Feedback local optimality principle applied to rocket vertical landing VTVL

Vertical landing is becoming popular in the last fifteen years, a technology known under the acronym VTVL, Vertical Takeoff and Vertical Landing [1,2]. The interest in such landing technology is dictated by possible cost reductions [3,4], that impose spaceship’s recycling. The rockets are not generally de- signed to perform landing operations, rather their design is aimed at takeoff operations, guaranteeing a very high forward acceleration to gain the velocity needed to escape the gravitational force. In this paper a new control method based on Feedback Local Optimality Principle, named FLOP is applied to the rocket landing problem. The FLOP belongs to a special class of optimal controllers, developed by the mechatronic and vehicle dynamics lab of Sapienza, named Variational Feedback Controllers - VFC, that are part of an ongoing research and are recently applied in different field: nonlinear system [5], marine and terrestrial autonomous vehicles [6,7,8], multi agents interactions and vibration control [9, 10]. The paper is devoted to show the robustness of the nonlinear controlled system, comparing the performances with the LQR, one of the most acknowledged methods in optimal control

A reconfigurable optical header recognition system for optical packet routing applications

We demonstrate a reconfigurable all-optical packet processing system. The key device is a code-reconfigurable header decoder based on a fiber Bragg grating. The performance of the system is tested for different packet headers, and error-free operation is confirmed

Rapidly reconfigurable optical phase encoder-decoders based on fiber Bragg gratings

We demonstrate the capacity for fast dynamic reconfiguration of optical code-division multiple access (OCDMA) phase en/decoders based on fiber Bragg gratings and a thermal phase-tuning technique. The tuning time between two different phase codes is measured to be less than 2 s. An OCDMA system using tunable-phase decoders is compared with a system using fixed-phase decoders and, although the system using fixed-phase decoders exhibits a shorter output autocorrelation pulsewidth and lower sidelobes, the system using tunable-phase decoders has advantages of flexibility and a more relaxed requirement on the input pulsewidth

First-principles calculations of phase transition, low elastic modulus, and superconductivity for zirconium

The elasticity, dynamic properties, and superconductivity of $\alpha$, $\omega$, and $\beta$ Zr are investigated by using first-principles methods. Our calculated elastic constants, elastic moduli, and Debye temperatures of $\alpha$ and $\omega$ phases are in excellent agreement with experiments. Electron-phonon coupling constant $\lambda$ and electronic density of states at the Fermi level $N$(\emph{E}$_{\rm{F}}$) are found to increase with pressure for these two hexagonal structures. For cubic $\beta$ phase, the critical pressure for mechanical stability is predicted to be 3.13 GPa and at \emph{P}=4 GPa the low elastic modulus ($E$=31.97 GPa) can be obtained. Besides, the critical pressure for dynamic stability of $\beta$ phase is achieved by phonon dispersion calculations to be $\mathtt{\sim}$26 GPa. Over this pressure, $\lambda$ and $N$(\emph{E}$_{\rm{F}}$) of $\beta$ phase decrease upon further compression. Our calculations show that the large value of superconducting transition temperature \emph{T}_{\rm{c}} at 30 GPa for $\beta$ Zr is mainly due to the TA1 soft mode. Under further compression, the soft vibrational mode will gradually fade away.Comment: 15 pages, 5 figure

The Application of Advanced Materials on the Water or Wastewater Treatment

Water scarcity is being recognized as a present and future threat to human activity, and, as a consequence, water purification technologies are gaining major worldwide attention. Advanced materials have many properties, such as strong adsorption, enhanced redox, and photocatalytic properties, providing unprecedented opportunities to treat surface water, groundwater, and industrial wastewater that are contaminated with toxic metals, organic and inorganic compounds, bacteria, and viruses. Currently, tremendous progress has been made in development of advanced materials for their environmental applications, and knowledge has been accumulated of the effects of these advanced materials on and their applications in the environment security, recycling, and reuse of raw materials and treatment agents, economic benefits, and potential problems to our society.This special issue aims to provide an up-to-date account of advancement in these areas as well as insights gained through field experience

Further Development of the Improved QMD Model and its Applications to Fusion Reaction near Barrier

The Improved Quantum Molecular Dynamics model is further developed by introducing new parameters in interaction potential energy functional based on Skyrme interaction of SkM$^{*}$ and SLy series. The properties of ground states of selected nuclei can be reproduced very well. The Coulomb barriers for a series of reaction systems are studied and compared with the results of the proximity potential. The fusion excitation functions for a series of fusion reactions are calculated and the results are in good agreement with experimental data.Comment: 17 pages, 10 figures, PRC accepte

Pectin modified metal nanoparticles and their application in property modification of biosensors

Pectin is a structural anionic heteropolysaccharide and abundantly found in the cell wall of terrestrial trees and plants. It exhibits several advantageous properties such as non-toxicity, cheap, biodegradable, biocompatible, abundant, flexible, etc. Functional groups like carboxylic acid and hydroxyl make pectin suitable to be covalently bonded with other biomolecules and proteins. Based on these properties, pectin is being extensively employed to encapsulate/coat metal nanoparticles (MNPs) to inhibit their aggregation and enhancing the suitability of MNPs for a wide range of applications in healthcare like drug delivery, antimicrobial activity, antioxidant etc. Another important application of pectin is to enhance the electrochemical performances of sensors in which electrode materials are modified with pectin, which immobilizes the enzyme without disturbing the basic electron transfer properties of the electrode. Thus pectin is found to have great potential for developments in future in various fields like sensing, drug delivery etc. This review covers the application of pectin for MNPs stabilization and electrochemical sensors to improve their properties. The review also emphasizes synthetic strategies and electrochemical analysis of analytes. This review will provide a comprehensive overview of pectin’s applicability and can help to design novel and efficient MNPs and electrochemical sensors for a wide range of applications

Soot measurement in diluted methane diffusion flames by multi-pass extinction and laser-induced incandescence

Multi-pass cavity line-of-sight extinction (MPC-LOSE) and laser- induced incandescence (LII) techniques are deployed to measure the soot volume fraction in a series of nitrogen-diluted flames, which produce only ppm volume mass fractions of soot. The separate suppression effects on soot formation of direct fuel dilution and indirect effects of temperature and res- idence time are interpreted by using a numerically calculated flow velocity and temperature field using a one-step fast chemistry model. The experi- mentally determined rate of soot formation is shown to obey approximately the same function of the local temperature for all dilution cases. The results show that a simple one-step reaction model using previously measured acti- vation energies can account for the dilution effect with good accuracy. The results show that the direct effect of dilution on concentration is comparable to the effects of changing the temperature estimated local temperature and residence time

A benchmark study on error-correction by read-pairing and tag-clustering in amplicon-based deep sequencing

Figure S1. Sequence properties of protein G. (a) The sequence of 88 bp template was shown in DRuMS color schemes. The overlapping region of target sequence and forward primer or reverse primer was shown. (b) The A-T C-G density plot along the target sequence. Matlab nucleotide sequence analysis toolbox was used to plot this figure. (EPS 498 kb