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Second Chern crystals with inherently non-trivial topology

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National Science Review 2023年第8期10卷 148-155页

作者： Xiao-Dong Chen Fu-Long Shi Jian-Wei Liu ke shen Xin-Tao He C.T. Chan Wen-Jie Chen Jian-Wen Dong School of Physics and State key Laboratory of Optoelectronic Materials and Technologies Sun Yat-sen University Department of Physics The Hong Kong University of Science and Technology

Chern insulators have been generalized to many classical wave systems and thereby lead to many potential applications such as robust waveguides, quantum computation and high-performance lasers. However, the band structure of a material can be either topologically trivial or non-trivial, depending on how the crystal structure is designed. Here, we propose a second Chern crystal in a four-dimensional parameter space by introducing two extra synthetic translation dimensions. Since the topology of the bulk bands in the synthetic translation space is intrinsically non-trivial, our proposed four-dimensional crystal is guaranteed to be topologically non-trivial regardless of the crystal’s detailed configuration. We derive the topologically protected modes on the lower dimensional boundaries of such a crystal via dimension ***, we observe the one-dimensional gapless dislocation modes and confirm their robustness in experiments. Our findings provide novel perspectives on topologically non-trivial crystals and may inspire designs of classical wave devices.

关键词： topological photonics synthetic dimension photonic crystals dislocation mode

激发室空气吸附对火花放电原子发射光谱法测定汽车板钢氧含量精密度的影响

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冶金分析 2018年第10期38卷 23-27页

作者：沈克宝钢股份武钢有限质量检验中心

针对采用火花放电原子发射光谱法(SDOES)测定氧时检出限较高的问题,实验探讨了激发室空气吸附对SDOES测定汽车板钢中氧精密度的影响。研究发现,由于伯努利效应,空气被吸入激发室而产生吸附,吸入的氧气、水蒸气不能被放电前的预冲氩完全... 详细信息

针对采用火花放电原子发射光谱法(SDOES)测定氧时检出限较高的问题,实验探讨了激发室空气吸附对SDOES测定汽车板钢中氧精密度的影响。研究发现,由于伯努利效应,空气被吸入激发室而产生吸附,吸入的氧气、水蒸气不能被放电前的预冲氩完全除去,导致氧分析精密度变差。采取在不分析样品时将用的密封块把激发孔盖上,此外分析时注意将试样加工平整、保持样品与激发平台弥合、减少大气吸入等隔离空气的措施后,O 130.1nm谱线的背景波动得到有效控制,氧测定结果的相对标准偏差(RSD)由密封前的14.2%降低至密封后的5.5%。用低合金钢标准样品绘制氧校准曲线的相关系数(r)为0.990 2,测定下限降至0.000 96%。对氧质量分数分别为0.003 7%和0.001 1%的样品进行精密度考察,结果的RSD分别为7.5%和9.8%。汽车板试样的实验方法分析结果与国家标准脉冲加热惰气熔融-红外线吸收法分析结果之差小于GB/T 11261—2006临界差(CD0.95)。在实验条件下,批量分析氧试样时工作效率优于红外法。

关键词：火花放电原子发射光谱法汽车板钢氧定量分析气体吸附精密度

Electrochemical reconstruction: a new perspective on Sn metal-organic complex microbelts as robust anode for lithium storage

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Rare Metals 2024年第1期43卷 76-86页

作者： Jin-ke shen Nai-Teng Wu Li-Yuan Wang Gang Jiang Dong-Lei Guo Jin Li Gui-Long Liu Hong-Yu Mi Huan Pang Xian-Ming Liu key Laboratory of Function-oriented Porous Materials of Henan Province College of Chemistry and Chemical EngineeringLuoyang Normal UniversityLuoyang 471934China State key Laboratory of Chemistry and Utilization of Carbon Based Energy Resources School of Chemical Engineering and TechnologyXinjiang UniversityUrumqi 830046China School of Chemistry and Chemical Engineering Institute for Innovative Materials and EnergyYangzhou UniversityYangzhou 225009JiangsuChina

Tin-based materials with high theoretical capacity and suitable working voltage are ideal anode materials for lithium-ion batteries(LIBs). However, to overcome their shortcomings(volume expansion and inferior stability), the preparation processes are usually complicated and expensive. Herein, a tin-based metal-organic complex(tin 1,2-benzenedicarboxylic acid, Sn-BDC)with one-dimensional microbelt morphology is synthesized by a facile, rapid and low-cost co-precipitation method, and served as anode material for LIBs without any post-treatment. Sn-BDC exhibits a high reversible capacity with609/440 m Ah·g^(-1) at 50/2000 m A·g^(-1), and robust cycling stability of 856 m Ah·g^(-1) after 200 cycles at 200 m A·g^(-1),which are obviously superior to that of the Sn Ox/C counterparts. Moreover, an electrochemical reconstruction perspective on the lithium storage mechanism of Sn-BDC is proposed by systematic ex-situ characterizations. The reconstructed SnO_(2) replaces Sn-BDC and becomes the active material in the subsequent cycles. As the by-product of the lithiation reaction, the formed Li-based metal-organic complex(Li-BDC, wrapped around the reconstructed SnO_(2)) plays an important role in alleviating volume expansion and accelerating the charge transfer *** work is beneficial to design and construct the new electrode materials based on the electrochemical reconstruction for advanced LIBs.

关键词： Electrochemical reconstruction Metal-organic complex Anode Lithium storage mechanism Lithium-ion batteries

Feasibility of Field Evaluation of Rice Nitrogen Status From Reflectance Spectra of Canopy *1

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Pedosphere 1998年第2期8卷 121-126页

作者： WANG RENCHAO, WANG ke and shen ZHANGQUAN Institute of Agricultural Remote Sensing and Information Application, Zhejiang Agricultural University, Hangzhou 310029 (China) Inst. Agric. Remote Sensing Info. A. Zhejiang Agricultural University Hangzhou 310029 China

Techniques for measurement of the N status of rice can be an aid to making management decisions with economic and environmental implications. A field experiment was conducted to identify spectral variables most sensitive to N deficiency detection in rice canopy with the possibility for their use as a management tool. Spectral and agronomic measurements were collected in the evaluation experiment of N status from rice canopy under five N treatments in a silt loam soil. Nitrogen fertilization effects were seen across the entire wavelength measured. Red reflectance decreased and near infrared reflectance increased with increasing N fertilizer application. Spectral differences between treatments were seen throughout the test period. The near infrared reflectance/red reflectance ratio (RVI) differed more between treatments than between single bands. Variations in canopy reflectances due to other environmental factors were reduced by the use of RVI. In the spectral variables examined, the RVI separated the treatments most effectively, and three or four treatments can be separated. Differences in spectral responses between the treatments were attributable to leaf area index, leaf chlorophyll concentration and phytomass, which all changed with N fertilization.

关键词： canopy spectra nitrogen fertilizer nitrogen status evaluation rice

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中国老年人口多维度健康状况分析

中华预防医学杂志 2010年第2期44卷 108-114页

作者：曾毅沈可北京大学国家发展研究院中国经济研究中心 100871 Geriatric Division and Center for the Study of Aging and Human Development School of Medicine Duke University

目的分析中国老年人口的多维度健康状况。方法采用非等比例抽样方法，从我国22个省（市、自治区）抽取65岁以上老人16219名。调查其日常生活自理能力（ADL）、躯体功能、认知功能、自评健康和自评生活满意度。分别从年龄、城乡、性别角... 详细信息

目的分析中国老年人口的多维度健康状况。方法采用非等比例抽样方法，从我国22个省（市、自治区）抽取65岁以上老人16219名。调查其日常生活自理能力（ADL）、躯体功能、认知功能、自评健康和自评生活满意度。分别从年龄、城乡、性别角度进行中国老年人口多维度健康状况的对比分析。结果65～、70～、80～、90～与100～岁年龄段男性老人生活完全自理的比率分别为98．8％（730／739）、95．2％（1445／1518）、89．1％（1913／2147）、76．3％（1447／1897）和51．6％（329／638），女性老人分别为98．1％（654／667）、94．9％（1291／1361）、87．2％（1851／2124）、70．0％（1888／2699）和46．8％（1136／2428）（x2性别=293．00，P〈0．01）；相应年龄段城镇老人生活完全自理的比率分别为98．0％（561／572）、93．6％（1090／1165）、85．5％（1413／1653）、69．3％（1311／1892）、37．4％（434／1161），农村老人分别为98．7％（823／834）、96．O％（1646／1714）、89．8％（2351／2618）、74．9％（2024／2704）、54．1％（1031／1905）（x城乡=85．97，P〈0．01）。65～、70～、80～、90～与100～岁年龄段男性老人认知功能良好的比率分别为96．5％（713／739）、90．0％（1364／1516）、72．1％（1547／2145）、49．2％（929／1890）和35．0％（218／623），女性老人分别为94．1％（627／666）、81．9％（1113／1359）、57．2％（1211／2116）、32．4％（870／2688）和17．5％（418／2395）（x2性别=893．89，P〈0．01）；相应年龄段城镇老人认知功能良好的比率分别为97．0％（555／572）、87．9％（1023／1164）、68．5％（1129／1648）、43．6％（820／1881）、23．0％（258／1124），农村老人分别为94．2％（785／833）、85．0％（1454／1711）、62．3％（1629／2613）、36．3％（979／2679）、20．0％（378／1894）（x2城乡=57．92，P〈0．01）。65～、70～、80～、90～和100-年龄段男性老人自评健康好的比率分别为56．3％（416／739）、50．7％（770／1518）、46．O％（988／2148）、42．7％（809／1897）和43．1％（175／638），女性老人自评健康好的比率分别为48．7％（325／667）、46．1％（627／1361）、43．0％（914／2124）、39．3％（1061／2699）和34．5％（838／2428），各年龄段男性老人自评健康等级优于女性（x2=233．91，P〈0．01）。65～、70～、80～、90～和100～岁年龄段男性老人对目前生活较满意的比率分别为56．2％（415／739）、56．0％（850／1518）、55．7％（1194／2418）、52．9％（1003／1897）和50．5％（322／638），女性老人分别为54．9％（366／667），55．8％（759／1361），53．9％（1144／2124），50．6％（1365／2699）和43．4％（1054／2428）。65一岁年龄段男女老人自评生活满意度差异没有统计学意义（x2=0．51，P=0．916）；70岁以上男性老人的自评生活满意度优于女性（x2=218．25，P〈0．01）。结论老人生理健康和认知功能良好的比例均随年龄增长而下降；老人的自评健康和自评生活满意度随年龄增长而下降的趋势比较缓慢。农村老人的ADL明显优于城镇老人。男性老人ADL、躯体功能、认知功能和自评健康优于同年龄段女性老人。

关键词：老年人日常生活活动躯体功能认知健康状况自我评价(心理学) 长寿

SnO_(2)/metal organic complex composite derived from low-temperature activated metal organic complex for advanced lithium storage

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Rare Metals 2024年第7期43卷 3032-3043页

作者： Gui-Long Liu Zi-Han Zhao Jin-ke shen Zi-Bo Zhao Nai-Teng Wu Dong-Lei Guo Wei-Wei Yuan Yong Liu Ye-Hua Su Xian-Ming Liu Luoyang key Laboratory of Green Energy Materials College of Chemistry and Chemical EngineeringLuoyang Normal UniversityLuoyang 471934China School of Materials Science and Engineering Henan University of Science and TechnologyLuoyang 471023China Inner Mongolia Shijie Chemical Co. Ltd.Alxa League 737300

Sn-based metal organic complexes with coordination bonds,multi-active sites,and high theoretical capacity have attracted much attention as promising anodes for lithium ion ***,the low electrical conductivity and huge volume changes restricted their electrochemical stability and practical ***,Snbased anode with superior electrochemical performance,including a high reversible capacity of 1050.1 mAh·g^(-1)at 2 A·g^(-1)and a stable capacity of 1105.5 mAh·g^(-1)after 500 cycles at 1 A·g^(-1),was fabricated via a low-temperature calcination strategy from Sn metal organic *** low-temperature calcination process regulates Sn-O bond and prevents the agglomeration of SnO_(2),generating highly dispersed SnO_(2) decorated metal organic complexes and providing sufficient active sites for ion *** situ characterizations expound that the undecomposed Sn-based metal organic complexes could be transformed into SnO_(2) during lithiation and delithiation,which enhances the electrical conductivity and induces a strong pseudo-capacitive behavior,accelerating the electrochemical kinetics;the multiple solid electrolyte interface with inflexible LiF and flexible ROCO_(2)Li buffers the volume variation of the electrode,resulting in its high electrochemical *** work provides a simple strategy for preparing excellent Sn-based anodes from metal organic complexes and reveals the lithium storage mechanism of the prepared Snbased anode.

关键词： Metal organic complex Lithium ion battery Electrochemical activation Low-temperature activation Partial decomposition

Oxygen-deficient ammonium vanadate/GO composites with suppressed vanadium dissolution for ultra-stable high-rate aqueous zinc-ion batteries

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Rare Metals 2023年第11期42卷 3729-3740页

作者： Gui-Long Liu Ting Zhang Xiao-Jie Li Ru-Ping Cao Jin-ke shen Dong-Lei Guo Nai-Teng Wu Wei-Wei Yuan Ang Cao Xian-Ming Liu key Laboratory of Function-Oriented Porous Materials of Henan Province College of Chemistry and Chemical EngineeringLuoyang Normal UniversityLuoyang471934China Department of Physics Technical University of DenmarkKongens Lyngby2800Denmark

The structural engineering of hydrated ammonium vanadate as a cathode for aqueous Zn-ion batteries has attracted significant research interest because of its ability to suppress vanadium dissolution and accelerate the electrochemical ***,a feasible fabrication strategy for oxygen-deficient(NH_(4))_(2)V_(10)O_(25)·xH_(2)O/GO(NVOH@GO)composites was proposed,and the charge storage mechanism was *** results of characterization analysis showed that the introduction of graphene oxide(GO)not only enlarged the layer spacing and improved electrical conductivity,providing spacious channels for Zn^(2+)(de)intercalation and accelerating the ion diffusion dynamics,but also induced more oxygen vacancies,inhibited the dissolution of vanadium,and reduced self-discharging,offering additional and stable active sites for ion *** optimized NVOH@GO electrode delivered extraordinarily stable capacities of 334 mAh·g^(-1)after 2000 cycles at 5 A·g^(-1)and 238 mAh·g^(-1)after 10,000cycles at 20 A·g^(-1).Furthermore,ex-situ X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),and Raman results systematically revealed the electrochemical mechanism,including a phase transition reaction and subsequent Zn^(2+)/H_(2)O co-(de)intercalation *** study provides an effective strategy for expanding the interlayer spacing,inducing defect engineering,and enhancing the structural stability of vanadium-based cathodes for Zn-ion batteries and other multivalent aqueous ion batteries.

关键词： Aqueous Zn-ion batteries Vanadium-based cathode Dissolution restraint Oxygen defects Phase transition

双线高密度电阻率法分析断层产状的原理和算法

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公路交通科技 2017年第12期34卷 97-102页

作者：沈可广州市中心区交通项目领导小组办公室广东广州510030

断层产状计算是工程勘探中一个重要内容,一般利用地质罗盘和皮尺测量断层露头的方法进行计算,其运用范围受到了极大限制。利用高密度电法勘探可得到沿测线走向剖面上地下构造的电阻率剖面,结合已知的地层信息可以判断断层的存在和规模,... 详细信息

断层产状计算是工程勘探中一个重要内容,一般利用地质罗盘和皮尺测量断层露头的方法进行计算,其运用范围受到了极大限制。利用高密度电法勘探可得到沿测线走向剖面上地下构造的电阻率剖面,结合已知的地层信息可以判断断层的存在和规模,但无法准确确定其产状。文中提出采用双线电法勘探的方法分析并准确计算断层产状,包括倾向、倾角和宽度指标。该方法假设断层同时切割两条测线,且在测线间断层结构面无较大褶曲,可简化为平面。计算过程中,首先根据单线电阻率剖面判断断层的范围和边界,采用最小二乘法确定其切割面参数,然后根据断层在两个剖面上的投影反算断层的倾向、倾角,最后根据断层和电阻率剖面的空间交互关系反推断层宽度。文中详细介绍了该方法的理论基础和推导过程,并对其运用条件进行了阐述。文中对该方法在厦门市某隧道勘探中断层产状计算成果进行了归纳、统计和分析,并选择断层出露地面位置的计算结果与采用传统地质罗盘测量结果进行了对比分析。结果表明根据文中计算分析方法得出的断层产状和宽度与实际测量结果相比有一定误差,倾向相差3°~5°,倾角相差2°~6°,宽度相差11%~16%,主要是因为断层延伸过程中受地质构造作用而发生几何性状变化引起的,但是在较小的勘探区域内仍然能够较为准确地反映实际情况。

关键词：隧道工程断层产状算法双线高密度电阻率法断层最小二乘法

儿童时期的社会经济地位对中国高龄老人死亡风险的影响

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中国人口科学 2008年第3期 56-63页

作者：沈可北京大学中国经济研究中心

文章应用中国老年健康长寿影响因素跟踪调查1998、2000、2002和2005年的面板数据,分析儿童时期社会经济地位对高龄老人死亡风险的影响。结果发现,儿童时期社会经济地位的影响部分通过成年时期社会经济地位的中介作用,而健康行为并没有... 详细信息

文章应用中国老年健康长寿影响因素跟踪调查1998、2000、2002和2005年的面板数据,分析儿童时期社会经济地位对高龄老人死亡风险的影响。结果发现,儿童时期社会经济地位的影响部分通过成年时期社会经济地位的中介作用,而健康行为并没有在儿童时期社会经济地位对死亡风险的影响中发挥中介作用。而在控制成年时期社会经济地位和健康行为后,父亲职业仍对死亡风险有显著的直接影响。

关键词：社会经济地位健康行为死亡风险中介作用