The effect on the entropy production and MHD convection of the hybrid nanofluid Al
2
O
3
–Cu/water (water with Cu and Al
2
O
3
nanoparticles) in a porous square enclosure is studied numerically via ...Galerkin finite element method. The enclosure used for flow and natural convection analysis is subjected to sinusoidal varying temperatures at the boundaries. Calculations were performed for specific parameters of the Rayleigh number (Ra = 10
3
–10
6
), porosity ratio (
ε
= 0.1–0.9), Darcy number (Da = 10
−5
–10
−2
), Hartmann number (Ha = 0–100) and nanoparticles concentration (
φ
= 0–0.08). The numerical results are presented by velocity profiles, isotherms, streamlines, and Nusselt number. They indicate that the isotherms subject to estimation variations under Ha boost from 0 to 100 as Ra enhances. At high Ha, the conduction transfer mechanism is more obvious. Also, it is seen that the convective heat transfer becomes stronger with the enhancement of the Ra while it detracts with the rise in Ha. Due to the Ra increase, the flow cell becomes stronger. For Ra = 10
6
and higher Hartmann numbers, the isotherms remain constant which is an indication of convection predominance.
This article is concerned with the problem of magnetohydrodynamic (MHD) mixed convection flow of Cobalt-kerosene ferrofluid adjacent a non-isothermal wedge under the influence of thermal radiation ...and partial slip. Such type of problems are posed by electric generators and biomedical enforcement. The governing equations are solved using the Thomas algorithm with finite-difference type and solutions for a wide range of magnet parameter are presented. It is found that local Nusselt number manifests a considerable diminishing for magnetic parameter and magnifies intensively in case of slip factor, thermal radiation and surface temperature parameters. Further, the skin friction coefficient visualizes a sufficient enhancement for the parameters thermal radiation, surface temperature and magnetic field, but a huge reduction is recorded by promoting the slip factor.
In this work, the influences of heat generation/absorption and nanofluid volume fraction on the entropy generation and MHD combined convection heat transfer in a porous enclosure filled with a ...Cu–water nanofluid are studied numerically with of partial slip effect. The finite volume technique is utilized to solve the dimensionless equations governing the problem. A comparison with already published studies is conducted, and the data are found to be in an excellent agreement. The minimization of entropy generation and the local heat transfer according to various values of the controlling parameters are reported in detail. The outcome indicates that an augmentation in the heat generation/absorption parameter decreases the Nusselt number. Also, when the volume fraction is raised, the Nusselt number and entropy generation are reduced. The impact of Hartmann number on heat transfer and the Richardson number on the entropy generation and the thermal rendering criteria are also presented and discussed.
In this paper, numerical investigations for magnetohydrodynamic natural convection from two heating systems inside fined triangular enclosures filled with an isotropic porous medium using the ...nanofluids are performed. The two heating modes are represented by two cases, namely, case 1 a triangular enclosure with a heated part at the left wall and including a cold fin at the bottom wall and case 2 in which a cold part at the left wall and a heated fin located at the bottom wall. The copper is considered as nanoparticles and the Darcy model is applied to the porous medium. The triangular physical model is transformed to a rectangular computational model using suitable grid transformations and then the finite-volume method is applied to solve the resulting system. The key parameters in this study are the height, width and locations of the fin, different lengths and locations of the active part, nanoparticles volume fraction, heat generation/absorption parameter, and the Hartmann number. The results revealed that the increase in height of the fins decays the nanofluid flow in case 1, but in case 2, it accelerates the fluid motion. In addition, the increase in width and height of the fin enhances the rate of the heat transfer regardless the heating mode.
The chemical and mechanical stability of slag activated with two different concentrations of sodium sulfate (Na2SO4) after exposure to elevated temperatures ranging from 200 to 800°C with an ...increment of 200°C has been examined. Compressive strengths and pH of the hardened pastes before and after the exposure were determined. The various decomposition phases formed were identified using X-ray diffraction, thermogravimetric analysis and scanning electron microscopy. The results indicated that Na2SO4 activated slag has a better resistance to the degradation caused by exposure to elevated temperature up to 600°C than Portland cement system as its relative strengths are superior. The finer slag and higher Na2SO4 concentration gave better temperature resistance. Whilst the pH of the hardened pastes decreased with an increase in temperature, it still maintained a sufficiently high pH for the protection of reinforcing bar against corrosion.
Abstract
The aim of this study was to determine the properties and quality characteristics of hair and cashmere fibres of three goat breeds raised in Southwest China, namely; Dazu black goat (DBG, n ...= 203; ♂99, ♀104), Inner Mongolia cashmere goat (IMCG, n = 65; 21♂, 44♀) and their first cross (F
1
, n = 79; 39♂, 40♀). Totals of 5219, 2130 and 2981 fibre samples, from the three breeds respectively, were taken prior to shearing at 32.5 ± 01.25 months of age from four body sites; shoulder, side-portion, abdomen and leg. Breed effect was significant (
P
< 0.01) for most hair and cashmere properties. IMCG and F
1
hair lengths were longer (
P
< 0.001) with less variable lengths than DBG. Shoulder hair diameters of the three breeds were not different (
P
> 0.05) but biggest of the side-portion and abdomen sites of DBG were bigger (
P
> 0.01), however, the biggest (
P
< 0.001) hair diameter was recorded for the leg site of F
1
and the smallest (
P
> 0.01) for IMCG. IMCG recorded the longest value for cashmere lengths followed by DBG, while F
1
recorded the lowest (
P
= 0.001), whilst F
1
recorded the biggest (
P
= 0.001) diameter whereas no differences existed between parents' breeds. The cortical cell lengths of IMCG and DBG were 94.57 and 86.85 μm without significant difference detected between breeds. Differences between hair length and diameter for body sites of the studied goat breeds were significant (
P
< 0.01) but between whiteness, cashmere diameter and diameter of cortical cells were not. Sex had no significant effect on all hair/cashmere properties. Quality characteristics of cashmere fibres from IMCG and F
1
were better (
P
< 0.001) than from DBG. Leg hair diameter, curl recovery rate and cashmere diameter were superior in the crossbred F
1
compared to pure breed parents, and DBG was superior to IMCG for fibre elasticity and intensity traits.
FGF-5
gene was detected as a candidate gene for hair and cashmere traits in IMCG breed. Whilst,
KIT
gene was found to be associated with coat colour in the studied breeds. Extra investigations to examine more cashmere goat breeds and crosses are needed to discover genetic variability in cashmere production locally and worldwide.
This investigation addresses bioconvection of oxytactic microorganisms in a porous square enclosure by thermal radiation impact. The bioconvection flow and heat transfer in porous media are ...formulated based on Darcy model of Boussinesq approximation. Appropriate transformations lead to the non-dimensionalized governing partial differential equations. Galerkin finite element method for the resulting equations is computed. The role of relevant parameters on the streamlines, isotherms, isoconcentrations of oxygen and microorganisms and average Nusselt number is analysed in the outputs. It is revealed that the flow intensity of bioconvection is pronounced with larger Rayleigh number and reduced with radiation parameter. Furthermore, the temperature distribution is affected significantly with Rayleigh number. Radiation parameter serves to fasten the heat transfer in the enclosure. Oxygen density is enhanced with Rayleigh number and radiation parameter. The profile of motile isoconcentrations is boosted with Rayleigh number. The stability of microorganisms is improved with the radiation parameter.
Abstract
The photo-Fenton process is an appropriate method of the Advanced Oxidation Process that is used in the photocatalysis of organic dyes like crystal violet (CV). La
3+
ion substituted ...gadolinium zirconium oxide Gd
(2−
x
)
La
(
x
)
Zr
2
O
7
nanopowders (x = 0.1, 0.2, 0.3, and 0.5) have been successfully prepared by using sol–gel auto-combustion method to be used for the efficient photocatalysis of CV with photo-Fenton process. The well-crystallized defect-fluorite, structured with space group: Fm-3m, was detected using X-ray diffraction analysis. The lattice parameters were found to increase with the evaluated La
3+
ion concentration. The grain size of the synthesized powders increased with the increase in La
3+
ion content. The SAED patterns depicted fluorite structured fluorite. UV/Vis. spectrophotometer was used for the determination of band gap energy of Gd
(2−
x
)
La
(
x
)
Zr
2
O
7
nanopowders which increased with increasing La
3+
ion content. It was found to enhance from 4 to 3.6 eV. The visible spectrophotometer was used for determining unknown concentrations during the photocatalysis process to assure the effectiveness of the process. Overall, results illustrate that the photo-Fenton reaction on Gd
(2−x)
La
(x)
Zr
2
O
7
performed excellently in removing crystal violet (CV). The photo-remediation ratio of CV reached 90% within 1 h.
A numerical investigation of entropy generation due to MHD-free convective of Cu–water nanofluid in a porous I-shaped cavity is reported. The cavity is under Darcy law with inclined uniform magnetic ...field. The cavity is cooled from the top and a part of bottom wall subjected to uniform heat flux, while the other parts of walls of the cavity are adiabatic. Mathematical pattern formulated employing the single-phase nanofluid approach in governing equations the problem has been solved by finite difference technique. Prime efforts have been concentrated on the impacts of the pertinent parameters on the fluid flow and heat transfer inside the cavity. Numerical data have been plotted in the form of streamlines, isotherms, and average Nusselt numbers. The results show that the Nu number decreases via increasing the Ha number. It increases when the Ra number is increased. The maximum and minimum values of Nusselt occur at
B
= 0.2 and
B
= 0.8, respectively. Exerting an angle for magnetic flux leads to the improvement in thermal performance for all amount of
B
. The effects of Ha, nanofluid volume fraction, heat source size, location and angle of magnetic field on heat transfer, entropy generation, and thermal performance are completely studied and discussed.
Abstract
The aggregate udder shape (Bowl, Round, Cup), udder measurements (udder width, UW, udder front depth, UFD, udder rear depth, URD, udder levelness, ULV, udder heights, UH) and teat ...measurements (teat diameters, TD, front teat length, FTL, rear teat length, RTL, distance between front teats, DFT and distance between rear teats, DRT) were measured on 1300 Friesian cows located in a commercial farm under subtropical conditions (Egypt) to appraise udder and teats status and to evaluate the possible relationships with some milk production characteristics in conjunction with udder shape, age at first calving, sire and inbreeding effects on udder morphological traits and milk production ability. For such an available sample size, parity had affected (
P
< 0.01) UFD, TD, FTL and RTL. In addition, udder shape affected (
P
< 0.01) UW, UFD, URD, ULV and DFT. None of the other studied factors affected milk production traits. The bowl udder shape (
P
< 0.01) yielded a high total milk yield (3267.19 kg), adjusted milk yield (2443.01 kg) and lactation length (480.70 d) compared to other udder shapes. The genetic correlations of UW with total milk yield and persistency were strongly positive (0.86 and 0.93, respectively). However, strong negative genetic correlations were found between UW with peak milk yield and lactation length (− 0.92 and − 0.80, respectively), between RTL with peak milk yield (− 0.92) and DRT with persistency (− 0.79). As found from the stepwise multiple regression, UW and URD can be used as good indicators for predicting milk yield and lactation length. Additionally, this study spotlights the genetic background of udder characteristics based on reliable studies and the QTL database for cattle as a first step toward applying this knowledge side by side with phenotypic traits to improve the productivity of the Holstein breed under subtropical conditions.
