Relationship between solid retention time and phosphorus removal in anaerobic-intermittent aeration process

Solid retention time (SRT) is one of the most important control parameters in biological phosphorus removal. In this study, lab-scale biological nutrient removal (BNR) reactors using anaerobic-intermittent aeration (AIA) were operated at various SRTs (i.e., 15, 20, and 30 d) to evaluate their phosphorus removal efficiencies. Sludge wasting load decreased as SRT increased; however, the phosphorus content in the biomass increased as SRT increased. The highest phosphorus removal efficiency was 93% at an SRT of 20 d and the phosphorus wasting load was also highest at that SRT, which indicates that the optimal SRT for the highest phosphorus removal is not proportional to the phosphorus content in the biomass. Aerobic digestion experiments were also carried out to determine the number of phosphate-accumulating organisms (PAOs) in the biomass produced in different reactors. All three activated sludges from BNR at SRTs of 15, 20, and 30 d showed a slower volatile suspended solid (VSS) destruction rate and a larger amount of phosphorus released than the conventional activated sludge (CAS), suggesting that the activated sludge from BNR has more PAOs than CAS. Also, the sludge at an SRT of 30 d showed a slower VSS destruction rate and a larger amount of phosphorus released than the sludge at an SRT of 15 d, suggesting that PAOs are more predominant at longer SRTs. Thus, to improve phosphorus removal efficiency, it is recommended that SRT be increased to maximize the number of PAOs in the system and that SRT be determined to maximize phosphorus wasting load.     

Cationic Conjugated Polyelectrolytes with Molecular Spacers for Efficient Fluorescence Energy Transfer to Dye‐Labeled DNA

Two water‐soluble conjugated polyelectrolytes, poly(9,9′‐bis(6‐N,N,N‐trimethylammoniumhexyl)fluorene‐alt‐1,4‐(2,5‐bis(6‐N,N,N‐trimethylammoniumhexyloxy))phenylene) tetrabromide ( P1i ) and poly((10,10′‐bis(6‐N,N,N‐trimethylammoniumhexyl)‐10H‐spiro(anthracene‐9,9′‐fluorene))‐alt‐1,4‐(2,5‐bis(6‐N,N,N‐trimethylammoniumhexyloxy))phenylene) tetrabromide ( P2i ) are synthesized, characterized, and used in fluorescence resonance energy transfer (FRET) experiments with fluorescein‐labeled single‐stranded DNA (ssDNA‐Fl). P1i and P2i have nearly identical π‐conjugated backbones, as determined by cyclic voltammetry and UV‐vis spectroscopy. The main structural difference is the presence of an anthracenyl substituent, orthogonal to the main chain in each of the P2i repeat units, which increases the average interchain separation in aggregated phases. It is possible to observe emission from ssDNA‐Fl via FRET upon excitation of P2i . Fluorescein is not emissive within the ssDNA‐Fl/ P1i electrostatic complex, suggesting Fl emission quenching through photoinduced charge transfer (PCT). We propose that the presence of the anthracenyl “molecular bumper” in P2i increases the distance between optical partners, which decreases PCT more acutely relative to FRET.     

An approach to multi-agent interactive control in an intelligent space

International Journal of Control, Automation and Systems - A new type of multi-agent interactive control is proposed in an intelligent space system, which is based on heterogeneous multiple vision...     

Solution Processable Monosubstituted Hexa‐Peri‐Hexabenzocoronene Self‐Assembling Dyes

Molecular organization behavior and visible light absorption ability are important factors for organic materials to be used in efficient bulk heterojunction solar cells applications. In this context, a series of monosubstituted fluorenyl hexa‐peri‐hexabenzocoronene (FHBC) are synthesized with the aim to combine the self‐association property of the FHBC unit with broadened light absorption of a small molecule organic dye, bisthienylbenzothiadiazole (TBT). Optical and electrochemical properties of the FHBC compounds vary according to their structures. Introduction of a TBT unit into the FHBC system broadens the absorption. All of the FHBC compounds show strong π–π intermolecular association in solution. X‐ray scattering measurements on thermally extruded filaments and thin films showed ordered alignment of these compounds in the solid state. In atomic force microscopy experiments, nanoscale phase separation is observed in thin films of FHBC and fullerene derivative blends. Solar cell devices with these compounds as donors are fabricated. FHBC compounds with the TBT unit show higher short circuit current while the high open circuit voltages are maintained. With C₆₀ derivative as acceptor, power conversion efficiency of 1.12% is achieved in the unoptimized solar cell devices under simulated solar irradiation. The efficiency was further improved to 1.64% when C₇₀ derivative was used as the acceptor.     

Humidity‐Tolerant Roll‐to‐Roll Fabrication of Perovskite Solar Cells via Polymer‐Additive‐Assisted Hot Slot Die Deposition

Heating‐assisted deposition is an industry‐friendly scalable deposition method. This manufacturing method is employed together with slot die coating to fabricate perovskite solar cells via a roll‐to‐roll process. The feasibility of the method is demonstrated after initial testing on a rigid substrate using a benchtop slot die coater in air. The fabricated solar cells exhibit power conversion efficiencies (PCEs) up to 14.7%. A nonelectroactive polymer additive is used with the perovskite formulation and found to improve its humidity tolerance significantly. These deposition parameters are also used in the roll‐to‐roll setup. The perovskite layer and other solution‐processed layers are slot die‐coated, and the fabricated device shows PCEs up to 11.7%, which is the highest efficiency obtained from a fully roll‐to‐roll processed perovskite solar cell to date.     

Three‐Dimensional Bulk Heterojunction Morphology for Achieving High Internal Quantum Efficiency in Polymer Solar Cells

Here, an investigation of three‐dimensional (3D) morphologies for bulk heterojunction (BHJ) films based on regioregular poly(3‐hexylthiophene) (P3HT) and [6,6]‐phenyl‐C₆₁‐butyric acid methyl ester (PCBM) is reported. Based on the results, it is demonstrated that optimized post‐treatment, such as solvent annealing, forces the PCBM molecules to migrate or diffuse toward the top surface of the BHJ composite films, which induces a new vertical component distribution favorable for enhancing the internal quantum efficiency (η_IQE ) of the devices. To investigate the 3D BHJ morphology, novel time‐of‐flight secondary‐ion mass spectroscopy studies are employed along with conventional methods, such as UV‐vis absorption, X‐ray diffraction, and high‐resolution transmission electron microscopy studies. The η_IQE of the devices are also compared after solvent annealing for different times, which clearly shows the effect of the vertical component distribution on the performance of BHJ polymer solar cells. In addition, the fabrication of high‐performance P3HT:PCBM solar cells using the optimized solvent‐annealing method is reported, and these cells show a mean power‐conversion efficiency of 4.12% under AM 1.5G illumination conditions at an intensity of 100 mW cm^?2.     

Silver nanocrystal-modified silicon nanowires as substrates for surface-enhanced Raman and hyper-Raman scattering

Metal catalyzed, CVD-grown silicon nanowires decorated by chemical assembly of closely spaced Ag nanocrystals were modified with the well-known "silver mirror" reaction and investigated as substrates for surface-enhanced Raman (SERS) and hyper-Raman (SEHRS) spectroscopy. Four chromophores were examined: Rhodamine 6G, crystal violet, a cyanine dye, and a cationic donor-acceptor substituted stilbene. After soaking the substrates overnight in 10(-4) M aqueous chromophore solutions, all four chromophores gave good-quality SERS spectra in < or =60 s using <1 microW of 458-nm cw laser power, and SEHRS spectra are obtained in < or =120 s using <1 mW of mode-locked 916-nm laser power. Results from this substrate are compared with those on colloidal silver nanoparticles deposited as a film, as well as surfaces grown by the silver mirror reaction.     

Surface Oxidation of the High-Strength Steels Electrodeposited with Cu or Fe and the Resultant Defect Formation in Their Coating during the Following Galvanizing and Galvannealing Processes

This study examined the surface oxidation of high-strength steels electrodeposited with Cu or Fe and the resultant defect formation in their coating during the following galvanizing and galvannealing processes. The high-strength steels were coated with an Cu or Fe layer by the electroplating method. Then, the coated steels were annealed in a reducing atmosphere, dipped in a molten zinc, and finally transformed into galvannealed steels through the galvannealing process. The formation of Si and Mn oxides on the surface of the high-strength steel was effectively suppressed, and the density of surface defects on the galvanized steel was significantly reduced by the pre-electrodeposition of Cu and Fe. This effect was more prominent for the steels electrodeposited at higher cathodic current densities. The finer electrodeposit layer formed at higher cathodic current density on the steels enabled the suppression of partial surface oxidation by Mn or Si and better wetting of Zn on the surface of the steels in the following galvanizing process. Furthermore, the pre-electrodeposited steels exhibited a smoother surface without surface cracks after the galvannealing process compared with the untreated steel. The diffusion of Fe and Zn in the Zn coating layer in the pre-electrodeposited steels appears to occur more uniformly during the galvannealing process due to the low density of surface defects induced by oxides.