• Special Issue of the Society of Naval Architects of Korea
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• 2007.09a
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• pp.1-6
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• 2007

To improve productivity of the LNG carriers which are growing bigger and bigger, many researches are being carried out by shipyards. In this regard, we reviewed possible problems which could occur during the erection of 216K LNG carrier's motor/compressor room with all outfittings pre-installed. As a first item, the weights of hull and outfittings were precisely estimated to make sure that the erection is carried out within yard's capability. In the next place, deflection and safety of the structure were verified by FEM analysis. As a result, the erection was finished successfully and yard's productivity was also improved. This review is a good example which shows the importance of through study and preparation for improving yard's productivity which is already reached its limit.

• Special Issue of the Society of Naval Architects of Korea
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• 2008.09a
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• pp.106-111
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• 2008

A hull form is 181K DWT Bulk Carrier, of which new design and hull form have been developed using CFD tools and model tests. The basic concept design of hull form has been carried out with considering the factors, which are a lot of influence of the wave and viscosity resistance. The considered factors of particular are LCB, DLWL shape, tern and stem profile, Cp-curve shape, etc. Numerical calculations are carried out in the initial design stage and experimental model tests are also carried out in towing tank of MOERI. The variation of the significantly effective characteristics is carried out to achieve optimized hull form. The results from numerical calculations and model test as well as the design procedures to obtain an optimized hull form resent in this paper.

• Journal of the Optical Society of Korea
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• v.19 no.6
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• pp.629-637
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• 2015

Compact system cameras (CSCs) are commonly used nowadays and feature enhanced video functions and thin yet light interchangeable lenses. They differ from digital single-lens reflex (DSLR) cameras in their lack of mirror boxes. CSCs, however, have autofocus (AF) speeds lower than those of conventional DSLRs, requiring weight reduction of their AF groups. To ensure the marketability of large telephoto zoom lenses with fixed f/2.8 regardless of field angle variation, in particular, light weight AF groups are essential. In this paper, we introduce a paraxial optical design method and present a new, large, telephoto zoom lens with f/2.8 regardless of the field angle variation, plus a lightweight AF group consisting of only one lens. Using the basic paraxial optical design and optimization methods, we fabricated a new and lighter zoom lens system, including a single-lens, lightweight AF group with almost the same performance.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.829-834
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• 2009

Alluvial soil is one of the most difficult grounds for tunneling works due to the insufficient ground strength and excessive ground water inflow. Dduk island in Seoul has a wide alluvium developed by two rivers, Han and Jung-Ryang. Subway tunnel of $\bigcirc\bigcirc$ line planed across Dduk island has highly poor ground conditions due to small cover and deeply developed alluvium. Moreover, much part of this tunnel is located parallel to the bridge foundations of another railway with a small horizontal distance. Original design was done in 2002 and construction has been in progress. During the construction, tunnel design has been partly changed and adjusted for the complex ground condition and the demand from related organizations. This paper intend to introduce the urban tunnel design and construction in alluvial soils. This line could be divided three sections(A, B, C) according to ground and adjacent conditions. Section A is featured by mixed tunnel faces consisted with alluvial soils and weathered or weak rocks. The feature of section B is that tunnel underpasses near the bridge foundations of another subway. Lastly, section C with a very short length is the most difficult construction conditions due to the small cover, poor ground, obstacles on and underneath ground surface.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.1
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• pp.103-108
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• 2012

In this paper, the optimal design of a spring-type gravity compensation system for an articulated robot is presented. Sequential quadratic programming (SQP) is adopted to resolve various nonlinear constraints in spring design such as stress, buckling, and fatigue constraints, and to reduce computation time. In addition, continuous relaxation method is used to explain the integer-valued design variables. The simulation results show that the gravity compensation system designed by proposed method improves the performance effectively without additional weight gain in the main workspace.

• Advances in concrete construction
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• v.12 no.6
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• pp.451-459
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• 2021

The mechanical behaviors and chloride resistance performance of fiber reinforced cementitious composites (FRCC) with hybrid polyethylene (PE) and steel fiber (in total 2% by volume) were investigated. Based on micro-mechanics and fracture mechanics, the reason why the tensile strain capacity of FRCC changed obviously was obtained. Besides, the effects of the total surface area of fiber in FRCC on compressive strength and chloride content were clarified. It is found that the improvement of the tensile strain capacity of FRCC with hybrid fiber is attributed to the growth of strain-hardening performance index (the ratio of complementary energy to crack tip toughness). As the total surface area of fiber related with the interfacial transition zone (ITZ) between fiber and matrix increases, compressive strength decreases obviously. Since the total surface area of fiber is small, the chloride resistance performance of FRCC with hybrid PE and steel fiber is better than that of FRCC containing only PE fiber.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.25 no.4
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• pp.173-179
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• 2013

Middle-sized $CO_2$ water heater having compressor power of 7.45 kW was designed, and its performances were experimentally tested. Besides, optimum design of the $CO_2$ water heater was conducted by cycle simulation. When ambient temperature of $7^{\circ}C$ and hot water outlet temperature of $80^{\circ}C$ the $CO_2$ water heater showed the COP of 3.2. As hot water temperature increased the COP is getting decreased due to significant increase of compressor power consumption compared to increasing rate of heating capacity. When ambient temperature increased from $-3^{\circ}C$ to $12^{\circ}C$ the COP increased by 30%. The optimum components design of a gas cooler, an internal heat exchanger, and an evaporator were conducted, and the experimental correlation between amount of EEV opening and ambient temperature, and hot water temperature was suggested.

• Journal of the Korean Society of Industry Convergence
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• v.20 no.4
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• pp.299-305
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• 2017

This study proposes a new technique to design and control of robot hand gripper for assembling and disassembling of a machine parts. The motion equation describing dynamics of the manipulators and object together with geometric constraint is formulated by Lagrange-Euler's equation. And the problems of controlling both the grasping force and the rotation angle of the grasped object under the constraints are analyzed. The effect of geometric constraints and a method of computer simulation for overall system is verified. Finally, it is illustrated that even in case of there exists a sensory feedback from sensing data of the rotational angle of the object to command inputs control of joint and this feedback connection from sensing data to control grasping of machinery parts.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.1
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• pp.74-85
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• 2010

In order to formulate the compounded polypropylene(C-PP) which is suitable to an automotive door trim panel, 9 sorts of properties were measured after manufacturing the C-PP using an extruder and an injection machine with polypropylene(PP), ethylene-octene rubber(EOR) and talc. Mixture design, especially extreme vertices design, in DOE with MINITAB - commercial software was used to analyze the data. The relations between each property and each component, for example, $y=0.00907222x_1+0.00870556x_2+0.0155722x_3$ for specific gravity, were found out by the regression analysis and the variance analysis. The optimized formulation of the C-PP for an automotive door trim panel was acquired at PP(77.6962), EOR(11.0238) and talc(10.2800) by use of the response optimizer(mixture) in MINITAB.

• Journal of Power Electronics
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• v.10 no.3
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• pp.262-269
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• 2010

This paper proposes a practical design for a Cascaded H-Bridge Multilevel (CHBM) inverter based on Power Electronics Building Blocks (PEBB) and high performance control to improve current control and increase fault tolerance. It is shown that the expansion and modularization characteristics of the CHBM inverter are improved since the individual inverter modules operate more independently, when using the PEBB concept. It is also shown that the performance of current control can be improved with voltage delay compensation and the fault tolerance can be increased by using unbalance three-phase control. The proposed design and control methods are described in detail and the validity of the proposed system is verified experimentally in various industrial fields.