• 열처리공학회지
• /
• 제32권3호
• /
• pp.118-123
• /
• 2019

The aim of this study investigates the feasibility of scanning acoustic microscope (SAM) with high frequency transducer for material degradation. The test specimen was prepared by artificial heat treatment of Co-base superalloy. The high frequency 200 MHz acoustic lens was used to generate the leaky surface acoustic wave (LSAW) on the test specimens. The matrix precipitates coarsened with thermal aging time, and then grow up to several tens of micrometers. The velocity of LSAW decreased with increasing aging time. Also, it has a good correlation between LSAW and hardness. Consequently, V(z) curve methods of SAM using high frequency transducer is useful tool to evaluate the heat treatment effects on microstructure.

• 한국정보처리학회:학술대회논문집
• /
• 한국정보처리학회 2017년도 춘계학술발표대회
• /
• pp.1201-1202
• /
• 2017

최근 IoT 관련 제품들과 IoT를 구현하기 위한 저전력 무선통신에 대한 관심이 높아지고 있다. 저전력 무선통신의 대표적인 예로는 BLE, Zigbee, Wifi, Z-Wave 등이 있다. 본 논문에서는 이러한 저전력 무선통신을 이용하는 디바이스들과 실시간으로 연동할 수 있는 저전력 무선통신 인터페이스 플랫폼을 설계하는 방법을 설명한다.

• 전기의세계
• /
• 제31권2호
• /
• pp.141-146
• /
• 1982

In this paper, surface acoustic wave (SAW) bandpass filter is designed using the Fourier series approach and the I$_{0}$-shin window function. And also we studied a method to realize SAW filter using the apodized ID transducer which was fabricated with aluminum metallization of about 1500 A over .deg. thickness on Y-cut Z-propagating LiNbO$_{3}$, crystal by photolithographic technique (lift-off method). Experimental results on SAW bandpass filter responses show good agreements with the theoretical characteristics.s.

• 약학회지
• /
• 제5권1호
• /
• pp.24-26
• /
• 1960

Micro-determination of Lead by Dithizone Method was studied as follows: 1) Max. absorption wave length of Dithizone-pb complex in CC $l_{4}$ soln. is 510m.mu., 2) at the range of 5.gamma.-120.gamma. pb content, Bourguer-Beer's law hold good, 3) co-existence of F $e^{++}$ Z $n^{++}$, and C $u^{++}$ interfere.rfere.

• Ocean Systems Engineering
• /
• 제1권4호
• /
• pp.317-336
• /
• 2011

A time domain finite element based method is employed to analyze wave radiation by multiple cylinders. The nonlinear free surface and body surface boundary conditions are satisfied based on the perturbation method up to the second order. The first- and second-order velocity potential problems at each time step are solved through a finite element method (FEM). The matrix equation of the FEM is solved through an iteration and the initial solution is obtained from the result at the previous time step. The three-dimensional (3D) mesh required is generated based on a two-dimensional (2D) hybrid mesh on a horizontal plane and its extension in the vertical direction. The hybrid mesh is generated by combining an unstructured grid away from cylinders and two structured grids near the cylinder and the artificial boundary, respectively. The fluid velocity on the free surface and the cylinder surface are calculated by using a differential method. Results for various configurations including two-cylinder and four-cylinder cases are provided to show the mutual influence due to cylinders on the first and second waves and forces.

• 대한기계학회논문집A
• /
• 제24권8호
• /
• pp.2074-2082
• /
• 2000

In this study, to investigate and to predict the crack growth behavior under variable amplitude loading, crack growth tests are conducted on 7075-T6 aluminum alloy. The loading wave forms are generated by normal random number generator. All wave forms have same average and RMS(root mean square) value, but different standard deviation, which is to vary the maximum load in each wave. The modified Forman's equation is used as crack growth equation. Using the retardation coefficient D defined in previous study, the load interaction effect is considered. The variability in crack growth process is described by the random variable Z which was obtained from crack growth tests under constant amplitude loading in previous work. From these, a statistical model is developed. The curves predicted by the proposed model well describe the crack growth behavior under variable amplitude loading and agree with experimental data. In addition, this model well predicts the variability in crack growth process under variable amplitude loading.

• Structural Engineering and Mechanics
• /
• 제20권4호
• /
• pp.421-434
• /
• 2005

In this paper, the finite element method is applied to investigate the effect of the lateral boundary in homogenous soil on the seismic response of a superstructure. Some influencing factors are presented and discussed, and several parameters are identified to be important for conducting soil-structure interaction experiments on shaking tables. Numerical results show that the cross-section width L, thickness H, wave propagation velocity and lateral boundaries of soil layer have certain influences on the computational accuracy. The dimensionless parameter L/H is the most significant one among the influencing factors. In other words, a greater depth of soil layer near the foundation should be considered in shaking table tests as the thickness of the soil layer increases, which can be regarded as a linear relationship approximately. It is also found that the wave propagation velocity in soil layer affects the numerical accuracy and it is suggested to consider a greater depth of the soil layer as the wave propagation velocity increases. A numerical study on a soil-structure experimental model with a rubber ring surrounding the soil on a shaking table is also conducted. It is found the rubber ring has great effect on the soil-structure interaction experiments on shaking table. The experimental precision can be improved by reasonably choosing the elastic parameter and width of the rubber ring.

• Ocean Systems Engineering
• /
• 제9권3호
• /
• pp.219-240
• /
• 2019

This paper presents the comparison between SFT response with linear and nonlinear cables. The dynamic response analysis of submerged floating tunnel (SFT) is presented computationally with linear and nonlinear tension legs cables. The analysis is performed computationally for two wave directions one at 90 degrees (perpendicular) to tunnel and other at 45 degrees to the tunnel. The tension legs or cables are assumed as linear and non- linear and the analysis is also performed by assuming one tension leg or cable is failed. The Response Amplitude Operators (RAO's) are computed for first order waves, second order waves for both failure and non-failure case of cables. For first order waves- the SFT response is higher for sway and heave degree of freedom with nonlinear cables as compared with linear cables. For second order waves the SFT response in sway degree of freedom is bit higher response with linear cables as compared with nonlinear cables and the SFT in heave degree of freedom has higher response at low time periods with nonlinear cables as compared with linear cables. For irregular waves the power spectral densities (PSD's) has been computed for sway and heave degrees of freedom, at $45^0$ wave direction PSD's are higher with linear cables as compared with nonlinear cables and at $90^0$ wave direction the PSD's are higher with non-linear cables. The mooring force responses are also computed in y and z directions for linear and nonlinear cables.

• Ocean and Polar Research
• /
• 제24권4호
• /
• pp.345-357
• /
• 2002

한국에 자생하는 거머리말속(Zostera, Zosteraceae)에 포함되는 수거머리말(Z. caulescen Miki)의 형태 및 생태학적 특성을 파악하기 위하여 생육환경, 외부형태학적 형질, 잎과 종자의 미세 구조를 비교 분석하였다. 우리나라 해역에서는 남해연안의 거제 가배리와 진도 죽림리에서만 수거머리말의 실체가 확인되었으며, 생육지의 환경은 파랑의 영향이 적은 내만의 수심 $3.0{\sim}6.5m$의 사니질 또는 니사질의 퇴적환경에서 출현하였다. 생식지의 길이, 잎 너비, 엽맥 수, 잎 표피 세포의 크기와 수, 종피의 늑골 수, 생식지 상에 수관 형성 여부, 잎 가장자리와 중앙의 두께 및 색조의 차이, 종자 표면의 anthocyanin색소 집적에 따른 자주색의 반점,잎 표피세포의 기본모양에서 수거미리 말은 뚜렷하게 구별되었다. 남해안 가배와 죽림의 집단에서 생육지에 따른 외부 형태학적 차이는 나타나지 않았으나, 하계의 생육밀도와 생물량은 가배리$(367.3m^{-2},\;725.7g\;dry\;wt\p;m^{-2})$에서 죽림리$(112.5m^{-2},\;392.0\;g\;dry\;wt\;m^{-2})$보다 높게 나타났다. 지상부의 생물량은 지하부보다 높게 나타났으며, 생육밀도와 생물량은 생식지의 개체수와 개체 당 생물량에 따라 큰 차이를 나타내었다.

• 조명전기설비학회논문지
• /
• 제22권6호
• /
• pp.79-88
• /
• 2008

본 연구에서는 전력선 근방의 전자파 전자계를 쌍극자 안테나 이론에 의해 도출하였으며 수직 전선배열의 3상전력선 근방의 전자계를 정식화함으로써 전자계 계산을 쉽게 할 수 있도록 하였다. 이 계산식들은 송전선로 및 배전선로의 설계시 전자파 전자계의 검토에 활용할 수 있을 것으로 생각된다. 이와 같이 정식화한 각 전자계 성분요소의 식들을 송전선로 모델에 적용하였으며 매틀랩 프로그램을 작성하여 계산하였다. 이 계산 결과를 요약하면 다음과 같다. 전자계의 x성분 $B_x$ 및 $E_x$는 무시할 수 있을 정도의 작은 값을 나타내며 대지내의 반사파에 의한 영향만을 반영한다. 수평거리 변화에 대하여 $E_y$와 $B_z$의 윤곽이 같으며, $B_y$와 $E_z$의 윤곽도 같다. 이와 같은 사실은 전자파 전계와 자계의 결합요소가 서로 직각으로서 $x{\rightarrow}E_y{\rightarrow}B_z$와 같은 우수계의 전파방향을 갖고 있음을 의미한다. 합성전계 E는 $E_y$요소가 지배적이며 합성자계 B는 $B_z$요소가 지배적이다.