• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.3
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• pp.235-241
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• 2016

Underwater weapon system is required to structurally strong material, since as it is directly exposed to external shock. It should also be using the lightweight material in order to take advantage of buoyancy. Composite materials meet these requirements simultaneously. Particularly in the case of submarine, composite materials are widely used. It is important to have a high strength enough to be able to withstand external shock, but it is also important to attenuate it. In a method for the shock damping, viscoelastic damping materials are inserted between the high strength composite material as a sandwich structure. Shock attenuation can be evaluated in the loss factor. In ASTM(American Society of Testing Materials), evaluation method of the loss factor of cantilever specimens is specified. In this paper, mode tests of the cantilever are performed by the ASTM standard, in order to calculate the loss factor of the viscoelastic damping material by the specified expression. Further, for verifying of the calculated loss factor, mode test of compound beams is carried out. In addition, the characteristics of the material were analyzed the effect on the loss factor.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.15-218
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• 1999

Concrete is the most generous, universal main structural material. There is active study for processing quality, stable quality mangement. Especially, strength is basic factor of evaluating stability of concrete building. Regaining required strength and homogeneity is very important to get self-stability in building to evaluate another characteristic. Concrete strength is important to the quality management. But, result of hardened concrete's quality test is hardly reflected to works immediately. When required strength is not enough, it could bring out safe problem, economic and administrative cost. It is pointed out that problems from strength evaluation, so early evaluation of concrete quality is required. From the trend that accelerating high quality concrete development, improving the method of quality test and early evaluation measure is urgent project. Throughout this report, it is suggested the method with use of microwave to evaluate 28-days concrete strength.

• Journal of the Korea Concrete Institute
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• v.13 no.6
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• pp.536-543
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• 2001

Nowadays, with high-stoned and large-sized of structures, high-strength concrete is applicable to various methods. When high-strength concrete is used jointly with system form, seizing on the development of compressive strength at early age is very important in aspect of construction process. Because system form is stripped more faster than ordinary form. But, we have little data of compressive strength before system-form is stripped, and it isn't yet established that decision criterion of the time when system-form is stripped. So this paper deals with the development of compressive strength at early age before system-form is stripped. In this study, the experimental results indicate the boundary of curing temperature and mixing factor that is able to get needful early-strength in the application of slip-form method, and curing temperature must be kept over 15 degrees in winter season.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.1029-1034
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• 2001

The purpose of this research is to develop rapid setting cement latex modified concrete (RSLMC) which will be used to overlay bridge deck for maintaining and repairing. The main experimental variables were the types of rapid setting cement and variation of latex and antifoam agent contents were selected as admixture factor, then the properties of workability and strength development and durability properties were investigated. The results of this study show that latex content give increment of a slump due to surface tension in polymer particles and reduce unit weight of water for preservation of workability. In addition, When no and 1.6~3.2% antifoam agent were mixed, 8%, 2.0~3.8% were respectively obtained. An increasing the amount of latex produced concrete with increased flexural strength, but with slightly lower compressive strength. Rapid chloride permeability and freezing-thawing test carried out. As a results, according to increment of containing ratio antifoamer, strength of RSLMC increase, permeability showed lower value than ignorable 100 coulombs. Also, in the case of more than antifoamer 1.6%, the relativity dynamic modulus is mantained more than 90%, but in case of 0, 5%, it decrease. In consequence, with the view of strength and workability of RSLMC, it is considered that appropriate content ratio of antifoam agent and latex solid are respectively 1.6% by latex weight, 15% by cement weight.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.673-676
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• 2006

Steel FibreReinforced Shotcrete(SFRS) is one of the main tunnel support along with the rock bolt during the excavation and after the completion of the tunnel. In the standard qualification of the SFRS defined by Korea Highway Corporation, 28 day core specimen has to meet the compressive strength of 19.6 MPa and over 90 % fibre contents. Furthermore, for the 28 days brick shaped specimen made by shooting, flexural strength should be over 4.4 MPa and flexural toughness ratio which can be calculated from flexural toughness factor has to meet more than 68% of flexural strength. In shotcrete, accelerating agent is added for the rapid strength development. Silicate and aluminate type agents are known to develop shotcrete strength rapidly, however, has such problem to degrade the middle and long term strength. Hence, using poly carboxylic super plasticizer, it was aimed to enhance the quality of the shotcrete with the lower water-cement ratio and the same level of workability. The present paper shows the part of the field test result and its analysis.

• Journal of Korean Academy of Nursing
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• v.32 no.4
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• pp.560-569
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• 2002

The purpose of this study was to develop an instrument to measure family resilience for Korean families with a chronically ill child, and to test the validity and reliability of the instrument. Method: The items of instruments used based on the researchers' previous study of concept analysis of Korean family resilience. Nineteen item scales were developed with five domains. In order to test reliability and validity of the scale, data were collected from 231 families, who had a child with a chronic illness. Data was collected between August and September of 2001 in a 3rd level University Hospital in Seoul, Korea. Result: The results were as follows: As a result of the item analysis, 19 items were selected from the total of 37 items, excluding items with low correlation with the total scale. Five factors were evolved by factor analysis, which explained 56.4% of the total variance. The first factor 'Family strength' explained 28.5%, 2nd factor 'Family maturity' 8.7%, 3rd factor 'The ability to use of external resources' 7.0%, 4th factor 'Control' 6.6%, 5th factor 'The driving force for finance' 5.7%. The attributes in these factors were different with those identified by concept analysis of the family resilience in Korean families from the previous study. Cronbach's $\alpha$ coefficient of this scale was .8039 and Guttman spilt- half coefficient was .8184. Conclusion: The study support the reliability and validity of the scale. Because the main concept of family resilience was family strength, there were distinct differences in dimensions of family functioning scales.

• Journal of the Korea Institute of Building Construction
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• v.14 no.1
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• pp.11-20
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• 2014

This research examined the effect of the quality of aggregate on concrete workability and compressive strength through an investigation into regional aggregate used in domestic ready mixed concrete plants. Through the research, it was found that aggregate for ready mixed concrete shows poor quality overall. The main factor of deterioration in the quality of the concrete is the particle size of fine aggregate and fine particle content in coarse aggregate. The quality of aggregate significantly influences concrete's workability, which is defined based on 0.08mm passage related with powder and absorption. In addition, poor aggregate quality leads to increased water content in concrete to secure workability, which is related with a decline in the compressive strength and durability of concrete.

• Journal of Fisheries and Marine Sciences Education
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• v.25 no.6
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• pp.1419-1428
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• 2013

This Study is to suggest marine tourism development strategy of Yeosu city using a A'WOT analysis technique. Main findings of this study are summarized as following. First, SO(strength-opportunity) strategy is considered as the most important strategy and followed by ST(strength-threat), WO(weakness-opportunity) and WT(weakness-threat) strategy. Second, it can be concluded that marine tourism facility and contents development is considered as the most important factor and followed by marine sport-related marine training program development and so on. For further research, more concrete and empirical study is to be performed by each strategy in the future.

• Structural Engineering and Mechanics
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• v.89 no.6
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• pp.579-588
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• 2024

The present paper investigates the curvature ductility of confined reinforced concrete (RC) beams with normal (NSC) and high strength concrete (HSC). For the purpose of predicting the curvature ductility factor, an analytical model was developed based on the equilibrium of internal forces of confined concrete and reinforcement. In this context, the curvatures were calculated at first yielding of tension reinforcement and at ultimate when the confined concrete strain reaches the ultimate value. To best simulate the situation of confined RC beams in flexure, a modified version of an ancient confined concrete model was adopted for this study. In order to show the accuracy of the proposed model, an experimental database was collected from the literature. The statistical comparison between experimental and predicted results showed that the proposed model has a good performance. Then, the data generated from the validated theoretical model were used to train the artificial neural network (ANN) prediction model. The R² values for theoretical and experimental results are equal to 0.98 and 0.95, respectively which proves the high performance of the ANN model. Finally, a parametric study was implemented to analyze the effect of different parameters on the curvature ductility factor using theoretical and ANN models. The results are similar to those extracted from experiments, where the concrete strength, the compression reinforcement ratio, the yield strength, and the volumetric ratio of transverse reinforcement have a positive effect. In contrast, the ratio and the yield strength of tension reinforcement have a negative effect.

• Science of Emotion and Sensibility
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• v.25 no.3
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• pp.77-90
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• 2022

This study seeks to develop a stretch sensor for measuring the wrist movements of people using fishing lures. In order to confirm wrist movement, a stretch sensor was attached to the wrist band, and measurements of the dorsiflexion, plantar flexion, and fishing landing motion were measured using a scale to gauge factor, tensile strength, and elongation recovery rate. A conductive sensor using CNT dispersion was developed and applied to the E-band under the same conditions. A total of 15 sensors of the same size and five types of impregnation once, twice, and three times each were used to measure the gauge factor using UTM. The sensor that was impregnated twice had the best gauge rate, and the prototypes were manufactured with three sensors with high gauge rates and tensile strength. The results of the operation test conducted by connecting to the Arduino showed that Sample 1, which had the highest tensile strength and gauge factor, had a stable graph wavelength in three operations. Samples 2 and 3 showed stable wavelengths in the dorsiflexion and the plantar flexion; however, signal noise appeared in the fishing landing motion. This showed stable wavelengths in the two motions, but the wavelengths of the graphs differ depending on the tensile strength and gauge factor in the fishing landing motion. As a result, it was possible to identify the conditions necessary for manufacturing a stretch sensor for measuring wrist movement. This study will contribute to the development of smart wearable products for lure fishing.