• Journal of Mechanical Science and Technology
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• 제17권6호
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• pp.787-795
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• 2003

Mechanical properties of the materials used for transportations and industrial machinery under high strain rate loading conditions such as seismic loading are required to provide appropriate safety assessment to these mechanical structures. The Split Hopkinson Pressure Bar (SHPB) technique with a special experimental apparatus can be used to obtain the material behavior under high strain rate loading conditions. In this paper, dynamic deformation behaviors of the aluminum alloys such as A12024-T4, A1606 IT-6 and A17075-T6 under both high strain rate compressive and tensile loading conditions are determined using the SHPB technique.

• Journal of Electrical Engineering and Technology
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• 제7권4호
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• pp.570-575
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• 2012

In a wireless communication RF transmitter, the output of a quadrature modulator (QM) is distorted by not only the linear imperfection features such as in/quadrature-phase (I/Q) input gain imbalance, local phase imbalance, and local gain imbalance but also the nonlinear imperfection features such as direct current (DC) offset and mixer nonlinearity related to in-band spurious signal. In this paper, we propose the unified QM model to analyze the combined effects of the linear and nonlinear imperfection features on the performance of the QM. The unified QM model consists of two identical nonlinear systems and modified I/Q inputs based on the two-port nonlinear mixer model. The unified QM model shows that the output signals can be expressed by mixer circuit parameters such as intercept point and gain as well as the imperfection features. The proposed approach is validated by not only simulation but also measurement.

• ETRI Journal
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• 제29권3호
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• pp.336-352
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• 2007

Sequential pattern mining has become an essential task with broad applications. Most sequential pattern mining algorithms use a minimum support threshold to prune the combinatorial search space. This strategy provides basic pruning; however, it cannot mine correlated sequential patterns with similar support and/or weight levels. If the minimum support is low, many spurious patterns having items with different support levels are found; if the minimum support is high, meaningful sequential patterns with low support levels may be missed. We present a new algorithm, weighted interesting sequential (WIS) pattern mining based on a pattern growth method in which new measures, sequential s-confidence and w-confidence, are suggested. Using these measures, weighted interesting sequential patterns with similar levels of support and/or weight are mined. The WIS algorithm gives a balance between the measures of support and weight, and considers correlation between items within sequential patterns. A performance analysis shows that WIS is efficient and scalable in weighted sequential pattern mining.

• ETRI Journal
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• 제35권1호
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• pp.158-161
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• 2013

This letter proposes a low-power current-steering digital-to-analog converter (DAC). The proposed DAC reduces the clock power by cutting the clock signal to the current-source cells in which the data will not be changed. The 10-bit DAC is implemented using a $0.13-{\mu}m$ CMOS process with $V_{DD}$=1.2 V. Its area is $0.21\;mm^2$. It consumes 4.46 mW at a 1-MHz signal frequency and 200-MHz sampling rate. The clock power is reduced to 30.9% and 36.2% of a conventional DAC at 1.25-MHz and 10-MHz signal frequencies, respectively. The measured spurious free dynamic ranges are 72.8 dB and 56.1 dB at 1-MHz and 50-MHz signal frequencies, respectively.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 추계종합학술대회 논문집(1)
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• pp.489-492
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• 2000

Film Bulk Acoustic Wave Resonator(FBAR) used in microwave region was analyzed with Finite Difference Time-Domain Methods(FDTD) in this paper. FBAR have been analyzed with one dimensional Mason model analysis or Finite Element methods(FEM), but the first couldn't analyze effect of area variation and spurious characteristics, the second had difficulty in element separation because of thin electrode. So in this paper FBAR was analyzed by Finite Difference Time-Domain Methods and it's results were transformed to frequency domain using Discrete Fourier Transform.

• JSTS:Journal of Semiconductor Technology and Science
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• 제4권3호
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• pp.182-188
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• 2004

We demonstrate a $2.1\;{\times}\;1.0\;{\times}\;0.1cm^3$ sized compact transmitter using LTCC System-in-Package (SiP) technology for 60GHz-band wireless communication applications. For low-attenuation characteristics and resonance suppression of the SiP, we have proposed and demonstrated a coplanar double wire-bond transition and novel CPW-to-stripline transition integrating air-cavities as well as novel air-cavities embedded CPW line. The fabricated transmitter achieves an output of 13dBm at a RF frequency of 62GHz, an IF frequency of 2.4GHz, and a LO frequency of 59.6GHz. The up-conversion gain is 11dB, while the LO signal is suppressed with the image rejection mixer below -21.4dBc, and the image and spurious signals are also suppressed below -31dBc.

• 전기전자학회논문지
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• 제3권1호
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• pp.39-49
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• 1999

This paper describes a 1 GHz, low-phase-noise CMOS fractional-N frequency synthesizer with an integrated LC VCO. The proposed frequency synthesizer, which uses a high-order delta-sigma modulator to suppress the fractional spurious tones at all multiples of the fractional frequency resolution offset, has 64 programmable frequency channels with frequency resolution of $f_ref/64$. The measured phase noise is as low as -110 dBc/Hz at a 200 KHz offset frequency from a carrier frequency of 980 MHz. The reference sideband spurs are -73.5 dBc. The prototype is implemented in a $0.5{\mu}m$ CMOS process with triple metal layers. The active chip area is about $4mm^2$ and the prototype consumes 43 mW, including the VCO buffer power consumption, from a 3.3 V supply voltage.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 추계종합학술대회 논문집
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• pp.1089-1092
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• 1998

Conventional floating-point adders have one data-path that is used for all operations. This paper describes a floatingpoint adder eeveloped for low power consumption, which has three data-paths one of which is selected according to the exponent difference. The first is applied to the case that the absolute exponent difference (AED) of two operands is less than 1, and the second is for 1

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1991년도 가을 학술발표회 논문집
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• pp.75-80
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• 1991

The purpose of this study is to ascertain the robustness of p-version model with hierarchic intergrals of Legendre shape functions in various applications including plane stress/strain, axisymmetric and shell problems. The most important symptoms of accuracy failure in modern finite elements are spurious mechanisms and a phenomenon known as locking which are exhibited for incompressible materials and irregular shapes which contain aspect ratios(R/t, a/b), tapered ratio(d/b), and skewness. The condition numbers and energy norms are used to estimate numerical errors, convergence characteristics and algorithmic efficiencies for verifying the aforementioned symptoms of accuracy failure. Numerical results from p-version models are compared wi th those from NASTRAN, SAP90, and Cheung's hybrid elements.

• 대한기계학회논문집A
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• 제22권3호
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• pp.519-528
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• 1998

A numerical method is presented for the dynamic analysis of cam and follower. Contact and separation between the cam and the follower are analyzed by imposing dynamic contact condition. The correct solution is obtained without spurious oscillation by imposing the velocity and acceleration constraints as well as the displacement constraint on the possible contact point. The constraints are satisfied by iteratively reducing the constraint errors toward zero, and a simple time integration of ordinary differential equation is employed for the solution of the equation of motion. The solution procedure associated with the iterative scheme is presented, and numerical simulations are conducted to demonstrate the accuracy of the solution.