Integrated Risk of Progress-Based Costs and Schedule Delays in Construction Projects

This article aims to explore the impact of the integration of risk factors into delayed milestones for construction projects. A simulation model was developed to determine the impact of schedule variability on cost estimation. To generate random scenarios a Monte Carlo Simulation (MCS) technique was applied. The developed model computes the cost impact of delayed milestone in the expected budget. Using a risk integration approach revealed the critical time frame that may lead to a budget deficit for a project. As a result, a number of cost-sensitive risk factors and schedule delays were identified for the critical time period where the risk of budget deficit increases. The method of integration proposed in this article highlights the priority of risk factors and schedule delays for construction contracts involving Payments at Event Occurrences (PEO). Consequently, the developed method can be useful for practitioners in anticipation of potential increase of costs, hence, prevention of failure due to budget deficit.     

Removal of metal ions using lignite in aqueous solution—Low cost biosorbents

Turkish lignite can be used as a new adsorption material for removing some toxic metals from aqueous solution. The adsorption of lignite (brown young coals) to remove copper (Cu²⁺), lead (Pb²⁺), and nickel (Ni²⁺) from aqueous solutions was studied as a function of pH, contact time, metal concentration and temperature. Adsorption equilibrium was achieved between 40 and 70 min for all studied cations except Pb²⁺, which is between 10 and 30 min. The adsorption capacities are 17.8 mg/g for Cu²⁺, 56.7 mg/g for Pb²⁺, 13.0 mg/g for Ni²⁺ for BC₁ (Ilg?n lignite) and 18.9 mg/g for Cu²⁺, 68.5 mg/g for Pb²⁺, 12.0 mg/g for Ni²⁺ for BC₂ (Beysehir lignite) and 7.2 mg/g for Cu²⁺, 62.3 mg/g for Pb²⁺, 5.4 mg/g for Ni²⁺ for AC (activated carbon). More than 67% of studied cations were removed by BC₁ and 60% BC₂, respectively from aqueous solution in single step. Whereas about 30% of studied cations except Pb²⁺, which is 90%, were removed by activated carbon. Effective removal of metal ions was demonstrated at pH values of 3.8–5.5. The adsorption isotherms were measured at 20 °C, using adsorptive solutions at the optimum pH value to determine the adsorption capacity. The Langmuir adsorption isotherm was used to describe observed sorption phenomena. The rise in temperature caused a slight decrease in the value of the equilibrium constant (K_c) for the sorption of metal ions. The mechanism for cations removal by the lignite includes ion exchange, complexation and sorption. The process is very efficient especially in the case of low concentrations of pollutants in aqueous solution, where common methods are either economically unfavorable or technically complicated.     

REACTIONS OF METHOXY-SUBSTITUTED AROMATIC COAL MOOELS IN SUPERCRITICAL SOLVENTS

Abstract

Reactions of α- and β-methoxy naphthalene and anisole in supercritical benzene and toluene were studied at 420 °C and 3.9-4.4 MPa pressure. The decomposition of these lower rank coal related model compounds in both solvents was found to obey the first order rate law. While naphthols were present in the reaction mixture of methoxy naphthalenes, phenol and cresoles were present in that of anisole. In addition to these products, diphenyl or dibenzyl was also present in the reaction mixture of supercritical benzene or toluene, respectively. The reactions between models and solvents might be explained by free radical and intermolecular rearrangement reaction pathways.     

EURAMET Project to Examine Underlying Parameters in Radiance Temperature Scale Realization, 156\,^{\circ }\mathrm{C} to 1000\,^{\circ }\mathrm{C}

Over the medium temperature range (from \(156\,^{\circ }\mathrm{C}\) to \(1000\,^{\circ }\mathrm{C}\) ), radiation thermometry is usually established within a national metrology institute (NMI) by means of variable temperature blackbody radiation sources, whose temperature is determined using a platinum resistance thermometer or thermocouple, calibrated in terms of the International Temperature Scale of 1990 (ITS-90), positioned in close proximity to the back radiating surface of the blackbody. It is also reasonably common to establish a scale using a suitable radiation thermometer, such as an indium gallium arsenide (InGaAs) detector-based narrow band radiation thermometer, calibrated using a number of fixed-point blackbody sources from the indium (In) to silver (Ag) (or copper (Cu)) points, with the calibration results fitted using a parameterized Planckian interpolation function. During 2007 and 2008, two InGaAs-based radiation thermometers were circulated around seven NMIs within the European Association of National Metrology Institutes (EURAMET) region in order to undertake a comparison of parameters necessary for radiation thermometry over the medium temperature range. Measurements were made of the size-of-source effect and gain (range) ratios of the two thermometers along with an assessment of the effect of changes in the ambient temperature and humidity on the thermometer output. The thermometers were also calibrated using fixed-point and/or variable temperature blackbody sources at each institute. A brief overview of the results obtained by this project is presented in this paper.     

Fermentation and oxygen transfer characteristics in serine alkaline protease production by recombinant Bacillus subtilis in molasses‐based complex medium

Serine alkaline protease (SAP) production in a complex medium based on physically pretreated molasses by recombinant Bacillus subtilis carrying pHV1431::subC gene is described. The effects of oxygen transfer were investigated in 3.5 dm³ bioreactor systems with controls for agitation rate, dissolved oxygen, pH, temperature, and foam formation under two different agitation rates, ie N = 500 and 750 min^?1, and four different air flow rates, ie Q/V_R = 0.2, 0.5, 0.7, and 1.0 vvm, at a molasses concentration equivalent to initial sucrose concentration (C_So) of 20 kg m^?3. The yield values (Y_X/S, Y_X/O, Y_S/O) and maintenance coefficient of oxygen (m_O), were calculated. m_O decreased with the increase in the air‐inlet rate. Increase in oxygen transfer rate increased the rate of growth and SAP activity, and affected the cultivation time to achieve maximum expression of SAP activity. At Q/V_R = 0.5 vvm and N = 750 min^?1, SAP activity reached 2250 U cm^?3 at t = 36 h. The oxygen transfer coefficient (K_La) and oxygen uptake rate (?r_O) were measured throughout the fermentations and their variation with the oxygen transfer conditions determined. New correlations for the calculation of K_La and ?r_O are proposed. Copyright © 2004 Society of Chemical Industry     

Water and water vapor sorption studies in polypropylene–zeolite composites

Water and water vapor sorption to porous polypropylene–zeolite composites prepared by hot pressing have been studied as a function of zeolite loading. This work presents the first report on the effect of the zeolite as a filler on the water‐sorption properties of PP composites. Water swelling experiments were conducted at 25°C using pure PP and PP–zeolite films samples having different zeolite loadings (6–40 wt %). Because PP is a hydrophobic polymer, it does not sorp any water, but the composites having 10, 20, 30, and 40% zeolites have sorbed 0.63, 1.00, 1.72 and 3.74% water, respectively. The zeolite itself at the same conditions sorbed 24.5% water. As the filler loading in the composites increased, equilibrium uptake values increased also. On the other hand, water vapor sorption and kinetics has been studied using a Cahn 2000 gravimetric sorption system. Within in the range of 0.35–0.95% water vapor was adsorbed by the composites containing 10–40 wt % zeolites. Experimental effective water vapor diffusivities of the composite films was about one order of magnitude higher (10‐fold) than the experimental water diffusion coefficient in composites. The transport of water in composites was slower than that in the liquid water due to the longer diffusion pathway and adsorption on the surface of the composites. Although the liquid water may fill all the voids in the composite, water vapor is adsorbed on the surface of the zeolite only. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3069–3075, 2003     

Chromium(VI) Adsorption by Brown Coals

The ability of brown coals (leonardites) to remove chromium(VI) from aqueous solutions was studied as a function of pH, contact time, adsorbent nature, and concentration of metal solutions. The adsorption of Cr(VI) was higher between pH 2.0 and 3.0 for all brown coals and maximum sorption was observed at pH 3.0. The Langmuir adsorption isotherm was used to describe observed sorption phenomena, and the constants were evaluated. The maximum adsorption capacity of 0.92 mmol of Cr(VI)/g for YK, 0.98 mmol of Cr(VI)/g for KK was found from experimental data. KK was the best among the selected adsorbents for the sorption of Cr(VI) at pH 3 and the sorption was 81% out of 100 ppm Cr(VI) after 120 min of stirring.     

Hexavalent chromium removal by Osage Orange

This study explores the sorption potential of Osage Orange (Maclura Pomifera) for the removal of Cr(VI) ion. The influence of contact time, solution pH, initial metal concentration, amount of biosorbent and ionic strength on the removal of Cr(VI) ion was studied. The biosorption of Cr(VI) with pulp and peel was investigated in a batch arrangement. The initial and equilibrium concentrations of Cr(VI) ions in aqueous phase were determined by spectrophotometry. The sorption process was pH and concentration dependent. The sorption of Cr(VI) ions increased with a decreasing pH until pH 2. The increase in initial Cr(VI) ions concentration in aqueous phase increased the sorption. The sorption data fitted well with the Langmuir sorption model within the concentration range studied. The observed maximum biosorption capacity by Langmuir sorption model at pH of 2 for M. Pomifera pulp was 0.92 mmol of Cr(VI)/g and for M. Pomifera peel was 0.55 mmol of Cr(VI)/g.