• Title/Summary/Keyword: Inversion intensity

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Nocturnal Inversion Layer observed by Tethersonde and AWS System and its Relation to Air Pollution at Ulsan (Tethersonde와 기상탑 관측 자료를 이용한 울산지역 야간 역전에 따른 대기오염도 변화와의 관계)

  • Lim Yun-Kyu;Kim Yoo-Keun;Oh In-Bo;Song Sang-Keun
    • Journal of Environmental Science International
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    • v.14 no.6
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    • pp.555-563
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    • 2005
  • This study presents the characteristics of nocturnal inversion layer and their effect on the concentration variations of surface air pollutants using tethersonde and automatic weather station (AWS, 2 layer tower) system in Ulsan during 2003, The method for the distinction of inversion intensity was decided based on the sum of nocturnal temperature gradient. As the results, there was a close correlation (correlation coefficient of 0,76) between the maximum inversion height obtained from tethersonde and the sum of nocturnal temperature gradient. The air pollutant concentration was also directly proportional to the inversion intensity. When the inversion intensity was strong in the nighttime, ozone $(O_3)$ concentration was lower, while nitrogen dioxide $(NO_2)$ concentration was higher. The carbon monoxide (CO) concentration was gradually higher according to the nocturnal inversion intensity, whereas sulfur dioxide $(SO_2)$ concentration was relatively constant. In addition, we found that there was no correlation between the inversion intensity and TSP concentration.

Meteorological Factors Affecting Winter Particulate Air Pollution in Ulaanbaatar from 2008 to 2016

  • Wang, Minrui;Kai, Kenji;Sugimoto, Nobuo;Enkhmaa, Sarangerel
    • Asian Journal of Atmospheric Environment
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    • v.12 no.3
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    • pp.244-254
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    • 2018
  • Ulaanbaatar, the capital of Mongolia, is subject to high levels of atmospheric pollution during winter, which severely threatens the health of the population. By analyzing surface meteorological data, ground-based LIDAR data, and radiosonde data collected from 2008 to 2016, we studied seasonal variations in particulate matter (PM) concentration, visibility, relative humidity, temperature inversion layer thickness, and temperature inversion intensity. PM concentrations started to exceed the 24-h average standard ($50{\mu}g/m^3$) in mid-October and peaked from December to January. Visibility showed a significant negative correlation with PM concentration. Relative humidity was within the range of 60-80% when there were high PM concentrations. Both temperature inversion layer thickness and intensity reached maxima in January and showed similar seasonal variations with respect to PM concentration. The monthly average temperature inversion intensity showed a strong positive correlation with the monthly average $PM_{2.5}$ concentration. Furthermore, the temperature inversion layer thickness exceeded 500 m in midwinter and overlaid the weak mixed layer during daytime. Radiative cooling enhanced by the basin-like terrain led to a stable urban atmosphere, which strengthened particulate air pollution.

INTENSITY VARIATION OF THE SiO MASER LINE OF LONG PERIOD VARIABLES : MASER PUMPING MECHANISM (장주기 변광성의 SiO 메이저 선 세기 변화 연구 : 메이저 펌핑 기작)

  • Kim, Eun-Hyeok;Lee, Sang-Gak
    • Publications of The Korean Astronomical Society
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    • v.8 no.1
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    • pp.83-104
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    • 1993
  • In principle, both radiation and collision are capable of pumping the SiO masers. In order to check which pumping mechanism is more efficient, we calculated the rate equation for our model including the 3 vibrational slates with 7 rotational states of each vibrational slate. Through solving the radiative transfer equation with the Sovolev approximation, we estimated the line profiles from an expanding envelope for several transitions. It is found that the collision works more efficiently than the radiation for the inversion in excited vibrational stales. However in an expanding envelope model we could not get the strong line intensity as observed one because the population inversion is possible only in a small restricted region. For the enough population inversion to get type observed maser intensity. the number density of SiO and hydrogen molecules should be up to about $2{\times}10^5\;cm^{-3}$ and $1{\times}10^9\;cm^{-3}$, respectively, and the inversion should be occured in the region of no Jess than 11014cm.

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A Study on the Characteristics of Inversion Layer Observed at Kimhae (김해에서 관측한 접지역전층의 특성에 관한 연구)

  • 박종길;원경미
    • Journal of Environmental Science International
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    • v.3 no.4
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    • pp.305-315
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    • 1994
  • The field observation was carried out to investigate the characteristics of surface inversion layer at Kimhae using the feild observed date and upper layer meteorological data during 4-5 February 1993. The results of the study can be summarized as follows : The maximum height of surface inversion layer observed at Kimhae is 193m and the height of upper level inversion layer ranges from 2nm to 300m. The surface weather elements was influenced the formation of surface inversion layer. According to the pasquill stability and time variation of temperature with height, both the surface heating from insolation and the disturbance of upper level of inversion layer was influenced the disappearance of inversion layer. And the stability of surface temperature inversion layer generally belongs to the class of F, that of upper level temperature inversion layer commonly to the class of E.

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SRS Inversion of Flame Temperature/concentration Profile with Radiation/Turbulence Interaction (복사/난류간 상호작용이 고려된 화염의 온도 및 농도분포의 SRS 역계산)

  • Ko, Ju-Yong;Kim, Hyun-Keol;Song, Tae-Ho
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.30 no.9 s.252
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    • pp.891-897
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    • 2006
  • The SRS method is applied to a turbulent flame with radiation/turbulence interaction to invert the temperature and concentration profile. The flame is conditioned as optically thin per each fluctuation length and the flame spectral intensity is measured for inversion. From inversion result, we find that SRS can successfully invert the coupled temperature/concentration fluctuation amplitudes. For two cases of experiments, inverted values are within approximately 1% over the full range of fluctuation amplitude. However, SRS cannot find the detailed local fluctuation parameters such as pattern and phase, etc. as far as they do not affect the resulting radiation intensity. Important available parameters are the mean temperature and the temperature fluctuation amplitude. The radiation/turbulence interaction effect is verified to play an important role in the radiation.

Cross Phase Modulation Effects on 120 Gbps WDM Transmission Systems with Mid-Span Spectral Inversion for Compensation of Distorted Optical Pulse (광 펄스 왜곡의 보상을 위해 Mid-Span Spectral Inversion 기법을 채택한 120 Gbps WDM 시스템에서 채널간 상호 위상 변조 현상의 영향)

  • 이성렬;권순녀;이윤현
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.14 no.7
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    • pp.741-749
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    • 2003
  • In this paper, we investigated the degree of compensation for WDM channel signal distortion due to chromatic dispersion, self phase modulation(SPM) and cross phase modulation(XPM). The considered system is 120 Gbps (3${\times}$40 Gbps) intensity modulation direct detection(IM/DD) WDM transmission system with path-averaged intensity approximation(PAIA) mid-span spectral inversion(MSSI) as compensation method. This system have highly nonlinear dispersion shifted fiber(HNL-DSF) as nonlinear medium in optical phase conjugator(OPC). We use 1 dB eye opening peralty(EOP) in order to evaluate the characteristics of compensation for distorted WDM channels. We confirmed that improvement of transmission distance and performance is achieved by MSSI method to distorted long-haul IM/DD WDM channels due to chromatic dispersion, SPM and XPM. And in the aspect of compensation for distorted pulse due to XPM, the MSSI method is effective to IM/DD WDM transmission system with high fiber dispersion coefficient.

Wideband Optical Phase Conjugator using HNL-DSF in WDM Systems with Path-Averaged Intensity Approximation Mid-Span Spectral Inversion (경로 평균 강도 근사 기법의 MSSI를 채택한 WDM 시스템에서 HNL-DSF를 갖는 광대역 광 위상 공액기)

  • Lee, Seong-Real;Lee, Yun-Hyun
    • Journal of Advanced Navigation Technology
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    • v.7 no.1
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    • pp.14-21
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    • 2003
  • We investigated the optimum pump light power compensating distorted WDM signal due to both chromatic dispersion and self phase modulation (SPM). The considered system is $3{\times}40$ Gbps intensity modulation direct detection (IM/DD) WDM transmission system with path-averaged intensity approximation (PAIA) mid-span spectral inversion (MSSI) as compensation method. This system have highly nonlinear dispersion shifted fiber (HNL-DSF) as nonlinear medium of optical phase conjugator (OPC) in the mid-way of total transmission line. We confirmed that HNL-DSF is an useful nonlinear medium in OPC for wideband WDM transmission, and the excellent compensation is obtained when the pump light power of HNL-DSF OPC was selected to equalize the conjugated light power into the second half fiber section with the input WDM signal light power depending on total transmission length. By this approach, it is verified the possibility to realize a long-haul high capacities WDM system by using PAIA MSSI compensation method, which have HNL-DSF OPC with optimal pump light power depending on transmission length.

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Elimination of car's magnetic effect as noise in a car-borne magnetic exploration system (차량 자력탐사에서 차량의 영향의 제거)

  • Lim, Mu-Taek;Park, Yeong-Sue;Chung, Hyun-Key;Rim, Hyoung-Rae;Koo, Sung-Bon;Lee, Young-Chal
    • 한국지구물리탐사학회:학술대회논문집
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    • 2006.06a
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    • pp.141-151
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    • 2006
  • A blank test was done to calculatee the car itself's magnetic effect as noise and to eliminate it from the data set of total magnetic intensity(=magnetic flux density) exploration in a car-borne magnetic exploration system. To calculate the induced magnetic intensity(= magnetization) and the remanent magnetic intensity(= magnetization) of the car itself, we have installed the magnetometer on a fixed point and measured the magnetic intensity letting the car move around the magnetometer, and we have changed the data set into an analogous data set as if acquired in the condition that we have parked the car on the same fixed point and measured the magnetic intensity moving the magnetometer around the magnetometer. Through an inversion with the later data set as input, we have calculated the magnetic center and the magnetic moments of the induced magnetic intensity(= magnetization) and the remanent magnetic intensity(= magnetization) of the car itself with the two centers coincided because of some barriers of the inversion algorithm that we have used in this study. On the other hand, we have extracted the magnetic anomaly by reducing i. e. vectorially eliminating the induced magnetic intensity(= magnetization) and the remanent magnetic intensity(= magnetization) of the car itself calculated forwardly, from the magnetic exploration data set acquired by the car-borne magnetic exploration system.

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Compensation of Distorted WDM signals due to Cross Phase Modulation Effects using Mid-Span Spectral Inversion (상호 위상 변조에 의해 왜곡된 WDM 신호의 Mid-Span Spectral Inversion을 이용한 보상)

  • Lee, Seong-Real
    • Journal of Advanced Navigation Technology
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    • v.7 no.2
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    • pp.128-134
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    • 2003
  • In this paper, we investigated the degree of compensation for WDM channel signal distortion due to chromatic dispersion, self phase modulation (SPM) and cross phase modulation (XPM) as a function of transmission length using mid-span spectral inversion (MSSI) compensation method. The considered system is $3{\times}40$ Gbps intensity modulation direct detection (IM/DD) WDM transmission system. This system has highly nonlinear dispersion shifted fiber (HNL-DSF) as a nonlinear medium in optical phase conjugator (OPC). We confirmed that the transmission length is more increased by applying MSSI to distorted signal due to chromatic dispersion, SPM and XPM as dispersion coefficient of fiber becomes higher. And the compensation degree of distorted WDM channels due to chromatic dispersion, SPM and XPM becomes better stable as dispersion coefficient of fiber becomes higher.

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A Potential Diagnostic Pitfall in the Differentiation of Hemorrhagic and Fatty Lesions Using Short Inversion Time Inversion Recovery: a Case Report

  • Kim, Jee Hye;Kang, Woo Young;Cho, Bum Sang;Yi, Kyung Sik
    • Investigative Magnetic Resonance Imaging
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    • v.20 no.3
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    • pp.181-184
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    • 2016
  • Short inversion time inversion recovery (STIR) is widely used for spinal magnetic resonance imaging (MRI) because the pulse sequence of STIR is insensitive to magnetic field inhomogeneity and can be used to scan a large field of view. In this case report, we present a case of spinal epidural hematoma with unexpected signal decrease on a STIR image. The MRI showed an epidural mass that appeared with high signal intensity on both T1- and T2-weighted images. However, a signal decrease was encountered on the STIR image. This nonspecific decrease of signal in tissue with a short T1 relaxation time that is similar to that of fat (i.e., hemorrhage) could lead to a diagnostic pitfall; one could falsely diagnose this decrease of signal as fat instead of hemorrhage. Awareness of the nonselective signal suppression achieved with STIR pulse sequences may avert an erroneous diagnosis in image interpretation.