Optimum Aperture Research Articles

Stray light suppression for Thomson scattering diagnostic on linear magnetized plasma device

In Thomson scattering (TS) diagnostic system, the stray light greatly affects the signal-to-noise ratio (SNR). The suppression issue is particularly severe for the low density and low temperature plasma due to very few scattered photons and narrow line broadening. The traditional methods, such as Brewster window, beam dump and transmission pipe with black-coated internal surface, have been adopted in the stray light suppression system on our Linear Magnetized Plasma (LMP) device. Moreover, an assembly of tapered apertures are placed in the optical path. Via numerical simulation, the optimal configuration of the adjustable aperture tube (size, location, and orientation) that provide the best suppression has been found. Numerical results show that the optimal aperture group with 6 mm and 8 mm tapered apertures can maintain over 97% transmission rate of the main laser energy while reducing stray light by 99.6%.

Experimental analysis of vacuum membrane dehumidifier: Hollow fiber module designs and dehumidification performance

The aim of this study was to experimentally investigate the dehumidification performance of the vacuum membrane dehumidifier with the variance of the air-flow channel in hollow fiber modules. A prototype of a vacuum membrane dehumidifier consisting of five membrane modules was fabricated. The air-flow channel of membrane modules was adjusted by changing an aperture ratio of the module housing that facing the outer surface of hollow fibers. As indicators of dehumidification performance, humidity difference, moisture removal rate, and a pressure loss were considered. A total of 12 experiment sets were designed based on four cases of module configurations and three level of air flow rate to investigate dehumidification performance according to the module configurations. The pressure loss in accordance with the air flow rate for each case were also analyzed based on the additional test results. Finally, a multi-objective optimization analysis was conducted to derive optimal aperture ratios to achieve maximum dehumidification performance and minimum pressure loss. The results showed that the membrane dehumidifier presented 1.06–3.02 g/kg of humidity difference and 28.1–81.8 g/h of moisture removal rate according to the variance of aperture ratio and air flow rate. This indicates that the membrane dehumidifier with lower aperture ratio showed higher dehumidification performance but caused higher pressure loss owing to the longer contacting path between process air and membrane. Moreover, the optimum aperture ratio of membrane module was determined to be 0.2–0.271 m2/m2 when providing a higher weight to maximizing the dehumidification performance, while 0.502–0.586 m2/m2 aperture ratio is required when predominantly focusing on minimizing pressure loss.

A method to interpret fracture aperture of rock slope using adaptive shape and unmanned aerial vehicle multi-angle nap-of-the-object photogrammetry

The aperture of natural rock fractures significantly affects the deformation and strength properties of rock masses, as well as the hydrodynamic properties of fractured rock masses. The conventional measurement methods are inadequate for collecting data on high-steep rock slopes in complex mountainous regions. This study establishes a high-resolution three-dimensional model of a rock slope using unmanned aerial vehicle (UAV) multi-angle nap-of-the-object photogrammetry to obtain edge feature points of fractures. Fracture opening morphology is characterized using coordinate projection and transformation. Fracture central axis is determined using vertical measuring lines, allowing for the interpretation of aperture of adaptive fracture shape. The feasibility and reliability of the new method are verified at a construction site of a railway in southeast Tibet, China. The study shows that the fracture aperture has a significant interval effect and size effect. The optimal sampling length for fractures is approximately 0.5–1 m, and the optimal aperture interpretation results can be achieved when the measuring line spacing is 1% of the sampling length. Tensile fractures in the study area generally have larger apertures than shear fractures, and their tendency to increase with slope height is also greater than that of shear fractures. The aperture of tensile fractures is generally positively correlated with their trace length, while the correlation between the aperture of shear fractures and their trace length appears to be weak. Fractures of different orientations exhibit certain differences in their distribution of aperture, but generally follow the forms of normal, log-normal, and gamma distributions. This study provides essential data support for rock and slope stability evaluation, which is of significant practical importance.

The injection-production performance of an enhanced geothermal system considering fracture network complexity and thermo-hydro-mechanical coupling in numerical simulations

The effect of fracture networks on EGS performance remains worth further investigation to guide the formulation of geothermal extraction strategy. We established models that account for thermo-hydraulic-mechanical (THM) coupling and that are based on the framework of discrete fracture network (DFN) to evaluate the heat extraction performance in deep-seated fractured reservoir. Our numerical results reveal that the zones of temperature, pressure, and stress perturbation diffuse asynchronously during the circulation of injection-production, and the stress perturbation always lags behind the other two. Furthermore, the effects of the fracture network characteristics including randomness, geometry, length, aperture, and injection parameters on the heat production are quantitatively investigated. Under the same number of fractures, different network geometry leads to different EGS production performance, the network with horizontal fracture set shows better thermal extraction performance but poor injection performance, which is because the fracture dip affects the thermal evolution on the horizontal plane. The effect of fracture length on EGS performance highly depends on its orientation, the excessive increase of fracture length towards injection-production wells is detrimental to heat extraction. The fracture aperture affects the working fluid transport and thus the EGS performance, the fractured reservoir with smaller fracture aperture shows the worse fluid flow performance but the better geothermal extraction performance, thus we believe that the optimal fracture aperture should be kept at a level of 0.5–1.0 mm in a self-propping fractured granitic system. The main influence of injection parameters on thermal extraction from the fractured reservoirs is the injection mass rate, because a high injection rate results in significant solid responses, including failure stress concentration, decreased safety factor, and increased permeability, which occur in those fractures that are originally connected to the injection well. These results of our research and the insights obtained have important implications for deep geothermal geoengineering activities.

Droplets size characterization for cold water clouds by means of Generalised Scattering Imaging

This paper describes an experimental investigation carried out at the Italian Aerospace Research Centre (CIRA) laboratory for the application of the Generalized Scattering Imaging (GSI) technique. The droplets were generated by a monodisperse droplet generator and a multi-disperse conical nozzle. This latter is currently used for making the artificial cloud in the CIRA Icing Wind Tunnel (IWT). The measurements are devoted to assessing the application of GSI for the characterization of the cold cloud of CIRA-IWT. The experiments were conducted considering two camera models and demanding technical solutions for the illumination and layout constraints faced for the future implementation of GSI in IWT. To reduce into a linear pattern the enlarged defocused interference fringes, it is found that the optimal aperture of the slit is 5 mm. For the monodisperse droplet distribution, the results show discrepancies between the predicted and the measured diameters regardless of the sharp distribution of the occurrences of the droplet diameters. However, the dispersion found for the droplets generated by the conical nozzle exhibits the expected large variability. This effect is more emphasized when the imaged region is discretized in sub-windows, the number of droplets in each dramatically decreases, however compromising the results of the statistics. Different camera models and imaging configurations led to a variety of measurements at different spatial resolutions.

Particle Behavior and Aperture Optimization of Variable Vibration-Amplitude Screening Based on Discrete Element Method Simulation.

Recently, some novel screens were proposed based on the improved understanding of screening processes from particle-scale studies, one of which is the novel variable amplitude equal thickness vibration screen (VAETVS). This paper presents an investigation of using different aperture sizes to further optimize the VAETVS by the discrete element method (DEM). The screen was divided into three panels, and the aperture size of each panel was varied in the simulation. The particles' dynamics and spatial distribution were investigated to better understand the effects of varied amplitudes and aperture sizes on the screening efficiency. The results showed that the VAETVS can be effectively optimized by varied amplitude as well as varied aperture size for different screen panels. The amplitude variance is more effective for hard sieve particles and hindrance particles. It is also found that from the feed end to the discharge end, the difference in the distribution of particle mass between the coarse particles and the fine particles increases. Generally, such a difference can be increased with increasing aperture sizes. However, the effects of the apertures of the different panels were not the same. The simulated data were further analyzed by the Box-Behnken response surface method, which gave a mathematical model to predict the screening efficiency η with the varied apertures. From the model, the optimal aperture sizes are 7.5, 7.58, and 6.81 mm, yielding the maximum screening efficiency of 86.35%, and the optimal opening areas for the three panels are 35, 40, and 40%, respectively, yielding the maximum screening efficiency of 87.82%.

The 3D Seismic Survey Design of South Walio Offshore, Indonesia: Optimizing the 3D Survey Design Parameters

The background of this research is to support the plan to carry out 3D seismic acquisition in the Salawati Kepala Burung Working Area located in Sorong Regency. The 3D seismic design study was applied to better understand the physical properties of the Mesozoic clastic reservoir in the Salawati basin and its surroundings, especially in the offshore area. The study aims to evaluate the parameters of a reliable 3D seismic acquisition design to meet efficiency in financing in realizing the 3D seismic data acquisition program. Determine the recording parameters to image the Kais Formation and Waripi Formation targets by building a geophysical analysis model using existing 2D data and well-log information. Based on this model, using the Kais and Waripi formation properties to calculate and analyze vertical and horizontal resolution, bin size, aperture migration, and maximum offset. Synthetic acquisition 2D modeling is applied in this study to perform vertical and horizontal resolution analysis and obtain optimum and reliable bin size parameters and aperture migration. With this knowledge, we calculate the theoretical parameters of the survey. After determining the most critical theoretical parameters of the study, the next step is to determine the distance between the source and receiver. Then define the recording template. It is done by considering the bin size for the 3D model, offset boundaries, and suitable folds for inner targets. In the second, an analysis of the other two most important attributes is carried out, namely the offset and azimuth distribution. It is realized that every 3D survey design compromises technical factors affecting 3D survey costs starting from the technical requirements of field activities. The results of this study are recommendations and suggestions for two main alternative models of recording parameters and templates in the form of ideal source-receiver layout models, namely orthogonal and diagonal, and the minimum prerequisites that are expected to be able to map and determine the characteristics of the shallow and deep play type models in the South Walio offshore areas.

Maximum directivity of flanged open-ended waveguides

Directional beams have extensive applications in communication and sound reproduction. This paper investigates the theoretical maximum directivity of infinitely flanged open-ended waveguides and the radiation pattern synthesis. We derive a rigorous solution for the maximum directivity factor of a flanged aperture with arbitrary shape by projecting its surface velocity on the waveguide modes, enabling the creation of a directional beam in any desired direction. We present case studies for a three-dimensional circular waveguide and a bidimensional waveguide. The theoretical beam that is obtained in a subspace spanned by all the propagating modes can then be synthesized by a group of incident modes or a point-source array within the waveguide. The optimality of the beam is demonstrated by comparing it with Gaussian shaded modes radiated from the waveguide. If the evanescent modes are taken into account, the maximum directivity factor increases with considerable loss to the radiation efficiency. Nevertheless, the optimum aperture velocity dominated by its evanescent components is capable of precise beam steering in extreme directions and could be useful for designing material-filled horns. Our work provides benchmark directivity factors and patterns for the practical design of horn antennas. In addition, we present a generalized form of Bouwkamp's impedance theorem.

Effect of reciprocity-breaking on fine-track tip/tilt systems.

We analyze here a candidate system for correcting the wander of a self-channeled laser pulse using a fast-steering mirror along with a cooperative beacon imaged with a telescope. For our model system, the imaging telescope is coaxial with the propagation of the outgoing pulse. In the ideal case, any incoming light gathered from the beacon would be collimated, such that taking a centroid beacon image would yield the precise tip and tilt required for the self-channeled pulse to propagate back to the beacon on the reciprocal path. The degree to which reality differs from this ideal case determines the effectiveness of the wander correction. We simulate our system for a range of propagation and imaging conditions. We also show that in the absence of image noise (i.e., when the beacon power is arbitrarily high, and the signal-to-noise ratio is not an important consideration), the system exhibits its best performance when the receiving aperture diameter of the imaging system is close to the transverse size of the outgoing pulse, maximizing reciprocity. When realistic noise and finite beacon power are included in the simulation, however, we find that this reciprocity advantage may not be sufficient to compensate for the reduced photon count and resolving power of a small receiving aperture. In this case, the optimal aperture diameter will be the smallest possible, which allows for an acceptable signal-to-noise ratio.

Analysis Method for Determining Optimal Synthetic Aperture Time Using Estimated Range and Doppler Cone Angle at the Center of Synthetic Aperture Length

Synthetic aperture time (SAT) is a crucial component for acquiring high-quality synthetic aperture radar images with an excellent target cross-range resolution. SAT is analyzed using the range and Doppler cone angle at the center of the synthetic aperture length (SAL). However, in a real flight mission setting, only the range and Doppler cone angle at the SAL’s starting point are determined. Therefore, we present a method for estimating the range and Doppler cone angle at the center of the SAL to calculate an accurate SAT that is suitable for the spatial resolution of the assigned mission. We performed an iterative analysis of SAT at the range and Doppler cone angle at the starting point of the SAL (original SAT) and at the center of the SAL (proposed SAT). Consequently, the proposed SAT decreased by 0.69%–16.14% compared to the original SAT at a resolution of 0.1–3.0 m.

Crosscorrelation-based Marchenko imaging with an optimal aperture

The Marchenko method can retrieve Green’s functions among virtual sources in the subsurface and receivers at the surface from single-sided reflection data. This process, called Marchenko redatuming, allows the estimation of the full-wavefield information in the inhomogeneous subsurface. The retrieved Green’s functions form the input for creating the subsurface image free of artifacts caused by internal multiples. However, when using the crosscorrelation imaging condition in Marchenko imaging, the shallower regions of the obtained image suffer from reduced resolution due to unwanted interference, which occurs in the crosscorrelation gathers at far offsets. With a simple model, we have found that the image resolution obtained using the crosscorrelation Marchenko imaging (CCMI) method is influenced by image position and the integral range of the crosscorrelation function. To overcome this problem, we develop an optimal aperture-bounded crosscorrelation imaging condition using only the constructive wavefields during integration. The optimal aperture is defined as an intercept at which the time difference between the first arrivals of up- and downgoing Green’s functions equals one wavelet period. The integration of the crosscorrelation function is then performed over the determined optimal range that varies with the image position rather than a fixed aperture. As a result, we exclude the unwanted destructive interference from the crosscorrelation gather, resulting in a high-resolution image. The effectiveness of our method has been validated with its applications to synthetic and field data tests.

Influence of aperture size on the performance of square footing resting on rattan reinforced sand

ABSTRACT Rattan fibre as a reinforcement material can be a promising candidate for fabricating mattresses that improves the bearing capacity and settlement reduction of sand. Apart from observing the potential of rattan mats in reinforcing the sand beds, an attempt is made to understand the role of apertures with varying dimensions in enhancing the load bearing performance of sand. A series of plate load tests were performed to study the effect of the depth of top layer reinforcement, width, aperture size of rattan mats and number of reinforcement layers. After comparing the test results of various aperture sized mats, openly woven rattan mats performed superior to closely woven mats. The incorporation of rattan mats under the most effective reinforcement configuration has enhanced the bearing strength improvement factor and settlement reduction factor to 7.1 and 0.85, respectively, for closely woven rattan mats and about 8.16 and 0.94 for openly woven rattan mats with optimum aperture sizes.

Thermo-poro-elastic analytical model of the heat extraction performance of EGS inlaid with multi-linked fractures

The existing analytical model of the heat extraction performance of EGS ignored the influences of both thermo-poro-elastic effect and multi-linked fractures. Therefore, a thermo-poro-elastic analytical model was proposed to simulate heat extraction performance of EGS inlaid with multi-linked fractures. First, the mathematical models of fluid flow, heat transfer, and fracture aperture variation were established based on the conservation of energy and mass. Second, the partial differential equations were converted to ordinary differential equations by Laplace transformation, and the analytical solutions of water and rock temperatures were obtained. Then, the proposed model was verified with the published single-fracture model, which has been demonstrated to be efficient. Finally, the influencing factors, including geothermal reservoir parameters, production parameters, thermo-poro-elastic effect, and fracture morphology, were systematically analyzed and discussed. The results indicated that both the thermo-poro-elastic effect and multi-linked fractures have significant influence on the heat extraction performance of the EGS. The thermo-poro-elasticity effect tends to cause the fracture aperture to increase. The heat extraction performance of the EGS inlaid with multi-linked fractures is much better than that of single fracture EGS. Compared to the uncoupled situation, the production temperature is lowered and the output energy is increased by the thermo-poro-elastic effect at a constant flow rate in the fracture due to the increase in injection rate caused by the increase in fracture aperture. With the increasing of initial fracture aperture, the production temperature gradually decreases, while the output energy first increases and then decreases, so that the optimal initial fracture aperture is 2 mm. The results can provide important guidance for the design and production of an EGS inlaid with multi-linked fractures.

Development of a passive sampler for analysis of nicotine in non-smoking areas

Passive cigarette smoking has been a concern owing to the harmful health risks it poses to humans. Nicotine is used as an indicator of tobacco smoke in the environment, to assess the effects of passive smoking. Passive samplers, which do not require a power source, are a low-cost method for collecting nicotine; however, they are affected by wind, resulting in low accuracy. We developed a passive sampler coupled with perforated covers to reduce the effects of wind on sampling. Because covering the collection surface would reduce the amount of nicotine collected by passive samplers, a highly sensitive nicotine analysis method using liquid chromatography with tandem mass spectrometry (LC-MS/MS) was developed. Chamber tests were used to determine the optimal cover aperture ratio. Finally, we measured the nicotine concentrations indoors at 15 sites using active samplers. The nicotine concentration determined using the active samplers were compared to the amount of nicotine collected in the passive samplers, to estimate the sampling rate (SR; m3 min−1) of the passive samplers. The limit of quantitation for nicotine obtained using LC-MS/MS was 8.6 ng L−1, which was 0.0016–0.043 times those obtained using conventional methods. The optimal aperture of the membrane and the SR of the developed sampler were 1.8% and (1.17 ± 0.05) × 10−6 m3 min−1, respectively. The relative standard deviation of the developed sampler was 0.57 times those of the conventional samplers, indicating that the developed samplers have improved accuracy. The nicotine concentrations in the rooms ranged from <0.06–37 μg m−3. The samples with the lowest concentrations could not be quantified using conventional analytical methods. Thus, the proposed analytical method and passive sampler are promising tools for monitoring nicotine.

Aperture Design Optimization of Wire-Wrapped Screens for SAGD Production Wells

Wire-wrapped screens have been established as one of the primary sand control devices in Steam-Assisted Gravity Drainage (SAGD) wells due to the high open-to-flow area and superior plugging attributes. However, their design is still a point of interest for thermal operations. Generally, existing approaches rely on one or more particular points of reservoir sands’ particle size distribution (PSD) and rules of thumb inferred from other devices like the slotted liners. This study used Sand Retention Testing (SRT) to analyze the performance of WWS under various testing conditions, which were neglected in the current design criteria. The experimental investigation leads to a set of graphical design criteria that provide an optimum aperture size window. The results show that the sand retention performance of WWS is highly dependent on the flow velocities of the wetting phase. Moreover, the testing showed satisfactory plugging performance of WWS even with narrow aperture sizes, proving a superior performance for low-quality oil sands.

Generalized Bessel Gaussian vortex in the turbulent media of absorbing seawater

We investigate the effects of turbulent absorbing seawater and generalized Bessel Gaussian (GBG) vortex structural parameters on the transmission of orbital angular momentum (OAM). The receiving probability spectrum and bit error probability of OAM mode carried by GBG vortex are deduced with the orthogonal spiral phase expansion of random GBG vortex and signal-to-noise ratio of OAM mode. By numerical analysis, the underwater transmission invariance of GBG vortex is studied, and the optimal aperture angle of GBG vortex corresponding to the maximum received probability of OAM signal is obtained. The impact of seawater parameters and optical transceiver systems on bit error probability is analyzed by using optimal aperture angle. We found that the transmission invariance of OAM modes of GBG vortex is well maintained even in weak turbulent absorbing seawater. Moreover, received probability and bit error probability are significantly affected even if the deviation of the aperture angle from its optimal position is minimal, and Durnin-ring radius should be the minimum within the experimental allowable range. According to signal transmission distance, the selection of high SNR transceiver system, optimal aperture angle, low order OAM topological charge, and minimum Durnin-ring radius allowed by the experiment can optimize the OAM signal transmission efficiency.

Technological considerations for delivering focused ultrasound exposures to the spinal cord

Focused ultrasound opening of the blood-brain barrier (BBB) has reached clinical investigations and seems poised to revolutionize the treatment of brain disorders. Far less attention has been paid to the spinal cord and functionally equivalent blood-spinal cord barrier (BSCB). Small and large animal studies demonstrate that ultrasound and microbubbles can be used to modulate the BSCB in a similar manner to the BBB. However, the complex bony geometry of the vertebral column poses a challenge to the non-invasive delivery of therapeutic ultrasound exposures to the spinal canal. This talk will review work developing spine-specific ultrasound pulse trains and identifying optimal apertures for maximizing sound transmission through the vertebral arch.

Analysis of the working mechanism and detection sensitivity of a flash detector

Abstract Flash detectors are mainly used to detect the brief light flashing when projectiles are launched or exploded in the air. They can output trigger pulse signals in real time to start a test instrument and carry out data collection. Because flash detectors cannot work reliably under strong background light radiation, this work studied the flash detector mechanism. The influence of background light radiance, lens aperture, and detection distance on the effective signal was analyzed, a mathematical model of detection sensitivity based on the background radiation brightness control was proposed, a mathematical formula of the detection distance of the flash detector was deduced, and the optimal working conditions were obtained. The researched model was verified by simulation analysis and actual test experiments, in the same external circumstances, the limit detection distance of the optimal aperture compared to the maximum aperture increased by 20%, and the effective signal voltage amplitude was twice the amplitude at the maximum aperture, and the results showed the correctness of the analysis. The proposed detection sensitivity model can be applied for a dynamic photoelectric detection instrument, which broadens its potential application in the engineering field.

Sequential Separation of Linear, Mono-, and Di-Branched Hexane Isomers on a Robust Coordination Polymer with Nonbonding Flexibility.

Efficient separation of hexane isomers is a crucial process for upgrading gasoline. Herein, the sequential separation of linear, mono-, and di-branched hexane isomers by a robust stacked 1D coordination polymer termed as Mn-dhbq([Mn(dhbq)(H2 O)2 ],H2 dhbq = 2,5-dihydroxy-1,4-benzoquinone)is reported. The interchain space of the activated polymer is of optimal aperture size (5.58 Å) that could exclude 2,3-dimethylbutane, while the chain structure can discriminate n-hexane with high capacity (1.53mmol g-1 at 393 K, 6.67kPa) by high-density open metal sites (5.18mmol g-1 ). With the temperature- and adsorbate-dependent swelling of interchain spaces, the affinity between 3-methylpentane and Mn-dhbq can be deliberately controlled from sorption to exclusion, and thus a complete separation of ternary mixture can be achieved. Column breakthrough experiments confirm the excellent separation performance of Mn-dhbq. The ultrahigh stability and easy scalability further highlight the application prospect of Mn-dhbq for separation of hexane isomers.

Visualization experiment and flow homogenization optimization of the multi-path plenum chamber system using a perforated plate

Plenum chambers are commonly used to provide flow homogenization in ventilation and air conditioning systems. To reduce energy consumption and improve ventilation performance, the interior flow characteristics of a multi-path plenum chamber system were investigated through visualization experiments of flow field. As the flow distribution remained uneven after the primary structural parameters of the traditional chamber were optimized, a flow homogenization chamber was proposed by inserting a perforated plate to further improve flow uniformity. Taking the “one-inlet and two-outlet” chamber configuration as a case study, the proposed flow homogenization mechanism was analyzed in terms of flow control. The effects of the perforated plate geometry on flow uniformity and resistance performance were studied using two typical chambers with cross-sectional aspect ratio (W/H) of 1/1 and 5/1. The recommended dimensionless installation location of the perforated plate (y/L) in each chamber was determined to be 0.1 and 0.3 of the chamber length from the input, respectively, with an optimal aperture diameter (d) of 30 mm. In addition, the effectiveness of the flow homogenization chamber was verified using four commonly used air duct sizes, and different application scenarios were discussed for multi-path duct connections. The results show that the adjustment of perforated plate on flow field improved the flow distribution uniformity for chamber system with W/H = 1/1 and 5/1 by up to 87.50% and 56.71%, respectively, compared with the standard 90° T-junction connection.