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改进的YOLOv5图书梯标检测算法
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作者 杨祥 王华彬 董明刚 《桂林理工大学学报》 CAS 北大核心 2024年第2期330-338,共9页
对于印刷行业而言,确保每本书的页码、页面正确排序是提高印刷厂生产率的重点。为了解决目前印刷厂对于图书梯标的检测存在漏检、误检的问题,提出了一种改进YOLOv5的梯标检测算法。该算法增加一个检测尺度以解决漏检问题和提高梯标的识... 对于印刷行业而言,确保每本书的页码、页面正确排序是提高印刷厂生产率的重点。为了解决目前印刷厂对于图书梯标的检测存在漏检、误检的问题,提出了一种改进YOLOv5的梯标检测算法。该算法增加一个检测尺度以解决漏检问题和提高梯标的识别精度,将主干网络中的C3数量减少,使用深度可分离卷积替代颈部网络中的部分卷积,在能够保证精度稳定的同时降低模型的参数量和计算量;使用SPConv替换Resunit结构里的Conv,形成SPConv-C3结构,SPConv-C3结构不仅能够降低模型的参数量,还能提升网络对图书梯标的检测精度;根据深度可分离卷积和SPConv-C3结构设计特征融合网络结构,能够大幅度提升网络模型的特征融合能力。将所改进的检测算法在自建数据集上进行验证,结果表明,改进后的算法Pm,A@0.5∶0.95达到了64.7%,比原YOLOv5s提高7.5百分点,参数量下降了3.16%,能够满足实际需求。 展开更多
关键词 YOLOv5 梯标检测 检测 基于拆分的卷积
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书籍装订中基于相位相关性的自适应梯标检测方法 被引量:2
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作者 盛国 舒新文 《包装工程》 CAS 北大核心 2018年第19期14-17,共4页
目的针对传统人工检查书籍配帖是否合格的方法带来的劳动强度过大,且容易出错等问题,提出一种基于相位相关性的自适应梯标检测方法。方法通过相位相关配准技术,利用CCD摄像机采集到梯标视频帧,计算其与模板梯标的相位相关性,并进行2帧... 目的针对传统人工检查书籍配帖是否合格的方法带来的劳动强度过大,且容易出错等问题,提出一种基于相位相关性的自适应梯标检测方法。方法通过相位相关配准技术,利用CCD摄像机采集到梯标视频帧,计算其与模板梯标的相位相关性,并进行2帧图像的配准,然后对2帧图像的帧差进行分析,从而判断配帖是否出错。结果实验结果显示,文中提出的方法可以减少合格配帖的误检率,还可以对不合格的配帖进行检测。结论文中所提出的方法可以提高配帖梯标检测的鲁棒性。 展开更多
关键词 梯标 检测 配帖 相位相关性
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书籍装订中梯标在线检测系统的开发 被引量:2
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作者 王梅 彭湘敏 《包装工程》 CAS CSCD 北大核心 2016年第7期171-174,共4页
目的书籍装订中利用梯标进行配帖质量的检测,一般是配帖完成后通过目测来判断配帖是否合格,工作量大且受主观因素的影响,文中旨在开发一种检测配帖质量的在线检测系统。方法通过电荷耦合器件(CCD)采集配帖完成后的梯标图像,应用机器视... 目的书籍装订中利用梯标进行配帖质量的检测,一般是配帖完成后通过目测来判断配帖是否合格,工作量大且受主观因素的影响,文中旨在开发一种检测配帖质量的在线检测系统。方法通过电荷耦合器件(CCD)采集配帖完成后的梯标图像,应用机器视觉技术,利用Matlab高级程序语言实现梯标图像的识别。结果通过将标准梯标图像与实际采集梯标图像进行比对,利用有效的识别算法,能够高效地对配帖的质量进行判断。结论该识别算法适用性强,可应用于多种类型的梯标图像的检测。 展开更多
关键词 梯标 在线检测系统 机器视觉 图像识别
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HYBRID MULTI-OBJECTIVE GRADIENT ALGORITHM FOR INVERSE PLANNING OF IMRT
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作者 李国丽 盛大宁 +3 位作者 王俊椋 景佳 王超 闫冰 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI 2010年第1期97-101,共5页
The intelligent optimization of a multi-objective evolutionary algorithm is combined with a gradient algorithm. The hybrid multi-objective gradient algorithm is framed by the real number. Test functions are used to an... The intelligent optimization of a multi-objective evolutionary algorithm is combined with a gradient algorithm. The hybrid multi-objective gradient algorithm is framed by the real number. Test functions are used to analyze the efficiency of the algorithm. In the simulation case of the water phantom, the algorithm is applied to an inverse planning process of intensity modulated radiation treatment (IMRT). The objective functions of planning target volume (PTV) and normal tissue (NT) are based on the average dose distribution. The obtained intensity profile shows that the hybrid multi-objective gradient algorithm saves the computational time and has good accuracy, thus meeting the requirements of practical applications. 展开更多
关键词 gradient methods inverse planning multi-objective optimization hybrid gradient algorithm
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Full tensor gravity gradiometry data inversion:Performance analysis of parallel computing algorithms 被引量:2
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作者 侯振隆 魏晓辉 +1 位作者 黄大年 孙煦 《Applied Geophysics》 SCIE CSCD 2015年第3期292-302,465,共12页
We apply reweighted inversion focusing to full tensor gravity gradiometry data using message-passing interface (MPI) and compute unified device architecture (CUDA) parallel computing algorithms, and then combine M... We apply reweighted inversion focusing to full tensor gravity gradiometry data using message-passing interface (MPI) and compute unified device architecture (CUDA) parallel computing algorithms, and then combine MPI with CUDA to formulate a hybrid algorithm. Parallel computing performance metrics are introduced to analyze and compare the performance of the algorithms. We summarize the rules for the performance evaluation of parallel algorithms. We use model and real data from the Vinton salt dome to test the algorithms. We find good match between model efficiency and feasibility of parallel computing gravity gradiometry data. and real density data, and verify the high algorithms in the inversion of full tensor 展开更多
关键词 MPI CUDA performance metrics full tensor gravity gradiometry density inversion
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Dating of the topmost terrace in the Jingxian Basin,Anhui Province:an indication of the establishment of the Qingyijiang River 被引量:2
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作者 HU Chun-sheng HU Chen-qi +3 位作者 LIU Shao-chen XU Guang-lai WU Li YANG Li-hui 《Journal of Mountain Science》 SCIE CSCD 2017年第3期549-557,共9页
On the northern fringe of Mt. Huangshan, many fiver terraces are developed at the junction between mountains and plains. The fiver terraces are most typical in the Jingxian Basin, Anhui Province, where the Qingyijiang... On the northern fringe of Mt. Huangshan, many fiver terraces are developed at the junction between mountains and plains. The fiver terraces are most typical in the Jingxian Basin, Anhui Province, where the Qingyijiang River, one of the longest tributaries of the lower Yangtze River, developed three staircase terraces. The topmost terrace (i.e., the T3 terrace) tread is 38 - 39 m above fiver level, and the top of the gravels is generally covered by 3 - 10.9 m of red clay deposits. Systematic magnetostratigraphy and electron spin resonance dating are used to research the timing of the establishment of the Qingyijiang River. The main results show that the topmost terrace developed no later than 900 kyr ago and that the appearance of the Qingyijiang River occurred correspondingly at least before 900 kyr ago on the northern fringe of Mt. Huangshan. In view of the almost synchronous age,the establishment of the Qingyijiang River was seemingly a response to the Mid-Pleistocene Revolution when the 100 kyr cycle commenced, and the Kunlun-Huanghe movement during the early- middle Pleistocene transition. In addition, the establishment of the Qingyijiang River possibly reflected the birth of the modem Yangtze River to some degree. Therefore the timing of the formation of the Yangtze River is restricted to no later than 900 kyr ago based on the appearance of the Qingyijiang River . 展开更多
关键词 Qingyijiang River Topmost terrace MAGNETOSTRATIGRAPHY Electron Spin Resonance dating Establishment timing Jingxian Basin
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Elevator Group-Control Policy Based on Neural Network Optimized by Genetic Algorithm 被引量:1
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作者 沈虹 万健如 +2 位作者 张志超 刘英培 李光叶 《Transactions of Tianjin University》 EI CAS 2009年第4期245-248,共4页
Aiming at the diversity and nonlinearity of the elevator system control target, an effective group method based on a hybrid algorithm of genetic algorithm and neural network is presented in this paper. The genetic alg... Aiming at the diversity and nonlinearity of the elevator system control target, an effective group method based on a hybrid algorithm of genetic algorithm and neural network is presented in this paper. The genetic algorithm is used to search the weight of the neural network. At the same time, the multi-objective-based evaluation function is adopted, in which there are three main indicators including the passenger waiting time, car passengers number and the number of stops. Different weights are given to meet the actual needs. The optimal values of the evaluation function are obtained, and the optimal dispatch control of the elevator group control system based on neural network is realized. By analyzing the running of the elevator group control system, all the processes and steps are presented. The validity of the hybrid algorithm is verified by the dynamic imitation performance. 展开更多
关键词 elevator group control genetic algorithm neural network hybrid algorithm
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Characteristics of pressure gradient force errors in a terrain-following coordinate 被引量:1
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作者 LI Jin-Xi LI Yi-Yuan WANG Bin 《Atmospheric and Oceanic Science Letters》 CSCD 2016年第3期211-218,共8页
A terrain-following coordinate (a-coordinate) in which the computational form of pressure gradient force (PGF) is two-term (the so-called classic method) has significant PGF errors near steep terrain. Using the ... A terrain-following coordinate (a-coordinate) in which the computational form of pressure gradient force (PGF) is two-term (the so-called classic method) has significant PGF errors near steep terrain. Using the covariant equations of the a-coordinate to create a one-term PGF (the covariant method) can reduce the PGF errors. This study investigates the factors inducing the PGF errors of these two methods, through geometric analysis and idealized experiments. The geometric analysis first demonstrates that the terrain slope and the vertical pressure gradient can induce the PGF errors of the classic method, and then generalize the effect of the terrain slope to the effect of the slope of each vertical layer (φ). More importantly, a new factor, the direction of PGF (a), is proposed by the geometric analysis, and the effects of φ and a are quantified by tan φ.tan a. When tan φ.tan a is greater than 1/9 or smaller than -10/9, the two terms of PGF of the classic method are of the same order but opposite in sign, and then the PGF errors of the classic method are large. Finally, the effects of three factors on inducing the PGF errors of the classic method are validated by a series of idealized experiments using various terrain types and pressure fields. The experimental results also demonstrate that the PGF errors of the covariant method are affected little by the three factors. 展开更多
关键词 Terrain-following coordinatepressure gradient forceerrors direction of pressuregradient slope of eachvertical layer nonlinearvertical pressure gradient pressure gradient alongvertical layer
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Standards of Ecological Compensation for Traditional Ecoagriculture:Taking Rice-Fish System in Hani Terrace as an Example 被引量:33
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作者 LIU Mou-cheng XIONG Yin +3 位作者 YUAN Zheng MIN Qing-wen SUN Ye-hong Anthony M.Fuller 《Journal of Mountain Science》 SCIE CSCD 2014年第4期1049-1059,共11页
Traditional eco-agriculture provides many ecosystem services which are important for the local environment, especially in mountain areas. In order to encourage the farmers to engage in coo-agriculture, it is necessary... Traditional eco-agriculture provides many ecosystem services which are important for the local environment, especially in mountain areas. In order to encourage the farmers to engage in coo-agriculture, it is necessary to establish an eco-compensation mechanism for them. As the compensation standard is one of key issues in establishing eeo-compensation mechanism, this paper calculated the standard based on the farmers' willingness to accept (WTA) and the input-output analysis of eco-compensation. We took the traditional rice-fish eco-agriculture as the research object, conducting field surveys in Hani Terrace of Honghe County. Through the questionnaires in 2o11, we obtained the farmers' willingness to accept government compensation and market compensation. Then, the research evaluated the output of eco-compensation, the economic value of rice-fish paddy ecosystem services. Finally, under different market compensation standards, we compared the input and output of government compensation. The results show that, in 2011 the government should to pay farmers 7462 yuan.ha^-1·a^-1 to meet their willingness, but the output (ecological benefit) was only 7393 yuan.ha^-1·a^-1. However, whenthe rice price increases 1 yuan·kg-1 because of the limited use of chemicals in the next year, the government just has to pay farmers 4062 yuan.ha^-1·a^-1 and the surplus will be 3331 yuan.ha^-1·a^-1. 展开更多
关键词 Eco-compensation Eco-agriculture Ecosystem services Cultivation system Hani Terrace.
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Gradient principle of horizontal stress inducing rock burst in coal mine 被引量:6
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作者 何江 窦林名 《Journal of Central South University》 SCIE EI CAS 2012年第10期2926-2932,共7页
Based on the stress distribution characteristics of rock burst multiple sites, the criterion of horizontal stress inducing layer dislocation rock burst was established. Accordingly, the influencing factors were analyz... Based on the stress distribution characteristics of rock burst multiple sites, the criterion of horizontal stress inducing layer dislocation rock burst was established. Accordingly, the influencing factors were analyzed. The analysis results indicate that the stress condition, edge of etastic zone depth, supporting strength, and the friction angle and cohesion among coal stratum, roof and floor are sensitive factors. By introducing double-couple model, the layer dislocation rock burst was explained and the energy radiation characteristics were analyzed. The SOS micro-seismic monitoring system was applied to observe the rock burst hazards about a mining face. The results show that P- and S-wave energy radiations produced by rock burst have directional characteristics. The energy radiation characteristics of the 22 rock bursts occurring on 79Z6 long-wall face are basically the same as theoretical results, that is, the ratio of S-wave energy of sensor 4 to 6 is about 1.5 and that of P-wave is smaller than 0.5. The consistency of the monitored characteristics of the energy radiation theoretically increases with the total energy increasing. 展开更多
关键词 horizontal stress rock burst gradient principle micro-seismic monitoring directional characteristic energy radiation
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Optimal design of functionally graded Pm PV/CNT nanocomposite cylindrical tube for purpose of torque transmission 被引量:1
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作者 Abolfazl Khalkhali Sharif Khakshournia Parvaneh Saberi 《Journal of Central South University》 SCIE EI CAS CSCD 2016年第2期362-369,共8页
Carbon nanotube(CNT)/polymer nanocomposites have vast application in industry because of their light mass and high strength. In this work, a cylindrical tube which is made up of functionally graded(FG) PmP V/CNT nanoc... Carbon nanotube(CNT)/polymer nanocomposites have vast application in industry because of their light mass and high strength. In this work, a cylindrical tube which is made up of functionally graded(FG) PmP V/CNT nanocomposite, is optimally designed for the purpose of torque transmission. The main confining parameters of a rotating shaft in torque transmission process are mass of the shaft, critical speed of rotation and critical buckling torque. It is required to solve a multi-objective optimization problem(MOP) to consider these three targets simultaneously in the process of design. The three-objective optimization problem for this case is defined and solved using a hybrid method of FEM and modified non-dominated sorting genetic algorithm(NSGA-II), by coupling two softwares, MATLAB and ABAQUS. Optimization process provides a set of non-dominated optimal design vectors. Then, two methods, nearest to ideal point(NIP) and technique for ordering preferences by similarity to ideal solution(TOPSIS), are employed to choose trade-off optimum design vectors. Optimum parameters that are obtained from this work are compared with the results of previous studies for similar cylindrical tubes made from composite or a hybrid of aluminum and composite that more than 20% improvement is observed in all of the objective functions. 展开更多
关键词 NANOCOMPOSITE carbon nanotube (CNT) fimctionally graded materials (FGM) cylindrical tube finite element method(FEM) modified NSGA-II technique for ordering preferences by similarity to ideal solution (TOPSIS) nearest to ideal point (NIP)
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Full waveform inversion with spectral conjugategradient method
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作者 LIU Xiao LIU Mingchen +1 位作者 SUN Hui WANG Qianlong 《Global Geology》 2017年第1期40-45,共6页
Spectral conjugate gradient method is an algorithm obtained by combination of spectral gradient method and conjugate gradient method,which is characterized with global convergence and simplicity of spectral gradient m... Spectral conjugate gradient method is an algorithm obtained by combination of spectral gradient method and conjugate gradient method,which is characterized with global convergence and simplicity of spectral gradient method,and small storage of conjugate gradient method.Besides,the spectral conjugate gradient method was proved that the search direction at each iteration is a descent direction of objective function even without relying on any line search method.Spectral conjugate gradient method is applied to full waveform inversion for numerical tests on Marmousi model.The authors give a comparison on numerical results obtained by steepest descent method,conjugate gradient method and spectral conjugate gradient method,which shows that the spectral conjugate gradient method is superior to the other two methods. 展开更多
关键词 ful l waveform inversion spectral conjugate gradient method conjugate gradient method steepest descent method
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An Objective-Based Gradient Method for Locating the Pareto Domain
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作者 Allan Vandervoort Jules Thibault Yash Gupta 《Journal of Chemistry and Chemical Engineering》 2011年第7期608-623,共16页
In this paper, an objective-based gradient multi-objective optimization (MOO) technique, the Objective-Based Gradient Algorithm (OBGA), is proposed with the goal of defining the Pareto domain more precisely and ef... In this paper, an objective-based gradient multi-objective optimization (MOO) technique, the Objective-Based Gradient Algorithm (OBGA), is proposed with the goal of defining the Pareto domain more precisely and efficiently than current MOO techniques. The performance of the OBGA in locating the Pareto domain was evaluated in terms of precision, computation time and number of objective function calls, and compared to two current MOO algorithms: Dual Population Evolutionary Algorithm (DPEA) and Non-Dominated Sorting Genetic Algorithm I1 (NSGA-II), using four test problems. For all test problems, the OBGA systematically produced a more precise Pareto domain than DPEA and NSGA-II. With the adequate selection of the OBGA parameters, computation time required for the OBGA can be lower than that required for DPEA and NSGA-II. Results clearly show that the OBGA is a very effective and efficient algorithm for locating the Pareto domain. 展开更多
关键词 Pareto domain multi-objective optimization gradient method.
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Temperature gradient and its effect on flat steel box girder of long-span suspension bridge 被引量:19
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作者 MIAO ChangQing SHI ChangHua 《Science China(Technological Sciences)》 SCIE EI CAS 2013年第8期1929-1939,共11页
The temperature field variation law and distribution characteristics of an orthotropic flat steel box girder under sunny conditions were analyzed through a field temperature test on the steel box girder of the operati... The temperature field variation law and distribution characteristics of an orthotropic flat steel box girder under sunny conditions were analyzed through a field temperature test on the steel box girder of the operational Runyang Yangtze River Bridge(the suspension bridge part).Function optimization fitting and error analysis of the test data were conducted.A temperature gradient distribution curve applicable to a hexagonal flat steel box girder was proposed.Based on the measurement results,the temperature effect of an orthotropic flat steel box girder was analyzed using finite element method and the effects of different temperature gradient modes on the mechanical characteristics and stress distribution of the steel box girder were compared.Under sunny conditions,heat conduction in the flat steel box girder structure shows distinct "box-room effect" characteristics,and the actual temperature gradient distribution is inconsistent with the one suggested by the existing standards.The thermal stress of a steel box girder calculated from the measured temperature gradient mode exceeds that calculated from the standard,and the intensity approximates that under the action of designed vehicle loads.The temperature-induced stress is distributed centrally near the manufacturing welds of the orthotropic steel box girder,which should be considered in design,construction and research.Results from this study could supplement the existing bridge and culvert design standards. 展开更多
关键词 long-span bridge flat steel box girder temperature gradient temperature effect
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ON CONE D.C. OPTIMIZATION AND CONJUGATE DUALITY
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作者 M.SEMU 《Chinese Annals of Mathematics,Series B》 SCIE CSCD 2003年第4期521-528,共8页
This paper derives first order necessary and sufficient conditions for unconstrained coned.c. Programming problems where the underlined space is partially ordered with respect to acone. These conditions are given in t... This paper derives first order necessary and sufficient conditions for unconstrained coned.c. Programming problems where the underlined space is partially ordered with respect to acone. These conditions are given in terms of directional derivatives and subdifferentials of thecomponent functions. Moreover, conjugate duality for cone d.c. Optimization is discussed andweak duality theorem is proved in a more general partially ordered linear topological vectorspace (generalizing the results in [11]). 展开更多
关键词 Multi objective optimization Cone d.c. programming Optimality conditions Conjugate duality
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Soil Fertility Indices of Citrus Orchard Land Along Topographic Gradients in the Three Gorges Area of China 被引量:11
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作者 WU Dian-Ming YU Yuan-Chun +2 位作者 XIA Li-Zhong YIN Shi-Xue YANG Lin-Zhang 《Pedosphere》 SCIE CAS CSCD 2011年第6期782-792,共11页
In the Three Gorges Area of China, soil erosion and the resultant non-point source pollution and ecological degradation have endangered agricultural ecosystems and fresh water reservoirs. Although efforts have been un... In the Three Gorges Area of China, soil erosion and the resultant non-point source pollution and ecological degradation have endangered agricultural ecosystems and fresh water reservoirs. Although efforts have been undertaken to reduce soil and water losses from slope land used for citrus production, information on the effects of management practices on soil fertility indices is either limited or nonexistent. This study was conducted to compare the effects of 10 years of various management practices, citrus intercropped with white clover (WC), citrus mulched with straw (SM), citrus intercropped with contour hedgerows (CH), citrus orchard land with impermeable membrane (IM), and citrus intercropped with wheat (Triticum aestivum) and peanut (Arachris hypogaea) (WP), as treatments on soil fertility indices with that of the conventional citrus management (CM). Results showed that the soil organic carbon, total and available nitrogen, available potassium, and water-stable aggregate (> 0.25 mm) contents at the 0–5 cm depth were higher for the WC and SM treatments than the CM treatment. There was also spatial variation in soil fertility along slopes of the WC and SM treatments. The soil total and available nitrogen, phosphorus, and potassium, and water-stable aggregate (> 0.25 mm) contents at both the 0–5 and 5–20 cm depths were higher for the CH and IM treatments than the CM treatment. The average soil available nitrogen and available potassium contents were higher for the WP treatment than the CM treatment, but the WP treatment had little effect on the soil organic carbon, total nitrogen, and water-stable aggregate (> 0.25 mm) contents. These suggested that white clover intercropping and straw mulching were the most effective approaches to improve soil fertility in citrus orchard land of the Three Gorges area. 展开更多
关键词 INTERCROPPING slope land soil nutrients soil water-stable aggregates straw mulching
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TOOL ORIENTATION PLANNING FOR FIVE-AXIS CNC MACHINING OF OPEN FREE-FORM SURFACES 被引量:2
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作者 ZHAO Jibin ZHONG Bo +1 位作者 ZOU Qiang LIU Hongjun 《Journal of Systems Science & Complexity》 SCIE EI CSCD 2013年第5期667-675,共9页
For the geometry characteristics of open free-form surfaces,it is hard to consider global interference during the planning of feasible domains.Therefore,the optimal kinematic orientation of tool axis will no longer be... For the geometry characteristics of open free-form surfaces,it is hard to consider global interference during the planning of feasible domains.Therefore,the optimal kinematic orientation of tool axis will no longer be confined to the boundary of feasible domains.In this paper,according to the principle demanding that the tool should be fitted to a surface as close as possible and relevant processing parameters,a feasible domain of tool orientation for each cutter contact is planned in the local feed coordinates system.Then,these feasible domains of the tool orientation are transformed into the same coordinates system of the machine tool by the inverse kinematics transformation.The linear equations based feasible domain method and Rosen gradient projection algorithm are used to improve the optimization process in precision and efficiency of the algorithm.It constructs the variation of tool orientation optimization model and ensures the smoothness of tool orientation globally.Simulation and analysis of examples show that the proposed method has good kinematics performance and greatly improves the efficiency. 展开更多
关键词 Feasible domains five-axis CNC machining open free-form surface planning tool orien-tation.
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б-sharpen immersed boundary method(б-SIBM)—New method for solving the horizontal pressure-gradient force(PGF) problem of б-coordinate 被引量:1
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作者 HEI PengFei ZHOU Gang +2 位作者 JIA DongDong YE YunTao LEI Kun 《Science China Earth Sciences》 SCIE EI CAS 2014年第7期1681-1691,共11页
Although G-coordinate is one of the most popular methods used in marine and estuarine modeling, it has long suffered from the so-called "steep boundary problem", namely, the PGF problem. In this paper, a new method ... Although G-coordinate is one of the most popular methods used in marine and estuarine modeling, it has long suffered from the so-called "steep boundary problem", namely, the PGF problem. In this paper, a new method called the "σ-sharpen immersed boundary method" (σ-SIBM) is put forward. In this method, the virtual flat bottom boundary is creatively introduced in regions with the steep boundary and is taken as the boundary of numerical domain. By this, OH/Ox of numerical domain changes to be a controllable value and the steep bottom problem is then transformed to the non-conforming boundary problem, which is, in turn, solved by the SIBM. The accuracy and efficiency of the σ-sharpen immersed boundary method (σ-SIBM) has been showed by both comparative theoretical analysis and classical numerical tests. First, it is shown that the σ-SIBM is more effective than the z-level method, in that σ-SIBM needs special treatment only in the steep section, but the z-level method needs the special treatment in each grid note. Second, it is superior to the p-method in that it is not restricted by the density distribution. This paper revisits the classical seamount numerical test used in numerous studies to prove the sigma errors of the pressure gradient force (PGFE) and their long-term effects on circulation. It can be seen that, as for the maximum erroneous velocity and kinetic energy, the value of σ-SIBM is much less than that of the z-level method and the traditional σ-method. 展开更多
关键词 sharpen immersed boundary method (SIBM) immersed boundary method (IBM) direct forcing method o-coordinate pressure gradient force (PGF)
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Analysis of hydroxylated polybrominated diphenyl ethers in plant samples using ultra performance liquid chromatography-mass spectrometry
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作者 WANG Sen WU Tong +3 位作者 HUANG HongLin PING Hua LU AnXiang ZHANG ShuZhen 《Science China Chemistry》 SCIE EI CAS 2011年第11期1782-1788,共7页
A method was developed for the analysis of hydroxylated brominated diphenyl ethers (OH-PBDEs) in plant samples using an ultra performance liquid chromatography-triple quadrupole mass spectrometer (UPLC-ESI-MS/MS) in n... A method was developed for the analysis of hydroxylated brominated diphenyl ethers (OH-PBDEs) in plant samples using an ultra performance liquid chromatography-triple quadrupole mass spectrometer (UPLC-ESI-MS/MS) in negative mode. Plant samples were extracted and cleaned up through florisil column, resolved on a 100 mm C18 column with linear gradient elution and detected by mass spectrometry in multiple reaction monitoring (MRM) mode. The method provided good recoveries rang- ing from 68.2% to 94.6%, relative standard deviation (RSD) in the range of 3.2% - 9.1%, and limits of quantification (LOQ) defined as the signal-to-noise ratio of 10 of 0.3-2.1 ng/g. It allowed a fast separation and sensitive quantification of the isomers and homologues of seven OH-PBDE congeners 2′-OH-BDE-3, 3′-OH-BDE-7, 4′-OH-BDE-17, 3′-OH-BDE-28, 3-OH-BDE-47, 5-OH-BDE-47 and 6-OH-BDE-47. The method was successfully applied to identify and quantify the formation of hydroxylat- ed metabolites in alfalfa exposed to BDE-209. Five OH-PBDEs were detected in plant tissues, and more congeners were found in roots than in shoots. To our knowledge, this work represents the first attempt to validate UPLC-MS/MS method to quantify OH-PBDEs in plant samples without derivatization. 展开更多
关键词 OH-PBDE plant extraction ultra performance liquid chromatography mass spectrometry
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