• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.21 no.8
• /
• pp.900-904
• /
• 2010

In this paper, a frequency tunable zeroth-order resonant(ZOR) antenna has been implemented. The ZOR characteristics of the proposed antenna is realized by using a composite right-and left-handed(CRLH) transmission line which consists of a rectangular slot on the ground plane of a mushroom structured antenna in order to minimize the antenna size. In addition, the tunable devices are introduced on the slotted ground plane for frequency tuning capability. Depending on the on and off states of the tunable device on the slotted ground plane, a shunt inductance value of the CRLH transmission line is changed and its resonant frequency becomes tunable. From the experimental results, the resonant frequency of the proposed antenna is changed from 4.92 GHz to 2.96 GHz. Additionally, the proposed antenna's size is reduced by 94.24 % compared with the half-wavelength patch antenna.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.14 no.1
• /
• pp.197-206
• /
• 1990

Numerical results of heat transfer from a horizontal isothermal surface are presented for wall temperature T$_{w}$ = 0 .deg. C and ambient water temperature, T$_{\infty}$, from 1 .deg. C to 15 .deg. C. They include streamlines, temperature profiles, local heat transfer coefficients and average Nusselt numbers for the entire flow fields. For a upward-facing horizontal isothermal surface, the results show steady two dimensional flow regimes for T$_{\infty}$ .leg. 4.4 .deg. C, but no solution was obtained above T$_{\infty}$ = 4.4 .deg. C. For a downward-facing horizontal isothermal surface, the flow regimes are steady two dimensional flow for T$_{\infty}$ .geq. 4.9 .deg. C, and the numerical calculation was failed below this ambient water temperature. The mean Nusselt number has its maximum value at about T$_{\infty}$ = 3.4 .deg. C for upward-facing horizontal isothermal surface. For the case of downward-facing horizontal isothermal surface, the mean Nusselt number increases as the ambient water temperature increases.es.s.s.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2005.05b
• /
• pp.1031-1035
• /
• 2005

조력발전 건설사업에서 우선적으로 고려되어야 할 사항은 조수간만에 의해 외해부와 조지부 사이를 이동하는 해수를 적절히 소통시키는 것이다. 즉, 조력발전소에서 수문구조물의 목적은 주어진 조건 하에서 계획된 유량을 충분히 그리고 안전하게 배제시키는 것이다. 본 연구에서는 수문구조물에 대한 Apron의 길이와 경사의 변화에 의한 외해 조위와 시화호 수위차 조건에 따른 유량계수를 구해 배수능력과 유$\cdot$출입부, 외해, 시화호 및 큰가리섬 주위의 흐름 특성을 검토하고자 하였다. 이를 위해 시화호를 실험대상으로 하여 구조물을 중심으로 외해측으로 1,000m, 시화호측으로 500m, 폭 1,500m의 범위를 선정하였다. 수리모형을 1대50의 축척비로 제작하였다. 표 1은 실험별 Apron과 수문구조물의 제원을 나타내며, 수문구조물은 7기로 이루어졌다. 시화호의 흐름은 관성력과 중력이 지배력이 되며, 이때 상사법칙은 Froude 상사법칙을 적용할 수 있다. 실험III은 실험II에서 Apron의 경사를 1대10에서 1대5로 수정한 실험으로 수위조건은 외해측 -2.530 EL.m이고, 시화호측은 -1.603EL.m이다. 유량계수를 산정하기 위하여 6개 실험조건을 기본계획에서 제시된 수위-조위 조건에서 수위차 및 통수유량을 분배하여 결정하였고 유량계수 산정식에 따라 구조물의 유입부와 유출부에서 유속-면적법에 의해서 유량을 측정하였다. 그리고 국부평면 실험모형에서의 전체적인 해류의 흐름을 분석하기 위해 2차원 유속을 측정하였다. 또한, 유$\cdot$출입부 안정성을 검토하기 위해 Apron 지점과 수문구조물 지점에 3점법으로 유속을 측정하였으며, 색소를 이용하여 유황을 관찰하였다. 시화호와 외해의 수위차가 1.011 m일 때의 전체 수문구조물을 통과하는 유량을 비교한 결과, 실험II 및 실험III의 통과유량은 각각 $10,924m^3/s$ 및 $10,075m^3/s$로서 실험 I의 $2,757m^3/s$에 비해 통수능이 많이 개선되었음을 알 수 있다.

• Journal of the Korean Society of Radiology
• /
• v.9 no.7
• /
• pp.501-508
• /
• 2015

There are various Intercondyloid fossa X-ray taking methods. The methods carried out in clinics are Holmblad method, Camp-Conventry method, and Beclere method. Taking image of Intercondyloid fossa is carried a lot as basic examination for diagnosis related to simple fracture and cruciate ligament. Considering the condition and pains of patients, safe method is chosen but because Holmblad method can cause pains to knee part adhering to cassette, it is not easily used. In this study self-produced plane circular cone was attached to a cassette and in the posture for Holmblad method questionnaires of 100 applicants were analyzed to understand cognition on alleviation of pains, and the concentration of imge quality by scattering rays was measured with densitometer by taking human body phantom with X-ray. As a result, in the posture for Holmblad method, cognition on pains was alleviated by average 99%, and the change of concentration of X-ray film taken using phantom by scattering rays decreased statistically significantly compared to the cassette which did not use self-produced plane cone, therefor it is thought that the method can be valuably used in clinics.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.34 no.8
• /
• pp.16-23
• /
• 2006

The effects of strake planform shapes on the vortex formation, interaction, and breakdown characteristics of double-delta wings were investigated through pressure measurements of upper wing surface and off-surface flow visualization. Three different shapes of strakes were attached to a delta wing respectively to form double-delta wing configurations and tested in a medium-sized subsonic wind tunnel. The results of the pressure measurements indicated that the strake planform having a higher sweep angle generated more concentrated vortex systems at upstream locations, which, however, tended to diffuse and break down much faster at the downstream locations. It was also found from the off-surface visualization results that the cause for the vortex concentration was due to the acceleration of coiling and merging processes between the wing and strake vortices.

• Journal of Korean Society for Geospatial Information Science
• /
• v.10 no.3 s.21
• /
• pp.115-122
• /
• 2002

The mainly used technique to rectify satellite images with distortion is to develop a mathematical relationship between the pixel coordinates on the image and the corresponding points on the ground. By defining the relationship between two coordinate systems, a polynomial model is designed and various linear transformations are used. These GCP based geometric correction has performed overall plane to plane mapping. In the overall plane mapping, overall structure of a scene is considered, but local variation is discarded. The highly variant height of region is resampled with distortion in the rectified image. To solve this problem, this paper proposed the TIN-based rectification on a satellite image. The TIN based rectification is good to correct local distortion, but insufficient to reflect overall structure of one scene. So, this paper shows the experimental result and the analysis of each rectification model. It also describes the relationship GCP distribution and rectification model. We can choose a geometric correction model as the structural characteristic of a satellite image and the acquired GCP distribution.

• Journal of Digital Convergence
• /
• v.14 no.12
• /
• pp.231-236
• /
• 2016

Currently, a traffic monitoring service using a surveillance camera is provided through internet. In general, if the user points a certain location on a map, then this service shows the real-time image of the camera where it is mounted. In this paper, we proposed the intuitive surveillance monitoring system which displays a real-time camera image on the map by warping with bird's-eye view and with the top of image as the north. In order to robustly estimate the road plane using camera image, we used the motion vectors which can be detected to changes in brightness. We applied a re-adjustment process to have the same directivity with a map and presented a user-friendly interface that can be displayed on the map. In the experiment, the proposed method was presented as the result of warping image that the user can easily perceive like a map.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.18 no.3
• /
• pp.291-302
• /
• 2005

Due to the importance of the parameter in structural response, the uncertain elastic modulus was located at the center of stochastic analysis, where the response variability caused by the uncertain system parameters is pursued. However when we analyze the so-called stochastic systems, as many parameters as possible must be included in the analysis if we want to obtain the response variability that can reach a true one, even in an approximate sense. In this paper, a formulation to determine the statistical behavior of in-plane structures due to multiple uncertain material parameters, i.e., elastic modulus and Poisson's ratio, is suggested. To this end, the polynomial expansion on the coefficients of constitutive matrix is employed. In constructing the modified auto-and cross-correlation functions, use is made of the general equation for n-th moment. For the computational purpose, the infinite series of stochastic sub-stiffness matrices is truncated preserving required accuracy. To demons4rate the validity of the proposed formulation, an exemplary example is analyzed and the results are compared with those obtained by means of classical Monte Carlo simulation, which is based on the local averaging scheme.

• Education of Primary School Mathematics
• /
• v.26 no.4
• /
• pp.237-255
• /
• 2023

At a time when the textbooks publishing system is changing from government-administered to certified, it is necessary to analyze textbooks published in both systems. This study analyzed one government textbook and three certified textbooks on quadrilaterals based on the instructional components that must be taught in the area of 2-D shapes. As a result of the analysis, it was found that concept exploration was implemented appropriately, but classification activities were not presented in some lessons. In Defining Concepts, the definition of the concept was presented appropriately, but there were differences depending on the textbooks. In addition, it was found that there was little activity in talking about the components of shapes or shapes. In applying concepts, more diverse activities were presented in certified textbooks than in government textbooks. Knowing relationships are rarely presented in textbooks due to its influence on the curriculum. Based on the results of this analysis of quadrilaterals, this study provides textbook writers with implications on what to further consider is dealing with quadrilaterals.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.10 no.1
• /
• pp.164-170
• /
• 2006

Millimeter waves can be used for high resolution ranging and imaging. As the necessity of high-speed multimedia communication increases, millimeter wave systems are being developed since they are useful for wide band communication considering the shortage of available spectrum bands. However, it is necessary to analyze the characteristics of millimeter propagation in the atmosphere to assess the performance of millimeter wave systems. MCF and intensity fluctuations describe atmospheric effects on millimeter wave propagation. Using the quasi-optical method, a method is investigated to obtain MCF from the intensity distribution of focal plane. Also, a practical method is proposed to compute MCF from the flux measurement in the antenna focal plane.