• 전자공학회논문지D
• /
• 제34D권3호
• /
• pp.105-113
• /
• 1997

We constructed a very accurate fiber bragg grating sensor system using an unbalanced mach-zehnder interferometer which converts the measurand-induced bragg wavelength shift to phase change of th einterference signal. With a shielded reference grating, output phase drift which orginates from the thermal drift on the interferometer was compensated. Mesured accuracy of the constructed system was 0.03 .deg. C and 0.26.mu. strain for temperature and strain measuremtn, respectively. It is over 300 times better resolution compared to the conventional optical spectrum analyzer which has 0.1nm wavelength resolution capability.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1996년도 하계학술대회 논문집 C
• /
• pp.1898-1900
• /
• 1996

The Laser aided diagnostic method makes it possible to diagnose plasma characteristics which have never been done by other one. The aim of this study is to measure the electron density profile of an arc plasma by Mach-Zenhder interferometer. The two laser beams (He-Ne and Argon Lasers), which are different in wavelength, pass across an arc plasma and meet a change of refractivity which makes fringe shifts. From this effects we could find densities of electron and neutral particle.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2000년도 춘계학술대회논문집B
• /
• pp.290-295
• /
• 2000

An experimental study was carried out in a cavity with upper channel and square heat surface by visualization equipment with Mach-Zehnder interferometer and laser apparatus. The visualization system consists of 2-dimensional sheet light by Argon-Ion Laser with cylindrical lens and flow picture recording system. Instant simultaneous velocity vectors at whole field were measured by 2-D PIV system(CACTUS'2000). Obtained result showed various flow patterns. Severe unsteady flow fluctuation within the cavity are remarkable and sheared mixing layer phenomena are also found at the region where inlet flow is collided with the counter-clockwise rotating main primary vortex. Photographs of Mach-Zehnder are also compared in terms of constant heat flux.

• EDISON SW 활용 경진대회 논문집
• /
• 제1회(2012년)
• /
• pp.5-8
• /
• 2012

임계마하수란 에어포일의 표면에서 음속에 도달하는 부분이 생기기 시작하는 가장 낮은 Mach number라 한다. 임계마하수는 천음속에서 자유류가 임계마하수보다 조금 커지면 항력이 급격하게 증가하게 된다. 그렇기 때문에 임계마하수가 큰 에어포일이 천음속 항공기 설계에 있어서 매우 중요한 역할을 하게 된다. 이번 연구는 학부과정에서 배운 임계마하수에 대해 정의하고, EDISON_CFD를 이용하여 에어포일에 따라서 임계마하수가 달라지는 것을 확인해 보았다. 그 결과 에어포일이 두꺼워질수록 낮은 마하수에서 Shock이 발생하는 것을 확인할 수 있었다. 마지막으로 EDISON_CFD를 이용하여 계산된 임계마하수 값과 이론값을 비교한 결과, 높은 정확도를 확인할 수 있었다.

• EDISON SW 활용 경진대회 논문집
• /
• 제1회(2012년)
• /
• pp.97-100
• /
• 2012

항력계수와 양력계수는 각각 항력, 양력을 동압과 에어포일의 코드 길이로 나눈 값으로 정의된다. 항공기의 비행에 있어서 항력과 양력은 매우 중요한 요소로 작용하며 항공기의 속도에 따라 항력과 양력은 크게 변하게 된다. 첫째로 학부과정에서 배운 마하수에 따른 항력계수의 변화, 그 중에서도 마하수 1 이상에서의 항력계수 감소에 관한 이론을 살펴보고 EDISON_CFD를 이용하여 마하수에 따른 항력계수의 값을 실제로 측정해보고 비교해보았다. 두 번째로는 EDISON_CFD로 측정한 마하수버에 따른 양력계수 값과 앞서 측정한 항력계수 값을 이용하여 NACA0012의 마하수에 따른 양력과 항력의비 (양항비)를 구하여 실제고도에서 비행 시 NACA0012의 적정 효율을 가지는 마하수를 알아보았다.

• 에너지공학
• /
• 제24권2호
• /
• pp.110-114
• /
• 2015

A numerical investigation has been carried out on recirculation zone formed downstream of a compressible flow over a backward facing step. The study has been performed by solving Two-Dimensional Navier-Stokes equations. The system of governing equations has been solved, using an explicit Harten-Yee Non- MUSCL Modified flux type TVD scheme and a zero-equation algebraic turbulence model to calculate the eddy viscosity coefficient. The recirculation region dimensions are characterized over a range of Mach numbers of fixed step height 5mmThe detail of recirculation zone such as pressure, temperature, recirculation length, strength etc are reported. The variations of these characteristics due to change of Mach number are also presented.

• 천문학회지
• /
• 제34권4호
• /
• pp.321-323
• /
• 2001

Compressible, magnetohydrodynamic (MHD) turbulence in two dimension is studied through high-resolution, numerical simulations with the isothermal equation of state. First, hydrodynamic turbulence with Mach number $(M)_{rms}\;\~$1 is generated by enforcing a random force. Next, initial, uniform magnetic field of various strengths with Alfvenic Mach number Ma $\gg$ 1 is added. Then, the simulations are followed until MHD turbulence is fully developed. Such turbulence is expected to exist in a variety of astrophysical environments including clusters of galaxies. Although no dissipation is included explicitly in our simulations, truncation errors produce dissipation which induces numerical resistivity. It mimics a hyper-resistivity in our second-order accurate code. After saturation, the resulting flows are categorized as SF (strong field), WF (weak field), and VWF (very weak field) classes respectively, depending on the average magnetic field strength described with Alfvenic Mach number, $(Ma)_{rms}{\ge}1$, $(Ma)_{rms}{\~}1$, and $(Ma)_{rms}{\gg}1$. The characteristics of each class are discussed.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2001년도 제17회 학술발표회 논문초록집
• /
• pp.43-47
• /
• 2001

A numerical parametric study is conducted to simulate shock-induced combustion with a variation in freestream conditions. The analysis is limited to inviscid flow and includes chmical nonequilibrium. A steady combustion front is established if the freestream Mach number is above the Chapman-Jouguet speed of the mixture. On the other, an unsteady reaction fi:ont is established if the freestream Mach number is below or at the Chapman-Jouguet speed of the mixture. The three cases have been simulated for Machs 4.18, 5.11, and 6.46 with a projectile diameter of 15 mm. Machs 4.18 and 5.11 shows an unsteady reaction front, whereas Mach 6.46 represents a steady reaction front. Thus Chapman-Jouguet speed is one of deciding factor for the instabilities to trigger. The instabilities of the chemical front with a variation of projectiles diameters will be investigated.

• Journal of the Optical Society of Korea
• /
• 제18권1호
• /
• pp.65-70
• /
• 2014

This paper presents the simulation and design of an all-optical subtractor using a quantum-dot semiconductor optical amplifier Mach-Zehnder interferometer (QD-SOA MZI) structure consisting of two cascaded switches, the first of which produces the differential bit. Then the second switch produces the borrow bit by using the output of the first switch and the subtrahend data stream. Simulation results were obtained by solving the rate equations of the QD-SOA. The effects of QD-SOA length, peak power and current density have been investigated. The designed gate can operate at speeds of over 250 Gb/s. The simulation results demonstrate a high extinction ratio and a clear and wide-opening eye diagram.

• 대한전자공학회논문지
• /
• 제26권12호
• /
• pp.2032-2038
• /
• 1989

Single mode optical fiber interferometeric sensors using phase tracking homodyne detection are typically susceptible to environmentally indured temperature fluctuations and other types of disturbances. A simple and effective phase tracking feedback electronic circuit for compensator is described to achieve stabilizing signal output, maximum sensitivity and linearity in the fiber optic Mach-Zehnder infterferometer in the presence of differential phase drift. The phase tracking range of the piezoelectric cyclinder in the reference arm is \ulcorner.7 \ulcornerad and the prabe mass about 1 gram in the sensing arm was used for measurements of the gravity acceleration.