• 한국수자원학회논문집
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• 제48권3호
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• pp.233-243
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• 2015

이군집 응집현상은 수자원환경에서 점착성 유사가 결합-해체의 과정을 통해 응집핵-응집체의 이군집 입자크기분포 (Biomodal Floc Size Distribution)를 형성하는 일련의 과정을 의미한다. 본 연구는 저난류 및 고난류 두 가지 조건에서 수행한 응집-침전관 실험결과를 바탕으로 이군집 응집모형(TCPBE: Two Class Population Balance Equation)의 적용성을 단일군집 응집모형(SCPBE: Single Class Population Balance Equation) 및 다군집 응집모형(MCPBE: Multi Class Population Balance Equation)과 비교 평가하였다. 기존 SCPBE에 비하여, TCPBE는 응집핵-응집체의 상호작용 및 침강속도차에 따른 응집 기작을 모의할 수 있었다. 또한, 3개의 연립미분방정식을 가진 TCPBE는 30개 미분방정식을 가진 다군집 응집모형(MCPBE: Multi Class Population Balance Equation)과 대등한 모의 결과를 나타내었다. 따라서 TCPBE는 이군집 응집현상을 모의 할 수 있는 가장 단순한 모델로 검증되었고, 향후 수자원환경이나 수처리 공정에 다양하게 적용할 수 있으리라 판단된다.

• 한국건설순환자원학회논문집
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• 제3권1호
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• pp.22-33
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• 2015

Chloride ions in RC (Reinforced Concrete) structures can cause very severe corrosion in reinforcement steel. It is generally informed that chloride penetration can be considerably accelerated by enlarged chloride diffusion due to cracks. These cracks play a role in main routes through which chloride ions penetrate into the concrete, and also lead to steel corrosion in RC structures exposed to chloride attack, such as port and ocean structures. In this paper, field survey including evaluation of crack and chloride concentration distribution in concrete is performed to investigate an effect of crack on chloride diffusion. The service life of cracked concrete exposed to the marine environmental condition is estimated considering the crack effect on chloride diffusion. For this purpose, diffusion coefficients in cracked concrete are obtained based on the field survey. Using the relationship between diffusion coefficients in the cracked concrete and the crack widths, service life of the cracked concrete is predicted in a probabilistic framework. A bimodal distribution with two peaks, consisting of a weighted sum of two normal distributions is introduced to describe chloride diffusion of the concrete wharf with crack.

• 천문학논총
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• 제30권2호
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• pp.261-263
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• 2015

The metallicity distribution of globular clusters (GCs) provides a crucial clue for the star formation history of their host galaxy. With the assumption that GCs are generally old, GC colors have been used as a proxy for GC metallicities. Bimodal color distributions of GCs observed in most large galaxies have, for decades, been interpreted as bimodal metallicity distributions, indicating the presence of two populations within a galaxy. However, the conventional view has been challenged by a new theory that non-linear GC color-metallicity relations can cause a bimodal color distribution even from a single-peaked metallicity distribution. Using photometric and spectroscopic data of NGC 5128 GCs in combination with stellar population simulation models, we examine the effect of non-linearity in GC color-metallicity relations on transformation of the color distributions into the metallicity distributions. Although in some colors offsets are present between observations and models for the color-metallicity relations, their overall shape agrees well for various colors. After the offsets are corrected, the observed spectroscopic metallicity distribution is well reproduced via modeled color-metallicity relations from various color distributions having different morphologies. We discuss the implications of our results.

• 한국품질경영학회:학술대회논문집
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• 한국품질경영학회 1998년도 The 12th Asia Quality Management Symposium* Total Quality Management for Restoring Competitiveness
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• pp.544-555
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• 1998

Although the bimodal mixed weibull distribution is used to developing burn-in model widely, the failure times for a component or a system is often truncated at some time, T, due to the obsolescence in the electronics industry. In this paper, we will determine minimum total cost and burn-in time by using the bimodal mixed weibull distribution and the truncated bimodal mixed weibull distribution under the free warranty policy. The results of this study are summarized as follows. First, when products or system is not repairable, the width of the change of burn-in time can be larger by ${\beta}_1,\;{\beta}_2$ Second, if burn-in time become longer, it will be impossible to consider the bum-in in a long time, and in this case, the burn-in time should be shorten by the acceleration burn-in. Third, in case that opportunity loss cost or repair cost is exceed the warranty cost, or the total cost of considering burn-in is larger than that of not considering burn-in, it is not existed burn-in time which makes total cost to minimize. Forth, the shorter life-cycle of product, the more burn-in times will be decreased and the cost in considering burn-in will be increased

• Macromolecular Research
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• 제14권6호
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• pp.640-645
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• 2006

Polyethylene of bimodal molecular weight distribution was irradiated with an electron beam. The thermal and mechanical properties were examined by DSC, small and wide angle X-ray scattering and static tensile test according to the crystal morphology of the irradiated samples. The crystal morphology change upon irradiation, as revealed by wide angle X-ray scattering, correlated well with the changes in melting enthalpy, whereas the lamellar thickness and the amorphous gap thickness remained virtually unchanged at irradiation doses up to 500 kGy. Crosslinks in the crystal domains became evident at an energy level of 250 kGy, resulting in reduced crystallinity and crystal size of the (110) and (200) planes. The samples became stiff and brittle with increased irradiation dose, which seem to be more relevant to the amount of cross links than the crystal morphology changes.

• 한국환경보건학회지
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• 제26권2호
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• pp.108-115
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• 2000

The mass fraction of PM10 had a bimodal distribution in the middle of between 2.1 ${\mu}{\textrm}{m}$, and the average mass fraction of particles less than 2.1~3.1 ${\mu}{\textrm}{m}$ was 54.1% for Pb and 890.8 ng/㎥ for Fe, respectively. For the concentration of PM10 and metallic elements by seasonal variation, PM10 showed bimodal distribution, while metallic elements showed different distributions by their sources. The ratios of fine particles to total mass were 0.45 for PM10, 0.41 for Cr, and 0.20 for Fe, 0.57 for Zn, 0.68 for Cd and 0.63 for Pb, respectively. That facts indicated that PM10, Zn, Cd, Cr and Pb were from anthropogenic sources, and Fe was from natural source. The geometric means and geometric standard deviations by seasonal variations were 3.6 ${\mu}{\textrm}{m}$ , 2.31 ${\mu}{\textrm}{m}$ in winter, 3.0 ${\mu}{\textrm}{m}$ , 2.49 ${\mu}{\textrm}{m}$ in spring, 2.7 ${\mu}{\textrm}{m}$ , 2.03 ${\mu}{\textrm}{m}$ in summer respectively. And, total efficiency of cascade impactor by seasonal variations were 49.6% in winter, 45.9% in spring and 44.5% in summer.

• 한국정보과학회논문지:소프트웨어및응용
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• 제31권4호
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• pp.403-410
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• 2004

바이모달 음성인식기는 잡음 환경하 음성인식 성능을 향상하기 위해 고안되었다. 바이모달 음 성인식기에 있어 영상을 통한 시각 특징 추출은 매우 중요한 역할을 하며 이를 위한 입술 위치 검출은 시각 특징 추출을 위한 중요한 선결 과제이다 본 논문은 색상분포와 SVM을 이용하여 시각 특징 추출을 위한 입술 위치 검출 방법을 제안하였다. 제안된 방법은 얼굴색/입술 색상 분포를 학습하여 이로부터 입술의 초기 위치를 빠르게 찾아내고 SVM을 이용하여 입술의 정확한 위치를 찾음으로써 정확하고 빠르게 입술의 위치를 찾도록 하였으며 실험을 통해 바이모달 인식기에 적용하기에 적합함을 알 수 있었다.

• 대한원격탐사학회지
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• 제29권6호
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• pp.645-655
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• 2013

As one of segmentation techniques for Synthetic Aperture Radar (SAR) image with oil spill, we applied a bimodal histogram method to discriminate oil pixels from non-oil pixels. The threshold of each moving window was objectively determined using the two peaks in the histogram distribution of backscattering coefficients from ENVISAT ASAR image. To reduce the effect of wind speed on oil spill detection, we selected ASAR image which satisfied a limit of wind speeds for successful detection. Overall, a commonly used adaptive threshold method has been applied with a subjectively-determined single threshold. In contrast, the bimodal histogram method utilized herein produces a variety of thresholds objectively for each moving window by considering the characteristics of statistical distribution of backscattering coefficients. Comparison between the two methods revealed that the bimodal histogram method exhibited no significant difference in terms of performance when compared to the adaptive threshold method, except for around the edges of dark oil spots. Thus, we anticipate that the objective method based on the bimodality of oil slicks may also be applicable to the detection of oil spills from other SAR imagery.

• 대한기계학회논문집A
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• 제37권7호
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• pp.883-889
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• 2013

응답의 분포는 변수의 분포에 따라 달라진다. 특히 변수의 분포가 두 개 이상의 모드를 가질 때, 대부분 응답의 분포 또한 두 개 이상의 모드를 갖는다. 이런 문제에 대해 기존의 신뢰성해석 기법은 변수를 하나의 모드를 갖는 특정 연속확률분포로 가정하고 신뢰성해석을 수행한다. 하지만 실제 문제에서 변수들은 이산정보이면서 두 개 이상의 모드를 갖는 경우가 많기 때문에 변수의 분포에 대한 가정을 하지 않고 두 개 이상의 모드를 고려한 신뢰성해석을 수행하는 것은 매우 중요하다. 본 연구에서는 두 개 이상의 모드를 갖는 분포를 추정할 수 있는 기법인 아카이케정보척도와 최대엔트로피법칙을 이용하여 신뢰성해석을 수행한다. 수학예제를 통해 두 기법의 특징을 파악하고 몬테카를로 시뮬레이션의 결과와 비교하여 정확도를 검증한다.

• 한국환경과학회지
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• 제30권9호
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• pp.727-739
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• 2021

Measurements on mass size distribution of roadside aerosols were obtained in downtown Jeju City from July 2018 to May 2020 using an 8-stage cascade impactor sampler and the compositions of aerosols were analyzed. The mass size distribution of total aerosols was bimodal with aerosols existing in both the fine and coarse modes. The mass size distributions of Na⁺, Mg²⁺, Ca²⁺, Cl^-, NH₄⁺ and SO₄^2- were unimodal, whereas that of K⁺ was bimodal. For NO₃^-, the size distribution in winter and spring was bimodal with the peaks in both fine and coarse modes, whereas for summer and autumn the distribution was unimodal with a peak in the coarse mode. NH₄⁺ was found to co-exist with SO₄^2- in the fine mode with an average molar ratio of [NH₄⁺]/[SO₄^2-] equal to 2.05. Good correlation was observed between NO₃^- and NH₄⁺ in the fine mode particles in spring and winter. Based on the value of the marine enrichment factor for Cl^-, Mg²⁺, K⁺, Ca²⁺ and SO₄^2-, it may be inferred that a major part of the roadside aerosols in downtown Jeju City was largely contributed by terrigenous sources, although the influence of sea salt was normally present.