检索结果-南通市图书馆

维普期刊数据库博看期刊

[Solid-phase extraction coupled with high performance liquid chromatography-triple quadrupole mass spectrometry for simultaneous determination of seven coumarins in water samples from drinking water treatment plants]

在线全文

学校读者我要写书评

暂无评论

Se pu = Chinese journal of chromatography 2025年第1期43卷 78-86页

作者： Wen-Mei Jiao Jing-Ming Yang Ce Xu fu-Kang Gao Lu-Yao Shen Yu-Bo yuan Zhi-Fen Guo Guang Huang School of Life Sciences and Chemical Engineering Jiangsu Second Normal University Nanjing 211200 China. School of Stomatology Nanjing Medical University Nanjing 210029 China. School of Public Health Nanjing Medical University Nanjing 211166 China. Key Laboratory of Modern Toxicology Ministry of Education School of Public Health Nanjing Medical University Nanjing 211166 China.

Chlorinated coumarins, which are as cytotoxic as highly toxic halobenzoquinones toward CHO-K1 cells, have recently been identified as disinfection byproducts in drinking water disinfection processes. Therefore, detecting coumarins in water samples collected at various stages from drinking water treatment plants helps assess the formation of chlorinated coumarins in drinking water. Hence, a simple, rapid, accurate, and sensitive method for quantifying coumarins in water samples is required. In this study, a method was developed based on solid-phase extraction coupled with high performance liquid chromatography-triple-quadrupole mass spectrometry for analyzing seven coumarins in water samples from drinking water treatment plants, including 6,7-dihydroxycoumarin, 7-hydroxycoumarin, 6-hydroxy-4-methylcoumarin, 8-chloro-7-hydroxycoumarin, coumarin, 7-chloro-6-hydroxy-4-methylcoumarin, and 3,8-dichloro-7-hydroxycoumarin. Sample pretreatment involved solid-phase extraction using HLB columns, followed by elution with water and methanol, each containing 0.25% formic acid. The extracted solution was separated via gradient elution using a Phenomenex Luna C18 column (100 mm×2.0 mm, 3 mm) with 0.1% formic acid aqueous solution and methanol as the mobile phases, with analytes detected by triple-quadrupole mass spectrometry equipped with electrospray ionization source in multiple reaction monitoring mode. The matrix effect, precision, and accuracy of the developed method were investigated using raw and treated water as matrices. Matrix effects of 0.84-1.12 were recorded for the detection of 6,7-dihydroxycoumarin, 7-hydroxycoumarin, 6-hydroxy-4-methylcoumarin, and coumarin in raw water, while values of 0.67-0.70 were recorded for 8-chloro-7-hydroxycoumarin, 7-chloro-6-hydroxy-4-methylcoumarin, and 3,8-dichloro-7-hydroxycoumarin in finished water. The three chlorinated coumarins exhibited matrix effects above 0.80 after the finished water matrix had been diluted four times. These re

关键词： coumarins disinfection byproducts drinking water high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) solid-phase extraction (SPE)

New Neural Network Response Surface Methods for Reliability Analysis

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

Chinese Journal of Aeronautics 2011年第1期24卷 25-31页

作者： ren yuan BAI Guangchen School of Jet Propulsion Beijing University of Aeronautics and Astronautics Beijing 100191 China

This article presents two new kinds of artificial neural network （ANN） response surface methods （RSMs）： the ANN RSM based on early stopping technique （ANNRSM-1）, and the ANN RSM based on regularization theory （ANNRSM-2）. The following improvements are made to the conventional ANN RSM （ANNRSM-0）： 1） by monitoring the validation error during the training process, ANNRSM-1 determines the early stopping point and the training stopping point, and the weight vector at the early stopping point, which corresponds to the ANN model with the optimal generalization, is finally returned as the training result; 2） according to the regularization theory, ANNRSM-2 modifies the conventional training performance function by adding to it the sum of squares of the network weights, so the network weights are forced to have smaller values while the training error decreases. Tests show that the performance of ANN RSM becomes much better due to the above-mentioned improvements： first, ANNRSM-1 and ANNRSM-2 approximate to the limit state function （LSF） more accurately than ANNRSM-0; second, the estimated failure probabilities given by ANNRSM-1 and ANNRSM-2 have smaller errors than that obtained by ANNRSM-0; third, compared with ANNRSM-0, ANNRSM-1 and ANNRSM-2 require much fewer data samples to achieve stable failure probability results.

关键词： neural networks response surface reliability analysis early stopping regularization

Fractal analysis on the spatial distribution of acoustic emission in the failure process of rock specimens

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 2009年第1期16卷 19-24页

作者： Rui-fu yuan yuan-hui Li Energy Science and Engineering School Henan Polytechnic University Jiaozuo 454000 China College of Resource and Civil Engineering Northeastern University Shenyang 110004 China

The spatial distribution of acoustic emission （AE） events in the failure process of several rock specimens was acquired using an advanced AE acquiring and analyzing system. The box counting method （BCM） was employed to calculate the fractal dimension （FD） of AE spatial distribution. There is a similar correlation between the fractal dimension and the load strength for different rock specimens. The fractal dimension presents a decreasing trend with the increase of load strength. For the same kind of specimens, their FD values will decrease to the level below a relatively same value when they reach failure. This value can be regarded as the critical value, which implies that the specimen will reach failure soon. The results reflect that it is possible to correlate the damage of rock with a macroscopic parameter, the FD value of AE signals. furthermore, the FD value can be also used to forecast the final failure of rock. This conclusion allows identifying or predicting the damage in rock with a great advantage over the classic theory and is very crucial for forecasting rockburst or other dynamic disasters in mines.

关键词： rockburst acoustic emission spatial distribution fractal dimension critical value damage

Online Scheduling on Two Uniform Unbounded Parallel-Batch Machines to Minimize Makespan

在线全文

学校读者我要写书评

暂无评论

Journal of the Operations Research Society of China 2019年第2期7卷 303-319页

作者： Jin-Jiang yuan Li-Li ren Ji Tian Ru-Yan fu School of Mathematics and Statistics Zhengzhou UniversityZhengzhou 450001China School of Mathematics China University of Mining and TechnologyXuzhou 221116JiangsuChina

We study an online(over time)scheduling problem on two uniform unbounded parallel-batch machines with processing speed 1 and v(0<≤1),respectively,to minimize the *** first show that no online algorithm can have a competitive ratio less than 1+αL,whereαL=(√5−1)/2≈0.618 if 0≤1/2,andαL=α2(v)is the positive root ofα^(3)+3α^(2)+(3−1/v)α−1/v=0 if1/2≤*** lower bound is still valid when all jobs have the same processing ***,we provide an online algorithm with a competitive ratio at most min{(√5+1)/2,√2/v}.When the jobs have the same processing times,we present the best possible online algorithm with a competitive ratio 1+αL.

关键词： Online scheduling Uniform parallel-batch machines Makespan Competitive ratio

A new member of the structured light family:optical spatiotemporal vortices

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

Light(Science & Applications) 2023年第10期12卷 2003-2005页

作者： fu Feng Xiaocong yuan Research Center for Humanoid Sensing Zhejiang LabHangzhou 311100China Nanophotonics Research Centre Shenzhen UniversityShenzhen 518060China

The burgeoning growth of structured light has opened up new possibilities for harnessing the spatiotemporal coupling effects in *** spatiotemporal vortices,as a subset of spatiotemporal light,have emerged as a focal point of recent research,owing to their distinctive characteristics and vast range for *** unique structured light will endow photons with a new degree of freedom,promising to revolutionize researchers’understanding of *** thorough research on optical spatiotemporal vortices will establish a solid foundation for the development of innovative physical mechanisms and advanced applications in photonics.

关键词： light subset optical

融合语义分割与模糊推理的无人机应急降落选址算法

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

计算机工程与应用 2025年第1期61卷 174-185页

作者：李迪肖敏任东谢咏昶姚远三峡大学计算机与信息学院湖北宜昌443002 三峡大学湖北省农田环境监测工程技术研究中心湖北宜昌443002

随着无人机的应用领域从娱乐摄影拓展到物流、军事和灾害响应,对于无人机的自主智能化要求也越来越高。针对无人机紧急情况下自主降落区域复杂难以保证着陆安全的问题,提出了一种实时语义分割网络与模糊推理相结合的降落选址算法(STDC-L... 详细信息

随着无人机的应用领域从娱乐摄影拓展到物流、军事和灾害响应,对于无人机的自主智能化要求也越来越高。针对无人机紧急情况下自主降落区域复杂难以保证着陆安全的问题,提出了一种实时语义分割网络与模糊推理相结合的降落选址算法(STDC-LSSNet)。考虑到潜在危险因素在航拍图像上占比小、易被错误分割的问题,提出了小目标特征提取模块(small target feature capture module,STFCM),通过计算不同尺度特征的相似性并进行权重分配,强化小目标特征的表达。考虑到安全区域与危险区域边界混淆会导致无人机降落存在巨大风险,提出了边界特征融合模块(boundary feature fusion module,BFFM),将浅层网络由拉普拉斯卷积得到的边界信息与深层网络的语义信息进行特征融合,引入注意力机制,增强边界区域特征的表达。通过对分割得到的图像进行模糊推理,从而精确识别应急降落地点。所提算法在公开数据集Semantic Drone和AeroScapes上与最先进的算法进行了广泛的对比实验,mIoU提升1.72个百分点和3.89个百分点,实时分割速度达到210 FPS,选址的速度达到58.62 ms,实现了无人机在复杂情况下的应急降落选址。

关键词：无人机自主降落实时语义分割模糊推理注意力机制

同方期刊数据库

Dilatometric Analysis of Irreversible Volume Change during Phase Transformation in Pure Iron

在线全文

学校读者我要写书评

暂无评论

Journal of Iron and Steel Research International 2016年第8期23卷 828-833页

作者： ren-jie ZHAO Jian-xun fu Yu-yuan ZHU Ye-jin YANG Yan-xin WU State Key Laboratory of Advanced Special Steel & Shanghai Key Laboratory Advanced Ferrometallurgy &School of Materials Science and Engineering Shanghai University

One assumption underlying the conventional dilatometric analysis based on the lever rule is that the volume of the specimen changes isotropically during phase transformation,which conflicts with the irreversible length change shown in actual *** contribution of this irreversible effect to the dilation data of pure iron upon heating and cooling was respectively quantified via conversion equations based on lattice parameters.A model considering the elastic strain and creep deformation was established for both the interpretation of the irreversible volume change and the discrepancy between the results measured by a dilatometer and a micrometer.

关键词： irreversible Transformation micrometer interpretation specimen lever length creep ferrite shrinkage

Floquet analysis of fundamental,subharmonic and detuned secondary instabilities of Grtler vortices

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2014年第3期57卷 555-561页

作者： ren Jie fu Song School of Aerospace Engineering Tsinghua University

Nonlinear parabolized stability equations are employed in this work to investigate the nonlinear development of the G6rtler insta- bility up to the saturation stage. The perturbed boundary layer is highly inflectional both in the normalwise and spanwise directions and receptive to the secondary instabilities. The Floquet theory is applied to solve the fundamental, subharmonic and detuned secondary instabilities. With the Gortler-vortices-distorted base flow, two classes of secondary disturbances, i.e. odd modes and even modes, are identified according to the eigenfunctions of the disturbances. These modes may result in different patterns in the late stages of the transition process. Li and Malik [ 1 ] have shown the sinuous and varicose types of breakdown originating from the odd and even modes. The current study focuses on the four most amplified modes termed the even modes I ＆ Ⅱ and odd modes I ＆ lI. Odd mode II was missing in the work of Li and Malik [1] probably due to their inviscid simplifeation. The detuned modes are confirmed to be less amplifed than the fundamental （for the odd mode I） and subharmonic modes （for even modes I ＆ II and the odd mode II）.

关键词： Goirtler vortices secondary instability Floquet theory

Coupled effect of climate change and human activities on the restoration/degradation of the Qinghai-Tibet Plateau grassland

在线全文

学校读者我要写书评

暂无评论

Journal of Geographical Sciences 2021年第9期31卷 1299-1327页

作者： yuan Qin yuan Quanzhi ren Ping Institute of Geography and Resources Science Sichuan Normal UniversityChengdu 610101China Sustainable Development Research Center of Resources and Environment of Western Sichuan Sichuan Normal UniversityChengdu 610066China Key Laboratory of Land Resources Evaluation and Monitoring in Southwest Ministry of EducationSichuan Normal UniversityChengdu 610066China

Climate change(CC)and human activities(HA)are the main reasons for the restoration/degradation of the Qinghai-Tibet Plateau(QTP)*** related studies have been conducted thus far,but the impact mechanism of CC coupled with HA on QTP remains *** summarized the two main coupling factors in recent years(specifically,in the past five years)and obtained the following conclusions.(1)CC and HA have positive and negative effects on the QTP grassland *** primarily affects grassland ecology through temperature,humidification,and extreme climate,and HA mainly affects ecosystems through primary,secondary,and tertiary industries and restoration measures.(2)CC coupled with HA affects soil,plants,animals,and fungi/*** makes the snow line rise by increasing the temperature,which expands the zone for *** also restricts HA through hydrological changes,extreme climate,and outbreak of pikas and ***,measures are implemented through HA to control and adapt to ***,the grassland ecosystem is comprehensively influenced by CC and HA.(3)The grassland ecosystem dynamically adapts to the disturbance caused by CC and HA by changing its physiological characteristics,distribution range,diet structure,community structure,and physical ***,it responds to environmental changes through desertification,poisonous weeds,rodent outbreak,release of harmful gases,and other *** work can be used as a reference for the sustainable development of the QTP grassland.

关键词： Qinghai-Tibet Plateau geochemistry soil organic carbon net primary productivity pikas pests Cordyceps sinensis