1,917 research outputs found
Some stability properties of T. Chan’s preconditioner
AbstractA matrix is said to be stable if the real parts of all the eigenvalues are negative. In this paper, for any matrix An, we give some sufficient and necessary conditions for the stability of T. Chan’s preconditioner cU(An)
Investigation of the effects of platform motion on the aerodynamics of a floating offshore wind turbine
Along with the flourishing of the wind energy industry, floating offshore wind turbines have aroused much interest among the academia as well as enterprises. In this paper, the effects of the supporting platform motion on the aerodynamics of a floating wind turbine are studied using the open source CFD framework OpenFOAM. The platform motion responses, including surge, heave and pitch, are superimposed onto the rotation of the wind turbine. Thrust and torque on the wind turbine are compared and analysed for the cases of different platform motion patterns together with the flow field. It is shown that the movement of the supporting platform can have large influences on a floating offshore wind turbine and thus needs to be considered carefully during the design process
Constraints on the primordial gravitational waves with variable sound speed from current CMB data
We make a comprehensive investigation of the observational effect of the
inflation consistency relation. We focus on the general single-field inflation
model with the consistency relation , and investigate the
observational constraints of sound speed by using the Seven-Year WMAP
data, the BICEP tensor power spectrum data, and the constraints on and from the Five-Year WMAP
observations. We find that the constraints on the tensor-to-scalar ratio is
much tighter if is small, since a large tilt is strongly
constrained by the observations. We obtain and 0.09 () for =1, 0.1 and 0.01 models at 95.4% confidence level. When taking
smaller values of , the positive correlation between and also
leads to slightly tighter constraint on the upper bound of , while the
running of scalar spectral index is generally unaffected. For the
sound speed , it is not well constrained if only the CMB power spectrum
data is used, while the constraints are obtainable by taking and priors into account. With the
constraining data of and , we
find that, region is excluded at 99.7% CL, and the
case (the single-field slow-roll inflation) is slightly disfavored at 68.3% CL.
In addition, the inclusion of and into the analysis can improve the constraints on and . We
further discuss the implications of our constraints on the test of inflation
models.Comment: 15 pages, 7 figures, updated versio
Why Is Web-based Supply Chain Management Popular in China? A Factor Endowment’s Perspective
Web-based system-to-human integration and direct system-to-system integration are alternative information technologies for supply chain management. Although the system-to-system mode is known to be more effective than the Web-based mode for data sharing, the web-based mode is dominant in the supply chain of Chinese firms. Is it a suboptimal or the most appropriate choice? We develop an analytical model to investigate how a manufacturer selects an optimal mode from competing technologies, including manual mode, Web-based mode and system-to-system mode. The contribution of this study is three-fold. First, the expected degree of information sharing influences the manufacturer’s selection. Manual mode is the optimal selection when the expected degree of information sharing is low, whereas system-to-system mode is the optimal choice when the expected degree is high. When the expected degree of information sharing is intermediate, Web-based mode is the optimal choice. Second, based on factor endowment theory, we find that labor endowment and technology endowment can influence the adoption intervals of these three modes. And third, when labor endowment is on the decline and technology endowment is on the rise in the early stage, the Web-based mode is the optimal choice than manual mode or system-to-system mode. Theoretical and practical implications of these findings are discussed
A Residual Fully Convolutional Network (Res-FCN) for Electromagnetic Inversion of High Contrast Scatterers at an Arbitrary Frequency Within a Wide Frequency Band
Many successful machine learning methods have been developed for
electromagnetic inverse scattering problems. However, so far, their inversion
has been performed only at the specifically trained frequencies. To make the
machine-learning-based inversion method more generalizable for realistic
engineering applications, this work proposes a residual fully convolutional
network (Res-FCN) to perform EM inversion of high contrast scatterers at an
arbitrary frequency within a wide frequency band. The proposed Res-FCN combines
the advantages of the Res-Net and the fully convolutional network (FCN).
Res-FCN consists of an encoder and a decoder: the encoder is employed to
extract high-dimensional features from the measured scattered field through the
residual frameworks, while the decoder is employed to map from the
high-dimensional features extracted by the encoder to the electrical parameter
distribution in the inversion region by the up-sample layer and the residual
frameworks. Four numerical examples verify that the proposed Res-FCN can
achieve good performance in the 2-D EM inversion problem for high contrast
scatterers with anti-noise ability at an arbitrary frequency point within a
wide frequency band
Tissue-Specific Expression of the Chicken Calpain2 Gene
We quantified chicken calpain 2 (CAPN2) expression in two Chinese chicken breeds (mountainous black-bone chicken breed [MB] and a commercial meat type chicken breed [S01]) to discern the tissue and ontogenic expression pattern and its effect on muscle metabolism. Real-time quantitative PCR assay was developed for accurate measurement of the CAPN2 mRNA expression in various tissues from chickens of different ages (0, 2, 4, 6, 8, 10, and 12 weeks). Results showed that the breast muscle and leg muscle tissues had the highest expression of CAPN2 compared to the other tissues from the same individual (P < .05). Overall, the CAPN2 mRNA level exhibited a “rise” developmental change in all tissues. The S01 chicken had a higher expression of the CAPN2 mRNA in all tissues than the MB chicken. Our results suggest that chicken CAPN2 expression may be related to chicken breeds and tissues
Design of Single-Molecule Multiferroics for Efficient Ultrahigh-Density Nonvolatile Memories
It is known that an isolated single-molecule magnet tends to become super- paramagnetic even at an ultralow temperature of a few Kelvin due to the low spin switching barrier. Herein, single-molecule ferroelectrics/multiferroics is proposed, as the ultimate size limit of memory, such that every molecule can store 1 bit data. The primary strategy is to identify polar molecules that possess bistable states, moderate switching barriers, and polarizations fixed along the vertical direction for high-density perpendicular recording. First- principles computation shows that several selected magnetic metal porphyrin molecules possess buckled structures with switchable vertical polarizations that are robust at ambient conditions. When intercalated within a bilayer of 2D materials such as bilayer MoS2 or CrI3, the magnetization can alter the spin distribution or can be even switched by 180° upon ferroelectric switching, rendering efficient electric writing and magnetic reading. It is found that the upper limit of areal storage density can be enhanced by four orders of magnitude, from the previous super-paramagnetic limit of ≈40 to ≈106 GB in.−2, on the basis of the design of cross-point multiferroic tunneling junction array and multiferroic hard drive
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