Andrey G. Guschin

Photochemical properties of some Cl-containing halogenated alkanes.

Rate constants for the gas-phase reactions of OH radicals with three partially halogenated alkanes, CH3Cl (kMC), CHFClCFCl2 (k122a), and CH2FCFCl2 (k132c), were measured using a discharge flow-electron paramagnetic resonance technique over the temperature range from 298 to 460 K. The temperature dependences of the rate constants can be represented by the expressions kMC(298-460 K) = (3.09 ± 0.94) × 10(-12) exp[-(1411 ± 85)/T] cm(3) molecule(-1) s(-1), k122a(298-460 K) = (1.26 ± 0.24) × 10(-12) exp[-(1298 ± 66)/T] cm(3) molecule(-1) s(-1), and k132c(298-370 K) = (8.1 ± 2.2) × 10(-13) exp[-(1247 ± 89)/T] cm(3) molecule(-1) s(-1). The atmospheric lifetimes of CH3Cl, CHFClCFCl2, and CH2FCFCl2 due to their reaction with OH were estimated to be 1.6, 3.5, and 4.5 years, respectively. The UV absorption cross sections of halogenated ethanes, CHFClCFCl2, and CH2FCFCl2, were measured at T = 295 K between 190 and 240 nm, as were those for CHCl2CF2Cl (HCFC-122), CHCl2CF3 (HCFC-123), CHFClCF2Cl (HCFC-123a), and CH3CFCl2 (HCFC-141b). The atmospheric lifetimes due to stratospheric photolysis were also estimated.

P-persistent queue management to overcome channel failures in IEEE 802.11 networks for real-time multimedia streaming

In the paper, we consider real-time video streaming over an IEEE 802.11 network in the presence of short-term channel failures. The failures can dramatically decrease the received video quality at all network stations, even if the channel fails for one station only. In order to assist real-time video traffic to overcome short-term channel failures and to minimize video quality damage, we present the p-persistent queue management policy and propose a strategy for adaptive tuning the values of probabilities p assigned to queued packets.

Photochemical properties of hydrofluoroethers CH3OCHF2, CH3OCF3, and CHF2OCH2CF3: reactivity toward OH, IR absorption cross sections, atmospheric lifetimes, and global warming potentials.

Rate constants for the gas phase reactions of OH radicals with three partially fluorinated ethers, CH3OCF3 (kHFE-143a), CH3OCHF2 (kHFE-152a), and CHF2OCH2CF3 (kHFE-245fa2), were measured using a discharge flow-electron paramagnetic resonance technique over the temperature range 298-460 K. The temperature dependences of the rate constants can be represented by the following expressions: kHFE-143a(T) = (1.10 ± 0.20) × 10(-12) × exp{-(1324 ± 61)/T} cm(3) molecule(-1) s(-1); kHFE-152a(T) = (11.6 ± 4.2) × 10(-12) × exp{-(1728 ± 133)/T} cm(3) molecule(-1) s(-1); and kHFE-245fa2(T) = (3.04 ± 0.57) × 10(-12) × exp{-(1665 ± 66)/T} cm(3) molecule(-1) s(-1). The atmospheric lifetimes due to reactions with tropospheric OH were estimated to be 5.2, 1.9, and 5.6 years, respectively. The IR absorption cross sections of these fluorinated ethers were measured between 400 and 2000 cm(-1), and their global warming potentials were estimated.