• Journal of the Earthquake Engineering Society of Korea
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• 제14권3호
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• pp.31-38
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• 2010

The purpose of this study is to evaluate the seismic performance of gravity-designed post tensioned (PT) flat plate frames with and without slab bottom reinforcement passing through the column. In low and moderate seismic regions, buildings are often designed considering only gravity loads. This study focuses on the seismic performance of gravity load designed PT flat plate frames. For this purpose, 3-, 6- and 9-story PT flat plate frames are designed considering only gravity loads. For reinforced concrete flat plate frames, continuous slab bottom reinforcement (integrity reinforcement) passing through the column should be placed to prevent progressive collapse; however, for the PT flat plate frames, the slab bottom reinforcement is often omitted since the requirement for the slab bottom reinforcement for PT flat plates is not clearly specified in ACI 318-08. This study evaluates the seismic performance of the model frames, which was evaluated by conducting nonlinear time history analyses. For conducting nonlinear time history analyses, six sets of ground motions are used as input ground motions, which represent two different hazard levels (return periods of 475 and 2475 years) and three different locations (Boston, Seattle, and L.A.). This study shows that gravity designed PT flat plate frames have some seismic resistance. In addition, the seismic performance of PT flat plate frames is significantly improved by the placement of slab bottom reinforcement passing through the column.

• Journal of the Korean Crystal Growth and Crystal Technology
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• 제30권4호
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• pp.156-161
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• 2020

Recently, as there has been growing demand for aesthetic quality in structural materials, the development of excellent color cement concrete having good coloration properties has become a requirement. This study is designed to analyze the basic physical properties of mortar and the properties of keeping the coloration under an ultraviolet ray accelerated weathering test environment according to changes in the mixing ratio between carbon black and iron oxide used as colorants. The test results show that the use of carbon black and iron oxide reduces the initial flow by 6.3~17.2 % and the air content by 3.5~31.5 % but increases the unit volume weight by 3.4~5.5 %, compared to ordinary Portland cement (OPC). In addition, the study shows that the addition of iron oxide increases the self drying shrinkage. So, caution needs to be taken on the workability of the concrete. The brightness value L^⁎ represented by black showed the most excellent black colour when carbon black 3 % and iron oxide 5 % are added. According to UV accelerated weatherproof test, the brightness value L^⁎ was found to increase in all experiment specimens by 4.28~11.97 %, and the color change by UV was found to be higher for the case where carbon black colorant was not used. Therefore, in terms of color revelation characteristics, the case using carbon black 3 % and iron oxide 5 % was found to show the best black color.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• 제20권10호
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• pp.1061-1070
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• 2009

In this paper, we have designed TDL(True-time Delay Line) for eliminating beam-squint occurring in active phased array antenna with large electrical size operated in wide bandwidth, and have tested its electrical performance. The proposed TDL device is composed of 4-bit microstrip delay line structure and MMIC amplifier for compensation of the delay-line loss. The measured results of gain and phase versus delay state satisfy the electrical requirements, also P1dB output power and noise figure meet the requirement. To verify the performance of fabricated TDL, we have simulated the beam patterns of wide-band active phased array antenna using the measured results and have certified the beam pattern compensation performance. As a result of simulated beam pattern compensation with respect to the 675.8 mm size antenna which is operated in X-band, 800 MHz bandwidth, we have reduced the beam squint error of ${\pm}1^{\circ}$ with ${\pm}0.1^{\circ}$. So this TDL module is able to be applied to active phase array antenna system.

• Korean Journal of Construction Engineering and Management
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• 제5권6호
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• pp.203-211
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• 2004

This study is the results to survey on the problems and improvable Policies for current escalation system in construction contracts, through a Delphi survey to experts. From the survey results, it is desirable to decide the fluctuation rate of construction cost, which is the requirement of escalation clause, on the basis of inflation rate or construction cost index. The desirable price fluctuation rate is proposed as a $3\%$ level. However, it is difficult for construction companies to cope with the sudden increase of material price in advance, arising from short-term shock factors such as exchange rate and international raw material's price. Accordingly escalation system for specified materials, as an exceptional mode, should be introduced. As a method to calculate the fluctuation rate, ARCA(adjustment rate for the categories of articles) is more desirable than ARI(adjustment rate for an index), because the ARCA can be more reflected the characteristics of each construction work.To rationalize the ARI method, it is needed to announce the wage index, material index and machinery expense index via detailed classification by construction types. Also, it is desirable to prescribe the bidding date as a starting date of the price change, rather than contact signing date. considering the price change can happen since the biddiilg stage.

• Korean Journal of Environmental Agriculture
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• 제18권4호
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• pp.310-315
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• 1999

The feasibility of an absorbent biofilter system was examined for rural wastewater treatment. Hydraulic loading rates varied from 50 to 250 cm/day. Effluent of the septic tank was fed into the absorbent biofilter, and small ventilation fan was provided to supply air at the rate of 250 L/min to aerate the biofilter. The biofilter system demonstrated high removal rates for $BOD_5$ and TSS at the loading rate of 150 cm/day, generally meeting the Korean effluent water quality standard of 20 mg/L applicable to both. The nutrient removal was less satisfactory than the results of $BOD_5$ and TSS, but it was within the expected range of biological treatment processes. Considering the abnormally high influent concentration of nutrients during the experiment, better performance results could have been obtained if ordinary domestic wastewater was used. The system performance was not significantly affected by the hydraulic loading up to 150 cm/day, which is far more than the loading limit of the sand filter systems. Maintenance requirement was minimal, and no problems with noise, odor, flies or sludge arose. Since the biofilter system can be operated at a distance, operation in remote rural area and multi-system connected to one control office might be advantageous to the rural area. Overall, considering the cost-effectiveness, stable performance, and minimum maintenance, the biofilter system was thought to be a competitive alternative to treat wastewater in Korean rural communities.

• Fire Science and Engineering
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• 제32권2호
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• pp.57-66
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• 2018

The most urgent requirement in the event of disaster and fire in a skyscraper is to establish a system that enables people inside to evacuate safely. Hence, a practical direction needs to give evacuees confidence in the evacuation by reducing the psychological anxiety caused by the relatively large number of people inside and at the same time, the physically prolonged evacuation travel line. Evacuation tests with large numbers of people were conducted three times to solve these challenges and identify phenomena and issues that occurred during the experiment. The results revealed the factors that could cause a delay in evacuation and suggested improvements. The study results of this paper are as follows. First, a recent fire at a multipurpose high-rise resulted in a number of casualties due to a lack of experience with the disaster prevention system. To prevent such cases from occurring in advance, adaptability was achieved by conducting evacuation tests. Second, the data collected in the evacuation simulation statistics and the actual escape drills were compared and analyzed. Third, in the evacuation experiment, a large number of people could not participate in the experiment. The reasons for not participating were analyzed and their impact on the actual evacuation time was confirmed. Fourth, equipment aids were purchased to establish the optimal response measure to the causes of a delay in escape time and the standards for ensuring the safety of the evacuee were specified by developing improvements to minimize the evacuation delay time through comparative before and after analysis of the experiment. These results can be used for fire safety control of skyscrapers to improve the efficiency of evacuation.

• Journal of Advanced Navigation Technology
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• 제20권4호
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• pp.367-373
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• 2016

We propose an improved direction of arrival (DoA) estimation algorithm based on co-prime array and propagator method. The propagator method with co-prime array does not require singular value decomposition (SVD) requiring much less computational complexity but exhibiting somewhat worse performance in comparison with MUSIC based on co-prime array. We notice that one cause of the performance degradation was in the avoidance of the usage of the diagonal elements of the signal autocorrelation matrix that contains the noise power spectral density. So we propose an algorithm with the diagonal elements of the signal autocorrelation matrix based on the fact that the noise power spectral density can be estimated using noise observation over a long period of time. We observe, through simulations, that the proposed scheme in this paper improves the performance, with 4 times more computational requirement, by signal-to-noise ratio of 1.5dB and by DoA resolution of $0.7^{\circ}$ at the detection probability of 95% compared with the previously introduced co-prime array propagator scheme, resulting in performance much closer to that of co-prime array-based MUSIC scheme.

• Journal of the Korea Institute of Information and Communication Engineering
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• 제3권4호
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• pp.795-804
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• 1999

The increasing number of users of mobile communication systems and the corresponding need for increased system capacity require the use of a modulation scheme which is both power and spectrally efficient. In this paper, we numerically calculate the BER performance of DS/CDMA-BPSK system in different fading channel (Rayleigh, Rician, Shadow Rician). Also, we calculate BER performance and the channel capacity of DS/CDMA-BPSK system which is constant or nearly constant envelopes in 3-state fading channel model. The Shadow Rician fading model described in this paper apply the parameters of the Canadian Mobile Satellite (MSAT). And we assume that the 3-state fading channel model is consist of Rayleigh fading state, Rician fading state, and shadow Rician fading state. This model can be used as a basis for the simulation of the land mobile satellite channel. The dynamic 3-state fading channel model is considered corresponding to different environments and the transitions between these environments. From the numerically calculate results, the DS/CDMA-BPSK system with MUI-20, PG-511 can not achieve the BER performance ($P_b\leq10^{-5}$). And the channel capacity did not meet the system requirement. Also, we know that the BER performance is depend m the occupancy probability of radio channel and the degree of shadow. From the results, we how that during shadowed time intervals it is necessary to use some form of error control coding and receiver diversity in order to support reliable data communication.

• Journal of the Korea Institute of Information and Communication Engineering
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• 제15권6호
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• pp.1289-1300
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• 2011

In recent computer systems with high-performance, users execute programs needing large memory and programs intensively accessing files simultaneously. Such a large memory requirement makes virtual memory systems access swap spaces in disk, and intensive file accesses require file systems to access file system partitions in disk. Executing the two kinds of programs at once incurs large disk seeks between swap spaces and file system partitions frequently. To solve the problem, this paper proposes a new scheme called SAF to create several swap spaces in a file system partition, where pages to be paged out are stored. When a page is paged out, the scheme stores the page to one of the swap spaces close to a disk location where the most recently accessed file is located. The chosen swap space in the file system partition is closer to the disk location than the traditional swap space, so that our scheme can reduce the large disk seek time spent to move to the traditional swap space in paging out a page. The experiment of our scheme implemented in FreeBSD 6.2 shows that SAF reduces the execution time of several benchmarks over FreeBSD ranging from 14% to 42%.

• Journal of the Korea Institute of Information and Communication Engineering
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• 제22권5호
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• pp.754-763
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• 2018

The maritime ICT-convergence equipment are essentially required to a type approval (TA) certification that needs environmental and functional tests, to install in vessel. The environmental test is to experiment the possession for required durabilities of the target device in maritime environment, and the functional test is to check the required functions of target equipment based on international standard. In Korea, the environmental testing facilities amount to 227 sites, but there is no functional testing facility. Because of this, we establish a function test facility for the maritime ICT-equipment. In this paper, we analyze and design the functional testing requirement and required interlocking simulators for digital interfaces and navigation communication equipment. We propose the 2-steps of functional testing procedures, which are single test and integration test, to improve the reliability of testing result. The single test is to examine own functions of the target device, and the integration test is to check harmonized operation with other navigation and communication devices.