Burn-rate and knock reduction in the spark ignition engine

The dependence of knock on combustion chamber shape is investigated. Knock originating from the spark plug's ignition of the air-fuel charge (‘spark knock’) is assumed. Four general parameters that influence knock are isolated. Examination of the parameters reveal that manipulation of the burn history is favoured in curbing knock. By utilizing an existing model of knock, it was shown that slightly larger pressures and temperatures can be applied to an air-fuel charge for shorter times without knock. This explains the well-known observation that reducing the burn time in a spark ignition (SI) engine decreases the end-gas's propensity to knock. It was also shown that the increase in end-gas pressure and temperature associated with a higher burn rate is insufficient to re-introduce knock. Results for the engine data examined indicate that for a pressure trace at the onset of knock (reference trace), a twofold reduction in burn time can allow the combustion pressure to be scaled up by about 23% without knock occurring.     

Market mechanisms for resource allocation in pervasive sensor applications

This paper describes the use of market mechanisms for resource allocation in pervasive sensor applications to maximize their Value of Information (VoI), which combines the objectively measured Quality of Information (QoI) with the subjective value assigned to it by the users. The unique challenge of pervasive sensor applications that we address is the need for adjusting resource allocation in response to the changing application requirements and evolving sensor network conditions. We use two market mechanisms: auctions at individual sensor nodes to optimize routing, and switch options to optimize dynamic selection of sensor network services as well as switching between modes of operation in pervasive security applications. We also present scenarios of transient congestion management and home security system to motivate the proposed techniques.     

A framework for implicit human-centered image tagging inspired by attributed affect

In this paper, a framework for implicit human-centered tagging is presented. The proposed framework draws its inspiration from the psychologically established process of attribution. The latter strives to explain affect-related changes observed during an individual’s participation in an emotional episode, by bestowing the corresponding affect changing properties on a selected perceived stimulus. Our framework tries to reverse-engineer this attribution process. By monitoring the annotator’s focus of attention through gaze-tracking, we identify the stimulus attributed as the cause for the observed change in core affect. The latter is analyzed from the user’s facial expressions. Experimental results attained by a lightweight, cost-efficient application based on the proposed framework show promising accuracy in both the assessment of topical relevance and direct annotation scenarios. These results are especially encouraging given the fact that the behavioral analyzers used to obtain user affective response and eye gaze lack the level of sophistication and high cost usually encountered in the related literature.     

Effect of pulsed electric fields and high pressure on improved recovery of high-added-value compounds from olive pomace

Olive pomace is considered a solid by-product and a rich source of valuable compounds such as polyphenols, flavonoids with antioxidant properties, and proteins. Nonthermal technologies, which cause alterations to cell permeability, are being explored to assist conventional recovery techniques. The aim of this study was to assess the effect of pulsed electric fields (PEF) and high pressure (HP) on improved recovery yield of the high-added-value compounds or to shorten the extraction time of these compounds. Olive pomace (Tsounati cv) was pretreated with PEF (1.0 to 6.5 kV/cm, 0.9 to 51.1 kJ/kg, and 15 µs pulse width) or HP (200 to 600 MPa and 0 to 40 min). Evaluation of the intracellular compounds extracted via solid–liquid extraction (50% ethanol–water solution) was performed. More intense PEF and HP conditions resulted in a significant increase of the phenolic concentration up to 91.6% and 71.8%, respectively. The increased antioxidant capacity of each extract was correlated to phenolic compound concentration. The protein concentration that was achieved with PEF pretreatment was doubled; however, HP-pretreated extracts reached 88.1% higher yield than untreated for pressures up to 200 MPa. HP and PEF pretreatment decreased extraction completion time t₉₈ (needed time to recover the equal amount of phenolics and proteins of untreated after 60 min of conventional extraction) to 12 min and lower than 1 min, respectively. To conclude, both pretreatments are effective in improving the conventional extraction process for increased yield recovery of high-added-value compounds from olive pomace.     

Assessing Herbal Products with Health Claims

Herbs, herbal extracts, or phytochemicals are broadly used as foods, drugs, and as traditional medicines. These are well regulated in Europe, with thorough controls on both safety and efficacy or validity of health claims. However, the distinction between medicines and foods with health claims is not always clear. In addition, there are several cases of herbal products that claim benefits that are not scientifically demonstrated. This review details the European Union (EU) legislative framework that regulates the approval and marketing of herbal products bearing health claims as well as the scientific evidence that is needed to support such claims. To illustrate the latter, we focus on phytoecdysteroid (PE)-containing preparations, generally sold to sportsmen and bodybuilders. We review the limited published scientific evidence that supports claims for these products in humans. In addition, we model the in silico binding between different PEs and human nuclear receptors and discuss the implications of these putative bindings in terms of the mechanism of action of this family of compounds. We call for additional research to validate the safety and health-promoting properties of PEs and other herbal compounds, for the benefit of all consumers.     

Investigation of organic extractives from unifloral chestnut (Castanea sativa L.) and eucalyptus (Eucalyptus globulus Labill.) honeys and flowers to identification of botanical marker compounds

Ultrasound-assisted extraction was employed to investigate the composition of extractable compounds from unifloral chestnut and eucalyptus honeys. 1-phenylethanol and 2′-aminoacetophenone are the most powerful botanical markers of chestnut honey. Additionally, cis-cinnamyl alcohol, and p-hydroxyacetophenone were found exclusively in chestnut honey. Organic extractives from whole chestnut flowers were predominated by 1-phenylethanol, nonanal, benzyl alcohol, and nonanoic acid. Of the 16 compounds found in the flower extract, 13 were present in honey as well. Some of them are transferred directly to honey, while in other cases modification reactions take place. Eucalyptus honey is characterized by 2-hydroxy-5-methyl-3-hexanone and 3-hydroxy-5-methyl-3-hexanone, as well as exo-2-hydroxycineole and an unknown norisoprenoid. Aside from, acetoin, nonanal, methyl nonanoate, and dehydrovomifoliol were present in higher concentrations. In eucalyptus flower extracts, norisoprenoids were the most abundant compounds, all of which were also present in the honey samples. 3-Oxo-α-ionone comprised half of the total amount, followed by eucalyptol.     

On Modeling Hydrogen-Induced Crack Propagation Under Sustained Load

The failure of hydrogen containment components is generally associated with subcritical cracking. Understanding subcritical crack growth behavior and its dependence on material and environmental variables can lead to methods for designing structural components in a hydrogen environment and will be beneficial in developing materials resistant to hydrogen embrittlement. In order to identify the issues underlying crack propagation and arrest, we present a model for hydrogen-induced stress-controlled crack propagation under sustained loading. The model is based on the assumptions that (I) hydrogen reduces the material fracture strength and (II) crack propagation takes place when the opening stress over the characteristic distance ahead of a crack tip is greater than the local fracture strength. The model is used in a finite-element simulation of crack propagation coupled with simultaneous hydrogen diffusion in a model material through nodal release. The numerical simulations show that the same physics, i.e., diffusion-controlled crack propagation, can explain the existence of both stages I and II in the velocity versus stress intensity factor (V–K) curve.     

The Relationship Between Crack-Tip Strain and Subcritical Cracking Thresholds for Steels in High-Pressure Hydrogen Gas

Threshold stress intensity factors were measured in high-pressure hydrogen gas for a variety of low alloy ferritic steels using both constant crack opening displacement and rising crack opening displacement procedures. Thresholds for crack extension under rising displacement, K _THi, for crack extension under constant displacement, $ K_{\text{THi}}^{*} $ , and for crack arrest under constant displacement K _THa, were identified. These values were not found to be equivalent, i.e. K _THi < K _THa <  $ K_{\text{THi}}^{*} $ . The hydrogen assisted fracture mechanism was determined to be strain controlled for all of the alloys in this study, and the micromechanics of strain controlled fracture are used to explain the observed disparities between the different threshold measurements. K _THa and K _THi differ because the strain singularity of a stationary crack is stronger than that of a propagating crack; K _THa must be larger than K _THi to achieve equivalent crack tip strain at the same distance from the crack tip. Hydrogen interacts with deformation mechanisms, enhancing strain localization and consequently altering both the nucleation and growth stages of strain controlled fracture mechanisms. The timing of load application and hydrogen exposure, i.e., sequential for constant displacement tests and concurrent for rising displacement tests, leads to differences in the strain history relative to the environmental exposure history and promotes the disparity between $ K_{\text{THi}}^{*} $ and K _THi. K _THi is the only conservative measurement of fracture threshold among the methods presented here.