• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.5
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• pp.129-137
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• 2000

The powertrain is an important factor for the interior and exterior noise behavior of the vehicle Thus, the noise vibration and harshness(NVH) behavior of an engine is becoming a major target of the powertrain development. This paper describes the analyses with the aim to reduce the vibration and noise of an advanced inline 4-cylinder diesel engine block by use of CAE methods. The characteristics of an engine block as a main excitation source of car interior noise is studied. Particularly, The effect of balance shaft to reduce the 2nd order engine excitation force is calculated by forced vibration and radiated noise analysis. The engine exitation forces are obtained under real operating conditions. It is shown that the reduction of vibration and noise level by adapting blancing shaft is well predicted and rediated noise is directly related to the surface velocity of engine block.

• Annals of Clinical Neurophysiology
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• v.20 no.1
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• pp.49-52
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• 2018

Reversible conduction block (RCB) was rare in patients with acute motor sensory axonal neuropathy (AMSAN). A-46-year-old man presented with paresthesia, weakness, diplopia, and dysarthria. Nerve conduction study (NCS) exhibited axonal changes with conduction block in motor and sensory nerves. His symptoms were rapidly progressed and recovered. Conduction block was disappeared in the follow-up NCS performed after 2 weeks. The AMSAN case with RCB showed rapid progress and rapid recovery of clinical symptoms as acute motor axonal neuropathy patients with RCB.

• Journal of Venture Innovation
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• v.2 no.2
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• pp.21-29
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• 2019

In the public certificate technology commonly used in Korea, users have a cumbersome problem of always resetting when they forget their password. In this paper, as a solution to this problem, we propose a secure authentication certificate password recovery protocol using blockchain, PKI, and DID for distributed storage. DID is a schema for protecting block ID in blockchain system. The private key used in the PKI is configured as a user's biometric, for example, a fingerprint, so that it can completely replace the memory of the complex private key. To this end, based on the FIDO authentication technology that most users currently use on their smartphones, the process of authenticating a user to access data inside the block minimizes the risk of an attacker taking over the data.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.1
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• pp.280-295
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• 2015

Block cipher ARIA was first proposed by some South Korean experts in 2003, and later, it was established as a Korean Standard block cipher algorithm by Korean Agency for Technology and Standards. In this paper, we focus on the security evaluation of ARIA block cipher against the recent zero-correlation linear cryptanalysis. In addition, Partial-sum technique and FFT (Fast Fourier Transform) technique are used to speed up the cryptanalysis, respectively. We first introduce some 4-round linear approximations of ARIA with zero-correlation, and then present some key-recovery attacks on 6/7-round ARIA-128/256 with the Partial-sum technique and FFT technique. The key-recovery attack with Partial-sum technique on 6-round ARIA-128 needs $2^{123.6}$ known plaintexts (KPs), $2^{121}$ encryptions and $2^{90.3}$ bytes memory, and the attack with FFT technique requires $2^{124.1}$ KPs, $2^{121.5}$ encryptions and $2^{90.3}$ bytes memory. Moreover, applying Partial-sum technique, we can attack 7-round ARIA-256 with $2^{124.6}$ KPs, $2^{203.5}$ encryptions and $2^{152}$ bytes memory and 7-round ARIA-256 employing FFT technique, requires $2^{124.7}$ KPs, $2^{209.5}$ encryptions and $2^{152}$ bytes memory. Our results are the first zero-correlation linear cryptanalysis results on ARIA.

• Journal of Korea Multimedia Society
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• v.11 no.5
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• pp.651-660
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• 2008

Flash memory is widely used in embedded systems because of its benefits such as non-volatile, shock resistant, and low power consumption. However, NAND flash memory suffers from out-place-update, limited erase cycles, and page based read/write operations. To solve these problems, YAFFS and RFFS, the flash memory file systems, are proposed. However YAFFS takes long time to mount the file system, because all the files are scattered all around flash memory. Thus YAFFS needs to fully scan the flash memory. To provide fast mounting, RFFS has been proposed. It stores all the block information, the addresses of block information and meta data to use them at mounting time. However additional operations for the meta data management are decreasing the performance of the system. This paper presents a new NAND flash file system called ERFFS (Efficient and Reliable Flash File System) which provides fast mounting and recovery with minimum mata data management. Based on the experimental results, ERFFS reduces the flash mount/recovery time and the file system overhead.

• Journal of Broadcast Engineering
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• v.13 no.5
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• pp.612-621
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• 2008

Due to the various constraints such as feasible size of data payload and low transmission power, no technical specifications on the voice communication are included in the Zigbee standard. In this paper, a voice coding technique for application to the IEEE 802.15.4 standard, which is the basis of Zigbee communication, is presented. Here, both high compression and good waveform recovery are essential. To meet those requirements, a multi-stage discrete wavelet transform (DWT) block and a binary coding block consisting of two different pulse-code modulations are exploited. Theoretical analysis and simulation results in an indoor wireless channel show that the voice coder with 2-stage DWT is most appropriate from the viewpoint of compression and waveform recovery. When the line-of-sight component is dominant, the voice coding scheme has good recovery capability even in the moderate signal-to-noise power ratios. Hence, it is considered that the presented scheme will be a technical reference for the future recommendation of voice communication exploiting Zigbee.

• Journal of KIISE:Information Networking
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• v.33 no.4
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• pp.333-342
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• 2006

The cdma2000 lxEV - DO mobile communication system provides broadcast and multicast services (BCMCS) to meet an increasing demand from multimedia data services. The servicing of video streams over a BCMCS network must, however, face a challenge from the unreliable and error-prone nature of the radio channel. The BCMCS network uses Reed-Solomon coding integrated with the MAC protocol for error recovery. We analyze this coding technique and show that it is not effective in the case of slowly moving mobiles. To improve the playback quality of an MPEG-4 FGS video stream, we propose the Hybrid error recovery scheme, which combines Reed-Solomon with ARQ, using slots which are saved by reducing the Reed-Solomon coding overhead. The target packets to be retransmitted are prioritized by a utility function to reduce the packet error rate in the application layer within a fixed retransmission budget. This is achieved by considering of the map of the error control block at each mobile node. The proposed Hybrid error recovery scheme also uses the characteristics of MPEG-4 FGS (fine granularity scalability) to improve the video quality even when conditions are adverse: slow-moving nodes and a high error rate in the physical channel.

• Journal of Korean Neurosurgical Society
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• v.66 no.6
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• pp.652-663
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• 2023

Objective : This study compared the quality of recovery (QoR) after minicraniotomy for clipping of unruptured intracranial aneurysms (UIAs) between patients with and without scalp nerve block (SNB). Methods : Patients were randomly assigned to the SNB (SNB using ropivacaine with epinephrine, n=27) and control (SNB using normal saline, n=25) groups. SNB was performed at the end of surgery. To assess postoperative QoR, the QoR-40, a patient-reported questionnaire, was used. The QoR-40 scores were measured preoperatively, 1-3 days postoperatively, at hospital discharge, and 1 month postoperatively. Pain and intravenous patient-controlled analgesia (IV-PCA) consumption were evaluated 3, 6, 9, and 12 hours and 1-3 days postoperatively. Results : All QoR-40 scores, including those measured 1 day postoperatively (primary outcome measure; 155.0 [141.0-176.0] vs. 161.0 [140.5-179.5], p=0.464), did not significantly differ between the SNB and control groups. The SNB group had significantly less severe pain 3 (numeric rating scale [NRS]; 3.0 [2.0-4.0] vs. 5.0 [3.5-5.5], p=0.029), 9 (NRS; 3.0 [2.0-4.0] vs. 4.0 [3.0-5.0], p=0.048), and 12 (NRS; 3.0 [2.0-4.0] vs. 4.0 [3.0-5.0], p=0.035) hours postoperatively. The total amount of IV-PCA consumed was significantly less 3 hours postoperatively in the SNB group (2.0 [1.0-4.0] vs. 4.0 [2.0-5.0] mL, p=0.044). Conclusion : After minicraniotomy for clipping of UIAs, SNB reduced pain and IV-PCA consumption in the early postoperative period but did not improve the QoR-40 scores.

• Proceedings of the KIEE Conference
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• 2005.05a
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• pp.161-163
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• 2005

In this paper, we propose an efficient motion vector recovery algorithm for the new coding standard H.264, which makes use of the Lagrange interpolation formula. In H.264/AVC, a 16$\times$16 macroblock can be divided into different block shapes for motion estimation, and each block has its own motion vector. In the natural video the motion vector is likely to move in the same direction, hence the neighboring motion vectors are correlative. Because the motion vector in H.264 covers smaller area than previous coding standards, the correlation between neighboring motion vectors increases. We can use the Lagrange interpolation formula to constitute a polynomial that describes the motion tendency of motion vectors, and use this polynomial to recover the lost motion vector. The simulation result shows that our algorithm can efficiently improve the visual quality of the corrupted video.

• 한국정보통신설비학회:학술대회논문집
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• 2006.08a
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• pp.219-222
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• 2006

In this paper we present a cryptanalysis of the generalized patchwork algorithm under the assumption that the attacker possesses only a single copy of the watermarked audio. In the scheme, watermark is inserted by modifying randomly chosen DCT values in each block of the original audio. Towards the attack we first fit low degree polynomials (which minimize the mean square error) on the data available from each block of the watermarked content. Then we replace the corresponding DCT data of the at-tacked audio by the available data from the polynomials to construct an attacked audio. The technique nullifies the modification achieved during watermark embedding. Experimental results show that recovery of the watermark becomes difficult after the attack.