• Journal of The Korean Association of Information Education
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• v.9 no.3
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• pp.511-522
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• 2005

The rapid development of information & communication technology has changed the paradigm of education. Recently the area of education is introducing u-Learning, in which learning is possible at any time and in any place through personal information devices such as PDA, tablet PC and mobile phone terminals. Taking advantage of the mobility and individuality of personal information devices, u-Learning can provide learning customized to the characteristics of individual learners without the limitations of time and space and can be effective in situational learning and experiential learning. In order to identify the uses of PDA in teaching.learning and to develop a basic teachinglearning model using PDA, the present study applied PDA directly to classes and examined the effects. According to the result, most students were satisfied with classes utilizing PDA but problems were also found in connection, insufficient contents for PDA, the quality of screen, etc.

• Journal of Information Processing Systems
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• v.2 no.2
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• pp.76-81
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• 2006

A PDA is used mainly for downloading data from a stationary server such as a desktop PC in an infrastructure network based on wireless LAN. Thus, the overall performance depends heavily on the performance of such downloading with PDA. Unfortunately, for a PDA the time taken to receive data from a PC is longer than the time taken to send it by 53%. Thus, we measured and analyzed all possible factors that could cause the receiving time of a PDA to be delayed with a test bed system. There are crucial factors: the TCP window size, file access time of a PDA, and the inter-packet delay that affects the receiving time of a PDA. The window size of a PDA during the downstream is reduced dramatically to 686 bytes from 32,581 bytes. In addition, because flash memory is embedded into a PDA, writing data into the flash memory takes twice as long as reading the data from it. To alleviate these, we propose three distinct remedies: First, in order to keep the window size at a sender constant, both the size of a socket send buffer for a desktop PC and the size of a socket receive buffer for a PDA should be increased. Second, to shorten its internal file access time, the size of an application buffer implemented in an application should be doubled. Finally, the inter-packet delay of a PDA and a desktop PC at the application layer should be adjusted asymmetrically to lower the traffic bottleneck between these heterogeneous terminals.

• Proceedings of the KIEE Conference
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• 2005.10b
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• pp.385-387
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• 2005

In this study, we tried to implement a PDA (Personal Digital Assistant)-based audiometric system to test hearing disorder. Due to the inherent handy nature of PDA system, our hearing test system can be easily performed in a local environment and consequently the measured audiometric data are stored and queryed via a built-in a PDA database system.

• Applied Chemistry for Engineering
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• v.10 no.7
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• pp.1014-1019
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• 1999

Copolyamic acid PMDA/6FDA-PDA(PAA) and homopolyamic acids PMDA-PDA(PAA) and 6FDA-PDA(PAA) were synthesized from 1,2,4,5-benzenetetracarboxylic dianhydride(PMDA) and 2,2'-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride(6FDA) as the dianhydride and 1,4-phenylenediamine (PDA) as the diamine. Residual stresses were detected in-situ during thermal imidization of the co- and homopolyimide precursors as a function of processing temperature over the range of $25{\sim}400^{\circ}C$ using thin film stress analyzer(TFSA), and morphological structures were investigated by WAXD. In comparison, the resultant residual stress of polyimide films composed of different compositions decreased with the increasing content of PMDA unit in the chain and was about 5 Mpa in compression mode for PMDA-PDA. In this study, the synthesis of random PMDA/6FDA-PDA copolyimide could be completed and compensate for the difficulty of process due to high $T_g$ of PMDA-PDA and relatively higher stress of 6FDA-PDA. It showed that we can make a low level stress copolyimied having excellent mechanical properties by incorporating appropriate rod-like rigid structure PMDA-PDA unit into 6FDA-PDA polyimide backbone which generally shows higher stress due to rotational hinges such as bulky di(trifluoromethyl). Specially, PMDA/6FDA-PDA(0.9:0.1:1.0) satisfied excellent mechanical property and low level stress as an inter layer showing low dielectric constant.

• 한국정보교육학회:학술대회논문집
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• 2005.08a
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• pp.29-37
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• 2005

유비쿼터스 러닝을 가능하게 하기 위해서는 학습자의 지속적인 학습 결과 관리와 다양한 기기에 적합한 콘텐츠 표현 방안 그리고 이 기종 시스템들 간의 동기화 문제 등이 해결되어야 한다. 본 논문에서는 PDA를 사용하는 학습자들에게 학습 콘텐츠를 제공하고, PDA 상에서 학습을 할 수 있게 한 후, 학습자의 학습 결과를 서버로 동기화 할 수 있는 PDA 학습 시스템을 설계하고 구현하고자 한다. PDA 학습 시스템은 학습을 위한 PDA 어플리케이션과 학습 결과 처리를 위한 PDA 서버로 구성된다. PDA 서버는 XML형태의 문제 파일을 생성하고, PDA 어플리케이션에 이를 제공하며, PDA내의 학습 결과를 서버의 학습 결과와 동기화 시켜주는 기능을 한다. 제안하는 시스템을 교육 현장에 적용하고, 그 문제점을 분석하여 개선해 나간다면 유비쿼터스 러닝을 실천하기 위한 기반연구로서 활용될 수 있을 것이다.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2002.05a
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• pp.105-108
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• 2002

This paper represents the mobile robot control system remote controlled by PDA(personal digital assistance). So far, owing to the development of internet technologies, lots of remote control methods through internet have been proposed. To control a mobile robot through internet and guide it under unknown environment, We propose a control method activated by PDA. In a proposed system, PDA acts as a user interface to communicate with notebook as a controller of the mobile robot system using TCP/IP protocol, and the notebook controls the mobile robot system. The information about the direction and velocity of the mobile robot feedbacks to the PDA and the PDA send new control method produced from the fuzzy inference engine.

• Journal of Digital Contents Society
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• v.2 no.2
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• pp.147-156
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• 2001

This study aims to examine the environmental aspect of users of PDA, an information device whose use is on the rise. The focus is put on the display of PDA products to see how it considered effectiveness and visual effect for users. A better environment will be presented for users by analyzing problems in interface design, such as how easily users can access information and how simply and clearly users can process such information. Additionally, each of PDA products will be tested to see what difficulties users can face while carrying out tasks and how easily users can cope with a problem when facing it. In this study, the utilization of PDA was analyzed in terms of its basic functions such as information input and the output and use of wanted information. Based on the analysis results, a better alternative for uses of PDA will be presented.

• Journal of Digital Contents Society
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• v.3 no.2
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• pp.211-220
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• 2002

It has not been long since the current form of PDA began to be used widely. The PDA, which first came out in a recognizable form in the market a decade ago, multiplying the number of users, has recently been developed in various forms. It began to make cutting-edge technology available in PDA, and to be subdivided into various forms appropriate for special purposes, which reflected the recent intense competition in the market. It included the function of mobile phone, in tandem with the original function of PDA, by which it brought about other synergy effects and corresponded with the purpose more solidly. Due to these recent changes, PDA has had a dramatically increasing number of users, as well as the wider scope of usage and practical application by introducing new technology. However, research is required in the fields of basic usage and interface. It is important to recognize that PDA is an apparatus that stores for the users contents and information suitable for them, and that responds to them in case of need. PDA therefore needs to convey what the users require more easily and speedily without errors, and to provide them with appropriate information and contents. This paper examined the extent to which the interface of PDA including the input of contents required by the user would be efficient by questionnaires. In addition, alternatives concerning a general application environment of PDA were suggested based on the result of this survey.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.5
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• pp.25-32
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• 1994

A nonlinear control algorithm for the depth control of underwater vehicles is presented. In order to consider the deadzone effect of the flow control valve, a nonlinear fuzzy logic controller (FLC) is synthesized and combined with a linear proportional-derivative-acceleration (PDA) controller, which is called the PDA/FLC controller. And to show the effectiveness of the PDA/FLC control system, it is compared with the linear PDA control system through computer simulation. It is found that the PDA/FLC control system is suitable one to maintain the desirable depth of underwater vehicles with deadzone.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.55 no.1
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• pp.42-44
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• 2006

In this paper, we tried to implement a PDA (Personal Digital Assistant)-based audiometric system to test hearing disorder. Due to the inherent handy nature of PDA system, our hearing test system can be easily performed in an user's local environment and consequently the measured audiometric data can be stored and queryed locally via a built-in PDA database system.