• 조명전기설비학회논문지
• /
• 제17권1호
• /
• pp.116-123
• /
• 2003

본 논문에서는 SMPS의 교류 입력측 역률을 개선시킬 수 있는 전치 레귤레이터로서 interleaved 승압형 컨버터를 관하여 연구하였다. Interleaved 승압형 역률보상 컨버터(IBPFC)는 입력전류를 두 개의 스위칭 소자에 의하여 50%씩 나누어져 흐르게 함으로써, 내부 전류제어 루프 얼이 전압제어 루프만으로 제어계를 구성하여 입력전류 리플을 줄일 수 있다. 즉, IBPFC를 구성하는 각각의 부스트 컨버터 cell을 불연속 전류모드로 동작시키더라도 전체적인 입력전류의 파형은 연속이 되어 입력전류 리플이 감소하게 된다. 불연속 전류모드로 동작하는 IBPFC를 해석하기 위하여 스위칭 상태에 따라서 6개의 모드로 구분하여 상태방정식을 구하였다. 또한, 각 상태방정식을 상태공간 평균화법을 이용하여 모델링하고, 미소변동분을 고려한 소신호 해석을 통하여 제어전달함수를 구할 수 있다. 또한, 제어전달함수를 이용하여 단일 전압제어 루프를 가지는 제어계를 설계하였으며, 이러한 해석 및 설계를 바탕으로 실험을 통하여 IBPFC의 역률개선 및 리플저감을 확인하였다.

• 한국항공우주학회지
• /
• 제39권6호
• /
• pp.567-575
• /
• 2011

우주발사체 개발은 우주 선진국으로 도약하기 위해 반드시 필요한 중요한 사업이며 막대한 비용과 장기간의 개발기간이 소요되는 만큼 위험이 존재한다. 성공적이고 효율적인 우주발사체 개발을 위해서는 적절한 개발 비용 산정이 중요하다. 또한, 우주발사체를 상업용 발사체로 활용하기 위해서는 다른 우주발사체와의 경쟁력 비교를 위해 생산 및 운용 비용의 추정도 필요하다. 본 논문에서는 한국에서 개발되는 우주발사체의 생산 및 운용 비용을 추정할 수 있도록 한국의 인력 및 기술 수준, 평균 작업시간 등과 같은 요소를 반영할 수 있는 한국화요소에 대해 분석하였다. 또한, 한국화요소를 적용하여 KSLV-II의 생산 및 운용 비용을 추정해보고 해외 발사체의 발사 비용과 비교를 통해 발사체 서비스 시장에서 상업용 발사체로서 경쟁력을 평가하였다.

• 한국식품영양학회지
• /
• 제19권4호
• /
• pp.435-447
• /
• 2006

This study was carried out to investigate foodservice management of child care centers in Ansan and to suggest the basic data for foodservice management improvement. A questionnaire survey of 48 child care centers in Ansan was undertaken. Child care centers were categorized large (children eve. 100) and small(children less than 100) by size and public and private by type. Survey questionnaires consisted of general background, employee, food inspection and storage, kitchen, cooking facilities, food distribution and hygiene utensils. The results of this study are summarized as follows: because 46.9% to 56.3% of the centers took a dietitian in employment, foodservices in most of centers were not managed by professionals. The average of employee were 0.77 persons in smalll centers and 1.65 persons in large centers. The average space of kitchen were 3.86 pyung in smalll center, 6.06 pyung (1 pyung=$3.3058m^2$) in large centers. According to the data analyzed from Food inspection and storage, kitchen, cooking facilities, food distribution and hygiene utensils, the results indicate that the foodservice management of child care centers were in a relatively poor state. The director in child care centers should recognize the importance of the sanitation management and pay more attention to food service facilities. To improve foodservice performance at child care centers, it is required fur the Ministry of Gender Equality and Family to develop both the kitchen facility model based on the general sanitation standards and guidelines for child care centers.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제18권1호
• /
• pp.64-88
• /
• 2024

Security and reliability are the utmost importance facts in intelligent networked vehicles. Stochastic Petri Net and Z (SPZN) as an excellent formal verification tool for modeling concurrent systems, can effectively handles concurrent operations within a system, establishes relationships among components, and conducts verification and reasoning to ensure the system's safety and reliability in practical applications. However, the application of a system with numerous nodes to Petri Net often leads to the issue of state explosion. To tackle these challenges, a refinement and abstraction method based on SPZN is proposed in this paper. This approach can not only refine and abstract the Stochastic Petri Net but also establish a corresponding relationship with the Z language. In determining the implementation rate of transitions in Stochastic Petri Net, we employ the interval average and weighted average method, which significantly reduces the time and space complexity compared to alternative techniques and is suitable for expert systems at various levels. This reduction facilitates subsequent comprehensive system analysis and module analysis. Furthermore, by analyzing the properties of Markov Chain isomorphism in the case study, recommendations for minimizing system risks in the application of intelligent parking within the intelligent networked vehicle system can be put forward.

• Journal of Mechanical Science and Technology
• /
• 제16권11호
• /
• pp.1485-1496
• /
• 2002

In order to investigate the fire-induced smoke movement in a three-dimensional room with an open door, numerical and experimental study was performed. The center, wall, and corner fire plumes for various sized fires were studied experimentally in a rectangular pool fire using methanol as a fuel. The numerical results from a self-developed SMEP (Smoke Movement Estimating Program) field model were compared with experimental results obtained in this and from literature. Comparisons of SMEP and experimental results have shown reasonable agreement. As the fire strength became larger for the center fires, the air mass flow rate in the door, average hot layer temperature, flame angle and mean flame height were observed to increase but the doorway-neutral-planeheight and the steady-state time were observed to decrease. Also as the wall effect became larger in room fires, the hot layer temperature, mean flame height, doorway-neutral-planeheight and steady-state time were observed to increase. In the egress point of view considering the smoke filling time and the early spread of plume in the room space, the results of the center fire appeared to be more dangerous as compared with the wall and the corner fire. Thus it is necessary to consider the wall effect as an important factor in designing efficient fire protection systems.

• Geomechanics and Engineering
• /
• 제30권1호
• /
• pp.27-44
• /
• 2022

Gravelly soil is a kind of special geotechnical material, which is widely used in the subgrade engineering of railway, highway and airport. Its mechanical properties are very complex, and will greatly influence the stability of subgrade engineering. To investigate the mechanical properties and failure mechanism of gravelly soils, this paper introduced and verified a new discrete element method (DEM) of gravelly soils in large scale direct shear test, which considers the actual shape and broken characteristics of gravels. Then, the stress and strain characteristics, particle interaction, particle contact force, crack development and energy conversion in gravelly soils during the shear process were analyzed using this method. Moreover, the effects of gravel content (GC) on the mechanical properties and failure characteristics were discussed. The results reveal that as GC increases, the shear stress becomes more fluctuating, the peak shear stress increases, the volumetric strain tends to dilate, the average particle contact force increases, the cumulative number of cracks increases, and the shear failure plane becomes coarser. Higher GC will change the friction angle with a trend of "stability", "increase", and "stability". Differently, it affects the cohesion with a law of "increase", "stability" and "increase".

• 토지주택연구
• /
• 제4권2호
• /
• pp.153-165
• /
• 2013

Deficiency in access to housing is a major manifestation of poverty. In the city of Bangalore, the poor and the marginalized constitute nearly 30 percent of the 8.47 million population (2011 Census) and are living in the nearly 640 slums in addition to squatter settlements and pavements. The city sprawls over an area of 741 sq. kms (2007 estimates) and the poor have very little access to personal living space. According to the Integrated Housing and Slum Development Program guidelines, each household with four average members should have 25 sq. meters of living space. In the case of poor of Bangalore, the attainment of even this minimum is a far cry. In recognition of this acuteness with regard to the problem of housing, the government has introduced schemes like the Jawaharlal Nehru National Urban Renewal Mission and the Rajiv Awas Yojana. And these schemes have witnessed only a limited success. Whenever the problem of housing for the urban poor is considered, the state and location of slums get into focus. The people living in slums are a crucial and inevitable support to the city economy. Relocation of slum people is fraught with loss of productivity and strain on the transport system and on the incomes of the poor. Their needs like housing, schooling, health centers, creches, hospices etc. have to be provided for. Financial support to the poor with regard to their housing needs will have to be imaginatively provided by banks and related institutions.

• 한국태양에너지학회 논문집
• /
• 제30권2호
• /
• pp.87-95
• /
• 2010

This study analyzed the performance of solar chimney system for natural ventilation in underground space. A mathematical model of the solar chimney was proposed in order to predict its performance under varying parameters and Korea climatic condition. Steady state heat transfer equations were set up using a energy balanced equations and solved using a inverse matrix method. Numerical simulation program to analyze system was developed by using MATLAB. As the results, the ventilation performance of the solar chimney was determined by the temperature difference of air channel and inlet, and the temperature difference was influenced by insolation, stack height and distance of air gab. Also the solar chimney system can provide $262.9m^3/h$ of annual average ventilation rate. Because seasonal differences of ventilation rate was calculated within 25%, the solar chimney system can be used for every season in Korea climatic condition. Through this study, performance of solar chimney system for natural ventilation was verified by numerical method. Consequently, the solar chimney system is proved to be effective device for natural ventilation utilizing at all times, and the additional studies should be made through the experimental method for imagineering and commercialization.

• 대한교통학회지
• /
• 제19권3호
• /
• pp.61-73
• /
• 2001

본 연구는 부산의 도심에 위치한 대규모 교통유발시설 부설주차장의 적정규모 추정모형의 구축을 연구의 목적으로 하였다. 이를 위해 부설주차장 이용 차량의 평균 도착시간 간격과 평균 주차시간 간격을 이용한 대기행렬시뮬레이션인 GPSS모형을 사용하여 적정 주차장 규모를 산정한 후 연상면적과 적정주차면수의 관계를 용이하게 추출할 수 있는 회귀식을 이용하여 모형식을 구축하였다. 적정주차규모 모형을 구축한 결과 현재의 주차면 수는 적정주차면수에 비해 초과 공급되어 있어, 도심내의 주차장 과잉공급으로 인한 불필요한 승용차 이용을 방지하고, 토지이용의 효율성 제고를 위해서는 현 부설주차장의 설치기준에 대한 개선이 필요할 것으로 판단된다. 그러나 본 연구의 수행 과정에서 나타난 문제점은 대상시설의 선정에서 이용율이 현저히 떨어지고 있는 시설들을 포함시킴으로 인해 적정주차규모가 다소 적게 산정될 수 있다는 점이다. 또한 본 연구에서는 주차 이용행태만으로 적정주차규모를 산정했으나 주차장의 규모에 관한 연구는 토지이용과 교통여건, 상권 등이 종합적으로 고려된 연구가 되어야 할 것으로 판단된다.

• 한국생활과학회지
• /
• 제19권4호
• /
• pp.745-760
• /
• 2010

The purposes of this study were to investigate the state of indoor thermal and air environment during winter in the one-room type multi-family houses occupied by university students and to analyze factors which influenced this environment. Field survey was conducted in 10 houses between 30th January, 2009 and 13th February, 2009 which measured indoor thermal and air elements as well kept records of interviews with residents and other related factors. Measured elements were air temperature, relative humidity, as well as concentrations of $CO_2$, CO, TVOC, and PM-10. The results can be summarized as follows. 1) The mean air temperature in each house ranged from 19.3 to $25.3^{\circ}C$, so most houses were not suitable for evaluation criteria($20-22^{\circ}C$). The average $CO_2$ concentration in each house was 965~3259ppm, so most houses exceeded evaluation criteria(1000ppm). The average TVOC concentration in each house were 0.00~1.17ppm, 5 houses exceeded evaluation criteria(0.12ppm). 2) Relative humidity, CO concentration, and PM-10 concentration were suitable for evaluation criteria. Therefore, indoor thermal and air environment during winter in one-room type multi-family housing occupied by university students was found to be generally uncomfortable. Important factor which were found to influence air temperature and the concentration of $CO_2$ were smaller space capacity than general house. Other factors which were found to influence the environment of these houses were the existence of a balcony as well as factors relating to the behavior of occupants such whether or not heating were operated, whether windows were opened, whether fans used, whether occupants smoked or used cosmetics, and whether the space was dusted.