• Title, Summary, Keyword: Porous ratio

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Effect of Carbon Source on Porosity and Flexural Strength of Porous Self-Bonded Silicon Carbide Ceramics (탄소 원료가 다공질 Self-Bonded SiC (SBSC) 세라믹스의 기공율과 곡강도에 미치는 영향)

  • Lim, Kwang-Young;Kim, Young-Wook;Woo, Sang-Kuk;Han, In-Sub
    • Journal of the Korean Ceramic Society
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    • v.45 no.7
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    • pp.430-437
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    • 2008
  • Porous self-bonded silicon carbide (SBSC) ceramics were fabricated at temperatures ranging from 1700 to $1850^{\circ}C$ using SiC, silicon (Si), and three different carbon (C) sources, including carbon black, phenol resin, and xylene. The effects of the Si:C ratio and carbon source on porosity and strength were investigated as a function of sintering temperature. Porous SBSC ceramics fabricated from phenol resin showed higher porosity than the others. In contrast, porous SBSC ceramics fabricated from carbon black showed better strength than the others. Regardless of the carbon source, the porosity increased with decreasing the Si:C ratio whereas the strength increased with increasing the Si:C ratio.

A Retrospective Study of Sintered Porous-surfaced Dental Implants in Restoring the Edentulous Posterior Mandible: Up to Eight Years of Functioning (하악 구치부에 식립한 sintered porous surfaced implants의 후향적 다기관 연구)

  • Kim, Woo-Sung;An, Kyung-Mi;Sohn, Dong-Seok;Jung, Heui-Seung;Shin, Im-Hee
    • The journal of the Korean dental association
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    • v.47 no.12
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    • pp.823-829
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    • 2009
  • Purpose : The aim of this study was to evaluate the survival rate of sintered porous-surfaced implants placed in the edentulous posterior mandibles, in relation to implant length and diameter, crown-to-implant ratio, and types of prostheses, for a maximum of eight years of functioning. Material and Methods : The study group consisted of 43 partially edentulous patients who visited Catholic University Hospital of Daegu and one private dental clinic. A total of 122 sintered porous-surfaced implants n $Endopore^{(R)}$ (Inn ova Life Sciences, Toronto, Ontario, Canada) -- were placed in the edentulous posterior mandibles, Two diameter sizes (4.1 mm and 5.0 mm) and four lengths (5.0 mm, 7.0 mm, 9.0 mm, and 12.0 mm) were used. One hundred and three implants were splinted and 21 implants were nonsplinted. The survival rates of the implants in relation to length, diameter, crown-to-implant ratio, and types of prostheses were investigated. Statistical data were analyzed using SPSS Win.Ver 14.0 software with the Chi-square test. Results : The survival rate of the 4.1mm diameter implants was 100% and 91.2% for the 5.0mm diameter implants. The survival rates of the implants of differing diameters were found to be statistically different (p=0.005). The survival rates of both the 5.0mm and 7.0 mm length implants were 100%. The survival rate of the 9.0mm length implants was 97.9% and for the 12.0mm length implants was 95.1%. There was no statistical difference in survival rates for the differing lengths of implants. Of the 103 prostheses that were splinted, the survival rate was 98.0%. The survival rate of splinted prostheses was higher than that of the non-splinted prostheses, but was found to be not statistically different. There were no failed cases when the crown-to-implant ratio was under 1.0. When the crown-to-implant ratio was between 1.0 and 1.5, the failure rate of the implants was 6.7%. No failure was recorded with the ratio range of 1.5 to 2.0. Relative to the crown-to-implant ratio of 1.0, the failure rates were statistically different (p=0.048). Discussion and Conclusion : The cumulative survival rate of the porous-surfaced implants placed in the edentulous posterior mandibles was 97.5%. Short porous-surfaced implants showed satisfactory results after a maximum of nine years of functioning in the edentulous posterior mandibles.

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Combustion and Emission Characteristics of the Surface Flames in Porous Ceramic Burner (다공세라믹 버너를 이용한 표면화염의 연소 및 배기특성)

  • Hwang, Sang-Soon
    • Journal of the Korean Society of Combustion
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    • v.6 no.1
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    • pp.29-35
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    • 2001
  • The surface flames in porous ceramic burner are experimentally characterized to investigate the effects of equivalence ratio and firing rates. The results show that the surface flames are classified into green, red radiant and blue surface flame as decrease of equivalence ratio. And each flame is maintained very stably and shows the same flame characteristics at any orientation of ceramic burner. Particularly the blue surface flame was found to be very stable at very lean equivalence ratio at 200 to $800\;kw/m^2$ firing rates. And the exhausted NOx was analysed to find out which flame has lower NOx emission. The blue surface flame showed the lowest NOx emission regardless of the location of burner since it sustained very stable at lean mixture ratio.

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Combustion Performance of a Coaxial Porous Injector using Ethanol/N2O Propellant (동축형 다공성재 분사기의 에탄올/아산화질소 연소성능)

  • Kim, Dohun;Lee, Keonwoong;Koo, Jaye
    • Journal of the Korean Society of Propulsion Engineers
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    • v.17 no.5
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    • pp.37-46
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    • 2013
  • The gas jet from a coaxial porous injector for two-phase flows is discharged radially from the porous surface, which encloses the center liquid jet. Several hot-firing test using ethanol/nitrous oxide propellants was conducted to analyze the effect of oxidizer/fuel ratio on the combustion performance, and the uncertainty analysis was performed for the results. The characteristic velocity was affected by oxidizer/fuel ratio similarly with the results of CEA calculation except that the maximum characteristic velocity was appeared in the stoichiometric ratio. The characteristic velocity efficiency was increased as the oxidizer/fuel ratio increases.

Planting-Ability Valuation of Porous Concrete Using Industrial By-Products (산업부산물을 이용한 포러스콘크리트의 식생능력평가)

  • 박승범;이봉춘;김정환;윤덕열
    • Journal of the Korea Concrete Institute
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    • v.14 no.4
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    • pp.623-629
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    • 2002
  • Porous concrete enables water and air to pass through a firmly hardened material and allows required nutrients to reach roots of plants. The purpose of this study is to analyze void ratio, strength property and planting ability when using silica fume and fly ash, the change of aggregate gradation and ratio of paste to aggregate. The results of an experiment from the planting ability of the porous concrete to its influence on the compressive strength are reported in this paper. As a result of the experiment, the compressive strength is higher when the gradation of aggregate is smaller, and it also goes higher when the ratio of paste to aggregate gets larger. The planting ability of porous concrete is decided by the germination and the grass length of perennial ryegrass. The grass length of perennial ryegrass is longer when the gradation of aggregate is greater and the ratio of paste to aggregate gets smaller. Therefore the efficiency of planting goes through the perennial ryegrass is in compliance with the void ratio, aggregate gradation.

A Study on Mechanical Properties of Porous Concrete Using Cementless Binder

  • Lee, Jong-Won;Jang, Young-Il;Park, Wan-Shin;Kim, Sun-Woo
    • International Journal of Concrete Structures and Materials
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    • v.10 no.4
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    • pp.527-537
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    • 2016
  • This study evaluated the mechanical characteristics and durability of porous concrete produced with a cementless binder based on ground granulated blast furnace slag (BFS), fly ash (FA) and flue gas desulfurization gypsum (CP). As a result, the void ratio was increased slightly from the target void ratio, by 1.12-1.42 %. Through evaluating the compressive strength, it was found that the compressive strength of porous concrete with cementless binder decreased in comparison to the compressive strength of porous concrete with ordinary Portland cement (OPC), but the difference was insignificant, at 0.6-1.4 MPa. Through the freeze-thawing test to evaluate the durability, it was found that the relative dynamic elastic modulus of porous concrete with cementless binder decreased to 60 % or less at 80 cycles. The result of the chemical resistance test showed that the mass reduction rate was 12.3 % at 5 % HCl solution, and 12.7 % at 12.3 and 5 % $H_2SO_4$ solutions.

Buckling behavior of smart MEE-FG porous plate with various boundary conditions based on refined theory

  • Ebrahimi, Farzad;Jafari, Ali
    • Advances in materials Research
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    • v.5 no.4
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    • pp.279-298
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    • 2016
  • Present disquisition proposes an analytical solution method for exploring the buckling characteristics of porous magneto-electro-elastic functionally graded (MEE-FG) plates with various boundary conditions for the first time. Magneto electro mechanical properties of FGM plate are supposed to change through the thickness direction of plate. The rule of power-law is modified to consider influence of porosity according to two types of distribution namely even and uneven. Pores possibly occur inside FGMs due the result of technical problems that lead to creation of micro-voids in these materials. The variation of pores along the thickness direction influences the mechanical and physical properties. Four-variable tangential-exponential refined theory is employed to derive the governing equations and boundary conditions of porous FGM plate under magneto-electrical field via Hamilton's principle. An analytical solution procedure is exploited to achieve the non-dimensional buckling load of porous FG plate exposed to magneto-electrical field with various boundary condition. A parametric study is led to assess the efficacy of material graduation exponent, coefficient of porosity, porosity distribution, magnetic potential, electric voltage, boundary conditions, aspect ratio and side-to-thickness ratio on the non-dimensional buckling load of the plate made of magneto electro elastic FG materials with porosities. It is concluded that these parameters play remarkable roles on the dynamic behavior of porous MEE-FG plates. The results for simpler states are confirmed with known data in the literature. Presented numerical results can serve as benchmarks for future analyses of MEE-FG plates with porosity phases.

Effect of Additive Ball Clay on Physical Properties of Porous Ceramic (볼 클레이 첨가에 따른 세라믹 다공체의 물리적 특성변화)

  • Kang, Young-Sung;Kim, Sang-Sik
    • Journal of Korean Society of Environmental Engineers
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    • v.36 no.2
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    • pp.109-112
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    • 2014
  • A porous ceramic which has fine porosity and small specific gravity is made with Cenosphere and Ball Clay under condition of $1,250^{\circ}C$ in calcination temperature and 30 minutes of calcination time. The average size of porous ceramic was about $2.5{\times}10^{-5}$ m and pores are well developed. The void-fraction of porous ceramic was 67.1% under the input of Cenosphere and Ball clay with the weight ratio of 100 to 5. However, as weight ratio of Ball Clay increased to 20, 40, 100, the void fraction decreased to 58.4, 56.7, 47% respectively. When the weight ratio of Cenosphere and Ball Clay was 100 to 100, the apparent density of porous ceramic was $1.04g/cm^3$. which is twice the density when the weight ratio of Ball Clay was 5. On the other hand, absorption rate decreased by at least 100%. In condition of weight ratio of Cenosphere and Ball Clay was 100 to 100, compressive strength of porous ceramic was 30 (MPa), improve by about 76% or more when the weight ratio of Ball Clay was 5.

An Experimental Study on The Strength Elevation of Porous Concrete according to the Mixing Proportion (배합요인에 따른 포러스콘크리트의 강도향상에 관한 실험적 연구)

  • 백용관;김재환;반성수;박선규;김규용;김무한
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.255-258
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    • 1999
  • In recent years, the study on the porous concrete which has excellent permeability is actively advanced in the field of architectural and civil engineering. But porous concrete has a reciprocal concept in the aspect of comparative large and continuos void structure and reduction of void for insurance of the necessary strength on the mixing proportion, must have satisfied of the properties of these. Therefore this study is series of experiment for the strength elevation and evaluated the effect according to fine replacement ratio and levels of cement content. As a result, the strength of porous concrete was elevated by an increase of fine replacement ratio and cement content.

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