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Internal Resistance (internal + resistance)
Selected AbstractsEfficiency Enhancement in Organic Photovoltaic Cells: Consequences of Optimizing Series ResistanceADVANCED FUNCTIONAL MATERIALS, Issue 1 2010Jonathan D. Servaites Abstract Here, means to enhance power conversion efficiency (PCE or ,) in bulk-heterojunction (BHJ) organic photovoltaic (OPV) cells by optimizing the series resistance (Rs),also known as the cell internal resistance,are studied. It is shown that current state-of-the-art BHJ OPVs are approaching the limit for which efficiency can be improved via Rs reduction alone. This evaluation addresses OPVs based on a poly(3-hexylthiophene):6,6-phenyl C61 -butyric acid methyl ester (P3HT:PCBM) active layer, as well as future high-efficiency OPVs (,,>,10%). A diode-based modeling approach is used to assess changes in Rs. Given that typical published P3HT:PCBM test cells have relatively small areas (,0.1,cm2), the analysis is extended to consider efficiency losses for larger area cells and shows that the transparent anode conductivity is then the dominant materials parameter affecting Rs efficiency losses. A model is developed that uses cell sizes and anode conductivities to predict current,voltage response as a function of resistive losses. The results show that the losses due to Rs remain minimal until relatively large cell areas (>0.1,cm2) are employed. Finally, Rs effects on a projected high-efficiency OPV scenario are assessed, based on the goal of cell efficiencies >10%. Here, Rs optimization effects remain modest; however, there are now more pronounced losses due to cell size, and it is shown how these losses can be mitigated by using higher conductivity anodes. [source] Poly(3,4-ethylenedioxythiophene) (PEDOT)-Coated MWCNTs Tethered to Conducting Substrates: Facile Electrochemistry and Enhanced Coloring EfficiencyMACROMOLECULAR RAPID COMMUNICATIONS, Issue 24 2008Shweta Bhandari Abstract Composite films of poly(3,4-ethylenedioxythiophene) (PEDOT)-coated over functionalized multiwalled coiled and linear carbon nanotubes (CNTs) have been fabricated by a simple oxidative electropolymerization route. The nanotubular morphology of the polymer,CNT composite is responsible for the lower charge transfer impedance, lower internal resistance, and superior capacitive response in comparison to that shown by the control PEDOT film doped by trifluoromethanesulfonate ions. This facile electrochemistry exhibited by the PEDOT,CNT composite film ensues in a remarkably high coloration efficiency of 367 cm2,·,C,1 at 550 nm, hitherto unrealized for PEDOT; thus demonstrating the huge potential the PEDOT,CNT composite film has as cathode for the entire spectrum of electrochromic devices. [source] Sensitivity of Turbutester and Accuhaler tester in asthmatic children and adolescentsPEDIATRICS INTERNATIONAL, Issue 1 2010Wiparat Manuyakorn Abstract Background:, Dry powder inhalers (DPI) are alternative devices for delivering medication for treatment of asthma. The amount of drug delivery to the lungs is directly influenced by peak inspiratory flow rate (PIFR). A minimum PIFR of ,30 L/min is needed for the Turbuhaler and Accuhaler. Methods:, In order to evaluate the sensitivity of the Turbutester and Accuhaler tester in detecting the minimum and optimum PIFR for the Turbuhaler and Accuhaler in asthmatic children, PIFR was measured using the In-Check Dial through the internal resistance of the Turbuhaler and Accuhaler and compared according to the child's ability to make a whistle sound via both testers. Results:, A total of 259 asthmatic children were studied: 20 pre-school children, aged 5,6 years; 174 school-age children, aged 7,12 years; and 65 adolescents, aged 13,18 years. The sensitivity of the Turbutester and Accuhaler tester to detect optimum PIFR were 98.40% and 97.2%, respectively. In the comparison among age groups, the sensitivity of the Accuhaler tester to detect optimum or minimum PIFR for the Accuhaler was 95%, 97.7% and 95.4%, respectively. The sensitivity of the Turbutester to detect optimum PIFR for the Turbuhaler was 94.4%, 98.8% and 98.5%, respectively. The sensitivity of the Turbutester to detect minimum PIFR for the Turbuhaler was 94.7%, 100% and 100%, respectively. There were no significant differences in percentage of having optimum or minimum PIFR among asthma severity and current device usage in all age groups. Conclusions:, Most children aged at least 5 years could generate enough PIFR to use dry powder inhaler devices. Both the Turbutester and Accuhaler tester were found to have high sensitivity in detecting optimum and minimum required PIFR. [source] Ability of preschool children to use dry powder inhalers as evaluated by In-Check MeterPEDIATRICS INTERNATIONAL, Issue 1 2006YOKO S ADACHI Abstract Background: Although current guidelines recommend the pressurized metered-dose inhaler with a spacer for preschool children with asthma, dry powder inhalers (DPI) may be a valuable treatment alternative. Methods: To evaluate the ability of preschool children to inhale through DPI, peak inspiratory flow rates (PIFR) of 57 healthy children aged 3,6 years were measured with In-Check Meter after practising with an instructor. Two different calibrated resistances were attached to the Meter to mimic the internal resistance of each inhaler; Diskus and Turbuhaler. Results: The ability of children to generate adequate inspiratory flow increased with age. The percentages of the 3-, 4-, 5-, and 6-year-old children who were able to inhale reliably through the devices were 30% (3/10), 79.0% (15/19), 100% (16/16), and 100% (12/12), respectively. In these children, 100%, 93.3%, 100%, and 100% achieved an adequate PIFR for the Diskus (30 L/min). In contrast, 66.7%, 66.7%, 62.5%, and 91.7% generated an adequate PIFR for the Turbuhaler (60 L/min). Conclusions: The In-Check Meter is a useful device to assess the ability of preschool children to generate adequate PIFR for each inhaler. Most children aged ,5 years could use DPI. [source] C4 photosynthesis in a single C3 cell is theoretically inefficient but may ameliorate internal CO2 diffusion limitations of C3 leavesPLANT CELL & ENVIRONMENT, Issue 8 2003S. VON CAEMMERER ABSTRACT Attempts are being made to introduce C4 photosynthetic characteristics into C3 crop plants by genetic manipulation. This research has focused on engineering single-celled C4 -type CO2 concentrating mechanisms into C3 plants such as rice. Herein the pros and cons of such approaches are discussed with a focus on CO2 diffusion, utilizing a mathematical model of single-cell C4 photosynthesis. It is shown that a high bundle sheath resistance to CO2 diffusion is an essential feature of energy-efficient C4 photosynthesis. The large chloroplast surface area appressed to the intercellular airspace in C3 leaves generates low internal resistance to CO2 diffusion, thereby limiting the energy efficiency of a single-cell C4 concentrating mechanism, which relies on concentrating CO2 within chloroplasts of C3 leaves. Nevertheless the model demonstrates that the drop in CO2 partial pressure, pCO2, that exists between intercellular airspace and chloroplasts in C3 leaves at high photosynthetic rates, can be reversed under high irradiance when energy is not limiting. The model shows that this is particularly effective at lower intercellular pCO2. Such a system may therefore be of benefit in water-limited conditions when stomata are closed and low intercellular pCO2 increases photorespiration. [source] Electricity generation from the treatment of wastewater with a hybrid up-flow microbial fuel cellBIOTECHNOLOGY & BIOENGINEERING, Issue 1 2010Krishna P. Katuri Abstract The performance of a prototype up-flow single-chambered microbial fuel cell (MFC) for electrical power generation using brewery wastewater as fuel is reported. The designed reactor consisted of three zones, namely a lower anaerobic digestion zone, a central MFC zone, and an upper effluent clarifier zone. Tests were conducted in batch mode using a beer wastewater as the fuel/electron donor (COD concentration: 430,mg/L) and mixed consortia (both sewage microflora and anaerobic sludge) as a source of electrogenic bacteria. A stable current density of ,2,270,mA/m2 was generated under continuous polarization with a constant external resistance (0.01,k,) and cell polarization gave a peak power density of 330,mW/m2 at a current density of 1,680,mA/m2. Electrochemical impedance analysis showed that the overall internal resistance of the reactor was quite low, that is, 8.0,,. Cyclic voltammetric analysis of the anodic biofilm at low scan rate revealed quite complex processes at the anode, with three redox peaks, at potentials of 116, 214, and 319,mV (vs. NHE). Biotechnol. Bioeng. 2010;107: 52,58. © 2010 Wiley Periodicals, Inc. [source] Mass transport and thermodynamic analysis of PAHs in partitioning systems in the presence and absence of ultrasonicationAICHE JOURNAL, Issue 10 2010Pedro A. Isaza Abstract Transport of PAHs from Desmopan polymers to methanol under various mixing conditions and in the presence of ultrasound was analyzed. PAH transport was influenced by external transport resistances; however, agitation greater than 800 rpm yielded PAH transport completely limited by internal resistances. Delivery rates of phenanthrene, fluoranthene, and pyrene with ultrasonication were faster than that under any mixing condition, suggesting enhanced internal transport properties. Ultrasound also induced increased concentrations of PAHs in solution at equilibrium. The model developed described PAH delivery under sonicated/non-sonicated conditions, while quantifying diffusive and thermodynamic properties. Diffusivities with and without ultrasound decreased with permeant molecular size agreeing with coefficients determined for similar aromatic compounds in polymers. Partitioning coefficients under sonicated and non-sonicated conditions conclusively differed from each other and decreased as a function of PAH molecular size. Quantitative structure-property relationship data of PAHs yielded factors predicting thermodynamic and transport behaviors, with polarizability being the best descriptor. © 2010 American Institute of Chemical Engineers AIChE J, 2010 [source] | |||||||||||||