Effect Of Slit Width Research Articles

Research and optimization of slit issues in the kW-scale redox flow batteries stack

The assembly of the frame and bipolar plates in redox flow batteries (RFBs) often results in assembly gaps, forming ‘slit.’ Due to differing coefficients of thermal expansion between the plate frame and bipolar plates, thermal expansion and contraction occur under the influence of assembly environment temperatures and operational temperatures of RFBs, exacerbating the ‘slit’ issue. The presence of ‘slits’ can reduce the utilization rate of the electrolyte and decrease mass transfer efficiency during the battery cycling process. However, the flow channel design for kilowatt (kW)-scale stacks often overlooks the impact of these slits. Therefore, this paper examines the influence of ‘slit’ structures on the flow characteristics of electrolytes within carbon cloth using kW-scale stacks with interdigitated flow channel structures as an example, and optimizes the interdigitated flow field with slits. The study analyzes the flow characteristics of electrolytes on carbon cloth in flow field structures with no slits, slits at both ends and slits on three sides. It further investigates the effects of slit width and the length of interdigitated flow channels on the flow patterns of electrolytes on carbon cloth when slits are present. Through numerical simulation, velocity and pressure distribution maps at the center of the carbon cloth, as well as velocity distributions at various positions, are obtained. The results show that slits affect the position and extent of the low-speed zone on the carbon cloth. As slit width increases, the resistance of the slit decreases, gradually increasing the flow velocity of the electrolyte towards the carbon cloth. However, when the slit width exceeds 0.5 mm, the impact of the slit on flow over the carbon cloth remains largely unchanged. With a fixed slit width of 0.5 mm, increasing the length of the interdigitated flow channels reduces the flow velocity and pressure within the carbon cloth but significantly improves the uniformity of the carbon cloth. Extending the interdigitated flow channel length by 15 mm demonstrates the best overall effect.

Molecular dynamics simulation of hexagonal boron nitride slit membranes for wastewater treatment

Nanoporous boron nitride (BN) nanosheets are promising reverse-osmosis membrane materials, suitable for the removal of hazardous heavy metals, with advantages such as separation energy efficiency, eco-friendliness, heat resistance, acid resistance, and good antifouling properties. BN slit membranes (BNSMs) are a special class of nanoporous BN membranes that have not yet been extensively explored for heavy metal ion separation. To address the existing knowledge gap regarding these membranes, molecular dynamics (MD) simulations were performed herein to investigate the performance of BNSMs in purifying water from arsenic (As3+) and mercuric (Hg2+) cations, as well as chloride (Cl-) anions. For this purpose, the effects of slit width in monolayer, bilayer, and trilayer BN, interlayer distance, and membrane flexibility were evaluated. Based on the results obtained in this work, water flow rate increases, while ion rejection decreases, with increasing slit width. For rigid monolayer BNSMs having slit widths of 8–10 Å, the ion rejection percentage was in the order of As3+ > Cl- > Hg2+. The highest rejection percentage of As3+ cations in these membranes is attributed to their largest repulsive interaction energies of 27 kcal/mol with the membrane surface and the largest hydration radii of these cations (3.8 Å). For a rigid monolayer BNSM with the slit width of 7 Å, the rejection percentages of all ions were approximately equal to 100 % due to the dominant effect of slit geometric constraints against ion transport. For a rigid bilayer BNSM, both the number of filtered water molecules and water flow rate decreased with a decrease in the interlayer distance. In terms of ion rejection performance, the geometric constraints (size exclusion mechanism) were again responsible for the high (above 98 %) ion rejection percentages in these membranes with interlayer distances of 7–9 Å. Finally, flexible monolayer BNSMs were found to provide higher water flow rates and lower ion rejection percentages when compared to the rigid membranes. This behavior can be attributed to the larger slit cavity that results from membrane flexibility, thereby facilitating water flow and ion transport through the membrane. The use of molecular dynamics simulations in this study demonstrates the potential of computational methods in the design and screening of novel membrane materials, paving the way for further computational and experimental investigations in this field.

Simulation of Slot-Scan imaging system with GATE and images quality evaluation

Interest in slot scanning imaging system has been increased recently because of its advantages such as high image resolution, reduction in patient dose and reduction in image distortion. The purpose of this study is to simulate a slot scanning imaging system using GATE multi-purpose Monte Carlo code and design an object phantom to evaluate image quality. The energy spectrum of X-ray in the radiological diagnostic range was simulated by GATE Monte Carlo code. An object phantom consisting of stripes with different thicknesses of copper was then designed to determine CNR and line pairs per millimeter to determine spatial resolution.The results showed that the simulated energy spectrum were in accordance with experiment. The evaluated parameters of image quality obtained from the simulations were compared with X-ray images using standard image quality criteria to determine the capabilities of the slot scanning imaging method. The spatial resolution of the simulated images was obtained to be 1.6 lp / mm for the slot scanning method, which is in the range of clinical radiology images. Therefore, this simulated model can be used to investigate and optimize other influential parameters such as filtration effect and collimator slit width effect, object distance to the detector ... in slot scanning imaging system.

Analysis of imbibition of n-alkanes in kerogen slits by molecular dynamics simulation for characterization of shale oil rocks

Shale oil formations contain both inorganic and organic media. The organic matter holds both free oil in the pores and dissolved oil within the kerogen molecules. The free oil flow in organic pores and the dissolved oil diffusion in kerogen molecules are coupled together. The molecular flow of free n -alkanes is an important process of shale oil accumulation and production. To study the dynamics of imbibition process of n -alkane molecules into kerogen slits, molecular dynamics (MD) simulations are conducted. Effects of slit width, temperature, and n -alkane types on the penetration speed, dynamic contact angle, and molecular conformations were analyzed. Results showed that molecular transportation of n -alkanes is dominated by molecular structure and molecular motion at this scale. The space-confinement conformational changes of molecules slow down the filling speeds in the narrow slits. The n -alkane molecules with long carbon chains require more time to undergo conformational changes. The high content of short-chain alkanes and high temperature facilitate the flow of alkane mixtures in kerogen slits. Results obtained from this study are useful for understanding the underlying nanoscale flow mechanism in shale formations.

Flow characteristics of elastically mounted slit cylinder at sub-critical Reynolds number

The present work numerically investigates vortex-induced vibrations (VIV) of a two-dimensional circular cylinder with an axisymmetric slit at Reynolds number 500. The study examines the effects of slit shape (i.e., converging, diverging, and parallel slits), the effect of slit-area ratios, slit width, and its angle with the freestream velocity on aerodynamic forces, vibration response, and associated flow characteristics. The results demonstrate that the addition of the slit assists the VIV suppression by adding an extra amount of flow to the main flow. It results in the stabilized wake with the pressure recovery downstream of the cylinder and causes a reduction in the lift force over the cylinder. Also, there exist different shedding patterns associated with different slit shapes. A proper orthogonal decomposition of the flow field suggests that among all the three slits, the parallel slit heavily modifies the flow behind the cylinder by distributing the amount of energy to a large number of modes as compared to other slits (converging slit and diverging slit), where the most of the energy is contained in a couple of modes. Further, increasing the slit angle (for parallel slit) with respect to the freestream increases the slit effectiveness up to a specific value of slit-angle and beyond that starts to affect the VIV suppression adversely. Observations for the effect of slit width are also reported from the perspective of suppression of VIV.

Measurements of slit-width effects in Young’s double-slit experiment for a partially-coherent source: erratum

We report here two inadvertent errors that appear in our original paper [OSA Continuum 1, 755 (2018)10.1364/OSAC.1.000755].

Retrieval of Optical Constants of Undoped Flash-Evaporated Lead Iodide Films from an Analysis of Their Normal Incidence Transmission Spectra Using Swanepoel’s Transmission Envelope Theory of Non-Uniform Films

Abstract: Normal-incidence transmission-wavelength (T_exp (λ)-λ) spectra of 1 and 1.2 m thick flash-evaporated lead iodide (PbI2) films on 1.1 mm thick glass slides held at 200 ℃ display well-spaced several interference-fringe maxima and minima in the λ-range 520-900 nm, without exhibiting a transparent region and with the maxima lying well below the substrate transmission. Below 520 nm, these T_exp (λ)-λ curves drop steeply to zero (at λ ≼ 505 nm), signifying crystalline-like PbI2 film absorption. As corrections of measured (PbI2 film/substrate) transmittance data for substrate absorption and spectrometer slit-width effect were marginal over the studied λ-range, the observed low transmittance of (PbI2 film/substrate) system was related to PbI2 film thickness non-uniformity (∆d), which causes shrinkage of both maxima and minima and leads to significant film optical absorption that reduces both maxima and minima. The McClain ENVELOPE algorithm was utilized, with a minor modification, to construct maxima T_M (λ_max/λ_min) and minima T_m (λ_min/λ_max) envelope curves, which were analyzed by Swanepoel’s envelope method of non-uniform films using an approach that takes account of dispersive substrate refractive index n_s (λ) and circumvents the non-availability of a high-λ transparency region. In such analytical approach, ∆d was varied till a re-generated T_gen (λ)-λ curve matches the T_exp (λ)-λ curve. An average thickness d ̅ of the film, besides its refractive index n(λ) and absorption coefficient α(λ) in the weak, medium and strong absorption regions, were then obtained. The energy-dependence of α(λ) is discussed in view of interband electronic transition models. The obtained results are consistent with other literature studies on similar flash-evaporated PbI2 films. Keywords: PbI2, Optical constants and bandgap, Swanepoel's transmission envelope method, Non-uniform films.

A new model for the calculation of homogeneously broadened Raman spectral bandwidths and bandshapes

AbstractRaman spectral bandwidths and bandshapes can provide detailed information on the physics and chemistry of a sample. The Raman band reported by a spectrometer (observed Raman band [ORB]) is a result of contributions from the true, intrinsic Raman band (IRB) and the spectrometer slit function. To obtain the IRB spectral width and shape, the effects of the spectrometer slit function must be removed from the ORB by measuring the spectrometer slit function and modeling the ORB as a convolution of the IRB and slit function. Though this model has proven to be useful, it is not based on physical parameters of the measurement and is limited. Thus, new ways to model Raman bandshape and bandwidth are needed. I previously developed a new method of modeling Raman bands using spectrometer geometric optics to examine the dependence of Raman band intensity on slit width. The model calculates the intensity of the ORB from the contributions of a continuum of dispersed slit functions. Here, I extend the use of this model for examining ORB spectral widths and shapes. I show that the model produces the same result as the convolution model when using Lorentzian Raman and Gaussian slit functions, confirming the validity of the model. However, in contrast to the convolution model, the new model is based on spectrometer geometric optics allowing one to account for various optical effects when modeling Raman spectra. This is demonstrated by modeling the effects of slit width on the Raman spectrum. I use the model to provide a detailed, physical understanding of the effects of slit width and IRB width on Raman bandshapes.

Effect of the spectrometer slit width and charge‐coupled device detector on Raman intensities

AbstractIt is well known that Raman intensities are affected by the spectrometer slit width. Wider slit widths provide increased Raman intensity at the cost of decreased spectral wavenumber resolution. However, the relationship between the spectrometer slit width and observed Raman intensities is poorly understood. In this work, we develop a model, based on spectrometer geometric optics, to quantify the effects of spectrometer slit width on observed Raman intensities. We find that the observed Raman intensities are strongly dependent on the ratio of the slit function width and intrinsic Raman band width. Thus, even for Raman spectra collected using the same slit width, the observed Raman intensities will be affected by the different intrinsic bandwidths of each Raman band. Thus, the effects of the slit function on Raman intensities must be considered for all Raman spectra when examining Raman intensities. In addition, we show that the spectrometer linear dispersion and charge‐coupled device (CCD) pixel size have a large dependence on the Raman intensities reported by the CCD. Thus, when comparing Raman intensities across instruments or for a single instrument with a nonlinear wavenumber calibration, Raman intensities must be calibrated for the effects of the CCD. Using our model, we develop a general method for correcting observed Raman intensities for the effects of the slit width, intrinsic Raman band width, and CCD.

Numerical investigation of axisymmetric bubble dynamics from a submerged circumferential slit on the cylinder

The boundary element method is adopted to study the ventilating axisymmetric bubble growth from a circumferential slit in a submerged cylindrical wall under vertical flow conditions in this paper. During the bubble growth, mesh subdivision and smoothing techniques are adopted in order to optimize mesh topology. In this study, the effects of inflow velocity, surface tension coefficient, ventilation rate and slit width on the bubble development process are studied. The results show that the bubble shape is mainly affected by the inflow velocity and the surface tension coefficient, the inflow velocity promotes the downward movement of the lower intersection point of the wall and bubble, meanwhile, the surface tension inhibits it. The effect of slit width is mainly reflected in the initial stage of the bubble development. And the bubble size basically increases as the ventilation rate increases. In addition, the effects of the Froude number, Weber number, and ventilation coefficient on bubble growth are analyzed. The maximum dimensionless length and thickness of the bubble increase with the increase of the Froude number and decrease with the increase of the Weber number. As the ventilation coefficient increases, the length decreases first and then stabilizes, the thickness decreases first and then increases.

Slit Width Effect on Signal-to-noise Ratio in Spectrophotometric Measurements

Signal-to-noise (S/N) ratio theory has proven to be useful in understanding, designing, and optimizing spectrophotometric measurement systems. Although a narrower spectral bandwidth does improve the resolution of closely spaced peaks, it also decreases the Signal-to-noise ratio. The narrowest slit width should be used that will yield an acceptable Signal-to-noise ratio. In this research, the wavelengths of peak absorbance of the holmium glass filter were determined to attain the optimum Signal-to-noise ratio accompanied with spectral bandwidths of 0.1 nm, 0.2 nm, 0.5 nm, 0.8 nm, 1 nm, 2 nm, 3 nm and 5 nm. The influence of spectral bandwidth on the Signal-to-noise ratio was by far the most important parameter affecting the location of the measured wavelengths of absorbance or transmittance of the sample.

Analytical solutions for the principal maxima in multiple slit diffraction: Effects of slit width

We present analytical solutions for the principal maxima in multiple slit diffraction. By expanding the angular position of the principal maxima in orders of a/d where d is the distance between two adjacent slits and a is the width of each slit, we obtain the angular position of the principal maxima up to the twelfth order in a/d.

Effect of slit width on surface plasmon resonance

In this paper, a hybrid resonator composed of an all-metal grating made of copper and a dielectric cavity filled with SiO2 between slits is simulated and calculated by the finite-difference time-domain method (FDTD). We study the effect of slit width on surface plasmon resonance by changing the size of the dielectric cavity. In the case of parallel light incident vertically, the resonator can achieve multi-band absorption and have a perfect absorption peak. The dielectric cavity can not only localize the incident light wave, but also enhance the effect of surface plasmon of metal structure. Our results can be widely used in the field of surface plasmon, which is beneficial to the development of surface plasmon resonators in sensing and detection.

Characterization of 3D-printed lenses and diffraction gratings made by DLP additive manufacturing

PurposeAn Autodesk Ember three-dimensional (3D) printer was used to print optical components from Clear PR48 photocurable resin. The cured PR48 was characterized by the per cent of light transmitted and the index of refraction, which was measured with a prism spectrometer. Lenses and diffraction gratings were also printed and characterized. The focal length of the printed lenses agreed with predictions based on the thin lens equation. The periodicity and effective slit width of the printed gratings were determined from both optical micrographs and fits to the Fraunhofer diffraction equation. This study aims to demonstrate the advantages offered by a layer-by-layer DLP printing process for the manufacture of optical components for use in the visible region of the electromagnetic spectrum.Design/methodology/approachA 3D printer was used to print both lenses and diffraction gratings from Standard Clear PR48 photocurable resin. The manufacturing process of the lenses and the diffraction gratings differ mainly in the printing angle with respect to the printer x-y-axes. The transmission diffraction gratings studied here were manufactured with nominal periodicities of 10, 25 and 50 µm. The aim of this study was to optically determine the effective values for the distance between slits, d, and the effective width of the slits, w, and to compare these values with the printed layer thickness.FindingsThe normalized diffraction patterns measured in this experiment for the printed gratings with layer thickness of 10, 25 and 50 µm are shown by the solid dots in Figures 8(a)-(c). Also shown as a red solid line are the fits to the experimental diffraction data. The effective values of d and w obtained from fitting the data are compared to the nominal layer thickness of the printed gratings. The effective distance between slits required to fit the diffraction patterns are well approximated by the printed layer thickness to within 14, 4 and 16 per cent for gratings with a nominal 10, 25 and 50 µm layer thickness, respectively.Research limitations/implicationsChromatic aberration is present in all polymer lenses, and the authors have not attempted to characterize it in this study. These materials could be used for achromatic lenses if paired with a crown-type material in an achromatic doublet configuration, because this would correct the chromatic aberration issues. It is worthwhile to compare the per cent transmission in cured PR48 resin (approximately 80 per cent) to the percent transmission found in common optical materials like BK7 (approximately 92 per cent) over the visible region. The authors attribute the lower transmission in PR48 to a combination of surface scattering and increased absorption. At the present time, the authors do not know what fraction of the lower transmission is related to the surface quality resulting from sample polishing.Practical implicationsThere are inherent limitations to the 3D manufacturing process that affect the performance of lenses. Approximations to a curved surface in the design software, the printing resolution of the Autodesk Ember printer and the anisotropy due to printing in layers are believed to be the main issues. The performance of the lenses is also affected by internal imperfections in the printed material, in particular the presence of bubbles and the inclusion of debris like dust or fibers suspended in air. In addition, the absorption of wavelengths in the blue/ultraviolet produces an undesirable yellowing in any printed part.Originality/valueOne of the most interesting results from this study was the manufacture of diffraction gratings using 3D printing. An analysis of the diffraction pattern produced by these printed gratings yielded estimates for the slit periodicity and effective slit width. These gratings are unique because the effective slit width fills the entire volume of the printed part. This aspect makes it possible to integrate two or more optical devices in a single printed part. For example, a lens combined with a diffraction grating now becomes possible.

Measurements of slit-width effects in Young’s double-slit experiment for a partially-coherent source

We provide measurements of Young’s double-slit experiment using a partially-coherent light source consisting of a helium-neon laser incident on a rotating piece of white paper. The data allow a quantitative comparison with both the standard theory that does not account for the width of the slits, and a full, analytic model that does. The data agree much more favorably with the full calculation.

Effects of slit width on water permeation through graphene membrane by molecular dynamics simulations

Graphene membranes can be used for nanoscale filtration to remove atoms and are expected to be used for separation. To realize high-permeability and high-filtration performance, we must understand the flow configuration in the nanochannels. In this study, we investigated the applicability of continuum-dynamics laws to water flow through a graphene slit. We calculated the permeability of the flow through a slit using classical molecular dynamics (MD) and compared the MD simulation results for different Knudsen numbers (Kn) to predictions based on the no-slip model and slip model. Consequently, the flow through the graphene nanoslit was treated as slip flow only in the range of Kn < 0.375. This study provides guidelines for the development of graphene filtration membranes.

Experimental study of the effect of slit width and slit spacing on the thermal performance of slit-glazed collectors

An experimental study on the thermal performance of slit-glazed collectors was conducted. Here, glass panes were used as slit glazing cover, and the air was blown continuously through the gaps betw...

Vascularization and innervation of slits within polydimethylsiloxane sheets in the subcutaneous space of athymic nude mice

Success of cell therapy in avascular sites will depend on providing sufficient blood supply to transplanted tissues. A popular strategy of providing blood supply is to embed cells within a functionalized hydrogel implanted within the host to stimulate neovascularization. However, hydrogel systems are not always amenable for removal post-transplantation; thus, it may be advantageous to implant a device that contains cells while also providing access to the circulation so retrieval is possible. Here we investigate one instance of providing access to a vessel network, a thin sheet with through-cut slits, and determine if it can be vascularized from autologous materials. We compared the effect of slit width on vascularization of a thin sheet following subcutaneous implantation into an animal model. Polydimethylsiloxane sheets with varying slit widths (approximately 150, 300, 500, or 1500 µm) were fabricated from three-dimensional printed molds. Subcutaneous implantation of sheets in immunodeficient mice revealed that smaller slit widths have evidence of angiogenesis and new tissue growth, while larger slit widths contain native mature tissue squeezing into the space. Our results show that engineered slit sheets may provide a simple approach to cell transplantation by providing a prevascularized and innervated environment.

The effect of gas pressure and slit width on the high order harmonic generation in helium-filled slab waveguide

We measured the dependence of the intensity of high harmonics on the gas pressure in slab waveguide. The phase matching of 61st high harmonic was obtained according to the quadratic dependence of the increase in efficiency with pressure. For higher order harmonics such as H91, periodic oscillations of the harmonic intensity with gas pressure was observed. We also studied the effect of the slit width of the slab waveguide on the high harmonics generation. The influence of the slit width on laser transverse mode and phase mismatching conditions can be used to explain this effect.

Plasmonic Bandgap in 1D Metallic Nanostructured Devices

This research work reports the excitation of surface plasmon polaritons (SPPs) in a 1D grating device in a gold film on glass substrate. Various grating structures have been modelled using finite element analysis (FEA) in comsol RF module. The periodicity in such devices remains constant, whereas slit width is changed for each structure. We have studied the effects of slit width on SPP resonances and formation of the plasmonic bandgap. The trend shows that bandgap energy increases with increasing slit width and reaches a maximum value for slit width nearly equal to half of the periodicity in the grating structure and then decreases which is a new and important observation. The possible reason for this optimum value of the slit width corresponds to the absence of higher plasmonic modes and the sinusoidal nature of the slit.