• Title, Summary, Keyword: 구속범위

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Dynamic Shear Modulus and Damping Ratio of Soft Clay (연약점토의 동력학적 전단탄성계수 및 감쇠비)

  • 하광현
    • Geotechnical Engineering
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    • v.2 no.1
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    • pp.55-66
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    • 1986
  • Considering the effects of confining pressure, initial shear stress, cyclic stress ratio and number of loading cycles, cyclic triaxial tests are carried out to clarify the soil dynamic properties such as shear modulus and value of material damping of clay under undrained cyclic loading conditions. The results show that no obvious dependency on initial shear stress and effective confining stress are recognized in the shear modulus and damping ratio plotted versus strain. However, the shear modulus decreases and the damping ratio increases with increasing axial strain. When compared with others, it is also revealed that the shear moduli are distributed within the range curves obtained using empirical equations derived by Marcuson et al. (3) and Kokusho et al. (4), and damping ratios are distributed between the curves obtained by Kokusho et al. (4) and Ishihara et al. (9).

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MEE 기법으로 성장한 InGaAs 양자점의 크기 변화에 따른 광발광 특성분석

  • Ha, Seung-Gyu;Jo, Nam-Gi;Song, Jin-Dong;Park, Jae-Gyu;Lee, Dong-Han;Choe, Won-Jun;Lee, Jeong-Il
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.116-116
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    • 2010
  • 단일 양자점의 특성 분석 및 이를 활용한 단광자 광원 등으로의 응용에 있어서 표면밀도 및 크기 등이 의도대로 조절된 양자점 성장이 필수적이며, 이와 관련하여 근적외선 파장 영역에서 발광 성분을 갖는 InGaAs/GaAs 양자점 시료를 MEE (Migration Enhanced Epitaxy) 기법으로 성장하였다. 이 때, 30 초 120 초 사이의 migration enhancing time 변화에 의하여 약 $350\;QDs/{\mu}m^2$에서 $3\;QDs/{\mu}m^2$ 사이의 범위로 양자점 표면 밀도가 조절되었으며 양자점의 크기도 변화하는 것을 확인하였다. 별도로 capping layer를 성장하지 않은 양자점 층에 대한 AFM 측정을 통하여 양자점의 크기를 예측하였으나, 실제 시료의 양자점 크기는 capping layer 성장시의 온도 및 압력에 따른 영향이나 물질 조성의 불균일성 등으로 인해 달라질 수 있으므로 비파괴 검사방법인 광발광 측정으로써 실제 양자점의 특성을 검증할 필요성이 존재한다. 먼저 양자점의 크기가 커짐에 따라 기저상태의 에너지 밴드갭 크기가 감소하는 경향이 있음을 확인하였다. 이는 양자점이 클수록 양자구속 효과가 작아지는 일반적인 경향과 일치한다. 또한, 양자점의 크기 차이에 따른 기저상태 및 고차 여기 상태의 에너지 밴드갭 차이의 변화 경향을 분석하였다. 일반적으로 양자점의 크기가 줄어들면 양자구속효과 또한 빠르게 증가하다가 결국에는 에너지 장벽(barrier)의 에너지 준위에서 포화상태에 도달하게 된다. 이러한 양자점 크기에 따른 양자구속효과 크기의 변화는 고차 여기 상태일수록 더욱 빠르며, 결국에는 양자 구속효과가 없어지는 상태(unbound exciton)에 이르기도 한다. 따라서 기저상태의 에너지 밴드갭은 양자점이 커짐에 따라 단조감소 경향을 보이나, 변화율의 차이 때문에 기저상태와 1차 여기상태의 에너지 차이인 level spacing 값은 단조감소 경향이 아닌 종 모양의 경향성을 보이며 측정 결과 또한 이와 일치하였다. 이와 같이 migration enhancing time의 조절로 광자와 상호작용하는 실질적인 양자점의 크기가 의도대로 조절되었음을 비파괴 광측정법으로 확인하였다.

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Gnawing and Escaping Behaviors of Monochamus alternatus (Coleoptera: Cerambycidae) in a Confined Environment: Suggesting a Bioassay Method of Netting for Adult Escape Prevention (인위적 구속환경에서 솔수염하늘소의 쏠기와 탈출행동: 성충탈출 방지용 그물망의 생물검정법 제안)

  • Ko, Gyeong hun;Kim, Dong-Soon
    • Korean journal of applied entomology
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    • v.56 no.2
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    • pp.187-193
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    • 2017
  • The Japanese pine sawyer, Monochamus alternatus Hope, is a representative vector of the pine wood nematode, Bursaphelenchus xylophilus, which causes wilting symptoms in pine trees. A control method using a net has been introduced, which is an alternative method to the fumigation for the control of dead pine trees by pine wilt disease. This study was carried out to investigate the factors that induce gnawing and escaping behaviors of M. alternatus. The behaviors were examined after M. alternatus adult was placed in a confined space at different temperatures. M. alternatus adults could escape through mesh net torn by gnawing when they were confined in a space of 30 mm or less in diameter. The success rate of escape was high at 20 to $30^{\circ}C$, and no adults escaped at $15^{\circ}C$. The enticement of M. alternatus adults by food didn't affect the success rate of escape. In the case of not being confined in a narrow space, the escaping hole could not be formed because the gnawing was not concentrated on one part. M. alternatus moved its body in a narrow space using the tarsus of middle and hind legs, and made an escape hole by concentrically gnawing the obstacle on the front side with mandible, and showed a behavior of getting out while supporting the body by supporting the front legs. The present results will be able to use as an important basic information for evaluating the performance of mesh net which confines M. alternatus adults and suggested by alternative method to fumigation technology.

Stress-Strain Responses of Concrete Confined by FRP Composites (FRP 합성재료에 의하여 구속된 콘크리트의 응력-변형률 응답 예측)

  • Cho, Soon-Ho
    • Journal of the Korea Concrete Institute
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    • v.19 no.6
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    • pp.803-810
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    • 2007
  • An analytical method capable of predicting various stress-strain responses in axially loaded concrete confined with FRP (fiber reinforced polymers) composites in a rational manner is presented. Its underlying idea is that the volumetric expansion due to progressive microcracking in mechanically loaded concrete is an important measure of the extent of damage in the material microstructure, and can be utilized to estimate the load-carrying capacity of concrete by considering the corresponding accumulated damage. Following from this, an elastic modulus expressed as a function of area strain and concrete porosity, the energy-balance equation relating the dilating concrete to the confining device interactively, the varying confining pressure, and an incremental calculation algorithm are included in the solution procedure. The proposed method enables the evaluation of lateral strains consecutively according to the related mechanical model and the energy-balance equation, rather than using an empirically derived equation for Poisson's ratio or dilation rate as in other analytical methods. Several existing analytical methods that can predict the overall response were also examined and discussed, particularly focusing on the way of considering the volumetric expansion. The results predicted by the proposed and Samaan's bilinear equation models correlated with observed results with a reasonable degree, however it can be judged that the latter is not capable of predicting the response of lateral strains correctly due to incorporating the initial Poisson's ratio and the final converged dilation rate only. Further, the proposed method seems to have greater benefits in other applications by the use of the fundamental principles of mechanics.

An Adaptive Viterbi Decoder Architecture Using Reduced State Transition Paths (감소된 상태천이 경로를 이용한 적응 비터비 복호기의 구조)

  • Ko, Hyoungmin;Cho, Won-Kyung;Kim, Jinsang
    • The Journal of Advanced Navigation Technology
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    • v.8 no.2
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    • pp.190-196
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    • 2004
  • The development of a new hardware structure which can implement the viterbi algorithm efficiently is required for applications such as a software radio because the viterbi algorithm, which is an error correction code function for the second and the third generation of mobile communication, needs a lot of arithmetic operations. The length of K in the viterbi algorithm different from each standard, for examples, K=7 in case of IS-95 standard and GSM standard, and K=9 in case of WCDMA and CDMA2000. In this paper, we propose a new hardware structure of an adaptive viterbi decoder which can decode the constraint length in K=3~9 and the data rate in 1/2 ~ 1/3. Prototyping results targeted to Altera Cyclon EPIC20F400C8, shows that the proposed hardware structure needs maximum 19,276 logic elements and power dissipation of 222.6 mW.

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Design Optimization of a RC Building Structure using an Approximate Optimization Technique (근사최적화 기법을 이용한 RC 빌딩의 구조 최적설계)

  • Park, Chang-Hyun;Ahn, Hee-Jae;Choi, Dong-Hoon;Jung, Cheul-Kyu
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.24 no.2
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    • pp.223-233
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    • 2011
  • A design optimization problem was formulated to minimize the volume of an RC building structure while satisfying design constraints on structural displacements under vertical, wind and seismic loads. We employed metamodel-based design optimization using design of experiments, metamodeling and optimization algorithm to circumvent the difficulty of the automation of structural analysis procedure. Especially, we proposed a design approach of repetitive design optimizations by stages with changing the side constraint values on design variables and limit values on design constraints until a satisfactory design result was obtained. Using the proposed design approach, the volume of the RC building structure has been reduced by 53.3 % compared to the initial one while satisfying all the design constraints. This design result clearly shows the validity of the proposed design approach.

Fractals and Fragmentation of Survivor Grains within Gouge Zones along Boundary Faults in the Tertiary Waeup Basin (제3기 와읍분지 경계단층을 따라 발달하는 단층비지 내 잔류입자의 프랙탈과 파쇄작용)

  • Chang, Tae-Woo
    • The Journal of Engineering Geology
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    • v.20 no.2
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    • pp.183-189
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    • 2010
  • Fault gouge samples were collected from the fault cores of the boundary faults between the Cretaceous Basement and the Tertiary Waeup Basin. Fractal dimensions (D) were obtained by using survivor grains which were analysed from six thin sections of the gouges under the optical microscope. The elliptical survivor grains show a shape preferred orientation almost parallel to clay foliation in matrix, suggesting that it was formed by the rotation of the survivor grains in abundant fine-grained matrix during repeated fault slips. The size distributions of the survivor grains follow power-laws with fractal dimensions in the 2.40-3.02 range. D values of all samples but one are higher than a specific D value equal to 2.58 which predicts the self similarity of fragmentation process in constrained comminution model (Sammis et al., 1987), which indicates large fault slip and multiple faulting. Probably the higher D values than 2.58 mean the non-self-similar evolution of cataclastic rocks where fragmentation mechanism changed from constrained comminution to the grain abrasion accompanying selective fracture of larger grains.

Dynamic Behavior of Unsaturated Decomposed Granite Soils under Low Shear Strain Amplitude (저전단변형율에서의 불포화화강풍화토의 동적 거동)

  • Huh, Kyung-Han;Baek, Joong-Yuk
    • Journal of Korean Society of Hazard Mitigation
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    • v.5 no.2
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    • pp.57-63
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    • 2005
  • In case of general structures, it has been known that the strain amplitude band experienced by the base in a state of service load is less than 1% and most of the base show low, strain amplitude behavior less than 0.01%. In this study examining the influence affected to dynamic behavior in a condition of the low strain amplitude of unsaturated decomposed granite soils, the resonant column test, using some samples in Su-won area, has been performed for each degree of saturation resulted from different void ratios and confined stress. It is found out that the minimum value of the damping ratio occurred in roughly $17{\sim}18%$ according to void ratios regardless of confined pressure in the same manner with the case of the maximum shear elastic modulus; and it is estimated that for the influence of surface tension in the optimum degree of saturation, the damping ratio appears to be least.

Evaluation of Shear Wave Velocity of Engineering Fill by Resonant Column and Torsional Shear Tests (공진주와 비틂전단시험에 의한 성토지반의 전단파속도 추정에 관한 연구)

  • Park, Jong-Bae;Sim, Young-Jong;Jung, Jong-Suk;Park, Yong-Boo
    • LHI Journal of Land, Housing, and Urban Affairs
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    • v.2 no.4
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    • pp.387-395
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    • 2011
  • According to the seismic design criteria for structural buildings in Korea, the ground is classified into 5 types based on the average shear wave velocity measured from elastic wave tests on site and seismic load applied to the structure is estimated. However, elastic wave tests in site, however, on the engineering fill, cannot be performed during the construction period. Therefore, to evaluate shear wave velocity considering field conditions, resonant column (RC) and torsional shear (TS) tests are performed and compared with various elastic wave test results. As a result, if confining pressure for the tests using engineering fill are considered properly, we can obtain similar results comparing with those of elastic wave tests. In addition, by considering the effect of maximum shear modulus and confining pressure by RC/TS tests, n values shows typical values ranging from 0.434 to 0.561 so that utilization of RC/TS tests can be useful to infer shear modulus in field.

Optimal Design of Nonuniform Transmission Lime Sections for Wide-Band Impedance Matching (광대역 임피이던스정합용 불균일군차선로의 최적설계)

  • 박송배
    • Journal of the Korean Institute of Telematics and Electronics
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    • v.11 no.6
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    • pp.38-43
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    • 1974
  • A design problem is studied for a nonuniform transmission line (NUTL) section to be inserted between an arbitrary source impedance and an arbitary load impedance for the purpose of impedance matching or providing a minimum input reflection coefficient over a frequency ranee as wide as possible. A special class of NUTL's, yet comprehensive enough to include almost all smoothly varying lines, are considered. Power series expansions of the ABCD parameters of such lines are used in the calculation of the input reflection coefficient. The design problem is formulated as a nonlinear programming problem withnonlinear constraints and is solved by a combined use of the sequential unconstrained minimization technique and tile Fletcher-Powell method. As a result, a line section was obtained which shows a marked improvement over any one hitherto published as a wide-band impedance matching device.

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