• 대한방사선치료학회지
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• 제15권1호
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• pp.19-27
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• 2003

I. 목적 Total Body Irradiation(TBI)와 Half Body Irradiation(HBI), Non-Hodgkin's lymphoma, E-Wing's sarcoma, lymphosarcoma, neuroblastoma 등의 특수한 경우에 넓은 광자선 조사면($40{\times}40cm2$ 이상)이 임상적으로 사용될 수 있다. 넓은 광자선 조사면의 선량분포는 매번 실제 측정 대신 좁은 광자선 조사면 (표준 SSD 100cm, 조사면의 크기 $40{\times}40cm2$ 미만)에서 얻은 측정결과를 이용하여 보정할 수 있으나, 단 순한 계산에 의한 방법만으로는 산란 방사선의 여러 가지 요인에 의한 실제 신체 각 부위의 선량 및 그 균일성을 알기는 힘들다. 본 연구에서는 치료거리 증가에 따른 넓은 광자선 조사면의 기본 parameter(PDD, TMR, Output, Sc, Sp)를 측정하고, 좁은 광자선 조사면에서 얻은 측정결과와 비교하여 그 차이를 확인해 보고 실제 적용여부를 알아보고자 한다. II. 대상 및 방법 표준 SSD 100cm에서 Multidata water phantom을 이용하여 조사면의 크기 변화에 따라 기본parameter(PDD, TMR, Output, Sc, Sp)를 측정하였다. 먼저 SSD 180cm에서(phantom이 치료실 바닥으로 수직방향) 조사면 증가에 따른 기본 parameter를 측정하였고, SSD 350cm에서(phantom이 치료실 벽면으로 수평방향이고 horizotal beam의 측정이 가능한 mylar를 가진 small water phantom을 이용) 같은 방법으로 측정하여 서로 비교해보았다. III. 결과 및 결론 SSD 180cm과 350cm에서 측정한 parameter들이 표준 선량측정 자료와 비교해서 오차범위가 실험적 오차에 있을 정도로 큰 차이가 없었음을 알 수 있었다. 정확한 자료를 얻기 위해 anthropomorphous phantom에서 선량측정을 하거나 이런 목적을 위해 특별히 고안된 unlimited phantom을 이용한 절대값을 얻을 수 있는 선량 측정이 요구된다. 부가적으로 작은 부피의 ionization chamber 사용과 넓은 조사면에 의한 cable과 stem effect를 고려해야 할 필요가 있다.

• 대한핵의학회지
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• 제31권1호
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• pp.83-89
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• 1997

CT에서도 악성 여부가 불명확한 단일 폐결절의 감별진단에 있어 PET이 어떠한 도움을 줄 수 있는지 알아보고자 이러한 환자 30명을 대상으로 FDG-PET을 시행하여 각 환자에서 구한 pSUV, aSUV, TAC 양상, 50/10비의 4가지 매개변수를 조직검사결과와 비교하여 다음과 같은 성적을 얻었다. 1) 4가지 매개변수의 악성판정 기준치로 $pSUV{\geq}3.5$, aSUV>2.5, TAC=상향, 50/10비${\geq}1.45$를 적용하였을 때 악성판정에 있어 각각의 예민도는 86.7%, 66.6%, 86.7%, 73.3%였으며, 특이도는 86.7%, 86.7%, 46.7%, 86.7%였다. 2) 4가지 매개변수중 구하기 용이한 점과 정확도를 감안할 때 임상적으로 pSUV가 가장 유용하였다. 3) pSUV를 사용하였을 경우 CT에서 불확실한 단일 폐결절의 87%에서 정확한 진단이 가능하였다. 4) 기관지 폐포암을 제외할 경우 예민도가 100%였다. 이상의 결과에서 FDG-PET에서 구한 pSUV는 여러 가지 매개변수중 가장 용이하게 구할 수 있으며 비 침습적으로 단일 폐결절의 악성여부를 가릴 수 있는 유용한 방법이었다.

• 응용통계연구
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• 제28권5호
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• pp.907-920
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• 2015

기하분포에 기초한 관리도는 불량품이 드물게 발생하는 고품질공정에서 불량률의 변화를 효율적으로 탐지할 수 있다고 알려져 있다. 이러한 관리도를 사용할 때 기본적인 가정은 관리상태일 때의 불량률이 알려져 있거나 또는 정확하게 추정되었다는 것이다. 그러나 고품질공정에서 불량률은 아주 작기 때문에 이를 정확하게 추정하기가 쉽지 않으며 또한 아주 큰 표본크기가 필요한 경우도 종종 발생한다. 일반적으로 제1국면에서 관리상태의 불량률을 추정할 때 최대우도추정량을 사용하지만, 이 논문에서는 베이즈추정량의 사용을 제안하였다. 베이즈추정량을 사용할 경우 실무자의 사전지식을 반영할 수 있으며 표본에 불량품이 발견되지 않을 경우 발생하는 최대우도추정량의 문제점을 해결할 수 있다는 장점이 있다. 기하 관리도와 기하누적합 관리도에서 베이즈추정량을 사용한 경우와 최대우도추정량을 사용한 경우를 비교한 결과, 표본의 크기가 크지 않은 경우 베이즈추정량을 사용하는 것의 효율이 더 좋음을 알 수 있었다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 추계학술대회 논문집
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• pp.431-434
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• 2008

In the present study, direct quenching of alloyed steel after hot forging was simulated using commercial finite element program, $FORGE^{TM}$. A typical heat treatment of alloyed steels consists of quenching for hard martensite and subsequent tempering for toughness. In the practice, forgings which cool down to room temperature are heated to temperature of austenite regime. As investigated in the present study, direct quenching of hot forged stock would be beneficial in terms of energy saving. This process has already been propose and termed as ausforging or forged hardening. However, it is well known that quenching temperature would be the most critical factor to control heat treated forging properties. And it is very difficult to control quenching temperature when forged stock gets directly quenched after forging. In this study, we have calculated final forging temperature of stock. Also, quenching simulation was conducted using a series of material parameter which were also calculated using JMATpro, a commercial program for physical properties of materials.

• 한국지진공학회논문집
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• 제21권3호
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• pp.137-144
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• 2017

The cyclic behavior of braces is complex due to their asymmetric properties in tension and compression. For accurately simulating the cyclic curves of braces, it is important to predict the major parameters such as cyclic brace growth, cyclic buckling load, incidence local buckling and fracture with good precision. For a given brace, the most accurate values of these parameters can be estimated throughout experiments. However, it is almost impossible to conduct experiments whenever an analytical model has to be established for many braces in building structures due to enormous cost and time. For avoid such difficulties, empirical equations for predicting constituent parameters are proposed from regression analyses based on test results of various braces. This study focuses on rectangular hollow structural section(HSS) steel braces, which have been popularly used in construction practice owing to its sectional efficiency.

• Journal of the Korean Academy of Child and Adolescent Psychiatry
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• 제28권2호
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• pp.46-57
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• 2017

Attention-deficit hyperactivity disorder (ADHD) is a common psychiatric disorder that can affect individuals across their lifespan. It is characterized by the core symptoms of inattention, impulsivity and hyperactivity. ADHD develops as a result of the complex interplay between genetic and environmental factors. Children and adults with ADHD usually suffer concomitantly from other psychiatric comorbidities, including both externalizing and internalizing disorders. It is associated with functional impairment and poor long-term outcomes. This review aims to summarize the key findings from recent research into ADHD and its prevalence, core symptoms, cause and comorbidities from childhood to adulthood.

• 대한기계학회논문집A
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• 제24권2호
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• pp.506-517
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• 2000

One dimensional performance model has been used for the design of torque converter. The model is based on the concept of constant mean flow path and constant flow angle. These constant-assumed para meters make the design procedure to be simple. In practice, some parameters are usually replaced with geometric raw data and, the constant experiential correction factors have been used to minimize the design error. These factors have no definite physical meaning and so they cannot be applied confidently to the other design condition. In this study, the detail dynamic model of torque converter is presented to establish the theoretical background of correction factors. To verify the validity of theoretical model, steady state performance test was carried out on the several input speed. The oil temperature effect on the performance is analysed and adjusted. The constant equivalent flow angles are determined at a part of performance region by comparing the theoretical model and the test data. The sensitivity of correction factors to the input speeds are studied and the change of torus flow is presented.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권9호
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• pp.4419-4441
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• 2016

A cause of vehicle accidents is the reduced visibility due to bad weather conditions such as fog. Therefore, an onboard vision system should take visibility detection into account. In this paper, we propose a simple and effective approach for measuring the visibility distance using a single camera placed onboard a moving vehicle. The proposed algorithm is controlled by a few parameters and mainly includes camera parameter estimation, region of interest (ROI) estimation and visibility computation. Thanks to the ROI extraction, the position of the inflection point may be measured in practice. Thus, combined with the estimated camera parameters, the visibility distance of the input foggy image can be computed with a single camera and just the presence of road and sky in the scene. To assess the accuracy of the proposed approach, a reference target based visibility detection method is also introduced. The comparative study and quantitative evaluation show that the proposed method can obtain good visibility detection results with relatively fast speed.

• Structural Engineering and Mechanics
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• 제58권1호
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• pp.121-142
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• 2016

The national standard being used in Turkey for suspended ceiling systems (SCS) regulates material and dimensional properties but does not contain regulations regarding installation instructions which cause substandard applications of SCSs in practice. The lack of installation instructions would potentially affect the dynamic performance of these systems. Also, the vast majority of these systems are manufactured using substandard low-quality materials, and this will inevitably increase SCS related damages during earthquakes. The experimental work presented here focuses on the issue of dynamic performance of SCSs with different types of carrier systems (lay-on and clip-in systems), different weight conditions, and material-workmanship qualities. Moreover, the effects of auxiliary fastening elements, so called seismic perimeter clips, in improving the dynamic performance of SCSs were experimentally investigated. Results show that clip-in ceiling system performs better than lay-on system regardless of material and workmanship qualities. On the other hand, the quality aspect becomes the most important parameter in affecting the dynamic performance of lay-on type systems as opposed to tile weights and usage of perimeter clips. When high quality system is used, tile weight does not change the performance of lay-on system, however in poor quality system, tile weight becomes an important factor where heavier tiles considerably decrease the performance level. Perimeter clips marginally increase the dynamic performance of lay-on ceiling system, but it has no effect on the clip-in ceiling system under the shaking levels considered.

• Wind and Structures
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• 제22권3호
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• pp.273-290
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• 2016

The flutter derivatives of bridge decks can be efficiently identified using the experimentally and/or numerically coupled forced vibration method. This paper addresses the issue of inherent requirement for adopting different frequencies of three modes in this method. The aerostatic force components and the inertia of force and moment are mathematically proved to exert no influence on identification results if the signal length (t) is integer (n=1,2,3...) times of the least common multiple (T) of three modal periods. It is one important contribution to flutter derivatives identification theory and engineering practice in this study. Therefore, it is unnecessary to worry about the determination accuracy of aerostatic force and inertia of force and moment. The influences of signal length, amplitude, and frequency ratio on flutter derivative are thoroughly investigated using a bridge example. If the signal length t is too short, the extraction results may be completely wrong, and particular attention should be paid to this issue. The signal length t=nT ($n{\geq}5$) is strongly recommended for improving parameter identification accuracy. The proposed viewpoints and conclusions are of great significance for better understanding the essences of flutter derivative identification through coupled forced vibration method.