• Journal of Broadcast Engineering
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• v.16 no.5
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• pp.722-737
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• 2011

In this paper, we propose an estimation of network jitter that occurs when transmitting TCP packets containing MPEG-2 TS in progressive streaming service over wired or wireless Internet networks. Based on the estimated network jitter size, we can calculate required de-jitter buffering time to absorb the network jitter at the receiver side. For this purpose, by exploiting the PCR timestamp existing in the TS packet header, we create a new timestamp information that is marked in the optional field of TCP packet header to estimate the network jitter. By using the proposed de-jitter buffering scheme, it is possible to employ the conventional T-STD buffer model without any modification in the progressive streaming service over IP networks. The proposed method can be applicable to the recently developed international standard, MPEG DASH (dynamic adaptive streaming over HTTP) technology.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.10a
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• pp.23-26
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• 2012

In MANET, the nodes, configuring a path, act as routers and they have various mobilities. If the path is broken by a node's moving, a new path has to be found again. For this reason, the node with high mobility should be excluded from configuring a path as far as possible. In this paper, we propose an algorithm which excludes nodes with high mobility from constructing a path by collecting and managing the information of mobility. As the result, the proposed algorithm provides more stable paths. In this algorithm, we appends MRecord Field and Relieve Field in the routing table to collect and manage the mobility information by extending current AOMDV. In addition, we add Mbl Field to RREP (Route Reply) message to adapt the collected information to configure the real path.

• The Journal of the Korea Contents Association
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• v.6 no.1
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• pp.8-13
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• 2006

In this thesis, an automatic door lock system using a dual tone multiple frequency(DTMF) signal generated as pushing the key button of mobile phone is proposed and implemented. This system consists of a transmitter module and a receiver module for processing the DTMF signal of mobile phone. The DTMF signal of mobile phone connected with ear-phone jack enter into the input terminal of DTMF receiver and those are encoded by a code-converter with 4-bits binary format in the DTMF receiver. The encoded output signals are transmitted to the amplitude shift keying(ASK) modulator of transmitter module and the modulated ASK signals which are converted into radio frequency(RF) signals propagate in a free space. The RF signals passed through a free space are demodulated by the ASK demodulator of receiver module and the demodulated ASK signals are sent to a micro-controller unit(MCU). The output signals processed by the MCU are compared with the secreted identification number which is prerecorded in a microprocessor and are transferred to a power relay. If the result is the same, the automatic door lock system opens a door. In the opposite case, it maintains closing the door. The implemented automatic door lock system operates well in mobile environments.

• Journal of Engineering Education Research
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• v.6 no.1
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• pp.56-64
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• 2003

In this paper, we designed and implemented a client/server distributed environment and developed a web-based virtual laboratory system for electronic circuits. Since our virtual laboratory system is implemented to describe the on-campus laboratory, the learners can obtain similar experimental data through it. The proposed virtual laboratory system is composed of four important components : Principle Classroom, Virtual Experiment Classroom, Evaluation Classroom and Overall Management System. Through our virtual laboratory, the learners will be capable of learning the concepts and theories related to electronic circuit experiments and how to operate the experimental equipments such as multimeters, function generators, digital oscilloscopes and DC power supplies. Also, every experimental activity occurred in our virtual laboratory is recorded on database and printed out on the preliminary report form. All of these can be achieved by the aid of the Management System. The database connectivity on the web is made by PHP and the virtual labol'atory environment is set up slightly differently for each learner. Finally, we have obtained several affirmative effects such as reducing the total experimental hours and the damage rate for experimental equipments and increasing learning efficiencies as well as faculty productivity.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.946-958
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• 2009

Lately, Seoul metro is changing transformation facilities which have been operated in subway line 1 and 2 for a long duration of time. Although the exiting protection relays in DC feeder system have such several functions as 76I, 50, 85, and 64P, the new protective relay have a great variety of functions such as 76I, 76D, DDL-I, DDL-T(Imin), 85, and 64P, as well as record and save various events and accident wave in order to review and analyze the working causes of the protective system. However, because the new digital relays are not used properly for protective propose, there are the cases that the electric accident is deteriorated more. Therefore, in this paper, we will describe that making the use studying installation intention, direction, and setting up value of the protection relay in DC breaker operation not only prevents from making the electric accident worse but also shows the efficient operation method of direct current protection system.

• Journal of the Korean Society of Marine Environment & Safety
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• v.21 no.5
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• pp.531-537
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• 2015

In order to maximize power output from the solar panels, one needs to keep the panels aligned with the sun. So solar tracker having high reliability must be designed. This paper cares about the design and evaluation of a two-axis solar tracker system based on fuzzy logic control with LabVIEW. The research focus on planning mechanical parts, making an intelligent controller which controls and monitors all parameters via user interface implemented of a fuzzy decision support system for control of photovoltaic panel movement. We also develop a real solar tracker system and analyze the influence indexes such as environment, weather, season, and light condition. The solar tracker is tested in real condition and all parameters related to the system operation are recorded and analyzed. The developed solar tracking system got a much higher efficiency about 38 % compare to fixed solar panel although the weather condition is affected a lot to the solar panel. So we confirmed the our auto tracking system is more effective and can allow more energy to be produced.

• Journal of the Korean Institute of Intelligent Systems
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• v.25 no.6
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• pp.571-577
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• 2015

In the paper, we propose a method for developing a physical training management module which sends physical data to smart devices using an wireless module attached to physical appliances. In the proposed stick-type physical appliance, the physical amount of data measured from sensors inside the appliance is sent to a smart device via wireless communication. And then the smart device records the physical amount of data categorized in person-based data and shows useful information about the user's physical training on the dedicated display. For the performance evaluation, indoor environment and electro magnetic wave tests are taken from national specialized organizations, and their results was very efficient. The proposed physical training management module is highly extensible since it is easily applicable to other physical appliances and useful to both Android and iOS platforms.

• Journal of KIISE:Computing Practices and Letters
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• v.13 no.4
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• pp.213-225
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• 2007

Flash memory is widely used as a storage device for potable equipments such as digital cameras, MP3 players and cellular phones because of its characteristics such as its large volume and nonvolatile feature, low power consumption, and good performance. However, a block in flash memories should be erased to write because of its hardware characteristic which is called as erase-before-write architecture. The erase operation is much slower than read or write operations. FTL is used to overcome this problem. We compared the performance of the existing FTL algorithms on Windows-based OS. We have developed a tool called FTL APAT in order to gather I/O patterns of the disk and analyze the performance of the FTL algorithms. It is the log buffer scheme with full associative sector translation(FAST) that the performance is best.

• The Journal of the Korea Contents Association
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• v.6 no.6
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• pp.16-25
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• 2006

Most water tanks operating have been managed by people's five senses. A human material resource have been wasted awfully at this. In the present study, we suggest the wireless integrated system for managing water tank of reducing the wastage human resources and on-line real time managing efforts of water tanks. Water level sensor works the pump sending the data from water tank control to the wireless control on sensing water level. At this time, every kind data which happens in the water tank transmits the line transmission modem. Data to be received from the line transmission modem is stored at the database after we record the logs by each hour. We display the result to the web pages, after checking the pump motion, the pump error, the water level, the solar battery error, the chemicals, and the telephone line to the foundation data to be saved. Furthermore, this paper suggests empirical applications of the proposed wireless integrated system for managing water tank in order to verify its feasibility.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.9
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• pp.198-203
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• 2019

An adhesive wireless bookbinding machine was designed with optimal motor control and automatic cover insertion for bookbinding. The noise level was improved by modifying the thrust of the machine and changing from a compressor method to an AC induction motor control method. The automatic cover insertion function was added to improve the task speed. Motor and decelerator damage can be caused by sudden braking and acceleration of the motor rotation (clockwise and counter-clockwise), so a buffer-type locational control system was developed to secure stable movement and durability. The complicated internal design was also simplified, and the volume and weight were decreased. The results show that the noise was decreased by 57% from 135 dB to 71.7 dB, and the task speed was decreased by 57% from 18 s to 9.58 s. The automatic cover insertion was designed to supply a maximum of 130 sheets per supply.