Signal patterns of piston slap of a four-cylinder diesel engine

This paper presents an experimental study on the vibration signal patterns associated with a simulated piston slap test of a four-cylinder diesel engine. It is found that a simulated worn-off piston results in an increase in vibration RMS peak amplitudes associated with the major mechanical events of the corresponding cylinder (i.e., inlet and exhaust valve closing and combustion of Cylinder 1). This then led to an increase of overall vibration amplitude of the time domain statistical features such as RMS, Crest Factor, Skewness and Kurtosis in all loading conditions. The simulated worn-off piston not only increased the impact amplitude of piston slap during the engine combustion, it also produced a distinct impulse response during the air induction stroke of the cylinder attributing to an increase of lateral impact force as a result of piston reciprocating motion and the increased clearance between the worn-off piston and the cylinder. The unique signal patterns of piston slap disclosed in this paper can be utilized to assist in the development of condition monitoring tools for automated diagnosis of similar diesel engine faults in practical applications

Assessment of Pollution in Sidi M'Hamed Benali Lake (Algeria) Based on Bioindicators and Physicochemical Parameters

peer reviewedThis study was carried out to investigate the degree, the nature and the origin of pollution in Sidi M’hamed Benali Lake using the physicochemical parameters, saprobic index and cladocerans. For this purpose, water and zooplankton sampling was collected from six sites in lake during five seasons. The average seasonal values of physicochemical parameters showed that the lake undergoes a slight anthropogenic and natural pollution in the dry and wet periods. Presence of certain toxic substances (CN-, Cr, Ni) require us to be more careful in irrigation, bathe and the consumption of fishes of that reservoir. Overall, oligo-mesosaprobic to beta-mesosaprobic rotifers have been prevailing in all five seasons indicating that the water was slightly or moderate polluted. The presence of Bosmina longirostris, Daphnia longispina, Daphnia cuculata, Daphnia ambiga and Sididae diaphonosoma brachyrum indicate bacterial contamination with the intense development of the phytoplankton in the lake, especially in springs and summer. Pearson correlation analysis revealed significant correlation between all of the physicochemical parameters. However, it revealed no significant correlation between zooplanktons occurrence and the majority environmental variables values. In present investigation, the Lake water is relatively little exposed to pollution and does not undergo strong organic pollution

Sélection de quelques plantes médicinales du Zerhoun (Maroc centrale) pour l’activité antibactérienne contre Pseudomonas aeruginosa

Objective: To evaluate the in vitro antibacterial activities of two extracts (Aqueous extract and ethanolic extract) from the leaves of fourteen medicinal plants found in Zerhoun (central Morocco) on the growth of six strains of Pseudomonas aeruginosa. Methodology and Results: The method of diffusion in solid and macromethod of dilution in liquid medium from active extract were used for antibacterial testing. The results showed that aqueous extracts were more active than the ethanol extracts. The plant extracts were more active against pigmented strains (pyocyanin) than against non-pigmented strains. Eight plants showed antibacterial activity against one or more bacterial strains. The aqueous extract of Eucalyptus gomphocephala presented the highest anti Pseudomonas aeruginosa activity against all strains tested with zones of inhibition between 16 and 18.5 mm, having an MIC value (6.25-12. 5mg/ml) and MBC (6.25-25mg/ml). Conclusion and Application: According to this study results, water was the best solvent in the concentration of the active ingredients of the plants. In addition, the antibacterial activities of the extracts from the leaves of eucalyptus in this study could justify the therapeutic use of this plant in traditional medicine in the treatment of many bacterial infections.Keywords: antibacterial activity; aqueous extracts; ethanol extracts; Pseudomonas aeruginosa; eucalyptus gomphocephala

Parasitoses opportunistes digestives chez les adultes infectés par le VIH : Aspects épidémiologiques Opportunistic digestive parasitic infections in adults infected with HIV: epidemiological expression

Introduction :Les parasitoses digestives opportunistes restent les principaux agents responsables de diarrhées chez les patients infectés par le VIH/Sida. Ce sont des infections classant Sida.le but de travail était de déterminer  la fréquence des parasitoses digestives opportunistes chez les patients infectés par le VIHMatériels et méthodes :Etude retroprospective descriptive de 20 mois déroulée dans le service de maladies infectieuses de casablanca. Ont  été inclus tous les patients infectés par le VIH et présentant une parasitose digestive opportuniste confirmée à l’EPS.Résultats :Nous avons colligé 70 patients.  L’âge moyen était de 37 ans. La médiane de lymphocytes CD4 était de 62celellule/mm³. Les parasitoses opportunistes digestives étaient révélatrices de l’infection à VIH dans 54 cas (77%)  et dans 16 cas (23%) elles sont survenues au décours d’un échec thérapeutique. Tous les patients présentaient des diarrhées liquidiennes. Ces agents parasitaires opportunistes étaient isolés seuls dans 56 cas dont 28 cas de Cryptosporidiose (40%),  22 cas de microsporidiose (31%), 4 cas d’Isospora belli (6%) et 2 cas de cyclosporose (3%).  Elles étaient associées dans 14 cas dont 13 cas de Cryptosporidiose + Microsporidiose (18,57%) et 1 cas de Cryptosporidiose + Isosporose (1,43%).  Sous HARRT, 86% des patients ont bien évolué (n=60) et nous avons enregistré 14% de décès (n=10).Conclusion :Les parasitoses digestives opportunistes restent fréquentes dans notre contexte à cause du diagnostic tardif  du VIH/SIDA. Le dépistage précoce du VIH permettra de les prévenir

On the Nyquist frequency of random sampled signals

In modern industry, the wide use of reliable and sophisticated sensors with their connection to internet has introduced the phenomena of Big Data, especially in the field of condition monitoring systems (CMSs) in e-maintenance applications. In particular, in the case of vibration signals, high-performance acquisition systems are required, characterized by anti-aliasing filtering and high uniform sampling rate, in order to properly digitalize the meaningful frequency content of the signals. In this context, the capability of non-uniform random sampling (RS) is assessed in this work. While in different fields, such astronomy, structural and biomedical studies, the RS is a problem to be resolved, due to the unavailability of samples at specific instants (missing data problem), in the field of fault detection & diagnosis (FDD), RS can be a chosen sampling method thanks to its advantages: Anti-aliasing property and low average sampling rate. Therefore, this paper focuses on studying the anti-aliasing property of the random sampled data, verifying the criterion proposed in literature for establish the Nyquist frequency, and analyzing its sensitivity to the sampling parameters. This study is carried out using simulated signals and computing the spectral window, giving the Nyquist frequency for different random sampling parameters; moreover, a spectral analysis method, the Schuster periodogram, is used to verify when the spectrum is actually free of alias. The results show that the Nyquist frequency depends on the numerical accuracy of the randomly generated time instants