Statistical design of np-charts with multiple control regions

Models were developed for the design of np-charts with three and four control regions, respectively. Procedures for obtaining solutions to the models were also developed. Numerical examples are given to illustrate the model and to study the properties of the charts. The results of the numerical examples show that changes in the specified values of most of the risks and powers associated with the chart--particularly those classified as 'critical risks'--affect the values of the design parameters of the charts. The OC and power curves drawn for some of the numerical examples show that the discriminatory power of an np-chart with multiple control regions depends on the values of the design parameters and the number of control regions--the more the number of its control regions, the less the discriminatory power of the chart, and vice versa.     

Dark fermentative biohydrogen production by Acinetobacter junii-AH4 utilizing various industry wastewaters

Hydrogen (H₂) is one of the most promising renewable energy sources, anaerobic bacterial H₂ fermentation is considered as one of the most environmentally sustainable alternatives to meet the potential fossil fuel demand. Bio-H₂ is the cleanest and most effective source of energy provided by the dark fermentation utilizing organic substrates and different wastewaters. In this study, the bio-H₂ production was achieved by using the bacteria Acinetobacter junii-AH4. Further, optimization was carried out at different pH (5.0–8.0) in the presence of wastewaters as substrates (Rice mill wastewater (RMWW), Food wastewater (FWW) and Sugar wastewater (SWW). In this way, the optimized experiments excelled with the maximum cumulative H₂ production of 566.44 ± 3.5 mL/L (100% FWW at pH 7.5) in the presence of Acinetobacter junii-AH4. To achieve this, a bioreactor (3 L) was employed for the effective production of H₂ and Acinetobacter junii-AH4 has shown the highest cumulative H₂ of 613.2 ± 3.0 mL/L, HPR of 8.5 ± 0.4 mL/L/h, HY of 1.8 ± 0.09 mol H₂/mol glucose. Altogether, the present study showed a COD removal efficiency of 79.9 ± 3.5% by utilizing 100% food wastewater at pH 7.5. The modeled data established a batch fermentation system for sustainable H₂ production. This study has aided to achieve an ecofriendly approach using specific wastewaters for the production of bio-H₂.     

Optimizing acido-basic profile of support in Ni supported La2O3+Al2O3 catalyst for dry reforming of methane

The increasing alarm of global warming always draws interest in reactions like dry reforming of methane (DRM) where both global warming gases (CO₂ and CH₄) are converted into value-added chemical building blocks, such as syngas. Nickel catalyst active sites along with support acid-base profiles play a key role in DRM. Herein, xLa₂O₃+(100-x) Al₂O₃ (x = 0, 10, 15, 20%) supports are prepared and followed by NiO dispersion over the produced support by impregnation method. It was tested for DRM reaction and characterized with TGA, XRD, TEM, IR, Surface area and porosity measurement, H₂-TPR, CO₂-TPD and NH₃-TPD techniques. Upon increasing the basic lanthana proportion in the acidic alumina support, the crystallinity of alumina and acidity of total support decline. Up to 15% Lanthana addition in support claims a low acid and rich basic surface including super basic sites (related to unidentate carbonates) which governed optimum catalytic performance 64% CH₄ conversion, 79% CO₂ conversion and H₂/CO ~ 1 up to 460-min in time on stream test. 20% lanthanum oxide loading led to inferior performance due to rapid loss of surface area, pore-volume, pore diameter, acidity and medium basic strength sites. Fine-tuning of acid-base lanthana-alumina support with dispersed Ni species are a means for understanding DRM.     

Iron catalyst for decomposition of methane: Influence of Al/Si ratio support

20% iron catalysts supported on combined alumina and silica through different proportions (Al₂O₃:SiO₂: 100:0.00, 90.0:10.0, 80.0:20.0 and 0.0:100.0) were tested for the catalytic decomposition of methane to produce H₂ and carbon. The catalysts were prepared via impregnation technique. The physicochemical properties of the catalysts were characterized with TGA, XRD, H2-TPR, and TEM techniques. The results specified no reaction for all temperatures when the catalysts were supported with bare silica. Indeed, the 20%Fe/(Si-80)-800 catalyst with 20% silica support operated at 800?°C produced CH₄ conversion profile that rapidly descended from 64% to 5% due to the high content of silica. Plain alumina supported catalyst demonstrated the best conversion and stability operated at 800?°C. The CH₄ conversion started from 83.4% and lasts at 82.2% after 300?min on stream.     

Weaning foods and their impact on child-feeding practices among low-income Nigerian mothers

BACKGROUND: Many children in rural communities of developing countries die of nutrition-related causes due to lack of nutrition education and low purchasing power of the families, which result in low-quality weaning foods and poor feeding practices. OBJECTIVE: To evaluate the nutritional composition of local weaning foods and their impact on child feeding practices among low-income Nigerian mothers. METHODS: A cross-sectional survey was conducted between March and June 2005 among 294 randomly selected pairs of nursing mothers and their children who attended the postnatal clinic of State Specialist Hospital and Comprehensive Health Centers in Akure community, Ondo State, Nigeria. A structured, self-or interviewer-administered questionnaire was used to collect information on infant demographic characteristics, feeding, and socioeconomic characteristics of the parents. The children's weights were recorded, and samples of the weaning foods were analyzed. RESULTS: The mothers' ages ranged from 22 to 37 years, and the children's from one to 12 months. Among the parents, two-fifths of the respondents worked as drivers, mechanics, carpenters, and the like, while the remaining respondents were civil servants, health professionals, teachers, merchants, and housewives. The educational attainment of the parents ranged from no formal education (1.4%) to higher education (46%); 13% had completed primary school, and 39.6% had completed secondary school. The average monthly family income was between 3,500 and 30,000 naira (US dollar 23.3-dollar 200). Among the children, 58.3% were of normal weight, 41.1% were mildly underweight, 0.3% moderately underweight, and 0.3% severely underweight; 23.1% were exclusively breastfed, 9.5% received breastmilk and traditional medicinal herbs, 15.6% received breastmilk and commercial weaning food, 7.4% received commercial weaning food only, 14.8% received local weaning foods only, 24.1% received local weaning foods plus breastmilk, and 5.8% received the family diet. CONCLUSIONS: We found that a high proportion of the nursing mothers used local ingredients to formulate weaning foods for their babies. The nutritional compositions of these foods is of high quality and are suitable as weaning foods, particularly for infants of low-income parents who do not have access to commercial weaning foods.     

A power function model for determining sample sizes for the operations of multivariate control charts

Using the hypothesis-testing approach, we develop a model for determining sample sizes for the operation of multivariate control charts. A simple solution procedure that can be processed on any personal or small computer is also developed. The effect of correlation between pairs of variables on the performance of the model is studied. The performances of multivariate and univariate control charts are compared under the model. Before the development of the model, a brief review of multivariate test of hypothesis and multivariate control charts was done. The model is recommended for any quality control engineer who may like to specify a desired level of protection against inferior quality.     

The choice of a log-linear model using a Cp-type statistic

Most methods of selecting an appropriate log-linear model for categorical data are sensitive to the underlying distributional assumptions. However, there are many situations in which the assumption that the data are randomly chosen from an underlying Poisson, multinomial or product-multinomial distribution cannot be sustained. In these cases we propose a criterion to select among log-linear models that is an analogue of the C_p statistic for regression models and describe a method to estimate the denominator of this statistic.