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Abstract Theoretical analysis of the interaction between concentrated solar radiation and a honeycomb matrix or a bed of particles cooled by a gas is presented. The computation and the experimental results show evidence of overheating of the solid near the irradiated surface. To prevent the upper surface from this phenomenon and to reduce the radiative heat losses, we propose to use selective semi-transparent porous absorbers. The first results about coatings on silica are presented.

In designing innovative space plant growth facilities (SPGF) for long duration space flight, various limitations must be addressed including onboard resources: volume, energy consumption, heat transfer and crew labor expenditure. The required accuracy in evaluating on board resources by using the equivalent mass methodology and applying it to the design of such facilities is not precise. This is due to the uncertainty of the structure and not completely understanding the properties of all associated hardware, including the technology in these systems. We present a simple criteria of optimization for horticultural regimes in SPGF: Qmax = max [M x (EBI)2/(V x E x T], where M is the crop harvest in terms of total dry biomass in the plant growth system; EBI is the edible biomass index (harvest index), V is volume occupied by the crop; E is the crop light energy supply during growth; T is the crop growth duration. The criterion reflects directly on the consumption of onboard resources for crop production.

In this work, we consider the practical issues of resource allocation problem in OFDMA two-way relay networks: the inaccuracy of channel-state information (CSI) available to the transmitters. Instead, only the estimated channel status is known by the transmitters. In this context, a joint optimization of subcarrier pairing and allocation, relay selection and transmit power allocation is formulated in the OFDMA two-way amplify-and-forward relay networks. Moreover, to ensure the Quality of Service (QoS) requirement, the energy consumption must be minimized without compromising the QoS. Therefore, by applying convex optimization techniques, energy efficient algorithms are developed with the objective to minimize the total transmit power while guaranteeing the required data rates. Through simulation studies, energy consumption performance of the systems under the proposed schemes are investigated. It is shown that the proposed scheme can improve the energy consumption performance without scarifying the QoS.

In this paper, we investigate how to apply industrial unmanned aerial vehicles (UAVs) for autonomous power line inspection in smart grid from an energy efficiency perspective. Firstly, the energy consumption minimization problem is formulated as a joint optimization problem, which involves both the large-timescale optimization and the small-timescale optimization. Then, the NP-hard joint optimization problem is transformed to a two- stage optimization problem based on energy consumption magnitude and optimization timescale differences. Next, the first-stage and second-stage problems are solved by exploring dynamic programming (DP) and auction matching, respectively. Finally, the proposed algorithm is verified based on realistic power grid topology. Simulation results demonstrate that the proposed scheme achieves significant energy consumption reduction.

We examine an opportunity for increasing cyclic process efficiency at the expense of taking into account speeds and times of running processes. We consider dynamic equilibrium systems, in which the equations of state include both parameters of the system and environment. At low flow speeds, conventional quasi-static methods apply. At high speeds, new regenerative cycles become possible. This requires the introduction of an extended interpretation of the second law of thermodynamics. This involves specifying the performance of a cycle by the relative difference of temperatures of the working fluid (but not of thermal sources) at the upper and lower temperature levels of the cycle.

Power variations and energy criteria have been the main motivations for developing regenerative drive converters for elevators. A better performing solution for power smoothing can be easily found by using a supercapacitor-based storage device, connected to the intermediary circuit of a variable-speed-drive system. In this paper, power and energy considerations are being accounted for in the design of the storage tank and regarding the maximum power demand from the feeding network. For the power-conversion circuit, which is necessary to compensate the voltage variations of the supercapacitors during charge and discharge, a high-efficiency converter, topology is proposed, which allows the bidirectional energy flow under soft-commutation conditions. Additionally it offers a good flexibility for the optimal sizing of the supercapacitor voltage level. The typical behavior of the special converter is given, together with an analysis of the advantages related to the specific application.

Abstract The relationship between fuel consumption in a multi-storey block of flats and climatic exposure is investigated. Fuel consumption anomalies between identical flats are attributed to vagaries in the airflow around the building and highlight the need for improved standards of thermal insulation and/or differential thermal insulation, dependent upon flat location. Climate and building design and the subject of building Climatology in architectural education are discussed briefly.

Disturbances threatening transient stability commence by accelerating generators in a limited area of the total transmission grid. Usually, only after one second, when this accelerating energy has been spread to other units, would stability be lost. Capitalising on this fact leads to a new approach to the control of transient stability. It would utilise simple, fast-acting measures capable of local control at major substations for meeting the initial impact of the disturbance. These measures involve the selective switching of shunt capacitors and reactors, only at substations surrounding the initially accelerating generators. This quarantines, and so diminishes the initial accelerating energy as it flows past these substations. A later switching on the backswing would further reduce the energy transfer between the system's generators, so damping inter-unit oscillations. The new control procedure is capable of extending existing transient stability limits.

We are thankful for the support received from the Istanbul Technical University Scientific Research Projects Coordination Unit.