• ETRI Journal
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• 제26권3호
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• pp.229-240
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• 2004

This paper reports on our development of a dual-mode transceiver for a CMOS high-rate Bluetooth system-onchip solution. The transceiver includes most of the radio building blocks such as an active complex filter, a Gaussian frequency shift keying (GFSK) demodulator, a variable gain amplifier (VGA), a dc offset cancellation circuit, a quadrature local oscillator (LO) generator, and an RF front-end. It is designed for both the normal-rate Bluetooth with an instantaneous bit rate of 1 Mb/s and the high-rate Bluetooth of up to 12 Mb/s. The receiver employs a dualconversion combined with a baseband dual-path architecture for resolving many problems such as flicker noise, dc offset, and power consumption of the dual-mode system. The transceiver requires none of the external image-rejection and intermediate frequency (IF) channel filters by using an LO of 1.6 GHz and the fifth order onchip filters. The chip is fabricated on a $6.5-mm^{2}$ die using a standard $0.25-{\mu}m$ CMOS technology. Experimental results show an in-band image-rejection ratio of 40 dB, an IIP3 of -5 dBm, and a sensitivity of -77 dBm for the Bluetooth mode when the losses from the external components are compensated. It consumes 42 mA in receive ${\pi}/4-diffrential$ quadrature phase-shift keying $({\pi}/4-DQPSK)$ mode of 8 Mb/s, 35 mA in receive GFSK mode of 1 Mb/s, and 32 mA in transmit mode from a 2.5-V supply. These results indicate that the architecture and circuits are adaptable to the implementation of a low-cost, multi-mode, high-speed wireless personal area network.

• 한국간호교육학회지
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• 제16권1호
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• pp.51-60
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• 2010

Purpose: The purpose of this study was to compare the effects of nursing simulations between multi-mode simulation and $SimMan^{(R)}$ simulation on nursing students' nursing competency, satisfaction, and simulation participation experience in nursing care for patients with dyspnea. Method: Subjects were 107 junior nursing students in R College of Nursing in Seoul from June to November in 2009. Students were allocated to either a Multi-mode simulation group or a $SimMan^{(R)}$ simulation group. The multi-mode simulation consisted of standardized patients combined with Vital Sim, comparing the $SimMan^{(R)}$ group. Result: The Multi-mode simulation group reported higher levels of nursing competency (p=.017) but lower communication skills (p<.001) compared to the $SimMan^{(R)}$ simulation group. There were no meaningful differences in satisfaction of simulation education between the two groups. The $SimMan^{(R)}$ simulation group received a substantial health assessment and the Multi-mode simulation group experienced reality in caring for standardized patients. Conclusion: The findings of this study demonstrated that Multi-mode simulation has similar educational effects like $SimMan^{(R)}$ simulation and suggest that nurse educators should match simulation fidelity with educational goals for effective education.

• 한국통신학회논문지
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• 제19권9호
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• pp.1702-1709
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• 1994

한글인식 후처리에서 문맥정보의 저장구조는 인식율 및 인식속도를 결정짓는 중요한 요소이다. 단어사전의 형태로 문맥정보를 표현하기 위해서는 트라이(trie)를 주로 이용하지만, 기억공간 이용효율이 저조하다는 단점이 있다. 따라서 이 논문에서는 트라이의 장점을 유지하면서 공간효율을 향상시키는 기억구조를 제안한다. 한글은 조합문자이기 때문에 자모나 문자별로 기억시킬 수 있다. 그런데 자모단위로 기억시키면(P-모드) 검색시간은 빠르지만 공간효율이 나쁘고, 또한 문자단위로 기억시키면(C-모드) 공간효율은 좋지만 검색시간이 길어진다. 따라서 노드이용율과 분산율로 최적레벨을 선정한 다음, 입력단어의 시작자모부터 최적레벨까지는 자모 단위의 트라이로 기억시키고, 그 이상은 문자단위의 순차연결구조로 저장시켰다. (H-모드). 6가지 단어집합에 대하여 실험한 결과, H-모드에서의 검색시간은 P-모드만큼 빠르면서, 공간효율은 C-모드와 같게 되어 그 효용성을 확인할 수 있었다.

• 한국정밀공학회지
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• 제13권10호
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• pp.139-145
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• 1996

The machining accuracy and performance is largely influenced by the static, dynamic and thermal characteristics of spindle systems in machine tools, because the spindle system is a intermedium for cutting force from tool and machine powef from motor. Large cutting force and power are transmitted by bearing with a point or line contact. So, the spindle system is the static and dynamic weakest point in machine structure. For improvement of static stiffness of spindle system can be changed design parameters, such as diameter of spindle, stiffness of bearing and bearing span. But for dynamic stiffness, the change of the design parameters are not useful. In this paper, the combined bearing arrangement is suggested for high damping spindle system. The combined bearing arrangement is composed of tandem double back to back arrangement type ball bearins and a high damping hydrostatic bearing. The variation of static deflection and amplitude in first natural frequency is evaluated with the location of hydrostatic bearing between front and rear ball bearing. The optimized location of hydrostatic bearing for high static and dynamic stiffness is determined rapidly and exactly using the mode shape and transfer function of spindle. The calculation of damping effect on vibration by unbalance of grinding wheel and pulley in optimized spindle system is carried out to verify the validity of the combined bearing arrangement. Finally, the simulation of grinding process show that the surface roughness of workpiece with high damping spindle system is 60% better than with ball bearing spindle system.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.529-534
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• 2002

The receptance method was applied for the analysis of a cylindrical shell with a curvaturated plate attached at the top of the shell. The boundary conditions of the shell considered here were clamped at the bottom and free at the top of the shell. Before the analysis of the shell/plate combined structure, the natural frequencies of the plate and the shell were calculated separately and then they were used in the calculation of the frequencies of the combined structure by the receptance method. The frequency equation of the combined structure was derived from the continuity condition at the junction of the shell and the plate. The frequencies for various curvature factors of the plate were presented and compared with those from ANSYS to show its validity of the present method.

• 한국안전학회지
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• 제17권4호
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• pp.52-60
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• 2002

Failure criterion is a parameter to represent the resistance to failure of locally wall thinned pipe, and it depends on material characteristics, defect geometry, applied loading type, and failure mode. Therefore, accurate prediction of integrity of wall thinned pipe requires a failure criterion adequately reflected the characteristics of defect shape and loading in the piping system. In the present study, the finite element analysis was performed and the results were compared with those of pipe experiment to develop a sound criterion for failure of internally wall thinned pipe subjected to combined pressure and bending loads. By comparing the predictions of failure to actual failure load and displacement, an appropriate criterion was investigated. From this investigation, it is concluded that true ultimate stress criterion is the most accurate to predict failure of wall thinned pipe under combined loads, but it is not conservative under some conditions. Engineering ultimate stress estimates the failure load and displacement reasonably for al conditions, although the predictions are less accurate compared with the results predicted by true ultimate stress criterion.

• Geomechanics and Engineering
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• 제28권3호
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• pp.209-224
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• 2022

In this study, the numerical analysis model of π-beam explosion is established to compare and analyze the failure modes of the π-beam under the action of explosive loads, thus verifying the accuracy of the numerical model. Then, based on the numerical analysis of different protection forms of π beams under explosive loads, the peak pressure of π beam under different protection conditions, the law of structural energy consumption, the damage pattern of the π beam after protection, and the protection efficiency of different protective layers was studied. The testing results indicate that the pressure peak of π beam is relatively small under the combined protection of steel plate and aluminum foam, and the peak value of pressure decays quickly along the beam longitudinal. Besides, as the longitudinal distance increases, the pressure peak attenuates most heavily on the roof's explosion-facing surface. Meanwhile, the combined protective layer has a strong energy consumption capacity, the energy consumed accounts for 90% of the three parts of the π beam (concrete, steel, and protective layer). The damaged area of π beam is relatively small under the combined protection of steel plate and aluminum foam. We also calculate the protection efficiency of π beams under different protection conditions using the maximum spalling area of concrete. The results show that the protective efficiency of the combined protective layer is 45%, demonstrating a relatively good protective ability.

• 대한조선학회논문집
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• 제32권3호
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• pp.98-106
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• 1995

대형구조물의 국부구조계에는 후판, 선체이중저와 같은 복판팬널 또는 FRP판과 같은 복합적층판에 집중질량, 질량-스프링계 또는 지지스프링 등으로 간주되는 부가제가 추가된 복합제의 진동해석을 수행하여야 되는 경우가 않다. 본 연구에서는 팬널의 receptance와 부가계의 receptance를 합성하여 복합제의 고유진동특성 및 강제진동응답을 효과적으로 얻을 수 있는 receptance 방법의 적용을 제시한다. 상기 팬널들은 전단변형 및 회전관성효과가 매우 크고 대부분 직교이방성 강성을 갖기 때문에 직교이방성 Mindlin판유추 구조계로 간주하였으며, Mindlin판유추 구조계의 receptance를 구하기 위해 assumed mode-Lagrange 운동방정식 원용에 의해 구하는 방법을 정식화하였다. 이때 진동파형은 Timoshenko 보함수 또는 이의 성질을 갖는 다항식을 사용하였다. 등방성후판 및 실선 이중저의 1/8축적 모델을 대상으로 일련의 수치계산을 수행하여 본연구에서 제시한 방법의 타당성을 보였다.

• The Journal of Advanced Prosthodontics
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• 제9권4호
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• pp.257-264
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• 2017

PURPOSE. To evaluate the adhesion to CAD/CAM feldspathic blocks by failure analysis and shear bond strength test (SBSt) of different restorative systems and different surface treatments, for purpose of moderate chipping repair. MATERIALS AND METHODS. A self-adhering flowable composite (Vertise Flow, Kerr) containing bi-functional phosphate monomers and a conventional flowable resin composite (Premise Flow, Kerr) applied with and without adhesive system (Optibond Solo Plus, Kerr) were combined with three different surface treatments (Hydrofluoric Acid Etching, Sandblasting, combination of both) for repairing feldspathic ceramics. Two commercial systems for ceramic repairing were tested as controls (Porcelain Repair Kit, Ultradent, and CoJet System, 3M). SBSt was performed and failure mode was evaluated using a digital microscope. A One-Way ANOVA (Tukey test for post hoc) was applied to the SBSt data and the Fisher's Exact Test was applied to the failure analysis data. RESULTS. The use of resin systems containing bi-functional phosphate monomers combined with hydrofluoric acid etching of the ceramic surface gave the highest values in terms of bond strength and of more favorable failure modalities. CONCLUSION. The simplified repairing method based on self-adhering flowable resin combined with the use of hydrofluoric acid etching showed high bond strength values and a favorable failure mode. Repairing of ceramic chipping with a self-adhering flowable resin associated with hydrofluoric acid etching showed high bond strength with a less time consuming and technique-sensitive procedure compared to standard procedure.

• 대한교통학회지
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• 제17권4호
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• pp.85-97
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• 1999

본 연구의 목적은 수단선택과 통행배정의 결합모형을 통하여 정보이용률, 정보제공전략, 혼잡상태의 변화에 따른 자가용 운전자와 버스승객의 정보제공효과를 비교, 평가하는 데 있다. 평가모형은 수단간 효용차를 웨이블 분포로 가정한 수단선택과 정보이용자와 비이용자의 노선선택시 비용인지오류크기를 상이하게 적용하여 노선선택행위를 설명한 확률적 사용자 평형모형으로 구성된다. 정보제공전략에 있어 사용자 최적과 체계 최적외에 두 전략의 혼합전략을 구사했을 경우를 비교하였다. 모의실험은 Sioux Falls Network에서 이뤄졌다. 평가결과 정적모형에서는 혼잡이 심하고, 체계최적상태에서 정보이용률이 0.4∼0.6일 때 총 통행시간의 절감효과가 크게 나타났으며. 이 때 버스 분담율도 증가하였다. 특히 정보이용률에 따른 총 통행비용의 분포가 U자 형태를 나타냄으로써 Braess의 역설이 존재함을 알 수 있었다. 그러나 일별동적모형에서는 시간이 경과함에 따라 정보이용률에 비례하여 정보제공효과가 나타남으로써 다소 상이한 결과를 보여주었다.