• Journal of Power Electronics
• /
• v.18 no.6
• /
• pp.1780-1790
• /
• 2018

Voltage feed-forward control (VFFC) is widely used in LCL-type grid-tied inverters due to its advantages in terms of disturbance rejection performance and fast dynamic response. However, VFFC may worsen the stability of inverters under weak grid conditions. It is revealed in this paper that a large phase-lag in the low-frequency range is introduced by VFFC, which reduces the phase margin significantly and leads to instability. To address this problem, a novel virtual-impedance-based control, where a phase-lead is introduced into the low-frequency area to compensate for the phase lag caused by VFFC, is proposed to improve system stability. The proposed control is realized with a high-pass filter, without high-order-derivative components. It features easy implementation and good noise immunity. A detailed design procedure for the virtual impedance control is presented. Both theoretical analysis and experimental results verify the effectiveness of the control proposed.

• Journal of the Korean Society of Systems Engineering
• /
• v.14 no.2
• /
• pp.41-48
• /
• 2018

This paper describes the systems engineering development process for the Departure from Nucleate Boiling Ratio (DNBR) algorithm using FPGA. Current Core Protection Calculator System (CPCS) requirement and DNBR logic are analyzed in the reverse engineering phase and the new FPGA based DNBR algorithm is designed in the re-engineering phase. FPGA based DNBR algorithm is developed by VHSIC Hardware Description Language (VHDL) in the implementation phase and VHDL DNBR software is verified in the software Verification & Validation phase. Test cases are developed to perform the software module test for VHDL software modules. The APR 1400 simulator is used to collect the inputs data in 100%, 75%, and 50% reactor power condition. Test input signals are injected to the software modules following test case tables and output signals are compared with the expected test value. Minimum DNBR value from developed DNBR algorithm is validated by KEPCO E&C CPCS development facility. This paper summarizes the process to develop the FPGA-based DNBR calculation algorithm using systems engineering approach.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2023.05a
• /
• pp.8-10
• /
• 2023

삼킴장애는 음식물이 입에서 식도로 가지않고 걸리거나 기도(Trachea)로 흡입되는 문제를 갖는 상태이다. 특히 노인이나 신경계 질환을 앓는 환자의 경우 기도로 흡입된 음식덩이가 폐렴을 일으키고 결국에는 사망으로 이어지기에 적절한 치료와 관리가 요구된다. 보통 영상으로 판단할 수 있는 삼킴단계는 구강준비단계(Oral Preparatory Phase), 구강단계(Oral Phase), 인두단계(Pharyngeal Phase), 식도단계(Esophageal Phase) 4가지로 분류하고 삼킴장애는 침습(Penetration)과 흡인(Aspiration)으로 크게 2가지로 분류한다. 본 논문에서는 이러한 6가지 클래스를 가지는 삼킴장애 환자 비디오 파일을 라벨링하기 위한 웹 애플리케이션을 제안한다. 이를 구현하기 위해서 대용량 멀티프레임 이미지를 수신해서 분리하여 저장하도록 개발하였다. 또한 음식덩이를 정교하게 분할할 수 있도록 GrabCut 알고리즘을 적용하여 라벨링할 수 있도록 하였다. 차후 라벨러와 전문의 간의 협업이 가능하도록 라벨링 데이터의 상태를 관리할 수 있도록 개발하고자 한다.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.17 no.7
• /
• pp.1538-1543
• /
• 2013

In this paper, a novel split ring resonator is proposed for improvement of phase noise characteristics that is weak point of oscillator using planar type microstrip line resonator. Oscillator using proposed split ring resonator is designed, it has improved phase noise characteristics. At the fundamental frequency of 5.8GHz, 7.22dBm output power and -83.5 dBc@100kHz phase noise have been measured for oscillator with split ring resonator. The phase noise characteristics of oscillator is improved about 9.7dB compared to one using the general ${\lambda}/4$ microstrip resonator. Next, we designed voltage controlled oscillator using proposed split ring resonator with varactor diode. The VCO has 125MHz tuning range from 5.833GHz to 5.845GHz, and phase noise characteristic is -118~-115.5 dBc/Hz@100KHz. Due to its simple fabrication process and planar type, it is expected that the technique in this paper can be widely used for low phase noise oscillators for both MIC and MMIC applications.

• Proceedings of the KIPE Conference
• /
• 2018.11a
• /
• pp.95-97
• /
• 2018

The power quality of Single Phase Grid-Connected Inverters (GCIs) has received much attention with the increasing number of Distributed Generation (DG) systems. However, the performance of single phase GCIs get degraded due to several factors such as the grid voltage harmonics, the dead time effect, and the turn ON/OFF of the switches, which causes the harmonics at the output of GCIs. Therefore, it is not easy to satisfy the harmonic standards such as IEEE 519 and P1547 without the help of harmonic compensator. To meet the harmonic standards a certain kind of harmonic controller needs to be added to the current control loop to effectively mitigate the low order harmonics. In this paper, the harmonic compensation is performed using a novel robust harmonic compensation method based on Digital Lock-in Amplifier (DLA). In the proposed technique, DLAs are used to extract the amplitude and phase information of the harmonics from the output current and compensate it by using a simple PI controller in the feedforward manner. In order to show the superior performance of the proposed harmonic compensation technique, it is compared with those of conventional harmonic compensation methods in terms of the effectiveness of harmonic elimination, complexity, and implementation. The validity of the proposed harmonic compensation techniques for the single phase GCIs is verified through the experimental results with a 5kW single phase GCI. Index Terms -Single Phase Grid Connected Inverter (SPGCI), Harmonic Compensation Method, Total Harmonic Distortion (THD) and Harmonic Standard.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.13 no.1
• /
• pp.284-295
• /
• 2012

The purpose of this study was to develop and evaluate patient safety reporting promoting strategy for nurses to improve nursing care quality. The process included three phase - construction, implementation and evaluation phase. Before the construction phase has two kinds of subcategories as analysis and verification. Analysis phase was consisted of literature review and field study, and verification was conducted by two specialist. At the construction phase, patient safety reporting system, educational materials, planning for public relation, and reward preparation were developed. After implementation during 12 weeks, we evaluated pre-post scores of satisfaction, stress of conscience, job performances. The participants were 51 nurses working for a hospitals. The program was developed and then administered to the experimental group for 12 weeks. One group pretest-posttest design was used for this study. Data were analyzed using descriptive analysis, paired t-test with the SPSS WIN 18.0 program. After the intervention, job performance scores improved significantly from 3.62 to 3.75(t=2.653, p=.009). But job stress didn't changed significantly(t=.785, p=.434). These strategy can be applied to many clinical setting that will be helpful to promote patient safety reporting for nurses.

• The Journal of Society for e-Business Studies
• /
• v.4 no.3
• /
• pp.139-158
• /
• 1999

In this paper we present the development of CITIS(Contractor Integrated Technical Information Service) reference model system which can be utilized for electronic commerce among enterprises. For the physical analysis target model, we selected switching system businesses of Korea Telecom. From analysis of life-cycle business process and data, we derived CITIS reference model containing CITIS To-Be model and CITIS scenario. Derived CITIS reference model is generalized so that it can be used not only for switching system businesses but other business areas regarding CITIS implementation. On the base of the derived CITIS reference model, We also developed CITIS information management system and CITIS-support workflow system as CITIS reference model system. Developed CITIS reference model system supports information and business process sharing among enterprises on internet and it does make a contribution to expansion of CITIS which is moving from conceptual research towards real implementation phase.

• Proceedings of the KIEE Conference
• /
• 1991.11a
• /
• pp.378-381
• /
• 1991

In this paper, the active noise controll system in duct is analyzed with real time implementation. The primary noise signal detected by microphone is modeled using adaptive algorithm and the secondary signal which has the same amplitude and $180^{\circ}$ phase shift with the primary noise signal is generated in the controller. The signal processor DSP56001 is used to implement the real-time controller and the experimental results shows that our system can reduce the noise level in duct to $20{\sim}40$ [db].

• Proceedings of the IEEK Conference
• /
• 1998.10a
• /
• pp.819-822
• /
• 1998

A new active power filter (APF) circuit with a current compesation estimation method is proposed. The current compensation estimation method replaces a current sensor with an estimating circuit and therefore reduces the implementation cost In addition, a simple control scheme, based on the energy balance concept, is adopted to control the voltage of a DC capacitor. Therefore energy change in the DC capacitor can be compensanted in the next cycle. Since a sampling technique is used, a larger DC capacitor voltage ripple can be permissible and a relatively smaller DC capacitor can be used. The proposed method has advantages of the reduction of one current sensor, low implementation cost, and fast transient responses. The theoretical analysis and simulation results are given. The proposed control method is successfully verified by computer simulation.

• Proceedings of the KSME Conference
• /
• 2004.11a
• /
• pp.465-467
• /
• 2004

Finite element analysis of welding processes, which entail phase evolution, heat transfer and deformation, is considered in this paper. Attention focuses on numerical implementation of the thermo-elastic-plastic constitutive equation proposed by Leblond et al in consideration of the transformation plasticity. Based upon the multiplicative decomposition of deformation gradient, hyperelastic formulation is employed for efficient numerical integration, and the algorithmic consistent moduli for elastic-plastic deformations including transformation plasticity are obtained in the closed form. The convergence behavior of the present implementation is demonstrated via a couple of numerical examples. Several locking phenomena removed by Solid-shell element.