• Journal of the Korea Institute of Information Security & Cryptology
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• v.13 no.6
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• pp.67-75
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• 2003

The development of mobile phone is growing fast in the all over the world. Besides the basic voice communication, many multimedia services and global roaming service are capable in the 3rd generation mobile telecommunication. Because mobile phone has been the essential tool to communicate, the protection of privacy and the safe transmission are critical ones. In synchronous, asynchronous mode IMT2000 service, the mechanism of mutual authentication and generation of cipher key and integrity key are implemented in smart card chip called UIM, USIM. In this paper, we describe the authentication mechanism of 3GPP and 3CPP2 and its implementation results. Then, we specify a few problems which are not defined in standard.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.16 no.5
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• pp.3-13
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• 2006

As computing devices become ubiquitous and increasingly mobile, it becomes obvious that a synchronous and direct peer-to-peer communication model is not sufficient in distributed computing environment. Using an indirect event service instead of other traditional communication model has an advantage of decreasing the coupling of applications in a distributed environment and removing the need for many static dependencies. In this paper, we design and implement the secure event service for providing secure ubiquitous computing environment. The Secure Event Service implemented enables users to perform content-based event retrieval, and supports only eligible event comsumer and event producer can publish and receive events through the secure event service. SPKI/SDSI certificate is used for supporting authentication and authorization in the secure event service. In order to provide a content-based event retrieval, an asynchronous communication between event producers and consumers, and a disconnectedness support for mobile devices, we modify and expand the Javaspace package.

• International Journal of Computer Science & Network Security
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• v.22 no.3
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• pp.245-251
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• 2022

In the context of the pandemic, educational institutions had to ensure an instant transition to remote technological models of communication within the new conditions of the educational environment. The purpose of the academic paper lies in determining the role of the communicative model of educational transformations in the realities of (post) modernity. The research methodology is based on a survey of 120 students from 10 higher educational institutions (HEIs) of Ukraine through an online form regarding the importance of live communication during a pandemic. Results. The communicative model changed significantly during the pandemic - the interaction was mainly due to technologies. The research has identified four communication models of educational transformations under the conditions of the pandemic, depending on learning models. The first traditional model of distance learning involves distance learning; the second model involves contact remote training using remote educational technologies; the third model is blended learning, which combines remote and traditional learning formats, synchronous and asynchronous modes of interaction; the fourth model is traditional contact training. The empirical study of the effectiveness of communication models proves that live communication remains extremely important for learning and understanding of educational materials by students, and technology has provided support for such communication. Along with this, seminars and video lectures with presentations combining live communication and communication technologies are as important as digital learning tools. The most effective teaching method for mastering and memorizing educational material was a live dialogue with a teacher at seminars in ZOOM, followed by individual written assignments on the studied topic.

• Journal of Chest Surgery
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• v.29 no.7
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• pp.689-699
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• 1996

An animal experiment was designed for the evaluation of in vivo performance of the newly developed electrohydraulic type ventricular assist device and its influence on the left ventricular function during pal- satile left ventricular assist. Eight adult sheep were incorporated into the study and data were collected from seven sheep. Total as- sist time ranged from 69 minutes to 7 days. The performance of the device was satisfactory both in asyn- chr nous and synchronous mode within the range of given native heart rate. More than 4 liters of device output could be reached within the range of normal left atral pressure without development of negative pressure in the left atrium. Moderate to severe degree of hemolysis was noted as evidenced by significant increase of plasma free hemoglobin level after 3 days of left ventricular support along with the presence of the small amount of thrombi around the floating disc type polymer valve apparatus reflecting that further study and refinement of the device need to be done in regard of biocompatibility and thromboresistance. The hemodynamics showed increase in heart rate (p < 0.05), cardiac output and left ventricular minute work (p < 0.05) after placement of the device at the flow rate of 2.0∼2.5 Llmin. The left atrial pressure, left ventricular pressure and LV dpldt were decreased after the device placement(p < 0.05). The endocardial viability ratio and oxygen contents of the mixed ven us blood and coronary venous blood were all increased (p < 0.05) after the device placement suggesting effective unloading of the left ventricle was accomplished. The myocardial perfusion was thought improved in synchronous counterpulsation as suggested by sig- nificant increase in endocardial viability ratio and coronary venous blood oxygen content in synchronous assist mode comparing with asynchronous mode.

• Journal of KIISE:Computing Practices and Letters
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• v.9 no.2
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• pp.146-157
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• 2003

Our experience with Internet-based scientific collaboratories indicates that they need to be user-extensible, allow users to add tools and objects dynamically to workspaces, per mit users to move work dynamically between private and shared workspaces, and be easily accessible on the Internet. We present the software architecture of a development environment, called Collaboratory Builder's Environment(CBE), for building collaboratories to meet such needs. CBE provides user extensibility by allowing a collaboratory to be constructed as a collection of collaborative applets. To support dynamic reconfiguration of shared workspaces, CBE uses the metaphor of room that can contain applets, users, and arbitrary data objects. Rooms can be used not only for synchronous collaboration but also for asynchronous collaboration by supporting persistence. For the access over the Internet room participants are given different roles with appropriate access rights. A prototype of the model has been implemented in Java and can be run from a Java-enabled Web browser. The implemented system had been used by 95 users including 79 space scientists around the world in a scientific campaign that ran for 4 days. The usage evaluation of the campaign is also presented.

• Reproductive and Developmental Biology
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• v.28 no.3
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• pp.141-145
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• 2004

Mucin coat is deposited on the embryos during passage through the oviduct in rabbit. When in vitro cultured blastocysts were transferred to the recipients, the lack of mucin coat might account in part for failure of pregnancy after transfer. The present study were carried out to investigate whether deposition of mucin coat were induced when in vitro cultured blastocysts were transferred to recipients. At 19 ～20 hours post-coitus one-cell embryos were collected by flushing oviducts. These embryos cultured for 72 hours were reached to blastocyst stage. And these blastocysts were transferred to the oviduct of asynchronized (one day later than the donors) and synchronized recipient. To confirm deposition of the mucin coat, blastocysts transferred to the oviduct were recovered at 24 and 48 hours after the transfer. Fifty eight percent of blastocysts recovered from uterus of asynchronous recipient at 24 hours after transfer and 92.9% of blastocysts recovered from uterus of synchronous recipient were 0～10 ㎛ of mucin coat thickness. And 11.8% of blastocysts of asynchronized recipients and 7.1% of blastocysts from asynchronized recipients were in 11～20 ㎛ of mucin coat thickness. When blastocysts were recovered from uterus at 48 hours after transfer, 87.0% of blastocysts from asynchronized recipients and 5.9% of blastocyst from synchronized recipients were in 0～10 ㎛ of mucin coat thickness. And 76.5% of blastocysts of synchronized recipients and 4.4% of blastocysts from asynchronized recipients were in 11～20 ㎛ of mucin coat thickness. From these results it is speculated that the low implantation rate of in vitro cultured rabbit blastocysts transferred to oviduct of recipient was caused by high degeneration of the embryo after transfer and inappropriate deposition of mucin coat.

• The Transactions of the Korea Information Processing Society
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• v.3 no.2
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• pp.295-304
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• 1996

Toprovide economical BISDN service, with which integration process of many types of media is possible, it is necessary to construct a system with ground network and satellite network combined. The method for this type of transmission using satellite is TDMA that can provide services to many users in various area. However, the most difficult task to connect TDMA which uses synchronous method to ATM which used asynchronous transfer mode is the deterioration n of ATM transmission quality such as cell delay variation. Therefore, it is necessary to develop delay variation compensation method which can confront to the ATM. Efficient ways to use satellite links under the conditions such that maximum efficiency of the delay variation is limited under the required value, and the burst characteristic of transmission cell does not increase are being researched for translation between in ATM and TDMA. This paper points out the problems when time stamp method, reviewd in ground network, is applied to the satellite links to compensate the delay variation .To solve the problem, discrete cell count method is introduced along with the calculation of transmission capacity and error rate.Also, from the observation of stab-ility of the system and verification of reliability even when singal error occurred in the cell transmission timing information, the proposed compensation method appeared to be excellent.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.43 no.1 s.343
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• pp.27-36
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• 2006

Conventional delay-insensitive (DI) data encodings usually require 2N+1 wires for transferring N-bit. To reduce complexity and power dissipation of wires in designing a large scaled chip, an encoder and a decoder circuits, where N-bit data transfer can be peformed with only N+l wires, are proposed. These circuits are based on a quasi delay-insensitive (QDI) model and designed by using current-mode multiple valued logic (CMMVL). The effectiveness of the proposed data transfer mechanism is validated by comparisons with conventional data transfer mechanisms using dual-rail and 1-of-4 encodings through simulation at the 0.25 um CMOS technology. In general, simulation results with wire lengths of 4 mm or larger show that the CMMVL scheme significantly reduces delay-power product ($D{\ast}P$) values of the dual-rail encoding with data rate of 5 MHz or more and the 1-of-4 encoding with data rate of 18 MHz or more. In addition, simulation results using the buffer-inserted dual-rail and 1-of-4 encodings for high performance with the wire length of 10 mm and 32-bit data demonstrate that the proposed CMMVL scheme reduces the D*P values of the dual-rail encoding with data rate of 4 MHz or more and 1-of-4 encoding with data rate of 25 MHz or more by up to $57.7\%\;and\;17.9\%,$ respectively.

• Journal of KIISE:Computer Systems and Theory
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• v.28 no.5
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• pp.213-217
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• 2001

Excessive memory buffer requirement in continuous media playback is a serious impediment of wide spread usage of on-line multimedia service. Skewed access frequency of available video files provides an opportunity of re-using the date blocks which has been loaded by one session for later usage. We present novel algorithm which minimizes the buffer requirement in multiple sessions of multimedia playbacks. In continuous media playback originated from the disk, a certain amount of memory buffer is required to synchronize asynchronous disk. Read operation and synchronous playback operation. As aggregate playback bandwodth increases, larger amount of buffer needs to be allocated for this synchronization purpose. The focus of this work is to study the asymptotic behavior of the synchronization buffer requirement and to develop an algorithm coping with this excessive buffer requirement under bandwidth congestioon. We argue that in a large scale continuous media server, it may not be necessary to read the blocks for each session directly from the disk. The beauty of our work lies in the fact that it dynamically adapts to disk utilization of the server and finds the optimal way of servicinh the individual sessions while minimizing the overall buffer space requirement. Optimality of the proposed algorithm is shown by proof. The effectiveness and performance of the proposed scheme is examined via simulation.

• KIPS Transactions on Computer and Communication Systems
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• v.3 no.9
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• pp.293-300
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• 2014

TDMA(Time Division Multiple Access) is a channel access scheme for shared medium networks. The shared frequency is divided into multiple time slots, some of which are assigned to a user for communication. Techniques for TDMA can be categorized into two classes: synchronous and asynchronous. Synchronization is not suitable for small scale networks because it is complicated and requires additional equipments. In contrast, in DESYNC, a biologically-inspired algorithm, the synchronization can be easily achieved without a global clock or other infrastructure overhead. However, DESYNC spends a great deal of time to complete synchronization and does not guarantee the maximum time to synch completion. In this paper, we propose a lightweight synchronization scheme, C-DESYNC, which counts the number of participating nodes with GP (Global Packet) signal including the information about the starting time of a period. The proposed algorithm is mush simpler than the existing synchronization TDMA techniques in terms of cost-effective method and guarantees the maximum time to synch completion. Our simulation results show that C-DESYNC guarantees the completion of the synchronization process within only 3 periods regardless of the number of nodes.