Search Results (29)

Carbon fiber (CF) and carbon fiber-reinforced polymers (CFRPs) are widely used in the aerospace, automotive, and energy sectors due to their high strength, stiffness, and low density. However, significant waste is generated during manufacturing and after the use of CFRPs. Traditional disposal methods like landfilling and incineration are unsustainable. CFRP machining processes, such as drilling and milling, produce fine chips and dust that are difficult to recycle due to their heterogeneity and contamination. This study investigates the oxidation behavior of CFRP drilling waste from two types of materials (tube and plate) under oxidative (non-inert) conditions. Thermogravimetric analysis (TGA) was performed from 200 °C to 800 °C to assess weight loss related to polymer degradation and carbon fiber integrity. Scanning electron microscopy (SEM) was used to analyze morphological changes and fiber damage. The optimal range for removing the polymer matrix without significant fiber degradation has been identified as 500–600 °C. At temperatures above 700 °C, notable surface and internal fiber damage occurred, along with nanostructure formation, which may pose health and environmental risks. The results show that partial fiber recovery is possible under ambient conditions, and this must be considered regarding the harmful risks to the human body if submicron particles are inhaled. This research supports sustainable CFRP recycling and fire hazard mitigation. Full article

While extensive research has focused on improving the efficiency and performance of heat exchangers (HXs), identifying the underlying causes of performance degradation remains equally important. Flow and temperature non-uniformities are among the most critical factors affecting performance, often reducing thermo-hydraulic efficiency by approximately 5–10%. These non-uniformities commonly manifest as thermal inconsistencies, airflow maldistribution, and uneven refrigerant distribution. Researchers have observed a notable performance degradation—up to 27%—due to flow maldistribution. Therefore, a clear understanding of their causes and effects is essential for developing effective mitigation strategies to enhance system performance. Despite the notable progress in this area, few studies have systematically classified the dominant non-uniformities associated with specific HX types. This article presents a two-decade review of the causes, impacts, and mitigation approaches related to non-uniformities across different HX configurations. The primary objective is to identify the most critical form of non-uniformity affecting performance in each category. This review specifically examines plate heat exchangers (PHXs), finned and tube heat exchangers (FTHXs), microchannel heat exchangers (MCHXs), and printed circuit heat exchangers (PCHXs). It also discusses mathematical models designed to account for non-uniformities in HXs. This article concludes by identifying key research gaps and outlining future directions to support the development of more reliable and energy-efficient HXs. Full article

A novel L-shaped concrete-filled steel tube (CFST) column is proposed in this study. A finite element model of the column is developed using ABAQUS software to analyze its load transfer mechanism and axial compressive behavior. The effects of factors such as the steel strength, steel tube thickness, support plate configuration, and perforation of the support plates on the compressive performance of the column are investigated. The simulation results reveal that the column exhibits robust axial compressive performance. Increasing the steel strength and incorporating support plates (SP) effectively enhance the column’s compressive bearing capacity and positively influence the bearing capacity coefficient (δ). However, increasing the steel tube thickness results in a reduction in δ, indicating that the rate of increase in the bearing capacity diminishes with increasing thickness. The failure mode is primarily characterized by local buckling in the midsection of the steel tube’s concave corner. Measures such as increasing the steel strength and tube thickness and the use of support plates help to mitigate buckling at the concave corner, improve concrete confinement, and enhance the overall compressive performance of the column. Full article

The primary aim of this work was to share the results from a Research Project supported by the Italian National Research Council, which led to the development of a versatile jacketed tower bioreactor. Designed to optimize oxygen transfer efficiency and process control, the reactor incorporated a reciprocating air compressor, centrifugal pumps, a draft tube with or without perforated plates, and a series of gas–liquid ejectors. Its flexible design enabled operation in both airlift and ejector-loop modes, making it suitable for a wide range of aerobic fermentation processes. By sharing the detailed engineering design, operational procedures of this pilot-scale bioreactor, as well as its performance data when cultivating yeasts on whey and potato wastewater, a detailed blueprint was given to researchers seeking to advance bioreactor technology, particularly in the context of emerging fields like cultured meat production, pharmaceutical manufacturing, and environmental bioremediation. Full article

Nonlinear acoustic effects become prominent when acoustic waves propagate through an orifice, particularly at higher pressure amplitudes, potentially generating vortex rings and transferring acoustic energy into the flow. This study develops and validates a predictive theoretical model for acoustic behaviour both within and outside an orifice under linear conditions. Using transfer matrices, the model predicts the external acoustic field, while finite element numerical simulations are employed to validate the theoretical predictions in the linear regime. The experimental setup includes an impedance tube with a plate and orifice, supported by a custom-built system, where a loudspeaker generates acoustic waves. A single microphone is used to measure acoustic particle velocity and characterize the phenomenon, enabling the identification of the onset of nonlinearity. The experimental data show good agreement with the linear theoretical predictions. This work represents the first observation of nonlinear effects in a free-field environment within a semi-anechoic chamber, eliminating reflections from external surfaces, and demonstrates the efficacy of a purely acoustic-based system (speaker and two microphones) for evaluating speaker velocity and the resulting velocity within the orifice. Full article

Candida albicans is one of the agents of invasive candidiasis, a life-threatening disease strongly associated with hospitalization, particularly among patients in intensive care units with central venous catheters. This study aimed to evaluate the synergistic activity of the antifungal peptide ToAP2 combined with fluconazole against C. albicans biofilms grown on various materials. We tested combinations of different concentrations of the peptide ToAP2 with fluconazole on C. albicans biofilms. These biofilms were generated on 96-well plates, intravenous catheters, and infusion tubes in RPMI medium at two maturation stages. Scanning electron microscopy and atomic force microscopy were employed to assess the biofilm structure. We also evaluated the expression of genes previously proven to be involved in C. albicans biofilm formation in planktonic and biofilm cells after treatment with the peptide ToAP2 using qPCR. ToAP2 demonstrated a synergistic effect with fluconazole at concentrations up to 25 µM during both the early and mature stages of biofilm formation in 96-well plates and on medical devices. Combinations of 50, 25, and 12.5 µM of ToAP2 with 52 µM of fluconazole significantly reduced the biofilm viability compared to individual treatments and untreated controls. These results were supported by substantial structural changes in the biofilms observed through both scanning and atomic force microscopy. The gene expression analysis of C. albicans cells treated with 25 µM of ToAP2 revealed a decrease in the expression of genes associated with membrane synthesis, along with an increase in the expression of genes involved in efflux pumps, adhesins, and filamentation. Our results highlight the efficacy of the combined ToAP2 and fluconazole treatment against C. albicans biofilms. This combination not only shows therapeutic potential but also suggests its utility in developing preventive biofilm tools for intravenous catheters. Full article

Detailed anatomical features of bark are used and interpreted in plant taxonomy, phylogenetics, and other areas of plant science. However, the delicate nature of bark cells, combined with the difficulty of obtaining high-quality sections and reliable data, limits the potential for utilizing and processing bark. In this study, the anatomical structure of the bark of 10 Quercus species growing in Yunnan Province, China, was characterized in detail. The results indicate that the anatomical features of the barks of 10 Quercus spp. show a certain degree of consistency. Specifically, sieve tubes are distributed in solitary elements or in small groups, mostly as compound sieve plates containing 2–8 sieve areas, suggesting that Quercus spp. may occupy a conservative evolutionary position. Additionally, for the first time, this study reports the presence of simple sieve plates in the sieve tube elements of Quercus phloem. Each sieve tube element has a companion cell on one side. The companion cell strands contain 2–7 cells. Axial parenchyma is diffuse, with parenchyma strands typically consisting of 4–7 cells; druses are present within chambered crystalliferous cells. Phloem rays are of two distinct sizes and often exhibit dilatation and sclerification, and the ray composition consists of procumbent cells. Sclerenchyma is composed of fibers and sclereids, both of which contain prismatic crystals. Most of the fibers are gelatinous fibers, which are distributed in discontinuous tangential bands of about five cells in width. Sclereids appear in clusters. The presence of sclerenchyma provides mechanical support to the bark, reducing the collapse of the phloem. Periderm usually consists of around 10–30 layers of phellem, and Quercus acutissima and Q. variabilis can reach dozens or hundreds layers. The phelloderm typically consists of from two to five layers, with Q. variabilis having up to ten or more layers. The filling tissue of lenticels in all Quercus species is nonstratified (homogeneous) and largely nonsuberized. Overall, this study enriches our comprehension of Quercus bark anatomy, elucidating evolutionary patterns, functional adaptations, and ecological ramifications within this significant botanical genus. Full article

In recent years, with the development of building technology, the Chinese construction industry has begun to gradually promote the prefabricated buildings to save on construction costs. Among them, composite slabs, as essential components of prefabricated buildings, have been widely used by designers mainly in favor of their low cost. However, is it possible to further reduce the cost without affecting the quality? Researchers think so if the operation cycle of support from the bottom of composite slabs can accelerate and the mechanical properties of their bottom plate can be optimized. To prove this hypothesis, researchers proposed a new type of prestressed concrete composite slab with removable rectangular steel-tube lattice girders (referred to as CDB composite slabs), whose bottom plate consists of a temporary structure composed of a prestressed concrete prefabricated plate and removable rectangular steel-tube lattice girders. Through static bending performance tests on three prefabricated bottom plates and one composite slab, researchers measured corresponding load-displacement curves, load-strain curves, crack development, and distribution, etc. The test results show that the top chord rectangular steel tubes connected to the bottom plate concrete through web reinforcement bars significantly improve the rigidity, crack resistance, and load-bearing capacity of the bottom plate and possess better ductility and out-of-plane stability. The number of supports at the bottom of the bottom plate is effectively reduced, with the maximum unsupported span reaching 4.8 m. Beyond 4.8 m, only one additional support is needed, and the maximum support span can be up to 9.0 m, which provides space for cost reduction. The cooperative load-bearing performance of the prefabricated bottom plate and the post-cast composite layer concrete is good. The top chord rectangular steel tubes are easy to dismantle and can be reused, which reduces the steel consumption by about 24% compared to that used for the same size of ordinary steel-tube lattice-girder concrete composite slabs. It can greatly decrease the cost. In conclusion, the results have shown that the new method researchers proposed here is practically applicable and also provides great space to save on financial costs. Full article

Corrugated web girders with plate flanges have been widely applied in buildings and bridges due to the large shear capacity of the corrugated web (CW). However, experiments on corrugated web girders with tubular flanges are limited. Accordingly, this paper explores, through four full-scale small-size experimental tests used on buildings, the shear behavior of a type of girder formed with a CW, concrete-filled tubular flange, and bottom flat plate flange (CWGCFTF) with different CW thicknesses, wavelengths, and concrete strengths. Based on the imprecise results of one current test, a novel simple support device is proposed to improve the accuracy of the shear test of the CWGCFTF. The test results also show that the shear ratios of the tubular flange to the entire cross-section range from 15–18% when the loading reaches that of the corresponding shear stress to 80% of the shear yield strength of the CWs. Moreover, local buckling appears at the top surface of the steel tube with the CW shear buckling failure of the CWGCFTF under the shear tests. At the end, a theoretical equation of the shear ratio of the CW to the whole cross-section is derived, and a shear yield strength equation of the CWGCFTF is proposed and verified by comparisons with the test results. Full article

This study introduces a continuous pedestrian-bridge design utilizing a circular tube girder and brackets for extended spans. The flexural performance evaluation in the negative moment region focuses on the support section of the continuous pedestrian bridge. In this regard, a full-scale test unit of the negative moment region was fabricated for a loading test. The test unit consists of a circular steel-tube girder, loading plates, vertical steel plates, and support. Subsequently, a finite element analysis (FEA) was employed to compare with the loading test results. The experimental and FEA results showed that the stresses in the members of the proposed pedestrian bridge are within the allowable stresses under service load. However, local buckling was observed in the circular steel-tube girder adjacent to the vertical steel plate under ultimate loading. To prevent the local buckling in the girder and improve the flexural performance of the negative moment region, a parametric study was performed by increasing the filling ratio of concrete inside the girder. The load–deflection relationship of the parametric study indicates that filling the negative moment region of a circular steel tube with concrete has a structural effect. Consequently, based on these results, an optimal filling ratio for the proposed bridge is suggested. Full article

In response to the lack of plasma bag-breaking equipment and time-consuming manual recovery of plasma in China, this study focuses on the distal end cutting of a plasma bag residual-input tube and designs a machine-vision-based plasma bag residual-input tube cutting system. The system comprises a plasma bag rotation device, a bottom disc, an image acquisition device, a cutting device, and a device control system. The image acquisition device captures images of the rotating plasma bag and calculates the Euclidean distance from the end of the plasma bag input-tube distal end to the outer edge of the bottom support plate and the distance from the input-tube distal end to the centerline of the plasma bag. Two distinct value acquisition algorithms are designed for the two types of input tubes. The screw slide moves accordingly. When the plasma bag is above the cutting part, the cutting part cuts the end of the residual-input tube of the plasma bag. The prototype performance tests reveal that the cutting error is within 10% of the end of the plasma bag input tube distal end, the cutting success rate is 100%, and the processing time for each bag is 2.5 s, which meets the time requirements of the plasma bag breaker. Full article

In a steam generator, the heat transfer tubes are supported by the contact with support plates and anti-vibration bars. The two-phase flow flows over the tubes and causes a vibration when operating. In fatigue analysis, the heat transfer tube is simplified to a beam model, and the contacts with the support plates and the anti-vibration bars are simplified as simple-supported boundary conditions. This linear simplification improves the computational efficiency but cannot simulate the actual situation of the contact area. In consideration of this situation, in the actual analysis, a downwards modified S–N fatigue curve is used to envelop the fretting. For different materials and contact pressure, this modification needs to be obtained through experimental and computational analysis. In this paper, the effect of fretting on fatigue performance of heat transfer tube material 690 alloy is discussed by means of high cycle fretting fatigue test of tube specimen in room temperature air, low cycle fretting fatigue test of sheet specimen in high temperature water environment, and SWT (Smith–Watson–Topper) fretting fatigue predicting simulation, and the conservatism of design fatigue curve is discussed. It is shown that, in range of low cycle and high cycle, the fatigue strength is lower than the mean curve, but it can still be enveloped by the design curve of ASME (the American Society of Mechanical Engineers). However, under the condition of ultra-high cycle, the design curve of ASME can no longer envelop the effect of fretting on fatigue performance, so a further downward modification is necessary to ensure the safety of design. Full article

Suborbital spaceflights now enable human-tended research investigating short-term gravitational effects in biological systems, eliminating the need for complex automation. Here, we discuss a method utilizing KSC Fixation Tubes (KFTs) to both carry biology to suborbital space as well as fix that biology at certain stages of flight. Plants on support media were inserted into the sample side of KFTs preloaded with RNAlater in the fixation chamber. The KFTs were activated at various stages of a simulated flight to fix the plants. RNA-seq analysis conducted on tissue samples housed in KFTs, showed that plants behaved consistently in KFTs when compared to petri-plates. Over the time course, roots adjusted to hypoxia and leaves adjusted to changes in photosynthesis. These responses were due in part to the environment imposed by the encased triple containment of the KFTs, which is a requirement for flight in human spacecraft. While plants exhibited expected reproducible transcriptomic alteration over time in the KFTs, responses to clinorotation during the simulated flight suggest that transcriptomic responses to suborbital spaceflight can be examined using this approach. Full article

Photovoltaics (PV) and Solar Thermal (ST) collectors are sometimes competitors, as investment capacity, energy demand, and roof space are limited. Therefore, a ratio that quantifies the difference in annual energy output between ST and PV for different locations is useful. A market survey assessing the average price and performance both in 2013 and 2021 was conducted, showing a factor of 3 cell price decrease combined with a 20% efficiency increase, while ST showed negligible variation. Winsun simulations were conducted, and the results were plotted on the world map. Despite variations due to local climate, the ratio of energy production (ST/PV) increases at lower latitudes mainly due to (a) higher air temperature increasing ST output but decreasing the PV output; (b) solar radiation reducing ST efficiency to zero while having a minor impact on PV efficiency. The ratio was calculated for several ST operating temperatures. For latitudes lower than 66°, the ratio of a flat plate at 50 °C to a PV module ranges from 1.85 to 4.46, while the ratio between a vacuum tube at 50 °C and a PV module ranges from 3.05 to 4.76. This ratio can support the decision between installing ST or PV while combining different factors such as energy value, system complexity, and installation cost. Full article

A three-dimensional numerical investigation of turbulent heat transfer and fluid flow characteristics of the new heat exchanger and self-support of a rectangular converging-diverging (SS-RCD) tube bundle heat exchanger with different inserts was performed. The values of the Reynolds number varied from 27,900 to 41,900. The baseline case (without an insert) was compared with two enhanced configurations: one circular hole in the baffle plate (one-circle case) and a rectangular hole in the baffle plate (one-rectangle case). Compared with the baseline case, the airside Nusselt number (Nu) of the enhanced cases improved by 39.6~48.0% and 36.2~40.2% and had an associated friction factor (f) penalty increase of 53.9–66.7% and 60.7–77.8%, respectively. The baseline case was compared with three enhanced configurations: one-circle case, two-circle case, and three-circle case baffle plate. Compared with the baseline case, Nu of the enhanced cases improved by 39.6–48.0%, 36.2–45.4%, and 35.0–44.2%, with f penalty increases of 53.9–66.7%, 44.9–60.0%, and 43.8–60.0%, respectively. The overall performance was conducted by heat transfer enhancement factor (η). It was found that the one circle case obtained the best overall performance. The numerical results were analyzed from the viewpoint of the field synergy principle. It was found that the reduction in the average intersection angle between the velocity vector and the temperature gradient (θ) was one of the essential factors influencing heat transfer performance. Full article