Behavior of particulate matter during high concentration episodes in Seoul

The behavior of particulate matter (PM) during high-concentration episodes was investigated using monitoring data from Guui station, a comprehensive air monitoring station in Seoul, Korea, from January 2008 to March 2010. Five non-Asian dust (ND) episodes and two Asian dust (AD) episodes of high PM concentrations were selected for the study. During the ND episode, primary air pollutants accumulated due to low wind speeds, and PM_2.5 increased along with most other air pollutants. Particles larger than PM_2.5 were also high since these particles were generated by vehicular traffic rather than wind erosion. During strong AD episodes, PM_10–2.5 primarily increased and gaseous primary air pollutants decreased under high wind speeds. However, even during the AD episode, PM_2.5 and gaseous primary air pollutants increased when the effects of AD were weak and wind speeds were low. This study corroborates that accumulation of air pollutants due to a drop in surface wind speed plays an important role in short-term high-concentration occurrences. However, low wind speeds could not be directly linked to local emissions because a significant portion of accumulated air pollutants resulted from long-range transport.     

Chemical characteristics of long-range transport aerosol at background sites in Korea

In this study, background concentration sites of Deokjeok and Gosan, which were deemed suitable for monitoring the impact of long-range transported air pollutants, were selected. An investigation of the source types of pollutants, their locations, and relative quantitative contributions to the particulate concentrations at both sites using appropriate methodologies to make initial estimations was conducted. Episodic measurements of PM_2.5, PM₁₀, and size distribution, along with its ion and carbon components were performed from 2005 to 2007, and a comprehensive analysis of the results was conducted utilizing back trajectory analysis. As for frequency of wind direction, it was quite apparent that the two sites are heavily influenced by air masses originating from the eastern and northern regions of China. For PM_2.5 and PM₁₀, the mass concentrations from north and east China were higher than other cases, originating from the ocean. In the northerly-wind case, meteorological properties for Deokjeok and Gosan and the influence of carbon emissions from northwest Korea resulted in a changing of air mass properties during transport. As was the case with mass concentration, the highest contribution for ionic and carbon components of PM_2.5 and PM₁₀ for both sites appeared for the westerly wind case. A specially high relative contribution, greater than 1.4 times, was apparent in the secondary aerosol case because of a large influence of long-range transported pollutants from east China. Carbon components exhibited different behaviors for the northerly and westerly wind cases compared with secondary aerosol. The major reason for this discrepancy appears to be the carbon emissions from northwest Korea.     

Using aliphatic alcohols as gaseous tracers in determination of water contents and air-water interfacial areas in unsaturated sands

A new type of gaseous tracer utilizing nontoxic aliphatic alcohols for the determination of water content and air-water interfacial area is tested on unsaturated sands of low water content. Alcohol vapors are generated at room temperature and passed through the experimental sand column. Breakthrough curves (BTCs) of these vapors are obtained by monitoring their effluent concentrations using GC-FID. The retardation factor with respect to each vapor transport process is obtained by optimizing BTCs data using the CXTFIT program in the reverse problem mode. The water content and the interfacial area are subsequently calculated from their retardation factors by both equilibrium and nonequilibrium transport models. Experimental results indicate that the pentanol tracer is feasible in the determination of water content at conditions when the degree of water saturation is low. In the determination of air-water interfacial area, decanol is selected due to its interfacial adsorption characteristics. By comparing to interfacial areas from theoretical predictions as well as other conventional tarcer methods, the ones determined from the decanol tracer tests are found to be close to the true interfacial areas when the water content is low.     

Evaluation of a Three‐Dimensional Hydrodynamic Model Applied to Chesapeake Bay Through Long‐Term Simulation of Transport Processes

A numerical model, the Curvilinear Hydrodynamics in 3‐Dimensions, Waterway Experiment Station version (CH3D‐WES), was applied to represent transport processes of the Chesapeake Bay. Grid resolution and spatial coverage, tied with realistic bathymetry, ensured dynamic responses along the channel and near the shoreline. The model was run with the forcing ranges from high frequency astronomical tides to lower frequency meteorological forcing, given by surface wind and heat flux, as well as hydrological forcing given by fresh water inflows both from upstream and distributed sources along the shoreline. To validate the model, a long‐term simulation over seven‐year time period between 1994 and 2000 was performed. The model results were compared with existing observation data including water level time series, which spans over a wide spectrum of time scales, and long‐term variations in salinity structures over varying parts of the Bay. The validated model is set to provide an appropriate transport mechanism to the water quality model through linkage, warranting that the model takes into account the complexity in time and spatial scales associated with the dynamic processes in the Chesapeake.     

Evaluation of Hook Handles in a Pulling Task

To evaluate the effect of handle design characteristics on subjective ratings and pulling forces, meat-hook handles with various handle shapes, sizes, and hook positions were tested in a pulling task. Finger and phalange force data measured by force sensitive resistors and subjective ratings of discomfort were also evaluated. Generally subjects preferred 37-mm double frustum, 30-mm oval handles followed by 30-mm double frustum handles, 37-mm oval, and 45-mm double frustum handles. In the analyses of total pulling force, 37- and 45-mm double frustum handles showed less required pulling force than the others. The averages of finger force contributions to the total pulling force were 27.2, 28.1, 23.9, and 20.8% in order from index to little fingers. The average of phalange force contributions were 28.8, 33.6, and 37.6% for the distal, middle, and proximal phalanges, respectively. The findings illustrate that the pulling finger forces and subjective discomfort ratings were related to the handle shape as well as handle size.     

A Systematic Procedure for Modeling Usability Based on Product Design Variables: A Case Study in Audiovisual Consumer Electronic Products

A systematic modeling approach to describing, prescribing, and predicting usability of a product has been presented. Given the evaluation results of the usability dimension (UD) and the measurement of the product’s design variables, referred to as the human interface elements (HIEs), the approach enables one to systematically assess the relationship between the UD and HIEs. The assessed relationship is called a usability model. Once built, such a usability model can relate, in a quantitative manner, the HIEs directly to the UDs, and thus can serve as an effective aid to designers by evaluating and predicting the usability of an existing or hypothetical product. A usability model for elegance of audiovisual consumer electronic products has been demonstrated.     

The impact of nudging coefficient for the initialization on the atmospheric flow field and the photochemical ozone concentration of Seoul,Korea

In order to incorporate correctly the large or local scale circulation in the model, a nudging term is introduced into the equation of motion. Nudging effects should be included properly in the model to reduce the uncertainties and improve the air flow field. To improve the meteorological components, the nudging coefficient should perform the adequate influence on complex area for the model initialization technique which related to data reliability and error suppression. Several numerical experiments have been undertaken in order to evaluate the effects on air quality modeling by comparing the performance of the meteorological result with variable nudging coefficient experiment. All experiments are calculated by the upper wind conditions (synoptic or asynoptic condition), respectively. Consequently, it is important to examine the model response to nudging effect of wind and mass information. The MM5–CMAQ model was used to assess the ozone differences in each case, during the episode day in Seoul, Korea and we revealed that there were large differences in the ozone concentration for each run.These results suggest that for the appropriate simulation of large or small-scale circulations, nudging considering the synoptic and asynoptic nudging coefficient does have a clear advantage over dynamic initialization, so appropriate limitation of these nudging coefficient values on its upper wind conditions is necessary before making an assessment. The statistical verifications showed that adequate nudging coefficient for both wind and temperature data throughout the model had a consistently positive impact on the atmospheric and air quality field. On the case dominated by large-scale circulation, a large nudging coefficient shows a minor improvement in the atmospheric and air quality field. However, when small-scale convection is present, the large nudging coefficient produces consistent improvement in the atmospheric and air quality field.