共查询到20条相似文献，搜索用时 22 毫秒
1.
Dong-lin Tang Xiao-dong Zhang Guang-hui Zhao Zhi-yong Dai Xin Lai Feng Guo 《浙江大学学报(A卷英文版)》2009,10(4):595-600
An investigation of the properties ofa LiNbO3 photoelastic waveguide via the acceleration-induced effect is presented. A novel three-component hybrid-integrated optical accelerometer based on a Mach-Zehnder interferometer with a LiNbO3 photoelastic waveguide has been designed, which is capable of detecting seismic acceleration in high-accuracy seismic exploration. The Mach-Zehnder interferometer was successfully fabricated and a lighting test used to check its quality. The frequency response characteristic of the accelerometer was measured2 The accelerometer with a resonant frequency of 3549 Hz was demonstrated to show good linear frequency responding characteristics in the range of 100-3000 Hz. The accelerometer also shows good stability and consistency. Experimental results indicate that the outputs of the on- and cross-axis are 147 and 21.3 mV, respectively. 相似文献
2.
对基于Mach-Zehnder(MZ)干涉型LiNbO3调制器的工作原理和各种光码型产生方案进行了分析,比较了几种目前DWDM光通信系统中常见的解决方案。理论分析表明,保持偏置工作点的稳定是产生NRZ、RZ以及CS-RZ码的关键。因此,提出了一种利用低频外调制的方法实现调制器工作稳定以及码型程控可调的方案。 相似文献
3.
A distributed optical fiber disturbance detection system consisted of a Sagnac interferometer and a Mach-Zehnder interferometer
is demonstrated. Two interferometers outputs are connected to an electric band-pass filter via a detector respectively. The central frequencies of the two filters are selected adaptively according to the disturbance
frequency. The disturbance frequency is obtained by either frequency spectrum of the two interferometers outputs. An alarm
is given out only when the Sagnac interferometer output is changed. A disturbance position is determined by calculating a
time difference with a cross-correlation method between the filter output connected to the Sagnac interferometer and derivative
of the filter output connected to the Mach-Zehnder interferometer. The frequency spectrum, derivative and cross-correlation
are obtained by a signal processing system. Theory analysis and simulation results are presented. They show that the system
structure and location method are effective, accurate, and immune to environmental variations. 相似文献
4.
全光纤的Mach-Zehnder干涉仪是一种重要的干涉器件,因其具有干涉现象、体积小、重量轻、结构紧凑、灵敏度高等特点,可用于光纤通讯和光纤传感领域。本文利用干涉分析方法,通过计算机数值模拟,研究了Mach-Zehnder干涉仪的传输特性．得出了输出端的谱线与两个耦合器的分光比变化的关系。 相似文献
5.
张娟 《上海大学学报(英文版)》2011,15(1):31-34
A novel flat-top and low-dispersion optical interleaver using ring cavities (RCs) in a Mach-Zehnder interferometer (MZI) is proposed. It is composed of eight mirrors and two nested prism pairs. Each prism and the two mirrors behave as a RC. Phase shift of RC is a periodic function of the frequency of the input light which acts as a phase dispersive mirror. The two phase shifts needed to achieve a flat-top spectral passband are provided by Fresnel reffectivities at the prism-air interface of the two RCs. The... 相似文献
6.
介绍了一种基于LabVlEW的Mach-Zehnder光纤干涉仪闭环工作点控制系统。详细阐述了用LabVlEW实现的基本思路,并对两种不同情况下的检测结果进行了比较。 相似文献
7.
按准解析法，从理论上给出了Ｔｉ：ＬｉＮｂＯ３条形波导沿深度方向有效折射率的解析表达式，并按此式计算了典型波导的场分布及模折射率．这对于研究有金属覆盖层的条形波导的传播特性是特别有用的．本文还明确给出了确定导模场最大值位置的方法，因而对波导与波导、波导与光纤的耦合有一定的指导意义 相似文献
8.
邢进华 《常熟理工学院学报》2011,25(10):76-79
通过分析圆偏振外差光束分别经透明板反射和透射后的s光和p光的相位差改变,得到了它们与透明板折射率和厚度的关系.利用改进的M-Z干涉仪设计和构建了能同时测定透明板的折射率和厚度的实验装置,通过测量从透明板反射的圆偏振外差光束的s光和p光的相位差,将测量数据代入理论上导出的特定方程,可以计算出被测透明板的折射率.同时,透明板又在改进的M-Z干涉仪的测量臂中,由波长偏移和光通过透明板引起s光和p光的相位差改变.由透明板折射率的测量值、相位差改变和波长偏移的特定值可得到透明板的厚度.从而实现在同一光学构造下完成对透明板的折射率和厚度的同时测量. 相似文献
9.
采用阳离子掺杂方法制备了Mg:Er:Yb:LiNbO3晶体,获得了光折变效率高和不影响其它性能的激光晶体.为了探究铌酸锂晶体的微观结构对光学性质的影响,测量了Mg:Er:Yb:LiNbO3晶体的折射率和晶格常数.分析了晶格常数变化的因素和寻常光折射率、非常光折射率变化的因素,这两种性质与Er3 /Yb3 成分的关系不是完全单调变化的,在晶体中,Er3 /Yb3 浓度在1.1—1.2mol%范围内时观察到异常变化.给出了铌酸锂晶体结构对折射率影响的关系,Er3 /Yb3 掺杂LiNbO3晶体的两个主折射率随晶格畸变ca增大而增大.Er3 /Yb3 双掺杂对折射率和晶格常数的变化行为可以用稀土离子浓度影响锂空位浓度和稀土离子在晶体内的位置来解释. 相似文献
10.
Xu-dong Zheng Zhong-he Jin Yue-lin Wang Wei-jun Lin Xiao-qi Zhou 《浙江大学学报(A卷英文版)》2009,10(10):1413-1420
We present a bulk micromachined in-plane capacitive accelerometer fabricated with an improved process flow, by etching only one-fifth of the wafer thickness at the back of the silicon while forming the bar-structure electrode for the sensing capacitor. The improved flow greatly lowers the footing effect during deep reactive ion etching （DRIE）, and increases the proof mass by 54% compared to the traditional way, resulting in both improved device quality and a higher yield rate. Acceleration in the X direction is sensed capacitively by varying the overlapped area of a differential capacitor pair, which eliminates the nonlinear behavior by fixing the parallel-plate gap. The damping coefficient of the sensing motion is low due to the slide-film damping. A large proof mass is made using DRIE, which also ensures that dimensions of the spring beams in the Y and Z directions can be made large to lower cross axis coupling and increase the pull-in voltage. The theoretical Brownian noise floor is 0.47 μg/Hz^1/2 at room temperature and atmospheric pressure. The tested frequency response of a prototype complies with the low damping design scheme. Output data for input acceleration from -1 g to 1 g are recorded by a digital multimeter and show very good linearity. The tested random bias of the prototype is 130 μg at an averaging time of around 6 s. 相似文献
11.
YANG Xiao-cheng DING Jian-ping WANG Bo-chu 《重庆大学学报(英文版)》2007,6(4):227-230
The root development of Actinidia chinensis plantlets was studied in exposure to environmental stress of mechanical vibration at respectively 1 Hz, 2 Hz, 3 Hz, 4 Hz and 5 Hz. The plantlets exposed to vibration stimuli at all those frequencies have a larger total number and a larger total length of roots and a smaller permeability of root plasma-membrane, compared with those cultivated in an environment without vibration stress. Vibration at respectively 1 Hz, 2 Hz, 3 Hz and 4 Hz enhances root activity and the 3 Hz vibration is the most favorable. There is an obvious negative correlation between root activity and permeability of root plasma-membrane. The effects may be explained by the likelihood that mechanical vibration at an appropriate frequency facilitates roots’ absorbing water and minerals which are indispensable to inducing and synthesizing in roots some active substances favorable to growth. Nevertheless, overstress damages the integrity of root plasm-membrane, increases the permeability, and results in the disability of protecting root cells. 相似文献
12.
文章介绍了一种利用SPCE061A单片机直接合成1Hz～20KHz范围的正弦波信号发生器。波形失真小;频率控制准确,1KHz以下步进频率1Hz,1KHz以上步进5Hz。电路简单,单片机外围元件少,输出峰峰值电压2V。功耗低,工作电源电压为3V。 相似文献
13.
Dynamic response of functional virtual prototyping of motorcycle under combined excitations 总被引：1，自引：0，他引：1
This paper developed 3D product models of motorcycle and engine by UGNX as well as virtual prototyping by ADAMS program with road roughness generated by MATLAB. Under the straight-line running condition, the dynamic responses of motorcycle multibody system to both road and engine excitations were compared with those to only road excitation in terms of vertical acceleration response, amplitude frequency response and power spectral density. The comparisons of simulation data showed that the response due to flat road excitation was around 20 Hz, while that to the combined excitations was in a wide frequency band, of which the major components focused on 10 Hz, 15 Hz, 35 Hz ,70 Hz, 100 Hz and even higher frequencies, reflecting the characteristics of engine excitation based on its unbalanced inertia force and torque. It is concluded that the high fidelity virtual prototyping can simulate the dynamics of motorcycle product well in investigating the vibration and ride comfort performance. 相似文献
14.
邱学云 《楚雄师范学院学报》2014,29(6):12-16
选用非金属材料塑料和硅橡胶,组合成一维二元声子晶体匀直杆状结构。通过单一改变结构中非金属材料塑料的密度或者硅橡胶的密度,寻找单一材料密度变化与声子晶体杆禁带特性的关系。结果表明:当选取塑料密度为1190kg·m-3、硅橡胶密度为1300kg·m-3,晶格常数为0.3m,两种材料组份比相同时,一维二元非金属塑料/硅橡胶声子晶体存在低频禁带带隙,第1禁带起始频率为43.07Hz、禁带带宽为33.09Hz,第2禁带起始频率为99.84Hz,第2禁带带宽为52.49Hz;当单一改变塑料的密度,随着密度由小到大线性增加,结构第1带隙的起始频率由66.58Hz逐步减小到34.04Hz;第1带隙的截止频率为76.17Hz,保持不变,带隙宽度展宽;当单一改变材料硅橡胶的密度时,随着材料硅橡胶的密度由小到大线性增加,第1带隙的带宽由109.894HZ减小为18.3748Hz。对于一维二元非金属型声子晶体,选用密度更小的非金属材料与密度更大的非金属材料组合,更容易获得低频宽带带隙。另外,基于密度变化的同时还可以通过改变结构晶格常数的取值来获得更为理想的声子晶体禁带带隙。 相似文献
15.
一类碳纤维手性材料的微波性能研究 总被引：2，自引：0，他引：2
利用微波圆波导法在8.5～11.0 GHz范围内测量了Fe3O4聚苯胺复合基体碳纤维手性材料的旋波性、圆二色性,计算出手性材料和非手性基体材料的自由空间短路反射系数,对这些物理性能受基体中浓度的影响作了分析,给出了一种手性材料设计参数. 相似文献
16.
为提高链条液压张紧器在振动过程中的阻尼性能,在对张紧器动力学分析的基础上,使用AVLExcite—TD软件建立其仿真模型．以阻尼能为评价指标对其关键参数进行正交试验,通过对试验结果极差、方差分析张紧器参数对阻尼性能的影响,实现其全面优化,参数优化后阻尼能提高59．70％．在25～200Hz激励频率下．阻尼能为3．2731～5．1337J,在各频率下均具有良好的阻尼性能． 相似文献
17.
Auditory Frequency Resolution in Human Infancy 总被引：1，自引：0，他引：1
Frequency resolution is a fundamental capacity of the auditory system that underlies the perception of all complex sounds. The development of this capacity has not been well characterized in humans. This investigation used a nonsimultaneous pulsation threshold technique to examine the development of infant frequency resolution. Psychophysical tuning curves were obtained for 3- and 6-month-olds and for adults at either 500, 1,000, or 4,000 Hz. Both the sensation level and the sound pressure level of the stimulus were varied for adults to determine the contribution of stimulus intensity to age differences in frequency resolution. At 500 and 1,000 Hz, 3- and 6-month-olds' tuning curve widths were equivalent to adults'. At 4,000 Hz, the 3-month-olds' tuning curves were broader than those of 6-month-olds and adults, even when absolute sound pressure level was equivalent. The maturation of psychophysical frequency resolution in infants is discussed in terms of the general development of the auditory system and of nonsensory factors that might contribute to age differences in performance. 相似文献
18.
A novel scheme of optical modulation in 40 GHz radio-over fiber (RoF) system is proposed. It generates optical QPSK/16QAM
signals in a serial-parallel structure of Mach-Zehnder modulators (MZMs). The millimeter-wave is obtained with optical frequency
multiplication (OFM). Furthermore, modulation on optical-wave is transferred onto millimeter-wave. It can be used to increase
transmission capacity of millimeter-wave RoF systems. 相似文献
19.
发声是动物间进行交流的信息方式,声音信号的特征对应于动物的某种行为.以Matlab为工具,对采集到的雌、雄地中海果蝇飞行时振翅产生的声音进行了时域和频域的分析、比较,并提取其声音信号特征参数,即正常飞行鸣声的波形都为正弦波,声音的基频为147Hz,并带有多个谐波,其窄带声谱图具有良好的频率分辨率.研究还表明这种果蝇种内雌雄两性飞行时振翅特征有很大相似性. 相似文献
20.
将隧道看成波导,列车的存在改变了隧道的截面形状和尺寸,从而影响了电磁波的截止频率.在对列车—隧道导波问题进行物理建模的基础上,应用有限元法研究了列车的高度、宽度和位置以及半椭圆形隧道椭圆的偏心率的变化对半椭圆形隧道电磁波截止频率的影响. 相似文献