Slit Height Research Articles

Robust global optimization of plasmonic filter based on Q factor analysis using graded index

Abstract To reduce the impact of uncertainties in various manufacturing processes while maintaining satisfactory performance level, we propose a robust global optimization approach for plasmonic filters based on extraordinary optical transmission by use of Q factor analysis with reasonable computational cost. The gradient index is employed as a metric for robustness, and the multiobjective genetic algorithm is selected as a global optimization tool. The figures of merit and gradient index are chosen as two objective functions with the design variables being the slit width, slit height, and period of the slit array, respectively. The finite element method is employed to investigate a variety of optical properties rigorously. The numerical optimization results demonstrate that the proposed approach provides improved effectiveness and efficiency in designing plasmonic filters under fabrication uncertainties by using Q factor analysis. The method proposed in this study enables systematic robust optimization while accounting for manufacturing uncertainties, which would be infeasible under typical time constraints. Specifically, within the proposed optimization framework, Q factor analysis can be employed due to a 20.60-times reduction in computational time. To the best of our knowledge, this represents the first robust optimization design for enhanced filter performance based on Q factor analysis in EOT, necessitating comprehensive spectrum calculations alongside fabrication tolerance considerations.

Design and simulation of a new type of fin-and-tube heat exchanger with trapezoidal slit fins

Slit fin-and-tube heat exchangers are extensively utilized in industry. The design of fin structure is crucial for improving the performance of heat exchanger and reducing energy losses. In this study, a new type of fin-and-tube heat exchanger with trapezoidal slit fins was proposed in this study. To determine the performance of the fins, physical and mathematical models of heat exchanger with the fin spacing Fp of 2.65 mm were established. The effects of structural parameters on heat exchanger performance were investigated by numerical simulation, which includes the slit height Sh, slit width Sw, transverse tube spacing Pt, and longitudinal tube spacing Pl. The effects of the four structural parameters on the comprehensive performance were analyzed by the evaluation index. The results revealed that the comprehensive performance of trapezoidal slit fins had increased by 9.6 % compared to flat fins. Furthermore, the influence degree of structural parameters on heat transfer performance was obtained based through the orthogonal experiments. The order of influence degree was as follows: Pl > Pt > Sh > Sw. Additionally, the optimal parameter combination was also obtained as follows: Sh = 1.47 mm, Pt = 42 mm, Pl = 27.5 mm, and Sw = 4 mm.

Ecological lifestyle and gill slit height across sharks.

Metabolic morphology-the morphological features related to metabolic rate-offers broad comparative insights into the physiological performance and ecological function of species. However, some metabolic morphological traits, such as gill surface area, require costly and lethal sampling. Measurements of gill slit height from anatomically accurate drawings, such as those in field guides, offer the opportunity to understand physiological and ecological function without the need for lethal sampling. Here, we examine the relationship between gill slit height and each of the three traits that comprise ecological lifestyle: activity, maximum body size, and depth across nearly all sharks (n = 455). We find that gill slit heights are positively related to activity (measured by the aspect ratio of the caudal fin) and maximum size but negatively related to depth. Overall, gill slit height is best explained by the suite of ecological lifestyle traits rather than any single trait. These results suggest that more active, larger and shallower species (and endothermic species) have higher metabolic throughput as indexed by gill slit height (oxygen uptake) and ecological lifestyle (oxygen expenditure). We show that meaningful ecophysiological relationships can be revealed through measurable metabolic morphological traits from anatomically accurate drawings, which offers the opportunity to estimate class-wide traits for analyses of life history theory and the relationship between biodiversity and ecological function.

Spray characteristics of a multi-slit type throttleable pintle injector with different slit heights

A pintle injector is a type of variable-area injector that has been effectively applied in throttleable rocket engines. Among the several types of pintle injectors, multi-slit type pintle injectors are advantageous in terms of combustion efficiency and suitability for continuous throttling. However, the spray characteristics of multi-slit type pintle injectors have been rarely investigated. Therefore, spray characteristics such as pressure drop, spray angle, and droplet size for a multi-slit type pintle injector were analyzed in this study based on slit height and throttling level. Cold flow experiments and numerical simulations using two types of pintle tips with different slit heights were conducted under a wide throttling range of 20–100 %. The experimental and numerical results indicated that adopting a vertically heightened slit significantly reduces the pressure drop, spray angle, and droplet size at high throttling levels, which can be beneficial in terms of combustion performance and combustion chamber durability. Moreover, changes in spray characteristics over a wide range of throttling levels can be alleviated by applying a vertically heightened slit. The numerical simulation models used in this study were validated such that these could be applied to predict the spray characteristics of multi-slit type pintle injectors.

Active control of sound transmission through a floor-level slit.

The floor-level slit between the door and the floor is one weak point in building noise insulation. In this paper, an active noise control system is proposed to reduce the sound transmission through a floor-level slit with evenly distributed secondary sources on its top boundary. The system performance is first investigated based on the analytical and numerical models, and simulation results indicate a decrease in active control performance with increasing frequency. The upper limit frequency of 10 dB effective control increases with a higher number of secondary sources, and the corresponding wavelength of the upper limit frequency is approximately the interval between the secondary sources when a plane wave is incident normally. Although the upper limit frequency decreases with the slit height, it approaches a constant when the slit height becomes significantly smaller than the wavelength in the incident sound. The experimental results based on a typical floor-level door slit support the findings in the numerical simulations. For a slit with a width of 0.9 m and a height of 0.005 m, the upper limit frequency of 10 dB noise reduction can reach up to 2830 Hz when ten secondary sources are employed in the experiments.

Study on the clogging mechanism of punching screen in sand control by the punching structure parameters

As an independent sand control unit or a common protective shell of a high-quality screen, the punching screen is the outermost sand retaining unit of the sand control pipe which is used in geothermal well or oil and gas well. However, most screens only consider the influence of the internal sand retaining medium parameters in the sand control performance design while ignoring the influence of the plugging of the punching screen on the overall sand retaining performance of the screen. To explore the clogging mechanism of the punching screen, this paper established the clogging mechanism calculation model of a single punching screen sand control unit by using the computational fluid mechanics-discrete element method (CFD-DEM) combined method. According to the combined motion of particles and fluids, the influence of the internal flow state on particle motion and accumulation was analyzed. The results showed that (1) the clogging process of the punching sand control unit is divided into three stages: initial clogging, aggravation of clogging and stability of clogging. In the initial stage of blockage, coarse particles form a loose bridge structure, and blockage often occurs preferentially at the streamline gathering place below chamfering inside the sand control unit. In the stage of blockage intensification, the particle mass develops into a relatively complete sand bridge, which develops from both ends of the opening to the center of the opening. In the stable plugging stage, the sand deposits show a “fan shape” and form a “V-shaped” gully inside the punching slot element. (2) Under a certain reservoir particle-size distribution, The slit length and opening height have a large influence on the permeability and blockage rate, while the slit width size has little influence on the permeability and blockage rate. The microscopic clogging mechanism and its law of the punching screen prevention unit are proposed in this study, which has some field guidance significance for the design of punching screen and sand prevention selection.

Molecular insight into minimum miscibility pressure estimation of shale oil/CO2 in organic nanopores using CO2 huff-n-puff

CO2-enhanced oil recovery (EOR) has been regarded as an essential means of tertiary oil recovery worldwide, which has been gradually applied in exploiting shale oil and gas resources. In this study, we proposed a new method to estimate the MMP (minimum miscibility pressure) of shale oil/CO2 systems using huff-n-puff molecular dynamics (MD) simulations. The bulk MMP of the shale oil/CO2 system obtained agrees reasonably well with the vanishing interfacial tension (VIT) and the available experimental results. The organic nanopore oil reservoir is modeled with graphene as a substrate and octane molecules as shale oil. We found that oil recovery increases up to near miscible pressure and plateaus after that. The oil recovery increases with the rise of the reservoir temperature and slit height. Due to the nanopore’s confinement effect, the predicted MMP is lower inside the nanopore than the bulk counterpart. The MMP inside the nanopore decreases with a slit height up to a specific size and then starts to climb up due to the increased adsorption effect of nanopore walls. It means that CO2 flooding will be more efficient in shale oil reservoirs with more prominent pores and throats. Some CO2 molecules remain inside the nanopore after the completion of the huff-n-puff process. Like the oil recovery, the amount of CO2 trapped inside the pore after the huff-n-puff procedure plateaus after some critical pressure. So, CO2 huff-n-puff has two benefits — oil recovery and carbon sequestration. Our method of simulating huff-n-puff using MD can be a quick and economic supplement to the CO2-EOR experiments, which might benefit the development of shale oil reservoirs.

Design approach for plasmonic filter using Q factor analysis

An efficient design method for plasmonic devices composed of a periodic slit array based on extraordinary optical transmission is proposed using Q factor analysis. The proposed method significantly reduces the required computation time for cavity resonance in slits by calculating the Q factor at a single frequency that is an eigenfrequency of the wave equation instead of computing the entire transmissions. The computation time is reduced by 20.60 times, and the device performance is increased by 2.43 times through a design based on Q factor analysis. The figure of merit for the overall performance is defined as a product of the transmission peak value and the Q factor. The design variables are the slit width, slit height, and period of slit array. The optical field distributions are calculated numerically using the finite element method, and the Q factor is obtained by solving an eigenfrequency for the wave equation for dispersive media.

Heat Transfer Slot Matrix for Compact Rotary Heat Exchangers with Ultra-High Regeneration Ratio for Microturbines

This paper considers the problem of the influence of distancing elements in slot matrix channels on the thermohydraulic characteristics of the matrix of a rotary heat exchanger having various values of the height of the slot channels. The following tasks were carried out: mathematical modeling of thermohydraulic processes in different slot channels having constant height along them (from 0.3 mm to 0.5 mm); analysis of the influence of the slit channels' height, the number of distancing elements in rows, the distance between rows and the total number of elements on the average value of the Nusselt number and on the pressure drop; analysis of the effect of changes in speed and temperature conditions on thermal and hydraulic characteristics. The most important results are the following facts: the influence of the relative location of the distancing elements on the thermohydraulic characteristics of the flow is negligible; changes in the temperature and speed regime of the laminar flow practically does not affect the intensity of convection in the matrix channels; an increase in the height of the slot channel leads to a relatively small decrease in the average value of the Nusselt number. The significance of the results obtained is that they can be the basis for adjusting the methods of design calculations of rotary heat exchangers taking into account the decrease in thermal efficiency caused by the presence of distancing elements in the channels of their matrices. Recommendations can be made to minimize the number of distancing elements without considering their mutual location.

Small telescopes being effective: MAGIC or not?

Abstract The paper describes the MAGIC multimode focal reducer (Monitoring of Active Galaxies by Investigation of their Cores), commissioned on the 1-m Zeiss-1000 telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences in 2020 September. Three observational modes are currently realized: photometry, polarimetry, and long-slit spectroscopy. Reducing the focal length makes it possible to obtain a sufficiently large field of view for photometry and a large slit height for spectroscopy of ∼12′ , as well as a large field of view for polarimetry with a quadrupole Wollaston prism of ∼6${_{.}^{\prime}}$4. This feature makes the complex study of extended nebulae and galaxies efficient. The MAGIC capabilities are presented in examples of observations of various astronomical objects. The spectral mode in the range of 4000–7200 ÅÅ provides the spectral resolution R ∼ 1000; for a starlike target up to 14 mag in medium-band filters with a seeing of 1″ for 20 min of total exposure, the photometry accuracy is better than 0.01 mag and the polarization accuracy is better than 0.6 per cent. Especially for the new focal reducer, an offset guide and a position angle rotation system were implemented. The results of the modernization of the baffle system in the optical scheme of the telescope for the suppression of scattered light are also described.

Finite Element Analysis of Restraint Intensities and Welding Residual Stresses in the Ti80 T-Joints

The restraint intensity of Ti80 T-joints was investigated using finite element analyses. The influence of slit height, vertical plate thickness and base plate thickness was studied, respectively. Results show that the slit height and vertical plate thickness have a significant impact, while the effect of base plate thickness is negligible. A prediction model of restraint intensity was constructed through binary linear regression; the error was estimated at about 10%. Then, finite element simulations were carried out to study the welding residual stresses of specimens with different restraint intensities. The results show that residual stresses on the backing weld surface are higher in the middle and lower at both ends, while the weld root shows opposite results. In general, stresses at the weld root are greater than those on the weld surface. The mean value of the residual stress at the weld root increases with the increase in restraint intensity but not uniformly, i.e., it is slow at first and then it increases rapidly. A prediction model of the residual stress was produced through cubic fitting, and the errors between the finite element simulations and predictions were about 8%. Using the prediction model, the residual stress of actual Ti80 alloy workpieces can be estimated before welding, and a corresponding strategy for avoiding cracks can be generated.

Transmission loss and directivity of sound transmitted through a slit on ground.

An analytical model is proposed for sound transmission through a slit on a rigid ground based on the modal superposition method to investigate the transmission loss (TL). A simple formula is derived for estimation of the TL for plane waves with and without the ground, which gives a more precise prediction than existing approaches. It is found that a larger slit height generally decreases the TL, except at the resonant frequencies of the slit. The slit width has little effect on the TL at high frequencies, and the slit depth affects the resonant frequencies significantly even though it has little effect on the overall TL. Compared with the same size slit in the free field, the rigid ground reduces the TL at most frequencies, and that reduction is a constant between 3 and 9 dB in the low frequency range. It is also found that the sound transmitted through the slit is almost omnidirectional at low frequencies, while most of the sound energy at high frequencies falls within the range where the long side of the slit is located. The experimental results demonstrate the validity of the analytical model and the findings in numerical simulations.

Effect of slit height on the spectral resolution of a monochromator

The predecessor of China Optics was China Optics and Applied Optics Digest, which was founded in 1985. At that time, it was the only retrieval journal in the field of optics in China. At the end of 2008, China Optics and Applied Optics Digest was renamed

Photocatalytic NOx abatement: The effect of high air flow velocity

In the literature, the abatement of nitrogen oxide (NOx) emissions by photocatalysis is rarely carried out at real-world air flow velocities. Here, we investigated the performance of two commercial photocatalysts, Aeroxide® TiO 2 P25 (Evonik Industries, Germany) and FN NANO®2 (Advanced Materials-JTJ, Czech Republic), P25 containing 88 % anatase and 12 % rutile, while FN 2 moreover 13 % of a binder. The degradation of NOx pollutants (0.1 and 1.0 ppmv) at air flow velocities ranging from 0.02 to 0.7 m s−1 was tested, the photocatalytic efficiency being determined for various slit heights (5–25 mm) and rate of volume flow (1500–11 000 cm 3 min−1). The photocatalysts achieved substantial NO and NO2 abatement. Pollutant conversion decreased as the air flow velocity increased, with the highest conversion (80%) occurring at 0.1 m s−1. The NOx conversions were slightly higher for NO than for NO2, and significantly higher for the NO concentration of 0.1 ppmv. Slit height had a negligible effect, indicating a substantial degree of mixing in the direction perpendicular to the flow; consequently, the flow cannot be laminar in nature as the ISO standard (22197-1:2016) states. This finding is supported by the nanoindentation technique showing that the surface roughness contributed to the formation of vortexes and enhancement of the mass transport. To our best knowledge, this is the first study to test commercial photocatalysts under such a wide range of air velocities and, in doing so, it has identified considerable implications for outdoor air purification.

Redescription of the longnose houndshark Iago garricki (Carcharhiniformes: Triakidae), based on specimens recently collected from the South China Sea

The longnose houndshark, Iago garricki Fourmanoir & Rivaton 1979, was described based on five specimens collected from Vanuatu. Five additional specimens were recently collected from the waters off Dongsha Atoll, South China Sea. A redescription of this species is provided based on the holotype, non-types collected near the type locality and off Dongsha Atoll. The species is characterized by eye length larger than gill slit height; first dorsal-fin origin not reaching a vertical line through pectoral-fin base; head length 20.2-22.2% TL; preoral length 7.2-8.3% TL; upper labial furrow 2.2-3.4% TL; lateral teeth with 1-3 small cusplets on lateral side basally; diplospondylous centra 53-61; precaudal centra 94-102; and total centra 149-157. The specimens collected from the South China Sea represent the northernmost distributional record of this species.

Time-varying stability and vibration properties of a pyrotechnic ejection plate in narrow space

This work simulates the pyrotechnic launch process which is commonly seen in aerospace engineering, and the dynamic responses of the projectile during pyrotechnic ejection are analyzed by studying the aeroelastic stability and nonlinear vibration of a rectangular plate subjected to time-varying axial blast load in a narrow space. During the launch, the plate is accelerated under the explosion effect, which makes the plate and airflow in narrow space a complicated time-varying fluid structure interaction system. The change of the plate velocity is derived from the momentum theorem. Considering the Von Karman nonlinear thin plate theory and the linear potential flow theory, the governing equation of the pyrotechnic ejection plate in narrow space is established. In the process of solving the equation, the Hamilton’s principle and the assumed mode method are employed. By applying the generalized eigenvalue method to linear time-varying system, the variations of the natural frequencies of the plate during pyrotechnic ejection are studied, from which the stability mechanism of the system is obtained. For nonlinear vibration of the system, the displacement time responses of the plate during pyrotechnic ejection are discussed by employing the Runge-Kutta method. From the results, the plate loses stability rapidly when the explosion occurs, and then with the increase of the velocity of the plate, the plate exhibits the flutter instability. In the process of pyrotechnic ejection, the amplitude jumping phenomenon of the plate is observed. Besides, the explosion strengthen, explosion position, slit height and aspect ratio of the plate have significant effects on the stability and displacement jumping amplitude of the pyrotechnic ejection plate.

Distribution of the Fraunhofer Diffraction Intensity by a Rectangular Slit Using a Razor Blade

This research was conducted by making a rectangular slit using a razor blade as a narrow gap in the Fraunhofer diffraction experiment. The intensity distribution measurement on the resulting diffraction pattern uses a voltage divider circuit. This circuit takes advantage of the nature of the LDR, which changes resistance when exposed to light. Experiments show that a diffraction pattern screen when a 560 nm coherent light passes through a narrow rectangular slit made of razor cut. We measured the narrow gap using a tracker application with the resulting gap size (0.3564 x 0.4677) mm. The ratio of the intensity distribution of the x-axis bright pattern on the Fraunhofer diffraction by a rectangular slit with slit size height x width = (0.4677 x 0.3564) mm from b = -5p to 5p (maximum 4, maximum 3, maximum 2, maximum 1, central maximum, maximum 1, maximum 2, maximum 3, maximum 4) is 0.000873; 0.000763; 0.005395; 0.020583; 1; 0.039658; 0.008088; 0.002554; 0.001218. The ratio of the intensity distribution of the y-axis bright pattern on the Fraunhofer diffraction by a rectangular slit with slit size height x width = (0.4677 x 0.3564) mm from g = -5p to 5p (maximum 4, maximum 3, maximum 2, maximum 1, central maximum, maximum 1, maximum 2, maximum 3, maximum 4) is 0.001890; 0.001469; 0.002447; 0.040516; 1; 0.037141; 0.006482; 0.001690; 0.000440. This study indicates that diffraction experiments and the measurement of the diffraction pattern’s intensity can be carried out with simple materials and equipment and can be used in the correct experiment.

Quantifying the effects of slit confinement on polymer knots using the tube model.

Knots can spontaneously form in DNA, proteins, and other polymers and affect their properties. These knots often experience spatial confinement in biological systems and experiments. While confinement dramatically affects the knot behavior, the physical mechanisms underlying the confinement effects are not fully understood. In this work, we provide a simple physical picture of the polymer knots in slit confinement using the tube model. In the tube model, the polymer segments in the knot core are assumed to be confined in a virtual tube due to the topological restriction. We first perform Monte Carlo simulation of a flexible knotted chain confined in a slit. We find that with the decrease of the slit height from H=+∞ (the 3D case) to H=2a (the 2D case), the most probable knot size L_{knot}^{*} dramatically shrinks from (L_{knot}^{*})_{3D}≈140a to (L_{knot}^{*})_{2D}≈26a, where a is the monomer diameter of the flexible chain. Then we quantitatively explain the confinement-induced knot shrinking and knot deformation using the tube model. Our results for H=2a can be applied to a polymer knot on a surface, which resembles DNA knots measured by atomic force microscopy under the conditions that DNA molecules are weakly absorbed on the surface and reach equilibrium 2D conformations. This work demonstrates the effectiveness of the tube model in understanding polymer knots.

Diffusion of Short Semiflexible DNA Polymer Chains in Strong and Moderate Confinement.

In many technological applications, DNA is confined within nanoenvironments that are smaller than the size of the unconfined polymer in solution. However, the dependence of the diffusion coefficient on molecular weight and characteristic confinement dimension remains poorly understood in this regime. Here, convex lens-induced confinement (CLiC) was leveraged to examine how the diffusion of short DNA fragments varied as a function of slit height by using single-molecule fluorescence tracking microscopy. The diffusion coefficient followed approximate power law behavior versus confinement height, with exponents of 0.27 ± 0.01, 0.32 ± 0.02, and 0.42 ± 0.06 for 692, 1343, and 2686 base pair chains, respectively. The weak dependence on slit height suggests that shorter semiflexible chains may adopt increasingly rodlike conformations and therefore experience weaker excluded-volume interactions as the confinement dimension is reduced. The diffusion coefficient versus molecular weight also exhibited apparent power law behavior, with exponents that varied slightly (from -0.89 to -0.85) with slit height, consistent with hydrodynamic interactions intermediate between Rouse and Zimm model predictions.

Impact of the Weir Slit Location, the Flow Intensity and the Bed Sand on the Scouring Area and Depth at the Dam Upstream

A total of 48 experiments were conducted to investigate the impact of slit weir dimensions and locations on the maximum scour depth and scour area created upstream. The slit weir model was a 110 mm slit opening, and it was installed at the end of the working section in a laboratory flume. The flume was 10.0 m long, 30 cm wide, 30 cm deep, and almost middle. It includes a 2 m working section with a mobile bed with 110 mm in thickness. In the mobile bed, two types of nonuniform sand (with a geometric standard deviation of 1.58 and 1.6) were tested separately. The weir dimensions and location were changed with flow rates. Then dimensions of the slit weir were changed from 60 x 110 mm to 60 x 70 mm (width x height), while the location of the slit weir was changed from the center of the flume to its side. Finally, the flow rates were changed from 2.6 to 8 l/s. The maximum value of scour depth and scour area was recorded 72 mm and 32357 mm2 when the slit height, the flow rate, D50 of the movable bed were 110 mm, 8 l/s, 0.3 mm, respectively.