• Geomechanics and Engineering
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• v.28 no.6
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• pp.599-611
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• 2022

Tendon reinforced cemented soil is applied extensively in foundation stabilisation and improvement, especially in areas with soft clay. To solve the deterioration problem led by steel corrosion, the glass fiber-reinforced polymer (GFRP) tendon is introduced to substitute the traditional steel tendon. The interface bond strength between the cemented soil matrix and GFRP tendon demonstrates the outstanding mechanical property of this composite. However, the lack of research between the influence factors and bond strength hinders the application. To evaluate these factors, back propagation neural network (BPNN) is applied to predict the relationship between them and bond strength. Since adjusting BPNN parameters is time-consuming and laborious, the particle swarm optimisation (PSO) algorithm is proposed. This study evaluated the influence of water content, cement content, curing time, and slip distance on the bond performance of GFRP tendon-reinforced cemented soils (GTRCS). The results showed that the ultimate and residual bond strengths were both in positive proportion to cement content and negative to water content. The sample cured for 28 days with 30% water content and 50% cement content had the largest ultimate strength (3879.40 kPa). The PSO-BPNN model was tuned with 3 neurons in the input layer, 10 in the hidden layer, and 1 in the output layer. It showed outstanding performance on a large database comprising 405 testing results. Its higher correlation coefficient (0.908) and lower root-mean-square error (239.11 kPa) were obtained compared to multiple linear regression (MLR) and logistic regression (LR). In addition, a sensitivity analysis was applied to acquire the ranking of the input variables. The results illustrated that the cement content performed the strongest influence on bond strength, followed by the water content and slip displacement.

• Journal of Preventive Medicine and Public Health
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• v.56 no.5
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• pp.458-466
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• 2023

Objectives: The association between long sleep duration and mortality is frequently attributed to the confounding influence of comorbidities. Nevertheless, past efforts to account for comorbidities have yielded inconsistent outcomes. The objective of this study was to evaluate this relationship using a large prospective cohort in Korea. Methods: The study included 114 205 participants from the Health Examinees Study, who were followed for a median of 9.1 years. A composite comorbidity score was developed to summarize the effects of 21 diseases. Using Cox proportional hazards regression, hazard ratios (HRs) and 95% confidence intervals (CIs) for all-cause, cancer, and cardiovascular mortality associated with sleep duration were estimated. These estimates were adjusted for socio-demographic factors, lifestyle factors, body mass index, and comorbidity score. Additionally, a stratified analysis by subgroups with and without comorbidities was conducted. Results: Throughout the follow-up period, 2675 deaths were recorded. After all adjustments, an association was observed between a sleep duration of 8 hours or more and all-cause mortality (HR, 1.10; 95% CI, 1.01 to 1.20). However, no such association was detected in the stratified analysis for the subgroups based on comorbidity status. Conclusions: Long sleep duration was found to be associated with all-cause mortality among Koreans, even after adjusting for comorbidities. Additional studies are required to explore the mechanism underlying the association between sleep duration and major causes of mortality.

• Current Optics and Photonics
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• v.8 no.4
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• pp.406-415
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• 2024

The major error factors that degrade the efficiency of coherent beam combining (CBC) are numerically studied in a comprehensive manner, paying particular attention to phase, tip-tilt, polarization angle, and beam quality. The power in the bucket (PIB), normalized to the zero-error PIB, is used as a figure of merit to quantify the effect of each error factor. To maintain a normalized PIB greater than or equal to 95% in a 3-channel CBC configuration, the errors in phase, tip-tilt, and polarization angle should be less than 1.06 radians, 1.25 ㎛, and 1.06 radians respectively, when each of the three parameters is calculated independently with the other two set to zero. In a worst-case scenario of the composite errors within the parameter range for the independent-95%-normalized-PIB condition, the aggregate effect would reduce the normalized PIB to 83.8%. It is noteworthy that the PIB performances of a CBC system, depending on phase and polarization-angle errors, share the same characteristic feature. A statistical approach for each error factor is also introduced, to assess a CBC system with an extended number of channels. The impact of the laser's beam-quality factor M² on the combining efficiency is also analyzed, based on a super-Gaussian beam. When M² increases from 1 to 1.3, the normalized PIB is reduced by 2.6%, 11.8%, 12.8%, and 13.2% for a single-channel configuration and 3-, 7-, and 19-channel CBC configurations respectively. This comprehensive numerical study is expected to pave the way for advances in the evaluation and design of multichannel CBC systems and other related applications.

• Composites Research
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• v.30 no.1
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• pp.71-76
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• 2017

The purpose of this study was to predict the long-term performance using the interlaminar shear strength of carbon fiber/epoxy composites exposed to environmental factors. Interlaminar shear specimens, manufactured by the filament winding method, were exposed to the conditions of drying at $50^{\circ}C$, $70^{\circ}C$, and $100^{\circ}C$ and of immersion at $25^{\circ}C$, $50^{\circ}C$, and $70^{\circ}C$ for up to 3000 hours, respectively. According to the results, the interlaminar shear strength did not vary significantly with the exposure time for the drying at $50^{\circ}C$ and $70^{\circ}C$, but it increased somewhat for the drying at $100^{\circ}C$ due to the post curing as the exposure time increased. The interlaminar shear strength of the specimens exposed to the immersion at $25^{\circ}C$ did not change significantly at the beginning of exposure, but it decreased with the exposure time and the degree of decrease increased as the environmental temperature increased. The linear regression equations for the environmental temperatures were obtained from the interlaminar shear strength of the specimens exposed to the immersion for up to 3000 hours. Using these linear regression equations, the interlaminar shear strength was estimated to be within 5.5% of the measured value at $25^{\circ}C$ and $50^{\circ}C$, and 2.3% of the measured value at $70^{\circ}C$. Therefore, the proposed performance prediction procedures can predict well the long-term interlaminar shear strength of carbon fiber/epoxy composites exposed to environmental factors.

• Journal of Convergence for Information Technology
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• v.11 no.3
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• pp.54-67
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• 2021

This study is a secondary data study that analyzes the factors affecting the quality of life of the elderly with metabolic syndrome and the elderly with metabolic syndrome with osteoporosis using data from the 7th year of the National Health and Nutrition Survey (2018). The subjects of this study were 639 patients with metabolic syndrome and 161 patients with metabolic syndrome with osteoporosis. For data analysis, the composite sample Rao-Scott χ2 test, general linear model t-test, and regression model were used. As a result of the study, the factors that lowered the quality of life of metabolic syndrome were age, cohabitation, strength training, subjective health status, activity restriction, body mass index and depression, and the explanatory power was 50.4% (F=515.96, p<.001). In metabolic syndrome with osteoporosis, age, subjective health status, activity restriction, and stress were the factors that lowered the quality of life, and the explanatory power was 48.6% (F=10.42, p<.001). Based on these results, it is necessary to develop and provide an intensive multidisciplinary program for the elderly with metabolic syndrome accompanied by osteoporosis to solve the problem of activity restrictions and manage stress reduction through positive acceptance of health status, instrumental and social support, and caring support.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.363-364
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• 2002

Although the factors that cause the failure of orthopedic implants were not clearly determined, it was reported that the shapes of wear debris affect the tribological behavior of artificial implant. Many researches were conducted to examine the wear mechanism by debris but the role of debris shape in inflammatory reaction remains unclear. To observe the debris shape by addition of reinforcement, carbon nanotubes ( CNTs ) were added to ultra high molecular weight polyethylene ( UHMWPE ) to investigate the reinforcement effect of CNTs. CNTs which have a diameter of about 10-50 nm, while their length is about 3-5 nm were produced by the catalytic decomposition of the acetylene gas using a tube furnace. Plate on disc type wear test were performed to evaluate the tribological performance of UHMWPE composites reinforced with CNTs in lubricating condition ( bovine serum ). The wear losses of CNT added UHMWPE in bovine serum were significantly reduced. Worn surface and wear debris of UHMWPE with CNTs and without CNTs were compared to investigate the reinforcement effect of CNT on tribological behavior.

• Convergence Security Journal
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• v.12 no.5
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• pp.71-77
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• 2012

Expenses in the form of personnel expenses in the past, in modern times, machine guards to gradually transition has been. This is because the machine guard is more efficient than personnel expenses. But due to false alarms, despite the high expectations of the effects of electronic security in the operation of the electronic security system due to factors that hinder the development of machine guards growth slows. Defect removal aspects of this paper, using IPA (Importance Performance Analysis) techniques to study the operation of electronic security systems and its importance in the development of machine guards, look at how high the technical aspects of electronic security systems composite type of malfunction to minimize crime sensor are presented.

• Structural Engineering and Mechanics
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• v.47 no.5
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• pp.623-641
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• 2013

The fiber-reinforced polymer (FRP) composite panel, with the benefits of light weight, high strength, good corrosion resistance, and long-term durability, has been considered as one of the prosperous alternatives for structural retrofits and replacements. Although with these advantages, a further application of FRPs in bridge engineering may be restricted, and that is partly due to some unsatisfied thermal performance observed in recent studies. In this regard, Kansas Department of Transportation (DOT) conducted a field monitoring program on a bridge with glass FRP (GFRP) honeycomb hollow section sandwich panels. The temperatures of the panel surfaces and ambient air were measured from December 2002 to July 2004. In this paper, the temperature distributing behaviors of the panels are firstly demonstrated and discussed based on the field measurements. Then, a numerical modeling procedure of temperature fields is developed and verified. This model is capable of predicting the temperature distributions with the local environmental conditions and material's thermal properties. Finally, a parametric study is employed to examine the sensitivities of several temperature influencing factors, including the hollow section configurations, environmental conditions, and material properties.

• Journal of Periodontal and Implant Science
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• v.41 no.6
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• pp.302-308
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• 2011

Purpose: The emergence profile concept of an implant restoration is one of the most important factors for the esthetics and health of peri-implant soft tissue. This paper reports on two cases of gingival recontouring by the fabrication of a provisional implant restoration to produce an optimal emergence profile of a definitive implant restoration. Methods: After the second surgery, a preliminary impression was taken to make a soft tissue working cast. A provisional crown was fabricated on the model. The soft tissue around the implant fixture on the model was trimmed with a laboratory scalpel to produce the scalloped gingival form. Light curing composite resin was added to fill the space between the provisional crown base and trimmed gingiva. After 4 to 6 weeks, the final impression was taken to make a definitive implant restoration, where the soft tissue and tooth form were in harmony with the adjacent tooth. Results: At the first insertion of the provisional restoration, gum bleaching revealed gingival pressure. Four to six weeks after placing the provisional restoration, the gum reformed with harmony between the peri-implant gingiva and adjacent dentition. Conclusions: Gingival recontouring with a provisional implant restoration is a non-surgical and non-procedure-sensitive method. The implant restoration with the optimal emergence profile is expected to provide superior esthetic and functional results.

• Steel and Composite Structures
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• v.16 no.2
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• pp.135-156
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• 2014

In this research the effect of seismic design level as a practical approach for progressive collapse mitigation and reaching desired structural safety against it in seismically designed concentric braced frame buildings was investigated. It was achieved by performing preliminary and advanced progressive collapse analysis of several split-X braced frame buildings, designed for each seismic zone according to UBC 97 and by applying various Seismic Load Factors (SLFs). The outer frames of such structures were studied for collapse progression while losing one column and connected brace in the first story. Preliminary analysis results showed the necessity of performing advanced element loss analysis, consisting of Vertical Incremental Dynamic Analysis (VIDA) and Performance-Based Analysis (PBA), in order to compute the progressive collapse safety of the structures while increasing SLF for each seismic zone. In addition, by sensitivity analysis it became possible to introduce the equation of structural safety against progressive collapse for concentrically braced frames as a function of SLF for each seismic zone. Finally, the equation of progressive collapse safety as a function of bracing member capacity was presented.