Numerical simulation of slip flow through rhombus microchannels

Microgeometry fluid dynamics has gotten a lot interest due to the arrival of Micro-Electro-Mechanical systems (MEMS). When the mean free path of a gas and characteristic length of the channel are in the same order, continuum assumption is no longer valid. In this situation velocity slip and temperature jump occur in the duct walls. Fully developed numerical analysis for characteristic laminar slip flow and heat transfer in rhombus microchannels are performed with slip velocity, and temperature-jump boundary condition at walls. The impacts of Reynolds number (0.1 < Re < 40), velocity slip, and temperature-jump on Poiseuille number, and Nusselt number for different aspect ratio (0.15 < A < 1.0), and Knudsen number are studied in detail. The contours of non-dimensional velocity for some cases are examined as well. The results show that aspect ratio and Knudsen number have important impact on Poiseuille number, and Nusselt number in rhombus microchannels. Reynolds number has considerable influence on Nusselt number at low Reynolds number, but its influence on Poiseuille number is not very important at the studied range.     

Structure--activity studies for alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropanoic acid receptors: acidic hydroxyphenylalanines

Antagonists of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropanoic acid (AMPA) receptors may have therapeutic potential as psychotropic agents. A series of mononitro- and dinitro-2- and 3-hydroxyphenylalanines was prepared, and their activity compared with willardiine, 5-nitrowillardiine, AMPA, and 2,4,5-trihydroxyphenylalanine (6-hydroxydopa) as inhibitors of specific [3H]AMPA and [3H]kainate binding in rat brain homogenates. The most active compounds were highly acidic (pKa 3-4), namely, 2-hydroxy-3,5-dinitro-DL-phenylalanine (13; [3H]AMPA IC50 approximately equal to 25 microM) and 3-hydroxy-2,4-dinitro-DL-phenylalanine (19; [3H]AMPA IC50 approximately equal to 5 microM). Two other dinitro-3-hydroxyphenylalanines, and 3,5-dinitro-DL-tyrosine, were considerably less active. Various mononitrohydroxyphenylalanines, which are less acidic, were also less active or inactive, and 2- and 3-hydroxyphenylalanine (o- and m-tyrosine) were inactive. Compounds 13 and 19, DL-willardiine (pKa 9.3, [3H]AMPA IC50 = 2 microM), and 5-nitro-DL-willardiine (pKa 6.4, [3H]AMPA IC50 = 0.2 microM) displayed AMPA > kainate selectivity in binding studies. Compound 19 was an AMPA-like agonist, but 13 was an antagonist in an AMPA-evoked norepinephrine release assay in rat hippocampal nerve endings. Also, compound 13 injected into the rat ventral pallidum antagonized the locomotor activity elicited by systemic amphetamine.     

Viscosity and rheological behavior of microbubbles in capillary tubes

The viscosity of microbubbles has been measured in capillary tubes. Experiments were conducted in tubes of different diameters and lengths, with a constant microbubble concentration. The effects of bubble void fraction and size distribution on the viscosity of microbubbles were also investigated. Microbubbles demonstrate shear‐thinning non‐Newtonian behavior. The viscosity of microbubbles decreases with a decrease in tube diameter and bubble void fraction, and with an increase in tube length. Although viscosity changes with tube dimensions, the flow index (n^′) is only influenced by the microbubble void fraction. It is also found that bubble size distribution in the range (1–12 µm) used in this study does not affect the viscosity of microbubbles. The data were then used to develop a correlation to predict viscosity of microbubbles, which represents the experimental viscosity data with an absolute average relative deviation less than 1.3%. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2660–2669, 2014     

Quasi-Isotropic Triaxially Braided Cellulose-Reinforced Composites

In this article, we investigate experimentally and analytically the mechanical properties of a natural fiber quasi-isotropic triaxially braided composite. The composite is prepared from triaxially braided regenerated cellulose fibers and a high-bio-content epoxy resin system using a resin infusion process. Simultaneous mechanical loading, digital image correlation, and acoustic emission tests were performed on notched and unnotched specimens to understand the tensile behavior of the composites and the initiation and propagation of damage. Experimental results were compared with the effective tensile properties determined using an analytical model. The model is a discrete three-layer analytical representation based on a mechanics transformation-based representation of the quasi-isotropic braided layers. The model is used to determine the elastic stiffness and Poisson effects based on the constituent properties such as the fiber volume fractions, the waviness of the bias tows, and the relative thickness of the braided preform. The experimental results show the analytical model's ability in predicting the composite's elastic properties. The unique fabric architecture is found to have a large influence on the strength properties across the different specimen geometries investigated.     

Calculation of aerosol deposition in human lung airways using Horsfield geometric model

Clinical investigation shows a dramatic relation between deposition of particles in lung’s pathways and respiratory system diseases. Particle deposition may also play a major role in drug delivery via respiratory system. Previous researches on symmetric and 5-lobe models for rat, dog, hamster and human show that, the deposition fraction of fine particles (between 0.1 and 0.7 μm) is minimum. A multi-path asymmetric 5-lobe model of Horsfield et al. is employed to construct the airway tree. Since the data are based on lung casting, asymmetric properties of the model are more realistic. Deposition of 0.01–10 μm particles is calculated during inhalation using published formulas in every branch. Here, we measured the deposition up to alveolar region. Accumulative deposition versus particle diameter predicts less deposition in comparison with symmetric models in as much as our model is asymmetric. The flow is divided based on distal volume. Particle deposition for 0.01 μm is in good agreement with other models but for 1 μm different trend in lower generations is observed. It is concluded that the asymmetric pattern gives different deposition fraction in all regions, since the distinctive geometric properties of the model is in some extent different from that of symmetric model. But, the accumulative deposition trend is similar in both symmetric and asymmetric models.     

Numerical simulation of square cyclones in small sizes

The idea of using square cyclones was first introduced in early 1990s because of some problems of big conventional (round) cyclones in Circulating Fluidized Bed (CFB) industries, such as huge volume and long start-stop time of cyclones. Now there is this question, in spite of the main reason for making square cyclones, how square cyclones behave in small sizes.In this paper, two small cyclones with the same hydraulic diameter, which one is square and the other one is round, are numerically compared. The Reynolds averaged Navier–Stokes equations with Reynolds Stress Turbulence Model (RSTM) are solved by use of the finite volume method based on the SIMPLE pressure correction algorithm in the computational domain. The Eulerian–Lagrangian computational procedure is used to predict particles tracking in the cyclones. The velocity fluctuations are simulated using the Discrete Random Walk (DRW).The results show that the pressure drop in small square cyclone is less than the pressure drop in small round one. Also at each flow rate collection efficiency of small square cyclone is less than round one, but by increasing flow rate this difference decreases.     

Utilisation of immobilised activated sludge for the biosorption of chromium (VI)

The objective of this investigation was to study the biosorption of Cr (VI) on immobilised activated sludge (IAS) and calcium alginate (CA) using batch system. The optimal pH for Cr (VI) biosorption by IAS and CA was 2.0 and 4.0, respectively. Equilibrium was attained at approximately 120 min for both biosorbents. For both biosorbents, the equilibrium biosorption capacity (mg/g) increased as the initial metal ion concentration increased and the concentration of biosorbent decreased. The rate of biosorption onto IAS and pure CA (as mg/g) increased from 5.02 to 87.66 and 4.97 to 79.09 as the concentration of Cr (VI) ions increased from 10 to 1000 mg/L, respectively. In the case of biosorbent concentration, as the concentration of IAS and pure CA increased from 1 to 20 g/L, the equilibrium uptake (q_e) decreased from 21.33 to 1.57 and 19.41 to 1.38 mg/g, respectively. The biosorption data showed that the Langmuir model was more suitable than the Freundlich model. Also, the results indicated that the pseudo‐second order model was the most suitable for Cr (VI) biosorption onto IAS and CA. © 2011 Canadian Society for Chemical Engineering     

Silica gel modified carbon paste electrode for electrochemical detection of insulin

A silica gel-modified carbon paste electrode (Si-CPE) was fabricated and used for selective and sensitive determination of insulin. The experimental results suggested that insulin effectively accumulated on surface of the modified electrode resulting in a marked enhancement of its oxidation current response. Therefore, the modified electrode was used as an electrochemical sensor for the differential pulse adsorptive stripping voltammetric and hydrodynamic amperometric determination of insulin. The influence of various experimental parameters on the voltammetric response of insulin was investigated. Using hydrodynamic amperometry, under optimum conditions, calibration plot for insulin was linear in the range of 90–1400 pM. The sensitivity and detection limit of the proposed amperometric method were found to be 107.3 pA/pM (1511.3 pA/pM cm²) and 36 pM, respectively. The electrode has the remarkable advantages of simple preparation using inexpensive material, high reproducibility, good chemical and mechanical stabilities, and easy surface renewal owing to bulk modification. The high selectivity of the modified electrode towards oxidation of insulin in the presence of sulfur containing amino acids including cystine, cysteine, and glutathione is a key advantage of the proposed electrode.     

An Interleaved Artificial Bee Colony algorithm for dynamic optimisation problems

Dynamic optimisation problems (DOPs) have attracted a lot of research attention in recent years due to their practical applications and complexity. DOPs are more challenging than static optimisation problems because the problem information or data is either revealed or changed during the course of an ongoing optimisation process. This requires an optimisation algorithm that should be able to monitor the movement of the optimal point and the changes in the landscape solutions. In this paper, we proposed an Interleaved Artificial Bee Colony (I-ABC) algorithm for DOPs. Artificial Bee Colony (ABC) is a nature inspired algorithm which has been successfully used in various optimisation problems. The proposed I-ABC algorithm has two populations, called ABC1 and ABC2, which worked in an interleaved manner. While ABC1 focused on exploring the search space though using a probabilistic solution acceptance mechanism, ABC2 worked inside ABC1 and focused on the search around the current best solutions by using a greedy mechanism. The proposed algorithm was tested on the Moving Peak Benchmark. The experimental results indicated that the proposed algorithm achieved better results than the compared methods for 8 out of 11 scenarios.     

A novel support vector machine based intrusion detection system for mobile ad hoc networks

Wireless Networks - The performance of mobile ad hoc networks (MANETs) is significantly affected by the malicious nodes. One of the most common attacks in MANETs is denial of service (DoS); a type...