最新刊期
卷 51 ， 期 3 ， 2012
- 摘要：The current status of dark matter direct detection experiments and their main results is briefly reviewed. Some experiments have claimed that some possible dark matter signals have been found, but the results of these experiments are inconsistent to each other. On the other hand, other experiments have excluded these possible signal regions. Further experiments are needed to give a convincing statement.关键词：dark matter;direct detection;weakly interacting massive particle
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发布时间：2023-12-11 - 摘要：Based on the Nozieres-Schmitt-Rink theory and expanded Luttinger theory, the electronic specific heat coefficient γ(T) is evaluated and ploted individually. The results indicated that the pseudo-gap phenomena are realized in quasi-two dimensional high temperature cuprate superconductors in the Nozieres-Schmitt-Rink theory and expanded Luttinger theory.关键词：high temperature cuprate superconductors;electronic specific heat;the specific heat coefficient;pseudo-gap
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发布时间：2023-12-11 - 摘要：250 nm amorphous silicon thin films were crystallized by a 355 nm YAG picosecond pulsed laser, then the crystallized samples were investigated by metallurgical microscope、Raman spectrometer and Xray spectrometer. The results show that with increasing laser energy the width of completely molten zone and partially molten zone increases remarkably. In the energy range from 15 μJ to 860 μJ, neither characteristic peak of amorphous silicon nor characteristic peak of crystalline silicon appears in Raman spectra of the completely molten zones in all samples, while Raman spectra of the partially molten zone exhibit the sharp characteristic peak of crystalline silicon, it might be because that the energy flux density received by completely molten zone was so big that the most of the amorphous silicon in this region was evaporated. This assumption was further reconfirmed by EDS(energy dispersive spectrometer)analysis results, which shows that the composition of the completely molten zone are mainly silicide produced by reaction between glass and silicon, and its surface are covered by silicon dioxide layer.关键词：YAG laser;amorphous silicon thin films;laser crystallization;polycrystalline silicon thin films
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发布时间：2023-12-11 - 摘要：One method ofN-dimensional block orthogonal was presented and the research of demodulation identification method was made.Based-on ordinary orthogonal modulation recognition,the research realized data block demodulation from the received signal samples extracted basic feature vector to estimate the signal parameters and achieved recognition of signal modulation through the matrix conversion, The simulations results under the conditions of an additive Gauss white noise channel，show that the method has a good performance of recognition to signal ofN-dimensional block orthogonal modulation:关键词：block orthogonal modulations ofN-dimensional;clustering example;demodulation;identification
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发布时间：2023-12-11 - 摘要：A method of background extraction and update for vehicle detection is proposed, which is special for the saturated intersection. According to the characteristics of traffic flow in intersections, a background evaluation mechanism is established by using the feedback of vehicle detection result. Then the true background image is updated from the noisy initial background iteratively combining evaluation mechanism, Median Filter and Inter-frame Difference algorithm. The experiments show that the algorithm has a faster convergence rate in saturated intersection, and satisfy complex engineering needs.关键词：background extraction;saturated intersection;median filter;inter-frame difference
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发布时间：2023-12-11 - 摘要：Two-dimensional compressible flows field for the interaction of shocks with the cylinder interface are directly simulated by using high order accurate upwind compact difference schemes with group velocity control combined with Level Set method. Numerical results are compared with the experimental observation. They show the right position of interface, right strength and velocity of shocks. The numerical results are satisfactory.关键词：fluid interface;group velocity control;upwind compact finite difference scheme;level set method
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发布时间：2023-12-11 - 摘要：A weakly dissipative periodic Camassa-Holm system with vorticity is studied. Using the structure of the system and the dissipation of energy, by introducing a suitable Lyapunov function, the global existence of strong solution of the system is proved.关键词：Camassa-Holm system with vorticity;weakly dissipative;global existence
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发布时间：2023-12-11 - 摘要：The notion of α－π－Armendariz rings is introduced for a ring endomorphism α. The examples of α－π－Armendariz rings are given, and the extensions of this class of rings are investigated.关键词：α－π－Armendariz rings;shew polynomial ring;nilpotent elements
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发布时间：2023-12-11 - 摘要：Under the assumption that the initial density is bounded away from zero, the local existence in some critical Besov spaces for the compressible magneto-hydrodynamic equations with density-dependent viscosities inRN(N≥2) is established by constructing a sequence of smooth solutions. And using a compactness argument,the convergence of the sequence is proved.关键词：compressible magneto-hydrodynamic equations;existence;critical Besov spaces;Bony paraproduct decomposition
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发布时间：2023-12-11 - 摘要：Based on Douady-Earle extension of homeomorphism from S1to S1a new extension map between unit discs called inverse extension is defined, which is conformal natural. And the inverse extension is shown not always to be equal to Douady-Earle extension by an example.关键词：Douady-Earle extension;inverse extension;quasiconformal mapping
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发布时间：2023-12-11 - 摘要：An image super-resolution processing by using Hidden Markov Tree model to express the wavelet coefficients of the probability of structure is proposed. According to the properties of multiscale wavelet coefficients, the persistency and the exponential decay, wavelet coefficients of the image are modeled as Hidden Markov Tree model. Wavelet-domain HMT model considers the statistical properties of wavelet coefficients.The image interpolation is formulated as a constrained optimization problem. The high-resolution interpolated image which is able to maintain the original image information in the rich high-frequency is obtained. Experiment results show that the algorithm improves the traditional sawtooth effect and smoothing effect caused by interpolation. The PSNR and visual effects of interpolated image are improved obviously.关键词：wavelet transform;super-resolution processing;interpolation algorithm;HMT model;peak signal to noise ratio
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发布时间：2023-12-11 - 摘要：La1-xFexNiO3(LNFeO-x)thin films were prepared on (100) Si substrates by a chemical solution deposition method (CSD). Their structure and room temperature resitivity were analyzed. X-ray diffraction show that the thin films annealed at 700 ℃ for 1 h were grown in perovskite structure and no secondary phase was detected. The thin films were smooth, density and crack-free. The room temperature resistivity increases from 1.7 Ω·cm to 3.9 Ω·cm as x increases from 0 to 0.15.关键词：La1-xFexNiO3;LNFeO-x;chemical solution deposition method;CSD
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发布时间：2023-12-11 - 摘要：Clematis chinensisOsbeck is a popular medicinal plant. Seven known compounds, pinoresinol (1), epipinoresinol (2), matairesinol (3), salicifoliol (4), 3,4,5-trihydroxybenzoic acid (5), 4hydroxy3,5dimethoxybenzoic acid (6), and 3hydroxy 4 methoxycinnamic acid (7) were isolated from the ethyl acetate extract ofClematis chinensisOsbeck by using the flash silica gel column chromatography and preparative high performance liquid chromatography. Their structures were elucidated mainly on the basis of NMR and MS data. These compounds could be fast and accurately detected from the extract by using HPLC and GCMS analytical methods. Lignans1,2,3,4have various bioactivities, and the lignans fromClematis chinensisOsbeck should have the potential application in drug development.关键词：Clematis chinensisOsbeck;lignan;pinoresinol;chemical constituents;bioactivity
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发布时间：2023-12-11 - 摘要：1,3,4-Oxadiazole compounds are a class of significant heterocyclic compounds widely used in medicinal chemistry, pesticide chemistry and materials science. In this work, a series of 1,3,4-oxadiazole derivatives containing imidazole unit were designed, synthesized and their structures were characterized by NMR spectroscopy, Mass and elemental analyses.关键词：imidazole;1;3;4-oxadiazoles;synthesis
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发布时间：2023-12-11 - 摘要：Electrochemical properties of SiW11O39Fe(Ⅲ)(H2O)5-(SiW11Fe) and its electrocatalysis for H2O2reduction in a solution of 0.1 mol·L-1NaHSO4+ Na2SO4were investigated in detail using the electrochemical methods such as cyclic voltammetry and AC impedance etc. At the same time, a comparison with PW11O39Fe(Ⅲ)(H2O)4-(PW11Fe) was made and an indirect electrocatalysis mechanism was proposed. Experimental results indicated that SiW11Fe possesses three pairs of redox waves attributed to the voltammetric responses of the Fe(Ⅲ)/Fe(Ⅱ) redox couple and the W-O skeleton, respectively, similar to PW11Fe. Compared with PW11Fe, all peak potentials of the three pairs of redox waves moved obviously to negative direction for SiW11Fe and were affected by the solution pH. The Fe(Ⅲ)/Fe(Ⅱ) redox couple of SiW11Fe has a worse reversibility of electron transfer than that of PW11Fe, but similarly exhibit a high electrocatalytic activity for H2O2reduction, which was affected by the solution pH. With increasing of the solution pH, the redox peak potentials of the Fe wave and W-O waves shifted negatively; the electrocatalytic activity of the Fe wave towards H2O2reduction declined or even was completely inhibited. Instead, the first W-O skeleton wave showed a distinct electrocatalysis for H2O2reduction.关键词：Fe(Ⅲ)-substituted heteropolyanion;electrocatalysis;cyclic voltammetry;alternating current impedance;H2O2
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发布时间：2023-12-11 - 摘要：The density and surface tension of pure ionic liquid ［BMIM］ClO4(1-butyl-3-methylimidazolium hydrosulfate) were measured in the temperature range of 293.2－353.2 K. Based on the Glasser's theory, the thermodynamic property of the ionic liquid was investigated, such as the standard molar entropy and lattice energy. The thermal expansion coefficient, α= 7.8 × 10-4K-1calculated by the interstice model was in good agreement with α (experimental) = 10.8 ×10-4K-1.关键词：ionic liquid;［BMIM］HSO4;density;surface tension;Glasser's theory;interstice model
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发布时间：2023-12-11 - 摘要：The red spotted grouper has been considered to be at risk of being overexploited in China and its artificial seeds had the low larval survival rates and low stability. Efficient measures therefore must be taken for surveillance, conservation and utilization of this species with its available genetic resources. In this study, a total of 7 simple sequence repeat (SSR) markers were used to assess genetic diversity for the red spotted groupers from 7 different typical fishing grounds across Southern China Sea and East China Sea. The high polymorphism information contents at the 7 markers implied that the red spotted groupers keep natural variation from different offshore fishing grounds in China. Analysis of genetic differentiation indicated substantial divergence among the red spotted groupers. Phylogenetic analyses displayed a remarkable degree of consistency between geographic locations and the pattern of genetic differentiation.关键词：Epinephelus akaar;simple sequence repeat marker;population genetics;genetic diversity
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发布时间：2023-12-11 - 摘要：Natural enemy-Cnaphalocrocis medinalis(Guenee) system was studied based on the principle and method of system sciences to seek possible ways or strategies for pest population control. Conceptual model describing interrelated or interacting activities among different generations ofCnaphalocrocis medinalisGuenee) and their natural enemy was established and further quantified with differential equations or function formulas. Dynamics ofCnaphalocrocis medinalis(Guenee) and natural enemy population density were simulated and analyzed respectively using STELLA. The results indicated that trends of bothCnaphalocrocis medinalis(Guenee) and natural enemy population in six pest-control scenarios were different in their peak values and occurrence time, etc. A considerable quantity of natural enemy was essential to the effective control of occurrence and development ofCnaphalocrocis medinalis(Guenee)〖WTBX〗.〖WTBZ〗 Supplement of a number of natural enemy to rice cropping field at the early period of insect pest occurrence were recommended for enhancement the control onCnaphalocrocis medinalis(Guenee) during the late growth period of paddy rice.
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发布时间：2023-12-11 - 摘要：The chloroplasttrnL-trnF sequences of 21 species in Tiliaceae, Sterculiaceae and Elaeocarpaceae and 4 species in Rosaceae were determined by sequencing cloned PCR products. In this study, the phylogeny was inferred using dataset of chloroplasttrnL-trnF, including 44 sequences from GenBank. The results from Bayesian inference, maximum parsimony, and maximum likelihood consistently showed that：①Muntingia calaburaformed an independent clade with high support values, which the foundation on Muntingiaceae was rational; ②Craigiaclosed to the generaPterospermumThespesiaSterculiaColaFirmianaandHeritierashould be placed in Sterculiaceae; ③ElaeocarpusandSloaneawere two valid genera in Elaeocarpaceae; ④ Tiliaceae and Sterculiaceae doesn't consist of two independent clades, but those are existed to be a close relationship among three families included Elaeocarpaceae.
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发布时间：2023-12-11 - 摘要：Euphyllophytes comprise ferns, gymnosperms, and angiosperms. Relatively abundant chloroplast genome sequence data has been available for them. In this research, chloroplast gene sequences of 29 euphyllophyte species were extracted from their completely sequenced chloroplast genomes; then an adaptive evolutionary analysis was performed on the chloroplast genes by running PAML under models allowing ω (nonsynonymous/synonymous rate ratio) to vary among sites. The results showed that:①The percentage of chloroplast genes under positive selection in ferns, gymnosperms, and angiosperms were 6.5%、7.5% and 19.2%, respectively. The number of positively selected genes in angiosperms appeared significantly larger than that of ferns and gymnosperms.②Most positively selected genes were genetic system or photosynthesisrelated genes. Their coding proteins often functioned in chloroplast protein synthesis, gene transcription, energy transformation and regulation, and photosynthesis. We infer that the chloroplast functional genes may have played key roles during the adaptation of euphyllophytes to terrestrial ecosystems.关键词：euphyllophytes;chloroplast genes;complete chloroplast genome sequences;positive selection
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发布时间：2023-12-11 - 摘要：The continuous wavelet transform was introduced to assay the oxygen isotope sequences of stalagmites since the Last Glacial Maximum (~30 000 aBP) at Hulu Cave, Sanbao Cave, and Dongge Cave in South China. The result shows that the climate fluctuation in glacial period was more prominent than that in interglacial period. The periods of oxygen isotope in both Dongge Cave and Sanbao Cave were characterized by three stages during the Holocene. However, the length, as well as the intensity of oxygen isotope periods displayed significant difference between two caves. The reason is that the climate in Sanbao Cave region was only controlled by the East Asian Summer Monsoon (EASM), while that in Dongge Cave region was jointly influenced by the Indian Summer Monsoon (ISM) and EASM. The weak periods in Dongge Cave may be correlated to the strong anti-phasing of the ISM and EASM. The climate transformation from stability to fluctuation at ~3 000 aBP was also presented by the analysis result.关键词：Southern China;stalagmite;oxygen isotope;wavelet transform;periods;climate change
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发布时间：2023-12-11 - 摘要：The Tianyang Maar Lake is situated in the southeastern Leizhou Peninsula, the transitional climate zone between tropical and subtropical region of China. In this paper,a study was carried out on the upper 40 meters of core TYC collected from the Tianyang Maar Lake. The results suggest that magnetic susceptibility (MS) correlates well with pollen records. Thus, variations of MS can be used as an indicator for climate and environmental changes in the Tianyang Maar Lake. Generally, a low MS indicates a warm and humid environmental condition, while a high MS suggests a cold or cool environment. Results of the MS analysis suggest that the environmental history of the Tianyang Maar lake area since the Middle Pleistocene can be divided into 9 stages: 346~301.4 ka BP, the climate was relatively warm and humid. 301.4~248.8 ka BP, the climate became relatively cool and dry. 248.8~188.8 ka BP, the climate was warm and humid. 188.8~125.2 ka BP, it was cold and dry. 125.2~69.3 ka BP, the climate was relatively warm and humid. 69.3~40.43 ka BP, the climate was cool. 40.43~25.5 ka BP, the climate was cool and the temperature was lower than the former stage, with a swamping transitional environment in Tianyang Maar Lake. 25.5 ~ 10.8 ka BP, the climate got even colder and drier, the water of Tianyang Maar Lake almost dried up. During the last 10.8 ka BP, the existence of human activities has probably resulted in high MS values.
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发布时间：2023-12-11 - 摘要：Bathymetry of lakes in the Arctic coastal plain plays an important role in understanding the regional geographical processes and environmental changes. Inversion of polar lake depth with remote sensing technique owns the advantage of rapidly processing large-scale data, but so far less research was done in Arctic. The aim of this article is to retrieve the bathymetry of shallow thaw lakes in the Arctic Coastal Plain of northern Alaska based on the multispectral remote sensing data. The inversion method proposed by Stumpf was inspected and verified. Then it was applied to retrieve the depth of 3 187 lakes distributed in the area of 16 380 km2. Validation for the model was implemented via field measurements obtained from ship-borne sonar, and the MAE (mean absolute error) and RMSE (root mean square error) were 0.37 m and 0.54 m respectively. This method is suitable for bathymetric retrieval from remote sensing data of thousands of lakes in the study area. The spatial pattern of lake depth shows that depth of lake decreases from hill foot of Brooks to the coastline.关键词：polar lakes;bathymetric inversion;Stumpf model;log-transform band ratio;Alaska
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发布时间：2023-12-11 - 摘要：The importance of spatial distribution of urban population data is analyzed. Aiming at the disadvantages of the usual methods of urban population distribution, a simulation model for urban population distribution is developed with integration of multi-agent and population migration theory (Simulation Model for Urban Population Distribution-SMUPD), which consists of external environment, multi-agent and rules. Residential land has been divided into regular residential cells,based on the initial condition; each residential cell has the same amount of agent. Agents decide whether to migrate or not, and select the appropriate residential cell to make migration. The population distribution is formed by means of the constant decision-making, consult and migration of agents. Experiments indicate that, the simulation result of SMUPD not only has higher accuracy, but also is close to the actual residential segregation pattern. In conclusion, the SMUPD provides a new way of modeling urban population distribution.关键词：population distribution;residential segregation;multi-agent;simulation;Guangzhou
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发布时间：2023-12-11 - 摘要：The marine actinomyceteStreptomycessp.V65, isolated from the soil sample underAcanthus ilicifoliusfrom Yangjiang intact mangrove, metabolized some red pigments in Gause‘s medium (Ⅰ). Undecylprodigiosin (Ⅰ) and metacycloprodigiosin(Ⅱ) with SW-B(Ⅲ) （(2E,4E)-2,4,6-trimethyldeca-2,4-dienamide）were isolated from its mycelia and fermentation using silica gel column chromatography, RP-18 silica gel column chromatography and Sephadex LH-20 column chromatography. Their structures were characterized by NMR spectroscopy and Mass analysis. The metabolites of the marine actinomycetesStreptomycessp.strain V65 from Yangjiang intact mangrove were first investigated.关键词：Yangjiang intact mangrove;marine actinomycete;metabolites
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发布时间：2023-12-11
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