• Advances in concrete construction
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• v.10 no.5
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• pp.381-391
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• 2020

This study aimed to develop reference materials (RMs) for mortar that can simulate the initial flow characteristics with constant quality over a long period. Through the previous research on the development of RMs for cement paste, the combination of limestone, glycerol, and water was used as the basic matrix for developing RMs for mortar in this study. In addition, glass beads of three particle sizes (0.5, 1.0, and 2.0 mm) and ISO standard sand were selected as tentative candidates to derive fine aggregate substitutes. The mixture of glass beads could simulate the initial flow characteristics of mortar, but under the same mixing ratio, replicates showed an unstable tendency to indicate inconsistent values due to the generation of electrostatic properties between materials and equipment. On the other hand, the mixture using ISO standard Sand not only simulates the constant flow characteristics for a long period of time, but also shows stable results with little error in replicates. Therefore, limestone, glycerol, ISO standard sand, and water were finally determined as components that met the required properties of RMs for mortar. The effect of each component on the flow characteristics of RMs was analyzed. It was found that glycerol increased the cohesion between the particles of standard sand, resulting in a constant increase both in the plastic viscosity and yield stress. Both limestone and standard sand had a dominant effect on the yield stress. The relationships between various mortar mixing ratios and the corresponding mixing ratios of RMs were established. In addition, the results of the verification experiment showed that the rheological properties of the RMs obtained through the relationships correlated with various water/cement ratios and the fine aggregate volume fractions of mortar obtained with same manner. In other words, the RMs for mortar developed in this study can be used as standard samples because they can simulate the initial flow characteristics of mortar of various mixing ratios for a long period without any chemical changes.

• Journal of the Earthquake Engineering Society of Korea
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• v.9 no.1 s.41
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• pp.9-16
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• 2005

The purpose of this paper is to present a design procedure of a friction damper for controlling elastic and inelastic responses of building structures under earthquake excitation. The equivalent damping and period increased by the friction damper are estimated using ATC-40 and ATC-55 procedures which provide equivalent linear system for bilinear one, and then a design formula to achieve target performance response level by the friction damper is presented. It is identified that there exists error between the responses obtained by this formula and by performing nonlinear analysis and the features of the error vary according to the hardening ratio, yield strength ratio, and structural period. Equations for compensating the error are proposed based on the least square method, and the results from numerical analysis indicate that the error is significantly reduced. The proposed formula can be used without much error for designing a friction damper for retrofitting a structure showing elastic or inelastic behavior.

• Safety and Health at Work
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• v.10 no.4
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• pp.445-451
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• 2019

Objective: The objective of this study was to evaluate the prevalence and incidence of accidents with biological material, the level of knowledge, and compliance to standard precautions (SPs) among dentists, physicians, nurses, and dental and medical students. Methods: A closed cohort study with a prospective and retrospective component was conducted between August 2014 and September 2015. The participants were contacted in two moments during the follow-up period, during which a structured questionnaire divided into six sections was used; the interviews were conducted during the follow-up period (Month 6) and at the end of the observation period (Month 12). Results: The global prevalence of accidents in the previous 12 months was 10.2%, with a difference between professionals and students (13.0% vs. 5.1%, respectively; p < 0.003). The incidence rate was 6.49 per 100 person/year, with difference between the groups (6.09 per 100 person/year in professionals and 7.26 per 100 person/year in students), type of specialization (hazard ratio, 3.27), and hours worked per week (hazard ratio, 2.27). The mean of compliance to SP was 31.99 (±3.85) points, with a median of 33 (30, 35) points against the expected 27.75 points. Adherence to SP was associated with the accident report (p < 0.020). Conclusion: We conclude that the proportion/incidence rate of accidents with biological material was high in relation to that in the literature, being higher in professionals and especially among physicians. The levels of knowledge and adherence to SP were good, with the best found in dentists and dental students.

• Asian-Australasian Journal of Animal Sciences
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• v.7 no.3
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• pp.421-426
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• 1994

Twelve cross bred cows ($300{\pm}20kg$) were fed a basal ration consisting of 1 kg concentrate and untreated or urea treated rice with or without urea-molasses-wheat bran lick block supplementation. The lick blocks were prepared locally using cement as a binding agent. The experiment lasted for 48 days consisting of a preliminary period of 14 days and a measurement period of 34 days. Daily dry ma tter intake (DMI) of straw and lick block, and daily milk yield were recorded during the measurement period. Intake of lick block when fed with untreated straw (US) was significantly higher (p < 0.01) than with urea treated (TS) straw (397 vs 307g $100kg^{-1}$), but lick block supplementation did not significantly affect the in take of US (1.80 vs 1.83kg $100kg^{-1}day^{-1}$) or TS (2.27 vs 2.17kg $100kg^{-1}day^{-1}$). Both urea treatment and lick block supplementation significantly increased (p < 0.01) the milk yield of cows, and the increase due to urea treatment was higher than that due to lick block supplementation. Benefit/cost ratio obtained for feeding US or TS with 1 kg dairy concentrate was similar (5.4), but the marginal return favours TS (5.4:1.0). The benefit/cost ratio for US and TS supplemented with lick block was 3.4 and 3.7. respectively, but the marginal return with US was higher than with TS (1.6:1.0 and 0.9:1.0, respectively).

• Fisheries and Aquatic Sciences
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• v.13 no.2
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• pp.89-95
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• 2010

This study was conducted to investigate the efficacy of using a coating of gelatin extracted from refiner discharge to extend the shelf life of salmon during cold storage ($5^{\circ}C$). Relative percentage of moisture loss in gelatin-coated salmon during cold storage was less than that of uncoated salmon. The treatment of salmon with gelatin reduced volatile basic nitrogen (VBN) formation throughout the entire storage period. Measurements of the peroxide value (POV), fatty acid composition, and (20:5n-3+22:6n-3)/16:0 ratio during cold storage indicated that the coating of salmon with gelatin from refiner discharge effectively suppressed lipid oxidation over the entire storage period. The extent of sensory color change during cold storage was less in the gelatin-coated than in the uncoated salmon. From the results of chemical measurements, such as relative moisture content, VBN, POV, fatty acid composition, (20:5n-3+22:6n-3)/16:0 ratio, and sensory color change, the conclusion was made that the coating treatment of salmon with refiner discharge gelatin effectively suppressed moisture loss, lipid oxidation, and color deterioration over the entire storage period.

• Journal of Life Science
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• v.14 no.1
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• pp.98-103
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• 2004

Various bacterial strains were isolated from water in a paddy field, and their seaweed degrading activities were investigated. As the result, 16 strains were obtained from the microflora sample. They were incubated in a liquid medium of sea tangle powder for 3 weeks. Ratios of reduced sugar to total sugar of the liquid medium were measured once a week during the incubation period. Ratio of reduced sugar to total sugar of 30A412 strain was highest. Accordingly, 30A412 strain was incubated in three different liquid media of sodium alginate, sea tangle powder, and sea mustard powder for 3 or 4 weeks. The ratios of reduced sugar to total sugar and cell growth were measured once a week during the incubation period. Ratios of reduced sugar to total sugar and cell growth were increased with the incubation period. Cell growth and degrading ratio were highest in the liquid medium with sea mustard powder.

• Journal of Korea Port Economic Association
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• v.31 no.3
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• pp.93-105
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• 2015

The purpose of this study is to outline the strategic implications of a structure analysis and trends of transferred air cargoes for the main airports of the North Asian region for 13 years from 2000 to 2012. To do so, it analyses the concentration levels using a Gini coefficient and Hirschmann Herfindahl index and represents the competitive positioning with regard to the main East Asian airports using the BCG framework and shift-share analysis. Currently, the concentration level is getting weaker in response to the emergence of Chinese airports in the north-east region. It is likely that the steady growth of air cargo of Shanghai airport (PVG) has caused the increase in concentration levels in the region. Seoul airport (ICN) may be directly in competition with PVG for air cargo in the region, giving consideration to reducing or maintaining an average increase ratio of air cargoes of ICN, NRT (Tokyo), and KIX (Osaka) for same period. In the same sense, the average increase in ratio for ICN for same period yields 1.3%, which is far behind the 6.2% and 5.2% of the north-east region and PVG respectively. Additionally, shift-share effect analysis indicates that ICN lost 422,180 tons in the north-east region during the same period, suggesting that transferred cargoes might have been forwarded to PVG.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.1131-1137
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• 2004

With the recent continuous expansion of subways, newly created subways tend to have lower locations and wider sections. Furthermore. since box structures and evacuating tunnels are classified into a category of mass-concrete. the thermal-stress, emitted from the inside. causes cracks to structures from the inception of constructing. In this paper, thermal-stress analysis and durability evaluation of box structure were carried out to investigate relationship between durability and parameter causing the heat of hydration. Through the examination, this paper tries to find out satisfactory solutions to regulated thermal crack and ensure the required duration period. The results of this paper showed that to control thermal crack and guarantee the required duration period it was more effective to use low-heat-portland cement and moderateheat-portland cement. As cement volume due to reduction of water-cement ratio increased, the possibility of thermal cracks occurrence increased but results of durability evaluation was different depending on evaluation method. The results showed that the appropriate water-cement ratio to control the heat of hydration and satisfy the required durability was $45\∼55\%$. And it was showed that during placement of concrete blocks ambient temperature affect the heat of hydration. thermal crack and long-term durability largely and when concrete was placed at low temperature to control thermal crack. it need to try to guarantee the required duration period. Henceforth, by studying not only internal and external conditions, such as the relative humidity and the unit weight. but also methods, to evaluate durability, in accordance with domestic situations, more reasonable design of durability should be achieved.

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.217-218
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• 2015

In this work, we present the result of our follow-up observations of SDSS J092741.73+332959.1 and SDSS J130733.49+215636.7 using the 2.35 m Thai National Telescope and ULTRASPEC instrument. Both systems are listed among the recently found white dwarf main sequence binaries from the Sloan Digital Sky Survey. SDSS J092741.73+332959.1 is a new PCEB with a period of 2.3 days, the longest orbital period known to date for white dwarf binaries. SDSS J130733.49+215636.7 is confirmed to be an eclipsing system with a period of 0.21 days from the Catalina Survey's light curve, however the parameters for the white dwarf are still uncertain. Our goal is to determine precise parameters for both systems using the Binary Maker 3 software. The observation for SDSS J0927+3329 was done on 9 January 2014 in the SDSS r' filter while the data for SDSS J1307+2156 were taken in the z' filter on 27 April 2014. Our models show that the red dwarf companions in both systems are well constrained inside their Roche Lobes. We find that the binary M2/M1 ratio in SDSS J0927+3329 is close to 0.5, with white dwarf and M-dwarf temperatures of 12000 K and 3300 K, respectively. Our preliminary result for SDSS J1307+2156 show that this system has an extreme mass ratio of 0.3. The white dwarf in this system has a temperature of 7500 K and the companion star has an effective temperature of 3150 K.

• Journal of Preventive Medicine and Public Health
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• v.37 no.3
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• pp.274-281
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• 2004

Objectives : This study was performed to investigate the injury rates and risk factors for preschool children in Daegu city and Kyungpook province. Method : A questionnaire survey about medically attended injuries during the preschool period was performed in nine primary schools located in Daegu city, Pohang city and Goryung County. The overall injury rate was estimated using person-year. The causes and patterns of the injuries, and their risk factors were examined. Result : A total of 469 medically attended injuries were reported in 330 of the 959 study subjects during the preschool period. The overall annual injury rate was 7.5 per 100 children. The injury rate increased sharply during the period from infant (2.4) to 1 year of age (7.5), and the peak injury rate (9.2) was reported for 5 year olds. The most common causes of injuries were falling (36.0%), followed by being struck by an object (23.7%), and traffic accidents (14.1%). Among the traffic accidents, 72.8% occurred while playing on the road, riding a bicycle or roller-skating. A proportional hazard model showed that males (hazard ratio=1.49, p<0.001 compared with female) and the mother's higher education level (hazard ratio of college or higher= 1.51, p=0.013; high school=1.32, p=0.085 compared with those of middle school or lower) were significant risk factors of childhood injury. Conclusion : The results of this study suggested that efforts for children's safety should be made, especially from the toddler stage, and in male children. To develop a more specific childhood injury prevention program, a surveillance system for injuries should be established. Further study of the relationship between mother's occupation and injury rates is also needed.