Fine Mesh Grid Research Articles

Towards a cutting‐edge metallization process for silicon heterojunction solar cells with very low silver laydown

AbstractWithin this work, we investigate the potential to optimize the screen‐printed front side metallization of silicon heterojunction (SHJ) solar cells. Three iterative experiments are conducted to evaluate the impact of the utilized fine mesh screen configurations and grid layout adaption (finger pitch) for the front side metallization on silver laydown and electrical performance of the solar cells. With respect to the screen configuration, we compare the performance of a fine‐mesh knotless screen to a conventionally angled screen demonstrating an additional gain of Δη = +0.1%abs due to reduced shading losses. Additionally, a grid layout is improved by increasing the number of contact fingers from 120 to 156. Furthermore, the current possibility to push the fine‐line printing process for low‐temperature pastes to the limit is investigated by reducing the nominal finger width wn to 20, 18, and 15 μm. It is shown that even the smallest nominal width of wn = 15 μm can be printed with high quality, leading to an additional efficiency gain of Δη = +0.15%abs as well as a reduction of silver paste laydown by −5 mg. Finally, a batch of champion cells is fabricated by applying the findings of the previous experiments, which results in a maximum efficiency of ηmax = 23.2%. Compared to the reference group without optimization, this corresponds to a gain of Δη = +0.17%abs, which comes along with an additional decrease of the silver paste laydown by approximately −2 mg. This emphasizes the significance of consistent optimization of the screen‐printing process in terms of cell performance and resource utilization for SHJ solar cells.

A semi-analytic study of self-interacting dark-matter haloes with baryons

ABSTRACT We combine the isothermal Jeans model and the model of adiabatic halo contraction into a semi-analytic procedure for computing the density profile of self-interacting dark-matter (SIDM) haloes with the gravitational influence from the inhabitant galaxies. The model agrees well with cosmological SIDM simulations over the entire core-forming stage up to the onset of gravothermal core-collapse. Using this model, we show that the halo response to baryons is more diverse in SIDM than in CDM and depends sensitively on galaxy size, a desirable feature in the context of the structural diversity of bright dwarfs. The fast speed of the method facilitates analyses that would be challenging for numerical simulations – notably, we quantify the SIDM halo response as functions of the baryonic properties, on a fine mesh grid spanned by the baryon-to-total-mass ratio, Mb/Mvir, and galaxy compactness, r1/2/Rvir; we show with high statistical precision that for typical Milky-Way-like systems, the SIDM profiles are similar to their CDM counterparts; and we delineate the regime of core-collapse in the Mb/Mvir − r1/2/Rvir space, for a given cross section and concentration. Finally, we compare the isothermal Jeans model with the more sophisticated gravothermal fluid model, and show that the former yields faster core formation and agrees better with cosmological simulations. We attribute the difference to whether the target CDM halo is used as a boundary condition or as the initial condition for the gravothermal evolution, and thus comment on possible improvements of the fluid model. We have made our model publicly available at https://github.com/JiangFangzhou/SIDM.

Automation of multi-modal beam focusing of an MeV sub-microprobe for ion beam analysis

We have developed an automatic beam-focusing system to reduce the experimental configuration time for a sub-micrometer-scaled beam probe of MeV ions with various analytical applications. Parasitic aberration due to misalignment and astigmatism must be eliminated or minimized to obtain an ideal beam spot size of less than 1 × 1 µm2, because astigmatism from excitation error and axial misalignment broaden the beam. The system involves a two-stage process of contrast and phase-difference detection that includes an automated minimization algorithm for astigmatism. The process can identify misalignments of axial rotation by measuring the line profiles of a fine mesh grid. The contrast method focused a proton microprobe to approximately 1 μm2 within 30 min, without the need for manual control when rotational misalignment was not present, while the phase-difference method successfully reduced the rotational error of lenses.

CFD and ANN approach to predict the flow pattern around the square and rectangular bluff body for high Reynolds number

The present numerical investigation consists of a detailed evaluation of flow over the bluff body to determine its behavior of boundary layer flow separation around the surfaces. In the present study, square and rectangle shape bluff body is investigated for higher Reynolds number ranging from 63,651 to 636,505 with three different cases of the angle of inclination 0°,10°, and 20°. Optimize k–∊ standard turbulent model with fine mesh grid is used to perform numerical investigation, and the results are validated from the literature in capturing flow separation from the surfaces. It is found that the flow separation regime behind the square and rectangular bluff body changes with Reynolds number and angle of inclination. It is also observed that the flow separation increases from the top side of the bluff body with an increase in the angle of inclination. The size and frequency of vortex generation increase with an increase in Reynolds number. A correlation is proposed for the vortex generation as a function of Reynolds number and angle of inclination. The prediction of vortices generation behind the square and rectangular bluff body is determined using the artificial neural network driven by CFD Data. A verification study is proposed in ANN approach based on neuron independent study to validate output field parameter of CFD.

Support based novel single layer nanoporous graphene membrane for efficacious water desalination

Among promising novel membrane materials for enhancing desalination performance, graphene has been realized as a high potential candidate due to its unique properties. However, large area graphene membrane, dominantly available through wet transfer and assistance of polymers, has inevitable features like defects, holes and cracks that could limit realistic prospects of industrial-scale production of desalination membranes. Here, using hole arrays in silicon as a secondary and a fine mesh grid as an initial support, we experimentally designed a mobile nanoporous graphene membrane with tunable salt rejection and water permeation by favourably limiting the undesired effects of defects and holes on the graphene. A model is also presented to support the experiments and give more insight into the possible superpositions (i.e. motifs) that occur by movements of graphene/grid over silicon hole arrays. Using the moveable assembly of graphene/grid/hole arrays and the consequent motifs, a range of high permeation (4.34 × 107–5.90 × 107 L m−2 h−1 bar−1) and NaCl rejection (58%–100%) values were obtained. The moveable assembly of graphene/grid on fixed silicon hole arrays opens possibilities of fabrication of scalable atomically thin membranes for water desalination and can be applied for many other separation purposes specifically ion selectivity and filtration of multivalent ions or larger molecules.

Effect of the Enhanced Breakdown Strength in Plasma-Filled Optical System of Electron Beam Formation

The article presents recent results of the dramatically enhanced electric breakdown strength observed in the accelerating gap of a plasma-filled optical system for the formation and focusing of a wide-aperture pulsed electron beams with currents up to 80 A and energies up to 35 keV. This system is a plasma-optical diode type device in which the acceleration and formation of the electron beam occurs in the double layer between the emissive surface of the plasma cathode (electron emitter) stabilized by a fine mesh grid and the open surface of the anode plasma. The anode plasma is created by the toroidal plasma generator of original design based on the ion source with closed drift of electrons with an anode layer.

Turbulent flow reduces oxygen consumption in the labriform swimming shiner perch, Cymatogaster aggregata.

Fish swimming energetics are often measured in laboratory environments which attempt to minimize turbulence, though turbulent flows are common in the natural environment. To test whether the swimming energetics and kinematics of shiner perch, Cymatogaster aggregata (a labriform swimmer), were affected by turbulence, two flow conditions were constructed in a swim-tunnel respirometer. A low-turbulence flow was created using a common swim-tunnel respirometry setup with a flow straightener and fine-mesh grid to minimize velocity fluctuations. A high-turbulence flow condition was created by allowing large velocity fluctuations to persist without a flow straightener or fine grid. The two conditions were tested with particle image velocimetry to confirm significantly different turbulence properties throughout a range of mean flow speeds. Oxygen consumption rate of the swimming fish increased with swimming speed and pectoral fin beat frequency in both flow conditions. Higher turbulence also caused a greater positional variability in swimming individuals (versus low-turbulence flow) at medium and high speeds. Surprisingly, fish used less oxygen in high-turbulence compared with low-turbulence flow at medium and high swimming speeds. Simultaneous measurements of swimming kinematics indicated that these reductions in oxygen consumption could not be explained by specific known flow-adaptive behaviours such as Kármán gaiting or entraining. Therefore, fish in high-turbulence flow may take advantage of the high variability in turbulent energy through time. These results suggest that swimming behaviour and energetics measured in the lab in straightened flow, typical of standard swimming respirometers, might differ from that of more turbulent, semi-natural flow conditions.

Wave Filtration of Pressure Fluctuations by Means of Fine Mesh Grids

Results of experimental investigations of the parameters of an element of a wave filter the structural design of which is based on the location of the pressure fluctuation detector in a cavity beneath a fine-mesh grid are presented. The optimal dimensions of the element at which maximal averaging of short wavelengths may be achieved are presented. A method of determining the efficiency of the filter is proposed.

Simulation of Typhoon Bolaven using Integrally Coupled Tide-Surge-Wave Models based on locally Enhanced Fine-Mesh Unstructured Grid System

ABSTRACT Kim, K.O.; Yuk, J.-H., and Choi, B.H., 2016. Simulation of Typhoon Bolaven using integrally coupled tide-surge-wave models based on locally enhanced fine-mesh unstructured grid system. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 1127 - 1131. Coconut Creek (Florida), ISSN 0749-0208. The integrally coupled wave-tide-surge models based on hydrodynamic and spectral wave models with an unstructured mesh system were tested in the typhoon Bolaven, which hit the Korean Peninsula in 2012 and caused the deaths of 19 victims. The identical and homogeneous mesh allows the physics of wave-circulation interactions to be correctly resolved in both models. The unstructured mesh can be applied to a large domain allowing all energy from deep to shallow waters to be seamlessly followed. The model results were compared with the observations, and the mode...

Shut-down dose rate analyses for the ITER electron cyclotron-heating upper launcher

The electron cyclotron resonance heating upper launcher (ECHUL) is going to be installed in the upper port of the ITER tokamak thermonuclear fusion reactor for plasma mode stabilization (neoclassical tearing modes and the sawtooth instability). The paper reports the latest neutronic modeling and analyses which have been performed for the ITER reference front steering launcher design. It focuses on the port accessibility after reactor shut-down for which dose rate (SDDR) distributions on a fine regular mesh grid were calculated. The results are compared to those obtained for the ITER Dummy Upper Port. The calculations showed that the heterogeneous ECHUL design gives rise to enhanced radiation streaming as compared to the homogenous dummy upper port. Therefore the used launcher geometry was upgraded to a more recent development stage. The inter-comparison shows a significant improvement of the launchers shielding properties but also the necessity to further upgrade the shielding performance. Furthermore, the analysis for the homogenous dummy upper port, which represents optimal shielding inside the launcher, demonstrates that the shielding upgrade also needs to include the launcher's environment.

Residual stress and quantitative phase mapping on complex geometries

As a consequence of substantial advances in computer-aided design and manufacturing technology, engineering parts are no longer restricted to combination of simple geometrical shapes. Implementing complex curved surfaces in engineering components in combination with finite-element geometry optimization has become a prevalent means of designing a part. Measuring residual stresses using X-ray diffraction (XRD) on complex curved surfaces requires further development of current measurement methods. Here we investigate how a laboratory XRD system equipped with a five-axis stage and two-dimensional detector can execute sin2ψ residual stress measurements on curved surfaces. Shadowing that blocks the diffracted beam to reach the detector was avoided using proper rotations and tilting of the sample. A standard video-laser alignment system commonly used to manually place the sample in the center of diffraction was used to also generate virtual maps of the sample's curved surfaces on a fine mesh grid. The geometry was then used for setting the required rotations and tilt angles. A set of diffraction frames collected using this method on a model zirconia dental ceramic, afforded the opportunity to superimpose phase and stresses on a complex geometry. This is a step forward for the XRD technology, and its usefulness applies to many different industries.

Electrostatic Plasma Lens Focusing of an Intense Electron Beam in an Electron Source With a Vacuum Arc Plasma Cathode

In this paper, we present the research results on focusing and transport of an intense (up to 100 A) nonrelativistic (up to 20 kV) pulsed electron beam using an axially symmetric device with a high-current plasma lens configuration. The electron source is based on electron extraction from the plasma of a hollow-anode vacuum arc discharge. The arc is initiated by a dielectric surface flashover. The emission hole is covered with a fine mesh grid. The beam is extracted and accelerated in a diode-type electro-optical system formed between the grid surface and an open anode plasma boundary. The anode plasma is produced in an electron beam transport channel through residual gas ionization by beam electrons and a plasma lens discharge. The plasma lens configuration of crossed electric and magnetic fields provides an attractive means to obtain a stable low-pressure plasma discharge. This geometry allows the compression of the electron beam in diameter from 6 to 1 cm with more than 100- <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\rm A}/{\rm cm}^{2}$</tex></formula> beam current density at the collector.

X-ray diffraction mapping on a curved surface

An efficient method for X-ray diffraction data collection mapping on a given curved surface has been developed. The method uses a laser–video autozalignment system to collect a map of heights on a fine mesh grid. It also reconstructs the surface geometry and determines surface normals on a three-dimensional surface fit. An algorithm was used to calculate the required rotation and tilt angles to coincide the sample normal with the diffraction center before each exposure. A set of diffraction frames collected using this technique was analyzed in order to superimpose a phase transformation map onto a typical zirconia ceramic sample. With this method, mapping of phase and stresses on a complex surface has been demonstrated. This approach is broadly applicable to many important areas of study.

Development of a stigmatic mass microscope using laser desorption∕ionization and a multi-turn time-of-flight mass spectrometer

A novel stigmatic mass microscope using laser desorption∕ionization and a multi-turn time-of-flight mass spectrometer, MULTUM-IMG, has been developed. Stigmatic ion images of crystal violet masked by a fine square mesh grid with a 12.7 μm pitch as well as microdot patterns with a 5 μm dot diameter and a 10 μm pitch made with rhodamine B were clearly observed. The estimated spatial resolution was about 3 μm in the linear mode with a 20-fold ion optical magnification. Separating stigmatic ion images according to the time-of-flight, i.e., the mass-to-charge ratio of the ions was successfully demonstrated by a microdot pattern made with two different dyes, crystal violet and methylene blue. Stigmatic ion images of a microdot pattern made with crystal violet were observed after circulation in MULTUM-IMG, and the pattern of the ion image was maintained after ten cycles in MULTUM-IMG. A section of a mouse brain stained with crystal violet and methylene blue was observed in the linear mode, and the stigmatic total ion image of crystal violet and methylene blue agreed well with the optical microphotograph of the hippocampus for the same section.

CFD ANALYSIS OF TURBULENT JET BEHAVIOR INDUCED BY A STEAM JET DISCHARGED THROUGH A VERTICAL UPWARD SINGLE HOLE IN A SUBCOOLED WATER POOL

Thermal mixing by steam jets in a pool is dominantly influenced by a turbulent water jet generated by the condensing steam jets, and the proper prediction of this turbulent jet behavior is critical for the pool mixing analysis. A turbulent jet flow induced by a steam jet discharged through a vertical upward single hole into a subcooled water pool was subjected to computational fluid dynamics (CFD) analysis. Based on the small-scale test data derived under a horizontal steam discharging condition, this analysis was performed to validate a CFD method of analysis previously developed for condensing jet-induced pool mixing phenomena. In previous validation work, the CFD results and the test data for a limited range of radial and axial directions were compared in terms of profiles of the turbulent jet velocity and temperature. Furthermore, the behavior of the turbulent jet induced by the steam jet through a horizontal single hole in a subcooled water pool failed to show the exact axisymmetric flow pattern with regards to an overall pool mixing, whereas the CFD analysis was done with an axisymmetric grid model. Therefore, another new small-scale test was conducted under a vertical upward steam discharging condition. The purpose of this test was to generate the velocity and temperature profiles of the turbulent jet by expanding the measurement ranges from the jet center to a location at about 5% of <TEX>$U_m$</TEX> and 10 cm to 30 cm from the exit of the discharge nozzle. The results of the new CFD analysis show that the recommended CFD model of the high turbulent intensity of 40% for the turbulent jet and the fine mesh grid model can accurately predict the test results within an error rate of about 10%. In this work, the turbulent jet model, which is used to simply predict the temperature and velocity profiles along the axial and radial directions by means of the empirical correlations and Tollmien's theory was improved on the basis of the new test data. The results validate the CFD model of analysis. Furthermore, the turbulent jet model developed in this study can be used to analyze pool thermal mixing when an ellipsoidal steam jet is discharged under a high steam mass flux in a subcooled water pool.

Grid-controlled current switching in cathode-spot discharge

The first results of an investigation of the complete current switching (initiation and quenching) using a fine-mesh grid in discharge with a cathode spot on liquid cesium are reported. Experimental data show the possibility of using this method of control at current densities within 5–25 A/cm2 in the grid plane.

Experimentation and direct numerical simulation of self-similar convergent detonation wave

The propagation of self similar convergent detonation wave in TATB-based explosive composition was studied both experimentally and numerically. The device constists in a 50 mm cylinder of TATB surrounded by an HMX tube. The detonation in HMX overdrives the detonation in TATB which adapts to the propagation velocity with a convergent front at centerline. We measured a curvature of κ = −21.2 m−1 for propagation velocity of 8750 m/s, which extends the knowledge of the (Dn ,κ ) law. A wide ranged EOS/reaction rate model inspired from previous work of Wescott et al. was calibrated to reproduce both the run-to-detonation distance and the newly extended (Dn ,κ ) law for the 1D sligthly curved detonation theory. 2D Direct Numerical Simulations (DNS) were made on fine resolved mesh grid for the experimental configuration and for various driver velocities. The simulation reproduces the experimental data both qualitatively (overall detonation structure) and quantitatively (κ = −25.4 m−1 ).

TIC rectifier with output voltage phase control. I. Cesium thyratron with a low direct potential drop

The results of investigation of the ignition voltage for a low-voltage cesium arc and direct voltage drops in the discharge in cesium triodes with fine-mesh (∼0.2 mm) and coarse-mesh (∼2 mm) control grids are presented. It is shown that in a cesium vapor pressure range of 0.05–0.1 Torr and for discharge currents of 5–10 A/cm2, direct voltage drops can be reduced to 0.7–0.5 V even for a fine-mesh grid. For a coarse-mesh grid whose holdoff voltage is sufficient for rectifying low voltages (∼15–20 V), direct voltage drops are almost the same as for a diode even for currents of 1 A/cm2 and lower. The critical factor of holdoff voltage loss is the grid emission level (∼1 mA/cm2).

NUMERICAL MODELLING OF CONCENTRATION PROFILES IN MEMBRANE CHANNEL

Numerical modelling of the flow and concentration polarization in pressure driven membrane process is challenged by the complex coupling in the flow, mass and energy equations along with any added effects of variable solution properties. The present study is directed towards the establishment of a numerical method capable of predicting the flow and concentration characteristics of the laminar channel flows with permeable wall taking into account the variable properties of the stream. The present results highlights the necessity of the fine mesh grid near the membrane wall to cope with the very steep changes in concentration and temperature there and to the importance of making the permeation velocity vary with concentration. The model was validated and the results showed a good agreement with the previous numerical and experimental results.

Mach Number and Freestream Turbulence Effects on Turbine Vane Aerodynamic Losses

The aerodynamic performance of a smooth. cambered turbine vane (which replicates one used in an operating gas turbine engine) is investigated in this paper. Three different Mach-number distributions are employed, which result in one transonic flow and two subsonic flows. All of these distributions match flow conditions in different industrial applications. A fine mesh grid and cross bars are used to augment the magnitudes of longitudinal turbulence intensity at the inlet of the test section. Wake-profile data are presented for two different locations downstream of the vane trailing edge (one axial chord length and 0.25 axial chord length). The contributions of varying Mach number and varying freestream turbulence intensity to aerodynamic losses, normalized kinetic energy profiles, normalized Mach-number profiles, integrated aerodynamies losses, and area-averaged loss coefficients are quantified. Results show that wake profiles are more sensitive to turbulence intensity variations at lower subsonic flow conditions than when transonic flow is present. Wake profiles are also broadened either as the exit Mach number increases or as the freestream turbulence intensity level increases. Higher losses in the freestream flow are present as the inlet turbulence intensity level increases. Also described are effects of increased turbulent diffusion, streamwise development, and profile asymmetry. Corresponding integrated aerodynamic losses and area-averaged loss coefficient Y A magnitudes increase with increasing Mach number or with increasing turbulence intensity level. Results additionally show larger loss magnitudes with flow turning and cambered airfoils, relative to symmetric airfoils, when compared at the same exit Mach number.