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Search Results: 1 - 10 of 101675 matches for " Xiang-Yu Huang "
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Four-dimensional variational data assimilation for a limited area model
Nils Gustafsson,Xiang-Yu Huang,Xiaohua Yang,Kristian Mogensen
Tellus A , 2012, DOI: 10.3402/tellusa.v64i0.14985
Abstract: A 4-dimensional variational data assimilation (4D-Var) scheme for the HIgh Resolution Limited Area Model (HIRLAM) forecasting system is described in this article. The innovative approaches to the multi-incremental formulation, the weak digital filter constraint and the semi-Lagrangian time integration are highlighted with some details. The implicit dynamical structure functions are discussed using single observation experiments, and the sensitivity to various parameters of the 4D-Var formulation is illustrated. To assess the meteorological impact of HIRLAM 4D-Var, data assimilation experiments for five periods of 1 month each were performed, using HIRLAM 3D-Var as a reference. It is shown that the HIRLAM 4D-Var consistently out-performs the HIRLAM 3D-Var, in particular for cases with strong mesoscale storm developments. The computational performance of the HIRLAM 4D-Var is also discussed.The review process was handled by Subject Editor Abdel Hannachi
An Observing System Simulation Experiment for the Impact of MTG Candidate Infrared Sounding Mission on Regional Forecasts: System Development and Preliminary Results
Hongli Wang,Xiang-Yu Huang,Yongsheng Chen
ISRN Meteorology , 2013, DOI: 10.1155/2013/971501
Abstract: An Observing System Simulation Experiment (OSSE) was designed and developed to assess the potential benefit of the Infrared Sounding on the Meteosat Third Generation (MTG-IRS) geostationary meteorological satellite system to regional forecasts. In the proposed OSSE framework, two different models, namely, the MM5 and WRF models, were used in a nature run and data assimilation experiments, respectively, to reduce the identical twin problem. The 5-day nature run, which included three convective storms that occurred during the period from 11 to 16 June 2002 over US Great Plains, was generated using MM5 with a 4?km. The simulated “conventional” observations and MTG-IRS retrieved temperature and humidity profiles, produced from the nature run, were then assimilated into the WRF model. Calibration experiments showed that assimilating real or simulated “conventional” observations yielded similar error statistics in analyses and forecasts, indicating that the developed OSSE system worked well. On average, the MTG-IRS retrieved profiles had positive impact on the analyses and forecasts. The analyses reduced the errors not only in the temperature and the humidity fields but in the horizontal wind fields as well. The forecast skills of these variables were improved up to 12?hours. The 18?h precipitation forecast accuracy was also increased. 1. Introduction Remotely sensed satellite observations play an important role in modern data assimilation and forecast systems [1, 2]. Satellite observations in the visible, infrared, and microwave spectrum provide a wealth of information on the atmosphere states. The variational data assimilation technique has been pursued in research communities and operational centres, with the main focus on large scale and mesoscale forecast, to assimilate clear sky and cloudy radiance. For example, at the European Centre for Medium-Range Weather Forecasts (ECMWF), an all-sky approach [3] has been developed to assimilate Special Sensor Microwave/Imager (SSM/I) and Advanced Microwave Scanning Radiometer for the Earth Observing system (AMSR-E) data. At National Oceanic and Atmospheric Administration (NOAA), Weng et al. [4] developed a hybrid variational scheme to use observations from the Advanced Microwave Sounding Unit (AMSU) instruments. Until recently, more attention has been directed towards cloud-resolving scale data assimilation. Cloudy infrared radiance assimilation at convection-resolving scale using a 4-dimensional variational data assimilation system was studied by Vukicevic et al. [5, 6]. Overall their results indicate that the
TAMDAR Observation Assimilation in WRF 3D-Var and Its Impact on Hurricane Ike (2008) Forecast
Hong-Li WANG,Xiang-Yu HUANG,
Hong-Li WANG
,Xiang-Yu HUANG

大气和海洋科学快报 , 2012,
Abstract: This study evaluates the impact of atmospheric observations from the Tropospheric Airborne Meteorological Data Reporting (TAMDAR) observing system on numerical weather prediction of hurricane Ike (2008) using three-dimensional data assimilation system for the Weather Research and Forecast (WRF) model (WRF 3D-Var). The TAMDAR data assimilation capabil- ity is added to WRF 3D-Var by incorporating the TAMDAR observation operator and corresponding observation processing procedure. Two 6-h cycling data assimilation and forecast experiments are conducted. Track and intensity forecasts are verified against the best track data from the National Hurricane Center. The results show that, on average, assimilating TAMDAR observations has a positive impact on the forecasts of hurricane Ike. The TAMDAR data assimilation reduces the track errors by about 30 km for 72-h forecasts. Improvements in intensity forecasts are also seen after four 6-h data assimilation cycles. Diagnostics show that assimilation of TAMDAR data improves subtropical ridge and steering flow in regions along Ike’s track, resulting in better forecasts.
A Review of Image Retrieval Techniques in the Compressed Domain
基于压缩域的图象检索技术研究进展

HUANG Xiang-yu,ZHANG Yu-jin,
黄翔宇
,章毓晋

中国图象图形学报 , 2003,
Abstract: The advent of compression standards, such as JPEG and MPEG, has led to the popularity of the compressed form of image data, and that has brought on the proliferation of image retrieval techniques in the compressed domain. In this paper, we make a comprehensive review and discussions on the compressed domain retrieval techniques proposed in the literature, including the lastest achievements in this field. First, we give the general concepts of the image retrieval technology. Secondly, we analyze different retrieval techniques, including transform domain techniques using Fourier transform, discrete cosine transform, subbands and wavelets, and spatial domain techniques using vector quantization and fractals. Thirdly, we discuss and compare these image retrieval techniques and draw some useful conclusions. In addition, an example application of image retrieval in the compressed domain is presented. Finally, we make a discussion on some open problems and point out possible directions for further research.
Diammonium aqua(ethylenediaminetetraacetato)iron(II) trihydrate
Hua-Ming Huang,Hong-Bing Yang,Xiang-Yu Li,Fang-Fang Ren
Acta Crystallographica Section E , 2009, DOI: 10.1107/s1600536808042190
Abstract: In the title compound, (NH4)2[Fe(C10H12N2O8)(H2O)]·3H2O, the FeII center is in a distorted pentagonal-bipyramidal geometry. Two carboxylate O and two N atoms from the ethylenediaminetetraacetate (EDTA) ion and one O atom from coordinated water comprise the equatorial plane. Two other carboxylate O atoms from the EDTA ion occupy the apical sites. Both ammonium cations and all water molecules function as hydrogen-bond donors, and ten N—H...O and nine O—H...O hydrogen bonds form a three-dimensional network between the complex anions, cations and the water molecules.
Assimilation of wind speed and direction observations: a new formulation and results from idealised experiments
Xiang-Yu Huang,Feng Gao,Neil A. Jacobs,Hongli Wang
Tellus A , 2013, DOI: 10.3402/tellusa.v65i0.19936
Abstract: This article presents a new methodology for assimilating wind observations in their observed form of speed and direction, while taking into account both speed and direction error. It ensures the analysed speed and direction will be consistent with their background and observed values. The new formulation is implemented in the Weather Research and Forecasting Data Assimilation system, and idealised experiments are used to demonstrate the potential benefit. The results suggest that analyses from the new formulation are more reasonable when compared to the conventional methodology. The forecasts generated in these idealised experiments also demonstrate the value of this new formulation. Preliminary results from real data experiments are in general agreement with results presented here, and they will be reported in a following article.
Advances in epidemiological study of post-traumatic stress disorders in postwar civilian survivors
Xiang-yu KONG,Li-ning XIAO,Wen HUANG,Zhao-shen LI
Medical Journal of Chinese People's Liberation Army , 2012,
Abstract: Post-traumatic stress disorder (PTSD) is a feeling of persecution arising from the exposure to a life-threatening event. PTSD shows three kinds of characteristic symptoms including intrusive, avoidance, and arousal syndromes. Numerous literatures had been published on the study of the PTSD epidemiology. However, research results varied due to different research subjects and evaluation methods used. A big difference exists between the studies on refugees, migrating population, and community population, because these studies are affected by different definitions of war trauma, difference in choice of samples, and application of psychological intervention. Therefore, no exact conclusions have been established on the accurate incidence of PTSD in civilians after having endured war trauma or mental torture. Currently, studies on PSTD are still inadequate. The first reason for this inadequacy is the difference existing between previous study methods. In addition, differences also exist in the statistical results between different research groups; the present study objects are all non-western ethnics or some specific population, thus selective bias existing in samples adopted. Secondly, the majority of the studies had no a control group, thus the results lacking reliability and universality. The third reason is that more attention should be paid to the impact of nationality and cultural background on the study of postwar PTSD. In summary, a large amount of work should be done in the field of PSTD epidemiology in the future. Therefore, it is very important to look for simple tools for screening and measuring PTSD in Chinese population, and investigate the incidence of PTSD after all kinds of traumatic events and its distribution for effectively preventing and treating PTSD.
Identifying effective multiple spreaders by coloring complex networks
Xiang-Yu Zhao,Bin Huang,Ming Tang,Hai-Feng Zhang,Duan-Bing Chen
Computer Science , 2014, DOI: 10.1209/0295-5075/108/68005
Abstract: How to identify influential nodes in social networks is of theoretical significance, which relates to how to prevent epidemic spreading or cascading failure, how to accelerate information diffusion, and so on. In this Letter, we make an attempt to find \emph{effective multiple spreaders} in complex networks by generalizing the idea of the coloring problem in graph theory to complex networks. In our method, each node in a network is colored by one kind of color and nodes with the same color are sorted into an independent set. Then, for a given centrality index, the nodes with the highest centrality in an independent set are chosen as multiple spreaders. Comparing this approach with the traditional method, in which nodes with the highest centrality from the \emph{entire} network perspective are chosen, we find that our method is more effective in accelerating the spreading process and maximizing the spreading coverage than the traditional method, no matter in network models or in real social networks. Meanwhile, the low computational complexity of the coloring algorithm guarantees the potential applications of our method.
Antidiabetic effects of Tangnaikang on obese Zucker rats and the mechanism
Xiang-yu GUO
Zhong Xi Yi Jie He Xue Bao , 2010,
Abstract: Objective: To observe the effects of Tangnaikang (TNK), a compound traditional Chinese herbal medicine, on glucose metabolism and insulin resistance in obese Zucker rats. Methods: Twelve male obese Zucker rats, 6 weeks old, were randomly divided into control group and TNK group (3.24 g/kg) after being fed for 2 weeks. All rats received high-fat diet and 4-week treatment. Body weight and blood glucose were tested every week. Oral glucose tolerance test (OGTT) was performed and fasting insulin level was tested on days 0, 14 and 28. Triglyceride, cholesterol, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C) and free fatty acids (FFA) were tested on day 28. Glucose infusion rate (GIR) was tested by hyperinsulinemic-euglycemic clamp from day 29. The protein expressions of protein kinase B (Akt), phospho-Akt (p-Akt) (Thr308) and glucose transporter protein 4 (GLUT4) in skeletal muscle and GLUT4 in adipose tissue were measured after hyperinsulinemic-euglycemic clamp test.Results: Compared with the control group, the fed blood glucose level and glucose level of OGTT at 120 min had a significant decline in TNK group on day 28, and TNK caused no alteration of the fasting serum insulin, and the GIR increased significantly in hyperinsulinemic-euglycemic clamp study. Furthermore, TNK increased Akt and p-Akt (Thr308) protein expressions in skeletal muscle and decreased the protein expression of GLUT4 in white adipose tissue. Body weight, and triglyceride, cholesterol, LDL-C and FFA contents were slightly decreased in the TNK group, but there were no statistically significant effects.Conclusion: TNK increases the protein expressions of Akt and p-Akt (Thr308) of the signal transduction pathway to influence the translocation of GLUT4 in skeletal muscle and improves glucose metabolism by reducing insulin resistance.
Integrable one-dimensional supersymmetric q-deformed extended Hubbard model with boundary Kondo impurity
Xiang-Yu Ge
Physics , 1999,
Abstract: This paper has been withdrawn by the author, due to an error in relation (11).
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