• Applied Chemistry for Engineering
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• v.22 no.5
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• pp.562-565
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• 2011

In this study, we developed a bioprocess using Clostridium ljungdahlii as a biological catalyst to produce bio-ethanol, and the effect of pH on microbial growth and ethanol production was investigated. From the results of fermentation at various initial pH condition without pH control, pH of fermentation broth decreased to 4.5 within 24 h due to accumulation of by-product acetic acid and both microbial growth and ethanol production were stopped. The experimental result of initial pH 8 showed the highest microbial growth and ethanol production (0.53 g/L), since the pH drop was relatively slow. From the experiment of pH 7 maintained fermentation using pH controllable bioreactor, the maximum cell dry weight of 1.65 g/L and the maximum ethanol concentration of 1.43 g/L were obtained within 24 h. In conclusion, the C. ljungdahlii growth was enhanced by pH maintenance of neutral range, and the ethanol production was also enhanced based on the growth-associated ethanol production characteristics of C. ljungdahlii.

• Korean Journal of Heritage: History & Science
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• v.56 no.1
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• pp.100-116
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• 2023

The Sinamsa Temple was built in the late Goryeo Dynasty and a gilt-bronze seated Buddha is enshrined in Geungnakjeon hall in the precinct. Various damages occurred in the gilt layer of the Buddha, such as peeling of the gilt layer and deteriorating gloss. In the study, the conservation conditions of the inside and outside on the statue were accurately investigated, and the making technique was interpreted through the material characteristics and non-destructive diagnosis of the statue. As a result, it is estimated that gold-gilding layer is pure gold, coloration pigment of black is carbon, green is malachite, atacamite and verdigris, red is red lead and cinnabar, respectively. In the deterioration evaluation, peeling, cracking, break out and exfoliation of the gilt layer are confirmed as damages, but the conservation condition is relatively wholesome. However, the gloss of the gilt layer is calculated to be wider in the poorer part than the maintenance part. The ultrasonic velocity of the statue was calculated to be 1,230 to 3,987 (mean 2,608) m/s and showed a relatively wide range. In infrared thermography, peeling was not confirmed, and no special bonding marks were found. In endoscope, some biological damage and corrosion were observed on the surface of the internal metal, and sealed artifacts were identified. Manufacturing technique based on the study, it is considered that the gilt-bronze seated Buddha was cast at once, and the mold was inverted to inject molten metal.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.1A
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• pp.53-59
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• 2010

Recently, NDTs (Non-Destructive Techniques) using infrared camera are widely studied for detection of damage and void in RC (reinforced concrete) structures and they are also considered as an effective techniques for maintenance of infrastructures. The temperature on concrete surface depends on material and thermal properties such as specific heat, thermal conductivity, and thermal diffusion coefficient. Different porosity on cement mortar due to different mixture proportions can show different heat behavior in cooling stage. The porosity can affect physical and durability properties like strength and chloride diffusion coefficient as well. In this paper, active thermography which uses flash for heat induction is utilized and thermal characteristics on surface are evaluated. Samples of cement mortar with W/C (water to cement ratio) of 0.55 and 0.65 are prepared and physical properties like porosity, compressive strength, and chloride diffusion coefficient are evaluated. Then infrared thermography technique is carried out in a constant room condition (temperature $20{\sim}22^{\circ}C$ and relative humidity 55-60%). The mortar samples with higher porosity shows higher residual temperature at the cooling stage and also shows reduced critical time which shows constant temperature due to back wall effect. Furthermore, simple equation for critical time of back wall effect is suggested with porosity and experimental constants. These characteristics indicate the applicability of infrared thermography as an NDT for quality assessment of cement based composite like concrete. Physical properties and thermal behavior in cement mortar with different porosity are analyzed in discussed in this paper.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.6
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• pp.135-146
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• 2011

Steel structures have been generally painted to prevent corrosion damage. However, the painted film is deteriorated with increase in service life, and then corrosion damage resulting in cross sectional area occurs on steel surface. As a result, the buckling strength of steel structures can be decreased due to the corrosion damages. The evaluation method of the axial buckling strength of columns about a variety of section shapes and supporting conditions have been presented, but evaluation method of buckling strength about irregular nonprismatic columns is not established. In this study, the axial buckling strength of corroded steels was evaluated based on the buckling test results of corroded steel specimens that were cut off at a temporary steel structure. The corroded specimens were picked up total 10 specimens according to various slenderness ratio from the web of a temporary structure's main beam. The length of specimens is 200, 300, 400, 500 and 600mm respectively. The rust productions were removed by the chemical treatment. Then, the surface geometry was measured at intervals of $1{\times}1mm$ by using the optical 3D digitizing system, and the residual thickness of the specimens was calculated. The axial buckling test was performed on 10 corroded specimens and 12 non-corroded specimens under the fixed-fixed support condition. From the test results, the effect of corrosion damages on axial buckling load was investigated. Regardless of corrosion damage degree, the axial buckling strength of corroded specimens and non-corroded specimens was evaluated identically by using minimum average residual thickness or average residual thickness to minus its standard deviation. Reasonable measuring intervals of residual thickness was proposed by using the results to apply for practical works.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.6
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• pp.53-62
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• 2018

Follofwing the accelerating speed-up of trains and rising demand for large-volume transfer capacity, not only in Korea, but also around the world, track structures for trains have been improving consistently. Precast concrete slab track (PST), a concrete structure track, was developed as a system that can fulfil new safety and economic requirements for railroad traffic. The purpose of this study is to provide the information required for the development and design of the system in the future, by analyzing the behavior of each structural member of the PST system. The stress distribution result for different combinations of appropriate loads according to the KRL-2012 train load and KRC code was analyzed by conducting a three-dimensional finite element analysis, while the result for different thicknesses of the grouting layer is also presented. Among the structural members, the largest stress took place on the grouting layer. The stress changed sensitively following the thickness and the combination of loads. When compared with a case of applying only a vertical KRL-2012 load, the stress increased by 3.3 times and 14.1 times on a concrete panel and HSB, respectively, from the starting load and temperature load. When the thickness of the grouting layer increased from 20 mm to 80 mm, the stress generated on the concrete panel decreased by 4%, while the stress increased by 24% on the grouting layer. As for the cracking condition, tension cracking was caused locally on the grouting layer. Such a result indicates that more attention should be paid to the flexure and tension behavior from horizontal loads rather than from vertical loads when developing PST systems. In addition, the safety of each structural member must be ensured by maintaining the thickness of the grouting layer at 40 mm or more.

• Korean Journal of Heritage: History & Science
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• v.44 no.1
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• pp.182-195
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• 2011

Old big tree transcends the simple meaning of trees as they are the natural monuments that embody the people's history and culture of this land. The Cultural Heritage Administration of Korea (CHA) defines and protects old big tree based not only on the size of the tree but also on its definitive cultural and natural factors such as value, implications, and originality. This research aims to identify and analyze the habitation and measurements, the soil conditions, as well as the protective facilities of 14 old big tree spread throughout the Gangwondo. The research examined the soundness of the arboreal form, the degree of damage on the bark, as well as the quantity of leafs levels to evaluate the overall condition of growth and development. Then, the tree height, the eastwest and south-north width of the crown, the sternum circumference, and the root circumference were recorded to identify the measurements of the selected old big tree. Also, the research analyzed 9 elements such as soil texture, pH levels, and organic contents in order to determine the scientific characteristics of soil upon which the trees draw nutrition. Finally, the research evaluated supporting pillars, lightning rods, iron pulling-facilities, as well as notice boards to study the protective facilities of old big tree. The research procedures revealed that 78.57% of the old big tree identified as natural monuments in the Gangwondo have average to above average habitation conditions. Also, the average tree height reaches 18.80m above ground while the average root circumference measures 7.34m. Moreover, the results of the scientific analyses conducted on the soil elements determined that most chemical values were within the defined levels, with the exception of phosphoric acid levels falling within the hyper-nutritious range. Finally, although most of the protective facilities did support the habitation of the Old big tree, there were some supporting pillars and iron pulling-facilities that actually damaged the trees. This research means to provide foundational reference data for the analysis of the habitation and management conditions of natural monument old big tree within the Gangwondo. A follow-up topic led by the results of this research is the identification and analysis of correlating environmental elements that affect the habitation of the old big tree.

• Journal of Bio-Environment Control
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• v.22 no.4
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• pp.341-348
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• 2013

Maintenance of adequate soil tension or content during the period of crop growth is necessary to support optimum plant growth and yields. A better understanding of soil tension and content for precision irrigation would allow optimal soil water condition to crops and minimize the adverse effects of water stress on crop growth and development. This research reports on a comparison of soil water tension and content variations in differently textured soils over time under drip irrigation using two different water management methods, i.e. pulse time and required water irrigation methods. The pulse time-based irrigation was performed by turning the solenoid valve on and off for preset times to allow the wetting front to disperse in root zone before additional water was applied. The required water estimation method was a new water control logic designed by Rural Development Administration that applies the amount of water required based on a conversion of the measured water tension into water content. The use of the pulse time irrigation method under drip irrigation at a high tension of -20 kPa and high temperatures over $30^{\circ}C$ was not successful at maintaining moisture tensions within an appropriate range of 5 kPa because the preset irrigation times used for water control could not compensate for the change in evapotranspiration during day and night. The response time and pattern of water contents for all of the tested soils measured with capacitance-based sensor probes were faster and more direct than those of water tensions measured with porous and ceramic cup-based tensiometers when water was applied, indicating water content would be a better control variable for automatic irrigation. The required water estimation-based irrigation method provided relatively stable control of moisture tension, even though somewhat lower tension values were obtained as compared to the target tension of -20 kPa, indicating that growers could expect to be effective in controlling low tensions ranging from -10 to -20 kPa with the required water estimation system.

• Journal of Korean Society of Forest Science
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• v.70 no.1
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• pp.1-6
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• 1985

The purpose of this experiment lies in finding the most appropriate cutting condition of Taxus cuspidata Sieb. et Zucc. which has been considered valuable tree species in gardening. Statistical analysis was focused on the comparison of the average ratios of rooting between greenhouses and fields, based on the observation rooted autogenis. To conduct this survey, hardwood cutting of Taxus cuspidata Sieb. et Zucc. were performed at both places of experiment above on April 20, 1982 with rooting results calculated on October 31, 1982. After formation of cuttings, it was soaked in IBA 200 ppm for 12 hours and than put in a bed. A summary of the result is presented as follows; 1) Cutting at the greenhouse showed higher average rate of rooting than at fields. Same tendency was found regardless of the differences in treatment. 2) It was clear that IBA-treatment contributed remarkably to causing higher average rooting rate. As an evidence, when twenty centimeter cuttings were inserted sandy media, IBA-treated area resulted in eighty six percent of average rooting rate, as compared with only twenty three percent in nontreatment case. In case of field cutting, IBA-treatment brought about fifty three percent of rooting in comparison with eleven percent nontreatment. 3) When sandy soil, loam and brown soil were separately used as cutting media, the highest rooting rate was found in case of sandy soil, without any difference between the two experimental places above. 4) As a result of the analysis to seek the impact of the length of cuttings on rooting, the range of length form fifteen to twenty centimeter was apparently most appropriate. It was also found that the rate of rooting declined beyond twenty five centimeter. 5) Two kinds of rooting pattern were observed. One was the case that callus cell lump was created on the lower cut side of cuttings. Importantly, root radical were formed inside the lump to influence the germination of root system. The other relates to the case that adventitious root which look like lateral roots appeared at the stem region. In abstract, first, sandy soil was effectively recommended in case of hardwood cutting in April. Second, the most appropriate length of cuttings ranged between fifteen and twenty centimeters. Third, high density IBA treatment was clearly effective. Forth, for proper environmental management, both pre-disinfection of sail by sterilizer and maintenance of high relative humidity were essentially required.

• Journal of the Korean Institute of Landscape Architecture
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• v.38 no.1
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• pp.39-48
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• 2010

Recreation forests are in the spotlight as the place for personality development, mind and body comfort, companionship, and environment education in forests and valleys. Visitors to recreation forests have been on the increase along with booming in recreation forest building since 1988. Recreation forests are being categorized according to some features such as regional and environmental condition. Recreation forests, however, have not met the expectations of some visitors who want to take a rest with calmness due to the influence of the 5-day-work-week system, increasing interest in rest, leisure, and well-being, and users converge during weekends, summer, and the tourist season. In order to improve visitors' satisfaction efficiently, this study surveyed the level of satisfaction in each cluster based on the precedent study which had classified 85 national or public recreation forests in Korea into clusters. Questionnaires were distributed properly to each cluster and, of the 1,132 questionnaires collected, 1,015 were valid and used for analysis. Reliability of questionnaires and statistical validity of the model were verified. As a result, there are meaningful differences in the ranking of independent variables which affect the level of satisfaction according to clusters. Variables in rest and fatigue recovery have the strongest influence on the level of satisfaction in the clusters of potential factor, internal activation factor, and mixed potential capacity factor. In the use performance and visiting condition factor cluster, appropriateness of visit cost is most influential and, in the education cluster, connectivity with tourist attractions around it is most affective. These results can provide priority in services and maintenance of recreation forests for improving the level of satisfaction and differentiate the distribution of resources according to clusters.

• Korean Journal of Ecology and Environment
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• v.51 no.4
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• pp.259-267
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• 2018

This study was conducted to confirm phenological response of main deciduous woody species in Korea according to elevated temperature. Based on seeds collected from the same place, 39 woody species were cultivated in field (control) and in greenhouse (treatment) that was maintained above base temperature ($4.8^{\circ}C$). And then, we observed phenotype change of leaves focused on phenological response and explained relation with their current distribution area. As a result, initiation period of leaves unfolding was 1st~3rd, May in control. It was 13, December~7, January in treatment. Period of leaves yellowing was 11~26, October in control. It was 30, October~13, November in treatment. Consequently, initiation period of leaves unfolding was faster by 119~140 days and period of leaves yellowing was slower by 3~32 days since elevated temperature. Period of leaves growth increased in treatment by 148 days than control. Quercus mongolica and Quercus serrata that cultivated in treatment was changed as evergreen trees which have grown up continuely during one year. Also, initiation period of leaves unfolding of Sorbus alnifolia in treatment was faster than in control. However, difference of the period between control and treatment was smallest. Because period of yellowing leaves was moved ahead. Phenological response of leaves according to elevated temperature had no relation of type of their current distribution area. This is the result of acclimation due to elevated temperature during the winter and suggests that the phenotype of leaves of 39 deciduous woody species is more sensitive to the current growth condition than to the past growth condition.