期刊文献+
共找到4,485篇文章
< 1 2 225 >
每页显示 20 50 100
Euler’s First-Order Explicit Method–Peridynamic Differential Operator for Solving Population Balance Equations of the Crystallization Process
1
作者 Chunlei Ruan Cengceng Dong +2 位作者 Kunfeng Liang Zhijun Liu Xinru Bao 《Computer Modeling in Engineering & Sciences》 SCIE EI 2024年第3期3033-3049,共17页
Using Euler’s first-order explicit(EE)method and the peridynamic differential operator(PDDO)to discretize the time and internal crystal-size derivatives,respectively,the Euler’s first-order explicit method–peridyna... Using Euler’s first-order explicit(EE)method and the peridynamic differential operator(PDDO)to discretize the time and internal crystal-size derivatives,respectively,the Euler’s first-order explicit method–peridynamic differential operator(EE–PDDO)was obtained for solving the one-dimensional population balance equation in crystallization.Four different conditions during crystallization were studied:size-independent growth,sizedependent growth in a batch process,nucleation and size-independent growth,and nucleation and size-dependent growth in a continuous process.The high accuracy of the EE–PDDO method was confirmed by comparing it with the numerical results obtained using the second-order upwind and HR-van methods.The method is characterized by non-oscillation and high accuracy,especially in the discontinuous and sharp crystal size distribution.The stability of the EE–PDDO method,choice of weight function in the PDDO method,and optimal time step are also discussed. 展开更多
关键词 Population balance equation CRYsTALLIZATION peridynamic differential operator Euler’s first-order explicit method
下载PDF
Energy Stable Nodal DG Methods for Maxwell’s Equations of Mixed-Order Form in Nonlinear Optical Media
2
作者 Maohui Lyu Vrushali A.Bokil +1 位作者 Yingda Cheng Fengyan Li 《Communications on Applied Mathematics and Computation》 EI 2024年第1期30-63,共34页
In this work,we develop energy stable numerical methods to simulate electromagnetic waves propagating in optical media where the media responses include the linear Lorentz dispersion,the instantaneous nonlinear cubic ... In this work,we develop energy stable numerical methods to simulate electromagnetic waves propagating in optical media where the media responses include the linear Lorentz dispersion,the instantaneous nonlinear cubic Kerr response,and the nonlinear delayed Raman molecular vibrational response.Unlike the first-order PDE-ODE governing equations considered previously in Bokil et al.(J Comput Phys 350:420–452,2017)and Lyu et al.(J Sci Comput 89:1–42,2021),a model of mixed-order form is adopted here that consists of the first-order PDE part for Maxwell’s equations coupled with the second-order ODE part(i.e.,the auxiliary differential equations)modeling the linear and nonlinear dispersion in the material.The main contribution is a new numerical strategy to treat the Kerr and Raman nonlinearities to achieve provable energy stability property within a second-order temporal discretization.A nodal discontinuous Galerkin(DG)method is further applied in space for efficiently handling nonlinear terms at the algebraic level,while preserving the energy stability and achieving high-order accuracy.Indeed with d_(E)as the number of the components of the electric field,only a d_(E)×d_(E)nonlinear algebraic system needs to be solved at each interpolation node,and more importantly,all these small nonlinear systems are completely decoupled over one time step,rendering very high parallel efficiency.We evaluate the proposed schemes by comparing them with the methods in Bokil et al.(2017)and Lyu et al.(2021)(implemented in nodal form)regarding the accuracy,computational efficiency,and energy stability,by a parallel scalability study,and also through the simulations of the soliton-like wave propagation in one dimension,as well as the spatial-soliton propagation and two-beam interactions modeled by the two-dimensional transverse electric(TE)mode of the equations. 展开更多
关键词 Maxwell’s equations Kerr and Raman Discontinuous Galerkin method Energy stability
下载PDF
The forecasting efficiency under different selected regions by Pattern Informatics Method and seismic potential estimation in the North-South Seismic Zone
3
作者 Weixi Tian Yongxian Zhang 《Earthquake Science》 2024年第4期368-382,共15页
In 2022,four earthquakes with M_(S)≥6.0 including the Menyuan M_(S)6.9 and Luding M_(S)6.8 earthquakes occurred in the North-South Seismic Zone(NSSZ),which demonstrated high and strong seismicity.Pattern Informatics(... In 2022,four earthquakes with M_(S)≥6.0 including the Menyuan M_(S)6.9 and Luding M_(S)6.8 earthquakes occurred in the North-South Seismic Zone(NSSZ),which demonstrated high and strong seismicity.Pattern Informatics(PI)method,as an effective long and medium term earthquake forecasting method,has been applied to the strong earthquake forecasting in Chinese mainland and results have shown the positive performance.The earthquake catalog with magnitude above M_(S)3.0 since 1970 provided by China Earthquake Networks Center was employed in this study and the Receiver Operating Characteristic(ROC)method was applied to test the forecasting efficiency of the PI method in each selected region related to the North-South Seismic Zone systematically.Based on this,we selected the area with the best ROC testing result and analyzed the evolution process of the PI hotspot map reflecting the small seismic activity pattern prior to the Menyuan M_(S)6.9 and Luding M_(S)6.8 earthquakes.A“forward”forecast for the area was carried out to assess seismic risk.The study shows the following.1)PI forecasting has higher forecasting efficiency in the selected study region where the difference of seismicity in any place of the region is smaller.2)In areas with smaller differences of seismicity,the activity pattern of small earthquakes prior to the Menyuan M_(S)6.9 and Luding M_(S)6.8 earthquakes can be obtained by analyzing the spatio-temporal evolution process of the PI hotspot map.3)The hotspot evolution in and around the southern Tazang fault in the study area is similar to that prior to the strong earthquakes,which suggests the possible seismic hazard in the future.This study could provide some ideas to the seismic hazard assessment in other regions with high seismicity,such as Japan,Californi,Turkey,and Indonesia. 展开更多
关键词 Luding M_(s)6.8 and Menyuan M_(s)6.9 earthquake Pattern Informatics method North-south seismic Zone earthquake forecasting seismic activity pattern.
下载PDF
Fischer–Tropsch synthesis using Co and Co-Ru bifunctional nanocatalyst supported on carbon nanotube prepared via chemical reduction method 被引量:2
4
作者 Jafar Shariati Ali Haghtalab Amir Mosayebi 《Journal of Energy Chemistry》 SCIE EI CAS CSCD 2019年第1期9-22,共14页
We used a chemical reduction method to synthesize the catalysts of cobalt(Co) and cobalt-ruthenium(Co-Ru) bifunctional supported on carbon nanotubes(CNTs) for Fischer–Tropsch synthesis(FTS) in a fixedbed reactor. The... We used a chemical reduction method to synthesize the catalysts of cobalt(Co) and cobalt-ruthenium(Co-Ru) bifunctional supported on carbon nanotubes(CNTs) for Fischer–Tropsch synthesis(FTS) in a fixedbed reactor. These Co-Ru/CNTs catalysts were synthesized with various weight proportions of Ru/Co(0.1 to 0.4 wt%) with keeping a fixed amount of cobalt(10 wt%). Moreover, for comparison purpose, CNTs supported Co-and Co(Ru)-based catalysts at same loading as the above catalysts were prepared through impregnation method. We characterize the present catalysts through the various techniques such as Energy–dispersive X-ray(EDX), Transmission Electron Microscopy(TEM), Brunauer–Emmett–Teller(BET),Hydrogen-Temperature-Programmed Reduction(H_2-TPR), Hydrogen-Temperature-Programmed Desorption(H_2-TPD) and O_2 titration. Thus using the chemical reduction method, a narrow particle size distribution was obtained so that the small cobalt particles were confined inside the CNTs. The Co-based catalyst prepared by impregnation was compared with the Co-Ru catalysts at the same loading. The results demonstrated that the use of chemical reduction method led to decrease the average Co oxide cluster size to8.7 nm so that the reduction enhanced about 24% and stabilized an earlier time at the stream. Among the prepared catalysts, the results indicated that the Co-Ru/CNTs catalysts demonstrated high catalytic activity with the highest long-chain hydrocarbons(C_(5+)), selectivity up to 74.76%, which was higher than those we obtained by the Co-Ru/γ-Al_2O_3(61._20%), Co/CNTs(43.68%) and Co/γ-Al_2O_3(37.69%). At the same time, comparing with those catalyst synthesized by impregnation, the use of chemical reduction led to enhancement of the C_(5+) selectivity from 59.30% to 68.83% and increment in FTS rate about 11% for the Co-Ru/CNTs catalyst. 展开更多
关键词 Cobalt-ruthenium Carbon nanotubes fischer-TROPsCH sYNTHEsIs Catalyst nanoparticles Chemical reduction method
下载PDF
2021年9月16日四川泸县M_(S)6.0地震前地磁扰动异常特征分析
5
作者 王玮铭 冯志生 +3 位作者 朱培育 廖晓峰 何畅 张致伟 《地震工程学报》 北大核心 2025年第1期229-239,共11页
选取四川地区3个地磁扰动台站的观测数据,利用基于脉冲幅度法的地磁垂直强度极化方法,对2021年9月16日四川泸县M_(S)6.0地震前的地磁扰动异常演化特征进行分析。研究结果表明:(1)在中强地震前,台站的垂直强度极化值和超阈值极化值频次... 选取四川地区3个地磁扰动台站的观测数据,利用基于脉冲幅度法的地磁垂直强度极化方法,对2021年9月16日四川泸县M_(S)6.0地震前的地磁扰动异常演化特征进行分析。研究结果表明:(1)在中强地震前,台站的垂直强度极化值和超阈值极化值频次逐日变化均会出现高值异常,其中频次异常呈现先增强后降低,再增强-降低的形态;(2)发生异常变化的多个台站距离震中300 km范围内,时间上属准同步变化;(3)地震多发生在异常出现的一个月后,频次异常值往往是研究时段的最高值;(4)机理上,这些异常演化形态和特征是由岩石的破裂特性决定的,一定程度上反映了地震的孕育过程;(5)这种震前的地磁扰动异常与外源场无关。 展开更多
关键词 地磁扰动 地磁垂直强度极化法 泸县M_(s)6.0地震 异常特征
下载PDF
^(125)I的俄歇电子和氚的β射线细胞S值及DNA损伤模拟研究
6
作者 沈江燕 朱坤 +3 位作者 李清 张德颂 李君利 闫聪冲 《原子能科学技术》 北大核心 2025年第2期478-486,共9页
氚的辐射生物效应一直是研究热点,特别是在福岛核电站排放核废水后成为公众关注的焦点。氚极易进入人体并参与机体代谢活动,衰变放出的β射线对人体具有极大的危害,而靶向放射治疗则利用摄入的俄歇电子发射体能够进入癌细胞,并放出俄歇... 氚的辐射生物效应一直是研究热点,特别是在福岛核电站排放核废水后成为公众关注的焦点。氚极易进入人体并参与机体代谢活动,衰变放出的β射线对人体具有极大的危害,而靶向放射治疗则利用摄入的俄歇电子发射体能够进入癌细胞,并放出俄歇电子造成DNA严重损伤这一特性,达到有效杀死癌细胞的目的。为探究β射线在微纳米尺度的辐射生物效应,本研究利用清华大学研发的纳剂量学程序NASIC模拟计算了^(125)I和氚在不同尺度细胞内的细胞S值以及造成的DNA双链断裂(DSB)产额,深入探讨了其DNA损伤机制。结果表明,由于研究方法和粒子截面的不同,细胞S值的计算结果存在偏差,尤其对于S(N←Cy),相对偏差可达26.35%。此外,相较于^(125)I或氚均匀分布在细胞核内,与DNA结合时造成的DSB产额显著增加:^(125)I结合到DNA时的DSB产额是均匀分布时的2倍;而氚结合到DNA中使得DSB产额从1.31×10^(-11)Gy^(-1)·Da^(-1)增加至1.46×10^(-11)Gy^(-1)·Da^(-1)。本研究深入探究了微纳米尺度下放射性核素的损伤作用效应,为精确医疗和环境放射性污染风险评估提供重要的理论基础。 展开更多
关键词 放射性核素 ^(125)I 俄歇电子 氚β射线 细胞s DNA损伤 蒙特卡罗方法
下载PDF
Research on the Application of Montessori Education Method in Cognitive Training of Patients with Alzheimer’s Disease
7
作者 Wei Wang Faridah Mohd Said 《Journal of Clinical and Nursing Research》 2024年第5期336-341,共6页
Objective:To study the application of the Montessori education method in cognitive training in patients with Alzheimer’s disease(AD).Methods:40 cases of senile dementia patients who were admitted to our hospital from... Objective:To study the application of the Montessori education method in cognitive training in patients with Alzheimer’s disease(AD).Methods:40 cases of senile dementia patients who were admitted to our hospital from January 2022 to January 2023 were selected and randomly divided into an intervention group and a control group according to the single and double number table method,with 20 cases in each group.The intervention group used the Montessori education method,the principle of which was to implement individualized health interventions based on the individual conditions of the patients,for a period of 6 months;the control group was given conventional treatment and nursing of the disease.The Mini-Mental State Examination(MMSE)was used to compare the effects of the two groups of patients before and after health intervention and conduct statistical analysis.Results:The score of the intervention group was higher than that of the control group,and there was a statistical difference between the two(P<0.05).Conclusion:Implementing the Montessori education method for diagnosed Alzheimer’s patients can effectively improve their cognitive function and delay the progress of further dementia. 展开更多
关键词 Montessori education method Alzheimer’s disease Cognitive training
下载PDF
Solid Waste Management:A MADM Approach Using Fuzzy Parameterized Possibility Single-Valued Neutrosophic Hypersoft Expert Settings
8
作者 Tmader Alballa Muhammad Ihsan +2 位作者 Atiqe Ur Rahman Noorah Ayed Alsorayea Hamiden Abd El-Wahed Khalifa 《Computer Modeling in Engineering & Sciences》 SCIE EI 2025年第1期531-553,共23页
The dramatic rise in the number of people living in cities has made many environmental and social problems worse.The search for a productive method for disposing of solid waste is the most notable of these problems.Ma... The dramatic rise in the number of people living in cities has made many environmental and social problems worse.The search for a productive method for disposing of solid waste is the most notable of these problems.Many scholars have referred to it as a fuzzy multi-attribute or multi-criteria decision-making problem using various fuzzy set-like approaches because of the inclusion of criteria and anticipated ambiguity.The goal of the current study is to use an innovative methodology to address the expected uncertainties in the problem of solid waste site selection.The characteristics(or sub-attributes)that decision-makers select and the degree of approximation they accept for various options can both be indicators of these uncertainties.To tackle these problems,a novel mathematical structure known as the fuzzy parameterized possibility single valued neutrosophic hypersoft expert set(ρˆ-set),which is initially described,is integrated with a modified version of Sanchez’s method.Following this,an intelligent algorithm is suggested.The steps of the suggested algorithm are explained with an example that explains itself.The compatibility of solid waste management sites and systems is discussed,and rankings are established along with detailed justifications for their viability.This study’s strengths lie in its application of fuzzy parameterization and possibility grading to effectively handle the uncertainties embodied in the parameters’nature and alternative approximations,respectively.It uses specific mathematical formulations to compute the fuzzy parameterized degrees and possibility grades that are missing from the prior literature.It is simpler for the decisionmakers to look at each option separately because the decision is uncertain.Comparing the computed results,it is discovered that they are consistent and dependable because of their preferred properties. 展开更多
关键词 Hypersoft expert set sanchez’s method decision making optimization solid waste management possibility grade fuzzy parameterization
下载PDF
Effects of King’s Theory of Goal Attainment Combined with Teach-Back Method on Improving Patients’ Standardization Rate of Eye Drop Use
9
作者 Qiuying Huang Guilian Jie Xiaohong Liu 《Journal of Clinical and Nursing Research》 2024年第12期22-27,共6页
Objective:To explore the effect of King’s Theory of Goal Attainment combined with teach-back method on improving the standardization rate of eye drop use in patients.Methods:A total of 200 patients who used more than... Objective:To explore the effect of King’s Theory of Goal Attainment combined with teach-back method on improving the standardization rate of eye drop use in patients.Methods:A total of 200 patients who used more than two types of eye drops in the Department of Ophthalmology of our hospital were selected as the research subjects,and were randomly divided into an observation group and a control group.The control group was given routine health education,while the observation group was given King’s Theory of Goal Attainment combined with teach-back method on the basis of the control group.The standardization rate of eye drop use,knowledge awareness rate,and nursing satisfaction were compared between the two groups before and after the intervention.Results:After the intervention,the standardization rate of eye drop use,the awareness rate of eye drop knowledge,and the nursing satisfaction of the observation group were significantly higher than those of the control group(P<0.05).Conclusion:King’s Theory of Goal Attainment combined with teach-back method can effectively improve the standardization rate of eye drop use in patients,increase their awareness of eye drop knowledge,and improve nursing satisfaction,which is worthy of clinical application. 展开更多
关键词 King’s Theory of Goal Attainment Teach-back method Eye drops standardization rate
下载PDF
Critical care nurses and their clinical reasoning for customizing monitor alarms:a mixed-method study
10
作者 Mohamad Al Nakhal Mirna Fawaz +3 位作者 Karim Khabaz Ahmad Rayan Salam Bani Hani Mohammed ALBashtawy 《Frontiers of Nursing》 2024年第4期457-468,共12页
Objective:To explore the clinical rationale of critical care nurses for personalizing monitor alarms.One of the most crucial jobs assigned to critical care nurses is monitoring patients'physiological indicators an... Objective:To explore the clinical rationale of critical care nurses for personalizing monitor alarms.One of the most crucial jobs assigned to critical care nurses is monitoring patients'physiological indicators and carrying out the necessary associated interventions.Successful use of equipment in the nursing practice environment will be improved by a thorough understanding of the nurse's approach to alarm configuration.Methods:A mixed-method design integrating quantitative and qualitative components was used.The sample of this study recruited a convenience sample of 60 nurses who have worked in critical care areas.This study took place at Lebanese American University Medical Center Rizk Hospital,utilizing a semi-structured interview with participants.Results:The study demonstrated the high incidence of nuisance alarms and the desensitization of critical care nurses to vital ones.According to the nurses,frequent false alarms and a shortage of staff are the 2 main causes of alarm desensitization.Age was significantly associated with the perception of Smart alarms,according to the data(P=0.03).Four interconnected themes and subcategories that reflect the clinical reasoning process for alarm customization were developed as a result of the study's qualitative component:(1)unit alarm environment;(2)nursing style;(3)motivation to customize;and(4)clinical and technological customization.Conclusions:According to this study,nurses believe that alarms are valuable.However,a qualitative analysis of the experiences revealed that customization has been severely limited since the healthcare team depends on nurses to complete these tasks independently.Additionally,a staffing shortage and lack of technical training at the start of placement have also hindered customization. 展开更多
关键词 CUsTOMIZATION critical care unit equipment mixed method monitor alarm MOTIVATION nurse’s perception practice environment
下载PDF
Exploration of the Methods and Insights in the Introduction to Critique of Hegel’s Philosophy of Right
11
作者 Mingjun Gao 《Journal of Contemporary Educational Research》 2024年第12期193-200,共8页
Marx,as one of the founders of Marxism,experienced a significant transformation in his thought during the period of 1843-1844.The Introduction to Critique of Hegel’s Philosophy of Right(hereafter referred to as the I... Marx,as one of the founders of Marxism,experienced a significant transformation in his thought during the period of 1843-1844.The Introduction to Critique of Hegel’s Philosophy of Right(hereafter referred to as the Introduction)is one of Marx’s most representative works from this time.Lenin noted that this text,along with Marx’s On the Jewish Question,marks Marx’s transition from idealism and revolutionary democracy to materialism.In this renowned text,Marx offers a rational critique of the absolute authority of religion,articulates a vision for human emancipation,and envisages the possibility of free and comprehensive human development.During this intellectual shift,Marx absorbed the essence of German classical philosophy and,from a positivist perspective,began employing critical thinking and materialist expression.This enabled him to embark on a path of critique addressing both the religious and real social worlds.In the new era,systematically studying Marxist classic works allows for the exploration of their contemporary relevance.By aligning these classics with specific directions outlined in reports such as those from the 20th CPC Central Committee’s Third Plenary Session,the vitality of these works can be reinvigorated for the modern age. 展开更多
关键词 Introduction to Critique of Hegel’s Philosophy of Right Marx method
下载PDF
基于谱比法的近海地震动S-net台站场地分类研究
12
作者 王时 王想 +1 位作者 胡磊 周旭彤 《振动与冲击》 北大核心 2025年第1期90-101,共12页
近海台站往往难以获得台站场地资料,并且海域场地工程特性是海洋重大工程设计、建造和运维的基础,也是研究海域地震动场地放大的重要参数。为了解决这一问题,基于日本海沟区域的S-net台网的150个台站的强地震动数据,得到了埋置和未埋台... 近海台站往往难以获得台站场地资料,并且海域场地工程特性是海洋重大工程设计、建造和运维的基础,也是研究海域地震动场地放大的重要参数。为了解决这一问题,基于日本海沟区域的S-net台网的150个台站的强地震动数据,得到了埋置和未埋台站的H/V谱比曲线并进行了场地分类。结果表明:海域的H/V谱比曲线有较大谱比值;各个场地类别的埋置和未埋台站的H/V谱比曲线在谱比值和谱比形状存在着巨大差异;震级和震中距对长周期的H/V谱比曲线有较大影响,震源深度对H/V谱比曲线几乎没有影响。研究成果可为海域地震动模拟、海域场地效应研究和海洋工程建设等提供参考。 展开更多
关键词 近海地震动 谱比法 海域场地 场地分类 s-net
下载PDF
Effect of preparation method on halloysite supported cobalt catalysts for Fischer-Tropsch synthesis
13
作者 Sufang Chen Jinlin Li +2 位作者 Yuhua Zhang Daohong Zhang Junjiang Zhu 《Journal of Natural Gas Chemistry》 EI CAS CSCD 2012年第4期426-430,共5页
Novel cobalt Fischer-Tropsch synthesis (FTS) catalysts were prepared from natural halloysite nanotubes (HNT) by double-solvent and wet- impregnation methods, and characterized by TEM, XRD, TPR and N2 adsorption-de... Novel cobalt Fischer-Tropsch synthesis (FTS) catalysts were prepared from natural halloysite nanotubes (HNT) by double-solvent and wet- impregnation methods, and characterized by TEM, XRD, TPR and N2 adsorption-desorption. Comparing with the catalyst prepared by wet- impregnation method, the catalyst prepared by double-solvent method reduces Co3O4 particle migration and agglomeration due to size-induced effect, thus showing higher catalytic activity for Fischer-Tropsch synthesis. 展开更多
关键词 fischer-Tropsch synthesis halloysite nanotubes double-solvent method
下载PDF
2021年云南漾濞M_(S)6.4地震前波速比变化特征
14
作者 刘淑娟 木英 和重慧 《四川地震》 2025年第1期47-51,共5页
为分析2021年漾濞M_(S)6.4地震前波速比的变化特征,选取云南台网2011年1月至2021年5月的地震波震相到时数据,采用单台和达法对漾濞M_(S)6.4地震前震中110km范围内台站的波速比变化情况进行时、空综合分析。结果表明:漾濞M_(S)6.4地震前... 为分析2021年漾濞M_(S)6.4地震前波速比的变化特征,选取云南台网2011年1月至2021年5月的地震波震相到时数据,采用单台和达法对漾濞M_(S)6.4地震前震中110km范围内台站的波速比变化情况进行时、空综合分析。结果表明:漾濞M_(S)6.4地震前波速比呈现低值异常,发震前在震中110km范围内有7个台站呈现下降-回升-发震的波速比低值现象;距离震中较近的台站出现下降的时间晚于相对较远台站的,且近台下降速率较快;不同方位的波速比在震前出现不同的时间变化过程:震中东南部出现低值-发震的过程,震中西北部台站呈现低值-回升-发震的过程。 展开更多
关键词 云南漾濞M_(s)6.4地震 波速比 单台多震和达法
下载PDF
Fischer法合成2,5-二甲基吲哚的工艺研究 被引量:2
15
作者 徐小军 尤庆亮 +1 位作者 余朋高 喻宗沅 《化学与生物工程》 CAS 2013年第4期59-62,共4页
采用Fischer法,以4-甲基苯肼盐酸盐为原料,经碱中和后与丙酮反应生成4-甲基丙酮苯腙,再在ZnCl2催化下进行成环反应,合成了2,5-二甲基吲哚,收率为64.4%,经乙醇与水重结晶后纯度达99.5%。产物结构经1 HNMR、13 CNMR、MS、IR表征确认。该... 采用Fischer法,以4-甲基苯肼盐酸盐为原料,经碱中和后与丙酮反应生成4-甲基丙酮苯腙,再在ZnCl2催化下进行成环反应,合成了2,5-二甲基吲哚,收率为64.4%,经乙醇与水重结晶后纯度达99.5%。产物结构经1 HNMR、13 CNMR、MS、IR表征确认。该工艺反应步骤少、原料价廉易得,适合规模化制备。 展开更多
关键词 fischer 2 5-二甲基吲哚 合成
下载PDF
基于重排S-method的多分量辐射源信号分析方法 被引量:2
16
作者 荣海娜 张葛祥 金炜东 《西南交通大学学报》 EI CSCD 北大核心 2009年第2期195-200,共6页
为实现多分量辐射源信号的有效检测和识别,提出了基于重排S-method(RSM)的多分量辐射源信号分析方法.针对Wigner-Ville分布交叉项严重和计算复杂度高的问题,采用RSM分析密集、交叠的辐射源信号,给出了其算法的硬件实现和计算复杂度分析... 为实现多分量辐射源信号的有效检测和识别,提出了基于重排S-method(RSM)的多分量辐射源信号分析方法.针对Wigner-Ville分布交叉项严重和计算复杂度高的问题,采用RSM分析密集、交叠的辐射源信号,给出了其算法的硬件实现和计算复杂度分析.该方法能处理线性和非线性调频信号,算法简单,易于实现.复杂体制多分量辐射源信号分析的实验结果表明,该方法能有效分析多分量辐射源信号,时频分辨率高,不受交叉项干扰,具有比Wigner-Ville分布和S-method更强的噪声抑制能力. 展开更多
关键词 时频分析 辐射源信号 多分量 重排s-method
下载PDF
基于S-method的多分量雷达辐射源信号检测 被引量:2
17
作者 荣海娜 张葛祥 金炜东 《四川大学学报(工程科学版)》 EI CAS CSCD 北大核心 2009年第1期174-179,共6页
针对传统时频方法在处理多分量雷达辐射源信号时存在交叉项,不能检测各分量信号时域参数,难以适应低信噪比环境的问题,提出一种基于S-method(SM)的多分量雷达辐射源信号检测新方法。该方法首先计算信号的SM时频分布,然后在时频面的基础... 针对传统时频方法在处理多分量雷达辐射源信号时存在交叉项,不能检测各分量信号时域参数,难以适应低信噪比环境的问题,提出一种基于S-method(SM)的多分量雷达辐射源信号检测新方法。该方法首先计算信号的SM时频分布,然后在时频面的基础上检测各信号分量的瞬时频率和脉冲起止时间。实验结果表明,该方法能处理线性及非线性调频信号、时频分辨率高且不受交叉项干扰,时域检测精度大于98.60%,频域检测精度大于99.48%,信噪比降低时仍然保持强检测能力。 展开更多
关键词 辐射源信号 时频分析 多分量 信号检测 s-method
下载PDF
Fischer投影式手性碳R/S构型判断新方法 被引量:1
18
作者 秦志强 刘海林 宋俊杰 《数理医药学杂志》 2002年第3期280-281,共2页
总结出一种新的 Fischer投影式手性碳 R/S构型简便判断法 ,并用数学上排列法将手性碳原子所有 Fischer投影式全部列出 。
关键词 fischer投影式 R/s模型 判断法 医用数学
下载PDF
复杂旋光异构体的简便Fischer投影方法 被引量:3
19
作者 李秋荣 王艳艺 +1 位作者 杜亚丽 陈新 《齐齐哈尔大学学报(自然科学版)》 1999年第4期65-68,共4页
对含有2个或2个以上手性碳原子的旋光异构体的立体透视式、锯架式及纽曼式,改写成Fischer投影式时,提供了一种简便而又准确的投影方法。
关键词 旋光异构体 fischer投影 投影方法 手性碳原子
下载PDF
Comparative Analysis of Improving Effects of 12 Maize Populations with Improved S_1 Selection Method
20
作者 孙峰成 冯勇 +6 位作者 付增娟 苏二虎 张来厚 赵瑞霞 刘志雄 石海波 李美娜 《Agricultural Science & Technology》 CAS 2014年第10期1687-1692,1713,共7页
ln this study, 12 maize populations were improved with the improved S1 selection method, aiming to increase the improvement efficiency of maize popula-tions. The results showed that number of rows per spike, number of... ln this study, 12 maize populations were improved with the improved S1 selection method, aiming to increase the improvement efficiency of maize popula-tions. The results showed that number of rows per spike, number of grains per row and 100-grain weight were the three important component traits of maize yield. The highest genetic increment was found in Mengqun 2, fol owed by Mengqun 4, Mengqun 1 and other 7 maize populations. Negative genetic increment was shown in Mengqun 3 and 3 introduced foreign maize populations. Some changes were shown in spikes, plant traits and genetic diversity of maize populations. Based on our results, we concluded that Mengqun 2, Mengqun 4, Zhongzong 7, Mengqun C and Mengqun A could be directly used for the line breeding by selfing for their higher genetic increment of yield and better improvement effects of other agricultural traits. Compared with these 5 populations, the improvement potential of other maize populations was limited for their lower genetic increment. 展开更多
关键词 lmproved s1 selection method Maize population Genetic gain Comparative analysis
下载PDF
上一页 1 2 225 下一页 到第
使用帮助 返回顶部