Assessing resource intensity and renewability of cellulosic ethanol technologies using eco-LCA

Recognizing the contributions of ecosystem services and the lack of their comprehensive accounting in life cycle assessment (LCA), an in-depth analysis of their contribution in the life cycle of cellulosic ethanol derived from five different feedstocks was conducted, with gasoline and corn ethanol as reference fuels. The relative use intensity of natural resources encompassing land and ecosystem goods and services by cellulosic ethanol was estimated using the Eco-LCA framework. Despite being resource intensive compared to gasoline, cellulosic ethanol offers the possibility of a reduction in crude oil consumption by as much as 96%. Soil erosion and land area requirements can be sources of concern for cellulosic ethanol derived directly from managed agriculture. The analysis of two broad types of thermodynamic metrics, namely: various types of physical return on investment and a renewability index, which indicate competitiveness and sustainability of cellulosic ethanol, respectively, show that only ethanol from waste resources combines a favorable thermodynamic return on investment with a higher renewability index. However, the production potential of ethanol from waste resources is limited. This finding conveys a possible dilemma of biofuels: combining high renewability, high thermodynamic return on investment, and large production capacity may remain elusive. A plot of renewability versus energy return on investment is suggested as one of the options for providing guidance on future biofuel selection.     

Sintering aid (ZnO) effect on proton transport in BaCe0.35Zr0.5Y0.15O3-δ and electrode phenomena studied by distribution function of relaxation times

In this work, we have employed an evolutionary programming technique to analyse the impedance spectroscopy (IS) of a ceramic proton conductor BaCe_0.35Zr_0.5Y_0.15O_3-δ (BCZY) to study its proton transport properties as well as the electrode reactions kinetics at the Pt|BCZY interface. The distribution functions of relaxation times (DFRT) obtained from the impedance analysis were used to evaluate the physical parameters such as relaxation time constant, resistance, reactance/capacitance, conductivities, activation energies, grain-boundary space charge potential Φ(0, T), and electrode polarization resistance. The effect of ZnO sintering aid (2 wt%) on charge-transfer processes at bulk, grain boundaries and Pt|BCZY interface were thoroughly studied. Φ(0, T) is increased and grain-boundary conductivity (σ_gb) is decreased by an order of magnitude due to the presence of Zn at the grain boundaries, whereas bulk properties appear to be unchanged. Variation in σ_gb with temperature is explained by correlating the grain-boundary capacitance (C_gb), relaxation time (τ_gb), space charge effect, and the defect associations (eg, Y-OH). The anodic functions, for example, hydrogen oxidation kinetics at the electrode (Pt) surface and Pt-BCZY interface, are explained through the symmetrical cell study and the behavior of relaxation time constants (τ) with temperature.     

Stable and extension class theory for logic programs and default logics

The stable model semantics (cf. Gelfond and Lifschitz [1]) for logic programs suffers from the problem that programs may not always have stable models. Likewise, default theories suffer from the problem that they do not always have extensions. In such cases, both these formalisms for non-monotonic reasoning have an inadequate semantics. In this paper, we propose a novel idea-that of extension classes for default logics, and of stable classes for logic programs. It is shown that the extension class and stable class semantics extend the extension and stable model semantics respectively. This allows us to reason about inconsistent default theories, and about logic programs with inconsistent completions. Our work extends the results of Marek and Truszczynski [2] relating logic programming and default logics.     

COMBINING KNOWLEDGE BASES CONSISTING OF FIRST-ORDER THEORIES

Consider the construction of an expert system by encoding the knowledge of different experts. Suppose the knowledge provided by each expert is encoded into a knowledge base. Then the process of combining the knowledge of these different experts is an important and nontrivial problem. We study this problem here when the expert systems are considered to be first-order theories. We present techniques for resolving inconsistencies in such knowledge bases. We also provide algorithms for implementing these techniques.     

Introduction: Logic programming, non-monotonicreasoning and reasoning about actions

On November 5, 1995, a special symposium on logic programming, non-monotonic reasoning and reasoning about actions, in honor of the 50th birthday of Professor Michael Gelfond, was held in El Paso, Texas. It was the first symposium of the El Paso Shell Oil Symposium series, jointly sponsored by the Shell Oil Company and by the University of Texas at El Paso. Overall, 16 talks were presented by researchers from the USA (New Mexico State University, Southern Methodist University, Stanford University, Syracuse University, University of Texas at Austin, and University of Texas at El Paso), Canada, and Finland. This issue contains the (peer-refereed) proceedings of this symposium. We are happy to present this collection to our readers, and we want to thank all those without whom this publication would not be possible: Shell Oil and the University of Texas at El Paso for generous support; the authors and all the participants of the symposium for their contributions; the referees for their tireless work; Martin Golumbic, the Editor-in-Chief of the Annals of Mathematics and Artificial Intelligence, for the opportunity to publish the proceedings as an issue of this journal; and, last but not the least, Michael Gelfond for being a wonderful person, a brilliant researcher, a good friend, and an inspiring teacher. This revised version was published online in June 2006 with corrections to the Cover Date.     

使用双极晶体管进行锂离子电池充电

序言 随着便携式手持设备(如手机、PDA等)的功能不断增加,加上对较小体积与更长电池寿命的要求,使得锂电池成为许多此类设备的首选供电能源.本文将讨论线性充电技术与相关的离散调节元件,并重点讨论主要离散参数与选择标准.     

Seasonal influence on urban dust PAH profile and toxicity in Sydney, Australia

Road dust is one of the major threats to the urban environment due to wash-off of dust to the surrounding catchments during wet weather period. The dust contains wide range of toxic contaminants such as heavy metals, polycyclic aromatic hydrocarbons (PAHS) and endocrine disrupting chemicals. Among the toxic contaminants, PAHs are of environmental concern due to their potential carcinogenic and mutagenic effect besides endocrine disruptive behaviour. Eighteen road dust samples from Sydney were collected in different time periods for a year and analysed for 16 US EPA PAHS. Total PAHs content range in the dust was 9-105 pg/g. Total and individual PAH contents were highest in the finest size fraction (<75 microm) and in winter compared to the other seasons. The PAH profiles in the different particle sizes were similar but different between the four seasons. The concentrations of higher molecular weight PAHS (4- and 5-rings) were much greater than the concentrations of lower molecular weight PAHs (2- and 3-rings). Toxicity equivalency factor application showed that the longer the dry weather period the higher the total PAHs content and toxicity in the dust.     

Ionic Transport Properties in Nanocrystalline Ce0.8A0.2O2-δ (with A = Eu,Gd, Dy,and Ho) Materials

The ionic transport properties of nanocrystalline 20 mol% Eu, Gd, Dy, and Ho doped cerias, with average grain size of around 14 nm were studied by correlating electrical, dielectric properties, and various dynamic parameters. Gd-doped nanocrystalline ceria shows higher value of conductivity (i.e., 1.8 × 10⁻⁴ S cm⁻¹ at 550°C) and a lower value of association energy of oxygen vacancies with trivalent dopants Gd³⁺ (i.e., 0.1 eV), compared to others. Mainly the lattice parameters and dielectric constants (ε_∞) are found to control the association energy of oxygen vacancies in these nanomaterials, which in turn resulted in the presence of grain and grain boundary conductivity in Gd- and Eu-doped cerias and only significant grain interior conductivity in Dy- and Ho-doped cerias.     

Attribute based specification, comparison and selection of feed stock for anaerobic digestion using MADM approach

Organic wastes are common in nature and generated at different sources which need to be treated before disposing into the environment. Anaerobic digestion (AD) process is a primary technique used for digestion and reduction of the ill effects of disposing the organic waste. Selection of appropriate feed stock for anaerobic digestion among the available options is a primary concern and the process efficiency and stability largely depend on this. The present paper describes a methodology for evaluation, comparison, ranking and optimum selection of a feed stock for anaerobic digestion. A 30 attribute coding scheme is proposed to evaluate the existing alternatives for feed stock of anaerobic digester. A three stage procedure which includes the elimination search is proposed to evaluate the available alternatives with the help of attributes quickly. Technique for order preference by similarity to ideal solution (TOPSIS) is a Multiple Attribute Decision Making (MADM) approach and graphical methods namely line graph and spider diagrams are used for optimum selection of feed stock among the available options. MATLAB code is written to execute the three stage procedure. The proposed methodology is explained through an illustrated example.     

Controlled Fabrication of PbS Quantum‐Dot/Carbon‐Nanotube Nanoarchitecture and its Significant Contribution to Near‐Infrared Photon‐to‐Current Conversion

A solution‐processed nanoarchitecture based on PbS quantum dots (QDs) and multi‐walled carbon nanotubes (MWCNTs) is synthesized by simply mixing the pre‐synthesized high‐quality PbS QDs and oleylamine (OLA) pre‐functionalized MWCNTs. Pre‐functionalization of MWCNTs with OLA is crucial for the attachment of PbS QDs and the coverage of QDs on the surface of MWCNTs can be tuned by varying the ratio of PbS QDs to MWCNTs. The apparent photoluminescence (steady‐state emission and fluorescence lifetime) “quenching” effect indicates efficient charge transfer from photo‐excited PbS QDs to MWCNTs. The as‐synthesized PbS‐QD/MWCNT nanoarchitecture is further incorporated into a hole‐conducting polymer poly(3‐hexylthiophene)‐(P3HT), forming the P3HT:PbS‐QD/MWCNT nanohybrid, in which the PbS QDs act as a light harvester for absorbing irradiation over a wide wavelength range of the solar spectrum up to near infrared (NIR, ≈1430 nm) range; whereas, the one‐dimensional MWCNTs and P3HT are used to collect and transport photoexcited electrons and holes to the cathode and anode, respectively. Even without performing the often required “ligand exchange” to remove the long‐chained OLA ligands, the built nanohybrid photovoltaic (PV) device exhibits a largely enhanced power conversion efficiency (PCE) of 3.03% as compared to 2.57% for the standard bulk hetero‐junction PV cell made with P3HT and [6,6]‐Phenyl‐C₆₁‐Butyric Acid Methyl Ester (PCBM) mixtures. The improved performance of P3HT:PbS‐QD/MWCNT nanohybrid PV device is attributed to the significantly extended absorption up to NIR by PbS QDs as well as the effectively enhanced charge separation and transportation due to the integrated MWCNTs and P3HT. Our research results suggest that properly integrating QDs, MWCNTs, and polymers into nanohybrid structures is a promising approach for the development of highly efficient PV devices.