Field Electron Emission from Diamond - like Carbon Films

A low turn-on field electron emission from diamond-like carbon films has been observed for the first time to author’s knowledge.Carbon films were prepared by microwave plasma chemical vapor deposition (CVD).Special pretreatment ceramic substrates were used. The characteristics of the film have been identified by using X-ray diffraction(XRD),and Raman spectrum. The field emission experiment has been performed in a vacuum chamber with a base pressure of about 10 -5 Pa. The turn-on field of 1.2 V/μm,and the current density of 1.25 mA/cm 2 at electric field of 6 V/μm were obtained.

Emission profiling of diesel and gasoline cars at a city traffic junction

In congested urban roads, cars must stop at intersections because of city traffic lights. As a result, pedestri- ans and traffic police personnel are exposed to pollutants emanating from the tailpipe of various vehicles at such city trafficjunctions. In this study, various gasoline- and diesel-fueled cars complying with differ- ent emission standards were tested for their emissions in simulated city traffic junction conditions. The engine exhaust from these cars was subjected to physicochemical characterization at different engine speeds under no-load conditions. These engine conditions were chosen because the cars idle at differ- ent engine speeds at a city traffic junction. Gravimetric and real-time measurements were performed for the tailpipe exhaust sampled from these vehicles. Exhaust particles were collected on 47 mm diameter quartz filter papers and subjected to gravimetric analysis for determining the total particulate mass （TPM） and trace metals while the engines were operated at two different engine idling speeds, 1500 rpm （representing low idling） and 2500 rpm （representing high idling）. At similar engine operating condi- tions, TPM and trace metals were lower for the exhaust from gasoline engines compared to the exhaust from diesel engines. Real-time measurements were performed for particle-bound poly-aromatic hydro- carbons （PAHs）, particle number and size distribution, regulated gaseous emissions and smoke opacity of the exhaust at four different engine speeds, 1500, 2000, 2500, and 3000 rpm. Particle-bound PAHs showed a decreasing trend for the vehicles that complied with stricter vehicular emission standards. Higher particle peak number concentrations were observed for diesel exhausts compared to the results for gasoline exhaust. Regulated gaseous emissions were also comoared.

Determination of time-and size-dependent fine particle emission with varied oil heating in an experimental kitchen

Particulate matter（PM） from cooking has caused seriously indoor air pollutant and aroused risk to human health.It is urged to get deep knowledge of their spatial-temporal distribution of source emission characteristics,especially ultrafine particles（UFP ＆lt; 100 nm） and accumulation mode particles（AMP 100-555 nm）.Four commercial cooking oils are auto dipped water to simulate cooking fume under heating to 255℃ to investigate PM emission and decay features between 0.03 and 10 μm size dimension by electrical low pressure impactor（ELPI） without ventilation.Rapeseed and sunflower produced high PM_（2.5） around5.1 mg/m^3,in comparison with those of soybean and corn（5.87 and 4.55 mg/m^3,respectively）at peak emission time between 340 and 450 sec since heating oil,but with the same level of particle numbers 6-9 × 10~5/cm^3.Mean values of PM_（1.0）/PM_（2.5） and PM_（2.5）/PM_（10） at peak emission time are around 0.51-0.55 and 0.23-0.29.After 15 min naturally deposition,decay rates of PM_（1.0）,PM_（2.5） and PM_（10） are 13.3%-29.8%,20.1%-33.9%and 41.2%-54.7%,which manifest that PM_（1.0） is quite hard to decay than larger particles,PM_（2.5） and PM_（1.0）.The majority of the particle emission locates at 43 nm with the largest decay rate at 75%,and shifts to a larger size between137 and 555 nm after 15 min decay.The decay rates of the particles are sensitive to the oil type.

Origin of high particle number concentrations reaching the St. Louis, Midwest Supersite

Ultrafine particles are associated with adverse health effects. Total Particle Number Concentration（TNC） of fine particles were measured during 2002 at the St. Louis — Midwest supersite. The time series showed overall low level with frequent large peaks. The time series was analyzed alongside criteria pollutant measurements and meteorological observations. Multiple regression analysis was used to identify further contributing factors and to determine the association of different pollutants with TNC levels. This showed the strong contribution of sulfur dioxide（SO2） and nitrogen oxides（NO x） to high TNC levels. The analysis also suggested that increased dispersion resulting from faster winds and higher mixing heights led to higher TNC levels. Overall, the results show that there were intense particle nucleation events in a SO2 rich plume reaching the site which contributed around 29% of TNC. A further 40% was associated with primary emissions from mobile sources. By separating the remaining TNC by time of day and clear sky conditions,we suggest that most likely 8% of TNC are due to regional nucleation events and 23% are associated with the general urban background.

Characterization of particulate matter from diesel passenger cars tested on chassis dynamometers

Emission characterization of particle number as well as particle mass from three diesel passenger cars equipped with diesel particulate filter（DPF）, diesel oxidation catalyst（DOC）and exhaust gas recirculation（EGR） under the vehicle driving cycles and regulatory cycle.Total particle number emissions（PNEs） decreased gradually during speed-up of vehicle from 17.3 to 97.3 km/hr. As the average vehicle speed increases, the size-segregated peak of particle number concentration shifts to smaller size ranges of particles. The correlation analysis with various particulate components such as particle number concentration（PNC）,ultrafine particle number concentration（UFPNC） and particulate matter（PM） mass was conducted to compare gaseous compounds（CO, CO2, HC and NOx）. The UFPNC and PM were not only emitted highly in Seoul during severe traffic jam conditions, but also have good correlation with hydrocarbons and NOxinfluencing high potential on secondary aerosol generation. The effect of the dilution temperature on total PNC under the New European Driving Cycle（NEDC）, was slightly higher than the dilution ratio. In addition, the nuclei mode（DP： ≤ 13 nm） was confirmed to be more sensitive to the dilution temperature rather than other particle size ranges. Comparison with particle composition between vehicle speed cycles and regulatory cycle showed that sulfate was slightly increased at regulatory cycle, while other components were relatively similar. During cold start test, semivolatile nucleation particles were increased due to effect of cold environment. Research on particle formation dependent on dilution conditions of diesel passenger cars under the NEDC is important to verify impact on vehicular traffic and secondary aerosol formation in Seoul.