Search Results (124)

The evaluation of heat transfer in a back-pass channel for an industrial circulating fluidized bed (CFB) reactor was studied. The authors proposed a heat transfer model taking into account (i) convective heat transfer on the tube side, (ii) convective heat transfer on the shell side, and (iii) radiative heat transfer on the shell side. The analysis of heat transfer is based on measured data from tubular heat exchangers (superheater SH Ia, reheaters RH Ia and RH Ib, and economizer ECO). Performance tests were conducted over a wide range of CFB reactor loads (from 40% MCR to 100% MCR) and also at a secondary air-to-primary air ratio of 0.11. The experimental data as a function of flue gas temperature, maximum flue gas velocity, CO₂ partial pressure, fly ash concentration, and particle size are discussed. During performance tests, the temperature and velocity of flue gas are no more than 1206 K and 16.3 m/s, respectively. As the CFB reactor load decreases from 100% MCR to 40% MCR, the overall heat transfer coefficient of tubular heat exchangers decreases from 60.61 W/(m² × K) to 30.1 W/(m² × K). The overall heat transfer coefficient was higher when the fly ash concentration was higher (from 0.0412 kg/m³ to 0.0612 kg/m³) in the back-pass channel of the CFB reactor. Mean particle size of fly ash corresponds to the maximum overall heat transfer coefficient at bigger (d₅₀ = 0.038 mm) and smaller (d₅₀ = 0.015 mm) particle diameters. Achieved heat transfer findings were calculated at carbon dioxide partial pressure varied between 8.48 kPa and 11.53 kPa. Research studies conducted on an industrial CFB reactor showed that the thermodynamic parameters of steam also influenced heat transfer. The geometry of the heat exchange surfaces affected heat transfer augmentation in the back-pass channel of the CFB reactor. For practicality, the relationships between the heat transfer data and other operational parameters are proposed using regression analysis. Comparing the operational data and the model results, the average absolute error is 19.23%. The heat transfer findings may be used in data-driven design, scale-up, commissioning, and operation of commercial CFB reactors. Full article

This paper addresses the topological optimization of composite floor systems, specifically focusing on tubular composite trusses with and without concrete filling in the upper chord. The optimization problem is formulated and solved using particle swarm optimization (PSO) and the Bonobo Algorithm (BO), both with CO₂ emissions reduction as the objective. A comparative analysis is conducted against literature models using full-web beams, revealing a notable 20%+ reduction in total CO₂ emissions for the proposed composite truss configuration. Additionally, a parametric analysis examines how various design parameters affect the optimization solution. Results indicate that the use of concrete in the upper chord has a substantial effect on reducing overall CO₂ emissions, especially with concrete strengths exceeding 25 MPa. Notably, the Bonobo Algorithm outperforms PSO in finding optimal solutions for the composite floor system. The study contributes to the underexplored field of topological optimization for composite truss beams, providing valuable insights into sustainable design practices for structural engineering applications. Full article

Chronic kidney disease (CKD) involves uremic toxin-driven tubular injury and systemic vascular dysfunction, in which mitochondrial impairment and apoptotic cell loss contribute to progressive tissue deterioration. Accordingly, a targeted EV platform is required to enable efficient miRNA delivery to the toxin-stressed tubular–endothelial compartment. Based on our previous study showing that melatonin restores miR-4516 levels under CKD-related stress, we directly loaded miR-4516 into engineered extracellular vesicles (EVs) to evaluate its effects on mitochondrial function and cell survival. Here, we engineered EVs with a G3-C12/RGD surface modification and established a miR-4516 loading strategy to enhance delivery to kidney proximal tubule cells and vascular endothelial cells. miR-4516 loading increased EV-associated miR-4516 levels without major changes in particle size distribution, and EV identity was supported by CD9 and CD81 expression. Confocal microscopy and flow cytometry demonstrated increased cellular uptake of miR-4516-loaded G3-C12/RGD-EVs compared with control EVs in TH1 proximal tubule cells and HUVECs. Under indoxyl sulfate stress, engineered EV treatment restored intracellular miR-4516 and improved mitochondrial function, as indicated by recovery of respiratory Complex I and Complex IV activities and improved Seahorse bioenergetic parameters (OCR/ECAR, basal and maximal respiration, ATP-linked respiration, and spare respiratory capacity). Annexin V staining further indicated reduced toxin-induced apoptosis. In an adenine diet-induced CKD mouse model, intravenous administration of miR-4516-loaded G3-C12/RGD-EVs improved urinary albumin-to-creatinine ratio (UACR), blood urea nitrogen (BUN), and serum creatinine. These findings indicate that miR-4516-loaded, targeting-engineered EVs may mitigate uremic toxin-associated mitochondrial dysfunction and renal impairment in CKD. Full article

This study examined rubberized concrete-filled steel tubular (RuCFST) columns as a sustainable option for structural applications. Eccentric compression tests were conducted on eight groups of square specimens, with two identical specimens per group. The main parameters were slenderness ratio, load eccentricity, and rubber replacement level for fine aggregates. Full load–displacement and load-strain curves were obtained. Results indicated that rubber particles inhibit concrete cracking. Increasing slenderness ratio reduces bearing capacity, with ductility peaking at moderate slenderness. Eccentricity significantly degrades bearing capacity and stiffness. A higher rubber replacement ratio lowers capacity but optimizes particle interaction and distribution, leading to stiffness recovery at higher ratios. Filling the steel tube with core concrete transforms it into a composite member, substantially improving load-bearing performance. Comparisons with seven design standards (including GB 50936-2014, CECS 254:2012, Eurocode 4, and AISC 360-16) revealed that Eurocode 4 provided the most reliable predictions, whereas AISC was the most cautious. None of the codes accounts for the effect of rubber on core concrete behavior. These results offer useful guidance for incorporating recycled rubber particles into composite columns to promote sustainable building practices. Full article

Large-scale bulk models offer a promising approach for the experimental investigation of flow in porous media. However, conventional configurations frequently lack adequate confinement systems, resulting in model instability under dynamic flow conditions. This paper introduces a novel experimental apparatus designed for large-scale porous media flooding studies. The porous medium is represented by a tubular granular bulk model measuring one meter in length and 95 mm in diameter. An integrated array of distributed pressure, temperature, and electrical resistance sensors allows for the acquisition of a longitudinal pressure profile, the evaluation of the model’s consolidation state, and the assessment of its stress sensitivity. Comparative studies of filtration processes are presented for a granular bulk model under both confined and unconfined conditions. The results indicate that in the absence of confinement, the model exhibits high sensitivity to pressure differentials, manifesting as a nonlinear relationship between flow rate and pressure drop alongside significant fluctuations in electrical resistance. Conversely, cyclic loading under confining pressure promotes uniform and stable consolidation of the model, thereby minimizing hysteresis and particle displacement. These findings underscore that effective confinement is critical for ensuring the representativeness of data derived from large-scale bulk models of unconsolidated porous media. Full article

To address the challenge of fabricating metal-based composite coatings on the inner surfaces of tubular and internal hole components, a novel cylindrical electro-spark powder deposition (CEPD) technique is introduced. Utilizing the CEPD process, Ni-based composite coatings are successfully prepared on the inner surface of 316L stainless-steel tubes. The resultant Ni-based composite coatings completely covered the inner surface, exhibiting a splattered morphology and forming a robust metallurgical bond. Microstructural analysis revealed that the composite coatings primarily consisted of submicron-sized fine dendrites, with the main phases identified as Ni, FeNi₃, and Fe₃Ni₂, in addition to Ag particles. These fine grains and reinforcing phases contributed to a substantial increase in coating hardness, with an average value of 673.33 HV, representing approximately 2.82 times the hardness of the substrate. Tribological testing indicated that the high-hardness Ni-based composite coatings nearly doubled the surface wear resistance of the substrate and exhibited a significantly lower friction coefficient. Compared to other existing inner surface coating techniques, the CEPD process offers simplicity, low cost, and the ability to produce functional composite coatings with complex compositions. The prepared coatings exhibit considerable development potential and may offer a novel approach for the advancement of coating techniques for non-line-of-sight surfaces. Full article

Although crucial transport equipment in coal mining enterprises, tubular belt conveyors cause serious noise pollution. In this paper, the sound absorption and isolation performance of three kinds of highly efficient sound-absorbing and -insulating materials were studied by finite element multiphysics field software COMSOL and acoustic tests, and the structure of highly efficient sound-absorbing and -insulating materials was optimized and designed. The results show that the acoustic superstructure plate has an excellent sound insulation effect of 36 dB, and achieves an excellent sound absorption coefficient of 0.95 at 210 Hz on the acoustic simulation test. The simulated weighted sound insulation of acoustic metamaterial plate is 37 dB, and the simulated weighted sound insulation of acoustic metamaterial plate filled with particle material is 42 dB, which improves the sound insulation effect by 4~7 dB after filling with particle material, and the comprehensive absorption coefficient of the high-frequency noise of more than 800 Hz reaches 0.94, and it can effectively absorb and block the low-frequency noise as well; rock wool acoustic panels in the 500 Hz to achieve a better acoustic capacity, the absorption coefficient of 0.8 or more, but the low-frequency noise acoustic capacity is still lacking, and can not be a good solution to the full-frequency band of the acoustic problem. It can be seen that the acoustic metamaterial plate has the best sound absorption and insulation effect. At the same time, the acoustic metamaterials based on the honeycomb structure are optimized, and the sound absorption and insulation structure with the angle of 60° of the inclined plate and the length of 693 mm of the inclined plate is the optimal structure. It provides a solution to the noise pollution caused by tubular belt conveyors. Full article

Polymer fouling in batch and tubular reactors creates safety hazards from heat buildup and blockages. The continuous Corning Advanced-Flow™ Reactor (AFR) offers enhanced mass and heat transfer, improving safety and efficiency. This study evaluated three reactor systems—a monolithic AFR, an AFR with an external pipe, and a conventional tubular reactor—for the mini-emulsion polymerization of styrene and subsequent styrene–acrylic acid copolymerization. The AFR operability under varying monomer concentrations was assessed and investigated, with the residence time’s effects on conversion. For styrene polymerization at 20–35 wt% monomer, the highest conversions achieved were 88.0% in the AFR, 85.8% in the tubular reactor, and 98.9% in the AFR with pipe. Uniform particles were obtained at ≤30 wt%, whereas at 35 wt%, the monolithic AFR experienced clogging and loss of particle uniformity. Similarly, in styrene–acrylic acid copolymerization (15–17.5 wt% monomer), the maximum conversions reached 80.1% in the AFR and 95.4% in the AFR with pipe, while the monolithic AFR again experienced blockage at 17.5 wt%. In conclusion, integrating an external pipe with the AFR, coupled with higher flow rates, significantly improved initiator diffusion, enhanced monomer conversion, and mitigated blockage. This approach enabled the efficient, continuous production of nanoscale, uniformly sized polystyrene and styrene–acrylic acid copolymers even at high monomer concentrations. Full article

Wheat straw, which is a by-product of wheat production and has a tubular structure, is typically used for animal feed and compost. This study estimated the sound absorption coefficient of wheat straw based on cross-sectional computed tomography (CT) images. After image processing, the surface area of the wheat straw skeletal outline and the volume of the void area were determined. The propagation constant and characteristic impedance of the void area were obtained by approximating the clearance between two parallel planes representing the void area walls. Each CT image was represented as a transfer matrix to calculate the sound pressure and particle velocity, and the transfer matrix method was used to derive the normal incidence sound absorption coefficients. The measured tortuosity was considered when calculating the normal incidence sound absorption coefficient. The CT images were corrected to reflect the lack of sound absorption by the porous part of the thick-walled portion by considering it as a solid structure. The theoretical sound absorption coefficients calculated from the corrected images were in good agreement with the measured sound absorption coefficients. Full article

Addressing the stability requirements of photonic integrated devices operating over wide temperature ranges, this work achieves controlled fabrication of femtosecond-laser direct-written Type II double-line waveguides and Type III depressed-cladding tubular waveguides within ultra-low-expansion LAS glass-ceramics. The light-guiding mechanisms were elucidated through finite element modeling. The influences of laser writing parameters and waveguide geometric structures on guiding performance were systematically investigated. Experimental results demonstrate that the double-line waveguides exhibit optimal single-mode guiding performance at 30 μm spacing and 120 mW writing power. For the tubular depressed-cladding waveguides, both single-mode and multi-mode fields are attainable across a broad processing parameter window. Large-mode-area characteristics manifested in the 50 μm core waveguide, exhibiting an edge-shifted intensity profile for higher-order modes that generated a hollow beam, enabling applications in atom guidance and particle trapping. Full article

Co-firing large-sized straw biomass in pulverized coal boilers is a potential pathway for carbon emission reduction in China’s thermal power plants. However, experimental data on large-sized straw combustion under pulverized coal boiler combustion conditions are critically lacking. This study selected typical large-sized wheat straw particles. Employing a two-mode experimental setup in a drop tube furnace (DTF) system simulating pulverized coal boiler conditions, we systematically investigated the combustion behavior and alkali metal release characteristics of this large-sized straw biomass, with combustion processes summarized for diverse particle types. The findings reveal asynchronous combustion progression across particle surfaces due to heterogeneous mass transfer and gas diffusion; unique behaviors distinct from denser woody biomass, including bending deformation, fiber branching, and fragmentation, occur; significant and morphology-specific deformations occur during devolatilization; fragmentation universally produces particles of varied shapes (needle-like, flaky, blocky, semi-tubular) during char combustion; and potassium release exceeds 35% after complete devolatilization and surpasses 50% at a burnout degree exceeding 80%. This work provides essential experimental data on the fundamental combustion characteristics and alkali metal release of large-sized wheat straw particles under pulverized coal boiler combustion conditions, offering engineering application guidance for the direct co-firing of large-sized flexible straw biomass in pulverized coal boilers. Full article

Constructing a heterojunction is considered one of the most effective strategies for enhancing photocatalytic activity. Herein, we employ Ta₃N₅ and tubular graphitic carbon nitride (TCN) to construct a Ta₃N₅/TCN van der Waals heterojunction via electrostatic self-assembly for enhanced photocatalytic H₂ production. SEM and TEM results show that Ta₃N₅ particles (~300 nm in size) are successfully anchored onto the surface of TCN. The light absorption capability of the Ta₃N₅/TCN heterojunction is between those of Ta₃N₅ and TCN. The strong interaction between Ta₃N₅ and TCN with different energy structures (Fermi levels) by van der Waals force renders the formation of an interfacial electric field to drive the separation and transfer of photogenerated charge carriers in the Ta₃N₅/TCN heterojunction, as evidenced by the photoluminescence (PL) and photoelectrochemical (PEC) characterization results. Consequently, the optimal Ta₃N₅/TCN heterojunction exhibits a remarkable H₂ production rate of 12.73 mmol g⁻¹ h⁻¹ under visible light irradiation, which is 3.3 and 16.8 times those of TCN and Ta₃N₅, respectively. Meanwhile, the cyclic experiment demonstrates excellent stability of the Ta₃N₅/TCN heterojunction upon photocatalytic reaction. Notably, the photocatalytic performance of 15-TaN/TCN outperforms the most previously reported CN-based and Ta₃N₅-based heterojunctions for H₂ production. This work provides a new avenue for the rational design of CN-based van der Waals heterojunction photocatalysts with enhanced photocatalytic activity. Full article

Nanostructures obtained as a by-product of the electrochemical synthesis of ZrO₂ nanotube membranes have scarcely received any attention despite their enormous potential. This is mainly due to their size properties, morphology, and composition. In the present work, these nanostructures are characterized, and their potential application as an additive in PVA-based coatings is analyzed. The characterization was performed by X-ray fluorescence, scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, and X-ray diffraction. The results showed that the nanostructures consist of tubular fragments generated during the formation of the ZrO₂ membrane, with a dimension of 626.74 nm in width, a length of 1906.39 nm, and a clear cubic structure. The ZrO₂-PVA coating, which is prepared by using the spin coating technique, presented a uniform and homogenous particle distribution, which was later confirmed by Fourier transform infrared spectroscopy, scanning electron microscopy, and atomic force microscopy. The optical transparency and thermal resistance were evaluated through UV-Vis spectroscopy and thermogravimetric analysis, showing that the incorporation of ZrO₂ as an additive improved its UV absorption properties and thermal stability during the pyrolysis stage. The results suggest that the ZrO₂ nanostructures enhance the thermal and protective properties of the PVA-based coatings by acting as physical barriers and stabilizers within the polymer matrix. Full article

Mammary gland tumors in dogs are very common in clinical practice. Betulinic acid is currently a compound considered to have anticancer properties in human mammary tumors via nanoemulsions. In this study, betulinic acid nanoemulsions with a particle size of less than 300 nm were prepared. Biopsies were obtained from five female dogs with mammary tumors for histopathological analysis, confirming that two were tubular mammary carcinomas (MMTs, malignant) and three were complex mammary adenomas (BMTs, benign). The five female dogs were administered with a daily oral dose of nanoemulsion containing 5 mg/kg of betulinic acid for 30 days. Tumor size was measured every 7 days, and the response to treatment was assessed according to RECIST (Response Evaluation Criteria In Solid Tumors) standards. In one of the females with MMTs treated with the nanoemulsion, the tumor size was reduced by approximately 38%, while in the BMT female dogs, the nanoemulsion reduced the tumor size by 25.3%. It was concluded that oral administration of betulinic acid nanoemulsions reduced the size of canine mammary tumors. Experimental studies are still needed to further evaluate this preparation. Full article

Based on a review of the existing literature on the use of diatomite and the functioning of phase-change heat accumulators, in this study, we conducted empirical research on the creation of a phase-change composite based on Carpathian diatomite. As part of our mineralogical research, we determined the phase composition of the Carpathian diatomites in this work. Their internal nanostructure was identified. Nanopores create regular systems that, depending on the variety of diatoms, may have sieve, tubular, or “honeycomb” shapes. Diatomites’ internal structure benefits the absorption capacity of phase-change materials (PCM). The obtained calorimetric thermograms of the organic phase-change material and the diatomite compound highlighted an extension of the temperature range in which phase transformation occurs from 4–5 °C (for pure PCM RT28HC) to 15–17 °C for the composites tested with weight proportions of 1:1 and 4:6. In the case of water-rich varieties, the presence of mixed-package minerals, i.e., montmorillonite, with its small size and specific 2:1 package structure, can hinder the penetration and accumulation of PCM. The ability to bind and accumulate heat will be influenced by the size of the diatomite particles or the relative size of the PCM and pores, i.e., structural and textural features. Full article