Effect of non-equilibrium condensation of moist air on unsteady behaviour of shock waves around a circular arc blade

The unsteady phenomena in the transonic flow around airfoils are observed in the flow field of fan,compressorblades and butterfly valves,and this often causes serious problems such as the aeroacoustic noise,the vibration.In the transonic or supersonic flow where vapour is contained in the main flow,the rapid expansion of the flowmay give rise to a non-equilibrium condensation.However,the effect of non-equilibrium condensation on thetransonic internal flows around the airfoil has not yet been clarified satisfactorily.In the present study,the effectof non-equilibrium condensation of moist air on the self-excited shock wave oscillation on a circular arc bladewas investigated numerically.The results showed that in the case with non-equilibrium condensation,frequenciesof the flow oscillation became smaller than those without the non-equilibrium condensation.     

Influence of TiO2/electrode interface on electron transport properties in back contact dye-sensitized solar cells

The influence of the TiO₂/electrode interface was investigated on electron transport properties at the interface and in TiO₂ porous film in back contact dye-sensitized solar cells. Analysis of dye-sensitized solar cells (DSCs) with Ti and TCO indicated that electron transport properties at TiO₂/Ti and TiO₂/TCO interfaces are similar despite the former's lack of a ‘built-in potential’. The dependence of short circuit current density on TiO₂ thickness indicated that TiO₂ electron transport is not affected by ‘built-in potential’ or electrode structure. Electron transport thus appears similar in back contact dye-sensitized solar cells and DSCs. A back contact dye-sensitized solar cell fabricated with a Ti electrode and optimum TiO₂ porous film showed a conversion efficiency of 7.8% with a metal mask under an air mass of 1.5 sunlight.     

Jet impingement quenching phenomena for hot surfaces well above the limiting temperature for solid–liquid contact

Experiments were conducted to understand the phenomena that happen just after a subcooled free-surface circular water jet impinges on a high temperature surface. A 2 mm-water-jet of 5–80 K subcooling and 3–15 m/s velocity was impinged on the flat surface of a cylindrical steel/brass block that was preheated to 500–600 °C. The transient temperature data were recorded and used to predict the surface temperature by an inverse heat conduction technique. A high-speed video camera was also employed to capture the flow condition. It is found that for a certain period of time the surface temperature remains well above the thermodynamic limiting temperature that allows stable solid–liquid contact. What happens during this period and what makes the surface temperature drop to the limiting temperature are important questions whose possible answers are given in this article. The cooling curves at the center of the impinging surface for different experimental conditions are also explained in relation with the limiting temperature and three characteristic regions having different types of flow patterns are identified.     

Influence of branch content,comonomer type,and crosshead speed on the mechanical properties of metallocene linear low‐density polyethylenes

The effects of branch content (BC) and comonomer type on the mechanical properties of metallocene linear low‐density polyethylene (m‐LLDPEs) were studied by means of a stress–strain experiment at room temperature. A total of 16 samples with different BCs and comonomer types were used. In addition, the effect of crosshead speed on the mechanical properties of m‐LLDPEs with different BCs was examined. The degree of crystallinity (X_t) of these copolymers was determined by differential scanning calorimetry. In addition, Ziegler–Natta linear low‐density polyethylenes (ZN‐LLDPEs) were also studied for comparison purposes. The increase in BC of m‐LLDPEs decreased X_t and the modulus. However, the ZN‐LLDPEs showed higher small‐strain properties but lower ultimate properties than the m‐LLDPEs with similar weight‐average molecular weights and BCs. In comparison with low‐BC resins, m‐LLDPEs with high BCs exhibited a stronger strain hardening during the stress–strain experiments. Strain hardening was modeled by a modified Avrami equation, and the order of the mechanically induced crystal growth was in the range of 1–2, which suggested athermal nucleation. The crosshead speed was varied in the range 10–500 mm/min. For low‐BC m‐LLDPEs, there existed a narrow crosshead speed window within which the maxima in modulus and ultimate properties were observed. The location of the maxima were independent of BC. The effect of the crosshead speed on the mechanical properties of the m‐LLDPEs was a strong function of BC. However, highly branched m‐LLDPE in this experiment showed a weak dependence on the crosshead speed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 5019–5033, 2006     

Novel ruthenium sensitizer with multiple butadiene equivalent thienyls as conjugation on ancillary ligand for dye-sensitized solar cells

A heteroleptic polypyridyl ruthenium complex ‘cis-Ru(4,4′-bis(3,5-bis(5-hexylthiophen-2-yl)phenyl)-2,2′-bipyridine)(4,4′-dicarboxyl-2,2′-bipyridine) (NCS)₂, MC102′, with a high molar extinction coefficient was synthesized and characterized with IR, ¹H NMR, Mass, UV–Vis spectroscopy. The test cell DSSC devices constructed with 0.23 cm² active area photo-electrode in combination with an electrolyte composed of 0.6 M dimethylpropyl-imidazolium iodide (DMPII), 0.05 M I₂, and 0.1 M LiI in acetonitrile yielded solar to electric energy conversion efficiency (η) of 4.42% under Air Mass (AM) 1.5 sunlight, while the reference N719 sensitized solar cell fabricated and evaluated under similar conditions exhibited η-value of 5.84%.     

Online self-tuning ANN-based speed control of a PM DC motor

This paper presents an online self-tuning artificial-neural-network (ANN)-based speed control scheme of a permanent magnet (PM) DC motor. For precise speed control, an online training algorithm with an adaptive learning rate is introduced, rather than using fixed weights and biases of the ANN. The complete system is implemented in real time using a digital signal processor controller board (DS1102) on a laboratory PM DC motor. To validate its efficacy, the performances of the proposed ANN-based scheme are compared with a proportional-integral controller-based PM DC motor drive system under different operating conditions. The comparative results show that the ANN-based speed control scheme is robust, accurate, and insensitive to parameter variations and load disturbances     

Fractal Web Design of a Hemispherical Photodetector Array with Organic-Dye-Sensitized Graphene Hybrid Composites

The vision system of arthropods consists of a dense array of individual photodetecting elements across a curvilinear surface. This compound-eye architecture could be a useful model for optoelectronic sensing devices that require a large field of view and high sensitivity to motion. Strategies that aim to mimic the compound-eye architecture involve integrating photodetector pixels with a curved microlens, but their fabrication on a curvilinear surface is challenged by the use of standard microfabrication processes that are traditionally designed for planar, rigid substrates (e.g., Si wafers). Here, a fractal web design of a hemispherical photodetector array that contains an organic-dye-sensitized graphene hybrid composite is reported to serve as an effective photoactive component with enhanced light-absorbing capabilities. The device is first fabricated on a planar Si wafer at the microscale and then transferred to transparent hemispherical domes with different curvatures in a deterministic manner. The unique structural property of the fractal web design provides protection of the device from damage by effectively tolerating various external loads. Comprehensive experimental and computational studies reveal the essential design features and optoelectronic properties of the device, followed by the evaluation of its utility in the measurement of both the direction and intensity of incident light.     

Solar photocatalytic decomposition of Probenazole in water with TiO2 in the presence of H2O2

The photocatalytic decomposition of Probenazole in water using TiO₂/H₂O₂ under sunlight illumination is studied. The addition of H₂O₂ is effective for the improvement of photocatalytic decomposition of Probenazole with TiO₂. Furthermore, the operating conditions, such as photocatalyst dosage, temperature, pH, sunlight intensity and illumination time are also optimized. The kinetics of photocatalytic decomposition follow a pseudo–first–order kinetic law, and the rate constant is 0.129 min^?1. The activation energy (E_a) is 11.34 kJ/mol. The photocatalytic decomposition mechanism is discussed on the basis of molecular orbital (MO) simulation for frontier electron density.