• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.4
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• pp.997-1005
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• 1998

This paper presents a modified on-off algorithm based on the gradient method for providing the phase of each antenna element more accurately and simply compared to the conventional on-off algorithm. The sup4erisority of theproposed method is due to the fact that the proposed method finds the increase and decrease of the array output power more accurately by utilizing the gradient of array output power with respect to the instantaneous phase of array element. The array antenna adopting to the proposed method formsmaximum beam-pattern along the direction of the desired signal by aligning the phase of every antenna enement. The proposed method is applied to both linear and two-dimentional aray for analyzing the result. The capability of the real-time processing of the proposed technique is confirmed by implementing the proposed algorithm with TMS320C30 Evaluation Module. Since the computational load required to form the beam-pattern per snapshot is small, the proposed method is suitable for the mobile communication system of which the response must be fast. By the results obtained from the application of the proposed method to the CDMA mobile communication environment, it is vreified that the performance of the received signal is consideralbly improved.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.4
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• pp.513-520
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• 2001

In this paper, the directional coupler using three layer microstrip substrate is proposed and the design method is notified. Modified re-entrant mode coupler is the proposed structure that one layer is added on upper plane of coupled transmission lines and the floating conductor is placed on added layer's upper planes. This structure has high coupling for the increase of odd mode capacitance and also has good performance in VSWR, isolation, phase difference because the difference of effective permittivity is small in each mode. We have designed the coupler from the calculation of impedance, effective permittivity, coupling coefficient using even, odd mode analysis method. From the simulation and measurement, proposed coupler has about 2 dB more tighter coupling than conventional coupler and also has good performance in VSWR, isolation, phase difference.

• Journal of the Korea Society of Computer and Information
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• v.14 no.1
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• pp.135-143
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• 2009

Recently, in the mobile device, the increase of the need for encoding and decoding of high-resolution images requires an efficient implementation of the image codec. This paper proposes a time-optimized color conversion method for the JPEG decoder, which reduces the number of calculations in the color conversion by the rearrangement of arithmetic operations being possible due to the linearity of the IDCT and the color conversion matrices and brings down the time complexity of the color conversion itself by the integer mapping replacing floating-point operations to the optimal fixed-point shift and addition operations, eventually reducing the time complexity of the JPEG decoder. And the proposed method compensates a decline of image quality incurred by the quantification error of the operation arrangement and the integer mapping by using the multi-mode chrominance reconstruction. The performance evaluation performed on the development platform of embedded systems showed that, compared to previous color conversion methods, the proposed method greatly reduces the image decoding time, minimizing the distortion of decoded images.

• Proceedings of the KIEE Conference
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• 2006.07d
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• pp.1864-1865
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• 2006

무인지능형로봇 시스템에 있어서 자세의 정확도를 향상시키기 위한 많은 연구가 이루어져 왔다. 시스템의 자세 제어는 사용되는 모터의 위치 제어로 대응된다. 이와 같은 시스템은 운용 시에 충격 진동이 발생하게 된다. 이러한 충격 진동 외란을 잘 제거해야 요구되는 위치 정도로 제어를 수행할 수 있다. 로봇 제어 분야에서 불확실한 로봇에 대한 자세 제어 분야는 가장 기본적이면서 중요한 분야중의 하나이다. 이러한 문제를 다루기 위하여 계산 토크 방식에 기초한 선형 제어 기법이나 적응 제어 기법, 강인 제어 기법 등을 이용한 연구 결과들이 발표되고 있다. 그러나 그러한 기법은 일반적으로 로봇의 정확한 동력학식을 알아야 하며, 구현하기 복잡하다. 따라서 본 논문에서는 적응 규칙에 의하여 모델의 불확실성, 시스템의 변화, 외란으로 인해 발생하는 공칭 플랜트와의 오차를 보상하도록 제어 입력을 생성하는 내부 루프 부분과 공칭 플랜트 모델의 명령을 추종하도록 하는 제어 입력을 생성하는 외부 루프 부분으로 구성되는 방법인 외란관측기(Disturbance OBserver : DOB) 제어 알고리즘을 제안한다. 또한 프로세서의 신뢰성과 수치 연산 및 알고리즘의 빠른 처리를 위해 현재 사용 빈도가 높은 TI사의 DSP시리즈 중에서 부동 소수점 연산 기능을 가지면서 모터 제어에 적합한 TMS320C2000계열의 TMS320F2812을 사용하여, 운용 시 발생되는 진동 둥에 대한 외란 제거를 목적으로 한다. 본 논문은 규명된 시스템 모델식을 바탕으로 DOB 제어 시뮬레이션을 수행하고 PMSM 모터모델 시뮬링크 블록을 구성하여 검증된 외란 관측기 제어 알고리즘을 검증한다. 시뮬레이션으로 검증된 DOB 모터 자세 제어 알고리즘을 DSP에 적용하기 위해 코드변환하고 모터 실험 시스템에 실제 적용함으로써 타당성을 검증하여 상용 제어기로 실제 현장에 적용 가능함을 입증한다.

• Nuclear Engineering and Technology
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• v.16 no.4
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• pp.181-194
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• 1984

The in-core fuel management problem was studied by use of the calculus of variations. Two functions of interest to a public power utility, the profit function and the cost function, were subjected to the constraints of criticality, the reactor turnup equations and an inequality constraint on the maximum allowable power density. The variational solution of the initial profit rate demonstrated that there are two distinct regions of the reactor, a constant power region and a minimum inventory or flat thermal flux region. The transition point between these regions is dependent on the relative importance of the profit for generating power and the interest charges for the fuel. The fuel cycle cost function was then used to optimize a three equal volume region reactor with a constant fuel enrichment. The inequality constraint on the maximum allowable power density requires that the inequality become an equality constraint at some points in the reactor. and at all times throughout the core cycle. The finite difference equations for reactor criticality and fuel burnup in conjunction with the equality constraint on power density were solved, and the method of gradients was used to locate an optimum enrichment. The results of this calculation showed that standard non-linear optimization techniques can be used to optimize a reactor when the inequality constraints are properly applied.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.9
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• pp.59-70
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• 2007

In this paper, we proposed an effective T&L(Transform & Lighting) Processor architecture for a real time 3D graphics acceleration SoC(System on a Chip) in a mobile system. We designed Floating point arithmetic IPs for a T&L processor. And we verified IPs using a SoC Platform. Designed T&L Processor consists of 24 bit floating point data format and 16 bit fixed point data format, and supports the pipeline keeping the balance between Transform process and Lighting process using a parallel computation of 3D graphics. The delay of pipeline processing only Transform operation is almost same as the delay processing both Transform operation and Lighting operation. Designed T&L Processor is implemented and verified using a SoC Platform. The T&L Processor operates at 80MHz frequency in Xilinx-Virtex4 FPGA. The processing speed is measured at the rate of 20M Vertexes/sec.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.44 no.3
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• pp.64-69
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• 2007

Motion control of the system is a position control of motor. Motion control of an uncertain robot system is considered as one of the most important and fundamental research directions in the robotics. Some distinguished works using linear control, adaptive control, robust control strategies based on computed torque methodology have been reported. However, it is generally recognized within the control community that these strategies suffer from the following problems : the exact robot dynamics are needed and hard to implement, the adaptive control cannot guarantee the performance during the transient period for adaptation under the variation, the robust control algorithms such as the sliding mode control need information on the bounds of the possible uncertainty and disturbance. And it produces a large control input as well. In this dissertation, a motion control for the unmanned intelligent robot system using disturbance observer is studied. This system is affected with an impact vibration disturbance. This paper describes a stable motion control of the system with the consideration of external disturbance. To obtain the stable motion independently against the external disturbance, the disturbance rejection is strongly required. To address the above issue, this paper presents a Disturbance OBserver(DOB) control algorithm. The validity of the suggested DOB robust control scheme is confirmed by several computer simulation results. And the experiments with a motor system is performed to give the validity of applicability in the industrial field. This results make the easier implementation of the controller possible in the field.

• Journal of Food Hygiene and Safety
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• v.34 no.3
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• pp.263-268
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• 2019

Methanol is a toxic alcohol used in various products such as antifreeze, detergent, disinfectant and industrial solvent. In the human body, methanol is oxidized to formaldehyde and formic acid, which can lead to metabolic acidosis, optic nerve impairment, and death. In this study, the methanol levels in detergents (n=191) and rinse aids (n=13) were analyzed by gas chromatography-headspace-mass spectrometry (GC-HS-MS). Limit of detection was 1.09 mg/kg, accuracy and precision were 91.1-97.9% and <10%, and it was suitable for quantitative analysis. This analysis method was simple and fast with a higher recovery rate than the conventional MFDS (Ministry of Food and Drug Safety) method of diluting the sample in water and putting it in a headspace vial.