253,648 research outputs found
Biharmonic hypersurfaces in Riemannian manifolds
We study biharmonic hypersurfaces in a generic Riemannian manifold. We first
derive an invariant equation for such hypersurfaces generalizing the biharmonic
hypersurface equation in space forms studied in \cite{Ji2}, \cite{CH},
\cite{CMO1}, \cite{CMO2}. We then apply the equation to show that the
generalized
Chen's conjecture is true for totally umbilical biharmonic hypersurfaces in
an Einstein space, and construct a (2-parameter) family of conformally flat
metrics and a (4-parameter) family of multiply warped product metrics each of
which turns the foliation of an upper-half space of \mathhbb{R}^m by parallel
hyperplanes into a foliation with each leave a proper biharmonic hypersurface.
We also characterize proper biharmonic vertical cylinders in and .Comment: 16 pages with a correction to Theorem 3.
Deep Reinforcement Learning for Resource Allocation in V2V Communications
In this article, we develop a decentralized resource allocation mechanism for
vehicle-to-vehicle (V2V) communication systems based on deep reinforcement
learning. Each V2V link is considered as an agent, making its own decisions to
find optimal sub-band and power level for transmission. Since the proposed
method is decentralized, the global information is not required for each agent
to make its decisions, hence the transmission overhead is small. From the
simulation results, each agent can learn how to satisfy the V2V constraints
while minimizing the interference to vehicle-to-infrastructure (V2I)
communications
Sound generated by rubbing objects
In the present paper, we investigate the properties of the sound generated by
rubbing two objects. It is clear that the sound is generated because of the
rubbing between the contacting rough surfaces of the objects. A model is
presented to account for the role played by the surface roughness. The results
indicate that tonal features of the sound can be generated due to the
finiteness of the rubbing surfaces. In addition, the analysis shows that with
increasing rubbing speed, more and more high frequency tones can be excited and
the frequency band gets broader and broader, a feature which appears to agree
with our intuition or experience.Comment: 3 pages, 2 figure
Initiation and Propagation of Transverse Cracking in Composite Laminates
The matrix cracking transverse to loading direction is usually the one of most
common observations of damages in composite laminates. The initiation and
propagation of transverse cracks have been a longstanding issue in the last few
decades. In this paper, a three-dimensional stress analysis method based on the state
space approach is used to compute the stresses, including the inter-laminar stresses
near transverse cracks in laminated composites. The stress field is then used to
estimate the energy release rate, from which the initiation and propagation of
transverse cracking are predicted. The proposed method is illustrated by numerical
solutions and is validated by available experimental results. To the best knowledge of
the authors, the predictions of crack behaviour for non-symmetrical laminates and
laminates subject to in-plane shearing are presented for the first time in the literature
Recommended from our members
Diversification in the international construction business
Economic globalization has created an interdependent market that allows companies to transcend traditional national boundaries to conduct business overseas. In the international construction market, companies often adopt diversification as a strategy for growth, for risk management or for both. However, the diversification patterns of international construction companies (ICCs) as a group are barely clear. The primary aim of this research is to cover this knowledge void by mapping ICCs’ diversification patterns in both business sectors and geographical dispersal. It starts from a literature review of diversification theories. Based on the review, a series of hypotheses relating to ICCs’ diversification are proposed. Data are gleaned from Engineering News-Record, i.e. Bloomberg and Capital IQ, ranging from 2001 to 2015. By testing the hypotheses, it is found that larger ICCs prefer to diversify than their smaller counterparts. Most of the ICCs tend to diversify to geographical markets with similar cultural or institutional environment. Market demands drive ICCs to diversify to different geographical markets while they are more prudential in venturing into new business sectors. The research provides not only valuable insights into diversification patterns of ICCs, but also a solid point of departure for future theoretical and empirical studies
- …