• Korean Journal of Optics and Photonics
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• v.23 no.5
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• pp.189-196
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• 2012

A floating optical system is a system that moves more than 2 groups to focus at the camera lens. At the camera optics, the floating system that is mainly used is an optical system such as a macro lens which changes magnification very much. When the floating system is assembled and fabricated in the factory, there are differences between the image plane of the sensor and the focal plane of the infinity or macro state. Therefore, in a considerable proportion of cases, the focus adjustment to minimize the difference of BWD(Back Working Distance) is carried out in the process of manufacturing. In this paper, in order to decide the movement of each group in a floating system, we evaluated the rotation angle of CAM for the focus adjustment. We know that the maximum magnification of macro state is corrected by this numerical method for the focus adjustment, too. We investigated the limit of CAM rotation angle of the system by using statistical analysis for CAM rotation angle, which uses the focus adjustment of the floating system with symmetric error factors.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.6
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• pp.482-489
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• 2020

This study conducted a prototype development and evaluation by performing die-casting mold design, mold manufacturing, and injection condition optimization based on flow and solidification analysis to meet the needs of the coupling parts produced by die casting. Through flow analysis, the injection conditions suitable for 100% filling in the cavity were found to be a molten metal temperature of 670 ℃, injection speed of 1.164 m/s, and filling pressure of 6.324~18.77 MPa. In addition, solidification close to 100 % occurred in all four cavities when the solidification rate was 69.47 %. A defect inspection on the surface and inside the product revealed defects, such as poor molding and pores. In addition, the dimensions of the injected product were within the target tolerance and showed good results. Through the feedback of the results of flow and solidification analysis, it was possible to optimize the mold design, and the injection optimization conditions were confirmed to be a total cycle time of approximately 6.5 seconds. Good quality carrier parts with an average surface hardness of approximately 45 mm from the gate measured at 97.48(Hv) could be produced.

• The Korean Journal of Air & Space Law and Policy
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• v.30 no.1
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• pp.151-180
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• 2015

South Korea is advancing the unmanned aircraft private commercial business. Unmanned aerial vehciles industry has been developing for several years also abroad. However, unmanned aerial vehciles industry, can be an accident occurs. Accident of unmanned aerial vehciles to occur material damage and casualties. Particularly if an accident because of a defect in the unmanned aerial vehciles has occurred, it is necessary to analyze the liability for this. The defect accidents unmanned aerial vehciles has been the different manufacturing and design product is intended, whether it is important how to prove to this. This is because, unmanned aerial vehciles are designed in any intent of the original, it is impossible to victims know. So imposing a responsibility to prove the design by the manufacturer intended consumer is not fair. Moreover, the consumer, it is necessary to prove only that the product is one that normally dangerous lacked safety can be expected. This is a detailed issue of judgment of defects of unmanned aerial vehciles, the manufacturer to bear the accountability. In the case where the defect on the display of the unmanned aircraft is a problem, and if it reasonable indication, it is not appropriate to be required to prove that it was possible to prevent damage to the victim.

• Polymer(Korea)
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• v.38 no.2
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• pp.144-149
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• 2014

Large residual stresses are remained in the conventional injection molded products because of the high cavity pressure in packing phase during injection molding process. Conventional injection molding (CIM) invokes distribution of cavity pressure and it has a limitation to obtain product with uniform physical property. Multi-cavity conventional injection molding contains quality deviation among the cavities since flow imbalance occurs during filling phase. Injection compression molding (ICM) is adopted to overcome these limitations of CIM. In this study, molding characteristics of CIM and ICM have been investigated using multi-cavity injection mold. Researches were performed by both experiment and computer simulation through observations of birefringence for transparent resins, polycarbonate and polystyrene in CIM and ICM. As a result, low and uniform birefringence and mold shrinkage were showed in the specimens by ICM that could give a uniform cavity pressure. Deviation of physical property among the specimens in multi-cavity mold shown in CIM was significantly reduced in the specimens by ICM. Through this study it was concluded that the ICM in multi-cavity molding was valid for molding products with uniform property in an individual cavity and also reduced property deviation among the cavities.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.4
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• pp.575-581
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• 2020

A colorless antistatic agent was prepared for use in antistatic films for liquid crystal displays (LCDs) requiring low surface resistance and high transmittance. Among various lithium-fluoro compounds and quaternary ammonium salts, antistatic materials were selected based on their electrical conductivity, and antistatic agents were prepared to measure the surface resistance. As a result, the material with high conductivity showed a relatively low surface resistance, i.e., relatively good antistatic performance. Based on the antistatic materials selected, the formulation ratio for producing the best antistatic agent was established through the experimental design method and the effects of each factor were analyzed. The higher the use of lithium- fluoro compounds as antistatic materials, the higher the ratio of oligomer use with multi-functional groups, and the smaller the surface resistance. The quaternary ammonium salts increased the antistatic performance of the lithium-fluoro compounds, but the effects of the amount used were not relatively large. After manufacturing the antistatic PET film, the properties of the antistatic film showed low surface resistance values (<10⁹ Ω/sq.), high permeability (>92%), low haze (<0.5%), and high whiteness (L^⁎>95). In addition, the antistatic film reliability was found to be excellent by showing a stable surface-resistance change rate of less than 10%, even under high temperature and high humidity conditions.

• Journal of Digital Convergence
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• v.12 no.11
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• pp.289-298
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• 2014

Recently, the traditional paradigm in railroad technology is changing as more efficient and cost-effective electric vehicle (EV) technologies have emerged. The original concept of PRT (Personal Rapid Transit) proposed in the past has come to be regarded as unrealistic, but its feasibility is improving through the utilization of an EV platform. In particular, battery-powered vehicles pose difficult technical challenges in attempts to achieve reliable and efficient operation. However, based on the inductive power transfer (IPT) technology, the fast charging of supercapacitors with high energy density can contribute to overcoming this technical challenge and promote the transition to electric-powered ground transportation by improving the appearance of cities. This study discusses the development process of a power supply system for PRT, including concept design, numerical analysis, and device manufacturing, along with performance predictions and evaluations. In terms of results, the system was found to meet the performance requirements for power supply modules on a test-bed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.6
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• pp.160-166
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• 2018

The worldwide semi-conductor market has been growing for a long time. Manufacturing lines of semi-conductors need to handle several types of toxic gases. In particular, they need to be controlled accurately in real time. This type of toxic gas control system consists of many different kinds of parts, e.g., fittings, valves, tubes, filters, and regulators. These parts obviously need to be manufactured precisely and be corrosion resistant because they have to control high pressure gases for long periods without any leakage. For this, surface machining and hardening technologies of the metal block and metal gasket need to be studied. This type of study depends on various factors, such as geometric shapes, part materials, surface hardening method, and gas pressures. This paper presents strong concerns on a series of simulation processes regarding the differences between the inlet and outlet pressures considering several different fluid velocity, tube diameters, and V-angles. Indeed, this study will very helpful to determine the important design factors as well as precisely manufacture these parts. The EP (Electrolytic Polishing) process was used to obtain cleaner surfaces, and hardness tests were carried out after the EP process.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.9
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• pp.1009-1015
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• 2012

Valves are one of the most important components of a pipeline system in a nuclear power plant, and it is important to ensure their structural safety under seismic loads. A crucial aspect of structural safety verification is the seismic qualification, and therefore, an optimal shape design and experimental seismic qualification is necessary in case the configuration of the valve parts needs to be modified and their performance needs to be improved. Recently, intensive numerical analyses have been performed before the experimental verification in order to determine the appropriate design variables that satisfy the performance requirements under seismic loads. In this study, static and dynamic numerical structural analyses of a 200A butterfly valve for a nuclear power plant were performed according to the KEPIC MFA. The result of static analysis considering an equivalent static load under SSE condition gave an applied stress of 135 MPa. In addition, the result of dynamic analysis gave an applied stress of 183 MPa, where the CQC method using response spectrums was taken into account. These values are under the allowable strength of the materials used for manufacturing the butterfly valve, and therefore, its structural safety satisfies the requirements of KEPIC MFA.

• The Journal of Korean Academy of Prosthodontics
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• v.59 no.1
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• pp.97-106
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• 2021

Dental implants should be placed at ideal sites for implant-supported restorations. For a patient with insufficient residual ridge, mouth preparation including surgical intervention can be indicated to establish a soft and hard tissue environment favorable for a definitive prosthesis. Prosthodontic design based on computer-guided surgery and computer-aided design-computer-aided manufacturing (CAD-CAM) provides a visual blueprint allowing a clinician to assess the necessity of such a surgical intervention beforehand. In this case, a definitive restoration was planned and made via a CAD-CAM system according to the patient's oral status before treatment, simulated surgical interventions and serial provisional restorations. Based on the planning, a guided template was made and the implants were installed with bone augmentation using the template. Customized abutments, the first and the second provisional restorations were designed and fabricated by CAD-CAM. The definitive restorations were digitally made following the shape of the second provisional prostheses, which were confirmed in the patient's mouth. The patient was satisfied with the masticatory, phonetic and aesthetic functions of these definitive prostheses.

• Journal of the Korea Fashion and Costume Design Association
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• v.23 no.1
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• pp.37-45
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• 2021

This study observed the release of microplastics according to washing weights and filtering conditions, measured microplastic generation rates, fiber lengths, and fiber diameters. This study attempted to present data for the development of filters that decrease microplastic generation. For test samples, polyester piled knit fabric (cut-pile) was selected, which currently has the highest amount of consumption in the clothing industry, but can easily cause marine pollution because of its low biodegradability. For test equipment, a drum washer was used and microplastics were collected using two filter pore sizes, 5 ㎛ and 20-25 ㎛. Microplastic fibers weights and lengths were measured. The results of the experiment showed the following: 1) The release of microplastics differed according to the fabric weights and washing process; 2) washing fabric weights showed a differences in the collection amount according to the filter pore size (5 ㎛, 20-25 ㎛); 3) observations of differences in the lengths of the microplastics that occur during the washing process by filter pore size were made. Fibers with shorter lengths appeared with filter pore sizes of 5㎛ in comparison to filter pore sizes of 20-25㎛. The results from this study on microplastic generation by fabric during washing, demonstrated the following conclusions that can be used to reduce the release of microplastics. First, the release of microplastics according to fabric weights and washing courses are affected by physical force. Therefore, it is necessary to reduce the amount of physical force due to water flow, increase the fabric weight, or wash the material in low temperatures. Second, in the manufacturing of washing machines, microplastic filtration can be promoted or legislatation supporting microplastic filtration can be introduced.