• Weed & Turfgrass Science
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• v.2 no.4
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• pp.402-407
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• 2013

Bermudagrass (Cynodon dactylon.) is one of the most difficult weedy species to control in turfgrass because it's high tolerant to various environmental and management stresses. This experiment was performed to find the integrated weed management including cultural practices to suppress bermudagrass in Zoysiagrass matrella (L) Merr. As results, two sequential applications of Fluazifop-P-butyl 0.05 ml $m^{-2}$ + Triclopyr-TEA 0.5 ml $m^{-2}$ and Fenoxaprop-P-ethyl 0.1 ml $m^{-2}$ + Triclopyr-TEA 0.5 ml $m^{-2}$ applied on 20 days intervals were evaluated the primary option for bermudagrass suppression and turfgrass injury was acceptable in zoysiagrass. In both treatments, turf injury was observed during 30days after the first application and almost recovered at 40days. While Fenoxaprop-Pethyl 0.1 ml $m^{-2}$ + Triclopyr-TEA 0.5 ml $m^{-22}$ were lightly phytotoxic to zoysiagrass in chlorophyll content test, there was no growth inhibition of zoysiagrass. Verticut practice (4 mm depth) just before herbicides application where zoyisagrass is contaminated with bermudagrass was not helpful to reduce turf injury in this experiment. However, alone verticut management was utilized to decrease about 12-14% bermudagrass population. Thus the application of Fenoxaprop-P-ethyl 0.1 ml $m^{-2}$ + Triclopyr-TEA 0.5 ml $m^{-2}$ which are permitted for turfgrass after zoysiagrass is perfectly recovered from turf injury by verticut practice should be utilized for bermudagrass reduction in zoysiagrass.

• Weed & Turfgrass Science
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• v.2 no.4
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• pp.368-375
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• 2013

Whole genome transcriptomes from Miscanthus species were sequenced and analyzed, which provided 50 different types of transcription factor (TF) involving various developmental processes or environmental stresses. Among the explored TF, WRKY gene family was the major type and one of the WRKY genes, MSIR7180_WRKY4, induced under low temperature environment was selected to investigate how the Miscanthus-originated MSIR7180_WRKY4 TF responds when exposed to low temperature in four warm-season turfgrasses (Z. matrella 'Semil', bermudagrass, St. Augustinegrass, and seashore paspalum). The MSIR7180_WRKY4 was expressed higher during low temperature period in Bermudagrass, but the expression was enhanced in St. Augustinegrass. In contrast, the gene in 'Semil' cultivar was barely expressed and relatively less expressed, but repressed gradually in seashore paspalum, which seems to allow two turfgrasses stay-green longer in the fall season. The results indicate that bermudagrass and St. Augustinegrass adapt to low temperature quickly, but relative tolerance to low or cold temperature at the molecular level needs to be further investigated at different physiological stages and the corresponding genes systematically.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.2 no.3
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• pp.87-99
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• 1982

This study proposes a reliability based design criteria for the R.C. superstructures of highway bridges. Uncertainties associated with the resistance of T or rectangular sections are investigated, and a set of appropriate uncertainties associated with the bridge dead and traffic live loads are proposed by reflecting our level of practice. Major 2nd moment reliability analysis and design theories including both Cornell's MFOSM(Mean First Order 2nd Moment) Methods and Lind-Hasofer's AFOSM(Advanced First Order 2nd Moment) Methods are summarized and compared, and it has been found that Ellingwood's algorithm and an approximate log-normal type reliability formula are well suited for the proposed reliability study. A target reliability index (${\beta}_0=3.5$) is selected as an optimal value considering our practice based on the calibration with the current R.C. bridge design safety provisions. A set of load and resistance factors is derived by the proposed uncertainties and the methods corresponding to the target reliability. Furthermore, a set of nominal safety factors and allowable stresses are proposed for the current W.S.D. design provisions. It may be asserted that the proposed L.R.F.D. reliability based design criteria for the R.C. highway bridges may have to be incorporated into the current R.C. bridge design codes as a design provision corresponding to the U.S.D. provisions of the current R.C. design code.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.2 no.3
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• pp.1-13
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• 1982

Transition process of plastic region. displacements, stresses and strains ahead the flaw tips were analysed by the finite element method on the steel plate with the circular hole and the one with the elliptical hole under completely alternating load (repetition of tensile loading, unloading and compressive loading). As the results, the followings were obtained. Transition process of elastic failure (yielding) region was estimated. From this the tendency was confirmed that the fracture would be initiated from ahead the flaw tip, and propagated along the $45^{\circ}$ direction. The fundamental data available in estimating the stress intensity factor that was considered as the core in analysing the fracture mechanism of steel plates were obtained. It was indicated that when unloading after tension the effect of compressive loading, and even the compressive reyield, was occured ahead the flaw tip. Similarly it was indicated that when unloading after compression the effect of tensile loading, and even the tensile reyield, was occured ahead the flaw tip. It was considered that these phenomena were occured because the unloading effect was constrained by the residual strains when unloading. It was considered that the fatigue phenomenon was occured ahead, the flaw tip by repetition of tensile yield, the above compressive reyield, compressive yeild and the above tensile reyield. In addition, the tendency was confirmed that the fracture ahead the flaw tip was occured as the flaw was changed from the circular hole to the elliptical hole and became to be the crack lastly.

• Journal of Wetlands Research
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• v.22 no.2
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• pp.113-120
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• 2020

For the conservation of both Sericinus montela (vulnerable species by red book of Korea) and A. contorta, we investigated environmental factors affecting the growth and reproduction of Aristolochia contorta. We selected four A. contorta habitats at Gapyeong, Pyeongtaek, Cheongju, and Yeoju in Korea and surveyed community and habitat characteristics of companion species, herbivore appearance, support types, and soil physicochemical properties in July and October, 2018. Habitat environments and the growth and reproduction characteristics of A. contorta were different according to four habitats of different regions. In particular, the fastest growth speed and earliest flowering and fruiting were observed in Pyeongtaek. Growth of A. contorta in Cheongju and Yeoju were interrupted by aboveground damage from human disturbance. In this study, support types seemed to be important for growth speed of A. contorta. Flowering and fruiting timing were likely to be related to combined effects of soil cation contents and competitive and herbivore stresses. Therefore, providing effective support and reducing biological stress should be necessary for stable growth and proper flowering and fruiting timing of A. contorta. In addition, experimental evidence would be needed to figure out the effect of soil cation and biological stress on flowering and fruiting of A. contorta in detail.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.3 no.1
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• pp.65-72
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• 1983

Dry sand specimens for both normally consolidated and overconsolidated triaxial compression tests were prestressed on the path with five different coefficients of earth pressure 1.0, 3/4, 0.55, $K_0$ and 1/3. Deformation resistance of normally consolidated sand increased with increasing the initial stress for all coefficients of earth pressure during consolidation, and the deformation modulus at a certain initial stress showed a tendency to increase with increasing the coefficient of earth pressure. And deformation moduli($E_i$, $E_{50}$), were found to be proportional to the $n_{th}$ power of initial stresses[${\sigma}_{m0}{^{\prime}}$, ${\sigma}_{10}{^{\prime}}$, ${\sigma}_{30}{^{\prime}}$, $({\sigma}_1-{\sigma}_3)_0$] for both isotropically and anisotropically normally consolidated samples, where n varied from 0.37 to 0.92. Overconsolidated sand with the higher overconsolidation ratio showed the higher deformation modulus. It is concluded that the $K_0$-anisotropically consolidated triaxial compression test is necessary to obtain the more accurate value of in-situ deformation modulus.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.3
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• pp.25-34
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• 1993

The long-term behavior, such as in excavation problems of weak medium, can be dealt with by the elasto-viscoplasticity models. In this paper, a combined formulation of elasto-viscoplasticity using boundary elements and finite elements without using internal cells is presented. The domain integral introduced due to the viscoplastic stresses is transformed into a boundary integral applying direct integration in cylindrical coordinates. The results of the developed boundary element analysis are compared with those from the explicit solution and from the finite element analysis. It is observed that the boundary element analysis without internal cells results in some error because of its deficiency in handling the nonlinearity in local stress concentration. Therefore, a coupled analysis of boundary elements and finite elements, in which finite elements are used in the area of stress concentration, is developed. The coupled method is applied to a time dependent inelastic problem with semi-infinite boundaries. It results in reasonable solution compared with other methods where relatively higher degree of freedoms are employed. Thus, it is concluded that the combined analysis may be used for such problems in the effective manner.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.4C
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• pp.169-175
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• 2012

Soil water retention characteristics are influenced by factors of the confining stress and hysteresis in the variably saturated soil. In the description of effective stress based on hydraulic characteristics, the contribution of a matric suction to effective stress then varies with depth or is different between the processes of infiltration and evaporation. Unsaturated effective stress can be described based on suction stress characteristic curve, in which a representative soil water retention curve is required to evaluate. Pressure palate extractor tests under various confining stresses were performed and the hysteresis of drying and wetting process was also acquired. In the process of drying or wetting, a unique relationship has been estimated on the effective volumetric water content and the matric suction, which defines suction stress characteristic curve. In the unsaturated shear strength from triaxial tests, the suction stress and the effective stress were evaluated by matric suctions. The failure envelop by effective stress based on soil water retention characteristics was unique and the same as the saturated one. The measured suction stress from triaxial tests was similar to that from the soil water retention curve. Therefore it is verified that a representative soil water retention curve can be defined which is independent of the confining effect under wetting or drying process of the hysteresis.

• Korean Journal of Medicinal Crop Science
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• v.24 no.5
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• pp.386-392
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• 2016

Background: Sorghum is a major cereal food crop used in many parts of the world. It has been grown on a subsistence level by farmers, under various conditions of environmental stresses in the semi-arid tropics of Africa and Asia. This plant has received significant attention because of its ability to reduce cholesterol in the blood, and its anti-dementia, antioxidant, and antimicrobial properties. It is possible to develop a functional and commercially viable sorghum variety by using superior cultivars of sorghum. The objective of this study was to build a database of superior sorghum accession. Methods and Results: We used 250 sorghum accessions collected from different geographical bioregions in Korea. We determined various agronomic characters including germination rate and ear length of these accessions. To determine the antioxidant capacity, we measured the 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity, 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid)-diammonium salt radical scavenging activity, total phenolic contents, and total flavonoid contents. Accession 189 showed higher germination (> 80%) than the other accessions. Higher 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity was observed in 11-SB-078 ($RC_{50}$; $1.89{\pm}2.88{\mu}g/m{\ell}$), and higher 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid)-diammonium salt radical scavenging activity was recorded in 11-SB-116 ($RC_{50}$; $35.48{\pm}2.42{\mu}g/m{\ell}$) than in the other accessions. The ear length ranged from 15 cm to 48 cm, the total phenolic contents ranged from $3mg{\cdot}GAE/g$ to $77mg{\cdot}GAE/g$, and total flavonoid contents ranged from $0.09mg{\cdot}QE/g$ to $1.07mg{\cdot}QE/g$. Conclusions: Among 250 sorghum accessions, we selected 10 with both superior agronomic characters and highly functional food quality.

• Korean Journal of Microbiology
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• v.35 no.2
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• pp.139-145
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• 1999

Aromatic hydrocarbons which are not easily degraded by microorganisms can be accumulated in the conlaminated environment for a long lime, producing toxic effects on wild lives and humans. However, the sublethal concentrations of the chemicals induce the synthesis of stress-shock proteins in the cells and increase the adaptability of the organisms to the environmental stresses. In this study, therefore, the cells of Psezido~nonus sp. DJ- 12 treated with catechol at various concentrations were inveshgated for their survival, biodegtadability of catechol, production of stress-shock proteins, and cytological changes. The organisms were capable of degrading catechol at the range of 0.5 to 1.0 mM concentration wilhin 6 hours incubation, but they were killed by $10^2$-10$^3$ celllinl at 3 mM or higel- concentration without any catechol degradation. These cells treated with catechol begm lo produce DnaK and GroEL at 1 mM and 0.5 mM. respectively. Pseudumonas sp. DJ-12 treated with 10 mM catechol for I hour exhihiled some punctuated pores on the cell wall and contortion of the rod shape. The cells treated with he sublethal concentration of catechol showed the increased tolerance for suvival when exposed to the lethal concentration, and such tolerant effects were functioned crossly among benzoate, 4-chlorobenzoate, 'and catechol.