• Journal of Korea Foundry Society
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• v.15 no.2
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• pp.184-193
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• 1995

Effects of process parameters during thixocasting, such as solid volume fraction, mold temperature and extrusion ratio, on the mold filling behaviour and fluidity of Mg alloy(AZ91D) have been investigated. The semi-solid ingot held for 60 minutes at the semi-solid temperature range did not contain the equilibrium volume fraction of solid as expected from the phase diagram. Therefore, in order to obtain the desired solid fractions, and to suppress the exaggerated grain growth during heating, it was required to heat the ingot rapidly up to the temperature $10^{\circ}C$ higher than the semi-solid temperature suggested from the phase diagram for a specific volume fraction of solid. The experimental results show that mold filling behaviour and fluidity can be improved with the use of the higher mold temperature and the lower volume fraction of solid, but remain nearly unaffected by the change of extrusion ratio.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.8
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• pp.733-741
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• 2013

This is the first paper on the combustion characteristics of landfill gas in a constant volume combustion chamber for a large displacement volume commercial engine, and it discusses the fundamental characteristics of fuel from the viewpoint of thermochemistry and thermodynamics and compares these results with experimental ones. The results show that the final pressures obtained from theoretical analysis vary under the same heating value owing to the change in the constant volume specific heat owing to the difference in the burned gas composition according to the fuel gas compositions; furthermore, the stoichiometric ratios and trends of analytical and experimental pressures coincide very well, although some minor differences are observed between the two. The root cause of the difference is the heat transfer, which changes the specific heat and lowers the temperature considerably, in the real combustion process. In addition, the large chamber volume and ignition position promote the heat transfer to the wall. Finally, the fuel conversion efficiency increases as the methane mol fraction decreases, and it is maximum when the stoichiometric ratio ranges from 0.8 to 0.9. These increases due to the composition and stoichiometric ratio could sufficiently compensate the decrease due to the specific heat ratio drop, LFG might be more advantageous than pure methane in a real engine.

• Journal of Climate Change Research
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• v.8 no.4
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• pp.415-424
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• 2017

This study was conducted to estimate carbon stocks of Pinus densiflora with drawing volume of trees in each tree height and DBH applying the suitable stem taper equation and tree specific carbon emission factors, using collected growth data from all over the country. Information on distribution area, tree age, tree number per hectare, tree volume and volume stocks were obtained from the $5^{th}$ National Forest Inventory (2006~2010) and Statistical yearbook of forest (2016), and method provided in IPCC GPG was applied to estimate carbon stock and uptake. Performance in predicting stem diameter at a specific point along a stem in Pinus densiflora by applying Kozak's model, $d=a_{1}DBH^{a_2}a_3^{DBH}X^{b_{1}Z^2+b_2ln(Z+0.001)+b_3\sqrt{Z}+b_4e^z+b_5(\frac{DBH}{H})}$, which is well known equation in stem taper estimation, was evaluated with validations statistics, Fitness Index, Bias and Standard Error of Bias. Consequently, Kozak's model turned out to be suitable in all validations statistics. Stem volume table of P. densiflora was derived by applying Kozak's model and carbon stock tables in each tree height and DBH were developed with country-specific carbon emission factors ($WD=0.445t/m^3$, BEF = 1.445, R = 0.255) of P. densiflora. As the results of analysis in carbon uptake for each province, the values were high with Gangwon-do $9.4tCO_2/ha/yr$, Gyeongsandnam-do and Gyeonggi-do $8.7tCO_2/ha/yr$, Chungcheongnam-do $7.9tCO_2/ha/yr$ and Gyeongsangbuk-do $7.8tCO_2/ha/yr$ in order, and Jeju-do was the lowest with $6.8tC/ha/yr$. Total carbon stocks of P. densiflora were 127,677 thousands tC which is 25.5% compared with total percentage of forest and carbon stock per hectare (ha) was $84.5tC/ha/yr$ and $7.8tCO_2/ha/yr$, respectively.

• Journal of Climate Change Research
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• v.6 no.4
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• pp.357-366
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• 2015

This study was conducted to estimate carbon stocks of Quercus serrata with drawing volume of trees in each tree height and DBH applying the suitable stem taper equation and tree specific carbon emission factors, using collected growth data from all over the country. Information on distribution area, tree number per hectare, tree volume and volume stocks were obtained from the $5^{th}$ National Forest Inventory (2006~2010), and method provided in IPCC GPG was applied to estimate carbon storage and removals. Performance in predicting stem diameter at a specific point along a stem in Quercus serrata by applying Kozak's model,$d=a_1DBH^{a_2}a_3^{DBH}X^{b_1Z^2+b_2ln(Z+0.001)+b_3{\sqrt{Z}}+b_4e^Z+b_5({\frac{DBH}{H}})}$, which is well known equation in stem taper estimation, was evaluated with validations statistics, Fitness Index, Bias and Standard Error of Bias. Consequently, Kozak's model turned out to be suitable in all validations statistics. Stem volume tables of Quercus serrata were derived by applying Kozak's model and carbon stock tables in each tree height and DBH were developed with country-specific carbon emission factors ($WD=0.65t/m^3$, BEF=1.55, R=0.43) of Quercus serrata. As a result of carbon stock analysis by age class in Quercus serrata, carbon stocks of IV age class (11,358 ha, 36.5%) and V age class (10,432; 33.5%) which take up the largest area in distribution of age class were 957,000 tC and 1,312,000 tC. Total carbon stocks of Quercus serrata were 3,191,000 tC which is 3% compared with total percentage of broad-leaved forest and carbon sequestration per hectare(ha) was 3.8 tC/ha/yr, $13.9tCO_2/ha/yr$, respectively.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.182-182
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• 2017

Many small island nations rely on groundwater as their only other source of freshwater in addition to rainwater harvesting. The volume of groundwater resource of small island nations are further limited by their smaller surface area and specific hydrogeology. The rapid growth of population and tourism has led to increasing water demands and pollution of available groundwater resources. The predicted climate change effects pose significant threats to the already vulnerable freshwater lens of small islands in the form of rise in sea level, coastal inundation, saltwater intrusion, varied pattern of precipitation leading to droughts and storm surges. The effects of climate change are further aggravated by manmade stresses like increased pumping. Thus small island water resources are highly threatened under the effects of climate change. But due to the limited technical and financial capacity most of the small island developing states were unable to conduct detailed technical investigations on the effects of climate change on their water resources. In this study, we investigate how well small island countries are preparing for climate change. The current state of freshwater resources, impacts of predicted climate change along with adaptation and management strategies planned and implemented by small island countries are reviewed. Proper assessment and management practices can aid in sustaining the groundwater resources of small islands under climate change.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.6
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• pp.499-505
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• 2004

The objective of this study is to investigate the effect of supercooling repression on the TMA clathrate by adding ethylene glycol. For this purpose, phase change temperature, supercooling, specific heat, latent heat and rate of volume change were measured and evaluated experimentally for heat source temperatures of -6$^{\circ}C$, -7$^{\circ}C$, -8$^{\circ}C$. The results show that supercooling was decreased. Thus the experimental results are expected to be used for the increase of coefficient of performance of low temperature thermal storage system in the building.

• Applied Chemistry for Engineering
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• v.18 no.5
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• pp.467-474
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• 2007

The palladium and gold nanoparticles containing PAN-based active carbon fiber (ACF) with a high specific surface area were prepared. Using the BET, TEM, FE-SEM, and XPS, their specific surface area and pore volume, pore structure, and the change in surface oxygen groups with time were analyzed and $SO_2$ adsorption performances were investigated. Because of the impregnating process, the micropore volume was mostly decreased from 95.5% to 30.5~43.7% compared with the total pore volume. And the change in surface oxygen groups with time was higher for the metal salt than the nanoparticles. Also, $SO_2$ breakthrough time of PAN-ACFs impregnated with Au nanoparticles and metal salts did not change compared with that of the non-impregnated PAN-ACF. But the PAN-ACF impregnated with Pd nanoparticles (100 ppm) showed good $SO_2$ adsorption performance as the breakthrough time of 880 sec. These results indicated that the $SO_2$ adsorption performance depended on the change in surface oxygen groups with time and the moderate impregnation of Pd nanoparticles on the PAN-ACF caused the increase in the $SO_2$ adsorption performance by a catalytic action.

• Journal of the Korean Society of Food Science and Nutrition
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• v.34 no.3
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• pp.403-407
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• 2005

A study was conducted to evaluate the effect of substitution of the flour with Lycium chinense powder on the characteristics of yellow layer cake. Physical properties including specific gravity, specific volume, cake index and color were measured. Also, the hardness change during 6 storage days at 22℃ were measured. Even though the specific gravity of batter decreased significantly with respective addition of 12%, 16% and 20% Lycium chinense powder, the specific volume of cakes did not show difference except the case of 20% addition. The addition of Lycium chinense powder did not influence on cakes' appearance negatively except that of 20% cake. The crust became darker as the level of Lycium chinense powder increased. The crumb color turned into dark orange with addition of Lycium chinense powder, and the intensity became stronger as the level of Lycium chinense powder increased. Both 4% and 8% Lycium chinense powder cakes were scored as same as control in moistness and softness. And they were favored as much as control.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.8 no.1
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• pp.27-32
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• 1997

Recently, many people suffering from voice color change visit otolaryngologist. There is no specific data which can be evaluated objectively for voice color change in korean. In aerodynamic study, maximum phonation time, mean air flow rate, phonatory flow volume and subglottal pressure were tested by using Aerophone II voice function analyzer in korean. 112 male and 122 female aged from 10 to 69 years were randomly selected. Maximum phonation time was 20.8${\pm}$6.4sec in male and 17.2${\pm}$4.1sec in female. Mean air flow rate was 167.1${\pm}$61.4ml/sec. in male and 129.6${\pm}$49.3ml/sec in female. Phonatory flow volume was 3184.5${\pm}$646.0ml in male and 2122.1${\pm}$670.5ml in female. Subglottal pressure was 4.1${\pm}$1.8 cmH2O in male and 3.5${\pm}$1.4cm $H_2O$ in female. There was no statistically significant difference among age groups in all above results.

• Carbon letters
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• v.6 no.4
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• pp.243-247
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• 2005

Plasma polymerization of allylamine subsequently after plasma pre-treatment was conducted on the activated carbon fibers (ACFs) for the immobilization of amine groups in the surface of ACFs. The change of structural properties of ACFs with respect to different polymerization conditions was investigated through BET method. The change of surface morphologies of ACFs with respect to different plasma polymerization power was also studied through AFM. It was found that the structural properties such as specific surface area and micropore volume could be optimized under certain plasma deposition conditions. It was reckoned that treatment and deposition showed adverse effect on plasma polymerization, in which the former developed the micro-structures of the ACFs and the latter tended to block the micro pores. The Fourier transform infrared spectroscopy (FTIR) revealed that the poly(allylamine) was successfully immobilized on the surface of ACFs and the amount of the deposited polymer layer was related to the plasma polymerization power. SEM results showed that the plasma deposited polymer layer were small and homogenously distributed. The size and the distribution of particles deposited were closely related to the plasma polymerization power, too.