Virtual Probe Research Articles

Virtual cavity probe for the real-time identification of cavity burst-noise type in superconducting radio-frequency systems

Burst-noise events are primary trip sources at the China Accelerator Facility for superheavy Elements (CAFE2), characterized by a rapid burst noise in the cavity pick-up signal categorizable into three distinct types: flashover, electronic quench (E-quench), and partial E-quench. Herein, we design an algorithm identifying the burst-noise event types in real time to realize a real-time discrimination of the three types of burst-noise events. This algorithm is based on a virtual cavity probe constructed with the forward and reflected signals of the cavity and integrated into a field-programmable gate array (FPGA). Moreover, we introduce an innovative method for calibrating the transmission delay in channels. This FPGA-based low-level radio-frequency algorithm identifies the burst-noise event type in real time. Its effectiveness has been validated in the CAFE2 facility, offering valuable data support for future advancements in machine learning-based fault classification and dark-current characterization.

3D Hybrid modeling for the ultrasonic phased array inspection of porosity in heavy plates: Simulation and experimental validation

Quantitative NDT modeling and simulation tools are important in design and fabrication of ultrasonic phased array probes with optimum characteristics and reduce the number of experimental efforts and development time. In order to achieve high accuracy (Amplitude deviation < 1 dB) with a low computational time in the simulation, the modeling tools require not only the high-frequency approximation of the ultrasonic wave propagation but also the high-precision electro-acoustic coupling model. This paper describes a computationally efficient 3D time-dependent hybrid model for the simulation of ultrasonic phased array inspection of porosity in heavy plates. This method combines the results of both 3D finite element analysis (PZFLex-FEA) and the semi-analytical ultrasonic simulation “Ray-Tracing”. As a first step, we demonstrate the FEA modeling of an ultrasonic phased array probe, which includes the full 1-3 piezocomposite design with the arrangement of array elements, conducting electrodes, multi-phase backing material, acoustical matching layer and electrical circuit of a 50 Ohm coaxial cable. In the current FEA simulation, we considered the acoustical and electrical cross-talk between the adjacent elements of an ultrasonic array sensor. In the second step, the FEA-simulated ultrasonic pulse-echo signal and its frequency spectrum of an array element in the farfield region are further used as the reference input signal in the CIVA-UT software to simulate the imaging of porosity in heavy plates, quantitatively. The design of the 3D wedge-geometry of the application specific array sensor is modeled and optimized using the CIVA raytracing and multi-phase backing models. The real excitation pulse of the industrial ultrasonic testing equipment “ROMIS (ROSEN Modular Inspection System)” is also included in the simulation to achieve high accuracy in the current hybrid modeling. The dependency of the detectability of the porosity on the frequency of the array sensor and the active element group so-called “Virtual Probe” are quantitatively analyzed. Finally, the 3D hybrid model simulated Time Corrected Gain (TCG) curves of the porosity like defects in the reference steel plates are compared with the real experiments and a good quantitative agreement is achieved.

Transonic Compressor Darmstadt Open Test Case: Experimental Investigation of Stator Secondary Flows and Hub Leakage

Abstract The future trend of clean sky aviation has led to a smaller core engine, resulting in highly loaded stages with increased relative tip gaps and leakage flows, which causes a reinforced influence of secondary flow phenomena. This article experimentally investigates the secondary flow effects in the 3D-optimized shrouded stator of the TUDa-GLR-OpenStage, representative of a transonic high-pressure compressor front stage, and its susceptibility to typical hub leakage flows. The impact of stator hub leakage on efficiency and total pressure ratio is investigated for several operating speeds, from subsonic to nominal transonic operating conditions. Steady five-hole probe and time-resolved virtual multi-hole probe measurements at different operating conditions at nominal speed are conducted to investigate the underlying loss mechanisms. The leakage mass flow is determined using the measured pressure difference within the fin seal. Steady results show that the optimized 3D stator effectively suppresses the hub corner separation compared to the predecessor 2D stator, but its performance is further limited by a near-tip separation. With the increased stator hub leakage (at a leakage-to-main flow ratio of about 0.4%), the compressor isentropic efficiency generally drops (by about −0.5%) at the full operating range due to an enhanced hub corner separation effect. However, the increased leakage also helps alleviate the tip-corner separation when operating near stall, leading to a smaller efficiency penalty under these conditions. Unsteady results reveal the sensitivity of transient compressor performance to the passing rotor wake, but limited interaction between this phenomenon and the increased leakage is observed. These findings provide insight into the stator hub leakage-related penalties on the compressor aerodynamics efficiency.

High-precision measurement of gear tooth profile using line spectral confocal method

The optical measurement of gear tooth profile has the advantages of high efficiency and non-contact, but its measurement accuracy has not reached the accuracy of the existing contact method. Therefore, a line spectral confocal high-precision gear tooth profile measurement method is proposed. First, the gear optical measurement coordinate system is established using a standard mandrel and the optimal measurement position model for the measured tooth profile not blocked by the adjacent tooth is established. Then, to solve the problem that the tooth profile information contained in the optical measurement results and contact measurement results is inconsistent and cannot be directly compared, a virtual probe envelope filtering method for the tooth profile optical measurement data is proposed. Next, to verify the accuracy of the line spectral confocal gear measurement system, the tooth profile deviation measurement experiments using a two-accuracy-level gear involute master are conducted. The results show that the proposed line spectral confocal method has high measurement repeatability and accuracy. The maximum absolute difference between the tooth profile deviation measurement results and the verification results is 0.16 µm, and that the tooth profile deviation curve maintains highly consistent with the verification curve. Finally, the tooth profile deviation measurement experiments using a two-accuracy-level spur gear are performed. The results indicate that the maximum absolute difference between the tooth profile deviation evaluation results measured with the proposed method and the gear measuring center is 0.28 µm. The maximum absolute difference between the two profile deviation curves by point-to-point is 0.52 μm, and the average absolute difference is 0.16 μm. The proposed line spectral confocal method can realize the high-precision measurement of gear tooth profile.

SiteFerret: Beyond Simple Pocket Identification in Proteins.

We present a novel method for the automatic detection of pockets on protein molecular surfaces. The algorithm is based on an ad hoc hierarchical clustering of virtual probe spheres obtained from the geometrical primitives used by the NanoShaper software to build the solvent-excluded molecular surface. The final ranking of putative pockets is based on the Isolation Forest method, an unsupervised learning approach originally developed for anomaly detection. A detailed importance analysis of pocket features provides insight into which geometrical (clustering) and chemical (amino acidic composition) properties characterize a good binding site. The method also provides a segmentation of pockets into smaller subpockets. We prove that subpockets are a convenient representation to pinpoint the binding site with great precision. SiteFerret is outstanding in its versatility, accurately predicting a wide range of binding sites, from those binding small molecules to those binding peptides, including difficult shallow sites.

Human teleoperation - a haptically enabled mixed reality system for teleultrasound

ABSTRACT Current teleultrasound methods include audiovisual guidance and robotic teleoperation, which constitute tradeoffs between precision and latency versus flexibility and cost. We present a novel concept of “human teleoperation” which bridges the gap between these two methods. In the concept, an expert remotely teloperates a person (the follower) wearing a mixed-reality headset by controlling a virtual ultrasound probe projected into the person’s scene. The follower matches the pose and force of the virtual device with a real probe. The pose, force, video, ultrasound images, and 3-dimensional mesh of the scene are fed back to the expert. This control framework, where the actuation is carried out by people, allows more precision and speed than verbal guidance, yet is more flexible and inexpensive than robotic teleoperation. The purpose of this paper is to introduce this concept as well as a prototype teleultrasound system with limited haptics and local communication. The system was tested to show its potential, including mean teleoperation latencies of 0.32 ± 0.05 seconds and steady-state errors of 4.4 ± 2.8 mm and 5.4 ± 2.8 ∘ in position and orientation tracking respectively. A preliminary test with an ultrasonographer and four patients was completed, showing lower measurement error and a completion time of 1:36 ± 0:23 minutes using human teleoperation compared to 4:13 ± 3:58 using audiovisual teleguidance.

Simultaneous Trapping and Manipulation of Micro-Specimens Using an All-Dielectric One-Dimensional Photonic Crystal

We demonstrate a platform where optical evanescent vortex has been realized by focusing a laser beam with orbital angular momentum (OAM) onto an all-dielectric one-dimensional photonic crystal (1DPC). This platform can simultaneously trap and manipulate various micro-scale specimens (i.e., polymer microsphere, inorganic microwire, yeast cells and Escherichia coli cells). The working principle lies in the low loss of the excited Bloch surface waves (BSWs) that propagate on the dielectric 1DPC and form a virtual probe for trapping the specimens. The OAM encoded by the BSWs will then simultaneously manipulate the specimens, such as inducing the rotation or orbital motion. Both experimental and simulation results verify that the capability of this new platform is due to the two kinds of optical force induced by the BSWs, which presents a different mechanism from that by the commonly optical electric-field vortex. Optical trapping or manipulation of micro & nano specimens play important roles in physics, life and materials sciences, thus, this new platform will find applications in microscale assembly, cell-cell interaction, bioprinting and biosensing research, and also expand our understanding of the physics interaction between vector beam and BSWs.

Mining and Characterization of Thermophilic Glucose Isomerase Based on Virtual Probe Technology.

Fructose, which is produced by the isomerization of glucose isomerase, is a crucial precursor for the biosynthesis of rare sugars. In this study, thermophilic glucose isomerases (GI) from Caldicellulosiruptor acetigenus (CAGI), Thermoanaerobacter thermocopriae (TTGI), and Thermotoga petrophila (TPGI) were screened from GenBank database by a virtual probe and were successfully expressed in Escherichia coli BL21(DE3). The results of characterization demonstrated that the optimal pH for CAGI and TTGI were 8.0 and were maintained at 80% in a slightly acidic environment. The relative residual activities of CAGI and TTGI were found to be 40.6% and 52.6%, respectively, following an incubation period of 24h at 90 ℃. Furthermore, CAGI and TTGI exhibited superior catalytic performance that their reaction equilibrium both reached only after an hour at 85 ℃ with 200g/L glucose, and the highest conversion rates were 54.2% and 54.1%, respectively. This study identifies competitive enzyme candidates for fructose production in the industry with appreciable cost reduction.

Explosive dispersal of particles in high speed environments

In this paper, we present the results of the explosive dispersal of particles in high-speed environments. We carry out Euler–Lagrange numerical simulations of a source at quiescent ambient conditions as well as moving at Mach numbers of 3 and 6. Particle volume fractions of 0%, 1%, and 4.5% are presented. The detonation profile is computed with the Jones–Wilkins–Lee equation of state using a reactive burn model. Non-static cases provide a framework to consider the effect of a bow shock and pre-existing high-speed flow conditions on the dispersal process. We also compute averages of both static and dynamic pressures, as well as impulse density histories on virtual probe planes to characterize the momentum of the flow and particles that would deposit on a target. Results suggest that the presence of the particles can have a substantial effect on the pressure average of the virtual target planes.

Virtually probing “Faraday three-dimensional nanoprinting”

Three-dimensional (3D) nanoprinting is designed to harness properties such as size, geometry, material, and topology to obtain metamaterials for nano-photonics and nano-electronics with unique functionalities. Although previous works based on charged aerosols have printed various 3D nanostructures, understanding the additive process remains essentially unexplored. Here, we uncover the physics of 3D nanoprinting by observing anomalous nanoparticle structures originating from a floating layer of concentrated charged nanoparticles (named nano-dust cloud and being the source for additive manufacturing) over a charged surface. An analytical approach has been developed to extract essential printing parameters – the charge concentration of the floating layer and the charge density on the dielectric surface – from the experimental data of a designed virtual probe. Our work can provide new vistas for controlling and programming 3D nanoprinting via charged aerosols. • An analytical approach explains how the electric fields are reconfigured to an electrical funnel. • The parameters of the Faraday 3D nanoprinting are revealed theoretically and experimentally. • The printed structures function as virtual probes for operando evaluation of the printing process. • Due to the ‘cushion’ field, nano-dust cloud is lifted above a dielectric surface. • The nano-dust cloud can be controlled to be present or not.

Optimization of time domain diffuse correlation spectroscopy parameters for measuring brain blood flow.

.Significance: Time domain diffuse correlation spectroscopy (TD-DCS) can offer increased sensitivity to cerebral hemodynamics and reduced contamination from extracerebral layers by differentiating photons based on their travel time in tissue. We have developed rigorous simulation and evaluation procedures to determine the optimal time gate parameters for monitoring cerebral perfusion considering instrumentation characteristics and realistic measurement noise.Aim: We simulate TD-DCS cerebral perfusion monitoring performance for different instrument response functions (IRFs) in the presence of realistic experimental noise and evaluate metrics of sensitivity to brain blood flow, signal-to-noise ratio (SNR), and ability to reject the influence of extracerebral blood flow across a variety of time gates to determine optimal operating parameters.Approach: Light propagation was modeled on an MRI-derived human head geometry using Monte Carlo simulations for 765- and 1064-nm excitation wavelengths. We use a virtual probe with a source–detector separation of 1 cm placed in the pre-frontal region. Performance metrics described above were evaluated to determine optimal time gate(s) for different IRFs. Validation of simulation noise estimates was done with experiments conducted on an intralipid-based liquid phantom.Results: We find that TD-DCS performance strongly depends on the system IRF. Among Gaussian pulse shapes, pulse length appears to offer the best performance, at wide gates (500 ps and larger) with start times 400 and 600 ps after the peak of the TPSF at 765 and 1064 nm, respectively, for a 1-s integration time at photon detection rates seen experimentally (600 kcps at 765 nm and 4 Mcps at 1064 nm).Conclusions: Our work shows that optimal time gates satisfy competing requirements for sufficient sensitivity and sufficient SNR. The achievable performance is further impacted by system IRF with quasi-Gaussian pulse obtained using electro-optic laser shaping providing the best results.

Uncertainty Evaluation on Multi-Hole Aerodynamic Pressure Probes

Abstract In the frame of a continuous improvement of the performance and accuracy in the experimental testing of turbomachines, the uncertainty analysis on measurements instrumentation and techniques is of paramount importance. For this reason, since the beginning of the experimental activities at the Laboratory of Fluid Machines (LFM) located at Politecnico di Milano (Italy), this issue has been addressed and different methodologies have been applied. This paper proposes a comparison of the results collected applying two methods for the measurement uncertainty quantification to two different aerodynamic pressure probes: sensor calibration, aerodynamic calibration and probe application are considered. The first uncertainty evaluation method is the so-called “uncertainty propagation” method (UPM); the second is based on the “Monte Carlo” method (MCM). Two miniaturized pressure probes have been selected for this investigation: a pneumatic five-hole probe and a spherical fast-response aerodynamic pressure probe (sFRAPP), the latter applied as a virtual four-hole probe. Since the sFRAPP is equipped with two miniaturized pressure transducers installed inside the probe head, a specific calibration procedure and a dedicated uncertainty analysis are required.

Light-Addressable Square Wave Voltammetry (LASWV) Based on a Field-Effect Structure for Electrochemical Sensing and Imaging.

Here, we describe a new photoelectrochemical imaging method termed light-addressable square wave voltammetry (LASWV). It measures local SWV currents at an unstructured electrolyte/insulator/semiconductor (EIS) field-effect substrate by illuminating and addressing the substrate with an intensity-constant laser. Due to the continuous generation of charge carriers in the light-irradiated semiconductor, the drift and diffusion of photoinjected carriers within the semiconductor bulk would slow down the equilibrium processes of charge and discharge in one potential pulse cycle. Therefore, even though SWV is sampled at the end of the direct and reverse pulses to reject capacitive currents, in our approach, photoinduced capacitive current can still be detected as an effective sensory signal. The obtained current-potential (I-V) curve shows a typical shape corresponding to the accumulation, depletion, and inversion regions of field-effect devices. We demonstrated that LASWV can be used as a field-effect chemical sensor to measure the solution pH and monitor enzymatic reactions. More importantly, since the charge carriers are only generated in the illuminated area, the laser spot in the device can be used as a virtual probe to record local electrochemical properties such as impedance with microresolution.

Virtual probe stimulated tip-enhanced Raman spectroscopy: The extreme field enhancement in virtual-real probe dimer

Tip-enhanced Raman spectroscopy (TERS) can be used for scanning imaging, molecular detection, and chemical analysis. The improvement of detection sensitivity, which is related to the electric field enhancement in the TERS substrate, has attracted much attention from researchers. In this work, we numerically studied the local electric field enhancement in the virtual-real probe dimer structure with a vertical gap. We mainly analyzed the influence of the structure parameters on the field enhancement using the finite-difference time-domain method. The Raman enhancement factor could reach up to 1.6×1015. The local field enhancement benefits from plasmon hybridization between the longitudinal component of the virtual probe and the local surface plasmon of the real probe. We also found that the full width at half maximum of the electric field was as narrow as 7.8 nm, and the volume of the hotspot for single-molecule detection can reach a maximum value of 155 nm3. The virtual-real probe dimer structure has ultrahigh field enhancement and spatial resolution, which is promising for high-sensitivity detection and high-resolution imaging.

A Case Study on Pathogen Transport, Deposition, Evaporation and Transmission: Linking High-Fidelity Computational Fluid Dynamics Simulations to Probability of Infection

A high-fidelity, low-Mach computational fluid dynamics simulation tool that includes evaporating droplets and variable-density turbulent flow coupling is well-suited to ascertain transmission probability and supports risk mitigation methods development for airborne infectious diseases such as COVID-19. A multi-physics large-eddy simulation-based paradigm is used to explore droplet and aerosol pathogen transport from a synthetic cough emanating from a kneeling humanoid. For an outdoor configuration that mimics the recent open-space social distance strategy of San Francisco, maximum primary droplet deposition distances are shown to approach 8.1 m in a moderate wind configuration with the aerosol plume transported in excess of 15 m. In quiescent conditions, the aerosol plume extends to approximately 4 m before the emanating pulsed jet becomes neutrally buoyant. A dose–response model, which is based on previous SARS coronavirus (SARS-CoV) data, is exercised on the high-fidelity aerosol transport database to establish relative risk at eighteen virtual receptor probe locations.

A New Experimental Study and SPH Comparison for the Sequential Dam-Break Problem

The floods following the event of a dam collapse can have a significant impact on the downstream environment and ecology. Due to the limited number of real-case data for dam-break floods, laboratory experiments and numerical models are used to understand the complex flow behavior and to analyze the impact of the dam-break wave for different scenarios. In this study, a newly designed experimental campaign was conducted for the sequential dam-break problem in a rectangular channel with a steep slope, and the obtained results were compared against those of a particle-based numerical model. The laboratory tests permitted a better understanding of the physical process, highlighting five successive stages observed in the downstream reservoirs: dam-break wave propagation, overtopping, reflection wave, run-up, and oscillations. Experimental data were acquired using a virtual wave probe based on an image processing technique. A professional camera and a smartphone camera were used to obtain the footage of the experiment to examine the effect of the resolution and frame rate on image processing. The numerical results were obtained through the Smoothed Particle Hydrodynamics (SPH) method using free DualSPHysics software. The experimental and numerical results were in good agreement generally. Hence, the presented data can be used as a benchmark in future studies to validate the SPH and other Computational Fluid Dynamics (CFD) methods.

Development of a VR Simulator for Training of Posterior Cervical Spine Fusion Surgery

AbstractIt is important to avoid iatrogenic injuries of nerves and blood vessels during the pedicle screw insertion stage of posterior cervical spine decompression and fusion surgery. First, it is necessary to determine the length and angulation of the pedicle screws for safety and stability. Second, it is necessary to drill precise preparation holes for the pedicle screws using a pedicle probe. In this work, we developed a VR training system for pedicle screw planning and basic drilling skills. The VR system was built with a pen‐style haptic device and a head‐mounted display. Trainees used the haptic pen as a virtual pedicle probe. In order to simulate bone hardness and stress accumulation at the virtual pedicle probe tip in the virtual surgery, we developed a voxel‐based bone drilling simulator. To reduce the heavy load required for voxel processing, the simulator was constructed as a hybrid system that included a removal volume voxel model for drilling areas and a fixed polygonal mesh model for other areas. 3D models of a cervical spine were generated from CT scan images of a patient. This paper evaluated the system through a subjective evaluation by a specialist and via the training results for novice trainees. We discuss the evaluation results and training effectiveness with the simulator. © 2020 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Minor impact of constraint from perivascular flow probes on wave intensity analysis

Perivascular flow probes are considered the gold-standard for measuring volumetric blood flow in animal studies. Although flow probes are generally placed non-constrictively around the vessel of interest, pressure-elevating interventions performed during an experiment may lead to vessel expansion and some probe-vessel impingement, particularly in highly compliant vessels such as adult sheep aorta or major pulmonary arteries in fetus lambs. This study assessed to what extent such mild flow probe constraint may impact on wave intensity analysis. We also investigated whether errors arising from flow probe constraint could explain apparent pressure reflection indices (Rp > 1) that have been observed in fetus lamb pulmonary arteries under some experimental conditions. These questions were investigated with one-dimensional models of an adult sheep aorta and fetus lamb pulmonary artery, with a virtual flow probe incorporated as a non-linear external constraint term in the vessel constitutive equation. Model-derived flow and pressure were subjected to standard analysis procedures that would be applied experimentally (correcting for apparent velocity lags and calculating wave speed via the PU-loop method). For the adult sheep model, simulations covering a wide range of haemodynamic conditions revealed a mostly minor effect (<10%) of probe constraint on the intensity and pressure effects of the three major waves (forward compression wave, forward decompression wave, backward compression wave). Moreover, flow probe constraint had essentially no impact on Rp in the fetus lamb model, suggesting that such constraint is unlikely to be responsible for an observed Rp > 1. Mild flow probe constraint is likely to have little impact on wave intensity analysis.

Experimental and Numerical Analysis of a Dam-Break Flow through Different Contraction Geometries of the Channel

Dam-break wave propagation usually occurs over irregular topography, due for example to natural contraction-expansion of the river bed and to the presence of natural or artificial obstacles. Due to limited available dam-break real-case data, laboratory and numerical modeling studies are significant for understanding this type of complex flow problems. To contribute to the related field, a dam-break flow over a channel with a contracting reach was investigated experimentally and numerically. Laboratory tests were carried out in a smooth rectangular channel with a horizontal dry bed for three different lateral contraction geometries. A non-intrusive digital imaging technique was utilized to analyze the dam-break wave propagation. Free surface profiles and time variation of water levels in selected sections were obtained directly from three synchronized CCD video camera records through a virtual wave probe. The experimental results were compared against the numerical solution of VOF (Volume of Fluid)-based Shallow Water Equations (SWEs) and Reynolds-Averaged Navier-Stokes (RANS) equations with the k-ε turbulence model. Good agreements were obtained between computed and measured results. However, the RANS solution shows a better correspondence with the experimental results compared with the SWEs one. The presented new experimental data can be used to validate numerical models for the simulation of dam-break flows over irregular topography.

Quantitative, experimentally-validated, model of MoS2 nanoribbon Schottky field-effect transistors from subthreshold to saturation

We investigate the channel length dependence of the electrical characteristics of chemical vapor transport (CVT)-grown MoS2 nanoribbon (NR) Schottky barrier field-effect transistors to provide insights into the transport properties of such nanostructures. The MoS2 NRs form spontaneously during the CVT growth, without the application of etching. Back gated transmission line measurement FETs were fabricated on a 45μm-long NR with channel lengths ranging between 200 nm and 3μm. Contact and sheet resistances were extracted from the electrical measurements and their back-gate bias dependence was analyzed. Numerical modeling based on a virtual probe approach combined with the Landauer formalism shows excellent agreement with the measurements. The model enables a quantitative extraction of the intrinsic FET properties, e.g., mean-free-path and electron mobility, and their dependence on carrier density and investigation of plausible trap distributions. A record electron mobility for a MoS2 NR channel of ∼81cm2/Vs was achieved.