Cavity Dimensions Research Articles

Assessment of cardiac dimensions in children diagnosed with hypertrophic cardiomyopathy.

Hypertrophic cardiomyopathy (HCM) is an inherited autosomal dominant heart disease, characterized by increased left ventricular wall thickness and abnormal loading conditions. Imaging modalities are the first choice for diagnosis and risk stratification. Although heart dimensions have been characterized widely in HCM adults from cardiac imaging, there is limited information about children affected by HCM. The aim of this study is to evaluate left ventricular function and left heart dimensions in a small population of children diagnosed with HCM. A total of 16 (seven male, nine female) pediatric patients with an average age of 14.0±2.5 years diagnosed with HCM at Great Ormond Street Hospital for Children were included in this study. Cardiac magnetic resonance (CMR) images were used to measure left and right ventricular dimensions, and septal and left ventricular free wall thicknesses in Simpleware ScanIP. The gender groups were compared using student t-test or non-parametric Mann-Whitney U-test depending on the sample distribution. Differences in heart rate, left ventricular end-diastolic volume and end-diastolic volume index, left ventricular stroke volume and stroke volume index, left ventricular end-systolic long axis length, left ventricular end-systolic long axis length index, left ventricular end-diastolic mid-cavity diameter, left ventricular end-diastolic free wall thickness, left ventricular end-diastolic free wall thickness index, right ventricular end-diastolic long axis length were statistically significant in males and females. Left ventricular wall and intraventricular septal thickness increase affecting left ventricle cavity dimensions and there may be differences in anatomical and physiological parameters in males and females affected by HCM.

Design and manufacture of an all-polymeric integrated multimode interferometer for visible photonics.

This work demonstrates an integrated multimode interferometer (MMI) based on a fully polymeric platform and optimized for visible range operation. The dimensions of a 2×2 MMI are first calculated analytically and simulated using finite elements method. The devices are manufactured using two layers of negative tone photoresists. The top layer is patterned by e-beam lithography demonstrating the adaptability of this material, naturally designed to respond to UV radiation. Fabrication tolerance was smaller than 100 nm. Devices were optically characterized with a 635 nm input source and the best performance for a 3 dB power splitter was found at an interferometric cavity dimension of 10.5 × 190.68 µm. Other interferometric lengths were characterized to establish a process design kit that allows future use of this platform in more complex photonic integrated circuits architectures.

Determination of Dimensions of Glenoid Cavity from other Scapular Parameters

Background: Different pathological conditions are associated with the anatomical variations in glenoid cavity. For getting insights into these variations the anthropometric parameters knowledge is highly required. Objective: The purpose of the study was the determination of the anthropometric relationship present between the left and right side of the glenoid cavity of the scapula and the application of the obtained knowledge in the forensic medicine. Place and Duration: In the department of anatomy, Multan Medical and Dental College and Bacha Khan Medical Complex Swabi for six months duration, from January 2021 to June 2021. Material and Methods: The data of 190 patients included in the study, was collected from the anatomy department of our institute. The sample was withdrawn from the non-deformed and well macerated scapulae bone of the 190 patients. The calibrated sliding digital caliper was used to measure the anthropometric parameters of glenoid cavity. The glenoid height, width and index were calculated by SPSS software. Results: The 34.8±4.0 (R=38 ± 4.98 and L=27.9-46.78) and 24.9 ±3.90 (R=27.2 ± 3.43 and L=20.1- 36) was the calculated mean standard deviation of Maximum glenoid height (MGH) and Maximum glenoid width (MGW) respectively. The statistically significant and greater values of MGH and MGW on the right side were obtained by using ANOVA and t-test. While calculated values of glenoid Index (GI) was smaller on the right side as compared to the left. Conclusion: The kinanthropological applications of the scapula are indicated by the study that which side can be more commonly used. This study provides with in-depth knowledge of biological profiling and develops better understanding required during reconstruction of the damaged skeleton. Keywords: Glenoid cavity, Maximum glenoid height (MGH), Maximum glenoid width (MGW).

Synthetic dimensions in optical cavities and their analogies to two-dimensional materials

A method to produce synthetic dimensions in an optical cavity is presented. The system is obtained by coupling two one-dimensional optical cavities by means of a moving mirror. Its translation generates a new synthetic dimension resulting in a transmittance pattern that corresponds to the energy dispersion of electrons in a two-dimensional lattice: in this case a strained triangular lattice. We elucidate the analogy between these two systems by relating the distribution of transmittances of the optical cavity to the density of states of the two-dimensional lattice and the Bragg diffraction modes to the Van Hove singularities. Our mapping makes the coupled optical cavity a simulator for lattice Hamiltonians found in solid-state physics, providing an easier alternative platform to access some of their properties, as for example, the electronic conductivity, which is found here using the Boltzmann formula. Moreover, it is proved that the truly synthetic behavior appears only when the two cavities have an irrational length ratio as modes resonant on one cavity are never resonant in the other. Mathematically, wave phase differences act independently as they are given by a function that behaves as a pseudorandom number generator. This provides an elegant way to study synthetic dimensions without the need to move the central mirror, i.e., in a single, fixed geometry device. Thus, our work establishes a bridge between the fields of optical cavities, synthetic dimensions, and two-dimensional materials.

SERS using nanostar‐in‐cavity structures

AbstractParticle in cavity nanostructures were produced by sedimentation of silver nanostars (AgNSs) onto sphere segment void (SSV) cavity structures produced by electrodeposition of gold around templates formed by assembling close packed monolayer arrays of 220 or 600 nm diameter polystyrene spheres. The resulting AgNS@SSV nanostructures were characterized by scanning electron microscopy and their performance as substrates for surface enhanced Raman spectroscopy (SERS) was examined. The enhancement factors obtained for the different structures were evaluated using benzenethiol as Raman probe, which adsorbs on Ag and Au to form a monolayer with uniform coverage, so allowing the enhancement to be quantified. Higher enhancements were obtained for the AgNSs@SSV substrates as compared with the gold SSV structures. The greatest enhancements were obtained when matching cavity and nanostar dimension so that only one nanostar could be accommodated in the cavity. The AgNS@SSV substrates were then shown to be promising substrates for the highly sensitive detection of dyes and, particularly, for the lake‐pigment cochineal lake, providing useful information and novel analytical tool for application in the field of cultural heritage diagnostics and conservation.

Influence of Embedded Charging Units Characteristics on Long-Term Structural Behavior of E-Roads

The use of Electric Vehicles (EV) seems to be a promising solution to achieve a sustainable road transport system. Among the contactless dynamic vehicle charging technologies, the use of Charging Units (CUs)—cement concrete box—embedded into the road pavement seems to be a favorable option. The available scientific papers related to the structural effects of embedding CUs in road pavements consider the CU as a solid box, even if a cavity is needed for the electrical technologies’ accommodation. This is why the current research is aimed at studying electrified roads (e-road) with different CU cavity shapes and dimensions. In detail, pavement structural responses are investigated, as a first step, adopting a Finite Element Model (FEM), and, as a second step, the long-term performances (fatigue cracking/rutting proneness) are evaluated. The study is divided into two phases: the theoretical fatigue/rutting assessment, which allows to calculate the critical load repetitions leading to pavement failure, and an urban case study with the goals of both assessing the theoretical results and computing fatigue/rutting performance with real scale traffic conditions. The outcomes demonstrate that CUs can be used with no significant impacts on the long-term road pavement structural performance, laying the foundation for a future upgrading of the existing urban road networks.

Nest preference and ecology of cavity-nesting bees (Hymenoptera: Apoidea) in Punjab, Pakistan

• Artificial nest boxes, an effective tool for nesting and conservation of bees. • Colonization of bees helpful in studying ecology and nesting biology. • The efficacy of nest boxes depends on nesting materials and dimensions of cavities. • Bamboo and drilled wooden log is the most preferred nesting material. • Six bee species along with one parasitic bee did nesting in our nesting materials. Among bees, 85 % are solitary species, most of them are ground-nester and some are cavity-nesting and construct their nests in pre-existing cavities. This work was conducted to evaluate the substrate preference and nest architecture (acceptance, occupation percentage, seasonality and parasitism) of cavity-nesting bees in different substrates. Trap nests offered comprised five different materials (drilled cavities in wood, bamboo, cardboard tubes, plastic soda straws, and mud blocks). These were installed in four districts for two years. The nesting cavities of five different diameters (6, 8, 10, 12 and 14 mm) were provided in each nesting material with an average length of 180 ± 9.92 mm. In all the materials, 5400 nesting cavities were offered, out of which 628 were colonized by bees from two families (Megachilidae and Apidae) and six species ( Megachile cephalotes, M. lanata, M. bicolor, Xylocopa basalis, X. fenestrata and Ceratina smaragdula ), including one parasitic bee ( Euaspis carbonaria ). The bee species differed significantly in occupying five nesting materials. The most preferred diameters were 8 mm and 10 mm, with 52.20% and 29.45% of colonization, respectively. Nesting was done throughout the year except in winter. This study will serve as a baseline for future studies and conservation programs of cavity-nesting bees in Pakistan.

Effect of bariatric surgery on cardiac function in obese patients: An echocardiographic assessment.

Objectives:To analyze the clinical and echocardiographic changes in individuals with morbid obesity who underwent bariatric surgery.Methods:In total, 59 obese patients with body mass index >35 kg/m 2 were prospectively enrolled. We assessed baseline pre-operative and a 6-month post-operative lipid profile, hemoglobin A1c, echocardiography, lifetime, and a 10-year risks of atherosclerotic disease for all patients.Results:The mean patients’ age was 37±12 years, with 40 (67.8%) women. We found that the pre-operative total cholesterol (4.2±1.1 vs. 4.4±1.1, p=0.014) and triglyceride levels (1.4±0.7 vs. 1.8±0.8, p<0.0001) were significantly lower than post-operative levels, while post-operative high-density lipoprotein levels were significantly higher (1.5±0.5 vs. 1.2±0.3, p<0.0001). The calculated 10-year risk of atherosclerotic cardiovascular disease was significantly lower post-operatively (1.1±1.6% vs. 1.6±1.8%, p<0.0001). Echocardiography follow-up revealed that diastolic dysfunction was more prevalent pre-operatively than that post-operatively (41% vs. 10%, p<0.0001). Post-operative left ventricular (LV) mass was significantly lesser than the pre-operative mass (168±252 g vs. 187±255 g, p=0.019), whereas the post-operative LV diastolic (46.5±7 mm vs. 38.5±18 mm, p=0.002) and systolic dimensions (31±5 mm vs. 25±11 mm, p=0.001) were significantly smaller.Conclusion:Bariatric surgery resulted in a significant amelioration in lipid profile, reduction in LV mass, and LV cavity dimensions.

Electric field strengths within a micro cavity plasma array measured by Stark shift and splitting of a helium line pair

The electric field is a fundamental parameter for plasma sources and devices. Its knowledge is a dominant setscrew for many processes such as controllable fluxes and energies of charged particles onto surfaces and for the electron energy distribution function. However, experimental data of electric field strengths in micro-structured surface dielectric barrier discharges are rare. Due to geometric configurations and dimensions in micrometer scale, probe-based investigations are challenging. To tackle these issues, we exploit the optical access into micro cavities of a plasma array operated with pure helium to use the Stark effect of the allowed 492.19 nm and forbidden 492.06 nm helium line . Based on it, we present spatially-integrated and time-resolved electric field strengths in a range between 20 kV cm−1 and 60 kV cm−1 depending on various parameters such as cavity diameters in 100 μm range and excitation properties. The obtained electric fields can be controlled just by bipolarity of applied voltage and show a good agreement to previous simulated field strengths in pore and silicon-based devices. As expected from simulation dealing with discharges in pores, a smaller cavity dimension yields higher electric field strengths. Due to these high electric fields and the option of this plasma source to easily integrate a catalyst in the discharge volume, this micro cavity plasma array promises further insights into plasma-enhanced catalysis.

P320 LEFT DOMINANT ARRHYTHMOGENIC CARDIOMYOPATHY: HOW TO STRATIFY THE ARRHYTHMIC RISK? EARLY ONSET CLINICAL CASE

Abstract Introduction Arrhythmogenic cardiomyopathy (ACM) is a genetic disease characterized by the progressive replacement of myocardiocytes by fibroadipose tissue that becomes a susbstrate for ventricular arrhythmias with risk of sudden cardiac death. Arrhythmogenic cardiomyopathy can manifest itself through three different phenotypes: the classic phenotype, the most frequent, involving only the right ventricle, the biventricular variant with possible right or left dominance and the rare variant involving only the left ventricle. We present a case of left ventricular arrhythmogenic cardiomyopathy. Case Report 16–year–old male patient in complete physical well–being, with no significant medical history and a negative family history of heart disease and/or sudden cardiac death (Fig. 1). He practiced competitive sports for years with periodic medical–sports visits. In 2017, ventricular extrasystole was detected on the electrocardiogram, for which he performed cardiological investigations. On electrocardiogram: sinus rhythm with QRS fragmented into DIII and aVL and negative T waves from V4 to V6 (Fig. 2). On transthoracic echocardiography, evidence of normal cavity dimensions, ejection fraction at lower normal limits (42%) and left ventricular trabeculation, in the absence of significant valvulopathy. He then performed a cardiac MRI that showed: left ventricle moderately dilated and hypokinetic with widespread alterations of myocardial signal secondary to fibroadipose replacement phenomena, configuring a picture of left ventricular dilation and dysfunction referable to arrhythmogenic left ventricular cardiomyopathy (Fig. 3). The patient was also subjected to genetic analysis aimed at searching for mutations of genes involved in arrhythmic heart disease, which was negative. In light of the absence of conclusive scientific evidence on the implantation of a defribrillator in primary prevention in clinical–instrumental cases such as the present, the risk of infection and the risk of inappropriate discharges, it was proposed the implantation of a loop–recorder in order to monitor and record any arrhythmic events, starting beta–blocker therapy. The possibility of continuing competitive physical activity was therefore denied. Conclusions Currently, guidelines on ACM and diagnostic criteria focus mainly on the right variant, so there are no clear indications to stratify arrhythmic risk in left ventricular ACM.

A preliminary study of 4He convective heat switches

Heat switches are key components in sub-kelvin refrigeration. It is widely used in cryogenic systems, such as controlling thermodynamic cycle, coupling/decoupling redundant cryocoolers, accelerating the cooling of cryogenic components and so on. Convective heat switch features simple structure, no moving parts and great thermal conductance, which is mainly used to precool cryogenic components. In order to accelerate the pre-cooling of a test platform to 4K, the passive convective heat switch is investigated in this paper, which consists of a circuit comprising two identical stainless steel tubes and two copper cavities respectively connected to the cold and warm stages. The ON/OFF state of the switch is realized by the presence/absence of a gravity-driven convective helium-4 gas loop. Several convective heat switches with different cavity structures and charge pressures are designed and assembled. The preliminary experimental results on thermal conductance are presented. With a typical dimension of a cylindrical cavity with a diameter of 28mm and a height of 16.8mm, a stainless steel tube with a diameter of 9.6mm and a length of 72mm, thermal conductance of 40-50mW/K in ON state has been obtained.

Effect of p-Tyrosol on the Process of Left-Ventricular Remodeling in the Long Period after Myocardial Infarction.

The effect of p-tyrosol on the main hemodynamic parameters and contractile function of the heart was studied and a morphometric assessment of left-ventricular remodeling was performed in Wistar rats 2 months after acute 1-h myocardial ischemia followed by reperfusion. p-Tyrosol in a dose of 20 mg/kg was injected intraperitoneally 5 times: 20 min before the start of reperfusion, 4 h after the start of reperfusion, and then once a day over the next 3 days. Administration of p-tyrosol to animals in the acute period of myocardial infarction slowed down the formation of systolic and diastolic myocardial dysfunction, improved the pumping function of the heart, maintained the hemodynamic parameters at a significantly higher level, and reduced left-ventricular remodeling in the late period of myocardial infarction. In 2 months after acute myocardial ischemia modeling, the dimensions of the left-ventricular cavity, the area of the postinfarction focus, and the area of connective tissue in rats treated with p-tyrosol were significantly lower than in the control group. In the group treated with p-tyrosol, no anterior left-ventricular wall aneurysms were found.

Personalized Health Care Technology in Managing Postoperative Gastrointestinal Surgery Complications: Proof of Concept Study

Background: Advances in three-dimensional (3D) printing technology have allowed the development of customized medical devices. Endoscopic internal drainage (EID) is a novel method to facilitate drainage of an abscess cavity into the lumen of the gastrointestinal tract by placing a double pigtail biliary stent through the fistula opening, originally designed for biliary drainage. They are available in manufacture-determined sizes and shapes. The aim of this study is to explore the feasibility of 3D printing personalized internal drainage stents for the treatment of leaks following gastrointestinal surgery over a sequential period. Methods: We retrospectively identified patients who underwent gastrointestinal anastomotic surgery complicated by postoperative leaks and underwent serial EID for treatment. Computerized Tomography scans were reviewed over a period of time, abscess cavity dimensions and characterizations were evaluated, and 3D reconstructions were obtained. The stents were designed, their shape and size were customized to the unique dimensions of the abscess and lumen of the patient. Stereolithography (SLA) 3D printing technique was used to produce the stents. Results: A total of 8 stents were produced, representing 3 patients. These stents corresponded to 2 or 3 stents per patients. Each patient underwent several endoscopic treatments, before resolution of leak. Conclusions: Customized stents may improve drainage of intra-abdominal abscesses after gastrointestinal surgery, if based on unique anatomy. This proof-of-concept study is a real-world application of personalized health care, which introduces the novel description of customizable 3D printed stents to manage complications following gastrointestinal surgery and may advance therapy for this complex clinical condition. Research Ethics Committees (REC) number is A-2021-012.

Design of a 330-GHz Frequency-Tunable Gyrotron With a Prebunched Circuit

The design of a 330-GHz second harmonic gyrotron with broadband tunability is presented in this article. Loaded with a prebunched cavity, the output power is almost doubled (~216 W, corresponding to the output efficiency of 3.6%) compared with a conventional open-cavity scheme, and the tuning range is ~1.85 GHz. To further reveal the feasibility of the prebunching section for the harmonic operations, it is theoretically demonstrated that the phase shift inside the prebunching Section plays an important role in improving the interaction performance. The dependence of the phase shift on the cavity dimension and propagation constant is explored, which instructs the circuit optimization. Moreover, the engineering designs of the magnetron injection gun, the output window, and the collector are presented under a 10-T super-conducting magnet. The overall configuration of the tube is exhibited at the end of the article.

Machine Learning to Predict Quasi TE₀₁₁ Mode Resonances in Double-Stacked Dielectric Cavities

We have applied machine learning in a neural network to calculate the quasi TE₀₁₁ mode of a cylindrical microwave cavity with two symmetrically stacked dielectric resonators (DRs) inside, with aspect ratios of the overall cavity being limited to the range of 0.25&#x2013;4. The neural network was trained with 99 970 samples and evaluated using 9564 samples from a holdout dataset. The samples were created using a supercomputer to solve random cavity configurations via finite-element method (FEM) programming. The trained neural network predicts the resonant frequency of the quasi TE₀₁₁ mode and expresses the mode in terms of expansion coefficients of empty cavity TE<inline-formula> <tex-math notation="LaTeX">$_{\mathrm {0\,np}}$ </tex-math></inline-formula> modes, from which plots of the electric and magnetic fields can be made. The predictions are extremely quick, taking &#x007E;0.05&#x2013;0.2 s running on a typical personal computer, and are very accurate when judged against the FEM results: the overall median error in the frequency neural network is 0.2&#x0025;, and the overall median error of the expansion coefficients neural network is 0.003&#x0025;. This should allow designers to much more rapidly determine optimal cavity and DR dimensions and other parameters in order to achieve the frequency and mode they desire, with a speedup of approximately <inline-formula> <tex-math notation="LaTeX">$10\,\,000\times $ </tex-math></inline-formula> compared with FEM calculations alone. A link to the Python implementation of our FEM code and our trained neural network code is provided.

IDF21-0582 Cardiac structure and function prediabetes and diabetes without heart failure: A hospital based cross-sectional study

Background: Individuals with diabetes mellitus and pre-diabetes are at particularly high risk of incident heart failure (HF) or death, even after accounting for known confounders. Prior studies have shown that individuals with diabetes have increased left ventricular (LV) wall thickness and mass, and impaired diastolic function in the absence of overt LV systolic dysfunction; the alterations in cardiac structure and function in less impaired glycemic states without prevalent cardiovascular disease are less well described. Also most previous studies have only performed limited measures of cardiac structure and function, and none have comprehensively evaluated cardiac parameters, particularly diastolic function. Aim: This study was done with the aim of studying the cardiac structure and functions in normotensive patients with prediabetes and diabetes who don’t have symptoms of heart failure. Method: The study was an analytical cross sectional study with a comparison group. The study was conducted in department of Medicine which caters to more than 11000 in patients annually out of which at least 4-5% are suffering from diabetes mellitus. We estimated number of diabetic patients as 30, prediabetics as 130 and normal patients in the comparison group were estimated to be 130. All consecutive patients who was known case of diabetes mellitus or on anti-diabetic medication are followed up regularly in out-patient (OPD) of medicine department and worked up and managed according to American diabetes association (ADA) standards of care for patients with diabetes mellitus. All patients included in the study was subjected to 2D echocardiography. An echocardiography examination, including M-mode, two dimensional (2D) and Left ventricular mass and left ventricular mass indexed to body surface area estimated by LV cavity dimension and wall thickness at end-diastole. Results: We enrolled a total of 300 study participants out of which 40 diabetics, 130 prediabetes and 130 normal individuals which were used as a comparator group for both diabetic patients and prediabetes patients. The mean age of our study participants was 54.85 ± 13.65 in diabetes, 53.72 ± 12.18 in prediabetes and 49.49 ± 11.88 in the comparator group. The diabetic patients showed significantly increased LA volume in prediabetes (38.27 ± 8.74) and diabetes patients (34.26 ±10.82) as compared to the normal (27.47 ± 8.81). The dimensions of LV interventricular septum in systole and diastole were increased in diabetic and prediabetes patients as compared to normal individuals. Similarly, the EDV was significantly higher in diabetic and prediabetes patients. The LVEF was reduced significantly in the diabetic (50.26 ±5.41) and prediabetes (52.43 ±4.69) as compared to the normal individuals. The E/A ratio was increased in diabetic patients (0.78±0.10) and prediabetics (0.84±0.09) as compared to normal individuals. LV mass was also more in the diabetic and prediabetic patients. Discussion: We demonstrated several indices of LV systolic and diastolic dysfunction were increased in both diabetes and prediabetes, LV geometry differed significantly and decrease ejection fraction, increase LV mass in prediabetes and diabetes as compared to comparator group. We have performed robust characterization of cardiac structure and function beyond ejection fraction and LV mass and looked at LA volume indices.

Effect of Different Cavity Dimensions and Curing Systems on Cuspal Deflection of some types of Composite Resin Restorations

The cuspal deflection of different composite resin restorations cured with different systems and restoring different cavity dimensions were investigated using a total 60 freshly extracted human maxillary premolars. These teeth were divided into three main equal groups, based upon the tested restorative materials. Group (I) used T-Econpm Plus, Group (A1) (II) used Filtek Z250 XT (A2), and Group (III) used Filtek P90 (A3). Each group was subdivided into two subgroups based upon the prepared cavity dimensions. Each subgroup was further subdivided into two groups whether cured with Halogen (C1), or LED (C2). MOD cavity with two different dimensions, each restorative material was packed according to the manufacturer's instructions and cured. Dye penetration technique was used and specimens were sectioned in mesiodistal direction and examined by stereomicroscope. Collected data was statistically analyzed. The result showed T-Econom plus had statistically significant higher microleakage value, while Filtek P90 had statistically significant lower microleakage value. There was no statistically significant difference between groups cured with Halogen and LED. It can be concluded that silorane based composite, LED curing system, and smaller cavity dimension could significantly decreased cuspal deflection.

On the acoustic performance of double degree of freedom helmholtz resonator based acoustic liners

This study investigates the acoustic performance of double degree of freedom Helmholtz resonators and multi cell acoustic liners made of these resonators, both experimentally and through finite element analysis. The dimensions of the resonator internal cavities were varied to assess the effect of the volume ratio on the acoustic performance of the system. Experiments were performed using a grazing flow impedance tube and instrumented 3D printed modular resonators, which can be switched between a single and double degree of freedom resonating cavity configuration. An aluminium acoustic liner with 16 modular resonating cavities was also used in experiments. The effect of the volume ratio is investigated by presenting the transmission loss and transmission coefficient induced and the changes in sound pressure level within the resonator. The underlying sound attenuation mechanisms are further elaborated through the finite element analysis results of the acoustic pressure and velocity fields in the different resonator configurations. The results showed that as the volume ratio is increased, the difference between the first and second resonance frequencies tends to have a convex behaviour. This may indicate the presence of an optimum volume ratio of the two internal cavities for a broad bandwidth of sound absorption. Moreover, the finite element analysis results showed that increasing the volume ratio increased both the transmission loss induced and the bandwidth of frequencies attenuated at the first resonance frequency due to an in-phase velocity magnitude relation, for both the neck and septum of the resonator. Conversely, for the second resonance frequency, there is an out-of-phase relation between the neck and septum velocity magnitudes. In addition to the single resonator analysis, the acoustic performance of liner configurations with 16 resonators was also investigated. The results showed an increase in the bandwidth of attenuated frequencies when each resonating cavity had a different volume ratio, as compared to a fixed volume ratio. In addition, the order of the resonators of different volume ratio in the liner arrangement did not seem to have a significant effect on the overall sound attenuation performance.

Role of Void Orientation and Shape on The Electric Field Distortion in High Voltage Cable

One of the problems that face the use of XLPE insulators is the appearance of defects. These defects appear during the manufacturing processes of the insulator, and one of these defects is air cavities or voids. The defects presence within the insulators of high voltage cables affects the distribution of the electric field within the cable layers. The distortion of the electric field due to the presence of air cavities is the main reason for the treeing appearance inside the insulator, which eventually leads to the emergence of partial discharges that reduce the life of the cable. In this study, the effect of the presence of an air cavity inside an XLPE insulator was studied by changing the dimensions of the cavity, that is, changing the ratio of the dimensions of the cavity parallel to the electric field and vertical to it and the effect of this on the value of the electric field in the center of the cavity. It was noted that the electric field in the cavity is higher than in the external electric field. The increase in the field in the cavity center does not depend on the cavity size, but rather on the ratio of the cavity dimensions parallel to the electric field to the vertical to it. The electric field enhancement factor was calculated based on the simulation results, which showed a reasonable agreement with the theoretical values.

Acoustic Performance of a Metascreen-Based Coating for Maritime Applications

Abstract Time- and frequency-domain numerical models are developed to investigate the acoustic performance of metascreen-based coatings for maritime applications. The coating designs are composed of periodic air-filled cavities embedded in a soft elastic medium, which is attached to a hard backing and submerged in water. Numerical results for an acoustic coating with cylindrical cavities are favorably compared with analytical and experimental results from the literature. Frequencies associated with peak sound absorption as a function of the geometric parameters of the cavities and material properties of the host medium are predicted. Variation in the cavity dimensions that modifies the cylindrical-shaped cavities to flat disks or thin needles is modeled. Results reveal that high sound absorption occurs when either the diameter or length of the cavities is reduced. Physical mechanisms governing sound absorption for the various cavity designs are described.