Methodologies for Assessing Risks of Accidents in Chemical Process Industries

Journal of Failure Analysis and Prevention - Chemical process industries often handle, store and transport chemicals which are flammable and/or toxic. Also, often, processes are employed which are...     

Offline Error Detection in MEDA-Based Digital Microfluidic Biochips Using Oscillation-Based Testing Methodology

Digital microfluidics is an emerging class of lab-on-a-chip system. Reliability is a critical performance parameter as these biochips are employed in various safety-critical biomedical applications. With the introduction of highly scalable, reconfigurable and field programmable Micro-Electrode-Dot-Array (MEDA) architecture, the limitation of conventional DMFBs in varying the droplet size/volume in fine grain manner has been resolved. However, the MEDA-based biochips must be adequately tested upon fabrication to guarantee the correctness of bioassays. In this work, an offline testing approach based on Oscillation-Based Testing (OBT) methodology is presented for MEDA-based digital microfluidic biochips. Various simulations were performed for droplet-electrode short fault model involving single and multiple micro-electrodes. Furthermore, the loss of droplet volume due to the presence of defect was analyzed using COMSOL Multiphysics. The simulation results based on PSpice and COMSOL show that the proposed approach is effective for detecting defects in MEDA-based biochips.     

International facilities location: A heuristic procedure for the dynamic uncapacitated problem

It is now well known that most major companies no longer operate in a single market. To penetrate global markets and obtain their benefits, companies are under tremendous pressure to reduce the price of their products, and thus their production and material costs. When a foreign location is used, the components of a product are produced there and final assembly takes place either at the foreign location or at the parent domestic plant. This paper first presents the issues related to international facilities location (IFL) problems, and provides the framework required to deal with such problems. It then presents a heuristic algorithm for solving the IFL problem. Extensive computational experience was gained by solving a variety of IFL problems of different sizes.     

Optimization of the Abencor system to extract olive oil from irrigated orchards

Studying the composition of olive oil requires cold‐press olive oil extraction. One of the most common laboratorial mills is the Abencor system. However, its operation protocol was formulated decades ago for Spanish olive varieties from traditionally rain‐fed orchards. We modified this protocol for use with “Barnea” and “Picual” olives from irrigated orchards that are characterized by high water content. Independent effects of malaxation time, temperature, water addition and talc addition on extraction efficiency, and major quality indices of virgin olive oil were studied. Overall, addition of talc to the fruit paste was the most significant treatment in terms of yield and quality of the oil although its effect was cultivar dependent. Improved oil yield was particularly significant for “Picual.” Extended malaxation time was also effective in improving oil extractability. Addition of talc generally improved oil‐quality parameters, while water addition had the opposite effect. Yet, quality parameters remained within the extra virgin level. Temperature increments reduced oil quality. The need to adapt a modified protocol for use with fruits from irrigated orchards that will facilitate critical comparison of results obtained from different agronomic theses and different laboratories is highlighted. It is recommended that each laboratory develops an appropriate protocol for the operation of the Abencor system in accordance to the characteristics of the olive fruit they are working with. Practical applications: Abencor system serves as the major laboratorial mill world‐wide. Those mills allow the researchers to characterize olive oil in accordance to the treatments received by the trees. This cannot be done in commercial mills. The system operation protocol was established decades ago for fruits from rain‐fed orchards. In the past decade there was a rapid increase in the use of irrigation in olive orchards and therefore it is crucial to optimize the operation protocol for fruit with relatively high water content. In the current work we have evaluated the influence of a series of technological parameters (i.e., talc and water addition, malaxation time, and temperature) on the extraction efficiency and quality indices of olive oil. This allowed us to present a modified protocol for the Abencor system operation suitable for olive fruit of irrigated orchards that will facilitate a reliable representation of the influence of different treatments on the yield and characteristics of the olive oil.     

Status of biodiesel research and development in Pakistan

Performance of biodiesel in engines is well established and biodiesel is currently adjudged as a low carbon fuel with the most potential of replacing fossil fuels. The fossil fuel sources are dwindling in Pakistan resulting in importation of about 8.1 million tonnes at approximately US$ 9.4 billion per annum. In the ambit of this justification, augmenting the energy scarce resources in Pakistan through intense harnessing of the varied biodiesel sources can adequately address the deficiency and can ensure energy security. Towards this end, the progress attained in biodiesel related researches in Pakistan are evaluated and presented with the view of highlighting ways of achieving the target set by the Government. A feedstock that drew less attention is spent triglycerides, and the little work reported by some organizations appeared promising. Now the onus is upon organizations such as the Alternative Energy Development Board and Pakistan State Oil to harness the research results from several indigenous Universities and develop a full-scale biodiesel economy in Pakistan.     

Mitigation of connector damage during disengaging DC loads using polymeric arc suppressor

Although connectors are generally not designed to disconnect electrical loads under power, in some circumstances they are mated and unmated under load. For instance, during repairs, diagnostic procedures, or when blown fuses are replaced under short circuit conditions. At dc system voltage levels significantly higher than the minimum arc voltage of metals such hot-disconnections may impact the reliability of the connection, the electrical distribution system, and automotive safety. Gassing polymers mounted onto connector terminals may reduce the damage resulting from disconnections under dc loads, and therefore enable connector designs with occasionally (forward running) arcing terminals. The authors discuss the effects of different types of gassing polymers on arc extinction and connector damage of standard automotive connectors.     

A Hybrid Neural Network and Box-Jenkins Models for Time Series Forecasting

Time series forecasting plays a significant role in numerous applications, including but not limited to, industrial planning, water consumption, medical domains, exchange rates and consumer price index. The main problem is insufficient forecasting accuracy. The present study proposes a hybrid forecasting methods to address this need. The proposed method includes three models. The first model is based on the autoregressive integrated moving average (ARIMA) statistical model; the second model is a back propagation neural network (BPNN) with adaptive slope and momentum parameters; and the third model is a hybridization between ARIMA and BPNN (ARIMA/BPNN) and artificial neural networks and ARIMA (ARIMA/ANN) to gain the benefits of linear and nonlinear modeling. The forecasting models proposed in this study are used to predict the indices of the consumer price index (CPI), and predict the expected number of cancer patients in the Ibb Province in Yemen. Statistical standard measures used to evaluate the proposed method include (i) mean square error, (ii) mean absolute error, (iii) root mean square error, and (iv) mean absolute percentage error. Based on the computational results, the improvement rate of forecasting the CPI dataset was 5%, 71%, and 4% for ARIMA/BPNN model, ARIMA/ANN model, and BPNN model respectively; while the result for cancer patients’ dataset was 7%, 200%, and 19% for ARIMA/BPNN model, ARIMA/ANN model, and BPNN model respectively. Therefore, it is obvious that the proposed method reduced the randomness degree, and the alterations affected the time series with data non-linearity. The ARIMA/ANN model outperformed each of its components when it was applied separately in terms of increasing the accuracy of forecasting and decreasing the overall errors of forecasting.

     

Properties of fly ash concrete modified with hydrated lime and silica fume

This paper presents the results of an experimental investigation on the properties of fly ash concrete incorporating either hydrated lime or silica fume to improve the early strength of concrete. Test results indicated that the addition of lime and silica fume improved the early age compressive strength of fly ash concrete. The inclusion of silica fume was also found to increase the 28 days strength significantly. The air permeability of concrete containing lime and silica fume either decreased or remained almost the same when compared to the concrete without these. The addition of lime and silica fume also improved the sorptivity of concrete.Through the use of differential scanning calorimetry and thermogravimetric analysis (DSC/TG), it was demonstrated that the addition of hydrated lime increased the Ca(OH)₂ content; whereas the addition of silica fume decreased the Ca(OH)₂ content in the cement paste. The mercury intrusion porosimetry (MIP) data confirmed the beneficial action of hydrated lime and silica fume, towards decreasing the total pore volume of fly ash cement paste.     

Freeze–thaw resistance of concretes treated with pore liners

A laboratory investigation was carried out with surface treated and untreated concretes, using ASTM C666 Procedure A test and RILEM fresh water and salt water tests which give different exposure conditions during freezing and thawing. Concrete specimens with three different water–cement ratios were used to study the performance of concrete with varying pore structures. Three different pore liners were used for the investigation. To study the effect of depth of penetration of treatment the concretes were exposed to two different moisture conditions before applying the treatments. Results indicate that the surface treated concretes not only withstand the freezing and thawing but also improve the freeze–thaw resistance even in the case of the most porous concrete used in the study. Furthermore, it was seen that the deterioration of treated concrete varied under different test conditions used for the study.