4,046 research outputs found
Onset of unsteady horizontal convection in rectangle tank at
The horizontal convection within a rectangle tank is numerically simulated.
The flow is found to be unsteady at high Rayleigh numbers. There is a Hopf
bifurcation of from steady solutions to periodic solutions, and the
critical Rayleigh number is obtained as for the
middle plume forcing at , which is much larger than the formerly obtained
value. Besides, the unstable perturbations are always generated from the
central jet, which implies that the onset of instability is due to velocity
shear (shear instability) other than thermally dynamics (thermal instability).
Finally, Paparella and Young's [J. Fluid Mech. 466 (2002) 205] first hypotheses
about the destabilization of the flow is numerically proved, i.e. the middle
plume forcing can lead to a destabilization of the flow.Comment: 4pages, 6 figures, extension of Chin. Phys. Lett. 2008, 25(6), in
pres
Identification of Seawater Quality by Multivariate Statistical Analysis in Xisha Islands, South China Sea
Xisha waters are considered to be in pristine condition, while facing the fast increasing stress under anthropogenic activities. Water quality around Yongxing Island (YX) has been measured in May, 2012. The results show that the water quality is of the first class standards as compared to the water quality of China, with insignificant difference among the monitoring stations. Robust principal component analysis (PCA) was used to identify the spatial pattern of water quality. YX is characterized by high DO, salinity, and Chl-a with low nutrients, indicating phytoplankton photosynthesis is stronger in YX island waters than the rest of the study areas. Beidao (BD) is characterized by high NH4-N and COD, and low pH, implying that these areas may have higher organic matter decomposition than rest of the areas. The water quality monitoring stations should cover spatially and temporally around Xisha waters for protecting the marine environment
Developing Knowledge Absorptive Capacity of SMEs in China
Small and medium-sized enterpreises (SMEs) are a crucial driver of the fast growing Chinese economy. This study aims to investigate how the external structures influence SMEs’ knowledge absorptive capacity for competence enhancement and performance improvement. Taking the “structure-conduct-performance” paradigm as an overarching framework, this research extends and enriches this framework by integrating social networking theory and absorptive capacity theory into it. More specific, we partition the “structure” into environmental structure and social network structure outside of a focal firm, and specify the “conduct” as knowledge absorptive capacity development including knowledge acquisition and transformation. To verify our research model, a survey method is employed involving 77 SMEs from China. The results show the distinct roles of environmental hostility, customer network ties, and knowledge absorptive capacities on SMEs’ performance. Theoretical contributions and managerial implications are also discussed
Medial patellofemoral ligament reconstruction using a bone groove and a suture anchor at patellar: a safe and firm fixation technique and 3-year follow-up study
A Heterogeneous Multiattribute Group Decision-Making Method Based on Intuitionistic Triangular Fuzzy Information
Usage of Rapid Prototyping Technique in Customized Craniomaxillofacial Bone Tissue Engineering Scaffold
Negative Parity N* Resonances in an Extended GBE
In this paper, we calculate the masses and mixing angles of L=1 negative
parity N* resonances in an extended GBE (Goldstone-boson-exchange model) with
harmonic-oscillator wave functions. By using those mixing angles, we get their
photoproduction amplitudes, and compare them with experimental data and the
results of OPE (one-pion-exchange model), OPsE (only pseudoscalar meson
exchange model), and OGE (one-gluon-exchange model). We find that the extended
GBE gives right internal wave functions. It is essential to extend GBE to
include not only pseudoscalar meson exchanges but also vector meson exchanges.Comment: 11 pages, no figure, accepted by Nucl. Phys.
Isospin dependence of projectile-like fragment production at intermediate energies
The cross sections of fragments produced in 140 MeV Ca + Be
and Ni + Be reactions are calculated by the statistical
abration-ablation(SAA) model and compared to the experimental results measured
at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State
University. The fragment isotopic and isotonic cross section distributions of
Ca and Ca, Ni and Ni, Ca and Ni, and
Ca and Ni are compared and the isospin dependence of the
projectile fragmentation is studied. It is found that the isospin dependence
decreases and disappears in the central collisions. The shapes of the fragment
isotopic and isotonic cross section distributions are found to be very similar
for symmetric projectile nuclei. The shapes of the fragment isotopic and
isotonic distributions of different asymmetric projectiles produced in
peripheral reactions are found very similar. The similarity of the
distributions are related to the similar proton and neutron density
distributions inside the nucleus in framework of the SAA model.Comment: 7 pages, 4 figures; to be published in Phys Rev
Chemometry use in the evaluation of the sanya bay water quality
No presente estudo foi realizada a identificação dos efeitos antropogênicos e das características naturais marinhas das águas da Baía de Sanya, situada ao sul do Mar da China, através de método quimiométrico. A análise de componentes principais (PCA) aplicada aos dados extraiu quatro eixos que explicaram 85,52% da variância total dos dados. Através das análises de Agrupamento e PCA foram identificados três padrões diferentes de qualidade das águas, baseados nos efeitos antropogênicos e nas características marinhas: Grupo I, localizado nas partes externa e mediana da baía; Grupo II, próximo do centro urbano de Sanya; Grupo III, localizado no estuário do Rio Sanya. Quanto ao padrão temporal, as referidas análises distinguiram uma estação seca, de novembro a abril, e uma estação chuvosa, de maio a outubro, relacionadas ao clima e características naturais. Foi visto que tanto a fonte poluidora externa, representada pelo Rio Sanya, quanto as águas do Mar do Sul da China influenciam a qualidade das águas da Baía de Sanya. Esses resultados podem ser relevantes quando considerados sob o ponto de vista do desenvolvimento socioeconômico e de saúde humana dessa região.In this study, chemometric method is employed to identify anthropogenic effects on the water quality in Sanya Bay, South China Sea, and its marine and natural characteristics. Principal component analysis has extracted the four latent factors, thus explaining 85.52% of the total variance. Cluster analysis and principal component analysis have identified three different patterns of water quality based on anthropogenic effects and marine characteristics: Cluster I located in the outer and middle parts of the bay, Cluster II close to downtown Sanya, Cluster III located in the Sanya River estuary. In terms of the temporal pattern, principal component analysis and cluster analysis have distinguished the dry season from November to the following April, and the rainy season from May to October. The temporal pattern is related to climate and natural characteristics. The similarity index between variables and scores of samples can further distinguish the contribution of the variables to the samples. Both the polluting sources external to the Sanya River and the water from the South China Sea exercise an important influence on the water quality in Sanya Bay. These results may be valuable for socioeconomic development and human health in the Sanya Bay area
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