CHEN , Weidong

The hydroxyl (OH) free radical plays an important role in atmospheric chemistry due to its high reactivity with volatile organic compounds (VOCs) and trace species (CH4, CO, SO2, etc) [1]. Due to its very short lifetime (~1 s or less) and very low concentration in the atmosphere (in the order of 106 cm-3), in situ and direct measurement of OH...

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Nitrous acid (HONO) is one of the important atmospheric trace gases due to its contribution to the cycles of nitrogen oxides (NOx) and hydrogen oxides (HOx). In particular it acts as a precursor of tropospheric OH radicals, which is responsible for the self-cleansing capacity of the atmosphere [1,2]. We developed an instrument based on...

A hollow waveguide (HWG) based mid-infrared gas sensor using a 2.73 µm distributed feedback (DFB) laser was developed for simultaneously measuring the concentration changes of the three isotopologues 13 CO 2 , 12 CO 2 , and 18 OC 16 O in exhaled breath by direct absorption spectroscopy, and then determining the 13 CO 2 / 12 CO 2 isotope ratio...

Heterodyne phase-sensitive dispersion spectrometer (HPSDS) retrieves the concentration of gas samples by measuring the refractive index fluctuations near the molecular resonance. Compared to previous HPSDS studies focusing on pure intensity modulation, it is attractive to investigate the performance of HPSDS sensor based on a distributed...

Our research is focused on the development of an at-home health care biomonitoringmobile robot for the people in demand. Main task of the robot is to detect and track a designated subject while recognizing his/her activity for analysis and to provide warning in an emergency. In order to push forward the system towards its real application, in...

We report a new spectroscopic platform coupled to an atmospheric simulation chamber for the direct determination of chemical rate constants with high accuracy at a second time-scale resolution. These developed analytical instruments consist of an incoherent broadband cavity enhanced absorption spectrometer using a red light emitting diode (LED)...