• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.35 no.2
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• pp.93-101
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• 1999

A simple experimental method was used in an attempt to realize the elevation of the fishing ability of purse seine in the sea area of Cheju Island, the changes of seine volume and tension in the purseline during pursing. Experiments carried out on the six types simplified reduced model seines which were made of knotless nettings. The nettings were woven in different leg length 4.3, 5.0, 5.5, 6.0, 6.6 and 7.7mm of polyester 28 tex two threads two-ply twine, and each of the seines were named I, II, III, IV, V and Ⅵ seine. Dimension of seine models were 450cm for corkline and 85cmfor seine depth, each seines rigged up 160g of float for a floatline and 50g (underwater weight) of lead for a leadline. These model purse seines were made of the scale of 1/200 of its full scale, a 120 ton in the near sea of Cheju Island. Designing and testing for the model purse seines were based on the Tauti's law. Experiments were measured in the observation channel of a flume tank at the static conditions set up shooting and pursing equipments. Motion of purse seine during purse line was recorded by the two sets video camera for VTR which were placed in top and front of the model seine. The reading coordinate of seine volume carried out by the video digitization system, disk data for the purseline tension. An analysis were performed on the changes seine volume and tension in the purseline during pursing. The results obtained were as follows: 1. The seine volume during pursing was largest for Ⅵ seine with smallest d/l followed by V, IV, III, II and I seines, and tension in the purseline was small. 2. Seine volume during pursing can be expressed by the following equation; CVt=l-EXP[｛2.79 (d/l）＋0.35｝t-33.37 (d/l) ＋ 0.57] Where CVt is volume ratio, d is twine diameter, l is leg length and t is pursing time (sec). 3. Tension in the purse line during pursing can be expressed by the following equation; T= 1- EXP ｛0.57t ＋ 13.36 (d/l)+2.97｝ Where T is tension (kg) in the purseline during pursing.

• Research in Plant Disease
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• v.15 no.2
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• pp.94-100
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• 2009

These experiments were conducted to improve the effect of seed disinfection on rice seed severely infected Bakanae disease by seed soaking into mixed solution of prochloraz EC and fludioxonil FS. We investigated the effects of various concentrations of two fungicides mixed solution on spore germination and mycelial growth of Fusarium fujikuroi. Mycelial growth was inhibited 100% at $10{\mu}g$/ml of prochloraz and 33.3% at $80{\mu}g$/ml of fludioxonil. Spore germination was inhibited 81.4% at $40{\mu}g$/ml of prochloraz. Interestingly, mixed solution of $5{\mu}g$/ml or $10{\mu}g$/ml of each fungicide inhibitied 100% of mycelial growoth and 99.2% of spore germination, respectively. Severely infected rice seeds soaked into mixed solution composed of $125{\mu}l$/ml of prochloraz and $50{\mu}l$/ml of fludioxonil showed 2.1% of disease symptoms compared to 20.4% of prochloraz $125{\mu}l$/ml, but higher concentrations of prochloraz decreased the seedling stand rate. When the seed soaking time was longer and temperature was higher, control effect on Bakanae disease was improved, but seedling stand was lower about 80% over $35^{\circ}C$.

• Journal of radiological science and technology
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• v.27 no.4
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• pp.11-16
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• 2004

Classification of esophageal motility disorders not yet finalized and is still ongoing as the new disorders are reported, and the existing classification is changed or removed. In terms of radiology, the primary peristalsis does not exist, and the lower end of the esophagus show the smooth, tapered, beak-like appearance. The esophageal motility disorder, which mostly occurs in the smooth muscle area, show the symptoms of reduction or loss (hypomotility) or abnormal increase (hypermotility) of peristalsis of the esophagus. It is important to understand the anatomy and physiology of the esophagus for the appropriate radiological method and diagnosis. Furthermore, the symptom of the patient and the manometry finding must be closely referred for the radiological diagnosis. The lower esophageal sphincter can be normally functioning and open completely as the food moves lower. Sperandio M et al. argues that the name diffuse esophageal spasm must be changed to distal esophageal spasm (DES) as most of the spasm occurs in the distal esophagus, composed of the smooth muscle. According to Ott et al., usefulness of barium method for diagnosing the esophageal motility disorder is Achalasia 95%, DES 71% and NEMD 46%, with the overall sensitivity of 56%. However, excluding the nutcracker esophagus or nonspecific disorder which cannot be diagnosed with the radiological methods, the sensitivity increases to 89%. Using videofluoroscopy and 5 time swallows, the average sensitivity was over 90%. In conclusion, the barium method is a simple primary testing method for esophageal motility test. Using not only the image but also the videofluoroscopy with good knowledge of the anatomy and physiology, it is believed that the method will yield the accurate diagnosis.

• Korean Journal of Environmental Biology
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• v.37 no.4
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• pp.625-639
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• 2019

Microplastics are one of the substances threatening the marine ecosystem. Here, we summarize the status of research on the effect of microplastics on marine life and suggest future research directions. Microplastics are synthetic polymeric compounds smaller than 5 mm and these materials released into the environment are not only physically small but do not decompose over time. Thus, they accumulate extensively on land, from the coast to the sea, and from the surface to the deep sea. Microplastic can be ingested and accumulated in marine life. Furthermore, the elution of chemicals added to plastic represents another risk. Microplastics accumulated in the ocean affect the growth, development, behavior, reproduction, and death of marine life. However, the properties of microplastics vary widely in size, material, shape, and other aspects and toxicity tests conducted on several properties of microplastics cannot represent the hazards of all other microplastics. It is necessary to evaluate the risks according to the types of microplastic, but due to their variety and the lack of uniformity in research results, it is difficult to compare and analyze the results of previous studies. Therefore, it is necessary to derive a standard test method to estimate the biological risk from different types of microplastics. In addition, while most of the previous studies were conducted mostly on spheres for the convenience of the experiments, they do not properly reflect the reality that fibers and fragments are the main forms of microplastics in the marine environment and in fish and shellfish. Furthermore, studies have been conducted on additives and POPs (persistent organic pollutants) in plastics, but little is known about their toxic effects on the body. The effects of microplastics on the marine ecosystems and humans could be identified in more detail if standard testing methods are developed, microplastics in the form of fibers and fragments rather than spheres are tested, and additives and POPs are analyzed. These investigations will allow us to identify the impact of microplastics on marine ecosystems and humans in more detail.

• Journal of the korean academy of Pediatric Dentistry
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• v.26 no.4
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• pp.677-687
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• 1999

This study was performed to evaluate the effect of aging and thermal cycling on the tensile strength of six commercially available glass-ionomer materials: two chemically set glass-ionomer materials(Fuji II, Fuji IX), two resin-modified glass-ionomer materials(Fuji II LC, Vitremer), and two polyacid-modified composite resins(Compoglass, Dyract). Rectangular tension test specimens were fabricated in a teflon mold giving 5mm in gauge length and 2mm in thickness. All samples were divided into 3 groups. Group 1 was immersed in a $37^{\circ}C$ distilled water for 1 hour. Group 2 was immersed in a $37^{\circ}C$ distilled water for 30 days. Group 3 was subjected to 10,000 thermal cycles between $5^{\circ}C$ and $55^{\circ}C$, and the immersion time in each bath was 15 seconds per cycle. Tensile testing was carried out at a cross-head speed of 0.5mm/min and fracture surfaces were examined with scanning electron microscope. The results obtained were summarized as follows; 1. The polyacid-modified composite resins were stronger than the resin-modified glass-ionomer materials, which were much stronger than the conventional glass-ionomer materials. 2. Tensile strengths were slightly increased after aging treatments for 30days. 3. Tensile strengths of conventional glass ionomers were significantly increased after thermal cycling treatment(p<0.01). 4. The highest tensile strength value of 45.4MPa was observed in the Dyract group and the lowest value of 13.3MPa was observed in the Fuji II LC group after the thermal cycling test, and the strengths of polyacid-modified composite groups were significantly higher than those of other groups. 5. The highest characteristic strength value of 48.6MPa was obtained in the Dyract group, however the highest Weibull modulus value of 8.9MPa was obtained in the Compoglass group after thermal cycling test.

• Journal of Aquaculture
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• v.11 no.4
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• pp.449-455
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• 1998

The small size food organism(under the size 150${\mu}m$) is needed as food for early stage of marine fish larvae of small mouse (e.g the group of grouper). This study was investigated to develop a method for copepod Apocyclops sp. culture in combination with the rotifer B. rachionus for stable culture of copepod species and harvest of various size food organisms. The culture conditions as temperature, salinity, culture volume, photo period, culture preiod and observation interval were 25${\circ}C$, 22ppt, 40ml, all dark except to observation time, 16 days and every two day during the experimental period, respectively. The Tetraselmis suecica was used as the food for the two testing orgtanisms. After every two day counting, theses two organisms were transferred to fresh culture tanks with Tetraselmis suecica of $7{\times}10^5$cells/ml. In the mixed culture of B. rotundiformis and A. sp., growth of rotifer was suppressed by mixed culture with A. sp. whereas the growth of copepod Apocyclops was promoted in the mixed culture with rotifer B. rotundiformis (the maximum density was 22 individuals/ml through the 16 culture days). Moreover, the number of copepod nauplius were promoted about 2 times in the mixed culture compared to the numbers in single species culture. With this combination culture, the havested two food organisms of variable sizes. This size variation of food organisms was useful tools for larval rearing of small mouse marine fish larvae and next step food organism size of post hatched larvae.

• Nuclear Engineering and Technology
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• v.39 no.5
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• pp.603-616
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• 2007

Roy Huddle, having invented the coated particle in Harwell 1957, stated in the early 1970s that we know now everything about particles and coatings and should be going over to deal with other problems. This was on the occasion of the Dragon fuel performance information meeting London 1973: How wrong a genius be! It took until 1978 that really good particles were made in Germany, then during the Japanese HTTR production in the 1990s and finally the Chinese 2000-2001 campaign for HTR-10. Here, we present a review of history and present status. Today, good fuel is measured by different standards from the seventies: where $9*10^{-4}$ initial free heavy metal fraction was typical for early AVR carbide fuel and $3*10^{-4}$ initial free heavy metal fraction was acceptable for oxide fuel in THTR, we insist on values more than an order of magnitude below this value today. Half a percent of particle failure at the end-of-irradiation, another ancient standard, is not even acceptable today, even for the most severe accidents. While legislation and licensing has not changed, one of the reasons we insist on these improvements is the preference for passive systems rather than active controls of earlier times. After renewed HTGR interest, we are reporting about the start of new or reactivated coated particle work in several parts of the world, considering the aspects of designs/ traditional and new materials, manufacturing technologies/ quality control quality assurance, irradiation and accident performance, modeling and performance predictions, and fuel cycle aspects and spent fuel treatment. In very general terms, the coated particle should be strong, reliable, retentive, and affordable. These properties have to be quantified and will be eventually optimized for a specific application system. Results obtained so far indicate that the same particle can be used for steam cycle applications with $700-750^{\circ}C$ helium coolant gas exit, for gas turbine applications at $850-900^{\circ}C$ and for process heat/hydrogen generation applications with $950^{\circ}C$ outlet temperatures. There is a clear set of standards for modem high quality fuel in terms of low levels of heavy metal contamination, manufacture-induced particle defects during fuel body and fuel element making, irradiation/accident induced particle failures and limits on fission product release from intact particles. While gas-cooled reactor design is still open-ended with blocks for the prismatic and spherical fuel elements for the pebble-bed design, there is near worldwide agreement on high quality fuel: a $500{\mu}m$ diameter $UO_2$ kernel of 10% enrichment is surrounded by a $100{\mu}m$ thick sacrificial buffer layer to be followed by a dense inner pyrocarbon layer, a high quality silicon carbide layer of $35{\mu}m$ thickness and theoretical density and another outer pyrocarbon layer. Good performance has been demonstrated both under operational and under accident conditions, i.e. to 10% FIMA and maximum $1600^{\circ}C$ afterwards. And it is the wide-ranging demonstration experience that makes this particle superior. Recommendations are made for further work: 1. Generation of data for presently manufactured materials, e.g. SiC strength and strength distribution, PyC creep and shrinkage and many more material data sets. 2. Renewed start of irradiation and accident testing of modem coated particle fuel. 3. Analysis of existing and newly created data with a view to demonstrate satisfactory performance at burnups beyond 10% FIMA and complete fission product retention even in accidents that go beyond $1600^{\circ}C$ for a short period of time. This work should proceed at both national and international level.

• Radiation Oncology Journal
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• v.26 no.4
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• pp.257-262
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• 2008

Purpose: Oral mucositis induced by radiotherapy to the head and neck area, is a common acute complication and is considered as the most severe symptom for cancer patients in the early stages of treatment. This study was proposed to establish the oral mucositis mouse model induced by a single dose of radiation for the facility of testing therapeutic candidates which can be used for the oral mucositis treatments. Materials and Methods: Fifty-five BALB/c mice were divided into four groups: control, 16 Gy, 18 Gy, and 20 Gy. Oral mucositis was induced by a single dose of radiation to the head and neck using 6 MV x-Ray from linear accelerator. After irradiation, body weight and physical abnormalities were checked daily. Tongue tissues from all groups were taken on days 1, 2, 3, 5, 7, 9, and 14, respectively and H&E staining was conducted to examine morphological changes. Results: Body weight dramatically decreased after day 5 in all irradiated mice. In the 16 Gy treatment group, body weight was recovered on day 14. The histology data showed that the thickness of the epithelial cell layer was decreased by the accumulated time after radiation treatment, up to day 9. Severe ulceration was revealed on day 9. Conclusion: A single dose of 16 Gy is sufficient dose to induce oral mucositis in Balb/C mice. Significant changes were observed in the Balb/C mice on days 7 and 9 after radiation. It is suggested that this mouse model might be a useful standard tool for studying oral mucositis induced by radiation.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.3
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• pp.329-336
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• 2006

Iron manufacturing process involves production of various by-product including slag, sludge, sintering and EAF(Electric Arc furnace dust). Some of the by-products such as EAF and sintering dust are disposed of as waste due to their high heavy metal contents. It has been notice for many years that the EAF dust also contain about 65% of Fe(0) and Fe(II) and then the possible utilization of the iron. One possibility is to apply the EAF as a lining material in conjunction with clay or HDPE liners, in waste landfill. The probable reaction between the leachate containing toxic elements such as TCE, PCE dioxine and $Cr^{6+}$ is reduction of the toxic materials in corresponding to the oxidation of the reduced iron and therefore diminishing the toxicity of the leachate. It is, however, prerequisite to evaluate the leaching characteristics of the EAF dust before application. Amelioration of the leachate would be archived only when the level of toxic elements in the treated leachate is less than that of in the untreated leachate. Several leaching techniques were selected to cover different conditions and variable environments including time, pH and contact method. The testing methods include availability test, pH-stat test and continuous column test. Cr and Zn are potentially leachable elements among the trace metals. The pH of the EAF dust is highly alkaline, recording around 12 and Zn is unlikely to be leached under the condition. On the contrary Cr is more leachable under alkaline environment. However, the released Cr should be reduced to $Cr^{3+}$ and then removed as $Cr(OH)_3$. Removal of the Cr is observed in the column test and further study on the specific reaction of Cr and EAF dust is underway.

• Geophysics and Geophysical Exploration
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• v.9 no.3
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• pp.207-224
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• 2006

It has been widely known that the seismic piezo-cone penetration test (SCPTu) is one of the most useful techniques for investigating the geotechnical characteristics such as static and dynamic soil properties. As practical applications in Korea, SCPTu was carried out at two sites in Busan and four sites in Incheon, which are mainly composed of alluvial or marine soil deposits. From the SCPTu waveform data obtained from the testing sites, the first arrival times of shear waves and the corresponding time differences with depth were determined using the cross-over method, and the shear wave velocity $(V_S)$ profiles with depth were derived based on the refracted ray path method based on Snell's law. Comparing the determined $V_S$ profile with the cone tip resistance $(q_t)$ profile, both trends of profiles with depth were similar. For the application of the conventional CPTu to earthquake engineering practices, the correlations between $V_S$ and CPTu data were deduced based on the SCPTu results. For the empirical evaluation of $V_S$ for all soils together with clays and sands which are classified unambiguously in this study by the soil behavior type classification index $(I_C)$, the authors suggested the $V_S-CPTu$ data correlations expressed as a function of four parameters, $q_t,\;f_s,\;\sigma'_{v0}$ and $B_q$, determined by multiple statistical regression modeling. Despite the incompatible strain levels of the downhole seismic test during SCPTu and the conventional CPTu, it is shown that the $V_S-CPTu$ data correlations for all soils, clays and sands suggested in this study is applicable to the preliminary estimation of $V_S$ for the soil deposits at a part in Korea and is more reliable than the previous correlations proposed by other researchers.