• Journal of the Korean Ceramic Society
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• v.43 no.1 s.284
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• pp.4-9
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• 2006

To test the fracture toughness of alumina; a Surface-Crack-in-Flexure (SCF) method, a Single-Edge-Precracked-Beam (SEPB) method and a Single-Edge-V-Notched-Beam (SEVNB) method were used at crosshead rates ranging from 0.005 mm/min to 2 mm/ min and relative humidity ranging from $15\%\;to\;80\%$. The results show that the fracture toughness tested by the SCF method increases with either an increasing loading rate or decreasing relative humidity; in contrast, the toughness by the SEPB method and the SEVNB method does not depend on the loading rate or the relative humidity. Theoretical analysis of the way slow crack growth affects the apparent fracture toughness indicates that the three testing methods have different effects with respect to the loading rate and the relative humidity; moreover, these differences are attributable to differences in the size of the cracks or notches.

• ALGAE
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• v.37 no.4
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• pp.293-299
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• 2022

To examine the effects of substratum types on the growth of Caulerpa okamurae, sand surface and sand burial experiments were conducted. Five assimilators (erect fronds) per replicate were cultured for 15 d on the surface of three different treatments: fine sand (200 ㎛), coarse sand (600 ㎛), and no sand (control). Also, three stolons and three assimilators were buried by fine grain or coarse grain sands and incubated for 15 d. In both experiments, other culture conditions included 25℃, 30 μmol photons m^-2 s^-1, and 16 : 8 h L : D (light : dark). In both experiments, stolon + assimilator-, assimilator-, and stolon-weights were measured. Relative growth rates (RGRs) of stolon + assimilator weights ranged from 0.43 to 1.95% d^-1 at no sand and fine sand treatment, respectively. RGRs for the weight of stolon + assimilator and new assimilators were significantly greater on the fine- and coarse sand surface than the control. In the burial experiments, RGRs of stolons (4.28% d^-1 at coarse sand and 5.57% d^-1 at fine sand, respectively) were significantly greater than those of assimilators (1.38% d^-1 at fine sand and 1.82% d^-1 at coarse sand, respectively). When stolons were buried, RGRs for assimilators were greater at the fine sand than at the coarse sand treatment. On the other hand, RGRs of buried assimilators for total frond weights and for newly produced stolons were significantly greater at the coarse sands than at the fine sands. In conclusion, C. okamurae grew well with all substrates of sands and showed better growth on fine sands than coarse ones. This result suggests that the growth of stolons and assimilators of C. okamurae is stimulated after stable attachment to the sand substrates by rhizophores. In addition, stolons showed higher growth rates than the assimilators in the sand burial states, indicating that stolons are more tolerant to low light than assimilators of C. okamurae.

• The korean journal of orthodontics
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• v.15 no.1
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• pp.23-42
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• 1985

The morphology and growth changes of the Craniofacial Complex are important in orthodontics and cephalometrics for analysis and evaluation of facial bone growth are widely used. The author analyzed the data using lateral cephalometric roentgenogram of 75 Korean male and 50 Korean females age of 6 to 10 with normal occlusion to provide informations-relative rates of facial bone growth of Korean which is to be contributed in Korean standard. The results were as follows: 1. Means, standard deviation and coefficient of variation of Korean children were obtained. 2. The item which showed significent difference between male and female was craniofacial height in absolute dimension. 9. No difference of sex was showed in increment of craniofacial height and depth. 4. Among the craniofacial depth increments, the lower facial depth dimension increased most, midfacial depth dimension increased less, and cranial depth dimension increased the least. 5. The horizontal body of mandible showed rapid growing tendency more than did the ascending ramus.

• Journal of The Korean Society of Agricultural Engineers
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• v.46 no.7
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• pp.35-44
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• 2004

In this study, a ventilation model was developed to determine a ventilation rate for the balance of heat, moisture and $CO_{2}$ in a mushroom house. Internal and external temperature, relative humidity and $CO_{2}$ concentration were measured and used to validate the ventilation model. The effects of various environmental factors on physiological responses of mushroom were also investigated. The verified model was simulated under the observed ventilation rates with a difference of$ 0.001{\~}0.065\;m^{3}{\cdot}S^{-1}$ (relative error of $0.3{\~}18.9\%$) when external temperature varied 22.5 to $24.8^{circ}C$ and average ventilation rates was $0.35m^{3}{\cdot}S^{-1}$. The optimal conditions for mushroom growth (internal temperature $22 ^{circ}C$, relative humidity $80\%$, $CO_{2}$ concentration 1,000 ppm) were used for the model application with external temperature, relative humidity and $CO_{2}$ concentration of $27.5{\~}33.5^{circ}C$, $60\%$, and 355 ppm, respectively. Thermal balance was a important factor for an optimum ventilation up to the external temperature of $32^{circ}C$, while $CO_{2}$ concentration balance was more important over $32^{circ}C$. This suggests that humidification for moisture balance is required to maintain temperature and $CO_{2}$ concentration at an optimal level by ventilation in a mushroom house.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1475-1480
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• 2004

Plasma Enhanced Chemical Vapor Deposition (PECVD) process uses unique property of plasma to modify surfaces and to achieve the high deposition rates. In this study, a vertical thermal RF-PECVD (Radio Frequency-PECVD) reactor is modeled to investigate thermal flow and the deposition rates with various shapes of the showerhead. The showerhead in the CVD reactor has the shape of a ring and gases are injected in parallel with the susceptor, which is a rotating disk. In order to achieve the high deposition rates, we have simulated the thermal flow fields in the reactor with several showerhead models. Especially the effects of the number of injection holes and the rotating speed of the susceptor are studied. Using a commercial code, CFDACE, which uses FVM (Finite Volume Method) and SIMPLE algorithm, governing equations have been solved for the pressure, mass-flow rates and temperature distributions in the CVD reactor. With the help of the Nusselt number and Sherwood number, the heat and mass transfers on the susceptor are investigated. In order to characteristics of measure the flatness of the layer, furthermore, the relative growth rate (RGR) is considered.

• The Korean Journal of Ecology
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• v.16 no.3
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• pp.329-339
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• 1993

Effects of relative light intensity and N, P fertilization on the growth and ramet dynamics of the rhizomatous plants, Arundinella hirta, Miscanthus sinensi and Spdiopogon sibiricus were studied in Chuncheon, Kangweon-Do. Ramets emerged in one pulse a year, withered in one pulse at the end of the growing season in M. sinensis and S. sibircus stands, while the birth and death pulse in A. hirta stands were two times. Total births of ramet were 9 times and 3.6 times greater in the unshaded fertilized stands of A. hirta and M. sinensis than in the shaded, However, those of S.sibiricus were 2.1 times greater in the shaded stands. Flowering rates of A. hirta, M.sinensis and S.sibiricus I the unshaded fertilized stands were 1.8, 2.7 and 1.04 times greater than in the shaded unfertilized stands, respectively. Height of ramets of A. hirta and M.sinensis were the hightest in the unshaded fertilized stands. However, that of s.sibiricus was the highest in the shaded fertilized stand. Aboveground production of A.hirta in the fertilized stand was 2.4 times greater in the unshaded stand than in the shaded one. Results of inflorescence frequency, shoot height and the ratio of aboveground to belowground were smiliar to the total births. The added fertilizer markedly increased the ramet density and the shoot productivity of three rhizomatous plants, especially of A. hirta.

• Asian-Australasian Journal of Animal Sciences
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• v.5 no.2
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• pp.369-374
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• 1992

In order to determine the effect of dietary cellulose levels on chick performance, 1-week-old White Leghorn male chicks were fed semi-purified diets containing either 5%, 10%, 15% or 20% cellulose for 3 weeks. All diets were iso-nitrogenous and iso-caloric. Feed intake and body weight were increased as the cellulose level was increased. Feed conversion was lower in the 5% cellulose diet than in the other diets. Compared to the case of 10% to 20% cellulose diets, relative length (per 100 g body weight) of esophagus, duodenum, small intestine and cecum was longer, and relative weight of esophagus, duodenum and crop was also heavier in the chicks fed the 5% cellulose diet. The other internal organs were not affected by the cellulose level. The retention rates of dry matter and nitrogen were lower in the 5% cellulose group than in the other groups. Concentration of carcass phospholipids was higher in the 5% cellulose group, and that of carcass cholesterol was increased as the cellulose level increased. In conclusion, the dietary cellulose level should be more than 5% to give an adequate chick performance, and no ill effect was found even at 20% level.

• Speech Sciences
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• v.13 no.3
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• pp.83-95
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• 2006

This study attempts to suggest a criterion of Korean language development. For this purpose we investigated speaking rates of the spontaneous utterances produced by 144 children, aged 3 to 8. We analyzed each subject's speaking rate and its relevance with speaker's age, gender and utterance length. To determine the relative contributions of variables to the speaking rate, multiple regression was conducted. Results of this study can be summarized as follows: (1) The mean and maximum values of the speaking rate increased with the growth of age. (2) A statistically significant increase in speaking rate appeared at two-year intervals. (3) There was no significant difference between male and female groups in the speaking rate. (4) The multiple regression analysis has shown that along with the speaker's age, the utterance length(the mean number of syllables per utterance) is also important in estimating the speaking rates.

• Journal of the Economic Geographical Society of Korea
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• v.4 no.2
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• pp.57-77
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• 2001

The Honam region has been recognized as one of the most lagging regions in Korea. Drawing upon some decompositions oi Gross Regional Domestic Product(GRDP) per head and labor productivity, the overall trend of inequalities in Korea has been revealed and the trajectory of the Honam region's economic change has been identified by examining how the region's economic performance changed relative to that of Korea in the 1990s. There are some findings. First of all, Korea is characterized by strong divergence in the development of its region economies, in terms o\ulcorner per capita GRDP, which relies upon productivity differentials rather than differences in employment rates. Second, the Honam region has displayed poor economic performances in terms of GRDP per head except for Jeonnam. Third, the dramatic fall in cumulative population growth relative to the national average has been an important factor in the Jeonnam's overwhelming economic performance measured by per capita GRDP. Fourth, the decline in the relative productivity of the Honam region is mostly explained by falling relative regional productivity growth in construction, transport and manufacturing, although it should be noted that the latter sector has made positive contribution to raising relative regional productivity of Jeonnam. Fifth, overall the shift in employment to service sector, especially to social, personal, public, health, education, other services other than distribution, hotels, catering has tended to support relative regional productivities, along with the positive contribution being made oi agriculture, forestry and fishing to relative regional productivity growth in the Honam region.

• Journal of Microbiology and Biotechnology
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• v.10 no.4
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• pp.455-461
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• 2000

Abstract Spirulina platensis was grown in SWlUe waste to reduce inorganic compowlds and simultaneously produce feed resources. Spirulina platensis prefers nitrogenous compounds in Ibe order: $NH_4^{+}-N>NO_3^{-}-N>simple-N$ such as urea and simple amino acids. It even consumes $NH_4^{+}-N$ first when urea or nitrate are present. Therefore, the content of residual $NH_4^{+}-N$ in Spimlina platensis cultures can be determined by the relative extent of the following processes: (i) algal uptake and assimilation; (ii) ammonia stripping; and (iii) decomposition of urea to NH;-N by urease-positive bacteria. The removal rates of total nitrogen ffild total phosphorus were estimated as an indicator of the treatment effIciency. It was found that Spirulina platensis was able to reduce 70-93% of $P_4^{3-}-P$, 67-93% of inorganic nitrogen, 80-90% of COD, and 37-56% of organic nitrogen in various concentrations of swine waste over 12 days of batch cultivation. The removal of inorganic compounds from swine waste was mainly used for cell growth, however, the organic nitrogen removal was not related to cell growlb. A maximum cell density of 1.52 dry-g/l was maintained with a dilution rate of 0.2l/day in continuous cultivation by adding 30% swine waste. The nitrogen and phosphorus removal rates were correlated to the dilution rates. Based on the amino acid profile, the quality of the proteins in the Spirulina platensis grown in the waste was the same as that in a clean culture.ulture.