• Journal of Korean Society on Water Environment
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• v.25 no.4
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• pp.530-538
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• 2009

The Oxic-Settling-Anaerobic (OSA) treatment process, a modified Conventional Activated Sludge (CAS) process, was developed for the purpose of sludge reduction. The insertion of a sludge holding tank into a sludge return line, an anaerobic reactor, forming an OSA process, may provide a cost-effective way of reducing excess sludge production during a process. The OSA process was evaluated for its sludge reduction ability by kinetic parameter and mass balance, with an observed excess sludge reduction of 63.5%, as $P_{X.VSS}$, compared with the conventional activated sludge process.

• Asian-Australasian Journal of Animal Sciences
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• v.30 no.5
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• pp.672-682
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• 2017

Objective: This study was conducted to investigate the effects of probiotic, prebiotic and synbiotic with and without feed restriction on broilers performance, blood parameters, carcass characteristics, and feed cost of production from 1 to 56 days of age. Methods: Two hundred and forty unsexed one day-old chicks of Arbor Acres breed were used. Two trials, I and II, were conducted, with 120 birds in both. Each trial was divided into 4 equal groups. The birds in trial I were fed ad libitum throughout the experiment, while the chicks in trial II were fed ad libitum during the first week of age, then subjected to 5 hours/d of feed restriction from the beginning of the second week up to the end of the experiment. In both trials, the birds in group 1 were fed on a control diet while the other groups were given the same control diet supplemented either with a probiotic in group 2, prebiotic in group 3, or synbiotic in group 4. Results: It was found that chicks fed diets supplemented with probiotic, prebiotic and synbiotic (with and without feed restriction) exhibited higher body weight and feed efficiency than chicks fed the control diets. The feed additives in both trials did not affect hemoglobin, serum total protein, albumin, globulin, glucose, and total cholesterol, except the packed cell volume which was increased in the additive treatments with restriction at the end of the experiment. Moreover, the dietary treatments did not influence the carcass yield. However, the relative weights of liver, gizzard and proventriculus, small intestine and bursa of fabricius were found to be increased. The additives decreased the visible fat in the carcass, with more decreasing effect in the additive groups with restriction. The lowest feed cost per kg of weight gain was observed in the birds fed diets supplemented with synbiotic, probiotic and prebiotic. Feed restriction improved the feed conversion ratio, economic return, but decreased the feed intake, serum total cholesterol and visible fat in comparison with non-restricted groups. Conclusion: The biological feed additives could be routinely added to broiler diets, especially when a feed restriction program is followed. Finally, it can be recommended to restrict feed, and add probiotic or synbiotic to increase weight, improve feed conversion rate and reduce feed cost of production.

• Asian-Australasian Journal of Animal Sciences
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• v.21 no.1
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• pp.66-74
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• 2008

Two experiments were conducted to assess the effect of replacing a conventional concentrate with mixed cassava (Manihot esculenta) foliage and legume (Phaseolus calcaratus) foliage. In Exp. 1, three rumen fistulated crossbred cows were used for in sacco rumen degradability studies. In vitro gas production was also studied. In Exp. 2, 11 crossbred F2 heifers (Red Sindhi$\times$Holstein Friesian), with initial live weight of $129{\pm}6kg$ and aged six months, were allocated in a Completely Randomized Design (CRD) to evaluate a mixture (ratio 3:1) of cassava and legume foliage (CA-LE feed) as a protein source compared to a traditional concentrate feed (Control) in diets based on fresh elephant grass (Pennisetum purpureum) and urea treated rice straw ad libitum. The Control feed was replaced by the CA-LE feed at levels of 0% (Control), 40% (CA-LE40), and 60% (CA-LE60) based on dry matter (DM). The in sacco degradation of CA-LE feed was higher than Control feed (p<0.05). After 48 h incubation the degradation of CA-LE feed and Control feed was 73% vs. 58% of DM and 83% vs. 65% of CP, respectively. The gas production of CA-LE feed was also significantly higher than of Control feed during the first 12 h of incubation. The results of the performance study (Exp. 2) showed that the level of CA-LE feed in the concentrate had no effect on total dry matter intake (p>0.05), but live weight gains (LWG) in CA-LE40 and CA-LE60 were significantly higher (551 and 609 g/d, respectively) than in the Control group (281 g/d). The intake of CP was higher (p<0.05) for the treatments CA-LE40 and CA-LE60 (556 and 590 g/d, respectively) compared to that of Control (458 g/d), while there was no significant difference in ME intake. The feed conversion ratio was 16.8, 9.0 and 7.9 kg DM/kg LWG in Control, CA-LE40 and CA-LE60, respectively. The feed cost of CA-LE40 and CA-LE60 corresponded to 43% and 35%, respectively, of the feed cost of Control feed. The best results were found when CA-LE feed replaced 60% of DM in Control feed and considerably decreased feed cost. It is concluded that feeding cassava foliage in combination with Phaseolus calcaratus legume as a protein supplement could be a potentially valuable strategy which leads to reduced feed costs and a more sustainable system in smallholder dairy production in Vietnam.

• Journal of Korea Port Economic Association
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• v.38 no.3
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• pp.69-86
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• 2022

This study analyses the necessity of the large-size shipyard and explores competitiveness factors of it. Furthermore, the competitiveness is evaluated and the economic feasibility of building and operation of shipyard is examined. As a result of AHP analysis of the determining factors of the competitiveness of the repairing shipyard, the importance of the factors was found in the order of arrival and departure safety, repair technology, dock and wharf facilities, repair cost, repair period (on time delivery), and repair parts supply. Moving distance, repair service quality, repair parts supply, arrival and departure safety, repair technology, dock and quay wall facilities, and repair period (on time delivery) were identified as key factors in the AHP analysis for competitiveness of the Busan Port repair shipyard to be built in the future. As a result of the analysing economic feasibility, the net present value of the Busan Port repair shipyard construction and operation investment project was KRW 435.6 billion, and the internal rate of return was 9.8%, higher than the social discount rate (4.5%), and the cost-benefit ratio (B/C) was high at 1.167. As a result of the study, the necessity and economic feasibility of the Busan Port repair shipyard are sufficiently ensured, and the competitiveness assessment was highly positive.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.5
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• pp.363-370
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• 2013

Small scale hydropower is one of most attractive and cost-effective energy technologies for installation within sewage treatment plants. This study was conducted to evaluate the potential of a semi-kaplan micro-hydropower (MHP) system for application to sewage treatment plants with high flow fluctuations and a low head. The semi-kaplan MHP is equipped with an adjustable runner blade, and is without a guide vane, so as to reduce the incidence of mechanical problems. A MHP rating 13.4 kWp with a semi-kaplan turbine has been considered for Kiheung Respia sewage treatment plant, and this installation is estimated to generate 86.8 MWh of electricity annually, which is enough to supply electricity to over 25 households, and equivalent to an annual reduction of 49 ton $CO_2$. The semi-kaplan turbine showed a 90.2% energy conversion efficiency at the design flow rate of 0.35 $m^3/s$ and net head of 4.7 m, and was adaptable to a wide range of flow fluctuations. Through the MHP operation, approximately 2.1% of total electricity demand of Kiheung Respia sewage treatment plant will be achievable. Based on financial analysis, an exploiting MHP is considered economically acceptable with an internal rate of return of 6.1%, net present value of 15,539,000 Korean Won, benefit-cost ratio of 1.08, and payback year of 15.5, respectively, if initial investment cost is 200,000,000 Korean Won.

• Journal of Korean Society of Forest Science
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• v.102 no.1
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• pp.107-112
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• 2013

The purpose of the study is to give ROI information about management status and investment returns to someone who will newly cultivate Rhus verniciflura and expand area of Rhus verniciflura cultivation. In this study, IRR (Internal Rate of Returns), B/C Ratio and NPV are applied for ROI analysis. We basically surveyed thirty household among Rhus verniciflura cultivation farmhouses in chief producing districts Won-ju in Gang- Won, Ok-Cheon in Chung-Buk, Ham-Yang in Gyeong-Nam in Korea from May until October in 2011. Hence, the research surveyed these farmers about production cost, management cost, input labors and materials, land price and etc. by working process to calculate production and operation cost. As the result of farm survey, the result of the analysis shows income rate 27.76%, B/C Ratio 2.5, and NPV 121,830,831 won in $16,500m^2$ with 10 years period when local price of Rhus verniciflura is 2,200,000 won/3.75 kg at locals with 3% discount rate is applied. Therefore, starting open field cultivation of Rhus verniciflura, which requires intensive labor or expanding the cultivation area needs more labor force.

• Korean Chemical Engineering Research
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• v.59 no.1
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• pp.60-67
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• 2021

This study presented techno-economic analysis of a 500 MWe oxy-coal power plant with CO2 capture. The power plant included a circulating fluidized-bed (CFB), ultra-supercritical steam turbine, flue gas conditioning (FGC), air separation unit (ASU), and CO2 processing unit (CPU). The dry flue gas recirculation (FGR) was used to control the combustion temperature of CFB. One FGR heat exchanger, one heat exchanger for N2 stream exiting ASU, and a heat recovery from CPU compressor were considered to enhance heat efficiency. The decrease in the temperature difference (ΔT) of the FGR heat exchanger that means the increase in heat recovery from flue gas enhanced the electricity and exergy efficiencies. The annual cost including the FGR heat exchanger and FGC cooling water was minimized at ΔT = 10 ℃, where the electricity efficiency, total capital cost, total production cost, and return on investment were 39%, 1371 M$, 90 M$, and 7%/y, respectively.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.11
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• pp.6630-6638
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• 2014

The concerns for higher returns among investors in Korea are increasing as local interest rates lag behind the global market. The aim of this study was to provide a basis for estimating the precise return on investment to private investors and stakeholders of office buildings by identifying the optimal scale estimation of office building space, derived from managerial expenses. The literature on the economies theories of scales were reviewed, and the average administrative costs on an appropriate scale were assessed by cross-analysis and regression analysis using the U-shaped quadratic and cubic function. The findings suggest that the average office building managerial costs are approximately 6-11% according to the region, 10-13% according to the grade, and 8-9% according to size. Corporate-owned buildings represent the highest in terms of the average managerial costs, and there is an approximately 11.5% difference when it comes to outsourcing. In addition, the elapsed year showed that approximately 5.3 years to meet the lowest U-shaped curve of the average managerial cost. The 'Total floor area' variable shows a ${\bigcap}$-shape as it continue to increase to 72,000-Pyung then decrease gradually. This study presents the fundamental proposition of efficient and practical management of cost, lease and operation for real estate management firms by utilizing LCC.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.8
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• pp.127-132
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• 2016

This study evaluated the economic value of the development of a new variety of Citrus unshiu using the income approach, Net Present Value (NPV), Internal Rate of Return (IRR), and Benefit/Cost (B/C) ratio. The new variety of Citrus unshiu was developed by the national institute of horticultural and herbal science in Korea, rural development administration. The technological evaluation of the development of a new variety of Citrus unshiu can be used to improve the efficiency and practicality of the development of a new variety of citrus. From the research results, the technological value of development of a new variety of Citrus unshui was evaluated at 109,455(discount rate=8%, minimum), 195,040(discount rate=4%, maximum), and 145,375(discount rate=6%, average) million won. The IRR was 51.4%, which was greater than the discount rate(4~8%). The NPV was evaluated at 145.3 billion won(discount rate=6%, average), 195.0 billion won(discount rate=4%, maximum) and 109.4 billion won(discount rate=8%, minimum), all of which were greater than 0. The B/C ratio was evaluated at 60.9(discount rate=6%, average), 81.3(discount rate=4%, maximum) and 46.1(discount rate=8%, minimum), all of which were greater than 1. Therefore, the economic validity of the development of a new variety of Citrus unshiu was identified by this technological evaluation.

• Journal of Climate Change Research
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• v.1 no.3
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• pp.219-226
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• 2010

This study is analyzed the financial feasibility of biomass power plant in China in terms of fuel marginal price of biomass power plant. The range of fuel price is 150~300 RMB and IRR(Internal Rate of Return), NPV(Net Present Value), DSCR(Debt Service Coverage Ratio) and operation time are analyzed by 10 RMB from 150 RMB. The sensitivity of IRR went down by 1.35 on average. The sensibility of NPV showed big difference by 20% on 260 RMB and 270 RMB. In addition, DSCR of loan is at 1.0 at raw cost of 242 RMB and at lower than 1.0 when the raw cost over 242 RMB. It means that the pay-off of principal and interest of the loan is expected to be difficult in that case. The operation time of power plant should be 88% against standard operation time to maintain over 1.0 of DSCR. Therefore, the factors affecting the cost of raw material to build the power plant and to operate it should be prioritized.