• Journal of KIISE:Information Networking
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• v.35 no.1
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• pp.1-10
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• 2008

Once the sensor node in wireless sensor networks is installed, it usually operates without human intervention for a long time. The remote code update scheme is required because it is difficult to recall the sensor node in many situations. Therefore, studies on the reliable and efficient transport protocol for code propagation in wireless sensor networks have been increasingly done. However, by considering only the stability aspect of transmission, most of previous works ignore the consideration on the fast code propagation. This results the energy inefficiency by consuming unnecessary energy due to the slow code propagation. In this paper, in order to overcome limitation of the previous code propagation protocols, we propose a new code propagation protocol called "FCPP(Fast Code Propagation Protocol)". The FCPP aims at improving the reliability at well as performance. For this purpose, the FCPP accomplishes the fast code propagation by using the RTT-based transmission rate control and NACK suppression scheme, which provides a better the network utilization and avoids a unnecessary transmission delay. Based on the ns-2 simulation result, we prove that the FCPP Improves significantly both reliability and performance.

• Journal of the Korean Society of Safety
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• v.11 no.3
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• pp.3-9
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• 1996

Dynamic fracture characteristics of Polycarbonate WL-RDCB specimen were investigated. The dynamic crack propagation velocities in these specimens were measured by using both high speed camera system and silver paint grid method developed and justified in the INHA Fracture Mechanics Laboratory. The measured crack propagation velocities were fed into the INSAMCR code(a dynamic finite element code which has been developed in the INBA Fracture Mechanics Laboratory) to extract the dynamic stress intensity factors. It has been confirmed that both dynamic crack arrest toughness and the static crack arrest toughness depend on both the geometry and the dynamic crack propagation velocity of specimens. The maximum dynamic crack propagation velocity of Polycarbonate WL-RDCB specimen was found to be dependent on the material property, geometry and the type of loading. The dynamic cracks in these Polycarbonate WL-RDCB specimens seemed to propagate in a successive manner, involving distinguished 'propagation-arrest-propagation-arrest' steps on the microsecond time scale. It was also found that the relat-ionship between dynamic stress intensity factor and dynamic crack propagation velocities might be represented by the typical '$\Gamma$'shape.

• The Journal of the Korea Contents Association
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• v.6 no.12
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• pp.155-162
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• 2006

It was well known that how much seriously the Internet worm such as the Code Red had an effect on our daily activities. Recently the rapid growth of the Internet speed will produce more swift damage us in a short term period. In order to defend against future worm, we need to understand the propagation pattern during the lifetime of worms. In this paper, we analyze the propagation pattern of the Code Red worm by a computer simulation. In particular, we show that an existing simulation result about the number of infectious hosts does not match the observed data, and then we introduce a factor of revised human countermeasures into the simulation. We also show the simulation results presenting the importance of patching and pre-patching of the Internet worm.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1997.10a
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• pp.50-54
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• 1997

To trace crack propagation process in cracked structure is very important thing in view of maintenance and repair of the structure. But it is a little troublesome work due to the continuous remesh work, because a new crack tip is formed in each propagation step. It is more difficult if it should be studied in the three dimensional region. By the way, lately the CFG(Cornell Fracture Group) makes the crack propagation analysis in three dimensional problems possible by developing a new code for them. The use of the code will be expected to spread widely. So a brief introduction of the contents of the code via the theorems used and numerical examples is the purpose of this paper.

• Journal of Korea Society of Digital Industry and Information Management
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• v.11 no.3
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• pp.45-51
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• 2015

In this paper, we discuss the belief propagation decoding algorithm for polar codes. The performance of Polar codes for shorter lengths is not satisfactory. Motivated by this, we propose a novel technique to improve its performance at short lengths. We showed that the probability of messages passed along the factor graph of polar codes, can be increased by multiplying the current message of nodes with their previous message. This is like a feedback path in which the present signal is updated by multiplying with its previous signal. Thus the experimental results show that performance of belief propagation polar decoder can be improved using this proposed technique. Simulation results in binary-input additive white Gaussian noise channel (BI-AWGNC) show that the proposed belief propagation polar decoder can provide significant gain of 2 dB over the original belief propagation polar decoder with code rate 0.5 and code length 128 at the bit error rate (BER) of $10^{-4}$.

• Journal of Korea Multimedia Society
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• v.10 no.5
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• pp.687-697
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• 2007

Although the Java bytecode has numerous advantages, there are also shortcomings such as slow execution speed and difficulty in analysis. Therefore, in order for the Java class file to be effectively executed under the execution environment such as the network, it is necessary to convert it into optimized code. We implemented CTOC for transforming to optimized code. In Optimization, SSA Form that distinguish variable by assignment is used to determine value and type statically. Copy propagation, dead code elimination optimization is applied to SSA Form. However, existing SSA Form is related to variable than expression. Therefore, in this paper, to performing optimization to SSA Form expression, after performing copy propagation and dead code elimination, in addition to that, partial redundant expression elimination is performed

• International Journal of Advanced Culture Technology
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• v.9 no.4
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• pp.288-294
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• 2021

There are various ways to be infected with malicious code due to the increase in Internet use, such as the web, affiliate programs, P2P, illegal software, DNS alteration of routers, word processor vulnerabilities, spam mail, and storage media. In addition, malicious codes are produced more easily than before through automatic generation programs due to evasion technology according to the advancement of production technology. In the past, the propagation speed of malicious code was slow, the infection route was limited, and the propagation technology had a simple structure, so there was enough time to study countermeasures. However, current malicious codes have become very intelligent by absorbing technologies such as concealment technology and self-transformation, causing problems such as distributed denial of service attacks (DDoS), spam sending and personal information theft. The existing malware detection technique, which is a signature detection technique, cannot respond when it encounters a malicious code whose attack pattern has been changed or a new type of malicious code. In addition, it is difficult to perform static analysis on malicious code to which code obfuscation, encryption, and packing techniques are applied to make malicious code analysis difficult. Therefore, in this paper, a method to detect malicious code through dynamic analysis and static analysis using Trojan-type Downloader/Dropper malicious code was showed, and suggested to malicious code detection and countermeasures.

• Nuclear Engineering and Technology
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• v.36 no.4
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• pp.285-294
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• 2004

Pressure wave propagation in the discharge piping with a sparger submerged in a water pool, following the opening of a safety relief valve, is analyzed. To predict the pressure transient behavior, a RELAP5/MOD3 code is used. The applicability of the RELAP5 code and the adequacy of the present modeling scheme are confirmed by simulating the applicable experiment on a water hammer with voiding. As a base case, the modeling scheme was used to calculate the wave propagation inside a vertical pipe with sparger holes and submerged within a water pool. In addition, the effects on wave propagation of geometric factors, such as the loss coefficient, the pipe configuration, and the subdivision of sparger pipe, are investigated. The effects of inflow conditions, such as water slug inflow and the slow opening of a safety relief valve are also examined.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.12
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• pp.1820-1823
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• 2013

An overhead catenary system is the one of the main subjects for increasing speed in electric railway. When a vehicle increases the speed over 350km/h, vibrations and wave propagation reflections occur severely. Therefore, the system suitable for the speed are needed. A wave propagation speed of contact wire is the main criteria to determine the tension for the system. Therefore, a train speed is restricted below 70% of wave propagation speed of it in European railway code. In this study, we measured a strain and uplift of contact wire while HEMU-430X tain is operated for the speed-up trial test in Kyungbu high-speed railway. The measured strain and uplift are analyzed with wave propagation speed according to the speed-up. The more a train speed reaches to a propagation speed, the more measured strain is high. Through the study, an experimental approach is performed about the code which a train speed is restricted below 70% of wave propagation speed of it.

• Journal of Korea Society of Industrial Information Systems
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• v.13 no.5
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• pp.168-177
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• 2008

The code propagation is one of the most important technic for software update in wireless sensor networks. This paper presents a new scheme for code propagation using network coding. The proposed code propagation method roughly shows 20$\sim$25% performance improvement according to network environments in terms of the number of data exchange compared with the previously proposed pipelining scheme. As a result, we can efficiently perform the software update from the viewpoint of speed, energy, and network congestion when the proposed code propagation system is applied. In addition, the proposed system solves the overhearing problems of network coding such as the loss of original messages and decoding error using the predefined message. Therefore, our system allows a software update system to exchange reliable data in wireless sensor networks.