• 방송공학회논문지
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• 제20권6호
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• pp.818-826
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• 2015

인간 시각 체계(Human Visual System: HVS)의 영상 화질 인지 특성을 정교하게 반영하는 객관적 영상 화질 측정(Image Quality Assessment: IQA)방법들이 최근 활발히 연구되어 왔다. 이와 관련된 HVS의 특성 중, 광적응(Luminance Adaptation: LA)효과는 HVS의 왜곡에 대한 민감도가 영상 배경 밝기에 따라 달라지는 특성을 가리키며, 이 효과는 베버의 법칙(Weber's law) 모델을 통해 많은 IQA 방법들에 반영되어져 왔다. 본 논문에서는 처음으로 이러한 베버의 법칙 모델을 기반으로 하는 기존 IQA 방법들이 LA 효과를 부정확하게 반영해 왔다는 점을 수학적/정신물리학적 분석을 통해 밝힌다. 이러한 분석을 기반으로 우리는 IQA 방법에 LA 효과가 정교하게 적용될 수 있는 새로운 LA 효과 기반 국부 가중치 함수(LA effect-based Local weight Function: LALF)를 제안한다. 우리는 제안 LALF를 SSIM(Structural SIMilarity) 및 PSNR 척도(metric)에 적용하여 제안 방법의 효과를 검증하였다. 실험 결과, LALF가 적용된 SSIM은 기존 SSIM 대비 측정된 주관적 화질 점수와의 스피어 랭크 순위 상관계수 기준 약 5% 포인트가 향상될 정도로 제안 방법의 큰 효과성을 입증하였다. 또한, 제안한 LALF는 PSNR에 적용된 경우에도 기존 PSNR 대비 약 2.5% 포인트의 성능 향상을 보였다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2009년도 춘계학술대회 논문집
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• pp.267-274
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• 2009

아음속 영역의 대류에 평행하게 압력형 스월 제트를 분사시켜 액막 분열 및 액적 크기와 분포를 실험적으로 측정하였다. 대류로 인한 거시적과 미시적인 분무 특성의 영향을 제트 $We_{\iota}$수와 기상에 대한 액상의 운동량 비를 사용하여 광학적인 방법으로 측정하였다. 낮은 제트 $We_{\iota}$수일 때는 제트의 원심력 부족으로 인해 액막을 형성하지 못하고 Rayleigh 제트 분열을 하게 된다. 높은 $We_{\iota}$수에서는 거시적인 분무 특성은 대류의 영향을 거의 받지 않지만 미시적인 분무 특성은 운동량 비가 높을수록 2차 미립화 과정을 통해 대류의 영향을 많이 받았다. 대류는 제트의 분열을 촉진시키고 스월 제트의 분무 특성을 향상하는 것으로 관찰되었다.

• 한국분무공학회지
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• 제16권4호
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• pp.176-185
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• 2011

The empirical correlations for the prediction of penetration height of liquid jet in crossflow are reviewed and classified in this study. Around thirty different correlations had been proposed by many investigators. It has generally known that the penetration height of a liquid jet in a cross-flow is a function of the liquid to air momentum flux ratio and the normalized downstream distance from the injector. However, several researchers incorporated the Weber number, liquid-to-water or air viscosity ratio, pressure ratio or Reynolds number, temperature ratio in the empirical correlations. The existing correlations can be grouped as correlations in a power-law, logarithmic, and exponential forms, respectively. Correlations in a power-law form can be further classified as three groups such as basic form, Weber number form and other parameters form. It should be pointed out that correlations in a logarithmic form in terms of Weber number or any other parameters could not be found. Universal correlation has still not been established due to the significant discrepancies between various correlations suggested to date. Several of the studies reported the significant discrepancies of predicted values by the existing correlations. The possible reasons for discrepancies will be summarized as measurement technique, assumptions made in defining terms in the liquid to air momentum flux ratio, difficulties in defining the boundaries of the liquid jets, and nozzle/injector geometry. Evaluation of validity for the correlations proposed recently by several investigators is essentially required. Those include eight power-law forms, two logarithmic forms, and one exponential form.

• 한국분무공학회지
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• 제18권1호
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• pp.35-43
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• 2013

The empirical correlations for the prediction of breakup length of liquid jet in uniform cross flow are reviewed and classified in this study. The breakup length of liquid jets in cross flow was normally discussed in terms of the distances from the nozzle exit to the column breakup location in the x and y directions, called as column fracture distance and column fracture height, respectively. The empirical correlations for the prediction of column fracture distance can be classified as constant form, momentum flux ratio form, Weber number form and other parameter form, respectively. In addition, the empirical correlations for the prediction of column fracture height can be grouped as momentum flux ratio form, Weber number form and other parameter form, respectively. It can be summarized that the breakup length of liquid jet in a cross flow is a basically function of the liquid to air momentum flux ratio. However, Weber number, liquid-to-air viscosity ratio and density ratio, Reynolds number or Ohnesorge number were incorporated in the empirical correlations depending on the investigators. It is clear that there exist the remarkable discrepancies of predicted values by the existing correlations even though many correlations have the same functional form. The possible reasons for discrepancies can be summarized as the different experimental conditions including jet operating condition and nozzle geometry, measurement and image processing techniques introduced in the experiment, difficulties in defining the breakup location etc. The evaluation of the existing empirical correlations for the prediction of breakup length of liquid jet in a uniform cross flow is required.

• 대한통합의학회지
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• 제9권4호
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• pp.85-89
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• 2021

Background : Klippel-Trenaunay-Weber syndrome (KTS) is a rare congenital medical condition characterized by complex vascular malformation. KTS consists of a classic triad of capillary malformation (hemangioma), venous malformations and bone or soft tissue hypertrophy causing limb asymmetry. The aim of this report is to describe management for gait disturbance and foot pain in a Patient with KTS using custom-made total contact insole. Case presentation : A 32-year-old man with KTS presented with a 3-year history of gait disturbance on hard surface due to right first toe pain and Achilles tendon tightness. The patient had soft tissue hypertrophy, varicose veins and port-wine stains over the right lower limb associated with KTS. True leg length discrepancy was 2 cm. We prescribed custom-made total contact insole to protect his deformed foot and correct leg length discrepancy. The insole of right side included wedge shaped heel lift and the insole of left side included full length lift to add extra support on unaffected side. Also, we provided compression stocking and physiotherapy including manual lymphatic drainage for lymphedema and stretching exercise for tightness in right lower extremity. At 3 years follow-up, postural alignment including pelvic obliquity was improved using a custom-made total contact insole. The degree of scoliosis and foot pain were also reduced. Conclusion : An individualized and multidisciplinary approach is essential regarding the complexity of comorbidities in patients with KTS. For patients with KTS, orthotic management should be considered to prevent and correct deformities related to KTS. Active orthotic management, compression stocking and physiotherapy can enhance the quality of life and function in patients.

• 한국철도학회논문집
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• 제16권2호
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• pp.104-109
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• 2013

The paper will outline how hazard identification and risk evaluation can effectively be performed to obtain Tolerable Hazard Rates (THR). As a target group manufacturers are addressed, who face the situation, that for a generic application THRs are needed for compliance with EN 50129 [1]. Focusing on functional hazards this paper shows a possible hazard log and the relevant analysis methods. The terms safety barrier and barrier function will be introduced and used instead of the term "safety function". As functional hazards and barrier functions depend on each other, emphasis will be put on a comprehensive and detailed definition of barrier functions and the usage of function lists. By using detailed and complete hazard and barrier function definitions THRs can be obtained while at the same time the approach becomes clear how the hazard rates (HR) will be established.

• 전자공학회논문지D
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• 제35D권3호
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• pp.18-27
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• 1998

Molecular dynamicsinvestigations of ion implantation considering point defect generation were performed with ion energies in the range of ~1keV, Simulation starts perfect diamond cubic lattice site. Stillinger-Weber potential and ZBL potential were used to calculate forces between atoms. We have simulated slowing-down of ion velocity, ion trajectory and coupled-coing between ion and silicon. We also discussed distribution of point defect using rdial distribution function. We found that interstitial produced by ion bombardment mainly formed interstitial cluster.

• 대한족부족관절학회지
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• 제10권1호
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• pp.88-91
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• 2006

Purpose: To evaluate the effect on clinical course of heterotopic ossification of distal tibiofibular syndesmosis after ankle fractures. Materials and Methods: From June 2001 to May 2004, we found nine cases of heterotopic ossification of distal tibiofibular syndesmosis after ankle fractures. There were 8 male patients and 1 female patient; their mean age was 42 years old. There were 6 Weber type B and 2 Weber type C fractures, and there is 1 case with posterior malleolus fracture only. Among them, 8 ankle fractures were operated. Follow up period was averaged for 14 months. We were able to review radiographs at initial injury and to review clinical menifestation and radiographs at last follow up. We used an ankle-hindfoot scoring system of AOFAS which combined symptom, function and alignment with maximum score of 100 point. Results: In all cases ankle dorsiflexion and plantarflexion were not significantly different from that of the contralateral side. The patients who had developed heterotopic ossification in distal tibiofibular syndesmosis had a similar functional score. The mean ankle-hind foot score was 94 points. Conclusion: We concluded that the heterotopic ossification of distal tibiafibular syndesmosis after ankle fractures had little effect on clinical course and range of motion of ankle joint.

• 한국분무공학회지
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• 제11권2호
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• pp.89-97
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• 2006

An inviscid axisymmetric model capable of predicting droplet bouncing and the detailed pre-impact motion, influenced by the ambient pressure, has been developed using boundary element method (BEM). Because most droplet impact simulations of previous studies assumed that a droplet was already in contact with the impacting substrate at the simulation start, the previous simulations could not accurately describe the effect of the gas compressed between a failing droplet and the impacting substrate. To properly account for the surrounding gas effect, an effect is made to release a droplet from a certain height. High gas pressures are computationally observed in the region between the droplet and the impact surface at instances just prior to impact. The current simulation shows that the droplet retains its spherical shape when the surface tension energy is dominant over the dissipative energy. When increasing the Weber number, the droplet surface structure is highly deformed due to the appearance of the capillary waves and, consequently, a pyramidal surface structure is formed; this phenomenon was verified with our experiment. Parametric studies using our model include the pre-impact behavior which varies as a function of the Weber number and the surrounding gas pressure.

• Ocean Systems Engineering
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• 제10권3호
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• pp.317-332
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• 2020

This study examines the behaviors and properties of discharged liquid CO₂ from a long elastic pipe moving with a vessel for the oceanic CO₂ sequestration by considering pipe dynamics and vessel motions. The coupled vessel-pipe dynamic analysis for a typical configuration is done in the frequency and time domain using the ORCAFLEX program. The system's characteristics, such as vessel RAOs and pipe-axial-velocity transfer function, are identified by applying a broadband white noise wave spectrum to the vessel-pipe dynamic system. The frequency shift of the vessel's RAO due to the encounter-frequency effect is also investigated through the system identification method. Additionally, the time histories of the tip-of-pipe velocities, along with the corresponding discharged droplet size and Weber numbers, are generated for two different sea states. The comparison between the stiff non-oscillating pipe with the flexible oscillating pipe shows the effect of the vessel and pipe dynamics to the discharged CO₂ droplet size and Weber number. The pipe's axial-mode resonance is the leading cause of the fluctuation of the discharged CO₂ properties. The significant variation of the discharged CO₂ properties observed in this study shows the importance of considering the vessel-pipe motions when designing oceanic CO₂ sequestration strategy, including suitable sequestration locations, discharge rate, towing speed, and sea states.