Specific Absorption Research Articles

Testing on Energy Absorption of Banana Fiber Polyester Composite

Natural fibers are now becoming a subject of interest to replace synthetic fiber as reinforcement materials where the development of natural fiber composites has been conducted in the last few decades. The objective of this research is to investigate the energy absorption capacity of banana fiber polyester composite and its specific energy absorption capacity as well. Banana fibers are extracted and cut into 10mm, 20mm and 30mm fiber length. Fabrication of rectangular bar as composite samples with different banana fiber length and fiber volume fraction (1%, 2%, and 3%) were conducted and the results are studied and analyzed. The information on energy absorption and specific energy absorption capacity are useful for applications such as automotive structures where the ability to absorb impact may save life. The increase of banana fiber content and length shows an increase of maximum load and energy absorption values for all specimens.

Suspended Particulate Matter Concentrations Retrieved from Self-Calibrated Multispectral Satellite Imagery

Suspended Particulate Matter Concentrations Retrieved from Self-Calibrated Multispectral Satellite ImageryInland waters are known to be laden with high levels of suspended particulate matter (SPM). Remotely sensed data have been shown to provide a true synoptic view of SPM over vast areas. However, as to date, there is no universal technique that would be capable of retrieving SPM concentrations without a complete reliance on time-consuming and costly ground measurements ora prioriknowledge of inherent optical properties of water-borne constituents. The goal of this paper is to present a novel approach making use of the synergy found between the reflectance in the visual domain (~ 400-700 nm) with the near-infrared portion of the spectrum (~ 700-900 nm). The paper begins with a brief discourse of how the shape and spectral dependence of reflectance is determined by high concentrations of SPM. A modeled example is presented to mimic real-world conditions in fluvial systems, with specific absorption and scattering coefficients of the virtual optically active constituents taken from the literature. Using an optical model, we show that in the visual spectral domain (~ 400-700 nm) the water-leaving radiance responds to increasing SPM (0-100 g m-3) in a non-linear manner. Contrarily to the visual spectra, reflectance in the near infrared domain (~ 700-900 nm) appears to be almost linearly related to a broad range of SPM concentrations. To reduce the number of parameters, the reflectance function (optical model) was approximated with a previously experimentally verified exponential equation (Schiebeet al., 1992: Remote sensing of suspended sediments: the Lake Chicot, Arkansas project, Int. J. Remote Sensing,13, 8, 1487-1509). The SPM term in Schiebe's equation was expressed as a linear function of top-of-atmosphere reflectance. This made it possible to calibrate the reflectance in the visual domain by reflectance values from the near-IR portion of the spectrum. The possibility to retrieve SPM concentrations from only remote sensing data without any auxiliary ground mea-surements is tested on a Landsat ETM + scene acquired over a reservoir with moderately turbid water with SPM concentrations between 15-70 g m-3. The retrieved concentrations (on average) differ from in-situ measurement by ~ 10.5 g m-3.

Research on Energy Absorption Characteristics of Honeycomb Sandwich Panels

Due to the excellent mechanical properties combined with high strength to weight ratio, honeycomb sandwich panels (HSP) are used increasingly in aerospace, automobile and marine industries. In order to improve the crashworthiness of vehicle body, it is of great significance to study the energy absorption characteristics of the components. For this reason, specific energy absorption (SEA: the energy absorption per unit mass) of HSP was selected to be the objective function in order to find an optimal design of HSP under impact loading. The explicit finite element analysis (FEA) was used to derive response surface (RS) model of SEA, and a single-objective optimization was performed to get the optimal design. Before the optimization design of HSP, the energy-absorptions of HSP and the honeycomb core (HC) were compared with each other. It was found that HSP could absorb much more impact energy than HC due to the stabilizing effect of the face sheets during the process of crushing.

Stress Induced Phase Transformations in TRIP-Steel / Mg-PSZ Composites

Composite materials and micro- and macrostructure designs have been the focus of numerous scientific studies over the past few years according to their crashworthiness [1-3]. Crashworthiness is concerned with the absorption of energy through controlled failure mechanisms and modes that enable a defined load profile during energy absorption [4]. Cellular materials, such as metal foams, are materials which display a unique combination of physical and mechanical properties, e.g. for crash box applications. The defining characteristic of metal foams is a very high porosity, typically in the range of 70 to 90 vol. %. In principle, cellular metals can be manufactured from gas, liquid or solid phases and currently the most advanced methods involve melt-metallurgical processes [5]. Several groups have produced foam structures by using hollow spheres to form the cells of the material [5, 6]. These materials exhibited plateau stresses of 5 MPa and 23 MPa respectively, with volume specific energy absorptions SEA of 2 MJ/m3 and 10 MJ/m3 respectively, up to 50 % strain [6, 7]. By combining ceramics with ductile metals, failure-tolerant metal matrix composites (MMCs) can be created. With regard to application of the MMCs as wear resistant materials in metal forming tools a prolongation of the life time and the resultant reduced equipment downtimes have been achieved by active steel infiltrating of porous zirconia structures with the aid of Ti as activator [8]. A very promising approach concerning zirconia/steel - composite materials with superior mechanical properties has been demonstrated by Guo et al. using a low-alloyed TRIP steel in combination with an Y-PSZ – ceramic [9, 10]. In a previous study honeycomb structures were formed from composites of high-alloyed austenitic stainless TRIP-steel AISI 304 with Mg-PSZ with different mixing proportions due to ceramic extrusion at room temperature and sintering at 1350 °C for 2 h in an 99.9 % Argon atmosphere [11]. One of the most promising manufacturing route to produce open cell composite foams is based on the patent of Schwartzwalder [12] by the replication method using polyurethane sponge as a template. The polymer foam is impregnated in a powder slurry (this first coating contributes as an adhesive porous layer for further coating processes), the ceramic slurry is squeezed out of the functional pores and cold spray coatings are applied in order to eliminate defects out of the squeezing process and reach the critical wall thickness for acceptable mechanical properties. In [13] the authors reported about foams with 90 Vol% high alloyed TRIP-steel and 10 Vol% Mg-PSZ. Up to 50 % compressive strain a remarkable enhancement of the SEA was observed in comparison to comparable structures with TRIP-steel only.

A Novel Grating Modulation Technique for Photonic Bandgap Fiber Gas Sensors

We present a novel grating modulation technique for photonic bandgap fiber (PBF) gas sensors. The grating modulation technique involves modulating the Bragg wavelength around a specific gas absorption line and measuring the second-harmonic signals for optical gas sensing. The responses of the PBF gas sensors employing the grating modulation technique to different acetylene concentrations ranging from 0% to 10% agree well with the prediction. Both 0.8- and 1.3-m-long PBF gas sensors are demonstrated.

The optimisation of the energy absorption of partially Al foam-filled commercial 1050H14 and 6061T4 Al crash boxes

Partially Alulight and Hydro Al closed-cell foam-filled commercial 1050H14 Al and 6061T4 Al crash boxes were optimised using the response surface methodology in order to maximise specific energy absorption (SEA). The quasi-static crushing of empty and filled crash boxes was simulated using LS-DYNA, and the results were further confirmed with experimental quasi-static crushing testing of empty and Alulight foam-filled commercial 1050H14 Al crash boxes. Results showed that partial foam filling of commercial crash boxes increased both SEA and mean load because of foam filler axial and lateral deformation in between the progressing folds of the crash box. Within the studied constraint range of box mean load, box wall thickness and foam filler density, the optimised Alulight and Hydro foam-filled 1050H14 and 6061T4 crash boxes resulted in 26%–40% increase in total energy absorption as compared with empty crash boxes. Considering the same weight basis, the use of a higher yield strength box wall material and higher plateau stresses of Al foam filler resulted in higher energy absorptions in partial foam-filled boxes at relatively low displacements.

Fatty acid composition and degradation level of the oils used in canned fish as a function of the different types of fish

An experimental investigation was carried out to assess the fatty acid composition and the degradation level of the covering oil present in canned fish. The most commonly marketed canned fish types were considered (tuna, sardines, anchovies, mackerels), as well as different kinds of covering oil: extra virgin olive oil, olive oil, refined seed oil. A total of 68 samples were analyzed. Two-way analysis of variance, followed by Fisher's Least Significant Difference test for multiple comparisons, and principal component analysis were carried out to compare the effect of both type of oil used and kind of fish on oil quality. The obtained results showed the lowest extent of both hydrolytic and oxidative degradation in samples containing extra virgin olive oil. In particular, the contents of triacylglycerol oligopolymers, imputable to secondary oxidative degradation, were equal to 0.17%, 0.50% and 0.74% for extra virgin olive oil, olive oil and refined seed oil, respectively. Olive oil showed significantly higher hydrolytic degradation, with diacylglycerols equal to 3.37%, but lower oxidative degradation and trans isomers content than refined seed oil. Finally, the type of fish did not seem to influence the extent of oxidative and hydrolytic degradation, with the only exception of sardines’ covering oil. This oil, characterized by the highest polyunsaturated fatty acid content, showed the highest values of oxidized triacylglycerols (1.32%) and specific absorption at 232 ( K 232, 4.030), indices of primary oxidative degradation.

Static and Dynamic Crushing Behaviors of Aluminum Foam

Quasi-static and dynamic axial crushing tests were carried out to investigate the energy absorption capacity of aluminum foam with several densities. First, aluminum foam samples with three densities were crushed quasi-statically to study their compression characteristics, the stress strain relationship curves and energy absorption capacities were achieved from the test results; then dynamic crushing tests were carried out to check the crushing behaviors of the corresponding samples; finally, the energy absorption capacities of tested samples were compared. According to the tests results, all the aluminum foam samples showed very good isotropy and very high mass specific energy absorption capacities. For the crushing tests, the dynamic crushing behaviors were very similar to the static ones, which meant aluminum foam was insensitive to the crash velocity tested.

Design Optimization of Bi-Tubular Thin Walled Columns for Crashworthiness Application

Improving crashworthiness of vehicles is considered to be one of the main concerns in traffic safety. The study focused on new designs that can be incorporated into existing vehicles. The paper presents a crashworthiness design of a bi-tubular thin walled column for different dimension profiles. To formulate the complex crashworthiness design problem, the response surface method (RSM) was utilized. The design of experiments of the factorial design is used to construct the response surface for the specific energy absorption (SEA). This surface was optimized for SEA. Results from a finite element analysis of elastic plastic square bi-tubular steel tubes subjected to dynamic axial impact load are reported. The bi-tubular design has shown good potential as an efficient energy absorber in comparison to existing conventional energy absorbing structures.

Effect of Ultrasound and Xylanase Treatment on the Physical-Mechanical Properties of Bleached Eucalyptus Kraft Pulp

The modification on the fiber structure of bleached eucalyptus kraft pulp is a very attractive alternative for improve- ments in the properties of paper production. The enzymatic treatment by xylanases and ultrassonic treatments modify the characteristics of the fibers, has been reported. Therefore, the purpose of this study was to evaluate the influence of ultrasonic waves as a facilitator of the action of enzymes (hemicellulase) by modifying the physicochemical nature of fiber eucalyptus Kraft pulp, in order to improve the physical and mechanical properties of the paper. But it was observed the that idea of ultrasound acts as facilitator for action of enzymes can’t be affirmed, since in most properties XA-1 and XA-2 were equal statistically. It may be noted that the junction of ultrasound and xylanase provided improves on tensile index, specific elastic modulus and tensile energy absorption and a decrease of tear index on the mechanical properties of handsheet and it increased the opacity when the ultrasound was applied before xylanase.

Energy-Absorption Property of Ceramic Fiber Reinforced Concrete

Full-automatic concrete pressure machine and 100-mm-diameter split Hopkinson pressure bar (SHPB) apparatus were used to investigate quasi-static and dynamic energy absorption property of ceramic fiber reinforced concrete (CRFRC) subjected to various high strain rates, which is compared to carbon fiber reinforced concrete at the same volume fraction of 0.1%, 0.2% and 0.3%. And the absorbing mechanism of CRFRC is analyzed. The results show that the quasi-static energy-absorption property of CRFRC increases with the volume of ceramic fiber and the relation presents linear approximations; the specific energy absorption of ceramic fiber reinforced concrete is strain rate-dependent dynamic strength-dependent under impact load, and the effect can be expressed by linear approximations. And the strain rate is more distinct when volume fraction of ceramic fiber increases. The energy absorption property of ceramic fiber reinforced concrete is superior to plain and carbon fiber reinforced concrete, especially at higher strain rate and volume.

ESD currents induced in a charged human body approaching a vehicle

The finite-difference time-domain (FDTD) method is used to calculate electrostatic discharge (ESD) currents induced in a charged human body approaching a vehicle. Maximum current densities induced in the human body are much higher than the threshold current density of 1 μA/cm 2 for the steady-state current flow cases, which may cause biological effects. It is found that the ESD current induced in the heart is smaller than the threshold current required to produce ventricular fibrillation in humans. The specific absorption (SA) induced in the human body is considerably smaller than the value of 28.8 J/kg regulated by the ANSI.

Seeing Is Believing: Opportunities, Challenges, and Solutions in Plant Cell Biology

Seeing Is Believing: Opportunities, Challenges, and Solutions in Plant Cell Biology

Characterization of dissolved organic matter in urban sewage using excitation emission matrix fluorescence spectroscopy and parallel factor analysis

Wastewater dissolved organic matter (DOM) from different processing stages of a sewage treatment plant in Xiamen was characterized using fluorescence and absorption spectroscopy. Parallel factor analysis modeling of excitation-emission matrix spectra revealed five fluorescent components occurring in sewage DOM: one protein-like (C1), three humic-like (C2, C4 and C5) and one xenobiotic-like (C3) components. During the aerated grit chamber and primary sedimentation tank stage, there was only a slight decrease in fluorescence intensity and the absorption coefficient at 350 nm ( a 350). During the second aeration stage, high concentration of protein-like and short-wavelength-excited humic-like components were significantly degraded accompanied by significant loss of DOC (80%) and a 350 (30%), indicating that C1 and C2 were the dominant constituents of sewage DOM. As a result, long-wavelength-excited C4 and C5 became the dominant humic-like components and the DOM molecular size inferred from the variation of spectral slope S (300-650 nm) and specific absorption ( a 280/DOC) increased. Combination use of F max of C1 and the ratio of C1/C5, or a 350 may provide a quantitative indication for the relative amount of raw or treated sewage in aquatic environment.

Application of a spectroscopic method to estimate the olive oil oxidative status

AbstractA rapid Fourier transformed infrared (FTIR) attenuated total reflectance (ATR) spectroscopic method coupled with partial least squares (PLS), was developed to estimate the oxidation degree of extra virgin olive oil (EVOO). The reference values of EVOO oxidation for the FTIR calibration were obtained by the specific absorptions at 232 and 270 nm, due to the presence of conjugated diene (CD) and conjugated triene (CT) groups, as monitored by the UV spectrophotometric determination. Specific washing procedures were applied to the EVOO to obtain EVOOP and EVOOTP samples, without phenolic compounds and without tocopherols and phenols, respectively. To obtain different oxidation degrees covering wide CD and CT ranges, EVOO, EVOOP, and EVOOTP samples were subjected to a forced oxidation at 60°C for 20 days and aliquots of the oils were daily analyzed. Regression of the FTIR/PLS‐predicted CD and CT of individual oxidized oils EVOO, EVOOP, EVOOTP, and all combined oils (EVOOALL) against UV–Visible reference values demonstrated the good quality of the models in terms of R2 and RMSECV values. The results of the study indicated that a strong correlation existed between FTIR and UV–Visible peak intensities.Practical applications: The FTIR‐ATR method coupled with PLS elaboration was developed and applied to predict the oxidation degree of EVOO samples with considerable advantages in terms of simplicity, analysis time, and solvent consumption as compared to the standard method. Moreover, suitable adjustments of the equipment could permit a rapid control at‐line in oil sector.

Crashworthiness design of thin-walled curved beams with box and channel cross sections

This paper presents a crashworthiness design of thin-walled curved steel beams with box and channel cross section. Three parameters are chosen as design variables and optimised to acquire the maximisation of the beam's energy absorption capacity during crashes. In this study, the thin-walled curved beam's energy absorption capacity is expressed in terms of the specific energy absorption (SEA), and the response surface method is employed to formulate the SEA as a function of the three design variables. Finite element (FE) models for such beams are created and used for crashworthiness analyses for the objective of deriving such functions. After having the optimal designs, the effects of the design variables on the curved beam's crash performance are investigated through parametric studies. Finally, simplified FE models are created for the thin-walled curved beams again and used for the same optimisation problem. The optimal designs obtained from the simplified FE models are compared to the previous ones to validate the simplified FE models as well as the simplified modelling method.

The specific inherent optical properties of three sub-tropical and tropical water reservoirs in Queensland, Australia

The underwater light climate, which is a major influence on the ecology of aquatic systems, is affected by the absorption and scattering processes that take place within the water column. Knowledge of the specific inherent optical properties (SIOPs) of water quality parameters and their spatial variation is essential for the modelling of underwater light fields and remote sensing applications. We measured the SIOPs and water quality parameter concentrations of three large inland water impoundments in Queensland, Australia. The measurements ranged from 0.9 to 42.7 μg l−1 for chlorophyll a concentration, 0.9–170.4 mg l−1 for tripton concentration, 0.36–1.59 m−1 for a CDOM(440) and 0.15–2.5 m for Secchi depth. The SIOP measurements showed that there is sufficient intra-impoundment variation in the specific absorption and specific scattering of phytoplankton and tripton to require a well distributed network of measurement stations to fully characterise the SIOPs of the optical water quality parameters. While significantly different SIOP sets were measured for each of the study sites the measurements were consistent with published values in other inland waters. The multiple measurement stations were allocated into optical domains as a necessary step to parameterise a semi-analytical inversion remote sensing algorithm. This article also addresses the paucity of published global inland water SIOP sets by contributing Australian SIOP sets to allow international and national comparison.

Assessment of Quasi-Three-Dimensional Composites - with Discussions on Fiber Straining and Weaving Effectiveness

The usage of laminated composite materials in critical applications requiring high specific stiffness, high specific strength, and high impact resistance is commonly hindered by the phenomenon of delamination. Once delamination sets in, for example, due to impact loading, the structural integrity of the composites is at risk of degrading unless delamination is controlled. This study explores the viability of interlaminar integration, so-called quasi-three-dimensional (Q3D) weave, as a potential solution to delamination. Compressive stiffness and strength and impact-induced damage and energy absorption processes for three Q3D configurations were experimentally studied and compared with those of laminated and two-dimensional woven composites. It was found that rear-layer fiber straining and weaving mechanisms had significant effects on composite’s energy absorption and damage processes. A five-harness quasi-three-dimensional (Q3DO5) composite was found to have lower impact-induced damage, higher specific energy absorption, lower impact-induced structural degradation, and competitive in-plane properties than the laminated counterpart.

Structural, Optical and Photocatalytic Properties of Sol–Gel Synthesized Mesoporous TiO<SUB>2</SUB> Film

TiO2 surfactant-templated nanostructured film was fabricated by supramolecular templating technique using TiCl4 and P-123 as raw material and surfactant, respectively. The film was produced by sol-gel dip coating procedure. Characterization of the product was carried out by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) specific surface areas, thermogravimetry (TG), and UV-vis absorption spectroscopy. Detailed characterization reveals that film is transparent and has a wormlike mesostructured with high surface area. It is about 2 microm thick and is composed of closely packed anatase particles. The estimated band gap value of TiO2 thin film in the present work is 3.69 eV which is about 0.3 eV larger than value reported in literature for anatase thin film. It could be due to quantum size effect arising from the small size of TiO2 nanocrystallite in this thin film. The photocatalytic activity of the prepared TiO2 film was evaluated by Crystalviolet dye degradation. The film has excellent photocatalytic efficiencies and more than 70% of dye was decolorized in 60 minutes.

Safety Assessment of UWB Radio Systems for Body Area Network by the ${\rm FD}^{2}{\rm TD}$ Method

The paper deals with the numerical prediction of the specific absorption (SA) of ultra wideband (UWB) radio systems for wireless body area network (BAN). The electro-magnetic analysis is performed by a frequency-dependent finite difference time domain (FD2TD) method here proposed with a new formulation based on a total current density approach. A first order Debye approximation is used to model the frequency-dependent properties of the human body in the frequency range of the UWB signals. The proposed method permits to assess the specific absorption and power loss in the human body exposed to an UWB pulsed source. Different numerical models of the human bodies are finally considered in order to investigate safety aspects.