• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.152-152
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• 2017

Plants exposed to environmental stress for long durations often can adapt to stress conditions with improved tolerance. Moreover this acquired tolerance to stress can be retained even after reverting to destressed growth conditions, which is known to stress memory. In these adaptation and stress memory processes, epigenetic regulation, such as DNA methylation and histone modifications play a key role. Here, we showed that regenerated rice plants from embryogenic callus exposed to gradually increasing NaCl concentrations (up to 120 mM NaCl) acquired salt tolerance and their enhanced tolerance are inherited to subsequent generations. The rice plants (R0) regenerated from rice callus under saline conditions were transplanted into normal paddy field and R1 seeds were harvested. These R1 seeds displayed higher germination rate on MS medium containing 100mM NaCl than wild-type. The callus derived from R1 seeds showed better growth than control callus on high salinity medium. And the salt-adapted R1 plants exhibited higher chlorophyll contents and also higher $K^+/Na^+$ ratio than wild-type rice under saline conditions. The results indicated that rice plants successfully adapted to saline growth conditions during regeneration on high salt medium and moreover this acquired tolerance to salt stress was inherited subsequent generation.

• Journal of Korean society of Dental Hygiene
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• v.15 no.5
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• pp.917-924
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• 2015

Objectives: The aim of this study was to investigate the association between work-related stress and depressive symptoms among dental hygienists. Methods: This survey of dental hygienists was conducted in Gyeonggi province, South Korea. Total of 198 dental hygienists were interviewed in 2014. The occupational stress was evaluated by depression symptoms, which was assessed by the Beck Depression Inventory Scale. To estimate the odds ratio with 95% confidence intervals, logistic regression model was used. Results: Depressive symptoms were reported 46.0%(n=91) among dental hygienists. We found that the work-related stress increased with age, smoking(OR=5.16; 95% CI 1.73-15.3), and those who had the poor perceived health status(OR=4.22; 95% CI=1.50-11.86) was associated with the risk of depressive symptoms. After controlling potential confounders, such as dental hospital(OR=11.05; 95% CI=1.02-118.9), 5-7 years time since first employment(OR=0.15; 95% CI=0.03-0.89), and the group with the high job stress(OR=2.84; 95% CI=1.22-6.79) showed higher risks of depressive symptoms than did no depressive symptoms. Conclusion: Our findings suggest that the risk of depression appears to be related to age, smoking, self-reported health status, type of dental facility, years of practice and the stress of job.

• The Journal of Internal Korean Medicine
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• v.19 no.1
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• pp.247-270
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• 1998

The more society has complicated, the more we have met stressful circumstance. And it is found that many physical and mental symptoms induced by stress. Soyosan(SYS) is one of the well-known oriental medicine for the treatment of general syndrome induced by emotional stress. This study was taken to know effects of SYS water extract on immune-depressed mice induced by stress. The results obtained in this study were as follows : 1. SYS inhibited murine weight-loss induced by stress 2. In vivo& in vitro, SYS increased phagocytic activity. 3. SYS enhanced the production of such reactive oxygen intermediates as superoxide and hydrogen peroxide from macrophages. 4. In vitro, SYS little influenced the production of reactive nitrogen intermediates. 5. SYS increased the number of the rosette forming cells of spleen. 6. SYS changed the ratio of helper and suppressor T cells by increasing $CD4^+$ T cells and decreasing $CD8^+$ T cells. 7. SYS increased cytotoxic activity on human lymphoma cell line(K562). 8. SYS increased the plasma level of GH and DHEA. whereas it decreased that of ACTH and cortisol. According to the above results, it might be considered that SYS would be used for immune-depressive disease induced by stress.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.7 no.1
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• pp.17-26
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• 2011

CANDU reactor core is composed a few hundreds pressure tubes, which support and locate the nuclear fuels in the reactor. Each pressure tube provides pressure boundary and flow path of primary heat transport system in the core region. In order to guarantee the structural integrity of pressure tube flaws which can be found by in-service inspection, crack growth and fracture initiation assessment have to be performed. Stress intensity factors are important and basic information for structural integrity assessment of planar and laminar flaws (e. g. crack). This paper reviews and confirms the stress intensity factor of axial crack, proposed in CSA N285.8-05, which is an fitness-for-service evaluation code for pressure tubes in CANDU nuclear reactors. The stress intensity factors in CSA N285.8-05 were compared with stress intensity factors calculated by three methods (finite element results, API 579-1/ASME FFS-1 2007 Fitness-For-Service and ASME Boiler and Pressure Vessel Code Section XI). The effects of Poisson's ratio and anisotropic elastic modulus on stress intensity factors were also discussed.

• Journal of Advanced Marine Engineering and Technology
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• v.23 no.4
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• pp.453-461
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• 1999

The estimation of fatigue life at the design stage is very important in order to arrive at feasible and cost effective solutions considering the total lifetime of the structure and machinery compo-nents. In this study the practical procedure of prediction of fatigue life by use of cumulative damage factors based on Miner-Palmgren hypothesis and probability density function is shown with a $135,000m^3$ LNG tank being used as an example. In particular the parameters of Weibull distribution taht determine the stress spectrum are dis-cussed. At the end some of uncertainties associated with fatigue life prediction are discussed. The main results obtained from this study are as follows: 1. The practical procedure of prediction of fatigue life by use of cumulative damage factors expressed in combination of probability density function and S-N data is proposed. 2. The calculated fatigue life is influenced by the shape parameter and stress block. The conser-vative fatigue design can be achieved when using higher value of shape parameter and the stress blocks divded into more stress blocks.

• Journal of Korean Academy of Nursing Administration
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• v.17 no.1
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• pp.115-126
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• 2011

Purpose: This study was done to identify differences in work environment, work stress, turnover intention and burnout and investigate the relationship among these variables in nurses in Korean Neonatal Intensive Care Units. Method: Participants were 242 nurses working in 13 general hospitals. Burnout was measured by the Maslach Burnout Inventory (MBI), work stress with the instrument by Gu & Kim (1994), and turnover intention with the scale by Kim & Lee (2001). Size of the NICU, nurse to patient ratio, and communication satisfaction were included in work environment. Data were analyzed using Pearson correlation coefficients and multiple regression analysis with SPSS WIN program. Results: The mean score for work stress in NICU nurses was 3.43 points, for burnout, 2.72 points, and for turnover intention, 4.64 points. Burnout and turnover intention level of participants were moderate-high. Work stress, communication dissatisfaction with physician, and clinical career accounted for 33% of variance in burnout. Significant differences were found between size of NICU and staffing related to environmental characteristics in turnover intention and burnout. Conclusions: Results indicate that effective communication with coworkers and institutional support for appropriate staffing according to number of beds will help to prevent work stress, burnout, and ultimately, nurses' resignations.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.5
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• pp.532-538
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• 2004

MEMS technology applying to the sensors and micro-electro devices is complete system. These microsystems are made by variable processes. Especially, the mentallization process has very important functions to transfer the power operating the sensor and signal induced from sensor part. But in the structures of MEMS the local stress concentration and deformation are often yielded by an irregular geometrical shape and different constraint. Therefore, this paper studies the effect of supporting type and thickness ratio about thin film of the substrate on the residual stress variation when the thermal loads is applied to the multi-layer thin film fabricated by metallization process. Specimens were made from several materials such as Al, Au and Cu. Then, uniform thermal load was applied, repeatedly. The residual stress was measured by FE Analysis and nano-indentation method using AFM. Generally, the specimen made of Al induced the larger residual stress than that of made of other materials. Specimen made of Cu and Au having the low thermal expansion coefficient induces the minimum residual stress. Similarly, the lowest indentation length was measured by nano-indentation method in the Si/Au/Cu specimen. Particularly, clusters are created in the specimen made of Cu by thermal load and the indentation length became increasingly large by cluster formation.

• Geotechnical Engineering
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• v.9 no.4
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• pp.83-92
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• 1993

A series of drained triaxial tests on sand was performed using the cubical triaxial appaiatus, in which three principal stress could be loaded independently. The test results indicated that the intermediate principal stress influenced on both stress strain behavior and strength of sand. The axial strain at failure decreased and volumetric strain increased with an increase of the intermediate stress under constant minor principal stress. The internal friction angle of sand increased in general with increase of the deviator stress ratio b(=(G.:-c, )1(G, -G, )) except slight decrease of the internal friction angle as b value approached to 1. Finally Lade's failure criterion presented good coincidence with the exper imental strengttL while Mohr Coulomb failure criterion underestimated the experimental strength.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.1
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• pp.1-7
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• 2007

In this study, the influence of compressive residual stress and corrosive condition for corrosion fatigue crack was investigated, after immersing in 3.5%NaCl, $10%HNO_3+3%HF,\;6%FeCl_3$. The immersion period was performed for 90days. The fatigue characterization of a spring steel with processed shot peening were performed by considering the several corrosion environments in the range of stress ratio of 0.05 by means of opening mode displacement. By using the methods mentioned above, the following conclusions have been drawn: The fatigue life shows more improvement in the shot peened material than that in the un peened material. And the fatigue life shows improvement in ambient than in corrosion conditions. Threshold stress intensity factor range of the shot peened materials has higher than of the un peened materials. And the threshold stress intensity factor range was decreased in corrosion environments over ambient.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.5
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• pp.938-946
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• 1989

Using the CT specimen of carbon steel(SM45C), we estimated the fatigue crack propagation behavior in stable crack propagation range. Furthermore the fatigue crack propagation rate, Acoustic Emission(AE) count rate, and fractography characteristics were also compared among others. The following results were confirmed by experimental observation. Near-threshold stress intensity factor range(.DELTA. $K_{th}$) is influenced by stress ratio but not at the upper limit of stable crack propagation range. As stress intensity factor range(.DELTA.K) and(or) stress amplitude increase (s), both crack propagation rate(da/dN) and AE count rate(dn/dN) increase. Effective stress intensity factor range(.DELTA. $K_{off}$) determined from the crack closure point measurement by AE method is useful for the evaluation of fatigue crack propagation rate. Fractography in stable crack propagation range showed striation, and agreed with the crack propagation rate obtained either by experiment of by the results of microscopic measurements.s.