• Mycobiology
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• v.38 no.3
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• pp.210-214
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• 2010

Selection of fungal strains with high virulence against the developmental stages of Bemisia tabaci was performed using internal transcribed spacer regions. The growth rate of hyphae was measured and bioassay of each developmental stage of B. tabaci was conducted for seven days. All of the fungal strains tested were identified as Lecanicillium spp., with strain 4078 showing the fastest mycelium growth rate (colony diameter, 16.3 $\pm$ 0.9 mm) among the strains. Compared to strain 4075, which showed the slowest growth rate, the growth rate of strain 4078 was increased almost 2-fold after seven days. Strains 4078 and Btab01 were most virulent against the egg and larva stages, respectively. The virulence of fungal strains against the adult stage was high, except for strains 41185 and 3387. Based on the growth rate of mycelium and level of virulence, strains 4078 and Btab01 were selected as the best fungal strains for application to B. tabaci, regardless of developmental stage.

• Korean Journal of Metals and Materials
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• v.47 no.7
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• pp.391-396
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• 2009

Tensile, low cycle fatigue, and fatigue crack growth rate tests were conducted at RT and $300^{\circ}C$ for type 304 stainless steel. Tensile was tested under displacement control and low cycle fatigue was tested under strain control. Fatigue crack growth rate test was conducted under load control and crack was measured by DCPD method. Yield strength and elongation decreased at $300^{\circ}C$. Dynamic strain aging was not detected at $300^{\circ}C$. Low cycle fatigue life increased but fatigue strength decreased at $300^{\circ}C$. Fatigue crack growth rate increased at $300^{\circ}C$. Dislocation structures were mixed with cell and planar and did not change with temperature. Grain size did not change but plastic strain increased at $300^{\circ}C$. Strain induced martensite after low cycle fatigue test increased at RT but decreased at $300^{\circ}C$. It was concluded that the increase of low cycle fatigue life at $300^{\circ}C$ was due to the decrease of strain induced martensite at which crack was initiated.

• Smart Structures and Systems
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• v.20 no.1
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• pp.11-22
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• 2017

The long-term effect of ambient temperature on bridge strain is an important and challenging problem. To investigate this issue, one year data of strain and ambient temperature of a long-span cable-stayed bridge is studied in this paper. The measured strain-time history is decomposed into two parts to obtain the strains due to vehicle load and temperature alone. A linear regression model between the temperature and the strain due to temperature is established. It is shown that for every $1^{\circ}C$ increase in temperature, the stress is increased by 0.148 MPa. Furthmore, the extreme value distributions of the strains due to vehicle load, temperature and the combination effect of them during the remaining service period are estimated by the average conditional exceedance rate approach. This approach avoids the problem of declustering of data to ensure independence. The estimated results demonstrate that the 95% quantile of the extreme strain distribution due to temperature is up to $1.488{\times}10^{-4}$ which is 2.38 times larger than that due to vehicle load. The study also indicates that the estimated extreme strain can reflect the long-term effect of temperature on bridge strain state, which has reference significance for the reliability estimation and safety assessment.

• Transactions of Materials Processing
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• v.9 no.1
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• pp.80-87
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• 2000

The static softening behavior of SCM 440 could be characterized by the hot torsion test in the temperature ranges of 90$0^{\circ}C$~110$0^{\circ}C$and strain rate ranges of 0.05/sec~5/sec. Interrupted deformation was performed with 2 pass deformation in the pass strain ranges of 0.25$\varepsilon$p~3$\varepsilon$p and interrupted time ranges of 0.5~100sec. The dependences of process variables, pass strain ($\varepsilon$i), stain rate ($\varepsilon$), temperature (T) and interpass time (ti), on static recrystallization (SRX) and metadynamic recrystallization (MDRX)were individually predicted from the modified Avrami's equations, The dependence of pass strain on MDRX was neglectable. Comparison of the softening kinetics between MDRX and SRX showed that the rate of MDRX was more rapid than that of SRX for the same deformation variables. Controlled multipass deformations were performed using static and metadynamic recrystallization of SCM 440.

• Coupled systems mechanics
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• v.13 no.2
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• pp.153-170
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• 2024

The problem considered in this theoretical paper is the delamination of a multilayered inhomogeneous beam structure that has viscoelastic behaviour under angle of twist, horizontal and vertical displacements which vary smoothly with time according to prescribed laws. The cross-section of the beam is a rectangle. The layers are made of different materials which are smoothly inhomogeneous along the length of the beam. The beam under consideration represents statically undetermined structure since it is clamped in its two ends. The problem of the strain energy release rate is solved. For this purpose, the strain energy stored in the beam structure is analyzed. In order to verify the solution obtained, the strain energy release rate is found also analyzing the time-dependent compliances of the beam under prescribed angle of twist and displacements. A parametric investigation is carried-out by applying the solution obtained. Special attention is paid to the effect of the parameters which control the variation of the angle of twist and the displacements with time on the strain energy release rate.

• Korean Journal of Materials Research
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• v.26 no.4
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• pp.167-172
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• 2016

The high temperature deformation behavior of $Ni_3Al$ and $Ni_3(Al,Mo)$ single crystals that were oriented near <112> was investigated at low strain rates in the temperature range above the flow stress peak temperature. Three types of behavior were found under the present experimental conditions. In the relatively high strain rate region, the strain rate dependence of the flow stress is small, and the deformation may be controlled by the dislocation glide mainly on the {001} slip plane in both crystals. At low strain rates, the octahedral glide is still active in $Ni_3Al$ above the peak temperature, but the active slip system in $Ni_3(Al,Mo)$ changes from octahedral glide to cube glide at the peak temperature. These results suggest that the deformation rate controlling mechanism of $Ni_3Al$ is viscous glide of dislocations by the <110>{111} slip, whereas that of $Ni_3(Al,Mo)$ is a recovery process of dislocation climb in the substructures formed by the <110>{001} slip. The results of TEM observation show that the characteristics of dislocation structures are uniform distribution in $Ni_3Al$ and subboundary formation in $Ni_3(Al,Mo)$. Activation energies for deformation in $Ni_3Al$ and $Ni_3(Al,Mo)$ were obtained in the low strain rate region. The values of the activation energy are 360 kJ/mol for $Ni_3Al$ and 300 kJ/mol for $Ni_3(Al,Mo)$.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1997.03a
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• pp.81-84
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• 1997

The hot deformation behavior of SiCp/AA2024 composites reinforced with different sizes of SiCp reinforcements (1, 8, 15, 36, and 44${\mu}{\textrm}{m}$) was investigated by hot torsion tests. The hot restoration of the composites depending on the SiCp reinforcements particle size was studied from the effective stress - strain curves. Dynamic recrystallization (DRX) was occurred in the SiCp/AA2024 composites during the hot deformation at 320 - 43$0^{\circ}C$ under a strain rate of 1.0/sec. Also, the critical strain for DRX decreased with decreasing the reinforcement size of SiCp from 44 to 8${\mu}{\textrm}{m}$. The composite reinforced with SiCp of 8${\mu}{\textrm}{m}$ showed the highest flow stress (265 MPa) and the work hardening rate at 32$0^{\circ}C$ under a strain rate of 1.0/sec.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.1
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• pp.127-130
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• 2010

This paper deals with the formability of DP590 steel considering the strain rate. The strain hardening coefficient, elongation and r-value were obtained from the static and dynamic tensile test. As strain rate increases from static to 100/s, the strain hardening coefficient and the uniform elongation decrease and the elongation at fracture and r-value decrease to 0.1/s and increase again to 100/s. The high speed forming limit tests with hemi-spherical punch were carried out using the high speed crash testing machine and high speed forming jig. The high speed forming limit of DP590(order of $10^2$/s) decreases compared to the static forming limit(order of $10^{-3}$/s) and the forming limit band in high speed forming test is narrower than that in the static forming test. This tendency may be due to the development of brittleness with increase of stain rate.

• Mycobiology
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• v.40 no.2
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• pp.111-116
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• 2012

Ten strains of the entomopathogenic fungi Metarhizium anisopliae and Beauveria bassiana were evaluated to find the most effective strain for optimization studies. The first criterion tested for strain selection was the mortality (> 50%) of Spodoptera litura larvae after inoculation of the fungus for 4 days. Results on several bioassays revealed that B. bassiana BNBCRC showed the most virulence on mortality S. litura larvae (80% mortality). B. bassiana BNBCRC also showed the highest germination rate (72.22%). However, its conidia yield ($7.2{\times}10^8$ conidia/mL) was lower than those of B. bassiana B 14841 ($8.3{\times}10^8$ conidia/mL) and M. anisopliae M6 ($8.2{\times}10^8$ conidia/mL). The highest accumulative radial growth was obtained from the strain B14841 (37.10 mm/day) while the strain BNBCRC showed moderate radial growth (24.40 mm/day). M. anisopliae M6 possessed the highest protease activity (145.00 mU/mL) while M. anisopliae M8 possessed the highest chitinase activity (20.00 mU/mL) during 96~144 hr cultivation. Amongst these criteria, selection based on virulence and germination rate lead to the selection of B. bassiana BNBCRC. B. bassiana B14841 would be selected if based on growth rate while M. anisopliae M6 and M8 possessed the highest enzyme activities.

• 한국금형공학회:학술대회논문집
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• 2008.06a
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• pp.23-26
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• 2008

In order to examine the deformation characteristics of Al circular pipe underthe biaxial compression, the horizontal biaxial compression die for the experiment was manufactured. From this, in the various compressive strain rate (1 mm/min. ${\sim}$ 400 mm/min.)conditions, the circular pipes, which were made by Al materials, were investigated based on the properties change of cross section area, punch load and deformation behavior. The tensile and compressive strains were evaluated from micro Vickers hardness tester. From these results, the punch load and deformation characteristic of Al circular pipes were highly changed in the compressive strain rate about 200 mm/min. The Al circular pipes had the tendency that the punch load decreased with increasing the compressive strain rate. In addition, following as the change of the shape and position of neutral axis due to the deformation proceeding of the circular pipe, the special point of the internal circular pipe at maximum load showed the maximum deformation strain and the maximum measured hardness value. The CAE (computer aided engineering) simulation using Deform-2D program was performed on the circular pipe in order to know and verify the exact compressive deformation behavior. From these results, the experimentally measured results were reasonably in good agreement with the simulation results.