• The Transactions of the Korean Institute of Electrical Engineers P
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• v.60 no.2
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• pp.91-93
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• 2011

This paper is presented for the performance of the Fluid Dynamic Bearing(FDB) by the groove design and the tooling condition. Recently, spindle motors which require smaller size, lower sound noise, lower vibration, and higher speed of the rotation have been placed in high value-added products including Digital Lightening Processors(DLP), Hard Disk Drives(HDD), and ODDs. The spindle motors using the sintered porous metal bearing have higher vibration and acoustic noise by dry contact and large tolerance of the bearing parts. The Fluid Dynamic Bearing (FDB) with grooves is appropriate for spindle motors adequate in regards to mechanical vibration and acoustic noise. The paper shows the performance comparisons of between sintered porous metal bearing and FDB, and each FDBs according to the tooling deviations of grooves by the Finite Element Analysis(FEA) of the mechanical field. This paper shows the methods to make the grooves, the groove's depth, and the prototype of the motor with the fluid dynamic bearing. The performance characteristics of the grooves with the FDB are verified by the experimental results.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.8
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• pp.1215-1221
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• 2017

Parametric array transducers are used for highly directional speaker in an air environments. Piezoelectric micromachined ultrasonic transducers for parametric array transducers need DC-biased voltage driving signals in order to get high-directional quality-sound features. The existing power amplifier such as class A amplifiers has low efficiency and require large volume heatsinks. To overcome the above-mentioned disadvantages of the conventional amplifier, this paper proposes a new power amplifier system. The proposed power amplifier system ensures high linearity of output characteristic by utilizing the push-pull class B type amplifier. Furthermore, the proposed power amplifier system gets high efficiency because it contains the DC-DC converter-type power supply which can perform energy recovery and envelope tracking function. Also the paper suggests the detailed circuit topology. Its characteristics are verified by the detailed experimental results.

• Journal of Satellite, Information and Communications
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• v.8 no.4
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• pp.17-20
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• 2013

In this study, we introduce an LED Driving circuit in order that the information state can indicate audio signal gain and radiate pattern of ultrasonic speaker system for a sign board. Ultrasonic speaker system decreases energy loss and transmits the sound farther. Ultrasonic speaker having such characteristics is useful in that it can be widely used in daily life. Additionally, Proposed LED circuit indicates the information state as linear LED brightness taken from interface of ultrasonic speaker system. Designed circuit is confirmed through $0.35{\mu}m$ CMOS process by Dong-bu.

• Wind and Structures
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• v.11 no.5
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• pp.361-376
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• 2008

This paper considers internal pressure fluctuations for a range of building volumes and dominant wall opening areas. The study recognizes that the air flow in and out of the dominant opening in the envelope generates Helmholtz resonance, which can amplify the internal pressure fluctuations compared to the external pressure, at the opening. Numerical methods were used to estimate fluctuating standard deviation and peak (i.e. design) internal pressures from full-scale measured external pressures. The ratios of standard deviation and peak internal pressures to the external pressures at a dominant windward wall opening of area, AW are presented in terms of the non-dimensional opening size to volume parameter, $S^*=(a_s/\bar{U}_h)^2(A_W^{3/2}/V_{Ie})$ where $a_s$ is the speed of sound, $\bar{U}_h$ is the mean wind speed at the top of the building and $V_{Ie}$ is the effective internal volume. The standard deviation of internal pressure exceeds the external pressures at the opening, for $S^*$ greater than about 0.75, showing increasing amplification with increasing $S^*$. The peak internal pressure can be expected to exceed the peak external pressure at the opening by 10% to 50%, for $S^*$ greater than about 5. A dominant leeward wall opening also produces similar fluctuating internal pressure characteristics.

• Journal of Korea Multimedia Society
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• v.8 no.6
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• pp.827-835
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• 2005

In this paper, self-networking and replaceable structure in vector graphics contents are presented for wireless internet service. The wireless networks over 2G or 3G are limited in the sense of the speed and the cost. Considering these characteristics of wireless network, self-networking method and replaceable structure in downloaded contents are introduced in order to save the amount of data and provide variations for contents. During the display of contents, a certain data for the contents is downloaded from the server and it is managed appropriately for the operation of the contents. The downloaded materials are reflected to the original contents using replaceable structure. Also, the downloading and modification are independent of the play. In this implementation, the data consists of control data for control and resource data for image, sound or text. Comparing to the conventional methods which download the whole data, the amount of the transmitted data is very small since only the difference is downloaded. Also, during the play of the contents, the changes are adopted immediately. The whole functions are implemented in wireless handset and the various applications are discussed.

• Journal of the Korea Computer Industry Society
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• v.2 no.3
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• pp.377-388
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• 2001

Software metrics provide effective methods for characterizing software. Metrics have traditionally been composed through the definition of an equation, but this approach restricted within a full understanding of every interrelationships among the parameters. This paper use fuzzy logic system that is capable of uniformly approximating any nonlinear function and applying cognitive psychology theory. First of all, we extract multiple regression equation from the factors of 12 software complexity metrics collected from Java programs. We apply cognitive psychology theory in program volume factor, and then measure program volume complexity to execute fuzzy learning. This approach is sound, thus serving as the groundwork for further exploration into the analysis and design of software metrics.

• Journal of Distribution Science
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• v.10 no.10
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• pp.5-9
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• 2012

Purpose - The purpose of this study is to explore, examine, and analyze Journal of Distribution Science and its articles based on five key factors of journal selection process by Thompson and to provide foundations for further knowledge creation and theory building in the areas of distribution and distribution science. Research design, data, methodology - This study used an exploratory case study method to engage article analysis and reviews of Journal of Distribution Science. Thompson's five journal selection factors were used as criteria for the journal and article analyses and review. Results - Journal of Distribution Science is currently meeting or at least in the progress of meeting the following factors: timeliness of publication, international editorial convention, international diversity, and citation analysis. However, JDS is short of meeting the factor of editorial content. The research topics were not new, emerging, and/or distinctive, and they were not directly associated with specific region or country other than Korea. Conclusions - The findings from this study could lead the field of distribution to reexamine the core knowledge, to reestablish the fundamental concepts and principles, to formulate and propose academically and practically sound research methods, and to develop and focus on unique research topics in the area of distribution.

• KIEAE Journal
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• v.16 no.1
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• pp.47-55
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• 2016

Purpose: Long-life housing causes unavoidable cost increase while providing higher durability, flexibility, and repair easiness compare to those of normal apartment. The effectiveness should be evaluated considering the level of passing mandatory Long-life housing Certification System when supplying specific size of apartment complex. Thus, it is essential to identify the estimated costs and the obtainable grade by applying the optional element technologies selectively during the design phase. This study aimed to suggest the technology influence matrix(TIM) to support decision-making of element technologies in planning stage of long-life housing. Method: The technology influence matrix was established based on the property information about applicable element technologies for long-life housing such as construction methods, interface types, cost data, and certification-related characteristics. The usefulness of TIM was verified through case study, in which TIM was applied to the exclusive housing unit and the influences from four areas of quantity, cost, certification, and schedule were identified and calculated. Result: TIMs covering four areas representing the essential planning factors were developed, and are expected to contribute to sound decision-making in planning long-life housing.

• Safety and Health at Work
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• v.7 no.3
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• pp.225-230
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• 2016

Background: This study seeks to examine the relationship and impact of occupational health and safety on employees' organizational commitment in Ghana's mining industry. The study explores occupational health and safety and the different dimensions of organizational commitment. Methods: A cross-sectional survey design was used for this study. The respondents were selected based on simple random sampling. Out of 400 questionnaires administered, 370 were returned (77.3% male and 22.7% female) and used for the study. Correlation and multiple regression analysis were used to determine the relationship and impact between the variables. Results: The findings of this study revealed positive and significant relationship between occupational health and safety management, and affective, normative, and continuance commitment. Additionally, the results revealed the significant impact of occupational health and safety on affective, normative, and continuance commitment. Conclusion: Management within the mining sector of Ghana must recognize the fact that workers who feel healthy and safe in the performance of their duties, develop emotional attachment and have a sense of obligation to their organization and are most likely committed to the organization. Employees do not just become committed to the organization; rather, they expect management to first think about their health and safety needs by instituting good and sound policy measures. Thus, management should invest in the protection of employees' health and safety in organizations.

• Journal of Information Technology Applications and Management
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• v.15 no.1
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• pp.99-116
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• 2008

This study explores the impacts of e-learning system characteristics on learner committment and satisfaction by surveying the firms utilizing e-learning systems for learning. In the study, we have, first, drawn the key factors and instruments to measure e-learning system characteristics through intensive literature review. Second, we have investigated whether the characteristics contribute to increasing learner's commitment and satisfaction. Finally, we have examined the mediating effect of learner's commitment between the characteristics of e-learning system and learner satisfaction. We have conducted a survey on the employees having experience in using e-learning systems for learning, and collected a total of 93 responses. The results of a statistical analysis show the following: First, expression and interaction affect the learner's commitment. The results indicate that a learner should engage in e-learning and ultimately be more committed on it when there is a coherence in design and organization of learning contents, and when the system offers various multimedia options including audio, sound, image, graphics, etc. Second, leaner's commitment leads to higher learning satisfaction. Finally, our results show that the commitment plays a mediating role between learner characteristics (expression, control, and trust) and learner satisfaction.