• Title, Summary, Keyword: variable viscosity

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Rheological Properties and Particle Size Distribution of Northeast Mixed Hardwood for Enzymatic Saccharification Processing with High Substrates Loading

  • Um, Byung-Hwan
    • Journal of the Korean Wood Science and Technology
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    • v.36 no.5
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    • pp.56-65
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    • 2008
  • In this paper experimental results are presented for the rheological behavior of high-solids saccharification of mixed northeast hardwood as a model feedstock. The experimental determination of the viscosity, shear stress, and shear rate relationships of the 10 to 20 percent slurry concentrations with constant enzyme concentrations were performed under variable rotational speed of a viscometer (2.0 to 200 RPM) at combined temperatures (50 to $30^{\circ}C$) for the initial four hours. The viscosities of saccharification slurries observed were in the ranges of 0.024 to 0.028, 0.401 to 0.058, and 0.840 to 0.087 Pa s for shear rates up to 100 reciprocal seconds at 10, 15, and 20 percent initial solids (w/v) respectively. The fluid behavior of the suspensions was modeled using the power-law, the Herschel-Bulkley, the Casson, and the Bingham model. The results showed that broth slurries were pseudoplastic with a yield stress. The model slope increased and the model intercept decreased with increasing fermentation time at shear rates normal for the fermentor. The broth slurries exhibited Newtonian behavior at high and low shear rates during initial saccharification process. The solid particle size ranged from 57.8 to $70.0{\mu}m$ for $40^{\circ}C$ and from 44.0 to 57.5 11m for combined temperatures at 10, 15, and 20 percent initial solids (w/v) respectively.

In Vitro Proliferation Model of Helicobacter pylori Required for Large-Scale Cultivation

  • Oh, Heung-Il;Lee, Heung-Shick;Kim, Kyung-Hyun;Paek, Se-Hwan
    • Journal of Microbiology and Biotechnology
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    • v.10 no.3
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    • pp.367-374
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    • 2000
  • The composition of dissolved gases and nutrients in a liquid medium were determined for establishment of the optimum conditions for in vitro culture of Helicobacter pylori. A microaerobic condition facored by the organism was prepared by adjusting the partial pressure of the gas, agitation speed, and viscosity of the medium. The gaseous concentrations were controlled by utilizing CampyPak Plus that reduced oxygen while augmenting carbon dioxide. Agitation of the broth facilitated the oxygen transfer to the cells, yet inhibited the growth at high rates. An increase of viscosity in the medium repressed the culture although this variable was relatively insignificant. The chemical constituents of the liquid broth were examined to establish an economic model for H. pylori cultivation. The microbe required a neutral pH for optimum growth, and yet was also able to proliferate in an acidic condition, presumably by releasing the acidity-modulating enzyme, urease. Cyclodextrin and casamino acid were investigated as growth enhancers in place of serum, while yeast extract unexpectedly inhibited the cells. A low concentration of glucose, the unique carbon source for the organism, increased the cell density, yet high concentrations resulted in an adverse effect. Under optimally dissolved gas conditions, the cell concentration in brucella broth supplemented with serum substitutes and glucose reached $1.6{\times}10^8$ viable cells/ml which was approximately 50% higher than that obtained in the liquid medium added with only cyclodextrin or serum.

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Study on Bread-making Quality with Mixture of Waxy Barley-Wheat Flour 1. Rheological Properties of Dough Made with Waxy Barley-Wheat Flour Mixture (흰찰쌀보리 가루를 이용한 제빵특성 연구 1. 흰찰쌀보리-밀가루 혼합분 박죽의 물성)

  • 유정희
    • Journal of the Korean Society of Food Science and Nutrition
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    • v.28 no.5
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    • pp.1034-1043
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    • 1999
  • Rheological properties of dough made from waxy barley(Iri28) flour wheat flour mixtures with additives were investigated for the preparation of waxy barley bread using farinograph, extensograph and amy lograph. The water absorption, development time and dough weakness increased as the waxy barley flour level increased in all blends; however, dough stability decreased. Farinogram properties of 10% waxy barley flour added mixture were similar to those of 100% wheat flour. The addition of A.A(ascorbic acid), gluten, HPMC(hydroxy propyl methyl cellulose) improved rheological properties of dough with 30% waxy barley flour added mixture. In particular, stability and weakness of the dough showed greater dough improving effect by addition of A.A. For the extensograph data, strength, resistance and extensibility of dough decreased with increasing level of waxy barley flour. With the addition of additives, extensogram properties were variable for 30% waxy barley flour mixture. Of these additives, gluten had highest value in strength of dough. Addition of A.A and HPMC to 30% waxy barley flour added mixture resulted in an increase in the resistance and a decrease in the extensibility. Waxy barley flour added mixtures showed little higher gelatinization temperature on amylograph data than control. Maximum viscosity reduced as the waxy barley flour level increased. Also 30% waxy barley flour added mixture containing A.A and HPMC showed a decrease in maximum viscosity. But addition of gluten to 30% waxy barley flour mixture resulted an increase in the maximum viscosity. All of 30% waxy barley flour added mixture with additives had lower gelatinization temperature than those without additives. In the SEM images, starch granules were dispersed in a protein matrix. A non continuous, loose protein starch matrix was observed in all waxy barley flour mixture by SEM. Addition of additives gave the dough a more continuous structure with interactions between the starch granule and protein component.

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A New Groutability Criterion of Cement-based Grout with Consideration of Viscosity and Filtration Phenomenon (점도변화와 흡착현상을 고려한 시멘트계 그라우트재의 새로운 침투 기준)

  • Kim, Jong-Sun;Lee, In-Mo;Lee, Mun-Seon;Choi, Hang-Seok
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.154-163
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    • 2009
  • The groutability depends on the properties of the grout, its injection processes, and on the mechanical properties of the soil formation. During the process of pouring cement-based grouting into a porous medium, a variation with time occurs in the viscosity of grout suspension. In addition the particle filtration phenomenon will limit the expansion of the grouted zone because cement particles are progressively stagnant within the soil matrix. In this paper, a closed-form solution was derived by implementing the mass balance equations and the generalized phenomenological filtration law, which can be used to evaluate the deposition of cement-based grout in the soil matrix. The closed-form solution relevant to a particular spherical flow was modified by a step-wise numerical calculation, considering the variable viscosity caused by a chemical reaction, and the decrease in porosity resulting from grout particle deposition in the soil pores. A series of pilot-scale chamber injection tests was performed to verify that the developed step-wise numerical calculation is able to evaluate the injectable volume of grout and the deposition of grout particles. The results of the chamber injection tests concurred well with that of the step-wise numerical calculation. Based on the filtration phenomenon, a new groutability criterion of cement-based grout in a porous medium was proposed, which might facilitate a new insight in the design of the grouting process.

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Dynamic Characteristics of Semi-Active Shock Absorber Using Electrorheological Fluid (ER 유체를 이용한 반능동 완충장치의 동적 특성)

  • Kim, Do-Hyung;Cho, Ki-Dae;Jung, Yong-Hyun;Lee, In;Oshima, Nobuo;Fukuda, Takehito
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.11 no.4
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    • pp.13-21
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    • 2001
  • Electrorheological(ER) fluid is a kind of smart material with variable shear stress and dynamic viscosity under various electric field intensity. Electric field can control the damping characteristics of ER damper. The objective of this study is the analysis of the performance of ER damper and its application to shock absorber. Idealized nonlinear Bingham plastic shear flow model is used to predict the velocity profile between electrodes. Cylindrical dashpot ER damper with moving electrode is constructed and tested under various electric fields. The analytic and experimental results for damping force are compared and discussed. Drop test system using ER damper is prepared to identify transient vibration characteristics. The rebound is eased as the applied electric field increases. When semi-active control algorithm is applied, rebound phenomenon disappears and vibration energy level decays faster than the case of zero electric field.

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Diffusion-hydraulic properties of grouting geological rough fractures with power-law slurry

  • Mu, Wenqiang;Li, Lianchong;Liu, Xige;Zhang, Liaoyuan;Zhang, Zilin;Huang, Bo;Chen, Yong
    • Geomechanics and Engineering
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    • v.21 no.4
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    • pp.357-369
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    • 2020
  • Different from the conventional planar fracture and simplified Newton model, for power-law slurries with a lower water-cement ratio commonly used in grouting engineering, flow model in geological rough fractures is built based on ten standard profiles from Barton (1977) in this study. The numerical algorithm is validated by experimental results. The flow mechanism, grout superiority, and water plugging of pseudo plastic slurry are revealed. The representations of hydraulic grouting properties for JRCs are obtained. The results show that effective plugging is based on the mechanical mechanisms of the fluctuant structural surface and higher viscosity at the middle of the fissure. The formulas of grouting parameters are always variable with the roughness and shear movement, which play a key role in grouting. The roughness can only be neglected after reaching a threshold. Grouting pressure increases with increasing roughness and has variable responses for different apertures within standard profiles. The whole process can be divided into three stationary zones and three transition zones, and there is a mutation region (10 < JRCs < 14) in smaller geological fractures. The fitting equations of different JRCs are obtained of power-law models satisfying the condition of -2 < coefficient < 0. The effects of small apertures and moderate to larger roughness (JRCs > 10.8) on the permeability of surfaces cannot be underestimated. The determination of grouting parameters depends on the slurry groutability in terms of its weakest link with discontinuous streamlines. For grouting water plugging, the water-cement ratio, grouting pressure and grouting additives should be determined by combining the flow conditions and the apparent widths of the main fracture and rough surface. This study provides a calculation method of grouting parameters for variable cement-based slurries. And the findings can help for better understanding of fluid flow and diffusion in geological fractures.

Studies of Lithium Diffusivity of Silicon-Based Film Electrodes for Rechargeable Lithium Batteries

  • Nguyen, Cao Cuong;Song, Seung-Wan
    • Journal of Electrochemical Science and Technology
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    • v.4 no.3
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    • pp.108-112
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    • 2013
  • Lithium diffusivity of the silicon (Si)-based materials of Si-Cu and $SiO_x$ (x = 0.4, 0.85) with improved interfacial stability to electrolyte have been determined, using variable rate cyclic voltammetry with film model electrodes. Lithium diffusivity is found to depend on the intrinsic properties of anode material and electrolyte; the fraction of oxygen for $SiO_x$ (x = 0.4, 0.85), which is directly related to electrical conductivity, and the electrolyte type with different ionic conductivity and viscosity, carbonate-based liquid electrolyte or ionic liquid-based electrolyte, affect the lithium diffusivity.

Numerical simulation of transient laminar compressible convection in a rectangular enclosure (사각형(四角形) 밀폐공간내(密閉空間內)의 과도(過度) 층류(層流) 압축성(壓縮性) 자연(自然) 대류(對流)에 관(關)한 수치해석적(數値解析的) 연구(硏究))

  • Kim, Byung-Yong
    • Solar Energy
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    • v.2 no.1
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    • pp.9-16
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    • 1982
  • The problem of transient laminar natural convection in compressible fluid in a rectangular enclosure is considered. The upper and lower boundaries of the enclosure are thermally insulating and the side boundaries are maintained at fixed temperatures. The fluid is considered to be a perfect gas with constant viscosity and thermal conductivity and the formulation differs from the boussinesq simplification in that the effects of variable density are completely retained. The motions are restricted to two dimensions. For incompressible fluid, the natural convection is driven mainly by buoyancy force. But the solutions show that for compressible fluid, the natural convection is driven by pressure and buoyancy forces and the thermally induced motion is acoustic in nature.

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The Lubrication Characteristics of the Vane Tip Under Inlet Pressure Boundary Conditions for an Oil Hydraulic Vane Pump

  • Cho Ihn-Sung;Oh Seok-Hyung;Jung Jae-Youn
    • Journal of Mechanical Science and Technology
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    • v.19 no.12
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    • pp.2179-2186
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    • 2005
  • The lubrication modes of line contact between the vane and the camring in an oil hydraulic vane pump have been investigated. First, variations of the radial acting force of a vane were calculated from previously measured results of the dynamic internal pressure in four chambers surrounding a vane. Next, distinctions of the lubrication modes were made using Hooke's chart, which represents an improvement over Johnson's chart. Finally, the influence of boundary conditions in the lubrication region on fluid film lubrication was examined by calculating film pressure distributions. The results show that the lubrication modes of the vane tip are a rigid-variable viscosity region. This region discharges pressure higher than 7 MPa, and exerts a great influence on oil film pressure in the large arc section due to the Piezo-viscous effect.

Single-panel simulation on liquid crystal on silicon

  • Liao, Engle;Chiu, Jack;Peng, James
    • 한국정보디스플레이학회:학술대회논문집
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    • pp.939-942
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    • 2004
  • In this study, we report simulation results of single-panel LCOS (liquid crystal on silicon). Reflective LCOS microdisplays are widely used in various projection and near-eye application. For one panel system, liquid crystal response time is an important variable. The panel must switch fast enough to support the display of Field color sequential with high field rates. In order to have fast response and good contrast, a vertical alignment (VA) cell was used in this study. With suitable selection on LC parameters like temperature, viscosity, elastic constant and birefringence, it is possible to get response time of around 2ms from a 2.0 um-thick vertical alignment cell. This result also indicates an ease of production control on 2.0 um cells than 1.0 um cells.

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