1,359 research outputs found
A pilot-scale trial comparing mesophilic and thermophilic digestion for the stabilisation of source segregated kitchen waste
No full textSource segregated food waste was collected from domestic properties and its composition determined together with the average weight produced per household, which was 2.91 kg per week. The waste was fed over a trial period lasting 58 weeks to an identical pair of 1.5 m3 anaerobic digesters, one at a mesophilic (36.5 oC) and the other at a thermophilic temperature (56 oC). The digesters were monitored daily for gas production, solids destruction and regularly for digestate characteristics including alkalinity, pH, volatile fatty acid (VFA) and ammonia concentrations. Both digesters showed high VFA and ammonia concentrations but in the mesophilic digester the pH remained stable at around 7.4, buffered by a high alkalinity of 13,000 mg l-1; whereas in the thermophilic digester VFA levels reached 45,000 mg l-1 causing a drop in pH and digester instability. In the mesophilic digester volatile solids (VS) destruction and specific gas yield were favourable, with 67% of the organic solids being converted to biogas at a methane content of 58% giving a biogas yield of 0.63 m3 kg-1 VS added. Digestion under thermophilic conditions showed potentially better VS destruction at 70% VS and a biogas yield of 0.67 m3 kg-1 VS added, but the shifts in alkalinity and the high VFA concentrations required a reduced loading to be applied. The maximum beneficial loading that could be achieved in the mesophilic digester was 4.0 kg VS m-3 d-1
Investigation of the role of cadmium sulfide in the surface passivation of lead sulfide quantum dots
No full textSurface passivation of PbS nanocrystals (NC), resulting in strong photoluminescence, can be achieved by the introduction of CdS precursors. The role of CdS in the surface passivation of PbS NCs is uncertain, as the crystalline structure of CdS and PbS are different, which should impede effective epitaxial overgrowth. Absorption spectroscopy is used to show that the CdS precursors strongly interact with the PbS NC surface. Electron microscopy reveals that the introduction of CdS precursors results in an increased particle size, consistent with overcoating. However, we also find the process to be highly non-uniform. Nevertheless, evidence for epitaxial growth is found, suggesting that effective surface passivation may be possible
A pilot-scale comparison of mesophilic and thermophilic digestion of source segregated domestic food waste
No full textSource segregated food waste was collected from domestic properties and its composition determined together with the average weight produced per household, which was 2.91 kg per week. The waste was fed over a trial period lasting 58 weeks to an identical pair of 1.5 m3 anaerobic digesters, one at a mesophilic (36.5°C) and the other at a thermophilic temperature (56°C). The digesters were monitored daily for gas production, solids destruction and regularly for digestate characteristics including alkalinity, pH, volatile fatty acid (VFA) and ammonia concentrations. Both digesters showed high VFA and ammonia concentrations but in the mesophilic digester the pH remained stable at around 7.4, buffered by a high alkalinity of 13,000 mg l-1; whereas in the thermophilic digester VFA levels reached 45,000 mg l-1 causing a drop in pH and digester instability. In the mesophilic digester volatile solids (VS) destruction and specific gas yield were favourable, with 67% of the organic solids being converted to biogas at a methane content of 58% giving a biogas yield of 0.63 m3 kg-1 VSadded. Digestion under thermophilic conditions showed potentially better VS destruction at 70% VS and a biogas yield of 0.67 m3 kg-1 VSadded, but the shifts in alkalinity and the high VFA concentrations required a reduced loading to be applied. The maximum beneficial loading that could be achieved in the mesophilic digester was 4.0 kg VS m-3 d-1
Metalorganic chemical vapor deposition of GaAsN epilayers: microstructures and optical properties
No full textIn this article, we investigate the parameters used in the MOCVD growth of GaAsN epilayers on GaAs substrates and some of their microstructures and optical properties. The N incorporation was found to mainly depend on the growth temperature and the fractional 1,1-dimethylhydrazine molar flow. A thin highly strained interface layer was observed between GaAsN and GaAs, which, contrary to previously published results, was not N enriched. The low-temperature (10 K) photoluminescence spectra were composed of several emissions that we attribute to a combination of interband transition and transitions involving localized defect states. (C) 2004 Elsevier B.V. All rights reserved
Allen C. Jones Camp of the United Confederate Veterans in Greensboro, Alabama.
No full textFirst row, left to right (numbers 1 through 11): T. J. Kinnaird; William N. Knight; W. C. Tunstall; R. B. Waller; H. T. Waller; Charles E. Waller; George Nabors; N. B. Jones; R. H. Jackson; A. J. Moore; and S. M. Hosmer. Second row, left to right (numbers 12 through 21): John H. Turpin; H. T. Stringfellow; W. G. Britton; T. J. Crawford; Cud Jones; J. A. Ellerbe; Bell [?] Singley; J. Huggins; W. C. Christian; and John G. Apsey
Organometallic vapor-phase epitaxy: theory and practice
No full textHere is one of the first single-author treatments of organometallic vapor-phase epitaxy (OMVPE)--a leading technique for the fabrication of semiconductor materials and devices. Also included are metal-organic molecular-beam epitaxy (MOMBE) and chemical-beam epitaxy (CBE) ultra-high-vacuum deposition techniques using organometallic source molecules. Of interest to researchers, students, and people in the semiconductor industry, this book provides a basic foundation for understanding the technique and the application of OMVPE for the growth of both III-V and II-VI semiconductor materials and th
Frictional Effects in the Buckling Delamination of a Compressed Thin Film and Implications for Interfacial Fracture
No full textABSTRACTAs a film in residual compression delaminates from a substrate, the post-buckling response of the film tends to drive it into the substrate in the region directly behind the delamination front. We consider the process of frictional interaction between the film and the substrate during the delamination process in order to assess the effect of Coulomb friction on the energy release rate, G, driving the delamination. For the case in which the film and the substrate have identical elastic properties, we derive a singular integral equation to determine the relative sliding displacement of the opposing faces of the interface. Using an analytical model, we find that G decreases by about 35% when the coefficient of interfacial friction is equal to one. Using finite element methods, we then investigate the effects of compliance differences between the film and the substrate. We find that, when the film is more compliant than the substrate, frictional interaction is enhanced and the calculated energy release rate decreases substantially. We conclude that frictional effects can account for a significant portion of the energy dissipation during the delamination process, and thus can play an important role in the observed arrest of spreading delaminations.</jats:p
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