Average Relative Difference Research Articles

High-Order Perturbation Method for Updating Response Functions for Time-Dependent Transport Calculations

The hybrid stochastic deterministic continuous-energy coarse mesh transport method (COMET) has been recently extended for high-fidelity efficient kinetics calculations in highly heterogeneous reactor cores. The method discretizes the time variable as a series of time grids and solves the resulting set of steady-state neutron transport equations. In this work, a high-order perturbation method is developed to update the COMET unperturbed response function library on the fly for changes in the discretized time step size Δ t h . The unperturbed response functions are precomputed with 1 / v Δ t h = 0 . The perturbation expansion coefficients are also generated during the unperturbed response function library precomputation. The adjoint solution needed by the perturbation method is calculated using the reciprocity relation without solving the corresponding adjoint problems. As a result, the method can be easily implemented into any stochastic code to generate the perturbation expansion coefficients together with the unperturbed response functions. The high-order perturbation method is benchmarked by comparing both the response functions and the time-dependent COMET core solution (fission density) with the corresponding reference solutions. It is found that the response functions generated by the perturbation method at second order are in excellent agreement with those directly computed by the Monte Carlo method. When Δ t h changes from 1.0E-4 s to infinity, the average and maximum relative differences in the various response functions were found to be in the range of 0.0000106% to 0.00116% and 0.000011% to 0.00121%, respectively. The fission density as a function of time calculated by COMET using the perturbation method is in excellent agreement with the reference solutions, with an average relative difference of 0.0065% to 0.075%. These comparisons indicate that the perturbation method at second order is highly accurate.

Automated cardiovascular risk categorization through AI-driven coronary calcium quantification in cardiac PET acquired attenuation correction CT

BackgroundWe present an automatic method for coronary artery calcium (CAC) quantification and cardiovascular risk categorization in CT attenuation correction (CTAC) scans acquired at rest and stress during cardiac PET/CT. The method segments CAC according to visual assessment rather than the commonly used CT-number threshold. MethodsThe method decomposes an image containing CAC into a synthetic image without CAC and an image showing only CAC. Extensive evaluation was performed in a set of 98 patients, each having rest and stress CTAC scans and a dedicated calcium scoring CT (CSCT). Standard manual calcium scoring in CSCT provided the reference standard. ResultsThe interscan reproducibility of CAC quantification computed as average absolute relative differences between CTAC and CSCT scan pairs was 75% and 85% at rest and stress using the automatic method compared to 121% and 114% using clinical calcium scoring. Agreement between automatic risk assessment in CTAC and clinical risk categorization in CSCT resulted in linearly weighted kappa of 0.65 compared to 0.40 between CTAC and CSCT using clinically used calcium scoring. ConclusionThe increased interscan reproducibility achieved by our method may allow routine cardiovascular risk assessment in CTAC, potentially relieving the need for dedicated CSCT.

Estimation of brain tissue response by electrical stimulation in a subject-specific model implemented by conductivity tensor imaging.

Electrical stimulation such as transcranial direct current stimulation (tDCS) is widely used to treat neuropsychiatric diseases and neurological disorders. Computational modeling is an important approach to understand the mechanisms underlying tDCS and optimize treatment planning. When applying computational modeling to treatment planning, uncertainties exist due to insufficient conductivity information inside the brain. In this feasibility study, we performed in vivo MR-based conductivity tensor imaging (CTI) experiments on the entire brain to precisely estimate the tissue response to the electrical stimulation. A recent CTI method was applied to obtain low-frequency conductivity tensor images. Subject-specific three-dimensional finite element models (FEMs) of the head were implemented by segmenting anatomical MR images and integrating a conductivity tensor distribution. The electric field and current density of brain tissues following electrical stimulation were calculated using a conductivity tensor-based model and compared to results using an isotropic conductivity model from literature values. The current density by the conductivity tensor was different from the isotropic conductivity model, with an average relative difference |rD| of 52 to 73%, respectively, across two normal volunteers. When applied to two tDCS electrode montages of C3-FP2 and F4-F3, the current density showed a focused distribution with high signal intensity which is consistent with the current flowing from the anode to the cathode electrodes through the white matter. The gray matter tended to carry larger amounts of current densities regardless of directional information. We suggest this CTI-based subject-specific model can provide detailed information on tissue responses for personalized tDCS treatment planning.

A Consistent Low-Order Acceleration Technique for Coarse Mesh Transport (COMET) Methods

The COarse MEsh Transport (COMET) method, a hybrid continuous energy stochastic and deterministic transport method/tool based on the incident flux response expansion theory, is capable of providing highly accurate and efficient continuous energy whole-core neutron solutions to various heterogeneous reactor cores. In this work, a novel low-order (zeroth-order) acceleration technique is developed to significantly improve COMET’s computational efficiency for core calculations. This new method is based on consistent coupled low-order and high-order calculations to obtain the COMET core solution. In the low-order calculations, COMET is used to converge the total partial current escaping from each coarse mesh and the core eigenvalue. The resulting fixed-source problem in which the off-diagonal terms (equivalent to the scattering and fission neutron sources) are constructed by the zeroth-order solution are efficiently solved by the high-order COMET calculations. The resulting high-order angular flux on each coarse mesh bounding surface is then used to update (collapse) the low-order response coefficients. The coupled low-order and high-order calculations are repeated until both the eigenvalue and the low-order response coefficients are converged. The new acceleration method is implemented into COMET and tested in a set of stylized Advanced High Temperature Reactor (AHTR) benchmark problems. It is found that the core eigenvalues and the local fission density distributions predicted by COMET with the low-order acceleration agree very well with those computed by the original COMET. The eigenvalue discrepancy varies from 0 to 1 pcm, and the average relative differences in the stripewise and assembly-average fission density distributions are in the range of 0.021% to 0.032% and 0.004% to 0.01%, respectively. The comparisons have shown that the new low-order acceleration method can maintain COMET’s accuracy while improving its computational efficiency for core calculations by 12 to 16 times.

Vicarious Radiometric Calibration of the Multispectral Imager Onboard SDGSAT-1 over the Dunhuang Calibration Site, China

The multispectral imager (MII), onboard the Sustainable Development Science Satellite 1 (SDGSAT-1), performs detailed terrestrial change detection and coastal monitoring. SDGSAT-1 was launched at 2:19 UTC on 5 November 2021, as the world’s first Earth science satellite to serve the United Nations 2030 Sustainable Development Agenda. A vicarious radiometric calibration experiment was conducted at the Dunhuang calibration site (Gobi Desert, China) on 14 December 2021. In-situ measurements of ground reflectance, aerosol optical depth (AOD), total columnar water vapor, radiosonde data, and diffuse-to-global irradiance (DG) ratio were performed to predict the top-of-atmosphere radiance by the reflectance-, irradiance-, and improved irradiance-based methods using the moderate resolution atmospheric transmission model. The MII calibration coefficients were calculated by dividing the top-of-atmosphere radiance by the average digital number value of the image. The radiometric calibration coefficients calculated by the three calibration methods were reliable (average relative differences: 2.20% (reflectance-based vs. irradiance-based method) and 1.43% (reflectance-based vs. improved irradiance-based method)). The total calibration uncertainties of the reflectance-, irradiance-, and improved irradiance-based methods were 2.77–5.23%, 3.62–5.79%, and 3.50–5.23%, respectively. The extra DG ratio measurements in the latter two methods did not improve the calibration accuracy for AODs ≤ 0.1. The calibrated MII images were verified using Landsat-8 Operational Land Imager (OLI) and Sentinel-2A MultiSpectral Instrument (MSI) images. The retrieved ground reflectances of the MII over different surface types were cross-compared with those of OLI and MSI using the FAST Line-of-sight Atmospheric Analysis of Hypercubes software. The MII retrievals differed by <0.0075 (7.13%) from OLI retrievals and <0.0084 (7.47%) from MSI retrievals for calibration coefficients from the reflectance-based method; <0.0089 (7.57%) from OLI retrievals and <0.0111 (8.65%) from MSI retrievals for the irradiance-based method; and <0.0082 (7.33%) from OLI retrievals and <0.0101 (8.59%) from MSI retrievals for the improved irradiance-based method. Thus, our findings support the application of SDGSAT-1 data.

Calculation of surface spectral irradiance using the Geant4 Monte Carlo toolkit

The spectral direct normal irradiance (DNI) of the surface spectral irradiance, with a spectral resolution of 1 nm in the range of 280–1600 nm, and 5 nm in the range of 1600–3000 nm, has been calculated for the first time with the Geant4 Monte Carlo simulation toolkit using the US Standard Atmosphere 1976 model and the reference extraterrestrial solar spectrum SOLAR-ISS. The atmospheric attenuation of DNI has been studied with and without aerosols. In the presence of aerosols corresponding to 10 km visibility, the total solar DNI attenuation can reach about 84% in the UV domain, 56% in the visible domain and 35.08% in the rest of the infrared domain. The Geant4 results have been compared to those calculated by the MYSTIC code of LibRadtran package and the Beer–Lambert law under the same atmospheric conditions. The average relative transmittance difference between Geant4 and MYSTIC is of the order of few percent in the entire solar spectrum. In the case of atmosphere with aerosols corresponding to 23 km visibility, the most important average of the relative difference between Geant4 and MYSTIC transmittances is about 7.5% in the UV domain and stays between 1.19% and, 3.31% in the rest of the spectrum. More importantly, in this last case of the atmosphere, the values of the spectral transmittance of Geant4 remain intermediate between those of MYSTIC and Beer–Lambert law in the entire visible range up to 800 nm.

Tensile strength and modulus of FRP pultruded composites at varying load angles relative to the pultrusion direction

Tensile strength and modulus are key material properties for the design of pultruded fiber reinforced polymer (FRP) composite members and connections. Pultruded FRP composites are orthotropic materials and thus both the tensile strength and modulus vary with the angle between the pultrusion direction and the applied force. In current design standards, the variation of material properties with load direction is addressed by prescribing the use of longitudinal properties for angles between zero and five degrees, and the use of transversal properties for angles greater than five degrees. To derive a more precise and representative equational relationship between load angle and tensile material properties, 228 coupons extracted from pultruded FRP profiles were tested in tension in accordance with ASTM D638-22 to determine the resulting average tensile strength and tensile modulus values. Coupons were taken from different profiles from different manufacturers, different section locations (e.g., web versus flange), as well as varying angles between the pultrusion direction and the applied force. The characteristic design value of the tensile strength and tensile modulus at each tested angle was determined in accordance with ASTM D7290-22. Using this dataset, a predictive relationship based on a generalized form of Hankinson’s equation was developed for both average and characteristic tensile strength and both average and characteristic tensile modulus as a function of three factors: 1) the differential angle between the pultrusion direction and the applied force, 2) the longitudinal tensile property (i.e., strength or modulus), and 3) the transverse tensile property (i.e., strength or modulus). The average relative difference between tested and predicted values using the developed equations varied between 4.4% and 8.3%, depending on the considered mechanical property.

Hybridization of Particle Swarm Optimization with Variable Neighborhood Search and Simulated Annealing for Improved Handling of the Permutation Flow-Shop Scheduling Problem

Permutation flow-shop scheduling is the strategy that ensures the processing of jobs on each subsequent machine in the exact same order while optimizing an objective, which generally is the minimization of makespan. Because of its NP-Complete nature, a substantial portion of the literature has mainly focused on computational efficiency and the development of different AI-based hybrid techniques. Particle Swarm Optimization (PSO) has also been frequently used for this purpose in the recent past. Following the trend and to further explore the optimizing capabilities of PSO, first, a standard PSO was developed during this research, then the same PSO was hybridized with Variable Neighborhood Search (PSO-VNS) and later on with Simulated Annealing (PSO-VNS-SA) to handle Permutation Flow-Shop Scheduling Problems (PFSP). The effect of hybridization was validated through an internal comparison based on the results of 120 different instances devised by Taillard with variable problem sizes. Moreover, further comparison with other reported hybrid metaheuristics has proved that the hybrid PSO (HPSO) developed during this research performed exceedingly well. A smaller value of 0.48 of ARPD (Average Relative Performance Difference) for the algorithm is evidence of its robust nature and significantly improved performance in optimizing the makespan as compared to other algorithms.

Radiometric Calibration of GF5-02 Advanced Hyperspectral Imager Based on RadCalNet Baotou Site

In this study, an on-orbit radiometric calibration campaign of the GF5-02 AHSI was performed at the RadCalNet Baotou site, based on the automated observation of reflectance and atmospheric parameters of a 300 m × 300 m homogeneous desert area. The consistency of the radiometric calibration coefficients was validated both at the Dunhuang calibration site and the Baotou site. The average relative difference between the calibrated top-of-atmospheric (TOA) radiance and the predicted TOA radiance were less than 7%. The R2 of these two TOA radiances were all higher than 0.99. These results showed that the accuracy of calibration coefficients could meet the requirements of hyperspectral quantification applications. The uncertainty of GF5-02 AHSI radiometric calibration was 6.18%. This study also demonstrated that automated observation data of the Baotou site were reliable for high-frequency radiometric calibration and radiometric performance monitoring of GF5-02 AHSI.

18F-PSMA-1007 salivary gland dosimetry: comparison between different methods for dose calculation and assessment of inter- and intra-patient variability

Objective. Simplified calculation approaches and geometries are usually adopted for salivary glands (SGs) dosimetry. Our aims were (i) to compare different dosimetry methods to calculate SGs absorbed doses (ADs) following [18F]-PSMA-1007 injection, and (ii) to assess the AD variation across patients and single SG components. Approach. Five patients with prostate cancer underwent sequential positron-emission tomography/computed tomography (PET/CT) acquisitions of the head and neck, 0.5, 2 and 4 h after [18F]-PSMA-1007 injection. Parotid and submandibular glands were segmented on CT to derive SGs volumes and masses, while PET images were used to derive Time-Integrated Activity Coefficients. Average ADs to single SG components or total SG (tSG) were calculated with the following methods: (i) direct Monte Carlo simulation with GATE/GEANT4 considering radioactivity in the entire PET/CT field-of-view (MC) or in the SGs only (MCsgo); (ii) spherical model (SM) of OLINDA/EXM 2.1, adopting either patient-specific or standard ICRP89 organ masses (SMstd); (iii) ellipsoidal model (EM); (iv) MIRD approach with organ S-factors from OLINDA/EXM 2.1 and OpenDose collaboration, with or without contribution from cross irradiation originating outside the SGs. The maximum percent AD difference across SG components (δ max) and across patients (Δmax) were calculated. Main results. Compared to MC, ADs to single SG components were significantly underestimated by all methods (average relative differences ranging between −11.9% and −30.5%). δ max values were never below 25%. The highest δ max (=702%) was obtained with SMstd. Concerning tSG, results within 10% of the MC were obtained only if cross-irradiation from the remainder of the body or from the remainder of the head was accounted for. The Δmax ranged between 58% and 78% across patients. Significance. Simple geometrical models for SG dosimetry considerably underestimated ADs compared to MC, particularly if neglecting cross-irradiation from neighboring regions. Specific masses of single SG components should always be considered given their large intra- and inter-patient variability.

Extended MCDHF Calculations of Energy Levels and Transition Data for N i

Accurate and extensive atomic data are essential for spectroscopic analyses of stellar atmospheres and other astronomical objects. We present energy levels, lifetimes, and transition probabilities for neutral nitrogen, the sixth most abundant element in the cosmos. The calculations employ the fully relativistic multiconfiguration Dirac–Hartree–Fock and relativistic configuration interaction methods, and span the 103 lowest states up to and including 2s22p25s. Our theoretical energies are in excellent agreement with the experimental data, with an average relative difference of 0.07%. In addition, our transition probabilities are in good agreement with available experimental and theoretical data. We further verify the agreement of our data with experimental results via a reanalysis of the solar nitrogen abundance, with the results from the Babushkin and Coulomb gauges consistent to 2% or 0.01 dex. We estimated the uncertainties of the computed transition data based on a statistical analysis of the differences between the transition rates in the Babushkin and Coulomb gauges. Out of the 1701 computed electric dipole transitions in this work, 83 (536) are associated with uncertainties smaller than 5% (10%).

PCDD/Fs emissions in a large-scale hazardous waste incinerator under different operation conditions: Effective reduction strategies and an applicable correlation

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) emissions from hazardous waste incinerators (HWIs) have emerged as a great threat to environmental safety and human health, resulting in urgent effective control of the high emissions. In this study, the emission characteristics of chlorobenzenes (CBzs), PCDD/Fs from a large-scale HWI in China were studied under different conditions (inhibitor injection; feeding waste component). The total concentrations of CBzs and PCDD/Fs in stack gas from the HWI ranged from 2.18 to 22.94 μg/Nm3 and 0.98–18.53 ng/Nm3, respectively. Increased chlorine content of feeding waste led to increased PCDD/Fs concentrations, especially PCDDs. The inhibition efficiency of NH4H2PO4 with thiourea and Ca(OH)2 is 42.2% and 9.4% respectively. 2,3,4,7,8-PeCDF (30.7%–44.2%) and 1,3-DiCBz (61%–83%) was the dominating congener of I-TEQ values and CBzs concentration under all conditions, respectively. Furthermore, the relationship among PCDD/Fs, CBzs, traditional pollutants (carbon dioxide, sulfur dioxide, nitric oxide, hydrogen chloride, and particulate matter), and operational parameters were analyzed under six conditions to predict PCDD/Fs by indicators. Results indicated that PeCBz (r = 0.764), HCBz (r = 0.814), and quench tower water spray rate (r = −0.796) present strong correlations with I-TEQ values. Considering the effect of multicollinearity, the multiple regression model with PeCBz and water spray rate of quench tower as indicator variables (R2 = 0.801) has the best fitting effect, with an average absolute relative difference between measured and predicted I-TEQ of 34.8%. The study not only reveals the effects of hazardous waste composition and air pollution control devices (APCDs) parameters on PCDD/Fs emission characteristics, but also provided an accurate prediction method for PCDD/Fs emissions.

A high resolution Fourier transform ion trap enabled by image current splicing: a theoretical study.

The relatively high work pressure within an ion trap has limited the implementation of the Fourier transform technique for high resolution mass analysis. The main reason is that high buffer gas pressure will cause the rapid decay of ion oscillations. In this study, an image current splicing method based on the filter diagonalization method (FDM) and the Hilbert transform was developed to increase the resolving power of nondestructive mass analysis in a linear ion trap. First, multiple repeated experiments (or ion trajectory simulations) were performed to collect multiple sets of data. Using the FDM, the frequency component distribution was extracted from short image current transients collected from each experiment. The Hilbert transform was then applied to calculate and normalize the decay envelope of each transient. The relative abundance was calculated by counting the envelopes. Finally, image current transients collected from these multiple experiments were spliced and merged into a whole signal with much longer duration and continuous phase. This splicing method could effectively increase the duration of the image current, and thus improve the mass resolution of the ion trap mass analyzer. The mass resolution (m/Δm) was improved from 183.5 to 5.8 × 103, and the average relative difference was 2.8%. The proposed method resolved 3 adjacent peaks which originally could not be resolved from the raw signal by the fast Fourier transform (FFT). Besides simulated data, this method was also applied to the experimental data collected from a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer. The influence of electronic noise on the proposed method was also discussed in this study.

Analytical solution for heat and mass transfer in desiccant coated heat exchangers

• Heat and moisture transfer in a desiccant-coated heat exchanger (DC-HX) is studied. • A new closed-form analytical solution is proposed. • Linear and exponential profiles are assumed for air temperature and humidity ratio. • A new DC-HX coated with AQSOA™-FAM-Z02 is also fabricated and tested. Due to the complicated nature of desiccant-coated heat exchangers (DC-HXs), solving the highly-coupled transient heat and mass transfer equations using numerical simulations are rather time-consuming and as a result may be impractical for real-time system optimization and seasonal simulations. On the other hand, the approach of majority of studies associated with DC-HXs is numerical and experimental analyses and there is no analytical model that can accurately predict the heat and moisture transfer in a DC-HX in the literature. Thus, in this paper, a new closed-form analytical solution is proposed to accurately predict the heat and moisture transfer in a DC-HX for the first time. The governing equations are simplified to a set of linear ordinary differential equations with initial conditions and then solved analytically. In the present analytical model, both linear and exponential profiles are assumed for the air temperature and humidity ratio along the DC-HX and the results are compared to experimental data collected in our lab. A new DC-HX coated with AQSOA™-FAM-Z02 is also fabricated and tested in our custom-built testbed under a wide range of operating conditions for model validation and performance assessment. Our results indicate that the present analytical solution with exponential profile assumption predicts the experimental data with an average relative difference of less than 10%, while the linear profile assumption results in a relative difference of ∼ 20% with the experimental data. The new analytical solution is capable of predicting the performance of DC-HXs, which is crucial for design, optimization and operating dehumidification systems in a variety of applications.

Automatic segmentation of prostate MRI based on 3D pyramid pooling Unet.

Automatic segmentation of prostate magnetic resonance (MR) images is crucial for the diagnosis, evaluation, and prognosis of prostate diseases (including prostate cancer). In recent years, the mainstream segmentation method for the prostate has been converted to convolutional neural networks. However, owing to the complexity of the tissue structure in MR images and the limitations of existing methods in spatial context modeling, the segmentation performance should be improved further. In this study, we proposed a novel 3D pyramid pool Unet that benefits from the pyramid pooling structure embedded in the skip connection (SC) and the deep supervision (DS) in the up-sampling of the 3D Unet. The parallel SC of the conventional 3D Unet network causes low-resolution information to be sent to the feature map repeatedly, resulting in blurred image features. To overcome the shortcomings of the conventional 3D Unet, we merge each decoder layer with the feature map of the same scale as the encoder and the smaller scale feature map of the pyramid pooling encoder. This SC combines the low-level details and high-level semantics at two different levels of feature maps. In addition, pyramid pooling performs multifaceted feature extraction on each image behind the convolutional layer, and DS learns hierarchical representations from comprehensive aggregated feature maps, which can improve the accuracy of the task. Experiments on 3D prostate MR images of 78 patients demonstrated that our results were highly correlated with expert manual segmentation. The average relative volume difference and Dice similarity coefficient of the prostate volume area were 2.32% and 91.03%, respectively. Quantitative experiments demonstrate that, compared with other methods, the results of our method are highly consistent with the expert manual segmentation.

Indoor Particle's Pollution in Bucharest, Romania.

Air pollution risk factor on human health was surpassed only by high blood pressure, tobacco use and poor diet. Total number of deaths due to air pollution worldwide was estimated to 6.67 million people in 2019. In the European Union, 97% of the urban population is exposed to levels of fine particulate matter above the latest guideline levels set by the World Health Organization. Air pollution accounts for 20% of newborn deaths worldwide, most related to complications of low birth weight and preterm birth. Low birth weight and preterm birth are responsible for 1.8 million deaths worldwide. Bucharest is the capital city of Romania and one of the most polluted cities in Europe, ranking in the 9th position out of 96 of the top cities from Europe and in the 4th position out of 32 of the top cities in Eastern Europe, data from June 2022. The aim of this study was to measure the real time level of indoor particulate pollution levels in different indoor environments from Bucharest, during the pandemic period. The PM2.5/PM10 ratio and its rate of change were also determined for the measured data. The PM2.5/PM10 ratio and its rate of change were also calculated based on the measurement data. The PM2.5/PM10 ratio showed an upward trend on weekends compared to weekdays, suggesting a relationship with outdoor PM where leisure activities and traffic infiltrated the indoors. The fluctuation range of the PM2.5/PM10 ratio was 0.44~0.95, and low measured values were detected on weekdays. Of the seasons, the proportion of particulate in autumn and its rate of change tended to be higher than in summer. It was suggested that outdoor air may have permeated the room. In addition, the relationship was considered, such as it is a holiday period, there are few rainy days, the concentration of coarse particles is high, and the number of residents in the city decreases. When it comes to indoor air quality, the higher this ratio, the more serious the air pollution. PM10 concentrations decreased by 29.1% in the absence of human activity and increased by 35.1% in the presence of humans. PM2.5 concentration decreased by 30.3% without human activity and increased by 3.1% with the presence of humans. Certain trends were suggested for the resumption of human activity and an increase in PM2.5 concentrations. The average relative difference between October 2021, a pandemic period, and October 2022, a post pandemic period, was 64% for PM10 and 47% for PM2.5. The pandemic period brought a significantly better indoor air quality from the particulate pollution point of view.

Water vapour and ozone in the upper troposphere–lower stratosphere: global climatologies from three Canadian limb-viewing instruments

Abstract. This study presents upper troposphere–lower stratosphere (UTLS) water vapour and ozone climatologies generated from 14 years (June 2004 to May 2018) of measurements made by three Canadian limb-viewing satellite instruments: the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS), the Measurement of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation (MAESTRO), and the Optical Spectrograph and InfraRed Imaging System (OSIRIS; ozone only). This selection of instruments was chosen to explore the capability of these Canadian instruments in representing the UTLS and to enable analysis of the impact of different measurement sampling patterns. The water vapour and ozone climatologies have been constructed using tropopause-relative potential temperature and equivalent-latitude coordinates in an effort to best represent the distribution of these two gases in the UTLS, which is characterized by a high degree of dynamic and geophysical variability. Zonal-mean multiyear-mean climatologies are provided with 5∘ equivalent latitude and 10 K potential temperature spacing and have been constructed on a monthly, seasonal (3-month), and yearly basis. These climatologies are examined in-depth for two 3-month periods, December–January–February and June–July–August, and are compared to reference climatologies constructed from the Canadian Middle Atmosphere Model 39-year specified dynamics (CMAM39-SD) run, subsampled to the times and locations of the satellite measurements, in order to evaluate the consistency of water vapour and ozone between the datasets. Specifically, this method of using a subsampled model addresses the impact of each instrument's measuring pattern and allows for the quantification of the influence of different measurement patterns on multiyear climatologies. This in turn permits a more consistent evaluation of the distributions of these two gas species, as assessed through the differences between the model and measurement climatologies. For water vapour, the average absolute relative difference between CMAM39-SD and ACE-FTS differed between the two versions of ACE-FTS by less than 8 %, while the MAESTRO climatologies were found to differ by 15 %–41 % from ACE-FTS, depending on the version of ACE-FTS and the season. When considering the ozone climatologies, those constructed from the two ACE-FTS versions agreed to within 2 % overall, and the OSIRIS ozone climatologies agreed with these to within 10 %. The MAESTRO ozone climatologies differ from those from ACE-FTS and OSIRIS by 30 %–35 % and 25 %, respectively, albeit with regions of better agreement within the UTLS. These findings indicate that this set of Canadian limb sounders yields generally similar water vapour and ozone distributions in the UTLS, with some exceptions for MAESTRO depending on the season and gas species.

Dosimetric validation of a GPU-based dose engine for a fast in silico patient-specific quality assurance program in light ion beam therapy.

With rapid evolutions of fast and sophisticated calculation techniques and delivery technologies, clinics are almost facing a daily patient-specific (PS) plan adaptation, which would make a conventional experimental quality assurance (QA) workflow unlikely to be routinely feasible. Therefore, in silico approaches are foreseen by means of second-check independent dose calculation systems possibly handling machine log-files. To validate the in-house developed GPU-dose engine, FRoG, for light ion beam therapy (protons and carbon ions) as a second-check independent calculation system and to integrate machine log-file analysis into the patient-specific quality assurance (PSQA) program. Spot sizes, depth-dose distributions, and absolute dose calibrations were configured into FRoG and a set of nine regular-shaped targets in combination with more than 170 clinical treatment fields were tested against pinpoint ionization chamber measurements. Both the treatment planning system DICOM RTplans and machine treatment log-files were used as input for the dose kernel in water, and a 3D local γ (1mm/2%) index was used as the main evaluation metric. Calculated configuration data matched experimental measurements with submillimetric agreement. For regular-shaped targets, the unsigned average relative difference between calculated and measured dose values was less than 2% for both protons and carbon ions. The mean γ passing rate (PR) was around 98% for both particle species. For clinical treatment beams, DICOM-based recalculations showed a γ-PR more than 99% for both particle species. The same level of agreement was preserved for protons when moving to log-file-based recalculations. A score of around 95% was registered for carbon ion beams, once excluding low-quality machine log-files. Unsigned average relative difference against acquired data was less than 2% also for real clinical beams. FRoG was proven as an accurate and reliable tool for PSQA in scanning light ion beam therapy. The proposed method allows for an extremely efficient workflow, without compromising the quality of the plan verification procedure.

Evaluation of MRI-only based online adaptive radiotherapy of abdominal region on MR-linac.

A hybrid magnetic resonance linear accelerator (MRL) can perform magnetic resonance imaging (MRI) with high soft-tissue contrast to be used for online adaptive radiotherapy (oART). To obtain electron densities needed for the oART dose calculation, a computed tomography (CT) is often deformably registered to MRI. Our aim was to evaluate an MRI-only based synthetic CT (sCT) generation as an alternative to the deformed CT (dCT)-based oART in the abdominal region. The study data consisted of 57 patients who were treated on a 0.35T MRL system mainly for abdominal tumors. Simulation MRI-CT pairs of 43 patients were used for training and validation of a prototype convolutional neural network sCT-generation algorithm, based on HighRes3DNet, for the abdominal region. For remaining test patients, sCT images were produced from simulation MRIs and daily MRIs. The dCT-based plans were re-calculated on sCT with identical calculation parameters. The sCT and dCT were compared in terms of geometric agreement and calculated dose. The mean and one standard deviation of the geometric agreement metrics over dCT-sCT-pairs were: mean error of 8±10 HU, mean absolute error of 49±10 HU, and Dice similarity coefficient of 55±12%, 60±5%, and 82±15% for bone, fat, and lung tissues, respectively. The dose differences between the sCT and dCT-based dose for planning target volumes were 0.5±0.9%, 0.6±0.8%, and 0.5±0.8% at D2% , D50% , and D98% in physical dose and 0.8±1.4%, 0.8±1.2%, and 0.6±1.1% in biologically effective dose (BED). For organs-at-risk, the dose differences of all evaluated dose-volume histogram points were within [-4.5%, 7.8%] and [-1.1 Gy, 3.5 Gy] in both physical dose and BED. The geometric agreement metrics were within typically reported values and most average relative dose differences were within 1%. Thus, an MRI-only sCT-based approach is a promising alternative to the current clinical practice of the abdominal oART on MRL.

Experimental study of heat transfer coefficient in heat exchanger reactors with square millimetric zigzag channels

Heat transfer performances of compact heat exchanger reactors were experimentally characterized and measurement uncertainties were evaluated using the derivation method. Prototypes presenting two kinds of process channel configurations (zigzag and straight channels) with square cross-section were investigated, from 2 mm to 4 mm depth. Water or glycerol-water mixture were used as the process fluid, cooled by water as the utility fluid. Reynolds number ranged between 15 and 7300 and Prandtl number between 3.1 and 115. From the measurements of the fluid temperatures and flow rates, local heat transfer coefficients were calculated. In zigzag channels, it ranged from 760 to 15,000 W.m−2.K−1, with an average uncertainty of 15.7%. With water as the process fluid, the heat transfer coefficients in zigzag channel were 2 to 5 times higher than in straight channel. The experimental data were then used to establish a correlation for the Nusselt number in the zigzag channels as a function of the channel geometry, the fluid properties and flow rates expressed in terms of dimensionless numbers. The average relative difference between experimental and calculated values was 9.1%. Finally, the consistency of the correlation was confirmed by comparison with data obtained in a previous work based on CFD.