• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 하계종합학술대회 논문집(4)
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• pp.73-76
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• 2002

This paper has been studied an algorithm for segmenting gaseous object images. A new methodology for segmenting gaseous object images is introduced. Proposed method consists offuzzy-based boundary detector applicable to gaseous as well as rigid objects and concave region filling to recover object regions.

• Journal of Advanced Marine Engineering and Technology
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• 제27권5호
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• pp.648-656
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• 2003

An experimental research was performed to study turbulent flow characteristic in a $90^{\circ}$ circular bend by using the PIV(Particle Image Velocimetry) method, this study found the time-mean velocity distribution, time-mean turbulent intensity with turbulent flow for Re = 10,000, 15,000, 20,000, and 25,000 along the test bend. It was found that the highest streamwise velocity of turbulent flow occurs near y/D = 0.5 and the flow moved to y/D =0.15. The peak turbulence intensity shifted toward the concave wall from $\theta= 45 and as \theta$ increased. the intensity decayed along the test tube.

• 대한기계학회논문집
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• 제19권5호
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• pp.1308-1318
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• 1995

The influence of varying rotation speed of both crystal and crucible was numerically investigated for the Czochralski silicon-crystal growth. Based on a simplified model assuming flatness of free surfrae, the Navier-Stokes Boussinesq equations were employed to identify the flow pattern, temperature distribution as well as the shape of the melt/crystal interface. The present results showed that the interface shape was relatively convex with respect to the melt at lower pulling rate and tended to be concave as the pulling rate increased. In particular, the experimentally observed gull-winged shape of the interface was qualitatively in agreement with the predicted shape. The rotation of crystal alone little affected the growth system. When the rotation speed of the crucible was increased, there occurred inversion of the interface shape from convex to concave pattern. At rapid rotation of the crucible, an interesting channel formation was predictied primarily due to the assumption of laminar flow.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 1999년도 추계학술발표대회 논문집
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• pp.95-100
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• 1999

A FEA(finite element analysis model) was proposed to study stress and strain distributions in thick composites with fiber waviness and initial curvature under flexural loading. Three types of model with initial curvature were considered in this study: flat, concave and concave models. In the analysis, both material and geometrical nonlinearities were incorporated. Four point flexural tests were conducted on the flat specimens to obtain the flexural behavior of thick composites experimentally. It was concluded that the predictions from the models were in good agreement with the experimental results. It was shown that the stress and strain distributions as well as nonlinear flexural behaviors of thick composites were significantly affected by the fiber waviness and initial curvature.

• 대한화학회지
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• 제36권2호
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• pp.329-334
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• 1992

단백질 수용액 중의 초음파흡수 mechanism을 규명하기 위하여 pH 7의 소혈청 albumin(BSA)수용액의 초음파흡수 측정을 주파수 100 kHz에서 1600 MHz에 걸쳐 행하였다. 측정방법은 plano-concave 공명법(0.1${\sim}$10 MHz)과 고분해능 Bragg 반사법(120${\sim}$1600 MHz)을 사용하였다. pH7에서의 초음파흡수스펙트럼은 Davidson-Cole 분포식의 거울상인 분포함수를 사용한 완화곡선과 일치하였다. 이 완화현상을 BSA 분자의 수화평행에 의한 것으로 해석하였다.

• Journal of the Korean Data and Information Science Society
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• 제26권3호
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• pp.593-610
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• 2015

적응 기각 추출 (adaptive rejection sampling)방법은 특정한 형태의 확률분포로 부터 확률표본을 추출하기 위한 대표적인 난수생성기 (random number generator)로서, 추출된 표본으로부터 제안분포 (proposal distribution)가 개선이 되는 장점을 가지고 있다. 그러나, 기존에 제안된 적응기각추출 방법은 확률분포의 형태가 로그-오목 함수 (log-concave function)인 경우에만 사용이 가능하기 때문에 적용범위가 제한적이다. 최근의 연구결과에서는, 이러한 단점을 보완하기 위해 다양한 형태의 적응기각추출이 진행되고 있으며, 이에 본 논문에서는 기존의 적응기각추출 방법을 포함한 총 5가지의 난수 생성 방법에 대해서 고찰하고, 아울러 모의실험을 통해 각 방법들간의 성능에 대하여, 적합성과 효율성의 관점에서 실증적으로 비교 분석하도록 한다.

• 식물분류학회지
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• 제38권1호
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• pp.1-16
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• 2008

한국 고유종인 모데미풀의 분류학적 검토를 위하여 모데미풀과 근연분류군의 종피 형태를 관찰하였다. 모데미풀의 종피 형태는 외종피 세포가 책상조직모양의 후벽세포로 발달하는 외종피외층형으로 나타났고, 종피의 표면은 오목형 구조를 보였다. 근연분류군인 동의나물의 외종피 외층은 입방형(cuboid)이며, 표면구조는 매끄러워서 모데미풀과 같은 책상조직 형태의 후벽세포로 잘 발달하였으며, 종피 표면 구조는 오목형과 볼록형이 연속적으로 나타났다. 이것은 모데미풀속의 종피구조가 금매화속의 종피구조 범위내에 포함됨을 암시하고 있다. 따라서 동의나물 아족에서는 종피의 해부형태와 표면구조가 아족내에서 분류학적 평가에 유용하게 사용될 수 있었다. 결론적으로, 종피의 표면구조와 행부형태 특징은 고유종인 모데미풀이 동의나물속이나 Calathodes속보다는 금매화속에 보다 가깝다는 것을 나타내었다. 종피의 오목형 표면구조와 잘 발달된 외종피 외층형 종피유형은 모데미풀과 금매화속이 함께 공유하는 형질이었다.

• 한국세라믹학회지
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• 제29권12호
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• pp.926-934
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• 1992

Uniform diamond films in a few $\textrm{mm}^2$ size and locally isolated diamond single crystals in size of 60 $\mu\textrm{m}$ were synthesized on Si-wafer and Al2O3 substrate by the method of acetylene flame. The effects of substrate temperature and flow ratio of oxygen to acetylene on the morphology of deposited diamond were investigated. According to the observations of growth behavior of diamond on Si substrate with respect to substrate surface pretreatment and flow ratio, it was shown that well faceted diamonds could grow uniformly when flow ratio was above 0.9 and substrates were densely scratched. With increasing substrates temperature, the crystal morphology changes from octahedron bounded by only {111} plane below 850$^{\circ}C$ to cubo-octahedron with almost equal development of {111} and {100} plane in the temperature range of 850∼950$^{\circ}C$. Between 950∼1050$^{\circ}C$, the {111} faces become rough and concave. Above 1050$^{\circ}C$, new crystallites begin to grow on concave {111} surface and overall morphology looks like cubo-octahedron with degenerated {111} faces. These changes of morphology can be understood in terms of the different growth mode of each crystallographic plane with respect to the substrate temperature and supersaturation. And the observed phenomena on {111} planes can be related to the face instability and twin generation.

• Journal of Communications and Networks
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• 제15권4호
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• pp.362-369
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• 2013

The optimal number of users achieving the maximum sum throughput is analyzed in zero-forcing (ZF) based multiuser multiple-input multiple-output (MIMO) systems with a large number of base station (BS) antennas. By utilizing deterministic ergodic sum rates for the ZF-beam forming (ZF-BF) and ZF-receiver (ZF-R) with a large number of BS antennas [1], [2], we can obtain the ergodic sum throughputs for the ZF-BF and ZF-R for the uplink and downlink frame structures, respectively. Then, we can also formulate and solve the optimization problems maximizing the ergodic sum throughputs with respect to the number of users. This paper shows that the approximate downlink sum throughput for the ZF-BF is a concave function and the approximate uplink sum throughput for the ZF-R is also a concave function in a feasible range with respect to the number of users. The simulation results verify the analyses and show that the derived numbers of users provide the maximum sum throughputs for the ZF-BF as well as ZF-R in multiuser MIMO systems with a large number of BS antennas.

• 대한기계학회논문집B
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• 제21권5호
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• pp.691-699
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• 1997

The effects of concave hemispherical surface curvature on the local heat transfer from a turbulent round impinging jet were experimentally investigated. The liquid crystal transient method was used for these measurements. This method, which is a variation on the transient method, suddenly exposes a preheated wall to an impinging jet while video recording the response of liquid crystals for the measurement of the surface temperature. The Reynolds number ranges from Re=11,000 to 50,000, the nozzle-to- surface distance from L/d=2 to 10, and the surface curvature from D/d=6 to 12.The present results are also compared to those for the flat plate case. In the experiment, the local Nusselt numbers tend to increase in all regions with an increasing surface curvature. The maximum Nusselt number for all Reynolds numbers occurred at L/d .ident. 6 and a second maximum in the Nusselt number occurred at R/d .ident. 2 for both Re=23,000 and Re=50,000 in the case of L/d=2 and for Re=50,000 only in the case of L/d=4. Meanwhile, as the surface curvature increases, the value of the secondary maximum Nusselt number decreases. All the other cases exhibit monotonically decreasing values of the Nusselt number along the curved surface. The stagnation point Nusselt numbers are well correlated with Re, L/d, and D/d.