• Journal of the Korean Society of Propulsion Engineers
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• v.10 no.1
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• pp.44-53
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• 2006

In this study, the non-destructive computed tomography was adopted to observe the density profile of the needle-punched Carbon/Carbon(C/C) composites nozzle throat. The density profile of C/C was evaluated within ${\pm}0.01g/cm^3$ with 98.74% confidence when the correction of the image and high signal-to-noise ratio were achieved by the optimization of the beam hardening, the electrical noise and the scattered X-ray. The density variation of C/C with the computed tomography was in good agreement with the results obtained by the water immersion method and the observation with scanning electron microscope.

• Carbon letters
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• v.12 no.1
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• pp.26-30
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• 2011

For polyacrylonitrile (PAN) based carbon fiber (CF) process, we developed a lab scale wet spinning line and a continuous tailor-made stabilization system with ten columns for controlling temperature profile. PAN precursor was spun with a different spinning rate. PAN spun fibers were stabilized with a total duration of 45 to 110 min at a given temperature profile. Furthermore, a stabilization temperature profile was varied with the last column temperature from 230 to $275^{\circ}C$. Stabilized fibers were carbonized in nitrogen atmosphere at $1200^{\circ}C$ in a furnace. Morphologies of spun and CFs were observed using optical and scanning electron microscopy, respectively. Tensile properties of resulting CFs were measured. The results revealed that process conditions such as spinning rate, stabilization time, and temperature profile affect microstructure and tensile properties of CFs significantly.

• Journal of Biosystems Engineering
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• v.34 no.5
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• pp.382-389
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• 2009

An in-situ probe-based spectrophotometer has been developed. This system used two spectrometers to measure soil reflectance spectra from 450 nm to 2200 nm. It collects soil electrical conductivity (EC) and insertion force measurements in addition to the optical data. Six fields in Kansas were mapped with the VIS-NIR (visible-near infrared) probe module and sampled for calibration and validation. Results showed that VIS-NIR correlated well with carbon in all six fields, with RPD (the ratio of standard deviation to root mean square error of prediction) of 1.8 or better, RMSE of 0.14 to 0.22%, and $R^2$ of 0.69 to 0.89. From the investigation of carbon variability within the soil profile and by tillage practice, the 0-5 cm depth in a no-till field contained significantly higher levels of carbon than any other locations. Using the selected calibration model with the soil NIR probe data, a soil profile map of estimated carbon was produced, and it was found that estimated carbon values are highly correlated to the lab values. The array of sensors (VIS-NIR, electrical conductivity, insertion force) used in the probe allowed estimating bulk density, and three of the six fields were satisfactory. The VIS-NIR probe also showed the obtained spectra data were well correlated with nitrogen for all fields with RPD scores of 1.84 or better and coefficient of determination ($R^2$) of 0.7 or higher.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.460-460
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• 2012

반도체 Device가 Shrink 함에 따라 Pattern Size가 작아지게 되고, 이로 인해 Photo Resist 물질 자체만으로는 원하는 Patterning 물질들을 Plasma Etching 하기가 어려워지고 있다. 이로 인해 Photoresist를 대체할 Hard Mask 개념이 도입되었으며, 이 Hardmask Layer 중 Amorphous Carbon Layer 가 가장 널리 사용되고 지고 있다. 이 Amorphous Carbon 계열의 Hardmask를 Etching 하기 위해서 기본적으로 O2 Plasma가 사용되는데, 이 O2 Plasma 내의 Oxygen Species들이 가지는 등 방성 Diffusion 특성으로 인해, 원하고자 하는 미세 Pattern의 Vertical Profile을 얻는데 많은 어려움이 있어왔다. 이를 Control 하기 인해 O2 Plasma Parameter들의 변화 및 Source/Bias Power 등의 변수가 연구되어 왔으며, 이와 다른 접근으로, N2 및 CO, CO2, SO2 등의 여러 Additive Gas 들의 첨가를 통해 미세 Pattern의 Profile을 개선하고, Plasma Etching 특성을 개선하는 연구가 같이 진행되어져 왔다. 본 논문에서 VLSI Device의 Masking Layer로 사용되는, Carbon 계 유기 층의 Plasma 식각 특성에 대한 연구를 진행하였다. Plasma Etchant로 사용되는 O2 Plasma에 새로운 첨가제 가스인 카르보닐 황화물 (COS) Gas를 추가하였을 시 나타나는 Plasma 내의 변화를 Plasma Parameter 및 IR 및 XPS, OES 분석을 통하여 규명하고, 이로 인한 Etch Rate 및 Plasma Potential에 대해 비교 분석하였다. COS Gas를 정량적으로 추가할 시, Plasma의 변화 및 이로 인해 얻어지는 Pattern에서의 Etchant Species들의 변화를 통해 Profile의 변화를 Mechanism 적으로 규명할 수 있었으며, 이로 인해 기존의 O2 Plasma를 통해 얻어진 Vertical Profile 대비, COS Additive Gas를 추가하였을 경우, Pattern Profile 변화가 개선됨을 최종적으로 확인 할 수 있었다.

• Journal of the Korean Ceramic Society
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• v.32 no.6
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• pp.659-668
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• 1995

Zirconium carbide was prepared from the mixture of metal zirconium and carbon powders in argon atmosphere by Self-propagating High-temperature Synthesis (SHS) in order to obtain the best carbon source and dilution contents. The most exellent result was obtained in the case that active carbon was added as a starting material, 20~30 wt% dilution content. From thermal profile analysis an apparent activation energy of 118 KJ/mol was calculated. The maximum heating rate achieved during 15 wt% ZrC reaction by product dilution method was approximately 1.54$\times$105 K/s. Coupling this value with the measured wave velocity of 1.026cm/s yielded a maximum thermal gradient fo $1.5\times$105 K/cm. Using the definition of t* and the measured wave velocity, the effective thermal diffusivity, $\alpha$, was calculated to be 0.62$\times$102 $\textrm{cm}^2$/s.

• Journal of Animal Science and Technology
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• v.50 no.4
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• pp.561-572
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• 2008

Responses of real-time control parameters, such as ORP, DO and pH, to the conditions of biological animal wastewater treatment process were examined to evaluate the stability of real-time control using each parameter. Also an optimum index for supplemental carbon source addition based on NOx-N level was determined under a consideration of denitrification rate by endogenous respiration of microorganism and residual organic matter in liquor. Experiment was performed with lab-scale sequencing batch reactor(SBR) and working volume of the process was 45L. The distinctive nitrogen break point(NBP) on ORP-and DO-time profiles, which mean the termination of nitrification, started disappearing with the maintenance of low NH4-N loading rate. Also the NBP on ORP-and DO-time profiles was no longer observed when high NOx-N was loaded into the reactor, and the sensitivity of ORP became dull with the increase of NOx-N level. However, the distinctive NBP was constantly occurred on pH(mV)-time profile, maintaining unique profile patterns. This stable occurrence of NBP on pH(mV)-time profile was lasted even at very high NOx-N:NH4-N ratio(over 80:1) in reactor, and the specific point could be easily detected by tracking moving slope change(MSC) of the curve. Revelation of NBP on pH(mV)-time profile and recognition of the realtime control point using MSC were stable at a condition of over 300mg/L NOx-N level in reactor. The occurrence of distinctive NBP was persistent on pH(mV)-time profile even at a level of 10,000mg/L STOC(soluble total organic carbon) and the recognition of NBP was feasible by tracing MSC, but that point on ORP and DO-time profiles began to disappear with the increase of STOC level in reactor. The denitrfication rate by endogenous respiration and residual organic matter was about 0.4mg/L.hr., and it was found that 0.83 would be accepted as an index for supplemental carbon source addition when 0.1 of safety factor was applied.

• Nuclear Engineering and Technology
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• v.48 no.1
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• pp.175-181
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• 2016

This study investigates the dispersibility of carbon in carbon contained ammonium diuranate (C-ADU) gel particles and the characteristics of C-ADU gel liquid droplets produced by the vibrating nozzle and integrated aging-washing-drying equipment. It was noted that the excellent stability of carbon dispersion was only observed in the C-ADU gel particle that contained carbon black named CB 10. ADU gel liquid droplets containing carbon particles with the excellent sphericity of approximately 1,950 mm were then obtained using an 80-100-Hz vibrating nozzle system. Dried C-ADU gel particles obtained by the aging-washing-drying equipment were thermal decomposed until $500^{\circ}C$ at a rate of $1^{\circ}C/min$ in an air or in 4% $H_2$ gas atmosphere. The thermally decomposed C-ADU gel particles showed 24% weight loss and a more complicated profile than that of ADU gel particles.

• Journal of Korean Society for Atmospheric Environment
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• v.31 no.5
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• pp.449-460
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• 2015

Carbonaceous aerosol is generally classified into OC (organic carbon) and EC (elemental carbon) by thermal optical analysis. Both NIOSH (National institute of occupational safety and health) with high temperature (HighT) and IMPROVE-A (Interagency monitoring of protected visual environments) with low temperature (LowT) protocols are widely used. In this study, both protocols were applied for ambient $PM_{2.5}$ samples (Daejeon, Korea) in order to underpin differences in OC and EC measurements. An excellent agreement between NIOSH and IMPROVE-A protocol was observed for TC (total carbon). However, significant differences between OC and EC appeared and the differences were larger for EC than OC. The main differences between two protocols are temperature profile and charring correction method. For the same charring correction method, HighT_OC was 10% higher than LowT_ OC, while HighT_EC was 15% and 33% lower than LowT_EC for TOT (thermal-optical transmittance) and TOR (thermal-optical reflectance), respectively. This difference may be caused by the temperature of OC4 in He step and possibly difference in POC (pryorilized OC) formation. For the same temperature profile, OC by TOT was about 26% higher than that by TOR. In contrast, EC by TOT was about 50% lower than that by TOR. POC was also dependent on both temperature profile and the charring correction method, showing much distinctive differences for the charring correction method (i.e., POC by TOT to POC by TOR ratio is about 2). This difference might be caused by different characteristics between transmittance and reflectance for monitoring POC formation within filters. Results from this study showed that OC and EC depends on applied analysis protocol as shown other studies. Because of the nature of the thermal optical analysis, it may not be possible to have an absolute standard analysis protocol that is applicable for any ambient $PM_{2.5}$. Nevertheless, in order to provide consistent measurement results for scientists and policy makers, future studies should focus on developing a harmonized standard analysis protocol that is suitable for a specific air domain and minimizes variations in OC and EC measurement results. In addition, future elaborate studies are required to find and understand the causes of the differences.

• Applied Chemistry for Engineering
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• v.34 no.5
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• pp.488-492
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• 2023

In this study, a carbon film derived from a polymer/lignin composite precursor was produced by a carbonization cycle with a controlled temperature profile. The feasibility of successful formation of the carbon film using the carbonization cycle was monitored. The adsorption behavior of the carbon film toward various molecules, such as nonpolar and polar organic molecules, and dyes was investigated using ultraviolet/visible (UV/Vis) spectroscopy compared with that of carbonized lignin. Cyclic voltammetry (CV) analysis proved that a robust carbon film was prepared by the carbonization cycle. It was also demonstrated that the carbonized lignin and carbon film showed adsorption capability toward all types of organic molecules, in particular organic dyes, owing to the carbonized lignin. This work provides important information for future relevant research.

• The Korean Journal of Ecology
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• v.15 no.3
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• pp.267-279
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• 1992

The relationship between pb, zn, cd, and the microbial biomass and activity were investigated in three public park soils of central and outer london. Variability with distance from the roadside and profile were studied. The heavey metal concentrations were the highest in hampstead heath and hyde park with high trafic density and the lowest in hainault. The highest concentrations of heavy metals were found adjacent to the roadside in the upper parts of the soil profile. Dehydrogenase activity, adenosine tri-phosphate and ergosterol contents used as indices of micrbial biomass and activity, were generally higher in hainadult, and also higher in the upper pats of the soil profile. Simple regression analysis indicated that the microbial biomass and activity were affected significantly by moisture content, water holding capacity, total organic carbon, total nitrogen, and organic mater rather than heavy metal concentration. Highest inputs of nitrogen and carbon were associated with high inputs of heavey metals, all three being derived from vehicle emissions adjacent to the road. The hyde park and hampstead heath microbial populations were able to respond to the c and n input positively by increase in biomass and activity, whereas the hainault populations could not. This rsult suggrsts adaptation in he former to heavy matals, but not in the latter.