• 한국지반공학회논문집
• /
• 제30권10호
• /
• pp.5-18
• /
• 2014

세계의 많은 지역이 강우에 의한 사면파괴가 취약하다. 사면파괴의 발생 메커니즘을 파악하기 위해 지금까지 다양한 방법들이 제안되어져 왔으나 현재 사용되는 방법들은 비균질한 지반분포와 수리학적 거동이 강우로 인한 사면파괴에 미치는 효과를 고려하지 못한다. 본 연구에서는 강우 시 토층의 두께에 따른 사면파괴의 발생 메커니즘을 연구하기 위하여 불투수 기반암 위에 존재하는 풍화 잔류토 사면에 대한 확률론적 사면안정 해석을 수행하였다. 불균질한 투수계수의 공간적 분포로 인한 불확실성이 강우침투에 의한 불포화 사면의 파괴에 미치는 영향을 고려하기 위하여 일차원 랜덤필드에 기초한 일련의 침투해석과 사면 안정해석을 수행하였다. 해석결과에 의하면 확률론적 해석법은 사면에 대한 강우의 침투 평가 시 투수계수의 공간적인 변동에 의하여 발생하는 다양한 파괴 패턴을 효과적으로 고려할 수 있음을 보여준다.

• 한국정보통신학회논문지
• /
• 제17권9호
• /
• pp.2105-2112
• /
• 2013

본 논문에서는 대용량 전자메일 서버의 성능 데이터를 수집해 그 분석 결과를 웹 기반으로 관리자에게 제공하는 모니터링 시스템을 구현하였다. 이를 위해 전자메일 서버의 성능 데이터 수집 항목을 도출하고, 각 항목별 측정 임계치를 설정하여 전자메일 서버의 성능을 객관적인 수치로 표현될 수 있도록 하였다. 전자메일 서버의 성능 데이터 수집은 SCOM 2007 서버 모니터링 도구를 이용하였으며, 성능 분석 파라미터 설정은 마이크로소프트사에서 제공하는 Exchange 서버 관리 팩과 SCOM 2007에서 제공하는 모니터링 규칙을 이용하였다. ASP.NET 프레임워크 기반의 C# 프로그래밍을 통해 웹 기반의 성능 모니터링 프로그램을 개발했으며, 성능 분석 결과는 관리자에게 웹 기반의 성능보고서, 장애 보고서 및 가용성 보고서 형태로 제공된다. 장애 요소를 사전에 효율적으로 감지할 수 있어 본 시스템 적용 전후 비교시 60% 이상 장애 건수를 줄일 수 있었으며, 장애 발생시에도 복구에 소요되는 시간을 획기적으로 단축할 수 있었다.

• International Journal of Advanced Culture Technology
• /
• 제6권4호
• /
• pp.58-64
• /
• 2018

The Extraposition phenomenon in English has been analyzed mainly through two approaches: a derivational approach under the Principles & Parameters framework (P&P) and a representational approach under the early Minimalist framework (MP). The first one tries to understand the phenomenon as a result of the movement of a Big Subject first to the end of a sentence which is then followed by the insertion of an expletive 'it' to the empty Subject position. On the other hand, the second one tries to understand it by way of assuming a Big Subject originally base-generated at the end of a sentence which is followed by the insertion of an expletive 'it' to the empty Subject position. The two approaches, however, are not free from theoretical defects at all: the full derivational approach was under controversy in terms of (1) the failure of the Binding Theory and (2) its inability to suggest anything about the marginal reading issue. On the while, the representational approach has been argued (1) to violate the thematic hierarchy that should be kept in D-structure, and (2) to be also unable to suggest the slightest difference in marginal reading issue as the first one. In this paper I focus mainly on analyzing the 'It'-Extraposition phenomenon in the Optimality Theory. I will show that by way of (i) some newly developed constraints such as Subj., and AHSubj. and (ii) a constraint hierarchy of Subj.>>AHSubj., the controversies of 'It-Extraposition' such as (1) the analysis of construction and (2) the very closely related issue of 'marginal reading issue' can be explained properly.

• Structural Engineering and Mechanics
• /
• 제84권3호
• /
• pp.323-335
• /
• 2022

The main idea of the framework is to seamlessly combine a reasonably accurate and fast surrogate model with the importance sampling strategy. Developing a surrogate model for predicting structures' dynamic responses is challenging because it involves high-dimensional inputs and outputs. For this purpose, a novel surrogate model based on cutting-edge deep learning architectures specialized for capturing temporal relationships within time-series data, namely Long-Short term memory layer and Transformer layer, is designed. After being properly trained, the surrogate model could be utilized in place of the finite element method to evaluate structures' responses without requiring any specialized software. On the other hand, the importance sampling is adopted to reduce the number of calculations required when computing the failure probability by drawing more relevant samples near critical areas. Thanks to the portability of the trained surrogate model, one can integrate the latter with the Importance sampling in a straightforward fashion, forming an efficient framework called TTIS, which represents double advantages: less number of calculations is needed, and the computational time of each calculation is significantly reduced. The proposed approach's applicability and efficiency are demonstrated through three examples with increasing complexity, involving a 1D beam, a 2D frame, and a 3D building structure. The results show that compared to the conventional Monte Carlo simulation, the proposed method can provide highly similar reliability results with a reduction of up to four orders of magnitudes in time complexity.

• Wind and Structures
• /
• 제13권2호
• /
• pp.191-206
• /
• 2010

Windborne debris is a major cause of structural damage during severe windstorms and hurricanes owing to its direct impact on building envelopes as well as to the 'chain reaction' failure mechanism it induces by interacting with wind pressure damage. Estimation of debris risk is an important component in evaluating wind damage risk to residential developments. A debris risk model developed by the authors enables one to analytically aggregate damage threats to a building from different types of debris originating from neighboring buildings. This model is extended herein to a general debris risk analysis methodology that is then incorporated into a vulnerability model accounting for the temporal evolution of the interaction between pressure damage and debris damage during storm passage. The current paper (Part I) introduces the debris risk analysis methodology, establishing the mathematical modeling framework. Stochastic models are proposed to estimate the probability distributions of debris trajectory parameters used in the method. It is shown that model statistics can be estimated from available information from wind-tunnel experiments and post-damage surveys. The incorporation of the methodology into vulnerability modeling is described in Part II.

• Wind and Structures
• /
• 제31권5호
• /
• pp.381-392
• /
• 2020

Despite that the failure of sign structure may not have disastrous consequence, its sheer number still ensures the need for rigorous safety standard to regulate their maintenance and construction. During its service life, a sign structure is subject to extensive wind load, sometimes well over its permissible design load. A fragility analysis of a sign structure offers a tool for rational decision making and safety evaluation by using a probabilistic framework to consider the various sources of uncertainty that affect its performance. Wind fragility analysis was used to determine the performance of sign structure based on the performance of its connection components. In this study, basic wind fragility concepts and data required to support the fragility analysis of the sign structure such as sign panel's parameters, connection component's parameters, as well as wind load parameters were presented. Fragility and compound fragility analysis showed disparity between connection component. Additionally, reinforcement of the connection system was introduced as an example of the utilization of wind fragility results in the retrofit decision making.

• Journal of Information Technology Applications and Management
• /
• 제29권6호
• /
• pp.63-80
• /
• 2022

In this paper, we study structural changes and performance gains in condition-based maintenance process redesign when mobile IoT technology is embedded into urban railway rolling stock. We first develop condition-based maintenance To-Be process model in accordance with the IoT deployment scheme. Secondly, we draw upon theoretical framework of redesign process analysis to develop performance evaluation method suitable to predictive maintenance shift from As-Is ordinary maintenance practice. Subsequently, To-Be process performance evaluations are conducted adopting both the quantitative and qualitative method for time, cost, and dependability dimensions. The results ascertain the considerable benefits captured through detection abnormality prior to actual rolling stock failure occurrence, and details of performance improvements and enhancement of standardization level is revealed. The procedures and results presented in this paper offers useful insights in the fields of IoT economic analysis, condition based maintenance, and business process redesign.

• 한국기계가공학회지
• /
• 제19권9호
• /
• pp.47-52
• /
• 2020

With the 4th industrial revolution, condition monitoring using machine learning techniques has become popular among researchers. An overload due to complex operations causes several irregularities in MOSFETs. This study investigated the acquired voltage to analyze the overcurrent effects on MOSFETs using a failure mode effect analysis (FMEA). The results indicated that the voltage pattern changes greatly when the current is beyond the threshold value. Several features were extracted from the collected voltage signals that indicate the health state of a switched-mode power supply (SMPS). Then, the data were reduced to a smaller sample space by using a principal component analysis (PCA). A robust machine learning algorithm, the support vector machine (SVM), was used to classify different health states of an SMPS, and the classification results are presented for different parameters. An SVM approach assisted by a PCA algorithm provides a strong fault diagnosis framework for an SMPS.

• Nuclear Engineering and Technology
• /
• 제49권2호
• /
• pp.327-334
• /
• 2017

Common-cause failure (CCF) events can significantly impact the availability of safety systems of nuclear power plants. For this reason, the International Common Cause Data Exchange (ICDE) project was initiated by several countries in 1994. Since 1997 it has been operated within the Organisation for Economic Co-operation and Development (OECD)/Nuclear Energy Agency (NEA) framework and has successfully been operated over six consecutive terms (the current term being 2015-2017). The ICDE project allows multiple countries to collaborate and exchange CCF data to enhance the quality of risk analyses, which include CCF modeling. As CCF events are typically rare, most countries do not experience enough CCF events to perform meaningful analyses. Data combined from several countries, however, have yielded sufficient data for more rigorous analyses. The ICDE project has meanwhile published 11 reports on the collection and analysis of CCF events of specific component types (centrifugal pumps, emergency diesel generators, motor operated valves, safety and relief valves, check valves, circuit breakers, level measurement, control rod drive assemblies, and heat exchangers) and two topical reports. This paper presents recent activities and lessons learnt from the data collection and the results of topical analysis on emergency diesel generator CCF impacting entire exposed population.

• 품질경영학회지
• /
• 제45권4호
• /
• pp.665-676
• /
• 2017

Purpose: The purpose of this paper proposes an effective and systematic methods of risk management in product development project. Methods: This paper first discusses what risk factors be considered during product development period and then presented a model for preventive risk management. For that, this paper proposes how to evaluate the risk factors and risk events, and how to select prevention action for managing risk factors effectively. For this process, this paper uses well-known quality tools such as House of Quality (HOQ) and Failure Mode and Effects Criticality Analysis (FMECA) methods. Results: There is an inherent need for the development of robust risk management framework in order for product development projects to be successful. The identification and quantification of risk factors, risk events, and prevention actions can have significant effects on the success of a product development projects. Project managers can implement the proposed model to improve project success. Conclusion: The findings showed that this method would be effective for project managements in dealing with risk management issues in product development projects. This method presented would be an one of good guidelines for practitioners in the industry.