• Korean Journal of Construction Engineering and Management
• /
• v.7 no.5
• /
• pp.167-176
• /
• 2006

It was found that Korean Standard of Estimate which has been used as the only basis of cost estimate of public construction projects had some side effects such as jerry-build construction and over-estimation because it failed to reflect the current price and the state-of-the-art construction methods in a changing construction environment. Therefore, the government decided to gradually introduce historical construction cost into cost estimate of public construction projects from 2004. This paper presents analytic criteria and a process model for deducing more current and reasonable historical construction cost for contract items from not only previous contract prices but also all of the other bid prices that were not contracted. The procedure of estimating actual unit cost proposed in this paper focuses on the removal of abnormal values including strategically too low or high prices and the time correction. In addition, basic research is conducted for the correction of actual unit cost through the analysis of fluctuation of bid price depending on bidding types and rates of successful bid. It is anticipated that the effective use of the proposed process model for estimating actual unit cost would make the cost estimation more current and reasonable.

• Korean Journal of Construction Engineering and Management
• /
• v.1 no.1 s.1
• /
• pp.63-71
• /
• 2000

The paper considers two non-deterministic methods of analysing the risk exposure in a cost estimate The fist method(referred to as the 'conventional statistical' method) analyses cost data directly, to describe a probability distribution for total cost. The second method(referred to as the 'Monte Carlo simulation' method) interprets cost data directly, to generate a probability distribution for total costs from the descriptions of elemental cost distribution. The common practice of allowing for risk through an all-embracing contingency sum or percentage addition is challenged. Rather than excluding conventional, non-deterministic methods, they are here presented as possibly the only of effective foundation on which to risk management in cost estimating.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2021.06a
• /
• pp.178-178
• /
• 2021

최근 들어 기후변화로 인한 극심한 가뭄 피해가 한반도에 발생하고 있다. 가뭄 상황에 대비하여 댐을 안정적으로 운영하기 위해서는 갈수빈도 유입량에 대한 분석이 필수적이다. 갈수빈도해석의 경우, 홍수빈도해석과 유사하게 확률밀도함수의 극값에 대한 확률값을 산정하며, 확률 분포형의 역함수에 비초과확률을 대입하여 산정한다. 그러나 홍수와 달리 가뭄은 지속기간이 긴 특성 탓에 자기상관을 고려해야하며, 댐 및 저수지 등 대규모 시설물의 경우 일반적인 하천과 달리 저류효과로 인해 누적 유량에 대한 고려가 필요하다. 이에 K-water는 자체 제작한 누가차분법 및 Disaggregation 두 가지 방법을 채택하여 실무에서 사용해왔다. 그러나 누가차분법을 사용할 경우, 빈도유입량이 지나치게 크게 산정되는 문제가 있으며, Disaggregation 방법을 사용하는 경우, 특정 빈도 이상의 극한가뭄에서 유입량의 차이가 유의미하지 않아 산정된 빈도유입량과 최근 발생한 극심한 가뭄의 실측유입량간 큰 차이가 발생하고 있다. 따라서 본 연구에서는 자기상관을 고려한 선형회귀모형에 근거하여 빈도유입량을 배분하는 방법을 제안한다. 또한, 앞서 서술한 네 가지 빈도유입량 방법(월빈도분석, 누가차분법, K-water Disaggregation, 자기상관 선형회귀모형)에 대한 수식적 비교를 수행하며, 국내 댐 유역에 적용 및 평가를 통해 자료 특성에 따른 적절한 빈도유입량 산정방식에 대한 기준을 제안한다. 본 연구를 통해 가뭄특성을 고려한 합리적인 댐 유입량을 산정함으로써 보다 유연한 수자원시설물의 가뭄대응이 이루어질 것으로 기대된다.

• Journal of Digital Convergence
• /
• v.15 no.11
• /
• pp.107-112
• /
• 2017

This paper performed an experimental study to test the validity of the prospect theory proposed by Tversky and Kahneman as an alternative to the expected utility theory. 115 college students attended the hypothetical games to choose one of two lotteries, one is safe option while the other one is risky. The risky options were set up to have low, medium or high probability of payoffs or losses. The amount of payoffs and losses of the lotteries was either large or small. Maximum likelihood estimation of the hypothetical games have shown that in case of high probability of positive payoffs the respondents were risk averse and when the probability of positive payoffs were small the respondents were risk loving. when the possibility of loss is high they were risk loving, while the probability is of loss is low the respondents were found to be risk averse. When the probability of risky options were medium the results were significant statistically in case of only losses. The amount of positive payoff or losses does not affect the results. Overall the results of this experiments support the prospect theory more than those of Laury & Holts (2008).

• Journal of Korea Society of Industrial Information Systems
• /
• v.28 no.1
• /
• pp.27-34
• /
• 2023

The optimal assignment problem between agents and tasks is known as one of the representative problems of combinatorial optimization and an NP-hard problem. This paper covers multi agent-multi task assignment problems with uncertain completion probability. The completion probabilities are generally uncertain due to endogenous (agent or task) or exogenous factors in the system. Assignment decisions without considering uncertainty can be ineffective in a real situation that has volatility. To consider uncertain completion probability mathematically, a mathematical formulation with stochastic programming is illustrated. We also present an algorithm by using the sample average approximation method to solve the problem efficiently. The algorithm can obtain an assignment decision and the upper and lower bounds of the assignment problem. Through numerical experiments, we present the optimality gap and the variance of the gap to confirm the performances of the results. This shows the excellence and robustness of the assignment decisions obtained by the algorithm in the problem with uncertainty.

• Journal of KIISE:Computing Practices and Letters
• /
• v.13 no.2
• /
• pp.100-109
• /
• 2007

Object recognition of service robots is very important for most of services such as delivery, and errand. Conventional methods are based on the geometric models in static industrial environments, but they have limitations in indoor environments where the condition is changable and the movement of service robots occur because the interesting object can be occluded or small in the image according to their location. For solving these uncertain situations, in this paper, we propose the method that exploits observed objects as context information for predicting interesting one. For this, we propose the method for modeling domain knowledge in probabilistic frame by adopting Bayesian networks and ontology together, and creating knowledge model dynamically to extend reasoning models. We verify the performance of our method through the experiments and show the merit of inductive reasoning in the probabilistic model

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.23 no.7
• /
• pp.783-790
• /
• 2017

An acceptable proximity assessment collision probability is widely considered to be less than $10^{-4}$ in maritime traffic safety audit schemes. In the 1970s, Fujii, Macduff and colleagues introduced various models for collision probability of aberrancy in the community. Although existing studies ensured acceptable proximity collision probability, around $10^{-4}$, they were constrained by assumptions. A lack of support for the proximity probability criterion has been investigated in this study for practical use. The appropriate proximity probability for different size vessels in both straight and curved lanes has been analyzed based on GICOMS data. As a result, reasonable proximity collision probabilities were determined for various vessel traffic conditions. Accordingly, necessary improvements in the maritime traffic system have been suggested in consideration for various maritime traffic situations and conditions.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2017.05a
• /
• pp.349-349
• /
• 2017

표준강수지수(Standardized precipitation index, SPI)는 가장 널리 사용되고 있는 가뭄지수로, 우리나라 뿐만 아니라 세계기상기구(World Meteorological Organization)에서도 추천하고 있는 대표적인 기상학적 가뭄 지수라고 할 수 있다. 현재 표준강수지수는 2변수 gamma 분포를 적용하여 강수 부족 상황을 지수화하여 나타내고 있는데, 일부 연구에서는 다른 확률분포형의 적용하기도 하였다(Guttman, 1999; Lloyd-Hughes and Saunders, 2002; Stagge et al., 2015). 우리나라에서는 유원희(2000)에 의해 Pearson type 3, 2변수 gamma, generalized logistic, GEV, 3변수 log-normal 분포에 따른 SPI 산정 결과를 비교한 연구가 수행되었는데, SPI 산정에는 분포형별 차이가 뚜렷하지 않다는 결론을 얻었다. 그러나 이때 금강유역 내 지점에 국한하여 적용하였고, 분포형별 적합도 검정을 수행하지 않고 SPI 산정결과만을 비교하여 우리나라에 일반적으로 적용하기에는 어려움이 있다. 따라서 본 연구에서는 우리나라의 강우특성을 반영할 수 있도록 다양한 확률분포형을 고려하여 표준강수지수를 분석하고자 한다. 이를 위해 관측기간이 30년 이상인 기상관측소의 월단위 강우자료를 구축하고, 월단위 강우자료에 다양한 확률분포형을 적용하고자 한다. 이때 적용하는 확률분포형은 2변수 gamma, Gumbel, normal 분포이다. 적정 확률분포형 선정을 위해 적합도 검정을 수행하고자 한다. 또한 각 분포형별로 산정된 표준강수지수를 기존 표준강수지수와 비교검토하고자 한다.

• Proceedings of the Korean Institute Of Construction Engineering and Management
• /
• 2007.11a
• /
• pp.54-59
• /
• 2007

Recently, Apartment Reconstruction Projects are performing only with the basis of profitability without establishing either certain criteria or standard guideline. In addition, the profitability information contained in a disposal plan tends to be considered as a fixed value, and it is frequently changeable because reconstruction projects have such a long time to complete and many participants with respective interests. As mentioned above, the new approach needs to be developed which covers the limitation of the unvaried one. Consequently, this study focuses on the probability approach considering not only variances that affect the profit, but the relationship between profit and risk, and then is modeling. This study is anticipated to improve the reliability and accuracy of expected value as well as apply to the decision making criteria quantitively about potentially hidden risks in that projects.

• Proceedings of the Korean Institute of Industrial Safety Conference
• /
• 2003.10a
• /
• pp.225-230
• /
• 2003

원자력발전소의 안전성을 평가하는 확률론적 안전성평가(PSA) 기법 내에서 인간신뢰도분석(HRA： Human Reliability Analysis)은 파악된 사고경위 중 부적절한 인적행위사건에 대한 분석 및 평가를 담당하고 있다. 여러 HRA 전문가들이 제기하고 있는 기존 PSA HRA의 개선점 중 정성적 분석 관점에서 중요하게 고려되는 사항을 정리하면 다음과 같다. 첫째, 운전원의 진단 및 상황판단 또는 의사결정 단계에서의 특정한 오류 유발사항(error producing conditions or error forcing context)을 분석할 수 있는 방법이 필요하며, 둘째, 다양한 인적오류사건의 고려이다.(중략)