期刊文献+
共找到17篇文章
< 1 >
每页显示 20 50 100
用Kane方法建立末敏弹减速和稳态扫描段模型
1
作者 谢永高 秦子增 《上海航天》 2003年第1期17-20,共4页
引入多刚体运动模型 ,详细分析了伞刚体和弹刚体的受力和运动特性 ,运用Kane方法建立末敏弹在减速运动和稳态扫描段的完整运动模型 ,并进行数字仿真。仿真结果与实验结果有很好的一致性 。
关键词 KANE方法 末敏弹 稳态扫描段 伪速度 减速运动 运动模型
下载PDF
基于拓扑信息的扫描路径生成算法 被引量:6
2
作者 李忠锋 王从军 黄树槐 《华中科技大学学报(自然科学版)》 EI CAS CSCD 北大核心 2003年第6期7-8,19,共3页
提出了一种基于拓扑信息的扫描路径生成算法 ,该算法在生成路径的同时就根据拓扑信息进行分区 ,既能获得较快的路径生成速度 ,又能获得较好的分区效果 .同时由于该算法对拓扑关系检查严格 ,还可以用于解决偏置扫描中难以解决的快速处理... 提出了一种基于拓扑信息的扫描路径生成算法 ,该算法在生成路径的同时就根据拓扑信息进行分区 ,既能获得较快的路径生成速度 ,又能获得较好的分区效果 .同时由于该算法对拓扑关系检查严格 ,还可以用于解决偏置扫描中难以解决的快速处理外环与内环、内环与内环的相交以及环的自交问题 . 展开更多
关键词 快速原型 路径 单调链 扫描段 工作扫描段
下载PDF
全身平移扫描放射治疗装置的研制 被引量:2
3
作者 王慈勇 马胜林 +1 位作者 马松庆 朱德初 《医疗卫生装备》 CAS 2005年第3期1-2,共2页
全身平移扫描治疗装置是一由计算机控制的可升降、床面可纵向移动的特别的床。床面运动的距离可达2.3m。为了使人体不同厚度的躯段在扫描过程中能获得相等的中平面剂量,在软件设计中将全程扫描分为4个躯段。医者可根据病人人体情况分成... 全身平移扫描治疗装置是一由计算机控制的可升降、床面可纵向移动的特别的床。床面运动的距离可达2.3m。为了使人体不同厚度的躯段在扫描过程中能获得相等的中平面剂量,在软件设计中将全程扫描分为4个躯段。医者可根据病人人体情况分成数段,并任选各段的长度和扫描速度,系统会自动改变其相应速度完成设定的要求。系统还设有安全可靠的联锁系统,确保治疗的安全。经检测,装置在计算机的控制下,运动平稳、匀速,在扫描范围内剂量分布均匀。 展开更多
关键词 全身平移扫描 放射治疗 扫描
下载PDF
端点预搜索的Freeman直线段识别算法 被引量:1
4
作者 聂珊 李征 吴仲光 《四川大学学报(自然科学版)》 CAS CSCD 北大核心 2006年第6期1231-1235,共5页
直线段提取对于数字图像中规则目标的形状分析、识别来说是一个基本且必要的前期信息提取步骤.本文提出了一种以角点充当直线段的端点,在得到直线段端点和直线段主次方向基础上使用Freeman准则对直线段进行扫描.由于在直线段搜索前已经... 直线段提取对于数字图像中规则目标的形状分析、识别来说是一个基本且必要的前期信息提取步骤.本文提出了一种以角点充当直线段的端点,在得到直线段端点和直线段主次方向基础上使用Freeman准则对直线段进行扫描.由于在直线段搜索前已经获取了直线段端点的位置信息,因此该算法能够高速准确地对直线段进行扫描,具有较强的抗噪声能力.实验结果验证了该算法的有效性,并且该算法对较粗直线段也具有良好的检测能力. 展开更多
关键词 直线扫描 FREEMAN链码
下载PDF
160 mm超宽体探测器CT在肾上腺扫描中的应用
5
作者 尹炜 陈疆红 +1 位作者 李娟 钟朝辉 《临床和实验医学杂志》 2019年第23期2546-2549,共4页
目的研究应用160 mm超宽体探测器CT轴位扫描方式在降低腹部肾上腺检查中辐射剂量中的作用。方法采用前瞻性病例对照研究设计,选取2018年1~12月于首都医科大学附属北京友谊医院行上腹部肾上腺160 mm超宽体CT增强扫描的成年患者50例,采用... 目的研究应用160 mm超宽体探测器CT轴位扫描方式在降低腹部肾上腺检查中辐射剂量中的作用。方法采用前瞻性病例对照研究设计,选取2018年1~12月于首都医科大学附属北京友谊医院行上腹部肾上腺160 mm超宽体CT增强扫描的成年患者50例,采用随机数字表法将患者分成A组(n=24)和B组(n=26),A组患者采用螺旋扫描方式,自动管电流控制,管电压120 kV,噪声指数(NI)为10,使用30%自适应迭代重建算法(ASIR);B组患者采用轴扫节段扫描方式,其余参数同A组。分别对两组患者进行平扫和增强扫描,并对增强动脉期进行多平面冠状位重建,由两位资深影像科医师对平扫期、增强动脉期、冠状位重建后的增强动脉期3组图像的图像质量进行主观评分,并比较两组患者图像的客观噪声(SD)、信噪比(SNR)、对比噪声比(CNR)比及有效剂量。结果两组患者平扫期、增强动脉期、冠状位重建后的增强动脉期图像主观评分之间比较,差异无统计学意义(P>0.05)。两组患者的图像平扫及增强后SD、SNR、CNR水平之间比较,差异无统计学意义(P>0.05)。X线有效剂量B组比A组降低13.0%,差异有显著统计学意义(P<0.01)。结论应用160 mm超宽体探测器CT对腹部肾上腺组织进行轴扫扫描相比于螺旋扫描,在保证图像质量的前提下能够降低X线辐射剂量。 展开更多
关键词 肾上腺CT检查 160 mm超宽体探测器CT 轴扫节扫描 螺旋扫描 有效剂量
下载PDF
一种高亮度超多位LED数码显示驱动算法的实现
6
作者 王云平 《辽宁师专学报(自然科学版)》 2010年第4期20-22,共3页
介绍一种高亮度超多位LED数码显示驱动算法——按段扫描算法,该算法既具有成本低的优点,又弥补了亮度受限的缺点.利用该算法,理论上可以达到2 500多个数码管的高亮度显示,彻底解决在显示多位LED数码管时亮度低的问题.
关键词 扫描 多位LED 高亮度显示
下载PDF
Gd-EOB-DTPA-enhanced magnetic resonance imaging features of hepatic hemangioma compared with enhanced computed tomography 被引量:19
7
作者 Akihiro Tateyama Yoshihiko Fukukura +4 位作者 Koji Takumi Toshikazu Shindo Yuichi Kumagae Kiyohisa Kamimura Masayuki Nakajo 《World Journal of Gastroenterology》 SCIE CAS CSCD 2012年第43期6269-6276,共8页
AIM:To clarify features of hepatic hemangiomas on gadolinium-ethoxybenzyl-diethylenetriaminpentaacetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance imaging (MRI) compared with enhanced computed tomography (CT). METH... AIM:To clarify features of hepatic hemangiomas on gadolinium-ethoxybenzyl-diethylenetriaminpentaacetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance imaging (MRI) compared with enhanced computed tomography (CT). METHODS:Twenty-six patients with 61 hepatic hem- angiomas who underwent both Gd-EOB-DTPA-enhanced MRI and enhanced CT were retrospectively reviewed. Hemangioma appearances (presence of peripheral nodular enhancement, central nodular enhancement, diffuse homogenous enhancement, and arterioportal shunt during the arterial phase, fill-in enhancement during the portal venous phase, and prolonged enhancement during the equilibrium phase) on Gd-EOB-DTPA-enhanced MRI and enhanced CT were evaluated.The degree of contrast enhancement at the enhancing portion within the hemangioma was visually assessed using a five-point scale during each phase. For quantitative analysis, the tumor-muscle signal intensity ratio (SIR), the liver-muscle SIR, and the attenuation value of the tumor and liver parenchyma were calculated. The McNemar test and the Wilcoxon's signed rank test were used to assess the significance of differences in the appearances of hemangiomas and in the visual grade of tumor contrast enhancement between Gd-EOB-DTPA-enhanced MRI and enhanced CT. RESULTS:There was no significant difference between Gd-EOB-DTPA-enhanced MRI and enhanced CT in the presence of peripheral nodular enhancement (85% vs 82%), central nodular enhancement (3% vs 3%), diffuse enhancement (11% vs 16%), or arterioportal shunt (23% vs 34%) during arterial phase, or fill-in enhancement (79% vs 80%) during portal venous phase. Prolonged enhancement during equilibrium phase was observed less frequently on Gd-EOB-DTPA-enhanced MRI than on enhanced CT (52% vs 100%, P < 0.001). On visual inspection, there was significantly less contrast enhancement of the enhancing portion on Gd-EOB-DTPA-enhanced MRI than on enhanced CT during the arterial (3.94 ± 0.98 vs 4.57 ± 0.64, respectively, P < 0.001), portal venous (3.72 ± 0.82 vs 4.36 ± 0.53, respectively, P < 0.001), and equilibrium phases (2.01 ± 0.95 vs 4.04 ± 0.51, respectively, P < 0.001). In the quantitative analysis, the tumor-muscle SIR and the liver-muscle SIR observed with Gd-EOB-DTPA-enhanced MRI were 0.80 ± 0.24 and 1.28 ± 0.33 precontrast, 1.92 ± 0.58 and 1.57 ± 0.55 during the arterial phase, 1.87 ± 0.44 and 1.73 ± 0.39 during the portal venous phase, 1.63 ± 0.41 and 1.78 ± 0.39 during the equilibrium phase, and 1.10 ± 0.43 and 1.92 ± 0.50 during the hepatobiliary phase, respectively. The attenuation values in the tumor and liver parenchyma observed with enhanced CT were 40.60 ± 8.78 and 53.78 ± 7.37 precontrast, 172.66 ± 73.89 and 92.76 ± 17.92 during the arterial phase, 152.76 ± 35.73 and 120.12 ± 18.02 during the portal venous phase, and 108.74 ± 18.70 and 89.04 ± 7.25 during the equilibrium phase, respectively. Hemangiomas demonstrated peak enhancement during the arterial phase, and both the SIR with Gd-EOB-DTPA-enhanced MRI and the attenuation value with enhanced CT decreased with time. The SIR of hemangiomas was lower than that of liver parenchyma during the equilibrium and hepatobiliary phases on Gd-EOB-DTPA-enhanced MRI. However, the attenuation of hemangiomas after contrast injection was higher than that of liver parenchyma during all phases of enhanced CT. CONCLUSION:Prolonged enhancement during the equilibrium phase was observed less frequently on Gd-EOB-DTPA-enhanced MRI than enhanced CT, which may exacerbate differentiating between hemangiomas and malignant tumors. 展开更多
关键词 Liver HEMANGIOMA Magnetic resonance imaging Gadolinium-ethoxybenzyl-diethylenetriamin-pentaacetic acid Multidetector-row computed tomography
下载PDF
Characteristics and mechanism of low permeability beach-bar sandstone reservoir of Es4 in Dongying sag 被引量:4
8
作者 WANG Hua-ai ZHONG Jian-hua +2 位作者 ZHONG Fu-ping NIU Yong-bin WANG Pei-jun 《Mining Science and Technology》 EI CAS 2009年第6期788-795,共8页
Core and cast sections observation and description,and logging,scanning electron microscope and core lab analysis data etc. were applied to the present research of the characteristics and mechanism of low permeability... Core and cast sections observation and description,and logging,scanning electron microscope and core lab analysis data etc. were applied to the present research of the characteristics and mechanism of low permeability beach-bar sandstone reservoir of Es4 in Dongying sag. The results indicated the reservoir has the characteristics of middle-low pores,low-permeability,low compositional and structural maturity,and thin throat. The low-permeability is mainly due to sedimentation (fine particles and argillaceous inter beds) and diagenesis (compaction,cementation,and dissolution). The cementation reduced the physical property of the reservoir mainly by carbonate cementation,quartz autogeny and enragement,and autogeny clay. Clay minerals usually jam the pores by filling holes,close-fitting the wall of hole,bridging,wrapping grains,and separate attaching the pores and so on. The dissolution is insufficient so as not to improve the porosity and permeability of the reservoir obviously. So it is also an important factor of forming low-permeability reservoir. 展开更多
关键词 beach-bar sandstone low-permeability reservoir characteristics SEDIMENTATION DIAGENESIS
下载PDF
Carcinoma of the papilla of Vater following treatment of pancreaticobiliary maljunction 被引量:1
9
作者 Masato Watanabe Yutaka Midorikawa +5 位作者 Taketoshi Yamano Hiroyuki Mushiake Naoto Fukuda Takashi Kirita Kunio Mizuguchi Yasuyuki Sugiyama 《World Journal of Gastroenterology》 SCIE CAS CSCD 2009年第48期6126-6128,共3页
Pancreaticobiliary maljunction(PBM)is frequently associated with biliary cancer due to reflux of pancreatic enzymes into the choledochus,and even after surgery to correct the PBM such patients still have a risk of res... Pancreaticobiliary maljunction(PBM)is frequently associated with biliary cancer due to reflux of pancreatic enzymes into the choledochus,and even after surgery to correct the PBM such patients still have a risk of residual bile duct cancer.Here,we report the case of a 59-year-old female with carcinoma of the papilla of Vater which developed 2.5 years after choledochoduodenostomy for PBM.During the postoperative follow-up period,computed tomography obtained 2 years after the first operation demonstrated a tumor in the distal end of the choledochus,although she did not have jaundice and laboratory tests showed no abnormalities caused by the previous operation.As a result,carcinoma of the papilla of Vater was diagnosed at an early stage,followed by surgical cure.For early detection of periampullary cancer in patients undergoing surgery for PBM,careful long-term follow-up is needed. 展开更多
关键词 Pancreaticobiliary maljunction Biliary cancer Carcinoma of the papilla of Vater
下载PDF
螺旋CT扫描节段重建在急症头颅CT中的应用
10
作者 徐玉新 潘春霞 《医用放射技术杂志》 2003年第5期33-33,共1页
关键词 螺旋CT扫描 急症 头颅CT 扫描重建
原文传递
用陆地卫星MSS资料确定的牧场径流曲线数
11
作者 A.W.泽温培根 R.H.霍金斯 顾钟炜 《遥感技术与应用》 CSCD 1989年第4期30-35,15,共7页
在若干流域,我们己经找到了卫星资料与水文学上确定的径流数(CN)之间的关系。根据小的牧场盆地的降雨径流资料计算的流域径流数(CN),与变换成19个反射指数模型(RIM)的陆地卫星多谱段扫描仪资料进行了相关。本研究中,选择了9个小流域,并... 在若干流域,我们己经找到了卫星资料与水文学上确定的径流数(CN)之间的关系。根据小的牧场盆地的降雨径流资料计算的流域径流数(CN),与变换成19个反射指数模型(RIM)的陆地卫星多谱段扫描仪资料进行了相关。本研究中,选择了9个小流域,并有足够的CN资料和陆地卫星资料可以得到。去掉了多余的或与RIM相关性差的以后,选择了5个有意义的、RIM与CN回归关系相关性好的(r>|0.90|)来研究牧场径流。所作的大部分试验是为了证实这种方法,而试验结果表明,卫星资料最终可用于直接或间接地计算牧场的CN,这种经验方法有可能用于规划研究和综合牧区资源模型的研究。 展开更多
关键词 MSS 陆地卫星 指数模型 多谱扫描 土壤图 资源模型 线性回归方法 回归关系 相关系数 土地管理
下载PDF
Diagenesis and porosity evolution of sandstone reservoirs in the East II part of Sulige gas field, Ordos Basin 被引量:20
12
作者 Yang Renchao Fan Aiping Han Zuozhen Wang Xiuping 《International Journal of Mining Science and Technology》 SCIE EI 2012年第3期311-316,共6页
It is becoming an important controlling factor of gas exploration and exploitation in the east part of Sulige gas field in the Ordos Basin where the reservoir of main gas formations is tight sandstones. Employing expe... It is becoming an important controlling factor of gas exploration and exploitation in the east part of Sulige gas field in the Ordos Basin where the reservoir of main gas formations is tight sandstones. Employing experimental methods of slice identification, casting slice, scan electron microscope, and X-ray diffrac- tions, we studied the characteristics of petrology and diagenesis on reservoirs in Shanl section of Shanxi formation and He8 section of Shihezi formation of the Permian system in the East II part of Sulige gas field. The results include: (1) the main sandstones in these areas are dominated by lithic sandstone and litbic silicarenite with low grade of maturity; (2) the diagenesis of sandstone in these areas mainly include compaction, cementation, corrosion and alteration. Conclusions are as follows: (1) the diagenetic stage reached period B of the middle diagenetic stage; (2) the early diagenetic compaction is one of the main factors to decreasing porosity; (3) the secondary pores formed by corrosion in acidity medium con- ditions in period A of the middle diagenetic stage can distinctly ameliorate the poor reservoir capability of sandstone and, (4) cementation in period B of the middle diagenetic stage is the most important factor leading; to poor physical property of sandstone reservoirs. 展开更多
关键词 Ordos BasinPermianSandstone reservoirsDiagenesisPorosity evolution
下载PDF
第一颗地球资源卫星
13
《国防科技》 2002年第4期82-82,共1页
关键词 地球资源卫星 美国 “陆地卫星”1号 地球信息 多谱扫描 返束光导管摄像机
下载PDF
Non-isothermal crystallization kinetics of Nylon 10T and Nylon 10T/1010 copolymers:Effect of sebacic acid as a third comonomer 被引量:6
14
作者 Zhongqiang Wang Guosheng Hu +2 位作者 Jingting Zhang Jiusheng Xu Wenbo Shi 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2017年第7期963-970,共8页
Nylon 10 T and Nylon 10T/1010 samples were synthesized by direct melt polymerization. The non-isothermal crystallization kinetics of Nylon 10 T and Nylon 10T/1010 was investigated by means of differential scanning cal... Nylon 10 T and Nylon 10T/1010 samples were synthesized by direct melt polymerization. The non-isothermal crystallization kinetics of Nylon 10 T and Nylon 10T/1010 was investigated by means of differential scanning calorimetry(DSC). Jeziorny equation and Mo equation were applied to describe the non-isothermal crystallization kinetics of the Nylon 10 T and the Nylon 10T/1010. The activation energies for non-isothermal crystallization were obtained by Vyazovkin's method and Friedman's method, respectively. These results showed that Jeziorny equation and Mo equation well described the non-isothermal crystallization kinetics of the Nylon 10 T and the Nylon 10T/1010. It was found that the values of the activation energy for non-isothermal crystallization of the Nylon 10T/1010 were lower than those of the Nylon 10 T at a given temperature or relative crystallinity degree,which revealed that crystallization ability of the Nylon 10T/1010 was higher. The crystal morphology was observed by means of a polarized optical microscope(POM) and X-ray diffraction(XRD). It was found that the addition of sebacic acid comonomer not only did not change the crystal form of the Nylon 10 T, but also significantly increased the number and decreased the size of spherulites. Comparing with the Nylon 10 T, the crystallization rate was increased with the addition of the sebacic acid comonomer. 展开更多
关键词 Melt polymerization Nylon 10TNylon 10T/1010 Semiaromatic polyamides Crystallization kinetics Non-isothermal crystallization
下载PDF
MSS数字图像谱类地学解译图精度检验与修正
15
作者 杨俊泉 《广西农业大学学报》 CSCD 1992年第3期77-82,共6页
通过对MSS数字图像的分类解译图与全野外调绘的土地利用现状图的系统抽样对比及野外验证结果的分析,对于在地形、地块破碎的南方丘陵,山地使用该图像进行土地分类的精度、存在问题和实用价值作出评价,提出了改进方法。采用光谱学分析与... 通过对MSS数字图像的分类解译图与全野外调绘的土地利用现状图的系统抽样对比及野外验证结果的分析,对于在地形、地块破碎的南方丘陵,山地使用该图像进行土地分类的精度、存在问题和实用价值作出评价,提出了改进方法。采用光谱学分析与地学分析相结合的方法,建立地理控制系统,编制透明地理要素底图,制定解译规则,以对图像自动分类图进行解译制图。利用成数点抽样数学模型,对两图抽样对比结果进行面积修正和精度评定的模拟计算。由此,提出了将遥感与地理信息系统、抽样技术相结合的资源与环境监测体系的构想。 展开更多
关键词 卫星遥感 陆地卫星 多谱扫描 数字图像 解译 精度
原文传递
行星影像
16
作者 Alison Marsh 《科技纵览》 2022年第7期78-78,共1页
50年前,人们还没有很好的方法从太空中研究地球.1972年7月23日,美国国家航空航天局(NASA)发射了地球资源技术卫星(ERTS).ERTS携带了一个电视摄像系统,以及一个实验性多谱段扫描仪系统(MSS),该系统能够利用光纤在4个不同的光谱波段(绿、... 50年前,人们还没有很好的方法从太空中研究地球.1972年7月23日,美国国家航空航天局(NASA)发射了地球资源技术卫星(ERTS).ERTS携带了一个电视摄像系统,以及一个实验性多谱段扫描仪系统(MSS),该系统能够利用光纤在4个不同的光谱波段(绿、红和两个不同的近红外波段)收集数据.所有人都认为电视摄像机会成为该任务的主力,但最终却是MSS成为了制胜技术. 展开更多
关键词 电视摄像系统 电视摄像机 多谱扫描 光谱波 近红外波 MSS
原文传递
情报工具与反谋利器
17
作者 国力 《兵器知识》 1999年第11期28-30,共3页
上海市南市区谢朝阳、湖北襄樊市徐文军等朋友来信说:贵刊的"超级间谍"系列文章中介绍了不少间谍使用的武器,让人大开眼界,贵刊能否再介绍一些间谍传递情报用的工具及各种反间谍工具。为此,本刊再次诚邀系列文章的作者国力先... 上海市南市区谢朝阳、湖北襄樊市徐文军等朋友来信说:贵刊的"超级间谍"系列文章中介绍了不少间谍使用的武器,让人大开眼界,贵刊能否再介绍一些间谍传递情报用的工具及各种反间谍工具。为此,本刊再次诚邀系列文章的作者国力先生为朋友们撰写下此文。间谍使用的工具,除了那些致命的杀人武器之外,还有许多是为传递情报用的。时至今日。 展开更多
关键词 隐显墨水 间谍工具 间谍活动 情报工具 多谱扫描 遥感器 合成孔径雷达 传递 照相侦察卫星 上海市
原文传递
上一页 1 下一页 到第
使用帮助 返回顶部