• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2003년도 봄 학술발표회 논문집
• /
• pp.671-680
• /
• 2003

The accuracy of inflow into tunnel estimates depends largely on how well permeability is characterized. But, the average of the packer test results will always underestimate the upper end of the permeability range, and therefore underestimate the inflow. Taking an average of the test results always underestimates inflow because the average permeability does not really exist. The distribution of packer-test data may not accurately reflect permeability, however, due to the limits of the test method and the luck of the field investigation. These discrepancies may be overcome by using Raymer(2001)'s log-normal plots and Heuer(1995)'s histograms of the data to develop a permeability model that will be used in lieu of the data to calculate inflow. Furthermore, the influence on the inflow is examined by the geological characteristics based upon the hundred times of packer test OO tunnel project.

• 문화기술의 융합
• /
• 제8권2호
• /
• pp.139-148
• /
• 2022

우리는 제 16차 청소년건강행태조사 자료를 이용하여 청소년의 일반적 특성, 외모스트레스, 불안이 청소년의 신체 이미지 왜곡에 어떠한 영향을 미치는지 확인하고자 시도하였다. 우리는 대상자의 38.2%에서 신체이미지 왜곡을 확인하였고 19.9%에서 신체 이미지에 대한 과소평가(underestimate), 18.3%에서 과대평가(overestimate)하는 결과를 확인하였다. 과소평가(underestimate)와 과대평가(overestimate) 집단 모두에서 외모스트레스, 불안이 영향을 주는 것으로 확인되었다. 우리는 성별, 경제적 수준, 학업수준등의 인구학적 특성이 과소평가와 과대평가 집단에서 각각 다른 양상으로 영향을 미치는 것을 확인하였다. 따라서, 우리는 청소년의 체중에 대한 주관적인 인식을 과대평가와 과소평가의 경우로 세분화하여 포괄적인 평가를 하는 것이 추후 정신건강과 체중 조절 행동을 결정하는 중요한 요소가 될 것으로 제언한다.

• Genomics & Informatics
• /
• 제20권1호
• /
• pp.9.1-9.6
• /
• 2022

Mendelian randomization (MR) uses genetic variation as a natural experiment to investigate the causal effects of modifiable risk factors (exposures) on outcomes. Two-sample Mendelian randomization (2SMR) is widely used to measure causal effects between exposures and outcomes via genome-wide association studies. 2SMR can increase statistical power by utilizing summary statistics from large consortia such as the UK Biobank. However, the first-order term approximation of standard error is commonly used when applying 2SMR. This approximation can underestimate the variance of causal effects in MR, which can lead to an increased false-positive rate. An alternative is to use the second-order approximation of the standard error, which can considerably correct for the deviation of the first-order approximation. In this study, we simulated MR to show the degree to which the first-order approximation underestimates the variance. We show that depending on the specific situation, the first-order approximation can underestimate the variance almost by half when compared to the true variance, whereas the second-order approximation is robust and accurate.

• Journal of Trauma and Injury
• /
• 제35권4호
• /
• pp.232-239
• /
• 2022

Purpose: The recent increase in electric scooter (e-scooter) use has been accompanied by an increase in injuries from e-scooter-related accidents. Studies have reported that most such injuries are minor, and physicians may therefore underestimate the severity of such injuries. This study investigated the types and severity of injuries caused by isolated e-scooter accidents (i.e., those that did not involve colliding with other cars or falling from heights). Methods: This prospective observational study was conducted from May to December 2021 at Dankook University Hospital tertiary medical center. The demographic data of patients injured in isolated e-scooter-related accidents were collected. All injuries were categorized by body part. Results: Fifty eligible patients visited our emergency department during the study period. Of these, 76% were categorized as nonemergency, and 62% were discharged after initial evaluation and treatment at the emergency department. Another 10% were admitted to the intensive care unit (ICU) and 18% to the ward, with nine patients receiving at least one operation. The average hospital stays were 2.4 days in the ICU and 9 days in the ward. One death occurred due to traumatic brain injury (overall mortality rate, 2%). Multiple fractures of the left third through ninth ribs combined with lung laceration and fractures of T12 and L4 were noted. Conclusions: Various types and severities of injuries can occur in isolated e-scooter accidents. While most such injuries are minor, some will require ICU admission or surgery, and deaths can occur. Physicians should not underestimate the severity of such injuries.

• Imaging Science in Dentistry
• /
• 제46권4호
• /
• pp.297-297
• /
• 2016

• 전산구조공학
• /
• 제5권3호
• /
• pp.139-146
• /
• 1992

본 연구에서는 트럭하중에 의한 도로형교의 진동거동을 조사하여 충격계수를 합리적으로 산출하는 경험공식을 제시한다. 이를 위해 진동해석을 위한 가장 합리적인 차량 모델링을 제시하고, 노면조도, 차량의 속도, 교량의 길이별 충격계수를 산출한다. 연구결과, 현행 시방서규정은 충격계수를 과소평가하는 경향이 있음을 알 수 있었다.

• Wind and Structures
• /
• 제19권3호
• /
• pp.271-294
• /
• 2014

The impact of artefacts in archived wind observations on the design wind speed obtained by extreme value analysis is demonstrated using case studies. A signpost protocol for detecting candidate artefacts is described and its performance assessed by comparing results against previously validated data. The protocol targets artefacts by exploiting the serial correlation between observations. Additional "sieve" algorithms are proposed to identify types of correctable artefact from their "signature" in the data. In extreme value analysis, artefacts displace valid observations only when they are larger, hence always increase the design wind speed. Care must be taken not identify large valid values as artefacts, since their removal will tend to underestimate the design wind speed.

• Communications for Statistical Applications and Methods
• /
• 제6권2호
• /
• pp.383-395
• /
• 1999

This study is concerned with the evaluation of predictive ability of classification models with ordered multiple categories. If categories can be ordered or ranked the spread of misclassification should be considered to evaluate the performance of the classification models using loss rate since the apparent error rate can not measure the spread of misclassification. Since loss rate is known to underestimate the true loss rate the bootstrap method were used to estimate the true loss rate. thus this study suggests the method to evaluate the predictive power of the classification models using loss rate and the bootstrap estimate of the true loss rate.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2003년도 가을 학술발표회 논문집
• /
• pp.234-237
• /
• 2003

Previous researches about headed reinforcement have not been concerned about bond failure which is quite important is some cases. In this paper, failure mechanism including bond failure was presented in order to define the contribution of bond stress at the time failure occurs. Examined with design codes and test results, it is proved to be rational to consider the contribution of bond stress in determining the ultimate pull-out capacity of headed reinforcement. Direct adaptation of design code for anchor bolt without modification for the contribution of bond stress will lead to underestimate the capacity of headed reinforcement.

• 전산구조공학
• /
• 제5권2호
• /
• pp.87-91
• /
• 1992

본 연구에서는 트럭하중에 의한 도로형교의 진동거동을 조사하여 충격계수를 합리적으로 산출하는 경험공식을 제시한다. 이를 위해 진동해석을 위한 가장 합리적인 차량 모델링을 제시하고, 노면조도, 차량의 속도, 교량의 길이별 충격계수를 산출한다. 연구결과, 현행 시방서규정은 충격계수를 과소평가하는 경향이 있음을 알 수 있었다.