• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.5
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• pp.845-850
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• 2021

In this study, the energy conversion characteristics and design of electric vehicle (EV: Electric Vehicle) powertrain were performed. An interior permanent magnet synchronous motor (IPMSM) was targeted as a power source for the EV powertrain, and control was performed. In order to drive the IPMSM, two regions are considered: a constant torque and a constant output (field-weakening) region. The design of the control system for IPMSM was constructed based on the d-q reference frame (vector control). To determine the static characteristics of motor torque appearing in two areas of IPMSM, a torque control system and a d axis current control system of IPMSM were implemented and proposed. Matlab-Simulink software was used for characteristic analysis. Finally, by applying IPMSM to the powertrain model under the actual EV vehicle level conditions, simulation results of the proposed control system were performed and characteristics were analyzed.

• The Journal of the Acoustical Society of Korea
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• v.38 no.1
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• pp.1-8
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• 2019

This paper estimated communication parameters according to underwater channel environment of lake for underwater acoustic communication. This paper calculated coherence time and coherence bandwidth through two experiments in actual lake environments. In both experiments, the chirp signal for channel estimation and the BPSK (Binary Phase Shift Keying) signal for calculating the bit error rate were transmitted. In each experiment, the distance between transmitter and receiver was 300 m to 400 m, and 500 m to 600 m. The coherence times calculated in experiment 1 and experiment 2 are 175 msec and 340 msec, and the coherence bandwidths are 10 Hz and 5.71 Hz, respectively. It is confirmed that the experimental results are more appropriate because the synchronization and the bit error rate performance are better only when the length of the synchronization signal and the interval of the pilot signal in the frame are shorter than the coherence time.

• The Journal of Korean Association of Computer Education
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• v.15 no.4
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• pp.25-39
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• 2012

Smart education is defined as creating new values through connecting educational elements based on smart devices and infrastructure. In the study, we propose a theoretical and procedural framework for developing smart learning activities, which is considered characteristic of smart education, as well as environments in smart schools of Sejong Special Autonomous city. In addition, we discuss an instructional model developed from the framework. A smart learning activity as a basic unit in instruction is represented as a block when design and instruction focuses on smart learning activities. The block consists of components from learning activities, motivation, information activities, and tools when a teacher has smart learning ideas. Based on the theoretical and procedural framework, the thought-sharing model (i.e., that learners share ideas and opinions with classmates, review classmates' work, and enhance their own work) is an instructional model that leads to smart education. We discuss considerations for developing instructional models using the framework.

• Journal of Broadcast Engineering
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• v.8 no.1
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• pp.72-79
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• 2003

The Eureka-147 Digital Audio Broadcasting(DAB) system is the new international standard for mobile broadcasting services including high-quality audio, program associated data and other multimedia data. In this paper, we design the transport frame structures for the mobile multimedia services by using the configuration of the Eureka-147 DAB multiplex and MPEG system specifications, and then compare their performances in terms of functionality and overhead. Especially, we suggest and analyze the effective transport structures, which are improved in the efficiency of media multiplexing architecture, by removing the functionally overlapped parts between DAB and MPEG systems. In addition, we evaluate the transmission environments of various DAB data channels and demonstrate the transmission error effects on the low bit rate video stream.

• The Journal of the Korea Contents Association
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• v.16 no.8
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• pp.39-47
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• 2016

The purpose of this study is to investigate the smartwork use resistance and Non-Class-Related Behavior of attendees in university smartwork class with the perspective of Motivation-Threat-Ability. To do this, this study built a research model and examined how smartwork switching cost, threat and self-efficacy affect Non-Class-Related Behavior through smartwork use resistance. We also examined the relationship between self-efficacy and Non-Class-Related Behavior. The survey method was used for this paper, and data from a total of 80 university students were used for the analysis. And structural equation model was used to analyze the data. The results of this empirical study is summarized as followings. First, switching cost and threat have direct effects on the use resistance of smartwork services. Second, smartwork use resistance has a negative effect on Non-Class-Related Behavior but self-efficacy has a positive effect on it. Further, it will provide meaning suggestion point of the importance of use resistance motivations in establishing the use policy of smartwork services.

• The KIPS Transactions:PartB
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• v.11B no.1
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• pp.45-52
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• 2004

We propose ESS_WMCE. This paper explains the design and implementation of the EDSS running on ESS_WMCE. EDSS is a synchronization error control system for web based multimedia collaboration environment. We have an error detection approach by using hooking method. The technique of an error transmission is a mended model of utilizing an application sharing system. DOORAE is a good framework model for supporting development on application for computer supported cooperated works. It has primitive service functions. Service functions are implemented with an object oriented concept. It is a system that is suitable for detecting and sharing a software error rapidly occurring on web based multimedia collaboration environment by using software techniques. It is able to share an error as well as providing URL synchronization to access shared objects. When an error occurs, this system detects an error by using hooking methods in MS-Windows API(Application Program Interface) function. If an error is found, it is able to provide an error sharing to access shared objects.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.20 no.2
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• pp.75-80
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• 2020

There are so many low power MAC protocols for wireless sensor network. IEEE802.15.4 among them has disadvantage of a large power consumption for synchronization. To save power consumption it use the superframe operation alternating sleep mode and awake mode. But latency is longer result from superframe operation. B-MAC can have shorter latency according to check interval. But transmitter consumes more power because of long preamble. And receiver is suffering from overhearing. In this paper, we use the adaptive check interval scheme[1] of B-MAC for enhancing the power consumption. Its maximum throughput and minimum delay is evaluated by comparing the proposed scheme with a typical single channel IEEE802.15.4.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.6B
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• pp.1059-1067
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• 1999

In this paper characteristics of ATM-PON is described and a TC layer controller for ATM-PON OLT is designed. This paper proposes an algorithm of economically controlling the grant information written by CPU to dynamically allocate the upstream bandwidth on the PON among the ONUs in a fair way and of encrypting the downstream data using a lower standard of encryption, termed data churning, which is used to distinguish it from existing transmission system scramblers and higher layer encryption methods. This paper also proposes a method of allocating churning-related message into the PLOAM cell in order to synchronously change the churning key between the OLT and the ONU.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.9C
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• pp.905-913
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• 2006

In the impulse radio ultra-wideband communication systems, the residual timing offset exists when the acquisition and tracking of the timing synchronization is well done. And the offset affects the performance of the system dramatically. In order to compensate the offset, we present the digital phase-locked loop that uses the reference signal in the correlation detection receiver. First, we show the degradation of BER performance that is caused by the offset, and then compensation process of the timing tracker and performance improvement. In this paper, the timing detector in the tracker operates at the sampling period of frame level uses the correlation between received and reference signal. Also, we present the performance comparison by using the computer simulation results for different Gaussian monocycle pulses.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.8B
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• pp.609-614
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• 2008

Upstream data frame of TDM-PON includes various types of overheads, and there exist guard bands between consecutive frames from different ONUs. Although they are indispensible in synchronization and performance, they cause bandwidth waste at the same time. To solve this problem, a new TDM-PON that uses two types of wavelengths in upstream transmission is suggested. By even distribution of two wavelengths among ONUs and overhead overlap between frames that use different wavelengths, almost 100% bandwidth efficiency could be achieved. A serializer that multiplexes signals from two wavelengths is implemented for this purpose.