• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.4
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• pp.653-659
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• 2017

In this study, the complex forging process of an outer support ring was developed and the prototype was manufactured. The current process, hot forging and MCT machining, has a disadvantage of excessive material removal rates and longer machining hours. To overcome this disadvantage, a general shape is given through hot forging and the precision is achieved through cold forging. The complex forging process was developed with the minimal machining process. Forging analysis was carried out to design a forging process using the commercial program, Deform-3D. The hot and cold forging processes were set up based on the analyzed result. The mold and prototype were manufactured. Hardness, surface roughness, internal defect, the grain low line of the prototype were evaluated. The results showed no particular problems, and there were no problems in mass production. Using complex forging, the material was reduced by approximately 27 % compared to the process using hot forging and MCT machining. In addition, the production speed was improved 2.15 fold compared to that of hot forging and MCT machining. Through this study, a cost-effective process and mold design technology were established, which is expected to have positive effects on other related automotive parts production.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.10
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• pp.140-148
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• 2019

Large cast iron structures are used in casings and pipes in shipsand chemical plants. Broken parts in the casings and pipescan result in failures even when stresses are below the yield strength of the part's materials. Fatigue failure of a large cast iron structure is inevitable due to the design constraints and low reliability of the material strength. A small structure can be repaired by welding, but a large structure cannot because it cannot be preheated slowly and uniformly. This study shows that a large structure can be repaired by a cold joint method using a crack repair screw. Large cast iron structures were manufactured by GC 300, and their design stress is below 3.5 MPa. The tensile strength on notched specimens repaired by crack repair screws was 8.2 MPa. Therefore, the safety factors of structures repaired by crack repair screws have a value above 2.3 and are considered to be high values.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.5
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• pp.34-41
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• 2021

Sidewalks are facilities used for the safe and comfortable passage of pedestrians and are paved with blocks of various materials. Currently, Korea does not have a quantitative survey method for the pavement condition of sidewalks, so it is necessary to develop an efficient survey method. Drones are being used as an efficient survey tool in various fields, but there are limited studies in which sidewalks have been investigated. This study investigates the possibility of detection by limiting the missing sidewalk blocks using a drone. This study is an initial study on the development of a method for detecting damage in sidewalk blocks. For this, sidewalk blocks were artificially removed to simulate a dropout situation, and images were acquired with 0.7-cm resolution using a drone. As a characteristic of the point cloud data acquired through image pre-processing, there was high variance of the elevation of the points in the missing area of the sidewalk block. Using these characteristics, an experiment was conducted to detect the missing parts of the sidewalk block by applying four thresholds to the variance of the elevation of points included in the grid corresponding to the sidewalk area. As a result, the detection accuracy was shown with a positive detection ratio of 70-80%, omission errors of 20-30%, and commission errors lower than 2%. It is judged that the possibility of detecting missing sidewalk blocks is high. This study focused on detecting a simulated missing sidewalk block in a limited environment. Therefore, it is expected that an efficient and quantitative method of detecting damaged sidewalk blocks can be developed in the future through additional research with considerations of the actual environment.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.8
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• pp.264-270
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• 2019

The purpose of this study is to examine the change of study crafting and nursing recognition after applying a documentary form of education to nursing students, and also to confirm the nursing students' satisfaction with the documentary style of education. The subjects of the study were 84 nursing students in their first year in the B area. The data collection period ran from March 11, 2019 to April 15, 2019. The collected data was analyzed using frequencies, percentages, means, standard deviations and paired t-test by employing the SPSS WIN 24.0 computer program. The program consisted of four parts and was operated for 3 hours and 30 minutes, and three domestic documentaries were applied. The study crafting of nursing students increased after the education but there was no statistical significance for this. The nursing recognition was significant (t=-4.49, p<.001) In detail, traditional image, social image and nursing prospect were significant (t=-2.13, p=.036; t=-5.09, p<.001; t=-4.17, p=<.001). Satisfaction with the use of documentaries averaged 4.54 points, as detailed items, the satisfaction with the learning method was 4.54, the satisfaction with the contents of the education was 4.62 points, the benefit was 4.56, the interest was 4.44 and the interest induction was 4.55 points. This study showed that documentaries could be used as a teaching and learning method because the documentaries had a positive effect on nursing students' recognition of nursing and satisfaction of education.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.8
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• pp.649-656
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• 2019

Flux cored arc welding (FCAW), which is used widely in many fields, such as shipyards, bridge structures, construction machinery, and plant industry, is an alternative to shielded metal arc welding (SMAW). FCAW is used largely in the welding of carbon and alloy steel because it can be welded in all poses and obtain excellent quality in the field under a range of working conditions. In this study, the mechanical properties of welded parts were analyzed after different welding of SS400 and SM490A using FCAW. The following conclusions were drawn. The tensile test results satisfied the KS standard tensile strength in the range of 400~510 N/mm2 in all welding positions. The bending test confirmed that most of the specimens did not show surface breakage or other defects during bending and exhibited sufficient toughness, even after plastic deformation. The hardness test results were lower than the standard value of 350 Hv of KS B 0893. Similar to the hardness test, were greater than the KS reference value. The macro test revealed no internal flaws, non-metallic inclusions, bubbles or impurities on the entire cross section of the weld, and there were no concerns regarding lamination.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.1
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• pp.179-183
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• 2019

The system stability must be ensured from the switching noise due to the power conversion efficiency and power conversion system miniaturization. Therefore, countermeasures to reduce switching noise during power conversion are essential. Thus, in the previous paper, we constructed the DC / DC Buck Converter circuit using MPQ4432 driver of MPS, and simulated the switching noise characteristics which occurs when the components are arranged differently in the 4 - layer PCB circuit structure with reference plane. In this paper, two different simulated circuits are fabricated and the characteristics of the conducted emission and the radiated emission are analyzed in the same way as the simulation. As a result, it was confirmed that the Conducted Emission characteristic was reduced by 2 ~ 9dB in the low frequency band and 6 ~ 7dB in the high frequency band depending on the configuration of the current return path. And the radiated emission characteristic is reduced by 9 dB. Conducted emission simulation results show that 6 ~ 7dB in the low frequency range and 2 ~ 9dB in the measurement result are somewhat different. In the high frequency band, it is confirmed that the experimental and simulation results are about 7dB. And Radiated Emission confirmed 12dB decrease in simulation, but confirmed decrease of 9dB in measurement result. It is confirmed that there is a slight difference in the amount of reduction, but the design of the power conversion circuit improves the noise characteristics according to the configuration of the current return path.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.12
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• pp.541-551
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• 2018

This paper is on the colonial history of the African continent. It was the origin of mankind, which was called "Hometown of humanity" or "Warm region" since ancient Greece and ancient Egypt. However, the place came to be the invasion target of Western powers. Western nations, based on strong military and economic power, slaughtered sturdy African men and stripped off major resources for their own interests, devastating many parts of the African continent since the 15th century. This unfortunate history seems to have met a happy ending in the mid-twentieth century, after the independence of many African nations that have been committed to national self-determination since World War II. However, African countries have not been recognized as equal partners in the international arena. They were only poor and powerless countries that could be maintained only through the aid of advanced nations like France, as before. Of course, in the 21st century, Africa has begun to be thought to be a new market with high potentiality for development. Various countries, including India, China, Russia and Brazil, as well as major European countries, which have traditionally maintained friendly relations with France, are making efforts to increase their influence in Africa. Therefore, to understand this new trend, it is necessary to give a top priority to grasp the colonial history surrounding African continent.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.5
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• pp.73-80
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• 2019

In this paper, the basic design of the electric hydraulic sliding deck system was developed to develop the electric hydraulic sliding deck which can easily upgrade the loading and unloading of the agricultural machinery by modifying the load of the existing 5ton cargo truck. Through the kinematic analysis, The length and structure of the specimens were designed and the materials were selected for safety and economical efficiency through structural analysis. For the basic design of the sliding deck system, we surveyed the agricultural machinery to be transported and selected necessary elements. And have devised a system using a hydraulic cylinder that can meet selected factors. Through the simplified modeling and kinematic diagram, the operating structure of the sliding deck system was grasped and the minimum length and structure of the sliding deck were devised, In order to select the sliding deck material satisfying, four representative materials used in the automobile structure were selected. Selected the parts to be analyzed and compared the stresses and deformation amounts according to the material under the conditions of maximum load through simplified modeling. As a result, SS41P material was used to reduce the unit cost and to achieve safety. The winch system was designed and applied for moving up and down of the farm machinery which can not be operated.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.7
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• pp.310-316
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• 2019

In automotive application, customers are demanding high efficiency and various functions for convenience. The demand for these automotive applications is steadily increasing. In this study, it has been studied the analysis of heat flow to improve the PCB(printed circuit board) heating performance of WPC (wireless power charger) recently developed for convenience. The charging performance of the wireless charger has been reduced due to power dissipation and thermal resistance of PCB. Therefore, it has been proposed optimal PCB design, layout and position of electronic parts through the simulation of heat flow analysis and PCB design was analyzed and decided at each design stage. Then, the experimental test is performed to verify the consistency of the analysis results under actual environmental conditions. In this paper, The PCB modeling and heat flow simulation in transient response were performed using HyperLynx Thermal and FloTHERM. In addition, the measurement was performed using infrared thermal imaging camera and used to verify the analysis results. In the final comparison, the error between analysis and experiment was found to be less than 10 % and the heating performance of PCB was also improved.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.7
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• pp.353-362
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• 2019

Thermodynamic analysis of cascade refrigeration systems has attracted considerable research attention. On the other hand, a system evaluation based on thermodynamic analyses of the individual parts, including the evaporator, condenser, intercooler, expansion valve, etc., has received less attention. In this study, performance analysis was conducted on a cascade refrigeration system, which has an individual cooling and refrigeration evaporator, and equips the intercooler and air-cooled condenser in a series in a lower cycle. The thermo-fluid design was then performed on the major components of the system - upper condenser, lower condenser, cooling evaporator, refrigeration evaporator, intercooler, compressor, electronic expansion valve - of 15 kW refrigeration, and 8 kW cooling capacity using R-410A. A series of simulations were conducted on the designed system. The change in outdoor temperature from 26 C to 38 C resulted in the cooling capacity of the lower evaporator remaining approximately the same, whereas it decreased by 9% at the upper evaporator and by 63% at the intercooler. The COP decreased with increasing outdoor temperature. In addition, the COP of the cycle with the intercooler operation was higher that of the cycle without the intercooler operation. Furthermore, the increase in the upper condenser size by two fold increased the upper evaporator by 4%. On the other hand, the lower evaporator capacity remained the same. The COP of the upper cycle increased with increasing upper condenser size, whereas that of the lower cycle remained almost the same. When the size of the lower condenser was increased 2.8 fold, the intercooler capacity increased by 8%, whereas those of upper and the lower evaporator remained approximately the same. Furthermore, the COP of the lower cycle increased with an increase in the lower condenser. On the other hand, the change of the upper condenser was minimal.