Review of machining metal matrix composites

Monotonic fault progression is an important assumption for a number of prognostic models. This assumption can be violated through human intervention and self‐healing and result in non-monotonic degradation data which not only increases the uncertainty but also may cause model failure. Methods to analyze and handle non-monotonic degradation in repairable systems are practically nonexistent in the literature. In this research, we intend to consider repairable systems in which self‐healing is possible and human interventions are desirable. We presented a novel example of self-healing for fatigue cracks analyzed by acoustic emission. The aim of the present paper is to initiate a new research area on using non-monotonic measures in degradation-based prognostics. However, this research is not a review of trend analysis techniques, and therefore, there are more techniques to be considered or developed in future studies. In effect, trend analysis should be considered as an integral part of prognostics and health management. This study considers trend analysis for three classes of data, (1) prognostic parameters, (2) degradation waveform, and (3) multivariate data. A new form of crest factor is introduced for more effective waveform analysis of non-monotonic data. In addition, two algorithms are introduced to treat non-monotonic trend. The prognostic model used in this research does not produce results without treating non-monotonicity. These kinds of algorithm have promising potential to treat non-monotonicity and deal with arbitrary stationary noise in degradation data.     

Meta-analysis of indoor temperatures in new-build housing

ABSTRACT

Despite growing concerns about overheating, a lack of evidence exists on the scale of the problem, particularly in contemporary UK housing. This paper presents the results of a meta-analysis of indoor temperatures in selected low-energy housing. Temperature data recorded at five-minute intervals in 60 dwellings across 19 demonstration projects (2012–14) were collated and analysed to investigate the prevalence of overheating. Findings evidence high summertime temperatures, with 27% of living rooms exceeding 28°C during August. Based on the Chartered Institution of Building Services Engineers (CIBSE) threshold of 5% annual occupied hours > 25°C, 57% of bedrooms and 75% of living rooms were classified as having overheated. Overall, 30% of living rooms exceeded the adaptive comfort threshold of > 3% occupied hours ΔT?≥?1?K. The results suggest a fundamental relationship between ventilation and indoor temperatures. The higher minimum and average summertime temperatures observed in mechanical ventilation with heat recovery (MVHR) homes (p?<?0.05) and lower temperature range (p?<?0.001) suggest the need for greater attention to adequate summertime ventilation provision in airtight homes. The results demonstrate a high prevalence of overheating in exemplary housing, indicating the need for greater efforts to ensure the effective implementation of strategies to minimize overheating and improve ventilation in low-energy homes.     

Analysis of the standard deletion algorithms in exact fit domain binary search trees

It is well known that the expected search time in anN node binary search tree generated by a random sequence of insertions isO(logN). Little has been published about the asymptotic cost when insertions and deletions are made following the usual algorithms with no attempt to retain balance. We show that after a sufficient number of updates, each consisting of choosing an element at random, removing it, and reinserting the same value, that the average search cost is (N ^1/2).This work was done in part while the first author was at the University of Waterloo. This work was supported by an NSERC '67 Science Scholarship and Grant A-8237 and the Information Technology Research Centre of Ontario.     

Structural Requirements of Jasmonates and Mimics for Nicotine Induction inNicotiana sylvestris

Jasmonic acid (JA) is strongly implicated in the long-distance signal transduction cascade increasing nicotine synthesis in the roots of plants after leaf wounding. In order to explore the structural requirements of the inducing signal, we examined jasmonates, mimics, and a biosynthetic precursor for nicotine-inducing activity (NIA). We examine the importance of the keto group on the five-membered ring and the double bond in then-pentenyl chain by comparing the NIA of methyl jasmonate (MJ) with that of cucurbic acid, 1,3-dithiolane-MJ, 1,3-dioxolane-MJ, methyl dihydrojasmonate (DHMJ), 1,3-dioxolane-DHMJ, 1-oxo-indan-4-carboxylic acid ILE-methyl ester, and 1-hydroxyl-indan-4-carboxylic acid ILE-methyl ester. We found that: 1,3-dioxolane MJ, cucurbic acid, and 1,3-dioxolane DHMJ were less active than MJ and that the isoleucine (ILE) conjugates of 1-oxo- and l-hydroxyindanon-4-carboxylic acid had the same NIA as MJ. The activities of these indanon amino acid conjugates may be due to the structural similarity of their keto or hydroxyl groups on the five-membered ring to MJ or to the keto-enolized MJ. These results support the hypothesis that the enolization of the keto group during or prior to its interaction with the putative JA receptor is required for activity. We explore the importance of the esterification of the carboxyl functional group by comparing the NIAs of cucurbic acid and cucurbic acid methyl ester, l-oxo-indan-4-carboxylic acid, 1-oxo-indan-4-carboxylic acid methyl ester, and l-oxo-indan-4-carboxylic acid ILE-methyl ester. In all cases, the esters were more active than the free acids. We compared the NIA of MJ of different epimeric composition (8% and 20% 3R,7S-MJ); 12-oxophytodienoic acid (12-oxo-PDA) methyl ester, an important precursor of JA; and coronatine (a well-known phytotoxin and putative structural mimic of 12-oxo-PDA).We found that: (1) the epimeric composition of MJ did not affect its NIA; (2) 12-oxo-PDA methyl ester had lower NIA than MJ; and (3) coronatine significantly inhibited plant growth but did not increase nicotine biosynthesis. In summary, JA, rather than its biosynthetic precursor, 12-oxo-PDA, is likely the endogenous signal inNicotiana sylvestris, and the keto functional group on the five-membered ring and the double bond in then-pentenyl side chain are crucial components of JA for NIA.     

Reactivity of petroleum coke to carbon dioxide between 1030 and 1180 K

Measurements were made of the reaction rate of three sizes (2.9, 0.9 and 0.22 mm) of petroleum-coke particles with carbon dioxide over the temperature range 1018–1178 K, and at carbon dioxide partial pressures between 26 and 118 kPa. A limited number of similar measurements were made on samples of a commercial aluminium-smelting anode, an experimental anode, and AGKSP graphite. The materials were all reacted under conditions of chemical rate control alone: there were no rate limitations due to transport processes without or within the carbon particles. The order of the rate with respect to carbon dioxide concentration was found to be close to 0.6 for the petroleum coke and anode carbons, and between 0.6 and 0.8 for the graphite. Activation energies in the range 203–237 kJ/mol were found for petroleum coke; 187–237 kJ/mol for electrode carbon; and 293 kJ/mol for the graphite. For the petroleum coke, the order was found to be constant up to 45% burn-off and the activation energy essentially constant between 21 and 45% burn-off. The reactivity ?_s, based on unit pore surface area of the petroleum coke at a carbon dioxide pressure of 101 kPa, can be represented by: $\text{?}{}_{\mathrm{s}}\text{= α exp [?}\text{E}\text{(RT)}\text{]}$. For the 2.9 and 0.9 mm particles, α = 6.1 /sx 10⁶ g/m² min and E = 215 kJ/mol; for the 0.22 mm particles the respective values are 1.8 /sx 10⁷ and 222. The reactivity ? of the commercial electrode on a weight basis was within the range of those of the coke and experimental electrode. For AGKSP graphite, values of ?_s were close to those found by Walker and Raats¹⁴.     

Bromine levels in tissue lipids of rats fed brominated fatty acids

Lipids - Rats have been fed diets containing either 0.8% brominated corn oil or 0.5% of the ethyl ester of 9,10-dibromostearate or 9,10,12,13-tetrabromostearate. The brominated compounds were...     

Dietary fish oil inhibits human breast carcinoma growth: A function of increased lipid peroxidation

Female athymic nude mice were implanted subcutaneously with human breast carcinoma MDA-MB231. Seven to ten days later, the mice were divided into groups and fed a purified diet containing the following types of fat (% of diet):(i) 20% corn oil (CO); (ii) 15% CO:5% fish (menhaden) oil (FO); (iii) 10% CO:10% FO; (iv) 5% CO:15% FO; (v) 1% CO:19% FO; and (vi) 1% CO:19% FO plus antioxidants (α-tocopherol acetate, 2000 IU/kg diet and tertiary butyl-hydroquinone, 2% of the total fat). The linoleic acid levels (% of diet) of the groups were 12.0, 9.1, 6.2, 3.3, 0.9 and 0.9%, respectively. After 6–8 wk, the carcinomas were assessed for tumor volume (cm³) and assayed for thiobarbituric acid reactive substances (TBARS). Human breast carcinoma growth was suppressed in mice consuming FO diets without antioxidants as compared to mice fed CO; the greater the amount of dietary FO fed, the greater the carcinoma growth suppression (P<0.05). The addition of antioxidants to the FO diet significantly (P<0.05) reversed the FO-induced carcinoma growth suppression. Concentrations of TBARS in the human breast carcinomas were increased in all the FO (without antioxidants) fed mice, compared to mice fed CO; the level of increase in TBARS was directly related to the increase in the level of FO fed (P<0.05). The addition of antioxidants to the FO diet significantly (P<0.05) reduced the concentration of TBARS in the breast carcinomas. Thus, these results provide evidence that dietary FO can significantly suppress growth of human breast carcinoma MDA-MB231, even in the presence of substantial amounts of linoleic acid (3.3–9.1%). The inhibitory effect of FO on growth of these carcinomas was associated with an increased concentration of TBARS in the tumor tissue. In conclusion, dietary FO induced suppression of human breast carcinoma growth is a function, at least in part, of an accumulation of lipid peroxidation products in the tumor tissues.     

Dissolution of a Sphene Glass-Ceramic, and of Its Component Sphene and Glass Phases, in Ca-Na-Cl Brines

Leaching experiments for up to 569 d have been performed to examine the dissolution in Ca-Na-Cl groundwater of a sphene (CaTiSiO₅)-based glass-ceramic, a candidate material for immobilizing nuclear fuel recycle wastes. The experiments involved leaching of samples of a simulated-waste-loaded glass-ceramic, doped with ²²Na or ⁴⁵Ca, in a synthetic groundwater at 25° and 100°C. The results are compared with those from separate leaching experiments with ²²Na- or ⁴⁵Ca-doped samples of aluminosilicate glass and ceramic sphene, representing the component phases of the glass-ceramic. The comparison supports a model in which the glass-ceramic dissolution rate may be approximately derived from the weighted average of the separate dissolution rates of its component glass and ceramic phases. No synergistic effects in the leaching of the glass and ceramic phases in the glass-ceramic were found.     

Patterns and sources of leaf tannin variation in yellow birch (Betula allegheniensis) and sugar maple (Acer saccharum)

Leaves from forest-grown sugar maple (Acer saccharum Marsh) and yellow birch (Betula allegheniensis Britt.) trees were analyzed for four tannin measures (hydrolyzable and condensed tannins, total phenolics, and protein binding) at three times during the growing season. Fifteen-year-old half-sib sugar maples from four provenances, representing the geographical extremes of the sugar maple range and growing in a common garden, were examined for the same traits. We found no significant geographic or seed source component to variation in three of the four tannin measures. We found significant seasonal changes in both birch and maple leaf tannins. Withincanopy leaf tannin variation tended to obscure differences between trees in maple, but in birches between-tree differences in leaf tannin content were more readily found. We also found a significant negative correlation between leaf protein binding capacity and leaf wet weight.     

Effect of Nb Doping on the Microstructure of Sol—Gel-Derived PZT Thin Films

Aliovalent Nb doping (<10 at.%) of sol—gel-derived lead zirconate titanate (PZT) thin films was investigated with the intention of improving the ferroelectric properties. Nb addition was found to significantly alter the perovskite crystallization by stabilizing the transient pyrochlore phase, resulting in the retention of pyrochlore second phases and an increase in the perovskite lateral grain size and columnarity. The occurrence and composition of Zr-rich (surface) pyrochlore phases were found to depend on Nb concentration, annealing temperature, and Pb content. The observed changes in ferroelectric and dielectric properties as a function of Nb dopant addition were found to be strongly influenced by microstructural effects and the occurrence of pyrochlore, and hence the intrinsic effects of Nb incorporation in the perovskite lattice could not be directly ascertained.