• Korean System Dynamics Review
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• v.12 no.2
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• pp.127-151
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• 2011

The purpose of this study is to examine measures to improve government's supply oriented housing policy in population declining cities. For this purpose, system dynamics simulation method was used to build urban-housing model and different sets of housing policies were tested to see their impact on local housing problems. Simulation result shows that there is no best set of housing policies that can solve all housing problems in population declining cities. It also indicates that housing policy that solve one type of problems can worsen other type of problems. Housing policy that increases population size has negative effect of housing oversupply. It also increases proportion of old houses in population declining cities. However, housing policy that makes city younger with newer houses tends to increase housing shortage and housing price. So, policy choice needs to be made with clear understanding of trade off between different policies. The result also shows it is difficult to expect a full scale effect of housing policy on local housing problems unless it is executed with regional economic development policy because local housing problems are so closely related with local economic problem in population declining local cities.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.1905-1913
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• 2011

The dynamic characteristic of bogie that is driving system of railway vehicle is very important regarding decision of vehicle characteristics as running safety and comport. The dynamic characteristic test of bogie is tested on full size in place on field testing on track. But, the testing on the full size caused many problems. To overcome these problem by full size test, the Railway Safety Research Center in Seoul National University of Science & Technology developed 1/5 scale size of small scale derailment simulator and is currently testing running stability of 1/5 scaled bogie. Also To take effectively advantage of running stability test using small scale derailment simulator in actuality design and reliability estimation, it is necessary comparison and examination with field test and theoretical analysis result In this paper. to achieve running stability analysis of 1/5 scaled bogie on small scale derailment. the program using MATLAB that is fast compose and analysis the motion equation of Saemaul power bogie is developed. It is achieved analysis according to various specification (weight, size, suspension, etc..) and is evaluated corelation between test result and dynamic characteristic of actual railway vehicle.

• Journal of the Korean housing association
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• v.24 no.2
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• pp.97-104
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• 2013

This study involves 2 newly built apartment houses which are A with 23 floors as 150 mm slab width and B with 16 floors as 180 mm slab width. The impact was added by tapping and bang machine at the middle floor level of these 2 apartments and the test was arranged in terms of the characteristic of vibration and sound level which transferred to upper or down floors. As a result, impact floor shows the highest value in terms of both sound and vibration level and followed was at down floor of the Impact floor. Also, blocking function for the lightweight and heavyweight floor impact sound level was tested for each room of the apartment A and B including living room, main room, room 1 and 2. As a result, sound blocking function of B apartment was better than that of A and the function was getting worse when the room size is getting smaller.

• Journal of the Korean Society for Library and Information Science
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• v.48 no.3
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• pp.431-458
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• 2014

This research looked into both meaning and value of library catalog through the information behavior of user and suggested a plan to improve the quality and search functions, which are reflected the users' information needs and search behavior. U-CAT, a experimentally developed with reinforcing the contents and search functions of current library catalogs, was tested with the degree of satisfaction by the sample user group. The test results showed that the user's satisfaction on U-CAT was very high. The result verified that a little change with current library catalogs (to upgrade its quality) could result in a higher satisfaction of user group.

• Journal of Information Processing Systems
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• v.9 no.2
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• pp.217-236
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• 2013

Ranking thousands of web documents so that they are matched in response to a user query is really a challenging task. For this purpose, search engines use different ranking mechanisms on apparently related resultant web documents to decide the order in which documents should be displayed. Existing ranking mechanisms decide on the order of a web page based on the amount and popularity of the links pointed to and emerging from it. Sometime search engines result in placing less relevant documents in the top positions in response to a user query. There is a strong need to improve the ranking strategy. In this paper, a novel ranking mechanism is being proposed to rank the web documents that consider both the HTML structure of a page and the contextual senses of keywords that are present within it and its back-links. The approach has been tested on data sets of URLs and on their back-links in relation to different topics. The experimental result shows that the overall search results, in response to user queries, are improved. The ordering of the links that have been obtained is compared with the ordering that has been done by using the page rank score. The results obtained thereafter shows that the proposed mechanism contextually puts more related web pages in the top order, as compared to the page rank score.

• Journal of the Korean Society of Earth Science Education
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• v.4 no.3
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• pp.218-230
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• 2011

The aim of this current study is to survey and analyze the degree of concern and difficult of elementary school teachers in elementary school science classes, and providing the results to teachers as a basic reference to improve their scientific specialties. As a result, firstly, the degree of concern of elementary school teacher in science class is more than normal level. Secondly, the degree of concern in science class differs dependent on environmental factors. Next, the degree of difficulty about science class was under normal level. Among area surveyed, physical and psychological environment were lower compared with other areas, and the difficulty in evaluation of class result was comparably higher than others. At fourth, teacher's degree of difficulty in science class was dependent on environment factors, but not on gender. Finally, there was reverse correlation between degree of concern and the degree of difficulty of elementary school teachers in science class. Further, the degree of concern in student knowledge showed more significant reverse correlation with all of area tested.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.104.1-104.1
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• 2010

We investigated combustion characteristics of wood pellets in a combustion equipment with adjusting amount of flue gas. Maximum temperature in a combustion chamber was $850^{\circ}C$. Higher heating Value of a domestic wood pellet tested is 19.1 MJ/kg and water content was 8.3%. Amount of flue gas causes big effect on burning characteristics in $450{\sim}600^{\circ}C$. Wood pellet does not burn in low temperature atmosphere less than $450^{\circ}C$ and low flue gas flow rate. We made burning the pellet that is made in Korea, USA, Chile and Canada. Color of foreign pellets are bright brown and they made by mainly sawdust. Korean pellet is a dark brown color because it contains bark. There are some differences in the result of elementary analysis and technical analysis. According to the result of burning experiment, burning times of each countries's pellet are similar.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.2037-2040
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• 2004

In this paper we introduce a new prototype based classifiers for overlapping data, where training pattern can be overlap on the feature space. The proposed classifier is based on the prototype from neural network classifier (NNC)[1] for overlap data. The method automatically chooses the initial center and two radiuses for each class. The center is used as a mean representative of training data for each class. The unclassified pattern is classified by measure distance from the class center. If the distance is in the lower (shorter radius) the unknown pattern has the high percentage of being in this class. If the distance is between the lower and upper (further radius), the pattern has the probability of being in this class or others. But if the distance is outside the upper, the pattern is not in this class. We borrow the words upper and lower from the rough set to represent the region of certainty [3]. The training algorithm to find number of cluster and their parameters (center, lower, upper) is presented. The clustering result is tested using patterns from Thai handwritten letter and the clustering result is very similar to human eyes clustering.

• Proceedings of the IEEK Conference
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• 2004.06a
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• pp.189-192
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• 2004

A LNA module, integrated microwave assemblies (IMAs) were developed for use in Ka-band Satellite Communication Satellite Payload that operates in the frequency range of 29,6 ${\~}$ 30.0GHz. The module will be placed directly behind their respective antenna feed horns to minimize the required waveguide and system noise figure impact. Two MMIC LNA Chips were used in the module design. The measured result shows that the module has 32dB gain and 2.4dB NF performance. The module size is 51m ${\times}$ 36m ${\times}$ 22 and the mass is 92g. The Noise Figure performance is the best result of currently available modules for satellite payload operating in the same frequency range. The module will be assembled using space-qualified process and tested for space qualification.

• Journal of Internet Computing and Services
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• v.21 no.4
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• pp.127-135
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• 2020

The purpose of this study is to develop a human activity recognition (HAR) system, which distinguishes 13 activities, including five activities commonly dealt with in conventional HAR researches and eight activities from the Eastern-Asian culture. The eight special activities include floor-sitting/standing, chair-sitting/standing, floor-lying/up, and bed-lying/up. We used a 3-axis accelerometer sensor on the wrist for data collection and designed a machine learning model for the activity classification. Data clustering through preprocessing and feature extraction/reduction is performed. We then tested six machine learning algorithms for recognition accuracy comparison. As a result, we have achieved an average accuracy of 99.7% for the 13 activities. This result is far better than the average accuracy of current HAR researches based on a smartwatch (89.4%). The superiority of the HAR system developed in this study is proven because we have achieved 98.7% accuracy with publically available 'pamap2' dataset of 12 activities, whose conventionally met the best accuracy is 96.6%.