• Smart Structures and Systems
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• v.18 no.6
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• pp.1125-1143
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• 2016

Forced vibration analysis of a simple supported viscoelastic nanobeam is studied based on modified couple stress theory (MCST). The nanobeam is excited by a transverse triangular force impulse modulated by a harmonic motion. The elastic medium is considered as Winkler-Pasternak elastic foundation.The damping effect is considered by using the Kelvin-Voigt viscoelastic model. The inclusion of an additional material parameter enables the new beam model to capture the size effect. The new non-classical beam model reduces to the classical beam model when the length scale parameter is set to zero. The considered problem is investigated within the Timoshenko beam theory by using finite element method. The effects of the transverse shear deformation and rotary inertia are included according to the Timoshenko beam theory. The obtained system of differential equations is reduced to a linear algebraic equation system and solved in the time domain by using Newmark average acceleration method. Numerical results are presented to investigate the influences the material length scale parameter, the parameter of the elastic medium and aspect ratio on the dynamic response of the nanobeam. Also, the difference between the classical beam theory (CBT) and modified couple stress theory is investigated for forced vibration responses of nanobeams.

• Geomechanics and Engineering
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• v.30 no.1
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• pp.27-44
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• 2022

Gravelly soil is a kind of special geotechnical material, which is widely used in the subgrade engineering of railway, highway and airport. Its mechanical properties are very complex, and will greatly influence the stability of subgrade engineering. To investigate the mechanical properties and failure mechanism of gravelly soils, this paper introduced and verified a new discrete element method (DEM) of gravelly soils in large scale direct shear test, which considers the actual shape and broken characteristics of gravels. Then, the stress and strain characteristics, particle interaction, particle contact force, crack development and energy conversion in gravelly soils during the shear process were analyzed using this method. Moreover, the effects of gravel content (GC) on the mechanical properties and failure characteristics were discussed. The results reveal that as GC increases, the shear stress becomes more fluctuating, the peak shear stress increases, the volumetric strain tends to dilate, the average particle contact force increases, the cumulative number of cracks increases, and the shear failure plane becomes coarser. Higher GC will change the friction angle with a trend of "stability", "increase", and "stability". Differently, it affects the cohesion with a law of "increase", "stability" and "increase".

• The Korean Journal of Food And Nutrition
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• v.30 no.4
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• pp.759-770
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• 2017

Stress has been associated with poor eating behavior and diet quality. Yet, the relationship between nutrient and food intake and perceived stress in Korean female adults has not been validated. The purpose of this study is to identify the relationship between nutrient and food intake and perceived stress in Korean female adults. This is a cross-sectional study based on the 2014-2015 Korean National Health and Nutritional Examination Survey data. This study investigated 2,010 female adults age 19~64. In this study, according to subjects' perceived stress, we classified subjects into very low-stress recognition group (VLSRG) (n=211), low-stress recognition group (VSRG) (n=1,223), high-stress recognition group (HSRG) (n=488) and very high-stress recognition group (VHSRG) (n=88). Daily nutrients and food group intake, food groups consumed (Dietary Diversity Score, DDS) were analyzed using data from the 24-recall method. The VHSRG had a larger proportion of subjects that were younger (p<0.0001), single (p<0.0001) and smokers (p<0.0001) compared to the VLSRG. Energy and food intake did not differ between the four groups. Percentage of subjects with protein (p=0.0322), vitamin A (p=0.0364) and vitamin C (p=0.0115) intake lower than the EAR (estimated average requirement) in the VHSRG were significantly lowest in the four groups. Also, food intake percentage from fruits and seaweed groups in the VHSRG were lower than other groups (p=0.0034, p=0.0015). DDS in the VHSRG (3.87) was significantly lowest in the four groups (p=0.0022). Results suggest that perceived stress in Korean female adults may by significant to consider in nutritional education programs.

• Journal of Korean Tunnelling and Underground Space Association
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• v.15 no.6
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• pp.547-557
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• 2013

The mode II fracture toughness and strength due to shear stress are important parameters in the stability of caprock and injection zone with application to geological sequestration of carbon dioxide. In this research, a short beam compression test has been used to determine the shear strength and the mode II fracture toughness for Coconino sandstone. The average value of the shear strength and mode II fracture toughness are estimated to be 23.53 MPa and 1.58 MPa${\surd}$m respectively. The stress intensity factor is suggested by finite element analysis using the displacement extrapolation method. The effect of biaxial stress and water saturation on the fracture toughness has also been investigated. The fracture toughness increases with confining stresses, but decreases by 11.4% in fully saturated condition.

• Steel and Composite Structures
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• v.33 no.4
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• pp.489-507
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• 2019

In order to obtain high bearing capacity and good ductility simultaneously, a structural column with hybrid normal and high strength steel (HNHSS) welded box section has been developed. Residual stress is an important factor that can influence the behaviour of a structural member in steel structures. Accordingly, the magnitudes and distributions of residual stresses in HNHSS welded box sections were investigated experimentally using the sectioning method. In this study, the following four box sections were tested: one normal strength steel (NSS) section, one high strength steel (HSS) section, and two HNHSS sections. Based on the experimental data from previous studies and the test results of this study, the effects of the width-to-thickness ratio of plate, yield strength of plate, and the plate thickness of the residual stresses of welded box sections were investigated in detail. A unified residual stress model for NSS, HSS and HNHSS welded box sections was proposed, and the corresponding simplified prediction equations for the maximum tensile residual stress ratio (${\sigma}_{rt}/f_y$) and average compressive residual stress ratio (${\sigma}_{rc}/f_y$) in the model were quantitatively established. The predicted magnitudes and distributions of residual stresses for four tested sections in this study by using the proposed residual stress model were compared with the experimental results, and the feasibility of this proposed model was shown to be in good agreement.

• Restorative Dentistry and Endodontics
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• v.33 no.5
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• pp.457-462
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• 2008

"Residual stress" can be developed during polymerization of the dental composite and it can be remained after this process was completed. The total amount of the force which applied to the composite restoration can be calculated by the sum of external and internal force. For the complete understanding of the restoration failure behavior. these two factors should be considered. In this experiment. I compared the residual stress of the recently developed nanofilled dental composite by ring slitting methods. The composites used in this study can be categorized in two groups. one is microhybrid type-Z250, as control group, and nanofilled type-Grandio, Filtek Supreme. Ceram-X, as experimental ones. Composite ring was made and marked two reference points on the surface. Then measure the change of the distance between these two points before and after ring slitting. From the distance change, average circumferential residual stress $({\sigma}{\theta})$ was calculated. In 10 minutes and 1 hour measurement groups, Filtek Supreme showed higher residual stress than Z250 and Ceram-X. In 24 hour group, Filtek showed higher stress than the other groups. Following the result of this experiment, nanofilled composite showed similar or higher residual stress than Z250, and when comparing the Z250 and Filtek Supreme, which have quite similar matrix components. Filtek Supreme groups showed higher residual stress.

• Journal of Naturopathy
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• v.10 no.1
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• pp.10-18
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• 2021

Purposes: Stress is known as a factor inducing various diseases in the human body. The purpose was to conduct a study on the stress change of 62 subjects who performed the newly developed "Holistic Healing(HH)Program" through the Happy Healing Group Program. Methods: Six sessions of the HH program were performed once a week (90 minutes) at the Happy Healing Meeting, and were surveyed activities of each session in detail. The HH program was developed to be applied to the general public, and it was composed of three detailed introduction-development-finish phases for each session. Results: After performing the Happiness Healing Meeting with the HH program the stress factor significantly decreased to 26.371 points in the post-test average value than the pre-test average value (p<.000). Psychological and social stress was reduced considerably to 9.096 points in post-test than in the pre-test measurement. Stress-coping method was significantly higher in the post-test with 201.661 points compared to the pre-test. Mood state was 69.451 points in the pre-test and 123.983 points in the post-test, showing a significant difference (p<.000). Conclusions: In the subjects who have been applied the holistic therapy program to the happiness healing small group, was significantly decreased general or psychosocial stress, and the stress-coping style and mood state change tended to increase. When evaluating this result, the SERIP Holistic Healing Program has been determined to be one of the very new holistic and beneficial natural healing therapies for the happiness healing small group.

• The Korean Journal of Emergency Medical Services
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• v.13 no.3
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• pp.91-105
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• 2009

Purpose : The purpose of this study was to describe the current status of 119 EMT to violence experiences in Korea. Method : The number of 119 EMT in this study 2522. Self-administering questionnaire data were collected from April 27 to March 8 in 2009. Collected data were analyzed using SPSS 14.0 program. Real number, percentage, mean and standard deviation were calculated. Pearson correlation coefficient was analyzed. Result : 119 EMTs experienced 95.32%-verbal insults, 61.54%-violence aggression, 60.51%- potential violence, 38.70%-physical assault. Within 30 days from the most recent period of violence experienced verbal insults and violence aggression-51.07%, potential violence and physical assault-48.41%. The patients(50.59%) and the patients and patient's carers(38.26%) proved to be violent offender. The main reason of violent act was drug or alcohol addiction(56.15%). Recent exposure to violence was 34.82% by 7 point reward of stress level. 5-point scale showed the average of experiences of violence. Response average of emotional reactions was 2.66 points and that of physical reaction was 2.18 points. Social reaction was 2.06 points. Conclusion : This study was based on the violence experience of 119 EMT. It is necessary to prevent the violence from emergency scene. So we proposed the preventive measure against violence as well as critical incident stress debriefing(CISD). Policy for CISD and stress management will be implemented in the near future in Korea.

• Journal of Korean Foot and Ankle Society
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• v.8 no.1
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• pp.81-85
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• 2004

Purpose: The purpose of this study is to evaluate the surgical results of modified $Brostr{\ddot{o}}m$ procedure for chronic lateral ankle instability and to assess whether or not associated injuries may affect postoperative satisfaction. Materials and Methods: Twenty- four patients with chronic lateral ankle instability were evaluated retrospectively from August 1998 to March 2002. Average age was 29.3 years. All patients were performed pre & postoperative ankle anteroposterior and lateral view, stress anterior drawer and varus test using Telos device, MRI and intraoperative arthroscopic evaluations before ligament reconstruction. Results: Of the 24 cases, 23 cases was improved more than average 12 points on AOFAS scales. On modified scales of Hamilton, 3 excellent, 20 good, 1 fair results. On stress view, average 2.2 mm difference was improved on anterior drawer test and average 1.7 degree on varus test. Associated injuries were 8 osteochondral defects, 4 anterior impingements, 2 loose bodies, 2 os subfibulare, 2 os submalleolare and 2 partial ruptures of peroneus brevis. 8 cases with no associated injuries rated excellent or good. Conclusion: The modified $Brostr{\ddot{o}}m$ procedure is believed to be an effective and successful method for chronic lateral ankle instability that didn't respond to conservative treatment. Because associated injuries in chronic lateral ankle instability may affect postoperative satisfaction, appropriate detection and treatment may need for postoperative satisfaction.

• Korean Journal of Health Education and Promotion
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• v.25 no.3
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• pp.125-138
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• 2008

Purpose: This study was attempted to find out female smoking behavior and the smoking related factors. Method: Study subjects were 226 female smokers who have visited temporary clinic or smoking cessation clinic run by 10 public health centers in Incheon. The data were collected through the questionnaire specially designed for this study from April 1 to June 30, 2008. The data were analyzed by the SPSS 12.0 program. Result: 68.0% of feale smokers have smoked habitually. The average daily smoking amount of the subjects was $12.0{\pm}8.7$ ea, average rate of nicotine dependence was $4.2{\pm}2.2$ points, the mean smoking duration was $12.7{\pm}9.3$ years, and the smoking start age was $23.1{\pm}8.5$ year old. The smoking behavior by the drinking frequency showed significant difference in average daily smoking amount and rate of nicotine dependence(p<.05). Also the smoking behavior by exercise showed significant difference in current smoking frequency(p<.05). There was positive relation between female smoking behavior and monthly income, frequency of drinking, exercise, and stress respectively(p<.05, p<.01). Conclusion: Compared to a male smoker, the average daily smoking amount of a female smoker was less and the duration of smoking was longer. This study suggests that not only a social movement about a female smoking cessation is imperative but also smoking cessation programs should be combined with reduced drinking consumption, exercise and stress relief programs. Moreover, early intervention for preventing teenager smoking should be added to smoking cessation programs.