The Washout Effect of Precipitation on Atmospheric PM<SUB>10</SUB> Concentrations in Busan Metropolitan City

Sunyurp Park(박선엽) 대한지리학회 2017 대한지리학회지 Vol.52 No.3

우리나라 대기 중 고농도 PM10 현상의 빈번한 발생은 공중 보건을 직접적으로 위협하는 심각한 환경문제로 인식되고 있으나, PM10 농도에 미치는 강수 인자의 영향은 충분히 알려져 있지 않다. 본 연구는 부산광역시에서 지난 15년간 관측된 PM10 자료를 분석하여 대기 PM10 농도에 대한 강수현상의 세정효과를 파악하고자 하였다. 강수의 세정효과는 합산세정율(Aggregated Washout Ratio, AWR)과 개별강우세정율(Immediate Washout Ratio, IWR) 등 두 가지 서로 다른 세정율로 지표화하였다. 계절별 세정효과의 크기는 합산세정율과 개별강우세정율 모두 봄>여름>가을>겨울 순으로 나타났다. 그러나 월별로 세분한 분석결과에 따르면, 각 세정율은 강우량, 강우강도, 강우빈도, 연속강우일수 등의 주요 강수변수와 일관된 상관관계를 보이지 않았다. 대부분 1~4일 범위에 걸쳐있는 연속강우일수와 연속강우기간 중 누적 강우량 역시 PM10 세정율과 일관성 있는 상관성을 나타내지 않았다. 연속강우일수 또는 연속강우기간 누적강우량이 PM10농도의 개별강우세정율과 유의한 상관관계를 보이는 경우는 월별로 제한적으로 나타났다. Frequent occurrences of high PM10(particulate matter ≤10μm) concentrations have become a serious environmental concern in Korea due to their direct threat to public health, but the impacts of rainfall factors on PM10 concentrations are not well known. This study analyzed 15-year long PM10 data over Busan Metropolitan City(BMC) to quantify the washout effect of precipitation on PM10 concentrations in the city. Two different washout ratios, the aggregated washout ratio(AWR) and the immediate washout ratio(IWR), were suggested as a washout indicator. Seasonal mean washout ratios were highest in spring followed by summer, fall, and winter for both washout ratios. However, monthly analyses showed that rainfall variables, such as its amount, frequency, intensity, and the number of consecutive rainy days, did not have consistent correlations with the washout ratios. The cumulative impact of consecutive rainy days, typically ranging from 1 to 4 days, on the PM10 washout effect was also inconsistent. Study results indicated that the cumulative rainfall during a rainy period and the length of a rainy period had only a limited correlation with IWR on the monthly basis.

Clinical Outcome of Fine Needle Aspiration Cytology and Washout Thyroglobulin in Suspicious Lymph Nodes in Differentiated Thyroid Carcinoma: Discordant Results in Real-World Practice

( Jeongmin Lee ),( Hye Lim Park ),( Kwanhoon Jo ),( Min-hee Kim ),( Ja Seong Bae ),( Sohee Lee ),( Chan Kwon Jung ),( So-lyung Jung ),( Dong-jun Lim ) 대한갑상선학회 2021 International Journal of Thyroidology Vol.14 No.1

Background and Objectives: Fine needle aspiration cytology (FNAC) combined with washout thyroglobulin (Tg) measurement is the gold standard for the evaluation of metastatic lymph nodes (LNs) in thyroid cancer. However, few studies have assessed the clinical outcomes of discordant results between FNAC and washout Tg based on surgery status and follow-up imaging in real-world practice. Materials and Methods: A total of 707 LNs in 512 patients who underwent FNAC and washout Tg measurements from 2015 to 2017 were analyzed. The final LN outcomes were confirmed through postoperative histology, or through metastatic FNAC findings combined with high washout Tg level, follow-up imaging studies, or repeat FNA, if LNs were not dissected. Results: The cut-off values of washout Tg for indicating LN metastasis in preoperative and postoperative LNs were 9.6 ng/mL and 2.1 ng/mL. The diagnostic accuracy was improved by applying washout Tg according to surgery status and the results of discordant rate was reduced, Discordant between results of FNAC with washout Tg and final outcome were 9.2% (27/295) of preoperative LNs and 8.7% (36/412) of postoperative LNs. Due to inconclusive results, unnecessary neck dissection can occur in 13.9% (36/259 dissected cases). Conclusion: To improve diagnostic accuracy, cut-off values of washout Tg should be applied depending on surgery status. New biomarkers in washout fluid is necessary to resolve discordant findings.

Intraindividual Comparison of Hepatocellular Carcinoma Washout between MRIs with Hepatobiliary and Extracellular Contrast Agents

Kim Yeun-Yoon,Kim Young Kon,Min Ji Hye,Cha Dong Ik,Kim Jong Man,Choi Gyu Seong,Ahn Soohyun 대한영상의학회 2021 Korean Journal of Radiology Vol.22 No.5

Objective: To intraindividually compare hepatocellular carcinoma (HCC) washout between MRIs using hepatobiliary agent (HBA) and extracellular agent (ECA). Materials and Methods: This study included 114 prospectively enrolled patients with chronic liver disease (mean age, 55 ± 9 years; 94 men) who underwent both HBA-MRI and ECA-MRI before surgical resection for HCC between November 2016 and May 2019. For 114 HCCs, the lesion-to-liver visual signal intensity ratio (SIR) using a 5-point scale (-2 to +2) was evaluated in each phase. Washout was defined as negative visual SIR with temporal reduction of visual SIR from the arterial phase. Illusional washout (IW) was defined as a visual SIR of 0 with an enhancing capsule. The frequency of washout and MRI sensitivity for HCC using LR-5 or its modifications were compared between HBA-MRI and ECA-MRI. Subgroup analysis was performed according to lesion size (< 20 mm or ≥ 20 mm). Results: The frequency of portal venous phase (PP) washout with HBA-MRI was comparable to that of delayed phase (DP) washout with ECA-MRI (77.2% [88/114] vs. 68.4% [78/114]; p = 0.134). The frequencies were also comparable when IW was allowed (79.8% [91/114] for HBA-MRI vs. 81.6% [93/114] for ECA-MRI; p = 0.845). The sensitivities for HCC of LR-5 (using PP or DP washout) were comparable between HBA-MRI and ECA-MRI (78.1% [89/114] vs. 73.7% [84/114]; p = 0.458). In HCCs < 20 mm, the sensitivity of LR-5 was higher on HBA-MRI than on ECA-MRI (70.8% [34/48] vs. 50.0% [24/48]; p = 0.034). The sensitivity was similar to each other if IW was added to LR-5 (72.9% [35/48] for HBA-MRI vs. 70.8% [34/48] for ECA-MRI; p > 0.999). Conclusion: Extracellular phase washout for HCC diagnosis was comparable between MRIs with both contrast agents, except for tumors < 20 mm. Adding IW could improve the sensitivity for HCC on ECA-MRI in tumors < 20 mm.

New indices for wet scavenging of air pollutants (O₃, CO, NO₂, SO₂, and PM₁₀) by summertime rain

Yoo, J.M.,Lee, Y.R.,Kim, D.,Jeong, M.J.,Stockwell, W.R.,Kundu, P.K.,Oh, S.M.,Shin, D.B.,Lee, S.J. Pergamon Press ; Elsevier [distribution] 2014 Atmospheric environment Vol.82 No.-

The washout effect of summertime rain on surface air pollutants (O<SUB>3</SUB>, CO, NO<SUB>2</SUB>, SO<SUB>2</SUB>, and PM<SUB>10</SUB>) has been investigated over South Korea during 2002-2012 using routinely available air-monitored and meteorological data. Three new washout indices for PM<SUB>10</SUB>, SO<SUB>2</SUB>, NO<SUB>2</SUB>, and CO are developed to express the effect of precipitation scavenging on these pollutants. All of these pollutants show statistically significant negative correlations between their concentrations and rain intensity due to washout or convection. The washout effect is estimated for precipitation episodes classified by rain intensity (one set included all episodes and another included a subset of moderate intensity episodes that exclude Changma and typhoons), based on the log-transformed hourly data. The most sensitive air pollutant to the rain onset among these five air pollutants is PM<SUB>10</SUB>. The relative effect of the rainfall washout on the air pollutant concentrations is estimated to be: PM<SUB>10</SUB> > SO<SUB>2</SUB> > NO<SUB>2</SUB> > CO > O<SUB>3</SUB>, indicating that PM<SUB>10</SUB> is most effectively scavenged by rainfall. The analysis suggests that the O<SUB>3</SUB> concentrations may increase due to vertical mixing leading to its downward transport from the lower stratosphere/upper troposphere. The concentrations of CO are reduced, probably due to both the washout and convection. The concentrations of NO<SUB>2</SUB> are affected by the opposing influences of lightning-generation and washout and this are discussed as well.

Development and Verfication of a New Washout Algorithm for a Vehicle Driving Simulator

Moon-Sik Kim,Young-Gun Moon,Gyung-Dal Kim,Min-Cheol Lee 한국자동차공학회 2008 한국자동차공학회 Symposium Vol.2008 No.9

Vehicle driving simulator(VDS) is a virtual reality based device which makes a human feel as if one drives an actual vehicle. VDS has been used by some automotive manufactures, research centers and universities instead of the T-car. Unlike actual vehicle, VDS has limited kinematics workspace and bounded dynamic characteristics. So it is very difficult to simulate dynamic motions of a actual vehicle. In order to solve these problems, washout algorithm which restricts workspace of VDS within the kinematic limit and makes a human feel a sense of the movement of a real vehicle is needed. However, a classical washout algorithm contains several problems such as time delay and generation of wrong motion signal caused by characteristics of filters. So the driver feels simulator sickness such as fatigue, vomit, a headache and so on because of differences between the sense of movement of VDS and one of the real vehicle. Specially, the classical washout algorithm make the driver feel more simulator sickness during reckless driving. In this paper, a new washout algorithm including tilt coordination system and partial range scaling method is developed to enhance the sense of motion and reduce simulator sickness, it is verified by a signal simulation, survey and a bio signal analysis using electrocardiogram(EEG).

수중 불분리성 그라우트 개발 기술 동향

( Khaqan Baluch ),김정규 ( Jung-gyu Kim ),김종관 ( Jong-gwan Kim ),유지윤 ( Ji-yun Yu ),양형식 ( Hyung-sik Yang ) 대한화약발파공학회 2020 화약발파 Vol.38 No.4

수중 불분리성 그라우트는 수중 현장에 광범위하게 사용된다. 그러나 접합강도, 펌프 능력 및 강도 손실과 같은 주요 문제점이 여전히 존재한다. 본 연구에서는 자기충전, 비파괴 방지 그라우트 연구에 기초하여 이 분야의 현황을 파악하기 위해 수중 시공 및 카르스트 공동 실링에 관한 연구 동향에 대해 검토하였다. 그라우트를 수중에 사용할 경우, 공기 중에서 시공하는 것에 비해 강도와 접합강도가 손실될 것이다. 이를 방지하기 위해 고점도의 그라우트를 통해 카르스트 공동을 실링하고 있지만, 대심도에서는 그라우트의 펌핑 능력에 심각한 문제를 발생시키므로 기존의 수중 불분리성 그라우트와 콘크리트는 대심도 환경에 적합하지 않음을 의미한다. Although anti-washout grouts are used extensively in underwater targets, major constraints continue to be associated with their use. These include poor bonding strength, poor pumpability, and loss of high strength in everyday engineering applications. In this study, based on the literature pertaining to self-compacted, non-dispersive, anti-washout grouts, a review of research trends in anti-washout grouts for underwater construction and sealing of karst cavities was carried out in order to determine the problems faced in this field. Grouts used under water suffer a loss of strength and bonding strength in comparison to grouts cast in air. Researchers are designing high-viscosity grouts to overcome the inrush of water and seal karst cavities; however, in doing so, they have inadvertently caused serious problems pertaining to the pumpability of these grouts and concretes in deep target locations. Thus, the majority of the anti-washout grouts and concretes that have been developed are not applicable to deep target environments, instead being suitable for only near-surface targets.

Washout of Tritiated Water Vapor by Precipitation in the Vicinity of Wolsong Nuclear Power Plant Site

Kim, C.K.,Lee, S.K.,Rho, B.H.,Park, G.J.,Kim, W.,Kang, H.D. The Korean Association for Radiation Protection 2003 방사선방어학회지 Vol.28 No.4

On a basis of the washout model and concentrations of anthropogenic tritium in rainwater around the Wolsong site, the washout coefficients of tritium by rainwater were calculated, and the validity of washout deposition model are estimated. As the result of that, the washout coefficients in 10 sampling stations around Wolsong site were in the range of $2.9{\times}10^{-5}\;-\;16{\times}10^{-5}\;s^{-1}$ with the mean value of $7.21{\times}10^{-5}\;s^{-1}$. The validity of the washout deposition model was confirmed by comparing the observed data with the calculated ones.

Washout Removal Efficiencies of Major Air Pollutants by Precipitation

Kim, Dong-Sool,Lim, Deuk-Yong,Heo, Jeong-Sook Korean Society for Atmospheric Environment 2002 한국대기환경학회지 Vol.18 No.E2

The purpose of this study was to quantitatively estimate the washout removal efficiencies of criteria air pollutants such as SO$_2$, TSP, PM10, CO, NO$_2$, and O$_3$corresponding to the amounts and durations of precipitation. The removal patters by washout were studied with air pollutants data and the corresponding precipitation data in Seoul, Korea during the periods of 1990 to 1999. In addition, washout patterns were classified into four seasons and four time Bones, i.e., night, morning, afternoon, and evening. In this study, natures of air pollutants by sequential precipitation were also intensively studied by examining the linear relationships between removal efficiencies and the amounts and durations of precipitation for each pollutant. The results of this study showed that SO$_2$, TSP, and O$_3$were rapidly removed by initial precipitation; however, NO$_2$was slowly removed 2-hour after precipitation. Both CO and PM10 were weakly removed by washout and their removal patters showed to be irregular.

점성개질제를 이용한 수중 불분리성 그라우트재의 수중 속채움 보강 특성 분석

김욱기(Uk-Gie Kim),조삼덕(Sam-Deok Cho),박봉근(Bong-Geun Park),김주형(Juhyong Kim) 한국지반신소재학회 2013 한국지반신소재학회 논문집 Vol.12 No.2

본 연구에서는 계면활성제계 개질제를 이용하여 수중에서 재료분리가 발생하지 않으면서도 유동성을 충분히 갖는 수중 불분리성 점탄성 그라우트재와 일반 그라우팅 재료의 강도 특성과 속채움 보강 재료로서의 특성을 분석하였다. 특히, 해수를 활용하여 점탄성 그라우팅 재료를 제작하는 경우에 대해 중점적으로 시험을 수행한 결과, 담수를 사용하여 그라우트 재료를 제작하는 경우와 마찬가지로 수중 불분리성 특성을 잘 나타내었으며, 이에 따른 균질한 점탄성 그라우트재의 강도를 확보할 수 있을 것으로 평가되었다. 또한, 모형시험을 통해 그라우트재의 침투성을 이용하여 속채움 골재의 보강특성을 평가한 결과, 수중 불분리성 그라우팅 재료는 일반 그라우트재와 비교하여 충분한 강도가 발휘되었으며, 점성에 의한 수중 불분리 특성으로 속채움 보강재로서 좋은 시공 품질을 확보할 수 있을 것으로 평가되었다. This study introduces strength characteristics of the anti-washout grouting material using viscous modifiers and its characteristics mixed with coarse materials. Especially, this study focused on the strength characteristics of the grouts mixed with sea water. It is found that the anti-washout grout mixed with sea water has enough strength and good resistance to segregation just like that with fresh water. Also, a small scale test was performed to evaluate the solidification characteristic of the anti-washout grout mixed with coarse fill materials. It is also found that the strength of anti-washout grout mixed with coarse fill materials is greater and better segregation resistance than those of conventional grout with fill materials.

계면활성제 혼화제를 첨가한 시멘트 그라우트의 수중 불분리 특성 발현과 점도 증가 효과 연구

장인규 ( In Kyu Jang ),서승리 ( Seung Ree Seo ),박승규 ( Seung Kyu Park ) 한국공업화학회 2012 공업화학 Vol.23 No.5

구조재료로 사용되는 콘크리트란 시멘트, 모래, 자갈과 같은 고형분들이 물에 분산되어 있는 복합물질이다. 수중에 콘크리트 몰탈을 타설할때, 점탄성 특성이 우수하면 재료 분리가 적고, 물에 쓸려 내려가는 성질이 적고, 또 콘크리트가 잘충진되어 강도가 강화될 수 있다는 점에서 콘크리트의 레올로지 물성은 매우 중요하다. 본 연구에서는 음이온 계면 활성제, 양이온 계면활성제, 고분자계 증점제의 사용에 따른 콘크리트 첨가제의 최적 혼합 비율을 알아보았으며, 콘크 리트나 몰탈의 레올로지 물성의 변화와 수중불분리성에 대해 연구하였다. 음이온과 양이온 혼합계면활성제를 사용하는 pseudo-polymeric system을 적용한 콘크리트는 고점성이면서 수중불분리성은 우수하지만 펌핑성이 떨어지지만, 여기에 poly methyl vinyl ether (PMVE)를 소량 첨가하면 오히려 점도는 감소되면서 점탄성이 증가되고, 흐름성이 우수하며, 수중불분리성, 펌핑성 및 콘크리트 충진성이 향상되었다. Concrete, the mixture of cement, sand, gravel and water, is a suspension substance extensively used to construct building materials. When a concrete mortar is applied to the underwater construction, the rheology of concrete is of great importance to its flow performance, placement, anti-washout and consolidation. In this research, the anti-washout and rheological properties of concrete have been investigated with concrete admixtures prepared by adding anionic surfactants, cationic surfactants, and polymeric thickeners. The concrete mortar formulated by pseudo-polymeric systems with the electrostatic association of anionic and cationic surfactants, showed high viscosities and suitable anti-washout properties, but poor pumpabilities. The addition of poly methyl vinyl ether to the mixed surfactant system exhibits synergistic effects by improving the concrete mortar properties of the concrete mortar such as fluidity, visco-elastic property, self-leveling, and anti-washout.