Showing 5 results for Gas
Mr. Hassan Arman, Dr Saeed Olyaee, Mr. Ahmad Mohebzadeh-Bahabady,
Volume 9, Issue 2 (11-2015)
Abstract
One concern in using photonic band-gap fiber (PBGF) as a gas sensor is the response time. In this type of the gas sensors, response time is the time required for gas to diffuse into the hollow-core. So considering a large hollow-core PBGF (HC-PBGF), the response time can be significantly reduced. But in the large HC-PBGF, the fundamental issue is the presence of higher order modes (HOMs). Sometimes the leakage loss of the HOMs is comparable to those of the fundamental mode. So in order to suppression of the HOMs, six small-cores with reasonable radius were incorporated in the cladding of the proposed fiber. In other words, due to resonant-coupling mechanism of HOMs in central core with fundamental mode of outer cores, the leakage loss of the HOMs can be enhanced. Considering optimum parameters such as hollow-core radius, air filling factor, and the distance between the center-to-center of two adjacent air holes, the small-cores are surface-mode-free and proposed structure can be considered effectively single mode. So at the wavelength of 1550nm the relative sensitivity of the gas sensor was improved to 97%. The results proved the ability of proposed design as a sensitive gas sensor with low response time.
Mahmoud Zolfaghari,
Volume 13, Issue 2 (12-2019)
Abstract
A comparative study of anti-resonance effects in InSe and InSe doped with GaS, using the resonant Raman spectroscopy is presented. The nonpolar optical phonon of
symmetry in InSe exhibits a pronounced decrease in the Raman cross-section at excitation energy 2.585 eV. In InSe doped with GaS samples, it is found that the anti-resonance behavior decreases as doping contents are increased. To account these observations, a model is applied to explain and interpret the Raman intensity evolution versus incident photon energy. The agreement between theory and experiment is good.
Samaneh Biabani, Gholamreza Foroutan,
Volume 13, Issue 2 (12-2019)
Abstract
The dynamics of fast gas heating in a high power microwave discharge in air, is investigated in the framework of FDTD simulations of the Maxwell equations coupled with the fluid simulations of the plasma. It is shown that, an ultra-fast gas heating of the order of several 100 Kelvins occurs in less than 100 ns. The main role in the heating is played by the electron impact dissociation of , dissociation via quenching of metastable states of , as well as, quenching by nitrogen molecules. Among the electronically excited metastable states, are the most important species. Slow heating of the gas above 1 is attributed to the vibrational relaxation processes of , among them vibrational-translational relaxation of demonstrates the highest heating rate. The heating rate and thus the gas temperature are significantly increased with increasing of the microwave pulse amplitude, pulse width, and the gas pressure. In all cases, enhanced dissociation is the main factor behind the enhanced gas heating. The same effects are observed for increasing of the initial gas temperature, and percentage in a mixture.
Mr Patrick Enenche, Dr Michael David, Dr Caroline Alenoghena, Mr Supreme Okoh,
Volume 15, Issue 2 (7-2021)
Abstract
The value of ozone absorption cross section (OACS) is a key parameter used in the configuration of gas sensors. Sadly, the variations of certain parameters among others such as temperature, pressure, and optical path-length in a given spectrum can affect the values of OACS. As a result, there have been several discrepancies in the value of OACS. Recently, the simultaneous effects of optical path-length were investigated in the visible spectrum. Hence, there is the need to also carry out the same investigation in the UV spectrum. So, in this paper, we have reported the combined variation effects of temperature (100 K–350 K), and optical path-length (0.75 cm–130 cm) on OACS in the UV spectrum. We used the method of optical absorption spectroscopy as deployed in a model software called Spectralcalc. The software comprising the HITRAN12 latest line list was used to simulate OACS values. Simulated results were obtained using the latest available line list on the HITRAN12 Spectralcalc simulator. Our obtained results were slightly different from those reported for the visible spectrum but followed a similar trend, in that it showed a decrease in the OACS with an increase in the temperature from 100 K to 350 K at 279.95 nm and 257.34 nm by 1.09 % and 1.43 % respectively. While optical path-length had zero effect on it. We, therefore, conclude that at constant pressure, OACS depends on both temperature and absorption wavelength but not on optical path-length. The analysis reported in this work only seeks to address the differences in the OACS relative to temperature in the UV spectrum. So, the results obtained in this paper can be used to optimally configure ozone gas sensors to obtain an accurate measurement.
Zahra Ahmadimanesh, Babak Jaleh, Mahtab Eslamipanah, Milad Daneshnazar, Hassan Hassan Sepehrmansourie, Mohammad Ali Zolfigol,
Volume 17, Issue 2 (6-2023)
Abstract
In this research, palladium nanoparticles (Pd NPs) were first synthesized using laser ablation in the deionized (DI) water environment. Also, metal-organic framework (MOF) was produced using the solvothermal method at a temperature of 150°C. To accumulate Pd NPs on the synthesized MOF, ultrasonic and magnetic stirring methods were used. Different analytical methods were used to investigate the structure and morphology of the synthesized nanocomposite. Also, the sensitivity of the synthesized nanocomposite to ethanol and methanol organic vapors was investigated. The results showed an increase in the response of the MOF in the presence of nanoparticles.
