• PNF and Movement
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• v.20 no.1
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• pp.125-134
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• 2022

Purpose: The aim of this study was to establish an association between grip strength and gait variability in the elderly. Methods: The participants in this experiment (n = 20) were aged 65 or older. Power grip and lateral pinch forces were obtained in grip strength tests, and spatiotemporal gait parameters were collected from IMU sensors during 6 min actual walking to test the gait of participants. The collected gait parameters were converted to coefficient of variation (CV) values. To confirm the association between grip strength and gait variability, a partial correlation analysis was conducted in which height, weight, and gait speed were input as controlling variables. Results: Grip power showed a significant negative correlation with the stride length CV (r = -0.52), and the lateral pinch force showed a significant negative correlation with the stance CV (r = -0.65) and swing CV (r = -0.63). Conclusion: This study reveals that gait variability decreases as grip strength increases, although height, weight, and gait speed were controlled. Thus, grip strength testing, a simple aging evaluation method, can help identify unstable gait in older adults at risk of falling, and grip strength can be utilized as a non-invasive measurement method for frailty management and prevention.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.177-178
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• 2023

In this study, the mass production process was simulated using a 1m³ batcher plant to evaluate the application of high-strength fire resistance concrete. The strength ranges of concrete were set to 50, 60, 70, and 80 MPa, and each concrete mix proportions was selected through preliminary experiments in the laboratory. For the selected concrete mix proportions, after the mixer load value was stabilized in the batcher plant, the slump flow and air content of the fresh concrete were evaluated, and the compressive strength was evaluated up to 56 days. As a result of the experiment, both the slump flow and air content of the fresh concrete satisfied the target performance, and in the case of compressive strength, 50 and 60 MPa satisfied the target performance at 28 days and 70 and 80 MPa at 56 days.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2008.11a
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• pp.484-489
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• 2008

We carried out a one-way heating experiment on the PC panel manufactured by changing the filling depths(20,30,40,50mm) of concrete regarding the fire strength in order to measure the inner concrete pressure which is a direct cause of concrete spalling. This fire experiment was conducted under the fire strength conditions of ISO 834 Standard, Modified Hydrocarbon and the maximum value of Pore Pressure was measured. As a result of analyzing the time it took to reach maximum pressure, it showed that the time rising to the maximum pressure of high strength concrete of 40MPa is slower than that of a 24MPa tunnel lining. In case of ISO fire conditions, spalling damage might take place in heating period of $20{\sim}40$ minutes in the range of $100{\sim}200^{\circ}C$ temperature. In case of MHC fire conditions, the area damaged by fire can appear after a lapse of $25{\sim}50$ minutes in the range of $150{\sim}250^{\circ}C$ temperature.

• Journal of Advanced Navigation Technology
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• v.12 no.5
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• pp.483-493
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• 2008

For effective wireless localization utilizing signal strength measurements based on IEEE 802.11 WLAN standard diversity of mobile hardware, characteristics of is one of the important problems to be considered for advanced location-based services. For improved accuracy regardless of a bias originating from the mobile hardware characteristics, this paper proposes a new localization algorithm, which is named as the hybrid Kriging algorithm. To evaluate the performance characteristics of the proposed algorithm, simulation and experiment results are illustrated. By the simulation and experiment result, the proposed algorithm is more accurate than the well-known location finger-print method given the same density of reference measurements.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.6
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• pp.38-45
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• 2010

Welding structures are designed to endure its expected life. The most important factors are life. Especially on welded structure, fatigue strength is critical. So this study performed a research on Box and T shape weldment specimen to examine the influence of welding type. In this experiment, the results indicate Box shape was available in more than T shape. Fatigue tests were performed to evaluate the fatigue strength of the both as-welded and statically pre-loaded specimens by 3 point bending load. Fatigue life can be improved by using Ultrasonic Impact Treatment(UIT) effect. Ultrasonic Impact Treatment(UIT) is excellent for eliminating the tensile residual stresses and generating compressive residual stresses which elevate fatigue strength of welded structures. Also, this shows that welding part has better fatigue life and welding was performed well. In this study, to evaluate the Ultrasonic Impact Treatment(UIT) effect, for welding structure, the experiment was conducted at various levels of stress range between 100MPa and 500MPa. From the test results, it was indicated that fatigue performance was improving by Ultrasonic Impact Treatment(UIT)

• Journal of the Korean Society of Propulsion Engineers
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• v.15 no.2
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• pp.50-55
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• 2011

A preburner for the high performance, staged combustion cycle liquid rocket engine is being developed. For the structural design processes, strength experiments and finite element analyses on specimens simulating the brazing joints of the preburner, were performed and compared. Total two kinds of the specimen were manufactured for the tests. One simulated the joints between the oxygen injectors and the head junctioned by the conventional vacuum brazing. The another was made to test the brazing surfaces by vacuum compression between the combustion chamber cooling channel and the outer wall. During the burst experiments, it was observed that the fractures were occurred not at the brazed joining but in the middle of the face plate and the cooling wall. In addition, the analysis showed that the predicted fracture locations and the strains were well matched with the experiment results.

• Journal of Korean Society of Steel Construction
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• v.14 no.1
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• pp.59-67
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• 2002

The ultimate strength testing of a two-story, single-bay, and sway allowed space steel frame was performed. Considering a majority of large-scale frame tests in the past, only two-dimensional frames were experimentally studied. Therefore, three-dimensional experiment is needed to extend the knowledge of this field. The steel frame subjected to non-proportional vertical and horizontal load was tested. The load-displacement curve of the test frame is provided. The experiment results are useful for verification of the three-dimensional numerical analysis. The results obtained from 3D non-linear analysis using ABAQUS were compared with experimental data.

• Korean Journal of Materials Research
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• v.28 no.1
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• pp.62-67
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• 2018

Active clay, bentonite and zeolite were used as porous materials for humidity controlling ceramic boards. The specific area and the pore volume of active clay were higher than bentonite and zeolite. The flexible strength of the gypsum board decreased with an increasing amount of porous material, and the flexible strength was lowest when active clay with a higher specific surface area than others porous materials was added. The specific surface area and total pore volume of ceramic boards containing porous material were highest at $102.25m^2/g$, $0.142cm^3/g$, respectively, when the active clay was added. In addition, as the amount of added porous materials increased, the specific surface area and total pore volume of the ceramic board increased, but the average pore diameter decreased. The addition of s porous materials with a high specific area and a large pore volume improved the moisture absorptive and desorptive performance of the ceramic board. Therefore, in this experiment, the moisture absorptive and desorptive properties were the best when active clay was added. Furthermore, as the amount of added porous materials increased, the moisture absorptive and desorptive properties improved. When 70 mass% of active clay was added to ${\alpha}$-type gypsum, the hygroscopicity was the highest, about $300g/m^2$, in this experiment.

• Journal of the Society of Naval Architects of Korea
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• v.44 no.3 s.153
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• pp.296-304
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• 2007

The objective of this paper is to investigate the dynamic strength characteristics of LNG carriers cargo containment system under impact loads experimentally. The material properties were experimentally obtained for individual components of MARK III insulation system. A series of impact tests was performed using a custom-built drop experiment facility as varying heights and weights of the drop object. Crack initiation and propagation were measured during the cyclic dry drop experiment. The quantitative relationship between impact load and crack initiation as well as the cycle number and crack propagation were reported.

• Elastomers and Composites
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• v.50 no.3
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• pp.167-174
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• 2015

Anionic epoxy compound was synthesized and added to asphalt aiming to prepare self-healing asphalt. Epoxy-modified asphalt showed excellent modification effect and healing effect as well. The results revealed that with 5% addition of polymer the tensile strength, impact strength and complex shear modulus of the polymer-modified asphalt increased by 65%. 64% and 35%, respectively. It seems that high interaction occurs between polymer and asphalt matrix. Self-healing efficiency of the polymer-modified asphalt based on tensile strength showed 100%, comparing to 79% of straight asphalt. In impact experiment the polymer-modified asphalt showed 99% of healing efficiency, comparing to 77% of straight asphalt. In rheological experiment the polymer-modified asphalt showed 103% of healing efficiency, comparing to 72% of straight asphalt. It appears that the ionic bonding existing in epoxy polymers contributed to high values of self-healing efficiency. The polymer which has high intermolecular force fills the crack of the asphalt, pulling the opponent side each other, and so the original properties were restored.