• The Journal of the Acoustical Society of Korea
• /
• v.41 no.6
• /
• pp.601-609
• /
• 2022

In August 2007, coastal upwelling occurred off the east coast of Korea, and vertical water temperature and salinity data were obtained from a real-time surface ocean buoy. Based on the time series observation data, a vertical sound velocity structure was calculated before, during, and after the occurrence of the coastal upwelling, and how the coastal upwelling affects the sound propagation and detection environment through acoustic modeling considering the horizontal scale and actual seabed topography. As a result of comparing and analyzing the low-frequency (500 Hz) sound transmission loss and the target detection range by depth using the parabolic equation model, it was analyzed that if coastal upwelling occurs, a detection gain of up to about 10 dB can be expected. In addition, through this study, it was confirmed that the characteristics of sound propagation can be greatly changed even in a short period of about 2 to 3 days before and after coastal upwelling.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.26 no.3B
• /
• pp.241-251
• /
• 2006

This study analyzed the topographical characteristics by extracting property factors of stream (stream order, number of stream, stream length, mean stream length) and property factors of basin (basin area, basin length, total stream length, total number of stream, basin mean width, form factor, maximum stream order, basin density, stream frequency, relief ratio, mean elevation, mean, slope, maximum elevation) from DEM (digital elevation model) and stream network generated by 1:5,000 NGIS (national geographical information system) data for the Bukhan-river basin. In addition, topographical factors for upper, mid stream and lower stream were analyzed and the mutuality of the factors by linear and nonlinear regression curve was identified.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.26 no.3B
• /
• pp.233-240
• /
• 2006

One of the main factor that effects on the CN's value in SCS Curve Number method for the estimation of direct runoff is the antecedent soil moisture condition (AMC). It is also common to use the AMC-III in hydrologic practice, which provides the largest runoff as possible. In this paper, AMC defending on the rainfall characteristics is analyzed using daily rainfall data at rainy season (June~September) of the Seoul station from 1961 to 2002. The probability mass function of AMC is also investigated to analyze the variation of AMC based on climate change, scenarios from several General Circulation Model (GCM) predictions. As a results we can find that the occurrence of AMC-I is reduced, and AMC-III is increased, whereas AMC-II does not change.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.28 no.6B
• /
• pp.627-634
• /
• 2008

In a numerical simulation of open channel turbulent flows using RANS (Reynolds averaged Navier-Stokes) equations model equipped with VOF (Volume of Fluid) scheme, the determination of wall roughness for wall function was studied. The roughness constant, based on the law-of-the-wall for flow on rough walls, obtained by experimental works for pipe flows is employed in general wall functions. However, this constant of wall function is the function of Froude number in open channel flows. Thus, the wall roughness should be determined by taking into account the effect of Froude number. In addition, the wall roughness should be corresponding to Manning's roughness coefficient widely used for open channels. In this study, the relation between wall roughness height as an input condition and Manning's roughness coefficient was investigated, and an equation for effective wall roughness height considering the characteristics of numerical models was proposed as a function of Manning's roughness coefficient.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.30 no.6B
• /
• pp.533-540
• /
• 2010

Recently management of vegetation distributed in the watercourse is very important not only for safety but also for river restoration. In general, vegetations in the watercourse increase hydraulic resistance and accordingly decrease conveyance capacity which may yield levee overflow. This paper simulates water level rise using 1D and 2D hydro dynamic model to check the possibility of overflow in downstream of the Soyang Reservoir by assigning different roughness coefficient corresponding to different types of vegetation. In this study, 3 different vegetation types of tree, shrub, and main channel were considered and corresponding Manning's roughness coefficient n was assigned based on the vegetation map generated from the site investigation. As results, the water level raised about 0.1 to 0.7 m comparing with the case without considering vegetation and a proper measurements is necessary where overflow occurs due to low level levee.

• Journal of Veterinary Science
• /
• v.25 no.3
• /
• pp.36.1-36.15
• /
• 2024

Importance: The intravenous administration of adipose tissue-derived mesenchymal stem cells (AdMSCs) in veterinary medicine is an attractive treatment option. On the other hand, it can result in severe complications, including pulmonary thromboembolism (PTE). Objective: The present study assessed the occurrence of PTE after the intravenous infusion of canine AdMSCs (cAdMSCs) into experimental animals. Methods: Five-week-old male BALB/c hairless mice were categorized into groups labeled A to G. In the control group (A), fluorescently stained 2×10⁶ cAdMSCs were diluted in 200 µL of suspension and injected into the tail vein as a single bolus. The remaining groups included the following: group B with 5×10⁶ cells, group C with 3×10⁶ cells, group D with 1×10⁶ cells, group E with 1×10⁶ cells injected twice with a one-day interval, group F with 2×10⁶ cells in 100 µL of suspension, and group G with 2×10⁶ cells in 300 µL of suspension. Results: Group D achieved a 100% survival rate, while none of the subjects in groups B and C survived (p = 0.002). Blood tests revealed a tendency for the D-dimer levels to increase as the cell dose increased (p = 0.006). The platelet count was higher in the low cell concentration groups and lower in the high cell concentration groups (p = 0.028). A histological examination revealed PTE in most deceased subjects (96.30%). Conclusions and Relevance: PTE was verified, and various variables were identified as potential contributing factors, including the cell dose, injection frequency, and suspension volume.

• Transactions of the Korean Society of Pressure Vessels and Piping
• /
• v.20 no.1
• /
• pp.49-55
• /
• 2024

Stainless 630 (or 17-4PH) is a precipitation-hardening martensitic stainless steel that has excellent mechanical properties and corrosion resistance. These characteristics make the STS630 to be used as a consisting material for various components such as spider, pin, spring, and spring retainer, of the control rod drive mechanism (CRDM) in pressurized water reactors (PWRs). In general, it is well known that the oxide layer of stainless steel consists of a duplex layer, a compact inner layer of FeCr₂O₄ spinel, and a coarse-grained outer layer of Fe₃O₄ spinel in PWR primary coolant condition. However, the characteristics of the oxide layer can be sensitively influenced by various water chemistry conditions such as temperature, dissolved oxygen, dissolved hydrogen, pH, pH adjuster type, and exposure time. In this work, we investigate the corrosion properties of the STS630 as a function of coolant temperature in an NH3 alkaline solution for its boron-free application in a small modular reactor, to confirm the feasibility for usage as a boron-free SMR structural material. As a result, oxide layer of corroded STS630 is consist of double-layer oxides consisting of a Cr-rich dense inner oxide and a Fe-rich polyhedral outer particles like as that in commercial PWR primary coolant. The corrosion rate of STS630 increases with increase in test time and temperature and the corrosion rate-time model equation was developed based on experimental data. Overall, it is expected that the results in this study provides useful data for the corrosion behavior of STS630 in alkaline environments, contributing to the development of selecting suitable materials for SMRs.

• Journal of the Korean Applied Science and Technology
• /
• v.40 no.6
• /
• pp.1238-1248
• /
• 2023

The purpose of this study was to examine the effects of job stress of hair designers on flourishing, and to verify whether work engagement and career commitment have dual mediating effects. For this purpose, a survey was conducted on 177 hair designers of various positions who are engaged in domestic B brand, and the relationships of variables was verified using statistical package SPSS 21.0 and SPSS Process Macro v. 3.3. The research model of dual mediating effect was demonstrated. First, it was confirmed that the job stress of the hair designer had a negative effect on the flourishing through the simple regression analysis. Second, job stress had a negative indirect effect on flourishing showing the dual mediating effect of work engagement and career commitment, and the direct effect of job stress of hair designers on flourishing turned out to be insignificant confirming a complete double mediating effect. These results means, job stress reduces successively job engagement, career commitment and finally harms the well-being of hair designer.

• Safety and Health at Work
• /
• v.15 no.2
• /
• pp.181-186
• /
• 2024

Background: This study aimed to analyze the trend of occupational noise-induced hearing loss (ONIHL) in Brazilian workers at a metallurgical plant with a hearing conservation program (HCP), which has been addressed in a previous study. Methods: All 152 workers in this time series (20032018) participated in the HCP and used personal protective equipment. All annual audiometry records in the company's software were collected from the electronic database. The trend of ONIHL was analyzed with the joinpoint regression model. The hearing thresholds of ONIHL cases at the end of the series were compared with those found in a national reference study. Results: The binaural mean hearing thresholds at 3, 4, and 6 kHz at the end of the series were higher for ages ≥50 years, exposures ≥85 dB (A), time since admission >20 years, and maintenance workers. Significance was found only in the group divided by age. There was an increasing time trend of ONIHL, though with a low percentage variation for the period (AAPC = 3.5%; p = 0.01). Hearing thresholds in this study differed from the reference one. Conclusion: Despite the unmet expectation of a stationary trend in the study period, the time pace of ONIHL evolution did not follow what was expected for a population exposed to noise. These findings signal to the scientific community and public authorities that good ONIHL control is possible when HCP is well implemented.

• Journal of Rhinology
• /
• v.59 no.6
• /
• pp.528-537
• /
• 2021

Background: Urban particulate matter (UPM) in ambient air is implicated in a variety of human health issues worldwide, however, few studies exist on the effect of UPM on the olfactory system. This study aimed to identify the factors affecting the destruction of the olfactory system in a mouse model following UPM exposure. Methods: Mice were divided into: control and four UPM-exposed groups (200 ㎍ UPM at 1 and 2 weeks, and 400 ㎍ UPM at 1 and 2 weeks [standard reference material 1649b; average particle diameter 10.5 ㎛]). The olfactory neuroepithelium was harvested for histologic examination, gene ontology, quantitative real-time polymerase chain reaction, and western blotting. Results: Compared to the control group, olfactory marker protein, Olfr1507, ADCY3, and GNAL mRNA levels were lower, and S-100, CNPase, NGFRAP1, BDNF, and TACR3 mRNA levels were higher in the olfactory neuroepithelium of the UPM groups. Moderately positive correlation was present between the 1- and 2-week groups. After analyzing the 200 and 400 UPM groups separately, the strength of the association between the 200 UPM 1- and 2-week groups was moderately positive. No differences was present in the neuroepithelial inflammatory marker levels between the UPM and control groups. Conclusions: UPM could have cytotoxic effects on the olfactory epithelium. The exposure time and particular concentration of UPM exposure could affect the degree of destruction of the olfactory neuroepithelium. The olfactory regeneration mechanism could be related to the neurotrophic factors, olfactory ensheathing cell stimulation, and trigeminal nerve support.