• 제목/요약/키워드: Sub System

검색결과 8,105건 처리시간 0.034초

BASIC RESEARCH OF SUB-PACKAGE PROBLEM IN KOREAN CONSTRUCTION INDUSTRY

  • Jinho Shin;Furusaka Shuzo
    • 국제학술발표논문집
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    • The 3th International Conference on Construction Engineering and Project Management
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    • pp.635-641
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    • 2009
  • In the building construction, the specialist contractors play the important roles in the point of the quality securing. Therefore, it is very important for the construction industry to study the sub-package problem. The sub-package problem includes two problems which should be solved. One is to decide the scope of works of each specialist contractor, and another one is to decide the particular specialist contractor which carries out the work. However, the sub-package problem in Korea is not clarified yet, although the circumstance around it has changed rapidly. Many factors influence to the sub-package problem regardless of internal factors or external factors of the project. The general contractor usually decides the sub-package under considering the project conditions. In case of the internal factors, each general contractor manages the organization and materials. But the external factors are relatively more difficult to control and predict than internal ones. But out of the external factors, the legal system has very close relationship with a sub-package problem especially in Korean construction system. So, this paper clarifies relationship between the legal system relating subcontracting and the state of sub-package.

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미세먼지 계절관리제 시행 여부에 따른 실내 PM2.5 농도 분포 및 노출에 따른 건강위해성 평가 (Indoor PM2.5 Concentration Distribution and Health Risk Assessment according to the Implementation of a Seasonal Management System)

  • 박신영;윤단기;장혁;윤성원;이철민
    • 한국환경보건학회지
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    • 제49권4호
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    • pp.218-227
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    • 2023
  • Background: Since 2019, the Ministry of Environment has implemented a seasonal fine dust management system from December to March, targeting high PM2.5 levels with the aim of reducing PM2.5 concentrations and protecting public health. The focus of improving the seasonal management system lies in the atmospheric PM2.5 levels. Considering the primary goal of protecting public health, it is necessary to analyze the policy effects from an exposure perspective rather than a concentration-based approach. Objectives: This study aims to quantitatively assess the improvement of indoor PM2.5 levels and the health impacts of the seasonal management system by comparing the periods before and during its implementation in residential environments. Methods: PM2.5 concentrations within residential environments in a metropolitan area were measured using an optical particle counter (IAQ-C7, K-weather, Ltd, Korea) at one-minute intervals during the pre-implementation period (November 21~25, 2022) and during the implementation period (December 19~23, 2022). Based on the measured PM2.5 concentrations, a quantitative evaluation of cancer and mortality risks was conducted according to age and gender. Results: The results of comparing indoor and outdoor PM2.5 concentrations before and during the implementation of the seasonal management system showed a decrease of approximately 56.6% and 47.9%, respectively. Health risk assessments revealed that both the safety-limit-based and safety-target-based Hazard Quotients (HQ) exceeded the threshold of 0.1 for children under 19 years of age, both before and after the implementation. The mortality risk decreased by approximately 47.9% after the implementation, with children aged 0-9 showing the highest mortality risk at 0.9%. Conclusions: The findings of this study confirmed the positive health impacts of the seasonal management system across all age groups, particularly children under 19 who are more vulnerable to fine dust exposure.

Refractive-index Prediction for High-refractive-index Optical Glasses Based on the B2O3-La2O3-Ta2O5-SiO2 System Using Machine Learning

  • Seok Jin Hong;Jung Hee Lee;Devarajulu Gelija;Woon Jin Chung
    • Current Optics and Photonics
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    • 제8권3호
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    • pp.230-238
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    • 2024
  • The refractive index is a key material-design parameter, especially for high-refractive-index glasses, which are used for precision optics and devices. Increased demand for high-precision optical lenses produced by the glass-mold-press (GMP) process has spurred extensive studies of proper glass materials. B2O3, SiO2, and multiple heavy-metal oxides such as Ta2O5, Nb2O5, La2O3, and Gd2O3 mostly compose the high-refractive-index glasses for GMP. However, due to many oxides including up to 10 components, it is hard to predict the refractivity solely from the composition of the glass. In this study, the refractive index of optical glasses based on the B2O3-La2O3-Ta2O5-SiO2 system is predicted using machine learning (ML) and compared to experimental data. A dataset comprising up to 271 glasses with 10 components is collected and used for training. Various ML algorithms (linear-regression, Bayesian-ridge-regression, nearest-neighbor, and random-forest models) are employed to train the data. Along with composition, the polarizability and density of the glasses are also considered independent parameters to predict the refractive index. After obtaining the best-fitting model by R2 value, the trained model is examined alongside the experimentally obtained refractive indices of B2O3-La2O3-Ta2O5-SiO2 quaternary glasses.

가스발생기의 연료과잉가스 후연소용 O2/CH4 가스 공급시스템 설계 (Modeling and Simulation of O2/CH4 Gas Supply System of Afterburner for Fuel-rich Gas of Gas Generator)

  • 왕승원;이광진;정용갑;한영민
    • 한국추진공학회지
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    • 제18권2호
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    • pp.86-92
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    • 2014
  • 나로우주센터에 구축되는 연소기 연소시험설비(CCTF)에는 한국형발사체(KSLV-II)에 적용된 터보펌프식 엔진의 가스발생기 시험시 생성되는 연료과잉가스를 연소시키기 위한 후연소시스템이 포함되어 있다. 후연소시스템은 $O_2$$CH_4$ 가스를 공급받아 연료과잉가스를 소모시킨다. 본 연구는 연소기 연소시험설비의 상세설계 자료를 바탕으로 후연소시스템의 가스공급시스템에 대해 AMESim 상용프로그램을 이용하여 해석하였다. 그 결과 상세설계에 적용된 레귤레이터, 공급배관, 오리피스크기 등으로 가스사용량을 예측하고, 상세설계의 타당성을 검증하였다.

SF6 분해 및 무해화 시스템의 개념 설계 및 운영 결과 (Conceptual Design and Operation Results for SF6 Decomposition and Pollution Control System )

  • 이중원;김미영;안지호;변영환
    • KEPCO Journal on Electric Power and Energy
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    • 제8권2호
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    • pp.111-118
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    • 2022
  • SF6 is used as an insulating gas because of its excellent electrical insulation properties, non-toxicity, and non-inflammability. On the other hand, the global warming potential of SF6 is 23,900 times higher than that of CO2. The Korea electric power cooperation (KEPCO) is responsible for 80% of the domestic SF6 usage, and approximately 6,000 tons are currently charged in electrical and power facilities. KEPCO will gradually replace the insulating gas with SF6-free gas from 2023. SF6 decomposition facilities are required because more than 60 tons of SF6 will need to be disposed of annually from existing equipment. This study developed a novel decomposition and pollution control system that can process 60 tons of SF6 per year. This facility can decompose more than 97.7% of SF6, with the emissions of hazardous and toxic materials below the legal limit.

The Effect of TiO2 Addition on Low-temperature Sintering Behaviors in a SnO2-CoO-CuO System

  • Jae-Sang Lee;Kyung-Sik Oh;Yeong-Kyeun Paek
    • 한국분말재료학회지
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    • 제31권2호
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    • pp.146-151
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    • 2024
  • Pure SnO2 has proven very difficult to densify. This poor densification can be useful for the fabrication of SnO2 with a porous microstructure, which is used in electronic devices such as gas sensors. Most electronic devices based on SnO2 have a porous microstructure, with a porosity of > 40%. In pure SnO2, a high sintering temperature of approximately 1300℃ is required to obtain > 40% porosity. In an attempt to reduce the required sintering temperature, the present study investigated the low-temperature sinterability of a current system. With the addition of TiO2, the compositions of the samples were Sn1-xTixO2-CoO(0.3wt%)-CuO(2wt%) in the range of x ≤ 0.04. Compared to the samples without added TiO2, densification was shown to be improved when the samples were sintered at 950℃. The dominant mass transport mechanism appears to be grain-boundary diffusion during heat treatment at 950℃.

공간자료구조를 활용한 단층인식 시스템 (Fault Detection System Using Spatial Index Structure)

  • 방갑산
    • 대한전자공학회:학술대회논문집
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    • 대한전자공학회 2005년도 추계종합학술대회
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    • pp.1205-1208
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    • 2005
  • By adding user interface to the usual router, an improved functional router is implemented in this paper. Due to the massive amount of spatial data processing, spatial information processing area has been rapidly grown up in recent years based on powerful computer hardware and software development. Spatial index structures are the core engine of geographic information system(GIS). Analyzing and processing of spatial information using GIS has a lot of applications and the number application will be increased in the future. However, study on the under ground is in its infancy due to invisible characteristic of this information. This paper proposes the sub-surface fault detection system using the sub-surface layer information gathered from elastic wave. Detection of sub-surface fault provides very important information to the safety of above and sub-surface man made structures. Development of sub-surface fault detection system will serve as a pre-processing system assisting the interpretation of the geologist.

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EXPERIMENT AND SIMULATION OF A WIND-DRIVEN REVERSE OSMOSIS DESALINATION SYSTEM

  • Park, Sang-Jin;Clark C.K. Liu
    • Water Engineering Research
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    • 제4권1호
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    • pp.1-17
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    • 2003
  • A mathematical model was developed to simulate the performance of a prototype wind-powered reverse osmosis desalination system. The model consists of two sub-models operated in a series. The first sub-model is the wind-energy conversion sub-model, which has wind energy and feed water as its input and pressurized feed water as its output. The second sub-model is a reverse osmosis (RO) process sub-model, with pressurized feed water as its input and the flow and salinity of the product water or permeate as its output. Model coefficients were determined based on field experiments of a prototype wind powered RO desalination system of the University of Hawaii, from June to December 2001. The mathematical model developed by this study predicts the performance of wind-powered RO desalination systems under different design conditions. The system optimization is achieved using a linear programming approach. Based on the results of system optimization, a design guide is prepared, which can be used by both manufacturer and end-user of the wind-driven reverse osmosis system.

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체계중복 설정문제에 있어서 Redundancy 우선배치에 관한 연구 (A study for setting prior allocation of redundancy in parallel series system)

  • 조남호
    • 산업경영시스템학회지
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    • 제9권14호
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    • pp.45-48
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    • 1986
  • This paper studies reliability growth model in redundancy allocation of Parallel-series system in which several series system is linked parallelly, The model is generalized by system redundancy of sub-system that have components redundancy. The stage of components in each sub-system is established differently. At the same time by assigned the different number of constraints to the sub-system, this paper deals with rather practical reliability growth model.

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Al(OH)3-SiO2-AlF3계에서 기상-고상반응에 의한 뮬라이트 휘스커 합성 (Synthesis of Mullite Whiskers by Vapor-Solid Reaction in the System of Al(OH)3-SiO2-AlF3)

  • 이홍림;강종봉
    • 한국세라믹학회지
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    • 제43권6호
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    • pp.376-382
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    • 2006
  • In the $Al(OH)_3-SiO_2-AlF_3$ system, leaf-shaped fluorotopaz was first formed at $800^{\circ}C$ and mullite whisker was formed at $1,100^{\circ}C$. The mass transportation of Al and Si as gas phase, the fast reaction and growth, and the absence of liquid phase existence in mullite whisker showed that the formation and growth of mullite was from the solid-vapor reaction.