Use of the Riccatti Equation On-Line for Adaptively Controlling a CSTR Chemical Reactor.

An idealised nonlinear model of an isothermal continuous stirred-tank reactor (CSTR) is analysed and simulated for optimal control based on the continuous on-line recomputation of a Riccati Controller as proposed by Banks (1). The controller and resulting behaviour are derived analytically and confirmed to be optimal by derivation also via Dynamic Programming. For comparison purposes, the behaviour of the same model under linear proportional control (with feedforward compensation)is derived also and the predicted behavioural patterns confirmed by SIMULINK simulation in both cases. The Banks controller is shown to out perform the linear version not only in terms of the pre-formulated quadratic cost function but also in terms of response time for systems of equal maximum input excursion. It is shown to tolerate non-negative flow constraints omitted from the pre-formulated cost function

Use of the Riccati Equation On-Line for Adaptively Controlling a CSTS Distillation Column

A third order CSTS model for the separation dynamics of packed distillation columns is converted to a form expressed in terms of deviations of input and output from steady-state. This form has been found to be necessary for the application of the Banks' method of On-Line Riccati Control. The state-dependant coefficient matrices of the process are derived analytically in terms of the fundamental length, volatility and capacitance parameters of the process. Having successfully tested the modified model against the original, whole-value, simulation model and against analytic behavioural prediction, simulation experiments are conducted, comparing the responses and costs of the Banks' -controlled system with linear output feedback. The optimal control is found to be significantly superior to linear control for equal input excursions, in terms of cost-function-value, energy consumption and for large turn-down ratios, speed-of-response. The results offer promise for the control method when applied to tubular columns in the future

The Simulation Testing of Analytically-Derived, Steady-State and Transfer-Function Models for CSTC Binary Distillation Columns

Parametric steady-state and transfer-functions models, analytically-derived for separation occurring within a packed CSTC distillation column reported in ACSE RR573, 1995 are here validated by comprehensive time domain simulation. Both large-signal steady-state and small signal dynamic responses are found to be in complete accord with the analytical predictions under both open and linear, closed-loop control conditions. Differences in large signal behaviour are demonstrated and are explained in terms of the non-linear reversing gain characteristic of the process here derived. The work is undertaken and reported as essential preliminaries to using the models for future behavioural prediction, in particular, under the On Line Riccati Control strategy of Banks {2}

Interpretation and Utilisation of Parametric Models of Binary Distillation Columns; Relating Plant and Control Design

Previously published analytical models (1) (2) for the separation dynamics of CSTC and tubular packed distillation columns are rederived using common notation for detailed comparison purposes. The separation and total composition equations are now successfully separated at an early stage in the derivation which is thus simplified. The analyses produce parametric formulae for steady-state separation and for the transfer functions of both columns in terms of length, relative volatility, evaporation-and nominal vapour-rate, parameters only plus columns and end-vessel capacitance. A second order, nonminimum-phase structure derived from high-and low-frequency asymptotic behaviour is shown to fit all types and on the basis of this, analytic stability and critical error criteria for linear closed-loop control are derived; again requiring the substitution only of the above mentioned plant parameters. It is shown that, for equal parameters, tubular columns out perform CSTC types. However, matching of the two types for separation and stability is achievable by fictitious inflation of the CSTC length and volatility coefficient. This may permit use of an equivalent but simpler CSTC model for unified tubular plant and control design. Finally the CSTC column is formulated as a parametric, bilinear third-order, state space model having a state-dependent, input-coefficient matrix. This is derived with a view to future application of optimal control based on the on-line Riccatti solution method of Banks (3) already successfully tested on a bilinear CSTR chemical reactor model (4)

The Reaction of a Nitro-Capped Cobalt(III) Cage Complex With Base: the Crystal Structure of a Contracted Cage Complex, and the Mechanism of Its Formation

The synthesis, properties and crystal structure of the cage complex (1-hydroxy-8-methyl-3,6,10,13,15,18-hexaazabicyclo[6.6.5]nonadecane)cobalt(III) chloride hydrate ([Co(Me,OH-absar)] C13.H2O) are reported. The mechanism of the formation of this contracted cavity cage from a nitro-capped hexaazabicycloicosane type cage has been investigated. Treatment of (1-methyl-8-nitro-3,6,10,13,16,19-hexaazabicyclo[6.6.6]icosane)cobalt(III) chloride ([Co(Me,NO2-sar)] 3+) with excess base in aqueous solution leads initially to rapid (t1/2 < 1 ms) and reversible deprotonation of one coordinated secondary amine. This species undergoes a retro-Mannich type reaction and imine hydrolysis (t1/2 almost-equal-to 90 s). Quenching the reaction with acid gives rise to a pair of isomeric intermediate species which have been isolated and characterized. They have a pendant arm macrocyclic structure, resulting from the loss of a methylene unit from one of the arms of the cap. Heating either isomer in aqueous solution gives the new cage compound with the contracted cap. It is postulated that this occurs through a Nef reaction, resulting in the formation of a ketone which then condenses with the coordinated primary amine. A comparison with the corresponding bicycloicosane analogue indicates a reduced chromophoric cavity size for the contracted cage. The reduction potential of the cobalt(III)/cobalt(II) couple is 170 mV more negative for the smaller cage, and, in the electronic spectrum of the cobalt(III) complex, the d-d transitions are both shifted to higher energy, corresponding to a stronger ligand field

The Effects Of Dry And Chilled Air On Tool Wear Behavior During Face Milling Of Inconel 718

Tool wear is one of the important criteria during the cutting process. It is mostly caused by the machining parameters, namely; cutting speed, feed rate, depth of cut, cooling condition, etc. This paper presents the behavior of cutting tool during dry and chilled air condition of face mill with the cutting speed of 20 to 40 m/min, the feed rate of 0.1 to 0.2 mm/tooth and axial depth of 0.1 mm. The analysis of variance (ANOVA) is applied to identify the significance of these factors effect on tool performance, later the mathematical model for the tool life prediction was developed. The investigation revealed that the cutting speed, feed rate dominating wear rate whilst the chilled air found to be marginally significant. Finally, the optimum condition for machining parameter for greater tool life can be obtained by the combination cutting speed of 20 m/min, the feed rate of 0.1 mm/tooth under chilled air condition. Implementation of chilled air contributed 7% improvement with 45 min compared to a dry condition. The study exhibited the round type insert of dry face milling is more prone to rapid flank wear than chilled air with no BUE appearance on the tool cutting edge

The global burden of cancer attributable to risk factors, 2010–19: a systematic analysis for the Global Burden of Disease Study 2019

BACKGROUND: Understanding the magnitude of cancer burden attributable to potentially modifiable risk factors is crucial for development of effective prevention and mitigation strategies. We analysed results from the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2019 to inform cancer control planning efforts globally. METHODS: The GBD 2019 comparative risk assessment framework was used to estimate cancer burden attributable to behavioural, environmental and occupational, and metabolic risk factors. A total of 82 risk–outcome pairs were included on the basis of the World Cancer Research Fund criteria. Estimated cancer deaths and disability-adjusted life-years (DALYs) in 2019 and change in these measures between 2010 and 2019 are presented. FINDINGS: Globally, in 2019, the risk factors included in this analysis accounted for 4·45 million (95% uncertainty interval 4·01–4·94) deaths and 105 million (95·0–116) DALYs for both sexes combined, representing 44·4% (41·3–48·4) of all cancer deaths and 42·0% (39·1–45·6) of all DALYs. There were 2·88 million (2·60–3·18) risk-attributable cancer deaths in males (50·6% [47·8–54·1] of all male cancer deaths) and 1·58 million (1·36–1·84) risk-attributable cancer deaths in females (36·3% [32·5–41·3] of all female cancer deaths). The leading risk factors at the most detailed level globally for risk-attributable cancer deaths and DALYs in 2019 for both sexes combined were smoking, followed by alcohol use and high BMI. Risk-attributable cancer burden varied by world region and Socio-demographic Index (SDI), with smoking, unsafe sex, and alcohol use being the three leading risk factors for risk-attributable cancer DALYs in low SDI locations in 2019, whereas DALYs in high SDI locations mirrored the top three global risk factor rankings. From 2010 to 2019, global risk-attributable cancer deaths increased by 20·4% (12·6–28·4) and DALYs by 16·8% (8·8–25·0), with the greatest percentage increase in metabolic risks (34·7% [27·9–42·8] and 33·3% [25·8–42·0]). INTERPRETATION: The leading risk factors contributing to global cancer burden in 2019 were behavioural, whereas metabolic risk factors saw the largest increases between 2010 and 2019. Reducing exposure to these modifiable risk factors would decrease cancer mortality and DALY rates worldwide, and policies should be tailored appropriately to local cancer risk factor burden