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Boiling Point Distribution of Hydrocarbon Types in Diesel Using Solid-Phase Extraction Followed by GC/FID-EIMS 被引量:1
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作者 Li Chengwei Tian Songbai Liu Zelong Zhu Xinyi 《China Petroleum Processing & Petrochemical Technology》 SCIE CAS 2008年第3期13-21,共9页
In this paper, a method was established to determine the boiling point distribution of hydrocarbon types in diesel. The diesel sample was separated into the saturate and aromatic fractions by means of solid-phase extr... In this paper, a method was established to determine the boiling point distribution of hydrocarbon types in diesel. The diesel sample was separated into the saturate and aromatic fractions by means of solid-phase extraction (SPE), and each fraction was analyzed by GC/FID-EIMS. According to the relationship between boiling point and retention time of n-paraffins in the chromatogram, the percentages of saturates and aromatics at each temperature interval were calculated. According to the average mass spectra of the saturate and aromatic fractions at each temperature interval, the hydrocarbon types of the sample were identified through summation of characteristic mass fragments. Using this method, the changes in composition of diesel during hydrotreating process were studied. The results showed that hydrogenation of aromatics is the main reaction during the hydrotreating process. The more rings the aromatics have, the easier the hydrogenation reactions would take place. The aromatics were converted into cycloparaffins via the hydrogenation and saturation process, leading to an increase in low boiling point fractions in the hydrotreated oil. 展开更多
关键词 boiling point distribution hydrocarbon type DIESEL GC/FID-EIMS solid-phase extraction
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CHARACTERIZATION OF BRANCHING POINT DISTRIBUTION IN THE SOL OF IRRADIATED POLYSTYRENE WITH SEC-LALLS
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作者 张万喜 王谋智 孙家珍 《Chinese Journal of Polymer Science》 SCIE CAS CSCD 1991年第2期177-179,共3页
In this paper, the change behavior of branching point distribution of irradiated polystyrene in sol has been first studied by the SEC-LALLS method. The experimental results show that branching parameter of the part wi... In this paper, the change behavior of branching point distribution of irradiated polystyrene in sol has been first studied by the SEC-LALLS method. The experimental results show that branching parameter of the part with lower molecular weight in the sol changes little at the early stage of irradiation and that of the part with the higher molecular weight becomes greater with the increase in radiation dose. 展开更多
关键词 Irradiation of polystyrene Branching point distribution of the sol Branching parameter SEC-LALLS.
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Spatial pattern analysis and associations of different growth stages of populations of Abies georgei var.smithii in Southeast Tibet,China 被引量:3
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作者 SHEN Zhi-qiang LU Jie +1 位作者 HUA Min FANG Jiang-ping 《Journal of Mountain Science》 SCIE CSCD 2016年第12期2170-2181,共12页
Abies georgei var.smithii is an important plant species in Southeast Tibet,China.It has high ecological value in terms of biodiversity protection,as well as soil and water conservation.We analyzed the spatial pattern ... Abies georgei var.smithii is an important plant species in Southeast Tibet,China.It has high ecological value in terms of biodiversity protection,as well as soil and water conservation.We analyzed the spatial pattern and associations of A.georgei var.smithii populations at different growth stages by using Ripley's L function for point pattern analysis.The diameter structure was a nearly reverse 'J' shape.The amount of saplings and medium-sized trees accounts for a large part of the entire population,suggesting a high regeneration rate and an expanding population.In the transition from saplings to medium trees or to large trees,saplings show a significant aggregation distribution at small scales,while medium trees and large trees show a random distribution.There are significant inverse associations between saplings and medium trees and large trees at small scales,while there are no obvious associations between medium trees and large trees.The natural regeneration was affected by interspecific competition,and it was also affected by intraspecific competition.The joint effects of biological characteristics and environmental factors contribute to the spatial distribution pattern and associations of this A.georgei var.sm ithii population. 展开更多
关键词 Southeastern Tibet Abies georgei var.smithii Point pattern analysis distribution pattern Spatial association
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Towards uniform point distribution in feature-preserving point cloud filtering 被引量:1
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作者 Shuaijun Chen Jinxi Wang +3 位作者 Wei Pan Shang Gao Meili Wang Xuequan Lu 《Computational Visual Media》 SCIE EI CSCD 2023年第2期249-263,共15页
While a popular representation of 3D data,point clouds may contain noise and need filtering before use.Existing point cloud filtering methods either cannot preserve sharp features or result in uneven point distributio... While a popular representation of 3D data,point clouds may contain noise and need filtering before use.Existing point cloud filtering methods either cannot preserve sharp features or result in uneven point distributions in the filtered output.To address this problem,this paper introduces a point cloud filtering method that considers both point distribution and feature preservation during filtering.The key idea is to incorporate a repulsion term with a data term in energy minimization.The repulsion term is responsible for the point distribution,while the data term aims to approximate the noisy surfaces while preserving geometric features.This method is capable of handling models with fine-scale features and sharp features.Extensive experiments show that our method quickly yields good results with relatively uniform point distribution. 展开更多
关键词 point cloud filtering point distribution feature preservation
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STRUCTURAL CHARACTERIZATION OF POLYETHYLENES BY DSC ANALYSIS AFTER CRYSTALLIZATION SEGREGATION
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作者 徐懋 《Chinese Journal of Polymer Science》 SCIE CAS CSCD 2000年第6期557-564,共8页
The molecular structure of polyethylene (PE) samples with various comonomers including propylene, I-butane and 1-hexene was investigated by DSC and C-13-NMR techniques. The density of the samples varies from 0.948 g/c... The molecular structure of polyethylene (PE) samples with various comonomers including propylene, I-butane and 1-hexene was investigated by DSC and C-13-NMR techniques. The density of the samples varies from 0.948 g/cm(3) to 0.917 g/cm(3), and the molecular weight determined by the GPC method is in the range of 1 similar to2 x 10(5). The branch paint content of the samples was determined by C-13-NMR measurements and was found to be less than 20 per 1000 C atoms along the main chain. Crystallization segregation DSC technique (CSDSC) was used to characterize the branch point distribution or the segment length distribution of PEs. The crystallization segregation was performed in a successive annealing process at decreasing temperatures. The interval of two successive annealing temperatures was 6 K, and the time length of each annealing step was 2.5 h. The CSDSC results clearly indicate that all the PE samples used, including some metallocene PEs, more or less exhibit their non-uniformity in segment length distribution, and bimodal or multimodal CSDSC curves were usually observed. For quantitative characterization of the CSDSC curves and the segment length distribution two parameters, the average melting point, T-mAV, and the root-mean-square deviation of melting temperature, (DeltaT(m)(AV)(2))(1/2), were proposed. TmAV is corresponding to the average segment length due to branching and (DeltaT(m)(AV)(2))(1/2) gives information about the: width of the segment length distribution. Experimental results show that both the degree of average melting temperature depression and the width of the distribution seem to increase with increasing the branching content and are dependent on the type of comonomers. Very good reproducibility and additivity of the CSDSC method were evidenced experimentally. It was concluded that the CSDSC technique is a sensitive and convenient method for characterizing the segment length distribution of branched polyethylenes and will be of great interest in structure-property relationship studies of crystalline polymers. 展开更多
关键词 POLYETHYLENE branch point distribution segment length distribution crystallization segregation DSC
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ON THE ORDER OF SUMMABILITY OF THE FOURIER INVERSION FORMULA
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作者 Jasson Vindas Ricardo Estrada 《Analysis in Theory and Applications》 2010年第1期13-42,共30页
In this article we show that the order of the point value, in the sense of Lojasiewicz, of a tempered distribution and the order of summability of the pointwise Fourier inversion formula are closely related. Assuming ... In this article we show that the order of the point value, in the sense of Lojasiewicz, of a tempered distribution and the order of summability of the pointwise Fourier inversion formula are closely related. Assuming that the order of the point values and certain order of growth at infinity are given for a tempered distribution, we estimate the order of summability of the Fourier inversion formula. For Fourier series, and in other cases, it is shown that if the distribution has a distributional point value of order k, then its Fourier series is e.v. Cesaro summable to the distributional point value of order k+1. Conversely, we also show that if the pointwise Fourier inversion formula is e.v. Cesaro summable of order k, then the distribution is the (k + 1)-th derivative of a locally integrable function, and the distribution has a distributional point value of order k + 2. We also establish connections between orders of summability and local behavior for other Fourier inversion problems. 展开更多
关键词 Fourier inversion formula tempered distribution distributional point value Cesaro summability of Fourier series and integrals summability of distributional evaluations
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A Remark on Pl Type Interpolation on Non-Uniformly Distributed Nodes on the Unit Circle
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作者 Neha Mathur P.Mathur 《Analysis in Theory and Applications》 2014年第2期173-192,共20页
In this paper we study the problem of explicit representation and convergence of Pal type (0;1) interpolation and its converse, with some additional conditions, on the non-uniformly distributed nodes on the unit cir... In this paper we study the problem of explicit representation and convergence of Pal type (0;1) interpolation and its converse, with some additional conditions, on the non-uniformly distributed nodes on the unit circle obtaIned by projecting the interlaced zeros of Pn (x) and Pn′ (x) on the unit circle. The motivation to this problem can be traced to the recent studies on the regularity of Birkhoff interpolation and Pal type interpolations on non-uniformly distributed zeros on the unit circle. 展开更多
关键词 Pal type interpolation non-uniformly distributed set of points on unit circle Legendre polynomials.
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The Proof of Riemann Hypothesis, the Key to the Door Is the Periodicity
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作者 Jinliang Wang 《Applied Mathematics》 2021年第8期723-765,共43页
The Riemann hypothesis is a well-known mathematical problem that has been in suspense for 162 years. Its difficulty lies in the fact that it is involved in an infinite integral which includes infinite series with comp... The Riemann hypothesis is a well-known mathematical problem that has been in suspense for 162 years. Its difficulty lies in the fact that it is involved in an infinite integral which includes infinite series with complex variables. To detour this is in vain, since all the messages are hid in it. To unscramble them, there is a totally new idea, that is, the “periodicity”! By investigating the numerical approximate values of zero points, an explicit distribution law on the critical line was found. To accord with this, a periodic form for the real part of Xi function was constructed and rigidly proved. The Riemann hypothesis can be divided into three progressive propositions. The first proposition (the number of zero points in the critical strip satisfies a certain estimation) had been proved in 1905. The second proposition (the number of zero points on the critical line satisfies the same estimation as in the critical strip) is ever in suspense. It can be solved perfectly with the newly found “periodicity”. The third proposition (all the nontrivial zero points are on the critical line), that is, the Riemann hypothesis, is also true. The proof is a combination of the symmetry, monotonicity, periodicity of the Xi function and the extremum principle of the harmonic functions. It is the moment to draw full stop for this suspending problem. 展开更多
关键词 Riemann Hypothesis Riemann Zeta Function distribution Law of Zero Point PERIODICITY MONOTONICITY Extremum Principle
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Shape Retrieval Using ECPDH with Dynamic Programming
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作者 Xin Shu Lei Pan Yunsong Qi 《Journal of Computer and Communications》 2016年第16期63-78,共16页
The matching and retrieval of the 2D shapes are challenging issues in object recognition and computer vision. In this paper, we propose a new object contour descriptor termed ECPDH (Elliptic Contour Points Distributio... The matching and retrieval of the 2D shapes are challenging issues in object recognition and computer vision. In this paper, we propose a new object contour descriptor termed ECPDH (Elliptic Contour Points Distribution Histogram), which is based on the distribution of the points on an object contour under the polar coordinates. ECPDH has the essential merits of invariance to scale and translation. Dynamic Programming (DP) algorithm is used to measure the distance between the ECPDHs. The effectiveness of the proposed method is demonstrated using some standard tests on MPEG-7 shape database. The results show the precision and recall of our method over other recent methods in the literature. 展开更多
关键词 Shape Descriptor Shape Retrieval Elliptic Contour points distribution Histogram Dynamic Programming
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3D Layout Algorithm for Laying Rectangular Tiles on Ship Hull
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作者 CHEN Zhi-biao ZHAO Yao YAN Jun 《Computer Aided Drafting,Design and Manufacturing》 2006年第1期24-30,共7页
A new 3D layout algorithm to lay rectangular tiles on the 3D hull surface model is proposed to improve the algorithm performance in accelerating layout process and enhancing design accuracy. Three times optimizations ... A new 3D layout algorithm to lay rectangular tiles on the 3D hull surface model is proposed to improve the algorithm performance in accelerating layout process and enhancing design accuracy. Three times optimizations are carried out upon the original basic algorithm, namely optimization of calculating range, separation of surface flattening computation from laying computation, and optimization of interior point distribution. By testing, the generated surface layout drawing by the refined system is fairly applicable to guide the actual tiles' coating process. 展开更多
关键词 ship hull rectangular tile layout calculating range surface initialization interior point distribution
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Design of a Level-3 electric vehicle charging station using a 1-MW solar system via the distributed maximum power point tracking technique
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作者 Afshin Balal Michael Giesselmann 《Clean Energy》 EI CSCD 2024年第1期23-35,共13页
Solar power is mostly influenced by solar irradiation,weather conditions,solar array mismatches and partial shading conditions.Therefore,before installing solar arrays,it is necessary to simulate and determine the pos... Solar power is mostly influenced by solar irradiation,weather conditions,solar array mismatches and partial shading conditions.Therefore,before installing solar arrays,it is necessary to simulate and determine the possible power generated.Maximum power point tracking is needed in order to make sure that,at any time,the maximum power will be extracted from the photovoltaic system.However,maximum power point tracking is not a suitable solution for mismatches and partial shading conditions.To overcome the drawbacks of maximum power point tracking due to mismatches and shadows,distributed maximum power point tracking is util-ized in this paper.The solar farm can be distributed in different ways,including one DC-DC converter per group of modules or per module.In this paper,distributed maximum power point tracking per module is implemented,which has the highest efficiency.This technology is applied to electric vehicles(EVs)that can be charged with a Level 3 charging station in<1 hour.However,the problem is that charging an EV in<1 hour puts a lot of stress on the power grid,and there is not always enough peak power reserve in the existing power grid to charge EVs at that rate.Therefore,a Level 3(fast DC)EV charging station using a solar farm by implementing distributed maximum power point tracking is utilized to address this issue.Finally,the simulation result is reported using MATLAB®,LTSPICE and the System Advisor Model.Simulation results show that the proposed 1-MW solar system will provide 5 MWh of power each day,which is enough to fully charge~120 EVs each day.Additionally,the use of the proposed photovoltaic system benefits the environment by removing a huge amount of greenhouse gases and hazardous pollutants.For example,instead of supplying EVs with power from coal-fired power plants,1989 pounds of CO_(2) will be eliminated from the air per hour. 展开更多
关键词 electric vehicles(EVs) distributed maximum power point tracking solar farm DC fast-charging station step-up DC-DC converter System Advisor Model economic analysis
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Effect of assisted transverse magnetic field on distortion behavior of thin-walled components in WEDM process 被引量:4
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作者 Yanming ZHANG Guojun ZHANG +2 位作者 Zhen ZHANG Yi ZHANG Yu HUANG 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2022年第2期291-307,共17页
Machining performance of thin-walled components made by aeronautical difficult-toprocess materials is a significant issue in the aviation manufacturing industry.Although wire electric discharge machining-low speed(WED... Machining performance of thin-walled components made by aeronautical difficult-toprocess materials is a significant issue in the aviation manufacturing industry.Although wire electric discharge machining-low speed(WEDM-LS)is one of typical non-contact machining processes without macro cutting force,which does well in removing hardness and brittleness materials via pulsed discharge at high temperature,but few researchers have studied the thermal distortion behavior leading to a considerable geometric error in the WEDM-LS of thin-walled components.In this paper,a transverse magnetic field assisted method is applied for affecting the uniformity of discharge point distribution so as to reduce the distortion in WEDM-LS processing thin-wall component.First,the generation mechanism of this new distortion behavior and the impact mechanism of transverse magnetic field(TMF)on distortion are demonstrated by theoretical analysis.In order to further figure out the distortion behavior in the TMF-WEDM process,a new thermophysical model considering the discharge point distribution is established to simulate temperature field,residual stress field and distortion profiles.Then a large number of Taguchi experiments are carried out to investigate the influences of process parameters including pulse discharge energy(pulse on time,pulse off time,and current)and magnetic field strength on distortion in WEDM-LS.To comparatively analyze simulated and experimental results,the accuracy of established thermophysical model is verified within a relative error of 18.38%in distortion.Moreover,it can be revealed that transverse magnetic field contribute to significantly improve the longitudinal distribution uniformity with maximum increase of 12.32%at magnetic field strength:0.15 T,leading to significant reductions of 32.77%in distortion and 22.68%in recast layer.Eventually,we also presented the variation of residual stress and recast layer along thickness direction under different distortion behavior,which are in good agreement with that of distortion behavior. 展开更多
关键词 Distortion behavior distribution of discharge points Thin-walled components Transverse magnetic field Wire electrical discharge machining
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Fast uniform content-based satellite image registration using the scale-invariant feature transform descriptor 被引量:3
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作者 Hamed BOZORGI Ali JAFARI 《Frontiers of Information Technology & Electronic Engineering》 SCIE EI CSCD 2017年第8期1108-1116,共9页
Content-based satellite image registration is a difficult issue in the fields of remote sensing and image processing. The difficulty is more significant in the case of matching multisource remote sensing images which ... Content-based satellite image registration is a difficult issue in the fields of remote sensing and image processing. The difficulty is more significant in the case of matching multisource remote sensing images which suffer from illumination, rotation, and source differences. The scale-invariant feature transform (SIFT) algorithm has been used successfully in satellite image registration problems. Also, many researchers have applied a local SIFT descriptor to improve the image retrieval process. Despite its robustness, this algorithm has some difficulties with the quality and quantity of the extracted local feature points in multisource remote sensing. Furthermore, high dimensionality of the local features extracted by SIFT results in time-consuming computational processes alongside high storage requirements for saving the relevant information, which are important factors in content-based image retrieval (CBIR) applications. In this paper, a novel method is introduced to transform the local SIFT features to global features for multisource remote sensing. The quality and quantity of SIFT local features have been enhanced by applying contrast equalization on images in a pre-processing stage. Considering the local features of each image in the reference database as a separate class, linear discriminant analysis (LDA) is used to transform the local features to global features while reducing di- mensionality of the feature space. This will also significantly reduce the computational time and storage required. Applying the trained kernel on verification data and mapping them showed a successful retrieval rate of 91.67% for test feature points. 展开更多
关键词 Content-based image retrieval Feature point distribution Image registration Linear discriminant analysis REMOTESENSING Scale-invariant feature transform
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Personalized Multi-View Face Animation with Lifelike Textures
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作者 柳杨华 徐光祐 《Tsinghua Science and Technology》 SCIE EI CAS 2007年第1期51-57,共7页
Realistic personalized face animation mainly depends on a picture-perfect appearance and natural head rotation. This paper describes a face model for generation of novel view facial textures with various realistic exp... Realistic personalized face animation mainly depends on a picture-perfect appearance and natural head rotation. This paper describes a face model for generation of novel view facial textures with various realistic expressions and poses. The model is achieved from corpora of a talking person using machine learning techniques. In face modeling, the facial texture variation is expressed by a multi-view facial texture space model, with the facial shape variation represented by a compact 3-D point distribution model (PDM). The facial texture space and the shape space are connected by bridging 2-D mesh structures. Levenberg-Marquardt optimization is employed for fine model fitting. Animation trajectory is trained for smooth and continuous image sequences. The test results show that this approach can achieve a vivid talking face sequence in various views. Moreover, the animation complexity is significantly reduced by the vector representation. 展开更多
关键词 face animation point distribution model (PDM) TEXTURE MULTI-VIEW
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THEORETICAL ANALYSES ON DISCRETE FORMULAE OF DIRECTIONAL DIFFERENTIALS IN THE FINITE POINT METHOD
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作者 Guixia Lv Longjun Shen 《Journal of Computational Mathematics》 SCIE CSCD 2022年第1期1-25,共25页
For the five-point discrete formulae of directional derivatives in the finite point method,overcoming the challenge resulted from scattered point sets and making full use of the explicit expressions and accuracy of th... For the five-point discrete formulae of directional derivatives in the finite point method,overcoming the challenge resulted from scattered point sets and making full use of the explicit expressions and accuracy of the formulae,this paper obtains a number of theoretical results:(1)a concise expression with definite meaning of the complicated directional difference coefficient matrix is presented,which characterizes the correlation between coefficients and the connection between coefficients and scattered geometric characteristics;(2)various expressions of the discriminant function for the solvability of numerical differentials along with the estimation of its lower bound are given,which are the bases for selecting neighboring points and making analysis;(3)the estimations of combinatorial elements and of each element in the directional difference coefficient matrix are put out,which exclude the existence of singularity.Finally,the theoretical analysis results are verified by numerical calculations.The results of this paper have strong regularity,which lay the foundation for further research on the finite point method for solving partial differential equations. 展开更多
关键词 Finite point method Finite difference Scattered point distribution Discrete directional differentials Theoretical analysis
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Position optimization of particular solution sources for distributed source boundary point method by volume velocity-matching
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作者 WU Shaowei XIANG Yang LI Shengyang 《Chinese Journal of Acoustics》 CSCD 2015年第2期123-137,共15页
Choosing particular solution source and its position have great influence on accu- racy of sound field prediction in distributed source boundary point method. An optimization method for determining the position of par... Choosing particular solution source and its position have great influence on accu- racy of sound field prediction in distributed source boundary point method. An optimization method for determining the position of particular solution sources is proposed to get high accu- racy prediction result. In this method, tripole is chosen as the particular solution. The upper limit frequency of calculation is predicted by setting 1% volume velocity relative error limit using vibration velocity of structure surface. Then, the optimal position of particular solution sources, in which the relative error of volume velocity is minimum, is determined within the range of upper limit frequency by searching algorithm using volume velocity matching. The transfer matrix between pressure and surface volume velocity is constructed in the optimal position. After that, the sound radiation of structure is calculated by the matrix. The results of numerical simulation show that the calculation error is significantly reduced by the proposed method. When there are vibration velocity measurement errors, the calculation errors can be controlled within 5% by the method. 展开更多
关键词 Position optimization of particular solution sources for distributed source boundary point method by volume velocity-matching
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