• Journal of the Society of Naval Architects of Korea
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• v.47 no.5
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• pp.733-742
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• 2010

In this study, optimization was performed to improve the conventional liquefaction process of offshore plants, such as a LNG-FPSO(Liquefied Natural Gas-Floating, Production, Storage, and Offloading unit) by maximizing the energy efficiency of the process. The major equipments of the liquefaction process are compressors, expanders, and heat exchangers. These are connected by stream which has some thermodynamic properties, such as the temperature, pressure, enthalpy or specific volume, and entropy. For this, a process design problem for the liquefaction process of offshore plants was mathematically formulated as an optimization problem. The minimization of the total energy requirement of the liquefaction process was used as an objective function. Governing equations and other equations derived from thermodynamic laws acted as constraints. To solve this problem, the sequential quadratic programming(SQP) method was used. To evaluate the proposed method in this study, it was applied to the natural gas liquefaction process of the LNG-FPSO. The result showed that the proposed method could present the improved liquefaction process minimizing the total energy requirement as compared to conventional process.

• Economic and Environmental Geology
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• v.41 no.5
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• pp.497-507
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• 2008

This study identified and quantified the hidden flows for steel and iron production in Korea using MIPS (Material Input per Service) methodology. In order to estimate the input orientated impact on the environment caused by the manufacture or services of a product, MIPS indicates the quantity of resources used for this product or service. In 2005, 71 million tons of raw materials were used to produce $17.6 million of added value and 4.8 thousand tons of finished steel. The amount of natural resources extracted from natural environments for the purpose of steel production was 245 million tons of TMR(Total Material Requirement), 1524 million tons of water, and 34 million tons of air. The material intensities for steel production by natural inputs (raw materials and energy) was 4.3 ton/ton of TMR, 28 ton/ton of water, and 0.5 ton/ton of air.

• Korean Journal of Poultry Science
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• v.14 no.1
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• pp.39-53
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• 1987

A total of 1,440 White Leghorn pullets hatched in summer and winter, aged 20 to 72 weeks were fed 9 rations differing in dietary protein (13, 15 and 17%) and energy (2,500, 2,700 and 2,900 kcal/kg) levels for a period of 52 weeks in order to evaluate the optimum dietary energy and protein levels for laying hens. As metabolizable energy level increased from 2,500 to 2,900 kcal/kg of feed egg production, daily feed and protein intake and egg shell quality decreased, but reverse was true for the daily energy intake, energy requirement and feed cost per kg egg, body weight gain, nutrients utilizability and abdominal fat accumulation, Egg weight, viability and egg yolk Pigmentation were not affected by the dietary energy level. On the other hand, as dietary protein level increased from 13 to 17%, egg production, egg weight, daily protein intake, protein requirement per kg egg and body weight gain icreased, but daily feed and energy intake, feed and energy requirement per kg egg, egg yolk pigmentation and dry matter utilizability decreased, and no significant difference in the feed cost per kg egg, viability and egg shell quality was observed among dietary protein levels. However: the hens fed 15% and 17% Protein diets did not show significant differences in egg production, egg weight and body weight gain. For the entire laying period of 52 weeks, metabolizable energy level of 2,500 kcal/kg of feed and 15% dietary protein level were considered to be adequate to support the optimum productivity.

• Journal of Animal Science and Technology
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• v.45 no.1
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• pp.123-130
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• 2003

Metabolizable energy requirements for maintenance (MEm) of Hanwoo bulls were estimated in twelves metabolism trials using three different feeds at four stages of body weight(100, 200, 300 and 400kg). Three feeds were composed of 1) concentrates and rice straw, 2) concentrates and mixed grass hay, 3) concentrates and corn silage, respectively. Three energy levels were 1) maintenance (M) requirement, 2) 1.5 ${\times}$ M, and 3) 2.0 ${\times}$ M. All bulls were received 60% of their energy from concentrates and 40% form roughages. Three cattle for each trials fed different energy level were housed in metabolism stalls during the 5days of collection period, a total collection of feces and urine. Thereafter, during the 2days of respiration period the heat production was measured by indirect calorimetry using respiratory chamber. MEm were 99.80, 94.48, 94.80, and 97.68 kcal/W0.75 at 100, 200, 300 and 400kg. Mean value of MEm and efficiency of utilization ME for retained energy(Kg) were 95.80 kcal/W0.75 and 0.44.

• Journal of Nutrition and Health
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• v.27 no.8
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• pp.844-855
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• 1994

The purpose of this study is to investigate the nutritional status and dietary intake of gastrectomized cancer patients. For this study, from 1993. 1 to 1993. 8, 50 postoperative gastric cancer patients were selected to examine anthropometric and laboratory data(Body Weight, Body Fat, serum Albumin, Total Lympocyte count), and dietary intake related symptoms. The results were 1) All anthropometric and laboratory data were significantly deteriorated by gastrectomy(s-Albumin, TLC. Body Fat : p<0.001). Weight loss of gastrectomized patients was 8.23$\pm$3.72% from admission to discharge. 2) In many gastrectomized cancer patients, preoperative dietary intake was decreased by abdominal discomfort, indigestion, early satiety, and anorexia. 3) Postoperative energy intake was 602$\pm$158㎉, and it is correspond to 31.18$\pm$.90% of daily energy requirement(1918$\pm$236㎉). The cause of poor oral intake is mostly fear, abdominal distension and fullness, and early satiety. In consideration of the fact that an inadequate energy intake was the main cause of the decreasing nutritional status, a careful nutritional care and dietary education is necessry after gastrectomy.

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.252-255
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• 2005

The effort to realize the concept of stratospheric airship, which can fly at about 20km altitude, has been persevered since late 1980's. Referring to the feasibility study of ensuring the flight duration of the airship over 1year, total weight is about 30 tons, the length is about 200m. There are lots of key technologies to be solved to develop the system, and one of the essential prerequisite technologies is regenerative fuel cell system. In this paper, design requirement of regenerative fuel cell system is introduced with the feasibility study results of the challenging stratospheric airship.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.21 no.2
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• pp.283-294
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• 2023

APro, developed in KAERI for the process-based total system performance assessment (TSPA) of deep geological disposal systems, performs finite element method (FEM)-based multiphysics analysis. In the FEM-based analysis, the mesh element quality influences the numerical solution accuracy, memory requirement, and computation time. Therefore, an appropriate mesh structure should be constructed before the mesh stability analysis to achieve an accurate and efficient process-based TSPA. A generic reference case of DECOVALEX-2023 Task F, which has been proposed for simulating stationary groundwater flow and time-dependent conservative transport of two tracers, was used in this study for mesh stability analysis. The relative differences in tracer concentration varying mesh structures were determined by comparing with the results for the finest mesh structure. For calculation efficiency, the memory requirements and computation time were compared. Based on the mesh stability analysis, an approach based on adaptive mesh refinement was developed to resolve the error in the early stage of the simulation time-period. It was observed that the relative difference in the tracer concentration significantly decreased with high calculation efficiency.

• Clean Technology
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• v.26 no.1
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• pp.55-64
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• 2020

According to the Korean Renewable Energy 3020 Implementation Plan, the installation capacity of renewable energy is expected to increase whereas technology for storing excess electricity and stabilizing the power supply of renewable energy sources is extremely required. Power-to-Gas is one of energy storage technologies where electricity is converted into gas fuel such as hydrogen and methane. Basically, Power-to-Gas system could be effectively utilized to store excess electricity generated by an imbalance between supply and demand. In this study, the economic feasibility analysis of Power-to-Gas reflecting the domestic situation was carried out. Total revenue requirement method was utilized to estimate the levelized cost of hydrogen. Validation on the economic analysis method in this study was conducted by comparison of the result, which is published by the International Energy Agency. The levelized cost of hydrogen of a 100-MW Power-to-Gas system reflecting the current economic status in Korea is 8,344 won kg^-1. The sensitivity analysis was carried out, applying the main analysis economic factors such as electricity cost, electrolyser cost, and operating year. Based on the sensitivity analysis, the conditions for economic feasibility were suggested by comparing the cost of producing hydrogen using renewable energy with the cost of producing natural gas reformed hydrogen with carbon capture and storage.

• Transactions of the Korean hydrogen and new energy society
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• v.33 no.3
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• pp.247-254
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• 2022

Slush hydrogen containing liquid and solid hydrogen is expected to achieve zero boil-off by suppressing boil-off gas because heat of fusion for solid absorbe the heat ingress from atmosphere. In this paper, quantitative analysis on storage cost considering specific energy consumption between 1,000 m³ class liquid hydrogen storage system with re-liquefaction and slush hydrogen storage system during equivalent zero boil off period. Even though approximately 50% of total storage capacity should be converted into solid phase during the initial cargo bunkering, total energy consumption to convert into slush hydrogen is relatively 25% less than re-liquefaction energy for boil off hydrogen during zero boil off period. That's because energy consumption of slush phase change take up only 1.8% of liquefaction energy. moreover, annual revenue requirement including CAPEX, OPEX and electric cost for slush hydrogen storage could be more reduced approximately 32.5% than those of liquid hydrogen storage and specific energy storage cost ($/kg-H₂) could also be lowered by about 41.7% compared with liquid hydrogen storage.

• New & Renewable Energy
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• v.7 no.4
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• pp.10-17
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• 2011

Recently, electricity industry is facing high market uncertainty which has ever had and which increase risks in power market. In this study, we analyze risk factors such as discount rates, initial investment (overnight cost), plant factor, fuel cost, carbon price, etc, for the perspective of investor. For the analysis of risk factors, we used LCOE method. The results of this study show that renewable energy is more affected by plant factor and overnight cost than other risk factors. First, Renewable energy has higher proportion of overnight cost in the total investment than that of other technologies. Second, renewable energy is free of fuel cost and carbon price so plant factor is the most important factor, in other words, competitiveness of renewable energy depends on plant factor. Furthermore, we conducted economic feasibility of wind power and PV in domestic case study. The minimum requirement condition to get profitability is that plant factor 15% and overnight cost \6,000,000/kW and 26%, \2,200,000/kW for PV and Wind Power, respectively.