• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.25 no.11
• /
• pp.1887-1894
• /
• 2001

The effects of carbon black on the material properties and the fatigue life of the carbon-black filled natural rubbers were investigated. Different kinds of carbon blacks resulted in different fatigue lives, hysteresis, and critical J-values. It was noticed that the hysteresis was inversely proportional to the difference between DBPA and CTAB, and the critical J-value was almost the same regardless of the length of a precrack. In addition, different kinds of carbon blacks resulted in different fracture morphologies, and micro-scale and macro-scale roughnesses. The critical J-value was proportional to the micro-scale roughness. and it seemed relate to the size distribution of carbon black particles. By reviewing all the experimental data. it was finally noticed that the logarithmic value of the fatigue life could be linearly expressed by a multiplication of the critical J-value and the logarithmic value of the hysteresis.

• Journal of the Korean Society of Safety
• /
• v.21 no.5 s.77
• /
• pp.6-11
• /
• 2006

This study aims to measure a smoke density and velocity by using the PIV method in case a fire occurs in tunnels. By doing so, this will estimate a critical velocity, examine its appropriateness, and present the basic materials necessary for designing a smoke control equipment. For this study, a visualization test was conducted based on the 1/20 miniature of a real tunnel according to the Froude scaling. As a part of basic experiments, a correlation between smoke density and brightness was analyzed here, and a critical velocity was estimated on the condition that a fire breaks out in tunnels. As a result, this study finds that there is a correlation between smoke density and brightness within a range of 100% to 30% transmittance, from which a quantitative smoke density can be obtained. The study also suggests that a critical velocity calculated from the Kennedy formula shows about 10% difference from that estimated in the test.

• Geomechanics and Engineering
• /
• v.16 no.2
• /
• pp.205-215
• /
• 2018

Strain-based criteria are known as a direct method in determining the stability of the geomechanical structures. In spite of the widely use of Sakurai critical strain criterion, it is so conservative to make use of them in rocks with initial plastic deformation on account of the considerable difference between the failure and critical strains. In this study, a new criterion has been developed on the basis of the failure strain to attain more reasonable results in determining the stability status of the tunnels excavated in the rocks mostly characterized by plastic-elastic/plastic behavior. Firstly, the stress-strain curve was obtained having conducted uniaxial compression strength tests on 91 samples of eight rock types. Then, the initial plastic deformation was omitted making use of axis translation technique and the criterion was presented allowing for the modified secant modulus and by use of the failure strain. The results depicted that the use of failure strain criterion in such rocks not only decreases the conservativeness of the critical strain criterion up to 42%, but also it determines the stability status of the tunnel more accurately.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2009.05a
• /
• pp.7-8
• /
• 2009

Non-contact critical current measurement apparatus was developed using hall probe which measures the magnetic field distribution across the width of superconducting tape. The hall probe consists of 7 independent hall sensors which lie in a line 600 ${\mu}m$. The difference between maximum and minimum magnetic field in the magnetic filed distribution is a main parameter to determine the critical current. As preliminary research, we calculated the magnetic field intensity at the middle sensor, which is a minimum magnetic field and generated by the circular shielding current modeled by Bean model. We confirmed that there are some parameters that affect on the minimum magnetic field; the distance between superconducting layer and hall sensor, the width of superconducting tape, and the critical current distribution across the width of superconducting tape. Among these parameters, the distance between superconducting layer and hall sensor highly influences on the minimum magnetic field.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.29 no.4
• /
• pp.43-50
• /
• 2006

The objective of this research is to select the most effective technique from AMT (Advanced Manufacturing Technologies) and IMP (Innovative Management Practices) for improving manufacturing performance in shipbuilding enterprises. The research consists of several principal steps. The first step is to design critical criteria in evaluating manufacturing performance in shipbuilding enterprises. The second step is to develop sub-criteria of the critical criteria. The third step is to develop a four level AHP (Analytic Hierarchy Process) structure using the critical criteria, sub-criteria and techniques from AMT and IMP. The fourth step is to develope the pairwise comparison matrix by each level of AHP structure, which was based on survey data collected at the H heavy industry. And the last step is to select the most effective technique from AMT and IMP by using AHP analysis. The results of AHP analysis did not show clear difference in priority between techniques of AMT and IMP in terms of manufacturing performance of the shipbuilding enterprise. Thus, each critical criterion was assigned modified weights and examined the priority change of techniques by conducting performance sensitivity analysis.

• Journal of Korean Academy of Fundamentals of Nursing
• /
• v.25 no.4
• /
• pp.259-268
• /
• 2018

Purpose: The purpose of this study was to identify the effects of the action learning approach on the self-confidence and knowledge of health assessment, critical thinking ability and class satisfaction in students taking health assessment courses. Methods: This non-equivalent control group pretest-posttest study enrolled 127 nursing students as participants, with 64 and 63 in the experimental and control group, respectively. These two groups attended 33 hours (2 or 4 hours per week for 11 weeks) of action learning and traditional classes, respectively. Differences in the dependent variables between the two groups were compared before and after the intervention using independent t-test. Results: The action learning group reported significantly greater self-confidence in health assessment (t=5.10, p<.001) and critical thinking ability (t=2.23, p=.027) than the control group. There was no significant difference in knowledge of health assessment or class satisfaction between two groups (p>.05). Conclusion: These findings indicate that action learning is an effective intervention for enhancing self-confidence and critical thinking ability in nursing education.

• Journal of Korean Academy of Nursing
• /
• v.36 no.8
• /
• pp.1340-1351
• /
• 2006

Purpose. To determine and compare the perception among nurses and doctors of the roles and tasks of critical care advanced practice nurses (APNs) in order to establish standardized and formally agreed role criteria for such critical care APNs. Method. This study measured and analyzed the necessity of each of the roles and tasks of critical care APNs, as perceived by nurses and doctors, through a survey of 121 participants: 71 nurses in 7 intensive care units (ICUs) at a general hospital in Seoul, and 50 doctors who used ICUs. Data collection utilized a questionnaire of 128 questions in the following fields: direct practice (79), leadership and change agent (17), consultation and collaboration (15), education and counseling (11), and research (6). Results. Both the nurses' and the doctors' groups confirmed the necessity of critical care APNs, with doctors who frequently used ICUs indicating a particularly strong need. As for the priority of each role of critical care APNs, the nurses considered direct practice to be the most critical, followed by education and counseling, research, consultation and collaboration, and leadership and change agent. The doctors also considered direct practice to be the most critical, followed by education and counseling, consultation and collaboration, research, and leadership and change agent. There was a statistically significant difference between how the two groups regarded all the roles, except for the consultation and collaboration roles. As for the necessity of each role of critical care APNs, the nurses considered research to be the most necessary, followed by education and counseling, consultation and collaboration, leadership and change agent, and direct practice. The doctors, on the other hand, considered education and counseling to be the most necessary, followed by research, consultation and collaboration, leadership and change agent, and direct practice. The responses of the two groups to all the roles, except for education and counseling roles, were significantly different. Conclusion. Nurses and doctors have different perceptions of the roles and tasks of critical care APNs. Thus, it is necessary for the combined nursing and medical fields to reach an official agreement on a set of criteria to standardize for the roles and tasks of critical care APNs.

• Proceedings of the Korea Air Pollution Research Association Conference
• /
• 2008.04a
• /
• pp.532-534
• /
• 2008

• Journal of the Korean Ceramic Society
• /
• v.36 no.9
• /
• pp.997-1005
• /
• 1999

• The Journal of the Convergence on Culture Technology
• /
• v.8 no.5
• /
• pp.445-451
• /
• 2022

This study was conducted to confirm the differences in nursing process competence, critical thinking disposition, and education satisfaction between clinical practicum and school practicum in the prolonged COVID19 pandemic. As an inequality control post-hoc design study, 55 students who agreed to participate in the study among the third year of nursing college students who took adult nursing practice were targeted. Data were collected by classifying the students who participated in the school practicum into the experimental group(N=29) and the students who participated in the clinical practicum into the control group(N=26). The collected data were analyzed using SPSS/WIN 22.0 program. As a result of the study, there was no significant difference in nursing process competence and critical thinking disposition between the two groups. However, in the control group, overall satisfaction with education (t=-9.82, p=.040) and recommendations to other students (t=-1.88, p<.001) were found to be significantly higher. Although it was not possible to confirm the difference between the effects of clinical practicum and school practicum as a result of the study, the significance of the study could be found in that there was no difference. In line with the post-corona era, future research on the development of a practicum program consisting of various contents, teaching methods, and practice to achieve the goal of practicum and analysis of the effectiveness of the program is suggested.