Biomedical subjects

Wen-qing Liu

Publications and source records attributed to Wen-qing Liu.

12 recordsLinked to original sources

PubMed2006

[Passive FTIR remote sensing of gaseous pollutant in heated plume].

The principle and techniques of passive remote sensing of gaseous pollutant in heated plume was illustrated and discussed in this paper. The algorithm of radiance spectra and transmittance spectra in measured region was proposed, and the method of retrieving gas concentrations with NLLS fitting algorithm was also proposed. The remote senseing of actual gaseous pollutant of smokestack was done, and the quantitative analysis of SO2 and CO2 was completed.

English Abstract↗

PubMed2006

[Concentration calibration method of ambient trace-gas monitoring with tunable diode laser absorption spectroscopy].

Tunable diode laser absorption spectroscopy (TDLAS) is a new method to detect trace-gas qualitatively or quantificationally based on the scan characteristic of the diode laser used to obtain the absorption spectroscopy in the characteristic absorption region It needs to be combined with a long absorption path in the ambient trace-gas measurements. TDLAS is a new trace gas detective method developed with the combination of a tunable diode laser source and a long absorption path; it has significant advantages not only in the sensitivity but also in rapidity of response. It has been widely used in many atmospheric trace-gases detection, ground trace-gas detection and, gas leakage detection. On-line calibrating is necessary to most trace gas monitor, and in the present paper the authors introduced a simple and accurate method, analyzed it in the theory, and proved it's feasibility in the experiment.

English Abstract↗

PubMed2006

[Error analysis and calibration method of complex spectrum of Fourier transform infrared spectrometer].

The phase shift in complex spectrum of Fourier transform infrared (FTIR) spectrometer was discussed. A rigorous derivation showed the relation between the phase shift and complex spectrum. The reason for the radiation offset in FTIR measurement was analysed. The present article presents a calibration method of FTIR complex spectrum, which can adjust the radiation offset. The comparison between experiment data and theoretical computation showed that the method is precise.

English Abstract↗

PubMed2006

[The fluorescence emission of water at upconversion of frequency by laser induced fluorescence].

The fluorescence spectra of several types of water samples in combination with laser-induced fluorescence (LIF) measurements using 532 nm wavelength excitation source were measured in the laboratory, and the fluorescence matters such as dissolved organic matter (DOM), chlorophyll a (Chl a) and carotenoids were pointed out with spectral fluorescent signature (SFS) technique. It is considered that the peak at 455 nm in the spectrum is contributed by carotenoid (PPC). Finally, the dynamic model of PPC's fluorescence emission is showed.

English Abstract↗

PubMed2006

[The study of infrared background radiation of earth and atmosphere by airborne FTIR spectrometer].

The present article describes the experiment of airborne Fourier transform infrared (FTIR) spectrometer detecting the background radiation of earth and atmosphere. Considering the surface radiation and atmospheric absorbance and emission, the expression of radiations measured by airborne FTIR is given. It is indicated that the background radiations depend on four parameters: surface temperature, surface emissivity, atmospheric transmission and temperature. Based on theoretic analysis the measured spectra are compared and analyzed according to the differences in altitude and surface. Spectral characters of infrared background radiation are described.

English Abstract↗

PubMed2006

[The influence of temperature change on determined concentrations of dissolved organic matter in water].

The influence of temperature change on the determined concentrations of dissolved organic matter (DOM) in water was investigated by laser induced fluorescence (LIF) technique in laboratory. The temperature was altered within the range of 20 to 75 degrees C, and the intensity of DOM fluorescence and water Raman scattering were found to decrease with rising temperature. A linear fit of the normalized fluorescence intensity versus temperature yielded a mean value of the temperature coefficient of -5.24 x 10(-4) x degrees C(-1), and a mean value of the temperature coefficient of -3.42 x 10(-3)(mg x L(-1)) x degrees C(-1) was obtained according to the relationship between normalized fluorescence intensity and concentration of DOM. The temperature change will cause relative changes of up to 8.45% in DOM concentration within the range of 20 to 75 degrees C if we assume that the normalized fluorescence intensity remains the same.

English Abstract↗

PubMed2006

[Determination of the error of aerosol extinction coefficient measured by DOAS].

The method of defining the error of aerosol extinction coefficient measured by differential optical absorption spectroscopy (DOAS) is described. Some factors which could bring errors to result, such as variation of source, integral time, atmospheric turbulence, calibration of system parameter, displacement of system, and back scattering of particles, are analyzed. The error of aerosol extinction coefficient, 0.03 km(-1), is determined by theoretical analysis and practical measurement.

English Abstract↗

PubMed2005

[Passive remote sensing of VOC in atmosphere by FTIR spectrometry].

The paper expatiates the passive remote sensing experiment of VOC in atmosphere by FTIR spectrometry, a mode of simulated spectra for pollution gas in a complicated environment is proposed, and the detecting limit of passive FTIR remote sensing is discussed. Using this measurement technique and the data analysis method, the authors can obtain column density and effective radiation temperature of target-gas that does not require a previously measured background spectrum.

Air Pollutants↗

PubMed2005

[Study on characteristics of fluorescence spectra of dissolved organic matter with different water quality].

The fluorescence spectra of dissolved organic matter (DOM) in several types of water samples in combination with laser-induced fluorescence (LIF) measurements were measured in the laboratory, and the spectral characteristics of DOM were analysed. The curve of normalized fluorescence intensity against corresponding concentration of humic acid is showed. The results demonstrate the possibilities of water quality monitoring based upon fluorescence spectral characteristics of DOM by means of LIF method.

Fluorescence↗

PubMed2005

[Study the characteristics of dissolved organic matter and turbidity of water using laser induced fluorescence and laser scattering].

In the experiment a frequency doubled radiation of Nd:YAG laser was used for excitation at 532 nm. The fluorescence spectra of dissolved organic matter (DOM) and chlorophyll a (Chl-a) in several types of water samples with laser-induced fluorescence (LIF) measurements using a 532 nm wavelength excitation source were measured in the laboratory, and the spectral characteristics of DOM and Chl-a were analysed. The characteristics of turbidity were investigated by measuring the amount of scattering light of suspended particles in the water volume. The curve of scattering intensity against corresponding turbidity of SiO2 is showed. The possibilities of water quality monitoring based upon the fluorescence spectral characteristics of contaminations and the turbidity by means of LIF method.

Environmental Monitoring↗

PubMed2005

[Study on UV-visible DOAS system based on photodiode array (PDA)].

A long-path differential optical absorption spectroscopy (DOAS) system is introduced. A photodiode array is employed as the detector to replace the complicated SD detector which consists of a PMT and a slotted disk. The properties of the detector and the spectrometer unit such as offset, dark current, noise, linearity, resolution, and wavelength range were measured. This system was also tested to measure SO2 and NO2 in the atmosphere. The detection limits of this system for SO2, and NO2 over a 713 m light path were determined.

Algorithms↗

PubMed2005

[Application of FTIR spectra fitting method in retrieving gas concentrations].

The method of retrieving gas concentrations by FTIR spectra measurement system is studied. NLLS fitting algorithm is used to complete the quantitative analysis of CO gas under WINDOWS operating system. The spectra of HITRAN database is employed as calibrating and training sets during the procedure of fitting FTIR spectrum. The measured IR transmittance spectra of CO are best fitted with the calculated spectra in HITRAN. The CO concentrations are acquired after the best fitting. The absolute accuracy of the results of retrieve achieves 1%-5%.

English Abstract↗