Adaptive super-twisting observer for fault reconstruction in electro-hydraulic systems

An adaptive-gain super-twisting sliding mode observer is proposed for fault reconstruction in electro-hydraulic servo systems (EHSS) receiving bounded perturbations with unknown bounds. The objective is to address challenging problems in classic sliding mode observers: chattering effect, conservatism of observer gains, strong condition on the distribution of faults and uncertainties. In this paper, the proposed super-twisting sliding mode observer relaxes the condition on the distribution of uncertainties and faults, and the gain adaptation law leads to eliminate observer gain overestimation and attenuate chattering effects. After using the equivalent output-error-injection feature of sliding mode techniques, a fault reconstruction strategy is proposed. The experimental results are presented, confirming the effectiveness of the proposed adaptive super-twisting observer for precise fault reconstruction in electro-hydraulic servo systems.Comment: Final versio

RTE: A computer code for Rocket Thermal Evaluation

The numerical model for a rocket thermal analysis code (RTE) is discussed. RTE is a comprehensive thermal analysis code for thermal analysis of regeneratively cooled rocket engines. The input to the code consists of the composition of fuel/oxidant mixture and flow rates, chamber pressure, coolant temperature and pressure. dimensions of the engine, materials and the number of nodes in different parts of the engine. The code allows for temperature variation in axial, radial and circumferential directions. By implementing an iterative scheme, it provides nodal temperature distribution, rates of heat transfer, hot gas and coolant thermal and transport properties. The fuel/oxidant mixture ratio can be varied along the thrust chamber. This feature allows the user to incorporate a non-equilibrium model or an energy release model for the hot-gas-side. The user has the option of bypassing the hot-gas-side calculations and directly inputting the gas-side fluxes. This feature is used to link RTE to a boundary layer module for the hot-gas-side heat flux calculations

Environmental and energy performances optimization of a neighborhood in Tehran, via IMM® methodology.

Due to the fact that urbanization, as a dominating global development process, has been reached a dramatic measure, series of questions have been arisen about its environmental impacts. The urbanization soaring rate, which its impetus has been provided by unprecedented population growth, has had serious of direct consequences such as inconceivable and unbalanced consumption of natural resources and global warming rate acceleration. In such a dramatic circumstances how urban planning and governance could contribute to climate mitigation and emissions reduction? How urban vulnerability and urban resilience should be managed? Again, how urban transformation should be propelled in order to address these challenges. To demonstrate that sustainability and environmental efficiency is an urban issue this paper shows the application of IMM® (Integrated Modification Methodology) on Shahrak-e Golestan, a newly settled neighborhood located in District 22 of Tehran. Forming this neighborhood for accommodating a part of city’s growing population is a well representative of the common developing manners in Tehran, therefore the transformed model resulted from the study could be considered as a model for further developments of the other districts

Synthesis and characterization of a new nano lead(II) 0-D coordination supramolecular compound : a precursor to produce pure phase nano-sized lead(II) oxide

Nano-structure of a new 0D Pb(II) coordination supramolecular compound, [Pb(8-Quin)](ClO)(1), L = 8-HQuin = 8-hydroxyquinolin ligand has been synthesized by use of a sonochemical process and characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRPD), Fourier transform infrared spectroscopy (FTIR) and elemental analyses. The structure of compound 1 was determined by single-crystal X-ray diffraction. The single crystal X-ray data of compound 1 implies that the Pb ions are five coordinated. Each lead atom is coordinated to nitrogen and oxygen atoms of 8-hydroxyquinolin ligand. Topological analysis shows that the compound 1 is 1,2,3,4,4M12-1net. Nanoparticles of lead(II) oxide have been prepared by calcination of lead(II) coordination polymer at 500 °C that were characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRPD) and IR spectroscopy

Biological control of Verticillium wilt of greenhouse cucumber by Talaromyces flavus

Talaromyces flavus, a fungal antagonist, was isolated from soil samples collected from cucumber greenhouses in Varamin district, Tehran province, Iran. The antagonistic effects of T. flavus isolates against Verticillium albo-atrum, the causal agent of greenhouse cucumber wilt were investigated under laboratory and greenhouse conditions. T. flavus colonies were recovered after three weeks from soil samples plated on a selective medium. Effects of volatile and non-volatile extracts of T. flavus isolates on V. albo-atrum growth were investigated in the laboratory, and five isolates that inhibited V. albo-atrum more strongly, were selected for greenhouse experiments. The infection index in the greenhouse was compared in a split plot trial with five isolates applied to the soil, the seed, or both seed + soil, arranged in a randomized complete block design with four replications. The greenhouse experiments on the different T. flavus treatments indicated that there was no significant difference among them. Of the five T. flavus isolates, the most effective was Tf-Cu-V-60. The interactions between the T. flavus treatments and the T. flavus isolates showed that the lowest infection index was achieved when the soil was treated with Tf-Cu-V-60. The study showed that T. flavus may control greenhouse Verticillium wilt of cucumber

Assessing MWCNT-graphene surface energy through in situ SEM peeling

Carbon nanotubes (CNTs) are envisioned as ideal filaments for next-generation nanocomposites due to their high strength-to-weight ratios. However, while individual nanotubes are strong, interfaces between tubes cannot bear significant load due to the weak van der Waals forces that govern their behavior. Premature interfacial failure could thus counteract the inherent strength of carbon nanotubes and, in turn, prevent CNT-based composites from achieving optimal mechanical performance. To increase the load bearing capacity of these interfaces, interlayer crosslinking schemes have been proposed using chemical functionalization. For instance, introduction of hydrogen bonds or additional van der Waals bonds between tubes could improve load transfer between CNTs. While introducing chemical groups on CNT surfaces may enhance intermolecular interactions at these interfaces, a means of quantitatively evaluating changes in interlayer adhesion as a result of to these treatments needs to be defined. In addition, as sizes of CNTs will inherently vary within a composite, it is important that such energy measurements be normalized irrespective of tube dimensions. Here we report an experimental peeling technique that can be used to measure the adhesion energy between multiwalled carbon nanotubes (MWCNTs) and graphene. Peeling tests conducted in situ a scanning electron microscope allow direct visualization of the nanoscale peeling process which, in turn, enables adhesion energy to be estimated through classical fracture analysis. The applicability of this analysis is validated by finite element simulations with boundary conditions derived from experiments. The effective contact width between tubes and graphene is estimated via atomistic simulations, providing a means to normalize interaction energy per unit area. The surface energies of bare MWCNT-graphene interfaces found in this study compare favorably with theoretical and experimental values reported for graphite. This method can serve as a foundation for evaluating the enhancements afforded by chemical functionalization, which is a critical step toward the development of strong, lightweight composites that effectively utilize the full mechanical potential of CNTs

Direct Load Control Programs by using of Logarithmic Modeling in Electricity Markets

Abstract: In this study a logarithmic modeling for Direct Load Control programs (DLC) as incentive-based Demand Response Programs (DRPs) is presented. The proposed model considers nonlinear behavioral characteristic of elastic loads which causes to more realistic modeling of demand response to DLC rates. To demonstrate the validity of the proposed technique, a real world power system is considered as test system. Where, Iranian power system is investigated. Simulation results emphasis on the effectiveness impact of running DLC programs using proposed logarithmic model on load profile of the peak day of the proposed power system

Reactive Power Planning for Loss Minimization Using Simulated Annealing

Abstract: This paper addresses an optimal Reactive Power Planning (RPP) of power system. The Static Var Compensator (SVC) is introduced into power system in order to reactive power support and voltage control. The locations and the outputs of SVCs are determined using our proposed optimal reactive power planning model. The proposed method optimizes several objective functions at the same time within one general objective. The optimized objectives are minimization of total investment in reactive power support, average voltage deviation and minimization of total system loss. These objective functions are one of the most important objectives for every transmission and distribution systems. Simulated Annealing technique (SA) is used to solve the optimization problem. The validity of the proposed method is tested on a typical power system

Carbonized Micro- and Nanostructures: Can Downsizing Really Help?

In this manuscript, we discuss relationships between morphology and mechanical strength of carbonized structures, obtained via pyrolysis of polymeric precursors, across multiple length scales, from carbon fibers (CFs) with diameters of 5–10 µm to submicron thick carbon nanofibers (CNFs). Our research points to radial inhomogeneity, skin–core structure, as a size-dependent feature of polyacrylonitrile-based CFs. This inhomogeneity is a surface effect, caused by suppressed diffusion of oxygen and stabilization byproducts during stabilization through skin. Hence, reducing the precursor diameters from tens of microns to submicron appears as an effective strategy to develop homogeneous carbonized structures. Our research establishes the significance of this downsizing in developing lightweight structural materials by comparing intrinsic strength of radially inhomogeneous CFs with that of radially homogeneous CNF. While experimental studies on the strength of CNFs have targeted randomly oriented turbostratic domains, via continuum modeling, we have estimated that strength of CNFs can reach 14 GPa, when the basal planes of graphitic domains are parallel to nanofiber axis. The CNFs in our model are treated as composites of amorphous carbon (matrix), reinforced with turbostratic domains, and their strength is predicted using Tsai–Hill criterion. The model was calibrated with existing experimental data