Actual Absorption Research Articles

Comparative analysis of the performance of Thin Spray-on Liner with shotcrete and mesh support

In order to study the effect of different surface protection components, such as Thin Spray-on Liner (TSL), in the support system of prestressed bolts on the critical rock mass, based on the similarity theory, physical modeling tests were designed and carried out for the support of the critical rock mass by the combination of NPR bolts and PR bolts with three types of surface protection components, such as TSL, sprayed concrete, and metal mesh, respectively. The test results show that the three types of surface protection components can significantly increase the threshold value of crack development of the critical rock specimen and effectively improve the peak bearing capacity of the critical rock body, and at the same time, the NPR bolts with higher strength and elongation have a more significant effect on the improvement of the peak bearing capacity of the critical rock specimen. In addition, TSL and spray-mixed support and specimen surface can realize close fit, in the loading of the early support response is more timely, in the late loading, compared with the spray-mixed material in the rupture of debris collapse, TSL in the occurrence of tearing can still be tightly adhered to the specimen proximity surface of the rock specimen, to prevent specimen debris fall. For the phenomenon of TSL coating rupture in the experiments, the energy balance equation was established to analyze the connection between the actual energy absorption effect and the theoretical value of the combination of TSL and bolts under the pre-stressed bolts support system, and it was found that the combination of pre-stressed bolts and TSL greatly improved the actual energy absorption effect of the support system as a whole, and the analytical results of the various experimental subgroups showed better results than the theoretical values. The analysis results of the subgroups show a good fit.

The two-cavity method for characterizing acoustical materials-an interlaboratory study

The study focuses on understanding the sound absorption and transmission characteristics of porous acoustical materials, which are determined by two key parameters independent of material thickness: characteristic impedance and propagation constant. These parameters can be characterized by testing a porous sample concept in a normal incidence impedance tube using either the two-thickness or the two-cavity method. In the two-thickness method, two samples of varying thicknesses are required. In contrast, the two-cavity method requires testing one sample at two air cavity depths. This method is particularly advantageous for materials that are costly or challenging to fabricate. This interlaboratory study evaluates the variability of characteristic properties determined using the two-cavity method. Porous acoustical materials were additively manufactured and tested in the Liner Technology Facility at NASA Langley Research Center and the Mechanics, Acoustics and Dynamics Lab (MADLab) at Michigan Technological University. The characteristic properties, derived from various cavity depth combinations, were used to predict the sound absorption curves of the sample with a rigid backing. These predictions were then compared with actual experimental absorption curves. The findings indicate that both the combinations of cavity depths and the sample's static airflow resistivity significantly influence the accuracy of the deduced properties.

Improving physical properties, microstructure and actual carbon sequestration of steel slag based autoclaved aerated concrete by accelerated carbonation

This study presents an autoclaved aerated concrete (AAC) with steel slag (SS) as carbonate-able binder. The traditional autoclaving process was augmented with a carbonation stage to improve the physical properties, microstructure and actual carbon sequestration of steel slag based autoclaved aerated concrete (SS-AAC). The macroscopic and microscopic test results showed that the carbonation process stimulated the reactivity of SS to generate gel products, allowing the additional formation of tobermorite during the autoclaving process. Under the synergistic positive effect of the densification-induced micro-pore refinement caused by calcium carbonate precipitation and the excellent gas permeability of AAC, the intervention of carbonation process resulted in SS-AAC with higher compressive strength, more homogeneous carbonation, and more outstanding actual CO2 absorption efficiency. The research provides a potential method for preparing high-volume solid waste AAC with large-scale CO2 utilization to encourage the concrete sector to adopt a sustainable stance.

Enhancing microwave absorption via ion exchange-regulated metal elemental-alloy transition behavior

Metal-organic frameworks (MOFs) are considered as suitable candidates for excellent microwave absorption (MA) materials. However, the influence of the transition behavior from metal to alloy dominated by the metal ion ratio and the accompanying multi-phase coexistence model on the MA mechanism is unclear. This study successfully prepared a series of porous electromagnetic composite materials through ion-exchange in-situ pyrolysis synergistic strategy. The results indicate that the modulation of the Fe/Co ion ratio can easily manipulate the phase transition from Co metal to FeCo alloy-cobalt ferrite and the crystal defects within. The state of metal/alloy coexistence obtained at a low ion exchange degree has the highest concentration of vacancies, which is conducive to wideband absorption (6.03 GHz) and efficient loss (−67.44 dB) of MA performance. In contrast, the MA performance of samples at medium/high ion exchange degrees is not ideal. In addition, the application prospects of this material were demonstrated by simulating the actual absorption situation using radar cross-section. In summary, this work reveals the intrinsic relationship between the phase evolution behavior determined by the ion exchange degree in MOF derivatives and the electromagnetic performance, as well as the MA mechanism, providing a new reference for the preparation and design of outstanding MA materials.

Adsorption of Phosphate by Two-Step Synthesis of Ceramsite from Electrolytic Manganese Residue/Dredged Sludge.

Carrying out research on the management of electrolytic manganese residue (EMR) is necessary to maintain the environment and human health. The dredged sludge (DS) and water hyacinth (WH) generated from dredging projects are potential environmental threats, and therefore suitable methods need to be found for their treatment. In this study, ceramsite was prepared by a two-step low-temperature firing method using DS and EMR as raw materials, WH as a pore-forming additive, and aluminate cement as a binder for the adsorption of phosphorus from wastewater. The optimal ratio and process parameters of the ceramsite were determined by mechanical and adsorption properties. The static adsorption experiments were conducted to study the effect of ceramsite dosage and solution pH on the removal of phosphorus. At the same time, dynamic adsorption experiments were designed to consider the influence of flow rate on its actual absorption effect, to explore the actual effect of ceramsite in wastewater treatment, and to derive a dynamic adsorption model that can provide technical support and theoretical guidance for environmental management.

Урал и Украина в системе межрегиональных противоречий 1920-х — 1930-х гг. (продолжение)

The study continues a series of articles devoted to the problem of interregional economic contradictions between the Urals and the Ukraine in the USSR during the interwar period. In the second part of the work, the author examines the trends in the territorial organization of the Soviet ferrous metallurgy around the Urals and the Ukraine in the context of changes in the economic, political and social conjuncture occurred in the wake of the October Revolution. These trends were expressed in a shift in the location of the productive forces of the Soviet ferrous metallurgy to the western borders of the USSR, with their predominant concentration in the Ukraine. At the same time, in comparison with pre-revolutionary times, this shift was more pronounced, which was caused by the crisis phenomena accompanying the restoration of the Ural industry in the 1920s. The latter were caused by the inability to preserve the technology of charcoal metallurgy in the region in a pre-revolutionary volume and form. Attempts to adapt the Ural metallurgy to the existing conditions without structural technological changes proved unsuccessful and led to the threat of its actual absorption by the Ukrainian production through the organization of a union-wide metallurgical syndicate dominated by Ukrainian trusts. This led to the intensification of regionalism tendencies in the Urals, aggravated by its economic contradictions with Siberia and manifested during the mineralization of the Ural fuel balance with coal from the Kuznetsk basin. Against the background of the «metal famine» unfolding in the country, the tendency to concentrate metallurgical production in the Ukraine predetermined the opposition not only of the industrial Urals, but also of the central government, which would soon lead to a surge of regionalism tendencies in the Ukraine as well.

Research on intensity–difference squeezing enhancement of phase-sensitive amplifier based on coherent feedback

The intensity-difference squeezed state is an important concept in quantum optics, which is not only of great significance for fundamental research in quantum physics, but also an important quantum resource in the fields of quantum communication, quantum computing, and quantum precision measurement. The optical parametric amplifier based on atomic four-wave mixing is one of the most effective means to achieve intensity-difference squeezed light. However, due to the absorption loss of atomic vapor in the light field, the output squeezing still needs improving. By feeding the non-classical optical field from the optical parametric amplifier back to the input port, the quantum characteristics of its output optical field can be enhanced. However, the intensity-difference squeezing enhancement from a phase-insensitive amplifier is experimentally realized based on coherent feedback control. The intensity-difference squeezing enhancement of the phase-sensitive amplifier has not been discussed. In this work, a two-port coherent feedback-controlled phase-sensitive amplifier is analyzed theoretically. The dependence of the intensity-difference squeezing, respectively, on the feedback intensity, the intensity gain of the optical parametric amplifier, and the losses of the system are investigated. For the ideal case in which the losses of the system are ignored, infinite squeezing can be achieved by adjusting the strength and phase of feedback. Considering the actual atomic absorption losses, squeezing enhancement can also be achieved over a wide range of intensity gains within a certain feedback intensity range. In addition, the squeezing enhancement is quite efficient for the medium intensity gain range. The intensity-difference squeezing enhancement strongly depends on the absorption loss of atomic vapor. The smaller the absorption loss, the more significant the squeezing enhancement effect is. Furthermore, the experimental feasibility of this scheme is also considered in detail. Our research can provide useful references for achieving high-quality non classical light fields in experiment, which may find applications in quantum information processing and quantum precise measurement.

An Investigation of Modular Composable Acoustic Metamaterials with Multiple Nonunique Chambers.

To make the sound absorber easy to fabricate and convenient for practical application, a modular composable acoustic metamaterial with multiple nonunique chambers (MCAM-MNCs) was proposed and investigated, which was divided into a front panel with the same perforated apertures and a rear chamber with a nonunique grouped cavity. Through the acoustic finite element simulation, the parametric studies of the diameter of aperture d, depth of chamber T0, and thickness of panel t0 were conducted, which could tune the sound absorption performances of MCAM-MNCs-1 and MCAM-MNCs-2 for the expected noise reduction effect. The effective sound absorption band of MCAM-MNCs-1 was 556 Hz (773-1329 Hz), 456 Hz (646-1102 Hz), and 387 Hz (564-951 Hz) for T = 30 mm, T = 40 mm, and T = 50 mm, respectively, and the corresponding average sound absorption coefficient was 0.8696, 0.8854, and 0.8916, accordingly, which exhibited excellent noise attenuation performance. The sound absorption mechanism of MCAM-MNCs was investigated by the distributions of the total sound energy density (TSED). The components used to assemble the MCAM-MNCs sample were fabricated by additive manufacturing, and its actual sound absorption coefficients were tested according to the transfer matrix method, which demonstrated its feasibility and promoted its actual application.

MOFs-derived Co/C nanoparticle embedded in N, S co-doped graphene for superior electromagnetic wave absorption capacity

Due to their physicochemical properties, the three-dimensional Metal-organic frameworks (MOFs) derived composites show great potential as electromagnetic wave (EMW) absorbers. However, poor impedance matching limits their actual EMW absorption performance. Composite materials that combine magnetic and dielectric losses offer a potential solution to enhance impedance match and significantly improve microwave absorption. In this work, a novel N,S-GS/Co/C composite was fabricated via a solvothermal method and a subsequent pyrolysis process to introducing nitrogen and sulfur co-doped graphene (N,S-GS) into Co-MOF. By co-doping nitrogen and sulfur, abundant defects and disordered sites were introduced on graphene, which stimulate interfacial polarization and dipole polarization. The minimum reflection loss (RL) of the sample obtained by pyrolysis at 600 °C is −68.8 dB at 9.7 GHz. Simultaneously, the thickness is 2.51 mm, and the effective absorption bandwidth (EAB) can reach 3.04 GHz. Its excellent EMW absorption performance is mainly attributed to interfacial polarization, multiple reflections, dipole polarization, magnetic resonance and eddy current loss. Accordingly, the N,S-GS/Co/C composite is convinced to be a competent candidate among EMW absorbers with high absorption intensity.

Analysis of Influencing Factors for Stackable and Expandable Acoustic Metamaterial with Multiple Tortuous Channels.

To reduce the noise generated by large mechanical equipment, a stackable and expandable acoustic metamaterial with multiple tortuous channels (SEAM-MTCs) was developed in this study. The proposed SEAM-MTCs consisted of odd panels, even panels, chambers, and a final closing plate, and these component parts could be fabricated separately and then assembled. The influencing factors, including the number of layers N, the thickness of panel t0, the size of square aperture a, and the depth of chamber T0 were investigated using acoustic finite element simulation. The sound absorption mechanism was exhibited by the distributions of the total acoustic energy density at the resonance frequencies. The number of resonance frequencies increased from 13 to 31 with the number of layers N increasing from 2 to 6, and the average sound absorption coefficients in [200 Hz, 6000 Hz] was improved from 0.5169 to 0.6160. The experimental validation of actual sound absorption coefficients in [200 Hz, 1600 Hz] showed excellent consistency with simulation data, which proved the accuracy of the finite element simulation model and the reliability of the analysis of influencing factors. The proposed SEAM-MTCs has great potential in the field of equipment noise reduction.

Comparison of thermal performance in solution heat exchangers with different chevron angles in absorption system

In this study, a solution heat exchanger (SHEX), one of the components of LiBr–H2O absorption refrigeration, is selected as a 60° and 30° chevron angle brazing-type plate heat exchanger, and its performance is experimentally investigated. The result shows that as the mass flow rate of the strong solution side increased, the heat transfer rate increased significantly. When the chevron angle is 60° in the SHEX, the overall heat transfer coefficient, j-factor, differential pressure, f-factor, and JF-factor of the solution heat exchanger increased by 86%–149 %, 72%–180 %, 221%–376 %, 220%–378 %, and 16.6%–66.2 %, respectively, compared with the SHEX with a 30°-chevron angle. The SHEX with a 30°-chevron angle shows a 138%–221 % higher performance index than that with a 60°-chevron angle. In addition, the Nusselt number prediction correlation of the SHEX, including various chevron angles and Reynolds numbers, was proposed, which can provide essential information for designing SHEXs in actual absorption systems.

Absorptive noise barrier development

This paper reveals the development of an absorptive, self-supporting noise barrier panel for external applications. Designed for use as a temporary external noise barrier for construction sites and roadside noise barriers. The absorptive noise barrier panel is a module base design that is easy to assemble, disassemble, and re-deploy. The barrier panel utilizes recycled plastic materials, such as milk bottles and other soft plastics, making it one of the most environmentally friendly products. The barrier is manufactured in one process via a unique rotation molding method. It is weather resistant, aesthetically appealing, and offers great design flexibility. Standard size panels are 100 mm thick, by 2000 m wide x 500 mm high. The acoustic design is modeled to achieve NRC 0.85 at 100 mm thick based on an advanced air-flow resistive layer technique combined with an air cavity. The actual sound absorption measurement results are well in line with the predicted modeling. Such a case study potentially uncovers a whole new range of innovative absorptive noise barriers. Further studies and investigations are also recommended.

Properties of waterborne polyurethane chemically modified composite materials and their application in gushing water protection

The absence of organic solutions during the preparation of waterborne polyurethane has resulted in a decline in its overall performance. To address this issue, this study introduces nano zirconia as a modifier to enhance the properties of the polyurethane material. A novel composite material combining waterborne polyurethane and zirconium oxide nanoparticles (ZrO2 NPs) was proposed, and its performance was experimentally analyzed. The particle size of ZrO2@CA is as high as 80 nm, which exceeds the 23 nm of ZrO2@MA and the 21 nm of ZrO2@AA. Transmission electron microscopy reveals that the emulsion droplets in the composite lotion exhibit excellent spherical uniformity and dispersion. Moreover, there is not a significant difference in size between composite lotions with different zirconia contents. Remarkably, even with a zirconia content of only 0.5 wt%, the specimen exhibits high mechanical properties, with the tensile strength increasing from 11.9 MPa to 14.3 MPa and the elongation at break increasing from 560% to 712%. Additionally, a higher doping amount of ZrO2 leads to an increased water absorption rate, with the actual water absorption rate rising from 7% to 14.4%. In practical engineering projects A and B, the initial water output of four holes in engineering A is maintained at 48–580 m3/h. However, as time progresses, the water output gradually decreases, approaching 0 m3/h. In project B, the composite material coating exhibits a tensile strength greater than 15 MPa, reaching 18.26 MPa, which significantly surpasses the performance of the comparison material. Overall, the composite materials demonstrate excellent mechanical and water protection properties, proving to be crucial for practical water inrush protection applications.

Enhancement of sound absorption performance of Helmholtz resonators by space division and chamber grouping

Sound absorption performance of the Helmholtz resonator was enhanced by space division and chamber grouping in this research, which aimed to achieve high sound absorption coefficient and broad absorption band simultaneously. Based on acoustic finite element simulation, it could be found that the effective sound absorption frequency band of multiple divided Helmholtz resonators shifted to high frequency direction and the effective absorption bandwidth rose gradually with the increase of division number Ns from 1 to 24, and the effective sound absorption band of multiple divided and grouped Helmholtz resonators with the certain division number Ns would shift to the high frequency direction gradually and its width was improved normally with the increase of grouping number Gs. Moreover, the multiple divided and grouped Helmholtz resonators with division number Ns = 18 and grouping number Gs = 6 was optimized for the certain practical demand, and the optimal geometric parameters were obtained by the joint simulation method incorporating the finite element simulation and the cuckoo search algorithm. Furthermore, its actual sound absorption coefficients were obtained through sample fabrication by the additive manufacturing and standing wave tube measurement by the AWA6290T, and all the actual sound absorption coefficients in 400–800 Hz were above 0.8 and the average value in this range was up to 0.8729 with limited total thickness of 40 mm. Enhancement of the sound absorption performance of multiple divided and grouped Helmholtz resonators would be favorable to promote the practical applications of acoustic metamaterials in the noise reduction field.

Sound propagation for a low height impulsive source over an absorbing ground

Noise contours around military training areas are calculated by using: a) the measured source strength for the impulsive sources and b) the calculated sound propagation using a representative set of meteorological situations. For high-energy impulsive sounds the source strength is measured at distances beyond 100 meters, where peak levels are below 154 dB. A linear model is used to correct for the sound propagation from the source to the measurement position. In this way a linear source strength is determined that can be used with linear sound propagation models. Previous results showed that the source strengths at higher frequencies (above 250 to 500 Hz) were overestimated when the impulsive source is on the ground. Apparently, the calculated sound propagation over an absorbing ground, used to determine the source strength, is accounting for too much ground effect. Note that the actual meteorology and ground absorption are measured during the measurements. In this paper an impulsive reference source is used at two heights and the sound propagation is measured and calculated at increasing distances. It is shown that the measured ground effect saturates for higher frequencies. Next, an unknown impulsive source was measured and the effect of saturation was demonstrated.

Adjustable Sound Absorber of Multiple Parallel-Connection Helmholtz Resonators with Tunable Apertures Prepared by Low-Force Stereolithography of Photopolymer Resin.

The variable noise spectrum for many actual application scenarios requires a sound absorber to adapt to this variation. An adjustable sound absorber of multiple parallel-connection Helmholtz resonators with tunable apertures (TA-MPCHRs) is prepared by the low-force stereolithography of photopolymer resin, which aims to improve the applicability of the proposed sound absorber for noise with various frequency ranges. The proposed TA-MPCHR metamaterial contains five metamaterial cells. Each metamaterial cell contains nine single Helmholtz resonators. It is treated as a basic structural unit for an array arrangement. The tunable aperture is realized by utilizing four segments of extendable cylindrical chambers with length l0, which indicates that the length of the aperture l is in the range of [l0, 4l0], and that it is tunable. With a certain group of specific parameters for the proposed TA-MPCHR, the influence of the tunable aperture with a variable length is investigated by acoustic finite element simulation with a two-dimensional rotational symmetric model. For the given noise spectrum of certain actual equipment with four operating modes, the TA-MPCHR sample with a limited total thickness of 40 mm is optimized, which is made of photopolymer resin by the low-force stereolithography, and its actual average sound absorption coefficients for the frequency ranges of 500-800 Hz, 550-900 Hz, 600-1000 Hz and 700-1150 Hz reach 0.9203, 0.9202, 0.9436 and 0.9561, respectively. Relative to common non-adjustable metamaterials, the TA-MPCHR made of photopolymer resin can reduce occupied space and improve absorption efficiency, which is favorable in promoting its practical applications in the noise pollution prevention.

Real-Time Experimental Monitoring for Water Absorption Evolution Behaviors of Sandstone in Mogao Grottoes, China

Rock mass has typical pore structure, and the induced coupling effects of fluid and solid matrix appear in the disaster evolution process of deep energy exploitation and overground rock hydration. As a representative case, influenced by the water absorption environment, the surrounding rock and murals of Mogao Grottoes produce hydration diseases, which may be related to unclear interaction mechanisms between the surrounding rock and water. In this study, the self-developed physical experimental system for real-time experimental monitoring was applied to test the water absorption evolution behaviors of sandstone. The experimental results showed that the water evaporation of the rock sample during the process of water absorption could be measured through this well-designed physical experimental system, and the actual water absorption of the rock sample is the difference between the decrease of water in the water storage bucket, measured by the balance and the water evaporation in the process of experiment; by drawing the actual water absorption curve of the rock sample, the time when the water absorption of the rock sample reaches saturation could be determined accurately; and the curve of water absorption with time could be expressed as an exponential function. The experimental techniques and methods in this study provide a feasible research idea for studying the water absorption evolution behaviors and mechanisms of the surrounding rock weathering when it meets water, and have significance for revealing the disease mechanisms of the surrounding sandstone in Mogao Grottoes, China.

Reducing and Delaying Nitrogen Recommended by Leaf Critical SPAD Value Was More Suitable for Nitrogen Utilization of Spring Wheat under a New Type of Drip-Irrigated System

Timely and accurate judgment of the nitrogen nutritional status of crops is the key to develop an optimal nitrogen application strategy. However, the evaluation criteria of nitrogen nutrition and nitrogen application strategies at each growth stage of wheat are not clear for the new type of drip-irrigated spring wheat system, TR6S (where one drip tube serves six rows of wheat, with a row spacing (RS) of 10 cm, inter-block space (IBS) of 25 cm and the lateral spacing (LS) of 80 cm, which achieved a lower drip-tube input and higher profit compared with the traditional planting system in Xinjiang). Therefore, we studied the recommendation mechanism of nitrogen fertilizer in different growth stages of wheat based on the critical SPAD values of leaves under TR6S. We set four nitrogen treatments (N1 (300 kg ha−1), N2 (270 kg ha−1), N3 (240 kg ha−1) and N4 (0 kg ha−1)) during two spring wheat growth seasons. The results revealed that the correlation coefficient (r2) between SPAD (soil plant analysis development) value and plant nitrogen content in the middle of first top leaf (L1-M) of wheat was higher than that in other leaf types and leaf positions under TR6S. A quadratic function relationship existed between a SPAD value of L1-M and grain yield. The critical SPAD values at the jointing, booting, anthesis, early milk, and late milk stages were 37.34, 39.40, 42.25, 45.57, and 35.91, respectively. In addition, through the establishment of the nitrogen application recommendation model for various wheat growth stages based on the critical SPAD value, the recommended optimal nitrogen application rates at jointing, booting, anthesis, early milk, and late milk stages were observed to be 69.4, 80.0, 90.8, 44.0, and 6.0 kg ha−1, respectively. This recommended nitrogen application strategy exhibited a better parallel relationship with the nitrogen nutrition index (NNI) of each growth period than the conventional nitrogen application strategy. Therefore, it was more in line with the actual absorption and utilization of nitrogen in wheat of TR6S. In conclusion, the SPAD values of L1-M could be relatively more accurate to evaluate the nitrogen nutrition status of wheat. Compared to traditional nitrogen application strategy, reducing and delaying nitrogen application, recommended based on the leaf SPAD model, was more suitable for nitrogen utilization under TR6S. The results can be applied in other arid and semiarid regions.

Selected mechanical properties of human cancellous bone subjected to different treatments: short-term immersion in physiological saline and acetone treatment with subsequent immersion in physiological saline

BackgroundPhysiological saline (0.9% NaCl) and acetone are extensively used for storage (as well as hydration) and removal of bone marrow, respectively, of cancellous bone during preparation and mechanical testing. Our study aimed to investigate the mechanical properties of cancellous bone subjected to short-term immersion in saline and acetone treatment with subsequent immersion in saline.MethodsCylindrical samples (Ø6 × 12 mm) were harvested from three positions (left, middle, and right) of 1 thoracic vertebral body, 19 lumbar vertebral bodies, and 5 sacral bones, as well as from 9 femoral heads. All samples were divided into two groups according to the different treatments, (i) samples from the left and middle sides were immersed in saline at 4℃ for 43 h (saline-immersed group, n = 48); (ii) samples from the respective right side were treated with a combination of acetone and ultrasonic bath (4 h), air-dried at room temperature (21℃, 15 h), and then immersed in saline at room temperature (21℃, 24 h) (acetone and saline-treated group, n = 38). All samples were subjected, both before and after treatment, to a non-destructive compression test with a strain of 0.45%, and finally destructive tests with a strain of 50%. Actual density (ρact), initial modulus (E0), maximum stress (σmax), energy absorption (W), and plateau stress (σp) were calculated as evaluation indicators.ResultsBased on visual observation, a combination of acetone and ultrasonic bath for 4 h failed to completely remove bone marrow from cancellous bone samples. The mean values of ρact, σmax, W, and σp were significantly higher in the femoral head than in the spine. There was no significant difference in E0 between non-treated and saline-immersed samples (non-treated 63.98 ± 20.23 vs. saline-immersed 66.29 ± 20.61, p = 0.132). The average E0 of acetone and saline-treated samples was significantly higher than that of non-treated ones (non-treated 62.17 ± 21.08 vs. acetone and saline-treated 74.97 ± 23.98, p = 0.043).ConclusionShort-term storage in physiological saline is an appropriate choice and has no effect on the E0 of cancellous bone. Treatment of cancellous bone with acetone resulted in changes in mechanical properties that could not be reversed by subsequent immersion in physiological saline.

Surrogate modeling of open-celled metal foam sound absorbers with stepwise property gradients

In this paper, we develop a Kriging-based surrogate model to predict the sound absorption performance of open-celled metal foams with user-defined stepwise relative density gradients. An experimentally validated transfer matrix model is used to generate training data capturing the absorption profiles of metal foams with various geometrical parameters. We deploy a spatial analysis method to create influence surfaces around each sample data point and depict its effect on the observed output by using Kriging's basis functions. The surrogate model has an in-built machine learning framework that uses a genetic algorithm and a maximum likelihood function to tune the weights that define these influence surfaces. Using this approach, we successfully developed a data-fed, supervised prediction model that estimates absorption coefficient of a virtual metal foam sample. Post-validation predicted values for unknown sample configurations show satisfactory agreement with their actual absorption coefficients. Finally, we implement the developed metamodel as an iOS application as a potential low-cost tool to reduce testing costs and enable rapid design iterations for acoustic design problems.