Performance of Spectral Photon-Counting Coronary CT Angiography and Comparison with Energy-Integrating-Detector CT: Objective Assessment with Model Observer

Aims: To evaluate spectral photon-counting CT’s (SPCCT) objective image quality characteristics in vitro, compared with standard-of-care energy-integrating-detector (EID) CT. Methods: We scanned a thorax phantom with a coronary artery module at 10 mGy on a prototype SPCCT and a clinical dual-layer EID-CT under various conditions of simulated patient size (small, medium, and large). We used filtered back-projection with a soft-tissue kernel. We assessed noise and contrast-dependent spatial resolution with noise power spectra (NPS) and target transfer functions (TTF), respectively. Detectability indices (d’) of simulated non-calcified and lipid-rich atherosclerotic plaques were computed using the non-pre-whitening with eye filter model observer. Results: SPCCT provided lower noise magnitude (9–38% lower NPS amplitude) and higher noise frequency peaks (sharper noise texture). Furthermore, SPCCT provided consistently higher spatial resolution (30–33% better TTF10). In the detectability analysis, SPCCT outperformed EID-CT in all investigated conditions, providing superior d’. SPCCT reached almost perfect detectability (AUC ≈ 95%) for simulated 0.5-mm-thick non-calcified plaques (for large-sized patients), whereas EID-CT had lower d’ (AUC ≈ 75%). For lipid-rich atherosclerotic plaques, SPCCT achieved 85% AUC vs. 77.5% with EID-CT. Conclusions: SPCCT outperformed EID-CT in detecting simulated coronary atherosclerosis and might enhance diagnostic accuracy by providing lower noise magnitude, markedly improved spatial resolution, and superior lipid core detectability.

Electrical Transport and Fluctuation Processes in NbRe and NbReN Ultrathin Films for Superconducting Electronics Applications

NbRe-based superconducting thin films recently received relevant interest in the field of low-temperature electronics. However, for these materials the electrical conduction mechanisms, in particular in the normal state, still need to be investigated in more detail. Here, NbRe and NbReN films of different thicknesses have been deposited on two different substrates, namely monocrystalline Si and SiO2 buffered Si. The films were characterized by DC electrical transport measurements. Moreover, a connection with the charge carriers fluctuation processes has been made by analyzing the electrical noise generated in the normal state region. Despite the films morphology seems not to be affected by the substrate used, a lower noise level has been found for the ones grown on SiO2, in particular for NbReN. From this study it emerges that both NbRe and NbReN ultrathin films are of very good quality, as far as the low-temperature electrical noise and conduction are concerned, with noise levels competitive with NbN. These results may further support the proposal of using these materials in a nanowire form in the field of superconducting electronics.

Sleep Disturbance and Noise Annoyance and Environmental Noise Exposure in Residents of Two Major Slovakian Cities

The significant growth in traffic density in Slovakia, combined with the country’s economic change, has resulted in new environmental noise issues, particularly in road traffic noise. The objective of this study was to assess and evaluate the impact of environmental noise on the psychosocial well-being of young healthy individuals in the two main Slovak cities of Bratislava and Kosice. To assess noise annoyance, interference with activities, and sleep disturbance, the ICBEN (The International Commission on the Biological Effects of Noise) anonymous validated “Noise annoyance questionnaire” was applied; noise levels were objectified by direct measurements using a sound level analyzer with a frequency analysis module. Young individuals between the ages of 20 and 30 were interviewed in Bratislava (533 respondents, 155 males) and Kosice (355 respondents, 111 males). The majority of the respondents in both cities were exposed to medium levels of road traffic noise LAeq ≥ 60 dB. In Bratislava, 27.82 % of respondents resided in the higher noise exposure category LAeq ≥ 70 dB, while in Kosice, 39.9 % resided in the lower noise exposure category LAeq < 50 dB. Road traffic noise annoys respondents in the higher noise exposure category in Bratislava 63.51 %, and even in the lower noise exposure category in Kosice, it interferes with reading and mental work, sleep and falling asleep 46.51 %. The study has identified traffic noise as an environmental issue in large cities, emphasizing the need for vulnerable individuals to be protected, particularly at night.

Sound mapping and acoustic simulations in the implementation of the northern stretch of the Green Line in Curitiba, Paraná, Brazil

The present study aims to study environmental noise pollution in areas close to the northern stretch of the Green Line, in Curitiba, PR, Brazil, which has a length of approximately 8 km. For this purpose, in situ measurements of sound levels were carried out and noise pollution was evaluated through the calculation of noise maps in addition to acoustic simulations. Measurements were recorded at 16 points following the guidelines of the NBR 10151. Acoustic maps were made for each point using proper acoustic software. The aim was to verify whether measured values were within a margin error of up to 4.6 dB(A) compared to simulated values. After validating the maps and verifying the noise pollution at the selected points, one of the points, which is close to a hospital, was analyzed alone to evaluate different simulation scenarios. The selected scenarios were replacement of common asphalt for one with porous properties; 90% restriction on the quantity of heavy vehicles; reduction of average speed of vehicles from 80 km/h to 60 km/h; 50% restriction on the number of vehicles of all categories; and acoustic situation of the site, including all the measurements proposed in the previous scenarios. All scenarios presented in this work reveal that the measurements adopted were not sufficient to reach 55 dB(A) near sensitive areas such as hospitals. They also show that just one control measure is not enough to lower noise efficiently. A plan with several joint measures is needed to alleviate the problem.

Improved eddy current testing sensitivity using phase information

This paper describes a two-coil eddy current sensor being used in a transmit-receive arrangement at 1 MHz, where the drive and amplification electronics are miniaturised and built directly behind the coil to reduce noise and the effects from cable length. Small, simulated defects are detected, less than 500 microns in length, on titanium and titanium aluminide, which is an increasingly important alloy for aerospace applications. Data is analysed quantitatively in a parametric approach. This experiment uses a transmitting coil driven by a constant current source and a separate receiving coil, where the magnitude and phase of the induced voltage signals on both coils are measured independently. Experimental measurements are validated using finite element modelling and the phase of the signal on the receiving coil in particular is less susceptible to variations caused by changes in lift-off. A combination of experimental and simulation data of 2D surface scans and lift-off measurements show the variation in the magnitude and phase of the eddy current signal with lift-off on Ti, TiAl (Ti-45Al-2Mn-2Nb-1B) and 316L stainless steel. It is also shown that the high-frequency lower noise approach can reliably detect defects of less than 500 microns in length in both Ti and TiAl.

Frequency multiplexed coherent φ-OTDR

We present a comprehensive analysis of a frequency multiplexed phase-measuring φ-OTDR sensor platform. The system uses a train of frequency-shifted pulses to increase the average power injected into the fiber and provide a diversity of uncorrelated Rayleigh backscattering measurements. Through a combination of simulations, numerical analysis, and experimental measurements, we show that this approach not only enables lower noise and mitigates interference fading, but also improves the sensor linearity. We investigate the sensor dependence on the length of the pulse train and characterize the sensor performance as a function of range, demonstrating operation from 1 to 50 km. Despite its relative simplicity, this platform enables state-of-the-art performance, including low crosstalk, high linearity, and a minimum detectable strain of only 0.6 p$$\varepsilon /\sqrt{\text{Hz}}$$ ε / Hz in a 10 km fiber with 10 m spatial resolution and a bandwidth of 5 kHz.

CFD Analysis of Journal Bearing with a Heterogeneous Rough/Smooth Surface

In the present study, a computational investigation into acoustic and tribological performances in journal bearings is presented. A heterogeneous pattern, in which a rough surface is engineered in certain regions and is absent in others, is employed to the bearing surface. The roughness is assumed to follow the sand-grain roughness model, while the bearing noise is solved based on broadband noise source theory. Three types of heterogeneous rough/smooth journal bearings exhibiting different placement and number of the rough zone are evaluated at different combinations of eccentricity ratio using the CFD method. Numerical results show that the heterogeneous rough/smooth bearings can supply lower noise and larger load-carrying capacity in comparison with conventional bearings. Moreover, the effect on the friction force is also discussed.

Indoor and outdoor noise changes due to the COVID-19 lockdown and their effects on individuals’ expectations and preferences

The COVID-19 pandemic significantly modified our urban territories. One of the most strongly affected parameters was outdoor noise, caused by traffic and human activity in general, all of which were forced to stop during the spring of 2020. This caused an indubitable noise reduction both inside and outside the home. This study investigates how people reacted to this new unexpected, unwanted and unpredictable situation. Using field measurements, it was possible to demonstrate how the outdoor sound pressure level clearly decreased. Furthermore, by means of an international survey, it was discovered that people had positive reaction to the lower noise level. This preference was generally not related to home typology or location in the city, but rather to a generalized wish to live in a quieter urban environment.

Inter-Observer Agreement and Image Quality of Model-Based Algorithm Applied to the Coronary Artery Disease Reporting and Data System Score

Purpose: To evaluate the inter-observer agreement of the CAD-RADS reporting system and compare image quality between model-based iterative reconstruction algorithm (MBIR) and standard iterative reconstruction algorithm (IR) of low dose cardiac computed tomography angiography (CCTA). Methods: One-hundred-sixty patients undergone a 256-slice MDCT scanner using low-dose CCTA combined with prospective ECG-gated techniques were prospectively enrolled. CCTA protocols were reconstructed with both MBIR and IR. Each study was evaluated by two readers using the CAD-RADS lexicon. Vessels enhancement, image noise, SNR, and CNR were computed in the axial native images and inter-observer agreement was assessed. Radiation dose exposure as dose–length product (DLP) and effective dose (ED) were finally reported. Results: The overall agreement was very good (k = 0.90). Moreover, a significantly higher value of subjective qualitative analysis, SNR, and CNR in MBIR images compared to IR were found, due to a lower noise level (p<0.05). The mean DLP measured was 63.9 mGy*cm and the mean effective dose was 0.9 mSv.Conclusion: Inter-observer agreement of CAD-RADS was excellent confirming the importance, the feasibility, and the reproducibility of the CAD-RADS scoring system for CCTA. Moreover, lower noise and higher image quality with MBIR compared to IR were found.

Noise assessment of taxibotted versus conventional taxiing operations using a phased microphone array

In sustainable aviation the focus is mostly applied to the greenhouse gas emissions during flight. However airports have an increasing interest in reducing emissions during ground operations such as taxiing for example to improve the local air quality. Amsterdam Airport Schiphol started a pilot for sustainable taxiing with a pilot-controlled hybrid-electric aircraft towing vehicle called TaxiBot in 2020. The COVID-19 pandemic created an opportunity for extensive operational testing on a near-empty airport. Due to the low background noise levels in this situation, also a noise assessment of taxiing with the TaxiBot versus conventional two-engine taxiing was performed. This assessment can be used to evaluate the noise levels to which ground workers or neighbouring communities are exposed due to TaxiBot operations. For the noise measurements a phased microphone array was used, which allowed not only for a noise level and directionality assessment, but also for noise source identification. This paper compares the noise emissions and noise sources between a taxibotted and conventional taxiing operation. The results show that a taxibotted taxiing operation produces significantly lower noise levels. Additionally, acoustic imaging shows that the TaxiBot engine is the main noise source for a taxibotted pass-by manoeuvre.