Experiments are carried out to study flow and heat transfer characteristics over NACA0018 aerofoil when the body approaches the wall of a wind tunnel. Investigations have been done to study the effect of wall proximity due to flow separation around the body at Reynolds number 2.5 × 105, different height ratios and various angles of attack. The static pressure distribution has been measured on upper and lower surfaces of the aerofoil. The results have been presented in the form of pressure coefficient, drag coefficient for different height ratios. Pressure coefficient values are decreased and then increased on the lower surface of the aerofoil and decreased on the upper surface of the aerofoil at all angles of attack. The negative pressure coefficient and drag coefficient decreases as the body approaches the upper wall of wind tunnel. The maximum value of drag coefficient has been observed at an angle of attack 30° for the aerofoil at all height ratios. The Heat transfer experiments have been carried out under constant heat flux condition. Heat transfer coefficients are determined from the measured wall temperature and ambient temperature and presented in the form of Nusselt number. The variation of local as well as average Nusselt number has been shown with non dimensional distance for different angles of attack and for various height ratios. The local as well as average Nusselt number decreases as the height ratio decreases for all non-dimensional distance and angles of attack respectively. Maximum value of average Nusselt number has been observed at an angle of attack 40°. 相似文献
The electrochemical behavior of Hg2+ was investigated in poly(Eriochrome Black T)-modified carbon paste electrode (CPE) using cyclic voltammetry (CV). Poly(Eriochrome Black T) was prepared in an alkaline medium on the surface of the CPE using a solution of Eriochrome Black T with the CV technique. The electrochemical impedance study revealed a better charge transfer kinetics at the modified electrode. The effects of variation of the experimental conditions, such as the concentration of electrolytes, pH, deposition time, and the deposition potential, which maximize current efficiency were studied. The optimum response of Hg2+ was observed in 1.0 M KCl solution. The differential pulse anodic stripping voltammetric technique was employed successfully to detect Hg2+, which gave a good linear response at low concentration levels of Hg2+. The detection limit was found to be 2.2?×?10?10 M (S/N?=?3), which is comparable with that achieved in multiwall carbon nanotube-modified electrode. The remarkable electroanalytical performance of the modified electrode makes it amenable to employ it successfully as an electrochemical sensor for the determination of hazardous pollutant Hg2+ in environmental samples. 相似文献
A method of computing general Stokes flows in the presence of rigid boundaries of arbitrary shape is proposed. The solution satisfies the governing field equations exactly and the boundary conditions approximately. The method has been illustrated with three examples. The advantage of the method lies in the ease of implementation for rigid bodies of arbitrary shape, providing an approximate but analytical solution throughout the domain. 相似文献
Research on Chemical Intermediates - We have prepared B-doped BiVO4 (B-BiVO4) with oval-shaped morphology through a simple, one-step hydrothermal route employing sodium citrate as the chelating... 相似文献
When a measure \(\varPsi(x)\) on the real line is subjected to the modification \(d\varPsi^{(t)}(x) = e^{-tx} d \varPsi(x)\), then the coefficients of the recurrence relation of the orthogonal polynomials in \(x\) with respect to the measure \(\varPsi^{(t)}(x)\) are known to satisfy the so-called Toda lattice formulas as functions of \(t\). In this paper we consider a modification of the form \(e^{-t(\mathfrak{p}x+ \mathfrak{q}/x)}\) of measures or, more generally, of moment functionals, associated with orthogonal L-polynomials and show that the coefficients of the recurrence relation of these L-orthogonal polynomials satisfy what we call an extended relativistic Toda lattice. Most importantly, we also establish the so called Lax pair representation associated with this extended relativistic Toda lattice. These results also cover the (ordinary) relativistic Toda lattice formulations considered in the literature by assuming either \(\mathfrak{p}=0\) or \(\mathfrak{q}=0\). However, as far as Lax pair representation is concern, no complete Lax pair representations were established before for the respective relativistic Toda lattice formulations. Some explicit examples of extended relativistic Toda lattice and Langmuir lattice are also presented. As further results, the lattice formulas that follow from the three term recurrence relations associated with kernel polynomials on the unit circle are also established.
Dual‐photosensitized stable EuΙΙΙ and TbΙΙΙ complexes, namely [Eu(dpq)(tfnb)3] ( 1 ) and [Tb(dpq)(tfnb)3] ( 2 ), in which dpq=dipyrido[3,2‐d:2′,3′‐f]quinoxaline and Htfnb=4,4,4‐trifluoro‐1‐(2‐napthyl)‐1,3‐butanedione, were designed as bioimaging and light‐responsive therapeutic agents. Their X‐ray structures, photophysical properties, biological interactions, photoinduced DNA damage, photocytotoxicity, and cellular uptake properties were studied. Discrete mononuclear complexes adopt an eight‐coordinated {LnN2O6} distorted square antiprism geometry with bidentate N,N‐donor dpq and O,O‐donor tfnb ligands. The designed probes have the advantage of dual‐sensitizing antennae (dpq, Htfnb) to modulate their desirable optical properties for cellular imaging and light‐responsive intracellular damage. The remarkable photostability, absence of inner‐sphere water (q<1), and longer excited‐state lifetimes of the complexes make them suitable as cellular‐imaging probes. The dpq 3T state is well located energetically to allow efficient energy transfer (ET) to the emissive 5D0 and 5D4 states of EuΙΙΙ and TbΙΙΙ. This leads to higher quantum yields (φ=0.15–0.20) in aqueous media and makes these compounds suitable cellular‐imaging probes. The complexes display significant binding ability toward DNA and bovine serum albumin (K≈105 m ?1). They effectively cleave supercoiled DNA to its nicked circular form at λ=365 nm through photoredox pathways. The cellular internalization studies showed cytosolic and nuclear localization. The remarkable photocytotoxicity of these probes offers a strategy towards developing photoresponsive LnΙΙΙ probes as cellular‐imaging and phototherapeutic agents. 相似文献
Nearly every cargo that is transported by ship is boxed in standardized containers. The land to ship and ship to land handling
of containers is performed by container cranes. These cranes dominate the throughput of the containers in ports. The operators
need to be well-trained and skilled because of the requirements of the task to load or unload the ships. During container
handling, the crane-load system can be compared to a pendulum of rope length L and deflection f{\phi} . It is referred to as an underactuated system. Whenever the fixed point of the pendulum is displaced, the load starts oscillating.
In the nonlinear dynamics literature, one finds the field of resonant coupling to transfer energy from actuated controllable
modes to underactuated uncontrollable modes. This work presents a novel normal form approach in order to identify the mode
coupling. The proposed method decomposes a nonlinear control system into controllable and uncontrollable subsystem. Only the
normal form terms in the controllable subsystem are utilized to design a general controller. Simulation results are given
to highlight the load oscillation suppression. 相似文献
Iserles et al. (J. Approx. Theory 65:151–175, 1991) introduced the concepts of coherent pairs and symmetrically coherent pairs of measures with the aim of obtaining Sobolev
inner products with their respective orthogonal polynomials satisfying a particular type of recurrence relation. Groenevelt
(J. Approx. Theory 114:115–140, 2002) considered the special Gegenbauer-Sobolev inner products, covering all possible types of coherent pairs, and proves certain
interlacing properties of the zeros of the associated orthogonal polynomials. In this paper we extend the results of Groenevelt,
when the pair of measures in the Gegenbauer-Sobolev inner product no longer form a coherent pair.
This research is supported by grants from CNPq and FAPESP. 相似文献
To reveal the inner mechanisms of a combustion accident in a coalmine, the key stages and characteristics of premixed flame front evolution such as the flame shapes, propagation speeds, acceleration rates, run-up distances and flame-generated velocity profiles are scrutinised. The theories of globally spherical, expanding flames and of finger-flame acceleration are combined into a general analytical formulation. Two-dimensional and cylindrical mining passages are studied, with noticeably stronger acceleration found in the cylindrical geometry. The entire acceleration scenario may promote the total burning rate by up to two orders of magnitude, to a near-sonic value. Starting with gaseous combustion, the analysis is subsequently extended to gaseous-dusty environments. Specifically, combustible dust (e.g. coal), inert dust (e.g. sand), and their combination are considered, and the influence of the size and concentration of the dust particles is quantified. In particular, small particles influence flame propagation more than large ones, and flame acceleration increases with the concentration of a combustible dust, until the concentration attains a certain limit. 相似文献