• Proceedings of the Korea Concrete Institute Conference
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• 1993.04a
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• pp.148-153
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• 1993

The paper presents the results of shaking table test conducted on the 1/3.3 scaled large concrete panel model. The behaviors of large concrete panel structures subjected to seismic excitations are controlled by capacity of horizontal and vertical joints. To Study the seismic capacity of the large concrete panel structures, experimental researches for joints and structural assemblage are needed. Especially, since the magnitude of seismic loads are depended on the variation of time, period and accelerations, dynamic test is needed for estimating the seismic resistance of large concrete panel structures. The objective of this paper is to study the behaviors of large concrete panel structures on seismic excitations and to estimate the safety. Test results are as follows : 1) Test model was critically damaged in the first floor horizontal joint by rocking. 2) Elastic limit(0.12kg) of test model was 5times higher than that of korean seismic design code. 3) Maxium base shear of test model at the ground acceleration of 0.12g was 3.5 times higher than the result of equivalent static analysis. 4) Damping ratio of test model turned out 3.9~5.3% and the period at 0.12g was 0.065sec.

• The korean journal of orthodontics
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• v.19 no.1 s.27
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• pp.219-243
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• 1989

The purpose of this study was to evaluate the effects of the chincap therapy on the craniofacial structure in persons with skeletal Class III malocclusion. The patients selected for this study were treated with extra-oral chincap therapy only. Both control and treatment samples were obtained from Seoul National University Hospital where these longitudinal data were gathered. 55 treated patients and 14 control patients were studied. The mean ages at the 1st evaluation was 8 years 3 months in the treatment sample and 9 years 4 months in the control sample. The duration of chincap therapy was variable but averaged 2 years of treatment. Post-treatment observation procedeeded for 1 year 2 months. Active treatment and post treatment effects were evaluated. The results were as follows: 1. Neither significant restraint nor acceleration of growth was found in the cranial base and maxilla during treatment. 2. A distal rotation of the mandibular complex was seen. 3. Some amount of restraint of growth was found in mandibular body length, ramus height, mandibular length during treatment. 4. The genial angle was reduced. 5. After removal of the chin-cap, forward displacement of the mandible took place.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.1 s.178
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• pp.113-120
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• 2006

This paper proposed the control algorithm fur aspheric surface grinding and was verified by the experiment. The functions of the algorithm were simultaneous control of the position and interpolation of the aspheric curve. The non-linear formula of the tool position was derived from the aspheric equations and the shape of the tool. The function was partitioned by an certain interval and the control parameters were calculated at each control section. The movement in a session was interpolated with acceleration and velocity. The position error was feed-backed by rotary encorder. The concept of feedback algorithm was correcting position error by increasing or decreasing the speed. In the experiment, two-axis machine was controlled to track the aspheric surface by the proposed algorithm. The effect of the control and process parameters was monitored. The result showed that the maximum tracking error was under sub-micro level for the concave and convex surfaces.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.4
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• pp.853-871
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• 2012

The location based service is divided into GPS that uses the artificial satellite or base transceiver station in order to cover the wide area and RTLS(Real Time Location System) using the Zigbee, RFID, CSS(Chirp Spread Spectrum), UWB, Bluetooth and Wi-Fi equipment in the space(close range) limited like the building inside or park. Moreover it also repeats the technical development upon through the acceleration of the development of the wire and wireless infrastructure and determination technology, the development of the Internet, diversification of the contents, and etc. As a result, it is expected to develop around the determination technology, witch is common core technology element, contents technology, Internet and mobile communication technology, and etc. afterward. In this research, the direction we investigate was to find and analyze new technology and standardization trend of LBS in order to contribute to the related industry.

• Journal of Korean Neurosurgical Society
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• v.49 no.1
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• pp.49-52
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• 2011

Traumatic intracranial aneurysms are rare, comprising 1% or less of all cerebral aneurysms. The majority of these aneurysms arise at the skull base or in the distal anterior and middle cerebral arteries or their branches following direct mural injury or acceleration-induced shearing force. We present a 50-year-old patient in whom subarachnoid hemorrhage (SAH) was developed as a result of traumatic aneurysm rupture after a closed craniofacial injury. Through careful evaluation of the three-dimensional computed tomography and conventional angiographies, the possible mechanism of the traumatic internal carotid artery trunk aneurysm is correlated with a hit injury by the bony protuberances on the anterior and posterior clinoid processes. This traumatic aneurysm was successfully obliterated with clipping and wrapping technique. The possibility of a traumatic intracranial aneurysm should be considered when patient with SAH demonstrates bony protuberances on the clinoid process as a traumatic aneurysm may result from mechanical injury by the sharp bony edges.

• Structural Engineering and Mechanics
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• v.17 no.3_4
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• pp.331-346
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• 2004

A new sensor system is proposed for measuring damage indexes. The damage index is a physical value that is well correlated to a critical damage in a device or a structure. The mechanism proposed here utilizes elastic buckling of a thin wire and does not require any external power supply for memorizing the index. The mechanisms to detect peak strain, peak displacement, peak acceleration and cumulative deformation as examples of damage indexes are presented. Furthermore, passive and active wireless data retrieval mechanisms using electromagnetic induction are proposed. The passive wireless system is achieved by forming a closed LC circuit to oscillate at its natural frequency. The active wireless sensor can transmit the data much further than the passive system at the sacrifice of slightly complicated electric circuit for the sensor. For wireless data retrieval, no wire is needed for the sensor to supply electrical power. For the active system, electrical power is supplied to the sensor by radio waves emitted from the retrieval system. Thus, external power supply is only needed for the retrieval system when the retrieval becomes necessary. Theoretical and experimental studies to show excellent performance of the proposed sensor are presented. Finally, a prototype damage index sensor installed into a 7 storey base-isolated building is explained.

• Tribology and Lubricants
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• v.30 no.1
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• pp.21-28
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• 2014

Damage to the cylinder liner of large ship engines, such as scuffing on the surface, can occur very easily because it is operated in a corrosive environment. This scuffing may be due to oil film destruction and corrosive wear caused by water and sulfur included in the fuel, abrasive impurities, and poor lubricants. Thus, a method for monitoring the condition and diagnosing the failure of the cylinder liner and piston ring is needed. In this study, a reciprocating friction and wear test was carried out with a cast iron specimen, which simulated an engine cylinder in a corrosive atmosphere. The lubricants used were base oil, stirred oil with distilled water, a NaCl solution, and dilute sulfuric acid. The friction coefficient and frequency spectrum were measured using a load cell and acceleration sense in each experimental condition. We then used these results to diagnose the failure of the cylinder liner.

• Journal of the Earthquake Engineering Society of Korea
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• v.2 no.3
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• pp.87-98
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• 1998

In this paper, the potential ground motion in terms of the peak ground accelerations(PGAs) due to long-distance Sumatra earthquakes is investigated for Singapore, following the probabilistic seismic hazard assessment a, pp.oach. The case investigated differs from a conventional one, in that few attenuation equations for long-distance major earthquakes are readily available. The attenuation relationships developed for other regions of the world are thus reviewed. It is found that the existing attenuation equations, when extrapolated to distant major earthquakes, tend to underestimate the PGAs. By comparing with the PGAs recorded over long distances at stations of the Japanese Meteorological Agency for major earthquakes in Japan, an attenuation equation is chosen for this study. With the chosen attenuation equation, the probability of PGAs exceeding selected levels for various exposure periods of time is then computed. The results show that at Singapore there is a 10% probability in 50 years for the PGA at rock sites to exceed 1.1% g. In view of the results and the associated uncertainties, a base shear coefficient of 1.5% is being recommended as the tentative seismic loading in Singapore. The tentative seismic loading reflects the design value of the notional horizontal load, equal to 1.5% of the characteristic building weigh as specified in the BS code, which usualy governs the design of most buildings in Singapors.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.3
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• pp.23-30
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• 2003

The seismic base isolation design approach has been reviewed and modified to fit the nonlinear static analysis procedure for determination of the performance point of structures in a simpler way, such an adaptation may be possible for the fact that a structural system under development of damage due to earthquake loading keeps softening to result in period shifting toward longer side. The superiority of the proposed method to the state-of-the-practice approach is that the reasonably accurate performance point can be obtained without constructing the so-called acceleration displacement response spectrum required in application of capacity spectrum method. The validity of the proposed approach was verified by comparing the predicted values to the exact ones presented in the literature.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.04a
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• pp.401-406
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• 2013

This paper presents experimental evaluation of IRE (isolation roller bearing) seismic isolation device. From the combination of base isolation on the IRE system displacement response spectrum and acceleration response spectrum, the compressive strength and the coefficient of friction experiments. Also the IRE system is evaluated by environment test according to KS standards. Both the resonance and seismic experiments using a combination of the IRE and Natural Rubber Bearing (NRB) are performed in order to analyze the seismic isolation of the IRE system dynamic characteristics. For the given load and exciting frequency, the resonant frequency becomes lower, but the resonant magnification remains to be same. However, it is shown that when we consider the IRE only, the vibration on the table with the horizontal movement and the independent horizontal displacement due to the rolling motion of the plate and roller are significantly reduced. This result verifies that the proposed optimal design method of the IRE system is very effective.