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        • 고속 반도체 광변조기의 설계 및 성능평가에 관한 연구

          李鐘昌,崔旺燁 弘益大學校 科學技術硏究所 2001 科學技術硏究論文集 Vol.12 No.-

          In this paper we investigate the phase efficiency in the electrooptic phase modulator using PPpinNN GaAs / AlGaAs W waveguide. The phase change is affected by the refractive index change taking place inside the depletion region. The behavior of the modulator can be understood in terms of two electric field-related and two carrier-related effects linear electrooptic, quadratic electrooptic, plasma, and bandgap shift. As a result, the phase modulation efficiency was measured about 34.6[˚V·mm] for the TE polarized light. The quadratic electrooptic coefficient R = 5.82 x 10^(-15) [㎠/V²] is obtained and the phase efficiency caused by the quadratic electrooptic effect is about 10 times larger than that from the conventional linear electrooptic effect.

        • 광대역무선통신(LMDS) 마이크로스트립 패치 안테나 설계 및 제작

          吳二錫,弘振榮 弘益大學校 科學技術硏究所 2001 科學技術硏究論文集 Vol.12 No.-

          Design, fabrication and measurement of an LMDS microstrip array antenna are presented in this thesis. At first, basic principles for antenna design has been reviewed. Then 8x8 microstrip array antenna was designed using EM simulators at 24.5GHz. The return losses and the patterns of the microstrip array antennas were simulated using CAD tools to get optimum results. For Tx/Rx antenna, The single-fed dual resonance patch antenna drives perpendicular polarizations at two resonant frequencies from a rectangular patch radiator, using aperture coupling via a bended single-feeding line and a cross-shaped slot. The 8 X 8 array antennas were fabricated based on the simulation results and measured using the network analyzer. the measurements show that this 8x8 array antenna has the resonant frequency of 24.6GHz, the return loss of -21.3dB at the frequency, Band width of 720MHz(VSWR < 2), the gain of 25.47dBi. E-plane and H-plane of the side-lobe level are -19dB, -17dB respectively. The HPBWs of the principal E-plane and principal H-plane are 9.5?respectively.

        • 광자 크리스탈 광 분배기의 수치 연산 해석

          鄭敎龐,尹志秀 弘益大學校 科學技術硏究所 2001 科學技術硏究論文集 Vol.12 No.-

          We design a 1-by-4 optical splitter made of photonic crystal waveguides and analyze the properties of the optical splitter using the finite-difference time-domain method with perfectly-matched-layer absorbing boundaries. The photonic crystal is constructed by cylindrical rods in air on a square lattice. Our simulation results show that there are different transmission properties for four bend geometries and different incident-wave frequencies, and the incident power splits in the four arms with almost the same ratio. Moreover, we perform numerical simulations of T-shaped waveguide branches to reduce the reflections at the T-branches in the splitter. The branching region is treated as a cavity that couples the input and output waveguides. The improvement of transmission is achieved by placing the defects of extra rods in the branching region.

        • 자동 선별기 설계 및 제작

          朴寅圭 弘益大學校 科學技術硏究所 2001 科學技術硏究論文集 Vol.12 No.-

          Core is the main component of inductor. This core should be classified into around 10 classes according to the value of inductance and Q. The coil should be winded with the outer-boundary of this core by different number of turns. Theses kind of precise inductors would be required in the future environment which PCs and communication devices demand more high speed and lower voltage level. It would be quite unefficient that only one core is classified once a time. There, it will be developed so that 10 cores are classified simultaneously. For the operation of classifying 10 cores once in a time, suppose 10 test instruments could be used. In this case, it would take much money since a test instrument is expensive. So, by using only one test instrument, it is really more desirable that this system is developed. Each core classified by 10 different classes is to be stored into the corresponding box through the correspoding rubber hose. 10 cores are passed on a serial line and are placed on each testing slot. Here. each core located at each slot is tested, and then the bowl located on the top of a step motor is moved into the corresponding spot by rotating step motor with some. angles. Each bowl connected with the corresponding box through rubber hose. Actually 100 hoses are connected, 10 step motors are rotated at 10 different angles, so the size is reall so big, the shape of connecting 100 hoses is so complicated. Therefore it is anticipated that the system would be going to be easily out of ordered. In this paper the main purpose is to make several suggestions to be able to work well in these kinds of being affected by the abnormal operation of motors and the flow of cores.

        • 무선 네트워크에서의 서비스 공정성

          方志豪,河蘭 弘益大學校 科學技術硏究所 2001 科學技術硏究論文集 Vol.12 No.-

          The popular web site is formed hundreds of connections at the same time. Accordingly, for such connections due to be scheduled, efficient connection scheduling techniques is needed. The ancient connection scheduling using SRPT(Shortest Remaining Processing Time first) has improved the response time of connections in HTTP/1.0. But, in HTTP/1.1 clients can request multiple static documents. When multiple static documents are requested in HTTP/1.1, the response time of each static document may be improved by the connection scheduling using SRPT. But, we can't guarantee the response time of total connections to be improved. In this paper, we proposed the pipelining based connection scheduling techniques with better response time in HTTP/1.1. In simulation, we can find the response time of total connections to be improved.

        • XML을 이용한 웹 상의 멀티미디어 내용 기반 검색 시스템

          林海喆,金宣炅,金連姬 弘益大學校 科學技術硏究所 2001 科學技術硏究論文集 Vol.12 No.-

          Recently the increase of multimedia data on the web and the user's various requirements lead many multimedia retrieval systems to develop usefully. This paper shows new multimedia content-based retrieval system that manages database for images independently and can retrieve most similar image like query image chosen by user. The proposed system represents text information using XML and exchanges information among modules. So, this system supports retrieval through structure of XML document and integrates easily in heterogeneous environments.

        • 무한 실린더 주위의 축방향 난류운동의 스펙트럼 해석

          申東信,朴昶範 弘益大學校 科學技術硏究所 2001 科學技術硏究論文集 Vol.12 No.-

          Direct numerical simulation data base of an axial turbulent boundary layer is used to compute frequency and wavenumber spectra of the wall shear-stress fluctuations in a low-Reynolds number axial turbulent boundary layer. One-dimensional and two-dimensional power spectra of flow variables are calculated and compared. At low wave numbers and frequencies, the power of streamwise shear stress is larger than that of spanwise shear stress, while the powers of both stresses are almost the same at high wavenumbers and frequencies. The frequency/streamwise wavenumber spectra of the wall flow variables show that large-scale fluctuations to the rms value is largest for the streamwise shear stress, while that of small-scale fluctuations to the is value is largest for pressure.

        • STEP 표현 2차원 조형층 정밀도 향상에 관한 연구

          池海成,李秉烈 弘益大學校 科學技術硏究所 2001 科學技術硏究論文集 Vol.12 No.-

          Nowadays, there are several different CAD softwares that can create product geometries with different applications. Similarly, most recent RP processes have quite different capabilities, and most are not even isotropic, so that machine-dependent information such as part orientation, position, and size during the fabrication process becomes a crucial issue in integrating a heterogeneous environment of CAD and RP processes using the data exchange standard. Current method using the de facto industry standard STL have at times resulted in problems such as accuracy, redundancy, and integrity in its representing CAD models. STEP is the upcoming standard. Many major companies are already working with it. This is one of the biggest reason why STEP can be a useful way of exchanging CAD-SFF data. This research project proposes a method of slicing and editing STEP-based RP models for the next generation data transfer paradigm between CAD systems and RP systems using STEP. As an approach for the purpose, this proposes a method for acquiring improved accuracy of 2D sliced layers in STEP with a tentative schema of SFF process features. The new data exchange standard must be compatible with, but independent of, process fabrication features. A software implementation of visualizing, editing, and slicing CAD model based on STEP information model for a complete data exchange is also proposed. As for future works, various optimal slicing algorithm will help acquire accurate RP parts.

        • PID 제어기 조율을 위한 공정 모사

          崔民鎬 弘益大學校 科學技術硏究所 2001 科學技術硏究論文集 Vol.12 No.-

          This article Proposes a closed-loop, reaction-curve method to provide a procedure for establishing controller settings on the classical three-mole (PID) controllers. It uses the partial extreme data available during the early period of step set-point change under portional control mode to determine the ultimate period and the ultimate gain of the open-loop process. The resulting ultimate data are critical for subsequent controller settings according to Ziegler-Nichols rules.

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