• Smart Structures and Systems
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• 제14권5호
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• pp.831-845
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• 2014

This paper proposed a discrete wavelet transform based method for time-varying physical parameter identification of shear type structures. The time-varying physical parameters are dispersed and expanded at multi-scale as profile and detail signal using discrete wavelet basis. To reduce the number of unknown quantity, the wavelet coefficients that reflect the detail signal are ignored by setting as zero value. Consequently, the time-varying parameter can be approximately estimated only using the scale coefficients that reflect the profile signal, and the identification task is transformed to an equivalent time-invariant scale coefficient estimation. The time-invariant scale coefficients can be simply estimated using regular least-squares methods, and then the original time-varying physical parameters can be reconstructed by using the identified time-invariant scale coefficients. To reduce the influence of the ill-posed problem of equation resolving caused by noise, the Tikhonov regularization method instead of regular least-squares method is used in the paper to estimate the scale coefficients. A two-story shear type frame structure with time-varying stiffness and damping are simulated to validate the effectiveness and accuracy of the proposed method. It is demonstrated that the identified time-varying stiffness is with a good accuracy, while the identified damping is sensitive to noise.

• The Journal of Asian Finance, Economics and Business
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• 제6권1호
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• pp.149-158
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• 2019

Due to the rapid development of IT (information technology) and internet, products become smart and able to collect, process and produce information and can think of themselves to provide better service to consumers. However, research on the characteristics of smart product is still sparse. In this paper, we report the systemic development of a scale to measure the perceived product smartness associated with smart product. To develop product smartness scale, this study follows systemic scale development processes of item generation, item reduction, scale validation, reliability and validity test consequently. And, after acquiring a large amount of qualitative interview data asking the definition of smart product, we add a unique process to reduce the initial items using both a text mining method using 'r' s/w and traditional reliability and validity tests including factor analysis. Based on an initial qualitative inquiry and subsequent quantitative survey, an eight-factor scale of product smartness is developed. The eight factors are multi-functionality, human-like touch, ability to cooperate, autonomy, situatedness, network connectivity, integrity, and learning capability consequently. Results from Korean samples support the proposed measures of product smartness in terms of reliability, validity, and dimensionality. Implications and directions for further study are discussed. The developed scale offers important theoretical and pragmatic implications for researchers and practitioners.

• 콘크리트학회논문집
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• 제17권6호
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• pp.939-946
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• 2005

비균질 재료인 콘크리트의 강성 특성과 성능저하 현상을 웨이블릿 변환을 이용한 다중해상도해석을 통해 각 관찰 규모에 따라 동질화 과정의 적용성 및 거시적 손상지수의 평가 등을 연구하였다. 연속적인 Haar 웨이블릿 변환은 기존 강성행렬의 특성을 연속적인 축소규모로의 복제를 통해 미세규모로부터 거시규모로의 축소 또는 복원 과정을 나타내었고 이는 선형구조계의 크기별 스펙트럼 특성의 보존, 즉 타원성, 철면성 그리고 양의 정부호성을 보존하여 각 규모별 해의 유효성을 확인하였다. 웨이블릿 계수를 이용한 기존 강성의 평균은 거시단계의 변형에너지와 상호관계를 가지고 아래 단계로의 축소, 윗 단계로의 복원을 자유롭게 할 수 있는 장점이 있다. 이러한 다중해상도해석의 예제로서 1차원 및 2차원 2상복합체를 가지고 유한요소해석을 통해 기존 이론의 검증과 최소고유치의 각 크기단계별 변화 과정, 원 축소 구조계의 해의 유일성 그리고 국부적 손상지수의 동질화 여부 등을 검사하였다. 이러한 동질화 축소 과정은 자유도가 큰 비선형 구조계로의 적용의 첫 단계를 제공하였다.

• 한국정밀공학회지
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• 제29권2호
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• pp.129-138
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• 2012

In this study, three types of large scale multi-tasking machine tools together with core technologies involved have been developed and introduced; a multi-tasking machine tool for large scale marine engine crankshafts, a multi-tasking vertical lathe for windmill parts, and a large scale 5-axis machine tool of gantry type. Several special purpose devices has been necessarily developed for the purpose of handling and machining big and heavy workpieces accurately, such as PTD (Pin Turning Device) with revolving ring spindle for machining eccentric crankshaft pins, hydrostatic rotary table and steady rest for supporting and resting heavy workpieces, and 2-axis automatic swiveling head for high-quality free surface machining. Core technologies have been also developed and adopted on their detail design stage; 1) structural design optimization with FEM structural analysis, 2) theoretical hydrostatic analysis for the PTD and rotary table bearings, 3) box-in-box type cross-rail and octagonal ram design to secure machine rigidity and accuracy, 4) constant spindle rpm control against gravitational torque due to unbalanced workpiece.

• 한국사회복지학
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• 제63권2호
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• pp.319-336
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• 2011

본 연구는 외국인 며느리를 둔 시부모를 대상으로 하여 문화적응 스트레스를 측정하기 위한 척도를 개발하고 그 신뢰도와 타당도를 검증해보고자 하였다. 이를 위하여 기존의 유학생을 대상으로 하는 문화적응 스트레스 척도를 기본척도로 하여 다문화 가정의 시부모에 적합하도록 재구성하였다. 분석 결과, 문항의 제거와 표본의 이상치 점검을 위한 문항분석을 통하여 최종적으로 11문항이 선정되었다. 다음으로 문화적응 스트레스 척도의 요인구성을 살펴보기 위하여 탐색적 요인분석을 실시하였으며 시부모의 문화적응 스트레스 척도는 '편견 및 차별감 지각', '문화적 가치관 차이로 인한 갈등', '일상생활의 불편'의 세 가지 요인으로 구성됨을 확인하였다. 이렇게 구성된 척도의 타당도를 검증하기 위하여 구조모형을 통한 확인적 요인분석을 실시하였으며 그 결과 양호한 모형적합도를 보여주었다. 척도의 신뢰도는 Cronbach's ${\alpha}$로 검증하였으며 0.86으로 나타났다.

• 천문학회보
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• 제45권1호
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• pp.39.1-39.1
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• 2020

We examine how the mass assembly of central galaxies depends on their location in the cosmic web. The HORIZON-AGN simulation is analysed at z~2 using the DISPERSE code to extract multi-scale cosmic filaments. We find that the dependency of galaxy properties on large-scale environment is mostly inherited from the (large-scale) environmental dependency of their host halo mass. When adopting a residual analysis that removes the host halo mass effect, we detect a direct and non-negligible influence of cosmic filaments. Proximity to filaments enhances the build-up of stellar mass, a result in agreement with previous studies. However, our multi-scale analysis also reveals that, at the edge of filaments, star formation is suppressed. In addition, we find clues for compaction of the stellar distribution at close proximity to filaments. We suggest that gas transfer from the outside to the inside of the haloes (where galaxies reside) becomes less efficient closer to filaments, due to high angular momentum supply at the vorticity-rich edge of filaments. This quenching mechanism may partly explain the larger fraction of passive galaxies in filaments, as inferred from observations at lower redshifts.

• 대한전자공학회논문지SP
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• 제41권3호
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• pp.221-229
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• 2004

The Continuous Wavelets Transform project signal f(t) to "Time-scale"plan utilizing the time varied function which called "wavelets". This Transformation permit to analyze scale time dependence of signal f(t) thus the local or global scale properties can be extracted. Moreover, the signal f(t) can be reconstructed stably by utilizing the Inverse Continuous Wavelets Transform. In this paper, the EEG signal is analyzed by wavelets coherence method and the De-noising procedure is represented.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.413-417
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• 2004

Recent experiments have shown the 'size effects' in micro/nano scale. But the classical plasticity theories can not predict these size dependent deformation behaviors because their constitutive models have no characteristic material length scale. The Mechanism - based Strain Gradient(MSG) plasticity is proposed to analyze the non-uniform deformation behavior in micro/nano scale. The MSG plasticity is a multi-scale analysis connecting macro-scale deformation of the Statistically Stored Dislocation(SSD) and Geometrically Necessary Dislocation(GND) to the meso-scale deformation using the strain gradient. In this research we present a study of nano-indentation by the MSG plasticity. Using W. D. Nix and H. Gao s model, the analytic solution(including depth dependence of hardness) is obtained for the nano indentation , and furthermore it validated by the experiments.

• Advances in biomechanics and applications
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• 제1권1호
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• pp.23-40
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• 2014

This paper examines the blood chamber of a left ventricular assist device (LVAD) under static loading conditions and standard operating temperatures. The LVAD's walls are made of a temperature-sensitive polymer (ChronoFlex C 55D) and are covered with a titanium nitride (TiN) nano-coating (deposited by laser ablation) to improve their haemocompatibility. A loss of cohesion may be observed near the coating-substrate boundary. Therefore, a micro-scale stress-strain analysis of the multilayered blood chamber was conducted with FE (finite element) code. The multi-scale model included a macro-model of the LVAD's blood chamber and a micro-model of the TiN coating. The theories of non-linear elasticity and elasto-plasticity were applied. The formulated problems were solved with a finite element method. The micro-scale problem was solved for a representative volume element (RVE). This micro-model accounted for the residual stress, a material model of the TiN coating, the stress results under loading pressures, the thickness of the TiN coating and the wave parameters of the TiN surface. The numerical results (displacements and strains) were experimentally validated using digital image correlation (DIC) during static blood pressure deformations. The maximum strain and stress were determined at static pressure steps in a macro-scale FE simulation. The strain and stress were also computed at the same loading conditions in a micro-scale FE simulation.

• 대한간호학회지
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• 제48권4호
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• pp.419-431
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• 2018

Purpose: The purpose of this study was to develop and establish the psychometric properties of a clinical nursing competency evaluation tool to be utilized by clinical preceptors. Methods: The initial items were identified through in-depth literature review and field interviews based on a hybrid model. Content validation of the items was evaluated through three rounds of content validity testing. Participants were 34 clinical preceptors and 443 nursing students participating in clinical practice. Data were analyzed using exploratory and confirmatory factor analysis, convergence and discriminant validity, internal consistency and inter-rater reliability. Results: The final scale consisted of 23 items and four factors, fundamental nursing skills performance, critical thinking skills based on the nursing process, basic nursing knowledge, and professional attitude; these factor explained 69.7% of the total variance. The analysis with multi-trait/multi-item matrix correlation coefficients yielded 100.0% and 95.7 % convergence and discriminant validity, respectively. Cronbach's alpha for the total items was .95. The four subscale model tested by confirmatory factor analysis was satisfactory. Inter-rater reliability ranged from .912 to .967. Conclusion: This scale was found to be a reliable and valid instrument that clinical preceptors can apply for evaluating the clinical nursing competency of nursing students in clinical settings.