Evaluation of tree-based routing Ethernet

Tree-based Routing (TRE) revisits Tree-based Routing Architecture for Irregular Networks (TRAIN)—a forwarding scheme based on a spanning tree that was extended to use some shortcut links.We propose its adaptation to Ethernet, using a new type of hierarchical Ethernet addresses and a procedure to assign them to bridges. We show that compared to RSTP, TRE offers improved throughput. The impact of transient loops in TRE is lower compared to the application of the classical shortest path routing protocols to Ethernet. Finally, TRE is self-configuring and its forwarding process is simpler and more efficient than in standard Ethernet and shortest path routing proposals.Publicad

Hierarchical Up/Down Routing Architecture for Ethernet backbones and campus networks

We describe a new layer two distributed and scalable routing architecture. It uses an automatic hierarchical node identifier assignment mechanism associated to the rapid spanning tree protocol. Enhanced up/down mechanisms are used to prohibit some turns at nodes to break cycles, instead of blocking links like the spannning tree protocol does. The protocol performance is similar or better than other turn prohibition algorithms recently proposed with lower complexity O(Nd) and better scalability. Simulations show that the fraction of prohibited turns over random networks is less than 0.2. The effect of root bridge election on the performance of the protocol is limited both in the random and regular networks studied. The use of hierarchical, tree-descriptive addresses simplifies the routing, and avoids the need of all nodes having a global knowleddge of the network topology. Routing frames through the hierarchical tree at very high speed is possible by progressive decoding of frame destination address, without routing tables or port address learning. Coexistence with standard bridges is achieved using combined devices: bridges that forward the frames having global destination MAC addresses as standard bridges and frames with local MAC frames with the proposed protocol.Publicad

S,O-Ligand Promoted meta-C−H Arylation of Anisole Derivatives via Palladium/Norbornene Catalysis

Reversing the conventional site-selectivity of C−H activation processes provides new retrosynthetic disconnections to otherwise unreactive bonds. Here, we report a new catalytic system based on palladium/norbornene and an S,O-ligand for the meta-C−H arylation of aryl ethers that significantly outperforms previously reported systems. We demonstrate the unique ability of this system to employ alkoxyarene substrates bearing electron donating and withdrawing substituents. Additionally, ortho-substituted aryl ethers are well tolerated, overcoming the “ortho constraint”, which is the necessity to have a meta-substituent on the alkoxyarene to achieve high reaction efficiency, by enlisting novel norbornene mediators. Remarkably, for the first time the monoarylation of alkoxyarenes is achieved efficiently enabling the subsequent introduction of a second, different aryl coupling partner to rapidly furnish unsymmetrical terphenyls. Further insight into the reaction mechanism was achieved by isolation and characterization of some Pd-complexes—before and after meta C−H activation—prior to evaluation of their respective catalytic activities

Recent Advances in the Catalytic Enantioselective Reformatsky Reaction

This paper reviews the present state of the catalytic enantioselective Reformatsky reaction. Advancements in asymmetric versions of this reaction have recently led to a considerable extension of its scope and applicability, principally due to the use of highly active chiral ligands and very specific reaction conditions.M. A. F. I. is grateful for financial support from the Ministerio de Economía y Competitividad (MINECO) (CTQ 2012-35790) and the Consejería de Educación de la Comunidad de Madrid (programme AVANCAT, S2009/PPQ-1634). B. M. thanks the European Commission for a Marie Curie Integration Grant (FP7-PEOPLE-2012-CIG). I. M. P. and D. A. A. are grateful for financial support from the Spanish Ministerio de Ciencia e Innovación (MICINN) (project numbers CTQ2011-24165 and CTQ2010-20387, respectively) and from the University of Alicante

A review of solar thermal energy storage in beds of particles: Packed and fluidized beds

This review summarizes different solar thermal energy storage techniques from a particle technology perspective, including sensible, latent and thermochemical techniques for low- and high-temperature applications that use particles as the storage medium in the thermal energy storage system. The focus is on applications, experimental results, modeling and future trends. This review describes two different particle technologies used to store thermal energy: packed and fluidized beds. The advantages and disadvantages of both technologies are reviewed throughout different studies found in the literature for various thermal energy storage systems. Packed beds have the main advantage of thermal stratification, which increases the efficiency of solar collectors in low-temperature sensible energy storage systems and augments the exergy content in the bed. Moreover, they have been proven to be suitable as dual-media thermocline storage systems for CSP plants. In contrast, the high mixing rates of fluidized beds makes them suitable for the rapid distribution of concentrated solar energy in particle receiver CSP systems. In addition, their high heat and mass transfer rates, compared with those of packed beds, make them the preferred particle technology for thermochemical energy storage applications. This review also notes that it is important to find new materials with an appropriate size and density that can be properly used in a fluidized bed. Additionally, more specific research efforts are necessary to improve the understanding of the behavior of these materials during the fluidization process and over a high number of charging/discharging cycles

<i>Meta</i>-C-H arylation of aniline derivatives via palladium/S,O-ligand/norbornene cooperative catalysis

Aromatic amines are ubiquitous moieties in organic molecules and their direct functionalization is of great interest in many research areas due to their prevalence in pharmaceuticals and organic electronics. While several synthetic tools exist for the ortho- and para-functionalization of anilines, the functionalization of the less reactive meta-position is not easy to achieve with current methods. To date, the meta-C-H arylation of aniline derivatives has been restricted to either the use of directing groups templates, or their transformation into anilides quaternary anilinium salts. Herein, we report the first general and efficient meta-C-H-arylation of non-directed aniline derivatives via cooperative catalysis with a palladium-S,O-ligand-norbornene system. The reaction proceeds under mild conditions with a wide range of aniline derivatives and aryl iodides, while being operationally simple and scalable. Our preliminary mechanistic investigation-including the isolation of several palladium complexes and deuterium experiments-reveal useful insights into the substituent-effects of both the aniline-substrate and the NBE-mediator during the meta-C-H activation step

Flow and heat transfer analysis of a gas-particle fluidized dense suspension in a tube for CSP applications

This work presents a numerical study of the flow of particles in a gas–particle fluidized dense suspension for CSP applications using the Multi-Phase Particle in Cell (MP-PIC) method, implemented in CPFD-Barracuda software. The study covers two different numerical simulations. The first is a cold and isothermal model in which the fluctuations and control of the mass flow of particles ascending along the vertical tube was studied. In the second, a high-temperature boundary condition was imposed on the external surface of the tube and the energy equation was solved. In this second case, the heat transfer coefficient between the inner surface of the tube and the particles was numerically computed. The numerical results in the cold model are highly consistent with experimental data available in the literature (with values up to 150 kg/h and differences of approximately ±10 kg/h) and underline the significant impact of the pressure at the bottom of the bed and of the aeration flow rate on the mass flow of particles. The results of the non-isothermal case present heat transfer coefficients in the range of 300–400 W∕(m2 K) with transient fluctuations during the fluidization process. These fluctuations may be an influence on the mechanical damage of the tube, which is exposed to high levels of concentrated irradiation.This work was partially funded by the project PID2021-127322OB-I00, funded by the Ministerio de Ciencia e Innovación MICIN/AEI/10.13039/501100011033/ and by FEDER Una manera de hacer Europa; Project SBPLY/21/180501/000017, funded by the Regional Government of Castilla-La Mancha and by FEDER Una manera de hacer Europa; Project RED2018-102431-T, funded by the Ministerio de Ciencia, Innovación y Universidades - Agencia Estatal de Investigación (AEI) and Project 2020-GRIN-28725, funded by Universidad de Castilla-La Mancha