• Title/Summary/Keyword: hollow particle

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Lattice discrete particle modeling of compressive failure in hollow concrete blocks

  • Javidan, Fatemeh;Shahbeyk, Sharif;Safarnejad, Mohammad
    • Computers and Concrete
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    • v.13 no.4
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    • pp.437-456
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    • 2014
  • This work incorporates newly introduced Lattice Discrete Particle Model (LDPM) to assess the failure mechanism and strength of hollow concrete blocks. Alongside, a method for the graphical representation of cracked surfaces in the LDPM is outlined. A slightly modified calibration procedure is also suggested and used to estimate required model parameters for a tested concrete sample. Next, the model is verified for a compressively loaded hollow block made of the very same concrete. Finally, four geometries commonly used in the production of hollow concrete blocks are selected, numerically simulated, and their failure properties are explored under concentric and eccentric compressions.

Synthesis of Hollow Silica Using PMMA Particle as a Template (PMMA 고분자 입자를 템플릿으로 이용한 실리카 중공체의 제조)

  • Hwang, Ha-Soo;Cho, Kye-Min;Park, In
    • Applied Chemistry for Engineering
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    • v.21 no.3
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    • pp.353-355
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    • 2010
  • Poly(methyl methacrylate) (PMMA) particles were prepared by soap-free emulsion polymerization of MMA in the presence of a cationic initiator, 2,2'-azobis(2-methylpropionamidine) (AIBA). The Stober method has been adopted to coat silica on the surface of these cationic particles. Negatively charged silica precursors were coated onto cationic particle surfaces by electronic interaction. During the coating process, hollow particles were directly obtained by dissolution of PMMA.

Electrorhelological Properties of Monodispersed Submicron-sized Hollow Polyaniline Adipate Suspension

  • Sung, Bo-Hyun;Choi, Ung-Su
    • KSTLE International Journal
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    • v.6 no.1
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    • pp.28-32
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    • 2005
  • The electrorheoloRical (ER) fluids are composed of a colloidal dispersion of polarizable particles in insulating oil, and it's the rheological property changes by the applied electric field. These changed are reversible and occur fast within a fewmilliseconds. The ER properties of the ER fluid such as increment of viscosity and yield stress come from the particle chain structure induced by electric fleld. When formulating the ER fluid for a speciflc application, some requirement must besatisfled, which are high yield stress under electric field, rapid response, and dispersion stability. While this characteristic makes valuable ER fluids in valious industrial applications, their lung term and quiescent application has been limited because ofproblems with particle sedimentation. In an effort to overcome sedimentation problem of ER fluids, the anhydrous ER materials of monodispersed hollow polyaniline (PANI) and adipate derivative respectively with submicron-sized suspension providing wide operating temperature range and other advantage were synthesized in a four-step procedure. The ER fluidswere characterized by FT-lR, TGA, DLS, SEM, and TEM. Stability of the suspensions was examined by an UV spectroscopy.The rheological and electrical properties of the suspension were investigated Couette-type rheometer with a high voltagegenerator, current density, and conductivity. And the behavior of ER suspensions was observed by a video camera attached toan optical microscope under 3kV/mm. The suspensions showed good ER properties, durability, and particle dispersion.

A Study on the Preparation of Hollow Microspheres Using Waste Polystyrene (폐 Polystyrene을 이용한 중공 미세구 제조에 관한 연구)

  • Kwon, Soon Young;Woo, Je-Wan
    • Clean Technology
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    • v.12 no.4
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    • pp.205-210
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    • 2006
  • In this study, polystyrene hollow microspheres were prepared via optimized purifying steps for the reuse of waste polystyrene. PS/PVA double layered hollow microspheres were prepared using the multiple emulsion ($W_1/O/W_2$) method with recycled polystyrene. The sonication treatment at the first stage of $W_1/O$ emulsion formation was very important factor of control of particle size and its distribution. When sonication was treated for 20 seconds, the average particle size and distribution were $1.35{\mu}m$ and $0.8{\mu}m{\sim}2.8{\mu}m$, respectively. The double layered hollow microspheres that have smaller and uniformed particle size distribution were manufactured when gelatin or Tween 80 was used as surfactants in the $W_2$ phase.

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Numerical Investigation of a Steady Non-Evaporating Hollow-Cone Spray Interacting with an Annular Air Jet (정상 할로우 콘 분무와 환형 공기 제트의 상호작용에 관한 수치적 연구)

  • Kim, Woo-Tae;Huh, Kang-Y.
    • Journal of ILASS-Korea
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    • v.5 no.2
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    • pp.43-52
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    • 2000
  • Numerical simulation of steady, non-evaporating hollow-cone sprays interacting with concentric annular air jets is performed using the discrete stochastic particle method in KIVA. The spray characteristics such as SMD, mean droplet velocity, liquid volume flux, air/liquid mass ratio, and droplet number density arc obtained and compared with the measurements involving different air flow rates in large and small annuli. Overall satisfactory agreement is achieved between calculation and experiment except for the deviation in the downstream SMD arising from uncertainty in the size distribution function at injection, and inaccuracy in the averaged spray parameters due to the small volumes of axisymmetric 2-D sector meshes close to the axis.

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Hollow Sb93Pt7 Nanospheres Prepared by Galvanic Displacement Reaction for a Highly Li Reactive Material

  • Kim, Hyun-Jung;Cho, Jae-Phil
    • Journal of the Korean Electrochemical Society
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    • v.11 no.3
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    • pp.154-158
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    • 2008
  • The synthesis of hollow ${Sb_93}{Pt_7}$ nanospheres smaller than 30 nm with a shell consisting of smaller nanoparticles, with an average particle size of ${\sim}$ 3 nm is reported. The formation of this alloy is driven by galvanic replacement reaction involving Sb nanoparticles and ${H_2}{PtCl_6} $ without need for any additional reductants. Further, the reaction proceeds selectively as long as the redox potential between two metals is favorable. The capacities of the hollow samples are 669 and 587mAh/g at rates of 1 and 7C, respectively, while those values for the nanoparticles are 647 and 480mAh/g at rates of 1, 7C, respectively. This result shows the significantly improved capacity retention of the hollow sample at higher C rates, indicating that high surface area of the hollow nanospheres makes the current density more effective than that for the solid counterpart.

COLLOIDAL PROPERTIES OF HOLLOW LATICES AND THEIR ROLES IN CONTROLLING COLORIMETRIC PARAMETERS OF COATED PAPER SURFACE

  • Hitomi HAMADA;Yoko SAITO
    • Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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    • 1999.04b
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    • pp.309-314
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    • 1999
  • With a view to seek the influence of hollow sphere pigments of latex upon the printed color on coated paper surface, the hollow sphere pigments were compared with filled ones in a variety of experimental approaches. Colloidal properties of latices were determined by measuring zeta potential and particle size distribution. For the amphoteric filled sphere pigment of latex, the polarity was reversed from the negative side to the positive side with decreasing pH. An extraordinarily high peak in the particle size distribution of the amphoteric filled evidenced aggregation between latex particles near the isoelectric point, depending on the electrolyte concentration and pH of the suspending medium. Coated papers containing the hollow sphere pigment in their coating improved optical properties like gloss and brightness. Optical parameters solely of the coating could account for this finding. An equation derived from the Kubelka-Munk equation calculated them fro twice measurements of reflectance of a coated paper over two substrates of different reflectances. This method permitted to predict brightness of coated paper of which coat weight would be different fro the actual one. The colorimetric parameters of solid-printed surfaces of the coated papers closely related to optical and structural properties of the coated papers. The color of the printed surfaces was dominated by the brightness and the smoothness of the coated papers. The hollow sphere pigments were proved to improve optical properties of coated paper and to control minutely colorimetric parameters of printed surfaces.

Effect of Sheath Structure on Operating Stability in an Anode Layer Thruster

  • Yasui, Shinsuke;Yamamoto, Naoji;Komurasaki, Kimiya;Arakawa, Yoshihiro
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2004.03a
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    • pp.245-250
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    • 2004
  • The discharge current oscillation has been measured for various hollow anode widths and its axial positions using a 1㎾-class anode layer hall thruster. As a result, there were thresholds of magnetic flux density for stable discharge. The plasma structure inside the hollow anode was numerically analyzed using the fully kinetic 2D3V Particle-in-Cell (PIC) and Direct Simulation Monte Carlo (DSMC) methods. The results reproduced both stable and unstable operation modes. In the stable operation case, which corresponds to the case with low magnetic flux, the plasma penetrated into the hollow anode deeper than the case with higher magnetic flux density case. This suggests that comparably large substantial anode area should contribute to stable operation.

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The effect of ball size on the hollow center cracked disc (HCCD) in Brazilian test

  • Haeri, Hadi;Sarfarazi, Vahab;Zhu, Zheming;Moradizadeh, Masih
    • Computers and Concrete
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    • v.22 no.4
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    • pp.373-381
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    • 2018
  • Hollow center cracked disc (HCCD) in Brazilian test was modelled numerically to study the crack propagation in the pre-cracked disc. The pre-existing edge cracks in the disc models were considered to investigate the crack propagation and coalescence paths within the modelled samples. The effect of particle size on the hollow center cracked disc (HCCD) in Brazilian test were considered too. The results shows that Failure pattern is constant by increasing the ball diameter. Tensile cracks are dominant mode of failure. These crack initiates from notch tip, propagate parallel to loading axis and coalescence with upper model boundary. Number of cracks increase by decreasing the ball diameter. Also, tensile fracture toughness was decreased with increasing the particle size. In this research, it is tried to improve the understanding of the crack propagation and crack coalescence phenomena in brittle materials which is of paramount importance in the stability analyses of rock and concrete structures, such as the underground openings, rock slopes and tunnel construction.

Syntheses of Mesoporous Silica Hollow Spheres Using Polystyrene Template (폴리스티렌 주형 중공형 중간세공 나노 입자의 합성)

  • Chu, Sang-Wook;Sung, A-Reum;Park, Sung Soo;Ha, Chang-Sik
    • Journal of Adhesion and Interface
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    • v.13 no.4
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    • pp.151-155
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    • 2012
  • In the present study, we synthesized mesoporous silica hollow spheres with different wall thickness using polystyrene (PS) spheres as a structure template, tetraethoxysilane (TEOS) as a silica source, cetyltrimethylammonium bromide (CTAB) as a template. Particle size and dispersion of PS spheres were strongly depended on the concentration of surfactant in the aqueous solutions. The size of PS spheres was increased with decreasing concentration of surfactants. Dispersion of PS particle was improved when the surfactant concentration was lower than 0.5 g of surfactant.