• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.91-93
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• 2009

A large steel ingot needs to be larger and larger in size and an ultra high clean, no defect in quality with a low hot top ratio for the resent heavy industry. The demands are very difficult to achieve simultaneously because of their contradictive effect to each other in results. In this study, 30ton steel ingot was cast in a foundry with an optimized design parameter of cast mold and cast process conditions for the low hot top ratio, 12%. The cast ingot was analyzed in macro defect, segregations, and cleanness. No macro defect was founded in central surface of the ingot. The degree of segregation and cleanness are in the controlled range with a sound quality.

• Korean Chemical Engineering Research
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• v.44 no.2
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• pp.200-206
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• 2006

In a biological aerated filter (BAF) packed with ceramic media (void fraction of BAF=0.32), nitrite accumulation was studied with the variation of hydraulic retention time (HRT) and superficial air velocity. Synthetic ammonium wastewater and petrochemical wastewater were fed at a constant load of $1.6kgNH_4^+-N/m^3{\cdot}d$. Ammonium removal rate was mainly affected by the superficial air velocity in BAF, but nitrite ratio($NO_2-N/NO_x-N$) in the effluent was dependent on both HRT and superficial air velocity. For a fixed HRT of 0.23 hr (corresponding to the empty bed contact time of 0.7 hr) ammonium removal rate was 73/90/92％ and nitrite ratio was 0.92/0.82/0.48 at the superficial air velocity of 0.23/0.45/0.56 cm/s, respectively. When HRT is increased to 0.9 hr with superficial air velocity ranging from 0.34 to 0.45 cm/s, the ammonium removal rate was 89％ on average. However nitrite ratio decreased significantly down to 0.13. When HRT was further increased to 1.4 hr, ammonium removal rate decreased, thereby resulting in the free ammonia ($NH_3-N$, FA) build-up and nitrite ratio gradually increased (>0.95). Although aeration rate and FA concentration at HRT of 0.23 hr were unfavorable for nitrite accumulation compared with those at HRT of 0.9 hr, nitrite ratio at HRT of 0.23 hr was higher. Taken together, HRT and nitrogen load were found to be critical, in addition to FA concentration and aeration condition, for nitrite accumulation in the BAF tested in the present study.

• Journal of the East Asian Society of Dietary Life
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• v.1 no.1
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• pp.99-111
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• 1991

In each nuruk using today, effect of pH on glucoamylase activity and viable cell count of yeast and bacteria was measured. Common components during fermentation, alcohol, acetaldehyde and acetone, amino acid composition, and total sugars and mineral content were determined in yakju(korean wine) brewed from different ingredients and by different methods. Results are summarized as follows ; 1. The lower the pH, the lower the glucoamylase activity in JK, BK, JK-S BK-S and JN. But the higher the glucoamylase activity ratio in Koji and KN. 2. Yeast and bacteria cell count could not determined in nuruk inoculated of seed. In JK, BK and JN, yeast cell count was 50${\times}$104∼80${\times}$104, bacteria cell count was 5${\times}$106∼24${\times}$106. 3. In yakju during fermentation, pH was higher in RU, total acidity content was higher in ST-N, ST-K, RU and ST-RUPO and alcohol content was lower in RUPO and ST-RUPO. 4. Ethanol and acetaldehyde content were highest in dukyunju. Trace amount of acetone was determined only in ST-K, RUPO and ST-RUPO . n-Propyl alcohol content was higher in ST-K, ST-RUPO and ST-N, iso-butyl alcohol content was higher in L-RUPO, Dukyunju and Songyupju and iso-amyl alcohol content was higher in Songyupju, RU, L-RUPO and Dukyunju. 5. In amino acids composition of each yakju, Pro, Ala and Val content was higher than other amino acids. Total amino acids content was the highest in Dukyunju and second highest in ST-N, NH3 was higher in ST-N, Dukyunju, RUPO than other samples. 6. Total sugars content was the highest in ST-N and second highest in RU. 7. P, K and Mg content were higher in Dukyunju and ST-N than in other samples. In Dukyunju, Ca and P ratio was 0.075 because of low Ca content and high P content.

• Journal of Korean Society on Water Environment
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• v.31 no.3
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• pp.304-312
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• 2015

In this study, we tried to determine the vertical variation of sediment structure and geochemical characteristics, core sediment was collected in the Nakdong River midstream on August, 2014. Core sediment mainly composed of sand (51.48%) and silt (46.21%) and coarsing upward changed from sM to mS facies. IL and TOC were decreased from lower to upper layer. C/N ratio was lower than 10 so the organic matters were originated from underwater creatures and C/S ratio was decreased from lower to upper layer. Heavy metal (Al, Fe, Zn, Cr, Pb, Ni, Cu, Cd) content were decreased from lower to upper layer and seriously polluted condition is not. These results are thought to be due to the effect of natural and anthropogenic in the fluctuation of flow.

• International Journal of Industrial Entomology and Biomaterials
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• v.17 no.2
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• pp.205-209
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• 2008

Impact of food plant on reproductive and commercial parameters in Antheraea mylitta, a polyphagous insect of economic importance was studied upon feeding the insect larvae on the same host plants for six continuous generations. A. mylitta larvae were fed upon Terminalia tomentosa, Terminalia arjuna and Zizyphus jujuba and restricted them to the same host plant for six generations to document the quantitative improvement in reproductive and commercial parameters. The parameters showed significant improvement in all the host plants studied over their respective controls. Fecundity among the reproductive parameters was highly improved than others (85.9% in T. tomentosa; 58% in T. arjuna and 49.7% in Z. jujuba). Likewise in commercial parameters, the shell weight in male showed the highest improvement (by 52.9%, 45.8% and 42.1% in T. tomentosa; T. arjuna and Z. jujuba respectively). On the other hand, the shell ratio percentage in female recorded the lowest improvement. The values for all characters were recorded a decline in T. arjuna and Z. jujuba fed ones over T. tomentosa, except that of shell ratio percentage in female has registered an increase in Z jujuba fed. The study thus revealed the comparative superiority of T. tomentosa over T. arjuna and Z. jujuba.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.8 s.101
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• pp.980-987
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• 2005

It is very difficult to reduce ambient noise level in the downtown. The best method is to improve the sound amenity of the districts, considering concept of soundscape. This study aims to survey the effect of introducing sound and masking to reduce the background noise level. We carried out the evaluating test for 18 introducing sounds varied S/N ratio(-5, 0, +5) in the city riverside. In these test, subjects evaluated the sound environment with five bipolar adjective scales. It was evaluated that introducing sounds improved the sound environment, and that S/N +5 dB was very appropriate to mask the background noise. But the hearing level was suggested to be S/N 0 dB or less.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.607-610
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• 2005

It is very difficult to reduce traffic noise level in the downtown. The best method is to improve the sound amenity of the districts, considering concept of soundscape. ?his study aims to survey the effect of introducing sound and masking to reduce the background noise level. We carried out the evaluating test for 18 introducing sounds varied S/N ratio(-5, 0, +5) in the city riverside. In these test, subjects evaluated the sound environment with five bipolar adjective scales. It was evaluated that introducing sounds improved the sound environment and that S/N + 5dB was very appropriate to mask the background noise. But the hearing level was suggested to be S/N 0 dB or less.

• Proceedings of the National Institute of Ecology of the Republic of Korea
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• v.2 no.4
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• pp.259-273
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• 2021

We conducted a study to investigate the characteristics of the carbon cycle of two streams (located in Shig a Prefecture, Japan), having similar size, namely, the Adokawa stream (length: 52 km, area: 305 km², watershed population: 8,000) and the Yasukawa stream (length: 62 km, area: 380 km², watershed population: 120,000), but with different degree of human activity. Samples were collected from these two streams at 14 (Adokawa stream) and 23 (Yasukawa stream) stations in the flowing direction. The dissolved inorganic carbon (DIC) concentration and the stable carbon isotope ratio of DIC (δ¹³C-DIC) were measured in addition to the watershed features and the chemical variables of the stream water. The δ¹³C-DIC (-9.50 ± 2.54‰), DIC concentration (249 ± 76 µM), and electric conductivity (52 ± 13 µS/cm) in Adokawa stream showed small variations from upstream to downstream. However, the δ¹³C-DIC (-8.68 ± 2.3‰) upstream of Yasukawa stream was similar to that of Adokawa stream and decreased downstream (-12.13 ± 0.43‰). DIC concentration (upstream: 272 ± 89 µM, downstream: 690 ± 37 µM) and electric conductivity (upstream: 69 ± 17 µS/cm, downstream: 193 ± 37 µS/cm) were higher downstream than upstream of Yasukawa stream. The DIC concentration of Yasukawa stream was significantly correlated with watershed environmental variables, such as, watershed population density (r = 0.8581, p<0.0001, n = 23), and forest area percentage of the watershed (r = -0.9188, p<0.0001, n = 23). δ¹³C-DIC showed significant negative correlation with the DIC concentration (r = -0.7734, p<0.0001, n = 23), electric conductivity (r = -0.5396, p = 0.0079, n = 23), and watershed population density (r = -0.6836, p = 0.0003, n = 23). Our approach using a stable carbon isotope ratio suggests that DIC concentration and δ¹³C-DIC could be used as indicators for monitoring the health of stream ecosystems with different watershed characteristics.

• Macromolecular Research
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• v.17 no.10
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• pp.797-806
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• 2009

The mechanical and thermal behaviors of polyamide-6/clay nanocomposites were studied using the continuum-based, micromechanical models such as Mori-Tanaka, Halpin-Tsai and shear lag. Mechanic-based model prediction provides a better understanding regarding the dependence of the nanocomposites' reinforcement efficiency on conventional filler structural parameters such as filler aspect ratio ($\alpha$), filler orientation (S), filler weight fraction (${\Psi}_f$), and filler/matrix stiffness ratio ($E_f/E_m$). For an intercalated and exfoliated nanocomposite, an effective, filler-based, micromechanical model that includes effective filler structural parameters, the number of platelets per stack (n) and the silicate inter-layer spacing ($d_{001}$), is proposed to describe the mesoscopic intercalated filler and the nanoscopic exfoliated filler. The proposed model nicely captures the experimental modulus behaviors for both intercalated and exfoliated nanocomposites. In addition, the model prediction of the heat distortion temperature is examined for nanocomposites with different filler aspect ratio. The predicted heat distortion temperature appears to be reasonable compared to the heat distortion temperature obtained by experimental tests. Based on both the experimental results and model prediction, the reinforcement efficiency and heat resistance of the polyamide-6/clay nanocomposites definitely depend on both conventional (${\alpha},\;S,\;{\Psi}_f,\;E_f/E_m$) and effective (n, $d_{001}$) filler structural parameters.

• Journal of Welding and Joining
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• v.18 no.1
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• pp.83-90
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• 2000

It was attempted to improve seam-tracking performance by applying a new arc-sensing algorithm for FCAW(flux-cored arc welding) process in fillet joints. For this study the authors have introduced three different weight factors: $\circled1$ arc currents at the weaving end are more weighted, $\circled2$ arc currents are evenly weighted along the weaving, and $\circled3$ arc currents at the weaving center are more weighted. To evaluate the 3 factors the values of signal-to-noise(S/N) ratio has been measured. The values were obtained for various welding conditions with different gaps in horizontal and vertical fillet joints. The test results showed that the S/N ratio of the 1st case was highest which resulted in the best of seam tracking performance. In addition, the comparison between the seam tracking performance in horizontal fillet joints and that in vertical ones has been done, and the result showed that tracking performance in vertical joints was relatively better than that in horizontal joints.