• Journal of Power Electronics
• /
• v.16 no.6
• /
• pp.2350-2358
• /
• 2016

The one cycle control (OCC) scheme for active power filters (APFs) has shown excellent harmonic suppression and implementation simplicity. However, its real world application is limited because the non-ideal supply voltage for APFs can influence its performance so that the source currents are still distorted after compensation. This paper proposes a modified one cycle control (MOCC) scheme to improve the performance of three-phase shunt APFs under non-ideal supply voltage conditions. In this paper a detailed mathematical derivation has been presented and the key control law of the MOCC has been developed for adaption to the non-ideal supply voltages, following the control philosophy of simplicity. A relatively simple sequence filter is introduced to extract the harmonic components of supply voltages. The modified scheme can be easily implemented. The proposed control strategy has excellent performance and a 5kVA APF hardware platform has been implemented to validate the feasibility and performance of the proposed strategy.

• Journal of Power Electronics
• /
• v.16 no.6
• /
• pp.2109-2118
• /
• 2016

Based on the space vector pulse width modulation (SVPWM) theory, this paper realizes an easier SVPWM strategy, which is equivalently implemented by CBSPWM with zero-sequence voltage injection. The traditional SVPWM strategy has no effect on controlling the neutral-point voltage balance. In order to solve the neutral-point voltage unbalance problem for neutral-point-clamped (NPC) three-level inverters, this paper proposes a neutral-point voltage balance controller. The proposed controller realizes controlling the neutral-point voltage balance by dynamically calculating the offset superimposed to the three-phase modulation waves of an equivalent SVPWM strategy. Compared with the traditional SVPWM strategy, the proposed neutral-point voltage balance controller has a strong ability to balance the neutral-point voltage, has good steady-state performance, improves the output waveforms quality and is easy for digital implementation. An experiment has been carried out on a NPC three-level inverter prototype based on a digital signal processor-complex programmable logic device (DSP-CPLD). The obtained experimental results verify the effectiveness of the proposed neutral-point voltage balance controller.

• Journal of Biomedical Engineering Research
• /
• v.27 no.3
• /
• pp.117-124
• /
• 2006

Recently, active research has been going on to measure the elastic modulus of human soft tissue with medical ultrasound imaging systems for the purpose of diagnosing cancers or tumors which have been difficult to detect with conventional B-mode imaging techniques. In this paper, a real-time ultrasonic elasticity imaging system is implemented in software on a Pentium processor-based ultrasonic diagnostic imaging system. Soft tissue is subjected to external vibration, and the resulting tissue displacements change the phase of received echoes, which is in turn used to estimate tissue elasticity. It was confirmed from experiment with a phantom that the implemented elasticity imaging system could differentiate between soft and hard regions, where the latter is twice harder than the former, while operating at an adequate frame rate of 20 frames/s.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2003.05a
• /
• pp.1128-1133
• /
• 2003

A gas driven heat pump (GHP) core design comprises internal combustion engine, compressors incorporated to a cooling/heating system, rubber mountings and belt transmissions. Main excitation farces are generated by an engine, compressors themselves and belt fluctuation. It leads to high vibration level of the mount that can cause damage of GHP elements. Therefore an appropriate design of the mounting system is crucial in terms of reliability and vibration reduction. In this paper oscillation of the engine mount is explored both experimentally and analytically. Experimental analysis of natural frequencies and operational frequency response of the GHP engine mounting system enables to create simplified model for numerical and analytical investigations. It is worked out criteria f3r vibration abatement of the isolated structure. Influence of bracket stiffness between engine and compressors, suspension locations and damper performance is investigated. Ways to reduce excitation forces and improve dynamic performance of the engine-compressor mounting system are considered from these analyses. Implementation of the proposed approach permits to choose appropriate rubber mountings and their location as well as joining elements design A phase matching technique can be employed to control forces from main exciters. It enables to changing vibration response of the structure by control of natural modes contribution. Proposed changes lead to significant vibration reduction and can be easily utilized in engineering practice.

• Journal of The Korean Association of Information Education
• /
• v.16 no.1
• /
• pp.61-70
• /
• 2012

In this study, the newly designed course related to creative problem solving is introduced. According to the characteristics of multimedia engineering, the Alice, which is well known as an effective 3D interactive authoring tool, is adopted as the supporting tool to validate the accomplishment of study goals set up for software design. Each creative problem solving phase could be clearly implemented and its expected performance could be evaluated efficiently by using Alice. The result of curricular implementation and performance evaluation is shown.

• Journal of Industrial Technology
• /
• v.20 no.B
• /
• pp.155-162
• /
• 2000

Although Fuzzy Logic Controller(FLC) adopted three terms as input gives better performance, FLC is in general composed of two-term control because of the difficulty in the construction of fuzzy rule base. In this paper, a three-term FLC which is similar to PID control but acts as a nonlinear controller is proposed. To reduce the complexity of the rule base design and to increase efficiency. a simplified fuzzy PID control is induced from a hybrid velocity/position type PID algorithm by sharing a common rule base for both fuzzy PI and fuzzy PD parts. It is simple in structure, easy in implementation, and fast in calculation. The phase plane technique is applied to obtain the rule base for fuzzy two-term control and the resultant rule base is Macvicar-Whelan type. And the membership function is a Gaussian function. The frequency response information is used in tuning of the membership functions. Also a tuning strategy for the scaling factors is proposed based on the relationship between PID gain and the scaling factors. Simulation results show better performance and the effectiveness of the proposed method.

• Journal of Gastric Cancer
• /
• v.17 no.3
• /
• pp.193-203
• /
• 2017

The implementation of national cancer screening has increased the detection rates of early gastric cancer (EGC) in Korea. Since the successful introduction of laparoscopic gastrectomy for gastric cancer in the early 1990s, this technique has demonstrated improved short-term outcomes without compromising long-term oncologic results. It is associated with reduced pain, shorter hospitalization, reduced morbidity rates, better cosmetic outcomes, and equivalent mortality rates as those for open surgery. Laparoscopic gastrectomy improves patients' quality of life (QOL) and provides favorable prognosis. Single-incision laparoscopic gastrectomy (SILG) is one extremely minimally invasive method, theoretically offering improved cosmetic results, less postoperative pain, and earlier recovery after surgery than conventional multiport laparoscopic gastrectomy. In this context, SILG is thought to be an optimal method to promote and maximize patients' QOL in the acute postoperative phase. However, the technical difficulties of this procedure have limited its use. Since the first report describing single-incision distal gastrectomy in 2011, only 16 studies to date have evaluated SILG. Most of these studies have focused on the technical feasibility and safety of SILG because its long-term outcomes have not been reported. This article reviews the advantages and limitations of SILG.

• Journal of the Korean Society of Safety
• /
• v.25 no.6
• /
• pp.75-80
• /
• 2010

The present study presented the implementation of a remote control/supervision system for guard lamps used in public illumination with little endeavor by far for safe management, which makes possible to supervise the state and to control the functions remotely including electric safety elements. Especially, the developed system adopts the measurement algorithm for detecting resistive leakage current(Igr) flowing based on the phase difference checkable for sensing at a monitor, being allowable for monitoring at MMI and transmitter for data transmittance. To verify reliability about the algorithm to accurately detect Igr leakage current, the laboratory-based functional test was performed.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.8 no.6
• /
• pp.1147-1152
• /
• 2004

This paper presents the design of a multi-standard NTSC/PAL video encoder. The encoder converts International Telecommunication Union-Recommendation (ITU-R) BT.601 4:2:2, ITU-R BT.656 or RGB inputs from various video sources into National Television Standards Committee (NTSC) or phase-alternate line (PAL) TV signals in both S-video and composite video baseband signals (CVBS). The encoder adopts multiplier-free structures to reduce hardware complexity. The hardware bit width of programmable digital filters for luminance and chrominance signals, along with other operating blocks, are carefully determined to produce high-quality digital video signals of 1 least significant bit (LSB) error or less. The proposed encode. is experimentally demonstrated by using the Altera APEX20K600EBC652-3 device.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.13 no.6
• /
• pp.1058-1063
• /
• 2010

In this paper, we designed self-frequency synchronizing circuit using image rejection mixer(IRM) and single-sideband(SSB) up-converter which can effectively eliminate the image frequencies occurred in multi-channel super-heterodyne receivers and help us to match inter-channel phase. Also the self-frequency synchronizing circuit simplifies system because there need no extra devices for making intermediate frequency(IF) by creating the local signal within several nanoseconds by means of generating the same frequency of IF signal and modulating radio frequency(RF) signal. We adopt the limiting amplifier for the purpose of protecting the circuit from spurious signals which come from the front end side having wide instantaneous bandwidth characteristics and constantly injecting same level into the input local signal of IRM. The IRM we fabricated has image rejection ratio of 27dB, which is good over 7dB for foreign company's. Also, the SSB up-converter we fabricated has 1dB compression point of 18dBm, which is good over 16dB for foreign company's. And the size is compact about one-forth.