Relative Flow Speed Research Articles

Function of flow wakes for queuing trilobites: Positioning rather than drag reduction – Criteria for drag force assessment in palaeontological CFD simulations

Trilobites are one of the most important invertebrate clades in the Palaeozoic, with significant disparity in morphology and behaviour, the latter including intriguing instances of queueing. Previous studies employed Computational Fluid Dynamics (CFD) to investigate queuing behaviour in the Devonian trilobite Trimerocephalus chopini and found drag reduction effects. Novel calculations that define a ratio between drag force and Apparent Gravity (W), along with the Submerged Froude Number (Frsub), however, reveal that the obtained drag force was practically negligible in terms of the underwater mobility of trilobites. A trilobite would start to experience difficulty in forward walking only when the relative flow speed was over 42 cm/s, which is inconsistent with the interpreted palaeoenvironment or the predicted moving speed of trilobites. Nevertheless, according to the proposed cantilever model, a trilobite had the ability to sense very minute change in fluid velocity (>7.16 μm/s). High-sensitivity mechanical sensors distributed along the body, either on the exoskeleton or limbs, empowered queuing individuals to discern the fixed self-similar pattern of the wake generated by their predecessors in the queue. In general, if a trilobite were out of the wake, the asymmetrical velocity and pressure field would aid in repositioning itself, facilitating the maintenance of migratory queues. This permitted blind trilobites to securely sense their companions, compensating for lack of long-range visual capability. This paradigm of force assessment is suitable to Computational Fluid Dynamic analyses in other extinct animal-environment interactions, offering a framework to evaluate whether drags and wakes impact more on organism's mobility (W≫0.1,Frsub≫1) or their mechanical sensors, and provides a unique cross-scale insight into animals' adaptation to palaeohydrodynamic variation.

Design and Demonstration of a Passive Pitch System for Tidal Turbines

Tidal currents are renewable and predictable energy sources that could prove fundamental to the transition to a sustainable use of renewable energy resources. Over a tidal period, changes in the flow speed in a tidal channel require that the blade pitch is adjusted to maximise power extraction. This is currently achieved with active pitch actuation, which however increases the capital and maintenance cost of the turbine. Furthermore, because of turbulence in the tidal stream, turbine yaw, wave-induced currents, etc., tidal turbine blades experience high-frequency velocity fluctuations that result in power and thrust unsteadiness, both of which are transmitted to the generator, the tower, and the active pitching mechanism, shortening the operating life due to fatigue loading.
 A passive morphing blade concept capable of reducing the load fluctuations without affecting the mean loads has recently been formulated and demonstrated with low-order simulations (https://doi.org/10.1016/j.renene.2021.10.085) and measurements (https://doi.org/10.1016/j.renene.2023.01.051). The system allows both passive pitch adjustment to changes in the mean flow speed over the tidal period, and the mitigation of high-frequency fluctuations.
 In this paper, we present the recent progress on the development of morphing blade technology, including with numerical simulations and experimental tests on a 1.2-m diameter turbine. Two different design concepts have been tested in the FloWave facility at the University of Edinburgh and in the recirculating channel at the Institute for Marine Engineering of the Italian National Research Council, respectively.
 Experimental results show that the amplitude of power variations over a wide range of flow speeds is substantially decreased, while thrust variations with changes in freestream speed are essentially suppressed. The detrimental effect of yawed inflow is, in addition, almost entirely cancelled. The fluctuations in the root-bending moment, thrust and torque are consistently reduced over a broad range of tip-speed ratios. We also show that such a system, if improperly designed, could result in a negative starting torque, and we show the steps necessary to avoid this issue.
 Furthermore, we present a theoretical and numerical framework that allows the design of passive pitch blades that can cancel either thrust or power fluctuations in specific flow conditions, as well as mitigating both types of fluctuations over a wide range of conditions. Specifically, we show that for any quasi-steady change in the relative flow speed and direction, there is a pitching axis that allows a chosen force component to be kept constant. High-frequency force fluctuations can also be substantially mitigated, and the extent of the mitigation depends on the inertia and friction in the system.
 Overall this paper demonstrates experimentally the effectiveness of morphing blades for tidal turbines and presents a theoretical and numerical framework for the future development of this technology.

Evolutionary Sequence of Spacetime and Intrinsic Spacetime and Associated Sequence of Geometries in Metric Force Fields IV

The flat two-dimensional relative proper intrinsic metric spacetime (\(\varnothing \rho^{\prime}, \varnothing c_s \varnothing t^{\prime}\)) underlying the flat four-dimensional relative proper metric spacetime \(\left(\mathbb{E}^{\prime 3}, c_s t^{\prime}\right)\), which emerges at the first stage of evolution of metric spacetime and intrinsic metric spacetime in long-range metric force fields, isolated in the first three parts of this paper, endures for no moment before transforming into a curved two-dimensional relative proper intrinsic metric spacetime with pseudo-orthogonal curvilinear intrinsic dimensions, (\(\varnothing \rho^{\prime}\) and \(\varnothing c_s \varnothing t^{\prime}\)), on the vertical intrinsic metric spacetime hyperplane, on the larger spacetime and intrinsic spacetime of combined positive (or our) universe and the negative universe. It therefore possesses intrinsic Lorentzian metric tensor at every point. It projects an underlying flat relativistic intrinsic metric spacetime \(\left(\varnothing \rho, \varnothing c_s \varnothing t\right)\), which is made manifested outwardly in a flat four-dimensional relativistic metric spacetime \(\left(\mathbb{E}^3, c_s t\right)\), at the second (and final) stage of evolution of metric spacetime and intrinsic metric spacetime in long-range metric force fields. The conclusion that the four-dimensional metric spacetime is everywhere flat in every Iong-range metric force field is reached.The curved 'two-dimensional' absolute intrinsic metric spacetime (\(\varnothing \hat{\rho}, \varnothing \hat{c}_s \varnothing \hat{t}\)) with absolute intrinsic sub-Riemannian metric tensor \(\varnothing \hat{g}_{i k}\), which evolves at the first stage is brought forward to the second stage. The basic aspects of the theory of relativity on the flat relativistic metric spacetime, intrinsic theory of relativity on the underlying flat relativistic intrinsic metric spacetime and absolute intrinsic metric theory on the curved absolute intrinsic metric spacetime, associated with the presence of a metric force field in spacetime and intrinsic metric force field in intrinsic spacetime, are developed in terms of certain derived geometrical parameters, referred to as relative proper static flow speed, relative proper intrinsic static flow speed and absolute intrinsic static flow speed respectively. Particularization to the gravitational field will be a straight forward process, while using the results of this paper as template.

Mix Design Processing for Self Compacting Geopolymer Mortar

The mortar flow and flow speed of self-compacting geopolymer mortar (SCGM) were determined by considering the various influencing parameters for the normal self-compacting mortar (SCM) and geopolymer mortar (GM). The test results showed that the effect of volume of water to volume of powder on the relative flow area (Gm) and relative flow speed (Rm) was different compared to normal SCM due to the high viscosity of matrix. The flow properties of SCGM were analyzed in terms of volume of water to volume of powder ratio, and superplasticizer to powder ratio, powder to sand ratio, viscosity of alkaline liquid and the water to geopolymer solid ratio. According to the analysis, flow prediction models for SCGM were formulated based on the parameters of both physical and chemical point of view. Moreover, a mix design of SCGM including a flow chart and mathematical expression was also proposed. This indicates that the typical volume ratio of SCGM was similar to SCM considering the volume of alkaline liquid with water in SCGM was equivalent to the volume of water in SCM.

Visualization of three-dimensional microcirculation of rodents\u2019 retina and choroid for studies of critical illness using optical coherence tomography angiography

We developed a method to measure the relative blood flow speed using optical coherence tomography angiography (OCTA) in retina and choroid, and investigated the feasibility of this method for assessing microcirculatory function in rat models of sepsis and hemorrhagic shock. Two sepsis models, 6-h severe sepsis without treatment and 30-h moderate sepsis maintaining mean arterial pressure, and volume controlled hemorrhagic shock and fluid resuscitation model were used to see the change of microcirculation. The blood flow index (BFI), which was calculated from the OCTA images to represent the average relative blood flow, was decreasing during the 6-h severe sepsis model. Its change is in parallel with the mean arterial blood pressure (MAP) and blood lactate levels. In the 30-h moderate sepsis model, the BFI was decreased while maintaining MAP, and lactate was increased. In the hemorrhagic shock model, the change of BFI is in line with MAP and lactate levels. In all models, BFI change is more sensitive in choroid than in retina. This study presents the OCTA-based retinal and choroidal microcirculatory blood flow monitoring method and shows its utility for assessment of critical illness.

Mechanowetting drives droplet and fluid transport on traveling surface waves generated by light-responsive liquid crystal polymers

In nature, capillary forces are often driving microfluidic propulsion and droplet manipulation, and technologies have been developed to utilize these forces in applications such as lab-on-a-chip biosensors and microfluidic systems. At the same time, responsive materials have been developed that can be activated by a variety of external triggers, including light, electric fields, and temperature, to locally deform and create dynamic surface structures, such as traveling waves. Here, we combine these developments into a system that enables capillary-driven droplet transport and fluid propulsion generated by light-induced surface waves in azobenzene-embedded liquid crystal polymers. We demonstrate that the traveling waves are able to efficiently propel fluids by means of mechanowetting. We couple the wave profiles to the fluid simulations using a multiphase computational fluid dynamics approach. We study three different fluid propulsion systems, i.e., peristaltic flow, liquid slug transport, and free-standing droplet transport. The first system operates on a fluid-filled single channel and achieves relative flow speeds of u/uwave<0.01. In contrast, the slugs and droplets are transported at two orders of magnitude higher speed equal to the wave speed (u/uwave=1) by exploiting the mechanowetting effect. We quantify the capillary forces generated by the traveling surface waves. Our method opens new avenues in light-driven (digital) microfluidic systems with enhanced control of fluid flow.

Analyzing Relative Flow Speeds in Diabetic Retinopathy Using Variable Interscan Time Analysis OCT Angiography

Further insight into the flow characteristics of the vascular features associated with diabetic retinopathy (DR) may improve assessment and treatment of disease progression. The variable interscan time analysis (VISTA) algorithm is an extension of OCT angiography (OCTA) that detects relative blood flow speeds, which then can be depicted on a color-coded map. This study used VISTA to analyze relative blood flow speeds in the microvascular changes associated with DR. Cross-sectional study. Thirteen patients with varying severities of DR treated at New England Eye Center, Boston, Massachusetts. OCT angiography images centered at the fovea were obtained on a prototype swept-source OCT device, and the VISTA algorithm was applied to visualize relative blood flow speeds. Descriptive flow analysis of the retinal vascular features of DR was conducted on the VISTA-generated images. Twenty-six eyes were included in this study. Of these, 3 eyes had mild nonproliferative DR (NPDR), 6eyes had moderate NPDR, 4 eyes had severe NPDR, 9 eyes had proliferative DR, and 4 eyes were normal controls. Microaneurysms, intraretinal microvascular abnormalities (IRMAs), and neovascularization appeared to originate from areas of relatively slow blood flow speeds. Microaneurysms showed relatively slower flow, IRMAs showed turbulent, intermediate to slow flow, and venous beading and looping presented with relatively high flow speeds that tapered progressively. Neovascularization of venous origin demonstrated slower flow speeds, whereas that of arterial origin showed relatively high flow speeds. Additionally, increased disease severity was associated with globally slower flow speeds, with particularly slower flow around the foveal avascular zone. The VISTA algorithm seems to be a useful extension of OCTA that overcomes some of the limitations of normal gray-scale OCTA. It seems to have some potential in providing relevant insight into the pathogenesis of the microvascular changes associated with DR. These findings may assist in improving our understanding of the pathogenic changes that take place in DR.

Space-directional approach to improve blood vessel visualization and temporal resolution in laser speckle contrast imaging.

.Blood flow is a parameter used to diagnose vascular diseases based on flow speed, blood pressure, and vessel size. Different techniques have been developed to estimate the relative blood flow speed and to improve the visualization of deep blood vessels; one such technique is laser speckle contrast imaging (LSCI). LSCI images contain a high level of noise mainly when deep blood vessels are imaged. To improve their visualization, several approaches for contrast computation have been developed. However, there is a compromise between noise attenuation and temporal resolution. On the one hand, spatial approaches have low spatial resolution, high temporal resolution, and significant noise attenuation, while temporal approaches have the opposite. A recent approach combines a temporal base with a directional process that allows improving the visualization of blood vessels. Nevertheless, it still contains a high level of noise and requires a high number of raw frames for its base. We propose, a space-directional approach focused on improving noise attenuation and temporal resolution for contrast computation. The results of reference approaches and the proposed one are compared quantitatively. Moreover, it is shown that the visualization of blood vessels in LSCI images can be improved by a general morphological process when the noise level is reduced.

Flame Spread Over Ultra-thin Solids: Effect of Area Density and Concurrent-Opposed Spread Reversal Phenomenon

There are no existing experimental studies of flame spread rate trends for ultra-thin solid samples. Previous theory has predicted that for concurrent flame in kinetic regime, the flame spread rate decreases as the sample thickness decreases and there is a critical thickness below which burning is not possible. To test this hypothesis, a series of microgravity experiments of concurrent-flow flame spread over samples of ultra-low area densities are conducted using NASA Glenn Research Center’s Zero Gravity Research Facility (the 5.18 s drop tower). The tested samples are cellulose-based materials of various area densities, ranging from 0.2 mg/cm2 to 13 mg/cm2, as low as one order of magnitude less than those ever tested before. Each sample is 30 cm long by 5 cm wide and is burned in a low-speed concurrent air flow (5 to 30 cm/s). The results show that the concurrent flame spread rate is proportional to the flow velocity relative to the flame and is inversely proportional to the sample area density. A theoretical formulation, provided in this work, suggests that the flame length has a linear relationship with the relative flow speed and has no direct dependency on the sample area density. The experimental data supports this conclusion. From the images recorded in the experiments, a unique flame base tubular structure directed upstream away from the burnout zone is observed for thin samples. This structure is suspected to be due to flame stretching and localized blowoff caused by the oxidative pyrolysis Stefan flows at the sample burnout. This can be an indication that the chemical time becomes comparable to the flow time of the Stefan flow and the tested samples are approaching the kinetically-limited thickness. For the thinnest tested sample (0.2 mg/cm2), flames with concurrent and opposed dual natures are observed when the air flow rate is low (< 20 cm/s). At the lowest tested flow rate (5 cm/s), the flame spread rate exceeds the air flow rate and the flame transits to an opposed flame in the concurrent flow. The dual nature and flame transition are presented and discussed. This study provides detailed examination through high-resolution images of the transition between the concurrent to opposed flame spread modes.

Retinal Blood Vessel Caliber Estimation for Optical Coherence Tomography Angiography Images Based on 3D Superellipsoid Modeling

Changes of retinal blood vessel calibers may reflect various retinal diseases and even several non-retinal diseases. We propose a new method to estimate retinal vessel calibers from 3D optical coherence tomography angiography (OCTA) images based on 3D modeling using superellipsoids. Taking advantage of 3D visualization of the retinal tissue microstructures in vivo provided by OCTA, our method can detect retinal blood vessels precisely, estimate their calibers reliably, and show the relative flow speed visually.

Stochastic Model Predictive Control of Air Conditioning System for Electric Vehicles: Sensitivity Study, Comparison, and Improvement

A stochastic model predictive controller (SMPC) of air conditioning (AC) system is proposed to improve the energy efficiency of electric vehicles (EVs). A Markov-chain based velocity predictor is adopted to provide a sense of the future disturbances over the SMPC control horizon. The sensitivity of electrified AC plant to solar radiation, ambient temperature, and relative air flow speed is quantificationally analyzed from an energy efficiency perspective. Three control approaches are compared in terms of the electricity consumption, cabin temperature, and comfort fluctuation, which include the proposed SMPC method, a generally used bang-bang controller, and dynamic programming as the benchmark. Real solar radiation and ambient temperature data are measured to validate the effectiveness of the SMPC. Comparison results illustrate that SMPC is able to improve the AC energy economy by 12% compared to the rule-based controller. The cabin temperature variation is reduced by more than 50.4%, resulting with a much better cabin comfort.

Polypoidal Choroidal Vasculopathy on Swept-Source Optical Coherence Tomography Angiography with Variable Interscan Time Analysis.

PurposeTo use a novel optical coherence tomography angiography (OCTA) algorithm termed variable interscan time analysis (VISTA) to evaluate relative blood flow speeds in polypoidal choroidal vasculopathy (PCV).MethodsProspective cross-sectional study enrolling patients with confirmed diagnosis of PCV. OCTA of the retina and choroid was obtained with a prototype swept-source OCT system. The acquired OCT volumes were centered on the branching vascular network (BVN) and polyps as determined by indocyanine-green angiography (ICGA). The relative blood flow speeds were characterized on VISTA-OCTA.ResultsSeven eyes from seven patients were evaluated. Swept-source OCTA enabled detailed enface visualization of the BVN and polyps in six eyes. VISTA-OCTA revealed variable blood flow speeds in different PCV lesion components of the same eye, with faster flow in the periphery of polyps and slower flow in the center of each polyp, as well as relatively slow flow in BVN when compared with retinal vessels. BVNs demonstrated relatively faster blood flow speeds in the larger trunk vessels and relatively slower speeds in the smaller vessels.ConclusionsSwept-source OCTA identifies polyps in most, but not all, PCV lesions. This limitation that may be related to relatively slow blood flow within the polyp, which may be below the OCTA's sensitivity. VISTA-OCTA showed heterogeneous blood flow speeds within the polyps, which may indicate turbulent flow in the polyps.Translational RelevanceThese results bring relevant insights into disease mechanisms that can account for the variable course of PCV, and can be relevant for diagnosis and management of patients with PCV.

Analyzing Relative Blood Flow Speeds in Choroidal Neovascularization Using Variable Interscan Time Analysis OCT Angiography

Longitudinally visualizing relative blood flow speeds within choroidal neovascularization (CNV) may provide valuable information regarding the evolution of CNV and the response to vascular endothelial growth factor (VEGF) inhibitors. Retrospective, longitudinal case series conducted at the New England Eye Center. Patients with either treatment-naïve or previously treated CNV secondary to neovascular age-related macular degeneration. Optical coherence tomography angiography (OCTA) was performed using a 400-kHz, 1050-nm swept-source OCT system with a 5-repeat B-scan protocol. Variable interscan time analysis (VISTA) was used to compute relative flow speeds from pairs of B-scans having 1.5- and 3.0-ms separations; VISTA signals then were mapped to a color space for display. Quantitative outcomes included OCTA-based area and volume measurements of CNV at initial and follow-up visits. Qualitative outcomes included VISTA OCTA analysis of relative blood flow speeds, along with analysis of contraction, expansion, densification, and rarefication of CNV. Seven eyes of 6 patients (4 women and 2 men) with neovascular age-related macular degeneration were evaluated. Two eyes were treatment naïve at the initial visit. Choroidal neovascularization in all eyes at each visit showed relatively higher flow speeds in the trunk, central, and larger vessels and lower flow speed in the small vessels, which generally were located at the periphery of the CNV complex. Overall, the CNV appeared to expand over time despite retention of good visual acuity in all patients. In the treatment-naïve patients, slower-flow-speed vessels contracted with treatment, whereas the larger vessels with higher flow speed remained constant. Variable interscan time analysis OCTA allows for longitudinal observations of relative blood flow speeds in CNV treated with anti-VEGF intravitreal injections. A common finding in this study is that the main trunk and larger vessels seem to have relatively faster blood flow speeds compared with the lesions' peripheral vasculature. Moreover, an overall growth of chronically treated CNV was seen despite retention of good visual acuity. The VISTA framework may prove useful for developing clinical end points, as well as for studying hemodynamics, disease pathogenesis, and treatment response.

Corrosion-erosion tests of fusion reactor materials in flowing nanofluids

The rotating experimental devices are designed to investigate the compatibility of fusion reactor materials with Al2O3-water nanofluids. The specimens are exposed to different nanofluids with relative flow speed from 1.00 m/s to 3.25 m/s at 70 °C for 1224 h and 2136 h. The analysis of surface morphology and component is performed through SEM, EDS and XPS. The preliminary results indicate that the compatibility of RAFM and 316 L(N) steel with nanofluids is better than that of CuCrZr alloy. Metallic oxide layer with pitting holes and cracks is found on the surface of CuCrZr alloy, and its morphology is strongly influenced by the test duration, flow speed and composition of nanofluid. The present results suggest that the domain corrosion behavior is a coupling effect from both chemical corrosion and mechanical erosion.

Use of kurtosis for locating deep blood vessels in raw speckle imaging using a homogeneity representation.

Visualization of deep blood vessels in speckle images is an important task as it is used to analyze the dynamics of the blood flow and the health status of biological tissue. Laser speckle imaging is a wide-field optical technique to measure relative blood flow speed based on the local speckle contrast analysis. However, it has been reported that this technique is limited to certain deep blood vessels (about ? = 300 ?? ? m ) because of the high scattering of the sample; beyond this depth, the quality of the vessel’s image decreases. The use of a representation based on homogeneity values, computed from the co-occurrence matrix, is proposed as it provides an improved vessel definition and its corresponding diameter. Moreover, a methodology is proposed for automatic blood vessel location based on the kurtosis analysis. Results were obtained from the different skin phantoms, showing that it is possible to identify the vessel region for different morphologies, even up to 900 ?? ? m in depth.

Intratumoural interleukin 12 gene therapy stimulates the immune system and decreases angiogenesis in dogs with spontaneous cancer.

Interleukin 12 (IL-12) is a powerful immunostimulatory cytokine with a strong antitumoural activity. In this work, the immunological, anti-angiogenic and clinical effects of three consecutive intratumoural IL-12 electrogene therapy (EGT) treatments were evaluated in nine dogs with spontaneous cancer. In all the dogs, tumour biopsies and blood samples were taken prior, during and after the intratumoural IL-12 EGT (on days 1, 8, 35 and 1, 3, 8, 15, 35, respectively). An initial decrease in immune cells was followed by an increase above baseline 1-3 weeks after treatment initiation. Interestingly, the decrease in peripheral leukocytes 2 days after the first intratumoural IL-12 EGT coincided with erythema and tumour swelling. Transient increases of IL-12 and interferon γ were measured in the serum and the tumour tissue, whereas IL-10 transiently increased only in the serum. The effect of intratumoural IL-12 EGT on the levels of IL-24 and vascular endothelial growth factor in the sera and tumour biopsies differed per dog. Via contrast-enhanced ultrasound (US) (on days 1, 8 and 35), we demonstrated that intratumoural IL-12 EGT resulted in a significant decrease of the relative blood volume and blood flow speed in the tumour compared with baseline. Metastases were present in two dogs. In one of these dogs, IL-12 EGT of the primary tumour caused a transient partial regression of the metastases, but not of the primary tumour. The second dog with metastases did not survive long enough to complete the entire treatment cycle. Despite encouraging immunostimulatory and anti-angiogenic effects after intratumoural IL-12 EGT, no clinically relevant outcomes were observed in this study, as persistent tumour regression could not be obtained. On the other hand, the laboratory and US results hold great promise for combinatorial strategies of intratumoural IL-12 EGT with conventional antitumour (immuno)therapies.

A novel highly efficient algorithm for laser speckle imaging

Laser speckle imaging (LSI) is a non-invasive optical imaging technique able to provide wide-field two-dimensional maps of blood flow. The observer can either define different sizes for the region of interest to reduce the spatial variability or different time duration over which the blood flow values are averaged to decrease temporal variability. In this paper, we present a new algorithm for integrated speckle contrast, which accounts not only for temporal integration but for spatial integration as well, using a low time – consuming efficient algorithm. As a result, we find that an efficiency factor should be introduced to the measured speckle contrast to properly normalize and eliminate background noise; otherwise, the measured contrast is affected. Furthermore, we demonstrate its feasibility for relative flow speed assessing.

対水船速の計測精度向上に関する研究

The flow under bow bottom of ships was calculated using CFD methods and characteristics of flow-speed distribution were analysed. In the study, it was confirmed that flow speed under the bow bottom of a ship changes according to water depth by disturbance of the sailing ship and a range of the field where the disturbance effects depends on types of ships, draft and ship speed. In this report, a developed measuring system named "multi-layered relative velocity meter" is introduced to measure distributions of relative flow speed along water depth. After testing a function of the measuring system on a test boat, the measuring system was installed on a PCC and the relative flow speed at each layer was measured during a voyage. The obtained data were evaluated by comparing with the result of CFD analysis and it was confirmed that relative flow speed measured on the PCC had a similar distribution with the result of CFD analysis. Considering both the CFD analysis result and the onboard measured data, finally a new method to improve measurement accuracy of ship's speed through water is proposed.

Spatial versus temporal laser speckle contrast analyses in the presence of static optical scatterers.

Previously published data demonstrate that the temporal processing algorithm for laser speckle contrast imaging (LSCI) can improve the visibility of deep blood vessels and is less susceptible to static speckle artifacts when compared with the spatial algorithm. To the best of our knowledge, the extent to which the temporal algorithm can accurately predict the speckle contrast associated with flow in deep blood vessels has not been quantified. Here, we employed two phantom systems and imaging setups (epi-illumination and transillumination) to study the contrast predicted by the spatial and temporal algorithms in subsurface capillary tubes as a function of the camera exposure time and the actual flow speed. Our data with both imaging setups suggest that the contrast predicted by the temporal algorithm, and therefore the relative flow speed, is nearly independent of the degree of static optical scattering that contributes to the overall measured speckle pattern. Collectively, these results strongly suggest the potential of temporal LSCI at a single-exposure time to assess accurately the changes in blood flow even in the presence of substantial static optical scattering.

Trial examination of direct pebble fabrication for advanced tritium breeders by the emulsion method

Demonstration power plant reactors require advanced tritium breeders with high thermal stability. For the mass production of advanced tritium breeder pebbles, pebble fabrication by the emulsion method is a promising technique. To develop the most efficient pebble fabrication method, a new direct pebble fabrication process utilizing the emulsion method was implemented. A prior pebble fabrication process consisted of the preparation of raw materials followed by granulation. The new process integrates the preparation and granulation of raw materials. The slurry for the emulsion granulation of Li2TiO3 or Li4SiO4 as a tritium breeder consists of mixtures of Li2CO3 and TiO2 or SiO2 at specific ratios. Subsequently, gel spheres of tritium breeders are fabricated by controlling the relative flow speeds of slurry and oil. The average diameter and crush load of the obtained sintered Li2TiO3 or Li4SiO4 pebbles were 1.0 or 1.5mm and 37.2 or 59.3N, respectively. The trial fabrication results suggest that the new process has the potential to increase the fabrication efficiency of advanced tritium breeder pebbles.