• Advances in materials Research
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• v.11 no.1
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• pp.75-90
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• 2022

In this paper, functionality of soft computing algorithms such as Group method of data handling (GMDH), Random forest (RF), Random tree (RT), Linear regression (LR), M5P, and artificial neural network (ANN) have been looked out to predict the compressive strength of concrete mixed with marble powder. Assessment of result suggests that, the overall performance of ANN based model gives preferable results over the different applied algorithms for the estimate of compressive strength of concrete. The results of coefficient of correlation were maximum in ANN model (0.9139) accompanied through RT with coefficient of correlation (CC) value 0.8241 and minimum root mean square error (RMSE) value of ANN (4.5611) followed by RT with RMSE (5.4246). Similarly, other evaluating parameters like, Willmott's index and Nash-sutcliffe coefficient value of ANN was 0.9458 and 0.7502 followed by RT model (0.8763 and 0.6628). The end result showed that, for both subsets i.e., training and testing subset, ANN has the potential to estimate the compressive strength of concrete. Also, the results of sensitivity suggest that the water-cement ratio has a massive impact in estimating the compressive strength of concrete with marble powder with ANN based model in evaluation with the different parameters for this data set.

• Journal of the Korean Institute of Gas
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• v.12 no.3
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• pp.38-42
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• 2008

Effect of polyol structure and NCO index on adhesion of PU adhesive at room ($25^{\circ}C$) and extremely low temperature ($-190^{\circ}C$) was investigated. At room temperature adhesive strength of PU adhesive tends to decrease as molecular weight of polyol increases, however, the strength at $-190^{\circ}C$ shows opposite tendency. Adhesive strength of the PU turned out to be directly proportional to the amount of MDI. PU containing aliphatic polyol was higher in shear strength at $-190^{\circ}C$ and the strength of PU with aromatic polyol was higher at room temperature.

• Journal of the Korea Convergence Society
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• v.10 no.5
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• pp.165-171
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• 2019

Engineering and Technology have been influencing a lot in the field of sports. Competitiveness, attributes of sports, have forced not only sports players but sports goods to enhance those performance. Particularly in the field of motorsports, the convergence of sports and technology has long been done to satisfy between performance and safety. In this study, strength analysis was carried with FEM to develop CFRP Laminate(Carbon Fiber Reinforced Plastic Laminate) bucket seat targeted to motorsports and car tuning industries and FIA($F\acute{e}d\acute{e}ration$ Internationale de l'Automobile) regulation was applied to design the racing seat and evaluate its strength. FEM modeling considered the attributes of composites was followed by strength evaluation based on Tsai-Wu failure index were done according to Lay-up sequence and layer numbers. The result showed that the lay-up sequence with stacking angle such as $[0^{\circ}/30^{\circ}/60^{\circ}/90^{\circ}/-30^{\circ}/-60^{\circ}]_4$ with 3mm form core was optimal selection in the field of weight and strength evaluation.

• Magazine of the Korea Concrete Institute
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• v.7 no.3
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• pp.139-148
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• 1995

The test results from three one fourth scale models using high strength Reinforced Concrete $f_x=704\;kg/cm^2,\;f_y=5.830\;kg/cm^2$ are presented. Such specimens are considered to represent the critical 3 storics of 60-story tall building of a structural wall system in area of high seismicity respectively. They are tested under inplane vertical and horizontal loading. The main varlable is the level of axial stress. The amounts of vertical and horizontal reinforcement are identical for the three walls testcd. The cross-section of all walls is barbell shape. The aspectratio($h_w/I_w$) of test specimen is 1.8. The aim of the study is to investigate the effects of levels of applied axial stresses on the inelastic behavior of high-strength R /C tall walls. Experimental results of high strength R /C tall walls subjected to axial load and simulated sels rnic loading show that it is possible to insure a ductlle dominant performance by promotmg flex ural yielding of vertical reinforcement and that axial stresses within $O.21f_x$ causes an increase in horizontal load-carrying capacity, initial secant st~ffness characteristics, but an decrease in displacement ductility. energy dissipation index and work damage index of high strength K /C tall walls

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2000.04a
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• pp.70-70
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• 2000

This study is a continuation of the previous experimental analysis and is mostly focused on handsheet strength properties. Four completely different fibers, which were Hw-BKP, Sw-BKP, white ledger, and OCC, were selected to investigate the effect of mechanical pre-treatment by Hobart mixer on handsheet strength properties. After equal time mechanical pre-treatment, the fibers were refined with laboratory valley beater for 10, 20 and 30 minutes, and handsheets were prepared from the fibers for physical strength comparison. Handsheets from SW-BKP and OCC showed 5-30% increase of breaking length, burst index, tear index, and compression index while handsheets from HW-BKP and white ledger no Increase except tear index. In Hobart mixer pre-treatment, HW-BKP and white ledger fibers were easily attached to the wall of the mixer bowl and mechanical action was not effectively applied. The fiber length of Hw-BKP and white ledger were 0.837mm and 1.591 mm, respectively, while SW-BKP and OCC were 2.744 mn and 2.033 mm, respectively, in weight weighted length. The effective mechanical pre-treatment seems to be related to the fiber length. Tear indexes of the pre-treated furnish were much higher than no pre-treatment at the same breaking length level.

• Journal of Preventive Medicine and Public Health
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• v.6 no.1
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• pp.87-99
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• 1973

The purpose of this project is offering fundamental and proper informations for the better health control and personnel management of the enlisted men of Marine corps in Korea. Survey has been done under 1,001 marine enlisted men for the purpose of understanding their condition of physique, vital capacity, and bodily strength. 1. Under the subject of physique, 7 items, body weight, chest-girth, relative body weight, relative chest-girth, Vervaeck index, and Roehrer index are listed, and under the subject of vital capacity, BTPS vital capacity and percent predicted vital capacity are listed, and under the subject of bodily strength, 7 items, grasping power, chinning-up, throwing a hanp-grenade, forward jumping, sitting-up, 100 meter sprinting, are listed. The total items are 16 and mean score of each one is as follow. 1)Physique : a. Height : $$168{\pm}0.15cm$$ b. Body weight : $$62.7{\pm}0.17kg$$ c. Chest-girth : $$91.4{\pm}0.16cm$$ d. Relative body weight : $$37.2{\pm}0.09$$ e. Relative chest-girth : $$54.3{\pm}0.10$$ f. Vervaeck index : $$91.6{\pm}0.15$$ g. Roehrer index : $$1.31{\pm}0.003$$ 2) Vital capacity : a. BTPS vital capacity : $$4470{\pm}20cc$$ b. % Predicted vital capacity : $$150{\pm}5.1%$$ 3) Bodily strength : a. Grasping power : $$41.4{\pm}0.26kg$$ b. Chinning-up : $$5.7{\pm}0.10$$ c. Throwing a hand-grenade : $$39.7{\pm}0.20m$$ d. Forward jumping : $$214{\pm}0.58cm$$ e. Sitting-up : $$19.1{\pm}0.25$$ f. Pushing-up : $$22.1{\pm}0.18$$ g. 100 meter sprinting : $$16.1{\pm}0.04sec$$. 2. Comparative analysis has been done about the conditional classes of marine enlisted men with the results of above mentioned 16 items. 7 classes according to the branches, 3 according to the ranks, 9 according to tile length of service are adopted respectively.

• Structural Engineering and Mechanics
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• v.87 no.6
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• pp.585-599
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• 2023

Geopolymer concrete (GC) can be competently utilized as a practical replacement for cement to prevent a high carbon footprint and to give a direction toward sustainable concrete construction. Moreover, previous studies mostly focused on the axial response of glass fiber reinforced polymer (glass-FRP) concrete compressive elements without determining the effectiveness of repairing them after their partial damage. The goal of this study is to assess the structural effectiveness of partially damaged GC columns that have been restored using carbon fiber reinforced polymer (carbon-FRP). Bars made of glass-FRP and helix made of glass-FRP are used to reinforce these columns. For comparative study, six of the twelve circular specimens-each measuring 300 mm×1200 mm-are reinforced with steel bars, while the other four are axially strengthened using glass-FRP bars (referred to as GSG columns). The broken columns are repaired and strengthened using carbon-FRP sheets after the specimens have been subjected to concentric and eccentric compression until a 30% loss in axial strength is attained in the post-peak phase. The study investigates the effects of various variables on important response metrics like axial strength, axial deflection, load-deflection response, stiffness index, strength index, ductility index, and damage response. These variables include concentric and eccentric compression, helix pitch, steel bars, carbon-FRP wrapping, and glass-FRP bars. Both before and after the quick repair process, these metrics are evaluated. The results of the investigation show that the axial strengths of the reconstructed SSG and GSG columns are, respectively, 15.3% and 20.9% higher than those of their original counterparts. In addition, compared to their SSG counterparts, the repaired GSG samples exhibit an improvement in average ductility indices of 2.92% and a drop in average stiffness indices of 3.2%.

• Geomechanics and Engineering
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• v.33 no.3
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• pp.279-289
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• 2023

Brittleness index (BI) is an important property of rocks because it is a good index to predict rockburst. Due to its importance, several empirical and soft computing (SC) models have been proposed in the literature based on the punch penetration test (PPT) results. These models are very important as there is no clear-cut experimental means for measuring BI asides the PPT which is very costly and time consuming to perform. This study used a novel Multivariate Adaptive regression spline (MARS), M5P, and white-box ANN to predict the BI of rocks using the available data in the literature for an improved BI prediction. The rock density, uniaxial compressive strength (σ_c) and tensile strength (σ_t) were used as the input parameters into the models while the BI was the targeted output. The models were implemented in the MATLAB software. The results of the proposed models were compared with those from existing multilinear regression, linear and nonlinear particle swarm optimization (PSO) and genetic algorithm (GA) based models using similar datasets. The coefficient of determination (R²), adjusted R² (Adj R²), root-mean squared error (RMSE) and mean absolute percentage error (MAPE) were the indices used for the comparison. The outcomes of the comparison revealed that the proposed ANN and MARS models performed better than the other models with R² and Adj R² values above 0.9 and least error values while the M5P gave similar performance to those of the existing models. Weight partitioning method was also used to examine the percentage contribution of model predictors to the predicted BI and tensile strength was found to have the highest influence on the predicted BI.

• Journal of the Korean Society of Safety
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• v.35 no.3
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• pp.16-23
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• 2020

The use of construction machinery has been increasing every year due to the large scale, high-rise and lack of workers in construction work. On the other hand, deaths are on the rise every year due to inadequate risk management for construction machinery work. In addition, the number of deaths caused by the lack of signals or insufficient signals during construction machinery work is increasing rapidly, and it is deemed necessary to analyze the actual conditions and take countermeasures. Therefore this study has developed the Strength Risk Index (SRI) based on the Frequency Risk Index (FRI) and the 5W1H by analyzing in-depth deaths caused by construction machinery over the past five years. The risk index (RI) was assessed using the frequency and strength risk index derived to determine whether it is acceptable (acceptable risk < 0.25 ≦ unacceptable risk) and the risk assessment method for reducing risk was proposed by applying 3E (Engineering, Education, Enforcement) measures for each level of risk for unacceptable risk. It also proposed measures to improve the system, such as requirements for signal numbers, mandatory placement standards, and mandatory installation of side and rear monitoring cameras, as measures for accidents caused by failure to deploy signals or insufficient signals, which account for the highest proportion of deaths among construction machinery operators and workers.

• Journal of the Korean Wood Science and Technology
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• v.27 no.1
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• pp.88-104
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• 1999

This study was carried out to classify the Hanjis into three groups that were indigenous Hanji, traditional Hanji, and improved Hanji handmade by paper making method according to the physical properties of each paper sheet such as tensile, bursting and tearing strength, folding endurance and fiber orientation in each layer. The results obtained were summarized as follows: 1. The multi-layered Hanjis made by "Oebal" Hanji making method in different direction of fiber orientation have good properties in tearing resistance. 2. The multi-layered Hanji in different direction of fiber orientation has good properties in the tearing resistance, but the burst index and the breaking length results were lower than the single layered Hanjis. 3. The different fiber orientation and multi-layered method didn't increase, the three indexes(burst index, tear index, breaking length). Only, the different direction of fiber orientation decreased the difference of width and length strength (tensile, tear) of the Hanji. 4. "Dochim"(Korean finishing touch process for indigenous Hanji by fulling round sticks) greatly increase folding endurance(double folds, not $log_{10}$) and good effect to tensile strength and burst strength. 5. The today's Oebal Hanji were the maximum of 2 layers and the indigenous Oebal Hanji were 16 layers the maximum. In addition, average of the indigenous Oebal Hanji was 4 layers(all 4-layer Hanji were the different fiber orientation of each layer). 6, The indigenous Hanji(multi-layered, and different fiber orientation) was good condition with "Dochim". Dochim increased tensile strength and burst strength of the indigenous Hanji. So the three-strength indexes were similar level("--"). 7. When the number of layer which were same fiber orientation increase, the increased Hanji became similar strength pattern("V", breaking length and burst index was higher than tear index) with "Ssangbal" Hanji. 8. The single layered papers that made by "Oebal" Hanji making method were similar strength pattern with Ssangbal Hanji. 9. There was no way to find the width and length direction of multi-layered Hanji by comparison between the difference of tensile strength and the difference of tearing resistance. 10. The compared pattern of tensile strength and tearing resistance of indigenous Oebal Hanji was different from today's Oebal Hanji. Especially, the tearing resistance of all indigenous Oebal Hanji(16 samples) was stronger on width of tearing resistance. And in the half of indigenous Oebal Hanji samples, the width of tensile strength and tearing resistance was stronger than length strength (Indigenous Oebal: '$\ulcorner\lrcorner$' 50%, '$\bigcup$' 50% $\leftrightarrow$ Today's Oebal: '$\ulcorner\lrcorner$' 12%, '$\bigcup$'6%, '$\llcorner\urcorner$'17%, '$\bigcap$'65%). In 65% today's Oebal, the length direction of tensile strength and tearing resistance was stronger than the width direction.