• Journal of IKEEE
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• v.22 no.2
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• pp.339-343
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• 2018

Power semiconductors are semiconductors capable of controlling power over 1W and are mainly used as switches. This power semiconductor device has been developed with the goal of reducing power consumption and high breakdown voltage. This research was analyzed electrical characteristics of IGBT(Insulated Gate Biopolar Transistor) according to diffusion length of JFET region. The Diffusion length of JFET region was controlled by temperature and time using T-CAD simulator. As a result of experiments, we could obtain 1.14V low on state voltage drop by fixing 1440V breakdown voltage.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.7
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• pp.529-535
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• 2016

In this theoretical study, the strength parameters of the Drucker-Prager yield criterion and Mohr-Coulomb yield criterion were set to equal values, in order to analyze the correlation among the parameters. The Drucker-Prager strength parameters ${\alpha}$ and k were represented by the Mohr-Coulomb strength parameters c and ${\phi}$. Specifically it can be seen that k is function of c, ${\phi}$ and ${\alpha}$ is function of ${\phi}$ alone. Drucker-Prager strength parameter ${\alpha}$ increases as the internal friction angle of soil increases. ${\alpha}_{av}$ which is the average of ${\alpha}_c$ and ${\alpha}_i$ was proportional to internal friction angle in which ${\alpha}_c$ and ${\alpha}_i$ are ${\alpha}$ values corresponding to the circles of the Drucker-Prager yield cirteria circumscribes and inscribes the Mohr-Coulomb yield criterion respectively. The values of the ${\alpha}_{av}$ was 0.07 and 0.29 which correspond to the internal friction angle of $10^{\circ}$ and $45^{\circ}$ respectively. In addition, value of ${\alpha}_c/{\alpha}_i$ was proportional to internal friction angle of soil and the values of ${\alpha}_c/{\alpha}_i$ 1.12 and 1.62 which corresponds to internal friction angle of $10^{\circ}$ and $45^{\circ}$ respectively.The influence of the Mohr-Coulomb strength parameters on the Drucker-Prager strength parameter k was investigated and it was found that k was mainly influenced by the cohesion of the soil, except in the case of the minimum assumed value of c of 10kPa. The deviator stresses, $S_{c0}$ and $S_{t0}$, which correspond to the cases of the Mohr-Coulomb yield criterion under uniaxial compression and uniaxial tension, respectively, and $S_{0(ave)}$, which is the average value of $S_{c0}$ and $S_{t0}$, decrease as the internal friction angle increases. Furthermore, the hexagon, which represents the Mohr-Coulomb yield locus, becomes more irregular, and the deviations of $S_{c0}$ and $S_{t0}$ from $S_{0(ave)}$ also increase, as the internal friction angle increases.

• The Korean Journal of Rheology
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• v.9 no.4
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• pp.200-205
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• 1997

등방상에서는 폴리파라페닐렌테레프탈아미드(PPD-T)와 히드록시 프로필 셀룰로오 스(HPC)가 비슷한 유변학적 거동을 보였다. 그러나 이방성에서는 네마틱상을 형성하는 PPD-T와 콜레스테릭상(또는 꼬인 네마틱상)을 형성하는 HPC는 상이한 유변학적 특성을 나타냈다. 이방상을 나타내는 임계농도(C*)이상의 농도에서 Herchel-Bulkey 모델에 의해 얻 어진 항복응력을 보면 HPC의 경우 농도에 관계없이 거의 일정한 값을 나타낸 반면PPD-T 의경우에는 농도증가와 더불어 항북응력값이 크게 증가하였다. 또한 PPD-T가 일\ulcorner거으로 HPC보다 큰값의 항복응력을 나타냈다. 진동수 1 rad/s 에서는 PPD-T와 HPCahen 탄성계 수 G＇/2G＂가 농도의 증가와 더불어 증가하엿다. 그러나 100rad/s 에서는 HPCdmlruddn 임계농도이상의 농도에서 농도증가와 더불어 탄성계수값이 단순감소한 반면 PPD-T의 경우 에는 포화농도(B-point)이상의 농도에서 농도증가와 더불어 탄성계수값이 계속적으로 증가 하였다. HPC의 경우 저장탄성률이 변형정도의 영향을 받지 않았으나 PPD-T의 경우에는 저장탄성률이 변형정도에 매우 민감하였다.

• Journal of the Korean GEO-environmental Society
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• v.18 no.3
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• pp.25-30
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• 2017

This paper introduces a novel method to quantify the morphological evolution of the strain response envelope. The strain response envelope is defined as an image in strain increment space corresponding to the unit stress input in stress space. Based on the shape of strain response envelopes, the deformation characteristics of soils can be described using the framework of elastic-plastic theory. Fourier descriptor analysis was used to investigate the morphological characteristics of strain response envelopes. The numerical results show that when the stress input remains in the initial yield surface the Fourier descriptors remain constant. Once the stress input crosses the initial yield surface, every descriptors deals in this study change. Numerical and experimental results of this study show that clear yielding response is only found in natural block samples. Among the Fourier descriptors, the descriptor called as asymmetry is the best for detecting the yield and is minimally sensitive to the number of input stress paths.

• Journal of the Korean Wood Science and Technology
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• v.44 no.1
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• pp.67-74
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• 2016

The yield shear strength of bolt connection in glass fiber reinforced glulam was predicted using a design-based equation, and was compared to the empirical yield shear strength. For the predicted equation, the mechanical properties of member (the elastic modulus, Poisson's ratio, shear modulus) was tested. The fracture toughness factor ($K_{ft}$) of glass fiber reinforced glulam was reflected to the revision of the design equation of bolted connection. The compressive strength properties to grain direction was influenced by annual ring angle and width of lamina. Compared with the revised yield shear strength of reinforced glulam, it was tended to be similar to the empirical yield shear strength on the diameter of bolt and the reinforcements. The revised yield shear strength from proposed formula of KBC was most appropriately matched in the bolt connection of the glass fiber reinforced glulam.

• Journal of Korean Society of Steel Construction
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• v.19 no.3
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• pp.291-301
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• 2007

The overlay model is a certain kinds of numerical analysis method to present the material non-lineariy which is represented the baushinger effect and the strain hardening. This model simulates the complex behavior of material by controlling the properties of the layers which like the hardening ratio, the section area and the yield stress. In this paper, the constitutive equation and plastic flow rule of each layer which are laid in the plane stress field are obtained by using the thermodynamics. Two numerical examples were tested for the validity of proposed method in uniaxial stress and plane stress field with comparable experimental results. The only parameter for the test is the yield stress distribution of each layers.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.3
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• pp.672-677
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• 2013

This paper have analyzed the change of breakdown voltage for channel dimension of double gate(DG) MOSFET. The breakdown voltage to have the small value among the short channel effects of DGMOSFET to be next-generation devices have to be precisely analyzed. The analytical solution of Poisson's equation have been used to analyze the breakdown voltage, and Gaussian function been used as carrier distribution to analyze closely for experimental results. The breakdown voltages have been analyzed for device parameters such as channel thickness and doping concentration, and projected range and standard projected deviation of Gaussian function. Since this potential model has been verified in the previous papers, we have used this model to analyze the breakdown voltage. As a result, we know the breakdown voltage is influenced on Gaussian function and device parameters for DGMOSFET.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.10a
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• pp.811-814
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• 2012

This paper have analyzed the change of breakdown voltage for channel dimension of double gate(DG) MOSFET. The breakdown voltage to have the small value among the short channel effects of DGMOSFET to be next-generation devices have to be precisely analyzed. The analytical solution of Poisson's equation have been used to analyze the breakdown voltage, and Gaussian function been used as carrier distribution to analyze closely for experimental results. The breakdown voltages have been analyzed for device parameters such as channel thickness and doping concentration, and projected range and standard projected deviation of Gaussian function. Since this potential model has been verified in the previous papers, we have used this model to analyze the breakdown voltage. Resultly, we know the breakdown voltage is influenced on Gaussian function and device parameters for DGMOSFET.

• Journal of the Korea Institute of Building Construction
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• v.16 no.6
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• pp.505-512
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• 2016

Even though high performance concrete was developed according to the trend of bigger and higher of reinforced concrete building, the rheological evaluations such as viscosity, yield stress are not enough to use as input data to accomplish the numerical analysis for the construction design. So there are many problems in the harden concrete such as poor compaction, rock pocket and crack, etc. in the field. In this study, consistency curves were measured by the viscometer as hydration reaction time passed. At the same time the slump flow test and Vicat setting test were carried out for comparing with the results of rheological properties. The fluidity of the W/B 30% decreased as the increase of replacement ratio of blast furnace slag. But in case of W/B 40%, the replacement ration did not significantly influenced to the slump flow value with the passage of hydration time. By the replacement of blast furnace slag to cement, initial setting was delayed and the time gap between initial and final setting became shorten. Through the regression analysis using Bingham model, there are a sudden changes of viscosity and yield stress around initial setting in case of low W/B 30%. The increase of workability by the change of free water in cement paste was offset by the coating effect of impermeable layer in case of W/B 40%.

• Journal of the Korean Society of Food Science and Nutrition
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• v.22 no.2
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• pp.181-185
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• 1993

The effects of concentrations (6~9%), heating temperatures (80, 85, 90 and 95$^{\circ}C$) and heating methods (continuous, method A and instantaneous, method B) on the flow properties of cowpea flour (air-dried sediment) at 6$0^{\circ}C$ were studied. The gelatinized cowpea flour dispersions by method B had higher values of yield stress and consistency index but lower value of flow behavior index compared to those values of method A. The log values of consistency index were positively correlated with the concentration and heating temperature for both methods. The rate of increase in the consistency index value by method B at the same concentration was greater in all heating temperatures than that by method A.