• Journal of IKEEE
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• v.10 no.1 s.18
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• pp.30-39
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• 2006

The TCP protocol can provide some reliability using sliding window mechanism for data transmission, flow control, and congestion control. However, TCP has some limitations in that it has basically been designed solely for wired communication environments. If traditional TCP protocol is used also in wireless networks, the end-to-end data transmission performance degrades dramatically due to frequent packet losses caused by transmission errors and hand-offs. While there have been some research efforts on TCP enhancements considering the mobility of wireless communication devices, in this paper we propose a new method to improve the TCP performance by combining the Snoop and the Freeze-TCP methods. In the proposed scheme, the TCP end-to-end semantics is maintained and no changes of existing protocols in sending systems or in routers are required. It has the advantage of simple implementation because TCP code changes are limited to mobile devices for applying the Freeze-TCP and it requires only to add Snoop modules in base stations. Accordingly, the proposed scheme can operate well in the existing networks. Finally, in this study, we compared the performance of the proposed scheme with traditional TCP, other approaches through simulations using ns-2.

• Nuclear Engineering and Technology
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• v.20 no.1
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• pp.27-34
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• 1988

Since the lack of the spent fuel storage capcity has been expected for all Korean nuclear power plants in the mid-1990s, the maximum density rack (MDR) with consolidated fuels can be proposed to overcome the shortage of the storage capacity in KNU 9 & 10 which have most limited capacities. To ensure the safety when the alternatives are applied in the KNU 9 & 10, the multiplication factor are calculated with varying the rack pitch and the thickness of consolidated storage box by the AMPX-KENO IV codes. The computing system is verified by the benchmark calculation with criticality experiments for arrays of consolidated fuel modules, which was reported by B & W in 1981. Also an abnormal condition, i.e. malposition accident, is simulated. The results indicate that the KNU 9 & 10 storage pools with consolidated fuel are safe in the view of the criticality. Thus the storage capacity can be expanded from 9/3 cores into 27/3 cores even with considering equipments and cooling spaces.

• Journal of KIISE:Computer Systems and Theory
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• v.27 no.8
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• pp.710-718
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• 2000

Many multiprocessing systems have been developed to exploit the parallelism and to improve the performance. However, the naive multiprocessing schemes were not successful as many researchers thought, due to the heavy cost of communication and synchronization resulting from parallelization. In this paper, we will identify the reasons for the poor performance and the compiler requirements for the performance improvement. We realized that the decisions for multiprocessing should be derived by the overhead information. We applied this idea to the automatic parallelizing compiler, SUIF. We substituted the original backend of SUIF with our backend using MPI, and gave it the capability to validate parallelization decisions based on overhead parameters. This backend converts the intermediate code containing spacification of parallelizable regions into the distributed-memory based parallel program with MPI function calls without excessive parallelization that may cause performance degradation.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2005.06a
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• pp.457-463
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• 2005

KHNP(Korea Hydro and Nuclear Power Ltd., Co.) is developing a HIC transport package which is satisfying domestic and IAEA regulations and NETEC(Nuclear Environment Technology Institute) is conducting a conceptual design. In this study, the shielding thickness was calculated using the data from radionuclide assay program which is currently using in nuclear sites and Micro Shield code. Considering the structural safety, carbon steel was chosen as shielding material and the shielding thickness was calculated for 500 R/hr and 100 R/hr at HIC surface, respectively. Through the shielding analysis, it was evaluated that the regulation limit is satisfied when the shielding thickness is 22 cm for 500 R/hr and 17 cm for 100/hr.

• The Journal of Engineering Geology
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• v.11 no.3
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• pp.245-254
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• 2001

The experimental study on disposal cover through the performance test facility offers reliability in the safety of near surface disposal of low and intermediate level radioactive waste. To ensure the long-term safety of the repository, the impermeability, integrity, resistance to degradation and ease of maintenance might be considered as the basic performance requirement of the disposal cover. considering the difficulties to meet these performance requirement by using single layer, the disposal cover design which is composed of top layer, middle drainage layer and bottom low permeability layer is schemed for the test facility. The water balance of the cover was evaluated by using HELP code. For the long-term monitoring of the soil moisture content and matric potential, TDR probes and tensiometers will be installed in 6 test cells. Each test cell is dimensioned 3$\times$3$\times$3.3m.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.10
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• pp.85-94
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• 2004

In this paper, a register allocation techlique that translates memory accesses to register accesses Is presented to enhance embedded software performance. In the proposed method, a source code is profiled to generate a memory trace. From the profiling results, target functions with high dynamic call counts are selected, and the proposed register allocation technique is applied only to the target functions to save the compilation time. The memory trace of the target functions is searched for the memory accesses that result in cycle count reduction when replaced by register accesses, and they are translated to register accesses by modifying the intermediate code and allocating Promotion registers. The experiments where the performance is measured in terms of the cycle count on MediaBench and DSPstone benchmark programs show that the proposed method increases the performance by 14% and 18% on the average for ARM and MCORE, respectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37C no.10
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• pp.949-964
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• 2012

Our PC have been under constant threat of malicious codes and viruses today. As many new ways of cyber attacks are being developed, such as zero-day-attack, nobody's PC is guaranteed to be safe from the attacks. In case where a user uses the existing verification protocol on a unsecured PC, the user's verification information may well be threatened by sniffing or man-in-the-middle attack. Especially, deadly attacks like memory hacking would give hard time for users to even recognize any symptom of virus infection. Therefore, this paper designs secured QR-Login user verification protocol for smart devices that are ready to communicate with QR-Code and proposes a way to keep critical data safe when using the internet. This way, user would be able to safeguard his/her critical data even when under attack by unknown attacks and safely carry out extremely sensitive task, like financial trading, on the device.

• Journal of Engineering Education Research
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• v.15 no.2
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• pp.3-9
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• 2012

Normally, people think the results of engineering design project can be seen and be touched, however, it's not easy to develop such design subjects at IT related program. This matter turns into an initiative of Seoul Accord corresponding to the Washington Accord. In this paper, an engineering design project is developed from the lecture course that can hardly develop a touchable project due to the lack of expanse or the own characteristics of the course in the IT related program that follows the Washington Accord. An open-ended design project with the pre-defined design components and realistic constraints is developed for the Computer Network Design course. Each team consisted of 2 or 3 students performs the project for more than 5 weeks utilizing a software simulator, the Packet Tracer. In order to analyze the effectiveness, we have used various evaluation tools such as final presentation, peer evaluation, survey results, and mid/final exams. We concluded that the hard and soft skills of students have been improved considerably through the project.

• Korean Journal of Microbiology
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• v.38 no.3
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• pp.173-179
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• 2002

The functions of riboflavin synthesis genes ( ribI,II,III and IV) found immediately downstream of luxG in the lux operon from Photobacterium species were identified using the biochemical and genetical analysis. The ribI-III gene codes for protein corresponding to that coded by the second (riboflavin synthase), third (3,4-dihydroxy 2-butanone 4-phosphate synthase/GTP cyclohydrolase II) and fourth (lumazine synthase) gene, respectively, of Bacillus subtilis rib operon with the respective gene procuct sharing 41-50% amino acid sequence identity. Unexpectedly, the sequence of the ribIV product of Photobacterium phosphoreum does not correspond in sequence to the protein encoded by the fifth rib gene of Bacillus subtilis. Instead the gene (ribIV) codes for a polypeptide similar in sequence to GTP cyclohydrolase II of Escherichia coli and the carboxy terminal domain of the third rib gene from Bacillus subtilis. Complementation of Escherichia coli riboflavin auxotrophs showed that the function of the gene products of ribII and ribIV are DHBP synthase and GTP cyclohydrolase II, respectively. In addition the experiment, showing that increase in thermal stability of riboflavin synthase coded by ribIon coexpression with ribIII, provided indirect evidence that the latter gene codes for lumazine synthase.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.5
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• pp.1-11
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• 2014

Sympathetic detonation (SD) of high explosives occurs when a detonating donor initiates neighboring acceptors. The present study focuses on the hydrodynamic simulation of one-on-one sympathetic detonation of 155 mm charge filled with PBXN-109. Both unbuffered and buffered SD configurations are performed while changing the distance between each charge, in order to investigate the detonation sensitivity to a donor initiation. The cause of a SD is by a shock impact for the unbuffered case at a close range, while at a distant range, blast fragment penetration is the primary cause. The buffers can reduce the incident sensitivity to a SD by reducing the strengths of shock wave and impinging fragments.