening the construction of teachers. 展开更多
关键词 Promoting teaching by competition Teaching model Tourism management specialty
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What Competition Model for Economic Development Should China Adopt at the Present Stage?
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作者 华民 《China Economist》 2008年第3期116-125,共10页
As a major developing country,China has attracted significant attention as to whichpathitshouldfol owfortechnologicalprogress.Accordingtotheauthorofthispaper,Chinashouldcontinueto pursue the international division of ... As a major developing country,China has attracted significant attention as to whichpathitshouldfol owfortechnologicalprogress.Accordingtotheauthorofthispaper,Chinashouldcontinueto pursue the international division of labor and competition strategy based on comparative advantages.Meanwhile,China should,through reform and adjustment,build a national innovation system capable ofplaying an e ective role in the future.However,laying too much emphasis on proprietary innovation atthe present stage wil bring about undesirable consequences.The timing for China to embark on a path oftechnologicaldevelopmentthroughproprietaryinnovationissubjecttothechangesbothintradeconditionsandin income distribution e ects arising from proprietary innovation. 展开更多
关键词 What competition model for Economic Development Should China Adopt at the Present Stage
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Design of Simulation Competition Platform Based on Cognitive Behavior Modeling
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作者 Junjie Zeng Qi Zhang +3 位作者 Yunxiu Zeng Long Qin Mei Yang Quanjun Yin 《Journal of Contemporary Educational Research》 2021年第8期174-179,共6页
Cognitive behavior modeling of agent is an important component of simulation system,and there are some difficulties in the simulation of course teaching.When students make simulation experiments about cognitive behavi... Cognitive behavior modeling of agent is an important component of simulation system,and there are some difficulties in the simulation of course teaching.When students make simulation experiments about cognitive behavior modeling,such as algorithm design and model construction,there is no simulation competition platform that is controllable,flexible and scalable.To solve this problem,we propose a simulation competition platform based on cognitive behavior modeling,called TankSim,for undergraduate and graduate students.This platform aims to cultivate studenfs team collaboration and innovation capability,and improve their learning motivation.This paper elaborates the proposed platform from three aspects,including demand analysis,platform design,and content design. 展开更多
关键词 Simulation discipline Design of the competition platform Cognitive behavior modeling Agent
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Test of Resource Competition Theory Between Microalga and Macroalga Under Phosphate Limitation 被引量:8
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作者 南春容 董双林 金秋 《Acta Botanica Sinica》 CSCD 2003年第3期282-288,共7页
Short_term batch cultures were used to measure the phosphate_dependent growth kinetics for a marine microalga, Tetraselmis subcordiformis (Wille) Hazen, and a marine macroalga, Ulva pertusa Kjellm. Results wer... Short_term batch cultures were used to measure the phosphate_dependent growth kinetics for a marine microalga, Tetraselmis subcordiformis (Wille) Hazen, and a marine macroalga, Ulva pertusa Kjellm. Results were fitted to the Monod model. U. pertusa had a lower half_saturation constant and maximum growth rate, which were 0.016 μmol/L and 0.16 d -1 respectively, while the growth kinetics of T. subcordiformis were 0.021 μmol/L and 0.83 d -1 . Long_term semicontinuous nutrient competition experiments were performed between T. subcordiformis and U. pertusa under phosphate limitation in laboratory. Loss rates were manipulated to get the same or different resource requirement values ( R * ) of the two species. Comparison between the theoretical predictions derived from Monod kinetics and the outcome of competition experiments indicated that the Monod model could predict the results only when the R * values of the two species were significantly different, and T. subcordiformis displaced U. pertusa when they had the same resource requirements. The Monod model can only partly predict the competition results between microalga and macroalga. 展开更多
关键词 MACROALGA MICROALGA Monod model PHOSPHATE resource competition theory R * _rule
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Analysis on the Competitiveness of Industrial Real Estate Based on Diamond Model ——Taking Jiangxi Province as an Example 被引量:1
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作者 刘群红 周杨一 朱梦梅 《Agricultural Science & Technology》 CAS 2017年第8期1531-1535,共5页
Based on the current development of industrial real estate of Jiangxi Province, comprehensive analysis was conducted to 6 aspects using the idea of diamond model, namely, factor conditions, demand conditions, related ... Based on the current development of industrial real estate of Jiangxi Province, comprehensive analysis was conducted to 6 aspects using the idea of diamond model, namely, factor conditions, demand conditions, related and supporting industries, firm strategy, structure and rivalry, government and chance through the comparison with the other industrial real estates and analysis on horizontal competition in China. Development countermeasures were investigated to improve the competitiveness of the industrial real estate in Guangxi, putting forward the strategies of developing the role of government and business, seizing the opportunities of the times, city-industry integration development, implementation of industrial integration and integration of city development, the implementation of industrial integration and investment planning. 展开更多
关键词 Diamond model Industrial real estate competitIVENESS
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Analysis on the Core Competitiveness of Rice Seed Industry in Guangxi Province Based on Diamond Model
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作者 张晓丽 薛艳霞 +6 位作者 吕荣华 王强 陈雷 唐茂艳 陶伟 高国庆 梁天锋 《Agricultural Science & Technology》 CAS 2016年第8期1963-1967,1977,共6页
By using diamond model, the current development status and core competitiveness of the rice seed industry in Guangxi Province were analyzed in detail from the 6 aspects of production factors, demand factors, related i... By using diamond model, the current development status and core competitiveness of the rice seed industry in Guangxi Province were analyzed in detail from the 6 aspects of production factors, demand factors, related industries and support industries, firm strategy, chance factor and government factor, which clarified the advantages of the rice seed industry of Guangxi in the nature and technological factors, firm strategy and government policy, and the disadvantages in demand factors, production cost, infrastructure and related industries. And the corresponding countermeasures were proposed to enhance the competitiveness of the rice seed industry of Guangxi. 展开更多
关键词 Diamond model RICE Core competitiveness GUANGXI
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A New Competitive Adsorption Isothermal Model of Heavy Metals in Soils 被引量:7
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作者 XUE Wen-Bo YI Ai-Hua +3 位作者 ZHANG Zeng-Qiang TANG Ci-Lai ZHANG Xing-Chang GAO Jin-Ming 《Pedosphere》 SCIE CAS CSCD 2009年第2期251-257,共7页
A new competitive adsorption isothermal model(CAIM)was developed for the coexistent and competitive binding of heavy metals to the soil surface.This model extended the earlier adsorption isothermal models by consideri... A new competitive adsorption isothermal model(CAIM)was developed for the coexistent and competitive binding of heavy metals to the soil surface.This model extended the earlier adsorption isothermal models by considering more than one kind of ion adsorption on the soil surface.It was compared with the Langmuir model using different conditions, and it was found that CAIM,which was suitable for competitive ion adsorption at the soil solid-liquid surface,had more advantages than the Langmuir model.The new competitive adsorption isothermal model was used to fit the data of heavy metal(Zn and Cd)competitive adsorption by a yellow soil at two temperatures.The results showed that CAIM was appropriate for the competitive adsorption of heavy metals on the soil surface at different temperatures.The fitted parameters of CAIM had explicit physical meaning.The model allowed for the calculation of the standard molar Gibbs free energy change,the standard molar enthalpy change,and the standard molar entropy change of the competitive adsorption of the heavy metals,Zn and Cd,by the yellow soil at two temperatures using the thermodynamic equilibrium constants. 展开更多
关键词 combined pollution competitive adsorption isothermal model heavy metal thermodynamic parameters
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Problems with models assessing influences of tree size and inter-tree competitive processes on individual tree growth:a cautionary tale 被引量:1
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作者 P.W.West D.A.Ratkowsky 《Journal of Forestry Research》 SCIE CAS CSCD 2022年第2期565-577,共13页
In forest growing at any one site, the growth rate of an individual tree is determined principally by its size, which reflects its metabolic capacity, and by competition from neighboring trees. Competitive effects of ... In forest growing at any one site, the growth rate of an individual tree is determined principally by its size, which reflects its metabolic capacity, and by competition from neighboring trees. Competitive effects of a tree may be proportional to its size;such competition is termed ‘sym-metric’ and generally involves competition below ground for nutrients and water from the soil. Competition may also be ‘asymmetric’, where its effects are disproportionate to the size of the tree;this generally involves competition above ground for sunlight, when larger trees shade smaller, but the reverse cannot occur. This work examines three model systems often seen as exemplars relating individual tree growth rates to tree size and both competitive processes. Data of tree stem basal area growth rates in plots of even- aged, monoculture forest of blackbutt (Eucalyptus pilularis Smith) growing in sub-tropical eastern Australia were used to test these systems. It was found that none could distin-guish between size and competitive effects at any time in any one stand and, thus, allow quantification of the contribution of each to explaining tree growth rates. They were prevented from doing so both by collinearity between the terms used to describe each of the effects and technical problems involved in the use of nonlinear least-squares regression to fit the models to any one data set. It is concluded that quite new approaches need to be devised if the effects on tree growth of tree size and competitive processes are to be quantified and modelled successfully. 展开更多
关键词 Symmetric competition Asymmetric competition Tree growth rate Growth modeling Nonlinear modeling
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