359 research outputs found
Non-Gaussianity of a single scalar field in general covariant Ho\v{r}ava-Lifshitz gravity
In this paper, we study non-Gaussianity generated by a single scalar field in
slow-roll inflation in the framework of the non-relativistic general covariant
Ho\v{r}ava-Lifshitz theory of gravity with the projectability condition and an
arbitrary coupling constant , where characterizes the
deviation of the theory from general relativity (GR) in the infrared. We find
that the leading effect of self-interaction, in contrary to the case of minimal
scenario of GR, is in general of the order ,
where is a slow-roll parameter, and
are the dimensionless coupling coefficients of the six-order operators of the
Lifshitz scalar, and have no contributions to power spectra and indices of both
scalar and tensor. The bispectrum, comparing with the standard one given in GR,
is enhanced, and gives rise to a large value of the nonlinearity parameter
.We study how the modified dispersion relation with high order
moment terms affects the evaluation of the mode function and in turn the
bispectrum, and show explicitly that the mode function takes various asymptotic
forms during different periods of its evolution. In particular, we find that it
is in general of superpositions of oscillatory functions, instead of plane
waves like in the minimal scenario of GR. This results in a large enhancement
of the folded shape in the bispectrum.Comment: Added new references and corrected some typos. 5 figures, revtex4.
Phys. Rev. D86, 103523 (2012
Web3D learning framework for 3D shape retrieval based on hybrid convolutional neural networks
With the rapid development of Web3D technologies, sketch-based model retrieval has become an increasingly important challenge, while the application of Virtual Reality and 3D technologies has made shape retrieval of furniture over a web browser feasible. In this paper, we propose a learning framework for shape retrieval based on two Siamese VGG-16 Convolutional Neural Networks (CNNs), and a CNN-based hybrid learning algorithm to select the best view for a shape. In this algorithm, the AlexNet and VGG-16 CNN architectures are used to perform classification tasks and to extract features, respectively. In addition, a feature fusion method is used to measure the similarity relation of the output features from the two Siamese networks. The proposed framework can provide new alternatives for furniture retrieval in the Web3D environment. The primary innovation is in the employment of deep learning methods to solve the challenge of obtaining the best view of 3D furniture, and to address cross-domain feature learning problems. We conduct an experiment to verify the feasibility of the framework and the results show our approach to be superior in comparison to many mainstream state-of-the-art approaches
Application of BEMD in Extraction of Regional and Local Gravity Anomalies Reflecting Geological Structures Associated with Mineral Resources
The bi-dimensional empirical mode decomposition (BEMD) method is an adaptive analysis method for nonlinear and nonstationary data. With the sifting process of BEMD, the data can be decomposed into a series of bi-dimensional intrinsic mode functions (BIMFs), which may present the relative local feature of the data. In this study, the BEMD method was successfully used for analyzing the Bouguer gravity data of Gejiu tin-copper polymetallic ore field in Yunnan Province and Tongshi gold field in Western Shandong Uplift Block to extract different-scale anomalies. In these two cases, regional and local components were separated, which can reflect the geological structures at different depths and some intrusive bodies which may be associated with mineral deposits. The results reveals the spatial distribution relationship between the different intrusive bodies and the various types of mineral deposits in the aforementioned two study area, which provide some reliable evidence for exploration of new concealed mineral deposits
Formation Control with Unknown Directions and General Coupling Coefficients
Generally, the normal displacement-based formation control has a sensing mode
that requires the agent not only to have certain knowledge of its direction,
but also to gather its local information characterized by nonnegative coupling
coefficients. However, the direction may be unknown in the sensing processes,
and the coupling coefficients may also involve negative ones due to some
circumstances. This paper introduces these phenomena into a class of
displacement-based formation control problem. Then, a geometric approach have
been employed to overcome the difficulty of analysis on the introduced
phenomena. The purpose of this approach is to construct some convex polytopes
for containing the effects caused by the unknown direction, and to analyze the
non-convexity by admitting the negative coupling coefficients in a certain
range. Under the actions of these phenomena, the constructed polytopes are
shown to be invariant in view of the contractive set method. It means that the
convergence of formation shape can be guaranteed. Subsequently, an example is
given to examine the applicability of derived result
TiNi-based thin films for MEMS applications
In this paper, some critical issues and problems in the development of TiNi thin films were discussed, including preparation and characterization considerations, residual stress and adhesion, frequency improvement, fatigue and stability, as well as functionally graded or composite thin film design. Different types of MEMS applications were reviewed and the prospects for future advances in fabrication process and device development were discussed.Singapore-MIT Alliance (SMA
Network traffic characteristics of hyperscale data centers in the era of cloud applications
We present the network architecture of Alibaba Cloud DCs and investigate their traffic characteristics based on statistical data and captured traces. The statistical coarse-grained data are in the granularity of one minute, while the captured traces are fine-grained data that are in the granularity of one packet. We study the traffic features from the perspective of a macroscopic view, network performance, and microscopic view. The results report that the average utilization ratio of spine switches is stable when the observation time period reaches one day and the intra-ToR traffic ratio is in the range of 2%-10%. By mapping the folded-Clos topology to a tree topology and considering logical switching planes, we obtain the traffic matrix among pods from the average port utilization ratio. As we further investigate the perspective of network performance and the microscopic view, we find that there is no cell loss happening as the normalized queue speed Q_s is lower than 0.4. The normalized queue speed Q_s is defined as the total bytes of a queue sent in 1 s divided by 100 Gb, which reflects the packet sending speed of the queue. The observed maximum buffer size for one port conforms with the calculated maximum buffer occupation of 2.8 MB. By analyzing the captured traces, we find that the packet length is subject to a trimodal distribution. Under a time granularity of 10 ms, the instant bandwidth of one ToR port could reach 96 Gb/s at an average load of around 0.2 under a maximum link bandwidth of 100 Gb/s.</p
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