• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.549-553
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• 2002

Although the magnetostrictive sensors have received much attention in recent years. the investigations on the selection of a desired mode have not been reported. The purpose of this investigation is to present a technique to select a desired mode in a solid ferromagnetic cylinder using a non-contact magnetostrictive sensor. To achieve this goal. we propose new bias magnet configurations to select longitudinal and flexural waves. A few experimental results confirm the validity of the present investigation.

• 한국주조공학회지
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• 제26권1호
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• pp.27-33
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• 2006

Phase evolutions involving nucleation stages together with diffusional growth have been examined in order to provide a guideline for determining rate limiting stages during phase evolutions. In multiphase materials systems in coatings, composites or multilayered structures, diffusion treatments often result in the development of metastable/intermediate phases at the reaction interfaces. The development of metastable phases during solid state interdiffusion demonstrates that the nucleation reaction can be one controlling factor. Also, the concentration gradient and the relative magnitudes of the component diffusivities provide a basis for a phase selection and the application of a kinetic bias strategy in the phase selection. For multicomponent alloy systems, the identification of the operative diffusion pathway is central to control phase formation. Experimental access to the nucleation and growth stage is discussed in thin film multi layers and bulk samples.

• Communications for Statistical Applications and Methods
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• 제26권1호
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• pp.47-55
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• 2019

It is important to identify informative variables in high dimensional data analysis; however, it becomes a challenging task when covariates are contaminated by measurement error due to the bias induced by measurement error. In this article, we present a two-step approach for variable selection in the presence of measurement error. In the first step, we directly select important variables from the contaminated covariates as if there is no measurement error. We then apply, in the following step, orthogonal regression to obtain the unbiased estimates of regression coefficients identified in the previous step. In addition, we propose a modification of the two-step approach to further enhance the variable selection performance. Various simulation studies demonstrate the promising performance of the proposed method.

• Journal of Positioning, Navigation, and Timing
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• 제12권1호
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• pp.11-22
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• 2023

In this paper, we propose an efficient satellite selection method for multi-constellation GNSS. The number of visible satellites has increased dramatically recently due to multi-constellation GNSS. By the increased availability, the overall GNSS performance can be improved. Whereas, due to the increase of the number of visible satellites, the computational burden in implementing advanced processing such as integer ambiguity resolution and fault detection can be increased considerably. As widely known, the optimal satellite selection method requires very large computational burden and its real-time implementation is practically impossible. To reduce computational burden, several sub-optimal but efficient satellite selection methods have been proposed recently. However, these methods are prone to the local optimum problem and do not fully utilize the information redundancy between different constellation systems. To solve this problem, the proposed method utilizes the inter-system biases and geometric assignments. As a result, the proposed method can be implemented in real-time, avoids the local optimum problem, and does not exclude any single-satellite constellation. The performance of the proposed method is compared with the optimal method and two popular sub-optimal methods by a simulation and an experiment.

• 한국조사연구학회지:조사연구
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• 제7권2호
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• pp.53-69
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• 2006

표본조사에서 가중치는 설계 단계와 분석 단계에서 만들어지고 부여될 수 있다. 설계 단계의 가중치는 추출확률이나 응답률 등과 같은 표본 데이터 획득 지표에 관련되어 있고 분석 단계의 가중치는 모집단 수치나 다른 보조 변수정보 등과 같은 외적인 정보와 관련되어 있다. 그리고 최종가중치는 설계 단계의 가중치와 분석 단계의 가중치의 곱으로 만들어진다. 이 논문에서는 분석 단계에서 부여되는 가중치에 초점을 맞추어 가중평균으로 모평균을 추정할 때 가중평균에 포함된 가중치가 모평균 추론에 미치는 영향을 고찰하였다. 유한모집단에서 각 조사단위에 조사변수와 가중치가 쌍으로 있고 표본추출확률이 균등한 경우를 가정하였다. 이러한 조건에서 가중평균의 편향과 평균제곱오차를 구하여 가중평균은 모평균의 편향 추정량임을 보였고, 편향의 방향과 크기는 조사변수와 가중치의 상관관계로 설명할 수 있음을 보였다. 즉, 만일 가중치와 조사변수가 양의 상관관계가 있으면 가중평균은 모평균을 과대 추정하게 되고, 만일 음의 상관관계가 있으면 모평균을 과소 추정하게 된다. 그리고 두 변수의 상관계수가 크면 편향은 증가한다. 가중평균에 대한 이론적인 수식 유도와 함께 편향의 크기와 평균제곱오차의 크기를 수치적으로 검토하기 위하여 모의실험을 실시하였다. 모의실험에서는 상관계수가 -0.2과 0.6사이에 있는 9개의 가중치를 생성하였고, 표본수는 100부터 400까지 고려하여 편향의 크기와 평균제곱오차의 크기를 수치적으로 구하였다. 하나의 결과로써 상관계수가 0.55이고 표본수가 400인 경우에 가중평균의 편향의 제곱이 평균제곱오차에서 차지하는 비율은 무려 82%에 이르는 것으로 나타났는데, 이는 가중평균의 편향이 어떤 경우에는 매우 심각할 수도 있음을 보여주는 것이다.

• 노동경제논집
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• 제27권3호
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• pp.1-23
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• 2004

"한국노동패널"을 이용하여 조기은퇴 행위와 지연은퇴 행위가 은퇴 전 후 소비에 미치는 영향을 2단계 전환회귀분석방법으로 분석하였다. 추정 과정에서 본 논문에서는 조기은퇴 결정이 은퇴 전 후 소비에 미치는 영향을 크게 두 가지로 구분하였다. 첫 번째는 조기은퇴 결정이 존재하는 경우와 존재하지 않는 경우를 비교하는 것으로서 추정결과 선택편의(selection bias)가 존재하는지를 통해 살펴보았다. 두 번째는 조기은퇴 결정 후 조기은퇴자의 소비를 지연은퇴자의 소비와 비교하는 것으로서, 소비의 소득탄력성을 비교하여 살펴보았다. 추정 결과 조기은퇴를 결정했을 경우 조기은퇴 결정이 존재하지 않는 경우와 비교했을 때 은퇴 전 소비가 감소하는 것으로 나타났다. 그리고 조기은퇴자와 지연은퇴자의 소비의 소득탄력성을 비교해 본 결과 소득이 증가하였을 때 조기은퇴자의 소비 증가폭이 지연은퇴자보다 작았다. 이상의 결과는 조기은퇴 결정 이후 상대적으로 길어진 은퇴 기간이 은퇴 전 소비에 영향을 미치고 있음을 보여주는 것이다.

• 정보교육학회논문지
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• 제26권4호
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• pp.273-284
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• 2022

본고의 목표는 데이터 편향 인식 교육에서 기계학습 플랫폼의 사용을 제안하는 것이다. 학습자들이 인공지능 데이터 및 시스템을 다루거나 인공지능윤리 요소 중 데이터 편향에 의한 피해를 방지하고자 할 때 인지할 수 있는 역량을 배양할 수 있다. 구체적으로, 머신러닝포키즈를 활용해 데이터편향 학습을 하는 방법을 AI야구심판 사례를 통해 제시한다. 학습자는 구체적 주제선정, 선행연구 검토, 기계학습 플랫폼에서 편향/비편향 데이터의 입력 및 테스트 데이터 구성, 기계학습의 결과 비교, 결과를 통해 얻을 수 있는 데이터 편향에 대한 함의를 제시한다. 이러한 과정을 통해서 학습자는 인공지능 데이터 편향이 최소화되어야 한다는 점과 데이터 수집 및 선정이 사회에 미치는 영향을 체험적으로 배울 수 있다. 이 학습방법은 문제기반의 자기주도 학습의 용이성, 코딩교육과의 결합가능성, 그리고 인문사회적 주제와 인공지능 리터러시와 결합을 추동한다는 의의를 가진다.

• 대한물리의학회지
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• 제18권4호
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• pp.109-119
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• 2023

PURPOSE: The definition and scope of biofeedback are broad and lack a clear framework. Therefore, efforts are needed to clearly understand the exact range and definition of biofeedback based on the research and development conducted to date. Thus, the purpose of this study was to arrive at the definition and scope of biofeedback through a literature review and analysis of its application methods. METHODS: This study is a systematic literature review conducted to understand the various types and effects of biofeedback. International databases such as Google Scholar and PubMed were used. Domestic databases utilized for keyword searches included the Research Information Sharing Service (RISS) and the National Digital Science Library (NDSL). Quality assessment of the selected studies in the selection process was done using the Cochrane risk of bias, and the research was analyzed according to the population, intervention, control, and outcomes (PICO) format. RESULTS: Studies conducted between 2019 and 2021 were selected, with 4 papers falling under physiological classifications and 7 under biomechanical classifications. The quality assessment results showed that random sequence generation, allocation concealment, performance bias, and reporting bias were unclear. Detection bias was moderate, and attrition bias and other biases were low. Out of the 11 papers, 9 dealt with physical function outcomes, 5 with daily life activities, and 3 with mental functions. CONCLUSION: Physiological biofeedback tended to influence psychological factors more than physical functions, while biomechanical biofeedback tended to have a positive impact on physical functions.

• Korean Journal of Acupuncture
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• 제37권3호
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• pp.131-144
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• 2020

Objectives : The aim of this study is to analyze the details of acupuncture treatment methods and the reporting quality of acupuncture on Carpal Tunnel Syndrome (CTS). Methods : Search was conducted in Pubmed, EMBASE, and Cochrane Library for acupuncture studies on CTS. The reporting quality of acupuncture treatment was assessed using the following guidelines: Standards for Reporting Interventions in Clinical Trials of Acupuncture (STRICTA) for analyzing the method of acupuncture treatment, Consolidated Standards of Reporting Trials (CONSORT) for analyzing study design and study process, and Risk of Bias (ROB) for analyzing bias. The number of reported items was calculated and evaluated as a proportion. The reported proportion of each study was classified into three grades: Grade A (% score ≥75), Grade B (50≤ % score <75), and Grade C (% score <50). Results : A total of 9 Randomized Controlled Trials (RCTs) were included in this study. All trials reported 12 items (66.67%) on average in STRICTA guidelines. Five studies were conducted with manual acupuncture and 3 studies were conducted with electroacupuncture. PC7 (Daereung) was most frequently used to treat CTS. In STRICTA guideline evaluation, 3 studies were classified as Grade A, 5 studies were classified as Grade B, and 1 study was classified as Grade C. In the CONSORT statement assessment, all trials reported an average of 20.56 items. Of the 9 RCTs, 6 studies were classified as Grade B and 3 studies were classified as Grade C. In ROB assessment, most studies showed a low (63.49%) or unclear (26.98%) risk of bias. The selective reporting bias and the incomplete outcome data bias were found to have the lowest risk of bias, and the allocation concealment of selection bias was found to have the most unclear risk of bias. Conclusions : Recent acupuncture studies on CTS showed moderate reporting quality. However, more detailed reports on acupuncture are still needed to establish more solid evidence of acupuncture treatment.

• 동의신경정신과학회지
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• 제28권3호
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• pp.165-182
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• 2017

Objectives: The purpose of this systematic review was to understand clinical usefulness of Emotional Freedom Techniques (EFT) on students' mental health. Methods: Ten databases were included to extract clinical studies on effects of EFT intervention with students. Characteristics of selected studies were described, and biases were assessed with Risk of Bias (RoB) or Risk of Bias Assessment for Non-Randomized Studies (RoBANS). Results: A total of 14 clinical trials were extracted for analysis. There were 8 randomized-controlled trials (RCTs), 2 non-randomized-controlled trials (nRCTs), and 4 before-after studies. EFT have significant clinical usefulness in public speaking anxiety, test anxiety, stress, depression, learning related emotions, adolescent anxiety, and eating issues. The risk of selection bias in most studies was high or uncertain. Conclusions: EFT is an effective clinical technique for managing students' mental health issues. However, the included studies have been conducted with relatively poor quality and small sample size. Clinical trials with high quality study design and well-designed EFT education programs are needed to generalize clinical usefulness.