Evaluation of parameter uncertainties in nonlinear regression using Microsoft Excel Spreadsheet

Hu, Wei; Xie, Jing; Chau, Henry Wai; Cheng, Bing

doi:10.1186/s40068-015-0031-4

Cited by 67 publications

(53 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…5 are plotted as error bars showing the standard deviation calculated from Monte Carlo simulation. 19 The agreement between the results in Fig. 3 from the electrochemical method (Eq.…”

Section: Resultssupporting

confidence: 60%

Determination of the Stoichiometry of Ethanol Oxidation from the Flow Rate Dependence of the Current in a Proton Exchange Membrane Electrolysis Cell

Altarawneh

Pickup

2018

J. Electrochem. Soc.

View full text Add to dashboard Cite

Measurement of the stoichiometry of ethanol oxidation is crucial in the development of direct ethanol fuel cell technology because it determines how efficiently the fuel is used. Here, it has been determined in fuel cell hardware at 80 • C for various anodes prepared with commercial Pt/C, PtRu/C and PtSn/C catalysts. Average numbers of electrons transferred per ethanol molecule (n av ) obtained from the flow rate dependence of the current (electrochemical method) are critically compared with values obtained from the amount of ethanol consumed and yields of acetaldehyde, acetic acid, and carbon dioxide (chemical analysis). In general, the electrochemical method provides accurate values of n av . Crossover of ethanol to the cathode causes a small (<10%) underestimation of n av , but this is generally less than the uncertainly of the measurement. However, when yields of carbon dioxide are high (>50%), the dependence of n av on the ethanol concentration can lead to its overestimation, and to impossibly high values. This can be diagnosed by comparing results obtained over different flow rate ranges, and the accuracy can be improved by use of a narrow range of flow rates. The electrochemical method can be routinely applied during measurement of a polarization curve, without any addition equipment, and is well suited for rapid assessment of the effects of operating conditions and changes over time. Ethanol is an attractive fuel for direct liquid fuel cells.1,2 However, the high theoretical efficiency of 98% for a direct ethanol fuel cell (DEFC) is based on complete oxidation of ethanol to CO 2 (Eq. 1), which generates 12 electrons (n = 12), while the main products from a DEFC are acetic acid (Eq. 2; n = 4) and acetaldehyde (Eq. 3; n = 2). Since the overall efficiency of a DEFC is proportional to the number of electrons transferred, 3 measurement of the stoichiometry of ethanol oxidation (average number of electrons transferred per molecule, n av ) plays a crucial role in the development of more efficient anode catalysts for DEFCs. 3,6 Simple and fast methods are required for routine evaluation of the efficiency of catalysts over a wide range of conditions.The faradaic efficiency (ε F ) of a DEFC is determined by the ratio of n av to the maximum of n = 12 for the complete oxidation of ethanol to carbon dioxide (ε F = n av /12), while n av is determined by the product distribution according to Eq. 4,where n i is the number of electrons transferred to form product i and f i is the fraction of ethanol converted to product i (CO 2 , acetic acid and acetaldehyde account for >99% of the ethanol consumed 8 ). Various experimental methods are available for measuring n av , including analysis of the amount of ethanol consumed, 9,10 the product distribution, 7,10 and several electrochemical methods. 11,12Determination of n av from the dependence of the current on the flow rate of the ethanol solution, in proton exchange membrane fuel cell (PEMFC) hardware, is particularly convenient. 11,13 In this method, the concentration of the...

show abstract

“…5 are plotted as error bars showing the standard deviation calculated from Monte Carlo simulation. 19 The agreement between the results in Fig. 3 from the electrochemical method (Eq.…”

Section: Resultssupporting

confidence: 60%

Determination of the Stoichiometry of Ethanol Oxidation from the Flow Rate Dependence of the Current in a Proton Exchange Membrane Electrolysis Cell

Altarawneh

Pickup

2018

J. Electrochem. Soc.

View full text Add to dashboard Cite

show abstract

“…To account for the depth-dependent transmission through SPT VI, the sum of the squares of the SPT I/II linear regression residuals was minimized by nonlinear regression analysis by using the Solver capability in Excel. The 95% confidence interval (CI) on the DNA-PF was determined by using a Monte Carlo technique (32). Figure 1 demonstrates an epidermal gradient for T,.T in SPT VI with less T,.T staining in the basal epidermis compared with a more even epidermal distribution in SPT I/II.…”

Section: Statistical Analysis and Determination Of Dna-pf For Melaninmentioning

confidence: 99%

Melanin distribution in human epidermis affords localized protection against DNA photodamage and concurs with skin cancer incidence difference in extreme phototypes

et al. 2018

View full text Add to dashboard Cite

Epidermal DNA damage, especially to the basal layer, is an established cause of keratinocyte cancers (KCs). Large differences in KC incidence (20- to 60-fold) between white and black populations are largely attributable to epidermal melanin photoprotection in the latter. The cyclobutane pyrimidine dimer (CPD) is the most mutagenic DNA photolesion; however, most studies suggest that melanin photoprotection against CPD is modest and cannot explain the considerable skin color-based differences in KC incidence. Along with melanin quantity, solar-simulated radiation-induced CPD assessed immediately postexposure in the overall epidermis and within 3 epidermal zones was compared in black West Africans and fair Europeans. Melanin in black skin protected against CPD by 8.0-fold in the overall epidermis and by 59.0-, 16.5-, and 5.0-fold in the basal, middle, and upper epidermis, respectively. Protection was related to the distribution of melanin, which was most concentrated in the basal layer of black skin. These results may explain, at least in part, the considerable skin color differences in KC incidence. These data suggest that a DNA protection factor of at least 60 is necessary in sunscreens to reduce white skin KC incidence to a level that is comparable with that of black skin.-Fajuyigbe, D., Lwin, S. M., Diffey, B. L., Baker, R., Tobin, D. J., Sarkany, R. P. E., Young, A. R. Melanin distribution in human epidermis affords localized protection against DNA photodamage and concurs with skin cancer incidence difference in extreme phototypes.

show abstract

“…The internal diameter is thought to be linked to the metal particle size [42] (the reduction of Co3O4 particles with a size of 14 nm is expected to yield in the absence of sintering metal particles with a size of 10−11 nm). The enhanced activity for CO dissociation as indicated by the shift in the on-set of the Boudouard reaction to lower temperatures upon increasing the aluminum content in the samples and as argued to be the origin of the change in the kinetic coefficients and the change in the selectivity has been linked to the Lewis acid property of the promoter [25,42,43]. Carbon monoxide may act as a weak Lewis base, which can donate electrons from the 4σ molecular orbital to a Lewis acid [15].…”

Section: Resultsmentioning

confidence: 99%

Cobalt-Based Fischer–Tropsch Synthesis: A Kinetic Evaluation of Metal–Support Interactions Using an Inverse Model System

et al. 2019

View full text Add to dashboard Cite

Metal–support interactions in the cobalt–alumina system are evaluated using an inverse model system generated by impregnating Co3O4 with a solution of aluminum sec-butoxide in n-hexane. This results in the formation of nano-sized alumina islands on the surface of cobalt oxide. The activated model systems were kinetically evaluated for their activity and selectivity in the Fischer–Tropsch synthesis under industrially relevant conditions (220 °C, 20 bar). The kinetic measurements were complemented by H2-chemisorption, CO-TPR, and pyridine TPD. It is shown that the introduction of aluminum in the model system results in the formation of strong acid sites and enhanced CO dissociation, as evidenced in the CO-TPR. The incorporation of aluminum in the model systems led to a strong increase in the activity factor per surface atom of cobalt in the rate expression proposed by Botes et al. (2009). However, the addition of aluminum also resulted in a strong increase in the kinetic inhibition factor. This is accompanied by a strong decrease in the methane selectivity, and an increase in the desired C5+ selectivity. The observed activity and selectivity changes are attributed to the increase in the coverage of the surface with carbon with increasing aluminum content, due to the facilitation of CO dissociation in the presence of Lewis acid sites associated with the alumina islands on the catalytically active material.

show abstract

Evaluation of parameter uncertainties in nonlinear regression using Microsoft Excel Spreadsheet

Cited by 67 publications

References 17 publications

Determination of the Stoichiometry of Ethanol Oxidation from the Flow Rate Dependence of the Current in a Proton Exchange Membrane Electrolysis Cell

Determination of the Stoichiometry of Ethanol Oxidation from the Flow Rate Dependence of the Current in a Proton Exchange Membrane Electrolysis Cell

Melanin distribution in human epidermis affords localized protection against DNA photodamage and concurs with skin cancer incidence difference in extreme phototypes

Cobalt-Based Fischer–Tropsch Synthesis: A Kinetic Evaluation of Metal–Support Interactions Using an Inverse Model System

Contact Info

Product

Resources

About