• Journal of the Korean Society of Hazard Mitigation
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• v.7 no.4
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• pp.59-66
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• 2007

The bridge crossing river is the one of the major factors causing backwater level rising. Furthermore, the bridges in the mountainous areas increase the flood damage in the upstream of the bridge due to the blockage by debris. In this research, the effects of debris to the magnitude of flood damage in the study river basin were simulated by using HEC-RAS and HEC-GeoRAS models. With assumption that the backwater caused by debris blocking the space between bridge piers is the only factor causing inundation, the unsteady flow simulation was carried out with various case studies. The potential inundation area with the overflow locations and volumes could be estimated as the results of simulation. However, the simulation results also reveal the limitations of inaccurate estimation of inundation area and depth. To overcome these hindrances, DEM and satellite images were applied to the simulation. By readjusting the inundation area using digital maps and satellite images and calibrating overflow volume and depth using DEM, the accuracy of simulation could be increased resulting more accurate flood damage estimation.

• Geomechanics and Engineering
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• v.12 no.6
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• pp.1003-1020
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• 2017

Estimation of groundwater inflow into underground opening is of critical importance for the design and construction of underground structures. Groundwater inflow into a pilot underground storage facility in China was estimated using analytical equations, numerical modeling and field measurement. The applicability of analytical and numerical methods was examined by comparing the estimated and measured results. Field geological investigation indicated that in local scale the high groundwater inflows are associated with the appearance of open joints, fractured zone or dykes induced by shear and/or tensile tectonic stresses. It was found that 8 groundwater inflow spots with high inflow rates account for about 82% of the total rate for the 9 caverns. On the prediction of the magnitude of groundwater inflow rate, it was found that could both (Finite Element Method) FEM and (Discrete Element Method) DEM perform better than analytical equations, due to the fact that in analytical equations simplified assumptions were adopted. However, on the prediction of the spatial distribution estimation of groundwater inflow, both analytical and numerical methods failed to predict at the present state. Nevertheless, numerical simulations would prevail over analytical methods to predict the distribution if more details in the simulations were taken into consideration.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.3
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• pp.95-103
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• 2008

Knowledge of expected losses in terms of physical, economic, and social damages due to a potential earthquake will be helpful in the effort to mitigate seismic hazards. In this study, losses due to a magnitude 6.7 scenario earthquake in the Gyeongju area have been estimated using the deterministic method in HAZUS. The attenuation relation proposed by Sadigh et al.(1997) for site classes B, C, and D, which are assumed to represent the characteristics of the strong-motion attenuation in the Korean Peninsula, has been applied. Losses due to the hypothetical earthquake have been also calculated using other attenuation relationships to examine their roles in the loss estimation. The findings indicate differences among the estimates based on various attenuation relationships. Estimated losses of the Gyeongju area by a scenario earthquake using HAZUS should be seriously considered in the planning of disaster response and hazard mitigation.

• Journal of the Earthquake Engineering Society of Korea
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• v.20 no.6
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• pp.391-400
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• 2016

For earthquake loss estimation of building structures in Gangnam-Gu district in Seoul, three scenario earthquakes were selected by comparison of the response spectra of these scenario earthquakes with the design spectrum in Korean Building Code (KBC 2009), and then direct losses of the building structures in the Gangnam-Gu district under each scenario earthquake are estimated. The following conclusions are drawn from the results of damage and loss in the second scenario earthquake, which has a magnitude = 6.5 and epicentral distance =15 km: (1) The ratio of building stocks undergoing the extensive and complete damage level is 40.0% of the total. (2) The amount of direct economic losses appears approximately 19 trillion won, which is 1.2% of the national GDP of Korea. (3) About 25% of high-rise (over 10-story) RC building wall structures, were inflicted with the damage exceeding moderate level, when compared to 60% of low-rise building structures. (4) From the economical view point, the main loss, approximately 50%, was caused by the damage in the high-rise RC wall building structures.

• Nuclear Engineering and Technology
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• v.54 no.12
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• pp.4636-4643
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• 2022

A time-of-flight and energy (TOF-E) detection system for the measurement of ²³⁶U accelerator mass spectrometry (AMS) has been developed to improve the ²³⁶U/²³⁸U sensitivity at Micro Analysis Laboratory, Tandem accelerator (MALT), The University of Tokyo. With observing TOF distribution of ²³⁵U, ²³⁶U and ²³⁸U, this TOF-E detection system has clearly separated ²³⁶U from the interference of ²³⁵U and ²³⁸U when measuring three kinds of uranium standards. In addition, we have developed a novel method combining kernel-based density estimation method and multi-Gaussian fitting method to estimate the ²³⁶U/²³⁸U sensitivity of the TOF-E detection system. Using this new estimation method, 3.4 × 10^-12 of ²³⁶U/²³⁸U sensitivity and 1.9 ns of time resolution are obtained. ²³⁶U/²³⁸U sensitivity of TOF-E detection system has improved two orders of magnitude better than that of previous gas ionization chamber. Moreover, unknown species other than uranium isotopes were also observed in the measurement of a surface soil sample, which has demonstrated that TOF-E detection system has a higher sensitivity in particle identification. With its high sensibility in mass determination, this TOF-E detection system could also be used in other heavy isotope AMS.

• Journal of Mechanical Science and Technology
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• v.16 no.11
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• pp.1367-1378
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• 2002

This paper investigates observability properties of strapdown INS aided by a GPS antenna array. The motivation to consider a GPS antenna array is that the lever-arms between the GPS antennas and IMU play an important role in the estimation of vehicle attitude and biases of IMU. It is shown that time-invariant INS error models are observable with measurements from at least three GPS antennas. It is also shown that time-varying error models are instantaneously observable with measurements from three antennas. Numerical simulation results are given to show the effectiveness of multiple GPS antennas on estimating vehicle attitude and biases of IMU when IMU has considerable magnitude of biases.

• The Journal of Information Technology
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• v.8 no.1
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• pp.63-81
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• 2005

The purpose of this study is primarily to analyse empirically the productivity effects of worker participation in capital by Korean employee stock ownership plan that had taken newly effect on and after January 1,2002, and secondarily to examine the impact of unionization on productivity. The analysis data are those of 150 firms that listed or registered on the stock market, and introduced ESOP. The result of this study can be summarized as follows. First, the worker participation in capitia have significantly a positive effect on productivity, but the magnitude of those effects vary according to estimation models and sectors. The elasticity of stock share owned by employees on productivity is from 0.03 to 0.24. Second, there is no unitary relationship between unionization and productivity. The coefficients of union dummy variable are positive or negative according to models and sectors as well as insignificant.

• Proceedings of the ESK Conference
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• 1998.04a
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• pp.36-39
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• 1998

In this study, the postural stresses in automobile assembly tasks were evaluated through an experiment. We had 19 subjects who simulated 42 different working postures occuring in the automobile assembly tasks for1 min and rated their whole body discomforts subjectively. We sued a free modulus magnitude estimation technique, commonly used as a psycophysical rating technique, and fully trained the subjects for the technique. The postures were selected through the analysis of the characteristics of te automobile assembly tasks and the expected difficulties. The subjective discomfort rating data were normalized by min-max standardization method. The consistency of the rating data was guaranteed by the analysis of spear man rank-order. The postures were ranked on their ratings and the relationships between the whole body discomfort ratings, and joint discomfort ratings were analysed. It is expected taht a system for evaluating postural stresses, which was specific to automobile assembly tasks, can be developed based on the relationship and can also be expended to a general purpose system with a minor modification.

• Journal of Institute of Control, Robotics and Systems
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• v.5 no.4
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• pp.462-470
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• 1999

In this paper, we proposed a cross-couple controller for compensating nonlinear friction of the X-Y table of CNC machines. Due to the nonlinearity of the frictions, large contour errors, referred to as quadrant glitches, occur when each axis of the X-Y table makes a zero velocity crossing. To reduce the quadrant glitches the friction compensators and nonlinear friction observers for estimating Coulomb frictions are employed in the proposed method. A hyperbolic tangent function is used in reducing the magnitude of quadrant glitches and the CEM (Contour Error Model) is utilized for the estimation of the velocities. The performance of the proposed compensators is evaluated for several trajectories by computer simulations.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.65-68
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• 2003

This paper presents a design and construction of IIR multiple notch filter by modifying the pole-zero placement with least square estimation to find the appropriate gain and pole positions for the filter within a unit circle in z-plane. The appropriated gain and pole position will render the controllable unit gain of filter magnitude. Algorithm design and system simulation are performed on MATLAB while the actual implementation is done on the TMS320C31 digital signal processing board.