Numerical Study of Frequency and Deflection Responses of Natural Fiber (Luffa) Reinforced Polymer Composite and Experimental Validation

ABSTRACT

The natural fiber (Luffa cylindrica fiber) reinforced epoxy composite has been fabricated and their structural responses (frequency and deflection) have been computed experimentally and numerically first time using the corresponding experimental elastic properties. The numerical responses are obtained with the help of an in-house MATLAB code developed based on the higher order finite element (FE) model. The completeness of the model has been examined by comparing the current FE solutions (frequency and the central deflection) with the reference as well as in-house experimental data. The effect of fiber volume fractions on the elastic properties is verified for four different weight percentage of treated Luffa fiber (0%, 3.2%, 6.4%, and 9.6%). Finally, the inclusive behavior of the current higher order FE model and the corresponding influence of the significant design parameter of Luffa fiber-reinforced composite structure have been debated by solving different numerical examples.     

Loading and Controlled Release of Poorly Water-Soluble Drug Telmisartan from Porous Silicon Microparticles

Silicon - To prepare porous silicon microparticles by electrochemical etching process and study telmisartan loading and release kinetics to develop controlled drug delivery system. A...     

Harmonics elimination algorithm for operational modal analysis using random decrement technique

Operational modal analysis (OMA) extracts modal parameters of a structure using their output response, during operation in general. OMA, when applied to mechanical engineering structures is often faced with the problem of harmonics present in the output response, and can cause erroneous modal extraction. This paper demonstrates for the first time that the random decrement (RD) method can be efficiently employed to eliminate the harmonics from the randomdec signatures. Further, the research work shows effective elimination of large amplitude harmonics also by proposing inclusion of additional random excitation. This obviously need not be recorded for analysis, as is the case with any other OMA method. The free decays obtained from RD have been used for system modal identification using eigen-system realization algorithm (ERA). The proposed harmonic elimination method has an advantage over previous methods in that it does not require the harmonic frequencies to be known and can be used for multiple harmonics, including periodic signals. The theory behind harmonic elimination is first developed and validated. The effectiveness of the method is demonstrated through a simulated study and then by experimental studies on a beam and a more complex F-shape structure, which resembles in shape to the skeleton of a drilling or milling machine tool. Cases with presence of single and multiple harmonics in the response are considered.     

Turbulent Flow Friction Factor Calculation Using a Mathematically Exact Alternative to the Colebrook–White Equation

We present a novel, mathematically equivalent representation of the Colebrook–White equation to compute friction factor for turbulent flow in rough pipes. This new form is simple, no iterative calculations are necessary, and is well suited for accurate friction factor estimation. A limiting case of this equation provided friction factor estimates with a maximum absolute error of 0.029 and a maximum percentage error of 1% over a 20×500 grid of ε/D and R values (10?6 ? ε/D ? 5×10?2; 4×103相似文献   

Importance of Price in Telecommunications Managers' Choice of Local Access Provider

The decision making strategies of telecommunications managers and Chief Information Officers in the USA are changing as new companies are providing local access (residential/office) telephone services in addition to the Regional Bell Operating Companies. The choice of local access providers is critical to a company since they furnish the physical connection between the company's location and the public telephone network. Using experimental research, this paper investigates whether price is an important factor to the telecommunications managers in deciding whether to stay with the current provider or switch to an alternate provider.Fifty-two telecommunications managers participated in an experiment that provided them with a local access decision situation. The managers were given the opportunity to consider information associated with different decision factors and asked to determine the percent of service they would acquire from each of two competing local access providers. A software recorded actions taken by the managers during the experiment. The managers also ranked the decision factors in a post-experiment questionnaire. The experimental results show the most important decision factors for the managers to be price, technical quality, responsiveness, and maintenance ability. Price emerged as the most important factor in the experiment, although, it was ranked only fourth in the post-experiment questionnaire.     

Hygro-Thermo-Electric Properties of Carbon Nanotube Epoxy Nanocomposites with Agglomeration Effects

In the present study, the effective electric, thermal, and moisture properties of carbon nanotube (CNT) epoxy composites are derived by considering the agglomeration effect of CNT concentrations in the epoxy matrix. In this direction, the Voigt and Reuss homogenization method is adopted in the derivations. It is well known from experiments that the CNT thermal and electrical conductivities and the epoxy hygro-thermal expansion coefficients have significant effects on the behavior of CNT nanocomposites. Moreover, it has been experimentally proved that the agglomeration of CNTs in the matrix with high and low concentrations of the CNTs certainly affects the resistivity and, hence, the thermal expansion properties. Therefore, the effective elastic, thermal, electrical, and moisture properties for the randomly distributed CNTs in the matrix has been derived in terms of the agglomeration volume fractions of CNTs. In the effective relations, a single agglomeration parameter is considered to be active for a given potential. The results of variation in the hygro-electro-thermal properties due to change in CNT volume fraction as well as agglomeration parameters have been presented. The results and observation show that CNT agglomeration has a strong influence on the effective hygro-thermo-electric properties of the nanocomposites.     

GaSb Thermophotovoltaic Cells Grown on GaAs Substrate Using the Interfacial Misfit Array Method

We present gallium antimonide (GaSb) p–i–n photodiodes for use as thermophotovoltaic (TPV) cells grown on gallium arsenide (100) substrates using the interfacial misfit array method. Devices were grown using molecular beam epitaxy and fabricated using standard microfabrication processes. X-ray diffraction was used to measure the strain, and current–voltage (I–V) tests were performed to determine the photovoltaic properties of the TPV cells. Energy generation at low efficiencies was achieved, and device performance was critically analyzed.     

Competitive Substrate Biodegradation during Surfactant-Enhanced Remediation

The impact of synthetic surfactants on the aqueous phase biodegradation of benzene, toluene, and p-xylene (BTpX) was studied using two anionic surfactants, sodium dodecyl sulfate (SDS) and sodium dodecyl benzene sulfonate (SDBS), and two nonionic surfactants, POE(20) sorbitan monooleate (T-maz-80) and octylphenolpoly(ethyleneoxy) ethanol (CA-620). Batch biodegradation experiments were performed to evaluate surfactant biodegradability using two different microbial cultures. Of the four surfactants used in this study, SDS and T-maz-80 were readily degraded by a microbial consortium obtained from an activated sludge treatment system, whereas only SDS was degraded by a microbial culture that was acclimated to BTpX. Biodegradation kinetic parameters associated with SDS and T-maz-80 degradation by the activated sludge consortium were estimated using respirometric data in conjunction with a nonlinear parameter estimation technique as μmax = 0.93 h?1, Ks = 96.18 mg∕L and μmax = 0.41 h?1, Ks = 31.92 mg∕L, respectively. When both BTpX and surfactant were present in the reactor along with BTpX-acclimated microorganisms, two distinct biodegradation patterns were seen. SDS was preferentially utilized inhibiting hydrocarbon biodegradation, whereas the other three surfactants had no impact on BTpX biodegradation. None of the four surfactants were toxic to the microbial cultures used in this study. Readily biodegradable surfactants are not very effective for subsurface remediation applications as they are rapidly consumed, and also because of their potential inhibitory effects on intrinsic hydrocarbon biodegradation. This greatly increases treatment costs as surfactant recovery and reuse are adversely affected.     

Contact Analysis of Non-Gaussian Surfaces for Minimum Static and Kinetic Friction and Wear

Most statistical contact analyses assume that surface heights and peak (summit) height distributions follow a Gaussian distribution. However, engineering surfaces are frequently non-Gaussian with a degree of non-Gaussian character dependent upon materials and surface finishing processes used. For example, magnetic rigid disk surfaces used in magnetic storage industry are highly non Gaussian. The use of a Gaussian analysis in such cases can lead to erroneous results. This study for the first time presents a method to carry out a statistical analysis of non-Gaussian surfaces. Real area of contact, number of contacts, contact pressure and meniscus force (in wet interfaces) are calculated for probability density functions having different skewness and kurtosis. From these curves, the optimum value of skewness and kurtosis can be predicted for minimum static/kinetic friction. It is found that a range of positive skewness (between 0.3–0.7) and a high kurtosis (greater than five) significantly lower the real area of contact and meniscus contribution implying low friction and wear. Also, sensitivity of film thickness to static friction goes down for a surface with a positive skewness and a high kurtosis.     

Study of uranium adsorption using amidoximated polyacrylonitrile‐encapsulated macroporous beads

Polyacrylonitrile beads, containing the amidoximated polyacrylonitrile, were prepared for adsorption of uranium. The synthesized amidoximated polyacrylonitrile chelating beads were evaluated, for their ability to adsorb uranium from aqueous solution, at different temperatures and pH values. The kinetic measurement showed that about 120 min of equilibration time was enough, to remove saturation amount of uranium from the solution. The pseudo first‐order and pseudo second‐order equations were used to analyze the kinetic data, and the rate constants were determined. The equilibrium adsorption data were examined by the Langmuir, Freundlich, and Temkin isotherms. The data showed a better fit to the Langmuir isotherm. The loaded uranium could also be leached out from the beads, by treating with dilute acids. The uranium uptake capacity of the polymeric beads was found to be 3.5 mg/g of the swollen beads. Reusability of the beads was also established by multiple adsorption–desorption experiments. The pore volume and the surface area of the dried beads, measured by BET method, were found to be 1.93 cc/g and 320 m²/g, respectively. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013