Medium strength self-compacting concrete containing fly ash: Modelling using factorial experimental plans

Fresh self-compacting concrete (SCC) flows into place and around obstructions under its own weight to fill the formwork completely and self-compact, without any segregation and blocking. The elimination of the need for compaction leads to better quality concrete and substantial improvement of working conditions. SCC mixes generally have a much higher content of fine fillers, including cement, and produce excessively high compressive strength concrete, which narrows its field of application to special concrete only. To obtain maximum benefit from SCC, it has to be adopted in general concrete construction practice. Such practice requires inexpensive and medium strength concrete.This investigation aims to develop medium strength SCC (MS-SCC). The cost of materials will be decreased by reducing the cement content and by using pulverised fuel ash (PFA) with a minimum amount of superplasticizer (SP). A factorial design was carried out to mathematically model the influence of five key parameters on filling and passing abilities, segregation and compressive strength, which are important for the successful development of medium strength self-compacting concrete incorporating PFA. The parameters considered in the study were the contents of cement and PFA, water-to-powder (cement+PFA) ratio (W/P) and dosage of SP. The responses of the derived statistical models are slump flow, fluidity loss, Orimet time, V-funnel time, L-box, JRing combined to the Orimet, JRing combined to cone, rheological parameters, segregation and compressive strength at 7, 28 and 90 days. Twenty-one mixes were prepared to derive the statistical models, and five were used for the verification and the accuracy of the developed models. The models are valid for mixes made with 0.38 to 0.72 W/P, 60 to 216 kg/m³ of cement content, 183 to 317 kg/m³ of PFA and 0% to 1% of SP, by mass of powder. The influences of W/P, cement and PFA contents, and the dosage of SP were characterised and analysed using polynomial regression, which can identify the primary factors and their interactions on the measured properties. The results show tha MS-SCC can be achieved with a 28-day compressive strength of 30 to 35 MPa by using up to 210 kg/m³ of PFA.     

Effects Of Ozone On Kraft Process Pulp Mill Effluent

Effluent from a kraft process pulp mill was studied in a batch reactor for ozone doses between 50 and 200 mg O₃/L to identify the relative suitability of ozone application locations in the treatment process and see the improvements in biotreatability of wastewaters from a kraft process pulp mill. Laboratory acclimatized seed were used for BOD tests for ozonated and unozonated samples. The inhibitory effects were minimized by using optimum dilutions. The studies were divided into three major sections: characterization of mill effluent; ozone system calibration, and reactor design; and ozonation of mill effluent. Seed for Biochemical Oxygen Demand tests were acclimatized in batch units for primary, bleach and secondary effluents separately. The inhibitory effects which were noted with unacclimatized seed, were reduced by using laboratory acclimatized seed and optimum dilution which were determined during the characterization phase.

The batch reactor designed for the studies consisted of a cylindrical section for holding effluent, and a top spherical section for ozone/oxygen mixture. The reactor proved to be effective for controlling ozone dose. The variation in the applied ozone dose was less than 5 mg/L.

Bleach and primary effluents were treated with 50 and 100 mg/L ozone doses. Duplicate experiments were conducted for these effluents. Secondary effluent was studied for 50,100,150 and 200 mg/L ozone doses. Six replicate experiments were conducted for 50 and 100 mg/L ozone doses, whereas two experiments were carried out for 150 mg/L and one experiment for 200 mg/L ozone dose.

The results were analyzed using 't' test for paired experiments and ANOVA table for statistical confirmation. Residuals were plotted to check the assumptions of constant variance and normal distribution. The results indicated that 50 and 100 mg O₃/L effectively removed color from bleach effluent and primary effluent, but did not significantly change the BOD. Ozone was found to be effective for secondary effluent, as BOD₅ was increased by 65% for 50 and 100% for 100 mg O₃/L doses. The corresponding reduction in color was 62% and 82%, respectively. K_e and L_o values for the BOD equation were calculated by using the non-linear least square method for the BOD equation, giving joint confidence regions for the calculated parameters. It was concluded that ozone is most effective for the removal of color and the increase of BOD in secondary effluent.     

Effect of sodium lauryl sulfate on the polymerization of acrylonitrile

Micellar catalyzed polymerization of acrylonitrile using ceric(IV)–glycerol redox system in aqueous sulfuric acid solution in the presence of sodium lauryl sulfate (NaLS) has been studied. The polymerization experiments were conducted between 15°C and 25°C, under conditions where no oxidation of sodium lauryl sulfate by ceric ion would we expected. The rate of polymerization (R_p) increases with increasing concentration of NaLS. The rate of monomer (AN) disappearance was proportional to [AN]^1.5 and [glycerol]^0.5, but, however, R_p changes in a nonlinear manner with increase in Ce(IV) concentration in the presence of the surfactant. The rate of Ce(IV) disappearance was not proportional to its original concentration. The chain length of the polymer could not be determined viscometrically, as the polymer obtained in presence of NaLS was insoluble in organic solvents. The activation energy of this polymerization process was calculated by conducting the experiment at different temperatures. The infrared spectra of the polymers in the presence and absence of surfactant have also been examined.     

A comprehensive review of past and present vision-based techniques for gait recognition

Global security concerns have raised a proliferation of video surveillance devices. Intelligent surveillance systems seek to discover possible threats automatically and raise alerts. Being able to identify the surveyed object can help determine its threat level. The current generation of devices provide digital video data to be analysed for time varying features to assist in the identification process. Commonly, people queue up to access a facility and approach a video camera in full frontal view. In this environment, a variety of biometrics are available—for example, gait which includes temporal features like stride period. Gait can be measured unobtrusively at a distance. The video data will also include face features, which are short-range biometrics. In this way, one can combine biometrics naturally using one set of data. In this paper we survey current techniques of gait recognition and modelling with the environment in which the research was conducted. We also discuss in detail the issues arising from deriving gait data, such as perspective and occlusion effects, together with the associated computer vision challenges of reliable tracking of human movement. Then, after highlighting these issues and challenges related to gait processing, we proceed to discuss the frameworks combining gait with other biometrics. We then provide motivations for a novel paradigm in biometrics-based human recognition, i.e. the use of the fronto-normal view of gait as a far-range biometrics combined with biometrics operating at a near distance.     

Effect of aggressive pH media on peat treated by cement and sodium silicate grout

The effects of aggressive peat nature (pH) on the strength of peat treated by cement and cement-sodium silicate grout were investigated by evaluating the changes in unconfined compressive strength,moisture content,and scanning electron microscopy (SEM) of samples with time in different pH media.The results indicate that peats treated by cement-silicate have higher strength than peats treated by cement,due to an increase in pH value of the media.Furthermore,cement and cement-silicate are highly effective in ...     

Role of fibers in controlling unrestrained expansion and arresting cracking in Portland cement concrete undergoing alkali-silica reaction

An experimental study was undertaken to investigate the role of polypropylene or brass-coated steel fibers in controlling unrestrained expansions and delaying and arresting cracking in Portland cement concrete due to alkali-silica reaction. Portland cement concrete and fiber-reinforced concrete (FRC) mixtures were prepared at a w/c ratio of 0.40 using modified Type I cement, reactive fine particles, and coarse limestone aggregates. Prism (5×5×30 cm) and plate (13.5×13.5×3 cm) specimens were prepared and cured for 7 or 28 days before exposure to a special treatment to accelerate ASR. Expansion, time of cracking, and ultrasonic pulse velocity were determined over a treatment period of 65 days using prism specimens. Ultimate cracking pattern and extent were determined after a treatment period of 85 days using plate specimens. The results showed that while fibers did not contribute significantly to controlling pre-cracking and post-cracking expansions, they played a significant role in delaying cracks formation and limiting their extent. Considering its lower cost and content, the performance of polypropylene fibers was superior to that of brass-coated steel ones. The potential of brass-coated fibers in arresting ASR cracking was significantly affected by age of concrete when subjected to treatment.     

Comparative modelling of major house dust mite allergen Der p I: structure validation using an extended environmental amino acid propensity table

A model of the 3-D structure of a major house dust mite allergenDer p I associated with hypersensitivity reactions in humanswas built from its amino acid sequence and its homology to threeknown structures, papain, actinidin and papaya proteinase flof the cysteine proteinase family. Comparative modelling usingCOMPOSER was used to arrive at an initial model. This was refinedusing interactive graphics and energy minimization with theAMBER force field incorporated in SYBYL (Tripos Associates).Compatibility of the Der p I amino add sequence with the cysteineproteinase fold was checked using an environment-dependent aminoadd propensity table incorporated into a new program HARMONYwith a variable length windowing facility. A fiveresidue windowwas used to probe local conformational integrity. Propensitieswere derived from a structural alignment database of homologousproteins using a robust entropy-driven smoothing procedure.Der p I shares essential structural and mechanistic featureswith other papain-like cysteine proteinases, including cathepsinB. The active-site t iolate-imidazolium ion pair comprises theside chains of Cys34 and Hisl70. A cystine disulfide not presentin other known structures bridges residue 4 of an N-terminalextension and the core residue 117. Two conserved disulfidebridges are formed by residues 31 and 71 and residues 65 and103. Model building of peptide substrate analogue complexessuggests a preference for phenylalanyl or bask residues at theP₂ position, whilst selectivity may be of minor importance atthe S₁ subsite. The electrostatic influences on the Der p Iactive-site ion pair and extended peptide binding region aremarkedly different from those in known structures. A highlyimmunogenic surface exposed region (residues 107–131),comprising several overlapping T cell epitope sites, has noshared sequence identity with human liver cathepsin B and containsthree insertion-deletion sites. The structure provides a basisfor testing the substrate specificity of Der p I and the potentialrole of proteinase activity in hypersensitivity reactions. Thesestudies may offer a new treatment strategy by hyposensitizationwith inactive mutants or mutants with significantly alteredproteinase activity, either alone or complexed with antibody.     

13C nuclear magnetic resonance spectroscopic analysis of the triacylglycerol composition ofBiota orientalis and carrot seed oil

¹³C nuclear magnetic resonance (NMR) spectroscopic analysis of the whole oil (triacylglycerols) ofBiota orientalis seeds confirms the presence of oleate [18:1(9Z)], linoleate [18:2(9Z, 12Z)], linolenate [18:3((9Z, 12Z, 15Z)], 20:3 (5Z, 11Z, 14Z), 20:4(5Z, 11Z, 14Z, 17Z), and saturated fatty acids in the acyl groups by comparing the observed carbon shifts with previously established shift data for model triacylglycerols. This technique shows that the saturated, 20:3 and 20:4 fatty acids are distributed mainly in the α-acyl positions, whereas oleate, linoleate, and linolenate are randomly acylated to the α- and β-positions of the glycerol “backbone”. Stereospecific hydrolysis of theBiota oil with pancreatic lipase, followed by chromatographic analysis of fatty esters, reveals the presence of trace amounts of 16:0(0.7%), 18:0(0.5%), 20:3 (0.4%), and 20:4 (1.3%) in the β-position of the glycerol “backbone”, which are undetectable by¹³C NMR technique on the whole oil. Semiquantitative assessment of the¹³C NMR signal intensities gives the relative percentages of the fatty acid distribution as: saturated 16:0, 18:0 (12.0% α-acyl), oleate (7.7% α-acyl 8.7% β-acyl), total linoleate and linolenate (31.7% α-acyl; 24.2% βacyl), total 20:3 and 20:4 (15.7% α-acyl). The¹³C NMR spectroscopic analysis of carrot seed oil identifies the presence of saturated (18:0), 18:1(6Z), 18:1(9Z), and 18:2(9Z, 12Z). The saturated fatty acid is found in the α-acyl positions. Semi-quantitative assessment of the signal intensities gives the relative percentages of the fatty acids as: 18:0 (4.5% α-acyl), 18:1(6Z) (49.6% α-acyl; 19.7% β-acyl), oleate (6.5% α-acyl; 8.6% β-acyl) and linoleate (5.2% α-acyl; 6.9% β-acyl).     

Advantages of an Emulsion‐Produced Ziegler‐Natta Catalyst Over a Conventional Ziegler‐Natta Catalyst

Summary: Self‐supported and MgCl₂‐supported Ziegler‐Natta catalysts, produced by two catalyst synthesis methods are compared. Borealis Polymers OY (Finland), who supplied the catalysts, developed the catalyst synthesis methods. The first method (Method One) is based on an emulsion system and consists of an in situ single step preparation. The second method (Method Two) consists mainly of two steps: formation of the catalyst carrier particles, and their subsequent impregnation with the active material. The results showed that Method One produced catalysts of compact, spherical particles with good intra‐particle homogeneity and a narrow particle size distribution. On the other hand, Method Two produced catalyst particles whose properties depended directly on that of the catalyst carrier: they were spherical but very porous, with a broad particle size distribution. Polymer particles produced with the two catalyst systems are perfect replicas of the catalyst particles. Fines formed either during catalyst preparation or during polymerization were observed only with the catalyst prepared using Method Two. The particles of the catalysts produced using Methods One and Two had similar activities, independent of the initial particle size. Fragmentation of catalyst particles was very fast for both catalyst systems and was only observed to be 100% completed using the catalyst produced with Method One. Studies of the thermal properties showed that the catalyst prepared using Method One produced poly(propylene) of higher crystallinity and with a narrower melting peak.

SEM images of polymer particles produced by (A) Method One and (B) Method Two.     

Pitting corrosion of lead in sodium carbonate solutions containing NO3 ions

Pitting corrosion of Pb in Na₂CO₃ solutions (pH=10.8) containing NaNO₃ as a pitting corrosion agent has been studied using potentiodynamic anodic polarization, cyclic voltammetry and chronoamperometry techniques, complemented with scanning electron microscopy (SEM) examinations of the electrode surface. In the absence of NO₃⁻, the anodic voltammetric response exhibits three anodic peaks prior to oxygen evolution. The first anodic peak A₁ corresponds to the formation of PbCO₃ layer and soluble Pb²⁺ species in solution. The second anodic peak A₂ is due to the formation of PbO beneath the carbonate layer. Peak A₂ is followed by a wide passive region which extends up to the appearance of the third anodic peak A₃. The later is related to the formation of PbO₂. Addition of NO₃⁻ to the carbonate solution stimulates the anodic dissolution through peaks A₁ and A₂ and breaks down the dual passive layer prior to peak A₃. The breakdown potential decreases with an increase in nitrate concentration, temperature and electrode rotation rate, but increases with an increase in carbonate concentration and potential scan rate. Successive cycling leads to a progressive increase in breakdown potential. The current/time transients show that the incubation time for passivity breakdown decreases with increasing the applied anodic potential, nitrate concentration and temperature.