• Journal of The Korean Society of Agricultural Engineers
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• v.46 no.3
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• pp.93-105
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• 2004

The Shihwa wetland, a newly developed constructed wetland prototype in Korea with an area of approximately 104 ha, was established to improve the water quality severely polluted inflow streams into Lake Shihwa. Because this wetland could play a role as an ecological park in addition to improving the water quality, an ecological impact of the Shihwa constructed wetland has been a national concern. This paper focused on reporting the survey results for fauna among the entire investigation results for 3 years. A total of 129 terrestrial insect species have been observed from August 2001 to June 2002. Among them, Ischnura asiatica (Brauer) (order Odonata), Scymnus species (order Coleoptera) and Orthopteran species were frequently found in the reed bushes. A total of 77 bird species were recorded in a seasonal count, the maximum number of species was 34 in winter and the maximum number of individuals was 4,599 in summer. For the freshwater fish, only 4 species were found in 2000, however in 2001 and 2002, 12 species and 459 individuals were collected at four survey points. Among these 12 species, the dominant species were Mugil cephalus(36%), followed by Carassius auratus (25%) and Rhinogobius brunneus (22%). Meanwhile,12 individuals of Oryzias latipes were observed nearby, mostly downstream of the wetland. For the Herpetofauna at four survey areas, 3 species of amphibians and 3 species of reptiles were recorded. Because of remaining salinity in the soil of the Shiwha constructed wetland, Herpetofauna inflow to the wetland was scanty and mainly inhabited the upstream area. A total of 8 mammal species were recorded. Small-sized species were the striped field mouse, the Ussurian harvest-mouse, the Manchurian reed vole and the brown rat. Middle- and large-sized species were Korean water-deer, Korean raccoon dogs, Korean yellow weasels and feral cats.

• Journal of radiological science and technology
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• v.11 no.2
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• pp.65-71
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• 1988

Radiation dose outside the radiotherapy treatment field can be significant and therefore is of clinical interest estimating organ dose. We have made measurements of dose at distances up to 70 cm from the central axis of $5{\times}5$, $10{\times}10$, $15{\times}15$, and $25{\times}25$ cm radiation fields of Co-60 ${\gamma}-ray$, at 5 cm depth in water. Contributions to the total secondary radiation dose from water scatter, machine (collimator) scatter and leakage radiation have been seperated. We have found that the component of dose from water scatter can be described by simple exponential function of distance from the central axis of the radiation field for all field sizes. Machine scatter contributes 20 to 60% of the total secondary dose depending on field size and distance from the field. Leakage radiation contributes very little dose, but becomes the dominant componant at distance beyond 40 cm from the central axis. Then, wedges can cause a factor 2 to 3 increase in dose at any point outside the field compared with the dose when no wedge is used. Adding blocks to a treatment field can cause an increase in dose at points outside the field, but the effect is much smaller than the effect of a wedge. From the results of these measurements, doses to selected organs outside the field for specified treatment geometries were estimated, and the potential for reducing these organ doses by additional shielding was assessed.

• Nuclear Engineering and Technology
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• v.31 no.5
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• pp.486-497
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• 1999

The local heat transfer coefficient is experimentally investigated for the reflux condensation in a countercurrent flow between the steam-air mixture and the condensate, A single vertical tube has a geometry which is a length of 2.4m, inner diameter of 16.56mm and outer diameter of 19.05mm and is made of stainless steel. Air is used as a noncondensible gas. The secondary side has a shape of annulus around vertical tube and the lost heat by primary condensation is transferred to the coolant water. The local temperatures are measured at 11 locations in the vertical direction and each location has 3 measurement points in the radial direction, which are installed at the tube center, at the outer wall and at the coolant side. In three different pressures, the 27 sets of data are obtained in the range of inlet steam flow rate 1.348∼3.282kg/hr, of inlet air mass fraction 11.8∼55.0%. The investigation of the flooding is preceded to find the upper limit of the reflux condensation. Onset of flooding is lower than that of Wallis' correlation. The local heat transfer coefficient increases as the increase of inlet steam flow rate and decreases as the increase of inlet air mass fraction. As an increase of the system pressure, the active condensing region is contracted and the heat transfer capability in this region is magnified. The empirical correlation is developed by 165 data of the local heat transfer. As a result, the Jacob number and film Reynolds number are dominant parameters to govern the local heat transfer coefficient. The rms error is 17.7% between the results by the experiment and by the correlation.

• Korean Journal of Materials Research
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• v.22 no.10
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• pp.562-568
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• 2012

Metal nanowires can be coated on various substrates to create transparent conducting films that can potentially replace the dominant transparent conductor, indium tin oxide, in displays, solar cells, organic light-emitting diodes, and electrochromic windows. One issue with these metal nanowire based transparent conductive films is that the resistance between the nanowires is still high because of their low aspect ratio. Here, we demonstrate high-performance transparent conductive films with silver nanofiber networks synthesized by a low-cost and scalable electrospinning process followed by two-step sequential thermal treatments. First, the PVP/$AgNO_3$ precursor nanofibers, which have an average diameter of 208 nm and are several thousands of micrometers in length, were synthesized by the electrospinning process. The thermal behavior and the phase and morphology evolution in the thermal treatment processes were systematically investigated to determine the thermal treatment atmosphere and temperature. PVP/$AgNO_3$ nanofibers were transformed stepwise into PVP/Ag and Ag nanofibers by two-step sequential thermal treatments (i.e., $150^{\circ}C$ in $H_2$ for 0.5 h and $300^{\circ}C$ in Ar for 3 h); however, the fibrous shape was perfectly maintained. The silver nanofibers have ultrahigh aspect ratios of up to 10000 and a small average diameter of 142 nm; they also have fused crossing points with ultra-low junction resistances, which result in high transmittance at low sheet resistance.

• Structural Engineering and Mechanics
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• v.72 no.4
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• pp.421-432
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• 2019

In high-speed railway (HSR) system, the structure-borne noise inside viaduct at low frequency has been extensively investigated for its mitigation as a research hotspot owing to its harm to the nearby residents. This study proposed a novel acoustic optimization method for declining the structure-borne noise in viaduct-like structures by separating the acoustic contribution of each structural component in the measured acoustic field. The structural vibration and related acoustic sourcing, propagation, and radiation characteristics for the viaduct box girder under passing vehicle loading are studied by incorporating Finite Element Method (FEM) with Modal Acoustic Vector (MAV) analysis. Based on the Modal Acoustic Transfer Vector (MATV), the structural vibration mode that contributes maximum to the structure-borne noise shall be hereinafter filtered for the acoustic radiation. With vibration mode shapes, the locations of maximum amplitudes for being ribbed to mitigate the structure-borne noise are then obtained, and the structure-borne noise mitigation performance shall be eventually analyzed regarding to the ribbing conduction. The results demonstrate that the structural vibration and structure-borne noise of the viaduct box girder mainly occupy both in the range within 100 Hz, and the dominant frequency bands both are [31.5, 80] Hz. The peak frequency for the structure-borne noise of the viaduct box girder is mainly caused by $16^{th}$ and $62^{th}$ vibration modes; these two mode shapes mainly reflect the local vibration of the wing plate and top plate. By introducing web plate at the maximum amplitude of main mode shapes that contribute most to the acoustic modal contribution factors, the acoustic pressure peaks at the field-testing points are hereinafter obviously declined, this implies that the structure-borne noise mitigation performance is relatively promising for the viaduct.

• Animal Systematics, Evolution and Diversity
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• v.8 no.2
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• pp.279-300
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• 1992

The Korean marine hydrioid fauna identified up to data consists of 120 species of 55 genera in 17 families. Of which Abientiunaria filicula (Ellis and Solander, 1786) is new to the Korean fauna, and the dominant species of hydroids in Korean water is Sertularella miurensis Stechow, 1921 which is collected from 33 points of 96 localities. The coastal waters of Korea are divided into four regions : the East Sea, the South Sea, the Yellow sea and the Chejudo. Concerning the total number of species occured in each region, 43 species in the East Sea, 52 species in the Yellow Sea, 73 species in the South Sea and 83 species in the Chejudo and its vicinity. From the results above described it can be salid that the Chejudo region shows the most diversity of the Korea hydroids. The community coefficient of the East Sea-the Yellow Sea is 0.444, that of the East Sea-the South Sea 0.553, that of the East Sea-Chejudo 0.519, that of the Yellow Sea-the Sea 0.682, that of the Yellow Sea-the Chejudo 0.533 and that of the South Sea-the Chejudo 0.642. So that the zoogeographical relatinship between the Yellow Sea and the South Sea is the highest and between the East Sea and the Yellow Sea is the lowest on the hydroids distribution.

• Journal of Ecology and Environment
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• v.43 no.1
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• pp.22-30
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• 2019

Background: Piton du Milieu (PdM) impounding reservoir is suspected to be eutrophic based on the elevated level of orthophosphate and nitrate. Water supplies from three adjacent rivers are primarily thought to contribute to the nutrient enrichment of the reservoir. It is also suspected that there is leaching of orthophosphate, nitrate and organic matter into the rivers during rainfall events and also as a result of anthropogenic activities within the catchment area. The aim of this study was to ascertain the impact of nutrient loading on the water quality of PdM water and on the population of freshwater microalgae in the reservoir. The enumeration and identification of algae from PdM were performed by differential interference contrast microscopy. Dissolved oxygen (DO) and pH were determined by electrometric methods, whereas nutrient levels, silica and total organic carbon (TOC) were determined by instrumentation techniques. Results: Annual mean orthophosphate, nitrate and total organic carbon input from the three feeders within the catchment area of PdM reached levels as high as 0.09 mg/L, 0.4 mg/L and 2.62 ppm respectively. Over a 12-month period, mean TOC concentration in the reservoir was 2.32 ppm while the mean algal cell count was 4601 cells/mL. The dominant algal species identified were Oscillatoria, Cyclotella, Navicula and Cosmarium. Conclusion: This study highlights the trophic state of the reservoir water and clearly points to the need for constant monitoring in order to avoid the occurrence of an impending harmful algal bloom.

• Asian-Australasian Journal of Animal Sciences
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• v.32 no.1
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• pp.49-57
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• 2019

Objective: The first stage in both breeding and programs for the conservation of genetic resources are the identification of genetic diversity in the relevant population. The aim of the present study is to identify genetic diversity of six brown layer pure chicken lines (Rhode Island Red [RIRI, RIRII], Barred Rock [BARI, BARII], Columbian Rock [COL], and line 54 [L-54]) with microsatellite markers. Furthermore, the study aims to employ its findings to discuss the possibilities for the conservation and sustainable use of these lines that have been bred as closed populations for a long time. Methods: In the present study, a total number of 180 samples belonging to RIRI (n = 30), RIRII (n = 30), BARI (n = 30), BARII (n = 30), L-54 (n = 30), and COL (n = 30) lines were genotyped using 22 microsatellite loci. Microsatellite markers are extremely useful tools in the identification of genetic diversity since they are distributed throughout the eukaryotic genome in multitudes, demonstrate co-dominant inheritance and they feature a high rate of polymorphism and repeatability. Results: In this study, we found all loci to be polymorphic and identified the average number of alleles per locus to be in the range between 4.41 (BARI) and 5.45 (RIRI); the observed heterozygosity to be in the range between 0.31 (RIRII) and 0.50 (BARII); and $F_{IS}$ (inbreeding coefficient) values in the range between 0.16 (L-54) and 0.46 (RIRII). The $F_{IS}$ values obtained in this context points out to a deviation from Hardy-Weinberg equilibrium due to heterozygote deficiency in six different populations. The Neighbour-Joining tree, Factorial Correspondence Analysis and STRUCTURE clustering analyzes showed that six brown layer lines were separated according to their genetic origins. Conclusion: The results obtained from the study indicate a medium level of genetic diversity, high level inbreeding in chicken lines and high level genetic differentiation between chicken lines.

• The Journal of Engineering Geology
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• v.31 no.3
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• pp.257-267
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• 2021

Constraints on the structure and composition of the active layer are important for understanding permafrost evolution. Soil convection owing to repeated moisture-induced freeze-thaw cycles within the active layer promotes the formation of self-organized patterned ground. Here we present the results of ground penetrating radar (GPR) surveys across a selected sorted circle near King Sejong Station, Antarctica, to better delineate the active layer and its relation to the observed patterned ground structure. We acquire GPR data in both bistatic mode (common mid-points) for precise velocity constraints and monostatic mode (common-offset) for subsurface imaging. Reflections are derived from the active layer-permafrost boundary, organic layer-weathered soil boundary within the active layer, and frozen rock-fracture-filled ice boundary within the permafrost. The base of the imaged sorted circle possesses a convex-down shape in the central silty zone, which is typical for the pattern associated with convection-like soil motion within the active layer. The boundary between the central fine-silty domain and coarse-grained stone border is effectively identified in a radar amplitude contour at the assumed active layer depth, and is further examined in the frequency spectra of the near- and far-offset traces. The far-offset traces and the traces from the lower frequency components dominant on the far-offset traces would be associated with rapid absorption of higher frequency radiowave due to the voids in gravel-rich zone. The presented correlation strategies for analyzing very shallow, thin-layered GPR reflection data can potentially be applied to the various types of patterned ground, particularly for acquiring time-lapse imaging, when electric resistivity tomography is incorporated into the analysis.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.6D
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• pp.819-829
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• 2008

Fatigue cracking occurs over long time period because dynamic strength of slab continuously decreases by vehicle loading repetitively applied to the concrete pavement. To more accurately predict the fatigue life of the concrete pavement, the stress due to environmental loading should be considered prior to calculating the stress due to the vehicle loading because the stress due to temperature and moisture distribution always exists within the slab. Accordingly, a new fatigue model considering the environmental loading was developed in this research by evaluating factors of existing fatigue models most widely used and by making data points from the models. The applicability of the new model was evaluated by performing a fatigue analysis on the general concrete pavement structure using local climatic and traffic conditions in Korea. It was concluded that the top-down cracking due to the tensile stress at top of the slab is dominant cause of the fatigue failure than the bottom-up cracking occurred at bottom of the slab. More advanced fatigue analysis considering vehicle speed is expected by developing this study.