• Fire Science and Engineering
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• v.32 no.6
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• pp.28-33
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• 2018

To measure the full scale fire test and heat release rate of bed mattresses according to the building compartment space, a fire test was performed using the Standard test method to determine the heat release rate of mattresses and mattress sets (KS F ISO 12949: 2011). Both test locations showed similar fire growth until approximately 3 minutes after burner ignition. After 3 minutes, the heat release rate in the test room was higher than the open calorimeter. For bed mattresses (SS), the maximum heat release rate in the open calorimeter was 735 kW and the maximum heat release rate in the test room was 992 kW. For bed mattresses (Q), the heat release rate in the test room increased more rapidly than the open calorimeter. The maximum heat release rate in the open calorimeter was 1,087 kW (346 s) and the maximum heat release rate in the test room was 2,127 kW (287 s). The difference between the maximum heat release rate and the measurement time according to the test location was confirmed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2010.05a
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• pp.44-44
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• 2010

In this presentation, noise control materials will be discussed from several points-of-view. First, materials will be categorized in terms of their intended function: i.e., as dissipative materials, as barriers, and as media intended to modify some aspect of the sound field. Within each category, example implementations will be described as will modeling procedures. In the context of barrier materials, recent developments in the area of metamaterials will be described briefly, and problems with some recently suggested approaches will be highlighted. Acoustical cloaking will be described as a method of modifying a sound field in such a way that a sensitive area is shielded from noise exposure; the practical difficulties of this approach will also be described. Finally, within each category of material and approach, a series of suggested research challenges will be described.

• Korean Journal of Materials Research
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• v.29 no.2
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• pp.97-105
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• 2019

In the current steel structures of high-rise buildings, high heat input welding techniques are used to improve productivity in the construction industry. Under the high heat input welding, however, the microstructures of the weld metal (WM) and heat-affected zone (HAZ) coarsen, resulting in the deterioration of impact toughness. This study focuses mainly on the effects of fine TiN precipitates dispersed in steel plates and B addition in welding materials on grain refinement of the HAZ microstructure under submerged arc welding (SAW) with a high heat input of 200 kJ/cm. The study reveals that, different from that in conventional steel, the ${\gamma}$ grain coarsening is notably retarded in the coarse grain HAZ (CGHAZ) of a newly developed steel with TiN precipitates below 70 nm in size even under the high heat input welding, and the refinement of HAZ microstructure is confirmed to have improved impact toughness. Furthermore, energy dispersive spectroscopy (EDS) and secondary-ion mass spectrometry (SIMS) analyses demonstrate that B is was identified at the interface of TiN in CGHAZ. It is likely that B atoms in the WM are diffused to CGHAZ and are segregated at the outer part of undissolved TiN, which contributes partly to a further grain refinement, and consequently, improved mechanical properties are achieved.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.08a
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• pp.317-326
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• 2004

This study investigated tile local austenite grain size (AGS) distribution In rolling of SCM435 steel which is commonly used for high strength bolt. To investigate AGS distribution, round-oval (R-O) and square-diamond (S-D) rolling experiments were carried out with pilot mill. In round-oval rolling, local AGS has a tendency to increase when it goes to outward. In square-diamond rolling, local AGS has a tendency to increase when it goes to free surface. To investigate relation between AGS and process parameter, three dimensional FE analysis was carried out along with rolling experiment. To validate accuracy of FE analysis, we compared deformed geometry with FE result. The AGS prediction combined AGS model with numerical analysis was also carried out for center node of S-D rolling. Although this study brought experimental observation and its qualitative analysis into focus and quantitative AGS prediction will be done as a further work.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.4
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• pp.72-81
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• 2009

The purpose of this paper is to accomplish the stable humanoid robot walking on the soft terrains. The goal of the humanoid robot development is to make the robotic system perform some tasks in human living environment. However, human dwelling environments are very different from those of laboratories, where varied experiments are performed by the robot. In many cases, the ground is soft or elastic unlike the floor of a laboratory. When a robot walks on the soft ground, the sole of robot contacts the uneven ground. This results in unstable walking or walking may be impossible according to the degree of softness. Therefore, the algorithm that facilitates stable walking on the soft ground surface is required. In this paper, we suggest an algorithm that controls the ankle to help the robot walk stably on the soft ground using the humanoid robot (ISHURO-II) as a real model. A humanoid robot walking on the soft ground was simulated to verify that the proposed algorithm results in stable walking.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.22 no.11
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• pp.727-734
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• 2010

The present study numerically investigates the motion of a solid body suspended in the square enclosure with natural convection. A two-dimensional circular cylinder levitated thermally has been simulated by using thermal lattice Boltzmann method(TLBM) with the direct-forcing immersed boundary method. To deal with the ascending, falling or levitation of a circular cylinder in natural convection, the immersed boundary method is expanded and coupled with the TLBM. The circular cylinder is located at the bottom of a square enclosure with no restriction on the motion and freely migrates due to the Boussinesq approximation which is employed for the coupling between the flow and temperature fields. For different density ratio between the cylinder and the fluid, the motion characteristics of the circular cylinder for various Grashof numbers have been carried out. The Prandtl number is fixed as 0.7.

• Journal of the Earthquake Engineering Society of Korea
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• v.26 no.1
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• pp.1-11
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• 2022

In this study, the seismic performance of a two-story unreinforced masonry (URM) building was assessed following the linear and nonlinear static procedures specified in the seismic evaluation guideline of existing buildings. First, the provisions to assess failure modes and shear strengths of URM walls and wall piers were reviewed. Then, a two-story URM building was assessed by the linear static procedure using m-factors. The results showed that the walls and wall piers with aspect ratios h_e // (i.e., effective height-to-length ratio) > 1.5 were unsafe due to rocking or toe crushing, whereas the walls with h_e // ≤ 1.5 and governed by bed-joint sliding mainly were safe. Axial stresses and shear forces acted upon individual masonry walls, and wall piers differed depending on whether the openings were modeled. The masonry building was reevaluated according to the nonlinear static procedure for a more refined assessment. Based on the linear and nonlinear assessment results, considerations of seismic evaluation for low-rise masonry buildings were given with a focus on the effects of openings.

• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.2
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• pp.46-54
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• 2015

Nitrous oxide is known as green and safe propellant, and can be supplied by its own vapor pressure. So, many liquid propulsion research institutes and university laboratories use nitrous oxide as oxidizer of experimental liquid rocket engine. However, the unknown explosions occurred twice during hot fire experiments using subscale ethanol/nitrous oxide thruster. In this paper, we surmised that the explosions were caused by the decomposition of nitrous oxide in the injector body and the recondensation of nitrous oxide. Improvement and the safe handling methods are suggested.

• Journal of Electrical Engineering and Technology
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• v.9 no.6
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• pp.1928-1934
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• 2014

Induction motors are widely used due to their rugged, robust and easy to care features. Since they are heavily used in industry, testing of three phase induction motors have play a vital role. In order to determine motor equivalent circuit parameters, efficiency of motor, squirrel caged laboratory sized an induction motor test setup is prepared. It is suitable for the induction motor with the frame size of 100 and 112. A virtual Instrumentation typed engineering workbench (called as LabVIEW) software packet, is utilized as a graphical user interface program. Motor input power is measured by measuring the input voltage, current and power factor with the help of hall effect typed voltage and current transformers. Also, the output power is measured by measuring the speed and torque with the help of an encoder and torque sensor. All outputs of the voltage and current transformer, encoder and temperature, torque sensors are given to the Data Acquisition Card (DAQ) which acquires the data for processing and then the equivalent circuit parameters, efficiency, performance and loading characteristics are found out, using LabVIEW based user interface. It is suggested to use this test rig for the quality control of produced motors in industry, and an educational experiment setup in the school laboratories.

• ETRI Journal
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• v.34 no.5
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• pp.655-665
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• 2012

Based on wideband precoding (WBP) in the multiple-input multiple-output orthogonal frequency division multiplexing system, an adaptive nonuniform codebook is presented in this paper. The relationship between the precoder distribution and spatial correlation is analyzed at first. A closed-form expression based on overlapped isosceles triangles is proposed as an approximation of the precoder distribution. Then, the adaptive codebook design is derived with the approximate distribution to minimize quantization errors. The capacity and bit error rate performance demonstrate that the adaptive codebook with WBP outperforms the conventional fixed uniform codebook.