• Magazine of the Korean Society of Hazard Mitigation
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• v.5 no.4 s.19
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• pp.106-114
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• 2005

• Journal of Communications and Networks
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• v.18 no.2
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• pp.210-217
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• 2016

In this paper, we propose a low complexity multiple-input multiple-output (MIMO) detection algorithm with adaptive interference mitigation in downlink multiuser MIMO (DL MU-MIMO) systems with quantization error of the channel state information (CSI) feedback. In DL MU-MIMO systems using the imperfect precoding matrix caused by quantization error of the CSI feedback, the station receives the desired signal as well as the residual interference signal. Therefore, a complexMIMO detection algorithm with interference mitigation is required for mitigating the residual interference. To reduce the computational complexity, we propose a MIMO detection algorithm with adaptive interference mitigation. The proposed algorithm adaptively mitigates the residual interference by using the maximum likelihood detection (MLD) error criterion (MEC). We derive a theoretical MEC by using the MLD error condition and a practical MEC by approximating the theoretical MEC. In conclusion, the proposed algorithm adaptively performs interference mitigation when satisfying the practical MEC. Simulation results show that the proposed algorithm reduces the computational complexity and has the same performance, compared to the generalized sphere decoder, which always performs interference mitigation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.9
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• pp.5801-5812
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• 2014

The retention basin is a hydraulic structure for flood mitigation by storing river flow over a design flood. In this study, numerical models were adopted to simulate the flood mitigation effects by a retention basin. The large flood condition was applied as a boundary condition to consider an abnormal flood caused by climate change. Furthermore, the two-dimensional numerical model was adopted to regenerate the complex flow pattern due to the topography and lateral flow near the retention basin. The numerical results of the one- and two-dimensional model were analyzed and compared. The results showed that the two-dimensional model is more applicable to assessing flood mitigation by the retention basin with a complex topography and lateral flow patterns.

• Journal of the Korean Society of Hazard Mitigation
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• v.10 no.1
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• pp.103-109
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• 2010

In this study, a three-dimensional non-hydrostatic pressure model based on a normalized vertical coordinate system for free surface flows is presented. To strongly couple the free surface and non-hydrostatic pressure with the momentum equations, a double predictor-corrector method is employed. The study is especially focused on implementing the dynamic boundary condition (a zero pressure condition) at the free surface with ignoring of the atmospheric pressure. It is shown that the boundary condition can be specified easily with a slight modification to existing models.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.3
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• pp.9-17
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• 2009

Most of the current drainage criteria have been developed on the basis of experimental field results and theoretical analyses of infiltration under saturated conditions. The objective of this study is to extend the understanding of pavement drainage systems by considering unsaturated condition in the sublayers. Analyses of unsaturated flows through pavements was performed by running finite element program(SEEP/W) with a range of pavement materials and drainage parameters. Meanwhile, the widely used DRIP program developed by FHWA is based on assumption of saturated condition of pavements. Differences between saturated and unsaturated condition in the sublayers of the pavements are verified. It is verified that for unsaturated conditions time to drain would take longer time compared to saturated condition.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.6
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• pp.67-71
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• 2008

This study is to retest of seoul traffic, all sorts of statistical data, the present condition of urban railway that local government and all sorts of research institution had researched. Even though, or something else with population and regional industrial distribution of seoul with worker and the present condition of the registrated cars and the change of increase, we have predicted the medium term and long-range solution. we have proposed the alternative plan about both of the problem that is the developmental construction direction of seoul urban railway and the resource insurance for urban railway construction.

• Computers and Concrete
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• v.19 no.1
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• pp.111-120
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• 2017

This study aimed to design the accelerated life testing (ALT) of concrete, which stimulating the special natural environment maximumly. Its evaluation indexes, such as dynamic elastic modulus, mass and ultrasonic velocity were measured, and the variation of relative mass and relative dynamic elastic modulus of concrete were studied. Meanwhile, the microanalysis method was used. Moreover, an exploratory application of the stochastic approach, the Weibull distribution and the lognormal distribution, were made to assess the durability of concrete structures. The results show that the ALT for simulating natural environment is more close to the service process of concrete structure under actual conditions; The relative dynamic elastic modulus can be used as the dominant durability evaluation parameters, because it is more sensitive to the environmental factors compared with the relative quality evaluation parameters; In the course of the concrete deterioration, the destruction of the salt freezing cycle is the dominant factor, supplemented by other factors; Both of those two stochastic approaches can be used to evaluate the reliability of concrete specimens under the condition of ALT; By comparison, The lognormal distribution method is better to describe the reliability process.

• Structural Monitoring and Maintenance
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• v.5 no.2
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• pp.313-323
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• 2018

The presence of water inside concrete structures is an essential condition for the deterioration of the structures. The free water in the concrete pores and micro-cracks is the culprit for the durability related problems, such as alkali-aggregate reaction, carbonation, freeze-thaw damage, and corrosion of steel reinforcement. To ensure the integrity and safe operation of the concrete structures, it is very important to monitor water seepage inside the concrete. This paper presents the experimental investigation of water seepage monitoring in a concrete slab using piezoelectric-based smart aggregates. In the experimental setup, an $800mm{\times}800mm{\times}100mm$ concrete slab was fabricated with 15 SAs distributed inside the slab. The water seepage process was monitored through interrogating the SA pairs. In each SA pair, one SA was used as actuator to emit harmonic sine wave, and the other was used as sensor to receive the transmitted stress wave. The amplitudes of the received signals were able to indicate the water seepage process inside the concrete slab.

• Journal of Auto-vehicle Safety Association
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• v.7 no.4
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• pp.16-19
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• 2015

FMVSS226 Ejection Mitigation Impact Test is usually performed by real vehicle. But it is necessary to perform the test using by Reinforced B.I.W. with considering vehicle developing timing and roof rail airbag (RRAB) supplier capacity. We sometimes need tendency (quick data) instead of slow accurate data to fix RRAB design as proper timing. Test with Reinforced B.I.W. is helpful saving time and cost. But it should be confirmed how much different between vehicle conditioned test result and Reinforced B.I.W. conditioned test result. There are some points to be improved even in the test with vehicle. Understanding of deviation of Reinforced B.I.W. conditioned test result from vehicle conditioned test result is needed to get benefits with using Reinforced B.I.W. conditioned in the test.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.4
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• pp.35-41
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• 2019

Contrail is a kind of cloud that is formed during the flight by vapor condensation of engine exhaust in a cold atmospheric condition. Owing to the negative effects of contrails on the environment and in military applications, several studies for contrail mitigation had been performed in developed countries. The goal of this research is to design a lab-scale contrail generator, and to validate the contrail mitigation technology suggested by previous studies. The contrail generator was made using superheated vapor and a low temperature wind tunnel. Using this generator, the ineffectiveness of ethanol and surfactant suggested in the previous paper on contrail mitigation was found experimentally.