• International Journal of Contents
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• 제11권4호
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• pp.38-43
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• 2015

Non-orthogonal multiple access (NOMA) where all users share the entire time and frequency resource has paid attention as one of the key technologies to enhance the spectral efficiency and the total throughput. Nevertheless, as the number of users and SIC error increase, the inter-user interference and the residual interference due to the SIC error also increase, resulting in performance degradation. In order to mitigate the performance degradation, we propose grouping-based NOMA system. In the proposed scheme, all users are divided into two groups based on the distance between the BS and each user, where one utilizes the first half of the bandwidth and the other utilizes the rest in the orthogonal manner. On the other hand, users in each group share the spectrum in the non-orthogonal manner. Grouping users can reduce both the inter-user interference and residual interference due to the SIC error, so it can outperform conventional NOMA system, especially in case that the number of users and the SIC error increase. Based on that, we also present the hybrid operation of the conventional and the proposed NOMA systems. In numerical results, the total throughput of the proposed NOMA systems is compared with that of the conventional NOMA systems with regard to the number of users and SIC error. It is confirmed that the proposed NOMA system outperforms the conventional NOMA system as the number of users and the SIC error increase.

• Nuclear Engineering and Technology
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• 제54권1호
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• pp.357-373
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• 2022

The high-temperature gas-cooled reactor pebble-bed module project is the first commercial Generation-IV NPP(Nuclear Power Plant) in China. A new joint is used for the vertical support of RPV(Reactor Pressure Vessel). The steel corbel is integrally embedded into the reactor-cabin wall through eight asymmetrically arranged pre-stressed high-strength bolts, achieving the different path transmission of shear force and moment. The vertical monotonic loading test of two specimens is conducted. The results show that the failure mode of the joint is bolt fracture. There is no prominent yield stage in the whole loading process. The stress of bolts is linearly distributed along the height of corbel at initial loading. As the load increases, the height of neutral axis of bolts gradually decreases. The upper and lower edges of the wall opening contact the corbel plate to restrict the rotation of the corbel. During the loading, the pre-stress of some bolts decreases. The increase of the pre-stress strength ratio of bolts has no noticeable effect on the structure stiffness, but it reduces the ultimate bearing capacity of the joint. A simplified calculation model for the elastic stage of the joint is established, and the estimation results are in good agreement with the experimental results.

• 드라이브 ㆍ 컨트롤
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• 제21권1호
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• pp.46-52
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• 2024

The advancement of autonomous driving technology has heightened the importance of Autonomous Mobile Robotics (AMR) within smart factories. Notably, in tasks involving the transportation of heavy objects, the consideration of weight in route optimization and path planning has become crucial. There is ongoing research on local path planning, such as Dijkstra, A^*, and RRT^*, focusing on minimizing travel time and distance within smart factory warehouses. Additionally, there are ongoing simultaneous studies on route optimization, including TSP algorithms for various path explorations and on minimizing energy consumption in mobile robotics operations. However, previous studies have often overlooked the weight of the objects being transported, emphasizing only minimal travel time or distance. Therefore, this research proposes route planning that accounts for the maximum payload capacity of mobile robotics and offers load-optimized path planning for multi-destination transportation. Considering the load, a genetic algorithm with the objectives of minimizing both travel time and distance, as well as energy consumption is employed. This approach is expected to enhance the efficiency of mobility within smart factories.

• 한국자동차공학회논문집
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• 제19권6호
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• pp.113-118
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• 2011

Fuel Cell Hybrid Vehicle (FCHV) is one of the most promising candidates for the next generation of transportation. It has many outstanding advantages such as higher energy efficiency and much lower emissions than internal combustion engine vehicles. It also has the ability of recovering braking energy. In order to design an FCHV drive train, we need to determine the size of the electric motor, the Fuel Cell System (FCS), and the battery. In this paper, the methodology for the sizing of these components is introduced based on the driveability constraints of the FCHV. A power management strategy is also presented because the battery energy capacity depends on it. The warm-up time of the FCS is also considered in the power management strategy and the simulation result is compared to that without considering the warm-up time.

• 한국안전학회지
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• 제25권1호
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• pp.87-92
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• 2010

Urban transit system must secure fast, safe and reliable transportation capacity as a metropolitan mass transit. For this purpose, it is important to make all the sub-systems (which consist of EMU, power feeding, signaling & telecommunication, railway, platform facility, and control system and so on) work well. To operate all the systems effectively and reliably, a maintenance measure optimal to each system's characteristics is needed to be established and executed. So, highly reliable maintenance should be performed. But, EMU maintenance methods suitable to its own model and EMU lines are not yet introduced. This study examined few examples mainly to secure reliability on a maintenance quality in operating method and the features of train maintenance system based on travel distance.

• International Journal of Contents
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• 제5권3호
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• pp.71-78
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• 2009

Recently, interest has heightened over 'critical infrastructures' and their reliability in the face of potential terrorist attack. Assault on any of the critical infrastructures as transportation, power, water, telecommunications, and financial services, entails great consequences for their users as well as the other interdependent critical infrastructures. How to protect our vital critical infrastructures is the key question in this paper. The purpose of this article is to suggest the implications for crisis and emergency management to protect the critical infrastructures in our society. For achieving the purpose, we examined the concept of comprehensive security, national crisis, and critical infrastructure and, using the holistic approach, we examined the comprehensive emergency management for suggesting the implications for establishing the critical infrastructure protection system; building up the high reliability organization, organizing and partnering, assessing the risk, preparing first responders, working with private owners of critical infrastructures, working with communities, improving the administrative capacity.

• 국제초고층학회논문집
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• 제11권2호
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• pp.137-144
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• 2022

As one of the most important vertical transportation equipment in super high-rise buildings, the construction elevator directly affects the project period, cost, and effectiveness. The paper proposes a new construction elevator with single-guide rail and multi-cages. It can solve the problems of single construction elevator capacity shortage and efficacy decrease with height reduction, the occupancy of plan and elevation position of multiple construction elevators, and extension of total construction period by cycling operation of multi-cages on a single-guide rail. The paper focuses on the design and research of the main components of the equipment, such as the rotating guide rail mechanism, vertical bearing mast tie system, segmented electrical power supply system, group control scheduling system, and safety anti-collision system.

• 대한교통학회지
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• 제33권2호
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• pp.145-158
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• 2015

네트워크 경쟁력은 항공산업 본연의 경쟁력으로, 잠재수요를 확보한 목적지에 신규노선을 개설하는 것은 네트워크 경쟁력을 강화하기 위한 대표적인 방법이다. 최근 들어 공항당국을 중심으로 신규항공사를 유치하고 노선을 증설하며 운항을 증편하는 활동이 활발해지고 있는 추세이며, 이에 따라 유발수요를 추정하는 방법에 대한 필요성이 증대하고 있다. 따라서 본 연구는 신규노선을 개설하는 경우 수요 예측에 대한 모델을 제안한다. 선행 연구 검토를 통해 유발 수요를 네 가지 유형, 즉 직항, 이원, 배후 및 브리지 수요로 구분하였으며, 수요 유형별로 통계적으로 유의한 설명변수를 선정하였다. 거리, 주변 공항 대비 상대적 용량 및 우회도가 주요 독립변수로 검토되었고, 인천공항의 사례를 중심으로 이 독립변수들과 통계적으로 유의한 계수값을 도출하여 신규 노선 개설 시 유발 수요를 예측하기 위한 모델을 제안하였다. 본 연구가 항공관련 기관들이 신규 항공 노선을 개발관련 연구를 촉진시키는 계기가 되기를 기대해 본다.

• Korean Chemical Engineering Research
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• 제58권1호
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• pp.150-162
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• 2020

The proprietary post-combustion CO₂ solvent (KoSol) developed by the Korea Electric Power Research Institute (KEPRI) was applied at the Shanghai Shidongkou CO₂ Capture Pilot Plant (China Huaneng CERI, capacity: 120,000 ton CO₂/yr) of the China Huaneng Group (CHNG) for performance evaluation. The key results of the pilot test and data on the South Korean/Chinese electric power market were used to calculate the predicted cost of CO₂ avoided upon deployment of CO₂ capture technology in commercial-scale coal-fired power plants. Sensitivity analysis was performed for the key factors. It is estimated that, in the case of South Korea, the calculated cost of CO₂ avoided for an 960 MW ultra-supercritical (USC) coal-fired power plant is approximately 35~44 USD/tCO₂ (excluding CO₂ transportation and storage costs). Conversely, applying the same technology to a 1,000 MW USC coal-fired power plant in Shanghai, China, results in a slightly lower cost (32~42 USD/tCO₂). This study confirms the importance of international cooperation that takes into consideration the geographical locations and the performance of CO₂ capture technology for the involved countries in the process of advancing the economic efficiency of large-scale CCS technology aimed to reduce greenhouse gases

• 농업과학연구
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• 제43권3호
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• pp.450-458
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• 2016

High performance small and mid-sized tractors are required for dryland and orchard operations. A power transmission system is the most important issue for the design of high performance tractors. Many operations, such as loading and lifting, use hydraulic power. In the present study, a hydraulic power transmission system for the 3-point hitch of a 50 kW narrow tractor was developed and its performance was evaluated. First, major components were designed based on target design parameters. Target operations were spraying, weeding, and transportation. Main design parameters were determined through mathematical calculation and computer simulation. The capacity of the hydraulic cylinder was calculated taking the lifting force required for the weight of the implements into consideration. Then, a prototype was fabricated. Major components were the lifting valve, hydraulic cylinder, and 3-point hitch. Finally, performance was evaluated through laboratory tests. Tests were conducted using load weights, lift arm sensor, and lift arm height from the ground. Test results showed that the lifting force was in the range of 23.5 - 29.4 kN. This force was greater than lifting forces of competing foreign tractors by 3.9 - 4.9 kN. These results satisfied the design target value of 20.6 kN, determined by survey of advanced foreign products. The prototype will be commercialized after revision based on various field tests. Improvement of reliability should be also achieved.