• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.3 s.234
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• pp.470-476
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• 2005

Ultra light metal structures have been studied for several years because of their superior specific stiffness, strength and potential of multi functions. Many studies have been focused on how to manufacture ultra light metal structures and optimize them. In this study, we introduced a new idea to make sandwich panels having octet truss cores. Wires bent in a shape of triangular wave were assembled to construct an Octet truss core and it was bonded with two face sheets to be a sandwich panel. The bending & compressive strength and stiffness were estimated through elementary mechanics for the sandwich specimens with two kinds of face sheets and the results were compared with the ones measured by experiments. Some aspects of assembling and mechanical behavior were discussed compared with Kagome core fabricated from wire, which had been introduced in the authors' previous work.

• Transactions of Materials Processing
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• v.19 no.7
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• pp.411-415
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• 2010

A sandwich panel which is comprised of truss cores faced with solid face sheets is lightweight and multi-functional. So it is widely used to not only structural material but also heat transfer media in transportation field such as airplane, train and vessel. There are various core topologies such as pyramidal and tetrahedral truss, square honeycombs and kagome truss. The study focused on analytical approach to optimize compression and shear quality of the unit cell of PCM with pyramidal configuration. With various unit cell models which have the same core weight per unit area but different truss member angle, analytical solution for effective stress ($\bar{\sigma},\bar{\tau}$), peak stress ($\bar{\sigma}_{peak},\bar{\tau}_{peak}$) by yielding and buckling, relative density ($\bar{\rho}_c$) and effective stiffness ($\bar{E},\bar{G}$) have been computed and compared each other. With this approach, the most optimal core configuration was predicted. The result has become the efficient guidelines for the design of PCM core structure.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.3
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• pp.168-174
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• 2016

A conductive oxide-based sapphire glass indium tin oxide/metal electrode and the optical coating, through patterning process was studied in excellent optical properties and integrated touch panel has a high strength. Indium tin oxide conductive oxides of the sapphire glass to 0.3 A at DC magnetron sputtering method of 10 min, gas flow Ar 10 Sccm Ar, $O_2$ 1.0 Sccm the formation conditions of the thin film after annealing at $550^{\circ}C$ for 30min was achieved through a 86% transmittance. In addition, the coating 130 nm hollow silica sol-gel was to improve the optical transmittance of the indium tin oxide to 91%. For the measurement by the modeling hollow silica sol by Macleod simulation and calculated the average values of silica part to the presence or absence in analogy to actual. Refractive index value and the actual value of the material on the simulation the transmittance difference is it does not completely match the air region similar to the actual value (transmission) could be confirmed that the measurement is set to a value of between 5 nm and 10 nm.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.04a
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• pp.129-132
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• 2000

The PDP(Plasma Display Panel) barrier rib material on the glass substrate was patterned for fabrication of the PDP cell using Nd:YAG laser(1064 nm) which can generate the second(532 nm) and forth(266 nm) harmonic wave by HGM(harmonic generation modules). At a scan speed of 20 ${\mu}m/s$ with the second harmonic wave(532 nm) of Nd:YAG laser, the etching threshold laser fluence of the PDP material was 6.5 $mJ/cm^2$ and a sample(thickness = 180 ${\mu}m$) on the glass substrate was removed clearly at a laser fluence of 19.5 $mJ/cm^2$. In order to increase the throughput of the fabrication we divided a single-beam into multi-beams by using a metal mask between the sample and the focusing lens. As a result, 10 lines of PDP cell were formed by one laser beam scanning at a scan speed of 200 ${\mu}m/s$ and a laser fluence of 2.86 $J/cm^2$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.10
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• pp.936-940
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• 2005

IMML(Inorganic metal multi-layer) was used as cathode in the OLED devices to reduce the reflectance or ITO and increase the contrast ratio. Device structure was $ITO/{\alpha}-NPD/Alq_3:DCJTB/Alq_3/IMML/Al$. $Alq_3$ and DCJTB (4 - (dicyanomethylene) - 2 - ( 1 - propyls) 6 - methy 4H - pyrans) as host material lot red emission and red emitting guest material. IMML made three different layer: thin aluminum layer, aluminum layer doped with silicon monoxide, thick aluminum layer. The red OLED device with IMML showed the average reflectance of $4.97\%$, and then normal OLED with or without polarizer showed the average reflectance of $4.55\%$, $46\%$ at visible range from 380 nm to 780 nm. The brightness of OLED with IMML at 13 V was 5557 $cd/m^2$, and that of normal OLED with polarizer was 4872 $cd/m^2$. IMML could be the substitution for polarizer with same reflection, low cost, easy process in flat panel display market.

• Journal of Korean Tunnelling and Underground Space Association
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• v.3 no.3
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• pp.3-13
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• 2001

The behavior of the masonry lining is studied to gain basic information on how to reinforce the masonry tunnels. Apart from the previous works on the masonry structures, the multi-course masonry structure, realistic in field condition, is considered and the constitutive relationship of the masonry is, therefore, established. The design charts of the orthotropic material properties are proposed according to the stiffness ratio and the crack initiation and subsequent propagation model is also considered to model the brittle nature of the masonry. A numerical analysis on the masonry panel is investigated to verify the proposed model and future works of the masonry lining are briefly explained.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.9
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• pp.1410-1415
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• 2001

Active control of sound radiation from a vibrating rectangular plate by a steady-state harmonic point force disturbance is experimentally studied. Structural excitation is achieved by two piezoceramic actuators mounted on the panel. Two accelerometers are implemented as error sensors. Estimated radiated sound signals using vibro-acoustic path transfer function are used as error signals. The vibro-acoustic path transfer function represents system between accelerometers and microphones. The approach is based on a multi-channel filtered-x LMS algorithm. The results shows that attenuation of sound levels of 11dB, 10dB is achieved.

• Current Optics and Photonics
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• v.8 no.4
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• pp.375-381
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• 2024

In this report, we present the design, fabrication, and experiment of a static solar system for electric vehicle (EV) applications. The static concentration component is composed of compound parabolic concentrators (CPCs) couplings with multi-junction solar cells, where a flat silicon panel is added to the bottom of the CPV structure to maximize power generation. This design allows the system to collect both direct sunlight and diffused sunlight. The CPCs were fabricated with acrylic with a geometric concentration ratio of 4×. We built a prototype with a (3 × 3) cell array of CPCs with a thickness of 25 mm, which is as thin as conventional flat photovoltaic panels, and performed an outdoor experiment that showed that after six hours of operation, the system had an acceptance angle of approximately 43° and an average daily efficiency of 22.85%.

• Proceedings of the Korean Association for Survey Research Conference
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• 2000.06a
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• pp.117-135
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• 2000

The corporate restructuring following the economic crisis in Korea has brought about fundamental changes in the structure and practice of employment relations. However the lack of information on processes and consequences of such changes hinder the appropriate policy making on shop-floor industrial relations. Correct assessment of realities an effective policy making require information on human resource management practices and structure of employment relations at the workplace level. This paper critically examines the experiences of workplace-employee integrated surveys carried out in advanced countries including Australia, Canada, and Britain, to extract methodological implications for such survey in Korea. We focus on the backgrounds of the surveys and practical issues involved in multi-level, longitudinal survey design.

• Survey Research
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• v.1 no.2
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• pp.117-135
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• 2000

The corporate restructuring following the economic crisis in Korea has brought about fundamental changes in the structure and practice of employment relations. However the lack of information on processes and consequences of such changes hider the appropriate policy making on shopfloor industrial relations. Correct assessment of realities and effective policy making require information on human resource management practices and structure of employment relations at the workplace level. This paper critically examines the experiences of workplace-employee integrated surveys carried out in advanced countries including Australia, Canada, and Britain, to extract methodological implications for such survey in Korea. We focus on the backgrounds of the surveys and practical issues involved in multi-level, longitudinal survey design.