• Ecology and Resilient Infrastructure
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• v.7 no.4
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• pp.248-255
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• 2020

In this study, we analyze the current state of domestic food waste (FW) recycling and propose a management plan for greenhouse gas (GHG) emissions. First, the composting potential of the GW demonstrates considerable promise. In particular, the GW (phytoplankton, periphyton, macrophyte, etc.) as a third-generation biomass shows strong performance as a functional additive that mitigates the disadvantages associated with composting FW and improves the quality of the final composted product. Alternatively, the final product (e.g., soil ameliorant) can be used to produce bio-filters that are effective pollutant buffers, with high applicability for green infrastructure. The proposed ecological approaches create new opportunities for FW as a resource for the reduction of GHG emissions, and are expected to contribute to the establishment of effective net-zero carbon systems in the future.

• Industry Promotion Research
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• v.9 no.1
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• pp.47-55
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• 2024

In the transportation sector, reducing total vehicle mileage and passenger vehicle traffic are proposed as strategies to achieve carbon neutrality. To achieve this, MaaS services must be actively promoted with the goal of revitalizing public transportation. In order to promote MaaS, individual movement data is required, such as the individual's means of movement, route, and conversion of the individual's means of use. However, in Korea, there are legal limitations in collecting and utilizing data on individual movements. As the right to request transmission of personal information was newly established in the revised Personal Information Protection Act in 2023, a law was established to collect and utilize data on individual movements. However, enforcement ordinance, detailed rules, instructions, guidelines must be prepared, and the standardization of data format and transmission system for collecting my data needs to take precedence.

• Journal of the Korean Society of Marine Environment & Safety
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• v.30 no.1
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• pp.135-145
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• 2024

At the 80th session of the MEPC, the IMO presented an enhanced GHG reduction strategy. The strategy is more specific and robust than the initial strategy presented at the 72nd session. The IMO aims to achieve 'Net Zero' GHG emissions from international shipping by 2050. In this study, a risk assessment was conducted for representative green fuels, namely. LNG, hydrogen, methanol, and ammonia. The fuzzy method was used to resolve the subjective ambiguity of results from the survey of the experts, and the positive and negative ef ects of the fuzziness were derived through the TOPSIS method. Finally, the closeness coefficients of the considered alternative fuels were determined using the Vertex method. As a result, methanol, LNG, hydrogen, and ammonia were preferred. This study suggests that the proposed approach can be used as a collective decision-making tool for selecting alternative fuels.

• The Korean Journal of Applied Statistics
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• v.30 no.1
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• pp.135-145
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• 2017

Principal component analysis (PCA) describes the variation of multivariate data in terms of a set of uncorrelated variables. Since each principal component is a linear combination of all variables and the loadings are typically non-zero, it is difficult to interpret the derived principal components. Sparse principal component analysis (SPCA) is a specialized technique using the elastic net penalty function to produce sparse loadings in principal component analysis. When data are structured by groups of variables, it is desirable to select variables in a grouped manner. In this paper, we propose a new PCA method to improve variable selection performance when variables are grouped, which not only selects important groups but also removes unimportant variables within identified groups. To incorporate group information into model fitting, we consider a hierarchical lasso penalty instead of the elastic net penalty in SPCA. Real data analyses demonstrate the performance and usefulness of the proposed method.

• Korean Journal of Agricultural Science
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• v.17 no.2
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• pp.115-129
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• 1990

This study was carried out to develop a microcomputer-based data acquisition system and software for analysis of engine vibration. Due to this development of system and software, studies on the vibration of engine was able to conduct efficiently. From the display of CRT, the outputs of test was compared and analysed on a zero-base motoring. The results obtained are summarized as follows : 1. Data acquisition system in microcomputer were designed and programmed and operated accurately. 2. The result of test was easily compared in monitoring of zero-base at color monitor. 3. This system and program developed was able to control the measuring intervals, no. of channels, and no. of data as wated. 4. The type of vibration of engine was type of bi-mode from the FFT and statistical analysis. 5. The maxima of engine vibration were 9.11 G at X-axis. 11.27 G at Y-axis, and 4.9 G at Z axis for full load of net output 6. The maxima of engine vibration unloaded were 4.28 G, 5.59 G, 2.68 G at 2200 rpm.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.16 no.2
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• pp.203-209
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• 2018

To correctly predict the neutron behavior based on diffusion calculations, it is necessary to adopt well-specified boundary conditions using suitable diffusion approximations to transport boundary conditions. Boundary conditions such as the zero net-current, the Marshak, the Mark, the zero scalar flux, and the Albedo condition have been used extensively in diffusion theory to approximate the reflective and vacuum conditions in transport theory. In this paper, we derive and analyze these conditions to prove their mathematical validity and to understand their physical implications, as well as their relationships with one another. To show the validity of these diffusion boundary conditions, we solve a sample problem. The results show that solutions of the diffusion equation with these well-formulated boundary conditions are very close to the solution of the transport equation with transport boundary conditions.

• Nuclear Engineering and Technology
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• v.52 no.5
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• pp.878-888
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• 2020

This paper presents the validation of UNIST in-house Monte Carlo code MCS used for the high-fidelity simulation of commercial pressurized water reactors (PWRs). Its focus is on the accurate, spatially detailed neutronic analyses of startup physics tests for the initial core of the Watts Bar Nuclear 1 reactor, which is a vital step in evaluating core phenomena in an operating nuclear power reactor. The MCS solutions for the Consortium for Advanced Simulation of Light Water Reactors (CASL) Virtual Environment for Reactor Applications (VERA) core physics benchmark progression problems 1 to 5 were verified with KENO-VI and Serpent 2 solutions for geometries ranging from a single-pin cell to a full core. MCS was also validated by comparing with results of reactor zero-power physics tests in a full-core simulation. MCS exhibits an excellent consistency against the measured data with a bias of ±3 pcm at the initial criticality whole-core problem. Furthermore, MCS solutions for rod worth are consistent with measured data, and reasonable agreement is obtained for the isothermal temperature coefficient and soluble boron worth. This favorable comparison with measured parameters exhibited by MCS continues to broaden its validation basis. These results provide confidence in MCS's capability in high-fidelity calculations for practical PWR cores.

• Nuclear Engineering and Technology
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• v.55 no.4
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• pp.1244-1249
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• 2023

Recently, the Kingdom of Saudi Arabia (KSA) announced the development of first-of-a-kind(FOAK) and most advanced futuristic vertical city and named as 'The LINE'. The project will have zero carbon dioxide emissions and will be powered by clean energy sources. Therefore, a study was designed to understand which clean energy sources might be a better choice. Because of its nearly carbon-free footprint, nuclear energy may be a good choice. Nowadays, the development of very small modular reactors (vSMRs) is gaining attention due to many salient features such as cost efficiency and zero carbon emissions. These reactors are one step down to actual small modular reactors (SMRs) in terms of power and size. SMRs typically have a power range of 20 MWe to 300 MWe, while vSMRs have a power range of 1-20 MWe. Therefore, a study was conducted to discuss different vSMRs in terms of design, technology types, safety features, capabilities, potential, and economics. After conducting the comparative test and analysis, the fuel cycle modeling of optimal and suitable reactor was calculated. Furthermore, the levelized unit cost of electricity for each reactor was compared to determine the most suitable vSMR, which is then compared other generation SMRs to evaluate the cost variations per MWe in terms of size and operation. The main objective of the research was to identify the most cost effective and simple vSMR that can be easily installed and deployed.

• Journal of the Society of Naval Architects of Korea
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• v.60 no.3
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• pp.146-154
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• 2023

Efforts have been made to reduce the greenhouse gas emissions from ships by limiting the energy efficiency index, and net zero CO₂ emission was proposed recently. The most ideal measure to achieve zero emission ship is electrification, and fuel cells are considered as a practical power source of the electrified propulsion system. The electric efficiency in the electrochemical reaction of fuel cells can be achieved up to 60% practically. The remaining energy is converted to heat energy but most of them are dissipated by cooling. In the author's previous research, a hybrid propulsion system utilizing not only electricity but also heat was introduced by combining electric motor and steam turbine. In this article, long term efficiency is evaluated for the introduced hybrid propulsion system by considering a virtual 24,000 TEU class container carrier model. To reflect a more practical operating condition, the actual navigation data of a similar real ship in the real world were collected from automatic identification system data and applied. From the result, the overall efficiency of the hybrid propulsion system is expected to be higher than a conventional electric propulsion fuel cell ship by 30%.

• Proceedings of the Society of Korea Industrial and System Engineering Conference
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• 2002.05a
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• pp.9-18
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• 2002

A capital investment problem is essentially one of determining whether the anticipated cash Inflows from a proposed project are sufficiently attractive to invest funds in the project. The net present value(NPV) criterion and internal rate of return(IRR) criterion are widely used as means of making investment decisions. A positive NPV means the equivalent worth of the inflows is greater than the equivalent worth of outflows, so, the project makes profit. Business people are familiar with rates of return because they all borrow money to finance ventures, even If the money they borrow is their own. Thus they are apt to use the IRR in preference to the NPV. The IRR can be defined as the discount rate that causes the net present value of a cash flow to equal zero. Why the project are accepted if the project's IRR is greater than the investor's minimum attractive rate of return. Against the NPV, the definition cannot distinctly explain the concept of the IRR as decision criterion. We present a new definition of the IRR as the ratio of profit on the invested capital.