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Effect of Quantum Fluctuation on Two-Dimensional Spatially Anisotropic Heisenberg Antiferromagnet with Integer Spin

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Communications in Theoretical Physics 2006年第6期45卷 1137-1146页

作者： ji An-Chun tian Guang-Shan School of Physics Peking University Beijing 100871 China

In the present paper, we calculate the Gaussian correction to the critical value J^c⊥ caused by quantum spin fluctuation in a two-dimensional spatially anisotropic Heisenberg antiferromagnet with integer spin S. Previously, some authors computed this quantity by the mean-field theory based on the Sehwinger boson representation of spin operators. However, for S = 1, their result is much less than the one derived by numerical calculations. By taking the effect of quantum spin fluctuation into consideration, we are able to produce a greatly improved result.

关键词： spatially anisotropic Heisenberg model functional integration Schwinger boson representation

Graphene-Based Active Tunable Metasurfaces for Dynamic Terahertz Absorption and Polarization Conversion

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Journal of Renewable Materials 2023年第2期11卷 731-743页

作者： Haoran Wei tian ji jianqing Huang College of Applied Science and Technology Hainan UniversityDanzhou571737China

Simultaneous broadband absorption and polarization conversion are crucial in many practical applications,especially in terahertz ***,actively tunable metamaterial systems can exploit the graphene-based nanomaterials derived from renewable resources because of the flexible surface conductivity and selective permeability of the nanomaterials at terahertz *** this paper,we propose a graphene-based active tunable bifunctional metasurface for dynamic terahertz absorption and polarization *** graphene ring presents a certain opening angle(A)along the diagonal of the xoy *** A=0°,the proposed metasurface behaves as a broadband *** results show the feasibility of achieving this polarization-insensitive absorber with nearly 100%absorptance,and the bandwidth of its 90%absorptance is 1.22 THz under normal ***,when A=40°after optimization,the proposed metasurface serves as a broadband polarization convertor,resulting in robust broadband polarization conversion ratio(PCR)curves with a bandwidth surpassing 0.5 THz in the reflection *** tune the PCR response or the broad absorption spectrum of graphene,we change the Fermi energy of graphene dynamically from 0 to 0.9 ***,both the broadband absorption and the linear polarization conversion spectra of the proposed metasurface exhibit insensitivity to the incident angle,allowing large incident angles within 40°under high-performance operating *** demonstrate the physical process,we present the impedance matching theory and measure electric field *** architecture in the THz frequency range has several applications,such as in modulators,sensors,stealth,and optoelectronic *** wave polarization and beam steering also have broad application prospects in the field of intelligent systems.

关键词： Metasurface broadband absorption polarization conversion bi-functional renewable resources

Scalable Preparation of SrTiO_3 Submicro-wires from Layered Titanate Nanowires

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Chinese Journal of Aeronautics 2007年第2期20卷 177-180页

作者： TANG Mao-yu ji tian-hao XIE jian School of Materials Science and Engineering Beijing University of Aeronautics and Astronautics Beijing 100083 China

SrTiO3 submicro-wires were prepared by the reaction of layered titanatc nanowircs with Sr（OH）2 powder in an autoclave. The wires were investigated using X-ray diffraction （XRD）, scanning electron microscope （SEM）, transmission electron microscope （TEM）, Ultra-violet visible （UV-vis）, photoluminescence （PL） and Raman spectroscopy. The XRD measurement shows that the prepared SrTiO3 submicro-wircs hardly have impurity phases. The SEM and TEM images demonstrate that the scalable wires, which need to be processed at the reaction temperature of 180℃ for about 48 hours, are not composed of single crystals. The PL shows that the wire-like SrTiO3 has emission peaks at the wavelengths of 568 and 585 nm. Further, the Raman spectroscopy reveals structural changes in the products through different reaction time.

关键词： oxide titanate nanowires strontium titanate SrTiO3 wires

Superconducting Correlations in Small Metallic Grains

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Communications in Theoretical Physics 2001年第12期36卷 705-714页

作者： WANG jing ji An-Chun tian Guang-Shan Department of Physics Peking University Beijing 100871 China Department of Physics Peking University Beijing 100871 China Department of Physics Peking University Beijing 100871 China

By applying the path-integral formulation and the Feynman theorem, we calculate the off-diagonal superconducting correlation in an ultrasmall metallic grain. Unlike its behavior in the bulk limit, we find that this correlation function is an intensive quantity in this case. Therefore, superconductivity is indeed completely suppressed by quantum fluctuations as the diameter of the grain shrinks to the nanometer scale. This conclusion confirms the previous results by numerical calculations. Furthermore, it also imposes a strong constraint on the delocalizing amplitude of the pair-mixing function, which was recently proposed to characterize superconductivity in the canonical *** numbers: ***, ***, 74.80.

关键词： ultrasmall superconducting grain, the off-diagonal correlation function, path integral formulation and resolvent expansion method

Online Over Time Scheduling on Parallel-Batch Machines:A Survey

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Journal of the Operations Research Society of China 2014年第4期2卷 445-454页

作者： ji tian Ruyan Fu jinjiang Yuan College of Sciences China University of Mining and TechnologyXuzhou 221116JiangsuChina School of Mathematics and Statistics Zhengzhou UniversityZhengzhou 450001China

Online scheduling is a rapidly developed branch in scheduling *** this paper,we present an extensive survey for online over time scheduling on parallel-batch *** open problems are proposed for further research.

关键词： Online scheduling Parallel-batch machines Competitive ratio

Phytic Acid Contents of Wheat Flours from Different Mill Streams

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Agricultural Sciences in China 2010年第11期9卷 1684-1688页

作者： WU Peng ZHAO Tao tian ji-chun State Key Laboratory of Crop Biology Shandong Agricultural University Tai ＇an 271018 P.R.China College of Food Science and Engineering Shandong Agricultural University Tai＇an 271018 P.R.China College of Horticulture Science and Engineering Shandong Agricultural University Tai ＇an 271018 P.R. China

The phytic acid contents of eight fractions of wheat flours from different mill streams and those in wheat brans, which were separated by different sieves into various sizes, were determined and analyzed. A rapid method for phytic acid assay by adding thioglycolic acid （mercapto acetic acid） with 2,2-bipyridine was used, with an acidic iron-Ⅲ-solution of known iron content. The amount ofphytate was indicated by the decrease in iron in the supernatant. Significant differences were observed in phytic acid content among different milling streams and different cultivars （P〈0.05）. On an average, coarse bran had the highest phytic acid content （53.85 mg g^-1）, and the shorts had 28.48 mg g^-1. The B5 break flour had a higher phytic acid content （4.8 mg g^-1） than the B7 （2.75 mg g^-1） and B8 （2.03 mg g^-1） reduction flours. Lower values were found in the B3, B6 and B7 flours （1.07, 0.79, and 0.76 mg g^-1, respectively）. The phytic acid contents of bran decreased with smaller bran sizes, ranging from 54 to 5.09 mg g^-1.

关键词： phytic acid wheat mill streams bran flour

Effect of incubation temperature and wet-dry cycle on the availabilities of Cd,Pb and Zn in soil

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Journal of Environmental Sciences 2006年第6期18卷 1119-1123页

作者： SI ji-tao tian Bao-guo WANG Hong-tao Department of Environmental Science and Engineering Tsinghua University Beijing 100084 China

The effect of incubation temperature and wet-dry cycle on the availabilities of Cd, Pb and Zn was studied. Three soils with pH ranging from 3.8 to 7.3, organic carbon （OC） from 0.7% to 2.4%, and clay from 12.3% to 35.6% were selected. Soils were spiked with reagent grade Cd（NO3）2, Pb（NO3）2, and Zn（NO3）2 at concentrations of 30 mg Cd/kg soil, 300 mg Zn/kg soil and 2000 mg Pb/kg soil. The soils were incubated at 35, 60, 105℃, respectively and went through four wet-dry cycles. Metal availability in soils was estimated by soil extraction with 0.1 mol/L Ca（NO3）2. According to this study, the effect of the spiking temperature on the metal availabilities was different among the metals, soils and wet-dry cycles. Mostly, 35 ~C was the first recommended spiking temperature for Cd and Pb while no spiking temperature was obviously better than others for Zn. Three wet-dry cycles was recommended regardless of the type of metals and incubation temperature.

关键词： availability wet-dry cycle cadmium (Cd) zinc (Zn) lead (Pb)

CONDENSATION HEAT TRANSFER OF R-134A IN HORIZONTAL STRAIGHT AND HELICALLY COILED TUBE-IN-TUBE HEAT EXCHANGERS

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Journal of Hydrodynamics 2007年第6期19卷 677-682页

作者： SHAO Li HAN ji-tian SU Guo-ping PAN ji-hong School of Energy and Power Engineering Shandong University Jinan 250061 China School of Vehicle and Energy Yanshan University Qinhuangdao 066004 China

This article presents an experimental investigation on condensation heat transfer of R-134a in horizontal straight and helically coiled tube-in-tube heat exchangers. The experiments were carried out at three saturation temperatures（35 ℃ , 40 ℃ and 45 ℃ ） with the refrigerant mass flux varying from 100 kg/m2 s to 400 kg/m2 s and the vapor quality ranging from 0.1 to 0.8. The effects of vapor quality and mass flux of R-134a on the condensation heat transfer coefficient were investigated. The results indicate that the condensation heat transfer coefficients of the helical section are 4%-13.8% higher than that of the straight section. The experimental results were compared with the data available in literature for helical and straight pipes.

关键词： R-134a helically coiled tube two-phase heat transfer

THE FLOW ANALYSIS OF FLUIDS IN FRACTAL RESERVOIR WITH THE FRACTIONAL DERIVATIVE

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Journal of Hydrodynamics 2006年第3期18卷 287-293页

作者： tian ji TONG Deng-ke Institute of Mechanics Chinese Academy of ScienceBeijing 100080China Gudong Petroleum Factory of Shengli Petroleum Administration Dongying 256504China Departmentof Applied Mathematics China University of Petroleum Dongying 257061 China

In this paper, fractional order derivative, fractal dimension and spectral dimension are introduced into the seepage flow mechanics to establish the flow models of fluids in fractal reservoirs with the fractional derivative. The flow characteristics of fluids through a fractal reservoir with the fractional order derivative are studied by using the finite integral transform, the discrete Laplace transform of sequential fractional derivatives and the generalized Mittag-Leffler function. Exact solutions are obtained for arbitrary fractional order derivative. The long-time and short-time asymptotic solutions for an infinite formation are also obtained. The pressure transient behavior of fluids flow through an infinite fractal reservoir is studied by using the Stehfest＇s inversion method of the numerical Laplace transform. It shows that the order of the fractional derivative affect the whole pressure behavior, particularly, the effect of pressure behavior of the early-time stage is larger The new type flow model of fluid in fractal reservoir with fractional derivative is provided a new mathematical model for studying the seepage mechanics of fluid in fractal porous media.

关键词： fractional calculus porous media fractal,integral transform exact solution