• 센서학회지
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• 제32권6호
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• pp.475-480
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• 2023

When modeling a sensor system mathematically, we assume that the sensor noise is Gaussian and white to simplify the model. If this assumption fails, the performance of the sensor model-based controller or estimator degrades due to incorrect modeling. In practice, non-Gaussian or non-white noise sources often arise in many digital sensor systems. Additionally, the noise parameters of the sensor model are not known in advance without additional noise statistical information. Moreover, disturbances or high nonlinearities often cause unknown sensor modeling errors. To estimate the uncertain noise and model parameters of a sensor system, this paper proposes an iterative batch calibration method using data-driven machine learning. Our simulation results validate the calibration performance of the proposed approach.

• Journal of the Korean Data and Information Science Society
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• 제21권2호
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• pp.251-262
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• 2010

최근 대부분의 기업이 정보시스템 개발을 아웃소싱에 의존하면서, 도입하고자 하는 정보시스템을 효과적으로 활용하는데 필요한 데이터와 현재 기업이 가지고 있는 데이터간의 차이에 대한 사전 분석이 성공적인 정보시스템 도입을 위해 반드시 필요하다. 그 예로 고객관계관리 시스템의 도입 사례의 경우 가장 큰 실패 요인이 사전에 기업이 가지고 있는 데이터에 대한 분석을 간과한 것에 기인하고 있다. 하지만, 아직까지 데이터 관점에서 정보시스템 도입 방법론을 체계적으로 제안한 연구가 존재하지 않았다. 본 연구에서 정보시스템 도입과 관련된 데이터 비용을 사전에 분석하여 도입 의사결정에 활용할 수 있는 정보시스템 도입 방법론을 제안하고 실제 사례에서 어떻게 활용 될 수 있는지를 사례 시뮬레이션을 통해 보여주고자 한다. 제안된 방법론을 이용해 실제 기업의 정보시스템 도입 의사결정자들은 기업의 전략에 따라 다양한 정보시스템을 디자인하고 그에 따른 데이터 관련 비용을 장, 단기적인 계획 하에서 분석 가능하므로, 도입 단계에서 숨어있는 데이터 관련 비용에 의해 발생할 수 있는 정보시스템 도입 실패에 대한 위험 부담을 사전에 방지할 수 있다.

• ETRI Journal
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• 제36권5호
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• pp.714-720
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• 2014

In this paper, we propose the use of data-driven probabilistic utterance-level decision logic to improve Weighted Finite State Transducer (WFST)-based endpoint detection. In general, endpoint detection is dealt with using two cascaded decision processes. The first process is frame-level speech/non-speech classification based on statistical hypothesis testing, and the second process is a heuristic-knowledge-based utterance-level speech boundary decision. To handle these two processes within a unified framework, we propose a WFST-based approach. However, a WFST-based approach has the same limitations as conventional approaches in that the utterance-level decision is based on heuristic knowledge and the decision parameters are tuned sequentially. Therefore, to obtain decision knowledge from a speech corpus and optimize the parameters at the same time, we propose the use of data-driven probabilistic utterance-level decision logic. The proposed method reduces the average detection failure rate by about 14% for various noisy-speech corpora collected for an endpoint detection evaluation.

• 한국해안해양공학회지
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• 제6권3호
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• pp.226-233
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• 1994

전난류에서 파와 해류가 합성하였을 때 발생하는 해저면 마찰력을 계산하는 방법을 고찰하였다. 전난류에서 일방향 흐름에 의한 마찰력의 산정방법으로 절점조정법을 제시하며, Bijker의 관측자료와 비교하여 절점조정치를 산정하였다. 파와 해류의 합성류에 의한 마찰력 계산방법으로 수정된 Bijker 모형(BYO Model)과 수정된 Fredsoe 모형(FY Model)을 Bijker의 관측자료에 적용하였으며, 두 모형 모두 한가지씩 새로운 개선책을 제시하였다.

• Smart Structures and Systems
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• 제15권3호
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• pp.897-911
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• 2015

This study presents a novel approach based on advancements in Evolutionary Computation for data-driven modeling of complex multi-dimensional memory-dependent systems. The investigated example is a benchmark coupled three-dimensional system that incorporates 6 Bouc-Wen elements, and is subjected to external excitations at three points. The proposed technique of this research adapts Genetic Programming for discovering the optimum structure of the differential equation of an auxiliary variable associated with every specific degree-of-freedom of this system that integrates the imposed effect of vibrations at all other degrees-of-freedom. After the termination of the first phase of the optimization process, a system of differential equations is formed that represent the multi-dimensional hysteretic system. Then, the parameters of this system of differential equations are optimized in the second phase using Genetic Algorithms to yield accurate response estimates globally, because the separately obtained differential equations are coupled essentially, and their true performance can be assessed only when the entire system of coupled differential equations is solved. The resultant model after the second phase of optimization is a low-order low-complexity surrogate computational model that represents the investigated three-dimensional memory-dependent system. Hence, this research presents a promising data-driven modeling technique for obtaining optimized representative models for multi-dimensional hysteretic systems that yield reasonably accurate results, and can be generalized to many problems, in various fields, ranging from engineering to economics as well as biology.

• 한국어교육
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• 제29권3호
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• pp.255-292
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• 2018

Most grading scales of Korean language proficiency tests are based on existing grading scales that are not empirically verified. The purpose of this study is to develop an empirically verified scale descriptor. The 'Performance data-driven approach' that is suggested by Fulcher (1987) was used to develop the detailed description of characteristics for each level of performance. This study is focused on the functional phase of speech samples analysis (coding data) to create explanatory categories of discourse skills into which individual observations of speech phenomena can be scored. The speech samples that were collected through this study demonstrated stages of speech that can be a foundation of a grading scale. The data used in the study was collected from 23 native speakers of Korean. Speech samples were recorded from simulated speaking tests using the 'REFUSAL' task, and transcribed for analysis. The transcript was analyzed using discourse analysis. The result showed that the 'REFUSAL' task needs to go through four functional phases in actual communication. Furthermore, this study found specific and detailed explanatory categories of discourse competence based on the actual native speaker's speech data. Such findings are expected to contribute to the development of more valid and reliable speaking assessment.

• 기록학연구
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• 제79호
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• pp.305-341
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• 2024

이 연구는 디지털 환경에서 데이터가 중심이 되는 전자기록의 출처에 새롭게 접근하기 위해, 데이터 출처 개념과 출처 모델을 검토하고 수용하여, 어떻게 전자기록을 대상으로 새롭게 출처 개념을 적용할 수 있을지의 가능성을 살펴보았다. 이어서 데이터 중심의 전자기록을 대상으로 한 출처 표현 모델을 개발하기 위해 기초 연구를 진행하였다. 특히 소급형 출처와 전망형 출처 개념으로 전환할 것과, 기록관리 메타데이터와는 별개의 모델을 통해 출처를 표현하고 기록과 연결할 수 있는 모델을 개발할 것을 제안하였다. 기록과 동적 관계를 맺으면서도 독립적으로 출처를 표현할 수 있는 모델을 개발할 수 있다면, 오히려 기록의 유동성을 보장할 수 있으면서도, 기록의 속성과 이를 지원할 출처의 역할을 더 충실히 수행할 수 있을 것이다. 결국, 이 연구가 제안한 기본적인 모델 개발 방향을 수용하는 출처 모델은 기록의 고정성과 활동의 재현성, 재현의 신빙성을 뒷받침할 수 있을 것이며, 디지털환경에서 적합한 출처 모델로서 역할을 할 수 있을 것이다.

• Structural Engineering and Mechanics
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• 제74권1호
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• pp.55-67
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• 2020

The common practice to predict the characteristic structural load effects (LEs) in long reference periods is to employ the extreme value theory (EVT) for building limit distributions. However, most applications ignore that LEs are driven by multiple loading events and thus do not have the identical distribution, a prerequisite for EVT. In this study, we propose the composite extreme value modeling approach using clustering to (a) cluster initial blended samples into finite identical distributed subsamples using the finite mixture model, expectation-maximization algorithm, and the Akaike information criterion; (b) combine limit distributions of subsamples into a composite prediction equation using the generalized Pareto distribution based on a joint threshold. The proposed approach was validated both through numerical examples with known solutions and engineering applications of bridge traffic LEs on a long-span bridge. The results indicate that a joint threshold largely benefits the composite extreme value modeling, many appropriate tail approaching models can be used, and the equation form is simply the sum of the weighted models. In numerical examples, the proposed approach using clustering generated accurate extrema prediction of any reference period compared with the known solutions, whereas the common practice of employing EVT without clustering on the mixture data showed large deviations. Real-world bridge traffic LEs are driven by multi-events and present multipeak distributions, and the proposed approach is more capable of capturing the tendency of tailed LEs than the conventional approach. The proposed approach is expected to have wide applications to general problems such as samples that are driven by multiple events and that do not have the identical distribution.

• 시스템엔지니어링학술지
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• 제16권2호
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• pp.67-77
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• 2020

Traditionally nuclear thermal hydraulic and nuclear safety has relied on numerical simulations to predict the system response of a nuclear power plant either under normal operation or accident condition. However, this approach may sometimes be rather time consuming particularly for design and optimization problems. To expedite the decision-making process data-driven models can be used to deduce the statistical relationships between inputs and outputs rather than solving physics-based models. Compared to the traditional approach, data driven models can provide a fast and cost-effective framework to predict the behavior of highly complex and non-linear systems where otherwise great computational efforts would be required. The objective of this work is to develop an AI algorithm to predict the peak fuel cladding temperature as a metric for the successful implementation of FLEX strategies under extended station black out. To achieve this, the model requires to be conditioned using pre-existing database created using the thermal-hydraulic analysis code, MARS-KS. In the development stage, the model hyper-parameters are tuned and optimized using the talos tool.

• 국제학술발표논문집
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• The 6th International Conference on Construction Engineering and Project Management
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• pp.496-500
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• 2015

International construction projects are inherently more risky than domestic projects with multi-dimensional uncertainties that require complementary risk management at both the country and project levels. However, despite a growing need for systematic country evaluations, most studies have focused on project-level decisions and lack country-based approaches for firms in the construction industry. Accordingly, this study suggests data-driven approaches for evaluating countries using two quantitative models. The first is a two-stage country segmentation model that not only screens negative countries based on country attractiveness (macro-segmentation) but also identifies promising countries based on the level of past project performance in a given country (micro-segmentation). The second is a multi-criteria country segmentation model that combines a firm's business objective with the country evaluation process based on Kraljic's matrix and fuzzy preference relations (FPR). These models utilize not only secondary data from internationally reputable institutions but also performance data on Korean firms from 1990 to 2014 to evaluate 29 countries. The proposed approaches enable firms to enhance their decision-making capacity for evaluating and selecting countries at the early stage of corporate strategy development.