Thermally stimulated depolarization currents in γ-irradiated β-spodumene solid solution ceramic

Thermally stimulated depolarization currents (TSDC) in unirradiated and -irradiated press prepared -spodumene solid solution ceramic have been investigated within the wide temperature range 20–160°C. Doses in the range 10–10⁵ Gy were used. The TSDC spectrum at relatively high polarizing fields shows two relaxation peaks whose positions and intensities depend on the polarization conditions and -doses. Discussion of data is given on the basis that dipolar and space-charge polarization coexist in the used ceramic material. Activation energies for space-charge peak are determined from the initial rise of thermal current peak under different -doses. Aging effect clearify that the longer the aging time, the smaller the polarization. Pyroelectric current data provide further support to space charge effects.     

On the mechanical properties of polymer Portland cement concrete

Abstract

In this paper, epoxy which is the most common type of polymer used by civil engineers, and polyester, which is cheaper than most other types of polymers, were utilized to produce Polymer Portland Cement Concrete (PPCC). A rich concrete mix was designed and then five different ratios of cement (0, 20, 40, 60 and 100%) were replaced by either epoxy or polyester, rendering five different mixes for each type of polymer. Three types of samples were cast, compacted and then cured for 28 days. The three types of samples are standard beams of size 150×150×600 mm, standard cubes and standard cylinders. One third of the specimens were tested at room temperature, while the rest of the specimens were heated in an oven for 24 hours. Specimens were heated to two temperature stations of 80°C and 150°C. Samples received for flexure, compression, split tension, and direct shear tests, using a specially manufactured apparatus that was used before and found to be effective. The variations of compressive strength, split tensile strength, direct shear strength, and flexural strength with different variables such as temperature, percentage of polymer and type of polymer were determined and assessed.     

Integrated performance assessment model for water distribution networks

The American infrastructure report card in 2013 rated the US water system infrastructure with grade of ‘D’. The Canadian infrastructure report card in 2012 stated that around 15.4% of Canada’s water infrastructure has a condition of fair to very poor. Thus, there is a critical need to develop efficient inspection, maintenance and rehabilitation plans for water distribution networks. However, such plans require an assessment tool to evaluate the performance and condition of water distribution networks. Therefore, the main purpose of this paper is to develop an integrated performance assessment model for water distribution networks. Two modules were developed to assess the performance of water pipelines and accessories, respectively. A third module was developed to assess the performance of water segments that includes pipelines and accessories. Moreover, a fourth module was built to assess the performance of each sub-network and the entire network based on the segments’ connection type using a reliability-based approach. To assess the performance of the water distribution network, the critical factors affecting its pipelines and accessories were identified and studied. The fuzzy analytic network process technique was used to obtain the importance weights of the identified factors.     

Simulation-based deterioration patterns of water pipelines

Water pipelines deteriorate overtime due to several distressing factors. To keep water pipelines in good condition, municipalities need to use reliable and credible deterioration models and inspection plans to better manage their rehabilitation and maintenance. Thus, this paper presents the development of deterioration models and patterns of water pipelines. The deterioration models consider different water pipe sizes and materials as well as different surrounding environmental conditions which affect their deterioration rates. As a prerequisite to the development of such deterioration models, a condition assessment model for water pipelines was first developed. Questionnaires were distributed among experts to determine the weights of the factors affecting water pipeline conditions using the fuzzy analytic network process. Monte-Carlo simulation was used to account for the large uncertainties of the calculated weights in the development of the condition assessment model. The validation of the model, which was performed using historical data, yielded an average validity percentage of 93.59%. The developed models are expected to help municipalities and decision makers to accurately plan for future water pipelines maintenance and rehabilitation activities based on their different deterioration patterns. It takes into consideration both the uncertainties at the initial stage and those accumulated during the calculation process.     

Optimizing Material Procurement and Storage on Construction Sites

Efficient planning of materials procurement and storage on construction sites can lead to significant improvements in construction productivity and project profitability. Existing research studies focus on material procurement and storage layout as two separate planning tasks without considering their critical and mutual interdependencies. This paper presents the development of a new optimization model for construction logistics planning that is capable of simultaneously integrating and optimizing the critical planning decisions of material procurement and material storage on construction sites. The model utilizes genetic algorithms to minimize construction logistics costs that cover material ordering, financing, stock-out, and layout costs. The model incorporates newly developed algorithms to estimate the impact of potential material shortages on-site because of late delivery on project delays and stock-out costs. An application example is analyzed to demonstrate the capabilities of the construction logistics planning model in simultaneously optimizing material procurement decisions and storage layout plans.     

Novel amphiphilic conetworks based on compatibilized NBR/SBR–montmorillonite nanovulcanizates as membranes for dehydrative pervaporation of water–butanol mixtures

Nanocomposite vulcanizates comprising the poorly compatible acrylonitrile butadiene rubber/styrene butadiene rubber blend are homogenized with 20 parts per hundred montmorillonite forms showing various levels of amphiphathicity: slightly hydrophobic (Mont‐25/50) and highly hydrophobic (Mont75/100) as compared to the highly hydrophilic pristine form (Mont‐0). The purpose of the amphiphathicity is to afford simultaneous binding sites for the poorly compatible components. Thus maximum compatibility is reached with either Mont‐75 or Mont‐50 which improves the mechanical properties. Scanning electron microscopy corroborates cocontinuous morphology. Water vapor permeation through sheets/membranes fabricated from these compositions follows best performance with Mont‐25 followed by Mont‐50 while Mont‐75 and Mont‐100 based membranes acquire an organized continuous drop. This highlights the role of organophilicity in dominating the morphology and performance in pervaporation application. Dehydration of butanol is effective using such membranes with superiority for Mont‐25 based membrane. A plausible model for the transport mechanism was proposed and supported by activation energy calculations for the permeation of the individual components and the sorption affinity measurements as well. All these parameters together suggest the arrest of the n‐butanol within the macrmolecular chains of the membranes, favored by its chemical affinity. This allows therefore a passageway for the water to cross to the other side of the membrane through plasticization of the chains and creation of free volumes which is known as solution diffusion mechanism. POLYM. ENG. SCI., 54:1560–1570, 2014. © 2013 Society of Plastics Engineers     

Phosphorylation of starch and dextrin by dry‐heating in the presence of phosphate,and their calcium phosphate‐solubilizing ability

Starch and dextrin were phosphorylated by dry‐heating in the presence of phosphate, and their properties were examined. The phosphorylation of starch was accelerated with decreasing moisture, rising incubation temperature and prolongation of the incubation period. However, a rise in incubation temperature, and lengthened incubation period caused increased browning and degradation. A decrease in the pH from 5.5 to 3.0 resulted in a modest increase of phosphorylation, but also marked browning and degradation. When potato starch was phosphorylated at 140°C and pH 5.5 for 24 h, its phosphorus content was increased up to 3.47%, with fewer side reactions. Phosphorlylated starch and dextrin had calcium phosphate‐solubilizing abitity. Phosphorylated dextrin with 2.42% phosphorus had about half the calcium phosphate‐solubilizing ability of casein phosphopeptide (CPP). The possibility of substituting of phosphorylated starch and dextrin for CPP as a calcium phosphate‐absorption enhancing material is discussed herein.     

Physicochemical and morphological evaluation of chitosan/poly(vinyl alcohol)/methylcellulose chemically cross-linked ternary blends

Chitosan/poly(vinyl alcohol)/methylcellulose (CS/PVA/MC) ternary blend was prepared and chemically cross-linked with glutaraldehyde. The prepared ternary blends were characterized by Fourier transform infrared spectroscopy (FTIR), Thermogravimetric analysis (TGA), and X-ray diffraction (XRD). The FTIR results showed that the strong intermolecular hydrogen bonds took place between CS and PVA. TGA showed the thermostability of the blend is enhanced by glutaraldehyde as crosslink agent. Results of XRD indicated that the relative crystalline of pure CS film was reduced when the polymeric network was reticulated by glutaraldehyde. Finally, the results of scanning electron microscopy (SEM) indicated that the morphology of the blend is rough and heterogenous, further it confirms the interaction between the functional groups of the blend components.     

Heavy metal removal from copper smelting effluent using electrochemical cylindrical flow reactor

The purpose of this study is mainly to evaluate the performance of the continuous recirculation flow cell at low current density and pH (the pH at which the effluents are available) in removing heavy metals from copper smelting effluent by cathodic reduction. During the electrolysis at different pH, % removal of heavy metals removal, energy consumption and heterogeneous reaction rate constants were investigated at given flow rate and current density on the selected industrial effluent. The overall specific energy consumption at the pH 0.64 was observed to be lowest, which is 10.99kWh/kg of heavy metal removal.     

Special-Purpose Simulation Model for Balanced Cantilever Bridges

Construction of bridges’ decks involves different types of resources that interact in a cyclic manner. Further, the construction operation inherits uncertainties and a variety of demands. Contractors have to select the construction method that suits project constraints including: project conditions, technical, financial, and time constraints. There are several construction methods that can be used to construct bridges’ decks. This paper presents a special-purpose simulation model that aids government agencies and/or their representative in planning the construction of bridges’ decks using cast-in-place and precast balanced cantilever techniques. The pouring of concrete in cast-in-place balanced cantilever techniques can be executed either by using pump station and pump line, or truck mixers, whereas, the precast balanced cantilever technique is carried out using two methods: (1) placement by an independent lifting apparatus; and (2) placement with the help of a beam and winch carried by the bridge deck itself. The developments made to model these methods are detailed in the paper. The proposed special purpose simulation model utilizes STROBOSCOPE as a simulation engine and is coded utilizing Visual Basic 6.0. All actual project data are fed to the developed model in order to carry out the what-if analysis.