• Composites Research
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• v.36 no.1
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• pp.1-15
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• 2023

Demand for energy consumption reduction is increasing according to the development expectations of future mobility. Lightweight structural materials are known as a method to reduce greenhouse gas emissions and improve energy efficiency. In particular, fiber reinforced polymer composite (FRP) is attracting attention as a material that can replace existing metal alloys due to its excellent mechanical properties and light weight. In this paper, industrial applications and research trends of carbon fiber reinforced composites (CFRP, carbon FRP) and self-reinforced composites (SRC) were reviewed based on the reinforcement, polymer matrix, and manufacturing process. In order to overcome the expensive process cost and long manufacturing time of the epoxy resin-based autoclave method, which is mainly used in the aircraft field, mass production of CFRP-applied electric vehicles has been reported using a high-pressure resin transfer molding process including fast-curing epoxy. In addition, thermoplastic resin-based CFRP and interface enhancement methods to solve the recycling issue of carbon fiber composites were reviewed in terms of materials and processes. To form a perfect matrix-reinforcement interface, which is known as the major factor inducing the excellent mechanical properties of FRP, studies on SRC impregnated with the same matrix in polymer fibers have been reported. The physical and mechanical properties of SRC based on various thermoplastic polymers were reviewed in terms of polymer orientation and composite structure. In addition, a copolymer matrix strategy for extending the processing window of highly drawn polypropylene fiber-based SRC was discussed. The application of CFRP and SRC as lightweight structural materials can provide potential options for improving the energy efficiency of future mobility.

• Journal of Chest Surgery
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• v.41 no.3
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• pp.295-304
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• 2008

Background: Various experimental trials for the development of bioprosthetic devices are actively underway, secondary to the limited supply of autologous and homograft tissue to treat cardiac diseases. In this study, porcine bioprostheses that were treated with glutaraldehyde (GA), ethanol, or sodium dodecylsulfate (SDS) were examined with light microscopy and transmission electron microscopy for mechanical and physical imperfections before implantation, Material and Method: 1) Porcine pericardium, aortic valve, and pulmonary valve were examined using light microscopy and JEM-100CX II transmission electron microscopy, then compared with human pericardium and commercially produced heterografts. 2) Sections from six treated groups (GA-Ethanol, Ethanol-GA, SDS only, SDS-GA, Ethanol-SDS-GA and SDS-Ethanol-GA) were observed using the same methods. Result: 1) Porcine pericardium was composed of a serosal layer, fibrosa, and epicardial connective tissue. Treatment with GA, ethanol, or SDS had little influence on the collagen skeleton of porcine pericardium, except in the case of SDS pre-treatment. There was no alteration in the collagen skeleton of the porcine pericardium compared to commercially produced heterografts. 2) Porcine aortic valve was composed of lamina fibrosa, lamina spongiosa, and lamina ventricularis. Treatment with GA, ethanol, or SDS had little influence on these three layers and the collagen skeleton of porcine aortic valve, except in the case of SDS pre-treatment. There were no alterations in the three layers or the collagen. skeleton of porcine aortic valve compared to commercially produced heterografts. Conclusion: There was little physical and mechanical damage incurred in porcine bioprosthesis structures during various glutaraldehyde fixation processes combined with anti-calcification or decellularization treatments. However, SDS treatment preceding GA fixation changed the collagen fibers into a slightly condensed form, which degraded during transmission electron micrograph. The optimal methods and conditions for sodium dodecylsulfate (SDS) treatment need to be modified.

• Journal of Korean Society of Transportation
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• v.26 no.3
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• pp.31-40
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• 2008

There have been a lot of efforts to find more accurate evaluation methods for traffic signal control effectiveness for a long period of time. Nowadays a newly advanced method called HILSS, 'Hardware-in-the-Loop-Simulation System', is used to evaluate the overall traffic control's effectiveness including physical control environments like communication conditions, hardware performance, controller's mechanical operations and so on. In this study, an Online-HILSS model has been developed, which runs on CORSIM(5.0) micro traffic simulation model on-lined to COSMOS. For the verification of the model, three tests are performed as follows; (1) a comparison of TMC's timing plan with the simulated green interval, (2) as a case study, a delay distribution comparison of the online simulation with the CORSIM stand-alone simulation. The result of the first test shows that the model can run the simulation green interval by TMC's timing plan correctly. The result of second test shows that the online simulation of the model brings the same simulation results with the CORSIM offline simulation in case of the same timing plan. These results mean that the online evaluation model could be a reliable tool to measure a real-time signal control effectiveness of a wide area street network with the HILSS method.

• Journal of the Korean Magnetics Society
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• v.14 no.2
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• pp.83-88
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• 2004

Magnetism of molecular nanomagnet, which attracted a lot of academic attention after the discovery of the macroscopic quantum tunneling of magnetism, is reviewed. Molecular nanomagnet is metal-organic material in which magnetic ions are regularly located in the organic skeleton. Also, the interaction between the molecules is very small and those molecules form macroscopic molecular crystal in which molecules are residing at the element points in the crystal. Molecular nanomagnets show a lot of interesting features, especially, equivalence of macroscopic magnetic properties and molecular magnetic properties. In this paper, research results on molecular nanomagnet with microscopic tool like NMR are reviewed mainly. The new method to observe the quantum tunneling of magnetization discovered in Mnl2-ac with NMR is shown and the research results on the microscopic aspects of the macroscopic quantum tunneling of magnetization using the new method are shown. Also, the physical aspect of the level crossing effect which has been reported originally with NMR in molecular nanomagnet is reviewed with experiment results. The research results on the molecular nanomagnets will reveal the important information about the limit of the miniaturization of magnetic memory units and give us the basic scientific knowledge which is needed for the application for the quantum computation. Moreover, academically, many quantum mechanical theories which have not been checked the validity can be checked with experiments.

• Geophysics and Geophysical Exploration
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• v.13 no.1
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• pp.102-108
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• 2010

The internal structure of a river embankment must be delineated as part of investigations to evaluate its safety. Geophysical methods can be most effective means for that purpose, if they are used together with geotechnical methods such as the cone penetration test (CPT) and drilling. Since the dyke body and subsoil in general consist of material with a wide range of grain size, the properties and stratification of the soil must be accurately estimated to predict the mechanical stability and water infiltration in the river embankment. The strength and water content of the levee soil are also parameters required for such prediction. These parameters are usually estimated from CPT data, drilled core samples and laboratory tests. In this study we attempt to utilise geophysical data to estimate these parameters more effectively for very long river embankments. S-wave velocity and resistivity of the levee soils obtained with geophysical surveys are used to classify the soils. The classification is based on a physical soil model, called the unconsolidated sand model. Using this model, a soil profile along the river embankment is constructed from S-wave velocity and resistivity profiles. The soil profile thus obtained has been verified by geotechnical logs, which proves its usefulness for investigation of a river embankment.

• Journal of the Korea Institute of Building Construction
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• v.14 no.4
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• pp.308-313
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• 2014

Recently, for longevity of resident building, the main trend is that the change of the inside space organization of resident building from wall construction to rhamen construction, which resulted in increase in use of lightweight composite panel. Thus, in this study, authors analyzed the engineering property of oxide of magnesium depending on the magnesium chloride addition ratio. The results of this research is expected to contribute on providing a fundamental material for the surface materials of lightweight composite panel. As the result of the experiment, as fluidity increased, air content decreased and initial set and final set as the magnesium chloride addition ratio increase. In the aspect of flexural strength and compressive strength, the test specimen showed the highest strength at 40% of the magnesium chloride addition ratio. At 20% of the magnesium chloride addition ratio, the test specimen showed the lowest water absorption rate. As the magnesium chloride addition ratio increases, the expansibility tends to increase as well in the aspect of shrinkage strain. After observing microstructure, we can see hydration products in the form of needle. It appeared high flexural strength because the hydration products have mineral fibrous tissue shape, which also contribute to the cause of the expansibility.

• Journal of the Ergonomics Society of Korea
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• v.33 no.4
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• pp.281-287
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• 2014

Objective: The objective of the study is to develop a portable assistance device to help elderly users reduce strain on the knee and leg muscle while the elderly are standing up. Background: The pose of standing up from a chair is a basic movement, but the elderly often have difficulty standing up due to their weak muscles. We focus on designing a solution that helps the elderly reduce physical problems and support them standing up. Method: This study consists of three parts. Part I explores the way to reduce the refrain of leg muscle while standing up from a chair. In the process of structural development, we found that the moment is minimized when user pushes down the armrests due to a decrease in the force acting on the center of mass. In part II, a user test of 20 participants was carried out to rank the order of comfort of two stimuli: the chair with fixed armrests and the chair with the four-link mechanism that we created-in three different ways; (1) to stand up without touching armrests, (2) to stand up by pushing down on fixed armrests, and (3) to stand up by pushing down on armrests and being supported by the mechanism. To examine the statistically significant differences among the rank means, a Friedman test was conducted. In part III, we analyze the results of the user test and interview feedbacks, focusing on establishing a design strategy from UPO and visualizing it in 1:1 scale. Results: In part I, we decided to develop the four-link mechanism. The bottom is lifted up as the link rises. In part II, based on the rank data, we empirically found that UPO was assessed as the most comfortable during the stimuli. The thigh angle is smaller and the bottom of UPO is separated from a seat. In part III, after assessing the results and feedbacks, we created a visualization strategy for UPO: light, friendly, and novel. Conclusion: The portable and non-mechanical UPO comprises a four-link system that lifts the user's hips while standing. It can help users avoid knee and leg muscle strain. Its universal design considers the elderly's difficulties. Application: In a future study, combining light and durable material in UPO is expected to increase its usability. And this study is an opportunity to design various types of standing assistance devices.

• Journal of Korean Society of Forest Science
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• v.46 no.1
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• pp.1-9
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• 1980

This study was carried out to examine the substitution possibility into fiber pot instead of Jiffy pot for the good transplanting. Fiber pot was made of fiber, wood waste particle, and bark powder (10% of the particle weight) and also latex was added into the furnish as a binder. The pots were sprayed with just enough urea solution to prevent nitrogen deficiency of pot media coming from the breakdown of wood fiber in the pot wan during the plant growing. The utility of fiber pot was compared with that of Jiffy pot in the service test of two tree species under a green-house condition. The results obtained can be summarized as follows ; 1. Fiber pot made of 30% wood fiber+70% particle including 10% of bark powder, and 3%-latex has shown a good results like that of Jiffy pot in the sp. gr., tear factor and burst factor. For water absorption, fiber pot made of 50% fiber+50% particle, and 3%-latex got the best result. In the consideration of the above physical and mechanical properties of the fiber pot for good root penetration through the pot wall and facile handling, fiber pot made of 30% fiber+70% particle, and 3%-latex may be seemed to be good. 2. There were no harms in sapling growth in fiber pot as well as in Jiffy pot. The root penetration ability through the fiber pot was slightly inferior to that of Jiffy pot, and yet the pot damage through transportation seemed to be slighter in fiber pot than in Jiffy pot.

• Journal of the Korean Wood Science and Technology
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• v.40 no.3
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• pp.177-185
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• 2012

The interest to develop adhesives from renewable resources is growing to substitute petroleum-based adhesive resins in the manufacture of wood based panels. In our study, rapeseed flour (RSF), which is the by-product of bio-diesel produced from rapeseed, were hydrolyzed with acid and alkali. As a crosslinking agents of the RSF hydrolyzates, phenol-formaldehyde prepolymers (PF) were prepared. The RSF hydrolyzates and PF were mixed to complete the formulation of RSF-based adhesive resins, and the resins were applied to make the medium density fiberboard (MDF). The physical and mechanical properties of the MDF were measured to examine whether RSF can be used as raw materials of adhesive resins for the manufacture of MDF or not. The average moisture content and density of the MDF made with RSF-based adhesive resins satisfied the minimum requirement of KS standard, but the thickness swelling was not. The bending strengths of the MDF made with RSF-based adhesive resins were lower than that of the MDF made with commercial UF resins, but the internal bonding strengths of tested MDF in some make-up conditions of RSF-based adhesive resins were higher than that of MDF made with commercial UF resins. These results showed the potential of RSF as a raw material of adhesives for the production of MDF. Future works on the optimal manufacturing process conditions of MDF made with RSF-based adhesive resins are required to improve the performance of MDF made with RSF-based resins.

• Korean journal of applied entomology
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• v.15 no.3 s.28
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• pp.137-145
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• 1976

Orchids have been propagated vegetatively for a long time without adequate control measures against virus diseases in Korea. As a result, it is presumed that most of the orchid varieties in Korea may have been degenerated. Nevertheless there has been little work on the virus diseases of orchids in Korea. Therefore studies were initiated to isolate an4 characterize the orchid viruses occurring in Korea. The results obtained are summerized as follows. 1. Symptoms of virus diseases on orchid varieties can be grouped 1) mosaic, 2) necrotic streak with mosaic, 3) ring necrosis, 4) chlorotkc ring and 5) necrotic spot. 2. A total of 102 orchid plants representing 4 genera were investigated on the occurrence of Cymbidium mosaic virus and tobacco mosaic virus by serological agar-gel double diffusion test. The test revealed that approximately $45\%$ of the orchids were infected with Cymbidium mosaic virus. None of the plants were found to be infected with tobacco mosaic virus. 3. Local lesions appeared on the inoculated leaves of Chenopodium amaranticolor Cassia occidentalis and Datura stramonium 7-12 days after mechanical inoculation with Cymbidium mosaic virus. 4. Physical properties of the Cymbidium mosaic virus determined by inoculation on Chenopodium amaranticolor were as follows: Thermal inactivation Point; $75-80^{\circ}C$, dilution end Point; $10^{-5}-10^{-6}\%$ aging in vitro; 8 days. 5. Three different buffers at pH 7.0 and pH 9.0 were compared for the efficiency of agar-gel double diffusion test with Cymbidium mosaic virus. Phosphate, imidazol and tris buffer at pH 7.0 gave equally satisfactory results. 6. Electron microscopic examination of the Cymbidium mosaic virus revealed rod shaped particles measuring 460-580mu.