• 전기전자학회논문지
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• 제26권4호
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• pp.736-741
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• 2022

격자 기반 암호화는 최악의 경우를 기반으로 한 강력한 보안, 비교적 효율적인 구현 및 단순성을 누리기 때문에 포스트 양자 암호화 방식 중 가장 실용적인 방식이다. 오류가 있는 링 학습(R-LWE)은 격자 기반 암호화(LBC)의 공개키암호화(Public Key Encryption: PKE) 방식이며, R-LWE의 가장 중요한 연산은 링의 모듈러 다항식 곱셈이다. 본 논문은 R-LWE 암호 시스템의 중간 보안 수준의 매개 변수 집합을 대상으로 하여 근사 컴퓨팅(Approximate Computing: AC) 기술을 기반으로 한 모듈러 곱셈기를 최적화하는 방법을 제안한다. 먼저 복잡한 로직을 간단하게 구현하는 방법으로 LUT을 사용하여 근사 곱셈 연산 중 일부의 연산 과정을 생략하고, 2의 보수 방법을 활용하여 입력 데이터의 값을 이진수로 변환 시 값이 1인 비트의 개수를 최소화하여 필요한 덧셈기의 개수를 절감하는 총 두 가지 방법을 제안한다. 제안된 LUT 기반의 모듈식 곱셈기는 기존 R-LWE 모듈식 곱셈기 대비 속도와 면적 모두 9%까지 줄어들었고, 2의 보수 방법을 적용한 모듈식 곱셈기는 면적을 40%까지 줄이고 속도는 2% 향상되는 것으로 나타났다. 마지막으로 이 두 방법을 모두 적용한 최적화된 모듈식 곱셈기의 면적은 기존대비 43%까지 감소하고 속도는 10%까지 감소하는 것으로 나타났다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 춘계학술대회 논문집
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• pp.401-404
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• 2007

Inertia welding is a solid-state welding process in which butt welds in materials are made in bar and in ring form at the joint face, and energy required for welding is obtained from a rotating flywheel. The stored energy is converted to frictional heat at the interface under axial load. The quality of the welded joint depends on many parameters, including axial force, initial revolution speed and energy, amount of upset, working time, and residual stresses in the joint. Inertia welding was conducted to make the large rotor shaft for low speed marine diesel engine, alloy steel for shaft of 140mm. Due to different material characteristics, such as, thermal conductivity and flow stress, on the two sides of the weld interface, modeling is crucial in determining the optimal weld geometry and parameters. FE simulation was performed by the commercial code DEFORM-2D. A good agreement between the predicted and actual welded shape is observed. It is expected that modeling will significantly reduce the number of experimental trials needed to determine the weld parameters.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.829-834
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• 2004

This research is to development advanced health(condition) monitoring system of superconducting motors. Development of advanced condition monitoring systems offers the prospect of improved performance, assessment, and operation, simplified design, enhanced safety, and reduced overall cost of advanced and next generation superconducting motor. For advanced and next generation superconducting motor design, the opportunity exists to develop and implement real-time and continuous monitoring systems by integrating wireless and computational technique. Generally, condition monitoring and control of temperature is essential for managing the superconducting motor components, rotor and structures. In this research, development of advanced monitoring in low temperature and high speed operating environments offers the potential to greatly improve the control of harsh environments. In conventional method, slip rings have been used to acquire data from these sensors. However, the increase of sensors leads to vibration of the rotation axis and noise signals due to kinematics contact. In this study, the wireless data acquisition technique was employed to develop more stable monitoring system adequate for high speed rotating system.

• 한국생산제조학회지
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• 제21권2호
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• pp.305-310
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• 2012

Planetary gear box is a power transmitter having very high gear ratio in compact volume. The planetary step-down gear box converts high speed and low torque into low speed and high torque, which is widely used in constructional and industrial machinery field. And, the planetary step-up gear box does vice versa working, which is used as main gear box of large sized wind mill system. The large sized planetary gear box must be performed the normal-opposite rotation test as a its durability test for achieving the reliability. The large sized planetary gear box is composed by triple gear trains of sun gear, carrier, and ring gear. If input power is supplied into one of them and the other is fixed, and then another becomes the output part. In this paper, we designed a new test equipment which can do rapid normal and opposite rotational change with only small displacement by supplying test power using the above rotation (driving) characteristics and hydraulic cylinder and link, and also compared and analyzed with existing method through various experiments.

• 대한수학회보
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• 제49권4호
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• pp.875-883
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• 2012

Let $\mathbb{F}_q$ be a finite field with q elements and $\mathbb{F}_q((X^{-1}))$ be the field of all formal Laurent series with coefficients lying in $\mathbb{F}_q$. This paper concerns with the size of the set of points $x{\in}\mathbb{F}_q((X^{-1}))$ with their partial quotients $A_n(x)$ both lying in a given subset $\mathbb{B}$ of polynomials in $\mathbb{F}_q[X]$ ($\mathbb{F}_q[X]$ denotes the ring of polynomials with coefficients in $\mathbb{F}_q$) and deg $A_n(x)$ tends to infinity at least with some given speed. Write $E_{\mathbb{B}}=\{x:A_n(x){\in}\mathbb{B},\;deg\;A_n(x){\rightarrow}{\infty}\;as\;n{\rightarrow}{\infty}\}$. It was shown in [8] that the Hausdorff dimension of $E_{\mathbb{B}}$ is inf{$s:{\sum}_{b{\in}\mathbb{B}}(q^{-2\;deg\;b})^s$ < ${\infty}$}. In this note, we will show that the above result is sharp. Moreover, we also attempt to give conditions under which the above dimensional formula still valid if we require the given speed of deg $A_n(x)$ tends to infinity.

• 로봇학회논문지
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• 제8권4호
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• pp.247-255
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• 2013

This paper shows the development of a snake robot (KAEROT-snake V) which consists of 16 1-DOF actuator modules and head module. The modules are connected serially and the joint axis of each module is rotated by $90^{\circ}$ with respect to the previous joint so that the snake robot can move in the 3D space. A tail actuator module includes slip-ring and metal connector. KAEROT-snake IV developed in prior research could move in the 3D space and climb up in a narrow pipe. But its design was not appropriate to the unstructured tough environment and its speed was somewhat slow. A new actuator module is designed to enclose all parts of the module so that any wire is not exposed. The size and weight of the new module was slightly reduced. And the rotation speed and torque of the joint was increased by about twice when compared with pre-module. An embedded controller was developed so small that it can be mounted inside the module. The performance of the developed robot was demonstrated through various locomotion experiments.

• Journal of Mechanical Science and Technology
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• 제17권2호
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• pp.181-186
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• 2003

In order to assure the quality of the bent axis design axial piston pumps driven by tapered pistons, it is necessary to know the characteristics of force applied to tapered pistons and the mechanism for driving the tapered pistons. Since they are able to perform both reciprocating and spinning motions in cylinder block, it is difficult to understand the driving mechanismand-tomeasure the forces applied to tapered pistons experimentally In the present study, the theoretical mechanism for driving the tapered pistons is studied by use of the geometric method. The driving area of the tapered pistons is measured by measuring the strain of a cylinder forced against a tapered piston using an electric strain gauge and a slip ring. The forces applied to tapered pistons is also investigated with the change of discharge pressure and the rotational speed. As a results of this investigation, it is concluded that the cylinder block is driven by one tapered piston in a limited area and the driving area is changed due to space angle of the tapered pistons and the swivel angle of the cylinder block. It is also observed that the force applied to tapered pistons increases as the discharge pressure and the rotational speed increase.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 심포지엄 논문집 정보 및 제어부문
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• pp.267-269
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• 2007

PLL(Phase Locked Loop) are widely used circuit technique in modern electronic systems. In this paper, We propose the low voltage and high speed PLL. We design the PFD(Phase Frequency Detector) by using TSPC (True Single Phase Clock) circuit to improve the performance and solve the dead-zone problem. We use CP(Charge Pump} and LP(Loop filter) for Negative feedback and current reusing in order to solve current mismatch and switch mismatch problem. The VCO(Voltage controlled Oscillator) with 5-stage differential ring oscillator is used to exact output frequency. The divider is implemented by using D-type flip flops asynchronous dividing. The frequency divider has a constant division ratio 32. The frequency range of VCO has from 200MHz to 1.1GHz and have 1.7GHz/v of voltage gain. The proposed PLL is designed by using 0.18um CMOS processor with 1.8V supply voltage. Oscillator's input frequency is 25MHz, VCO output frequency is 800MHz and lock time is 5us. It is evaluated by using cadence spectra RF tools.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.220.2-220.2
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• 2014

플라즈마 질화 기술은 기존의 침탄 혹은 고주파 표면 경화 기술 대비 낮은 온도에서 열처리 공정이 진행됨에 따라 열 변형을 최소화 시킬 수 있으며, 후 가공을 간소화 시킬 수 있다는 장점으로 인해 자동차 부품 및 기타 응용 산업 분야에 있어 큰 관심을 받고 있다. 그러나 공정 진행에 장시간이 소요되고 복잡한 형상 및 홀 가공에 의한 기능부, 특히 내경부에 대한 균일 질화 처리가 어려워 실제 응용분야 확장에 큰 제약이 따르고 있다. 이를 해결하기 위해 본 연구에서는 일반 글로우 방전 대비 플라즈마 밀도가 10배 이상 높은 공공 음극 방전(Hollow Cathode Discharge, 이하 HCD) 현상을 이용하여 고속 고균일 질화공정을 개발하고자 하였으며, 상용화 적용을 위한 연구를 함께 진행하였다. 사용된 시료로는 실제 자동차 부품으로 사용되는 SCM415 소재의 ring gear와 slip yoke pipe를 사용하였으며, HCD 형성을 위해 특화된 플라즈마 질화장비를 활용, 공정 압력 및 인가 전력 등을 변수로 실험을 진행 하였다. 그 결과 질화 처리 속도에 있어 기존 글로우 방전 플라즈마 질화 대비 1/4 이하 수준으로 그 소요 시간을 단축시킬 수 있었으며, 다량 장입된 시료의 내경 기능부에 있어서도 높은 균일도를 갖는 질화표면이 형성됨을 확인할 수 있었다. 또한 기능부 표면에 형성된 HCD 현상을 열원으로 사용함으로써 외부가열 장치를 사용하지 않으면서도 기존의 hot wall 방식보다 높은 질화 균일도 구현이 가능하였으며, 소요 자원 및 전력 사용 측면에 있어서도 공정 시간 단축 및 외부 가열 공정 제거에 의한 높은 수준의 에너지 절약이 가능하였다.

• 소성∙가공
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• 제16권4호
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• pp.266-270
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• 2007

Inertia welding is a solid-state welding process in which butt welds in materials are made in bar and in ring form at the joint face, and energy required for welding is obtained from a rotating flywheel. The stored energy is converted to frictional heat at the interface under axial load. The quality of the welded joint depends on many parameters, including axial force, initial revolution speed and energy, amount of upset, working time, and residual stresses in the joint. Inertia welding was conducted to make the large rotor shaft for low speed marine diesel engine, alloy steel for shaft of 140mm. Due to material characteristics, such as, thermal conductivity and high temperature flow stress, on the two sides of the weld interface, modeling is crucial in determining the optimal weld parameters. FE simulation is performed by the commercial code DEFORM-2D. A good agreement between the predicted and actual welded shape is observed. It is expected that modeling will significantly reduce the number of experimental trials needed to determine the weld parameters.