Application of neural networks to predict the steady state performance of a Run-Around Membrane Energy Exchanger

Modeling the performance characteristics of thermal systems has been a research interest for many decades with moisture transfer systems experiencing a resurgence over the last decade, especially in heating, ventilating, and air conditioning (HVAC) applications. In this study, a neural network (NN) model is developed to predict the heat and moisture transfer performances (i.e., the sensible and latent effectivenesses) of a novel HVAC energy exchanger called the Run-Around Membrane Energy Exchanger (RAMEE) which is able to transfer both heat and moisture between exhaust and supply air streams. The training data set for the NN model covers a wide range of design and operating parameters and is produced using an experimentally validated finite difference (FD) model. Two separate NNs (one for sensible and one for latent energy transfer) each with five inputs and one output, are selected to represent the RAMEE. The results from NN models are numerically and experimentally validated. The root mean squared error (RMSE) between the FD and NN models are 0.05 °C and 2 × 10^?5 kg_v/kg_a, indicating satisfactory agreement for energy exchange calculations. The paper reports the weights and biases to make the results of this study reproducible. These NN models are very fast and easy to use therefore, they might be used for design and for estimating the annual energy savings in different buildings which use the RAMEE in their HVAC system. Additionally, the NN models can be used with optimization algorithms to maximize energy savings and minimize life-cycle costs for a given system.     

Microstructural, electrical, and mechanical characterization of Bi2Cu0.1V0.9O5.35 (BICUVOX) ceramics fabricated from co-precipitated precursor powders

Copper-doped bismuth vanadate (Bi₂Cu_0.1V_0.9O_5.35, BICUVOX) was synthesized by a co-precipitation process which resulted in a homogenous, fine-grained powder with an average particle size of ~0.45 μm. The consolidated BICUVOX powder was sintered at temperatures between 625 and 800 °C for 0–8 h in air. The correlation between the thermal processing schedule and the final microstructure were completed for all conditions through stereological analysis of the resultant cross-sectional scanning electron microscope images. From this work, the sintering schedule of 675 °C for 1 h resulted in acquiring a BICUVOX ceramic microstructure that displayed ~97 % relative density with an average grain size of ~1.29 μm. This processing condition was ~75–125 °C lower than typical sintering temperatures for the same density, and resulted in a final grain size that is ~5–10 μm smaller in size. The four-point conductivity testing of the BICUVOX ceramics in air showed values of ~0.003–0.007 and ~0.07–0.12 S/m at 300 °C and 500 °C, respectively, depending upon the thermal processing schedule. The average flexure strength of the same BICUVOX membrane was measured using a ring-on-ring configuration, and this measurement showed flexural strengths as high as 159.3 MPa. This strength is ~92 % greater than previously reported values for BICUVOX membranes.     

A slip-line approach to the machining with rounded-edge tool

In this paper, a new slip-line model approach for modeling the orthogonal cutting process with rounded-edge tools and its associated hodograph are proposed. This model consists of eight regions, which include a dead region in front of the rake face of tool. Dewhurst and Collins’s matrix technique for numerically solving the slip-line problem is employed in the mathematical formulation of the new model. The experimental results show that a small dead region is seen in front of the rake face of tool during cutting with a rounded-edge cutting tool. The unknown slip-line angle pair was solved depending on the force data obtained experimentally and variation of the subregions with cutting edge radius was determined. Cutting force, thrust force, and dead zone grow as cutting edge radius increases in cutting edge-radiused tools.     

Leaching kinetics of colemanite in ammonium hydrogen sulphate solutions

The aim of the study was to investigate the dissolution kinetics of colemanite in ammonium hydrogen sulphate solutions in a mechanical agitation system and to declare an alternative reactant to produce boric acid. Reaction temperature, concentration of ammonium hydrogen sulphate, stirring speed, solid/liquid ratio and particle size were selected as parameters on the dissolution rate of colemanite. The experimental results were successfully correlated by linear regression using Statistica Package Program. Dissolution curves were evaluated in order to test shrinking core models for solid–fluid systems. It was observed that increase in the reaction temperature and decrease in the solid/liquid ratio causes an increase the dissolution rate of colemanite. The dissolution extent is highly increased with increase the stirring speed rate between 100 and 500 rpm and the dissolution extent is slowly increased with increase the stirring speed between 500 and 700 rpm in experimental conditions. The activation energy was found to be 32.66 kJ/mol. The leaching of colemanite was controlled by diffusion through the ash or product layer. The rate expression associated with the dissolution rate of colemanite depending on the parameters chosen may be summarized as follows: 1 ? 3(1 ? X)^2/3 + 2(1 ? X) = 8.99 × C^1.08 × W^1.39 × D^?1.27 × (S/L)^?0.54 × e^(?32.66/RT)t.     

Prehydrolysis in softwood pulping produces a valuable biorefinery fraction for material utilization

A scaled-up prehydrolysis process was elaborated to demonstrate an industrially feasible operation step in a pulping process that generates a valuable side product in addition to the cellulose pulp. The valuable side product is aqueous process liquor, a softwood hydrolysate (SWH) herein produced in 60 L batches, and its components were recovered and utilized as materials. The process parameters were shown to influence the yield, composition, and quality of the obtained hydrolysates. Furthermore, the process conditions were shown to influence the ability of SWHs to form free-standing, foldable films in blends with either microfibrillated cellulose (MFC) or carboxymethyl cellulose (CMC). Films with oxygen permeabilities (OP) as low as 0.35 cm(3) μm day(-1) m(-2) kPa(-1) at 50% relative humidity, were produced from aqueous solutions providing a viable and green alternative to petroleum-based packaging barriers. The OPs were very low regardless of SWH film composition and upgrading conditions, whereas the films' tensile performance was directly controlled by the ratio of SWH to cocomponent.     

The birefringence and anisotropic planar shrinkage of polycarbonate/organoclay injection moldings

The main objective of the present work was the study of the effect of organoclay on planar shrinkage anisotropy of polymeric injection‐molded products by means of a rheological technique, in conjunction with birefringence measurements, performed on polycarbonate/organoclay samples. Polarized optical microscopy at elevated temperatures revealed that the birefringence due to the ordered‐silicate layers had a negative contribution to the overall birefringence of the samples. The maximum value of the calculated‐order parameter based on these results was found to be near unity, indicating an appreciable degree of flow alignment for the silicate layers. Different states of silicate layer orientation, with some layers aligned parallel to the in‐plane direction at the skin layer or partially tilted from the planar direction at the core region, were observed through the optical analysis along the thickness direction. The anisotropic shrinkage measurements showed that organoclay reduced both in‐flow and cross‐flow shrinkages, resulting in a low extent of planar shrinkage anisotropy. This can be attributed to the flow alignment of clay particles closely parallel to the in‐plane direction. Prolonged relaxation of the flow‐induced molecular orientation combined with faster solidification were also found to play an appreciable role in the decreased shrinkage anisotropy. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

Miniaturized integrated antennas for far-field wireless powering

This paper describes a series of high-efficiency miniaturized antennas of different sizes that can be integrated with the same wireless-powered RFID chip. Since this RFID chip has power scavenging capability in different ISM bands, several integrated on-chip and off-chip antennas in the three ISM bands of 900 MHz, 2.4 GHz and 5.8 GHz are designed, including one antenna integrated on chip. All proposed antennas are derived from a new planar antenna structure which can be designed toward arbitrary input impedance within a given area constraint. The measurement results for the presented antennas show a different read range. The resulting read range versus antenna size diagram specifies the best operating frequency band for a given read range and occupied area. Though this diagram depends on the chip's specifications like the power-on sensitivity and input impedance, it can be generated for any chip. In addition, the measurement results concerning read range and radiation patterns for the proposed antennas are presented and compared with simulation results, showing very good agreement.     

Probing charge transfer at surfaces using graphene transistors

Graphene field effect transistors (FETs) are extremely sensitive to gas exposure. Charge transfer doping of graphene FETs by atmospheric gas is ubiquitous but not yet understood. We have used graphene FETs to probe minute changes in electrochemical potential during high-purity gas exposure experiments. Our study shows quantitatively that electrochemistry involving adsorbed water, graphene, and the substrate is responsible for doping. We not only identify the water/oxygen redox couple as the underlying mechanism but also capture the kinetics of this reaction. The graphene FET is highlighted here as an extremely sensitive potentiometer for probing electrochemical reactions at interfaces, arising from the unique density of states of graphene. This work establishes a fundamental basis on which new electrochemical nanoprobes and gas sensors can be developed with graphene.     

Use of a Reflectance Spectroscopy Accessory for Optical Characterization of ZnO-Bi(2)O(3)-TiO(2) Ceramics

The optical band-gap energy (E(g)) is an important feature of semiconductors which determines their applications in optoelectronics. Therefore, it is necessary to investigate the electronic states of ceramic ZnO and the effect of doped impurities under different processing conditions. E(g) of the ceramic ZnO + xBi(2)O(3) + xTiO(2), where x = 0.5 mol%, was determined using a UV-Vis spectrophotometer attached to a Reflectance Spectroscopy Accessory for powdered samples. The samples was prepared using the solid-state route and sintered at temperatures from 1140 to 1260 °C for 45 and 90 minutes. E(g) was observed to decrease with an increase of sintering temperature. XRD analysis indicated hexagonal ZnO and few small peaks of intergranular layers of secondary phases. The relative density of the sintered ceramics decreased and the average grain size increased with the increase of sintering temperature.     

Investigation of electromagnetic shielding effectiveness of needle punched nonwoven fabrics with staple polypropylene and carbon fibres

Conductive needle punched nonwoven fabrics are developed from staple polypropylene (PP) and varying weight fractions (10, 20 and 30 wt.%) of staple carbon fibres. A fibrous webs of staple PP and carbon fibres were formed at a wool-type carding machine, and these webs subsequently bonded on needle punching machine with 132 punches/cm² and 13.5 mm needle penetration depth. The electromagnetic shielding effectiveness (EMSE), absorption and reflection characteristics of as-produced needle punched nonwoven fabrics were determined using a network analyser as specified in ASTM D4935-10 in the frequency range 15–3000 MHz. The surface resistivity measurements were carried out in accordance with ASTM D 257-07 standard. These results indicate that the EMSE values increase incrementally with frequency in the 15–3000 MHz range. The nonwoven sample with 30 wt.% carbon fibre showed the lowest surface resistivity of 3.348 kΩ and corresponding highest EMSE of ~42.1 dB in the 3000 MHz frequency range. In comparison, the highest EMSE values from 10 to 20 wt.% staple carbon fibre were found to be 15.6 and 32.2 dB in the 3000 MHz frequency, respectively. It was observed that the absorbance and reflectance curves of each nonwoven fabric move at opposite directions to each other. It was found that as the amount of carbon fibre in the nonwoven fabric increases, absorbance values decrease, but reflectance values increase. The resultant nonwoven fabric samples are expected to be used as garment interlining after thermal bonding and wall interlayer in the future.