• Title/Summary/Keyword: carrier model

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Ionosphere Modeling and Estimation Using Regional GPS Data (지역적인 GPS 관측 데이터를 이용한 이온층 모델링 및 추정)

  • 황유라;박관동;박필호;임형철;조정호
    • Korean Journal of Remote Sensing
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    • v.19 no.4
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    • pp.277-284
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    • 2003
  • We present a GPS-derived regional ionosphere model, which estimates Total Electron Content (TEC) in a rectangular grid on the spherical shell over Korea. After dividing longitude and latitude over Korea with 1$^{\circ}$$\times$1$^{\circ}$ spatial resolution, the TEC at the vertex of the grid was estimated by the Kalman filter. The GPS data received from nine nationwide GPS stations, operated by Korea Astronomy Observatory (KAO), were used for this study. To reduce inherent noises, the pseudorange data were phase-leveled by a linear combination of pseudoranges and carrier phases. The solar-geomagnetic reference frame, which is less variable to the ionosphere movement due to the Sun and the geomagnetic field than an Earth-fixed frame, was used. During a quiet time of solar activity, the KAO's regional ionosphere map indicated 30-45 Total Electron Content Unit at the peak of the diurnal variation. In comparison with the Global ionosphere Map of the Center for Orbit Determination in Europe, RMS differences were at the level of 4-5 TECU for five days.

3D Explosion Analyses of Hydrogen Refueling Station Structure Using Portable LiDAR Scanner and AUTODYN (휴대형 라이다 스캐너와 AUTODYN를 이용한 수소 충전소 구조물의 3차원 폭발해석)

  • Baluch, Khaqan;Shin, Chanhwi;Cho, Yongdon;Cho, Sangho
    • Explosives and Blasting
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    • v.40 no.3
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    • pp.19-32
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    • 2022
  • Hydrogen is a fuel having the highest energy compared with other common fuels. This means hydrogen is a clean energy source for the future. However, using hydrogen as a fuel has implication regarding carrier and storage issues, as hydrogen is highly inflammable and unstable gas susceptible to explosion. Explosions resulting from hydrogen-air mixtures have already been encountered and well documented in research experiments. However, there are still large gaps in this research field as the use of numerical tools and field experiments are required to fully understand the safety measures necessary to prevent hydrogen explosions. The purpose of this present study is to develop and simulate 3D numerical modelling of an existing hydrogen gas station in Jeonju by using handheld LiDAR and Ansys AUTODYN, as well as the processing of point cloud scans and use of cloud dataset to develop FEM 3D meshed model for the numerical simulation to predict peak-over pressures. The results show that the Lidar scanning technique combined with the ANSYS AUTODYN can help to determine the safety distance and as well as construct, simulate and predict the peak over-pressures for hydrogen refueling station explosions.

Investigation of Applying Technical Measures for Improving Energy Efficiency Design Index (EEDI) for KCS and KVLCC2

  • Jun-Yup Park;Jong-Yeon Jung;Yu-Taek Seo
    • Journal of Ocean Engineering and Technology
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    • v.37 no.2
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    • pp.58-67
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    • 2023
  • While extensive research is being conducted to reduce greenhouse gases in industrial fields, the International Maritime Organization (IMO) has implemented regulations to actively reduce CO2 emissions from ships, such as energy efficiency design index (EEDI), energy efficiency existing ship index (EEXI), energy efficiency operational indicator (EEOI), and carbon intensity indicator (CII). These regulations play an important role for the design and operation of ships. However, the calculation of the index and indicator might be complex depending on the types and size of the ship. Here, to calculate the EEDI of two target vessels, first, the ships were set as Deadweight (DWT) 50K container and 300K very large crude-oil carrier (VLCC) considering the type and size of those ships along with the engine types and power. Equations and parameters from the marine pollution treaty (MARPOL) Annex VI, IMO marine environment protection committee (MEPC) resolution were used to estimate the EEDI and their changes. Technical measures were subsequently applied to satisfy the IMO regulations, such as reducing speed, energy saving devices (ESD), and onboard CO2 capture system. Process simulation model using Aspen Plus v10 was developed for the onboard CO2 capture system. The obtained results suggested that the fuel change from Marine diesel oil (MDO) to liquefied natural gas (LNG) was the most effective way to reduce EEDI, considering the limited supply of the alternative clean fuels. Decreasing ship speed was the next effective option to meet the regulation until Phase 4. In case of container, the attained EEDI while converting fuel from Diesel oil (DO) to LNG was reduced by 27.35%. With speed reduction, the EEDI was improved by 21.76% of the EEDI based on DO. Pertaining to VLCC, 27.31% and 22.10% improvements were observed, which were comparable to those for the container. However, for both vessels, additional measure is required to meet Phase 5, demanding the reduction of 70%. Therefore, onboard CO2 capture system was designed for both KCS (Korea Research Institute of Ships & Ocean Engineering (KRISO) container ship) and KVLCC2 (KRISO VLCC) to meet the Phase 5 standard in the process simulation. The absorber column was designed with a diameter of 1.2-3.5 m and height of 11.3 m. The stripper column was 0.6-1.5 m in diameter and 8.8-9.6 m in height. The obtained results suggested that a combination of ESD, speed reduction, and fuel change was effective for reducing the EEDI; and onboard CO2 capture system may be required for Phase 5.

Experimental Study on the Analysis and Estimation of Metacentric Height in Response to Roll Period and Moment of Inertia Variations in Ships (선박의 횡요주기와 관성모멘트 변화에 따른 GM 추정 및 분석을 위한 실험 연구)

  • LeeChan Choi;JungHwi Kim;DongHyup Youn
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.29 no.4
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    • pp.380-388
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    • 2023
  • This study estimates the metacentric height (GM) of a model ship by varying the transverse weight distribution, considering the effects of the roll period and moment of inertia, and compares it with the GM values measured by the inclining test. In the process, the relationship between the values is analyzed. Three types of ships-a 7-ton fishing vessel, 20-ton fishing vessel, and KRISO Very Large Crude-oil Carrier (KVLCC)-were used for the experiment and comparison. The roll period and moment of inertia were measured using the free roll decay and swing frame tests, and the GM was measured using inclining test. The estimated GM from the roll period and moment of inertia showed the same trend as the GM measured using the inclining test in the change of the weight distribution. However, the GM values measured using the inclining test were lower. Therefore, additional correction factors or parameters other than the roll period and moment of inertia are necessary for estimating GM. In the future, the relationship between the weight center and the estimated GM will be analyzed to derive the correction factors.

Effect of Temperature and Various Pre-treatments on Germination of Hippophae rhamnoides Seeds (갈매보리수나무 종자의 온도 및 여러 가지 전처리에 따른 발아반응)

  • Choi, Chung-Ho
    • Korean Journal of Plant Resources
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    • v.25 no.1
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    • pp.132-141
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    • 2012
  • This study was carried out to test seed germination responses to temperatures and pre-treatments in Hippophae rhamnoides, which has many abilities in antioxidant activity, soil improvement and erosion control. H. rhamnoides seeds were placed at 10, 15, 20, 25, 30 and $35^{\circ}C$ under light condition. As the results, germination percentage (GP) was the highest at 15 and $20^{\circ}C$, and mean germination time (MGT), germination rate (GR) and germination value (GV) were the highest at $25^{\circ}C$. Quadratic and linear regression model were used to determine the cardinal temperatures such as base ($T_b$), maximum ($T_m$) and optimum ($T_o$) temperature for germination. In quadratic regression model using PG, $T_b$, $T_m$ and $T_o$ was estimated as 0.6, 36.4 and $18.5^{\circ}C$, respectively, and temperature range for germination was $35.8^{\circ}C$. In linear regression model using GR, $T_b$, $T_m$ and $T_o$ was estimated as 8.3, 35.4 and $25.3^{\circ}C$, respectively, and temperature range for germination was $27.2^{\circ}C$. Germination properties were investigated after H. rhamnoides seeds were treated by prechilling (1, 2, 4, 6 and 8 weeks), stratification (2, 4, 6 and 8 weeks), solid matrix priming (seed : carrier : water = 5 : 1 : 7, 8, 9 and 10), osmo-priming (-0.25, -0.5, -1.0 and -1.5 MPa) and calcium chloride ($CaCl_2$) -priming (100, 200, 300 and 400 mM). The highest GP was observed in $CaCl_2$ 300 and 400 mM treatments, and MGT was the shortest in stratification 6 and 8 weeks treatments. GR and GV were the highest and GP was the second highest when seeds were prechilled for 1 and 2 weeks. Consequently, prechilling 1 or 2 weeks treatment was considered as the appropriate method when we contemplate qualitative and quantitative effects in seedling production.

Effect of K2CO3 Loading on the Adsorption Performance of Inorganic Adsorbent for H2S Removal (K2CO3 첨가에 따른 H2S 제거용 무기계 흡착제의 흡착성능 영향에 관한 연구)

  • Jang, Kil Nam;Song, Young Sang;Hong, Ji Sook;You, Young-Woo;Hwang, Taek Sung
    • Clean Technology
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    • v.23 no.3
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    • pp.286-293
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    • 2017
  • The goal of this paper was to improve the performance of the adsorbent to remove $H_2S$. Pellet type adsorbents were prepared by using four kinds of materials ($Fe_2O_3$, $Ca(OH)_2$, Activated carbon, $Al(OH)_2)$ for use as a basic carrier. As the results of $H_2S$ adsorption tests, $Fe_2O_3$ and Activated Carbon improved the adsorption performance of $H_2S$ by 1.5 ~ 2 times, and $Ca(OH)_2$ and $Al(OH)_2$ showed no effect on $H_2S$ adsorption performance. Four basic materials were as carriers, and 5 wt% of KI, KOH and $K_2CO_3$ were added on the carriers, respectively. As the results of $H_2S$ adsorption tests, adsorbent containing $K_2CO_3$ showed the best performance. As a result of $H_2S$ adsorption test with varying $K_2CO_3$ content from 5 to 30 wt%, it was confirmed that adsorption performance was increased up to 20 wt% of $K_2CO_3$ and adsorption performance decreased to 30 wt%. The $H_2S$ adsorption performance was modeled by using Thomas model with varying $K_2CO_3$ contents and the results were used for the adsorption tower design. It was shown that the experimental values and the simulated values were in good agreement with the contents range of $K_2CO_3$ up to 20 wt%. Based on these results, it is expected that not only the adsorption performance of $H_2S$ adsorbent is improved but also life time of the adsorbent is increased.

Synthesis of $[^{51}Cr]Cr(III)$-EDTA Complex and Measurement of Glomerular Filtration Rate br Radioactivity Counting of Head and Neck Region ($[^{51}Cr]Cr(III)$-EDTA 착물 합성 및 $[^{51}Cr]Cr(III)$-EDTA 주사후 두경부 방사능 계측에 의한 사구체 여과율 측정)

  • Yang, Seung-Dae;Lim, Sang-Moo;Chun, Kwon-Soo;Suh, Yong-Sup;Yoon, Yong-Ki;Park, Hyun;Woo, Kwang-Sun;Chung, Wi-Sup;Oh, Ok-Doo;Lee, Jung-Doo
    • The Korean Journal of Nuclear Medicine
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    • v.28 no.3
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    • pp.364-370
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    • 1994
  • The purpose of this study is to evaluate the clinical application of the no carrier added $[^{51}Cr]Cr(III)$-EDTA complexes, produced at Korea Cancer Center Hospital. The $[^{51}Cr]Cr(III)$-EDTA complexes, usefut for measurement of GFR were prepared at room temperature in the presence of bicarbonate catalysts. The radiochemical purity of $[^{51}Cr]Cr(III)$-EDTA was over 99% by paper electrophoresis. The time activity curves were obtained by counting the blood samples from 5 volunteers and counting the head and neck regions with whole body counter after injection of the $^{51}Cr$-EDTA, respectively. After the nonlinear regression, the area under curve was obtained. The plasma clearance of the $^{51}Cr$-EDTA was calculated with injected dose/AUC. The clearance rate calculated with the head and neck counting data was in good agreement with the result from the plasma sample radioactivity at 1-3 hrs after injection. From this result, the counting of head and neck region and the nonlinear regression by 2-compartment model could be applied for the measurement of the clearance rate. Using MIRD system, the absorbed radiation dose was calculated by residence $time{\times}S$. The absorbed whole body radiation dose was negligibly small.

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The Effect of Cultured Perichondrial Cell Sheet Covered Highly Active Engineered Cartilage: in vivo Comparative Assessment (배양연골막이 피복된 고효능 인공연골의 생체내 효과)

  • Park, Se-Il;Moon, Young-Mi;Jeong, Jae-Ho;Jang, Kwang-Ho;Ahn, Myun-Hwan
    • Journal of Veterinary Clinics
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    • v.28 no.5
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    • pp.486-496
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    • 2011
  • A special mesenchymal tissue layer called perichondrium has a chondrogenic capacity and is a candidate tissue for engineering of cartilage. To overcome limited potential for chondrocyte proliferation and re-absorption, we studied a method of cartilage tissue engineering comprising chondrocyte-hydrogel pluronic complex (CPC) and cultured perichondrial cell sheet (cPCs) which entirely cover CPC. For effective cartilage regeneration, cell-sheet engineering technique of high-density culture was used for fabrication of cPCs. Hydrogel pluronic as a biomimetic cell carrier used for stable and maintains the chondrocytes. The human cPCs was cultured as a single layer and entirely covered CPC. The tissue engineered constructs were implanted into the dorsal subcutaneous tissue pocket on nude mice (n = 6). CPC without cPCs were used as a controls (N = 6). Engineered cartilage specimens were harvested at 12 weeks after implantation and evaluated with gross morphology and histological examination. Biological analysis was also performed for glycosaminoglycan (GAG) and type II collagen. Indeed, we performed additional in vivo studies of cartilage regeneration using canine large fullthickness chondrial defect model. The dogs were allocated to the experimental groups as treated chondrocyte sheets with perichondrial cell sheet group (n = 4), and chondrocyte sheets only group (n = 4). The histological and biochemical studies performed 12 weeks later as same manners as nude mouse but additional immunofluorescence study. Grossly, the size of cartilage specimen of cPCs covered group was larger than that of the control. On histological examination, the specimen of cPCs covered group showed typical characteristics of cartilage tissue. The contents of GAG and type II collagen were higher in cPCs covered group than that of the control. These studies demonstrated the potential of such CPC/cPCs constructs to support chondrogenesis in vivo. In conclusion, the method of cartilage tissue engineering using cPCs supposed to be an effective method with higher cartilage tissue gain. We suggest a new method of cartilage tissue engineering using cultured perichondrial cell sheet as a promising strategy for cartilage tissue reconstruction.

Shipping Industry Support Plan based on Research of Factors Affecting on the Freight Rate of Bulk Carriers by Sizes (부정기선 운임변동성 영향 요인 분석에 따른 우리나라 해운정책 지원 방안)

  • Cheon, Min-Soo;Mun, Ae-ri;Kim, Seog-Soo
    • Journal of Korea Port Economic Association
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    • v.36 no.4
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    • pp.17-30
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    • 2020
  • In the shipping industry, it is essential to engage in the preemptive prediction of freight rate volatility through market monitoring. Considering that freight rates have already started to fall, the loss of shipping companies will soon be uncontrollable. Therefore, in this study, factors affecting the freight rates of bulk carriers, which have relatively large freight rate volatility as compared to container freight rates, were quantified and analyzed. In doing so, we intended to contribute to future shipping market monitoring. We performed an analysis using a vector error correction model and estimated the influence of six independent variables on the charter rates of bulk carriers by Handy Size, Supramax, Panamax, and Cape Size. The six independent variables included the bulk carrier fleet volume, iron ore traffic volume, ribo interest rate, bunker oil price, and Euro-Dollar exchange rate. The dependent variables were handy size (32,000 DWT) spot charter rates, Supramax 6 T/C average charter rates, Pana Max (75,000 DWT) spot charter, and Cape Size (170,000 DWT) spot charter. The study examined charter rates by size of bulk carriers, which was different from studies on existing specific types of ships or fares in oil tankers and chemical carriers other than bulk carriers. Findings revealed that influencing factors differed for each ship size. The Libo interest rate had a significant effect on all four ship types, and the iron ore traffic volume had a significant effect on three ship types. The Ribo rate showed a negative (-) relationship with Handy Size, Supramax, Panamax, and Cape Size. Iron ore traffic influenced three types of linearity, except for Panamax. The size of shipping companies differed depending on their characteristics. These findings are expected to contribute to the establishment of a management strategy for shipping companies by analyzing the factors influencing changes in the freight rates of charterers, which have a profound effect on the management performance of shipping companies.

Optimization for Ammonia Decomposition over Ruthenium Alumina Catalyst Coated on Metallic Monolith Using Response Surface Methodology (반응표면분석법을 이용한 루테늄 알루미나 메탈모노리스 코팅촉매의 암모니아 분해 최적화)

  • Choi, Jae Hyung;Lee, Sung-Chan;Lee, Junhyeok;Kim, Gyeong-Min;Lim, Dong-Ha
    • Clean Technology
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    • v.28 no.3
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    • pp.218-226
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    • 2022
  • As a result of the recent social transformation towards a hydrogen economy and carbon-neutrality, the demands for hydrogen energy have been increasing rapidly worldwide. As such, eco-friendly hydrogen production technologies that do not produce carbon dioxide (CO2) emissions are being focused on. Among them, ammonia (NH3) is an economical hydrogen carrier that can easily produce hydrogen (H2). In this study, Ru/Al2O3 catalyst coated onmetallic monolith for hydrogen production from ammonia was prepared by a dip-coating method using a catalyst slurry mixture composed of Ru/Al2O3 catalyst, inorganic binder (alumina sol) and organic binder (methyl cellulose). At the optimized 1:1:0.1 weight ratio of catalyst/inorganic binder/organic binder, the amount of catalyst coated on the metallic monolith after one cycle coating was about 61.6 g L-1. The uniform thickness (about 42 ㎛) and crystal structure of the catalyst coated on the metallic monolith surface were confirmed through scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. Also, a numerical optimization regression equation for NH3 conversion according to the independent variables of reaction temperature (400-600 ℃) and gas hourly space velocity (1,000-5,000 h-1) was calculated by response surface methodology (RSM). This model indicated a determination coefficient (R2) of 0.991 and had statistically significant predictors. This regression model could contribute to the commercial process design of hydrogen production by ammonia decomposition.