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Search Results: 1 - 10 of 74236 matches for " TANG Jian-Jun "
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Liang Tang,Wei-Xin Xie,Jian-Jun Huang
Image Analysis and Stereology , 2004, DOI: 10.5566/ias.v23.p23-31
Abstract: An automatic multilevel image segmentation method based on sup-star fuzzy reasoning (SSFR) is presented. Using the well-known sup-star fuzzy reasoning technique, the proposed algorithm combines the global statistical information implied in the histogram with the local information represented by the fuzzy sets of gray-levels, and aggregates all the gray-levels into several classes characterized by the local maximum values of the histogram. The presented method has the merits of determining the number of the segmentation classes automatically, and avoiding to calculating thresholds of segmentation. Emulating and real image segmentation experiments demonstrate that the SSFR is effective.
Frustration induced noncollinear magnetic order phase in one-dimensional Heisenberg chain with alternating antiferromagnetic and ferromagnetic next nearest neighbor interactions
Jian-Jun Jiang,Fei Tang,Cui-Hong Yang
Physics , 2014, DOI: 10.7566/JPSJ.84.124710
Abstract: By using the coupled cluster method, the numerical exact diagonalization method, and the numerical density matrix renormalization group method, we investigated the properties of the one-dimensional Heisenberg chain with alternating antiferromagnetic and ferromagnetic next nearest neighbor interactions. In the classical limit, the ground state is in the collinear Neel state if a<1/2, while for a>1/2, there is an noncollinear canted state. For the quantum case, we found that, although the classical Neel state is absent, the canted state exists if the frustration parameter a exceeds a critical point ac1. The precise critical point ac1 can be determined by using the coupled cluster method and the numerical exact diagonalization method separately. The results of the coupled cluster method and the exact diagonalization method both disclose that the type of phase transition occurring at ac1 changes from a classical second-order transition to a quantum first-order transition due to quantum fluctuation. Although there is another critical point ac2 in a finite system at which the ground state evolves from the canted state to the collinear Neel plus ferromagnetic state, that state is absent because ac2 tends to infinity in the thermodynamic limit.
Coupled cluster treatment of one quasi-one-dimensional coupled spin triangles
Jian-Jun Jiang,Yong-Jun Liu,Fei Tang,Cui-Hong Yang
Physics , 2015,
Abstract: By using the coupled cluster method (CCM) and the numerical exact diagonalization (ED) method, we investigated the properties of the one quasi-one-dimensional coupled spin triangles. The results of ED disclose that the system is in the exact tetramer-dimer (TD) state if aac1, we find that CCM results for some physical quantities, such as the ground state energy, the magnetization and the antiferromagnetic gap are in excellent agreement with the results obtained by ED. Thus, CCM can be used to accurately analyze the properties of the quasi-one-dimensional coupled spin triangles in the whole parameter region. We believe that it can also be applied to investigating the properties of other quasi-one spin systems reliably.
Coupled Cluster Treatment of the Alternating Bond Diamond Chain
Jian-Jun Jiang,Yong-Jun Liu,Fei Tang,Cui-Hong Yang
Physics , 2015, DOI: 10.7566/JPSJ.84.114713
Abstract: By the analytical coupled cluster method (CCM), we study both the ground state and lowest-lying excited-state properties of the alternating bond diamond chain. The numerical exact diagonalization (ED) method is also applied to the chain to verify the accuracy of CCM results. The ED results show that the ground-state phase diagram contains two exact spin cluster solid ground states, namely, the tetramer-dimer (TD) state and dimer state, and the ferrimagnetic long-range-ordered state. We prove that the two exact spin cluster solid ground states can both be formed by CCM. Moreover, the exact spin gap in the TD state can be obtained by CCM. In the ferrimagnetic region, we find that the CCM results for some physical quantities, such as the ground-state energy, the sublattice magnetizations, and the antiferromagnetic gap, are comparable to the results obtained by numerical methods. The critical line dividing the TD state from the ferrimagnetic state is also given by CCM and is in perfect agreement with that determined by the ED method.
Utilization of biodiversity in agriculture: today and tomorrow

CHEN Xin,TANG Jian-Jun,
陈 欣

中国生态农业学报 , 2013,
Abstract: Currently, world agriculture was faced with drastic challenges to produce sufficient food while minimizing negative environmental effects of crop cultivation. Unlike traditional agriculture, which used local biodiversity and species interactions to sustain food production, modern agriculture used fewer high-yield crop varieties and largely ignored species interactions. Modern agriculture relied on chemically-driven modern varieties and irrigation to ensure high production. At the same time, modern high production induced negative environmental effects, pest resistance to pesticides and high agro-production costs. Whether and how biodiversity integrated into modern agriculture was a recent trend of research. Here, we reviewed the researches on the utilization of biodiversity in agriculture in the last decades. We then proposed future researches on intensified development of sustainable global agriculture with integrated biotechnology, precision agro-technology and biodiversity utilization. Unlike natural ecosystems, agro-ecosystem species consisted of productive biota (e.g., crops, forest trees and animals), resource biota (e.g., pollinating insects and crop-related wild species) and destructive biota (e.g., weeds and insect pests). Productive biota cultured by farmers dominated agro-systems and contributed to food production. Thus designing productive biota diversity was critical for biodiversity utilization of agro-systems. Utilization of productive biota diversity in agriculture included applications of genetic, species and landscape diversity. Studies indicated that uses of multi-gene varieties and mixtures of varieties were the key approaches to genetic diversity. This effectively controlled diseases in coffee, barley, wheat and rice crops. Genetic diversity mechanisms controlled diseases via resistant plant pathogen dilution or physical isolation. For species diversity utilization, intercropping and co-culture of crops and animals were the two common approaches. Legume-cereal intercropping and rice-fish co-cultures were the two successful examples of species diversity use in agro-systems. Species intercrops or co-cultures reduced the applications of chemical fertilizers and pesticides and promoted super-harvests. Positive species interactions and complementary resource uses explained why intercrops and co-cultures promoted super-harvests. For example, super-harvests often occurred in legume-cereal intercrops mainly as a result of facilitative root interactions, including nitrogen transfers and nutrient mobilizations. In rice-fish systems, fish reduced rice pests whereas rice moderated fish water environment which in turn enhanced pest removal. This positive relationship between rice and fish resulted in reduced pesticide use. Experiments also indicated that complementary use of nitrogen (N) in rice-fish systems resulted in low N fertilizer use and low N release into the environment. Within agricultural areas, diverse croplands in mosaic patt
Three-dimensional interfacial wave theory of dendritic growth: (II). non-axi-symmetric global wave modes and selection criterion of pattern formation

Chen Yong-Qiang,Tang Xiong-Xin,Xu Jian-Jun,

中国物理 B , 2009,
Abstract: This paper is the continuation of part (I), which completes the derivations of the 3D global wave modes solutions, yields the stability criterion and, on the basis of the results obtained, demonstrates the selection criterion of pattern formation.
Three-dimensional interfacial wave theory of dendritic growth: (I). multiple variables expansion solutions

Chen Yong-Qiang,Tang Xiong-Xin,Xu Jian-Jun,

中国物理 B , 2009,
Abstract: Dendritic pattern formation at the interface between liquid and solid is a commonly observed phenomenon in crystal growth and solidification process. The theoretical investigation of dendritic growth is one of the most profound and highly challenging subjects in the broad areas of interfacial pattern formation, condensed matter physics and materials science, preoccupying many researchers from various areas. Some longstanding key issues on this subject finally gained a breakthrough in the late of last century, via the `{Interfacial Wave} (IFW) Theory' on the ground of systematical global stability analysis of the basic state of dendritic growth. The original form of the IFW theory mainly focus on the investigation of various axi-symmetric unsteady perturbed modes solutions around the axi-symmetric basic state of system of dendritic growth. In reality, the system may allow various non-axi-symmetric, unsteady perturbed states. Whether or not the system of dendritic growth allows some growing non-axi-symmetric modes? Will the stationary dendritic pattern be destroyed by some of such non-axi-symmetric modes? Or, in one word, what is the stability property of the system, once the non-axi-symmetric modes can be evoked? The answers for these questions are important for the solid foundation of IFW theory. The present work attempts to settle down these issues and develop a three-dimensional (3D) interfacial wave theory of dendritic growth. Our investigations verify that dendritic growth indeed allows a discrete set of non-axi-symmetric unstable global wave modes, which gives rise to a set of multiple arms spiral waves propagating along the Ivantsov's paraboloid.
Effects of Rashba spin-orbit coupling and a magnetic field on a polygonal quantum ring
Han-Zhao Tang,Li-Xue Zhai,Man Shen,Jian-Jun Liu
Physics , 2014, DOI: 10.1016/j.physleta.2014.07.039
Abstract: Using standard quantum network method, we analytically investigate the effect of Rashba spin-orbit coupling (RSOC) and a magnetic field on the spin transport properties of a polygonal quantum ring. Using Landauer-Buttiker formula, we have found that the polarization direction and phase of transmitted electrons can be controlled by both the magnetic field and RSOC. A device to generate a spin-polarized conductance in a polygon with an arbitrary number of sides is discussed. This device would permit precise control of spin and selectively provide spin filtering for either spin up or spin down simply by interchanging the source and drain.
Photon assisted tunneling through three quantum dots with spin-orbit-coupling
Han-Zhao Tang,Xing-Tao An,Ai-Kun Wang,Jian-Jun Liu
Physics , 2014, DOI: 10.1063/1.4892822
Abstract: The effect of an ac electric field on quantum transport properties in a system of three quantum dots, two of which are connected in parallel while the third is coupled to one of the other two, is investigated theoretically. Based on the Keldysh nonequilibrium Green's function method, the spin-dependent current, occupation number and spin accumulation can be obtained in our model. An external magnetic flux, Rashba spin orbit coupling (SOC) and intradot Coulomb interactions are considered. The magnitude of the spin-dependent average current and the positions of the photon assisted tunneling (PAT) peaks can be accurately controlled and manipulated by simply varying the strength of the coupling and the frequency of the ac field. A particularly interesting result is the observation of a new kind of PAT peak and a multiple electron-photon pump effect that can generated and controlled by the coupling between the quantum dots. In addition, the spin occupation number and spin accumulation can be well controlled by the Rashba SOC and the magnetic flux.
Differential measurement of atmospheric refraction with a telescope with double fields of view
Yong Yu,Jian-Jun Cao,Zheng-Hong Tang,Hao Luo,Ming Zhao
Physics , 2015, DOI: 10.1088/1674-4527/15/10/011
Abstract: For the sake of complete theoretical research of atmospheric refraction, the atmospheric refraction under the condition of lower angles of elevation is still worthy to be analyzed and explored. In some engineering applications, the objects with larger zenith distance must be observed sometimes. Carrying out observational research of the atmospheric refraction at lower angles of elevation has an important significance. It has been considered difficult to measure the atmospheric refraction at lower angles of elevation. A new idea for determining atmospheric refraction by utilizing differential measurement with double fields of view is proposed. Taking the observational principle of HIPPARCOS satellite as a reference, a schematic prototype with double fields of view was developed. In August of 2013, experimental observations were carried out and the atmospheric refractions at lower angles of elevation can be obtained by the schematic prototype. The measured value of the atmospheric refraction at the zenith distance of 78.8 degree is $240.23"\pm0.27"$, and the feasibility of differential measurement of atmospheric refraction with double fields of view was justified. The limitations of the schematic prototype such as inadequate ability of gathering light, lack of accurate meteorological data recording and lower automatic level of observation and data processing were also pointed out, which need to be improved in subsequent work.
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