Line Source Research Articles

Descattering for transmissive inspection in production line using slanted linear image sensors.

We propose a descattering method that can be easily applied to food production lines. The system consists of several sets of linear image sensors and linear light sources slanted at different angles. The images captured by these sensors are partially clear along the direction perpendicular to the sensors. We computationally integrate these images on the frequency domain into a single clear image. The effectiveness of the proposed method is assessed by simulation and real-world experiments. The results show that our method recovers clear images. We demonstrate the applicability of the proposed method to a real production line by a prototype system.

Electrically stimulated droplet injector for reduced sample consumption in serial crystallography

With advances in X-ray free-electron lasers (XFELs), serial femtosecond crystallography (SFX) has enabled the static and dynamic structure determination for challenging proteins such as membrane protein complexes. In SFX with XFELs, the crystals are typically destroyed after interacting with a single XFEL pulse. Therefore, thousands of new crystals must be sequentially introduced into the X-ray beam to collect full data sets. Because of the serial nature of any SFX experiment, up to 99% of the sample delivered to the X-ray beam during its “off-time” between X-ray pulses is wasted due to the intrinsic pulsed nature of all current XFELs. To solve this major problem of large and often limiting sample consumption, we report on improvements of a revolutionary sample-saving method that is compatible with all current XFELs. We previously reported 3D-printed injection devices coupled with gas dynamic virtual nozzles (GDVNs) capable of generating samples containing droplets segmented by an immiscible oil phase for jetting crystal-laden droplets into the path of an XFEL. Here, we have further improved the device design by including metal electrodes inducing electrowetting effects for improved control over droplet generation frequency to stimulate the droplet release to matching the XFEL repetition rate by employing an electrical feedback mechanism. We report the improvements in this electrically triggered segmented flow approach for sample conservation in comparison with a continuous GDVN injection using the microcrystals of lysozyme and 3-deoxy-D-manno-octulosonate 8-phosphate synthase and report the segmented flow approach for sample injection applied at the Macromolecular Femtosecond Crystallography instrument at the Linear Coherent Light Source for the first time.

Comparison of terrain corrections based on the point source and line source DC methods

In the direct current (DC) exploration method, topographic relief distorts the apparent resistivity curve. To eliminate effects of terrain fluctuations, two undulating terrains comprising valleys and ridges were investigated in the present study. An unstructured triangular mesh method in which the wave number k and its coefficient g were obtained using the integral method and the point and line source surveys were conducted using comsol multiphysics. Current sources were evaluated using two-dimensional (2-D) finite element forward modeling, whereas terrain correction was performed using both the comparison and conformal transformation methods. The results reveal comparable theoretical curves for the line and point sources, but quantitative characteristics of the curves differ. The comparison method is suitable for both curves, whereas the conformal transformation method is only applicable to the line source. Even though electric fields associated with the line and point sources differ, the comparison method that is based on the electrical cross-section curve of the line source and the electric profile curve of the point source remains effective.

Ultrasonic line source and its coupling with the tool induced heat generation and material flow in friction stir welding

To understand the synchronous interaction mechanism between the ultrasonic vibration exerted on the tool and the tool induced thermo-mechanical behavior in ultrasonic vibration-assisted friction stir welding (UVaFSW) process, the geometric shape of the contact surface between the horn and the tool was considered, and a previous point source of ultrasound was replaced by a line source which is more in line with the actual situation. With the established ultrasonic field model based on a line source of sound, the friction coefficient on the tool/workpiece interface was modified by considering the ultrasonic action from different directions. Combined with the computational fluid dynamics model, the UVaFSW process was numerically simulated. It was found that the line source of ultrasonic energy improved the computation accuracy of ultrasound pressure distribution, and ultrasonic antifriction effect greatly reduced the interfacial friction coefficient near the pin. The exerted ultrasonic vibration led to a slight overall decrease in total amount of heat generation in UVaFSW due to the dual effects of acoustic softening and ultrasonic antifriction. The model was validated by comparing the calculated thermal cycles and the thermo-mechanically affected zone with the experimental measurements.

A Quasi-Quadratic Inverse Scattering Approach to Detect and Localize Metallic Bars within a Dielectric

The inverse scattering problem related to the localization of metal bars embedded within a finite-dimensional dielectric was studied in two-dimensional geometry. The dielectric was placed in air and illuminated from the outside using a linear microwave source and a multi-monostatic configuration. The discontinuity at the interface between the air and the dielectric causes reflections that are neglected if a simple linear Born approximation of scattering is assumed. Herein, a new formulation was proposed based on a quadratic approximation of the scattering equation. The formulation maintained the interaction between the metal bars and the dielectric edge, whereas the mutual coupling between the bars was neglected. By exploiting the knowledge of the permittivity of the dielectric and the shape of its section, a relatively simple approximate expression for the scattered field was derived, which allowed for formulation of an inverse linear problem. Numerical examples demonstrated the feasibility of this approach.

Picard groups for blocks with normal defect groups and linear source bimodules

It is an open problem as to whether any bimodule inducing a Morita auto-equivalence of a block must have endopermutation source. We prove that, for blocks b with normal defect groups in odd characteristic, a stronger result holds, namely that all such bimodules have linear source. We also prove the analogous result in characteristic 2, provided that the defect group is of a specific, slightly restrictive, form.

Full‐Stokes imaging polarimetry via random retarder rotation

We report and demonstrate full-Stokes imaging polarimetry via random retarder rotation (R3). The method adds an assistant imaging channel comprising a linear polarization array and light source to the classical full-Stokes imaging optical path. Further, an alternating iterative algorithm of the polarization information matrix is used to solve the rotation angle of the phase retarder to obtain the full-Stokes information of the imaging target. Theoretical analysis, numerical simulations, and comparative experiments are conducted to verify that the proposed method can achieve accurate full-Stokes imaging measurements via R3. To the best of our knowledge, this is the first time that a full-Stokes imaging method with high precision performance has been proposed that does not depend on accuracy of rotation angle.

Flow mechanism of Gaussian light-induced vortex motion inside a nanofluid droplet

PurposeThe purpose of this study is to use a weak light source with spatial distribution to realize light-driven fluid by adding high-absorbing nanoparticles to the droplets, thereby replacing a highly focused strong linear light source acting on pure droplets.Design/methodology/approachFirst, Fe3O4 nanoparticles with high light response characteristics were added to the droplets to prepare nanofluid droplets, and through the Gaussian light-driven flow experiment, the Marangoni effect inside a nanofluid droplet was studied, which can produce the surface tension gradient on the air/liquid interface and induce the vortex motion inside a droplet. Then, the numerical simulation method of multiphysics field coupling was used to study the effects of droplet height and Gaussian light distribution on the flow characteristics inside a droplet.FindingsNanoparticles can significantly enhance the light absorption, so that the Gaussian light is enough to drive the flow, and the formation of vortex can be regulated by light distribution. The multiphysics field coupling model can accurately describe this problem.Originality/valueThis study is helpful to understand the flow behavior and heat transfer phenomenon in optical microfluidic systems, and provides a feasible way to construct the rapid flow inside a tiny droplet by light.

Alternative Simplified Analytical Models for the Electric Field, in Shoreline Pond Electrode Preliminary Design, in the Case of HVDC Transmission Systems

In Greece, a new bi-polar high voltage direct current (HVDC) transmission system with a ground return was designed with nominal characteristics of ±500 kV, 1 GW, between Attica in the continental country and the island of Crete, which is an autonomous power system based on thermal diesel units. The interconnection line has a total length of about 380 km. The undersea section is 330 km long. In this paper, the use of the Aegean Sea as an active part of the ground return, based on shoreline pond electrodes, was proposed to avoid EUR 200 Μ of expenses. According to the general guidelines for HVDC electrode design by the International Council on Large Electric Systems (CIGRE) working group B4.61/2017, the electric field and ground potential rise of shoreline electrodes should be studied to analyze safety, electrical interference and corrosion impacts related to the operation of the electrodes. Two kinds of studies are available; one is a simplified approach based on a spherical/pointed electrode centered at the edge of the seashore and seabed, assuming it to be sloping to the horizontal, and the other is a detailed simulated model using a suitable electric field software package. The first approach usually gives more unfavorable results than the second one, especially in the near electric field, while it can not take into account obstacles, i.e., dams, near to electrode position. The second approach demands a detailed description of the wider installation area, which cannot be available during the preliminary study, significant computational time and considerable financial resources for the purchase of a reliable specialized software package. In this research, a two-step modification of the CIGRE simplified model was proposed. The first modification deals with the obstacles in the near electric field, and the second modification deals with the use of a linear current source (instead of a point one), which can give more accurate results. Additionally, the electric field for complex electrode formation is calculated by applying the superposition method, which can be easily achieved using a common software package, i.e., MATLAB. The proposed simplified approaches were applied on shoreline pond electrode locations for the Attica–Crete HVDC interconnection line (between Stachtoroi island in Attica and Korakia beach in Crete), allowing the preliminary study to be conducted swiftly, giving satisfactory results about electric field gradient, ground potential rise and resistance to remote earth of electrodes stations for the near and far electric field.

Sound Radiation of a Line Source with General Time Dependence Moving Above an Interface Between Two Homogeneous Semi-Infinite Fluid Media

In this paper, the sound field due to a line source moving above a homogeneous semi-infinite fluid medium emitting an arbitrary time signal is deduced. The source moves with a constant velocity parallel to the flat interface at a fixed height. The expression for the velocity potential is obtained from the impulse response of the stationary line source by including the motion of the source in the source density function. The resulting sound field is expressed in terms of convolution integrals. The correctness of the formulas is verified by comparing them with the results known for the case of a continuous harmonic line source. Two examples, the sound field due to a delta pulse and a Gaussian pulse, are computed and presented. Finally, the relation between the solutions obtained here and the ones obtained when the source moves above an absorbing impedance surface is shown.

Surrounding line sources optimally reproduce diffuse envelopment at off-center listening positions.

Listener envelopment has previously been studied in the fields of room acoustics and multichannel sound reproduction. However, the potentially detrimental effect of a directional imbalance remains uninvestigated. This paper presents a listening experiment under anechoic conditions using a ring of 24 loudspeakers. Participants rated perceived envelopment for various loudspeaker subsets fed by incoherent noise signals. Off-center listening positions were simulated for different acoustic source models: -6 dB (point source), -3 dB (line source), or 0 dB attenuation for every doubling of distance. Only the line-source model preserved envelopment off-center, providing a low interaural level difference and a low interaural coherence as perceptual cues.

A Low Profile Circularly Polarized Beam Scanning Patch Array Fed by Parallel Plate Waveguide

A low-cost, low-profile circularly polarized beam scanning patch array is presented. The patch array is fed by the coupling slots of parallel plate waveguide (PPW), which is excited by a substrate integrated waveguide-based plane wave line source generator. By suggesting a new impedance match method, the coupling slots and truncated patch array are combined for circularly polarized radiation. The beam scanning capability is achieved by the variable inclination method. In the PPW guiding wave layer, a circular plate is cut and separated from the main body of the PPW to make it rotatable around its axis. By rotating the assembly of the circular plate and the above patch layer, the phase difference between the adjacent radiation elements could be controlled. Thus, the circularly polarized beam scanning is realized. A Ku-band prototype array is fabricated and measured to verify the design. The measured peak gain is 19.6 dBi and the scanning range is ±40°, in which range the gain variation is below 2.7 dB and the axial ratio is less than 2.8 dB.

A Statistical DOI Estimation Algorithm for a SiPM-Based Clinical SPECT Insert

A prototype clinical brain single-photon emission computed tomography (SPECT) insert has been designed for use in simultaneous SPECT/MRI. The system utilizes novel slit-slat collimators which, like pinhole collimators, suffers from parallax errors due to the large incident angle of photons. A statistical algorithm has been developed to determine the depth-of-interaction (DOI) with a view to improving image performance. The importance of DOI correction was demonstrated using Monte Carlo simulation. This simulation also indicated that four DOI layers ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3 \times 1.5\, \textrm {mm} + 3.5\, \textrm {mm}$ </tex-math></inline-formula> ) may be sufficient. The improvement in event localization was demonstrated on a single detector before implementing the algorithm on the full clinical prototype where some limitations in event localization in layers close to the readout plane were observed. Nevertheless, DOI enabled the rejection of poorly localized events with improved resolution in reconstructed line sources.

Experimental investigation of effectiveness variation of borehole heat exchangers for cooling mode operation

• Parallel configuration shows higher effectiveness of 0.88 than series configuration with 0.81. • Borehole limiting ratio for parallel configuration is higher than that of series one. • Experimental study of space cooling operation using ground dource heat pump system. • Maximum rise in the tube-interface temperature is observed at 73 m depth of borehole. In the present research work, a novel technique is proposed to estimate real time variation of borehole temperature based on measured interface temperature along the depth of a double U-tube borehole heat exchanger (BHE). Experimentally determined transient variation of effectiveness of BHE is discussed in detail for experimental simulation of line source model and actual operation of a GSHP system for cooling mode operation. The real time borehole temperature computed using the present technique during actual operation of a GSHP system makes it possible to compute the actual variation of effectiveness of BHE. The above set of experiments were performed for both single and double U-tube BHEs considering series and parallel mode operations during peak summer conditions at a location situated closer to the Himalayan region in northern part of India. Effectiveness of BHEs was computed using varying borehole temperature obtained from line source model and the real time varying borehole temperature proposed in the present work. For the actual cooling mode GSHP experiments, the average value of thermal effectiveness of double U-tube BHE computed with constant borehole temperature is observed to be 0.72 for both series and parallel mode operations. However, with the use of real time varying borehole temperature, the effectiveness is observed to increase by 12% and 22% for series and parallel flow operations respectively.

Numerical research on the heat transfer model and performance of deep borehole heat exchangers combined with geothermal wells

• A deep borehole heat exchanger combined with the geothermal wells is proposed. • A three-dimensional mathematical model considering the forced seepage is established. • The dimensionless analytical solutions are developed and verified. • The effect of the exploitation quantity of geothermal water on the DBHE is analysed. • The thermal diffusion radius under different exploitation quantities is studied. For the purpose of carbon neutrality, deep borehole heat exchanger (DBHE) is widely utilized in building heating by efficiently developing hydrothermal geothermal resources. In this study, a DBHE combined with the geothermal wells is proposed given that there are abundant hydrothermal geothermal resources in the BoHai Bay basin, China. A three-dimensional unsteady heat and mass transfer model coupled with DBHE and thermal reservoir is developed taking into account the forced seepage. Based on the moving finite line source model, the transient dimensionless analytical solutions are derived by applying Fourier and Laplace transform. The proposed model and solving method are validated against the experimental data determined from a field test and the previous numerical simulations, respectively. The calculation results indicate that the heat transfer power per unit buried depth increases by 39.60 W/m and its decline rate throughout the operating period decreases by 7.17% when the exploitation quantity of geothermal water increases from 0 m 3 /h to 120 m 3 /h. With the increase of exploitation quantity, the thermal diffusion radius ranges from 10.11 m to 20.34 m at the downstream, however, the thermal diffusion radius decreases from 10.11 m to 9.01 m at the upstream. When the exploitation quantity of geothermal water is 0 m 3 /h, 60 m 3 /h and 120 m 3 /h, the average heat transfer power increases by 139.37 kW, 174.20 kW and 200.80 kW respectively with the increase of circular quantity of DBHE from 10 m 3 /h to 60 m 3 /h. When the exploitation quantity of geothermal water increases, the forced seepage (Darcy flow rate) in the thermal reservoir is enhanced, and the influence of the circular quantity of the DBHE on the heat transfer performance is improved. The DBHE combined with the geothermal wells can be utilized in the case of existing geothermal well construction, which will enhance the heat transfer performance of DBHE substantially. The conclusions obtained from this research will be a reference to guide further research and application of the DBHE or DBHE array combined with the geothermal wells under different geological conditions and operation modes.

Solving Thin-Body Acoustic Problems Over an Impedance Plane with a Fast Multipole Indirect Boundary Element Method

This paper presents a fast multipole indirect boundary element solver for the thin-body acoustic problems over an infinite impedance plane. The half-space impedance Green’s function involving a complex line source to approximate the porous ground effects is employed in the indirect boundary integral equation (IBIE), which makes that both mass-like and spring-like impedance conditions on the infinite plane are explicitly satisfied. A nonsingular IBIE formulation is derived to implement the fast multipole method (FMM) easily. The image relations of multipole moments are used to avoid the computation and translation of multipole/local expansion coefficients in the image domain. To deal with the numerical instability in the local translation of image multipole moments, a half-space tree structure is elaborately constructed for the FMM. The validity of the method is testified by a benchmark example and the potential of the method is investigated by the numerical simulation of noise barriers with different geometrical configurations.

Electromagnetic Method for Steatotic Liver Detection Using Contrast in Effective Dispersive Permittivity

Hepatic steatosis is one of the most prevalent chronic liver conditions. Traditional non-invasive imaging modalities are not suitable for observation and treatment evaluation of this disease. Hence, this study proposes an electromagnetic technique to assist in observation and detection of hepatic steatosis. Effective permittivity contrast between left and right sides of the torso is exploited for the aim of detection. Firstly, the transfer functions of the transmitter-receiver paths on the left and right sides of the torso are modeled using a 2D line source approximation to form a non-linear equation system. Secondly, the system is solved with respect to the vector of effective permittivity values in a successive iteration. Thirdly, the estimated permittivity values are stacked together to create a dispersive permittivity curve. Permittivity modeling and statistical frequency selection are performed to remove outliers. Finally, the left/right effective permittivity contrast is calculated over the selected samples. The method is validated by realistic computer simulations and human measurements. In both scenarios, left/right permittivity contrast is higher and distinguishable in steatotic livers, which have 15% more diffused fat than healthy cases. The results verify the potential of electromagnetic systems, which are safe, low-cost, and portable, in the detection of hepatic steatosis.

Rupture Directivity of the 2021MW6.0 Yangbi, Yunnan Earthquake

AbstractThe 2021MW6.0 Yangbi, Yunnan strike‐slip earthquake occurred on an unmapped crustal fault near the Weixi‐Qiaoho‐Weishan Fault along the southeast margin of the Tibetan Plateau. Using near‐source broadband seismic data from ChinArray, we investigate the spatial and temporal rupture evolution of the mainshock using apparent moment‐rate functions (AMRFs) determined by the empirical Green's function (EGF) method. Assuming a 1D line source on the fault plane, the rupture propagated unilaterally southeastward (∼144°) over a rupture length of ∼8.0 km with an estimated rupture speed of 2.1 km/s to 2.4 km/s. A 2D coseismic slip distribution for an assumed maximum rupture propagation speed of 2.2 km/s indicates that the rupture propagated to the southeast ∼8.0 km along strike and ∼5.0 km downdip with a peak slip of ∼2.1 m before stopping near the largest foreshock, where three bifurcating subfaults intersect. Using the AMRFs, the radiated energy of the mainshock is estimated as ∼. The relatively low moment scaled radiated energyof 1.5 × 10−5and intense foreshock and aftershock activity might indicate reactivation of an immature fault. The earthquake sequence is mainly distributed along a northwest‐southeast trend, and aftershocks and foreshocks are distributed near the periphery of the mainshock large‐slip area, suggesting that the stress in the mainshock slip zone is significantly reduced to below the level for more than a few overlapping aftershock to occur.

Study about photoinduction-based technology for trapping small brown planthopper

To provide a theory to guide the selection of the illumination parameters of light emitting diode (LED)-based light sources used for trapping Laodelphax striatellus, we used LED light sources and devices built in-house to detect L. striatellus phototactic behavior. Through phototaxis screening experiments of different light sources and the comparative experimental method, we analyzed the response patterns of L. striatellus to wavelength, light intensity, layout, flash frequency of monochromatic light sources, as well as combined color light sources, and discussed the mechanisms of the phototactic behavior of L. striatellus under different light sources. The results of the monochromatic light experiment showed that the trapping rate of the L. striatellus to the linear blue light source of 460 nm was the highest and was also significantly affected by the light intensity. The results of the experiments with the combined color light sources showed that compared with the linear 460 nm blue light source, the trapping rate of the L. striatellus was significantly improved by the polychromatic light, and the blue–green light led to the best improvement, reaching 1.5 times that of the trapping rate in the case of monochromatic light sources. The wavelength composition, light intensity, shape, and flash frequency of the light source used in this study can provide a theoretical basis for the development of LED-based light traps specifically for L. striatellus.

Aerodynamic sound generation in thermoviscous fluids: A canonical problem revisited

Although the Lighthill–Curle acoustic analogy theory is formally exact, the presence of linear source terms related to viscous stresses and non-isentropic density changes makes it unsuitable for studying aerodynamic sound generation in low Reynolds number thermoviscous flows. Here we use an extension of the Ffowcs Williams and Hawkings formulation, with thermoviscous effects explicitly included, to find an analytical solution to the canonical problem of sound radiation from a circular cylinder immersed in a viscous heat-conducting fluid and rotating sinusoidally about its axis. Existing published solutions are compared and an earlier null result is explained. The new analysis reveals the dominant source of sound at low Mach numbers to be unsteady viscous dissipation rather than Reynolds-stress quadrupoles, unless the fluid parameter B=αc2/cp is zero.