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Green structures, such as green roofs or green façades, are great examples of climate change mitigation. Their impact is mainly focused on roofs in the area of overheating reduction. In this paper, initial measurement results of a green façade experimental test setup are provided. The green façade uses an innovative board from recycled materials with vegetation rooted directly on the board. The tested green façade is divided into three segments. These segments differ from each other in their watering regimes, which are crucial for cooling effectiveness. Watering operates with the assistance of gravity; water flows from the top gutter through the boards. In this paper, these three segments are compared to each other with respect to temperatures on the surface of a regular external thermal insulation composite system façade (ETICS) during two summer days. The green façade showed an impact on the temperature in the ventilated air gap, where the temperature is almost the same as the outdoor air temperature in the morning with direct solar radiation on the façade and lower than the outdoor air temperature in the afternoon. At the peaks, the surface temperatures within the air cavity surface are up to 8 °C lower than those on a new white ETICS coating. This demonstrates a cooling potential, although the surface temperatures are always higher than the outdoor air temperatures during daylight hours. [ABSTRACT FROM AUTHOR]

Ship bow wave breaking contains complex flow mechanism, which is very important for ship performance. In this study, a practical numerical simulation scheme for bow wave breaking is proposed and the scheme is applied to the simulation of bow wave breaking of KCS ship model with Fr = 0.26, 0.30, 0.35, 0.40, analyzing the impact of speed on the bow wave breaking. The results indicate that an increase in speed leads to a significant rise in viscous pressure resistance and more pronounced bow wave breaking. Moreover, it is found that the traditional wave height function in OpenFOAM is not suitable for detailed studies of bow wave breaking. This study extracts different free surfaces through top and bottom views to further analyze the free surface overturning, droplet splashing, and cavity entrainment in bow wave breaking. Additionally, the spatial and temporal distribution of cavities at Fr = 0.40 is analyzed, revealing that cavity distribution is closely related to vortex structures and exhibits a periodic pulsation characteristic of approximately 12 s. [ABSTRACT FROM AUTHOR]

In this study, we investigate the enhancement of effective transconductance and gain linearity in submicrometer gate AlGaN-barrier-based transistors utilizing ScAlN/GaN coupling-channel structures. A novel asymmetric gate design, incorporating an AlGaN cap on ScAlN/GaN HEMT, is proposed. This configuration demonstrates a flat transconductance profile and significantly reduced transconductance derivative, thereby improving the linearity of GaN-based transistors. For transistors with a gate length of 0.5 μm, both the current gain cut-off frequency and power gain cut-off frequency are measured at 53.52 GHz and 72.98 GHz, respectively. These values represent a more than threefold increase from the corresponding frequencies of conventional devices. Moreover, the theoretical Output Third-Order Intercept value of the proposed structure has increased by 7.5 dBm compared to conventional HEMTs. This superior linear performance can be attributed to the combined effect of AlGaN cap layer and air cavity. Furthermore, the introduction of the ScAlN layer results in a substantial impact, including a decrease in electron concentration from 4.96 × 1019/cm3 to 1.98 × 1019/cm3 and an increase in electron velocity from 4.5 × 107 to 7.6 × 108 cm/s. These findings underscore the potential of the proposed device for high-frequency applications requiring superior linearity.

Green structures, such as green roofs or green façades, are great examples of climate change mitigation. Their impact is mainly focused on roofs in the area of overheating reduction. In this paper, initial measurement results of a green façade experimental test setup are provided. The green façade uses an innovative board from recycled materials with vegetation rooted directly on the board. The tested green façade is divided into three segments. These segments differ from each other in their watering regimes, which are crucial for cooling effectiveness. Watering operates with the assistance of gravity; water flows from the top gutter through the boards. In this paper, these three segments are compared to each other with respect to temperatures on the surface of a regular external thermal insulation composite system façade (ETICS) during two summer days. The green façade showed an impact on the temperature in the ventilated air gap, where the temperature is almost the same as the outdoor air temperature in the morning with direct solar radiation on the façade and lower than the outdoor air temperature in the afternoon. At the peaks, the surface temperatures within the air cavity surface are up to 8 °C lower than those on a new white ETICS coating. This demonstrates a cooling potential, although the surface temperatures are always higher than the outdoor air temperatures during daylight hours.

This review explores a variety of techniques that utilize air injections beneath a vessel’s hull to reduce drag and consequently improve energy efficiency. It focuses on the methodologies of microbubble drag reduction (MBDR), air layer drag reduction (ALDR), and air cavity drag reduction (ACDR), offering insights into their design, operational mechanisms, and potential applications. This review provides a detailed examination of the underlying principles of these technologies, incorporating a blend of experimental research, numerical simulations, and mathematical modelling to offer a comprehensive understanding. It references recent experimental data, highlighting how these findings corroborate with numerical simulations and are further explained through mathematical models. Conclusively, this review accentuates the transformative influence of air injection methods in drag reduction within the maritime industry, emphasizing their pivotal role in boosting operational efficiency, reducing environmental impact, and driving the evolution of naval design and transportation. Through a balanced and detailed analysis, this review provides a holistic view of the current state and future prospects of these innovative resistance reduction strategies.

For the marine industry, resistance reduction can reduce energy consumption and achieve protection of the marine environment. The use of air lubrication to reduce the resistance of ships is one of the most important ways. With this technology, high-speed air cavity crafts show immense potential as they can be utilized in various marine activities, such as emergency rescue, supply, and maritime security. Through experiments, this study presents an in-depth analysis of the effects of bubble chamber pressure and initial stern inclination on the resistance of high-speed air cavity crafts at different speeds. The results show that air pressure has a significant impact on resistance. It was found that as the speed of the ship increased, the resistance reduction effect became more prominent under the same pressure conditions. Moreover, the resistance tended to stabilize when the pressure reached a certain value. In addition to the air pressure, the longitudinal inclination does have an effect on resistance reduction. To achieve better resistance reduction, the initial stern inclination angle should be chosen appropriately. Furthermore, adjusting the angle with speed changes can optimize the resistance reduction effect. This experimental study provides critical support for conducting further research on high-speed air cavity crafts. The findings offer valuable insights into improving hull forms, guiding host selection, and assessing performance. [ABSTRACT FROM AUTHOR]

The evolution of water-entry cavities gives rise to interesting dynamic phenomena that occur in nature and engineering fields. The evolution and seal types of the cavities remain unsettled at Bo less than 10−2 since it is difficult to propel a small sphere to impact a water surface at high speed. In the present study, an experiment based on the laserdriven principle is conducted to accelerate a small sphere to hundreds m/s. The types of cavity seal are classified as quasi-static, shallow seal, deep seal, and surface seal within a Bo range of 1–7.57×10−2. The transition mechanism from a shallow seal to a deep seal is investigated by analyzing the cross-sectional characteristics of cavity necks. With a further decrease in Bo (5.69×10−2–8.41×10−3), the shallow seal is changed directly to a surface seal since the pinch-off time of the cross section at the cavity neck decreases with Bo, and hence, the deep seal disappears. Finally, a parameter study is conducted by varying We and Bo in the air cavity. Two boundaries are obtained: We ≈ 64 for the transition between quasi-static and shallow seals and We ≈ 326 for the transition between shallow seals and surface seals. [ABSTRACT FROM AUTHOR]

Vetiver grass (Chrysopogon zizanioides)-based porous pine board material of lower thickness and density has been designed using magnesium oxide (MgO) as a binding agent. This pine board can be utilized in the new constructions and existing buildings for noise absorption. Attempts were made to optimize low density 400 kg/m3 and 20-mm-thick material. The sound absorption measurement of these manufactured pine boards has been taken in the reverberation chamber for sound absorption coefficient (SAC) and noise reduction coefficient (NRC) as per International standard ISO 354-2003 and ASTM 423-90. Efforts have been made to observe the variation in SAC and NRC when the glass wool layer was inserted below the developed material. NRC of the developed material was found 0.33 and 0.80 without and with a glass wool layer inserted below the specimen at rigid backing. Further, the sample's SAC and NRC measurements were examined by creating different air cavities behind the developed pinewood sample, starting from rigid backing (0 mm) to 25 mm, 50 mm, 100 mm and 300 mm to get the best combination for improving noise absorption acoustic properties of the material. An attempt has been made to counter the low-frequency noise; outcome results have been analysed and discussed in the present work. The manufactured pine boards of density 400 kg/m3 and 20 mm thickness satisfied all the physical and mechanical properties requirements of the Indian Standards. [ABSTRACT FROM AUTHOR]

To further improve the low-frequency broadband sound absorption capability of the underwater anechoic layer (UAL) on the surface of marine equipment, a novel sound absorption structure with cavities (NSSC) is designed by adding resonators and honeycombs to the traditional sound absorption structure with cavities (SSC). Based on the principle of shear dissipation, the original intention of the design is to allow more parts of the viscoelastic material to participate the dissipation of acoustic energy. The approximate multilayer sound absorption theoretical model based on the modified transfer matrix method is used to verify the accuracy of finite element calculations. In the frequency range of 1100 Hz–10,000 Hz, the sound absorption coefficient (α) of NSSC can reach 0.8. The effects of the presence and size of cylindrical oscillators and honeycomb structures on sound absorption are discussed in detail. The results show that expanding the effective sound absorption range of the damping area of the structure is the key to improve the wideband sound absorption effect. This design concept could guide the structural design of the UAL. [ABSTRACT FROM AUTHOR]

Different air phase regimes are formed by controlled air injection in a spatially developing flat plate turbulent boundary layer (TBL). The air is introduced via a slot type injector without the use of a backward-facing step or cavitator upstream of the air injection position. The effect of different incoming liquid flow characteristics on the different regimes is investigated by varying both the liquid freestream velocity and the incoming TBL thickness. The latter is realized through changing the position of the air injection along the length of the water tunnel facility. That resulted in a downstream distance based Reynolds number from 1 to 5 million. Three different air phase regimes are identified under different air flow rates and freestream velocities: the bubbly regime, the transitional, and the air layer regime. The morphological differences of each one are described and quantitative analysis is performed based on the non-wetted area in each condition. The incoming TBL as well as the flow around the air layer are measured with planar particle image velocimetry. The latter enabled the determination of the air layer thickness. In addition, the ratio of the air layer to the incoming boundary layer thickness t a i r / δ is also calculated (≈ 0.04 – 0.5). This is a significant dimensionless parameter for scaling, which indicates the extent to which the air layer is embedded within the incoming TBL. Depending on the incoming flow conditions, a two or three branch air layer is formed. The length of the air layer is found to increase with increasing liquid freestream velocities. A good agreement between the air layer length and a half gravity wave predicted by the dispersion relation is found. An increase of the air layer length is observed with a decreasing incoming TBL thickness. This is attributed to a decrease in the local mean velocity at the air–water interface due to the TBL growth. Finally, increasing the incoming TBL thickness delays the onset of the air layer regime. [Display omitted] • Bubbly, transitional and air layer regimes are formed along a turbulent boundary layer. • Morphological differences of each regime are quantified by means of the non-wetted area. • Incoming TBL thickness affects both the regime transitions and the air layer length. • The ratio of air layer to boundary layer thickness is used to explain TBL effects. [ABSTRACT FROM AUTHOR]

Innovative cladding panels were developed by integrating phase change material into foamed concrete (PCMFC). The panels can be installed on walls via the wet method using cementitious/specialized adhesives or the dry method using special tools to mount the panels. The dry method creates an air cavity separating the panels from the wall, which can be of different sizes, either ventilated or unventilated. This study investigates the impacts of installation methods on the thermal performance of walls finished with PCMFC cladding panels. Experimental testing was conducted using three cells under actual weather conditions: a reference cell with cement render, a cell with PCMFC panels installed using the wet method, and a cell with PCMFC panels installed using different alternatives of the dry method. The results revealed improved performance for the dry method, showcasing reductions of about 7.10 °C in peak internal surface temperature (TSᵢ) with a 5 mm air cavity compared to the reference cell, while the reduction raised to about 8.70 °C by increasing the cavity size to 20 mm, and reached about 9.75 °C when permitting free ventilation inside the cavity. These reductions in peak TSᵢ were higher by about 1.14 °C, 1.79 °C, and 2.76 °C, respectively, compared to the wet method. Furthermore, overheating intensity decreased by 54 % with the ventilated 20 mm air cavity compared to the reference, i.e., 23 percentage points higher than the wet method. Thus, the dry installation method has proven to be highly effective in enhancing the thermal performance of PCMFC cladding panels. • PCMFC cladding panels' performance with different installation methods was studied. • PCMFC cladding panels' performance improved with air cavity due to added insulation. • PCMFC cladding panels with ventilated air cavity achieved lower peak TSᵢ by 9.75 °C. • Ventilated air cavity reduced the peak TSᵢ by up to 2.76 °C more than no air cavity. • Ventilated air cavity assists latent heat removal at night, preventing temperature rise. [ABSTRACT FROM AUTHOR]

Developing countries are severely affected by water scarcity. To meet the growing demand for clean drinking water, minimal, small-scale methods that don't use much energy are needed. Saline water desalination utilising the solar still, which depends only on solar radiation, is a realistic option for rural coastal communities. The current research focuses on increasing the daily production of solar still distillate yield. This paper provides a modified design that incorporates an air cavity connected to a solar still absorber plate and an effort to calculate the solar stills technological and economic assessment. The current study extensively focuses on the usefulness of an air cavity in improving solar still performance under diverse climatic conditions. The experimentation was performed at varying depths of saline water in two different material solar stills. During the experimentation, the maximum saline water temperature observed was 89°C and the lowest temperature was found as 29 °C. Aluminium and polycarbonate stills had an average energy and exergy efficiency of 48.8 %, 3.44 %, and 42.4 %, 2.3 %, respectively. The daily yields for aluminium and polycarbonate stills were 2.8 to 3.8 l/m2/day and 1.8 to 3.4 l/m2/day, respectively. The cost per litre of the distillate from aluminium and polycarbonate stills was determined to be Rs. 0.723 and Rs. 1.361, respectively, with a payback time of 10 and 11 months. Overall, at 1.8 cm saline water depth, the aluminium still provides improved distillate yield than the polycarbonate still, and the addition of air cavity reprises in the improvement of the efficiency of the solar still. From the experimental findings of both the solar stills, we can conclude that they are long-term viable and cost-effective in producing more distillate than expected with a short payback time. [Display omitted] • A novel solar still design with an air cavity coupled to the absorber plate has been investigated. • Aluminium still yielded more distillate than polycarbonate still. • The average energy and exergy efficiency of aluminium stills were found to be 48.8 % and 3.44 %, respectively. • The cost per litre of distillate and payback time is calculated for two life expectancies of 12 and 15 years. • The cost per litre and payback period are Rs. 0.723/− and 10 months, respectively. [ABSTRACT FROM AUTHOR]

The emptying process of initially stagnant full-pipe flows in sewer systems and water transmission lines was extensively studied in the literature. The following air intrusion and depressurization wavefronts can cause several issues such as the collapse of pipes, damage to joints, and valves. However, there is a lack of study on the emptying process when the flow has initial velocity. Thus, the present study focuses on the emptying process of a full-pipe flow with an initial flow rate, which decreases during the emptying process. For this purpose, two experiments without and with initial flow rates were performed in a reservoir-circular pipe system. In both experiments, an air cavity intrusion starts downstream of the pipe at the top of the free-surface flow and propagates upstream. It was found that when there is no initial flow rate, the pressure inside the cavity is atmospheric. However, when there is an initial flow rate, at the onset of the air intrusion, a subatmospheric pressure develops inside the air cavity. It was also found that the magnitude of this subatmospheric pressure decreases when the cavity further propagates upstream. In addition, when there is an initial flow rate, the cavity appears at a certain driving pressure. [ABSTRACT FROM AUTHOR]

Air lubrication is a promising drag reduction technology for ships because it is considered to reduce the skin-friction resistance of ships by changing the energy of turbulent boundary layers. Air lubrication drag reduction can be classified into: microbubble drag reduction (injection of microbubbles along the hull), air film drag reduction (using a larger film of air to cover the ship bottom), and air cavity drag reduction (recesses underneath the hull are filled with air). In this paper, the research progress of the air lubrication drag reduction technology is reviewed from experimental and numerical aspects. For these three drag reduction methods, based on the aspect of experimental research, the main research focus is the analysis and evaluation of the influencing factors such as the gas injection form and drag reduction rate; in terms of theoretical research, the accuracy of the simulation calculation depends on the selection of the theoretical calculation model and the analysis of the drag reduction mechanism. The paper introduces, in detail, the typical experimental phenomena and the theoretical results of a numerical study of three types of drag reduction methods, revealing the essence of air lubrication technology to achieve drag reduction by changing the physical properties of the turbulent boundary layer. [ABSTRACT FROM AUTHOR]

Introduction. Known vibrational energy harvesting methods use a source of vibration to harvest electric energy. Piezoelectric material works as a sensing element converted mechanical energy (vibration) to electrical energy (electric field). The existing piezoelectric energy harvesting (PEHs) devices have low sensitivity, low energy conversion, and low bandwidth. The novelty of the proposed work consists of the design of PEH’s structure. Air cavity was implemented in the design where it is located under the sensing membrane to improve sensitivity. Another novelty is also consisting in the design structure where the flexural membrane was located at the top of electrodes. The third novelty is a new design structure of printed circuit board (PCB). The purpose of improvised design is to increase the stress in between the edges of PEH and increase energy conversion. With the new structure of PCB, it will work as a substrate that absorbs surrounding vibration energy and transfers it to sensing element. Methods. Three techniques were successfully designed in PEH and fabricated namely PEH A, PEH B, and PEH C were characterized by two experiments: load and vibration. The load experiment measured load pressure towards the PEH, whereas the vibration experiment measured stress towards the PEH. Results. PEH C has the highest induced voltage for a weight of 5.2 kg at the frequency of 50 Hz and the highest stored voltage for a period of 4 min. The three techniques applied in PEHs were showed improvement in transducer sensitivity and energy conversion. Practical value. A piezoelectric acoustic generator was used in the experiment to compare the performance of the designed PEH with available piezoelectric transducers in the market. The new flexible membrane worked as a sensing element was worked as a cantilever beam. PVDF was used as a sensing element due to the flexibility of the polymer material, which is expected to improve sensitivity and operating bandwidth.

Objective: To investigate the impact of different magnetic field strengths and orientations on the dose deposition from lateral opposing photon beams irradiating a laryngeal geometry, with particular attention focused on the dose homogeneity of the area around the air cavity inside the larynx. Methods: Geant4 simulation toolkit was used to perform Monte Carlo simulations on a phantom resembling the larynx. The energy spectrum of a 6 ​MV photon beam from a Varian Clinac iX machine was used to provide the source of radiation. Three configurations of the Magnetic Resonance Image-Guided Radiation Therapy (MRIgRT) system were simulated: the Fixed Cylindrical (FC) geometry, the Longitudinal Rotating Biplanar (LRBP) geometry, and the Transverse Rotating Biplanar (TRBP) geometry. Uniform magnetic fields of different field strengths were applied. The relative dose maps and the homogeneity index (HI) were obtained for evaluations. Results: The LRBP geometry together with a magnetic field strength of 0.5 ​T produced the most homogeneous dose distribution with a HI of 0.139 for the region of interest around the air cavity, compared with a HI of 0.180 when the magnetic field was absent. For TRBP geometry, the dose distribution shifted towards the cranial direction, leading to a region of hot spots at the superior edge and a region of cold spots at the inferior edge of the irradiated volume. The HI around the air cavity was therefore worse. In addition, strong electron streaming effect (ESE) was observed. For the FC geometry, hot and cold spots were formed around the air cavity which increased the HI. Conclusions: Out of the three configurations of the MRIgRT systems, the LRBP geometry produced the most clinically beneficial dose distribution in which it provided a higher dose to the treatment area and a boost in dose to the tissue immediately adjacent to the air cavity.

For the marine industry, resistance reduction can reduce energy consumption and achieve protection of the marine environment. The use of air lubrication to reduce the resistance of ships is one of the most important ways. With this technology, high-speed air cavity crafts show immense potential as they can be utilized in various marine activities, such as emergency rescue, supply, and maritime security. Through experiments, this study presents an in-depth analysis of the effects of bubble chamber pressure and initial stern inclination on the resistance of high-speed air cavity crafts at different speeds. The results show that air pressure has a significant impact on resistance. It was found that as the speed of the ship increased, the resistance reduction effect became more prominent under the same pressure conditions. Moreover, the resistance tended to stabilize when the pressure reached a certain value. In addition to the air pressure, the longitudinal inclination does have an effect on resistance reduction. To achieve better resistance reduction, the initial stern inclination angle should be chosen appropriately. Furthermore, adjusting the angle with speed changes can optimize the resistance reduction effect. This experimental study provides critical support for conducting further research on high-speed air cavity crafts. The findings offer valuable insights into improving hull forms, guiding host selection, and assessing performance.

• An asymmetric gate design incorporating an AlGaN cap on ScAlN/GaN HEMT demonstrates a flat g m profile and significantly reduced g m derivative, leading to improved linearity of GaN-based transistors. • HEMTs with air cavity design is comprehensively studied in detail. • Describing the influence of ScAlN layer thickness on device frequency, we analyzed how the ScAlN layer increases device frequency and linearity. • The effect of the thickness and aluminum composition of the AlGaN cap layer on the linearity of ScAlN/GaN HEMTs with asymmetric gate design is described. In this study, we investigate the enhancement of effective transconductance and gain linearity in submicrometer gate AlGaN-barrier-based transistors utilizing ScAlN/GaN coupling-channel structures. A novel asymmetric gate design, incorporating an AlGaN cap on ScAlN/GaN HEMT, is proposed. This configuration demonstrates a flat transconductance profile and significantly reduced transconductance derivative, thereby improving the linearity of GaN-based transistors. For transistors with a gate length of 0.5 μm, both the current gain cut-off frequency and power gain cut-off frequency are measured at 53.52 GHz and 72.98 GHz, respectively. These values represent a more than threefold increase from the corresponding frequencies of conventional devices. Moreover, the theoretical Output Third-Order Intercept value of the proposed structure has increased by 7.5 dBm compared to conventional HEMTs. This superior linear performance can be attributed to the combined effect of AlGaN cap layer and air cavity. Furthermore, the introduction of the ScAlN layer results in a substantial impact, including a decrease in electron concentration from 4.96 × 1019/cm3 to 1.98 × 1019/cm3 and an increase in electron velocity from 4.5 × 107 to 7.6 × 108 cm/s. These findings underscore the potential of the proposed device for high-frequency applications requiring superior linearity. [ABSTRACT FROM AUTHOR]

Accurate values for the climatic conditions in an air cavity, hereby called the microclimate, are crucial when calculating and simulating the performance of a ventilated roof and façade system. The climatic stress of its components and their mould and rot potential influence the long-term durability of the roof or façade. A scoping study is conducted to gain an overview on research and the scientific literature on the microclimate of air cavities in ventilated roofing and claddings in Nordic climates. From the body of the research literature, 21 scientific works were of particular interest, and their findings are summarized. The review shows that only a limited number of studies discuss the microclimate of air cavities. Roofs are discussed to a greater and more varied degree compared to façades and air cavities behind solar panels. However, the results cannot be compared and validated against each other to generally describe the microclimate of air cavities, as the surveyed papers approach the subject differently. This knowledge gap indicates that calculations and simulations can be performed without knowing whether the results represent reality. If the structure of ventilated roof and façade systems are only designed based on experience, it can be difficult to be proactive and adapt to future climate changes. Further studies are needed to determine the relation between the exterior climate and the air cavity microclimate, so that future climate predictions can be used to simulate the long-term performance of ventilated roof and façade systems. [ABSTRACT FROM AUTHOR]

Green façades with an active water regime and the water flowing through the substrate itself are not common. This system reduces the temperatures and incorporates the evapotranspiration, which could be more effective than by the regular green façades. The use of a double-skin façade with a ventilated air cavity can reduce the heat load, but the evapotranspiration can reduce it even more with additional benefits. Green façades could also serve as a key element for reducing the surface temperatures of the insulated metal panels (IMP), which are mostly used as a façade system for production facilities or factories. In this paper, a prototype of a double-skin façade, which consisted of vegetation board from recycled materials and IMP, is tested in a climate chamber to evaluate the function and benefits of such a combination. The outdoor skin is made from board, the surface of which is covered by the rooted succulent plants. Measurement results are represented as a direct comparison of single sunny day surface temperatures with and without a double-skin (green) façade. The use of the green façade reduces the indoor surface temperature of IMP by 2.8 °C in this measurement. The use of water circulation through the outdoor skin reduces the temperature of the vegetation board by 28 °C. This could have a great impact on the microclimate around the façade. Because of the controlled environment and ventilation system in a climate chamber, it is not possible to investigate the airflow and solar chimney effect within the ventilated cavity. In addition, it is complicated to show the potential of microclimate change caused by the wet vegetation surface. For the mentioned reasons, the need to carry out "in situ" tests on a model wall under the real conditions was indicated. [ABSTRACT FROM AUTHOR]

To evaluate the dosimetric effect of intensity-modulated radiation therapy (IMRT) for postoperative non-small cell lung cancer (NSCLC), with and without the air cavity in the planning target volume (PTV). Two kinds of IMRT plans were made for 21 postoperative NSCLC patients. In Plan-0: PTV included the tracheal air cavity, and in Plan-1: the air cavity was subtracted from the PTV. For PTV, the dosimetric parameters, including D mean , D 98 , D 95 , D 2 , D 0.2 , conformity index (CI), and homogeneity index (HI) were evaluated. For organs at risk (OARs), the evaluation indexes, included the V 5 , V 20 and the mean lung dose (MLD) of total lung, the V 30 , V 40 , and the mean heart dose (MHD) of heart, the spinal cord D max , and the V 35 and the mean esophageal dose (MED) of esophagus. The number of segments and MUs were also recorded. Additionally, the correlation between the Plan-1 dosimetric change value relative to Plan-0, the size of air cavity, and the volume proportion of the cavity in the PTV was also analyzed. The D mean of PTV, D 2 , D 0.2 , HI and CI in Plan-1 decreased compared with those in Plan-0. For OARs, the V 30 , MHD, and MED also decreased. The CI change value of Plan-1 relative to Plan-0 had a significantly negative correlation with the size and the volume proportion of air cavity, and the MED change value also had a significantly negative correlation with the air cavity size. The IMRT plans for patients with postoperative NSCLC can achieve a better target dose distribution and offer an improved sparing of the heart and esophagus by removing the PTV air cavity, while reducing the target conformity. The change value of CI and MED had a significantly negative correlation with the air cavity size. [ABSTRACT FROM AUTHOR]

In order to improve the underwater acoustic target strength of corner reflectors, according to the principle of acoustic impedance mismatch of the boundary layer, the method of using air cavity to increase the underwater acoustic target strength of corner reflectors is proposed. The acoustic reflection coefficients of underwater air layer and single layer metal sheet are calculated and compared. The results show that the reflection coefficient of single layer metal sheet is greatly affected by frequency and incidence angle, and the reflection coefficient of air layer in water is large and little affected by frequency and incidence angle. On this basis, a new kind of airfilled cavity corner reflector is designed. The acoustic scattering characteristics of underwater airfilled cavity corner reflector are calculated cumulatively, and the results are compared with the monolayer metal sheet corner reflector. The simulation results show that the acoustic reflection effect of the airfilled cavity corner reflector is better. In order to verify the correctness of the method, the test was carried out in the silencing tank. The experimental results show that the simulation results are in good agreement with the experimental results, and the airfilled cavity can improve on acoustic reflection performance of the underwater corner reflector.

To further improve the low-frequency broadband sound absorption capability of the underwater anechoic layer (UAL) on the surface of marine equipment, a novel sound absorption structure with cavities (NSSC) is designed by adding resonators and honeycombs to the traditional sound absorption structure with cavities (SSC). Based on the principle of shear dissipation, the original intention of the design is to allow more parts of the viscoelastic material to participate the dissipation of acoustic energy. The approximate multilayer sound absorption theoretical model based on the modified transfer matrix method is used to verify the accuracy of finite element calculations. In the frequency range of 1100 Hz–10,000 Hz, the sound absorption coefficient (α) of NSSC can reach 0.8. The effects of the presence and size of cylindrical oscillators and honeycomb structures on sound absorption are discussed in detail. The results show that expanding the effective sound absorption range of the damping area of the structure is the key to improve the wideband sound absorption effect. This design concept could guide the structural design of the UAL.

Providing an air cavity behind vinyl siding within a building envelope is an approach to mitigating building moisture-related issues, which also improves the building's thermal performance. Previous studies commonly assume the cavity air as still and thus neglect the influence of mixed convection on the performance of the building envelope. Additionally, the air cavity is usually considered uniformly rectangular, neglecting the effects of its geometric irregularity and complexity. Therefore, to comprehensively investigate the effects of air cavities, this study analyzes ratios of siding depth to cavity depth in the mixed convection of air cavities, through rigorously formulating the problem and solving it using the perturbation method. The results show that increasing the ratio of the vinyl siding depth to the air cavity depth amplifies the metrics directly related to the energy performance of the building envelope, including the cavity air's velocity, temperature, and mass fraction; the skin friction at cavity walls; as well as heat and mass transfer across the cavity. The effects of other critical parameters are also investigated, including the Reynolds number and temperature of the irregular cavity wall. This study provides guidance for comprehensively evaluating the thermal performance of an air cavity behind vinyl siding and improving the design of vinyl siding. [ABSTRACT FROM AUTHOR]

Acoustic panels with different configurations (layered structure with different absorbing materials) are broadly used to attenuate the noise. Multiple panels are preferred due to the presence of multiple air cavities and the repeated reflections which lead to increased sound attenuation. The paper presents an experimental study of sound propagation through multiple panels. A novel design of acoustic panel is proposed by incorporating the sonic crystal in the air cavities of the panel. Sonic crystal (SC) consists of a periodic arrangement of sound hard scatterers which provide the sound reduction in a particular frequency range due to destructive interference in periodic scatterers. The results are based on experimental observations which are supported by the literature. The results show that increasing the number of panels increases the sound insertion loss from the multiple panel structure. However, the panels with air cavity suffer from the sound insertion loss dip, which makes the panel ineffective. The novel acoustic panel (double and triple panel with SC) provides an additional sound reduction due to SC which can be tailored for certain frequency band. For the present case, SC is designed to overcome the insertion loss dip. The novel panel provides an additional insertion loss, reaching a maximum value of 19 and 11 dB, respectively (for the double and triple panel), overcoming the insertion loss dip due to structural vibration. [ABSTRACT FROM AUTHOR]

Introduction. Known vibrational energy harvesting methods use a source of vibration to harvest electric energy. Piezoelectric material works as a sensing element converted mechanical energy (vibration) to electrical energy (electric field). The existing piezoelectric energy harvesting (PEHs) devices have low sensitivity, low energy conversion, and low bandwidth. The novelty of the proposed work consists of the design of PEH’s structure. Air cavity was implemented in the design where it is located under the sensing membrane to improve sensitivity. Another novelty is also consisting in the design structure where the flexural membrane was located at the top of electrodes. The third novelty is a new design structure of printed circuit board (PCB). The purpose of improvised design is to increase the stress in between the edges of PEH and increase energy conversion. With the new structure of PCB, it will work as a substrate that absorbs surrounding vibration energy and transfers it to sensing element. Methods. Three techniques were successfully designed in PEH and fabricated namely PEH A, PEH B, and PEH C were characterized by two experiments: load and vibration. The load experiment measured load pressure towards the PEH, whereas the vibration experiment measured stress towards the PEH. Results. PEH C has the highest induced voltage for a weight of 5.2 kg at the frequency of 50 Hz and the highest stored voltage for a period of 4 min. The three techniques applied in PEHs were showed improvement in transducer sensitivity and energy conversion. Practical value. A piezoelectric acoustic generator was used in the experiment to compare the performance of the designed PEH with available piezoelectric transducers in the market. The new flexible membrane worked as a sensing element was worked as a cantilever beam. PVDF was used as a sensing element due to the flexibility of the polymer material, which is expected to improve sensitivity and operating bandwidth. [ABSTRACT FROM AUTHOR]

Air lubrication is a promising drag reduction technology for ships because it is considered to reduce the skin-friction resistance of ships by changing the energy of turbulent boundary layers. Air lubrication drag reduction can be classified into: microbubble drag reduction (injection of microbubbles along the hull), air film drag reduction (using a larger film of air to cover the ship bottom), and air cavity drag reduction (recesses underneath the hull are filled with air). In this paper, the research progress of the air lubrication drag reduction technology is reviewed from experimental and numerical aspects. For these three drag reduction methods, based on the aspect of experimental research, the main research focus is the analysis and evaluation of the influencing factors such as the gas injection form and drag reduction rate; in terms of theoretical research, the accuracy of the simulation calculation depends on the selection of the theoretical calculation model and the analysis of the drag reduction mechanism. The paper introduces, in detail, the typical experimental phenomena and the theoretical results of a numerical study of three types of drag reduction methods, revealing the essence of air lubrication technology to achieve drag reduction by changing the physical properties of the turbulent boundary layer.

Metal curving or metal denting is usually an unwanted phenomenon in the printed circuit board (PCB) process. However, curved metal could provide some benefits to enhance performance of radio frequency components. In this article, an approach is proposed to develop a double-curved metal (DCM) in a multilayer PCB process by allocating a metal upon an air cavity and then laminating with buffer layers under suitable pressure and temperature. This approach could increase the degree of freedom on radio frequency component design in PCB process. Based on this approach, a millimeter-wave (mmWave) aperture-coupled patch antenna is produced with the improved characteristics of high gain, wide bandwidth, and compact size. Prototypes of the proposed antenna are designed, manufactured, measured, analyzed, dissected, and observed under a metallographic microscope. The measurements and simulations are in good agreement and demonstrate that the proposed antenna achieves a maximum gain of 8 dBi over an operating bandwidth of 27.4–34.2 GHz. Compared with an aperture-coupled patch antenna with a flat metal, the fractional bandwidth of that with a double-curved metal is enhanced by a factor of two. [ABSTRACT FROM AUTHOR]

Mathematical formulations of two-phase flows at an aerator remain a challenging issue for spillway design. Due to their complexities in terms of water–air interactions subjected to high flow velocities, experiments play an essential role in evaluations of numerical models. The paper focuses on the underlying influence of the air–water momentum exchange in the two-phase Two-Fluid Model. It is modified to better represent the drag force acting on a group of air bubbles and the wall lubrication force accounting for near-wall phase interactions. Based on data from a large aerator rig with an approach velocity of 14.3 m/s, the models are evaluated for calculations of entrained air characteristics of a flow mixture. The air bubble diameter used in the modeling ranges from 0.5 to 4 mm as suggested by the experiments. In terms of air cavity configurations and aerator air demand, smaller air bubbles lead to better agreement with the test results. As far as air concentrations are concerned, the modified model gains by comparison. In the air cavity zone, smaller bubble sizes also provide better matches with the experiments. However, the near-base air concentration remains overestimated downstream from the impact area. The fact that the program user must pre-define a single air bubble size in simulations presumably limits the correct reproduction of near-base air concentrations and of their decay.

A new type of optimized riser structure was proposed, in which a low-emissivity board was inserted into the hollow interlayer of the material to increase the yield of the steel ingot. The insulation effect of different riser heights on the solidification process of steel ingot is numerical simulated. The results show that when the riser height can be reduced from 350 mm to 300 mm, the ingot yield can be increased by 1,92 %. As the number of low-emissivity boards is increases, the riser insulation performance is also increased.

Accurate values for the climatic conditions in an air cavity, hereby called the microclimate, are crucial when calculating and simulating the performance of a ventilated roof and façade system. The climatic stress of its components and their mould and rot potential influence the long-term durability of the roof or façade. A scoping study is conducted to gain an overview on research and the scientific literature on the microclimate of air cavities in ventilated roofing and claddings in Nordic climates. From the body of the research literature, 21 scientific works were of particular interest, and their findings are summarized. The review shows that only a limited number of studies discuss the microclimate of air cavities. Roofs are discussed to a greater and more varied degree compared to façades and air cavities behind solar panels. However, the results cannot be compared and validated against each other to generally describe the microclimate of air cavities, as the surveyed papers approach the subject differently. This knowledge gap indicates that calculations and simulations can be performed without knowing whether the results represent reality. If the structure of ventilated roof and façade systems are only designed based on experience, it can be difficult to be proactive and adapt to future climate changes. Further studies are needed to determine the relation between the exterior climate and the air cavity microclimate, so that future climate predictions can be used to simulate the long-term performance of ventilated roof and façade systems.

• The impact of air cavity on performance of PV-DSF was studied experimentally. • A photovoltaic triple skin facade system was investigated and compared with PV-DSF system. • The impact of perforation ratio was studied on performance of PV-TSF and light transmittance. A new skin of perforated metallic sheet is introduced in the cavity of a photo-voltaic double skin façade (PV-DSF) system for an efficient heat removal from the cavity without losing substantial light into the built space. Quantitative experimental analysis is conducted to evaluate its thermal and electrical performance for various combinations of ventilation modes, air cavities, and perforation ratios. The advantages of Photo-Voltaic Triple Skin Facade system (PV-TSF) over commonly used PV-DSF are also evaluated experimentally. The results showed that naturally ventilated PV-TSF provides lower temperatures and Solar Heat Gain Coefficient (SHGC) with slightly higher power when compared to no ventilation mode in PV-DSF system. The SHGC of the PV-DSF system can be reduced by nearly 4.7% with variation in air cavity (Thickness 50–200 mm); after which no noticeable improvement is observed. In the case of PV-TSF system, SHGC can be reduced by almost 14.7% compared to the PV-DSF system without significant loss of natural daylight into built space. Experimental results also showed that the reduction in perforation ratio from 60% to 20% reduced the SHGC by 3.8% with an average illuminance of 334 lux (minimum perforation, 20%). It was also observed that the addition of a perforated sheet can offset the large air cavity of a PV-DSF system. Therefore, the benefit of the PV-TSF system is profound as compared to PV-DSF. [ABSTRACT FROM AUTHOR]

To realize the high-efficiency acquisition of environmental mechanical energy, traditional triboelectric nanogenerators (TENGs) based on contact-separation consist of two separate triboelectric layers. Their large contact-separation gap increases the overall volume of the device, making it difficult to realize miniaturization and flexibility. This work, therefore, presents a fully enclosed all-in-one-shaped flexible TENG (FEAST) with an air cavity using rubber mixing and high-temperature vulcanization. The air pressure inside the enclosed air cavity facilitates effective contact-separation of the FEAST. The homogeneous integration between the triboelectric layer and the electrode layer enhances structural firmness without using extra spacer materials. The developed FEAST presents excellent mechanical durability even after 10000 cycles. By increasing the active contact area between the triboelectric materials, a maximum peak-peak output voltage, current, and power density of 130 V, 1.1 µA, and 277 mW/m2, respectively, were obtained with an effective stress area of 1 cm2. Moreover, the fully enclosed structure ensures that the output performance is not affected by the external environment. The FEAST was fixed onto the sole of a shoe to demonstrate its applicability in harvesting mechanical energy from human motions. Overall, the developed method provides a simple approach for optimizing the structure of TENGs and is compatible with large-scale manufacturing. [ABSTRACT FROM AUTHOR]

• Heat transfer characteristics of closed and circulated air cavities are obtained. • Design of insulation inside the cavity is proposed for a TW in Western China. • Indoor thermal environment of a CTW room is analyzed. Integrating the design of insulation, heat storage, and solar heating can help to improve indoor thermal environment during winter in Western China. However, insulation at night is often overlooked for Trombe walls (TWs). The present study considers a panel curtain installed in the cavity to enhance the preservation of heat of TWs at night. The effects of the structural parameters related to insulation inside the cavity on the TWs were analyzed in Western China and a design approach for insulation inside the cavity was proposed. In addition, the indoor air temperature of a TW with a built-in panel curtain (CTW) room was analyzed. The results indicate that the heat efficiency in the nighttime can be significantly improved by setting a panel curtain in the air cavity. Low emissivity film should be attached to the closed cavity side. The emissivity of the panel curtain's exterior surface plays an important role in the closed cavity and the effect is more significant with low emissivity. The optimum thickness depends on the climate, i.e., 0.02–0.06 m for a large solar radiant heat loss ratio (SHLR), 0.02–0.05 m for a medium SHLR, and 0.02–0.04 m for a low SHLR. The thickness of the circulated cavity should be larger than 0.07 m, and the effect varies within a small range when the thickness exceeds 0.1 m. A panel curtain can significantly improve the indoor air temperature in a CTW room. [ABSTRACT FROM AUTHOR]

Aside from external cladding pressure loads that are always considered in IGU design, a variety of unique factors must also be addressed when analyzing the structural performance of a slumped IGU with a large air cavity. These factors include the volume of air within the cavity, the stiffness and strength of the outer and inner lites of glass, elevation changes between the glass fabrication facility and the building site, temperature changes over time, fluctuations in barometric pressure, and increased stress on the secondary structural perimeter seal. Appropriate deflection limits for mullions or other elements supporting the IGU must also be established due to the increased stiffness of the IGU resulting from the slumped glass geometry. Engineering challenges related to the design of slumped IGU’s will be highlighted and explained using Nike’s new retail flagship store in New York City, Nike House of Innovation 000, as a case study for a dynamic facade featuring custom carved and slumped insulating glass units. Principal analysis methods, testing procedures, and a summary of the various software tools used to evaluate the slumped IGU’s will be provided. The solutions shown will illustrate how the fundamental design and engineering approach taken for Nike can be successfully applied to other projects that incorporate slumped IGU’s into their facades.

Green façades with an active water regime and the water flowing through the substrate itself are not common. This system reduces the temperatures and incorporates the evapotranspiration, which could be more effective than by the regular green façades. The use of a double-skin façade with a ventilated air cavity can reduce the heat load, but the evapotranspiration can reduce it even more with additional benefits. Green façades could also serve as a key element for reducing the surface temperatures of the insulated metal panels (IMP), which are mostly used as a façade system for production facilities or factories. In this paper, a prototype of a double-skin façade, which consisted of vegetation board from recycled materials and IMP, is tested in a climate chamber to evaluate the function and benefits of such a combination. The outdoor skin is made from board, the surface of which is covered by the rooted succulent plants. Measurement results are represented as a direct comparison of single sunny day surface temperatures with and without a double-skin (green) façade. The use of the green façade reduces the indoor surface temperature of IMP by 2.8 °C in this measurement. The use of water circulation through the outdoor skin reduces the temperature of the vegetation board by 28 °C. This could have a great impact on the microclimate around the façade. Because of the controlled environment and ventilation system in a climate chamber, it is not possible to investigate the airflow and solar chimney effect within the ventilated cavity. In addition, it is complicated to show the potential of microclimate change caused by the wet vegetation surface. For the mentioned reasons, the need to carry out “in situ” tests on a model wall under the real conditions was indicated.

A plunging liquid jet is defined as a moving column of liquid passing through a gaseous headspace, air in our case, before impinging a free surface of receiving liquid pool. The mechanism of air entrainment due to plunging liquid jets is very complex and the complete mechanism of air entrainment is not fully understood so far. The present paper is an unsteady numerical simulation of air entrainment by water jet plunging, using the Volume Of Fluid (VOF) model. The piece wise linear interface construction algorithm (PLIC) for interface tracking is used, to describe the phase distributions of entirely immiscible air and liquid phases. The aim of this work is to investigate the performance and accuracy of the VOF method in predicting the initial impact between the descending jet and water free surface, air entrainment and the developing flow region under free surface. Three scale models based on geometric similarities (Froude number and dimensionless free jet length) are used for validation according to Chanson (2004) experience. The simulations show with accuracy, the air cavity formation steps, caused by the initial jet impact, its deep stretching under the pool free surface, until breakdown due to the shear created by a toroidal vortex. In terms of, air entrainment estimation, bubble dispersion and radial distribution of air volume fraction, large-scale models present a good agreement with the experience. However, for the smallest scale model, the results lead to suggest that air entrainment is governed by more parameters than the geometric similarities.

In order to improve the explosion-proof, puncture-proof and safety performance of tires, a new type of modular deformable tires which can be used in complex road conditions has been put forward. The main innovation is the absence of so-called inner tubes and the modular design of the tire — which mainly consist of six petal-shaped connecting blocks and wheel frames. Firstly, this paper analyzes the structure and working principle of the tire. On this basis, the mechanical modeling of the tire under driving and braking conditions has been established. At last, through ADAMS software, the dynamic simulation of this tire under four circumstances of driving, accelerating, decelerating and braking has been carried out, and the response characteristic curves have been obtained The simulation results show that the force transmission performance of the modular deformable tire is rather good under the above four conditions. The simulation results provide a theoretical foundation and guidance for the structural design of new modular deformable tires. [ABSTRACT FROM AUTHOR]

The study of water entry cavity and the analysis of load characteristics are hot topics in water entry research. The coupled Euler–Lagrange method is used to carry out simulation research on the water entry process of a cylinder. Aiming at the water vapor mixing phenomenon caused by structure slamming on the water at the initial time of water entry, the slamming load is further studied by correcting the sound speed in the water. The differences between the calculated results obtained by adjusting the number of units in the numerical simulation prove the convergence of the numerical method. Water entry experiments of a cylinder were carried out, and the results are in good agreement with the simulation data. The motion state simulation and analysis are carried out for the process of water entry with different initial speeds and angles. The changes in the structure’s positions, air cavities, and slamming loads are obtained. The rule of slamming pressure with the water entry angle and the relationship between pressure and acceleration are determined. [ABSTRACT FROM AUTHOR]

A quad recurrence Dielectric Resonator antenna intended for the remote correspondence with a working recurrence of 2.52GHz, 4.68GHz, 5.53GHz and 6.61GHz. The radiator is a air cavity based resonator with high dielectric constant estimation of 22 by means of the rectangular opening in the ground structure. The opening in the ground plane is scratched in order to encourage the force structure from the excitatory to the radiator. The general component having a size of 100mm×35mm×0.8mm. It is having quad recurrence of activity at the frequencies of 2.52GHz, 4.68GHz, 5.53GHz and 6.61GHz with an gain of 7.49dB, 5.77dB, 4.81dB and 12.72dB individually. Economically accessible 3D test system Ansys HFSS programming has been utilized to plan the proposed antenna. [ABSTRACT FROM AUTHOR]

In this paper, we propose a diplexer design method and present the design result using it. Along with a series of synthesis processes of a filter, it indicates the limitations of the traditional process. To overcome the limitations, two five-stage Chebyshev interdigital band pass filters are designed with parameters of resonance frequency, coupling coefficient between resonators, and external quality factors of input/output including the antenna connection obtained through Electromagnetic simulation from the beginning of the design. The tuning direction of the initial design result is determined using the internal port tuning method, and the result is reflected to the Electromagnetic simulation. Therefore, rapid optimization is possible. The final design of the diplexer had an insertion loss of less than 0.5 dB, return loss of less than 18 dB, and more than 80 dB of isolation at the target frequency band. [ABSTRACT FROM AUTHOR]

• The vibroacoustic interaction between a flexible membrane backed by acoustic cavity is investigated. • Traditional and alternative methodologies for the vibroacoustics analysis are compared. • The alternative approach showed superiority over the traditional one in addressing numerical challenges. • The roles of cavity depth and membrane stiffness on the vibroacoustic behavior are explored. • Propagating and localized vibroacoustic modes are identified. This paper investigates a vibroacoustic model consisting of a flexible rectangular membrane backed by an acoustic air cavity of large lateral extent. A traditional methodology (termed Approach I) for analyzing the interaction between the acoustic airfield in the cavity and the flexible membrane is initially revisited and employed. In this approach, the transversal deformation of the mid-membrane is represented as an infinite series of eigenfunctions (normal modes) that satisfy the clamped boundary conditions for the in-vacuo membrane, regardless of the presence of the cavity. However, numerical challenges and limitations are encountered in obtaining direct insights into system characteristics, as this method heavily relies on matrix inversions and computing the roots of determinants. These operations can be computationally expensive and prone to inaccuracies and numerical instabilities, particularly when dealing with high-dimensional, non-sparse (dense) and nearly singular matrices. To overcome these limitations, an alternative methodology (termed Approach II) is proposed, which enables a precise analysis of the acoustically forced membrane and provides explicit expressions for the steady-state response, mode shapes, governed by a single transcendental characteristic equation for determining the vibroacoustic natural frequencies. Through a comparative analysis, we demonstrate the effectiveness and reliability of the proposed approach, showcasing its potential advantages over the traditional method in addressing numerical challenges. The influence of cavity depth on the vibroacoustic natural frequencies is examined across various levels of membrane stiffness, including low, intermediate, and high values. The analysis reveals the presence of both softening and hardening effects with respect to the in-vacuo case, suggesting that the air pressure plays a dual role in the system, i.e., influencing both the overall stiffness and inertia. The vibroacoustic membrane mode shapes exhibit significant deviations for soft and intermediate-stiff membranes but resemble in-vacuo mode shapes for stiff membranes, with the resemblance dependent on the selected cavity depth. Additionally, two qualitatively distinct mode families for the acoustic pressure, namely, propagating, and localized modes, are identified. The propagating modes are spatially extended and are characterized by the deformation of the volume of the medium, rendering them volume modes. In contrast, the localized modes are distinguished by localized vibrations occurring in the near field close the membrane surface, without significant energy transport or sound wave propagation in the cavity; as a result, they can be regarded as surface modes. The proposed methodology reveals features common to more complex vibroacoustic systems and offers a comprehensive and efficient approach for predictively designing the dynamics of such systems. [ABSTRACT FROM AUTHOR]

The present work combines the properties of sonic crystal (SC), locally resonant sonic crystal (LRSC) and porous material in the triple panel to increase the overall sound transmission loss through the combined structure. SC is a periodic structure which is mainly used for sound reduction in a particular frequency range. In the present work, sound transmission loss through the triple panels is investigated using an analytical method. Finite element simulations are also performed using acoustic structure interaction to predict sound transmission loss. The simulation predictions are validated by the analytical results. Multiple panels separated by the air gaps offer high sound reduction due to multiple reflections and discontinuities in the path of wave propagation. However, due to the 1D periodic structure made by multiple panels, there can be sudden losses in the sound attenuation, also referred to Bragg's dip in the sound transmission loss curve. The results show that there are two types of sudden dips in sound transmission loss i.e. Bragg's dip and dips due to the panel vibrations. To get rid of sudden dips in sound transmission loss, a porous material is filled in the air cavities. It is found that insertion of porous material in the air cavities between the triple panels does not alter the sound transmission loss curve except at certain frequencies. For enhancement of sound transmission loss, SC and LRSC are inserted along with glass wool in the triple panel. It is found that the panel with SC-glass wool assembly performs well in a specific frequency region around Bragg's frequency whereas the panel with LRSC-glass wool assembly performs better in low frequency region as well as in high frequency region. [ABSTRACT FROM AUTHOR]

For early-stage glottic cancers, intensity-modulated radiation therapy (IMRT) has been shown to have comparable local control to 3D-conformal radiotherapy with the advantage of decreased dose to the carotid arteries. The planning target volume (PTV) for early glottic cancers typically includes the entire larynx, plus a 3 to 5 mm uniform margin. The air cavity within the larynx creates a challenge for the inverse optimization process as the software attempts to "build up" dose within the air. This unnecessary attempt at dose build-up in air can lead to hot spots within the rest of the PTV and surrounding soft tissue. We hypothesized that removal of the air from the PTV would decrease hot spots and allow for a more homogeneous plan while still maintaining adequate coverage of the PTV. We analyzed 20 consecutive patients with early-stage glottic cancer, T1-2N0, who received IMRT at our institution from April 2015 to December 2016. Each patient received 63 to 65.25 Gy in 2.25 Gy per fraction. Two plans were created for each case: one in which the PTV included the laryngeal air cavity and one in which the air cavity was subtracted from the PTV to create a new PTV-air structure. Dosimetric variables were collected for PTV-air structure from both IMRT plans, including V100%, D98% D2%, and D0.2%. Dosimetric variables for spinal cord and the carotid arteries were also recorded. Homogeneity index (HI) defined as D98/D2 was calculated. Two-sided t-tests were used to compare dosimetric variables. The median PTV volume was 69.9 cc (standard deviation [SD] ± 28.7 cc) and the median air cavity volume removed was 11.0 cc (SD ± 3.4 cc). A 2-sided t-test revealed a statistically significant decrease in max dose (112.7% vs 108.8%, p value = 0.0002) and improvement of HI (0.93 vs 0.91, p value = 0.0023) for the PTV air in the IMRT plan optimized for PTV air, which had air excluded, compared to the IMRT plan optimized for PTV with air included. There was no significant worsening of PTV-air coverage or significant increase in doses to the organs at risk (OARs). The removal of the air cavity from the PTV for early-stage glottic cancers does not compromise PTV coverage or sparing of OARs and can result in a more homogeneous IMRT plan. A more homogeneous plan has the potential to reduce treatment morbidity, although further study is warranted to investigate the clinical impact of air cavity removal from the PTV. [ABSTRACT FROM AUTHOR]