Incident Position Research Articles

Numerical Study on the Influence of Suction near Expansion Corner on Separation Bubble

Suction is an important control method in the shock wave and boundary layer interaction (SWBLI). Aimed at the problem of separation bubbles induced at the expansion corners, this study investigates the influence of suction on both the dimensions of bubble and the structure of the flow field at varying positions and back pressures under Ma = 2.73. As the upstream suction hole moves to the shoulder point, the size of the separation bubble decreases slightly. The decrease in back pressure leads to an increase in flow deflection angle αh. The low-kinetic-energy fluid in the boundary layer is removed and the thickness of the boundary layer decreases. Suction downstream of the shoulder point leads to an obvious change in separation bubble size. When the bleed position is upstream of the actual location of incident shock (Ddown = 2δ), the separation zone is located at the trailing edge of the hole, and the convergence of the separation shock wave (SS) and the barrier shock wave (BSW) leads to a large increase in the pressure plateau. At the downstream of the incident shock (Ddown = 5δ), the separation zone is situated at the leading edge of the hole, resulting in a substantial reduction in the size of the separation bubble. The flow reaches 88.5% of the theoretical expansion value at the shoulder point and directly turns into the bleeding area at the leeward side of the separation bubble. The deflection angle αh reaches the maximum of 46°, and the sonic flow coefficient Qsonic increases significantly. At the theoretical incident shock position (Ddown = 7δ), the separation zone is far from the suction hole position; the two are almost decoupled. The size of the bubble increases rapidly and the reattachment shock wave (RS) appears.

Investigation of Single Event Transient Effect in Double-Gate InP-Based HEMT

An investigation of single event transient (SET) effect in double-gate InP-based HEMT (DG-HEMT) was conducted by simulations. The effects of different drain voltages (V DS), ion incident positions and angles, linear energy transfer (LET) on SET effect in DG-HEMT were comprehensively analyzed. The simulation results showed that the incident position in gate for DG-HEMT is the most sensitive to SET effect. A higher transient peak drain current (I peak) induced by SET effect was obtained with the higher LET and V DS. At the larger LET and V DS, more electrons were produced by the larger impact ionization rate, leading to the higher I peak. As the incident angle reduces, the track length of incident ions become longer, that is, the sensitive area becomes larger, resulting in the higher I peak. Compared with the single gate InP-based HEMT, the irradiation resistance of device with double gate is improved significantly.

Single pixel readout of a MaPMT-based neutron anger camera system with waveform digitizers

In the neutron-sensitive Anger camera, the scintillator is directly coupled to the photodetectors, such as multiplier tubes or silicon-photomultipliers (SiPMs), and the incident position of the neutron is determined by the center of gravity of the photon distribution from the scintillating material. The photodetectors in the neutron Anger camera are typically arranged in arrays with multiple pixel outputs. To reduce the number of readout channels, the front-end electronics often employ analog signal multiplexing methods, such as row-column summation and resistor networks. However, these methods increase channel crosstalk and noise after compression. In this paper, we propose reading out each pixel of the multi-anode photomultiplier tube (MaPMT) individually and digitizing each analog channel via waveform capture. This approach allows direct collection of the signal from each analog channel, and we use the pulse amplitude method to achieve neutron-gamma discrimination for GS20 scintillator. We tested the neutron two-dimensional imaging capability of the anger camera system using a Cf-252 slowed neutron beam in the laboratory. The neutron position resolution was estimated using the knife-edge function method with B4C mask. By combining this with the traditional center-of-gravity method, we achieved a position resolution of 1.2 mm (FWHM).

Spatial-Dependent Spectral Response of Acousto-Optic Tunable Filters with Inhomogeneous Acoustic Distribution.

The spectral response of an acousto-optic tunable filter (AOTF) is crucial for an AOTF based spectral imaging system. The acousto-optic (AO) interaction within the spatial-distributed area of the acoustic field determines the spectral response of the light incidence. Assuming an ideally uniform acoustic field distribution, phase-matching geometries can be applied to calculate the anisotropic Bragg diffraction in AO interactions, determining the wavelength and direction of the diffracted light. In this ideal scenario, the wavelength of the diffracted light depends solely on the direction of the incident light. However, due to the non-ideal nature of the acoustic field, the wavelength of the diffracted light exhibits slight variations with incident position. In this paper, an analytical model is proposed to calculate the spatial-dependent spectral response of the diffracted light under non-uniform acoustic field distribution. The study computes the variation pattern of the diffracted light amplitude caused by the inhomogeneous acoustic distribution. The theoretical considerations and computational model are confirmed by AOTF frequency scanning experiments. The study demonstrates that the distribution of the acoustic field leads to non-uniform spatial-spectral response in the AOTF, and the spatial AO interaction computational model can provide data support for calibrating AOTF systems in imaging applications.

Observing multi-frequency structured illumination patterns based on an evanescent field in a millimeter-scale polymer slide.

Millimeter-scale slide optical waveguides (OWGs) show the potential to break the barrier of easy-to-use and versatility for total internal reflection (TIR) fluorescence technology. In this paper, multi-frequency structured illumination (SI) patterns resulting from the evanescent field (EF) on the surface of a millimeter-scale polymer slide OWG are observed by measuring the fluorescence intensity distribution of fluorescent dyes deposited on the top of the OWG. The frequency, intensity, and stability of the SI patterns show a strong dependence on the coupling angle of the incident light (changing with the incident position). The distribution of multi-frequency SI patterns in the frequency space is demonstrated for different numerical aperture (NA) imaging systems (NA = 0.3, 0.6, and 0.8), indicating the potential for enhanced resolution for low NA systems with a simple and cheap polymer slide.

Gain-type photodetector with GFET-coupled MoS2/WSe2 heterojunction

Due to its exceptional photovoltaic properties and freedom from crystal lattice matching constraints, transition-metal dichalcogenides (TMDCs) have gained increased attention as a prospective two-dimensional (2D) layered material. Van der Waals heterojunctions (vdWHs) constituted of these materials afford chances for the advancement of high-performance photodetectors and solar cells. However, low light absorption efficiency and electron/hole traps at heterointerfaces make it difficult to improve the response speed and sensitivity of TMDCs vdWH based photodetectors. Here, we designed and realized a GFET-coupled MoS2/WSe2 heterojunction gain photodetector. An interfacial amplification effect is induced when a graphene field-effect transistor (GFET) is coupled to a MoS2/WSe2 heterojunction because of the lengthy carrier lifetime of MoS2 and the ultrahigh mobility of graphene. This effect leads to a high gain for our device, enhancing the photovoltaic response. Compared to the pristine MoS2/WSe2 heterojunction, the device exhibits two to three orders of magnitude improvement in responsivity, up to 50 A/W. Rising and decaying times of 67 μs and 2 μs are also achieved, respectively. By utilizing the strong correlation between the incident light spot position and the photocurrent, the device also enables sensitive detection of the spot position. This research offers an attainable method for developing gain-type, high-speed photodetectors.

Radiation effects on multi-channel Forksheet-FET and Nanosheet-FET considering the bottom dielectric isolation scheme

This study analyzes the single-event transient (SET) characteristics of alpha particles on multi-channel Forksheet-FET and Nanosheet-FET at the device and circuit levels through 3D TCAD simulations. The study investigates the differences in SET responses based on the energy and incident position of incoming alpha particles, considering the structural variances between Forksheet-FET and Nanosheet-FET, as well as the presence or absence of bottom dielectric isolation (BDI) in the fabrication process. Specifically, the introduction of BDI is observed to significantly suppress the voltage drop caused by ‘unintended' current, as it can block the substantial electron-hole pairs (EHP) generated by injected alpha particles in the bulk substrate from reaching the FET terminals. Furthermore, it was confirmed that the size of abnormal current decreases as the energy of the injected alpha particle increases. Additionally, evaluating the response to SET based on the fundamental logic circuit, the CMOS inverter, revealed relatively small abnormal voltage drops for both Forksheet and Nanosheet when BDI was applied, confirming high immunity to radiation effects. Moreover, it can be observed that the application of BDI enhances reliability from a memory perspective by effectively suppressing voltage flips in the SRAM's cross-coupled latch circuit.

Retrospective analysis of the effects of impacted third molar on hematologic patients undergoing hematopoietic stem cell transplantation

ObjectiveThis study aimed to investigate the incidence, treatment status, and impact position of impacted third molars (ITM) and their effects on patients undergoing hematopoietic stem cell transplantation (HSCT). MethodsA retrospective analysis was conducted on the medical records of 454 patients who underwent HSCT, out of which 188 patients had ITM. The presence of ITM and its association with transplant-related infections and complications were recorded and analyzed. ResultsPatients with ITM were significantly younger. The number of mandibular ITM was notably higher than maxillary ones, and the risk of pericoronitis in mandibular ITM was significantly higher than in maxillary ones. Out of 311 ITM in 188 patients, 25 were extracted before transplantation. The proportion of extraction and treatment for ITM with pericoronitis or caries was significantly higher than that for ITM without such problems. Moreover, patients with a history of pre-transplant pericoronitis had a significantly higher probability of developing tooth-related complications during transplantation, caused by pericoronitis in ITM compared to patients without a history of pericoronitis. ConclusionPre-transplant examination and treatment of ITM are essential, especially in cases with a history of pericoronitis. Oral intervention can significantly reduce the occurrence of tooth-related complications related to ITM during transplantation.

Application of modified acetabular anteversion and inclination angles test system in patients undergoing total hip arthroplasty after lumbar fusion

To investigate the accuracy and effectiveness of acetabular cup placement in total hip arthroplasty (THA) after lumbar fusion applying of modified acetabular anteversion and inclination angles test system. A clinical data of 45 patients undergoing THA for osteoarthritis between January 2018 and June 2023 was retrospectively analyzed. All patients had previously received lumbar fusion. The modified acetabular anteversion and inclination angle test system was used in 26 cases (observation group) and not used in 19 cases (control group) during THA. There was no significant difference in baseline data such as gender, age, body mass index, operative side, number of lumbar fusion segments, and preoperative Harris score between the two groups ( P>0.05). The position of acetabular prosthesis, hip function (Harris score), and incidence of complications were compared between the two groups. In the observation group, all acetabular cups were in the safe zone (anteversion angle, 25°-30°) during operation, and 1 acetabular cup (3.85%) was not in the safe zone after operation. In the control group, 9 acetabular cups (47.37%) were not in the safe zone. The postoperative difference between the two groups was significant ( P<0.05). There was no significant difference between intra- and post-operative acetabular inclination angles in the observation group ( P>0.05), and the postoperative acetabular inclination angle was significantly smaller in the observation group than in the control group ( P<0.05). All incisions healed by first intention and no infection occurred. All patients were followed up 6 months. There was no significant difference in Harris score between the two groups at different time point ( P>0.05), and there were significant differences between different time points in the two groups ( P<0.05). No joint dislocation occurred in the observation group during follow-up, while dislocation occurred in 2 cases and femoral impingement syndrome occurred in 1 case of the control group. There was no significant difference in the incidence of complications between the two groups ( P>0.05). For THA patients with lumbar fusion, the ideal placement angle of the acetabular cup can be obtained by using the modified acetabular anteversion and inclination angles test system during operation.

True exponentially enhanced sensing in the non-Hermitian topological phase

Non-Hermitian systems have been employed to construct a high-sensitivity sensor. To evaluate the performance of the sensors, the quantum Fisher information per photon, or equivalently signal-to-noise ratio per photon, is provided as a “true” sensing criterion, which avoids the trivial contribution from the photon numbers. The specific properties of non-Hermitian systems, e.g., exceptional points and skin effect, have been connected to the true exponentially enhanced sensing performance. To date, the relation between the non-Hermitian topological phase and the true sensing performance has not been reported clearly. Here, we construct the high-sensitivity sensor based on the non-Hermitian Su–Schrieffer–Heeger lattice and establish the relationship between the exponentially enhanced sensing and the non-Hermitian topologically nontrivial phase. The saturation of sensing with the size emerges in the sense of one perturbation. Such a limitation can be surpassed through the change of incident positions of driving fields, and the exponentially enhanced sensing reappears.

Development of porous structure for broadening Bragg-peak in scanning carbon-ion radiotherapy: Monte Carlo simulation and experimental validation

PurposeThe present study aimed to develop a porous structure with plug-ins (PSP) to broaden the Bragg peak width (BPW, defined as the distance in water between the proximal and distal 80% dose) of the carbon ion beam while maintaining a sharp distal falloff width (DFW, defined as the distance along the beam axis where the dose in water reduces from 80% to 20%). MethodsThe binary voxel models of porous structure (PS) and PSP were established in the Monte Carlo code FLUKA and the corresponding physical models were manufactured by 3D printing. Both experiment and simulation were performed for evaluating the modulation capacity of PS and PSP. BPWs and DFWs derived from each integral depth dose curves were compared. Fluence homogeneity of 430 MeV/u carbon-ion beam passing through the PSP was recorded by analyzing radiochromic films at six different locations downstream the PSP in the experiment. Additionally, by changing the beam spot size and incident position on the PSP, totally 48 different carbon-ion beams were simulated and corresponding deviations of beam metrics were evaluated to test the modulating stability of PSP. ResultsAccording to the measurement data, the use of PSP resulted in an average increase of 0.63 mm in BPW and a decrease of 0.74 mm in DFW compared to PS. The 2D radiation field inhomogeneities were lower than 3 % when the beam passing through a ≥ 10 cm PMMA medium. Furthermore, employing a spot size of ≥ 6 mm ensures that beam metric deviations, including BPW, DFW, and range, remain within a deviation of 0.1 mm across various incident positions. ConclusionThe developed PSP demonstrated its capability to effectively broaden the BPW of carbon ion beams while maintaining a sharp DFW comparing to PS. The superior performance of PSP, indicates its potential for clinical use in the future.

First demonstration of a single-end readout position-sensitive optical fiber radiation sensor inside the Fukushima Daiichi Nuclear Power Station based on wavelength-resolving analysis

We have developed a new position-sensitive optical fiber radiation sensor that achieves single-end readout and high dose rate application. The sensor determines the incident position of radiation on the optical fiber by using the wavelength dependence of light attenuation within the fiber. Through analysis of the wavelength spectrum output from the fiber end, the incident position of radiation on the optical fiber can be inversely estimated via spectrum unfolding. Using this optical fiber sensor, we measured the radiation distribution inside the Fukushima Daiichi Nuclear Power Station (FDNPS). The actual trend of the incident position of radiation was successfully reproduced in a high dose rate area, with the maximum dose rate exceeding 100 mSv/h. This validates the effectiveness of our new position-sensitive optical fiber radiation sensor.

Performance and Damage Study of Composite Rotor Blades under Impact.

A military helicopter is easily attacked by bullets in a battlefield environment. The composite blade is the main lifting surface and control surface of the helicopter. Its ballistic performance directly determines the vulnerability and survivability of the helicopter in the battlefield environment. To study the ballistic performance of the composite helicopter blade, the damage characteristics of the impacted composite rotor blade are obtained by experiments. A numerical simulation model is established by applying Abaqus software to predict the blade ballistic damage. The three-dimensional progressive damage failure model is used to analyze the ballistic damage under the experimental conditions. The effectiveness and accuracy of the numerical simulation model are verified through a comparison with the experimental results. The ballistic damage of composite blades under three experimental conditions was investigated. The results show that the ballistic damage type of composite blade mainly includes delamination, fiber breakage, and foam collapse. The damage to the composite material at the position of bullet incidence is mainly local shear fracture, while the damage to the composite material at the exit position is mainly fiber tensile fracture. The ballistic damage size of the composite blade is closely related to the ballistic position, incident angle, and structure characteristics along the ballistic path. The larger the incident angle, the smaller the ballistic damage size of the blade. The greater the structural stiffness of the structure near the exit, the greater the damage size of the exit. The numerical simulation model presented in this paper can provide a reference for research on the ballistic performance of composite helicopter blades.

Monte Carlo simulation of spatial resolution of lens-coupled LYSO scintillator for intense pulsed gamma-ray imaging system with large field of view

In this paper, we use a Monte Carlo (MC) simulation based on Geant4 to investigate the influence of four parameters on the spatial resolution of the lens-coupled lutetium yttrium orthosilicate (LYSO) scintillator, including the thickness of the LYSO scintillator, the F-number and minification factor of the lens, and the incident position of the gamma-rays. Simulation results show that when the gamma-rays are incident along the lens axis, the smaller the thickness, the larger the F-number, the larger the minification factor, the higher the spatial resolution, with an isotropic point spread function (PSF). As the incident position of the gamma-rays deviates from the lens axis, the spatial resolution decreases, and the PSF becomes anisotropic. In addition, by analyzing the whole physical process of the lens-coupled LYSO scintillator from gamma-rays to secondary electrons to fluorescence photons, we aim to provide a detailed analysis of the influence of each parameter on the spatial resolution. The results show that the PSF of the secondary electrons energy deposition is almost constant in the simulation, which determines the upper limit of the spatial resolution. Meanwhile, the dispersion process of the fluorescence photons can explain the reason why each parameter affects the spatial resolution.

Investigation of proton single-event transient in CMOS image sensor

With the increasingly widespread application of CMOS image sensors (CIS) in radiation environments, such as aerospace, their radiation effects have gained attention. This paper investigates single-event transient (SET) caused by the proton direct ionization on CIS, combining both experimental and simulation methods. The proton beam energy used in the experiment is 12 MeV, with a flux up to 3.5 × 108 p/(cm2 s). Due to the periodicity of the proton beam, the CIS output displays a phenomenon of alternating brightness and darkness. When the proton beam flux is low, numerous SET bright spots with different outputs are observed. To comprehensively analyze these experimental phenomena, a typical three-dimensional 4T pinned photodiode model is constructed in TCAD, and relevant SET simulation is carried out. The results indicate that incident position, incident time, and the number of incident protons significantly affect the output of SET-generated bright spots, which are key factors contributing to the different bright spots observed in the experiment.

Precision tailoring of laser beam propagation in a single crystalline diamond tool for in situ laser-assisted diamond turning.

The characteristics of laser beam propagation within a diamond tool critically influence the applied thermal softening capability of in situ laser-assisted diamond turning (In-LAT). In the present work, we perform optical geometric analysis, optical simulation and experimental validation to propose a novel diamond tool configuration for precisely tailoring laser beam propagation in In-LAT. First, the characteristics of laser beam propagation in the current In-LAT diamond tool are theoretically and experimentally explored. Second, according to the issues discovered in the current In-LAT diamond tool, an improved tool configuration based on the total internal reflection of a laser beam within the diamond tool is proposed, aiming for promoting refraction of the laser beam from the rake face of the diamond tool as well as eliminating the reflection of laser beam to tool holder. Finally, the optimization of laser beam incident position is carried out for achieving the superior profile and intensity of the emitted laser spot. Current work provides rational laser beam propagation for improving the thermal-softening capability of an In-LAT diamond tool.

Deep Learning Approach for High-accuracy Electron Counting of Monolithic Active Pixel Sensor-type Direct Electron Detectors at Increased Electron Dose.

Electron counting can be performed algorithmically for monolithic active pixel sensor direct electron detectors to eliminate readout noise and Landau noise arising from the variability in the amount of deposited energy for each electron. Errors in existing counting algorithms include mistakenly counting a multielectron strike as a single electron event, and inaccurately locating the incident position of the electron due to lateral spread of deposited energy and dark noise. Here, we report a supervised deep learning (DL) approach based on Faster region-based convolutional neural network (R-CNN) to recognize single electron events at varying electron doses and voltages. The DL approach shows high accuracy according to the near-ideal modulation transfer function (MTF) and detector quantum efficiency for sparse images. It predicts, on average, 0.47 pixel deviation from the incident positions for 200 kV electrons versus 0.59 pixel using the conventional counting method. The DL approach also shows better robustness against coincidence loss as the electron dose increases, maintaining the MTF at half Nyquist frequency above 0.83 as the electron density increases to 0.06 e-/pixel. Thus, the DL model extends the advantages of counting analysis to higher dose rates than conventional methods.

Effect of large-angle incidence on particle identification performance for light-charged ([formula omitted]) particles by pulse shape analysis with a pad-type nTD silicon detector

In recent years, particle discrimination methods based on digital waveform analysis techniques for neutron-transmutation-doped silicon (nTD-Si) detectors have become widely used for the identification of low-energy charged particles. Although the particle discrimination capability of this method has been well demonstrated for small incident angles, the particle discrimination performance may be affected by changes in the detector response when the detector is moved closer to the charged particle source and the incident position distribution and incident angle distribution to the detector become wide. In this study, we performed a beam test for particle discrimination in light-charged (Z≤2) particles using the digital waveform analysis method with a pad-type nTD-Si detector and investigated the dependence of the performance of the particle discrimination on the incident position and incident angle. As the incident angle increased, a decrease in the maximum current was observed, which was sufficient to affect the performance of the particle discrimination. This decrease can be expressed as a function of the penetration depth of the charged particles into the detector, which varies for each nuclide.

Multi-peak solitons in parity-time symmetry composite Mathieu lattices

This paper numerically investigates the existence, stability, and transmission characteristics of multi-peak solitons in parity-time (PT) symmetric composite Mathieu lattices in self-focusing Kerr nonlinear media. These multi-peak solitons are highly sensitive to the incident light power, position, and phase. Different incident lights generate solitons with different transmission characteristics, especially the generation of breather soliton transmission characteristics. These findings have significant theoretical and practical implications for the fields of photonics and nonlinear optics.

Risk of thromboembolic and bleeding events in patients with atrial fibrillation after valvular intervention in either aortic or mitral position

Abstract Background The optimal oral anticoagulant treatment (OAC) for patients with atrial fibrillation (AF) undergoing valvular intervention is uncertain. Mitral valve prostheses are believed to be more thrombogenic than the aortic due to lower flow velocity across the valves. The only randomized controlled trial of AF patients with biological valve prostheses included only patients receiving mitral valve prostheses (1). It is unclear if these findings could be extrapolated to patients receiving aortic valve prostheses. Purpose To describe baseline characteristics and comorbidities of patients receiving biological valve prostheses in aortic or mitral valve position and to investigate possible associations between valve position and the incidence of cardiovascular (CV) death, ischemic stroke or systemic embolism and major bleeding. Methods All patients in Sweden undergoing open heart surgery with aortic or mitral valve replacement with biological prostheses between 2010-2016 with known AF were included. The study cohort was identified in the SWEDEHEART registry. Information on comorbidities, drug exposure and occurrence of outcome events was collected from SWEDEHEART and other national registries. Association between the position of valve prosthesis (mitral and aortic) and incidence of outcome events was investigated using Cox regression analysis. Multivariable adjustments were made for comorbidities. Results In total, 2359 patients with AF underwent aortic (n=2103) or mitral (n=256) valve replacement. The median age was 75 and 73 years, respectively. Hypertension, diabetes mellitus and previous TIA were more common in the aortic valve group, whereas heart failure and previous major bleeding was more frequently observed in the mitral group. In both groups, about 50% of the patients were not on OAC treatment at time of discharge from valve intervention, despite that the mean CHA2DS-VASc score was 3.3 and 3.2, respectively. Mitral valve prostheses were associated with similar risk of CV death (hazard ratio (HR) 1.09; 95% confidence interval (CI), 0.77 – 1.56), ischemic stroke and systemic embolism (HR 1.27; 95% CI, 0.85-1.92) compared to aortic valve prostheses. In contrast, receiving mitral valve prosthesis was associated with lower risk of major bleeding compared to aortic prosthesis (HR 0.58; 95% CI 0.38 – 0.88). Conclusion(s) The study indicated similar risk of CV death, ischemic stroke and systemic embolism among patients with AF undergoing valve replacement with biological prostheses in either aortic or mitral position. Mitral valve replacement was associated with lower risk of major bleeding.