Entire Cross Section Research Articles

A novel rapid microwave crystallization of photocatalysts for practical utility in the removal of phenol derivatives

A new concept of the microwave-assisted process was used for the crystallization of titania nanoparticles. The presented microwave crystallization can be indicated as truly environmentally friendly due to its energy efficiency and very short process time. In addition, it allows one to obtain pure materials without surface defects, which was confirmed by the EPR analysis. The physicochemical properties (such as crystallinity, morphology, and textural properties) of the synthesized TiO2 nanomaterials are strongly dependent on the microwave crystallization temperature. In this work, for the first time, the novel and convenient LED photoreactor was compared directly with the classic high-pressure mercury lamp. Photocatalytic studies showed higher activity in the oxidation of phenol and 4-chlorophenol under UV-LED light, compare to high-pressure Hg-lamp. The reason for improving photo-oxidation performance under LED light is indicated that each of the LEDs has the same parameters, so they can be considered as many single sources of UV radiation occurring throughout the entire cross-section of the reactor. This confirms that microwave-assisted crystallization of TiO2-photocatalysts and application of LEDs as light sources can be elements of a novel photocatalytic approach toward environmental protection. The presented results show that the simultaneous approach to the development of photocatalysts and novel light is the right route to further develop photocatalysis to enter this process into truly environmental protection.

Helium line ratio imaging in the C-2W divertor.

A 2D imaging instrument has been designed and deployed on C-2W ("Norman") [H. Gota et al., Nucl. Fusion 61, 106039 (2021)] to study the plasma in the expander divertor by simultaneously measuring three neutral helium spectral lines. Ratios of these images, in conjunction with a collisional-radiative model, yield 2D maps of electron temperature and density. Almost the entire radial plasma cross-section (∼60cm) can be mapped with a spatial resolution ≲1cm. These data can, in principle, be acquired at 3kHz. The neutral helium target is provided by a custom-built supersonic gas injector located inside the divertor vessel, which injects helium toward the magnetic axis and perpendicular to the camera sight-cone. Images of helium emission and reconstructed electron density and temperature profiles of the plasma produced from an end gun are presented. Voltages applied to concentric annular electrodes located in the divertors are used to stabilize beam-driven field reversed configuration plasmas. Magnetic field expansion is also employed to thermally isolate electrons from the end electrodes. Measurements of electron temperature and density in the divertor are important in order to study the effects of both the electrostatic biasing and the divertor magnetic field on electron confinement, neutral gas transport, and the overall machine performance.

Research on temperature effect on reinforced concrete bridge pylon during strong cooling weather event

The temperate continental mountain climate is typically characterized by strong solar radiation, high wind speed, obvious temperature fluctuations between day and night, and frequent strong cooling weather. The reinforced concrete (RC) bridge pylon under such harsh environment could suffer from severe temperature-induced durability and serviceability issues. In this paper, a general analytical methodology for evaluating the temperature effect on RC bridge pylon during strong cooling weather event is proposed considering the effect of wind, reinforcement as well as sheltering. A numerical simulation program is developed by integrating the FLUENT and ANSYS based on this model. Subsequently, a typical case study is performed and the effects of several key factors, i.e., wind, reinforcement arrangement, mutual sheltering, and terrain sheltering, on the temperature field and temperature-induced stress field are examined. The results show that the consideration of heat convection due to wind speed could result in a remarkable increase in temperature-induced stress during strong cooling weather event. Meanwhile, the influence of wind speed and wind direction cannot be ignored either, since the heat convection across the pylon exterior surface under different wind speed and directions varies greatly. In addition, relative high reinforcement ratio and the inclusion of the stirrup bar could help to reduce the temperature-induced stress at both interior and exterior surface of the RC bridge pylon. Moreover, the mutual sheltering has negligible influence on the temperature-induced stress of the entire cross-section of the bridge pylon, while the terrain sheltering leads to an increase in the temperature-induced stress difference between the interior and exterior surface.

Optical fiber point sensors based on forward Brillouin scattering.

Forward Brillouin scattering interactions support the sensing and analysis of media outside the cladding boundaries of standard fibers, where light cannot reach. Quantitative point-sensing based on this principle has yet to be reported. In this work, we report a forward Brillouin scattering point-sensor in a commercially available, off-the-shelf multi-core fiber. Pump light at the inner, on-axis core of the fiber is used to stimulate a guided acoustic mode of the entire fiber cross-section. The acoustic wave, in turn, induces photoelastic perturbations to the reflectivity of a Bragg grating inscribed in an outer, off-axis core of the same fiber. The measurements successfully analyze refractive index perturbations on the tenth decimal point and distinguish between ethanol and water outside the centimeter-long grating. The measured forward Brillouin scattering linewidths agree with predictions. The acquired spectra are unaffected by forward Brillouin scattering outside the grating region. The results add point-analysis to the portfolio of forward Brillouin scattering optical fiber sensors.

Microfluidic Device with Room Temperature Ionic Liquids for Detecting Low Concentrations of CO2

In this work we report the use of a gas sensor that can be used in inline configuration for applications like organ-on-a-chip. The key element of the device is a microfluidic channel with a thickness of 140 μm and width of 500 μm. This microfluidic channel is sandwiched between a top and bottom substrate, each substrate containing microelectrodes making this a non-planar interdigitated microelectrode (NP-IμE) configuration. Room temperature ionic liquids (RTILs) are used as electrolyte in the microfluidic channel. Due to the dimensions of the microfluidic channel only low volume of RTILs are required as electrolyte. RTILs can be tuned to selectively capture specific gases. This in addition to other favourable properties such as wide electrochemical window, thermal stability and negligible vapor pressure makes it a good candidate as the selective electrolyte in electrochemical gas sensor. The use of NP-IμE makes the electric field penetrate through the channel. This allows us to register the perturbations in signal caused by absorption of CO2 from the entire cross-section of the channel, thereby increasing the sensitivity of the device (as compared to a planar architecture). 1-ethyl-3-methylimidazolium 2-cyanopyrolide ([EMIM][2-CNpyr]) was used as the RTIL, as it has been shown to be a good sorbent of CO2 with high capacity at low partial pressures due to its chemical affinity. The RTILs exposed to different concentrations of CO2 was injected into the microfluidic channel. Cyclic Voltammetry (CV), Differential pulse voltammetry (DPV) and Electrochemical impedance spectroscopy (EIS) experiments were done using our microfluidic device. During the CV and DPV experiments, RTIL exposed to CO2 shows a reduction peak (of CO2). This along with the changes in EIS spectrum (Nyquist plot) can be used to detect the presence of CO2. We used CO2 as a test gas to analyse the sensitivity of our microfluidic device combined with RTIL. In future we will be using this same setup to sense biomarker gases and other toxic gases by changing the RTIL and tuning its affinity towards the target analytes.

Effect of the nozzle temperature on the microstructure and interlaminar strength in 3D printing of carbon fiber/polyphenylene sulfide composites

We investigated the effect of nozzle temperature on the transverse tensile strength of continuous carbon fiber/polyphenylene sulfide (PPS) composites fabricated using fused deposition modeling 3D printers. In particular, we aimed at clarifying the parameters inside the material that would better represent the strength in the thickness direction. First, the nozzle temperature was varied and the printed crystallinity, void fraction and interlaminar strength were measured. High strength was observed at both ends of the printable temperature whereas a minimum was observed at the intermediate temperature. Although the relationship between the strength, crystallinity, and void fraction was obtained, no clear trend was observed. The filament bundle deformation due to melting was focused on by observing the entire cross-section, and the extent of the deformation was quantified by defining the filament area fraction. The same trends between the strength and filament area fraction were obtained for the temperature change. In addition, the mechanism underlying the change in the filament area fraction with increasing nozzle temperature was explained.

Effective material model for cold-formed rectangular hollow sections in beam element-based advanced analysis

This study develops and validates an effective material model for cold-formed rectangular hollow sections. Advanced design methods utilize non-linear finite element analysis in design. An accurate calculation model, which is usually beam element-based, is crucial such that the design outcome is safe but economical. Unfortunately, cold-formed sections have non-linear residual stress distribution over the material thickness, that cannot be explicitly modelled in general-purpose beam elements. Additionally, corner regions of cold-formed sections have higher material strength compared to flat regions. This beneficial feature is usually disregarded by assuming the flat region properties for the entire cross-section. This study develops an effective material model that replicates a stress-strain curve that would be obtained if the tensile test was made for the entire cross-section instead of a separate tensile coupon. Consequently, the effects of residual stresses and corner strength enhancements are included in the effective material model such that their consideration in beam element-based advanced design method is effortless. The effective material model is validated for the steel grade S700 against numerical shell element buckling tests and excellent modelling accuracy is achieved.

Characterization of large LGAD sensors for proton counting in particle therapy

A proton counter prototype based on Low Gain Avalanche Detector (LGAD) technology is being developed for the online monitoring of the fluence rate of therapeutic proton beams. The laboratory characterization of thin (45 μm and 60 μm) LGAD sensors segmented in 146 strips with an unprecedented large area of 2.6 × 2.6 cm2, covering the entire beam cross-section, is presented and discussed. The production includes 14 wafers with different characteristics, designed and produced at Fondazione Bruno Kessler (FBK) of Trento in 2020. The laboratory characterization was carried out at FBK, right after production, and at the University of Torino, after cutting the sensors, using a probe station with a power analyzer for the static DC electrical tests. The tests proved that the production was of very high quality. From 16 sensors randomly selected from different wafers, we observed consistency between the measurements performed at FBK and at the University of Torino, indicating that the cut did not degrade the performance. The sensors were also exposed to the clinical proton beam of the National Center for Oncological Hadrontherapy (CNAO, Pavia, Italy). The results show that LGADs allow achieving, in a very thin active thickness, a good separation between the proton signal, a peak of a very short duration, and the noise. This, combined with the large active area, will allow counting protons delivered with high efficiency at the high rates of a clinical beam.

Determining the effect of the structural and technological parameters of a gas blower unit on the air flow distribution in a gas generator

The object of this study is the structural and technological parameters of the gas blower unit in the gasification chamber of a gas generator. The task to enable uniform distribution of air masses in the gas generator has been solved using the ANSYS Fluent software. The study is based on a simulation of the movement of air flows in the characteristic cross-sections of the gas generator, in particular the cross-section of the gasification chamber at the border of the oxidation and reduction zones. Seven structures of the gas blower unit were analyzed, the effectiveness of which was determined by the coefficient of variation. The most effective was the design whose value of the coefficient of variation is the smallest and equal to 93 %. At the same time, the total area of zones with no movement of air masses, that is, the absence of a gasification process, does not exceed 12 % of the total cross-sectional area of the gas generator. The speed of air masses at the boundary of the oxidation and reduction zones is aligned in the entire cross-section of the chamber and is V»4.5 m/s. The average value of the vertical component of the speed of air masses in the cross-section at the inlet to the recovery zone of the gasification chamber is V»0.6 m/s. Under such conditions, the production of synthesis gas of high calorific value with the absence of resins, acids, heavy hydrocarbons, and mechanical impurities is ensured. The correspondence of the simulation results with experimental data is confirmed by the coefficient of determination, which amounted to 0.87. The results reported here could be the basis of a modernized methodology for the study of aerodynamic, heat and mass exchange processes that occur during biomass gasification. This would make it possible to define the rational structural and technological parameters of gas generators and improve the efficiency of the gasification process as a whole.

Shear mechanism and design of small-scale tubular flange corrugated web girders

This paper explores numerically the shear behaviour and web strength of a new type of corrugated web girders (CWGs) consisting of an upper tubular flange, a corrugated web and a lower flat plate flange. The current finite element (FE) models, simulate by ABAQUS software, are validated using the results of three new small-scale experimentally tested girders that have been recently published by the authors. Three main points are studied in this paper, namely the propagation of the plastic shear hinges (PSHs), the effect of the corrugation wavelength and the development of a new elastic design model for the girders. First, the girders are simulated to unveil their shear failure mechanism, focusing on the propagation of the plastic shear hinges (PSHs) that characterise the shear failure of conventional flat-webbed girders. Through comparisons between the tubular flange CWG and the corresponding CWG with flat plate flanges (called hereafter as the conventional CWG), it is found that PSHs occur in the lower flange of former girder at the ultimate load whatever the type of the shear buckling is, while the later does not show PSHs for cases failing by local or interactive buckling. The effect of the wavelength of the corrugation of the tubular flange CWG is secondly analysed and the results show that as the corrugation wavelength decreases, the shear capacity increases with the local shear buckling or interactive shear buckling, but this rule is not suitable for the global shear buckling mode. Finally the shear ratio of the tube to that of the entire cross-section is derived and the shear strength equation of the tubular flange CWG is provided and verified through comparisons with test results.

Bark Inclusions in Canes of Southern Highbush Blueberry and Their Impact on Cane Union Strength and Association with Botryosphaeria Stem Blight

Bark inclusions are an understudied structural defect in trees and shrubs. They consist of areas of bark on adjacent parts of stems or scaffolds, typically on the inner faces of a narrow fork, which become overgrown and internalized to occupy part of the wood between the stems. Here, bark inclusions are described for the first time to occur in cane unions at the crown of southern highbush blueberry (Vaccinium corymbosum interspecific hybrids) cultivars ‘Farthing’ and ‘Meadowlark’, both of which are characterized by a narrow, vase-shaped architecture at the base of the plant, leading to crowding of the canes. When affected canes were dissected at their bases, bark inclusions were visible internally as a line of compressed bark within the wood of adjoining canes, or as bark invaginations and fissures across part of or the entire cross-section of the cane. Externally, blueberry crowns with included bark were characterized by either an inward ridgeline of bark between canes of similar diameters emerging from the crown at a narrow angle from each other, or by the presence of girdling roots. Bark inclusions were observed in plants of all ages, from the nursery to mature production fields. The internal length of the bark inclusion correlated strongly with the external length of the inward stem bark ridgeline symptom as measured by destructive sampling in the field (r = 0.916, p < 0.0001, n = 20). When plants with and without bark inclusions were subjected to a winch test in the field, the probability of breakage for canes without included bark was significantly lower (p < 0.0002) than for those with included bark, and at the maximum applied force of 972.4 N, 95.2% of the canes with bark inclusions failed (i.e., broke at the crown), compared with only 52.6% for canes without included bark. In a survey across three fields, the number of bark inclusions per plant was significantly associated with an index of cane crowding (r = 0.286. p = 0.0267, n = 60), suggesting that plants with tight, crowded bases had more bark inclusions. In addition, there was a significant association (p < 0.0001) between the presence or length of bark inclusions and the intensity of Botryosphaeria stem blight in these fields. This study showed that bark inclusions occur commonly in certain southern highbush blueberry cultivars in the production conditions of Georgia and Florida, with negative implications for cane integrity and plant health.

Flow pattern transition and void fraction prediction of gas–liquid flow in helically coiled tubes

• Flow patterns in helically coiled tubes (HCTs) are classified by visual observation. • Flow-regime map is proposed and mechanisms of flow transitions are presented. • Void fraction for the entire tube cross-section is measured by WMS technique. • New correlations of distribution parameter and drift velocity are proposed. Helically coiled tubes (HCTs) are widely used in industries owing to their compact structure and excellent heat and mass transfer efficiency. Due to the complexity of three-dimensional flow in HCTs, profound knowledge on the flow pattern characteristics is not well documented in existing literature. In this paper, we employ the wire-mesh sensor (WMS) and image tomography technique to measure a series of essential parameters (e.g. flow structures, phase fraction) to explore the flow pattern transition mechanism. According to our observation, bubbly, plug, slug, wavy and annular flow are recognized, and the mechanisms of flow pattern transitions are carefully discussed based on the analysis of the forces. In addition, the variation of void fraction in both temporal and spatial dimensions is discussed in detail. By introducing the drift flux analysis, new correlations of distribution parameter and drift velocity are proposed taking both HCTs structure and flow condition into account.

Stress recovery of laminated non-prismatic beams under layerwise traction and body forces

Emerging manufacturing technologies, including 3D printing and additive layer manufacturing, offer scope for making slender heterogeneous structures with complex geometry. Modern applications include tapered sandwich beams employed in the aeronautical industry, wind turbine blades and concrete beams used in construction. It is noteworthy that state-of-the-art closed form solutions for stresses are often excessively simple to be representative of real laminated tapered beams. For example, centroidal variation with respect to the neutral axis is neglected, and the transverse direct stress component is disregarded. Also, non-classical terms arise due to interactions between stiffness and external load distributions. Another drawback is that the external load is assumed to react uniformly through the cross-section in classical beam formulations, which is an inaccurate assumption for slender structures loaded on only a sub-section of the entire cross-section. To address these limitations, a simple and efficient yet accurate analytical stress recovery method is presented for laminated non-prismatic beams with arbitrary cross-sectional shapes under layerwise body forces and traction loads. Moreover, closed-form solutions are deduced for rectangular cross-sections. The proposed method invokes Cauchy stress equilibrium followed by implementing appropriate interfacial boundary conditions. The main novelties comprise the 2D transverse stress field recovery considering centroidal variation with respect to the neutral axis, application of layerwise external loads, and consideration of effects where stiffness and external load distributions differ. A state of plane stress under small linear-elastic strains is assumed, for cases where beam thickness taper is restricted to 15^{circ }. The model is validated by comparison with finite element analysis and relevant analytical formulations.

Одержання виливків із доевтектичних силумінів способом тиксолиття

Experimental studies of the method of thixocasting of AK7ч hypoeutectic silumin using cylindrical billets with different initial prepared structure (dendritic and non-dendritic – rosette-like and globular) of the primary solid phase were carried out. It is shown that after casting using billets with the initial dendritic structure of aluminum solid solution, the structure in shaped castings remains dendritic. At the same time, a certain number of destroyed dendrites are observed in the structure, predominantly melted. The thixocasting of the hypoeutectic silumin AK7ч using billets with the initial rosette-like structure of primary aluminum crystals ensures the production of shaped castings with a globular structure of the primary phase with a globular size of 80–100 μm. At the same time resulting the globular structure of the primary solid phase in castings is homogeneous and evenly distributed over the entire cross section. Thixocasting of silumin AK7ч using billets with the initial globular structure of the primary solid phase does not lead to a change of the structure of the casting. This slightly increases the size of the globules in the casting. Eutectic colonies in shaped castings obtained by thixocasting are characterized by a higher degree of differentiation compared to the initial structures of billets. Determination of mechanical properties showed an increased plasticity of the investigated hypoeutectic silumin in castings obtained after thixocasting without additional hardening heat treatment. Keywords: thixocasting, hypoeutectic silumin, non-dendritic structure, globular structure, rosette-like structure, solid-liquid billet, shaped casting.

Insertion Guidance Based on Impedance Measurements of a Cochlear Electrode Array.

The cochlear implantable neuromodulator provides substantial auditory perception to those with severe or profound impaired hearing. Correct electrode array positioning in the cochlea is one of the important factors for quality hearing, and misplacement may lead to additional injury to the cochlea. Visual inspection of the progress of electrode insertion is limited and mainly relies on the surgeon's tactile skills, and there is a need to detect in real-time the electrode array position in the cochlea during insertion. The available clinical measurement presently provides very limited information. Impedance measurement may be used to assist with the insertion of the electrode array. Using computational modeling of the cochlea, and its local tissue layers merging with the associated neuromodulator electrode array parameters, the impedance variations at different insertion depths and the proximities to the cochlea walls have been analyzed. In this study, an anatomical computational model of the temporal region of a patient is used to derive the relationship between impedance variations and the electrode proximity to the cochlea wall and electrode insertion depth. The aim was to examine whether the use of electrode impedance variations can be an effective marker of electrode proximity and electrode insertion depth. The proposed anatomical model simulates the quasi-static electrode impedance variations at different selected points but at considerable computation cost. A much less computationally intensive geometric model (~1/30) provided comparative impedance measurements with differences of <2%. Both use finite element analysis over the entire cross-section area of the scala tympani. It is shown that the magnitude of the impedance varies with both electrode insertion depth and electrode proximity to the adjacent anatomical layers (e.g., cochlea wall). In particular, there is a 1,400% increase when the electrode array is moved very close to the cochlea wall. This may help the surgeon to find the optimal electrode position within the scala tympani by observation of such impedance characteristics. The misplacement of the electrode array within the scala tympani may be eliminated by using the impedance variation metric during electrode array insertion if the results are validated with an experimental study.

Strength analysis of laminated glass/EVA interfaces: Microstructure, peel force and energy of adhesion

The aim of this study is to analyze the adhesive strength of laminated glass with an interlayer material based on ethylene-vinyl acetate (EVA) copolymer. To investigate the microstructure within the entire cross-section of glass laminates, cryo-fracture surfaces of the samples were prepared. SEM images illustrate the boundary layers on the glass surfaces with the thicknesses within the range from few nm to 100μm. Tensile and 180∘ peel tests were performed to estimate the adhesive strength. No significant differences in peel force values were obtained for the EVA/tin side and EVA/air side interfaces. A direct approach to evaluate the energy of adhesion based on the results of tensile tests and peel tests is developed. The evaluated energy of adhesion is nearly the same for temperatures of 20 °C and 40 °C and increases by a factor of 2 for the temperature of −20 °C.

Cross-sectional geometry of the femoral diaphyseal cortical bones: analysis of central mass distribution.

A detailed analysis of differences in skeletal shape among many individuals is expected to reveal the mechanical significance behind various morphological features. To confirm the distribution of the cortical bone region in cross sections, the relative position of the central mass distribution (CMD) of the cortical bone region to the CMD of the entire cross section was examined. A total of 90 right human femoral skeletons were examined using clinical multi-slice computed tomography. For nine cross sections of each femur, we determined the CMD of the whole area, including both cortical bone and medullary areas, as CMD-W, and that of the cortical bone region in the same cross section as CMD-C, and they were compared. The medial and anterior portion of the cortex was relatively thick just below the lesser trochanter. The posterior cortical bone tended to be relatively thick in the region from the center to the distal part of the diaphysis. Females had a significantly more medially deviated CMD than males throughout the entire diaphysis. These results suggest that femurs with advanced cortical bone thinning tend to have a concentration of cortical bone in their medial portion. CMD-C was located farther from the diaphysis axis as the degree of medial bending increased. Conversely, the greater the lateral bending of the diaphysis, the closer CMD-C was to the diaphysis axis. As the amount of bone decreases with age, self-adjustment could occur so that the cortical bone's critical area remains to prevent a decrease in mechanical strength.

Estimates of foil thickness, signal, noise, and nuclear heating of imaging bolometers for ITER

Imaging bolometers have been studied for ITER to serve as a complementary diagnostic to the resistive bolometers for the measurement of radiated power. Two tangentially viewing InfraRed imaging Video Bolometers (IRVB) could be proposed for an ITER equatorial port, one having a view of the entire plasma cross-section (core viewing) and one tilted down 43 degrees from the horizontal to view the divertor (divertor viewing). The IRVBs have 7 cm (horizontal) by 9 cm (vertical) Pt sensor foils, 6 mm × 6 mm apertures, 15 × 20 pixels and focal lengths of 7.8 cm and 21 cm, respectively. Using SANCO and SOLPS models for a 840 m3 plasma radiating 67.3 MW, synthetic images from the IRVBs are calculated to estimate the maximum signal strengths to be 246 W/m2 and 62 W/m2, respectively. We propagate the X-ray energy spectra from the models through the synthetic diagnostics to give the photon energy spectrum for each IRVB pixel, which are used to calculate the fraction of the power absorbed by the foil as a function of foil thickness. Using a criteria of >95% absorbed power fraction, we selected foil thicknesses of 30 μm and 10 μm, respectively. We used these thicknesses and assumed IR systems having 105 fps, 1024×1280 pixels and sensitivities of 15 mK, to calculate the IRVB sensitivities of 3.19 W/m2 and 1.05 W/m2, and signal to noise ratios of 77 and 59, respectively. Using the Monte Carlo Nuclear Particle code we calculated for the core viewing IRVB the foil heating by neutrons to be 1.0 W/m2 and by gammas to be 117 W/m2. This indicates that countermeasures may be needed to remove the nuclear heating signal.

Study on fatigue life prediction method of composite laminates

Advanced composites have been widely used in aerospace field and transportation field in ground due to their excellent mechanical properties. Fatigue damage and life prediction of composites have always been the important and difficult issues in the field of composite mechanics. In this paper, the maximum stress criterion and Puck criterion were extended to fatigue failure criterion, and the fatigue damage analysis model of composite laminates was established by combining the gradual degradation model of material properties, the regularized fatigue life analysis method and the fatigue damage accumulation theory. Then, the model was used to predict the damage evolution and failure mechanism of composite laminates, and the fatigue tests with three stress levels (55%, 60% and 65%) were conducted. The fatigue life and failure mode of the numerical results matches well with the test results. Under fatigue loadings, the fatigue damage initiated from free edges on both sides of the plate to the inside of the laminates. The matrix damage first appeared in the 90° plies on two free sides, then the matrix damage and fiber damage of 45° plies were induced. The fiber damage of 0° ply finally appears and rapidly spreads to the center of laminates until the damage covers the entire cross section.

Numerical study of the characteristics of smoke spread in tunnel fires during construction and method for improvement of smoke control

In this study, the characteristics of smoke spread in tunnel fires during construction were investigated using numerical modelling. Besides, the method for improvement of smoke control was investigated. The results indicate that the smoke still maintains a good layered structure after hitting the excavation face when the fire is very close to the excavation face. In contrast, the stratification of smoke is destroyed after hitting the excavation face, after which the smoke seems to spread over the entire cross-section of the tunnel when the fire is far away from the excavation face. The construction shaft becomes a common access for natural ventilation and smoke exhaust, which causes the smoke to fill the tunnel quickly because of the large vortex produced by the interaction between the airflow and smoke flow. A drainage device was placed in the middle of the construction shaft to divide the accesses for natural ventilation and smoke exhaust, after which the temperature rise in the tunnel decreases significantly and the mass flow rate of smoke through the construction shaft increases. This study is useful for tunnel fire protection engineering, providing a theoretical basis and technical support for fire detection, early warning, and control in tunnels during construction.