Uniqueness and reciprocity in the boundary-initial value problem for a mixture of two elastic solids occupying an unbounded domain

Summary In this paper two uniqueness theorems for an anisotropic mixture of two linear elastic solids are established: The former concerns the mixed boundary-value problem, the latter the displacement problem. These theorems are proved for unbounded domains in the absence of artificial restrictions upon the behaviour of the unknown fields at infinity. A reciprocity theorem is also given.     

Reduction of sludge production from WWTP using thermal pretreatment and enhanced anaerobic methanisation.

The objective of the study presented here was to investigate the performance of an enhanced two-step anaerobic process for the treatment of WWTP sludge. This process was developed to answer the urgent need currently faced by WWTP operators to reduce the production of biosolids, for which disposal pathways are facing increasing difficulties. A pilot plant was operated on a full-scale WWTP (2,500 p.e.) over a period of 4 months. It consisted of a thermal pre-treatment of excess sludge at 175 degrees C and 40 min, followed by dewatering and methanisation of the centrate in a fixed-film reactor. The thermal lysis had a two-fold enhancing effect on sludge reduction efficiency: firstly, it allowed a decrease of the HRT in the methaniser to 2.9 days and secondly, it yielded biosolids with a high dewaterability. This contributed to further reductions in the final volume of sludge to be disposed of. The two-step process achieved a sludge reduction efficiency of 65% as TSS, thus giving an interesting treatment option for WWTP facing sludge disposal problems.     

Acceleration waves through a mixture of two non-linear elastic solids

Summary In this paper we study the propagation of acceleration waves through an anisotropic isothermal mixture of two non-linear elastic solids. First of all, we show that, under suitable hypotheses on the constitutive equations, there exist twelve real normal speeds of propagation; then by means of Nariboli method, we state the evolution law of the discontinuities along the rays associated with the wave front.Work performed under the auspices of C.N.R. (GNFM) and supported by M.P.I. of Italy.     

Simulation and Prediction of Methyl‐mercaptan Removal by Chemical Scrubbing with Hydrogen Peroxide

A model has been developed in order to predict the behavior of methylmercaptan chemical scrubbing using hydrogen peroxide. New constants concerning reactions involving methylmercaptan have been proposed based on mass transfer and kinetic equations for the dissociation of methylmercaptan by the hydroxide and the reaction with perhydroxyl ions. Once this step has been achieved, the model is used to characterize the influences of the different chemical scrubbing operating parameters, i.e., the gas‐liquid contact time, the oxidant concentration, and the pH. As expected, an increase in the hydrogen peroxide concentration, the contact time, or the pH leads to an increase in the methylmercaptan removal level. However, the most interesting aspect of the model lies in the possibility of defining a new or limiting value for each parameter, below which the process is not efficient enough to be industrially implemented.     

Techno-Economic Evaluation of Biodiesel Production from Waste Cooking Oil—A Case Study of Hong Kong

Fossil fuel shortage is a major challenge worldwide. Therefore, research is currently underway to investigate potential renewable energy sources. Biodiesel is one of the major renewable energy sources that can be obtained from oils and fats by transesterification. However, biodiesel obtained from vegetable oils as feedstock is expensive. Thus, an alternative and inexpensive feedstock such as waste cooking oil (WCO) can be used as feedstock for biodiesel production. In this project, techno-economic analyses were performed on the biodiesel production in Hong Kong using WCO as a feedstock. Three different catalysts such as acid, base, and lipase were evaluated for the biodiesel production from WCO. These economic analyses were then compared to determine the most cost-effective method for the biodiesel production. The internal rate of return (IRR) sensitivity analyses on the WCO price and biodiesel price variation are performed. Acid was found to be the most cost-effective catalyst for the biodiesel production; whereas, lipase was the most expensive catalyst for biodiesel production. In the IRR sensitivity analyses, the acid catalyst can also acquire acceptable IRR despite the variation of the WCO and biodiesel prices.     

The Effect of Vitamin D3 and Silver Nanoparticles on HaCaT Cell Viability

Vitamin D3, known to regulate bone homeostasis, has recently been shown to have many pleiotropic effects in different tissues and organs due to the presence of its receptor in a wide range of cells. Our previous study demonstrated that vitamin D3 was able to increase the wound healing respect to the control sample, 24 h after cutting, without however leading to a complete repair. The aim of the study was to combine vitamin D3 with silver nanoparticles to possibly enable a faster reparative effect. The results showed that this association was capable of inducing a complete wound healing only after 18 h. Moreover, a treatment of vitamin D3 + silver nanoparticles yielded a small percentage of keratinocytes vimentin-positive, suggesting the possibility that the treatment was responsible for epithelial to mesenchymal transition of the cells, facilitating wound healing repair. Since vitamin D3 acts via sphingolipid metabolism, we studied the expression of gene encoding for the metabolic enzymes and protein level. We found an increase in neutral sphingomyelinase without involvement of neutral ceramidase or sphingosine kinase2. In support, an increase in ceramide level was identified by Ultrafast Liquid Chromatography–Tandem Mass Spectrometry, suggesting a possible involvement of ceramides in wound healing process.     

Acceleration waves through an isotropic mixture of two non-linear elastic solids

Summary In this paper we study the propagation of acceleration waves through an isotropic isothermal mixture of two non-linear elastic solids. After giving the constitutive equations of the mixture, we calculate the possible normal speeds of propagation. Then we state that, in general, it is possible to distinguish between longitudinal and transverse acceleration waves. Finally, we establish the evolution law of the discontinuities along the normal trajectories associated with the wave front.Work performed under the auspices of C.N.R. (GNFM) and supported by M.P.I. of Italy.     

Energy bounds for a mixture of two linear elastic solids occupying a semi-infinite cylinder

Summary The aim of this paper is to establish some forms of the Saint-Venant principle for a mixture of two linear elastic solids occupying a semi-infinite prismatic cylinder. We examine the behaviour of the energy for both static and dynamical problems. Under mild assumptions on the asymptotic behaviour of the unknown fields at infinity, we show that in the static case the elastic energy of the portion of the cylinder beyond a distancex ₃ from the loaded region decays exponentially withx ₃. For the dynamical problem we estimate through the data the total energy stored in that part of the cylinder whose minimum distance from the loaded end isx ₃; these estimates, which are based on the assumption that the initial total energy is finite, depend uponx ₃ but do not depend upon the timet.     

Use of hydrogen peroxide in scrubbing towers for odor removal in wastewater treatment plants.

The aim of this work was to replace sodium hypochlorite (NaCIO) with hydrogen peroxide (H202) in chemical scrubbing towers, in order to avoid the formation of chlorinated species, harmful for human health. Some previous studies have already shown the ability of H2O2 to treat the hydrogen sulfide (H2S) pollution. However, an important decomposition of the oxidant was observed in the scrubbing solution (carbonates, transition metal and high pH are responsible for this decomposition) leading to high reactant consumption. Consequently, this study first focused on research into a compound able to reduce the hydrogen peroxide degradation. Experiments were conducted on a pilot unit (3,000 m3 h(-1)) in a wastewater treatment plant. The sodium silicate (Na2SiO3) proved to be a good scrubbing solution stabilizer. A very good removal of hydrogen sulfide (up to 98%) was also obtained. Finally, the study resulted in the determination of the best operating conditions to achieve both an efficient and economical process.