• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.638-642
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• 2005

For gas hydrate exploration, long offset multichannel seismic data acquired using by the 4km streamer length in Ulleung basin of the East Sea. The dataset was processed to define the BSRs (Bottom Simulating Reflectors) and to estimate the amount of gas hydrates. Confirmation of the presence of Bottom Simulating reflectors (BSR) and investigation of its physical properties from seismic section are important for gas hydrate detection. Specially, faster interval velocity overlying slower interval velocity indicates the likely presences of gas hydrate above BSR and free gas underneath BSR. In consequence, estimation of correct interval velocities and analysis of their spatial variations are critical processes for gas hydrate detection using seismic reflection data. Using Dix's equation, Root Mean Square (RMS) velocities can be converted into interval velocities. However, it is not a proper way to investigate interval velocities above and below BSR considering the fact that RMS velocities have poor resolution and correctness and the assumption that interval velocities increase along the depth. Therefore, we incorporated Migration Velocity Analysis (MVA) software produced by Landmark CO. to estimate correct interval velocities in detail. MVA is a process to yield velocities of sediments between layers using Common Mid Point (CMP) gathered seismic data. The CMP gathered data for MVA should be produced after basic processing steps to enhance the signal to noise ratio of the first reflections. Prestack depth migrated section is produced using interval velocities and interval velocities are key parameters governing qualities of prestack depth migration section. Correctness of interval velocities can be examined by the presence of Residual Move Out (RMO) on CMP gathered data. If there is no RMO, peaks of primary reflection events are flat in horizontal direction for all offsets of Common Reflection Point (CRP) gathers and it proves that prestack depth migration is done with correct velocity field. Used method in this study, Tomographic inversion needs two initial input data. One is the dataset obtained from the results of preprocessing by removing multiples and noise and stacked partially. The other is the depth domain velocity model build by smoothing and editing the interval velocity converted from RMS velocity. After the three times iteration of tomography inversion, Optimum interval velocity field can be fixed. The conclusion of this study as follow, the final Interval velocity around the BSR decreased to 1400 m/s from 2500 m/s abruptly. BSR is showed about 200m depth under the seabottom

• Journal of Korean Society of Water and Wastewater
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• v.28 no.2
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• pp.207-215
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• 2014

Wastewater containing heavy metals such as copper (Cu) and nickel (Ni) is harmful to humans and the environment due to its high toxicity. Crystallization in a fluidized bed reactor (FBR) has recently received significant attention for heavy metal removal and recovery. It is necessary to find optimum reaction conditions to enhance crystallization efficacy. In this study, the effects of crystallization reagent and pH were investigated to maximize crystallization efficacy of Cu-S and Ni-S in a FBR. CaS and $Na_2S{\cdot}9H_2O$ were used as crystallization reagent, and pH were varied in the range of 1 to 7. Additionally, each optimum crystallization condition for Cu and Ni were sequentially employed in two FBRs for their selective removal from the mixture of Cu and Ni. As major results, the crystallization of Cu was most effective in the range of pH 1-2 for both CaS and $Na_2S{\cdot}9H_2O$ reagents. At pH 1, Cu was completely removed within five minutes. Ni showed a superior reactivity with S in $Na_2S{\cdot}9H_2O$ compared to that in CaS at pH 7. When applying each optimum crystallization condition sequentially, only Cu was firstly crystallized at pH 1 with CaS, and then, in the second FBR, the residual Ni was completely removed at pH 7 with $Na_2S{\cdot}9H_2O$. Each crystal recovered from two different FBRs was mainly composed of CuxSy and NiS, respectively. Our results revealed that Cu and Ni can be selectively recovered as reusable resources from the mixture by controlling pH and choosing crystallization reagent accordingly.

• Journal of the Korean Vacuum Society
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• v.18 no.3
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• pp.213-220
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• 2009

The optimal condition of low temperature deposition of transparent conductive Al-doped zinc oxide (AZO) films is studied by RF magnetron sputtering method. To achieve enhanced-electrical property and good crystallites quality, we tried to deposit on glass using a two-step growth process. This process was to deposit AZO buffer layer with optimal growth condition on glass in-situ state. The AZO film grown at rf 120 W on buffer layer prepared at RF $50{\sim}60\;W$ shows the electrical resistivity $3.9{\times}10^{-4}{\Omega}cm$, Carrier concentration $1.22{\times}10^{21}/cm^3$, and mobility $9.9\;cm^2/Vs$ in these results, The crystallinity of AZO film on buffer layer was similar to that of AZO film on glass with no buffer later but the electrical properties of the AZO film were 30% improved than that of the AZO film with no buffer layer. Therefore, the cause of enhanced electrical properties was explained to be dependent on degree of crystallization and on buffer layer's compressive stress by variation of $Ar^+$ ion impinging energy.

• The Korean Journal of Mycology
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• v.9 no.3
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• pp.117-122
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• 1981

A tunnel system of mushroom cultivation was designed to compare with the conventional cultivation method in Korea. The bed and air temperature during the phase II the tunnel system was more stably controlled than in the conventional house. The indipensable energy was much saved in the tunnel system than in the conventional method, as this system did not require additional heat supply in the phase II. Compost fermented in the tunnel was proved to contain higher total nitrogen and moisture than compost in the conventional house. Residual ammonia content of compost fermented in the tunnel did not exceed 300ppm. Mushlroom mycelial growth in the tunnel was as good as in conventional house. The tunnel system did not require additional heat supply during mycelial growth period. Mushroom yield and quality from the tunnel system was 5 per cent higher and better than that of the conventional method.

• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.4
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• pp.323-330
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• 2009

The objective of this research was to develop a practical integrated approach using extracted features from electrical resistance measurements and coupled electromechanical models of damage, for in-situ damage detection and sensing in carbon fiber reinforced plastic(CFRP) composites. To achieve this objective, we introduced specific known damage (in terms of type, size, and location) into CFRP laminates and established quantitative relationships with the electrical resistance measurements. For processing of numerous measurement data, an autonomous data acquisition system was devised. We also established a specimen preparation procedure and a method for electrode setup. Coupon and panel CFRP laminate specimens with several known damage were tested. Coupon specimens with various sizes of artificial delaminations obtained by inserting Teflon film were manufactured and the resistance was measured. The measurement results showed that increase of delamination size led to increase of resistance implying that it is possible to sense the existence and size of delamination. A quasi-isotropic panel was manufactured and electrical resistance was measured. Then three different sizes of holes were drilled at a chosen location. The panel was prepared using the established procedures with six electrode connections on each side making a total of twenty-four electrodes. Vertical, horizontal, and diagonal pairs of electrodes were chosen and the resistance was measured. The measurement results showed the possibility of the established measurement system for an in-situ damage detection method for CFRP composite structures.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.1
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• pp.63-77
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• 2015

Tsunami take away life, wash houses away and bring devastation to social infrastructures such as breakwaters, bridges and ports. The coastal structure targeted object in this study can be damaged mainly by the wave pressure together with foundation ground failure due to scouring and liquefaction. The increase of excess pore water pressure composed of oscillatory and residual components may reduce effective stress and, consequently, the seabed may liquefy. If liquefaction occurs in the seabed, the structure may sink, overturn, and eventually increase the failure potential. In this study, the bore was generated using the water level difference, its propagation and interaction with a vertical revetment analyzed by applying 2D-NIT(Two-Dimensional Numerical Irregular wave Tank) model, and the dynamic wave pressure acting on the seabed and the surface boundary of the vertical revetment estimated by this model. Simulation results were used as input data in a finite element computer program(FLIP) for elasto-plastic seabed response. The time and spatial variations in excess pore water pressure ratio, effective stress path, seabed deformation, structure displacement and liquefaction potential in the seabed were estimated. From the results of the analysis, the stability of the vertical revetment was evaluated.

• Korean Journal of Environmental Agriculture
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• v.35 no.2
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• pp.121-127
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• 2016

BACKGROUND: Anaerobic digestion is the most feasible technology because not only the energy embedded in organic matters can be recovered, but also they are stabilized while being degraded. This study carried out to improve methane yield of slaughterhouse wastewater treatment sludge cake by the thermal pre-treatment prior to anaerobic digestion.METHODS AND RESULTS: Slaughterhouse wastewater treatment sludge cake was pre-treated by the closed hydrothermal reactor at reaction temperature of 190℃. BMPs (Biochemical methane potential) of the thermal hydrolysate was tested in the different S(Substrate)/I(Inoculum) ratio conditions. COD(Chemical oxygen demand) and SCOD(Soluble chemical oxygen demand) contents of thermal hydrolysate were 10.99% and 10.55%, respectively, then, the 96.00% of COD was remained as a soluble form. The theoretical methane potential of thermal hydrolysate was 0.51 Nm³ kg^-1-VS_added. And BMPs were decreased from 0.56 to 0.22 Nm³ kg^-1-VS_added when S/I ratio were increased from 0.1 to 2.0 in the VS content basis. Those were decreased from 0.32 to 0.13 Nm³ kg^-1-COD_added when S/I ratio were increased from 0.1 to 2.0 based on COD content. The anaerobic degradability of VS basis have showed 196.9%, 102.2%, 80.7%, 67.4%, and 39.4% in S/I ratios of 0.1, 0.3, 0.5, 1.0, and 2.0, respectively. Also the COD of 119.6%, 76.3%, 70.1%, 69.0%, and 43.1% were degraded anaerobically in S/I ratios of 0.1, 0.3, 0.5, 1.0, and 2.0, respectively.CONCLUSION: BMPs obtained in the S/I ratios of 0.1 and 0.3 was overestimated by the residual organic matters remaining at the inoculum. And inhibitory effect was observed in the highest S/I ratio of 2.0. The optimum S/I ratios giving reasonable BMPs might be in the range of 0.5 and 1.0 in S/I ratio. Therefore VS biodegradability of thermal hydrolysate was in 67.4-80.7% and COD biodegradability showed 69.0-70.1%.

• The Journal of Engineering Geology
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• v.28 no.3
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• pp.465-473
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• 2018

The application of singular value decomposition (SVD) filtering is examined for attenuation of the ground-roll in land seismic data. Prior to the SVD computation to seek singular values containing the highly correlatable reflection energy, processing steps such as automatic gain control, elevation and refraction statics, NMO correction, and residual statics are performed to enhance the horizontal correlationships and continuities of reflections. Optimal parameters of SVD filtering are effectively chosen with diagnostic display of inverse NMO (INMO) corrected CSP (common shot point) gather. On the field data with dispersion of ground-roll overwhelmed, continuities of reflection events are much improved by SVD filtering than f-k filtering by eliminating the ground-roll with preserving the low-frequency reflections. This is well explained in the average amplitude spectra of the f-k and SVD filtered data. The reflectors including horizontal layer of the reservoir are much clearer on the stack section, with laminated events by SVD filtering and subsequent processing steps of spiking deconvolution and time-variant spectral whitening.

• Journal of the Korean Vacuum Society
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• v.21 no.2
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• pp.78-85
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• 2012

In order to improve the adhesion between poly-monochloro-para-xylylene (Parylene-C) film and Aluminum thin film, the surface of Parylene-C film was irradiated by ${O_2}^+$ and $Ar^+$ ion beam generated by duoplamatron ion source. The ion dose of $Ar^+$ and ${O_2}^+$ was changed from $5{\times}10^{14}$ to $1{\times}10^{17}/cm^2$ and the ion beam energy was 1 kV. Contact angles of water on Parylene-C modified by $Ar^+$ and ${O_2}^+$ ion irradiation decreased from $78^{\circ}$ to around $17^{\circ}$, and $9^{\circ}$, respectively. X-ray photoelectron spectroscopy analysis shows that the hydrophilic groups were formed on the surface of Parylene-C by chemical reaction between the unstable chains induced by the ion irradiation and oxygen ions or residual oxygen gas. The hydrophilic groups were identified as C-O bond, C=O bond and (C=O)-O bond. The cross cut tape test which was applied to characterize the adhesion between Al thin film and Parylene-C film modified by ${O_2}^+$ ions irradiation shows that the adhesion strength was improved as increasing ion dose.

• Journal of the Korean Society for Advanced Composite Structures
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• v.2 no.4
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• pp.1-10
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• 2011

This study investigates the performance of composite (steel-concrete) frame structures through numerical experiments on individual connections. The innovative aspects of this research are in the use of connections between steel beams and concrete-filled tube (CFT)columns that utilize a combination of low-carbon steel and shape memory alloy (SMA) components. In these new connections, the intent is to utilize the recentering provided by super-elastic shape memory alloy tension bars to reduce building damage and residual drift after a major earthquake. The low-carbon steel components provide excellent energy dissipation. The analysis and design of these structures is complicated because the connections cannot be modeled as being simply pins or full fixity ones they are partial restraint (PR). A refined finite element (FE) model with sophisticated three dimensional (3D) solid elements was developed to conduct numerical experiments on PR-CFT joints to obtain the global behavior of the connection. Based on behavioral information obtained from these FE tests, simplified connection models were formulated by using joint elements with spring components. The behavior of entire frames under cyclic loads was conducted and compared with the monotonic behavior obtained from the 3D FE simulations. Good agreement was found between the simple and sophisticated models, verifying the robustness of the approach.