Struktur und Reaktivität heterosubstituierter Nitrile. XIX [1]. Kinetik und Mechanismus der Addition sekundärer aliphatischer Amine an Arylcyanate

Structure and Reactivity of Heterosubstituted Nitriles. XIX. Kinetics and Mechanism of the Addition of Secondary Aliphatic Amines to Aryl Cyanates The N,N-dialkyl-O-aryl isourea formation by the addition of secondary aliphatic amines to aryl cyanates was studied by kinetic methods in dioxane and dioxane water mixtures. Linear relationships between the rate constants and the water concentrations, the basicity of the amines and the electrophilicity of the aryl cyanates have been found. These data and the activation parameters support two concurrent reactions, a direct nucleophilic attack of the amine to aryl cyanate and one involving a six membered transition state between a molecule of cyanate, amine and water.     

Designing and building SDN testbeds for energy-aware traffic engineering services

As experimenting with energy-aware techniques on large-scale production infrastructure is prohibitive, a large number of proposed traffic engineering strategies have been evaluated only using discrete-event simulations. The present work discusses (i) challenges towards building testbeds that allow researchers and practitioners to validate and evaluate the performance and quality of energy-aware traffic engineering strategies, (ii) requirements to fulfil when porting simulations to testbeds, and (iii) two proof-of-concept testbeds. One testbed uses and provides software-defined network (SDN) services created on the open-network operating system while the other is a composition of virtual Open vSwitches controlled by the Ryu SDN framework. The aim of the testbeds is to validate previously proposed energy-aware traffic engineering strategies in different environments. We detail the platforms and illustrate how they have been used for performance evaluation. Additionally, the paper compares results obtained in the testbeds with evaluations performed using discrete-event simulations and presents challenges faced while implementing energy-aware traffic engineering mechanisms as SDN services in testbed environments.     

Thermally acceptable temperature drifts can reduce the energy consumption for cooling in office buildings

The energy consumption and cost in large office buildings can be reduced by allowing the indoor environment to deviate from the optimum comfort conditions to situations which are still acceptable by most occupants. One such strategy is to allow the indoor temperature to increase in the afternoon in summer. A computer program was developed to predict the thermal sensation and discomfort under transient conditions, and the detailed computer program BLAST was used to evaluate the indoor temperature, space cooling load, chilled water consumption and seasonal energy use. This paper presents a comparison performed for a reference office building in Montréal between a conventional design, with constant set-point temperature during the operating hours, and a new design, where the indoor temperature is allowed to increase after 3:00 p.m. The results show a reduction of seasonal consumption for chilled water between 34 and 40%, and a reduction of energy budget for HVAC systems of 11%.     

Nanostructured quaternary Ni1-xCuxFe2-yCeyO4 complex system: Cerium content and copper substitution dependence of cation distribution and magnetic-electric properties in spinel ferrites

Quaternary Ni_1-xCu_xFe_2-yCe_yO₄ complex nano-ferrites system with different cerium content ratio and copper substitution degree were synthesized via co-precipitation wet chemical technique. The newly obtained nanoparticles, with general formula Ni_1-xCu_xFe_2-yCe_yO₄ (where x = 0.0, 0.3, 0.6 and y = 0.00, 0.03, 0.05, 0.08 and 0.10) were heated up to 600 °C to stabilize the specific crystalline spinel structure. The limit of cerium content was quantitively determined to be around 0.08 and up to 0.10. Furthermore, the powders were pelletized in a 13 mm wide pellets and thermally treated at 950 °C. The thermal treatment affected even more the phases segregation process, as CeO₂ was identified in the sample with lowest degree of cerium insertion – 0.03. Also, a difference in color and size of pelletized samples was noticed after the 950 °C thermal treatment. The Rietveld refinement, crystal structure confirmation, morphology magnetic and electrical properties of samples have been deeply studied. The cation distribution carried out from Rietveld refinement confirms the occupancy of (Fe³⁺) on tetrahedral sites and [Ni²⁺], [Cu²⁺], [Fe³⁺] and [Ce²⁺] on octahedral sites in the crystal lattice. Preliminary information regarding the cation distribution in spinel structures were suggested by FTIR spectral results, precisely in the 650-520 cm^?1 region, as a consequence of peak shape and lack of shiftiness of M^Td – O bond. Spherical-shaped quaternary nano-ferrites of 17–28 nm were determined from FE-SEM analysis and the samples composition was confirmed by EDX analysis. Hysteresis loops shows modifications in coercivity, magnetization and magnetic remanence with Ni²⁺ and Cu²⁺ ions doping in Ni_1-xCu_xFe_2-yCe_yO₄ complex systems with typical ferrimagnetic behavior. Dielectric measurements were employed in order to determine the electrical permittivity, dielectric losses and conductivity values in a 10 Hz – 1 MHz frequency range.