Values Of Absorption Coefficient Research Articles

Effect of air gap on sound absorption in layered composite structures produced of sustainable materials

Numerous materials have been produced to isolate the noise that negatively impacts people’s health and productivity at work. Some of these materials are not preferred for usage because they are expensive, inefficient, or harmful to the environment. In this study, composite materials were produced with waste chicken feathers (CF) and polyvinyl acetate (PVAC) binder in different mixture ratios. After CF was washed and cleaned, it was shredded into 2–3 mm lengths with a chopper. Then CF was mixed with PVAC binder and thermal bonding was applied. As a result of the process, composites with a thickness of 10 mm and dimensions of 15 cm × 15 cm were formed. These composite plates are supported by sandwich constructions made of various varieties of polyester-based felt (NW), knitted fabric (KF), leather (L), spacer fabric (SF), and air gap (AG5, AG10, AG15) in thicknesses of 5, 10, and 15 mm. Impedance tubes with four microphones were used to evaluate the sound absorption coefficient and sound transmission loss values of these manufactured structures, and the resulting data were analyzed. According to this; The NW + CFC1 two-layer structure is 0.33 (500 Hz), but when a 15 mm thick air gap layer is added, it is seen that it increases to 0.85 (500 Hz). Other sandwich structures produced also show similar results. The best results were achieved with layered composite structures. Adding an air gap layer between the composite layers to increase sound absorption has improved results, especially at low frequencies. The air gap layer can significantly reduce production costs because it can be used instead of a material layer. The production of textile-based sound insulation structures from the waste material CF is also of great importance in terms of sustainability.

The Influence of the Soil Profile on the Formation of the Elemental Image of Grapes and Wine of the Cabernet Sauvignon Variety.

The features for assessing the authenticity of wines by region of origin are studied, based on the relationship between the mineral composition of the wine, the grapes, and the soil profile (0 to 160 cm) from the place of growth of Cabernet Sauvignon grapes. Soil, grape, and wine samples were taken from the territories of six vineyards in the Anapa district of Krasnodar Territory, Russia. Using the methods of ICP-OES, thermal, and X-ray phase analysis, the soils were differentiated into three groups, differing in mineralogical and mineral compositions. The soil samples of the first group contained up to 31% quartz, the second group up to 25% quartz and 19% mixed calcite, and the third group up to 32% calcite and 15% quartz. The formation of the elemental image of the grapes was studied, taking into account the total content and mobile forms of metals in the soil. The territorial proximity of the vineyards did not affect the extraction of elements from the soil into the grape berry, and the migration of metals for each territory was selective. According to the values of the biological absorption coefficient, the degree of transition of metals from the soil to a berry was estimated. For K, Ti, Zn, Rb, Cu, and Fe in all berries, the coefficient was higher than 1.00, which means that the berry extracts contained not only mobile-form, but also difficult-to-dissolve metal compounds. The migration of macro-components from the soil to the berry was low, and amounted to 6-7% for Ca, 0.8-3.0% for Na, and 25-70% for Mg of the concentration of their mobile forms. For all territories, the maximum correlation between metal concentrations in grapes and soil was observed for samples from a depth of 0-40 cm. The discriminant model based on concentrations of Rb, Al, K, Sr, Co, Na, Pb, Ca, and Ni showed the formation of clusters in the territories of vineyard cultivation. The developed model allow the problems of identifying wines by region to be solved with high accuracy, using their elemental image.

Investigation of structural, electronic, optical and thermoelectric properties of hallide double perovskite Rb2AlAgX6 (X = Cl, I): A first-principles DFT study

In order to meet the demands of the energy consumption, double perovskites (DP) are a dependable green energy source. Consequently, there is a great deal of promise for thermoelectric and optoelectronic device applications when studying these perovskite halides. Our work examined the thermoelectric and optoelectronic properties of Rb2AlAgCl6 and Rb2AlAgI6 halides using Density Functional Theory (DFT). The tolerance factor and energy of formation for the halides that were examined show that they are stable in the cubic phase, structurally and thermodynamically. We calculated the bandgaps for Rb2AlAgCl6 (Eg = 3.82 eV) and Rb2AlAgI6 (Eg = 1.321 eV) using mBJ potentials, and compared them to the reported values. The optical characteristics of the materials under investigation were revealed through the use of a complicated dielectric function. The computed optical findings show that the materials are suitable for optoelectronic applications, with maximal light absorption occurring in the ultraviolet (UV) and infrared (IR) ranges. Optical parameters obtained includes large values of absorption coefficients (∼105cm−1), low reflectivity (∼1–15 %), and high optical conductivity (∼1015 sec−1). Thermoelectric properties revealed enhanced power factor for Rb2AlAgI6 as compared to Rb2AlAgCl6. These results imply that these materials are appropriate for application in optical and thermoelectric devices.

The scientific landmarks for the development and evaluation of the effectiveness of vibration and noise absorbing materials

The mastic compositions with vibration and noise absorbing properties have been developed to reduce the level of noise and vibration in the low- and high-frequency range of the spectrum. Evaluation of the effectiveness of the developed vibration and noise absorbing mastic compositions “Vibroshtil” and “Vibroshtilmaxi” was carried out on an experimental installation by the method of free damping of plate vibrations with the determination of the decrement of vibrations. Mastic compositions are characterized by a high value of the sound absorption coefficient and the coefficient of mechanical losses in the range of operating speeds. The introduction of developed vibration and noise absorbing materials with an extended spectrum of action at the workplaces of workers will reduce the level of vibration and noise in the low- and high-frequency range of the spectrum by 7–15 dB and create safe working conditions. The main characteristic of the vibration and noise absorbing composite is the sound absorption coefficient, the value of which is in the range from 0 to 1. The main advantage of these compositions over the existing ones is the ease of manufacture, the ability to apply them to any surface by spraying or puttying.

Photoresponse in sequentially stacked antimony selenide thin films

Antimony selenide (Sb2Se3), a binary semiconducting compound has widespread research attention due to its excellent optoelectronic properties in the visible region and usefulness in applications such as solar cells, photosensors and photoelectrodes. The presented study explores the thickness dependent photoresponse in Sb2Se3 thin films, prepared by reactive selenization of antimony films having thickness values of ∼938 nm and ∼1879 nm when stacked second time. Growth orientation along [001] direction was achieved through carefully optimized selenization conditions to enable favourable charge transport in anisotropic Sb2Se3. Predominant Sb2Se3 formation was inferred from x-ray diffraction, Raman spectroscopy, secondary electron microscopy and energy-dispersive X-ray analyses. High optical absorption coefficient values of about 1 × 105 cm−1 and 5.7 × 104 cm−1 were observed for ∼938 nm and ∼1879 nm thick Sb2Se3 thin films. Further, the optoelectronic properties were elucidated through current–voltage and transient photoresponse measurements under dark and illumination conditions. The measurements were done under zero and different bias voltages. Sb2Se3 films having∼ 938 nm thickness exhibited self-driven photoresponse with a responsivity of 4.3×10−8 A W−1 and detectivity of 3.5 × 106 jones respectively, under AM 1.5 G illumination conditions.

Recent advancement in the synthesis of zinc sulphide thin films

This research work has given an overview on the preparation of zinc sulphide thin films on different types of substrates (quartz, soda lime glass, silicon, polyethylene terephthalate film, fluorine-doped tin oxide glass, indium tin oxide coated glass, silica, stainless steel, mica, microscopy glass slide and (100) GaAs substrate) using different types of deposition methods. XRD data showed information about the different phases (cubic, wurtzite and hexagonal) presented in the obtained as-deposited films and annealed samples. Based on optical studies, the band gap was observed in the range of 2.6 eV to 3.87 eV with good absorption coefficient value (105 to 106 cm-1). Experimental results indicated these films could be used in solar cell applications, anti-reflection coating, photocatalysts, photo detector devices and laser-oriented coating applications.

Promoting the optoelectronic and nonlinear optics properties of MoS2 nanosheets via metal Al anchoring

Molybdenum disulfide (MoS2) has attracted much attention in the field of optoelectronic materials due to its stability and adjustable bandgap structure. However, improving the optoelectronic properties of MoS2 is still a challenging research. Herein, Al doped MoS2 (AMS) films were prepared by a simple single-step magnetron sputtering method. The bonding modes of Al implantation and auxiliary MoS2 were investigated by adjusting metal Al anchoring. The successful synthesis of AMS films was confirmed by the analysis of X-ray diffraction and X-ray photoelectron spectroscopy measurements to investigate the diffraction peaks of Al and Al2S3 and the valence electron structures of Al3+. Compared to MoS2, the A1g Raman peaks of AMS films are slightly blue-shifted, and the peak positions of both Mo3d and S2p are slightly shifted towards higher binding energies. This is attributed to the surface plasmon resonance effect produced by Al doping resulting in a large amount of electron transfer to the conduction band (CB) of MoS2. In addition, the density functional theory calculations reveal that Al doping of MoS2 results in a higher concentration of electrons in CB of MoS2, the band gap of MoS2 can be adjusted by changing the doping concentration of Al. The Z-scan results illustrated that MoS2 was converted from saturable absorption to reverse saturable absorption (RSA) by adjusting the sputtering power of Al. This is attributed to the fact that Al doping increases the electron concentration in the CB of MoS2, which promotes the RSA of the excited states and doping energy levels of AMS films. The values of the nonlinear absorption coefficients of AMS films are 2–5 times higher than those of MoS2, which significantly improves the nonlinear absorption performance of MoS2. The carrier relaxation process and kinetic mechanism of AMS films were investigated by transient absorption spectroscopy, moderate doping of Al can effectively improve the carrier lifetime. This implies that AMS films have good optoelectronic properties and have a wide application potential in optoelectronic devices.

Investigation of structural, electrical, magnetic, and optical properties of Cu (111) and the impact of Ag adatoms adsorption: A density functional theory study

Our study conducts a comprehensive investigation on the structural, electrical, magnetic and optical properties of pure Cu with a (111) crystallographic orientation, as well as the impact of the adsorption of Ag adatoms on a Cu (111) surface. To perform this analysis, we utilized the full potential linearized augmented plane-wave (FP-LAPW) approach in conjunction with Generalized Gradient Approximations (GGA + U) and the Wien2k simulation software. Specifically, we calculated electrical and optical properties including the band structure, density of states (DOS) for the Cu (111) surface with and without the presence of adsorbed Ag atoms. Based on the observed results, the overlapping of the electronic bands for simple Cu (111) is comparatively less than that of adsorbed Ag/Cu (111) slab, indicating higher conductivity. Moreover, the evolutions are also observed which are mainly due to d orbitals of Cu and Ag for Cu (111) and Cu/Ag (111) respectively. The calculated magnetic optimization and weak diamagnetic magnetic moments shows weak diamagnetism in these materials. The optical properties like Dielectric Function(ε), Refractive index(n), Extinction co-efficient(k), Reflectivity(R), Energy Loss (L), Absorption (α) and Optical conduction (σ) are calculated. Our research examines the importance of band structure calculation in relation to optical properties. We discuss how plasmon-energy plays a crucial role in producing peaks in the energy loss function, with a crystallographic axis of 13.7 eV and 13.6 eV for both Cu (111) and Ag/Cu (111) slab. In addition, we calculated the static dielectric function, absorption coefficient, and refraction values for these materials. Reflectivity spectra for both Cu (111) and Ag/Cu (111) exhibits Infra-red region, indicating good coating materials to reduce heating, for the application of electrical appliances and for optical application like anti-reflecting coating, optical fibers and solar cells.

Charcoal-containing microwave electromagnetic radiation absorbers with relief surface

A new technology for manufacturing microwave electromagnetic radiation (EMR) absorbers characterized by a geometrically inhomogeneous surface is presented. The novelty of the presented technology lies in the use of radiotransparent polymer forms with hemispherical depressions of the same volume, which are the component for the formation of the surface layer of absorbers. The technology consists in filling these molds with a mixture of powdered activated (birch) charcoal and the binder in the liquid phase and further drying it in the forms. Compared with analogues, the developed technology is characterized by low complexity of reproduction. Most of the time required to implement the presented technology is associated with the drying process of a mixture of powdered activated birch charcoal and a binder. The experimentally established patterns of changes in the values of electromagnetic radiation reflection and absorption coefficients in the frequency range 1.0–28.0 GHz of the absorbers manufactured in accordance with the presented technology are provided, depending on the type of binder contained in them (polyvinyl acetate aqueous solution, gypsum aqueous solution, polyurethane mastic). It was determined that the most effective of the EMR absorbers studied in the course of establishing the indicated patterns are those ones that contain an aqueous solution of polyvinyl acetate. Electromagnetic radiation absorption coefficient values in the frequency range 1.0–28.0 GHz of such absorbers vary from 0.75 to 0.99. In addition, the mass per unit area of such absorbers is 1.5–2.0 times less than the mass per unit area of absorbers containing an gypsum aqueous solution or polyurethane mastic. Microwave EMR absorbers manufactured using the presented technology are characterized by higher mechanical strength, as well as lower cost compared to analogues and are recommended for use in the creation of anechoic chambers.

SOUND AND THERMAL INSULATION PROPERTIES OF SANDWICH COMPOSITES MADE OF WASTE KEVLAR® MATERIALS

This paper examines the thermal and acoustic insulation characteristics of sandwich composites with waste Kevlar® fiber-reinforced face materials and polyurethane/paper cardboard cores. Waste Kevlar® short fibers (carding waste) were reinforced into the sandwich composites’ core part in varying ratios (2%, 5%, and 10%). Kevlar® fabric edge waste (waste of weaving process) was used to produce the face materials of sandwich composites. Sandwich composites were also stitched using Kevlar® yarns to observe the effect of the through-thickness reinforcement on sound and thermal insulation properties. The sound insulation test results showed that reinforcement of short Kevlar® fibers into the core parts of sandwich composites somewhat raised their sound absorption coefficients. Because the stitching holes created air spaces for sound vibrations, the sound absorption coefficient values improved. The sound transmission losses of sandwich composites were also increased up to 30 dB after short Kevlar® fiber addition. The thermal conductivity coefficient of sandwich composites decreased, indicating that the addition of Kevlar® fibers increased their insulation properties.

Strongly Polarized π-Extended 1,4-Dihydropyrrolo[3,2-b]pyrroles Fused with Tetrazolo[1,5-a]quinolines.

A straightforward route to 1,4-dihydropyrrolo[3,2-b]pyrroles comprised of two electron-withdrawing quinoline or tetrazolo[1,5-a]quinoline scaffolds has been developed. The versatile multicomponent reaction affording 1,4-dihydropyrrolo[3,2-b]pyrroles combined with intramolecular direct arylation enables assembly of these products in just three steps from anilines with overall yields exceeding 30%. The planarized, ladder-type heteroacenes possess up to 14 conjugated rings. These nominally quadrupolar materials exhibit efficient fluorescence with wavelengths spanning most of the visible spectrum from green-yellow for the dyes possessing biaryl bridges and orange-red for the fully fused systems. In many cases, the fluorescence quantum yields are large, the solvatofluorochromic effects are strong, and the fluorescence is maintained even in crystalline state. Analysis of the electronic structure of these molecular architectures using quantum chemical methods suggests that the character and position of the flanking heterocycle determine the shape of HOMO and LUMO and their extension to N-aryl substituents, influencing the values of molar absorption coefficient. An experimental study of the two-photon absorption (2PA) properties has revealed that it occurs in the 700-800 nm range with apparent deviation from the Laporte parity selection rule, which may be attributed to Hertzberg-Teller contribution to vibronically allowed 2PA transition.

MICROWAVE ABSORBERS BASED ON MÖBIUS STRIP RESONATORS

The paper deals with technology of manufacturing of microwave absorbers with ordered and structured surface layer. This layer contains Möbius strip resonators, located on the fixed distance from each other. The technology was developed by the authors on the base of the following data: 1) results of theoretical study of microwaves interaction with Möbius strip resonator; 2) results of experimental study of electromagnetic radiation reflection, transmission and absorption coefficients in the microwave frequency range of the experimental samples of microwave absorbers based on Möbius strip resonators, which differ by the distance between these resonators. It was established on the base to the listed results that the microwave absorbers manufactured in accordance to the technology proposed by the authors are wide-band ones. Electromagnetic radiation absorption coefficient values of these absorbers changes from 0.5 to 0.97 in frequency range 2.0–17.0 GHz if the distance between the Möbius strip resonators containing in their surface layer, is 15.0 mm. If the distance between the Möbius strip resonators containing in the surface layer of the considered absorbers is less than 15.0 mm their electromagnetic radiation absorption coefficient in the indicated frequency bands is lower than presented values. The considered absorbers are promising for use in shielded rooms and anechoic chambers.

Development of dissolved organic matter-based indicators to understand the degradation of organic contaminants in reverse osmosis concentrate from potable reuse systems

Reverse osmosis (RO)-based treatment of municipal wastewater effluent allows for potable reuse, but this process generates reverse osmosis concentrate (ROC) that needs further treatment before disposal. This study investigated the application of UV-based advanced oxidation processes (AOPs) to degrade nine contaminants of emerging concern (CECs) from real ROC waste streams, using UV-only and UV-AOPs with hydrogen peroxide, free chlorine, and persulfate. Dissolved organic matter (DOM) in ROC was characterized using fluorescence excitation emission matrix data and analyzed by a four-component parallel factor (PARAFAC) analysis model. UV-only treatment showed considerable removal of CECs that displayed high values of quantum yields and molar absorption coefficients. UV-AOP treatment of ROC exhibited heavy scavenging of reactive species during CEC degradation. A probe-based approach established that hydroxyl radical was the dominant reactive species in all UV-AOPs. A kinetic analysis of PARAFAC components of DOM showed that the visible humic-like and protein-like components exhibited the higher reaction kinetics compared to UV humic-like and nutrient-like components. The strong linear correlation of protein-like component and seven of the nine CECs across multiple AOPs indicated that they have similar reactivity, enabling the establishment of chemical-reactivity based surrogates for prediction CEC fate in ROC wastes.

Metasurfaces for sound absorption over a broad range of wave incidence angles

Control of reflected waves that meet surfaces from oblique directions is crucial, for instance, in closed spaces. Metasurfaces composed of Helmholtz resonators can be efficient and compact absorbers but have limited ability to achieve high absorption over a wide incidence angle range, especially when designed for high performance in the region approaching grazing incidence. In turn, sonic crystals can be used to manipulate wave propagation direction at low frequencies. We propose a type of absorber that combines a surface of 2D Helmholtz resonators and a 2D sonic crystal with cylindrical scatterers arranged in a hexagonal lattice. The combined effect of both structures yields a metasurface that can achieve high absorption over a broad range of incidence angles. Here, an analytic model to estimate the behavior of the absorbers for wavelengths that are much longer than the unit cell dimensions is presented. The model is used in combination with an optimization strategy to realize designs for single frequency and octave-band performance. The test cases show that surfaces with absorption coefficient values above 0.9 for the range of incidence angle extending from 0∘ until 83∘ can be realized. The performance of the absorbers is verified with a finite element model and experimentally.

Freeze-cast porous Al2O3/MgO ceramics as potential acoustic sound absorption

In acoustic engineering and architecture, materials called acoustic absorbers are widely used. There are currently numerous options for such materials, and many more are being researched. This study is conducted on porous ceramics produced via the freeze-casting process to propose new solutions with unique properties, like resistance to harsh environments. The freeze-casting method allows for the controlled creation of open-connected porous structures for different class materials through the cryogenic freezing of the suspension. The material samples are produced with Al2O3 (alumina)/MgO (magnesium oxide) material using camphene as solvent. The specimen samples are prepared using three different concentrations of the two solid components (60/40, 72/28, and 90/10 in weight). Each sample concentration achieves different morphology phase compositions and porous structures. Hence, we explore in the paper how those concentration parameters could interfere with acoustic absorption. Further, the samples were characterised using numerical and experimental methods related to sound absorption and microstructure. The 60/40 and 90/10 samples achieve sound absorption coefficient values upwards of 0.7 around the 2000-3000 Hz frequency range. The microstructure characteristics show the porosity gradually changing along its thickness, interfering with their sound absorption properties. Our findings highlight the complexities of characterising porous ceramics and emphasise the significance of understanding some material composition factors affecting sound absorption. Hence, this study provides valuable insights into the intricate nature of porous ceramic freeze-cast materials and their acoustic properties, substantially contributing to the ongoing exploration in this domain.

Investigations on Chemically Synthesized Pure and Doped Manganese Dioxide Nanoparticles for Dye Removal and Photocatalytic Applications.

Pure and Mg2+, Ni2+, Cd2+ doped MnO2 nanoparticles were synthesized by chemical co-precipitation method. These samples were characterised by PXRD, SEM, EDX, FTIR, UV-Vis-NIR, PL, Antibacterial, Cyclic Voltammetry, Dye Degradation and Photocatalytic studies. From the powder XRD studies, the crystallite size of the particle was calculated using Scherer formula and found that the synthesized nanoparticles were in the range from 10 to 12nm. The morphology of all the synthesized samples was viewed from SEM micrograph. The composition and purity of the samples were identified from EDX studies. In FTIR spectra metal-oxygen stretching and bending modes of vibrations were observed. From the absorption spectra of UV-Vis optical analysis values of absorption coefficient, extinction coefficient, refractive index, real and imaginary part of optical dielectric constant and optical conductivity were compared. The band gap energy obtained from Tauc's plot varies from 1.21 to 1.51eV exhibits semiconducting behaviour of all the synthesized samples. Investigations on photoluminecsence spectrum reveals blue shift in wavelength for doped nanooxides compared to pure MnO2. Antimicrobial activity of synthesised samples against gram positive and gram negative bacteria was determined. The obtained results reveal very high bacterial resistance in Cd2+ doped MnO2 nanoparticles with higher activity towards bacterial resistance compared to standard drug. The specific capacitance values were determined from Cyclic Voltammetry studies. Using the batch method of dye removing technique the percentage of malachite green dye removal was calculated. Also the photocatalytic efficiency of all the synthesized MnO2 samples in removing malachite green dye was studied by exposing to sunlight for different dosage and contact time. Ni2+ doped MnO2 shows relatively higher % of dye degradation capacity about 93% for 0.1g of dosage of photocatalysts.

Insight into the Role of NH3/NH4+ and NOx/NO3- in the Formation of Nitrogen-Containing Brown Carbon in Chinese Megacities.

Particulate brown carbon (BrC) plays a crucial role in the global radiative balance due to its ability to absorb light. However, the effect of molecular formation on the light absorption properties of BrC remains poorly understood. In this study, atmospheric BrC samples collected from six Chinese megacities in winter and summer were characterized through ultrahigh-performance liquid chromatography coupled with Orbitrap mass spectrometry (UHPLC-Orbitrap MS) and light absorption measurements. The average values of BrC light absorption coefficient at a wavelength of 365 nm (babs365) in winter were approximately 4.0 times higher than those in summer. Nitrogen-containing organic molecules (CHNO) were identified as critical components of light-absorbing substances in both seasons, underscoring the importance of N-addition in BrC. These nitrogen-containing BrC chromophores were more closely related to nitro-containing compounds originating from biomass burning and nitrogen oxides (NOx)/nitrate (NO3-) reactions in winter. In summer, they were related to reduced N-containing compounds formed in ammonia (NH3)/ammonium (NH4+) reactions. The NH3/NH4+-mediated reactions contributed more to secondary BrC in summer than winter, particularly in southern cities. Compared with winter, the higher O/Cw, lower molecule conjugation indicator (double bond equivalent, DBE), and reduced BrC babs365 in summer suggest a possible bleaching mechanism during the oxidation process. These findings strengthen the connection between molecular composition and the light-absorbing properties of BrC, providing insights into the formation mechanisms of BrC chromophores across northern and southern Chinese cities in different seasons.

The sound absorption of air permeable structures produced by 3D printing using PLA material

The aim of the contribution is comparison of noise absorption properties of two designs of acoustic dampening air permeable structures. A circular test samples with a diameter of 89 mm and three different thicknesses of samples were produced using of 3D printing process. In addition to the thickness, the internal structure of the samples was also changed. The prepared samples were tested using an impedance tube. The acoustic properties of the test samples were investigated in accordance with the standards ASTM E1050-19, E2611-17 and ISO 10534-2. A two-microphone method based on the calculation of transfer function method was used to determine the absorption coefficient of the designed structures. The Brüel&Kjær PULSE system was used to estimate the frequency dependence of sound absorption coefficient of test samples. In the paper are presented the experimentally obtained values of the sound absorption coefficient for different structure design and thicknesses of samples produced by 3D printing technology. The measurements were evaluated in the range of working frequencies of the impedance tube.

The investigation of diesel soot emission using instrument combination of multi-wavelength photoacoustic spectroscopy and scanning mobility particle sizer

The parallel measurements of wavelength dependent optical absorption, particle number size distribution have made by a multi wavelength photoacoustic spectrometer (4λ-PAS) and scanning mobility particle sizer (SMPS) respectively at different modes of a diesel engine using two different types of fuel. The thermal evolution of the emission was also investigated using posterior temperature treatment of emission. The bimodal size distribution of emitted particles at a set reference temperature has been observed regardless of the applied fuel at idle. However, the emitted particulate assembly had lognormal size distribution falls into the accumulation mode at all other defined engine modes and both fuel types. The total number- and volume concentration (TNC and TVC) showed retrograde tendency with the increasing torque and rpm independently of the applied fuel types. The TNC values decreased up to 50% for both fuels with engine operation changes from idle engine mode(em#1) to low engine mode(em#2). With further increase in torque and rpm of engine, the change in TNC is negligible. On the other hand, the TVC remains more or less the same for idle to low engine mode transition and increased more than 60% for high mode (em#3) transition. The Optical Absorption Coefficient (OAC) values measured at the operational wavelengths of the 4λ-PAS instrument decreased at all wavelengths with increasing rpm and torque. The wavelength dependency quantified by Aerosol Ängström Exponent (AAE) was applied here for qualitative analysis of the carbonaceous emission and showed decreased values towards the higher engine speed and torque output of the engine. The proposed technique can be used as real-time, precise and accurate measurement of light absorption by DPM aerosols, which opens up novel possibilities for the volatility and thermal evolution investigation of diesel emissions.

Investigation into the Acoustic Properties of Polylactic Acid Sound-Absorbing Panels Manufactured by 3D Printing Technology: The Influence of Nozzle Diameters and Internal Configurations.

Sound-absorbing panels are widely used in the acoustic design of aircraft parts, buildings and vehicles as well as in sound insulation and absorption in areas with heavy traffic. This paper studied the acoustic properties of sound-absorbing panels manufactured with three nozzle diameters (0.4 mm, 0.6 mm and 0.8 mm) by 3D printing from three types of polylactic acid filaments (Grey Tough PLA; Black PLA Pro; Natural PLA) and with six internal configurations with labyrinthine zigzag channels (Z1 and Z2). The absorption coefficient of the sample with the Z2 pattern, a 5.33 mm height, a 0.6 mm nozzle diameter and with Black PLA Pro showed the maximum value (α = 0.93) for the nozzle diameter of 0.6 mm. Next in position were the three samples with the Z1 pattern (4 mm height) made from all three materials used and printed with a nozzle diameter of 0.4 mm with a sound absorption coefficient value (α = 0.91) at 500 Hz. The highest value of the sound transmission loss (56 dB) was found for the sample printed with a nozzle size of 0.8 mm with the Z2 pattern (8 mm height) and with Black PLA Pro. The extruded material, the nozzle diameter and the internal configuration had a significant impact on the acoustic performance of the 3D-printed samples.