Integrator Windup Protection-Techniques and a STOVL Aircraft Engine Controller Application

Integrators are included in the feedback loop of a control system to eliminate the steady state errors in the commanded variables. The integrator windup problem arises if the control actuators encounter operational limits before the steady state errors are driven to zero by the integrator. The typical effects of windup are large system oscillations, high steady state error, and a delayed system response following the windup. In this study, methods to prevent the integrator windup are examined to provide Integrator Windup Protection (IW) for an engine controller of a Short Take-Off and Vertical Landing (STOVL) aircraft. An unified performance index is defined to optimize the performance of the Conventional Anti-Windup (CAW) and the Modified Anti-Windup (MAW) methods. A modified Genetic Algorithm search procedure with stochastic parameter encoding is implemented to obtain the optimal parameters of the CAW scheme. The advantages and drawbacks of the CAW and MAW techniques are discussed and recommendations are made for the choice of the IWP scheme, given some characteristics of the system

Hard Exudate Extraction from Fundus Images using Watershed Transform

Diabetic Retinopathy is a medical condition which affects the eyes due to increased blood sugar levels. This is characterized by presence of exudates - deposits of lipids in the posterior pole of the retina. If this ailment is not treated in earlier stages these deposits can cause blurred vision or even permanent blindness. This paper concentrates on extraction of hard exudates and optic disc from the retinal images of eyes using Marker based Watershed approach, which uses the minima imposition method to create mask and marker. The varying contrast across all the images has been taken care by a non-linear equation. Once these bright objects have been extracted from fundus images, area estimation is performed to eliminate the optic disk, thus retaining only exudates. These images have been procured from publicly available databases. Though software systems are easy to install, they prove to be expensive in terms of time and cost; thus this method has also been implemented on FPGA for an on-chip solution. The precision and sensitivity for exudate extraction sans optic disk are found to be 92.4% and 83.78% respectively.  Though other techniques exist which provide better accuracy, the method described in this paper is found to be hardware friendly in comparison with other proven methods. Few steps of the algorithm developed are implemented on FPGA to provide an embedded system approach to this work, considering the advantages of a hardware-software combination

Exactly Hittable Interval Graphs

Given a set system $\mathcal{X} = \{\mathcal{U},\mathcal{S}\}$, where $\mathcal{U}$ is a set of elements and $\mathcal{S}$ is a set of subsets of $\mathcal{U}$, an exact hitting set $\mathcal{U}'$ is a subset of $\mathcal{U}$ such that each subset in $\mathcal{S}$ contains exactly one element in $\mathcal{U}'$. We refer to a set system as exactly hittable if it has an exact hitting set. In this paper, we study interval graphs which have intersection models that are exactly hittable. We refer to these interval graphs as exactly hittable interval graphs (EHIG). We present a forbidden structure characterization for EHIG. We also show that the class of proper interval graphs is a strict subclass of EHIG. Finally, we give an algorithm that runs in polynomial time to recognize graphs belonging to the class of EHIG.Comment: 17 pages. arXiv admin note: text overlap with arXiv:1707.0507

Chemical composition of essential oil of Psidium cattleianum var. lucidum (Myrtaceae)

The aim of this study was to investigate the essential oil composition of Psidium cattleianum var. lucidum from South Africa. The essential oils were extracted by hydrodistillation and the components were identified by gas chromatography coupled to mass spectrometry (GC-MS) to determine the chemical composition of the essential oil. A total of 53 chemical components were identified, accounting for 61% of the essential oil. The major component was caryophyllene oxide (12.43%), while other predominant constituents were identified as bicyclo(4.4.0)dec-l-ene (6.61%), 2,3-butanediol diacetate (4.84%) and patchoulene (4.73%). The presence of many terpenic and ester compounds is thought to contribute to the unique flavor of the P. cattleianum var. lucidum leaves.Keywords: Psidium cattleianum var. lucidum, essential oil, hydrodistillation, caryophyllene oxid

A review of the drug pregabalin

Pregabalin (PGB) is a well-established anticonvulsant and analgesic agent. The stydy reviewed the mechanism of action, pharmacokinetics, adverse drug reactions, contraindications, and various uses of PGB. Literature search was done to identify the relevant studies. PGB is an antagonist of voltage-gated calcium channels and specifically binds to α2-δ subunit to produce antiepileptic and analgesic activity. It has less protein binding activity and lacks hepatic metabolism. It is unlikely to cause pharmacokinetic drug-drug interactions. It has a wide safety margin and does not require serum drug monitoring. The above-mentioned favorable pharmacological benefits of PGB makes it a first-line or adjunctive therapy in various conditions like diabetic peripheral neuropathy, post-herpetic neuralgia, in partial seizures and generalized anxiety disorders

LOW CYCLE FATIGUE LIFE ESTIMATION OF A TURBINE BLISK

This paper deals with low cycle life estimation of a turbine blisk. The turbine blisk operates at extreme conditions; hence it is subjected to aerodynamic loads and high centrifugal loads. The loads on the turbine blisk vary due to the mission profile of the vehicle that includes takeoff, cruise and landing. An elastic-plastic finite element analysis is carried out. The life at the obtained stress and strain values is estimated using nCode DesignLife tool. Strain life approach is followed to estimate the life and Smith Watson Topper's approach is followed to carry out the mean stress correction.This paper deals with low cycle life estimation of a turbine blisk. The turbine blisk operates at extreme conditions; hence it is subjected to aerodynamic loads and high centrifugal loads. The loads on the turbine blisk vary due to the mission profile of the vehicle that includes takeoff, cruise and landing. An elastic-plastic finite element analysis is carried out. The life at the obtained stress and strain values is estimated using nCode DesignLife tool. Strain life approach is followed to estimate the life and Smith Watson Topper's approach is followed to carry out the mean stress correction

Temperature in nonequilibrium systems with conserved energy

We study a class of nonequilibrium lattice models which describe local redistributions of a globally conserved energy. A particular subclass can be solved analytically, allowing to define a temperature T_{th} along the same lines as in the equilibrium microcanonical ensemble. The fluctuation-dissipation relation is explicitely found to be linear, but its slope differs from the inverse temperature T_{th}^{-1}. A numerical renormalization group procedure suggests that, at a coarse-grained level, all models behave similarly, leading to a two-parameter description of their macroscopic properties.Comment: 4 pages, 1 figure, final versio