• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.2 s.93
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• pp.217-221
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• 2005

The E-field intensity by mobile handsets in a phantom is measured by a 3 axes miniature probe. The detected DC voltage by a Schottky diode in a probe has nonlinear characteristics by itself. If a pertinent diode compression point (DCP) is applied for the compensation specific absorption rate(SAR) as much as 200 W/kg can be measured with a good measurement accuracy.

• Current Optics and Photonics
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• v.1 no.6
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• pp.649-654
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• 2017

In this communication, we present an expression to determine thermal lensing in isotropic materials. The heat equation is analytically solved when a Gaussian spatial laser beam profile is introduced to a cylindrical geometry of optics using a complete set of Bessel functions. This expression permits explicit calculation of variation of focal length induced by thermal lensing and allows thermal effects for various material parameters on the optics. We applied our model to a high absorption material (Ti:sapphire) and also transparent material (thallium garnet or TGG) and found that the thermal lensing can be reduced more than 4 times by adjusting the laser beam waist and optics dimensions. Our analysis is completely general and applicable to any optical system.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.298-303
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• 2001

The critical thickness of an epitaxial film on a substrate in electronic or optoelectronic devices is studied on the basis of equilibrium dislocation analysis. Two geometric models, a single dislocation and an array of dislocations in heteroepitaxial system, are considered respectively to calculate the misfit dislocation formation energy. The isotropic linearly elastic stress fields for the models are obtained by means of complex potential method combined with alternating technique, and are used for calculating the formation energies. As a result, the effect of elastic mismatch between film and substrate on critical thickness is presented and $Si_xGe_{1-x}/Si$ epitaxial structure is analyzed to predict the critical thickness with varying germanium concentration.

• Journal of Pharmaceutical Investigation
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• v.40 no.5
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• pp.263-267
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• 2010

Nanoemulsions have been widely investigated for many years because of their attractive and unique characteristics. Nanoemulsions are composed of oil, surfactant, co-surfactant and water. Especially, cosurfactant plays a critical role in formation of nanoemulsions. In pharmaceutical area, a pre-concentrate form of nanoemulsions which is known as self-nanoemulsifying drug delivery systems (SNEDDS) was available for some water-insoluble drugs. In this study, we investigated the functional behaviors of cosurfactant in design of SNEDDS and nanoemulsions. Cremophor RH 40$^{(R)}$, Propylene carbonate and medium chain triglyceride were selected for surfactant, cosurfactant and oil, respectively. Cyclosporine was employed as a drug. Phase diagrams showed the area of isotropic o/w region which forms o/w nanoemulsions was not significantly affected by the compositional ratio of cosurfactant. But, drug solubilization capacity, droplet size of nanoemulsions and drug release rate were greatly affected by the cosurfactant.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1994.10a
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• pp.617-622
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• 1994

In this paper, we perform a two-stage, kinematic optimal design for 3 degree-of-freedom excavator system which consists of boom, arm, and bucket. The objective of the first stage is to find the optimal joint parameters which maximize the force-torque transmission ratio between the hydraulic actuator and the rotating joint. The objective of the first stage is to find the optimal link parameters which maximize the isotropic characteristic throughout the workspace. It is illustrated that performances of the optimized excavator are improved compared to those of HE280 excavator, with respect to the described performace index and maximum load handling capacity.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.696-702
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• 2006

Flutter characteristics of composite curved wing were investigated in this study. The efficient and robust system for the flutter optimization of general composite curved wing models has been developed using the coupled computational method based on both the standard genetic algorithm and the micro genetic algorithms. Micro genetic algorithm is used as an alternative method to overcome the relatively poor exploitation characteristics of the standard genetic algorithm. The present results show that the micro genetic algorithm is more efficient in order to find optimized lay-ups for a composite curved wing model. It is found that the flutter stability of curved wing model can be significantly increased using composite materials with proper optimum lamination design when compared to the case of isotropic wing model under the same weight condition.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.13 no.2
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• pp.67-74
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• 2017

Recently there have been many concerns on structural integrity of nuclear piping under seismic loadings. In terms of failure of nuclear piping due to seismic loadings, an important failure mechanism is low cycle fatigue with large cyclic displacements. To investigate the effects of seismic loading on low cycle fatigue behavior of nuclear piping, the cyclic behavior of materials and nuclear piping needs to be accurately estimated. In this paper, the non-linear finite element (FE) analyses have been carried out to evaluate the effects of three different cyclic hardening models on cyclic behavior of materials and nuclear piping, such as isotropic hardening, kinematic hardening and combined hardening.

• 한국정보디스플레이학회:학술대회논문집
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• 2000.01a
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• pp.61-62
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• 2000

We have studied the molecular orientation by the phase transitions of the chiral smectic liquid crystals, 4-(1-Trifluoromethyl-6-ethoxy-hexyloxycarbonlphenyl)-4-nonyloxybiphenyl-4-carbo-xylate (R-TFMEOHPNBC) to seek the original solution of the zig-zag defect using two different experimental techniques; optical system and x-ray scattering. The phase sequence is gamma ferroelectric $(SmC{\gamma}\;^*)$ ${\rightarrow}$ smectic A (SmA) ${\rightarrow}$ isotropic (I). Existence of two layer spacing at chiral smectic phase gives a possibility of the molecular orientation in two different tilt angles, ${\theta}\;_1$ and ${\theta}\;_2$, which are separated each other to the layer normal at a given temperature. The gamma ferroelectric-like phase is, first, discovered in the single compound.

• Journal of the Korean Society for Railway
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• v.9 no.1 s.32
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• pp.57-62
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• 2006

Composite thin-walled members for civil engineering application are mainly produced by pultrusion technique, and they are generally made of a polymeric resin system reinforced by E-glass fibers due to economical reason. This material combination results in low elastic moduli of the composite materials and makes the design of composite members to be governed by stability limit state. Therefore the buckling behavior of composite thin-walled members was experimentally investigated in the present study. Axial compression was applied on each specimens by a hydraulic ram and knife edge fixtures were placed at both ends to simulate simple boundary condition. Axial compression, lateral displacements and twisting at the mid-height of each specimen were measured by a set of transducers during buckling test. The experimental buckling loads were compared with analytical results obtained through isotropic formulas. In the calculation of analytical results, elastic properties such as Young's modulus(E) and shear modulus(G) were replaced with EL and GLT obtained from coupon tests, respectively.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.11a
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• pp.106-109
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• 2000

Impact tester was build up to evaluate the characterization of CFRP laminate plates under the low velocity impact. The tests were conducted on several laminates of different ply orientation A system was budded for the impact strength of CFRP laminates in consideration of stress wave propagation theory using drop-weight impact tester as one of impact test. Results indicate that absorbed energy of quasi-isotropic specimen having four interfaces is higher than that of orthotropic laminates with two interfaces. Also the damage area was measured with ultrasonic C-scanner on some samples. In the specimens the relationship was linear between damaged area and absorbed energy to some degree. Absorbed energy in the specimen that ply number, interface number and fiber stacking sequences is same but having hybrid is higher than that of orthotropic laminates without hybrid.