• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.6
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• pp.643-648
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• 2010

Portable fuel cells are commonly operated in the dead-end mode because of such as high fuel utilization. However, the performance of such systems deteriorates continuously with an increase in the amount of by-products such as water vapor and nitrogen. In this study, to verify the effect of water vapor on Proton Exchange Membrane Fuel Cells (PEMFCs), constant-load experiments were carried out for a current density of 600 mA/cm2 and a voltage of 0.4 V, respectively. The performance of the cell was more stable under constant voltage conditions than under constant current density conditions. Condensed water accumulated in the anode channel near the cell outlet. The experimental results show how the relative humidity (RH = 0.15, 0.4 and 0.75) of air at the cathode side affect the performance of PEMFCs with dead-end anode. At RH values higher than 0.15, the mean power density increased by up to 51% and the mean purge duration decreased by up to 25% compared to the corresponding initial values.

• KIPS Transactions on Computer and Communication Systems
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• v.2 no.9
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• pp.399-404
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• 2013

MSEC(Microsoft Security Engineering Center) performed fuzz testing Windows Vista with 350 million test cases for 14 months before launching it. They analyzed crashes resulted from the testing and developed crash analyzer !exploitable based on the data used to determine exploitability. In this paper, we describe how MS crash analyzer determines exploitability of crashes. Besides, we suggest an improvement to overcome the limitations found in the MS crash analyzer during the analysis.

• 한국신재생에너지학회:학술대회논문집
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• 2006.11a
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• pp.494-497
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• 2006

For commercialization of polymer electrolytemembrane fuel cell (PEMFC), durability of membrane electrode assemblies (MEAs) has to be improved. Especially, long-term stability of MEA is one of the most important issues for frequent shut-down and start-up processes of PEMFC. The degradation of MEA could be attributed to chemical attack of hydrogen peroxide radicals that are formed at high cell voltages without any special treatment to remove residual hydrogen from anode gas channel after shut-down of the fuel cell. In this study, we investigated the long-term stability of MEA under different on/off operation conditions. Residential hydrogen gas was removed from the anode flow channel by purging air or nitrogen. Also, a dummy resistance was applied to the fuel cell to exhaust residential hydrogen at the anode. In these cases, MEA showed much more stable durability. Electrochemical characteristics of the fuel cell were measured byrepeating the on/off cycles with the hydrogen removal processes. Also, degradation of MEA components was examined by SEM, TEM and XRD analyses.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.32 no.2
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• pp.417-437
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• 2022

The quality of the fuzzing seed file is one of the important factors to discover vulnerabilities faster. Although the prior seed generation paradigm, using dynamic taint analysis and symbolic execution techniques, enhanced fuzzing efficiency, the yare not extensively applied owing to their high complexity and need for expertise. This study proposed the DDRFuzz system, which creates seed files based on sequence-to-sequence models. We evaluated DDRFuzz on five open-source applications that used multimedia input files. Following experimental results, DDRFuzz showed the best performance compared with the state-of-the-art studies in terms of fuzzing efficiency.

• KIISE Transactions on Computing Practices
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• v.22 no.4
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• pp.178-183
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• 2016

To enhance the reliability of programs, developers use fuzzing tools in test processes to identify vulnerabilities so that they can be fixed ahead of time. In this case, the developers consider the security-related vulnerabilities to be the most critical ones that should be urgently fixed to avoid possible exploitation by attackers. However, developers without much experience of analysis of vulnerabilities usually rely on tools to pick out the security-related crashes from the normal crashes. In this paper, we suggest a static analysis-based tool to help developers to make their programs more reliable by identifying security-related crashes among them. This paper includes experimental results, and compares them to the results from MSEC !exploitable for the same sets of crashes.

• Smart Media Journal
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• v.9 no.3
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• pp.71-79
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• 2020

Mobile network is used by many users worldwide for diverse services, including phone-call, messaging and data transfer over the Internet. However, this network may experience massive damage if it is exposed to cyber-attacks or denial-of-service attacks via wireless communication interference. Because the mobile network is also used as an emergency network in cases of disaster, evaluation or verification for security and safety is necessary as an important nation-wide asset. However, it is not easy to analyze the mobile core network because it's built and serviced by private service providers, exclusively operated, and there is even no separate network for testing. Thus, in this paper, a virtual mobile network is built using OpenAirInterface, which is implemented based on 3GPP standards and provided as an open source software, and the structure and protocols of the core network are analyzed. In particular, the S1AP protocol messages captured on S1-MME, the interface between the base station eNodeB and the mobility manager MME, are analyzed to identify potential security threats by evaluating the effect of the messages sent from the user terminal UE to the mobile core network.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.753-756
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• 2015

Internet technology is universal, news from the Web browser, shopping, search, etc., various activities have been carried out. Its size becomes large, increasing the scale of information security incidents, as damage to this increases the safety for the use of the Internet is emphasized. IE browser is ASLR, such as Isolated Heap, but has been continually patch a number of vulnerabilities, such as various protection measures, this vulnerability, have come up constantly. And, therefore, in order to prevent security incidents, it is necessary to be removed to find before that is used to exploit this vulnerability. Therefore, in this paper, we introduce the purge is a technique that is used in the discovery of the vulnerability, we describe the automation technology related thereto. And utilizing the known vulnerabilities, and try to show any of the typical procedures for the analysis of the vulnerability.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.28 no.1
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• pp.179-186
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• 2018

The number of devices connect to the internet is rapidly increasing with the advent of the IoT(Internet of Things). The IoT has improved the convenience of life. However, it makes security issues such as privacy violations. Therefore cybersecurity is the most important issue to be discussed nowadays. Especially, various protocols are used for same purpose due to rapidly increase of IoT market. To deal with this security threat noble vulnerability analysis is needed. In this paper, we contribute to the IoT security by proposing a new randomness-based test case evaluation methodology using variance and entropy. The test case evaluation method proposed in this paper can evaluate the test cases at a high speed regardless of the test set size, unlike the traditional technique.

• KIPS Transactions on Computer and Communication Systems
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• v.3 no.2
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• pp.31-42
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• 2014

Debugger systems are necessary to apply dynamic program analysis when evaluating security properties of embedded system software. It may be possible to make the use of software-based debugger and/or DBI framework if target devices support general purpose operating systems, however, constraints on applicability as well as environmental transparency might be incurred thereby hindering overall analyzability. Analysis with JTAG (IEEE 1149.1) debugging devices can overcome these difficulties in that no change would be involved in terms of internal software environment. In that sense, JTAG API can facilitate to practically perform dynamic program analysis for evaluating security properties of target device software. In this paper, we introduce an implementation of JTAG API to enable analysis of ARM core based embedded systems. The API function set includes the categories of debugger and target device controls: debugging environment and operation. To verify API applicability, we also provide example analysis tool implementations: our JTAG API could be used to build kernel function fuzzing and live memory forensics modules.

• Journal of the Korean Institute of Gas
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• v.8 no.2 s.23
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• pp.54-60
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• 2004

In this paper, the maximum von Mises stress and maximum displacement of the corner protection and secondary bottom structures have been analyzed using a finite element analysis technique. The design criterion of the comer protection is 1,500Pa for a normal nitrogen gas purging process at the beginning stage of start-up procedure. This pressure is very safe for the structure safety of the comer protection and secondary bottom plates. The corner protection and secondary bottom plates fabricated by $9\%$ nickel steel sheet may plastically be distorted and fractured for the increased gas pressure of 8,475Pa, which produces the maximum von Mises stress of 833MPa and maximum displacement of 1.9m at the center of secondary bottom plate.