Xz Plane Research Articles

Non-invasive focalized stimulation in deep brain using the spatially symmetric array

As a non-invasive neuromodulation technology, transcranial magnetic stimulation (TMS) shows great potential in the treatment of mental diseases. Using TMS to stimulate deep brain targets has significant scientific research value for the exploration of the causes of psychiatric diseases. However, the focalized induced electrical field (E-field) generated by traditional TMS coils or coil arrays is largely restricted to superficial cortical targets. To achieve focalized stimulation in the deep brain, a novel spatially symmetric array based on curved θ-type coils (the θ-SSA) is proposed in this paper. Four θ-type coils in the array are symmetrical to the YZ and XZ planes. Each θ-type coil is placed tangent to the human scalp and bent away from the human head to reduce the non-longitudinal component accumulation of the induced E-field and enhance the stimulation focalization. The finite-element method is used to obtain the 3D spatial distributions of the intracranial induced E-field generated by the proposed array. Results show that the θ-SSA can form an obvious focusing area in the deep brain 11 cm below the scalp. Under identical stimulation current excitation, the θ-SSA can increase the intracranial longitudinal attenuation ratio by 77% compared to the traditional TMS coil. In addition, when generating the same focusing area, the stimulation depth of the θ-SSA is 1.67 times deeper than that of the traditional TMS coil. Meanwhile, the proposed array can dynamically steer the intracranial stimulated area, and the spatial coordinates of the intracranial stimulation target point can be flexibly and continuously adjusted when changing the stimulation current parameters applied to the array. An anatomically realistic human head model with gray matter is employed in this paper to verify our method.

Numerical study of the effect of flow nonuniformities on the low-pressure side of a Cooled Cooling Air heat exchanger

The Cooled Cooling Air (CCA) heat exchanger is a precooler that cools the bleed air from the compressor stages and is located inside the bypass duct of the aeroengine. Nonuniform flows enter the core of the heat exchanger because the cold side is the off-take from the fan flow, compromising its aerothermal performance. These aspects has been disregarded in the literature until now. In this study, the aerothermal performance of a CCA heat exchanger with flow nonuniformities on its Low-Pressure (LP) side is investigated. Three-wire meshes were designed using correlations from the literature, showing three off-design cases, namely, Cases 1, 2, and 3. The porous media and dual cell heat exchanger models were used in numerical simulations for the baseline and off-design cases. Experiments were performed at hot and cold conditions to validate the numerical simulations under actual gas turbine operating conditions. It has been found that heat transfer rate increases in Case 1 and 2 by 1.0% and 1.5%, as the flow non-uniformity is symmetric with respect to XZ plane. In contrast, in Case 3, the heat transfer rate reduces by 4.2% because the flow non-uniformity is asymmetric with respect to XZ plane, inducing cross-flows immediately upstream of the heat exchanger core. • Aerothermal performance with flow nonuniformities along LP side was investigated. • The porous media and dual cell heat exchanger models were used. • Experiments were performed under actual gas turbine operating conditions. • The overall heat transfer rates were improved by 1.0% and 1.5% in Cases 1 and 2. • The overall heat transfer rate declined by 4.2% in Case 3.

Direction dependent crystalline perfection, Z-scan studies and fabrication of Type-I and Type-II SHG elements using imidazolium L-tartrate crystals for optical modulator applications

Monoclinic phase (P21) imidazolium l-tartrate (IMLT) has received considerable research interest because of its wide transparency range, good SHG efficiency and phase matchable non-linear optical (NLO) materials. Organic single crystals of IMLT have been grown via a slow cooling method. The grown crystals were oriented using powder X-ray diffraction. The quality of the grown crystals was evaluated using HRXRD studies. Polarized Raman spectroscopy was carried out on b-cut and c-cut IMLT wafers. The third order NLO characteristics of the <1 0 0>, <0 1 0> and <0 0 1> orientated IMLT crystals have been studied using Z-scan measurements with a Hi-Ne laser (632.8 nm). The second-harmonic generation (SHG) intensity was measured for the powdered grown crystals with various particle sizes to explore the second order NLO properties and phase matchability in the crystals. Furthermore, the type-I and type-II phase-matching angle of the XY and XZ (θ <Ω) planes were calculated.

A new three-dimensional elastography using phase based shifted Fourier transform

Elastography is an imaging technique with the ability to determine low quantities of some of the mechanical properties of tissues. The aim of our research is to design a new 3D algorithm using the Shifted Fourier Transform (SFT) to perform a quasi-static elastography. Our innovative idea is implementation of a 3D convolution instead of using three 2D convulsions. At first, we collected the raw data from Abaqus engineering software in the form of breast tissue with a coefficient of elasticity of healthy tissue and tumor tissue with a coefficient of elasticity of tumor tissue. The primary raw data consists of a number of points with x, y and z specified for tumor and healthy breast tissue. At this step, we simulated the displacements in directions of x, y and z at each point of the prescribed tissues for 15 ​mm displacement of probe in –Y direction then we collected 1831 points for tumor and 4186 points for breast before and after pressure. After applying a novel reconstruction algorithm, we convolved all images with the 3D Gabor filters to obtain phases, represented displacements of the breast and tumor images for before and after pressure. To reach this goal, we designed a Gabor filter bank based on the dimensions of the input images in different scales, directions, and deviations. Using the 3D SFT, we calculated the displacements of the breast and tumor tissues followed by 3D elastogram representation of the images. Finally, we implemented a 2D analysis of SFT in order to investigate validation of the 3D SFT. In 2D algorithm, we used three two-dimensional convulsions in XY, YZ and XZ planes. The results obtained from the small displacements marked by circles, confirmed the accuracy of the 3D SFT algorithm. These areas of interest are the tumor areas in the 2D analysis.

Binary Feature Description of 3D Point Cloud Based on Retina-like Sampling on Projection Planes

A binary feature description and registration algorithm for a 3D point cloud based on retina-like sampling on projection planes (RSPP) are proposed in this paper. The algorithm first projects the point cloud within the support radius around the key point to the XY, YZ, and XZ planes of the Local Reference Frame (LRF) and performs retina-like sampling on the projection plane. Then, the binarized Gaussian density weight values at the sampling points are calculated and encoded to obtain the RSPP descriptor. Finally, rough registration of point clouds is performed based on the RSPP descriptor, and the RANSAC algorithm is used to optimize the registration results. The performance of the proposed algorithm is tested on public point cloud datasets. The test results show that the RSPP-based point cloud registration algorithm has a good registration effect under no noise, 0.25 mr, and 0.5 mr Gaussian noise. The experimental results verify the correctness and robustness of the proposed registration method, which can provide theoretical and technical support for the 3D point cloud registration application.

Three-Dimensional Large Eddy Simulations and Proper Orthogonal Decomposition Analysis of Flow Around a Flexibly Supported Circular Cylinder

Abstract Three-dimensional (3D) numerical simulations of the flow around a cylinder undergoing vortex-induced vibration (VIV) at Re = 3900 (defined as Re = U∞D/ν, where U∞ is the inlet flow velocity, D is the diameter of the cylinder, and ν is the fluid kinematic viscosity) are performed using large eddy simulations (LES). Detailed mesh and time-step convergence studies are carried out for the flow past a stationary cylinder to obtain the optimal mesh and time-step. The validation studies are performed by comparing the present results with the previous published experimental data and numerical results to confirm feasibility of the present numerical model for predicting the wake characteristics. The numerical model is then applied to investigate the flow around a self-excited cylinder vibrating in the cross-flow direction at three different reduced velocities. The effects of the reduced velocity are analyzed based on the cross-flow vibration amplitudes, the power spectral densities of lift and drag coefficients, and the wake flow coherent structures. Different vortex shedding modes are identified and categorized using the iso-surfaces of the pressure coefficient and the Q-criterion. The dominant 3D wake flow features are extracted and discussed by carrying out the proper orthogonal decomposition (POD) for flow velocities on multiple two-dimensional (2D) sampling planes in the wake region. The modes on the XY planes display a traveling-wave behavior and the modes on the XZ planes show cells of streamwise vortices, which display the three-dimensionality of the wake flow.

Efficient generation of mid-infrared few-cycle pulses by the intrapulse difference-frequency generation in YCOB.

Yttrium calcium oxyborate (YCOB) crystals have been widely applied for generating intense near-infrared laser pulses by optical parametric amplification. Here, we show that the YCOB crystals oriented in both the XZ and XY principal planes possess broadband phase-matching property of intrapulse difference-frequency generation in the mid-infrared region. Few-cycle pulses tunable from 2 to 4 µm are experimentally produced by using a 7.5-fs pump laser at 800 nm, in which the conversion efficiency can be as high as 2.5%. With a large-size crystal and high-power pump laser, intrapulse difference-frequency generation based on YCOB may provide a new route for directly producing intense few-cycle mid-infrared pulses.

In-situ investigations via confocal video-processing analyses of mullite vs. alumina refractories for application to biomass-fueled gasifiers

The National Energy Technology Laboratory (NETL) targets modular gasifiers that can accommodate diversified carbon feedstock such as biomass and waste plastics. Towards this goal, it is necessary to better understand interactions of candidate refractory ceramics with feedstock ashes. In this work, confocal scanning laser microscopy in conjunction with a variety of image-processing techniques was utilized to assess these interactions in-situ with biomass ashes. We found that various ash components followed different timelines. A key factor which further affected these timelines was proximity to chemical and/or topological boundaries, including but not limited to other ash or slag, pores, cracks, crevices, grain boundaries, and matrix-aggregate boundaries. Alignment techniques such as Scale-Invariant Features Transformation (SIFT) enabled increased comparability of features as ZY or XZ planes could be aligned fully onto a consistent location of an ash. In tandem with thresholding techniques and assessment of useful features, SIFT allows potential for future rapid analyses of otherwise difficult to quantify videography.

3D FEM analysis of induced current in the shield of the buried cable by non-vertical channel

The induced current in the buried cable shield is evaluated by solving the full-wave Maxwell equations with the Finite Element Method (FEM). Three different cases are considered for the lightning channel, including the “straight inclined” channel, “bent channel”, and “Tortuous channel”. Straight inclined lightning is one part channel that could have different angles with Z-axis at XZ and YZ plane. The bent lightning is included the upper part and lower part that are joined to each other at the “bent” point at height Ha. Different sizes are considered for the Ha, and angle of each part. The tortuous channel is a linear piecewise approximation of realistic lightning. The impact of the channel shape, channel angle, bent height, and lightning current waveform on the induced current in the buried cable shield is investigated. The results reveal that waveforms and peak value of the induced current are significantly affected by channel shape. Comparing the results of different lightning shapes reveals that the induced current peak and waveforms highly depends on the lightning channel shape between ground to 250 m height from the ground. Comparing the tortuous channel results with inclined and bent lightning reveals that bent lightning is a better approximation than inclined lightning. Statistical analysis of the results shows the effect of the channel shape for the case that lightning current waveform have faster rising time is more significant.

Optical SCMA coding technique based on fully interleaved 3D codebook

In the paper, an optical Sparse code division multiple access (SCMA) coding technique based on fully interleaved 3D codebook is proposed. We design a completely interleaved 3D codebook, the projection of all constellation points in the joint constellation on the XY, XZ and YZ planes are all interleaved, which is beneficial for making the complexity of message passing algorithm (MPA) lower. We used 3D amplitude and phase modulation (3D-CAP) to modulate 3D-SCMA signal, and then transmitted the signal with 7-core fiber. The feasibility of 3D-SCMA is proved by experiments. Our proposed 3D-SCMA has the same resource block efficiency as traditional two-dimensional SCMA: 150%. Due to the larger Euclidean distance of the 3D joint constellation, 3D-SCMA has lower decoding complexity and better reception sensitivity. Compared with 2D-SCMA, the complexity of 3D-SCMA is 66.66% lower and the receiving sensitivity is 3.5 dBm higher, which indicates that it not only reduces the complexity of the MPA algorithm, but also reduces the energy consumption of the system and saves the transmission cost. In this paper, optical 3D-SCMA is proposed creatively, which is an effective improvement on the traditional optical 2D-SCMA. This research can be applied in the future access network.

Constant-Beamwidth Kronecker Product Beamforming With Nonuniform Planar Arrays

In this paper, we address the problem of constant-beamwidth beamforming using nonuniform planar arrays. We propose two techniques for designing planar beamformers that can maintain different beamwidths in the XZ and YZ planes based on constant-beamwidth linear arrays. In the first technique, we utilize Kronecker product beamforming to find the weights, thus eliminating matrix inversion. The second technique provides a closed-form solution that allows for a tradeoff between white noise gain and directivity factor. The second technique is applicable even when only a subset of the sensors is used. Since our techniques are based on linear arrays, we also consider symmetric linear arrays. We present a method that determines where sensors should be placed to maximize the directivity and increase the frequency range over which the beamwidth remains constant, with a minimal number of sensors. Simulations demonstrate the advantages of the proposed design methods compared to the state-of-the-art. Specifically, our method yields a 1000-fold faster runtime than the competing method, while improving the wideband directivity factor by over 8 dB without compromising the wideband white noise gain in the simulated scenario.

Circularly polarized rectangular dielectric resonator antenna with metallic strips load for WLAN application

AbstractThis article presents a circularly polarized rectangular dielectric resonator antenna (CP RDRA) loaded with metallic strips. The dielectric resonator (DR) with metallic strips on the top surface is excited by a slot aperture feed that excites two orthogonal modes to provide circular polarization. The proposed CP RDRA does not require any complex‐shaped dielectric resonator and simplifies the overall design. A prototype of the proposed antenna has been fabricated and validated. It has measured impedance bandwidth between 4.8 and 5.6 GHz and 3 dB axial ratio bandwidth between 5.1 and 5.43 GHz. The axial ratio beamwidth of more than 155° in the XZ and YZ planes is obtained.

Defect-Correlated Vickers Microhardness of Al-Si-Mg Alloy Manufactured by Laser Powder Bed Fusion with Post-process Heat Treatments

Laser powder bed fusion is an additive manufacturing process characterized by different advantages like the manufacture of samples with complex geometry without the use of tools and/or molds. Generally, the manufactured samples are characterized by high tensile strengths which, however, can be affected by the presence of defects due to the unoptimized process parameters. In a large applications field, a low density of the as-built AlSi10Mg samples is a very important parameter to considered, e.g., due to both the loss of the tensile strengths correlated with a premature failure of the samples and the increase in time and costs associated with the manufacturing process. In addition, different post-process heat treatments can increase these effects leading to an ineffective manufacturing process. In this scenario, the present work shows the analysis of spherical and lack-of-fusion pores induced by the laser powder bed fusion process on the AlSi10Mg samples and their variations after different heat treatments (direct aging and T6). At the same time, the influence of pores on the Vickers microhardness and the tensile properties has been studied in the same AlSi10Mg samples (bars and billets) that were printed with single- and double-laser machine setup. Different process parameters were also analyzed and compared. The study was supported by the microstructural and pore analysis performed by optical microscopy along the XZ plane (build direction) and the XY plane. Finally, the greatest effects of pores were observed on the Vickers microhardness values; in fact, two different relationships between microhardness and density variation are discussed. The T6 heat treatment leads to a rounding of the pores already formed in the as-built samples and to a formation of new small pores.Graphical

Microstructural and Hardness Behavior of H13 Tool Steel Manufactured by Ultrasound-Assisted Laser-Directed Energy Deposition

Metal additive manufacturing (AM) by Laser-Directed Energy Deposition (L-DED) usually results in the formation of textured columnar grains along the build direction, leading to anisotropic mechanical properties. This can negatively affect the intended application of the product. Anisotropy can be eliminated by modifying the material through an additional exposure to ultrasound (US-assisted) during the L-DED process. In this paper, a multi-track sample was manufactured from AISI H13 (TLS Technik, Bitterfeld-Wolfen, Germany) tool steel by a US-assisted (28 kHz) L-DED process using a specially designed cooling system. The study also included post-process annealing and quenching with the tempering heat treatment of the modified steel, resulting in the retention of the properties, as confirmed by hardness measurements. XRD analysis was used to measure the structural parameters of the unit cell, and the hardness properties were measured in two directions: longitudinally and parallel to the deposition direction. It was found that US-assisted L-DED allows us to obtain a more isotropic structure with an equal size of the coherent scattering region in two printing directions, and to reduce the residual stresses in the material. The anisotropy of the hardness was significantly reduced, with 636 and 640 HV found between the XY and XZ planes. Based on the obtained hardness data, it should be noted that some of the heat treatments studied herein can also result in a decrease in the anisotropy of the properties, similarly to the US-assisted effect.

Subtalar axis determined by combining digital twins and artificial intelligence: influence of the orientation of this axis for hindfoot compensation of varus and valgus knees

Previous studies evaluating hindfoot and knee alignment have suggested compensation between the knee and the hindfoot deformities. However, these studies did not investigate the influence of the orientation of the subtalar axis on the results. Using computed tomography data of patients without osteoarthritis, digital twins, and artificial intelligence, we identified the orientation of the axis of the subtalar joint. Compensation was evaluated in the subtalar joint according to angular knee deformity and subtalar axis direction. With the inclination angle defined as the angle between the axis and the XY plane (horizontal) and the deviation angle defined as the angle between the projection of axis on the XZ plane, the inclination angle of the subtalar helical axis showed an average angle of 35.3° (range 5° to 48°). The mean deviation angle for the helical axis was 6.4° (range - 4° to + 12°). Our findings indicated that an increase of the inclination angle of the subtalar axis tends to limit adjustment in the hindfoot alignment toward re-balance of the whole lower limb toward a neutral weight-bearing axis when malalignment of the knee occurs. Malalignment of the knee and different compensations in the hindfoot contribute to various combined deformities in the population: associated valgus or varus deformities and inverse associations of varus/valgus deformities.

Design and Characterization of 10-Elements MIMO Antenna With Improved Isolation and Radiation Characteristics for mm-Wave 5G Applications

A ten-elements MIMO antenna with improved isolation and reduction of X-polar radiation (XPR) in millimeter (mm) wave region is presented. The individual antenna element consists of stub loaded coplanar waveguide (CPW) structure with elliptical shaped radiator. Defected ground structure (DGS) has been incorporated by engraving partial elliptical shaped slots at the coplanar ground to reduce the mutual coupling effect between the adjacent antenna pairs of the MIMO. The backside of the substrate has a metallic plane with defects which is not connected to the coplanar ground of the antenna. This defected metal structure (DMS) acts as a reflector to improve the radiation characteristics by lowering of XPR as well as improving the co-pol to X-pol isolation. The proposed MIMO structure has a fractional bandwidth of 23.52% (22.5GHz-28.5 GHz) which entails the mm-wave 5G frequency spectrum n258 (24.25-27.5 GHz). The isolation| characteristics of the proposed MIMO antenna are below -35 dB over the operating bandwidth for any pair of adjacent antenna elements which imply significantly improved isolation between the adjacent antenna elements with highly compact layout area of 3.4λ × 8.5λ, where λ is wavelength corresponding to the mid-point of the bandwidth. The inter-element spacing of the MIMO structure is 0.44 λ. The main attractive feature offered by this structure is reduction of XPR in the operating frequency range thus improving the co-pol to X-pol isolation up to 20 dB and 28 dB in the boresight direction in both the XZ and YZ planes respectively. Furthermore, the co-pol to X-pol isolation is maintained above 15 dB almost throughout the elevation angular region -180° to 180° thereby negating the hindrance imposed by surface waves in mm-wave region. The diversity performances in terms of Envelope Correlation Coefficient (ECC), Diversity Gain (DG) and Channel Capacity Loss (CCL) are obtained as 0.1 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-6</sup> , 10 dB and 0.005 bps/Hz respectively which are within the acceptable limits. Mean effective gain (MEG) values with respect to the excited port 2 and port 3 is identical and approximately -3dB thus indicating the mean value of these two ports to be almost 1 dB. The multiplexing efficiency of the proposed MIMO antenna is satisfactory over the bandwidth. The group delay is investigated and found to be almost constant with a variation of 1.2 ns thus indicating linear phase characteristic of the antenna. The proposed structure is compared with other mm-wave MIMO antennas and found to be advantageous with respect to the number of antenna elements, compactness, low mutual coupling, co-pol to X-pol isolation, and ECC. A prototype of the proposed 10-elements MIMO is fabricated, and the measured results resemble with the simulated results.

A dual-beam steering one dimensional periodic leaky-wave antenna for large coverage

This paper proposes a dual-beam leaky-wave antenna (LWA) based on substrate integrated waveguide (SIW) technology. The unit cell of the proposed SIW LWA consists pair of transverse and longitudinal slots etched on the top and bottom surface of the SIW. The unit cell characteristics of LAW have been investigated using dispersion analysis. As a result, the open stopband (OSB) problem is suppressed in the broadside direction. As a result, the dual radiating beam of LWA scans the entire space of the elevation plane (XZ plane) without any severe gain degradation at the broadside and endfire. The proposed SIW LWA antenna works in the band of 11.5 to 15.5 GHz with a peak gain of 13 dBi. The measured results are in accord with simulation results.

Study on microstructure and tribological behavior of the selective laser melted MgZnCa alloy

In the current work, MgZnCa alloy was fabricated via selective laser melting (SLM) technology. Microstructural evolution and wear performance of the SLM MgZnCa samples were studied. Tribological behavior of the SLM MgZnCa alloy in a 3.5 wt% NaCl solution was explored. Fine equiaxed grains can be detected both in the XY plane and XZ plane within the SLM samples. Average microhardness of MgZnCa alloy can be enhanced from 65.4 ± 2.04HV0.05 (MgZnCa powder) to 70.6 ± 2.72HV0.05 (SLM MgZnCa samples) owing to the ultra-high cooling rate of SLM process. For tribological behavior of the SLM MgZnCa alloy, adhesive and oxidation wear are the wear mechanisms for the dry friction; while corrosive and adhesive wear are the dominant wear mechanism for the wet friction. Correspondingly, average wear rate of the wet friction [24.21 ± 3.28 × 10−3 mm3/(N∙m)] is 232.10% larger than that of the dry friction [7.29 ± 0.58 × 10−3 mm3/(N∙m)].

Velocity field and diameter distribution of long-chain alcohol-aviation kerosene transverse jet

The velocity field and diameter distribution of long-chain alcohol-aviation kerosene transverse jets were measured and analyzed. Aviation kerosene was chosen as the base fuel. During the transverse jet process, the droplet velocity direction transformed from the vertical direction to the horizontal direction, i.e., to the crossflow direction. The highest turbulence intensity appeared in the liquid–air interaction field. Both the resultant velocities on XZ and XY planes, Uxz and Uxy, and the component velocities along X, Y and Z coordinates, Ux, Uz, and Uy, increased at first and then decreased with the increment of long-chain alcohol volume proportion while the corresponding proportions are different between that of n-butanol and that of n-pentanol. The existence of vortex region was determined in the liquid–air interaction field and the near-field region in the downstream of the transverse jet. The particle size field analysis showed that the droplet size and shape factor and number density were mainly affected by Weg (Weber number of cross gas flow). The characteristics were different under different breakup modes. With the increase in the volume fraction of long-chain alcohol, the droplet size and Sf (shape factor) first increased and then decreased. The addition of long-chain alcohol also reduced the range of particle size with the largest number density. The maximum size of the droplets in the particle size field of n-pentanol-aviation kerosene was larger than that of n-butanol-aviation kerosene.

Resistance of Polymeric Laminates Reinforced with Fabrics against the Growth of Delaminations.

Dependence of the initiation values of the Strain Energy Release Rate, GCi, on the orientation of the reinforcement direction α relative to the delamination front was investigated for two laminates of different interfacial ply arrangements. In the case of the first laminate, the delamination was located at the interface of the layers reinforced with symmetric fabric and unidirectional fabric. In the case of the second laminate, the delamination was located at the interface of layers reinforced with symmetric fabric. In both laminates, the orientation of fibers in the layers separated by the delamination differed by 45° regarding the warp directions. The investigations were carried out for Mode I, Mode II, and Mixed-Mode I/II (GII/GI = 1 and GII/GI = 1.7) loadings using hybrid beam specimens. The major problem appearing in the intended tests was the inevitable lack of symmetry in the xz and xy planes of the specimens and the resulting deformation and stress–strain couplings, causing undesired loading modes. To decrease these couplings, especially designed hybrid beam specimens were used. An auxiliary finite element analysis was performed to assess the remaining effects of the reduced couplings. To ascertain whether statistically significant differences between Gci values for different α occurred, the one-way analysis of variance supplemented by Levene’s test was carried out. The dependence of Gci on α was found out for both laminates. However, it was not equally strong, and it turned out that the loading mode and the interfacial ply were arrangement sensitive.