Modelling and simulation framework for reactive transport of organic contaminants in bed-sediments using a pure java object - oriented paradigm

Numerical modelling and simulation of organic contaminant reactive transport in the environment is being increasingly relied upon for a wide range of tasks associated with risk-based decision-making, such as prediction of contaminant profiles, optimisation of remediation methods, and monitoring of changes resulting from an implemented remediation scheme. The lack of integration of multiple mechanistic models to a single modelling framework, however, has prevented the field of reactive transport modelling in bed-sediments from developing a cohesive understanding of contaminant fate and behaviour in the aquatic sediment environment. This paper will investigate the problems involved in the model integration process, discuss modelling and software development approaches, and present preliminary results from use of CORETRANS, a predictive modelling framework that simulates 1-dimensional organic contaminant reaction and transport in bed-sediments

Adoption of unconventional approaches in construction: The case of cross-laminated timber

Achieving sustainable development requires the decoupling of economic growth from the use of non-renewable resources. This depends on industry adopting unconventional approaches to production. This research explores the root causes of barriers to the adoption of such approaches in the construction industry, and applies a behavioural model to assess whether companies are hindered by capability, opportunity or motivation. The long history of lowest-cost tendering in construction has led to a path-dependent lock-in to conventional market-driven objectives of cost and risk reduction; it is suggested that locked-in companies lack the commercial opportunity and hence motivation, rather than the capability, to adopt approaches perceived to increase cost or risk. Such companies will therefore tend to resist unconventional approaches, restricting the physical opportunity for other project participants. This theory is explored in a case study of first adoptions of cross-laminated timber (CLT) in UK projects, using a survey and series of semi-structured interviews. The case study found that project contexts created market niches. This provided designers, who were motivated to use CLT, the opportunity to promote its use in the project. CLT was seen as key to successful resolution of project constraints, thereby providing motivation to other project participants to adopt the material

Global life cycle paper flows, recycling metrics and material efficiency

Despite major improvements in recycling over the last decades, the pulp and paper sector is a significant contributor to global greenhouse gas emissions and other environmental pressures. Further reduction of virgin material requirements and environmental impacts requires a detailed understanding of the global material flows in paper production and consumption. This study constructs a Sankey diagram of global material flows in the paper life cycle, from primary inputs to end-of-life waste treatment, based on a review of publicly available data. It then analyses potential improvements in material flows and discusses recycling and material efficiency metrics. The article argues that the use of the collection rate as a recycling metric does not directly stimulate avoidance of virgin inputs and associated impacts. An alternative metric compares paper for recycling (recovered paper) with total fibrous inputs and indicates that the current rate is at just over half of the technical potential. Material efficiency metrics are found to be more useful if they relate to the reuse potential of wastes. The material balance developed in this research provides a solid basis for further study of global sustainable production and consumption of paper. The conclusions on recycling and efficiency should be considered for improving environmental performance assessment methods

Evolution of E2 transition strength in deformed hafnium isotopes from new measurements on 172^{172}Hf, 174^{174}Hf, and 176^{176}Hf

The available data for E2 transition strengths in the region between neutron-deficient Hf and Pt isotopes are far from complete. More and precise data are needed to enhance the picture of structure evolution in this region and to test state-of-the-art nuclear models. In a simple model, the maximum collectivity is expected at the middle of the major shell. However, for actual nuclei, this picture may no longer be the case, and one should use a more realistic nuclear-structure model. We address this point by studying the spectroscopy of Hf. We remeasure the 2^+_1 half-lives of 172,174,176Hf, for which there is some disagreement in the literature. The main goal is to measure, for the first time, the half-lives of higher-lying states of the rotational band. The new results are compared to a theoretical calculation for absolute transition strengths. The half-lives were measured using \gamma-\gamma and conversion-electron-\gamma delayed coincidences with the fast timing method. For the determination of half-lives in the picosecond region, the generalized centroid difference method was applied. For the theoretical calculation of the spectroscopic properties, the interacting boson model is employed, whose Hamiltonian is determined based on microscopic energy-density functional calculations. The measured 2^+_1 half-lives disagree with results from earlier \gamma-\gamma fast timing measurements, but are in agreement with data from Coulomb excitation experiments and other methods. Half-lives of the 4^+_1 and 6^+_1 states were measured, as well as a lower limit for the 8^+_1 states. We show the importance of the mass-dependence of effective boson charge in the description of E2 transition rates in chains of nuclei. It encourages further studies of the microscopic origin of this mass dependence. New data on transition rates in nuclei from neighboring isotopic chains could support these studies.Comment: 16 pages, 16 figures, 7 tables; Abstract shortened due to character limi

Modellierung von Quanteneffekten in einem ladungsbasierten MOS-Transistor-Modell zur Simulation von nanoskalierten CMOS-Analogschaltungen

Aufgrund der fortschreitenden Miniaturisierung der Bauelemente in CMOS-Schaltungen und den dadurch erreichten Strukturgrößen nehmen quantenmechanische Effekte zunehmenden Einfluss auf die Funktion von Transistoren und damit auf die gesamte Schaltung. Unter Einbeziehung der Energiequantisierung an der Si/SiO<sub>2</sub>-Grenzfläche wird untersucht, wie sich durch eine Modifikation der Beschreibung des Oberflächenpotenzials die Inversionsladung quantenmechanisch formulieren lässt. Im Hinblick auf den Entwurf und die Simulation von CMOS-Analogschaltungen wird dazu ein ladungsbasiertes MOS-Transistor-Modell zugrunde gelegt. Die sich daraus ergebenden Veränderungen für die Kapazitäten und die Inversionsladung werden dabei für die Modellierung des quasiballistischen Drain-Source-Stromes verwendet. Dazu wird innerhalb dieses Modells ein Streufaktor berechnet, mit dem nanoskalierte MOS-Transistoren mit einer Kanallänge von unter 20 nm simuliert werden können. Ausgehend von Parametern eines CMOS-Prozesses werden mit MATLAB die Einflüsse der quantenmechanischen Effekte bei der Skalierung des Transistors analysiert

Life cycle assessment of biomass densification systems

Several recent life cycle assessments (LCA) of biomass densification have been carried out. This paper reviews data from 19 sources with 48 case scenarios to assess the current status of LCA of biomass densification. It describes the specific units in a reference “gate-to-gate” LCA in relation to the existing studies, and summarises key differences between them. Finally, it provides a qualitative analysis of the associated sources of uncertainty. Existing LCA studies of biomass densification were found to provide insufficient and inconsistent information for full transparency and comparability, due to different choices in system boundary, functional unit, allocation procedure, densification technology and biomass residues. Most of the reviewed studies attributed most of the energy use and greenhouse gas (GHG) emissions to transportation, drying and densification. The energy and GHG emissions of the gate-to-gate densification system were highly sensitive to the technology, feed material used in densification and scale of production. Apart from one study with zero energy consumption as a result of the use of manual operations, the normalised values of energy consumption for the reviewed studies ranged from 20 to 900 kJ MJ-1. Neglecting three outlier values, GHG emissions as mass of CO2-eq for the reviewed studies ranged from 600 t MJ-1 to 50 g MJ-1. Similar variations in result and outlier cases have been reported for other bioenergy processes, by other authors. Assuming that the biggest impact of densification processes is on transport fuel use, and based on 5 studies that reported densification ratios, the net energy and GHG emissions savings resulting from densification ranged from 200 to 1000 kJ MJ-1 and 9 to 50 CO2-eq (g MJ-1), respectively. On this basis, it can be concluded that biomass densification is a worthwhile addition to the biomass energy conversion system. There is a need for more transparent reporting and analysis of uncertainty in the modelling, to better understand the wide variation in outcomes

Nonuniform friction-area dependency for antimony oxide surfaces sliding on graphite

Cataloged from PDF version of article.We present frictional measurements involving controlled lateral manipulation of antimony nanoparticles on graphite featuring atomically smooth particle-substrate interfaces via tapping- and contact-mode atomic force microscopy. As expected from earlier studies, the power required for lateral manipulation as well as the frictional forces recorded during the manipulation events exhibit a linear dependence on the contact area over a wide size range from 2000 nm2 to 120 000 nm2. However, we observe a significant and abrupt increase in frictional force and dissipated power per contact area at a value of about 20 000 nm2, coinciding with a phase transition from amorphous to crystalline within the antimony particles. Our results suggest that variations in the structural arrangement and stoichiometry of antimony oxide at the interface between the particles and the substrate may be responsible for the observed effect. © 2013 American Physical Society

Interdigitated back contact silicon heterojunction solar cells Towards an industrially applicable structuring method

We report on the investigation and comparison of two different processing approaches for interdigitated back contacted silicon heterojunction solar cells our photolithography based reference procedure and our newly developed shadow mask process. To this end, we analyse fill factor losses in different stages of the fabrication process. We find that although comparably high minority carrier lifetimes of about 4 ms can be observed for both concepts, the shadow masked solar cells suffer yet from poorly passivated emitter regions and significantly higher series resistance. Approaches for addressing the observed issues are outlined and first solar cell results with efficiencies of about 17 and 23 for shadow masked and photolithographically structured solar cells, respectively, are presente

Influence of chlorine on the fate of Pb and Cu during clinkerization

The fate of heavy metals during clinkerization is of crucial significance to the utilization of solid waste as fuels and raw materials in cement kiln producing clinker. A ternary system of clinker-heavy metal-chlorine was developed that is more coincident with the condition of co-processing of solid waste in cement kiln. The main goal of this study was to investigate the relationships among chlorine, volatilization and solidification of Cu/Pb, and mineral phases of the clinker during clinkirization. The AlCl3·6H2O (chlorine source) and PbO/CuO were mixed with cement raw meal in appropriate ratios to produce co-processed clinkers. The volatilization and solidification of Pb and Cu were investigated experimentally using a combination of atomic absorption spectrometry, electron probe micro-analysis, scanning electron microscopy with energy-dispersive X-ray spectroscopy, optical microscope, thermogravimetric and X-ray diffraction quantitative analyses. The volatilization ratios of Pb and Cu increased up to 46.18% and 34.04%, respectively, with increasing AlCl3·6H2O content up to 1.6%. comparing to the cement mixtures without AlCl3·6H2O addition (Pb and Cu volatilisation ratios are 49.90% and 27.21%, respectively). Pb and Cu oxides can be transformed into Pb and Cu chlorides, that are not stable and have high vapor pressure. Pb and Cu are mainly concentrated in the interstitial phases of the clinker. The addition of AlCl3·6H2O led to increase the crystal size of alite and belite. X-ray diffraction quantitative analyses proved that the content of silicate phase increased with the corresponding content of interstitial phases decreased during clinkerization with the addition of AlCl3·6H2O, that decreased the ability of clinker to solidify Pb and Cu in the produced clinkers. This research can help to promote understanding of the fate of heavy metals during the cement kiln co-processing of solid wastes and meaningfully for energy conservation and sustainable development