Novel Air Purification System for Installation in Air Handling Units： Development, Assembly and Experimental Analysis

Nowadays, people pass 90% of their time in closed spaces, therefore, an increasing care in the creation and upkeep of healthier environments as a personal and as professional level become a major issue. The present project has as goal the verification and optimization of the implicit need of an OCRAMclima~ AHU （air handling units） in IAQ （indoor air quality） and its effectiveness in treatment and/or air purification, having as basis the legal national and European requirements for IAQ. This work was based on the study of the state of the art of the techniques in air purification and in the evaluation of their performance, culminating in the production of the prototype OCRAMclima~ NPS （nano purifying system）. The purifying phenomena involved are UVGI （ultraviolet germicidal irradiation） and catalytic ionization of air. The performance test was accomplished in a closed loop circuit, which results, obtained by an independent IAQ analyst, were satisfactory, indicating the viability of application of this system to indoor air disinfection. The outcome revealed that the conjugating of both phenomena, the air sterilizing by UV and catalytic ionization, is efficient when used for air purification, mainly for volatile organic compounds and bioaerosols.     

Space-state robust control of a Buck converter with amorphous core coil and variable load

Pulse-width modulation is widely used to control electronic converters. One of the most frequently used topologies for high DC voltage/low DC voltage conversion is the Buck converter. These converters are described by a second order system with an LC filter between the switching subsystem and the load. The use of a coil with an amorphous magnetic material core rather than an air core permits the design of smaller converters. If high switching frequencies are used to obtain high quality voltage output, then the value of the auto inductance L is reduced over time. Robust controllers are thus needed if the accuracy of the converter response must be preserved under auto inductance and payload variations. This paper presents a robust controller for a Buck converter based on a state space feedback control system combined with an additional virtual space variable which minimizes the effects of the inductance and load variations when a switching frequency that is not too high is applied. The system exhibits a null steady-state average error response for the entire range of parameter variations. Simulation results and a comparison with a standard PID controller are also presented.     

Describing and modeling the release of an antimicrobial agent from an active PP/EVOH/PP package for salmon

Natural antimicrobial active packaging is an emerging technology for fresh fish preservation in which a chemical compound of natural origin is purposely incorporated into a packaging material to be released into the food surface in order to protect it from spoilage by foodborne microorganisms. The maximum efficiency of an antimicrobial package can only be obtained when an adequate activity is achieved immediately after the packaging operation and is maintained constant throughout the product’s shelf life. This work develops an active package designed for the preservation of fresh farmed salmon in cubes or slices, made up of a rigid polypropylene (PP)/ethylene–vinyl alcohol copolymer (EVOH)/PP tray heat-sealed with an active PP/EVOH/PP film lid in which 6.5% carvacrol is incorporated in the EVOH kernel as an antimicrobial active agent. The work also includes the measurement of the carvacrol kinetics and equilibrium parameters in the preserved salmon fillets, and proposes a mathematical model based on the finite element method to describe and simulate the common performance of the developed package/food system, and to predict its behavior under different working conditions or system configurations with the objective of finding the optimum combination of variables that ensure the best packaging performance. The results obtained from the determination of parameters showed a rapid migration of the active compound through the fish muscle, and a low affinity of the agent molecules for the food matrix. The active package was successfully developed, and the proposed model was satisfactorily used to detect the key factors that govern the package performance, and also to improve the package design by modifying the thickness distribution of the multilayer active film.     

Virus,protozoa and organic compounds decay in depurated oysters

Aims

(1) Evaluate the dynamic of the depuration process of Crassostrea gigas oysters using different ultraviolet doses with different amounts of contaminants (virus, protozoa and organic contaminants) and (2) investigate the morphological changes in the oysters' tissues produced by the depuration procedures.

Methods

The oysters were allocated in sites with different degrees of contamination and analyzed after 14 days. Some animals were used as positive controls by artificial bioaccumulation with HAdV2 and MNV1 and subjected to depuration assays using UV lamps (18 or 36 W) for 168 h. The following pollutants were researched in the naturally contaminated oysters, oysters after 14 days in sites and oysters during the depuration processes: virus (HAdV, HAV, HuNoV GI/GII and JCPyV), by (RT) qPCR; protozoa (Cryptosporidium and Giardia species), by immunomagnetic separation and immunofluorescence; and organic compounds (AHs, PAHs, LABs, PCBs and organochlorine pesticides—OCs), by chromatography. Changes in the oysters' tissues produced by the depuration processes were also evaluated using histochemical analysis by light microscopy. In the artificially bioaccumulated oysters, only HAdV2 and MNV1 were investigated by (RT) qPCR before the depuration procedures and after 96 and 168 h of these procedures.

Results

At 14 days post-allocation, HAdV was found in all the sites (6.2 × 105 to 4.4 × 107 GC g^− 1), and Giardia species in only one site. Levels of PCBs and OCs in the oyster's tissues were below the detection limit for all samples. AHs (3.5 to 4.4 μg g^− 1), PAHs (11 to 191 ng g^− 1) and LABs (57 to 751 ng g^− 1) were detected in the samples from 3 sites. During the depuration assays, we found HAdV, Giardia and Cryptosporidium species until 168 h, independent of UV treatment. AHs, PAHs and LABs were found also after 168 h of depuration (36 W and without UV lamp). The depuration procedures did not produce changes in the oysters' tissues. In the artificially contaminated and depurated oysters, we detected HAdV until 168 h and MNV1 until 96 h of depuration.

Conclusion

The applied depuration treatments were unable to eliminate the protozoa or to degrade the HAdV genomes but were able to degrade the MNV1 genomes. Similarly, the UV water treatment was not efficient for aliphatic hydrocarbons, PAHs and LABs, as their concentrations were equivalent or higher to the concentrations of the control samples and samples from depuration tanks without UV treatment.     

Powder hydrophobicity and flow properties: Effect of feed frame design and operating parameters

The effect of feed frames, a device used in rotary tablet presses to drive the powders into compression dies, on the properties of the powders entering the dies is systematically described in this article. The work focuses on the effect of blend composition, feed frame parameters (blade speed and residence time), and rotary die disc parameters (die disc speed and die diameter) on powder overlubrication, the flow properties of the blends, and the resulting tablet properties (tablet hardness and dissolution). For lubricated blends, the feed frame had a large impact on powder hydrophobicity and powder flow properties. Hydrophobicity results demonstrated that the shear applied by the feed frame caused overlubrication of the powders, which improved the powder flow properties but affected adversely the tablet hardness and dissolution. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

Sensory acceptance and survival of probiotic bacteria in ice cream produced with different overrun levels

The effect of different overrun levels on the sensory acceptance and survival of probiotic bacteria in ice cream was investigated. Vanilla ice creams supplemented with Lactobacillus acidophilus were processed with overruns of 45%, 60%, and 90%. Viable probiotic bacterial counts and sensory acceptance were assessed. All the ice creams presented a minimum count of 6 log CFU/g at the end of 60 d of frozen storage. However, higher overrun levels negatively influenced cell viability, being reported a decrease of 2 log CFU/g for the 90% overrun treatment. In addition, it was not reported an influence about acceptability with respect to appearance, aroma, and taste of the ice creams (P > 0.05). Overall, the results suggest that lower overrun levels should be adopted during the manufacture of ice cream in order to maintain its probiotic status through the shelf life.     

Multi‐core scalable and efficient pathfinding with Parallel Ripple Search

Game developers are often faced with very demanding requirements on huge numbers of agents moving naturally through increasingly large and detailed virtual worlds. With the advent of multi‐core architectures, new approaches to accelerate expensive pathfinding operations are worth being investigated. Traditional single‐processor pathfinding strategies, such as A^* and its derivatives, have been long praised for their flexibility. We implemented several parallel versions of such algorithms to analyze their intrinsic behavior, concluding that they have a large overhead, yield far from optimal paths, do not scale up to many cores or are cache unfriendly. In this article, we propose Parallel Ripple Search, a novel parallel pathfinding algorithm that largely solves these limitations. It utilizes a high‐level graph to assign local search areas to CPU cores at “equidistant” intervals. These cores then use A^* flooding behavior to expand towards each other, yielding good “guesstimate points” at border touch on. The process does not rely on expensive parallel programming synchronization locks but instead relies on the opportunistic use of node collisions among cooperating cores, exploiting the multi‐core's shared memory architecture. As a result, all cores effectively run at full speed until enough way‐points are found. We show that this approach is a fast, practical and scalable solution and that it flexibly handles dynamic obstacles in a natural way. Copyright © 2012 John Wiley & Sons, Ltd.     

Nitrogen‐Doped Graphitic Nanoribbons: Synthesis,Characterization, and Transport

Nitrogen‐doped graphitic nanoribbons (N_x‐GNRs), synthesized by chemical vapor deposition (CVD) using pyrazine as a nitrogen precursor, are reported for the first time. Scanning electron microscopy (SEM) and high‐resolution transmission electron microscopy (HRTEM) reveal that the synthesized materials are formed by multilayered corrugated GNRs, which in most cases exhibit the formation of curved graphene edges (loops). This suggests that during growth, nitrogen atoms promote loop formation; undoped GNRs do not form loops at their edges. Transport measurements on individual pure GNRs exhibit a linear I–V (current‐voltage) behavior, whereas N_x‐GNRs show reduced current responses following a semiconducting‐like behavior, which becomes more prominent for high nitrogen concentrations. To better understand the experimental findings, electron density of states (DOS), quantum conductance for nitrogen‐doped zigzag and armchair single‐layer GNRs are calculated for different N doping concentrations using density functional theory (DFT) and non‐equilibrium Green functions. These calculations confirm the crucial role of nitrogen atoms in the transport properties, confirming that the nonlinear I–V curves are due to the presence of nitrogen atoms within the N_x‐GNRs lattice that act as scattering sites. These characteristic N_x‐GNRs transport properties could be advantageous in the fabrication of electronic devices including sensors in which metal‐like undoped GNRs are unsuitable.