Fraction Ratio Research Articles

The Effect of the Mixing Ratio of Sewage Sludge and Organic Fraction of Municipals Solid Waste on Biogas Production in Anaerobic Digestion Process

Anaerobic digestion was the best way to treat organic waste biologically. It uses microorganisms to biodegrade biosolids without oxygen, producing biogas and compost. The study involved conducting batch experiments to investigate biogas and fertilizer production. Three digestive systems (A, B, and C) with three different mixing ratios were operated simultaneously and had a retention time of thirty-five days. The organic fraction of municipal solid waste, sewage sludge, and bacteria were employed in the experiments. The Al-Rustamiyah wastewater treatment plant was the source of the sewage sludge. The organic municipal solid waste fraction was utilized as materials, including fruit peels, rotten fruits, vegetable peels, eggshells, rotten vegetables, and garden leaves. The bacterial strain used in this research was E. coli, isolated directly from the local sewage sample and selected as an eco-friendly bacteria after conducting many tests. The digester's initial temperature was 30 °C, and it reached a high of 42 °C on the 16th day. Three digesters had initial pH values (6.7, 6.3, 6) and final values (7.3, 7.1, 7). The results showed good anaerobic digestion performance. The digester (C) achieved the highest biogas production, with a maximum cumulative biogas production value of 0.0549 m3. It also demonstrated removal efficiencies of 78.30% for TS, 89.13% for VS, 86.36% for BOD5, and 80.5% for COD. Additionally, the moisture content was measured at 43.30%. The anaerobic digestion’s final product was used as a high-quality fertilizer.

Flexural capacity prediction of reinforced UHPC beams using an interpretable machine learning model

Addressing the issues of inconsistency and limited accuracy in the current prediction models for the flexural capacity of reinforced ultrahigh-performance concrete (UHPC) beams, this paper proposes a machine-learning prediction model for the flexural capacity of reinforced UHPC beams based on interpretable Extreme Gradient Boosting (XGBoost) model. Firstly, a database containing 221 sets of experimental UHPC beam data is established, and the database quality is evaluated by Pearson correlation coefficient and Mahalanobis distance. Then, ten-fold cross-validation and the whale optimization algorithm (WOA) are employed to find the optimal hyperparameter combination for XGBoost. Different indices are used to evaluate the prediction accuracy of the XGBoost model with four typical machine learning models and other computational methods. The Shapley additive explanations (SHAP) method is used to provide interpretations of the prediction results. The results indicate that the XGBoost model outperforms the four other machine learning models and related standards. Compared with the existing formulas, the proposed prediction model demonstrates higher accuracy in predicting the flexural capacity of UHPC beams. The SHAP method effectively explains the prediction results of the XGBoost model, providing insights into accurately assessing the factors influencing the flexural capacity of UHPC beams. SHAP analysis reveals that the most significant factors affecting the flexural capacity of UHPC beams are the cross-sectional height and reinforcement ratio, while the least significant factors are the aspect ratio of steel fibers and volume fraction of steel fibers.

Magnetohydrodynamic Effects on Double Diffusion of Non‐Newtonian Hybrid Nanofluid in Circular Eccentric Annuli

ABSTRACTThe numerical investigation conducted in this study focuses on the heat and mass transfer in magnetohydrodynamic non‐Newtonian power‐law fluid flow of temperature‐dependent Al2O3–Fe3O4–water hybrid nanofluid within cylindrical annuli across four different eccentricities. This type of problem finds widespread application in various engineering contexts, where hybrid non‐Newtonian fluids offer enhanced efficiency for cooling and insulation purposes. In this configuration, the inner circle of the geometry is hot while the outer circle is cold, with the nanofluid filling the space between the cylinders. The governing equations are simulated using the Galerkin weighted residual finite element method. Various parameters are controlled in the study, including the Rayleigh number ranging from to , power‐law index ranging from to , nanoparticle volume fraction ranging from to , Hartmann number ranging from to , Buoyancy ratio ranging from to , and Lewis number ranging from to , in addition to the fixed Prandtl number (6.8377). The study presents visualizations such as streamlines, isotherms, and iso‐concentration contours, along with the assessment of heat and mass transfer rates expressed in terms of Nusselt and Sherwood numbers. The findings reveal that the heat transfer rate increases with higher nanoparticle volume fraction, Rayleigh number, and Buoyancy ratio. Similarly, the mass transfer rate is enhanced with increased Rayleigh number, Lewis number, and power‐law index. Notably, elevating the power‐law index leads to a decrease of 50.1% in the local Nusselt number and 52.4% in the local Sherwood number, respectively. With and , increasing from to raises and .

Modeling the Nonlinear–To–Linear Relationship Between Bulk and Pore Water Electrical Conductivity in Saturated Porous Media Using a Padé Approximant

AbstractA petrophysical model that accurately relates bulk electrical conductivity (σ) to pore fluid conductivity (σw) is critical to the interpretation of geophysical measurements. Classical models are either only applicable over a limited salinity regime or incorrectly explain the nonlinear‐to‐linear behavior of the σ(σw) relationship. In this study, asymptotic limits at zero and infinite salinity are first established in which, σ is expressed as a linear function of σw with four parameters: cementation exponent (m), the equivalent value of volumetric surface electrical conductivity (σs), the volume fraction of overlapped diffuse layer (ϕod) and parameter χ representing the ratio of the volume fraction of the water phase to that of the solid phases in the surface conduction pathway. Subsequently, we bridge the gap between the two extremes by employing the Padé approximant (PA). Given that parameter χ exhibits a marginal influence on the σ(σw) curve, based on measurements for 15 samples, we identify its optimal value to be 0.4. After setting the optimal value of χ, we proceed to evaluate the performance of the PA model by comparing its estimates and estimates made by two existing models to measured values from 27 rock samples and eight sediment samples. The comparison confirms that the PA model estimates are more accurate than estimates made by existing models, particularly at low salinity and for samples with higher cation exchange capacity. The PA model is advantageous in scenarios involving the interpretation of electrical data in freshwater environments.

A simple formula to fabricate high performance lithium metal capacitors

Energy storage technologies that are low-cost, with long cyclability, high rate-capability as well as high energy and power densities are under intensive investigation for sustainable clean energy transition. In this paper, we report a high-performance lithium metal capacitor (LMC) achieved by a simple slurry modification during the cathode film preparation. We show that a mere substitution of ~0.4 wt% conductive carbon by single walled carbon nanotubes (SWCNTs) increased the specific energy of LMCs by 22 %. Porous carbon cathode in this study was obtained from a non-edible biomass (coconut rachis); the optimized sample showed desirable surface characteristics (surface area ~1933 m2⸱g−1 and pore diameter ~2.0 nm) as well as high edge-plane fraction (ratio between relative density of edge and basal plane ~0.4). Cathode with no SWCNTs show a specific capacitance (CS) of ~133 F·g−1@0.1 A·g−1 in the potential window 2.0–4.0 V in the Li//LiPF6//AC device configuration. Removal of conductive carbon by SWCNTs up to ~0.6 wt% increased electrical conductivity of the cathode; however, the charge storability enhancements were only up to ~0.4 wt%. The optimum device delivered a CS ~188 F·g−1@100 mA·g−1 in the potential window 2.0–4.0 V with improved rate capability and cycling stability. Electrochemical impedance spectroscopy was used as a tool to understand the charge kinetics at the electrode; these studies collectively validated the observed enhancements in the charge storability. The device hereby developed showed superior specific capacity than most of the reported lithium-ion capacitors and comparable to some of the LMBs. The perceived 22 % increase in the specific energy by a mere 0.4 wt% SWCNT substitution is a step forward in fabricating the high-performance LMCs in addition to support the sustainability agenda through the carbon-negative precursors.

Lithium-ion storage in honeycomb-structured biomass-derived porous carbon

Honeycomb-shaped porous carbon (HSPC) offers unique surface properties for rapid ion transport through the bulk and hence could deliver desirable electrochemical charge storage performance; however, their fabrication is through time and cost intensive sacrificial template methods. Herein, HSPC was synthesized from a carefully selected plant component (coconut rachis) containing a dense network of phloem and xylem. The synthesized activated carbon has relatively high carbon content (>80 %), desirable textural characteristics (specific surface area ~ 1290 m2⸱g−1 and pore diameter ~ 2.0 nm), and high edge-plane fraction (ratio between relative density of edge and basal plane ~0.26). The HSPC electrodes delivered specific capacitance up to ~126 F⸱g−1 at 100 mA⸱g−1 at a potential window of 2–4 V in the HSPC//LiPF6//Li lithium metal capacitor configuration and retained ~98 % of its initial capacity after 1000 cycles with coulombic efficiency ~100 %. The performance of the device has been validated by electrochemical impedance spectroscopy before and after cycling. A postmortem analysis confirmed structural and chemical stability of the device upon cycling.

Non-invasive prenatal detection of dominant single-gene disorders in fetal structural abnormalities: a clinical feasibility study.

This study evaluated the accuracy of non-invasive prenatal testing (NIPT-SGDs) for dominant monogenic genetic diseases associated with fetal structural abnormalities and to assess the feasibility of clinical application. Pregnant women requiring prenatal diagnosis due to fetal structural abnormalities were enrolled. Maternal peripheral blood was analyzed for cell-free DNA (cfDNA) using coordinative allele-aware target enrichment sequencing (COATE-seq). This assessed fetal allele depth distribution, fraction and variation ratio. The variation's origin was then determined to obtain fetal variation information. Finally, NIPT-SGDs results were confirmed via invasive prenatal diagnosis (IPD). Upon examination of 113 samples using NIPT-SGDs, COATE-seq successfully analyzed 112 for fetal variation, excluding one due to hemolysis. The study detected six positive cases, yielding a 5.36% detection rate. These disorders included tuberous sclerosis complex (TSC1 and TSC2 being its causative genes), Noonan syndrome (PTPN11), polycystic kidney disease (PKD1), and Kabuki syndrome (KMT2D), occurring twice each, except for Noonan and polycystic kidney disease. Two false positives were due to the mother being a genetic mosaicism. Compared to invasive whole-exome sequencing (WES), NIPT-SGDs did not detect nine positive cases of IPD dominant monogenic diseases, accurately identifying 90.18% (101/112) of the actual positive and negative cases. Our findings demonstrate the clinical utility of NIPT-SGDs using COATE-seq in effectively identifying fetuses with dominant single-gene disorders. Furthermore, this method can be applied to all fetuses.

Impact of Natural Polymer Proportions on the Fire-Retardant Properties of Bioplastics

This research investigates the influence of varying proportions of natural polymers on the fire-retardant properties of bioplastic. Tapioca starch (Manihot esculenta) and corn starch (Zea mays) were selected as the bioplastic materials, with different weight fractions employed in the analysis. These materials, as naturally occurring polymers, are biodegradable and serve as promising components in the development of bioplastics. Fire resistance testing was conducted in accordance with ASTM D635-03, utilizing weight ratios of tapioca to corn starch at 70:30, 60:40, and 50:50. The results included photographic documentation of each specimen alongside the corresponding outcomes from the fire resistance tests. These images provide insight into the physical condition of the specimens prior to testing, emphasizing any notable morphological features that may affect their fire resistance properties. The optimal burning rate was observed in the bioplastic with a 50:50 weight fraction ratio of tapioca starch to corn starch, which exhibited a combustion rate of 8.420 mm/s. Additionally, the bioplastic with the highest weight loss rate, recorded at 0.0346 g/s, was also composed of a 50:50 weight fraction of the two starches. The observed increase was 2.36% relative to the 60:40 weight fraction and 13% relative to the 70:30 weight fraction. This increased weight loss rate can be attributed to the higher corn starch content, which is characterized by inherent flammability due to its structural composition.

Observation of D+→f0(500)μ+νμ and study of D+→π+π−ℓ+νℓ decay dynamics

Using 2.93 fb−1 of e+e− collision data collected with the BESIII detector at the center-of-mass energy of 3.773 GeV, we investigate the semileptonic decays D+→π+π−ℓ+νℓ (ℓ=e and μ). The D+→f0(500)μ+νμ decay is observed for the first time. By analyzing simultaneously the differential decay rates of D+→f0(500)μ+νμ and D+→f0(500)e+νe in different ℓ+νℓ four-momentum transfer intervals, the product of the relevant hadronic form factor f+f0(0) and the magnitude of the c→d Cabibbo-Kobayashi-Maskawa matrix element |Vcd| is determined to be f+f0(0)|Vcd|=0.143±0.014stat±0.011syst for the first time. With the input of |Vcd| from the global fit in the standard model, we determine f+f0(0)=0.63±0.06stat±0.05syst. The absolute branching fractions of D+→f0(500)(π+π−)μ+νμ and D+→ρ(π+π−)0μ+νμ are determined as (0.72±0.13stat±0.08syst)×10−3 and (1.64±0.13stat±0.10syst)×10−3. Combining these results with those of previous BESIII measurements on their semielectronic counterparts from the same data sample, we test lepton flavor universality by measuring the branching fraction ratios BD+→ρ0μ+νμ/BD+→ρ0e+νe=0.88±0.10 and BD+→f0(500)μ+νμ/BD+→f0(500)e+νe=1.14±0.26, which are compatible with the standard model expectation. Published by the American Physical Society 2024

Spectrally selective and interleaved water imaging and fat imaging (siWIFI).

To develop a novel imaging sequence that independently acquires water and fat images while being inherently insensitive to motion. The new sequence, termed spectrally selective and interleaved water imaging and fat imaging (siWIFI), uses a narrow bandwidth RF pulse for selective excitation of water and fat separately. The interleaved acquisition method ensures that the obtained water and fat images are inherently coregistered. A radial sampling strategy further reduces motion-induced artifacts. Phantoms with lipid concentrations ranging from 0% to 50% were scanned to measure fat fraction. Moreover, healthy volunteers were scanned to assess the in vivo feasibility of fat fraction measurement at the hip, knee, and liver. In vivo fat fraction measurements were compared with those from vendor-provided iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL) scans. Furthermore, a magnetization transfer (MT) preparation module was incorporated to demonstrate the feasibility of simultaneous measurement of fat fraction and MT ratio utilizing the siWIFI framework. The phantom fat fractions measured by siWIFI showed excellent correlation with lipid concentrations (R2 = 0.9995, p < 0.0001). In vivo studies demonstrated that the fat fractions obtained from siWIFI were comparable to those from IDEAL. Additionally, siWIFI demonstrates reduced motion artifacts from pulsatile flow in knee imaging compared to IDEAL scans and exhibits less sensitivity to respiratory motion in liver imaging compared to IDEAL scans without breath-hold. The knee imaging study demonstrated that MT-prepared siWIFI is capable of generating fat fraction and MT ratio maps simultaneously. The proposed siWIFI sequence allows selective water-fat imaging and quantification with reduced motion artifacts.

A Numerical Study of Dynamic Behaviors of Graphene-Platelet-Reinforced ETFE Tensile Membrane Structures Subjected to Harmonic Excitation

This study presents a numerical investigation of the dynamic behavior of graphene platelet (GPL)-reinforced ethylene tetrafluoroethylene (ETFE) tensile membrane structures subjected to harmonic excitation. Modal and harmonic response analyses were performed to assess both the natural frequencies and the dynamic responses of the ETFE membrane. GPLs were employed as the reinforcements to enhance the mechanical properties of the membrane materials, whose Young’s modulus was predicted through the effective medium theory (EMT). Parametric studies were conducted to examine the impact of pre-strain and the attributes of the GPL reinforcements, including weight fraction and aspect ratio, on the natural frequencies and amplitude–frequency response curves of the membrane structure. The first natural frequency substantially increased from 5.46 Hz without initial strain to 31.0 Hz with the application of 0.1% initial strain, resulting in a frequency shift that moved the natural frequency out of the range of typical wind-induced pulsations. Embedding GPL fillers into ETFE membrane was another potential solution to enhance the dynamic stability of the membrane structure, with a 1% addition of GPLs resulting in a 48.6% increase in the natural frequency and a 45.1% reduction in resonance amplitude. GPLs with larger aspect ratios provided better reinforcement, offering a means to fine-tune the membrane’s dynamic response. These results underscore that by strategically adjusting both pre-strain levels and GPL characteristics, the membrane’s dynamic behavior can be optimized, offering a promising approach for improving the stability of structures subjected to wind-induced loads.

Associations of Left Atrial Volume Index to Left Ventricular Ejection Fraction Ratio with Clinical Outcomes in Transthyretin Cardiac Amyloidosis.

Transthyretin amyloid cardiomyopathy (ATTR-CM) affects all cardiac chambers to cause left ventricular (LV) deformation as well as left atrial (LA) remodeling and functional impairment. We investigated the associations of the LA volume index (LAVI):LV ejection fraction (LVEF) ratio with the increased risk of death, heart transplant, or LV assist device implantation (LVAD) in patients with ATTR-CM. This was a retrospective cohort study involving 69 heart failure (HF) patients with ATTR-CM at an academic medical center between 1 November 2008 and 31 March 2024. ATTR-CM was diagnosed using a technetium-diphosphonate/pyrophosphate scan or an endomyocardial biopsy. The LAVI and LVEF were measured by echocardiography. Cox proportional hazards models were used for the analysis. The mean (SD) age of the participants was 77.5 (9.3) years. Over a median (IQR) follow-up period of 1.96 (0.67-2.82) years, we observed 24 composite events that included twenty-two deaths, two heart transplants, and two LVAD implantations (who subsequently died). In multivariable-adjusted analyses that accounted for age and the glomerular filtration rate, a one-unit increase in the LAVI:LVEF ratio was associated with a doubling of the risk (HR, 95% CI: 2.06, 1.11-3.82) of experiencing the composite outcome. A one-unit increase in the LAVI:LVEF ratio was associated with an increased risk of death, heart transplant, or LVAD implantation in patients with ATTR-CM.

Weakly-negatively-charged loose nanofiltration membranes tailored by polyethyleneimine for dye/salt separation

Loose nanofiltration membranes with a weakly negatively charged surface were made from interfacial polymerization between natural hydrophilic polymer carboxylated chitosan (C-CS) and trimesoyl chloride (TMC) firstly and further depositing branched polyethyleneimine (PEI) on top of the surface to tailor the membrane structures and surface charge properties. This kind of membrane was exploited for dye/salt separation in textile wastewater treatment. The effects of contents and molecular weights of PEI on the morphologies, surface charge, hydrophilicity, pore size, and dye/salt separation performance of the membrane were comprehensively investigated. We found that the top layer of PEI with a moderate molecular weight is suitable to form a loose structure for dye/salt separation. The optimized membrane has a comparable high water permeability (44.4 L/m2.h.bar), a low salt rejections (2.6 % for Na2SO4, 7.7 % for NaCl, and 6.8 % for MgCl2), a relatively high dye rejection (96.9 % for Congo Red, 85.4 % for Methyl Blue, 51.1 % for Bromophenol Blue, and 48.3 % for Reactive Black 5), and an extremely high CR/Na2SO4 fractionation ratio (37.27). Moreover, the resultant membrane shows excellent anti-fouling performance after 5 cycles (50 h) of filtration. It maintains a high Congo Red rejection during a 10-day long-term run. This study shows an easy way to fabricate and adjust the properties of loose nanofiltration membranes that work well for dye/salt separation using common and low-cost polymers. It shows promising potential in the application of textile wastewater treatment and resource recovery.

Formation of Superhydrophobic Coatings Based on Dispersion Compositions of Hexyl Methacrylate Copolymers with Glycidyl Methacrylate and Silica Nanoparticles.

In the last decade, the task of developing environmentally friendly and cost-effective methods for obtaining stable superhydrophobic coatings has become topical. In this study, we examined the effect of the concentrations of filler and polymer binder on the hydrophobic properties and surface roughness of composite coatings made from organic-aqueous compositions based on hexyl methacrylate (HMA) and glycidyl methacrylate (GMA) copolymers. Silicon dioxide nanoparticles were used as a filler. A single-stage "all-in-one" aerosol application method was used to form the coatings without additional intermediate steps for attaching the adhesive layer or texturing the substrate surface, as well as pre-modification of the surface of filler nanoparticles. As the ratio of the mass fraction of polymer binder (Wn) to filler (Wp) increases, the coatings show the lowest roll-off angles among the whole range of samples studied. Coatings with an optimal mass fraction ratio (Wn/Wp = 1.2 ÷ 1.6) of the filler to polymer binder maintained superhydrophobic properties for 24 h in contact with a drop of water in a chamber saturated with water vapor and exhibited roll-off angles of 6.1° ± 1°.

On the Interrelationship of Electrical and Hydraulic Conductivities in Carbonate Rocks

Carbonate reservoir exhibits "low-resistivity and (ultra) low-permeability" anomaly due to complex pore structure. It means that hydraulic conductivity, closely related to permeability (K), is not simply equivalent to electrical conductivity in this case. As a result, the conventionally well-established permeability-resistivity relationship does not apply to carbonate reservoirs any longer, and this poses a big challenge for the interpretation and evaluation of carbonate reservoirs. In this study, we found that the relationship between permeability and formation factor is non-monotonic and scattering through direct-current (DC) resistivity and nuclear magnetic resonance (NMR) experiments, and this means that the hydraulic conductivity is not well correlated with the electrical conductivity in carbonate rocks as one expects. There are the two factors, the volume fraction ratio of macro- and micro-pores, and the number of dolomitization-formed micropores, predominantly control hydraulic conductivity and electric conductivity, respectively. Moreover, the non-uniform distribution of intercrystalline pore networks will significantly reduce hydraulic conductivity. To more accurately estimate the permeability of carbonate rocks, the new permeability model based on NMR spectra rather than formation factor has been proposed. In this model, the characteristic relaxation time () was defined, which is associated with the macropores that contribute most significantly to permeability and can be used to distinguish between macro- and micro- pores. This model demonstrates a minimal average absolute logarithmic deviation () and exhibits generalizability across various carbonate rocks. The study addresses the mechanism analysis of "low-resistivity and (ultra) low-permeability" phenomenon in carbonate reservoir, and has potential to facilitate the interpretation and evaluation of carbonate reservoir.

Test of lepton flavor universality with a measurement of R(D*) using hadronic B tagging at the Belle II experiment

The ratio of branching fractions R(D*)=B(B¯→D*τ−ν¯τ)/B(B¯→D*ℓ−ν¯ℓ), where ℓ is an electron or muon, is measured using a Belle II data sample with an integrated luminosity of 189 fb−1 at the SuperKEKB asymmetric-energy e+e− collider. Data is collected at the ϒ(4S) resonance, and one B meson in the ϒ(4S)→BB¯ decay is fully reconstructed in hadronic decay modes. The accompanying signal B meson is reconstructed as B¯→D*τ−ν¯τ using leptonic τ decays. The normalization decay, B¯→D*ℓ−ν¯ℓ, produces the same observable final-state particles. The ratio of branching fractions is extracted in a simultaneous fit to two signal-discriminating variables in both channels and yields R(D*)=0.262−0.039+0.041(stat)−0.032+0.035(syst). This result is consistent with the current world average and with Standard Model predictions. Published by the American Physical Society 2024

Optimization of extraction for efficient recovery of kenaf seed protein isolates: evaluation of physicochemical and techno-functional characteristics.

Kenaf seeds are a rich source of protein; however, finding the best extraction method is crucial to obtaining high-quality protein from these underutilized seeds. This research devised an optimized extraction process for best recovery of kenaf seeds protein using response surface methodology. The key parameters affecting the yield and protein content were optimized, including extraction pH (2-11), seed:water ratio (5:1-50:1), temperature (30-90 °C), and duration (20-360 min). The physicochemical and techno-functional properties of kenaf seed protein isolates (KSPIs) were examined. A maximum protein yield of 12.05 g/100 g with purity level 91.94 g/100 g was obtained using an optimized extraction with pH 11.0, seed:water ratio 50:1, 360 min duration, and temperature 50 °C. The oil and water retention capacities of KSPI were 1.14 mL g-1 and 1.37 mL g-1 respectively. After 30 min at pH 7, KSPIs demonstrated remarkable emulsion capacity (83.12%) and stability (75.63%), along with high foaming capacity (106%) and stability (18.3%). As per high-performance liquid chromatography analysis, arginine, glutamic acid, leucine, phenylalanine, and lysine were the most abundant amino acids detected in KPSIs. The KSPIs' globular protein structure was successfully verified using analytical approaches, including Fourier transform infrared spectroscopy, protein fraction ratios, and differential scanning calorimetry. Sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis revealed that KPSI has a molecular weight distribution ranging from 10 kDa to 50 kDa. The results of this study support the application of the proposed response-surface-methodology-optimized extraction method for efficient recovery of high-quality kenaf seed proteins that meet the necessary physicochemical and techno-functional requirements. © 2024 Society of Chemical Industry.

Mechanical behaviour of double lining with outer segmental lining and inner fibre reinforced concrete lining under internal water pressure

Double lining with outer segmental lining and inner reinforced concrete lining is extensively used for water conveyance tunnel with internal water pressure. In order to improve the performance of the double lining, the steel rebar and fibre reinforced concrete (R/FRC) is designed for inner lining to enhance the tensile strength of reinforced concrete (RC). Full-scale tests were conducted to compare the mechanical behaviour of double lining with inner RC and R/FRC linings. The test results showed that both types of lining failed in four stages: elastic stage, inner lining cracking stage, crack stabilization and segmental joint damage stage, and failure stage. The cracks firstly occurred in the inner lining near the segmental joints and then propagated to the whole inner lining ring. Finally, the crack width and segmental joint opening successively exceeded the thresholds, and the double lining failed until the breaking of segmental joints. Compared with inner RC lining, R/FRC lining had better performance in terms of the initial cracking load, cracking-control ability, post-cracking stiffness, service limit capacity of inner lining and waterproof capacity of segmental lining. The improvement ratios were 36.3%, 50.3%, 46.3%, 37.2% and 31.1%, respectively. The influences of fibre volume fraction, fibre aspect ratio, and reinforcement ratio of steel rebar on the mechanical performance of R/FRC lining were also investigated based on a previously proposed analytical model. The parametric analysis demonstrated that higher fibre volume fraction and fibre aspect ratio can result in more significant increase of mechanical performance of R/FRC lining. The steel fibres were found to have more significant effects on the post-cracking behaviour of the lining than same amounts of reinforcing bars. Finally, an optimized function was proposed to fulfil a balance of lining performance and economy. The experimental and analytical results indicated that R/FRC lining can substitute RC lining and perform higher mechanical performance in water conveyance tunnels.

Enhancement of carbon nanotubes/kerosene nanofluids on mixed convective heat transfer in rectangular enclosures

With the objective of understanding how the mixed convective and the geometrical parameters together influence the nanofluid behavior (enhancement or deterioration) and finding the best configuration of the moving walls for engineering purposes, this paper investigates the single lid-driven mixed convective flow of carbon nanotubes/kerosene nanofluids confined in vertical and horizontal cavities with non-uniform boundary conditions applied to the vertical walls. The findings of this paper can provide crucial conclusions into the behavior and optimization of nanofluids in mixed convective flows in enclosed systems for engineering applications. The system of the governing equations is tackled by a validated in-house code, where we compared the code accuracy with previous experimental and numerical works. The governing parameters are -50 ≤ Pe ≤ 50, 0.5 ≤ A ≤ 4, and 0 ≤ φ ≤ 3%. The effective nanofluid properties are calculated using special experimental models. The outcomes revealed that the carbon nanotube effect on heat transfer depends on the aspect ratio. The greater the aspect ratio, the more pronounced the negative impact of the nanotube concentration where Nusselt number is reduced by 4.49% and 16.17% for φ = 0.01 and 0.03, respectively, in the case of Pe = 0 and A = 4. The Peclet number also has a significant impact on the heat transfer, especially for higher aspect ratios, and diminishes the critical aspect ratio where the nanofluid's behavior changes. An augmentation in the aspect ratio and Peclet number brings about an augmentation in the Nusselt number. Additionally, the Peclet number can reverse the conjugated effect of carbon nanotube volume fraction and aspect ratio on nanofluid enhancement. When Pe = 50 in C1, heat transfer rate is 1.75% and 1.11% enhanced for φ = 0.01 and 0.03, respectively, and A = 4. Moving horizontal walls exhibits higher heat transfer enhancement compared to vertical ones.

Studying the relationship of the type of higher nervous activity with the milk productivity of cows

The purpose of the presented research was to study the influence of the type of higher nervous activity (HNA) on the secretion of organic components of milk in various milking conditions. The studies were carried out in 2 periods. The first period was standard, and in the second there was a conditioned stimulus - the presence of an outsider. Black-and-white cows were assigned to four types of higher nervous activity: type 1 - strong, balanced; type 2 - strong, unbalanced; 3 - strong, inert; 4 - weak, inhibitory. In the first period, type 2 cows showed a significant decrease in the amount of milk, fat and glucose, but the mass fraction of protein in milk tended to increase separately for each milking by 0.22 %. The ratio of the mass fraction of protein to the percentage of lactose for two milkings was significantly higher by 0.06, in relation to type 1. In type 3, in general, for two milkings, an increase in lactose by 13.3 g, fat - by 7.0 g was noted, in contrast to the indicators of the first type. Animals of the fourth type tended to reduce milk secretion to 18.3 %. Also, the mass fraction of fat in milk was lower to 0.53 % (P &lt; 0.05) and protein to 0.28 %, and the proportion of lactose in milk, on the contrary, was consistently higher in both milkings by 0.25-0,26 % (P &lt; 0.05). In the second period (with a conditioned stimulus), cows of the second group showed a positive trend towards an increase in the mass fraction of protein in the morning with machine milking by 0.26 % (P &lt; 0.05), and with manual milking by 0.32 % (P &lt; 0.05), in relation to the first group. The mass fraction of fat during machine and manual milking in animals of the second type tended to decrease. In the third group, the indicators of milk of the first streams in the morning were higher by 0.99 % (P &lt; 0.05) - fat, by 0.33 % - protein, by 0.09 % - lactose, in relation to the first type of higher nervous activity. In cows with a weak, inhibitory nervous system, the influence of the conditioned stimulus contributed to a decrease in the ratios of the mass fraction of fat and protein in milk to lactose to 0.14 and 0.09, compared with type 1 cows.