• 조명전기설비학회논문지
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• 제29권3호
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• pp.69-80
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• 2015

This paper is writing about developing magnet power supply. It is very important for power supply to obtain output current in high precision and high stability. As a switching noise and a power noise are the cause of disrupting the stability of output current, to remove these at the front end, low pass filter with 300Hz cutoff frequency is designed and placed. And also to minimize switching noise of the current into magnet and to stop abrupt fluctuations, output filter should be designed, when doing this, we design it by considering load has high value inductance. As power supply demands the stability of less than 5ppm, high precision 24bit(300nV/bit) analog digital converter is needed. As resolving power of 24bit(300nV/bit) analog digital converter is high, it is also very important to design the input stage of analog digital converter. To remove input noise, 4th order low pass filter is composed. Due to the limitation of clock, to minimize quantization error between 15bit DPWM and output of ADC having 24bit resolving power, ${\Sigma}-{\Delta}$ modulation is used and bit contracted DPWM is constituted. And before implementing, to maximize efficiency, simulink is used.

• 한국주조공학회지
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• 제29권4호
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• pp.181-186
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• 2009

The interrelationship between new parameter ${\sigma}$ and maximum diameter $D_{max}$ is elaborated and discussed in comparison with four other glass forming ability (GFA) parameters, i.e. (1) super-cooled liquid region ${\Delta}T_x (=T_x - T_g)$, (2) reduced glass transition temperature $T_{rg} (=T_g/T_l)$, (3) K parameter $K (=[T_x-T_g]/[T_l -T_x])$, and (4) gamma parameter ${\gamma}(=[T_x]/[T_l+T_g])$ in Ca-based bulk metallic glass (BMG) systems. The ${\sigma}$ parameter, defined as ${\Delta}T^*{\times}P^'$, has a far better correlation with $D_{max}$ than the GFA parameters suggested so far, clearly indicating that the liquid phase stability and atomic size mismatch dominantly affect the GFA of Ca-based BMGs. Thus, it can be understood that the GFA of BMGs can be properly described by considering structural aspects for glass formation as well as thermodynamic and kinetic aspects for glass formation.

• 대한기계학회논문집A
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• 제34권5호
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• pp.561-565
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• 2010

용접부는 일반적으로 잘 알려져 있는 바와 같이, 외력에 의한 응력 집중원(stress concentration source)이 되는 것은 물론 용접과정에서의 입열(heat input)로 인한 성분과 조직의 변화에 의해 반복하중에 대한 피로강도(fatigue strength)가 모재의 그것에 비해 훨씬 떨어져서 피로균열(fatigue crack)의 발단이 되고 있다. 따라서, 본 연구에서는 실제로 철도차량에 적용되는 가스용접 이음재 가운데 대표적인 형상시편들을 재질별로 피로실험을 수행하여 피로하중범위-피로수명(${\Delta}P-N_f$) 관계를 도출하여 비교 평가하였다. 또한, 수치 해석적 유한요소법을 이용하여 용접이음재의 응력분포를 해석한 후, 용접이음부에 발생하는 최대주응력으로 (${\Delta}P-N_f$) 관계를 $\Delta\sigma-N_f$ 관계로 재정리하였다. 이상의 결과들을 바탕으로, 가스용접이 적용된 철도차량 차체의 경제적이고 합리적인 피로설계를 위한 기초정보로 사용하고자 하였다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -1
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• pp.231-234
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• 2002

A transceiver for ADSL systems contains an interpolated combfilter, halfband filters, oversampling sigma delta modulator, a current steering DAC and an analog filler. The circuit complexity of the architecture makes it necessary to use behavioral models to determine the system features. For this reason, we need a specific behavioral simulation environment using the Matlab program. The Matlab is crucial for these circuits to be rapidly incorporated in larger systems, in particular in the context of mixed-signal-test schemes. Design trade-off among the blocks has also been discussed. The design methodology is based on behavioral design and CMOS process.

• JSTS:Journal of Semiconductor Technology and Science
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• 제17권2호
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• pp.294-301
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• 2017

This paper presents a low power ${\Sigma}{\Delta}$ modulator for an implantable chip to acquire a bio-signal such as EEG, DBS, and EMG. In order to reduce a power consumption of the proposed fourth order modulator, two op-amps utilized for the first two integrators are reconfigured to drive the second two integrators. The KT/C noise reduction circuit in the first two integrators is employed to enhance SNR of the modulator. The proposed circuit was fabricated in a 0.18 um CMOS n-well 1 poly 6 metal process with the active chip core area of $900um{\times}800um$ and the power consumption of 830 uW. Measurement results were demonstrated to be SNDR of 76 dB, DR of 77 dB, ENOB of 12.3 bit at the input frequency of 250 Hz and the clock frequency of 256 kHz. FOM1 and FOM2 were measured to be 41 pJ/step and 142.4 dB, respectively.

• 대한화학회지
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• 제44권3호
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• pp.184-189
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• 2000

메타-치환 피리딘의 치환기 효과를 조사하기 위하여 ab initio 계산을 수행하였다. 여러 메타-치환 피리딘의 최적화 된 구조로부터 정전기전위를 계산하였으며, 그 결과 피리딘의 질소 원자에서 최소정전기전위 값을 나타내었다. 최소정전기전위 값을 나타내었다. 최소정전기전위 값을 Hammett 치환기 상수, ${\sigma}_m$ 및 ${\Delta}pK_a$ 와 비교한 결과 흘륭한 상관성이 있음을 알았으며, 따라서 최소정전기전위가 치환기 효과를 나타내는 유용한 척도로 사용될 수 있음을 알 수 있었다.

• JSTS:Journal of Semiconductor Technology and Science
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• 제10권4호
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• pp.276-281
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• 2010

A 2.5 V feed-forward second-order deltasigma modulator for audio application is presented. A 9-level quantizer with a tree-structured dynamic element matching (DEM) was employed to improve the linearity by shaping the distortion resulted from the capacitor mismatch of the feedback digital-toanalog converter (DAC). A chopper stabilization technique (CHS) is used to reduce the flicker noise in the first integrator. The prototype delta-sigma analogto-digital converter (ADC) implemented in a 65 nm 1P8M CMOS process occupies 0.747 $mm^2$ and achieves 109.1 dB dynamic range (DR), 85.4 dB signal-to-noise ratio (SNR) in a 24 kHz audio signal bandwidth, while consuming 14.75 mW from a 2.5 V supply.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2017년도 춘계학술발표대회
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• pp.1020-1023
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• 2017

Viola와 Jones가 제안한 AdaBoost(Adaptive Boosting) 알고리즘은 기존의 물체 검출기에 비해 속도와 정확도 면에서 우수하여 실시간 물체 검출기로써 좋은 성능을 보인다. 하지만 여전히 많은 계산량 때문에 성능이 낮은 임베디드 환경에서는 실시간 검출에 대한 아쉬움이 있다. 본 논문에서는 계산량을 줄이기 위해 모션 검출을 통해 배경 영역을 제거하고 얼굴 영역을 추정한다. 제거된 배경 영역은 AdaBoost 알고리즘의 검출 과정에서 제외되며 추정된 얼굴 영역에 대해서만 검출을 하게 된다. 모션검출은 ${\Sigma}-{\Delta}$(Sigma-Delta) 배경 추정에 기반한 알고리즘을 사용한다.

• 대한수학회보
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• 제32권1호
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• pp.123-132
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• 1995

Our interest is to study the existence of positive solutions to the following elliptic system involving competing interaction $$ (1) { -\partial(x,u,\upsilon)\Delta u = uf(x,u,v) { - \psi(x,u,\upsilon)\Delta \upsilon = \upsilon g(x,u,\upsilon) { \frac{\partial n}{\partial u} + ku = 0 on \partial\Omega { \frac{\partial n}{\partial\upsilon} + \sigma\upsilon = 0 $$ in a bounded region $\Omega$ in $R^n$ with a smooth boundary, where the diffusion terms $\varphi, \psi$ are strictly positive nondecreasing function, and k, $\sigma$ are positive constants. Also we assume that the growth rates f, g are $C^1$ monotone functions. The variables u, $\upsilon$ may represent the population densities of the interacting species in problems from ecology, microbiology, immunology, etc.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 1999년도 High Temperature Superconductivity Vol.IX
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• pp.48-53
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• 1999

We demonstrate small-scale high-T$_c$ superconductor RSFQ(Rapid Single Flux Quantum) circuits using multilayer bicrystal technology. An RSFQ balanced comparator is demonstrated with good current resolution, and its operating conditions are discussed in some detail. A single-loop delta-sigma modulator is realized adding a feedback loop to the comparator. The effect of the feedback is confirmed by dc measurement and simulation. A design of an RSFQ toggle flip-flop with the same multilayer bicrystal technology is suggested.