• Journal of Environmental Health Sciences
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• v.47 no.5
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• pp.496-503
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• 2021

Background: Considering the expenses of and difficulties in arsenic speciation by high performance liquid chromatography-inductively coupled plasma-mass spectrometry (HPLC-ICP-MS), alternative measurement methods should be useful, especially for large-scale research and projects. Objectives: A measurement method was developed for arsenic speciation using HPLC-atomic fluorescence spectrometry (HPLC-AFS) as an alternative to HPLC-ICP-MS. Methods: Total arsenic and toxic arsenic species in some seafoods were determined by atomic absorption spectrometry coupled with hydride vapor generation (AAS-HVG) and HPLC-AFS, respectively. Recovery rate of arsenic species in seafood was evaluated by ultra sonication, microwave and enzyme (pepsin) for the optimal extraction method. Results: Limits of detection of HPLC-AFS for As³⁺, dimethylarsinate (DMA), monomethylarsonate (MMA) and As⁵⁺ were 0.39, 0.53, 0.60 and 0.64 ㎍/L, respectively. The average accuracy ranged from 97.5 to 108.7%, and the coefficient of variation was in the range of 1.2~16.7%. As³⁺, DMA, MMA and As⁵⁺ were detected in kelp, the sum of toxic arsenic in kelp was 40.4 mg/kg. As³⁺, DMA, MMA and As⁵⁺ were not detected in shrimp and squid, but total arsenic (iAS and oAS) content in shrimp and squid analyzed by AAS-HVG were 18.1 and 24.7 mg/kg, respectively. Conclusions: HPLC-AFS was recommendable for the quantitative analysis method of arsenic species. As toxic arsenic species are detected in seaweeds, further researches are needed for the contribution degree of seafood in arsenic exposure.

• Journal of Korean Society on Water Environment
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• v.37 no.2
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• pp.92-102
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• 2021

In this study, the distribution characteristics according to the type of BOD and the effect of nitrogenous oxygen demand (NOD) and algal oxygen demand on BOD in three streams (Bokhacheon, Byeongseongcheon, and Gulpocheon) were evaluated. Although the BOD and NOD concentrations demonstrated a difference in the three streams, the carbonaceous BOD(CBOD)/BOD ratio was 0.75 (p=0.053, one-way ANOVA), and there was no significant difference in the three streams (r2≥0.92, p<0.0001). The NOD concentration of the Bokhacheon with high NH3-N was 1.7±1.3 mg/L, which was the highest among the three streams and showed a significant correlation with BOD. Seasonal variations in NOD in the three streams did not show a significant correlation with changes in NH3-N concentration (r2<0.28, p≥0.1789), and there was no significant difference in NOD even though NH3-N concentration in Gulpocheon was about twice that of Byeongseongcheon (p=0.870, one way ANOVA). The particulate CBOD(PCBOD)/CBOD ratio of the three streams was 0.55~0.64, and about 60% of the biodegradable organic matter was present in the particulate form. When the Chl.a concentration in the stream was more than 7 ㎍/L, the PCBOD tended to increase with the Chl.a concentration (r2=0.61, p=0.003). In the three streams, particulate NOD accounted for 81% of NOD; however, despite the large variation in NH3-N concentration (0.075~3.182 mg/L), there was no significant difference in soluble NOD(SNOD) concentration that ranged from 0.1 to 0.3 mg/L. In this study, the low contribution rate of SNOD to NOD is considered as a result of the removal of nitrifying bacteria along with the particles during the filtration process.

• Journal of Preventive Medicine and Public Health
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• v.52 no.5
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• pp.308-315
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• 2019

Objectives: Estimating influenza-associated mortality is important since seasonal influenza affects persons of all ages, causing severe illness or death. This study aimed to estimate influenza-associated mortality, considering both periodic changes and age-specific mortality by influenza subtypes. Methods: Using the Microdata Integrated Service from Statistics Korea, we collected weekly mortality data including cause of death. Laboratory surveillance data of respiratory viruses from 2009 to 2016 were obtained from the Korea Centers for Disease Control and Prevention. After adjusting for the annual age-specific population size, we used a negative binomial regression model by age group and influenza subtype. Results: Overall, 1 859 890 deaths were observed and the average rate of influenza virus positivity was 14.7% (standard deviation [SD], 5.8), with the following subtype distribution: A(H1N1), 5.0% (SD, 5.8); A(H3N2), 4.4% (SD, 3.4); and B, 5.3% (SD, 3.7). As a result, among individuals under 65 years old, 6774 (0.51%) all-cause deaths, 2521 (3.05%) respiratory or circulatory deaths, and 1048 (18.23%) influenza or pneumonia deaths were estimated. Among those 65 years of age or older, 30 414 (2.27%) all-cause deaths, 16 411 (3.42%) respiratory or circulatory deaths, and 4906 (6.87%) influenza or pneumonia deaths were estimated. Influenza A(H3N2) virus was the major contributor to influenza-associated all-cause and respiratory or circulatory deaths in both age groups. However, influenza A(H1N1) virus-associated influenza or pneumonia deaths were more common in those under 65 years old. Conclusions: Influenza-associated mortality was substantial during this period, especially in the elderly. By subtype, influenza A(H3N2) virus made the largest contribution to influenza-associated mortality.

• Wind and Structures
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• v.29 no.4
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• pp.235-246
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• 2019

Wind loading is one of important loadings that should be considered in the design of large hyperbolic natural-draught cooling towers. Both external and internal surfaces of cooling tower are under the action of wind loading for cooling circulating water. In the previous studies, the wind loads on the external surface attracted concernedly attention, while the study on the internal surface was relatively ware. In the present study, the wind pressure on the internal surface of a 220 m high cooling tower is measured through wind tunnel testing, and the effect of ventilation rate of the packing layer on internal pressure is a major concern. The characteristics of internal wind pressure distribution and its effect on wind-induced responses calculated by finite element method are investigated. The results indicate that the wind loading on internal surface of the cooling tower behaves remarkable three-dimensional effect, and the pressure coefficient varies along both of height and circumferential directions. The non-uniformity is particularly strong during the construction stage. Analysis results of the effect of internal pressure on wind-induced responses show that the size and distribution characteristics of internal pressure will have some influence on wind-induced response, however, the outer pressure plays a dominant role in the wind-induced response of cooling tower, and the contribution of internal pressure to the response is small.

• Structural Engineering and Mechanics
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• v.69 no.5
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• pp.537-545
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• 2019

Stress analysis of bottom-hole rock has to be considered with much care to further understand rock fragmentation mechanism and high penetration rate. This original study establishes a fully coupled simulation model and explores the effects of overburden pressure, horizontal in-situ stresses, drilling mud pressure, pore pressure and temperature on the stress distribution in bottom-hole rock. The research finds that in air drilling, as the well depth increases, the more easily the bottom-hole rock is to be broken. Moreover, the mud pressure has a great effect on the bottom-hole rock. The bigger the mud pressure is, the more difficult to break the bottom-hole rock is. Furthermore, the maximum principal stress of the bottom-hole increases as the mud pressure, well depth and temperature difference increase. The bottom-hole rock can be divided into three main regions according to the stress state, namely a) three directions tensile area, b) two directions compression areas and c) three directions compression area, which are classified as a) easy, b) normal and c) hard, respectively, for the corresponding fragmentation degree of difficulty. The main contribution of this paper is that it presents for the first time a thorough study of the effect of related factors, including stress distribution and temperature, on the bottom-hole rock fracture rather than the well wall, using a thermo-poroelastoplasticity model.

• Journal of the Korean institute of surface engineering
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• v.54 no.2
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• pp.53-61
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• 2021

The properties of tetrahedral amorphous Carbon (ta-C) film can be determined by multiple parameters and comprehensive effects of those parameters during a deposition process with filtered cathodic vacuum arc (FCVA). In this study, Taguchi method was adopted to design the optimized FCVA deposition process of ta-C for improving deposition efficiency and mechanical properties of the deposited ta-C thin film. The influence and contribution of variables, such as arc current, substrate bias voltage, frequency, and duty cycle, on the properties of ta-C were investigated in terms of deposition efficiency and mechanical properties. It was revealed that the deposition rate was linearly increased following the increasing arc current (around 10 nm/min @ 60 A and 17 nm/min @ 100A). The hardness and I_D/I_G showed a correlation with substrate bias voltage (over 30 GPa @ 50 V and under 30 GPa @ 250 V). The scratch tests were conducted to specify the effect of each parameter on the resistance to plastic deformation of films. The analysis on variances showed that the arc current and substrate bias voltage were the most effective controlling parameters influencing properties of ta-C films. The optimized parameters were extracted for the target applications in various industrial fields.

• Asia-Pacific Journal of Business
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• v.11 no.3
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• pp.169-184
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• 2020

Purpose - This research is intended to analyze the current status and problems of tax benefits in the R&D sector and suggest ways to improve tax credit for research and manpower development expenses when various countries fiercely develop efforts to enhance national competitiveness through increased investment in R&D Design/methodology/approach - This study will examine the current status of the tax support system for domestic and foreign R&D, and suggest improvement measures to expand research and development activities in the future. Findings - First, a plan may be considered to abolish and perpetuate the sunset deadline for tax credit for research and manpower development expenses as in the case of the United States and Japan. This perpetuation can be a proactive measure to actively support long-term R & D investment in companies facing economic decisions under uncertainty. Second, it should be revised to raise the tax credit rate of large corporations, which are shrinking every year, compared to SMEs, so that both large corporations and SMEs can improve their international competitiveness and secure excellent technologies through R & D. Finally, the target technologies for each new growth engine and source technology should be expanded to various fields, including national cybersecurity enhancement technology, aviation engine technology, carbon emission and global cooling technologies, which are areas of interest in major overseas R&D countries, to help active R&D and investment in these areas. Research implications or Originality - This study can find a contribution in comparing and analyzing the national R&D tax support system and presenting improvement measures at a time when the benefits of tax credit for research and manpower development expenses of large companies are decreasing due to frequent tax law revisions and the government's factors of increasing tax revenues. In addition, recent research and development items and research technologies of foreign countries were analyzed by Nature's top 10 major science and technology issues, and advanced technologies that should be applied to target technology areas by new growth engine and source technology were specifically investigated and presented.

• Journal of Ecology and Environment
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• v.44 no.4
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• pp.241-255
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• 2020

Background: The stem exclusion stage is a stage of forest development that is important for understanding the subsequent understory reinitiation stage and maturation stage during which horizontal heterogeneity is formed. Over the past 11 years (2009-2019), we observed a deciduous broad-leaved forest in the Albongbunji Basin in Ulleungdo, South Korea in its stem exclusion stage, where Fagus engleriana (Engler's beech) is the dominant species, thereby analyzing the changes in the structure (density and size distributions), function (biomass and species richness), and demographics. Results: The mean stem density data presented a bell-shaped curve with initially increasing, peaking, and subsequently decreasing trends in stem density over time, and the mean biomass data showed a sigmoidal pattern indicating that the rate of biomass accumulation slowed over time. Changes in the density and biomass of Fagus engleriana showed a similar trend to the changes in density and biomass at the community level, which is indicative of the strong influence of this species on the changing patterns of forest structure and function. Around 2015, a shift between recruitment and mortality rates was observed. Deterministic processes were the predominant cause of tree mortality in our study; however, soil deposition that began in 2017 in some of the quadrats resulted in an increase in the contribution of stochastic processes (15% in 2019) to tree mortality. The development of horizontal heterogeneity was observed in forest gaps. Conclusions: Our observations showed a dramatic shift between the recruitment and mortality rates in the stem exclusion stage, and that disturbance increases the uncertainty in forest development increases. The minor changes in species composition are likely linked to regional species pool and the limited role of the life-history strategy of species such as shade tolerance and habitat affinity. Our midterm records of ecological succession exhibited detailed demographic dynamics and contributed to the improvement of an ecological perspective in the stem exclusion stage.

• Animal Bioscience
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• v.34 no.4
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• pp.506-515
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• 2021

Objective: Initial consequence of inbreeding is inbreeding depression which impairs the performance of growth, production, health, fertility and survival traits in different animal breeds and populations. The effect of inbreeding on economically important traits should be accurately estimated. The effect of inbreeding depression on growth traits in sheep has been reported in many breeds. Based on this, the main objective of the present research was to evaluate the impact of inbreeding on some growth traits of Iranian Baluchi sheep breed using quantile regression model. Methods: Pedigree and growth traits records of 13,633 Baluchi lambs born from year 1989 to 2016 were used in this research. The traits were birth weight, weaning weight, six-month weight, nine-month weight, and yearling weight. The contribution, inbreeding and co-ancestry software was used to calculate the pedigree statistics and inbreeding coefficients. To evaluate the impact of inbreeding on different quantiles of each growth trait, a series of quantile regression models were fitted using QUANTREG procedure of SAS software. Annual trend of inbreeding was also estimated fitting a simple linear regression of lamb's inbreeding coefficient on the birth year. Results: Average inbreeding coefficient of the population was 1.63 percent. Annual increase rate of inbreeding of the flock was 0.11 percent (p<0.01). The results showed that the effect of inbreeding in different quantiles of growth traits is not similar. Also, inbreeding affected differently on growth traits, considering lambs' sex and type of birth. Conclusion: Quantile regression revealed that inbreeding did not have similar effect on different quantiles of growth traits in Iranian Baluchi lambs indicating that at a given age and inbreeding coefficient, lambs with different sex and birth type were not equally influenced by inbreeding.

• Computers and Concrete
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• v.29 no.1
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• pp.15-29
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• 2022

Concrete-filled steel tubes (CFSTs) are increasingly used as composite sections in structures owing to their excellent load bearing capacity. Therefore, predicting the mechanical behavior of CFST sections under axial compression loading is vital for design purposes. This paper presents the first study on the nonlinear analysis of heated CFSTs with high-strength concrete core containing steel fiber and waste tire rubber under axial compression loading. CFSTs had steel fibers with 0, 1, and 1.5% volume fractions and 0, 5, and 10% rubber particles as sand alternative material. They were subjected to 20, 250, 500, and 750℃ temperatures. Using flow rule and analytical analysis, a model is developed to predict the load bearing capacity of steel tube, and hoop strain-axial strain relationship, and axial stress-volumetric strain relationship of CFSTs. An elastic-plastic analysis method is applied to determine the axial and hoop stresses of the steel tube, considering elastic, yield, and strain hardening stages of steel in its stress-strain curve. The axial stress in the concrete core is determined as the difference between the total experimental axial stress and the axial stress of steel tube obtained from modeling. The results show that steel tube in CFSTs under 750℃ exhibits a higher load bearing contribution compared to those under 20, 250, and 500℃. It is also found that the ratio of load bearing capacity of steel tube at peak point to the load bearing capacity of CFST at peak load is noticeable such that this ratio is in the ranges of 0.21-0.33 and 0.31-0.38 for the CFST specimens with a steel tube thickness of 2 and 3.5 mm, respectively. In addition, after the steel tube yielding, the load bearing capacity of the tube decreases due to the reduction of its axial stiffness and the increase of hoop strain rate, which is in the range of about 20 to 40%.