• The Journal of the Acoustical Society of Korea
• /
• v.43 no.1
• /
• pp.89-94
• /
• 2024

Since Ultra-Short BaseLine (USBL) uses an array with narrow sensor spacing, precise synchronization is required to improve source localization performances. However, in the underwater environment, synchronization errors occur due to relatively strong noise and underwater acoustic channels such as multipath and Doppler, which deteriorates the source localization performances. This paper proposes a covariance-based synchronization compensation method to improve the source localization performances of the underwater USBL systems. The proposed method arranges the received signals through cross-correlation and calculates the covariance of the arranged signals. The synchronization error is related to the phase difference in the covariance. Thus, the phase difference is estimated as the covariance and compensated. Computer simulations demonstrate that the proposed method has better source localization performances than the conventional cross-correlation method.

• KIPS Transactions on Software and Data Engineering
• /
• v.2 no.5
• /
• pp.311-318
• /
• 2013

Recently, there have been many studies on RFID-based SCM. Yet, studies of synchronizing errors caused by tracking logistics information in supply chain, and activating & monitoring RFID infra is still insufficient. Also, there is no case of developing the intelligent SCM system enabling total monitoring and controlling RFID Infra by applying these technologies. Logistics information synchronization based Smart SCM model is intelligent supply chain service model to monitor the status of the RFID equipments in supply chain and the synchronization of the logistics process in each logistics point through one integrated view, as well as to react instantly by providing the information to help the various decision makings, when the emergency occurs. By adopting global logistics standard, RFID related standard specification, EPCIS standard, and SSI middleware platform, this model provides the domestic standard specification.

• Journal of KIISE:Information Networking
• /
• v.28 no.3
• /
• pp.347-354
• /
• 2001

This paper proposes and analyzes an error control scheme which tries to recover the transmission error within the deadline of a message on FDDI networks. The error control procedure does not interfere other normal message transmissions by delivering retransmission request via asynchronous traffic as well as by delivering retarnsmitted message via overallocated bandwidth which is inevitably produced by the bandwidth allocation scheme for hard real-time guarantee. The receiver counts the number of tokens which it meets, determines the completion of message transmission, and finally sends error report. The analysis results along with simulation performed via SMPL show that the proposed scheme is able to enhance the deadline meet ratio of messages by overcoming the network errors. Using the proposed error control scheme, the hard real-time network can be built at cost lower than, but performacne comparable to the dual link network.

• Journal of KIISE:Computer Systems and Theory
• /
• v.27 no.5
• /
• pp.485-495
• /
• 2000

The parallel computer system that uses parallel program on the application such as a large scale business or complex operation is required. One of crucial operation of parallel computer system is synchronization. A representative method of synchronization is barrier synchronization. A barrier forces all process to wait until all the process reach the barrier and then releases all of the processes. There are software schemes, hardware scheme, or combinations of these mechanism to achieve barrier synchronization which tends to use hardware scheme. Besides, barrier synchronization lets parallel computer system fast because it has fewer start-up overhead. In this paper, we propose a new switch module that can implement fast and fault-tolerant barrier synchronization in hardware scheme. A proposed barrier synchronization is operated not in full-switch-driven method but in processor-driven method. An effective barrier synchronization is executed with inexpensive hardware supports. Therefore, a new proposed hardware barrier synchronization is designed that it is operated in arbitrary network topology. In this paper, we only show comparison of barrier synchronization on Multistage Interconnection Network. This research results in 24.6-24.8% reduced average delay. Through this result, we can expect lower average delay in irregular network.

• Journal of The Korean Association For Science Education
• /
• v.30 no.5
• /
• pp.668-680
• /
• 2010

In this study, we investigated the characteristics, the mapping understanding, the mapping errors, and the perceptions of student-generated analogies on the separation of mixtures using the sizes of particles by elementary school students' approaches to learning. Fourth graders (N=92) were selected and administered with the tests on the approaches to learning, self-generating analogies, and perception of self-generating analogies. The results revealed that the meaningful learners made more analogies, especially structural/functional, enriched, and higher systematic ones than the rote learners. However, there were little difference in students' approaches to learning in the subcategories of representation (verbal, pictorial, and verbal/pictorial), artificiality (artificial and everyday), and abstraction (abstract and concrete). The meaningful learners had deeper understanding of the analogy and fewer mapping errors than the rote learners. In addition, the numbers of the shared attributes included in student-generated analogies and the scores of the mapping understanding of the meaningful learners were significantly higher than those of the rote learners. Many students, regardless of students' approaches to learning, had positive perceptions of the self-generating analogies in various cognitive and motivational aspects. However, they also point out the various difficulties in the self-generating analogies as their disadvantages. Educational implications of these findings are discussed.

• Journal of The Korean Association For Science Education
• /
• v.32 no.2
• /
• pp.402-414
• /
• 2012

This study investigated the effects of the instructions using analogies in learning the concept of saturated solution by the analogy presentation types and the verbal learning styles upon the mapping understanding, the mapping errors, and the perceptions of the instruction. Fifth graders (N=123) at an elementary school were selected and assigned to VA (n=63) and VPA (n=60) groups. As a pretest, a test on the verbal learning style was administered. The students in the VA group learned the target concept with a verbal analogy, while those in the VPA group learned it with a verbal/pictorial analogy. After the students learned it, a mapping understanding test was administered. The students in the VPA group also administered the test on the perceptions of the instruction and some of them were interviewed in depth. The results revealed that the scores of the students with strong verbal learning preference in the VPA group were significantly lower than those in the VA group in the mapping understanding test. However, the scores of the students with weak verbal learning preference were not significantly different between the two groups. Five types of mapping errors were identified: failure to map, mismapping, rash mapping, impossible mapping, and mapping of a surficial feature. According to students' verbal learning styles, there were some differences in the frequencies of mapping errors in the two groups. Many students in the VPA group, regardless of their verbal learning styles, had positive perceptions of the instruction in various cognitive and motivational aspects. However, some of them also pointed out a few difficulties of the instruction. Educational implications of these findings are discussed.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2003.10a
• /
• pp.369-372
• /
• 2003

This paper describes a design of OFDM (Orthogoanl Frequency Division Multiplexing) based wireless LAN system receiver, defined in IEEE 802.11a standards. Because OFDM system uses several orthogonal sequence sets, it ran avoid selective fading of fast data transfer problem when it is used with error correction code. But if the receiver is not synchronized, the orthogonal of between sub-ralliers will be destroyed and the data interruption will be generated. So it makes error property get worse very murk. For improving the noise error, we use the relationship of phasor between sub-carriers and make system synchronization using one tab equalizer. The designed OFDM block is described by Verilog HDL for the efficient and small size hardware. And we preform the functional verification and evaluation using the vector of standards.

• The Transactions of the Korea Information Processing Society
• /
• v.5 no.3
• /
• pp.715-719
• /
• 1998

In this paper, we propose a color enhancement system which is based on the improvement of transition time problem and specific color detection stability. The proposcd system apply the time difference correction step to corrects time difference which is taken place at the transimission process between color signal and color subcarrier signal and to reduce detection errors. And also, we proposed stability method to improve transition time problem and detection efficiency as the control of reference color. The proposed system controls specific color when the mean difference value of detected voltages greater than the value of minimum discriminate voltages of two adjacent color signals. Thus, the color enhancement system improves detection efficiency and controls specific color from the color signal without overlapping of correction range.

• Journal of the Korea Computer Industry Society
• /
• v.3 no.2
• /
• pp.243-258
• /
• 2002

The web-based multimedia development tool was implemented to create and edit multimedia contents under the graphic user interface environment with icons. The development process enables the developers to verify the contents being developed by checking for errors, exchanging feedbacks and utilizing the pre-execution feature. By applying the tree structure to the internal data format, the tool uses inherent display features among media objects with time and spatial relations to efficiently process the synchronism of media objects that participate in the presentation and asynchronism according to user interaction.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2012.11a
• /
• pp.1595-1598
• /
• 2012

최근들어 RFID 기반의 SCM에 대한 연구는 많이 진행되고 있다. 그러나 공급망상에서 이동중인 물류정보의 오류를 동기화하고, 장치기반 인프라의 상태정보를 모니터링하여 활성화해주는 연구와 기술은 아직 미흡하다. "물류정보동기화 기반의 Smart SCM 모델"은 실시간으로 각 물류 거점에 설치된 RFID 인프라 장치 및 물류 프로세스 동기화 현황을 Dashboard를 통하여 모니터링하고, 예외상황 발생시에 다양한 의사결정 지원정보 제공을 통해 즉각적인 상황 조치가 가능한 지능형 공급망 통합관제 서비스 모델이다. 본 연구 모델은 물류국제 표준, RFID관련 국제 표준 규격, EPCIS 표준, SSI 미들웨어 플랫폼을 준용하여 표준화 하므로써 관련 기술 국내 표준 규격을 제시하고자 하였다.