• Advances in concrete construction
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• 제13권6호
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• pp.471-479
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• 2022

In this paper, vibrational attributes of double-walled carbon nanotubes (CNTs) has been studied based upon nonlocal elastic shell theory. The implication of small scale is being perceived by establishing nonlocal Love shell model. The wave propagation approach has been operated to frame the governing equations as eigen value system. The comparison of local and nonlocal model has been overtly explored by means of scaling parameter. An appropriate selection of material properties and nonlocal parameter has been considered. The influence of changing mechanical parameter Young's modulus has been studied in detail. The dominance of end condition via nonlocal parameter is explained graphically. The results generated furnish the evidence regarding applicability of nonlocal shell model and also verified by earlier published literature.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1996년도 가을 학술발표회 논문집
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• pp.358-365
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• 1996

Lightweight foamed concrete is a concrete which is lighter than normal concrete by mixing prefoamed foam in cement slurry. The objective of this study are to develop prefoamed optimal lightweight foamed concrete using polymer foam agent and to obtain its mechanical characteristics experimentally. This paper presents extensive test data on young's modulus, poisson's ratio, stress-strain curve, the characteristics of strength of the foamed concrete and also presents the mechanical characteristics of the foamed concrete according to foam sizes.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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• pp.211-219
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• 2008

The hazard warning levels are necessary for the rational design and safety construction of underground space, as mountain and urban tunnel. Sakurai provided the hazard warning levels for assessing the stability of tunnels using the critical strain of rock mass, which is defined as a ratio between uni-axial compressive strength and the Young's modulus. The concept of critical strain guidelines is introduced in this study for the assessment of tunnel safety during excavation. Moreover, in this paper, the critical strain properties of sedimentary rock in Korea has investigated and analysed in detail by Lab. test, as the uniaxial compression tests. Finally, critical strain properties of sedimentary rock is discussed the relationship of failure strain values, uniaxial compression strengths and Young's modulus.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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• pp.821-832
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• 2008

The hazard warning levels are necessary for the rational design and safety construction of underground space, as mountain and urban tunnel. Sakurai provided the hazard warning levels for assessing the stability of tunnels using the critical strain of rock mass, which is defined as a ratio between uni-axial compressive strength and the Young's modulus. The concept of critical strain guidelines is introduced in this study for the assessment of tunnel safety during excavation. Moreover, in this paper, the critical strain properties of sedimentary rock in Korea has investigated and analysed in detail by Lab. test, as the uniaxial and triaxial compression tests. Finally, critical strain properties of sedimentary rock on uniaxial and triaxial stress condition is discussed the relationship of failure strain values, uniaxial and triaxial compression strengths, confining pressure and Young's modulus.

• 한국잠사곤충학회지
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• 제37권1호
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• pp.33-38
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• 1995

견 fibroin을 8M LiBr 수용액에 침지하여 연신처리에 의한 견의 구조와 물성변화를 시험해 보았다. 1. 연사의 역학적 성질은 8M LiBr 수용액의 처리온도 상승에 따라서 강도와 신도는 증가하나 Young's율은 감소하는 경향이었다. 8$0^{\circ}C$ 처리의 X선회절에 있어서는 염축에 의해 분자배향은 흐트러지나 SilkII형의 결정구조는 변하지 않았다. 2. 8M LiBr수용액을 사용하여 8$0^{\circ}C$에서 1시간 처리하면 160%정도 연신이 가능하며 고연신시의 역학적 성질에 있어서는 강도와 Young's율은 증가하고 신도는 감소하였으나 X선회절에서는 연신율의 증가와 함께 결정이 고배향화되는 경향이었다. 3. DSC의 시차열 Thermogram에서 무처리의 연사와 8M LiBr 수용액에 처리되어진 미연신의 연사사이에는 열분해거동이 다른 것이 관찰되었으며 열분해 최대 Peak점의 온도는 연신율의 증가에 따라 조금씩 고온쪽으로 이동함으로써 X선회절사진의 결과와 일치하고 있다.

• 반도체디스플레이기술학회지
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• 제17권4호
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• pp.42-45
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• 2018

As The semiconductor decrease from 10 nanometer to 7 nanometer, It is suggested that "More than Moore" is needed to follow Moore's Law, which has been a guide for the semiconductor industry. Fan-Out Wafer Level Package(FOWLP) is considered as the key to "More than Moore" to lead the next generation in semiconductors, and the reasons are as follows. the fan-out WLP does not require a substrate, unlike conventional wire bonding and flip-chip bonding packages. As a result, the thickness of the package reduces, and the interconnection becomes shorter. It is easy to increase the number of I / Os and apply it to the multi-layered 3D package. However, FOWLP has many issues that need to be resolved in order for mass production to become feasible. One of the most critical problem is the warpage problem in a process. Due to the nature of the FOWLP structure, the RDL is wired to multiple layers. The warpage problem arises when a new RDL layer is created. It occurs because the solder ball reflow process is exposed to high temperatures for long periods of time, which may cause cracks inside the package. For this reason, we have studied warpage in the FOWLP structure using commercial simulation software through the implementation of the reflow process. Simulation was performed to reproduce the experiment of products of molding compound company. Young's modulus and poisson's ratio were found to be influenced by the order of influence of the factors affecting the distortion. We confirmed that the lower young's modulus and poisson's ratio, the lower warpage.

• 터널과지하공간
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• 제16권4호
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• pp.334-346
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• 2006

개별요소법을 사용한 수치해석 프로그램인 PFC2D는 암석역학에 많이 사용되고 있다. 그러나 해석 모델을 구성하는 입자와 접촉의 특성을 결정하기 위해서는 시행오차적인 지루한 반복 과정을 거쳐야 한다. 본 연구에서는 해석 모델을 정의하는 미시변수가 일축압축시험으로부터 얻어지는 거시 물성에 미치는 영향을 분석하였다. 또한 분석 결과에 기초하여 간단하고 신뢰할 수 있는 정량적인 미시변수 결정법을 제안하였다. 제안된 미시변수 결정법을 검증하기 위하여 10종류의 암석 시험편을 생성하기 위한 수치 실험을 수행하였다. 그 결과 단 2회의 수치 실험만으로 탄성계수 포아송비 그리고 일축압축강도를 실험실 시험값과의 상대오차 % 내외로 재현할 수 있었다.

• 비파괴검사학회지
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• 제23권2호
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• pp.98-106
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• 2003

비파괴시험(NDT)은 구조물의 기능에 손상을 주지 않으면서 콘크리트에 대한 많은 정보를 준다. 여러 가지 NDT 방법들 중에서, 초음파 속도법과 충격반향기법과 같이 탄성파의 속도를 이용하는 방법은 콘크리트의 압축강도, 탄성계수, 포아송비의 추정뿐만 아니라, 내부 미세구조 변화 모니터링과 결함 탐지 등을 위해 이용되고 있다. 본 연구에서는 물-결합재비가 $0.27{\sim}0.50$이고 시멘트 중량의 20%를 플라이 애쉬로 대체 사용한 콘크리트를 제조한 후, 동일한 콘크리트에 대해 초음파 속도법과 충격반향기법을 이용하여 종파 속도를 각각 측정하여 서로 비교하였다. 실험 결과, 콘크리트 공시체로부터 측정된 초음파 속도가 충격반향기법에 의해 측정된 종파 속도, 즉 막대파 속도보다 큰 경향을 나타내었으며, 이들의 차이는 재령이 증가함에 따라 그리고 콘크리트의 강도가 커질수록 각각 감소하는 경향을 나타내었다. 또한, 동포아송비, 정탄성계수, 동탄성계수, 속도-강도의 상관관계 등을 실험적으로 결정하였다. 그 결과, 동적인 방법으로 결정되는 포아송비와 탄성계수가 정적인 시험에 의한 것보다 크게 나타났다. 따라서, 탄성파 속도를 이용하여 콘크리트의 성질들을 보다 정확하게 추정하기 위해서는 속도 특성에 대한 이해가 필요할 것으로 사료된다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 춘계 학술발표회
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• pp.482-489
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• 2009

Various model piles with different sections such as reinforced concrete, steel, steel-concrete composite without rebar and steel-concrete composite with rebar were made, and vertical load test was conducted using a large scaled UTM(Universal Test Machine) to evaluate Young's modulus and ultimate load of the model piles. Based on the tests, ultimate load of steel-concrete composite pile is 31% greater than the sum of it of reinforced concrete pile and it of steel pile. This is caused that ultimate load and Young's modulus of inner concrete increase due to confining effect by outer steel casing. Variation of ultimate load is also insignificant depending on the ratio of length to diameter(L/D), therefore bucking has not an effect on change of ultimate load in case of the L/D below 10.

• Journal of Magnetics
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• 제14권2호
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• pp.66-70
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• 2009

The dynamic magneto-mechanical behaviors in a type of iron-nickel-based ferromagnetic alloy with constant elasticity were investigated as a function of both the DC bias magnetic field ($H_{dc}$) and the frequency. The rectangular plate-like samples were excited to vibrate at a half-wavelength, longitudinal resonance by an AC magnetic field superimposed with various $H_{dc}$. The experimental results found that the strain coefficient at resonance reached 819.34 nm/A and the effective mechanical quality factor ($Q_m$) was greater than 2000. The ratio of the maximum variation of the Young's modulus over $H_{dc}$ to the value of the Young's modulus at a zero bias field was only ${\sim}0.83%o$ because of the so-called constant elasticity. The resonant strain coefficients and $Q_m$ are strongly dependent on $H_{dc}$, which indicates a promising potential for use in DC and quasistatic magnetic field sensing.