Cavity Dimensions Research Articles

Sex-related effect of exercise on RV-PC coupling in asymptomatic patients with significant primary mitral regurgitation

Abstract Background Right ventricular–pulmonary circulation (RV-PC coupling) serves as an index to evaluate RV function in relation to underlying RV afterload. Although impaired RV-PC coupling has been proposed as a predictor of adverse outcomes in heart failure (HF) patients with secondary mitral regurgitation (MR), there is limited data available for patients with primary MR and moreover, if there is a sex-related trend. Purpose This study aimed to assess RV-PC coupling at rest and during exercise with bicycle stress echocardiography in patients with asymptomatic moderate to severe primary MR and compare these alterations between men and women. Methods All patients and controls underwent stress echocardiography with a supine bicycle. RV systolic function was evaluated with TAPSE and S’. The non-invasively measured RV-PC coupling was evaluated by indexing TAPSE to right ventricular systolic pressure (RVSP) during baseline echocardiogram and peak workload stages of bicycle SE. Results Among the 48 patients, 28 (58%) were women and 20 (42%) were men (mean age 54.07+14.16 and 52.7±16.81 years, p. NS, respectively). 39 patients had moderate MR (81.3%), 5 patients had moderate-to-severe MR(10.4%), and 4 patients had severe MR(8.3%). The duration of stress echocardiogram was significantly longer in the male MR group (9.32+1.62 min vs 7.22+2.50 min, respectively; p .001). Left Ventricular Ejection Fraction (LVEF) was within normal limits in both groups {67.59+13.71 % vs 72.93+10.21 %(p=NS)} and the dimensions of left ventricular cavity (end-diastolic and end-systolic diameters) were significantly larger in the male group compared to female group (51.5+5.10 mm vs 47.64+4.73mm (p .011) and 34.00+4.06mm vs 30.25+3.74mm (p .002) respectively}. TAPSE and RVSP increased from baseline to peak dose for both men [Rest: 22.95±2.93mm and 14.13±1.99cm/sec (p. NS) respectively, Peak exercise: 29.55 ±3.41mm and 20.84±2.00cm/sec (p. NS) respectively] and women [Rest: 23.86±3.13 and 14.54±1.88cm/sec (p.NS), Peak: 30.21±3.56mm and 20.07±2.60cm/sec (p. NS) respectively]. Moreover, a steady decrease was observed in TAPSE/RVSP from baseline to peak workload both in men (0.81±0,13mm/mmHg to 0.75±0.21mm/mmHg) and women (0.86±0.16mm/mmHg to 0.69±0.16mm/mmHg, respectively). Interestingly, a significant change was observed between men and women in TAPSE/RVSP (-0.05±0.17 and -0.16±0.17, p .029 respectively). Conclusions RV-PC coupling decreases during exercise in asymptomatic men and women with moderate to severe MR. Therefore, future studies should aim to evaluate the incremental role of this novel index not only in the assessment and evaluation of men and women with MR but also as a potential prognostic marker between them. TAPSE/RVSP change Graph

Analysis on plasma and electric field property of TM<sub>011</sub> mode MPT and its tuning experiment

Microwave plasma thruster (MPT) is a kind of electrothermal thruster. Inside its cylindrical cavity, the plasma process, microwave electric field distribution, and TM<sub>011</sub> mode resonant state are important factors affecting the performance of MPT seriously. According to previous MPT formed through continuous regulation in the resonant sate of cylindrical cavity, the research is needed on a newly fixed and simple MPT, which will simplify the resonant state regulation and lays an important foundation for further study. Therefore the plasma process is analyzed to find the optimal gas discharge condition, and the microwave electric field intensity and power density distribution inside the cavity running in TM<sub>011</sub> resonant sate are calculated to analyse how the parameters are influenced by the cavity dimensions. The resonant state is finely regulated to study how it is influenced by the dimensions of cylindrical cavity and microwave coupling probe with ball and half ball structure. The results of theoretical analysis and calculation show that the discharge power of helium gas is the lowest under the condition of 489 Pa and when the ratio of length to diameter is greater than 1, the microwave electric density distribution inside the cavity is beneficial. Owing to the appropriate length and radius of microwave coupling ball probe, the experiment on resonant state regulation shows that the shortest cylinder cavity is in the optimal resonant sate, with a resonance frequency very close to 2.45 GHz. The helium discharge experiment proves that the cavity and matching ball probe enable high microwave utilization and easy helium gas discharge, and the structure scheme is correct and reliable.

Evaluation of Volume to Area Ratio to Aluminum Alloy Microstructure

The volume to area ratio of the cavity dimension in aluminum alloy is the foundation of this study. Afterwards, the metal casting product's hardness and grain size at various points were compared. A hardness test and optical microstructure observation were part of the experiment. The findings indicate a correlation between the microstructure and the volume to area ratio. The harder and stronger the material, the smaller the grain size and the higher the ratio.

The fracture resistance of restored mandibular molars using different cavity designs: An in vitro comparative evaluation

Background: The stress distribution of a restored tooth is different from that of an intact sound tooth. The fracture resistance of a restored tooth depends on cavity design, remaining tooth structure, and material used. Aim: This in vitro study evaluated and compared the fracture resistance of mandibular molars restored using composite resin. Materials and Methods: Forty freshly extracted, intact mandibular molars were used, with their roots embedded in acrylic resin for stability. Cavities were prepared using a No. 2 round bur and straight fissure diamond, then divided into four groups with specific variations in cavity dimensions. Samples were tested using a universal testing machine, applying vertical load along the long axis at the central fossa to record fracture load. Statistical Analysis: One-way analysis of variance and Tukey’s post hoc analysis were used for statistical analysis. Results: Fracture resistance of the groups, listed in descending order, was: Lingual wall 1.5 mm (2417 ± 160 N) > Buccal wall 1.5 mm (2122 ± 75.9 N) > Lingual wall 1 mm (1966 ± 75.7 N) > Buccal wall 1 mm (1335 ± 216 N). Conclusion: The lingual wall 1.5 mm exhibited the highest fracture resistance, while the buccal wall with 1 mm thickness showed the least resistance.

Hyenas: X-ray bubbles and cavities in the intragroup medium

ABSTRACT We investigate the role of the simba feedback model on the structure of the intragroup medium (IGrM) in the new hyenas suite of cutting-edge cosmological zoom-in simulations. Using 34 high-resolution zooms of haloes spanning from $10^{13}-10^{14}$${\rm M_\odot}$ at $z=0.286$, we follow haloes for 700 Myr, over several major active galactic nuclei (AGNs) jet feedback events. We use the moxha package to generate mock Chandra X-ray observations, as well as predictive mocks for the upcoming LEM mission, identifying many feedback-generated features such as cavities, shock-fronts, and hot-spots, closely mimicking real observations. Our sample comprises 105 snapshots with identified cavities, 50 with single bubbles, and 55 with two, and spans three orders of magnitude in observed cavity enthalpies, from $10^{41}-10^{44}$ erg s−1. Comparing semimajor axis length, midpoint radius, and eccentricity to a matched sample of observations, we find good agreement in cavity dimensions with real catalogues. We estimate cavity power from our mock maps following observational procedures, showing that this is typically more than enough to offset halo cooling, particularly in low-mass haloes, where we match the observed excess in energy relative to cooling. Bubble enthalpy as measured with the usual midpoint pressure typically exceeds the energy released by the most recent jet event, hinting that the mechanical work is done predominantly at a lower pressure against the IGrM. We demonstrate for the first time that X-ray cavities are observable in a modern large-scale simulation suite and discuss the use of realistic cavity mock observations as new halo-scale constraints on feedback models in cosmological simulations.

Inhomogeneity detection within a head-sized phantom using tracking of charged nuclear fragments in ion beam therapy

Objective.The highly conformal carbon-ion radiotherapy is associated with an increased sensitivity of the dose distributions to internal changes in the patient during the treatment course. Hence, monitoring methodologies capable of detecting such changes are of vital importance. We established experimental setup conditions to address the sensitivity of a monitoring approach based on secondary-fragment tracking for detecting clinically motivated air cavity dimensions in a homogeneous head-sized PMMA phantom in 40 mm depth.Approach.The air cavities were positioned within the entrance channel of a treatment field of 50 mm diameter at three lateral positions. The measured secondary-fragment emission profiles were compared to a reference measurement without cavities. The experiments were conducted at the Heidelberg Ion-Beam Therapy Center in Germany at typical doses and dose rates.Main results.Significances above a detectability threshold of 2σfor the larger cavities (20 mm diameter and 4 mm thickness, and 20 mm diameter and 2 mm thickness) across the entire treatment field. The smallest cavity of 10 mm diameter and 2 mm thickness, which is on the lower limit of clinical interest, could not be detected at any position. We also demonstrated that it is feasible to reconstruct the lateral position of the cavity on average within 2.8 mm, once the cavity is detected. This is sufficient for the clinicians to estimate medical effects of such a cavity and to decide about the need for a control imaging CT.Significance.This investigation defines well-controlled reference conditions for the evaluation of the performance of any kind of treatment monitoring method and its capability to detect internal changes within head-sized objects. Four air cavities with volumes between 0.31 cm3and 1.26 cm3were narrowed down around the detectability threshold of this secondary-fragment-based monitoring method.

Resonant cavity structural design of carbon-based intrinsic metamaterial absorbers for broadening the effective absorption bandwidth

The effective absorption bandwidth (EAB) of absorptive materials has always been a bottleneck limiting their applications. Particularly, the combination of macroscopic structural design and the loss functions at the microscopic level of materials provides an efficient solution to this issue. Herein, a novel approach was proposed, integrating macroscopic structural design with microscopic loss functions to broaden the effective absorption bandwidth (EAB) through designing an intrinsic metamaterial absorber composed of a uniform blend of carbon-based absorbing materials and polydimethylsiloxane. A key innovation lies in the dual cubic resonant cavity design, where the multiple dimensions of the resonant cavities enable the absorber to achieve effective impedance matching across a wide frequency range. Additionally, the generation of a bottom ring current induces a magnetic field, which enhances the metamaterial absorber’s capability for further attenuation of electromagnetic wave energy. These innovative designs enable traditional carbon-based absorbing materials to achieve exceptional absorption performance, with the EAB being 2.37 times that of the skin structure, addressing the narrow EAB issue of traditional carbon-based absorptive materials. Experimental results demonstrate that the prepared samples achieve an absorption rate of 90 % for electromagnetic waves in the frequency range of 5.74–18 GHz under normal incidence, consistent with the simulation results. This absorber boasts advantages of broadband, with an equivalent thickness of only 2.94 mm. Its structure is easy to manufacture, demonstrating certain potential applications, and providing valuable insights for the work of other researchers.

The effect of exercise on RV-PC coupling in asymptomatic patients with significant primary mitral regurgitation

Abstract Background Right ventricular–pulmonary circulation (RV-PC coupling) serves as an index to evaluate RV function in relation to underlying RV afterload. Although impaired RV-PC coupling has been proposed as a predictor of adverse outcomes in heart failure (HF) patients with secondary mitral regurgitation (MR), there is limited data available for patients with primary MR. Purpose The objective of this study was to assess and compare alterations in RV-PC coupling during exercise with bicycle stress echocardiography in individuals with asymptomatic moderate to severe primary MR (MR group) and normal subjects (Control group). Μethods All patients and controls underwent stress echocardiography with a supine bicycle. RV systolic function was evaluated with TAPSE and S’. The non-invasively measured RV-PC coupling was evaluated by indexing TAPSE and S’ to right ventricular systolic pressure (RVSP) during baseline echocardiogram and peak workload stages of bicycle SE. Results Among the 48 patients in the MR group (mean age 53.5±15.16 years, 58.3% female), 39 patients had moderate MR(81.3%), 5 patients had moderate-to-severe MR(10.4%), and 4 patients had severe MR(8.3%). The duration of stress echocardiogram was significantly shorter in the MR group compared to control group (8.11±2.39 min vs 10.5±1.05 min, respectively; p<.001). Left Ventricular Ejection Fraction (LVEF) was within normal limits in both groups {70.7±11.9 % vs 72.6±12.1 %(p=NS} and the dimensions of left ventricular cavity (end-diastolic and end-systolic diameters) were significantly larger in the MR group compared to control group (49.25±5.21 mm vs 45.6±4.08mm (p .016) and 31.81±4.27mm vs 29.07±4.21mm (p .033) respectively}. TAPSE and RVSP increased from baseline to peak dose [23.48 ±3.05mm vs 29.94±3.48mm (p < .001), 8.54±4.56mmHg vs 43.79±5.27mmHg (p < .001), respectively]. There were no significant differences in TAPSE/RVSP and S’/RVSP between the two groups at rest. However, a significantly steady decrease was observed from baseline to peak dose (0.84±0.16 mm/mmHg vs 0.72±0.19mm/mmHg (p <.001) and 0.52±0.11 cm/sec/mmHg vs 0.50±0.15 cm/sec/mmHg (p .004), respectively). Conversely, these parameters did not exhibit a significant decrease in the control group. Finally, there was no significant correlation observed between the changes in the index TAPSE/RVSP , ratio E/E’ and systolic blood pressure. Conclusions RV-PC coupling decreases during exercise in asymptomatic patients with moderate to severe MR, independently of left ventricular dynamic changes. In contrast , there is no significant change in RV-PC coupling observed in the control group. Therefore, future studies should aim to evaluate the incremental role of this novel index not only in the assessment and evaluation of patients with MR but also as a potential prognostic marker.TAPSE/RVSP GraphTable of echocardiographic measurements

Dynamic Interplay of Loop Motions Governs the Molecular Level Regulatory Dynamics in Spleen Tyrosine Kinase: Insights from Molecular Dynamics Simulations.

The spleen tyrosine kinase (Syk) is a key regulator in immune cell signaling and is linked to various mechanisms in cancer and neurodegenerative diseases. Although most computational research on Syk focuses on novel drug design, the molecular-level regulatory dynamics remain unexplored. In this study, we utilized 5 × 1 μs all-atom molecular dynamics simulations of the Syk kinase domain, examining it in combinations of activation segment phosphorylated/unphosphorylated (at Tyr525, Tyr526) and the "DFG"-Asp protonated/deprotonated (at Asp512) states to investigate conformational variations and regulatory dynamics of various loops and motifs within the kinase domain. Our findings revealed that the formation and disruption of several electrostatic interactions among residues within and near the activation segment likely influenced its dynamics. The protein structure network analysis indicated that the N-terminal and C-terminal anchors were stabilized by connections with the nearby stable helical regions. The P-loop showed conformational variation characterized by movements toward and away from the conserved "HRD"-motif. Additionally, there was a significant correlation between the movement of the β3-αC loop and the P-loop, which controls the dimensions of the adenine-binding cavity of the C-spine region. Overall, understanding these significant motions of the Syk kinase domain enhances our knowledge of its functional regulatory mechanism and can guide future research.

Conformational Modulation of Efficient Macrocyclic Emitters Featuring Delayed Fluorescence by Conjugation Length and Cavity Dimensions.

The π-conjugated macrocyclic emitters with thermally activated delayed fluorescence (TADF) characteristics have attracted widespread attention in the field of organic electroluminescence (EL) materials due to their unique geometries and excellent luminescence performance. Despite the significant impact of conjugation length and cavity dimensions on molecular conformation, the influence of these factors on the excited-state properties remains understudied. Herein, we formulated a strategy aimed at modulating the conformation of TADF macrocyclic molecules containing aniline as the donor (D) unit, and triazine as the acceptor (A), linked in D-A and D-π-A alternative macrocyclic construction (MC-TNT and MC-TST). Corroborated by experimental and theoretical analyses, the compact and conformationally twisted MC-TNT exhibits efficient blue luminescence in crystalline state, facilitating EL at high doping concentrations with maximum external quantum efficiency (EQEmax) of 13.9%, leading the field of blue macrocyclic emitters. Notably, MC-TST with π-bridge and flat conformation, demonstrates diminished Coulombic repulsion, achieving nearly 100% photoluminescence quantum yield and superior horizontal dipole orientation of 85% in 5 wt% doped films, and the corresponding device's EQEmax reaches record-high 32.7% within the TADF macrocyclic domain.

Conformational Modulation of Efficient Macrocyclic Emitters Featuring Delayed Fluorescence by Conjugation Length and Cavity Dimensions

The π‐conjugated macrocyclic emitters with thermally activated delayed fluorescence (TADF) characteristics have attracted widespread attention in the field of organic electroluminescence (EL) materials due to their unique geometries and excellent luminescence performance. Despite the significant impact of conjugation length and cavity dimensions on molecular conformation, the influence of these factors on the excited‐state properties remains understudied. Herein, we formulated a strategy aimed at modulating the conformation of TADF macrocyclic molecules containing aniline as the donor (D) unit, and triazine as the acceptor (A), linked in D‐A and D‐π‐A alternative macrocyclic construction (MC‐TNT and MC‐TST). Corroborated by experimental and theoretical analyses, the compact and conformationally twisted MC‐TNT exhibits efficient blue luminescence in crystalline state, facilitating EL at high doping concentrations with maximum external quantum efficiency (EQEmax) of 13.9%, leading the field of blue macrocyclic emitters. Notably, MC‐TST with π‐bridge and flat conformation, demonstrates diminished Coulombic repulsion, achieving nearly 100% photoluminescence quantum yield and superior horizontal dipole orientation of 85% in 5 wt% doped films, and the corresponding device's EQEmax reaches record‐high 32.7% within the TADF macrocyclic domain.

Unveiling Structural Variations in Armchair-Edge Coronoids by Spectroscopies.

This study explores the electronic and vibrational properties of armchair coronoids (ACs), a unique class of polycyclic aromatic hydrocarbons with varying molecular and cavity sizes. Through density functional theory simulations, we investigated the X-ray photoelectron spectroscopy (XPS) and Raman spectra of C222, C114, C42, and their derivatives with different cavity sizes. The results reveal that band gaps and electronic properties of ACs can be precisely tuned by adjusting the molecular and cavity dimensions. XPS spectra demonstrated shifts in binding energy correlating with bandgap variations, while Raman spectra exhibited distinct C-C stretching and breathing modes. Notably, the introduction of cavities led to shifts in the breathing mode band, providing insights into the structural identification of ACs through Raman spectroscopy. The findings suggest that combining XPS and Raman spectroscopy can effectively characterize ACs, offering a comprehensive understanding of their structure-property relationships. This research lays the groundwork for future experimental and theoretical studies on the potential applications of ACs in electronic materials.

Sub-THz and THz Cherenkov radiation source with two-dimensional periodic surface lattice and multistage depressed collector

We present the theory, concept and design of an efficient, megawatt coherent Cherenkov radiation source based on a two-dimensional periodic surface lattice (2D-PSL) cavity combined with a novel energy recovery system for the generation of highly efficient (> 50%) single-frequency radiation. We demonstrate the scalability of the transverse dimension of the 2D-PSL cavity of the Cherenkov source and thus the potential for efficient, continuous-wave, high-power (> 1 MW) operation; fundamental to the eventual realization of clean, fusion energy. These new sources, with the capacity to operate in the 0.1-10THz range, hold strong promise to address the long-standing “Terahertz gap”. By combining a Cherenkov oscillator driven by a non-gyrating beam with an innovative four-stage depressed collector energy recovery system, the overall device efficiency can be increased to be competitive with gyrotrons in the requirements for heating and current drive in fusion plasma. In these Cherenkov devices, the frequency independence of the magnetic guide field enables advantageous frequency scaling without deployment constraints, making them especially attractive for high-impact applications in fusion science, turbulence diagnostics, non-destructive testing and biochemical spectroscopy. The novel energy recovery techniques presented in this paper have broad applicability to many electron-beam driven devices, bringing revolutionary potential to future THz source technologies.

Prediction of interface morphology formed by the oblique gas jet impinging on a liquid surface

This study presents a theoretical analysis of the oblique gas jet impingement process on a liquid surface, elucidating the evolution of the flow field distribution and the influence of jet parameters on cavity shape dynamics. By integrating surface tension effects, the existing Blanks and Chandrasekhara model was refined to develop an advanced predictive model for cavity morphology. The theoretical framework was substantiated through numerical simulations and corroborated with experimental measurements of cavity dimensions, captured using state-of-the-art machine vision technology. The findings reveal a consistent trend in cavity dimension variations: an increase in the cavity surface width with the elevation of the impinging angle from the vertical and an escalation in gas jet velocity. Conversely, a reduction in the impinging angle coupled with an increase in jet velocity leads to a deeper cavity. To enhance the predictive accuracy, the model underwent iterative optimization, incorporating experimental data and accounting for jet parameters. The refined model demonstrated achieved a maximum error of 0.135 mm and a minimum error of 0.03 mm, providing reliable forecasts of cavity depth, which is pivotal for applications in fluid dynamics and related engineering fields.

Analysing fluid flow and heat transfer comparatively in flow passage systems: Evaluating thermal impacts and geometric configurations

This research thoroughly examines heat transfer and fluid flow in a passage flow system, highlighting the difficulties posed by different geometric arrangements and temperature conditions that may affect the system's performance. The main aim is to evaluate the impacts of different geometric characteristics on the velocity, pressure, and temperature profiles inside the flow route. These factors encompass cavity dimensions, tube diameter, and input conditions. An inclusive comparison of three different geometric designs at controlled temperatures is conducted using computational fluid dynamics (CFD) simulations. The findings indicate that the optimal geometric parameters improve thermal performance, with certain arrangements displaying improvements in heat transfer rates up to 30 %. In this regard, the higher cavity dimensions and suitable input velocities are exposed as advantages. The first sample exhibited a higher velocity of 0.024 m s-1 due to its simpler geometry and favorable heating conditions, while the third sample demonstrated a higher temperature of 465 K due to its complex cavity shape and multiple heating sources. This study suggests that enhancing efficiency in heat management applications necessitates a strategic design approach for passage flow systems, which must account for flow characteristics and geometric specifications. This research would provide insightful information for designers and engineers looking at enhancing fluid flow systems across a range of industrial applications.

The impact of cone beam CT on outcomes associated with endodontic access cavity preparation: a controlled human analogue study using 3D-printed first maxillary molars.

To identify if supplemental preoperative cone beam CT (CBCT) imaging could improve outcomes related to endodontic access cavity preparation, using 3D-printed maxillary first molars (M1Ms) in a rigorously simulated, controlled human analogue study. Eighteen operators with 3 experience-levels took part in 2 simulated clinical sessions, 1 with and 1 without the availability of CBCT imaging, in a randomized order and with an intervening 8-week washout period. Operators attempted the location of all 4 root canals in each of 3 custom-made M1Ms (2 non-complex and 1 complex mesiobuccal [MB] canal anatomy). The primary outcome was tooth volume removed. Secondary outcomes were linear cavity dimensions, canals located, and procedural time. Operator confidence and "helpfulness" of available imaging were recorded. Statistical analysis of data included: paired t-tests, Fisher's exact test, linear mixed-effect modelling, and Mann-Whitney U test, with an alpha level of .05 for all. When supplemental preoperative CBCT was available, there were significant reductions in volume of the access cavity and procedural times, with significantly increased MB2 canal location, but only for teeth with non-complex anatomies and for more experienced operators. Linear mixed-effect modelling identified image type and operator experience as significant predictors of tooth volume removed and procedural time. There was significantly lower confidence in canal location and perceived "helpfulness" (all Experience Groups) when conventional imaging only was used compared with when CBCT was available. Supplemental preoperative CBCT had several beneficial impacts on access cavity preparation, although this only applied to teeth with non-complex anatomy and for more experienced operators.

Performance optimization for magnetoelectric antennas based on a multi-field coupling analysis model

This paper presents a multi-field coupling model for magnetoelectric (ME) antennas, encompassing a ME film, electrode layers, and a substrate featuring a cavity structure. This model accounts for the nonlinear magnetoelastic coupling within the radiation layer and employs a combined DC and AC simulation methodology to capture the antenna's radiation mechanism. Leveraging this multi-field coupling model, performance differences between the ME antenna and an ideal ME composite film are analyzed. By exploring optimization schemes based on multi-physics fields, electrode materials, and structural design, the ME antenna's radiation performance is significantly enhanced. The findings demonstrate that the complete antenna structure, with its increased thickness and cavity design, exhibits a lower resonance frequency and a higher converse ME (CME) coefficient compared to the ideal ME film. The optimal CME effect is achieved under proper external stimuli, leading to a broader 3 dB bandwidth. Expanding the cavity dimensions enhances the CME coefficient by 42% and reduces the resonance frequency due to decreased acoustic wave loss. Adopting electrode materials with higher acoustic impedance elevates the CME coefficient, yet narrows the bandwidth. Conversely, using silver (Ag) electrodes promotes a broader bandwidth. Additionally, ME antenna arrays are designed to broaden the bandwidth by 300%.

Experimental Study on Submerged Nozzle Damping Characteristics of Solid Rocket Motor

Acoustic instabilities in solid rocket motors (SRMs) can lead to severe performance deterioration and structural damage. Nozzle damping accounts for the main acoustic dissipation source, and it is highly dependent on geometric parameters and operating conditions. This study experimentally investigated the acoustic damping characteristics of submerged nozzles in SRMs, focusing on the effects of submerged cavity dimensions, nozzle convergent angle, throat-to-port area ratio, and mean pressure variations on the longitudinal instability. The steady-state wave decay method was used to quantify the acoustic damping, and a designed rotary valve system was employed to introduce periodic pressure oscillations in the high-pressure combustion chamber. The results revealed that a larger submerged cavity would reduce the nozzle damping efficiency, with the elimination of the submerged cavity enhancing the nozzle decay coefficient magnitude by 41.9%. Furthermore, increasing the nozzle convergent angle was found to amplify acoustic wave reflection, thereby diminishing damping performance. A linear inverse relationship was observed between the throat-to-port area ratio and the decay coefficient, with a 125% increase in the ratio resulting in a 24.3% reduction in the decay coefficient. Interestingly, despite the formation of complex vortices in the submerged cavity, the mean pressure variation presented negligible effects on acoustic damping characteristics, and its damping performance is similar to a simple nozzle without a cavity. These findings provide valuable experimental data for predicting the stability of a solid rocket motor with a submerged nozzle and offer insights into the optimization of submerged nozzle designs for higher acoustic damping in SRMs.

Sb2Te3–Bi2Te3 Direct Photo–Thermoelectric Mid‐Infrared Detection

AbstractA compact and responsive thermoelectric photodetector is introduced for the mid‐infrared. By resonantly coupling mid‐infrared light to a Sb2Te3‐Bi2Te3 thermoelectric junction, a thermocouple is formed that is directly heated by narrow‐band mid‐infrared radiation. Near‐perfect absorption is achieved at this hot junction through the resonantly enhanced coupling of light to free‐electrons in the Bi2Te3 and Sb2Te3 materials. The fabricated devices operate at 3.6 µm and demonstrate a responsivity of 10.2 V W−1, a specific detectivity of 4.6 × 106 cm Hz1/2 W−1, and a bandwidth in the order of 1 kHz. The optimal detection wavelength can be spectrally tuned by changing the resonant cavity dimensions. This work shows a path toward miniaturized mid‐infrared detectors and spectrometers with high sensitivity, responsivity, and bandwidth. Importantly, the device presented here is ideal for industrial production, which it is hoped will provide wider access to mid‐infrared technologies for chemical sensing, medicine, and security.

Utilization of carbon dioxide during borehole underground coal gasification

Purpose. To develop an innovative approach for carbon dioxide utilization during the borehole underground gasification of coal at the SE “Lvivvuhillia”. Methods. The determination of stratification cavity parameters in the rock mass during underground coal gasification was based on analytical studies. These studies employed the method of stress-strain state calculation of rock layers implemented in the “GeoDynamics Lite” software. This method involves obtaining geometric and physical distribution parameters for characteristic rock layers from the coal seam to the surface. Input data for the research included data on the geological and mining conditions of coal seams and the technological parameters of the mining operations. Findings. Analysis of the rock layers’ geometric and physical load parameters confirmed the expansion of abnormal pressure zones in the rock mass. It was established that these parameters change from the coal seam to the surface, both toward the rock mass and in the direction of the gasified cavity as the combustion face advances. These dynamic changes in the roof structure promote the formation of stratification cavities, which can be used as localized sites for efficient carbon dioxide sequestration. Originality. The dependencies of changes in the dimensions of stratification cavities in the rocks of roof above an underground gasifier on the rate of combustible face advance have been established. Taking this dependency into account allows for predicting the degree of carbon dioxide utilization in technologically created cavities. Practical implications. For the Chervonohrad mine, the parameters of stratification cavities within the rock mass at seams n7n, n7 and n7v levels during the gasification of seam n7n were determined. These findings allow for the assessment of carbon dioxide utilization volumes in the future.