• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.32 no.2
• /
• pp.141-148
• /
• 2008

A numerical simulation of brushless DC motor is performed to elucidate thermo-flow characteristics in winding and bearing with heat generation. Rotation of rotor and blades drives influx of ambient air into the rotor inlet. Recirculation zone exists in the tiny interfaces between windings. The flow separation causes poor cooling performance in bearing part and therefore the redesign of the bearing groove is required. The design parameters such as the inlet location, geometry and bearing groove threshold angle have been selected in the present simulation. As the inlet location moves inward in the radial direction, total incoming flow rate and heat transfer rate are increased. Total incoming flow rate is increased with increasing the inlet inner length. The effect of the bearing groove threshold angle on the thermal performance is less than that of other design parameters.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.20 no.42
• /
• pp.39-47
• /
• 1997

There are four parameters (i.e. overall density, local density, grouping, layout complexity) to consider in designing screen of a visual display terminal. Among these, only the optimum level of overall density is known to be about 25~30% by some studies. Therefore, the present experiment is conducted to define the optimum levels of the other parameters to achieve the user's best performance in visual search task. The results are as follows; (1) The function related to the levels of local density and user's search times is shown to be U -shaped. When the level of local density is about 40%, the search time is shorter than those of any other levels. (2) In the experiment of grouping, user's performance is best when the number of group is 5, and the size of group does not exceed visual angle $5^{\circ}$ (0,088rad). (3) The user performance is improved as the layout becomes less complex.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.14 no.1
• /
• pp.32-39
• /
• 2004

This research is to investigate the performance of a flexible matrix composite driveshaft with respect to shaft design parameters such as the number of layers, ply orientations, and material properties. A finite element formulation is utilized to estimate the allowable misalignment under given driving torque, the maximum temperature at steady states, and external damping for ensuring whirling stability under supercritical speed. Results indicate that the system performance can be greatly affected by the shaft laminate parameters, especially the ply orientations. Several sets of shaft parameters that will provide satisfactory overall system performance are derived.

• Tunnel and Underground Space
• /
• v.10 no.2
• /
• pp.218-226
• /
• 2000

In order to determine the performance of an explosive, various parameters such as the detonation pressure, detonation velocity, heat generation, and fume generation of the explosive should be accurately described. In this study, the pressure increase, volume expansion, temperature increase, and detonation velocity of high explosives were tried to determined theoretically based on thermochemical theories. From this study, a Fortran program for calculating the explosion parameters, which can influence on the performance of explosives, was developed and applied to the high-explosives, ANFO and NG.

• Nuclear Engineering and Technology
• /
• v.31 no.3
• /
• pp.276-286
• /
• 1999

A computer code PARS2 is developed for the analysis of PSDRS, which is the safety grade RHRS of HAMMER, and applied to the investigation of the relation between design parameters and performance of PSDRS. The concept of the heat transfer resistance network is applied in assessing the importance of the various heat transfer modes. From the analysis results, the qualitative relations between the PSDRS performance and design parameters are found and guidelines for the PSDRS design procedures are also proposed.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
• /
• v.14 no.3
• /
• pp.29-34
• /
• 2018

To present the design direction of the thermoelectric module (TEM) refrigerator, analysis of the effect of the design parameters on the energy efficiency and performance of the refrigerator is performed. The design parameters considered are the cooling capacity of the TEM and the heat transfer performance of the heating and cooling surface of the TEM. The heat transfer performance is the most effective design parameter for improving cooling power. The smaller ΔT and cooling capacity of the TEM make the higher efficiency of the refrigerator.

• Journal of Power Electronics
• /
• v.10 no.1
• /
• pp.58-64
• /
• 2010

In this paper, the dynamic performance of oscillating linear motors, which are used in household refrigerators, is improved by means of efficient parameter identification. Oscillating linear motor parameters are identified as a function of the piston position and the motor current. They are stored in a ROM table and used later for an accurate estimation of piston position. The identified motor parameters are also approximated to the $2^{nd}$-order surface functions, which are divided into 2 or 4 subsections in order to decrease identification errors. Experimental results are given to show that the proposed control scheme can provide oscillating linear motors with high dynamic performance.

• Progress in Superconductivity and Cryogenics
• /
• v.6 no.2
• /
• pp.35-39
• /
• 2004

The split-type free displacer Stirling refrigerators have been widely used for the cooling of infrared sensors and HTS filters. The thermodynamic and electric performance of the Stirling refrigerator is depending on the design and operating parameters. In the Stirling refrigerator with a free displacer, the refrigeration power is a function of the pressure wave in the expansion space, dynamics of a displacer, driving frequency, and etc.. In this study, the analysis of the small Stirling refrigerator was performed to investigate the effects of design parameters on the cooling capacity. The results show the effects of charging pressure, driving frequency, cold end temperature, natural frequency of a displacer and volume of expansion space on the performance of the Stirling refrigerator.

• Wind and Structures
• /
• v.31 no.5
• /
• pp.381-392
• /
• 2020

Despite that the failure of sign structure may not have disastrous consequence, its sheer number still ensures the need for rigorous safety standard to regulate their maintenance and construction. During its service life, a sign structure is subject to extensive wind load, sometimes well over its permissible design load. A fragility analysis of a sign structure offers a tool for rational decision making and safety evaluation by using a probabilistic framework to consider the various sources of uncertainty that affect its performance. Wind fragility analysis was used to determine the performance of sign structure based on the performance of its connection components. In this study, basic wind fragility concepts and data required to support the fragility analysis of the sign structure such as sign panel's parameters, connection component's parameters, as well as wind load parameters were presented. Fragility and compound fragility analysis showed disparity between connection component. Additionally, reinforcement of the connection system was introduced as an example of the utilization of wind fragility results in the retrofit decision making.

• Structural Engineering and Mechanics
• /
• v.31 no.5
• /
• pp.527-544
• /
• 2009

In this study, the periodic seismic performance evaluation scheme is proposed using a structural health monitoring system in terms of seismic fragility. An instrumented highway bridge is used to demonstrate the evaluation procedure involving (1) measuring ambient vibration of a bridge under general vehicle loadings, (2) identifying modal parameters from the measured acceleration data by applying output-only modal identification method, (3) updating a preliminary finite element model (obtained from structural design drawings) with the identified modal parameters using real-coded genetic algorithm, (4) analyzing nonlinear response time histories of the structure under earthquake excitations, and finally (5) developing fragility curves represented by a log-normal distribution function using maximum likelihood estimation. It is found that the seismic fragility of a highway bridge can be updated using extracted modal parameters and can also be monitored further by utilizing the instrumented structural health monitoring system.