Soil engineering in vivo: harnessing natural biogeochemical systems for sustainable,multi-functional engineering solutions

Carbon sequestration, infrastructure rehabilitation, brownfields clean-up, hazardous waste disposal, water resources protection and global warming—these twenty-first century challenges can neither be solved by the high-energy consumptive practices that hallmark industry today, nor by minor tweaking or optimization of these processes. A more radical, holistic approach is required to develop the sustainable solutions society needs. Most of the above challenges occur within, are supported on, are enabled by or grown from soil. Soil, contrary to conventional civil engineering thought, is a living system host to multiple simultaneous processes. It is proposed herein that ‘soil engineering in vivo’, wherein the natural capacity of soil as a living ecosystem is used to provide multiple solutions simultaneously, may provide new, innovative, sustainable solutions to some of these great challenges of the twenty-first century. This requires a multi-disciplinary perspective that embraces the science of biology, chemistry and physics and applies this knowledge to provide multi-functional civil and environmental engineering designs for the soil environment. For example, can native soil bacterial species moderate the carbonate cycle in soils to simultaneously solidify liquefiable soil, immobilize reactive heavy metals and sequester carbon—effectively providing civil engineering functionality while clarifying the ground water and removing carbon from the atmosphere? Exploration of these ideas has begun in earnest in recent years. This paper explores the potential, challenges and opportunities of this new field, and highlights one biogeochemical function of soil that has shown promise and is developing rapidly as a new technology. The example is used to propose a generalized approach in which the potential of this new field can be fully realized.     

Viscosity of aqueous NaCl solutions in the temperature range 25–200 °C and in the pressure range 0.1–30 MPa

New precise viscosity data are presented for aqueous solutions of NaCl; these data cover the temperature range 25–200 °C, the pressure range 0.1–30 MPa, and the concentration range 0–6 mol · kg^–1. The experimental precision is ±0.5%; a comparison of the present results with data available in the literature indicates that the accuracy of the present data is also of the order of ±0.5%. Two empirical correlations that reproduce the data within the precision are also given.     

Photoluminescence of n-GaN: Influence of chemical treatment of the surface using sulfide solutions

Results are presented of the photoluminescence of n-GaN (T=300 K) after chemical treatment of the surface using solutions of inorganic sulfides (Na₂S and (NH₄)₂S) in water or isopropanol. It is shown that the maximum intensity of the photoluminescence spectrum of n-GaN increases after chemical treatment of the surface using alcohol solutions of sulfides and this increase is greater for solutions of the strong-base sulfide Na₂S compared with the weak-base sulfide (NH₄)₂S. Pis’ma Zh. Tekh. Fiz. 24, 90–93 (December 26, 1998)     

Assessing the impact of alternative continuous improvement programmes in a flow shop using system dynamics

We use a system dynamics simulation model based on the Factory Physics perspective to study the cumulative effect of continuous improvement in arrival variability, process variability, defect rate, time to failure, repair time and set-up time on operating curves in a flow-shop environment. We find that small, simultaneous improvements at multiple locations in the line can provide reductions in cycle time comparable to, or sometimes superior to, those obtained by a major improvement at a single location. The reduction of process variability is often an excellent alternative to reducing the mean of a parameter, because process variability at a given station affects not only that station, but all downstream stations due to its impact on flow variability. Improvements at non-bottleneck stations also have significant benefits, again by reducing the variability of flow to the bottleneck station. These results suggest a broader interpretation of some aspects of the Theory of Constraints, and help explain the successful results of the Toyota Production System.     

Studies of the corrosion inhibition of copper in sodium chloride solutions using chemical and electrochemical measurements

The inhibiting effects of 2-mercapto-4-amino-5-nitroso-6-hydroxy pyrimidine (MAP) at various concentrations on the copper corrosion in 3.5% NaCl solutions at 25 °C are examined. The inhibiting efficiency of MAP is evaluated from weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and electrochemical frequency modulation (EFM) measurements. Experimental investigations showed that MAP reduces markedly the copper corrosion in 3.5% NaCl solutions, and this reduction in corrosion rates enhances with increasing concentration of this compound. The results obtained from the different corrosion evaluation techniques are in good agreement. Polarization curves indicate that MAP is a mixed-type inhibitor. The results of EIS indicate that the value of CPEs tends to decrease and both charge transfer resistance and inhibition efficiency tend to increase by increasing the inhibitor concentration. EFM can be used as a rapid and non-destructive technique for corrosion rate measurements without prior knowledge of Tafel constants.     

Effect of a phase-transfer catalyst on the chemical modification of poly(vinyl chloride) by substitution with thiocyanate as a nucleophile

This study examined the effect of the phase-transfer catalysts tetrabutylammonium bromide (TBAB) and tetrabutylammonium hydrogen sulfate (TBAHS) on the chemical modification of poly(vinyl chloride) (PVC) by substitution with thiocyanate as a nucleophile. TBAB accelerated the dechlorination of PVC in SCN/ethylene glycol (EG) solution. Furthermore, the addition of TBAB to SCN/EG solution improved the substitution of the Cl in PVC with SCN in solution. The addition of TBAB or TBAHS to SCN/H₂O solution promoted the dechlorination of PVC, whereas dechlorination did not occur without the catalyst. The catalysts preferred substitution to the elimination of HCl in SCN/H₂O solution, and TBAB was slightly superior to TBAHS in terms of the degree and selectivity of the substitution. The addition of nitrobenzene to SCN/H₂O solution with TBAB increased the degree of substitution. Consequently, phase-transfer catalysts, particularly TBAB, were very effective at promoting the substitution of Cl in PVC with SCN in solution.     

Functionality improvement of Nimesulide by eutectic formation with nicotinamide: Exploration using temperature-composition phase diagram

The aim of present work was to explore the temperature-composition phase diagram for detection of formation of a multi-component system. Fusion of model drug Nimesulide (NIM) and Nicotinamide (NIC) was prepared and evaluated for possible interaction using thermal analysis. Phase diagram and the appearance of single endotherm confirmed Eutectic formation with the molar ratio of 1:2 (NIM: NIC). Spray dried powder in same molar ratio showed improved functionality in terms of solubility (14 folds), dissolution (2 folds) in distilled water and drug content (92.27%). SEM study revealed that the particles of eutectic mixture were of nearly same size in all directions in shape with bigger particle size compared to the pure drug, which was responsible for its improved flow. The compressibility of prepared eutectic was greatly enhanced which was followed by formation of directly compressible tablets. FT-IR study explained the possibility of formation of hydrogen bond between both the components. Stability data proved the stable nature of the eutectic mixture as well as its prepared formulation. The study explained the way to prepare thermal phase diagram by taking solidus and liquidus points in DSC diagram, which was finally used as a confirmatory parameter for the formation of the eutectic. Simultaneous improvement in physicochemical and mechanical properties was highlighted.     

Improvement of the properties and electrical performance on TiCl4-based TiN film using sequential flow chemical vapor deposition process

Sequential flow chemical vapor deposition (SFCVD), utilizing TiCl₄/NH₃ as reactants and immediate NH₃ treatment after film deposition, is applied to produce TiN barrier films in the contact process. Secondary ion mass spectroscopy results indicate that the SFCVD TiN film can effectively block the diffusion of WF₆ into the underlying Ti layer during W deposition. NH₃ treatment immediately after film deposition causes SFCVD TiN films to be less contaminated with carbon than TiN films that are formed by metallic organic compounds chemical vapor deposition (MOCVD) and to contain less chlorine residue than conventional TiCl₄/NH₃ CVD TiN layers even at a low reaction temperature. According to the resistance measurement of Kelvin contacts, the SFCVD process yields a lower resistance and a more uniform distribution than the MOCVD or CVD process. Transmission electron microscopic observations demonstrate that WF₆ can diffuse through the MOCVD TiN to react with the underlying Ti layer, causing a rupture at the Ti/TiN interface and poor W adhesion. The SFCVD TiN can serve as a sufficient diffusion barrier against WF₆ penetration during W CVD deposition.     

Testing the asymptotic behaviour of shell elements—Part II: New limit tests: analytical solutions and the RFNS element case

The asymptotic behaviour of classical benchmark tests was investigated in the first part of this work. In the present second part, the behaviour of some new limit problems, recently proposed as being specifically applicable to benchmark testing of the asymptotic behaviour of shell elements, is analytically and numerically investigated. Exact analytical solutions are obtained based on Flugge's theory for cylindrical shells. These analytical solutions are used along with, and in comparison to, the corresponding solutions obtained earlier by symbolic calculus using the Reissner–Mindlin shell model. The reformulated four‐node shell (RFNS) element is employed in the numerical analyses in a parallel, supportive–comparative character, next to the analytical investigation of the asymptotic behaviour of the new limit tests. As with the case of the classical benchmark tests, in the course of the numerical investigation, the reliability and efficiency of the RFNS element is re‐confirmed in all cases of the new asymptotic tests. A good agreement with the boundary layers described analytically is obtained even in very thin shell element applications. The various load‐carrying mechanisms shown numerically to be active in the cases under investigation follow closely the analytical predictions. The energy components appear to be more sensitive to the modelling of boundary layers in cases of mixed mode problems. In several cases, the solutions obtained earlier by using symbolic calculus are shown to be inadequate. Copyright © 2002 John Wiley & Sons, Ltd.     

On accuracy improvement of microscopic stress/stress sensitivity analysis with the mesh superposition method for heterogeneous materials considering geometrical variation of inclusions

In this paper, a new method is proposed for improving accuracy of microscopic stress analysis/stress sensitivity analysis of heterogeneous materials considering a geometrical variation of inclusions using the mesh superposition method-based approach. In particular, the analysis, which considers a location variation of inclusions in heterogeneous materials with location change of a local mesh, is a target problem. This problem must be accurately solved for, eg, reliability evaluation with the multiscale stochastic stress analysis considering a microscopic geometrical variation of composites. The influence of a geometrical random variation of inclusions on the stress field is not negligible; further, a finite element mesh must be substantially updated for the evaluation of stress field for a significant realization. Therefore, the mesh superposition method based approach is adopted. In this paper, a problem point in the stress/stress sensitivity analysis considering the geometrical variation of inclusions when using the mesh superposition method is discussed, and improved approaches based on an improved formulation and a relocalization analysis are proposed. The proposed approaches are applied to a stress/stress sensitivity analysis of a heterogeneous material associated with a microstructure of composites. With the numerical results, effectiveness of the proposed approach is discussed.     

Structural and opto-electrical properties of the tin-doped indium oxide thin films fabricated by the wet chemical method with different indium starting materials

Tin-doped indium oxide (ITO) thin films were fabricated by the sol-gel spin-coating method with different indium precursor solutions synthesized from In(NO₃)₃ or InCl₃ (denoted as N-ITO and Cl-ITO, respectively). For both N-ITO and Cl-ITO thin films, the increase of mobility/conductivity and the reduction of carrier concentration with increasing annealing temperatures from 400 to 700 °C are related to the increase of crystallization/densification and the annihilation of oxygen vacancies. The refractive index (1.84 at λ = 550 nm), packing density (0.83), conductivity [(234 (Ω-cm)^− 1], and optical band gap (3.95 eV) of N-ITO thin films are higher than that of Cl-ITO thin films, which can be attributed to the higher densification, lower crystallinity, and more free charge carriers of N-ITO thin films. These properties make the indium nitrate-derived ITO thin films have better potential applications for some commercial products.     

Stress intensity factor computation using the method of fundamental solutions: mixed‐mode problems

The method of fundamental solutions is applied to the computation of stress intensity factors in linear elastic fracture mechanics. The displacements are approximated by linear combinations of the fundamental solutions of the Cauchy–Navier equations of elasticity and the leading terms for the displacement near the crack tip. Two algorithms are developed, one using a single domain and one using domain decomposition. Numerical results are given. Copyright © 2006 John Wiley & Sons, Ltd.     

Development and gamma scintigraphy evaluation of gastro retentive calcium ion-based oral formulation: an innovative approach for the management of gastro-esophageal reflux disease (GERD)

Calcium chloride is an essential calcium channel agonist which plays an important role in the contraction of muscles by triggering calcium channel. First time hypothesized about its role in the treatment of GER (gastro-esophageal reflux) and vomiting disorder due to its local action. There are two objectives covered in this study as first, the development and optimization of floating formulation of calcium chloride and another objective was to evaluate optimized formulation through gamma scintigraphy in human subjects. Gastro retentive formulation of calcium chloride was prepared by direct compression method. Thirteen tablet formulations were designed with the help of sodium chloride, HPMC-K4M, and carbopol-934 along with effervescing agent sodium bicarbonate and citric acid. Formulation (F8) fitted best for Korsmeyer–Peppas equation with an R² value of 0.993. The optimized formulation was radiolabelled with ^99mTc-99?m pertechnetate for its evaluation by gamma scintigraphy. Gastric retention (6?h) was evaluated by gamma scintigraphy in healthy human subjects and efficacy of present formulation confirmed in GER positive human subjects. Gamma scintigraphy results indicated its usefulness in order to manage GERD. Stability studies of the developed formulation were carried out as per ICH guidelines for region IV and found out to be stable for 24?months.     

Solution of potential flow problems by the modified method of fundamental solutions: Formulations with the single layer and the double layer fundamental solutions

This paper describes an application of the recently proposed modified method of fundamental solutions (MMFS) to potential flow problems. The solution in two-dimensional Cartesian coordinates is represented in terms of the single layer and the double layer fundamental solutions. Collocation is used for the determination of the expansion coefficients. This novel method does not require a fictitious boundary as the conventional method of fundamental solutions (MFS). The source and the collocation points thus coincide on the physical boundary of the system. The desingularised values, consistent with the fundamental solutions used, are deduced from the direct boundary element method (BEM) integral equations by assuming a linear shape of the boundary between the collocation points. The respective values of the derivatives of the fundamental solution in the coordinate directions, as required in potential flow calculations, are calculated indirectly from the considerations of the constant potential field. The normal on the boundary is calculated by parametrisation of its length and the use of the cubic radial basis functions with the second-order polynomial augmentation. The components of the normal are calculated in an analytical way. A numerical example of potential flow around a two-dimensional circular region is presented. The results with the new MMFS are compared with the results of the classical MFS and the analytical solution. It is shown that the MMFS gives better accuracy for the potential, velocity components (partial derivatives of the potential), and absolute value of the velocity as compared with the classical MFS. The results with the single layer fundamental solution are more accurate than the results with the double layer fundamental solution.     

Measurement of the thermal conductivity of KNO3-NaNO3 mixtures using a transient hot-wire method with a liquid metal in a capillary probe

The thermal conductivity of KNO₃-NaNO₃ mixtures was measured by a modified transient hot-wire method using liquid metal in a capillary as a heat source. The method was developed for measurements on electrically conducting liquids at high temperatures. Measurements were performed on pure NaNO₃ and its three mixtures with KNO₃ in the temperature range from 498 to 593 K.     

Detection of DEMP vapors using SnO2-based gas sensors: understanding of the chemical reactional mechanism

Tin dioxide-based gas sensors make it possible to detect diethyl methyl phosphonate vapors (DEMP). However, the responses present drifts that can be observed vs. time. Such a problem raises the question of the reliability of these devices. The results presented in this article are two-fold: first, they are concerned with the study of the thermal degradation of DEMP by thermal degradation in an oxidizing atmosphere, and second, they are involved in the characterization of the chemical degradation on the tin dioxide-based gas sensors. Gas chromatography and infrared spectroscopy shows that, from 300 °C on, the thermal degradation of DEMP leads to the formation of ethylene (gas phase) and ethyl methyl phosphonic acid (condensed phase). Given that thermal degradation may occur at the sensor's surface, which can reach temperatures as high as 500 °C, these results showed that responses obtained using the DEMP vapors are principally due to ethylene and the drift in the responses vs. time is probably due to the adsorption of phosphorous compounds to the sensor's surface. The aim of this article is to describe the reactional mechanism of the DEMP interaction at the surfaces of tin dioxide-based sensors for temperatures ranging from 200 to 500 °C.     

Determination of the out-of-plane tensile strength using four-point bending tests on laminated L-angle specimens with different stacking sequences and total thicknesses

Laminated composite materials are increasingly used for the design of aircraft primary structures subjected to complex 3D loadings. The delamination observed in curved parts ensuring the junction between the different perpendicular panels is one of the most critical failure mechanisms. The present article proposes a complete protocol to identify the out-of-plane tensile strength of specimens composed of unidirectional plies. Firstly, a method to design a four-point bending (4 PB) test on L-angle specimens has been proposed. Secondly, a test campaign on T700GC/M21 laminated L-angle specimens has been performed at ONERA. Thirdly, the analysis of these tests with different methods has been performed to demonstrate that such a test is relevant to determine the material out-of-plane tensile strength, which seems to be independent of the stacking sequence and of the total thickness of the specimen, thus allowing the use of this strength in a 3D failure criterion. Finally, the different advantages and drawbacks of 4 PB tests performed on curved beams are discussed.     

Comparison of surface passivation of crystalline silicon by a-Si:H with and without atomic hydrogen treatment using hot-wire chemical vapor deposition

We compared surface passivation of c-Si by a-Si:H with and without atomic hydrogen treatment prior to a-Si:H deposition. The atomic hydrogen is produced by hot-wire chemical vapor deposition (HWCVD). For this purpose, we deposited a-Si:H layers onto both sides of n-type FZ c-Si wafers and measured the minority carrier effective lifetime and implied V_OC for different H treatment times ranging from 5 s to 30 s prior to a-Si:H deposition. We found that increasing hydrogen treatment times led to lower effective lifetimes and implied V_OC values for the used conditions. The treatments have been performed in a new virgin chamber to exclude Si deposition from the chamber walls. Our results show that a short atomic hydrogen pretreatment is already detrimental for the passivation quality which might be due to the creation of defects in the c-Si. AFM measurements do not show any change in the surface roughness of the different samples.     

Effect of thermal annealing on the properties of a-SiCN:H films by hot wire chemical vapor deposition using hexamethyldisilazane

We investigated the effect of thermal annealing on the properties of a-SiCN:H films prepared by HWCVD using hexamethyldisilazane focusing on the change in the passivation quality. We found that annealing a-SiCN:H films at the temperature around 600 °C led to an effective hydrogen diffusion, resulting in the enhancement of the passivation effect. The performance of cast polycrystalline silicon solar cells using a-SiCN:H films showed a strong dependence on the contact firing temperature. The best efficiency of 13.75% was achieved at the firing temperature of 750 °C.