• Transactions of the Korean Society of Pressure Vessels and Piping
• /
• v.11 no.2
• /
• pp.25-30
• /
• 2015

In the present study, complex leakage probabilities of nuclear pipes due to fatigue and stress corrosion cracking are evaluated by using the PINTIN(Piping INTegrity INner flaws) that is developed based on the existing PRAISE(Piping Reliability Analysis Including Seismic Events) program. With regard to the aging and crack instability, small leak and big leak probabilities are calculated for several pipes in a reactor coolant system of domestic nuclear plant. Moreover, sensitivity analysis is also performed to find out the effect of parameters for the leakage of pipes, which shows the coolant temperature is the most influencing parameter.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 2003.11a
• /
• pp.241-247
• /
• 2003

The sealing performance of O-ring is effected in environments of the O-ring seal, like that applied pressure, working temperature, pre-compressed ratio and materials. In this paper, design of composite O-ring under pressurized, compressed was optimized based on Taguchi experimental design method. and it analysed numerically using non-linear finite element method. Ogden model in which is developed based on the experimental data is used for simulating the contact stress and strain in NBR and PTFE materials. Sensitivity analysis was performed with FEM results, which are contact stress, strain and temperature as variable.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2002.05a
• /
• pp.159-162
• /
• 2002

In this paper the stress-strain curves of bearing steels at hot working conditions are obtained by compression test with a computer controlled servo-hydraulic Gleeble 3800 testing machine and elongations and reductions of area of the bearing steels are obtained by tensile test with a computer controlled servo-hydraulic Gleeble 1500 testing machine. These tests have been focused to obtain the flow stress data and optimal hot forging conditions under various conditions of strain rates and temperatures. The strain rate sensitivity exponent and reduction of area of the materials are evaluated. Experimental results are resented for various conditions of temperatures and strain rates.

• Transactions of Materials Processing
• /
• v.22 no.4
• /
• pp.216-222
• /
• 2013

Solid polymers exhibit rate-dependent deformation behavior such as nonlinear strain rate sensitivity and stress relaxation like metallic materials. Despite the different microstructures of polymeric and metallic materials, they have common properties with respect to inelastic deformation. Unlike most metallic materials, solid polymers and shape memory alloys (SMAs) exhibit highly nonlinear stress-strain behavior upon unloading. The present work employs the viscoplasticity theory [K. Ho, 2011, Trans. Mater. Process. 20, 350-356] developed for the pseudoelastic behavior of SMAs, which is based on unified state variable theory for the rate-dependent inelastic deformation behavior of typical metallic materials, to depict the curved unloading behavior of polyphenylene oxide (PPO). The constitutive equations are characterized by the evolution laws of two state variables that are related to the elastic modulus and the back stress. The simulation results are compared with the experimental data obtained by Krempl and Khan [2003, Int. J. Plasticity 19, 1069-1095].

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2003.10a
• /
• pp.285-292
• /
• 2003

The soft structure can make large space more effectively, and its construction is easy and simple as well. However, it is not easy to realize this in the actual space. Therefore, two works are needed to be done for effective and accurate construction of soft structures. First, making a working scenario to complete the final objective form; second revising construction errors occurred in the middle of the actual works. These works are called constructional analysis. At this time, geometric nonlinearity should be considered to reflect the sensitivity by the initial stress of flexible structures, constructional analysis comes down to a nonlinear problem after all. This study approaches nonlinear constructional analysis with the numerical method for adjusting stress of cable-dome structures which are a soft structure system, and then verifies it.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.17 no.6
• /
• pp.586-591
• /
• 2004

We studied the dependence of hot-tarrier-induced degradation characteristics on nitrogen concentration in NO(Nitrided-Oxide) gate of nMOS, under ac and dc stresses. The $\Delta$V$_{t}$ and $\Delta$G$_{m}$ dependence of nitrogen concentration were observed, We observed that device degradation was suppressed significantly when the nitrogen concentration in the gate was increased. Compared to $N_2$O oxynitride, NO oxynitride gate devices show a smaller sensitivity to ac stress frequency. Results suggest that the improved at-hot carrier immunity of the device with NO gate may be due to the significantly suppressed interface state generation and neutral trap generation during stress.ess.

• Korean Journal of Psychosomatic Medicine
• /
• v.11 no.1
• /
• pp.15-24
• /
• 2003

Objectives: The object of this study was to compare perceived stress and quality of life among patients with HIV infection, patients with pulmonary tuberculosis and normal controls. Methods: Stress response inventory(SRI) and Symptom checklist 90-Revised(SCL-90-R) were used to measure perceived stress responses and psychopathology. Smithklein Beecham quality of life scale was used to measure quality of life. Results: Patients with HIV infection scored significantly higher on scores of tension, anger, depression, fatigue and frustration subscale of the SRI than those with pulmonary tuberculosis and normal controls. Scores of the SCL-90-R, somatization, depression, anxiety, hostility, phobic anxiety, paranoid ideation and psychoticism subscale were also significantly higher in patients with HIV infection than those with pulmonary tuberculosis and normal controls. Patients with HIV infection scored significantly lower in quality of life than those with pulmonary tuberculosis. In patients with HIV infection, age had a significantly negative correlation with scores of somatization, obsessive-compulsive, interpersonal sensitivity, phobic anxiety, paranoid ideation and psychoticism subscale of the SCL-90-R. but the level of education had a significantly positive correlation with somatization, obsessive-compulsive, interpersonal sensitivity, phobic anxiety, paranoid ideation and psychoticism subscale of the SCL-90-R. Conclusion: The results suggest that patients with HIV positive were likely to have higher levels of perceived stress response and psychopathology, and lower quality of life than those with pulmonary tuberculosis and normal controls.

• Korean Journal of Psychosomatic Medicine
• /
• v.10 no.2
• /
• pp.120-129
• /
• 2002

Objectives : The object of this study was to compare perceived stress and quality of life among patients with HIV infection, patients with pulmonary tuberculosis and normal controls Methods: Stress Response Inventory(SRI) and Symptom checklist 90-Revised(SCL-90-R) were used to measure perceived stress responses and psychopathology. Smithklein Beecham quality of life scale was used to measure quality of life. Results : Patients with HIV infection scored significantly higher on scores of tension, anger, depression, fatigue and frustration subscale of the SRI than those with pulmonary tuberculosis and normal controls. Scores of the SCL-90-R, somatization, depression, anxiety, hostility, phobic anxiety, paranoid ideation and psychoticism subscale were also significantly higher in patients with HIV infection than those with pulmonary tuberculosis and normal controls. Patients with HIV infection scored significantly lower in quality of life than those with pulmonary tuberculosis. In patients with HIV infection, age had a significantly negative correlation with scores of somatization, obsessive-compulsive, interpersonal sensitivity, phobic anxiety, paranoid ideation and psychoticism sub scale of the SCL-90-R. but the level of education had a significantly positive correlation with somatization, obsessive-compulsive, interpersonal sensitivity, phobic anxiety, paranoid ideation and psychoticism sub scale of the SCL-90-R. Conclusion : The results suggest that patients with HIV positive were likely to have higher levels of perceived stress response and psychopathology, and lower quality of life than those with pulmonary tuberculosis and normal controls.

• Journal of the Microelectronics and Packaging Society
• /
• v.25 no.3
• /
• pp.55-59
• /
• 2018

In this paper, we investigated the characteristics of shear stress type piezoresistor on a diaphragm structure formed by MEMS (Microelectromechanical System) technology of silicon-direct-bonding (SDB) wafers with Si/$SiO_2$/Si-sub. The diaphragm structure formed by etching the backside of the wafer using a TMAH aqueous solution can be used for manufacturing various sensors. In this study, the optimum shape condition of the shear stress type piezoresistor formed on the diaphragm is found through ANSYS simulation, and the diaphragm structure is formed by using the semiconductor microfabrication technique and the shear stress formed by boron implantation. The characteristics of the piezoelectric resistance are compared with the simulation results. The sensing diaphragm was made in the shape of an exact square. It has been experimentally found that the maximum shear stress for the same pressure at the center of the edge of the diaphragm is generated when the structure is in the exact square shape. Thus, the sensing part of the sensor has been designed to be placed at the center of the edge of the diaphragm. The prepared shear stress type piezoresistor was in good agreement with the simulation results, and the sensitivity of the piezoresistor formed on the $2200{\mu}m{\times}2200{\mu}m$ diaphragm was $183.7{\mu}V/kPa$ and the linearity of 1.3 %FS at the pressure range of 0~100 kPa and the symmetry of sensitivity was also excellent.

• Bulletin of the Korean Chemical Society
• /
• v.22 no.5
• /
• pp.514-518
• /
• 2001

We have explored the importance of two ATP binding domains of Hsp104 protein in protection of yeast cells from cadmium exposure. In the previous study we have discovered that the presence of two ATP binding sites was essential in providing heat sh ock protection as well as rescuing cells from oxidative stress. In this paper we first report wild type cell with functional hsp104 gene is more resistant to cadmium stress than hsp104-deleted mutant cell, judging from decrease in survival rates as a result of cadmium exposure. In order to demonstrate functional role of two ATP binding sites in cadmium defense, we have transformed both wild type (SP1) and hyperactivated ras mutant (IR2.5) strains with several plasmids differing in the presence of ATP binding sites. When an extra copy of functional hsp104 gene with both ATP binding sites was overexpressed with GPD-promoter, cells showed increased survival rate against cadmium stress than mutants with ATP binding sites changed. The degree of protection in the presence of two ATP binding sites was similarly observed in ira2-deleted hyperactivated ras mutant, which was more sensitive to oxidative stress than wild type cell. We have concluded that the greater sensitivity to cadmium stress in the absence of two ATP binding sites is attributed to the higher concentration of reactive oxygen species (ROS) produced by cadmium exposure based on the fluorescence tests. These findings, taken all together, imply that the mechanism by which cadmium put forth toxic effects may be closely associated with the oxidative stress, which is regulated independently of the Ras-cAMP pathway. Our study provides a better understanding of cadmium defense itself and cross-talks between oxidative stress and metal stress, which can be applied to control human diseases due to similar toxic environments.