oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

2019 ( 94 )

2018 ( 2015 )

2017 ( 2096 )

2016 ( 2055 )

Custom range...

Search Results: 1 - 10 of 87869 matches for " 谢海情 "
All listed articles are free for downloading (OA Articles)
Page 1 /87869
Display every page Item
带宽对平顶高斯宽带激光传输特性的影响
彭润伍,李乐,李亚捷,,唐立军
强激光与粒子束 , 2013,
Abstract: ?研究了横向分布为平顶高斯模式的宽带激光在自由空间的传输特性,分析了频带宽度对其强度分布的影响。首先推导了平顶高斯模式宽带激光的每一频率分量在自由空间的传输公式,然后将频率域的传输公式通过傅里叶变换得到时间域的传输公式。基于推导的公式通过数值算例给出了不同频带宽度激光光束的强度分布结果,详细分析了空间模式的变化和时空耦合现象。研究结果表明:随着传输距离增大,平顶高斯空间模式趋于高斯分布。同时随着带宽增大,平顶高斯模式宽带激光表现出更强的时空耦合现象,并导致其空间横向分布发生明显变化。变化的主要特征为波前的强度分布随带宽增大而变窄,波后的强度分布则随带宽增大而远离轴中心向外扩展。
一种低噪声交叉耦合结构集成石英晶体振荡器
,曾承伟,曾健平,唐俊龙,贾新亮,彭永达,王超
- , 2017,
Abstract: 通过改进电路结构,采用CMOS交叉耦合结构提供负阻,设计一种20 MHz的集成石英晶体振荡器.在该振荡器中,采用共模反馈使其输出稳定的直流电平,并增加RC高通滤波器和预抑制电路降低其相位噪声.基于NUVOTON 0.35 μm CMOS工艺,利用Cadence Spectre对电路进行仿真,结果表明,在电源电压为3.3 V,偏置电流约400 μA时,该振荡器的起振时间约为1.5 ms,输出波形峰〖CD*2〗峰值为1.08 V,输出直流电平约为801.6 mV.输出信号频率为19.95 MHz,相位噪声分别可以达到-155 dBc/Hz@1 kHz,-164 dBc/Hz@10 kHz.
By improving the circuit structure and adopting the CMOS cross-coupled structure to provide negative resistance, a 20 MHz integrated quartz crystal oscillator was proposed. In this oscillator, the common-mode feedback was adopted to achieve stable DC output, and the RC high filter circuit and the pre-rejection circuit were designed to reduce the phase noise. With NUVOTON 0.35 μm CMOS process, the circuit was designed and simulated by the Spectre in Cadence. Under the supply voltage of 3.3 V and the bias current of 400 μA, the results indicated that start-up time of the oscillator was about 1.5 ms, the peak value of the output waveform was 1.08 V, the DC output was about 801.6 mV, the frequency of output was 20 MHz, and the phase noise reaches -155 dBc/Hz@1 kHz and -164 dBc/Hz@10 kHz, respectively.
Improved Kalman filter algorithm in positioning system for autonomous mobile robot
自主移动机器人定位系统中Kalman滤波算法改进*

ZENG Jian-ping,WANG Bao-tong,XIE Hai-qing,
曾健平
,王保同,

计算机应用研究 , 2011,
Abstract: In order to solve the problem that the large amount of computation and low accuracy of kalman filtering algorithm to the conventional mobile robot localization process, according to the analysis of the traditional kalman filter,the article gived a method of improving the conventional kalman filter by U-T parameter transformation, the improved kalman filtering algorithm reduced the error that brought by the traditional kalman filter which can not ignore the high-end items.The experimental results show that the maximum position deviation was reduced by the improved kalman filtering algorithm.The accuracy of the mobile robot positioning has been significantly improved. Error Simulation curve shows the results of the improved positioning error deviation is not obvious, the stability of the positioning system has been greatly improved.
交叉耦合结构集成石英晶体振荡器相位噪声与稳定性研究
,曾承伟,曾健平,贾新亮,王超,王龙,陈玉辉,李洁颖
- , 2018,
Abstract: 通过对相位噪声进行频域分析,构建Lesson噪声优化模型,优化电路参数;并分析预抑制电路的小信号模型,优化其元器件参数,研究带RC滤波器的CMOS交叉耦合结构振荡器的相位噪声和稳定性.基于NUVOTON 0.35 μm工艺,采用Cadence完成电路设计、优化与仿真,版图设计与后仿真,并最终完成流片、测试.结果表明:在电源电压为3.3 V时,该振荡器的输出信号频率为20 MHz,相位噪声分别为-135 dBc/Hz@1kHz,-156.4 dBc/Hz@10 kHz,-169.2 dBc/Hz@1MHz.当电源电压在±10%范围变化时,频率波动小于81×10-6;在工作温度-25 ℃至85 ℃范围内,频率波动小于71×10-6.
By the frequency domain analysis of phase noise, the optimization model of Lesson noise was established and the parameters in the circuit were improved. Meanwhile, the small signal model was established to optimize the parameters in the pre-suppression circuit. In this way, the phase noise and stability were studied for the cross-coupled integrated quartz crystal oscillator with RC filter. Furthermore, the circuit and layout were designed, simulated and optimized by Cadence with NUVOTON 0.35 μm process. Subsequently, the fabrication and test were carried out under the supply voltage of 3.3 V. The results indicated that the frequency of output was 20 MHz and the phase noise of the oscillator can reach -135 dBc/Hz @ 1 Hz, -156.4 dBc / Hz @ 10 kHz, and -169.2 dBc/Hz @ 1 Hz, respectively. The ripple wave was less than 81 ppm and 71 ppm, respectively, with the variation of the supply voltage in the range of ± 10% and the temperature range from -25 ℃ to 85 ℃ .
诱导喷嘴改进滤筒脉冲清灰效果的实验研究
,,巨敏,陈俊东
环境工程 , 2012, DOI: 10.13205/j.hjgc.201201017
Abstract: 改善清灰效果是提高滤筒除尘效率的关键和难点问题。运用自制脉冲喷吹实验台,采用诱导喷嘴(超音速引流喷嘴和气流散射器)对325mm×660mm滤筒进行脉冲喷吹清灰实验研究,并与采用普通喷吹孔的实验结果进行比较分析,得出采用诱导喷嘴时侧壁正压力峰值平均值是普通喷吹孔的1.465倍;且采用诱导喷嘴时各测点的不均衡系数为0.768~1.336,普通喷口为0.270~2.251,而不均衡系数越接近于1,其清灰效果越好;同时,采用诱导喷嘴时各测点基本在同一时刻达到正峰值。实验充分表明采用诱导喷嘴确保了滤筒长度方向上内壁清灰压力的均匀性,且对滤筒清灰效果有明显的改善作用。
基于第二代bandelet变换和斜变换的半脆弱水印算法
王枢,张敏,申军伟,
计算机应用 , 2012,
Abstract: ?针对图像的常规操作和恶意攻击,提出一种新的半脆弱水印算法。在该算法中,先将原图像压缩后的数据作为恢复比特嵌入到图像的最低有效位,再把经过turbo码编码后的第二代bandelet变换系数嵌入到分块的斜变换的中频区域。认证时,通过turbo码产生的误码和bandelet系数的比对实现认证和篡改定位。仿真实验表明,该算法对于图像的常规操作具有良好的鲁棒性,可以精确地检测与定位恶意篡改区域,并且具有较好的篡改恢复能力。
渤海湾盆地中、新生代岩石圈热结构研究
左银辉,邱楠生,常健,,李宗星,李佳蔚,李文正,彩虹
地质学报 , 2013,
Abstract: 本文以浅部沉积盆地热历史恢复结果为基础,结合地热学的有关理论计算得到渤海湾盆地中生代以来不同地质时期壳幔热流配分及莫霍面温度。结果显示,渤海湾盆地在早白垩世晚期和古近纪中晚期达到两次地幔热流与地表热流之比高峰,其两期地幔热流占地表热流比例都超过65%。莫霍面温度在早白垩世晚期、古近纪中晚期及新近纪早期(仅在临清坳陷、沧县隆起和冀中坳陷)出现3次高峰,其温度分别为900~1100℃、820~900℃和770~810℃。本文的研究不仅揭示出白垩纪是渤海湾盆地岩石圈热结构的重要转型期,即由三叠纪和侏罗纪的“冷幔热壳”型转变为白垩纪以来的“热幔冷壳”型的岩石圈热结构,还揭示出渤海湾盆地在早白垩世晚期和古近纪中晚期发生两期强烈的构造裂陷作用。因此,本文的研究可以为中国东部大陆岩石圈地球动力学的研究提供地热学参数。
世界铁矿石资源

地理科学进展 , 1982, DOI: 10.11820/dlkxjz.1982.03.018
Abstract: 根据最新的统计资料,全世界已探明的铁矿储量为1946亿吨,其中85%主要集中在11个国家苏联510亿吨、巴西260亿吨、加拿大260亿吨、澳大利亚180亿吨、美国177亿吨、印度80亿吨、中国64亿吨.
世界大洋中的矿物原料

地理科学进展 , 1985, DOI: 10.11820/dlkxjz.1985.01.016
Abstract:
国际洞穴学联合会第八届大会

地理科学进展 , 1984, DOI: 10.11820/dlkxjz.1984.02.015
Abstract: 国际洞穴学联合会第八届大会具有很大的吸引力。尽管这次会议是在欧洲以外地区召开的第一次会议,但是参加的人数之多,是历届会议所没有的。出版两部大部头的会议文集就充分说明了这一点。当然,与上次会议比较,会议参加者的地理分布有了明显的变化,上次会议多以讲盎格鲁——撒克逊语国家为主,这次会议也是由于地理位置近和有共同语言特点,美国和加拿大地区或喀斯特系统的专著特别多,相反,东方国家的作品比较少,拉丁美洲国家的更少。从代表团人数来看,美国居首位(526名),法国居第二位(134入)。
Page 1 /87869
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.