• Journal of the Korea Concrete Institute
• /
• v.27 no.2
• /
• pp.157-167
• /
• 2015

Cement composites subjected to high-velocity projectile shows local failure and it can be suppressed by improvement of flexural toughness with reinforcement of fiber. Therefore, researches on impact resistance performance of cement composites are in progress and a number of types of fiber reinforcement are being developed. Since bonding properties of fiber with matrix, specific surface area and numbers of fiber are different by fiber reinforcement type, mechanical properties of fiber reinforced cement composites and improvement of impact resistance performance need to be considered. In this study, improvement of flexural toughness and failure reduction effect by impact of high-velocity projectile have been evaluated according to fiber type by mixing steel fiber, polyamide, nylon and polyethylene which are have different shape and mechanical properties. As results, flexural toughness was improved by redistribution of stress and crack prevention with bridge effect of reinforced fibers, and scabbing by high-velocity impact was suppressed. Since it is possible to decrease scabbing limit thickness from impact energy, thickness can be thinner when it is applied to protection. Scabbing of steel fiber reinforced cement composites was occurred and it was observed that desquamation of partial fragment was suppressed by adhesion between fiber and matrix. Scabbing by high-velocity impact of synthetic fiber reinforced cement composites was decreased by microcrack, impact wave neutralization and energy dispersion with a large number of fibers.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2018.11a
• /
• pp.158-161
• /
• 2018

In this paper, the towing force is calculated for the LNG bunker barge. LNG bunkering barge is being developed as an infrastructure for the bunkering of LNG(Liquefied Natural Gas), an eco-friendly energy source. In the case of the LNG bunker barge, a self-propulsion is considered through retrofit from an operating point. Therefore, the LNG bunker barge is similar to the shape of the ship as compared to a towed barge, so a rule of the towed barge overestimates the towing force. In order to improve accuracy, the calm water resistance is calculated according to the ITTC 1978 method considering the wave resistance by the Rankine source method. The added resistance in waves is calculated using the modified radiated energy method considering the shortwave correction method of NMRI. The performance of the towing resistances through the calm water resistance and the added resistance in waves was compared with rules of the towed barge.

• Journal of the Korean Magnetics Society
• /
• v.22 no.2
• /
• pp.37-41
• /
• 2012

The Ag nanoparticles attached $La_{0.7}Sr_{0.3}Co_{0.3}Fe_{0.7}O_{3-{\delta}}$ (LSCF) perovskites were prepared by plasma method. The Ag nanoparticles with size of several nanometers deposited from the Ag target were coated on the surface of LSCF powders with size range from 0.2 to 3 ${\mu}m$. The agglomeration of Ag particles annealed at $800^{\circ}C$ under inert gas of Ar were rarely observed. The inter-diffusion between surface Ag and core LSCF is effectively strong to prevent aggregation of Ag nanoparticles. The wave number of FT-IR spectra for LSCF were largely shifted as the concentration of Ag on LSCF up to 2.11 wt.%. The ionic states of irons in LSCF were measured by M$\ddot{o}$ssbauer spectroscopy. The small amount of $Fe^{4+}$ ions are converted to $Fe^{3+}$ ions after Ag nanopartcles were coated on LSCF.

• Journal of the Korean Magnetics Society
• /
• v.18 no.6
• /
• pp.206-210
• /
• 2008

According to the recent reports the bulk bcc Rh is ferromagnetic with a small difference of energy compared to paramagnetic state. In this study, the electronic structure and magnetism for bcc Rh(001) surface are investigated by means of the all-electron full potential linearized augmented plane wave method within the generalized gradient approximation. It is found that the surface ferromagnetic state is preferable over the paramagnetic one. For unrelaxed system, the magnetic moment of the surface layer, $0.48{\mu}B$, is slightly increased comparing with the bulk value, $0.41{\mu}B$ while the value of the subsurface layer, $0.23{\mu}B$, is much smaller than the bulk value. The total energy and atomic force calculations show that the surface layer is relaxed downward and the subsurface layer moves upward to reduce the layer distance between the surface and subsurface layers by 7.0 %. The relaxation effect leads to weakening the surface magnetic properties. Specifically, the value of the magnetic moment of the surface atom is decreased to $0.36{\mu}B$. Since the spin polarization of the subsurface layer is only $0.14{\mu}B$, it is concluded that the bcc Rh(001) surface is rather weakly ferromagnetic.

• Geophysics and Geophysical Exploration
• /
• v.14 no.3
• /
• pp.227-233
• /
• 2011

Attention has been focused on geothermal energy as an alternative energy because it is continuously operable without external supply. Most of geothermal anomalies in Korea are related to deep circulation of groundwater through a fracture system in granite area. Therefore it is very important to understand the distribution of the fracture system which is the main channel of ground water. In this research, we constructed the velocity models with a fracture system and the layered sediments, respectively, and generated synthetic data sets with them to verify the presented vertical seismic profiling (VSP) preprocessing scheme. We compared the results from conventional VSP preprocessing flow to those from VSP preprocessing flow considering fracture system. We noticed that the preprocessing flow considering fracture system retains more sufficient signal including down-going wave than conventional preprocessing. In addition, we applied 3D VSP prestack phase screen migration to the preprocessed reversed VSP (RVSP) data from Seokmo Island so that we were able to image fracture structure of the geothermal site in Seokmo Island.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.25 no.10
• /
• pp.805-810
• /
• 2012

Transparent conducting oxides (TCOs) have wide range of application areas in transparent electrode for display devices, Transparent coating for solar energy heat mirrors, and electromagnetic wave shield. $SnO_2$ is intrinsically an n-type semiconductor due to oxygen deficiencies and has a high energy-band gap more than 3.5 eV. It is known as a transparent conducting oxide because of its low resistivity of $10^{-3}{\Omega}{\cdot}cm$ and high transmittance over 90% in visible region. In this study, co-doping effects of Al and Y on the properties of $SnO_2$ were investigated. The addition of Y in $SnO_2$ was tried to create oxygen vacancies that increase the diffusivity of oxygen ions for the densification of $SnO_2$. The addition of Al was expected to increase the electron concentration. Once, we observed solubility limit of $SnO_2$ single-doped with Al and Y. $\{(x/2)Al_2O_3+(x/2)Y_2O_3\}-SnO_2$ was used for the source of Al and Y to prevent the evaporation of $Al_2O_3$ and for the charge compensation. And we observed the valence changes of aluminium oxide because generally reported of valence changes of aluminium oxide in Tin - Aluminium binary system. The electrical properties, solubility limit, densification and microstructure of $SnO_2$ co-doped with Al and Y will be discussed.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.8
• /
• pp.55-63
• /
• 2017

Due to spatial problems and system size,conventional measurement methods used to acquire the information needed for existing electrical energy and management have been limited to new buildings or areas where replacement is possible. This electric load management method is problematic when applying it to energy and safety management of vulnerable areas or existing homes or offices. The problem with installing a measurement module in every branch is that the system is too large. Even if the measurement module is installed, the type of load is not recognized, and efficient management is not performed. In particular, it is very difficult to apply it to traditional markets and backward facilities in Korea. In this paper, we apply NIALM technology and arc detection technology to solve these problems and verify the feasibility of NIALM for normal arc generation. Also, based on the verification results, we propose a new smart home safety management system that can effectively manage electrical safety and that can be applied to conventional market and existing home safety management systems. The proposed system conducts a comparative performance test with an existing safety management system. In addition, it achieves 95% or more load recognition for four loads, which is impossible in 40% of the existing systems, and the arc detection function was confirmed.

• Journal of the Korean Magnetics Society
• /
• v.26 no.1
• /
• pp.1-6
• /
• 2016

Pd has the highest magnetic susceptibility among single element metals and often shows ferromagnetism under some special environments. In this paper, we report magnetism of 5- and 9-monolayers (ML) calculated by using full-potential linearized augmented plane wave method. Exchange-correlation interaction is taken into account in local density approximation (LDA) and generalized gradient approximation (GGA) and calculational results in LDA and GGA are compared with each other. It is found that calculations by LDA are more reliable compared to those by GGA because LDA prediction of paramagnetism of bulk Pd is consistent with experiments, whereas GGA predicts wrongly ferromagnetim of bulk Pd. Calculational results in LDA on a 5-ML Pd(111) thin film shows a ferromagnetic ground state unlike a paramagnetic ground state of bulk Pd. The center Pd layer of the 5-ML Pd(111) thin film has the largest magnetic moment ($0.273{\mu}_B$) among the layers and |m| = 1 orbital states play a dominant role in stabilizing the ferromagnetism of the 5-ML Pd(111) thin film. A 9-ML Pd(111) thin film in a ferromagnetic state has almost the same total energy as in a paramagnetic state. Since the magnetization of the 9-ML Pd(111) thin film is stable, the ferromagnetic state may be meta-stable.

• Journal of Navigation and Port Research
• /
• v.42 no.6
• /
• pp.378-387
• /
• 2018

In this paper, the towing force for the LNG bunkering barge was investigated. Currently, LNG bunkering barge is being developed as an infrastructure for the bunkering of LNG (Liquefied Natural Gas), an eco-friendly energy source. In the case of the LNG bunkering barge, self-propulsion is considered through retrofit from an operating point. Therefore, the LNG bunkering barge's shape is similar to that of the ship as compared to a towed barge, so a rule of the towed barge overestimates the towing force. In order to improve accuracy, the calm water resistance was calculated using ITTC 1978 method which considers wave resistance by the Rankine source method. The added resistance in waves was calculated using the modified radiated energy method which considers the shortwave correction method of NMRI. The performance of the towing resistances through the calm water resistance and the added resistance in waves was compared to rules associated with towed barges.

• Geophysics and Geophysical Exploration
• /
• v.24 no.3
• /
• pp.89-97
• /
• 2021

Fault detection in seismic data is well suited to the application of machine learning algorithms. Accordingly, various machine learning techniques are being developed. In recent studies, machine learning models, which utilize synthetic data, are the particular focus when training with deep learning. The use of synthetic training data has many advantages; Securing massive data for training becomes easy and generating exact fault labels is possible with the help of synthetic training data. To interpret real data with the model trained by synthetic data, the synthetic data used for training should be geologically realistic. In this study, we introduce a method to generate realistic synthetic seismic data. Initially, reflectivity models are generated to include realistic fault structures, and then, a one-way wave equation is applied to efficiently generate seismic stack sections. Next, a migration algorithm is used to remove diffraction artifacts and random noise is added to mimic actual field data. A convolutional neural network model based on the U-Net structure is used to verify the generated synthetic data set. From the results of the experiment, we confirm that realistic synthetic data effectively creates a deep learning model that can be applied to field data.