• The Bulletin of The Korean Astronomical Society
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• v.38 no.1
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• pp.57.1-57.1
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• 2013

Non-LTE 항성대기모형인 Tlusty 모형의 합성색지수와 성간소광을 매우 적게 받은 산개성단에 있는 별들의 색지수를 바탕으로 O와 B형 별의 고유색지수 관계를 채택하였다. 태양인근 3kpc 내에 있는 약 190개 젊은 산개성단의 가시광 및 근적외선 2MASS JHKs 관측자료와 위에서 채택한 고유 색지수 관계를 적용하여 색 초과비 E(V-I)/E(B-V), E(V-J)/E(B-V), E(V-H)/E(B-V), 및 E(V-Ks)/E(B-V)를 얻고, 색 초과비와 $R_V$의 관계를 사용하여, 각 성단의 성간소광법칙 $R_V$를 결정하였다. 국부 나선팔의 백조자리 방향과 Per 나선팔에 있는 산개성단들은 약간 작은 $R_V$를 보이며, 큰개자리 방향의 국부 나선팔에 있는 산개성단은 정상적인$R_V$를, 그리고 Sgr-Car 나선팔에 있는 산개성단들은 약간 큰 값을 보였다. 이 결과는 최대 편광도를 보이는 파장과 $R_V$의 관계로 얻을 수 있는 양상과 잘 일치한다.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2460-2464
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• 2008

The present paper suggests new method to know the effects of molecular diffusion and the helicity of microchannel flows on mixing in passive micromixers, which are essential components of a microfluidic chip. In this study, 'Helix Index' is newly defined as the magnitude of chaotic advection. Relationship between Helix Index and Mixing Index is analyzed numerically such as the wide range of Peclet and Reynolds numbers in three dimensional serpentine microchannel when using soluble solutions (water/glycerol). As a result, a simple algebraic equation is derived by this relationship based on a regression analysis. The algebraic equation is found to be able to accurately predict the mixing performance without solving the coupled, complex momentum and mass transfer equations.

• Publications of The Korean Astronomical Society
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• v.6 no.1
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• pp.1-15
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• 1991

원반 및 해일로의 이중역 (two-zone) 모형을 바탕으로하여 나선은하의 화학적 진화 모형을 만들었다. 모형의 검증을 위하여 구체적인 수치계산을 수행하고 그 결과를 태양 부근에서 관측된 중원소 분포 등, 화학적 진화와 관련된 제반 관측 사실과 비교함으로써 은하계의 진화를 추론하였다. 모형의 수치계산 결과에 의하면 나선은하의 화학적 진화는 헤일로외 붕괴 과정과 별탄생율에 크게 의존하며, 원반의 초기질량함수와 별탄생율에 따라 서로 다른 양상을 보인다. 태양 부근 원반의 중원소 분포 등을 성공적으로 설명할 수 있는 진화 모형에서, 별탄생율은 가스의 질량 또는 표면밀도의 멱승에 비례하거나 시간에 따라 단조 감소하는 지수함수로써 표현되며, 초기질량함수는 헤일로에서는 다양한 형태의 함수 모두로써 가능하지만, 원반의 경우에는 시간에 따라 변화하는 질량함수를 채택하여야 한다. 우리 은하의 헤일로의 고속붕괴 모형에서는 시간에 따라 지수함수로 변화하는 별탄생율이 관측과 부하되지만, 반면 저속붕괴의 경우에는 가스 질량의 멱함수로 표현되는 별탄생율이 관측과 부합된다.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.5
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• pp.8-15
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• 2002

We optimally designed the VCO(voltage-controlled oscillator) with spiral inductor using the MOSIS HP 0.5${\mu}{\textrm}{m}$ CMOS process. With the developed SPICE model of spiral inductor, the quality factor of spiral inductor was maximized at the operating frequency by varying the layout parameters, e.g., metal width, number of turns, radius, space of the metal lines. For the operation frequency of 2㎓, the inductance of about 3nH, and the MOSIS HP 0.5 CMOS process with the metal thickness of 0.8${\mu}{\textrm}{m}$, oxide thickness of 3${\mu}{\textrm}{m}$, the optimal width of metal lines is about 20${\mu}{\textrm}{m}$ for the maximum Quality factor. With the optimized spiral inductor, the VCO with LC tuning tank was designed, fabricated and measured. The measurements were peformed on-wafer using the HP8593E spectrum analyzer. The oscillation frequency was about 1.610Hz, the frequency variation of 250MHz(15%) with control voltage of 0V - 2V, and the phase noise of -108.4㏈c(@600KHz) from output spectrum.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.706-709
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• 1997

Extruders are the heart of the polymer processing industry. The single most important mechanical element of a screw extruder is the screw. The proper design of the geometriy of the extruder screw is of crucial importance to the proper functioning of the extruder. If material transport instabilities occur as a result of improper screw geometry, even the most sophisticated computerized control system cannot solve the problem. For this purpose, characteristics design on helix angle of the extruder screw. This paper presents strength of the screw flight, optimum helix angle versus dimensionless down channel pressure gradient, optimum helix angle versus the power law index in simultaneous optimization, volumetric efficiency versus helix angle at various number of flights and power consumption versus helix angle in the barrel of screw extruder.

• Journal of Digital Convergence
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• v.15 no.4
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• pp.529-536
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• 2017

The purpose of this study is to examine the immediate effects of spiral taping applied to an affected leg on gait ability in stroke patients. Forty two stroke patients were divided into a spiral taping group (n=21) and a quadriceps femoris group (n=21), and each taping method was applied. Spatiotemporal Gait Parameters (Cadence, speed, gait cycle duration, stance phase duration, double support duration) were measured using the 10-meter walk test, the dynamic gait index (DGI) and an accelerometer for both groups. Both groups showed a significant increase in a 10-minute walk, the DGI, cadence, speed before and after the intervention, whereas no significant difference was detected in stance phase duration, gait cycle duration and double support duration on the affected side in all groups. All groups revealed no significant difference in variation. It has been found that the two taping methods augment gait ability in patients with stroke. This study suggests that spiral taping can be an easily applicable method at home.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.3
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• pp.311-320
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• 2008

In this paper, a new variable active inductor using a conventional grounded active inductor with feedback variable LC-resonator is proposed. The grounded active inductor is realized by the gyrator-C topology and the variable LC-resonator is realized by the low-Q spiral inductor and varactor. This variable LC-resonator can compensate the degradation of Q-factor due to parasitic capacitance of a transistor, and the frequency range with high Q-factor is adjustable by resonance frequency adjustment of LC-resonator. The fabricated variable active inductor with Magnachip $0.18{\mu}m$ CMOS process shows that high-Q frequency range can be adjusted according to varactor control voltage from 4.66 GHz to 5.45 GHz and Q-factor is higher than 50 in the operating frequency ranges. The measured inductance at 4.9GHz can be controlled from 4.12 nH to 5.97 nH by control voltage.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.86.1-86.1
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• 2012

Sloan Digital Sky Survey (SDSS) DR7 분광자료를 이용하여 z < 0.01에 존재하는 필드(field) 은하 505개를 선별하였다. SDSS의 컬러 영상을 이용하여 필드은하들의 형태(morphology)를 타원은하/왜소타원은하, 렌즈은하/왜소렌즈은하, 나선은하, 그리고 불규칙은하로 분류하였으며, 이들 은하들에 대한 측광을 수행하였다. 한편, Galex Evolution Explorer (GALEX) 자외광 영상으로부터 선별된 은하들에 대한 자외광 측광도 수행하였다. 서로 다른 환경에 있는 은하들의 최근 별탄생 활동이 어떻게 변화하는지 파악하기 위하여 처녀자리은하단 (Virgo cluster)에 있는 은하들과 비교하여 필드은하들의 자외광-가시광 색-등급 분포를 조사하였다. 처녀자리은하단 은하들에 비하여 필드은하들은 작은 자외광-가시광색지수를 가지는 만기형 은하들의 비율이 높았다. 특히, 조기형 필드은하들의 색지수 값이 처녀자리은하단 조기형 은하들에 비해 전반적으로 더 작은 값을 나타내고, 이 특징은 질량이 작은 왜소은하에서 더욱 크게 나타남을 알 수 있었다. 한편, 환경적 효과를 거의 받지 않는 필드은하들은 환경적 효과가 큰 은하단 은하들의 진화 연구에서 환경적 효과의 크기 및 기작을 규명하는 기본 자료로 사용될 수 있음을 토의하고자 한다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.3 no.4
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• pp.11-20
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• 1983

This study investigates reliability based design criteria for the spiral R.C. columns, and proposes practical algorithm which is based on Ellingwood's algorithm for the reliability analysis and the derivation of reliability based design criteria. Cornell's MFOSM theory is used for the derivation of the algorithm for the evaluation of uncertainties associated with resistances, whereas the magnitude of the uncertainties associated with load effects are chosen primarily by considering our level of practice. And thus the uncertainties so obtained are applied for the relilability analysis and the derivation of reliability based design criteria. A target reliability (${\beta}_0=3.5$) is selected as an appropriate value by comparing the values used in foreign countries and by analyzing, the reliability levels of our current USD and WSD design standards. Then, a set of load and resistance factors corresponding to the target reliability is proposed as a reliability based design provision, and furthermore a set of allowable stresses for reinforcing steel and concrete having same level of reliability with the corresponding LRFD criteria is also propared for the current WSD design provision. It may be concluded that the proposed LRFD reliability based design provisions and the corresponding allowable stresses give more rational design than the current code for spiral R.C. columns.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.7
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• pp.713-721
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• 2004

This paper presents a high Performance LNA based on InGaP/GaAs HBT for 5.4㎓ WAM band applications. During the past days, InGaP/GaAs HBT has been being used for mainly high power amplifiers, but InCaP/GaAs is recognized as a suitable device for RF single chip. At this point, the research about a high performance LNA based on InGaP/GaAs HBT must be preceded, and in this paper, a excellent linearity and noise characteristics LNA based on InGaP/GaAs HBT is desisted and fabricated. The LNA is integrated in new of 0.9${\times}$0.9$\textrm{mm}^2$ single chip with high Q spiral inductors and MIM capacitors. The proposed LNA is biased at current point for optimum noise figure and gain characteristics, futhermore, excellent linearity is achieved. The proposed LNA shows 13㏈ gain, 2.1㏈ noise figure, and excellent linearity in terms of IIP3 of 5.5㏈m.