• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.04a
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• pp.195-198
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• 2005

The role of elastic/plastic mismatch on the contact crack initiation is investigated for designing desirable surface-coated asymmetric layered composites. Various layered composites such as $Si_3N_4$ ceramics on $Si_3N_4+BN$ composite, soda-lime glass on various substrates with different elastic modulus for the analysis. Spherical indentation is conducted for producing contact cracks from the surface or interface between the coating and the substrate layer. A finite element analysis of the stress fields in the loaded layer composites enables a direct correlation between the damage patterns and the stress distributions. Implications of these conclusions concerning the design of asymmetric layered composites indicate that the elastic modulus mismatch is one of the important parameter for designing layered composite to prevent the initiation of contact cracks.

• Journal of electromagnetic engineering and science
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• v.16 no.4
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• pp.206-209
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• 2016

This letter proposes a reconfigurable directional coupler that uses a variable impedance mismatch reflector to achieve high isolation characteristics in the antenna front end. The reconfigurable coupler consists of a directional coupler and a single-pole four-throw (SP4T) switch with different load impedances as a variable load mismatch reflector. Selection of the load impedance by the reflector allows cancellation of the reflected signal due to antenna load mismatch and the leakage from the input to isolation port of the directional coupler, resulting in high isolation characteristics. The performance of the proposed architecture in separating the received (Rx) signal from the transmitted (Tx) signal in the antenna front end was verified by implementing and testing the reconfigurable coupler at 917 MHz for UHF radio-frequency identification (RFID) applications. The proposed reconfigurable directional coupler showed an improvement in the isolation characteristics of more than 20 dB at the operation frequency band.

• Journal of Mechanical Science and Technology
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• v.17 no.11
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• pp.1638-1649
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• 2003

A study is made on the characterization of damage tolerance by spherical indentation in hardly coated layer structure with modest elastic modulus mismatch. A hard silicon nitride is prepared for the coating material and silicon nitride with 5wt% of boron nitride composites for underlayer. Hot pressing to eliminate the effect of interface delamination during the fracture makes strong interfacial bonding. The elastic modulus mismatch between the layers is not only large enough to suppress the surface crack initiation from the coating layer but sufficiently small to prevent the initiation of radial crack from the interface. The strength degradation of the layer structure after sphere contact indentation does not significantly occur, while the degradation of silicon nitride-boron nitride composite is critical at a high load and high number of contacts.

• Journal of the Korean Arthroscopy Society
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• v.1 no.1
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• pp.55-62
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• 1997

Various surgical techniques has been advocated for reconstruction of anterior cruciate ligament using the bone-patella tendon-bone graft. Recently endoscopic technique provides good clinical results, with minimal skin incision, accurate positioning of the graft to the femoral tunnel, and decreasing wear rate of the graft. But the graft-tunnel mismatch remains problematic in endoscopic technique. The purpose of this paper is to described causes of the graft-tunnel mismatch and to provide important steps to prevent or minimize the graft-runnel mismatch following anterior cruciate ligament while using the endoscopic technique. Our guideline for prevention of the graft-tunnel mismatch are as follows: (1) The tunnel should he positioned closely to isometric point as much as possible. (2) Anterior placement of the tunnel should be avoided. (3) The change of graft length should be within 2mm between flexion and extension position.

• Proceedings of the Korean Society for Cognitive Science Conference
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• 2000.05a
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• pp.49-54
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• 2000

인지 기능의 신경생리적 지표로 널리 사용되고 있는 P300은 정보처리 과정 중 통제정보처리를 반영한다고 알려져 있다. P300 이전에 관찰되는 mismatch negativity 역시 정보처리과정의 초기단계를 반영하며 불수의적 주의력이나 자동적 각성수준 혹은 감각 기억의 기능을 갖고 있다고 한다. 이러한 초기 단계의 과정을 나타내는 mismatch negativity(MMN)가 P300과 어떤 관련을 갖는가를 조사하였다. 실험 결과 Fz와 Cz에서 측정한 MMN의 진폭과 Pz에서의 P300 진폭사이에 유의미한 상관이 있음이 관찰되었다. 이는 정보의 처리가 효율적으로 처리되기 위해서는 처리 과정의 초기 단계인 자동적 정보처리와 통제정보처리가 서로 밀접하게 연관되어 작용한다는 것을 시사한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.4
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• pp.206-208
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• 2014

In this letter, IQ mismatch of a CA-supporting terminal for LTE-A is analyzed and each of the analog blocks is modeled mathematically. Based on the model, a new digital calibration algorithm is proposed and verified using simulation results.

• ETRI Journal
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• v.28 no.2
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• pp.231-234
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• 2006

The cancellation performance of a linearization loop is limited by the degree of an amplitude imbalance and a phase imbalance. A delay mismatch causes a phase variation as a function of frequency. Therefore, the cancellation performance and linearization bandwidth are limited by a delay mismatch. The expression for the effects of an amplitude imbalance, a phase imbalance, and a delay mismatch on the characteristics of a linearization loop is derived and analyzed. The simulation results are compared with the results obtained by means of using a commercial simulation tool and the exact agreement is reported. The derived equation could be used in designing a linearization loop and predicting the cancellation performance of the linearization loop usefully. Some useful characteristics, known from the simulation results obtained by using the derived equation, of a linearization loop for designing and implementing feedforward amplifiers are described in detail.

• Journal of the Korea Institute of Military Science and Technology
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• v.3 no.2
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• pp.213-218
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• 2000

An experimental study was performed to investigate the effect of surface temperature mismatch on measurements of skin friction using a plug-type skin friction gage mounted on the side wall of a supersonic wind tunnel. The freestream Mach number was 2.4 and Reynolds number per meter was $5.25 {\times}10^7$ with total pressure of 50 psi and total temperature of 275K. Temperature mismatch between the gage surface and surrounding wall surface was generated by hot water injection using the active temperature control system. Results of the tests showed that the temperature mismatch made sizable effects on the measurements of skin friction.

• ETRI Journal
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• v.27 no.4
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• pp.377-384
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• 2005

We investigate near-infrared light (NIR) propagation in a model of an adult head using an extensive Monte Carlo (MC) simulation. The adult head model is a four-layered slab which consists of a surface layer, a cerebrospinal fluid layer, a gray-matter layer, and a white-matter layer. We study the effects of a refractive index mismatch on the model, calculating the intensity of detected light, mean flight time, and partial mean flight time of each layer for various refractive indices of the cerebrospinal fluid layer as functions of source-detector spacing. The Monte Carlo simulation shows that the refractive index mismatch presents very rich results including rapidly decaying intensity of detected light and a peak and cross-over in the partial mean flight time with source-detector spacing. We also investigate spatial sensitivity profiles at various source-detector spacings, discussing the index mismatch effect on the model.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.2
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• pp.315-319
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• 2011

A switched-capacitor cyclic DAC scheme with mismatch compensation of capacitors is designed. In cyclic DAC, a little error between two capacitors is accumulated every cycle. As a result, the accumulated error influences the final analog output which is wrong data. Therefore, a mismatch compensation technique was proposed and the error can be effectively reduced, which alleviates the matching requirement. In order to verify the operation of the proposed DAC, an 8-bit switched-capacitor cyclic DAC is designed through HSPICE simulation and implemented through magna 0.18um standard CMOS process.