Papers by Keyword: Absorption Coefficient

Abstract: This paper presents a multi-criteria decision-making approach for selecting sound-absorbing materials used in building noise management. Several types of sound-absorbing materials were evaluated, and the selection criteria for identifying the optimal solution were established. The author presents detailed calculations for one of the multi-criteria decision-making methods, namely the Simple Additive Weighting (SAW) method. The results of the research determine the most suitable material to achieve acoustic comfort in enclosed spaces. The paper provides guidance to institutions, organizations, and the general public on how to select sound-absorbing materials using the SAW method.

Abstract: The review article focuses on the growth of thin film and its characterization by UV-Vis-NIR spectroscopy. For UV-Vis-NIR spectroscopy of thin films, they are usually deposited on translucent quartz glass surfaces. The article reports the extraction of various thin film optical parameters viz., absorption coefficient (α), Urbach energy (E_u), optical band gap (E_g), refractive index (n), extinction coefficient (k), dielectric constants, dissipation factor (tanδ) and optical conductivity (σ_optical) by using optical spectra (absorption(A)/transmittance (T)/reflectance (R)). Furthermore, the effect of thin film substrate temperature (T_s) and/or thickness (d) and/or post-deposition annealing temperature (T_a) on various optical parameters is discussed in detail.

Abstract: A series of GaAsBi/GaAs multiple quantum well p-i-n diodes was grown using molecular beam epitaxy and the opto-electrical characterisations are presented. The result shows that devices experience low carrier extractions when light is absorbed due to hole trapping in the valence band. Carrier enhancement can be achieved by applying slight reverse bias when the measurement was taken. The absorption coefficient of the devices is confirmed to be similar with other Bi-based work. GaAsBi/GaAs multiple quantum well do have a lot of room for improvement especially on growth, structure and strain level of the material. If these components can be catered, GaAsBi can be a competitive alternative for 1 eV junction in multiple junction solar cells.

Abstract: Bruggeman's symmetric effective-medium model of vanadium oxide is introduced, in which the transmittance was studied because of its importance in the subject of smart windows, it was studied from ( 5 nm-1000 nm) for each of the regions of the electromagnetic spectrum, the ultraviolet and visible region, and the near and medium sub-regions of the infrared and the results showed that the importance of studying the transmittance of vanadium oxide as a good candidate For this kind of industries. Our results showed that the small sizes of the material guarantee an almost constant and high transmittance to the visible region; this is due to the agreement of the direction of the dipoles in the material with the direction of the internal electric field, which leads to an increase in the value of the refractive index. The refractive index represents the gain in the permittivity of the material presented by Bruggeman's model. For the other regions where the transmittance is not desirable, it can be controlled by the film’s size of the transmittance on the one hand and the wavelength on the other hand.

Abstract: This paper considers the results of modes testing for surface laser hardening. It also includes the development of compositions for light-absorbing coating for industrial application of laser hardening. The paper presents the influence of the light-absorbing coating on the structuring of the surface layer under laser hardening of medium-carbon alloy steel.

Abstract: The photosensitizer is an important part of Dye-Sensitized Solar Cells (DSSC). Photosensitizers function like photosynthesis by absorbing sunlight and turning it into energy. Photosensitizers also contribute to the efficiency of improving DSSC performance. This research is a continuation of previous research to find a candidate for natural and environmentally friendly photosensitizer (bio-energy) based local area in Indonesia. The photosensitizer used in this simulation is Tagetes erecta, Nyctanthes arbor-tritis, Brassica rapa Sub. Sp pekinensis, Delonix regia, Lawsonia inermis, Callistemon citrinus, and Daucus Carota. The purpose of this simulation is finding several candidates for bio-energy local area photosensitizer that produce high efficiency by displaying J-V curves and P-V curves. The highest efficiency was produced by photosensitizer Tagetes erecta at 1.5% [Voc 0.6385 Volt, 0.00383 A / cm2 Jsc, FF 0.605 and Pmax 0.00148 Watt], while the lowest efficiency was produced by photosensitizer Callistemon citrinus at 1.1% [Voc 0.6162 Volt, Jsc 0.0032 A / cm2, FF 0.557 and Pmax 0,0011 Watts]. These simulation results perform that one of reason give influence at DSSC performance is the absorption coefficient value in each bio-energy local area photosensitizer. The absorption coefficient also determines how much efficiency is produced and how much the photosensitizer's ability to absorb sunlight.

Abstract: One of the considerations for renewable energy that can be accepted by society is energy based on nature (green future) and environmentally friendly (local wisdom). Dye-sensitized solar cells give to the world, easily and simple implemented technology for future renewable energy. This research was conducted by simulating the performance of DSSC using dye based on green future and local wisdom. Dye is one of the most important components influencing solar cell performance because dye determines the photoresponse of the DSSC. Several dyes that used in this research included Vasica nees, W. fruticose L, U. dioical L, R. arborium, Myrica nagi, Curcuma angustifiola dan Berberies aristate. The reason for this choice of dye included it is easily found in Indonesia, does not cause environmental pollution, and is thought to have good prospects to be applied to DSSC. The best performance results produced by DSSC are using dye W.fruticose L with an efficiency of 1.6%, and the lowest performance are using dye R. arborium with an efficiency of 1 %.

Abstract: Thin (200-600 nm) Si-Sn alloy films were grown under ultrahigh vacuum conditions by co-deposition of Si and Sn on the Si (100) substrate at room temperature. Investigations of the film structure by X-ray diffraction showed the preservation of the amorphous structure of Si-Sn films without the contribution of the Si_1-xSn_x alloy with sphalerite lattice at Sn concentration in the range of x=0.14-0.19. Analysis of optical spectra and calculations showed that an amorphous Si-Sn film with a Sn concentration of 19% is a semiconductor with indirect fundamental optical transition with very high absorption at photon energies 0.2 – 1.0 eV. It was found that precipitation of β-Sn occurs with an increase of Sn concentration up to 40%, which is accompanied by an increase in the reflection coefficient to 0.6-0.8 at photon energies below 0.8 eV. The limited temperature stability of amorphous Si-Sn films is shown for high-energy and long-term (10 minutes) laser irradiation due to the formation of metallic precipitates of β-Sn.

Abstract: The spectra of refractive index and absorption coefficient in thin films of Ge_23.5Pb₂₀S_56.5 glassy system were calculated on the base of analysis of transmission spectra. The refractive index has values between 2.0 and 2.6 in the spectral range between 500 nm and 1200 nm. The existence of indirect allowed transitions with energy E_g = 1.70 ± 0.01 eV and phonon energy of w_ph= 0.11 eV at room temperature was found. For values of the absorption coefficient a < 10³см ^–1 the fundamental absorption edge is described by exponential function known as Urbach-rule. The static structure disorder parameter w_o, is equal to 0.06 eV.

Abstract: The water vapour transport and the liquid water transport of high performance concrete (HPC) with the content of natural pozzolana are the described in this paper. Studied properties are presented by means of water vapour diffusion coefficient, water vapour diffusion resistance factor and absorption coefficient respectively. The natural pozzolana (NP), namely natural zeolite, is used as supplementary cementitious material which affects the durability properties of the end product. The obtained results revealed the effectiveness of NP in the terms of both studied properties when used in small amounts, i.e. at about 20% of cement weight. On the other hand substitutions higher than 40% result in worsening of the resistance of the concrete to water and water vapour ingress and its movement trough the material.