• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.11a
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• pp.230-236
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• 2001

We developed a built-in sensor bearing to measure the rotor motion of a rolling piston type compressor for the air conditioner. Because of needs for the high efficiency and long life span of compressor, and the usage of alternative refrigerants, the operating condition of the compressor becomes more severe. The accurate measurement of the rotor motion of the compressor can contribute greatly to the design and analysis of the hydrodynamic bearing. However, it is difficult to measure accurately the shaft behavior of small compressor because of the small space for the sensor mount, high temperature and pressure of compressor, oil mixed with refrigerant, and electromagnetic noise of the motor. To overcome these difficulties, we develop the cylindrical capacitive sensor that is built in the hydrodynamic bearing and calibrate the built-in sensor bearing indirectly through measuring the oil relative permittivity. We measured the rotor motion as well as suction and discharge pressures in various conditions. The several experimental results show that the developed built-in sensor bearing can measure the rotor motion not only in steady state but also in transient state.

• ETRI Journal
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• v.27 no.6
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• pp.777-787
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• 2005

In this paper, we propose an urgency- and efficiency-based wireless packet scheduling (UEPS) algorithm that is able to schedule real-time (RT) and non-real-time (NRT) traffics at the same time while supporting multiple users simultaneously at any given scheduling time instant. The UEPS algorithm is designed to support wireless downlink packet scheduling in an orthogonal frequency division multiple access (OFDMA) system, which is a strong candidate as a wireless access method for the next generation of wireless communications. The UEPS algorithm uses the time-utility function as a scheduling urgency factor and the relative status of the current channel to the average channel status as an efficiency indicator of radio resource usage. The design goal of the UEPS algorithm is to maximize throughput of NRT traffics while satisfying quality-of-service (QoS) requirements of RT traffics. The simulation study shows that the UEPS algorithm is able to give better throughput performance than existing wireless packet scheduling algorithms such as proportional fair (PF) and modified-largest weighted delay first (M-LWDF), while satisfying the QoS requirements of RT traffics such as average delay and packet loss rate under various traffic loads.

• The Research Journal of the Costume Culture
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• v.27 no.6
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• pp.666-680
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• 2019

Prevalent usage of mobile devices among consumers has been well recognized and this is especially imperative among young adult consumers. The mobile phone became the gateway of their communication, media consumption, retail transaction, education, and (virtual) social life. However, there is little empirical research explaining the dynamics behind the psychological underpinning of young adult consumers, specifically Generation Y, to understand their usages and dependency on mobile phones. This study, therefore, aims to unveil antecedents and consequences of Gen Y consumers' mobile phone dependency from a media psychological perspective. We developed a conceptual model based on theory of self-monitoring (Snyder 1974, 1987), extended self-concept (Belk, 1988), and media dependency theory (Ball-Rokeach & Defluer, 1976). Four hundred ninety-eight students in the U.S. provided usable responses to our pencil-and-paper survey. Causal modeling analysis results demonstrated that both ability to modify one's behavior and sensitivity to cues for social appropriate behavior dimensions of the self-monitoring tendency positively predicted one's level of fashion involvement, which in turn positively predicted his/her mobile phone dependency. Individual's mobile phone dependency, fashion involvement and self-monitoring's ability dimension exhibited positive and direct impact on one's perception of the salience of mobile phone case product attributes. Based on the findings, we provided pragmatic and theoretical implications for the industry and academia.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.1
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• pp.33-38
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• 2012

As underwater channel is very complex and time-varying, don't supports good-quality for communication service. In this paper, a multi-carrier CDMA(MC-CDMA) system for the reliability and robust service in the underwater acoustic channel is proposed and analyzed for its performance. Applied variable rate algorithm to the proposed system gets a channel state information from relationship between SINR and user data-rate. Using channel state information make spectrum usage more efficient and overall system performance improved. In this paper, the performance of proposed system analyzed by simulation. And Pseudo-Random spread codes used in the system are discussed.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.8 s.185
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• pp.64-71
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• 2006

In this paper, a uniform speed controller for an ultrasonic rotary motor is developed using the phase-difference method. The phase difference method uses traveling waves to drive the ultrasonic motor. The traveling waves are obtained by adding two standing waves that have a different phase to each other. A compact phase-difference driver system is designed and integrated by combining VCO(Voltage Controlled Oscillator) and phase shifter. Theoretically the relationship between the phase difference in time and the rotational speed of the ultrasonic motor is sine function, which is verified by experiments. Then a series of experiments under various loading conditions are conducted to characterize the motor's performance that is the relationship between the speed and torque. Proportional-integral control is adopted for the uniform speed control. The proportional control unit calculates the compensating phase-difference using the rotating speed which is measured by an encoder and fed back. Integral control is used to eliminate steady-state errors. Differential control for reducing overshoot is not used since the response of ultrasonic motor is prompt due to its low inertia and friction-driving characteristics. The developed controller demonstrates reasonable performance overcoming disturbing torque and the changes in material properties due to continuous usage.

• Genomics & Informatics
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• v.19 no.3
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• pp.21.1-21.5
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• 2021

The use of social media data, like Twitter, for biomedical research has been gradually increasing over the years. With the coronavirus disease 2019 (COVID-19) pandemic, researchers have turned to more non-traditional sources of clinical data to characterize the disease in near-real time, study the societal implications of interventions, as well as the sequelae that recovered COVID-19 cases present. However, manually curated social media datasets are difficult to come by due to the expensive costs of manual annotation and the efforts needed to identify the correct texts. When datasets are available, they are usually very small and their annotations don't generalize well over time or to larger sets of documents. As part of the 2021 Biomedical Linked Annotation Hackathon, we release our dataset of over 120 million automatically annotated tweets for biomedical research purposes. Incorporating best-practices, we identify tweets with potentially high clinical relevance. We evaluated our work by comparing several SpaCy-based annotation frameworks against a manually annotated gold-standard dataset. Selecting the best method to use for automatic annotation, we then annotated 120 million tweets and released them publicly for future downstream usage within the biomedical domain.

• Nuclear Engineering and Technology
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• v.54 no.10
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• pp.3803-3810
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• 2022

OpenMC is a community-driven open-source Monte Carlo neutron and photon transport simulation code. The Weight Window Mesh (WWM) function and an automatic Global Variance Reduction (GVR) method was recently developed and implemented in a developmental branch of OpenMC. This WWM function and GVR method broaden OpenMC's usage in general purposes deep penetration shielding calculations. However, the Local Variance Reduction (LVR) method, which suits the source-detector problem, is still missing in OpenMC. In this work, the Weight Window Generator (WWG) function has been developed and benchmarked for the same branch. This WWG function allows OpenMC to generate the WWM for the source-detector problem on its own. Single-material cases with varying shielding and sources were used to benchmark the WWG function and investigate how to set up the particle histories utilized in WWG-run and WWM-run. Results show that there is a maximum improvement of WWM generated by WWG. Based on the above results, instructions on determining the particle histories utilized in WWG-run and WWM-run for optimal computation efficiency are given and tested with a few multi-material cases. These benchmarks demonstrate the ability of the OpenMC WWG function and the above instructions for the source-detector problem. This developmental branch will be released and merged into the main distribution in the future.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.18 no.3
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• pp.633-652
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• 2024

Software testing is an important phase as it ensures the software quality. The software testing process comprises of three steps: generation, execution, and evaluation of test cases. Literature claims the usage of single and multiple 'Unified Modeling Language' (UML) diagrams to generate test cases. Using multiple UML diagrams increases test case coverage. However, the existing approaches show limitations in test case generation from UML diagrams. Therefore, in this research study, we propose an approach to generate the test cases using UML State Chart Diagram (SCD), Activity Diagram (AD), and Sequence Diagram (SD). The proposed approach transforms UML diagrams into intermediate forms: SCD Graph, AD Graph, and SD Graph respectively. Furthermore, by integrating these three graphs, a System Testing Graph (STG) is formed. Finally, test cases are identified from STG by using a traversal algorithm such as Depth First Search (DFS) that is an optimization method. The results show that the proposed approach is better compared to existing approaches in terms of coverage and performance. Moreover, the generated test cases have the ability to detect faults at the unit level, integration, and system level testing.

• Journal of Distribution Science
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• v.13 no.4
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• pp.77-87
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• 2015

Purpose - This study aims to investigate the current state of distribution terminology usage by retailers and consumers nationwide, and to suggest a practical improvement plan for its standardization. The Korean distribution industry is closely related to consumers' daily lives. However, in reality, there exists a gap among producers, distributors, and consumers in terms of the definition, understanding, and perception of the terminology. Therefore, standardizing this terminology is essential for more smooth communication. This paper suggests the necessity of committing overall research and survey activities to the actual conditions of using Korean distribution terminology by organizations and their respective management situations, and further, the necessity of probing the problem and its measures in line with the objective and mission of the "Fundamental Law of the Korean Language." Research design, data, and methodology - This study's scope is limited to wholesale and retail including some information systems. First, the study covers most written material including lexicons and glossary of distribution terminology, university textbooks and teaching material for national certificate of qualification, and related laws and ordinances. Second, the survey covers retailers' management situations by store format. The retailers used as the sample for the survey include department stores, discount stores, SSM, and convenience stores. Altogether, 20 specialists were interviewed in their respective sectors or retail formats. Finally, the project team surveyed a sample of 1,300 consumers nationwide on 50 distribution terms mainly used by consumers, including those about awareness, understanding, usage, and attitude. Results - In total, 1,249 terms are drawn through literature research including distribution terminology used in the related literature, glossary and lexicons, distribution terminology in textbooks, and legal terminology. A classified table comprises four large categories including general distribution, distribution marketing, distribution information, and merchandise. The results of the three-step research including literature survey, field survey of retailers, and consumer survey were advised to be screened by academia (retail associations, faculty etc.), retailers (major retail management by store format), retail specialists and consultants, consumers, and Korean linguists. In total, 1,300 questionnaires for 50 terms of the distribution terminology closely associated with consumers were distributed to subjects nationwide. Conclusions - The desired and expected results from this study are summarized from three perspectives as follows: First, from retailers' perspective, a new concept, or coinage of new terms of the distribution industry stems from advanced countries such as America and Europe. However, the original meaning and definition are diluted and distorted with changes in the language users' situations and context. This study provides basic guidelines for standardization of distribution terms used among various retail formats in most daily life situations that consumers encounter. Second, from the nation's perspective, this study suggests optimal choices of distribution terminology in the context of laws and ordinances regarding concerned Ministries. Last, from the consumers' perspective, this paper enables consumers to understand and use distribution terms properly in their daily life.

• Journal of Digital Contents Society
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• v.16 no.1
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• pp.137-144
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• 2015

This study tried to anticipate the near future changes of domestic online video, music service and media usage through the status quo. The research group was focused on the twenties, University students because they are the active media contents users. It surveyed the students in Busan, and used the method of descriptive statistics analysis for the understanding of the present state and near future prospect. This study shows that almost half of them use both services, and three people out of ten are the heavy users who use the services for over 3 hours a week. The streaming method is higher proportion than download method in using type. They are getting accustomed to pay contents cost, but it couldn't be said the paying content cost has been established. Preferred contents genre appears to be the RMC(Ready Made Contents) such as existing broadcaster contents and movies. Notable result on media usage was the proportion of the so-called 'Zero-TV'. It was 32%, significantly higher than the proportion of the total population(4.4%). Integrating the analysis results, we can expect that the usage pattern will be changed gradually, thus the advent of various revenue models will emerge.