• 한국건설관리학회논문집
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• 제6권5호
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• pp.69-77
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• 2005

Change is inevitable and is a reality of construction projects. Most construction contracts include change clauses and allowing contractors an equitable adjustment to the contract price and duration caused by change. However, the actions of a contractor can cause a loss of productivity and furthermore can result in disruption of the whole project because of a cumulative or ripple effect. Because of its complicated nature, it becomes a complex issue to determine the cumulative impact (ripple effect) caused by single or multiple change orders. Furthermore, owners and contractors do not always agree on the adjusted contract price for the cumulative Impact of the changes. A number of studies have attempted to quantify the impact of change orders on project costs and schedule. Many of these attempted to develop regression models to quantify the loss. However, regression analysis has shortcomings in dealing with many qualitative or noisy input data. This study develops ANN models to classify and quantify the labor productivity losses that are caused by the cumulative impact of change orders. The results skew that ANN models give significantly improved performance compared to traditional statistical models.

• Structural Engineering and Mechanics
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• 제34권5호
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• pp.625-634
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• 2010

The objective of this paper is to apply a new proposed accuracy indicator to quantify the true and false modes for Eigensystem Realization Algorithm using output-based responses. First, a discrete mass-spring system and a simply supported continuous beam were modelled using finite element method. Then responses are simulated under random excitation. Natural Excitation Technique using only response measurements is applied to compute the impulse responses. Eigensystem Realization Algorithm is employed to identify the modal parameters on the simulated responses. A new accuracy indicator, Normalized Occurrence Number-NON, is developed to quantitatively partition the realized modes into true and false modes so that the false portions can be disregarded. Numerical simulation demonstrates that the new accuracy indicator can determine the true system modes accurately.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2004년도 임시총회 및 추계학술발표회
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• pp.25-28
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• 2004

The capillary number is used to represent the mobilization potential of organic phase trapped within porous media. The capillary number has been defined by three different forms, according to types of flow velocity and viscosity used in the definition of capillary number. This study evaluated the suitability of the capillary number definitions for representing TCE mobilization by constructing capillary number-TCE saturation relationships. The results implied that the capillary number should be correctly employed, according to interest of scale and fluid flow behavior. This study suggests that the pore-scale capillary number may be used only for investigating the organic-phase mobilization at the pore scale because it is defined by the pore-velocity and the dynamic viscosity. The Newtonian-fluid capillary number using Darcy velocity and the dynamic viscosity may be suitable to quantify flood systems representing Newtonian fluid behavior. For viscous-force modified flood systems such as surfactant-foam floods, the apparent capillary number definition employing macroscopic properties (permeability and potential gradient) may be used to appropriately represent the desaturation of organic-phases from porous media.

• 한국건설관리학회논문집
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• 제7권2호
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• pp.171-180
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• 2006

Change is inevitable and is a reality of construction projects. Most construction contracts include change clauses and allowing contractors an equitable adjustment to the contract price and duration caused by change. However, the actions of a contractor can cause a loss of productivity and furthermore can result in disruption of the whole project because of a cumulative or ripple effect. Because of its complicated nature, it becomes a complex issue to determine the cumulative impact (ripple effect) caused by single or multiple change orders. Furthermore, owners and contractors do not always agree on the adjusted contract price for the cumulative impact of the changes. A number of studies have attempted to quantify the impact of change orders on project costs and schedule. Many of these attempted to develop regression models to quantify the loss. However, regression analysis has shortcomings in dealing with many qualitative or noisy input data. This study develops ANN models to classify and quantify the labor productivity losses that are caused by the cumulative impact of change orders. The results show that ANN models give significantly improved performance compared to traditional statistical models.

• 한국수학사학회지
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• 제18권2호
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• pp.9-22
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• 2005

본 연구는 자연수 개념이 역사적으로 전개된 방식을 이해하는 것이 수학적$\cdot$ 교육적으로 매우 중요함에도 불구하고, 그 역사적 고찰이 미진한 상태에 있다는 데에 문제 의식을 갖고 출발하였다. 그리하여 자연수 개념이 역사적으로 어떻게 논의되어 왔는지 살펴보고자 하였다. 수학의 발달 과정에서 수가 어떤 의미를 지녔는지, 문화적$\cdot$사회적 요소가 수 개념을 이해하는 방식과 수 개념의 발달에 어떤 영향을 주었는지 밝힘으로써 자연수 개념에 대한 이해를 풍부하게 하고자 하였다. 그리고 자연수 개념의 역사에 나타난 특징을 드러내고자 하였다.

• Annals of Clinical Neurophysiology
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• 제5권1호
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• pp.27-33
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• 2003

Background: Motor unit number estimation (MUNE) can directly assess motor neuron populations in muscle and quantify the degree of physiologic and/or pathologic motor neuron degeneration. A high degree of reproducibility and reliability is required from a good quantitative tool. MUNE, in various ways, is being increasingly applied clinically and statistical MUNE has several advantages over alternative techniques. Nevertheless, the optimal method of applying statistical MUNE to improve reproducibility has not been established. Methods: We performed statistical MUNE by selecting the most compensated compound muscle action potential (CMAP) area as a test area and modified the results obtained by weighted mean surface-recorded motor unit potential (SMUP). Results: MUNE measures in amyotrophic lateral sclerosis (ALS) patients showed better reproducibility with sizeweighted modification. Conclusions: We suggest size-weighted MUNE testing of "neurogenically compensated"CMAP areas present an optimal method for statistical MUNE in ALS patients.

• 한국양봉학회지
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• 제34권1호
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• pp.27-37
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• 2019

Rapid detection of Tropilaelaps, an external parasite of honeybees that lead to malformation of honeybee or colony collapse disorder, is becoming important. But it is very difficult to find with the naked eye of Tropilaelaps. In this study, we have developed a method to detect the specific gene of Tropilaelaps from the hive debris and to know the number of Tropilaelaps in the hive through Tropilaelaps-specific quantitative detection. Tropilaelaps-specific gene amplified in DNA extracted from hive debris by consecutive PCR (1st detection, 2nd nested PCR). It could detect 101 molecules level of Tropilaelaps-specific gene and confirm the amplification of the Tropilaelaps-specific gene. It was possible to accurately quantify the number of Tropilaelaps from the hive debris sample, which is difficult to discriminate the presence of Tropilaelaps visually, through Tropilaelaps-specific detection. Under the microscope, Tropilaelaps was collected and quantitative detection of Tropilaelaps-specific genes was performed. It was possible to quantify the number of Tropilaelaps present in the hive through the molecules of the quantified Tropilaelaps-specific genes. We suggest that hive debris can represent as a micro-environment to hive and show that it can be a simpler and more accurate sample than using a parasitic host honeybee. We expect that hive debris should facilitate the monitoring of Tropilaelaps in hive.

• ETRI Journal
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• 제30권2호
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• pp.194-204
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• 2008

The online collection of coarse-grained traffic information, such as the total number of flows, is gaining in importance due to a wide range of applications, such as congestion control and network security. In this paper, we focus on an active queue management scheme called SRED since it estimates the number of active flows and uses the quantity to indicate the level of congestion. However, SRED has several limitations, such as instability in estimating the number of active flows and underestimation of active flows in the presence of non-responsive traffic. We present a Markov model to examine the capability of SRED in estimating the number of flows. We show how the SRED cache hit rate can be used to quantify the number of active flows. We then propose a modified SRED scheme, called hash-based two-level caching (HaTCh), which uses hashing and a two-level caching mechanism to accurately estimate the number of active flows under various workloads. Simulation results indicate that the proposed scheme provides a more accurate estimation of the number of active flows than SRED, stabilizes the estimation with respect to workload fluctuations, and prevents performance degradation by efficiently isolating non-responsive flows.

• 대한교통학회지
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• 제19권1호
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• pp.17-28
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• 2001

본 연구의 목적은 기업과 소비자간 전자상거래에서 물류운송체계의 물류비용을 상품운송 유형에 따라 분석하는 것이다. 먼저 물류운송체계를 3가지 유형 즉, 공급업체에서 소비자에게 직송하는 방법(유형 I), 자가물류업체를 통해 각 권역에 운송센타를 두어 운송하는 방법(유형 II), 3자 물류업체에게 운송에 관한 모든 일체를 위임하는 방법(유형 III)으로 분류하고 각 유형의 물류비 항목을 운송비, 보관비, 물류정보비로 구성하였다. 전자상거래에서의 물류는 다품종 소량 다빈도 특성을 가지고 있고, 주문특성 및 상황에 따라 소요물류비용이 변한다. 그러므로 본 연구에서는 대상권역의 주문에 대한 1일 주문건수 운송거리, 운송량, 그리고 1일 배정화물트럭대수에 따라 변하는 물류비용함수를 도출하였고, 가상네트웍을 구성하여 시뮬레이션 함으로서 각 운송유형의 주문특성에 따른 물류비용의 변화를 분석하였다. 하지만, 본 연구는 공급업체의 물류인프라와 운송서비스 시간에 대한 고려를 하지 않았기 때문에 현실에 적용하기에 한계가 있다. 만일 이에 대한 연구가 보충된다면 전자상거래에서 일정 단위기간 동안 상품운송에 소요되는 물류비를 좀더 정확히 추정하여 전자상거래에서의 효율적인 화물운송방안을 제시할 수 있을 것이다. 본 연구의 결과로 전자상거래에서의 1일 주문발생 빈도와 공급상품의 중량. 그리고 운송거리에 따라 변하는 물류비용을 추정할 수 있다.

• 항공우주의학회지
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• 제30권2호
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• pp.70-74
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• 2020

This study aimed to quantify the causes of Korean airline pilots' medical disqualification during 2015~2019. The airline pilot disqualification data is important for grasping what health problems are common to pilots and establishing preventive health care programs. We were able to obtain data from official sources at the Korean Civil Aviation Authority during 2015~2019. The total number of pilots was 29,095, and the number of disqualified professional pilots in Korea was 36. Looking at airline pilots' status by age group, the 40s were the highest with 38%. However, the disqualification rate per 1,000 pilots was the highest in the 60s, at 4.6. When the different diagnostic categories classified the disqualification results, cardiovascular disease was the highest with 12 cases (33.3%), followed by eye disease, malignancy, neurology, psychiatry, otorhinolaryngology, and respiratory disease. The total number of pilots during 2015~2019 was 29,095, and the overall disqualification rate of 1.6/1,000 pilots.