• International journal of steel structures
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• v.18 no.4
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• pp.1153-1166
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• 2018

This paper was concerned with the nonlinear analysis on the overall stability of H-type honeycombed composite column with rectangular concrete-filled steel tube flanges (STHCC). The nonlinear analysis was performed using ABAQUS, a commercially available finite element (FE) program. Nonlinear buckling analysis was carried out by inducing the first buckling mode shape of the hinged column to the model as the initial imperfection with imperfection amplitude value of L/1000 and importing the simplified constitutive model of steel and nonlinear constitutive model of concrete considering hoop effect. Close agreement was shown between the experimental results of 17 concrete-filled steel tube (CFST) specimens and 4 I-beams with top flanges of rectangular concrete-filled steel tube (CFSFB) specimens conducted by former researchers and the predicted results, verifying the correctness of the method of FE analysis. Then, the FE models of 30 STHCC columns were established to investigate the influences of the concrete strength grade, the nominal slenderness ratio, the hoop coefficient and the flange width on the nonlinear stability capacity of SHTCC column. It was found that the hoop coefficient and the nominal slenderness ratio affected the nonlinear stability capacity more significantly. Based on the results of parameter analysis, a formula was proposed to predict the nonlinear stability capacity of STHCC column which laid the foundation of the application of STHCC column in practical engineering.

• Geomechanics and Engineering
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• v.10 no.1
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• pp.49-57
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• 2016

The high permeability-high strength concrete belongs to the typical of porous materials. It is mainly used in underground engineering for cold area, it can act the role of heat preservation, also to be the bailing and buffer layer. In order to establish a suitable model to predict the thermal conductivity and directly applied for engineering, according to the structure characteristics, the thermal conductivity predicting model was built by resistance network model of parallel three-phase medium. For the selected geometric and physical cell model, the thermal conductivity forecast model can be set up with aggregate particle size and mixture ratio directly. Comparing with the experimental data and classic model, the prediction model could reflect the mixture ratio intuitively. When the experimental and calculating data are contrasted, the value of experiment is slightly higher than predicting, and the average relative error is about 6.6%. If the material can be used in underground engineering instead by the commonly insulation material, it can achieve the basic requirements to be the heat insulation material as well.

• Journal of Korean Society of Forest Science
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• v.104 no.3
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• pp.352-359
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• 2015

This study was conducted to evaluate how the special protection area designations of degraded trails effect on the soil and vegetation recovery of degraded trails. The study areas were established on an opened trail and a 16-year closed trail, which was prohibited to enter after the designation as a special protection area for recovery, at Bukhansan National Park. Soil core sampling and measurements of vegetation cover were performed to compare soil and vegetation properties of the trails. Soil bulk density increased and soil water total nitrogen decreased on the opened trail, while no significant differences were found on bulk density, soil water, total nitrogen, acidity, and organic matter on the closed trail. On the opened trail, vegetation cover was seemed to be degraded, because vegetation litter cover ratio was low and barren rock cover ratio was high. On the closed trail, litter rock barren cover ratio of the closed trail was recovered, but only limited recovery was found on vegetation cover by applying environmental damage condition rating class. In conclusion, the closed trail was recovered by designation of special protection area, while difference in recovery progress of soil and vegetation was found. Therefore, designation of special protection area of degraded area should be based on scientific basis of recovery characteristics of the area. In order to improve the effectiveness of special protection area system, further specific standards for special protection area designation and management would be needed, considering ecological and social importance of target areas.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.637-640
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• 2006

Corrosion from various causes of reinforcing steel in concrete structures not only shortened the life of structures but also it is necessary a great repair cost to return and protect to the health condition. Using Nitrite inhibitors is a typical protection method. But there is no materials for the study about corrosion protection using nitrite. Therefore it is important to evaluate the additional rate and influence on congealment using the nitrite inhibitors in cement paste which is originally the basic material and crucial factors consisting concrete. The purpose of this study is finding influence of the type of nitrite inhibitors and mixing ratio on congealment of cement paste, and finding best corrosion inhibitors and ratio in cement paste.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.11 s.102
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• pp.1138-1146
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• 2005

This paper makes a study of a formulation of net filter discrimination(NFD) and its computation for analyzing adjacent channel interference and suggests a systematic algorithm for calculating protection ratios of co-channel and adjacent channel applicable to frequency coordination in the fixed radio relay networks. It is shown that adjacent channel protection ratio can be derived from two factors: One is NFD depending upon receiver filter characteristic as well as transmitter spectrum mask and the other is co-channel protection ratio given by a function of fade margin, modulation scheme, and allowable interference. Actually to show the computing procedure from transmitter spectrum mask and receiver filter characteristic, NFD has been obtained for channel bandwidth of 29.65 and 40 MHz at 6.2 and 6.7 GHz band, respectively. According to the results, NFDs at the first adjacent channel of 29.65 and 40 MHz provide 27.4 and 28.9 dB, respectively. From these data, adjacent channel protection ratios corresponding to each channel bandwidth yield 47.5 and 46.3 dB for a given 64-QAM and 60 km. The proposed method gives some merits of an easy calculation, systematic extension, and applying the same concept to frequency coordination in millimeter radio relay networks.

• Journal of Welding and Joining
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• v.19 no.2
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• pp.182-190
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• 2001

A marine structural material was well known to have high tensile strength, good weldability and proper corrosion resistance. Cu-containing high strength low alloy(HSLA) steel was recently developed for their purposes mentioned above. And the steel is free about preheating for welding, therefore it is reported that shipbuilding cost by using it can be saved more or less. However the marine structural materials like Cu-containing HSLA steel are being generally adopted with cathodic protection method in severe corrosive environment like natural sea water but the high strength steel may give rise to Hydrogen Embrittlement due to over protection at high cathodic current density for cathodic protection. In this study Cu-containing HSLA steel using well for marine atructure was investigated about the susceptibility of Hydrogen Embrittlement as functions of tensile strength, strain ratio, fracture time, and fracture mode, etc. and an optimum cathodic protection potential by slow strain rate test(SSRT) method as well as corrosion properties in natural sea water. And its corrosion resistance was superior to SS400 steel, but Hydrogen Embrittlement susceptibility of Cu-containing HSLA steel was higer than that of SS400 steel. However Hydrogen Embrittlement of its steel by SSRT method was showed with pheonomena such as decreasing of fracture time, strain ratio and fracture mode of QC(quasi-cleavage). Eventually it is suggested that an optimum cathodic protection potential not presenting Hydrogen Embrittlement of Cu-containing of HSLA steel by SSRT method was from-770mv(SCE) to - 900mV(SCE)under natural sea water.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.5
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• pp.854-859
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• 2007

A wind farm consists of many wind generator(WG)s therefore, it is generally a complex power system. A wind farm as a distributed generation(DG) affects utility power system. If a conventional protection schemes are applied, it is difficult to detect faults correctly and the schemes can't provide proper coordination in some cases. This paper presents a protection algorithm for a wind farm which consists of a looped collection circuit. Because the proposed algorithm can distinguish between an internal fault and an external fault in a wind farm, The proposed algorithm can disconnect the faulted section in a wind farm. This algorithm is based on an overcurrent protection technique with the change of the ratio of the output current of a generator to the current of the looped line connected to each generator to collect the each generator's power. In addition, operating time of the algorithm is shortened by using the voltage drop at a generator collection point. The performance of the proposed algorithm was verified under various fault conditions using PSCAD/EMTDC simulations.

• Journal of Communications and Networks
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• v.10 no.3
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• pp.331-337
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• 2008

In this paper, we investigate survivability in wavelength division multiplexing (WDM) mesh networks and propose a new algorithm called improved shared-path protection (ISPP) to completely tolerate the double-link failures. Compared with previous algorithms for protecting double-link failures, i.e., shared-path protection (SPP) and shared-link protection (SLP), the advantage of ISPP is to allow primary paths and backup paths to share the mixed wavelength-links based on the proposed new rules in which some primary wavelength-links can be changed to mixed wavelength-links, which can be shared by primary paths and backup paths. In addition, some mixed wavelength-links also can be shared by different backup paths for saving resources. Simulation results show that ISPP algorithm performs better in resource utilization ratio and blocking probability than conventional SPP and SLP algorithms.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.28 no.1
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• pp.53-60
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• 1992

In this study, cathodic protection experiment was carried out by Al-alloy sacrificial anode in marine environments which have specific resistance($\rho$) if 25~7000$\Omega$.cm and investigated protection potential, current density and loss rate of Al-alloy sacrificial anode. The main results resistance($\rho$) of 400$\Omega$.cm, the cathodic protection potential appears high about-720 mV(SCE). But below specific resistance($\rho$) of 300$\Omega$.cm, the cathodic protection potential appears low about-770 mV(SCE) and simultaneously, cathode is protected sufficiently. 2) The loss rate of Al-Alloy sacrificial anode became large with decreasing specific resistance and increasing the ratio(A sub(c)/A sub(a) of bared surface area of anode and cathode. 3) The loss rate of Al-alloy sacrificial anode(w) to the mean current density of anode(i) is as follows. w=ai+b (a, b : experimental constants)

• Animal Bioscience
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• v.35 no.1
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• pp.147-152
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• 2022

Objective: This study was conducted to obtain an objective index that can be quantified and used for establishing an animal welfare certification standard in Korea. For this purpose rumen pH, ruminating time, milk yield, milk quality, and blood components of cows reared in farms feeding high forage level (90%) and farms feeding low forage level (40%) were compared. Methods: Data on rumen pH, rumination time, milk yield, milk fat ratio, milk protein ratio, and blood metabolism were collected from 12 heads from a welfare farm (forage rate 88.5%) and 13 heads from a conventional farm (forage rate 34.5%) for three days in October 2019. Results: The rumination time was longer in cattle on the welfare farm than on the conventional farm (p<0.01), but ruminal pH fluctuation was greater in the cattle on conventional farm than the welfare farm (p<0.01). Conventional farms with a high ratio of concentrated feed were higher in average daily milk yield than welfare farms, but milk fat and milk production efficiency (milk fat and milk protein corrected milk/total digestible nutrients) was higher in cattle on welfare farms. Blood test results showed a normal range for both farm types, but concentrations of total cholesterol and non-esterified fatty acid were significantly higher in cows from conventional farms with a high milk yield (p<0.01). Conclusion: The results of this study confirmed that cows on the animal welfare farm with a high percentage of grass feed had higher milk production efficiency with healthier rumen pH and blood metabolism parameters compared to those on the conventional farm.