Optimal design of large‐scale chemical processes under uncertainty: A ranking‐based approach

An approach for the optimal design of chemical processes in the presence of uncertainty was presented. The key idea in this work is to approximate the process constraint functions and model outputs using Power Series Expansions (PSE)‐based functions. The PSE functions are used to efficiently identify the variability in the process constraint functions and model outputs due to multiple realizations in the uncertain parameters using Monte Carlo (MC) sampling methods. A ranking‐based approach is adopted here where the user can assign priorities or probabilities of satisfaction for the different process constraints and model outputs considered in the analysis. The methodology was tested on a reactor–heat exchanger system and the Tennessee Eastman process. The results show that the present method is computationally attractive since the optimal process design is accomplished in shorter computational times when compared to the use of the MC method applied to the full plant model. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3243–3257, 2014     

Growth and surface engineering of vertically-aligned low-wall-number carbon nanotubes

A novel catalyst of cobalt supported by single crystal MgO was prepared by atomic layer deposition and used for carbon nanotube growth. With CO as carbon source, vertically-aligned carbon nanotubes with predominant double-walled (82%) were produced at 700 °C. Similar carbon nanotube array with a majority of single-walled tubes (62%) was produced at 900 °C using methane as the carbon source. Due to their high flexibility compared with multi-walled carbon nanotubes, the low-wall-number carbon nanotube array could form a 3-dimensional honeycomb-like network when being spread with acetone.     

Image reproduction with compensation of luminance adaptation

We introduce an image reproduction model that retargets colors for printing purposes to ensure similar luminance perception under photopic and scotopic vision. Our model is based on the physiological functioning of the rod and cone cells in the retina in varying lighting conditions, so that the human visual system exhibits responses akin to a printed output of the model for different illumination levels. Prior to retargeting, digital color images are converted to spectral representations and their photopic and scotopic luminance responses are obtained. The color retargeting is realized by optimizing our compensation function over the color space. In addition, we present a spatially varying operator to enhance the color coherence over salient regions. Reproduction results demonstrate substantially decreased difference between the two luminance responses. Further, it is validated through psychophysical evaluation that our model on average provides superior recognition rates in dark environments, while keeping the noticeable differences in aesthetic appeal acceptable in well-lit environments.     

Resistance factors for blind bolts in direct tension

Blind bolts are developed to be used in applications where access for installation is from one side of the connection only, as in the case of connecting the end-plate of a beam to a hollow column. Blind fasteners offer many advantages including strengths and sizes comparable to A325 fasteners, potential use in tension applications as well as in moment-resisting connections and ease of installation. In this study, reliability analyses are conducted in order to develop resistance factors for blind bolts designed following the AISC's LRFD specification. The limit state that is considered is the direct tension only. The applied loading consists of dead load, live load and wind. Probabilistic resistance models are developed for blind fasteners based on experimental test results. The statistics of load models on building structures are compiled from the available literature. The study considers a wide range of live-to-dead load ratios and several wind load intensities. The results of the reliability analysis indicate that a resistance factor in the order of 0.65 is adequate.     

Detoxification of Tunisian landfill leachates by selected fungi

Young landfill leachates (LFL) collected from Djebel Chekir (Tunisia) discharge area were found to be highly loaded with organic matter, ammonia, salts, heavy metals, phenols and hydrocarbons. Despite the possibility of their biodegradability, they represent a threat to the environment and show some resistance to conventional wastewater treatment processes. For these reasons, this study attempted to develop a biological process for the treatment of LFL using selected strains of Trametes trogii, Phanerochaete chrysosporium, Lentinus tigrinus and Aspergillus niger. Experiments were undertaken at different concentrations of the effluent up to 100%. COD removal efficiencies for P. chrysosporium, T. trogii and L. tigrinus were of 68, 79 and 90%, respectively, when LFL underwent a two-fold dilution. COD abatements were accompanied with an important enzyme secretion and a high reduction in the toxicity, expressed as percent bioluminescence inhibition (%BI < 20%). Above 50% of LFL, the effluent was toxic to these strains and caused growth inhibition indicating the sensitivity of these strains to concentrated LFL. Comparatively to the other tested strains, A. niger showed to tolerate raw LFL since it grew at 100% of LFL. However, this strain is inefficient in removing phenols and hydrocarbons. Consequently, toxicity abatement was very low (%BI > 70%).     

Finite Element Model Updating Using Evolutionary Strategy for Damage Detection

Abstract: Structural health monitoring through the use of finite element model updating techniques for dispersed civil infrastructures usually deals with minimizing a complex, nonlinear, nonconvex, high‐dimensional cost function with several local minima. Hence, stochastic optimization algorithms with promising performance in solving global optimization problems have received considerable attention for finite element model updating purposes in recent years. In this study, the performance of an evolutionary strategy in the finite element model updating approach was investigated for damage detection in a quarter‐scale two‐span reinforced concrete bridge system which was tested experimentally at the University of Nevada, Reno. The damage sequence in the structure was induced by a range of progressively increasing excitations in the transverse direction of the specimen. Intermediate nondestructive white noise excitations and response measurements were used for system identification and damage detection purposes. It is shown that, when evaluated together with the strain gauge measurements and visual inspection results, the applied finite element model updating algorithm of this article could accurately detect, localize, and quantify the damage in the tested bridge columns throughout the different phases of the experiment.     

Color image segmentation using mean shift and improved ant clustering

To improve the segmentation quality and efficiency of color image, a novel approach which combines the advantages of the mean shift (MS) segmentation and improved ant clustering method is proposed. The regions which can preserve the discontinuity characteristics of an image are segmented by MS algorithm, and then they are represented by a graph in which every region is represented by a node. In order to solve the graph partition problem, an improved ant clustering algorithm, called similarity carrying ant model (SCAM-ant), is proposed, in which a new similarity calculation method is given. Using SCAM-ant, the maximum number of items that each ant can carry will increase, the clustering time will be effectively reduced, and globally optimized clustering can also be realized. Because the graph is not based on the pixels of original image but on the segmentation result of MS algorithm, the computational complexity is greatly reduced. Experiments show that the proposed method can realize color image segmentation efficiently, and compared with the conventional methods based on the image pixels, it improves the image segmentation quality and the anti-interference ability.     

Reactions of Asymmetric Bis-(p-alkoxyphenyl) ethylenes with dimethylaniline

1,1-Bis-[p-methoxy(or ethoxy)phenyl]ethylene 1 gave in boiling dimethylaniline in the presence of hydrogen chloride or zinc chloride 1,1-bis-[p-methoxy(or ethoxy)phenyl]-1-p-dimethylaminophenylethane 2 1,1-bis-[p-methoxy(or ethoxy)phenyl]ethane, 1,1-bis-[p-hydroxyphenyl]-ethane and bis-[p-dimethylaminophenyl]methane. The structure of the triarylethanes 2 was proven by synthesis. The isomeric 1,1-bis-[p-methoxy(or ethoxy)phenyl]-2-p-dimethylaminophenylethane 6 was also synthesised.