Optimal Configuration of Multiple Pump Powers and Wavelengths for Balanced Pre- and Post-pumped Raman Fiber Amplifiers

A novel configuration algorithm for bi-directionally pumped Raman amplifier is developed by adopting simulated annealing algorithm. Automatic design of optical fiber Raman amplifier using 10 laser diode pumps with different wavelengths and powers is demonstrated for 64 channels DWDM systems. The resulted gain ripple is less than 2.6 dB in amplification bandwidth of more than 50 nm for a transmission span of more than 300 km. The algorithm can be practically applied to desired signal channel number and gain profile.     

Optimal Configuration of Multiple Pump Powers and Wavelengths for Balanced Pre- and Post-pumped Raman Fiber Amplifiers

A novel configuration algorithm for bi-directionally pumped Raman amplifier is developed by adopting simulated annealing algorithm. Automatic design of optical fiber Raman amplifier using 10 laser diode pumps with different wavelengths and powers is demonstrated for 64 channels DWDM systems. The resulted gain ripple is less than 2.6 dB in amplification bandwidth of more than 50 nm for a transmission span of more than 300 km. The algorithm can be practically applied to desired signal channel number and gain profile.     

Simultaneous extraction and determination of albendazole and triclabendazole by a novel syringe to syringe dispersive liquid phase microextraction-solidified floating organic drop combined with high performance liquid chromatography

A syringe to syringe dispersive liquid phase microextraction-solidified floating organic drop was introduced and used for the simultaneous extraction of trace amounts of albendazole and triclabendazole from different matrices. The extracted analytes were determined by high performance liquid chromatography along with fluorescence detection. The analytical parameters affecting the microextraction efficiency including the nature and volume of the extraction solvent, sample volume, sample pH, ionic strength and the cycles of extraction were optimized. The calibration curves were linear in the range of 0.1–30.0 μg L⁻¹ and 0.2–30.0 μg L⁻¹ with determination coefficients of 0.9999 and 0.9998 for albendazole and triclabendazole respectively. The detection limits defined as three folds of the signal to noise ratio were found to be 0.02 μg L⁻¹ for albendazole and 0.06 μg L⁻¹ for triclabendazole. The inter-day and intra-day precision (RSD%) for both analytes at three concentration levels (0.5, 2.0 and 10.0 μg L⁻¹) were in the range of 6.3–10.1% and 5.0–7.5% respectively. The developed method was successfully applied to determine albendazole and triclabendazole in water, cow milk, honey, and urine samples.     

Nonequilibrium noise and instabilities in membranes with active pumps

We study the statistical properties and dynamics of flexible fluid membranes containing active transmembrane proteins and find that such active membranes can be either stable or unstable to small disturbances, depending on the signs of certain crucial parameters characterising the protein-membrane interaction. A major finding is that the shape-fluctuation spectrum in the stable case for a zero-tension active membrane has the same form over a large range of length scales as at equilibrium, but with a nonequilibrium “noise temperature” determined by the activity.     

A proposed through-flow inverse method for the design of mixed-flow pumps

A through-flow (hub-to-shroud) truly inverse method is proposed and described in this paper. It uses as a initial design specification, an imposition of mean swirl, i.e. radius times mean tangential velocity, given throughout the meridional section of the turbomachine. In the present implementation, it is assumed that the fluid is invsicid, incompressible and irrotational at inlet and the blades are supposed to have zero thickness. Only blade rows that impart to the fluid a constant work along the span will be considered. An application of this procedure to design the rotor of a mixed-flow pump will be described in detail. The strategy used to find a suitable mean swirl distribution and the other design inputs is also described. The final blade shape and pressure distributions on the blade surface are presented, showing that it is possible to obtain feasible designs using this technique. Another advantage of this technique is the fact that it does not require large amounts of CPU time.     

Experimental results for nucleating steam flow in a two-dimensional supersonic duct and comparison with theory

Results are presented of experiments conducted in a two-dimensional duct carrying a supersonic flow of condensing steam. The measurements comprised static pressure readings along the profiled surfaces of the duct and ‘fog’ droplet sizing using a light attenuation technique. Three sets of results for dry supercooled and nucleating steam flows are presented, are are compared with the predictions of a two-dimensional numerical calculation method.     

Flow analysis for a double suction centrifugal machine in the pump and turbine operation modes

A double suction centrifugal machine has been studied, both experimentally and numerically, operating as a pump and as a turbine. Experimentally, the static performance of the machine working as a pump was obtained. These measurements were compared with equivalent numerical results from a URANS calculation. As a second step, the numerical results have been exploited to get detailed information about the flow in both operating modes (pump and turbine). The main goals of the study are, first, the validation of the numerical procedure proposed and second, the possible turbine operation of the impeller, which could point out a wider working range for the machine. The first aspect is handled by detailed analysis in the pump mode, according to previous experience of the research group. The second objective is obtained by using the numerical model to explore the flow fields obtained, when working in an inverse mode. Therefore, the presented results join the use of a numerical methodology and the turbine mode of operation for a centrifugal impeller, providing insight into the flow characteristics. When working as a pump, the flow at the suction side is characterized by the existence of an inlet tongue, which tends to enforce a uniform flow for the nominal conditions. For the turbine mode, flow patterns in the impeller, volute and suction regions are carefully investigated. The influence of the specific geometrical arrangement is also considered for this operation mode. Copyright © 2008 John Wiley & Sons, Ltd.     

Photodriven Active Ion Transport Through a Janus Microporous Membrane

Precise control of ion transport is a fundamental characteristic for the sustainability of life. It remains a great challenge to develop practical and high‐performance artificial ion‐transport system that can allow active transport of ions (protons) in an all solid‐state nanoporous material. Herein, we develop a Janus microporous membrane by combining reduced graphene oxide (rGO) and conjugated microporous polymer (CMP) for controllable photodriven ion transport. Upon light illumination, a net ionic current is generated from the CMP to the rGO side of the membrane, indicating that the rGO/CMP Janus membrane can realize photodriven directional and anti‐gradient ion transport. Analogously to the p‐n junction in photovoltaic devices, light is firstly converted into separated charges to trigger a transmembrane potential, which subsequently drives directional ion movement. For the first time, this method enables integration of a photovoltaic effect with an ionic field to drive active ion transport. With the advantages of scaled up production and easy fabrication, the concept of photovoltaic ion transport based on Janus microporous membrane may find wide application in energy storage and conversion, photodriven ion‐sieving, and water treatment.     

DC voltage profile of a 1D pumped wire with two dynamical and one static impurities

In this work we study the behavior of the voltage profile of a 1D quantum wire with an impurity when transport is induced by two ac voltages that oscillating with a phase lag define a quantum pump. The voltage profile sensed along the wire by the voltage probe, that we assume weakly coupled to the system, exhibits a Friedel's oscillations structure inside the region delimited by the position of the two ac voltages that induce transport. On the other hand, outside this region the oscillations are suppressed. Using perturbation theory in the coupling constant of the voltage probe we derived analytical expressions for the DC current valid for the adiabatic regime. We also compare our analytical results with the exact numerical calculations using Keldysh non-equilibrium Green's functions formalism.     

A moment method for analysis the gain spectrum in fiber Raman amplifier with broadband pumps

The governing equations of optical fiber Raman amplifier with broadband pumps in the steady state are systems of uncountable nonlinear ordinary differential equations (NODE). In this paper, the Moment method is used to reduce the uncountable system of NODE to a system of finite number of NODE. This system of equations is solved numerically. The results are compared with that of the full numerical method. It was shown that the Moment method is a precise and efficient technique for analysis of optical fiber Raman amplifier with broadband pumps.