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An analysis of carbone monoxide distribution in large tunnel fires
Atta Sojoudi,Hossein Afshin,Bijan Farhanieh 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.5
Fire events and the related toxicants such as CO are responsible for many fatalities in the current century. These hazardous events aremuch more dangerous when they occur in enclosed spaces. In the present study, a theoretical relation is developed for horizontal distributionof CO in a large tunnel fire. Then, the developed criterion is used to study the effect of some rudimentary parameters such as the heatrelease rate (HRR) of fire and tunnel's aspect ratio (AR) on CO and temperature stratification. Theoretical results of various heat releaserates and aspect ratios for horizontal distribution of CO are compared with numerical results using fire dynamics simulator (FDS5.5). It isfound that big fires have higher rates of CO concentration decay in comparison to the smaller ones due to higher air entrainment into thetravelling plume. It is indicated that the smoke travelling at higher values of tunnel AR, dilutes faster. Moreover, using FDS5.5, the relevantvariations in temperature and CO concentration are discussed for tunnel angles ranging from -20˚ to 20˚.
Atta Heidari,Abdollah Moossavi,Fariba Yadegari,Enayatollah Bakhshi,Mohsen Ahadi 대한청각학회 2018 Journal of Audiology & Otology Vol.22 No.3
Numerous studies have indicated deterioration of speechperception in noisy conditions among the elderly even those with normal hearing capabilities. The aim of this study was to investigate the effects of age on the speech-in-noise identificationby speech-in-noise (SIN) test, subjective ratings of hearing difficulties by speech,spatial, and qualities of hearing scale (SSQ) questionnaire and encoding of fundamental frequency(F0) by Speech auditory brainstem response (ABR) in the elderly and comparing theresults with young people. Subjects and Methods: The present study was conducted on32 elderly people aged over 60 years old (17 male and 15 female) with the mean age of68.9 (standard deviation=6.33) possessing normal peripheral hearing and 32 young subjects(16 male and 16 female) aged 18-25 years old. Results: Findings showed that thescore of SIN test is lower among the elderly people as compared with young people in signal-to-noise ratios of 0 and -10 based on Iranian version of SSQ questionnaire (p<0.001). The range of F0 amplitude in the elderly people is also lower than young people (p<0.001) inSpeech ABR. Conclusions: It seems that speech processing in older people is deterioratedcomparing with young people regardless of their normal peripheral auditory thresholds. Thisdecrease will result in weaker perception and improper segregation of speech from othercompeting sources.
Influence of Nano-silica on the Leaching Attack upon Photocatalytic Cement Mortars
Atta ur rehman,Abdul Qudoos,Sadam Hussain Jakhrani,김홍기,류재석 한국콘크리트학회 2019 International Journal of Concrete Structures and M Vol.13 No.5
Photocatalytic cementitious materials are used in the exterior of the buildings and infrastructure for self-cleaning and air-purifying purposes. These materials are exposed to the aggressive exposure conditions like acid rain, runoff water and are subjected to the deterioration due to the leaching of calcium. The knowledge of leaching attack upon photocatalytic cementitious materials after the addition of nano-materials is necessary. In the current study, the influ-ence of nano-silica addition on the leaching attack upon photocatalytic cement mortars was thoroughly investigated. For this purpose, photocatalytic mortars were made by adding 3% TiO2 and variable amount (0–2%) of nano-silica. Accelerated leaching environment was created by immersing mortars in 6 M ammonium nitrate (NH4NO3) solution. The progressive development of the leaching depth in mortars was measured. The loss of hardened properties was monitored by evaluating the compressive strength, flexural strength, porosity, and dynamic modulus of elasticity. X-ray diffraction, thermogravimetry, Fourier transform infrared spectroscopy, scanning electron microscopy tests were conducted to know the microstructural deteriorations. Results indicated that the leaching attack induced mechanical and microstructural damages in the mortars, but the addition of nano-silica decreased mechanical and microstruc-tural damages in the photocatalytic mortars and increased the resistance of photocatalytic mortars to leaching attack.
Atta ur rehman,Jeong Bae Lee,Abdul Qudoos,Sadam Hussain Jakhrani,Hong-Gi Kim,Jae-Suk Ryou 한양대학교 세라믹연구소 2019 Journal of Ceramic Processing Research Vol.20 No.3
In this study, nano titanium dioxide and nano silica have been added in white Portland cement mortars. The dosage of nano-TiO2 was fixed to 3% while the dosage of nano-SiO2 was varied from 0%-3%. Water/binder ratio was 0.45% and binder/sandratio was 1:3. The workability, water absorption, compressive and flexural strengths of mortars was measured. Thepermeability of mortars was measured using Nordest test and the carbonation resistance was measured in a carbonationchamber. The degradation of rhodamine B dye on the surface of mortars was measured after exposure of the white mortarsto the ultraviolet light. Addition of nano-SiO2 increased the compressive and flexural strengths of mortars, reduced the waterabsorption of mortars and resisted the penetration of chloride ions. The self-cleaning of the white mortars was unaffected bythe addition of nano-SiO2 particles.
Atta M.M.,Abdel Reheem A.M. 한국물리학회 2022 Current Applied Physics Vol.36 No.-
This work examines the properties of polyvinyl alcohol (PVA)/starch film containing glycerol as a plasticizer under exposure to different nitrogen ion fluence. The prepared PVA/starch blend was irradiated with ion fluence from 3 × 1017 to 12 × 1017 ions.cm− 2 . From FTIR, the ion beam irradiation attack and weakens the C–H bond in PVA/starch blend. From XRD findings, the crystallite size of the blend decreased at 3 × 1017 ions/cm2 while it increased at higher fluence up to 9 × 1017 ions/cm2 . This indicates the degradation of the blend at low ion fluence compared to crosslinking at high ion fluence. Also, the optical bandgap of the blend was decreased with an increase in ion fluence. Furthermore, the effect of N+ ions on some optical dispersion parameters is studied. The thermal stability of the PVA/starch blend shows a decrease in thermal stability upon irradiation with 3 × 1017 ions/cm2 compared to higher thermal stability at higher doses up to 9 × 1017 ions/cm2 .
Atta Shubhadip,Halder Monalisa,Dey Santanu,Raul Chandan Kumar,Meikap Ajit Kumar 한국물리학회 2023 Current Applied Physics Vol.47 No.-
We have reported dielectric and magnetocaloric effects in flexible Neodymium (Nd) doped nickel ferrite (NiNdxFe2-xO4) - polyvinyl-alcohol nanocomposite films. The samples are characterized by X-ray diffraction, scanning electron microscopy, vibrating sample magnetometer and broadband dielectric spectroscopy. The dielectric permittivity is enhanced in the composite for a particular filler concentration. The magnetic entropy change decreases by higher doping in the polymer chain. The magnetodielectric coefficient is enhanced in higher frequency and with the rise in doping concentration. The observed skin depth value of the polymer nanocomposite is lower than the film’s thickness which is suitable for electromagnetic shielding.