Air-to-Air Heat and Moisture Recovery in a Plate-Frame Exchanger Using Composite and Asymmetric Membranes.

The present work studied an air-to-air exchanger comprising a flat plate module with a diagonal channel and a counterflow configuration for the air streams. The objective of this study was to remove moisture and sensible heat from an exhaust air stream by indirect contact with another air stream. The temperature and flow rate of the exhaust air was in the range of 40-80 °C and 1-5 L·min-1, respectively, and the fresh ambient air to exhaust air flow ratio was 1-5. An asymmetric porous membrane (P-MEM), a thin film composite membrane (C-MEM), and a kraft paper were used as the core for the heat exchange module. The most influential parameter was the humid air temperature, with a direct positive effect (50-60%) due to the increase in the kinetic energy of the water molecules. The other effective parameter was the flow rate of the humid gas with a reverse effect on the enthalpy exchanger performance (25-37%). The ratio of "fresh" air to "exhaust" air had the lowest positive effect (8-10%) on the total effectiveness. The sensible effectiveness of different membranes under the studied conditions was relatively the same, showing their similar heat conductivity. However, the kraft paper showed the best performance compared to the synthetic membranes due to having a porous/hydrophile texture. P-MEM with an asymmetric porous texture showed the closest performance to kraft paper. Furthermore, it was found that under limited conditions, such as higher temperatures (70 and 80 °C) and flow rates (5 L·min-1) for the humid air, the performance of P-MEM was a little better than the kraft paper. However, C-MEM with the lowest total effectiveness and overall heat transfer coefficient (150-210 W·m-2·K-1) showed that the hydrophile PEBAX layer could not contribute to moisture recovery due to its high thickness.

A sensor-less control and optimal energy management algorithm for a stand-alone photovoltaic system considering partial shading condition.

One of the most important part of a stand-alone photovoltaic system is energy management. This part uses several sensors to measure solar radiations, load power and battery energy to determine operation of the system components. Reduction the number of sensors and optimization of energy management system are two key steps to improve the efficiency and reliability of the system without additional cost. Hence, in this paper, a comprehensive energy management algorithm along with a complementary algorithm to estimate radiation under uniform and partial shading conditions is proposed. According to the system state, the energy management algorithm commands to activate/ deactivate a part or entire of photovoltaic system which can increase the system lifetime and thus increase the system reliability. Another feature of the proposed algorithm is a new mode in the absence of radiation for parallelizing and sharing the battery's current to the load by unidirectional and bidirectional converters. Furthermore, a sensor-less complementary algorithm to determine the amount of radiation and also the partial shading condition is proposed. To prove the feasibility of the proposed algorithms, the system was simulated and constructed. The simulation and experimental results are found closely comparable and confirm the effectiveness of the proposed methods.

Evaluation of interleukin-32 and cyclooxygenase-2 expression in HAM/TSP patients and HTLV-1 asymptomatic carriers.

OBJECTIVES: HTLV-1 associated myelopathy/tropical spastic paraparesis (HAM/TSP) is a neuroinflammatory disorder associated with HTLV-1. Cytokines and inflammatory mediators have a major role in forming inflammation in HAM/TSP patients. This study aimed to measure the levels of IL-32, a proinflammatory cytokine associated with autoinflammatory disorders, and also cyclooxygenase -2 (COX-2) as a key mediator of inflammatory pathways in HAM/TSP patients and HTLV-1 asymptomatic carriers (ACs). MATERIALS AND METHODS: Peripheral blood monocyte cells (PBMCs) were isolated from HAM/TSP patients, ACs, and healthy controls (HCs), and DNA and RNA were extracted to evaluate HTLV-1 proviral load (PVL) and expression of IL-32 and COX-2, using real-time PCR. Serum levels of IL-32 were determined by using an ELISA assay. RESULTS: The expression level of IL-32 was significantly higher in ACs compared with HAM/TSP patients and HCs (P<0.0001 and P>0.05, respectively). There were no statistically significant differences in the expression levels of Cox-2 and protein levels of IL-32 between the study groups. HTLV-1 PVL was higher in HAM/TSP patients compared with ACs. CONCLUSION: Results showed increased mRNA levels of IL-32 in ACs. Since HTLV-1 PVL in ACs is lower than in HAM/TSP patients, it could be concluded that IL-32 might be an HTLV-1 inhibitor that seems to control virus replication. Despite the difference in IL-32 mRNA levels between study groups, no statistically significant differences were observed in IL-32 serum levels. Also, there were no significant differences in COX-2 expression.

Optimal mixed control of Axial Flux Permanent Magnet Synchronous generator wind turbines with modular stator structure.

Wind turbine systems are constructed using different types of generators, aero-mechanical components and control systems. Due to their ability to work in low speed, Axial Flux Permanent Magnet (AFPM) generators are becoming widespread in wind energy systems which contributes to eliminating the gearbox from the system, noticeable increase in efficiency and decrease in system weight. Due to the modular nature of the stator in AFPM generators, it is possible to control each module independently. In this paper, in addition to obtain the dynamic model of the turbine and AFPM generator, a control strategy is designed based on Mixed Integer Nonlinear Programming (MINLP) to incorporate both pitch angle and the number of active stator modules as control input signals. These control signals are used in order to maximize system efficiency and regulate output voltage in different wind speeds and electrical loads. Simulation results for a typical generator shows the effectiveness of the proposed method in speed control of the generator.

A Pixelated Microwave Near-Field Sensor for Precise Characterization of Dielectric Materials.

A highly sensitive microwave near-field sensor based on electrically-small planar resonators is proposed for highly accurate characterization of dielectric materials. The proposed sensor was developed in a robust complete-cycle topology optimization procedure wherein first the sensing area was pixelated. By maximizing the sensitivity as our goal, a binary particle swarm optimization algorithm was applied to determine whether each pixel is metalized or not. The outcome of the optimization is a pixelated pattern of the resonator yielding the maximum possible sensitivity. A curve fitting method was applied to the full-wave simulation results to derive a closed form expression for extracting the dielectric constant of a chemical material from the shift in the resonance frequency of the sensor. As a proof of concept, the sensor was fabricated and used to measure the permittivity of two known liquids (cyclohexane and chloroform) and their mixtures with different volume ratios. The experimentally extracted dielectric constants were in an excellent agreement with the reference data (for pure cyclohexane and chloroform) or those obtained by mixture formulas.

Ionic liquid tethered PEG-based polyurethane-siloxane membranes for efficient CO2/CH4 separation.

This study introduces a new polyethylene glycol (PEG) based polyurethane-siloxane membrane containing a quaternary ammonium ionic liquid for CO2/CH4 separation. The designed ionic liquid was prepared in two steps: (i) (3-chloropropyl)triethoxysilane (CPS) and N,N-dimethylpropyl amine (NDPA) were reacted with each other to form the methoxysilane-functionalized quaternary ammonium component, then (ii) chloride ion (Cl-) of the product was exchanged with tetrafluoroborate ion (BF4-). The resulting compound, a reactive methoxysilane-functionalized ionic liquid (Si-IL) was chemically anchored to the polymer backbone through the sol-gel hydrolysis and condensation reaction. Based on the permeation tests, the IL containing PEG-based polyurethane-siloxane membranes at different concentration of Si-IL (XSi-PPUIL) were found to be potential candidates for CO2 removal from CH4. For instance, the CO2/CH4 selectivity of XSi-PPUIL membranes with the Si-IL content of 10 wt% was 3.3-fold greater than the Si-IL free membranes; while, the CO2 permeability for IL tethered membranes was 9.7% higher than the corresponding IL-free membrane.

Antifouling polyvinylidene fluoride ultrafiltration membrane fabricated from embedding polypyrrole coated multiwalled carbon nanotubes.

Polypyrrole (PPy) coated raw and oxidized multiwalled carbon nanotubes (MWCNTs) nanocomposites were synthesized and used for hydrophilic modification of polyvinylidene fluoride (PVDF) ultrafiltration membranes. The prepared nanocomposites were characterized using XRD, FTIR and SEM techniques. The hydrophilicity of the fabricated membranes was evaluated using water contact angle measurements, where the mixed matrix membranes presented lower contact angle compared with the bare one. The performance results showed that the pure water flux increased from 152.8 L/m2 h (for bare PVDF membrane) to 378.8 and 399.3 L/m2 h for 0.1 and 1 wt% of PPy: raw and PPy:ox-MWCNT hybrid membranes, respectively. The results showed an increase in reversible resistance value for all hybrid membranes indicating improved antifouling properties of the prepared membranes in Bovine serum albumin (BSA) filtration. The rejection results revealed that the increase in the surface porosity and mean pore size did not affect the efficiency of the membranes for BSA rejection.