• Journal of the Optical Society of Korea
• /
• 제13권2호
• /
• pp.261-266
• /
• 2009

The angular dispersion-type non-scanning Fabry-Perot was applied to an ethanol-water mixture in order to investigate its acoustic properties such as the sound velocity and the absorption coefficient. The scattered light from the mixture was analyzed by using the charge-coupled-device area detector, which made the measurement time much shorter than that obtained by using the conventional scanning tandem multi-pass Fabry-Perot interferometer. The sound velocity showed a deviation from ultrasonic sound velocities at low temperatures accompanied by the increase in the absorption coefficient, indicating acoustic dispersion due to the coupling between the acoustic waves and some relaxation process. Based on a simplified viscoelastic theory, the temperature dependence of the relaxation time was obtained. The addition of water molecules to ethanol reduced the relaxation time, consistent with dielectric measurements. The present study showed that the angular dispersion-type Fabry-Perot interferometer combined with an area detector could be a very powerful tool in the real-time monitoring of the acoustic properties of condensed matter.

• Current Optics and Photonics
• /
• 제3권4호
• /
• pp.298-303
• /
• 2019

We propose a photonic quasi-crystal fiber (PQF) for supporting up to 14 orbital angular momentum (OAM) modes with low and ultra-flat dispersion characteristics over the C+L bands. The designed PQF which consists of a large hollow center and quasi structural small air holes in the clad region exhibits low confinement losses and a large effective index separation (>$10^{-4}$) between the vector modes. This proposed fiber could potentially be exploited for mode division multiplexing and other OAM mode applications in fibers.

• 한국자기학회지
• /
• 제7권4호
• /
• pp.186-190
• /
• 1997

2축 Helmholtz 코일을 이용해서 연자성박막의 이방성 분산을 측정할 수 있는 장치를 제작하여 TBP(Transverse Biased Permeability) 측정 방법으로 rf 스파터방법으로 제작한 퍼말로이박막의 이방성 불균일성을 측정하였다. 각도불균일분포함수의 경우 Lorentz 함수형태를 띄며, 크기불균일 분포함수의 경우 자장이 큰 영역에서의 분산 값이 커져 대칭분포에서 벗어난다. 퍼말로이 박막의 두께가 증가할수록 이방성의 각도 및 크기분산이 커지고 각도 분산의 경우 이것은 두께 증가에 따른 결정립 크기의 증대와 국소이방성의 증가로 설명할 수 있었다.

• 한국군사과학기술학회지
• /
• 제27권2호
• /
• pp.230-237
• /
• 2024

Dispersion munitions are often equipped with dispersive submunitions used to scatter bombs over a wide area, and one of the types of dispersive submunitions is the Magnus rotor, commonly referred to as a self-rotating flying body. The Magnus rotor is designed to be dispered over a wide area by utilizing the principle of the Magnus effect through self-rotation, and has various trajectories depending on the initial conditions from the mother dispersion munition. In this paper, an index to evaluate the dispersion uniformity of footprint of the dispersive submunition is presented and the dispersion uniformity according to various initial release conditions is evaluated, and it is getting larger with high incidence angle and get max value at certain initial angular velocity.

• Advances in nano research
• /
• 제6권3호
• /
• pp.201-217
• /
• 2018

In the present research, wave propagation characteristics of a rotating FG nanobeam undergoing rotation is studied based on nonlocal strain gradient theory. Material properties of nanobeam are assumed to change gradually across the thickness of nanobeam according to Mori-Tanaka distribution model. The governing partial differential equations are derived for the rotating FG nanobeam by applying the Hamilton's principle in the framework of Euler-Bernoulli beam model. An analytical solution is applied to obtain wave frequencies, phase velocities and escape frequencies. It is observed that wave dispersion characteristics of rotating FG nanobeams are extremely influenced by angular velocity, wave number, nonlocal parameter, length scale parameter, temperature change and material graduation.

• 비파괴검사학회지
• /
• 제16권4호
• /
• pp.241-250
• /
• 1997

액체/고체 경계면에서 후방 복사된 초음파의 주파수 분석에 의해 Si layer/mesh Au/Si substrate 시편에 존재하는 표면 탄성파의 주파수 의존성이 측정되었다. 사용된 광역 탐촉자(2, 5, 10MHz)의 주파수에 따라 다르게 나타난 후방 복사의 입사각 의존성은 이 현상이 표면 지역에 발생된 표면파로부터의 에너지 복사에 의한 것임을 보여주었다. 후방 산란된 초음파의 입사각 의존성을 연속적으로 측정하기 위한 초음파 각도계가 제작되었고 다른 비율의 구리 분말이 섞인 에폭시에 의해 접착된 Ni layer/Al substrate 시편에 대해 후방복사 세기의 입사각 의존성이 측정되었다. (5MHz) 후방 복사의 폭과 패턴은 표면파 속도의 주파수 의존성, layer 접합의 질 그리고 표면 지역의 구조 등 여러 정보를 가지고 있음이 밝혀졌다.

• 세라미스트
• /
• 제22권4호
• /
• pp.350-356
• /
• 2019

Recently, transition metal dichalcogenide (TMDC) monolayers have been the subject of research exploring the physical phenomenon generated by low dimensionality and high symmetry. One of the keys to understanding new physical observations is the electronic band structure of 2D TMDCs. Angle-resolved photoelectron spectroscopy (ARPES) is, to this point, the best technique for obtaining information on the electronic structure of 2D TMDCs. However, through ARPES research, obtaining the long-range well-ordered single crystal samples always proves a challenging and obstacle presenting issue, which has been limiting towards measuring the electronic band structures of samples. This is particularly true in general 2D TMDCs cases. Here, we introduce the approach, with a mathematical framework, to overcome such ARPES limitations by employing the high level of symmetry of 2D TMDCs. Their high symmetry enables measurement of the clear and sharp electronic band dispersion, which is dominated by the band dispersion of single-crystal TMDCs along the two high symmetry directions Γ-K and Γ-M. In addition, we present two important studies and observations for the direct measuring of the exciton binding energy and charge transfer of 2D TMDCs, both being established by the above novel approach.

• 한국해양공학회지
• /
• 제21권1호
• /
• pp.18-24
• /
• 2007

When the wind blows strong, most waves are breaking at sea. Breaking waves occur by exceeding the limitation of wave steepness (wave height/wave length = 1/7). Because a wave of single angular frequency couldn't generate the breaking phenomena at a two-dimensional ocean engineering basin, the breaking wave can be generated by the superposition of waves with various angular frequencies based on dispersion relation. This study investigates the particle kinematics in the breaking wave and the magnitude of the breaking wave exciting force at the breaking point and breaking region. We compare the regular wave load in a regular wave, which has same specifications (wave height, period and length), with the breaking waveload. Also, the experimental results of wave exciting force and particle velocity are investigated, by comparison with the analytic results using the potential theory.

• ETRI Journal
• /
• 제38권6호
• /
• pp.1031-1041
• /
• 2016

This paper presents millimeter-wave (mmWave) propagation characteristics and channel model parameters including path loss, delay, and angular properties based on 28 GHz and 38 GHz field measurement data. We conducted measurement campaigns in both outdoor and indoor at the best potential hotspots. In particular, the model parameters are compared to sub-6 GHz parameters, and system design issues are considered for mmWave 5G Giga communications. For path loss modeling, we derived parameters for both the close-in free space model and the alpha-beta-gamma model. For multipath models, we extracted delay and angular dispersion characteristics including clustering results.

• 한국해양공학회:학술대회논문집
• /
• 한국해양공학회 2004년도 학술대회지
• /
• pp.96-101
• /
• 2004

When the wind blows hard, most waves are breaking in sea. Breaking waves occur, exceeding limitation of wave steepness(wave height/wave length=l/7). Because a wave of single angular frequency couldn't generate the breaking phenomena at two dimensional ocean engineering basin, the breaking wave can be generated by the superposition of waves with various angular frequencies. We research how are the particle kinematics in the breaking wave and the magnitude of the breaking wave exciting force. We compare the force in a regular wave which has same specifications(wave height, period and length) as the breaking wave. Also the experimental results of wave exciting force and particle velocity are investigated by comparison on the analytic results using the potential theory.