• Transactions of Materials Processing
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• v.19 no.1
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• pp.50-58
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• 2010

In order to successfully implement hot die forging process for the large-size titanium alloy products, it is necessary to devise a customized heating method for the billets and the die tools, as well as the die tool design. This study aims at establishing a hot die forging process of the large-size titanium alloy container products by applying the warm die, semi-hot die and hot die forging process step-wise. To accomplish this purpose, forging mechanism and the die tools were designed considering the strength of die materials at the given die heating temperature. The movable heating devices for the billet and the die tools were also introduced to prevent overcooling of billet and die tools. To verify the applicability of the designed forging process, real-size forging tests were carried out and the quality of forged products, including dimension, surface condition, microstructure and the mechanical properties was evaluated.

• The Journal of the Korea institute of electronic communication sciences
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• v.17 no.5
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• pp.783-790
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• 2022

The development of SNS and video platforms provided an opportunity to explode the activation of content production and consumption. However, in the legacy system, due to the host-based location-oriented data transmission, there are inherent limitations in efficient operation and management. As an alternative to this, a Contents Centric Network (CCN) was studied. In this paper, when intermediate nodes located between the information provider and the information requester between the real-time streaming services in the CCN environment move or restrict their use, failure through monitoring of wireless reception strength to solve problems like disconnection of transmission quality at the information consumer. We propose a stable intermediate node management mechanism through active response before occurrence.

• KEPCO Journal on Electric Power and Energy
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• v.6 no.3
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• pp.305-313
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• 2020

The use of cable tunnels for electric power transmission as well as their construction in difficult conditions such as in subsea terrains and large overburden areas has increased. So, in order to efficiently operate the small diameter shield TBM (Tunnel Boring Machine), the estimation of advance rate and development of a design model is necessary. However, due to limited scope of survey and face mapping, it is very difficult to match the rock mass characteristics and TBM operational data in order to achieve their mutual relationships and to develop an advance rate model. Also, the working mechanism of previously utilized linear cutting machine is slightly different than the real excavation mechanism owing to the penetration of a number of disc cutters taking place at the same time in the rock mass in conjunction with rotation of the cutterhead. So, in order to suggest the advance rate and machine design models for small diameter TBMs, an EPB (Earth Pressure Balance) shield TBM having 3.54 m diameter cutterhead was manufactured and 19 cases of full-scale tunneling tests were performed each in 87.5 ㎥ volume of artificial rock mass. The relationships between advance rate and machine data were effectively analyzed by performing the tests in homogeneous rock mass with 70 MPa uniaxial compressive strength according to the TBM operational parameters such as thrust force and RPM of cutterhead. The utilization of the recorded penetration depth and torque values in the development of models is more accurate and realistic since they were derived through real excavation mechanism. The relationships between normal force on single disc cutter and penetration depth as well as between normal force and rolling force were suggested in this study. The prediction of advance rate and design of TBM can be performed in rock mass having 70 MPa strength using these relationships. An effort was made to improve the application of the developed model by applying the FPI (Field Penetration Index) concept which can overcome the limitation of 100% RQD (Rock Quality Designation) in artificial rock mass.

• Knowledge Management Research
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• v.23 no.4
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• pp.275-294
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• 2022

In recent years, with the continuous integrative development of e-commerce and social media, social commerce, as a trust-centered social transaction mode, has become an important performance form of e-commerce. The good experience of online community and abundant user-generated content (UGC) attract more and more users and businesses to participate in the community contribution. In this context, the cost of accessing information is continuously decreasing, which not only makes the purchase process more concise and efficient, but also greatly increases the possibility of consumers' impulsive consumption. However, there are very few empirical studies on the internal influencing mechanism of consumers' impulsive consumption based on the characteristics of UGC for social commerce. In view of this, based on S-O-R model, this study constructs a model of consumers' impulsive consumption in the context of social commerce from the characteristics of UGC, with perceived risk as the mediating variable and tie strength as the moderating variable. The results show that content authenticity, content usefulness, and content valence of UGC have significant negative impacts on consumers' risk perception in the process of purchase decision-making, and consumers' perceived risk has a significant negative impact on consumers' impulsive consumption. Meanwhile, the tie strength between UGC producer and UGC receiver plays a moderating role between content usefulness and perceived risk, as well as between perceived risk and impulsive consumption. Finally, combined with the above findings, this study provides effective suggestions for relevant participants in social commerce in terms of business management.

• Microbiology and Biotechnology Letters
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• v.40 no.3
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• pp.169-179
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• 2012

Microbiological calcium carbonate precipitation (MCCP) is being applied for the aesthetic restoration of cement buildings destroyed by biochemical processes and to block water penetration into the cement's inner structure. After determining the advantages of this technique, many related studies in the area of architecture concerning the application of microorganisms to improve construction material have been reported in both America and Europe. The techniques compatibility with cement material is especially interesting because of the needed screening of various calcium carbonate forming-bacteria and the required development of their application methods. The purpose of this review is to describe the mechanism of MCCP and related researches with eco-friendly construction materials. Mainly, we describe the methodological studies focused on biodeposition on the surface of building materials and the research trends concerning the addition of microorganisms to improve the durability of cement structures. Additionally, the concepts and technical aspects focused on the development of self-healing smart concrete, with the use of multi-functional bacteria, have been considered.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.6
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• pp.1073-1080
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• 2023

The development and speed improvement of the Internet network, and the development of many platforms based on it, have brought about a rapid expansion of production and consumption of various contents. However, the existing IP-based Internet system cannot efficiently cope with such an urgent increase in data. Accordingly, an alternative called the CCN(Contents Centric Network) has emerged, enabling more efficient data transmission and reception centered on content rather than host. In this paper, we will deal with the mobility of intermediate nodes in CCN real-time streaming service, which is one of the major research fields of CCN, and minimize network overload through more efficient path switching through RSSI detection. In other words, by improving the method of selecting and switching a spare path when an intermediate node located between the requester(consumer) and the provider moves, a mechanism for managing data transmission is not interrupted and unnecessary load due to route switching does not occur in the network.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.05a
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• pp.459-462
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• 2017

This paper, A large hair dryer was developed to shorten the drying time of the user's hair. The mechanism that determines the strength and stability of large hair dryer products is 'motor'. In a typical hair dryer to determine the wind speed using a 5V or 12V DC motor, Outer air vents are also great ways to use a long time, power consumption by a single blow. But, In the case of large hair dryers using multiple blows, the aim is to reduce the power consumption by increasing the intensity of the wind speed in a short time. Looking at the simulation results of a typical hair dryer, It was found that women spent an average of 20 minutes and that large hair dryers took an average of 5 minutes. This paper, In order to shorten the average drying time, it is necessary to determine the efficiency of the motor, the blow position of the outer frame, and the power consumption and studied for product development. As a result of the research and simulation, the power consumption is 0.8 times, the wind speed is 1.5 times, and the drying time is about 5 minutes. Therefore, it was found that the large hair dryer developed in this study can maximize the user 's average drying time and the efficiency of the motor.

• Geomechanics and Engineering
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• v.24 no.3
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• pp.215-226
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• 2021

To study the evolution mechanism of cracks in rocks with multiple defects, rock-like samples with multiple defects, such as strip-shaped through-going cracks and cavity groups, are used, and the crack propagation law and changes in AE (acoustic emission) and strain of cavity groups under different inclination angles are studied. According to the test results, an increase in the cavity group inclination angle can facilitate the initial damage degree of the rock and weaken the crack initiation stress; the initial crack initiation direction is approximately 90°, and the extension angle is approximately 75~90° from the strip-shaped through-going cracks; thus, the relationship between crack development and cavity group initiation strengthens. The specific performance is as follows: when the initiation angle is 30°, the cracks between the cavities in the cavity group develop relatively independently along the parallel direction of the external load; when the angle is 75°, the cracks between the cavities in the cavity group can interpenetrate, and slip can occur along the inclination of the cavity group under the action of the shear mechanism rupture. With the increase in the inclination angle of the cavity group, the AE energy fluctuation frequency at the peak stress increases, and the stress drop is obvious. The larger the cavity group inclination angle is, the more obvious the energy accumulation and the more severe the rock damage; when the cavity group angle is 30° or 75°, the peak strain of the local area below the strip-shaped through-going fracture plane is approximately three times that when the cavity group angle is 45° and 60°, indicating that cracks are easily generated in the local area monitored by the strain gauge at this angle, and the further development of the cracks weakens the strength of the rock, thereby increasing the probability of major engineering quality damage. The research results will have important reference value for hazard prevention in underground engineering projects through rock with natural and artificial defects, including tunnels and air-raid shelters.

• International Journal of Highway Engineering
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• v.7 no.2 s.24
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• pp.33-43
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• 2005

This paper describes a new approach to minimize the amount of shrinkage cracking in cement treated base(CTB). CTB is a stiffness base having lots of merits such as higher rutting resistance, minimizing fatigue cracking, and the ability to distribute upper loads. However, It is not applied to asphalt pavement system in Korea because of possible cracks caused by dry shrinkage. The goal of this study is the development of cement treated base with lower shrinkage for preventing reflection cracks and rutting. After identifying factors affecting dry shrinkage and analyzing mechanism of each admixture, the laboratory and field tests were designed and performed. Through the preliminary tests, the mix design containing 25 percent o( fly ash and 7 percent of cement was suggested. This mix design was satisfied with strength for Korea specification standard. According to the results considering strength, shrinkage, and economical efficiency, two mix designs were selected; 1) containing 25 percent of fly ash and 2) containing 25 percent of fly ash with 10 percent of expensive additive. For field test based on the result of laboratory test, the optimized alternative in cement treated base with lower shrinkage was the mix design containing 25 percent of fly ash with 10 percent of expansive additive.

• Korea and Global Affairs
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• v.3 no.2
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• pp.183-220
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• 2019

Nowadays, soft power is playing a more important role in international communication and cooperation, and as cultural exchange in regional cooperation is deeply influenced by national soft powers, the development is usually unbalanced. Bangladesh, China, India and Myanmar are adjacent to each other with a long history of intercourse. In the year 2013, initiation of constructing Bangladesh-China-India-Myanmar Economic Corridor advocated by China and India was responded positively by Bangladesh and Myanmar. Since then, the world has witnessed an increasing connection of these four countries. Being the critical bond connecting the southwestern areas of China and Bangladesh, India as well as Myanmar, Bangladesh-China-India-Myanmar Economic Corridor is characterized by multiple regional cultures along with frequent connections in cultural products and activities. However, cultural exchange now is dominated by imbalanced development due to potent soft power of China and India that these two countries export more cultural products to the rest, which has an impact in many fields of Bangladesh and Myanmar. Priority should be given to coordinated development in cultural exchange regarding the construction of Bangladesh-China-India-Myanmar Economic Corridor. Only by developing a sustainable development mechanism for cultural exchange, to coordinate the influences of soft powers of these four countries, then a fine complexion of "all flowers are in bloom" can be created, returning to five original intention of the construction of this economic corridor: "Policy Communication" and "Strength People-to-people Ties", etc.