• 한국세라믹학회지
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• 제35권9호
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• pp.988-994
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• 1998

In the manufacturing of vitreous bonded CBN tool the porosity change associated with various processing conditions, I. e. the sintering temperature and the size and the amount of abrasive grits was observed. In the case of sintering of vitreous bond material only the specimen density reached the maximum at 950$^{\circ}C$ and then the total porosity was increased slightly with the temperature above 950$^{\circ}C$. In the sintering of a-brasive grits and the vitreous bond material together a marked increase in the total porosity was found with the temperature above 950$^{\circ}C$ Reducing the grit size at the constant volume fraction of abrasive grits showed an increase in the total porosity at whole sintering temperature. On the contrary. it was observed that increasing the volume fraction of abrasive grits with a same size showed the increased open porosity simultaneously with decreased closed porosity at whole sintering temperature.

• Coupled systems mechanics
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• 제6권4호
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• pp.399-415
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• 2017

This paper deals with the nonlinear static deflections of functionally graded (FG) porous under thermal effect. Material properties vary in both position-dependent and temperature-dependent. The considered nonlinear problem is solved by using Total Lagrangian finite element method within two-dimensional (2-D) continuum model in the Newton-Raphson iteration method. In numerical examples, the effects of material distribution, porosity parameters, temperature rising on the nonlinear large deflections of FG beams are presented and discussed with porosity effects. Also, the effects of the different porosity models on the FG beams are investigated in temperature rising.

• Steel and Composite Structures
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• 제24권5호
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• pp.579-589
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• 2017

The objective of this work is to analyze post-buckling of functionally graded (FG) beams with porosity effect under compression load. Material properties of the beam change in the thickness direction according to power-law distributions with different porosity models. It is known that post-buckling problems are geometrically nonlinear problems. In the nonlinear kinematic model of the beam, total Lagrangian finite element model of two dimensional (2-D) continuum is used in conjunction with the Newton-Raphson method. In the study, the effects of material distribution, porosity parameters, compression loads on the post-buckling behavior of FG beams are investigated and discussed with porosity effects. Also, the effects of the different porosity models on the FG beams are investigated in post-buckling case.

• Wind and Structures
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• 제27권1호
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• pp.59-70
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• 2018

In this paper, geometrically non-linear analysis of a functionally graded simple supported beam is investigated with porosity effect. The material properties of the beam are assumed to vary though height direction according to a prescribed power-law distributions with different porosity models. In the nonlinear kinematic model of the beam, the total Lagrangian approach is used within Timoshenko beam theory. In the solution of the nonlinear problem, the finite element method is used in conjunction with the Newton-Raphson method. In the study, the effects of material distribution such as power-law exponents, porosity coefficients, nonlinear effects on the static behavior of functionally graded beams are examined and discussed with porosity effects. The difference between the geometrically linear and nonlinear analysis of functionally graded porous beam is investigated in detail. Also, the effects of the different porosity models on the functionally graded beams are investigated both linear and nonlinear cases.

• Weed & Turfgrass Science
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• 제3권2호
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• pp.143-149
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• 2014

본 연구는 아메리카동애등에분변토(soldier fly casts; SFC)의 단점을 개량하기 위해 코코피트(cocopeat; Coco)와 혼합된 토양개량제의 골프장 토양개량제로서의 사용가능성을 평가하기 위해 모래와 혼합비율 별 물리화학성을 조사하였다. 토양개량제는 SFC, Coco, 25% SFC+75% Coco(Mix1), 50% SFC+50% Coco (Mix2) 및 75% SFC+25% Coco (Mix3)이었고, 각각 3%, 5%, 7% 및 10% 씩 혼합되어 모래상토를 조성하였다. SFC, Mix1, Mix2 및 Mix3는 토양 pH와 EC에서 고도의 상관성(P<0.01)을 나타내어 토양개량제의 혼합에 의해 모래상토의 토양화학성에 영향을 주었다. SFC, Coco, Mix1, Mix2 및 Mix3은 모세관공극, 비모세관공극 및 공극이 USGA기준에 적합하였고, 혼합비율이 증가할수록 모세관공극과 총공극이 증가하였으며(P<0.05), Mix1과 Mix3의 비모세관공극은 모세관공극과 수리전도도에서 부의 상관성을 보였다(P<0.01). Mix1, Mix2 및 Mix3에서 SFC는 상토의 모세관공극의 변화에 영향을 주었고, Coco는 모세관공극과 총공극의 변화에 영향을 주었다. 이들 결과를 종합할 때, SFC와 Coco가 혼합된 토양개량제(Mix1~3)는 SFC보다 모래상토의 모세관 공극과 수리전도도를 개선하여 SFC의 단점을 보완한 것으로 평가되었다.

• 한국기계가공학회지
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• 제6권2호
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• pp.9-16
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• 2007

The fatigue test of the fillet weldments were executed with different groove angles and porosity. The groove angles of $90^{\circ}$, $45^{\circ}$ and $55^{\circ}$ were compared with fatigue lives. After the fillet weldment failure, the porosity which found at the fractured surface were observed to account the effect on fatigue life. Finite element analysis were performed to correlate the fatigue strength and the size & the location of porosity. The stress-strain field were severely affected by the length of notch and the size & location of porosity. Based on the quantitative analysis of porosity effect, the total volume of porosity was key factor for fatigue strength of the fillet weldment.

• Nuclear Engineering and Technology
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• 제34권5호
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• pp.433-435
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• 2002

The relation between sintered densities and porosities in UO$_2$ pellets is investigated. The open porosity decreases linearly up to about 95% T.D.,(theoretical density) as the sintered density increases whereas, above 96% T.D., sintered UO$_2$ pellets do not have any open pores. The fraction of open porosity to the total porosity also decreases linearly as the sintered density increases, though the slope is lower than that of open porosity and, above 95% T.D., the fraction decreases rapidly to approach a zero.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2006년도 총회 및 춘계학술발표회
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• pp.411-414
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• 2006

This study was examined to determine hydraulic conductivity of vadose zone($K_s$) and effective porosity(${\phi}_e$) of undisturbed soil profiles collected at each vadose zone of 6 study areas in South Korea. Effective porosity was approximately 19% of total porosity for each soil profile. Applied to Ahuja's equation, the correlation between $K_s$ and ${\phi}_e$ showed $y=1.3{\times}10^{-7}x^{2.15}(r^2=0.37)$ for total soil profiles. Although the small numbers of soil profile were used for this study, the result of this study might be used for other soil hydraulic studies as reasonable data.

• Restorative Dentistry and Endodontics
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• 제46권4호
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• pp.57.1-57.9
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• 2021

Objectives: This study aimed to compare and evaluate the porosity and pore size distribution of high-viscosity glass ionomer cements (HVGICs) and conventional glass ionomer cements (GICs) using micro-computed tomography (micro-CT). Materials and Methods: Forty cylindrical specimens (n = 10) were produced in standardized molds using HVGICs and conventional GICs (Ketac Molar Easymix, Vitro Molar, MaxxionR, and Riva Self-Cure). The specimens were prepared according to ISO 9917-1 standards, scanned in a high-energy micro-CT device, and reconstructed using specific parameters. After reconstruction, segmentation procedures, and image analysis, total porosity and pore size distribution were obtained for specimens in each group. After checking the normality of the data distribution, the Kruskal-Wallis test followed by the Student-Newman-Keuls test was used to detect differences in porosity among the experimental groups with a 5% significance level. Results: Ketac Molar Easymix showed statistically significantly lower total porosity (0.15%) than MaxxionR (0.62%), Riva (0.42%), and Vitro Molar (0.57%). The pore size in all experimental cements was within the small-size range (< 0.01 mm³), but Vitro Molar showed statistically significantly more pores/defects with a larger size (> 0.01 mm³). Conclusions: Major differences in porosity and pore size were identified among the evaluated GICs. Among these, the Ketac Molar Easymix HVGIC showed the lowest porosity and void size.

• 대한치과기공학회지
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• 제13권1호
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• pp.15-19
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• 1991

This study was made to effect on the porosity when model making for control of vibrator. Samples of total 600 were made by plaster and stone divided low, medium and high which is 100 each. The following results were obtained to observation porosity of surface by eyes. 1. Second stage was fewer than third stage, first stage was fewer than third stage in porosity number of plaster model. 2. Second stage was fewer than first stage in porosity number of stone model. 3. Stone model was fewer than plaster model in porosity number of third stage.