• Composites Research
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• v.36 no.4
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• pp.259-263
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• 2023

This study investigated the open hole tensile (OHT) properties of carbon fiber/epoxy composites and compared them to bolt joint tensile (BJT) properties. The net nominal modulus and strength (1376 MPa) were found to be higher than the gross nominal strength (1041 MPa), likely due to increasing hole size. The OHT and BJT specimens exhibited similar stiffness, as expected without bolt rotation causing secondary bending. OHT specimens experienced a sharp drop in stress indicating unstable crack propagation, delamination, and catastrophic failure. BJT specimens failed through shear out on the bolt side and bearing failure on the nut side, involving fiber kinking, matrix splitting, and delamination, resulting in lower strength compared to OHT specimens. The strength retention of carbon fiber/epoxy composites with open holes was 66%. Delamination initiation at the hole's edge caused a reduction in the stress concentration factor. Filling the hole with a bolt suppressed this relieving mechanism, leading to lower strength in BJT specimens compared to OHT specimens. Bolt joint efficiency was calculated as 15%. The reduction in strength in bolted joints was attributed to fiber-matrix splitting and delamination, aligning with Hart Smith's bolted joint efficiency diagram. These findings contribute to materials selection and structural reliability estimation for carbon fiber/epoxy composites. They highlight the behavior of open hole and bolt joint configurations under tensile loading, providing valuable insights for engineering applications.

• Wind and Structures
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• v.37 no.4
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• pp.289-302
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• 2023

Insulating glass units (IGUs) have been widely used in buildings in recent years due to their superior thermal insulation performance. However, because of the panel reciprocating motion and fatigue deterioration of sealants under long-term wind loads, many IGUs have the problem of early failure of watertight properties in real usage. This study aimed to propose a statistical method for wind-induced deflection of IGU panels during the whole life service period, for further precise analysis of the accumulated fatigue damage at the sealed part of the edge bond. By the estimation of the wind occurrence regularity based on wind pressure return period, the events of each wind speed interval during the whole life were obtained for the IGUs at 50m height in Beijing, which are in good agreement with the measured data. Also, the wind-induced deflection analysis method of IGUs based on the formula of airspace coefficient was proposed and verified as an improvement of the original stiffness distribution method with the average relative error compared to the test being about 3% or less. Combining the two methods above, the deformation of the outer and inner panes under wind loads during 30 years was precisely calculated, and the deflection and stress state at selected locations were obtained finally. The results show that the compression displacement at the secondary sealant under the maximum wind pressure is close to 0.3mm (strain 2.5%), and the IGUs are in tens of thousands of times the low amplitude tensile-compression cycle and several times to dozens of times the relatively high amplitude tensile-compression cycle environment. The approach proposed in this paper provides a basis for subsequent studies on the durability of IGUs and the wind-resistant behaviors of curtain wall structures.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.11
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• pp.1335-1343
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• 2012

In this study, the lightweight modular design of hybrid railway carbody structures made of sandwich composites and aluminum extrusions was investigated by using topology and size optimization techniques. The topology optimum design was used to select the best material for parts of the carbody structure at the initial design stage, and then, the size optimum design was used to find the optimal design parameters of hybrid carbody structures using first-order and sub-problem methods. Through the topology optimization analysis, it was found that aluminum extrusions were suitable for primary members such as the underframe and lower side panel module to improve the stiffness and manufacturability of the carbody structures, and sandwich composites were appropriate for secondary members such as the roof and middle side panel module to minimize its weight. Furthermore, the results obtained by size optimization analysis showed that the weight of hybrid carbody structures composed of aluminum extrusions and sandwich composites could be reduced by a maximum of approximately 17.7% in comparison with carbody structures made of only sandwich composites.

• Journal of the korean academy of Pediatric Dentistry
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• v.38 no.3
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• pp.284-289
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• 2011

Lesch-Nyhan syndrome is a disease caused by metabolic disorder of purine. General muscle stiffness and hyposomia are shown from infancy and symptoms can include involuntary or irregular movements of arms and legs, mental retardation, and compulsive self-mutilating behaviors. Self-mutilating behaviors begin at approximately the first year or sometimes at late teens. The patients bite their lips, especially lower lip, tongue, buccal mucosa, hands and fingers. Tongue and lips can be injured or mutilated in severe cases. As the patient gets older, self-mutilating behaviors become more serious and extensive and secondary infection of injured areas is possible. Periodic soft tissue damage due to self-mutilating may evolve to cancer. Medical treatment, appliance treatment, extraction of tooth and surgical operation was attempted to control self-mutilaing behaviors. We hereby report the case of child Lesch-Nyhan syndrome patient who has self-inflicted labial damage as chief complaint. When patient was treated with conservate therapy, such as removable or fixed appliance, the frequency of labial damage could be subdued and yielded favorable results.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.9
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• pp.643-651
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• 2020

A capsule train runs inside a sub-vacuum tube and can reach very high speed due to the low air resistance. A capsule train uses a superconducting electrodynamic suspension (SC-EDS) method for levitation, which allows for a large levitation gap and does not require gap control. However, SC-EDS has inherent characteristics such as the large gap variation and a small damping effect in the levitation force, which can degrade the running stability and ride comfort. To overcome this, a stability improvement device should be designed and applied based on dynamic analysis. In this study, a 1/10 small-scale testbed was developed to replicate the dynamic characteristics of a capsule train and investigate the performance of stability improvement devices. The testbed is composed of a 6-degree-of-freedom Stewart platform for the realization of bogie motion, a secondary suspension with a running stabilization device, and a carbody. Based on the dynamic similarity law proposed by Jaschinski, the small-scale testbed was manufactured, and a bogie motion algorithm was applied with the consideration of guideway irregularity and levitation stiffness. The experimental results from the testbed were compared with simulation results to investigate the performance of the testbed.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.14
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• pp.117-121
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• 1973

This experiment was conducted to study the effects of nitrogen top-dressed at the different growth stages on the morphological and physical characteristics of barley culm. The results obtained are summarized as follows: 1. By top-dressing of nitrogen in March, each internode length from the third to the fifth internode was shortened, and total fresh weight of the top, dry weight per unit culm, inside or outside culm diameter and thickness of culm were increased. Therefore these characteristics related to lodging indicated the beneficial changes for lodging resistance by top-dressing of nitrogen in March. 2. Both weight of culm at breaking and bending moment of culm at breaking, expressing lodging resistance of culm, were increased in the plots of nitrogen top-dressed in March. Accordingly lodging resistance became higher by top-dressing of nitrogen in March. 3. Both section modulus and secondary moment of inertia, expressing bending stiffness of culm, were increased by top-dressing of nitrogen in March. Accordingly lodging index, expressing comprehensive lodging resistance, became low by top-dressing of nitrogen in March. 4. Both spike weight and grain yield were increased by top-dressing of nitrogen in March. Consequently we came to the conclusion that the suitable top-dressing time of nitrogen was in March.

• Journal of the Society of Disaster Information
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• v.11 no.1
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• pp.45-54
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• 2015

In the case of railway facilities in cities such as a railway station or a bridge, the significance of design for reducing vibration and noise is getting more significant. The vibration control solution is in need especially for an elevated railway station to block vibration of a train and secondary noise effectively. Even though a vertical vibration isolation device is able to be applied effectively to railway facilities such as elevated railway stations which transfer vibration directly from a train to a structure, the development of the vertical device is much slower than a horizontal vibration isolation device. In this paper, a vibration isolation device using wedge type friction material which is currently developing to reduce train-induced vibration effectively is introduced and test results for verification of dynamic performance is also presented. The vibration test on a concrete structure equipped with the developed vibration isolation device is conducted through which the isolation performance and dynamic properties are verified and needs for improving the performance of the device is identified.

• Journal of Pharmacopuncture
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• v.21 no.3
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• pp.151-158
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• 2018

Objectives: We investigated the efficacy and safety of miniscalpel acupuncture (MA) for knee osteoarthritis (KOA) in an assessor-blinded randomized controlled pilot trial; this would provide information for a large-scale randomized controlled trial. Methods: Participants (n = 24) were recruited and randomly allocated to the MA group (experimental) or acupuncture group (control). The MA group received treatment once a week for 3 weeks (total of 3 treatments), while the acupuncture group received treatment two times per week for 3 weeks (total of 6 treatments). The primary outcome was pain as assessed by a visual analogue scale (VAS). The secondary outcomes (intensity of current pain, stiffness, and physical function) were assessed using the short-form McGill Pain Questionnaire (SF-MPQ) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Assessments were performed at baseline, 1, 2, and 3 during treatment and at week 5 (2 weeks after the end of treatment). Results: Of the 24 participants, 23 completed the study. Both groups showed significant improvements in VAS, SF-MPQ, and WOMAC. However, there were no significant differences between the MA and acupuncture groups. No serious adverse event occurred and blood test results were within normal limits. Conclusion: Our results suggest that although both MA and acupuncture provide similar effects with regard to pain control in patients with KOA, MA may be more effective in providing pain relief because the same relief was obtained with fewer treatments. A large-scale clinical study is warranted to further clarify these findings.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.11
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• pp.561-567
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• 2018

This study was carried out to improve the ride quality of high-speed electric multiple unit. Through dynamic analysis of the HEMU-430X, the range of the equivalent conicity with a critical speed of 300 km/h was between 0.05 and 0.25. The initial adopted wheel profile of HEMU-430X was S1002. The equivalent conicity of S1002 with the mileage of more than 40,000 km was about 0.033 and it was confirmed that XP55 is more suitable for stable operation because XP55 has the equivalent conicity of over 0.061. In order to improve ride quality of high-speed electric multiple unit, the change of installation angle of the yaw damper was suggested from $7.35^{\circ}$ to $0^{\circ}$. From sensitivity analysis and optimization, the air spring lateral and vertical stiffness was suggested to be reduced by 30% and the secondary vertical and lateral damper damping coefficient was increased by 50%. By applying this, it was expected that the car body acceleration could be improved by about 20% on average. The HEMU-430X's yaw damper installation angle was changed to $0^{\circ}$ and the damping coefficient of the lateral damper was increased by 30%. When the test run was carried out at the speed of 300 km/h on the Kyungbu high-speed line, the vehicle lateral acceleration had improved by 34.3%. The effect of additional improvement measures proposed in this paper will be tested in the on track test. The riding quality improvement process used in this study can be used to solve ride quality problems that can occur in commercial operation of high-speed electric multiple unit in the future.

• Herbal Formula Science
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• v.30 no.2
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• pp.95-100
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• 2022

Objectives : Recent studies reported that Dokwhalkisaeng-tang (DHJST) could relieve the clinical rheumatoid arthritis (RA) symptoms and the level of RA-related blood test. However, evidence-based review on effectiveness and safety of DHJST with medication on RA was not yet provided. Methods : Searching randomized controlled trials on the use of DHJST for RA will be performed using multiple electronic databases, manual search, and contact to author. Studies will be selected according to the pre-defined criteria and collected data on study participants, interventions, control groups, outcome measurements, the results, adverse events, and risk of bias will be summarized. Primary outcome will be the disease activity score (including effective rate, swollen joint count, tender joint count, and morning stiffness), and the secondary outcomes will be RA-related blood test and adverse events. We will use Review Manager software to perform a meta-analysis, Cochrane Collaboration "risk of bias" tool for assessing the risk of bias, and Grades of Recommendation, Assessment, Development and Evaluation for the determination of quality of evidence. Results : We are going to investigate the effectiveness and safety of DHJST with medication for RA. Conclusion : This study will provide reliable evidence on whether DHJST combined with medicine is more effective on RA than medicine monotherapy.