• Journal of the Korean Society of Clothing and Textiles
• /
• v.47 no.6
• /
• pp.1193-1203
• /
• 2023

This study aims to provide primary data regarding the thermal stress of disposable personal protective coveralls. Thermal stress and surface temperature measurements were taken among ten men wearing coveralls. The size of the ten men corresponds to a size eight in Size Korea. As a result of thermal stress, sensations of humidity and discomfort were higher when wearing Level C compared to Level D. Level D felt significant thermal stress in their upper body after exercise. However, they did not feel such stress in their lower body. Level C felt thermal stress in their upper and lower body after exercise. In addition, in Level C, the ratings of perceived exertion blood pressure and pulse rate after exercise were higher than those of Level D. Furthermore, the surface temperature of disposable personal protective coveralls among Level C was slightly higher than that of Level D.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.54 no.3
• /
• pp.109-113
• /
• 2005

It has been reported that the failure phenomenon and variation of electrical characteristic due to the effect of electrostatic discharge(ESD) in silicon devices. But we had fess reports about the phenomenon due to the ESD in the compound semiconductors. So there are a lot of difficulty to the phenomenon analysis and to select the protection method of main circuits or the devices. It has not been reported that the relation between the ESD stress and GaN devices, which is remarkable to apply the operation in high temperature and high voltage due to the superior material characteristic. We studied that the characteristic variation of the AlGaN/GaN HEMT current, the leakage current, the transconductance(gm) and the failure phenomenon of device due to the ESD stress. We have applied the ESD stress by transmission line pulse(TLP) method, which is widely used in ESD stress experiments, and observed the variation of the electrical characteristic before and after applying the ESD stress. The on-current trended to increase after applying the ESD stress. The leakage current and transconductance were changed slightly. The failure point of device was mainly located in middle and edge sides of the gate, was considered the increase of temperature due to a leakage current. The GaN devices have poor thermal characteristic due to usage of the sapphire substrate, so it have been shown to easily fail at low voltage compared to the conventional GaAs devices.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.41 no.1
• /
• pp.27-33
• /
• 2014

There are several ways to analyse stress resulting from anxiety and fear within dental treatment for children. Surveying questionnaires and monitoring biologic reaction are the most common ways for evaluating stress. Pulse oximeter is a popular device for detecting heart rate but not appropriate for moving children. In this study, we compared a recently introduced wrist- watch type heart rate monitor(Alpha, MIO, USA) with a pulse oximeter(MP110, MECKIS, Republic of Korea) for 10 attendants with two conditions including resting state and excited state after exercise. Data were analyzed using Wilcoxon Signed Rank test and there is no statistical difference between two devices(p < 0.05).

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.65 no.3
• /
• pp.493-498
• /
• 2016

Heart Rate Variability (HRV) represents beat-to-beat fluctuations of R-R intervals in Electrocardiogram (ECG). On of the clinical applications of HRV is to assess the mental-stress state by evaluating its power spectral density distribution. This study aims at finding new discriminative role of the coupled-oscillating coupling constants, Cs and Cp in the Integral Pulse Frequency Modulation (IPFM) model. Based on comparing with power spectral density of HRV in terms of the relative ratio of the low and high-frequency power component, we can conclude the fact that the coupling parameters Cs and Cp can replace the role of HRV power spectrum interpretation for judging the mental-stress state.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.32 no.9
• /
• pp.740-753
• /
• 2008

The conventional Split Hopkinson Pressure Bar (C-SHPB) technique with aluminum pressure bars to achieve a closer impedance match between the pressure bars and the specimen materials such as hot temperature degraded POM (Poly Oxy Methylene) and PP (Poly Propylene) to obtain more distinguishable experimental signals is used to obtain a dynamic behavior of material deformation under a high strain rate loading condition. An experimental modification with Pulse shaper is introduced to reduce the nonequilibrium on the dynamic material response during a short test period to increase the rise time of the incident pulse for two polymeric materials. For the dynamic stress strain curve obtained from SHPB experiment under high strain rate, the Johnson-Cook model is applied as a constitutive equation, and we verify the applicability of this constitutive equation to the probabilistic reliability estimation method. The methodology to estimate the reliability using the probabilistic method such as the FORM and the SORM has been proposed, after compose the limit state function using Johnson-Cook model. It is found that the failure probability estimated by using the SORM is more reliable than those of the FORM, and the failure probability increases with the increase of applied stress. Moreover, it is noted that the parameters of Johnson-Cook model such as A and n, and applied stress affect the failure probability more than the other random variables according to the sensitivity analysis.

• Anxiety and mood
• /
• v.9 no.2
• /
• pp.121-127
• /
• 2013

Objective : Several studies have reported the association between posttraumatic stress disorder (PTSD) and hypertension (HTN). The aim of this study was to evaluate the impact of PTSD symptoms on blood pressure. Methods : Korean veterans of the Vietnam War with (n=62) or without PTSD (n=87) participated in this study. The clinician administered PTSD scale (CAPS) and alcohol use disorder identification test (AUDIT) were applied. Blood pressure, pulse rate, risk factors of HTN and demographic data of the subjects were collected. Effects of potential explanatory variables on HTN were analyzed with logistic regression. Results : Diastolic blood pressure was significantly higher in PTSD group (p=0.015). However, PTSD subjects showed significantly lower pulse rate than non-PTSD subjects (p=0.004). Logistic regression analysis showed that avoidance symptom might be a predictor for hypertension (OR=1.065, p=0.030). Conclusion : These results suggest that PTSD, especially avoidance symptom, might be a risk factor on HTN in the elderly with PTSD. Further studies are needed to evaluate the change of blood pressure according to the clinical improvement of PTSD.

• Journal of Korean Biological Nursing Science
• /
• v.21 no.3
• /
• pp.178-187
• /
• 2019

Purpose: The purpose of this study was to investigate how college students' perceived stress, cognitive stress, and somatization affect their heart rate variability (HRV). Methods: This study is a cross-sectional survey research on 191 university students, registered at the G University. The perceived stress scale (PSS) and cognitive stress response scale, were used to assess level of stress. The somatization symptom scale of the Symptom Check List 90 (SCL-90), was used to assess level of somatization caused by stress. To assess heart rate variability (HRV), we conducted a five-minute test using a pulse wave analyzer, to analyze short-term HRV. Results: The SCL-90 somatization score had relatively high positive correlation (p< .001) with cognitive stress, but low positive correlation (p< .001) with perceived stress. Cognitive stress response had low negative correlation (p< .001) with 1nSDNN and 1nRMSSD among HRV parameters. Perceived stress was not correlated with HRV. Multiple regression analysis showed that variables of perceived stress, cognitive stress, and somatization symptoms, could not explain HRV. By contrast, one of the HRV indicators, 1nSDNN, was affected by age, gender, and aggressive-hostile thought, the latter being a subscale of the cognitive stress response scale. Conclusion: This study suggests that stress evaluation for people in early adulthood will be more effective, if the evaluation examines cognitive stress and heart rate variability.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.25 no.7
• /
• pp.780-790
• /
• 1988

We have studied the hot-carrier-induced degradation caused by the high channel electric field due to the decrease of the gate length of MOSFET used in VLSI. Under DC stress, the condition in which maximum substrate current occures gave the worst degradation. Under AC dynamic stress, other conditions, the pulse shape and the falling rate, gave enormous effects on the degradation phenomena, especially at 77K. Threshold voltage, transconductance, channel conductance and gate current were measured and compared under various stress conditions. The threshold voltage was almost completely recovered by hot-injection stress as a reverse-stress. But, the transconductance was rapidly degraded under hot-hole injection and recovered by sequential hot-electron stress. The Si-SiO2 interface state density was analyzed by a charge pumping technique and the charge pumping current showed the same trend as the threshold voltage shift in degradation process.

• Coupled systems mechanics
• /
• v.9 no.4
• /
• pp.343-358
• /
• 2020

The present research deals with the time-harmonic deformation in transversely isotropic magneto thermoelastic solid with two temperature (2T), rotation due to inclined load and laser pulse. Generalized theory of thermoelasticity has been formulated for this mathematical model. The entire thermo-elastic medium is rotating with uniform angular velocity and subjected to thermally insulated and isothermal boundaries. The inclined load is supposed to be a linear combination of a normal load and a tangential load. The Fourier transform techniques have been used to find the solution to the problem. The displacement components, stress components, and conductive temperature distribution with the horizontal distance are computed in the transformed domain and further calculated in the physical domain using numerical inversion techniques. The effect of angle of inclination of normal and tangential load for Green Lindsay Model and time-harmonic source for Lord Shulman model is depicted graphically on the resulting quantities.

• Earthquakes and Structures
• /
• v.13 no.2
• /
• pp.201-209
• /
• 2017

This work aims to analyze the thermo-viscoelastic interaction in an orthotropic solid cylinder. The medium is considered to be variable thermal conductivity and subjected to temperature pulse. Analytical solution based on dual-phase-lags model with Voigt-type for behavior of viscoelastic material has been effectively proposed. All variables are deduced using method of Laplace transforms. Numerical results for different distribution fields, such as temperature, displacement and stress components are graphically presented. Results are discussed to illustrate the effect of variability thermal conductivity parameter as well as phase-lags and viscoelasticity on the field quantities. Results are obtained when the viscosity is ignored with and without considering variability of thermal conductivity. A comparison study is made and all results are investigated.