• Advances in concrete construction
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• v.8 no.1
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• pp.65-76
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• 2019

This paper investigates the effect of recycled glass powder (RGP) on flowing properties of self-compacting mortars (SCMs) containing different ratios of fillers and superplasticizer dosages. Fly ash (FA), nano-silica (NS), micro-silica (MS), metakaolin (MK) and rice husk ash (RHA) are used as fillers and their synergistic effect with RFP is studied. The effects of fillers and high-range water reducer (HRWR) on flowing ability of mortars are primarily determined by slump flow and V-funnel flow time tests. The results showed that for composites with a higher RGP content, the mortar flowing ability increased but tended to decrease when the composites containing 10% MK or 5% RHA. However, the flowing ability of samples incorporating 5% RGP and 10% SF or 25% FA showed an opposite result that their slump flow spread decreased and then increased with increasing RGP content. For specimens with 3% NS, the influence of RGP content on flowing properties was not significant. Except RHA and MS, the fillers studied in this paper could reduce the dosage of HRWR required for achieving the same followability. Also, the mixture parameters were determined and indicated that the flowability of mixtures was also affected by the content of sand and specific surface area of cement materials. It is believed that excess fine particles provided ball-bearing effect, which could facilitate the movement of coarse particles and alleviate the interlocking action among particles. Also, it can be concluded that using fillers in conjunction with RGP as cementitious materials can reduce the material costs of SCM significantly.

• ALGAE
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• v.34 no.2
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• pp.71-90
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• 2019

A new encrusting red alga was found growing abundantly on glass debris items that drifted ashore along the coasts of Oregon and Washington. These included discarded fluorescent tubes, incandescent light bulbs, capped liquor bottles, and ball-shaped fishing-net floats. Field collections and unialgal cultures of the alga revealed that it consisted of two morphological phases: a young loosely aggregated turf and a mature consolidated mucilaginous crust. The turf phase consisted of a basal layer of globose cells that produced erect, rarely branched, uniseriate to multiseriate filaments up to $500{\mu}m$ long with closely spaced cells lacking pit-plugs. These filaments expanded in size from their bases to their tips and released single cells as spores. At maturity, a second phase of growth occurred that produced a consolidated crust, up to $370{\mu}m$ thick. It consisted of a basal layer of small, tightly appressed ellipsoidal-to-elongate cells that generated a mucilaginous perithallial matrix containing a second type of filament with irregularly spaced cells often undergoing binary division. At the matrix surface, the original filaments continued to grow and release spores but often also eroded. Individual cells, examined using confocal microscopy and SYBR Green staining, were found to contain a central nucleus, a single highly lobed peripheral chloroplast without a pyrenoid, and numerous chloroplast nucleoids. Morphological data from field and culture isolates and molecular data (rbcL, psbA, and SSU) show that this alga is a new genus and species which we name Viator vitreocola, "a traveller on glass."

• Journal of Surface Science and Engineering
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• v.52 no.1
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• pp.16-22
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• 2019

The structural change of DLC coatings during long-term wear test and dicing test under the low loading condition was investigated. DLC coatings were applied for the precision injection molds of a modified SNCM steel for the extension of life and the micro-diamond blades for the high cutting efficiency and the increase in life. A ball-on-disc wear tests in the mold steel and a dicing tests in the micro-diamond blades were conducted to understand degradation of DLC coatings. The degradation of DLC coatings for the injection mold steel and the micro-diamond blades during the wear and dicing tests were studied with Raman Spectroscopy. Raman peaks were divided two bands(D band and G band) to study the degradation process of DLC structure. By the wear test, polished condition of wear marks were observed to be maintained until 10 hrs of wear test period is given, but small striation marks appeared in 20 hours wear test. It was observed that $I_D/I_G$ ratios changed as the degradation of DLC coatings is proceeded during the wear tests and the dicing tests. It is suggested that the change in $I_D/I_G$ value possibly reflected from the composition of $sp^2$ and $sp^3$ bondings in DLC layers relevant to the change in mechanical and physical property.

• Physical Therapy Rehabilitation Science
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• v.8 no.1
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• pp.40-44
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• 2019

Objective: The purpose of this study was to examine the changes in postural stability according to ankle fixation in healthy university students. Design: Cross-sectional study. Methods: Thirty healthy subjects (15 males and 15 females, 20.13 years, 167.49 cm, 65.87 kg) were recruited on a voluntary basis. The BT4 system (HUR Laps Oy, Tampere, Finland) was used to measure the static (standing posture with eyes open and eyes closed) and dynamic (external perturbation and limits of stability (LOS) in the forward, backward, left, and right side) balance abilities. External perturbation was measured by the subject's postural sway velocity and area for 20 seconds after being impacted by a gym ball. Static and dynamic stabilities were measured with ankle joint fixation and non-fixation conditions. Ankle fixation was provided using Mueller tape on both ankle joints. Results: For static stability under the standing posture, there was no significant difference between standing with ankle joint fixation and non-fixation conditions. However, dynamic stability (external perturbation and LOS in the forward, backward, left, and right side) was significantly higher in the standing with the non-fixation condition compared to the standing with ankle joint fixation condition (p<0.05). Conclusions: Our results reveal that ankle joint fixation can influence dynamic stability during standing. Thus, we believe that this result provides basic information for making improvements in postural control and may be useful in balance training for fall prevention.

• Journal of Powder Materials
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• v.28 no.4
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• pp.336-341
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• 2021

In this study, a nanocrystalline FeNiCrMoMnSiC alloy was fabricated, and its austenite stability, microstructure, and mechanical properties were investigated. A sintered FeNiCrMoMnSiC alloy sample with nanosized crystal was obtained by high-energy ball milling and spark plasma sintering. The sintering behavior was investigated by measuring the displacement according to the temperature of the sintered body. Through microstructural analysis, it was confirmed that a compact sintered body with few pores was produced, and cementite was formed. The stability of the austenite phase in the sintered samples was evaluated by X-ray diffraction analysis and electron backscatter diffraction. Results revealed a measured value of 51.6% and that the alloy had seven times more austenite stability than AISI 4340 wrought steel. The hardness of the sintered alloy was 60.4 HRC, which was up to 2.4 times higher than that of wrought steel.

• Journal of the Korean GEO-environmental Society
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• v.20 no.11
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• pp.5-10
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• 2019

For the development of long-wavelength responding photocatalyst, Ag was applied to commercial $TiO_2$ to produce $Ag/TiO_2$ photocatalyst. Moreover, micro-emulsion method was used in order to increase the efficiency of the photocatalyst by enhancing the dispersion of Ag. Physical properties of the manufactured catalyst were analyzed by scanning electron microscopy (SEM), field emission transmission electron microscopy (FE-TEM) and diffuse reflectance spectroscopy (DRS). For the catalytic performance measurement, RO 16 (Reactive Orange 16) removal was performed with 25 ppm RO 16 under UV-A (365 nm) irradiation. In addition, ball milling and dip-coating method were used to synthesize the photocatalyst for the comparison of the outcomes of using different synthesis methods. In addition, catalytic performance was improved by varying the Ag content and surfactant content. The highest catalytic performance was shown at $Ag/TiO_2$ synthesized by micro-emulsion method with 2 wt% of Ag content, and 0.5 g of the surfactant.

• Journal of Powder Materials
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• v.28 no.1
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• pp.20-24
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• 2021

Ti-based alloys are widely used in biomaterials owing to their excellent biocompatibility. In this study, Ti-Mn-Cu alloys are prepared by high-energy ball milling, magnetic pulsed compaction, and pressureless sintering. The microstructure and microhardness of the Ti-Mn-Cu alloys with variation of the Cu addition and compaction pressure are analyzed. The correlation between the composition, compaction pressure, and density is investigated by measuring the green density and sintered density for samples with different compositions, subjected to various compaction pressures. For all compositions, it is confirmed that the green density increases proportionally as the compaction pressure increases, but the sintered density decreases owing to gas formation from the pyrolysis of TiH2 powders and reduction of oxides on the surface of the starting powders during the sintering process. In addition, an increase in the amount of Cu addition changes the volume fractions of the α-Ti and β-Ti phases, and the microstructure of the alloys with different compositions also changes. It is demonstrated that these changes in the phase volume fraction and microstructure are closely related to the mechanical properties of the Ti-Mn-Cu alloys.

• Human Ecology Research
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• v.59 no.1
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• pp.83-97
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• 2021

This study developed safety clothing that is essential for adolescent to protect their bodies from accidents, pursue activities and individuality. Therefore, the developed safety clothing was first based on international standards, while changing design to emphasize creativity, activity, and functionality. Two suits of boy's clothes and a girl's suit were developed as safety clothing for sportswear, along with two pairs of girl's clothes and a pair of boy's clothes for entertainment. It was confirmed that the difference in visibility was revealed by testing under different lighting conditions. Second, the survey on adolescents indicated no significant gender difference in sportswear. Round shirt+shorts for both boys and girls were the most preferred for ball game sportswear. However, there was a significant difference by gender in the design of safety clothing for entertainment. Male students preferred jump suit=cape+pants the most, and female students preferred jump suit>cape+pants in the order (p<0.05). In the safety clothes with the highest preference for entertainment, there was no gender difference. All students preferred the jump suit at the most. Checking at each school level, it was found that both middle and high school students preferred jump suit designs, and in safety clothing, middle school students preferred high-neck shirt blouse+tight skirt, and high school students preferred jump suits. Third, 35.5% responded that they would wear it more if current safety clothing is improved. This indicated the necessity of developing various safety clothing for adolescence.

• PNF and Movement
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• v.12 no.4
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• pp.233-241
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• 2014

Purpose: The purpose of this study is to investigate the effects of exercising on a stable and unstable surface for a period of six weeks on the arms of female university students in their twenties. Methods: The subjects consisted of 20 female university students. The experimental group consisted of ten individuals who exercised on an unstable surface, and the control group consisted of ten individuals who exercised on a stable surface. The exercise program was composed of aerobic exercises (i.e. Back and forth movements for clapping and raising cross with both arms) and muscle-strengthening exercises (i.e. Push-ups and raising arms). We measured the subjects before the experiment and after the exercise program using the following measurements tool: a ruler and T-scan plus. The same person measured changes in arm size with a ruler three times and calculated the average to minimize any errors in measurement. We controlled the subjects to measure the amount of arm muscle with a T-scan plus. Twelve hours before the measurements were taken subjects were not permitted to exercise, and four hours before the measurements were taken subjects were not permitted to eat anything. Results: The two groups had no significant difference, but each group felt the effect of the exercise program. Conclusion: There was no difference between the experimental group and the control group. However, it was determined that the exercise had a greater effect on an unstable surface than a stable surface.

• Journal of the Korean Physical Society
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• v.73 no.12
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• pp.1863-1866
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• 2018

The sodium-iron phosphate maricite-$NaFe_{0.9}Mn_{0.1}PO_4$ was synthesized using the ball mill method. The crystal structure and magnetic properties of the prepared materials were studied using X-ray diffraction (XRD), vibrating sample magnetometer (VSM), and $M{\ddot{o}}ssbauer$ spectroscopy. Structural refinement of maricite-$NaFe_{0.9}Mn_{0.1}PO_4$ was analyzed using the FullProf program. From the XRD patterns, the crystal structure of maricite-$NaFe_{0.9}Mn_{0.1}PO_4$ was found to be orthorhombic with the space group Pmnb. The lattice parameters of maricite-$NaFe_{0.9}Mn_{0.1}PO_4$ are as follows: $a_0=6.866{\AA}$, $b_0=8.988{\AA}$, $c_0=5.047{\AA}$, and $V=311.544{\AA}^3$. Maricite-$NaFePO_4$ has an edge-sharing structure that consists of $FeO_6$ octahedral. Under an applied field of 100 Oe, the temperature dependences of zero-field-cooled (ZFC) and field-cooled (FC) curves were measured from 4.2 to 295 K. $M{\ddot{o}}ssbauer$ spectra were also recorded at various temperatures ranging from 4.2 to 295 K. We thus confirmed that the $N{\acute{e}}el$ temperature of $NaFe_{0.9}Mn_{0.1}PO_4$ ($T_N=14K$) was lower than that of maricite-$NaFePO_4$ ($T_N=15K$).