Chul-Woo Park

Low-noise single-photon detector for the 1.5-μm wavelength region

A simple argument is given that a traversable Cauchy horizon inside a black hole is incompatible with unitary black hole evolution. The argument assumes the validity of black hole complementarity and applies to a generic black hole carrying angular momentum and/or charge. In the second part of the paper we review recent work on the semiclassical geometry of two-dimensional charged black holes.

Strategy for robotization of lower limb fracture reduction

This paper introduces strategy for robotization of lower limb fracture reduction. The procedure of fracture surgery is modeled and the role of a robotic system is suggested. We divide femur fracture in three types along fractured position. Forms of proximal and distal bone fragment after fracture is described with respect to each fracture types. We discuss the reduction methods using the robot for effective fracture reduction; surgical posture of limb, pin insertion, a passive arm for proximal bone fixation, and the bone positioning robot for position-controlling of a distal bone. We expect our discussion will help in the development of the fracture reduction robotic system.

Design of Robust Stability Maximizing PI Controller in Motor Parameter Variation

This paper propose a PI controller that maximizes the degree of stability using a stability in a simplified motor model the applies decoupling control. The PI controller gains are directly from the motor parameters, thereby reducing the element of trial and error, and, the Kharitonov equation was used to evaluate the robustness of the gains to changes in the motor parameters. In addition, the system poles are located in the same position, the proposed method can provide a fast response. The effectiveness of the proposed controller is verified by simulation results.

Development of Automatic Gamma Optimization System for Mobile TFT-LCD

This paper presents an automatic LCD gamma control system using gamma curve optimization. It controls automatically gamma adjustment registers in mobile LCD driver IC to reduce gamma correction error and adjusting time. The proposed gamma system contains Module-Under-Test (MUT, LCD module), PC installed with program, multimedia display tester for measuring luminance, and control board for interface between PC and LCD module. Proposed algorithm and program are applicable for most of the LCD modules. It is realized to calibrate gamma values of 1.8, 2.0, 2.2 and 3.0. The control board is designed with DSP and FPGA, and it supports various interfaces such as RGB and CPU. Developed automatic gamma control system showed significantly reduced gamma adjusting time of 240 sec. and much less average gamma error of 11% than 42h and 27% with conventional manual method. We believe that the proposed system is very useful to provide high-quality LCD and to improve production process.

Response Time Optimization of DVR for 3-Phase Phase-Controlled Rectifier

In this paper, we present optimization technique for the response time of DVR (Dynamic Voltage Restorer) and the possible compensation range of voltage dip by the DVR system. To protect 3-phase phase-controlled rectifier from voltage dip, DVR system needs to have optimum response time as an important design factor. Although the fast response time of DVR ensures wider range of voltage dip, DVR controller has so high cost and poor stability. This paper proposes DVR system with optimum response time required for certain intensity of voltage dips and good stability to support possible compensation range of voltage dip. Proposed technique showed optimum response time and good stability for overall system. We believe that proposed technique is reliable and useful in DVR design.