• 대한방사선기술학회지:방사선기술과학
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• 제46권4호
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• pp.277-285
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• 2023

In this study, pneumonia identification networks with the small number of layers were constructed by using chest X-ray images. The networks had similar trainable-parameters, and the performance of the trained models was quantitatively evaluated with the modification of the network architectures. A total of 6 networks were constructed: convolutional neural network (CNN), VGGNet, GoogleNet, residual network with identity blocks, ResNet with bottleneck blocks and ResNet with identity and bottleneck blocks. Trainable parameters for the 6 networks were set in a range of 273,921-294,817 by adjusting the output channels of convolution layers. The network training was implemented with binary cross entropy (BCE) loss function, sigmoid activation function, adaptive moment estimation (Adam) optimizer and 100 epochs. The performance of the trained models was evaluated in terms of training time, accuracy, precision, recall, specificity and F1-score. The results showed that the trained models with the small number of layers precisely detect pneumonia from chest X-ray images. In particular, the overall quantitative performance of the trained models based on the ResNets was above 0.9, and the performance levels were similar or superior to those based on the CNN, VGGNet and GoogleNet. Also, the residual blocks affected the performance of the trained models based on the ResNets. Therefore, in this study, we demonstrated that the object detection networks with the small number of layers are suitable for detecting pneumonia using chest X-ray images. And, the trained models based on the ResNets can be optimized by applying appropriate residual-blocks.

• 방송공학회논문지
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• 제5권2호
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• pp.211-219
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• 2000

IBAC DAB 시스템은 기존의 FM 방송 대역내의 가드밴드를 사용하게 됨에 따라 기존의 FM 방송신호로 인해 간섭을 받게 된다. IBAC(In Band Adjacent Channel) DAB 시스템의 성능평가에 있어서 FM 간섭신호는 중요한 요소가 된다. 국내 FM 공중파 방송신호를 실제 측정하여 수시로 변하는 FM 스펙트럼의 특성과, FM 채널 특성에 따라 FM 신호의 평균적인 스펙트럼의 특성을 구하였다. 본 논문에서는 제안한 IBAC DAB 시스템을 기반으로 한 이런 다양한 FM 간섭신호를 C로 모델링하여 IBAC DAB 시스템의 성능과 점유 대역폭에 따른 FM 간섭의 영향을 분석하고, 본 시스템의 성능이 유지될 수 있는 FM 간섭비를 제시한다. 실험결과 FM PSD의 평균 특성에 따라 IBAC DAB 시스템의 성능변화가 크며, 시스템의 성능이 유지 될 수 있는 FM 간섭 혼신비가 10dB임을 알 수 있었다.

• 한국안전학회지
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• 제31권5호
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• pp.1-6
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• 2016

The performance of a set of low-cost optical components used for measuring the optical density of PM particles was evaluated in the present study. To this end, the set of low-cost optical components was replaced with that of general optical components used to measure the PM optical density under identical experimental conditions. The optical densities measured from the set of general optical components were then compared to those obtained from the set of low-cost optical components. While the optical density is measured, another key parameter, the dimensionless extinction constant of PM particles (which is needed to optically measure the PM concentration) was also determined in the present study. The experimental results indicate that the optical density and PM concentration measurements performed by low-cost optical components are feasible, producing trackable variations in the OD and concentrations compared to values obtained from the set of general optical components.

• Structural Engineering and Mechanics
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• 제67권6호
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• pp.587-601
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• 2018

Elevated water tanks are inverted pendulum type structures where drift limit is an important criterion for seismic design and performance evaluation. Explicit drift criteria for elevated water tanks are not available in the literature. In this study, probabilistic approach is used to determine maximum drift limit for damage state of yielding and damage state of collapse for the elevated water tanks supported on RC frame staging. The two damage states are defined using results of incremental dynamic analysis wherein a total of 2160 nonlinear time history analyses are performed using twelve artificial spectrum compatible ground motions. Analytical fragility curves are developed using two-parameter lognormal distribution. The maximum allowable drifts corresponding to yield and collapse level requirements are estimated for different tank capacities. Finally, a single fragility curve is developed which provides maximum drift values for the different probability of damage. Further, for rational consideration of the uncertainties in design, three confidence levels are selected and corresponding drift limits for damage states of yielding and collapse are proposed. These values of maximum drift can be used in performance-based seismic design for a particular damage state depending on the level of confidence.

• 대한기계학회논문집B
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• 제24권11호
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• pp.1523-1534
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• 2000

The performance of a number of existing dynamic subgrid-scale(SGS) models is evaluated in large-eddy simulations(LES) of two prototype transitional and turbulent shear flows, a planar jet and a channel flow. The dynamic SGS models applied include the dynamic Smagorinsky model(DSM);Germano et al. 1991, Lully 1992), the dynamic tow-component model(DTM; Akhavan et al. 2000), the dynamic mixed model(DMM;Zang et al, 1993). and the dynamic two-parameter model(DTPM; Salvetti & Banerjee 1995). The results are compared with those for DNS for their evaluation. The LES results demonstrate the superior performance of DTM with use of a sharp cutoff filter and DMM with use of a box filter, as compared to their respect counterpart DSM, in predicting the mean statistics, spectra and large-scale structure of the flow, Such features of DTM and DMM derive from the construction of the models in which tow separate terms are included to represent the SGS interactions; a Smagorinsky edd-viscosity term to account for the non-local interactions, and a local-interaction term to account for the nonlinear dynamics between the resolved and subgrid scales in the vicinity of the LES cutoff. As well, overall the SGS models using a sharp cutoff filter are more successful than those using a box filter in capturing the statistics and structure of the flow. Finally, DTPM is found to be compatible or inferior to DMM.

• 한국소음진동공학회논문집
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• 제25권10호
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• pp.685-691
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• 2015

In this work, to identify effective parameter for performance of piezoelectric jetting dispenser, experimental investigation is carried out based on design of experiment. After preparing jetting dispenser using two stack-type piezoelectric actuators, basic working principle of the jetting dispenser is described. Eight operating conditions are chose as main factors and it is assumed that each factor has two levels. To reduce number of experiments for performance evaluation, the experimental sets are designed based on factional factorial design method. Experimental setup is established and the weight of single dot is measured by using precision scale. The main and interaction effects of factors are analyzed using commercial statistical program and optimal operating condition for small amount and small variation of weight of dispensed single dot are determined.

• 한국농공학회논문집
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• 제58권5호
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• pp.59-69
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• 2016

This study aims to evaluate the Soil and Water Assessment Tool (SWAT) hourly hydrological modeling performance and compare it with daily SWAT modeling parameters. For the Byeolmicheon catchment ($1.17km^2$) located in the upstream of Gyeongancheon watershed and total 18 storm events measured during 3 years (2011-2013), the hourly SWAT was calibrated and validated using the Green and Ampt (G&A) infiltration equation. The determination coefficient ($R^2$) and Nash-Sutcliffe model efficiency (NSE) of hourly SWAT discharge were 0.81 and 0.73 respectively, and the most sensitive parameter was soil saturated hydraulic conductivity (SOL_K) and calibrated with the average value of 0.075 mm/hr. In addition, the hourly SWAT simulation by G&A was compared with the daily SWAT simulation by SCS-CN (Soil Conservation Service-Curve Number) method for the whole 3 years period. The houlrly G&A results showed $R^2$ and NSE of 0.71 and 0.50, and the daily SCS-CN results were 0.71 and 0.66, respectively. The SOL_K by daily SCS_CN method was calibrated at 75.5 mm/hr, 1,000 times greater than the hourly G&A method. The next sensitive parameters for the hourly simulation were lag time of lateral flow (LAT_TIME) and lag time of surface runoff (SURLAG).

• 한국전기전자재료학회논문지
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• 제36권2호
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• pp.164-169
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• 2023

Nano Pt particles were dispersed on carbon-based supports by a polyol process for a catalyst application in a polymer electrolyte fuel cell. We tried to optimize the effect of pH on the electrostatic forces between the support and the Pt colloids. We investigated the relationship among the surface charges on the carbon support, the solution pH, and the concentration of a glycolate, and the Pt particle size. The produced catalyst with nano Pt particles on the support was evaluated by the long-term cyclic voltammetry (CV) performance test and compared with the results from a commercial catalyst. Our experimental results reveal that the pH-control can modify the particle size distribution and the dispersion of the nano Pt particles. This resulted in a cost-effective method for the synthesis of highly Pt loaded Pt/C catalysts for fuel cells better than a commercial catalyst system.

• Earthquakes and Structures
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• 제3권1호
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• pp.59-81
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• 2012

A ductility inverse-mapping method for SDOF systems including passive dampers is proposed which enables one to find the maximum acceleration of ground motion for the prescribed maximum response deformation. In the conventional capacity spectrum method, the maximum response deformation is computed through iterative procedures for the prescribed maximum acceleration of ground motion. This is because the equivalent linear model for response evaluation is described in terms of unknown maximum deformation. While successive calculations are needed, no numerically unstable iterative procedure is required in the proposed method. This ductility inverse-mapping method is applied to an SDOF model of bilinear hysteresis. The SDOF models without and with passive dampers (viscous, viscoelastic and hysteretic dampers) are taken into account to investigate the effectiveness of passive dampers for seismic retrofitting of building structures. Since the maximum response deformation is the principal parameter and specified sequentially, the proposed ductility inverse-mapping method is suitable for the implementation of the performance-based design.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2007년도 Proceedings of ISRS 2007
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• pp.282-285
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• 2007

Satellite observed brightness temperature simulation using a radiative transfer model (here after, RTM) is useful for various fields, for example sensor design and channel selection by using theoretically calculated radiance data, development of satellite data processing algorithm and algorithm parameter determination before launch. This study is focused on elaborating the simulation procedure, and analyzing of difference between observed and modelled clear sky brightness temperatures. For the CMDPS (COMS Meteorological Data Processing System) development, the simulated clear sky brightness temperatures are used to determine whether the corresponding pixels are cloud-contaminated in cloud mask algorithm as a reference data. Also it provides important information for calibrating satellite observed radiances. Meanwhile, simulated brightness temperatures of COMS channels plan to be used for assessing the CMDPS performance test. For these applications, the RTM requires fast calculation and high accuracy. The simulated clear sky brightness temperatures are compared with those of MTSAT-1R observation to assess the model performance and the quality of the observation. The results show that there is good agreement in the ocean mostly, while in the land disagreement is partially found due to surface characteristics such as land surface temperature, surface vegetation, terrain effect, and so on.