Effective Diameter Research Articles

Investigation of iron oxide nanoparticle formation in a spray-flame synthesis process using laser-induced incandescence

In this work, iron-oxide nanoparticle formation in the spray-flame synthesis (SFS) process of the standardized SpraySyn 2.0 burner was investigated in situ using laser-induced incandescence (LII). For the evaluation of these measurements, prior LII-experiments within iron-oxide aerosols (Fe3O4 and α-Fe2O3) with known primary particle size distribution and morphological properties were performed to determine the thermal accommodation coefficient (TAC) α, which led to approx. α = 0.08. The applicability of the TAC results within the flame was validated using spectrally and temporally resolved measurements in the flame at 65 mm HAB employing a spectrograph. Data for a bimodal particle size distribution, obtained from Transmission Electron Microscopy (TEM), were used in the LII-evaluation. The validated TAC was then used to evaluate the primary particle size evolution from in situ Time-Resolved (TiRe) LII-measurements using PMTs along the centre axis of the burner, ranging from 10 mm to 50 mm HAB. These measurements reveal a relatively constant effective particle diameter along HAB with dp,eff ≈ 300 nm. To further investigate particle formation in SFS, 2-dimensional time-resolved LII-measurements in the SFS flame were performed, showing a clear particle formation region up to approx. 30 mm HAB, from where on a constant particle mass is observed.

True pinch mode of magnetorheological fluids

Abstract Magnetorheological (MR) fluids are representatives of smart materials. They react to magnetic fields by developing a yield stress. The effect has been employed in real-world applications such as automotive chassis systems or optical finishing. By convention, MR devices can be operated in at least one of the fundamental modes: flow, shear, squeeze, gradient pinch of which the former has been the least studied and understood. In pinch mode, the material in the flow channel is exposed to non-uniform magnetic fields in the direction parallel to fluid flow. As a result, only the volume of MR fluid near the channel walls are energized to modify the particular material property (yield stress). The result is the channel’s effective diameter change. The behavior of the material in pinch mode is unique and unseen in the other controllable fluids. To study the material’s characteristics in the specific mode, the authors developed a novel circuit concept for energizing the material in an effort to achieve the ’true-zero’ pinch mode magnetic behavior. Contrary to the existing pinch mode valve concepts, the concept valve allows to achieve zero magnetic flux density in the center of the flow channel regardless of the current level. To test the hypothesis a prototype valve was modeled, manufactured and tested across a range of external (flow rate, current/magnetic flux) stimuli. The obtained results yield sufficient evidence proven by results of magnetic simulations to support the underlying hypothesis. The experimental results illustrate the pinch mode type behaviour, i.e. the slope change in the pressure vs flow rate characteristics.

Generation of terahertz radiation with a specified spectral profile from a mosaic combined organic crystal

We present a method for the generation of terahertz (THz) pulses with a high optical-to-THz conversion efficiency and a smooth spectrum. The method is based on the optical rectification of near-infrared femtosecond laser pulses with a wavelength of 1240 nm in a mosaic combined crystal, consisting of two pieces of nonlinear organic crystals, OH1 and DSTMS. The mosaic combined crystal produces a relatively smooth spectrum in the 0.3–4.5 THz range with no pronounced absorption dips and with a maximum in a spectral amplitude at about 2 THz. The peak field strength is 9.6 MV/cm for an effective crystal diameter of 4.3 mm.

Comparisons of MR and EM inferred tissue microstructure properties using a human autopsy corpus callosum sample

Degeneration of white matter (WM) microstructure in the central nervous system is characteristic of many neurodegenerative conditions. Previous research indicates that axonal degeneration visible in ex vivo electron microscopy (EM) photomicrographs precede the onset of clinical symptoms. Measuring WM microstructural features, such as axon diameter and packing fraction, currently require these highly invasive methods of analysis and it is therefore of great importance to develop methods for in vivo measurements. Diffusion weighted Magnetic Resonance Imaging (MRI) is a non-invasive method which can be used in conjunction with temporal diffusion spectroscopy (TDS) and an oscillating gradient spin echo (OGSE) pulse sequence to probe micron-scale structures within neural tissue. The current experiment aims to compare axon diameter measurements, mean effective axon diameter (AxD¯), and packing fractions calculated from EM histopathological analysis and inferred values from MR images. Mathematical models of axon diameters used for analysis include the ActiveAx Frequency-Dependent Extra-Axonal Diffusion (AAD) model and the AxCaliber Frequency-Dependent Extra-Axonal Diffusion (ACD) model using ROI (Region of Interest) based analysis (RBA) and voxel-based analysis (VBA), respectively. Overall, it was observed that MRI inferred WM microstructural parameters overestimate those calculated from EM. This may be attributable to tissue shrinkage during EM dehydration, the sensitivity of MR pulse sequences to larger diameter axons, and/or inaccurate model assumptions. The results of the current study provide a means to characterize the precision and accuracy of RBA-ACD and VBA-AAD OGSE-TDS and highlight the need for further research investigating the relationship between ex vivo MRI and EM, with the goal of reaching in vivo MRI.

Comparative Study of Thermal Criteria and Fluid-Flow Criteria in Micro and Mini Channel Design Constrains with or without Insert Made of Aluminum Material

Through experimental and simulation results, a comparison between mini and micro channels with inserts or without inserts is conducted; in this case, water is the only working fluid used for present experimentation. In order to research the fluid flow and micro channel features, the results of fluid flowing inside the mini channel and micro channel with insert or without insert separately were admitted. Experiments were performed for various operating and design parameters under counter-flow conditions, with hot water moving into a concentric tube with a 30 mm diameter at 0.00078 kg/sec flow rate. The fluid is moving separately through mini channels with a 2 mm diameter and micro channels with lower than 1 mm dia. at a varying flow rate 0.00015 kg/sec to 0.0062 kg/sec. The working temperatures for hot water and cold fluid were 323 K and 303K, respectively. According to the results, the suggested design of the micro channel with insert performed better than a conventional mini channel, micro channel without insert and mini channel with inserts due to the better thermal conductivity of the aluminum material, effective diameter (1mm) to length ratio of micro channel in which heat exchanges with minimum volume ratio and the additional exposed area made possible by the rectangular shape of the insert, whereas micro channel with micro insert having rectangular shape showing best results as compared with the other designs of channel due to the rich heat passage and effective pressure drop and temperature. Experimentation and simulation results are coming in positive direction, it is directly observed from the error percentage i.e. 2.41% to 4.29%.

Usefulness of percutaneous transluminal coronary balloon angioplasty for coronary artery stenosis after surgery for CHD.

Coronary artery involvements occur rarely both during cardiac repair and in the late period after surgery, and it may result in myocardial ischaemia and infarction. We present six cases who underwent percutaneous transluminal coronary balloon angioplasty for coronary artery stenosis in the late period after surgery. The patients included four boys and two girls. Post-operative states involving anomalous origin of the left coronary artery from the pulmonary artery and d-transposition of the great arteries were observed in two patients each. Two patients with univentricular heart had coronary artery injuries during surgery. The age at the angioplasty ranged from 1 month to 14 years, with a median of 3 years. The interval from the operation to angioplasty ranged from 37 days to 14 years (median 8 months). The interval from the angioplasty to follow-up coronary angiography ranged from 2 months to 14 years (median 11 months). The follow-up period ranged from 2 months to 20 years (median 8 years). One patient underwent a stent implantation because of post-procedure recoil. Coronary artery stenosis improved immediately after procedure in the six patients without complication, and restenosis occurred post-procedure in one patient. Five patients had no cardiac events. Although the angioplasty's initial effect may not be dramatic, it can improve late after the procedure. It was considered that the optimal balloon-reference vessel ratio to obtain a minimal effective lumen diameter was about 1.0. Angioplasty post-surgery for CHD in children was feasible and without complications.

A New Powerful Magnetic Dark Catalyst Based on rGO/Fe3O4/CdSe Nanocomposite for Ultrafast Degradation of Methylene Blue Dye.

In the present study, Rgo/Fe3O4/CdSe as a dark catalyst material was synthesized by a refluxing method. The synthesized magnetic nanocomposites were studied by various analyses such as Fourier transform infrared (FTIR), energy-dispersive X-ray spectroscopy (EDS), field emission scanning electron microscopy (FESEM), X-ray diffractometer (XRD), Raman, Zeta and vibrating sample magnetometer (VSM). Characterization of structural analysis showed that the nanocomposites were successfully synthesized. The absorption spectrum was used to determine the dark catalyst activity of rGO/Fe3O4/CdSe nanocomposite. Analysis of the absorption spectrum showed that the prepared nanocomposites degrade the MB organic dye completely (100%) after 2min of stirring in the dark, also experimenting with different pH showed that the best performance for the degradation of MB occurs in neutral and alkaline media. The Raman spectrum analysis showed that the Fe3O4/CdSe quantum dots (QDs) were correctly incorporated on the reduced graphene oxide (rGO) nanosheets. Zeta potential analysis showed that rGO/Fe3O4/CdSe has a large amount of negative charge on its surface and the surface charge increased by about 16 mV compared to the Fe3O4/CdSe compound. BET and BJH techniques were used to determine the effective surface area and pore size diameter, BET results to determine the effective surface area showed that by adding graphene to the compound, the specific surface area increased from 42.877 m2g-1 to 54.1896 m2g-1. The radical scavenger experiment showed that electrons play an essential role in the degradation process. VSM analysis showed that the prepared nanocomposites have excellent superparamagnetic behavior, this advantage enables the easy collection of nanocatalysts by magnets from wastewater after dye degradation.

Numerical Analysis of the Influence of Preadsorbed Water on Methane Transport in Crushed Shale

Summary Methane migration in shale is affected by preadsorbed water. To understand this effect, we examined several key parameters, including the effective pore diameter Le, the pore volume distribution of Le, the effective porosity ϕe, the equivalent particle diameter da, and the water film thickness h. Using these parameters, we established an equivalent relationship linking the particle packing da and the Le and the ϕe of the capillary pores within a unit-length cuboid of particles. Based on this relationship, a conceptual model was developed to simulate methane adsorption and transport in partially saturated crushed shale, incorporating parameter estimation for the tangential momentum adjustment factor δ and methane desorption rate coefficient kd, where δ characterizes the slip flow intensity and kd is related to the Langmuir adsorption constant. The finite element method was used to calculate the methane permeability ke, Knudsen diffusion coefficient Dke, surface diffusion coefficient Ds, and adsorption phase transition rate Rm, which are all affected by adsorbed water. The model’s numerical results were validated through comparison with the results from adsorption experiments. These results revealed three distinct regions in the trend of the variation in δ with Le: a rapid increase in Region I (Le < 10 nm), a slowing increase in Region II (10 ≤ Le ≤ 100 nm), and a gradual increase in Region III (Le > 100 nm). In addition, kd is positively correlated with da. kd is also correlated with water saturation S; specifically, kd decreases when S ≤ 12%, increases when S = 12% to 45.8%, and decreases again when S exceeds 45.8%. The results also reveal overall negative correlations between h and ke, Dke, Ds and Rm. Furthermore, the rates of change in ke, Dke, Ds and Rm with increasing ε (ε is the bending coefficient associated with adsorbed water) range from 7.5% to 49.4%. Similarly, ke, Dke, and Ds increase by factors of 0.73–7.19 with increasing χ (χ is the coverage rate of the adsorbed water film). Additionally, as the adsorption time t increases, Ds initially increases rapidly, followed by a gradual increase. Between t = 500 seconds and 1,500 seconds, the rate of change in Ds decreases by 20%. Rm shows a three-stage relationship with t, namely, a rapid decrease from t = 0 seconds to 500 seconds, a steady decrease from 500 seconds to 1,000 seconds, and a stabilization from 1,000 seconds to 1,500 seconds, with Rm ranging from 1.10×10-11 mol/(m3·s) to 9.45×10-11 mol/(m3·s) overall. Ds increases with the adsorption amount ratio Ed (Ed is the ratio of the adsorption amount at t to the equilibrium adsorption amount). As Ed ranges from 0.2 to 0.6, the rate of change in Ds increases by 87% to 100%. Furthermore, Rm is negatively linearly correlated with Ed.

Effect of high-frequency ultrasonication on degradation of polytetrafluoroethylene (PTFE) microplastics/nanoplastics

Polytetrafluoroethylene (PTFE) particle might present a significant contamination in environment due to its dual classification as a microplastic and a fluorinated compound (a type of PFAS, or per- and polyfluoroalkyl substances), coupled with its extreme stability. Identifying an effective degradation method for PTFE microplastics is thus crucial towards remediation, along with the suitable monitoring approaches. This study is the first to use high-frequency (580 kHz) ultrasonication for the degradation of the PTFE microplastics with diameter of ∼1000 nm. Dispersion of PTFE microplastics with help of surfactant (SDS, or sodium dodecyl sulfate) followed by ultrasonication for 9 h under optimal conditions resulted in a defluorination percentage of ∼32 %. Particle size analysis demonstrated the effective diameter shrink of PTFE microplastics by ultrasonication (from ∼1000 nm to ∼330 nm that can be categorized as nanoplastics). SEM-EDS provided clear visualization of PTFE microplastics/nanoplastics, while Raman imaging confirmed the fine particles from molecular spectrum window. ImageJ analysis algorithms were utilized to estimate particle sizes as well. Based on these findings, a potential degradation mechanism for PTFE microplastics/nanoplastics was proposed. This study contributes to the understanding of PTFE degradation and may facilitate further research in this field.

A quantum-corrected Peng‒Robinson equation of state for helium-4 from 3 K to 50 K considering quantum swelling effects through the Feynman‒Hibbs correction of the EXP-6 potential

Accurate and efficient prediction of the properties of helium-4 (He-4) via an equation of state (EOS) is a prerequisite for evaluating liquid helium-4 (LHe-4) storage technology. However, the performance of the Peng–Robinson (PR) EOS in predicting the density of LHe-4 and vapour helium-4 (VHe-4) deteriorates within the thermodynamic ranges of the LHe-4 tank: 3–50 K and 60–600 kPa. To modify the PR EOS, we establish first-order and second-order Feynman–Hibbs (FH)-corrected EXP-6 potentials and propose a reduced effective particle diameter (REPD) correlation with four parameters to consider the quantum swelling effects of LHe-4. On the basis of the rational function form of the REPD correlation, we introduce a quantum-corrected covolume term to develop a regression model for the FH-corrected Peng–Robinson (FH-PR) EOS. Moreover, to improve the effectiveness of regression near the saturation curve, we propose a hypothetical boundary consisting of the saturation curve from 3 K to the critical temperature and a virtual saturation curve from the critical pressure to 600 kPa. The results indicate that the FH − PR EOS shows satisfactory engineering application performance in predicting the density of He-4 within the studied range. Under verification conditions, the average absolute relative deviation (AARD) of the density determined via the FH − PR EOS ranges from 0.72 % to 1.77 %, and the maximum relative deviation (MRD) ranges from 2.17 % to 5.62 %. Under test conditions, the AARD of the density ranged from 1.06 % to 1.71 %, and the MRD ranged from 3.77 % to 7.38 %.

Size specific dose estimates and effective dose in multiphase abdomen-pelvis CT examinations

This study estimated the size-specific dose estimates (SSDE) in different scan phases and inter-phase variations of multi-phase abdomen-pelvis CT examinations. Various methods employed for determination of SSDE, which takes into account the size of the patient, were compared for 51 multiphase abdomen-pelvis CT examinations using custom written software. These methods are based on effective diameter, water equivalent diameter derived from region of interest and segmentation techniques, diameter of central image and whole scan series. Significant variation was observed in SSDE of pre-contrast phase in comparison to other phases. The effective dose was also estimated and correlated with SSDE. The results indicate that the underestimation in the dose estimated using the machine parameter, CTDIvol, was in the range of 10%–60% when compared with SSDE. This study concludes that the average SSDE of the whole examination is a better representation of patient dose in the case of multi-phase examinations. It highlights the need for integration of SSDE calculating software in the CT scanner systems for accurate estimation of patient doses.

Carbon dioxide evaporation heat transfer coefficient prediction in porous media using Machine learning algorithms based on experimental data

The prediction of the internal heat transfer coefficient during evaporation is vital for vapor-compression refrigeration and closed-loop power cycles. Accurate measurements and understanding of CO2 heat transfer in porous evaporators are essential for optimal system design across various operating conditions. This study utilizes a reference dataset derived from previous experiments that investigated the impact of porous evaporators on CO2′s internal heat transfer coefficient under sub-critical conditions, employing gravel sand as the porous medium. The dataset encompasses key factors: gravel sand porosities ranging from 39.8 % to 44.5 %, evaporator inlet pressures between 3700 and 4300 kPa, CO2 mass flow rates from 10.7x10-5–18x10-5kg.s−1, and porous tube effective diameters spanning 1.53 x10-3–3.4x10-3m. Employing three machine learning techniques (SVM, GPR, OBEM), the study predicts the internal heat transfer coefficient using regression models. The models’ predictions are analyzed and compared to expected values for validation, evaluating their performance using four statistical criteria. Results indicate SVM, GPR, and OBEM models achieved RMSEs of 1.5471, 1.8212, and 3.6978, respectively, while MAE errors were 1.1479, 1.2418, and 2.9787, respectively. Comparison with the dimensional analysis method reveals the effectiveness of the proposed models in accurately predicting internal heat transfer coefficients. The models exhibit low uncertainty and maintain prediction quality on an extended dataset without overfitting concerns. Overall, this research contributes valuable insights for designing heat exchangers and systems in vapor-compression refrigeration and closed-loop power cycles.

The determination of coefficients for size specific effective dose for adult and pediatric patients undergoing routine computed tomography examinations.

The effective dose resulting from computed tomography (CT) scans provides an assessment of the risk associated with stochastic effects but does not account for the patient's size. Advances in Monte Carlo simulations offer the potential to obtain organ dose data from phantoms of varying stature, enabling derivation of a size-specific effective doses (SEDs) representing doses to individual patients. This study aimed to compute size-specific k-conversion factors for SED in routine CT examinations for adult and pediatric patients of different sizes. Radiation interactions were simulated for adult and pediatric phantom models of various sizes using National Cancer Institute CT version 3.0.20211123. Subsequent calculations of SED were performed, and coefficients for SED were derived, considering the variations in body sizes. The results revealed a strong correlation between effective diameter and weight, observed with size-specific k-conversion factors for adult and pediatric phantoms, respectively. While size-specific k-conversion factors for CT brain remained constant in adults, values for pediatric cases varied. When using the tube current modulation (TCM) system, size-specific k-conversion factors increased in larger phantoms and decreased in smaller ones. The extent of this increase or decrease correlated with the set TCM strength. This study provides coefficients for estimating SEDs in routine CT exams. Software utilizing look-up tables of coefficients can be used to provide dose information for CT scanners at local hospitals, offering guidance to practitioners on doses to individual patients and improving radiation risk awareness in clinical practice.

Effects of functional groups in polymers on rate of acid–rock reaction in reservoir stimulation

The focus of research on acid stimulation is to reduce the rate of the acid–rock reaction, which involves the infiltration of acid into deep formations. Gelled acids with high viscosity can decelerate the diffusion of hydrogen ions to decrease the rate of the acid–rock reaction. However, there have been few reports on the interactions between functional groups in polymers and rocks. In this study, three polymers (AA7, AA24, and AAS) with different functional groups were synthesized, and their effects on the acid–rock reaction were investigated. The results showed that the order of the abilities of the three polymers to delay the acid–rock reaction was as follows: AA24 > AA7 > AAS. The retardation rate for AA24, AA7, and AAS was 79.31%, 66.67%, and 40.23%, respectively. Adsorption experiments illustrated that AA7 and AA24 were adsorbed on the surface of calcite via hydrogen bonds formed by ethoxy groups, whereas AAS relied on the hydrophobic effect of the benzene ring. The anionic polymer AAS was subjected to a strong electrostatic effect in an acid solution, which caused the molecular chains to curl and impaired the retarding performance. This was proved by the fact that the viscosity dramatically decreased from 66.00 mPa s in an aqueous solution to 7.50 mPa s in an acid solution and the effective diameter decreased from 322.2 nm in an aqueous solution to 102.2 nm in an acid solution. In the cases of the nonionic polymers AA7 and AA24, there was little change in viscosity or effective diameter, whether in an acid solution or an aqueous solution. Scanning electron microscopy confirmed that the film formed by the adsorption of AA24 on the surface of calcite was denser than that formed by AA7 because more ethoxy groups were present in AA24, but the film exhibited some narrow cracks in the case of AAS. Atomic force microscopy demonstrated that the surface roughness of calcite etched by a retarding acid solution of AA24 was only 78 nm, whereas it was as high as 130 nm in the case of AAS, which was consistent with the retarding performance with regard to the acid–rock reaction. This research could contribute to improvements in carbonate acidizing for reservoir stimulation.

Modelling white matter microstructure using diffusion OGSE MRI: Model and analysis choices

Alterations in white matter (WM) microstructure of the central nervous system have been shown to be pathophysiological presentations of various neurodegenerative disorders. Current methods for measuring such WM features require ex vivo tissue samples analyzed using electron microscopy. Magnetic Resonance Imaging (MRI) diffusion-weighted pulse sequences provide a non-invasive tool for estimating such microstructural features in vivo. The current project investigated the use of two methods of analysis, including the ROI-based (Region of Interest, RBA) and voxel-based analysis (VBA), as well as four mathematical models of WM microstructure, including the ActiveAx Frequency-Independent Extra-Axonal Diffusion (AAI), ActiveAx Frequency-Dependent Extra-Axonal Diffusion (AAD), AxCaliber Frequency-Independent Extra-Axonal Diffusion (ACI), and AxCaliber Frequency-Dependent Extra-Axonal Diffusion (ACD) models. Two mice samples imaged at 7 T and 15.2 T were analyzed. Both the AAI and AAD models provide a single value for each of the fit parameters, including mean effective axon diameter AxD¯, packing fraction fin, intra-cellular and Din and extra-cellular Dex diffusion coefficients, as well as the frequency dependence of Dex, βex for the AAD model. The ACI and ACD models provide this, in addition to a distribution of axon diameters for a chosen ROI. VBA extends this, providing a parameter value for each voxel within the selected ROI, at the cost of increased computational load and analysis time. Overall, RBA-ACD and VBA-AAD were found to be optimal for parameter fitting to physically relevant values in a reasonable time frame. A full comparison of each combination of RBA and VBA with AAI, AAD, ACI, and ACD is provided to give the reader sufficient information to make an informed decision of which model is best for their own experiments.

Probe the Regolith Characteristics of Asteroids from 9 yr Infrared Observations of WISE/NEOWISE: A Case Study of The Main-belt Object (656) Beagle

This work presents the data processing, fitting procedure, modeling, and analyzing of 9 yr infrared light curves provided by the WISE/NEOWISE telescope, by which the regolith characteristics of Main-belt Object (656) Beagle is studied. Beagle locates in the Themis family, and was proposed to be the parent of the first main-belt comet (MBC) 133P. We determine Beagle’s effective diameter Deff=57.3−2.2+4.5 km, geometric albedo pv=0.05−0.007+0.004 , mean roughness θ RMS = 44 ± 4°, mean grain size b=100−90+350μm , mean specific heat capacity c p = 173 ∼ 516 J Kg−1 K−1, mean thermal conductivity κ = 0.7 ∼ 1.3 × 10−3 W m−1 K−1, and mean thermal inertia Γ = 14 ∼ 32 J m−2 s−0.5 K−1. The albedo of Beagle is a little anomalous that the albedos of Beagle’s neighboring asteroids are more close to (24) Themis, rather than Beagle itself. The W1-band near-infrared (NIR) light curves do not reveal significant heterogeneous NIR features on the surface of Beagle, being inconsistent with the expectation of a family parent that has members with diverse NIR spectral types. These results add new clues of Beagle probably being an interloper or a sister, rather than the parent of its neighboring asteroids including the famous MBC 133P, hence may lead to new scenarios about the origin of 133P. Besides, we found that asteroidal shape models from inversion of optical light curves are imperfect for modeling infrared lightcurves, thus could mislead evaluations of both the heterogeneity of regolith reflectivity at NIR and thermophysical characteristics at thermal infrared.

Assessment of image quality and establishment of local acceptable quality dose for computed tomography based on patient effective diameter.

We aim to develop modified clinical indication (CI)-based image quality scoring criteria (IQSC) for assessing image quality (IQ) and establishing acceptable quality doses (AQDs) in adult computed tomography (CT) examinations, based on CIs and patient sizes. CT images, volume CT dose index ( ), and dose length product (DLP) were collected retrospectively between September 2020 and September 2021 for eight common CIs from two CT scanners at a central hospital in the Kingdom of Bahrain. Using the modified CI-based IQSC and a Likert scale (0 to 4), three radiologists assessed the IQ of each examination. AQDs were then established as the median value of and DLP for images with an average score of 3 and compared to national diagnostic reference levels (NDRLs). Out of 581 examinations, 60 were excluded from the study due to average scores above or below 3. The established AQDs were lower than the NDRLs for all CIs, except for oncologic follow-up for large patients (28 versus 26mGy) in scanner A, besides abdominal pain for medium patients (16 versus 15mGy) and large patients (34 versus 27mGy), and diverticulitis/appendicitis for medium patients (15 versus 12mGy) and large patients (33 versus 30mGy) in scanner B, indicating the need for optimization. CI-based IQSC is crucial for IQ assessment and establishing AQDs according to patient size. It identifies stations requiring optimization of patient radiation exposure.

Assessing the inter-observer and intra-observer reliability of radiographic measurements for size-specific dose estimates

BackgroundCalculating size-specific dose estimates (SSDEs) requires measurement of the patient’s anteroposterior (AP) and lateral thickness based on computed tomography (CT) images. However, these measurements can be subject to variation due to inter-observer and intra-observer differences. This study aimed to investigate the impact of these variations on the accuracy of the calculated SSDE.MethodsFour radiographers with 1–10 years of experience were invited to measure the AP and lateral thickness on 30 chest, abdomen, and pelvic CT images. The images were sourced from an internet-based database and anonymized for analysis. The observers were trained to perform the measurements using MicroDicom software and asked to repeat the measurements 1 week later. The study was approved by the institutional review board at Taibah University, and written informed consent was obtained from the observers. Statistical analyses were performed using Python libraries Pingouin (version 0.5.3), Seaborn (version 0.12.2), and Matplotlib (version 3.7.1).ResultsThe study revealed excellent inter-observer agreement for the calculated effective diameter and AP thickness measurements, with Intraclass correlation coefficients (ICC) values of 0.95 and 0.96, respectively. The agreement for lateral thickness measurements was lower, with an ICC value of 0.89. The second round of measurements yielded nearly the same levels of inter-observer agreement, with ICC values of 0.97 for the effective diameter, 1.0 for AP thickness, and 0.88 for lateral thickness. When the consistency of the observer was examined, excellent consistency was found for the calculated effective diameter, with ICC values ranging from 0.91 to 1.0 for all observers. This was observed despite the lower consistency in the lateral thickness measurements, which had ICC values ranging from 0.78 to 1.0.ConclusionsThe study’s findings suggest that the measurements required for calculating SSDEs are robust to inter-observer and intra-observer differences. This is important for the clinical use of SSDEs to set diagnostic reference levels for CT scans.

Interfacial microstructure and mechanical property of dissimilar resistance spot welded joint of TC4 titanium alloy and 316L stainless steel with nickel interlayer

Dissimilar materials of TC4 titanium alloy and 316L stainless steel were joined by means of resistance spot welding with nickel interlayer in different thicknesses. A significant enhancement in terms of nugget morphology quality with less defects was achieved for the welded joints with nickel interlayer compared with that without interlayer. With increasing the nickel interlayer thickness from 50 μm to 300 μm, the effective nugget diameter increased gradually from ∼4.8 mm to ∼5.2 mm, which was lower than that of the interlayer-free welded joint being ∼5.9 mm. A thinner intermetallic compound layer with dual-layered structure features with thickness of ∼11 μm was formed at the nugget/titanium interface in the welded joint with nickel interlayer compared with that of the interlayer-free welded joint, meanwhile an intermetallic compound layer with thickness of ∼3 μm was formed at the nugget/stainless steel interface, which exhibited serrated structure features. The introduction of nickel interlayer in the welded joint could suppress the formation of the brittle Ti–Fe intermetallics such as Fe2Ti, and facilitate the formation of TiNi, Ti2Ni and TiNi3. A more homogeneous current density distribution and a lower peak temperature (1809 °C) during welding were achieved via employing nickel interlayer. With increasing nickel interlayer thickness from 0 μm to 300 μm, the tensile shear load of welded joints experienced an increased tendency first and then decreased, meanwhile the maximum tensile shear load of 3.7 kN was obtained with the interlayer thickness of 200 μm, which was 61% higher than that of the interlayer-free welded joint.

Study on the mechanism of soil erosion by submerged water jet vertical scouring in cohesive soils

The water jet trenching technique is widely used in the burial of submarine pipelines. However, its application in cohesive soils often leads to complexity in trench morphology and challenges in predicting trench dimensions due to unclear soil erosion mechanisms. These issues significantly impact pipeline burials. To investigate the soil erosion mechanism of water jet trenching in cohesive soils, two-dimensional physical simulation experiments of submerged vertical water jet erosion were conducted. The influence of jet pressure, impingement height, and nozzle diameter on the shape of the scour hole was analyzed. The erosion damage patterns of water jets on cohesive soils were studied, and a theoretical model for the development of scour holes was established. The study revealed that when the jet velocity reaches 1000 m/s and the nozzle diameter reaches 1 mm, a contracted neck forms at the upper part of the scour hole. The appearance of the contracted neck is due to excessive jet impact energy causing impact shear failure in the soil. The effective height and width of the contracted neck increase with jet pressure and nozzle diameter and decrease with impingement height. Based on Prandtl's bearing capacity model, a model for predicting impact shear failure in cohesive soils was established, and a predictive formula for the effective height and diameter of the neck was proposed. Experimental validation confirmed the accuracy of the predictive formula. These findings provide theoretical support for the application of water jet trenching techniques in cohesive seabed soils.