• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.520-526
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• 2012

The appearance of the negative differential pressure(NDP), in which the shot base pressure is higher than the breech pressure, indicates that a potential damage on the gun system is increased. In order to safeguard the gun system, the igniter must be designed to minimize the NDP during the firing process. From this reason, the effect of igniter's burning rate on the NDP of the interior ballistics has been investigated through the numerical simulations. The NDP has been increased with increment of the coefficient in the burning rate of the igniter. A sudden change of the chamber pressure has been shown in case of using a singular coefficient.

• Structural Engineering and Mechanics
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• v.71 no.3
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• pp.211-221
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• 2019

To study the eccentric compression behavior of ultra-high performance fiber reinforced concrete (UHPFRC) columns, six UHPFRC columns and one high-strength concrete (HSC) column were tested. Variation parameters include load eccentricity, volume of steel fibers and stirrup ratio. The crack pattern, failure mode, bearing capacity, and deformation of the specimens were studied. The results showed that the UHPFRC columns had different failure modes. The large eccentric compression failure mode was the longitudinal tensile reinforcements yielded and many horizontal cracks appeared in the tension zone. The small eccentric compression failure mode was the longitudinal compressive reinforcements yielded and vertical cracks appeared in the compressive zone. Because of the bridging effect of steel fibers, the number of cracks significantly increased, and the width of cracks decreased. The load-deflection curves of the UHPFRC columns showed gradually descending without sudden dropping, indicating that the specimens had better deformation. The finite element (FE) analysis was performed to stimulate the damage process of the specimens with monotonic loading. The concrete damaged plasticity (CDP) model was adopted to characterize the behaviour of UHPFRC. The contribution of the UHPFRC tensile strength was considered in the bearing capacity, and the theoretical calculation formulas were derived. The theoretical calculation results were consistent with the test results. This research can provide the experimental and theoretical basis for UHPFRC columns in engineering applications.

• Steel and Composite Structures
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• v.31 no.3
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• pp.233-242
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• 2019

Early detection of damage bonding state such as insufficient bonding strength and interface partial contact defect for the explosive clad pipe is crucial in order to avoid sudden failure and even catastrophic accidents. A generalized and efficient model of the explosive clad pipe can reveal the relationship between bonding state and vibration characteristics, and provide foundations and priory knowledge for bonding state detection by signal processing technique. In this paper, the slender explosive clad pipe is regarded as two parallel elastic beams continuously joined by an elastic layer, and the elastic layer is capable to describe the non-uniform bonding state. By taking the characteristic beam modal functions as the admissible functions, the Rayleigh-Ritz method is employed to derive the dynamic model which enables one to consider inhomogeneous system and any boundary conditions. Then, the proposed model is validated by both numerical results and experiment. Parametric studies are carried out to investigate the effects of bonding strength and the length of partial contact defect on the natural frequency and forced response of the explosive clad pipe. A potential method for identifying the bonding quality of the explosive clad pipe is also discussed in this paper.

• Journal of the Korean Society of Industry Convergence
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• v.25 no.1
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• pp.131-139
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• 2022

The exchange of goods over the sea is a situation in which the amount of trade between countries is gradually increasing. In order to maintain the optimal operating condition, the ship maintains stability and optimal operating conditions by inserting or withdrawing ballast water from the ballast tank according to the loading condition of cargo capacity is also increasing. Control valves play an important role in controlling fluid flow in these pipes. When the flow rate is controlled using a control valve, problems such as cavitation, flashing, and suffocating flow may occur due to high differential pressure, and in particular, damage to valves and pipes due to cavitation is a major problem. Therefore, in this study, the cavitation phenomenon is reduced by installing orifices at the front and rear ends of the high differential pressure control butterfly valve to reduce the sudden pressure drop at the limiting part of the butterfly valve step by step. The flow coefficient according to the shape of the orifice, the degree of cavitation occurrence, and the correlation were analyzed using a CFD(Cumputational Fluid Dynamics), and an optimal orifice design for reducing cavitation is derived.

• Natural Product Sciences
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• v.28 no.4
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• pp.194-200
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• 2022

Albizia julibrissin Durazz. (AJ; family Minosaceae) is widely distributed worldwide, and its stem bark has been used as a traditional herbal medicine. Acute kidney injury (AKI) is a clinical syndrome that results in sudden loss of renal function. This study aimed to investigate the effects of AJ against cisplatin-induced AKI using a human kidney proximal tubule epithelial cell line (HK-2) and cisplatin-treated mice. In vitro, cisplatin treatment increased apoptosis in HK-2 cells. However, AJ treatment decreased apoptosis of cisplatin-treated HK-2 cells. In vivo, cisplatin treatment accelerated renal injury by increasing the levels of renal injury markers, such as blood urea nitrogen, creatinine, kidney injury molecule 1, and neutrophil gelatinase-associated lipocalin, which were reversed by AJ treatment. Histopathologically, AJ treatment resulted in decreased renal damage with less tubular necrosis and brush border desquamation compared with the AKI group. Additionally, cisplatin treatment upregulated mitochondrial fission, a pathological characteristic of AKI, which was downregulated by AJ treatment. Along with increased mitochondrial fission, AJ treatment also reduced cisplatin-induced apoptosis. These results suggest that AJ may be a potential therapeutic agent for cisplatin-induced AKI.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.126-126
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• 2021

Stormwater reduction plays an important role in the safety and resilience to flooding in urban areas. Due to rapid climate change, the world is experiencing abnormal climate phenomena, and sudden floods and concentrated torrential rains are frequently occurring in urban basins and the amount of outflow due to stormwater increases. In addition, the damage caused by urban flooding and inundation due to extreme rainfall exceeding the events that occurred in the past increases. To solve this problem, water supply, drainage, and water supply for sustainable urban development, the water management paradigm is shifting from sewage maintenance to water circulation and water-sensitive cities. So, in this study, The purpose of this study is to examine measures to increase the resilience of urban ecosystem systems for urban excellence reduction by analyzing the effects of green infra structures and LID techniques and evaluating changes in resilience. In this study, for simulating and analysis of runoff for various stormwater patterns and LID applications, Storm Water Management Model (SWMM) was used.

• Steel and Composite Structures
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• v.44 no.4
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• pp.519-529
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• 2022

Sandwich structures with the superior mechanical properties such as high stiffness and strength-to-weight ratio, good thermal insulation, and high energy absorption capacity are used today in aerospace, automotive, marine, and civil engineering industries. These structures are composed of moderately stiff, thin face sheets that withstand the majority of transverse and in-plane loads, separated by a thick, lightweight core that resists shear forces. In this research, the finite element technique is used to simulate a sandwich panel with a truss core under axial compressive stress using ABAQUS software. A review of past experimental studies shows that the bondline between the core and face sheets plays a vital role in the critical failure load. Therefore, this modeling analyzes the damage initiation modes and debonding between face sheet and core by cohesive surface contact with traction-separation model. According to the results obtained from the modeling, it can be observed that the adhesive stiffness has a significant influence on the critical failure load of the specimens. To achieve the full strength of the structure as a continuum, a lower limit is obtained for the adhesive stiffness. By providing this limit stiffness between the core and the panel face sheets, sudden failure of the structure can be prevented.

• International journal of advanced smart convergence
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• v.12 no.4
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• pp.378-385
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• 2023

The importance of wearing respiratory protective equipment has been highlighted even more during the COVID-19 pandemic. Even if the suitability of respiratory protection has been confirmed through testing in a laboratory environment, there remains the potential for leakage points in the respirators due to improper application by the wearer, damage to the equipment, or sudden movements in real working conditions. In this paper, we propose a method to detect the occurrence of leak holes by measuring the pressure changes inside the mask according to the wearer's breathing activity by attaching an IoT sensor to a full-face respirator. We designed 9 experimental scenarios by adjusting the degree of leak holes of the respirator and the breathing cycle time, and acquired respiratory data for the wearer of the respirator accordingly. Additionally, we analyzed the respiratory data to identify the duration and pressure change range for each breath, utilizing this data to train a neural network model for detecting leak holes in the respirator. The experimental results applying the developed neural network model showed a sensitivity of 100%, specificity of 94.29%, and accuracy of 97.53%. We conclude that the effective detection of leak holes can be achieved by incorporating affordable, small-sized IoT sensors into respiratory protective equipment.

• The Journal of Internal Korean Medicine
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• v.45 no.1
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• pp.75-86
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• 2024

Spinal cord infarction is one of the rare strokes with no clear signs of serious nerve damage or after-effects. This study reports on the effectiveness of a combined treatment of Korean medicine and acupuncture on bilateral paraplegia, dysuria, and constipation in a patient with sudden-onset spinal cord infarction. An 84-year-old male patient was diagnosed with spinal cord infarction in August 2022. After diagnosis by whole spine MRI, he received treatment for two months at another hospital, but the improvement was insignificant. He then received Korean medicine treatment, and during this period, his lower extremity manual muscle test grade improved from 3 to 4 and his modified Rivermead mobility index score increased by 13 points, compared with hospitalization. Dysuria improved with acupuncture, and constipation improved with herbal medicine treatment. A combination of herbal medicine and acupuncture can be used to treat paraplegia, dysuria, and constipation caused by spinal cord infarction.

• The Korean Journal of Air & Space Law and Policy
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• v.27 no.1
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• pp.75-101
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• 2012

As the Reublic of Korea revised the Commercial Code including 40 articles of air transport enacted newly on May 23, 2011, so Korea became first legislative examples in the Commercial Code of the developed and developing countries. I would like to explain briefly the main contents of my paper such as (1) history of enacting newly Part VI (air transport) in the Korea's revised commercial law, (2) legal background enacting newly Part VI (air transport) in the Korea's revised commercial law and the problems on the conditions of air transport, (3) every countries' legislative examples on the civil liability of aircraft's operator, (4) unlawful Interference Convention and general risk convention of 2009, (5) main contents and prospects of the revised Commercial Code for the liability of aircraft's operator etc as the followings. Meanwhile as the Aviation Act, Commercial Code and Civil Code in Korea and Japan did not regulated at all the legal basis of solution on the disputes between victims and offender for the amount of compensation for damage due to personal or property damage caused by aircraft accidents in Korea and Japan, so it has been raised many legal problems such as protection of victims, standard of decision in trial in the event of aircraft accident's lawsuit case. But the Korean Revised Commercial Code including Part VI, air transport regulations was passed by the majority resolution of the Korean National Assembly on April 29, 2011 and then the South Korean government proclaimed it on May 23 same year. The Revised Commercial Code enforced into tothe territory of the South Korea from November 24, 2011 after six month of the proclaimed date by the Korean Government. Thus, though Korean Commercial Code regulated concretely and respectively the legal relations on the liability of compensation for damage in the contract of transport by land in it's Part II (commercial activities) and in the contract of transport by sea in its Part V (marine commerce), but the Amended Commercial Act regulated newly 40 articles in it's Part VI (air transport) relating to the air carrier's contract liability on the compensation for damage caused by aircraft accidents in the air passengers and goods transport and aircraft operator's tort liability on compensation for damage caused by the sudden falling or collision of aircraft to third parties on the surface and so it was equipped with reasonable and unified system among the transport by land, marine and air. The ICAO adopted two new air law conventions setting out international compensation and liability rules for damage caused by aircraft to third parties at a diplomatic conference hosted by it from April 20 to May 2, 2009. The fight against the effects of terrorism and the improvement of the status of victims in the event of damage to third parties that may result either from acts of unlawful interference involving aircraft or caused by ordinary operation of aircraft, forms the cornerstone of the two conventions. One legal instrument adopted by the Conference is "the Convention on Compensation for Damage to Third Parties, Resulting from Acts of Unlawful Interference Involving Aircraft" (Unlawful Interference Convention). The other instrument, "the Convention on Compensation for Damage Caused by Aircraft to Third Parties" (General Risk Convention), modernizes the current legal framework provided for under the 1952 Rome Convention and related Protocol of 1978. It is desirable for us to ratify quickly the abovementioned two conventions such as Unlawful Interference Convention and General Risk Convention in order to settle reasonably and justly as well as the protection of the South Korean peoples.