Prediction of influence of stepwise increment of initial acetic acid concentration in charging medium on acetification rate of semi-continuous process by artificial neural network

Based on industrial vinegar production, ethanol concentration in charging medium is normally considered as a strong variable influencing the acetification for a given initial acetic acid concentration. Moreover, high initial acetic acid concentration is considered when higher than 100 g L⁻¹ of acetic acid as finished product is obtained. This study assessed the effect of a stepwise increment of initial acetic acid concentration in fermentation medium of 45, 55, and 65 g L⁻¹ after charging at constant ethanol concentration of 35 g L⁻¹ on acetification rate (ETA) by high acid-tolerant strain of Acetobacter aceti WK. Average ETA was 8.144 + 0.09 g L⁻¹ d⁻¹ at 45 g L⁻¹ and 8.655 + 0.09 g L⁻¹ d⁻¹ at 55 g L⁻¹, and significant decreased to 6.819 + 0.23 g L⁻¹ d⁻¹ at 65 g L⁻¹. An artificial neural network (ANN) model was applied to predict the ETA in semi-continuous acetification under the conditions of the study. The optimized ANN structure was revealed to contain two hidden layers and seven neurons per layer. The experimental acetification correlated to the predicted data with R² of training and testing data set of 0.858 and validation data set of 0.831, respectively. Results indicated that the inputs as acetic acid and ethanol concentrations successfully predicted the ETA of semi-continuous acetification process.     

Optimized tuning of power oscillation damping controllers using probabilistic approach to enhance small-signal stability considering stochastic time delay

Electrical Engineering - Communication latency which inherently occurs in wide area measurement system greatly degrades small-signal stability (SSS) and is stochastic in nature, and thus, the...     

Empirical Circuit Breaker Failure Rate Assessment and Modeling in a Preventive Maintenance Application

This article presents an analysis of the failure rates of SF6 puffer circuit breakers in the 230-kV voltage class. Historical failure recorded data for existing power circuit breakers in high-voltage substations in Thailand from 1992 to 2011 were retrieved. Subsequently, the data were analyzed and classified based on the causes of failure related to circuit breaker sub-components. The failure rates of the individual circuit breaker sub-components were determined. These failure rates were then categorized into three main circuit breaker component categories based on their functionality, which includes the live part and insulation, operating mechanism, and control part. The failure rates of the individual circuit breaker sub-components were calculated, and their associated probability distributions were estimated using Weibull distribution functions. The resulting Weibull distribution parameters were subsequently utilized in a circuit breaker preventive maintenance application to aid in the decision-making process for setting the maintenance schedule of the circuit breaker components. Finally, circuit breaker reliability is also monitored. This proposed method can also be applied to other high-voltage equipment in power systems.     

Preparation and characterization of high MFR polypropylene and polypropylene/poly(ethylene‐co‐propylene) in‐reactor alloys

In this work, high melt flow rate (MFR) polypropylene (HF‐PP) and polypropylene/poly(ethylene‐co‐propylene) in‐reactor alloys (HF‐PP/EPR) with MFR ≈ 30 g/10 min were synthesized by spherical MgCl₂‐supported Ziegler–Natta catalyst with cyclohexylmethyldimethoxysilane (CHMDMS) or dicyclopentyldimethoxysilane (DCPDMS) as external donor (De). The effects of De on polymerization activity, chain structure, mechanical properties, and phase morphology of HF‐PP and HF‐PP/EPR were studied. Adding CHMDMS caused more sensitive change of the polymers MFR with H₂ than DCPDMS, and produced PP/EPR alloys containing more random ethylene‐propylene copolymer (r‐EP) and segmented ethylene‐propylene copolymer (s‐EP). CHMDMS also caused formation of s‐EP with higher level of blockiness than DCPDMS. HF‐PP/EPR alloy prepared in the presence of DCPDMS exhibited higher flexural properties but lower impact strength than that prepared with CHMDMS. Toughening efficiency of the rubber phase was nearly the same in the alloys prepared using CHMDMS or DCPDMS as De, but stiffness of the alloy can be improved by using DCPDMS. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42984.     

Xanthan Production by Mutant Strain of Xanthomonas campestris TISTR 840 in Raw Cassava Starch Medium

Raw cassava starch was used as carbon source in growing Xanthomonas campestris TISTR 840 for xanthan production due to its cheap price and mass production in Thailand. However, xanthan production with raw cassava starch yielded low content (4.31 g/l). A low level of amylase was detected in the XOL medium of X. campestris when raw cassava starch was used. Treatment of X. campestris TISTR 840 with ethyl methansulfonate resulted in the isolation of Xc-M, a strain that showed highest amylase overproduction. When cultured in bioreactor with a medium containing raw cassava starch, the growth of Xc-M cells was significantly higher than that of the wild type. The mutant produced 3.46- and 1.39-fold increased amylase activity and xanthan yield, respectively. Xc-M is useful for xanthan production in media containing raw starch as a carbon source.     

Life cycle analysis of retrofitting with high energy efficiency air-conditioner and fluorescent lamp in existing buildings

Life cycle analysis of mercury in discarded low energy efficiency fluorescent lamps (36 W) and of HCFC in air-conditioners (12,000 Btu) removed from service has been conducted in this study. The objective was to find out the environmental impact (EDIP 1997 category, waste evaluation) of the products that appear in the waste stream as a result of facility upgrades. The scope of the study starts from retrofitting of the lamps and air-conditioners through recycling and disposal. For a 36 W fluorescent lamp, the bulk waste 1.64E−5 kg, hazardous waste 1.11E−4 kg, radioactive waste 1.09E−9 kg, and slag–ash 6.02E−7 kg occurred at the end of life of the retrofitting cycle. For a 12,000 Btu air-conditioner, the bulk waste 0.58 kg, hazardous waste 0.11 kg, radioactive waste 0.0002 kg, and slag–ash 0.01 kg also occurred at the end of life of the retrofitting cycle. These small amounts become important when viewed at the country level. These quantities imply that the policy makers who deal with hazardous waste should be aware of this waste-generating characteristic before issuing any pertinent policy. Consideration of this characteristic and planning for appropriate waste management methods at the beginning stage will reduce any future problem of contamination by the hazardous waste.     

Modeling Nitrogen Transport in Duckweed Pond for Secondary Treatment of Swine Wastewater

A mathematical model was developed to describe nitrogen transport in duckweed-covered static ponds for nutrient recovery from swine lagoon water. A finite difference technique was used to solve the partial differential equations describing the ammonia transport and concentration in the pond. The key parameters in the model include the diffusion coefficient of ammonium in the medium (D) and kinetic constant of nitrogen uptake by duckweed (k). Using one order of magnitude parameter variations, the simulations showed that the model was clearly much more sensitive to D than to k, indicating the process of nitrogen removal in a static pond by duckweed is diffusion limited. Laboratory testing was conducted with Spirodela punctata 7776, a duckweed strain, to calibrate the model. The calibration of the model with experimental data yielded a new ammonium transport coefficient (T) that is 85 times of D value. Model results showed good agreement with depth-wise experimental ammonium concentration and the model also demonstrates that intermittent mixing every 3 h can enhance ammonium uptake. Additionally, an apparent drop in pH near the duckweed mat at the surface was observed that may explain low rates of ammonia emission from duckweed ponds.