• Journal of the Korea Society of Computer and Information
• /
• v.14 no.1
• /
• pp.65-72
• /
• 2009

This study presents a structural design optimizing sizes of high-rise steel plane truss members by maximizing stiffness subjected to given volume constraints. The sizing optimum design is evaluated by using a well-known optimality criteria (OC) of gradient-based optimization methods. In typical size optimization methods, truss structures are optimized with respect to minimum weight with constraints on the value of some displacement and on the member stresses. The proposed method is an inversed size optimization process in comparisons with the typical size optimization methods since it maximizes stiffness associated with stresses or displacements subjected to volume constraints related to weight. The inversed approach is another alternative to classical size optimization methods in order to optimize members' sizes in truss structures. Numerical applications of a round shape steel pipe truss structure are studied to verify that the proposed maximum stiffness-based size optimization design is suitable for optimally developing truss members's sizes.

• Tribology and Lubricants
• /
• v.26 no.4
• /
• pp.230-239
• /
• 2010

Mechanical face seal installed in boiler feedwater pump prevents leakage of working fluid using thin fluid film between stator and rotor. If the leakage of working fluid exceeds the allowable volume, serious malfunction of boiler feedwater pump will be happen. The thinner fluid film exists between stator and rotor, the less working fluid leaks out. However, if the thickness of fluid film is not enough, the wear of seal face will be increased. And it causes the decrease in life of mechanical face seal. Therefore appropriate design is necessary to maximize the performance and life of mechanical face seal. In this study, numerical analysis using finite volume method was conducted to investigate the static characteristics of wavy mechanical face seals which have 4 different wavy surface profiles on rotor. As a result, opening force, leakage volume of working fluid and friction torque were obtained. For the same minimum film thickness, the static characteristics of mechanical face seal were affected by the wavy surface profile which can change the thickness of working fluid film and pressure distribution.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.49 no.6
• /
• pp.421-430
• /
• 2000

This paper describes an optimal design method which is applied a weighted least square (WLS) method for Magnetic Resonance Imaging (MRI) system. An optimal design approach is presented for a homogeneity superconducting magnet with the superconducting active shield especially for a magnetic resonance imaging system. The WLS is used to obtain the optimal configurations using the least amount and minimum volume of conductor, exhibiting the smallest level of field inhomogeneity and resulting in the least level of stray field. The proposed model is used to design a multiple-shield configuration for a 1.5 T MRI magnet. The field homogeneity is required less than 5 gauss stray field contour within 4m axially and 3m radially from origin. The designed magnet with the actively magnetic shielding coil out of main coils is analyzed by FEM and theoretical analysis method, investigated the field homogeneity.

• Journal of Electrical Engineering and Technology
• /
• v.8 no.1
• /
• pp.124-129
• /
• 2013

Electro-Mechanical Batteries have important advantages compared with chemical batteries, especially in Low Earth Orbit satellites applications. High speed, slotless, external rotor, brushless DC machines are proposed and used in these systems as Motor/Generator. A simplified analytic design method is given for this type of machines and, the optimization of machine in order to have maximum efficiency and minimum volume and weight are given in this paper. Particle swarm optimization (PSO) is used as the optimization algorithm and the finite element-based simulations are used to confirm the design and optimization process and show less than 6% error in parametric design.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.7 no.4 s.19
• /
• pp.138-145
• /
• 2004

Experimental study was conducted on cylindrical supersonic diffuser in order to investigate the effects of the ratios of diffuser area to nozzle throat area (Ad/At), diffuser area to nozzle exit area (Ad/Ae), nozzle exit area to its throat area (Ae/At), and diffuser length to its diameter (L/D), the free volume of vacuum chamber, and the relative distance between nozzle exit and diffuser inlet on the diffuser performance. The study showed that the minimum diffuser starting pressure (Po/Pa)st increased monotonically with increase in (Ad/At) as predicted by the normal shock and momentum theory models and the volume of vacuum chamber affected vacuum pressure level during diffuser operation at lower value of (Ad/Ae). The results of this investigation will be utilized in the design of real-scale high-altitude simulation test facility.

• Journal of the Korean Institute of Navigation
• /
• v.21 no.2
• /
• pp.19-40
• /
• 1997

When designing new marine traffic routes, it is desirable that the congestion due to traffic volume is evaluated by theoretical traffic capacity or by traffic simulation. Most of these techniques are applied to single server which is not considered channel width. Over-taking or paralle sailing of two or more vessels is allowalbe in Dover, Uraga, Gaduk-sudo, etc under their traffic capacity. In this paper, the Bumper Model is introduced to multiple severs in narrow channel and applied to Uraga Channel in Japan. The minimum width of Uraga Channel is 1, 400 m and its design traffic capacity is evaluated 19.26 ~ 19.52% of the basic traffic capacity. The traffic capacity on Gaduk Channel according to Busan New Port Development in 2011 will be estimated 3.59 % of maximum density and equal to 18.6% of that on Uraga Channel in 1992. The channel width Gaduk-sudo is designed 1, 600~2, 460 m and evaluated safe enough.

• Structural Engineering and Mechanics
• /
• v.70 no.2
• /
• pp.169-178
• /
• 2019

The replacement of damaged components is an important task for long-span bridges. Conventional strategy for component replacement is to close the bridge to traffic, so that the influence of the surrounding environment is reduced to a minimum extent. However, complete traffic interruption would bring substantial economic losses and negative social influence nowadays. This paper investigates traffic control technologies without interruption for component replacement of long-span bridges. A numerical procedure of traffic control technologies is proposed incorporating traffic microsimulation and site-specific data, which is then implemented through a case study of cable replacement of a long-span cable-stayed bridge. Results indicate traffic load effects on the bridge are lower than the design values under current low daily traffic volume, and therefore cable replacement could be conducted without traffic control. However, considering a possible medium or high level of daily traffic volume, traffic load effects of girder bending moment and cable force nearest to the replaced cable become larger than the design level. This indicates a potential risk of failure, and traffic control should be implemented. Parametric studies show that speed control does not decrease but increase the load effects, and flow control using lane closure is not effectual. However, weight control and gap control are very effective to mitigate traffic load effects, and it is recommended to employ a weight control with gross vehicle weight no more than 65 t or/and a gap control with minimum vehicle gap no less than 40 m for the cable replacement of the case bridge.

• Tribology and Lubricants
• /
• v.28 no.2
• /
• pp.70-80
• /
• 2012

Non-contact type mechanical face seals installed in mechanical systems prevent leakage of working fluid using thin working fluid film between stator and rotor. For that purpose, various kinds of surface profiles, grooves and conings have been applied on seal surfaces of stator and rotor to generate hydrodynamic and hydrostatic pressure. The thickness distribution of working fluid film is one of important factors which affect the working performances of mechanical face seal, and it is strongly affected by the surface height profiles of stator and rotor. Therefore, appropriate design of surface height profiles of stator and rotor is necessary to optimize the working performances and life of mechanical face seal. In this study, numerical analysis using finite volume method was conducted to estimate the working performances of wavy mechanical face seals which have 36 coning combinations. As results, minimum thickness of working fluid film, leakage volume of working fluid and friction torque in static equilibrium condition of mechanical face seal, and stiffness of working fluid film were obtained. The results show that the working performances of mechanical face seal were affected by the coning combinations which can change the thickness distribution of working fluid film and pressure distribution in sealing region of mechanical face seal.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.29 no.1D
• /
• pp.41-48
• /
• 2009

The capacity analysis of signalized intersection usually includes a HCM method used at home and abroad and a ICU method this study presents. The HCM method focuses on operation analysis measuring an intersection's delay in terms of given traffic volume, signal operation, and intersection structure data. This method includes planning and design analysis, but these analyses are complex due to being possible through repetitive operation analysis. However the ICU method is a powerful tool for planning and design analysis, because these are possible through brief traffic volume and geometry structure data and consider minimum green time. In this study, the authors studied the ICU method and compared the HCM and ICU by analyzing traffic volume scenarios. Also to consider effectiveness for application of the ICU method, the authors applied the ICU to capacity analysis of intersections on urban arterial for setting major intersection and effect analysis for changing crosswalk type, the number of lane, lane use and operation form of left turn. The result of the analyses shows that the ICU method can measure correct capacity of intersection consist of a broad road in urban area, and is effective for planning and design analysis. This study is expected that traffic experts can grasp correct intersection's capacity and carry out a proper planning or improvement by applying the ICU method to planning and design analysis.

• Journal of the Ergonomics Society of Korea
• /
• v.33 no.5
• /
• pp.433-452
• /
• 2014

Objective: The aim of this study is to give ergonomists the brief summary of the recently published ISO standards on human-system interaction and tips for application of the standards. Background: Standard developers did hard work on developing a standard in a concise manner. But most of standards are often bulky in volume. Readers of the standards are difficult to catch key points from the voluminous contents of standards and intermingle among them. Method: Focused on newly developed display/control technology, this study reviewed the 14 ISO standards on human-system interaction published during 2008-2013 and summarized key points from them. Results: Schematic diagrams and tables concisely illustrated the processes, procedures, dimensions, or best practices recommended by the standards concerning conception, design, and usability testing for consumer products. Conclusion: The standards provided the minimum level of requirements on design and evaluation on the physical input devices, electronic displays, and control interfaces based on the current state of technology. But the minimum requirements specified in the standards nowadays become mandatory ergonomic requirements in global trade world. Application: Ergonomists can take a quick and broad view on international standardization activities on newly developed display/control technology from this summary study.