检索结果-南通市图书馆

RLS channel estimation with adaptive forgetting factor in space-time coded MIMO-OFDM systems

在线全文

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2006年第4期7卷 507-515页

作者： LIANG Yong-ming LUO Han-wen huang jian-guo Department of Electronic Engineering Shanghai Jiao Tong University Shanghai 200030 China College of Marine Engineering Northwestern Polytechnical University. Xi＇an 710072 China

Considering that channel estimation plays a crucial role in coherent detection, this paper addresses a method of Recursive-least-squares (RLS) channel estimation with adaptive forgetting factor in wireless space-time coded multiple-input and multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems. Because there are three different forgetting factor scenarios including adaptive, two-step and conventional ones applied to RLS channel estimation, this paper describes the principle of RLS channel estimation and analyzes the impact of different forgetting factor scenarios on the performances of RLS channel estimation. Simulation results proved that the RLS algorithm with adaptive forgetting factor (RLS-A) outperformed that with two-step forgetting factor (RLS-T) or with conventional forgetting factor (RLS-C) in both estimation accuracy and robustness over the multiple-input multiple-output (MIMO) channel, i.e., a wide-sense stationary uncorrelated scattering (WSSUS) and frequency-selective slowly fading channel. Hence, we can employ the RLS-A method by adjusting forgetting factor adaptively to track and estimate channel state parameters successfully in space-time coded MIMO-OFDM systems.

关键词： MIMO-OFDM Channel estimation RLS algorithm Adaptive forgetting factor

Influence of Arbuscular Mycorrhizal Fungi on Growth, Mineral Nutrition and Chlorogenic Acid Content of Lonicera confusa Seedlings Under Field Conditions

在线全文

学校读者我要写书评

暂无评论

Pedosphere 2013年第3期23卷 333-339页

作者： SHI An-Dong LI Qian huang jian-guo YUAN Ling College of Resources and Environment Southwest University

Lonicera confusa, a traditional Chinese medicine herb for treating cold, flu, acute fever, and so forth, is often grown artificially in acidic soils and suffers from phosphorus (P) deficiency. A five-year field experiment was carried out to study the colonization rate, growth, nutrition, and chlorogenic acid content of Lonicera confusa seedlings inoculated with arbuscular mycorrhizal (AM) fungi, Glomus etunicatum and Glomus intraradices. Before transplanting into a field, both AM-inoculated and uninoculated control plants were cultured in nursery beds. In the plants inoculated with the AM fungi, the colonization rate decreased linearly with time and a greater decrease was observed in the plants inoculated with G. intraradices than with G. etunicatum, while the AM colonization increased from 0% to 12.1% in the uninoculated control plants 5 years after transplanting. Plant height, crown diameter, number of new branches, and flower yield increased significantly by AM inoculation as compared to the uninoculated control. Phosphorus concentrations in leaves and flowers increased, and plant uptake of nutrients, e.g., nitrogen (N), P, and potassium (K), was also enhanced significantly by AM inoculation. The Lonicera confusa seedlings had a better response to inoculation of G. intraradices than G. etunicatum in both growth and chlorogenic acid content in flowers. In contrast, both plant P uptake and P concentrations in leaves and flowers were similar between two fungal inoculations. The positive responses of Lonicera confusa to AM inoculation in growth, nutrient uptake, flowering, and chlorogenic acid content in flowers suggested that AM inoculation in nursery beds could promote the plant growth and increase chlorogenic acid content in flowers of Lonicera confusa when grown on acidic and P-deficient soils.

关键词： Glomus colonization rate nursery beds nutrient uptake P deficiency

Measuring the effectiveness of methods for evaluating noise jammers

在线全文

学校读者我要写书评

暂无评论

Journal of Marine Science and Application 2007年第3期6卷 46-50页

作者： HU Fang huang jian-guo College of Marine Northwestern Polytechnical University Xi ＇an 710072 China

Reliable evaluations of a noise jammer's effectiveness are necessary to properly design, manufacture, and operate one, so it is important to have an evaluation model. Based on their characteristics and principles, relevant factors were classified in terms of their contribution to a unit's effectiveness. In this way an evaluation index system was established. In the proposed mathematical model a noise jammer is analyzed by combining the model of system effectiveness with the method of analytic hierarchical process. A simulation of underwater acoustic countermeasures was used to test the rationality and feasibility of the model. The results showed that this model is an effective way to solve the challenge of evaluating the effectiveness of non-offensive weapons under single working phase.

关键词： underwater acoustic countermeasure noise iammer index system evaluation

Instantaneous frequency estimation of multi-component Chirp signals in noisy environments

在线全文

学校读者我要写书评

暂无评论

Journal of Marine Science and Application 2007年第4期6卷 13-17页

作者： WANG Bai-he huang jian-guo College of Marine Engineering Northwestern Polytechnical University Xi ＇an 710072 China

A classical time-varying signal, the multi-component Chirp signal has been widely used and the ability to estimate its instantaneous frequency （IF） is very useful. But in noisy environments, it is hard to estimate the 1F of a multi-component Chirp signal accurately. Wigner distribution maxima （WDM） are usually utilized for this estimation. But in practice, estimation bias increases when some points deviate from the true IF in high noise environments. This paper presents a new method of multi-component Chirp signal 1F estimation named Wigner Viterbi fit （WVF）, based on Wigner-Ville distribution （WVD） and the Viterbi algorithm. First, we transform the WVD of the Chirp signal into digital image, and apply the Viterbi algorithm to separate the components and estimate their IF. At last, we establish a linear model to fit the estimation results. Theoretical analysis and simulation results prove that this new method has high precision and better performance than WDM in high noise environments, and better suppression of interference and the edge effect. Compared with WDM, WVF can reduce the mean square error （MSE） by 50% when the signal to noise ration （SNR） is in the range of-15dB to -11dB. WVF is an effective and promising 1F estimation method.

关键词： instantaneous frequency estimation multi-component Chirp signals Wigner-Villedistribution Viterbi algorithm linear fit

Mobilization of Inorganic Phosphorus from Soils by Ectomycorrhizal Fungi

在线全文

学校读者我要写书评

暂无评论

Pedosphere 2014年第5期24卷 683-689页

作者： ZHANG Liang WANG Ming-Xia LI Hua YUAN Ling huang jian-guo C.PENFOLD College of Resources and Environment Southwest University School of Biotechnology and Chemical Engineering Taizhou College Nanjing Normal University School of Agriculture Food and Wine The University of Adelaide

Ectomycorrhizal(EM) fungi could form symbiosis with plant roots and participate in nutrient absorption; however, many EM species commonly found in forest soils, where phosphorus(P) concentration and availability are usually very low, particularly in tropical and subtropical areas, have not yet been investigated for their efficiencies to mobilize soil P. In this study, fungal growth, P absorption,efflux of protons and organic acids, and soil P depletion by four isolates of EM fungi isolated either from acidic or calcareous soils were compared in pure liquid culture using soil as a sole P source. Boletus sp. 7(Bo 7), Lactarius deliciosus 3(Ld 3), and Pisolithus tinctorius 715(Pt 715) from acidic and P-deficient soils of southwestern China showed higher biomass and P concentration and accumulation than Cenococcum geophilum 4(Cg 4) from a calcareous soil of Inner Mongolia, northern China, after 4 weeks of liquid culture. Oxalate, malate, succinate, acetate, and citrate concentrations in the culture solutions varied significantly with fungal species,and oxalate accounted for 51.5%–91.4% of the total organic acids. Organic acids, particularly oxalate, in the culture solutions may lead to the solubilization of iron-bound P(Fe-P), aluminum-bound P(Al-P), and occluded P(O-P) from soil phosphates. Fungal species also varied greatly in proton efflux, which decreased the culture solution pH and may dissolve calcium-bound P(Ca-P) in *** could be the reason for the increment of both inorganic P in the culture solutions and Olsen P in the soil when EM fungi were present. Total inorganic P, the sum of Al-P, Fe-P, O-P, and Ca-P, in the culture solutions was positively correlated with the total concentration of organic acids in the culture solutions(r = 0.918*, n = 5), but negatively with both the total inorganic P in soil(r =-0.970**, n = 5) and the culture solution pH(r =-0.830*, n = 5). These suggested variable efficiencies of EM fungal species to mobilize inorganic P fracti

关键词： EM fungal species inorganic P organic acid P availability proton soil phosphate

A New Route for Identification of Precipitates on Austenite Grain Boundary in an Nb-V-Ti Microalloyed Steel

在线全文

学校读者我要写书评

暂无评论

Journal of Iron and Steel Research International 2011年第8期18卷 53-57页

作者： SHA Qing-yun huang guo-jian GUAN Ju MA Xiao-jun LI Da-hang Technology Center Angang Steel Company Limited Anshan 114009 Liaoning China

The precipitates on austenite grain boundaries in an Nb-V-Ti microalloyed steel have been investigated by transmission electron microscope （TEM） examination of carbon extraction replica. The replica was prepared from specimen etched with saturated picric solution rather than Nital which is conventionally used. Then particles on both grain boundaries and triple point of grain [aoundaries were clearly observed and identified as （Nb,Ti）（C, N） parti- cles. In case of conventional way, it is difficult to determine the location of particles with respect to austenite grain boundaries. The number of particles observed in new way developed was greatly reduced compared with that found in replica prepared by the conventional way, which may be caused by the dissolution of partial precipitates during the etching with longer time and at higher temperature involved in new way. Despite this, the new way developed pro- vides an effective way to determine the precipitate particles on austenite urain boundaries_

关键词： precipitate austenite grain boundary replica etch

Austenitization Behaviors of X80 Pipeline Steel With High Nb and Trace Ti Treatment

在线全文

学校读者我要写书评

暂无评论

Journal of Iron and Steel Research International 2009年第6期16卷 58-62页

作者： LIU Qing-you SUN Xin-jun JIA Shu-jun ZHANG Lu-lin huang guo-jian REN Yi Central Iron and Steel ReseaTch Institute Beijing 100081 China Anshan Iron and Steel Group Corporation Anshan 114021 Liaoning China

The austenitization behaviors of two high niohium-containing X80 pipeline steels with different titanium contents, including the dissolution of microalloying precipitates and the austenite grain growth, were investigated by using physical-chemical phase analysis method and microstructural observation. The results illustrated that most niobium could be dissolved into austenite during soaking at 1 180 ℃, whereas little amount of titanium could be dissolved. It was found that during soaking, the austenite grain growth rate was initially high, and then decreased after soaking for 1 h; moreover, the austenite grains grew up more rapidly at temperatures above 1 180 ℃ than below 1 180 ℃. The results show that the steel with titanium content of 0. 016% has a larger austenite grain size than that with titanium content of 0. 012% under the same soaking conditions, which is explained by considering the particle size distribution.

关键词： high Nb steel X80 pipeline steel austenite grain growth dissolution microalloying precipitate

Plasma Current Profile During Current Reversal in a Tokamak

在线全文

学校读者我要写书评

暂无评论

Chinese Physics Letters 1999年第11期16卷 830-832页

作者： huang jian-guo YANG Xuan-zong ZHENG Shao-bai FENG Chun-hua ZHANG Hou-xian WANG Long Institute of Physics Chinese Academy of Sciences100080 Beijing

Alternating current operation with one full cycle and a current level of 2.5kA have been achieved in the CT-6B tokamak. The poloidal magnetic field in the plasma is measured with two internal magnetic probes in repeated discharges. The current distribution is reconstructed with an inversion algorithm. The inversed current first appears on the weak field side. The existence of magnetic surfaces and rotational transform provide particle confinement in the current reversal phase.

关键词： magnetic Plasma field

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

航天器内部充电效应及典型事例分析

物理学报 2010年第4期59卷 2907-2913页

作者：黄建国韩建伟中国科学院空间科学与应用研究中心北京100190

航天器内部充电效应是由空间高能电子诱发的,通常发生在航天器内部以及表面绝缘材料深层,所产生的放电击穿及静电放电脉冲干扰较表面充电更为严重.对内部充放电的一般规律进行了总结,并就一次典型的航天器异常事件,从异常的时空表现特... 详细信息

航天器内部充电效应是由空间高能电子诱发的,通常发生在航天器内部以及表面绝缘材料深层,所产生的放电击穿及静电放电脉冲干扰较表面充电更为严重.对内部充放电的一般规律进行了总结,并就一次典型的航天器异常事件,从异常的时空表现特征及其与高能电子环境扰动的相关性角度进行了深入分析和定量计算,得出了高能电子产生的内部充电引起的卫星异常的结论,为卫星异常诊断提供了范例.

关键词：高能电子内部充电静电放电空间环境