• Journal of the Korean Wood Science and Technology
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• v.18 no.3
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• pp.6-16
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• 1990

The objectives of this study were to investigate the relative effects of specific gravity and particle size on internal bond and tensile strengths and fracture toughness of particleboard and to compare mechanical strength with fracture toughness. The particleboard was manufactured with three different particle sizes at specific gravity levels of 0.6, 0.7, and 0.8 with a resin content of 10% based on oven dry weight. The results were summarized as follows: 1. Internal bond strength. fracture toughness in internal bond test. maximum tensile strength, and fracture toughness in tension test increased with the increase of specific gravity of particleboard. 2. As partcle size increased, internal bond strength, fracture toughness. maximum tensile strength. and fracture toughness in tension test increased. 3. The maximum tensile strength and fracture toughness appeared to be in a direct relationship, and then maximum tensile strength could be used for predicition of fracture toughness for tension test. 4. The fracture toughness in internal bond test was somewhat independent on induced crack length.

• International Journal of Concrete Structures and Materials
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• v.7 no.4
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• pp.287-293
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• 2013

Strength and some durability properties of concrete containing rice husk ash (RHA) predominantly composed of amorphous silica at a specific surface of 235 $m^2/kg$ produced using a charcoal incinerator were determined. The maximum ordinary Portland cement (OPC) replacement with the RHA increased with increase in water/binder (w/b) ratio of the concrete mixes. The results show that 15 % OPC could be substituted by the RHAwithout strength loss at w/b ratio of 0.50. The split tensile strength generally increased with increase in RHA content for the mixes.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.684-687
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• 2004

The purpose of this study is to obtain basic data on the properties of the development of lightweight mortar contained foam agent for various applications in the field. In the experiment, as a result of measurement the specific gravity by the change of the W/C and the foam agent into a variable and measuring the compressive strength of mortar, specific gravity checked that a compressive strength therefore increased. Mortar is using lightweight foam agent having the change of specific gravity, the water cement ratio $50\%,\;40\%,\;30\%$. This paper present extensive data on the characteristics of strength of the lightweight mortar and also presents the mechanical characteristics of the lightweight according to specific gravity.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2005.05a
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• pp.354-359
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• 2005

The objective of this research work is to investigate into static characteristics of ISB panels with the pyramidal structure as a internally structured material. In order to investigate the behavior of material deformation and fracture characteristics, several tensile tests have been carried out for the ISB panel and skin sheet. Through the results of the experiments, the mechanical properties of ISB panel and skin sheet and fracture characteristics have been obtained. In addition, the mechanical properties of the ISB panel have been compared with that of the skin sheet by the view point of a specific modulus, a specific yield strength and a specific strength. From the results of the comparision, it has been shown that the ISB panel has an excellent static characteristics.

• Journal of The Korean Digital Architecture Interior Association
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• v.11 no.4
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• pp.21-27
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• 2011

These materials in architecturally glass or metal have weaknesses such as inadequate insulating quality, combustibility and toxic gases in fires substance. However, Autoclaved Lightweight Concrete(ALC) has excellent thermal insulation properties and seem to possess the superb insulating quality as substitute of existing exterior materials. This research is to compare experimentally to the kind of the strength properties of ALC materials which mixed with blast furnace slag pounder and silica fume. For the purpose of increasing the strength, the plastic states of ALC evaluate the physical characteristics as microstructure and strength according to various specific gravity. According to the quicklime quantity the compressive strength is proportionate depend on the absolute dried specific gravity. When not putting in 10% quicklime, the compressive strength appeared most lowly with 14.0MPa. When putting in the quicklime, the strength appeared higher with 15.1MPa. And strength of specimen containing 2.25% silica fume is 15.6MPa increased 10.3% than reference specimen 14.0MPa.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.4
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• pp.562-570
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• 2020

This study explores manufacturing technology and basic properties of high strength cement composites at 2,000kg/㎥ of specific weight. It is suggested that lightweight-high strength cement composites can be produced by substituting silica sand in ulta-high performance concrete mixture with lightweight materials such as solid bubbles and lightweight fine aggregates. The 28-day compressive strengths of cement composites with solid bubbles were from 116MPa to 141MPa at below 2.0g/㎤ of unit density while the cement composites with lightweight aggregates possessed lower compressive strength and higher unit density. The specific weight calculated from mixture proportions did not have significant difference with unit density of hardened cement composites, indicating that unit density of hardened cement composites can be estimated from the specific weight in mixture proportions.

• Journal of the Korean Wood Science and Technology
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• v.24 no.1
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• pp.95-99
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• 1996

The bending and compression strength properties of two types Rhus verniciflua specimens, which made of no heat-treated wood and heat-treated wood for urushiol extraction, were measured. The heat-treated specimens were finger-jointed with either resorcinol-phenol or polyurethane resin adhesives, and the vertical type bending strength property was also measured in these specimens. The results obtained are as follows ; 1. The correlation coefficient between the compression strength and specific gravity in the specimens of no heat-treated and heat-treated wood was high. However there was no difference in compression strength property as affected by heat treatment. 2 The correlation coefficient between the bending strength and specific gravity in the specimens of no heat-treated and heat-treated wood was also high. However, there was no difference in bending strength property as affected by heat treatment. 3 The bending test showed high correlation between modulus of elasticity and modulus of rupture for the specimens made of no heat-treated and heat-treated wood. However, there was no difference in bending strength property between the specimens made of heat-treated and no heat-treated wood. 4. The efficiencies of bending strength test on the finger-jointed specimens of heat-treated wood with resorcinol-phenol and polyurethane resin adhesives were 0.85, 0.81. respectively.

• Journal of the Korean Wood Science and Technology
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• v.16 no.1
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• pp.21-44
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• 1988

As a way for the effective utilization of pallman chips and sawdusts, these furnish materials were combined with non-woody material of plastic (polypropylene) screen in board manufacturing to improve their weak physical and mechanical properties. The conventional boards were made with conditions of specific gravity 0.40, 0.55, 0.70, and 0.85, resin content 8, 10, 12 and 14%, and number of polypropylene screen 1, 2, 3 and 4, and press-lam boards were also manufactured. The physical and mechanical properties were measured and discussed on thickness swelling, bending modulus of rupture and elasticity, tensile strength, internal bond strength, and screw holding strength. The results obtained at this study were summarized as follows: 1. In thinckness swelling both of pallman chip board and sawdust board were improved by the increase of resin content, and press-lam boards showed lower thickness swelling than conventional boards. 2. Both the modulus of rupture and elasticity were increased with the increase of specific gravity, and press-lam boards showed higher modulus of rupture and elasticity than conventional boards. On the other hand, modulus of rupture was increased with the increase of number of polypropylene screen and resin content whereas these effects in modulus of elasticity was not recognized. 3. Tensile strength was increased with the increase of specific gravity, and the boards combined with polypropylene screen showed higher tensile strength than control boards. Also tensile strength was increased with the increase of number of polypropylene screen, and press-lam boards revealed higher tensile strength than conventional boards. 4. Internal bond strength was increased with the increase of specific gravity, and the boards combined with polypropylene screen were lower in internal bond strength than control boards. Also, the boards combined with odd number of polypropylene screen showed lower internal bond strength than those combined with even number of polypropylene screen. 5. Screw holding strength was increased with the increase of resin content and specific gravity but significant difference was not approved between boards combined with polypropylene screen and control boards. In press-lam boards, pallman chip boards of higher specific gravity but sawdust boards of lower specific gravity showed better screw holding strength than control boards.

• 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 Korean Society of Integrative Medicine
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• v.9 no.1
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• pp.151-161
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• 2021

Purpose : This study was to investigate the effectiveness of ESWT and plantar fascia-specific stretching exercise vs ESWT and high-load strengthening exercise in patients with chronic plantar fasciitis. Methods : The subjects were randomized to extracorporeal shock wave therapy ( ESWT, for 3 weeks) and daily plantar-specific stretching (Group I: Stretch group) or ESWT and high-load progressive strength (Group II: Strength group) performed every second day. The main outcome measures were ultrasound, visual analogue scale (VAS), and Korean Foot Function Index (KFFI). The ultrasound (plantar fascia thickness), pain intensity I, II (the most painful of the day?, the pain when you first step in the morning?) and KFFI (functional performance) were compared between the groups. Results : No significant difference was observed between the groups in the plantar fascia thickness but pain intensity I, II was significantly lower in Group 2 than in Group 1 at only 12weeks and functional performance was also significantly increased in Group 2 compared to Group 1 at only 12 weeks. Conclusion : The high-load strengthening exercise consisting of the progressive exercise protocol, resulted in superior after 12 weeks compared with plantar-specific stretching. High-load strength exercise may aid in a quicker reduction in pain and improvements in functional performance.