• The KIPS Transactions:PartC
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• v.19C no.4
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• pp.239-246
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• 2012

The function of location estimation in WPAN has been studied and specified on the ultra wide band optionally. But the devices based on CSS(Chirp Spread Spectrum) specification has been used widely in the market because of its functionality, cheapness and support of development. As the CSS device uses 2.4GHz for a carrier frequency and the sampling frequency is lower than that of the UWB, the resolution of a timestamp is very coarse. Then actually the error of a measured distance is very large about 30cm~1m at 10 m depart. And the location error in ($10m{\times}10m$) environment is known as about 1m~2m. So for some applications which require more accurate location information, it is very natural and important to develop a sophisticated post processing algorithm after distance measurements. In this paper, we have studied extended Kalman filter with the frequency offsets of anchor nodes, and proposed a novel algorithm frequency offset compensated extended Kalman filter. The frequency offsets are composed with a variable as a common frequency offset and constants as individual frequency offsets. The proposed algorithm shows that the accurate location estimation, less than 10cm distance error, with CSS WPAN nodes is possible practically.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.53 no.10
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• pp.542-549
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• 2004

The conventional fault location algorithms based on the travelling waves have an inherent problem. In cases of the close-up faults occurring near the relaying point and of the faults having zero degree inception angle of voltage signals, the conventional algorithms can not estimate an accurate fault distance. It is because the shapes of travelling waves are near sinusoidal in those cases. A new method solving this problem is presented in this paper. An FIR(Finite Impulse response) filter which makes high frequency components prominent and makes the power frequency component and dc-offset attenuated is used. With this method, the cross-correlation peak is to be very clear when a close-up fault or a fault having near zero-degree inception angle occurs. The cross-correlation peaks can be clearly distinguished and accurate fault location is practically possible consequently. A series of simulation studies using EMTP(Electromagnetic Transients Program) show that the proposed algorithm can calculate an accurate fault distance having maximum 2% or less error.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.459-463
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• 2003

A circularly polarized microstrip patch antenna (MPA) using electromagnetic (EM) coupled fed method is analyzed in view of the two types of coupling mechanisms viz. cavity and parasitic type, proposed earlier. The patch-ground plane distance is varied in order to achieve the fore-mentioned types of couplings. For each case of patch-ground plane distance, the offset position of feedline is optimized for perfect matching and the boresight axial ratio (AR) is observed. It is seen that CP operation is possible only for cavity-type coupling (smaller patch-ground plane distances). The simulated results for the boresight AR for the two types of coupling mechanisms are presented.

• Proceedings of the KIEE Conference
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• 1993.07a
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• pp.180-182
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• 1993

A distance protection algorithm for detecting faults at power transmission lines is presented in this paper. The algorithm is based on the differential equation related to the voltage and the current at an equivalent circuit of a transmission line which is composed of the lumped resistance and inductance. The presented integration method has high performance at though the fault voltage and the current are heavily distorted with the DC offset and harmonics which occurred at transient states after faults.

• Journal of Dental Rehabilitation and Applied Science
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• v.20 no.2
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• pp.71-81
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• 2004

The purpose of this study was to compare the distributing pattern of stress on the finite element models of two units implant prosthesis with one angulated placement of two implant fixtures. The two unit implant crowns simulated to mandibular first and second molars were made. The two kinds of finite element models were designed according to angulation of fixture ($4.0mm{\times}11.5mm$) : Model 1($15^{\circ}$ buccally angulated placement of one fixture on second molar area), Model 2($15^{\circ}$ lingually angulated placement of one fixture on second molar area). Axial loads of 200N were applied to the center of central fossa and to distance of 2mm and 4mm apart from the center of central fossa. Von-Mises stresses were recorded and compared in the fixtures, and buccolingual section of implants. The results were as follows: 1. Under axial loading at the central fossa, the stress was distributed along the straight fixture except apical portion, while on buccally or lingually angulated placement, the highest stresses were concentrated in the neck portion on the opposite side of the angulated fixture. 2. With offset distance increasing, the stresses were concentrated greater in buccal neck of lingually angulated fixture than in lingual neck of buccally angulated fixture. From the above results, in designing of the occlusal scheme for implant prosthesis with the angulated fixture, occlusal contacts should be placed to distribute stress axially in maximum intercuspation and to avoid offset force during eccentric movements.

• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.3
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• pp.189-204
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• 2015

This paper presents the results of reduced scale model tests on the effect of fault zone characteristics on the tunnel deformation behavior. A series of model tests were carried out on deep tunnels considering different fault zone orientations and offset distance. The tunnelling process was simulated in the model tests using compressed air technique. During the tests, the tunnel and ground deformation were mainly monitored while reducing the pressure inside the tunnel and the relationship between the pressure level and the tunnel deformation were established. The results indicate that for a given offset distance the tunnel behavior is influenced the most when the fault zone dips vertically while smallest influence occurs when the fault zone dips 45 degrees.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.192-194
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• 2002

We present the results on the calibration of iso-center positions using the quality assurance system established at PMRC for determination of center position in X-ray and proton irradiation fields. Details on the system are presented in another presentation in this session. The equipment in the system is mounted on a patient treatment bed in each proton exposure room, G1 or G2. A center of a stainless ball on the equipment is set at a cross of laser markers located around the iso-center and fixed on the room and on the snout in the gantry. A proton beam or an X-ray beam is exposed onto the ball through a brass collimator of 100 mm ${\times}$ 100 mm and projected onto the imaging plate set at I cm behind the ball. On the axis perpendicular to the thrust axis of the gantry on the imaging plate, a distance between a center of the collimator image and a center of the ball image varies as a cosine function of gantry angles unless the ball is set on the iso-center. An amplitude of the cosine curve shows the distance between the ball and the iso-center, an offset the offset of the collimator, and a phase shift at a zero crossing point the ball direction viewed from the iso-center. We present the relation among the iso-center position, the laser maker position, and the center of proton and X-ray irradiation fields. Its stability and its reproducibility are discussed.

• International Journal of Highway Engineering
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• v.19 no.5
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• pp.59-68
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• 2017

PURPOSES : The objective of this study is to evaluate the potential risk level of road cave-ins due to subsurface cavities based on the deflection basin measured with falling weight deflectometer (FWD) tests. METHODS: Ground penetrating radar (GPR) tests were conducted to detect road cavities. Then FWD tests were conducted on 13 pavement test sections with and without a cavity. FWD deflections and a deflection ratio was used to evaluate the effect of geometry of the cavity and pavement for road cave-in potentials. RESULTS : FWD deflection of cavity sections measured at 60 cm or a closer offset distance to a loading center were 50% greater than more robust sections. The average deflection ratio of the cavity sections to robust sections were 1.78 for high risk level cavities, 1.51 for medium risk level cavities, and 1.16 for low risk level cavities. The relative remaining service life of pavement with a cavity evaluated with an surface curvature index (SCI) was 8.1% for the high level, 21.8% for the medium level, and 89.8% compared to pavement without a cavity. CONCLUSIONS : FWD tests can be applied to detect a subsurface cavity by comparing FWD deflections with and without a cavity measured at 60 cm or a closer offset distance to loading center. In addition, the relative remaining service life of cavity sections based on the SCI can used to evaluate road cave-in potentials.

• Journal of the Korean Geotechnical Society
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• v.21 no.10
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• pp.49-60
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• 2005

This paper presents the results of an investigation on the effects of design variables on the behavior of geosynthetic-reinforced modular block walls in a tiered arrangement using the finite-element method of numerical analysis. A parametric study was performed by varying the offset distance between the tiers and reinforcement length of the lower and upper tier using verified finite-element model. The finite-element analysis provided relevant information on the mechanical behavior of the tier wall and interaction mechanism between the upper and lower tier, which was otherwise difficult to obtain from the limit-equilibrium analysis based current design approaches. Practical implications of the findings obtained from this study in the current design approaches are discussed in great detail.

• Journal of the Korean Geotechnical Society
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• v.18 no.3
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• pp.61-72
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• 2002

This paper presents the results of investigation on the behavior of soil-reinforced segmental retaining walls in tiered arrangement using the finite element method of analysis. 2D finite element analyses were performed on tiered walls with two levels of offset distance. Cases with equivalent surcharge as suggested by the NCMA design guideline were additionally analyzed in an attempt to confirm the appropriateness of the equivalent surcharge model adopted by NCMA. Deformation characteristics of a tiered wall with small offset distance suggest a compound mode of failure and support current design approaches requiring a global slope stability analysis for design. Also revealed is that the interaction between the upper and lower walls significantly affects not only the performance of the lower wall but also the upper wall, suggesting that the upper walls should also be designed with due consideration of the interaction.