Maximum power extraction from wind turbines using a fault-tolerant fractional-order nonsingular terminal sliding mode controller

This work presents a nonlinear control approach to maximise the power extraction of wind energy conversion systems (WECSs) operating below their rated wind speeds. Due to nonlinearities associated with the dynamics of WECSs, the stochastic nature of wind, and the inevitable presence of faults in practice, developing reliable fault-tolerant control strategies to guarantee maximum power production of WECSs has always been considered important. A fault-tolerant fractional-order nonsingular terminal sliding mode control (FNTSMC) strategy to maximize the captured power of wind turbines (WT) subjected to actuator faults is developed. A nonsingular terminal sliding surface is proposed to ensure fast finite-time convergence, whereas the incorporation of fractional calculus in the controller enhances the convergence speed of system states and simultaneously suppresses chattering, resulting in extracted power maximisation by precisely tracking the optimum rotor speed. Closed-loop stability is analysed and validated through the Lyapunov stability criterion. Comparative numerical simulation analysis is carried out on a two-mass WT, and superior power production performance of the proposed method over other methods is demonstrated, both in fault-free and faulty situations

Giant magnetocaloric effect in Mn 1-t (Ti 0.5 V 0.5 ) t as compounds near room temperature

International audienceMn 1-t (Ti 0.5 V 0.5) t As compounds with t varying from 0 to 0.20 were synthesised by arc melting and subsequently annealed. The X-ray diffraction analysis reveals pure and fairly crystallised samples. Magnetisation measurements show that the Curie temperature decreases to room temperature with t the substitution rate. The sharp and abrupt character of the 1 st order transition of MnAs-type turns to a less marked variation of the magnetic entropy in the vicinity of the transition temperature, profit made to a wider temperature range of MCE efficiency

Comparative Research of B2C Services in Cloud Computing

本論文主要研究雲端科技中的B2C服務，其中重要的問題是雲端服務者如何建立且利用忠實顧客而得到利益。在許多雲端服務中，作者集中研究範圍在個人網路硬碟、線上遊戲以及content on-demand進行探討。 研究分析三種可以比較目前雲端服務市場的策略模型。第一類模型針對僅做單一雲端商品並從頭開始的個人雲端服務公司。第二類模型定義出原本製造電子產品的公司，由於低利潤使得這些公司開始提供軟體產品給目前使用的顧客來改善其收入。第三類策略模型則是組織這些軟體與網路公司來擴大他們服務硬體商品的產品組合。 在使用TOWS分析，五力分析次解釋其動機在產業的聯盟與併購。 當建立顧客群，作者提出跨越鴻溝及Catalyst Code等理論，除此之外，作者也對雲端服務供應者的利潤及價格方法進行研究，同時證明了freemium模型 (免費+額外付費升級)是目前較流行的選擇。 由比較結果顯示，第二類模型中Apple公司擁有最大客戶群與最高收入， 並在第三類模型中探討Google公司，Google公司亦是以第二類模型的概念來擴展客戶群。另外，第一類模型的公司面臨激烈的競爭，其中Dropbox公司必須加強核心能力以及降低價格，另一方面，Zynga遊戲未來將有更多獲利的機會，而content on-demand的部分，Google、Apple與亞馬遜將掌控市場，最終結果顯示，第二類模型的策略可最有效的建立客戶數量，並且提高收入。This thesis introduced a comparative research of B2C services in cloud compu-ting. The underlying question of the research was how cloud services providers create a solid customer base to become profitable. As cloud services include many areas, the author chose personal cloud storage, online games and content on-demand for analysis. At the beginning, author proposed three strategic models that can be compared in current cloud service market. First model encompassed all individual cloud service providers that focus on one business only and had to build their base from scratch. The second model defined companies that originally manufactured consumer electronics, but started to face lower margins and decided to improve their revenues by offering soft-ware products to its current customers too. At last, the author organized software or internet companies that expanded its portfolio of services to hardware products as third strategic model. In order to understand cloud computing industry author used TOWS and Five forces analysis and also explained motives behind alliances and M&A’s in the industry. As to creating customer base, the author referred to Crossing the Chasm and Catalyst Code theories. Besides that, profitability and pricing methods of the cloud service pro-viders were researched, while freemium business model proved to be the most popular choice. As a result of customer base and revenue comparison, Apple exhibited the largest customer base at the time of writing and also the highest revenue. Google, which was researched as model 3, launched its personal cloud storage service also in the same way as companies in model 2. Therefore, strategic model 2 is the most suitable choice for personal cloud storage service customer base establishment. Dropbox, which was market leader until 2012, will have to increase its competitiveness and lower its freemium pricing. Regarding online games, Zynga will have more options to raise revenue than personal cloud storage companies. In terms of content on-demand platforms, Google, Apple and Amazon will be dominant, but there will be opportunity and need for consumer electronics manufacturers to enter this market segment

Froid magnétique

National audienc

X-Ray Crystallography, Spectral Analysis, DFT Studies, and Molecular Docking of (C9H15N3)[CdCl4] Hybrid Material against Methicillin-Resistant Staphylococcus aureus (MRSA)

International audienceThe one dimensional polymer complex (C9H15N3)[CdCl4], was synthesized and characterized by X-ray crystallography, FT-IR vibrational, and thermal analysis, UV-Visible and photoluminescence (PL) spectroscopic investigations. The crystal structure crystallizes in the monoclinic space group C2/c with Z = 4. The experimental geometric data of the crystalline molecule and the results of density functional theory (DFT) generated utilizing computational methods at DFT/omega B97XD and DFT/B3LYP-D3/Gen/6-311++G(d, p)//LanL2DZ levels of theory were compared. Significantly, in order to reveal the vibrational modes of the named chemical, the Infrared and Raman spectra were registered. Then, 13C and 113Cd solid-state NMR was employed to characterize this hybrid material using a polar solvent to conduct an investigation of the optical characteristics for the UV-visible range. Consequently, utilizing the highest occupied molecular orbital and the lowest unoccupied molecular orbital (HOMO-LUMO) calculations, the molecule's energy gap (Eg) was determined. More so, the PL tests revealed two peaks at about 400 and 423 nm while the Hirshfeld surface (HS) analysis and DFT calculations were also carried out to acquire insight into the role of weak molecular interactions in the complex that affect the self-assembly process and crystal packing. In addition, molecular docking experiments with the 6U3Y, 1SAX, and 2D45 receptors reveal ideal postures with intriguing binding affinities of -5.2, -5.6, and -5.7 kcal.mol(-1), respectively. Lastly, thermo-differential analysis techniques (DTA) and thermogravimetric analysis techniques (TGA) were used to account for the thermal degradation of the current complex

ABC method for Hysteresis Model Parameters Identification

International audienceThe paper deals with the application of the artificial bee colony (ABC) method for hysteresis parameters identification. For the first time, the ABC method will be applied on hysteresis model optimization. For this purpose, two hysteresis models are tested: the first is based on a physical magnetic material behavior, which is Jiles-Atherton and the second is simpler, Fröhlich hysteresis model built on mathematical considerations. This method’s robustness will be assessed, by comparing the experimental signals to model results

Modeling of a Nondestructive Online Testing System for Dual Phase Steels

International audienc

Finite element analysis of an incremental permeability based NDT device. Application to Dual phase steels

International audienc

Modélisation des pertes et du cycle d'hystérésis dynamique des tôles

International audienceThis paper gives the main results obtained in the frame of GDR « SDSE » group work on magnetic materials modeling. The models presented allow magnetic losses or hysteresis loops to be predicted for variable frequency and waveform excitation. A systematic comparison with experiment is done in order to analyze the models capabilities

Effet magnétocalorique géant des composés Mn1-t(Ti0.5V0.5)tAs autour de la température ambiante

National audienc