• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.2
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• pp.978-1002
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• 2019

With the rapid development of the Internet of Things, the problem of privacy protection has been paid great attention. Recently, Nikooghadam et al. pointed out that Kumari et al.'s protocol can neither resist off-line guessing attack nor preserve user anonymity. Moreover, the authors also proposed an authentication supportive session initial protocol, claiming to resist various vulnerability attacks. Unfortunately, this paper proves that the authentication protocols of Kumari et al. and Nikooghadam et al. have neither the ability to preserve perfect forward secrecy nor the ability to resist key-compromise impersonation attack. In order to remedy such flaws in their protocols, we design a lightweight authentication protocol using elliptic curve cryptography. By way of informal security analysis, it is shown that the proposed protocol can both resist a variety of attacks and provide more security. Afterward, it is also proved that the protocol is resistant against active and passive attacks under Dolev-Yao model by means of Burrows-Abadi-Needham logic (BAN-Logic), and fulfills mutual authentication using Automated Validation of Internet Security Protocols and Applications (AVISPA) software. Subsequently, we compare the protocol with the related scheme in terms of computational complexity and security. The comparative analytics witness that the proposed protocol is more suitable for practical application scenarios.

• Nuclear Engineering and Technology
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• v.54 no.4
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• pp.1271-1287
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• 2022

When abnormal operating conditions occur in nuclear power plants, operators must identify the occurrence cause and implement the necessary mitigation measures. Accordingly, the operator must rapidly and accurately analyze the symptom requirements of more than 200 abnormal scenarios from the trends of many variables to perform diagnostic tasks and implement mitigation actions rapidly. However, the probability of human error increases owing to the characteristics of the diagnostic tasks performed by the operator. Researches regarding diagnostic tasks based on Artificial Intelligence (AI) have been conducted recently to reduce the likelihood of human errors; however, reliability issues due to the black box characteristics of AI have been pointed out. Hence, the application of eXplainable Artificial Intelligence (XAI), which can provide AI diagnostic evidence for operators, is considered. In conclusion, the XAI to solve the reliability problem of AI is included in the AI-based diagnostic algorithm. A reliable intelligent diagnostic assistant based on a merged diagnostic algorithm, in the form of an operator support system, is developed, and includes an interface to efficiently inform operators.

• Nuclear Engineering and Technology
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• v.54 no.5
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• pp.1804-1812
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• 2022

The aim of this paper is to assess the reliability and accuracy of the PSI standard method, used in many previous works, for the quantification of ND uncertainties in the SPERT-III RIA transient, by quantifying the discrepancy between the actual inserted reactivity and the original static reactivity worth and their associated uncertainties. The assessment has shown that the inherent S3K neutron source renormalization scheme, introduced before starting the transient, alters the original static reactivity worth of the transient CR and reduces the associated uncertainty due to the ND perturbation. In order to overcome these limitations, two additional methods have been developed based on CR adjustment. The comparative study performed between the three methods has showed clearly the high sensitivity of the obtained results to the selected approach and pointed out the importance of using the right procedure in order to simulate correctly the effect of ND uncertainties on the overall parameters in a RIA transient. This study has proven that the approach that allows matching the original static reactivity worth and starting the transient from criticality is the most reliable method since it conservatively preserves the effect of the ND uncertainties on the inserted reactivity during a RIA transient.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.40 no.4
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• pp.183-190
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• 2017

This paper proposes a dynamic magnetic field emulator (DMFE), which can electrically emulate information for the magnetic stripes of most widely used credit cards. Payment transactions with most common credit cards are performed by reading the card's information, encoded in magnetic stripes, using the reader head of a point-of-sale (POS) system. A stripe-type permanent magnet is attached to the back side of the credit card, and information for payments or value-added service is reorganized by exposing it to strong magnetic field. The process of data recording and retrieving as stated above has been pointed out as a major cause of illegal credit card use, because the information on the magnetic stripe is always exposed, and is thus vulnerable to forgery or alteration. A dynamic magnetic field emulator displays card information only when necessary by using the principle of solenoidal magnets. The DMFE proposed in this paper can prevent fraudulent use if it is operated with a device, like a smart phone, or a separate user-authentication procedure. In addition, because it is possible to display various information as needed, it can be utilized for a smart multi-card application, in which information for multiple cards is stored in one card, and can be selected and used as needed. This paper introduces the necessity of the DMFE and its manufacturing principles. As a result, this study will be helpful for making various application cases in payment, which is a core area of the Fintech (a newly-coined word of finance and technology) industry.

• Journal of Korea Technology Innovation Society
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• v.17 no.3
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• pp.449-466
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• 2014

There have been various researches on the relationship between a company's R&D investment and the outcome from innovation. However, these studies failed to effectively analyze the decision-making process followed by companies in relation to knowledge production. Especially, in analyzing the patent of companies, the Poisson model has been commonly used, but its limitations have been pointed out. In recent years, many studies have adopted negative binomial models, but they still pose limitations in analyzing the selection process. This paper proposed a hurdle negative binomial model to effectively reflect the company's decision embedded within patent information and conduct an empirical analysis on a survey of businesses' activities. In particular, the study analyzed the selection process of companies in determining the number of patents. As a result of estimation, the presence of over-dispersion was identified. In addition, the Wald-test confirmed that setting up of hurdles was valid, and there was a difference between the results of hurdle models and those of general negative binomial settings.

• Journal of Communications and Networks
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• v.18 no.5
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• pp.744-761
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• 2016

For about the past decade and a half research efforts into cognitive radio networks (CRNs) have increased dramatically. This is because CRN is recognized as a technology that has the potential to squeeze the most out of the existing spectrum and hence virtually increase the effective capacity of a wireless communication system. The resulting increased capacity is still a limited resource and its optimal allocation is a critical requirement in order to realize its full benefits. Allocating these additional resources to the secondary users (SUs) in a CRN is an extremely challenging task and integer programming based optimization tools have to be employed to achieve the goals which include, among several aspects, increasing SUs throughput without interfering with the activities of primary users. The theory of the optimization tools that can be used for resource allocations (RA) in CRN have been well established in the literature; convex programming is one of them, in fact the major one. However when it comes to application and implementation, it is noticed that the practical problems do not fit exactly into the format of well established tools and researchers have to apply approximations of different forms to assist in the process. In this survey paper, the optimization tools that have been applied to RA in CRNs are reviewed. In some instances the limitations of techniques used are pointed out and creative tools developed by researchers to solve the problems are identified. Some ideas of tools to be considered by researchers are suggested, and direction for future research in this area in order to improve on the existing tools are presented.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.1
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• pp.79-86
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• 1995

The structural materials for cryogenic technology have been recently developed to support the many modern large-scale application from superconducting magnets for nuclear fusion reactor, magnetic levitation railway to LNG tankers. However it is pointed out that quenching phenomenon is one of the serious problems for the integrity of these applications, which is mainly attributed to the rapid temperature rising in the material due to some extrinsic factors of structures. From the viewpoint of fracture mechanics, it is therefore very important to clarify the mechanism of temperature rising of structural material due to cyclic loading at cryogenic temperature. From this purpose, fatigue test was carried out for high manganese steel at liquid helium temperature(4.2K) using triangular stress waveform to identify both the mechanism of temperature rising near crack tip and the effect of loading stress waveform on temperature rising near crack tip and the effect of loading stress waveforms on temperature rising. As the results, two types of temperature rising, that is, regular and burst types were observed. And a periodical temperature rising corresponding to the stress waveforms was also found. The peaks of the temperature rising were recorded near both the maximum and the minimum values of the applied stress. The sudden temperature rises, which indicated the higher values than those of periodical temperature rises under the repetition of stress, were observed at the final region of crack growth. It was shown that the peak values of the temperature rising increased with stress intensity factor range.

• Corrosion Science and Technology
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• v.6 no.3
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• pp.103-111
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• 2007

The effect of stress factors on the growing process of stress corrosion cracking (SCC) of the sensitized 18-8 stainless steel in high temperature water was investigated using equations of crack growth rate derived from applying electric circuits to SCC corrosion paths. Three kinds of cross sections have to be considered when electric circuit is constructed using total current. The first is ion flow passage area, $S_{sol}$, of solution in crack, the second is total dissolving surface area, $S_{dis}$, of metal on electrode of crack tip and the third is dissolving cross section, $S_{met}$, of metal on grain boundary or in base metal or in welding metal. Stress may affect each area. $S_{sol}$ may depend on applied stress, $\sigma_{\infty}$, related with crack depth. $S_{dis}$ is expressed using a factor of $\varepsilon(K)$ and may depend on stress intensity factor, K only. SCC crack growth rate is ordinarily estimated using a variable of K only as stress factor. However it may be expected that SCC crack growth rate depends on both applied stress $\sigma_{\infty}$ and K or both crack depth and K from this consideration.$\varepsilon(K)$ is expressed as ${\varepsilon}(K)=h_2{\cdot}K^2+h_3{\cdot}K^3$ when $h_{2}$ and $h_{3}$ are coefficients. Also, relationships between SCC crack growth rate, da/dt and K were simulated and compared with the literature data of JBWR-VIP-04, NRC NUREG-0313 Rev.2 and SKIFS Draft. It was pointed out in CT test that the difference of distance between a point of application of force and the end of starter notch (starting point of fatigue crack) may be important to estimate SCC crack growth rate. An anode dissolution current density was quantitatively evaluated using a derived equation.

• Journal of The Korean Association of Information Education
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• v.8 no.2
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• pp.261-268
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• 2004

The Government has established the infrastructure for knowledge and information-oriented society, strengthening the ICT technology education. Although information knowledge ability of learners is prerequisite to educate ICT, but systematic educating courses and time for that are insufficient, and many difficulties have been pointed out. In order to solve such problems, this study developed Web-based computerized adaptive testing system using the item response theory. This system enables the learners to evaluate their own ICT knowledge abilities in their school or home by using familiar web interface and to perform supplementary or deepening study according to the results, and consequently, smooth education of ICT application will be achieved. In addition, this system will be a very effective method for the elementary/middle/high-school ICT knowledge ability certification system.

• Journal of Electrical Engineering and Technology
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• v.9 no.5
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• pp.1654-1659
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• 2014

Tunneling field-effect transistors (TFETs) are very applicable to low standby-power application by their virtues of low off-current ($I_{off}$) and small subthreshold swing (S). However, low on-current ($I_{on}$) of silicon-based TFETs has been pointed out as a drawback. To improve $I_{on}$ of TFET, a gate-all-around (GAA) TFET based on III-V compound semiconductor with InAs/InGaAs/InP multiple-heterojunction structure is proposed and investigated. Its performances have been evaluated with the gallium (Ga) composition (x) for $In_{1-x}Ga_xAs$ in the channel region. According to the simulation results for $I_{on}$, $I_{off}$, S, and on/off current ratio ($I_{on}/I_{off}$), the device adopting $In_{0.53}Ga_{0.47}As$ channel showed the optimum direct-current (DC) performance, as a result of controlling the Ga fraction. By introducing an n-type InGaAs thin layer near the source end, improved DC characteristics and radio-frequency (RF) performances were obtained due to boosted band-to-band (BTB) tunneling efficiency.