• 정보처리학회논문지A
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• 제13A권3호
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• pp.199-204
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• 2006

리눅스 운영체제에서 커널 개발자의 오류로 인하여 발생되는 시스템 정지 현상을 줄이기 위해서 커널 하드닝이 필요하다. 그러나 기존의 커널 하드닝 방식은 고장 감내 기능을 통하여 제공되고 있기 때문에 구현이 어려울 뿐만 아니라 많은 비용이 소요된다. 본 논문에서 제안하는 커널 하드닝 방식은 패닉이 발생한 커널 주소에 대한 커널 스택 내의 값들을 정상적인 값으로 복구하기 위해서 커널 내의 panic() 함수 등 커널의 일부분을 수정하므로, 적은 비용으로 시스템 가용성을 높일 수 있다. 제안한 방식의 실험을 위하여 네트워크 모듈에 강제적인 패닉 현상 유발시키고, 잘못된 스택 값을 정상적인 값으로 복구하는 동작을 확인하였다.

• Structural Engineering and Mechanics
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• 제19권2호
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• pp.185-198
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• 2005

In the design of reinforced concrete beams, it is a standard practice to use the yield stress of the steel reinforcement for the evaluation of the flexural strength. However, because of strain hardening, the tensile strength of the steel reinforcement is often substantially higher than the yield stress. Thus, it is a common belief that the actual flexural strength should be higher than the theoretical flexural strength evaluated with strain hardening ignored. The possible increase in flexural strength due to strain hardening is a two-edge sword. In some cases, it may be treated as strength reserve contributing to extra safety. In other cases, it could lead to greater shear demand causing brittle shear failure of the beam or unexpected greater capacity of the beam causing violation of the strong column-weak beam design philosophy. Strain hardening may also have certain effect on the flexural ductility. In this paper, the effects of strain hardening on the post-peak flexural behaviour, particularly the flexural strength and ductility, of reinforced normal- and high-strength concrete beams are studied. The results reveal that the effects of strain hardening could be quite significant when the tension steel ratio is relatively small.

• Nuclear Engineering and Technology
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• 제54권3호
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• pp.1098-1108
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• 2022

The effect of the material hardening model of the canister on a finite element vertical cask drop simulation is investigated for the strain-based acceptance evaluation. Three different hardening models are considered in this paper: the isotropic hardening model, the strain rate-dependent Johnson-Cook (J-C) hardening model, and the modified J-C model which are believed to be the most accurate. By comparing the results using the modified J-C model, it is found that the use of the J-C model provides similar or larger stresses and strains depending on the magnitudes of the strain and strain rate. The use of the isotropic hardening model always yields larger stresses and strains. For the strain-based acceptance evaluation, the use of the isotropic hardening model can produce highly conservative assessment results. The use of the J-C model, however, produces satisfactory results.

• Structural Engineering and Mechanics
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• 제81권5호
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• pp.575-589
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• 2022

In order to enhance the greenness in the strain-hardening composites and to reduce the high cost of typical polyvinyl alcohol fiber reinforced engineered cementitious composite (PVA-ECC), an affordable strain-hardening composite with green binder content has been proposed. For optimizing the strain-hardening behavior of cementitious composites, this paper investigates the effects of polypropylene fibers on the first cracking strength, fracture properties, and micromechanical parameters of cementitious composites. For this purpose, digital image correlation (DIC) technique was utilized to monitor crack propagation. In addition, to have an in-depth understanding of fiber/matrix interaction, scanning electron microscope (SEM) analysis was used. To understand the effect of fibers on the strain hardening behavior of cementitious composites, ten mixes were designed with the variables of fiber length and volume. To investigate the micromechanical parameters from fracture tests on notched beam specimens, a novel technique has been suggested. In this regard, mechanical and fracture tests were carried out, and the results have been discussed utilizing both fracture and micromechanical concepts. This study shows that the fiber length and volume have optimal values; therefore, using fibers without considering the optimal values has negative effects on the strain-hardening behavior of cementitious composites.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1996년도 추계학술대회논문집
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• pp.131-138
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• 1996

A new yield criterion for metal powder compaction based on continuum mechanics has been proposed. It includes three parameters to characterize the geometrical hardening of powder compact and strain hardening of incompressible metal matrix. The elasto-plastic finite element method to describe compaction of metal powders has been formulated using the new yield criterion. The values of parameters in the yield criterion can be determined using cold isostatic pressing(CIP). The finite element method can simulate compaction behavior of various copper powders.

• International Journal of Computer Science & Network Security
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• 제22권12호
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• pp.57-62
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• 2022

The Sambodana project is a mobile communication security system development project using Hardening Android. The initial idea for this project is that information leakage occurs outside of a communications application with end-to-end cryptographic security. Android hardening prevents unwanted applications and bloatware from being installed, such as unavailable Google Play Store or install restrictions.

• Clinical and Experimental Reproductive Medicine
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• 제24권1호
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• pp.1-11
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• 1997

It is well known that the zona pellucidae of mouse oocytes become "hardened" when they are allowed to mature in vitro in the absence of serum components. To see if oocytes already undergone meiotic resumption in vivo exhibit similar zona hardening, hardening of ZP of cumulus-enclosed oocytes(CEOs) was examined after culture in vitro since their release from follicles various hours after hCG injection. When CEOs matured in vivo for 3h or longer were subjected to culture in vitro for 14h with BSA alone, zona hardening was significantly reduced compared to those cultured in vitro from the begining of maturation. However, when CEOs matured in vivo for 5h were freed from cumulus cells and then cultured in vitro with BSA alone, little reduction of zona hardening was observed. Preincubation of CEOs for 5h with fetuin, one of the well known inhibitor of in vitro zone hardening, did not prevent zona hardening during its subsequent culture of CEOs for 14h without fetuin. However, when CEOs precultured with both fetuin and PMSG for 5h and then further cultured with BSA alone for 14h, zona hardening was dramatically reduced. Under these conditions, the expansion of cumulus cell was observed. In addition, CEOs cultured with both BSA and dbcAMP to prevent their meiotic resumption showed a significant increase of zona hardening. Whether the observed zona hardening was correlated with the conversion of ZP2 to $ZP2_{f}$ was examined. Zona pellucida, isolated from CEOs matured for 5h in vivo and then further cultured with BSA alone was subjected to SDS-PAGE. Most of ZP2 molecules from these CEOs did not undergo conversion from ZP2 to $ZP2_{f}$. From these results, it is concluded that CEOs undergone meiotic resumption in vivo do not exhibit zona hardening when they were subsequently cultured in vitro without serum components. It appears that cumulus cells play an important role in this phenomenon.

• 한국건설순환자원학회논문집
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• 제3권4호
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• pp.355-365
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• 2015

본 연구에서는 친환경 무기질 고화재를 사용하여 무시멘트 황토모르타르의 유동성과 강도특성 및 내수성과 동결융해 등의 내구 특성을 검토하였다. 실험결과 황토모르타르의 재령 28일 압축 및 휨강도는 마사토와 황토 혼합비율에 관계없이 고화재 치환율이 증가할수록 증가하였고, 고화재 치환율에 관계없이 재령 14일까지의 강도증진효과는 크게 나타났으나 재령 14일 이후 강도증진 효과는 상대적으로 낮아 황토모르타르의 강도발현은 일반 콘크리트의 강도발현보다 빠른 것으로 나타났다. 또한, 고화재 10% 사용 시 평균 휨강도는 1.7MPa로 포장용 콘크리트의 재령 28일 휨강도 4.5MPa 이상을 만족시키지 못하였으나, 고화재 20%에서 약 4.0MPa, 고화재 30%에서 5.3MPa로 근접하거나 높게 나타나, 황토모르타르를 포장용 도로에 적용시 고화재 사용량은 최소 20% 이상 되어야 할 것으로 판단된다. 내수성 실험결과 흡수 건조의 반복은 황토의 혼합비율에 관계없이 질량을 감소시켰으며, 최대길이변화율은 황토 혼합비율과 고화재 치환율이 증가할수록 감소하는 것으로 나타났다. 동결융해 저항성 실험결과 동결융해 300 사이클에서 상대동탄성계수는 고화재 20%에서 75%, 고화재 30%에서 79%로 나타나, 황토모르타르의 상대동탄성계수 60% 이상을 만족시키기 위한 고화재 사용량은 20% 이상이 필요한 것으로 나타났다.

• 한국지진공학회논문집
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• 제7권5호
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• pp.47-56
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• 2003

본 논문에서는 기존 IWAN 모델을 수정하여 사질토 지반의 반복경화 현상을 나타낼 수 있는 지반의 반복경화모델을 개발하였다. 일반적으로 동적하중을 받는 지반재료는 하중 반복회수에 따라 동적 거동특성이 변화하게 되며 이는 반복 경화 및 연화현상으로 나타난다. 본 논문에서는 등방 경화 또는 등방 연화 거동을 하는 스프링슬라이더 요소를 기존 병렬 IWAN 모델에 추가함으로써 지반의 동적 변형특성 표현이 가능하였다. 등방 경화 거동을 보이는 요소들의 항복 응력은 각각 반복 경화함수에 의하여 증가하도록 정의되었으며, 반복 경화함수는 대칭 한계를 가지는 동적 비틂전단 시험결과로부터 정의되었다. 이렇게 정의된 반복 경화함수는 지반의 동적 변형 특성을 묘사하기 위하여 하나의 독립 변수를 가지게 되며, 사용된 독립변수는 지반의 동적 한계 변형률의 특성을 포함하는 누적전단변형률로 사용되었다. 누적 전단변형률은 반복 전단한계 변형률 이상의 변형률의 누적으로 정의되며, 역재하 및 재재하 곡선에서는 Masing의 법칙을 적용하여 계산될 수 있다. 본 논문에서는 모델의 개발과정을 서술하였고, 모델에 대한 검증은 동반논문인 검증편에 설명하였다.

• 대한기계학회논문집A
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• 제32권6호
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• pp.488-495
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• 2008

In order to achieve long fatigue lifetimes for cyclically pressurized thick cylinders, multi-layered compound cylinder has been proposed. Such compound cylinder involves a shrink-fit procedure incorporating a monobloc tube which has previously undergone autofrettage. The basic autofrettage theory assumes elastic-perfectly plastic behaviour. Because of the Bauschinger effect and strain-hardening, most materials do not display elastic-perfectly plastic properties and consequently various autofrettage mo dels are based on different simplified material strain-hardening models, which is assumed that combination of linear strain-hardenig and power strain-hardening model. This approach gives a more accurate prediction than the elastic-perfectly plastic model and is suitable for different strain-hardening materials. In this paper, a general autofrettage model that incorporates the material strain-hardening relationship and the Bauschinger effect, based upon the actual tensile-compressive stress-strain curve of a material was proposed. The model was obtained using the von Mises yield criterion and plane strain condition. The tensile-compressive stress-strain curve was obtained by experiment. The parameters needed in the model were determined by fitting the actual tensile-compressive curve of the material. Finally, strain- hardening model was compared with elastic-perfectly plastic model.