Green Materials Comparation of Sawdust and Coconut Fibre Acoustical Waffle Panel

Abstract. The natural wealth of Indonesia produces a wide range of natural resources. This research will discuss sawdust and coconut fibre for example from natural resources which can be processed into building materials. The use of the absorber as a facade is needed, especially for buildings located in noisy urban areas. Various research has studied the absorber made from sawdust and coconut fibre, but only a few studies that study the absorber material that has the texture of waffle on its surface. The research method used is the method comparisons of the value of the absorption coefficient, density and Sound Transmission Loss (STL) impedance tube with 1/3 octave filter. The result is that the waffle the panel from the sawdust has a higher density than waffle the panel from coconut fibre. The value of the coconut fibre panel STL ranged 46,134 – 51,312 dB. This value is lower than the STL material from sawdust that has a value between 47,301 – 62,688 STL. Absorption coefficient, coconut fibre panels between 0,432 – 0,511, while the value of the coefficient of absorption sawdust panel range 0,469 – 0,529. (max 200 words)

Physical and acoustic properties of petroleum and renewable based polyurethane foam filled with shorea leprosula

Physical and acoustic properties of petroleum-based polyurethane (PU) and renewable based polyurethane (RPU) foam composites filled with Shorea Leprosula (Red Meranti) fiber filler has been investigated. Shorea Leprosula wood dust namely as SL was used as the filler. RPU was used with hope to substitute the current polyurethane. This research was carried out to investigate the physical and acoustical properties and the ability of polymer foam composites (PF) towards sound absorption coefficient (SAC) based on the wood fiber size with range of 150-200 μm (powder), 250-300 μm (fibrous) and 900-1000 μm (flakes). 5 wt%, 10 wt%, 15 wt% and 20 wt% of SL filler content and thickness of 10 mm, 20 mm and 30 mm were used for each PF sample. PF samples have been tested by using Impedance Tube test, Scanning Electron Microscopy (SEM) and Mettler Toledo Density kit. As a result, the sound absorption coefficient (SAC) shows value at achievable frequency range at low (0-1500 Hz) and high (1501-6000 Hz) frequency absorption level. PU with powder fiber size (UP20), average pore size with 425.4 μm (smallest), and density 857.9 kg/m3 (highest) shows better sound behaviour with SAC value of 0.2478 and 0.9598 at low and high frequency absorption level. Meanwhile, for RPU with powder fiber size (RP20), average pore size with 479.8 μm (smallest), and density 839.0 kg/m3 (highest) shows better sound behaviour with SAC value of 0.2478 and 0.9940 at low frequency and high frequency absorption level. Moreover, UP20 and RP20 give the highest SAC value with 30 mm in thickness 0.9037 and 0.9909, and 0.9784 and 0.9809 at low and high frequency absorption level respectively. In conclusion, acoustical characteristics of PF samples shows the ability to influence the absorption coefficient of polymeric foam at different frequency levels. Both type of PF produce is suitable for sound absorbing materials for indoor and outdoor sound applications

Performance analysis of a direct-absorption parabolic trough solar collector

A parabolic trough solar collector is a dominant technology for high-temperature industrial applications, but efficient use of a conventional surface-based parabolic trough solar collector (SBPTSC) is limited by its high radiation loss due to the high surface temperature. Recently, direct-absorption parabolic trough solar collector (DAPTSC) using nanofluids has been proposed, and its thermal efficiency has been reported to be 5-10$\%$ higher than the conventional SBPTSC for inlet temperature up to 250$^\circ$C. However, the inner tubes of the receivers of the existing DAPTSCs are all transparent, so the sun rays entering the inner tube can only travel once through the nanofluids. As a result, the optical path length for the sun rays is limited by the inner tube size, which in turn requires high value of the absorption coefficient of nanofluids. Due to the approximately linear relation between the absorption coefficient and the particle concentration, higher absorption coefficient is likely to cause particle agglomeration, leading to detrimental effects on maintaining stable collector performance. In the current study, the transparent DAPTSC is improved by applying a reflective coating on the upper half of the inner tube outer surface, such that the optical path length is doubled compared to the transparent DAPTSC; thus, the absorption coefficient of the nanofluids can be reduced accordingly. The coated DAPTSC is found to have obvious advantage compared to the transparent DAPTSC at absorption coefficient below 0.5 cm$^{-1}$ for a receiver with inner tube diameter of 7 cm. In addition, performance of the transparent DAPTSC, the coated DAPTSC and the SBPTSC with black chrome coating have been compared to explore their advantageous operation conditions, such as inner tube diameter, flow rate, and inlet temperature, with or without a glass envelope for vacuum evacuation.Comment: 6 figure

Light absorption coefficient of an ordered array of spherical quantum dot chains

We considered intersubband electron transitions in an array of one-dimensional chains of spherical quantum dots in the GaAs/Al$_{x}$Ga$_{1-x}$As semiconductor system. The absorption coefficient caused by these transitions was calculated depending on frequency and polarization of incident light and on Fermi level position, and temperature. We established the existence of two maxima of the absorption coefficient at the edges of the absorption band. It is shown that the absorption coefficient reaches its maximal value at the center of the region between the $s$-, $p$-like subbands and slightly varies with temperature. The change of the direction of the linearly polarized light wave incident on the chains from perpendicular to parallel leads to a sharp narrowing of the absorption band. It is obtained that the absorption bandwidth increases with the reduction of the quantum dot radius. We also analyzed the dependence of the absorption coefficient of GaAs/Al$_{x}$Ga$_{1-x}$As superlattice on concentration of aluminium in the matrix.Comment: 9 pages, 7 figure

Interplay between localization and absorption in disordered waveguides

This work presents results of ab-initio simulations of continuous wave transport in disordered absorbing waveguides. Wave interference effects cause deviations from diffusive picture of wave transport and make the diffusion coefficient position- and absorption-dependent. As a consequence, the true limit of a zero diffusion coefficient is never reached in an absorbing random medium of infinite size, instead, the diffusion coefficient saturates at some finite constant value. Transition to this absorption-limited diffusion exhibits a universality which can be captured within the framework of the self-consistent theory (SCT) of localization. The results of this work (i) justify use of SCT in analyses of experiments in localized regime, provided that absorption is not weak; (ii) open the possibility of diffusive description of wave transport in the saturation regime even when localization effects are strong.Comment: 10 pages, 3 figure

Seasonal Variability of Light Absorption Coefficient of Surface Water

Absorption coefficient measurement can be used in estimating water quality, optical characteristic of water column, and marine bio-optical models. The purposes of this research were to determine values and variability of sea surface absorption coefficient in the northeastern Gulf of Mexico (NEGOM) based on various seasons. The data were collected in spring, summer, and fall seasons in 1999-2000 with AC-9 instrument. The spatial distribution of absorption coefficient showed that relatively high values were generally found along the run off Missisippi, Mobile, Chochawati, Escambia, Apalachicola, and Suwannee rivers, as well as Tampa Bay. Meanwhile, relatively low values were found in offshore region. This pattern followed the distribution pattern of chlorophyll and CDOM. Based on the local region comparison of spectral average value of absorption coefficient, we found a significant difference (α = 95%) among regions with the highest value in the run off of the Mississippi and Mobile rivers, and the lowest value in the offshore region. Comparison of spectral average value of absorption coefficient among seasons at the three primary wavelengths (blue=440 nm, green=510 nm, and red=676 nm) also showed a significant difference (α = 95%) with the highest value during the summer 1999 (Su-99) and the lowest value during the spring of 2000 (Sp-00). Absorption coefficient values were influenced by oceanographic factors that varied in every season such as wind, surface currents, upwelling, the location and speed of the Loop Current, and the river discharge of fresh water into the NEGOM

Optical parameters of leaves of seven weed species

The absorption coefficient (k), infinite reflectance (R), and scattering coefficient (s) were tabulated for five wavelengths and analyzed for statistical differences for seven weed species. The wavelengths were: 0.55-micrometer, 0.65-micrometers, 0.85-micrometer, 1.65-micrometers, and 2.20-micrometer. The R of common lambsquarters (Chenopodium album L.), Johnsongrass (Sorghum halepense (L.) Pers.), and annual sowthistle (Sonchus oleraceus L.) leaves at the 0.85-micrometer wavelength were significantly (p=0.05) higher than for sunflower (Heliantus annus L.), ragweed parthenium (Parthenium hysterophorus L.), or London rocket (Sisymbrium irio L.). Annual sowthistle had the largest k value, and Plamer amaranth (Amaranthus palmer S. Wats.) had the smallest k value at the 0.65 approximately chlorophyll absorption wavelength. In general, john-songress, ragweed parthenium, or London rocket had the largest s values among the five wavelengths, wereas annual sowthistle and plamar amaranth were usually lowest

Modelling of Stochastic Absorption in a Random Medium

We report a detailed and systematic study of wave propagation through a stochastic absorbing random medium. Stochastic absorption is modeled by introducing an attenuation constant per unit length $\alpha$ in the free propagation region of the one-dimensional disordered chain of delta function scatterers. The average value of the logarithm of transmission coefficient decreases linearly with the length of the sample. The localization length is given by $\xi ~ = ~ \xi_w \xi_\alpha / (\xi_w + \xi_\alpha)$, where $\xi_w$ and $\xi_\alpha$ are the localization lengths in the presence of only disorder and of only absorption respectively. Absorption does not introduce any additional reflection in the limit of large $\alpha$, i.e., reflection shows a monotonic decrease with $\alpha$ and tends to zero in the limit of $\alpha\to\infty$, in contrast to the behavior observed in case of coherent absorption. The stationary distribution of reflection coefficient agrees well with the analytical results obtained within random phase approximation (RPA) in a larger parameter space. We also emphasize the major differences between the results of stochastic and coherent absorption.Comment: 7 pages RevTex, 9 eps figures included, modified version of cond-mat/9909327, to appear in PRB, mpeg simulations at http://www.iopb.res.in/~joshi/mpg.htm