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基于直射线近似的一步法基准面校正方法研究 被引量:1
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作者 杨锴 蔡杰雄 +1 位作者 范旭 毛海波 《地球物理学报》 SCIE EI CAS CSCD 北大核心 2009年第4期1078-1088,共11页
地形基准面校正算子(Topographic Datuming Operator,以下简称TDO)是一种基于直射线近似得到的基准面延拓算子.TDO可以视为是两步法波动方程基准面校正与常规静校正之间的一种过渡算法,该方法的最大特点在于它可以基于共炮点道集将炮点... 地形基准面校正算子(Topographic Datuming Operator,以下简称TDO)是一种基于直射线近似得到的基准面延拓算子.TDO可以视为是两步法波动方程基准面校正与常规静校正之间的一种过渡算法,该方法的最大特点在于它可以基于共炮点道集将炮点和检波点同时延拓到给定的水平基准面,因此相对于常规的两步法叠前波动方程基准面校正,TDO方法可以认为是一种更为高效的一步法基准面延拓方法.本文基于理论与实际数据论证了上述观点. 展开更多
关键词 地形基准面校正算子(TDO) 直射线近似 一步法基准面校正 延拓
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变速直射线空校法
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作者 宋建国 李建华 蒋传林 《中国煤田地质》 1989年第3期53-55,共3页
速度是地震勘探解释中的重要参数,它直接影响解释的精度。在地层岩性横向变化剧烈、构造复杂地区,利用变速直射线空校法将地震勘探获取的法向时间改为垂直时间、再利用钻探的垂直深度,查清速度分布规律,编制平均速度分布图,用以进行时... 速度是地震勘探解释中的重要参数,它直接影响解释的精度。在地层岩性横向变化剧烈、构造复杂地区,利用变速直射线空校法将地震勘探获取的法向时间改为垂直时间、再利用钻探的垂直深度,查清速度分布规律,编制平均速度分布图,用以进行时深转换,来解决复杂地区的地震勘探精度问题。 展开更多
关键词 变速直射线 空间校正 地震勘探
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改进Moser法射线追踪 被引量:24
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作者 许琨 吴律 王妙月 《地球物理学进展》 CSCD 1998年第4期60-66,共7页
地震波场正演模拟、层析成像、偏移成像经常需要用到射线追踪,本文在基于图形理论的Moser法基础上,改进其网格节点的划分、追踪时路径的选取,并增加直射线追踪以消除在速度变化不大时射线受节点布置影响出现不合理的折曲现象.
关键词 图形理论 堆排序算法 直射线追踪 地震勘探
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井间地震射线走时层析成像数值模拟 被引量:21
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作者 刘良琼 刘江平 张英德 《工程地球物理学报》 2004年第5期441-446,共6页
介绍了CT成像的基本原理、反演算法中的BPT法和SIRT法、网格划分及程序设计思路,并进行了数值模拟。结果表明以BPT方法的重建结果作为SIRT法迭代初值,加快了收敛速度,取得了较好的重建结果图像,是一种比较好的迭代算法。但由于射线有限... 介绍了CT成像的基本原理、反演算法中的BPT法和SIRT法、网格划分及程序设计思路,并进行了数值模拟。结果表明以BPT方法的重建结果作为SIRT法迭代初值,加快了收敛速度,取得了较好的重建结果图像,是一种比较好的迭代算法。但由于射线有限广角的限制和SIRT算法的光滑效应,井间地震CT存在横向模糊的问题。文中通过数值模拟展现了井间地震CT横向逐渐模糊的过程并对产生横向模糊的原因进行了分析。 展开更多
关键词 井间地震 层析成像 直射线理论 反演
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基于VC++软件的无线电磁波CT层析成像反演技术研究
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作者 何继斌 《计算机光盘软件与应用》 2012年第15期242-242,244,共2页
主要研究壤层工作面无线电磁波层析成像反演,根据煤层对电磁波吸收特征以及电磁波在煤层中传播特点,选择直射线追踪,反投影法(BPT)、代数重建法(ART)、联合迭代重建法(SIRT)等图像重建方法,对比分析了不同方法的优缺点,最后选择SIRT方... 主要研究壤层工作面无线电磁波层析成像反演,根据煤层对电磁波吸收特征以及电磁波在煤层中传播特点,选择直射线追踪,反投影法(BPT)、代数重建法(ART)、联合迭代重建法(SIRT)等图像重建方法,对比分析了不同方法的优缺点,最后选择SIRT方法利用VC++软件编制程序实现,在实际资料处理中取得良好效果。 展开更多
关键词 CT成像 直射线追踪 反投影重建 代数重建 联合迭代重建
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井地地震CT技术及其应用 被引量:12
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作者 李红立 潘冬明 徐红利 《煤田地质与勘探》 CAS CSCD 北大核心 2008年第3期71-74,共4页
井地地震是在井间地震方法基础上提出,其技术核心主要是观测系统设计以及数据的采集和处理。观测系统设计旨在增加探测目标的覆盖次数、均匀程度和提高工作效率;数据采集从震源和检波器两个方面优化,选用激发能量强、频率高、成本低、... 井地地震是在井间地震方法基础上提出,其技术核心主要是观测系统设计以及数据的采集和处理。观测系统设计旨在增加探测目标的覆盖次数、均匀程度和提高工作效率;数据采集从震源和检波器两个方面优化,选用激发能量强、频率高、成本低、效率高的震源,以及灵敏度高、抗噪能力好的检波器;数据处理分为拾取初至、建立正演模型和反演层析成像。工程应用实例说明,井地地震具有很好的应用前景。 展开更多
关键词 井地地震 层析成像 直射线追踪 SIRT
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地震走时层析成像反演在速度模型中的应用 被引量:5
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作者 陈爱琼 周霞 +1 位作者 朱海东 杜浩坤 《长江大学学报(自然科学版)》 CAS 2011年第6期41-43,共3页
基于在均匀介质中的波射线传播理论,应用直射线追踪方法进行了射线走时正演计算,并选用了SIRT算法根据不同的点源和不同的检波点的走时观测值进行快速反演成像,并对不同的反演结果进行比较,获得了在不同走时观测值所反演得到速度异常区... 基于在均匀介质中的波射线传播理论,应用直射线追踪方法进行了射线走时正演计算,并选用了SIRT算法根据不同的点源和不同的检波点的走时观测值进行快速反演成像,并对不同的反演结果进行比较,获得了在不同走时观测值所反演得到速度异常区域的位置。 展开更多
关键词 地震走时层析成像 反演 直射线追踪 SIRT算法
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用地震CT技术探测煤层的不连续性 被引量:2
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作者 曹德欣 曹思远 《CT理论与应用研究(中英文)》 1992年第3期1-6,共6页
本文利用直射线地震CT技术探测煤层的不连续性,给出了若干数值汁算结果,由此表明了方法的可行性。
关键词 直射线地震CT 煤层不连续性 ART算法 反演
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克希霍夫叠前时间偏移走时算法应用效果评价 被引量:2
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作者 许建国 《中外能源》 CAS 2015年第5期36-40,共5页
地震资料成像效果与走时精度有关,在克希霍夫叠前时间偏移中,通常有两种计算旅行时的算法,即直射线法和弯曲射线法,不同的旅行时算法成像精度有一定差别。直射线法根据均方根速度计算旅行时;弯曲射线法利用层速度模型计算旅行时,虽然考... 地震资料成像效果与走时精度有关,在克希霍夫叠前时间偏移中,通常有两种计算旅行时的算法,即直射线法和弯曲射线法,不同的旅行时算法成像精度有一定差别。直射线法根据均方根速度计算旅行时;弯曲射线法利用层速度模型计算旅行时,虽然考虑了速度的横向变化,但仍然假设炮点或成像点两侧的走时是对称的。非对称走时Kirchhoff叠前时间偏移算法中含有水平源像距的多次项以及关于速度的横向导数(非对称项),能够有效提高走时计算精度,从而改善地震波的聚焦效果。对3种旅行时算法从理论公式、对速度的适应性方面进行应用效果分析,并在SB地区实测,认为弯曲射线与非对称走时的速度建模较为相似,两者速度的适应性较好。横向速度相对变化较大时,直射线较非对称走时所需均方根速度偏高。在速度横向变化较小的平层,效果相当;在速度横向变化较大时,非对称走时算法计算精度较弯曲射线稍高,较直射线有较大优势;直射线走时算法对断点和断面的分辨率略低。 展开更多
关键词 直射线 弯曲射线 非对称走时 叠前时间偏移
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基于程函方程的克希霍夫全平面域偏移成像方法
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作者 智敏 朱建刚 《物探与化探》 CAS 北大核心 2020年第4期756-762,共7页
本文分别以直射线和弯曲射线初至波层析反演技术重建的速度为偏移速度,采用波前扩展外推方式求解程函方程,求取了成像区域内各节点初至波时间场,应用克希霍夫积分偏移技术对复杂模型叠前数据进行全平面偏移成像,成像结果表明:弯曲射线... 本文分别以直射线和弯曲射线初至波层析反演技术重建的速度为偏移速度,采用波前扩展外推方式求解程函方程,求取了成像区域内各节点初至波时间场,应用克希霍夫积分偏移技术对复杂模型叠前数据进行全平面偏移成像,成像结果表明:弯曲射线层析反演方法获得的速度场较直射线层析结果对速度异常体的刻画更准确,以弯曲射线层析反演速度场作为偏移速度可以获得较好的偏移成像结果。 展开更多
关键词 程函方程 克希霍夫积分法 全平面偏移成像 弯曲射线层析反演 直射线层析反演
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孔间电磁波CT技术正演模型研究
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作者 丁朋 皮开荣 +1 位作者 马云龙 杜兴忠 《水利规划与设计》 2023年第4期71-76,共6页
孔间电磁波CT(Computerized Tomography层析成像)技术根据不同介质对电磁波吸收存在差异达到精确探测地质体的目的。正演是孔间电磁波CT技术的基础,但业内对电磁波CT正演方法的系统研究较少,缺少自主开发的正演模型构建软件。通过阐述... 孔间电磁波CT(Computerized Tomography层析成像)技术根据不同介质对电磁波吸收存在差异达到精确探测地质体的目的。正演是孔间电磁波CT技术的基础,但业内对电磁波CT正演方法的系统研究较少,缺少自主开发的正演模型构建软件。通过阐述孔间电磁波CT技术的原理,推导了正演模型的计算公式,并基于电磁波直射线传播理论和连续模型离散化处理方法开发了正演模型软件,最后,对此软件构建的几种典型的溶洞正演模型进行反演,验证了该正演软件的实用性。 展开更多
关键词 孔间电磁波CT 电磁波吸收 正演模型 直射线传播 连续模型离散化
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1234567890数之10 (初一、初二、初三)
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作者 周国镇 《数理天地(初中版)》 2002年第9期2-3,共2页
(5)无理数的近似值无理数的近似值是和无理数近似相等的有理数。例如 3,3.1,3.14,3.141,3.1415都是圆周率π的近似值.可以看出它们都是有理数; 它们都比π小,所以叫做π的不足近似值;
关键词 无理数 不足近似值 过剩近似值 有理数 圆周率 近似相等 精确 线 直射线 线
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Adjuvant therapies for colorectal cancer 被引量:8
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作者 Suzanne Kosmider Lara Lipton 《World Journal of Gastroenterology》 SCIE CAS CSCD 2007年第28期3799-3805,共7页
The management of colon and rectal cancer has changed dramatically over the last 25 years. The use of adjuvant therapies has become standard practice in locally advanced (stage M and selected stage 11) colorectal ca... The management of colon and rectal cancer has changed dramatically over the last 25 years. The use of adjuvant therapies has become standard practice in locally advanced (stage M and selected stage 11) colorectal cancer. Improved surgical techniques, chemotherapeutics and radiotherapy are resulting in higher cure rates and the development of agents targeting proliferative and angiogenic pathways offer further promise. Here we explore risk factors for local and distant recurrence after resection of colon and rectal cancer, and the role of adjuvant treatments. Discussion will focus on the evidence base for adjuvant therapies utilised in colorectal cancer, and the treatment of sub-groups such as the elderly and stage 11 disease. The role of adjuvant radiotherapy in rectal cancer in reduction of recurrence will be explored and the role and optimal methods for surveillance post-curative resection with or without adjuvant therapy will also be addressed. 展开更多
关键词 Colon cancer Rectal cancer CHEMOTHERAPY RADIOTHERAPY Adjuvant treatment
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Calibration method for multi-line structured light vision sensor based on Plücker line 被引量:2
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作者 QIN Guan-yu WANG Xiang-jun YIN Lei 《Journal of Measurement Science and Instrumentation》 CAS CSCD 2020年第2期103-111,共9页
For the rapid calibration of multi-line structured light system,a method based on Plücker line was proposed.Most of the conventional line-structured light calibration methods extract the feature points and transf... For the rapid calibration of multi-line structured light system,a method based on Plücker line was proposed.Most of the conventional line-structured light calibration methods extract the feature points and transform the coordinates of points to obtain the plane equation.However,a large number of points lead to complicated operation which is not suitable for the application scenarios of multi-line structured light.To solve this issue,a new calibration method was proposed that applied the form of Plücker matrix throughout the whole calibration process,instead of using the point characteristics directly.The advantage of this method is that the light plane equation can be obtained quickly and accurately in the camera coordinate frame.Correspondingly a planar target particularly for calibrating multi-line structured light was also designed.The regular lines were transformed into Plücker lines by extending the two-dimensional image plane and defining a new image space.To transform the coordinate frame of Plücker lines,the perspective projection mathematical model was re-expressed based on the Plücker matrix.According to the properties of the line and plane in the Plücker space,a linear matrix equation was efficiently constructed by combining the Plücker matrices of several coplanar lines so that the line-structured light plane equation could be furtherly solved.The experiments performed validate the proposed method and demonstrate the significant improvement in the calibration accuracy,when the test distance is 1.8 m,the root mean square(RMS)error of the three-dimensional point is within 0.08 mm. 展开更多
关键词 multi-line structured light Plücker line CALIBRATION perspective projection plane fitting
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VEGF-D expression correlates with colorectal cancer aggressiveness and is downregulated by cetuximab 被引量:16
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作者 Markus Moehler Christian Frings +9 位作者 Annett Mueller Ines Gockel Carl C Schimanski Stefan Biesterfeld Institute of Pathology Johannes Gutenberg University Mainz 55101 Germany Peter R Galle Martin H Holtmann 《World Journal of Gastroenterology》 SCIE CAS CSCD 2008年第26期4156-4167,共12页
AIM:To gain mechanistic insights into the role played by epidermal growth factor receptor (EGFR) in the regulation of vascular endothelial growth factors (VEGFs) in colorectal cancer (CRC). METHODS:The impact of high-... AIM:To gain mechanistic insights into the role played by epidermal growth factor receptor (EGFR) in the regulation of vascular endothelial growth factors (VEGFs) in colorectal cancer (CRC). METHODS:The impact of high-level expression of the growth factor receptors EGFR and VEGF receptor (VEGFR)3 and the VEGFR3 ligands VEGF-C and VEGF-D on disease progression and prognosis in human CRC was investigated in 108 patients using immunohistochemistry. Furthermore, the expression of the lymphangiogenic factors in response to the modulation of EGFR signalling by the EGFR-targeted monoclonal antibody cetuximab was investigated at the mRNA and protein level in human SW480 and SW620 CRC cell lines and a mouse xenograft model. RESULTS: Human CRC specimens and cell lines displayed EGFR, VEGF-C and VEGF-D expression with varying intensities. VEGF-C expression was associated with histological grade. Strong expression of VEGF-D was significantly associated with lymph node metastases and linked to a trend for decreased survival in lymph node-positive patients. EGFR blockade with cetuximab resulted in a significant decrease of VEGF-D expression in vitro and in vivo. CONCLUSION:In conclusion, the expression of VEGF-D in colorectal tumours is significantly associated with lymphatic involvement in CRC patients and such expression might be blocked effectively by cetuximab. 展开更多
关键词 Human colorectal cancer LYMPHANGIOGENESIS Vascular endothelial growth factor-C Vascular endothelial growth factor-D Epidermal growth factor receptor
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Efficacies of ^(89)Sr and combination treatments with regional extra-beam radiotherapy for cancer patients with multiple bone metastasis 被引量:4
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作者 Jianqiang Wang Chunxiao Cao Hong Yin Qi Yang Guoli Zeng 《The Chinese-German Journal of Clinical Oncology》 CAS 2010年第9期536-538,共3页
Objective:The aim of the study was to observe the efficacies of 89Sr and combination treatments with regional extra-beam radiotherapy for cancer patients with multiple bone metastasis.Methods:A total of 106 patients w... Objective:The aim of the study was to observe the efficacies of 89Sr and combination treatments with regional extra-beam radiotherapy for cancer patients with multiple bone metastasis.Methods:A total of 106 patients were divided into two groups, and each group were 53 patients:the simple 89Sr treatment group (simple group), and local radiotherapy and 89Sr treatment group (combination group).The dose of 4 mci of 89Sr was made in every patient by intravenous injection, 6 MV linear accelerator external irradiation dose was given 30-60 Gy/2-4 weeks.Results:The effective rates of simple and combination groups were respectively 83.01% and 90.56%; the effective improvement rates of the bone focus of two groups were 75.48% and 86.8%, respectively.There was homologous improvement in general conditions.Conclusion:89Sr treatment has a certain effect to the cancers of whole-body multiple bone metastases.And the combined treatment with regional radiotherapy can improve the efficacy and life quality of cancer patients with bone metastasis. 展开更多
关键词 NEOPLASM bone metastases 89Sr radionuclide RADIOTHERAPY combination
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The research of the staggered lamination linear pulse launcher
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作者 宋立伟 张千帆 程树康 《Journal of Harbin Institute of Technology(New Series)》 EI CAS 2004年第6期601-604,共4页
This paper proposes a new type of pulse launcher that applies the principle of linear motors. The stator, viz. gun barrel, of the launcher has a new structure of one segment of iron core consisting of 3 staggered lami... This paper proposes a new type of pulse launcher that applies the principle of linear motors. The stator, viz. gun barrel, of the launcher has a new structure of one segment of iron core consisting of 3 staggered laminations. This structure is helpful in advancing the thrust force per volume. Based on introducing the structure and the working principles, this paper resolves the electromagnetic thrusting force and performs mechanical analysis and experiments on the sample launcher. The research shows that this launcher is simple and brushless structure with brief controlling. 展开更多
关键词 staggered lamination pulse launcher linear step motor
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An experimental inter-comparison of radiotherapic dosimetric delivery to assess X-Ray linear accelerator output characteristics
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作者 K Masood T Zafar +1 位作者 J Zafar H Zafar 《Journal of Measurement Science and Instrumentation》 CAS 2014年第3期83-86,共4页
The dosimetric inter-comparison studies carry pertinent significance to ensure uniform radiation dose delivery for clinical trials. This paper investigates the comparative performance analysis of an X-ray high power l... The dosimetric inter-comparison studies carry pertinent significance to ensure uniform radiation dose delivery for clinical trials. This paper investigates the comparative performance analysis of an X-ray high power linear accelerator per- formed by the International Dosimetry Survey Mission and Institute of Nuclear Medicine & Oncology (INMOL), Lahore. The measurements were made using cylindrical ionization chambers based on the International Atomic Energy Agency (IAEA) TRS-398 protocol for absorbed dose-to-water dosimetric standards, and the percentage deviation was found to be between 0.5 % - 1%. The dosimetric analysis concerning linear X-ray accelerator output performed by INMOL, Lahore was found to be in good agreement with the results of IAEA Dosimtery Survey Mission. 展开更多
关键词 X-ray linear accelerator dosimetric analysis absorbed chamber PHANTOM
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Comparison of two methods for assessing leakage radiation dose around the head of the medical linear accelerators 被引量:1
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作者 Ehab M. Attalla 《The Chinese-German Journal of Clinical Oncology》 CAS 2013年第9期435-438,共4页
Objective:The aim of this study was to measure the leakage by two methods with ion chamber and ready packs film,and to investigate the feasibility and the advantages of using two dosimetry methods for assessing leakag... Objective:The aim of this study was to measure the leakage by two methods with ion chamber and ready packs film,and to investigate the feasibility and the advantages of using two dosimetry methods for assessing leakage radiation around the head of the linear accelerators.Methods:Measurements were performed using a 30 cm3ion chamber;the gantry at 0°,the X-ray head at 0°,the field size at between the central axis and a plane surface at a FSD of 100 as a reference,a series of concentric circles having radii of 50,75,and 100 cm with their common centre at the reference point.The absorbed dose was measured at the reference point,and this would be used as the reference dose.With the diaphragm closed,the measurements were taken along the circumference of the three circles and at 45°intervals.Results:Leakage radiations while the treatment head was in the vertical position varied between 0.016%–0.04%.With the head lying horizontally,leakage radiation was the same order magnitude and varied between 0.02%–0.07%.In the second method,the verification was accomplished by closing the collimator jaws and covering the head of the treatment unit with the ready pack films.The films were marked to permit the determination of their positions on the machine after exposed and processed.With the diaphragm closed,and the ready packs films around the linear accelerator the beam turned on for 2500 cGy(2500 MU).The optical density of these films was measured and compared with this of the reference dose.Leakage radiation varied according to the film positions and the magnitude of leakage was between 0.005%–0.075%.Conclusion:The differences between the values of the leakage radiation levels observed at different measurement points do not only reflect differences in the effective shielding thickness of the head wall,but are also related to differences in the distances between the target and the measurement points.The experimental errors involved in dosimetric measurement also contribute to such differences. 展开更多
关键词 leakage radiation acceptance testing linear accelerator ion chamber ready packs film
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Mechanism and optimization of fuel injection parameters on combustion noise of DI diesel engine 被引量:7
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作者 张庆辉 郝志勇 +2 位作者 郑旭 杨文英 毛杰 《Journal of Central South University》 SCIE EI CAS CSCD 2016年第2期379-393,共15页
Combustion noise takes large proportion in diesel engine noise and the studies of its influence factors play an important role in noise reduction. Engine noise and cylinder pressure measurement experiments were carrie... Combustion noise takes large proportion in diesel engine noise and the studies of its influence factors play an important role in noise reduction. Engine noise and cylinder pressure measurement experiments were carried out. And the improved attenuation curves were obtained, by which the engine noise was predicted. The effect of fuel injection parameters in combustion noise was investigated during the combustion process. At last, the method combining single variable optimization and multivariate combination was introduced to online optimize the combustion noise. The results show that injection parameters can affect the cylinder pressure rise rate and heat release rate, and consequently affect the cylinder pressure load and pressure oscillation to influence the combustion noise. Among these parameters, main injection advance angle has the greatest influence on the combustion noise, while the pilot injection interval time takes the second place, and the pilot injection quantity is of minimal impact. After the optimal design of the combustion noise, the average sound pressure level of the engine is distinctly reduced by 1.0 d B(A) generally. Meanwhile, the power, emission and economy performances are ensured. 展开更多
关键词 diesel engine injection parameters pilot injection combustion noise online optimization
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