• Earthquakes and Structures
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• v.10 no.6
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• pp.1391-1404
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• 2016

Peninsular Malaysia lying on the stable Sunda Plate has traditionally been considered safe with low to moderate seismicity. However, far field Sumatran mega-earthquakes have been shown to be capable of triggering ground motions felt in high rise structures in the major Malaysian cities while seismic impact from local earthquakes of moment magnitude 3.8 have reportedly induced nominal structural damages to nearby buildings. This paper presents an overview of the recent seismic activities in and around Peninsular Malaysia with reference to prominent earthquakes generated by far field interplate and local intraplate sources. Records of ground motion data and seismic hazard assessment (SHA) results available in the literature have been analyzed and discussed. The peak ground acceleration (PGA) values from historical records for few local intraplate events were observed to be higher than those for the events from Sumatran Subduction Zone. This clearly points to the need for a detailed and comprehensive SHA incorporating both far field and local sources. Such an analysis would contribute the knowledge required for secure and reliable infrastructure design and safeguard the Malaysian people and economy.

• Current Optics and Photonics
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• v.6 no.2
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• pp.191-195
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• 2022

We investigate the lateral far-field pattern characteristics, including divergence angle change and far-field pattern analysis as output power increases, of narrow-emitter-width 850 nm GaAs/AlGaAs laser diodes (LDs). Each LD has a cavity of 1200 and 1500 ㎛ and narrow emitter width of 2.4 ㎛ for the top and 4.6 ㎛ for the bottom. The threshold currents are 35 and 40 mA, and L-I kinks appear at power levels of 326 and 403 mW, respectively. The divergence angle tends to increase due to the occurrence of first-order lateral mode and the thermal lensing effect. But with the L-I kink, the divergence angle decreases and the far-field pattern becomes asymmetric. This is due to coherent superposition between the fundamental and the first-order lateral mode. We provide detailed explanations for these observations based on high-power laser diode simulation results.

• Structural Engineering and Mechanics
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• v.1 no.1
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• pp.103-118
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• 1993

The near field is discretized into finite elements, and the far field into infinite elements. Closed form far-field solutions to three fundamental problems are used as the shape functions of the infinite elements. Such infinite elements are capable of transmitting all surface and body waves. An efficient scheme to integrate numerically the stiffness and mass matrices of these elements in presented. Results agree closely with those obtained by others.

• Journal of Ocean Engineering and Technology
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• v.16 no.3
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• pp.8-18
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• 2002

Formulation of the far-field method for the prediction of time-mean hydrodynamic force and moment acting on a 3-D surface-piercing body in waves is reviewed. It is found that the inequality between the weight of the floating body and its buoyancy force permits the replacement of the fluid particles inside the control surface by the fluid particles outside the control surface. Under such circumstances, momentum exchanges across the control surface make the time-mean value of the time rate of the momentum of the fluid inside the control surface non-vanishing. It is a second-order quantity which is hard to calculate by the far-field method. The drift forces and moments on half-immersed ellipsoids are calculated by both the far-field method and the near-field method. The discrepancy between two numerical results is presented and discussed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1752-1761
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• 2000

This paper describes the far-field estimation using the near-field measurement data. Measurement in far-field region gives us the acoustical characteristics of the source but in general measurement is made in near-field such as acoustic water tank or anechoic chamber, so far-field acoustical characteristics of the source should be predicted from near-field data. In this case, the number of measurement points in the near field which relates to the accuracy of the predicted field and the amount of data processing, should be optimized. Existing papers say that measurement points is proportional to kL and depends on geometry and directivity of the source. But they do not give us any definite criterion for the required number of measurement points. Boundary Collocation Method which is one of the far-field prediction methods, is analyzed based on Helmholtz integral equation and Green function and it has been found that the number of measurement points is optimized as 0.54kL which is about one half of the existing results.

• The Journal of the Korea Contents Association
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• v.6 no.2
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• pp.51-58
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• 2006

The enhancement of antenna near-field measurements is obtained using a general probe compensation equation based on the Lorentz reciprocity theorem and reciprocity notation. The probe compensation is an essential process of the near-field to far-field transformations. Applying the equation proposed in this paper to a planar scanning for a rectangular horn antenna shows that our near-field radiation pattern is similar to that of a far-field and our theory is very simple to use and suitable for most practical applications.

• The Journal of the Acoustical Society of Korea
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• v.18 no.6
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• pp.31-37
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• 1999

This paper describes the far-field estimation using the near-field measurement data. Measurement in far-field region gives us the acoustical characteristics of the source but in general measurement is made in near-field such as acoustic water tank or anechoic chamber, so far-field acoustical characteristics of the source should be predicted from near-field data. In this case, the number of measurement points in the near field which relates to the accuracy of the predicted field and the amount of data processing, should be optimized. Existing papers say that measurement points is proportional to kL and depends on geometry and directivity of the source. But they do not give us any definite criterion for the required number of measurement points. Boundary Collocation Method which is one of the far-field prediction methods, is analyzed based on Helmholtz integral equation and Green function and it has been found that the number of measurement points is optimized as 0.54kL which is about one half of the existing results.

• Structural Monitoring and Maintenance
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• v.7 no.4
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• pp.367-392
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• 2020

The specific characteristics of near-field earthquake records can lead to different dynamic responses of bridges compared to far-field records. However, the effect of near-field strong ground motion has often been neglected in the seismic performance assessment of the bridges. Furthermore, damage to horizontally curved multi-frame RC box-girder bridges in the past earthquakes has intensified the potential of seismic vulnerability of these structures due to their distinctive dynamic behavior. Based on the nonlinear time history analyses in OpenSEES, this article, assesses the effects of near-field versus far-field earthquakes on the seismic performance of horizontally curved multi-frame RC box-girder bridges by accounting the vertical component of the earthquake records. Analytical seismic fragility curves have been derived thru considering uncertainties in the earthquake records, material and geometric properties of bridges. The findings indicate that near-field effects reasonably increase the seismic vulnerability in this bridge sub-class. The results pave the way for future regional risk assessments regarding the importance of either including or excluding near-field effects on the seismic performance of horizontally curved bridges.

• Earthquakes and Structures
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• v.18 no.3
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• pp.391-405
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• 2020

The use of passive energy dissipation devices has been widely used in the construction industry to minimize the probability of damage occurred under intense ground motion. In this study, collapse margin ratio (CMR) and fragility curves are the main parameters in the assessment to characterize the collapse safety of the structures. The assessment is done on three types of RC frame structures, incorporating three types of dampers, viscoelastic, friction, and BRB dampers. The Incremental dynamic analyses (IDA) were performed by simulating an array of 20 strong ground motion (SGM) records considering both far-field and near-field seismic scenarios that were followed by fragility curves. With respect to far-field ground motion records, the CMR values of the selected frames indicate to be higher and reachable to safety margin more than those under near-field ground motion records that introduce a high devastating impact on the structures compared to far-field excitations. This implies that the near field impact affects the ground movements at the site by attenuation the direction and causing high-frequency filtration. Besides that, the results show that the viscoelastic damper gives better performance for the structures in terms of reducing the damages compared to the other energy dissipation devices during earthquakes.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.4
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• pp.266-269
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• 2012

The most recently IGBT (insulated gate bipolar mode transistor) devices are in the most current conduction capable devices and designed to the big switching power device. Use this number of the devices are need to high voltage and low on-state voltage drop. And then in this paper design of field stop IGBT is insert N buffer layer structure in NPT planar IGBT and optimization design of field stop IGBT and trench field stop IGBT, both devices have a comparative analysis and reflection of the electrical characteristics. As a simulation result, trench field stop IGBT is electrical characteristics better than field stop IGBT.