Total Volume Fraction Research Articles

Cognitive Impairment, Associated Clinical Factors, and MR Volumetric Measures in Myelin Oligodendrocyte Glycoprotein-IgG-Associated Disease.

Cognitive impairment is a common and challenging symptom in multiple sclerosis and neuromyelitis optica spectrum disease; however, data in myelin oligodendrocyte glycoprotein-IgG-associated disease (MOGAD) remain scarce. In this cross-sectional study, we investigated the frequency of cognitive impairment, associated clinical factors, and MRI volumetric measures in MOGAD. Participants were investigated in a single center by certified psychologists and underwent a standardized 3-T-MRI protocol. MRI data were processed with FreeSurfer for gray and white matter volume estimation, presented as a fraction of total intracranial volume. Sera screening for antineural antibodies has been conducted using cell-based assays. The following clinical factors were included in the multivariate logistic regression analysis: sex, age, overall number of previous relapses, and specifically the history of acute disseminated encephalomyelitis (ADEM)/ADEM-like episodes and other brain relapses. Thirty-two patients with MOGAD (19 female, median age 29.4 years) after a median of 2 relapses with a median EDSS of 1.0 were recruited. Seven patients (21.9%) demonstrated cognitive impairment with the most prevalent deficits in mental flexibility (16.7%), attention (11.1%-14.8%), and verbal working memory (10.3%). 72.4% suffered from fatigue and 42.9% from signs of depression, moderate to severe in 28.6%. The overall number of previous relapses (odds ratio [OR] 1.789, 95% CI 1.041-3.074) and specifically ADEM/ADEM-like episodes (OR 16.929, 95% CI 1.228-233.427) were the only clinical factors associated with cognitive impairment in a multivariate logistic regression model. Screening for antineuronal antibodies remained negative. Cerebral white matter (WM) (0.300 vs 0.317, p = 0.003) and deep gray matter (DGM) (0.036 vs 0.038, p = 0.002) volumes were reduced in patients with MOGAD compared with healthy controls (n = 32). Both cognitive impairment (0.031 vs 0.036, p = 0.003) and history of ADEM/ADEM-like episodes (0.032 vs 0.036, p = 0.006) were associated with reduced DGM volume compared with unaffected patients with MOGAD. Despite a low overall disability, every 5th patient with MOGAD experiences cognitive impairment. Cognitive impairment is associated with a higher number of relapses and particularly ADEM/ADEM-like attacks. Although both WM and DGM atrophies are apparent in MOGAD, the latter only seems to have an association with cognitive impairment.

A two‐scale numerical analysis of intra‐yarn hybrid natural/synthetic woven composites

AbstractThis paper investigates how combining natural and synthetic fibers within yarns, altering the degree of hybridisation, and varying weave architectures affect the homogenized elastic properties and stress distributions in 2D woven composite laminae using a two‐scale homogenization scheme. The novelty lies in integrating a micro‐scale representative volume element model with a meso‐scale repeating unit cell model to capture intra‐yarn natural/synthetic fiber hybridisation. The study focuses on 2/2 twill and 5‐harness satin woven laminae with flax/E‐glass, hemp/E‐glass and basalt/E‐glass hybrid yarns, all with a total fiber volume fraction of 0.6. Fiber distributions are created through a random sequential expansion algorithm for hybrid RVEs, while periodic meso‐structures are used to define weave architectures for RUCs. Results show that yarn‐level fiber hybridisation significantly influences matrix stress distributions, with variations of up to 22%. In contrast, weave architecture has a minimal effect, with variations in homogenized properties below 2%. Varying fiber types, degrees of hybridisation and weave architectures allow for the tailoring of yarn and lamina properties and altering the stress distributions at micro‐ and meso‐scales and potentially influencing damage mechanisms. The modeling approach for analyzing the mechanical behavior of intra‐yarn hybrid natural/synthetic woven laminae could potentially be used to tailor their tolerance to damage.Highlights Two‐scale homogenization integrates RVE and RUC for 2D woven hybrid composites. Analyzed flax/E‐glass, hemp/E‐glass, basalt/E‐glass in twill and satin weaves. Intra‐yarn hybridisation significantly affects properties and stress fields. Hybridizing fibers offers tailored properties and may improve damage tolerance.

Effects of stirring friction on the microstructure, texture and mechanical properties of 7055 aluminum alloy

Aluminum alloys are widely used in aerospace, transportation, and many other fields due to their excellent properties such as lightweight, ultra-strength, and high toughness. This paper analyzed the influence mechanism of friction stir on the microstructure, texture, and mechanical properties to realize the strength and toughness of 7055 aluminum alloys and optimize their deformation process. The results show that the aluminum alloys change from uneven banded grains to uniform and fine equiaxed grains after friction stir processing, and the grain size is refined from 14 μm to 0.71 μm. The high-angle grain boundary and texture intensity present an initial increase but a subsequent decrease due to the combined effect of recrystallization and high-temperature softening caused by the heat input of friction stir processing. The total texture intensity and volume fraction of the friction stir processed aluminum alloys decrease significantly, and the intensity of RtG {110} <110>, A {110} <111>, E {110} <111>, and F {111} <112> texture significantly decrease or disappear, while the Brass (B) {110} <112> texture increases. The yield strength of FSP aluminum alloys decreases with increasing heat input (w/v), which mainly depends on the weakening of the texture strengthening effect. However, the increase of geometrically necessary dislocations (GND) caused by grain boundary sliding leads to the significant improvement of the deformation hardening ability and plasticity of the material. In addition, the effect of texture on the plasticity of aluminum alloys was calculated by using Schmid law. It is found that the equivalent slip factor (ESF) and maximum Schmid factor (μmax) of A, E, and Cu textures are equal to 0. The small ESF and μmax of the S texture are not conducive to the plastic deformation property of materials, while the 1000 × 70 sample with more ESF (8) and μmax (0.41) of the Cube texture ({001} <100>) shows better plasticity.

7500 Effect Of Orchiectomy On Bone Microarchitecture In Male Mice With Kidney Disease

Abstract Disclosure: D. Wu: None. A. Patwardhan: None. O. Marks: None. Y. Komaru: None. E. Kefalogianni: None. R. Aurora: None. S. Dhindsa: None. A. Herrlich: None. Background: Chronic kidney disease (CKD) leads to decreased bone density and increased fracture risk. In males, an additional factor contributes to the low bone density. Around half of the men with CKD have low serum testosterone concentrations. We hypothesized that CKD and low testosterone would have an additive and detrimental effect on bone. Methods: Forty male C57BL/6 mice were divided into 4 groups: 1) renal injury, induced by ischemia-induced reperfusion (IRI) and sham orchidectomy (IRI-sham, N=8) at 2 months of age; 2) orchidectomy (ORX), performed 4 weeks after IRI (IRI + ORX, N=11); 3) sham-ORX, N=9; and 4) sham-sham surgery, N=12. 12 weeks after IRI, the mice developed renal fibrosis and decreased glomerular filtration rate, indicative of CKD. The mice were sacrificed when they were 7 months old. Femur and tibia were harvested for both histology and μCT analysis. Results: Bone volume to total volume fraction (BV/TV) was lower in the IRI-ORX (0.06±0.02) and sham-ORX (0.08±0.02), as compared to IRI-sham (0.10±0.03, p&amp;lt;0.05) and sham-sham group (0.14±0.03, p&amp;lt;0.05) respectively. Similarly, the volumetric bone mineral density (vBMD) in IRI-ORX (93±27 mgHA/cm3) and sham-ORX (112±39 mgHA/cm3) groups were lower than IRI-sham (150±43 mgHA/cm3, p&amp;lt;0.05) and sham-sham (187±30 mgHA/cm3, p&amp;lt;0.05) mice. Trabecular number (Tb.N) was decreased in the IRI-ORX group (2.7±0.7 #/mm) compared to IRI-sham group (4.1±1.1 #/mm, p&amp;lt;0.05). Tb.N was also lower in sham-ORX (3.2±1.1 #/mm) mice than sham-sham (4.5±0.2 #/mm), but not IRI-sham mice. In contrast, trabecular thickness (Tb.Th) was lower in IRI-ORX (0.035±0.002 mm) and IRI-sham (0.038±0.002 mm) compared to sham-ORX (0.045±0.005 mm) and sham-sham (0.047±0.005 mm, p&amp;lt;0.05). Trabecular spacing (Tb.Sp) was increased by 47% in IRI-ORX group compared to IRI-sham group (0.26±0.09 mm). Decreased trabecular numbers and increased spacing results in reduced connectivity density (Conn.Den), which was decreased by 60% in the IRI-ORX sham-ORX groups as compared to sham-sham group (423±58 #/mm3, p&amp;lt;0.05). 2 way ANOVA analysis showed that ORX significantly contributed to the variance in BV/TV (p&amp;lt;0.001), vBMD (p&amp;lt;0.001), Tb.N (p&amp;lt;0.01), Tb.Sp (p&amp;lt;0.01) and Conn.Den (p&amp;lt;0.001), while IRI contributed to Tb.Th (p&amp;lt;0.0001). There was no significant interaction between IRI and ORX in all endpoints. Conclusions: Taken together, these data indicate that even in the presence of established CKD, ORX has a greater effect on bone mass. ORX decreased trabecular number (Tb.N) and increased trabecular spacing (Tb.Sp) to a greater extent than IRI. IRI decreased trabecular thickness (Tb.Th) while ORX had no effect on that parameter. Trabecular bone loss starts by trabecular thinning. Eventually, the trabeculae will be completely resorbed, resulting in decreased trabecular numbers and increased spacing. Our data indicate that IRI and ORX affect bone at different time points. Presentation: 6/1/2024

Improving mechanical and electrical properties of Cu-Ni-Si alloy via machine learning assisted optimization of two-stage aging processing

Recent studies have shown that synergistic precipitation of continuous precipitates (CPs) and discontinuous precipitates (DPs) is a promising method to simultaneously improve the strength and electrical conductivity of Cu-Ni-Si alloy. However, the complex relationship between precipitates and two-stage aging process presents a significant challenge for the optimization of process parameters. In this study, machine learning models were established based on orthogonal experiment to mine the relationship between two-stage aging parameters and properties of Cu-5.3Ni-1.3Si-0.12Nb alloy with preferred formation of DPs. Two-stage aging parameters of 400 °C/75 min + 400 °C/30 min were then obtained by multi-objective optimization combined with an experimental iteration strategy, resulting in a tensile strength of 875 MPa and a conductivity of 41.43 %IACS, respectively. Such an excellent comprehensive performance of the alloy is attributed to the combined precipitation of DPs and CPs (with a total volume fraction of 5.4% and a volume ratio of CPs to DPs of 6.7). This study could provide a new approach and insight for improving the comprehensive properties of the Cu-Ni-Si alloys.

TECHNOLOGICAL SOLUTION FOR COMBATING HYDROGEN SULFIDE AT THE FIELD

One of the urgent problems in the production of hydrogen sulfide-containing oils is the problem of increasing the efficiency of hydrogen sulfide removal. Optimization of costs associated with the production, transportation and preparation of oil is very important at the present time. In order to reduce the costs of oil preparation, the use of a differentiated approach to solving the problem of its purification from hydrogen sulfide at the Kashagan field depends on the volumes of oil preparation, the mass fraction of hydrogen sulfide in the oil, the presence of gas near the high-sulfur oil preparation unit (UPVSN) that does not contain hydrogen sulfide, the presence of a gas collection system and the possibility of transporting increased volumes of hydrogen sulfide-containing gas to the sulfur purification unit. Taking these factors into account, it is necessary to identify the maximum values ​​​​of the volume fractions of methane, ethane, nitrogen and carbon dioxide in the composition of the stripping gas, at which the mass of oil will be preserved, as well as the conditions under which it will be purified from hydrogen sulfide in the conditions of the Kashagan field. Studies have shown that with an increase in the oil heating temperature and a decrease in the pressure in the desorption column, the maximum total volume fraction of methane and nitrogen in the mixture in the composition of the stripping gas decreases. A decrease in the mass fraction of hydrogen sulfide in oil below 100 ppm and maintaining the mass yield of oil depending on the proportion of these components in the composition of the stripping gas is possible if the oil temperature and pressure in the column are optimized. An increase in the total volume fraction of methane and nitrogen in the composition of the stripping gas leads to a decrease in its required consumption to achieve a certain efficiency of oil purification from hydrogen sulfide at specified operating parameters of the column.

A numerical study on the turbulence characteristics in an air–water upward bubbly pipe flow

A high-resolution numerical simulation of an air–water turbulent upward bubbly flow in a pipe is performed to investigate the turbulence characteristics and bubble interaction with the wall. We consider three bubble equivalent diameters and three total bubble volume fractions. The bulk and bubble Reynolds numbers are $Re_{bulk}= u_{bulk} D/\nu _w = 5300$ and $Re_{bub}= (\langle u_{bub}\rangle - u_{bulk}) d_{eq}/\nu _w = 533\unicode{x2013}1000$ , respectively, where $u_{bulk}$ is the water bulk velocity, $\langle u_{bub}\rangle$ is the overall bubble mean velocity, $D$ is the pipe diameter and $\nu _w$ is the water kinematic viscosity. The mean water velocity near the wall significantly increases due to bubble interaction with the wall, and the root-mean-square water velocity fluctuations are proportional to $\bar {\psi }(r)^{0.4}$ , where $\bar {\psi } (r)$ is the mean bubble volume fraction. For the cases considered, the bubble-induced turbulence suppresses the shear-induced turbulence and becomes the dominant flow characteristic at all radial locations including near the wall. Rising bubbles near the wall mostly bounce against the wall rather than slide along the wall or hang around the wall without collision. Low-speed streaks observed in the near-wall region in the absence of bubbles nearly disappear due to the bouncing bubbles. These bouncing bubbles generate counter-rotating vortices in their wake, and increase the skin friction by sweeping high-speed water towards the wall. We also suggest an algebraic Reynolds-averaged Navier–Stokes model considering the interaction between shear-induced and bubble-induced turbulence. This model provides accurate predictions for a wide range of liquid bulk Reynolds numbers.

Bubbles Counting Using Organic Pollutants Degradation as a Probe

Relying on the fact that both of chemical and physical impacts of sonication are in strong relation to the number of acoustic cavities, the present paper introduces an innovative technique for the estimation of the number of active bubbles using the degradation of nonvolatile pollutants in the bulk liquid as a probe. The internal (gas pages) and external (liquid) bubble sonochemistry were simulated to track the radicals generation and use for nonvolatile pollutants degradation (in the liquid phase). To this end, COPASI® chemical kinetics software has been used for optimizing the acoustic bubble number density by linking the instantaneous bubble gas reaction (described by a bubble dynamic model accounting for the radical dissolution mechanism) and the aqueous free radicals degradation kinetics [i.e. concentration vs. time] of several nonvolatile organics (phenol, 4-chlorophenol, dyes…). Based on this strategy, the number density of active bubbles was determined for different operating circumstances (i.e. acoustic intensity, frequency, liquid temperature and saturation gas type). The performance of our method was evaluated by comparing our findings to those available in the literature, where an excellent agreement was established. Our technique showed that the number density monotonously goes up with increasing ultrasound frequency from 200 to 1140kHz, regardless of the experimental conditions used in this investigation. The opposite behavior has been obtained with the increase of the liquid temperature and acoustic intensity. Additionally, it has been noticed that the variation in the number of cavities with respect to the nature of saturating gas is frequency-dependent. At a frequency of 200kHz, the number of bubbles is in the order: O2>Ar>air. However, over this frequency (>200kHz), the number of acoustic bubbles is in the order: O2>air>Ar. On the other hand, it has been shown that below a frequency of ~860kHz, the variation of void fraction (ε) is synchronized with change in number density (N); nevertheless, over this value (>860kHz), these two parameters (N, ε) are no longer closely connected. As a result, in this case (>860kHz), the evaluation of number density from the total volume fraction of bubbles could not be directly performed without more information regarding the bubbles population, (e.g. size distribution, bubble-bubble interactions, bubbles deformation…etc.). Finally, the current proposed technique is flexible and can determine the number density of active bubbles for a wide range of operating conditions and circumstances.

Comparison of non-reactive solute transport models for the evaluation of fluid flow in packed beds with implications for heap leaching practice

This study investigated the effects of mean particle size fraction, bottom particle size, particle porosity and wettability on solution scale preferential flow behaviour via step input tracer tests in drip irrigated, narrowly and mixed-sized beds under steady state fluid flux. Nine solute transport models were used to quantify this behaviour reflected in the residence time distribution (RTD) profiles. Four were empirical models: three compartmental model configurations (CM-1, CM-2, CM-3) and tanks-in-series (TIS) model. The remainder five models were semi-empirical: advection dispersion (AD), piston exchange (PE), piston exchange - diffusion variant (PE-D), piston dispersion and exchange (PDE) and piston dispersion and exchange - diffusion variant (PDED). The model fit results showed that the mono-porosity TIS, AD and CM-2 models were the worst performers, while the dual porosity PDE and novel PDE-D models achieved the lowest average error values across the various systems. Higher levels of particle wettability coupled with capillary effects produced peculiar RTD curves that were relatively more difficult for the mono-porosity models to simulate. The model parameters investigated included the longitudinal dispersion coefficient (Dds), dead to total volume fraction (VD/VT), dynamic to total saturation fraction (βd/βT), overall mass transfer coefficient (Kma) and maximum diffusional pore length (X). The results showed that an increase in the average particle size within the beds led to higher VD/VT, Dds and X values, but lower βd/βT and Kma values. These indicate an overall increase in solution scale preferential flow behaviour. Decreased capillary suction and connectivity between particle pores and inter-particle voids were deemed responsible for the results. Higher levels of particle porosity acted as a buffer against these effects. Overall, the results highlight the benefit of the addition of fines (0.1–1 mm particles) during the agglomeration process in heaps to help reduce solution scale preferential flow behaviour and increase liquid hold-up. This is more necessary when the ore has low to moderate levels of porosity (surface area: <2 m2/g) and will also increase the modelling options available as most models performed better fitting data from such beds.

Buoyancy-driven micropolar ternary hybrid nano-suspension within an oblique incinerator-shaped chamber: Thermal and second law analyses

Since performance of thermal systems may depend on fluids’ thermal conductivities being utilized as coolants, improvement of thermal efficiencies of fluids having micro-structures and involving ternary hybrid nanomaterials may be highly valued. In fact, microrotation of ternary hybrid nanofluids (THNFs) in oblique incinerator-shaped chamber may find applications in industrial processes involving polymeric solutions and lubricants where they help in reduction of drag forces and act as better cooling agent. In view of this, the present study carries out thermal and second law dissection of micropolar THNF within an oblique incinerator-shaped chamber heated from bottom emplacing a roundish heater under a fixed heat flux. The THNF comprises of Al2O3, CNT and graphene as nanoparticles. The study reveals that streamlines and isotherms undergo prominent change due to inclination of the chamber. When Raleigh number and diameter of heater amplify streamlines, microrotations, and entropy generation intensify while average Bejan number whittles down. Average heat transfer rate ameliorates by 4.54 % and 2.17 % when total volume fraction augments from 1.5 % to 3 % and 3 %–4.5 %, respectively. Heat transfer rate reduces by 1.23 %, 0.48 %, 3.33 %, 5.24 %, 2.07 %, and 1.66 % when inclination angle increases from 0° to 90° with inclination angle step 15°.

Tension Lap Splices in Recycled-Aggregate Concrete Strengthened with Steel–Polyolefin Fibers

The bond strength of tension lap splices in recycled-coarse-aggregate-reinforced concrete strengthened with hybrid (steel–polyolefin) fibers was experimentally investigated. This study was conducted with the help of twelve lap-spliced beam specimens. The replacement level of coarse natural aggregates with recycled concrete aggregate (RCA) was 100%. The following variables were investigated: various ranges of steel–polyolefin fibers—100–0%, 75–25%, 50–50%, 25–75%, and 0–100%—in which the total volume fraction of fibers (Vf) remains constant at 1%; and two lengths of lap splices for rebars of 16 mm diameter (db): 10 db and 15 db. The test results showed that the best range of steel–polyolefin fibers that gave the highest bond strength was 50–50%. The ductility of the fiber-reinforced recycled-aggregate (FR-RA) concrete was significantly improved for all the cases of various relative ratios of steel and polyolefin fibers. The bond strength was also predicted using three empirical equations proposed by Orangun et al., Darwin et al., and Harajli. This study showed that the Harajli equation gave a more accurate estimation of the bond strength of reinforcing bars embedded in FR-RA concrete than those proposed by Orangun et al. and Darwin et al.

Study on mechanical properties and meso-damage mechanism of carbon-polyvinyl alcohol hybrid fiber reinforced recycled coarse aggregate concrete under the coupling action of sodium sulfate and dry-wet cycles

In order to investigate the influence of the coupling effect of sodium sulfate dry-wet (DW) cycles on the mechanical properties of carbon-polyvinyl alcohol hybrid fiber reinforced recycled coarse aggregate concrete (HFRAC), HFRAC specimens were subjected to uniaxial compression tests. The total volume fraction of fibers was kept constant at 0.4%, and various volume fractions of carbon fibers (CF) were added to the recycled coarse aggregate concrete (RAC), namely 0%, 0.1%, 0.2%, 0.3%, and 0.4%, with polyvinyl alcohol (PVA) fibers replacing a portion of CF in equivalent volume. Uniaxial compressive stress–strain curves were obtained for HFRAC specimens subjected to different numbers of DW cycles (0, 30, 60, and 120 cycles). Microscopic testing methods including acoustic emission (AE), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and nuclear magnetic resonance (NMR) were employed to analyze the microstructure, erosion product composition, and pore structure changes of the specimens. The results revealed that, for RAC specimens, the peak stress (σp) and elastic modulus (E) initially increased and then decreased, whereas the peak strain (εp) initially decreased and then increased with an increase in the number of DW cycles. After adding hybrid fibers, the σp values of CF, Hybrid 3:1, Hybrid 1:1, Hybrid 1:3, and PVA specimens increased (or decreased) by 12.0%, 11.43%, 0.9%, −9.5%, and −8.5%, respectively, compared to RAC. The Hybrid 1:3 specimen exhibited a negative hybrid effect. With an increase in the erosion age, the Hybrid 3:1 specimen demonstrated enhanced resistance to sulfate attack and achieved the highest σp value after 120 cycles. The influence of sulfate DW cycles coupling on the microscopic damage mechanism of HFRAC was analyzed using a statistical damage constitutive model. The microscopic damage evolution process was characterized by five characteristic parameters: E0, εa, εh, εb, and H. The analysis results indicated a clear correlation between the variation of these characteristic parameters and the number of DW cycles. An effective connection was established between the microscopic damage mechanism and the macroscopic nonlinear constitutive behavior. The phenomenon of relative lagging of acoustic emission signals during the uniaxial compression process was explained from the perspective of effective stress. This study provides a theoretical basis for the promotion and application of RAC under sulfate DW cycle environments.

Effect of Heat Treatment on the Interfacial Structure and Microstructure of Al/Al/Cu Composites Prepared by Different Accumulative Roll Bonding Passes

The effects of heat treatment ((300–500 °C) × 30 min) on the interfacial structure, microstructure, and tensile properties of Al4343/Al3003/Cu composites prepared by different accumulative roll bonding (ARB) passes are studied by scanning electron microscopy, energy dispersion spectrometry, electron backscattered diffraction, and tensile tests at room temperature. The results show that the total thickness of the diffusion layer at the Al3003/Cu interface in the same ARB pass Al/Al/Cu composite increases with the increase in temperature. At the same temperature, the total thickness of the diffusion layer at the Al3003/Cu interface increases from ARB0 to ARB3 passes and decreases at ARB5 passes. In the same ARB pass Al/Al/Cu composites, the grains of Al4343 grow with the increase of temperature; the grain of Al3003 increases slightly from 300 to 400 °C, and grows along the interface direction after 500 °C. After 400 and 500 °C, the final average grain size of Cu decreases from ARB0 to ARB3 passes and increases slightly at ARB5 passes. The tensile properties of the composites are affected by recovery and recrystallization at lower temperatures and ARB passes, and by the total thickness and volume fraction of the diffusion layer at higher temperatures and ARB passes.

Experimental study on combustion characteristics of a 40 MW pulverized coal boiler based on a new low NOx burner with preheating function

In this study, a novel low NOx burner is proposed and tested on a 40 MW pilot pulverized coal combustion system, aiming to experimentally investigate the impact of preheating temperature, air ratio distribution, and thermal power on furnace combustion characteristics. The experimental results demonstrate that the pulverized coal could be preheated stably above 700 °C in the designed burner. Furthermore, an increase in preheating temperature from 500 °C to 750 °C corresponds to a proportional rise in the total volume fraction of combustible pyrolysis gases released from pulverized coal, ranging from 18.34 % to 22.85 %. Consequently, the release and combustion of pyrolysis gases effectively improve the combustion characteristics within the boiler furnace and lead to reduced NOx emissions at the furnace outlet. When the thermal power is increased from 22.5 MW to 37.5 MW, the NOx emissions at the furnace output range from 46.8 mg/Nm3 to 98.3 mg/Nm3 (at 9 % O2). Under a specific thermal power of 25MWth, the boiler furnace output NOx emissions are reduced to 47.9 mg/Nm3 (@9 % O2) without any additional NOx reduction equipment. These findings offer valuable insights for advancing cleaner and more efficient low-NOx pulverized coal combustion technology.

Effect of aging on the structure and mechanical properties of austenite stainless steel N50 alloyed with nitrogen, niobium and vanadium

In this study, the austenitic, corrosion-resistant N50 steel alloyed with different nitrogen, niobium and vanadium content was investigated. This steel is used in the production of high-strength, cryogenic pipes. The production process for these pipes involves aging at 650 °C–665 °C for 50–100 h. Therefore, steels were examined in their as-delivered state, after aging at 650 °C, 100 h and after solid solution heat treatment. The structure of the steel was analyzed using optical and scanning microscopy, tensile and impact strength tests were conducted at room temperature and at −196 °C. It was found that the total volume fraction of the precipitated phase after aging is more dependent on the total concentration of nitride-forming elements—Nb and V, than on nitrogen. Aging does not affect the basic operational properties at room temperature, but it can significantly affect toughness at −196 °C.

Qualitative Model of Electrical Conductivity of Irradiated Semiconductor

There is constructed a qualitative model of the electrical conductivity of semiconductors irradiated with sufficiently high-energy particles. At certain conditions (irradiation temperature and dose, and subsequent thermal treatment), high-energy particles fluence, in addition to primary and secondary point radiation defects, forms a number of nano-sized disordered regions, highly conductive (“metallic”) compared to the semiconductor matrix. Their high total volume fraction can lead to the charge major carriers’ effective Hall mobility significantly exceeding that of the matrix. Due to elastic stresses created by these disordered inclusions, a high concentration of point radiation defects tends to form defective shells. In certain temperature ranges, such nanosized core-shell structures act as capacitors storing the electric charge sufficient for the Coulomb blockade of the major current carriers. Transformation of high-conductive inclusions into low-conductive (“dielectric”) ones manifests in a noticeable decrease in effective Hall mobility. The proposed model qualitatively explains all the experimental data available on single-crystalline n- and p-type silicon irradiated with high-energy electrons and protons and isochronously annealed.

Three-Dimensional Osseointegration Patterns of Cementless Femoral Stems: An ex Vivo Study with High-Resolution Imaging and Histological Evaluation.

Osseointegration is essential for the long-term survival of cementless femoral stems and is dependent on periprosthetic bone quality and correct implantation technique. The aim of this study was to evaluate the 3-dimensional long-term fixation patterns of, and bone microarchitecture around, cementless hip stems. Four specimens with varying degrees of bone quality and fixation characteristics from body donors who had received Alloclassic Zweymüller hip stems during their lifetime (mean time in situ at the time of death: 12.73 years) were evaluated with use of radiographs, high-resolution computed tomography (CT) scans, and hard-tissue histology. The CT voxel size was 85 µm, and the following parameters were calculated: total bone volume, total bone volume fraction, trabecular bone volume, trabecular bone volume fraction, cortical bone volume, cortical bone volume fraction, and cortical thickness. Bone-implant contact and canal fill index values for each Gruen zone of the specimens were calculated with use of histological samples. Femoral stems with apparently good cortical contact on clinical radiographs showed higher values for cortical bone volume, trabecular bone volume, and cortical thickness in the high-resolution CT analysis than femoral stems with apparently weak cortical contact on clinical radiographs. Based on the histological evaluation, the mean bone-implant contact ranged from 22.94% to 57.24% and the mean canal fill index ranged from 52.33% to 69.67% among the specimens. This study demonstrated different osseointegration patterns of cementless femoral stems on the basis of radiographs, high-resolution CT scans, and histological evaluation. Femora with high cortical bone volume and cortical thickness were associated with higher canal fill indices, whereas femora with low cortical bone volume and cortical thickness had lower canal fill indices and showed a characteristic corner-anchorage pattern. Osseointegration patterns and thus the long-term survival of cementless femoral stems are dependent on cortical bone volume and cortical thickness.

Synergism of steel fibres and PVA fibres on the fracture and mechanical properties of ultra-high-performance concrete

The influence of the volume fraction (VF) of steel fibres, polyvinyl alcohol (PVA) fibres and their combination on the mechanical and fracture mechanical properties of ultra-high-performance concrete (UHPC) was studied. To analyse the synergistic effect of steel fibres and PVA fibres on the deformation properties of UHPC, the gain ratios (the ratios of the mechanical properties of UHPC reinforced with hybrid fibres (HUHPC) with those of UHPC reinforced with steel fibres (SUHPC)) were obtained for equal total fibre VFs and equal steel fibre VFs. The steel and PVA fibres reduced the compressive strength of the UHPC to some extent and, with increasing VF, the ratios of flexural strength/compressive strength and tensile strength/compressive strength increased gradually. The fracture mechanical properties of the UHPC were significantly improved with the addition of steel fibres and PVA fibres; the latter were superior in improving the deformation properties of the UHPC. Except for compressive strength, the gain ratios of mechanical parameters of HUHPC to SUHPC calculated with equal steel fibre VF were higher than for equal total fibre VF; 0.25% PVA fibres mixed with SUHPC further improved the bending tensile and fracture mechanical properties.

Insights into primary carbides and nanoparticles in an additively manufactured high-alloy steel

This paper reports the use of combined electron microscopy and small-angle neutron scattering (SANS) to probe into the compositional and size evolution of the primary carbides and nanoparticles (defined by a size threshold of 100 nm) in an additively manufactured high-alloy steel before and after heat treatment. The primary carbides exhibit marginal changes in their total volume fraction and size after the austenitising and tempering. However, those carbides located at the prior-austenite boundaries provide a pinning effect to impede grain growth during the austenitising. The grain size increases from 1.7 µm in the as-manufactured to 2.8 µm in the as-tempered conditions, resulting in a limited strength loss of 33–126 MPa as estimated by using the Hall-Petch relationship. Atom probe tomography, which offers atomic spatial resolution examining a sample volume of 6.6 × 105 nm3, reveals the presence of numerous V and Cr-enriched nanoparticles with sizes of 1 to 10 nm within the steel matrix after the tempering. In contrast, the complementary SANS which examines a significantly larger sample volume of 0.9 mm3 but lacking spatial resolution, provides nanoparticle size information. It reveals a radius reduction from 7.6 to 1.0 nm and a volume fraction increase from 1.6 % to 2.3 %, in the as-manufactured and as-tempered conditions, respectively. The nanoparticles induced during tempering can contribute to a strength enhancement of 691 MPa, primarily through the Orowan bypass mechanism. This suggests that the combination of limited prior-austenite grain growth and the presence of nanoparticles is the key factor responsible for the unprecedented material strength.

Effect of hybrid ratio on the flexural properties of Arenga Pinnata fiber/E-glass fiber/polyester hybrid composites

Hybrid ratio effect on flexural properties of sugar palm/E-glass fiber hybrid-reinforced polyester composites has been investigated. Before being embedded, the sugar palm fiber was taken off from its original mesh, washed, alkali-treated, and chopped into ~10 mm long. The specimens were cut from composite plates having different hybrid ratios, fabricated using cold pressed technique. The total fiber volume fraction was kept at ~0.21, where four hybrid ratios, and two span-to-depth ratios were used. The E-glass was arranged unidirectionally and placed right on the surface of a bottom mold and wetted using the matrix, and the SPF was then evenly poured on the wet E-glass arrangement in randomly oriented pattern. Specimen preparation and testing were carried out according to the ASTM D790 standard, where the E-glass sides were placed in tension sides of the beams. It was found that flexural strength, and strain at maximum stress significantly increase with the increase of hybrid ratio.