Absorbance Characteristics Research Articles

Incident angle dependent tunable multiband infrared absorption based sensor

The effect of electromagnetic (EM) resonance in the graphene resonator and multiple reflections taking place in the dielectric spacer can provide the multiband infrared absorption. The intensity of resonance spectrum occurring due to the formation of EM dipoles in resonator can be controlled by patterning it using desired perturbation. The absorber response can be set with the multiple narrow and broad absorption peaks together by modulating the electrical properties of graphene material. The proposed absorber provides the incident angle dependent behavior with linear variation in the resonant wavelengths by maintaining the high absorption. This can provide a new way of tuning the antenna response by angle of incidence. The implemented absorber can provide the triple narrow bands which can be utilized for performing the refractive index sensing. The proposed absorber provides a significant value of sensing performance parameters including sensitivity, full-width-half-maxima, and figure-of-merit with the high value of quality factor. Moreover, the proposed absorber offers the ability of generating an extra narrow absorption band in the case of presence of sensing analyte of specific thickness and refractive index range making it highly sensitive for the detection of specific surroundings including the bio-cells, chemicals and humidity in the air. The broadband characteristics of the proposer absorber can be utilized in implementing the infrared EM shields and thermal storage components.

High‐Performance Self‐Assembled ZnO Nanowrinkle Network Structured Photodetectors

Herein, the effect of prebake temperature on the surface structure of zinc oxide (ZnO) nanowrinkle structures formed in a sol–gel growth process for UV photodetection is demonstrated. The sol–gel solutions are spin‐coated on glass and c‐plane sapphire substrates, and the resulting ZnO films are subjected to prebake and crystallization processes at 800 °C for an hour. In the sol–gel process, the prebake process is crucial in forming the nanowrinkle structure on the surface of the ZnO film. The maximum nanowrinkle structure of ZnO film is achieved at the prebake temperature of 150 °C. In addition to the formation of the optimized nanowrinkle structure, the UV response of the photodetector is further enhanced through the prebake temperature control. The nanowrinkle network structure significantly improves the optical absorbance and photoluminescence characteristics of the ZnO film, leading to high photocurrent, photoresponsivity, and external quantum efficiency for UV light. The results demonstrate the potential of sol–gel‐derived ZnO photodetectors with nanowrinkle network structures for UV sensing applications.

Quasi-static compressive performance of 3D printed polymer composite cellular cubic structures-An experimental study

Light weight cellular structures have gained extensive attention in the impact energy absorption applications owing to their superior specific strength and excellent crashworthiness characteristics. The main objective of the present research work is to utilize this benefit to tailor and to improve the structural design and material type of cellular structures for crashworthiness applications. Cubic structures with four different types of design patterns such as concave, convex, hyperbola, and hexagon were proposed and fabricated through three-dimensional (3D) printing technique. Four polymeric filament materials such as Poly lactic acid (PLA), Acrylonitrile butadiene styrene (ABS), PLA mixed carbon fiber (PLA/CF), and Polyethylene terephthalate glycol (PETG), mixed carbon fiber (PETG/CF) were utilized. Accordingly, the compression tests were performed on the fabricated cellular cubic structures under quasi-static loading to examine the effect of design pattern, and material types on the compressive behavior and energy absorbing characteristics. The results revealed that the convex design pattern of 3D printed PETG/CF cubic structure showed the significant energy absorbing characteristics compared to the other three design patterns. It is emphasized that the proposed 3D printed cubic cellular structures have great prospective to substitute the traditional energy absorbing structures in automotive vehicles and high speed trains.

A Linear Variable Parameter Observer-Based Road Profile Height Estimation for Suspension Nonlinear Dynamics Improvements

The accuracy of road profile height estimation has a significant impact on suspension control quality, which in turn influences handling, stability of vehicle motion and occupants' comfort. Based on our previous published work, this article designs and proposes a novel method for road profile estimation that is based on suspension nonlinear dynamics. The proposed approach first establishes the road profile height estimation model considering a real suspension design, including nonlinear characteristics of the shock absorber, bushing stiffness and damping, actual geometry of the control arms, and positioning of absorber. Unlike the conventional sprung-unsprung mass model, the real nonlinear suspension model provides much higher output prediction accuracy as computational and experimental results demonstrated. Moreover, the established estimation method and model require only two easily measurable parameters, which are the acceleration of the sprung mass and the travel of the shock absorber. While considering nonlinearity and hysteretic characteristics of the damping force, the proposed approach is based on the estimation framework of linear parameter-varying systems and establishes a sliding mode observer for estimating the road profile height. The stability of estimation error dynamics of the observer is guaranteed by the Lyapunov stability analysis. As bench-test experiments of a hardware implementation of the suspension-wheel unit validated the computational results. The tests demonstrated that the proposed method allows for real-time estimating of the road profile height in different road conditions and electric currents of the suspension damper and is robust to uncertainty of the payload.

EXPERIMENTAL STUDY OF THE PERFORMANCE CHARACTERISTICS OF SHOCK ABSORBERS

The article discusses the methodology for determining the performance characteristics of Toyota Prius 20 shock absorbers. The study was conducted using a stand for the diagnosis of shock absorbers developed by the Department of Road Transport of INRTU (Irkutsk National Research Technical University). Tests were carried out for five front suspension shock absorbers, one – a new serviceable shock absorber, the rest – shock absorbers that were previously in operation. The experimental dependences of the change in the resistance force of the shock absorber on the speed of movement of its rod are analyzed. The level of operational characteristics of the shock absorber under study was determined by comparing the obtained parameters with the parameters of the new shock absorber.
 The results of experimental studies are presented in the form of operational characteristics of tested shock absorbers and indicators that determine the level of operational characteristics of shock absorbers. The developed methods and the equipment implementing them make it possible to determine the functional dependencies and the level of performance of shock absorbers that were in the operating conditions of the vehicle.

Calculation of the parameters of the electromechanical shock absorber of the high-speed electric train

The article examines the issue of the chassis system of a high-speed electric train with body inclination and a vibration recovery system. The advantages of using an electromechanical shock absorber over hydraulic, pneumatic and similar systems are described. The authors considered the main characteristics of the DC electromechanical shock absorber. The main overall parameters of the shock absorber were presented. Attention is paid to the relevance of using an electromechanical shock absorber of a linear type, in comparison with analogues, including the ability to recover energy. Attention is drawn to the structure of the DC electromechanical shock absorber. The functional control scheme of the electromechanical shock absorber is considered and the control algorithm is described. The calculation areas of the parameters of the electromechanical shock absorber are determined. A 3D model of an electromechanical shock absorber in the Ansys Electronics software environment is presented. A finite-element mesh was built for further calculations of the magnetic field and inductance. In the article, attention is paid to the calculation of the magnetic field in the most intense mode. A picture of the shock absorber's magnetic field at the maximum working clearance was obtained and interim results were discussed. The results of calculating the inductance depending on the operating gap of the shock absorber are presented. Conclusions were made based on the results of calculations of magnetic and electrical parameters of an electromechanical shock absorber based on a linear direct current motor.

Perovskite Solar Cells with an SbX3 (X = Cl, I) Interface Dipole Layer

Forming an interface dipole moment pointing from the absorber to the oxide substrate can improve the open-circuit voltage (VOC) of perovskite solar cells (PSCs) without affecting photocurrent. In past studies, however, interface dipole layers were generally formed using organic self-assembled monolayers or polyelectrolytes, which raises concerns about intrinsic stability. Meanwhile, perovskites’ substrate-dependent electronic properties question the apparent correlation between the oxide’s work function and the built-in voltage. In this work, we propose an interface dipole layer based on solution-processable metal halides, which increases the built-in voltage of the n–i–p diode by simultaneously reducing the electron transport layer’s work function and strengthening the n-type characteristics of the perovskite absorber. The n–i–p-structured PSCs with the SbX3 dipole layer achieve substantially enhanced VOC (1.171 V) and power conversion efficiency (23.11%). Further experiments and calculations confirm that the proposed dipole model can explain the VOC enhancement qualitatively and quantitatively.

Frequency-dependent automotive suspension damping systems: State of the art review

Configuration of a passive suspension of a passenger vehicle most often requires a compromise between its handling, road-holding, and ride (passenger) comfort. Nowadays, car manufacturers (automotive OEMs) are forced to develop ways for enhancing the functionality of shock absorbers and yet keeping their costs low. The use of so-called frequency-dependent (FD) valves in hydraulic passive suspension dampers, which allow the damping force to vary with the frequency of the excitation (or its change rate), is a satisfactory solution to the problem by means of adaptive passive valves. In this study, the effectiveness of the FD technology in passenger vehicles is demonstrated on the basis of a quarter-car simulation model. This is followed by a comprehensive review of several FD type valve structures currently offered by various automotive damper suppliers. Their advantages as well as potential drawbacks are shown and hydraulic circuits are formulated for each of the considered designs. Exemplary characteristics of a FD shock absorber obtained from own measurements are shown, too. The results of subjective qualitative evaluation of analyzed cases are presented and appropriate directions for further development steps are proposed. Finally, simulation results of functional model of FD shock absorber are presented.

Effect of atmospheric pin-to-plate cold plasma on oat protein: Structural, chemical, and foaming characteristics

The impact of novel pin-to-plate atmospheric cold plasma was investigated with input voltage (170 V, 230 V) and exposure time (15 & 30 min) on oat protein by studying structural (FTIR, circular dichroism (CD), UV–vis, Fluorescence), morphological (particle size analysis, SEM, turbidity), chemical (pH, redox potential (ORP), ζ potential, carbonyl, sulfhydryl, surface hydrophobicity), and foaming characteristics. The plasma treatment reduced the pH while increasing the ORP of the dispersions. These ionic environment changes affected the ζ potential and particle size leading to the formation of larger aggregates (170–15; 230–15) and distorted smaller ones (170–30; 230–30) as confirmed by SEM. The FTIR spectra showed reduced intensity at specific amide bands (1600–1700 cm−1) and also an increase in carbonyl stretching (1743 cm−1) representing oxidative carbonylation (increase in carbonyl content). Thus, the partial exposure of hydrophobic amino acids increases surface hydrophobicity. The altered secondary structure (rise in α-helix, decrement in β-sheets and turns), and tertiary structures were observed in circular dichroism (CD) and UV absorbance and fluorescence characteristics of proteins respectively. Furthermore, the increase in free sulfhydryl content and disulfide content was highly affected by the plasma treatments due to observed protein unfolding and aggregations. Besides, the increased solubility and reduced surface tension contributed to the improved foaming characteristics. Thus, plasma processing influences protein structure affecting their characteristics and other functionalities.

Analysis of electromagnetic/thermal coupling of Debye media using HIE-FDTD method

In this paper, the multi-physical working mechanism of the Debye dispersive media is studied in detail, and the coupling analysis of Maxwell's and heat conduction equations is carried out. The hybrid-implicit-explicit finite difference time domain (HIE-FDTD) method is applied to accelerate calculation of the electromagnetic(EM). The Debye model, introduced to HIE-FDTD through the auxiliary difference equation (ADE) technique by utilizing polarization current, describes the dispersion characteristics of a water-based absorber. In addition, a new expression of transient power loss density is proposed with the polarization current, which overcomes the negative power loss in the traditional method and makes the computation more accurate. Finally, the analysis proves that the ADE-HIE-FDTD method has good performance in the EM-thermal coupling calculation, and the absorption rate of the absorber shows the interaction effect between temperature distribution and dielectric material.

Preparation, stabilization, and thermal characterization of CuO/water nanofluids applicable to domestic solar water heater

In this contribution, an experimental investigation has been carried out to analyze the stability and light absorbance characteristics of CuO/water nanofluids applicable to domestic solar water heaters. Nanofluids are prepared at 0.01–0.05 wt% by dispersing dry CuO nanopowder in water in presence of Gum Acacia (GA) stabilizer via ultrasonic agitation. The stability of the nanofluids is examined through gravity sedimentation. The samples are exposed to natural sunlight as well as LED light to examine their light absorbance potential by virtue of temperature rise. The light absorbance potential of nanofluids as compared to water is expressed as Temperature Variation Ratio (TVR). The nanofluids remain stable for six months. The sedimentation is more in higher concentration relative to their dilute counterparts. The absorbance capacities of the nanofluids augment with the nanoparticle addition to base fluid. However, 0.01 and 0.05 wt% samples show relatively lower absorbance due to a higher sedimentation rate. Maximum absorbance is observed with 0.03 wt% which shows a maximum temperature rise up to 60 °C under sunlight and 56 °C under LED light. Whereas, water shows a maximum increase up to 52 °C under sunlight and 48 °C under LED. The TVR shows the highest values of 2.3 and 1.86 with 0.03 wt% sample when kept under sunlight and LED lights respectively. Hence, nanofluids are recommended as working fluids in solar water heating applications.

Experimental and numerical investigation on energy absorbing characteristics of empty and cellular filled composite crash boxes

Composite structures have been used in the automotive and aircraft industries because of their superior properties such as specific energy absorption ability, lightweight and crashworthiness. This paper aims to determine energy absorbing and deformation behaviours of composite crash boxes designed in different geometries by an innovative approach. The hand-layup vacuum bagging method was utilized to produce the composite crash boxes, which were developed with three different outer wall geometries (square, hexagon, and cylinder), and cellular filled square and hexagonal interiors. Carbon fibre reinforced polymer (CFRP) material was used in fabrication of the crash boxes. Experimental and numerical studies were conducted to investigate the energy absorbing and deformation behaviours under static compression load of the composite crash boxes. A commercial finite elements (FE) software (Ls-Dyna) was used for the numerical model. The study's findings revealed that cellular-filled composite crash boxes perform significantly better in terms of energy absorption performance. It was observed that filling an empty square type composite crash box with hexagonal cells increased the box's specific energy absorption capacity by around 140%.

Numerical Simulation of a Planar Model of a Ball Absorber in a Spherical Dish

This paper aims to investigate the behavior of a spherical absorber composed of two parts, an inner sphere and a supporting convex spherical dish in which the ball is placed. Considering only the planar behavior of the system, a set of governing nonlinear differential equations was derived and solved numerically. Firstly, the system is exposed to the harmonic excitation of the supporting bowl and its time response is analyzed for all time dependent variables. By gradually changing the angular frequency of the excitation, a resonance curve is obtained, which is examined in detail with respect to the changing amplitudes of the excitation force and the nonlinear behavior. The effect of internal damping and different settings of the absorber characteristics are also investigated. The effect of initial conditions without the presence of an external excitation force is also numerically analyzed by means of phase portraits for selected pairs of initial conditions.

Synthesis of Composite Hydrogel Made of Woven Fabrics Stitched with PVA Yarn

In this study, a new method to prepare polyvinyl alcohol (PVA) hydrogel-based woven fabric composite is presented. In this method, the woven fabric was first stitched with PVA yarn and then subjected to the borax solution for simultaneously dissolving and crosslinking PVA. The prepared PVA hydrogel-based woven fabric composite was chemically, mechanically, and thermally characterized. FTIR analysis was performed to confirm the crosslinking of PVA on the reinforced fabric surface. X-ray diffraction analysis was carried out to investigate the crystallinity of the composite. An optical microscope was used to investigate the surface morphology of the composites. Moreover, a DSC analysis was done to investigate the thermal characteristics of the composite. The mechanical and fluid absorbency characteristics of the composite were analyzed to investigate the effect of the concentration of PVA yarn on the tensile strength and water absorbency of composites. The results showed that the tensile strength and rigidity of the composite increased by increasing the PVA yarn content in the composite.

Hydrothermally development of boron-integrated graphene nanoparticles for p-n junction diode applications

In this work, boron doped graphene nanoparticles (NPs) were synthesized by the hydrothermal route with different boron tribromide concentrations such as 52, 104, and 156 μL. The structural, morphological and optical properties of the prepared NPs were studied using different characterization techniques such as X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), atomic force microscopy (AFM), UV–vis spectroscopy and photoluminescence spectroscopy (PL). The XRD pattern reveals the hexagonal crystal structure. The SEM image showed textured sheet-like layers which got agglomerated to form fluffy structures. The TEM images recorded single-crystalline nature and also confirms the particle size was reduced upon increasing boron tribromide solution concentration with recognizable particle shape. The topographic properties of the synthesized B-doped graphene NPs were also studied through AFM images. The UV visible absorbance characteristics peaks 243 and 372 nm were observed correspond to π – π* in C–C bands and n- π* transition. After that as grown NPs were used to fabricate diode junctions on p-Si substrates (p-Si/n-B-doped graphene). The electrical performance of each p-Si/n-B-doped graphene diodes junction was examined using I–V characteristics and electrical parameters of diode junction such as ideality factor, barrier height and reverse saturation current were found 2.9–4.3, 0.75–0.83 eV and 4.88 × 10−6-7.26 × 10−6 A. The calculated ideality factor values of the p-Si/n-B-doped graphene diodes are decreased with increase in boron tribromide solution concentration.

Research on dynamic characteristics of a novel triple-magnet magnetic suspension dynamic vibration absorber

A novel Triple-magnet Magnetic Suspension Dynamic Vibration Absorber is designed and modeled in this paper. The equivalent dynamic model of the Triple-magnet Magnetic Suspension Dynamic Vibration Absorber vibration reduction system is established. Meanwhile, the calculation model of the nonlinear magnetic suspension force is derived. Based on the force model, it is found that the nonlinear stiffness feature can be adjusted by changing the magnet distance of the Triple-magnet Magnetic Suspension Dynamic Vibration Absorber. Then the dynamic equations of the vibration reduction system are solved by using the Complex Variable Average method. And the correctness of the derivation procedure is verified through the Runge–Kutta method. From the numerical solutions, bifurcation phenomena occur in the system responses when the excitation amplitude is larger than a certain value. Adjusting the magnet distance and the damping coefficient of the Triple-magnet Magnetic Suspension Dynamic Vibration Absorber can delay or avoid bifurcation behaviors. When the excitation amplitude varies over a wide range, the Triple-magnet Magnetic Suspension Dynamic Vibration Absorber with a larger magnet distance and damping coefficient shows better vibration reduction performance. This study provides a theoretical basis for the practical application of the Triple-magnet Magnetic Suspension Dynamic Vibration Absorber and new ideas for controlling the bifurcation of traditional nonlinear dynamic vibration absorbers.

Effect of Fillers on Impact Resistance of Ultrahigh Molecular Weight Polyethylene [UHMWPE] reinforced Polyester Composites

In this work, the Ultra High Molecular Weight Polyethylene [UHMWPE] fabric sample was coated using hand-lay technique with polyester resin and two types of fillers to improve the impact resistance property. The matrix comprises polyester resin with fillers like, Coconut shell powder and Boron carbide separately, in four different weight ratios [0%, 10%, 20% and 30%]. The influence of Coconut shell powder as well as Boron carbide on impact energy absorbing characteristics of the composites was studied. The impact resistance was found to be higher with the use of fillers. The Coconut shell powder provided better impact resistance about 45% higher than the Boron carbide. The average total energy absorbed by the Coconut shell powder sample ranged from 68 J to 69 J whereas the control sample absorb 47 J. Similarly the Boron carbide too provided better impact resistance by 19-36% compared with the control sample. The average total energy absorbed by the sample ranged from 56 J to 64 J. Results reveal that the increase in the percentage of Coconut shell powder filler did not significantly increase the impact resistance of UHMWPE whereas an increase in the percentage of Boron carbide improved the impact resistance, however higher percentages were found to reduce the impact resistance.

Evaluation of energy absorption enhancement of additively manufactured polymer composite lattice structures

The unique compressive behaviour of lattice cubic structures as well as their high specific strength and significant energy absorbing characteristics makes them an attractive solution for crashworthiness applications. Hence in this research study, the crashworthiness behaviour and energy absorbing characteristics of the thermoplastic polymer composite lattice cubic structures were experimentally investigated under quasi-static compression. Four design patterns such as Cuboctahedron, Kelvin cell, Truncated cube in square and dividend square geometrics were considered and fabricated through fused deposition modelling technique. The proposed structures were additively manufactured with four different thermoplastic polymer based filament materials and their influence on the crashworthiness characteristics were investigated experimentally. The obtained results revealed that the PLA-CF based KC configuration exhibited SEA of 2.50 kJ g−1 and the maximum value of CFE is 84.91% for PETG-CF based KC configuration. Furthermore, the experimental results indicated that the proposed thermoplastic polymer composite based lattice cubic structures are potentially a suitable component for crashworthiness applications owing to their significant energy absorption ability.

Prediction of the Absorption Characteristics of Non-Uniform Acoustic Absorbers with Grazing Flow

In this paper, planar and the cylindrical broadband non-uniform acoustic absorbers were constructed, both of which use broadband absorption units (BAUs) as their building blocks. The impedance boundary Navier–Stokes equation (IBNSE) method was developed to predict the absorption characteristics of the lined duct with non-uniform acoustic absorbers, in which each small piece of perforated plate is acoustically equivalent to a semi-empirical impedance model through the boundary condition. A total of four semi-empirical impedance models were compared under different control parameters. The full Navier–Stokes equation (FNSE) method was used to verify the accuracy of these impedance models. It was found that the IBNSE method with the Goodrich model had the highest prediction accuracy. Finally, the planar and the cylindrical non-uniform acoustic absorbers were constructed through spatial extensions of the BAU. The transmission losses and the absorption coefficients of the rectangular duct–planar acoustic absorber (RDPAA) and annular duct–cylindrical acoustic absorber (ADCAA) systems under grazing flow were predicted, respectively. The results demonstrated that the broadband absorption of the designed non-uniform acoustic absorbers was achieved. The developed IBNSE method with Goodrich model was accurate and computationally efficient, and can be used to predict the absorption characteristics of an acoustically treated duct in the presence of grazing flow.

The Influence of Interface Roughness on the Vibration Reduction Characteristics of an Under-Platform Damper

Analysis of the vibration reduction characteristics of shock absorbers is crucial for engines. In this study, the fractal theory was applied to the contact surface of an under-platform damper (UPD), and the influence of the excitation force in the same and opposite directions on the roughness of the contact surface was studied. First, based on fractal geometry theory (FGT), the roughness characterization method of a UPD contact surface was proposed. Then, the friction mechanical model of the rough contact surface was established by combining it with a 3D contact mechanical model. Furthermore, a finite element dynamic model of a blade with a UPD structure was set up. Next, the harmonic balance method was used to calculate the nonlinear response characteristics of a blade under different levels of contact surface roughness. Finally, the influence of the contact surface roughness on the vibration reduction ability of a UPD under different excitation modes was analyzed. According to the simulation results, as the contact surface became rougher, the vibration suppression ability of the UPD on the blade became stronger and stronger. With the change in the centrifugal force of the UPD and the amplitude of the same/reverse excitation force, the influencing law of the contact surface roughness on the vibration suppression ability of the UPD remained unchanged, indicating that the rougher the contact surface roughness, the better the vibration suppression effect.