共查询到20条相似文献，搜索用时 312 毫秒
1.
徐海斌 《湖州师范学院学报》2005,27(2):36-39
从非线性耦合的基本方程出发,描述了光学二次谐波（SHG）产生,分析了影响二次谐波转换效率的各个因素,阐述了相位匹配的概念,解释了准相位匹配（QPM）技术对提高非线性光频转换效率的作用,最后与传统的双折射相位匹配（BPM）相比较,总结得出利用准相位匹配技术在实现非线性光频转换过程中所具有的优点. 相似文献
2.
波长变换技术是组成全光分组交换网中的重要技术之一,而当前比较成熟的基于半导体光放大器的波长转换技术在传输速率、信号格式、波长转换通道数和灵活性上还存在缺陷,不利于今后高速大容量光网络的发展。本文提出了基于周期极化掺氧化镁铌酸锂（PPMgLN）晶体的非线性波长转换方案,该方案采用I型准相位匹配（QPM）技术实现宽带倍频（SHG）、和频（SFG）和差频（DFG）,再通过级联二阶倍频差频（cSHG/DFG）或级联二阶和频差频（cSFG/DFG）波长转换机制,实现全光通信波长转换。在全光网络中,该方案能够很好地解决波长竞争、传输格式达到完全透明、降低网络阻塞率、提高网络传输速率等问题。 相似文献
3.
A deep understanding of the spectral gain characteristics of optical parametric oscillators （OPOs） and optical parametric amplifiers （OPAs） is important for a highly efficient optical parametric conversion. We numerically calculated the spectral gain characteristics of a quasi-phase-matching （QPM） parametric conversion process using the periodically poled 6% （mol/mol） MgO doped LiNbO3 （PPMgLN） as the nonlinear crystal. In the simulation we utilized the approach of a transformative matrix of the periodically poled nonlinear medium, which results from the small-signal approximation of three-wave mixed nonlinear equations. Numerical simulation results show that： （1） The full width at half maximum （FWHM） of the spectral gain of the parametric process becomes wider with the increase of parametric wavelength and reaches the maximum at degeneration; （2） The gain coefficient decreases gradually with the increase of parametric wavelength; （3） The spectral gain bandwidth decreases correspondingly with the increase of the nonlinear material length; （4） There exists an optimal parametric wavelength band, which is most suitable for the high gain parametric conversion when pumped by a laser source with a wide wavelength band, such as the high power fiber laser. 相似文献
4.
吴丽双 《泉州师范学院学报》1999,(4)
用５ｍ ｍ 的 Ｋ Ｔ Ｐ（ Ｋ Ｔｉ Ｏ Ｐ Ｏ４）和 Ｂ Ｂ Ｏ（β Ｂａ Ｂ２ Ｏ４）非线性晶体,对皮秒的 Ｃ Ｐ Ｍ , Ｎｄ： Ｙ Ａ Ｇ 脉冲激光的腔外倍频效应进行研究,获得倍频能量转换效率分别为４２％ 和３２％ ,证明 Ｋ Ｔ Ｐ倍频效率高于 Ｂ Ｂ Ｏ,结果与理论分析相符 相似文献
5.
基于广义的惠更斯-菲涅尔原理和Wigner分布函数(WDF)二阶矩的定义,对常规厄米-高斯(SHG)光束和复宗量厄米-高斯(EHG)光束通过湍流大气的M2因子和相对M2因子进行了对比分析.结果表明,大气湍流中在相同条件下的SHG和EHG光束的M2因子存在明显的差异,仅有阶数m=0、m=1时SHG和EHG光束的M2因子的相等,当m≥2时,EHG光束的M2因子比SHG光束显著小,但SHG光束的相对M2因子比EHG光束的显著小,说明SHG光束比EHG光束受湍流大气影响更小. 相似文献
6.
1 Introduction X-ray emission from laser-produced plasma is notonly of considerable interest for inertial confinementfusion application,but is also of i mportance to a num-ber of other applications[1-3].Thelaser-plasma interac-tion can be efficient , bright , and versatile source ofX-rays . X-ray emission shows a remarkable variation withlaser wavelength . Shorter wavelengths are more effi-cient for producing quasi-thermal plasma emission.Longer wavelength laser-plasma interactions have pro-d… 相似文献
7.
Electro-Discharge Fine Truing of Metal-Bonded Fine-Grain Diamond Wheel Based on Real-Time Monitoring 总被引：2，自引：0，他引：2
A data acquisition system based on LabVlEW is designed and implemented, and electrodischarge(ED) fine truing of metal-bonded fine-grain diamond wheel based on real-time monitoring is researched. Real-time monitoring not only makes efficient impulse specification of ED truing easily obtained, but also is good for timely identifying no-load, avoiding short circuit and arc discharge phenomena and then for obtaining normal machining state. ED fine truing of the fine-grain wheel includes two steps: rough truing for high efficiency and fine truing for high precision. Final ED truing precision and efficiency not only depend on electric process specification, but also is concerned with electrode shape, insulated performance of operating fluid and vertical feed quantity value and frequency. Experiments indicate that ED fine truing based on real-time monitoring can improve the truing precision and efficiency. Average machining efficiency of W10 wheel is about 0.95μm/min； the final run-out by ED truing is less than 2μm. 相似文献
8.
Conversion efficiency of soft X-ray from 0.35 μm pulse laser-irradiated aluminium planar target at laser intensities 1013–1015 W/cm2 on the Xingguang-II facility (laser energy 5–90 J, focal spot ⊃ Ф 200 μm full width of half maximun (FWHM) 400–800 ps) was measured. A simple model was given to explain soft X-ray conversion
efficiency. In this model, because of the heat conduction from the laser-heated spot, the conversion was very small at lower
irradiance limit, while at higher limit it was bounded by the energy lost in blow off plasma. Consequently, at the laser intensity
around 2×1014 W/cm2, the X-ray conversion efficiency reaches a maximum.
Project suppoted by Shanghai Leading Academic Discipline Foundation (Grant No. T0104), and Science Foundation of Shanghai
Municipal Commission of Education (Grant No. 214680) 相似文献
9.
This study proposes a model of syngas production from municipal solid waste （MSW） gasification with air in fixed bed reactors. The model （using Aspen plus simulator） is used to predict the results of MSW gasification and to provide some process fundamentals concerning syngas production from MSW gasification. The effects of gasification temperature, air equiva- lence ratio and moisture concentration on the composition of syngas, lower heating value （LHV） of syngas, heat conversion efficiency, and carbon conversion are discussed. The results indicate that higher temperature improves gasification, and higher air equivalence ratio increases the carbon conversion while decreasing syngas LHV. Heat conversion efficiency increases and reaches the maximum and then decreases with the increase of air equivalence ratio. Higher moisture concentration increases the carbon conversion and increases the heat conversion efficiency at lower ratios. Higher temperature and a lower equivalence ratio are favorable for obtaining a higher LHV of syngas at the same moisture concentration. 相似文献
10.
A high-speed dual-modulus divide-by-32/33 prescaler has been developed using 0.25μm CMOS technology. The source-coupled logic (SCL) structure is used to reduce the switching noise and to ameliorate the power-speed tradeoff. The proposed prescaler can operate at high frequency with a low-power consumption. Based on the 2.5 V, 0.25μm CMOS model, simulation results indicate that the maximum input frequency of the prescaler is up to 3.2 GHz. Running at 2.5 V, the circuit consumes only 4.6 mA at an input frequency 2.5 GHz. 相似文献
11.
A high-speed dual-modulus divide-by-32/33 prescaler has been developed using 0.25 μm CMOS technology. The source-coupled logic (SCL) structure is used to reduce the switching noise and to ameliorate the power-speed tradeoff. The proposed prescaler can operate at high frequency with a low-power consumption. Based on the 2.5 V, 0.25 μm CMOS model, simulation results indicate that the maximum input frequency of the prescaler is up to 3. 2 GHz. Running at 2. 5 V, the circuit consumes only 4.6 mA at an input frequency 2.5 GHz. 相似文献
12.
LIU Zuohu LIU Renlong DU Jun TAO Changyuan LI Xiaohong College of Chemistry & Chemical Engineering Chongqing University Chongqing P. R. China College of Resources & Environmental Science Chongqing University Chongqing P. R. Chin 《重庆大学学报(英文版)》2004,3(1):61-64
1.IntroductionPhenolisanimportantchemicalindustrymaterial,butitalsoaboundswithserioushazardtoenvironmentandthreatstohumanhealth.Rigidruleshavebeenmadeoutonthephenoldischargeconcentration.Researchesonthetreatmentofphenolwastewaterwerecarriedoutinvariouscountries[1-5].Membraneseparationmethodsincludingreverseosmosis,ultrafiltrationandpervaporationhaveattractedmuchattentionforphenolwastewatertreatment,withcelluloseacetate(CA)membraneemployedmostly[6].Membranedistillationisanewmembraneseparation… 相似文献
13.
Amorphous InGaZnO (a-IGZO) film is deposited on the glass substrate by radio-frequency sputtering and the influence of annealing on wet etch of a-IGZO films were investigated.The results show that etch rate of IGZO films decrease with the increase of annealing temperature.Etching taper angle is less than 60 and critical dimension (CD) loss is less than 1 μm in over-etching time of 30 s.The fact implies that IGZO films etching with oxalic acid may be a good wet etching way for the thin-film transistor (TFT) ... 相似文献
14.
提出了一种两阶段多功能光伏逆变器(QMFI),有功功率借助于该结构可以在一个功率转换器内从光伏阵列直接传输到电网或负载,从而提高转换效率。此外,考虑QMFI最大功率点跟踪(MPPT)的实现和非有功电流的补偿,提出了QMFI的数学模型,从而获得有效的控制参数。在求解过程中,采用基于旋转坐标系的分析模型,并推导了QMFI的空间矢量脉冲宽度调制策略,直观地揭示了非有功电流补偿对两阶段有功潮流的影响。最后,通过3 kVA样机验证了所提方案的可行性和有效性。 相似文献
15.
The resonant tunneling diode (RTD) is an ultra-highspeed and ultra-high frequency quantum-transport deviceaccompanied with negative differential resistance (NDR)I-Vcharacteristic originating fromresonant tunneling effect .The core structure of RTDis doubl… 相似文献
16.
王军锋 《陕西教育学院学报》2012,28(1):100-102
以ANS-Brig35为荧光指示剂,研究了流动注射和光导纤维技术测定锰的催化动力学分析方法,线性范围为0.1-1.2μg.ml-1,检测下限为0.01μg.ml-1,对0.14μg.ml-1 Mn(Ⅱ)进行测定的相对标准偏差为0.22%,可以实现对茶叶、铝合金中的痕量锰的直接测定。 相似文献
17.
Determination of theophylline concentration in serum by chemiluminescent immunoassay 总被引：2，自引：0，他引：2
INTRODUCTION Theophylline is one of the antiasthmatic drugs commonly used in a clinic.The individual difference of its bio-availability and the elimination rate in vivo is very large(Vergin et al.,2003).Its valid blood drug level is10~20mg/L,and it has a narrow safety range(Dawson and Whyte,1999;Li et al.,2000).As it is apt to result in the serious side-effect if the blood drug level exceeds20mg/L,monitoring the blood drug level of theophylline is necessary.In many different methods fo… 相似文献
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19.
This paper focused on the removal and transformation of the dissolved organic matter （DOM） in secondary effluent during the granular activated carbon （GAC） treatment. Using XAD-8/XAD-4 resins, DOM was fractionated into five classes： hydrophobic acid （HPO-A）, hydrophobic neutral （HPO-N）, transphilic acid （TPI-A）, transphilic neutral （TPI-N） and hydrophilic fraction （HPI）. Subsequently, the water quality parameters of dissolved organic carbon （DOC）, absorbance of ultraviolet light at 254 nm （UV-254）, specific ultraviolet light absorbance （SUVA） and trihalomethane formation potential （THMFP） were analyzed for the unfractionated and fractionated water samples. The results showed that the order of the DOC removal with respect to DOM fractions was observed to be HPI〉HPO-A〉HPO-N〉TPI-A〉TPI-N. During the GAC treatment, the THMFP of the unfractionated water samples decreased from 397.4 μg/L to 176.5 μg/L, resulting in a removal efficiency of 55.6%. The removal order of the trilaalomethanes （THMs） precursor was as follows： HPO-A〉TPI-A〉TPI-N〉HPO-N〉HPI. By the GAC treatment, the specific THMFP of HPO-A, TPI-A, TPI-N and the original unfractionated water samples had a noticeable decrease, while that of HPO-N and HPI showed a converse trend. The Fourier transform infrared （FTIR） results showed that the hydroxide groups, carboxylic acids, aliphatic C-H were significantly reduced by GAC treatment. 相似文献
20.
研究UV254光照下,Fe(Ⅲ)-EDTA/H2O2对苯酚的催化光降解效能。首先考察反应时间、溶液初始pH值、Fe(Ⅲ)与EDTA的浓度比值对UV/Fe(Ⅲ)-EDTA催化光降解苯酚的影响,进而考察UV/Fe(Ⅲ)-EDTA/H2O2体系对苯酚的降解效能。结果表明:当溶液pH为7,Fe(Ⅲ)/EDTA浓度比值为1:1时,经过1h反应,UV/Fe(Ⅲ)-EDTA体系对苯酚的催化光降解效率达61.13%。在溶液初始pH为37时,UV/Fe(Ⅲ)-EDTA对苯酚的降解率均可达60%以上。在中性条件下,UV/Fe(Ⅲ)-EDTA体系添加H2O2后可把苯酚的降解率从61.13%提高到91.30%。反应前后溶液的紫外扫描光谱表明光降解过程中苯酚的苯环共轭结构被破坏。最后对UV/Fe(Ⅲ)-EDTA/H2O2体系催化光降解机理进行了初步探讨。 相似文献