期刊文献+
共找到729篇文章
< 1 2 37 >
每页显示 20 50 100
Working condition recognition of sucker rod pumping system based on 4-segment time-frequency signature matrix and deep learning
1
作者 Yun-Peng He Hai-Bo Cheng +4 位作者 Peng Zeng Chuan-Zhi Zang Qing-Wei Dong Guang-Xi Wan Xiao-Ting Dong 《Petroleum Science》 SCIE EI CAS CSCD 2024年第1期641-653,共13页
High-precision and real-time diagnosis of sucker rod pumping system(SRPS)is important for quickly mastering oil well operations.Deep learning-based method for classifying the dynamometer card(DC)of oil wells is an eff... High-precision and real-time diagnosis of sucker rod pumping system(SRPS)is important for quickly mastering oil well operations.Deep learning-based method for classifying the dynamometer card(DC)of oil wells is an efficient diagnosis method.However,the input of the DC as a two-dimensional image into the deep learning framework suffers from low feature utilization and high computational effort.Additionally,different SRPSs in an oil field have various system parameters,and the same SRPS generates different DCs at different moments.Thus,there is heterogeneity in field data,which can dramatically impair the diagnostic accuracy.To solve the above problems,a working condition recognition method based on 4-segment time-frequency signature matrix(4S-TFSM)and deep learning is presented in this paper.First,the 4-segment time-frequency signature(4S-TFS)method that can reduce the computing power requirements is proposed for feature extraction of DC data.Subsequently,the 4S-TFSM is constructed by relative normalization and matrix calculation to synthesize the features of multiple data and solve the problem of data heterogeneity.Finally,a convolutional neural network(CNN),one of the deep learning frameworks,is used to determine the functioning conditions based on the 4S-TFSM.Experiments on field data verify that the proposed diagnostic method based on 4S-TFSM and CNN(4S-TFSM-CNN)can significantly improve the accuracy of working condition recognition with lower computational cost.To the best of our knowledge,this is the first work to discuss the effect of data heterogeneity on the working condition recognition performance of SRPS. 展开更多
关键词 Sucker-rod pumping system Dynamometer card Working condition recognition Deep learning time-frequency signature time-frequency signature matrix
下载PDF
Porcine vesical acellular matrix graft of tunica albuginea for penile reconstruction 被引量:5
2
作者 Kwan-Joong Joo Byung-Soo Kim +3 位作者 Jeong-Ho Han Chang-Ju Kim Chil-HunKwon Heung-JaePark 《Asian Journal of Andrology》 SCIE CAS CSCD 2006年第5期543-548,共6页
Aim: To characterize the feasibility of the surgical replacement of the penile tunica albuginea (TA) and to evaluate the value of a porcine bladder acellular matrix (BAM) graft. Methods: Acellular matrices were ... Aim: To characterize the feasibility of the surgical replacement of the penile tunica albuginea (TA) and to evaluate the value of a porcine bladder acellular matrix (BAM) graft. Methods: Acellular matrices were constructed from pigs' bladders by cell lysis, and then examined by scanning electron microscopy (SEM). Expression levels of the mRNA of the vascular endothelial growth factor (VEGF) receptor, fibroblast growth factor (FGF)-1 receptor, neuregulin, and brain-derived neurotrophic factor (BDNF) in the acellular matrix and submucosa of the pigs' bladders were determined through the reverse transcription-polymerase chain reaction (PCR). A 5 mm× 5 mm square was excised from the penile TA of nine rabbits. The defective TA was then covered in porcine BAM. Equal numbers of animals were sacrificed and histochemically examined at 2, 4 and 6 months after implantation. Results: SEM of the BAM showed collagen fibers with many pores. VEGF receptor, FGF-1 receptor and neuregulin mRNA were expressed in the porcine BAM; BDNF mRNA was not detected. Two months after implantation, the graft sites exhibited excellent healing without contracture, and the fusion between the graft and the neighboring normal TA appeared to be well established. There were no significant histological differences between the implanted tunica and the normal control tunica at 6 months after implantation. Conclusion: The porcine BAM graft resulted in a structure which was sufficiently like that of the normal TA. This implantation might be considered applicable to the reconstruction of the TA in conditions such as trauma or Peyronie's disease. 展开更多
关键词 tissue engineering extracellular matrix PENIS reconstructive surgical procedure graft survival
下载PDF
Fast and accurate covariance matrix reconstruction for adaptive beamforming using Gauss-Legendre quadrature 被引量:4
3
作者 LIU Shuai ZHANG Xue +2 位作者 YAN Fenggang WANG Jun JIN Ming 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2021年第1期38-43,共6页
Most of the reconstruction-based robust adaptive beamforming(RAB)algorithms require the covariance matrix reconstruction(CMR)by high-complexity integral computation.A Gauss-Legendre quadrature(GLQ)method with the high... Most of the reconstruction-based robust adaptive beamforming(RAB)algorithms require the covariance matrix reconstruction(CMR)by high-complexity integral computation.A Gauss-Legendre quadrature(GLQ)method with the highest algebraic precision in the interpolation-type quadrature is proposed to reduce the complexity.The interference angular sector in RAB is regarded as the GLQ integral range,and the zeros of the threeorder Legendre orthogonal polynomial is selected as the GLQ nodes.Consequently,the CMR can be efficiently obtained by simple summation with respect to the three GLQ nodes without integral.The new method has significantly reduced the complexity as compared to most state-of-the-art reconstruction-based RAB techniques,and it is able to provide the similar performance close to the optimal.These advantages are verified by numerical simulations. 展开更多
关键词 robust adaptive beamforming(RAB) covariance matrix reconstruction(CMR) Gauss-Legendre quadrature(GLQ) complexity reduction
下载PDF
Ureteral reconstruction with decellularized small intestinal submucosa matrix for ureteral stricture: A preliminary report of two cases 被引量:1
4
作者 Qingkang Xu Chen Chen +7 位作者 Zhefeng Xu Feng Chen Yongtao Yu Xiang Hong Shengli Xu Jiajia Chen Qin Ding Hong Chen 《Asian Journal of Urology》 CSCD 2020年第1期51-55,共5页
Objective:To determine the feasibility of decellularized small intestinal submu-cosa(5IS)matrix in repairing ureteral strictures.Methods:Two patients with ureteral stenoses underwent ureteral reconstruction with SIS m... Objective:To determine the feasibility of decellularized small intestinal submu-cosa(5IS)matrix in repairing ureteral strictures.Methods:Two patients with ureteral stenoses underwent ureteral reconstruction with SIS ma-trix at the Zhejiang Provincial Corps Hospital of Chinese People's Armed Forces between June 2014 and June 2016.The ureteral stenoses were repaired with a semi-tubular SIS matrix and the postoperative recoveries were observed.Results:Both operations were successfully completed.The average operative time was 90 min and the average length of hospital stay was 15 days.No fevers,incision infections,intestinal obstruction,graft rejection,or other serious complications were noted.After 2 months,ure-teroscopic examinations showed that the surfaces of the original patches were covered by mu-Cosa and there were no apparent stenoses in the lumens.The ureteral stents were replaced every 2 months postoperatively and removed 12 months postoperatively.No infections or uri-nary leakage occurred after removal of the stents.Intravenous urography was performed 6 and 12 months postoperatively.The results showed that the ureters were not obstructed and there was no apparent stenosis at the anastomosis sites.The average follow-up time was>12 months.Long-term follow-up is still ongoing,and computed tomography examin ations of the urinary tract have been conducted in the outpatient department of our hospital 1,3,and 6 months after removal of the double-J stents,suggesting the absence of hydronephrosis.The serum creatinine levels remained stable during the follow-up.Conclusion:SIS matrix reconstruction is a feasible method to repair ureters stenosis. 展开更多
关键词 Ureteral stenosis Decellularized matrix URETEROPLASTY Ureteral reconstruction Ureteral obstruction
下载PDF
Reconstruction of the abdominal wall by using a combination of the human acellular dermal matrix implant and an interpositional omentum flap after extensive tumor resection in patients with abdominal wall neoplasm: A preliminary result 被引量:10
5
作者 Yan Gu Rui Tang +1 位作者 Ding-Quan Gong Yun-Liang Qian 《World Journal of Gastroenterology》 SCIE CAS CSCD 2008年第5期752-757,共6页
AIM:To present our trial using a combination of the human acellular dermal matrix (HADM) implant and an interpositional omentum flap to repair giant abdominal wall defects after extensive tumor resection. METHODS:Betw... AIM:To present our trial using a combination of the human acellular dermal matrix (HADM) implant and an interpositional omentum flap to repair giant abdominal wall defects after extensive tumor resection. METHODS:Between February and October of 2007, three patients with giant defects of the abdominal wall after extensive tumor resection underwent reconstruction with a combination of HADM and omentum flap. Postoperative morbidities and signs of herniation were monitored. RESULTS:The abdominal wall reconstruction was successful in these three patients, there was no severe morbidity and no signs of herniation in the follow-up period. CONCLUSION:The combination of HADM and omentum flap offers a new, safe and effective alternative to traditional forms in the repair of giant abdominal wall defects. Further analysis of the long-term outcome and more cases are needed to assess the reliability of this technique. 展开更多
关键词 腹壁肿瘤 病变腹壁 症状 手术治疗
下载PDF
Oversample Reconstruction Based on a Strong Inter-Diagonal Matrix for an Optical Microscanning Thermal Microscope Imaging System
6
作者 Meijing Gao Ailing Tan +3 位作者 Jie Xu Weiqi Jin Zhenlong Zu Ming Yang 《Journal of Beijing Institute of Technology》 EI CAS 2018年第1期65-73,共9页
Based on a strong inter-diagonal matrix and Taylor series expansions,an oversample reconstruction method was proposed to calibrate the optical micro-scanning error. The technique can obtain regular 2 ×2 microscan... Based on a strong inter-diagonal matrix and Taylor series expansions,an oversample reconstruction method was proposed to calibrate the optical micro-scanning error. The technique can obtain regular 2 ×2 microscanning undersampling images from the real irregular undersampling images,and can then obtain a high spatial oversample resolution image. Simulations and experiments show that the proposed technique can reduce optical micro-scanning error and improve the system's spatial resolution. The algorithm is simple,fast and has low computational complexity. It can also be applied to other electro-optical imaging systems to improve their spatial resolution and has a widespread application prospect. 展开更多
关键词 optical microscanning strong inter-diagonal matrix oversample reconstruction thermal microscope imaging system
下载PDF
The Utility of the Galea in Scalp Reconstruction
7
作者 Jack D. Sudduth John M. Sullivan Marc E. Walker 《Modern Plastic Surgery》 2023年第1期16-22,共7页
Total scalp avulsion is a time-sensitive, catastrophic injury requiring quick, complex decision-making. Traditionally, these injuries were treated with split-thickness skin grafts. With advancements in microsurgery, t... Total scalp avulsion is a time-sensitive, catastrophic injury requiring quick, complex decision-making. Traditionally, these injuries were treated with split-thickness skin grafts. With advancements in microsurgery, treatments evolved to scalp replantation, becoming the standard of care in scalp reconstruction. Although the integrity of the scalp’s blood vessels is pivotal for successful replantation, the authors believe that scalp replantation should be considered at all costs. In the presented case, a 54-year-old female presented to the emergency room following an incident with an auger that completely avulsed her scalp. She was taken back to the operating room, where scalp replantation was performed. Following replantation, scalp necrosis led to serial debridings in the operating room, and eventually, all of the scalp was debrided down to healthy tissue. Surprisingly, the galea survived despite this, which provided a healthy base for skin grafts. Before definitive coverage was placed, it was decided to utilize a bilaminar acellular dermal matrix along with negative pressure wound therapy to create a more robust bed of granulation tissue. After three weeks of this treatment plan, the patient returned to the operating room, where a healthy, viable bed of granulating tissue was revealed beneath the dermal matrix. Split-thickness skin grafts were taken from her thighs bilaterally and sewn together in a quilt-like fashion to cover the wound bed. The entirety of the graft healed without complication except for one small area that required full-thickness skin grafting in an outpatient setting. Even though the replantation ultimately failed, it allowed the galea to survive, which saved the patient from undergoing a free tissue transfer and allowed her scalp to be reconstructed with split-thickness skin grafts. Even in the setting of polytrauma, the authors hope that anyone treating a scalp avulsion would consider scalp replantation at all costs. 展开更多
关键词 Scalp reconstruction Scalp Replantation Failed Replantation Galea POLYTRAUMA Split-Thickness Skin Grafts Bilaminar Acellular Dermal matrix
下载PDF
修正-联合正则化的冲击载荷识别与响应重构
8
作者 殷红 石咏荷 +1 位作者 彭珍瑞 王增辉 《浙江大学学报(工学版)》 EI CAS CSCD 北大核心 2024年第5期1029-1039,共11页
针对传统结构响应重构中正则化方法对冲击载荷峰值识别精度低、非加载区识别结果振荡且识别精度易受噪声干扰等问题,提出基于修正-联合正则化的冲击载荷识别与结构响应重构方法.基于状态空间模型,推导冲击载荷及结构响应的重构方程.对... 针对传统结构响应重构中正则化方法对冲击载荷峰值识别精度低、非加载区识别结果振荡且识别精度易受噪声干扰等问题,提出基于修正-联合正则化的冲击载荷识别与结构响应重构方法.基于状态空间模型,推导冲击载荷及结构响应的重构方程.对测量响应降噪,利用降噪后响应与识别响应的差值修正L2正则化解.联合L1正则化解的稀疏性优势,在保证冲击载荷非加载区域识别稳定的同时,获得更高精度的峰值识别结果,实现结构动态响应的重构.通过数值和实验案例验证了所提方法的有效性,对比了传递矩阵法和粒子滤波法的响应重构效果.结果表明,所提方法具有良好的抗噪性,能够较准确地识别冲击载荷,有效地重构结构动态响应. 展开更多
关键词 响应重构 冲击载荷 正则化 传递矩阵 粒子滤波
下载PDF
基于改进型LBP译码的LDPC码稀疏校验矩阵重建
9
作者 张天骐 李春运 +1 位作者 吴仙越 吴云戈 《通信学报》 EI CSCD 北大核心 2024年第5期70-79,共10页
针对LDPC码稀疏校验矩阵重建问题,基于改进型LBP译码的思想提出了一种高误码率下的LDPC码稀疏校验矩阵重建算法。首先,从码字矩阵中随机抽取部分比特构建码字分析矩阵,并对其做高斯消元求对偶空间;其次,通过判定对偶空间向量是否稀疏,... 针对LDPC码稀疏校验矩阵重建问题,基于改进型LBP译码的思想提出了一种高误码率下的LDPC码稀疏校验矩阵重建算法。首先,从码字矩阵中随机抽取部分比特构建码字分析矩阵,并对其做高斯消元求对偶空间;其次,通过判定对偶空间向量是否稀疏,提高了后续疑似校验向量判定的效率;最后,在接收码字个数不足时,利用已知校验向量结合改进型LBP译码方法纠正错误码字,加快LDPC码稀疏校验矩阵的重建速度,提高重建性能。仿真结果表明,所提算法在高误码率0.0045的条件下,对于IEEE802.11n协议下的(648,324)LDPC码,相比于现有算法,稀疏校验矩阵重建率提升了52.16%,可达到92.28%。 展开更多
关键词 低密度奇偶校验码 稀疏校验矩阵 高斯消元 改进型LBP译码 重建
下载PDF
基于混合正则化方法的结构载荷识别与响应重构
10
作者 彭珍瑞 周雪文 《振动与冲击》 EI CSCD 北大核心 2024年第6期104-112,共9页
针对结构载荷识别与响应重构问题中存在的不适定性,提出一种最小平方残差(least square minimal residual,LSMR)算法与Tikhonov正则化方法相结合的混合正则化方法,实现利用结构有限测点的加速度响应识别载荷并重构未知的各类型响应。首... 针对结构载荷识别与响应重构问题中存在的不适定性,提出一种最小平方残差(least square minimal residual,LSMR)算法与Tikhonov正则化方法相结合的混合正则化方法,实现利用结构有限测点的加速度响应识别载荷并重构未知的各类型响应。首先,基于时域状态空间模型构建结构的传递矩阵,并建立载荷识别与响应重构方程;其次,采用混合正则化方法改善载荷识别问题的不适定性,得到载荷的正则化解,并结合响应重构方程的传递矩阵对结构的位移、速度和加速度响应进行重构;最后,通过简支梁数值仿真和试验分析验证所提方法的可行性。结果表明,所提方法能改善重构方程的不适定性,从而对结构未知载荷和各类型响应进行有效重构。 展开更多
关键词 载荷识别 响应重构 不适定性 传递矩阵 混合正则化
下载PDF
基于小快拍场景的联合校正稳健波束形成算法
11
作者 张秀清 伊宏波 王晓君 《无线电工程》 2024年第8期1900-1907,共8页
针对传统的自适应波束形成算法在目标导向矢量失配及接收数据的协方差矩阵存在误差时,性能急剧下降的问题,提出了一种基于小快拍场景的联合协方差矩阵重构,及导向矢量优化的稳健波束形成算法。对不确定集约束求解得到干扰导向矢量,根据... 针对传统的自适应波束形成算法在目标导向矢量失配及接收数据的协方差矩阵存在误差时,性能急剧下降的问题,提出了一种基于小快拍场景的联合协方差矩阵重构,及导向矢量优化的稳健波束形成算法。对不确定集约束求解得到干扰导向矢量,根据稀疏干扰来向的导向矢量近似正交,求出干扰导向矢量对应的干扰功率,从而完成协方差矩阵重构;对期望信号来向及其邻域进行权值求解,对加权后的数据特征分解,利用多信号分类(Multiple Signal Classification, MUSIC)谱估计算法对信号区域积分得到信号协方差矩阵,将其主特征值近似为期望信号的导向矢量完成重新估计。仿真结果表明,在无误差时,算法输出信干噪比(Signal to Interference Plus Noise Ratio, SINR)接近理论最优;在多种误差环境下输出性能随信噪比(Signal to Noise Ratio, SNR)的变化均具有较好的稳健性,并且在信号来向可精准形成波束;在小快拍时可以较快收敛至理论最优值。 展开更多
关键词 小快拍 协方差矩阵重构 稳健波束形成 导向矢量估计
下载PDF
1024×1024重建矩阵结合迭代重建算法在胃部CT血管成像中的应用
12
作者 童小雨 李贝贝 +3 位作者 王旭 陈安良 刘爱连 刘义军 《中国医学影像学杂志》 CSCD 北大核心 2024年第6期622-627,共6页
目的 探究1 024×1 024重建矩阵结合迭代重建(Karl)算法在胃部血管及肿瘤供血动脉CT血管成像中的应用价值。资料与方法 前瞻性收集大连医科大学附属第一医院2022年3—6月行胃部CT血管成像的胃部肿瘤患者30例,对CT扫描图像原始数据... 目的 探究1 024×1 024重建矩阵结合迭代重建(Karl)算法在胃部血管及肿瘤供血动脉CT血管成像中的应用价值。资料与方法 前瞻性收集大连医科大学附属第一医院2022年3—6月行胃部CT血管成像的胃部肿瘤患者30例,对CT扫描图像原始数据进行分组重建。A组采用常规512×512矩阵结合Karl 5级重建;B组采用1 024×1 024大重建矩阵结合不同等级Karl算法重建,分为B1(Karl 5)、B2(Karl 7)及B3(Karl 9)3个亚组。在轴位图像上测量胃左动脉起始部的腹主动脉、腹腔干、脾动脉、肝动脉及同层面腹壁皮下脂肪组织的CT值和SD值,计算信噪比(SNR)、对比噪声比(CNR)。由2名观察者采用5分法评估各组图像质量。结果 2名观察者主观评价一致性较好(Kappa=0.782~0.789,P<0.05),B1~B3组图像主观评分均优于A组,B2组得分最高(二维评分:χ^(2)=27.309、24.250;三维评分:χ^(2)=21.964、21.294;P均<0.05),30例患者中25例见胃动脉系统参与肿瘤供血,B2组各血管的清晰显示率均优于A组;A与B1、B2组各血管CT值差异无统计学意义(t=-1.918~2.720,P>0.05),B2组较A组血管SD值、SNR、CNR和背景噪声值,除腹主动脉SD、肝动脉CNR外差异均无统计学意义(t=-5.909~5.768,P>0.05);B1~3组图像随着Karl算法等级提高,SD值逐渐降低(F=2.881~27.109,P<0.05),SNR、CNR逐渐升高(F=3.612~12.149,P<0.05)。结论 1 024×1 024重建矩阵结合Karl 7级算法可以改善图像质量,增强胃部微细血管及肿瘤供血动脉分支的显示效果,在临床上有很好的应用价值。 展开更多
关键词 胃肿瘤 胃动脉 重建矩阵 迭代重建算法 体层摄影术 X线计算机
下载PDF
基于先验信息的压缩感知重建温度场技术
13
作者 黄俊瑜 李文昌 +2 位作者 刘剑 张天一 朱旻琦 《仪表技术与传感器》 CSCD 北大核心 2024年第4期71-75,80,共6页
针对利用压缩感知方法重建微处理器芯片温度场存在错失真实热点、从而影响重建精度的问题,提出了一种基于先验信息的压缩感知重建温度场方法。通过对温度场先验信息的处理,结合主成分分析和模拟退火算法有针对性地设计观测矩阵,优化温... 针对利用压缩感知方法重建微处理器芯片温度场存在错失真实热点、从而影响重建精度的问题,提出了一种基于先验信息的压缩感知重建温度场方法。通过对温度场先验信息的处理,结合主成分分析和模拟退火算法有针对性地设计观测矩阵,优化温度传感器的布置,提高重建精度。实验结果表明:与基于特征图的重建方法、基于模拟退火算法布置传感器的方法和基于随机采样的压缩感知重建温度场方法相比,该方法在平均温度误差、最大温度误差和均方误差方面至少分别提升了29.9%、46.6%和53.7%,有更优越的温度场重建性能。 展开更多
关键词 温度场重建 压缩感知 观测矩阵 温度传感器 先验信息
下载PDF
基于JADE-斜投影的鲁棒波束形成算法
14
作者 程永杰 李纯 +1 位作者 刘帅 金铭 《系统工程与电子技术》 EI CSCD 北大核心 2024年第2期401-406,共6页
针对矩阵重构类波束形成算法对阵列幅相误差敏感的问题,提出一种基于盲源信号分离和斜投影的矩阵重构鲁棒波束形成算法。首先,依靠盲源分离技术得到接收信号和混合矩阵,结合期望信号先验信息完成混合矩阵中信号导向矢量的搜索。然后,利... 针对矩阵重构类波束形成算法对阵列幅相误差敏感的问题,提出一种基于盲源信号分离和斜投影的矩阵重构鲁棒波束形成算法。首先,依靠盲源分离技术得到接收信号和混合矩阵,结合期望信号先验信息完成混合矩阵中信号导向矢量的搜索。然后,利用盲源分离得到的信号协方差矩阵完成阵列幅相误差估计。最后,基于幅相误差校准的混合矩阵和斜投影思想,构建各干扰的斜投影算子,将接收数据分别向干扰斜投影空间进行投影,得到对应的干扰信号,完成干扰噪声协方差矩阵重构。仿真结果表明,所提方法对阵列幅相误差具有较好的鲁棒性,验证了算法的有效性。 展开更多
关键词 鲁棒波束形成 矩阵重构 幅相误差 盲源信号分离 斜投影
下载PDF
MRI CS-3D-MATRIX序列在膝关节前交叉韧带损伤诊断中的应用研究 被引量:13
15
作者 宋春娟 张怡 《医疗卫生装备》 CAS 2020年第6期73-76,共4页
目的:探讨CS-3D-MATRIX序列结合多平面重建(multiplanar reconstruction,MPR)技术在膝关节前交叉韧带(anterior cruciate ligament,ACL)损伤诊断中的应用价值。方法:选取44例因膝关节疼痛来院进行MRI扫描的患者,分别行2D-FSE序列和CS-3D... 目的:探讨CS-3D-MATRIX序列结合多平面重建(multiplanar reconstruction,MPR)技术在膝关节前交叉韧带(anterior cruciate ligament,ACL)损伤诊断中的应用价值。方法:选取44例因膝关节疼痛来院进行MRI扫描的患者,分别行2D-FSE序列和CS-3D-MATRIX序列扫描,将采用CS-3D-MATRIX序列扫描得到的原始图像传至后处理工作站进行MPR。比较2组序列图像的信噪比(signal to noise ratio,SNR)、膝关节ACL显示完整度,以及膝关节图像的运动伪影、ACL边缘的锐利度及图像整体质量。采用SPSS 20.0软件进行数据处理。结果:2组序列的SNR值比较差异无统计学意义(P=0.124>0.05),2组序列图像的运动伪影(P=0.467>0.05)和图像综合质量评分(P=0.617>0.05)比较差异无统计学意义,CS-3D-MATRIX序列的ACL显示完整度例数(43例)高于2D-FSE序列(19例)(P=0.000<0.05),CS-3D-MATRIX序列的ACL锐利度略低于2D-FSE序列(P=0.025<0.05)。结论:CS-3D-MATRIX序列扫描速度快、分辨力高,结合MPR技术可以完整显示ACL图像的形态和结构,尤其是在显示ACL完整度方面更具优势,在膝关节ACL损伤诊断中具有较高的应用价值。 展开更多
关键词 MRI CS-3D-matrix序列 2D-FSE序列 前交叉韧带 多平面重建
下载PDF
基于非负矩阵分解的中红外地表特性光谱重建方法
16
作者 李殷娜 李正强 +7 位作者 郑杨 侯伟真 徐文斌 马䶮 樊程 葛邦宇 姚前 史正 《光谱学与光谱分析》 SCIE EI CAS CSCD 北大核心 2024年第2期563-570,共8页
在中红外遥感领域,高光谱地表反射率/发射率等地表特性具有极高的应用价值和应用需求,但利用卫星遥感手段难以获取吸收波段的高光谱地表反射/发射特性,且通过光谱重建获取全波段的地表特性方法仍存在很多问题。为解决中红外全波段地表... 在中红外遥感领域,高光谱地表反射率/发射率等地表特性具有极高的应用价值和应用需求,但利用卫星遥感手段难以获取吸收波段的高光谱地表反射/发射特性,且通过光谱重建获取全波段的地表特性方法仍存在很多问题。为解决中红外全波段地表特性光谱重建所面临的难题,基于约翰霍普金斯大学(Johns Hopkins University,JHU)地物波谱库和中分辨率成像光谱仪(MODIS)短波红外和中红外地表多光谱卫星产品,提出了一种利用非负矩阵分解(NMF)重建高光谱地表反射率的方法,对2.5~5.0μm中红外光谱范围内的地表反射/发射率进行光谱重建,重建后的光谱分辨率可达10 nm。首先基于JHU地物波谱库选取4种典型地物类型(土壤、植被、人造材料和岩石),建立地物光谱库样本信息,再利用MODIS传感器光谱响应函数,根据等效计算公式将2.0~5.0μm波段范围反射率结果重采样到10 nm光谱间隔、共301个波段,得到JHU地表反射率光谱数据集。对光谱数据集进行非负矩阵分解处理,提取4条端元向量光谱曲线,结合MODIS短波红外和中红外4个波段(2.13、3.75、3.96和4.05μm)的全球月均地表反射率/发射率产品,可计算每个像元对应的权重系数向量,从而进行任意波段的光谱重建,得到全球范围内陆地5 km×5 km分辨率的月均地表反射率重建结果。同时为综合评价该光谱重建方法,从光谱数据集中提取MODIS短波红外和中红外4个波段(2.13、3.75、3.96和4.05μm)的子数据集,计算对应的权重系数向量,进行2.0~5.0μm光谱范围内的全波段的反射率光谱重建。重建结果对应的平均绝对误差优于0.01,平均相对误差优于10%,在只有MODIS卫星4个波段数据可用的低秩病态的情况下,可较好地满足光谱重建的精度要求。并且为满足重建结果可视化需求,基于网络地理信息系统(WebGIS)技术,利用Cesium框架,采用浏览器/服务器架构,搭建了二三维一体化可视化系统,将卫星底图、地形数据与光谱重建结果等集成展示,从而进行直观的多因素分析,为卫星产品的展示与验证提供支撑。 展开更多
关键词 高光谱 非负矩阵分解 地表反射率 光谱重建 MODIS WEBGIS
下载PDF
基于相机RGB值的光谱反射率重建方法研究 被引量:1
17
作者 张飞 刘珩 +4 位作者 杨洁 渠立永 吕琪 黄伟 李浩 《兵器装备工程学报》 CAS CSCD 北大核心 2024年第2期284-290,共7页
光谱反射率重建技术可实现背景颜色数据准确校正和复制还原,以此为基础可设计实施高融合迷彩,为机动装备在不同背景环境下提供有效防护屏障,具有重要价值。参照光谱成像技术特点,根据颜色形成原理和三刺激值定量计算公式,通过控制单一... 光谱反射率重建技术可实现背景颜色数据准确校正和复制还原,以此为基础可设计实施高融合迷彩,为机动装备在不同背景环境下提供有效防护屏障,具有重要价值。参照光谱成像技术特点,根据颜色形成原理和三刺激值定量计算公式,通过控制单一变量法设计实验方案,提出加权平均光谱反射率重建方法(TWA),利用相机和光谱仪分别获取训练样本的成像系统响应值(RGB)和光谱反射率数据,对所提取的样本RGB值和光谱反射率数据分别采用传统最小二乘法(OLS)、正则化最小二乘法(RLS)、偏最小二乘法(PLS)、主成分分析法(PCA)和本文中提出的加权平均法(TWA)进行光谱反射率重建训练,获得光谱重建矩阵,最后利用光谱重建矩阵对测试样本响应值进行光谱反射率重建,并对实验结果进行分析,对比不同方法的光谱反射率重建效果。研究结果表明,加权平均法在光谱均方根误差SRMSE、平均拟合优度系数GFC、平均色差等指标上效果更优,重建所得光谱反射率精度更高,颜色校正效果更佳。 展开更多
关键词 光谱反射率 加权平均法 重建矩阵 光谱曲线 颜色校正
下载PDF
基于变分模态提取的动力响应重构方法研究
18
作者 余恒 殷红 彭珍瑞 《噪声与振动控制》 CSCD 北大核心 2024年第3期43-49,共7页
基于经验模态分解的响应重构方法依赖于参数繁多的带通滤波器,且不适用于具有密集模态的结构,因此,提出一种基于变分模态提取的动力响应重构方法。首先,在时域内使用变分模态提取将由传感器测得的动力响应分解为各阶模态响应;随后,通过... 基于经验模态分解的响应重构方法依赖于参数繁多的带通滤波器,且不适用于具有密集模态的结构,因此,提出一种基于变分模态提取的动力响应重构方法。首先,在时域内使用变分模态提取将由传感器测得的动力响应分解为各阶模态响应;随后,通过根据有限元建模或模态试验导出的模态转换矩阵计算得到响应未知位置的各阶模态响应,再根据模态叠加法完成其余位置动力响应的重构;最后,对非密集模态的悬臂梁和密集模态的3层剪切框架进行数值模拟,并通过简支梁进行试验分析,验证了所提方法的有效性和较好的鲁棒性。 展开更多
关键词 振动与波 密集模态 变分模态提取 动力响应重构 模态转换矩阵 模态叠加法
下载PDF
基于人工边界条件的波面相位解析重建
19
作者 刘晓蕾 尹弘栗 +2 位作者 韩博宇 马学文 张云驰 《哈尔滨工程大学学报(英文版)》 CSCD 2024年第1期101-112,共12页
At present,the measurement of the near wave field of ships mostly relies on shipborne radar.The commonly used shipborne radar is incoherent and cannot obtain information on wave surface velocity.Therefore,the mathemat... At present,the measurement of the near wave field of ships mostly relies on shipborne radar.The commonly used shipborne radar is incoherent and cannot obtain information on wave surface velocity.Therefore,the mathematical model of wave reconstruction is remarkably complex.As a new type of radar,coherent radar can obtain the radial velocity of the wave surface.Most wave surface reconstruction methods that use wave velocity are currently based on velocity potential.The difficulty of these methods lies in determining the initial value of the velocity integral.This paper proposes a wave surface reconstruction method based on an artificial boundary matrix.Numerical simulation data of regular and short-crest waves are used to verify the accuracy of this method.Simultaneously,the reconstruction stability under different wave velocity measurement errors is analyzed.The calculation results show that the proposed method can effectively realize the reconstruction of wave field. 展开更多
关键词 Coherent radar Wave velocity field Artificial boundary matrix Wave surface reconstruction Calculation stability
下载PDF
基于Kaczmarz算法的磁粒子成像快速重建算法研究
20
作者 谌继超 柯丽 白石 《医疗卫生装备》 CAS 2024年第1期9-14,共6页
目的:为了解决磁粒子断层成像中系统矩阵方法成像时间长、计算复杂的问题,提出一种基于Kaczmarz算法的磁粒子成像快速重建算法。方法:首先,分析经典Kaczmarz算法及其变体算法的收敛速度,并计算在任意矩阵下的迭代次数和计算时间;其次,... 目的:为了解决磁粒子断层成像中系统矩阵方法成像时间长、计算复杂的问题,提出一种基于Kaczmarz算法的磁粒子成像快速重建算法。方法:首先,分析经典Kaczmarz算法及其变体算法的收敛速度,并计算在任意矩阵下的迭代次数和计算时间;其次,比较欧氏距离和余弦距离对系统数据的区分能力,并运用基于余弦距离的K-means算法来增强块Kaczmarz算法的运算能力,缩短系统矩阵重建时间并最终实现磁粒子成像快速重建。最后,通过计算机仿真实验验证提出的算法的有效性。结果:提出的算法大幅缩短了重建时间,提高了重建图像的空间分辨力和质量。结论:提出的算法可以实现磁粒子成像的快速重建,并且在处理含有噪声的数据时具备较强的重建能力。 展开更多
关键词 磁粒子成像 系统矩阵 Kaczmarz算法 块Kaczmarz算法 图像重建 余弦聚类
下载PDF
上一页 1 2 37 下一页 到第
使用帮助 返回顶部