• 한국산학기술학회논문지
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• 제17권11호
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• pp.663-669
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• 2016

본 논문에서는 높은 감도의 테라헤르츠 센서로 응용이 가능한 고품질 비대칭 분리고리공진기(ASLR: Asymmetric Split-Loop Resonator) 메타물질의 구조적인 비대칭 정도에 따른 ASLR의 공진특성 변화를 전자기 시뮬레이션을 통하여 분석하였다. 특히, ASLR의 구조적 비대칭성은 높은 품질인자를 갖는 파노공진을 발생시키므로 ASLR의 비대칭성 정도에 따라서 ASLR 고유공진과 파노공진의 공진주파수 변화와 투과계수 및 품질인자의 변화를 분석하였다. 또한, ASLR의 구조적 비대칭성에 따른 ASLR의 공진 특성 변화의 원인을 분석하기 위해 표면전류밀도를 계산하여 ASLR 공진의 공진주파수, 투과계수, 그리고 품질인자가 변화하는 이유를 분석하였다. 이를 통하여 ASLR 고유공진의 표면전류밀도는 이중 극자를 형성하여 높은 방사 손실을 가지게 되므로 품질인자가 낮아지게 되고, 파노공진의 표면전류밀도는 닫힌 모드 또는 사중 극자를 형성하여 이중 극자에 비하여 낮은 방사 손실을 가지므로 파노공진 상태의 ASLR이 높은 품질인자를 가지게 됨을 확인하였다. 이러한 ASLR의 파노공진 특성 분석 결과를 바탕으로 메타물질의 비대칭성을 조절하면 높은 품질인자를 가지는 테라헤르츠 고성능 필터 또는 고감도 센서 개발이 가능하다. 이러한 고감도 고성능 테라헤르츠 소자 개발은 테라헤르츠 메타물질의 실질적인 산업 응용을 유도할 것으로 기대한다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1110-1115
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• 2004

Acoustic behavior in gas turbine combustor with acoustic resonator is investigated numerically by adopting linear acoustic analysis. Helmholtz-type resonator is employed as acoustic resonator to suppress acoustic instability passively. The tuning frequency of acoustic resonator is adjusted by varying its length. Through harmonic analysis, acoustic-pressure responses of chamber to acoustic excitation are obtained and the resonant acoustic modes are identified. Acoustic damping effect of acoustic resonator is quantified by damping factor. As the tuning frequency of acoustic resonator approaches the target frequency of the resonant mode to be suppressed, mode split from the original resonant mode to lower and upper modes appears and thereby complex patterns of acoustic responses show up. Considering mode split and damping effect as a function of tuning frequency, it is desirable to make acoustic resonator tuned to broad-band frequencies near the maximum frequency of those of the possible upper modes.

• 대한기계학회논문집B
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• 제29권1호
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• pp.95-102
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• 2005

Acoustic behavior in gas turbine combustor with acoustic resonator is investigated numerically by adopting linear acoustic analysis. Helmholtz-type resonator is employed as acoustic resonator to suppress acoustic instability passively. The tuning frequency of acoustic resonator is adjusted by varying its length. Through harmonic analysis, acoustic-pressure responses of chamber to acoustic excitation are obtained and the resonant acoustic modes are identified. Acoustic damping effect of acoustic resonator is quantified by damping factor. As the tuning frequency of acoustic resonator approaches the target frequency of the resonant mode to be suppressed. mode split from the original resonant mode to lower and upper modes appears and thereby complex patterns of acoustic responses show up. Considering mode split and damping effect as a function of tuning frequency, it is desirable to make acoustic resonator tuned to broad-band frequencies near the maximum frequency of those of the possible upper modes.

• International Journal of Precision Engineering and Manufacturing
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• 제3권3호
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• pp.69-75
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• 2002

Measuring dynamic fracture toughness of brittle and small ceramic specimen is very difficult in a SHPB (Split Hopkinson Pressure Bar). As a countermeasure to this difficulty, a dynamic fracture toughness measuring method by the Chevron-notch ceramic specimen was proposed. Tested chevron specimens were of Chevron notch angles of 90$^{\circ}$, 100$^{\circ}$ and 110$^{\circ}$. Through finite element analysis, shape parameters of the Chevron-notch specimens according to notch angles were calculated. And the static fracture tough1ess of the Chevron-notch alumina specimen was measured as 3.8MPa√m similar to that of CT specimen with a precrack. Dynamic fracture toughness was 4.5MPa√m slightly higher than the static one. It was shown in this study that the proposed Chevron-notch specimens are valid to measure dynamic fracture toughness of extremely brittle materials such as ceramic.

• ETRI Journal
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• 제33권2호
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• pp.291-294
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• 2011

This letter proposes an open-ended waveguide antenna with a single split-ring resonator. In contrast to the waveguide antennas incorporating multiple rings reported in a previous study, which exhibited narrow bandwidth, the proposed antenna uses only one ring to achieve broader bandwidth while keeping the aperture small. A single ring has a relatively low quality factor compared to multiple rings. The simulated and measured fractional bandwidth was 4.13% and 4.03%, respectively, which is much broader than the fractional bandwidth of about 1% demonstrated in a previous study. This simple technique can be used in many applications that require small apertures including near-field probes and array elements.

• 대한간호학회지
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• 제29권2호
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• pp.304-313
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• 1999

The purpose of this study is to test the reliability and validity test of PWI to utility of PWI. this newly developed by Sejin Jang which measures stress. The subject were 186 workers in service area. Cronbach's a and Guttman split-half coefficient is used to test the reliability of PWI. Factor analysis and the correlation of the GHQ-60. GHQ-30, GHQ-28, GHQ-20, and GHQ-12 with the PWI is used to convergent validity and discriminant validity. The important results of this study are as follows : Cronbach's $\alpha$ coefficient of data was 0.894 and Guttman split-half coefficient was 0.7097. The PWI was classified as 13 principle component (eigenvalue＞1.0). After exploring 4 factor structure according to previous study result, 4 factors was explained 40.5% out of the total variance. The factor 1 was explained 15.9% and then the rest three factor was 24.6%. Factor 2 and 4 showed good agreement but factor 1 and 3 did not. Depression-related items were classified two factors. Anxiety and depression-related items were loaded unifactor. It was not clear that the PWI was consist of 4 concepts(factors). The correlation of the GHQ-60, GHQ-30, GHQ-28, GHQ-20, and GHQ-12 with the PWI were 0.744~0.905. According to findings of this study. the PWI showed a high degree of validity and reliability. Thus it is recommended to use the PWI in general setting for screening for stress. In addition, it is necessary to clarify the concept of depression and anxiety. In the further study. it my be considered to the factor structure of PWI and studied to two or unidimensional factor structure.

• International Journal of Concrete Structures and Materials
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• 제10권2호
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• pp.163-175
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• 2016

This paper presents a revised procedure for computation of double-K fracture parameters of concrete split-tension cube specimen using weight function of the centrally cracked plate of finite strip with a finite width. This is an improvement over the previous work of the authors in which the determination of double-K fracture parameters of concrete for split-tension cube test using weight function of the centrally cracked plate of infinite strip with a finite width was presented. In a recent research, it was pointed out that there are great differences between a finite strip and an infinite strip regarding their weight function and the solution of infinite strip can be utilized in the split-tension specimens when the notch size is very small. In the present work, improved version of LEFM formulas for stress intensity factor, crack mouth opening displacement and crack opening displacement profile presented in the recent research work are incorporated. The results of the double-K fracture parameters obtained using revised procedure and the previous work of the authors is compared. The double-K fracture parameters of split-tension cube specimen are also compared with those obtained for standard three point bend test specimen. The input data required for determining double-K fracture parameters for both the specimen geometries for laboratory size specimens are obtained using well known version of the Fictitious Crack Model.

• 대한간호학회지
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• 제35권6호
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• pp.1072-1080
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• 2005

Purpose: This paper was conducted to test the reliability and validity of rd-SLS, developed by Podsakoff, et al. (1993) which measured 'substitutes for leadership'. Method: The subjects were 345 nurses in 5 general hospitals. Cronbach's and the Guttman split-half coefficient were used to test the reliability of rd-SLS. Factor analysis, and the correlations of the rv-SLS and SLS with rd-SLS were used for convergent and discriminant validity. Result: Cronbach's data was 0.76 and the Guttman split-half coefficient was 0.52. Twelve factors evolved by factor analysis, which explained $70.4\%$ of the total variance. This result was similar to previous study results. However, 'Indifference toward organizational rewards'-related items were classified two factors. It was not clear t hat the rd-SLS consisted of 13 concepts(factors). The correlations of the rv-SLS and SLS with the rd-SLS were 0.93 and 0.87 respectively. Conclusion: The rd-SLS showed a moderate degree of validity and reliability. Thus, it is recommended to use the rd-SLS in general nursing organizations for screening for leadership substitutes. In addition, it is necessary to clarify the concept of organizational rewards. In a further study, the factor structure of the rd-SLS may be considered.

• 동서간호학연구지
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• 제25권1호
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• pp.26-32
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• 2019

Purpose: The purpose of this methodological study was to examine the validity and reliability of a translated Korean version of Templer's death anxiety scale among older adults. Methods: The translated Korean scale was administered to 203 older people who aged over 65 years. Exploratory factor analysis was utilized to assess the factor structure of the scale. Internal consistency of the scale was determined using Cronbach's ${\alpha}$ and Guttman's split-half coefficient. Results: Factor loadings of the scale ranged from .43 to .86. The scale showed good internal consistencies of both total scale (13 items, ${\alpha}=.83$) and three sub-scales: meaning of death (6 items, ${\alpha}=.77$), death-related event (5 items, ${\alpha}=.72$), and time of death (2 items, ${\alpha}=.80$). The concurrent validity compare with Fear of Death Scale was significant. The Cronbach's alpha and Guttman's split-half coefficient were .83 and .80, respectively. Conclusion: The findings of this study demonstrate that the Korean version of Templer's death anxiety scale had satisfactory validity and reliability to measure death anxiety among Korean older people.

• Clinical and Experimental Reproductive Medicine
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• 제34권4호
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• pp.305-312
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• 2007

목 적: 본 연구에서는 일반적인 체외수정과 세포질내 정자주입술을 병행하여 시행하는 분할 수정법의 효용성을 정상적인 정자 소견을 나타내는 비남성요인 불임 환자의 체외수정 및 배아이식술에서 살펴보고자 하였다. 연구방법: 제일병원 아이소망센터에서 정자 소견상 결함이 없는 비남성요인 불임 환자에게 분할 수정법을 이용한 505주기의 임상 결과를 후향적으로 분석하였다. 획득된 난자는 무작위로 나누어 일반적인 체외수정이나 세포질내 정자주입술을 이용하여 수정을 시켰다. 수정란은 이식할 때까지 2$\sim$5일간 배양하였고, 잉여의 수정란과 배아는 동결보관하여 동결-융해 이식에 사용하였다. 수정 방법에 따른 임상 결과를 통계학적인 방법으로 비교하였다. 결 과: 획득된 난자의 수정율은 분할 수정법을 시행하였을 때 일반적인 체외수정보다 세포질내 정자주입술에서 통계적으로 유의하게 높게 나타났다 (52.9$\pm$28.0% vs 62.5$\pm$22.3%, p<0.01). 전체적인 수정의 실패는 분할 수정법을 시행한 505주기 중에서 단지 2주기에서만 (0.4%) 나타났으며, 수정 실패와 0$\sim$30% 이하의 수정률을 나타내는 빈도는 세포질내 정자주입술에서 일반적인 체외수정보다 통계적으로 유의하게 낮았다 (1.1% and 7.5% vs 8.5% and 22.0%, p<0.01). 분할 수정주기에서의 신선 배아와 동결-융해 배아이식 후 분만율은 각각 40.0% (185/462)와 35.0% (55/157)였으며, 일반적인 체외수정이나 세포질내 정 자주입술로 얻어진 배아의 착상률과 분만율은 유의적인 차이가 나타나지 않았다. 결 론: 결론적으로 비남성요인 불임 환자의 보조생식술에서 분할 수정법이 수정 실패와 낮은 수정율을 방지하고 성공적인 임상 결과를 제공할 수 있는 효과적인 방법으로 사료된다.