• Smart Structures and Systems
• /
• v.4 no.5
• /
• pp.583-603
• /
• 2008

In this study, a real-time damage detection method using output-only acceleration signals and artificial neural networks (ANN) is developed to monitor the occurrence of damage and the location of damage in structures. A theoretical approach of an ANN algorithm that uses acceleration signals to detect changes in structural parameters in real-time is newly designed. Cross-covariance functions of two acceleration responses measured before and after damage at two different sensor locations are selected as the features representing the structural conditions. By means of the acceleration features, multiple neural networks are trained for a series of potential loading patterns and damage scenarios of the target structure for which its actual loading history and structural conditions are unknown. The feasibility of the proposed method is evaluated using a numerical beam model under the effect of model uncertainty due to the variability of impulse excitation patterns used for training neural networks. The practicality of the method is also evaluated from laboratory-model tests on free-free beams for which acceleration responses were measured for several damage cases.

• Wind and Structures
• /
• v.24 no.2
• /
• pp.119-144
• /
• 2017

The traditional method for the simulation of high Reynolds number (Re) effects on wind loads on cooling tower models in wind tunnels focuses only on the mean wind pressure distribution. Based on observed effects of some key factors on static/dynamic flow characteristics around cooling towers, the study reported in this paper describes a comprehensive simulation method using both mean and fluctuating wind pressure distributions at high Re as simulation targets, which is indispensable for obtaining the complete full-scale wind effects in wind tunnels. After being presented in this paper using a case study, the proposed method is examined by comparing the full covariance matrices and the cross-spectral densities of the simulated cases with those of the full-scale case. Besides, the cooling tower's dynamic structural responses obtained using the simulated wind pressure fields are compared with those obtained by using the full-scale one. Through these works, the applicability and superiority of the proposed method is validated.

• Journal of Korean Academy of Nursing
• /
• v.30 no.1
• /
• pp.29-38
• /
• 2000

To determine whether personal history of lactation in premenopausal women influence bone mineral density, a cross-sectional study was conducted. One hundred eighty-four premenopausal women were selected from women who had been checked for bone mineral density by dual energy x-ray absortiometry in lumbar spine, femoral neck, Ward's triangle, and trochanteric site at general hospitals in Seoul and Pusan. They completed a questionnaire including life style factors and reproductive history. In the data analysis, Pearson correlation coefficients were used to test any association between individual variables and bone mineral density and a statistical comparisons between long term lactation(>24 months) and short term lactation(<24 months) were made by one way analysis of covariance. The results were summarized as follows: 1) There was no significant difference in the bone mineral density of the lumbar vertebrae in premenopausal women between the long term lactation group(>24months) and the short term lactation group(<24months). 2) There was no significant difference in the bone mineral density of the femur neck, Ward's triangle, and trochanteric site in premenopausal women between the long term lactation group (>24months) and the short term lactation group (<24months). Considering these results, we suggest prospective studies that measure bone mineral density before and after, in addition to those during lactation. We also suggest the further study with premenopausal women less than 35 who have achieved peak adult bone mass.

• The Journal of Engineering Geology
• /
• v.3 no.1
• /
• pp.51-61
• /
• 1993

Restricted maximum likelihood(RML) method was used to determine the parameters of generalized covariance, and universal krigig with RML was applied to estimate a groundwater level distribution of nonstationarv random function. Universal kriging with RML was compared to IRF-k with weighted least squares method for the comparison of their accuracies. Cross validation shows that two methods have nearly the same ability for the estimation of groundwater levels. Scattergram of estimates versus true values and contour maps of groundwater levels have nearly the same results. The reason why two methods produced the same results is thought to be the non-Gaussian distribution and the snaall number of sample data.

• Nuclear Engineering and Technology
• /
• v.53 no.3
• /
• pp.715-731
• /
• 2021

Uncertainties are calculated for pressurized water reactor (PWR) spent nuclear fuel (SNF) characteristics. The deterministic code STREAM is currently being used as an SNF analysis tool to obtain isotopic inventory, radioactivity, decay heat, neutron and gamma source strengths. The SNF analysis capability of STREAM was recently validated. However, the uncertainty analysis is yet to be conducted. To estimate the uncertainty due to nuclear data, STREAM is used to perturb nuclear cross section (XS) and resonance integral (RI) libraries produced by NJOY99. The perturbation of XS and RI involves the stochastic sampling of ENDF/B-VII.1 covariance data. To estimate the uncertainty due to modeling parameters (fuel design and irradiation history), surrogate models are built based on polynomial chaos expansion (PCE) and variance-based sensitivity indices (i.e., Sobol' indices) are employed to perform global sensitivity analysis (GSA). The calculation results indicate that uncertainty of SNF due to modeling parameters are also very important and as a result can contribute significantly to the difference of uncertainties due to nuclear data and modeling parameters. In addition, the surrogate model offers a computationally efficient approach with significantly reduced computation time, to accurately evaluate uncertainties of SNF integral characteristics.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.48 no.6
• /
• pp.442-446
• /
• 2003

The Gene action for eight quantitative characters related to the plant type was estimated using diallel cross among three different plant types of sesame (Sesamum indicum L.) in 2001. The parental varieties used for diallel cross were Ahnnam and Yangbaeck as indeterminate type, ksan22 as semi-determinate type, and dt-45 and Suwon131 as determinate type. In variance and covariance analysis (Wr-Vr) for eight characters the mean square of array except for capsule length, 1,000 seed weight were significant, which suggest that varieties involved in diallel set cross may have epitasis. Complete dominance was observed in the flowering periods, and ratio of matured grains while partial dominance was observed in the plant height, no. of capsules per plant, and no. of branch per plant. Broad sense heritability for flowering periods, plant height, no. of capsules per plant, and no. of branch per plant ranged from 0.91 to 0.99. Narrow sense heritability for flowering periods, capsule length, ratio of matured grain, 1,000 seed eight were 0.18 to 0.34, and plant height, no. of capsules per plant and no. of branch per plant were ranged 0.77 to 0.81.

• Environmental Analysis Health and Toxicology
• /
• v.29
• /
• pp.12.1-12.8
• /
• 2014

Objectives Cohort studies of associations between air pollution and health have used exposure prediction approaches to estimate individual-level concentrations. A common prediction method used in Korean cohort studies is ordinary kriging. In this study, performance of ordinary kriging models for long-term particulate matter less than or equal to $10{\mu}m$ in diameter ($PM_{10}$) concentrations in seven major Korean cities was investigated with a focus on spatial prediction ability. Methods We obtained hourly $PM_{10}$ data for 2010 at 226 urban-ambient monitoring sites in South Korea and computed annual average $PM_{10}$ concentrations at each site. Given the annual averages, we developed ordinary kriging prediction models for each of the seven major cities and for the entire country by using an exponential covariance reference model and a maximum likelihood estimation method. For model evaluation, cross-validation was performed and mean square error and R-squared ($R^2$) statistics were computed. Results Mean annual average $PM_{10}$ concentrations in the seven major cities ranged between 45.5 and $66.0{\mu}g/m^3$ (standard deviation=2.40 and $9.51{\mu}g/m^3$, respectively). Cross-validated $R^2$ values in Seoul and Busan were 0.31 and 0.23, respectively, whereas the other five cities had $R^2$ values of zero. The national model produced a higher cross-validated $R^2$ (0.36) than those for the city-specific models. Conclusions In general, the ordinary kriging models performed poorly for the seven major cities and the entire country of South Korea, but the model performance was better in the national model. To improve model performance, future studies should examine different prediction approaches that incorporate $PM_{10}$ source characteristics.

• Asian-Australasian Journal of Animal Sciences
• /
• v.20 no.2
• /
• pp.160-165
• /
• 2007

Dispersion parameters for the number of piglets born alive were estimated using a repeatability and random regression model. Six sow breeds/lines were included in the analysis: Swedish Landrace, Large White and both crossbred lines between them, German Landrace and their cross with Large White. Fixed part of the model included sow genotype, mating season as month-year interaction, parity and weaning to conception interval as class effects. The age at farrowing was modelled as a quadratic regression nested within parity. The previous lactation length was fitted as a linear regression. Random regressions for parity on Legendre polynomials were included for direct additive genetic, permanent environmental, and common litter environmental effects. Orthogonal Legendre polynomials from the linear to the cubic power were fitted. In the repeatability model estimate of heritability was 0.07, permanent environmental effect as ratio was 0.04, and common litter environmental effect as ratio was 0.01. Estimates of genetic parameters with the random regression model were generally higher than in the repeatability model, except for the common litter environmental effect. Estimates of heritability ranged from 0.06 to 0.10. Permanent environmental effect as a ratio increased along a trajectory from 0.03 to 0.11. Magnitudes of common litter effect were small (around 0.01). The eigenvalues of covariance functions showed that between 7 and 8 % of genetic variability was explained by individual genetic curves of sows. This proportion was mainly covered by linear and quadratic coefficients. Results suggest that the random regression model could be used for genetic analysis of litter size.

• Journal of Korean Academy of Nursing
• /
• v.28 no.2
• /
• pp.510-518
• /
• 1998

It was assumed that the maternal identity in primi-gravida is one of the most attribute of the motherhood, that is not biological but cognitive phenomena, appears active process as intelligent human being. The purposes of this study were that the identification the cognitive structure and the influencing factors of the maternal identity in primi-gravida. Theoretical framework in this study, maternal identity in primi-gravida was constructed as a cognitive output, has the cognitive structure of cognitive-perceptual factor, cognitive-behavioral factor, and cognitive-emotional factor. Influencing factors of maternal identity was constructed as a cognitive input, which were pregnancy related perceptions (pregnancy intention, minor discomfort, value of motherhood), interpersonal relationship(relationship with mother, relationship with husband, relationship with social network), preparation to motherhood(maternal knowledge, antenatal self care), and biological factor (gestation period). This study was the descriptive correlational research design, was done from the 3rd January to the 15th March 1996, and the research subjects were selected conviniently 226 the primi-gravida during the gestation period, data collection method was self reported questionnaire cross-sectionally. Descriptive data analysis was done by SAS PC$^{+}$, testing the hypothetical model was done by covariance structural analysis using LISREL 8.03 program. The result of the hypothesis testing, the value of motherhood(y=.650, T=4.26) the maternal knowledge (y=.137, T=2.030), the gestation period( y=.113, T=2.621), showed significant causal effect on the maternal identity in primi-gravida. In conclusion, the maternal identity in primi-gravida had interrelated cognitive structure consist of perceptual, behavioral, and emotional factors. Significant causal factors influencing the maternal identity were value identified. It seems to contribute toward the understanding the characteristics of the maternal identity as a cognitive domains that has been regarded highly abstract concept, so has not been validated empirically.y.

• Asian Pacific Journal of Cancer Prevention
• /
• v.14 no.6
• /
• pp.3799-3804
• /
• 2013

Background: Colorectal cancer is the second most common cancer in Malaysia. The prognosis of the disease is excellent if detected at an early stage, but the majority of Malaysian patients present at late stages. We aimed to assess the awareness of cancer warning signs and anticipated delay in help-seeking as possible contributors to this phenomenon. Materials and Methods: A population-based cross-sectional survey using the Colorectal Cancer Awareness Measure was initiated in Perak, Malaysia. A total of 2,379 respondents aged 18 years and above were recruited using a multi-stage sampling in five locations. Analysis of covariance was used to examine independent sociodemographic predictors of scores for symptom awareness. Results: Younger age, being female, a higher education, and higher income were significantly associated with better scores for both recall and recognition of warning symptoms. Among the ethnic groups, Malays had better recognition of symptoms whereas Chinese recalled the most symptoms. Passing bloody stool was associated with the least anticipated delay and unexplained anal pain had the highest anticipated delay. Conclusions: The level of awareness across all ethnicities in Malaysia is generally low, especially among minorities. Targeted public education, which is culturally and linguistically appropriate, should be developed to encourage early help-seeking and improve clinical outcomes.