Displaying publications 1 - 20 of 255 in total

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  1. Aftab SM, Mohd Rafie AS, Razak NA, Ahmad KA
    PLoS One, 2016;11(4):e0153755.
    PMID: 27104354 DOI: 10.1371/journal.pone.0153755
    One of the major flow phenomena associated with low Reynolds number flow is the formation of separation bubbles on an airfoil's surface. NACA4415 airfoil is commonly used in wind turbines and UAV applications. The stall characteristics are gradual compared to thin airfoils. The primary criterion set for this work is the capture of laminar separation bubble. Flow is simulated for a Reynolds number of 120,000. The numerical analysis carried out shows the advantages and disadvantages of a few turbulence models. The turbulence models tested were: one equation Spallart Allmars (S-A), two equation SST K-ω, three equation Intermittency (γ) SST, k-kl-ω and finally, the four equation transition γ-Reθ SST. However, the variation in flow physics differs between these turbulence models. Procedure to establish the accuracy of the simulation, in accord with previous experimental results, has been discussed in detail.
    Matched MeSH terms: Viscosity
  2. Azizan A, Sieben M, Wandrey G, Büchs J
    Biotechnol Bioeng, 2019 11;116(11):2983-2995.
    PMID: 31350917 DOI: 10.1002/bit.27132
    Shake flasks are still the most relevant experimental tool in the development of viscous fermentation processes. The phase number, which defines the onset of the unfavorable out-of-phase (OP) phenomenon in shake flasks, was previously defined via specific power input measurements. In the OP state, the bulk liquid no longer follows the orbital movement of the imposed centrifugal force, which is for example, detrimental to oxygen transfer. In this study, an optical fluorescence technique was used to measure the three-dimensional liquid distribution in shake flasks. Four new optically derived evaluation criteria for the phase transition between the in-phase and OP condition were established: (a) thickness of the liquid film left on the glass wall by the rotating bulk liquid, (b) relative slope of the leading edge of bulk liquid (LB) lines, (c) trend of the angular position of LB, and (d) very high angular position of the leading edge. In contrast to the previously applied power input measurements, the new optical evaluation criteria describe the phase transition in greater detailed. Instead of Ph = 1.26, a less conservative value of Ph = 0.91 is now suggested for the phase transfer, which implies a broader operating window for shake flask cultivations with higher viscosities.
    Matched MeSH terms: Viscosity*
  3. Ahmed HM, Omar NS, Luddin N, Saini R, Saini D
    J Conserv Dent, 2011 Oct;14(4):406-8.
    PMID: 22144813 DOI: 10.4103/0972-0707.87212
    This study aims to evaluate the cytotoxicity of a new fast set highly viscous conventional glass ionomer cement (GIC) with L929 fibroblasts.
    Matched MeSH terms: Viscosity
  4. Shekholeslami M, Ashorynejad HR, Domairry D, Ishak Hashim
    Sains Malaysiana, 2012;41:1281-1285.
    In this paper, the problem of laminar viscous flow in a semi-porous channel in the presence of transverse magnetic field is studied. The Optimal Homotopy Asymptotic Method (OHAM) is employed to approximate the solution of the system of nonlinear differential equations governing the problem. The influence of the Hartmann number (Ha) and the Reynolds number (Re) on the flow was investigated. The results of the OHAM were compared with homotopy analysis method (HAM) and variation iteration method (VIM) results.
    Matched MeSH terms: Viscosity
  5. NUR IZZI MD.YUSOFF, MOHD ROSLI HAININ, MOUNIER D, AIREY GD
    Sains Malaysiana, 2013;42:1647-1654.
    According to the classical theory of viscoelasticity, a linear viscoelastic (LVE) function can be converted into another viscoelastic function even though they emphasize different information. In this study, dynamic tests were conducted on different conventional penetration grade bitumens using a dynamic shear rheometer (DSR) in the LVE region. The results showed that the dynamic data in the frequency domain can be converted into the time domain functions using a numerical technique. This was done with the aid of the non-linear regularization (NLREG) computer program. The NLREG software is a computer program for solving nonlinear ill-posed problem and is based on non-linear Tikhonov regularization method. The use of data interconversion equation is found suitable for converting from the frequency domain into the time domain of conventional penetration grade bitumens.
    Matched MeSH terms: Viscosity
  6. Gul T, Islam S, Shah RA, Khan I, Shafie S
    PLoS One, 2014;9(6):e97552.
    PMID: 24949988 DOI: 10.1371/journal.pone.0097552
    In this work, we have carried out the influence of temperature dependent viscosity on thin film flow of a magnetohydrodynamic (MHD) third grade fluid past a vertical belt. The governing coupled non-linear differential equations with appropriate boundary conditions are solved analytically by using Adomian Decomposition Method (ADM). In order to make comparison, the governing problem has also been solved by using Optimal Homotopy Asymptotic Method (OHAM). The physical characteristics of the problem have been well discussed in graphs for several parameter of interest.
    Matched MeSH terms: Viscosity*
  7. Yasin MH, Ishak A, Pop I
    Sci Rep, 2015;5:17848.
    PMID: 26647651 DOI: 10.1038/srep17848
    The steady two-dimensional stagnation-point flow and heat transfer past a permeable stretching/shrinking sheet with effects of viscous dissipation, Joule heating and partial velocity slip in the presence of a magnetic field is investigated. The partial differential equations are reduced to nonlinear ordinary differential equations by using a similarity transformation, before being solved numerically by shooting technique. Results indicate that the skin friction coefficient and the local Nusselt number increase as magnetic parameter increases. It is found that for the stretching sheet the solution is unique while for the shrinking sheet there exist nonunique solutions (dual solutions) in certain range of parameters. The stability analysis shows that the upper branch solution is stable while the lower branch solution is unstable.
    Matched MeSH terms: Viscosity
  8. Yusof R, Abdulmalek E, Sirat K, Rahman MB
    Molecules, 2014 Jun 13;19(6):8011-26.
    PMID: 24932572 DOI: 10.3390/molecules19068011
    Density, viscosity and ionic conductivity data sets of deep eutectic solvents (DESs) formed by tetrabutylammonium bromide (TBABr) paired with ethlyene glycol, 1,3-propanediol, 1,5-pentanediol and glycerol hydrogen bond donors (HBDs) are reported. The properties of DES were measured at temperatures between 303 K and 333 K for HBD percentages of 66.7% to 90%. The effects of HBDs under different temperature and percentages are systematically analyzed. As expected, the measured density and viscosity of the studied DESs decreased with an increase in temperature, while ionic conductivity increases with temperature. In general, DESs made of TBABr and glycerol showed the highest density and viscosity and the lowest ionic conductivity when compared to other DESs. The presence of an extra hydroxyl group on glycerol in a DES affected the properties of the DES.
    Matched MeSH terms: Viscosity
  9. Ahmad NH, Ahmed J, Hashim DM, Manap YA, Mustafa S
    J Food Sci Technol, 2015 May;52(5):2902-9.
    PMID: 25892789 DOI: 10.1007/s13197-014-1330-x
    Oscillatory and steady shear rheology of gellan (G) and dextran (D) solution individually, and in blends (G/D ratio 1:1, 1:2, and 1:3 w/v) with a total hydrocolloid concentration of 3 % (w/v) were studied at 25 °C. Individually, 1.5 % dextran and 1.5 % gellan in solution exhibited Newtonian and non-Newtonian behavior, respectively. A blend of equal proportion of dextran and gellan (G/D = 1:1) exhibits a distinct gel point (G' = G″), and further addition of dextran in the blend (G/D = 1:2 and 1:3) resulted predominating liquid-like (G″ > G') behavior. A plot of G' vs G″ distinctly showed the gradual transition of the blend. Shear stress (τ)-shear rate ([Formula: see text]) data fitted well the Herschel-Bulkley model. The G/D blend exhibited shear thinning behavior with flow behavior index less than unity. The Cox-Merz rule did not fit well for the complex shear viscosity (η*) and apparent viscosity (η) of the blend.
    Matched MeSH terms: Viscosity
  10. Noorlaila, A., Siti Aziah, A., Asmeda, R., Norizzah, A.R.
    MyJurnal
    The emulsifying properties of extracted okra (Abelmoschus esculentus L.) mucilage at different maturity indices (1, 2 and 3) were studied. The okra mucilage was prepared using water extraction method and was determined their viscosity at different temperature (10, 30, 50 and 70°C), water holding capacity (WHC), oil holding capacity (OHC), as well as their emulsion capacity (EC) and emulsion stability (ES). Results found that okra with maturity index 2 produced the highest percentage yield of mucilage (1.46%) and followed by index 1 (1.10%) and index 3 (0.31%) (p
    Matched MeSH terms: Viscosity
  11. Maskat, M.Y, Tan, S.M.
    MyJurnal
    Extract of mengkudu was heated using a bench-top tube heat exchanger at 30, 50, 70 and 90 o C for 0, 5, 10 and 15 min residence time. The treated mengkudu extract was then measured for pH, L * , a * , b * color parameters, clarity, viscosity and total polyphenol content. Results show that heating using temperature of 30 to 90 o C for 5 to 15 mins significantly (p
    Matched MeSH terms: Viscosity
  12. Zainal Abidin, N.F., Yusoff, A., Ahmad, N.
    MyJurnal
    Octenyl succinic anhydride (OSA) modified sago starch was prepared in order to improve the emulsification properties of native starch. In the present study, the major factors affecting esterification were investigated with respect to OSA concentration, pH and reaction time using response surface methodology (RSM) based on central composite rotatable design (CCRD) to obtain the highest value of degree of substitution (DS). Results shown that the optimum conditions for OSA concentration, pH and reaction time were 5.00%, pH 7.20 and 9.65 h, respectively. At optimum condition, the esterification of sago starch with OSA resulted in DS value of 0.0120. The DS increased linearly with the increase in amount of OSA, whilst pH and reaction time show a curvature trend on the value of DS. The value of DS was found to be significantly affected by all the three variables. The experimental values under optimum condition were in good consistent with the predicted values (0.0131), which suggested that the optimisation by RSM is more efficient process than conventional optimisation.
    Matched MeSH terms: Viscosity
  13. Nik Zarina Nik Mahmood, Noor Hayaty Abu Kasim, Mamat Azuddin, Noor Lide Abu Kassim
    Compendium of Oral Science, 2015;2(1):21-31.
    MyJurnal
    Objective: To evaluate the effect of type of viscosity and groove on surface detail reproduction of elastomeric impression materials. Methods: Two polyvinylsiloxane and polyether elastomeric impression materials were investigated. An aluminium cylindrical reference block with V- and U-shaped grooves of 1 mm and 2 mm in depth was machined using CAD-CAM system. Impressions of the block were taken to produce 35 master dies. Each die was immersed in distilled water for 5 minutes prior to impression making. Surface topography of the dies and impressions were captured using Alicona Imaging System. Mean difference in depth between the mas-ter dies and corresponding impressions’ grooves were analyzed. Results: Type of viscosities and groove showed significant main effects on surface detail (p < .01), but no significant interaction was observed between the two (p > .01). Express™ putty/light exhibited the lowest mean difference in depth for all grooves. The highest mean difference for U1 (38.3μm ± 21.55), U2 (52.96μm ± 30.39),V1 (45.02μm ± 34.82) and V2 (58.44μm ± 44.19) was obtained from Impregum medium, Aquasil medium, Impregum™ heavy/light and Impregum™ heavy/light groups respectively. Conclusion: Express putty/light-bodied material produced the best surface detail, and U-shaped groove showed superior detail reproduction.
    Matched MeSH terms: Viscosity
  14. Muhammad Khairul Anuar Mohamed, Nor Aida Zuraimi Md Noar, Mohd Zuki Salleh, Anuar Ishak
    Sains Malaysiana, 2016;45:189-296.
    In this paper, the problem of free convection boundary layer flow on a horizontal circular cylinder in a nanofluid with viscous dissipation and constant wall temperature is investigated. The transformed boundary layer equations are solved numerically using finite difference scheme namely the Keller-box method. Numerical solutions were obtained for the reduced skin friction coefficient, Nusselt number and Sherwood number as well as the velocity and temperature profiles.The features of the flow and heat transfer characteristics for various values of the Brownian motion parameter, thermophoresis parameter, Lewis number and Eckert number were analyzed and discussed.
    Matched MeSH terms: Viscosity
  15. Yahaya Shagaiya Daniel, Zainal Abdul Aziz, Zuhaila Ismail, Faisal Salah
    MATEMATIKA, 2018;34(2):393-417.
    MyJurnal
    Analyzed the effects of thermal radiation, chemical reaction, heat gener-
    ation/absorption, magnetic and electric fields on unsteady flow and heat transfer of
    nanofluid. The transport equations used passively controlled. A similarity solution is
    employed to transformed the governing equations from partial differential equations to
    a set of ordinary differential equations, and then solve using Keller box method. It was
    found that the temperature is a decreasing function with the thermal stratification due to
    the fact the density of the fluid in the lower vicinity is much higher compared to the upper
    region, whereas the thermal radiation, viscous dissipation and heat generation enhanced
    the nanofluid temperature and thermal layer thickness.
    Matched MeSH terms: Viscosity
  16. Asyraf MRM, Ishak MR, Sapuan SM, Yidris N
    Polymers (Basel), 2021 Feb 19;13(4).
    PMID: 33669491 DOI: 10.3390/polym13040620
    The application of pultruded glass fiber-reinforced polymer composites (PGFRPCs) as a replacement for conventional wooden cross-arms in transmission towers is relatively new. Although numerous studies have conducted creep tests on coupon-scale PGFRPC cross-arms, none had performed creep analyses on full-scale PGFRPC cross-arms under actual working load conditions. Thus, this work proposed to study the influence of an additional bracing system on the creep responses of PGFRPC cross-arms in a 132 kV transmission tower. The creep behaviors and responses of the main members in current and braced PGFRPC cross-arm designs were compared and evaluated in a transmission tower under actual working conditions. These PGFRPC cross-arms were subjected to actual working loads mimicking the actual weight of electrical cables and insulators for a duration of 1000 h. The cross-arms were installed on a custom test rig in an open area to simulate the actual environment of tropical climate conditions. Further creep analysis was performed by using Findley and Burger models on the basis of experimental data to link instantaneous and extended (transient and viscoelastic) creep strains. The addition of braced arms to the structure reduced the total strain of a cross-arm's main member beams and improved elastic and viscous moduli. The addition of bracing arms improved the structural integrity and stiffness of the cross-arm structure. The findings of this study suggested that the use of a bracing system in cross-arm structures could prolong the structures' service life and subsequently reduce maintenance effort and cost for long-term applications in transmission towers.
    Matched MeSH terms: Viscosity
  17. Lok YY, Anuar Ishak, Pop I
    Sains Malaysiana, 2011;40:1179-1186.
    A steady two-dimensional magnetohydrodynamic (MHD) stagnation-point flow of a viscous and electrically conducting fluid over a permeable shrinking sheet has been studied. The governing partial differential equations are reduced to the nonlinear ordinary differential equations by a similarity transformation. The resulting differential equations are then solved numerically using an implicit finite difference method. It is found that the solutions are non-unique for weak magnetic field, strong suction and large velocity ratio between free stream velocity and wall shrinking velocity.
    Matched MeSH terms: Viscosity
  18. Mutlag A, Md. Jashim Uddin, Ahmad Izani Md. Ismail
    Sains Malaysiana, 2014;43:1249-1257.
    We study and discuss the effect of thermal slip on steady free convection flow of a viscous, incompressible micropolar fluid past a vertical moving plate in a saturated porous medium. The effect of viscous dissipation is incorporated in the energy equation. The associated partial differential equations are transformed into a system of ordinary differential equations using similarity transformations generated by a group method and this system is then solved numerically. The effect of controlling parameters on the dimensionless velocity, angular velocity and temperature as well as friction factor, couple stress factor and heat transfer rate are shown graphically and discussed in detail. It is found that the dimensional velocity and angular velocity decrease whilst the temperature increases with velocity slip parameter. It is further found that thermal slip decreases the dimensional velocity and temperature but increases the dimensional angular velocity. Data from published work and our results are found to be in good agreement.
    Matched MeSH terms: Viscosity
  19. Khalil M, Aulia G, Budianto E, Mohamed Jan B, Habib SH, Amir Z, et al.
    ACS Omega, 2019 Dec 17;4(25):21477-21486.
    PMID: 31867543 DOI: 10.1021/acsomega.9b03174
    Superparamagnetic nanoparticles (SPNs) have been considered as one of the most studied nanomaterials for subsurface applications, including in enhanced oil recovery (EOR), due to their unique physicochemical properties. However, a comprehensive understanding of the effect of surface functionalization on the ability of the nanoparticles to improve secondary and tertiary oil recoveries remains unclear. Therefore, investigations on the application of bare and surface-functionalized SPNs in EOR using a sand pack were carried out in this study. Here, the as-prepared SPNs were functionalized using oleic acid (OA) and polyacrylamide (PAM) to obtain several types of nanostructure architectures such as OA-SPN, core-shell SPN@PAM, and SPN-PAM. Based on the result, it is found that both the viscosity and mobility of the nanofluids were significantly affected by not only the concentration of the nanoparticles but also the type and architecture of the surface modifier, which dictated particle hydrophilicity. According to the sand pack tests, the nanofluid containing SPN-PAM was able to recover as much as 19.28% of additional oil in a relatively low concentration (0.9% w/v). The high oil recovery enhancement was presumably due to the ability of suspended SPN-PAM to act as a mobility control and wettability alteration agent and facilitate the formation of a Pickering emulsion and disjoining pressure.
    Matched MeSH terms: Viscosity
  20. Yusrabbil Amiyati Yusof, Zafarizal Aldrin Azizul Hasan, Azhar Ariffin
    Sains Malaysiana, 2018;47:511-515.
    This paper reports the effects of glyceryl ether specifically mono-tert-butoxypropanediol on oil in water emulsion system.
    Based on 12 HLB value, screening for stable emulsions was carried out without the presence of glyceryl ether. A stable
    emulsion was used as a control. Then the effects of glyceryl ether on the emulsion system were investigated. The emulsions
    prepared were analyzed for stability, viscosity, pH value, particle size, in vitro dermal irritation potential, in vitro ocular
    irritation potential and also moisturizing property. The incorporation of glycerol in the emulsion system was also done
    for comparison. Emulsions with glyceryl ether showed lower viscosity values than emulsions with glycerol. Furthermore,
    the emulsions also exhibited moisturizing property compared to the control emulsion. Glyceryl ether is suitable to be
    used in cosmetic products which require reduced viscosity but retain its skin hydration property.
    Matched MeSH terms: Viscosity
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