• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.9
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• pp.1-10
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• 2021

Recently, the repair and recycling of damaged mechanical parts via metal additive manufacturing processes have been industrial points of interest. This is because the repair and recycling of damaged mechanical parts can reduce energy and resource consumption. The directed energy deposition(DED) process has various advantages such as the possibility of selective deposition, large building space, and a small heat-affected zone. Hence, it is a suitable process for repairing damaged mechanical parts. The shaft is a core component of various mechanical systems. Although there is a high demand for the repair of the shaft, it is difficult to repair with traditional welding processes because of the thermal deformation problem. The objective of this study is to propose a repair procedure for a damaged shaft using the DED process and discuss its applications. Three types of cases, including a small shaft with a damaged surface, a medium-size shaft with a worn bearing joint, and a large shaft with serious damage, were repaired using the proposed procedure. The microstructure and hardness were examined to discuss the characteristics of the repaired component. The efficiency of the repair of the damaged shaft is also discussed.

• Journal of Adhesion and Interface
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• v.20 no.2
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• pp.66-70
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• 2019

The surface of hydrophobic polypropylene (PP) fibers (spun-bonded fabric) was treated by an atmospheric plasma treatment method. These pre-treated hydrophilic PP fabrics were dip-coated in the aqueous poly(N-vinyl pyrrolidone) (PVP) solution. PVP layers on the surface of PP fiber were crosslinked by an irradiation of electron beam. The thickness of PVP hydrogels coated on the surface was easily controlled by changing the concentration of PVP in coating solution. The stepwise surface treatment, PVP coating, and hydrogel formation via electron beam irradiation were analyzed by the measurement of contact angle, scanning electron microscopy, and optical microscopy.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.12 no.1
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• pp.1-6
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• 2019

An extremely small size multi-loop phase-locked loop(PLL) keeping phase noise performances has been proposed. It has been designed to have the loop filter made of small single capacitor with multiple Frequency Voltage Converters (FVCs) because the main goal is to make the size of the proposed PLL extremely small. Multiple FVCs which are connected to voltage controlled oscillator(VCO) make multiple negative feedback loops in PLL. Those multiple negative feedback loops enable the PLL with the loop filter made of an extremely small size single capacitor operate stably. It has been designed with a 1.8V $0.18{\mu}m$ CMOS process. The simulation results show that the proposed PLL has the 1.6ps jitter and $10{\mu}s$ locking time.

• Journal of the Korean Geotechnical Society
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• v.24 no.10
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• pp.5-15
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• 2008

The purpose of this study is to examine the validity of recycled aggregates (RAs) as a substitute for Sand-Mat material for soft ground improvement in the housing site development. To evaluate the possibility of RAs as a substitute for sand mat material, first of all, the criteria and regulations related with the quality of lateral drain layer were collected and checked. Secondly, both of the properties of RAs were compared with the properties of natural sand for the lateral drain layer. The material properties related to coefficient of permeability, pressure at-rest state and so on satisfied most standards. On the basis of the test results, RAs were used to the construction site as lateral drain layer. Accordingly, if the quality of RAs can be managed well, the application of these RAs as lateral drain layer to replace natural sand was highly effective. Also, based on cost analysis of two materials, RAs are proved to be very competitive.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.8 no.4
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• pp.57-66
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• 2013

Domestic PCB industry formed by orders of demand companies is extremely vulnerable in its innovation infrastructure including high value-added technology development and information exchange. The majority of PCB products produced in the country relies on the imports from abroad and it causes its vulnerability to external market changes. Due to the negative perceptions about the industry (e.g., 3D job), low treatment (especially SMEs) and expertise employment avoidance in PCB industry, the job market conditions of PCB industry is not so good. In these circumstances, the PCB industry is completely dependent on the demand market such as cellular phones, and tablet PC, and as a result the responsiveness of PCB industry to the changes in demand market is also vulnerable. In this PCB industry, Korean government is trying to build the research infrastructure for PCB industry that realizes the sharing of information among companiesthrough the operation of the PCB industry innovation forum (information innovation), builds SME suppot platform and supports quality improvement (technology innovation), and supports enterprise collaboration processes (material-process-equipment) utilizing PCM open laboratory. The PCB industry technology infratstructure project is going to be promoted by the government(1.3 billion won, each year) and the private investmen(434 million won each year) from 2013 to 2017(5 years project)(table 1). This study analyzes the feasibility of the project, by using the AHP analysis and the results shows that this project is considered feasible because the AHP overall score is evaluated as 0.841, the overall score is greater than or equal to 0.55.

• Journal of Korean Institute of Industrial Engineers
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• v.6 no.2
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• pp.37-47
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• 1980

A system of conditional sampling plans composed of three stages is developed. In the first stage, the decision to accept or reject the lot is based on the information obtained from the current lot. When a decision is not made in the first stage, a second stage is introduced and the information from the immediately preceding lot as well as the information from the current lot is used for the decision. When a decision is not made in the first stage, a second stage is introduced and the information from the immediately preceding lot as well as the information from the current lot is used for the decision. When a decision is not made in the second stage either, the decision is deferred until the information from the immediately following lot is obtained. Existing tables for constructing double sampling plans with $_2$=$2n_1$ can be used to find the parameters of these plans. These sampling plans can bring sizable savings in the amount of inspection when the process is relatively stable. The response delay to the change in process quality and the deferred events may be considered as shortcomings of these plans. However, these are not serious in practical applications, and the reduction in sample size may more than offset these shortcomings.

• Journal of the Korean Institute of Gas
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• v.16 no.4
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• pp.52-58
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• 2012

Recently, waste gas incineration is increasing due to strong environmental regulatory system in Korea. These incinerating facilities are usually connected with the top of the storage tank through pipeline and incinerate off gas with the flame. Therefore, the flame originated from these facilities is likely to move back into pipeline and might cause an explosion of the storage tank. Accordingly, the purpose of this study is to suggest the preventive measures and the way to improve the safety of these incineration systems through the cause analysis of a major industrial accident occurred in a acrylic acid manufacturing process in Korea. As a result of the study, the preventive measures are suggested as follows. (1) Air or inert gas inflow facilities should be well designed to dilute flammable gases into air or inert gas sufficiently before the blower is restarted in order to prevent the explosion (2) It is needed for the detonation-type flame arresters to be installed on the top of the storage tanks. (3) In case of using the deflagration-type flame arresters, it is necessary to install a rupture disk before the arresters, or blow off the flame outside tanks by connecting the tank top and the incinerator with hood-type pipe. (4) TDR should be installed to be restarted automatically after the momentary power failure.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.4
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• pp.716-722
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• 2017

In this paper, a fully printed NFC tag operating at 13.56 MHz was designed and fabricated using silver nano-paste and carbon ink. The proposed NFC tag has a printed coil with an inductance of $2.74{\mu}H$ on a PI film for application to an NFC tag IC with an internal capacitance of 50 pF. Screen printing technology used in this paper has advantages such as large area printing for mass production, low cost and eco-friendly process compared to conventional PCB manufacturing process. The proposed structure consists of a circular coil implemented as a single layer using silver nano-paste and carbon ink, a jumper pattern for chip mounting between the outer edge and the center of the coil, and an insulation pattern between the coil and the jumper pattern. In order to verify the performance of the proposed NFC tag, we performed the measurements of the printing line width, thickness, line resistance, adhesion and environmental reliability, and confirmed the suitability of the NFC tag based on the full-printed manufacturing method.

• Journal of the Korean Society of Earth Science Education
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• v.10 no.1
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• pp.50-61
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• 2017

The purpose of this study is to analysis eye tracking for high school students' learning styles in the process of solving in the behavioral domains of the College Scholastic Ability Test on Earth Science I. The subjects of this study were 50 students from two classes out of 4 classes in E high school in Chungcheong province. Among them, we conducted experiments by randomly sampling 2 students of each type of learning based on the criteria that they had not encountered the problem of Earth Science I from the past two years. The findings indicate that the item correctness rate of divergers, assimilators, convergers, and accommodators were higher in the knowledge domain, application domain, knowledge-understanding domain, and understanding domain. This confirms that there is a difference among the four learning styles in the level of achievement according to the behavioral areas of the assessment questions. The latter finding was that the high eye-share of AOI 2 appeared higher than AOI 1, 3, 4 in the course of solving the problems. This is because the four types of learners pay more careful attention to the AOI 2 area, which is the cue-or-information area of problem solving, that is, the Table, Figure, and Graph area. Therefore, in order to secure the fairness and objectivity of the selection, it is necessary that an equal number of questions of each behavioral domain be selected on the Earth Science I Test of the College Scholastic Ability Test in general. Besides, it seems to be necessary that the knowledge, understanding, application, and the behavior area of the inquiry be highly correlated with the AOI 2 area in development of test questions.

• Korean Journal of Heritage: History & Science
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• v.54 no.4
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• pp.60-77
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• 2021

From 2007 to 2011, four Goryeo Dynasty vessels, namely the Taean treasure ship, Taean Mado Shipwreck No.1, No.2, No.3 were discovered in Taean area, Chungcheongnam-do province. From the shipwrecks, 175 pieces of mokkan (wooden tablet) were excavated. These mokkans are the only case of Goryeo Dynasty and represent the unique usage of mokkan as cargo tags, after the paper replaced the wooden tablets as writing materials. The Taean mokkans provide details, such as the year, recipient, port of origin, types of the cargo, quantity and unit, the name of the responsible person for shipment. Thus, they enable us to speculate about the characteristics of the cargo. Furthermore, through studying the writing style, form, material and manufacturing method, researchers can extract which form and characteristics were favored at that time. The Taean mokkans have no preset style for writing. Therefore, they can be written selectively and freely. And since the mokkan were attached to cargos, mokkans with furrows on upper side were favored, and efficiency and simplification of the manufacturing process were priorities in making mokkans. The Taean mokkans can be compared to those from the Shinan ship and the Quanzhou ship because those are of the same era and use. On the writing styles and information, Chinese mokkans are focused on the cargo owners, while The Taean mokkan includes more detailed information, such as the recipients. In forms, Chinese mokkans have maximum thickness of 1.0 centimeter and have pointed edges in lower parts, while mokkans from Taean do not have fixed thickness or edges. Furthermore, Chinese mokkans and Korean mokkans have different styles from manufacturing methods and material selections. These differences between Chinese and Goryeo mokkan are related to the differences between littoral-transport Goryeo ships and ocean-transport Chinese ships, such as shipping distances, types of cargo, shipping systems, packing methods, and transport operators. At the moment, because there are only small amount of data and materials of Chinese mokkan, comparative studies regarding Goryeo and Chinese mokkan can only be fragmentary. However, this article can be a base from which to expand the scope of Goryeo mokkan studies.