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Over the years, the building envelope has evolved from a protective barrier element to a complex filter system capable of optimizing the interactions between the external and internal environments. An efficient envelope reacts flexibly to variable external conditions, minimizing heat losses in the winter season. Therefore, insulating materials play a fundamental role in building's thermal performance. In this scenario, Additive Manufacturing represents an emerging and promising solution for the construction sector. Three-dimensional printing allows the creation of custom geometries, reduces material waste, and automates the construction process. This work aims to compare the thermal performance of a PLA (polylactic acid) 3D-printed block with an internal honeycomb structure whose air cavities are filled with natural and recyclable waste-insulating materials. The selected air cavity filling materials are (i) wood sawdust, (ii) sheep's wool, and (iii) hemp. The thermal behavior of the block with the different filling materials was experimentally tested via Heat Flow Meter (HFM) method in a controlled environment (Hot Box). The results showed that the introduction of waste material significantly improved the thermal performance of the 3D-printed block compared to the case of air cavities. A thermal transmittance (U-value) reduction of up to 57% was obtained. Moreover, the sheep's wool showed the best performance, with a U-value equal to 0.53 ± 0.02 W/m2K, i.e., 18.5% less than the wood sawdust and 19.7% less than hemp. [ABSTRACT FROM AUTHOR]

Abstract Background Both patient-specific dose recalculation and γ passing rate analysis are important for the quality assurance (QA) of intensity modulated radiotherapy (IMRT) plans. The aim of this study was to analyse the correlation between the γ passing rates and the volumes of air cavities (V air) and bony structures (V bone) in target volume of head and neck cancer. Methods Twenty nasopharyngeal carcinoma and twenty nasal natural killer T-cell lymphoma patients were enrolled in this study. Nine-field sliding window IMRT plans were produced and the dose distributions were calculated by anisotropic analytical algorithm (AAA), Acuros XB algorithm (AXB) and SciMoCa based on the Monte Carlo (MC) technique. The dose distributions and γ passing rates of the targets, organs at risk, air cavities and bony structures were compared among the different algorithms. Results The γ values obtained with AAA and AXB were 95.6 ± 1.9% and 96.2 ± 1.7%, respectively, with 3%/2 mm criteria (p > 0.05). There were significant differences (p

Over the years, the building envelope has evolved from a protective barrier element to a complex filter system capable of optimizing the interactions between the external and internal environments. An efficient envelope reacts flexibly to variable external conditions, minimizing heat losses in the winter season. Therefore, insulating materials play a fundamental role in building’s thermal performance. In this scenario, Additive Manufacturing represents an emerging and promising solution for the construction sector. Three-dimensional printing allows the creation of custom geometries, reduces material waste, and automates the construction process. This work aims to compare the thermal performance of a PLA (polylactic acid) 3D-printed block with an internal honeycomb structure whose air cavities are filled with natural and recyclable waste-insulating materials. The selected air cavity filling materials are (i) wood sawdust, (ii) sheep’s wool, and (iii) hemp. The thermal behavior of the block with the different filling materials was experimentally tested via Heat Flow Meter (HFM) method in a controlled environment (Hot Box). The results showed that the introduction of waste material significantly improved the thermal performance of the 3D-printed block compared to the case of air cavities. A thermal transmittance (U-value) reduction of up to 57% was obtained. Moreover, the sheep’s wool showed the best performance, with a U-value equal to 0.53 ± 0.02 W/m2K, i.e., 18.5% less than the wood sawdust and 19.7% less than hemp.

Background: Both patient-specific dose recalculation and γ passing rate analysis are important for the quality assurance (QA) of intensity modulated radiotherapy (IMRT) plans. The aim of this study was to analyse the correlation between the γ passing rates and the volumes of air cavities (Vair) and bony structures (Vbone) in target volume of head and neck cancer.Methods: Twenty nasopharyngeal carcinoma and twenty nasal natural killer T-cell lymphoma patients were enrolled in this study. Nine-field sliding window IMRT plans were produced and the dose distributions were calculated by anisotropic analytical algorithm (AAA), Acuros XB algorithm (AXB) and SciMoCa based on the Monte Carlo (MC) technique. The dose distributions and γ passing rates of the targets, organs at risk, air cavities and bony structures were compared among the different algorithms.Results: The γ values obtained with AAA and AXB were 95.6 ± 1.9% and 96.2 ± 1.7%, respectively, with 3%/2 mm criteria (p > 0.05). There were significant differences (p < 0.05) in the γ values between AAA and AXB in the air cavities (86.6 ± 9.4% vs. 98.0 ± 1.7%) and bony structures (82.7 ± 13.5% vs. 99.0 ± 1.7%). Using AAA, the γ values were proportional to the natural logarithm of Vair (R2 = 0.674) and inversely proportional to the natural logarithm of Vbone (R2 = 0.816). When the Vair in the targets was smaller than approximately 80 cc or the Vbone in the targets was larger than approximately 6 cc, the γ values of AAA were below 95%. Using AXB, no significant relationship was found between the γ values and Vair or Vbone.Conclusion: In clinical head and neck IMRT QA, greater attention should be paid to the effect of Vair and Vbone in the targets on the γ passing rates when using different dose calculation algorithms. [ABSTRACT FROM AUTHOR]

Background: Considering that some vital organs exist in the head and neck region, the treatment of tumors in this area is a crucial task. The existence of air cavities, namely sinuses, disrupt the radiotherapy dose distribution. The study aims to analyze the effect of maxillary, frontal, ethmoid and sphenoid sinuses on radiotherapy dose distribution by Monte Carlo method. Material and Methods: In order to analyze the effect of the cavities on dose distribution, the maxillary, frontal, ethmoid and sphenoid sinus cavities were simulated with (3×3.2×2) cm3 , (2×2×3.2) cm3 , (1×1×1.2) cm3 and (1×1×2) cm3 dimensions. Results: In the analysis of the dose distribution caused by cavities, some parameters were observed, including: inhomogeneity of dose distribution in the cavities, inhomogeneity of dose on the edges of the air cavities and dispersion of the radiations after the air cavity. The amount of the dose in various situations showed differences: before the cavity a 0.64% and a 2.76% decrease, a 12.06% and a 17.17% decrease in the air zone, and a 2.25% and a 5.9% increase after the cavity. Conclusion: The results indicate that a drop in dose before the air cavities and in the air zone occurs due to the lack of scattered radiation. Furthermore, the rise in dose was due to the passage of more radiation from the air cavity and dose deposition after the air cavity. The changes in dose distribution are dependent on the cavity size and depth. As a result, this has to be noted in the treatment planning and MU calculations of the patient.

Air cavities have quite often been used to reduce underground capillary humidity in buildings of heritage value. The design of these cavities is not supported by objective criteria which ensure they work properly. This study aims to present a method for on-site evaluation so as to understand the workings and evaluate the efficiency of the different kinds of cavities found in the Iberian Peninsula. It is a qualitative and semi-quantitative method, which has been specifically designed, based on the formal, construction and performance aspects of such systems. This process is supported by basic instrumentation and a highly accessible tool for calculation, and has been used on-site in more than eight cavities with satisfactory results. Analysis of the data collected has enabled an approach to the air dynamic in the cavities and the evaporation capacity. On the basis of a classification of types (which did not exist before), the simple method for research proposed here allows the evaluation of the functioning of air cavities on-site. A new and basic instrumentation is used which includes evaporimeters to calculate the cavities' capacity of evaporation. [ABSTRACT FROM AUTHOR]

The present experimental study focuses on the passive thermal regulation of electronic devices and concentrator photovoltaic (CPV) systems using phase change material (PCM). Therefore, a fabricated system was attached to a silicon rubber heater to imitate the heat dissipation from electronic devices or CPV cells. Several sets of experiments were performed to investigate the melting of three different PCMs (RT25HC, RT35HC, and RT44HC) at three distinct heat flux values of 2000, 2950, 3750 W/m2. Results revealed that using RT25HC, RT35HC, and RT44HC PCMs decreased the average front wall temperature associated with the electronic component or CPV cells by about 69.8, 80.44, and 74.44 °C when compared to that of the system without PCM. The solidification of RT44HC PCM was studied at different ambient temperatures of 20, 25, and 30 °C. It was noticed that, the time to reach the complete solid phase increases from 407 min to 501, and 585 min when the ambient temperature rises from 20 to 25, and 30 °C, respectively. Finally, the effect of cavity formation inside solid PCMs due to solidification shrinkage on their cooling performance was investigated. Results indicated that air cavities formation inside solid PCMs has insignificant effect on their cooling performance. • Cooling of electronic components and CPV systems using PCM based heat sinks. • Heat transfer characteristics during melting and solidification of different types of PCMs. • PCMs achieved a considerable reduction in the temperature of electronic components and CPV cells. • The time required to reach the complete solid phase rises with the increase in the ambient temperature. • Air cavities formation inside solid PCMs has insignificant effect on their cooling performance. [ABSTRACT FROM AUTHOR]

Background: Considering that some vital organs exist in the head and neck region, the treatment of tumors in this area is a crucial task. The existence of air cavities, namely sinuses, disrupt the radiotherapy dose distribution. The study aims to analyze the effect of maxillary, frontal, ethmoid and sphenoid sinuses on radiotherapy dose distribution by Monte Carlo method. Material and Methods: In order to analyze the effect of the cavities on dose distribution, the maxillary, frontal, ethmoid and sphenoid sinus cavities were simulated with (3×3.2×2) cm³, (2×2×3.2) cm³, (1×1×1.2) cm³ and (1×1×2) cm³ dimensions. Results: In the analysis of the dose distribution caused by cavities, some parameters were observed, including: inhomogeneity of dose distribution in the cavities, inhomogeneity of dose on the edges of the air cavities and dispersion of the radiations after the air cavity. The amount of the dose in various situations showed differences: before the cavity a 0.64% and a 2.76% decrease, a 12.06% and a 17.17% decrease in the air zone, and a 2.25% and a 5.9% increase after the cavity. Conclusion: The results indicate that a drop in dose before the air cavities and in the air zone occurs due to the lack of scattered radiation. Furthermore, the rise in dose was due to the passage of more radiation from the air cavity and dose deposition after the air cavity. The changes in dose distribution are dependent on the cavity size and depth. As a result, this has to be noted in the treatment planning and MU calculations of the patient. [ABSTRACT FROM AUTHOR]

Air cavities, i.e. air layers developed behind cavitators, are seen as a promising drag reducing method in the maritime industry. Here we utilize the Taylor–Couette (TC) geometry, i.e. the flow between two concentric, independently rotating cylinders, to study the effect of air cavities in this closed setup, which is well-accessible for drag measurements and optical flow visualizations. We show that stable air cavities can be formed, and that the cavity size increases with Reynolds number and void fraction. The streamwise cavity length strongly depends on the axial position due to buoyancy forces acting on the air. Strong secondary flows, which are introduced by a counter-rotating outer cylinder, clearly decrease the stability of the cavities, as air is captured in the Taylor rolls rather than in the cavity. Surprisingly, we observed that local air injection is not necessary to sustain the air cavities; as long as air is present in the system it is found to be captured in the cavity. We show that the drag is decreased significantly as compared to the case without air, but with the geometric modifications imposed on the TC system by the cavitators. As the void fraction increases, the drag of the system is decreased. However, the cavitators itself significantly increase the drag due to their hydrodynamic resistance (pressure drag): In fact, a net drag increase is found when compared to the standard smooth-wall TC case. Therefore, one must first overcome the added drag created by the cavitators before one obtains a net drag reduction. [ABSTRACT FROM AUTHOR]

Purpose: To perform comparative planning for intensity-modulated radiotherapy (IMRT) and proton therapy (PT) for malignant pleural mesothelioma after radical surgery. Methods and Materials: Eight patients treated with IMRT after extrapleural pleuropneumonectomy (EPP) were replanned for PT, comparing dose homogeneity, target volume coverage, and mean and maximal dose to organs at risk. Feasibility of PT was evaluated regarding the dose distribution with respect to air cavities after EPP. Results: Dose coverage and dose homogeneity of the planning target volume (PTV) were significantly better for PT than for IMRT regarding the volume covered by >95% (V95) for the high-dose PTV. The mean dose to the contralateral kidney, ipsilateral kidney, contralateral lung, liver, and heart and spinal cord dose were significantly reduced with PT compared with IMRT. After EPP, air cavities were common (range, 0–850 cm3), decreasing from 0 to 18.5 cm3/day. In 2 patients, air cavity changes during RT decreased the generalized equivalent uniform dose (gEUD) in the case of using an a value of < − 10 to the PTV2 to <2 Gy in the presence of changing cavities for PT, and to 40 Gy for IMRT. Small changes were observed for gEUD of PTV1 because PTV1 was reached by the beams before air. Conclusion: Both PT and IMRT achieved good target coverage and dose homogeneity. Proton therapy accomplished additional dose sparing of most organs at risk compared with IMRT. Proton therapy dose distributions were more susceptible to changing air cavities, emphasizing the need for adaptive RT and replanning. [Copyright &y& Elsevier]

Abstract: Finite element analyses using COMSOL have been carried out to study the heat transfer behavior and storing capacity of concrete walls with air cavities, and to explore the possibility of using one-layer and two-layer one-dimensional models with equivalent thermal conductivity and mass density to represent the effect of concrete walls with air cavities in a building energy simulation. Three typical wall geometries were chosen and both stationary and transient analyses have been carried out. The stationary analyses were performed first to find the equivalent thermal conductivity which was further used in the transient analyses to fit the equivalent mass density. Because of the presence of air cavities the equivalent thermal conductivities are always smaller than the bulk thermal conductivity. However, for the one-layer model an exaggerated equivalent mass density as high as two times the bulk density should be used in order to simulate the heat storing capacity of the concrete walls with air cavities. The values of the fitted equivalent mass density are strongly dependent on the wall thickness. [Copyright &y& Elsevier]

In the treatment of lung cancer using the radiotherapy technique of intracavitary brachytherapy with an192Ir source, the lung is normally assumed to be entirely composed of a homogenous mass of soft tissue. The aim of this study is to investigate whether there is the possibility that the air cavities in the lung influence the dose delivered to the lung at a prescribed distance from the source. The Monte Carlo code MCNP-4A was used to model the dose delivered by both192Ir and198Au as a function of treatment medium, density and composition, photon energy, and distance from the source. The suitability of MCNP-4A for this study was tested by producing depth-dose profiles for photons in water and comparing these to calculated profiles produced using well-documented methods. [ABSTRACT FROM AUTHOR]

We have implemented a novel high-Q low temperature co-fired ceramic (LTCC) stripline resonator by including air cavities in the LTCC substrate for millimeter-wave applications. This new resonator presents Q-factor of 290 and total loss of 0.03 dB/mm at 34.8 GHz, and they are improved by 138% and 58%, respectively, compared to the conventional one. Its dielectric loss is analyzed as small as 0.0003 dB/mm at the resonant frequency, and that improved by a factor of 120 compared to the conventional one. [ABSTRACT FROM PUBLISHER]

The concept of using additive manufacturing as a method to construct heterogeneous substrates from a single building material via stereolithography is introduced. The dynamic variation of air cavities within the bulk material is used to control the effective permittivity of the host medium. The digitally driven layer process enables full three‐dimensional variation of the local permittivity. The high resolution of stereolithography enables sub‐millimetre control of air inclusion features. Measurements of the effective permittivity with different air fractions have been compared to analytical results. [ABSTRACT FROM AUTHOR]