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Fast Fading Channel Estimation for OFDM Systems with Complexity Reduction

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Chinese Journal of Electronics 2021年第6期30卷 1173-1177页

作者： ZHANG Chen li dan College of Electronic Science and Technology National University of Defense Technology

Channel estimation plays a significant role in the Inter-carrier interference(ISI) mitigation and symbol detection in Orthogonal frequency division multiplexing(OFDM) systems. As the speed of mobile terminal increases, the channel changes rapidly, causing fast fading which will degrade the system performance. In this paper, a low complexity fast fading channel estimation method suited for scattered pilot OFDM systems is proposed. This method is characterized by estimating channel matrix directly in the frequency domain, which can significantly reduce the channel estimation complexity with good system performance. Simulation results verify its superiority over the existing estimation methods.

关键词： low complexity fast fading channel estimation OFDM modulation existing estimation methods channel estimation OFDM systems mobile terminal increases good system performance symbol detection channel estimation complexity frequency-domain analysis channel changes fading channels complexity reduction channel matrix

Quantitative structure-activity relationship study on the biodegradation of acid dyestuffs

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Journal of Environmental Sciences 2007年第7期19卷 800-804页

作者： li Yin XI dan-li College of Environmental Science and Engineering Dong Hua University Shanghai 201620 China.

Quantitative structure-biodegradability relationships （QSBRs） were established to develop predictive models and mechanistic explanations for acid dyestuffs as well as biological activities. With a total of four descriptors, molecular weight （MW）, energies of the highest occupied molecular orbital （EHOMO）, the lowest unoccupied molecular orbital （ELUMO）, and the excited state （EES）, calculated using quantum chemical semi-empirical methodology, a series of models were analyzed between the dye biodegradability and each descriptor. Results showed that EHOMO and Mw were the dominant parameters controlling the biodegradability of acid dyes. A statistically robust QSBR model was developed for all studied dyes, with the combined application of EHOMO and Mw. The calculated biodegradations fitted well with the experimental data monitored in a facultative-aerobic process, indicative of the reliable prediction and mechanistic character of the developed model.

关键词： quantitative structure-activity relationship (QSAR) acid dyestuff biodegradability decolorization

On 4-order Schrodinger operator and Beam operator

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Frontiers of Mathematics in China 2019年第6期14卷 1197-1211页

作者： dan li Junfeng li School of Mathematical Sciences Beijing Normal UniversityBeijing 100875China School of Mathematical Sciences Dalian University of TechnologyDalian 116024China

Wc show that there is no localization for the 4-order Schrodinger operator Jt,Af and Bearn operator 38%more precisely,on the one hand,we show that the 4-order Schrodinger operator Atf, does not converge pointwise to z... 详细信息

关键词： 4-Order Schrodinger operator Beam operator localization Sobolev space

天津市公立医院四类高危人群结核病监测能力现况调查

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中国防痨杂志 2025年第2期47卷 195-200页

作者：高丽陈盛玉张文倩李丹张国钦天津市结核病控制中心研究室天津300041

目的:掌握天津市公立医院四类高危人群(单侧胸腔积液、咯血、拟长期应用全身糖皮质激素、拟应用免疫抑制剂)结核病监测能力现况。方法:纳入天津市全部二级及以上公立综合医院和设置了呼吸科、感染科和/或免疫相关科室的专科医院(以下简... 详细信息

目的:掌握天津市公立医院四类高危人群(单侧胸腔积液、咯血、拟长期应用全身糖皮质激素、拟应用免疫抑制剂)结核病监测能力现况。方法:纳入天津市全部二级及以上公立综合医院和设置了呼吸科、感染科和/或免疫相关科室的专科医院(以下简称“监测机构”),采用现场问卷调查的方式获得监测机构重点科室设置(内科、呼吸科、感染科、免疫相关)、结核病检查方法及医务人员对结核病防治核心知识及监测工作的态度。结果:共纳入72家监测机构,包含10家结核病定点医院和62家非结核病定点医院。(1)重点科室设置:内科、呼吸科、感染科、风湿免疫科设置比例分别为97.22%(70/72)、62.50%(45/72)、59.72%(43/72)、37.50%(27/72)。(2)结核病检查方法:10家结核病定点医院均具备全部要求的结核病检查方法;62家非结核病定点医院全部具备胸部影像学检查,72.58%(45/62)至少具备病原学检查和/或免疫学检查中的任一种且以三级医院为主。(3)结核病防治核心知识知晓率:181名公共卫生科医务人员和重点临床科室医生完成问卷,结核病病因、典型症状全部知晓、主要传播途径全部知晓、是否可治愈的知晓率分别为90.61%(164/181)、71.82%(130/181)、44.20%(80/181)、97.24%(176/181)。(4)高危人群结核病监测相关知识知晓率及态度:90名重点科室临床医生完成问卷。四类高危人群类型、病原学检查方法、免疫学检查方法、结核分枝杆菌潜伏感染、预防性治疗的知晓率分别为96.67%(87/90)、86.67%(78/90)、93.33%(84/90)、60.00%(54/90)、56.67%(51/90)。81.11%(73/90)的重点科室临床医生认为四类人群有必要开展结核病监测。结论:非结核病定点医院尤其是二级医院,病原学、免疫学检查能力尚有欠缺;医务人员对结核病典型症状和主要传播途径的掌握不全面,潜伏感染和预防性治疗的知晓率偏低,对高危人群开展结核病监测的态度较为积极。

关键词：结核高危人群监测医院公立天津市

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A Carleson Problem for the Boussinesq Operator

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Acta Mathematica Sinica,English Series 2023年第1期39卷 119-148页

作者： dan li Jun Feng li School of Mathematics and Statistics Beijing Technology and Business UniversityBeijing 100048P.R.China School of Mathematical Sciences Dalian University of TechnologyDalian 116024P.R.China

In this paper,we show that the Boussinesq operator B_(t)f converges pointwise to its initial data.f∈H^(s)(R)as t→0 provided s≥1/4-more precisely-on one hand,by constructing a counterexample in R we discover that the optimal convergence index sc,1=1/4;on the other hand,we find that the Hausdorff dimension of the divergence set for B_(t)f isα1,b(s)={1-2s,as1/4≤s≤1/2;1,as 0lift was also obtained for f being radial.

关键词： Carleson problem Boussinesq operator pointwise convergence Hausdorff dimension Sobolev space

Study on the simultaneous reduction of methylmercury by SnCl_2 when analyzing inorganic Hg in aqueous samples

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Journal of Environmental Sciences 2018年第6期30卷 177-184页

作者： dan li Yanbin li Xiulin Wang Key Laboratory of Marine Chemistry Theory and Technology (Ocean University of China) Ministry of Education College of Environmental Science and Engineering Ocean University of China College of Chemistry and Chemical Engineering Ocean University of China

Mercury（Hg） is among the most concerned contaminants in the world. It has three major chemical forms in the environment, including Hg0, Hg2＋, and methylmercury（MeHg）. Due to their differences in toxicity, mobility, and bioavailability, speciation analysis is critical for understanding Hg cycling and fate in the environment. SnCl2 reduction-atomic fluorescence spectrometry detection is the most commonly used method for analyzing inorganic Hg. However, it should be noted that MeHg may also be reduced by SnCl2, which would result in the overestimation of inorganic Hg. In this study, the reduction of MeHg by SnCl2 in both de-ionized（DI） water and four natural waters was investigated. The results showed that MeHg could be reduced by SnCl2 in DI water whereas this reaction was hard to occur in tested natural waters. By investigating the effects of water chemical characteristics（dissolved organic matter, pH and common anions and cations） on this reaction, SO42- was identified to be the dominant factor prohibiting SnCl2 induced MeHg reduction in natural waters. SO2-4 in natural waters was evidenced to be reduced to S2- by SnCl2 and the generated S2-can complex with MeHg to form MeHg S-which is hard to be reduced by *** of this study indicate that the effect of MeHg reduction by SnCl2 on inorganic Hg analysis is negligible in natural waters; however, at simulated experimental systems without SO42-, SO42- should be added as protecting agents to prevent MeHg reduction when analyzing inorganic Hg if it would not cause any other unwanted effects.

关键词： MeHg reduction DI water Natural water Inorganic Hg SO42- and S2-

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电机绝缘结构热机械应力分布研究

绝缘材料 2025年第1期58卷 56-63页

作者：刘冠芳李丹吴有龙樊洁心中车永济电机有限公司山西永济044502 轨道交通牵引电机山西省重点实验室山西永济044502

为探索电机绝缘结构在高温下的热机械应力分布,本文以有机硅体系绝缘结构为研究对象,测试其在不同温度下的热膨胀系数及弹性模量,分析不同温度下的热应力参数对有机硅绝缘系统热机械应力的影响。结果表明:在温度为-50~200℃内,绝缘结构... 详细信息

为探索电机绝缘结构在高温下的热机械应力分布,本文以有机硅体系绝缘结构为研究对象,测试其在不同温度下的热膨胀系数及弹性模量,分析不同温度下的热应力参数对有机硅绝缘系统热机械应力的影响。结果表明:在温度为-50~200℃内,绝缘结构的热膨胀系数随着温度的升高先增大后减小再增大,其值为0.8×10^(-5)~1.7×10^(-5)K^(-1);弹性模量随着温度的升高呈先增大后减小的趋势,其值为0.2×10^(3)~3×10^(3)MPa。绝缘结构承受的热机械应力随着热膨胀系数、弹性模量的增加线性增大,绝缘结构的热机械应力随着温度的升高先增大后减小,取决于不同温度下热膨胀系数和弹性模量的大小。通过线棒和电机整机应力测试,验证了测试参数及仿真分析的可行性,仿真值与测试值的偏差在15%以内。仿真分析结果显示:在120℃下,电机绝缘最大热机械应力点位置位于槽口绝缘处,最大值为11.37MPa,灌封后槽口绝缘最大热机械应力值可降低45%左右。

关键词：绝缘结构热机械应力仿真技术电机

Subcategories of Fixed Points of Mutations by Exceptional Objects in Triangulated Categories

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Acta Mathematica Sinica,English Series 2016年第2期32卷 187-198页

作者： li dan TANG College of Mathematics and Computer Science Fuzhou University

We first prove that the subcategory of fixed points of mutation determined by an excep- tional object E in a triangulated category coincide with the perpendicular category of E. Based on this characterisation, we prove that the subcategory of fixed points of mutation in the derived category of the coherent sheaves on weighted projective line with genus one is equivalent to the derived category of a hereditary algebra. Meanwhile, we induce two new recollements by left and right mutations from a given recollement.

关键词： Subcategory of fixed points exceptional object recollement

新结构经济学视角下乡村特色农业产业发展的实现模式研究

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嘉应学院学报 2025年第1期43卷 45-48页

作者：丘缅李丹嘉应学院经济与管理学院广东梅州514015 中国工商银行梅州分行广东梅州514000

实现乡村特色农业产业发展需要选择适宜的模式,运用新结构经济学基本理论,构建了实现乡村特色农业产业发展的理论模型。研究发现,乡村特色农业产业发展模式的决定因素在于乡村异质性资源禀赋结构;异质性资源禀赋结构恰好形成乡村特色农... 详细信息

实现乡村特色农业产业发展需要选择适宜的模式,运用新结构经济学基本理论,构建了实现乡村特色农业产业发展的理论模型。研究发现,乡村特色农业产业发展模式的决定因素在于乡村异质性资源禀赋结构;异质性资源禀赋结构恰好形成乡村特色农业产业发展的比较优势路径;准确定位乡村特色农业产业功能进而基于区域异质性资源禀赋结构构建特色农业主导产业,充分发挥政府“有形的手”和市场机制“无形的手”的合力,是发展乡村特色农业产业的一条可行路径。

关键词：资源禀赋结构乡村特色农业产业发展模式新结构经济学