• Asian Journal of Atmospheric Environment
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• 제11권4호
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• pp.313-321
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• 2017

$PM_{10}$ and $PM_{2.5}$ were collected at the Gosan Site on Jeju Island from 2013 to 2015, and their ionic and elemental species were analyzed to examine the variations in their chemical compositional characteristics related to different meteorological conditions. Concentrations of nss-$SO_4{^{2-}}$ and $NH_4{^+}$ were respectively 6.5 and 4.7 times higher in the fine particle mode ($PM_{2.5}$) compared to the coarse particle mode ($PM_{10-2.5}$), however $NO_3{^-}$ concentrations were 2.4 times higher in the coarse mode compared to the fine particle mode. During Asian dust days, the concentrations of nss-$Ca^{2+}$ and $NO_3{^-}$ increased to 8.2 and 5.0 times higher in $PM_{10}$, and 3.5 and 6.0 times higher in $PM_{2.5}$, respectively. During haze days, the concentrations of secondary pollutants increased by 3.1-4.7 and 3.2-7.9 in $PM_{10}$ and $PM_{2.5}$, respectively, and they were, respectively, 1.2-2.1 and 0.9-2.1 times higher on mist days. The aerosols were acidified largely by sulfuric and nitric acids, and neutralized mainly by ammonia in the fine particle mode during the haze days, but neutralized by calcium carbonate in coarse particle mode during the Asian dust days. Clustered back trajectory analysis showed that concentrations of nss-$SO_4{^{2-}}$, $NO_3{^-}$, and $NH_4{^+}$ were relatively high when air masses travelled from China.

• 한국대기환경학회지
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• 제24권2호
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• pp.162-175
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• 2008

Gyeongju, which was the central city of the ancient civilization at Silla Kingdom, has various kinds of stone cultural properties. It is significantly important to preserve historical sources of Korea. However, recent air quality data measured in Gyeongju did not show good air quality level. In order to investigate variation of the concentration of the air pollutants with meteorological condition, an air quality monitoring and an aerosol sampling were conducted during the intensive monitoring period in Gyeongju. Impacts of the meteorological factors on the air pollutants were also analyzed based on the air mass pathway categories using HYSPLIT model and the local wind patterns using MM5 model. The prevailing air mass pathways were classified into four categories as following; category I affected by easterly marine aerosols, category II affected by northwesterly continental aerosols, category III affected by southwesterly continental aerosols, and category IV affected by northerly continental aerosols. The concentrations of the air quality standards were relatively lower during the fall intensive monitoring period. At that time, the easterly marine air mass pattern was dominated. The seasonal average mass concentration of $PM_{10,Opt}$, which optically measured at the monitoring site, was the highest value of $77.6{\pm}28.3\;{\mu}g\;m^{-3}$ during the spring intensive monitoring period but the lowest value of $20.1{\pm}5.3\;{\mu}g\;m^{-3}$ during the fall intensive monitoring period. The concentrations of $SO_2$ and CO were relatively higher when the air mass came from the northwestern continent or the northern continent. The concentrations of ${SO_4}^{2-}$ and ${NO_3}^-$ increased under the northwesterly continental condition. It was estimated that the acidic aerosols were dominated in the atmosphere of Gyeongju when the air mass came from the continental regions.

• 한국대기환경학회지
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• 제28권2호
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• pp.142-158
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• 2012

This paper investigates the physical and chemical characteristics of long-range transport (LRT) process of air pollutants by employing the MM5-CMAQ and its comparison with local emission dominant (LED) case over northeast Asia. We first classified high air pollution days into LRT and LED cases based on the synoptic meteorological variables of vorticity and geostrophic wind speed/direction at a geopotential level of over 850hPa. LRT cases are further categorized into three types of transport patterns (LRT-I-III) according to the air mass pathways from source regions. LRT-I-III are originated from northern, central, and southern China, respectively, identified by back trajectory analysis. Three LRT-I-III groups have different and unique locations of high pressure and transport pathways. The chemical characteristics showed that the simulated spatial distributions varied in terms of locations of maximum concentrations and the temporal variation of surface concentrations. The primary air pollutants such as $NO_x$, $PM_{10}$ and $SO_2$ of all of three LRT cases are well transported into Korea peninsula with different concentration levels. Of LRT cases, LRT-II has the greatest effect on air quality of Korea peninsula, followed by LRT-I and LRT-III. In comparison with LRT, the LED case shows relatively higher air pollution concentrations in general, but showed a variety of different air quality levels following the emission strength pattern. These widely varying patterns are impling the case dependent multi-directional approach for the development of indicators of long-range transport process over northeast Asia.

• Journal of Korean Neurosurgical Society
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• 제60권6호
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• pp.755-762
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• 2017

Objective : The purpose of this study is to describe the detailed surgical technique and short-term clinical and radiological outcomes of lateral lumbar interbody fusion (LLIF) and in situ lateral screw fixation using a conventional minimally invasive screw fixation system (MISF) for revision surgery to treat rostral lumbar adjacent segment disease. Methods : The medical and radiological records were retrospectively reviewed. The surgery was indicated in 10 consecutive patients with rostral adjacent segment stenosis and instability. After the insertion of the interbody cage, lateral screws were inserted into the cranial and caudal vertebra using the MISF through the same LLIF trajectory. The radiological and clinical outcomes were assessed preoperatively and at 1, 3, 6, and 12 months postoperatively. Results : The median follow-up period was 13 months (range, 3-48 months). Transient sensory changes in the left anterior thigh occurred in 3 patients, and 1 patient experienced subjective weakness; however, these symptoms normalized within 1 week. Back and leg pain were significantly improved (p<0.05). In the radiological analysis, both the segmental angle at the operated segment and anterior disc height were significantly increased. At 6 months postoperatively, solid bony fusion was confirmed in 7 patients. Subsidence and mechanical failure did not occur in any patients. Conclusion : This study demonstrates that LLIF and in situ lateral screw fixation may be an alternative surgical option for rostral lumbar adjacent segment disease.

• 제어로봇시스템학회논문지
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• 제12권9호
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• pp.926-934
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• 2006

This paper proposes intelligent control of a virtual walking machine that can generate infinite floor for various surfaces and can provide proprioceptive feedback of walking to a user. This machine allows users to participate in a life-like walking experience in virtual environments with various terrains. The controller of the machine is implemented hierarchically, at low-level for robust actuator control, at mid-level fur platform control to compensate the external forces by foot contact, and at high-level control for generating walking trajectory. The high level controller is suggested to generate continuous walking on an infinite floor for various terrains. For the high level control, each independent platform follows a man foot during the swing phase, while the other platform moves back during single stance phase. During double limb support, two platforms manipulate neutral positions to compensate the offset errors generated by velocity changes. This control can, therefore, satisfy natural walking conditions in any direction. Transition phase between the swing and the stance phases is detected by using simple switch sensor system, while human foot motions are sensed by careful calibration with a magnetic motion tracker attached to the shoe. Experimental results of walking simulations at level ground, slope, and stairs, show that with the proposed machine, a general person can walk naturally on various terrains with safety and without any considerable disturbances. This interface can be applied to various areas such as VR navigations, rehabilitation, and gait analysis.

• 분석과학
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• 제33권1호
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• pp.33-41
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• 2020

Wet precipitation samples were collected in Jeju City and Mt. Halla-1100 site (a site at an altitude of 1100 m on Mt. Halla) during 2011-2013, and their major ionic species were analyzed to examine the chemical composition and characteristics. A comparison of ion balance, electric conductivity, and acid fraction of precipitation revealed correlation coefficients in the range of r = 0.950~0.991, thereby implying the high quality of analytical data. Volume-weighted mean pH and electric conductivity corresponded to 4.86 and 25.5 µS/cm for Jeju City, and 4.98 and 15.1 µS/cm for Mt. Halla-1100 site, respectively. Ionic strengths of the wet precipitation in Jeju City and Mt. Halla-1100 site corresponded 0.3 ± 0.5 and 0.2 ± 0.2 mM, respectively, thereby indicating that more than 30 % of total precipitation was within a pure precipitation criteria. The precipitation with a pH range of 4.5 - 5.0 corresponded to 40.8 % in Jeju City, while the precipitation with a pH range of 5.0 - 5.5 corresponded to 56.9 % in Mt. Halla-1100 site, thereby indicating slightly more weak acidity than that in Jeju city. The volume-weighted mean concentration (µeq/L) of ionic species was in the order of Na⁺ > Cl^- > nss-SO₄^2- > NO₃^- > Mg²⁺ > NH₄⁺ > H⁺ > nss-Ca²⁺ > PO₄^3- > K⁺ > CH₃COO^- > HCOO^- > NO₂^- > F^- > HCO₃^- > CH₃SO₃^- at Jeju City area, while it corresponded to Na⁺ > Cl^- > nss-SO₄^2- > NO₃^- > NH₄⁺ > H⁺ > Mg²⁺ > nss-Ca²⁺ > PO₄^3- > CH₃COO^- > K⁺ > HCOO^- > NO₂^- > F^- > HCO₃^- > CH₃SO₃^- at Mt. Halla-1100 site. The compositions of sea salts (Na⁺, Cl^-, Mg²⁺) and secondary pollutants (NH₄⁺, nss-SO₄^2-, NO₃^-) corresponded to 66.1 % and 21.8 %, respectively, in Jeju City and, 49.9 % and 31.5 %, respectively, in Mt. Halla-1100 site. The acidity contributions in Jeju City and Mt. Halla-1100 site by inorganic acids, i.e., sulfuric acid and nitric acid, corresponded to 93.9 % and 91.4 %, respectively, and the acidity contributions by organic acids corresponded to 6.1 % and 8.6 %, respectively. The neutralization factors in Jeju City and Mt. Halla1100 site by ammonia corresponded to 29.8 % and 30.1 %, respectively, whereas the neutralization factors by calcium carbonate corresponded to 20.5 % and 25.2 %, respectively. From the clustered back trajectory analysis, the concentrations of most ionic components were higher when the airflow pathways were moved from the continent to Jeju area.

• 한국콘텐츠학회논문지
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• 제21권3호
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• pp.567-575
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• 2021

석탄화력발전소, 제철소 등 대규모 배출시설이 밀집되어 있는 충청남도 당진시는 지자체 차원에서 대기질 개선과 온실가스 감축 등을 위해 적극 노력하고 있음에도 불구하고 시민들의 건강에 대한 우려가 높다. 이에 본 연구에서는 석탄화력발전소와 외부요인 등이 지역 대기오염에 미치는 영향 파악을 위해 일반적으로 미세먼지 또는 초미세먼지 등의 기원 추적자로 이용하는 탄소 안정동위원소를 활용하여 지역 오염원의 기원을 추정하였다. 또한, 석탄화력발전소로부터의 이격거리를 고려하여 선정한 2지점에 대한 계절별 실측데이터와 선행연구 분석을 통해 구축한 라이브러리 및 역궤적 분석으로 오염원의 기원을 해석하였다. 탄소 안정동위원소비의 분석결과 겨울 > 봄 > 가을 > 여름 순으로 고농도 경향성을 보였으며, 라이브러리와의 매칭결과 이동오염원과 노천소각의 영향이 상대적으로 높은 것으로 분석되었다. 본 연구는 시범연구로 지속적인 모니터링과 데이터 축적을 통한 연구결과의 신뢰성 확보에 주력해야 할 것으로 판단된다.

• 분석과학
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• 제27권4호
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• pp.213-222
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• 2014

국내 배경지역인 제주도 고산측정소에서 2012~2013년에 대기 미세먼지를 채취하여 분석한 결과로부터 연무와 비현상일의 조성특성을 조사하였다. 연무 시 $nss-SO_4{^{2-}}$, $NO_3{^-}$, $NH_4{^+}$ 농도는 비현상일에 비해 조대입자에서 2.1~3.7배, 미세입자에서 3.1~6.5배로 미세입자에서 더 높게 증가하였고, 특히 $NO_3{^-}$ 농도가 미세입자에서 6.5배 상승하였다. 원소성분들 중에는 S, Zn, Pb, K 등이 비현상일보다 조대입자에서 3.0~5.6배, 미세입자에서 3.2~7.7배 증가하나 Al, Fe, Ca 등은 대부분 조대입자에서 농도가 크게 증가하는 경향을 보였다. 역궤적 분석 결과 연무 시 $nss-SO_4{^{2-}}$, $NO_3{^-}$ 농도는 중국으로부터 유입되었을 때 더 높은 농도를 나타내었고, 특히 기류가 중국남부를 통과했을 때 $NO_3{^-}$ 농도가 더 크게 상승하는 경향을 보였다. 또 $NO_3{^-}/nss-SO_4{^{2-}}$ 농도비는 중국에서 기류가 이동했을 때 조대입자에서 상대적으로 높은 비율을 보이나 미세입자에서는 오히려 한반도를 통과했을 때 더 높은 성분비를 나타내었다.

• 지구물리
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• 제9권4호
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• pp.361-369
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• 2006

본 연구에서는 AHRS IMU 센서를 이용하여 동적 위치 결정을 위해 초기화 시험을 실시하여 회귀분석을 통해 시간에 대한 이동체의 자세 보정각에 대해 유도하였으며, 동체 방향(Heading)각의 경우 60sec를 지난 후 1°이내의 변동률로 안정되는 것을 알 수 있었다. 이를 바탕으로 개할지와 준개할지로 구분하여 각 시스템 단독으로 동적 위치결정을 실험한 결과 개할지의 DGPS 단독 시스템인 경우 정확도 면에서는 우수하였지만 데이터 취득이 미비하여 이동간 거리가 12m 내외임을 알 수 있었으며, DGPS/IMU 결합 시스템의 경우 정확도와 데이터 취득 및 이동간 거리가 0.3m 내외임을 알 수 있었다. 준개할지에서 DGPS 단독 시스템의 경우 데이터 취득이 불가능한 곳을 제외하고 평균과 표준 오차를 구한 결과 DGPS〈 FIMU〈 DGPS/IMU 순으로 정확도가 우수한 것을 알 수 있었으며 이동간 거리는 개할지와 마찬가지였다. 그리고 DGPS의 경우 데이터 취득이 불가능한 곳을 여러 구간으로 비교하였을 때 DGPS 단독 시스템의 경우 최대 41.5m 가량 궤적에서 벗어나지만 결합 시스템의 경우 최대 2.2m 이내에 궤적을 구할 수 있었으며, 평균과 표준 오차를 크게 향상시킬 수 있었다. 이러한 항법 시스템을 결합하여 측량분야에 응용해 수치도화 작업내규의 지도에서 위치오차 0.2mm 오차와 비교하였을 때 축척 1 : 1,000 수치지도 작업까지도 가능한 것을 알 수 있었다.

• 한국대기환경학회지
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• 제32권1호
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• pp.67-81
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• 2016

In order to examine the variation characteristics of chemical compositions in accordance with the different meteorological conditions, $PM_{10}$ and $PM_{2.5}$ were collected at Gosan site of Jeju Island in 2014, and then their ionic and elemental species were analyzed. The concentrations of nss-$SO{_4}^{2-}$ and $NH_4{^+}$ were respectively 4.3 and 3.3 times higher in fine particle mode ($PM_{2.5}$) compared to coarse particle mode ($PM_{10-2.5}$), however $NO_3{^-}$ concentration was 1.6 times higher in coarse mode compared to fine particle mode. During Asian dust days, the concentrations of nss-$Ca^{2+}$ and $NO_3{^-}$ increased highly as 7.7 and 4.5 times in coarse particle mode, and 3.0 and 4.9 times higher in fine particles, respectively. Especially, the concentrations of the crustal species (Al, Fe, Ca, K, Mn, Ba, Sr, etc.) indicated a noticeable increase during the Asian dust days. For the haze days, the concentrations of secondary pollutants increased 2.2~2.7 and 2.9~6.0 times in coarse and fine particles, respectively, and they were 0.8~1.1 and 1.8~2.4 times, respectively, during the mist days. The aerosols were acidified largely by sulfuric and nitric acids, and neutralized mainly by ammonia in fine particle mode during the haze days, but neutralized by calcium carbonate in coarse particle mode during the Asian dust days. The clustered back trajectory analysis showed that the concentrations of nss-$SO{_4}^{2-}$, $NO_3{^-}$, and $NH_4{^+}$ were relatively high when the inflow pathway of air mass was from the southern part of China.