• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.8
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• pp.133-138
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• 2019

This study evaluated the tensile properties of SAPH440, a hot-rolled steel for automotive structural applications, based on GMAW lap welding, the welding current, the welding voltage, and the feed rate. Tensile tests were performed according to the joint parameters of the GMAW process, for which specimens were fabricated according to KS B ISO 9018 by lap welding. The bead appearance was observed in each condition, and the weldability was evaluated by the tensile test. Higher the welding current resulted in a deeper weld, but the tensile strength was not significantly different from when the parameter was fixed due to the fracture of the base material. When the current was higher than the voltage, as in the case of a welding current of 200 A and welding voltage of 17 V, a large amount of spatter is generated, the welding is unstable, and the welded part breaks. Higher the voltage resulted in the bead not causing defects in general, and it also affected the weldability. If the current and voltage were too low, the welding was not performed normally, and the tensile strength could not be measured. However, as the current increased, the increase of the voltage and the feed rate did not affect the tensile strength.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.4
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• pp.606-612
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• 2019

The main causes of subsidence and sinkholes in the lower part of urban roads are sewage line foundation and inadequate compaction of backfill material. This leads to many problems, such as the breakage of joints in sewer pipes, poor connection, pipe breakage, and cracks. To solve this problem, the support factor related to the sewer foundation and the safety factor according to the excavation depth were evaluated. For the foundation of rigidity tolerance, crushed stone foundation, and abandoned concrete foundation, a recently newly developed site assembly-type lightweight plastic foundation were used. Backfill materials were applied on site (sandy soil and clayey soil) and fluid backfill was recycled onsite. To evaluate the depth of excavation and the safety factor of each sewer pipe foundation, the design load considering the load factor and the support factor was evaluated. The support coefficients were 0.377 for a crushed stone foundation, 0.243 and 0.220 for an abandoned concrete foundation ($180^{\circ}$ and $120^{\circ}$), and 0.231 for a lightweight plastic foundation and fluid backfill. Overall, the safety factor was low when using the crushed stone foundation, and the safety rate was the highest when the foreclosed concrete foundation ($180^{\circ}$) was used. In addition, when the combination of lightweight plastic and fluid backfill materials was used, the safety factor was higher than that of abandoned concrete foundation ($120^{\circ}$), which means that the newly developed lightweight plastic foundation can be used as another alternative base of a steel pipe.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.4
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• pp.489-496
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• 2019

This paper is a study on the evaluation of loss factor of damping treatment materials to reduce the noise and vibration for panels of railway vehicles and automobiles. In order to determine the modal parameters of damping materials, beam excitation tests were carried out using different type PVC coated aluminum and steel base beam specimens. The specimens were excited from 10 Hz to 1000 Hz frequency range using sinusoidal force, and transfer mobility data were measured by using an accelerometer. The loss factors were determined by using integrated program, based on theories of Half Power Method, Minimum Tangent Error Method, Minimum Angle Error Method and Phase Change Method, which enable to evaluate the parameters using modal circle fit and least squares error method. In the case of lower loss factor and data of linear characteristics, any method could be applied for evaluation of parameters, however the case of higher loss factor or data including non-linear characteristics, the minimum angle error method could reduce the loss factor evaluation. The obtained dynamic properties of the coating material could be used for application of Finite Element Method analyzing the noise control effects of complex structures such as carbody or under-floor boxes of rolling stock. The damping material will be very useful to control the structural noise, because the obtained modal loss factors of each mode show very good effect on over $2^{nd}$ mode frequency range.

• Computers and Concrete
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• v.33 no.5
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• pp.497-507
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• 2024

In squat reinforced concrete walls, the displacement capacity for lateral deformation is low and the ability to resist the axial load can quickly be lost, generating collapse. This work consists of testing two squat reinforced concrete walls. One of the specimens is built with conventional detailing of reinforced concrete walls, while the second specimen is built applying an alternative design, including stirrups along the diagonal of the wall to improve its ductility. This solution differs from the detailing of beams or coupling elements that suggest building elements equivalent to columns located diagonally in the element. The dimensions of both specimens correspond to a wall with a low aspect ratio (1:1), where the height and length of the specimen are 1.4 m, with a thickness of 120 mm. The alternative wall included stirrups placed diagonally covering approximately 25% of the diagonal strut of the wall with alternative detailing. The walls were tested under a constant axial load of 0.1f'cAg and a cyclic lateral displacement was applied in the upper part of the wall. The results indicate that the lateral strength is almost identical between both specimens. On the other hand, the lateral displacement capacity increased by 25% with the alternative detailing, but it was also able to maintain the 3 complete hysteretic cycles up to a drift of 2.5%, reaching longitudinal reinforcement fracture, while the base specimen only reached the first cycle of 2% with rapid degradation due to failure of the diagonal compression strut. The alternative design also allows 46% more energy dissipation than the conventional design. A model was used to capture the global response, correctly representing the observed behavior. A parametric study with the model, varying the reinforcement amount and aspect ratio, was performed, indicating that the effectiveness of the alternative detailing can double de drift capacity for the case with a low aspect ratio (1.1) and a large longitudinal steel amount (1% in the web, 5% in the boundary), which decreases with lower amounts of longitudinal reinforcement and with the increment of aspect ratio, indicating that the alternative detailing approach is reasonable for walls with an aspect ratio up to 2, especially if the amount of longitudinal reinforcement is high.

• Journal of the Korean GEO-environmental Society
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• v.23 no.9
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• pp.33-40
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• 2022

Sedimentation and pH neutralization has been investigated as preteatment of acid contaminate water. The settling and neutralizing process derive more effective degradation efficiency as the pre-treatment process before the removal process of adsorption, volatile, biodegradation, or oxidation. Settling velocity, uniformity coefficient, coefficient of curvature, and grain size index can define in the sedimentation process for characteristics of the soil. The stainless steel sieve has been used to separate each particle size of the dry soil by assembling in order of 4, 10, 20, 40, 80, 100, and 200 mesh sizes. The soil from Gamcheon Port in Busan drops upper side of the sieve and shakes back and forth to separate each different size of the particle. The 1L of Imhoff cone and 200 mL of the mass cylinder were used as settling tanks to calculate settling velocity. Stokes' equation was used to figure out the average density of dry soil with a value from settling velocity. In the results, the average particle density and lowest settling velocity were 1.93 g/cm³ and 0.11 cm/s, respectively. These values can detect the range of settling points of sediment to prevent chemical accidents. In pH neutralization, the initial pH of 2, 3, 4, and 5 of nitric acid and sulfuric acid are used as an acid solution; 0.1, 0.01, and 0.001 M of sodium hydroxide and calcium hydroxide are used as a base solution. The main goal of this experiment is to figure out the volume percentage of the acid solution becomes pH 7. The concentration of 0.001 M of base solution exceeds all the conditions, 0.01 M exceeds partially, and 0.1 M does not exceed 5 v/v% except pH 2. Calcium hydroxide present less volume than sodium hydroxide at pH neutralization both sulfuric and nitric acid.

• The Journal of Korean Academy of Prosthodontics
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• v.43 no.2
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• pp.232-247
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• 2005

Purpose. The purposes of this investigation were to discover the possibility of clinical application in the areas of dental implants and bone grafts by investigating the bone formation histologically around specimen which was depending on the intensity of magnetic field of neodymium magnet inside of the specimens. Material and method. 1. Measurement of magnetic intensity - placed the magnet inside of the specimen, and measured the intensity of magnetic field around the 1st thread and 3rd thread of specimen 20 times by using a Gaussmeter(Kanetec Co., Japan). 2. Surgical Procedure - Male rabbit was anesthetised by constant amount of Ketamine (0.25ml/kg) and Rompun (0.25ml/kg). After incising the flat part of tibia, and planted the specimens of titanium implant, control group was stitched without magnet, while experimental groups were placed a magnedisc 500(Aichi Steel Co., Japan) or magnedisc 800(Aichi Steel Co., Japan) into it, fixed by pattern resin and stitched. 3. Management after the surgery - In order to prevent it from the infection of bacteria and for antiinflammation, Gentamycin and Ketopro were injected during 1 week from operation day, and dressed with potadine. 4. Preparation of histomorphometric analysis - At 2, 4 and 8 weeks after the surgery, the animals were sacrificed by excessed Ketamine, and then, specimens were obtained including the operated part and some parts of tibia, and fixed it to 10% of PBS buffer solution. After embedding specimens in Technovit 1200 and B.P solution, made a H-E stain. Samples width was 75$\mu$m . In histological findings through the optical microscope and using Kappa image base program(Olympus Co. Japan), the bone contact ratio and bone area ratio of each parts of specimens were measured and analyzed. 5. Statistical analysis - Statistical analysis was accomplished with Mann Whitney U-test. Results and conclusion. 1. In histomorphometric findings, increased new bone formation was shown in both control & experimental groups through the experiment performed for 2, 4 & 8 weeks. After 4 weeks, more osteoblasts and osteoclasts with significant bone remodeling were shown in experimental groups. 2. In histomorphometric analysis, the bone contact ratios were 38.5% for experimental group 1, 29.5% for experimental group 2 and 11.9% for control group. Experimental groups were higher than control group(p<0.05) (Fig. 6, Table IV). The bone area ratios were 60.9% for experimental group 2, 46.4% for experimental group 1 and 36.0% for control group. There was no significantly statistical difference between experimental groups and control group(p<0.05) (Fig. 8, Table VII) 3. In comparision of the bone contact ratios at each measurement sites according to magnetic intensity, experimental group 2(5.6mT) was higher than control group at the 1st thread (p<0.05) and experimental group 1 (1.8mT) was higher than control group at the 3rd thread(p<0.05) (Fig. 7, Table V, VI). 4. In comparision of the bone area ratios at each measurement sites according to magnetic intensity, experimental group 2(5.6mT) was higher than control group and experimental group 1 (4.0mT) at the 1st thread(p<0.1) and experimental group 2(4.4mT) was higher than experimental group 1 (1.8mT) at the 3rd thread(p<0.1) (Fig. 9, Table IX, X). Experiment group 2 was largest, followed by experiment group l and control group at the 3rd thread of implant. There was a significant difference at the 1st thread of control group & experiment group 2, and at 1st thread & 3rd thread of experiment group 1 & 2, and not at control group experiment group 1.(p<0.1)

• The korean journal of orthodontics
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• v.28 no.1 s.66
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• pp.43-49
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• 1998

The aim of this study were to measure and compare the stress level on three type brackets and each other material (stainless steel, ceramic) with tipping and torquing forces by using the finite element analysis and to design biomechanically favorable brackets. For this study, three kinds of brackets were selected(A:Transcend-RMO, B:Signature-Unitek, C:PAW: plain archwire appliance-applied for a patent in Yonsei Udiversity). The slot size of bracket was 0.022inch and the size of archwire was 0.0175x0.025inch and taper shaped archwire was used in PAW. Loading force in tipping was 4.27N and torquing force was 32.858N applied by archwire torsion with 19.7degree and 11.3 degree in C type bracket. The conclusions were that (1) The finite element method proved to be a useful tool in the stress analysis of orthodontic bracket subjected to various forces. (2) With tipping, the stresses were concentrated at the gingival wall of the wire slot where it meets the mesial bracket surface and the incisal wall of the wire slot where it meets the distal bracket surface and with torquing, the stresses were concentrated at the junction of the gingival or incisal wall and base of the slot. (3) The maximum stress value was higher in torquing force than tipping force and therefore it is desirable to design on the basis of torquing force. (4) It was considered that the change in material might be affect on the diminish of stress value in the place of stess concentration. (5) The maximum stress value was highest on PAW bracket when the tipping and torquing force was applied and therefore it would be desirable to use mechanically favorable material on PAW bracket.

• The Journal of Korean Academy of Prosthodontics
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• v.52 no.3
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• pp.177-185
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• 2014

Purpose: This study is designed to investigate the various impacts of different types of scaler tips such as cooper alloy base tip and the others on the surface roughness of teeth and implant by the method which is currently in clinical use. Materials and methods: Four different types of disc shaped porcelain, titanium, zirconia, and Type III gold alloy dental materials sized 15 mm diameter, 1.5 mm thickness were used for the experiment. Plastic hand curette (Group PS), cooper alloy new tip (Group IS), and stainless steel tip (Group SS) were used as testing appliances. A total of 64 specimens were used for this study; Four specimens for each material and appliance group. Surface roughness was formed with 15 degree angle in ultrasonic scaler tip and with 45 degree angle in hand curette of instrument tip and the specimen surface with 5 mm long, one horizontal-reciprocating motion per second for 30 seconds by 40 g force. To survey the surface roughness of each specimen, a field emission scanning electron microscope, an atomic force microscope, and a surface profiler were used. (Ra, ${\mu}m$). Results: According to SEM, most increased surface roughness was observed in SS group while IS groups had minimal roughness change. Measurement by atomic force microscope presented that the surface roughness of SS group was significantly greater than those of PS, IS and control groups in the type III gold alloy group (P<.05). IS group showed lesser surface roughness changes compared to SS group in porcelain and gold alloy group (P<.05). According to surface profiler, surface roughness of SS group showed greater than those of PS, IS and control groups and IS group showed lesser than those of SS group in all specimen groups. Type III gold alloy group had large changes on surface roughness than those of porcelain, titanium, zirconia (P<.05). Conclusion: The result of this study showed that newly developed copper alloy scaler tip can cause minimal roughness impacts on the surface of implant and dental materials; therefore this may be a useful alternative for prophylaxis of implant and restored teeth.

• International Commerce and Information Review
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• v.15 no.4
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• pp.457-479
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• 2013

Through a Chinese rise, Chinese dream is actualizing as the world's great power. According to outlook of World Bank and IMF, Around 2030 China will be a great power bigger than America's economic power. The rise of China will give a huge impact to the whole world. China expands her influence through a global manufacturing base and a global market. To actualize 'Peaceful Rise' Strategy, China has many constraints. Chinese society is facing many difficult social problem due to side effects of a rapid development. Such as the spread of corruption, the severity of wealth gap, environmental degradation and energy shortage. Internationally there are containment from hegemon so-called 'China threat' dispute, Taiwan issue and territorial disputes. Western countries are hostile to China for two reasons. Based on expectations, one is China's socialist system and the other is the rising China which will compete for supremacy with Europe and America. Recent emergence of Chinese nationalism and the containment of the neighboring countries are also serious limiting factors. Domestically they have the rampant corruption in the bureaucracy, weakened capacity of Communist rule, wealth disparity due to the discriminatory economic development strategy, seriousness of rural problem, social instability, lack of social security systems and the development gap between the eastern coastal areas and western inland areas, ethnic minorities problems, the constraint of sustainable development issues due to lack of resources, environmental pollution and energy constraints. Like the former Soviet Union, China may face a dismantlement. After the rise, China may encounter possibilities of a war between great powers or a collapse of Chinese society caused by deepening internal conflict. Serious economic polarization would make peasants and urban workers, who are social vulnerable people, to turn their back to communist party and threaten the justification and the appropriateness of the ruling communist party. Chinese government will think internal system security threat is more formidable risk factor than a system security threat from the hegemon. The decline of great country comes from internal reasons rather than external reasons. To achieve peaceful rise, unification with Taiwan is an essential prerequisite. Taiwan issues are complex problems which equipped with international and domestic factors. Lack of energy resources, environmental pollution in China will bring economic crisis to Korean enterprises. Important influence to Korean economy will be a changeover of the method in economic development. It will turn the balance of investment and consumption, GDP-centered growth to consumption and environment-centered growth. Services industries including finance, environment, culture, education, health care and social welfare will grow. Change in China's growth model will give a great challenge upon the intermediate goods industry in Korea. Korea should reduce the portion of machinery, automotive, semiconductor, steel and chemical-centered export industry to China, and should increase the proportion of the service industry.

• Korean Journal of Heritage: History & Science
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• v.42 no.3
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• pp.4-24
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• 2009

This paper examined archaeological resources that discuss how Silla entered the Gangneung area, the coastal region along the East Sea that has been excavated most actively. Silla expanded its territories while organizing the its system as an ancient state and acquired several independent townships in various regions, stretching its forces to the East Sea area faster than any other ancient states of the time. In particular, many early relics and heritages of Silla have been found in Gangneung, the center of the East Sea area. Many archaeological resources prove these circumstances of that time and provide brief texts that are valuable for our interpretation of historical facts. In this respect, it was possible for me to examine these resources to answer my question as to why early relics and heritages of Silla are found in the Gangneung area. Based on my research on Silla's advancement into the Gangneung area, I have acquired the following results: How did Silla rule this area after conquering Yeguk in the Gangneung area? After conquering the Gangneung area, Silla attempted an indirect ruling at first. Later, Silla adopted a direct ruling system. I divided the indirect ruling period into two phases: introduction and settlement. In detail, Silla's earthenware and stone chamber tombs first appeared in Hasi-dong in the fourth quarter of the 4th Century and the tombs spread to Chodang-dong in the second quarter of the 5th Century. A belt with dragon pattern openwork, which seems to be from the second quarter of the 5th Century, was found to tell us that the Gangneung region began receiving rewards from Silla during this time. Thus, the period from the fourth quarter of the 4th Century to the second quarter of the 5th Century is designated as the 1st Phase (Introduction) of indirect ruling in terms of aechaeological findings. This is when Silla was first advanced to the Gangneung area and tolerated independent administration of the conquered. In the third and fourth quarters of the 5th Century, old mound tombs appeared and burials of relics that symbolized power emerged. In the third quarter of the 5th Century, stone chamber tombs were prevalent, but wooden chamber tombs, stone mounded wooden chamber tombs, and lateral entrance stone chamber tombs began to emerge. Also, tombs that were clustered in Hasi-dong and Chodang-dong began to scatter to Byeongsan-dong, Yeongjin-ri, and Bangnae-ri nearby. Steel pots were the symbol of power that emerged at this time. In the fourth quarter of the 5th Century, stone chamber tombs were still dominating, but wooden chamber tombs, stone mounded wooden chamber tombs, and lateral entrance stone chamber tombs became more popular. More crowns, crown ornaments, big daggers, and belts were bestowed by Silla, mostly in Chodang-dong and Byeongsan-dong. The period from the third quarter to the fourth quarter of the 5th Century was designated as the 2nd Phase (Settlement) of indirect ruling in terms of aechaeological findings. At this time, Silla bestowed items of power to the ruling class of the Gangneung area and gave equal power to the rulers of Chodang-dong and Byeongsan-dong to keep them restrained by each other. However, Silla converted the ruling system to direct ruling once it recognized the Gangneung area as the base of its expedition of conquest to the north. In the first quarter of the 6th Century, old mound tombs disappeared and small/medium-sized mounds appeared in the western inlands and the northern areas. In this period, the tunnel entrance stone chamber tombs were large enough for people to enter with doors. A cluster of several tunnel entrance stone chamber tombs was formed in Yeongjin-ri and Bangnae-ri at this time, probably with the influence of Silla's direct ruling. In the first quarter of the 6th Century, Silla dispatched officers from the central government to complete the local administration system and replaced the ruling class of Chodang-dong and Byeongsan-dong with that of Silla-friendly Yeonjin-ri and Bangnae-ri to reorganize the local administration system and gain full control of the Gangneung area.