anling Hu

Retrieving aerosol backscattering coefficient for short range lidar using parameter selection at reference point

A new method is proposed based on the analysis of lidar equation which selects aerosol backscatter ratio at a reference point for short range lidar in data processing. Simulation computation and experimental comparison results show that this method is reasonable and feasible. The method is applied to short range lidars, such as atmospheric monitoring lidar-2 (AML-2) and micro-pulse lidar (MPL).

Measurement of tropospheric CO2 and aerosol extinction profiles with Raman lidar

A prototype Raman lidar was designed for monitoring tropospheric CO2 profile and other scientific investigations. The third harmonic of Nd:YAG laser (354.7-nm wavelength) was used as stimulated light source to provide nighttime measurements. Filter with high rejection ratio performance was used to extract CO2 Raman signals from Rayleigh-Mie scattering signals effectively. To improve the real time monitoring function, a two-channel signal collection system was designed to collect CO2 and N2 Raman scattering signals simultaneously. The N2 Raman scattering signals were used to retrieve aerosol extinction coefficient. Typical features of CO2 concentration profile and aerosol extinction coefficient in Hefei were presented. The mixing ratio of atmospheric CO2 in Hefei can reach about 360-400 ppmv.

Lidar measurements of stratospheric aerosol over Hefei, China during 1991-1996

The violent eruption of Philippine volcano Pinatubo in mid June of 1991 caused a serious perturbation on the stratospheric aerosols for a long period. In the paper, we report L625 lidar observational results in the period of 1991 - 1996, including evolution of volcano Pinatubo cloud. The time variation and vertical distribution of the volcanic cloud height, thickness, peak-scattering ratio, and integrated backscattering coefficients will be analyzed. L625 lidar measurement data of stratospheric aerosol reveal the characteristics of background period before the volcanic eruption, the evolution of the Pinatubo volcanic cloud, and present new background level.

A mobile lidar system for air pollution measurement

A differential absorption mobile lidar system for pollution monitoring for daytime and nighttime operation is described. It allows 3Dmeasurements by using a steering unit, and can measure four kinds of pollutants in atmosphere, Aerosol, so2, NO2, and 03. The lower detection limit ofthe SO2, NO2, 03, is a few ppb. The max. measurement range is about 3 —5 km. This system was developed at the Anhui Institute of Optics and Fine Mechanics, the Academy of Sciences of China. A few examples ofmeasured 03, SO2 , NO2, and aerosols distributions are presented. Keywords: Mobile lidar, differential absorption lidar, aerosols, 502, NO2, 03.

Electrochemical behavior of phenylalanine and its cobalt complex as corrosion inhibitors for mild steel in H2SO4

Corrosion inhibition of phenylalanine (phe) and its its cobalt complex(Co-phe) were evaluated using electrochemical polarization and electrochemical impedance spectroscopy (EIS) for mild steel in 0.1 M H2SO4 solution. The results indicate that the compounds inhibit the corrosion of mild steel in H2SO4 solutions and the extent of inhibition increases with inhibitor concentration and decreases with temperature. The order of inhibition efficiency obtained was Co-phe > phe. The adsorption characteristics of the inhibitor were approximated by Langmuir isotherm. Morphological study of the carbon steel electrode surface was undertaken by scanning electron microscope (SEM).

Failure Analysis of a Reboiler in the Waste Water Stripping Tower of a Petrochemical Plant

A severe leak occurred on the heat-exchanger tubes of a reboiler after approximately 9-month operation in the waste water stripping tower of a petrochemical plant. Failure analyses were carried out through the morphology observation and the chemical composition analysis of the corrosion products and water sample with optical microscopy, scanning electron microscopy, and X-ray diffraction techniques. The results reveal that the main compositions of the corrosion products are iron oxide, small amount of iron hydroxide, and iron silicate. Moreover, wall thinning and perforation obviously originated from the outer surface of the tube. Chloride ions play a catalysis role in accelerating the electrochemical corrosion. Some suggestions are proposed to alleviate and prevent the corrosion.

Convenient method for calibrating system constant of scanning water vapor Raman lidar

Lower tropospheric water vapor measurements are performed at nighttime using the mobile atmosphere monitoring lidar-2 (AML-2) which is operated by the Anhui Institute of Optics and Fine Mechanics. In this lidar system, a 354.7-nm light from a Nd:YAG laser is used as stimulating source, whose Raman shifted center wavelengths are at 386.7 and 407.5 nm for nitrogen and water vapor, respectively. We present a novel and convenient method for determining the Raman lidar calibration constant according to the scanning performance of this lidar. We are likewise able to realize the measurement of water vapor profile in the low troposphere. The error induced by the uncertainty of calibrated constants is within 7% for the Raman lidar system. Experimental results from two months of study indicate that the method of calibrating the lidar system constant is feasible, and the Raman lidar performance is stable and reliable.

Generation of UV laser by Raman shifters in D2 and D2/He pumped by the fourth harmonic Nd:YAG laser for SO2 measurements

The fourth harmonic (266nm) of a pulsed Nd: YAG laser is used to pump Raman cells filled with D2 and D2/He. The dependences of the energy conversion efficiency of stimulated Raman scattering radiations upon the system parameters such as the pump energy pressure of pure D2 and partial pressure of He in D2/He mixture were experimentally studied. The maximum energy conversion efficiency of the first Stokes radiation (S1, 289.O4nm) reaches 22.1% in D2/He. The conditions to improve the energy conversion efficiency of Si were found. The results have been used to optimize the laser transmitter system for a S02 differential absorption lidar (S02-DIAL).

Study of the first Stokes line of Raman cell full of CH4, H2, D2 and their mixture with Ar,He gases

Raman frequency shifter is a useful method extending laser wavelength the first Stokes of CH4, H2, and D2 pumped by the fourth harmonic of Nd:YAG laser can be used in DIAL measurement of the trace gases. The stability and energy of SRS are related to focal length of lens active gas pressure input energy buffer gas elements and pressure. We detect the stability and energy of the first Stokes line under pure active and mixture with Ar or He. From our experiment the stability of pure CH4, H2 are almost same under different pressure however the stability of pure D2 changes with pressure. The energy conversion efficiency on Si is different among pure gas (CH4, H2, D2). Furthermore the optimal output energy of the first Stokes line of CH4, H2, D2 are got independently at moderate active gas pressure mixing with moderate buffer pressure.

Mobile lidar for measurements of SO2 and O3 in the low troposphere

A new applied differential absorption lidar system for measurement of SO2 and O3 in the lower troposphere is developed. The emission wavelengths 289.04, 288.38 and 299.05 nm are obtained by stimulated Raman shifting of a Nd:YAG laser. The concentrations of SO2 and O3 have been measured quasi-simultaneously by use of the three wavelengths for compensating measurement results each other. The lidar measurements agree with in situ measurements. The measurement errors, which are primarily attributable to statistical error and variations in atmospheric backscattering intensity during the experiment, are discussed.