• Title, Summary, Keyword: $PM_{2.5}$ control strategy

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A Control Strategy of Fuel Injection Quantity and Common-rail Pressure to Reduce Particulate Matter Emissions in a Transient State of Diesel Engines (승용디젤엔진의 과도구간 입자상물질 저감 및 운전성능 향상을 위한 연료분사량 및 커먼레일압력 제어전략)

  • Hong, Seungwoo;Jung, Donghyuk;Sunwoo, Myoungho
    • Transactions of the Korean Society of Automotive Engineers
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    • v.23 no.6
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    • pp.623-632
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    • 2015
  • This study proposes a control strategy of the common rail pressure with a fuel injection limitation algorithm to reduce particulate matter (PM) emissions under transient states. The proposed control strategy consists of two parts: injection quantity limitation and rail pressure adaptation. The injection limitation algorithm determines the maximum allowable fuel injection quantity to avoid rich combustion under transient states. The fuel injection quantity is limited by predicting the burned gas rate after combustion; however, the reduced injection quantity leads to deterioration of engine torque. The common rail pressure adaptation strategy is designed to compensate for the reduced engine torque. An increase of the rail pressure under transient states contributes to enhancement of the engine torque as well as reduction of PM emissions by promoting atomization of the injected fuel. The proposed control strategy is validated through engine experiments. The rail pressure adaptation reduced the PM emission by 5-10% and enhanced the engine torque up to 2.5%.

Kolb learning styles and self-regulated learning strategies of dental hygiene students (치위생과학생의 Kolb 학습유형과 자기조절 학습전략)

  • Kim, Mi-Jeong;Lim, Cha-Young
    • Journal of Korean society of Dental Hygiene
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    • v.13 no.2
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    • pp.343-350
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    • 2013
  • Objectives : The objective of this study is to analyze about learning styles and self-regulated learning strategies of dental hygiene students and to find methods that may increase learning outcomes by selecting effective learning methods. Methods : The subjects of this study are 524 dental hygiene students in region of chonbuk from May, 2012 to June, 2012. collected informations are analyzed with SPSS. Results : 1. 38.1%, assimilator is most of learning styles of dental hygiene students, followed by 29.7%, converger, 16.2%, diverger, 15.8%, accommodator. 2. 28.0%, converger and diverger are most of subjects whose grade score is between 2.0-2.9, 41.50%, accommodator is most of 3.0-3.4, and 41.61% accommodator is most of 3.5-3.9, and 28.0%, converger is most of subjects whose grade score is more than 4.0. this results has statistically signification(p<0.01). 3. $8.71{\pm}1.78$, assimilation strategy is most self-regulated learning strategies of dental hygiene students, followed by $8.26{\pm}1.94$, control strategy, $7.52{\pm}2.00$, memorization strategy. accommodator is most showed $7.82{\pm}2.24$, $9.13{\pm}1.74$, $8.71{\pm}2.20$ in memorization strategy, assimilation strategy, control strategy. 4. It is showed that assimilator is significantly related with satisfaction for major(p<0.01), accommodator is significantly related with academic records(p<0.05), and diverger is significantly negative related with academic records, through the results of the analysis of factors that affects learning styles. Conclusions : Organizing above results, It is considered that instructor needs to acknowledge learning styles of students through understanding about various learning styles of students, and may has to develop suitable teaching method for students based on that.

Characteristics of Summertime High PM2.5 Episodes and Meteorological Relevance in Busan (부산지역 여름철 고농도 PM2.5 농도 사례와 기상학적 관련성)

  • Jeon, Byung-Il
    • Journal of Environmental Science International
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    • v.29 no.7
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    • pp.761-772
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    • 2020
  • This research investigated the meteorologically relevant characteristics of high PM2.5 episodes in Busan. The number of days when daily mean PM10 concentration exceeded 100 ㎍/㎥ and the PM2.5 concentration exceeded 50 ㎍/㎥ over the last four years in Busan were 24 and 58, respectively. Haze occurrence frequency was 37.6% in winter, 27.4% in spring, 18.6% in fall, and 16.4% in summer. Asian dust occurrence frequency was 81.8% in spring, 9.1% in fall and winter, and 0% in summer. During summer in Busan, high PM2.5 episode occurred under the following meteorological conditions. 1) Daytime sea breeze. 2) Mist and haze present throuout the day. 3) Anti-cyclone located around the Korean peninsula. 4) Stable layer formed in the lower atmosphere. 5) Air parcel reached Busan by local transport rather than by long-range transport. These results indicate that understanding the meteorological relevance of high PM2.5 episodes could provide insight for establishing a strategy to control urban air quality.

Spaciotemporal Variation of PM10 and PM2.5 Concentration for 2015 to 2018 in Busan (부산지역 최근 4년간(2015~2018년) PM10과 PM2.5농도의 시·공간적 변화 특성)

  • Jeon, Byung-Il
    • Journal of Environmental Science International
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    • v.29 no.7
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    • pp.749-760
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    • 2020
  • This study investigates the characteristics of diurnal, seasonal, and weekly roadside and residential concentrations of PM10 and PM2.5 in Busan, as well as relationship with meteorological phenomenon. Annual mean PM10 and PM2.5 concentrations in Busan were 44.2 ㎍/㎥ and 25.3 ㎍/㎥, respectively. The PM2.5/PM10 concentration ratio was 0.58. Diurnal variations of PM10 and PM2.5 concentrations in Busan were categorized into three types, depending on the number of peaks and times at which the peaks occurred. Roadside PM10 concentration was highest on Saturday and lowest on Friday. Residential PM10 concentration was highest on Monday and lowest on Friday. Residential PM2.5 concentration was highest on Monday and Tuesday and lowest on Friday. PM10 and PM2.5 concentrations were highest on Asian dust and haze, respectively. The results indicate that understanding the spaciotemporal variation of fine particles could provide insights into establishing a strategy to control urban air quality.

Characterization of PM10 and PM2.5 in Cheonan Area Using a Dust Monitor (Dust Monitor를 이용한 천안시 대기 중 PM10, PM2.5 오염특성 조사)

  • Lee, Hyun-Mi;Oh, Se-Won
    • Journal of Korean Society for Atmospheric Environment
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    • v.24 no.3
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    • pp.367-375
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    • 2008
  • To characterize atmospheric particles in Cheonan area, 5 monitoring sites representing highway area, commercial area, residential area, and industrial areas were selected, and the mass concentrations of PM10 and PM2.5 were monitored for 14 days at each site during 2007. The daily average PM10 and PM2.5 concentrations were in the range from 18.5 to $140.9{\mu}g/m^3$ and 8.2 to $116.6{\mu}g/m^3$, respectively, showing the highest mean concentrations at the commercial area site and the lowest concentration at the residential area site. The daily average PM 10 concentrations at Shinan (Commercial area) and Bakseok (Industrial area) sites were exceeded the current National Standard for 1 and 2 days during the monitoring periods. The fractions of PM2.5 in PM10 were above 70% for all sites, indicating fine particles are the major constituent of atmospheric particles in Cheonan. The results indicate that PM10 concentrations in Cheonan are at the concerning level, and the control strategy for fine particles is necessary to address this issue.

Characteristics of Fine Particle Concentration and Case during Haze Days in Busan (부산 지역 연무 발생일의 미세먼지 농도와 사례별 특성)

  • Jeon, Byung-Il
    • Journal of Environmental Science International
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    • v.26 no.6
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    • pp.751-765
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    • 2017
  • This research investigates the characteristics of meteorological variation and fine particles ($PM_{10}$ and $PM_{2.5}$) for case related to the haze occurrence (Asian dust, long range transport, stationary) in Busan. Haze occurrence day was 559 days for 20 years (from 1996 to 2015), haze occurrence frequency was 82 days (14.7%) in March, followed by 67 days (12.0%) in February and 56 days (10.0%) in May. Asian dust occurred most frequently in spring and least in winter, whereas haze occurrence frequency was 31.5% in spring, 29.7% in winter, 21.1% in fall, and 17.7% in summer. $PM_{10}$ concentration was highest in the occurrence of Asian dust, followed by haze and haze + mist, whereas $PM_{2.5}$ concentration was highest in the occurrence of haze. These results indicate that understanding the relation between meteorological phenomena and fine particle concentration can provide insight into establishing a strategy to control urban air quality.

Computed Tomography-Based Ventricular Volumes and Morphometric Parameters for Deciding the Treatment Strategy in Children with a Hypoplastic Left Ventricle: Preliminary Results

  • Goo, Hyun Woo;Park, Sang-Hyub
    • Korean Journal of Radiology
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    • v.19 no.6
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    • pp.1042-1052
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    • 2018
  • Objective: To determine the utility of computed tomography (CT) ventricular volumes and morphometric parameters for deciding the treatment strategy in children with a hypoplastic left ventricle (LV). Materials and Methods: Ninety-four consecutive children were included in this study and divided into small LV single ventricle repair (SVR) (n = 28), small LV biventricular repair (BVR) (n = 6), disease-matched control (n = 19), and control (n = 41) groups. The CT-based indexed LV volumes, LV-to-right-ventricular (LV/RV) volume ratio, left-to-right atrioventricular valve (AVV) area ratio, left-to-right AVV diameter ratio, and LV/RV long dimension ratio were compared between groups. Proportions of preferred SVR in the small LV SVR group suggested by the parameters were evaluated. Results: Indexed LV end-systolic (ES) and end-diastolic (ED) volumes in the small LV SVR group ($6.3{\pm}4.0mL/m^2$ and $14.4{\pm}10.2mL/m^2$, respectively) were significantly smaller than those in the disease-matched control group ($16.0{\pm}4.7mL/m^2$ and $37.7{\pm}12.0mL/m^2$, respectively; p < 0.001) and the control group ($16.0{\pm}5.5mL/m^2$ and $46.3{\pm}10.8mL/m^2$, respectively; p < 0.001). These volumes were $8.3{\pm}2.4mL/m^2$ and $21.4{\pm}5.3mL/m^2$, respectively, in the small LV BVR group. ES and ED indexed LV volumes of < $7mL/m^2$ and < $17mL/m^2$, LV/RV volume ratios of < 0.22 and < 0.25, AVV area ratios of < 0.33 and < 0.24, and AVV diameter ratios of < 0.52 and < 0.46, respectively, enabled the differentiation of a subset of patients in the small LV SVR group from those in the two control groups. One patient in the small LV biventricular group died after BVR, indicating that this patient might not have been a good candidate based on the suggested cut-off values. Conclusion: CT-based ventricular volumes and morphometric parameters can suggest cut-off values for SVR in children with a hypoplastic LV.

Field Weakening Control of a PM Electric Variable Transmission for HEV

  • Cheng, Yuan;Bouscayrol, Alain;Trigui, Rochdi;Espanet, Christophe;Cui, Shumei
    • Journal of Electrical Engineering and Technology
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    • v.8 no.5
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    • pp.1096-1106
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    • 2013
  • This paper presents the control of a Permanent Magnet Electric Variable Transmission (PM-EVT) for Hybrid Electric Vehicles (HEVs). Consisting of two electric machines, the EVT realizes the power split function in an electromagnetic way rather than in a mechanical way. A specific PM-EVT has been designed for Toyota Prius II. The control scheme of the entire vehicle is deduced using the Energetic Macroscopic Representation methodology. The energy management strategy yields local control references. A specific attention is paid for the field weakening for wide speed range. Simulation results are provided to illustrate the EVT modeling and control.

Characteristics of Fine Particles at Roadside and Urban Residential Locations in Busan (부산지역 도로변과 주거지역의 PM10과 PM2.5 농도 특성)

  • Jeon, Byung-Il
    • Journal of Environmental Science International
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    • v.27 no.7
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    • pp.577-586
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    • 2018
  • This research investigated the characteristics of $PM_{10}$ and $PM_{2.5}$ concentration at roadside (Choryangdong) and residential (Sujeongdong) locations in Busan. The $PM_{10}$ concentration at roadside and residential locations were 50.5 and $42.9{\mu}g/m^3$, respectively, and $PM_{2.5}$ at roadside and residential were 28.1 and $23.9{\mu}g/m^3$, respectively. The roadside/residential ratio of $PM_{10}$ and $PM_{2.5}$ concentration were 1.18, and the $PM_{2.5}/PM_{10}$ ratio at roadside and residential were 0.55 and 0.56, respectively. The $PM_{10}$ concentration in spring at roadside were $64.6{\mu}g/m^3$, and were the highest, followed by $48.0{\mu}g/m^3$ and $45.2{\mu}g/m^3$ in winter and summer. Number of exceedances per year of the daily limit value for $PM_{10}$ at roadside and residential were 66 and 39 days, respectively. The $PM_{10}$ and $PM_{2.5}$ concentration, and $PM_{2.5}/PM_{10}$ ratio at roadside were $53.0{\mu}g/m^3$, $29.0{\mu}g/m^3$ and 0.55 for day, and $45.5{\mu}g/m^3$, $26.7{\mu}g/m^3$ and 0.59 for night, respectively. These results indicate that understanding the relationship between roadside and residential could provide insight into establishing a strategy to control urban air quality.

PM2.5 Simulations for the Seoul Metropolitan Area: (III) Application of the Modeled and Observed PM2.5 Ratio on the Contribution Estimation (수도권 초미세먼지 농도모사: (III) 관측농도 대비 모사농도 비율 적용에 따른 기여도 변화 검토)

  • Bae, Changhan;Yoo, Chul;Kim, Byeong-Uk;Kim, Hyun Cheol;Kim, Soontae
    • Journal of Korean Society for Atmospheric Environment
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    • v.33 no.5
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    • pp.445-457
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    • 2017
  • In this study, we developed an approach to better account for uncertainties in estimated contributions from fine particulate matter ($PM_{2.5}$) modeling. Our approach computes a Concentration Correction Factor (CCF) which is a ratio of observed concentrations to baseline model concentrations. We multiply modeled direct contribution estimates with CCF to obtain revised contributions. Overall, the modeling system showed reasonably good performance, correlation coefficient R of 0.82 and normalized mean bias of 2%, although the model underestimated some PM species concentrations. We also noticed that model biases vary seasonally. We compared contribution estimates of major source sectors before and after applying CCFs. We observed that different source sectors showed variable magnitudes of sensitivities to the CCF application. For example, the total primary $PM_{2.5}$ contribution was increased $2.4{\mu}g/m^3$ or 63% after the CCF application. Out of a $2.4{\mu}g/m^3$ increment, line sources and area source made up $1.3{\mu}g/m^3$ and $0.9{\mu}g/m^3$ which is 92% of the total contribution changes. We postulated two major reasons for variations in estimated contributions after the CCF application: (1) monthly variability of unadjusted contributions due to emission source characteristics and (2) physico-chemical differences in environmental conditions that emitted precursors undergo. Since emissions-to-$PM_{2.5}$ concentration conversion rate is an important piece of information to prioritize control strategy, we examined the effects of CCF application on the estimated conversion rates. We found that the application of CCFs can alter the rank of conversion efficiencies of source sectors. Finally, we discussed caveats of our current approach such as no consideration of ion neutralization which warrants further studies.