Modelling and control of crystallization process

Batch crystallizers are predominantly used in chemical industries like pharmaceuticals, food industries and specialty chemicals. The nonlinear nature of the batch process leads to difficulties when the objective is to obtain a uniform Crystal Size Distribution (CSD). In this study, a linear PI controller is designed using classical controller tuning methods for controlling the crystallizer outlet temperature by manipulating the inlet jacket temperature; however, the response is not satisfactory. A simple PID controller cannot guarantee a satisfactory response that is why an optimal controller is designed to keep the concentration and temperature in a range that suits our needs. Any typical process operation has constraints on states, inputs and outputs. So, a nonlinear process needs to be operated satisfying the constraints. Hence, a nonlinear controller like Generic Model Controller (GMC) which is similar in structure to the PI controller is implemented. It minimizes the derivative of the squared error, thus improving the output response of the process. Minimization of crystal size variation is considered as an objective function in this study. Model predictive control is also designed that uses advanced optimization algorithm to minimize the error while linearizing the process. Constraints are fed into the MPC toolbox in MATLAB and Prediction, Control horizons and Performance weights are tuned using Sridhar and Cooper Method. Performances of all the three controllers (PID, GMC and MPC) are compared and it is found that MPC is the most superior one in terms of settling time and percentage overshoot

उत्तर तमिलनाडु के कूटल्लूर, पषयार और कावेरिपट्टणम से तारली की भारी पकड

कृपया पूरा लेखा पढ

On the Origin of the Wide HI Absorption Line Toward Sgr A*

We have imaged a region of about 5' extent surrounding Sgr A* in the HI 21 cm-line absorption using the Very Large Array. A Gaussian decomposition of the optical depth spectra at positions within about 2' (approx. 5 pc at 8.5 kpc) of Sgr A* detects a wide line underlying the many narrow absorption lines. The wide line has a mean peak optical depth of 0.32 +/- 0.12 centered at a mean velocity of V(lsr) = -4 +/- 15 km/s. The mean full width at half maximum is 119 +/- 42 km/s. Such a wide line is absent in the spectra at positions beyond about 2' from Sgr A*. The position-velocity diagrams in optical depth reveal that the wide line originates in various components of the circumnuclear disk (radius approx. 1.3') surrounding Sgr A*. These components contribute to the optical depth of the wide line in different velocity ranges. The position-velocity diagrams do not reveal any diffuse feature which could be attributed to a large number of HI clouds along the line of sight to Sgr A*. Consequently, the wide line has no implications either to a global population of shocked HI clouds in the Galaxy or to the energetics of the interstellar medium as was earlier thought.Comment: LaTeX, 12 pages and 9 figures, accepted for publication in J. Astrophys. Ast

The Sasa-Satsuma higher order nonlinear Schrodinger equation and its bilinearization and multi-soliton solutions

Higher order and multicomponent generalizations of the nonlinear Schrodinger equation are important in various applications, e.g., in optics. One of these equations, the integrable Sasa-Satsuma equation, has particularly interesting soliton solutions. Unfortunately the construction of multi-soliton solutions to this equation presents difficulties due to its complicated bilinearization. We discuss briefly some previous attempts and then give the correct bilinearization based on the interpretation of the Sasa-Satsuma equation as a reduction of the three-component Kadomtsev-Petvishvili hierarchy. In the process we also get bilinearizations and multi-soliton formulae for a two component generalization of the Sasa-Satsuma equation (the Yajima-Oikawa-Tasgal-Potasek model), and for a (2+1)-dimensional generalization.Comment: 13 pages in RevTex, added reference

Small-scale traditional spiny lobster fishery at Tikkoti, Calicut

The spiny lobster fishery at Tikkoti though lesser in magnitude is important from the fishery point of view. The traditional fishermen living in three adjacent villages of Kodikal, Kadaloor and Tikkoti are engaged in lobster fishing for the past five decades. The total landings have declined over the years but sudden fall in catches as is seen in 1996-'97 may probably due to natural fluctuations in environmental conditions and change in current pattern rather than due to over fishing. In 1960's fishing was restricted to only three months from August to October and now the fishing begins in September or October and continues up to April or May. Unlike the southwest and southeast coasts where lobster fishing activity has increased several fold due to pressure from the export market, there is no substantial increase in effort at Tikkoti. Establishment of artificial reefs may help in enhancement of lobster population and therefore increase in catches and more revenue for the fishermen

Results from the first Argo float deployed by India

Argo is a revolutionary concept in ocean observation system that envisages real-time sampling of the temperature and salinity profiles of the global oceans at an approximate spatial resolution of 300 km, once in ten days. Argo float is an autonomous drifting profiler that pops up and down in the ocean from the surface up to 2000 m, measuring two most important physical properties of the water column, viz. temperature and salinity as a function of pressure (depth). Moreover, it can provide an estimate of currents both at the surface and at the parking depth in near-real time. India is an active participant in the Argo programme and has already deployed 31 out of 150 proposed floats. In this article, we describe the data received from the first Argo float deployed by India in the southeastern Arabian Sea. The data demonstrate that the temperature and salinity profiles from Argo floats present possibilities for oceanographic studies and spatial and temporal scales that had been hitherto impossibl

Diversity of mantids in tea plantation

Abstrac

Computational Study of Flow Establishment in a Ram Accelerator

The temporal evolution of the combustion process established during projectile transition from the launch tube into the ram accelerator section containing an explosive hydrogen-oxygen-argon gas mixture is studied. The Navier-Stokes equations for chemically reacting flow are solved in a fully coupled manner, using an implicit, time accurate algorithm. The solution procedure is based on a spatially second order total variation diminishing scheme and a temporally second order, variable-step, backward differentiation formula method. The hydrogen-oxygen chemistry is modeled with a 9-species, 19-step mechanism. The accuracy of the solution method is first demonstrated by several benchmark calculations. Numerical simulations of two ram accelerator configurations are then presented. In particular, the temporal developments of shock-induced combustion and thrust forces are followed. Positive thrust is established in both cases; however, in one of the ram accelerator configurations studied, combustion in the boundary layer enhances its separation, ultimately resulting in unstart

Predictors of angiographic restenosis in patients with coronary artery disease who have undergone percutaneous coronary intervention with drug eluting stents

Background: Percutaneous transluminal coronary angioplasty (PTCA) is now widely accepted as a nonsurgical revascularization procedure for selected patients with CAD. In-stent restenosis (ISR) is a frequent complication after PCI which limits its long-term efficacy. Identification of those clinical and angiographic characteristics that may predict the risk of restenosis is extremely important to eliminate restenosis. In this context we conducted this study to assess the profile of patients with drug eluting stents - ISR with an emphasis on demographic characteristics, risk factors, mode of presentation and coronary angiographic characterization.Methods: This study was a Case control study based on the catheterization registry of all patients who have undergone PCI with DES during the period from October 2012 to April 2015. All patients who have undergone PCI with DES and repeat coronary angiogram for evaluation of symptoms and detected to have ISR during same period were taken as case and age matched patients who had previously undergone PCI with DES and repeat coronary angiogram for evaluation of symptoms between 1/10/2012 to 30/4/2015 and detected to have fully patent stents were taken as control.Results: A total of 26 patients were detected to have ISR during the study period as per the study protocol with equal number of age matched controls. The most common presentation of ISR was as chronic stable angina (70%). Binary logistic regression analysis of 6 factors namely diabetes, hypertension, lesion type, stent diameter, stent length and stent overlap found significant in univariate analysis, showed only the lesion type to be statistically significant with p value of 0.023.Conclusions: Patients who have undergone PCI with DES particularly for complex lesions, diabetics with longer stents, lesser diameter stents and overlapping stents need to be meticulously followed up to rule out the possibility of restenosis, as in a small number of patients the presentation could be ACS with comparatively bad prognosis

Effect of salinity and pH on selected immune functions of the Indian white shrimp, Fenneropenaeus indicus (H. Milne Edwards, 1837)

The Indian white shrimp, Fenneropenaeus indicus, was subjected to environmental stresses like high (9) and low (5.5) water pH and decreasing water salinity (34 ‰ to 18 ‰) for a period of one week and certain vital immunological functions like total hemocyte count, total hemolymph protein and phenoloxidase activity were analysed to understand the effect of the environmental stress factors on these functions. The results indicated that while stress induced by change in the salinity had no damaging effects on the immune functions, stress caused by lower water pH induced more immunological damage when compared to higher water pH. Significantly decreased total hemocyte count and phenoloxidase activity were observed in shrimps exposed to lower pH when compared to shrimps exposed to higher pH and control shrimps. Also, lower pH significantly reduced the hemolymph protein values. It is therefore concluded that Fenneropenaeus indicus that are exposed to extreme pH show lowered immunological activity which would render the shrimp susceptible to infectious agents