• Journal of Korea Water Resources Association
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• v.41 no.2
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• pp.137-147
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• 2008

Critical and allowable shear stress acting on the mattress revetment, is presented in this study. First of all, shear stress at each spot is computed when the hydraulic power act on the waterway. Secondly, median diameter of the filling rocks is computed using shear stress and Shields coefficient which are used to decide the critical motion of the particle. Finally, the range of critical and allowable shear stress is estimated which meet the particle stability and indicated that the mattress is a stable hydraulic structure in comparison with the riprap. Therefore the required median diameter of riprap is three times higher than that of mattress. Contrarily, this study also analyzed that resisting power of mattress to shear stress is three times higher than that of riprap on the same size.

• The Journal of Korean Academic Society of Nursing Education
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• v.17 no.3
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• pp.337-345
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• 2011

Purpose: This study was done to identify the relationship among Critical Thinking Disposition (CTD), stress of clinical practice and clinical competence in Korean nursing students. Methods: Participants were 407 baccalaureate nursing students (3rd and 4th grades) in Korea. Variables included CTD, stress of clinical practice, clinical competence, and demographic variables. Data was analyzed by frequencies, t-test, ANOVA, Pearson's correlation and multiple regression. Results: Clinical competence positively correlated with CTD, but negatively correlated with stress of clinical practice. The regression model explained 25.6% of clinical competence. The significant predictors of clinical competence were intellectual eagerness, intellectual fairness in CTD, conflict with patients, and clinical environment in stress of clinical practice. Conclusions: CTD and stress of clinical practice contribute to nursing student's clinical competence. Therefore, efforts to encourage nursing student's CTD, increase stress management skills, especially in conflict with patients, and build a supportive clinical environment should be made to strengthen clinical competence.

• Journal of Korean Critical Care Nursing
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• v.2 no.1
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• pp.1-14
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• 2009

Purpose: This study was designed to identify levels of job stress and assertiveness behaviors and the relationship between them among ICU nurses. Methods: A correlational descriptive survey was used to these relationships among 454 ICU nurses from 25 hospitals which were members of Korean Association of Critical Care Nurses. Data were collected using a structured questionnaire which included 58 items of job stress and assertiveness scale from November 4 to 14, 2008. Descriptive statistics, Pearson correlation coefficients were used to analyze the data. Results: ICU nurses experience mild to moderate degree of job stress, A score of assertiveness behaviors was 2.86. There was a negative relationship between job stress and assertiveness behaviors(r=-.106, p=.024) as influenced by role conflict, lack of professional knowledge and skills, and inappropriate treatment. Conclusion: ICU nurses, especially nurses with 3-6 year clinical experience, are in need of support to manage their job stress. These nurses should be supported through provision of adequate stress management and assertiveness program.

• International Journal of Highway Engineering
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• v.8 no.4 s.30
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• pp.13-24
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• 2006

The stresses in concrete pavement systems are larger when vehicle loads are applied at pavement edges, and these large stresses significantly affect the behavior and performance of pavements. Therefore, in this study, the stress distribution and the critical stresses in concrete pavements were investigated using a finite element model when dual-wheel single-, tandem-, and tridem-axle loads were applied at pavement edges. First, the stress distribution along the longitudinal and transverse directions was analyzed, and then the effects of slab thickness, concrete elastic modulus, and foundation stiffness on the stress distribution were investigated. The effect of the tire contact pressure related to the tire print area was also studied. The location of the critical stress occurrence in concrete pavements was finally investigated. From this study, it was found that the critical concrete stress due to edge loads became larger as the concrete elastic modulus increased, the slab thickness increased, and the foundation stiffness decreased. The effect of the tire contact pressure on the critical stress was clear as the slab thickness became smaller. The critical stress location in the transverse direction was independent of the concrete elastic modulus and the foundation stiffness; however, it moved into the interior as the slab thickness increased. The critical stress location in the longitudinal direction was under the axle for single- and tandem-axle loads, but for tridem-axle loads, it tended to move under the middle axle from the outer axles as the concrete elastic modulus and/or slab thickness increased and the foundation stiffness decreased.

• Journal of Korean Academy of Nursing Administration
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• v.21 no.2
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• pp.154-163
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• 2015

Purpose: This descriptive study was done to identify factors that influence stress related to clinical practice for nursing students. Methods: Structured questionnaires were used to collect data from 278 students from two nursing colleges located in G metropolitan city and one nursing college in C region. Results: The factors that most influenced stress for the nursing students during their clinical practice were critical thinking disposition, clinical competence, year, and gender. Especially, the result showed that higher critical thinking disposition and clinical competence correlated with lower stress in clinical practice. Conclusion: The results indicate that improving nursing students' critical thinking ability and clinical competence would help to relieve stress during clinical practice and increase the ability to cope with stress efficiently. The development of a variety of teaching and learning strategies and education in both theoretical and clinical practice education would be necessary to achieve this goal.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.6 s.249
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• pp.615-621
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• 2006

Increased application of optical disks requires more improved dynamic stability of rotating disks. In this study, a new concept of controlling the processing conditions of injection molded disks was developed to improve vibration characteristics. The critical speed, which shows stiffness and dynamic stability of disk, is affected by the residual stress distribution; this varies as functions of distance from the gate and processing condition. The critical speed of disk was calculated with the initial stress taken into consideration, which was determined from injection molding simulation. Choosing melt temperature, mold temperature, filling speed and packing pressure as design parameters, critical speed is maximized with the method of response surface. It is shown that the stability of injection molded disk has been improved for the new condition obtained as a result of the study proposed.

• International Journal of Railway
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• v.5 no.1
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• pp.48-54
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• 2012

The main purpose of this study is to highlight the importance and validity of introduction of stress-concerned aptitude items for the safety critical workers, corresponding to the radical environmental change in railway industry. To attain this purpose, the author performed a brief literature survey, and scrutinized the western practice in detail. Then, the necessity of introduction of stress-related aptitude items was suggested, based on the statistics resulted from a survey which has been once performed for experts and drivers. The final conclusion is that the present selection system through which the safety critical workers are being staffed, without any rigorous screening mechanisms cannot but have some limitations. So, an overall restructuring for aptitude management system needs to be done in order for us to advance to the position of upper-class railway country.

• International Journal of Concrete Structures and Materials
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• v.18 no.3E
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• pp.191-198
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• 2006

The objective of this study is to examine fracture characteristics of concrete at early ages, i.g. critical stress intensity factor, critical crack-tip opening displacement, fracture energy, and bilinear softening curve based on the concepts of effective-elastic crack model and cohesive crack model. A wedge splitting test for Mode I was performed on cubic wedge specimens with a notch at the edge. By experimenting with various strengths and ages, load-crack mouth opening curves were obtained, and the results were analyzed by linear elastic fracture mechanics and FEM(finite element method). The results from the test and analysis showed that critical stress intensity factor and facture energy increased while critical crack-tip opening displacement decreased with concrete aging from 1 day to 28 days. Four parameters of bilinear softening curve from 1 day to 28 days were obtained from a numerical analysis. The obtained fracture parameters and bilinear softening curves at early ages from this study are to be used as a fracture criterion and an input data for the finite element analysis of concrete at early ages.

• Journal of the Korea Concrete Institute
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• v.19 no.4
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• pp.449-456
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• 2007

This research was conducted to analyze the features of the critical tensile stresses at the top and bottom of the concrete slab in the jointed concrete pavement (JCP) when subjected to both the environmental and vehicle loads. First, the stress distribution in JCP was analyzed when the system was subjected to only the environmental loads or the vehicle loads by using the finite element model of JCP. Then, the stresses were analyzed when the system was subjected to the environmental and vehicle loads at the same time. From this study, it was found that the critical tensile stresses at the slab bottom under the vehicle loads were almost constant regardless of the loading positions once the loads were applied at the positions having some distance from the transverse joint. The critical tensile stresses at the slab bottom could be obtained using the model consisting of normal springs for underlying layers by adding the critical stresses due to the environmental loads and the vehicle loads for the curled-down slab, and by subtracting the critical stress due to the environmental loads from that due to the vehicle loads for the curled-up slab. The critical tensile stresses at the top of the slab could be obtained using the model consisting of tensionless springs for underlying layers by adding the critical stress due to the environmental loads and the stress at the middle of the slab under the vehicle loads applied at the joint for the curled-up slab. An alternative to obtain the critical stresses at the top of the slab for the curled-up slab was to use the critical stresses under only the environmental loads obtained from the model having normal springs for underlying layers.

• Progress in Superconductivity and Cryogenics
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• v.3 no.1
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• pp.6-10
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• 2001

Stress/stram dependencies of the critical current $I_c$ in AgMgNi sheathed multifilamentary Bi(2212) superconducting tapes were evaluated at 77K, 0T. The external reinforcement was accomplished by soldering Ag-Mg tapes to sin91e side or both sides of the sample. With the external reinforcement. the strength of tapes increased but $I_c$, decreased The $I_c$, degradation characteristic according to the external reinforcement was improved markedly in terms of the stress although it appeared less rectal.table on the basis of the strain. Effects of external reinforcement were discussed in a viewpoint of monitoring sensitivity of cracking in superconducting filaments by considering n-value representing the transport behavior of the current. It is closely associated with the location of them relative to the voltage-monitoring region in the tape.