提高CO传感器抗H2干扰能力的研究

基于单个商品化SnO2传感器,研究如何提高CO传感器抗H2干扰能力.利用多种周期性加热电压对传感器进行温度调制,通过实验对比,优选加热电压参数,在所选电压的调制加热下,获得传感器对CO/H2混合气体的动态响应曲线,利用支持向量机(SVM)估算混合气体中CO的浓度,平均估计误差为10.45%.     

提高CO传感器抗H2干扰能力的研究

基于单个商品化SnO2传感器，研究如何提高CO传感器抗H2干扰能力。利用多种周期性加热电压对传感器进行温度调制，通过实验对比，优选加热电压参数，在所选电压的调制加热下，获得传感器对CO/H2混合气体的动态响应曲线，利用支持向量机（SVM）估算混合气体中CO的浓度，平均估计误差为10.45%。     

基于CO传感器的安全监控装置的研究与设计

系统基于MSP430F2101单片机,采用新型CO气敏传感器,在常温下就能检测到50ppm的该有毒气体;传感器采用周期为30s,幅值为1V的正弦电压加热,提高了其抗H2干扰的能力;采用高度集成的模拟传感器信号处理器MAX1452进行信号调理。系统采用超低功耗器件,价格低廉、灵敏度好、精度高、可扩展性强。     

非链式电激励脉冲HF激光器

介绍了利用紫外预电离和横向放电结构建立的非链式电激励脉冲HF激光装置,对激光工作介质SF6/C2H6混合气体的放电特性以及不同气体总压和气体分数比条件下的激光能量变化进行了研究,并对激光脉冲信号和近场光斑的空间分布进行了实验测量.实验结果表明:混合气体的放电过程具有辉光放电、电压维持和电弧放电的阶段性特点.为获得最佳的激光输出,混合气体中的C2H6含量应控制在6%～8%之间,并且不同混合气体总压对应着不同的最佳充电电压.在充电电压为28kV、总气压为12 kPa、C2H6含量为8%时获得最大单脉冲能量为0.6 J,比能量输出达到8.5 J/l,激光器的电光转换效率约为2.5%.     

基于多波段混合气体吸收谱线的波长标定方法研究

为实现光纤扫描光源宽调谐范围内输出波长的高精度标定,提出了一种基于多波段混合气体吸收谱线的波长标定方法。采用分段阈值二阶导极值法和洛伦兹线型拟合法从混合气体吸收光谱中提取多条谱线中心位置,以其波长和驱动电压为参考点对Fabry-Perot(F-P)可调谐滤波器的迟滞非线性特性进行二次多项式拟合标定。将C2H2在C波段的吸收带与CO2在L波段的吸收带相结合,选取了21条C2H2谱线和16条CO2谱线作为波长参考。将本方法用于C+L波段的光纤光栅(FBG)波长解调,在0~60℃范围内波长拟合标准差小于3.3pm,线性相关系数大于0.999 8,系统稳定性误差小于2.6pm。     

变压器油溶解气的激光光声光谱分析

变压器油中溶解气分析能够预防变压器故障的发生。激光光声光谱检测技术具有灵敏度高、抗干扰能力强等优点,用于变压器油中溶解气分析的前景广阔。本文利用激光光声光谱检测系统,分别对C2H2、CO2及C2H2/CO2混合气体进行了检测,单一气体的检测极限灵敏度分别达到了12 ppb和36 ppm。通过自制高压脉冲发生器模拟变压器放电故障,并利用顶空油气分离装置,对变压器放电故障的特征气体C2H2的产气量进行了测量。     

混合气体成分光声光谱分析的非线性拟合法

采用激光腔内光声光谱技术分析微量气体含量，通过Levenberg-Marquardt拟合方法处理实验数据，有效地消除了混合气体中CO2气体对其他气体浓度检测结果的影响。利用该光谱信仪，分别对摩托车尾气和富士苹果释放的C2H4和CO2气体浓度进行了测量，结果证明了非线性拟合分析方法的有效性。     

小波变换在热电偶测温信号降噪中的应用

借助CO2激光器产生的瞬态高温脉冲信号对热电偶传感器的探头加热来模拟发动机工作过程中产生的瞬态尾焰温度场。对热电偶测得电压信号选用不同的小波基进行降噪处理,探讨不同的分解层数及阈值对小波分析的影响,利用MATLAB软件对信号进行降噪处理。仿真结果表明采用db3小波函数,‘s’软阈值,对信号进行三层分解时的降噪效果最佳。     

用气相色谱法研究封离型TECO2激光器放电产物

本研究工作中用气相色谱法分析了封离型TE CO2激光器放电引起激光器混合气体变质的问题,即便在含有大量N2的情况下,这种方法也能使我们精确地测定出CO的浓度.根据2CO22CO+O2这一可逆分解反应,系统中的[CO]/2[O2]比率应为1,但是我们发现它却明显地大于1,其氧浓度偏离平衡CO2分解方程所要求值的26%以上.并没有检测到氮的氧化物,当把变了质的混合气体加热至臭氧分解温度时失去的氧又得到恢复.     

基于波长调制光谱技术的二氧化碳浓度测量

以可调谐激光二极管吸收光谱技术为基础,结合波长调制光谱技术,对不同体积浓度的二氧化碳气体进行检测。分别分析正弦波调制信号的不同调制电压及调制频率对二次谐波信号波形及峰值的影响。结果显示当调制电压为0.25 V、调制频率为10 kHz时,得到的二次谐波信号较好。在此基础上,利用实验室中搭建的单光路测量系统对不同浓度的CO2气体进行检测,得到气体浓度与二次谐波峰值线性相关系数为0.998,系统的检测极限为450 ppm。研究为该类系统调制系数的选择提供了实验依据,为工业应用打下了基础。     

单脉冲激光诱导乙烯-氧爆燃反应的研究

本文研究以单脉冲TEACO_2激光诱导乙烯-氧爆燃反应,测定了激光频率、反应气体总压力、C_2H_2和O_2的比例以及金属Pt-Rh及电解银表面对引爆功率阈值的影响.并以红外光谱分析了反应产物.发现当激光选频为00~0～10~10的P(14)支线时,所需的引爆阈值最小.当存在金属表面时阈值明显降低.反应主要产物为C_2H_2、CO、CO_2、H_2O,它们的相对含量与反应气体的总压及氧的相对含量有关.     

Measuring trace gases in plumes from hyperspectral remotely sensed data

A method [joint reflectance and gas estimator (JRGE)] is developed to estimate a set of atmospheric gas concentrations in an unknown surface reflectance context from hyperspectral images. It is applicable for clear atmospheres without any aerosol in a spectral range between approximately 800 and 2500 nm. Standard gas by gas methods yield a 6% rms error in H/sub 2/O retrieval from Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data, reaching several tens percent for a set of widespread ground materials and resulting from an simplifying assumption of linear variations of the reflectance model within gas absorption bands and partial accounting of the gas induced signal. JRGE offers a theoretical framework consisting in a two steps algorithm that accounts for sensor characteristics, assumptions on gas concentrations and reflectance variations. It estimates variations in gas concentrations relatively to a standard atmosphere model. An adaptive cubic smoothing spline like estimation of the reflectance is first performed. Concentrations of several gaseous species are then simultaneously retrieved using a nonlinear procedure based on radiative transfer calculations. Applied to AVIRIS spectra simulated from reflectance databases and sensor characteristics, JRGE reduces the errors in H/sub 2/O retrieval to 2.87%. For an AVIRIS image acquired over the Quinault prescribed fire, far field CO/sub 2/ estimate (348 ppm, about 6% to 7% rms) is in agreement with in situ measurement (345-350 ppm) and aerosols yield an underestimation of total atmospheric CO/sub 2/ content equal to 5.35% about 2 km downwind the fire. JRGE smoothes and interpolates the reflectance for gas estimation but also provides nonsmoothed reflectance spectra. JRGE is shown to preserve various mineral absorption features included in the AVIRIS image of Cuprite Mining District test site.     

Current conduction mechanism and gas adsorption effects on deviceparameters of the Pt/SnOx/diamond gas sensor

This paper presents the results from analysis and modeling of the gas sensing performance, current conduction and gas detection mechanisms, and adsorption effects on device parameters of a Pt/SnO_x/diamond-based gas sensor. The sensor is sensitive and demonstrates high, repeatable, and reproducible reaction. The sensor response in seconds to small concentrations of O₂, CO, and H ₂ gases. The current conduction mechanism of the diamond-based CAIS (catalyst/adsorptive-oxide/intrinsic-diamond/semiconductor-diamond) diode was found to be dominated by space charge limited conduction in the forward bias region and tunneling in the reverse bias region, distinctively different from silicon based sensors. While gas adsorption causes a change in the barrier height and tunneling factor, no significant change was observed in the ideality factor over the temperature range investigated. The detection mechanism of the sensor is attributable to the change in occupancy ratio of the oxygen vacancies of the adsorptive oxide layer upon oxygen exposure, increasing the contact potential between adsorptive-oxide and intrinsic-diamond     

A new Pd-oxide-Al/sub 0.3/Ga/sub 0.7/As MOS hydrogen sensor

A new and interesting Pd-oxide-Al/sub 0.3/Ga/sub 0.7/As MOS hydrogen sensor has been fabricated and studied. The steady-state and transient responses with different hydrogen concentrations has been measured at various temperatures. Based on the large Schottky barrier height and presence of oxide layer, the studied device exhibits a high hydrogen detection sensitivity and wide temperature operating regime. The studied device exhibits the low-leakage current and obvious current changes when exposed to hydrogen-contained gas. Even at room temperature, a very high hydrogen detection sensitivity of 155.9 is obtained when a 9090 ppm H/sub 2//air gas is introduced. Furthermore, when exposed to hydrogen-contained gas at 95/spl deg/C, both the forward and reverse currents are substantially increased with increased hydrogen concentration. In other words, the studied device can be used as a hydrogen sensor under the applied bidirectional bias. Under the applied voltage of 0.35 V and 9090 ppm H/sub 2//air hydrogen ambient, a fast adsorption response time about 10 s is found. The transient and steady-state characteristics of hydrogen adsorption are also investigated.     

Experimental and theoretical study of noncooled CO laser with short pulse pumping

This paper describes experiments and theory relating to CO laser action in various CO mixtures with N2and/or He. Short-pulse electron beam excitation of1-2 mus produced laser output between 1600 and 1900 cm^-1; the most intense line was at 1788.4 cm^-1and the shortest pulses of 4 μs duration were generated in the CO:He mixture. Although the calculated maximum efficiency was 7 percent, the maximum measured efficiency was 3 percent.     

聚噻吩/WO_3复合纳米材料的制备及气敏性能

采用水合肼法制备WO3粉体,再以无水FeCl3作氧化剂,通过原位化学氧化聚合制备了不同聚噻吩(PTh)掺杂量的PTh/WO3复合纳米材料。并研究了用其制备的气敏元件的气敏性能。结果表明:气敏元件对H2S和NOx有较高的灵敏度和较好的选择性。用质量分数w(PTh)为5%的PTh/WO3复合纳米材料制备的气敏元件,在加热电压为2.25V时,对体积分数φ(NOx)为5×10–6的灵敏度可达77.14;用w(PTh)为20%的PTh/WO3复合纳米材料所制之气敏元件,在加热电压为2.43V时,对φ(H2S)为20×10–6的灵敏度达63.27。     

自加热气敏电阻振荡周期的分析

ＳｎＯ２气敏电阻在含ＣＯ空气中的振荡机理，给出了气敏电阻在含ＣＯ空气中的热学方程式，获得了振荡周期τ的近似表达式，气敏电阻起振的必要条件及振荡周期τ与ＣＯ气体浓度Ｎ、工作电压Ｖ的关系。     

固相法制备ZnO纳米粉及其气敏性能研究

以六水合硝酸锌和碳酸氢铵为原料,采用室温固相法制备前驱体碱式碳酸锌,然后在马弗炉中于600℃煅烧,得到ZnO纳米粉体。用XRD,TEM对其形貌、结构进行了表征。结果表明:所制备的ZnO结晶良好,其粒径为20~50 nm。用其制成气敏元件,并用静态配气法测试其气敏性能,发现在工作温度为290℃左右,该气敏元件对体积分数为0.001%的Cl2的灵敏度高达288。