期刊文献+
共找到605篇文章
< 1 2 31 >
每页显示 20 50 100
Gray code based gradient-free optimization algorithm for parameterized quantum circuit
1
作者 张安琪 武春辉 赵生妹 《Chinese Physics B》 SCIE EI CAS CSCD 2024年第2期189-194,共6页
A Gray code based gradient-free optimization(GCO)algorithm is proposed to update the parameters of parameterized quantum circuits(PQCs)in this work.Each parameter of PQCs is encoded as a binary string,named as a gene,... A Gray code based gradient-free optimization(GCO)algorithm is proposed to update the parameters of parameterized quantum circuits(PQCs)in this work.Each parameter of PQCs is encoded as a binary string,named as a gene,and a genetic-based method is adopted to select the offsprings.The individuals in the offspring are decoded in Gray code way to keep Hamming distance,and then are evaluated to obtain the best one with the lowest cost value in each iteration.The algorithm is performed iteratively for all parameters one by one until the cost value satisfies the stop condition or the number of iterations is reached.The GCO algorithm is demonstrated for classification tasks in Iris and MNIST datasets,and their performance are compared by those with the Bayesian optimization algorithm and binary code based optimization algorithm.The simulation results show that the GCO algorithm can reach high accuracies steadily for quantum classification tasks.Importantly,the GCO algorithm has a robust performance in the noise environment. 展开更多
关键词 gradient-free optimization gray code genetic-based method
下载PDF
Carbon efficiency evaluation method for urban energy system with multiple energy complementary
2
作者 Xianan Jiao Jiekang Wu +1 位作者 Yunshou Mao Mengxuan Yan 《Global Energy Interconnection》 EI CSCD 2024年第2期142-154,共13页
Urban energy systems(UESs)play a pivotal role in the consumption of clean energy and the promotion of energy cascade utilization.In the context of the construction and operation strategy of UESs with multiple compleme... Urban energy systems(UESs)play a pivotal role in the consumption of clean energy and the promotion of energy cascade utilization.In the context of the construction and operation strategy of UESs with multiple complementary energy resources,a comprehensive assessment of the energy efficiency is of paramount importance.First,a multi-dimensional evaluation system with four primary indexes of energy utilization,environmental protection,system operation,and economic efficiency and 21 secondary indexes is constructed to comprehensively portray the UES.Considering that the evaluation system may contain a large number of indexes and that there is overlapping information among them,an energy efficiency evaluation method based on data processing,dimensionality reduction,integration of combined weights,and gray correlation analysis is proposed.This method can effectively reduce the number of calculations and improve the accuracy of energy efficiency assessments.Third,a demonstration project for a UES in China is presented.The energy efficiency of each scenario is assessed using six operational scenarios.The results show that Scenario 5,in which parks operate independently and investors build shared energy-storage equipment,has the best results and is best suited for green and low-carbon development.The results of the comparative assessment methods show that the proposed method provides a good energy efficiency assessment.This study provides a reference for the optimal planning,construction,and operation of UESs with multiple energy sources. 展开更多
关键词 Urban energy systems(UESs) Multiple energy complementary system Carbon efficiency evaluation Data downscaling Subjective and objective weight gray correlation analysis
下载PDF
Optimization of short-circuit transition parameters of Q235B steel GMAW based on orthogonal gray relational analysis
3
作者 陈昌荣 唐宝林 +2 位作者 叶宇杰 练国富 黄旭 《China Welding》 CAS 2024年第2期39-49,共11页
In gas metal arc welding(GMAW)process,the short-circuit transition was the most typical transition observed in molten metal droplets.This paper used orthogonal tests to explore the coupling effect law of welding proce... In gas metal arc welding(GMAW)process,the short-circuit transition was the most typical transition observed in molten metal droplets.This paper used orthogonal tests to explore the coupling effect law of welding process parameters on the quality of weld forming under short-circuit transition,the design of 3 factors and 3 levels of a total of 9 groups of orthogonal tests,welding current,welding voltage,welding speed as input parameters:effective area ratio,humps,actual linear power density,aspect ratio,Vickers hardness as output paramet-ers(response targets).Using range analysis and trend charts,we can visually depict the relationship between input parameters and a single output parameter,ultimately determining the optimal process parameters that impact the single output index.Then combined with gray the-ory to transform the three response targets into a single gray relational grade(GRG)for analysis,the optimal combination of the weld mor-phology parameters as follows:welding current 100 A,welding voltage 25 V,welding speed 30 cm/min.Finally,validation experiments were conducted,and the results showed that the error between the gray relational grade and the predicted value was 2.74%.It was observed that the effective area ratio of the response target significantly improved,validating the reliability of the orthogonal gray relational method. 展开更多
关键词 short-circuit transition orthogonal test gray relational forming quality
下载PDF
顺应论视域下The Picture of Dorian Gray中译本的对比研究
4
作者 滕璐 《现代语言学》 2024年第6期265-271,共7页
The Picture of Dorian Gray是王尔德唯一一部长篇小说,小说语言唯美自然。本文从顺应论的角度出发,从语境顺应、结构顺应以及动态顺应三个方面分析孙宜学译本与荣如德译本的差异。文章发现,两译者对于自己的定位不同,即前者是源语文化... The Picture of Dorian Gray是王尔德唯一一部长篇小说,小说语言唯美自然。本文从顺应论的角度出发,从语境顺应、结构顺应以及动态顺应三个方面分析孙宜学译本与荣如德译本的差异。文章发现,两译者对于自己的定位不同,即前者是源语文化的传播者,后者则是文学作品的传播者,译者的意识程度以及自身定位影响着译者采取的翻译方法,只有找准定位才能更好地翻译,获得更大的阅读价值以及参考价值。 展开更多
关键词 The Picture of Dorian gray 英汉对比 顺应论 翻译对比
下载PDF
Research on Gray System and Quantitative Model About the Fund-Raising Ability to China Private Equity Fund
5
作者 蒙蒙 禹久泓 《Journal of Shanghai Jiaotong university(Science)》 EI 2016年第3期365-369,共5页
It is a rather challenging project to seek the amount of funds raised by funds-raising companies. This paper is focused on China private equity funds that have succeeded in raising their funds. The grey systemic model... It is a rather challenging project to seek the amount of funds raised by funds-raising companies. This paper is focused on China private equity funds that have succeeded in raising their funds. The grey systemic model is applied in the research and a formula is established for the law of fund-raising of the private equity funds in order to sum up the capacity of China private equity investment funds and to establish a model accordingly. 展开更多
关键词 gray system fund-raising ability private equity fund
原文传递
Analysis of the Relationship between Mechanical Properties and Pore Structure of MSW Incineration Bottom Ash Fine Aggregate Concrete after Freeze-Thaw Cycles Based on the Gray Theory
6
作者 Peng Zhang Dongsheng Shi +1 位作者 Ping Han Wenchao Jiang 《Journal of Renewable Materials》 SCIE EI 2023年第2期669-688,共20页
The destruction of concrete building materials in severely cold regions of the north is more severely affected by freeze-thaw cycles,and the relationship between the mechanical properties and pore structure of concret... The destruction of concrete building materials in severely cold regions of the north is more severely affected by freeze-thaw cycles,and the relationship between the mechanical properties and pore structure of concrete with fine aggregate from municipal solid waste(MSW)incineration bottom ash after freeze-thaw cycles is analyzed under the degree of freeze-thaw hazard variation.In this paper,the gray correlation method is used to calculate the correlation between the relative dynamic elastic modulus,compressive strength,and microscopic porosity parameters to speculate on the most important factors affecting their changes.The GM(1,1)model was established based on the compressive strength of the waste incineration ash aggregate concrete,the relative error between the simulated and actual values in the model was less than 5%,and the accuracy of the model was level 1,indicating that the GM(1,1)model can well reflect the change in the compressive strength of the MSW incineration bottom ash aggregate concrete during freeze-thaw cycles.Using the gray correlation method,the correlation between the relative dynamic elastic modulus,compressive strength,air content,specific surface area,pore spacing coefficient,and pore average chord length was calculated,and the pore spacing coefficient and pore average chord length were determined to be highly correlated with each other.This determination can help analyze and infer the deterioration mechanism of concrete subject to freeze-thaw cycles.These results can provide a theoretical basis for guiding the engineering practice of concrete with fine aggregates of household bottom ash in the northern cold region. 展开更多
关键词 Municipal solid waste incineration bottom ash CONCRETE gray system theory mechanical properties pore structure
下载PDF
Regional gray matter abnormality in hepatic myelopathy patients after transjugular intrahepatic portosystemic shunt: a voxel-based morphometry study 被引量:8
7
作者 Kang Liu Gang Chen +9 位作者 Shu-Yao Ren Yuan-Qiang Zhu Tian-Lei Yu Ping Tian Chen Li Yi-Bin Xi Zheng-Yu Wang Jian-Jun Ye Guo-Hong Han Hong Yin 《Neural Regeneration Research》 SCIE CAS CSCD 2019年第5期850-857,共8页
Hepatic myelopathy is a complication seen in patients with chronic liver failure with physiologic or iatrogenic portosystemic shunting. The main symptom is progressive lower limb dyskinesia. The role of the brain moto... Hepatic myelopathy is a complication seen in patients with chronic liver failure with physiologic or iatrogenic portosystemic shunting. The main symptom is progressive lower limb dyskinesia. The role of the brain motor control center in hepatic myelopathy is unknown. This study aimed to investigate the gray matter changes in patients with hepatic myelopathy secondary to transjugular intrahepatic portosystemic shunt and to examine their clinical relevance. This was a cross-sectional study. Twenty-three liver failure patients with hepatic myelopathy(hepatic myelopathy group), 23 liver failure patients without hepatic myelopathy(non-hepatic myelopathy group) after transjugular intrahepatic portosystemic shunt, and 23 demographically matched healthy volunteers were enrolled from March 2014 to November 2016 at Xijing Hospital, Air Force Military Medical University(Fourth Military Medical University), China. High-resolution magnetization-prepared rapid gradient-echo brain imaging was acquired. Group differences in regional gray matter were assessed using voxel-based morphometry analysis. The relationship between aberrant gray matter and motor characteristics was investigated. Results demonstrated that compared with the non-hepatic myelopathy group, gray matter volume abnormalities were asymmetric, with decreased volume in the left insula(P = 0.003), left thalamus(P = 0.029), left superior frontal gyrus(P = 0.006), and right middle cingulate cortex(P = 0.021), and increased volume in the right caudate nucleus(P = 0.017), corrected with open-source software. The volume of the right caudate nucleus in the hepatic myelopathy group negatively correlated with the lower limb clinical rating of the Fugl-Meyer Assessment(r = –0.53, P = 0.01). Compared with healthy controls, patients with and without hepatic myelopathy exhibited overall increased gray matter volume in both thalami, and decreased gray matter volume in both putamen, as well as in the globus pallidus, cerebellum, and vermis. The gray matter abnormalities we found predominantly involved motor-related regions, and may be associated with motor dysfunction. An enlarged right caudate nucleus might help to predict weak lower limb motor performance in patients with preclinical hepatic myelopathy after transjugular intrahepatic portosystemic shunt. This study was approved by the Ethics Committee of Xijing Hospital, Air Force Military Medical University(Fourth Military Medical University), China(approval No. 20140227-6) on February 27, 2014. 展开更多
关键词 portosystemic shunt HEPATIC MYELOPATHY HEPATIC encephalopathy magnetic resonance imaging gray matter lower limb FUGL-MEYER Assessment basal GANGLIA CAUDATE nucleus voxel-based MORPHOMETRY
下载PDF
Characterization and Pathogenicity of Pseudopestalotiopsis vietnamensis Causing Gray Blight of Wuyi Rock Tea(Camellia sinensis)in China and Specific Mechanisms of Disease Infection
8
作者 Guangheng Wu Lu Rui +6 位作者 Xiang Lu Libo Han Gan Lv Xianyu Fu Jinxian Liu Nong Zhou Chuanhai Zhang 《Phyton-International Journal of Experimental Botany》 SCIE 2023年第1期131-147,共17页
Gray blight disease(GBD)causes significant losses in tea production in China.Although genes and biological processes involved in resistance to fungal disease in tea plants have been identified,specific mechanisms of t... Gray blight disease(GBD)causes significant losses in tea production in China.Although genes and biological processes involved in resistance to fungal disease in tea plants have been identified,specific mechanisms of the GBD infection process remain unknown.In this study,morphological and multi-gene(TEF-TUB-ITS)phylogenetic characteristics were used to identify isolate CLBB1 of Pseudopestalotiopsis vietnamensis.Pathogenicity tests confirmed that isolate CLBB1 from tea leaves caused GBD in the susceptible tea cultivar Wuyi Rock(Camellia sinensis var.sinensis cv.Shuixian).Spores began to germinate 24 h after infection(hai),and after 48 h,elongated fungal hyphae formed from a single conidium.Transcriptome analysis revealed that 482,517,and 369 genes were differentially expressed at 24,48,and 72 hai,respectively,in Wuyi Rock tea leaves.Isolate CLBB1 infection elicited phenotype-related responses and activated defense-related pathways,including plant–pathogen interaction,MAPK signaling,and plant hormone signal transduction,suggesting a possible mechanism underlying phenotype-based susceptibility to CLBB1.Thus,a new Ps.vietnamensis strain causing GBD in the tea cultivar‘Shuixian’was discovered in this study.Transcriptome analysis indicated that pathogen invasion activated chitin-related MAPK pathways and that tea plants required a hormone to restrict CLBB1. 展开更多
关键词 Chitin-related MAPK pathways gray blight disease Pseudopestalotiopsis TEA transcriptional analysis
下载PDF
Support vector regression-based operational effectiveness evaluation approach to reconnaissance satellite system
9
作者 HAN Chi XIONG Wei +1 位作者 XIONG Minghui LIU Zhen 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2023年第6期1626-1644,共19页
As one of the most important part of weapon system of systems(WSoS),quantitative evaluation of reconnaissance satellite system(RSS)is indispensable during its construction and application.Aiming at the problem of nonl... As one of the most important part of weapon system of systems(WSoS),quantitative evaluation of reconnaissance satellite system(RSS)is indispensable during its construction and application.Aiming at the problem of nonlinear effectiveness evaluation under small sample conditions,we propose an evaluation method based on support vector regression(SVR)to effectively address the defects of traditional methods.Considering the performance of SVR is influenced by the penalty factor,kernel type,and other parameters deeply,the improved grey wolf optimizer(IGWO)is employed for parameter optimization.In the proposed IGWO algorithm,the opposition-based learning strategy is adopted to increase the probability of avoiding the local optima,the mutation operator is used to escape from premature convergence and differential convergence factors are applied to increase the rate of convergence.Numerical experiments of 14 test functions validate the applicability of IGWO algorithm dealing with global optimization.The index system and evaluation method are constructed based on the characteristics of RSS.To validate the proposed IGWO-SVR evaluation method,eight benchmark data sets and combat simulation are employed to estimate the evaluation accuracy,convergence performance and computational complexity.According to the experimental results,the proposed method outperforms several prediction based evaluation methods,verifies the superiority and effectiveness in RSS operational effectiveness evaluation. 展开更多
关键词 reconnaissance satellite system(RSS) support vector regression(SVR) gray wolf optimizer opposition-based learning parameter optimization effectiveness evaluation
下载PDF
Partner Selection Analysis and System Development Based on Gray Relation Analysis for an Agile Virtual Enterprise
10
作者 CHEN Hua CAO Yan ZHAO Ru-jia 《International Journal of Plant Engineering and Management》 2005年第4期241-248,共8页
This paper analyzes the state of the art of partner selection and enumerates the advantage of partner selection based on gray relation analysis comparing to the other algorithms of the partner selection. Furthermore, ... This paper analyzes the state of the art of partner selection and enumerates the advantage of partner selection based on gray relation analysis comparing to the other algorithms of the partner selection. Furthermore, partner selection system based on gray relation for an Agile Virtual Enterprise(AVE) is analyzed and designed based on the definition and characteristics of the AVE. According to J2EE mode, the architecture of the partner selection system is put forward and the system is developed t^ing JSP, EJB and SQL Server. The paper lays emphasis on a gray relational mathematic model, AVE evaluation infrastructure, a core algorithm of partner selection and a multi-layer gray relation selection process. 展开更多
关键词 partner selection gray relation analysis agile virtual enterprise AVE) multi-layergray relation selection evaluation infrastructure
下载PDF
Gray domain modeling of regional Karst groundwater flow system——a case study on the Karst system in a hydropower station area
11
《Global Geology》 1998年第1期74-74,共1页
关键词 a case study on the Karst system in a hydropower station area flow gray domain modeling of regional Karst groundwater flow system CASE
下载PDF
Welding Effect at the Heat Affected Zone by Joining a Gray Cast Iron with Stainless Steel E308-16
12
作者 Yajaira Curiel-Razo Enrique Curiel-Reyna +2 位作者 Minerva Robles-Agudo Alberto Lara-Guevara Ignacio Rojas-Rodríguez 《Materials Sciences and Applications》 2023年第6期336-345,共10页
Different investigations of the union of dissimilar materials such as stainless steel and different castings have been carried out, but rapid cooling immediately after welding has not been considered, in this work it ... Different investigations of the union of dissimilar materials such as stainless steel and different castings have been carried out, but rapid cooling immediately after welding has not been considered, in this work it was investigated how rapid cooling affects the metallurgical microstructure and consequently the mechanical properties. The effect of welding parameters on the microstructure and mechanical properties of the joint between dissimilar metals, an E-308-16 austenitic stainless steel and Gray Cast Iron was also analyzed. Gray cast iron samples (GCI) were fabricated, welded and cooled. The main welding parameters studied in this work are the welding technique and the type of filler electrodes. Flux-coated electrode E-308-16 was applied for this different joint. An experimental study was carried out for the analysis of welded joints of similar and dissimilar steels. The microstructure of the welded joints was analyzed using an optical microscope, in the base metals, heat affected zone (HAZ) and filler metal. The mechanical properties of the welded joints were evaluated by Vickers microhardness and tensile strength tests. The hardness profile showed differences in hardness between the base metals, the heat affected zone and the filler metal. The metallurgical microstructures observed along the welded areas corresponded to the profile. The hardness differences determined the effect on the mechanical and metallurgical characteristics of the welded samples as a result of the cooling rate differences. This research work is important because it allows us to analyze the possibility of reworking pieces of dissimilar materials by welding or, failing that, to determine if this may or may not be possible. 展开更多
关键词 gray Iron WELDING Hot Affected Zone Filler Metal Microstructure Dissimilar Metals
下载PDF
Henry Vandyke Carter (1831-1897): the forgotten co-author of Gray’s Anatomy
13
作者 Rafael Romero-Reverón 《History & Philosophy of Medicine》 2023年第4期10-12,共3页
Henry Vandyke Carter(1831–1897),physician and illustrator from Saint George’s Hospital in London,England.He worked with Henry Williamson Gray(1827–1861)on anatomical dissections and Carter’s illustrations contribu... Henry Vandyke Carter(1831–1897),physician and illustrator from Saint George’s Hospital in London,England.He worked with Henry Williamson Gray(1827–1861)on anatomical dissections and Carter’s illustrations contributed significantly to the success of the Treaty of Anatomy,Descriptive and Surgical.Henry Carter never achieved any credit or royalty for his work.This book is currently regarded as one of the most influential human anatomy textbooks.The paper aims to present a brief review of Henry Carter’s contributions to the medical field. 展开更多
关键词 ANATOMY ENGLAND Henry Vandyke Carter gray’s Anatomy medical education PROFESSOR
下载PDF
中国近海栉江珧属分类与地理分布研究进展
14
作者 薛东秀 王海艳 +1 位作者 马兴浩 张涛 《海洋科学》 CAS CSCD 北大核心 2024年第4期122-129,共8页
本文收集了涉及中国栉江珧属(Atrina Gray,1842)分类和分布的文献,结合近年来栉江珧属分子生物学的研究结果以及野外调查情况,对栉江珧属种类和地理分布情况进行了系统的梳理,确定了中国共有7种栉江珧属贝类,并对其分类分歧进行了讨论;... 本文收集了涉及中国栉江珧属(Atrina Gray,1842)分类和分布的文献,结合近年来栉江珧属分子生物学的研究结果以及野外调查情况,对栉江珧属种类和地理分布情况进行了系统的梳理,确定了中国共有7种栉江珧属贝类,并对其分类分歧进行了讨论;概括各栉江珧属种类的地理分布,广东是中国近海栉江珧属物种多样性最丰富的省份,其次为广西壮族自治区。根据目前中国栉江属种类的资源现状,对栉江珧属种类的开发利用与保护提出了建议,以期为深入开展全国范围的栉江珧属生物多样性保护和可持续利用提供科学依据。 展开更多
关键词 栉江珧属(Atrina gray 1842) 物种分类 地理分布 资源保护
下载PDF
基于Gray近似的弹性波阻抗方程及反演 被引量:63
15
作者 王保丽 印兴耀 张繁昌 《石油地球物理勘探》 EI CSCD 北大核心 2007年第4期435-439,共5页
为得到更准确的岩石物理参数数据体,减小计算误差的累积效应,人们希望通过某种方法直接提取岩石物理参数。用Connolly的弹性阻抗(EI)公式进行反演只能直接得到纵、横波速度和密度的信息,再通过计算得到相应的弹性参数,而且不同角度的弹... 为得到更准确的岩石物理参数数据体,减小计算误差的累积效应,人们希望通过某种方法直接提取岩石物理参数。用Connolly的弹性阻抗(EI)公式进行反演只能直接得到纵、横波速度和密度的信息,再通过计算得到相应的弹性参数,而且不同角度的弹性阻抗的量纲不统一。本文针对Connolly方法的不足,通过Gray近似把佐普里兹方程表示为反射系数是剪切模量μ、拉梅系数λ和密度ρ的函数,提出了以Gray的AVO近似方程为基础的一种新的弹性波阻抗反演公式,并对该公式进行了标准化以实现不同角度的弹性波阻抗间量纲的统一。文中用标准化后的弹性波阻抗反演公式对A地区的实际地震数据进行了反演,从反演得到的弹性阻抗数据体中可直接提取剪切模量μ、拉梅系数λ,表明用文中方法提取弹性参数更加稳定、准确。 展开更多
关键词 gray近似 弹性阻抗反演 标准化 拉梅参数
下载PDF
广义Gray码及其在数字图像置乱中的应用 被引量:74
16
作者 邹建成 李国富 齐东旭 《高校应用数学学报(A辑)》 CSCD 北大核心 2002年第3期363-370,共8页
以图像信息安全问题为背景 ,讨论了广义 Gray码及其在数字图像中的置乱作用 ,推广了丁玮等人 ( 1 999年 )的相关结果 .给出了图像置乱变换的周期 。
关键词 广义gray 数字图像 信息安全 置乱变换 周期性
下载PDF
改进的Gray World-Retinex图像自动白平衡方法 被引量:8
17
作者 张钰 姚素英 +1 位作者 张娜 金则群 《数据采集与处理》 CSCD 北大核心 2008年第6期673-677,共5页
提出了一种改进的白平衡方法,改善了Gray World-Retinex算法对色彩丰富度低、近白(灰)点数量较少的图像白平衡后仍然偏色的缺点。使用图像Cb和Cr分量的样本标准差分析图像色彩丰富度,并改进了确定图像近白(灰)点数量的方法,最终定量地... 提出了一种改进的白平衡方法,改善了Gray World-Retinex算法对色彩丰富度低、近白(灰)点数量较少的图像白平衡后仍然偏色的缺点。使用图像Cb和Cr分量的样本标准差分析图像色彩丰富度,并改进了确定图像近白(灰)点数量的方法,最终定量地给出适合采用Gray World-Retinex白平衡法的图像特征,对于样本标准差极低而且近白(灰)点很少的图像,给出一种求极大值增益的方法进行白平衡。对40幅色彩丰富度和近白(灰)点数量不同的偏色图像进行验证,并与Gray World-Retinex算法作了对比。结果表明,本文算法对于具有不同色彩丰富程度和近白(灰)点数量的偏色图像,都可以获得较理想的白平衡效果。该算法复杂度低,对图像实时处理具有很大吸引力。 展开更多
关键词 自动白平衡 样本标准差 gray World—Retinex算法 CMOS图像传感器
下载PDF
紧致的Hilbert曲线Gray码索引算法 被引量:6
18
作者 曹雪峰 万刚 张宗佩 《测绘学报》 EI CSCD 北大核心 2016年第B12期90-98,共9页
Hilbert曲线具有良好的聚簇性,使其成为设计全球立体网格多维数据索引的重要工具。但当数据集在不同维度上的分布密度存在较大差异时,常规Hilbert曲线索引会出现大量的冗余。对此,本文基于Gray码推导分析了Hilbert曲线索引的构造特点,... Hilbert曲线具有良好的聚簇性,使其成为设计全球立体网格多维数据索引的重要工具。但当数据集在不同维度上的分布密度存在较大差异时,常规Hilbert曲线索引会出现大量的冗余。对此,本文基于Gray码推导分析了Hilbert曲线索引的构造特点,进而设计实现了紧致Hilbert曲线索引算法,在保持Hilbert曲线良好聚簇性的同时,避免了数据维度分布差异带来的索引冗余问题。试验结果表明,相比常规Hilbert索引,紧致Hilbert曲线索引计算复杂度相当,在实例数据测试中编码耗时减少约40%,索引存储空间减少约46%,排序速度约为Hilbert排序的4.3倍。 展开更多
关键词 HILBERT曲线 gray 空间索引 全球离散网格
下载PDF
基于Gray码和线移条纹的结构光3D测量技术 被引量:11
19
作者 于晓洋 吴海滨 《仪器仪表学报》 EI CAS CSCD 北大核心 2008年第4期701-704,共4页
结构光3D测量的关键问题之一是准确地确定图像采样点并求其投射角。提出一种以时序向被测表面投射Gray码和线移条纹进行编码,以亚像素定位技术提取Gray码条纹边缘和线移条纹中心,将其上点作为图像采样点进行解码的方法。消除了Gray码固... 结构光3D测量的关键问题之一是准确地确定图像采样点并求其投射角。提出一种以时序向被测表面投射Gray码和线移条纹进行编码,以亚像素定位技术提取Gray码条纹边缘和线移条纹中心,将其上点作为图像采样点进行解码的方法。消除了Gray码固有的一位解码误差对投射角求取的影响,同时提高了采样密度。文中具体介绍该方法的编码解码原理,分析了编码图案正交投射对测量准确度的影响,给出了仿真实验结果。测量误差约为0.04%。 展开更多
关键词 3D测量 结构光 gray 线移
下载PDF
位平面与Gray码相结合的图像置乱方法 被引量:10
20
作者 谭永杰 马苗 《计算机工程与应用》 CSCD 北大核心 2010年第16期174-177,共4页
针对数字图像的传输安全问题,提出一种将位平面分解与Gray码相结合的图像置乱方法。该方法首先将图像分解成8个位平面,通过位异或操作改变携带图像有用信息的高4位位平面的值,然后对得到的初步置乱图像的灰度值进行Gray码变换,进一步置... 针对数字图像的传输安全问题,提出一种将位平面分解与Gray码相结合的图像置乱方法。该方法首先将图像分解成8个位平面,通过位异或操作改变携带图像有用信息的高4位位平面的值,然后对得到的初步置乱图像的灰度值进行Gray码变换,进一步置乱图像,从而得到加密图像。初步实验结果显示,该方法置乱效果明显优于Arnold法、Hilbert法等现有置乱方法,且实现简单。 展开更多
关键词 图像置乱 位平面 gray
下载PDF
上一页 1 2 31 下一页 到第
使用帮助 返回顶部