Transverse Uniformity Research Articles

Investigating the Influence of Die Structure on the Transverse Uniformity of Slot Coating

Abstract Transverse uniformity is an important measurement of the coating quality for slot coating. In this paper, the influence of die structure on the transverse uniformity is investigated according to a fully 3D mathematical modelling and numerical simulations. In the modelling part, the coating liquid is regarded as generalized Newtonian fluid and the fluid flow inner the die head is governed by the 3D incompressible Navier-Stokes equations. In solving the model, an efficient fractional step finite element method is used. Four kinds of commonly used die structures are simulated and analysed. The results show that the die structure has great influence on the transverse uniformity. Generally, dies with double cavities can get better transverse uniformity that single cavity.

Carbon nanotube-induced localized laser heating toward simultaneously enhanced laydown efficiency and fracture toughness of in-situ consolidated glass fiber thermoplastic composites

Thermoplastic composites suffer from weak inter-tape bonding during high-rate laser-assisted automated fiber placement (L-AFP). Here, we propose a strategy to simultaneously enhance the laser heating efficiency and fracture toughness of glass fiber-reinforced polypropylene prepreg tape for L-AFP process by depositing carbon nanotubes (CNTs) on the tape surface by a low-cost bath coating process. CNTs function as efficient light absorbing and photothermal coating to promote molecular inter-diffusion and interfacial healing between successive tapes, as well as toughen the weak interface by CNT pull-out and rupture. A 56 % increase in the near-infrared laser absorption of tapes results in a 946 % improvement in the laydown rate. CNTs also remarkably improve transverse temperature uniformity. Furthermore, double cantilever beam and pants tearing tests show that 0.5 wt% CNTs improve the mode I interlaminar fracture toughness and mode III fracture strength by 17 % and 52 %, respectively, attributed to the enhanced molecular inter-diffusion and CNT bridging effect.

Performance optimization of a SERF atomic magnetometer based on flat-top light beam

We explore the impact of pumping beams with different transverse intensity profiles on the performance of the spin-exchange relaxation-free (SERF) atomic magnetometers (AMs). We conduct experiments comparing the traditional Gaussian optically-pumped AM with that utilizing the flat-top optically-pumped (FTOP) method. Our findings reveal that the FTOP-based approach outperforms the conventional method, exhibiting a larger response, a narrower magnetic resonance linewidth, and a superior low-frequency noise performance. Specifically, the use of FTOP method leads to a 16% enhancement in average sensitivity within 1 Hz–30 Hz frequency range. Our research emphasizes the significance of achieving transverse polarization uniformity in AMs, providing insights for future optimization efforts and sensitivity improvements in miniaturized magnetometers.

Analysis of the Influence of Inlet Position on the Transverse Homogeneity of Slot Coating

Slot coating is a widely used method for high performance material production. Coating quality mainly depends on whether the coating liquid can be evenly coated on the material. To be evenly coated, the coating liquid is required to have good transverse velocity uniformity at the exit of the die. The position of the inlet of the die has an important effect on the horizontal uniformity of the die. In order to quantitatively analyze the influence of the inlet position of the die head on the transverse uniformity of the die, we respectively simulated the internal flow field of two different shapes of uniform cross section die head, and finally got the preliminary law. It is found that no matter the shape and structure of the cavity, the transverse uniformity of the coating can be greatly improved using the intermediate feeding method.

A Compact Broadband Monopole Tapered Slot Antenna With High Field Uniformity for Vehicle EMC Test From 20 to 220 MHz

A compact broadband monopole tapered slot antenna (MTSA) for vehicle electromagnetic compatibility (EMC) tests in the semi-anechoic chambers (SAC) is proposed and investigated. The proposed MTSA takes the metal ground of the SAC as part of an antenna. With the mirroring effect of the ground plate in the SAC, the proposed MTSA acts as a conventional tapered slot antenna (TSA) but with only a half size of the conventional TSA, and also avoids the adverse effect of the ground reflections on the field uniformity effectively. Moreover, the MTSA has a slot on its flaring plate that reduces its weight by 30%. Both the simulated and the measured results show that the proposed MTSA achieves a standing wave ratio (VSWR) below 2:1 from 20 MHz to 220 MHz, and a good uniformity, with radial uniformity better than 3 dB, transverse uniformity better than 4 dB. The simulated gains are from 6 dBi to 13.5 dBi with radiation efficiencies over 90% across almost the entire bandwidth.

Transverse Thermal Behavior of a Hot‐Rolled Strip During the Edge‐Induction‐Heating Process

To obtain the transverse temperature distribution of running strips under C‐type edge induction heaters during the hot‐rolling process, a coupled electromagnetic–thermal finite‐element model is established using COMSOL, in which the electromagnetic and temperature distributions regularity with various process parameters are systematically obtained. It is shown in the results that the temperature increase is directly proportional to the frequency and current and inversely proportional to the thickness. Meanwhile, the edge temperature drop can be rapidly compensated for using an edge heater, but it also leads to the appearance of a “cat‐ear” high‐temperature zone at the edge; thus, the transverse temperature uniformity cannot be guaranteed. To improve the temperature uniformity of the running strip, a magnetic shield plate is designed to weaken the effect of the cat ear, and the effects of the size and installation position of the shielding plate on the temperature distribution are analyzed. The standard deviation and uniformity of the temperature are used to determine the uniformity of the transverse temperature, and the optimal parameter combination mode of the magnetic shielding amounts is obtained, which can provide a reference for optimizing the heating process at the edge of the strip under moving conditions.

Quantitative Model of Hereditary Behavior for Carbon Segregation in Continuous Casting Billets Based on Grayscale Analysis

To obtain a reliable hereditary law of carbon segregation, the carbon element content in the entire area of the longitudinal sections of billet, wire rod and bolt samples is quantitatively calculated through the method of metal macrostructure grayscale analysis (MGA). Based on the calculation results, the hereditary behavior of carbon distribution characteristics at the “geometric similar” positions of the selected samples is quantitatively analyzed from three aspects: carbon element content, longitudinal carbon fluctuation and transverse carbon uniformity. The results show that the distribution characteristics of the carbon element content and carbon variation coefficient on the longitudinal sections of the selected samples are approximately the same, which can quantitatively reflect the hereditary behavior of the carbon segregation, and the corresponding hereditary equations during the rolling process are fitted. Then, the central segregation index, which can represent the transverse carbon uniformity, on the longitudinal sections of selected samples is calculated, and the corresponding hereditary equation is also obtained. According to the hereditary equation of central segregation index during the rolling process, to produce rolled products with more uniform quality and mechanical properties, the central segregation index of the corresponding billet should be controlled below 1.05.

On scalar transport in an oscillatory Couette–Poiseuille flow under the effects of heterogeneous and bulk chemical reactions: A multi-scale approach

This research presents an analytical solution to explore a two-dimensional concentration transport of solute in an oscillatory Couette–Poiseuille flow between two parallel plates in the presence of homogeneous and heterogeneous reactions. Mei's homogenization method up to second order approximation is used to find the multi-dimensional concentration distributions, namely, transverse concentration distribution, longitudinal concentration distribution, mean concentration distribution, Taylor dispersion coefficient, and the transverse uniformity simultaneously for three different flow conditions: steady, periodic, and the joint effect of steady and periodic Couette–Poiseuille flow for the first time. The distribution of transverse concentration of solute is studied due to its importance in oil lubrication and industrial applications. The transverse variation rate shows that the introduction of heterogeneous reactions cause transverse non-uniformity, but it is significant to note that homogeneous reaction has no effect on it. Furthermore, the maximum variation rate of the concentration cloud is obtained along the upstream and downstream directions when the boundary absorption is considered at steady and moving plates, respectively. To validate the present analytical model, a comparison is performed with the numerical solution and has achieved an excellent agreement. The outcomes of the present study may be helpful to develop a better understanding of the process of contamination and to prevent the pollution in the flow.

A miniaturized spin-exchange relaxation-free atomic magnetometer based on uniform light field

We experimentally study the dynamic characteristics of a miniaturized spin-exchange relaxation-free (SERF) magnetometer based on uniform light field. The ceramic ferrule is used to expand the Gaussian beam to improve light intensity uniformity, while the volume of the sensor is also reduced. This scheme makes the magnetometer have better sensitivity when the detected light intensity is less than 3.16 mW/cm2 at 120 °C. When the temperature rises to 150 °C the sensitivity under the action of uniform light field is 18.5 fT/Hz1/2. The bandwidth of the sensor remains at the original level and meets application needs. The proposed structure improves transverse polarization uniformity within the miniaturized sensor, which is ideal for the magnetoencephalography and magnetocardiography imaging systems.

On solute dispersion in an oscillatory magneto-hydrodynamics porous medium flow under the effect of heterogeneous and bulk chemical reaction

It is well known to all of us that there is a shortage of pure drinking water across the globe. Different types of pollutants (metallic and nonmetallic) mix with the water, and they cause several diseases such as cholera, typhoid, and various kinds of skin diseases, and even it is found that these kinds of particles may cause skin cancer. In the current study, an analytical solution of a two-dimensional convection–diffusion equation is obtained using Mei's multi-scale homogenization technique to investigate the influences of homogeneous and heterogeneous reactions on dispersion phenomena of the solute in an oscillatory magneto-hydrodynamics porous medium flow. In the appearance of the applied transverse magnetic field and oscillatory pressure gradient, a mathematical model of magneto-hydrodynamics dispersion between two parallel plates is presented. The analytical expressions of Taylor dispersivity, longitudinal mean and real concentration distributions, transverse concentration distribution, and transverse uniformity rate of the concentration are obtained. Also, the effect of various flow parameters such as Péclet number, Hartmann number, Schmidt number, Darcy number, oscillatory Reynolds number, porous parameter, dispersion time, downstream and upstream locations, chemical heterogeneous boundary reaction, and bulk reaction is discussed. How the transport phenomena of the solute display different natures with the various ranges of Darcy and Hartmann numbers with the aid of homogeneous and heterogeneous boundary reactions are highlighted. To show the effect of the absorption parameters on the transport coefficient, the third-order approximation of concentration is performed. It is seen that the dispersion coefficient (DT1) corresponding to the purely time-dependent flow increases with the enhancement of the Darcy number (Da). Moreover, it is found that as the Hartmann number (M) enhances, the total dispersivity (DT) decreases. Also, the transverse concentration distribution becomes flat for larger values of the Hartmann number. It is noticed that when Da≥1, the transverse variation curve turns into a trimodal distribution from a bimodal. This model may be helpful for separating various metallic and nonmetallic particles from the water to reduce the water pollution.

Flow and heat transfer in a novel convex cooling roller with axial variable boundary for planar flow casting

• Full-flow model is more versatile, its error is about 7.5% compare to the experiment. • Convex roller can improve the maximum heat transfer by 108%. • Convex roller can reduce the axial difference of the temperature and deformation. In order to improve the transverse thickness uniformity of amorphous ribbon by increasing the axial uniformity of cooling roller thermal characteristics during planar flow casting, a novel convex cooling roller was proposed. The flow characteristics, transient temperature, and thermal deformation of the proposed convex roller and existing straight roller were studied using a fluid–solid thermal coupling method based on a full-flow channel calculation model under axial variable boundary. In addition, the reliability of the simulation approach and results are verified by measuring the roller deformation on the spot. The results show that the heat transfer acting on the roller inner wall is unevenly and asymmetrically distributed in the axial direction. The full-flow channel model with coupling method provides high solution accuracy, the error between simulation and the experiment is about 7.5 %. Compare to the existing straight roller, the maximum heat transfer coefficient in the middle width direction increases by 108 %, the axial difference of the temperature and deformation decrease by 15.4 % and 26.9 %, respectively, when the convex roller with bending radius R = 300 mm. The maximum temperature, thermal deformation, and axial difference in the puddle contact zone decrease obviously with the increase of the roller bending radius. These results provide a promising strategy for improving the transverse thickness consistency of the amorphous ribbon.

Influence of guide vane angle of circulating hot blast stove sleeve on temperature field and flow field

In order to improve the heating efficiency and uniformity of the hot air circulation heater, a three-dimensional model of a hot blast stove of hot in-place recycling hot air circulating heater was established, based on the finite element method and CFD software ANSYS, the influence of the guide vane angle of the circulating hot blast stove sleeve on the temperature field and flow field of hot blast stove and air distribution pipe was studied by numerical simulation. The results show that the guide vane angle of the hot blast stove sleeve affects the temperature distribution at different positions of the air distribution pipe, has less influence on the internal temperature field of the hot blast stove, and has greater influence on the temperature distribution of the air distribution pipe. With the increase of the guide vane angle of the hot blast stove sleeve, the velocity and flow path of the circulating hot air in the hot blast stove sleeve increases, which improves the hot air distribution uniformity of the heating device. When the guide vane angle of hot blast stove sleeve is 45°, the hot air transverse distribution uniformity of heating device is the best.

Development of measurement system and analysis method for characterization of linear variable bandpass filters.

An automated measurement system was developed to characterize the spatial gradient, linearity of the spatial gradient, bandwidth and transverse uniformity of a linear variable filter (LVF). To demonstrate this, the LVF fabricated in our group has been measured and analyzed. Simulations for beam spot size effects on measurements were performed for various LVF spectral peak profiles with results indicting significant averaging effect due to beam spot size and this is consistent with experiment results. Moreover, to fit the peak profile more accurately, a modified Pearson VII function was proposed and demonstrated high capability to express complex shapes of peaks mathematically. This provides a methodology for deconvoluting the original LVF peak profile from a measured averaged peak profile and has been verified using actual measured data.

An exact analysis of scalar transport in hydromagnetic flow between two parallel plates: a multi-scale approach

The present paper explores an analytical solution to study the two-dimensional concentration distribution of a solute in a conducting fluid flowing between two parallel plates in the presence of a transverse magnetic field. Mei’s homogenization technique is used to acquire the mean concentration distributions up to the second-order approximation and the transverse concentration distributions up to third order. An uneven form of the concentration cloud and the transverse variation of the concentration distribution in a hydromagnetic flow are illustrated for the initial stage. The rate of progress towards uniformity of a solute cloud seems much slower than that of normality. It is observed that the peak of the transverse mean concentration and transverse variation of the concentration distribution of the solute significantly decrease with the increase in the magnetic field for small dispersion times. This is because, with an increase in the magnetic field, the velocity profiles flatten at the central core region between the parallel plates. The research proposes a time scale of 10 δ 2 / D (where δ is half the distance between two parallel plates and D is the molecular diffusivity) to characterize the dispersion process to approach the transverse uniformity.

Simulation of Granular Organic Fertilizer Application by Centrifugal Spreader

There is no specialized equipment designed to spread granular cylindrical organic fertilizer in the soil. There are also no rational recommendations available on how to spread this type of fertilizer. Mineral fertilizer spreaders are most often used for spreading granulated organic fertilizer. However, these fertilizers are significantly different from mineral fertilizers. Due to these differences, organic granular fertilizers often are spread unevenly, and the fertilizer does not reach the required working width. Furthermore, the rate of spreading is not accurate, and the fertilizer is often crushed too much. The objective of this research is to develop a simulation model for granular organic fertilizer applications with a centrifugal spreader in EDEM (extended distinct element method) software. It is possible to develop a numerical model that corresponds to a real spreader, and to determine the key physical–mechanical parameters for the application of granular organic fertilizer. This model can also be used for evaluating the transverse uniformity of the fertilizer in the field (along the trajectory normal to the machine). The results of this research show that the distance traveled by the fertilizer granules partially depends on the particle size, initial speed, type of fertilizer and the parameters of the spinning discs of the spreader.

Parameter studies on dielectric gratings as electron accelerators

Dielectric laser driven particle acceleration (DLA) is one of the candidates for novel high-gradient technologies to reduce the footprint of large scale particle acceleration facilities. On the other hand these devices can be used to interact with the particle beams of state-of-the-art photon science machines, especially with FELs, to manipulate the longitudinal phase space in a compact and cost effective way. The near-field surface modes of dielectric gratings can be used to interact with particle beams close to the surface. To achieve transversely homogeneous accelerating fields two gratings are opposed. The laser can be coupled from the side into the structure. In this work we present a study on the influence of the geometry parameters of the grating on the acceleration gradient and its transverse uniformity. Based on this study a design for production was chosen, which will be used for experiments at the ARES linac within the SINBAD facility at DESY. This work was carried out within the ACHIP project funded by the Gordon and Betty Moore Foundation (GBMF 4744).

Spatial autocorrelation study for laser beam quality estimation

High brightness electron beam is required by several applications in the accelerator physics field. In order to have a high brightness beam, that means a high current and a low emittance beam, it is important to study, among other things, the beams non uniformity due to the non perfect transverse laser beam uniformity. Regarding the transverse analysis of the beam, statistical tools as mean and standard deviation are usually used. In this work we will show how the autocorrelation function of a photocathode laser can be used for monitoring the spatial distribution of the beam non-uniformity, strictly connected with the high electron beam emittance: we will apply our analysis on the SPARC_LAB data.

Efficient Cherenkov-type optical-to-terahertz converter with terahertz beam combining.

A nonlinear structure for efficient Cherenkov-type terahertz emission from ultrashort laser pulses is proposed, modeled, and experimentally demonstrated. The structure comprises a thin (a few tens of micrometers thick) layer of lithium niobate sandwiched between two silicon prisms. A focused-to-a-line laser pulse propagates in the layer and generates a Cherenkov wedge of terahertz radiation in the prisms. The radiation experiences total internal reflection in the prisms and emerges into free space as two adjacent beams collinear to the pump laser beam. The structure can generate a centimeter-wide terahertz beam with high transverse uniformity and a flat frequency spectrum. An optical-to-terahertz conversion efficiency as high as 0.35% is achieved with 10-µJ laser pulses. It can be further enhanced by reducing the thickness of the lithium niobate layer.

Performance evaluation of digestate spreading machines in vineyards and citrus orchards: preliminary trials

This research was carried out to evaluate a local biogas plant's solid fraction digestate spreading in a citrus orchard and vineyard. Three spreaders were tested: a broadcast manure spreader in the citrus orchard, and two cylindrical-shaped spreaders in the vineyard; the first one working in broadcast configuration, the second one in localised configuration. Experimental tests assessed effective work time, mean work speed, digestate flow rate and longitudinal and transverse spreading uniformity. In the citrus orchard, the digestate was mainly spread in the centre of the inter-row (around 66%), with low variability between inter-rows (coefficient of variation (CV) equal to 2.7%) and much higher variability within inter-rows (CV = 31.4%). The effective work time was about 28% of total field time and real work capacity was about 0.96 ha h−1. In the vineyard, broadcast spreading released more on the right compared to the left (ratio 1.74) due to distributor disc rotation, whereas localised spreading was more uniform. Overall, variability between inter-rows had CV = 15.1% and within inter-rows CV = 33.3%. Real work capacity was about 0.16 ha h−1 for broadcast spreading and 0.26 ha h−1 for localised spreading. A preliminary economic evaluation, based on sub-contractor tariffs, produced the mean tariff for transaction and spreading costs of digestate in farms near the biogas plant.

Heating process monitoring and evaluation of hot in-place recycling of asphalt pavement using infrared thermal imaging

The original asphalt pavement heating plays a key role in the entire construction procedure of hot in-place recycling (HIR). At present, the temperature of heating process in HIR is monitored by infrared temperature gun with single or multiple test points which cannot fully understand real heating situation. Moreover, there are no evaluation indices for quantifying heating quality. To objectively perceive and evaluate the heating quality, the infrared thermal imaging (ITI) system was used to monitor heating process of HIR and the combination of digital image processing (DIP) and artificial neural network (ANN) was applied to extract and correct the distorted thermal image to restore pavement surface temperature. Based on corrected thermal images, the heating quality of HIR was firstly quantitatively evaluated using three proposed indices: transverse uniformity Tu for evaluating the temperature uniformity, represent temperature RT for assessing the heating effect and proportion of temperature above 200 °C PTA200 for judging the overheating. Furthermore, on-site heating quality of three heating systems: respectively flame, infrared radiation and recycled hot-wind system, was analyzed and compared based on the above three indices. The results indicate that the superiority of the flame system and the infrared heating system is strong heating effect to realize the higher pavement surface temperature, but the temperature uniformity is poor, even some areas are overheated. On the contrary, the recycled hot-wind heating system provides the better temperature uniformity and avoids overheating, but the heating effect is poor. In addition, a comprehensive analysis reveals that high RT and poor Tu are mainly cause of overheating and the better Tu is required to match the increasing pavement surface temperature for high level of the heating quality. Finally, when using 200 °C as the high temperature boundary, the evaluation indices Tu and RT preferably satisfy the following relationship RT + RT × Tu < 190 °C to avoid occurrence of overheating in HIR.