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1.
不典型肾脏血管平滑肌脂肪瘤的CT诊断   总被引:3,自引:0,他引:3  
分析了不典型肾脏血管平滑肌脂肪瘤的CT表现及其病理基础,以提高对该病的认识。方法;12例经CT扫描平扫和增强扫描。结果:该瘤的不典型CT特点为(1)肿瘤内缺乏脂肪成分;(2)肿瘤位特殊部位;(3)并发明显肾周血肿;(4)伴腹膜后淋巴结肿大。不典型肾脏血和平滑肌脂肪瘤虽有各种各样的表现,但12例中9例在病灶内仍可发现少量脂肪成分。  相似文献   

2.
MAX1246/MAX1247是MAXIM于1997年最新出品的12位串行输出A/D转换芯片,具有工作能耗低,采样,转换速度快,精度高,接口逻辑简单以及灵活的可编程控制模式等优点,详细分析和说明了该芯片的工作原理,特点及注意事项。  相似文献   

3.
研究了一种适用于物理光学实验中信号接收及数据采集的图象探测系统。该系统以自扫描光电二极管列阵SSPA作为光信号接收器件,以PC机作为控制和信息处理部分,从而提高了物理光学实验的测试水平。为满足上述要求,设计了适用于SSPA视频信号的12位A/D数据采集接口卡及相关程序。  相似文献   

4.
<正>单扫描快速采样方法及其在NMR中的应用赵明芳(厦门大学物理系,厦门361005)以离散编码单扫描快速采样方法为例阐明了单扫描快速采样方法的原理,介绍了连续幅度调制、连续相位调制等各种单扫  相似文献   

5.
设计和研制了一套IBM微机控制的数据采集系统。其硬件部分为一块 12位快速A/D转换卡,包括8路模拟信号输入通道、采样保持、A/D转换和 计算机接口等部分。将转换卡直接插入微机扩展槽即可运行。用汇编语言和 C语言开发了相应的软件。该软件具有实时图形显示功能,可取代一台高级 双笔记录仪应用于CO激光谱线的激光磁共振光谱仪。该系统有较高的通用 性,可用于其他数据记录。  相似文献   

6.
基于TSC695-FPGA架构的空间扫描运动控制系统设计   总被引:1,自引:0,他引:1  
朱钰 《科学技术与工程》2012,12(20):4965-4969
提出一种新型空间扫描运动控制系统TSC695—FPGA架构设计方案。方案以空间级32位浮点处理器TSC695为算法处理器,以XCV600 FPGA作为脉宽调制波形发生器和采样/通讯数据管理器,结合了TSC695的浮点运算单元和检错/纠错模块,以及FPGA的并行处理能力。实验证明,与传统的工业控制芯片相比,该架构能够显著提高空间扫描控制系统的可靠性和控制精度。  相似文献   

7.
基于非均匀采样间隔的数据关联算法研究   总被引:3,自引:3,他引:0  
针对工程中普遍存在的非均匀采样目标跟踪问题,给出了基于多扫描的后向递归概率数据关联算法实现过程,讨论了判断目标丢失的准则.对分别基于一维和多维扫描数据进行数据关联判决的不同算法的性能进行了仿真分析.仿真结果表明:在采样次数不变的条件下,和应用单扫描的PDAF算法相比,多扫描非均匀采样方法能够获得更好的航迹维持性能.当目标检测概率越大、杂波密度越大、目标机动性能越大时,非均匀采样和均匀采样方法航迹维持性能的差别越大.  相似文献   

8.
MAX1246/MAX1247是MAXIM于1997年最新出品的12位串行输出A/D转换芯片.具有工作能耗低、采样、转换速度快、精度高、接口逻辑简单以及灵活的可编程控制模式等优点.详细分析和说明了该芯片的工作原理、特点及注意事项  相似文献   

9.
准同步采样及其在常用电工参数数字化测量中的应用   总被引:4,自引:0,他引:4  
王石记  司锡才 《应用科技》2003,30(12):10-12
介绍了一种新的采样算法,即准同步采样,其采样周期不要求与信号周期严格同步.并将准同步采样算法应用于电工参数数字化测量中,具有良好的效果,与同步采样具有相当的准确度.计算的精确度和AD的位数有关,AD位数越高,计算也就越精确,通常,若AD的位数为16位,在工程中测量的精度可达万分之二.先介绍了准同步算法的理论依据,然后介绍了准同步系数的推导,最后介绍了如何在DSP中实现准同步算法.  相似文献   

10.
用单片微型计算机控制直流(电路或电源)瞬态响应测量仪器是一种数据采集 和处理系统,也是一种机械、电子一体化的设备,其组成部分包括: 12位 A/D转换器、 同步采样电路、存贮器、单片计算机、 D/A转换及微型打印机等。瞬态特性可用普通示 波器观测或由微型打印机记录。经过数据处理直接给出瞬态特征参数。实际应用证明, 仪器便于操作、准确度高而成本低。研究成果已通过鉴定。  相似文献   

11.
Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.  相似文献   

12.
何延凌 《科技信息》2008,(4):258-258
Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women's language from these perspectives: pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women's language, more attention should be paid to language use in social context. What's more, the linguistic phenomena in a speaking community can be understood more thoroughly.  相似文献   

13.
理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。  相似文献   

14.
As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.  相似文献   

15.
正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-  相似文献   

16.
We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-  相似文献   

17.
正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that  相似文献   

18.
For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the  相似文献   

19.
Franck-Condon factors bridge the gap between theoretical modeling and experimental observations for molecular electronic spectroscopy and electron transfer.Under the displaced harmonic oscillator approximation,multidimensional Franck-Condon factors are decomposed into a product of many one-dimensional(1D)Franck-Condon(FC)factors,and each 1D-FC factor is associated with one Huang-Rhys factor that determines the leading contribution of  相似文献   

20.
<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with  相似文献   

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