• The Plant Pathology Journal
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• v.31 no.3
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• pp.203-211
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• 2015

Maize is the dominant cereal crop produced in the US. One of the main fungal pathogens of maize is Fusarium verticillioides, the causative agent of ear and stalk rots. Significantly, the fungus produces a group of mycotoxins - fumonisins - on infested kernels, which have been linked to various illnesses in humans and animals. Nonetheless, durable resistance against F. verticillioides in maize is not currently available. In Texas, over 2.1 million acres of maize are vulnerable to fumonisin contamination, but understanding of the distribution of toxigenic F. verticillioides in maize-producing areas is currently lacking. Our goal was to investigate the genetic variability of F. verticillioides in Texas with an emphasis on fumonisin trait and geographical distribution. A total of 164 F. verticillioides cultures were isolated from 65 maize-producing counties. DNA from each isolate was extracted and analyzed by PCR for the presence of FUM1- a key fumonisin biosynthesis gene - and mating type genes. Results showed that all isolates are in fact F. verticillioides capable of producing fumonisins with a 1:1 mating-type gene ratio in the population. To further study the genetic diversity of the population, isolates were analyzed using RAPD fingerprinting. Polymorphic markers were identified and the analysis showed no clear correlation between the RAPD profile of the isolates and their corresponding geographical origin. Our data suggest the toxigenic F. verticillioides population in Texas is widely distributed wherever maize is grown. We also hypothesize that the population is fluid, with active movement and genetic recombination occurring in the field.

• Advances in concrete construction
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• v.6 no.4
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• pp.345-362
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• 2018

In this paper, mechanical and short-term durability properties of fly ash and slag based geopolymer concretes (FAGPC-SGPC) were investigated. The alkaline solution was prepared with a mixture of sodium silicate solution ($Na_2SiO_3$) and sodium hydroxide solution (NaOH) for geopolymer concretes. Ordinary Portland Cement (OPC) concrete was also produced for comparison. Main objective of the study was to examine the usability of geopolymer concretes instead of the ordinary Portland cement concrete for structural use. In addition to this, this study was aimed to make a contribution to standardization process of the geopolymer concretes in the construction industry. For this purpose; SGPC, FAGPC and OPC specimens were exposed to sulfuric acid ($H_2SO_4$), magnesium sulfate ($MgSO_4$) and sea water (NaCl) solutions with concentrations of 5%, 5% and 3.5%, respectively. Visual inspection and weight change of the specimens were evaluated in terms of durability aspects. For the mechanical aspects; compression, splitting tensile and flexural strength tests were conducted before and after the chemical attacks to investigate the residual mechanical strengths of geopolymer concretes under chemical attacks. Results indicated that SGPC (100% slag) is stronger and durable than the FAGPC due to more stable and strong cross-linked alumina-silicate polymer structure. In addition, FAGPC specimens (100% fly ash) showed better durability resistance than the OPC specimens. However, FAGPC specimens (100% fly ash) demonstrated lower mechanical performance as compared to OPC specimens due to low reactivity of fly ash particles, low amount of calcium and more porous structure. Among the chemical environments, sulfuric acid ($H_2SO_4$) was most dangerous environment for all concrete types.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.288-294
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• 2009

Various polymer electrolyte membrane fuel cell (PEMFC) startup procedures were tested to explore possible techniques for reducing performance decay and improving durability during repeated startup-shutdown cycles. The effects of applying a dummy load, which prevents cell reversal by consuming the air at the cathode, on the degradation of a membrane electrode assembly (MEA) were investigated via single cell experiments. The electrochemical results showed that application of a dummy load during the startup procedure significantly reduced the performance decay, the decrease in the electrochemically active surface area (EAS), and the increase in the charge transfer resistance ($R_{ct}$), which resulted in a dramatic improvement in durability. After 1200 startup-shutdown cycles, post-mortem analyses were carried out to investigate the degradation mechanisms via various physicochemical methods including FESEM, an on-line $CO_2$ analysis, EPMA, XRD, FETEM, SAED, FTIR. After 1200 startup-shutdown cycles, severe Pt particle sintering/agglomeration/dissolution and carbon corrosion were observed at the cathode catalyst layer when starting up a PEMFC without a dummy load, which significantly contributed to a loss of Pt surface area, and thus to cell performance degradation. However, applying a dummy load during the startup procedure remarkably mitigated such severe degradations, and should be used to increase the durability of MEAs in PEMFCs. Our results suggest that starting up PEMFCs while applying a dummy load is an effective method for mitigating performance degradation caused by reverse current under a repetition of unprotected startup cycles.

• Journal of Chest Surgery
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• v.31 no.12
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• pp.1222-1225
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• 1998

Aortic valve replacement in young patients has its problems. Biologic prosthetic valves degenerate and need replacement. Metalic prosthetic valves are more durable, however, anticoagulation which has its inherent problems is inevitable. The use of Ross procedure in young patients is gaining wider acceptance. The need of foreign pulmonary valve in right ventricular outflow tract(RVOT) will require reoperation due to RVOT obstruction, later. To overcome this problem, we reimplanted the native aortic valve in the pulmonary position in 21 year old female patient operated on utilizing the Ross procedure for aortic insufficiency. We experienced that the diseased aortic valve worked well in the pulmoanry position because of low pulmonary artery pressure and resistance.

• Journal of the Korea Institute of Building Construction
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• v.9 no.1
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• pp.103-109
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• 2009

Strong winds according to global warming cause the increase of the frequency and the repair cost of damaged roofs. In the United States, Factory Mutual Insurance Company(FMIC) promotes the roofing design that resists heavy wind-load, as the means of strict criteria. This fact reveals that more durable roofing system will be also required in Korea. Therefore, this study aims at developing such a system with high wind-resistance performance using Thermoplastic polyolefin(TPO) and Electromagnetic induction technology(EIT) than the previous systems. The system presented in this study consists of 4 main devices as follow; 1) a disc to fix sheets for TPO & EIT method, which can conduct structural design according to site condition, such as region, building height, and wind load. 2) a nail to have about 30% stronger lifting-up capacity than that of the previous nail. 3) a disc to fix sheets, which has triangle protuberance not to damage sheets in the repeatable wind load, and 4) a electromagnetic induction device to combine a disc and a sheet by heating uniformly and quickly adhesive agent on the disc. The results of mock-up test illustrate that the system provides wind-resistant performance to achieve satisfactorily the structural design criteria of FMIC. In addition, the system is faster, chipper, and easier than the existing system, and is expected that this roofing system can be applied to the rehabilitations of an existing as well as a new building.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.19 no.4
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• pp.320-328
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• 2007

The durability of marine concrete structures is severely degraded by corrosion due to seawater attack and diffusion of chloride in concrete. The deduction of durability causes high repair cost for maintenance of marine concrete structure. So, the applicability of high-durable materials is investigated to improve the durability in marine concrete structures. For these, the characteristics of corrosion prevention of marine concrete structures mixed with the mineral admixtures(SF, FA and BFS), the modified steel(stainless and coating steel), and corrosion inhibitors are evaluated using electro-chemical methods. As a results of this study, it is quantified for the effect of promotion of durability by high-durability materials in marine concrete structures.

• Steel and Composite Structures
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• v.30 no.4
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• pp.393-403
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• 2019

Cold-formed steel (CFS) has a great potential to meet the global challenge of fast-track and durable construction. CFS members undergo large buckling instabilities due to their small wall thickness. CFS beams with corrugated webs have shown great resistance towards web buckling under flexure, when compared to the conventional I-sections. However, the magnitude of global imperfections significantly affects the performance of CFS members. This paper presents the first attempt made to experimentally study the effect of global imperfections on the structural efficiency of various strengthening schemes implemented in CFS beams with corrugated webs. Different strengthening schemes were adopted for two types of beams, one with large global imperfections and the other with small imperfections. Strength and stiffness characteristics of the beams were used to evaluate the structural efficiency of the various strengthening schemes adopted. Six tests were performed with simply supported end conditions, under four-point loading conditions. The load vs. mid-span displacement response, failure loads and modes of failure of the test specimens were investigated. The test results would compensate the lack of experimental data in this area of research and would help in developing numerical models for extensive studies for the development of necessary guidelines on the same. Strengthening schemes assisted in enhancing the member performance significantly, both in terms of strength and stiffness. Hence, providing an economic and time saving solution to such practical structural engineering problems.

• Journal of the Korean GEO-environmental Society
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• v.24 no.6
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• pp.13-20
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• 2023

This paper is aimed to evaluate the mechanical properties and durability of high-flowable retaining wall material (RWM) with different levels of steel fiber (SF) content. To produce the specimens of RWM, some chemical agents such as superplasticizer (SP), air-entrained agent (AEA) and viscosity modifying agent (VMA) were added in the fresh RWM. The compressive and split tensile strength measurements were performed on the hardened RWM specimens at the predetermined periods. Additionally, surface electric resistivity and absorption tests according to ASTM standards were carried out to examine mechanical properties of RWM mixes. The durable performances such as chloride ions penetrability and freezing-thawing resistance of RWM mixes were experimentally investigated. As resutls, it was found that the performance of RWM mix with SF were much better than that without SF, especially at the 2% addition of SF. Thus, it is noted that the proper addition of SF in the RWM mix may have a beneficial effect to improve mechanical properties and durability of RWM mixes.

• Korean Journal of Breeding Science
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• v.41 no.3
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• pp.288-291
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• 2009

A new commercial rice variety "Donghaejinmi" is a japonica rice (Oryza sativa L.) with lodging resistance and high grain quality. It has been developed by the rice breeding team of Yeongdeog Substation, National Institute of Crop Science (NICS), RDA. This variety was derived from a cross between "Milyang 64" as a resistance source of brown planthopper (Bph) and "Milyang 165" as grain quality source. The donor parent, "Milyang64" has been backcrossed three times with recurrent parent, "Milyang165" and selected by the pedigree breeding method. The pedigree of "Donghaejinmi", designated as "Yeongdeog 41" in 2003, was YR21259-B-B-68-1. It has a short culm length with 69 cm and medium-late growth time. This variety is resistant to stripe virus and moderately resistant to leaf blast disease with durable resistance. It also has tolerance to unfavorable environment such as cold, dried wind and storm. Milled rice kernel of "Donghaejinmi" is translucent, clear in chalkness and good at eating quality in panel test. The merit of this variety is high head rice ratio, which is essential element to produce an article of superior quality rice brand. The yield potential of "Donhaejinmi" in milled rice is about 6.05 MT/ha at ordinary fertilizer level of local adaptability test. This cultivar would be adaptable to Yeongnam inland plains and eastern costal area of Yeongnam province.

• Journal of the Korea Concrete Institute
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• v.29 no.3
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• pp.307-314
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• 2017

Concrete is a durable and cost-benefit construction material, however performance degradation occurs due to steel corrosion exposed to chloride attack. Penetration of chloride ion usually decreases due to hydrates formation and reduction of pores, and the reduced chloride behavior is considered through decreasing diffusion coefficient with time. In the work, HPC (High Performance Concrete) samples are prepared with 3 levels of W/B (water to binder) ratios of 0.37, 0.42, and 0.27 and 3 levels of replacement ratios of 0%, 30% and 50%. Several tests containing chloride diffusion coefficient, passed charge, and compressive strength are performed considering age effect of 28 days and 180 days. Chloride diffusion is more reduced in OPC concrete with lower W/B ratio and GGBFS concrete with 50% replacement ratio shows significant reduction of chloride diffusion in higher W/B ratio. At the age of 28 days, GGBFS concrete with 50% replacement ratio shows more rapid reduction of chloride diffusion than strength development, which reveals that abundant GGBFS replacement has effective resistance to chloride penetration even in the early-aged condition.