• International Journal of High-Rise Buildings
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• v.3 no.1
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• pp.81-87
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• 2014

The use of Buckling Restrained Braces (BRB) for enhancing the performance of the buildings is gaining wider acceptance. This paper presents the first application of these devices in a major high-rise building in the Philippines. A 50-storey residential reinforced concrete building tower, with ductile core wall, with BRB system is investigated. The detailed modeling and design procedure of buckling restrained brace system is presented for the optimal design against the two distinct levels of earthquake ground motions; serviceable behavior for frequent earthquakes and very low probability of collapse under extremely rare earthquakes. The stiffness and strength of the buckling restrained brace system are adjusted to optimize the performance of the structural system under different levels of earthquakes. Response spectrum analysis is conducted for Design Basis Earthquake level and Service level, while nonlinear time history analysis is performed for the most credible earthquake. The case study results show the effectiveness of buckling restrained braces.

• Journal of the Korean Ceramic Society
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• v.45 no.10
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• pp.625-630
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• 2008

In the bone cement composed of dense granules of $\beta-Ca_3(PO_4){_2}(\beta-TCP)$ and $Ca(H_2PO_4){_2}H_2O$, the compressive strength, setting time and temperature rise were measured to observe the degradation of cement with respect to the stored days before setting. Decreases of compressive strength and temperature rise were observed, while setting time increased with respect to the stored days. The similar trends were repeated with the increase of temperature of storage. Such a change virtually meant the fading of the character of cement and it took place only when the two starting materials were mixed during storage. The degradation could be mitigated taking advantage of granular $\beta$-TCP instead of powdery one. The formation of $CaHPO_4$, which resulted from reaction with ambient humidity, was attributed to the degradation observed during storage. Dependence of the degradation behavior on mixing and temperature during storage was discussed in terms of the driving force for reaction of cement.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.5
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• pp.30-37
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• 2004

This paper presents the thermal characteristic analysis of a high-speed horizontal machining center with spindle speed of 50,000rpm and feedrate of 120m／min. The spindle system is designed based on the built-in motor, angular contact ceramic ball bearings, oil-air lubrication and oil-jacket cooling method. The X-axis and Y-axis feeding systems are composed of the linear motors and linear motion guides, and the Z-axis feeding system is composed of the servo-motor, ball screw and linear motion guides. The thermal characteristics such as the temperature distribution, temperature rise, thermal deformation and step response, are estimated based on the finite element model of machining center and the heat generation rates of heat sources related to the machine operation conditions. Especially, the thermal time constant assessed from the step response function is introduced as an index of thermal response characteristics.

• Earthquakes and Structures
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• v.17 no.6
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• pp.623-633
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• 2019

A large number of available concrete buildings designed only considering gravity load that require seismic rehabilitation because of failure to meet plasticity criteria. Using steel bracings are a common type of seismic rehabilitation. The eccentric bracings with vertical link reduce non-elastic deformation imposed on concrete members as well as elimination of probable buckling problems of bracings. In this study, three concrete frames of 10, 15, and 20 stories designed only for gravity load have been considered for seismic improvement using performance-based plastic design. Afterwards, nonlinear time series analysis was employed to evaluate seismic behavior of the models in two modes including before and after rehabilitation. The results revealed that shear link can yield desirable performance with the least time, cost and number of bracings of concrete frames. Also, it was found that the seismic rehabilitation can reduce maximum relative displacement in the middle stories about 40 to 80 percent. Generally, findings of this study demonstrated that the eccentric bracing with vertical link can be employed as a suitable proxy to achieve better seismic performance for existing high rise concrete frames.

• Korean Journal of Optics and Photonics
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• v.8 no.5
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• pp.410-414
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• 1997

Laser projection display is a full color display system for large area. In this system, laser beams are modulated at acousto optic modulators(AOM) according to the video signal. AOM consists of a $TeO_2$ crystal and a $LiNbO_3$ transducer. We calculated the acoustic wave propagating from transducer to acousto optic media and made AOM by the calculated results. We compared calculated results with fabricated AOM by measuring modulation efficiency at various frequency. The modulation efficiency of AOM is 85% at the carrier frequency of 144MHz and the rise time is 41.5 ns.

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1864-1866
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• 1996

Grounding is the art of making an electrical connection to the earth. In order to protect man, electrical and/or electric equipments from the lightning strokes, all the energy of lightning strokes must be diverted via a safe path to earth. It is essential to the transient grounding resistance against lightning strokes. In this paper, measurements and analyses of grounding surge impedance have been investigated. For measurements of grounding surge impedance the pulse generator was designed and fabricated. The pulse generator has rise time of 22.4 ns and pulse duration of $8\;{\mu}s$. The transient grounding resistance has been measuring by injecting low power and step current between the earthing system under test and a remote reference earth and measuring the potential rise caused by this current. As a result, the transient grounding resistance against lightning surge in the short time domain is much higher than steady state grounding resistance.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.32 no.5
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• pp.164-169
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• 1983

A method to control the luminous colour of a gaseous discharge tube has been investigated by using the saw-tooth wave of which rise-time was controlled by an electronic circuit. The luminous colour of a Ne - Hg lamp was changed from red to blue continuously and vice versa, and it's luminous characteristics are as follows: (a) With D.C. potentials, it showed blue colour and the relative intensity of the colour is increased first and saturated at about 17 mA as the discharge current is increased. (b) When the rise-time of the saw-tooth wave is about 10 $\mu\textrm{s}$, the red colour which is caused by Ne - excitation is dominant, and when about 200 $\mu\textrm{s}$, only the blue colour which is caused by Hg - excitation is shown. (c) With saw-tooth pulse, the relative intensity of blue is increased similarly as that with D.C. potential as the current peak of each pulse is increased, while that of red is increasing continuously and it's intensity shows about twice than blue. (d) The spectrum of red colour contains Ne - excitation lines and Hg - blue lines, but the apparent luminous colour is red because Ne - red lines are more plenty than Hg-blue lines. The spectrum of blue colour presents only Hg-blre lines.

• Journal of Biosystems Engineering
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• v.29 no.3
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• pp.261-266
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• 2004

This study was Performed to classify the acoustic emission(AE) signal due to surface cracking and moisture movement in the flat-sawn boards of oak(Quercus Variablilis) during drying using the principal component analysis(PCA) and artificial neural network(ANN). To reduce the multicollinearity among AE parameters such as peak amplitude, ring-down count event duration, ring-down count divided by event duration, energy, rise time, and peak amplitude divided by rise time and to extract the significant AE parameters, correlation analysis was performed. Over 96 of the variance of AE parameters could be accounted for by the first and second principal components. An ANN analysis was successfully used to classify the Af signals into two patterns. The ANN classifier based on PCA appeared to be a promising tool to classify the AE signals from wood drying.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2001.10a
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• pp.3-10
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• 2001

The box system that is composed only of reinforced concrete walls and slabs are adopted on many high-rise apartment buildings recently constructed in Korea. And the framed structure with shear wall core that can effectively resist horizontal forces is frequently adopted for the structural system for high-rise building structures. In these structures, a shear wall may have one or more openings for functional reasons. It is necessary to use subdivided finite elements for accurate analysis of the shear wall with openings. But it would take tremendous amount of computational time and memory if the entire building structure is subdivided into a finer mesh . An efficient analysis method that can be used regardless of the number, size and location of openings is proposed in this study, The analysis method uses super element, substructure, matrix condensation technique and fictitious beam technique. Three-dimensional analyses of the box system and the framed structure with shear wall core having various types of openings were performed to verify the efficiency of the proposed method. It was confirmed that the proposed method have outstanding accuracy with drastically reduced time and computer memory from the analyses of example structures.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.11a
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• pp.469-472
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• 2002

We made ESD tester to measure ESD threshold voltage of semiconductor devices. The HBM ESD test is the most popular method to measure the ESD threshold voltage of MMIC. We use flyback method which is one of the DC-DC converter to get high ESD voltage. With flyback method, we can isolate the low voltage part from the high voltage part of HBM ESD tester. We use an air gap of the relay which is used for switch to satisfy the rise time of ESD standard(MIL-STll-883D). As a result, with the flyback method and the air gap of relay, we can make ESD tester whose parasitic components are minimized.