Nonequilibrium Detailed Fluctuation Theorem for Repeated Discrete Feedback

We extend the framework of forward and reverse processes commonly utilized in the derivation and analysis of the nonequilibrium work relations to thermodynamic processes with repeated discrete feedback. Within this framework, we derive a generalization of the detailed fluctuation theorem, which is modified by the addition of a term that quantifies the change in uncertainty about the microscopic state of the system upon making measurements of physical observables during feedback. As an application, we extend two nonequilibrium work relations: the nonequilibrium work fluctuation theorem and the relative-entropy work relation.Comment: 7 pages, 3 figure

Escorted free energy simulations

We describe a strategy to improve the efficiency of free energy estimates by reducing dissipation in nonequilibrium Monte Carlo simulations. This strategy generalizes the targeted free energy perturbation approach [Phys. Rev. E. 65, 046122, 2002] to nonequilibrium switching simulations, and involves generating artificial, "escorted" trajectories by coupling the evolution of the system to updates in external work parameter. Our central results are: (1) a generalized fluctuation theorem for the escorted trajectories, and (2) estimators for the free energy difference Delta F in terms of these trajectories. We illustrate the method and its effectiveness on model systems.Comment: Accepted for publication in The Journal of Chemical Physic

HALL EFFECT OF CHEMICAL BATH DEPOSITED CdS THIN FILMS

ABSTRACT Thin films of CdS of different thickness have been prepared on glass substrates in various temperatures by Chemical bath deposition. The thickness of the films has been determined by quartz crystal monitor method. The Hall Effect and the electrical resistivity have been and continue to be the key parameters used in the investigations of the basic electrical conduction processes in semiconductor materials

ELECTRICAL PROPERTIES OF CHEMICAL BATH DEPOSITED CdS THIN FILMS

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Interaction between organic molecules and electrogenerated nickel fluoride films: the choice of organic reactants for electrochemical perfluorination

The interactions of organic molecules such as acetonitrile, propylene carbonate, and sulfolane on the electrogenerated nickel fluoride films were investigated using cyclic voltammetry and scanning electron microscopy. The effect of water, alkali metal fluorides, fluoride content, and acidity are also reported. Based on these studies, the potential effect of these factors on electrochemical perfluorination processes are projected. Water and alkali metal fluorides would enhance the dissolution of nickel fluoride film. Organic molecules like acetonitrile dissolve nickel fluoride film, while propylene carbonate forms thick polymeric layers on nickel surface. Higher acidity and fluoride ion content enhance the stability of a thin, catalytically active nickel fluoride film. Organic reactants like sulfolane form a composite film with nickel fluoride and, thus, enhance the long-term stability and electrocatalytic activity

Electrochemistry of metals and semiconductors in fluoride media

The electrochemical surface transformations and diverse applications of a variety of metals and semiconductors in a wide range of fluoride media such as aqueous, non-aqueous media, liquid HF media, room temperature fluoride melts and molten fluoride media with a melting range covering 50–1000 degree C are reviewed. Nickel shows excellent corrosion resistance in the absence of water. The anodic performance of this metal in electrochemical perfluorination and NF3 production is discussed. Compact carbon materials serve as anodes in fluorine generators. In high temperature melts, they perform as consumable anodes. Graphitic carbon undergoes intercalation/ de-intercalation process and related battery applications. Cu/CuF2 couple is a good reference electrode. Pt and vitreous carbon materials are the inert electrodes of choice for electro analytical applications. Electrodeposition of Lithium as a non-dendritic uniform phase is important in Lithium metal based secondary batteries. High temperature fluoride melts are used in electro-deposition of valve metals such as Nb, Ta, and Ti. The stability and decomposition of fluoride complexes in these media are of interest

Experimental studies on the effect of leading-edge tubercles on laminar separation bubble

An experimental investigation was carried out to study the influence of incorporating undulations (tubercles) at the leading edge of a NACA 4415 airfoil at a low Reynolds number of 120,000. Measurements were carried out at angles of attack of 6, 12, and 18 deg, which encompasses prestall (6 and 12 deg) and poststall (18 deg) regimes of the baseline, respectively. The aerodynamic performance of the NACA 4415 airfoil with leading-edge tubercles was compared against an airfoil without tubercles (baseline) through pressure measurements. Additionally, surface oilflow visualization and two-dimensional (2-D) particle image velocimetry (PIV) were carried out to obtain insight into the on-surface flow topology and off-body flowfield of the modified and baseline airfoils. At the lower angle of attack (a = 6 deg), the extent of the laminar separation bubble (in both length and height), which was the dominant flow feature over the baseline airfoil, was significantly altered by the presence of tubercles at the leading edge. The addition of tubercles resulted in the formation of pockets of smaller separation bubbles instead of one single long bubble spread along the span observed in the baseline airfoil. The 2-D PIV and oil-flow visualization results at an angle of attack of 18 deg prove that the tubercles are very much effective beyond the stall conditions of the baseline airfoil. The modified airfoil maintained attached flow until 50% of the chord, instead of complete separation starting from the leading edge, as noticed for the baseline case. The size of the recirculating zone downstream of the separation was also significantly reduced by the tubercles. All these factors contribute to the increased performance of the airfoil with leading-edge tubercles, especially at poststall angles of the baseline

Experimental Studies on the effect of Leading edge Tubercles on Laminar Separation Bubble

The effect of wavy leading ledge, in the manner seen in humpback whales, known as tubercles, to the leading edge of a NACA 4415 airfoil is investigated experimentally at low Reynolds number of 120,000. Comparisons are carried out against a baseline NACA-4415 airfoil is addressed through surface flow visualization, surface pressure and particle image velocimetry (2D-PIV) measurements. Experiments were carried out at angles of attack of 6° and 18° corresponding to pre-stall and post-stall conditions of the baseline airfoil with free stream velocity of 7.5 m/s. The oil-flow visualization studies reveal interesting complex flow features, repeating behind every tubercle at both angles of attack. At the lower angle of attack the extent of the laminar separation bubble, which is a dominant feature on the baseline airfoil, is significantly altered by the presence of the tubercles, which result in the formation of smaller separation bubbles spread along the span instead of one single bubble. The 2-D PIV and oil flow results angle of attack of 18° show that tubercles are very much effective beyond the stall conditions of the base line airfoil. They maintain attached flow till 50% of the cord at least in regions behind the tubercles, instead of complete separation at the leading edge as noticed for the baseline case. The size of recirculating zone downstream of the airfoil post-stall is also significantly reduced by the tubercles. All these factors contribute to the increased performance of the tubercles compared to the baseline NACA 4415 airfoil. However, post-stall the use of tubercles seems to impose a highly varying separation point and subsequently the associated wake width on the airfoil, the effects of which are yet to be explored in detail

Effect of Cation Distribution on Structural and Magnetic Properties of Nickel Cobalt Zinc Ferrites

Nanoparticles of Ni(0.8−x) Co(0.2) Zn(x) Fe2O4 ( = 0.2, 0.4, and 0.6) are prepared by chemical coprecipitation method. Effects of zinc substitution on structural and magnetic properties have been investigated. The X-ray diffraction and infrared spectroscopy are used to characterize the samples. The XRD pattern of the samples provides evidence of single phase formation of spinel structure with cubic symmetry. It is observed that the particle size decreases and lattice parameter increases with the increase in zinc concentration. TEM micrographs show a well-defined nanocrystalline state with an average particle size of around ≈17 nm. The B-H loops of all samples that are obtained by using vibrating sample magnetometer are displayed. The effect of Zn addition on saturation magnetization and the coercivity of all the samples are discussed

ELECTRICAL PROPERTIES OF CHEMICAL BATH DEPOSITED CdS THIN FILMS

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