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Search Results: 1 - 10 of 78397 matches for " Xiaoyi Chen "
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Recent Progress in Brillouin Scattering Based Fiber Sensors
Xiaoyi Bao,Liang Chen
Sensors , 2011, DOI: 10.3390/s110404152
Abstract: Brillouin scattering in optical fiber describes the interaction of an electro-magnetic field (photon) with a characteristic density variation of the fiber. When the electric field amplitude of an optical beam (so-called pump wave), and another wave is introduced at the downshifted Brillouin frequency (namely Stokes wave), the beating between the pump and Stokes waves creates a modified density change via the electrostriction effect, resulting in so-called the stimulated Brillouin scattering. The density variation is associated with a mechanical acoustic wave; and it may be affected by local temperature, strain, and vibration which induce changes in the fiber effective refractive index and sound velocity. Through the measurement of the static or dynamic changes in Brillouin frequency along the fiber one can realize a distributed fiber sensor for local temperature, strain and vibration over tens or hundreds of kilometers. This paper reviews the progress on improving sensing performance parameters like spatial resolution, sensing length limitation and simultaneous temperature and strain measurement. These kinds of sensors can be used in civil structural monitoring of pipelines, bridges, dams, and railroads for disaster prevention. Analogous to the static Bragg grating, one can write a moving Brillouin grating in fibers, with the lifetime of the acoustic wave. The length of the Brillouin grating can be controlled by the writing pulses at any position in fibers. Such gratings can be used to measure changes in birefringence, which is an important parameter in fiber communications. Applications for this kind of sensor can be found in aerospace, material processing and fine structures.
Recent Progress in Distributed Fiber Optic Sensors
Xiaoyi Bao,Liang Chen
Sensors , 2012, DOI: 10.3390/s120708601
Abstract: Rayleigh, Brillouin and Raman scatterings in fibers result from the interaction of photons with local material characteristic features like density, temperature and strain. For example an acoustic/mechanical wave generates a dynamic density variation; such a variation may be affected by local temperature, strain, vibration and birefringence. By detecting changes in the amplitude, frequency and phase of light scattered along a fiber, one can realize a distributed fiber sensor for measuring localized temperature, strain, vibration and birefringence over lengths ranging from meters to one hundred kilometers. Such a measurement can be made in the time domain or frequency domain to resolve location information. With coherent detection of the scattered light one can observe changes in birefringence and beat length for fibers and devices. The progress on state of the art technology for sensing performance, in terms of spatial resolution and limitations on sensing length is reviewed. These distributed sensors can be used for disaster prevention in the civil structural monitoring of pipelines, bridges, dams and railroads. A sensor with centimeter spatial resolution and high precision measurement of temperature, strain, vibration and birefringence can find applications in aerospace smart structures, material processing, and the characterization of optical materials and devices.
Recent progress in optical fiber sensors based on Brillouin scattering at university of Ottawa
Xiaoyi Bao,Liang Chen
Photonic Sensors , 2011, DOI: 10.1007/s13320-011-0026-3
Abstract: The distributed sensor is proven to be a powerful tool for civil structural and material process monitoring. Brillouin scattering in fiber can be used as point sensors or distributed sensors for measurement of temperature, strain, birefringence and vibration over centimeters (Brillouin grating length) for point sensor or the pulse length for the distributed sensor. Simultaneous strain and temperature measurement with a spatial resolution of 20 cm is demonstrated in a Panda fiber using Brillouin grating technique with the temperature accuracy and strain accuracy of 0.4 °C and 9 μ . This technique can also be used for distributed birefringence measurement. For Brillouin optical time domain analysis (BOTDA), we have developed a new technique to measure differential Brillouin gain instead of Brillouin gain itself. This technique allows high precision temperature and strain measurement over long sensing length with sub-meter spatial resolution: 50-cm spatial resolution for 50-km length, using return-to-zero coded optical pulses of BOTDA with the temperature resolution of 0.7 °C, which is equivalent to strain accuracy of 12 μ . For over 50-km sensing length, we proposed and demonstrated frequency-division-multiplexing (FDM) and time-division-multiplexing (TDM) based BOTDA technique for 75-km and 100-km sensing length without inline amplification within the sensing length. The spatial resolution of 2 m (100 km) and Brillouin frequency shift accuracy of 1.5 MHz have been obtained for TDM based BOTDA and 1-m resolution (75 km) with Brillouin frequency shift accuracy of 1 MHz using FDM based BOTDA. The civil structural health monitoring with BOTDA technique has been demonstrated.
The Relationship among Social Capital, Service Types and Service Innovation Performance in Logistics Enterprises  [PDF]
Xue Tian, Chen Wang, Xiaoyi Li, Pengfei Niu, Weipeng Si
American Journal of Industrial and Business Management (AJIBM) , 2016, DOI: 10.4236/ajibm.2016.68087
Abstract: This study focuses on the relationship of social capital, service innovation types and service innovation performance. Through the empirical research on 210 logistics enterprises, we will find that vertical relationship capital can only promote the incremental service innovation, horizontal relationship capital can only promote the breakthrough service innovation, and social relationship capital can promote both types of service innovation. Both the two types of service innovations can improve the enterprise’s service innovation performance. Finally, the research puts forward suggestions for logistics enterprises and points out the limitations and trend for future research.
Analysis and comparison of spatial interpolation methods for temperature data in Xinjiang Uygur Autonomous Region, China  [PDF]
Huixia Chai, Weiming Cheng, Chenghu Zhou, Xi Chen, Xiaoyi Ma, Shangming Zhao
Natural Science (NS) , 2011, DOI: 10.4236/ns.2011.312125
Abstract: Spatial interpolation methods are frequently used to estimate values of meteorological data in locations where they are not measured. However, very little research has been investigated the relative performance of different interpolation methods in meteorological data of Xinjiang Uygur Autonomous Region (Xinjiang). Actually, it has importantly practical significance to as far as possibly improve the accuracy of interpolation results for meteorological data, especially in mountainous Xinjiang. There- fore, this paper focuses on the performance of different spatial interpolation methods for monthly temperature data in Xinjiang. The daily observed data of temperature are collected from 38 meteorological stations for the period 1960- 2004. Inverse distance weighting (IDW), ordinary kriging (OK), temperature lapse rate method (TLR) and multiple linear regressions (MLR) are selected as interpolated methods. Two rasterized methods, multiple regression plus space residual error and directly interpolated observed temperature (DIOT) data, are used to analyze and compare the performance of these interpolation methods respectively. Moreover, cross-validation is used to evaluate the performance of different spatial interpolation methods. The results are as follows: 1) The method of DIOT is unsuitable for the study area in this paper. 2) It is important to process the observed data by local regression model before the spatial interpolation. 3) The MLR-IDW is the optimum spatial interpolation method for the monthly mean temperature based on cross-validation. For the authors, the reliability of results and the influence of measurement accuracy, density, distribution and spatial variability on the accuracy of the interpolation methods will be tested and analyzed in the future.
A fourth-order Runge-Kutta in the interaction picture method for coupled nonlinear Schrodinger equation
Zhongxi Zhang,Liang Chen,Xiaoyi Bao
Physics , 2010, DOI: 10.1364/OE.18.008261
Abstract: A fourth-order Runge-Kutta in the interaction picture (RK4IP) method is presented for solving the coupled nonlinear Schrodinger equation (CNLSE) that governs the light propagation in optical fibers with randomly varying birefringence. The computational error of RK4IP is caused by the fourth-order Runge-Kutta algorithm, better than the split-step approximation limited by the step size. As a result, the step size of RK4IP can have the same order of magnitude as the dispersion length and/or the nonlinear length of the fiber, provided the birefringence effect is small. For communication fibers with random birefringence, the step size of RK4IP can be orders of magnitude larger than the correlation length and the beating length of the fibers, depending on the interaction between linear and nonlinear effects. Our approach can be applied to the fibers having the general form of local birefringence and treat the Kerr nonlinearity without approximation. For the systems with realistic parameters, the RK4IP results are consistent with those using Manakov-PMD approximation. However, increased interaction between the linear and nonlinear terms in CNLSE leads to increased discrepancy between RK4IP and Manakov-PMD approximation.
Pathways, Scaling Laws and Analytical Solutions for Crease Formations in a Gel Layer
Xiaoyi Chen,Hui-Hui Dai
Physics , 2014,
Abstract: An analytical study on crease formations in a swelling gel layer is conducted. By exploring the smallness of the layer thickness and using a method of coupled series-asymptotic expansions, the original nonlinear eigenvalue problem of partial differential equations is reduced to one of ordinary differential equations. The latter problem is then solved analytically to obtain closed-form solutions for all the post-bifurcation branches. With the available analytical results, a number of deep insights on crease formations are provided, including the unveiling of three pathways to crease (depending on the layer thickness), determination of the bifurcation type, establishment of a lower bound for mode numbers and two scaling laws. Also, a number of experimental results are captured, which are then nicely interpreted based on the analytical solutions. In particular, it is shown that some critical physical quantities are invariant with respect to the thickness at the moment of crease formation. It appears that the present work offers a comprehensive understanding on crease formation, a widely-spread phenomenon.
Moment-generating function method used to accurately evaluate the impact of the linearized optical noise amplified by EDFAs
Zhongxi Zhang,Liang Chen,Xiaoyi Bao
Physics , 2012,
Abstract: In a nonlinear optical fiber communication (OFC) system with signal power much stronger than noise power, the noise field in the fiber can be described by linearized noise equation (LNE). In this case, the noise impact on the system performance can be evaluated by moment-generating function (MGF) method. Many published MGF calculations were based on the LNE using continuous wave (CW) approximation, where the modulated signal needs to be artificially simplified as an unmodulated signal. Results thus obtained should be treated carefully. More reliable results can be obtained by improving the CW-based LNE with the accurate LNE proposed by Holzlohner et al in Ref. [1]. In this work we show that, for the case of linearized noise amplified by EDFAs, its MGF can be calculated by obtaining the noise propagation information directly from the accurate LNE. Our results agree well with the experimental data of multi-span DPSK systems.
Researches of Water Bloom Emergency Management Decision-making Method and System Based on Fuzzy Multiple Attribute Decision Making
Zaiwen Liu,Lin Li,Xiaoyi Wang,Chen Chen
International Journal of Computer Science Issues , 2012,
Abstract: The prevention and management of water blooms is an important measure of environment protection. At present, although there is a variety of research achievement in water bloom management methods, the related reports in water blooms emergency management decision are hardly ever. Because the forming mechanism of water bloom is still unknown, it is difficult to come up with optimal water bloom management decision-making methods. Based on the deep research of mechanism characteristic and emergency management decision model of water bloom, this paper puts forward a Multiple Attribute Decision Making (MADM) based on water bloom emergency management decision-making methods, and applying to the lake reservoir water bloom emergency management programs selection, making model validation according to the lake reservoir as well, and then providing effective informational decision basis for environmental protection department to prevent and manage the water bloom.
Quorum Quenching Enzymes and Their Application in Degrading Signal Molecules to Block Quorum Sensing-Dependent Infection
Fang Chen,Yuxin Gao,Xiaoyi Chen,Zhimin Yu,Xianzhen Li
International Journal of Molecular Sciences , 2013, DOI: 10.3390/ijms140917477
Abstract: With the emergence of antibiotic-resistant strains of bacteria, the available options for treating bacterial infections have become very limited, and the search for a novel general antibacterial therapy has received much greater attention. Quorum quenching can be used to control disease in a quorum sensing system by triggering the pathogenic phenotype. The interference with the quorum sensing system by the quorum quenching enzyme is a potential strategy for replacing traditional antibiotics because the quorum quenching strategy does not aim to kill the pathogen or limit cell growth but to shut down the expression of the pathogenic gene. Quorum quenching enzymes have been identified in quorum sensing and non-quorum sensing microbes, including lactonase, acylase, oxidoreductase and paraoxonase. Lactonase is widely conserved in a range of bacterial species and has variable substrate spectra. The existence of quorum quenching enzymes in the quorum sensing microbes can attenuate their quorum sensing, leading to blocking unnecessary gene expression and pathogenic phenotypes. In this review, we discuss the physiological function of quorum quenching enzymes in bacterial infection and elucidate the enzymatic protection in quorum sensing systems for host diseases and their application in resistance against microbial diseases.
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