• 한국표면공학회지
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• 제43권3호
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• pp.154-158
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• 2010

Numerical analysis is done to investigate the effects of pulse bias on the plasma processing characteristics like ion doping and ion nitriding by using fluid dynamic code with a 2D axi-symmetric model. For 10 mTorr of Ar plasma, -1 kV of pulse bias was simulated. Maximum sheath thickness was around 20 mm based on the electric potential profile. The peak electron temperature was about 20 eV, but did not affect the averaged plasma characteristics of the whole chamber. Maximum ion current density incident on the substrate was 200 $A/m^2$ at the center, but was decreased down to 1/10th at radius 100 mm, giving poor radial uniformity.

• Tribology and Lubricants
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• 제26권1호
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• pp.31-36
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• 2010

The brake system is an important part of the automobile safety system. The disc brake system is divided into two parts: a rotating axi-symmetrical disc, and the stationary pads. The frictional heat, which is generated on the interface of the disc and pads, can cause high temperatures during the braking process. The frictional heat source (the pads) is moving on the disc and the location is time-dependent. Our study applies a moving heat source, which is defined by the time and space variable on the frictional surface, in order to simulate the frictional heat behavior accurately during the braking process. The object of the present work is the determination of the temperature distribution and thermal stress in the solid disc by non-axisymmetric 3D modeling for repeated braking.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2015년도 추계학술발표대회
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• pp.740-743
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• 2015

The increasing complexity of integrated circuits and IP-based hardware designs have created the risk of hardware Trojans. This paper introduces a new type of threat, the coherence-exploiting hardware Trojan. This Trojan can be maliciously implanted in master components in a system, and continuously injects memory read transactions on to bus or main interconnect. The injected traffic forces the eviction of cache lines, taking advantage of cache coherence protocols. This type of Trojans insidiously slows down the system performance, incurring Denial-of-Service (DoS) attack. We used Xilinx Zynq-7000 device to implement and evaluate the coherence-exploiting Trojan. The malicious traffic was injected through the AXI ACP interface in Zynq-7000. Then, we collected the L2 cache eviction statistics with performance counters. The experiment results reveal the severe threats of the Trojan to the system performance.

• Nuclear Engineering and Technology
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• 제54권6호
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• pp.2023-2030
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• 2022

A novel pulse fitting analysis (PFA) method is presented for the acquisition of nuclear spectra. The charging process of the feedback capacitor in the resistive feedback charge-sensitive preamplifier is equivalent to the impulsive pulse, and its impulse response function (IRF) can be obtained by non-linear fitting of the falling edge of the nuclear pulse. The integral of the IRF excluding the baseline represents the energy deposition of the particles in the detector. In addition, since the non-linear fitting process in PFA method is difficult to achieve in the conventional architecture of spectroscopy system, a new multi-channel analyzer (MCA) based on Zynq SoC is proposed, which transmits all the data of nuclear pulses from the programmable logic (PL) to the processing system (PS) by high-speed AXI-Stream in order to implement PFA method with precision. The linearity of new MCA has been tested. The spectrum of ¹³⁷Cs was obtained using LaBr₃(Ce) scintillator detector, and was compared with commercial MCA by ORTEC. The results of tests indicate that the MCA based on PFA method has the same performance as the commercial MCA based on pulse height analysis (PHA) method and excellent linearity for γ-rays with different energies, which infers that PFA method is an effective and promising method for the acquisition of spectra. Furthermore, it provides a new solution for nuclear pulse processing algorithms involving regression and iterative processes.

• 대한기계학회논문집A
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• 제22권4호
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• pp.731-742
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• 1998

Bolted opening structures is widely applied for class 1 machinery of nuclear plant with strict design requirement. As the shape of the bolted opening structure is non-axisymmetric due to the existence of stud bolts although it is almost axi-symmetric, 3D analysis is required to satisfy such kind of design requirements. Because as much as possible trial computations are need to get an optimal design condition in the limited period of basic design, an easy and fast analysis tool is useful in the design stage. In the paper, a transformation technique of non-axisymmetric problem into quasi-axisymmetric has been proposed based on the general purpose commercial code ANSYS. Both the pre-processor which incorporates the technique and prepares data and post-processor which prepares arranged results from the huge output of commercial code have been developed to help the design engineers.

• 전산구조공학
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• 제8권3호
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• pp.59-66
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• 1995

점소성이론을 이용하여 충격하중을 받는 구조물의 거동을 하중시간에 따라 조사하였다. 점소성이론은 재료의 소성특성과 시간변화특성을 나타내는 Rheology 이론을 동시에 고려한 이론이다. 점소성 구성방정식을 구한 후, 이를 이차원 유한요소해석프로그램에서 심어서 평면응력, 평면 변형률, 축대칭 구조물의 동적 거동을 해석할 수 있도록 기존프로그램을 수정.개발하였다. Perzyna에 의한 점소성 구성방정식은 유한요소해석에서 Explicit 적분법을 사용해야 하는데 반하여, 본 연구에서 구한 구성방정식은 Implicit 적분법을 적용할 수 있도록 Algorithm을 개발하였다. 다양한 하중시간을 갖는 충격하중을 선택한 구조물에 가해 해석한 결과, 하중시간이 길수록 변형이 증가하여 점소성 거동을 하며, 높은 고유진동수 성분이 점소성거동으로 거의 소멸된다는 결론을 얻었다.

• 한국정보통신학회논문지
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• 제26권7호
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• pp.1071-1077
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• 2022

타원곡선 암호 (elliptic curve cryptography; ECC) 기반의 공개키 기반구조 구현에 사용될 수 있는 보안 SoC(system-on-chip)를 설계하였다. 보안 SoC는 타원곡선 디지털 서명 알고리듬 (elliptic curve digital signature algorithm; ECDSA)용 하드웨어 가속기가 AXI4-Lite 버스를 통해 Cortex-A53 CPU와 인터페이스된 구조를 갖는다. ECDSA 하드웨어 가속기는 고성능 ECC 프로세서, SHA3 (secure hash algorithm 3) 해시 코어, 난수 생성기, 모듈러 곱셈기, BRAM (block random access memory), 그리고 제어 FSM (finite state machine)으로 구성되며, 최소의 CPU 제어로 ECDSA 서명 생성과 서명 검증을 고성능으로 연산할 수 있도록 설계되었다. 보안 SoC를 Zynq UltraScale+ MPSoC 디바이스에 구현하여 하드웨어-소프트웨어 통합 검증을 하였으며, 150 MHz 클록 주파수로 동작하여 초당 약 1,000번의 ECDSA 서명 생성 또는 서명 검증 연산 성능을 갖는 것으로 평가되었다. ECDSA 하드웨어 가속기는 74,630개의 LUT (look-up table)와 23,356개의 플립플롭, 32kb BRAM 그리고 36개의 DSP (digital signal processing) 블록의 하드웨어 자원이 사용되었다.

• Journal of Advanced Marine Engineering and Technology
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• 제15권4호
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• pp.29-45
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• 1991

Lip type stern tube sealing systems have used in almost all the middle or large ships which are being constructed in these days. It seems that the pressure fluctuation of the seal ring interspace, the cross-section profile and the materials quality of the seal rings have great effects on the sealing fuction of this sealing system. In this paper, the mechanical movement of lip seal ring which plays the most important role in stern tube sealing system and the possibility of leakage caused by pressure fluctuation are studied by theory and experiment. Using the finite element method for the axi-symetric object which receives the torsional load, the displacement and stress analysis of the seal rings, and also the possibility of crack occurance is checked by theoretical analysis. If the force which seal ring lip periphery receives is too small, there will be the possibility of leakage caused by the pressure fluctuation of the seal ring interspace, and if this force is too large, the frictional force between the seal ring and the liner will become problematical. The possibility of leakage caused by hardening of seal ring materials and creep phenomena of tested seal rings are also examined. The trial seal rings were designed and manufactured using the program of displacement and stress analysis developed in this study and the experimental apparatus to test the trial seal rings was also designed and manufactured. This trial seal rings were fitted in the experimental apparatus which was made in the same form as an actual stern tube. The one side of this apparatus was filled with sea water and the other side of it was filled with the lubricating oil. The leakage of oil and sea water was checked and the temperature was measured, rotating the propeller shaft at the constant velocity by D.C. motor. It was proved that the trial seal rings made in Viton rubber functioned excellenty but the trial seal rings made in N.B.R. rubber had problem in its durability.

• 대한기계학회논문집A
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• 제38권2호
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• pp.177-184
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• 2014

본 논문에서는 보수용접부 폭 변화에 따른 이종금속 맞대기 용접부(Dissimilar metal butt weld) 용접잔류응력의 분포 및 동종금속용접/기계적 하중에 의한 재분배 거동을 평가하였다. 이를 위해 5가지 다른 보수용접부 폭을 고려한 상세 2차원 유한요소 열해석 및 응력해석을 수행하였다. 유한요소해석 결과를 바탕으로 보수용접에 의한 용접잔류응력 분포를 평가하였으며, 동종금속용접 및 기계적 하중에 의한 응력 재분배 특성을 평가하였다. 보수용접에 의해 배관 내면에서는 큰 인장 용접잔류응력이 축방향과 원주방향에 대해 발생하는 것으로 나타났으며 보수용접부 폭이 특정값 이상이 되면 용접잔류응력 분포가 변하는 것으로 나타났다. 그러나 동종금속용접과 기계적 하중을 고려하면 인장잔류응력값이 크게 감소하였으며 그 경향은 보수용접부 폭에 무관한 것으로 나타났다.

• 한국정보과학회논문지:컴퓨팅의 실제 및 레터
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• 제10권6호
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• pp.484-498
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• 2004

본 논문에서는 Apache Axis나 .Net과 같은 SOAP 기반 미들웨어 상에 존재하는 SOAP 노드에 대한 실시간 성능 모니터링을 수행하는 방법으로써 네트워크 패킷 필터링을 통한 SOAP 오퍼레이션 검출 방법인 "TCP 흐름을 이용한 SOAP 오퍼레이션 검출 방법"을 제시하였다. 네트워크 패킷 필터링에 의한 SOAP 오퍼레이션 검출 방법은 Raw 패킷 내부에 단편화되어서 전송되는 SOAP 메시지를 직접 분석하기 때문에 다양한 SOAP 기반 미들웨어에 독립적으로 SOAP 노드를 모니터링 할 수 있게 한다 그러나 Raw 패킷들로부터 SOAP 메시지를 추출하여 분석하는 과정은 시스템의 많은 자원을 필요로 한다. 이러한 문제점을 해결하기 위하여 본 논문에서는 "TCP 플래그를 이용한 선별적인 TCP 흐름에서의 SOAP 오퍼레이션 검출 방법"을 제시하고 첫 번째 방법과의 성능을 비교하였다. 본 논문에서는 제시한 검출 방법을 바탕으로, 패킷 필터링을 통하여 SOAP 오퍼레이션을 검출하는 SOAP Sniffer 컴포넌트와 이를 이용한 SOAP 모니터링 시스템을 구현하였다. 본 논문에서 구현한 SOAP 모니터링 시스템은 SOAP 기반 미들웨어에 독립적인 모니터링 방법을 제공하므로 서로 다른 SOAP 기반 미들웨어 상에 존재하는 SOAP 노드 간 트랜잭션 모니터링이나 로드밸런싱을 위한 모니터링 등의 다양한 활용이 가능할 것이다.