• Title/Summary/Keyword: Mean Radius

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Internal Flow Analysis of Urea-SCR System for Passenger Cars Considering Actual Driving Conditions (운전 조건을 고려한 승용차용 요소첨가 선택적 촉매환원장치의 내부 유동 해석에 관한 연구)

  • Moon, Seong Joon;Jo, Nak Won;Oh, Se Doo;Lee, Ho Kil;Park, Kyoung Woo
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.40 no.3
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    • pp.127-138
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    • 2016
  • Diesel vehicles should be equipped with urea-selective catalytic reduction(SCR) system as a high-performance catalyst, in order to reduce harmful nitrogen oxide emissions. In this study, a three-dimensional Eulerian-Lagrangian CFD analysis was used to numerically predict the multiphase flow characteristics of the urea-SCR system, coupled with the chemical reactions of the system's transport phenomena. Then, the numerical spray structure was modified by comparing the results with the measured values from spray visualization, such as the injection velocity, penentration length, spray radius, and sauter mean diameter. In addition, the analysis results were verified by comparison with the removal efficiency of the nitrogen oxide emissions during engine and chassis tests, resulting in accuracy of the relative error of less than 5%. Finally, a verified CFD analysis was used to calculate the interanl flow of the urea-SCR system, thereby analyzing the characteristics of pressure drop and velocity increase, and predicting the uniformity index and overdistribution positions of ammonia.

Reconfirmation of age and growth of the pointhead flounder, Hippoglossoides pinetorum in the coastal waters of the East Sea off Gyeongbuk (경북 동해안산 용가자미 (Hippoglossoides pinetorum) 연령과 성장의 재확인)

  • JEONG, Yeon Kyu;KIM, Sung Tae;YOON, Sang Chul;YANG, Jae Hyeong;JUNG, Kyung Mi;OH, Taek Yun;CHOI, Kwang Ho
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.53 no.4
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    • pp.363-375
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    • 2017
  • The age and growth of pointhead flounder, Hippoglossoides pinetorum caught by gill nets was analyzed in this study from March 2015 to July 2017. New annuli were formed in H. pinetorum otoliths annually, and the boundary was set between the opaque and translucent zones from March and April. The relationships between total length (TL) and body weight (BW) were $BW=0.0025TL^{3.409}$ ($r^2=0.9551$) for females and $BW=0.0057TL^{3.138}$ ($r^2=0.9163$) for males. In this study, the ring of pointhead flounder, H. pinetorum was formed between 3 and 8 for females and between 3 and 6 for males. Total length (TL) and otolith radius (OR) were measured as follows: TL = 7.142 OR + 0.769 ($r^2=0.793$) for females and TL = 6.498 OR + 1.706 ($r^2=0.652$) for males. The mean distances of first ring ($r_1$) were 0.92 mm and 0.91 mm for females and males respectively. The TLs at the time of annulus formation, back-calculated from the otolith-length relationship by reference to the von Bertalanffy growth curves, were $L_t=43.59(1-e^{-0.15(t+0.007)})$ for females and $L_t=28.13(1-e^{-0.26(t+0.006)})$ for males while the growth between female and male was different.

A Study on Stability of Levee Revetment in Meandering Channel (만곡수로 내의 호안 안정성 연구)

  • Kim, Sooyoung;Yoon, Kwang Seok;Kim, Hyung-Jun
    • Journal of Korea Water Resources Association
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    • v.48 no.12
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    • pp.1077-1087
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    • 2015
  • The levee protect lifes, houses, and properties by blocking overflow of river. The revetment is forced to be covered on the slope of levee in order to prevent erosion. The stability of revetment is very important enough to directly connected to the stability of levee. In this study, the weak points of revetment on meandering channel were found by movable revetment experiment and the velocity and the water surface elevation (WSE) were measured at main points. The 3-D numerical simulations were performed under same conditions with experiment. And unclear flow characteristics by the limit of measuring instruments were analyzed through numerical simulation. Consequently, the section of large wall shear stress and the failure section are almost the same. Despite of small wall shear stress, the revetments located at right bank were carried away because of circulation zone due to secondary flow by meandering. With existing riprap design formula, the sizes of riprap determined using maximum local velocity were 1.5~4.7 times greater than them using mean velocity. As a result of this study, it is necessary to calculate the size of riprap in other ways for meandering and straight channel. At a later study, if the weighted value considered the radius of curvature and shape of hydraulic structure is applied to riprap design formula, it is expected that the size of revetment was evaluated rationally and accurately.

Cadmium and Zinc Uptake Characteristics of Corn Plant in Arable Soil Contaminated by Smelting Factory Source

  • Hong, Chang-Oh;Gutierrez, Jessie;Oh, Ju-Hwan;Lee, Yong-Bok;Yu, Chan;Kim, Pil-Joo
    • Korean Journal of Environmental Agriculture
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    • v.26 no.3
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    • pp.210-216
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    • 2007
  • The cadmium (Cd) and zinc (Zn) contamination of soils and cultivated crop plants by zinc smelting activities was studied. In the study area of the vicinity of ${\triangle}{\triangle}$ zinc smelting factory in Korea, soils and corn plants were sampled at corn harvesting stage and analyzed Cd and Zn concentration as well as Cd and Zn fraction and chemical properties in soils. At 600 m radius of studied area, Cd and Zn were highly accumulated in the surface soils (0 - 20 cm) showed greater than the Korean warning criteria (Cd 1.5, Zn 300 mg $kg^{-1}$) with corresponding values 1.7 and 407 mg $kg^{-1}$, respectively. The leaf part gave higher Cd concentration with the corresponding value of 9.5 mg $kg^{-1}$ as compared to the stem and grains pare (1.6 and 0.18 mg $kg^{-1}$), respectively. Higher Zn concentration was also obtained from the leaf part of the corn plant which gave the value of 1,733 mg $kg^{-1}$. The stem and grain part gave corresponding values of 547 and 61 mg $kg^{-1}$. The order of the mean Cd concentration in fractions is F3 (oxidizable fraction) > F2 (reducible fraction) > F4 (residual fraction) > F1 (exchangeable + acidic fraction). A highly positive correlation is observed between F2 and concentration of Cd and Zn in both plant pare, leaf and grain. Highly positive correlations are shown in the pH exchangeable Ca and Mg, and CEC when correlated with Cd and Zn bound to F4 fractions. To reduce Cd and Zn uptake by corn plant in an arable land heavily contaminated with Cd and Zn as affected by smelting factory, an efficient and effective soil management to increase soil pH and CEC is thus recommended.

Malignant Transformation of Benign Giant Cell Tumor (양성 거대 세포종의 악성 변화)

  • Kong, Chang-Bae;Hong, Yun-Suk;Lee, Kwang-Youl;Cho, Sang-Hyun;Song, Won-Seok;Cho, Wan-Hyeong;Koh, Jae-Soo;Jeon, Dae-Geun
    • The Journal of the Korean bone and joint tumor society
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    • v.18 no.1
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    • pp.14-19
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    • 2012
  • Purpose: We analyzed the oncologic outcome of the malignant transformed benign giant cell tumor of bone. Materials and Methods: Between January 2000 and February 2012, 5 cases were referred with suspicious malignant transformation of benign giant cell tumor. No patients underwent radiation therapy. Results: After referral, all patients received the wide excision of the tumor and its' pathologic diagnosis were osteosarcoma. As classified by the location of tumor lesion, 3 cases were located in the distal femur, 1 case was in the distal radius and 1 case was in the proximal femur. The average latent period between diagnosis of benign giant cell tumor and diagnosis of secondary malignant giant cell tumor was 49.2 months. (range, 24-126 months) The mean follow-up period was 21.6 months. There were subsequent local recurrence in 2 cases and 3 patients developed distant metastasis. All patients with lung metastasis were dead. Conclusion: Malignant transformation of benign giant cell tumor of bone can be occurred within 5 years. Therefore, when benign giant cell tumor suspicious malignant transformation, it is necessary to do more aggressive treatment.

Development of Two Dimensional Blade Section with High Efficiency for Marine Propeller (선박 프로펠러용 고효율 2차원 날개단면 개발)

  • Na, Yun-Cheol;Song, In-Haeng;Ahn, Jong-Woo
    • Journal of the Society of Naval Architects of Korea
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    • v.34 no.1
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    • pp.11-23
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    • 1997
  • This paper contains a new approach to blade section design method for marine propellers. The hydrodynamic characteristics of 2-D section are highly influenced by its geometrical parameters i.e., thickness and camber distributions and leading edge radius etc. To consider fully turbulent flow field near 2-D section. the finite volume method with k-${\varepsilon}$ turbulent model which solve Reynolds time averaged Navier-Stokes(RANS) equation is applied. In this study, O-type grid system that can provide many calculation points on blade surface is used. The results were compared with those of the experiment of NACA0012 to confirm the accuracy of the developed codes. The goal of this study is the development of a blade section with high efficiency and low drag. To achieve this, we carried out the tests of lift, drag and cavitation characteristics in cavitation tunnel. The results of experiment were compared with numerical results in order to validate the proposed blades design method. By comparing the numerical results with the experiments, we found that the new blade section, KH28 allows superior performance in efficiency and cavitation avoidance characteristics. We further investigated the blade section design method and an application study of this section, KH28 to apply to the marine propeller. In order to improve the accuracy of numerical results on prediction of lift and drag, we conclude here that the 2-layer boundary model must be used.

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Combined 1D/2D Inundation Simulation of Riverside Farmland using HEC-RAS (HEC-RAS를 이용한 하천변 농경지의 1, 2차원 연계 침수 모의)

  • Jun, Sang Min;Song, Jung-Hun;Choi, Soon-Kun;Lee, Kyung-Do;Kang, Moon Seong
    • Journal of The Korean Society of Agricultural Engineers
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    • v.60 no.5
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    • pp.135-147
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    • 2018
  • The objective of this study was to analyze the characteristics of combined 1D/2D inundation simulation of riverside farmland using the Hydrologic Engineering Center - River Analysis System (HEC-RAS). We compared and analyzed inundation simulation results between 1D and combined 1D/2D hydraulic simulation using HEC-RAS. Calibration and validation of stream stage were performed using three rainfall events. The coefficient of determination ($R^2$) and root mean square error (RMSE) between simulated and observed stream stage were 0.935 - 0.957 and 0.250 m - 0.283 m in calibration and validation, respectively. The inundation area showed no significant difference in 1D and combined 1D/2D simulation ($8.48km^2$ in 1D simulation, $8.75km^2$ in combined 1D/2D simulation). The average inundation depth by 1D simulation was 1.4 m deeper than combined 1D/2D simulation. In the lower inundation depth, the inundation area by combined 1D/2D simulation was larger than inundation area by 1D simulation. As the inundation depth increased, the inundation area by 1D simulation became wider. In the case of the 1D/2D combined simulation, low elevation areas along the river bank were inundated widely. Compared to 1D/2D combined simulation, the flood radius in some sections was longer in 1D simulation. In the 1D analysis, because the low altitude riverside farmlands are also assumed to stream, it is calculated that riverside farmlands have the same stage as the mainstream when the stream is overflowed. Therefore, the inundation area seems to be overestimated in those sections. In other regions, the inundation areas tend to be broken depending on overflow by each stream cross-section. In the case of river flooding, the overflow is expected to flow to the lower area depending on the terrain, such as the results of the combined 1D/2D simulation. It is concluded that the results of combined 1D/2D inundation simulation reflected the topographical characteristics of low-lying farmland.

A Study on Non-uniformity Correction Method through Uniform Area Detection Using KOMPSAT-3 Side-Slider Image (사이드 슬리더 촬영 기반 KOMPSAT-3 위성 영상의 균일 영역 검출을 통한 비균일 보정 기법 연구 양식)

  • Kim, Hyun-ho;Seo, Doochun;Jung, JaeHeon;Kim, Yongwoo
    • Korean Journal of Remote Sensing
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    • v.37 no.5_1
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    • pp.1013-1027
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    • 2021
  • Images taken with KOMPSAT-3 have additional NIR and PAN bands, as well as RGB regions of the visible ray band, compared to imagestaken with a standard camera. Furthermore, electrical and optical properties must be considered because a wide radius area of approximately 17 km or more is photographed at an altitude of 685 km above the ground. In other words, the camera sensor of KOMPSAT-3 is distorted by each CCD pixel, characteristics of each band,sensitivity and time-dependent change, CCD geometry. In order to solve the distortion, correction of the sensors is essential. In this paper, we propose a method for detecting uniform regions in side-slider-based KOMPSAT-3 images using segment-based noise analysis. After detecting a uniform area with the corresponding algorithm, a correction table was created for each sensor to apply the non-uniformity correction algorithm, and satellite image correction was performed using the created correction table. As a result, the proposed method reduced the distortion of the satellite image,such as vertical noise, compared to the conventional method. The relative radiation accuracy index, which is an index based on mean square error (RA) and an index based on absolute error (RE), wasfound to have a comparative advantage of 0.3 percent and 0.15 percent, respectively, over the conventional method.

Preparation of Polysulfone Composite Ultrafiltration Hollow Fiber Membranes Incorporating Nano-size Fumed Silica with Enhanced Antifouling Properties (나노 크기의 Fumed Silica가 함유된 Polysulfone 한외여과 중공사막 제조 및 내오염성 분석)

  • Kang, Yesol;Lim, Joohwan;Kim, In S.
    • Membrane Journal
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    • v.28 no.6
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    • pp.379-387
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    • 2018
  • This study was conducted to improve the membrane characteristics and performance by increasing hydrophilicity by adding additives to the ultrafiltration polysulfone (PSf) hollow fiber membrane. The mixed matrix membranes (MMMs) were prepared by dispersing 15 nm of fumed silica (FS) in the spinning solution at 0.1, 0.3 and 0.5 wt%. SEM analysis was carried out to confirm the cross-section and surface condition. It was confirmed that mean pore radius of the hollow fiber increased by 4 nm as FS was added. In addition, contact angle measurement was carried out for the hydrophilicity analysis of hollow fiber membranes, and it was confirmed that the hydrophilicity of MMMs were increased by adding of FS. In the case of water permeability, the membrane including FS showed 91~96 LMH and showed 5~11% more increase than PSf membrane. In the antifouling performance test, relative flux reduction ratios of FS mixed hollow fiber membranes were lower than that of PSf membranes, and it was confirmed that increase of hydrophilicity hinders adsorption of hydrophobic BSA on the membrane surface.

Statistical Characteristics of East Sea Mesoscale Eddies Detected, Tracked, and Grouped Using Satellite Altimeter Data from 1993 to 2017 (인공위성 고도계 자료(1993-2017년)를 이용하여 탐지‧추적‧분류한 동해 중규모 소용돌이의 통계적 특성)

  • LEE, KYUNGJAE;NAM, SUNGHYUN;KIM, YOUNG-GYU
    • The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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    • v.24 no.2
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    • pp.267-281
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    • 2019
  • Energetic mesoscale eddies in the East Sea (ES) associated with strong mesoscale variability impacting circulation and environments were statistically characterized by analyzing satellite altimeter data collected during 1993-2017 and in-situ data obtained from four cruises conducted between 2015 and 2017. A total of 1,008 mesoscale eddies were detected, tracked, and identified and then classified into 27 groups characterized by mean lifetime (L, day), amplitude (H, m), radius (R, km), intensity per unit area (EI, $cm^2/s^2/km^2$), ellipticity (e), eddy kinetic energy (EKE, TJ), available potential energy (APE, TJ), and direction of movement. The center, boundary, and amplitude of mesoscale eddies identified from satellite altimeter data were compared to those from the in-situ observational data for the four cases, yielding uncertainties in the center position of 2-10 km, boundary position of 10-20 km, and amplitude of 0.6-5.9 cm. The mean L, H, R, EI, e, EKE, and APE of the ES mesoscale eddies during the total period are $95{\pm}104$ days, $3.5{\pm}1.5cm$, $39{\pm}6km$, $0.023{\pm}0.017cm^2/s^2/km^2$, $0.72{\pm}0.07$, $23{\pm}21TJ$, and $588{\pm}250TJ$, respectively. The ES mesoscale eddies tend to move following the mean surface current rather than propagating westward. The southern groups (south of the subpolar front) have a longer L, larger H, R, and higher EKE, APE; and stronger EI than those of the northern groups and tend to move a longer distance following surface currents. There are exceptions to the average characteristics, such as the quasi-stationary groups (the Wonsan Warm, Wonsan Cold, Western Japan Basin Warm, and Northern Subpolar Frontal Cold Eddy groups) and short-lived groups with a relatively larger H, higher EKE, and APE and stronger EI (the Yamato Coastal Warm, Central Yamato Warm, and Eastern Japan Basin Coastal Warm eddy groups). Small eddies in the northern ES hardly resolved using the satellite altimetry data only, were not identified here and discussed with potential over-estimations of the mean L, H, R, EI, EKE, and APE. This study suggests that the ES mesoscale eddies 1) include newly identified groups such as the Hokkaido and the Yamato Rise Warm Eddies in addition to relatively well-known groups (e.g., the Ulleung Warm and the Dok Cold Eddies); 2) have a shorter L; smaller H, R, and lower EKE; and stronger EI and higher APE than those of the global ocean, and move following surface currents rather than propagating westward; and 3) show large spatial inhomogeneity among groups.