• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.12
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• pp.918-923
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• 2018

The main function of a fuel tank is to store fuel. On the other hand, the structural soundness of the fuel tank is related directly to the survival of the crew in an emergency situation, such as an aircraft crash, and the relevant performance is demonstrated by a crash impact test. Because crash impact tests have a high risk of failure due to the high impact loads, various efforts have been made to minimize the possibility of trial and error in the actual test at the beginning of the design. Numerical analysis performed before the actual test is a part of such efforts. For the results of numerical analysis to be reflected in the design, however, the reliability of numerical analysis needs to be ensured. In this study, the results of numerical analysis and actual test data were compared to ensure the reliability of numerical analysis for the crash impact test of a rotorcraft fuel tank. For the numerical analysis of a crash impact test, LS-DYNA, crash analysis software, was used and the ALE (arbitrary Lagrangian Eulerian) technique was applied as the analysis method. To obtain actual test data, strain gages were installed on the metal fittings of the fuel tank and linked to the data acquisition equipment. The strain and stress of the fuel tank fitting were calculated by numerical analysis. The reliability of the numerical analysis was enhanced by assessing the error between the strain measurement of the upper fitting obtained from an actual fuel tank and the strain calculated from numerical analysis.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.41 no.3
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• pp.305-316
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• 2021

Construction accidents occur due to a number of reasons-worker carelessness, non-adoption of safety equipment, and failure to comply with safety rules are some examples. Because much construction work is done outdoors, weather conditions can also be a factor in accidents. Past construction accident data are useful for accident prevention, but since construction accident data are often in a text format consisting of natural language, extracting construction hazards from construction accident data can take a lot of time and that entails extra cost. Therefore, in this study, we extracted construction hazards from 2,026 domestic construction accident reports using text mining and performed a seasonal analysis of construction hazards through frequency analysis and centrality analysis. Of the 254 construction hazards defined by Korea's Ministry of Land, Infrastructure, and Transport, we extracted 51 risk factors from the construction accident data. The results showed that a significant hazard was "Formwork" in spring and autumn, "Scaffold" in summer, and "Crane" in winter. The proposed method would enable construction safety managers to prepare better safety measures against outdoor construction accidents according to weather, season, and climate.

• Journal of Chest Surgery
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• v.54 no.2
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• pp.99-105
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• 2021

Background: The number of heart transplantations (HTx) is increasing annually. Due to advances in medical and surgical support, the outcomes of HTx are also improving. Extracorporeal circulatory life support (ECLS) provides patients with decompensated heart failure a chance to undergo HTx. A medical approach involving collaboration among experienced experts in different fields should improve the outcomes and prognosis of ECLS-bridged HTx. Methods: From December 2003 to December 2018, 1,465 patients received ECLS at Samsung Medical Center. We excluded patients who had not undergone HTx or underwent repeated transplantations. Patients younger than 18 years were excluded. We also excluded patients who received an implantable durable left ventricular assist device before HTx. In total, 91 patients were included in this study. A multidisciplinary team approach began in March 2013 at our hospital. We divided the patients into 2 groups depending on whether they were treated before or after implementation of the team approach. Results: The 30-day mortality rate was significantly higher in the pre-ECLS team group than in the post-ECLS team group (n=5, 18.5% vs. n=2, 3.1%; p=0.023). The 1-year survival rate was better in the post-ECLS team group than in the pre-ECLS team group (n=57, 89.1% vs. n=19, 70.4%; p=0.023). Conclusion: We found that implementing a multidisciplinary team approach improved the outcomes of ECLS-bridged HTx. Team-based care should be adapted at HTx centers that perform high-risk HTx.

• Journal of the Microelectronics and Packaging Society
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• v.29 no.2
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• pp.49-52
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• 2022

As the difficulty of flip chip products increase, interest in stable PKG material technology from the viewpoint of reliability is increasing. Currently, the representative of poor reliability that are mainly occurring in flip chip PKG are Sn bridge and Cu dendrite. Two type defects are caused by void generated by the flux residue around the bump. In order to essentially minimize the risk of this type of reliability failure, the linkage between the composition of Molded Under-fill (MUF) and flux, which is related material, was reviewed. In this study, the correlation between base resin and filler, which is the main component of MUF, and flux, was defined, and the material composition design was carried out by refer to lesson learn. With the current material composition, it was confirmed that moisture absorption reliability 85%/85%/24hrs pass result and void did not occur during destructive analysis, and developed MUF has shown flux immunity improving result in flip Chip PKG. We think this study can be used in yield enhancement of flip chip process and give insights to study in compatibility between MUF and flux.

• Journal of the Korean Orthopaedic Association
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• v.56 no.1
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• pp.14-25
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• 2021

Several factors need to be considered for a successful anterior cruciate ligament (ACL) reconstruction, such as preoperative planning, operation technique, and postoperative rehabilitation. Graft choice, fixation, preparation method, maturation, incorporation to host bone, and graft tension should also be considered to achieve a good outcome after an ACL reconstruction. Factors to consider when selecting a graft are the graft strength, graft fixation, fixation site healing, and donor site morbidity, as well as the effects of initial strength, size, surface area, and origin of the graft on its potential for weakening during healing. There are two types of graft for an ACL reconstruction, autograft or allograft. Several autografts have been introduced, including the bone-patellar tendon-bone, hamstring tendon, and quadriceps tendon-bone. On the other hand, each has its advantages and disadvantages. The recent increased use of allografts for an ACL reconstruction is the lack of donor site morbidity, decreased surgical time, diminished postoperative pain, and good availability of source. Despite this, there are no reports suggesting that an allograft may have a better long-term outcome than an autograft. Allografts have inherent disadvantages, including a longer and less complete course of incorporation, remodeling, biomechanically inferiority to autograft, the potential risk of an immunogenic reaction and disease transmission. Higher long-term failure rates and poorer graft maturation scores were reported for allografts compared to autografts. An autograft in an ACL reconstruction should remain the gold standard, although the allograft is a reasonable alternative. If adequate length and diameter of autograft can be obtained for an ACL reconstruction, an autograft with adequate graft fixation and postoperative rehabilitation should be chosen instead of an allograft to achieve better results.

• Journal of the Korean Orthopaedic Association
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• v.55 no.6
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• pp.534-539
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• 2020

The management of severe scoliosis remains a challenge to spine surgeons. The rapid intraoperative correction of severe scoliosis may increase the risk of perioperative complications, such as neurological compromise and implant failure. To minimize these risks, various preoperative traction methods have been employed to achieve partial correction before performing definitive corrective surgery. On the other hand, some studies have shown that one of the complications associated with halo traction could lead to cranial nerve palsy, with the sixth nerve (abducens nerve) being most commonly affected. To reduce the complications, gradual increases in the traction weight and detailed neurological examinations are needed, particularly for patients who have previously undergone brain or cervical surgery. The authors report a case of sixth cranial nerve palsy by preoperative halo-pelvic traction in patients with severe scoliosis who underwent previous decompression surgery for a Chiari I malformation with a review of the relevant literature.

• Korean Journal of Materials Research
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• v.32 no.1
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• pp.9-13
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• 2022

Bullets flying with a light from the back are called "tracers". Tracers are ignited by the combustion gas of the propellant and emit bright light that allows the shooter to visually trace the flight path. Therefore, tracers mark the firing point for allies to assist shooters to hit target quickly and accurately. Conventional tracers are constructed with a mixture of an oxidizing agent, raw metal, and organic fuel. Upon ignition, the inside of the gun can be easily contaminated by the by-products, which can lead to firearm failure during long-term shooting. Moreover, there is a fire risk such as forest fires due to residual flames at impact site. Therefore, it is necessary to develop non-combustion type luminous material; however, this material must still use the heat generated from the propellant, so-called "thermoluminescence (TL)". This study aims to compare the TL emission of Dy³⁺, La³⁺ and Ho³⁺ doped MgB₄O₇ phosphors prepared by solid state reaction. The crystal structures of samples were determined by X-ray diffraction and matched with the standard pattern of MgB₄O₇. Luminescence of various doses (200 ~ 15,000 Gy) of gamma irradiated Dy³⁺, La³⁺ and Ho³⁺ (at different concentrations of 5, 10, 15 and 20 %) doped MgB₄O₇ were recorded using a luminance/color meter. The intensity of TL yellowish (CIE x = 0.401 ~ 0.486, y = 0.410 ~ 0.488) emission became stronger as the temperature increased and the total gamma-ray dose increased.

• Journal of Life Science
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• v.32 no.2
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• pp.94-100
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• 2022

Chronic infection by hepatitis B virus (HBV) greatly increases the risk for liver cirrhosis and hepatocellular carcinoma (HCC). The outcome of HBV infection is shaped by the complex interplay of the mode of transmission, host genetic factors, viral genotype, adaptive mutations, and environmental factors. The pregenomic RNA transcription of HBV for their replication is regulated by the core promoter activation. Core promoter mutations have been the reason for acute liver failure and are associated with HCC development. We obtained HBV genes from a patient in Myanmar who was infected with HBV and identified gene variations in the core promoter region. For measuring the relative transactivation activity of the core promoter, we prepared the core-promoter reporter construct. Among the gene variations of the core promoter, the mutations of C1731T and G1806A were associated with increase in the transactivation of the HBV core promoter. Through computer analysis for searching for a tentative transcription factor binding site, we showed that the mutations of C1713T and G1806A newly created C/EBPβ and XBP1-responsive elements of the core promoter, respectively. The ectopic expression of C/EBPβ largely increased the HBV core promoter containing the C1713T mutation and that of XBP1 activated the M95 promoter containing the G1806A mutation. Our efforts to treat and prevent HBV infections are hampered by the emergence of drug-resistant mutations and vaccine-escape mutations. Our results provide the biological properties and clinical significance of specific HBV core promoter mutations.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.7
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• pp.1082-1087
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• 2021

The propeller shaft has different pattern of behaviors at each static, dynamic, and transient condition to a ship shaft system due to the effects of propeller weight and eccentric thrust, which increases the potential risk of bearing failure by causing local load variations. To prevent this, the various research of the shafting system has been conducted with the emphasis on optimizing the relative slope and oil film retention between propeller shaft and stern tube bearing at quasi-static condition, mainly with respect to the Rules for the Classification of Steel Ships. However, to guarantee a stability of the shafting system, it is necessary to consider the dynamic condition including the transient state due to the sudden change in the stern wakefield during rudder turn. In this context, this study cross-validated the ef ect of propeller shaft behavior on the stern tube bearing during port turn operation, which is a typical transient condition, by using the strain gauge method and displacement sensor for 50,000 DWT medium class tanker. And it was confirmed that the propeller eccentric thrust change showing relief the load of the stern tube bearing.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.21 no.5
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• pp.171-182
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• 2022

The safe use of a structure requires it to be maintained in an undamaged state. Thus, a typical factor that determines the safety of a structure is a crack in it. In addition, cracks are caused by various reasons, damage the structure in various ways, and exist in different shapes. Making matters worse, if these cracks are unattended, the risk of structural failure increases and proceeds to a catastrophe. Hence, recently, methods of checking structural damage using deep learning and computer vision technology have been introduced. These methods usually have the premise that there should be a large amount of training image data. However, the amount of training image data is always insufficient. Particularly, this insufficiency negatively affects the performance of deep learning crack detection algorithms. Hence, in this study, a method of augmenting crack image data based on the image translation technique was developed. In particular, this method obtained the crack image data for training a deep learning neural network model by transforming a specific case of a asphalt crack image into a concrete crack image or vice versa . Eventually, this method expected that a robust crack detection algorithm could be developed by increasing the diversity of its training data.