• Analytical Science and Technology
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• v.29 no.2
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• pp.57-64
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• 2016

Many phthalic acid esters (PAEs), including DMP, DEP, DBP, BBP, and DEHP, as well as DEHA are widely used as plasticizers in plastics. An analytical method was developed and used to analyze these compounds at 41 industrial facilities. The coefficient of determination (R²) for each constructed curve was higher than 0.98. The method detection limit (MDL) values were 0.4–0.7 μg/L for PAEs and 0.6 μg/L for DEHA. In addition, the recovery rate was shown to be 77.0–92.3%, while the relative standard deviation was shown to be in the range of 5.8-10.5%. DMP (n = 3), DEP (n = 2), DBP (n = 2), BBP (n = 2), and DEHA (n = 3) were detected in the range of 2.2-11.1% in the influent. DEHP was a predominant compound and was detected at > MDL in both the influent (n = 16, 35.6%) and the effluent (n = 4, 10.0%) at a high removal efficiency (92–100%). The highest levels of residue in industrial wastewater influent were 137.4 μg/L of DEHP at plastic products manufacturing facility, 12.5 μg/L of DEHA at a chemical manufacturing facility, and 14.0 μg/L of DEP at an electronics facility. The highest concentration of effluent was 12.5 μg/L of DEHP at a chemical manufacturing facility, which indicated that the effluent was below the allowable concentration (800 μg/L). Therefore, the levels of PAEs and DEHA that are discharged into nearby streams could not influence the health of the ecosystem.

• Journal of the Korean Geotechnical Society
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• v.19 no.6
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• pp.71-84
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• 2003

The metallic shell of soil-steel structures are so weak in bending moment that it should sustain the applied load by the interaction of the backfill soil around the structures. The shell can be subjected to excessive bending moment during side backfilling or under live-load when the soil cover is less than the minimum value. The current design code specifies the allowable deformation and Duncan(1979) and McGrath et al.(2001) suggested the strength analysis methods to limit the moments by the plastic capacity of the shell. However, the allowable deformation is an empirically determined value and the strength analysis methods are based on the results of FE analysis, hence the experimental verification is necessary. In this study, the full-scale tests were conducted on the high-profile arch to investigate its behaviors during backfilling and under static live-loads. Based on the measurements, the allowable deformation of the tested structure could be estimated to be 1.45% of rise, which is smaller than the specified allowable deformation. The comparison between the measurements and the results of two strength analyses indicate that Duncan underestimates the earth-load moment and overestimates the live-load moment, while McGrath et al. predicts both values close to the actual values. However, as the predicted factors of safeties using two methods coincide with the actual factor of safety, it can be concluded that both methods can predict the structural stability under live-loads adequately when the cover is less than the minimum.

• Korean Journal of Soil Science and Fertilizer
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• v.41 no.4
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• pp.260-266
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• 2008

Small lysimeter experiment under rain shelter plastic film house was conducted to investigate the effect of soil characteristics on the leaching and soil solution concentration of nitrate and phosphate. Three soils were obtained from different agricultural sites of Korea: Soil A (mesic family of Typic Dystrudepts), Soil B (mixed, mesic family of Typic Udifluvents), and Soil C (artificially disturbed soils under greenhouse). Organic-C contents were in the order of Soil C ($32.4g\;kg^{-1}$) > Soil B ($15.0g\;kg^{-1}$) > Soil A ($8.1g\;kg^{-1}$). Inorganic-N concentration also differed significantly among soils, decreasing in the order of Soil B > Soil C > Soil A. Degree of P saturation (DPS) of Soil C was 178%, about three and fifteen times of Soil B (38%) and Soil A (6%). Prior to treatment, soils in lysimeters (dia. 300 mm, soil length 450 mm) were tabilized by repeated drying and wetting procedures for two weeks. After urea at $150kg\;N\;ha^{-1}$ and $KH_2PO_4$ at $100kg\;P_2O_5\;ha^{-1}$ were applied on the surface of each soil, total volume of irrigation was 213 mm at seven occasions for 65 days. At 13, 25, 35, 37, and 65 days after treatment, soil solution was sampled using rhizosampler at 10, 20, and 30 cm depth and leachate was sampled by free drain out of lysimeter. The volume of leachate was the highest in Soil C, and followed by the order of Soils A and B, whereas the amount of leached nitrate had a reverse trend, i.e. Soil B > Soil A > Soil C. Soil A and B had a significant increase of the nitrate concentration of soil solution at depth of 10 cm after urea-N treatment, but Soil C did not. High nitrate mobility of Soil B, compared to other soils, is presumably due to relatively high clay content, which could induce high extraction of nitrate of soil matrix by anion exclusion effect and slow rate of water flow. Contrary to Soil B, high organic matter content of Soil C could be responsible for its low mobility of nitrate, inducing preferential flow by water-repellency and rapid immobilization of nitrate by a microbial community. Leached phosphate was detected in Soil C only, and continuously increased with increasing amount of leachate. The phosphate concentration of soil solution in Soil B was much lower than in Soil C, and Soil A was below detection limit ($0.01mg\;L^{-1}$), overall similar to the order of degree of P saturation of soils. Phosphate mobility, therefore, could be largely influenced by degree of P saturation of soils but connect with apparent leaching loss only more than any threshold of P accumulation.

• The Journal of Korean Academy of Prosthodontics
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• v.47 no.2
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• pp.125-135
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• 2009

Statement of problem: Loosening or fracture of the abutment screw is one of the common problems related to the dental implant. Generally, in order to make the screw joint stable, the preload generated by tightening torque needs to be increased within the elastic limit of the screw. However, additional tensile forces can produce the plastic deformation of abutment screw when functional loads are superimposed on preload stresses, and they can elicit loosening or fracture of the abutment screw. Therefore, it is necessary to find the optimum tightening torque that maximizes a fatigue life and simultaneously offer a reasonable degree of protection against loosening. Purpose: The purpose of this study was to present the influence of tightening torque on the implant-abutment screw joint stability with the 3 dimensional finite element analysis. Material and methods: In this study, the finite element model of the implant system with external butt joint connection was designed and verified by comparison with additional theoretical and experimental results. Four different amount of tightening torques(10, 20, 30 and 40 Ncm) and the external loading(250 N, $30^{\circ}$) were applied to the model, and the equivalent stress distributions and the gap distances were calculated according to each tightening torque and the result was analyzed. Results: Within the limitation of this study, the following results were drawn; 1) There was the proportional relation between the tightening torque and the preload. 2) In case of applying only the tightening torque, the maximum stress was found at the screw neck. 3) The maximum stress was also shown at the screw neck under the external loading condition. However in case of applying 10 Ncm tightening torque, it was found at the undersurface of the screw head. 4) The joint opening was observed under the external loading in case of applying 10 Ncm and 20 Ncm of tightening torque. 5) When the tightening torque was applied at 40 Ncm, under the external loading the maximum stress exceeded the allowable stress value of the titanium alloy. Conclusion: Implant abutment screw must have a proper tightening torque that will be able to maintain joint stability of fixture and abutment.