• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.26 no.4
• /
• pp.374-380
• /
• 2015

With explosion of wireless traffic it is required to further investigate the technologies on acquiring available spectrum resources and on sharing frequency with existing users. In 3GPP, it is started to study on feasibility and functional requirement of LTE standard in order to extend cellular services offered on only licensed band to 5 GHz unlicensed band. Operating scenario on LTE in unlicensed band is focused on carrier aggregation with licensed band, and the coexistence with Wi-Fi services in 5 GHz band is concerned as a major requirement. For a single global solution framework for licensed assisted access to unlicensed spectrum, listen-before-talk(LBT) mechanism of European regulation for fair access to channel under the coexistence environments is currently examined in 3GPP. In this paper, we evaluate two types of LBT, frame based equipment and load based equipment, with considering LTE carrier aggregation feature and performances of file transferred time and throughput.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.23 no.2
• /
• pp.89-99
• /
• 2019

In order to increase the seismic safety of nuclear power plant (NPP) structures, a technique to reduce the seismic load transmitted to the NPP structure by using a seismic isolation device such as a lead-rubber bearing has recently been actively researched. In seismic design of NPP structures, three directional (two horizontal and one vertical directions) artificial synthetic earthquakes (G0 group) corresponding to the standard design spectrum are generally used. In this study, seismic analysis was performed by using three directional artificial synthetic earthquakes (M0 group) corresponding to the maximum-minimum spectrum reflecting uncertainty of incident direction of earthquake load. The design basis earthquake (DBE) and the beyond design basis earthquakes (BDBEs are equal to 150%, 167%, and 200% DBE) of G0 and M0 earthquake groups were respectively generated for 30 sets and used for the seismic analysis. The purpose of this study is to compare seismic responses and seismic fragility curves of seismically isolated NPP structures subjected to DBE and BDBE. From the seismic fragility curves, the probability of failure of the seismic isolation system when the peak ground acceleration (PGA) is 0.5 g is about 5% for the M0 earthquake group and about 3% for the G0 earthquake group.

• Journal of Biosystems Engineering
• /
• v.34 no.5
• /
• pp.325-330
• /
• 2009

This study was performed to develop accelerated life test methods for agricultural tractor transmission receiving variable load. To acquire parameters for calculation of accelerated life test, endurance tests were performed under different torque conditions. Test results showed that the shape factor of Weibull distribution was 1.5 and fatigue damage exponent was 5.4. The calculated test time was 5,877 hours under the conditions of average life (MTBF) 3,000 hours and 90% reliability for one test sample. According to the linear cumulative damage rule, test time could be reduced using increased test load. Test time could be reduced by 252 hours when 1.2 times of the rated load compared with 0.67 times of the rated equivalent load calculated by load spectrum of the agricultural tractor. Calculated acceleration coefficient was 23.3.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.27 no.6
• /
• pp.501-508
• /
• 2014

In this paper, a method on deducing the capacity spectrum based on nonlinear earthquake response analysis will be introduced. Damage assessment of general building draws the capacity spectrum through the Push-over analysis and the intersection point of capacity spectrum and demand spectrum is seen as performance point. Push-over analysis is the way to perform static analysis by using the equivalent static load changed from the effect of earthquake and predict the behavior of structures by earthquake. But, this method can not be taken into account in the effects of higher mode and the dynamic characteristic. Therefore, in order to calculate the capacity spectrum under dynamic properties of building. A capacity spectrum from going ahead with the nonlinear earthquake response analysis is suggested.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2001.10a
• /
• pp.451-458
• /
• 2001

The structural dynamic responses by wind load consist of alongwind, acrosswind and torsional behavior. Specially, dynamic alongwind response can be obtained from theoretical approach presented by Davenport, Vellozzi and Cohen. Generally the structural dynamic alongwind response can be obtained using the approximate analysis, under the condition that only the first mode shape of the structure is considered and the mode shape is assumed to be a linear function. In this paper, the dynamic alongwind responses are performed by using spectrum of longitudinal velocity fluctuations presented by Davenport and Kaimal, respectively.

• Journal of the Korean Society for Precision Engineering
• /
• v.14 no.6
• /
• pp.22-27
• /
• 1997

In general, the load which acts on the structure is almost independent of time in many locations. In this case. It is difficult to estimate the life with the service load history, because the structure is on the multi- axial and multi-point loading states. In this study, the service load of the excavator which is widely used in industry field was calculated using measured cylinder pressures and displacements. The fatigue life was estimated using the multi-axial and multi-point load counting method. Service load history of 4 pin joint which act independently each other is yielded by mult-axial and multi-point load counting method. The stress spectrum is yielded by superposition of the results of FEM stress analysis applied unit load. Palm- gren-Miner's cumulative Damage is 0.000804 for Von Mises equivalent stress sequence by one side fillet weld S-N curve. This result agress with Bench test results. As a result of this study, the fatigue life esti- mation using the multi-axial and multi-axial and multi-point load counting method is useful.

• Journal of Mechanical Science and Technology
• /
• v.20 no.4
• /
• pp.482-493
• /
• 2006

The carbody structure of a high speed train passing through a tunnel is subjected to pressure fluctuation. Fatigue strength of the carbody structure against the fluctuating pressure loading should be proved in the design stage for safety. In this study, to get the useful information on the pressure fluctuation in the tunnel, measurement has been conducted during test running of KHST on the high speed line for two years. The measured results were analyzed and arranged to be used for carbody design. A prediction method for the magnitude and frequency of pressure change was proposed and the propagating characteristics of pressure wave was investigated. By statistical analysis for the measured results, a pressure loading spectrum for the high speed train was given. The proposed method can also be used to estimate the pressure loading spectrum for new high speed line at design stage combined with the results of train performance simulation.

• Proceedings of the Korean Institute of Intelligent Systems Conference
• /
• 2001.12a
• /
• pp.5-9
• /
• 2001

In this paper, we propose the new audio watermarking method and can be used on line processing. Instead of the wavelet transform, we use the integer wavelet transform for the reduction of the computational load. The watermark associated with the chi-square distribution is inserted into the signal on the integer wavelet domain. When extracting the watermark, the spread spectrum methods are used with the coefficients associated with the covariance sequence. We show that the chi-square distribution is a good tool for the spread spectrum method on the wavelet domain. This watermarking technique may be used for the control of the electrical product which can be controlled with the hidden signals and can be moved according to the audible signals simultaneously.

• Proceedings of the KIPE Conference
• /
• 2004.07a
• /
• pp.283-288
• /
• 2004

In case while modulation index (M) is more than 0.7, the spectrum of motor voltage and current of a conventional two-phase SRP scheme are not reduced considerably. To solve the problems of a conventional two-phase SRP, this paper proposes a two-phase SRP(DZSRP) with double zero vector mode which zero vector is selected as V(111) in case of $M\;\geqq\;0.7$, and zero vector is selected as V(000) if M < 0.7. For the validity of the proposed method, a 16 bit micro-controller C167 was used and the experiments were conducted with the 1.5kw induction motor under load condition. And the experimental results show that the switching noise spectrum for all the M are spread to a wide band area.

• Proceedings of the KIEE Conference
• /
• 2005.10b
• /
• pp.29-31
• /
• 2005

Detection methods for atrial tachycardia and fibrillation on the time axis have the advantages of light operational load and are easy to apply to various applications. Despite these advantages, arrhythmia detection algorithm on the time axis cannot stand much noise such as motion artifacts, moreover the peak detection algorithm has high complexity. In this paper, we use a spectrum analysis method for the detection of atrial tachycardia and fibrillation. By applying spectrum analysis and digital filtering on obtained electrogram signals, we can diagnose heart arrhythmia without using peak detection algorithm.