Determination of Vibroacoustic Parameters of Polyurethane Mats for Residential Building Purposes

This paper is aimed at investigating the use of polyurethane mats, usually used as ballast mats, for residential building purposes. Ballast mats have features that may improve the vibroacoustic comfort in residential rooms. Their strength is certainly an advantage, along with vibration and acoustic insulation. However, the problem that an engineer has to deal with, for example in modeling these types of mats, is a limited knowledge of the material’s vibroacoustic parameters. Knowledge of these may be useful for residential buildings. This paper presents measurements of the vibroacoustic parameters of polyurethane mats, together with a suitable methodology and some results and analysis. The two main material parameters responsible for vibroacoustic protection were measured: the dynamic stiffness, which is related to the acoustic properties of the material, and the critical damping coefficient, which is obviously responsible for damping. The measurement methodology is clearly described. A total of five polyurethane materials with different densities were tested. It was possible to identify a relationship between the material density and the vibroacoustic parameters, which could offer an indication of which material to use, depending on the stimulus affecting a human in a given location.

Supervised Learning in image enhance from electron microscopy inversion results

In Nondestructive testing there is a variety of applications in Material Science, where the specimen is imaged by an Electron Microscope and then by image inversion, informationis extracted for the material interior. This type of information might contain noise either by the imaging procedure or by the numerical part of the inversion. We present a method that can improve the interior density results of an inversed material from a series of Scanning Electron Microscope (SEM) images. For this method, the material density can contain some discontinuity, such as regions where it is dense and regions where there are voids.The proposed method directly stands on the Bayesian learning framework, adopting Gaussian Stochastic Processes (GSPs). Two test sample cases that contain some discontinuities in the density are tested. We also provide a comparison between two different GSP modelling approaches; one is a typical GSP and the other accounts for discontinuity, by introducing hyperparameters. The GSP method gives reconstructed data in reasonable agreement with the known original density distribution, giving confidence that the method can be applied to experimentally obtained SEM images.

Особенности применения теоремы вириала для магнитных систем с квазибессиловыми обмотками

The article shows that in a magnetic system with a thin-walled balanced winding close to a force-free one, a significant increase in the parameter θ=WM γ/M σМ , is possible, which, according to the virial theorem, characterizes the ratio of the energy of the magnetic system WM to the weight of equipment with a material density γ, where under the action of electromagnetic forces there appears a mechanical stress σМ. In a quasi-force-free magnetic system, the main part of the winding is in a state of local equilibrium, and only a relatively small part of the equipment is subject to stress. This part determines the weight of the entire system, and this weight can be minimized. The configurations of balanced thin-walled windings are developed, at the boundaries two boundary conditions are fulfilled simultaneously - the absence of the induction component normal to the boundary and the constancy of the product of induction and radius. The authors consider an example of a system consisting of a main part - a sequence of balanced "transverse" modules in the form of flat discs and end parts, consisting of a combination of "transverse" modules and "longitudinal" ones, having the form of rings elongated along the axis with balanced end parts. It is shown that in the system under consideration, the characteristic dimensionless parameter θ with an unlimited increase in the number of elements of the main part can reach a value of about 24, and when the number of these elements changes within 20 - 40, it changes from 6 to 9.

New Methods, New Opportunities. Recent Advances in Archaeological Science and their Application in Arms and Armour Studies

The jubilee of Professor Andrzej Nadolski and Professor Marian Głosek is an excellent opportunity for discussing some most recent methods of technological analyses in archaeology and their applications in arms and armour studies. New opportunities are offered by Computed Tomography (CT) and by Neutron Imaging (NI). The latter is insensitive to material density; therefore details that are not detectable by X-ray or CT can be seen in NI images. A considerable progress has also been made in the field of radiocarbon dating. Yet another field are analyses of the chemical composition of smelting slag and slag inclusions in ferrous artefacts. Such analyses can be used for identification of smelting processes, as well as for provenance studies. These take a number of variables into consideration (major and trace elements, as well as isotopic ratios). What seems to be especially promising in provenance studies are isotopes of osmium (Os).

The Effect of Density on the Delicate Balance between Structural Requirements and Environmental Issues for AAC Blocks: An Experimental Investigation

Among other construction materials, Autoclaved Aerated Concrete (AAC) offers several advantages to face the pressing need to build more sustainable and energy-efficient buildings. From the building side, the low thermal conductivity of AAC allows the realization of energy-efficient building envelopes, with interesting savings in terms of heating and cooling processes. The equilibrium between structural performances (related to safety issues) and energy efficiency requirements is, however, very delicate since it is strictly related to the search for an “optimum” material density. Within this context, this work discusses the results of wide experimental research, showing the dependency of the most important mechanical properties (compressive strength, elastic modulus, flexural strength and fracture energy) from density, as well as the corresponding variation in thermal conductivity. In order to identify the better compromise solution, a sort of eco-mechanical index is also defined. The big challenge for future researches will be the improvement of this eco-mechanical index by working on pore structure and pore distribution within the material without significantly reducing the density and/or by improving the strength of the skeleton material.

A critical assessment of interatomic potentials for modelling lattice defects in forsterite Mg$$_2$$SiO$$_4$$ from 0 to 12 GPa

Five different interatomic potentials designed for modelling forsterite Mg$$_2$$ 2 SiO$$_4$$ 4 are compared to ab initio and experimental data. The set of tested properties include lattice constants, material density, elastic wave velocity, elastic stiffness tensor, free surface energies, generalized stacking faults, neutral Frenkel and Schottky defects, in the pressure range $$0-12$$ 0 - 12 GPa relevant to the Earth’s upper mantle. We conclude that all interatomic potentials are reliable and applicable to the study of point defects. Stacking faults are correctly described by the THB1 potential, and qualitatively by the Pedone2006 potential. Other rigid-ion potentials give a poor account of stacking fault energies, and should not be used to model planar defects or dislocations. These results constitute a database on the transferability of rigid-ion potentials, and provide strong physical ground for simulating diffusion, dislocations, or grain boundaries.

Optical Characterization of DebriSat Fragments in Support of Orbital Debris Environmental Models

The NASA Orbital Debris Program Office (ODPO) develops, maintains, and updates orbital debris environmental models, such as the NASA Orbital Debris Engineering Model (ORDEM), to support satellite designers and operators by estimating the risk from orbital debris impacts on their vehicles in orbit. Updates to ORDEM utilize the most recent validated datasets from radar, optical, and in situ sources to provide estimates of the debris flux as a function of size, material density, impact speed, and direction along a mission orbit. On-going efforts within the NASA ODPO to update the next version of ORDEM include a new parameter that highly affects the damage risk – shape. Shape can be binned by material density and size to better understand the damage assessments on spacecraft. The in situ and laboratory research activities at the NASA ODPO are focused on cataloging and characterizing fragments from a laboratory hypervelocity-impact test using a high-fidelity, mock-up satellite, DebriSat, in controlled and instrumented laboratory conditions. DebriSat is representative of present-day, low Earth orbit satellites, having been constructed with modern spacecraft materials and techniques. The DebriSat fragment ensemble provides a variety of shapes, bulk densities, and dimensions. Fragments down to 2 mm in size are being characterized by their physical and derived properties. A subset of fragments is being analyzed further in NASA’s Optical Measurement Center (OMC) using broadband, bidirectional reflectance measurements to provide insight into the optical-based NASA Size Estimation Model. Additionally, pre-impact spectral measurements on a subset of DebriSat materials were acquired for baseline material characterization. This paper provides an overview of DebriSat, the status of the project, and ongoing fragment characterization efforts within the OMC.

DESIGN AND FABRICATION OF CONCRETE-REINFORCED FLOATING PLATFORM FOR CANAL AND RIVER-SHORE PROTECTION

Erosion of canal and river-shore causes problems on agriculture activities and soil environment. This paper devotes to develop a floating platform to protect the shores. A concrete-reinforced floating platform was designed and fabricated in this study. Mechanical simulation was performed to ensure the design viability. The concrete-reinforced floating platform consists of three main parts: (1) steel structure, (2) foam-cement material, and (3) connecting joints. The dimension of the cement foam floating platform is 1.2 m in width, 3 m in length and 0.4 m in thickness. The cement used in this research is resistant to corrosion of sulfate and chloride from saltwater. Foam with density of 12 kg/m3 is mixed with concrete matrix so that the floating platform can float 60% or 0.16 m above the water surface. The foam cement material has the maximum compression stress of 1,951 kg ± 266.59 kg for the material density of 427.30 kg/m3 ± 19.30 kg/m3. The connecting joint part has the ultimate tensile load of 1,564 kg. The assemble floating platform has the compressive stress of 543.33 kg/m2 with the maximum vertical deformation of samples of 1 mm under the distribution load of 1,571 over the samples. Finally, from simulation with data from the material testing, the designed floating platform had a safety factor 3.46 which was higher than the design criteria of 3.

Thermal Energy Production in an Electrochemical Cell and Heat Transfer to Its Dark Surroundings

The theoretical formulation presented in this abridged paper was developed to predict the transient cell average temperature of a lithium-based cell during its discharge in dark, extremely low material density surroundings where the predominant mechanism of heat exchange between its shroud surface and surroundings is the thermal radiation process for a given cell discharge current and its initial temperature. The average computed temperature of an ideal lithium-based button cell, such as Li(s)/electrolyte/CF(s), is presented as a function of time in the form of plots at two discharge currents as an example of the application of the derived formulation. The presented data are briefly discussed in light of the lithium-based cell component stability and its safe discharge operation.