期刊文献+
共找到160,535篇文章
< 1 2 250 >
每页显示 20 50 100
基于Green函数的轮胎冲击载荷特性反演方法
1
作者 师桂杰 李强 王德禹 《中国舰船研究》 北大核心 2025年第3期165-173,共9页
[目的]旨在通过结构响应间接识别轮胎冲击载荷及其分布特性,为甲板设计与安全评估提供依据,提出一种基于Green函数的载荷反演方法。[方法]以某船甲板加筋板为研究对象,利用Green函数将冲击载荷表示为单位脉冲载荷的叠加,通过有限元仿真... [目的]旨在通过结构响应间接识别轮胎冲击载荷及其分布特性,为甲板设计与安全评估提供依据,提出一种基于Green函数的载荷反演方法。[方法]以某船甲板加筋板为研究对象,利用Green函数将冲击载荷表示为单位脉冲载荷的叠加,通过有限元仿真得到Green核函数矩阵,并结合广义交叉验证准则(GCV)的Tikhonov正则化方法,建立载荷反演模型。针对单个轮胎及多个轮胎冲击工况,分析多源载荷对反演精度的影响。对于凸型、马鞍型和凹型3种典型的轮印载荷分布形式,通过等效划分受力区域并施加单位脉冲载荷,完成载荷分布特性的反演。[结果]结果表明,所提方法能够有效识别轮胎冲击载荷的时间历程及其分布特性,反演相对误差均小于5%。其中,基于应变和位移响应的反演精度较高,误差低于2%;即使在5%噪声干扰下,反演载荷仍然与实际载荷基本一致。[结论]所提方法解决了冲击载荷作用时间短、结构响应范围有限以及多源载荷联合作用带来的反演难题,为实船轮印载荷识别提供了新思路,具有重要的工程应用价值。 展开更多
关键词 甲板设计 结构响应 动力响应 加筋板 承载能力 冲击载荷 轮印载荷分布 green函数 载荷反演
在线阅读 下载PDF
引入Green函数实现电阻率法总电位高精度三维正演
2
作者 熊彬 熊心如 +2 位作者 徐志锋 陆裕国 张健辉 《地球物理学报》 北大核心 2025年第7期2786-2791,共6页
在电阻率法正演中,采用有限单元法数值求解总电位V时,关于总电位V的泛函中含有点电流源项,而位函数V在源点处具有奇异性.为了有效模拟点电流源邻近总电位V的变化情况,人们采用线性插值、二次插值甚至更高次插值,也难以完全消除其影响,... 在电阻率法正演中,采用有限单元法数值求解总电位V时,关于总电位V的泛函中含有点电流源项,而位函数V在源点处具有奇异性.为了有效模拟点电流源邻近总电位V的变化情况,人们采用线性插值、二次插值甚至更高次插值,也难以完全消除其影响,均不能收获令人满意的精度.本文将满足Possion方程的Green函数引入稳定电流场所满足的边值问题,借助Galerkin加权余量法构建有限单元法控制方程,进而实现基于总电位的高精度电阻率法三维正演.理论计算结果表明,本文提出算法的稳定性颇佳,对网格的依赖性低,且计算精度与基于异常电位正演的计算精度相当. 展开更多
关键词 电阻率法 正演 有限单元法 green函数 总电位
在线阅读 下载PDF
基于SYBR GreenⅡ的BVDV NS3基因实时荧光定量PCR检测方法的建立与应用 被引量:1
3
作者 李阳 张世勋 +4 位作者 赫鸣睿 刘珊珊 岳山 刘宇 朱战波 《黑龙江八一农垦大学学报》 2025年第2期23-31,共9页
为了建立基于SYBR GreenⅡ的牛病毒性腹泻病毒(BVDV)NS3基因实时荧光定量PCR(qRT-PCR)检测方法,设计并筛选了BVDV NS3基因的qRT-PCR引物,建立了BVDV NS3 qRT-PCR检测方法,并利用CFX96和猪警-2000 qRT-PCR仪检测了临床牛血清样本。结果显... 为了建立基于SYBR GreenⅡ的牛病毒性腹泻病毒(BVDV)NS3基因实时荧光定量PCR(qRT-PCR)检测方法,设计并筛选了BVDV NS3基因的qRT-PCR引物,建立了BVDV NS3 qRT-PCR检测方法,并利用CFX96和猪警-2000 qRT-PCR仪检测了临床牛血清样本。结果显示,筛选出1对特异性好的引物,CFX96和猪警-2000 qRT-PCR的标准品最小检出值分别为1×10^(1)copies·μL^(-1)和1×10^(2) copies·μL^(-1),特异性和重复性均良好,且临床血清样本的检测结果准确、一致。研究为BVDV检测提供了技术手段。 展开更多
关键词 牛病毒性腹泻病毒 NS3基因 实时荧光定量PCR SYBR green
在线阅读 下载PDF
鸽疱疹病毒gB基因SYBR GreenⅠ荧光定量PCR检测方法的建立与应用
4
作者 李鹏 苏和 +4 位作者 韩慧敏 孟海 王昊 王凤雪 温永俊 《中国家禽》 北大核心 2025年第3期93-99,共7页
为建立检测鸽疱疹病毒(PiHV)的SYBR GreenⅠ荧光定量PCR(qPCR)方法,研究根据PiHV gB基因的高度保守区域设计特异性引物,构建质粒作为标准品建立PiHV qPCR检测方法,并进行敏感性和特异性试验。结果显示:建立的PiHV qPCR方法最低DNA检出... 为建立检测鸽疱疹病毒(PiHV)的SYBR GreenⅠ荧光定量PCR(qPCR)方法,研究根据PiHV gB基因的高度保守区域设计特异性引物,构建质粒作为标准品建立PiHV qPCR检测方法,并进行敏感性和特异性试验。结果显示:建立的PiHV qPCR方法最低DNA检出浓度为8.62×10^(2)拷贝/μL,敏感性比普通PCR方法高100倍,可特异性区分鸽疱疹病毒与其他多种常见感染鸽的细菌和病毒,其批内变异系数小于1%,批间变异系数小于2%;应用该方法对呼和浩特市及周边地区赛鸽公棚和鸽养殖场采集的30份疑似病鸽肝脏样品进行检测,可快速准确地检出样品中的PiHV,并且检出率比普通PCR方法高。研究表明,建立的PiHV qPCR检测方法特异性强,敏感性较高,能够应用于赛鸽、肉鸽等的鸽疱疹病毒快速检测。 展开更多
关键词 鸽疱疹病毒 SYBR green 荧光定量PCR 聚合酶链式反应 GB基因
在线阅读 下载PDF
柑橘黄龙病菌和溃疡病菌SYBR GreenⅠ双重qPCR检测体系的建立
5
作者 陈红 成璐伶 +4 位作者 何淙 张颖梓 王冰 李大志 戴素明 《中国果树》 2025年第8期93-97,共5页
柑橘黄龙病和溃疡病是严重影响柑橘产业发展的重要病害。针对这两种病害在生产过程中经常复合侵染柑橘的情况,通过引物组合筛选、引物浓度和退火温度优化,建立了可以同时检测柑橘黄龙病菌(Candidatus Liberibacter asiaticus,CLas)和溃... 柑橘黄龙病和溃疡病是严重影响柑橘产业发展的重要病害。针对这两种病害在生产过程中经常复合侵染柑橘的情况,通过引物组合筛选、引物浓度和退火温度优化,建立了可以同时检测柑橘黄龙病菌(Candidatus Liberibacter asiaticus,CLas)和溃疡病菌(Xanthomonas citri subsp.citri,Xcc)的SYBR GreenⅠ双重qPCR检测体系。该SYBR GreenⅠ双重qPCR检测体系最佳引物组合为CLA-1/Xcc2,CLA-1最适浓度为30μmol/L,Xcc2最适浓度为40μmol/L,最适退火温度为57℃。该检测体系对CLas和Xcc的检测极限分别可达11.23×10^(-3)ng/μL和6.75×10^(-4)ng/μL。将SYBR GreenⅠ双重qPCR检测体系应用于田间样品检测,检测结果与单重PCR方法基本一致。建立的SYBR GreenⅠ双重qPCR检测体系特异性好、灵敏度高,为CLas和Xcc的检测提供了技术手段。 展开更多
关键词 柑橘黄龙病 柑橘溃疡病 病原检测 SYBR green
在线阅读 下载PDF
Construction of Even-Variable 2-Output Almost Optimal Five-Valued Spectra Boolean Functions
6
作者 SONG Chao-Fan JI Yan-Han SUN Yu-Juan 《密码学报(中英文)》 北大核心 2025年第3期714-728,共15页
Five-valued Boolean functions play an important role in the design of symmetric cryptography.While the design and properties of single-output almost optimal five-valued spectra Boolean functions have been extensively ... Five-valued Boolean functions play an important role in the design of symmetric cryptography.While the design and properties of single-output almost optimal five-valued spectra Boolean functions have been extensively studied over the past few decades,there has been limited research on the construction of almost optimal five-valued spectra vectorial Boolean functions.In this paper,we present a construction method for even-variable 2-output almost optimal five-valued spectra balanced Boolean functions,whose Walsh spectra values belong to the set{0,±2^(n/2),±2^(n/2+1)},at the same time,we discuss the existence of sufficient conditions in the construction.Additionally,this paper presents a novel construction method for balanced single-output Boolean functions with even variables featuring a special five-valued spectral structure,whose Walsh spectra values are constrained to the set{0,±2^(n/2),±3·2^(n/2)}.These functions provide new canonical examples for the study of Boolean function spectral theory. 展开更多
关键词 Boolean function Walsh transform semi-bent function five-valued function totally disjoint spectra functions
在线阅读 下载PDF
猫传染性腹膜炎病毒SYBR Green实时荧光定量PCR检测方法的建立与临床应用
7
作者 李星颖 谢梓民 +11 位作者 原耀贤 孙铭澮 江文康 赵明明 何诗 何静 赖健仪 白银山 陈胜锋 陈志胜 马骏 王丙云 《中国兽医杂志》 北大核心 2025年第3期44-49,共6页
为了提高猫传染性腹膜炎(FIP)的临床检出率,本试验根据猫传染性腹膜炎病毒(FIPV)M基因设计特异性引物,将扩增的目的基因连接到p MD19-T载体上,获得重组质粒并作为标准阳性模板,建立针对FIPV的SYBR Green实时荧光定量PCR(q PCR)检测方法... 为了提高猫传染性腹膜炎(FIP)的临床检出率,本试验根据猫传染性腹膜炎病毒(FIPV)M基因设计特异性引物,将扩增的目的基因连接到p MD19-T载体上,获得重组质粒并作为标准阳性模板,建立针对FIPV的SYBR Green实时荧光定量PCR(q PCR)检测方法,并对其特异性、敏感性、重复性和临床检出率进行验证。结果显示,本方法梯度稀释的标准品与Ct值呈良好的线性关系,R^(2)=0.999 9,扩增效率为92.4%;与其他猫常见病毒未发生交叉反应;最低检测限为3.48×10^(2) copies/μL,敏感性是普通PCR检测方法的100倍;该方法重复性好,批内和批间变异系数均小于2.4%;应用该方法对临床阳性样本的检出率为100%,阴性样本检出率为0。结果表明,本试验建立的SYBR Green q PCR检测方法特异性强、敏感性高、重复性好、临床检测效果佳,可用于FIPV的临床诊断。 展开更多
关键词 猫传染性腹膜炎病毒 M基因 SYBR green 实时荧光定量PCR(qPCR)
在线阅读 下载PDF
F亚群禽白血病病毒SYBR GreenⅠ荧光定量PCR方法的建立
8
作者 潘洪艳 李锦群 +2 位作者 李琪 袁伊琳 曹伟胜 《广东畜牧兽医科技》 2025年第2期23-29,共7页
为精准检测F亚群禽白血病病毒(ALV⁃F),该研究针对ALV⁃F流行毒株env基因设计了一对特异性引物F1/F2,建立了ALV⁃F的SYBR GreenⅠ荧光定量PCR检测方法。条件优化试验结果显示,该方法最适退火温度为64.5℃,最适引物浓度为0.4μM。利用最适... 为精准检测F亚群禽白血病病毒(ALV⁃F),该研究针对ALV⁃F流行毒株env基因设计了一对特异性引物F1/F2,建立了ALV⁃F的SYBR GreenⅠ荧光定量PCR检测方法。条件优化试验结果显示,该方法最适退火温度为64.5℃,最适引物浓度为0.4μM。利用最适反应条件建立的标准曲线方程为y=-3.303x+42.525,R2=0.997,扩增效率E=100.8%,重组质粒标准品拷贝数与Ct值具有良好的线性关系。特异性试验结果表明,该方法仅能特异性检测ALV⁃F,对ALV⁃A、ALV⁃B、ALV⁃J、ALV⁃K、禽流感病毒(AIV)、马立克病毒(MDV)、网状内皮组织增生病病毒(REV)和鸡传染性贫血病病毒(CIAV)无交叉反应;敏感试验结果表明,该方法最低检测限度为4.67×10^(2)拷贝/μL,敏感性是普通PCR的1000倍;稳定性试验结果表明,批间和批内稳定性试验的变异系数均小于2%。利用该方法、ALV p27 ELISA和普通PCR方法分别对23份七彩山鸡胚所制备的原代细胞(PEF)样品进行检测,结果显示该方法和普通PCR方法阳性检出率均为95.65%(22/23),而ALV p27 ELISA阳性检出率仅为39.13%(9/23),该方法与普通PCR总符合率为100%,与ALV p27 ELISA总符合率为43.48%;进一步利用该方法、病毒分离法(结合ALV p27 ELISA)和普通PCR方法分别对20份七彩山鸡抗凝血样品进行检测,结果显示该方法和普通PCR方法阳性检出率分别为100.00%(20/20)和75.00%(15/20),两者总符合率为75.00%,而病毒分离法阳性检出率为0.00%(0/20)。本研究建立的方法具有良好的特异性、敏感性和稳定性,能够有效检测临床样品,可以为ALV⁃F的精准检测提供技术支持。 展开更多
关键词 禽白血病 ALV⁃F SYBR greenⅠ荧光定量PCR
在线阅读 下载PDF
Is digital transformation boosting green innovation in logistics enterprises?Evidence from listed firms in China’s logistics industry
9
作者 Jun Li Xi Chen Liang Wan 《中国科学技术大学学报》 北大核心 2025年第1期18-30,17,I0001,共15页
In the era of green logistics,digital transformation has become an effective means for the logistics industry’s high-quality development.Using listed companies in China’s logistics industry from 2010 to 2021 as the ... In the era of green logistics,digital transformation has become an effective means for the logistics industry’s high-quality development.Using listed companies in China’s logistics industry from 2010 to 2021 as the research samples,this paper conducts an empirical test on the impact of the digital transformation of logistics enterprises on their green in-novation.Specifically,enterprise digital transformation indicators are constructed through the text analysis method,and the fixed-effects model is applied for analysis.The results indicate that the digital transformation of logistics enterprises has a significant promoting effect on their green innovation;the promoting effect of the digital transformation of logistics enterprises on green innovation is primarily achieved by easing corporate financing constraints and reducing corporate en-vironmental uncertainty;and the impact of digital transformation on green innovation is geographically heterogeneous. 展开更多
关键词 DIGITALIZATION logistics enterprises green innovation
在线阅读 下载PDF
Water-promoted green synthesis of heterocyclicβ-ketosulfides
10
作者 GU Wen ZHANG Shu-ting +2 位作者 YANG Fei ZUO Yi-wei ZHAO Zhi-gang 《化学研究与应用》 北大核心 2025年第5期1274-1287,共14页
A strategy for the green synthesis of heterocyclicβ-ketosulfides via nucleophilic substitution ofα-halogenated ketone with het-eroaryl thiols in water media is presented.Compared with the available literature report... A strategy for the green synthesis of heterocyclicβ-ketosulfides via nucleophilic substitution ofα-halogenated ketone with het-eroaryl thiols in water media is presented.Compared with the available literature reports,this new method had the advantages of base-free,additives-free,simple operation,mild condition,greenness,high efficiency,tolerance of a broad scope of substrates.Furth-more,the reaction could easily be scaled up in gram scale and the products also could easily transformed to other useful organic compounds.Mechanism investigation indicated that the tautomerism of pyrimidine-2-thiol to pyrimidine-2(1H)-thione and the hy-drogen bonds played important roles in the reaction. 展开更多
关键词 green synthesis water media heterocyclicβ-ketosulfides base-free
在线阅读 下载PDF
Synthesis and Coloring Properties of A Novel Garnet-type Green Ceramic Pigment Y_(3)Ga_(3)MgSiO_(12)∶Cr^(3+)
11
作者 YANG Sihan ZHANG Qian +4 位作者 ZHAO Chuxin LIU Danhe GONG Xinjiao CHEN Yufei WANG Xuejiao 《发光学报》 北大核心 2025年第4期704-712,共9页
Novel green ceramic pigments Y_(3)Ga_(3)MgSiO_(12)∶xCr^(3+)(x=0−0.2)were successfully synthesized via the conventional solid-state approach.The properties of the pigments were studied by XRD,FE-SEM,UV-Vis spectroscop... Novel green ceramic pigments Y_(3)Ga_(3)MgSiO_(12)∶xCr^(3+)(x=0−0.2)were successfully synthesized via the conventional solid-state approach.The properties of the pigments were studied by XRD,FE-SEM,UV-Vis spectroscopy,XPS,and chromaticity analysis.The findings reveal that the trivalent chromium ions occupy the[Ga1O6]octahedral sites within the garnet lattice,and the relatively weak crystal field environment provided by the matrix endows the pigments with green characteristics.The samples prepared by calcination at 1400℃exhibit the most excellent performance in terms of phase purity,morphology,and color properties.The chromaticity values for the representative sample Y_(3)Ga_(3)MgSiO_(12)∶0.05Cr^(3+)are L^(*)=81.16,a^(*)=−12.53,and b^(*)=12.71,and the color remains stable after the stability test.Moreover,when glazed with Y_(3)Ga_(3)MgSiO_(12)∶xCr^(3+)(x=0−0.2)pigments,the smooth glaze surfaces exhibit vivid and saturated green tones,demonstrating their remarkable coloring capabilities and promising potential as a practical pigment for medium-temperature applications.This research underscores the vast application prospects of Y_(3)Ga_(3)MgSiO_(12)∶Cr^(3+)as an innovative green ceramic pigment. 展开更多
关键词 GARNET green pigments Cr^(3+)doping
在线阅读 下载PDF
Effective detection of malachite green by folic acid stabilized silver nanoclusters
12
作者 CAI Zhifeng WU Ying +3 位作者 LI Ya'nan MENG Guiyu MIAO Tianyu ZHANG Yihao 《无机化学学报》 北大核心 2025年第5期983-993,共11页
Herein,a one-pot chemical reduction method was reported to prepare folic acid(FA)-stabilized silver nanoclusters(FA@Ag NCs),in which FA,hydrazine hydrate,and silver nitrate were used as capping agent,reducing agent,an... Herein,a one-pot chemical reduction method was reported to prepare folic acid(FA)-stabilized silver nanoclusters(FA@Ag NCs),in which FA,hydrazine hydrate,and silver nitrate were used as capping agent,reducing agent,and precursor,respectively.Several technologies were employed to investigate the structures and optical properties of FA@Ag NCs,including transmission electron microscopy(TEM),X-ray photoelectron spectrometer(XPS),Fourier transform infrared spectrometer(FTIR),X-ray diffractometer(XRD),fluorescence spectrometer,and ultraviolet visible absorption spectrometer.FA@Ag NCs were suggested to be highly dispersed and spherical with a size of around 2.8 nm.Moreover,the maximum excitation and emission wavelengths of FA@Ag NCs were 370 and 447 nm,respectively.Under the optimal detection conditions,FA@Ag NCs could be used to effectively detect malachite green with the linear detection range of 0.5-200μmol·L^(-1).The detection limit was 0.084μmol·L^(-1).The fluorescence-quenching mechanism was ascribed to the static quenching.The detection system based on FA@AgNCs was successfully used for the detection of malachite green in actual samples with good accuracy and reproducibility. 展开更多
关键词 fluorescence probe silver nanoclusters folic acid malachite green static quenching
在线阅读 下载PDF
Public-Key Function-Private Inner-Product Predicate Encryption from Pairings
13
作者 WAN Ming WANG Geng GU Da-Wu 《密码学报(中英文)》 北大核心 2025年第1期227-246,共20页
This study constructs a function-private inner-product predicate encryption(FP-IPPE)and achieves standard enhanced function privacy.The enhanced function privacy guarantees that a predicate secret key skf reveals noth... This study constructs a function-private inner-product predicate encryption(FP-IPPE)and achieves standard enhanced function privacy.The enhanced function privacy guarantees that a predicate secret key skf reveals nothing about the predicate f,as long as f is drawn from an evasive distribution with sufficient entropy.The proposed scheme extends the group-based public-key function-private predicate encryption(FP-PE)for“small superset predicates”proposed by Bartusek et al.(Asiacrypt 19),to the setting of inner-product predicates.This is the first construction of public-key FP-PE with enhanced function privacy security beyond the equality predicates,which is previously proposed by Boneh et al.(CRYPTO 13).The proposed construction relies on bilinear groups,and the security is proved in the generic bilinear group model. 展开更多
关键词 predicate encryption function privacy inner product generic group model
在线阅读 下载PDF
Leverage or crowd out:the National Independent Innovation Demonstration Zone policies and green innovation efficiency of enterprises
14
作者 Haonan He Jiaxin Sun +2 位作者 Richard Samuel Freeman Dehong Li Shanyong Wang 《中国科学技术大学学报》 北大核心 2025年第1期32-44,31,I0001,共15页
The National Independent Innovation Demonstration Zone has been assigned the unique mission of demonstrating and leading national innovation and playing a key supportive role in enhancing green innovation.Based on the... The National Independent Innovation Demonstration Zone has been assigned the unique mission of demonstrating and leading national innovation and playing a key supportive role in enhancing green innovation.Based on the sample data of A-share listed companies in China from 2007 to 2021,we apply a multi-period difference-in-differences model to analyze whether the implementation of the National Independent Innovation Demonstration Zone policies plays a leverage effect or a crowd out effect on the green innovation efficiency of enterprises and systematically test the regulatory mechanism of government grants and media attention in the process of this influence.The empirical results show that the imple-mentation of the National Independent Innovation Demonstration Zone policies has a positive impact on the green innovation efficiency of enterprises and that the green innovation induced by this reform is not the leverage effect of additional R&D investment on the basis of the existing innovation activities of enterprises but rather the result of the reallocation of resources to crowd out existing non-green innovation.It is further found that government grants and media attention positively moderate the positive driving effect of National Independent Innovation Demonstration Zone policies on the green innovation efficiency of enterprises. 展开更多
关键词 National Independent Innovation Demonstration Zone policies green innovation efficiency leverage effect crowd out effect
在线阅读 下载PDF
上覆碳酸盐岩红土层对磷石膏水分运移的影响及Green-Ampt模型模拟
15
作者 陈浩 刘冬冬 +2 位作者 冯娜 杨娅 唐俊杰 《水土保持通报》 北大核心 2025年第1期225-234,共10页
[目的]分析上覆碳酸盐岩红土对磷石膏入渗特性的影响机制,为西南喀斯特地区磷石膏堆场合理处置及利用提供科学依据。[方法]通过室内扁平土柱入渗试验研究3种磷石膏容重(1.2,1.3,1.4 g/cm^(3))和3种上覆土层厚度(0,6,12 cm)对磷石膏水分... [目的]分析上覆碳酸盐岩红土对磷石膏入渗特性的影响机制,为西南喀斯特地区磷石膏堆场合理处置及利用提供科学依据。[方法]通过室内扁平土柱入渗试验研究3种磷石膏容重(1.2,1.3,1.4 g/cm^(3))和3种上覆土层厚度(0,6,12 cm)对磷石膏水分入渗过程的影响,并通过改进的分层型Green-Ampt模型进行入渗过程数值模拟。[结果](1)6和12 cm覆土厚度处理下水分入渗到底部的时间差异不显著(p>0.05),而在0与6 cm、0与12 cm覆土厚度处理下入渗时间差异显著(p<0.05)。覆土厚度为0 cm的初始入渗率、平均入渗率和稳定入渗率显著高于6,12 cm的初始入渗率、平均入渗率和稳定入渗率(p<0.05),稳定入渗率随覆土厚度增大而显著减小。6,12 cm覆土厚度累积入渗量差异不显著(p>0.05),其余覆土厚度之间累积入渗量差异显著(p<0.05)。(2)相同覆土厚度下,磷石膏容重对初始入渗率、平均入渗率和稳定入渗率的影响均不显著(p>0.05)。(3)湿润峰深度实测值与模拟值决定系数(R^(2))变化范围为0.951~0.995,均方根误差(RMSE)为12.174~40.856,平均绝对百分比误差(MAPE)为0.070~0.227。覆土6和12 cm时,累积入渗量实测值与模拟值决定系数(R~2)变化范围为0.963~0.999,均方根误差(RMSE)为1.471~11.201,平均绝对百分比误差(MAPE)为0.046~0.169。[结论]磷石膏覆土与未覆土的土壤水分入渗特征存在显著差异,改进的分层型Green-Ampt模型能够用于模拟上覆土层条件下磷石膏的入渗过程。 展开更多
关键词 覆土 磷石膏 水分运移 green-AMPT模型
在线阅读 下载PDF
牛副流感病毒5型SYBR Green Ⅰ荧光定量PCR检测方法的建立及应用
16
作者 尹柳祎 桑浩杰 +6 位作者 刘宇轩 王彤 郭帅 林浩 宋扬 翟景波 温树波 《中国预防兽医学报》 北大核心 2025年第4期370-375,共6页
为建立牛副流感病毒5型(BPIV5)的SYBR Green Ⅰ荧光定量PCR(qPCR)检测方法,本研究经PCR扩增BPIV5 L基因的保守片段,构建重组质粒p MD18-T-BPIV5,并经PCR、双酶切与测序鉴定正确后作为标准品,经各反应条件优化后初步建立检测BPIV5的qPCR... 为建立牛副流感病毒5型(BPIV5)的SYBR Green Ⅰ荧光定量PCR(qPCR)检测方法,本研究经PCR扩增BPIV5 L基因的保守片段,构建重组质粒p MD18-T-BPIV5,并经PCR、双酶切与测序鉴定正确后作为标准品,经各反应条件优化后初步建立检测BPIV5的qPCR方法。利用10倍倍比稀释的质粒标准品作为模板,利用优化的qPCR扩增,建立该方法的标准曲线,结果显示,重组质粒标准品的拷贝数与其Ct值呈良好的线性关系,相关系数为0.998,扩增效率为1.09。以BPIV5、牛肠道病毒(BEV)、牛病毒性腹泻病毒(BVDV)、牛诺如病毒(BNOV)、牛副流感病毒3型(BPIV3)和牛冠状病毒(BCOV)的cDNA作为模板,采用该qPCR扩增,评估该方法的特异性;以10倍倍比稀释的重组质粒标准品pMD18-T-BPIV5作为模板,利用本研究建立的qPCR方法扩增,评估该方法的敏感性;以3种不同浓度的质粒标准品作为模板,利用本研究建立的qPCR方法在同一时间和不同时间分别进行批内和批间重复性试验。结果显示,该方法仅能特异性扩增BPIV5,其他相关病毒均为阴性结果;对质粒标准品的检测限为6.43拷贝/μL;批内和批间重复性试验的变异系数均小于2%。利用该方法和已发表的qPCR方法分别检测采自内蒙古东部部分牛场的80份鼻拭子样品,结果显示,两种方法对样品的阳性检测率均为10%(8/80),阴性样品的检测率均为90%(72/80),二者的阳性符合率和总符合率均达100%。本研究建立的检测BPIV5的qPCR方法特异性较强、敏感性较高、重复性较好,可以用于临床样品的检测,为BPIV5的检测和流行病学调查提供了一种新的检测手段。 展开更多
关键词 牛副流感病毒5型 SYBR greenⅠ荧光定量PCR 敏感性
在线阅读 下载PDF
A series of iridium(Ⅲ)complexes with fluorophenyl isoquinoline ligand and low-efficiency roll-off properties:A density functional theory study
17
作者 QIN Zhengkun PAN Zicong +2 位作者 TIAN Hui ZHANG Wanyi SONG Mingxing 《无机化学学报》 北大核心 2025年第6期1235-1244,共10页
We have examined the theoretical implications of combining two main and three auxiliary ligands to form several Ir(Ⅲ)complexes featuring a transition metal as their core atom to identify some appropriate organic ligh... We have examined the theoretical implications of combining two main and three auxiliary ligands to form several Ir(Ⅲ)complexes featuring a transition metal as their core atom to identify some appropriate organic lightemitting diode(OLED)materials.By utilizing electronic structure,frontier molecular orbitals,minimum single-line absorption,triplet excited states,and emission spectral data derived from the density functional theory,the usefulness of these Ir(Ⅲ)complexes,including(piq)_(2)Ir(acac),(piq)_(2)Ir(tmd),(piq)_(2)Ir(tpip),(fpiq)_(2)Ir(acac),(fpiq)_(2)Ir(tmd),and(fpiq)_(2)Ir(tpip),in OLEDs was examined,where piq=1-phenylisoquinoline,fpiq=1-(4-fluorophenyl)isoquinoline,acac=(3Z)-4-hydroxypent-3-en-2-one,tmd=(4Z)-5-hydroxy-2,2,6,6-tetramethylhept-4-en-3-one,and tpip=tetraphenylimido-diphosphonate.These complexes all have low-efficiency roll-off properties,especially(fpiq)_(2)Ir(tpip).Some researchers have successfully synthesized complexes extremely similar to(piq)_(2)Ir(acac)through the Suzuki-Miyaura coupling reaction. 展开更多
关键词 density functional theory organic light-emitting diodes luminescent materials Ir(Ⅲ)complexes
在线阅读 下载PDF
rTMS Improves Cognitive Function and Brain Network Connectivity in Patients With Alzheimer’s Disease
18
作者 XU Gui-Zhi LIU Lin +4 位作者 GUO Miao-Miao WANG Tian GAO Jiao-Jiao JI Yong WANG Pan 《生物化学与生物物理进展》 北大核心 2025年第8期2131-2145,共15页
Objective Repetitive transcranial magnetic stimulation(rTMS)has demonstrated efficacy in enhancing neurocognitive performance in Alzheimer’s disease(AD),but the neurobiological mechanisms linking synaptic pathology,n... Objective Repetitive transcranial magnetic stimulation(rTMS)has demonstrated efficacy in enhancing neurocognitive performance in Alzheimer’s disease(AD),but the neurobiological mechanisms linking synaptic pathology,neural oscillatory dynamics,and brain network reorganization remain unclear.This investigation seeks to systematically evaluate the therapeutic potential of rTMS as a non-invasive neuromodulatory intervention through a multimodal framework integrating clinical assessments,molecular profiling,and neurophysiological monitoring.Methods In this prospective double-blind trial,12 AD patients underwent a 14-day protocol of 20 Hz rTMS,with comprehensive multimodal assessments performed pre-and postintervention.Cognitive functioning was quantified using the mini-mental state examination(MMSE)and Montreal cognitive assessment(MOCA),while daily living capacities and neuropsychiatric profiles were respectively evaluated through the activities of daily living(ADL)scale and combined neuropsychiatric inventory(NPI)-Hamilton depression rating scale(HAMD).Peripheral blood biomarkers,specifically Aβ1-40 and phosphorylated tau(p-tau181),were analyzed to investigate the effects of rTMS on molecular metabolism.Spectral power analysis was employed to investigate rTMS-induced modulations of neural rhythms in AD patients,while brain network analyses incorporating topological properties were conducted to examine stimulus-driven network reorganization.Furthermore,systematic assessment of correlations between cognitive scale scores,blood biomarkers,and network characteristics was performed to elucidate cross-modal therapeutic associations.Results Clinically,MMSE and MOCA scores improved significantly(P<0.05).Biomarker showed that Aβ1-40 level increased(P<0.05),contrasting with p-tau181 reduction.Moreover,the levels of Aβ1-40 were positively correlated with MMSE and MOCA scores.Post-intervention analyses revealed significant modulations in oscillatory power,characterized by pronounced reductions in delta(P<0.05)and theta bands(P<0.05),while concurrent enhancements were observed in alpha,beta,and gamma band activities(all P<0.05).Network analysis revealed frequency-specific reorganization:clustering coefficients were significantly decreased in delta,theta,and alpha bands(P<0.05),while global efficiency improvement was exclusively detected in the delta band(P<0.05).The alpha band demonstrated concurrent increases in average nodal degree(P<0.05)and characteristic path length reduction(P<0.05).Further research findings indicate that the changes in the clinical scale HAMD scores before and after rTMS stimulation are negatively correlated with the changes in the blood biomarkers Aβ1-40 and p-tau181.Additionally,the changes in the clinical scales MMSE and MoCA scores were negatively correlated with the changes in the node degree of the alpha frequency band and negatively correlated with the clustering coefficient of the delta frequency band.However,the changes in MMSE scores are positively correlated with the changes in global efficiency of both the delta and alpha frequency bands.Conclusion 20 Hz rTMS targeting dorsolateral prefrontal cortex(DLPFC)significantly improves cognitive function and enhances the metabolic clearance ofβ-amyloid and tau proteins in AD patients.This neurotherapeutic effect is mechanistically associated with rTMS-mediated frequency-selective neuromodulation,which enhances the connectivity of oscillatory networks through improved neuronal synchronization and optimized topological organization of functional brain networks.These findings not only support the efficacy of rTMS as an adjunctive therapy for AD but also underscore the importance of employing multiple assessment methods—including clinical scales,blood biomarkers,and EEG——in understanding and monitoring the progression of AD.This research provides a significant theoretical foundation and empirical evidence for further exploration of rTMS applications in AD treatment. 展开更多
关键词 transcranial magnetic stimulation Alzheimer’s disease power spectral density ELECTROENCEPHALOGRAM brain functional network
在线阅读 下载PDF
Generalized multiple-mode prolate spheroidal wave functions multi-carrier waveform with index modulation
19
作者 XU Zhichao LU Faping +5 位作者 ZHANG Lifan YANG Dongkai LIU Chuanhui KANG Jiafang AN Qi ZHANG Zhilin 《Journal of Systems Engineering and Electronics》 2025年第2期311-322,共12页
A generalized multiple-mode prolate spherical wave functions (PSWFs) multi-carrier with index modulation approach is proposed with the purpose of improving the spectral efficiency of PSWFs multi-carrier systems. The p... A generalized multiple-mode prolate spherical wave functions (PSWFs) multi-carrier with index modulation approach is proposed with the purpose of improving the spectral efficiency of PSWFs multi-carrier systems. The proposed method,based on the optimized multi-index modulation, does not limit the number of signals in the first and second constellations and abandons the concept of limiting the number of signals in different constellations. It successfully increases the spectrum efficiency of the system while expanding the number of modulation symbol combinations and the index dimension of PSWFs signals. The proposed method outperforms the PSWFs multi-carrier index modulation method based on optimized multiple indexes in terms of spectrum efficiency, but at the expense of system computational complexity and bit error performance. For example, with n=10 subcarriers and a bit error rate of 1×10^(-5),spectral efficiency can be raised by roughly 12.4%. 展开更多
关键词 prolate spherical wave function(PSWF) generalized multiple-mode index modulation spectral efficiency.
在线阅读 下载PDF
The Green's function of the harmonic horizontal force applied at the interior of the saturated half-space soil 被引量:10
20
作者 陆建飞 王建华 沈为平 《地震学报》 CSCD 北大核心 2001年第2期185-191,共7页
By using integral transform methods, the Green(s functions of horizontal harmonic force applied at the interior of the saturated half-space soil are obtained in the paper. The general solutions of the Biot dynamic equ... By using integral transform methods, the Green(s functions of horizontal harmonic force applied at the interior of the saturated half-space soil are obtained in the paper. The general solutions of the Biot dynamic equations in frequency domain are established through the use of Hankel integral transforms technique. Utilizing the above- mentioned general solutions, and the boundary conditions of the surface of the half-space and the continuous conditions at the plane of the horizontal force, the solutions of the boundary value problem can be determined. By the numerical inverse Hankel transforms method, the Green(s functions of the harmonic horizontal force are obtainable. The degenerate case of the results deduced from this paper agrees well with the known results. Two numerical examples are given in the paper. 展开更多
关键词 BIOT理论 HANKEL变换 green函数 非轴对称 非饱和土 简谐水平力
在线阅读 下载PDF
上一页 1 2 250 下一页 到第
使用帮助 返回顶部