• Journal of the Korea Concrete Institute
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• v.19 no.2
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• pp.153-161
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• 2007

This paper investigates the lap splice performance of structural steel bars embedded in high performance fiber reinforced cementitious composite(HPFRCC) with various matrix ductilities. Matrix ductility is governed fiber type and fiber volume fraction. Fiber types were polypropylene(PP), polyethylene(PE) and hybrid fiber[polyethylene fiber+steel cord(PE+SC)]. The lap splice length$(l_d)$ was calculated according to the relevant ACI code requirements for reinforcing bars in normal concrete. As the result of tests, lap splice strength of HPFRCC using PE1.5 and hybrid fiber increased by up to $82{\sim}91$ percent more than that of concrete. Splice strength and energy absorption capacity of PE0.75+SC0.75 or PE1.5(fiber volume fraction 1.5%) specimen increased more than that of PP2.0(fiber volume fraction 2.0%) specimen. Therefore lap splice performance depends on fiber tensile strength and Young's modulus more than fiber volume fraction. Also, HPFRCC appear multiple crack and ductile postpeak behavior due to bridging of fiber in cementitious composite.

• Journal of Forest and Environmental Science
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• v.13 no.1
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• pp.114-133
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• 1997

Perforation plate was observed in 78 species(45 genera, 25 families) of Korean native hardwoods using SEM and it was divided into three types, i.e., simple, scalariform and multiple perforation plates, Based on occurance of these types, the species examined were classfied into the following six groups : (1) 60species(35 genera, 21 families) having exclusively simple perforation, (2) 5 species(2 genera, 1 families) having exclusively scalariform perforation plates, (3) 4 species(4 genera, 3 families) having simple and scalariform perforation plates, (4) 2 species(2 genera, 1 families) having simple and multiple perforation plates, (5) 5 species(3 genera, 3 families) having scalariform and multiple perforation plates and (6) 2 species(2 genera, 2 families) having simple, scalariform and multiple perforation plates. Mismatching perforation plates were found in two species of Betulaceae, Alnus hirsuta var. sibirica and Alnus hirsuta and peculiar substructure between the bars of the scalariform perforation plate was observed in Betulaceae, Betula davurica and Cercidiphyllaceae, Cerdiphyllum japonicum and the vestured perforation plate was found in Quercus aliena.

• The Journal of the Korea Contents Association
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• v.21 no.2
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• pp.215-226
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• 2021

The purpose of this study was to analyze the alcohol volume consumed and alcohol dependancy according to multiple rounds of drinking. Sectional data collected in 2012 as part of an International Alcohol Control Study were used, and 855 of 1,789 drinker aged 19 to 64 were conducted. The proportion of multiple rounds drinking were significantly higher in males(χ²=37.607, p<.001), students(χ²=52.466, p<.001), single(χ²=34.205, p<.001), smoking experience and stressed(χ²=40,09, p<.001; χ²=21.66, p<.001) among drinkers. In particular, the alcohol volume consumed of unmarried people, smokers, and stress groups were significantly higher than married people, non-smokers and no-stress group. The highest alcohol intake in the first, 2nd and third rounds was found in bars in the liquor trade (F=67.8g, p<0.001). The total alcohol intake increased as the number of rounds increased (F=209.993, p=0.001) and the number of drinkers who tested positive for alcohol dependency increased, using the tests RAPS4 and DSM-IV(F=129.836, p<0.001; F=94.669, p<0.001). The OR of alcohol dependancy in males was 2.3(95% CI: 1.745-3.057), unemployed was 3.2(95% CI: 1.053-9.838), smokers was 3.9(95% CI: 1.230-12.292), and stress group was 2.1(95% CI: 1.561-2.768) compared to females, employed, non-smokers, and no-stress group respectively. In conclusion, it suggests that those consuming multiple rounds drinking can become more vulnerable to alcohol harms due to its relation to smoking, stress and increased dependence on alcohol.

• Journal of the Korean Society of Safety
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• v.26 no.2
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• pp.32-35
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• 2011

Experimental studies were carried out in an explosion chamber to investigate the influences of multiple cylinder obstacles on local flame propagation. The chamber dimension is 235 mm in height with a $1,000{\times}950\;mm^2$ rectangular cross section and a large vent area of $1,000{\times}320\;mm^2$. Multiple cylinder bars with obstruction ratio of 30% were used. In order to examine the interaction between the propagating flames and the obstacles, temporally resolved flame front images were recorded by a high speed video camera. The propagation behaviour of local flame fronts around the left obstacle was analyzed in terms of two different methods such as the incremental burnt area divided by the flame front length and the average of the local propagation velocity determined at each point along the flame front. It was found that two methods give good consistency.

• Advances in concrete construction
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• v.8 no.4
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• pp.285-294
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• 2019

In the present paper, the fiber theory has been employed to model the reinforced concrete (RC) deep beams (DBs) considering the reinforcing steel bar-concrete interaction. To simulate numerically the behavior of materials, the uniaxial materials' constitutive laws have been employed for reinforcements and concrete and the bond stress-slip between the reinforcing steel bars and surrounding concrete are taken into account. Because of the high sensitivity of DBs to shear deformations, the Timoshenko beam theory has been applied. The shear stress-strain (S-SS) relationship has been defined by the modified compression field theory (MCFT) model. By modeling about 300 RC panels and employing a produced numerical database, a study has been carried out to show the sensitivity of the MCFT model. This is performed based on the multiple linear regression (MLR) models. The results of this research also illustrate how different parameters such as characteristic compressive strength of concrete, yield strength of reinforcements and the percentages of reinforcements in different directions get involved in the shear behavior of RC panels without applying complex theories. Based on the results obtained from the analysis of the MCFT S-SS model, a relatively simplified numerical S-SS model has been proposed. Application of the proposed S-SS model in modeling and analyzing the considered samples indicates that there is a good agreement between the simulated and the experimental test results. The comparison between the proposed S-SS model and the MCFT model indicates that in addition to the advantage of better accuracy, the main advantage of the proposed method is simplicity in application.

• Korean Journal of Adult Nursing
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• v.20 no.3
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• pp.395-405
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• 2008

Purpose: The purpose of this study was to develop a Web-based flash content for fighting spirit promotion and to test its effect on cancer patients' fighting spirit. Methods: The 15-minute long Web-based flash content was developed using the following 5 process: analysis, planning, development, program operation and evaluation stages and utilized the multiple edition and revision processes from December 2005 to August 2006. The evaluation was done by one group pretest-posttest design. Study subjects were 17 cancer patients undergoing chemotherapy. The group were received a 2-week intervention, a day weekly, and measured the variables at baseline, 4 weeks later. The study was performed from August 2006 to February 2007 at a cancer center in Korea. Fighting spirit was measured by Mini-MAC(Mental Adjustment to Cancer). Data was analysed by descriptive statistics and paired t-test using SAS 9.13 program. Results: On the Web-based flash content, there are 4 menu bars that consisted of cancer diagnosis, symptom management, stress management, and cancer survivorship. The study group revealed significantly more fighting spirit than pre-test(t=-3.04, p=.008). Conclusion: This Web-based flash content can be utilized in psychosocial interventions for promoting fighting spirit in patients with cancer.

• Journal of the Korean housing association
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• v.15 no.4
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• pp.65-74
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• 2004

As the advent of an aging society, housing for the elderly has been of great concern. Because the majority of the elderly prefers living in their own familiar homes rather than moving to new ones, this study is concerned with the ways use and maintenance of the existing houses from the viewpoint of their independent living. The data was analyzed with frequency, percentage, mean, correlation, and multiple regression by using the SPSS 10.0 for Windows. The findings from the study were: Needs for Affordance of interior design(AID) were required slightly above the average. Among the items of AID, physiological maintenance was the most demanding, and social facilitation, behavioral facilitation, and perceptual maintenance were sequentially followed in the level of needs. The elements that should be considered in housing environment plans for the elderly household ire: (a) use of slip-proof tiles for the floor of the bathroom, (b) installation of safety bars in the bathroom, and (c) installation of emergency buttons. It also turned out that educational levels and health status were the most significant factors on the needs for AID.

• Computers and Concrete
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• v.16 no.5
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• pp.759-774
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• 2015

This study simulates the flexural behavior of ultra-high-performance fiber-reinforced concrete (UHPFRC) beams reinforced with steel and glass fiber-reinforced polymer (GFRP) rebars. For this, micromechanics-based modeling was first carried out on the basis of single fiber pullout models considering inclination angle. Two different tension-softening curves (TSCs) with the assumptions of 2-dimensional (2-D) and 3-dimensional (3-D) random fiber orientations were obtained from the micromechanics-based modeling, and linear elastic compressive and tensile models before the occurrence of cracks were obtained from the mechanical tests and rule of mixture. Finite element analysis incorporating smeared crack model was used due to the multiple cracking behaviors of structural UHPFRC beams, and the characteristic length of two times the element width (or two times the average crack spacing at the peak load) was suggested as a result of parametric study. Analytical results showed that the assumption of 2-D random fiber orientation is appropriate to a non-reinforced UHPFRC beam, whereas the assumption of 3-D random fiber orientation is suitable for UHPFRC beams reinforced with steel and GFRP rebars due to disorder of fiber alignment from the internal reinforcements. The micromechanics-based finite element analysis also well predicted the serviceability deflections of UHPFRC beams with GFRP rebars and hybrid reinforcements.

• Journal of the East Asian Society of Dietary Life
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• v.16 no.5
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• pp.623-633
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• 2006

This study surveyed the selection attributes and degree of satisfaction among Japanese restaurant customers by conducting frequency analysis on the data. Among all types of Japanese restaurants customers selected sushi bars the most (48.2%), and they considered taste (73.9%), price (34.8%), and service (22.2%) to be very important. When eating at Japanese restaurants, satisfaction differences among sanitation (p<0.05), price (p<0.05), and unique design (p<0.1) each had a significant difference with F values of 3.313, 3.208, and 2,702, respectively. factor analysis of the effect of selection attributes on Japanese restaurant performance revealed three factors; image, service, and food. Their combined satisfaction was 61.41%, and each of these three factors showed a Cronbach's ${\alpha}$ value of 0.744, 0.739, and 0.623 in the reliability analysis, respectively, thus demonstrating the overall level of reliability. Multiple regression analysis showed that increased overall satisfaction of Japanese food was related to the satisfaction levels of food and service, and not to that of surrounding satisfaction.

• Journal of Korean Association for Spatial Structures
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• v.23 no.3
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• pp.87-94
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• 2023

Chloride is one of the most common threats to reinforced concrete (RC) durability. Alkaline environment of concrete makes a passive layer on the surface of reinforcement bars that prevents the bar from corrosion. However, when the chloride concentration amount at the reinforcement bar reaches a certain level, deterioration of the passive protection layer occurs, causing corrosion and ultimately reducing the structure's safety and durability. Therefore, understanding the chloride diffusion and its prediction are important to evaluate the safety and durability of RC structure. In this study, the chloride diffusion coefficient is predicted by machine learning techniques. Various machine learning techniques such as multiple linear regression, decision tree, random forest, support vector machine, artificial neural networks, extreme gradient boosting annd k-nearest neighbor were used and accuracy of there models were compared. In order to evaluate the accuracy, root mean square error (RMSE), mean square error (MSE), mean absolute error (MAE) and coefficient of determination (R2) were used as prediction performance indices. The k-fold cross-validation procedure was used to estimate the performance of machine learning models when making predictions on data not used during training. Grid search was applied to hyperparameter optimization. It has been shown from numerical simulation that ensemble learning methods such as random forest and extreme gradient boosting successfully predicted the chloride diffusion coefficient and artificial neural networks also provided accurate result.