• BMB Reports
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• v.40 no.1
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• pp.100-106
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• 2007

The wound-inducible lipoxygenase obtained from maize is one of the nontraditional lipoxygenases that possess dual positional specificity. In this paper, we provide our results on the determination and comparison of the kinetic constants of the maize lipoxygenase, with or without detergents in the steady state, and characterization of the dependence of the kinetic lag phase or initial burst, on pH, substrate, and detergent in the pre-steady state of the lipoxygenase reaction. The oxidation of linoleic acid showed a typical lag phase in the pre-steady state of the lipoxygenase reaction at pH 7.5 in the presence of 0.25% Tween-20 detergent. The reciprocal correlation between the induction period and the enzyme level indicated that this lag phenomenon was attributable to the slow oxidative activation of Fe (II) to Fe (III) at the active site of the enzyme as observed in other lipoxygenase reactions. Contrary to the lagging phenomenon observed at pH 7.5 in the presence of Tween-20, a unique initial burst was observed at pH 6.2 in the absence of detergents. To our knowledge, the initial burst in the oxidation of linoleic acid at pH 6.2 is the first observation in the lipoxygenase reaction. Kinetic constants (Km and kcat values) were largely dependent on the presence of detergent. An inverse correlation of the initial burst period with enzyme levels and interpretations on kinetic constants suggested that the observed initial burst in the oxidation of linoleic acid could be due to the availability of free fatty acids as substrates for binding with the lipoxygenase enzyme.

• Journal of Ocean Engineering and Technology
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• v.22 no.6
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• pp.52-57
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• 2008

The short-term high temperature creep rupture behavior of Ni-based Alloy718 steel was investigated at the elevated temperatures range of 550 to $700^{\circ}C$ under constant stress conditions. The creep rupture characteristics such as creep stress, rupture time, steady state creep rate, and initial strain were evaluated. Creep stress has a quantitative correlation between creep rupture tim and steady state creep rate. The stress exponents (n, m) of the experimental data at 550, 600, 650 and $700^{\circ}C$ were derived as 33.5, -24.9, 26.1, -21.2, 16.8, -12.8 and 10, -8.2, respectively. The stress exponent decreased with increasing creep temperature. The creep lift prediction was derived by the Larson-Miller parameter (LMP) method and the resultant equation was obtained as follows: T($logt_r$+20)=-0.00252 ${\sigma}^2$-1.377${\sigma}$+-22718.

• Structural Engineering and Mechanics
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• v.74 no.3
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• pp.425-434
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• 2020

The present paper is concerned at investigating the effect of hydrostatic initial stress, gravity and magnetic field in fiber-reinforced thermoelastic solid, with variable thermal conductivity. The formulation of the problem applied in the context of the three-phase-lag model, Green-Naghdi theory with energy dissipation, as well as coupled theory. The exact expressions of the considered variables by using state-space approaches are obtained. Comparisons are performed in the absence and presence of the magnetic field as well as gravity. Also, a comparison was made in the three theories in the absence and presence of variable thermal conductivity as well as hydrostatic initial stress. The study finds applications in composite engineering, geology, seismology, control system and acoustics, exploration of valuable materials beneath the earth's surface.

• Geomechanics and Engineering
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• v.19 no.2
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• pp.141-151
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• 2019

A novel theoretical solution is presented for created (zero initial radius) cavity expansion problem based on CamClay model and considers the effect of initial anisotropic in-situ stress and drained conditions. Here the strain of this theoretical solution is small deformation in elastic region and large deformation in plastic region. The works for cylindrical and spherical cavities expanding in drained condition from zero initial radius are investigated. Most of the conventional solutions were based on the isotropic and undrained condition, however, the initial stress state of natural soil mass is anisotropy by soil deposition history, and drained cavity expansion calculation is closer to actual engineering in permeable soil mass. Finally, the parametric study is presented in order to the engineering significance of this work.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.74-79
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• 2003

When workability at the a certain bulk deformation process is defined as the maximum plastic deformation capability that the workpiece can sustain without causing any cracks or fracture, the workability is dependent on the microstructure, initial workpiece shape, stress state developed during the deformation process, strain rata and presence of the interfacial friction between workpiece and tool. For a review purpose, the workability definition and test methods are summarized depending on the applied stress state at bulk deformation process in Table 1 at the text. In this study, the cold workabilities of as-cast A16061 bulk material have been measured and comparatively analyzed at the primary tensile stress state by using tensile specimens, the primary compressive stress state by using cylindrical specimens, and the forming limit diagram by ductile fracture.

• Journal of Biosystems Engineering
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• v.15 no.3
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• pp.219-229
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• 1990

The compression creep behavior of grains when loaded depends not only on load but also on duration of load application. The most common methods of studying the load-time characteristics of agricultural products is by employing rheological models such as Burger's model. However it is sometimes not sufficient to describe the viscoelastic behavior of grains to be Burger's model. For this reason, this study was conducted to develop the rheological model which represented the creep compliance response of the rough rice kernel and was a function of initial stress applied and time. The effects of the initial stress applied and the moisture content on the compression creep behavior of the rough rice kernel were analyzed. The results were obtained from the study as follows: 1. Since the viscoelastic behavior of the rough rice kernel was nonlinear, the transient and steady state creep compliance was satisfactorily modelled as follows: $$J({\sigma},t)=A{\sigma}^B[C+Dt-exp(-Ft)]$$ But, for the every stress applied, the compression creep behavior of the samples tested can be well described by Burger's model respectively. 2. The creep compliance, the instantaneous elastic strain, the retarded elastic strain and the viscous strain of the sample tested generally increased in magnitude with increasing the applied initial stress and the moisture content used in the tests. At low moisture content, the creep compliance for the Japonica-type rough rice kernel Was a little higher than those for Indica-type and at high moisture content, vice versa at high moisture content. 3. The retardation times of the samples had not an uniform tendency by the initial stress and the moisture content. The retardation times ranged from 0.66 to 6.76 seconds, and the creep progressed from transient to steady state at a relatively high rate. 4. The less viscous strain than the instantaneous elastic strain for the samples tested indicated that rough rice kernel behaved as a viscoelastic body characterized by elasticity than viscosity.

• Journal of Ocean Engineering and Technology
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• v.6 no.1
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• pp.78-86
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• 1992

The creep behaviors of 1%Cr-Mo-V and 12%Cr steam turbine rotor steels under static or cyclic load were examined at 600 and $700^{\circ}C$. The relationship between these two kinds of phenomena was studied and the experimental results were summarized as follows: 1) It is confirmed that the cyclic creep strain dependent on time is more available for creep, behavior analysis according to frequency change than that dependent on number of cycles, and the static creep, the special case of cyclic creep with stress ratio of 1 can be also more effectively analyzed by time-dependence. 2) The steady cyclic creep rate vs. the steady static creep rate, increases according to the increase of stress ratio, and this phenomena may occur on occasion of the decrease of the internal stress. 3) The initial strain affects on all the creep properties of the transient region, the steady state region and the rupture time in cyclic creep as well as static creep, and the quantitative relationships among them exist.

• Journal of Korean Tunnelling and Underground Space Association
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• v.4 no.1
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• pp.57-70
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• 2002

Since early in the 90's, the need for construction of underground rock structures such as long and large section traffic tunnel, energy storage cavern, industrial facility, etc. has been largely increased because the Korean territory is not wide and about 65 % of the land consists of mountainous region. The initial rock stress measurement has been widely conducted to provide the quantitative information on the stress state of engineering site at the design stage of underground rock structures. Among the diverse methods developed for measuring rock stress, hydraulic fracturing test is most popularly used because it is applicable at pre-construction stage and has no limit in testing depth. In this paper, the characteristics of initial rock stress state in mountainous region were studied on the basis of the in-situ hydraulic fracturing stress measurement results from the 60 test boreholes in various parts of Korea.

• Smart Structures and Systems
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• v.22 no.3
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• pp.259-276
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• 2018

This paper studies the energies and energy release rate (ERR) for the initially rotationally symmetric compressed (or stretched) in the inward (outward) radial direction of the PZT/Elastic/PZT sandwich circular plate with interface penny-shaped cracks. The investigations are made by utilizing the so-called three-dimensional linearized field equations and relations of electro-elasticity for piezoelectric materials. The quantities related to the initial stress state are determined within the scope of the classical linear theory of piezoelectricity. Mathematical formulation of the corresponding problem and determination of the quantities related to the stress-strain state which appear as a result of the action of the uniformly normal additional opening forces acting on the penny-shaped crack's edges are made within the scope of the aforementioned three-dimensional linearized field equations solution which is obtained with the use of the FEM modelling. Numerical results of the energies and ERR and the influence of the problem parameters on these quantities are presented and discussed for the PZT- 5H/Al/PZT-5H, PZT-4/Al/PZT-4, $BaTiO_3/Al/BaTiO_3$ and PZT-5H/StPZT-5H sandwich plates. In particular, it is established that the magnitude of the influence of the piezoelectricity and initial loading on the ERR increases with crack radius length.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.561-564
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• 1999

The uniform state of prestress in a fully prestressed concrete members shows reductions of more than half of the initial prestress in the construction and coupling joint vicinity. Especially, at a zone x/d=0.2 above the construction joint where at the edge of the member, a quite localized reduced stress state of 1/3 of uniform stress is encountered. Five full-scale test specimens were segmentally constructed and post-tensioned and analytic models is used to verify and validate measured test results. The encountered highly nonuniform stress/strain state in the coupling joint vicinity requires special design consideration for the successful application of tendon couplers.