Slit Spacing Research Articles

Computational Fluid Dynamics of a Corrugated Plate-and-Frame Heat Exchanger Used for Ocean Thermal-Energy Conversion

AbstractComputational fluid dynamics (CFD) simulations were employed in this paper to analyze the dynamic flow patterns within extremely thin slit spaces of two corrugated heat exchanger (HEx) plat...

Measurement of Thermal expansion coefficient of solid Materials by double slit Interferometric method

Thermal expansion coefficient is a regular coefficient to describe the variation of geometric characteristics of matter under the action of thermal expansion and cold shrinkage effect, and it is an important index to measure the thermal stability of materials. A device for measuring the thermal expansion coefficient of solid materials by Yang’s double slit interferometric method with variable double slit spacing is mainly composed of laser, sliding Young double slit structure, temperature measuring and controlling instrument, shading tube, receiving device and solid material to be measured. The solid material is heated by ring heater, the temperature of solid material is displayed and controlled by temperature measuring and controlling instrument, and the change of stripe spacing is recorded by linear CCD image sensor. Compared with the traditional optical leverage method, this measuring device and method can significantly improve the accuracy of the measurement results and reduce the uncertainty of the measurement results.

Enhancements of preparation efficiency and magnetic properties for Fe-based amorphous magnetic flake powder cores upon the adoption of a novel double-paralleled slits nozzle

The thick and brittle amorphous ribbons with the maximum thickness up to 58 μm were successfully fabricated using melt-spinning method upon the adoption of a novel double-paralleled slits nozzle (DPSN). The magnetic properties of the two magnetic flake powder cores (MFPCs) prepared from the conventional thin ribbon pulverization and the thick ribbon pulverization were analyzed and compared. Hereinto, a coupling model of fluid flow with free surface and surface tension, and heat transfer with phase transform was developed to design the slit spacing for the DPSN, and sol-gel method was employed to create SiO2 insulation layer on the surfaces of the magnetic flake powders to improve electrical resistivity. Results show that a quasi-steady-state can be reached for the puddle with the upstream and downstream menisci in crescent and slope shapes, respectively, by adopting the DPSN with slit spaces of 2.0 mm and 2.5 mm. The embrittlement process for the conventional thin ribbon can be omitted to enhance the efficiency of the powder preparation when using the thick ribbon before the ribbon pulverization. The MFPCs fabricated using the thick amorphous ribbon pulverization exhibit a higher permeability of 65.27, lower total core loss with the frequency being less than 234 kHz for Bm = 0.08 T, and a better DC-bias property of 70.97% as compared to the MFPCs made from the conventional thin amorphous ribbon pulverization. This work provides a promising approach to further development of Fe-based amorphous MFPCs with high preparation efficiency and excellent magnetic properties at the frequency below 234 kHz.

Slit structures: Fundamental mechanisms of mechanical trapping of granular flows

Slit-structures are rigid structures with one or more slits. To retard steep-creek hazards, slit-structures are sometimes installed to reduce the peak discharge, as well as to mechanically trap grains for frictional flows. However, designs are empirical. It is not possible to assess whether boulders will be trapped, or if smaller discharge of harmless flow material can pass downstream. This study starts by reviewing the inherent difficulties of characterising mechanical trapping processes for granular flows. A calibrated Discrete Element Method (DEM) model is then used to conduct a parametric study of the number of slits, the slit spacing, the Froude number and the ratio between grain and slit size. Results from the DEM study allow three interaction regions to be identified: ‘self-cleaning’, ‘unstable’ and ‘trapping’. These regimes are extremely sensitive to the slit number, width and spacing, as well as the Froude number. This study shows that existing recommendations may coincide with the unstable region. However, the unstable region should be avoided because of unpredictable trapping behaviour. Additionally, increasing the slit spacing can increase material trapping because of an increase in the duration of binary grain contacts. This increase in the slit spacing tends to prevent shear transmission from slit to slit. Narrowly-spaced double slits may be most effective at the controlling outflow rate whilst enabling ‘self-cleaning’.

The complement of a subspace in a classical polar space

In a polar space, embeddable into a projective space, we fix a subspace, that is contained in some hyperplane. The complement of that subspace resembles a slit space or a semiaffine space. We prove that under some assumptions the ambient polar space can be recovered in this complement.

CMOS Light Field Image Sensor Building Block for Detection of Multicolor LED Blink Sequence From Heterogeneous Locations

A light field image sensor is fabricated on a standard complementary metal–oxide-semiconductor (CMOS) process. The sensor uses two grating layers of various layer-to-layer distances to take advantage of Talbot effect. The horizontal placement of the upper grating relative to the lower one has three types of configurations. By shifting the upper grating to the left or right or aligned position relative to the lower grating, light incident from left, right, and center can be differentiated. Furthermore, color selectivity is analyzed by varying grating slit spacing to favor a particular color’s wavelength to reach Talbot depth. We designed photodiodes each having area of $14\times15\,\,\mu {\mathrm{ m}}^{2}$ . We used a 180-nm five-metal CMOS process and achieved an angle differentiation accuracy error within 1.8° for the direct incidence on aligned configuration and within 3.6° of the expected angle for the left- and right-shifted configurations. In addition, we experimented with applying various wavelengths of light even to sensor structures favoring other wavelengths to analyze their effects. Combining these sensor characteristics, we show that red, green, and blue lights, clustered together at three different locations, can be recognized by a set of light field sensors. The sensor set can differentiate 6 different combinations of 3 different color blink sequences per cluster location, thus totaling 18 types of spatial temporal signals. Moreover, repeated measurements showed good immunity to noise. The standard deviation of the measured results between each repetition was less than 5 mV.

Natural and Technogenic Mineral Formation in the Aquifer of the Amur-Tunguska Interfluves

Changes in mineralogical composition occurring in the course of preparation of drinking water in-situ are studied based on the data from the monitoring wells of the Tunguska groundwater intake. Intensive dissolution of feldspars, pyroxenes, siderite, and, to a lesser extent, quartz with the formation of secondary minerals (amorphous silica, clay minerals, and secondary siderite) occur in the aquifer of the Tunguska intake. In addition, solid products of the destruction are formed, including microfragments of minerals, which together with the primary clay, secondary minerals, and oxides and hydroxides of iron and manganese that originated in the process of intralayer oxidation of water, participate in the colmatation of cracks and the slit space of the well filters. Regeneration actions result only in a partial recovery of the specific flow rate of the wells, since the hydrochloric acid used in them leaches only the oxide–hydroxide part of the colmatant, leaving virtually unchanged its aluminosilicate component.

Tunable terahertz guided-mode resonance filter with a variable grating period.

A variable grating period made of quartz has been applied to fabricate a tunable guided mode resonance (TGMR) filter with transverse-electric (TE) and -magnetic (TM) modes in the terahertz (THz) region. We prepared three TGMR filters with grating periods of 5.0, 3.3, and 1.7 μm/mm over the length of the filter. For the 5.0 μm/mm, the resolution of resonance frequency shift of the TE0,1, TE1.1, and TM0,1 was 3.6, 4.0, and 3.4 GHz/mm, respectively. With a metal slit spacing of 2 mm located in front of the TGMR filter, the movable range of the TGMR was 24 mm, and the resonance frequency could be shifted up to 87, 96, and 82 GHz, where the center frequencies of each resonance were 0.402, 0.579, and 0.460 THz, for the TE0,1, TE1.1, and TM0,1, respectively. Furthermore, because the TGMR and guided mode resonance (GMR) filters are placed independently in the THz beam path, both tunable and fixed resonances can be obtained at the same time in the spectrum.

Characteristics and simplified model of film slit irrigation

ABSTRACTResearch on the factors affecting the characteristics of film slit irrigation has not received sufficient attention, although this is a wide-adopted irrigation technology. Infiltration modelling based on fewer factors deserves priority in the field studies. A laboratory theoretical study was conducted to investigate the simulated effects of SWMS-2D (simulating water movement through soil in two-dimensional) on soil moisture and cumulative infiltration of film slit irrigation. Error analyses indicated that SWMS-2D was suitable for infiltration simulation. Besides, SWMS-2D was applied to investigate the cumulative infiltration affected by soil texture, initial soil moisture, irrigation water depth, soil structure, opening ratio (ρ), and film slit width (d) and spacing. Results showed that for a certain soil, initial soil moisture and irrigation water depth had the poorest effects, whereas ρ and d had the strongest effects on cumulative infiltration among the 6 influencing factors. Furthermore, a simplified model with only ρ and d was proposed and verified by 3 soil types, which indicated that the proposed double-factor model can be employed for cumulative infiltration estimation under film slit irrigation, due to small mean absolute error of 1.03–3.13 mm, root mean square error of 1.24–3.80 mm, and high Nash-Sutcliffe coefficient around 1.0.

RAISING ECONOMIC EFFICIENCY OF JACKET TECHNOLOGICAL DEVICES AT THE EXPENSE OF DECREASING METAL-CONSUMING AND POWER-CONSUMING CHARACTERISTICS

The article grounds economic expediency of using jacket thermal exchangers of the sheet-canal type. As a rule steam jackets of technological devices in food industry and catering enterprises have a form of an open slit space and for work under pressure they are made of walls of big thickness, which envisages their high metalconsumption. In contrast to standard slit jackets, sheet-canal panels are a structure made of two thick metal sheets welded by contact electric welding. Heating steam canals are formed between the sheets. Such structure allows us to decrease the wall thickness and therefore to cut metal-consumption and, consequently power-consumption of technological equipment. The article describes the method which could optimize sizes of inter-canal zones of sheetcanal panels used as jackets in devices of thermal treatment of food. In order to cut wall thickness of panels it is proposed to increase the square of inter-canal zones without declining the total thermal flow, which is passed by the panel to the agent being heated. This problem was resolved by the calculation method based on the use of thermal rib efficiency coefficient. The authors made calculations and provided optimal sizes of inter-canal zones in case of altering the wall thickness of jacket thermal exchanger made of chrome-nickel stainless steel of the brand 12X18H9T.

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...

Resolved Simulation of a Granular-Fluid Flow with a Coupled SPH-DCDEM Model

Debris flows represent some of the most relevant phenomena in geomorphological events. Because of the potential destructiveness of such flows, they are the subject of a vast amount of research. This paper addresses the need for a numerical model applicable to granular-fluid mixtures featuring high spatial and temporal resolution, and thus capable of resolving the motion of individual particles, including all interparticle contacts. The DualSPHysics meshless numerical implementation based on smoothed particle hydrodynamics (SPH) is expanded with a distributed-contact discrete-element method (DCDEM) in order to explicitly solve the fluid and solid phases. The specific objective is to test the SPH-DCDEM approach by comparing its results with experimental data. An experimental setup for stony debris flows in a slit check dam is reproduced numerically, where solid material is introduced through a hopper, assuring a constant solid discharge for the considered time interval. With each sediment particle possibly undergoing several simultaneous contacts, thousands of time-evolving interactions are efficiently treated because of the model’s algorithmic structure and the HPC implementation of DualSPHysics. The results, composed of mainly retention curves, are in good agreement with the measurements, correctly reproducing the changes in efficiency with slit spacing and density.

Effective birefringence to analyze sound transmission through a layer with subwavelength slits

We analyze the transmission of sound through a sound hard film or layer with periodic subwavelength slits. For wavelength comparable to or larger than the slit spacing, the transmission spectra are revisited in terms of the transmission through an equivalent birefringent layer. It is shown that the Fano-type resonances can be understood by means of the dispersion relations of guided waves within the birefringent layer in the homogenized problem, equivalent to spoof plasmons for gratings. This is done by extending the homogenization to the evanescent waves being excited in the near field of the actual perforated layer. Nous analysons les spectres de transmission par une lame rigide perforée périodiquement de trous sub-longueur d'onde. Pour des longueurs d'onde comparables ou plus grandes que l'espacement des perforations, les spectres de transmission sont revisités en termes de transmission par une lame équivalente biréfringente. Nous montrons que les résonances de Fano se comprennent au vu des relations de dispersion d'ondes guidées par la couche biréfringente, similaires aux spoof plasmons dans les réseaux en réflexion. Ces relations de dispersion sont obtenues en étendant l'homogénéisation aux ondes évanescentes excitées en champ proche dans le problème réel.

Evolutionary and Ecological Relationships of Gill Slit Morphology in Extant Sharks

One of the defining characteristics of Elasmobranchii is the external gill slits, through which water is expelled during exhalation. The morphology of the gill slits is presumed to vary among elasmobranchs, between ram and suction ventilators, and between pelagic and benthic species. However, the evolution of gill slit morphology and the relationship to behavior and ecology is not clear. The relative length of each slit, relative distance between adjacent pairs of slits, and number of slits positioned over the pectoral fin were quantified in 289 preserved specimens representing 185 species in 69 genera, 28 families, and 8 orders of sharks. Six character states of relative gill slit length, five character states of relative inter-gill slit spacing, and five gill slit positions over the pectoral fin were identified. Character mapping onto a phylogeny reveals that the basal state for extant Selachii is to possess slits of similar relative length and spacing with no slits over the pectoral fin. Multiple character states in various combinations evolved within the Carcharhiniformes, which is the most speciose extant group. Ontogenetic differences in gill slit morphology were found in the 12 genera in which adult and juvenile data were collected. Slit spacing in juveniles has an equal tendency to become more similar or more different in adults, whereas slit length changes more often from more similar in juveniles to increasingly different in adults. Exploring the relationships among gill slit morphology and ventilation mode in modern sharks reveals character complexes that are common to four body types. Macropelagic types are ram ventilators with a longer first slit length, similar slit spacing in most, and no slits over the pectoral fin. Most littoral types are ram ventilators, with decreasing slit length and spacing and with one slit over the fin. Benthic types are suction ventilators with decreasing slit length and spacing and up to four slits over the fin. Bathic and micropelagic types are suction ventilators with no slits over the fin and most having similar slit length and spacing. Morphological differences in gill slit morphology may correspond to hydrodynamic differences in exhaled water from the slits by habitat.

Constructal paddle design with “fingers”

Here, we show how the performance of a paddle that pushes a fluid can be increased by making parallel slits through it. The slit spacing is varied to see its effect on the drag force and the maximum stress in the paddle. The effect of water speed and paddle dimensions is documented. Designs with one or more slits are investigated. The drag force is maximum when the slit spacing matches the boundary layer thickness of the flow through the slit. Furthermore, the drag force is greater when the slit spacing is nonuniform: larger in the central slits than in the peripheral slits. The paddle with slits of one size performs almost as well as the best design with nonuniform spacings. The paddle design with slits achieves the same drag force and maximum stress with less material compared with a paddle without slits.

Effects of interplay between metal subwavelength slits on extraordinary optical transmission

In this paper we study the extraordinary optical transmission of one-dimensional multi-slits in an ideal metal film. The transmissivity is calculated as a function of various structural parameters. The transmissivity oscillates, with the period being just the light wavelength, as a function of the spacing between slits. As the number of slits increases, the transmissivity varies in one of three ways. It can increase, attenuate, or remain basically unchanged, depending on the spacing between slits. Each way is in an oscillatory manner. The slit interaction responsible for the oscillating transmission strength that depends on slit spacing is the subject of more detailed investigation. The interaction most intuitively manifests as a current distribution in the metal surface between slits. We find that this current is attenuated in an oscillating fashion from the slit corners to the center of the region between two adjacent slits, and we present a mathematical expression for its waveform.

D2/H2 quantum sieving in microporous carbons: a theoretical study on the effects of pore size and pressure

The adsorption of hydrogen and deuterium in slit-shaped carbon pores is studied by grand canonical Monte Carlo simulations. All interactions are assumed to be of Lennard–Jones type, while the Feynman–Hibbs expression is used to account for quantum effects. The interaction energy of both isotopes inside the slit pore space is discussed thoroughly. Furthermore, pure component adsorption isotherms of both isotopes were simulated at 77 K for pressures up to 20 bar in slit pores having widths of up to 2.0 nm. According to our simulations, in equilibrium, slit pores reveal slight deuterium selectivity over hydrogen, and this quantum-based selectivity depends both on pressure and pore size.

An almost paracontact structure on a Rizza manifold

We construct a class of framed f ( 3 , − 1 ) -structure on the slit tangent space of a Rizza manifold. In the special case, we show that this class induces on the indicatrix bundle an almost paracontact metric structure.

Note: Electrohydrodynamic atomization of liquid sheet

Novel electrohydrodynamic atomization via liquid sheet is presented herein to produce monodisperse. Instead of multiple capillaries/holes used in previous publication, the spray heads with a circular slit exit, shaping the spray liquid into a thin sheet, were utilized. A number of notches were machined along the outer edge of an annular slit to bifurcate the liquid sheet into multiple jets and anchor them to establish the stable multijet operation. The liquid-sheet electrospray heads with 6, 12, and 20 notches were investigated in this study. It is observed that, for spraying liquids of low electrical conductivity, the maximal liquid flowrate of a 20-notched head is 166 times higher than that of single capillary with an inner diameter the same as the slit spacing of studied heads. The above observation evidences that the liquid-sheet electrospray technique and heads have excellent potential for high mass throughput while keeping the spray head cost low.

Néron models and limits of Abel–Jacobi mappings

AbstractWe show that the limit of a one-parameter admissible normal function with no singularities lies in a non-classical sub-object of the limiting intermediate Jacobian. Using this, we construct a Hausdorff slit analytic space, with complex Lie group fibres, which ‘graphs’ such normal functions. For singular normal functions, an extension of the sub-object by a finite group leads to the Néron models. When the normal function comes from geometry, that is, a family of algebraic cycles on a semistably degenerating family of varieties, its limit may be interpreted via the Abel–Jacobi map on motivic cohomology of the singular fibre, hence via regulators onK-groups of its substrata. Two examples are worked out in detail, for families of 1-cycles on CY and abelian 3-folds, where this produces interesting arithmetic constraints on such limits. We also show how to compute the finite ‘singularity group’ in the geometric setting.