• Geomechanics and Engineering
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• v.38 no.6
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• pp.571-581
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• 2024

Concrete linings in tunnels constructed by drilling and blasting such as NATM serve as a secondary support structure. However, these linings can face unexpected earth pressures if the primary support deteriorates or if ground conditions become unfavorable. It is crucial to determine the loosening earth pressure that allows the lining to maintain its structural integrity and prevent damage caused by this pressure. This study proposes a numerical model for simulating the trapdoor test and developing a method for calculating the loosening earth pressure. The discrete element method (DEM) was employed to describe the soil characteristics around the tunnel. Using this numerical model, a sequence of experimental trapdoor steps was simulated, and the loosening earth pressure was analyzed. Contact parameters were calibrated based on an analysis of a triaxial compression test. The reliability of the developed model was confirmed through a comparison between simulation results and laboratory test findings. The model was used to calculate the contact force applied to the trapdoor plate and to assess the settlement of soil particles. Furthermore, the model accounted for the soil-arching effect, which effectively redistributes the load to the surrounding areas. The proposed model can be applied to analyze the tunnel's cross-sectional dimensions and design stability under various ground conditions.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.16
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• pp.6811-6817
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• 2014

Background: Breast cancer risk prediction models are widely used in clinical practice. They should be useful in identifying high risk women for screening in limited-resource countries. However, previous models showed poor performance in derived and validated settings. Therefore, we aimed to develop and validate a breast cancer risk prediction model for Thai women. Materials and Methods: This cross-sectional study consisted of derived and validation phases. Data collected at Ramathibodi and other two hospitals were used for deriving and externally validating models, respectively. Multiple logistic regression was applied to construct the model. Calibration and discrimination performances were assessed using the observed/expected ratio and concordance statistic (C-statistic), respectively. A bootstrap with 200 repetitions was applied for internal validation. Results: Age, menopausal status, body mass index, and use of oral contraceptives were significantly associated with breast cancer and were included in the model. Observed/expected ratio and C-statistic were 1.00 (95% CI: 0.82, 1.21) and 0.651 (95% CI: 0.595, 0.707), respectively. Internal validation showed good performance with a bias of 0.010 (95% CI: 0.002, 0.018) and C-statistic of 0.646(95% CI: 0.642, 0.650). The observed/expected ratio and C-statistic from external validation were 0.97 (95% CI: 0.68, 1.35) and 0.609 (95% CI: 0.511, 0.706), respectively. Risk scores were created and was stratified as low (0-0.86), low-intermediate (0.87-1.14), intermediate-high (1.15-1.52), and high-risk (1.53-3.40) groups. Conclusions: A Thai breast cancer risk prediction model was created with good calibration and fair discrimination performance. Risk stratification should aid to prioritize high risk women to receive an organized breast cancer screening program in Thailand and other limited-resource countries.

• Computers and Concrete
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• v.25 no.6
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• pp.497-507
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• 2020

This paper presents a numerical method for evaluating fire performance of prestressed concrete (PC) T shaped bridge girders under combined effect of structural loading and hydrocarbon fire exposure conditions. A numerical model, developed using the computer program ANSYS, is employed to investigate fire response of PC T shaped bridge girders by taking into consideration structural inherent parameters, namely; arrangement of prestressing strands with in the girder section, thickness of concrete cover over prestressing strands, effective degree of prestress and content of prestressing strands. Then, a sequential thermo-mechanical analysis is performed to predict cross sectional temperature followed by mechanical response of T shaped bridge girders. The validity of the numerical model is established by comparing temperatures, deflections and failure time generated from fire tests. Through numerical studies, it is shown that thickness of concrete cover and arrangement of prestressing strands in girder section have significant influence on the fire resistance of PC T shaped bridge girders. Increase in effective degree of prestress in strands with triangular shaped layout and content in prestressing strands can slow down the progression of deflections in PC T shaped bridge girder towards the final stages of fire exposure, to thereby preventing sudden collapse of the girder. Rate of deflection based failure criterion governs failure in PC T shaped bridge girders under most hydrocarbon fire exposure conditions. Structural inherent parameters incorporated into sectional configuration can significantly enhance fire resistance of PC bridge girders; thus mitigating fire induced collapse of these bridge girders.

• Asian Pacific Journal of Cancer Prevention
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• v.13 no.1
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• pp.295-300
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• 2012

Breast self-examination (BSE) is important for early diagnosis of breast cancer (BC). However, the majority of Turkish women do not perform regular BSE. We aimed to evaluate the effects of education level on the attitudes and behaviors of women towards BSE. A descriptive cross-sectional study was conducted on 413 women (20-59 years), divided into university graduates (Group I, n = 224) and high school or lower graduates (Group II, n = 189). They completed a 22-item scale assessing the knowledge level, attitudes and behaviors regarding BSE, and the Turkish version of the Champion's Revised Health Belief Model. A significantly higher number of women in Group II did not believe in early diagnosis of BC. A significantly higher number of Group I had conducted BSE at least once, and their BSE frequency was also significantly high. Moreover, a significantly lower number of Group I women considered themselves to not be at risk for BC and the scores for "perceived susceptibility" and "perceived barriers" were significantly higher. Logistic regression analysis identified the university graduate group to have a higher likelihood of performing BSE, by 1.8 times. Higher educational levels were positively associated with BSE performance. Overall, the results suggest that Turkish women, regardless of their education level, need better education on BSE. Consideration of the education level in women will help clinicians develop more effective educational programs, resulting in more regular practice and better use of BSE.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.113-116
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• 2008

In recent the construction of bridges having hollow sectional piers is gradually increasing since the hollow section is more effective than solid section in resistance against seismic load. It is, therefore, very important to understand the behavior of columns with hollow sections in seismic design. However, many past researches were concentrated only on the flexural deformability of them. In this study the shear characteristics of them have been studied with scale model tests. 7 models having different void and aspect ratios were designed and tested to investigate the effect of them on shear capacities. And then the validity of empirical equations to predict shear capacity was investigated compared with the test results. The test result 80 percent of the valid area of cross section should be adequate. And compared to the proposed four model the experimental shear capacities are in good agreement with the UCB.

• Journal of Dental Rehabilitation and Applied Science
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• v.35 no.2
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• pp.55-63
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• 2019

The aim of this article was to review various methods used to evaluate the accuracy of digital dental models. When evaluating the accuracy of digital models, the errors can be reduced by educating examiners and using artificial landmarks. The accuracy evaluation methods of digital dental models are divided into linear measurement, 2-dimensional cross-sectional analysis, and 3-dimensional best fit measurement. As the technology of scanners develops, many studies have been conducted to compare the accuracy of digital impression and conventional impression. According to improvement of scan technologies and development of 3-dimensional model analysis software, the ability to evaluate the accuracy of digital models is becoming more efficient. In this article, we describe the methods for evaluating the accuracy of a digital model and investigate effective accuracy analysis methods for each situation.

• Safety and Health at Work
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• v.13 no.2
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• pp.240-247
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• 2022

Background: Although insomnia and constipation are highly prevalent worldwide, studies examining a possible association between them are lacking. We examined the relationship between insomnia and constipation in shift workers who have a high prevalence of insomnia and other diseases. Methods: This study had a multicenter cross-sectional design and conducted using health examination data including self-reported questionnaires. In total, 12,879 and 4,650 shift workers were enrolled in Severance Hospital and Wonju Severance Hospital, respectively, during 2015-2017. Multivariate logistic regression models and subgroup analysis were performed in each center with the same protocol, using a common data model. Results: The mean age of the total population was 44.35 (standard deviation = 8.75); the proportion of males was 56.9%. Female sex, being underweight and non-smoker were strongly associated with an increased risk of constipation symptom (p < 0.001). Pooled odds ratios (ORs) were calculated using ORs of both centers with weights; there was a significant dose-response relationship (sub-threshold 1.76 [95% confidence interval [CI] 1.62-1.91]; moderate 2.28 [95% CI 2.01-2.60]; severe 4.15 [95% CI 3.18-5.41] in the final model, p for trend < 0.001). Subgroup analysis performed by stratifying sex and pooled ORs showed a similar trend to that of the entire group. Conclusion: We observed a strong correlation between insomnia and constipation in this population. Our findings may help in formulating guidelines and policies to improve quality of life in shift workers through the management of sleep quality and proper bowel function. This study is the first to report this relationship among people working in shifts.

• Journal of Preventive Medicine and Public Health
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• v.55 no.3
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• pp.297-306
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• 2022

Objectives: The incidence of cardiovascular disease (CVD) mortality is increasing in developing countries. This study aimed to decompose the socioeconomic inequality of CVD in Iran. Methods: This cross-sectional population-based study was conducted on 20 519 adults who enrolled in the Ardabil Non-Communicable Disease cohort study. Principal component analysis and multivariable logistic regression were used, respectively, to estimate socioeconomic status and to describe the relationships between CVD prevalence and the explanatory variables. The relative concentration index, concentration curve, and Blinder-Oaxaca decomposition model were used to measure and decompose the socioeconomic inequality. Results: The overall age-adjusted prevalence of CVD was 8.4% in northwest Iran. Multivariable logistic regression showed that older adults, overweight or obese adults, and people with hypertension and diabetes were more likely to have CVD. Moreover, people with low economic status were 38% more likely to have CVD than people with high economic status. The prevalence of CVD was mainly concentrated among the poor (concentration index, -0.077: 95% confidence interval, -0.103 to -0.060), and 78.66% of the gap between the poorest and richest groups was attributed to differences in the distribution of the explanatory variables included in the model. Conclusions: The most important factors affecting inequality in CVD were old age, chronic illness (hypertension and diabetes), marital status, and socioeconomic status. This study documented stark inequality in the prevalence of CVD, wherein the poor were more affected than the rich. Therefore, it is necessary to implement policies to monitor, screen, and control CVD in poor people living in northwest Iran.

• Advances in concrete construction
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• v.17 no.5
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• pp.285-292
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• 2024

In order to improve the mixing effect of slurry-foam during the preparation of foam concrete, this study takes an SK static mixer as the mixing device, establishes a three-dimensional physical model and a theoretical calculation model, and numerically simulates the effects of different parameters such as foam inlet angle and pipe inner diameter on the mixing of cement slurry and foam under the given boundary conditions, so as to optimize the structure of this mixing device. The results show that when the pipe diameter of the mixer is larger than 60 mm, the phenomenon of backflow occurs in the pipe, which affects the mixing effect. The smaller the pipe diameter, the shorter the distance required to stabilize the cross-sectional average density and density uniformity index. When the foam inlet angle is different, the average density and density uniformity index of the radial cross-section have the same rule of change along the length of the pipeline, and all of them tend to stabilize gradually. At Y = 0.5 m, the average density basically stabilizes at 964 kg/m³ and remains stable until the outlet. At Y = 0.6 m, the density uniformity index basically stabilizes above 0.995 and remains stable until the outlet. Except for the foam inlet position (Y = 0.04 m), the foam inlet angle has little effect on the cross-sectional average density and density uniformity index. Under the boundary conditions given in this study, a pipe diameter of 40 mm, a foam inlet angle of 90°, and a pipe length of 700 mm are the optimal geometries for the preparation of homogeneous foam concrete with a density of 964 kg/m³ in this static mixer.

• Journal of the Korean Geotechnical Society
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• v.40 no.4
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• pp.179-188
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• 2024

Nondestructive pile integrity tests are used to confirm the construction of drilled shafts as the foundation of many facilities. However, the safety of the foundation is determined only by the presence or absence of defects, and the location and scale of defects are not considered. In this study, we propose an analysis model for the lateral bearing capacity and section force connected building information modeling (BIM) by extracting the cross-sectional characteristics of the defect in piles and reviewing the safety of piles with defects. Defects at the top of piles had more effect on the change in the deflection of the pile head. Moreover, the decrease in the axial force-bending moment interaction diagram due to cross-sectional reduction increased the risk of destruction of the piles more than the change in the bending moments due to defects. The proposed method can help review the comprehensive safety of piles.