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肺部孤立性实性病变的磁共振DWI技术优选 预览
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作者 俞家熙 李新春 +3 位作者 雷强 万齐 王宇泽 胡剑锋 《放射学实践》 北大核心 2019年第8期874-878,共5页
目的:比较快速自旋回波扩散加权成像(TSE-DWI)与平面回波(EPI)DWI对肺部孤立性实性病灶的成像质量,探讨TSE-DWI在肺部孤立性病灶中的临床应用价值。方法:对40例肺孤立性实性病变患者分别行TSE-DWI及EPI-DWI扫描(b=600s/mm^2),测量并比... 目的:比较快速自旋回波扩散加权成像(TSE-DWI)与平面回波(EPI)DWI对肺部孤立性实性病灶的成像质量,探讨TSE-DWI在肺部孤立性病灶中的临床应用价值。方法:对40例肺孤立性实性病变患者分别行TSE-DWI及EPI-DWI扫描(b=600s/mm^2),测量并比较两个序列图像上病灶的信噪比、病灶及脊髓的ADC值、变形率、成像效率及图像质量的主观评分。结果:TSE-DWI序列的病灶成像效率为100%(40/40);EPI-DWI的成像效率为90%(36/40),4例病灶的图像变形严重,无法测量其ADC值。TSE-DWI序列上脊髓的ADC值高于EPI-DWI序列(P<0.01)。病灶在TSE-DWI上的ADC值高于EPI-DWI序列(P=0.007)。病灶在TSE-DWI上的变形率明显低于EPI-DWI序列(P<0.01)。图像质量的主观评分,TSE-DWI序列中39例为3分、1例为2分,EPI序列中主观评分19例为3分、17例为2分、4例为1分(图像变形无法测量),两组间图像质量主观评分的差异具有统计学意义(P<0.001)。结论:TSE-DWI的病灶变形率、成像效率及主观评分均较EPI-DWI序列高,可作为胸部孤立性病变的常规扫描序列。 展开更多
关键词 肺孤立性实性病变 扩散加权成像 表观扩散系数 图像质量 信号噪声比
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射频场滤波器对3.0T MR腰椎成像质量的影响 预览
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作者 戴艳芳 张苗 +3 位作者 齐志刚 张默 李坤成 卢洁 《中国医学影像技术》 CSCD 北大核心 2018年第11期1747-1749,共3页
MRI软组织分辨率和对比度较高,已成为诊断骨骼肌肉系统疾病的重要工具之一[1-3]。近年来,3.0T MR仪已普遍应用于临床。拉莫尔方程质子的进动频率与静磁场场强呈正相关,场强增高致质子进动频率加快;而频率与波长呈反比,激发质子共振的射... MRI软组织分辨率和对比度较高,已成为诊断骨骼肌肉系统疾病的重要工具之一[1-3]。近年来,3.0T MR仪已普遍应用于临床。拉莫尔方程质子的进动频率与静磁场场强呈正相关,场强增高致质子进动频率加快;而频率与波长呈反比,激发质子共振的射频脉冲波长缩短,与人体相互作用后,引起射频磁场(B 1场)不均匀性改变,从而产生或加重在1.5T及以下场强下没有或较轻的伪影,特别是驻波效应和介电伪影,导致MR图像质量下降。充分发挥高场强MRI的优势需消除或减轻上述影响。本研究比较3.0T MR快速自旋回波腰椎轴位T2WI中使用与不使用B 1滤波器时所获图像质量,探讨B 1滤波器对于改善超高场强下成像质量的价值。1 资料与方法1.1一般资料 选取2017年11月—12月在我院接受腰椎MR检查的30例患者,男14例,女16例,年龄19~80岁,平均(47.6±17.3)岁。纳入标准:①无MR检查禁忌证;②无腰椎手术史;③腹部无金属(含MR兼容金属)植入物。排除标准:①有幽闭恐惧症等其他原因未能完成检查;②运动伪影过重。 展开更多
关键词 磁共振成像 信号噪声比 对比噪声比 腰椎
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Target recognition based on phase noise of received laser signal in lidar jammer
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作者 Mahdi Nouri Mohsen Mivehchy Mohamad Farzan Sabahi 《中国光学快报:英文版》 SCIE EI CAS CSCD 2017年第10期11-14,共4页
In this Letter, a method based on the effects of imperfect oscillators in lasers is proposed to distinguish targets in continuous wave tracking lidar. This technique is based on the fact that each lidar signal source ... In this Letter, a method based on the effects of imperfect oscillators in lasers is proposed to distinguish targets in continuous wave tracking lidar. This technique is based on the fact that each lidar signal source has a specific influence on the phase noise that makes real targets from the false ones. A simulated signal is produced by complex circuits, modulators, memory, and signal oscillators. For example, a deception laser beam has an unequal and variable phase noise from a real target. Thus, the phase noise of transmitted and received signals does not have the same power levels and patterns. To consider the performance of the suggested method, the probability of detection(PD) is shown for various signal-to-noise ratios and signal-to-jammer ratios based on experimental outcomes. 展开更多
关键词 雷达干扰信号 目标识别方法 相位噪声 激光雷达 检测概率 雷达信号源 信号干扰比 信号噪声比
双源双能量CT胰腺虚拟平扫的临床应用价值研究 预览
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作者 叶荣 雷军强 +1 位作者 郭奇虹 乔吴高 《中国中西医结合影像学杂志》 2017年第5期526-529,533共5页
目的:探讨双源双能量CT胰腺虚拟平扫的临床应用价值.方法:50例患者行上腹部双源CT常规平扫及动脉期、门脉期、延迟期双能量CT增强扫描,通过双能量"Liver VNC"软件后处理分别得到动脉期、门脉期及延迟期的虚拟平扫图像,比较常规平扫... 目的:探讨双源双能量CT胰腺虚拟平扫的临床应用价值.方法:50例患者行上腹部双源CT常规平扫及动脉期、门脉期、延迟期双能量CT增强扫描,通过双能量"Liver VNC"软件后处理分别得到动脉期、门脉期及延迟期的虚拟平扫图像,比较常规平扫与3组虚拟平扫图像的胰腺平均CT值、竖脊肌平均CT值、SNR、对比噪声比(CNR)、图像主观质量、病灶显示情况及辐射剂量.结果:常规平扫与虚拟平扫图像的胰腺平均CT值、竖脊肌平均CT值差异均无统计学意义(均P〉0.05);虚拟平扫图像的SNR、CNR均高于常规平扫图像(均P〈0.05);常规平扫与虚拟平扫所有图像评分均在3分以上,差异有统计学意义(P〈0.05),均满足临床诊断需要;常规平扫与虚拟平扫图像对病灶有相似的检出功能;双能量扫描虚拟平扫的总有效剂量低于常规扫描(P〈0.05).结论:双源双能量CT胰腺虚拟平扫图像质量较常规平扫图像有一定程度下降,但可满足临床诊断需求,同时又减少一次平扫的辐射剂量,且SNR更高,因此具有潜在的临床应用价值. 展开更多
关键词 体层摄影术 X线计算机 双能量扫描 胰腺 虚拟平扫 信号噪声比 对比噪声比 辐射剂量
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双源CT非线性融合技术对超重或肥胖患者心脏成像质量优化初步研究 预览
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作者 王清波 戴慧 +2 位作者 陈蒙 李永超 郭亮 《医学影像学杂志》 2016年第6期993-997,共5页
目的探讨炫速双源CT非线性融合技术对超重或肥胖患者心脏CT成像质量的优化价值。方法 36位体质指数处于超重或肥胖的患者行双能量心脏增强扫描,每一位患者重建4组图像,A组:NLB1(λ=150HU,ω=200HU),B组:NLB2(λ=70HU,ω=200HU),C... 目的探讨炫速双源CT非线性融合技术对超重或肥胖患者心脏CT成像质量的优化价值。方法 36位体质指数处于超重或肥胖的患者行双能量心脏增强扫描,每一位患者重建4组图像,A组:NLB1(λ=150HU,ω=200HU),B组:NLB2(λ=70HU,ω=200HU),C组:NLB3(λ=260HU,ω=200HU),D组:NLB4(λ=260HU,ω=400HU),测量并计算上述图像主动脉根部、右冠状动脉中段、左冠状动脉主干和左心室前壁的CT值、图像噪声、SNR、CNR。采用TWO-WAY ANOVA及TUKEY检验客观评价各组图像质量。结果 4组图像间除心肌CT值无统计学差异外(F=2.492,P=0.064),余各部位CT值、噪声、SNR、CNR均具有统计学差异(P〈0.05)。各血管CT值B组最高,与A组均无统计学差异。各血管噪声B组最小,与A组无统计学差异。心肌噪声C组最小,与A组无统计学差异。各血管SNR A、B组较高,两组无统计学差异。心肌SNR以A、C、D组较大,与B组有统计学差异。各血管均以D组SNR最小。心肌SNR B组最小。所有CNR均以A组最高,与B组无统计学差异,D组最小。结论非线性融合技术选择合适的融合参数(λ=150HU,ω=200HU)既可以提升超重或肥胖患者冠状动脉的强化效果又可以抑制冠状动脉及心肌噪声,进一步提高心脏CT成像的CNR。 展开更多
关键词 肥胖 线性融合 非线性融合 信号噪声比 对比噪声比
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食管癌扩散加权成像的b值选取及其在恶性程度评估中的应用 预览 被引量:2
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作者 陈伟 朱艳 +4 位作者 徐青青 周胜利 柏根基 王亚婷 陆洋 《放射学实践》 北大核心 2016年第12期1182-1185,共4页
目的:探讨食管癌扩散加权成像的最佳b值及ADC值在预测食管癌恶性程度中的价值。方法:对45例经病理证实的食管癌患者行常规MRI及多b值DWI扫描,分别采用b值500、800和1000s/mm^2。结果:随着b值的升高,DWI图像上食管癌病变的信号噪声比... 目的:探讨食管癌扩散加权成像的最佳b值及ADC值在预测食管癌恶性程度中的价值。方法:对45例经病理证实的食管癌患者行常规MRI及多b值DWI扫描,分别采用b值500、800和1000s/mm^2。结果:随着b值的升高,DWI图像上食管癌病变的信号噪声比(SNR)、对比噪声比(CNR)逐渐下降(SNR分别为55.79±27.74、42.05±22.74、30.38±17.30;CNR分别为31.85±19.82、22.35±13.57和17.35±14.49)。经受试者工作特征(ROC)曲线分析,各b值下病变的ADC值均可作为评估肿瘤分化程度的有效指标,但以选取b值为500s/mm2时诊断效能最高,曲线下面积最大(AUC=0.902),ADC值的最佳阈值为1.72×10^-3) mm^2/s。结论:使用b值为500s/mm^2的DWI检查有利于食管癌病变的检出。DWI及ADC值在一定程度上能够反映肿瘤的分化情况,有助于食管癌的术前评估。 展开更多
关键词 食管癌 扩散加权成像 表现扩散系数 信号噪声比 对比噪声比
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不同BMI的疑诊颈椎病患者颈椎矢状位磁共振T_2WI扫描图像质量对比观察 预览 被引量:1
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作者 田俊 翟华俊 +2 位作者 杨民 刘浩 韩晖云 《山东医药》 CAS 北大核心 2016年第31期98-100,共3页
目的对比观察不同体质量指数(BMI)的疑诊颈椎病患者颈椎矢状位磁共振T_2WI扫描的图像质量。方法疑诊颈椎病行磁共振常规扫描的患者123例,按照BMI分组,偏轻组(BMI〈20)12例、正常组(20≤BMI〈24)34例、超重组(24≤BMI〈28)55例... 目的对比观察不同体质量指数(BMI)的疑诊颈椎病患者颈椎矢状位磁共振T_2WI扫描的图像质量。方法疑诊颈椎病行磁共振常规扫描的患者123例,按照BMI分组,偏轻组(BMI〈20)12例、正常组(20≤BMI〈24)34例、超重组(24≤BMI〈28)55例、肥胖组(BMI≥28)22例。采用GE HDxt3.0T超导型磁共振仪扫描,矢状位T_2WI扫描序列为快速恢复快速自旋回波序列成像。选择颈椎正中矢状位T_2WI像,分别测量C_5或C_6椎体和其后方对应颈髓的信噪比以及椎体与脊髓之间的对比噪声比。观察并比较各组介电效应和吞咽伪影出现情况。结果各组颈椎椎体、脊髓信噪比及椎体与脊髓之间对比噪声比相比,P均〉0.05。偏轻组、正常组、超重组、肥胖组分别有2、14、19、11例出现吞咽伪影,各组吞咽伪影发生例数相比,P均〉0.05。各组中,仅偏轻组发生介电效应3例,与其余各组相比,P均〈0.05。结论 BMI偏低(〈18.5)患者颈椎矢状位3.0T磁共振T_2WI图像的介电效应发生率相对较高,BMI可在一定程度上影响图像质量。 展开更多
关键词 体质量指数 磁共振成像 颈椎磁共振成像 信号噪声比 对比噪声比 颈椎病
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Design of 1.5 bit quantization correlator in satellite navigation software receiver 预览
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作者 Hongwei Zhou Tian Jin Fangyao Lü 《系统工程与电子技术:英文版》 SCIE EI CSCD 2016年第2期449-456,共8页
Currently, 1 bit or 2 bit signal quantization is widely used in satellite navigation software receivers. The bit-wise parallel algorithm has been proposed for 1 bit and 2 bit signal quantization, which performs correl... Currently, 1 bit or 2 bit signal quantization is widely used in satellite navigation software receivers. The bit-wise parallel algorithm has been proposed for 1 bit and 2 bit signal quantization, which performs correlation with high efficiency. In order to improve the performance of the correlator, this paper proposes a new 1.5 bit quantization method. Theoretical analyses are made from the aspects of complexity and quantization loss, and performance comparison between 1.5 bit quantization correlator and traditional correlators is discussed. The results show that the 1.5 bit quantization algorithm can save about 30 percent complexity under similar quantization loss, reduce more than 0.5 d B signal noise ratio(SNR) loss under similar complexity. It shows great performance improvement for correlators of satellite navigation software receivers. 展开更多
关键词 软件接收机 信号量化 卫星导航 相关器 设计 性能比较 信号噪声比 并行算法
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Analysis of 13 kinds of steroid hormones in raw milk using modified QuEChERS method combined with UPLC-QTOF-MS 预览
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作者 TAN Xin-tong LI Zeng-mei +2 位作者 DENG Li-gang ZHAO Shan-cang WANG Ming-lin 《农业科学学报:英文版》 SCIE CAS CSCD 2016年第9期2163-2174,共12页
Thirteen kinds of steroid hormones in raw milk(cow, goat and buffalo milk) were analyzed with ultra performance liquid chromatography-quadrupole time of flight mass spectrometry(UPLC-QTOF-MS) after extraction and ... Thirteen kinds of steroid hormones in raw milk(cow, goat and buffalo milk) were analyzed with ultra performance liquid chromatography-quadrupole time of flight mass spectrometry(UPLC-QTOF-MS) after extraction and cleanup with the modified Qu ECh ERS method. These steroid hormones included 17β-estradiol, estriol, estrone, diethylstilbestrol, progesterone, melengestrol acetate, megestrol acetate, chlormadinone acetate, 19-nortestosterone, metandienone, boldenone, epitestosterone, and testosterone. The limits of detection for the raw milk basing on 3 times the signal to noise ratios(S/N=3) was in range of 0.07-0.51 μg kg–1, and the limits of quantification(basing on S/N=10 method) covered the ranges from 0.23 to 1.7 μg kg–1. With matrix external standard method, the substances presented recoveries over the range 74.2–99.7%. Qualitative analysis was also done in the mass/mass spectrum(MS/MS) mode and each debris structure of 13 kinds of steroid hormones was achieved. The methodology was then applied in real raw milk samples which were collected in several areas of China and the progesterone was detected with high level. 展开更多
关键词 甾体激素 原料奶 S方法 超高效液相色谱 17Β-雌二醇 环氧氯丙烷 质谱分析 信号噪声比
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能谱CT显示前列腺病灶的最佳单能量研究 预览
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作者 张晓斐 许建荣 +2 位作者 朱正飞 胡超苏 章真 《放射学实践》 北大核心 2016年第8期747-751,共5页
目的:运用能谱CT研究显示前列腺病灶的最佳单能量值及其图像质量分析。方法:回顾性分析28例前列腺外周带病变患者的临床和影像资料,共发现38个病灶,包括前列腺癌20个、前列腺增生18个。患者均行三期动态增强(动脉期、静脉期及实质... 目的:运用能谱CT研究显示前列腺病灶的最佳单能量值及其图像质量分析。方法:回顾性分析28例前列腺外周带病变患者的临床和影像资料,共发现38个病灶,包括前列腺癌20个、前列腺增生18个。患者均行三期动态增强(动脉期、静脉期及实质期)CT能谱成像,在140kVp混合能量图像和40~140KeV各组单能量图像上测量和计算病灶的对比噪声比(cNR),记录每个病灶CNR最高的图像所对应的KeV值,每个病灶测量3次(选取3个不同层面),计算其均值。对不同期相的140kVp图像和50keV图像进行图像质量的主观评分(5级评分法)和客观评价(CNR),两组间比较采用配对t检验。结果:统计分析结果显示前列腺病灶的最佳单能量值为(50.7士1.53)keV。不同期相50keV图像的主观评分分别为3.88±0.64、3.88±0.64和3.63±0.74,140kVp图像的相应评分分别为2.63_4-0.52、2.88±0.64和2.50±0.54。病灶在不同期相50keV图像上的CNR(32.42±5.06、36.02士5.80和34.97±4.14)均高于140kVp图像(13.45±3.53、20.86±4.34和21.14±3.41),差异均有统计学意义(P〈0.05)。结论:能谱CT检查显示前列腺病灶的最佳单能量值为50keV,其图像质量明显优于普通混合能量图像,有利于前列腺外周带病灶的检出。 展开更多
关键词 体层摄影术 X线计算机 前列腺癌 前列腺增生 能谱成像 信号噪声比 图像质量
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A Two-Level Detection Algorithm for Optical Fiber Vibration
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作者 Fukun BI Xuecong REN Hongquan QU Ruiqing JIANG 《光子传感器:英文版》 EI CSCD 2015年第3期284-288,共5页
光纤维颤动被协调光时间领域思考技术检测。除了颤动信号,反映的信号包括喧嚷和噪音,它导致高虚惊率。平均经常的虚惊率算法的房间有高计算速度,而是它的察觉表演将在象多重目标那样的 nonhomogeneous 环境被拒绝。顺序统计常数虚惊... 光纤维颤动被协调光时间领域思考技术检测。除了颤动信号,反映的信号包括喧嚷和噪音,它导致高虚惊率。平均经常的虚惊率算法的房间有高计算速度,而是它的察觉表演将在象多重目标那样的 nonhomogeneous 环境被拒绝。顺序统计常数虚惊率算法在多重目标环境有一个明显的优点,但是它有更低的计算速度。一个聪明的二水平的察觉算法基于平均以连续方法,和平均经常的虚惊率和统计常数虚惊率分别地被保存的顺序的性能的房间的察觉速度工作的经常的虚惊率和目统计常数虚惊率的房间被介绍。通过适应选择,平均的房间在同类的环境被使用,并且二水平的察觉算法在 nonhomogeneous 环境被采用。我们的蒙特卡罗模拟结果证明就不同信号噪音比率而言,建议算法比顺序统计的给更好的察觉概率。 展开更多
关键词 振动信号 测算法 光纤 非均匀环境 恒虚警率 信号噪声比 统计数据 蒙特卡洛模拟
Characteristics of gravity signal and loading effect in China
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作者 Yi Shuang Sun Wenke 《大地测量与地球动力学:英文版》 2015年第4期280-285,共6页
The complex geographical environment in China makes its gravity signals miscellaneous.This work gives a comprehensive representation and explanation in secular trend of gravity change in different regions,the key feat... The complex geographical environment in China makes its gravity signals miscellaneous.This work gives a comprehensive representation and explanation in secular trend of gravity change in different regions,the key features of which include positive trend in inner Tibet Plateau and South China and negative trend in North China plain and high mountain Asia(HMA).We also present the patterns of amplitudes and phases of annual and semiannual change.The mechanism underlying the semiannual period is explicitly discussed.The displacement in three directions expressed in terms of geo-potential spherical coefficients and load Love numbers are given.A case study applied with these equations is presented.The results show that Global Positioning System(GPS) observations can be used to compare with Gravity Recovery and Climate Experiment(GRACE) derived displacement and the vertical direction has a signal-noise-ratio of about one order of magnitude larger than the horizontal directions. 展开更多
关键词 重力信号 荷载效应 特性 中国北方 全球定位系统 地理环境 信号噪声比 GRACE
凌华科技推出新款四通道12位80MS/s PCI Express高速数字化仪 预览
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《测控技术》 CSCD 2015年第12期153-154,共2页
凌华科技推出新款PCIExpress接口高速数字化仪——PcIe-9814。PCIe-9814提供四通道、可执行12位分辨率及高达80MS/s同步采样,并支持40MHz信号带宽及1GBDDR3内存。它具备优异的精度及动态测量性能表现,包含76dB的无杂波干扰动态范围(... 凌华科技推出新款PCIExpress接口高速数字化仪——PcIe-9814。PCIe-9814提供四通道、可执行12位分辨率及高达80MS/s同步采样,并支持40MHz信号带宽及1GBDDR3内存。它具备优异的精度及动态测量性能表现,包含76dB的无杂波干扰动态范围(SFDR)、64dB的信号噪声比(signal-to—noise)及-75dB的总谐波失真(THD),并提供高达640MB/s数据传输能力,及增值的31阶数字滤波器功能等。 展开更多
关键词 数字化仪 凌华科技 四通道 数据传输能力 总谐波失真 信号噪声比 数字滤波器 同步采样
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Compressed SNR-and-Channel Estimation for Beam Tracking in 60-GHz WLAN 预览
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作者 GAO Bo ZHANG Changming +1 位作者 JIN Depeng ZENG Lieguang 《中国通信:英文版》 SCIE CSCD 2015年第6期46-58,共13页
Signal-to-noise ratio(SNR) and channel estimations are critical for 60-GHz communications to track the optimal transmission and reception beam pairs.However,the excessive pilot overhead for the estimations severely re... Signal-to-noise ratio(SNR) and channel estimations are critical for 60-GHz communications to track the optimal transmission and reception beam pairs.However,the excessive pilot overhead for the estimations severely reduces system throughput in fast-rotation scenarios.In order to address this problem,we firstly demonstrate the potential sparseness property of 60-GHz channel in beam tracking;subsequently,via exploiting this property,we propose a novel compressed SNR-and-channel estimation.The estimation is conducted in a three-stage fashion,including the unstructured estimation,nonzero-tap detection,and structured estimation with nonzero-tap location.Numerical simulations show that,in the case of substantial reduction of the pilot overhead,the proposed estimator still reveals a significant improvement in terms of estimation performance over the scheme in IEEE 802.11 ad.Furthermore,it is also demonstrated that the proposed SNR and channel estimators can approach the lower bounds in sparse channels so long as SNR exceeds 8 dB. 展开更多
关键词 信道估计 信噪比 千兆赫 无线局域网 压缩 非结构化 稀疏信道 信号噪声比
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超声信号的小波增强与改进去噪研究 预览
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作者 徐钧 周西峰 郭前岗 《计算机技术与发展》 2015年第2期82-85,共4页
预处理技术广泛应用于图像处理领域,文中将预处理技术应用到超声回波信号处理中。传统的阈值函数存在着明显的缺点:硬阈值函数在函数域内存在不连续的问题,软阈值函数去噪后存在恒定偏差。文中提出的改进阈值函数能够弥补硬阈值函数... 预处理技术广泛应用于图像处理领域,文中将预处理技术应用到超声回波信号处理中。传统的阈值函数存在着明显的缺点:硬阈值函数在函数域内存在不连续的问题,软阈值函数去噪后存在恒定偏差。文中提出的改进阈值函数能够弥补硬阈值函数和软阈值函数方法的不足;提出的自适应阈值减小了由小波系数阈值不准确引起的误差。仿真结果表明,经过预处理的信号相比原始信号,信号特征有明显提高;使用改进阈值函数和自适应阈值较传统方法能明显提高去噪的效果,体现在信噪比的提高以及均方误差的减少等方面。 展开更多
关键词 预处理 改进阈值函数 自适应阈值 小波去噪 信号噪声比
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Modulation recognition of MIMO radar signal based on joint HOS and SNR algorithm 预览 被引量:2
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作者 Xiaojing Wang Ying Xiong +1 位作者 Yunhao Li Bin Tang 《系统工程与电子技术:英文版》 SCIE EI CSCD 2014年第2期226-236,共11页
This paper presents a joint high order statistics(HOS)and signal-to-noise ratio(SNR) algorithm for the recognition of multiple-input multiple-output(MIMO) radar signal without a priori knowledge of the signal paramete... This paper presents a joint high order statistics(HOS)and signal-to-noise ratio(SNR) algorithm for the recognition of multiple-input multiple-output(MIMO) radar signal without a priori knowledge of the signal parameters. This method is capable of recognizing the MIMO radar signal as well as discriminating it from single-carrier signal adopted by conventional radar. Meanwhile,the sub-carrier number of the none-coding MIMO radar signal is estimated. Extensive simulations are carried out in different operating conditions. Simulation results prove the feasibility and indicate that the recognition probability could reach over 90% when the value of SNR is above 0 dB. 展开更多
关键词 雷达信号 MIMO 调制识别 信噪比 算法 基础 多输入多输出 信号噪声比
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基于模糊支持向量机的车辆碰撞信号检测 预览 被引量:2
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作者 黄东 《计算机仿真》 CSCD 北大核心 2014年第1期157-160,共4页
摘要:研究车辆碰撞信号准确检测的问题。在车祸发生过程中,车辆以及周围的环境往往伴随大量噪声,使得真正碰撞声音信号发生“淹没”,传统信号检测方法针对这种含噪高频信号很难做到准确提取,造成检测困难。为解决上述问题,提出一... 摘要:研究车辆碰撞信号准确检测的问题。在车祸发生过程中,车辆以及周围的环境往往伴随大量噪声,使得真正碰撞声音信号发生“淹没”,传统信号检测方法针对这种含噪高频信号很难做到准确提取,造成检测困难。为解决上述问题,提出一种基于模糊支持向量机算法的车辆碰撞信号检测方法。利用瞬时频率估计方法,采集车辆信号,为车辆碰撞信号检测提供准确的依据。利用模糊支持向量机方法,获取最优分类平面,根据平面判断采集的信号是否属于车辆碰撞信号,从而完成车辆碰撞信号的检测。实验结果表明,应用改进后的算法进行车辆碰撞信号检测,能够提高车辆碰撞信号检测的准确性。 展开更多
关键词 模糊支持向量机 信号检测 信号噪声比
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Correspondence normalized ghost imaging on compressive sensing
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作者 赵生妹 庄鹏 《中国物理B:英文版》 SCIE EI CAS CSCD 2014年第5期287-291,共5页
Ghost imaging(GI) offers great potential with respect to conventional imaging techniques. It is an open problem in GI systems that a long acquisition time is be required for reconstructing images with good visibility ... Ghost imaging(GI) offers great potential with respect to conventional imaging techniques. It is an open problem in GI systems that a long acquisition time is be required for reconstructing images with good visibility and signal-to-noise ratios(SNRs). In this paper, we propose a new scheme to get good performance with a shorter construction time. We call it correspondence normalized ghost imaging based on compressive sensing(CCNGI). In the scheme, we enhance the signal-to-noise performance by normalizing the reference beam intensity to eliminate the noise caused by laser power fluctuations, and reduce the reconstruction time by using both compressive sensing(CS) and time-correspondence imaging(CI) techniques. It is shown that the qualities of the images have been improved and the reconstruction time has been reduced using CCNGI scheme. For the two-grayscale 'double-slit' image, the mean square error(MSE) by GI and the normalized GI(NGI) schemes with the measurement number of 5000 are 0.237 and 0.164, respectively, and that is 0.021by CCNGI scheme with 2500 measurements. For the eight-grayscale 'lena' object, the peak signal-to-noise rates(PSNRs)are 10.506 and 13.098, respectively using GI and NGI schemes while the value turns to 16.198 using CCNGI scheme. The results also show that a high-fidelity GI reconstruction has been achieved using only 44% of the number of measurements corresponding to the Nyquist limit for the two-grayscale 'double-slit' object. The qualities of the reconstructed images using CCNGI are almost the same as those from GI via sparsity constraints(GISC) with a shorter reconstruction time. 展开更多
关键词 成像技术 归一化 压缩 信号噪声比 采集时间 NGI计划 重建图像 幻影
Detection of long bones based on Barker code excited ultrasonic guided waves
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作者 ZHANG Huilin SONG Xiaojun TA De'an 《声学学报:英文版》 2014年第2期136-146,共11页
Single pulse excited ultrasonic guided wave surfers high attenuation during the propagation in long bones.This results in small amplitude and low signal-to-noise ratio(SNR)of measured signals.Thus,the Barker code exci... Single pulse excited ultrasonic guided wave surfers high attenuation during the propagation in long bones.This results in small amplitude and low signal-to-noise ratio(SNR)of measured signals.Thus,the Barker code excitation is introduced into long bone detection to improve the quality of received signals,due to its efficiency in increasing amplitude and SNR.Both simulation and in vitro experiment were performed,and the results were decoded by the weighted match filter(WMF) and the finite impulse response- least squares inverse filter(FIRLSIF),respectively.The comparison between the results of Barker code excitation and sine pulse excitation was presented.For 13-bit Barker code excitation,WMF produced 13 times larger amplitude than sine pulse excitation,while FIR-LSIF achieved higher peak-sidelobe-level(PSL) of —63.59 dB and better performance in noise suppression.The results show that the Barker code excited guided waves have the potential to be applied to the long bone detection. 展开更多
关键词 超声导波 码激励 长骨 检测 信号噪声比 有限脉冲响应 脉冲激励 匹配滤波器
Implementation of the direct demodulation method for natural gamma ray spectral logging 被引量:1
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作者 刘尊年 孙建孟 +1 位作者 王金良 任爱阁 《中国物理C:英文版》 SCIE CAS CSCD 2014年第4期75-79,共5页
Spectrum analysis of natural gamma ray spectral logging(SGR) data is a critical part of surface information processing systems. Due to the low resolution, which is an inherent weakness of SGR, and the low signal-to-no... Spectrum analysis of natural gamma ray spectral logging(SGR) data is a critical part of surface information processing systems. Due to the low resolution, which is an inherent weakness of SGR, and the low signal-to-noise ratio problem of logging measurements, SGR is usually treated with a low confidence level. The Direct Demodulation(DD) method is an advanced technique to solve modulation equations interactively under physical constraints. It has higher sensitivity and spatial resolution than the traditional methods and can effectively suppress the logging noise. Based on standard count rate spectral data obtained from the China Offshore Oil Logging Company SGR Calibration Facility, this paper presents the application of the DD method to gamma-ray logging. The results are compared with four traditional algorithmic methods, showing that the DD method is a credible choice, with higher sensitivity and higher spatial resolution in gamma-ray log interpretation. The Point-Spread-Function of the Shengli Oil Logging Company’s natural gamma ray spectroscopy instrument is obtained for the first time. The quantities of various radionuclides in their calibration pits are also obtained. The DD method was applied successfully to gamma-ray logging, offering a new option for SGR logging algorithm selection. 展开更多
关键词 自然伽马能谱测井 解调方法 海洋石油测井公司 空间分辨率 信号噪声比 信息处理系统 校准设备 射线测井
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