• Journal of Satellite, Information and Communications
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• v.9 no.2
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• pp.7-11
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• 2014

In this paper, we designed resistive MMIC mixer using $0.5{\mu}m$ p-HEMT process. This Mixer is designed to have a similar performance in -4 ~ 4 dBm local oscillator signal power level and to maintain a constant conversion loss and linear performance due to the variation of local signal. In order to have such characteristics, we designed new feedback circuit topology by using FET, and minimized performance change for LO signal power level variation, also obtain MMIC mixer characteristics which is able to apply in wideband. In the design result, When the LO signal power is -4 ~ 4 dBm, there was 6 dB conversion loss and it came up with the excellent result that IIP3 got over 30 dBm in 0.5 ~ 2.6GHz frequency band.

• The Journal of the Korea Contents Association
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• v.9 no.4
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• pp.34-44
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• 2009

Integrating 3D data acquired in multiple views is one of the most important techniques in 3D modeling. However, due to the presence of surface scanning noise and the modification of vertices consisting of surface, the existing integration methods are inadequate to some applications. In this paper, we propose a method of integrating surfaces by using the local surface topology. We first find all boundary vertex pairs satisfying a prescribed geometric condition on adjacent surfaces and then compute 2D planes suitable to each vertex pairs. Using each vertex pair and neighbouring boundary vertices projected to their 2d plane, we produce polygons and divide them to the triangles which will be inserted to empty space between the adjacent surfaces. A proposed method use local surface topology and not modify the vertices consisting of surface to integrate several of surfaces to one surface, so that it is robust and simple. We also integrate the transformed textures to a 2D image plane computed by using a cylindrical projection to composite 3D textured model. The textures will be integrated according to the partition lines which considering attribute of face object. Experimental results on real object data show that the suggested method is simple and robust.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.216-218
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• 2008

This paper presents a space vector pulse width modulation (SVPWM) technique for four-switch three-phase (4S3P) inverter topology. The method aims to apply Field Oriented Control (FOC) of Induction motor using 4S3P. The simulations are carried out and the experimental results are given to verify the feasibility of this method.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1283-1287
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• 2003

Reverse engineering technology refers to the process that creates a CAD model of an existing part using measuring devices. Recently, non-contact scanning devices have become more accurate and the speed of data acquisition has increased drastically. However, they generate thousands of points per second and various types of point data. Therefore. it becomes a important to handle the huge amount and various types of point data to generate a surface model efficiently. This paper proposes a new triangular mesh generation method using 3D grids. The geometric information of a part can be obtained from point cloud data by estimating normal values of the points. In our research, the non-uniform 3D grids are generated first for feature based data reduction based on the geometric information. Then, triangulation is performed with the reduced point data. The grid structure is efficiently used not only for neighbor point search that can speed up the mesh generation process but also for getting surface connectivity information to result in same topology surface with the point data. Through this integrated approach, it is possible to create surface models from scanned point data efficiently.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.8
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• pp.91-97
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• 2010

Micro-abrasive Jet Machining is one of the new technology which enables micro-scale machining on the surface of high brittle materials. In this technology it is very important to fabricate a mask that prevents excessive abrasives not to machine un-intend surface. Our previous work introduced the micro-stereolithography technology for the mask fabrication. And is good to not only planar material but also for non-planar materials. But the technology requires a 3 dimensional mask CAD model which is perfectly matched with the surface topology of parent material as an input. Therefore there is strong need to develop an automated modeling technology which produce adequate 3D mask CAD model in fast and simple way. This paper introduces a fast and simple mask modeling algorithm which represents geometry of models in voxel. Input of the modeling system is 2D pattern image, 3D CAD model of parent material and machining parameters for Micro-abrasive Jet Machining. And the output is CAD model of 3D mask which reflects machining parameters and geometry of the parent material. Finally the suggested algorithm is implemented as software and verified by some test cases.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.12
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• pp.14-24
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• 2001

An active MMIC L-band down converting mixer was designed by using GaAs FET with 0.5 ${\mu}$m gate length and 300 ${\mu}$m gate width. Main circuit topology was cascoded two active FETs. It consumed only 7.5 mA with 3V DC voltage supply. Conversion gain of 6.63 dB, minumium noise figure of 5.06 dB and Input $3^{rd}$ Order Intercept Point of 6.4 dBm were obtained. The chip size is 1.86 mm ${\times}$ 1.28 mm.

• Korean Journal of Computational Design and Engineering
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• v.11 no.2
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• pp.97-106
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• 2006

Voronoi diagrams have been known for numerous important applications in science and engineering including CAD/CAM. Especially, the Voronoi diagram for 3D spheres has been known as very useful tool to analyze spatial structural properties of molecules or materials modeled by a set of spherical atoms. In this paper, we present two algorithms, the edge-tracing algorithm and the region-expansion algorithm, for constructing the Voronoi diagram of 3D spheres and applications to protein structure analysis. The basic scheme of the edge-tracing algorithm is to follow Voronoi edges until the construction is completed in O(mn) time in the worst-case, where m and n are the numbers of edges and spheres, respectively. On the other hand, the region-expansion algorithm constructs the desired Voronoi diagram by expanding Voronoi regions for one sphere after another via a series of topology operations, starting from the ordinary Voronoi diagram for the centers of spheres. It turns out that the region-expansion algorithm also has the worst-case time complexity of O(mn). The Voronoi diagram for 3D spheres can play key roles in various analyses of protein structures such as the pocket recognition, molecular surface construction, and protein-protein interaction interface construction.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.8
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• pp.1-7
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• 1997

In ahigh power amplifier design, power combiner/divider is used to connect low power amplifiers in parallel. The raidal structure of the powe combiner/divider has not only a good characteristics of port-to-port isolation but also an advantage of giving a redundancy to the structure itself by using RF switches. The parastics of a power resistor, that would be a problem in design process, are removed by both slot lines and cavity resonators, and the comon node in the circuit is rdesigned as a planar topology, and thus a new type of 4-way radial power combiner/divider is accomplished at 1840 ~ 1870 MH PCS frequency band. The insertion loss, reflection, and isolation characteristics of 40way radial power combiner/divider which can be adaptable to PCS system in this thesis are -0.3dB, -24dB,a dn -27dB respectively.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2015.07a
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• pp.308-309
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• 2015

최근 들어 일반인들도 다중 콥터와 4k 고성능 카메라를 장착한 상용 드론을 구매하여 자신의 취미 활동용으로 사용하고 있다. 드론을 이용한 많은 동호회가 생겨나고 1인 1드론, 개인용 드론의 시대가 시작되고 있다. 또한 사물인터넷의 시대에 걸맞게 아두이노, 라즈베리파이와 같은 오픈하드웨어 플랫폼과 오픈 소스를 이용하고 저가형 3D printer 의 보급으로 자신만의 독특한 형태를 지니는 기체 제작을 시작하고 있다. 이에 본 논문에서는 3D 캐드를 이용한 위상최적화 기법을 적용하여 기존 상용 기체의 강성은 그대로 유지하되 기체 프레임 무게를 절반으로 줄인다. 또한, 풍동실험을 진행해서 기존 기체에서 발생하는 유체흐름을 분석하고 새로운 기체를 적용했을 경우에도 유사한 유체흐름이 나타나도록 설계하여 3D 프린터를 사용하여 제작하였다.

• Kyungpook Mathematical Journal
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• v.54 no.3
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• pp.387-399
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• 2014

We show that in quasi-topological spaces, separation axiom $T_2$ is equivalent to ${\alpha}-T_2$, $T_0$ is equivalent to semi - $T_0$, and semi - $T_{\frac{1}{2}}$ is equivalent to semi - $T_D$. Also, we give characterizations for ${\alpha}-T_1$, semi - $T_1$ and semi - $T_{\frac{1}{2}}$ generalized topological spaces.