Bottom Height Research Articles

Optimization of Hot Embossing Condition Using Taguchi Method and Evaluation of Microchannels for Flexible On-Chip Proton-Exchange Membrane Fuel Cell.

Hot embossing is a manufacturing technique used to create microchannels on polymer substrates. In recent years, microchannel fabrication technology based on hot embossing has attracted considerable attention due to its convenience and low cost. A new evaluation method of microchannels, as well as an approach to obtaining optimal hot embossing conditions based on the Taguchi method, is proposed in this paper to fabricate precise microchannels for a flexible proton-exchange membrane fuel cell (PEMFC). Our self-made hot embossing system can be used to fabricate assorted types of micro-channel structures on polymer substrates according to various applications, whose bottom width, top width, height and cross-sectional area vary in the aims of different situations. In order to obtain a high effective filling ratio, a new evaluation method is presented based on the four parameters of channel structures, and the Taguchi method is utilized to arrange three main factors (temperature, force and time) affecting the hot embossing in orthogonal arrays, quickly finding the optimal condition for the embossing process. The evaluation method for microchannels proposed in this paper, compared to traditional evaluation methods, incorporates the area factor, providing a more comprehensive assessment of the fabrication completeness of the microchannels. Additionally, it allows for the quick and simple identification of optimal conditions. The experimental results indicate that after determining the optimal embossing temperature, pressure and time using the Taguchi method, the effective filling rate remains above 95%, thereby enhancing the power density. Through variance analysis, it was found that temperature is the most significant factor affecting the hot embossing of microchannels. The high filling rate makes the process suitable for PEMFCs. The results demonstrate that under optimized process conditions, a self-made hot embossing system can effectively fabricate columnar structure microchannels for PEMFCs.

Auxetic hybrid metamaterial with tunable elastic wave bandgap

Auxetic metamaterials have shown good stability and uniform deformation capabilities against influences (vibration, temperature change, load change), making them significant in maintaining and adjusting the bandgap of phonon crystals. The low-frequency and broadband are the important goals of phonon crystals. For most traditional re-entrant honeycomb structures (T-RHS), the bandgap range is narrow and tunability is poor. Here, an auxetic hybrid structure with tunable acoustic bandgap (AHS-T) consisting of periodic mass inclusions integrated with traditional re-entrant honeycomb and chiral hybrid is proposed. Aiming at investigating the tunability of the bandgap in the low-frequency range. Compared with T-RHS, the bandgap real-time adjustment and wider bandwidth of the AHS-T be realized during compression and tension. The numerical results show that the bandgap of the AHS-T can be flexibly tailored by reasonably adjusting the strain and geometrical configurations of AHS-T. The bandwidth of AHS-T can be increased to 87.1% when the bottom diameter Db and column height H of the scatterer are changed reasonably. Moreover, the deformation behavior of auxetic material has an auxiliary effect on expanding the bandwidth. Compared with the structure which is not subjected to load, the adjustable amplitude of the bandgap is 41%. The findings of this work provide a design idea for manipulating elastic waves in dynamic environment.

Simulation and experimental research on the cavitation phenomenon of wedge-shaped triangular texture on the surface of 3D-printed titanium alloy materials

This study explores how wedge-shaped microtexturing enhances Ti6Al4V alloy's anti-friction and wear resistance, aiming to improve titanium alloy applications. A three-dimensional model was built using Ansys Software, and optimal parameters were selected: 900 µm for the bottom edge and height, 300 µm for the texture depth. The properties of Ti6Al4V samples with wedge-shaped triangular weave were tested using the MRTR-1 friction and wear experimental machine. The wear changes on the sample surface were analyzed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The results show that the texture significantly improves the load-carrying capacity of the oil film in a three-dimensional hydrodynamic model that takes into account the cavitation effect, and the direction and depth of the texture have a significant effect on the pressure. Friction experiments showed that the wedge-shaped triangular texture reduced the average coefficient of friction and wear compared to the non-textured surface. The Ti6Al4V material with a 3D printed wedge-shaped triangular texture showed the best friction and wear resistance at a texture depth of 300 µm and in a counterclockwise orientation. The vortex structure formed within the texture is the primary mechanism that provides hydrodynamic lubrication to the friction surface and effectively retains lubricant and debris. This helps to minimize three-body wear between the friction pair.

Comprehensive assessment of salt-alkali tolerance of different soybean varieties at the maturation stage

Soil salinization is a significant global challenge impacting food security and arable land safety. Biological amelioration for the development and utilization of salt-alkali land has gained attention in recent years but the breeding and selection of salt-alkali-tolerant crop varieties remain a challenge. Cultivated soybeans are moderately salt-tolerant crops; however, a precise threshold for salt-alkali conditions has not been determined and varies by genotype. Therefore, this study evaluated the salt-alkali tolerance of 15 different soybean varieties using correlation, principal component, membership function, and cluster analyses. The average soybean indices decreased with increasing salt-alkali stress concentrations. Under severe salt-alkali stress, the coefficients of variation for grain yield and biomass were significantly higher than those under mild salt-alkali stress. Plant height and node number were significantly positively correlated, whereas bottom pod height was significantly negatively correlated with branch number, effective pod number, and grain number per plant. Node and grain numbers per plant were significantly positively correlated. Branch number, effective pod number, grain number per plant, and hundred-grain weight were significantly and positively correlated. Effective pod number was significantly positively correlated with grain number per plant, biomass, and yield. Grain number per plant exhibited a significant negative correlation with hundred-grain weight. Biomass and yield were significantly positively correlated. The salt-alkali tolerance of 15 soybean varieties ranged from strong weak as follows: Cangdou 1438, 0734, 1426, 1418, 1453, 1327, 1846, 1412, 1817, 1301, 1821, 1819, 1815, 1814, and 1850. Salt-alkali-sensitive and salt-alkali-tolerant varieties were successfully identified.

Measuring the profile of aircraft engine blades using spectral confocal sensors

The geometric parameters of aircraft engine blades need to be precisely measured to ensure the quality of the blades for the normal operation of aircraft engines. This study aims to address the challenges of existing measurement systems in balancing efficiency, accuracy, and completeness. Additionally, it aims to enhance the accuracy and robustness of the algorithm for extracting blade profile characteristic parameters. In this paper, a spectral confocal sensor is employed to establish a blade profile measurement system. The design includes a probe sampling strategy, and a standard ball is used to calibrate the sensor probe’s light emission direction and the precise rotation center of the turntable. The paper proposes the use of methods such as partition search algorithm, binary search, and curvature segmentation to process point cloud data of blade body and tenon. We have conducted experimental measurements on the blades of an aircraft engine. The acquired three-dimensional point cloud data of multiple sets of blade cross-sections and dovetail sections were processed. After calculation, the maximum measurement errors for chord length, maximum blade thickness, tenon width, bottom height, top angle, and bottom angle are −0.0036 mm, −0.00721 mm, −0.0102 mm, −0.00928 mm, 0.0086°, and −0.0058°, respectively. This process validates the effectiveness of the proposed method and has high measurement accuracy. Compared with the CMM method, this method is more accurate in measuring small pits and large curvature micro surfaces, with higher measurement integrity and higher measurement efficiency.

Discharge performance of a submerged seawater intake in unsteady flows: Combination of physical models and decision tree algorithms

Developing impressive and cost-effective desalination technologies is crucial for addressing the increasing global demand for freshwater. In this regard, along with the process type and technology of desalination, the system's efficiency relies on the availability of a sufficient, constant, uniform, and high-quality discharge flow from the seawater intake structure. This investigation concerns the discharge flow performance of velocity caps, which serve as submerged seawater intake structures, in unsteady flows using physical models and decision tree algorithms. The observations indicate that the square caps are more prone to instability compared to the circular caps when exposed to waves. Additionally, circular caps can increase efficiency by about 12 % compared to square caps. Therefore, the circular velocity cap is more optimal than the square one. Results show that increasing wave height and period decreases the discharge through the intake due to increased interaction between wave and intake structure. Also, wave steepness leaves a significant reverse effect on seawater intake of about 40 %. The study also found that the optimal relative bottom height (w/h) is 1 for high flow depths and 0.5 for low flow depths, respectively. Finally, practical equations of discharge coefficients have been proposed based on decision tree algorithms with high accuracy. These high-accuracy equations show great potential for designing new desalination systems and optimizing existing ones.

Spatially quantifying and mapping the riverbed roughness of a tropical river via acoustic Doppler current profiler (ADCP) measurements to develop a 2-D numerical model

Field measurement of the bed roughness of tropical tidal rivers is a long and expensive process. In this study, we quantified the roughness coefficient from the acoustic Doppler current profiler (ADCP) measurements considering flow characteristics along a 240 km length of the Vu Gia Thu Bon River system, in central Vietnam. Our approach entailed the application of the logarithmic velocity distribution trend of turbulent flows to determine the bottom roughness height. Then, we applied the equation suggested by Strickler (1923) to calculate the Manning roughness coefficient. The TELEMAC-2D hydraulic model was then used to simulate the effect of the roughness coefficient on the estimated water level. Despite its uncertainty, the estimated bed roughness was sufficient for the accurate calculation of the hydraulic variables. Compared to those in previous research, the statistical indicators showed good performance in the first simulation process during both the calibration and validation periods along the river system.

Flexural properties of low-height prestressed T-beams: tests and numerical simulations

PurposeThis paper presents the experimental and numerical results of the bending properties of low-height prestressed T-beams. The purpose is to study the bearing capacity, failure state and strain distribution of low-height prestressed T-beams.Design/methodology/approachFirst, two 13 m-long full-size test beams were fabricated with different positions of prestressed steel bundles in the span. The load–deflection curves and failure patterns of each test beam were obtained through static load tests. Secondly, the test data were used to validate the finite element model developed to simulate the flexural behavior of low-height prestressed T-beams. Finally, the influence of different parameters (the number of prestressed steel bundles, initial prestress and concrete strength grade) on the flexural performance of the test beams is studied by using a finite element model.FindingsThe test results show that when the distance of the prestressed steel beam from the bottom height of the test beam increases from 40 to 120 mm, the cracking load of the test beam decreases from 550.00 to 450.00 kN, reducing by 18.18%, and the ultimate load decreases from 1338.15 to 1227.66 kN, reducing by 8.26%, therefore, the increase of the height of the prestressed steel beam reduces the bearing capacity of the test beam. The numerical simulation results show that when the number of steel bundles increases from 2 to 9, the cracking load increases by 183.60%, the yield load increases by 117.71% and the ultimate load increases by 132.95%. Therefore, the increase in the number of prestressed steel bundles can increase the cracking load, yield load and ultimate load of the test beam. When the initial prestress is from 695 to 1,395 MPa, the cracking load increases by 69.20%, the yield load of the bottom reinforcement increases by 31.61% and the ultimate load increases by 3.97%. Therefore, increasing the initial prestress can increase the cracking load and yield load of the test beam, but it has little effect on the ultimate load. The strength grade of concrete increases from C30 to C80, the cracking load is about 455.00 kN, the yield load is about 850.00 kN and the ultimate load is increased by 4.90%. Therefore, the improvement in concrete strength grade has little influence on the bearing capacity of the test beam.Originality/valueBased on the experimental study, the bearing capacity of low-height prestressed T-beams with different prestressed steel beam heights is calculated by finite element simulation, and the influence of different parameters on the bearing capacity is discussed. This method not only ensures the accuracy of bearing capacity assessment, but also does not require a large number of samples and has a certain economy. The study of prestressed low-height T-beams is of great significance for understanding the principle and application of prestressed technology. Research on the mechanical behavior and performance of low-height prestressed T beams can provide a scientific basis and technical support for the design and construction of prestressed concrete structures. In addition, the study of prestressed low-height T-beams can also provide a reference for the optimization design and construction of other structural types.

Entropy analysis and hydrothermal behavior of magnetohydrodynamic MOS2–Fe3O4/H2O hybrid nanofluid flow driven by buoyancy in a square enclosure with diverse fin heights

Fins, referred to as extended surfaces, play a crucial role in enhancing heat transfer across various industrial sectors. They achieve this by increasing the surface area available for convective heat transfer. These widespread applications span fields such as energy production, mechanical engineering, surface studies, heat recovery processes, and chemical engineering. The broad utility of fins has prompted researchers to enhance their precision through diverse methods, including numerical, experimental, and analytical approaches. Motivated by these practical applications, this study undertakes a theoretical investigation to analyze the effects of varying fin heights on the behavior of a hybrid hydromagnetic nanofluid within a porous square enclosure. The study explores three distinct cases. In the first case, fixed-height heat fins are attached to the upper and lower walls. In the second case, the fin attached to the upper wall remains static, while those on the lower wall are extended from 0.25L to 0.5L. Conversely, the third case involves extending the height of the upper fin from 0.25L to 0.5L. The in-house MATLAB code, coupled with a finite difference method, is employed to solve the governing equations, and its reliability is confirmed through comparison with prior publications. Thorough numerical simulations are conducted, encompassing control parameters such as thermal radiation, Rayleigh number, nanoparticle volume fraction, Hartmann number, heat generation/absorption, and Darcy number. The numerical results are visually presented through streamlines, isotherms, and average Nusselt number plots, elucidating the impact of these parameters across a range of scenarios. It is noticed that case 3 exposes a 96.06% higher heat transfer rate than case 2 with higher values of volume fraction and Rayleigh number. In all three cases, the Rayleigh number and Hartmann number cause a reduction in the entropy generation. For a higher Rayleigh number, employing a hybrid nanofluid containing a volume fraction of 5% causes a 110.41% reduction in heat transfer for the case involving bottom fin height compared to case 1. Similarly, extending the top fin leads to a heat transfer reduction of 100.41%.

Radar Characteristics and Causal Analysis of Two Consecutive Tornado Events Associated with Heavy Precipitation during the Mei-Yu Season

This paper comprehensively analyzed two consecutive tornado events associated with heavy precipitation during the Mei-yu season (a period of continuous rainy weather that occurs in the middle and lower reaches of the Yangtze River in China from mid-June to mid-July each year) and detailed the formation and development process of the tornadoes using Doppler weather radar, wind profiler radar, ERA5 reanalysis data, ground automatic station data and other multi-source data. The results showed that: (1) Small-scale vortices were triggered and developed during the eastward movement of the low vortex, forming two tornadoes successively on the eastern section of the Mei-yu front. (2) The presence of a gap on the front side of the reflectivity factor profile indicated that strong incoming airflow entered the updraft. Mesocyclones were detected with decreasing heights and increasing shear strengths. The bottom height of the tornado vortex signature (TVS) dropped to 0.7 km, and the shear value increased to 55.4 × 10−3 s−1. Tornado debris signatures (TDSs) could be seen with a low cross-correlation coefficient (CC) value area of 0.85–0.9 in the mesocyclone. The difference between the lowest-level difference velocity (LLDV) and the maximum difference velocity (MXDV) reached the largest value when a tornado occurred. (3) The continuously enhanced low-level jet propagated downward to form a super-low-level jet, and the strong wind direction and wind speed convergence in the boundary layer created a warm, moist and unstable atmosphere in Suzhou. With the entrainment of dry air, the northwest dry jet and the southeast moist jet stimulated the formation of a miniature supercell. (4) The low-level vertical wind shear of 0–1 km increased significantly upon tornado occurrence, which was more conducive to the formation and intensification of horizontal vorticity tubes. Encountering updrafts and downdrafts, the vorticity tubes might have been stretched and intensified. The first lightning jumps appeared 15 min and 66 min earlier than the Kunshan Bacheng tornado and the Taicang Liuhe tornado. The Liuhe tornado occurred during the stage when the lightning frequency reached its peak and then fell back.

Research on grouting structure design method of airport precast concrete pavement

Precast concrete pavement offers significant advantages such as reduced on-site construction time and faster traffic opening, making it highly suitable for airport applications. However, the provision of a fully supportive base structure for pavement panels has long been a challenging research area. In particular, there is a lack of comprehensive investigation into the grouting structure design for these panels. In this paper, a diffusion model of cement slurry beneath the panels is derived using theoretical methods. The study focuses on analyzing the diffusion mode, calculating the diffusion distance, and proposing a feasible design approach for the grouting structure of precast concrete pavement. Our analysis demonstrates that a rectangular grouting mode is preferable, with bottom void height of the panel ranging between 5-20mm. Moreover, it is recommended to maintain grouting sections with a width not exceeding 2.5m. For each panel, grouting is ideally performed in 2-4 sections. The findings of this study contribute to enhancing the overall effectiveness and durability of precast concrete pavement systems.

Study on the variation characteristics of ionospheric F2 layer in Qinghai-Tibet plateau and surrounding areas

The Qinghai-Tibet Plateau (QTP) region is the largest plateau in China and the highest altitude in the world, with a unique geographical environment. Based on the observation data of the 24th solar cycle from six sites on the QTP and its surrounding areas, the multi-station joint detection method is adopted to analyze the temporal variation and spatial distribution characteristics of the critical frequency of the F2 layer(foF2) and the bottom height of the F2 layer (h'F2). The results indicate that the critical frequency of the ionospheric F layer in the QTP is controlled by solar illumination conditions, and conforms to the ionospheric variation law of middle and low latitudes. The height of the F layer has significant regional characteristics, and the F layer height variation in Kunming and Chongqing is particularly drastic, and the average height of the F layer in Chongqing is significantly higher than that in Kunming, which is at a lower latitude, and Lhasa, which is at the same latitude as Chongqing. This phenomenon may be attributed to the unique geographical environment of the QTP, which has an influential effect on the motion of the lower atmosphere, and through the coupling mechanism between the lower and upper atmosphere, has a substantial impact on the F2 layer. The research findings of this article are of great interest to the study of the coupling mechanism between the upper and lower atmosphere.

Numerical Study on the Influence of Variable Section-Enhanced Mass Transfer Flow Field Design on PEMFC Performance Based on Underrib Convection Flow

The optimal design of variable section is a flow field optimization method that changes the pressure of the reacting gas in the flow channel by setting up a contraction surface in the flow channel, which is effective in improving many aspects of the proton exchange membrane fuel cell (PEMFC) performance. However, there are also problems such as uneven oxygen distribution in some of the flow channels, and the current density and net output power are not significantly improved. To find a balance among gas transfer efficiency, drainage capacity, uniformity of current density distribution, and output performance, this paper investigates the design of a variable cross-section-enhanced mass transfer flow field for PEMFC flow channel contraction by establishing a three-dimensional numerical model, starting from the sidewall width direction and the bottom height direction of the flow channel cross-section dimensions, in order to assess the effects of variable cross-section contraction at the bottom and sidewalls of the flow channel on the cell performance. The polarization curves, mass transfer capacity, current density distribution, and net output power of the variable cross-section contraction flow field are analyzed and compared with the straight flow field. On this basis, the optimum size parameters and operating parameter combinations are determined. Variable cross-sectional contraction flow field improves PEMFC output performance. The contraction of the variable cross-section contraction flow field at the sidewalls effectively improves reactive gas transfer efficiency and drainage capacity, improves current density distribution, and increases the net output power of the PEMFC. In particular, the sidewall contraction flow field has a 9.0% increase in power density, a 6.45% increase in the effective mass transfer coefficient (EMTC), a 6.52% increase in uniformity of current density distribution, and a 6.05% net power increment compared to the straight flow field, respectively. The best output performance, the highest oxygen concentration, and the lowest water concentration are achieved with a combination of parameters: number of sidewall contractions N = 6 , length L f = 6 mm , and width W f = 1.2 mm . And a wide range of air stoichiometry ratios are applied when the contraction of the variable cross-section contraction flow field is located at the sidewalls. Increasing the cathode stoichiometry ratio from 10 to 50 increased the cell power density by 25.5% and from 50 to 90 increased the cell power density by 9.5%. The simulation results can provide theoretical basis for the application of variable section flow field design for practical PEMFC.

Vertical distribution of air pollutants in an urban street canyon during winter air pollution episodes in Shenyang, China

Understanding the vertical distribution of air pollutants in urban street canyons is crucial to improve air quality in urban areas. Previous studies on air pollutants during air pollution episodes primarily focused on their distribution in rural areas, but rarely considered urban street canyons. To investigate such episodes in urban environments, we recorded concentrations of particulate matter (PM) with diameters of less than 2.5 μm and 10 μm (PM2.5 and PM10, respectively), ozone (O3), and carbon monoxide (CO), as well as air temperature, relative humidity, wind speed, wind direction, and atmospheric pressure, every minute, at bottom, middle, and roof levels in an urban street canyon in Shenyang, China, between December 2018 and March 2019. The study period included three air pollution episodes. Results indicated that PM was the primary contributor to air pollution during all episodes. During air pollution episodes, PM concentrations were higher at roof level, with increasing PM concentration differences between the bottom, middle, and roof height levels; O3 concentrations decreased; CO concentrations did not vary significantly. Additionally, higher relative humidity and lower air temperature enhanced particle formation but slowed photochemical reactions, yielding lower O3 concentrations. Finally, we established that wind speed in the street canyon depended more on canyon morphology than on the pollution level.

Double Inversion Layers Affect Fog–Haze Events over Eastern China—Based on Unmanned Aerial Vehicles Observation

The goal of this work is to analyze how double inversion layers affect fog–haze events and boundary layers over Eastern China based on unmanned aerial vehicle observations. During 10–12 December 2020, two successive fog–haze events occurred in Eastern China. Based on the unmanned aerial vehicle (UAV), wind, temperature, relative humidity (RH), and aerosol mass concentration were monitored simultaneously in Lianyungang, China. Several observations were found after analyzing the physical fields of these data. The results show that the concentrations of air pollutants during fog events were negatively correlated with horizontal visibilities. The mass concentrations of particulate matter increased rapidly (After 08:00 BJT 11) in the fog dissipation stages (PM2.5 and PM10 increased from 97 and 150 μg/m3 to 213 and 300 μg/m3, respectively). Double temperature inversion significantly affected fog events, where the enhancement of the lower-level temperature inversion (where the inversion layer top height was between 150 and 300 m) corresponded to the explosive growth of fog and the dissipation of the upper-level inversion layer. (The bottom height of the inversion layer was between 350 m and 600 m) This indicates the end of fog events. Fog layer thicknesses are negatively correlated with the concentrations of air pollutants in the near-surface layer. The thickening of the inversion layer near the surface corresponds to an increase (after 05:00 BJT 11 and 03:00 BJT 12) in fog layer height. The fog event is maintained when water vapor conditions are favorable enough or when there is a deep near-surface temperature inversion but the maintenance of the near-surface temperature inversion at an intensity of above 2 °C (100 m)−1 mainly contributes to the durations of these two fog events. Calculations through the trajectory model reveal that the air pollutant source varied during these two events, which was the main reason for the difference in air pollutant concentrations between the two events.

Comparing optic nerve head parameters in two Spanish dog breeds using digital planimetry

The optic discs of dogs exhibit considerable size, shape, and colour variations, depending on the degree of myelination. This variability makes the interpretation of lesions difficult, owing to the lack of reference patterns. This study aimed to compare optic nerve head (ONH) parameters determined by digital planimetry (DP) in two pure-bred dogs, Spanish Greyhound (SG) and Spanish Water Dog (SWD). The vertical and horizontal diameters, area, circularity, and the proportion of the ONH at the tapetal or non-tapetal zone (top height and bottom height) were calculated using image treatment software and compared between breeds.Significant between-breed differences were detected for all parameters, with SWD exhibiting greater height, width, area, top height, and lower circularity of the ONH than SG. Linear regression revealed that age significantly influenced mean disc height (R2 = 0.310; p = 0.0001), mean disc width (R2 = 0.280; p = 0.0001), mean disc area (R2 = 0.281; p = 0.0001), and circularity (R2 = 0.243; p = 0.0001). The multiple regression model significantly predicted mean disc height, width, and area [(S) (R2 = 0.715; p = 0.001), (R2 = 0.742; p = 0.001), and (S) (R2 = 0.736; p = 0.001), respectively], based on age and breed. Excellent concordance was observed between the measurements of experienced and novice researchers, and there were no differences between the parameters measured by the researcher and those obtained by the software. Planimetric ONH measurements can be easily performed by novice operators using a portable fundus camera and digital computer software. These results may be of considerable clinical value, but further studies are required because of the great variability of the ONH in dogs.

Axial and radial variation in physical and chemical properties of Borassus flabellifer L. (Palmyra palm)

ABSTRACT A variation study of physical and chemical properties at different radial and axial levels of Borassus flabellifer tree was carried out for the first time. An increasing trend in specific gravity from the centre (NC) towards near the bark (NB) has been observed at all three highest i.e. bottom, middle, and top of the tree. Colour analysis of the wood samples has shown a decreasing order of colour intensity (light to dark) from the NC to the NB positions. Holocellulose, hemicellulose, α-cellulose, and lignin content ranged from 64.19 to 73.42%, 17.5 to 26.85%, 42.22 to 51.02%, and 24.57 to 26.98% respectively. Lignin content was found maximum for the middle of the tree, followed by top and bottom height. Total extractives and ash content were found 1.92%–5.43% and 0.94%–1.69% respectively. This study found that B. flabellifer wood can be potentially utilised for various purposes, such as paper and pulp, and furniture making.

Low-velocity impact of square conical gradient aluminium foam-filled automobile energy-absorbing boxes

In this paper, the low-velocity impact and lightweight design of the square conical gradient aluminium foam-filled automobile energy-absorbing boxes (EABes) is numerically studied. Firstly, the validity of the finite element calculation model is verified by comparing with the experimental results. Then, the influences of the conical bottom angle, tube-wall thickness, the number, position, height and depth of induction grooves, and the parameters of gradient foam on the energy absorption properties of the EABes under axial low-velocity impact are studied. After that, the mitigation and energy absorption of square conical gradient aluminium foam-filled automobile EAB are optimised. The results indicate that the aluminium tube-wall thickness has no obvious effect on improving the energy absorption properties of the EAB, and other factors have good effects on improving the energy absorption properties of the EAB. Compared with the constant cross-section EAB before optimisation, the peak impact force (F max) of the finally optimised square conical gradient aluminium foam-filled automobile EAB reduces by 22.4%, and the specific energy absorption (SEA) increases by 59.8%. The investigation is helpful for the design of the square conical gradient aluminium foam-filled automobile EAB.

Application of multi-source data in a tornado process in Jiangsu province

This paper analyzes the weather background and triggering mechanism before the occurrence of an EF3 tornado on 14 May 2021, in southern Jiangsu, using multi-source data. Results show that 1) the tornado occurred in the warm and humid area inside the low-level shear line and the inverted trough at the surface, the southeast wind field to the east of the surface convergence line and high value area of water vapor flux on the left side of low altitude jet axis exit zone. 2) The intensity of the heavy rainfall supercell storm was strengthened after entering the Taihu Lake, and mesocyclones were detected with decreasing heights and increasing shear strengths which leading to the formation of the tornado parent storm. Tornado vortex storm bottom height dropped to 0.3km, the shear value increased to 169.1 × 10−3 s-1, strong echoes above 60 dBZ reached to the ground, the difference between the lowest elevation Radial velocity (LLDV) and the maximum Radial velocity (MXDV) reached up to the largest value when tornado occurred. 3) The strong convergence of the ground and the enhancement of mesoscale frontal zone resulted in the strong development of thunderstorm cells. The deep rear inflow behind the heavy precipitation supercell storm passed through the stratiform cloud area and produced strong updraft due to the convergence of wind direction and wind speed. The updrafts generated vertical vorticity under the influence of wind shear, which was further stretched in the middle layer of the troposphere to form the core of the tornado. 4) The flat underlying surface, abundant water vapor, lake surface thermal boundary, and strong wind convergence on the east bank of Taihu Lake provided favorable conditions for the occurrence of the tornado. The centers of the mesocyclones in the lower and middle layers were close to each other in the horizontal direction, which provided stable and vertical updrafts for the mesocyclones and strengthened the suction effect of the mesocyclones on the low-level vortices, facilitating the formation of the tornado.

Profiling of Aerosols and Clouds over High Altitude Urban Atmosphere in Eastern Himalaya: A Ground-Based Observation Using Raman LIDAR

Profiles of aerosols and cloud layers have been investigated over a high-altitude urban atmosphere in the eastern Himalayas in India, for the first time, using a Raman LIDAR. The study was conducted post-monsoon season over Darjeeling (latitude 27°01′ N longitude 88°36′ E, 2200 masl), a tourist destination in north-eastern India. In addition to the aerosols and cloud characterization and atmospheric boundary layer detection, the profile of the water vapor mixing ratio has also been analyzed. Effects of atmospheric dynamics have been studied using the vertical profiles of the normalized standard deviation of RCS along with the water vapor mixing ratio. The aerosol optical characteristics below and above the Atmospheric Boundary Layer (ABL) region were studied separately, along with the interrelation of their optical and microphysical properties with synoptic meteorological parameters. The backscatter coefficient and the extinction coefficient were found in the range from 7.15×10−10 m−1 sr−1 to 3.01×10−5 m−1 sr−1 and from 1.02×10−5 m−1 to 2.28×10−3 m−1, respectively. The LIDAR ratio varies between 3.9 to 78.39 sr over all altitudes. The variation of the linear depolarization ratio from 0.19 to 0.32 indicates the dominance, of non-spherical particles. The periodicity observed in different parameters may be indicative of atmospheric wave phenomena. Cloud parameters, such as scattering coefficients, top and bottom height, and optical depth for different cloud phases, have been evaluated. A co-located Micro Rain Radar has been used with LIDAR for cloud life cycle study.