• Journal of the Korean institute of surface engineering
• /
• v.38 no.1
• /
• pp.1-6
• /
• 2005

Ni-15at.% W coatings with film thicknesses of 20-40 ㎛ were electroplated on a steel substrate, and their oxidation behavior was investigated at 700 and 800℃ in air. For comparison, a pure Ni coating and a bulk Ni were also oxidized. The Ni-15at.%W coating displayed the worst oxidation resistance, due to the formation of less-protective NiO, Fe₂O₃, NiFe₂O₄ and NiWO₄. The corrosion behavior Ni-15at.%W coatings electroplated on a steel substrate was similarly investigated at 700 and 800℃ in the Ar-l%SO₂ atmosphere. For comparison, the uncoated steel substrate was also corrosion-tested in the Ar-l %SO₂ atmosphere. Severe scale spallation and the internal corrosion of the steel that occurred in the uncoated substrate were not observed in the coated specimen. However, it seemed that the Ni-15at.%W coating cannot be a potential candidate as a sulfidation-resistant coating, due to the formation of less-protective NiO, NiS, WO₃ and NiWO₄.

• Journal of the Korean Society of Safety
• /
• v.28 no.6
• /
• pp.23-28
• /
• 2013

In order to improve extinguishing performance of water mist, many studies of additives have been conducted. In this study, viscosity agent which has the ability to improve extinguishing performance by adhering to the surface on fire was used and fluorine-free surfactant was also added to water to enhance water's wetting ability. This study aimed to verify optimal concentration of extinguishing of additives according to fire source and extinguishing performance by comparison with pure water. In case of wood crib fire, the results show that flame suppression and extinguishing time of sodium alginate 0.4 wt.% are 3.4 times and 2.2 times shorter than those of pure water in 0.2 MPa respectively. It seems that large amount of water adhere to surface on fire, thus cooling effect on surface was enhanced. Also water consumption of sodium alginate 0.4wt.% is up to 65% lower than that of pure water. In case of heptane fire, extinguishing time of cocobetaine 0.1 wt.% is 9.7 times shorter than that of pure water in 0.2 MPa. It is thought that because cocobetaine can block oxygen and suppress oil mist by making emulsion film on fire surface due to a low surface tension. On the other hand, water consumption of cocobetaine 0.1 wt.% is 92% lower than that of pure water.

• Proceedings of the KSRS Conference
• /
• 1998.09a
• /
• pp.70-75
• /
• 1998

The comparison of Topex/Poseidon sea surface heights and Tide Gauge sea levels was studied in the South Indian Ocean after Topex/Poseidon mission of about 3 years (11- 121 cycles) from January 1993 through December 1995. The user's handbook (AVISO) for sea surface height data process was used in this study Topex/Poseidon sea suface heights ($\zeta$$^{T/P}$), satellite data at the point which is very closed to Tide Gauge station, were chosen in the same latitude of Tide Gauge station. These data were re-sampled by a linear interpolation with the interval of about 10 days, and were filtered by the gaussian filter with a 60 day-window. Tide Gauge sea levels ($\zeta$$^{Argos}$, $\zeta$$^{In-situ}$ and $\zeta$$^{Model}$), were also treated with the same method as satellite data. The main conclusions obtained from the root-mean-square and correlation coefficient were as follows: 1) to Produce Tide Gauge sea levels from bottom pressure, in-situ data of METEO-FRANCE showed very good values against to the model data of ECMWF and 2) to compare Topex/Poseidon sea surface heights of Tide Gauge sea levels, the results of the open sea areas were better than those of the coast and island areas.

• Journal of The Korean Society of Integrative Medicine
• /
• v.9 no.1
• /
• pp.1-11
• /
• 2021

Purpose : The purpose of this study was to investigate the effect of single limb stance exercise according to the support surface on dynamic balance ability and abdominal muscle thickness. Methods : We recruited 28 healthy subjects in this study. Subjects were assigned to 2 groups by matching method. The control group was 5 males and 9 females, and single limb stance exercise was performed on the stable support surface. The experimental group consisted of 6 males and 8 females, and trained to stand on the unstable support. During the single limb stance exercise, the dominant foot was set as the foot that appeared numerically through the exercise of the dynamic balance meter (Biorescue). Single limb stance exercise along the supporting surface was maintained for 15 seconds and then rested for 15 seconds. It was repeated 5 times. Particularly, the balance exercise on the unstable support surface was sufficiently practiced. Independent t test was performed for comparison between groups. Paired t test was performed to compare before and after each group. Results : There was no difference between the control group and the experimental group in the comparison of dynamic balance ability (p>.05). However, there were significant differences before and after exercise in both the control and experimental groups (p<.05). Similarly, in the comparison of abdominal muscle thickness, there was a significant difference within each group, especially internal oblique and transverse abdominis (p<.05), and no difference between groups (p>.05). Conclusion : Based on these results, although there was no difference between the groups, in the experimental group, numerical increase in dynamic balance ability and abdominal muscle thickness was confirmed. Therefore, single limb stance exercise on the unstable support surfaces activates core muscles and has a positive effect on dynamic balancing ability.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.27 no.12
• /
• pp.1681-1690
• /
• 2003

The effect of roughness is a change in the velocity and turbulence distributions near the surface. Turbulence models with surface roughness effect are applied to the fully developed flow in a two-dimensional, rough wall channel. Modified wall function model, low-Reynolds number k-$\varepsilon$ model, and k-$\omega$ model are selected for comparison. In order to make a fair comparison, the calculation results are compared with the experimental data. The modified wall function model and the low-Reynolds number k-$\varepsilon$ model require further refinement, while the k-$\omega$ model of Wilcox performs remarkably well over a wide range of roughness values.

• Journal of the Society of Naval Architects of Korea
• /
• v.52 no.6
• /
• pp.501-508
• /
• 2015

Lately, much research on hull plate forming has been successful in improving productivity of the forming process. Those researches include forming methods, forming information, and automation. After forming each plate, the fabricated surface is compared with the corresponding designed surface. Two sets of data from the designed and fabricated surfaces are matched in order to complete the forming process. However, only a few papers deals with comparison of two surfaces. This paper presents a new matching method based on the bounding volume hierarchy (BVH). By comparing the conventional method, this new approach using BVH shows not only good agreement but also better advantages.

• Journal of the Korea Safety Management & Science
• /
• v.5 no.1
• /
• pp.115-128
• /
• 2003

To comparison the surface treatment methods of stone board materials, the results of Dorry's abrasive test were 23.4 for water-jet system and 18.9 for flame-burner system. Therefore abrasive hardness, the stone board materials by the water-jet system was greater than one by flame-jet system. As a result of Shore's hardness test, the stone board materials by water-jet system was twice greater than one by flame-jet system. Authors carried out microscopic observation to survey a defection of the composition minerals for two methods, but all of the both methods have not founded a defection. Therefore, the stone board materials by water-jet system was greater durability than one by flame-jet for the surface treatment methods.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2022.11a
• /
• pp.63-64
• /
• 2022

In this study, the quality of mineral admixture, Comparison of blast-furnace slag(BS) and fly ash(FA)in Korea and China. In the case of BS, Korea is mainly classified into 1 type to 4 types according to the specific surface area, whereas China is classified into S105, 95, and 75 according to the activity index of 28 days of age. In the case of FA, Korea is like BS, is mainly classified into types 1 to 4 according to specific surface area, whereas China is classified into F, C (class F, class C) by ingredients and class I, II, and III according to powder and ignition loss.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 1994.10a
• /
• pp.157-164
• /
• 1994

Finite element analysis of material deformation is successfully utilized to understand metal forming processes such as forging, extrusion and deep drawing. However, such analysis involves contact problems; a free node touches a die surface and a contact node slips along the die surface. In the present investigation, appropriate contact algorithms were developed assuming that a three dimensional surface can be divided into bilinear patches and that nodal velocities are linear during an incremental time. The algorithms were coded into a computer program and tested for a simple surface. Comparison of the test result with that obtained from a commercial code is presented and discussed.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.7 no.5
• /
• pp.7-14
• /
• 1998

In this paper, Fractal analysis applied to evaluate machined surface profile. The spectrum method was used to calculate fractal dimension of generated surface profiles by Weierstrass-Mandelbrot fractal function. To avoid estimation errors by low frequency characteristics of FFT, the Maximum Entropy Method (MEM) was examined. We suggest a new criterion to define the MEM order m. MEM power spectrum with our criterion is proved to be advantageous by the comparison with the experimental results.