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Search Results: 1 - 10 of 78401 matches for " Yifan Chen "
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A New Family of Surfaces with K^2=7 and p_g=0
Yifan Chen
Mathematics , 2012,
Abstract: We construct a new family of minimal smooth surfaces of general type with K^2=7 and p_g= 0. We show that for a surface in this family, its canonical divisor is ample and its bicanonical morphism is birational. We prove that these surfaces satisfy Bloch's conjecture.
Notes on automorphisms of surfaces of general type with $p_g=0$ and $K^2=7$
Yifan Chen
Mathematics , 2014,
Abstract: Let $S$ be a smooth minimal complex surface of general type with $p_g=0$ and $K^2=7$. We prove that any involution on $S$ is in the center of the automorphism group of $S$. As an application, we show that the automorphism group of an Inoue surface with $K^2=7$ is isomorphic to $\mathbb{Z}_2^2$ or $\mathbb{Z}_2 \times \mathbb{Z}_4$. We construct a $2$-dimensional family of Inoue surfaces with automorphism groups isomorphic to $\mathbb{Z}_2 \times \mathbb{Z}_4$.
Commuting involutions on surfaces of general type with p_g=0 and K^2=7
Yifan Chen
Mathematics , 2014,
Abstract: The aim of this article is to classify the pairs (S, G), where S is a smooth minimal surface of general type with p_g=0 and K^2=7, G is a subgroup of the automorphism group of S and G is isomorphic to the group $\mathbb{Z}_2^2$. The Inoue surfaces with K^2=7, which are finite Galois $\mathbb{Z}_2^2$-covers of the 4-nodal cubic surface, are the first examples of such pairs. More recently, the author constructed a new family of such pairs. They are finite Galois $\mathbb{Z}_2^2$-covers of certain 6-nodal Del Pezzo surfaces of degree one. We prove that the base of the Kuranishi family of deformations of a surface in this family is smooth. We show that, in the Gieseker moduli space of canonical models of surfaces of general type, the subset corresponding to the surfaces in this family is an irreducible connected component, normal, unirational of dimension 3.
Double-Directional Information Azimuth Spectrum and Relay Network Tomography for a Decentralized Wireless Relay Network
Yifan Chen,Chau Yuen
Mathematics , 2010,
Abstract: A novel channel representation for a two-hop decentralized wireless relay network (DWRN) is proposed, where the relays operate in a completely distributive fashion. The modeling paradigm applies an analogous approach to the description method for a double-directional multipath propagation channel, and takes into account the finite system spatial resolution and the extended relay listening/transmitting time. Specifically, the double-directional information azimuth spectrum (IAS) is formulated to provide a compact representation of information flows in a DWRN. The proposed channel representation is then analyzed from a geometrically-based statistical modeling perspective. Finally, we look into the problem of relay network tomography (RNT), which solves an inverse problem to infer the internal structure of a DWRN by using the instantaneous doubledirectional IAS recorded at multiple measuring nodes exterior to the relay region.
On canonically polirized smooth 3-folds satisfying the Noether equality
Yifan Chen,Yong Hu
Mathematics , 2014,
Abstract: We completely classify canonically polarized smooth $3$-folds $X$ with $K_X^3=\frac{4}{3}p_g(X)-\frac {10}{3}$ and $p_g(X) \geq 7$. New examples of $3$-folds satisfying the properties above are constructed.
Research on the Influencing Effect between CHVA and CPI in China Based on VAR Models  [PDF]
Jinge Zhou, Juan Chen, Xiuli Yu, Yifan Li, Qifeng Lin
American Journal of Industrial and Business Management (AJIBM) , 2013, DOI: 10.4236/ajibm.2013.34044

The cointegration test, granger causality test, VAR model, impulse response function and other econometric methods are used in this paper to analyze the influencing effect between commercial housing vacancy rate and CPI and its delay impact. The results show that there is a long-term equilibrium relationship between commercial housing vacancy rate and CPI in China. There are at least one cointegration relationship between CHVR and CPI. The past values of the CPI appear to contain information which is useful for forecasting changes in the CHVR. CPI has a significant effect on CHVR and CPI rising drives CHVR.

Coal Deformation, Metamorphism and Tectonic Environment in Xinhua, Hunan  [PDF]
Huantong Li, Xiaoyan Zou, Jiafeng Mo, Yifan Wang, Fei Chen
Journal of Geoscience and Environment Protection (GEP) , 2018, DOI: 10.4236/gep.2018.69013
Abstract: This article discusses in detail chemical composition, molecular structure, microstructure phenomena, estimate of the palaeo-stress, paleo-temperature and the strain rate to deepen the knowledge for the correlation of coal deformation and metamorphism with structural environment in Xinhua Hunan by coal quality analysis, XRD and SEM methods, which provide dependable theoretical foundation for coal resource exploitation and utilization. The results show that 1) d002 value of six coal samples is from 3.36 to 3.39 nm, coal resolved itself into aphanitic graphite with the increase of coal rank during coalification, which is characterized by graphite flakes, and the crystallite size is from 50 nm to 250 nm; A certain degree of 3R-structure content is increases and the crystallite size is extend with the coalification process, but RH-structure content is decreased; 2) the tectonic environment of research area belongs to the ductile-brittle deformation, which was characterized by low temperature, low stress, high strain rate; 3) Tianlongshan magmatic intrusion provided heat source, its side-extrusion made the molecules structure of coal ordering, distance between layers decreased, finally it caused the formation of aphanitic graphite.
Human Respiration Rate Estimation Using Ultra-wideband Distributed Cognitive Radar System
Yifan Chen,Predrag Rapajic,

国际自动化与计算杂志 , 2008,
Abstract: It has been shown that remote monitoring of pulmonary activity can be achieved using ultra-wideband (UWB) systems,which shows promise in home healthcare, rescue, and security applications. In this paper, we first present a multi-ray propagation model for UWB signal, which is traveling through the human thorax and is reflected on the air/dry-skin/fat/muscle interfaces. A geometry-based statistical channel model is then developed for simulating the reception of UWB signals in the indoor propagation environment. This model enables replication of time-varying multipath profiles due to the displacement of a human chest. Subsequently,a UWB distributed cognitive radar system (UWB-DCRS) is developed for the robust detection of chest cavity motion and the accurate estimation of respiration rate. The analytical framework can serve as a basis in the planning and evaluation of future measurement programs. We also provide a case study on how the antenna beamwidth affects the estimation of respiration rate based on the proposed propagation models and system architecture.
Ultra-Wideband Source Localization Using a Particle-Swarm-Optimized Capon Estimator from a Frequency-Dependent Channel Modeling Viewpoint
Yifan Chen,Vimal K. Dubey
EURASIP Journal on Advances in Signal Processing , 2005, DOI: 10.1155/asp.2005.1854
Abstract: We introduce a realistic frequency-dependent channel model for ultra-wideband (UWB) communication systems and develop a generalized broadband Capon spatial spectrum estimator for localization of multiple incoherently distributed scattering clusters. The proposed estimator is able to address the three crucial features of practical UWB impulse propagation: presence of local scattering for multiple incoherently distributed clusters, wideband array signals, and frequency-dependent dispersive effects. The particle-swarm optimization, which is a recently invented high-performance optimizer based on the movement and intelligence of swarms, is then implemented to perform a multidimensional parameter search to jointly estimate the source central angles, the polynomial regression coefficients for angle spreads, and the frequency-dependence of various clusters. Numerical experiments are also carried out to examine the performance of the algorithm under various environments and model mismatches.
The Development Status, Problems and Countermeasures of China’s Carbon Financial Market  [PDF]
Yifan Yuan
Low Carbon Economy (LCE) , 2016, DOI: 10.4236/lce.2016.71007
Abstract: In recent years, the global climate governance is not just for a global environmental problem of climate change, more involved in international politics, economy, investment, technology and other fields, and involves the transformation of production and life style. Accompanied by global energy and technology revolution, the development of low carbon is our inevitable requirement. Recently, China submitted to UNFCCC (United Nations Framework Convention on Climate Change) the Secretariat of the national independent contribution plan and set emission reduction targets: carbon dioxide emissions reach the peak in 2030 and strive to reach the peak as early as possible; carbon emission intensity decreased by 60% - 65% compared with that in 2005. This means that our government will intensify its efforts to reduce carbon emissions. In the past, our target was to reduce carbon emissions intensity, but now our country is to realize the reduction of total carbon emissions, or “absolute reduction”. Carbon finance is an important breakthrough in the development of low carbon economy and the promotion of carbon emission reduction. This paper focuses on the analysis of the development status of China’s carbon financial market, the problems and the opportunities and challenges faced, and finally, the relevant countermeasures and suggestions are given from the perspectives of policy, talent, mechanism, international cooperation and so on, in order to promote the development of carbon financial market innovation, to seize the commanding heights of the era of low-carbon economy.
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