• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.229.1-229.1
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• 2014

Tactile sensors have widely been researched in the areas of electronics, robotic system and medical tools for extending to the form of bio inspired devices that generate feeling of touch mimicking those of humans. Recent efforts in adapting the tactile sensor have included the use of novel materials with both scalability and high sensitivity [1]. Graphene, a 2-D allotrope of carbon, is a prospective candidate for sensor technology, having strong mechanical properties [2] and flexibility, including recovery from mechanical stress. In addition, its truly 2-D nature allows the formation of continuous films that are intrinsically useful for realizing sensing functions. However, very few investigations have been carrier out to investigate sensing characteristics as a device form with the graphene subjected to strain/stress and pressure effects. In this study, we present a sensor of vertical forces based on single-layer graphene, with a working range that corresponds to the pressure of a gentle touch that can be perceived by humans. In spite of the low gauge factor that arises from the intrinsic electromechanical character of single-layer graphene, we achieve a resistance variation of about 30% in response to an applied vertical pressure of 5 kPa by introducing a pressure-amplifying structure in the sensor. In addition, we demonstrate a method to enhance the sensitivity of the sensor by applying resistive single-layer graphene.

• Journal of Chest Surgery
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• v.22 no.6
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• pp.927-935
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• 1989

Using an isolated Rat heart preparation of the Sprague Dawley strain, the YUMC cardioplegic solution k the St. Thomas Hospital Cardioplegic Solution were compared in the non waking K working heart perfusion systems by evaluating the hemodynamics, [bio] chemical, and light microscopic finding The heart rate k coronary flow of the two groups in the 20 minutes post ischemic recovery time were 288.6*6.5 vs 283.7*12 and 21.3*1.0 vs 19.0*1.7 respectively with no statistical significance existing. However the aortic systolic pressure, aortic overflow, cardiac output which were 81.7[4.2 vs 78.4*1.8, 18.3*1.1 vs 13.0*2.5 and 36.9*0.9 vs 32.0*3.2 respectively with P < 0.01 indicate that the comparison of these three parameters is statistically meaningful. The amount of CPK extracted in the 20 minutes post 120 minutes of ischemia was compared for the two cardioplegic solution, the results of which turned out to be similar, light microscopic findings were also found to be similar. It is thought that the YUMC cardioplegic solution provided better results than the St. Thomas hospital solution because of the differing composition of the two solution such as glucose, mannitol, albumin were put only in the former solution enhancing osmolarity of the cardioplegic solution providing better hemodynamic results.

• Journal of Welding and Joining
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• v.2 no.1
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• pp.49-57
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• 1984

The influence of weld defect, residual stress and microstructure on the Low Cycle Fatigue(L. C. F.) behaviour of AISI 304L austenitic stainless steel weldment has been studied. The specimens were welded by shielded metal are welding process, post weld heat treated(PWHT) at 900.deg.C for 1.5hrs, and tested under total strain controlled condition at room temperature. The results of the experiment showed that weld defect affected the L.C.F. behaviour of weldment deleteriously compared to the residual stress or microstructure, and it reduced the L.C.F. life about 70-80%. The PWHT exhibited beneficial effect on the L.C.F. behaviour and increased the L.C.F. life about 120%. This enhancement by PWHT was attributed to the removal of residual stress and recovery of weld metal ductility. The cyclic stress flow of as welded specimens showed intermediate cyclic softening, whereas those of heat treated specimens showed continuous cyclic hardening, and this difference was explained in terms of the residual stress removal and dislocation behaviour. Scanning electron microscopy studies of fatigue fracture surface showed that weld defects of large size and near weld surface were detrimental to the L.C.F. behaviour of weldment.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.3
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• pp.29-34
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• 2007

Numerical analyses are carried out to evaluate the cumulative impact damage of an automotive front end bumper under the low speed crash events(CMVSS215) by using explicit code. Results of first impact simulation, which are deformed shape, thickness, stress tensors and strain tensors, are used as the initial conditions for a next impact simulation. Between the events, the residual vibration is damped out by using nodal damping, and then recovery after each event is evaluated by several methods, one of which is a springback analysis with implicite finite element analysis code. The coupled analysis scheme for the evaluation of cumulative impact damage is verified through the comparison with test results.

• The Journal of Korean Medicine Ophthalmology and Otolaryngology and Dermatology
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• v.30 no.3
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• pp.211-219
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• 2017

Objectives : The purpose of this study is to report the effect of traditional Korean medical treatment and auricular acupuncture on the patient suffered from epiphora. Methods : One patient suffering from epiphora was treated with traditional Korean medical treatment including auricular acupuncture. HRQL(Health-related quality of life) and VAS(Visual Analogue Scale) were measured and compared to evaluate its treatment effectiveness. Results : We attained results which show recovery from watery eye, pain, eye strain in symptoms and improvement on quality of life. Conclusions : In this study, traditional Korean medical treatment can be effective in obtunding symtoms and improving quaility of life for patients suffering from epiphora.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.05a
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• pp.211-212
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• 2019

It is possible to realize the concept of long-life housing by utilizing the wall piping infill system. However, when using the wall piping infill system, there is no detailed standard in Korea. Problems may occur in actual use. In this study, we use the results obtained from the performance test method as a basic data. Since the load resistance test of the toilet is not available in Korea, GB 6952 (Sanitary wares) of China is applied. According to the experiment of load resistance of the toilet in this study, the strain recovery ability was good. However, it is not possible to exclude the possibility of permanent deformation of the toilet seat due to long - term repeated loading. Therefore, it is necessary to consider the stiffness enhancement of the wall (steel frame) to the fixing part when installing the toilet in the wall pipe infill system.

• Elastomers and Composites
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• v.55 no.2
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• pp.108-113
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• 2020

Wear particles of the model tread compounds for bus and truck tires were made using a laboratory abrasion tester and characterized based on their size distributions, shapes, and crosslink densities. The influence of the carbon black contents and rubber compositions (NR= 100 and NR/BR= 80/20) on the production of wear particles was investigated. The wear particles were separated according to size using a sieve shaker. The shape properties of the wear particles were analyzed using an image analyzer and scanning electron microscopy (SEM). Their shapes were observed as tiny stick cookies or sausages with bumpy surfaces. The particle size distribution tended to be smaller with increasing carbon black content. Moreover, the particle size distributions of the NR = 100 samples were larger than that of the NR/BR blend samples. There were different filaments in the wear particles. The filament diameters tended to be thinner with increasing carbon black content. The crosslink density increased with increasing carbon black content, and the crosslink densities of the NR= 100 samples were lower than those of the NR/BR blend ones. The particle size distribution tended to be smaller with increasing crosslink density. Based on the experimental results, the wear particles can be produced by detaching debris from the main body through repetitive strain and recovery.

• YAKHAK HOEJI
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• v.32 no.5
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• pp.343-350
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• 1988

Recent hypothesis suggested that intracellular accumulation of calcium is a common denominator of ischemic celullar damage. Flunarizine, a calcium entry blocker, posses vasodilating properties in cerebral vascular beds and clinically used in circulatory disorders. The present study was designed to evaluate the effect of flunarizine on ischemic and hypoxic brain damage. An ischemic model was made by bilateral carotid artery ligation (BCAL) in Wistar strain rat. Hypoxic model was made by intravenous injection(i.v.) of KCN to rats and mice. In mice, flunarizine not only reduced the mortality of KCN, but also delayed the onset time of convulsion. The contents of ATP, creatine phosphate and glucose, cerebral energy metabolite, decreased 30 minutes after BCAL and KCN i, v, while that of lactate increased. But these variations were suppressed by flunarizine. Furthermore, increase in the dosage of flunarizne generally promoted the recovery of cerebral energy metabolites in hypoxic animals. The results suggest that flunarizine had a protective effect against ischemic and hypoxic brain damage due to its ameliorating action on the cerebral energy metabolism.

• Journal of Microbiology
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• v.45 no.3
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• pp.241-245
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• 2007

This study was conducted to determine the optimal conditions for introduction of exogenous DNA into Synechocystis sp. PCC 6803. Of the three transformation techniques studied, electroporation, ultrasonic transformation and natural transformation, natural transformation showed the highest efficiency. Additionally, this study demonstrated that the higher plasmid concentration and longer homologous recombining fragments resulted in a greater number of transformants. For successful transformation, the lowest concentration of plasmid was $0.02\;{\mu}g/ml$, and the shortest homologous recombining fragment was 0.2 kb. Use of Synechocystis sp. PCC 6803 in the logarithmic growth phase resulted in two-fold higher transformation rate than that of the same organism when cells in the latent phase or the plateau phase were used for transformation. Pretreatment of the host strain, Synechocystis sp. PCC 6803, with EDTA (2 mM) for two days prior to transformation increased the transformation efficiency by 23%. Additionally, incubation of the cells and DNA for 5 h under light conditions increased the transformation efficiency by two orders of magnitude. Moreover, recovery treatment of the cells before they were plated onto antibiotic medium also increased the transformation efficiency.

• Journal of the Korean Society of Industry Convergence
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• v.23 no.4_2
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• pp.693-699
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• 2020

355nm UV pulse laser is irradiated on the surface of polyimide (PI) by LDW (Laser Direct Writing) method to produce a high sensitivity flexible humidity sensor using a simple one-step process. The LDW method continuously investigates 2-D CAD data using a galvano scanner and an F-lens. This method is non-contact, so it minimizes physical strain on the PI. Laser-induced graphene (LIG) produced by lasers has a high surface area due to its high flexibility and numerous pores and oxidizers compared to conductors. For this reason, it is highly useful as a flexible humidity sensor. The humidity sensor produced in this study was attached to the inside of a mask filter, which has become a hot topic recently, and its applicability was confirmed.The measurement of humidity measured the sensitivity, reactivity, stability and recovery behavior of the sensor by measuring changes in capacitance and resistance.