• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.10
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• pp.2498-2508
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• 1993

$Al/SiC/Al_{2}O_{3}$ hybrid composites are fabricated by squeeze infiltration method. From the misconstructive of $Al/SiC/Al_{2}O_{3}$ hybrid composites fabricated by squeeze infiltration method, uniform distribution of reinforcements and good bondings are found. Hardness value of $Al/SiC/Al_{2}O_{3}$ hybrid composites increases linearly with the volume fraction of reinforcement because SiC whisker and $Al_{2}$O$_{3}$ fiber have an outstanding hardness. Optimal aging conditions are obtained by examining the hardness of $Al/SiC/Al_{2}O_{3}$ hybrid composites with different aging time. Tensile properties such as Young's modulus and ultimate tensile strength are improved up to 30% and 40% by the addition of reinforcements, respectively. Failure mode of $Al/SiC/Al_{2}O_{3}$ hybrid composites is ductile on microstructural level. Through the abrasive wear test and wear surface analysis, wear behaviour and mechanism of 6061 aluminum and $Al/SiC/Al_{2}O_{3}$ hybrid composites are characterized under various testing conditions. The addition of SiC whisker to $Al/SiC/Al_{2}O_{3}$ composites gives rise to improvement of the wear resistance. The wear resistance of $Al/SiC/Al_{2}O_{3}$ hybrid composites is superior to that of Al/SiC composites. The wear mechanism of aluminum alloy is mainly abrasive wear at low speed range and adhesive and melt wear at high speed range. In contrast, that of $Al/SiC/Al_{2}O_{3}$ hybrid composites is abrasive wear at all speed range, but severe wear when counter material is stainless steel. As the testing temperature increases, wear loss of aluminum alloy decreases because the matrix is getting more ductile, but that of $Al/SiC/Al_{2}O_{3}$ hybrid composites is hardly varied. Oil lubricant is more effective to reduce the wear loss of aluminum alloy and $Al/SiC/Al_{2}O_{3}$ hybrid composites at high speed range.

• Environmental and Resource Economics Review
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• v.26 no.3
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• pp.399-416
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• 2017

This study examines the problem of efficient scheduling of waste collection in isolated regions like islands when the waste accumulated amount surpasses the standard ceiling by effectively tracking the accumulating trends based on the optimum checking model of Keller (1974). To grasp whether the waste accumulated amount in isolated regions exceeds the standard ceiling, the relevant authorities can tightly check during a set period, but this entails higher monitoring costs. On the other hand, if the accumulated waste over the ceiling is not immediately checked and collected, and continues for a set period of time, innovative efforts for waste management may be highly demanded. As such, the tradeoffs are considered to draw the optimal checking schedule. This study shows that the authorities get to check less frequently the waste accumulation trends if the monitoring costs increase or when the failure rate of waste management systems drops. On the other hand, they get to check more frequently if the accumulated waste amount in isolated regions exceeds the standard ceiling and welfare loss grows as a result. It also shows that frequent checking is the optimal choice if the social marginal benefits enjoyed from innovative efforts made to keep accumulated waste below the standard ceiling, are not significant.

• Journal of the Microelectronics and Packaging Society
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• v.12 no.2 s.35
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• pp.167-174
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• 2005

Smaller size and higher integration of electronic components make smaller gap between metal conducting layers in electronic package. Under harsh environmental conditions (high temperature/humidity), electronic component respond to applied voltages by electrochemically ionization of metal and metal filament formation, which lead to short failure and this phenomenon is termed electrochemical migration(ECM). In this work, printed circuit board(PCB) is used for determination of ECM characteristics. Copper leads of PCB are soldered by eutectic solder alloys. Insulation breakdown time is measured at $85^{\circ}C,\;85{\%}RH$. CAF is the main mechanism of ECM at PCB. Pb is more susceptible to CAF rather than Sn, which corresponds well to the corrosion resistance of solder materials in aqueous environment. Polarization tests in chloride or chloride-free solutions fur pure metal and eutectic solder alloys are performed to understand ECM characteristics. Lifetime results show well defined log-normal distribution which resulted in biased voltage factor(n=2) by voltage scaling. Details on migration mechanism and lifetime statistics will be presented and discussed.

• Advances in pediatric surgery
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• v.16 no.2
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• pp.126-133
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• 2010

Malrotation is a congenital anomaly that becomes symptomatic more frequently during infancy. The indication for surgical treatment at that age is straightforward. In older children, the diagnosis may be more difficult because of chronic and vague complaint. The aim of this study is to compare the symptoms, rate of volvulus and surgical findings in children younger and older than one year. A retrospective study of 40 patients in a a single medical center diagnosed with malrotation from April 1996 to May 2010 was performed. There were 20 (50 %) boys and 20 (50 %) girls. At the time of operation, 27 (67.5 %) patients were younger and 13 (32.5 %) were older than 1 year. Vomiting was seen in 20 cases (74.1 %) of the younger group compared to 2 cases (15.4 %) of the older group. Abdominal sonography and upper gastrointestinal series showed a sensitivity of 100%. Operative findings: 12 (44.4 %) of the younger group presented with volvulus compared to none of the older group. The Ladd's procedure was routinely performed with appendectomy in all cases and bowel resection was requires when volvulus included bowel necrosis or other anomalies were found. After definite procedures, surgical correction for adhesive obstruction was necessary in 5 menbers (18.5 %) of the younger group and 1 patient (7.7 %) in the older group. There was 1 death due to respiratory failure and pneumonia. Abdominal pain was more frequent symptom and bilious vomiting was less frequent. Volvulus did not occur in the older group. Malrotation should be diagnosed promptly in children over 1 year of age by upper gastrointestinal series and abdominal ultrasonography even though symptoms are not as clear cut as in infants.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.6
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• pp.615-624
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• 2014

It has been well known the sloshing pressure has complex shape and various patterns. The pattern of sloshing pressure is variously characterized by the pressure amplitude, duration time and skewness. The structural response induced by the sloshing pressure is also affected by the pattern of sloshing pressure and the type of structural members. In order to understand the structural response by the perspective view of categorized pattern, it is more efficient to make simple sloshing pressure pattern than to reflect the complex pressure history. In this study, the sloshing pressures obtained by the small scale model test are simplified with respect to their duration and skewness. Dynamic analyses of Mark-III LNG CCS are then parametrically performed with the consideration of various types of sloshing impact. Meanwhile, the failure pressures given the duration and skewness are investigated after parametric calculations are conducted to investigate the effect of pressure parameters on the structural response.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.7A
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• pp.649-658
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• 2006

Recently, Software Development was applied to new-approach methods as a various form : client-server system and web-programing, object-orient concept, distributed development with a network environments. On the other hand, it be concerned about the distributed development technology and increasing of object-oriented methodology. These technology is spread out the software quality and improve of software production, reduction of the software develop working. Futures, we considered about the distributed software development technique with a many workstation. In this paper, we discussed optimal release problem based on a stochastic differential equation model for the distributed Software development environments. In the past, the software reliability applied to quality a rough guess with a software development process and approach by the estimation of reliability for a test progress. But, in this paper, we decided to optimal release times two method: first, SRGM with an error counting model in fault detection phase by NHPP. Second, fault detection is change of continuous random variable by SDE(stochastic differential equation). Here, we decide to optimal release time as a minimum cost form the detected failure data and debugging fault data during the system test phase and operational phase. Especially, we discussed to limitation of reliability considering of total software cost probability distribution.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.4C
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• pp.365-373
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• 2003

In this paper, we design a versatle RS decoder which can decode RS codes of any block length n as well as any message length k, based on a modified Euclid's algorithm (MEA). This unique feature is favorable for a shortened RS code of any block length it eliminates the need to insert zeros before decoding a shortened RS code. Furthermore, the value of error correcting capability t can be changed in real time at every codeword block. Thus, when a return channel is available, the error correcting capability can be adaptiverly altered according to channel state. The decoder permits 4-step pipelined processing : (1) syndrome calculation (2) MEA block (3) error magnitude calculation (4) decoder failure check. Each step is designed to form a structure suitable for decoding a RS code with varying block length. A new architecture is proposed for a MEA block in step (2) and an architecture of outputting in reversed order is employed for a polynomial evaluation in step (3). To maintain to throughput rate with less circuitry, the MEA block uses not only a multiplexing and recursive technique but also an overclocking technique. The adaptive RS decoder over GF($2^8$) with the maximal error correcting capability of 10 has been designed in VHDL, and successfully synthesized in a FPGA.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2013.06a
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• pp.163-165
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• 2013

IMO(International Maritime Organization) is existed the movement for revising ISM Code so that the maintenance history and the trouble information given trading in a ship can be transferred. An empirical analysis was made on the influence that will have upon shipping industry through surveying on the recognition on ISM Code revision in employees of the relevant field and on the expected problems given being amended ISM Code as the above. In conclusion, the positive effect is judged to be more in the aspect of ship safety, which is the aim of ISM Code, rather than the negative effect, which may take place given being revised ISM Code. In other words, the clean market can be formed through this because fairness is maintained on both sides given trading in a ship by which opening the maintenance record and the trouble history is applied equally to a buyer and a seller. Ships can be reduced a loss of time and cost in preventing similar problems and seeking solution that may appear in important equipments, through this maintenance record. Also, based on these materials, it comes to be available for analyzing a risk of ship and preventing and managing a risk, thereby being increased ability of maintenance and repair in a ship, resulting in being judged to likely contributing to ship safety and environmental-pollution prevention.

• Journal of Veterinary Clinics
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• v.20 no.4
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• pp.443-448
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• 2003

To determine whether localization of tartrate-resistant acid phosphatase (TRAP) and cathepsin K was associated with rupture of the cranial cruciate ligament (CCL) in dogs. Tissue specimens were obtained from 30 dogs with CCL rupture during surgical treatment, 8 aged normal dogs, and 9 young normal dogs that were necropsied for reasons unrelated to this study and unrelated to musculoskeletal disease. The cranial cruciate ligament was examined histologically. $TRAP^+$ cells and cathepsin $K^+$ cells were identified by histochemical staining and immunohistochemical staining respectively. TRAP and cathepsin $K^+$ were co-localized within the same cells principally located within the epiligamentous region and to a lesser extent in the core region of ruptured CCL. Localization of $TRAP^+$ cells (P < 0.05) and cathepsin $K^+$ cells (P =0.05) within CCL tissue was significantly increased in dogs with CCL rupture, compared with aged-normal dogs, and young normal dogs (P < 0.05 - TRAP, P < 0.001 - cathepsin K). Localization of $TRAP^+$ cells and cathepsin $K^+$ cells within the CCL tissue of aged-normal dogs was also increased compared with young normal dogs (P < 0.05). Small numbers of $TRAP^+$ cells and cathepsin $K^+$ cells were seen in the intact ligaments of aged-normal dogs, which were associated with ligament fasicles in which there was chondroid transformation of ligament fibroblasts and disruption of the organized hierarchical structure of the extracellular matrix. $TRAP^+$ cells and cathepsin $K^+$ cells were not seen in CCL tissue from young-normal dogs. Localization of the proteinases $TRAP^+$ and cathepsin $K^+$ in CCL tissue was significantly associated with CCL rupture. Small numbers of proteinase positive cells were also localized in the CCL of agednormal dogs without CCL rupture, but were not detected in CCL from young-normal dogs. Taken together, these findings suggest that the cell signaling pathways that regulate expression of these proteinases in CCL tissue may form part of the mechanism that leads to upregulation of collagenolytic ligament remodeling and progressive structural failure of the CCL over time.

• Childhood Kidney Diseases
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• v.14 no.1
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• pp.32-41
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• 2010

Purpose : Glomerulonephropathy (GN) often manifests as proteinuria and progresses to chronic renal failure without specific therapy. Mesenchymal stem cell (MSC) has been tried as a therapeutic agent in experimental GN, and previous studies showed that administration of MSC concomitantly to the insult inducing GN or via intra-renal administration ameliorated proteinuria. The purpose of this study was to test the therapeutic potential of MSC administered via intravenous route at the time of clinically evident proteinuria. Methods : MSCs were administered intravenously via tail vain into the mice with adriamycin (ADR) induced nephropathy (ADR-GN), two weeks after ADR injection when massive proteinuria was evident. To test the capacity of MSC modulate the cytokine production in the inflammatory milieu, the concentrations of IFN-$\gamma$ and IL-10 were measured in the supernatant of in vitro mixed lymphocyte culture (MLC) with or without additional MSC. Results : MSCs administered intravenously into the proteinuric mice with ADR-GN accelerated the recovery of this experimental GN with disappearance of proteinuria in two weeks when the saline treated (control) mice still showed significant proteinuria. The mice treated with MSC also had a tendency of better survival. Addition of MSC decreased IFN-$\gamma$ and increased IL-10 in the supernatant of MLC. Conclusion : This study showed that MSC had a therapeutic potential even when administered in a more clinically relevant setting into a proteinuric glomerulonephropathy model. Further study to verify the mechanism and long-term safety of this phenomenon is required.