• Smart Media Journal
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• v.8 no.1
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• pp.19-26
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• 2019

At the opening ceremony of 2018 Winter Olympics in PyeongChang, an unknown cyber-attack occurred. The malicious code used in the attack is based on in-memory malware, which differs from other malicious code in its concealed location and is spreading rapidly to be found in more than 140 banks, telecommunications and government agencies. In-memory malware accounts for more than 15% of all malicious codes, and it does not store its own information in a non-volatile storage device such as a disk but resides in a RAM, a volatile storage device and penetrates into well-known processes (explorer.exe, iexplore.exe, javaw.exe). Such characteristics make it difficult to analyze it. The most recently released in-memory malicious code bypasses the endpoint protection and detection tools and hides from the user recognition. In this paper, we propose a method to efficiently extract the payload by unpacking injection through IDA Pro debugger for Dorkbot and Erger, which are in-memory malicious codes.

• Journal of Korea Society of Industrial Information Systems
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• v.17 no.2
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• pp.33-43
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• 2012

Digital signage is referred to as a smart electronic display system that delivers multimedia-based information and advertisements to customers. Typically, the digital signage starts its playback after downloading a list of multimedia contents from network storage to its local disk. However, a way of downloading the entire contents before its playback entails a long initial delay time. In this paper, we formulate a problem of the initial delay time and provide a solution to compute a minimally demanded initial delay time according to a given network bandwidth and qualities/sizes of the multimedia contents. In addition, we analyze the performance of the proposed solution with various multimedia contents on digital signage.

• Smart Structures and Systems
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• v.3 no.4
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• pp.439-454
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• 2007

In this paper a damage imaging technique using pre-stack migration is developed using Lamb (guided) wave propagation in composite structures for imaging multi damages by both numerical simulations and experimental studies. In particular, the paper focuses on the experimental study using a finite number of sensors for future practical applications. A composite laminate with a surface-mounted linear piezoelectric ceramic (PZT) disk array is illustrated as an example. Two types of damages, one straight-crack damage and two simulated circular-shaped delamination damage, have been studied. First, Mindlin plate theory is used to model Lamb waves propagating in laminates. The group velocities of flexural waves in the composite laminate are also derived from dispersion relations and validated by experiments. Then the pre-stack migration technique is performed by using a two-dimensional explicit finite difference algorithm to back-propagate the scattered energy to the damages and damages are imaged together with the excitation-time imaging conditions. Stacking these images together deduces the resulting image of damages. Both simulations and experimental results show that the pre-stack migration method is a promising method for damage identification in composite structures.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.151-156
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• 2001

Experimental frictional and wear characteristics of silicon graphite materials is studied in this paper. Those specimens are lubricated with high temperature and highly pressurized water to simulate the same operating condition for the journal bearing and the thrust bearing on the main coolant pump bearing in the newly developing nuclear reactor named SMART(System-integrated Modular Advanced ReacTor). Operating condition of the bearings is realized by the tribometer and the autoclave. Friction coefficient and wear loss are analyzed to choose the best silicon graphite material. Pin on plate test specimens are used and coned disk springs are used to control the applied force on the specimens. Wear loss ana wear width are measured by a precision balance and a micrometer. The friction force is measured by the strain gauge which can be used under high temperature and high pressure. Three kinds of silicon graphite materials are examined and compared with each other, and each material shows similar but different results on frictional and wear characteristics.

• Smart Structures and Systems
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• v.22 no.6
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• pp.663-673
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• 2018

In this study, the effect of particle size on the cracks propagation and coalescence or cracking pattern of the edge notched disc specimens are investigated. Firstly, calibration of PFC3D was performed using Brazilian experimental test output. Then micro parameters were used to build edge notched disc specimen. The horizontal wall of the assembly is let to move downward with a standard low speed of 0.016 m/s. The numerical results show that the tensile cracks are dominant failure pattern for the modeled discs. These tensile cracks initiate from the pre-existing notch tip and propagate parallel to the loading direction then interact with the upper boundary of the modeled specimen. As the size of the balls (ball diameter) decrease the number of tensile cracks increase. The tensile fracture toughness of the samples also decreases as the particle size increases. Understanding the crack propagation and crack coalescence phenomena in brittle materials such as concretes and rocks is of paramount importance in the stability analyses for engineering structures such as rock slopes, underground structures and tunneling.

• International journal of advanced smart convergence
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• v.8 no.2
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• pp.77-87
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• 2019

One of important concerns in information security is to control information flow. It is whether to protect confidential information from being leaked, or to protect trusted information from being tainted. In this paper, we present Piosk (Physical blockage of Information flow Kiosk) that addresses both the problems practically. Piosk can forestall and prevent the leakage of information, and defend inner tangible assets against a variety of malwares as well. When a visitor who carries a re-writable portable storage device, must insert the device into Piosk installed next to the security gate. Then, Piosk scans the device at the very moment, and detects & repairs malicious codes that might be exist. After that, Piosk writes the contents (including sanitized ones) on a new read-only portable device such as a compact disk. By doing so, the leakage of internal information through both insiders and outsiders can be prevented physically. We have designed and prototyped Piosk. The experimental verification of the Piosk prototype implementation reveals that, Piosk can accurately detect every malware at the same detection level as Virus Total and effectively prevent the leakage of internal information. In addition, we compare Piosk with the state-of-the-art methods and describe the special advantages of Piosk over existing methods.

• International journal of advanced smart convergence
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• v.10 no.1
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• pp.142-150
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• 2021

Open-channel SSD is a new type of Solid-State Disk (SSD) that improves the garbage collection overhead and write amplification due to physical constraints of NAND flash memory by exposing the internal structure of the SSD to the host. However, the host-level Flash Translation Layer (FTL) provided for open-channel SSDs in the current Linux kernel consumes host memory excessively because it use page-level mapping table to translate logical address to physical address. Therefore, in this paper, we implemente a selective mapping table loading scheme that loads only a currently required part of the mapping table to the mapping table cache from SSD instead of entire mapping table. In addition, to increase the hit ratio of the mapping table cache, filesystem information and mapping table access history are utilized for cache replacement policy. The proposed scheme is implemented in the host-level FTL of the Linux kernel and evaluated using open-channel SSD emulator. According to the evaluation results, we can achieve 80% of I/O performance using the only 32% of memory usage compared to the previous host-level FTL.

• The Journal of the Korea Contents Association
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• v.15 no.10
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• pp.607-615
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• 2015

Mosts user of internet and smart phone has certificate, and uses it when money transfer, stock trading, on-line shopping, etc. Mosts user stores certificate in a hard disk drive of PC, or the external storage medium. In particular, the certification agencies are encouraged for user to store certificate in external storage media such as USB memory rather than a hard disk drive. User think that the external storage medium is safe, but when it is connect to a PC, certificate may be copied easily, and can be exposed to hackers through malware or pharming site. Moreover, if a hacker knows the user's password, he can use user's certificate without restrictions. In this paper, we suggest secure management scheme of the private key file using a password of the encrypted private key file, and a USB Memory's hardware information. The private key file is protected safely even if the encrypted private key file is copied or exposed by a hacker. Also, if the password of the private key file is exposed, USB Memory's container ID, additional authentication factor keeps the private key file safe. Therefore, suggested scheme can improve the security of the external storage media for certificate.

• Journal of Dental Rehabilitation and Applied Science
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• v.23 no.2
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• pp.157-170
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• 2007

Purpose: This investigation was designed to determine the translucency and color stability of various core ceramics for all-ceramic restoration using the CIE $L^*a^*b^*$ system. Material and Methods: IPS e.max Press ceramic(Ivoclar-Vivadent, Liechtenstein), $LAVA^{TM}$ All Ceramic(3M-Espe, Germany), Cercon Smart Ceramic(Dentsply, Germany), and Z-match Ceramic(DentAim, Korea) were used for this study. For the specimens of zirconia oxide ceramics, the as-sintered cylindrical blanks($11.0{\times}25.0mm$) were machined into the shape of a disk(0.4, 0.8, 1.5 mm in thickness, 10 mm in diameters) with a diamond grind machine. The IPS e.max Press specimens ($0.8{\times}10mm$) were fabricated using the "lost wax" technique. CIE $L^*a^*b^*$ coordinates and light transmission were recorded for each specimen with a spectrophotometer(CM-2600d, Minolta, Japan). Color differences were calculated using the equation, ${\Delta}E^*ab=[({\Delta}L^*)2+({\Delta}a^*)2+({\Delta}b^*)2]1/2$. Results: The results were obtained as follows: 1. The most translucent group was IPS e.max Press ceramic that is a glass-ceramic, and $Lava^{TM}$ and Z-match ceramic were more translucent than Cercon Smart ceramic in zirconia ceramic group. 2. In the all groups, there was no significant translucent change after 6 times heat-treatments required to make a final restoration. 3. Colored zirconia was showed more yellowish and dark than uncolored zirconia. 4. After heat-pressing, IPS e.max Press ceramic was showed high ${\Delta}E^*ab$ value(4.1 of eM1, 6.8 of eM2) that means to be more whiter than before heat-pressing. However, there was no color change after additive heat treatments for final restoration. 5. In the colored zirconia groups, there was no significant color change after some heat-treatments required to make a final restoration.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.1
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• pp.103-108
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• 2014

The flash memory which is exploited on hand-held devices such as smart phones is a non-volatile storage and has the benefit that it can store mass data at a small sized chip. To process queries on the mass data stored in the flash memory, the index scheme should be exploited. However, since the write operation of the flash memory is slower than the read operation and the overwrite is not supported, it is required to reevaluate the performance of the index and find out the drawbacks. In this paper, we evaluate the performance of a space division typed index scheme on the flash memory. To do this, we implement the fixed grid file and measure the average speeds of the query and update processing on a various condition and compare the value of the flash memory with that of the magnetic disk.