• Title/Summary/Keyword: Number of Void

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In vitro Estimation of The Hounsfield Units and The Volume and Void of Canine Struvite Stones as Predictors of Fragility in Extracorporeal Shock Wave Lithotripsy

  • Wang, Ji-hwan;Hwang, Tae-sung;Jung, Dong-in;Yeon, Seong-chan;Lee, Hee-chun
    • Journal of Veterinary Clinics
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    • v.34 no.3
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    • pp.178-184
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    • 2017
  • The aim of this study was to determine whether Hounsfield units (HUs), volume, and various void parameters can predict stone fragility in extracorporeal shock wave lithotripsy (ESWL). HU, volume, porosity, number of voids/stone volume, and void distribution of 30 struvite stones were estimated using helical computed tomography (CT) and micro-CT. The number of shock waves necessary for full fragmentation was accepted as a measure of the stone fragility in ESWL. The correlations between the number of shock waves and the HU, volume, porosity, and number of voids/stone volume were examined. The number of shock waves of the two groups according to the void distribution was also compared. Stone volume correlated with the number of shock waves. Shell-patterned struvite stones were significantly less susceptible to fragmentation in ESWL than non-shell-patterned struvite stones. Stone volume and void distribution may be predictors of the outcome of ESWL treatment.

Evaluation methods for Void Closing Behavior in Large Ingot (기공닫힘부 폐쇄정도 결정을 위한 평가방법 연구)

  • Choi, I.J.;Choi, H.J.;Yoon, D.J.;Lee, G.A.;Lim, S.J.
    • Transactions of Materials Processing
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    • v.20 no.5
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    • pp.339-343
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    • 2011
  • This paper presents methods for analyzing the extent of cylindrical-shaped void closure. In addition, a quantitative relationship between change in void fraction and height reduction ratio of a compressed specimen is proposed. The height reduction ratio, number of deformation steps and billet rotation were chosen as key process parameters influencing the void closing behavior, namely, the changes in void shape and size during hot open die forging of a large ingot. The extent of void closure was analyzed from microscopic observations and estimated from tensile test results. The tensile strengths of specimens with closed voids and those without were compared for various reduction ratios in height. The results confirmed that void closure occurs at reduction ratios greater than 30 %. The void closing behavior could be expressed as a hyperbolic tangent function of reduction ratio in height, number of paths, and billet rotation. The knowledge presented in this paper could be helpful for optimizing deformation paths in open die forging processes.

Study on a methodology for estimation of void ratio of very fine clayey soil by using micro X-ray CT scan (Micro X-ray CT 촬영을 통한 세립 점성토의 간극비 추정 방법 연구)

  • Heo, Seong-Jun;Kim, Kwang-Yeom;Kwon, Young-Cheul;Kim, Hong-Taek;Shin, Hyu-Soung
    • Proceedings of the Korean Geotechical Society Conference
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    • 2010.09a
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    • pp.392-403
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    • 2010
  • In this study, a new methodology by using the X-ray CT scan is proposed for estimating void ratio of very fine clayey soil. Since the particle size of the clay is too fine to calculate the volume of void inside the clays, CT scanning tests with a number of clay specimens that were artificially set to have various designated void ratios have been carried out. From the tests, a relationship between the CT values and void ratios is given to be used for estimating the invisible void ratio of very fine clay from a representative CT value scanned. The linear relationship was able to be acquired finally. It is expected that micro X-ray CT scanning can be capable of capturing the void ratio of very fine soils without any errors inherent in the conventional specific gravity tests.

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Void Closing Conditions of Large Ingot by Path Schedules (대형 잉곳의 기공압착 효과 향상을 위한 폐쇄조건 연구)

  • Choi, I.J.;Choi, H.J.;Kim, D.W.;Choi, S.;Lim, S.J.
    • Transactions of Materials Processing
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    • v.19 no.8
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    • pp.480-485
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    • 2010
  • In this work, the closing behavior of cylindrical-shaped voids was experimentally investigated according to various parameters such as reduction ratio in height, initial void size and billet rotation during hot open die forging process. The reduction ratio in height, number of path, and billet rotation were chosen as key process parameters which influence the void closing behavior including the change of void shape and size. On the other hand, values of die overlapping and die width ratio were set to be constant. Void closing behavior was estimated by microscopic observation. Based on the observations, it was confirmed that application of billet rotation is more efficient to eliminate the void with less reduction ratio in height. The experimental results obtained from this study could be helpful to establish the optimum path schedule of open die forging process.

Characteristics of acoustic emission according to variation gap length on artificial needle shape void (인공적 침상보이드의 갭길이 변화에 따른 음향방출 특성)

  • 박재준;김상남
    • Electrical & Electronic Materials
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    • v.8 no.4
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    • pp.495-503
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    • 1995
  • As lengthen gap leng of artificial needle shape void 0.24.rarw.1.5[mm]), the amplitude of AE(Acoustic Emission) pulses was enlarged and number of pulses be generated was few. The longer gap length of void, the shorter breakdown time. As a result of this, I found that existen of void in insulation mate was fatal deterioration of insulation. According to phase angle of applied voltage, time being void was scattered largely in region of phase angle of pulses of origination in phase angle of applied voltage. The result will be used to analysis of void diagnosis.

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3D micro-CT analysis of void formations and push-out bonding strength of resin cements used for fiber post cementation

  • Uzun, Ismail Hakki;Malkoc, Meral Arslan;Keles, Ali;Ogreten, Ayse Tuba
    • The Journal of Advanced Prosthodontics
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    • v.8 no.2
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    • pp.101-109
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    • 2016
  • PURPOSE. To investigate the void parameters within the resin cements used for fiber post cementation by micro-CT (${\mu}CT$) and regional push-out bonding strength. MATERIALS AND METHODS. Twenty-one, single and round shaped roots were enlarged with a low-speed drill following by endodontic treatment. The roots were divided into three groups (n=7) and fiber posts were cemented with Maxcem Elite, Multilink N and Superbond C&B resin cements. Specimens were scanned using ${\mu}CT$ scanner at resolution of $13.7{\mu}m$. The number, area, and volume of voids between dentin and post were evaluated. A method of analysis based on the post segmentation was used, and coronal, middle and apical thirds considered separately. After the ${\mu}CT$ analysis, roots were embedded in epoxy resin and sectioned into 2 mm thick slices (63 sections in total). Push-out testing was performed with universal testing device at 0.5 mm/min cross-head speed. Data were analyzed with Kruskal-Wallis and Mann-Whitney U tests (${\alpha}=.05$). RESULTS. Overall, significant differences between the resin cements and the post level were observed in the void number, area, and volume (P<.05). Super-Bond C&B showed the most void formation ($44.86{\pm}22.71$). Multilink N showed the least void surface ($3.51{\pm}2.24mm^2$) and volume ($0.01{\pm}0.01mm^3$). Regional push-out bond strength of the cements was not different (P>.05). CONCLUSION. ${\mu}CT$ proved to be a powerful non-destructive 3D analysis tool for visualizing the void parameters. Multilink N had the lowest void parameters. When efficiency of all cements was evaluated, direct relationship between the post region and push-out bonding strength was not observed.

The Analysis of Discharge Distribution due to the Inner Void of Extra High Voltage Cable

  • Kim Tag-Yong;Hong Jin-Woong
    • KIEE International Transactions on Electrophysics and Applications
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    • v.5C no.4
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    • pp.155-160
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    • 2005
  • This paper addresses the discharge characteristics of cross-linked polyethylene according to void by the Weibull function. It analyzes discharge number and amount of discharge using Weibull distribution to identify the inter-relationship between partial discharge and defect. We detected a 10 second discharge. The applied voltage increased by 1 [kV] at discharge inception voltage. As a result, in a no-void specimen, the shape parameter was consistent according to the increase of voltage, whereas, in a void specimen, it increased according to the increase of voltage. As the result, the shape parameter expressed a fixed value at no-void specimen. However, in void specimen, according to increasing voltage shape parameter rapidly increases.

A STUDY ON THE VOID FORMATION AND DETAIL REPRODUCTION ACCORDING TO THE VARIOUS IMPRESSION MATERIALS AND MIXING METHODS (수종 인상재의 혼합방법에 따른 기포형성과 표면 재현력에 관한 연구)

  • Ryu, Hyeong-Seon;Lim, Heon-Song;Lim, Ju-Hwan;Cho, In-Ho
    • The Journal of Korean Academy of Prosthodontics
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    • v.40 no.2
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    • pp.140-155
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    • 2002
  • Void-free impression taking is important for the fabrication of accurate dental restorations. One of the essential properties of an impression material used for indirect fabrication of precision castings is the reproduction of the fine detail. The objective in this study was to determine the influence of mixing methods on the number of voids and surface detail reproduction. The number of voids and surface detail reproduction were evaluated with the steteomicroscope $SZ-PT^{(R)}$ and photographed. The results were as follows ; 1. In comparison of the void formation according to mixing methods of all impression materials, mechanical mixing was better than hand mixing and there was significant difference(p<0.05) 2. In comparison of the void formation according to hand mixing of alginate impression materials($TOKUSO\;A-1{\alpha}^{(R)},\;CAVEX\;IMPRESSIONAL^{(R)},\;AROMA \;FINE\;DF\;III^{(R)}$), there was no significant difference among alginate groups. But the number of void was increased in the order of $Panasil^{(R)}\;contact,\;TOKUSO\;A-1{\alpha}^{(R)},\;Permlastic^{(R)}$ light bodied and there was significant difference (p<0.05). 3. In comparison of the void formation according to mechanical mixing of alginate impression materials($TOKUSO\;A-1{\alpha}^{(R)},\;CAVEX\;IMPRESSIONAL^{(R)},\;AROMA FINE\;DF\;III^{(R)}$), there was no significant different among alginate groups. But the number of void was decreased in order of $TOKUSO\;A-1{\alpha}^{(R)},\;Permlastic^{(R)}light\;bodied,\;Panasil^{(R)}$ contact and there was significant difference (p<0.05). 4. In comparison of the surface detail reproduction according to mixing methods of 3 types of impression materials($TOKUSO\;A-1{\alpha}^{(R)},\;Permlastic^{(R)}\;light\;bodied,\;Panasil^{(R)}\;contact$), there was no significant difference between hand mixing and mechanical mixing method 5. The surface detail reproduction was only influenced by impression materials, and produced better in order of $TOKUSO\;A-1{\alpha}^{(R)},\;Panasil^{(R)}\;contact,\;Permlastic^{(R)}$ light bodied. There was significat difference among 3 type of impression materials(p<0.05). From the above results, void formation is influenced by mixing methods and surface detail reproduction is influenced by impression materials than mixing methods. Therefore, to fabricate accurate restorations, proper impression material and mechanical mixing method are more effective and available clinically.

An Experimental Study on the Effect of Capillary Pressure on the Void Formation in Resin Transfer Molding Process (수지이동 성형공정에서 기공형성에 미치는 모세관압의 영향에 관한 실험적 연구)

  • 이종훈;김세훈;김성우;이기준
    • The Korean Journal of Rheology
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    • v.10 no.4
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    • pp.185-194
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    • 1998
  • Flow-induced voids during resin impregnation and poor fiber wetting give serious effects on the mechanical properties of composites in resin transfer molding process. In order to better understand the characteristics of resin flow and to investigate the mechanism of void formation, flow visualization experiment for the resin impregnation was carried out on plain weaving glass fiber mats using silicon oils with various viscosity values. The permeability and the capillary pressure for the fiber mats of different porosities were obtained by measuring the penetration length of the resin with time and with various injection pressure. At low porosity and low operating pressure, the capillary pressure played a significant role in impregnation process. Video-assisted microscopy was used in taking the magnified photograph of the flow front of the resin to investigate the effect of the capillary pressure on the void formation. The results showed that the voids were formed easily when the capillary pressure was relatively high. No voids were detected above the critical capillary number of 2.75$\times$$10^{-3}, and below the critical number the void content increased exponentially with decrease of the capillary number. The content of void formed was independent of the viscosity of the resin. For a given capillary number, the void content reduced with the lower porosity of the fiber mat.

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An Experimental Study on Void Closure Behavior with respect to Reductions in Height (압하율에 따른 기공압착 거동에 관한 실험적 연구)

  • Choi, I.J.;Choi, H.J.;Park, H.J.;Choi, S.;Jung, T.W.;Park, D.K.;Choi, S.K.;Lim, S.J.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2009.05a
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    • pp.114-117
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    • 2009
  • In this work, closing behavior of the voids generated in a casting process was investigated for various parameters such as reductions in height void size and billet rotation during hot open die forging process. The reduction in height and path schedule including the number of paths and billet rotation were chosen as key process variables to express the change of geometrical void shape and void closing behavior. On the other hand, values of die overlapping and die width ratio were set to be constant. Extend of void closure was observed and evaluated using tensile test and microscope. Based on the experimental result, it is ensured that void closure do not occur at 15% and 30% reduction in height as well as one or two rotations of a billet. The useful datum obtained from this study could be utilized to establish an optimum path schedule in the open die forging process.

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