Characterization of Acoustic Emissions from Mechanical Seals for Fault Detection

The application of high-frequency Acoustic Emissions (AE) for mechanical seals diagnosis is gaining acceptance as a useful complimentary tool. This paper investigates the AE characteristics of mechanical seals under different rotational speed and fluid pressure (load) for develop a more comprehensive monitoring method. A theoretical relationship between friction in asperity contact and energy of AE signals is developed in present work. This model demonstrates a clear correlation between AE Root Mean Square (RMS) value and sliding speed, contact load and number of contact asperities. To benchmark the proposed model, a mechanical seal test rig was employed for collecting AE signals under different operating conditions. Then, the collected data was processed using time domain and frequency domain analysis methods to suppressing noise interferences from mechanical system for extracting reliably the AE signals from mechanical seals. The results reveal the potential of AE technology and data analysis method applied in this work for monitoring the contact condition of mechanical seals, which will be vital for developing a comprehensive monitoring systems and supporting the optimal design and operation of mechanical seals

Interethnic conjugal unions among 1.5 and 2nd generations of Arab Canadians

Dans cette étude, j’examine la propension à former une union interethnique parmi les Canadiens arabes de seconde génération et de génération 1.5 en utilisant les données du recensement canadien de 2016. L’analyse descriptive montre que les unions interethniques sont fréquentes au sein de cette population. Environ la moitié des hommes (56%) et des femmes (49%) sont dans une union interethnique avec une personne non-Arabe d’origine immigrante ou un(e) Canadien(ne) de troisième génération ou des générations suivantes. La régression logistique multinomiale révèle que les hommes et les femmes avec un niveau d’éducation plus élevé, une ascendance partiellement arabe et un statut d’immigrant de deuxième génération sont significativement plus enclins à être en union interethnique qu’à être en union intraethnique avec un immigrant de première génération. Conformément à la théorie de l’assimilation segmentée, ces résultats suggèrent que l’intégration socioéconomique et l’acculturation contribuent à la propension des descendants arabes à former des unions avec des individus non-arabes. La propension des descendants arabes à être en union intraethnique avec des immigrants de première génération ou des descendants est aussi une problématique dont je discute.In this study, I examine the propensity to form interethnic unions among the 1.5 and second generations of Arab Canadians using the 2016 Canadian census data. The descriptive analysis shows that interethnic unions are common within this population. About half the men (56%) and the women (49%) are in an interethnic union with a non-Arab person with an immigrant background or a Canadian of third generation or subsequent generations. The multinomial logistic regression reveals that men and women with higher educational attainment, part Arab ancestry and second-generation immigrant status are significantly more prone to be in an interethnic union than in an intraethnic union with a first-generation immigrant. In accordance with the segmented assimilation theory, these results suggest that socioeconomic integration and acculturation contribute to the propensity of Arab descendants to form unions with non-Arab individuals. The propensity of Arab descendants to be in intraethnic unions with first generation-immigrants or with descendants of immigrants (1.5 and second generations) is also discussed in this thesis

Journal bearing lubrication monitoring based on spectrum cluster analysis of vibration signals

Journal bearings are critical components for many important machines. Lubrication analysis techniques are often not timely and cost effective for monitoring journal bearings. This research investigates into vibration responses of such bearings using a clustering technique for identifying different lubrication regimes, and consequently for assessing bearing lubrication conditions. It firstly understands that the vibration sources are mainly due to the nonlinear effects including micro asperity collisions and fluid shearing interactions. These excitations together with complicated vibration paths are difficult to be characterized in a linear way for the purpose of condition monitoring. Therefore, a clustering analysis technique is adopted to classify the vibration spectrum in high frequency ranges around 10kHz into different representative responses that corresponds to different bearing modulus values and lubrication characteristics. In particular, the analysis allows sensitive signal components and sensor positions to be determined for monitoring the journal bearing effectively. Test results from self-aligning spherical journal bearings show that it allows different lubricant oils and different lubrication regimes to be identified appropriately, providing feasible ways to online monitoring bearing conditions

Flow trees for vertex-capacitated networks

AbstractGiven a graph G=(V,E) with a cost function c(S)⩾0∀S⊆V, we want to represent all possible min-cut values between pairs of vertices i and j. We consider also the special case with an additive cost c where there are vertex capacities c(v)⩾0 ∀v∈V, and for a subset S⊆V, c(S)=∑v∈Sc(v). We consider two variants of cuts: in the first one, separation, {i} and {j} are feasible cuts that disconnect i and j. In the second variant, vertex-cut, a cut-set that disconnects i from j does not include i or j. We consider both variants for undirected and directed graphs. We prove that there is a flow-tree for separations in undirected graphs. We also show that a compact representation does not exist for vertex-cuts in undirected graphs, even with additive costs. For directed graphs, a compact representation of the cut-values does not exist even with additive costs, for neither the separation nor the vertex-cut cases