Measurements of the Thermal Neutron Macroscopic Absorption Cross Section for Neutron Absorbing Layers

Objective of this study is measuring the macroscopic cross section of a neutron absorbing layer for thermal neutrons. For this purpose a neutron source and BF ₃ detector have been applied. For measuring macroscopic cross section of thermal neutrons by the \( I = BI_{0} e^{{ - \sum\nolimits_{tot} t}} \) Formula, it is necessary to provide suitable geometric conditions in order to assume the production and build-up coefficient to be the unit value (=1). To fulfill required conditions for this assumption, surface of the detector is covered with a 2 mm thick layer of cadmium. Radiation window of the detector has a 3 cm diameter, situated directly in front of the source. By placing the cadmium cover over the detector, variation of \( Ln{\frac{{I_{0}^{{}} }}{I}} \) values verses thickness of absorbent layer, renders linear function behavior, making it possible to measure the macroscopic cross section. The next stage is applying the MCNP code by simulating F1 tally and cosine-cards for calculating Total Macroscopic Cross-Section. Validation of this study is achieved through comparison of simulation by the MCNP code and results rendered by experiment measurements.     

Effect of deep cryogenic treatment on microstructure, creep and wear behaviors of AZ91 magnesium alloy

This paper focuses on the effect of deep cryogenic treatment (−196 °C) on microstructure and mechanical properties of AZ91 magnesium alloy. The execution of deep cryogenic treatment on samples changed the distribution of β precipitates. The tiny laminar β particles almost dissolved in the microstructure and the coarse divorced eutectic β phase penetrated into the matrix. This microstructural modification resulted in a significant improvement on mechanical properties of the alloy. The steady state creep rates were measured and it was found that the creep behavior of the alloy, which is dependent on the stability of the near grain boundary microstructure, was improved by the deep cryogenic treatment. For the AZ91 alloy, the results indicate a mixed mode of creep behavior, with some grain boundary effects contributing to the overall behavior. However for the deep cryogenic samples dislocation climb controlled creep is the dominant deformation mechanism. After the deep cryogenic treatment the sliding of grain boundaries was greatly suppressed due to morphological changes. As a result, the grain boundaries are less susceptible for grain boundary sliding at high temperatures. Dry sliding wear tests were also applied and the wear resistance of the alloy improved remarkably after deep cryogenic treatment.     

FSDPT based study for vibration analysis of piezoelectric coupled annular FGM plate

The vibration behavior of a piezoelectrically actuated thick functionally graded (FG) annular plate is studied based on first order shear deformation plate theory (FSDPT). A consistent formulation that satisfies the Maxwell static electricity equation is presented so that the full coupling effect of the piezoelectric layer on the dynamic characteristics of the annular FG plate can be estimated based on the free vibration results. The differential equations of motion are solved analytically for various boundary conditions of the plate. The analytical solutions are derived and validated by comparing the obtained resonant frequencies of the composite plate with those of an isotropic core plate. As a special case, assuming that the material composition of core plate varies continuously in the direction of the thickness according to a power law distribution, a comprehensive study is conducted to show the influence of functionally graded index on the vibration behavior of smart structure. Also, the good agreement between the results of this paper and those of the finite element (FE) analyses validates the presented approach. This paper was recommended for publication in revised form by Associate Editor Eung-Soo Shin Farzad Ebrahimi received his B.S. and M.S. degree in Mechanical Engineering from University of Tehran, Iran. He is currently working on his Ph.D. thesis under the title of “Vibration analysis of smart functionally graded plates” at Smart Materials and Structures Lab in Faculty of Mechanical Engineering of the University of Tehran. His research interests include vibration analysis of plates and shells, smart materials and structures and functionally graded materials.     

Buckling of magneto-electro-hygro-thermal piezoelectric nanoplates system embedded in a visco-Pasternak medium based on nonlocal theory

Microsystem Technologies - In this present work the critical loading of magneto-electro-viscoelastic-hygro-thermal (MEVHT) piezoelectric nanoplates embedded in a viscoelastic foundation are...     

Centrifugal compressor shape modification using a proposed inverse design method

This paper is concerned with a quasi-3D design method for the radial and axial diffusers of a centrifugal compressor on the meridional plane. The method integrates a novel inverse design algorithm, called ball-spine algorithm (BSA), and a quasi-3D analysis code. The Euler equation is solved on the meridional plane for a numerical domain, of which unknown boundaries (hub and shroud) are iteratively modified under the BSA until a prescribed pressure distribution is reached. In BSA, unknown walls are composed of a set of virtual balls that move freely along specified directions called spines. The difference between target and current pressure distributions causes the flexible boundary to deform at each modification step. In validating the quasi-3D analysis code, a full 3D Navier-Stokes code is used to analyze the existing and designed compressors numerically. Comparison of the quasi-3D analysis results with full 3D analysis results shows viable agreement. The 3D numerical analysis of the current compressor shows a huge total pressure loss on the 90° bend between the radial and axial diffusers. Geometric modification of the meridional plane causes the efficiency to improve by about 10%.     

Cr(III)‐containing Fe3O4/mercaptopropanoic acid‐poly(2‐hydroxyethyl acrylate) nanocomposite: Highly active magnetic catalyst for direct hydroxylation of benzene

In this study, polymer‐grafted magnetic nanoparticles containing chromium(III) ions incorporated onto Fe₃O₄/mercaptopropanoic acid‐poly(2‐hydroxyethyl acrylate) was prepared via a simple and in situ method. The obtained magnetic nanocomposite exhibited high catalytic activity and excellent selectivity in direct hydroxylation of benzene in the presence of hydrogen peroxide under solvent‐free condition. The magnetic catalyst could be also separated by an external magnet and reused seven times without any significant loss of activity/selectivity. Due to the Lewis acidity of the Fe³⁺ groups in the structure of magnetic nanoparticles, the high efficiency of this catalyst is possibly due to the synergetic effect of Cr³⁺ and Fe³⁺ groups in the structure of magnetic nanocomposite. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40383.     

Modeling and fuzzy control of the engine coolant conditioning system in an IC engine test bed

Mechanical and thermodynamical performance of internal combustion engines is significantly affected by the engine working temperature. In an engine test bed, the internal combustion engines are tested in different operating conditions using a dynamometer. It is required that the engine temperature be controlled precisely, particularly in transient states. This precise control can be achieved by an engine coolant conditioning system mainly consisting of a heat exchanger, a control valve, and a controller. In this study, constitutive equations of the system are derived first. These differential equations show the second-order nonlinear time-varying dynamics of the system. The model is validated with the experimental data providing satisfactory results. After presenting the dynamic equations of the system, a fuzzy controller is designed based on our prior knowledge of the system. The fuzzy rules and the membership functions are derived by a trial and error and heuristic method. Because of the nonlinear nature of the system the fuzzy rules are set to satisfy the requirements of the temperature control for different operating conditions of the engine. The performance of the fuzzy controller is compared with a PI one for different transient conditions. The results of the simulation show the better performance of the fuzzy controller. The main advantages of the fuzzy controller are the shorter settling time, smaller overshoot, and improved performance especially in the transient states of the system.     

Preparation of an optimized ciprofloxacin-loaded chitosan nanomicelle with enhanced antibacterial activity

Objective: The objective of this study was to evaluate the effect of lipid structure on physicochemical properties of chitosan-fatty acid nanomicelles and prepare an optimum ciprofloxacin-loaded formulation from these conjugates which could enhance the antibacterial effects of drug against some important pathogens like P. aeruginosa.

Significance: Nowadays, resistance in infectious diseases is a growing worldwide concern. Nanocarriers can increase the therapeutic index and consequently reduce the antibiotic resistance. By site-specific delivery of drug, the adverse effects of broad-spectrum antibiotics such as ciprofloxacin would be reduced.

Methods: Fatty acid grafted chitosan conjugates were synthetized in the presence of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide. The effects of fatty acid type (stearic acid, palmitic acid, and linoleic acid) on physicochemical properties of conjugates were investigated. Ciprofloxacin was encapsulated in nanomicelles by thin film hydration method. Also, the preparation process was optimized with a central composite design. The antibacterial effect of optimum formulation against P. aeruginosa, K. pneumoniae, and S. pneumoniae species was determined.

Results: All conjugates were synthetized with high yield values and the substitution degrees ranged between 2.13 and 35.46%. Ciprofloxacin was successfully encapsulated in nanomicelles. The optimum formulation showed high drug loading (≈?19%), with particle size of about 260?nm and a sustained release profile of ciprofloxacin. The minimum inhibitory concentrations of ciprofloxacin in optimum formulation against P. aeruginosa and K. pneumoniae species were 4 and 2 times lower in comparison with the free drug, respectively.

Conclusions: The antibacterial effect of ciprofloxacin was improved by encapsulation of drug in chitosan nanomicelles.     

Integration of VR with BIM to facilitate real-time creation of bill of quantities during the design phase: A proof of concept study

As building practices change, procedures that seemed indispensable at one point can be abandoned for others, one example of which is the bill of quantities (B/Q). Research into the extant literature attributes the declining use of B/Qs to a multitude of reasons, such as its complexity, the potentially long time required to produce it, the growth in popularity of non-traditional procurement systems, and the challenge of using the information within the document in a construction schedule. With these issues in mind, building information modeling (BIM) and virtual reality (VR) are combined and proposed as a potential solution that allows inclusion of the client into the design process. Following a literature review and precedent study, an experiment was carried out using this new process to simulate a client’s design decisions on window and interior furnishings. The choices made by the client using VR automatically updated a B/Q schedule built in Revit and allowed them to have a firm understanding of project costs. Besides giving the client more confidence in a pleasing final outcome, the technology also ensured an up-to-date, accurate, and easily understandable B/Q. The proposed method features great potential savings in cost and time and gives the B/Q a newfound importance in future construction processes. The research case presented in this paper is a stepping stone in exploring new opportunities offered by VR and BIM and how they could improve the reliability and accuracy of traditional procurement within construction, specifically within the B/Q document.     

Vibration analysis of parabolic shear-deformable piezoelectrically actuated nanoscale beams incorporating thermal effects

Thermoelectric-mechanical vibration behavior of functionally graded piezoelectric (FGP) nanobeams is first investigated in this article, based on the nonlocal theory and third-order parabolic beam theory by presenting a Navier-type solution. Electro-thermo-mechanical properties of a nanobeam are supposed to change continuously throughout the thickness based on the power-law model. To capture the small-size effects, Eringen's nonlocal elasticity theory is adopted. Using Hamilton's principle, the nonlocal governing equations for the third-order, shear deformable, piezoelectric, FG nanobeams are obtained and they are solved applying an analytical solution. By presenting some numerical results, it is demonstrated that the suggested model presents accurate frequency results of FGP nanobeams. The influences of several parameters, including external electric voltage, power-law exponent, nonlocal parameter, and mode number on the natural frequencies of the size-dependent FGP nanobeams are discussed in detail. The results should be relevant to the design and application of the piezoelectric nanodevices.