• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.21 no.1
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• pp.7-11
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• 1985

Underwater ambient noise in the depth 5m to 200m layers was measured at 14 point from the 24th of July to 2nd of August, 1984, in the Korean east sea areas. The underwater ambient noise pressure level was depended upon configuration of the sea bottom and sea condition, which was formed type of prevaling noise at a long distance from coast and type of intermittent and regional noise at a short distance from coast.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2006.05a
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• pp.49-52
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• 2006

Epoxy resin has less reaction shrinkage, has better water proofing and thermal resistance than other repairing materials, to it has been applied broadly to repair and finish buildings and infrastructures. Although the ambient temperature constructed is varied with the seasons and epoxy resin has to mix with appropriate hardener due to the non self-hardening, as the real construction of it, the ambient temperature is ignored and the blending ration of epoxy resin and hardener is fixed. Also, because of the hardening time is aimed to temperature condition and the tolerance of blending ratio, we investigated the variation of viscosity according to ambient temperatures and hardener ratios. As a results of study, we can select the economical blending ratio of the epoxy resin and hardener according to site situation.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.10
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• pp.648-652
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• 2014

We have investigated the effect of electrical properties of amorphous InGaZnO thin film transistors (a-IGZO TFTs) by post thermal annealing in $O_2$ ambient. The post-annealed in $O_2$ ambient a-IGZOTFT is found to be more stable to be used for oxide-based TFT devices, and has better performance, such as the on/off current ratios, sub-threshold voltage gate swing, and, as well as reasonable threshold voltage, than others do. The interface trap density is controlled to achieve the optimum value of TFT transfer and output characteristics. The device performance is significantly affected by adjusting the annealing condition. This effect is closely related with the modulation annealing method by reducing the localized trapping carriers and defect centers at the interface or in the channel layer.

• Structural Engineering and Mechanics
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• v.22 no.1
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• pp.53-70
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• 2006

The paper summarizes the dynamic-based assessment of a reinforced concrete arch bridge, dating back to the 50's. The outlined approach is based on ambient vibration testing, output-only modal identification and updating of the uncertain structural parameters of a finite element model. The Peak Picking and the Enhanced Frequency Domain Decomposition techniques were used to extract the modal parameters from ambient vibration data and a very good agreement in both identified frequencies and mode shapes has been found between the two techniques. In the theoretical study, vibration modes were determined using a 3D Finite Element model of the bridge and the information obtained from the field tests combined with a classic system identification technique provided a linear elastic updated model, accurately fitting the modal parameters of the bridge in its present condition. Hence, the use of output-only modal identification techniques and updating procedures provided a model that could be used to evaluate the overall safety of the tested bridge under the service loads.

• Computers and Concrete
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• v.20 no.6
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• pp.683-688
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• 2017

This paper presents the experimental investigations on the compressive strength and permeation properties of geopolymer concrete prepared with low calcium fly ash as the primary binder activated with different percentage of Alccofine. The durability aspect was investigated by performing permeable voids and water absorption tests since permeability directly influences the durability properties. The test results show that Alccofine significantly improves the compressive strength and reduces the water permeability thus enhances the durability of geopolymer concrete at ambient curing regime which encourages the use of geopolymer concrete at ambient curing condition thus promising its use in general construction also.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.362-362
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• 2009

$MgB_2$ bulk samples were sintered at different ambient. In this work, high purity Ar gas was added with oxygen and hydrogen gas, which can be regarded as impurity in a sense, as a possible dopant in the $MgB_2$. It was found that oxygen in the sintering ambient leads to a decrease in the critical current density $J_c$ at self field and lower fields. However, we can obtained higher $J_c$ at higher fields. It was also noted that $MgB_2$ samples sintered with 5% hydrogen in Ar revealed the increased $J_c$ at all fields compared to those processed in pure Ar ambient. From the XRD and FESEM analysis, the impurity gas in Ar can refine the $MgB_2$ grain size and result in increased grain. boundary, which can act as a strong flux pinning sites in $MgB_2$ samples. Also discussed are the effects of sintering ambient on irreversibility field, $H_{irr}$ and the upper critical field, $H_{C2}$.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.6
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• pp.104-109
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• 2004

On this paper study is concentrated on the breakup and atomization characteristics of spray formed by impinging jet injectors(like-doublet) used in liquid rocket engine(LRE). On the process of breakup and atomization, injection velocity and ambient gas pressure are the main parameters, so that these are used as variables that specify the experimental condition. Injection velocity varied from 3m/s to 30m/s and ambient gas pressure changed from 0.1MPa to 4.0MPa with nitrogen gas. As results, measured physical quantities decreased with increasing injection velocity and ambient gas pressure. But the decreasing ratios are different from those of the theory.

• Structural Engineering and Mechanics
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• v.50 no.2
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• pp.137-149
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• 2014

In this study, modal parameters such as natural frequencies, mode shapes and damping ratios of RC frames with low strength are determined for different construction stages using ambient vibration test. For this purpose full scaled, one bay and one story RC frames are produced and tested for plane, brick in-filled and brick in-filled with plaster conditions. Measurement time, frequency span and effective mode number are determined by considering similar studies and literature. To obtain experimental dynamic characteristics, Enhanced Frequency Domain Decomposition and Stochastic Subspace Identification techniques are used together. It is shown that the ambient vibration measurements are enough to identify the most significant modes of RC frames. The results indicate that modal parameters change significantly depending on the construction stages. In addition, Infill walls increase stiffness and change the mode shapes of the RC frame. There is a good agreement between mode shapes obtained from brick in-filled and in-filled with plaster conditions. However, some differences are seen in plane frame, like expected. Dynamic characteristics should be verified using finite element analysis. Finally, inconsistency between experimental and analytical dynamic characteristics should be minimize by finite element model updating using some uncertain parameters such as material properties, boundary condition and section properties to reflect the current behavior of the RC frames.

• Journal of ILASS-Korea
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• v.19 no.4
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• pp.188-196
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• 2014

The spray and combustion characteristics of n-dodecane fuel were investigated in a CVCC (constant volume combustion chamber). The selection of ambient conditions for the spray followed ECN (engine combustion network) guidelines, which simulates the ambient condition of diesel engines at start of fuel injection. ECN is a collaboration network whose main objective is to establish an internet library of well-documented experiments that are appropriate for model validation and the advancement of scientific understanding of combustion at conditions specific to engines. Therefore repeatability of the experiments with high accuracy was important. The ambient temperature was varied from 750 to 930 K while the density was fixed at around $23kg/m^3$. The injection pressure of the fuel was varied from 500 to 1500 bar. The spray was injected in both non-reacting ($O_2$ concentration of 0%) and reacting conditions ($O_2$ concentration of 15%) to examine the spray and the combustion characteristics. Direct imaging with Mie Scattering was used to obtain the liquid penetration length. Shadowgraph was implemented to observe vapor length and lift-off length at non-reacting and reacting conditions, respectively. Pressure data was analyzed to determine the ignition delay with respect to the spray and ambient conditions.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.4
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• pp.215-217
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• 2016

For the improvement of the anti-pollution properties of porcelain electrical insulators, in this study, we have applied the functional film to the surface of insulator. The functional films were coated on the ceramic substrates which components were like the porcelain electrical insulator. The coating material was applied to ceramic substrate by spray coating method and then the film was cured at around $300^{\circ}C$ for 10 minutes with different gas ambient, such as $O_2$, $N_2$, and only vacuum. We have measured the contact angle of the coated surface, and obtained the lowest angle ($8.9^{\circ}$) and a strong hydrophilic property at vacuum condition. The anti-pollution properties were measured, revealing that as the contact angle decreased, the anti-pollution properties improved. The mechanical hardness and adhesion were both excellent regardless of the annealing ambient.