Experimental comparison of two configurations of hybrid photovoltaic thermal collectors

The combination of a thermal collector and a photovoltaic module in a single system allows for increased efficiency of the total conversion of solar energy. A synergistic effect can be obtained in a structure combining these two devices in a judicious manner to those of thermal and photovoltaic system installed separately. Production of total energy from hybrid collector depends on the input (that is to say, the. energy of solar radiation, air temperature and wind speed) and output which is the electric production and the temperature of the system. Thin production also depends on the mode of heal extraction. In this paper, an experimental Study of two configurations of hybrid collectors is described. The configuration that the absorber is made by galvanized steel and in the second, the absorber is a copper serpentine. The advantages of the first configuration are mainly due to low cost and simplicity but the second configuration has the advantage of promoting the heat transfer between cells and fluid.     

Electricity trade and GHG emissions: Assessment of Quebec's hydropower in the Northeastern American market (2006–2008)

Worldwide electricity sector reforms open up electricity markets and increase trades. This has environmental consequences as exports and imports either increase or decrease local production and consequently greenhouse gas (GHG) emissions. This paper's objective is to illustrate the importance of electricity trade's impact on GHG emissions by providing an estimate of the net GHG emissions resulting from these trades. To achieve this objective, Quebec hourly electricity exchanges with adjacent jurisdictions were examined over the 2006–2008 period. In order to associate a specific GHG emission quantity to electricity trades, hourly marginal electricity production technologies were identified and validated using the Ontario hourly output per power plant and information released in the Quebec adjacent system operator reports. It is estimated that over three years, imports into Quebec were responsible for 7.7 Mt of GHG, while Quebec hydropower exports avoided 28.3 Mt of GHG emissions. Hence, the net result is 20.6 Mt of avoided emissions over 2006–2008, or about 7 Mt per year, which corresponds to more than 8% of the Quebec yearly GHG emissions. When GHG emissions from all life cycle stages (resource extraction to end-of-life) are accounted for, the net avoided GHG emissions increase by 35%, to 27.9 Mt.     

Stability limits and NO emissions of premixed swirl ammonia-air flames enriched with hydrogen or methane at elevated pressures

This study reports measurements of stability limits and exhaust NO mole fractions of technically-premixed swirl ammonia-air flames enriched with either methane or hydrogen. Experiments were conducted at different pressures from atmospheric to 5 bar, representative of commercial micro gas turbines. The full range of ammonia fractions in the fuel blend, x_NH3, was considered, from 0 (pure methane or hydrogen) to 1 (pure ammonia), covering very lean (φ = 0.25) to rich (φ = 1.60) equivalence ratios. Results show that increasing pressure widens the range of stable equivalence ratios for pure ammonia-air flames. Regardless of pressure, there is a critical ammonia fraction above which the range of stable equivalence ratios suddenly widens. This is because flashback does not occur anymore when the equivalence ratio is progressively increased towards stoichiometric and rich blowout occurs instead. This critical ammonia fraction increases with pressure and is larger for ammonia-hydrogen than for ammonia-methane. Provided that enough hydrogen is blended with ammonia (x_NH3 < 0.9), flames with very lean equivalence ratios (φ < 0.7) can be stabilized and these yield competitively low NO emissions (<200 ppm), regardless of pressure. For this reason, very lean swirl ammonia-hydrogen-air flames are promising candidates for micro gas turbines. However, N₂O emissions have the potential to be unacceptably large for these operating conditions if heat loss is too large or residence time is too short. As a consequence, the post flame region must be considered carefully. Due to the lower reactivity of methane compared to that of hydrogen, very lean swirl ammonia-methane-air flames could not be stabilized and good NO performance is limited to rich equivalence ratios for ammonia-methane fuel blends. The equivalence ratio above which good NO performance depends on pressure and bulk velocity.     

Gelation versus liquid crystal phase transitions in suspensions of plate-like particles

Gelation is a common effect in aqueous suspensions of charged colloidal clay platelets at concentrations as low as 1 wt%. However, in systems of charged gibbsite [Al(OH)3] platelets, gelation can be delayed to concentrations as high as 50 wt% depending on the ionic strength. We investigated the phase behaviour of this system approaching the state of gelation in the delicate region between attractive and repulsive states that originate from competition between Coulomb repulsion and van der Waals attraction. As a function of the ionic strength, isotropic-nematic, nematic-columnar and isotropic-columnar phase separations were observed. Moreover, compression by gravitational forces allowed us to observe phase separation that is arrested by gelation in the homogeneous suspensions.     

Berries anthocyanins as potential SARS-CoV–2 inhibitors targeting the viral attachment and replication; molecular docking simulation

The viral respiratory disease, severe acute respiratory syndrome (SARS), has turned into a global health concern. Till now, there is no drug or vaccine has yet been specifically approved for SARS-CoV-2. One of the urgent solutions against the recent COVID-19 disease is the use of dietary molecules, which can be found abundantly in functional food. In the current study, we have conducted a molecular docking approach for eighteen dietary molecules belong to the subclass of anthocyanins, as potential inhibitors of the main protease and spike glycoprotein of SARS-CoV-2. Both selected targets, playing a vital role in attachment and replication of the virus. The results indicated that cyanidin-3-arabinoside exhibited the lowest binding energy and located onto the pocket through a sufficient number of hydrogen bonds with the main protease virus. However, pelargonidin-3-glucoside and pelargonidin 3-rhamnoside display significant binding energy with the spike glycoprotein of SARS-CoV-2. All compounds mentioned above shown high drug-likeness and fulfils the Lipinski’s rule of five, as well as confer favorable toxicity parameters, in addition to ADME values. Considering the obtained results, regular consumption of berry fruits, which are rich in anthocyanin compounds, should be supportive to inhibit viral infectious by reducing of propagation and pathogenicity of SARS-CoV–2.     

A theoretical investigation on the properties of the new poly(N‐vinylcarbazole)‐3‐methylthiophene (PVK‐3MeT) synthesized graft copolymer

In this article, we present quantum chemical calculations, based on density functional theory (DFT), performed to investigate the geometries and the opto‐electronic properties of a new synthesized graft copolymer based on poly(N‐vinylcarbazole) (PVK) and poly(3‐methylthiophene) (PMeT) named PVK‐3MeT. First, we have theoretically computed and compared the structural, optical, and vibrational parameters of both neutral and doped states. In addition, the excited state was theoretically obtained by the ab initio RCIS/STO‐3G method. To assign the absorption and emission peaks observed experimentally, we computed the energies of the lowest singlet excited state with the time‐dependent density functional theory (TD‐DFT) method. Electronic parameters such as the HOMO‐LUMO band gap, the ionization potential (IP), and electron affinity (EA) are extracted. Calculations show that the PVK‐3MeT copolymer is nonplanar in its ground neutral state. Meanwhile, upon doping or photoexcitation, an enhancement of the planarity is observed, resulting on a decrease of the inter‐ring torsion angle between 3‐methylthiophene units. Such modifications in the geometric parameters induce a dramatic change on the HOMO and LUMO orbitals in the doped or excited states. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Self-reset logic for fast arithmetic applications

A new family of self-reset logic (SRL) cells is presented in this paper. The single-ended basic structure proposed realizes an incomplete logic family, since it is incapable of inverting logic. Thus, a dual-rail SRL (DRSRL) implementation is also proposed. These cells maintain small delay variations for all input combinations, once minimum timing requirements on inputs are satisfied, and produce output pulses of fairly constant width for varying fanout, leaving enough headroom in the design to accommodate process, supply voltage, and temperature variations. These properties simplify the implementation of data-path and control circuits where the logic depth does not affect the stage output pulse width, eliminating the need for pulse-width controlling circuits required in previous works on SRL. In SRL, power is consumed only if new data are pumped through the logic. The clock grid is limited to the registers that launch and receive the signal path. The clocking overhead is thus reduced, compared with other dynamic designs, and it is especially suitable for wave pipelining. Case study examples and simulated characterization data are included to show the design methodology.     

High voltage characterization of tin oxide varistors

High current characterization of SnO₂-based varistors have been carried out and the results obtained have been compared with those ZnO-based commercial surge arresters. It is shown that for a high temperature sintering (1350 °C), the leakage current, breakdown voltage and the saturation at high current density are similar between both types of surge arresters. The paper shows, for the first time, that the high breakdown voltage observed with tin dioxide cannot be easily maintained since the saturation of the ceramics is reached for current densities of several amperes per square centimetre.     

Prediction of concrete initial setting time in field conditions through multivariate regression analysis

Construction of large concrete structures usually requires pouring multiple batches of concrete mixes along 1 day, which creates setting irregularities that increase the potential of crack development within pours. For the case of bridge decks, it is recommended that the initial concrete material should stay plastic over the entire casting operation of a poured bridge segment. Uniform setting of multiple batches is possible if setting times could be predicted and controlled in field conditions. In this study, more than 70 different Class K concrete mixes were manufactured and cast in field conditions, which provided material characteristics along with environmental data that were used to predict concrete initial setting times through multivariate regression analysis. Two prediction models were achieved, corresponding to the addition of set retarding and set accelerating admixtures, respectively. Validating field tests demonstrated that good predictions of concrete initial setting times can be accomplished with 2% error, when accurate field weather forecasts are available. This work also demonstrates the use of the prediction relations, with the objective of achieving uniform thermo-mechanical properties of a pouring sequence in the field.