• Journal of Construction Engineering and Project Management
• /
• 제8권2호
• /
• pp.17-33
• /
• 2018

This study investigates the stability of professionals' cost variability factor-rankings across different levels of cost-variability and response scenarios. Descriptive statistics are used to examine the stability of factor-ranking for 20 cost variability factors and a Multinomial Logistic (MNL) regression model was implemented to examine the stability of cost variability factors across three cost variability levels. The finding on the descriptive statistics indicated that professionals' factors-rankings are stable only for external factors. The MNL regression results on factor-stability suggested that 8 out of the 20 evaluated factors were unstable determinant of lower cost variability levels. These factors are "risk associated with the project", "personal bias and poor professionalism of the estimators", "limited time available to complete the project", "lack of skills and experience by estimator" "geographical location of projects", "incomplete & rush designs for estimate", "unforeseen or unexpected site constraints", "high class bidders for the contractors". Similarly lack of experience and large size projects were observed to be unstable as well. These observations suggest that professionals' view on pre-tender cost variability factor-ranking yields unstable factor rankings hence should not be relied upon as the only mechanisms to mitigate cost related risks in construction projects.

• 한국경영과학회:학술대회논문집
• /
• 대한산업공학회/한국경영과학회 2004년도 춘계공동학술대회 논문집
• /
• pp.479-482
• /
• 2004

This paper proposes a new framework for variability analysis in QFD. The proposed framework considers the uncertainty of the information contained in the house of quality chart and analyzes the variability resulting in the outcome. A new framework provides a dominance index and a difference index for each pairwise ECs. The indices are helpful to evaluate priorities of each pairwise EC.

• 경영과학
• /
• 제31권3호
• /
• pp.27-39
• /
• 2014

We derive a generalized statistic form of Q control chart, which is especially suitable for short run productions and start-up processes, for the detection of process mean shifts. The generalization means that the derived control chart statistic concurrently uses within lot variability and between lot variability to explain the process variability. The latter variability source is noticeably prevalent in lot type production processes including semiconductor wafer fabrications. We first obtain the generalized Q control chart statistic when both the process mean and process variance are unknown, which represents the case of implementing statistical process control charting for short run productions and start-up processes. Also, we provide the corresponding generalized Q control chart statistics for the rest of three cases of previous Q control chart statistics : (1) both the process mean and process variance are known (2) only the process mean is unknown and (3) only the process variance is unknown.

• Journal of Biosystems Engineering
• /
• 제33권5호
• /
• pp.355-361
• /
• 2008

As agricultural machinery has become larger and tillage practices have changed in recent decades, compaction as a result of wheel traffic and tillage has caused increasing concern. If strategies to manage compaction, such as deep tillage, could be applied only where needed, economic and environmental benefits would result. For such site-specific compaction management to occur, compacted areas within fields must be efficiently sensed and mapped. We previously developed an on-the-go soil strength profile sensor (SSPS) for this purpose. The SSPS measures within-field variability in soil strength at five soil depths up to 50 cm. Determining the variability structure of SSPS data is needed for site-specific field management since the variability structure determines the required intensity of data collection and is related to the delineation of compaction management zones. In this paper, soil bin data were analyzed by a spectral analysis technique to determine the variability structure of the SSPS data, and to investigate causes and implications of this variability. In the soil bin, we observed a repeating pattern due to soil fracture with an approximate 12- to 19-cm period, especially at the 10-cm depth, possibly due to cyclic development of soil fracture on this interval. These findings will facilitate interpretation of soil strength data and enhance application of the SSPS.

• Journal of Biosystems Engineering
• /
• 제29권2호
• /
• pp.109-120
• /
• 2004

To obtain basic information for precision agriculture, spatial variability of rice growth condition was evaluated in 100m ${\times}$100m paddy field. The rice growth condition of four hundred locations in the field were investigated to analyze the spatial variability of their properties ; SPAD, plant length and tiller number. Geostatistical analysis was carried out to examine within-field spatial variability using semivariograms and kriged maps as well as descriptive statistics. Descriptive statistics showed that the coefficient of variation for SPAD, plant length, and tiller number exceeded 5.70 %, suggesting a relatively high variability. Geostatistical analysis indicated a high spatial dependence for all the properties except for the second tiller number. The range of spatial dependence was about 20 m for SPAD, plant length, and tiller number. Based on the results of spatial dependence, kriged maps were prepared for the properties to analyse their spatial distribution in the field. The results reflected the history of field management. In conclusion, the need for site-specific field management and possibility of precision agriculture were demonstrated even in an almost flat paddy field.

• Journal of Biosystems Engineering
• /
• 제31권1호
• /
• pp.24-32
• /
• 2006

Compaction is becoming a greater concern in crop production and the environment because it can have deleterious effects on growing conditions that are difficult to remediate. Because compaction can vary considerably from point to point within a field, and also from depth to depth within the soil profile, it is important to consider quantification and management of the spatial and vertical variability in soil compaction when developing an overall site-specific crop management plan. In this paper, the importance of soil compaction, techniques for quantification of its variability, and the concept of site-specific tillage are examined. Methods and systems to detect within-field variation in soil strength as a surrogate measure of soil compaction and related soil properties are also compared and discussed. Quantification of variability in soil compaction and site-specific compaction management was motivated recently, and sensors and control systems are still under development. Future study will need to address a number of issues related to understanding and applying the sensor measurements.

• 동의생리병리학회지
• /
• 제26권5호
• /
• pp.745-752
• /
• 2012

This study aims to show the change of Heart Rate Variability(HRV) and Pulse wave velocity(PWV) on menstruation in women at college. Heart Rate Variability(HRV) and Pulse wave velocity(PWV) of 122 women at college were measured at their menstruation and ordinary period. SDNN, RMSSD, SDSD, HRV Index(%), stress resistance and cardiac activity were significantly higher at their menstruation than ordinary period, but Total Power and pNN50(%) were opposite. The automatic nervous system balance and physical stress were decreased in groups without dysmenorrhea than with one. PWV(E-R) and PWV(E-L) were much higher at menstruation than ordinary period. PTT(F-R) and PTT(F-L) were decreased in groups without dysmenorrhea than with severe one. We demonstrated that menstruation can effect on Heart Rate Variability and Pulse wave velocity and dysmenorrhea can cause the imbalance of autonomic nervous system.

• 한국농공학회논문집
• /
• 제63권6호
• /
• pp.49-60
• /
• 2021

BCSA (Bias-Correction and Stochastic Analog) is a statistical downscaling technique designed to effectively correct the systematic errors of GCM (General Circulation Model) output and reproduce basic statistics and spatial variability of the observed precipitation filed. In this study, the applicability of BCSA was evaluated using the ASOS observation data over South Korea, which belongs to the monsoon climatic zone with large spatial variability of rainfall and different rainfall characteristics. The results presented the reproducibility of temporal and spatial variability of daily precipitation in various manners. As a result of comparing the spatial correlation with the observation data, it was found that the reproducibility of various climate indices including the average spatial correlation (variability) of rainfall events in South Korea was superior to the raw GCM output. In addition, the needs of future related studies to improve BCSA, such as supplementing algorithms to reduce calculation time, enhancing reproducibility of temporal rainfall patterns, and evaluating applicability to other meteorological factors, were pointed out. The results of this study can be used as the logical background for applying BCSA for reproducing spatial details of the rainfall characteristic over the Korean Peninsula.

• 한국습지학회지
• /
• 제13권3호
• /
• pp.427-441
• /
• 2011

본 연구는 수자원 상황을 평가하기 위하여 기존에 개발된 물 빈곤지수에 지역적 기후변동성 및 홍수피해를 평가할 수 있는 세부지표를 추가한 기후 변동성지수를 개발하여 국내에 적용하였다. 물이용 평가에 초점이 맞추어진 물 빈곤지수 세부지표를 선정하고 지역적 특성에 따른 치수 및 기후변동성 내용이 추가된 지역별 특성인자를 선정하여 1998년부터 2007년까지 물 빈곤지수와 기후 변동성지수에 대한 분석을 실시하여 지역별 변동성을 평가하고 물 부문 정책, 투자 및 적용에 대한 우선순위를 결정하는데 도움을 줄 수 있는 정보를 제공하고자 하였다. 물 빈곤지수는 복지 수준과 물이용간의 관련성을 나타낼 수 있으며 치수와 기후변동성을 함께 고려하여 지역별 특성인자를 추가한 기후 변동성지수는 물이용에 영향을 미치는 인자와 치수 및 기후변화를 함께 고려할 수 있으므로, 지역별로 기후변화에 대응하는 물이용뿐만 아니라 홍수관리에도 사용할 수 있을 것이다.

• 한국건설관리학회:학술대회논문집
• /
• 한국건설관리학회 2007년도 정기학술발표대회 논문집
• /
• pp.353-357
• /
• 2007

경제수준 및 주거수준 향상에 따른 생활양식의 변화로 공동주택 입주자의 가족 구성과 주거 선호도가 다변화되고 있다. 이에 따라 라이프 싸이클 및 라이프 스타일 만족을 위한 리모델링과 조기 재건축이 늘어나고 있으며, 공동주택 주거 계획의 핵심요소로써 오픈 하우징의 개념인 "가변성"이 강조되고 있다. 주거공간에 공간 가변성을 채택한 공동주택들은 점진적으로 증가하고 있지만, 구조 안정성, 경제성 및 거주자 사용성을 만족시키는 최적의 공간 가변형 복합구조시스템은 개발되지 못한 실정이다. 따라서 본 논문은 기존 공간 가변형 공동주택의 복합구조시스템 개발과정 및 특성을 분석하여 시스템 평가요소를 도출하고, 이것을 기준으로 각 시스템을 비교${\cdot}$분석하여 국내 실정에 맞는 모듈화된 시스템 개발을 위한 현행 가변형 구조시스템의 개선 방향을 제시하였다.