• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.70-73
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• 2002

Using zirconium ceramics makes the ferrule, which is the part of optical communications. The quality of optical communications is directly affected by the concentricity of the optic ferrule. The products of optic ferrule should be meet the following general conditions which are the outer diameter of 2.5mm and the inner diameter of 0.125mm, and high quality conditions which are the concentricity of 0.1~$0.3\mu\textrm{m}$, the form accuracy of $0.2\mu\textrm{m}$, the roundness and the cylindricity of $0.1\mu\textrm{m}$ and the surface roughness of 10nm. Generally, the diamond wheel is used for the high efficiency and precision grinding of the materials. It is good for keeping the shape as it has little wear. Because of the loading phenomena, however, it is difficult to keep the fresh surface of the wheel. In grinding process, grinding fragments resemble fine powders rather than chips. It can easily get attached to the wheel surface and thus cause a loading. The loading takes place, in which the impurities stick to the wheel surface, and the grinding characteristics of wheel is deteriorated. To prevent all of these, a suitable dressing method should be used for the wheel. In this research, the dressing system fur co-axial grinding machine was designed and produced for the machining of ferrule, which is a high performance part. The performance of the developed dressing system was evaluated by measuring the form accuracy of ferrule, which is machined by the dressed wheel in developed dressing system.

• Journal of environmental and Sanitary engineering
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• v.15 no.3
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• pp.94-100
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• 2000

This study was carried out to interpret hydraulic behavior and CO2 gas desorption in counter-current packing tower which packed 50mm plastic Hiflow-ring. The results are as follow : To compare with conventional packing, 50mm Hiflow-ring could save energy because of low pressure drop under high load. As relative error between calculated value and investigated value was less than 6% in the loading point and flooding point we found that we are predict results mathematically which occur in packing tower. The unique magnitude of packing which was used are as follows. $C_L=2.1{\times}10^{-4}$, n=0.787 so we can predict efficiency which occur

• Journal of Korean Society of Transportation
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• v.29 no.2
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• pp.25-35
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• 2011

In order to reduce Green House Gas(GHG) reduction in the road freight sector and thus establish green logistics, running efficiency of goods vehicles is of paramount importance. Providing effective transportation infrastructure can contribute to achieve the green logistics by reducing empty running of heavy goods vehicles and van, increasing the average payload on the vehicle, and shifting the transportation mode. In order to reduce the environmental impact from the road freight sector, it is essential to quantify the amount of environmental loading from the sector. However, any systematic survey on the environmental loading from the logistics companies has not been carried out in Korea. In this study, the environmental index for the road freight sector is defined as the amount of $CO_2$ emission per ton km generated from goods vehicles. The computational analysis shows that the average $CO_2$ emission per ton km generated by the logistics companies in Korea is $363g-CO_2/ton{\cdot}km$. Compared to UK (=$130g-CO_2/ton{\cdot}km$) and France (=$97g-CO_2/ton{\cdot}km$), the efficiency of logistics in Korea is 2.8 and 3.7 times as low as in the advanced countries. It also indicates that the main reasons for the low efficiency are mainly due to the high rate of empty operation of goods vehicles and the low payload.

• Journal of Korean Society on Water Environment
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• v.18 no.2
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• pp.189-199
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• 2002

Nitrogen, in its various forms, can deplete dissolved oxygen levels in receiving waters, stimulate aquatic growth, exhibit toxicity toward aquatic life and affect the suitability of sewage for reuse. Pilot-scale Rotating Biological Contactor(RBC) experiments were conducted to examine biological nitrification, respectively, of municipal sewage with five different internal recirculation ratios of 0, 1, 2, 3, and 4 using the constant hydraulic loading of $205L/m^2{\cdot}day$. The use of internal recirculation improved nitrification on account of the dilution of biodegradable organic carbon in influent sewage down to 15 mg/L of $SBOD_5$ or less. Ammonium nitrogen of $14.3{\pm}2.4%$ was consumed by cellular assimilation without the occurrence of denitrification. The thickness of biofilm didn't seem effect significantly the nitrification and denitrification. Nitrification with internal recirculation was found to occur using hydraulic loading rate of as high as $205L/m^2{\cdot}day$, which was beyond the generally known values of it.

• Journal of the Korean Electrochemical Society
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• v.24 no.2
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• pp.28-33
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• 2021

Many researchers have increased the loading level of electrodes to improve the energy density of secondary batteries. In this study, high-loading NCM523 (LiNi_0.5Co_0.2Mn_0.3O₂) positive electrode is manufactured using a polytetrafluoroethylene (PTFE) binder, not the conventional polyvinylidene fluoride (PVdF) binder, which has been commonly used in lithium-ion batteries. Through the kneading process using PTFE suspension, not the conventional slurry process using PVdF solution in N-methyl-2-pyrrolidinone (NMP), thick electrodes with high loading are easily manufactured. When the PTFE and PVdF-based electrodes are prepared at a loading level of 5.0 mAh/cm², respectively, the PTFE-based electrode shows better cycle performance and rate capability than those of PVdF-based electrodes. The electrode manufactured by the kneading process using a PTFE binder has high electrode porosity due to insufficient roll-press, but the porosity can be lowered by high temperature roll-press over 120℃. However, there is no significant difference in cycle performance according to the roll press temperature. In addition, the cycle performance of the high loading electrode is slightly improved by increasing the content of the conductive material. Overall, the PTFE binder can improve the performance of the high loading electrode, but additional solutions will be needed.

• Membrane Journal
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• v.19 no.2
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• pp.113-121
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• 2009

Porous affinity chitosan and chitin membranes with good mechanical strength and high protein binding capacity were prepared by using silica particles as porogen. The maximum binding capacity of affinity chitosan membrane for BSA protein is 21.8mg/mL, and that of affinity chitin membrane for lysozyme enzyme is 26.1mg/mL. Chromatographic separations of BSA and lysozyme proteins using the porous affinity chitosan and chitin membranes were performed with change of the flow rate, loading amount and concentration of protein loading solutions. Protein eluted amount and binding yield were calculated from the filtration chromatograms consisted of loading/washing/elution sequences. Protein binding amount and yield were increased with decreasing of flow rate, increasing of loading amount and concentration of protein loading solutions. Those results suggest that the porous chitosan and chitin membranes prepared by using silica particles as porogen are suitable in affinity filtration chromatography for large scale separation of proteins.

• Korean Journal of Environmental Agriculture
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• v.25 no.3
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• pp.247-256
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• 2006

This study has been conducted for the process of food wastes disposal using surplus capacity of established sewage treatment plant by co-digestion of fermented food wastes and sewage sludge after thermophilic acid fermentation of food wastes. The co-digestion of thermophilic acid fermented food wastes and sewage sludge was performed by semi-continous method in mesophilic anaerobic digestion reactor. It showed great digestion efficiency as the average SCOD and VS removal efficiency in organic loading rate 3.30g VS/L.d. were 74.2% and 73.6%, and the gas production rate and average methane content were 0.440 L/g $VS_{add}.d$ and 66.5%, respectively. Based on the results of this study, the co-digestion of thermophilic acid fermented food wastes and sewage sludge in sewage treatment plant is able to improve treatment efficiency of anaerobic digestion reactor and to dispose food wastes simultaneously, and was proved excellent economical efficiency comparing with any other treatment methods.

• Journal of Ocean Engineering and Technology
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• v.30 no.2
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• pp.100-108
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• 2016

A high-pressure ball valve was developed, and both the structural strength and sealing performance were assessed based on a nonlinear finite element analysis. Different parts were modeled with solid elements and assembled, taking into account both contact and sliding effects. Three different loading scenarios were analyzed, including a high-pressure closure test and fire and shell test conditions. The structural safety of each part was checked under each loading condition, and the sealing performance was also investigated to validate the performance of the valve.

• Structural Engineering and Mechanics
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• v.86 no.5
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• pp.607-619
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• 2023

This study, it was tried to evaluate the asphalt behavior under tensile loading conditions through indirect Brazilian and direct tensile tests, experimentally and numerically. This paper is important from two points of view. The first one, a new test method was developed for the determination of the direct tensile strength of asphalt and its difference was obtained from the indirect test method. The second one, the effects of particle size and loading rate have been cleared on the tensile fracture mechanism. The experimental direct tensile strength of the asphalt specimens was measured in the laboratory using the compression-to-tensile load converting (CTLC) device. Some special types of asphalt specimens were prepared in the form of slabs with a central hole. The CTLC device is then equipped with this specimen and placed in the universal testing machine. Then, the direct tensile strength of asphalt specimens with different sizes of ingredients can be measured at different loading rates in the laboratory. The particle flow code (PFC) was used to numerically simulate the direct tensile strength test of asphalt samples. This numerical modeling technique is based on the versatile discrete element method (DEM). Three different particle diameters were chosen and were tested under three different loading rates. The results show that when the loading rate was 0.016 mm/sec, two tensile cracks were initiated from the left and right of the hole and propagated perpendicular to the loading axis till coalescence to the model boundary. When the loading rate was 0.032 mm/sec, two tensile cracks were initiated from the left and right of the hole and propagated perpendicular to the loading axis. The branching occurs in these cracks. This shows that the crack propagation is under quasi-static conditions. When the loading rate was 0.064 mm/sec, mixed tensile and shear cracks were initiated below the loading walls and branching occurred in these cracks. This shows that the crack propagation is under dynamic conditions. The loading rate increases and the tensile strength increases. Because all defects mobilized under a low loading rate and this led to decreasing the tensile strength. The experimental results for the direct tensile strengths of asphalt specimens of different ingredients were in good accordance with their corresponding results approximated by DEM software.

• Korean Chemical Engineering Research
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• v.49 no.2
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• pp.256-262
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• 2011

Amine can undergo irreversible reactions by $O_{2}$ and high temperature in amine scrubbing process and these phenomena are called "degradation". Degradation causes not only a loss of valuable amine, but also operational problems such as foaming, corrosion and fouling. In this study, using various chemical absorbents(MEA; monoethanolamine, AMP; 2-amino-2-methyl-1-propanol, DAM; 1,8-diamino-p-menthane), we examined the following variable. I) loading ratio of $CO_{2}$ at $50^{\circ}C$ and $120^{\circ}C$, ii) concentration variation and initial degradation rate constant of absorbent in $CO_{2}$ and $CO_{2}/O_{2}$ system, and iii) effect of degradation by $O_{2}$. The $CO_{2}$ loading of 20 wt% DAM was 400% and 270% higher than that of 20 wt% MEA and AMP at 50, respectively and was the largest the difference of $CO_{2}$ loading between absorption $(50^{\circ}C)$ and regeneration $(120^{\circ}C)$ condition. The initial degradation rate constant of 20 wt% DAM was $2.254{\times}10^{-4}cycle^{-1}$ which was slower than that of MEA $(2.761{\times}10^{-4}cycle^{-1})$ and AMP $(2.461{\times}10^{-4}cycle^{-1})$ in $CO_{2}$ system. Also, it was increased 30% by $O_{2}$ that effects on the degradation by $O_{2}$ was less than 100% increased. these degradation reactions was able to identify by formation of new peak in GC and FT-IR spectrum analysis.