A computational and experimental study on the effective properties of Al2O3‐Ni composites

It has been demonstrated that effective medium approximation and mean field homogenization technique is a useful computational tool to predict the effective thermal and structural properties of alumina‐nickel (Al₂O₃‐Ni) composites. Nickel particle size and volume fraction, thermal interface resistance and porosity are found significant factors that affect thermal conductivity, elastoplastic behavior, elastic modulus and thermal expansion coefficient of Al₂O₃‐Ni composite. To complement the computational design, Al₂O₃‐Ni composite samples with designed range of volume fractions and nickel particle size are developed using spark plasma sintering process and properties are measured for model verification.     

Extension of grounding mechanism for abstract words: computational methods insights

The attempts to model cognitive phenomena effectively have split the research community in two paradigms: symbolic and connectionist. The extension of grounding phenomenon for abstract words is very important for social interactions of cognitive robots in real scenarios. This paper reviews the strength of symbolic and connectionist methods to address the abstract word grounding problem in cognitive robots. In particular, the presented work is focused on designing and simulating cognitive robotics model to achieve a grounding mechanism for abstract words by using the semantic network approach, as well as examining the utility of connectionist computation for the same problem. Two neuro-robotics models based on feed forward neural network and recurrent neural network are presented to see the pros and cons of connectionist approach. The simulation results and review of attributes of these methods reveal that the proposed symbolic model offers the solution to the problem of grounding abstract words with attributes like high data storage capacity with recall accuracy, structural integrity and temporal sequence handling. Whereas, connectionist computation based solutions give more natural solution to this problem with some shortcomings that include combinatorial ambiguity, low storage capacity and structural rigidity. The presented results are not only important for the advancement in communication system of cognitive robot, also provide evidence for embodied nature of abstract language.     

Determination of gas mixture adsorption equilibria by the tracer-pulse technique

A chromatographic technique using radiotracer gases has been used to determine pure gas isotherms and gas mixture adsorption equilibria over the entire concentration range. The ethane—ethylene-Molecular Sieve Type 13X and pure carbon monoxide-Molecular Sieve Type 5A systems were studied. The data obtained by this dynamic technique are shown to be in agreement with data obtained previously by a static (volumetric) method. The chromatographic method is much more efficient for obtaining mixture data and is considerably easier to adapt to wider pressure and temperature ranges than static methods.     

Tensile Lap Splicing of Bundled CFRP Reinforcing Bars in Concrete

In the case of heavily reinforced concrete structural members, bundled bars are required rather than spaced bars. The use of spliced bundled bars is necessary when available bar lengths are limited. No design recommendations regarding the use of bundled or spliced bundled FRP bars are available. The results of four-point flexural testing of nine concrete beams reinforced with spliced bundled CFRP bars are presented herein. The effects of the type of bundle and splice length on the bond strength of bundled CFRP bars are investigated. Based on the experimental results, a procedure for determining the critical splice length of FRP bars is presented and the corresponding values of bond stresses can be predicted. Moreover, the ultimate strength analysis method is used to predict the maximum stress in spliced bundled CFRP bars. Finally, comparisons with the existing recommendations regarding the use of bundled steel bars and the recommended modifications for bundled CFRP bars are presented.     

Design and Evaluation of Fiber-Reinforced Polymer Bond-Type Anchorages and Ground Anchors

This paper presents laboratory tests on a bond-type anchorage system and a full-scale ground anchor with fiber-reinforced polymer 9-bar tendons. A cement-based mortar filled steel tube was used to simulate a rock mass environment. Resistance strain gauges, fiber optic sensors, embedded strain gauges, and linear variable displacement transducers were used to monitor the behavior of the anchor and to study load transfer mechanism of the tendon to surrounding rock mass. The test results show that the developed bond-type anchorage performs well for post-tensing applications with the tendons. The tested anchor presents an acceptable tensile behavior for each loading stage investigated (up to a load level of 0.6ffu, where ffu=guaranteed capacity of the tendon) in accordance with existing codes. The anchor is similar in strain distribution profile to conventional steel anchors, except giving a shorter load transfer length. It is expected that the anchor require a minimum anchor bonded length of 2,000?mm with plain cement grouts.     

Stability of Anisotropic Laminated Rings and Long Cylinders Subjected to External Hydrostatic Pressure

The problem of buckling of rings under external pressure has attracted interest since the late 1950s; however, the formulations developed, to date, to obtain the critical pressure are limited to special cases of orthotropic laminated construction. In this work, analytical and numerical treatments are carried out to provide results on the buckling of thin and moderately thick anisotropic rings and long cylinders. A generalized closed-form analytical formula for the buckling of thin anisotropic laminated rings is developed. Standard energy-based formulation and classical lamination theory are used to obtain the equilibrium equations assuming an intermediate class of deformation. The constitutive equations are statically condensed, in terms of the ring’s boundary conditions, to produce the effective axial, coupling, and flexural rigidities. In addition, a three-dimensional (3D) tube finite-element model is developed for nonlinear analysis of anisotropic laminated composite rings or long cylinders. The element accounts for prebuckling ring twist and first-order shear deformations. Fourier series expansions are used to express the in-plane and out-of-plane components of deformation and geometry at the three nodes of the cylindrical element. Isoparametric quadratic shape functions are used to interpolate the displacement field in?between. Comparisons of the analytical and numerical results show excellent agreement for thin rings. Parametric studies are also conducted to address the effects of lamination, shell thickness, and initial out-of-roundness imperfection on the external buckling pressure.     

Strength-Fatigue Behavior of Fiber Reinforced Polymer Strengthened Prestressed Concrete T-Beams

Strengthening concrete girders with fiber-reinforced polymers (FRP) is becoming an increasingly common practice as more research investigations are favorably qualifying the technique. However, important behavioral aspects, such as fatigue in prestressed concrete beams, are yet to be adequately evaluated. An experimental program was conducted to test five pretensioned, prestressed concrete T beams designed for specific prestressing strand stress ranges under live-load conditions. The experimental testing consisted of precracking the beams, strengthening them with carbon FRP, and mechanically loading them to study the effect of increasing the live load on strand fatigue. The beams were either loaded monotonically to ultimate capacity or cyclically fatigued and then loaded monotonically to failure. All the beams were monotonically loaded past their cracking moment at midspan prior to strengthening, to simulate girders in the field. Beam 1 was tested as a control specimen under static loading up to failure. Beams 2 and 3 were strengthened with carbon FRP to have a design stress range of 124 MPa (18 ksi) under service load condition. Beams 4 and 5 were strengthened to have a higher stress range of 248 MPa (36 ksi). For all the strengthened beams, the failure mode observed was FRP rupture. The results favorably qualify the application of FRP strengthening to increase the live load of concrete beams prestressed with straight strands.     

Coupled Continuum-Discrete Model for Saturated Granular Soils

A coupled hydromechanical model was used to analyze the mesoscale pore fluid flow and microscale solid phase deformation of saturated granular soils. The fluid motion was idealized using averaged Navier–Stokes equations, and the discrete element method was employed to model the assemblage of solid particles. The fluid–particle interactions were quantified using established semiempirical relationships. Simulations were conducted to investigate the three-dimensional response of sandy deposits when subjected to critical and overcritical upward pore fluid flow. These simulations revealed complex response patterns after the onset of quicksand conditions and provided valuable insight into the associated mechanisms. The employed model provides an effective tool to assess the microscale mechanisms and characteristics of the partially drained response of saturated granular media.     

In vitro characterization studies of self-microemulsified bosentan systems

Context: Bosentan is a poorly soluble drug and pose challenges in designing of drug delivery systems.

Objective: The objective of this study is to enhance the solubility, dissolution and shelf-life of bosentan by formulating it as S-SMEDDS capsules.

Materials and methods: Solubility of bosentan was tested in various liquid vehicles such as oils (rice bran and sunflower), surfactants (span 20 and tween 80) and co-surfactants (PEG 400 and propylene glycol) and microemulsions were developed. Bosentan was incorporated into appropriate microemulsion systems which were previously identified from pseudo ternary phase diagrams. Bosentan-loaded SMEDDS were evaluated for drug content, drug release, zeta potential, and droplet size. The selected liquid SMEDDS were converted into solid SMEDDS by employing adsorption and melt granulation. Solid SMEDDS were characterized for micromeritics and evaluated for drug content, drug release, and shelf-life.

Results: Isotropic systems R5, R13, S5, and S13 with submicron droplet size had exhibited 85.45, 94.12, 81.67, and 96.64% drug release, respectively. Solid SMEDDS of MR13 and AS13 formulations with rapid reconstitution ability, exhibited 84.85 and 86.74% of on par drug release. The formulations were physicochemically intact for 1.02 and 1.56 years.

Discussion: Liquid SMEDDS composed with PEG400 had displayed optimal characters. Solid SMEDDS had high-dissolution profiles than bosentan due to modification in the crystalline structure of drug upon microemulsification.

Conclusion: Thus, solid SMEDDS addressed the solubility, dissolution, and stability issues of bosentan and becomes an alternate for clinical convenience.