• The Journal of Korean Academic Society of Nursing Education
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• v.20 no.4
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• pp.650-658
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• 2014

Purpose: This study compares differences in stress, depression and suicidal ideation between nursing and students of other academic disciplines. Method: Nursing students (n=105) and students of other majors (n=148) were surveyed on the degree of personal stress, depression and suicidal ideation. Participants were recruited from three universities in cities S and C in Korea. Data were collected from May 1 to 20, 2013. Measurement tools were the Revised Life Stress Scale for College Students, Center for Epidemiological Studies-Depression Scale(CES-D), and Scale for Suicide Ideation(SSI). PASW Statistics 18 was used for descriptive analysis, homogeneity test(chi-square distribution) and ANCOVA. Results: The level of stress among nursing students was lower than that of students in other majors. Among the subcategories of stress, however, stress among nursing students arising from the student-faculty relationship was higher than that of their non-nursing counterparts. Conversely, differences in the prevalence of depression were notsignificant between nursing students and non-nursing students. Ultimately, it was revealed that there exists a strong correlation among stress, depression and suicidal idea for nursing students. Conclusion: Developing stress and depression management programs for nursing students is highly recommended.

• Journal of Korean Society of Steel Construction
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• v.10 no.4 s.37
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• pp.709-720
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• 1998

In order to study the distribution of welding residual stress through the plate thickness. experiment and analysis of fillet welding details were carried out. Especially, a residual stress in the weld root part of T-joint fillet weld whose measurement was difficult up to now was measured. By using the heat input and the number of the weld layers as parameters, the distribution of the 3-dimensional residual stress was investigated. As a result, we can say that with increasing the heat input, the residual stress in the weld toe and weld root barely changes. But, the area of the tensile residual stress became wide. Then, comparing a single pass with multi-pass weld method, it was found that the residual stress decreased more in multi-pass than in single pass. Moreover, it was found the thing that the area of tensile residual stress by multi-pass is lower than that by single-pass in the near weld part.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.470-474
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• 2000

Cold expansion of fastener holes is a mechanical process widely used in the aerospace industry. This treatment leads to an improvement of fatigue behavior due to the developed compressive residual stresses on the hole surface. The residual stress profile depends on the parameters of cold expansion, which are, expanding rate, inserting direction of mandrel, material properties etc. and the method to confirm this profile is only measurement by X-ray diffractometer. Despite its importance to aerospace industries, little attention has been devoted to the accurate modelling of the process. In this paper, Two-dimensional axisymmetric finite element simulations have been conducted for the cold expansion in an aluminium plate in order to predict the magnitude and distribution of the residual stress and plastic deformation. Maximum compressive residual stress could be increase about 7 percent using the 2-step cold expansion method.

• Journal of Electrical Engineering and Technology
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• v.9 no.6
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• pp.2013-2018
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• 2014

According to the manufacturing process of the laminated stator core for an inserted permanent magnet synchronous motor (IPMSM), the iron loss may be different. It is because the mechanical stress imposed to electrical steel sheet is strongly dependent on the manufacturing process. This paper proposes a new iron loss measurement algorithm which utilizes the induced voltage of a search coil and exciting current. The method is effective even when the distribution of magnetic flux density is not uniform along the magnetic flux path as well as uniform. The developed iron loss measurement system is applied to bonded- and embossed-type segmented stator cores of an IPMSM, and the iron losses are quantitatively compared.

• The Journal of Korean Academy of Prosthodontics
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• v.37 no.1
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• pp.93-103
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• 1999

Stress distribution on mandibular implants supporting overdentures were registered in vitro experimental model by means of 4 rosette gauges which were placed around the implant. The overdenture attachments used in this study were the Resilient Dolder bar, Rigid Bolder bar, Round bar, Hader bar & Dal-Ro attachment. An occlusal jig was placed on the overdenture and the loading sites were 3 points which mimicked working, balancing, and median relations. With 5 and 10kg loading, strains were measured by strain indicator(P-3500, Measurement group, Raleigh, USA), and using these data, maximum and minimum principal stresses and Von Mises stress were calculated and evaluated. The results were as follows : There was a tendency of high stress concentration in the lingual side of the implant, and in the buccal side low stress was developed regardless of the attachment systems. The resilient Bolder bar concentrated highest stress among the attachment systems, and the Round bar and the Dal-Ro attachment provided comparatively low stresses around the implant. The rigid Bolder bar concentrated high stress in the mesial side, and the Dal-Ro attachment developed tensile stress patterns in the lingual and distal sides of the implant at the balancing relation.

• Journal of the Korean Society for Heat Treatment
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• v.33 no.4
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• pp.180-184
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• 2020

The crystallographic texture plays an important role in both the plastic deformation and the macroscopic anisotropy of magnesium alloys. In previous study for AZ80 magnesium alloy, it was found that the main texture components of the textures vary with the deformation conditions at high temperatures. Also, the basal texture was formed at stress of more than 15-20 MPa and the non-basal texture was formed at stress of less than 15-20 MPa. Therefore, in this study, uniaxial compression deformation of AZ80 magnesium alloy was carried out at high temperature (stress of 15-20 MPa). The uniaxial compression deformation is performed at temperature of 723 K and strain rate 3.0 × 10^-3s^-1, with a strain range of between -0.4 and -1.3. Texture measurement was carried out on the compression planes by the Schulz reflection method using nickel filtered Cu Kα radiation. EBSD measurement was also conducted in order to observe spatial distribution of orientation. As a result of high temperature deformation, the main component of texture and its development vary depending on deformation condition of this study.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.2
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• pp.149-154
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• 2012

The size and distribution of welding residual stress and welding deformation in welding structures have an effect on various sorts of damage like brittle failure, fatigue failure and stress corrosion cracking. So, research for this problem is necessary continuously. In this study, non-destructive technique using laser electronic speckle pattern interferometry, plate of welding specimen according to the external load on the entire behavior of residual stress are presented measurement techniques. Once, welding specimen force tensile loading, using electronic speckle pattern interferometry is measured. welding specimen of base metal and weld zone measure strain from measured result, this using measure elastic modulus. In this study, electronic speckle pattern interferometry use weld zone and base metal parts of the strain differences using were presented in residual stress calculated value, This residual stress value were calculated by numerical calculation. Consequently, weld zone of modulus high approximately 3.7 fold beside base metal and this measured approximately 8.46 MPa.

• Ecology and Resilient Infrastructure
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• v.4 no.4
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• pp.207-215
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• 2017

Hydraulic issues such as flow resistance, side wall correction, sediment, erosion and deposition, and channel design have close relation with distribution of bed shear stresses but the measurement of the distribution of bed shear stresses is not easy. In this study the Preston tube which makes possible relatively simple measurement of bed shear stresses is used to analyze the characteristics of bed shear distribution in compound open channels with different depth ratio. The Preston tubes are made and calibrated to develop the calibration formula and then they are applied to measure bed shear stress distribution in 5 cases depth ratio condition of compound channels. The results are compared with former experiment data, and characteristics of bed shear stress distributions are studied with different channel scales and Reynolds numbers. Although bed shear distributions with depth ratio show overall agreement with former studies, some differences are verified in bed shear variation, formation of inflection point in main channel, and distribution near floodplain junction which are due to high Reynolds number. Through the study applicability of the Preston tubes are also verified and characteristics of bed shear distribution in compound channels are suggested with Reynolds number and depth ratio.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.1
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• pp.21-26
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• 1993

A study on the fatigue fracture at electro discharge machined(E.D.M) surface has been made with special emphases on the microstructure variation and the residual stress distribution at the E.D.H heat affected zone. Results obtained are summarized as follows. (1) E.D.M brings about a variation of microstructure in heat affected zone, structures of molten, quenching, tempering are formed in order of formation from E.D.M surface. (2) Residual stress generated by E.D.M reduces the fatigue strength of the material through the influencing fatigue crack initiation and growth. (3) Magnitude of the residual stress existed in a microscopic area is approximately estimated by a COD measurement method which was originally suggested by authors.

• Journal of Korean Society for Quality Management
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• v.40 no.2
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• pp.117-125
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• 2012

For the highly reliable products, an accelerated degradation test (ADT) is a useful tool which has been employed in industry to obtain reliability-related information within an affordable amount of time and cost. In an ADT, as all other reliability tests, it is important to carefully design the ADT beforehand to obtain estimates of the quantities of interest as precisely as possible. In this paper, optimal ADTs are developed assuming that the constant-stress loading method is employed and the degradation characteristic follows a Wiener process. Under the constraint that the total cost does not exceed a pre-specified budget, the stress levels, the number of test units allocated to each stress level and the number of measurement (termination time) are determined such that the asymptotic variance of the maximum likelihood estimator of the q-th quantile of the lifetime distribution at the use condition is minimized.