• Asian Journal of Turfgrass Science
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• v.19 no.2
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• pp.115-123
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• 2005

The effect of sodium hypochlorite treatment on the germination of cattail (Typha spp.) seeds was investigated in growth chambers maintained on a 14-h photoperiod with various temperatures and light intensities. Germination rates of seeds were, in general, enhanced by the increase of light intensity and temperature regardless of cattail species. Seeds of T. oreientalis had 4.3, 13.0 and $7.3\%$ germination at temperatures of 20, 25 and $30^{circ}$C, respectively, under light intensity of 7.5${\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$. T. angustata showed higher germination rate, thus, 10.7, 22.7 and $50.7\%$ under same temperature and light environment. Under high light intensity of 79.5${\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$, the germination rates of T. oreintalis and T angustata were $78.3\%$ and $88.7\%$ at $30^{circ}$C, respectively. Scarification of seeds with NaOC1 ($4\%$, available chlorine) increased germination rate in both species, especially even at low temperature of $20^{circ}$C. Germination speed was also enhanced by NaOC1 treatment. High light intensity further increased the germination rate. When NaOC1 treated seeds were sowed on the soil surface in plastic house, the seedling emergence was nearly $100\%$. Untreated seeds of T. oreintalis and T. angustara showed 40 and $50\%$, respectively, in germination under same condition. However, when the depth of soil covering was over 1.0 cm, seedling emergence was retarded more than 1 month. On the process of seedling development, emergence of mesocoty1 occurred firstly and after than primary root and first leaf were developed on the end of elongated mesocotyl. These results suggest that the promotion of seed germination by NaOC1 pretreament may be induced from the increase of light absorptivity as well as water permeability through scarifying and bleaching the seed coat.

• Journal of Korean Tunnelling and Underground Space Association
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• v.18 no.5
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• pp.453-467
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• 2016

Overall risks that can occur in a shield TBM tunnelling are studied in this paper. Both the potential risk events that may occur during tunnel construction and their causes are identified, and the causal relationship between causes and events is obtained in a systematic way. Risk impact analysis is performed for the potential risk events and ways to mitigate the risks are summarized. Literature surveys as well as interviews with experts were made for this purpose. The potential risk events are classified into eight categories: cuttability reduction, collapse of a tunnel face, ground surface settlement and upheaval, spurts of slurry on the ground, incapability of mucking and excavation, and water leakage. The causes of these risks are categorized into three areas: geological, design and construction management factors. Bayesian Networks (BN) were established to systematically assess a causal relationship between causes and events. The risk impact analysis was performed to evaluate a risk response level by adopting an Analytic Hierarchy Process (AHP) with the consideration of the downtime and cost of measures. Based on the result of the risk impact analysis, the risk events are divided into four risk response levels and these levels are verified by comparing with the actual occurrences of risk events. Measures to mitigate the potential risk events during the design and/or construction stages are also proposed. Result of this research will be of the help to the designers and contractors of TBM tunnelling projects in identifying the potential risks and for preparing a systematic risk management through the evaluation of the risk response level and the migration methods in the design and construction stage.

• Economic and Environmental Geology
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• v.39 no.1 s.176
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• pp.83-93
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• 2006

The Kita-Yamato Trough is characterized by a SW-NE trending narrow graben between the Yamato Bank and the Kita-Yamato Bank in the central East Sea/Japan Sea (ES/JS). Core 20EEZ-1 was obtained in the flat summit of a small ridge from the southwest Kita-Yamato Trough. The sedimentation was mainly controlled by the supply of hemipelgic sediments and substantial tephras from explosive volcanic eruptions of the Quaternary volcanoes. The aim of this study is to reconstruct the tephrostratigraphy from the marine sediments collected from the Kita-Yamato Trough and to provide the atmosphere and ocean conditions during the explosive volcanic eruptions. According to the detailed tephrostratigraphy and lithofacies records, the core sediments were deposited during the last marine isotope stage (MIS) 7. The core consists of four lithofacies, idetified as, oxidized mud (OM), crudely laminated mud (CLM) and bioturbated mud (BM), interbedded with coarse-grained tephra (TP). The major element geochemistry and stratigraphic positions of seven tephra layers suggest that they originated from the Aira caldera in Kyushu area among the Japanese islands (AT tephra; 29.24 ka), unknown submarine volcano in the south Korea Plateau (SKP-I; MIS 3, SKP-II; MIS 4, SKP-IV; boundary between MIS 6 and MIS 5e, SKP-V; MIS 6, respectively), and the Baegdusan volcano in the Korean Peninsula (B-KY1; ca. 130 ka, B-KY2; ca. 196 ka). The absence of tephras originated trom Ulleung Island in core 20EEZ-l suggest that the tephras had not been transported into the Kita-Yamato Trough by atmosphere conditions during the eruptions. On the other hand, the B-KYI and the B-KY2 tephras derived from the Baegdusan volcano were founded in the Kita-Yamato Trough by a presence of prevailing westerly winds during the eruptions. Furthermore, the SKP tephras were characterized by the transport across the air-water interface, causing quickly thrust of raising eruption plumes from subaqueous explosive eruptions. Surface currents may play an important role in controlling the distribution patterns of the SKP tephras to distal areas. The tephrostratigraphic study in the Kita-Yamato Trough provides the important chronostratigraphic marker horizons and the detailed atmosphere and ocean conditions during the explosive eruptions.

• Journal of Energy Engineering
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• v.25 no.4
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• pp.103-109
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• 2016

Polyethylene pipes has useful benefits which are anti-corrosive and flexible material, so it is used to gas pipes but also class 3 water pipes of nuclear power plant, process pipes of petrochemical plant and chemical plant. So the usage of polyethylene pipes is widely increased. But it has been limited for the usage of polyethylene, because it can not be directly detected to fusion joints by using non destructive evaluation. Polyethylene pipes are connected by two methods, one is butt fusion and the other is electrofusion. Butt fusion is widely used to connecting the pipes. It is proposed to method for determining the reliability of joints in this study that is detection of the melt flow zone at fusion joints. In this study, middle density polyethylene is used, outside diameter of the test specimen is 225mm and thickness is 20.5mm. Speed of ultrasonic of this test specimen is 2,200m/s. Test specimens were fabricated by varying the heating time which means from 0% to 130% applying time through heating plate to polyethylene for detecting melt flow zone. Also 4 additional test specimens were made, one was made that not scrapping attached surface of pipes but applying 100% of the proper heating time and the others were made to include of soil, gravel and vinly tape paper at fusion joints, that were also applied 100% of proper heating time. Ultrasonic testing to measure the melt flow zone of 20 test specimens was conducted by using 3.5MHz and 5.0MHz ultrasonic probes and melt flow zone measuring was conducted to three times at different point to one specimen. To differentiate the melt flow zone signal, post image processing was equally conducted to all test results and image levels, contrast, sharpen, threshold were adopted to all teat results and the test results were displayed gray scale. From the results, for the shorter heating times the reflection area of multiple echo have been increased, so the data was obtained from the position where it can be eliminated as much as possible. At 80% of proper heating time(168 sec.), the signal of melt flow zone was obtained clearly, so measuring could be conducted. From 7% of proper heating time(15 sec.) to shorter heating times. we could not obtain the signal because test specimen was not fused. From the result, we can verify that measuring of melt flow zone by using phased array ultrasonic imaging method is possible. And we can verify to complete and incomplete butt fusion by measuring the melt flow zone.

• Ecology and Resilient Infrastructure
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• v.7 no.3
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• pp.208-217
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• 2020

A biopolymer based on microorganism-derived β-glucan and xanthan gum is being studied as a new eco-friendly material that stabilizes the riverbank slope, and also promotes vegetation growth. However, it is still inconclusive whether biopolymers have a positive effect on plant performance in the riverbanks which are subjected to various climatic factors and plant competitions. For a practical ecological evaluation of the biopolymers, their effect on plant growth promotion was studied in a natural environment. Considering the relationship between competition and plant community formation, the effects of biopolymers on competition were also investigated. For four plant species (Echinochloa crus-galli, Pennisetum alopecuroides, Leonurus japonicus, and Coreopsis lanceolata), the biopolymer effects under intra/interspecific competition were tested at the riverbank (20 m × 10 m) near Samjigyo Bridge in Damyang-gun, Jeollanam-do. A biopolymer powder was mixed with water and commercial soil following the manufacturer's recommendations. The soil mixed with the biopolymer was filled in a pot or applied to the surface of the commercial soil with a thickness of 3 cm. Across the competition treatments, the biopolymer treatment promoted root growth of the target plant species and decreased the specific leaf area. The total biomass and shoot dry weight of P. alopecuroides increased in response to the biopolymer treatment. The competition treatment decreased the total biomass and shoot dry weight compared to the case without competition. Notably, such a competitive effect was similar in all the biopolymer treatments. Thus, biopolymers, when mixed with soil, promote the growth of some plant species, but do not appear to affect the competitive ability of plants.

• The Korean Journal of Nuclear Medicine Technology
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• v.16 no.2
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• pp.81-86
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• 2012

Purpose : Combined MR/PET scanners that use the MRI for PET AC face the challenge of absent surface coils in MR images and thus cannot directly account for attenuation in the coils. To make up for the weak point of MR attenuation correction, Three Modality System (PET/CT +MR) were used in Severance hospital. The goal of this work was to investigate the effects of MR Torso Coil on CT attenuation correction for PET. Materials and Methods : PET artifacts were evaluated when the MR Torso Coil was present of CTAC data with changing various kV and mA in uniformity water phantom and 1994 NEMA cylinderical phantom. They evaluated and compared the following two scenarios: (1) The uniform cylinder phantom and the MR Torso Coil scanned and reconstructed using CT-AC; (2) 1994 NEMA cylinderical phantom and the MR Torso Coil scanned and reconstructed using CT-AC. Results : Streak artifacts were present in CT images containing the MR Torso Coil due to metal components. These artifacts persisted after the CT images were converted for PET-AC. CT scans tended to over-estimate the linear attenuation coefficient when the kV and mA is increasing of the metal components when using conventional methods for converting from CT number. Conclusion : The presence of MR coils during PET/CT scanning can cause subtle artifacts and potentially important quantification errors. Alternative CT techniques that mitigate artifacts should be used to improve AC accuracy. When possible, removing segments of an MR coil prior to the PET/CT exam is recommended. Further, MR coils could be redesigned to reduce artifacts by rearranging placement of the most attenuating materials.

• Korean Journal of Soil Science and Fertilizer
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• v.39 no.2
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• pp.65-72
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• 2006

Objective of this research was to remove the accumulated salts in the plastic film house soils by installing the perforated PVC (${\phi}10cm$) underdrainage pipes at 50 cm depth of soils with cultivating vegetables. Efficiency of the underdrainage pipes was assessed based on the changes of soil chemical properties such as pH, EC, and cations, and growth and yield parameters of the vegetables between the two treatments; the control and the underdrainage pipe treatments. The EC of the underdrainage pipes installed soils after two growing seasons were in the ranges of $1.42-2.88dS\;m^{-1}$ but those of the control were in the ranges of $3.86-4.53dS\;m^{-1}$, indication the underdrainage pipes effectively removed the accumulated salts in soils. The pHs of the control soils and the underdrainage pipe installed soil were in the ranges of 7.2-7.5 and 6.9-7.3, respectively. There was a significant correlation between pH and cation exchange capacity (CEC) of the soils ($CEC=17.107{\times}pH-106.2$, $r^2=0.759$, P < 0.05). The ECs of the soils at different depths were compared between the two treatments after cultivating vegetables with lettuce-lettuce-garland chrysanthemum rotation systems. The ECs of the control soils at depths of 0-10, 10-20, 20-30, 30-40, and 40-50 cm were 3.45, 3.47, 3.03, 2.03, and $2.28dS\;m^{-1}$, respectively, with decreasing with soil depths. On the other hand, the respective ECs of the underdrainage pipes installed soils were 2.43, 2.52, 2.28, 4.00, and $4.23dS\;m^{-1}$ with increasing with soil depths. This might be derived from the salts moved downward with the draining water into the subsoil. The order of cations moved downward was Mg > Ca > K, based on the ratios of cations at specific depth over those at the surface soil. The survival rates of lettuce after 15 days of transplanting in the underdrainage pipe installed soils were 98.2% as compared to 86.6% of the control. The underdrainage pipe treatment also increased the diameter of the lettuce stalk from 12.9mm of the control to 13.7mm. Overall results demonstrated that the installment of the underdrainage pipes in the subsoils of the salt accumulated plastic film house soil effectively removed the salts by leaching downward,resulting in lowering soil EC and enhancing the growth and yield of vegetables.

• Korean Journal of Ichthyology
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• v.4 no.2
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• pp.44-54
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• 1992

The blenniid fish, Pictiblennius yatabei(Jordan et Snyder) is ditributed in the central and southern Japan and southern Korea. The fish grows to a maximum size of 9cm in total length, and it seems to be matured in two years. Sex dimorphisms of the fish appear in the crest and the anal fin. Five egg masses of the fish were collected in Tongyoung Bay near Kyeong Nam on June 16 and 20, 1991. The eggs were laid on inner surface of empty shells of the oyster, Crassotrea gigas and blue mussel, Mytilus edulis. Each egg mass was guarded by the male parent. Numbers of eggs in each of masses were as about 450~1000.The eggs were spherical but somewhat oval in shape and ranged from 0.72 to 0.80mm in longer axis and from 0.55 to 0.65mm in shorter axis. Each egg was provided with an adhesive pedestal. Hatching took place in 105 hours after formation of embyo at the water temperature varying from 20.0 to $21.4^{\circ}C$. Melanophores appearing on the yolk remarkably changed in form during the embryonic development.The newly hatched larvae, having 32~34 somites, were from 2.71 to 3.35mm in total length. The larvae absorbed the yolk material and oil globule completely in 7 days after hatching and became postlarvae. Nine days after hatching, the larvae averaged 5.35mm in TL and the caudal notochord flex at $45^{\circ}$ Total lengths of the larvae reached 6.00 and 6.58mm in 11 and 13 days after the hatching, respectively.

• The Journal of Korean Academy of Prosthodontics
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• v.46 no.5
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• pp.511-519
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• 2008

Statement of problem: An incompatibility between the initiator systems of self-curing composite resins and light-curing adhesives was supposed recently. Purpose: The purpose of the study was to evaluate the influence of activators for self/dual bonding on dentin shear bonding strengths. Material and methods: Fifty human molars were divided into 5 groups. A flat dentin surface was created for each tooth. A self-curing composite resin (Luxacore) was bonded with the following adhesives (n = 10); One-Step, Prime&Bond NT, AdheSE, Prime&Bond NT and AdheSE were also used in combination with activators. Shear bond strengths were measured after 24 hours of water storage. The specimens were loaded in shear in the Instron until failure at a 1 mm/min crosshead speed. Data were compared using one-way ANOVA and Tukey HSD test (${\alpha}$= 0.05). Results: The dentin adhesive systems in order of decreasing median bond strength were One-Step > Prime&Bond NT with activator, AdheSE with activator > Prime&Bond NT, AdheSE. Among adhesives, One-Step had the highest bond strength. Prime&Bond NT with activator had higher bond strengths than Prime&Bond NT that was used alone, and so was AdheSE. Conclusion: Shear bond strengths were increased in Prime&Bond NT and AdheSE when these were used with activators comparing used without activators. But using activators was not effective clinically comparing One-Step.

• The Journal of Korean Academy of Prosthodontics
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• v.46 no.5
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• pp.535-543
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• 2008

Purpose: The objective of this study was to compare the bonding characteristics of a new self-adhesive resin cement to dentin, which does not require bonding and conditioning procedure of the tooth surface, and conventional resin cement. The effect of phosphoric acid etching prior to application of self-adhesive resin cement on the shear bond strength was also evaluated. Material and methods: Fortyfive non-carious human adult molars extracted within 6 months were embedded in chemically cured acrylic resin. The teeth were ground with a series of SiC-papers ending with 800 grit until the flat dentin surfaces of the teeth were exposed. The teeth were randomly divided into 3 experimental groups. In group 1, self-adhesive resin cement, RelyX Unicem (3M ESPE, Seefeld, Germany) was bonded without any conditioning of teeth. In group 2, RelyX Unicem was bonded to teeth after phosphoric acid etching. For group 3, Syntac Primer (Ivoclar Vivadent AG, Schaan, Liechtenstein) was applied to the teeth before Syntac adhesive (Ivoclar Vivadent AG, Schaan, Liechtenstein) and Helibond (Ivoclar Vivadent AG, Schaan, Liechtenstein) followed by conventional resin cement, Variolink II (Ivoclar Vivadent AG, Schaan, Liechtenstein). To make a shear bond strength test model, a plastic tuble (3 mm diameter, 3 mm height) was applied to the dentin surfaces at a right angle and filled it with respective resin cement, and light-polymerized for 40 seconds. All the specimens were stored in distilled water at $37^{\circ}C$ for 24 hours before test. Universal Testing Machine (Z020, Zwick, Ulm, Germany) at a cross head speed of 1 mm/min was used to evaluate the shear bond strength. The failure sites were inspected under a magnifier and Scanning Electron Microscope. The data was analyzed with One way ANOVA and Scheffe test at ${\alpha}$= 0.05. Results: (1) The shear bond strengths to dentin of RelyX Unicem was not significantly different from those of Variolink II/Syntac. (2) Phosphoric acid etching lowered the shear bond strength of RelyX Unicem significantly. (3) Most of RelyX Unicem and Variolink II showed mixed fractures, while all the specimens of RelyX Unicem with phosphoric acid etching demonstrated adhesive failure between dentin and resin cement. Conclusion: Shear bond strength to dentin of self-adhesive resin cement is not significantly different from conventional resin cement, and phosphoric acid etching decrease the shear bond strength to dentin of self-adhesive resin cement.