• The Journal of Korean Institute of Communications and Information Sciences
• /
• 제33권4A호
• /
• pp.440-449
• /
• 2008

In this paper, we propose a 16-QAM carrier recovery loop which is suitable for the implementation of Inmarsat M4 system receiver. Because the frequency offset of ${\pm}924\;Hz$ on signal bandwidth 33.6 kHz is recommended in Inmarsat M4 system specification, carrier recovery loop having stable operation in the channel environment with large relative frequency offset is required. the carrier recovery loop which adopts only PLL can't be stable in relatively large frequency offset environment. Therefore, we propose a carrier recovery loop which has stable operation in large relative frequency offset environment for Inmarsat M4 system. The proposed carrier recovery loop employed differential filter-based noncoherent UW detector which is robust to frequency offset, CP-AFC for initial frequency offset acquisition using UW signal, and 16-QAM DD-PLL for phase tracking using data signal to overcome large relative frequency offset and achieve stable carrier recovery performance. Simulation results show that the proposed carrier recovery loop has stable operation and satisfactory performance in large relative frequency offset environment for Inmarsat M4 system.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• 제7권2호
• /
• pp.52-59
• /
• 2008

The objective of this study is to develop an automatic object changer unit to improve processing problems existed in the conventional horizontal machining center. To achieve this goal, this study designed a horizontal transfer as the second project continued to the first project that designed a upward and downward traverse unit. A horizontal traverse unit shows a symmetric structure and consists of frame, which consists of four unit tools, motor and reducer, which are fixed at a frame, operation unit with pinions, first traverse unit, and second traverse unit. Constraint conditions based on the operation mechanism with these elements were configured and obtained following results after modeling a model for a traverse motor. In the kinematic expression of sliding motion with one degree of freedom, the sliding motion is constrained. Also, the rack 3 installed at a frame is used to configure possible kinematic constraint conditions of the rack 2 according to the rolling motion of the pinion 2 in the first traverse unit. In addition, the moment of inertia that is a type of kinetic energy in a converted horizontal traverse unit in the side of the reducer can be applied to introduce the moment of inertia of a converted horizontal traverse unit in the side of the reducer by using the sum of kinetic energy in the rack and pinion, which is a part of the horizontal traverse unit. Also, the equation of motion of the converted upward and downward traverse unit in the side of the motor using the equation of motion of the motor. Furthermore, the horizontal traverse unit predetermines the mass of the first and second traverse unit and applied load including the radius and reduction ratio of the pitch circle in the pinion 1 and applied load to the rack 2. Then, a proper motor can be determined using several parameters in the upward and downward traverse unit in order to verify such predetermined specifications. In future studies later this study, a simulation that verifies the results of the previous two stages of studies using a finite element method.

• Journal of the Korean Society of Marine Environment & Safety
• /
• 제22권1호
• /
• pp.108-117
• /
• 2016

In this paper, a portal system compatible with MRV regulation was designed to monitoring, reporting and verifying $CO_2$ emission and fuel consumption data from an international ship. A portal system supports monitoring and reporting task of international shipping companies and calculates national greenhouse gas inventory. EU MRV law, MRV discussions of IMO, responses of international shipping companies to ship energy efficiency and greenhouse gas regulation, and greenhouse gas statistics on international shipping were analyzed to drive portal system requirements. For ship energy efficiency and $CO_2$ emitted monitoring, a data collection module was designed based on on-board equipment, energy efficiency measuring device and navigation report. Data transfer module with easy management and minimized usage to transfer ship data to shore was designed. A portal system was designed to convert the collected data into the standard reporting format, perform monitoring, statical analysis, verification and auto report generation, and support national greenhouse gas inventory.

• Proceedings of the Korean Association of Geographic Inforamtion Studies Conference
• /
• 한국GIS학회 2003년도 공동 춘계학술대회 논문집
• /
• pp.3-8
• /
• 2003

모든 SAR 영상에는 전자기파 간의 간섭으로 인한 스페클 잡영(speckle)이 존재하며, 이를 제거하는 것은 양질의 SAR 영상을 얻기 위한 필수적인 전처리 과정 중 하나라고 할 수 있다. 그러나 이러한 스페클 잡영을 제거하기 위하여 기존에 제안되었던 알고리즘은 잡영은 효과적으로 감소시키는 반면 경계선과 같은 영상의 고유 정보까지 함께 감소시키는 한계가 있었다. 따라서 본 연구에서는 SAR 영상의 경계선은 보존시키면서 영상으로부터 불필요한 잡영을 제거할 수 있는 알고리즘을 구현하고, 기존의 알고리즘과 비교하여 그 효율성을 평가하고자 한다. 영상의 통계적 특성에 근거하는 기존의 알고리즘과는 달리 웨이블렛 변환(Wavelet transform)으로 경계선 및 특징 정보의 여부를 판별한 후 평균 필터(mean filter)를 적용하는 경계선 보존(edge sharpening) 알고리즘은 경계 정보의 신뢰성을 향상시킬 수 있으며, 1차원 필터를 수평, 수직, 대각선, 역대각선 방향으로 적용함으로써 하나의 영상소를 중심으로 모든 방향에 대한 경계선 여부를 확인할 수 있는 장점이 있다. 본 연구에서는 512 × 512로 절취한 1-look SAR 영상에 대하여 창 크기 5 × 5의 경계선 보존 필터를 적용하고 동일영상에 대하여 기존의 Lee, Kuan, Frost 필터 등의 실험결과를 비교함으로써 그 적합성을 판단하고자 하였다. 실험결과에 대한 수치적인 평가는 ①정규화 평균을 이용하여 평균값의 보존 여부, ②편차 계수를 이용한 스페클 잡영의 제거 여부, ③경계선 보존지수(EPI)를 이용한 경계선의 보존 정도를 통해 이루어졌다. 본 연구의 실험결과를 통해 경계선 보존 필터는 평균값의 보존 여부 및 스페클 잡영 제거 정도에 있어 다른 필터들과 큰 차이가 없지만 경계선보존지수는 다른 필터들에 비하여 가장 우수함을 확인할 수 있었다.rbon 탐식효율을 조사한 결과 B, D 및 E 분획에서 유의적인 효과를 나타내었다. 이상의 결과를 종합해볼 때, ${\beta}$-glucan은 고용량일 때 직접적으로 또는 $IFN-{\gamma}$ 존재시에는 저용량에서도 복강 큰 포식세로를 활성화시킬 뿐 아니라, 탐식효율도 높임으로써 면역기능을 증진 시키는 것으로 나타났고, 그 효과는 crude ${\beta}$-glucan의 추출조건에 따라 달라지는 것을 알 수 있었다.eveloped. Design concepts and control methods of a new crane will be introduced in this paper.and momentum balance was applied to the fluid field of bundle. while the movement of′ individual material was taken into account. The constitutive model relating the surface force and the deformation of bundle was introduced by considering a representative prodedure that stands for the bundle movement. Then a fundamental equations system could be simplified considering a steady state of the process. On the basis of the simplified model, the simulation was performed and the results could be confirmed by the experiments under various conditions.뢰, 결속 등 다차원

• Journal of the Institute of Electronics Engineers of Korea SC
• /
• 제47권2호
• /
• pp.25-34
• /
• 2010

This paper proposed a high-speed voltage-controlled ring-oscillator(VCRO) using a frequency doubling technique. The design of the proposed oscillator has been based on TSMC 0.18um 1.8V CMOS technology. The frequency doubling technique is achieved by AND-OR operations with 4 signals which have $90^{\circ}$ phase difference one another in one cycle. The proposed technique has been implemented using a 4-stage differential oscillator compose of differential latched inverters and NAND gates for AND and OR operations. The differential ring-oscillator can generate 4 output signals, which are $90^{\circ}$ out-of-phase one another, with low phase noise. The ANP-OR operations needed in the proposed technique are implemented using NAND gates, which is more area-efficient and provides faster switching speed than using NOR gates. Simulation results show that the proposed, VCRO operates in the frequency range of 3.72 GHz to 8 GHz with power consumption of 4.7mW at 4GHz and phase noise of ~-86.79dBc/Hz at 1MHz offset. Therefore, the proposed oscillator demonstrates superior performance compared with previous high-speed voltage-controlled ring-oscillators and can be used to build high-performance frequency synthesizers and phase-locked loops for radio-frequency applications.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• 제47권4호
• /
• pp.75-87
• /
• 2010

For two input-protection schemes suitable for RF ICs utilizing the thyristor and diode protection devices, which can be fabricated in standard CMOS processes, we attempt an in-depth comparison on HBM ESD robustness in terms of lattice heating inside protection devices and peak voltages developed across gate oxides in input buffers, based on DC, mixed-mode transient, and AC analyses utilizing a 2-dimensional device simulator. For this purpose, we construct an equivalent circuit for an input HBM test environment of a CMOS chip equipped with the input ESD protection circuits, which allows mixed-mode transient simulations for various HBM test modes. By executing mixed-mode simulations including up to six active protection devices in a circuit, we attempt a detailed analysis on the problems, which can occur in real tests. In the procedure, we suggest to a recipe to ease the bipolar trigger in the protection devices and figure out that oxide failure in internal circuits is determined by the junction breakdown voltage of the NMOS structure residing in the protection devices. We explain the characteristic differences of two protection schemes as an input ESD protection circuit for RF ICs, and suggest valuable guidelines relating design of the protection devices and circuits.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• 제48권7호
• /
• pp.37-47
• /
• 2011

Real picture like high quality computer graphic is widely used in various fields and shader processor, a key part of a graphic processor, has been advanced to programmable unified shader. However, The existing graphic processors have been optimized to commercial algorithms, so development of an algorithm which is not based on it requires an independent shader processor. In this paper, we have designed and implemented a control unit to support high quality 3 dimensional computer graphic image on programmable integrated shader processor. We have done evaluation through functional level simulation of designed control unit. Hardware resource usage rate are measured by implementing directly on FPGA Virtex-4 and execution speed are verified by applying ASIC library. the result of an evaluation shows that the control unit has the commands more about 1.5 times compared to the other shader processors that is a behavior similar to the control unit and with a number of processing units used in a shader processor, compared with the other processors, overall performance of the control unit is improved about 3.1 GFLOPS.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• 제26권6호
• /
• pp.423-430
• /
• 2013

In this research, a paramteric study to account for the effect of interfacial strength and nanotube agglomeration on the elastoplastic behavior of carbon nanotube reinforced polypropylene composites is performed. At first, the elastoplastic behavior of nanocomposites is predicted from molecular dynamics(MD) simulations. By combining the MD simulation results with the nonlinear micromechanics model based on the Mori-Tanaka model, a two-step domain decomposition method is applied to inversely identify the elastoplastic behavior of adsorption interphase zone inside nanocomposites. In nonlinear micromechanics model, the secant moduli method combined with field fluctuation method is used to predict the elastoplastic behavior of nanocomposites. To account for the imperfect material interface between nanotube and matrix polymer, displacement discontinuity condition is applied to the micromechanics model. Using the elastoplastic behavior of the adsorption interphase zone obtained from the present study, stress-strain relation of nanocomposites at various interfacial bonding condition and local nanotube agglomeration is predicted from nonlinear micromechanics model with and without the adsorption interphase zone. As a result, it has been found that local nanotube agglomeration is the most important design factor to maximize reinforcing effect of nanotube in elastic and plastic behavior.

• Journal of the Korean Society of Radiology
• /
• 제14권6호
• /
• pp.725-731
• /
• 2020

A radiation spectroscopy detector using a spherical scintillator was designed, and a system was developed to track the position of a radiation source using several detectors. The position tracking algorithm was designed based on the theory that the number of radiations decreases according to the inverse square law of distance, and the position of the radiation source was calculated by measuring the number of radiations generated from the radiation sources at various positions. The radiation generated from the radiation source is detected by different coefficients in each detector, and the difference between these detected coefficients varies in proportion to the inverse square of the distance. Geant4 Application for Tomographic Emission (GATE) simulation was performed to verify and evaluate the performance of the designed radiation source position tracking system, and radiation generated from radiation sources placed at different positions was counted with each detector. The number of measured radiations was tracked through the radiation source position tracking algorithm, and the error between the actual radiation source position and the position calculated by the algorithm was evaluated. The error between the position of the actual radiation source and the calculated position was measured as an average of 0.11% on the X-axis and 0.37% on the Y-axis, and it was verified that the position can be measured very accurately.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• 제22권3호
• /
• pp.115-121
• /
• 2012

Sapphire single crystals have been highlighted for epitaxial gallium nitride films in high-power laser and light emitting diode (LED) industries. Among the many crystal growth methods, the Kyropoulos process is an excellent commercial method for growing larger, high-optical-quality sapphire crystals with fewer defects. Because the properties and growth behavior of sapphire crystals are influenced largely by the temperature distribution and convection of molten sapphire during the manufacturing process, accurate predictions of the thermal fields and melt flow behavior are essential to design and optimize the Kyropoulos crystal growth process. In this study, computational fluid dynamic simulations were performed to examine the effects of the crucible geometry aspect ratio on melt convection during Kyropoulos sapphire crystal growth. The results through the evolution of various growth parameters on the temperature and velocity fields and convexity of the crystallization interface based on finite volume element simulations show that lower aspect ratio of the crucible geometry can be helpful for the quality of sapphire single crystal.