Single Absorber Research Articles

Scan-Free Absorbance Spectral Imaging A(x, y, λ) of Single Live Algal Cells for Quantifying Absorbance of Cell Suspensions.

Label-free, non-invasive, rapid absorbance spectral imaging A(x,y,λ) microscopy of single live cells at 1.2 μm × 1.2 μm resolution with an NA = 0.85 objective was developed and applied to unicellular green algae Chlamydomonas reinhardtii. By introducing the fiber assembly to rearrange a two-dimensional image to the one-dimensional array to fit the slit of an imaging spectrograph equipped with a CCD detector, scan-free acquisition of three-dimensional information of A(x,y,λ) was realized. The space-resolved absorbance spectra of the eyespot, an orange organelle about 1 μm, were extracted from the green-color background in a chlorophyll-rich single live cell absorbance image. Characteristic absorbance change in the cell suspension after hydrogen photoproduction in C. reinhardtii was investigated to find a single 715-nm absorption peak was locally distributed within single cells. The formula to calculate the absorbance of cell suspensions from that of single cells was presented to obtain a quantitative, parameter-free agreement with the experiment. It is quantitatively shown that the average number of chlorophylls per cell is significantly underestimated when it is evaluated from the absorbance of the cell suspensions due to the package effect.

Independent polarization and multi-band THz absorber base on Jerusalem cross

In this paper, we present the design and simulation of a single and multi-band perfect metamaterial absorber (MA) in the THz region base on Jerusalem cross (JC) and metamaterial load in unit cells. The structures consist of dual metallic layers for allowing near-perfect absorption with absorption peak of more than 99%. In this novel design, four-different shape of Jerusalem cross is presented and by adding L, U and W shape loaded to first structure, we tried to achieve a dual-band absorber. In addition, by good implementation of these loaded, we are able to control the absorption resonance at second resonance at 0.9, 0.7 and 0.85THz respectively. In the other hand, we achieved a semi stable designing at first resonance between 0.53 and 0.58THz. The proposed absorber has broadband polarization angle. The surface current modeled and proved the broadband polarization angle at prototype MA. The LC resonance of the metamaterial for Jerusalem cross and modified structures are extracting from equivalent circuit. As a result, proposed MA is useful for THz medical imaging and communication systems and the dual-band absorber has applications in many scientific and technological areas.

A finite-element formulation for room acoustics simulation with microperforated panel sound absorbing structures: Verification with electro-acoustical equivalent circuit theory and wave theory

A simple frequency-domain finite-element method (FD–FEM) for sound field analyses inside rooms installed with microperforated panel (MPP) sound absorbing structures is described here. This method can also analyze sound absorbing structures composed of MPPs and permeable membranes (PM) simply by changing the only material parameters of MPP into those of PM. As the first stage of the study, the validity of the present FD–FEM is tested through the numerical experiments based on the impedance tube method for measuring the absorption characteristics at normal incidence. In the numerical experiments, we calculated the absorption characteristics of a single MPP absorber, a double-leaf MPP space absorber and a space absorber composed of MPP and PM by using the FD–FEM in two-dimensions, and the computed absorption characteristics are compared with those calculated by an electro-acoustical equivalent circuit theory or a wave theory based on Helmholtz–Kirchhoff boundary integral equation. The results showed that the presented FD–FEM can analyze the absorption characteristics at normal incidence of the MPP sound absorbing structures accurately with the simplicity of the formulation.

Investigation of Thin and Broadband Capacitive Surface-Based Absorber by the Impedance Analysis Method

In this paper, a novel thin, broadband, single polarization capacitive surface-based absorber is proposed and investigated. First, the impedance of a substrate and matching surface are analyzed and used for the determination of the structure parameters of the microwave absorber. Second, by utilizing infinite strip gratings with lumped resistors, a capacitive surface-based absorber is presented with 48.6% thickness reduction and 11.7% bandwidth enhancement in comparison to the Salisbury screen. Finally, a prototype of the proposed absorber is fabricated and measured for validation. The proposed method provides an efficient way for the design of thin broadband microwave absorbers.

Modeling of Natural Convection Non Reversible Single Pass Pressurized and Non Pressurized Solar Hot Water Systems for Domestic Applications

This paper mainly deals with the problem of reverse flow and explicit expressions have been presented which shows that the placement of hot water storage tank above the collector helps to eliminates reverse flow and it was observed that if tank is kept very high above the collector then there is always some flow of liquid through the collector especially if the outlet of the collector is connected near the middle of the storage tank. This is due to considerable heat losses resulting poor thermal efficiency of the system. The new design based on single and multi pass systems for domestic hot water systems which completely eliminate reverse flow problems have been forwarded and studies in details. The single pass systems besides avoiding reverse flow has two distinct features: (i) Allows the place the main water storage tank at any desirable place (even below the collector) (ii) Water is obtained at pre-determined temperature irrespective of insolation levels. The numerical calculations for single pass natural convection pressurized solar hot water systems meander tube fluid flow channel absorber, serpentine tube collectors and for non pressurized thermosyphonic solar hot water systems using parallel tube absorber were performed. The experimental measurements on such modified systems were performed manually by noting thermosyphonic flow rate and temperatures at every half hours time interval. The theoretical results matches well with experimental results. It was found that the non pressurized solar hot water systems using parallel tube absorber have average thermal efficiency of 41 % in the single pass and 27. 3 % in the multi-pass modes. The system efficiency of pressurized solar hot water systems using meander tube absorber are 30 % in single pass mode and 20 % in the multi pass mode due to higher temperature of absorber and higher heat losses from absorber in pressurized solar hot water systems.

A Study of Ultra-Thin Single Layer Frequency Selective Surface Microwave Absorbers With Three Different Bandwidths Using Double Resonance

In this paper, we present three ultra-thin frequency selective surface (FSS) microwave absorbers on a single layer, that have three remarkable features. First, the various absorbing bandwidths can be obtained in our absorber by adjusting the two absorbing peaks, which are produced by two different resonance effects on the FSS. By manipulating the dimension parameters, we design the dual-band, 3-dB and 10-dB band absorbers. We achieved the absorber's thickness of $0.039\lambda_{\rm g}$ with the single layer due to high loss of inter-digital capacitor patterns on the FSS. Additionally, the proposed absorbers are insensitive to polarized electromagnetic (EM) waves because of the symmetric structure of the FSS. In this study, the absorber mechanism and transmission line (TL) modeling for the absorber design are studied. Each of the proposed absorbers is analyzed by using the TL equivalent circuit model and full-wave analysis. The loss factor is studied in order to demonstrate the origin of losses, and a parametric study is conducted to explain how to vary the absorbing bandwidths. The performances of each proposed absorber are also experimentally demonstrated.

Acoustic behavior of porous ceiling absorbers based on local and extended reaction.

The acoustic behavior of ceiling absorbers can be predicted under different surface reaction assumptions: Local and extended reaction. This study aims to experimentally validate acoustic transfer functions near a ceiling absorber in an anechoic chamber based on the two surface reaction models. First, a ceiling absorber with two mounting conditions is modeled by equivalent fluid models, such as Delany-Bazley's, Miki's, and Komatsu's model, in various ways: (1) Local vs extended reaction and (2) plane-wave vs spherical-wave incidence. For a single absorber under anechoic conditions, the acoustic transfer functions for four source-receiver pairs are simulated using a pressure-based image source model, and then compared with measurements. For a rigid backing condition, both the local and extended reaction models agree well with the measurement. For an absorber backed by an air cavity, the extended reaction model agrees better at larger incidence angles at lower frequencies than the local reaction model.

Classification of solar cells according to mechanisms of charge separation and charge collection.

In the last decade, photovoltaics (PV) has experienced an important transformation. Traditional solar cells formed by compact semiconductor layers have been joined by new kinds of cells that are constituted by a complex mixture of organic, inorganic and solid or liquid electrolyte materials, and rely on charge separation at the nanoscale. Recently, metal organic halide perovskites have appeared in the photovoltaic landscape showing large conversion efficiencies, and they may share characteristics of the two former types. In this paper we provide a general description of the photovoltaic mechanisms of the single absorber solar cell types, combining all-inorganic, hybrid and organic cells into a single framework. The operation of the solar cell relies on a number of internal processes that exploit internal charge separation and overall charge collection minimizing recombination. There are two main effects to achieve the required efficiency, first to exploit kinetics at interfaces, favouring the required forward process, and second to take advantage of internal electrical fields caused by a built-in voltage and by the distribution of photogenerated charges. These principles represented by selective contacts, interfaces and the main energy diagram, form a solid base for the discussion of the operation of future types of solar cells. Additional effects based on ferroelectric polarization and ionic drift provide interesting prospects for investigating new PV effects mainly in the perovskite materials.

A cost effective solution for development of broadband radar absorbing material using electronic waste

Electronic-waste items like disassembled mobile and computer printed circuit boards (PCBs) have been processed in a high energy planetary ball-mill for 10h, to investigate the dielectric, magnetic and radar absorbing properties. The main goal of present paper is to achieve wide bandwidth for <−10dB reflection loss at minimum cost in the frequency range of 8.2 to 12.4GHz. The frequency dependent complex permittivity and permeability values of electronic waste composite material have been measured using transmission/reflection approach, and are used for computation of reflection loss with varying absorber layer thickness ranging from 1.0 to 3.5mm. A single layer absorber is fabricated with optimal coating thickness of 2.5mm (i.e., thickness value for reflection loss <−10dB). The measured reflection loss value has been found to −27.98dB at 9.3GHz with absorber layer thickness of 2.5mm, which may ascribe to proper impedance matching and large dielectric loss. Moreover, broadest bandwidth (for <−10dB reflection loss) covering the maximum frequency range of X-band has been noticed as 3.9GHz. Results demonstrate the enormous potential of the electronic waste composite material to act as highly efficient, cost effective, and broadband radar wave absorber for various practical electromagnetic applications.

Line-driven radiative outflows in luminous quasars

An analysis of ~19500 narrow (<200 km/s) CIV 1548.2,1550.8 absorbers in ~34000 Sloan Digital Sky Survey quasar spectra is presented. The statistics of the number of absorbers as a function of outflow-velocity shows that in approximately two-thirds of outflows, with multiple CIV absorbers present, absorbers are line-locked at the 500 km/s velocity separation of the CIV absorber doublet; appearing as 'triplets' in the quasar spectra. Line-locking is an observational signature of radiative line driving in outflowing material, where the successive shielding of 'clouds' of material in the outflow locks the clouds together in outflow velocity. Line-locked absorbers are seen in both broad absorption line quasars (BALs) and non-BAL quasars with comparable frequencies and with velocities out to at least 20000 km/s. There are no detectable differences in the absorber properties and the dust content of single CIV doublets and line-locked CIV doublets. The gas associated with both single and line-locked CIV absorption systems includes material with a wide range of ionization potential (14-138 eV). Both single and line-locked CIV absorber systems show strong systematic trends in their ionization as a function of outflow velocity, with ionization decreasing rapidly with increasing outflow velocity. Initial simulations, employing CLOUDY, demonstrate that a rich spectrum of line-locked signals at various velocities may be expected due to significant opacities from resonance lines of Li-, He- and H-like ions of O, C and N, along with contributions from HeII and HI resonance lines. The simulations confirm that line driving can be the dominant acceleration mechanism for clouds with N(HI) ~ 10^19 cm^-2.

Equivalent circuit model of an ultra-thin polarization-independent triple band metamaterial absorber

This paper presents equivalent circuit modeling of an ultra-thin polarization-independent metamaterial microwave absorber consisting of three concentric closed ring resonators (CRR). The unit cell size as well as the other geometrical dimensions like radii and widths of the rings are optimized so that absorptions take place at three distinct frequencies near to the middle of the FCC defined radar spectrum eg., at 5.50 GHz, 9.52 GHz and 13.80 GHz with peak absorptivities of 94.1%, 99.6% and 99.4% respectively. The equivalent circuit model of the triple band absorber has been developed sequentially considering the single band and double band absorber models. The circuit simulation of the final model agrees well with the full-wave simulation, thus validating the modeling technique. The structure is also fabricated and experimental absorption peaks are found close to the simulated values.

Broadband Graphene Saturable Absorber for Pulsed Fiber Lasers at 1, 1.5, and 2 μm

Ultrafast fiber lasers with broad spectral coverage are in great demand for a variety of applications, such as spectroscopy, and biomedical diagnosis. Graphene is an ideal ultrawide-band saturable absorber. We report broadband (up to ~1000 nm) ultrafast pulse generation from three fiber lasers mode-locked by a single graphene saturable absorber device. The mode-locked pulses were based on Yb-, Er- and Tm:Ho-doped fiber lasers at the central wavelength of 1035, 1564, and 1908 nm, respectively. The maximum output energy is up to 16.2 nJ at 1908 nm. It is the first time that ultrafast fiber lasers covering 1, 1.5, and 2 μm spectral region are mode-locked with a single graphene device. Our results validate the intrinsic broadband operation property of graphene devices for all major fiber laser wavelengths from 1 to 2 μm.

Fast and sensitive optical toxicity bioassay based on dual wavelength analysis of bacterial ferricyanide reduction kinetics.

Global urban and industrial growth, with the associated environmental contamination, is promoting the development of rapid and inexpensive general toxicity methods. Current microbial methodologies for general toxicity determination rely on either bioluminescent bacteria and specific medium solution (i.e. Microtox(®)) or low sensitivity and diffusion limited protocols (i.e. amperometric microbial respirometry). In this work, fast and sensitive optical toxicity bioassay based on dual wavelength analysis of bacterial ferricyanide reduction kinetics is presented, using Escherichia coli as a bacterial model. Ferricyanide reduction kinetic analysis (variation of ferricyanide absorption with time), much more sensitive than single absorbance measurements, allowed for direct and fast toxicity determination without pre-incubation steps (assay time=10 min) and minimizing biomass interference. Dual wavelength analysis at 405 (ferricyanide and biomass) and 550 nm (biomass), allowed for ferricyanide monitoring without interference of biomass scattering. On the other hand, refractive index (RI) matching with saccharose reduced bacterial light scattering around 50%, expanding the analytical linear range in the determination of absorbent molecules. With this method, different toxicants such as metals and organic compounds were analyzed with good sensitivities. Half maximal effective concentrations (EC50) obtained after 10 min bioassay, 2.9, 1.0, 0.7 and 18.3 mg L(-1) for copper, zinc, acetic acid and 2-phenylethanol respectively, were in agreement with previously reported values for longer bioassays (around 60 min). This method represents a promising alternative for fast and sensitive water toxicity monitoring, opening the possibility of quick in situ analysis.

Flexible microwave absorbers based on barium hexaferrite, carbon black, and nitrile rubber for 2–12 GHz applications

Flexile single layer electromagnetic wave absorbers were designed by incorporating appropriate amounts of carbon black in a nitrile butadiene rubber matrix along with an optimized amount of magnetic counterpart, namely, barium hexaferrite for applications in S, C, and X-bands. Effective dielectric permittivity and magnetic permeability were measured using cavity perturbation method in the frequency range of 2–12 GHz. The microwave absorbing characteristics of the composites were studied in the S, C, and X-bands employing a model in which an electromagnetic wave is incident normally on a metal terminated single layer. Reflection loss exceeding −20 dB is obtained for all the samples in a wide frequency range of 2–12 GHz when an appropriate absorber thickness between 5 and 9 mm is chosen. The impact of carbon black is clearly observed in the optimized composites on the mechanical strength, thickness, band width of absorption, dielectric properties, and absorptivity.

A neutronic pin cell and full-core design analysis of the 4S reactor

The 4S (Super-safe small, and simple reactor) core, based on the Toshiba Gen-IV 10MWe fast reactor design, is modeled and simulated with the Monte Carlo code MCNP to obtain useful neutronics design information. This paper carries out a preliminary pin-cell simulation to obtain the neutron spectrum, the infinite multiplication k∞ and the effect of temperature and moderator density followed by a full-core simulation for the effective multiplication factor keff with a central absorber control rod. Two absorber materials are considered viz boron carbide (B4C) and hafnium (Hf) to determine the fuel inventory to balance the beginning of cycle (BOC) excess reactivity. It is found that for a single central absorber rod of radius 9cm, the maximum fuel rod radius is 6mm for hafnium and 6.2mm for B4C. This work is of use for the core design of small multipurpose Gen-IV reactors.

Multiband Metamaterial Absorber at Terahertz Frequencies

We propose a multi-band metamaterial absorber operating at terahertz frequencies. The design, characterization, and theoretical calculation of the high performance metamaterial absorber are reported. The multi-band metamaterial absorber consists of two metallic layers separated by a dielectric spacer. Theoretical and simulated results show that the metamaterial absorber has four distinct absorption points at frequencies 0.57 THz, 1.03 THz, 1.44 THz and 1.89 THz, with the absorption rates of 99.9%, 90.3%, 83.0%, 96.1%, respectively. Two single band metamaterial absorbers and a dual band metamaterial absorber on the top layer are designed. Some multi-band absorbers can be designed by virtue of combining some single band absorbers. The multiple-reflection theory is used to explain the absorption mechanism of our investigated structures.

Designing a hand rest tremor dynamic vibration absorber using H 2 optimization method

An optimal single DOF dynamic absorber is presented. A tremor has a random nature and then the system is subjected to a random excitation instead of a sinusoidal one; so the H2 optimization criterion is probably more desirable than the popular H∞ optimization method and was implemented in this research. The objective of H2 optimization criterion is to reduce the total vibration energy of the system for overall frequencies. An objective function, considering the elbow joint angle, θ2, tremor suppression as the main goal, was selected. The optimization was done by minimization of this objective function. The optimal system, including the absorber, performance was analyzed in both time and frequency domains. Implementing the optimal absorber, the frequency response amplitude of θ2 was reduced by more than 98% and 80% at the first and second natural frequencies of the primary system, respectively. A reduction of more than 94% and 78%, was observed for the shoulder joint angle, θ1. The objective function also decreased by more than 46%. Then, two types of random inputs were considered. For the first type, θ1 and θ2 revealed 60% and 39% reduction in their rms values, whereas for the second type, 33% and 50% decrease was observed.

Development of Broadband Ultra Micro-Perforated Panels Based on MEMS Technology

Fabrication process of ultra micro-perforated panels (ultra-MPPs) with perforations of diameter below 100 um based on MEMS technology is expatiated in this paper. As a promising alternative to the conventional porous absorbing materials, MPP absorber is now being widely used in noise control engineering. Theory reveals that the maximum sound absorption bandwidth of a single MPP absorber could be achieved by reducing the perforation diameter to a certain limit and the desirable perforation diameters are less than 100um under many circumstances. However, due to the limitation of traditional manufacturing tools and techniques, MPPs with ultra-micro perforations of diameter less than 100um, namely for ultra micro-perforated panel (ultra-MPPs), have seldom been investigated yet. In this study, micro electro mechanical systems (MEMS) technology was applied to a trial production of ultra-MPPs and the measurement of their normal absorption coefficients were carried out in the impedance tube. Results show that ultra-MPPs could attain high absorption over a broad frequency range, indicating that as a micro machining process, MEMS technology is suitable for fabricating ultra-MPPs in order to ensure the absorption performance.

Design and analyses of axial semi-active dynamic vibration absorbers based on magnetorheological elastomers

Magnetorheological elastomers are a new kind of magnetorheological materials mainly composed of polymer rubber and micro-sized magnetizable iron particles. Dynamic vibration absorbers based on magnetorheological elastomers are widely used in vibration systems with small amplitude since they have the advantages of no sealing equipments, good stability, and rapid response. In this article, a shear-mode semi-active dynamic vibration absorber based on magnetorheological elastomers is proposed, and the dynamic design principle of an axial semi-active dynamic vibration absorber attached to ship shafting is studied. The material preparation of magnetorheological elastomers and their properties under different magnetic fields are discussed. The structure of a single semi-active dynamic vibration absorber is designed, and theoretical analysis of shift-frequency property of a single semi-active dynamic vibration absorber is also investigated. The magnetic flux density of magnetorheological elastomers in the semi-active dynamic vibration absorber is analyzed using ANSYS software. A compact and efficient semi-active dynamic vibration absorber for shafting axial vibration control is proposed. Furthermore, a linear relationship is found between the excitation current and the natural frequency of a single semi-active dynamic vibration absorber. The results show that the designed axial semi-active dynamic vibration absorbers have better performance than classic passive dynamic vibration absorbers in terms of frequency-shift property and vibration absorption capacity.

Batch Adsorber Design for Different Solution Volume/Adsorbate Mass Ratios of Bentazon, Carbofuran and 2,4-D Adsorption on to Date Seeds Activated Carbon

The Adsorption isotherms and equilibrium of bentazon, carbofuran and 2,4-Dichlorophenoxyacetic acid (2,4-D) onto date seeds activated carbon (DSAC) were examined in batch process. Adsorption studies were conducted in the pesticides initial concentrations range of 25–250 mg/L and temperature of 30 oC. The experimental equilibrium data were analyzed by non-linear fitting using Langmuir, Freundlich and Temkin isotherm models. Equilibrium data fitted better with the Langmuir model showing maximum monolayer adsorption capacity of 78.13, 135.14 and 175.4 mg/g, for bentazon, carbofuran and 2,4-D respectively onto DSAC. A single stage batch absorber was designed for different operating line (V/M) ratios. Equilibrium data were obtained from the Langmuir isotherm at different V/M ratios using the mass balance equation for the batch absorber system. A simple linear expression relating the parameters involved in the batchabsorber design was proposed for the studied system.