Sinusoidal Pattern Research Articles

Three-dimensional measurement based on equal spacing binary fringe coding

Abstract Binary fringe projection technology can effectively avoid the measurement error caused by nonlinearity in structured light three-dimensional measurement system. In this paper, a binary fringe projection coding based on equal spacing is proposed firstly, the image sequence projected by binary fringes with equal spacing is corresponding to the sinusoidal intensity values in the same period one by one, and then the sinusoidal fringes are generated by weighted superposition. The experimental results show that, compared with the traditional four-step and 12-step phase shifting methods, the mean square error of the synthesized sinusoidal pattern is reduced by 36.74% and 18.24% respectively, and the mean square error of the distance between the obtained spherical point cloud of the standard sphere and the center of the fitting standard sphere is reduced by 89.36% and 77.27% respectively.

Sinusoidal parameter estimation technique for three-dimensional object reconstruction from a single object capture

Fringe projection profilometry is widely used for three-dimensional measurements. Sinusoidal patterns are commonly used; those patterns are modulated by the object’s topography, raising the necessity to relate this modulation with the object’s shape. Several approaches have been proposed and can be classified as spatial or temporal algorithms, making them suitable for dynamic or static objects. In this paper, an improvement of a different approach to analyze the modulated fringe pattern is proposed; from a single fringe pattern, the object’s shape can be found with the determination of maximums and minimums of the signal, avoiding the use of Fourier transform, wavelet transform, and Riez transform techniques.

Perceived competences by graduated nurses before and during COVID-19 restrictions: A repeated cross-sectional study from 2019 to 2022

AimsTo explore the differences, if any, in the competences perceived by newly graduated nurses who attended their education before and during the COrona VIrus Disease 19 (COVID-19) restrictions. BackgroundNursing education has undergone significant changes because of the COVID-19 restrictions. However, to date the perceived competences at the point of graduation have not been investigated over the restrictions years compared with the pre-restrictions era. DesignA repeated cross-sectional study followed by a pseudo-panel analysis. The Strengthening the Reporting of Observational Studies in Epidemiology checklist was used. Data on individual, nursing programme and perceived competences with Nurse Competence Scale (NCS) were collected and analysed by also using a pseudo-panel approach. MethodsTwo universities were involved. Those eligible were nursing students who graduated: (1) in 2020 (=323) as the first post-COVID-19 group, who were studying in the 3rd year at the onset of the restrictions; (2) in 2021 (=250) as the second post-COVID-19 graduated group, who were in the 2nd year at the restrictions onset; and (3) in 2022 (=247) as the third post-COVID-19 group, attending the 1st year of nursing education at the onset of the restrictions. Data were compared with those who graduated in 2019 (=336, pre-COVID-19 group). ResultsThe overall NCS score was higher in the pre-COVID-19 group (68 out of 100, 95 % Confidence of Interval [IC] 66.4–69.5), lower in the first post-COVID-19 graduates (62.9, 95 % CI 60–65.8), higher in the second (66.6, 95 % CI 63.6–69.4) and lower again in the third post-COVID-19 group (63.8, 95 % CI 60.9–66.5). A sinusoidal pattern also emerged for the frequency of use of the competences from the pre-COVID-19 (2.3 out of 3) and the first group (2.1) and increased between the second and the third group (from 2.1 to 2.3) (p< 0.001). These sinusoidal trends are also evident in the pseudo-panel analysis. ConclusionsA different degree of perceived competences at the point of graduation emerged, with higher competences in the pre-restrictions group, lower in the first post-COVID-19 generation, higher again in the second and third group. However, all scores were over 60 points out of 100, thus indicating sufficient competences. The frequency of use of such competences slightly changed over the years with limited practical relevance. The findings may inform reflections regarding innovations in the clinical placements pathways as well as in the strategies supporting newly graduates nurses in their transition from education to health-care settings.

Experimental study of wire arc additively manufactured steel sections stiffened by sinusoidal waves

Numerical models and initial tests conducted on specimens produced using selective laser melting have indicated that structural sections may be stiffened by imposing sinusoidal waveforms on their geometries which delay buckling and improve the overall buckling resistance. Wire arc additive manufacturing (WAAM) stands out as the most promising additive manufacturing technique for fabricating sections of the scale required in the construction industry, however, there is currently a lack of understanding of how the undulating surface finish inherent to WAAM will affect the stiffening effect of the sinusoidal waveforms. Therefore, this paper details an experimental study involving ten WAAM equal angle sections stiffened with two different sinusoidal wave patterns identified as the optimal patterns in previous numerical analysis. The production, geometric measurement and testing of the sections are described and the material properties of the WAAM material are determined. All equal angle section specimens tested fall within Eurocode 3 Class 4 and the stiffening wave patterns are shown to benefit the slenderer sections more. Comparative analysis between the material consumption and relative strength is provided, highlighting the potential for sinusoidal WAAM sections to improve the material efficiency and facilitate economic design practices within the steel construction industry.

Theoretical principles explain the structure of the insect head direction circuit.

To navigate their environment, insects need to keep track of their orientation. Previous work has shown that insects encode their head direction as a sinusoidal activity pattern around a ring of neurons arranged in an eight-column structure. However, it is unclear whether this sinusoidal encoding of head direction is just an evolutionary coincidence or if it offers a particular functional advantage. To address this question, we establish the basic mathematical requirements for direction encoding and show that it can be performed by many circuits, all with different activity patterns. Among these activity patterns, we prove that the sinusoidal one is the most noise-resilient, but only when coupled with a sinusoidal connectivity pattern between the encoding neurons. We compare this predicted optimal connectivity pattern with anatomical data from the head direction circuits of the locust and the fruit fly, finding that our theory agrees with experimental evidence. Furthermore, we demonstrate that our predicted circuit can emerge using Hebbian plasticity, implying that the neural connectivity does not need to be explicitly encoded in the genetic program of the insect but rather can emerge during development. Finally, we illustrate that in our theory, the consistent presence of the eight-column organisation of head direction circuits across multiple insect species is not a chance artefact but instead can be explained by basic evolutionary principles.

Three 1-bit speckle-embedded pulse-width modulation patterns for robust absolute 3D measurement

In three-dimensional (3D) shape measurement techniques using structured light, 1-bit pulse-width modulation (PWM) patterns and 1-bit speckle patterns can be projected at high speed. However, when combining PWM and speckle patterns to integrate their advantages, the decoupling problem is insurmountable. In this work, a novel 1-bit speckle-embedded PWM (SPPWM) method was proposed to achieve absolute 3D shape measurement using only three binary patterns. Our method consists of three main steps: First, a sinusoidal pattern reconstruction network was proposed to eliminate the high-order harmonics and speckle patterns in the SPPWM patterns and obtain high-quality sinusoidal patterns. Second, a multi-temporal spatial correlation matching algorithm was proposed to obtain a coarse disparity map from the three SPPWM patterns. Third, the high-accuracy wrapped phase map is used as an additional constraint for refining the coarse disparity map to obtain the final high-accuracy disparity map for absolute 3D measurement without phase unwrapping. Our method combines the advantages of fringe projection profilometry techniques for high-precision wrapped phase retrieval and speckle correlation matching algorithms for robust and unambiguous disparity map calculation. The experimental results demonstrated that our method could realize high-precision absolute 3D shape measurement with an accuracy of 0.057 mm using only three 1-bit SPPWM patterns. Furthermore, different simulation noises were used to demonstrate the robustness of the proposed method.

Commissioning of a novel PET-Linac for biology-guided radiotherapy (BgRT).

Biology-guided radiotherapy (BgRT) is a novel radiotherapy delivery technique that utilizes the tumor itself to guide dynamic delivery of treatment dose to the tumor. The RefleXion X1 system is the first radiotherapy system developed to deliver SCINTIX® BgRT. The X1 is characterized by its split arc design, employing two 90-degree positron emission tomography (PET) arcs to guide therapeutic radiation beams in real time, currently cleared by FDA to treat bone and lung tumors. This study aims to comprehensively evaluate the capabilities of the SCINTIX radiotherapy delivery system by evaluating its sensitivity to changes in PET contrast, its adaptability in the context of patient motion, and its performance across a spectrum of prescription doses. A series of experimental scenarios, both static and dynamic, were designed to assess the SCINTIX BgRT system's performance, including an end-to-end test. These experiments involved a range of factors, including changes in PET contrast, motion, and prescription doses. Measurements were performed using a custom-made ArcCHECK insert which included a 2.2cm spherical target and a c-shape structure that can be filled with a PET tracer with varying concentrations. Sinusoidal and cosine4 motion patterns, simulating patient breathing, was used to test the SCINTIX system's ability to deliver BgRT during motion-induced challenges. Each experiment was evaluated against specific metrics, including Activity Concentration (AC), Normalized Target Signal (NTS), and Biology Tracking Zone (BTZ) bounded dose-volume histogram (bDVH) pass rates. The accuracy of the delivered BgRT doses on ArcCHECK and EBT-XD film were evaluated using gamma 3%/2mm and 3%/3mm analysis. In static scenarios, the X1 system consistently demonstrated precision and robustness in SCINTIX dose delivery. The end-to-end delivery to the spherical target yielded good results, with AC and NTS values surpassing the critical thresholds of 5 kBq/mL and 2, respectively. Furthermore, bDVH analysis consistently confirmed 100% pass rates. These results were reaffirmed in scenarios involving changes in PET contrast, emphasizing the system's ability to adapt to varying PET avidities. Gamma analysis with 3%/2mm (10% dose threshold) criteria consistently achieved pass rates>91.5% for the static tests. In dynamic SCINTIX delivery scenarios, the X1 system exhibited adaptability under conditions of motion. Sinusoidal and cosine4 motion patterns resulted in 3%/3mm gamma pass rates>87%. Moreover, the comparison with gated stereotactic body radiotherapy (SBRT) delivery on a conventional c-arm Linac resulted in 93.9% gamma pass rates and used as comparison to evaluate the interplay effect. The 1cm step shift tests showed low overall gamma pass rates of 60.3% in ArcCHECK measurements, while the doses in the PTV agreed with the plan with 99.9% for 3%/3mm measured with film. The comprehensive evaluation of the X1 radiotherapy delivery system for SCINTIX BgRT demonstrated good agreement for the static tests. The system consistently achieved critical metrics and delivered the BgRT doses per plan. The motion tests demonstrated its ability to co-localize the dose where the PET signal is and deliver acceptable BgRT dose distributions.

Diurnal Fluctuations in Steroid Hormones Tied to Variation in Intrinsic Functional Connectivity in a Densely Sampled Male.

Most of mammalian physiology is under the control of biological rhythms, including the endocrine system with time-varying hormone secretion. Precision neuroimaging studies provide unique insights into how the endocrine system dynamically regulates aspects of the human brain. Recently, we established estrogen's ability to drive widespread patterns of connectivity and enhance the global efficiency of large-scale brain networks in a woman sampled every 24 h across 30 consecutive days, capturing a complete menstrual cycle. Steroid hormone production also follows a pronounced sinusoidal pattern, with a peak in testosterone between 6 and 7 A.M. and nadir between 7 and 8 P.M. To capture the brain's response to diurnal changes in hormone production, we carried out a companion precision imaging study of a healthy adult man who completed MRI and venipuncture every 12-24 h across 30 consecutive days. Results confirmed robust diurnal fluctuations in testosterone, 17β-estradiol-the primary form of estrogen-and cortisol. Standardized regression analyses revealed widespread associations between testosterone, estradiol, and cortisol concentrations and whole-brain patterns of coherence. In particular, functional connectivity in the Dorsal Attention Network was coupled with diurnally fluctuating hormones. Further, comparing dense-sampling datasets between a man and a naturally cycling woman revealed that fluctuations in sex hormones are tied to patterns of whole-brain coherence in both sexes and to a heightened degree in the male. Together, these findings enhance our understanding of steroid hormones as rapid neuromodulators and provide evidence that diurnal changes in steroid hormones are associated with patterns of whole-brain functional connectivity.

Hydrogel-Reactive-Microenvironment Powering Reconfiguration of Polymer Architectures.

Reconfiguration of architected structures has great significance for achieving new topologies and functions of engineering materials. Existing reconfigurable strategies have been reported, including approaches based on heat, mechanical instability, swelling, origami/kirigami designs, and electromagnetic actuation. However, these approaches mainly involve physical interactions between the host materials and the relevant stimuli. Herein, a novel, easy-manipulated, and controllable reconfiguration strategy for polymer architectures is proposed by using a chemical reaction of host material within a hydrogel reactive microenvironment. 3D printed polycaprolactone (PCL) lattices transformed in an aqueous polyacrylamide (PAAm) hydrogel precursor solution, in which ultraviolet (UV) light triggered heterogeneous grafting polymerization between PCL and AAm. In situ microscopy shows that PCL beams go through volumetric expansion and cooperative buckling, resulting in transformation of PCL lattices into sinusoidal patterns. The transformation process can be tuned easily and patterned through the adjustment of the PCL beam diameter, unit cell width, and UV light on-off state. Controlling domain formation is achieved by using UV masks. This framework enables the design, fabrication, and programming of architected materials and inspires the development of novel 4D printing approaches.

Manipulation of a turbulent boundary layer using sinusoidal riblets

We investigate experimentally the effects of micro-grooves on the development of a zero pressure gradient turbulent boundary layer at two different values of the friction Reynolds number. We consider both the well-known streamwise aligned riblets as well as wavy riblets, characterized by a sinusoidal pattern in the mean flow direction. Previous investigations by the authors showed that sinusoidal riblets yield larger values of drag reduction with respect to the streamwise aligned ones. We perform new particle image velocimetry experiments on wall-parallel planes to get insights into the effect of the sinusoidal shape on the near-wall organisation of the boundary layer and the structures responsible for the friction drag reduction and the turbulence generation. Conditional averages, aimed at identifying the topology of the low-speed streaks in the turbulent boundary layer, reveal that the flow is highly susceptible to wall manipulation. This is particularly evident in the cases that are associated with greater values of drag reduction. The results suggest a fragmentation and/or weakening of the streaks in the sinusoidal cases, that is triggered by the larger values of the wall-normal vorticity found at the streaks’ edges. The results are also confirmed by applying the variable interval spatial averaging events eduction technique. The turbulent kinetic energy budget also shows that the sinusoidal geometry significantly attenuates the turbulence production, hence supporting the idea of the manipulation of the turbulence regeneration cycle.

Use of heated grooves for reduction in friction resistance

An analysis of the use of heated grooves for resistance reduction was carried out. The model problem consisted of two parallel plates in a relative motion. The stationary plate was equipped with grooves characterized by a sinusoidal pattern and exposed to a pattern of sinusoidal heating. The force required to maintain plate movement was used to judge changes in flow resistance. It was shown that isothermal grooves increase resistance, periodic heating of smooth plate reduces resistance, while periodic heating of grooved plate may either increase or decrease this resistance. The net effect depends on the relative position of the groove and heating patterns, which controls the strength and direction of the pattern interaction effect, and correct selection of this position may eliminate a significant portion of resistance. Increasing groove amplitude and heating intensity reduces resistance similarly to reducing the Prandtl number. The formation of separation bubbles is essential to resistance reduction; an increase in the plate velocity washes these bubbles away, thus eliminating the resistance-reducing effect.

Play Activities Are Associated with Force Regulation in Primary School.

The daily exercise habits and play activities of children are known to have a significant impact on the development of body control. However, previous studies have not adequately explored the correlation between force regulation during submaximal visual effort, exercise, and play experience. This study aimed to examine the correlation between exercise habits and play experience and their impact on the ability to regulate force. This study involved 23 children with an average age of 9.2 ± 1.0 years. The participants were required to match their force exertion during submaximal effort to a varying demand value displayed in a sinusoidal pattern on a screen (controlled force exertion, CFE). Individual interviews were conducted to gather information on the exercise experience (time, frequency, and duration) and play activities (number of experiences and frequency). Multiple regression analysis was performed to determine the association among exercise experience, play activity, and CFE. The results indicated that the amount of exercise experience was not significantly associated with CFE (β = -0.203, p = 0.254). However, in terms of play activities, the number of play experiences was associated with CFE (β = -0.321, p = 0.038). On the contrary, play frequency was not significantly associated with CFE (β = -0.219, p = 0.191). These findings suggest that play activities are effective in improving force regulation during childhood and that a greater variety of play experiences may be important.

Quantitative Characterization of Respiratory Patterns on Dynamic Higher Temporal Resolution MRI to Stratify Postacute Covid-19 Patients by Cardiopulmonary Symptom Burden.

Postacute Covid-19 patients commonly present with respiratory symptoms; however, a noninvasive imaging method for quantitative characterization of respiratory patterns is lacking. To evaluate if quantitative characterization of respiratory pattern on free-breathing higher temporal resolution MRI stratifies patients by cardiopulmonary symptom burden. Prospective analysis of retrospectively acquired data. A total of 37 postacute Covid-19 patients (25 male; median [interquartile range (IQR)] age: 58 [42-64] years; median [IQR] days from acute infection: 335 [186-449]). 0.55 T/two-dimensional coronal true fast imaging with steady-state free precession (trueFISP) at higher temporal resolution. Patients were stratified into three groups based on presence of no (N = 11), 1 (N = 14), or ≥2 (N = 14) cardiopulmonary symptoms, assessed using a standardized symptom inventory within 1 month of MRI. An automated lung postprocessing workflow segmented each lung in each trueFISP image (temporal resolution 0.2 seconds) and respiratory curves were generated. Quantitative parameters were derived including tidal lung area, rates of inspiration and expiration, lung area coefficient of variability (CV), and respiratory incoherence (departure from sinusoidal pattern) were. Pulmonary function tests were recorded if within 1 month of MRI. Qualitative assessment of respiratory pattern and lung opacity was performed by three independent readers with 6, 9, and 23 years of experience. Analysis of variance to assess differences in demographic, clinical, and quantitative MRI parameters among groups; univariable analysis and multinomial logistic regression modeling to determine features predictive of patient symptom status; Akaike information criterion to compare the quality of regression models; Cohen and Fleiss kappa (κ) to quantify inter-reader reliability. Two-sided 5% significance level was used. Tidal area and lung area CV were significantly higher in patients with two or more symptoms than in those with one or no symptoms (area: 15.4 cm2 vs. 12.9 cm2 vs. 12.8 cm2 ; CV: 0.072, 0.067, and 0.058). Respiratory incoherence was significantly higher in patients with two or more symptoms than in those with one or no symptoms (0.05 vs. 0.043 vs. 0.033). There were no significant differences in patient age (P = 0.19), sex (P = 0.88), lung opacity severity (P = 0.48), or pulmonary function tests (P = 0.35-0.97) among groups. Qualitative reader assessment did not distinguish between groups and showed slight inter-reader agreement (κ = 0.05-0.11). Quantitative respiratory pattern measures derived from dynamic higher-temporal resolution MRI have potential to stratify patients by symptom burden in a postacute Covid-19 cohort. 3 TECHNICAL EFFICACY: Stage 3.

Mechanical Analysis of Semi-Rigid Base Asphalt Pavement under the Influence of Groundwater with the Spectral Element Method

Over prolonged exposure to groundwater conditions, semi-rigid base asphalt pavements can undergo significant changes in their internal moisture field, resulting in substantial variations in the pavement’s stiffness and, consequently, affecting the overall load-bearing capacity and stability of the road structure. This paper employs FWD non-destructive testing equipment to assess its mechanical performance and conduct data analysis and conducts a mechanical response study of asphalt road surfaces, considering the influence of roadbed moisture levels. Using the dynamic analytical theory, the fundamental equations and stiffness matrices for a linear elastic half-space model were established, leading to the development of a computational model for the mechanical response of semi-rigid base asphalt pavements under FWD dynamic loading, with an examination of the surface deflection in relation to changes in groundwater levels. Numerical examples and engineering applications were employed to validate the proposed model. The research findings indicate: With the passage of time, surface deflection values initially increase and then decrease, exhibiting a sinusoidal variation pattern similar to that of the applied load. As the distance from the loading center increases, the moment of peak deflection continually lags behind. The average absolute relative error between the results obtained using the method proposed in this study and the traditional ABAQUS finite element method was only 0.70%. The correlation coefficient between the theoretically computed deflection curve and the measured deflection curve using the spectral element method was greater than 0.9, with an average absolute relative error of 4.92% between the theoretical peak deflection and the measured peak deflection. As the groundwater level rises, surface deflection noticeably increases, with an approximately 40% increase in deflection values at the loading center. These research findings can be utilized to analyze the dynamic deflection of semi-rigid base asphalt pavements under various groundwater conditions, providing significant practical value for assessing road structural performance and serviceability.

Bulk wave propagation analysis of imperfect FG bio-composite beams resting on variable elastic medium

Bio-composites are outstanding alternatives to prevalent biomaterials in medical instruments due to their supreme material properties. On the other hand, mechanical analyses of bio-systems should be carried out to optimize the designed biomedical applications such as medical implants. Therefore, bulk wave propagation analysis of functionally graded (FG) bio-composite beams could serve as design targets of biomedical structures. Some applications like medical implants have a layered structure and FG composites will be an appropriate choice for constitutive material of such structures. In the current study, the influence of imperfection on the propagation of bulk waves in FG bio-composite beams with biomedical applications lying on a variable elastic medium has been evaluated for the first time. The constitutive materials of FG bio-composite beams are hydroxyapatite and gold alloy which are common materials in the biomedical industry. To determine the effective material properties of the structure under study, the conventional porosity-dependent homogenization scheme has been implemented. Various distribution patterns have been accounted for variable elastic medium. Moreover, a refined higher-order shear deformation theory and Hamilton’s principle have been exerted to obtain the partial differential governing equations and the derived equations are analytically solved via a harmonic function. To check the accuracy of the used methodology, the obtained result has been validated firstly with former investigations. Eventually, the sensitivity of various considerable parameters has comprehensively been probed and discussed. It is found that some parameters including wave number, power law index, and elastic foundation have positive effects and some parameters including slenderness ratio, ξ parameter, and imperfection coefficient have negative effects on the propagated bulk waves. Also, the sinusoidal pattern possesses less increasing effect than other ones.

Propulsion curve analysis and optimisation of biomimetic pectoral fin with three degree of freedom based on multi-layer perception

This paper aims to improve the swimming efficiency of biomimetic robotic fish by optimising its propulsion curve with three degree of freedom (DOF), in which the key is to minimise the resistance during swing backstroke of the pectoral fin. For this purpose, a reference point on the pectoral fin is first selected, and then an 8-shaped propulsion curve is constructed to coordinate rowing and flapping motions. Meanwhile, a propulsion curve of feathering motion is also given correspondingly. On this basis, the overall curvature and curve offset are proposed as measurement parameters for the deformation of the propulsion curve and the proportion of abdominal/dorsal circles in the propulsion curve, respectively. As the motion law of feathering is given in a sinusoidal pattern, a data set of hydrodynamic parameters is obtained for pectoral fin propulsion under different motion parameter conditions by computational fluid dynamics(CFD) numerical simulation. Once again, a propulsion curve optimisation model is established based on multi-layer perception(MLP), which uses the hydrodynamic parameters data set as input. The results show that the resistance of swing backstroke reached the minimum when overall curvature is π/10 and curve offset is 0.4, which is enhanced by 30.13% and 33.33% at thrust and lift direction compared to the existing design, respectively. Furthermore, the flow field structure and hydrodynamic parameters around the robotic fish are calculated by CFD. The results show that two sets of vortex rings are generated around the fish body during a propulsion cycle. The vortex rings detached towards the lower and upper sides of the fish body such that the lift is minimal, the thrust direction is relatively stable, and the resistance is minimal during the swing backstroke. The experimental results indicate that it can raise propulsion efficiency during the pectoral fin propulsion process, verifying the effectiveness of this method.

Abstract WP118: Ischemic Core Volumes and Collateral Status Have Diurnal Fluctuations - A Retrospective Cohort Study of 18137 Patients Using Automated Perfusion Imaging

Introduction: Circadian rhythms have recently been shown to influence stroke incidence and progression of infarct. We aimed to describe the diurnal variations in the incidence and perfusion profiles of patients with ischemic stroke using a large, multi-center, automated imaging database. Methods: The RAPID Insights database was queried from 02/01/2016 to 01/31/2022 for patients with perfusion imaging and automated detection of an ischemic stroke due to a presumed large vessel occlusion. Exclusion criteria included: patient age ≤25, mismatch volume of &lt;0 cc, and failure to register a positive value on either cerebral blood flow (CBF) reduction of 38% less than normal or total mismatch volume. Imaging time was subdivided into three epochs: Night: 23:00h-06:59h and Day: 07:00h-14:59h, and Evening: 15:00h-22:59h. Perfusion parameters were defined as the following: core volume was defined as CBF of &lt;30% of normal, penumbra was defined as a Tmax delay of &gt;6 seconds minus core volume, and collateral circulation was estimated with the Hypoperfusion Intensity Ratio (HIR = [Tmax&gt;10s]/[Tmax&gt;6s]), where a higher HIR suggests poorer collateral status. All perfusion parameters were analyzed on a 24-hour continuous cycle. Statistical significance was tested using a sinusoidal regression analysis. Results: A total of 18,137 cases were analyzed. The peak incidence of ischemic stroke occurred around noon. A sinusoidal pattern was present, with larger ischemic core volumes and higher HIR during the night compared to the day: peak ischemic core volume of 23.40 cc occurred with imaging performed at 3:56 AM (p&lt;0.001) and peak HIR of 0.35 at 3:40 AM (p&lt;0.001). Conclusion: We found that ischemic core volumes were larger and collateral status worse at nighttime compared to daytime in this large national database. These findings support the notion that poor collateral recruitment with subsequent larger ischemic stroke volumes may occur at night. Fig 1. Logarithmic values of ischemic core volumes and hypoperfusion intensity ratios (HIR) are plotted against a 24-hour cycle, demonstrating a sinusoidal pattern for both.

Adaptive phase retrieval algorithm for local highlight area based on a piecewise sine function.

Phase measuring profilometry (PMP) has been widely used in industries for three-dimensional (3D) shape measurement. However, phase information is often lost due to image saturation results from high-reflection object surfaces, leading to subsequent 3D reconstruction errors. To address the problem, we propose an adaptive phase retrieval algorithm that can accurately fit the sinusoidal fringes damaged by high reflection in the saturated regions to retrieve the lost phase information. Under the proposal, saturated regions are first identified through a minimum error thresholding technique to narrow down regions of interest and so that computation costs are reduced. Then, images with differing exposures are fused to locate peak-valley coordinates of the fitting sinusoidal fringes. And the corresponding values of peak-valley pixels are obtained based on a least squares method. Finally, an adaptive piecewise sine function is constructed to recover the sinusoidal fringe pattern by fitting the pattern intensity distribution. And the existing PMP technology is used to obtain phase information from the retrieved sinusoidal fringes. To apply the developed method, only one (or two) image with different exposure times is needed. Compared with existing methods for measuring reflective objects, the proposed method has the advantages of short operation time, reduced system complexity, and low demand on hardware equipment. The effectiveness of the proposed method is verified through two experiments. The developed methodology provides industry an alternative way to measure high-reflection objects in a wide range of applications.

Motion-resistant three-wavelength spatial frequency domain imaging system with ambient light suppression using an 8-tap CMOS image sensor.

We present a motion-resistant three-wavelength spatial frequency domain imaging (SFDI) system with ambient light suppression using an 8-tap complementary metal-oxide semiconductor (CMOS) image sensor (CIS) developed at Shizuoka University. The system addresses limitations in conventional SFDI systems, enabling reliable measurements in challenging imaging scenarios that are closer to real-world conditions. Our study demonstrates a three-wavelength SFDI system based on an 8-tap CIS. We demonstrate and evaluate the system's capability of mitigating motion artifacts and ambient light bias through tissue phantom reflectance experiments and in vivo volar forearm experiments. We incorporated the Hilbert transform to reduce the required number of projected patterns per wavelength from three to two per spatial frequency. The 8-tap image sensor has eight charge storage diodes per pixel; therefore, simultaneous image acquisition of eight images based on multi-exposure is possible. Taking advantage of this feature, the sensor simultaneously acquires images for planar illumination, sinusoidal pattern projection at three wavelengths, and ambient light. The ambient light bias is eliminated by subtracting the ambient light image from the others. Motion artifacts are suppressed by reducing the exposure and projection time for each pattern while maintaining sufficient signal levels by repeating the exposure. The system is compared to a conventional SFDI system in tissue phantom experiments and then in vivo measurements of human volar forearms. The 8-tap image sensor-based SFDI system achieved an acquisition rate of 9.4 frame sets per second, with three repeated exposures during each accumulation period. The diffuse reflectance maps of three different tissue phantoms using the conventional SFDI system and the 8-tap image sensor-based SFDI system showed good agreement except for high scattering phantoms. For the in vivo volar forearm measurements, our system successfully measured total hemoglobin concentration, tissue oxygen saturation, and reduced scattering coefficient maps of the subject during motion (16.5cm/s) and under ambient light (28.9lx), exhibiting fewer motion artifacts compared with the conventional SFDI. We demonstrated the potential for motion-resistant three-wavelength SFDI system with ambient light suppression using an 8-tap CIS.

Segregation of binary particles in pulsed gas-solid fluidized bed

Pulsating airflow-driven gas-solid fluidization is an effective method to segregate particles of different densities. The current article presents an elaborate computational study on the development of simulation methodology, and parametric trend identification of pulsating airflow-driven granular segregation for the first time using computational fluid dynamics (CFD), discrete element modeling (DEM) coupled analysis. The rigorous validation of the computational prediction has been produced against the experimental result reported by Li et al. (2021) and an excellent agreement has been observed. Segregation behavior for different density ratios of particles, different patterns of pulsation, and different particle shapes is presented in the current article. The segregation index improves with the density ratio of the binary mixture of particles, but the rate of increment of the segregation index is highly dependent on the airflow rate. Near the optimal value of airflow rate, the rate of increment of the segregation index reduces with the density ratio. Keeping the bed height and material property constant, different patterns of pulsation namely—sinusoidal, triangular, and exponential have been adopted. The segregation index is higher for sinusoidal patterns, whereas it reduces when the pattern is changed to triangular and exponential. Particles of constant volume with different shapes are also considered to understand the effect of particle shape on segregation. The segregation index deteriorates with the increasing surface area of the particle at constant volume.