• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2006년도 춘계학술대회 논문집
• /
• pp.373-376
• /
• 2006

The ring rolling design for a large-scale Ti-6Al-4V alloy ring was performed with a calculation method and FEM simulation. The ring rolling design includes geometry design and optimization of process variables. The calculation method was to determine geometry design such as initial billet and blank size, and final rolled ring shape. A commercial FEM code, SHAPE was used to simulate the effect of process variables in ring rolling on the distribution of the internal state variables such as strain, strain rate and temperature. In order to predict the forming defects during ring rolling, the process-map approach based on Ziegler's instability criterion was used with FEM simulation. Finally, an optimum process design to obtain sound Ti-6Al-4V rings without forming defects was suggested through combined approach of Ziegler's instability map and FEM simulation results.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2010년도 추계학술대회 논문집
• /
• pp.336-337
• /
• 2010

In the underwater veicle self-noise from the propeller reduces the sensor sensitivity. To increase the sensor sensitivity SNORE ring(Self-noise reduction ring) has been used. In this paper to calculate the effectiveness of the SNORE ring and de-coupeler numerical simulation is conducted. Based on the simulation results CRP(Carbon reinforced plastic)and SNORE ring reduced noise and vibration.

• Journal of electromagnetic engineering and science
• /
• 제14권4호
• /
• pp.367-375
• /
• 2014

In this paper, a novel triple-band circular-ring monopole antenna with a half-circular ring and ground slot for wireless local area network/Worldwide Interoperability of Microwave Access (WLAN/WiMAX) applications is proposed. The proposed antenna consists of one circular ring, a half-circular ring and a rectangular slot in the ground plane. Based on the concept, a prototype of the proposed triple-band antenna was designed, fabricated and tested. The numerical and experiment results demonstrated that the proposed antenna satisfied the -10 dB impedance bandwidth requirement while simultaneously covering the WLAN and WiMAX bands. Furthermore, this paper presents and discusses the 2D radiation patterns and 2D gains according to the results of the experiment.

• Korean Journal of Mathematics
• /
• 제29권3호
• /
• pp.483-492
• /
• 2021

This article concerns the property that for any element a in a ring, if a²ⁿ = aⁿ for some n ≥ 2 then a² = a. The class of rings with this property is large, but there also exist many kinds of rings without that, for example, rings of characteristic ≠2 and finite fields of characteristic ≥ 3. Rings with such a property is called reduced-over-idempotent. The study of reduced-over-idempotent rings is based on the fact that the characteristic is 2 and every nonzero non-identity element generates an infinite multiplicative semigroup without identity. It is proved that the reduced-over-idempotent property pass to polynomial rings, and we provide power series rings with a partial affirmative argument. It is also proved that every finitely generated subring of a locally finite reduced-over-idempotent ring is isomorphic to a finite direct product of copies of the prime field {0, 1}. A method to construct reduced-over-idempotent fields is also provided.

• 대한산업공학회지
• /
• 제34권2호
• /
• pp.151-159
• /
• 2008

An efficient location registration scheme is essential to accommodate continuously increasing mobile subscribers and to offer a variety of multimedia services with good quality. In this study, we consider a distance-based registration scheme where the number of location areas varies on the basis of cell-by-cell, not of ring-by-ring, to analyze the optimal size of the location area. Using our proposed cell-by-cell distance-based registration scheme with random walk mobility model, we analyze a variety of circumstances to obtain the optimal number of cells for location area that minimizes total signaling traffic on radio channels. From our analysis results, we show that the optimal number of cells for location area is between 4 and 6 in most cases, and our cell-by-cell distance-based location registration scheme has less signaling traffic than optimal ring-by-ring distance-based location registration scheme where optimal distance threshold is 2 (thus the optimal number of cells for location area is 7).

• 정보보호학회논문지
• /
• 제27권3호
• /
• pp.439-448
• /
• 2017

포스트 양자 암호라 할지라도 실제 디바이스에 이를 적용 할 때 부채널 분석 취약점이 존재한다는 것은 이미 알려져 있다. 코드 기반 McEliece 암호와 격자 기반 NTRU 암호에 대한 부채널 분석 연구 및 대응책 연구는 많이 이루어지고 있으나, ring-LWE 암호에 대한 부채널 분석 연구는 아직 미비하다. 이에 본 논문은 8비트 디바이스에서 ring-LWE 기반 암호가 동작할 때 적용 가능한 선택 암호문 SPA 공격을 제안한다. 제안하는 공격은 [$log_2q$]개의 파형으로 비밀키를 복구 할 수 있다. q는 보안 레벨과 관련된 파라미터로 128비트 또는 256비트의 보안 레벨을 만족하기 위해 각각 7681 또는 12289를 사용한다. 또한, 우리는 실제 디바이스에서 동작되는 ring-LWE 복호화 과정의 모듈러 덧셈에서 비밀키를 드러낼 수 있는 취약점이 존재함을 실험을 통해 보이고, 공격 시간 단축을 위한 두 벡터의 유사도 측정 방법을 이용한 공격에 대해 논한다.

• 한국정보과학회논문지:시스템및이론
• /
• 제29권2호
• /
• pp.105-115
• /
• 2002

NUMa 구조는 원격 메모리에 대한 접근이 불가피한 구조적 특성 때문에 상호 연결망이 시스템 성능을 좌우하는 큰 변수가 된다. 기존에 대중적으로 사용되던 버스는 물리적 확장성 및 대역폭에서 대규모 시스템을 구성하는데 한계를 보인다. 이를 대체하는 고속의 지점간 링크를 사용한 이중 링구조는 버스가 가지는 확장성 및 대역폭의 한계라는 단점을 개선하였으나, 많은 노드가 연결되는 경우에는 응답 지연시간이 증가하는 문제점을 가지고 있다. 본 논문에서는 스누핑 프로토콜이 적용된 이중 일 구조에서 노드개수 증가에 따른 응답지연시간 증가의 문제점을 보안하기 위해 코달 링 구조로의변화를 제안하고 이 구조에 효과적인 링크 제어기를 설계한다. 또한 확률 구동 시뮬레이터를통해 본 논문을 통해 제시한 코달 링 구조가 시스템의 성능 및 응답시간에 미치는 영향을 알아본다.

• Journal of Advanced Marine Engineering and Technology
• /
• 제36권4호
• /
• pp.512-519
• /
• 2012

본 논문은 원형 링 패턴의 인식에 기반한 물체의 3차원 위치/자세 추정 시스템을 제안한다. 단일 비전 기반의 자세추정 문제를 다루기 위하여, 본 논문은 물체인식 과정의 단순화를 위한 원형 링 패턴의 설계방법을 기술한다. 또한, 본 논문은 2차원 투영공간에서 원형 링 패턴이 가지는 기하학적 변환관계를 적극 활용한 실내용 위치/자세 추정 절차를 상세히 설명한다. 제안된 방법은 쿼드로터형 비행체의 3차원 위치/자세 추정에 적용되며 정확도 및 정밀도 분석을 통해 평가된다.

• Tribology and Lubricants
• /
• 제22권3호
• /
• pp.119-126
• /
• 2006

In this paper, the contact behavior characteristics of a primary sealing components such as a seal ring and a seal seat has been presented for a small hydro-power turbine. Using the non-linear FEM analysis, the maximum temperature, the axial displacement, radial differences between a seal ring and a seal seat, and maximum contact normal stress have been analyzed for three optimized sealing profiles in which are designed based on the FEM analysis and Taguchi's experimental method. The three primary sealing profiles between a seal ring and a seal seat are strongly related to a leakage of a water for a hydro-power turbine and wear of a primary sealing component. The computed results show that the contact rubbing area between a seal ring and a seal seat is very important for reducing a friction heating and wear in a sealing gap, and increasing a contact normal stress in primary sealing components. Based on the FEM computation, models II and III in which have a small rubbing surface of seal rings show low dilatation of primary sealing components, and high normal contact stress between a seal ring and a seal seat. Thus, the FEM computed results recommend a short contacting width of a primary sealing component for reducing a leakage and thermal distortions, and expanding a seal life. This means that a conventional primary sealing component may be switched to a reduced sealing face of seal rings.

• 한국시뮬레이션학회논문지
• /
• 제2권1호
• /
• pp.46-54
• /
• 1993

Analytic and simulation models for prioritized token ring are presented in this paper. Its protocol is based on prioritized token ring with reservation (R-PTR). Since the protocol of the R-PTR is simple and the performance of the R-PTR is not inferior to that of the IEEE-PTR under almost all traffic load environments, we use the R-PTR as our token ring model. By using the properties of Markovian process, the expressions for average throughput and average packet transmission delay are derived. The results obtained from the analytic model are compared with that of the discrete event simulation model.