• Journal of Korea Multimedia Society
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• v.21 no.4
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• pp.450-463
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• 2018

Sound based machine fault diagnosis is the process consisting of detecting automatically the damages that affect the machines by analyzing the sounds they produce during their operating time. The collected sounds being inevitably corrupted by random disturbance, the most important part of the diagnosis consists of discovering the hidden elements inside the data that can reveal the faulty patterns. This paper presents a novel feature extraction methodology that combines various digital signal processing and pattern recognition methods for the analysis of the sounds produced by the drills. Using the Fourier analysis, the magnitude spectrum of the sounds are extracted, converted into two-dimensional vectors and uniformly normalized in such a way that they can be represented as 8-bit grayscale images. Histogram equalization is then performed over the obtained images in order to adjust their very poor contrast. The obtained contrast enhanced images will be used as the features of our diagnosis system. Finally, principal component analysis is performed over the image features for reducing their dimensions and a nonlinear classifier is adopted to produce the final response. Unlike the conventional features, the results demonstrate that the proposed feature extraction method manages to capture the hidden health patterns of the sound.

• Architectural research
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• v.15 no.3
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• pp.151-158
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• 2013

Offshore oil and gas process plants are exposed to hazardous accidents such as explosion and fire, so that the structural components should resist such accidental loads. Given the possibilities of thousands of different scenarios for the occurrence of an accidental hazard, the best way to predict a reasonable size of a specific accidental load would be the employment of a probabilistic approach. Having the fact that a specific procedure for probabilistic accidental hazard analysis has not yet been established especially for explosion and fire hazards, it is widely accepted that engineers usually take simple and conservative figures in assuming uncertainties inherent in the procedure, resulting either in underestimation or more likely in overestimation in the topside structural design for offshore plants. The variation in the results of a probabilistic approach is determined by the assumptions accepted in the procedures of explosion probability computation, explosion analysis, and structural analysis. A design overpressure load for a sample offshore plant is determined according to the proposed probabilistic approach in this study. CFD analysis results using a Flame Acceleration Simulator, FLACS_v9.1, are utilized to create an overpressure hazard curve. Moreover, the negative impulse and frequency contents of a blast wave are considerably influencing structural responses, but those are completely ignored in a widely used triangular form of blast wave. An idealistic blast wave profile deploying both negative and positive pulses is proposed in this study. A topside process module and piperack with blast wall are 3D FE modeled for structural analysis using LS-DYNA. Three different types of blast wave profiles are applied, two of typical triangular forms having different impulse and the proposed load profile. In conclusion, it is found that a typical triangular blast load leads to overestimation in structural design.

• The Journal of Society for e-Business Studies
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• v.22 no.4
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• pp.103-115
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• 2017

Globally, frequency and scale of natural disasters are growing, also the damage is increasing. In view of the damage by natural disasters for several years, it is true that Korea is not free from such damages. In this paper, we propose a process to efficiently manage recovery resources in case of disaster damage. We utilize the IoT technology to detect the resource status in real time, and configure the process so that the state and movement of the recovery resource can be grasped in real time through the resource activity recognition module. In addition, we designed the database that is necessary to actualize it, and developed and experimented resource activity recognition module using smart-phone sensors. This will contribute to building a quick and efficient disaster response system.

• Korean Journal of Human Ecology
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• v.14 no.6
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• pp.899-913
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• 2005

The purpose of the study is to analyze the perception and expectation made by parents, regarding the goal, methods and management of kindergarten education. The study is designed to identify social needs for the early childhood education and to produce some important information necessary for the development of education programs for kindergarteners and for the management of a kindergarten. As subjects of the study, 623 mothers of kindergartens were sampled from kindergartens. The researcher constructed a questionnaire of multiple-choice type for surveying opinions of the subjects, based on the analysis of curriculum materials published by Korean Ministry of Education. In data analysis, frequency of response on each item of the questionnaire was tabulated, and chi-square test was applied for testing the difference between independent samples. The results of the study are summarized as followings: First, parents feel kindergarten education necessary because 'interaction with peers' itself must be an important condition for socialization of younger children. For an 'ideal personality' to be pursued in kindergarten education, parents place 'moral personality' in the first priority.' And for educational objective of kindergarten they select 'development of cooperative attitude' as the most important one. Second, 'play method' is emphasized by parents as the most desirable educational method for kindergartener. Third, they think it is necessary for parents to participate in the management of kindergarten. And they also feel that parents of kindergartener should be educated on the early childhood education. Fourth, parents emphasize that the early childhood education should be integrated into a public educational system in order to provide equal educational opportunity for all preschoolers.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.1
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• pp.146-153
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• 1996

A SCARA type direct drive robot which can be used in the assembly operation was designed and manufactured. Graphite fiber epoxy composite material was used in the fabrication of the robot arm structure in order to improve the speed of the robot arm with a high damping effect. For model-based control and sensitivity analysis of system parameters, the dynamic model of robot arm and drive servo amplifier parameters such as equivalent gains of PWM driver and velocity gains of servo system were estimated from frequency response tests. The complete dynamic model for overall robot system was used in the simulation of the open-loop control. The simulation results agreed reasonably well to the experimental results. The feedforward control using the dynamic models improved the trajectory tracking performance, decreasing the tracking error by factor of three compared with PID control. This study found that the inverse dynamic model of the robot arm including the drive servo system showed better performances than the case of arm dynamic model only.

• Journal of Power Electronics
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• v.16 no.2
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• pp.717-730
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• 2016

The harmonic components of grid voltage result in oscillations of the calculated phase obtained via phase synchronization. This affects the security and stability of grid-connected converters. Moving average filter, delayed signal cancellation and their related harmonic elimination algorithms are major methods for such issues. However, all of the existing methods have their limitations in dealing with multiple harmonics issues. Furthermore, few studies have focused on a comparison and evaluation of these algorithms to achieve optimal algorithm selections in specific applications. In this paper, these algorithms are quantitatively analyzed based on the derived mathematical models. Moreover, an enhanced moving average filter and enhanced delayed signal cancellation algorithms, which are applicable for eliminating a group of selective harmonics with only one calculation block, are proposed. On this basis, both a comprehensive comparison and a quantitative evaluation of all of the aforementioned algorithms are made from several aspects, including response speed, required data storage size, sensitivity to sampling frequency, and elimination of random noise and harmonics. With the conclusions derived in this paper, better overall performance in terms of harmonic elimination can be achieved. In addition, experimental results under different conditions demonstrate the validity of this study.

• Journal of the Korean Institute of Landscape Architecture
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• v.16 no.2
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• pp.23-41
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• 1988

Environmental design pattern of the nine Small Urban Spaces at C.B.D. in City of Seoul are surveyed and analyzed for user's satisfaction and behavior under the environmental design evaluation by using Chrisopher Alexander's Pattern Language. Small Urban Spaces as a part of streetscape are formed by physical factors as well as visual environment and interacting user's behavior. Therefore, user's satisfacuion and behavior at the nine Urban Small Spaces were investigated under the further search for some possibilities of a pplication of those Pattern Languages. A pattern language has a structure of a network. It is used in sequence, going through the patterns, moving always from large patterns to smaller, always from the ones which create comes simply from the obsernation that most of the wonderful places of the city were not made by architects but by the people. It defines the limited number of arrangements of spaces that make sense in any given culture. And it actually gives us the power to generate these coherent arrangement of space. As a results, 'Plazl', 'Seats' and 'Accessibility' related design patterns are highly evaluated by Pattern Frequency, Pattern Interaction and their Composition ranks, thus reconfirm Whyte's Praise of urban Small Spaces in our inner city design environments. According to the multiple regression analysis of user's evaluation, the environmental functins related to the satisfaction were 'Plaza', 'Accessibility' and 'Paving'. According to the free response, user's prefer such visually pleasing environmental design object as 'Waterscape' and 'Setting'. In addition to, the basic needs in Urban Small Spaces are amenity facilities as bench, drinking water and shade for rest.

• Journal of Korean Physical Therapy Science
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• v.13 no.3
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• pp.41-54
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• 2006

The purpose of this study was to analyze various forms of musculoskeletal pain during different stages such as antenatal, pregnancy, delivery, and postpartum. The data for this study were collected through a self-administered survey with a structured questionnaire to 113 subjects. The survey was administered from May, 2003 to March, 2004 with subjects selected from postpartum centers in 3 different areas: Kangnam, Kangbook, and Bucheon. Analytical tools used for this study were frequency analysis, crosstabulation, percentage analysis, independent t-test, chi-square, and multiple response analysis. The findings of this study were as follows: 1. Comparison study of musculoskeletal pain according to variables including a pregnant woman's age, delivery techniques, different types of delivery such as primiparity, multiparity, dystocia, easy delivery, shows that these relationships are statistically not significant (p>0.05). 2. A total of 61.9% gave positive responses for the question about the relationship between musculoskeletal pain during postpartum and that in preparation of labor, but shows that this relationship was statistically not significant (p>0.05). 3. Relationships between forms of musculoskeletal pain in different phases are significant (p<0.05). The compared phases are: premarriage and pre-pregnancy, premarriage and antenatal, premarriage and postpartum, premarriage and lactiferous phase, pre-pregnancy and antenatal, pre-pregnancy and postpartum, and pre-pregnancy and lactiferous phase. However, results for the comparison between antenatal and postpartum, antenatal and lactiferous phase, and postpartum and lactiferous phase show that these relationships are statistically not significant (p>0.05). According to this study, musculoskeletal pain which occurred during antenatal is significantly related to the pain occurring during postpartum. Results produced from this study might be used as a helpful tool for developing educational programs aiming at teaching self pain-detection performable at home or at the workplace and body maintenance during the course of antenatal and postpartum.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.13 no.2
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• pp.89-99
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• 2001

In the present paper, Helmholtz resonator, which is widely used as a sound-amplification device, is applied to the development of seawater-exchanging breakwater. The incident waves can induce a large response in the resonator when incident wave frequency is close to one of natural modes of the resonator. Largely amplified potential energy due to the resonance supplies clean seawater into the harbor side throughout the channel. Flow supplied by the resonator circulates the seawater of harbor and helps to improve water quality. Within the framework of linear potential theory, matched asymptotic expansion method is employed to analyze the wave responses in a resonator. The semi-circular shape of the resonator has been chosen as an analytic model for mathematical simplicity. The wave responses of both single and arrays of Helmholtz resonator are investi¬gated. To validate an analytic solution, model test is conducted at 2-dimensional wave tanle Wave hcights in the resonator and velocity at the channel are measured for the state of valve-on and valve-off.

• The Journal of the Korea Contents Association
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• v.9 no.3
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• pp.329-335
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• 2009

The purpose of this study was to analyze effect of participation satisfaction, absorption on exercise adherence of Elementary Student Hapkido participants. Data was collected from a questionnaire designed for this study consisted of fixed alternative choice response to item constructed to represent the operational definition for each variable. The inventory was administered to stratified cluster random sampling 315 Elementary Student Hapkido participant in Daejeon City Hapkido Alliance. Statistics employed the study to data analysis were frequency, correlation, regression analysis. Based on the result of the study, the following conclusion appears warranted: First, participation satisfaction of Hapkido influence exercise adherence of Elementary Student Hapkido participants. Secondly, participation absorption of Hapkido influence exercise adherence of Elementary Student Hapkido participant.