• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2014년도 추계 학술논문 발표대회
• /
• pp.98-99
• /
• 2014

Construction equipment cost is critical to estimate the total construction costs, particularly in large and complicated projects. Despite its importance, the construction equipment cost may not reflect the current market value since the equipment database is being updated every 6 years at most. To keep construction equipment cost up to date, it is highly recommended to use the standard market price that is reported each year by the Ministry of Security and Public Administration (MOSPA). However, there is still a gap to adopt the standard market price system for the construction equipment cost computing system. Therefore, this paper suggests an effective way to develop a construction equipment cost estimation system.

• 전력전자학회논문지
• /
• 제26권4호
• /
• pp.298-301
• /
• 2021

A mechanical angle estimator is presented in this study to achieve the sensorless control of permanent magnet synchronous motor (PMSM) used in driving a reciprocating compressor. Braking the PMSM at a specific mechanical angular position is critical for the silent stoppage of the reciprocating compressor. The performance of conventional mechanical angle observers used in reciprocating compressor drives can be seriously affected according to gains of the speed controller because such observers rely on the magnitude of current ripples. A speed ripple-based mechanical angle estimator is proposed to solve this problem. Experimental results showed the effectiveness of the proposed method.

• 한국소음진동공학회논문집
• /
• 제27권1호
• /
• pp.20-27
• /
• 2017

This study investigated the problems in current practice of drive-train resonance analysis procedure and suggested solutions. The first problem is the resonance occurrence at the un-identified resonance point by the current practice, as for a solution the force spectrum analysis for each critical force transmitting component was suggested. The second one is the inaccurate estimation of potential resonance point in eigenfrequency analysis because of the non-consideration about the eigenfrequency dependency on rotor-speed, the fine linearization at each rotor speed point all over operational range was proposed to account for the affection. Lastly the insufficient time for resonance activation under run-up simulation condition was recognized as a problem in resonance load increasing analysis, as an alternative, steady state condition was suggested to estimate the maximum load increasing level.

• Structural Engineering and Mechanics
• /
• 제89권4호
• /
• pp.363-374
• /
• 2024

Significant changes have been made to estimate the punching shear capacity for edge column-slab joints in the latest editions of most current codes. The revised equations account for axial forces as well as moments conveyed to columns from slabs, which have a substantial impact on the punching resistance of such joints. Many key design parameters, such as reinforcement-ratio, concrete strength, size-effect, and critical-section perimeter, were treated differently or even ignored in various code provisions. Consequently, wide ranges of predicted punching shear strength were detected by applying different code formulas. Therefore, it is essential to assess the various current Codes' design-equations. Because of the similarity in estimated outcomes, only the ACI, EC, and SNiP are used in this study to cover a wide range of estimation ranges from highly conservative to unconservative. This paper is devoted to analyzing the techniques in these code provisions, comparing the estimated punching resistance with available experimental data, and finally developing efficient models predicting the punching capacity of edge column-slab connections. 63 samples from past investigations were chosen for validation. To appropriately predict the punching shear, newly updated equations for ACI and SNiP are provided based on nonlinear regression analysis. The proposed equations'results match the experimental data quite well.

• 한국해양학회지
• /
• 제26권4호
• /
• pp.340-349
• /
• 1991

1987년 8월 24일부터 9월 28일까지 경기만에 발달한 조류 기원 사퇴위에서 측정한 조류 자료를 분석하여 해저면 상부 1.0 m 에서의 조류 속도(U /SUP 100/) 및 경계면에 서의 전단 속도(U /SUP */)를 구하였다. 전 조사기간 동안 평균 조류 속도는 중충(해 저면 상부 9.0 m)에서 창조시 56.3 cm/sec, 낙조시 63.7 cm/sec 의 지수는 0.15로 추 정된다. 해저 경계층에서의 유속 구조가 대수적 속도 구조 (logarithmix velocity profile) 가정을 이용하여 구한 U /SUP 100/, U /SUP */의 평균값은 각각 41.4 cm/sec로 계산되었다. 본 연구에서 계산된 평균 U /SUP */ 값은 (2.39 cm/sec)동일 지 역에서 최(1990)가 보고한 경계면에서의 임계전단 속도 U /SUP *c/ 보다 상당히 크며, 따라서 본 연구지역의 모래는 대부분의 조석 기간중 쉽게 침식 운반되는 것으로 보여 진다.

• Journal of the Korean Data and Information Science Society
• /
• 제21권6호
• /
• pp.1181-1190
• /
• 2010

보험회사가 보험계약자들의 적절한 보험료를 산출하는 것은 회사나 계약자들 모두에게 중요한 문제이다. 보험료를 결정하는 방법에는 보험회사가 보유하고 있는 매뉴얼에 근거하여 계약자들마다 같은 보험료를 부과하는 방법, 보험계약자 개인이나 집단에 관한 과거 기록에 바탕을 두어 보험료를 차등하여 정하는 방법, 그리고 위 두 가지 방법을 조합하여 보험료를 산정하는 방법 등이 있다. 이중 통계적인 모형에 기반을 둔 보험료 산정 방법에는 최대 정확도 신뢰도 이론이 있고, 이에 바탕을 둔 구체적인 접근법에는 뷸만 모형과 뷸만-스트라웁 모형 등이 있다. 본 논문에서는, 뷸만-스트라웁 모형을 확장하여, 자료 수가 늘어나면서 자료 평균의 변동성이 기대한 것보다 커지는 Hewitt의 아이디어를 반영한 모형에서, 새로운 비모수적 보험료 추정법을 제안한다. 또, 제안된 추정법을 모의자료에 적용해보고, 기존의 뷸만-스트라웁 추정량과 비교해본다.

• Geomechanics and Engineering
• /
• 제33권2호
• /
• pp.175-182
• /
• 2023

In general, the design of structures and its construction processes are fundamentally dependent on their foundation and supporting ground. Thus, it is imperative to understand the behavior of the soil under certain stress and drainage conditions. As it is well known that certain characteristics and behaviors of soils with fines are highly dependent on water content, it is critical to accurately measure and identify the status of the soils in terms of water contents. Liquid limit is one of the important soil index properties to define such characteristics. However, liquid limit measurement can be affected by the proficiency of the operator. On the other hand, dynamic properties of soils are also necessary in many different applications and current testing methods often require special equipment in the laboratory, which is often expensive and sensitive to test conditions. In order to address these concerns and advance the state of the art, this study explores a novel method to determine the liquid limit of cohesive soil by employing video-based vibration analysis. In this research, the modal characteristics of cohesive soil columns are extracted from videos by utilizing phase-based motion estimation. By utilizing the proposed method that analyzes the optical flow in every pixel of the series of frames that effectively represents the motion of corresponding points of the soil specimen, the vibration characteristics of the entire soil specimen could be assessed in a non-contact and non-destructive manner. The experimental investigation results compared with the liquid limit determined by the standard method verify that the proposed method reliably and straightforwardly identifies the liquid limit of clay. It is envisioned that the proposed approach could be applied to measuring liquid limit of soil in practical field, entertaining its simple implementation that only requires a digital camera or even a smartphone without the need for special equipment that may be subject to the proficiency of the operator.

• 교육녹색환경연구
• /
• 제14권1호
• /
• pp.1-9
• /
• 2015

정확한 공사비 추정은 성공적인 프로젝트의 개발에 필수적이다. BTL 사업과 같이 민간투자사업에 있어서 정확한 공사비 산정은 효과적인 예산확보와 파이낸싱에 필수적인 기본 정보가 된다. 공사비 견적의 정확도에 따라 입찰과 제안서의 정확도가 반영되므로 프로젝트를 통한 수익성 여부와 사업타당성을 확보할 수 있다. 본 연구는 정확한 공사비 분석과 활용을 위한 기초적인 연구로써 10년 정도 경과한 초 중등학교 민간투자사업(BTL)의 건축공사비를 분석하여 여러 참여주체들별로 공사를 할 수 있는 건축공사의 공종별 분포비율을 학교급별로 파악한다. 즉, 초 중등학교의 건축 공종별 구성비율을 전체 평균비율, 초등학교, 중학교, 고등학교별로 살펴보고 향후 유사한 공사를 수행하는 경우에 참여주체별로 활용할 수 있도록 하고자 한다.

• 대한토목학회논문집
• /
• 제28권1D호
• /
• pp.67-72
• /
• 2008

건설기계는 건설사업의 성공적인 수행을 위한 중요한 요인이다. 그리고 건설기계에 소요되는 비용이 건설공사비에서 차지하는 비중이 크다. 따라서 건설기계 비용의 산정은 건설계획 단계에서 중요한 업무이다. 이를 위해서 우리나라는 표준 품셈에 제시된 건설기계 시공능력 산정식을 이용하여 건설기계의 시간당 작업량을 계산하는 방식을 활용하고 있다. 그러나 건설기계의 성능은 개선되고 있으나 시공능력 산정식에서 활용되고 있는 작업효율은 이를 반영하지 못하는 실정이다. 이에 본 연구는 유압식 백호, 로우더, 덤프트럭을 대상으로 현장실사를 통해 작업효율을 실측하였다. 그 결과 백호와 로우더는 현재 활용중인 작업효율보다 현장실사 값이 높게 나타났으며, 덤프트럭은 낮게 나타났다. 본 연구결과를 바탕으로 건설기계의 작업효율 표준 산정식에 대한 정의가 수립되어야 하며, 체계적이고 장기적인 조사를 거쳐 작업효율의 개정이 필요할 것으로 사료된다.

• Fisheries and Aquatic Sciences
• /
• 제12권2호
• /
• pp.118-129
• /
• 2009

To develop a sustainable management model for oyster farming in Pukman Bay, Korea, we estimated the carrying capacity for oyster farming using food availability data. Optimal culture densities were calculated to be 124-133 individuals per unit flux area ($m^2$) and 310-330 individuals per string. The present annual production is approximately 1,038 tons/year, which is 87% of the estimated maximum yield of 1,193 tons/year. Therefore, considering annual fluctuations and a critical buffer to reduce ecological impacts, the current level is within optimal conditions. During periods of increased water temperature, energy demand was largely met by high primary production. The food supply significantly decreased as the harvest season approached, and 10 out of 21 oyster farms had a deficient food supply for at least 1 month. Therefore, these farms (39% of the farms within the bay) exceeded optimal densities.