The Reduction of Thermal Nitrogen Oxides（NOx） Emission Using Staged Combustion in Furnace

The experimental study described in this paper is to investigated the control of thermal nitrogen oxides emissions from a 2.28 MW gas-fired test furnace.Tests,including changing axial or radial air flow rate.adding cooling water,and adding staged air,were performed to characterize and opimize the fuel-rich burning zone and the fuel-lean burnout zone independently.Detailed measurements of O2,CO2,CO,NOand NOx were made at the fuel-rich burning zone and furnace exit.The influence of forming CO,NO and NOx was examined.Results indicated that adding staged air in the fuel-rich burning zone(75cm from burner)will reduce the maximum NO and NOx emissions.Adding cooling water in a right position may further lower the NO and NOx emissions.In addition,the least formation of thermal nitrogen oxides in the first stage fuel-rich burning zone will occur at the stoichiometric ratio‘s inverse value ,(φ1)^-1,0.65 to 0.7.     

Development of a four‐cell DMFC stack with air‐breathing cathode and dendrite flow field

A four‐cell direct methanol fuel cell (DMFC) stack with an air‐breathing cathode with an active area of 0.48 cm² for each cell is designed, fabricated and tested. A pure copper sheet 300 µm thick with innovative perforated flow plates (dendrite type) is fabricated and used for the cathode. For the anode, conventional serpentine flow channels made of pure copper sheets 250 µm thick are used. An extensive parametric study is conducted to determine the optimum working conditions for the fuel flow rate (anode), methanol solution concentration, channel‐to‐land ratio and stack temperature. Comparisons are made with conventional serpentine flow channels. In addition, CO₂ (water) bubbles in the anode (cathode) channels are visualized, and the results are presented and discussed. It is found that the maximum stack power of the four‐cell μDMFC stack is up to 40 mW/cm² with a limiting current density of 335 mA/cm² at a maximum volumetric and gravimetric power density of 11.16 mW/cm³ and 3.13 W/kg, respectively. Copyright © 2014 John Wiley & Sons, Ltd.     

Unstable vortex flow and new inertia-driven vortex rolls resulting from an air jet impinging onto a confined heated horizontal disk

An experiment combining flow visualization and temperature measurement is carried out here to investigate the possible presence of new inertia-driven vortex rolls and some unique characteristics of the time-dependent mixed convective vortex flow in a high-speed round air jet impinging onto a heated horizontal circular disk confined in a vertical cylindrical chamber. How the jet Reynolds and Rayleigh numbers and jet-to-disk separation distance affect the unique vortex flow characteristics is examined in detail. Specifically, the experiment is conducted for the jet Reynolds number varying from 0 to 1623 and Rayleigh number from 0 to 63,420 for the jet-to-disk separation distance fixed at 10.0, 20.0 and 30.0 mm. The results indicate that at sufficiently high Re_j the inertia-driven tertiary and quaternary rolls can be induced aside from the primary and secondary rolls. At an even higher Re_j the vortex flow becomes unstable due to the inertia-driven flow instability. Only for H = 20.0 mm the flow is also subjected to the buoyancy-driven instability for the ranges of the parameters covered here. Because of the simultaneous presence of the inertia- and buoyancy-driven flow instabilities, a reverse flow transition can take place in the chamber with H = 20.0 mm. At the large H of 30.0 mm the flow unsteadiness results from the mutual pushing and squeezing of the inertia- and buoyancy-driven rolls since they are relatively large and contact with each other. It is also noted that the critical Re_j for the onset of unsteady flow increases with ΔT for H = 10.0 and 20.0 mm. But for H = 30.0 mm the opposite is true and raising ΔT can destabilize the vortex flow. Based on the present data, flow regime maps delineating the temporal state of the flow are provided and correlating equations for the boundaries separating various flow regimes are proposed.     

Condensation heat transfer and pressure drop of refrigerant R-410A flow in a vertical plate heat exchanger

Heat transfer and associated frictional pressure drop in the condensing flow of the ozone friendly refrigerant R-410A in a vertical plate heat exchanger (PHE) are investigated experimentally in the present study. In the experiment two vertical counter flow channels are formed in the exchanger by three plates of commercial geometry with a corrugated sinusoidal shape of a chevron angle of 60°. Downflow of the condensing refrigerant R-410A in one channel releases heat to the upflow of cold water in the other channel. The effects of the refrigerant mass flux, imposed heat flux, system pressure (saturated temperature) and mean vapor quality of R-410A on the measured data are explored in detail. The results indicate that the R-410A condensation heat transfer coefficient and associated frictional pressure drop in the PHE increase almost linearly with the mean vapor quality, but the system pressure only exhibits rather slight effects. Furthermore, increases in the refrigerant mass flux and imposed heat flux result in better condensation heat transfer accompanying with a larger frictional pressure drop. Besides, the imposed heat flux exhibits stronger effects on the heat transfer coefficient and pressure drop than the refrigerant mass flux especially at low refrigerant vapor quality. The friction factor is found to be strongly influenced by the refrigerant mass flux and vapor quality, but is almost independent of the imposed heat flux and saturated pressure. Finally, an empirical correlation for the R-410A condensation heat transfer coefficient in the PHE is proposed. In addition, results for the friction factor are correlated against the Boiling number and equivalent Reynolds number of the two-phase condensing flow.     

Optimal minimal-order least-squares estimators via the generaltwo-stage Kalman filter

A direct derivation of the optimal minimal-order least squares estimator is presented using the general two-stage Kalman filter. Using this new result, the reduced-order estimators of O'Reilly (1982) and Fairman and Luk (1985) are readily shown to be equivalent. A practical implementation issue to consider these two estimators is also addressed     

Microbial Transglutaminase Affects Gel Properties of Golden Threadfin-bream and Pollack Surimi

ABSTRACT: The properties of surimi gels from threadfin-bream and pollack surimi set at 30 °C or 45 °C with microbial transglutaminase (MTGase) from Streptoverticillium ladakanum were determined. The optimal amounts of MTGase and setting conditions were: 0.3 unit/g surimi either at 30 °C for 90 min or at 45 °C for 20 min for threadfin-bream, and 0.2 unit/g surimi at 30 °C for 60 min for pollack. The strength of golden threadfin-bream surimi gels with 0.35 unit MTGase set at 30 °C for 90 min or 45 °C for 20 min was 3400 g cm, almost 3-fold of the control. SDS-PAGE analyses indicated that inter- and/or intramolecular cross-linking formed in the myosin heavy chain of MTGase-containing surimi gels.     

Effects of surface porosity on tungsten trioxide(WO3) films’ electrochromic performance

In this paper, the correlation between the electrochromic performance and the surface morphology of the tungsten trioxide (WO₃) thin films sputtered by dc reactive magnetron sputtering with widely varying target-substrate distances was investigated. It is found that the optical density change (ΔOD) of films is strongly affected by the target-substrate distance. The coloration efficiency (CE) at 633 nm was also found to be sensitive to the target-substrate distance, with 16 cm²/C of film sputtered at 6 cm and 50 cm²/C at 18 cm. X-ray diffraction showed that the crystal structure of films was amorphous. By using atomic force microscope to identify the surface porosity of the sputtered WO₃ films, we found that the film at longer target-substrate distance was rough, porous, and having a cone-shaped columns morphology, thus offering a good electrochromic performance for opto-switching applications.     

New insight into microstructure-mediated segmental dynamics in select model poly(urethane urea) elastomers

Segmental dynamics in a series of 4,4′-dicyclohexylmethane diisocyanate–diethyltoluenediamine–poly(tetramethylene oxide) based poly(urethane urea) (PUU) elastomers have been investigated through a multi-scale characterization approach. This includes broadband dielectric analysis, solid-state nuclear magnetic resonance (NMR), plate impact, and impulsive stimulated scattering. Dielectric relaxation measurements applicable at frequencies up to 10⁶ Hz are useful for interpreting the high strain-rate deformation response; i.e. at the moment of target interaction with an accelerating impact or MHz stress wave excitation. Additionally, the capability of solid-state NMR to differentiate the microstructure-mediated segmental dynamics; correspondingly, the presence of a rigid phase (those in the phase-mixed regions) and a mobile phase associated with the soft-segment domains is demonstrated. These new insights not only further elucidate the microstructure details discerned through atomic force microscopy, but also enable the prediction of the macroscopically dynamic response in these model PUUs, particularly on the temporal scale over the range of μs–ns.     

A 10 GHz Phase-Locked Loop With a Compact Low-Pass Filter in 0.18 $mu$ m CMOS

In this letter, a multi-gigahertz phase-locked loop (PLL) with a compact low-pass filter is presented. By using a novel dual-path control in the PLL architecture, the capacitance in the loop filter can be effectively reduced for high-level integration while maintaining the required loop bandwidth. Consequently, the noise resulted from off-chip components is therefore eliminated, leading to lower timing jitter at the PLL output waveforms. In addition, the timing jitter is further suppressed due to the use of decomposed phase and frequency detection. Based on the proposed techniques, a 10 GHz PLL is implemented in 0.18 mum CMOS for demonstration. Consuming a dc power of 113 mW from a 1.8 V supply, the fabricated circuit exhibits a locking range from 10.1 to 11 GHz. At an output frequency of 10.3 GHz, the measured peak-to-peak and rms jitter are 3.78 and 0.44 ps, respectively.     

Comparison of the effect of 360° versus two-dimensional virtual reality video on history taking and physical examination skills learning among undergraduate medical students: a randomized controlled trial

Virtual Reality - Before caring for patients, video instruction is commonly used for undergraduate medical students, and 360° virtual reality (VR) videos have gained increasing interest in...