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Packaging made from biodegradable biopolymers such as proteins, polysaccharides and lipids is a promising alternative to synthetic polymers. Films made from these biopolymers exhibit certain disadvantages in terms of their mechanical, barrier and physicochemical properties. Plasticisers, nanoparticles, lipids and antimicrobial compounds can be added to them to improve these properties. The tendency of biopolymer films to brittleness can be mitigated by adding plasticisers and/or nanoparticles. These films also tend to have high water vapour permeability, which can be reduced by adding lipids and/or nanoparticles. Incorporating natural compounds with antimicrobial activity into biopolymer films can provide them the advantages of maintaining food safety and extending shelf life. Addition of plasticisers, nanoparticles, lipids and/or antimicrobial compounds to biopolymer films can help to make them comparable to conventional synthetic films with the advantages that they reduce pollution and are biodegradable.  相似文献   
64.
This paper examines the aerodynamic properties of a rectangular tall building with sharp edges. The building has a section aspect ratio B/D = 2.6 and a height aspect ratio H/D = 9, giving in a quite slender prismatic configuration. The study was performed on sectional and three‐dimensional models of the building. The sectional model was tested in a smooth flow condition, and the aerodynamic coefficients of the section were determined. Forces and pressure distributions were measured on the three‐dimensional model to compare with the aerodynamic behavior of the sectional model. Both a rigid (non‐moving) and a moving model of the building were tested to analyze possible aeroelastic effects. Different levels of incoming wind turbulence were tested, since this is a key parameter in the aerodynamic behavior of the rectangular prism. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   
65.
The objective of this study was to carry out a mixed methods construction education study seeking to improve student learning. This study uses project-based learning (PrBL) and milestone deliverable pedagogy to teach a concrete industry project management course and compares the outcome to a control (non-PrBL) version of the same course. The intervention course was designed as a full semester learning experience for students. The students worked as project managers from start to finish constantly contributing to the completion of their team project. In the control scenario, delivered in Fall 2013, students were required to carry-out a traditional project due at the end of the semester. This study examines the impact of having the course project become the main learning mechanism and considers and measures the ways in which PrBL affects student performance. Pre and post questionnaires regarding self-perceptions of learning and skill development were administered and project and course grades were used to assess the impact of PrBL on the students’ performance. The questionnaires revealed a minimum increase of students’ perception of their understanding of 48%. The course grade comparison showed an average of 13% point increase in all student grades when the PrBL pedagogy was implemented.  相似文献   
66.
Ethanol is the alcoholic precursor of fatty acid ethyl esters (FAEEs) in virgin olive oil (VOO). Because of its miscibility, water addition during oil extraction may affect oil ethanol content and then, the FAEEs synthesis during oil storage. In this work, the effect of water addition on VOO ethanol content and composition is studied. Water addition at two extraction systems (two and three phases) is compared and for vertical centrifuge, water addition at different temperatures is assayed. Ethanol content, quality parameters, and healthy components are determined in the oils. Results indicate three phase system gives oils with a 25% lower ethanol content than two phases. Ethanol reduction because of water addition is more important for three phases system (≈14%). For vertical centrifugation, ethanol is lowered as water dose and temperature increase. In general, water addition for any of the extraction steps analyzed reduces the oil ethanol concentration but other aspects such as fruity intensity and phenol content are also lowered. Practical applications: Virgin olive oil final ethanol content, and then its FAEEs concentration, does not only depend on the health and conservation status of olives, but also on the extraction system used and the amount of water added to the extraction process. The knowledge of the impact on ethanol content of water addition during oil extraction can be useful for olive oil legislators in order to keep the approved limits of FAEEs or to modify them. For oil producers, results can help to reduce the oil ethanol content and then FAEEs synthesis during virgin olive oil storage.  相似文献   
67.
Summary  The synthesis of new N-4-trifluoromethylphenyl-exo-endo-norbornene-5,6-dicarboximide (TFmNDI, 2a) and N-3,5-difluorophenyl-exo-endo-norbornene-5,6-dicarboximide (DFNDI, 2b) was carried out. Polynorbornene dicarboximides, 3a and 3b, were obtained via ring opening metathesis polymerization (ROMP) using bis(tricyclohexylphosphine) benzylidene ruthenium(IV) dichloride (I) and tricyclohexylphosphine [1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene][benzylidene] ruthenium dichloride (II), respectively. Tg’s for polymers 3a and 3b were observed at 155 C and 142 C, respectively. Compared to polymer 3b, polymer 3a with the bulky trifluoromethyl group showed the highest glass transition temperature and improved mechanical properties.  相似文献   
68.
Ring opening polymerization (ROP) of 1,3,5-tri-n-hexyl,1,3,5-trimethylcyclotrisiloxane (D 3 Hexa ) and 1,3,5-tri-n-heptyl,1,3,5-trimethylcyclotrisiloxane (D 3 Hepta ) was promoted by acid-treated synthetic silica–alumina to obtain Gaussian homo asymmetric polysiloxanes. Mw was above 70?kg/mol, meaning that homo asymmetric bulky side-group polysiloxane chains with high molecular weight were obtained. The material was treated in an acidic medium to improve the contents of acid sites and successfully tested as an inorganic acidic catalyst for ROP of D 3 Hexa and D 3 Hepta cyclosiloxanes. The samples of poly(methylhexylsiloxane) (PMHS) and poly(methylheptylsiloxane) (PMHepS) obtained were structurally characterized mainly by 29Si NMR. All the experimental values including the refractive index increment (dn/dc), the second virial coefficient (A2), the square root of the mean square radius of gyration ( $ \langle {{\text{RMS}}_{\text{radius}}}^{ 2} \rangle^{ 1/ 2} $ ), the average molecular weight (Mw), the average molecular numeral (Mn), and the weight polydispersity (Mw/Mn) were obtained using a gel permeation chromatography/light scattering (GPC/LS) coupled system. The A2 experimental value for the two polymers (between 4 and 6.5?×?10?4?mol/mL?g2) indicated that toluene was a good solvent. In addition, PMHS and PMHepS $ \langle {{\text{RMS}}_{\text{radius}}}^{ 2} \rangle^{ 1/ 2} $ were greater than 30?nm, indicating that larger chains of high molecular weight were obtained.  相似文献   
69.
Carbon fibers in unidirectional fabric form are increasingly being used as a means of strengthening deteriorating and understrength concrete components and systems through application as externally bonded reinforcement. The use of wet layup process under ambient conditions makes these composites susceptible to moisture and environment-related deterioration. In addition since the composite is formed in the field, often in overhead or vertical configurations, by sequential placement of fabric layers, it is critical, for the assessment of materials integrity, to characterize damage mechanisms and durability of interlaminar and intralaminar performance characteristics. It is shown that aqueous exposure, as well as freeze–thaw, results in significant fiber–matrix debonding, and this causes deterioration in short-beam-shear and in-plane shear characteristics. Changes in interlaminar properties are seen to be correlated with moisture uptake. It is also seen that fracture toughness, in the short-term, is enhanced by some of these exposures due to plasticization and flexibilizing of the matrix, which assists in the blunting of crack front progression. However, when accompanied by chemical degradation, such as with immersion in alkali solution, and embrittlement caused by low temperature exposure, GIC values are seen to deteriorate as well. The data provides a crucial set of material characteristics for consideration side-by-side with fiber dominated characteristics (such as tensile strength and modulus, which are the only ones considered conventionally in rehabilitation design), since the matrix dominated properties will often be the critical links in determining service life.  相似文献   
70.
In this work, an analysis of the emission of different pollutants when replacing partially the fuel type used in a cement kiln is done. The wastes used to feed the kiln were tyres and two types of sewage sludge. The increasing mass flow of sludge is between 700kgh(-1) and 5500kgh(-1)1, for a total production of clinker of 150th(-1), whereas the fed tyres were in the flow range of 500-1500kgh(-1). Dioxins and furans, polycyclic aromatic hydrocarbons (PAHs) and other hydrocarbons, heavy metals, HCl and HF, CO, CO(2), NO(x) and other parameters of the stack were analyzed, according to the standard methods of sampling and determination, through more than 1 year in six series: one blank (no sewage sludge) and five more with increasing amount of sludge and/or tyres. The emission of PAHs and dioxins seems to increase with the amount of tyres fed to the kiln, probably due to the fed point used for this waste.  相似文献   
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