• Journal of Welding and Joining
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• v.16 no.5
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• pp.67-75
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• 1998

This study aimed at he experimental and finite element analytic investigation of the effect of preheating on he residual stress of weldment. In this study, an autogenous arc welding was used on type 304 stainless steel and MARC as F.E.M. common code was utilized in analysis The analyses include transient and moving heat source and thermal properties as function of temperature. During welding, the thermal cycles of four locations in the weldment were recorded to investigate of the behavior of thermal stress and residual stress. The experimental and analytic results had good coincidence and show that there are two factors influencing the formation of welding residual stress in preheat process. One is the elevation of welding equilibrium temperature and the other is the increase of amount of heat input. The former decrease welding residual stress and the latter increase welding residual stress. Therefore, the cumulative effects result in the welding residual stress not being improved significantly with preheating in 304 stainless steel.

• Journal of Korean Society of Steel Construction
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• v.8 no.4 s.29
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• pp.19-29
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• 1996

In this paper, it is presumed that the stress time history was generated by simulation method and investigated compatibility in regard to the reappearance of stress time history. In this procedure, the identified frequency distribution of stress range of the steel railroad bridge varies with the rational values of cut off point and bar width. Thus, we show variable aspect of the equivalent stress range results from change of cut off point and bar width. In addition, we analyze the variable of RMC and RMS model due to the cut off point and bar width of the measured stress history which influencs the prediction of fatigue life in the steel railroad bridge. The simulated stress time history is carried out by the superposition method incorporating the vertical load with rotation moment obtained from the Hermition interpolation function, and compared with developing stress results from measured maxi mum stress. Through this study, we can estimate the remaining fatigue life from a safety point of view and comparative accuracy.

• International Journal of Reliability and Applications
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• v.18 no.2
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• pp.21-44
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• 2017

Accelerated life tests (ALTs) are frequently used in manufacturing industries to evaluate the reliability of products within a reasonable amount of time and cost. Test units are subjected to elevated stresses which yield quick failures. Most of the previous works on designing ALT plans are focused on tests that involve a single stress. Many times more than one stress factor influence the product's functioning. This paper deals with the design of optimum modified ramp-stress ALT plan for Burr type XII distribution with Type-I censoring under two stress factors, viz., voltage and switching rate each at two levels- low and high. It is assumed that usage time to failure is power law function of switching rate, and voltage increases linearly with time according to modified ramp-stress scheme. The cumulative exposure model is used to incorporate the effect of changing stresses. The optimum plan is devised using D-optimality criterion wherein the ${\log}_{10}$ of the determinant of Fisher information matrix is maximized. The method developed has been explained using a numerical example and sensitivity carried out.

• Geomechanics and Engineering
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• v.25 no.4
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• pp.341-345
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• 2021

1D sand compression response to ko-loading experiences volume contraction from low to high effective stress regimes. Previous study suggested compressibility model with physically correct asymptotic void ratios at low and high stress levels and examined only for both remolded clays and natural clays. This study extends the validity of Enhanced Terzaghi model for different sand types complied from 1D compression data. The model involved with four parameters can adequately fit 1D sand compression data for a wide stress range. The low stress obtained from fitting parameters helps to identify the initial fabric conditions. In addition, strong correlation between compressibility and the void ratio at low stress facilitates determination of self-consistent fitting parameters. The computed tangent constrained modulus can capture monotonic stiffening effect induced by an increase in effective stress. The magnitude of tangent stiffness during large strain test should not be associated with small strain stiffness values. The use of a single continuous function to capture 1D stress-strain sand response to ko-loading can improve numerical efficiency and systematically quantify the yield stress instead of ad hoc methods.

• BMB Reports
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• v.55 no.12
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• pp.577-586
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• 2022

Stress granules (SGs) are stress-induced subcellular compartments, which carry out a particular function to cope with stress. These granules protect cells from stress-related damage and cell death through dynamic sequestration of numerous ribonucleoproteins (RNPs) and signaling proteins, thereby promoting cell survival under both physiological and pathological condition. During tumorigenesis, cancer cells are repeatedly exposed to diverse stress stimuli from the tumor microenvironment, and the dynamics of SGs is often modulated due to the alteration of gene expression patterns in cancer cells, leading to tumor progression as well as resistance to anticancer treatment. In this mini review, we provide a brief discussion about our current understanding of the fundamental roles of SGs during physiological stress and the effect of dysregulated SGs on cancer cell fitness and cancer therapy.

• Journal of Microbiology and Biotechnology
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• v.17 no.9
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• pp.1504-1512
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• 2007

The fpr gene, which encodes a ferredoxin-$NADP^+$ reductase, is known to participate in the reversible redox reactions between $NADP^+$/NADPH and electron carriers, such as ferredoxin or flavodoxin. The role of Fpr and its regulatory protein, FinR, in Pseudomonas putida KT2440 on the oxidative and osmotic stress responses has already been characterized [Lee at al. (2006). Biochem. Biophys. Res. Commun. 339, 1246-1254]. In the genome of P. putida KT2440, another Fpr homolog (FprB) has a 35.3% amino acid identity with Fpr. The fprB gene was cloned and expressed in Escherichia coli. The diaphorase activity assay was conducted using purified FprB to identify the function of FprB. In contrast to the fpr gene, the induction of fprB was not affected by oxidative stress agents, such as paraquat, menadione, $H_2O_2$, and t-butyl hydroperoxide. However, a higher level of fprB induction was observed under osmotic stress. Targeted disruption of fprB by homologous recombination resulted in a growth defect under high osmotic conditions. Recovery of oxidatively damaged aconitase activity was faster for the fprB mutant than for the fpr mutant, yet still slower than that for the wild type. Therefore, these data suggest that the catalytic function of FprB may have evolved to augment the function of Fpr in P. putida KT2440.

• The Journal of Internal Korean Medicine
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• v.36 no.4
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• pp.507-517
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• 2015

The bark of Magnolia officinalis has been used in traditional oriental medicine to treat a variety of mental disorders including anxiety and depression. The purpose of this study was to examine the effect of M. officinalis ethanol extract on stress-induced alterations in learning and cognitive function using a passive avoidance test (PAT) and also on anxiety-related behavior using the elevated plus-maze test (EPM) in female rats . The degree of Tyrosine hydroxylase (TH) in the region of the ventral tegmental area (VTA) and the locus coeruleus (LC) was measured using an immunohistochemical method. Corticosterone concentrations in serum were also measured. The ethanol extract from Magnolia officinalis was orally administered to female rats 30 minutes before evaluating their immobilization stress and anxiety-related behavior using an elevated plus-maze test and a passive avoidance test. Time spent in the open arms of the EPM increased in the M. officinalis-treated group compared with that of the saline-treated control group. In the passive avoidance test, the memory and cognitive function improved in the M. officinalis extract-treated group. M. officinalis extracts reduced elevated corticosterone concentrations in serum. Also, stress-induced TH increases were suppressed in the M. officinalis extract-treated group in the LC and the VTA region. These results suggest that M. officinalis might prove to be an effective anxiolytic anti-stress agent.

• Anatomy and Cell Biology
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• v.56 no.4
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• pp.526-537
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• 2023

Hepatitis C virus (HCV) infection is a major health problem worldwide and its eradication is mandatory. Direct acting HCV polymerase inhibitors, such as Sofosbuvir (SOF), is an effective regimen. However, it has some side effects like mutagenesis, carcinogenesis, and the impairment of testicular function. It is important to evaluate the safety of SOF on the ovary, as there are no studies yet. Increasing the production of Reactive Oxygen Species (ROS), causes oxidative stress, which affects ovulation process, female reproduction, and fertility. Accumulation of SOF in the cells was demonstrated to promote ROS generation. Vitamin E (Vit E) is an antioxidant agent that has an essential role in the female reproductive system, its deficiency can cause infertility. We explored the effect of SOF treatment alone and co-treated with Vit E on ovarian ROS level and ovarian morphology experimentally using biochemical and immunohistochemical studies. Significant changes in oxidative stress markers; nitric oxide and malondialdehyde lipid peroxidation, antioxidant enzymes; catalase, super oxide dismutase, and reduced glutathione, proliferating markers; proliferation cell nuclear antigen and Ki-67 antigen and caspase 3 apoptotic marker were demonstrated. It was shown that where SOF induced oxidative stress, it also aggravated ovarian dysfunction. The essential role of Vit E as an antioxidant agent in protecting the ovarian tissue from the effect of oxidative stress markers and preserving its function was also displayed. This could be guidance to add Vit E supplements to SOF regimens to limit its injurious effect on ovarian function.

• Structural Engineering and Mechanics
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• v.11 no.2
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• pp.221-236
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• 2001

A local point interpolation method (LPIM) is presented for the stress analysis of two-dimensional solids. A local weak form is developed using the weighted residual method locally in two-dimensional solids. The polynomial interpolation, which is based only on a group of arbitrarily distributed nodes, is used to obtain shape functions. The LPIM equations are derived, based on the local weak form and point interpolation. Since the shape functions possess the Kronecker delta function property, the essential boundary condition can be implemented with ease as in the conventional finite element method (FEM). The presented LPIM method is a truly meshless method, as it does not need any element or mesh for both field interpolation and background integration. The implementation procedure is as simple as strong form formulation methods. The LPIM has been coded in FORTRAN. The validity and efficiency of the present LPIM formulation are demonstrated through example problems. It is found that the present LPIM is very easy to implement, and very robust for obtaining displacements and stresses of desired accuracy in solids.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.2
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• pp.144-154
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• 1998

A functionally graded material is a nonhomogeneous material, which is composed of several different materials to maintain structural rigidity and endure high temperature loads. An analytical method is presenter to solve the unsteady heat conduction equation for nonhomogeneous materials. A one-dimensional infinite plate made of functionally graded material is considered. The approximate Green's function solution is derived and to be used to obtain the temperature distribution them the stress distributions may be obtained. The volume fraction, the porosity, the stress difference, and the stress ratio are the design parameters and are to be used to set up a systematic design procedure.