• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.1
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• pp.75-79
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• 2013

Demands for semiconductor devices are dramatically increasing, and advancements in fabrication technology are allowing a step-up in the number of devices per unit area. As a result, semiconductor devices require higher heat dissipation, and thus, cooling solutions have become important for guaranteeing their operational reliability. In particular, in chip-in-board packages, in which chips and passives are embedded in the substrates for efficient device layout, heat dissipation is of greater importance. In this study, a thermal model for layers of different materials has been proposed, and then, the heat transfer has been simulated by imposing a set of appropriate boundary conditions. Heat generation can be predicted based on the results, which will be utilized as practical data for actual package design.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.40 no.2
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• pp.239-245
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• 2020

Recently, BIM (Building Information Modeling) are widely being utilized in Construction industry. However, most structures that have been constructed in the past do not have BIM. For structures without BIM, the use of SfM (Structure from Motion) techniques in the 2D image obtained from the camera allows the generation of 3D model point cloud data and BIM to be established. However, since these generated point cloud data do not contain semantic information, it is necessary to manually classify what elements of the structure. Therefore, in this study, deep learning was applied to automate the process of classifying structural components. In the establishment of deep learning network, Inception-ResNet-v2 of CNN (Convolutional Neural Network) structure was used, and the components of bridge structure were learned through transfer learning. As a result of classifying components using the data collected to verify the developed system, the components of the bridge were classified with an accuracy of 96.13 %.

• The Korean Journal of Petroleum Geology
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• v.1 no.1 s.1
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• pp.29-35
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• 1993

Seismic reflection data can be used to extract information about the velocity structure of the earth. This process is called a velocity inversion of the seismic data. However, it is difficult to recover a broad band reflection coefficient series because the frequency band of seismic trace is limited. The linear programming method has been examined to find the simplest velocity model that has frequency components consistent with the usable frequencies of the seismic trace and interval velocity data. The velocity structure of the earth is displayed in pseudovelocity section. After the linear program had been tested with a synthetic seismic trace, it was applied to the seismic reflection data of the Block Ⅱ in the Yellow Sea. By comparing the pseudovelocity section with sonic logs obtained from the well in the same area, it was possible to define the lithostratigraphy and the boundaries of Cretaceous volcanics and Cretaceous metavolcanics.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.8
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• pp.55-62
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• 2006

This paper presents experimental evaluation of an insect-mimicking flapping-wing device actuated by a unimorph piezoceramic actuator. Length of each rod and hinge point in the linkage/amplification system are carefully chosen such that the resulting wing motion can mimic clapping of wings in a real insect at the end of upstroke. In addition to this, a pair of corrugated wings are fabricated mimicking zig-zag cross section of a real insect wing. Thanks to the two additional implementation, the improved flapping wing device can generate a larger lift force than the previous model even though area of the new wing is about 50% less than that of the previous wing. In this work, effects of the wing clapping, the wing corrugation, and the input wave form on the lift force generation have been also experimentally investigated. Finally, the vortex generated by the flapping device has been captured by a high speed camera, showing that vortices are produced during up- and down-strokes.

• Journal of KIISE:Databases
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• v.31 no.2
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• pp.195-204
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• 2004

The Semantic Web is proposed as the next generation Web technology. In the environment of the Semantic Web, resources are related with each other semantically and computers can process this information easily. The Resource Description Framework (RDF) supports this semantic relationship. RDF is the data model for describing metadata of the Web resources. To establish and develop the Semantic Web, methods for managing RDF data efficiently are the most important. So, in this research, we propose methods for storing and querying RDF data using an XML database system. Using an XML database system, XML data, main data of the Semantic Web, and RDF data, the metadata of XML data, can be managed in the same storage and by the same mechanism efficiently. In addition, we propose an efficient data retrieval method and several techniques to improve the system performance. Our query processing technique performs better than an existing system.

• The Journal of the Korea Contents Association
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• v.13 no.10
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• pp.92-102
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• 2013

The definition of mobile phone was a device that can make and receive telephone calls or messages for communication but it has rapidly developed from communication tool into multi-function device. Especially since release of smart phone, Korea is one of the highest country in the world and the statistics can be interpreted into people positively accept new technology. Therefore it's time to study on usage behavior according to different generation of mobile phone. Based on media richness theory and elaboration likelihood model, we analyzed factors affecting usage behavior of mobile phone. Case study methodology were constructed a survey to female university students from 20-24 years of age.

• Journal of Energy Engineering
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• v.26 no.4
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• pp.118-126
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• 2017

This study was performed to investigate the characteristics of combustion and emissions in pulverized coal fired boiler for using high moisture coal and dry coal through computational fluid dynamics(CFD). We validated this boiler model with performance data of the boiler. The results of flow characteristics showed that climbing speed of gases was increased as blending ratio of high moisture coal was increased. It can decrease a residence time of fuel in the furnace. And it influence coal combustion. The coal burnout and NOx generation in burner level were decreased as increasing blending ratio of high moisture coal. The gas temperature and NOx formation were increased after OFA level due to coal burnout delay.

• Smart Media Journal
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• v.7 no.1
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• pp.31-36
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• 2018

In this paper, we propose automatic screen on / off method of OST-HMD screen using gaze depth estimation technique. The proposed method uses MLP (Multi-layer Perceptron) to learn the user's gaze information and the corresponding distance of the object, and inputs the gaze information to estimate the distance. In the learning phase, eye-related features obtained using a wearable eye-tracker. These features are then entered into the Multi-layer Perceptron (MLP) for learning and model generation. In the inference step, eye - related features obtained from the eye tracker in real time input to the MLP to obtain the estimated depth value. Finally, we use the results of this calculation to determine whether to turn the display of the HMD on or off. A prototype was implemented and experiments were conducted to evaluate the feasibility of the proposed method.

• Journal of Korea Society of Industrial Information Systems
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• v.16 no.2
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• pp.65-72
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• 2011

In this paper, a real-time monocular vision based navigation system is developed for the disabled people, where online background learning and vector field histogram are used for identifying obstacles and recognizing avoidable paths. The proposed system is performed by three steps: obstacle classification, occupancy grid map generation and VFH-based path recommendation. Firstly, the obstacles are discriminated from images by subtracting with background model which is learned in real time. Thereafter, based on the classification results, an occupancy map sized at $32{\times}24$ is produced, each cell of which represents its own risk by 10 gray levels. Finally, the polar histogram is drawn from the occupancy map, then the sectors corresponding to the valley are chosen as safe paths. To assess the effectiveness of the proposed system, it was tested with a variety of obstacles at indoors and outdoors, then it showed the a'ccuracy of 88%. Moreover, it showed the superior performance when comparing with sensor based navigation systems, which proved the feasibility of the proposed system in using assistive devices of disabled people.

• Journal of Korea Society of Industrial Information Systems
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• v.19 no.6
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• pp.53-61
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• 2014

For monitoring the flight trajectory and the status of a launch vehicle, the mission control system in NARO space center process data acquired from the ground tracking system, which consists of two tracking radars, four telemetry stations, and one electro-optical tracking system. Each tracking unit exhibits its own tracking error mainly due to multi-path, clutter and radio refraction, and by utilizing only one among transmitted informations, it is not possible to determine the actual vehicle trajectory. This paper presents a way of generating flight trajectory via post-processing the data received from the ground tracking system. The post-processing algorithm is divided into two parts: compensation for atmosphere radio refraction and multi-sensor fusion, for which a decentralized Kalman filter was adopted and implemented based on constant acceleration model. Applications of the present scheme to real data resulted in the flight trajectory where the tracking errors were minimized than done by any one sensor.