Dendrimers dendritic structural design holds vast promises, predominantly for drug delivery, owing to their unique properties. Dendritic architecture is widespread topology found in nature and offers ...development of specific properties of chemical substances. Dendrimers are an ideal delivery vehicle candidate for open study of the effects of polymer size, charge, and composition on biologically relevant properties such as lipid bilayer interactions, cytotoxicity, bio-distribution, internalization, blood plasma retention time, and filtration. This article reviews role of dendrimers in advanced drug delivery and biomedical applications.
Flow forming, as a kind of metal spinning processes, is mainly used to produce thin-walled high-precision tubular components. In this study a coupled set of experiments and numerical simulations ...using the commercial finite element code ABAQUS/Explicit was used to study the evolution of redundant strains in a single-roller flow forming process in one pass. The modified embedded pins were used to evaluate the shear strains. It is shown that high shear strains occur not only at the longitudinal but also at the cross section. Sketched longitudinal lines also show that
ɛ
θz
of the cylindrical coordinate system cannot be neglected. Beside of the shear strains, reversal straining is recognized as another type of redundant work. It is shown that this type of redundant strain results from the incremental nature of flow forming process in which the deformation is highly localized. Good agreements between the force measurements of frictionless model simulations with the experiment imply that the frictional work can be neglected in comparison to the redundant work.
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•A 500 m2 industrial salinity-gradient solar pond was constructed in Granada, Spain.•SGSP was designed to supply a low-temperature heat (up to 60 °C).•In August 2014, the temperature ...in the storage zone reached approximately 90 °C.•The overall efficiencies were 10 and 12%, during 2014 and 2015, with maximum of 28%.•Fuel oil cost reductions of 52 and 68% were obtained during 2014 and 2015.
A 500 m2 industrial salinity-gradient solar pond (SGSP) was constructed in a mineral processing plant (Solvay Minerales) in Granada (Spain). This renewable energy technology was designed to supply a low-temperature heat (up to 60 °C) to achieve the temperature requirements of the flotation mineral purification stage. The low-temperature source was integrated to partially replace the fuel oil boiler used to heat the water used in the flotation stage. Theoretical calculations based on solar radiation indicated that the use of the SGSP would reduce the annual fuel consumption by more than 50%, thus providing a significant improvement at both economic and environmental levels. Two months after the SGSP was established, in August 2014, the temperature in the storage zone of the SGSP reached approximately 90 °C. The overall performance was evaluated in two periods (2014 and 2015) in terms of the retrofitting of mining facility with a solar pond and a new method to assess the thermal efficiency of the solar pond in a long-term perspective has been proposed. The overall efficiencies obtained after the first and second operation periods were 10 and 12%, respectively, with maximum values of 28 and 24% obtained during the first operation months. Regarding the economic savings, the fuel oil cost of the flotation unit was reduced by a higher percentage than the fuel oil consumption, due to the decreasing tendency of fuel oil prices during 2014 and 2015. Reductions of 52 and 68% were obtained in the first and second periods of operation, respectively, when compared to 2013. In addition, not only does the SGSP have considerably reduced operating costs but also the environmental costs are clearly reduced when considering the reduction of CO2 emissions.
This paper systematically investigates the effect of artificial aging (AA), solution (SHT), and T6-like (solution followed by artificial aging (SHA)) heat treatments on the microstructural evolution ...and mechanical properties of selective laser melted TiN/AlSi10Mg composites. Results show that the microstructure and mechanical properties reveal inconspicuous changes after AA where the eutectic fibrous Si networks remain. However, SHT vanishes the Si networks, precipitates and coarsens Si particles, and eventually softens the Al matrix, leading to a significant decrease in tensile strength and hardness of heat-treated composites and an increase in ductility. The addition of TiN nanoparticles plays a significant role in microstructural evolution during heat treatment. By increasing solution temperature from 460 °C to 540 °C, Mg2Si phase precipitates out of the Al matrix, followed by AlFeSi intermetallic at 500 °C and AlSiTi intermetallic at 540 °C, respectively. Interestingly, unexpected enhancements of hardness (from 91.5 ± 2.3 HV to 105.9 ± 2.1 HV) and tensile strength (from 268.7 ± 2.5 MPa to 336.8 ± 1.5 MPa) are achieved as the solution temperature increases. This abnormal phenomenon is attributed to the precipitation hardening by the Mg2Si precipitate and needle-like intermetallics, which overcomes the effects of microstructural coarsening and matrix softening. This paper sheds light on how the mechanical properties of as-built TiN/AlSi10Mg composites can be tailored using different heat treatment techniques.
•TiN/AlSi10Mg composites are fabricated by SLM and then heat treated.•The AlFeSi and AlSiTi intermetallics are formed at different solution temperatures.•The unexpected increase of hardness and strength is attributed to precipitate hardening.•The mechanical properties are found to be highly microstructural-dependent.
This study was conducted to investigate the effectiveness of fish meal substitution by Chlorella vulgaris meal in the diet of Pacific white shrimp, Litopenaeus vannamei. Experimental diets contained ...varying levels of fish meal (400, 300, 200, 100 and 0 g/kg) which was replaced by increasing levels of C. vulgaris (0, 97.2, 194.4, 291.6 and 388.8 g/kg). After 8 weeks of feeding trial, shrimp fed diet with 97.2 g/kg C. vulgaris showed significantly improved growth compared to other treatments including control. Similarly, shrimp fed diet with 97.2 g/kg C. vulgaris showed significantly higher amount of trypsin and amylase activities compared to other treatments. The contents of long‐chain polyunsaturated fatty acids including eicosapentaenoic acid, docosahexaenoic acid and arachidonic acid were significantly higher in the whole body of L. vannamei fed with different levels of C. vulgaris compared to those of control group. After exposure to hypoxia, the survival rate of shrimp fed diets contained different levels of C. vulgaris was higher than that of control group, while no significant differences were observed in ammonia tolerance among treatments. In conclusion, this study indicated that fish meal can be completely replaced with C. vulgaris in the diet of juvenile L. vannamei with no adverse effects on the performance of shrimp.
•The performance of commercially available Bi2Te3 TECs as heat engine is studied.•The conversion efficiency in the regime of low grade heat is presented.•Prolonged exposure to the high operating ...temperature should be avoided.•The damage occurs in prolonged high temperature is irreversible.
This paper presents performance and reliability study of commercially available Bi2Te3 thermoelectric cells (TEC1-12710T125) used as a thermoelectric generator (TEG). These TECs are tested in temperature regime from ambient temperature up to 250°C. This paper provides simple guide to estimate energy conversion efficiency of commercially available Bi2Te3 thermoelectric cells for power generation at a variety of operating conditions in low temperature regime. When these TECs were tested at hot side temperature of around 210°C continuously for 7h, their performance was seen to reduce by around 37% as compared to performance at lower temperatures. These cells when again tested at lower temperatures showed reduced efficiency and power output. This shows that the damage is irreversible although the process revert to lower hot side temperature (<100°C). Finally this paper presents performance of these TECs when subjected to thermal cycling and continuous operation at hot side temperature of about 160°C. It was observed that the open circuit voltage starts to jump beyond 300 cycles. This might be due to weakening of the soldered joints within the cell.
This article presents a new robust adaptive sliding mode controller for a class of uncertain nonlinear systems whereas only the system output is measurable. Firstly, a robust adaptive fuzzy observer ...is designed for the system in order to estimate its state variables. The robust asymptotic convergence of the proposed observer is proven by Lyapunov direct method. Then based on the observation states, a robust adaptive sliding mode controller is suggested such that the closed loop system to be asymptotically stable. Robust asymptotic stability of the overall system suggested by the controller is also confirmed based on Lyapunov theory. Simulation results illustrate practicality and effectiveness of the proposed technique for controlling uncertain nonlinear systems.
The paper presents a system for automatic, geo-registered, real-time 3D reconstruction from video of urban scenes. The system collects video streams, as well as GPS and inertia measurements in order ...to place the reconstructed models in geo-registered coordinates. It is designed using current state of the art real-time modules for all processing steps. It employs commodity graphics hardware and standard CPU’s to achieve real-time performance. We present the main considerations in designing the system and the steps of the processing pipeline. Our system extends existing algorithms to meet the robustness and variability necessary to operate out of the lab. To account for the large dynamic range of outdoor videos the processing pipeline estimates global camera gain changes in the feature tracking stage and efficiently compensates for these in stereo estimation without impacting the real-time performance. The required accuracy for many applications is achieved with a two-step stereo reconstruction process exploiting the redundancy across frames. We show results on real video sequences comprising hundreds of thousands of frames.
This research considers size effects in the linear three-dimensional elasticity analysis of micro-tori. The fundamental relations (displacement form) are derived for isotropic toroidal shells in the ...framework of the modified couple stress theory in the curvilinear coordinate system to predict the mechanical responses. A numerical solution for the displacement field is obtained using the GDQ method. The numerical results are in a close agreement with those found by the finite element and the Galerkin method. Parametric studies are conducted to explore the effect of size-dependency, micro-tori geometry, meridional and circumferential angle, toroidal shell thickness, and different boundary conditions on the distribution of the displacement fields. Numerical results for displacement also show that natural frequencies of micro-toroidal shells, predicted by modified couple stress theory, are less than those predicted by the classical theory, due to the significant effect of length scale parameter (related to material microstructures) on the mechanical responses. The use of general curvilinear coordinates in toroidal structures enables us to also study the mechanical behavior of irregular geometries, cap-shaped panel, saddle-shaped panel, and sectorial-shaped panel.
This paper studies the nonlinear buckling and postbuckling characteristics of piezoelectric cylindrical nanoshells subjected to an axial compressive mechanical load and an electrical load in the ...presence of surface free energy effects. The electrical field is applied along the transverse direction. A size-dependent shell model is adopted based on the Gurtin–Murdoch elasticity theory and von Karman geometrical nonlinearity. To satisfy the balance conditions on the surfaces of the nanoshell, a linear variation is considered for the normal stress of the bulk through the thickness. A boundary layer theory is employed including surface energy effects in conjunction with the effects of nonlinear prebuckling deformation, large deflections in the postbuckling regime and initial geometrical imperfections. Afterwards, a two-stepped singular perturbation technique is employed to obtain the size-dependent critical buckling load and the associated postbuckling equilibrium path for alternative electric loadings. It is found that the surface free energy and electrical load can cause an increase or decrease on the critical buckling load and the associated postbuckling strength of a nanoshell depending on the sign of surface properties and applied voltage. These anticipations are the same for the both perfect and imperfect piezoelectric nanoshells.
A piezoelectric nanoshell with surface layers subjected to combination of axial compression and electrical load Display omitted
•Development an efficient size-dependent shell model including surface free energy effects•Nonlinear postbuckling behavior of piezoelectric nanoshells under combinations of axial compression and electrical field•Prediction the surface effects on the critical buckling load and associated postbuckling path of piezoelectric nanoshell
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