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ANALYSIS ON GRAY NODES AND GRAYNESS DEGREE IN COMPLEX NETWORK 被引量:1
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作者 崔博 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI 2012年第2期125-130,共6页
Based on the theory of complex network and gray system, the sugesstion that there exist two types of gray nodes in complex networks, Gray Node I and Gray Node II, is concluded. The first one refers to the existent unk... Based on the theory of complex network and gray system, the sugesstion that there exist two types of gray nodes in complex networks, Gray Node I and Gray Node II, is concluded. The first one refers to the existent unknown gray nodes, and the second the evolution gray nodes. The relevant definitions are also given. Further- more, grayness degree in complex networks is described and divided into two forms--the relative grayness degree (RGD) and the absolute grayness degree (AGD), which are proved respectively. 展开更多
关键词 gray system complex network gray nodes grayness degree
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一种广义Gray码及其在数字图像置乱中的应用 被引量:3
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作者 王广超 罗来鹏 《赣南师范学院学报》 2007年第3期41-44,共4页
以图像的信息安全问题为背景,提出了一种新的广义Gray码,讨论了该码在数字图像置乱中的应用.实验表明该序码变换在数字图像置乱方面效果明显.
关键词 gray 广义gray 置乱广义gray 置乱变换 信息安全
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基于广义Gray码变换和广义Arnold映射的彩色图像加密算法
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作者 郭蓉蓉 陈星 +1 位作者 赵红旗 叶瑞松 《交叉科学快报》 2025年第3期380-393,共14页
本文通过结合混沌系统与数据编码,提出了一种新型彩色图像加密算法。该算法通过离散型广义Arnold映射对明文像素位置进行非线性置乱,破坏相邻像素相关性;引入广义Gray码变换对置乱后图像颜色分量值实施编码,初步隐藏视觉信息;利用连续... 本文通过结合混沌系统与数据编码,提出了一种新型彩色图像加密算法。该算法通过离散型广义Arnold映射对明文像素位置进行非线性置乱,破坏相邻像素相关性;引入广义Gray码变换对置乱后图像颜色分量值实施编码,初步隐藏视觉信息;利用连续型广义Arnold映射生成伪随机密钥流,对编码图像完成扩散运算,进一步破坏明文统计特征。加密算法融合了广义Gray码变换的局部混淆能力和广义Arnold映射的全局扩散特性,构建双重安全机制。一方面,离散型广义Arnold映射和广义Gray编码协同增强像素位置与灰度值的动态扰乱效果;另一方面,连续型广义Arnold映射扩展了加密算法的密钥空间。数值实验表明,该图像加密算法具有优良的加密性能,可以抵御蛮力攻击、统计分析攻击以及差分攻击等。The paper proposes a novel image encryption algorithm by integrating chaotic system with data coding. The algorithm employs a discrete generalized Arnold map to nonlinearly scramble plain image’s pixel positions, effectively disrupting adjacent pixel correlations. A generalized gray code transformation is introduced to perform encoding on color component values of the scrambled image, achieving preliminary visual information concealment. Subsequently, a continuous generalized Arnold map generates pseudo-random keystreams to execute diffusion operations on the encoded image, further eliminating statistical features of the plain image. Combining the local confusion capability of generalized gray code transformation with the global diffusion nature of generalized Arnold map, the encryption algorithm establishes a dual security mechanism. On the one hand, the collaborative effect of discrete generalized Arnold map and generalized gray coding enhances dynamic disruption of pixel positions and grayscale values;on the other hand, the continuous generalized Arnold map significantly expands the key space of the proposed encryption. Numerical experiments demonstrate that the proposed image encryption algorithm exhibits excellent performance and security, showing strong resistance against differential analysis attack, statistical attacks and brute-force attack, etc. 展开更多
关键词 图像加密 广义gray 广义Arnold映射 混沌映射
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基于广义Gray码和DCT-SVD的数字水印算法研究
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作者 易建隆 陈星月 +2 位作者 黄昱霖 胡橼丹 高仕龙 《图像与信号处理》 2025年第4期486-495,共10页
本文提出一种基于广义Gray码、离散余弦变换与奇异值分解的数字水印算法,有效提升了水印的鲁棒性。该算法先对水印信息实施广义Gray码变换,后通过分块离散余弦变换和奇异值分解,将水印嵌入到载体图像中频段的奇异值里。实验结果表明,相... 本文提出一种基于广义Gray码、离散余弦变换与奇异值分解的数字水印算法,有效提升了水印的鲁棒性。该算法先对水印信息实施广义Gray码变换,后通过分块离散余弦变换和奇异值分解,将水印嵌入到载体图像中频段的奇异值里。实验结果表明,相较于已有算法,该算法在JPEG压缩、噪声干扰、裁剪、旋转等多种攻击下,归一化相关系数表现更优,具备更强的鲁棒性。 展开更多
关键词 数字水印 离散余弦变换 奇异值分解 广义gray 鲁棒性
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Fetal Gray Matter Heterotopia 被引量:1
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作者 Jiaojiao Liu Lianxiang Xiao 《iRADIOLOGY》 2025年第3期231-233,共3页
A pregnant woman underwent fetal brain magnetic resonance imaging(MRI)following ultrasound detection of a posterior fossa cyst at 29 weeks'gestation.She presented with no relevant medical history and underwent a r... A pregnant woman underwent fetal brain magnetic resonance imaging(MRI)following ultrasound detection of a posterior fossa cyst at 29 weeks'gestation.She presented with no relevant medical history and underwent a routine obstetric examination during pregnancy.The fetal head position,fetal cranial development,and limb development remained normal until 29 weeks. 展开更多
关键词 fetal magnetic resonance imaging FETUS gray matter heterotopia
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5DGWO-GAN:A Novel Five-Dimensional Gray Wolf Optimizer for Generative Adversarial Network-Enabled Intrusion Detection in IoT Systems
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作者 Sarvenaz Sadat Khatami Mehrdad Shoeibi +2 位作者 Anita Ershadi Oskouei Diego Martín Maral Keramat Dashliboroun 《Computers, Materials & Continua》 SCIE EI 2025年第1期881-911,共31页
The Internet of Things(IoT)is integral to modern infrastructure,enabling connectivity among a wide range of devices from home automation to industrial control systems.With the exponential increase in data generated by... The Internet of Things(IoT)is integral to modern infrastructure,enabling connectivity among a wide range of devices from home automation to industrial control systems.With the exponential increase in data generated by these interconnected devices,robust anomaly detection mechanisms are essential.Anomaly detection in this dynamic environment necessitates methods that can accurately distinguish between normal and anomalous behavior by learning intricate patterns.This paper presents a novel approach utilizing generative adversarial networks(GANs)for anomaly detection in IoT systems.However,optimizing GANs involves tuning hyper-parameters such as learning rate,batch size,and optimization algorithms,which can be challenging due to the non-convex nature of GAN loss functions.To address this,we propose a five-dimensional Gray wolf optimizer(5DGWO)to optimize GAN hyper-parameters.The 5DGWO introduces two new types of wolves:gamma(γ)for improved exploitation and convergence,and theta(θ)for enhanced exploration and escaping local minima.The proposed system framework comprises four key stages:1)preprocessing,2)generative model training,3)autoencoder(AE)training,and 4)predictive model training.The generative models are utilized to assist the AE training,and the final predictive models(including convolutional neural network(CNN),deep belief network(DBN),recurrent neural network(RNN),random forest(RF),and extreme gradient boosting(XGBoost))are trained using the generated data and AE-encoded features.We evaluated the system on three benchmark datasets:NSL-KDD,UNSW-NB15,and IoT-23.Experiments conducted on diverse IoT datasets show that our method outperforms existing anomaly detection strategies and significantly reduces false positives.The 5DGWO-GAN-CNNAE exhibits superior performance in various metrics,including accuracy,recall,precision,root mean square error(RMSE),and convergence trend.The proposed 5DGWO-GAN-CNNAE achieved the lowest RMSE values across the NSL-KDD,UNSW-NB15,and IoT-23 datasets,with values of 0.24,1.10,and 0.09,respectively.Additionally,it attained the highest accuracy,ranging from 94%to 100%.These results suggest a promising direction for future IoT security frameworks,offering a scalable and efficient solution to safeguard against evolving cyber threats. 展开更多
关键词 Internet of things intrusion detection generative adversarial networks five-dimensional binary gray wolf optimizer deep learning
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Persistent alterations in gray matter in COVID-19 patients experiencing sleep disturbances:a 3-month longitudinal study
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作者 Kaixuan Zhou Gaoxiong Duan +19 位作者 Ying Liu Bei Peng Xiaoyan Zhou Lixia Qin Lingyan Liang Yichen Wei Qingping Zhang Xiaocheng Li Haixia Qin Yinqi Lai Yian Lu Yan Zhang Jiazhu Huang Jinli Huang Yinfei Ouyang Bolin Bin Mingming Zhao Jun Liu Jianrong Yang Demao Deng 《Neural Regeneration Research》 SCIE CAS 2025年第10期3013-3024,共12页
Sleep disturbances are among the most prevalent neuropsychiatric symptoms in individuals who have recovered from severe acute respiratory syndrome coronavirus 2 infections.Previous studies have demonstrated abnormal b... Sleep disturbances are among the most prevalent neuropsychiatric symptoms in individuals who have recovered from severe acute respiratory syndrome coronavirus 2 infections.Previous studies have demonstrated abnormal brain structures in patients with sleep disturbances who have recovered from coronavirus disease 2019(COVID-19).However,neuroimaging studies on sleep disturbances caused by COVID-19 are scarce,and existing studies have primarily focused on the long-term effects of the virus,with minimal acute phase data.As a result,little is known about the pathophysiology of sleep disturbances in the acute phase of COVID-19.To address this issue,we designed a longitudinal study to investigate whether alterations in brain structure occur during the acute phase of infection,and verified the results using 3-month follow-up data.A total of 26 COVID-19 patients with sleep disturbances(aged 51.5±13.57 years,8 women and 18 men),27 COVID-19 patients without sleep disturbances(aged 47.33±15.98 years,9 women and 18 men),and 31 age-and gender-matched healthy controls(aged 49.19±17.51 years,9 women and 22 men)were included in this study.Eleven COVID-19 patients with sleep disturbances were included in a longitudinal analysis.We found that COVID-19 patients with sleep disturbances exhibited brain structural changes in almost all brain lobes.The cortical thicknesses of the left pars opercularis and left precuneus were significantly negatively correlated with Pittsburgh Sleep Quality Index scores.Additionally,we observed changes in the volume of the hippocampus and its subfield regions in COVID-19 patients compared with the healthy controls.The 3-month follow-up data revealed indices of altered cerebral structure(cortical thickness,cortical grey matter volume,and cortical surface area)in the frontal-parietal cortex compared with the baseline in COVID-19 patients with sleep disturbances.Our findings indicate that the sleep disturbances patients had altered morphology in the cortical and hippocampal structures during the acute phase of infection and persistent changes in cortical regions at 3 months post-infection.These data improve our understanding of the pathophysiology of sleep disturbances caused by COVID-19. 展开更多
关键词 brain structure cortical gray matter volume cortical surface area cortical thickness HIPPOCAMPUS magnetic resonance imaging Pittsburgh Sleep Quality Index severe acute respiratory syndrome coronavirus 2 infections sleep disturbances sub-cortical volume
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Application of Gray Scale Method of Melanin Production in Zebrafish
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作者 Zheng Muchuang Xu Qitian +1 位作者 Ma Manhua Lei Cuiting 《China Detergent & Cosmetics》 2025年第3期47-52,共6页
Because the physiological characteristics and melanin regulation mechanism of zebrafish are highly similar with those of humans,it is of high reference value to use zebrafish model in the evaluation of cosmetic whiten... Because the physiological characteristics and melanin regulation mechanism of zebrafish are highly similar with those of humans,it is of high reference value to use zebrafish model in the evaluation of cosmetic whitening efficacy.In this study,zebrafish embryos are used as biological models to evaluate the whitening efficacy of six kinds of cosmetics raw materials,such as antioxidant,preservative and essence,and the formula of facial cleanser and facial mask products,and the limitations of the zebrafish melanin production grayscale detection method in practical application are discussed.The results show that the selection of different types of components can also reduce the production of melanin and show whitening effect.It can be seen that the gray scale method of melanin production in zebrafish is suitable for the evaluation of the efficacy of raw materials.In practical application,due to the complexity of the formula,the toxic effects of different types of ingredients may interfere with the melanin generation of zebrafish,affecting the judgment and evaluation of whitening efficacy.For the detection of whitening efficacy of products,a comprehensive evaluation system should be built together with other methods to accurately evaluate the whitening efficacy. 展开更多
关键词 zebrafish model skin whitening gray scale method MELANIN
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Gray zone and the need for expansion in chronic hepatitis B:From theory to clinical practice
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作者 Thang Viet Luong Ngoc Phan Hong Nguyen +3 位作者 Tri Van Nguyen Duong Hung Tran Thien Dinh Nguyen Hai Nguyen Ngoc Dang 《World Journal of Hepatology》 2025年第10期154-164,共11页
Chronic hepatitis B(CHB)remains a significant global health challenge.The natural course of CHB is traditionally divided into four phases:(1)Immune tolerance;(2)Immune activation;(3)Immune control;and(4)Immune escape.... Chronic hepatitis B(CHB)remains a significant global health challenge.The natural course of CHB is traditionally divided into four phases:(1)Immune tolerance;(2)Immune activation;(3)Immune control;and(4)Immune escape.However,approximately 20%-30%of patients referred to as the"gray zone"(GZ)do not fit neatly into these categories.These patients often exhibit elevated hepatitis B virus DNA levels alongside normal or mildly elevated alanine aminotransferase levels,placing them at significant risk for liver fibrosis,cirrhosis,and hepatocellular carcinoma.However,current clinical guidelines generally do not recommend antiviral therapy for GZ patients,increasing their vulnerability to adverse outcomes.This mini-review explores the challenges and gaps in CHB management,focusing on GZ patients.It also highlights recent advancements in therapeutic strategies and updates in clinical guidelines,emphasizing the need for a more inclusive,risk-adapted approach to treatment.By leveraging novel biomarkers,noninvasive fibrosis assessment tools,and artificial intelligencedriven predictive models,this article advocates for early intervention to mitigate disease progression and improve clinical outcomes in this overlooked population. 展开更多
关键词 Chronic hepatitis B gray zone Antiviral therapy Biomarkers Risk stratification Liver fibrosis
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Link of gray matter volume to cognitive and motor function in elderly patients with mild cognitive impairment
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作者 Yue-Bing Yue Man-Fei Xu +3 位作者 Zheng Xu Jian-Xia Xu Min Lin Yi Yang 《World Journal of Psychiatry》 2025年第4期51-59,共9页
BACKGROUND Mild cognitive impairment(MCI)is a transitional state between normal aging and Alzheimer's disease(AD),characterized by subtle cognitive decline.Amnestic MCI(aMCI),in particular,is a critical precursor ... BACKGROUND Mild cognitive impairment(MCI)is a transitional state between normal aging and Alzheimer's disease(AD),characterized by subtle cognitive decline.Amnestic MCI(aMCI),in particular,is a critical precursor often progressing to AD.There is growing interest in understanding the neuroanatomical correlates of aMCI,especially the role of gray matter volume(GMV)in cognitive and motor function decline.This study hypothesized that aMCI patients will exhibit reduced GMV,particularly in brain regions associated with cognition and motor control,impacting both cognitive performance and motor abilities.AIM To investigate the association of GMV with cognitive and motor functions in aMCI.METHODS In this cross-sectional study conducted from March 2022 to March 2024,45 aMCI patients and 45 normal controls from our Department of Geratology were enrolled.Voxel-based morphometry was used to compare GMV between groups.Correlation of differential GMV with cognitive scores and gait parameters was assessed via partial correlation analysis.Linear regression was used to assess associations between whole-brain GMV and gait measures.RESULTS GMV of aMCI region of interest(ROI)1 and ROI2 was negatively correlated with Activities of Daily Living(ADL)score.GMV of ROI6 was positively correlated with the total scores of Mini-Mental State Examination and Cambridge Cognitive Examination-Chinese Version(CAMCOG-C)and negatively correlated with ADL score.In the partial correlation analysis of cognitive and motor function parameters,age,gender,educational level,height,and weight were controlled,and the results showed that CAMCOG-C was negatively correlated with Dual Task of Time Up and Go Test(TUG)duration in the aMCI group.The volume of the left occipital gray matter in the aMCI group was negatively correlated with TUG.GMV of the bilateral frontal gyrus,right orbitofrontal gyrus,right occipital cleft,right supraoccipital gyrus,and left anterior central gyrus was positively correlated with walking speed.CONCLUSION GMV reduction in aMCI correlates with impaired cognition and motor function,emphasizing key roles for prefrontal,occipital,and central regions in gait disorders. 展开更多
关键词 Amnestic mild cognitive impairment gray matter volume Voxel-based morphometry Alzheimer's disease Motor function
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基于Gray—FAHP数学模型的我国农村金融风险评价体系研究
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作者 李香彬 《现代营销(下)》 2025年第4期22-24,共3页
如今,乡村振兴战略正紧锣密鼓地实施,而农村金融在现代农村经济中扮演着越来越重要的角色。农村金融在高速发展的同时又存在着许多风险,合适的金融风险评价方法可以对金融起到很好的监督预警作用。本文运用Gray—FAHP数学模型,从定性、... 如今,乡村振兴战略正紧锣密鼓地实施,而农村金融在现代农村经济中扮演着越来越重要的角色。农村金融在高速发展的同时又存在着许多风险,合适的金融风险评价方法可以对金融起到很好的监督预警作用。本文运用Gray—FAHP数学模型,从定性、定量的角度进行综合研判分析,建立多维评估指标体系,分析指标间的权重关系,揭示指标对农村金融安全性的内在影响,以达到对农村金融风险更加准确更加深刻的认知。为政府以及政策的制定者提供合理科学的数据支持,弥补农村金融安全性方面的不足,助力农村经济的安全、快速发展。 展开更多
关键词 gray—FAHP 农村金融 风险评价 定量分析
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Gray relational analysis and SBOA-BP for predicting settlement intervals of high-speed railway subgrade
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作者 Quanpeng He Shaoyuan Li 《Railway Sciences》 2025年第2期199-212,共14页
Purpose–The deformation of the roadbed is easily influenced by the external environment to improve the accuracy of high-speed railway subgrade settlement prediction.Design/methodology/approach–A high-speed railway s... Purpose–The deformation of the roadbed is easily influenced by the external environment to improve the accuracy of high-speed railway subgrade settlement prediction.Design/methodology/approach–A high-speed railway subgrade settlement interval prediction method using the secretary bird optimization(SBOA)algorithm to optimize the BP neural network under the premise of gray relational analysis is proposed.Findings–Using the SBOA algorithm to optimize the BP neural network,the optimal weights and thresholds are obtained,and the best parameter prediction model is combined.The data were collected from the sensors deployed through the subgrade settlement monitoring system,and the gray relational analysis is used to verify that all four influencing factors had a great correlation to the subgrade settlement,and the collected data are verified using the model.Originality/value–The experimental results show that the SBOA-BP model has higher prediction accuracy than the BP model,and the SBOA-BP model has a wider range of prediction intervals for a given confidence level,which can provide higher guiding value for practical engineering applications. 展开更多
关键词 gray relational analysis Secretary bird optimization algorithm Backpropagation neural network Subgrade settlement Interval prediction
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环F_4+uF_4上线性码及其对偶码的Gray像 被引量:1
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作者 刘修生 刘花璐 《通信学报》 EI CSCD 北大核心 2012年第8期134-137,共4页
研究了环F4+uF4与域F4上的线性码,利用环F4+uF4上码C的Gray重量wG,Gray距离d G和(F4+uF4)n到F4 2n的Gray映射φ,证明了环F4+uF4上线性码C及其对偶码的Gray像φ(C)为F4上的线性码和对偶且dH G(φ(C))dG(C)。同时,给出了F4+uF4上循环码C的... 研究了环F4+uF4与域F4上的线性码,利用环F4+uF4上码C的Gray重量wG,Gray距离d G和(F4+uF4)n到F4 2n的Gray映射φ,证明了环F4+uF4上线性码C及其对偶码的Gray像φ(C)为F4上的线性码和对偶且dH G(φ(C))dG(C)。同时,给出了F4+uF4上循环码C的Gray像φ(C)为F4上的2-拟循环码。 展开更多
关键词 线性码 对偶码 gray重量 gray映射
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基于Anti-Gray映射的4D-QPSK星座设计
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作者 郭常盈 梁云英 方伟伟 《通信技术》 2015年第7期776-779,共4页
多维映射通过增加星座的维度数而使得符号间的平均欧式距离大大增加,这可以大程度地提高数字通信系统的可靠性。然而已有的基于Gray映射的4D-QPSK星座在设计上,并没有充分利用四维星座的空间优势,对于相邻星座点的汉明距离并未达到最大... 多维映射通过增加星座的维度数而使得符号间的平均欧式距离大大增加,这可以大程度地提高数字通信系统的可靠性。然而已有的基于Gray映射的4D-QPSK星座在设计上,并没有充分利用四维星座的空间优势,对于相邻星座点的汉明距离并未达到最大。提出一种基于Anti-Gray映射的4D-QPSK星座设计方案,该方案中的比特映射方式按照相邻星座点汉明距离最大,汉明距离为1的星座点欧式距离最大的设计原则,使星座点间具有最大的分集度。仿真结果表明,该方案可以提高抵抗衰落信道的能力。 展开更多
关键词 gray映射 Anti-gray映射 多维映射 4D-QPSK
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基于Gray近似的弹性波阻抗方程及反演 被引量:66
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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
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广义Gray码及其在数字图像置乱中的应用 被引量:75
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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
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环F_p+vF_p上的v-常循环码及其Gray象 被引量:3
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作者 王敏 李捷 《大学数学》 2015年第6期87-91,共5页
定义了F_p+vF_p到F^2_p的Gray映射,其中v^2=1,证明了F_p+vF_p上长为n的v-常循环码在定义的Gray映射下的象是F_p上长为2n的距离不变的线性循环码,并进一步定义了F_p+vF_p上的广义Gray象,证明了其上线性码的广义Gray象是F_p上距离不变的... 定义了F_p+vF_p到F^2_p的Gray映射,其中v^2=1,证明了F_p+vF_p上长为n的v-常循环码在定义的Gray映射下的象是F_p上长为2n的距离不变的线性循环码,并进一步定义了F_p+vF_p上的广义Gray象,证明了其上线性码的广义Gray象是F_p上距离不变的线性码、循环码的广义Gray象是F_p上长为4n的4-准循环码. 展开更多
关键词 常循环码 准循环码 gray映射 广义gray映射
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紧致的Hilbert曲线Gray码索引算法 被引量:6
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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
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改进的Gray World-Retinex图像自动白平衡方法 被引量:8
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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
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基于Gray码和线移条纹的结构光3D测量技术 被引量:11
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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
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