• 콘크리트학회지
• /
• 제11권2호
• /
• pp.127-137
• /
• 1999

본 연구와 관련한 이전의 연구에서는 본 연구자들이 제안한 설계식의 타당성을 검증하기 위하여 선정된 변수별로 실험체를 제작하여 실험을 실시하였고 실험결과를 분석하였다. 본 연구에서는 실험결과에 대하여 본 연구자들이 제안한 설계식과 기존의 설계식들에 의한 해석결과를 비교분석하여 본 연구자들의 설계식의 타당성을 검증하였다. 사용된 기존의 설계식은 현행의 ACI 규준식, AASHTO LRFO 규준시, 변형도 적합조건에 의한 해석식, Harajli/Kanj의 설계식, Chakrabarti의 설계식 등이다. 비교${\cdot}$분석결과에 의하면 본 연구자득이 제안한 설계식이 비부착 긴장재의 응력을 평가하는데 보다 적절한 방법임을 증명하였다.

• 소성∙가공
• /
• 제14권8호통권80호
• /
• pp.704-711
• /
• 2005

The influence of process parameters in drawn wire on residual stresses was investigated. Based on a FE-simulation of the wire drawing process, the effects of process parameters such as semi-die angle, reduction, friction coefficient and bearing length on the residual stresses were investigated. The validity of the FE-simulation results was verified by the comparison of the previous simulated results with experimental data. In this study, semi-die angle and die reduction have significant effect on the residual stresses at the surface of drawn wire. Several methods such as, addition of axial tension, application of skin pass, straightening in multi-roll straightener etc, were suggested in the previous studies to reduce the residual stresses. In this study, the results show that the concurrent application of skin pass with low die reduction and low semi-die angle at the final stage of drawing operation reduces dramatically the both axial and hoop residual stresses after drawing

• Journal of Mechanical Science and Technology
• /
• 제14권11호
• /
• pp.1305-1318
• /
• 2000

The local wall shear stress in transitional boundary layer was estimated from the near-wall mean velocity data using the principle of Computational Preston Tube Method(CPM). The previous DNS and experimental databases of transitional boundary layers were used to demonstrate the accuracy of the method and to provide the applicable range of wall unit y(sup)+. The skin friction coefficients predicted by the CPM agreed well with those from previous studies. To reexamine the applicability of CPM, near-wall hot-wire measurement were conducted in developing transitional boundary layers on a flat plate with different freestream turbulence intensities. The intermittency profiles across the transitional boundary layers were reasonably obtained from the conditional sampling technique. An empirical correlation between the representative intermittency near the wall and free parameter K$_1$of the extended wall function of CPM has been newly proposed using the present and other experimental data. The CPM has been verified as a useful tool to measure the wall shear stress in transitional boundary layer with reasonable accuracy.

• Structural Engineering and Mechanics
• /
• 제62권6호
• /
• pp.739-748
• /
• 2017

Notches such as slots are typical geometric features on mechanical components that promote fatigue crack initiation. Unlike for components with open hole type notches, there are no conventional treatments to enhance fatigue behavior of components with slots. In this work we evaluate the viability of applying laser shock peening (LSP) to extend the fatigue life of 6061-T6 aluminum components with slots. The feasibility of using LSP is evaluated not only on damage free notched specimens, but also on samples with previous fatigue damage. For the LSP treatment a convergent lens was used to deliver 0.85 J and 6 ns laser pulses 1.5 mm in diameter by a Q-switch Nd: YAG laser, operating at 10 Hz with 1064 nm of wavelength. Residual stress distribution was assessed by the hole drilling method. A fatigue analysis of the notched specimens was conducted using the commercial code FE-Safe and different multiaxial fatigue criteria to predict fatigue lives of samples with and without LSP. The residual stress field produced by the LSP process was estimated by a finite element simulation of the process. A good comparison of the predicted and experimental fatigue lives was observed. The beneficial effect of LSP in extending fatigue life of notched components with and without previous damage is demonstrated.

• 대한간호학회지
• /
• 제40권2호
• /
• pp.225-235
• /
• 2010

Purpose: The aim of this study was to identify factors which influence breastfeeding adaptation from among the following: parity and feeding behavior, social support, psychological, and demographic factors. Methods: The respondents were 179 breastfeeding mothers. Data were collected from June 2 to 19, 2009 at two community health centers and one pediatric outpatient department. Data were analyzed using the SPSS program and included descriptive statistics, t-test, ANOVA, correlation, and multiple regression. Results: The major findings of this study were: 1) Significant differences in the level of breastfeeding adaptation were related to number of children, current problems related to breastfeeding, and lay supporters. 2) Level of breastfeeding adaptation was significantly related to marriage satisfaction, proportion of breastfeeding, length of previous breastfeeding, planned length of breastfeeding, parenting stress, and encouragement to breastfeed given by medical personnel. 3) Regression analysis showed that parenting stress, marriage satisfaction, current problems related to breastfeeding, and proportion of breastfeeding explained 44.3% of variance for breastfeeding adaptation. Length of previous breastfeeding also explained 9.7% of breastfeeding adaptation among mothers who had breastfed an elder child. Conclusion: Mothers with lower marriage satisfaction, breastfeeding problems, and higher parenting stress require more help from their family and nurses for breastfeeding adaptation. Future research should include variables, such as mother's and baby's behavior related to breastfeeding, knowledge about breastfeeding, and attitude toward breastfeeding.

• 한국간호교육학회지
• /
• 제18권1호
• /
• pp.5-13
• /
• 2012

Purpose: The purpose of this study was to investigate the factors affecting adaptation to school life of freshmen enrolled in nursing at a Junior College. Method: The data were collected from questionnaires filled out by 312 nursing students in two schools at J and I city from March 7-11, 2011. Data were analyzed using the SPSS/WIN18 program. Result: Self-esteem and adaptation to school life were higher than previous advanced research showed, self-efficacy was moderate and stress to school life was lower than other studies. School adaptation level was related to satisfaction of friendship, school life and the nursing program. The subjects who have chosen nursing by themselves and male students scored higher in their school adaptation. The greatest factors affecting adaptation to school life were satisfaction of school life and stress respectively. Conclusion: Inpre-admission, enough information about nursing school life through experience of previous students must be given. Then, a school adaptation program which incorporates counseling and mentoring should be provided for supporting understanding of school life.

• 대한원격탐사학회:학술대회논문집
• /
• 대한원격탐사학회 2007년도 Proceedings of ISRS 2007
• /
• pp.33-36
• /
• 2007

We have persistently constructed gridded products of surface wind/wind stress over the world ocean using satellite scatterometer (ERS and Qscat). They are available for users as the Japanese Ocean Flux data sets with Use of Remote sensing Observation (J-OFURO) data together with heat flux components. Recently, a new version data of the Qscat/SeaWinds based on improved algorithm for rain flag and high wind-speed range have been delivered, and allowed us to reconstruct gridded product with higher spatial resolution. These products are validated by comparisons with in-situ measurement data by mooring buoys such as TAO/TRITON, NDBC and the Kuroshio Extension Observation (KEO) buoys, together with numerical weather prediction model products such as the NCEP-1 and 2. Results reveal that the new product has almost the same magnitude in mean difference as the previous version of Qscat product and much smaller than the NCEP-1 and 2. On the other hand, it is slightly larger root-mean-square (RMS) difference than the previous one and NCEPs for the comparison using the KEO buoy data. This may be due to the deficit of high wind speed data in the buoy measurement. The high resolution product, together with sea surface temperature (SST) one, is used to examine a new type of relationship between the lower atmosphere and upper ocean in the Kuroshio Extension region.

• 대한기계학회논문집
• /
• 제17권1호
• /
• pp.78-89
• /
• 1993

본 연구에서는 Gillis 이론의 이와같은 단점을 보완하기 위하여 Gillis에 의 하여 제시된 수정운동량 보존법칙과 Hawkyard에 의하여 제시된 에너지보존법칙을 일반 화한 수정에너지보존법칙을 동시에 고려하여 재료의 동적항복응력을 결정할 수 있으며, 봉충격시험편의 충돌완료 후의 변형형상간의 관계를 고려할 수 있는 이론을 제시하였 다. 또한 기존의 실험결과로부터 제시된 이론의 타당성을 분석하였으며, 시험편의 변형형상의 측정오차가 동적항복응력의 결정에 미치는 영향을 분석하였다. 한편 압 축공기를 이용한 시험편 가속정치에 의하여 봉충격시험을 수행하여 괘삭황동(free -cutting brass)의 고변형률속도하에서의 변형특성과 동적항복응력을 결정하였다.

• Nuclear Engineering and Technology
• /
• 제49권4호
• /
• pp.838-849
• /
• 2017

This paper proposes penalty factor equations that take into consideration the weld strength over-match given in the classified form similar to the revised equations presented in the Code Case N-779 via cyclic elastic-plastic finite element analysis. It was found that the $K_e$ analysis data reflecting elastic follow-up can be consolidated by normalizing the primary-plus-secondary stress intensity ranges excluding the nonlinear thermal stress intensity component, $S_n$ to over-match degree of yield strength, $M_F$. For the effect of over-match on $K_n{\times}K_{\nu}$, dispersion of the $K_n{\times}K_{\nu}$ analysis data can be sharply reduced by dividing total stress intensity range, excluding local thermal stresses, $S_{p-lt}$ by $M_F$. Finally, the proposed equations were applied to the weld between the safe end and the piping of a pressurizer surge nozzle in pressurized water reactors in order to calculate a cumulative usage factor. The cumulative usage factor was then compared with those derived by the previous $K_e$ factor equations. The result shows that application of the proposed equations can significantly reduce conservatism of fatigue assessment using the previous $K_e$ factor equations.

• 한국지진공학회:학술대회논문집
• /
• 한국지진공학회 2002년도 춘계 학술발표회 논문집
• /
• pp.12-19
• /
• 2002

A high frequency level of Fourier amplitude relates with stress drop and seismic moment. When we can not use this relation owing to absence of digital earthquake data, stress drop and seismic moment can be determined from Peak Ground Velocity(PGV) and felt area. We have qualitatively evaluated the seismic characteristics using PGV, and Magnitude from the well determined felt area in seismological records of Korea(1978~2001) by Korea Meteorological Administration(KMA). Observed relations between felt area and magnitude in the Korean Peninsula are explained by attenuation(Q), and stress drops comparing with the previous researches on stress parameter. This results are preliminary work for the study of stress parameter using the relationship of high frequency lavel, PGV, and felt area.