• Structural Engineering and Mechanics
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• 제11권4호
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• pp.357-372
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• 2001

In this paper, cantilevered tall structures are treated as cantilever bars with varying cross-section for the analysis of their free longitudinal (or axial) vibrations. Using appropriate transformations, exact analytical solutions to determine the longitudinal natural frequencies and mode shapes for a one step non-uniform bar are derived by selecting suitable expressions, such as exponential functions, for the distributions of mass and axial stiffness. The frequency equation of a multi-step bar is established using the approach that combines the transfer matrix procedure or the recurrence formula and the closed-form solutions of one step bars, leading to a single frequency equation for any number of steps. The Ritz method is also applied to determine the natural frequencies and mode shapes in the vertical direction for cantilevered tall structures with variably distributed stiffness and mass. The formulae proposed in this paper are simple and convenient for engineering applications. Numerical example shows that the fundamental longitudinal natural frequency and mode shape of a 27-storey building determined by the proposed methods are in good agreement with the corresponding measured data. It is also shown that the selected expressions are suitable for describing the distributions of axial stiffness and mass of typical tall buildings.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1997년도 추계학술대회 논문집
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• pp.468-472
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• 1997

The effect of the surface state on the quantum efficiency of underlying GaAs/AlGaAs multi-quantum well(MQW) structures consisting of three GaAs quantum wells with different thickness, is studied by low temperature photoluminescence(PL). The structure was grown by molecular beam epitaxy(MBE) on (100) GaAs substrate. The thickness of three GaAs quantum wells was 3, 6 and 9 nm, respectively. The MQWs were placed apart from 50 nm AlGaAs edge-barriers including two inner-barriers with 15 nm in thickness. The samples used in this study were prepared with different growth temperatures. Particularly, the hydrogen passivation effect to the 9 nm quantum well located at near surface appeared much stronger than any others. Transition energy and optical gain related to the hydrogen passivation effects on the multi-quantum well structure was calculated by transfer matrix method.

• Composites Research
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• 제34권2호
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• pp.123-128
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• 2021

본 논문은 Mori-Tanaka법, 혼합법칙 및 Halpin-Tsai 이론식을 적용하여 굴곡진 탄소나노튜브(CNT)로 보강된 복합재의 멀티스케일 고유진동 특성을 규명하였다. Eshelby 텐서를 이용하여 곡률을 갖는 CNT가 함유된 폴리머의 하중 전달 특성값이론을 유도하였다. 도출된 수치해석 결과는 기존의 연구결과와 잘 일치하였다. 본 연구에서 제시한 새로운 결과는 적층 복합재의 CNT 함유량, 굴곡성 및 적층배열의 상호작용 특성을 규명하였다. 주요 결과에 대하여 분석하였으며, CNT 보강 복합재의 실용적 설계를 위한 중요 고려사항을 제시하였다.

• Smart Structures and Systems
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• 제23권6호
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• pp.669-682
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• 2019

Vibration mitigation of cables or hangers is one of the crucial problems for cable supported bridges. Previous research focused on the behaviors of cable with dampers or crossties, which could help engineering community apply these mitigation devices more efficiently. However, less studies are available for hybrid applied cross-ties and dampers, especially lack of both analytical and experimental verifications. This paper studied damping and frequency of two parallel identical cables with a connection cross-tie and an attached damper. The characteristic equation of system was derived based on transfer matrix method. The complex characteristic equation was numerically solved to find the solutions. Effects of non-dimensional spring stiffness and location on the maximum cable damping, the corresponding optimum damper constant and the corresponding frequency of lower vibration mode were further addressed. System with twin small-scale cables with a cross-link and a viscous damper were tested. The damping and frequency from the test were very close to the analytical ones. The two branches of solutions: in-phase modes and the out-of-phase modes, were identified; and the two branches of solutions were different for damping and frequency behaviors.

• Current Optics and Photonics
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• 제6권3호
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• pp.270-281
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• 2022

Based on the transfer-matrix method (TMM), we report the characteristics of the interface states in one-dimensional (1D) composite structures consisting of two photonic crystals (PCs) composed of binary dielectrics A and B, with unit-cell configurations ABA (PC I) and BAB (PC II). The dependence of the interface states on the number of unit cells N and the boundary factor x are displayed. It is verified that the interface states are independent of N when the PC has inversion symmetry (x = 0.5). Besides, the composite structures support the formation of interface states independent of the PC symmetry, except that the positions of the interface states will be varied within the photonic band gaps. Moreover, the robustness of the interface states against nonuniformities is investigated by adding Gaussian noise to the layer thickness. In the case of inversion symmetry (x = 0.5) the most robust interface states are achieved, while for the other cases (x ≠ 0.5) interface states decay linearly with position inside the band gap. This work could shed light on the development of robust photonic devices.

• Educational Technology International
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• 제19권1호
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• pp.35-60
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• 2018

The purpose of this study was to analyze the types of lesson and its effectiveness with digital textbook. To address those goals, we had observed five classes of the primary school, which designated as a research pilot school for digital textbook. Based on the result of observation, 3 types of lesson with digital textbook were categorized: Teacher-directed lecture (type 1), Blended learning (type 2), and Flipped learning (type 3). Depending on the type of lesson was analyzed the positive and negative effectiveness by means of matrix analysis method. As a result, in Teacher-directed lecture (type 1), there was found out the participation of the lesson in atmosphere of stable and comfortable as positive experience, also digital textbook operating immature and boring as negative experience. In Blended learning (type 2), there was found out the fun by sharing the product and peer feedback, and flow by learning transfer as positive experience, also digital textbook operating immature and understanding the difference between assignments as negative experience. In Flipped learning (type 3), there was shown the positive attitude and ownership in the lesson as positive experience, also distracting and boring in the lesson when learner was excluded in participation as negative experience. Based on the results, we suggested some strategies for improving positive experience and protecting negative experience in the lesson with using digital textbook.

• 한국자동차공학회논문집
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• 제12권2호
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• pp.109-116
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• 2004

Bent-axis piston pump have been commonly used in hydraulic systems because of high pressure level, best efficiency, low shear force on pistons and low operating costs. The other side, they have a few demerits like that they have the relatively high number of moving parts and more discharge pressure ripples. Especially, the discharge pressure ripples bring about vibrations and noises in hydraulic system components such as connecting pipes and control valves, so that these deteriorate the stability and accuracy of the systems. Therefore, the hydraulic systems having the bent-axis piston pump require the methods to reduce the discharge pressure ripples. So, the purpose of this paper is to reduce the discharge pressure ripples by the phase interference of pressure wave and to develope the analysis model of the pumps to predict the discharge pressure ripples. In this paper, the analysis model of the bent-axis piston pump was developed using the AMESim software, and the reliability of that was verified by the comparison with the experimental results. The hydraulic pipeline with a parallel line was used as the method to generate the phase interference of pressure wave. the dynamics characteristics of the hydraulic pipeline with a parallel line were analyzed by a transfer matrix method. the usefulness of the phase interference of pressure wave was investigated through the experiment and simulation. The results from the experiment and simulation said that the phase interference of pressure wave by the hydraulic pipeline with a parallel line could reduce the discharge pressure wave of the pump well. The analysis model of the bent-axis piston pump developed in this paper and the method of the phase interference by the hydraulic pipeline with a parallel line are expected to be helpful to achieve the design of the pump and to reduce the discharge pressure wave of the pump effectively.

• 한국광학회지
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• 제19권6호
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• pp.429-434
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• 2008

비대칭 이중-금속 장거리 표면-플라즈몬 구조는 두 금속 사이에 위치한 코어 유전체 층의 굴절률을 임의로 선택하여도 장거리 표면-플라즈몬 모드가 존재한다는 장점이 있다. 도파로의 코어 층에 격자를 형성함으로써 플라즈몬 밴드-갭에 기초한 통신대역 파장에서의 장거리 표면-플라즈몬 파장필터를 구현하였다. Method of Line과 전달행렬방법 등을 통해 장거리 표면-플라즈몬 모드의 유효굴절률, 모드 특성, 투과도 등의 분석을 통해 설계하였으며, 도파로의 코어 층에 홀로그램 리소 방식을 이용하여 523.3 nm 주기의 브래그격자를 형성하여 파장필터를 제작하여 통신대역인 1541 nm 파장에서 대략 2 nm의 반치폭과 50 dB 이상의 파장 소광률을 확인하였다. 본 연구에서 제안한 파장필터는 표면-플라즈몬 집적회로를 구성하는 소자로써 중요한 역할을 할 것이다.

• Nuclear Engineering and Technology
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• 제42권5호
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• pp.474-499
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• 2010

This paper presents the mostortant developments implemented in the APOLLO2 spectral code since its last general presentation at the 1999 M&C conference in Madrid. APOLLO2 has been provided with new capabilities in the domain of cross section self-shielding, including mixture effects and transfer matrix self-shielding, new or improved flux solvers (CPM for RZ geometry, heterogeneous cells for short MOC and the linear-surface scheme for long MOC), improved acceleration techniques ($DP_1$), that are also applied to thermal and external iterations, and a number of sophisticated modules and tools to help user calculations. The method of characteristics, which took over the collision probability method as the main flux solver of the code, allows for whole core two-dimensional heterogeneous calculations. A flux reconstruction technique leads to fast albeit accurate solutions used for industrial applications. The APOLLO2 code has been integrated (APOLLO2-A) within the $ARCADIA^{(R)}$ reactor code system of AREVA as cross section generator for PWR and BWR fuel assemblies. APOLLO2 is also extensively used by Electricite de France within its reactor calculation chain. A number of numerical examples are presented to illustrate APOLLO2 accuracy by comparison to Monte Carlo reference calculations. Results of the validation program are compared to the measured values on power plants and critical experiments.

• KSBB Journal
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• 제15권1호
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• pp.49-54
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• 2000

1.0%(w/v)의 CMC 담체는 고정화를 유지할 수 있는 점도를 가지며 0.1 M 이하의 양이온과 이온가교결합을 할 수 있는 농도이다. Luminometer tube내의 시료에 유동을 최소화함으로써 산소의 공급을 일정하게 하여 P. phosphoreum을 고정화 30분 후 bioluminescence intensity가 안정되어 바로 측정할 수 있는 장점을 가지고 있었다. 1.0%(w/v) CMC담체는 pH 6.92로 최적조건인 pH 7.0에 근접했으며, 발광기작에 필요한 산소전달(oxygen transfer)이 1.5%(w/v)~3.0%(w/v) CMC 담체보다 뛰어나 Bioluminescence intensity의 안정성을 부여하였다. Cr-화합물인 $Na_{2}CrO_{4}$, $K_{2}CrO_{4}$, $CrO_{3}$, CrK$(SO_4)_{2}$ 및 $CrCl_{3}$의 CMC담체에 대한 민감도는 $\gamma$값을 이용해서 $EC_{50}$값으로 나타내었을 때 $Na_{2}CrO_{4}$, $K_{2}CrO_{4}$, CrK$(SO_4)_{2}$ 및 $CrCl_{3}$ 의 $EC_{50}$값이 1.0%(w/v)CMC에서는 5.4~16.3 g/L으로 1.5%(w/v)~3.0%(w/v) CMC에서는 6.2~555.9 g/L의 범위로 나타났다. 이것은 1.0%(w/v) CMC가 낮은 독성 농도에서 bioluminescence intensity가 50% 감소함을 알 수 있고, 상관계수($R^2$)가 0.911~0.990 으로 높게 산출되었다. 따라서 1.0%(w/v) CMC 담체가 P. phosphoreum의 biolumincsene에 안정성을 주었으며, 독성물질에 가장 민감하다는 것을 알 수 있었다.