다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

To study the operational behaviour of λ-terms, we will use the denotational (mathematical) approach. A denotational semantics for a language is based on the choice of a space of semantics values, or denotations, where terms are to be interpreted. Choosing a space with nice mathematical properties can help in proving the semantic properties of terms, since to this aim standard mathematical techniques can be used.

λ Δ -Models

Public awareness of the need to reduce global warming and the significant increase in the prices of conventional energy sources have encouraged many countries to provide new energy policies that promote the renewable energy applications. Such renewable energy sources like wind, solar, hydro based energies, etc. are environment friendly and have potential to be more widely used. Combining these renewable energy sources with back-up units to form a hybrid system can provide a more economic, environment friendly and reliable supply of electricity in all load demand conditions compared to single-use of such systems. One of the most important issues in this type of hybrid system is to optimally size the hybrid system components as sufficient enough to meet all load requirements with possible minimum investment and operating costs. There are many studies about the optimization and sizing of hybrid renewable energy systems since the recent popular utilization of renewable energy sources. In this concept, this paper provides a detailed analysis of such optimum sizing approaches in the literature that can make significant contributions to wider renewable energy penetration by enhancing the system applicability in terms of economy.

Optimum design of hybrid renewable energy systems: Overview of different approaches

The demand for electricity is increasing day by day, which cannot be fulfilled by non-renewable energy sources alone. Renewable energy sources such as solar and wind are omnipresent and environmental friendly. The renewable emulnergy sources are emerging options to fulfill the energy demand, but unreliable due to the stochastic nature of their occurrence. Hybrid renewable energy system (HRES) combines two or more renewable energy sources like wind turbine and solar system. The objective of this paper is to present a comprehensive review of various aspects of HRES. This paper discusses prefeasibility analysis, optimum sizing, modeling, control aspects and reliability issues. The application of evolutionary technique and game theory in hybrid renewable energy is also presented in this paper.

Solar–wind hybrid renewable energy system: A review

Online fault diagnosis plays a crucial role in providing the required fault tolerance to drive systems used in safety-critical applications. Short-circuit faults are among the common faults occurring in electrical machines. This paper presents a review of existing techniques available for online stator interturn fault detection and diagnosis (FDD) in electrical machines. Special attention is given to short-circuit-fault diagnosis in permanent-magnet machines, which are fast replacing traditional machines in a wide variety of applications. Recent techniques that use signals analysis, models, or knowledge-based systems for FDD are reviewed in this paper. Motor current is the most commonly analyzed signal for fault diagnosis. Hence, motor current signature analysis is a topic of elaborate discussion in this paper. Additionally, parametric and finite-element models that were designed to simulate interturn-fault conditions are reviewed.

Recent Advances in Modeling and Online Detection of Stator Interturn Faults in Electrical Motors

The aim of this paper is to compare two approaches for modelling the vibro-acoustic behaviour of a three-phase discoidal switching flux permanent-magnet machine (DSFPM) due to electromagnetic origins. The first approach is based on a full transient vibro-acoustic analysis of the DSFPM emitted acoustic noise. The second modelling approach is based on a modal superposition analysis of the DSFPM vibro-acoustic behaviour. This multi-physic study is based on a weak coupling between two 3D Finite-Element (FE) models: an electromagnetic model computing the magnetic pressure and a vibroacoustic model to quantify the vibration/noise performances. Results comparison between the two modelling approaches shows the effectiveness of the modal superposition model in terms of precision and computation time.

http://ieeexplore.ieee.org/iel7/7469653/7476333/07476433.pdf

Magneto-vibro-acoustic analysis of a discoidal switching flux permanent magnet machine dedicated to wind turbine application

This paper presents an overview of the emerging trends in the development of electrical generators for large wind turbines. To describe the developments in the design of electrical generators, it is necessary to look at the conversion system as a whole, and then, the structural and mechanical performances of the drive train need to be considered. Many drive train configurations have been proposed for large wind turbines; they should ensure high reliability, long availability and reduced maintainability. Although most installed wind turbines are geared, directly driven wind turbines with permanent magnet generators have attracted growing interest in the last few years, which has been in parallel to the continuous increase of the per unit turbine power. The aim of this work is to present the recent commercial designs of electrical generators in large wind turbines. Both the strengths and weaknesses of the existing systems are discussed. The most emerging technologies in high-power, low-speed electrical generators are investigated. Furthermore, a comparative analysis of different electrical generator concepts is performed, and the generators are assessed upon a list of criteria such as the mass, cost, and mass-to-torque ratio. Within the framework of these criteria, it may help to determine whether the electrical generator is technically feasible and economically viable for high-power wind turbines. Finally, this review could help to determine suitable generators for use in large and ultra-large wind energy systems.

/pdf/electrical-generators-for-large-wind-turbine-trends-and-3k7a83xl.pdf

Electrical Generators for Large Wind Turbine: Trends and Challenges

An exact 2D analytical model for predicting the magnetic field in idealized structures of flat and tubular linear permanent magnet machines with surface-mounted magnets and semi-closed slots is described. The open-circuit and armature reaction magnetic field distributions are analytically derived and compared to those obtianed by finite elements analyses. The analytical model is then used for studying the effect of the slot-opening dimensions on the performance of linear machines. The developed analytical model can be advantageously used for the analysis and design of a class of linear machines.

Analytical Modeling of Flat and Tubular Linear PM Machines with Surface-Mounted Magnets and Semi-Closed Slots

This paper deals with the study of the behavior of stand alone wind energy converters (WEC) based on permanent magnet synchronous generator (PMSG). First, the WEC chain is described and the model of each component of the conversion set is studied. At this stage, a special attention is given to incorporate the saturation effect in the PMSG model. Then, the obtained model is used to analyze the dynamic behavior of this WEC face to typical wind site profile and a variable electrical load. The obtained results help the authors to analyze the WEC performances as well as the impact of the generator saturation on the power conversion.

Modeling and Test of a PM Synchronous Generator Based Small Stand Alone Wind Energy Converter

The aim of this paper is to present and compare two modeling methods of the inter-turn short circuit fault in the stator winding of a cage induction machine. The first method is a Coupled Magnetic Circuit Method (CMCM) and the second method is a Permeance Network Method (PNM) which allows taking into account the saturation effect on the fault signature. The simulation results show that by proper modeling of induction machine it is possible to detect the effect of inter-turn short circuit faults on the machine line currents. The effect of saturation on the machine line current signature is discussed. The detailed equations describing the performance of the machine in the two cases of modeling under inter-turns short circuit faults are presented. Simulation results are compared for both healthy and faulty cases.

Georges Barakat

Papers

Magneto-vibro-acoustic analysis of a discoidal switching flux permanent magnet machine dedicated to wind turbine application

Electrical Generators for Large Wind Turbine: Trends and Challenges

Analytical Modeling of Flat and Tubular Linear PM Machines with Surface-Mounted Magnets and Semi-Closed Slots

Modeling and Test of a PM Synchronous Generator Based Small Stand Alone Wind Energy Converter

Coupled magnetic circuit method and permeance network method modeling of stator faults in induction machines