Earticle

This study presents a dynamic simulation-based evaluation of a large-scale helium compressor test system developed for a 5-ton-per-day (TPD) hydrogen liquefaction plant. A one-dimensional transient simulation tool, EcosimPro, equipped with the CryoLib library was used to model the thermofluid behavior of the helium circulation loop and investigate start-up and pressure-control strategies relevant to helium refrigeration systems in cryogenic processes. The analysis focused on the coordinated operation of three pressure control valves—PCV501, PCV504, and PCV505—that regulate the suction and discharge pressures of the compressor. Through a series of dynamic simulations, appropriate control logic for stable pressurization and pressure regulation was derived. Sensitivity analysis further revealed that an initial loop pressure between 7 and 10 barA yields the most stable start-up condition. These findings demonstrate the usefulness of dynamic modeling using EcosimPro–CryoLib for optimizing control strategies in helium-based thermofluidic systems and provide valuable guidance and reference data for the future operation of hydrogen liquefaction infrastructure.

Among the many packaging materials used in cushion packaging, there is a lack of optimum design for the tray cup pad used in fruit packaging for export and domestic distribution. It causes over-packaging due to excessive material input, and this could be solved by applying various parameters needed to optimize the design of the tray cup pad considering the packaging material and the quantity of fruits in the box. In the case of a tray cup for fruits, the economic efficiency of material and thickness should be considered. Therefore, it is possible to design a tray cup pad depending on the packaging material used by applying appropriate design parameters. The static and dynamic characteristics of the materials used for packaging of pears were analyzed by using the FEM (finite element Method) simulation technique to derive the optimal design parameters. And by applying the appropriate design parameters considering the quantity of fruit and distribution environment, it is possible to design an appropriate fruit tray cup pad. In this study, as a result of simulating the contact stresses between the fruit and the tray cup for the PP, PE, and PS materials used in the fruit tray cup, the material with the lowest contact stress was PP and the value was found to be 398 Pa. The contact displacement between fruit and tray cup using this material was about 0.0463 mm, which was the lowest value compared with other materials. Also the resonance frequency band of tray cup made of PP material was below 36.81 Hz, and the strain energy was below 12.20 J. The resonant frequency band of the pear is more than 80 Hz and it could be applied to all the tray cup materials as compared with the resonance band of 38.81 Hz or less which is the resonance band of all tray cup pads for packaging. Finally, PP is the most suitable material for the tray cup pad.

최근 한반도 남동부에서 발생한 연이은 강진들로 인해 국내에서도 지진 방재에 대한 관심도가 높아지고 있 다. 본 연구에서는 최근 들어 급격히 진보하고 있는 시각지능과 가상현실 분야 기술들을 기반으로 하는, 맞춤형 지진 재해 대응을 위한 기술적 방법론에 대해 살펴보고자 한다. 해당 기술은 카메라를 이용한 생활공간 영상 정보의 취득, 개별 객체의 영상 기반 인식, 3차원 공간 정보의 추출, 이산요소법 등을 활용한 가상 지진의 동역학적 모의, 가상현실 환경에서의 모의 지진 실감화 등의 단계를 통해 구성된다. 본 연구에서는 이러한 전체 기술 프로세스를 구성하기 위한 각 단계의 프로세스, 해당 이슈와 관련한 현재 기술 동향, 실시를 위한 기술적 해결 과제 등을 분석하였다.

The recent occurrence of consecutive large earthquakes in the southeastern part of the Korean peninsula has brought significant attention to the prevention of earthquake damage in Korea. This article aims to explore a technology-based approach for earthquake drills using state-of-the-art visual intelligence and virtual reality technologies. The technical process consists of several stages, including acquisition of image information in living spaces using a camera, recognition of objects from the acquired image information, extraction of three dimensional geometric information, simulation of virtual earthquakes using dynamic modelling techniques such as the discrete element method, and realization of the simulated earthquake in a virtual reality environment. This article provides a comprehensive analysis of the individual processes at each stage of the technical process, a survey on the current status of related technologies, and discussion of the technical challenges in its execution.

Considering heat insulation and beautiful sight of construction, making use of exterior panels is increasing. Recently the exterior panels now are weak very much, and so in consequence of the weakness fire spreads rapidly. Compared with internal fire, external vertical fire spread rate goes rapidly and it is extensive in spread range, therefore it is dangerous very much. Accordingly, under present condition of poor standard of exterior panels, it is required to take measure to meet the appropriate situation. In this study, by making use of FDS(Fire Dynamic Simulation) program about external vertical fire of high rise building, fire behavior is searched by computer. It is important that realizing by computer fire modeling about external vertical fire must be included certainly in procedure of fire performance design in the future. In modeling program, FDS version 5 is available, and aluminium composite panel is applied in external panels. In this study, for realizing of actual fire condition, FDS is applied by details of fire scenarios considering influence of wind.

Recently, developing and applying of the double skin, which can utilize the natural energy with more aggressive characteristic, is now in study. The studies of the double skin are been constantly in progress in advanced countries as well as in domestic. And the double skin has lately been put to practical use. This study has selected the building with the box-typed double skin system and performed the thermal performance prediction of double skin system using TRNSYS. The U-value of the double skin system has been calculated. And this one has compared the measured U-value with the simulated U-value of double skin system. The results of comparison between experiment and the simulation were similar. So a prediction method on thermal performance of the box-typed double skin using TRNSYS simulation has secured a feasibility.

본 연구는 국가 AI 경쟁력을 정태적 순위 비교에 그치지 않고, 역량이 축적·확산되는 구조적 경 로와 정책 개입의 시간지연 효과를 규명하기 위해 시스템 다이내믹스(System Dynamics) 기반 분 석을 적용하였다. 분석 범위는 OECD 38개국이며, Tortoise Media의 Global AI Index가 제시하는 구 현(Implementation)·혁신(Innovation)·투자(Investment) 3대 축의 2023–2025년 점수(0–100 정규 화)를 활용하였다. 분석결과, OECD 내 점수 분포는 상위 소수 국가에 편중되어 있으며, 특히 투자 축에서 국가 간 격차가 크게 나타나 상위권 도약을 좌우하는 변별력 있는 축으로 기능하는 것으로 확인되었다. RQ1에 대해, 구현·혁신·투자는 ‘투자→혁신→채택(구현)→시장수요/상용화→추가투자’ 로 연결되는 강화루프와 ‘리스크 사건→신뢰 저하/규제·준수부담 증가→채택·투자 둔화’의 균형루프 가 동시에 작동하는 구조로 상호 영향을 주는 것으로 분석된다. RQ2에 대해, 정부 AI 예산은 R&D·공공 인프라를 통해 혁신(및 간접적으로 투자)을, 교육·훈련은 인재공급과 R&D 생산성을 통해 혁 신·구현을, 민간 AI 투자는 상용화·스케일업을 통해 투자 축을 가장 직접적으로 강화하며, 효과는 1.5–3년 내외의 시차를 두고 누적적으로 나타나는 것으로 분석되었다. RQ3에 대해, 한국이 투자 점수 OECD 3위에 도달하기 위해서는 민간 투자 레버리지의 상향을 핵심으로 하되 정부전략과 인재 기반을 결합한 패키지형 조합이 필요하며, 본 연구의 대표 조합(G=1.2, P=1.3, E=1.1)이 그 최소 조건 중 하나로 도출되었다.

This study applies a System Dynamics-based approach to move beyond static rank comparisons of national AI competitiveness and to identify the structural pathways through which capabilities accumulate and diffuse, as well as the time-lagged effects of policy interventions. The analysis covers 38 OECD countries and uses normalized (0-100) scores for 2023-2025 on the three pillars-Implementation, Innovation, and Investment-presented in Tortoise Media’s Global AI Index. The results show that score distributions within the OECD are concentrated among a small number of top countries. In particular, cross-country gaps are largest in the Investment pillar, confirming its role as a highly discriminating dimension that can determine whether a country breaks into the top tier. Regarding RQ1, Implementation, Innovation, and Investment are mutually reinforcing through a reinforcing loop-investment → innovation → adoption (implementation) → market demand/commercialization → additional investment-while simultaneously being constrained by a balancing loop in which risk events → declining trust / increased regulation and compliance burdens → slower adoption and investment. Regarding RQ2, government AI budgets strengthen Innovation (and indirectly Investment) through R&D and public infrastructure; education and training enhance Innovation and Implementation by expanding the talent supply and improving R&D productivity; and private AI investment most directly reinforces the Investment pillar via commercialization and scale-up. These effects accumulate over time and typically materialize with lags of approximately 1.5-3 years. Regarding RQ3, for Korea to reach third place in the OECD in the Investment score, increasing private-investment leverage should be the central lever, combined with a package of complementary measures that integrates government strategy and the talent base. One representative package identified in this study (G=1.2, P=1.3, E=1.1) is derived as one of the minimum conditions for achieving that target.

시뮬레이션이란 다양한 개체들이 모델링 된 정보에 따라 입력된 행동을 수행함으로써 실제 환경에서 실험하기 어려 운 문제들의 결과를 예측하고 검증하는 방법이다. 기존의 시뮬레이션 방법에서는 시뮬레이션이 시작되기 이전에 사 용자가 입력한 행동들을 시뮬레이션 개체들이 수행하거나 특정 조건에서 정의된 행동을 수행하여 시뮬레이션을 진 행했다. 하지만 기존의 방법을 통해 이루어지는 시뮬레이션의 경우, 사용자가 사전에 정의한 제한적인 범위 내에서 의 시뮬레이션만이 가능하며 실제 상황에서 발생될 수 있는 다양한 예외 상황을 고려하기 어렵다. 이러한 문제점을 극복하기 위해 본 논문에서는 시뮬레이션 개체들의 동적인 행위 계획을 위해 기존의 데이터 기반 학습과 지식 기반 학습을 상호 보완한 새로운 통합 학습 방법을 제안한다. 제안하는 통합 학습 방법을 통해 시뮬레이션 개체들은 다양 한 상황을 학습할 수 있으며 실제 시뮬레이션 과정에서 시뮬레이션 환경이 변경될 경우, 학습된 지식을 바탕으로 스 스로가 상황에 알맞은 새로운 행동을 계획할 수 있다. 또한, 제안하는 학습 방법을 군사 도메인의 시뮬레이션 상황 에 적용해보고 제안하는 학습 방법의 실제 적용 방법과 가능성을 검증한다.

The simulation is the method to predict and analyze the problem that is difficult to experiment in real world through the interaction between modeled entities. Existing simulation methods are operated based on initial input, which is entered when the simulation is started. But, it is only available to simulate limited and predefined situation, and impossible to handle the undefined exceptions. In order to overcome these problems, we propose unified learning approach, which is combining data-driven learning and knowledge-driven learning, for simulation planning. Proposed approach can plan new appropriate behaviors by learning many simulation experiences and domain knowledge in changing simulation environments. Also, we will verify the feasibility and effectiveness of proposed approach applying in the military simulation.

Due to the higher insulation and the air-tightness requirement in modern buildings have resulted NBS(New Building Syndrome) and SBS(Sick Building Syndrome) of IAQ problems. Therefore, energy efficient way of solving such IAQ issues are of major concern in these days and areas. This paper introduces a new technology and method to improve IAQ performance as well as to improve building energy performance with a DI(Dynamic Insulation) concept. The main idea to meet the goal is to use the DI concept similar to a heat recovery concept to prevent the heat loss path within the air path inside the dynamic insulation. The characteristic of the dynamic insulation is that the lower U-value as the higher air velocity through the DI. The porous media such as HEPA filter improves the IAQ to filter out the PM10 particles and other unhealthy particles. A energy performance simulation study has been conducted to show the energy impact of porous DI over the static insulation material. A twin test cell with a DI was modeled and simulated to show the DI energy saving impact for different ACH's. The results show that up tp 9 % energy with 2 ACH could be saved in the case with DI replaced in south faced insulation compared to the conventional insulation.

The molecular dynamic simulation method is usually used to analyse microscopic fluid fields. To use this method in engineering problems with real scales of molecules needs more time and greater computer power than we have now. To overcome these limitations, the expansion method using dimensionless and similarity of physical quantities of molecules is studied and introduced for the engineering scale fluid dynamics.

본 연구는 전통적 회귀분석 모형을 기반으로 하여 KOSPI200 지수선물을 사용해 개별주식에 대한 동적헤징을 실시할 때 모형 교체 없이 효율성을 안정적으로 높일 수 있는지에 대해 알아본다. 전통적 회귀분석 모형에서 벗어나 새로운 모형으로 베타계수를 계산하고자 했던 기존의 연구들과는 달리, 본 연구에서는 단순이동평균법의 윈도우 개념에 착안하여 전통적 회귀분석 모형을 그대로 사용하면서 베타계수의 윈도우 크기만을 조정하는 방식을 취함으로써 Model Risk를 최소화하고자 하였다. 그 결과 헤징에 사용할 베타계수를 계산하는 과정에서 윈도우 크기 조정을 거침으로써 후행성과 잔차의 영향 중 어떤 장애요소를 감소시킬지 추가적으로 선택할 수 있게 되었다. 분석 단계에서는 상관성‐반응크기 모형을 사용하여 가상의 KOSPI 주식을 생성한 후 몬테카를로 시뮬레이션을 실시하여 베타계수의 윈도우 크기에 따른 헤징효율을 분석하였으며, 그 결과 헤징기간 중 베타계수의 움직임이 나타내는 추세의 크기에 따라 최적의 효율성을 나타내는 윈도우 크기가 변화하는 모습을 보였다. 이를 통해 헤징시 단순히 베타계수만을 고려하는 것보다 상관계수를 통해 베타계수의 변동성을 예측하면서 헤지비율을 설정할 때 훨씬 더 효율적인 헤징성과를 거둘 수 있다는 점 역시 알 수 있었다.

This paper examines the possibility of performance innovation when we use KOSPI200 index futures and conventional regression model to dynamic hedge a specific stock in KOSPI200 market without any model changes. Unlike preceding studies which tried to give up conventional regression model and invent new ones to calculate beta coefficient, this paper holds conventional model and tries to enhance hedging performance just by adjusting length of criterion period of beta coefficient calculation, minimizing model risk. This method got its idea from 'Window Size' concept, which is a part of Simple Moving Average Method(SMA). In analysis phase, we create a virtual stock in KOSPI market by correlativity-reaction size model and identify hedging performance of each window size by Monte Carlo simulation. As a result, we found that appropriateness of specific window size varies with intensity of trend in beta coefficient movement.

In order to start belt conveyor softly, automated mechanical transmission (AMT) is used as a new soft-starting device. Constant belt acceleration control is proposed as a method for AMT’s application in belt conveyor’s soft starting. Belt velocity is adopted as the single parameter for shift schedule. Based on the idea of half engagement point, fast-slow-fast law is taken for clutch engagement. Simulation model is established in AMESim environment. On the basis of horizontal belt conveyor driven by one induction motor with 110 KW power, simulation research on start-up process in first gear and shift process from first gear to eighth gear are carried out respectively. Simulation results show that the constant belt acceleration with 0.2 m/s2 could achieve the purpose of AMT’s application in belt conveyor’s soft starting. The phenomenon of short-time belt acceleration mutations appears during shift process. The maximum value of belt acceleration is less than 1 m/s2 while the clutch is just at the beginning of engagement. Under the influence of belt acceleration mutations, main characteristic parameters of the system are within their allowable limits, such as belt maximum tension and driving pulley torque. After the completion of upshift process, the belt maximum tension and other parameters curves tend to be stable.

A principle of best engine valve timing is proposed based on the requirements of best engine valve timing. A novel variable valve timing system is designed according to the principle. The construction of the mathematical model of the system and its dynamic simulation are also presented. The adjust performance of system and the oil pressure are studied in the paper. Simulation and experimental results show that the system can achieve fully variable valve timing adjustment by regulating electromagnetic valve closing time according to the engine speed, and the system satisfies the principle of best engine valve timing proposed in the paper.

고온 용융염 전해환원 공정은 후행핵연료 주기의 대안 공정인 파이로공정의 산화물 사용후핵연료의 확대 를 위해 필수적인 공정이다. 사용후핵연료는 다성분 산화물로 이루어져 있으며 각 산화물은 전해환원 공정 에서 화학적 특성에 따라 산소를 잃게 된다. 본 연구에서는 건식분말화 공정 이후 전해환원 반응기에 도입되 는 사용후핵연료 조성을 기준으로 각 금속-산소 시스템을 독립적인 이상고용체로 가정하여 전해환원 반응거동을 계산하였다. 전해환원을 Li의 환원과 이어지는 Li과의 화학반응의 결합으로 산정하여 U을 비롯한 금 속 환원 거동을 계산하였다. 계산결과 대부분의 산화물들은 전해환원 공정에 의해 금속으로 전환되는 것으 로 예상되었다. 란타나이드 원소들의 경우 Li2O의 농도가 낮아지면 금속 전환율이 높아지나 대부분 산화물로 존재하는 것으로 나타났다. 추가적으로 U3O8의 전해환원 거동에 대해 Li의 확산과 Li과의 화학반응을 고려하 여 반실험적 모델이 제시되었다. 실험데이터를 활용하여 매개변수를 결정하였으며 시간에 대한 환원율 및 전류에 대한 99.9% 환원 시간을 계산하였다.

Electrolytic reduction technology is essential for the purpose of adopting pyroprocessing into spent oxide fuel as an alternative option in a back-end fuel cycle. Spent fuel consists of various metal oxides, and each metal oxide releases an oxygen element depending on its chemical characteristic during the electrolytic reduction process. In the present work, an electrolytic reduction behavior was estimated for voloxidized spent fuel based on the assumption that each metal-oxygen system is independent and behaves as an ideal solid solution. The electrolytic reduction was considered as a combination of a Li recovery and chemical reactions between the metal oxides such as uranium oxide and the produced Li metal. The calculated result revealed that most of the metal oxides were reduced by the process. It was evaluated that a reduced fraction of lanthanide oxides increased with a decreasing Li2O concentration. However, most of the lanthanides were expected to be stable in their oxide forms. In addition, a semi-empirical model for describing U3O8 electrolytic reduction behavior was proposed by considering Li diffusion and a chemical reaction between U3O8 and Li. Experimental data was used to determine model parameters and, then, the model was applied to calculate the reduction yield with time and to estimate the required time for a 99.9% reduction.