• 한국정밀공학회지
• /
• 제34권4호
• /
• pp.243-246
• /
• 2017

In this study, flexible fixtures and end effectors are conceptually designed for the holding of thin-walled carbon-fiber reinforced-plastic (CFRP) workpieces in machining processes. Firstly, the fixture scenarios and system requirements for the conceptual designs of flexible-fixture and core units are proposed, including the propounding of the workpiece-holding mechanism and the core-unit requirements. A ball-joint pneumatic system is determined as a locking mechanism of the flexible-fixture system for the machining of thin-walled components. Secondly, conceptual designs of the core units are suggested with the driven requirements from the fixture scenarios. A self-tilting mechanism and an end-effector return mechanism are also proposed. Finally, the prototypes of the core units are manufactured, and the workpiece-holding capacity of each prototype is measured.

• 한국정보처리학회논문지
• /
• 제6권9호
• /
• pp.2442-2450
• /
• 1999

감사 로깅 시스템은 시스템 사용 내역과 통신망을 통한 접근 내역을 기록한다. 이 내역은 불법적인 시스템 자원의 사용이나 통신망을 통한 불법 접근이 발생하였을 때, 그 경로를 추적하는 자료로 사용된다. 따라서, 로깅 시스템은 침입자의 일차적인 공격목표가 될 수 있다. 우리는 UNIX 시스템을 기반으로 로그인 정보와 명령어 수행 정보를 로그파일에 기록하는 로깅 시스템을 개발하였다. 또한, 로깅 시스템에 대한 침입자의 공격을 방어하기 위해서 자체 보호 장치를 두고 있다. 그것은 로깅 프로세스와 로그 파일을 보호하는 것이다. 로깅하는 프로세스를 보호하기 위해서 프로세스 ID를 계속해서 변경함으로써 침입자의 공격을 회피하도록 하였다. 로그 파일을 보호하기 위해서 하드링크와 강제적 파일 잠금을 사용하여 로그 파일에 대한 삭제나 변경을 할 수 없도록 하였다.

• 융합신호처리학회논문지
• /
• 제22권3호
• /
• pp.104-109
• /
• 2021

본 논문에서는 self-seeding FP-LD (Fabry Perot Laser Diode)를 이용하여 WDM-PON (Wavelength Division Multiplexing - Passive Optical Network)에서 사용될 수 있는 새로운 파장 가변 광원의 가능성을 검증한다. 파장 가변 광원을 이용한 WDM-PON의 기존 구현은 AWG (Arrayed Waveguide Grating) 소자의 중심 파장과 광원의 중심 파장을 세밀히 정렬해 주어야 하는 단점이 발생한다. 그러나, 본 논문에서 제안하는 파장 가변 광원은 매우 간단한 구조로 구성되며, 가변 파장이 AWG의 중심 파장에 자동 정렬되는 장점을 갖는다. 구현된 파장 가변 광원은 약 14 nm 정도 이상의 파장 가변 대역을 보였고, 상대적 세기 잡음, RIN (Relative Intensity Noise)은 최대 약 -124dB/Hz로 나타났으며, 외부 변조기를 통해 변조한 결과 10Gb/s 신호에 대한 변조 가능성을 확인 할 수 있었다.

• Journal of the Optical Society of Korea
• /
• 제17권2호
• /
• pp.117-129
• /
• 2013

We briefly review the recent progress in passively mode-locked fiber lasers (PMLFLs) based on semiconductor saturable absorber mirrors (SESAMs) and discuss the detailed characterization of a SESAM-based, passively mode-locked erbium-doped fiber (EDF) laser operating in the 1.5-${\mu}m$ spectral range for various configurations. A simple and compact design of the laser cavity enables the PMLFL to generate either femtosecond or wavelength-tunable picosecond pulses with high stability as the intra-cavity filtering method is altered. All the cavities investigated in our experiments present self-starting, continuous-wave mode-locking with no Q-switching instabilities. The excellent stability of the source eventually enables the wavelength-tunable PMLFL to be used as a master oscillator for a power-amplifier source based on a large-core EDF, generating picosecond pulses of >10-kW peak power and >100-nJ pulse energy.

• 대한기계학회논문집A
• /
• 제22권2호
• /
• pp.467-475
• /
• 1998

The Six Degree-of-Freedom manipulators are generally operated by linear actuators which are hydraulic cylinder, pneumatic cylinder, ball-screw. But these actuators are not adequate to have a wide work-space, and furthermore some of them have a self-locking property. Therfore, we have designed a new manipulator which fully overcomes these demerits. The new manipulating system consists of 6 DC-motors to generate operation forces and 6 position transducers to feedback displacement signals. This paper presents an overview of the design and characteristics of 6 Degree-of-Freedom force feedback manipulators for vitual reality implementation. we can operate Six Degree-of-Freedom manipulator with six motors and six potentiometers.

• 한국자동차공학회논문집
• /
• 제22권1호
• /
• pp.77-84
• /
• 2014

The worm gear is used in the motor drive system of automotive CVVL because of its compactness and self-locking ability. A ZK worm and an involute helical gear can be meshed in order to reduce production cost. However, the gearing is not suitable for the reliability and the NVH problem. To improve the dynamic performances, an optimal design process is considered. The transmission error is calculated theoretically and minimized with the several gear design parameters. An inequality condition such as the teeth interference elimination is added.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 1999년도 하계종합학술대회 논문집
• /
• pp.353-356
• /
• 1999

A 3.3V PLL(Phase Locked loop) is designed for a high frequency, low voltage, and low power applications. This paper proposes a new PLL architecture to improve voltage to frequency linearity of VCO(Voltage controlled oscillator) with new delay cell. The proposed VCO operates at a wide frequency range of 30MHz~1㎓ with a good linearity. The DC-DC voltage up/down converter is utilized to regulate the control voltage of the two-stage VCO. The designed PLL architecture is implemented on a 0.6${\mu}{\textrm}{m}$ n-well CMOS process. The simulation results show a locking time of 2.6$\mu$sec at 1Hz, Lock in range of 100MHz~1㎓, and a power dissipation of 112㎽.

• 한국정밀공학회지
• /
• 제32권7호
• /
• pp.591-595
• /
• 2015

The roller rig tester for safety performance evaluation of wheel derailment is a test facility which can give the test load condition to the test wheel, similar to the actual dynamic condition in actual running condition. This study describes the evaluation result on the durability of the resilient wheel equipped with the ring damper and the damping material, and installed in the half part of a full scaled bogie in combination with the primary spring when it rotates under the dynamic condition. The evaluation result on durability of resilient wheel after load test of 2 million cycles shows that the safety of wheel is not affected by the applied load in visual inspection and nondestructive test, however, in the bolt used for fastening the ring damper to the wheel the loosening was found. Accordingly the use of self-locking nut and washer is recommended.

• 정보저장시스템학회논문집
• /
• 제5권1호
• /
• pp.1-7
• /
• 2009

Recently, the growing market demand for small and slim mobile phone cameras requires the size reduction of the camera module. In this paper, an auto-focusing actuator for camera phones is proposed by converting the rotational motion by a rotary VCM actuator into the linear motion using a novel cam structure. This new concept for auto-focusing module enables the reduction of the module thickness and low power consumption. This paper presents the theoretical analysis and optimal design for VCM actuator, cam structure and preload spring. Finally, the experimental results using a prototype with the size of $9.9{\times}9.9{\times}5.9\;mm^3$ are compared with the theoretical predictions.

• 한국광학회지
• /
• 제10권3호
• /
• pp.221-225
• /
• 1999

레이저선속의 퍼짐각을 개선하기 위하여 공진기 내부에 선속분할기를 갖는 양영역 공초점 불안정공진기 구리증기레이저를 구성하였다. 기하광학적 배율 M=30인 공진기에서 0.15 mard의 최소 퍼짐각을 얻었고, M=60인 공진기를 사용하여 0.1 mard 의 값을 얻을 수 있었다. 퍼짐각 개선과 관련하여 상대적인 원거리 출력밀도가 최대 130배 증가된 레이저 출력을 얻을 수 있었으며, 자체잠김현상을 보이는 펄스 형태의 레이저 발진이 관측되었다.