Intermediate-volatility organic compounds (IVOCs) have been found as important sources for secondary organic aerosol (SOA) formation. IVOC emissions from nonroad construction machineries (NRCMs), including two road rollers and three motor graders, were characterized under three operation modes using an improved portable emission measurement system. The fuel-based IVOC emission factors (EFs) of NRCMs varied from 245.85 to 1802.19 mg/kg·fuel, which were comparable at magnitudes to the reported results of an ocean-going ship and on-road diesel vehicles without filters. The discrepancy of IVOC EFs is significant within different operation modes. IVOC EFs under the idling mode were 1.24–3.28 times higher than those under moving/working modes. Unspeciated b-alkanes and cyclic compounds, which were the unresolved components in IVOCs at the molecular level, accounted for approximately 91% of total IVOCs from NRCMs. The SOA production potential analysis shows that IVOCs dominated SOA formation of NRCMs. Our results demonstrate that IVOC emissions from NRCMs are non-negligible. Thus, an accurate estimation of their IVOC emissions would benefit the understanding of SOA formation in the urban atmosphere.

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A number of traffic characterization studies have been carried out on wireless LANs, which indicate that the wireless settings pose major challenges, especially for high bandwidth and delay sensitive applications. This paper aims to evaluate a number of Quality of Service (QoS) parameters related to video conferencing over three major WLAN Standards 802.11a, 802.11b and 802.11g. To study the traffic characterization behaviour of these WLAN standards, we have simulated the environment for each of these standards and performed experiments. Results are verified through the delivery of successful H.261 video traffic import in OPNET-14 Network simulator. We found that a trade-off exists between the selected data rate, physical characteristics and the frequency spectrum (number of channels) for every standard. The traffic of video conferencing is characterized over each standard in terms of delay performance, traffic performance and load and throughput performance. The results show that quality of video traffic is a function of the frequency band, physical characteristic, maximum data rate and buffer sizes of WLAN standards.

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