不同掺杂浓度光纤拉曼增益特性的研究

研究了受激拉曼散射增益系数和增益谱与泵浦功率、光纤掺杂浓度的关系,得出增益系数和峰值频移量由光纤特性决定,而与泵浦功率无关的结论。在对二氧化硅分子建模计算后,进一步利用LM算法对光纤的拉曼增益谱进行高斯分解。分解图谱表明掺杂物破坏了二氧化硅的分子结构,并在拉曼增益范围内产生了新的峰值,从理论上证明了光纤掺杂物对拉曼增益系数和增益谱的影响。     

孔末端效应对微孔包装内气体动态平衡的影响

设计、组装了一套简易的微孔包装。以CO2 为实验气体,理论上分析了微孔包装内CO2 气体浓度的动态变化规律,同时测定了微孔包装内CO2 气体浓度的动态变化数据。研究结果表明,微孔包装内实际测定的CO2气体浓度远高于理论值。采用孔末端效应对此差异进行了分析,并提出了孔有效长度矫正公式def =d+7r / 6。     

拉曼光谱测定变压器油中溶解气体的浓度

提出一种通过监测变压器油中熔解甲烷，乙炔气体特征拉曼散射谱峰处的拉曼散射信号强度，以实现变压器中溶解甲烷，乙炔气体浓度在线测量的新方法。     

二氧化碳在温室蔬菜栽培中如何应用

光合作用是植物吸收太阳光能,并将水利空气中的CO2气体合成有机物质的过程。在温室中,CO2气体是蔬菜进行光合作用、形成产量必不可少的原料。它的浓度大小直接影响产量的高低、品质的好坏。在冬春季节北方温室相对密闭栽培环境中。空气不流通,叫片光合作用消耗CO2,使温室内CO2浓度降低,光合作用减弱,抑制植物生长发育。     

煤自然发火指标气体与临界氧气浓度的确定

利用煤自然发火气体产物分析模拟试验装置测定煤样在不同温度条件下释放出的烃类指标气体，对测定结果进行分析得到煤自燃程度指标气体体系：在不同氧气浓度下测得CO、C2H4、C3H6发生的浓度和产生速率，确定煤自然发火临界氧气浓度为10％。     

CO2的浓度含量对超声波气体流量计的精度影响

文章设计了实验用以测试CO2的浓度含量对超声波气体流量计测量精度的影响，实验结果表明，由于在流量计中采用了“过零电平检测”、“随机多次测量声时后平均”等技术措施，即使在CO2的浓度较高的情况下，流量计依然可以保持在较高的测量精度。     

煤自燃注惰灭火降温特征的实验研究

实验以木城涧无烟煤为研究对象,使用CO2和N2作为注惰防灭火气体,开展注惰灭火降温过程的实验研究。实验设置空白对照组和实验组,在实验炉内对升温后的煤样进行注惰,最后对降温过程中的温度和气体参数进行分析。实验结果阐明:在降温程序中,煤样降温效果与N2浓度成正相关,且N2高于30%后降温效果显著;另一方面,相同浓度的CO2降温效果优于N2,10%CO2实验组抑制降温过程CO产生效果远优于N2——即相同浓度下的CO2防灭火效果要好于N2。     

小球藻光生物反应器脱除空气中二氧化碳的研究

采用自制的光生物反应器,研究了不同条件对小球藻脱除空气中CO2效果的影响.光生物反应器为圆柱形有机玻璃容器,底面积0.0154m2,高0.2m,容积为3L,反应器内小球藻藻体干重约为7.2g.实验结果表明,用小球藻来固定CO2不仅能脱除通入气体中的CO2,而且可以促进小球藻生长.通入气体的流量和CO2浓度对CO2的脱除率有很大影响.在适宜的实验条件下(通入气体流速为0.6L/min、CO2浓度约1%、温度25~30℃、光强3500lux、pH9.5~8.5),入口气体中CO2约有50%被脱除,该光生物反应器脱除CO2的能力约为0.118g/(L.h).可见利用小球藻光生物反应器固定CO2具有较好的脱除效果,值得进一步研究.     

运用自组织竞争网络进行气体定性分析的研究

优选了分析H2,CO气体的半导体气体传感器组成阵列，建立了实时数据采集系统，并与自组织竞争网络模式识别技术相结合，以进行气体定性分析的研究；同时为了消除气体浓度变化对传感器阵列输出的影响，提高自组织网络的识别效果，运用三种不同的数据归一化算法对传感器阵列的输出响应进行了预处理, 并对各自对应的网络识别结果进行了分析与讨论。实验结果表明，采用相对算法可实现H2,CO气体的准确识别。     

羊毛角蛋白膜的制备及其气体分离性能的研究

研究了羊毛角蛋白膜的制备及其气体分离性能．以角蛋白膜的CO2渗透速率和CO2相对于CH4的分离系数为指标，考察了制膜液中溶剂氨水的浓度、巯基乙酸和戊二醛的加入量对角蛋白膜的气体透过和分离性能的影响．     

Monitoring O3 with solar-blind Raman lidars

The benefits of retrieving ozone concentration profiles by a use of a single Raman signal rather than the Raman differential absorption lidar (DIAL) technique are investigated by numerical simulations applied either to KrF- (248 nm) or to quadrupled Nd:YAG- (266 nm) based Raman lidars, which are used for both daytime and nighttime monitoring of the tropospheric water-vapor mixing ratio. It is demonstrated that ozone concentration profiles of adequate accuracy and spatial and temporal resolution can be retrieved under low aerosol loading by a single Raman lidar because of the large value of the ozone absorption cross section both at 248 nm and at 266 nm. Then experimental measurements of Raman signals provided by the KrF-based lidar operating at the University of Lecce (40 degrees 20'N, 18 degrees 6'E) are used to retrieve ozone concentration profiles by use of the Raman DIAL technique and the nitrogen Raman signal.     

Feasibility of nonlinear Raman lidar based on stimulated Raman gain spectroscopy without a tunable laser

A novel technique of lidar for atmospheric gas detection by use of stimulated Raman gain spectroscopy without any tunable laser is proposed. Detection sensitivity and detectable range are estimated on the basis of the lidar equation for CO2, CH4, and H2 in the atmosphere. The feasibility study clearly shows that the technique has a potential for application to lidar and that, in addition, the construction of the system is simpler than those of traditional differential absorption lidars.     

Notes on Rayleigh scattering in lidar signals

Classical and quantum formulations are used to estimate Rayleigh scattering within lidar signals. Within the classical approach, three scenarios are used to characterize atmospheric molecular composition: 2-component atmosphere (N2 and O2), 4-component atmosphere (N2, O2, Ar, and CO2), and 5-component atmosphere (N2, O2, Ar, CO2, and water vapor). First, analysis focuses on Rayleigh scattering, showing the relative difference between the three scenarios within classical approach. The relative difference in molecular scattering between 2(4)-component atmosphere and 5-component atmosphere is below ~1%. The second analysis focuses on the lidar retrieval of aerosol backscatter and extinction coefficients showing the effect of different molecular formulations. A relative difference of ±3% was found between the molecular formulation of 2-component atmosphere and the molecular formulation of 5-component atmosphere. Consideration of the Raman rotational lines blocked by the interference filter is important for the elastic channels, but of little significance in the N2 Raman channel. For lidar retrieval of aerosol profiles, the 5-component approximation is the best when the water vapor profile is known, but 2-component is still adequate and quite accurate when water vapor is only poorly known.     

Lidar technique for remote measurement of temperature by use of vibrational-rotational Raman spectroscopy

Atmospheric temperature can be measured remotely by a lidar system that measures the ratio of backscattered signals from vibrational-rotational Raman scattering by N(2) to pure vibrational Raman scattering. We present simulations of the performance of an airborne lidar system (based on the Goddard Airborne Raman lidar) that employs this technique.     

Aerosol lidar intercomparison in the framework of the EARLINET project. 3. Raman lidar algorithm for aerosol extinction, backscatter, and lidar ratio

An intercomparison of the algorithms used to retrieve aerosol extinction and backscatter starting from Raman lidar signals has been performed by 11 groups of lidar scientists involved in the European Aerosol Research Lidar Network (EARLINET). This intercomparison is part of an extended quality assurance program performed on aerosol lidars in the EARLINET. Lidar instruments and aerosol backscatter algorithms were tested separately. The Raman lidar algorithms were tested by use of synthetic lidar data, simulated at 355, 532, 386, and 607 nm, with realistic experimental and atmospheric conditions taken into account. The intercomparison demonstrates that the data-handling procedures used by all the lidar groups provide satisfactory results. Extinction profiles show mean deviations from the correct solution within 10% in the planetary boundary layer (PBL), and backscatter profiles, retrieved by use of algorithms based on the combined Raman elastic-backscatter lidar technique, show mean deviations from solutions within 20% up to 2 km. The intercomparison was also carried out for the lidar ratio and produced profiles that show a mean deviation from the solution within 20% in the PBL. The mean value of this parameter was also calculated within a lofted aerosol layer at higher altitudes that is representative of typical layers related to special events such as Saharan dust outbreaks, forest fires, and volcanic eruptions. Here deviations were within 15%.     

Backscattering measurements of atmospheric aerosols at CO2 laser wavelengths: implications of aerosol spectral structure on differential-absorption lidar retrievals of molecular species

The volume backscattering coefficients of atmospheric aerosol were measured with a tunable CO2 lidar system at various wavelengths in Utah (a desert environment) along a horizontal path a few meters above the ground. In deducing the aerosol backscattering, a deconvolution (to remove the smearing effect of the long CO2 lidar pulse and the lidar limited bandwidth) and a constrained-slope method were employed. The spectral shape beta(lambda) was similar for all the 13 measurements during a 3-day period. A mean aerosol backscattering-wavelength dependence beta(lambda) was computed from the measurements and used to estimate the error Delta(CL) (concentration-path-length product) in differential-absorption lidar measurements for various gases caused by the systematic aerosol differential backscattering and the error that is due to fluctuations in the aerosol backscattering. The water-vapor concentration-path-length product CL and the average concentration C = /L for a path length L computed from the range-resolved lidar measurements is consistently in good agreement with the water-vapor concentration measured by a meteorological station. However, I was unable to deduce, reliably, the range-resolved water-vapor concentration C(r), which is the derivative of the range-dependent product CL, because of the effect of residual noise caused mainly by errors in the deconvolved lidar measurements.     

Simultaneous estimation of aerosol cloud concentration and spectral backscatter from multiple-wavelength lidar data

We present a sequential algorithm for estimating both concentration dependence on range and time and backscatter coefficient spectral dependence of optically thin localized atmospheric aerosols using data from rapidly tuned lidar. The range dependence of the aerosol is modeled as an expansion of the concentration in an orthonormal basis set whose coefficients carry the time dependence. Two estimators are run in parallel: a Kalman filter for the concentration range and time dependence and a maximum-likelihood estimator for the aerosol backscatter wavelength and time dependence. These two estimators exchange information continuously over the data-processing stream. The state model parameters of the Kalman filter are also estimated sequentially together with the concentration and backscatter. Lidar data collected prior to the aerosol release are used to estimate the ambient lidar return. The approach is illustrated on atmospheric backscatter long-wave infrared (CO2) lidar data.     

Refractive-index structure parameter in the planetary boundary layer: comparison of measurements taken with a 10.6-microm coherent lidar, a 0.9-microm scintillometer, and in situ sensors

An optical technique is described that determines the path-averaged value of a refractive-index structure parameter at 10.6 mum by use of a pulsed coherent CO(2) lidar in direct detection and hard-target returns. The lidar measurements are compared with measurements taken by a 0.9-mum scintillometer and temperature probe (with humidity corrections). The experimental results show good agreement for C(n)(2) >/= (-14) m(-2/3). With respect to practical applications the new technique permits C(n)(2) lidar measurements in a neutral meteorological situation to an unstably stratified convective boundary layer over long ranges (1 km or more).     

Two-micrometer heterodyne differential absorption lidar measurements of the atmospheric CO2 mixing ratio in the boundary layer

A 2 microm heterodyne differential absorption lidar (HDIAL) has been operated at the Inst?tut Pierre Simon Laplace, Laboratoire de Météorologie Dynamique (Paris) to monitor the CO(2) mixing ratio in absolute value at high accuracy in the atmospheric boundary layer. Horizontal measurements at increasing range are made to retrieve the optical depth. The experimental setup takes advantage of a heterodyne lidar developed for wind velocity measurements. A control unit based on a photoacoustic cell filled with CO(2) is tested to correct afterward for ON-line frequency drift. The HDIAL results are validated using in situ routine measurements. The Doppler capability is used to follow the change in wind direction in the Paris suburbs.     

Side-line tunable laser transmitter for differential absorption lidar measurements of CO2: design and application to atmospheric measurements

A 2 microm wavelength, 90 mJ, 5 Hz pulsed Ho laser is described with wavelength control to precisely tune and lock the wavelength at a desired offset up to 2.9 GHz from the center of a CO(2) absorption line. Once detuned from the line center the laser wavelength is actively locked to keep the wavelength within 1.9 MHz standard deviation about the setpoint. This wavelength control allows optimization of the optical depth for a differential absorption lidar (DIAL) measuring atmospheric CO(2) concentrations. The laser transmitter has been coupled with a coherent heterodyne receiver for measurements of CO(2) concentration using aerosol backscatter; wind and aerosols are also measured with the same lidar and provide useful additional information on atmospheric structure. Range-resolved CO(2) measurements were made with <2.4% standard deviation using 500 m range bins and 6.7 min? (1000 pulse pairs) integration time. Measurement of a horizontal column showed a precision of the CO(2) concentration to <0.7% standard deviation using a 30 min? (4500 pulse pairs) integration time, and comparison with a collocated in situ sensor showed the DIAL to measure the same trend of a diurnal variation and to detect shorter time scale CO(2) perturbations. For vertical column measurements the lidar was setup at the WLEF tall tower site in Wisconsin to provide meteorological profiles and to compare the DIAL measurements with the in situ sensors distributed on the tower up to 396 m height. Assuming the DIAL column measurement extending from 153 m altitude to 1353 m altitude should agree with the tower in situ sensor at 396 m altitude, there was a 7.9 ppm rms difference between the DIAL and the in situ sensor using a 30 min? rolling average on the DIAL measurement.