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Search Results: 1 - 10 of 23271 matches for " Huaqiang He "
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Preparation mechanism and luminescence of Sr2SiO4: Eu phosphor from (Sr, Eu)CO3@SiO2 core-shell precursor  [PDF]
Yunsheng Hu, Weidong Zhuang, Jianhua Hao, Xiaowei Huang, Huaqiang He
Open Journal of Inorganic Chemistry (OJIC) , 2012, DOI: 10.4236/ojic.2012.21002
Abstract: Sr2SiO4: Eu phosphor for white light emitting diodes (LEDs) was synthesized by employing an as-prepared (Sr, Eu)CO3@SiO2 core-shell precursor as starting materials, and the effect of the core-shell precursor was also discussed on the crystal structure, particle morphology and luminescent properties of the resultant phosphor. The results showed that the hybrid β- and α′-Sr2SiO4: Eu phosphor with fine particle size and narrow distribution could be obtained at a lower firing temperature than that in conventional solidstate reaction method, and its formation mechanism was deduced to be (Sr, Eu)CO3 diffusion controlled reaction process. Responded to its hybrid crystal structure, this phosphor exhibited the combined luminescence of β- and α′-Sr2SiO4: Eu.
On the Bongiorno's notion of absolute continuity
Beata Randrianantoanina,Huaqiang Xu
Mathematics , 2014,
Abstract: We show that the classes of $\alpha$-absolutely continuous functions in the sense of Bongiorno coincide for all $0<\alpha<1$.
Study on Co-combustion Characteristics of Superfine Coal with Conventional Size Coal in O2/CO2 Atmosphere  [PDF]
Yuhang Zhang, Mingyan Gu, Biao Ma, Huaqiang Chu
Energy and Power Engineering (EPE) , 2013, DOI: 10.4236/epe.2013.54B007
Abstract: The pulverized coal combustion in O2/CO2 atmosphere is one of the promising new technologies which can reduce the emission of carbon dioxide and NOx. In this study, the combustion behaviors of different mixing ratio of Shenhua coal with 20 μm and 74 μm particle size in the O2/CO2 atmosphere and air atmosphere were studied by using a thermal-gravimetric analyzer. The combustion characteristics such as ignition and burnout behavior were investigated in the temperature from 20 to 850. The influence of mixing ratio on combustion characteristics was conduced. The results obtained showed that the ignition temperature of the two kinds of particle size in O2/CO2 atmosphere is higher than in the air, while the activation energy in O2/CO2 atmosphere is lower. With the increasing ratio of 20 μm superfine pulverized coals, the ignition temperature and the activation energy decreased, while the DTG peak value increased, the maximum burning rate position advanced. There were three trends for the ignition temperature curve with the increasing of superfine coal ratio: the ignition of the mixed coal decreased rapidly, then changed less, at last reduced quickly.
Numerical simulations of intense meiyu rainfall in 1991 over the changjiang and huaihe river valleys by a regional climate model with p- σ incorporated coordinate system
Numerical Simulations of Intense Meiyu Rainfall in 1991 over the Changjiang and Huaihe River Valleys by a Regional Climate Model with p-б Incorporated Coordinate System

Liu Huaqiang,Qian Yongfu,
Liu Huaqiang
,Qian Yongfu

大气科学进展 , 1999,
Abstract: Based on the primitive equation model with p- σ incorporated coordinate system originally developed by Qian et al., a one-way nested fine mesh limited area model is developed. This model is nested with ECMWF T42 data to simulate the extra-intensive rainfall event occurring in the Changjiang and Huaihe River valleys in summer of 1991. The results show that the model has certain capacity to fairly reproduce the regional distribution and the movement of the main rainfall belts. Therefore it can be used as a regional climate model to simulate and predict the short-range regional climate changes. Jointly Sponsored by the National Natural Science Foundation of China (No. 49735170) and the Key Project of the National Fundamental Research “ Climate Dynamics and Prediction Theory .
Channel Estimation for SCM-OFDM Systems by Modified Kalman Filter  [PDF]
Tao Peng, Yue Xiao, Shaoqian Li, Huaqiang Shu, Eric Pierre Simon
Communications and Network (CN) , 2013, DOI: 10.4236/cn.2013.53B2119

In this paper, the problem of channel estimation for superposition coded modulation-orthogonal frequency division multiplexing (SCM-OFDM) systems over frequency selective channels is investigated. Assuming that the path delays are known, a new channel estimator based on modified Kalman filter algorithms is introduced for the estimation of the multipath Rayleigh channel complex gains (CG). In the simulation, the mean square error (MSE) and bit-error-rate (BER) performances are given to verify the effectiveness of the Kalman estimation algorithms for SCM-OFDM systems.

Signal Detection for OFDM-IDMA Uplink over Doubly Selective Channels  [PDF]
Tao Peng, Yue Xiao, Shaoqian Li, Huaqiang Shu, Eric Pierre Simon
Communications and Network (CN) , 2013, DOI: 10.4236/cn.2013.53B2046
Abstract: Orthogonal frequency division multiplexing-interleave division multiple access (OFDM-IDMA) systems may suffer from serious inter-carrier interference (ICI) in time-and frequency-selective (doubly selective) channels. In such case, the conventional OFDM-IDMA detection algorithm for quasi-static channels will result in significantly performance degradation. In this paper, signal detection is investigated for OFDM-IDMA uplink over doubly selective channels. Firstly, the impact of time-varying channels for OFDM-IDMA uplink is analyzed, which leads to the failure of the conventional algorithm. Secondly, a novel iterative detection algorithm is developed based on an integrated interference canceller, which can iteratively estimate and mitigate the ICI as well as multiple access interference (MAI) simultaneously. In addition, an improved detection algorithm is derived for reducing the complexity using an approximation to the mean and variance of the interference. Simulation results indicate that the proposed algorithm can significantly enhance the system performance to the conventional case, and the improved algorithm can strike a balance between performance and complexity.
On interval based generalizations of absolute continuity for functions on $\mathbb{R}^n$
Michael Dymond,Beata Randrianantoanina,Huaqiang Xu
Mathematics , 2013,
Abstract: We study notions of absolute continuity for functions defined on $\mathbb{R}^n$similar to the notion of $\alpha$-absolute continuity in the sense of Bongiorno. We confirm a conjecture of Mal\'y that 1-absolutely continuous functions do not need to be differentiable a.e., and we show several other pathological examples of functions in this class. We establish containment relations of the class $1-AC_{\rm WDN}$ which consits of all functions in $1-AC$ which are in the Sobolev space $W^{1,2}_{loc}$, are differentiable a.e. and satisfy the Luzin (N) property, with previously studied classes of absolutely continuous functions.
Effects of Nested Area Size upon Regional Climate Model Simulations

Liu Huaqiang,Qian Yongfu,Zheng Yiqun,
Liu Huaqiang
,Qian Yongfu,Zheng Yiqun

大气科学进展 , 2002,
Abstract: This paper presents a numerical study on the 1998 summer rainfall over the Yangtze River valley in central and eastern China, addressing effect of a nested area size on simulations in terms of the technique of nesting a regional climate model (RCM) upon a general circulation model (GCM). Evidence suggests that the size exerts greater impacts upon regional climate of the country, revealing that a larger nested size is superior to a small one for simulation in mitigating errors of GCM-provided lateral boundary forcing. Also, simulations show that the RCM should incorporate regions of climate systems of great importance into study and a low-resolution GCM yields more pronounced errors as a rule when used in the research of the Tibetan Plateau, and, in contrast, our PORCM can do a good job in describing the plateau's role in a more realistic and accurate way. It is for this reason that the tableland should be included in the nested area when the RCM is employed to investigate the regional climate. Our PJRCM nesting upon a GCM reaches more realistic results compared to a single GCM used.
Evaluation of humic acid removal by a flat submerged membrane photoreactor
Yong Wei,HuaQiang Chu,BingZhi Dong,Xuan Li
Chinese Science Bulletin , 2011, DOI: 10.1007/s11434-011-4712-8
Abstract: A flat submerged membrane combined with a TiO2/UV photocatalytic reactor (FSMPR) was employed in batch mode to remove humic acid (HA). HA removal efficiency was characterized by UV254 absorbance, UV-vis spectra, dissolved organic carbon (DOC) concentration, specific UV absorbance (SUVA), and trihalomethane formation potential (THMFP). The FSMPR process was effective in removing more than 86% of DOC and nearly 100% of UV254 absorbance, while the THMFPs of samples were reduced to < 19 μg/L after 150 min of treatment. In addition, changes in transmembrane pressure (TMP) with and without UV were evaluated; TiO2/UV was effective at controlling membrane fouling by HA. Analysis of the molecular weight (MW) distributions and three-dimensional excitation-emission matrix (EEM) fluorescence spectra of HAs revealed that the effectiveness in membrane fouling control is a result of changes in HA molecular characteristics. The TiO2/UV photocatalytic reactor caused the degradation of high MW, hydrophobic humic-like molecules to low MW, hydrophilic protein-like molecules, although this fraction was not completely removed during 150 min of treatment and was less responsible for membrane fouling.
On Nesting Area Selection of Regional Climate Models Coupled to a Global Climate Model

Qian Yongfu,Liu Huaqiang,

大气科学 , 2001,
Abstract: Three experiments are conducted in this paper. The first one uses a GCM only and its purpose is to access the GCM capability of predicting the regional climate change and to determine the model error distribution. The second and the third ones are the comparative nesting experiments. One of them has a model domain that we are interested in and a nesting area without special consideration of the error distribution in the GCM, while the other has a nesting area selected according to the GCM error distribution. In all of the three experiments the precipitation processes in May, June and July of 1998 in China are simulated and comparisons of the models' results are made. It is found that the results of modeling by only use of a GCM are the worst, while the results of the third experiment are the best. Therefore, the errors of the boundary values in a GCM are of important influences on the simulated results when a regional climate model is coupled to the GCM. If the nesting area is selected in the minimum error district of the GCM, the efficiency of regional climate modeling and prediction would be much better than that without such selection of a nesting area.
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