• Korean Journal of Environment and Ecology
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• v.34 no.1
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• pp.85-92
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• 2020

The purpose of this study is to provide base information that can be utilized in surveying the status of landscape management within apartment complexes and grasping the conditions of the soil for planting plants, as a way to improve the quality of green spaces by repairing poorly vegetated spaces within apartment complexes and remodeling them with diverse species of plants. Considering that trees and shrubs of equal sizes are simultaneously planted upon the completion of apartment complexes, they were divided based on their completion year at the interval of 5 years and differences in the growth of trees and the components of soil over time were analyzed. Out of the species of trees planted in all the 9 apartment complexes surveyed in this study, the growth of 4 species of needleleaf trees and 4 species of broadleaf trees were surveyed. Juniperus chinensis 'Kaizuka' and Pinus densiflora Siebold & Zucc. out of the needleleaf trees and Malus floribunda Siebold ex Van Houtte out of the broadleaf trees showed the highest growth rate when over 5 years passed after planting and their growth rate decreased when over 10 years passed. Platycladus orientalis and Acer palmatum Thunb. in the apartment complexes that were built over 10 years ago showed the highest growth rate, which indicates that the species require a relatively long period of time for growth. The hardness of the soil at the areas where trees were planted but their soil surface was bare was analyzed. When over 5 years passed after the completion of apartment complexes, over 20 mm of the soil was found to be stamped. The physicochemical properties of soil were also surveyed and the pH level was found to have been continuously high ever since the completion. The organic content in the surveyed soil was about 1/3 of the content in fertile soil, which means that additional fertilization is required. These results indicate that the stamped soil and the health of soil can be restored, when replanting plants in bare areas, by adding plans to improve soil, such as designing drain ways around the planted areas, transporting soil for the 50 cm depth of the ground and mixing organic matters such as chaff, and simply by planting groundcover plants in the lower part of tress and shrubs.

• Journal of Korean Society of Forest Science
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• v.83 no.3
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• pp.286-298
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• 1994

The object of this study was to examine the user's impacts on the environmental deteriorations of trail at Ticket Office - Paekryunsa (Temple) Hyangch$\hat{o}$kpong - Dongyupryung - Chilyun Fall area in T$\hat{o}$kyusan National Park. Four trails were sampled in the study area according to the amount of users. Then the user's impacts on trail were measured at each trail. The Ticket Office-Paekryunsa trail was the most used district and followed at Paekryunsa-Hyangch$\hat{o}$kpong trail, Hyangch$\hat{o}$kpong-Dongyupryung trail in descending order. Dongyupryung-Chilyun Fall trail is not used by people because of rest rotation system. The entire width of trail was greater at the more heavily used trail. Maximum depth, cross-sectional area loss, and surface texture and roughness of trail were the highest at Paekryunsa-Hyangch$\hat{o}$kpong trail. Soil hardness, soil acidity, soil moisture content, organic matter content, and exchange canon were influenced by trampling. Soil hardness, soil acidity and exchange canon increased in tramples soil, but content of soil moisture and organic matter decreased therein. Environmental deteriorations of trail were significantly influenced by the amount of users and the slope of trail. Bared lands about $2.000m^2$ were appeared by trampling and camping around Hyangch$\hat{o}$kpong. Effects of carrying of rest rotation system for National Park were partly recognized at Dongyupryung-Chilyun Fall trail.

• Korean Journal of Environmental Agriculture
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• v.36 no.2
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• pp.67-72
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• 2017

BACKGROUND:Cultivation of alternative crops in paddy fields is necessary because of the decrease in rice consumption and the increase in excess stock of rice. The study was conducted to investigate the effects of alternative crops cultivation in paddy fields on soil physico-chemical characteristics and crop yield. METHODS AND RESULTS: Soybean (Glycine max), red-clover (Trifolium pratense), and water convolvulus (Ipomoea aquatica) were selected for alternative crops in the first and/or second year and rice was planted in the third year. When alternative crops were cultivated in the previous year, soil bulk density, soil hardness, and water content were lower than those for rice cultivation. Water-depth decreasing rate and aggregate content were greater for the upland-upland-paddy cropping system than upland-paddy-paddy cropping system. Cultivation of red-clover and water convolvulus for two years resulted in the high soil organic matter content. In the third year, available phosphate, exchangeable potassium, and soil cation exchange capacity were relatively high when soybean was cultivated in the previous year. In the first year, water convolvulus cultivation showed greater productivity than red-clover cultivation while the opposite pattern was found in the second year. Rice yield in the third year was greater for soybean or red-clover as a previous crop than for water convolvulus as a previous crop. CONCLUSION: The results suggest that cultivation of alternative crops in paddy fields can improve soil physical properties including bulk density, hardness, water content, and aggregate content as well as rice productivity.

• Journal of Periodontal and Implant Science
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• v.42 no.3
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• pp.88-94
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• 2012

Purpose: The use of appropriate instruments to clean surfaces with minimal change, is critical for the successful maintenance of a dental implant. However, there is no consensus about the type and methodology for such instruments. The aim of this study was to characterize changes in the roughness of titanium surfaces treated by various scaling instruments. Methods: Thirty-seven identical disks (5 mm in diameter) were investigated in this study. The specimens were divided into eight groups according to the types of instrumentation and the angle of application. Ultrasonic scaling systems were applied on a titanium disk to simulate standard clinical conditions. The equipment included a piezoelectric ultrasonic scaler with a newly developed metallic tip (NS group), a piezoelectric ultrasonic scaler with a conventional tip (CS group), a piezoelectric root planer ultrasonic scaler with a conventional tip (PR group), and a plastic hand curette (PH group). In addition, the sites treated using piezoelectric ultrasonic scaler systems were divided two sub-groups: 15 and 45 degrees. The treated titanium surfaces were observed by scanning electron microscopy (SEM), and the average surface roughness (Ra) and mean roughness profile depth (Rz) were measured with a profilometer. Results: SEM no significant changes in the titanium surfaces in the NS group, regardless of the angle of application. The PH group also showed no marked changes to the titanium surface, although some smoothening was observed. All CS and PR sites lost their original texture and showed irregular surfaces in SEM analysis. The profilometer analysis demonstrated that the roughness values (Ra and Rz) of the titanium surfaces increased in all, except the PH and NS groups, which showed roughness decreases relative to the untreated control group. The Ra value differed significantly between the NS and PR groups (P<0.05). Conclusions: The results of this study indicated that changes in or damage to titanium surfaces might be more affected by the hardness of the scaler tip than by the application method. Within the limitations of this study, the newly developed metallic scaler tip might be especially suitable for peri-implant surface decontamination, due to its limited effects on the titanium surface.

• Journal of the korean academy of Pediatric Dentistry
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• v.43 no.4
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• pp.427-434
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• 2016

The aim of this study was to compare the mechanical properties of high viscosity bulk-fill resin composites, $Filtek^{TM}$ Bulk Fill Posterior Restorative (FBF) and $Tetric^{(R)}$ N-Ceram Bulk Fill (TBF), with conventional composite ($Filtek^{TM}$ Z-350 XT, Z-350). The Vickers hardness test which indicates the degree of conversion was performed and the dye penetration test was performed to measure the microleakage which indicates polymerization shrinkage amount. To minimize experimental error, the standardized 3D-printed molds and the bovine teeth were used. Obtained data were analyzed by the Kruskal-Wallis test and Mann-Whitney test with the confidence interval of 95%. In the microhardness test within 1 hour of polymerization, lower surface of FBF and TBF showed significantly lower value than that of Z-350 (p < 0.05). But after 24 hours, the microhardness of FBF had increased and showed no significant difference with Z-350 (p > 0.05). In top and 2 mm depth surface, mean microhardness values were in the following order: Z-350 > FBF > TBF (p < 0.05). The mean microleakage value of TBF was significantly lower than others (p < 0.05). For clinical application of bulk-fill resin composites, caution for applying masticatory forces during 24 hours after polymerization is advised and further studies to decrease microleakage should be conducted.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.4 no.2
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• pp.74-83
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• 2001

The purpose of this study was investigate to the influence of forest roads characteristics and environment factors on the soil erosion, stability and vegetation survival of cut slope in forest roads. The results obtained could be summarized as follows; 1. The correlated factors between slope erosion and variables in cut slope were altitude, convex, degree of slope, length of slope and soil depth. In the stepwise regression analysis, length of slope and soil hardness was a high significant and its regression equation was given by -89.6136 + 15.0667X14 + 16.6713X15($R^2$ = 0.6712). 2. The main factors influencing the stability of cut slope were significant in order of coverage, middle, convex, length of slope and north, and its discriminant equation was given by -1.019 + 0.064X22 - 0.808X8 - 0.622X24 + 0.742X11 - 0.172X14 - 0.545X6 ($R^2$ = 0.793). 3. The centroids value of discriminant function in the stability and unstability estimated to 1.244 and -1.348, respectively. The boundary value between two groups related to slope stability was -0.1038. The prediction rate of discriminant function for stability evaluation of was as high as 91.3%. 4. The dominant species of invasion vegetation on the cut slope consist with Carex humilis, Agropyron tsukushiense var. transiens, Calamagrostis arundinacea, Miscanthus sinensis var. purpurascens, and Ixeris dentata in survey area. The rate of vegetation invasion more increased by time passed. 5. The life form of invasion vegetation in cut slop showed to $H-D_1-R_{2,3}-e$ type of the hemicryptophyte of dormancy form, dissem inated widely by wind and water of dissminule type, moderate extent and narrowest extent of radicoid type, erect form of growth form. 6. The correlated factors between forest enviroment and coverage appeared north, passage years and middle position of slope at 5% level. The forest environment factors influencing the invasion plants in survey area were shown in order to altitude, passage years, rock(none), forest type(mixed) and stone amount. The regression equation was given by 17.5228 - 0.0911X3 + 3.6189X28 15.8493X22 19.8544X25 + 0.3558X26 ($R^2$ = 0.4026).

• Steel and Composite Structures
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• v.34 no.5
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• pp.681-698
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• 2020

The paper addresses contribution to the modeling and optimization of major machinability parameters (cutting force, surface roughness, and tool wear) in finish dry hard turning (FDHT) for machinability evaluation of hardened AISI grade die steel D₃ with PVD-TiN coated (Al₂O₃-TiCN) mixed ceramic tool insert. The turning trials are performed based on Taguchi's L₁₈ orthogonal array design of experiments for the development of regression model as well as adequate model prediction by considering tool approach angle, nose radius, cutting speed, feed rate, and depth of cut as major machining parameters. The models or correlations are developed by employing multiple regression analysis (MRA). In addition, statistical technique (response surface methodology) followed by computational approaches (genetic algorithm and particle swarm optimization) have been employed for multiple response optimization. Thereafter, the effectiveness of proposed three (RSM, GA, PSO) optimization techniques are evaluated by confirmation test and subsequently the best optimization results have been used for estimation of energy consumption which includes savings of carbon footprint towards green machining and for tool life estimation followed by cost analysis to justify the economic feasibility of PVD-TiN coated Al₂O₃+TiCN mixed ceramic tool in FDHT operation. Finally, estimation of energy savings, economic analysis, and sustainability assessment are performed by employing carbon footprint analysis, Gilbert approach, and Pugh matrix, respectively. Novelty aspects, the present work: (i) contributes to practical industrial application of finish hard turning for the shaft and die makers to select the optimum cutting conditions in a range of hardness of 45-60 HRC, (ii) demonstrates the replacement of expensive, time-consuming conventional cylindrical grinding process and proposes the alternative of costlier CBN tool by utilizing ceramic tool in hard turning processes considering technological, economical and ecological aspects, which are helpful and efficient from industrial point of view, (iii) provides environment friendliness, cleaner production for machining of hardened steels, (iv) helps to improve the desirable machinability characteristics, and (v) serves as a knowledge for the development of a common language for sustainable manufacturing in both research field and industrial practice.

• Korean Journal of Environment and Ecology
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• v.2 no.1
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• pp.50-65
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• 1988

Trail and campground deteriorations and their environmental changes of soil and vegetation were studied in Guryong district of Mt. Chiak National Park in 1988. The Widths of both the entire trail and the bare portion as the trail condition were significantly greater on the more heavily used trail. and regressions showed the significant positive relationship between slope along the trail and maximum depth of the trail($R^2$=0.35). Deterioration types of trail which had higher frequency for a total of 63 observations were rock exposure(48%), trail deepening(29%) and root exposure(27%) in the high order. And occurence of trail deterioration was considerably influenced by slope along the trail Ecological changes of soil and vegetation of trailsides were not found at a uniform tendency but could be grouped, by the types of user's disturbance. On campsites. tree damage types and their frequencies were basic as a means of which grasp the limits of user's impact. The area with damaged trees on campsite in pine forest were larger than that in mixed forest and the frequency by damage type of trees varied according to the distance from the core of campsite and to the crown layer. Water content, pH and hardness of soil. coverage of lower trees, species and individuals per 100$m^2$, basal areas of upper and middle layer of trees had significant relationship with the distance from campsite to forest. The range influenced by user's disturbance was more than 70-80m, md Staphylea bumalda, Morns bombycis, Stephanandra incisa and Securinega suffruticosa were considered as tolerant species to user's impact.

• Economic and Environmental Geology
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• v.30 no.1
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• pp.51-60
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• 1997

The high radon (Rn222) potentials of soil, groundwater, hotspring and indoor environments in the Taejon city area were delineated by use of an EDA RDA-200 radon detector. The U and Th contents were also analysed using a Multi Channel Analyzer to illustrate the sources of the radon potentials. The average U concentrations in Taejon vary according to the type of granites such as $4.14{\pm}2.36ppm$ in schistose granite (SG), $3.13{\pm}1.70ppm$ in biotite granite (BG) and $3.01{\pm}1.95ppm$ in two mica granite (TG). The U contents in the granites are closely related with the amounts of uraniferous minerals. However, the U contents in the soil are found to be $5.05{\pm}4.75ppm$ in TG, $4.07{\pm}1.69ppm$ in BG and $3.87{\pm}1.91ppm$ in SG which are mainly explained by the different cation exchange capacities (CEC) of the soils from various granites. The levels of soil radon are $552{\pm}656pCi/l$ in SG, in which levels at two locations exceed the level of 1,350 pCi/l established as guideline for follow-up action by the U.S. Environmental Protection Agency (EPA), $443{\pm}284pCi/l$ in TG and $224{\pm}115pCi/l$ in the BG. The soil radon concentrations are found to be proportional to the U content and hardness of the soils. The groundwater radon concentrations in the domestic wells of - 30~-100 m depth show that $6,907{\pm}4,665pCi/l$ in TG, $5,503{\pm}6,551pCi/l$ in SG and $2,104{\pm}1,157pCi/l$ in BG which are positively related with U contents in soils. The radon levels of six groundwater wells in TG and two in SG are greater than guideline for drinking water level, 10,000 pCi/l by EPA (1986). Average radon contents of hotsprings and public bathes in the TG area are $7,071{\pm}1,942pCi/l$ and $1,638{\pm}709pCi/l$, respectively, which are below the EPA standard for remedial action value of the 10,000 pCi/l. The mean indoor radon concentrations of the TG and SG areas are $1.60{\pm}1.20pCi/l$ and $1.60{\pm}0.70pCi/l$, respectively. The elevated indoor radon levels of 5.6 pCi/l and 6.7 pCi/l are found to be particularly in TG area, which exceeds 4 pCi/i guideline, correlating positively with the U contents in the soil and radon concentration in the groundwater.

• Korean Journal of Soil Science and Fertilizer
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• v.25 no.2
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• pp.127-132
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• 1992

This experiment was conducted to find out the useful data for upland crop cultivation in the newly reclaimed tidal land. Poseung silty clay loam soil was selected, and cotton(Mogpo VII) and tall fescue were cultivated under different drainage systems and soil ameliorator applications. Soil hardness and bulk density were decreased by subsurface drainage and plastic film installed at 40cm depth of the soil. Red earth application was also effective to loosen the soil, but zeolite and gypsum made the subsoil compact. Water content of the soil was high in surface drain than that of subsurface drain or plastic film curtain plot during dry season. The water content was in order of plastic film curtain, surface drain and subsurface drain. Electrical conductivity(EC) was decreased to lower than 0.4 Simens $meter^{-1}$ ($SM^{-1}$) in the subsurface drain during rainy season, and the EC of subsurface drain was maintained a quater to an half of surface drain. The yield of cotton and tall fescue were high in order of subsurface drain, plastic film curtain and surface drain plot. The yields of cotton were increased to 36-73 % by ameliorator application, and the red earth application was more effective for tall fescue growth compare to gypsum and zeolite.