hossain ahmed - Academia.edu (original) (raw)

Papers by hossain ahmed

viii flexible method to implement for complex geometries, spurious reflection, lower accuracy and... more viii flexible method to implement for complex geometries, spurious reflection, lower accuracy and higher computational time make it less effective. To overcome the disadvantages encountered by FEM, Spectral Element Method (SEM) is recently proposed for its higher accuracy and fast convergence. Therefore, in this dissertation, SEM has been proposed to visualize high frequency ultrasonic wave in a range of 1 MHz to 7.5 MHz, which is not available in current literature. Various modules of the computer code using MATLAB are developed and simulation was performed for wave propagation through a 24-ply laminated composite plate. The simulation results were compared with experimental observations, and a good agreement of simulation and experiment was observed. ix

World Academy of Science, Engineering and Technology, International Journal of Mechanical, Aerospace, Industrial, Mechatronic and Manufacturing Engineering, Jul 4, 2014

Vertical slotted walls can be used as permeable breakwaters to provide economical and environment... more Vertical slotted walls can be used as permeable breakwaters to provide economical and environmental protection from undesirable waves and currents inside the port. The permeable breakwaters are partially protection and have been suggested to overcome the environmental disadvantages of fully protection breakwaters. For regular waves a semi-analytical model is based on an eigenfunction expansion method and utilizes a boundary condition at the surface of each wall are developed to detect the energy dissipation through the slots. Extensive laboratory tests are carried out to validate the semi-analytic models. The structure of the physical model contains two walls and it consists of impermeable upper and lower part, where the draft is based a decimal multiple of the total depth. The middle part is permeable with a porosity of 50%. The second barrier is located at a distant of 0.5, 1, 1.5 and 2 times of the water depth from the first one. A comparison of the theoretical results with previous studies and experimental measurements of the present study show a good agreement and that, the semi-analytical model is able to adequately reproduce most the important features of the experiment.

Journal of Applied Physics, Apr 27, 2021

A unique non-diffracting hybrid order longitudinal Bessel beam with pronounced resilience to scat... more A unique non-diffracting hybrid order longitudinal Bessel beam with pronounced resilience to scattering using acoustic metamaterial, which we call hybrid Bessel beams (HYBEs), is currently unknown. Newly proposed hybrid Bessel beams are different than the conventional cross-sectional Bessel beams. In this article, we explain the physics of multifunctional ultrasonic capabilities of a bioinspired interlocking architecture of acoustic metamaterial. At first, for the newly proposed metastructure, understanding the physics and wave energy is predictively focused through attenuative surfaces at various ultrasonic frequencies (∼120 to ∼130 kHz). Finally, a zero-order first of its kind ultrasonic Bessel-like beam between frequencies of ∼265 and ∼272 kHz is shown propagating a long distance through the base material. The new propagation had minimal reduction in energy amplitude, while the displacement was nearly constant across the depth of the wave guide following a second-order Bessel function of the first kind. To explain the physics of the phenomena, mode shapes in the frequency-wavenumber domain are investigated. Furthermore, identification of the propagating wave vector using equi-frequency contours at multiple ranges confirmed the presence of the proposed acoustic features. These abilities of the proposed metamaterial have key advantages to propagate waves deeper into thick attenuative and aberrative structures such as brain tissue, soft skin and muscles, paint surface, and non-accessible composite materials. We envision potential applications of the proposed HYBE for the non-destructive evaluation (NDE) of attenuative materials that are not easily accessible for testing. To verify the wave focusing and long-distance wave propagation, an ad hoc metamaterial lens for the conventional NDE transducer is proposed, which demonstrated wave propagation through a 10 mm thick carbon fiber reinforced polymer composite structure.

Ultrasonics, Jul 1, 2019

Experimentally observed dissipated nonlinearity in Lamb wave propagation in composites due to str... more Experimentally observed dissipated nonlinearity in Lamb wave propagation in composites due to stress-relaxation is reported herein. It was found that the stress relaxation in composite is inherently coupled with the second order nonlinear parameter derived from the Lamb wave modes. Due to the combined effect of internal stresses and damage accumulation in composites, the second harmonic frequency was found to be shifted towards the lower frequency with increasing amplitude, which was partially recovered and shifted back during the stress relaxation. A comprehensive fatigue experiment was conducted on ASTM standard composite specimens with fatigue loading sequences and relaxation, while the guided Lamb wave signals were collected using piezoelectric sensors integrated with the specimens. A remarkable ~27% reduction of acoustic nonlinearity was observed during relaxation. Rate and degree of relaxation were found to be the function of number and frequency of loading cycles and inherently correlated with the remaining strength of the composites.

Journal of medical science and clinical research, Apr 30, 2019

Background: The reason of deciding the percentage of analgesics utilized in postoperative period ... more Background: The reason of deciding the percentage of analgesics utilized in postoperative period is to decide the genuine usage of opioid saving impact of nonsteroidal anti-inflammatory medications and the idea of multimodal analgesia. Objective: To identify the different analgesic drugs and techniques used in postoperative pain management. Method: This was a cross sectional study. 150 patients were chosen to discover the sorts of analgesics that are being utilized in the postoperative time frame regardless of the kinds of operation and anesthesia, premedication by analgesics and itraoperative analgesics utilized or not. Patients were isolated into a few age groups. Results: In the current imminent cross sectional study it is seen that blend of intramuscular injection of pethidine and nonsteroidal anti-inflammatory medications (either in suppository structure or intravenous or intramuscular route) has the most astounding rate in postoperative help with discomfort.

This thesis has been submitted in partial fulfillment of requirements for an advanced degree at T... more This thesis has been submitted in partial fulfillment of requirements for an advanced degree at The University of Arizona ard is deposited in the University Library to be made available to borrowers under the rules of the Library. Brief quotations from this thesis are allowable without special permission, provided that accurate acknowle dgement of source is made. Requests for permission for extended quotation from or reproduction of this manuscript in whole or in part may be granted by the head of the major department or the Dean of the Graduate College when in his or her judgment the proposed use of the material is in the interests of scholarship. In all other instances, however, permission must be obtained from the author.

Journal of Pharmacognosy and Phytochemistry, Jul 1, 2017

Azadirachta indica plants have been used for centuries in Indian folk medicine. This research was... more Azadirachta indica plants have been used for centuries in Indian folk medicine. This research was performed to determine the presence of major phytochemicals and to evaluate the analgesic and antioxidant activity of methanolic extract of Azadirachta indica leaves. Methanolic extract from the leaves of the plant was prepared by using drying, grinding, filtration and solvent evaporation methods. Phytochemical analysis of the leaves indicated the presence of Glycosides, Alkaloids, Flavonoids, Tannins, Saponins and Terpenoids. The analgesic activity of the samples was studied using acetic acid induced writhing model in mice. Significant analgesic effect was monitored (p<0.05) as the oral extract dose of 500 mg/kg showed 47.48% inhibition of writhing movements compared to standard drug Diclofenac-Na which inhibited 90.65% writhing movement. Anti-oxidant activity of the leaves was evaluated using DPPH free radical scavenging activity method. The methanolic extract of the leaves showed mild free radical scavenging activity. The IC 50 of the plant extract was 310.259 µg/ ml, whereas IC 50 of reference agent Ascorbic acid was found to be 17.33 µg/ ml.

The Journal of the Acoustical Society of America

Hermitian Dirac-like cones are proposed for creating acoustic logic gates herein. The predictive ... more Hermitian Dirac-like cones are proposed for creating acoustic logic gates herein. The predictive phenomenon of creating Dirac-like cones near a bipolar antisymmetric deaf band was found to be useful for acoustic computing of Boolean algebra. Unlike previous approaches, Dirac-like cone creates exclusive opportunity to perform all possible Boolean algebra computation with valid inputs. The phenomenon is demonstrated in two-dimensional phononic crystals (PnCs), consisting of tunable square columns in air media. By predictive tuning of the deaf bands, a triply to doubly degenerated Dirac-like cone is reported to form and is particularly useful for acoustic computing. It is only possible when a bottom band has a negative curvature that is lifted from a nearby doubly degenerated band with positive curvature, which is again degenerated with a deaf band. On the contrary, similar computing possibilities are difficult when the bottom band degenerates with the deaf band and the top band is lif...

Mechanical Systems and Signal Processing

Smart Structures and NDE for Energy Systems and Industry 4.0

Extracting improved mechanical properties such as high stiffness-high damping and high strength-h... more Extracting improved mechanical properties such as high stiffness-high damping and high strength-high toughness are being investigated recently using high symmetry interlocking micro-structures. On the other hand, development of artificially engineered composite metamaterials has significantly widen the usability of such materials in multiple acoustic applications. However, investigation of elastic wave propagation through high symmetry micro-structures is still in trivial stage. In this work, a novel interlocking micro-architecture design which has been reported previously for the extraction of improved mechanical properties has been investigated to explore its acoustic responses. The finite element simulations are performed under dynamic wave propagation load at multiple scales of the geometry and for a range of material properties in frequency domain. The proposed composite structure has shown high symmetry which is uncommon in fiber-reinforced polymer composites and a desirable feature for isotropic behavior. The existence of multiple acoustic features such as band gap and near-isotropic behavior have been established. An exotic wave propagation feature, wave trapping and attenuation, has shown energy encapsulation in a series of repeating structures in a frequency range of 0.5 kHz to 2 kHz.

International Journal of Solids and Structures

Structural Health Monitoring 2019

Assessment of material state damage in a composite structure using fundamental thermodynamic conc... more Assessment of material state damage in a composite structure using fundamental thermodynamic concept of entropy has been proposed in this article. The health management system of composite structure is mainly based on installation of piezoelectric material on the structure itself. To supplement this existing system, in this article, it has been demonstrated that the change in entropy due to material degradation can be used as a measure of damage. The advantage of this entropy-based damage index measurement is that it offers a unified and more comprehensive indication of damage irrespective of the path of the damage mode. Since the dissipation of energy due to structural loading initiates damage from an ideal material-state, an estimation of material state disorganization from an unloaded-state can be considered as a change in entropy. Over the years, many attempts had been made to implement this concept in metallic structure, however, the application of this approach to composite structure is far from trivial. To circumvent this gap, an entropic characterization of fatigue degradation mechanism under various loading rates has been proposed and demonstrated for carbon fiber based composite structure using material state property information. Essentially, an experimental setup was designed to assess the change in structural integrity of the composite specimens at multiple fatigue cycles using the stateof- the-art scanning acoustic microscope. The statistical mechanics-based probability distribution function for the change in structural properties are then expressed in terms of fundamental entropy distribution and a damage index of the structure is formulated. Next, the specimens went through a time dependent stress relief cycle, and the entropy as a thermodynamic state function for the damage was assessed by using the change in probability distributions. Based on initial results, the proposed methodology provides enough proof to effectively identify the damage initiation irrespective of its type and the localization of the damage

Health Monitoring of Structural and Biological Systems XIII, 2019

Recently, permeable breakwaters have been suggested to overcome the disadvantages of fully protec... more Recently, permeable breakwaters have been suggested to overcome the disadvantages of fully protection breakwaters. These protection structures have minor impacts on the coastal environment and neighboring beaches where they provide a more economical protection from waves and currents. For regular waves, a numerical model is used (FLOW-3D, VOF) to investigate the hydraulic performance of a permeable breakwater. The model of permeable breakwater consists of a pair of identical vertical slotted walls with an impermeable upper and lower part, where the draft is a decimal multiple of the total depth. The middle part is permeable with a porosity of 50%. The second barrier is located at distant of 0.5 and 1.5 of the water depth from the first one. The numerical model is validated by comparisons with previous laboratory data and semi-analytical results of the same model. A good agreement between the numerical results and both laboratory data and semi-analytical results has been shown and th...

Health Monitoring of Structural and Biological Systems XII, 2018

The unique phenomena in acoustic metamaterial at the Dirac-like cone, and at the exceptional spaw... more The unique phenomena in acoustic metamaterial at the Dirac-like cone, and at the exceptional spawning ring could transform the field of engineering with multiple new applications that was never possible before. Formation of localized conical dispersion (Dirac cone) at the Brillouin boundaries are the well-known facts, which exhibits many intriguing phenomena. However, Dirac cone like dispersion at the center of Brillouin zone (k =0) is rare and only happens due to accidental degeneracy at finite frequencies in two-dimensional periodic crystals (PCs), with or without microarchitectures. Additionally, a possible deformation of a Dirac cone instigates a degenerated state called spawning ring or exceptional ring, where two resonant modes coincides over a zonal wave numbers. The point of exceptional ring is called exceptional point, and known as parity-time symmetry breaking point. Exploiting the behaviors of Dirac cones and spawning rings at the origin and boundaries of the Brillouin zone, a directional and bifurcation lens were designed which will propagate sound wave in specific directions at multiple frequencies. In this article, PCs having a square array of cylindrical polyvinylchloride (PVC) inclusions in air media are studied numerically, that exhibits Dirac-like points and exceptional points simultaneously at k =0 by modulating the physical parameter of the cylindrical inclusions (PVC) in fixed lattice constant. Detailed numerical study of 2D PCs showed that by adjusting the system parameter, an accidental triple degeneracy of dispersion at Γ point can be achieved. The authenticity of the claim is demonstrated by simulating the phenomena in a designed zero-refractive index material.

Active and Passive Smart Structures and Integrated Systems XIII, 2019

This article presents the recent study in guiding acoustic waves by creating frequency band gaps ... more This article presents the recent study in guiding acoustic waves by creating frequency band gaps and harvesting energy simultaneously from the vibration of the structure using split ring metamaterial. Traditionally, conventional materials are unable to create frequency stop bands. So, split ring metamaterial has been used which has shown the ability to filter acoustic waves in a certain frequency range by creating frequency stop bands. In this article, a 3D unit cell of aluminum with continuous periodicity and certain split ring resonator pattern is discussed. PVDF film is used in the structure as a piezoelectric material. Here, a wide range of frequency (0-30kHz) is studied to demonstrate the ability of the cell to create stop bands within the study range. From the study, it can be seen that this unit cell is capable of creating stop bands and at the same time harvest ~2.4μW of energy simultaneously under 10kΩ resistive load.

A new magnet resonance machine has been developed to carry out high frequency fatigue tests for t... more A new magnet resonance machine has been developed to carry out high frequency fatigue tests for transverse butt welds. The technology uses the first natural frequency of a resonance body which consists of two steel beams. Due to four magnets at the ends of the steel beams a harmonic cyclic loading is applied. The maximum frequency for the fatigue tests is 400 Hz. The system allows to test specimens with transverse butt welds up to 10 9 cycles with moderate values for the mean force and amplitude. The test program comprised more than 110 specimens for analysing several influences, namely: (i) frequency of the test machine, (ii) temperature at hot spots and (iii) steel grade of the specimens. In addition, a test series was carried out to compare the as welded and treated conditions of butt welds. Some test specimens showing fatigue cracks after 10 8 cycles will be also documented.

Background. The objective of this study was to evaluate the analgesic potential of swollen stems ... more Background. The objective of this study was to evaluate the analgesic potential of swollen stems of Brassica oleracea var. gongylodes, which are eaten in the cooked or boiled form in many parts of the world. Methods. Analgesic activity was determined through decreases by the methanol extract of non-boiled and boiled stems in intraperitoneally administered acetic acid induced writhings in Swiss albino mice. Results. There were no appreciable differences between alleviation of pain by non-boiled versus boiled extract. At doses of 50, 100, 200 and 400 mg per kg body weight, the methanol extract of non-boiled stems dose-dependently and significantly reduced the number of acetic acid induced writhings by, respectively, 22.2, 40.7, 48.1, and 51.9%. At the same doses, the methanol extract of boiled stems dose-dependently and significantly reduced the number of writhings, respectively, by 22.2, 37.0, 48.1, and 51.9%. By comparison, a standard analgesic drug, aspirin, when administered at do...

ASME 2021 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, 2021

Acoustic metamaterials are artificially engineered smart structures designed to achieve unusual p... more Acoustic metamaterials are artificially engineered smart structures designed to achieve unusual properties that cannot be possible to obtain through natural materials. Hence, with the advancement of technology, metamaterials have received tremendous focus in recent days. Phononic and sonic crystals are the two classes of acoustic metamaterial. The frequency stopband is one of the common and primary features that can be attained from both the classes of acoustic metamaterials. Unit cell sonic crystals are composed of stiff resonators, placed inside comparatively softer matrix material. The frequency bandgap in a sonic crystal is a result of Bragg scattering and local resonance of the resonators in the unit cell. In this study, a comprehensive analysis is performed to understand the influence of resonators on frequency stopbands and the range/width of the bandgap. Two frequency bands in a dispersion curve form a bandgap. How and why those two bands shift up/down in a dispersion curve ...