3 research outputs found
On-line health monitoring of passive electronic components using digitally controlled power converter
This thesis presents System Identification based On-Line Health Monitoring to analyse the dynamic behaviour of the Switch-Mode Power Converter (SMPC), detect, and diagnose anomalies in passive electronic components. The anomaly detection in this research is determined by examining the change in passive component values due to degradation. Degradation, which is a long-term process, however, is characterised by inserting different component values in the power converter. The novel health-monitoring capability enables accurate detection of passive electronic components despite component variations and uncertainties and is valid for different topologies of the switch-mode power converter.
The need for a novel on-line health-monitoring capability is driven by the need to improve unscheduled in-service, logistics, and engineering costs, including the requirement of Integrated Vehicle Health Management (IVHM) for electronic systems and components. The detection and diagnosis of degradations and failures within power converters is of great importance for aircraft electronic manufacturers, such as Thales, where component failures result in equipment downtime and large maintenance costs. The fact that existing techniques, including built-in-self test, use of dedicated sensors, physics-of-failure, and data-driven based health-monitoring, have yet to deliver extensive application in IVHM, provides the motivation for this research ... [cont.]
Aging detection capability for switch-mode power converters
The detection of degradations and resulting failures in electronic components/systems is of paramount importance for complex industrial applications including nuclear power reactors, aerospace, automotive, and space applications. There is an increasing acceptance of the importance of detection of failures and degradations in electronic components and of the prospect of system-level health monitoring to make a key contribution to detecting and predicting any impending failures. This paper describes a parametric system identification-based health-monitoring method for detecting aging degradations of passive components in switch-mode power converters (SMPCs). A nonparametric system response is identified by perturbing the system with an optimized multitone sinusoidal signal of the order of mVs. The parametric system model is estimated from nonparametric system response using recursive weighted least-square (WLS) algorithm. Finally, the power-stage component values, including their parasitics, are extracted from numerator and denominator coefficients based on the assumed Laplace system model. These extracted component values provide direct diagnostic information of any degradation or anomalies in the components and the system. A proof of concept is initially verified on a simple point-of-load (POL) converter but the same methodology can be applied to other topologies of SMPC
An orally effective dihydropyrimidone (DHPM) analogue induces apoptosis-like cell death in clinical isolates of Leishmania donovani overexpressing pteridine reductase 1
The protozoan parasite Leishmania donovani is
the causative agent of visceral leishmaniasis. The enzyme
pteridine reductase 1 (PTR1) of L. donovani acts as a
metabolic bypass for drugs targeting dihydrofolate reductase
(DHFR); therefore, for successful antifolate chemotherapy
to be developed against Leishmania, it must target
both enzyme activities. Leishmania cells overexpressing
PTR1 tagged at the N-terminal with green fluorescent
protein were established to screen for proprietary dihydropyrimidone
(DHPM) derivatives of DHFR specificity
synthesised in our laboratory. A cell-permeable molecule
with impressive antileishmanial in vitro and in vivo oral
activity was identified. Structure activity relationship based on homology model drawn on our recombinant enzyme
established the highly selective inhibition of the enzyme by
this analogue. It was seen that the leishmanicidal effect of
this analogue is triggered by programmed cell death
mediated by the loss of plasma membrane integrity as
detected by binding of annexin V and propidium iodide
(PI), loss of mitochondrial membrane potential culminating
in cell cycle arrest at the sub-G0/G1 phase and oligonucleosomal
DNA fragmentation. Hence, this DHPM
analogue [(4-fluoro-phenyl)-6-methyl-2-thioxo-1, 2, 3, 4-
tetrahydropyrimidine-5-carboxylic acid ethyl ester] is a
potent antileishmanial agent that merits further pharmacological
investigation