• Journal of the Institute of Electronics Engineers of Korea SD
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• v.49 no.7
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• pp.1-9
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• 2012

In this paper, resistance temperature detector (RTD) integrated into the LED package is proposed in order to solve the temperature dependence of LED's optical properties. To measure the package temperature in real time, the RTD type temperature sensor having excellent accuracy and linearity between temperature change and resistance change was adopted. A stable metallic film is required for long term reliability and stability of the RTD type temperature sensor. Therefore, deposition and annealing condition for the film were determined. Based on the determined condition, the RTD type temperature sensor with the sensitivity of about $1.560{\Omega}/^{\circ}C$ was fabricated inside the LED package. In order to configurate the LED package system keeping the constant brightness regardless of the temperature, additional conversion circuit and control circuit boards were fabricated and added to the fabricated LED package. The proposed system was designed to compensate the light intensity caused by temperature change using the variable duty rate of driving current. As a result, the duty rate of PWM signal which is the output signal of the configurated system was changed with the temperature change, and the duty rate was similarly varied with the target duty rate. Consequently, it was focused the fabricated RTD can be used for compensating the optical properties of LED and the LED package which exhibits constant brightness regardless of the temperature change.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.3
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• pp.243-254
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• 2014

It is essential to predict the coil temperature under over load and over speed conditions for reliability in high speed low torque surface mounted PM synchronous motors(SPM). In the present study, the losses and coil temperature are measured under rated condition and calculated under over speed and over load conditions in the three different motors with 35PN440, 25PN250 and 15HTH1000. The heat transfer modeling has been performed based on acquired losses and temperature. The difference of coil temperature between heat transfer modeling and experiment is less than 6.4% under no load, over speed and over load conditions. Subsequently, the coil temperature of the motor with 15HTH1000 is 84.4% of the coil temperature of the motor with 35PN440 when speed is 0.9 and load is 3.0. The output of motor with 15HTH1000 is 85.2% greater than the output of the motor with 35PN440 when the dimensionless coil temperature is 1.0.

• The Korean Journal of Vision Science
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• v.20 no.4
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• pp.505-511
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• 2018

Purpose : This study investigated the visual functions of drivers aged over 65 year olds and drivers aged 50~65 year olds. In addition, difference of visual functions between professional drivers and normal drivers were investigated. Methods : Forty Driver aged over 65 year olds and 67 drivers aged less than 67 year olds were participated. All participants had more than 5 years of driving experiences and had no ocular pathology. Demographic data(gender, job, age, body condition) and visual functions such as contrast sensitivity(CS), stereopsis, glare recovery time and discomfort glare index were measured. Results : Constrast sensivity under photopic condition was higher with bus driver group. In addition, difference of CS at 12cpd and 18cpd were signifcantly different between normal drivers(1.57) and bus drivers(1.70) (p<0.05). There was no significant difference for glare recovery time, despite of trend of longer recovery time with age. Discomfort glare index was significantly different that normal drivers with more than 65 year olds had 3, taxi and truck driver presented almost 5 index score (p<0.05). Conclusion : Analysis of visual function of elderly drivers, it was confirmed that their visual functions decreased with age. Therefore, visual function tests such as CS, discomfort glare index and stereopsis in addition to current available test may need to be considered for drivers aged over 65.

• Korean Journal of Heritage: History & Science
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• v.46 no.2
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• pp.114-135
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• 2013

Among the UNESCO World Heritage Sites, the proportion of natural heritage to cultural heritage is relatively small. In 2007, the "Jeju Volcanic Island and Larva Tubes" was the first one that was designated as an UNESCO World Natural Heritage Site in Korea. The growing Korean geological heritage condition and conservation case studies on management of the geological heritage were examined in this study. Furthermore, the purpose of this study is to show future driving strategy for conservation and improvement plan on our geological heritage. Natural Monuments as a state-designated natural property and Geoparks as a new application system for geological heritage are important to conserve our geological heritage. Public engagement through establishment of visitor centers is definitely needed to improve education and promotion. The study includes field investigation for the "Wadden Sea", an World Natural Heritage Site for a mud flat, interviews with staffs and experts who are responsible for investigating and managing the site. Three factors can likely be attributed to its successful management and conservation policy for the "Wadden Sea". First of all, there is an operation for integrated management system and joint secretariat for research and monitoring. Next, researchers invigorate the visitor centers for promotion and education on geological heritage. Finally, experts and staffs implement various research topics and projects based on a long-range plan. The study was carried out to evaluate the present condition of our geological heritage and to make a proposal as a policy to improve value and conserve them. In conclusion, this study provided future discussion that may help researchers to make a decision on long-term policies for the geological subject of Korean natural heritage.

• Journal of the Korean Geotechnical Society
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• v.22 no.6
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• pp.15-26
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• 2006

Although numerous investigations have been performed over the years to predict the behavior and bearing capacity of piles, the mechanisms are not yet entirely understood. The prediction of bearing capacity is a difficult task, because large numbers of factors affect the capacity and also have complex relationship one another. Therefore, it is extremely difficult to search the essential factors among many factors, which are related with ground condition, pile type, driving condition and others, and then appropriately consider complicated relationship among the searched factors. The present paper describes the application of Artificial Neural Network (ANN) in predicting the capacity including its components at the tip and along the shaft from dynamic load test of the driven piles. Firstly, the effect of each factor on the value of bearing capacity is investigated on the basis of sensitivity analysis using ANN modeling. Secondly, the authors use the design methodology composed of ANN and genetic algorithm (GA) to find optimal neural network model to predict the bearing capacity. The authors allow this methodology to find the appropriate combination of input parameters, the number of hidden units and the transfer structure among the input, the hidden and the out layers. The results of this study indicate that the neural network model serves as a reliable and simple predictive tool for the bearing capacity of driven piles.

• Science of Emotion and Sensibility
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• v.26 no.4
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• pp.51-70
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• 2023

This study employed driving simulation to examine how takeover request (TOR) information modalities (visual, auditory, and visual + auditory) in Level-3 automated vehicles, and road types (straight and curved) influence the driver's control takeover time (TOT) and mental workload, assessed through subjective workload and heart rate variations. The findings reveal several key points. First, visual TOR resulted in the quickest TOT, while auditory TOR led to the longest. Second, TOT was considerably slower on curved roads compared to straight roads, with the greatest difference observed under the auditory TOR condition. Third, the auditory TOR condition generally induced lower subjective workload and heart rate variability than the visual or visual + auditory conditions. Finally, significant heart rate changes were predominantly observed in curved road conditions. These outcomes indicate that TOT and mental workload levels in drivers are influenced by both the TOR modality and road geometry. Notably, a faster TOT is associated with increased mental workload.

• Korean Journal of Agricultural and Forest Meteorology
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• v.18 no.4
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• pp.233-241
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• 2016

Experiments were carried out to quantify the topographic effects on attenuation of sunshine in complex terrain and the results are expected to help convert the coarse resolution sunshine duration information provided by the Korea Meteorological Administration (KMA) into a detailed map reflecting the terrain characteristics of mountainous watershed. Hourly shaded relief images for one year, each pixel consisting of 0 to 255 brightness value, were constructed by applying techniques of shadow modeling and skyline analysis to the 3m resolution digital elevation model for an experimental watershed on the southern slope of Mt. Jiri in Korea. By using a bimetal sunshine recorder, sunshine duration was measured at three points with different terrain conditions in the watershed from May 15, 2015 to May 14, 2016. The brightness values of the 3 corresponding pixel points on the shaded relief map were extracted and regressed to the measured sunshine duration, resulting in a brightness-sunshine duration response curve for a clear day. We devised a method to calibrate this curve equation according to sky condition categorized by cloud amount and used it to derive an empirical model for estimating sunshine duration over a complex terrain. When the performance of this model was compared with a conventional scheme for estimating sunshine duration over a horizontal plane, the estimation bias was improved remarkably and the root mean square error for daily sunshine hour was 1.7hr, which is a reduction by 37% from the conventional method. In order to apply this model to a given area, the clear-sky sunshine duration of each pixel should be produced on hourly intervals first, by driving the curve equation with the hourly shaded relief image of the area. Next, the cloud effect is corrected by 3-hourly 'sky condition' of the KMA digital forecast products. Finally, daily sunshine hour can be obtained by accumulating the hourly sunshine duration. A detailed sunshine duration distribution of 3m horizontal resolution was obtained by applying this procedure to the experimental watershed.

• Journal of the Korean Applied Science and Technology
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• v.34 no.4
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• pp.962-973
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• 2017

Concerns about an air pollution are gradually increasing at home and abroad. The automotive and fuel researchers are trying to reduce emissions and greenhouse gases of vehicles through a research on new engine designs and innovative after-treatment systems using clean fuels (eco-alternative fuel) and fuel quality improvements. In this paper, we stduy the emission characteristics of greenhouse gases on seven vehicles using gasoline, diesel, and LPG by legal test mode in domestic and abroad.(Urban mode, Highway mode, rapidly acceleration and deceleration, using air conditioner, low temperature condition) Regardless of fuels, most of the greenhouse gases tend to show the worst results in cold FTP-75 mode. In the case of A vehicles (2.0 MPI) and B vehicles (2.4 GDI) using a gasoline fuel, the factors that increase greenhouse gases are in order of a rapidly acceleration and deceleration, using air conditioner, low temperature condition. But G vehicles(LPLi) have different emission characteristics from another vehicles. In the case of A vehicles (2.0 w/o DPF) and B vehicles (2.2 with DPF) using a diesel fuel, the factors that increase greenhouse gases are in order of a rapidly acceleration and deceleration, using air conditioner, low temperature condition. However, the factor of F vehicles are in order of low temperature condition, using air conditioner, rapidly acceleration and deceleration. In conclusion, it will be an effective method to apply different technologies of emission reduction for each fuel.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.2
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• pp.355-365
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• 1994

An analytical model of return flow is presented outside the surf zone. The governing equation is derived from the Navier-Stokes equation and the continuity. Each term of the governing equation is evaluated by the ordering analysis. Then the infinitesimal terms, i.e. the turbulent normal stress, the squared vertical velocity of water particle and the streaming velocity, are neglected. The driving forces of return flow are calculated using the linear wave theory for the shallow water approximation. Especially, the space derivative of local wave heights is described considering a shoaling coefficient. The vertical distribution of eddy viscosity is discussed to the customary types which are the constant, the linear function and the exponential function. Each coefficient of the eddy viscosities which sensitively affect the precision of solutions is uniquely decided from the additional boundary condition which the velocity becomes zero at the wave trough level. Also the boundary conditions at the bottom and the continuity relation are used in the integration of the governing equation. The theoretical solutions of present model are compared with the various experimental results. The solutions show a good agreement with the experimental results in the case of constant or exponential function type eddy viscosity.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.14 no.5
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• pp.1-12
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• 2015

Length and the number of tunnels has increased 10% annually. Tunnel construction has positive effect in nature and driving condition. However, the structure of tunnels lead to a greater probability of major accidents. For this reason, tunnel is focusing its attention on the rapid incident handling and disaster management to build a tunnel management system in recently. In this study, tunnel management system adequacy analyzed in terms of operational safety using IPA and AHP analysis. IPA analysis results using the portfolio chart, incident management factors has a large gap between important and satisfaction. Disaster management is analyzed high ranking in priority. However, incident management factors are derived first priority in AHP analysis. This study determined that the results are meaningful to practitioners in the field is determined. In addition, practitioners comments should be reflected primarily for tunnel operational safely.