• Journal of the Korea Institute of Building Construction
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• v.21 no.3
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• pp.195-202
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• 2021

Concrete quality is mainly managed through the reliable prediction and control of compressive strength. Although related industries have established a relevant datasets based on the mixture proportions and compressive strength gain, whereas they have not been shared due to various reasons including technology leakage. Consequently, the costs and efforts for quality control have been wasted excessively. This study aimed to develop a web-based numerical model, which would present diverse optimal values including concrete strength prediction to the user, and to establish a sustainable database (DB) collection system by inducing the data entered by the user to be collected for the DB. The system handles the overall technology related to the concrete. Particularly, it predicts compressive strength at a mean accuracy of 89.2% by applying the artificial neural network method, modeled based on extensive DBs.

• Journal of the Korean Society of Physical Medicine
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• v.13 no.4
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• pp.75-84
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• 2018

PURPOSE: This study was conducted to determine the effects of whole-body tilt exercise with visual feedback on trunk control, strength, and balance in patients with acute stroke. METHODS: The study included 18 patients with acute stroke who were randomly allocated to a Whole Body Tilt Exercise Group (WBTEG, N=9) and a General Trunk Exercise Group (GTEG, N=9). The WBTEG conducted whole-body tilt exercises with visual feedback, and the GTEG performed general trunk exercises. Both groups performed the exercises five times a week for 4 weeks. Outcomes were assessed using the trunk impairment scale (TIS), the trunk flexor and extensor strength test, the static balance test, and the Brunel Balance Assessment. RESULTS: After 4 weeks of intervention, both groups showed significantly improved TIS scores, muscle strength, and balance components (p<.05 in both groups). However, the improvement in TIS, muscle strength, and static balance in the WBTEG was significantly better than that in the GTEG (p<.05). CONCLUSION: Although both groups in this study showed post-intervention improvement, patients from the WBTEG who received visual feedback demonstrated more improvement. These findings indicate that whole-body tilt exercise with visual feedback may be effective at improving trunk control, trunk muscle strength, and balance in patients with acute stroke. Further studies are needed to gain a better understanding of the effectiveness of whole-body tilt exercise in patients with acute stroke.

• Advances in concrete construction
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• v.6 no.6
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• pp.561-583
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• 2018

A variety of polycarboxylate ether (PCE)-based superplasticizers are commercially available. Their influence on the rheological retention and slump loss in respect of concrete differ considerably. Fluidity and slump loss are the cardinal features responsible for the quality of concrete. These are related to the dispersion of cement particles and the hydration process which are greatly influenced by type of polycarboxylate ether (PCE)-based superplasticizers. On the backdrop of relatively less studies in the context of rheological retention of high strength self-consolidating concrete (HS-SCC), the experimental investigations were carried out aiming at quantifying the effect of the six different PCE polymers (PCE 1-6) on the rheological retention of HS-SCC mixes containing two types of Ordinary Portland Cements (OPC) and unwashed crushed sand as the fine aggregate. The tests that were carried out included $T_{500}$, V-Funnel, yield stress and viscosity retention tests. The supplementary cementitious materials such as fly ash (FA) and micro-silica (MS) were also used in ternary blend keeping the mix paste volume and flow of concrete constant. Low water to binder ratio was used. The results reveal that not only the PCEs of different polymer groups behave differently, but even the PCEs of same polymer groups also behave differently. The study also indicates that the HS-SCC mixes containing PCE 6 and PCE 5 performed better as compared to the mixes containing PCE 1, PCE 2, PCE 3 and PCE 4 in respect of all the rheological tests. The PCE 6 is a new class of chemical admixtures known as Polyaryl Ether (PAE) developed by BASF to provide better rheological properties in even in HS-SCC mixes at low water to binder mix. In the present study, the PCE 6, is found to help not only in reduction in the plastic viscosity and yield stress, but also provide good rheological retention over the period of 180 minutes. Further, the early compressive strength properties (one day compressive strength) highly depend on the type of PCE polymer. The side chain length of PCE polymer and the fineness of the cement considerably affect the early strength gain.

• Advances in concrete construction
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• v.15 no.6
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• pp.359-376
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• 2023

Ultra-high-performance concrete (UHPC) has become an attractive cast-in-place repairing material for existing engineering structures. The present study aims to investigate age-dependent high-early-strength UHPC (HESUHPC) material properties (i.e., compressive strength, elastic modulus, flexural strength, and tensile strength) as well as interfacial shear properties of HESUHPC-normal strength concrete (NSC) composites cured at different season temperatures (i.e., summer, autumn, and winter). The typical temperatures were kept for at least seven days in different seasons from weather forecasting to guarantee an approximately consistent curing and testing condition (i.e., temperature and relative humidity) for specimens at different ages. The HESUHPC material properties are tested through standardized testing methods, and the interfacial bond performance is tested through a bi-surface shear testing method. The test results quantify the positive development of HESUHPC material properties at the early age, and the increasing amplitude decreases from summer to winter. Three-day mechanical properties in winter (with the lowest curing temperature) still gain more than 60% of the 28-day mechanical properties, and the impact of season temperatures becomes small at the later age. The HESUHPC shrinkage mainly occurs at the early age, and the final shrinkage value is not significant. The HESUHPC-NSC interface exhibits sound shear performance, the interface in most specimens does not fail, and most interfacial shear strengths are higher than the NSC-NSC composite. The HESUHPC-NSC composites at the shear failure do not exhibit a large relative slip and present a significant brittleness at the failure. The typical failures are characterized by thin-layer NSC debonding near the interface, and NSC pure shear failure. Two load-slip development patterns, and two types of main crack location are identified for the HESUHPC-NSC composites tested in different ages and seasons. In addition, shear capacity of the HESUHPC-NSC composite develops rapidly at the early age, and the increasing amplitude decreases as the season temperature decreases. This study will promote the HESUHPC application in practical engineering as a cast-in-place repairing material subjected to different natural environments.

• Food Science and Biotechnology
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• v.14 no.2
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• pp.242-248
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• 2005

The effect of calcium and boron supplementation on bone strength was determined in growing and ovariectomized (OVX) Sparague-Dawley rats. Rats were divided into 9 groups and fed diet with different intake levels of calcium and boron for 4 weeks. About fifty percentages of rats in each group were OVX and the others were sham-operated. The rats were fed same diets after operation for 8 weeks. The feed intake, body weight gain, and FER were significantly higher in OVX rats than those in sham-operated ones. Serum osteocalcin, bone formation biomarker, was significantly increased with increment in calcium and boron intakes. Serum estradiol was lower in OVX rats than in sham-operated ones. Bone mineral density of femur was significantly lower in OVX rats than in other group. The breaking forces of bones were not significantly different among the groups. The urinary excretion of deoxypyridinoline, osteolytic marker was significantly increased with increment in calcium intake and ovariectomy. The urinary calcium excretion was significantly increased with increment in calcium intake, but decreased with increment in boron intake. According to theses results, the boron supplementation resulted in higher serum osteocalcin and lower urinary calcium excretion. Therefore, it could be suggested that the boron supplementation may be complementary and useful to calcium nutrition for bone health.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2012.05a
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• pp.41-42
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• 2012

High temperature / high pressure spray equipment using a conventional method, unlike spray polyurea adjustable pot life and yellowing caused by UV light and chemicals do not occur, or discoloration of Self-Leveling Type of rugged hand-polyurea resin for technology development is underway. This new concept of polyurea resin roller, brush, airless spray, and they installed easily using the unfamiliar labor, and curing time of approximately four hours to gain control of the glass because it is Pot. Construction, but does not like the spray polyurea resin, compared to the existing degradation of the adhesion strength is concerned. In this study, Self-Leveling Type Manual of polyurea resin adhesion strength of target deterioration Let's minimize problems by reviewing existing domestic and infrastructure long-term durability for long life of the facility is to obtain.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2007.04a
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• pp.67-70
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• 2007

As construction industry is requiring competitive power and technique in national construction market with rapid fluctuation of construction environment and development, requirements upgrading performance in construction materials are increasing. But, national lightweight aggregate and lightweight concrete's inappropriateness when produced are also increasing. And there are not international standard of aggregates in using these construction materials because standards and characteristics of aggregate in each countries are different. Therefore, in this study, lightweight aggregate acquired due to wide range of use is tested and mixed for concrete to gain practicality and set the authorized manual in international. Also, basic data will be proposed to set a standard for concrete by analyzing lightweight aggregate characteristics. When lightweight aggregate absorptivity is high, concrete shows low strength and when it's density is low, concrete shows low weight of unit volume. Furthermore, compressive strength of lightweight aggregate is steep in first and longtime material age is tendency to cause low strength increasing rate.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.2 s.257
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• pp.245-252
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• 2007

Since the new millennium, truss PCMs(Periodic Cellular Metals) have drawn attention because of their superior specific stiffness, strength and multi-functionality. Prior studies have focused on the structural design and optimization. Kagome truss PCM has been proved to have the higher resistance to plastic buckling, more plastic deformation energy and lower anisotropy than other truss PCMs. In this study, we introduce a new idea to fabricate multi-layered Kagome truss PCM from continuous wires which can gain high strength as in piano wires and can be controlled to be defect free owing to drawing process. The relative density, the stiffness and the strength under bending and compressive load are estimated through elementary mechanics and compared with the results from experiments and FEA. The failure mechanisms are analyzed, and also mechanical performance and production are discussed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.519-520
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• 2007

In order to develop non-heated STAl(super thermal resistant Aluminum alloy) for ampacity gain conductor, the systematic research was carried out. Especially, the effect of a very small amount of Zr element in EC grade Al ingot on mechanical and electrical properties was our priority. As a result, it was found that the strength and recrystallization temperature of designed alloy was gradually increased with Zr addition up to 0.3wt.%. However, the electric conductivity showed no drastic change. The tensile strength and recrystalliztion temperature, $17.75\;kgf/mm^2$ and $420^{\circ}C$, was obtained at 0.3 wt.% Zr addition, respectively.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.8 no.5
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• pp.105-113
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• 2009

In this paper, a vehicle antenna for AM, FM, TDMB, GPS systems was designed and implemented. AM antenna loaded into small space of shark shape was designed by ferrite turn style antenna. For the FM and TDMB antenna, folded monopole antenna which helical is folded was applied. GPS antenna for achieving characteristics both bandwidth and gain improvement was designed microstrip patch that has air substrate and fractal structure. Receiving signal strengths by the measurement were presented for the AM, FM and TDMB antenna. AM signal strength was -65.7dBm, this strength is almost as same conventional pole antenna as -63.4dBm. It can be replaced conventional pole or glass antenna by the studied antenna. Signal strengths for FM and TDMB were -55.66 and -43.50dBm at center frequency, they are 5~10dB higher than conventional antenna. Measurements of bandwidth and gain for the GPS antenna showed 135 MHz under VSWR 2 : 1 and 4.31dBi, gains over GPS band were 3~5dB higher than ceramic patch antenna.