Proton exchange membrane electrolysis sustained by water vapor

The current–voltage characteristics of a proton exchange membrane (PEM) electrolyzer constructed with an IrRuOx water oxidation catalyst and a Pt black water reduction catalyst, under operation with water vapor from a humidified carrier gas, have been investigated as a function of the gas flow rate, the relative humidity, and the presence of oxygen. The performance of the system with water vapor was also compared to the performance when the device was immersed in liquid water. With a humidified Ar(g) input stream at 20 °C, an electrolysis current density of 10 mA cm^(−2) was sustained at an applied voltage of ~ 1.6 V, with a current density of 20 mA cm^(−2) observed at ~ 1.7 V. In the system evaluated, at current densities >40 mA cm^(−2) the electrolysis of water vapor was limited by the mass flux of water to the PEM. At <40 mA cm^(−2), the electrolysis of water vapor supported a given current density at a lower applied bias than did the electrolysis of liquid water. The relative humidity of the input carrier gas strongly affected the current–voltage behavior, with lower electrolysis current density attributed to dehydration of the PEM at reduced humidity values. The results provide a proof-of-concept that, with sufficiently active catalysts, an efficient solar photoelectrolyzer could be operated only with water vapor as the feedstock, even at the low operating temperatures that may result in the absence of active heating. This approach therefore offers a route to avoid the light attenuation and mass transport limitations that are associated with bubble formation in these systems

Prediction of the Containment of HIV Infection by Antiretroviral Therapy - a Variable Structure Control Approach

It is demonstrated that the reachability paradigm from variable structure control theory is a suitable framework to monitor and predict the progression of the human immunodeficiency virus (HIV) infection following initiation of antiretroviral therapy (ART). A manifold is selected which characterises the infection-free steady-state. A model of HIV infection together with an associated reachability analysis is used to formulate a dynamical condition for the containment of HIV infection on the manifold. This condition is tested using data from two different HIV clinical trials which contain measurements of the CD4+ T cell count and HIV load in the peripheral blood collected from HIV infected individuals for the six month period following initiation of ART. The biological rates of the model are estimated using the multi-point identification method and data points collected in the initial period of the trial. Using the parameter estimates and the numerical solutions of the model, the predictions of the reachability analysis are shown to be consistent with the clinical diagnosis at the conclusion of the trial. The methodology captures the dynamical characteristics of eventual successful, failed and marginal outcomes. The findings evidence that the reachability analysis is an appropriate tool to monitor and develop personalised antiretroviral treatment

Fast Formation of Swarm of UAVs in Congested Urban Environment

As Unmanned Aerial Vehicles (UAVs) become more readily available and reduce in cost, using multiple UAVs simultaneously to accomplish a task becomes increasingly attractive. Once swarms of UAVs share the same workspace (operational environment) it is necessary to have a means to rapidly adopt an optimal collision-free formation in the workspace. A popular approach for formation of an optimal swarm is to use Particle Swarm Optimization (PSO) techniques. A variant of PSO was recently introduced called nPSO which claims to exhibit more rapid convergence than other variants. In this paper nPSO is applied to the problem of finding optimal positions of UAVs forming a swarm in presence of large obstacles such as buildings in an urban environment. The experiments show that no more than 1000 iterations are required to obtain near optimal formation of swarm of UAVs for different maps, including maps relating to congested environments

Repeated epitaxial growth and transfer of arrays of patterned, vertically aligned, crystalline Si wires from a single Si(111) substrate

Multiple arrays of Si wires were sequentially grown and transferred into a flexible polymer film from a single Si(111) wafer. After growth from a patterned, oxide-coated substrate, the wires were embedded in a polymer and then mechanically separated from the substrate, preserving the array structure in the film. The wire stubs that remained were selectively etched from the Si(111) surface to regenerate the patterned substrate. Then the growth catalyst was electrodeposited into the holes in the patterned oxide. Cycling through this set of steps allowed regrowth and polymer film transfer of several wire arrays from a single Si wafer

Output feedback robust distributed model predictive control for parallel systems in process networks with competitive characteristics

The parallel structure is one of the basic system architectures found in process networks. This paper formulates control strategies for such parallel systems when the states are unmeasured. The competitive coupling and competitive constraints are addressed in the control design. A distributed buffer and pre-estimator are proposed to solve problems relating to coupling and timely communication whilst a distributed moving horizon estimator is employed to further improve the estimation accuracy in the presence of the constraints. An output feedback robust distributed model predictive control algorithm is then developed for such parallel systems. The Lyapunov method is used for the theoretical analysis which produces tractable linear matrix inequalities (LMI). Simulations and experimental results are provided to validate the effectiveness of the proposed approach

Static Output Feedback Model Predictive Control for Uncertain Linear Systems

A static output feedback model predictive control algorithm is proposed for an uncertain linear continuous system. An explicit expression for the static output feedback control law is developed in light of the projection lemma. An infinite time domain optimization problem is transformed into a linear programming problem. The solvability of the optimization problem and the stability are proved to underpin the proposed approach. The effectiveness of the proposed method is validated by using case studies

New Spread Type Dairy Product

A spread-type dairy product with about half the milk fat content of traditional spreads and with a substantial nonfat milk solids content has been developed by the Dairy Science Department of the Agricultural Experiment Station at South Dakota State University. The product meets a need as indicated from consumer-preference studies for a food item with spreadable consistency over a wide range of temperatures and, moreover, is in keeping with the trends to convenience foods and the lower consumption of visible fat and calories. It is hoped that such a product will add both to better nutrition and provide a new outlet for milk ingredients. Inquiries from about two dozen states and six overseas countries as well as generally good acceptable of the product by nearly 100 families have proven the concept to be sound

Time-Varying Sliding Mode Control for ABS Control of an Electric Car

Controller design for the Anti-Lock Braking System (ABS) of a wheeled vehicle is a challenging task because of the complex and nonlinear nature of the tyre-road interaction. An efficient ABS controller should be capable of maintaining the wheel slip at an optimal value, which is suitable for the particular road conditions experienced at a given instant in time, preventing the wheel from locking while braking. Many controller designs in the literature track either an optimal slip which is assumed constant or are not supported by experimental validation or simulation testing with higher order models. This paper first presents an ABS system based on a conventional Sliding Mode Control (SMC). The performance of this controller is tested on an experimental vehicle. The results are compared with simulation results obtained with both a quarter car model and a full-car model built in the Matlab/Simulink environment. The performance of this controller is improved by effective state estimation using a Sliding Mode Differentiator (SMD) where the results are benchmarked with an implementation using an Extended Kalman Filter (EKF). The paper then presents a controller based on Time-Varying Sliding Mode Control (TV-SMC) which tracks an optimal slip trajectory