Model-based approach to study the impact of biofuels on the sustainability of an ecological system

The importance and complexity of sustainability have been well recognized and a formal study of sustainability based on system theory approaches is imperative as many of the relationships between various components of the ecosystem could be nonlinear, intertwined and non-intuitive. A mathematical model capable of yielding qualitative inferences can serve as an important tool for policy makers as it can be simulated under various important scenarios and also help in evaluating different strategies and technologies. In this article, we consider a simplified ecological food web which comprises a macro-economic system, an industrial production sector, an energy generation sector, and elements of a human society along with a rudimentary legal system. The energy sector is designed to supply energy to the other components of the ecosystem either by using a finite, non-renewable energy source or by a combination of non-renewable source and biomass. Many of the components of the ecosystem depend directly or indirectly on the biomass used for energy production. Subsequently, this model is used to study the impact of using biomass for the production of energy on the sustainability of other components of ecosystem. We have also simulated the model under two commonly foreseen scenarios of population explosion and consumption increase to understand the effect of using biomass for the production of energy on the sustainability of the various components of the system.     

Oxygen Absorption in Free-Standing Porous Silicon: A Structural, Optical and Kinetic Analysis

Porous silicon (PSi) is a nanostructured material possessing a huge surface area per unit volume. In consequence, the adsorption and diffusion of oxygen in PSi are particularly important phenomena and frequently cause significant changes in its properties. In this paper, we study the thermal oxidation of p ⁺-type free-standing PSi fabricated by anodic electrochemical etching. These free-standing samples were characterized by nitrogen adsorption, thermogravimetry, atomic force microscopy and powder X-ray diffraction. The results show a structural phase transition from crystalline silicon to a combination of cristobalite and quartz, passing through amorphous silicon and amorphous silicon-oxide structures, when the thermal oxidation temperature increases from 400 to 900 °C. Moreover, we observe some evidence of a sinterization at 400 °C and an optimal oxygen-absorption temperature about 700 °C. Finally, the UV/Visible spectrophotometry reveals a red and a blue shift of the optical transmittance spectra for samples with oxidation temperatures lower and higher than 700 °C, respectively.     

Synthesis, characterization and electrochemical properties of copper phosphide (Cu3P) thick films prepared by solid-state reaction at low temperature: a probable anode for lithium ion batteries

Copper phosphide (Cu₃P) was produced as thick films over copper foils. The synthesis was performed by solid-state reaction at low temperature (400 °C). Similar attempts were carried out for other transition metals of the first series without success. Scanning electron microscopy (SEM) revealed the formation mechanism of the Cu₃P thick films. First, phosphorus diffuses into the copper foil followed by the subsequent formation of the binary compound. During this process, the Cu₃P particles seem to dig the copper foil, producing holes, where the Cu₃P crystallites nucleate and growth. Then, the thick films are formed by the conjugation of several agglomerates and their morphology is not homogeneous. Oxidation of Cu₃P occurs to a small extend on the top surface of the films. The electrochemical behaviour of the thick film was compared with a standard Cu₃P composite electrode, in which the active material is mixed with carbon and a binder. Although the two different electrodes presented some differences in their electrochemical behaviour, both electrodes showed promising qualities to be used as anode materials in lithium ion batteries or hybrid devices.     

调查能证实猜疑和揭示令人惊讶的问题

各地区的受访者都指出了工作量增大及缩短设计周期以将产品推向市场的问题. 我们EDN每年都要开展几项重大的调查.我们通过这些调查来对以后要报导的内容、以及如何向读者和网友提供信息等做出决策.每隔18个到24个月,就进行一次名为"工程师所关注的问题"的调查.该调查旨在了解读者所从事工作、工作压力、流行的可行技术、工程学科技能及信息资源和互连网使用等.整个调查的量十分大,但在这里我将展示几个选段给读者,在未来的栏目中也许会刊登更多选段.     

从以太中提取能量并为轻便系统供电的采集器 热、振动和射频源都具有为低功耗设备供电的潜力

世上没有免费的午餐,你的父母可能是这么教你的.当然,我们不可能从稀薄的空气中取得能量,是吗?但事实上,人体,工厂机器,各种型号的收音机,以及很多其它东西都在以热、振动或射频电波形式辐射能量.     

Kraft pulping of Drimys winteri wood chips biotreated with Ganoderma australe

Drimys winteri, a native hardwood from Chile, presents some interesting characteristics that make it suitable for the pulp and paper industry. In this work, the potential of D winteri for the conventional kraft and biokraft pulp production was evaluated. For biokraft pulping, wood chips were biotreated with the white‐rot fungus Ganoderma australe. During the biotreatment, a selective pattern of biodelignification was observed and the wood chips biotreated for 15, 30 and 45 days were submitted to kraft cooking. At low cooking severity (H‐factor below 1500 h^?1, 15% active alkali and 25% sulfidity), all biopulps presented lower kappa numbers than control pulps and approximately the same screened pulp yield. Biopulps were easily refined in a PFI mill, requiring less PFI revolutions to achieve the same fibrillation degree. The strength properties of the biopulps were similar to those of the control pulps. Copyright © 2005 Society of Chemical Industry     

Mechanical and UV‐shielding properties of in situ synthesized poly(acrylonitrile‐butadiene‐styrene)/zinc oxide nanocomposites

A series of poly(acrylonitrile‐butadiene‐styrene)/ZnO nanocomposites with different ZnO nanoparticles content were synthesized by a mass‐suspension polymerization process. Nanocomposites obtained through this technique presented high impact resistance despite the presence of agglomerates for high ZnO nanoparticles content so that, these samples were subjected to twin‐screw extrusion. The extrusion led to a dramatic morphological change and increased in impact resistance, higher than 100% in most of the cases. On the other hand, the higher the ZnO content, the higher the UV blocking (>95% for 1 and 3% of ZnO) for both materials, before and after extrusion. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of the Eu3+ Addition on Photoluminescence and Microstructure of ZnO–CdO–TeO2 Glasses

In this work, the role of europium doping of glasses formulated in the ternary system ZnO–CdO–TeO₂ is described. The Eu‐doped oxide glasses were prepared by the conventional melt‐quenching method and by using three different compositions. Structural studies reveal that there exists a good affinity between Cd and some rare earth (RE) ions to form the crystalline phase. The X‐ray diffraction (XRD) diagrams display that the structure of these glasses is amorphous and with the increase in CdO content and the compatibility of Eu³⁺, there is a tendency to form nanocrystals of CdTe₂O₅. The scanning electron microscopic (SEM) observation of their microstructure confirms the presence of phase separation. Differential thermal analysis (DTA) of these glasses showed small exothermic peaks noted around 450°C for the V2 glass and 480°C for V1 and V3 glasses, which could be attributed to the formation of these crystals. The infrared spectra showed a main absorption band around 800–600 cm^?1 corresponding to the Te–O stretching mode in TeO₄ and TeO₃ groups. By optical absorption (OA), the band gap (E_g) for each glass was determined; these values were 3.27, 3.14, and 3.3 eV for the V1–V3 glasses, respectively. Furthermore, the presence of Eu³⁺ was detected in the 370–470 nm short‐range wavelengths. The photoluminescence (PL) experiments of the glasses showed light emission due to the following transitions: ⁵D₀ → ⁷F₁, ⁵D₀ → ⁷F₂, ⁵D₀ → ⁷F₃, and ⁵D₀ → ⁷F₄.