Improved cascade control structure for enhanced performance

In conventional single feedback control, the corrective action for disturbances does not begin until the controlled variable deviates from the set point. In this case, a cascade control strategy can be used to improve the performance of a control system particularly in the presence of disturbances. In this paper, an improved cascade control structure and controller design based on standard forms, which was initially given by authors, is suggested to improve the performance of cascade control. Examples are given to illustrate the use of the proposed method and its superiority over some existing design methods

Mortality from gastrointestinal congenital anomalies at 264 hospitals in 74 low-income, middle-income, and high-income countries: a multicentre, international, prospective cohort study

Summary Background Congenital anomalies are the fifth leading cause of mortality in children younger than 5 years globally. Many gastrointestinal congenital anomalies are fatal without timely access to neonatal surgical care, but few studies have been done on these conditions in low-income and middle-income countries (LMICs). We compared outcomes of the seven most common gastrointestinal congenital anomalies in low-income, middle-income, and high-income countries globally, and identified factors associated with mortality. Methods We did a multicentre, international prospective cohort study of patients younger than 16 years, presenting to hospital for the first time with oesophageal atresia, congenital diaphragmatic hernia, intestinal atresia, gastroschisis, exomphalos, anorectal malformation, and Hirschsprung’s disease. Recruitment was of consecutive patients for a minimum of 1 month between October, 2018, and April, 2019. We collected data on patient demographics, clinical status, interventions, and outcomes using the REDCap platform. Patients were followed up for 30 days after primary intervention, or 30 days after admission if they did not receive an intervention. The primary outcome was all-cause, in-hospital mortality for all conditions combined and each condition individually, stratified by country income status. We did a complete case analysis. Findings We included 3849 patients with 3975 study conditions (560 with oesophageal atresia, 448 with congenital diaphragmatic hernia, 681 with intestinal atresia, 453 with gastroschisis, 325 with exomphalos, 991 with anorectal malformation, and 517 with Hirschsprung’s disease) from 264 hospitals (89 in high-income countries, 166 in middleincome countries, and nine in low-income countries) in 74 countries. Of the 3849 patients, 2231 (58·0%) were male. Median gestational age at birth was 38 weeks (IQR 36–39) and median bodyweight at presentation was 2·8 kg (2·3–3·3). Mortality among all patients was 37 (39·8%) of 93 in low-income countries, 583 (20·4%) of 2860 in middle-income countries, and 50 (5·6%) of 896 in high-income countries (p<0·0001 between all country income groups). Gastroschisis had the greatest difference in mortality between country income strata (nine [90·0%] of ten in lowincome countries, 97 [31·9%] of 304 in middle-income countries, and two [1·4%] of 139 in high-income countries; p≤0·0001 between all country income groups). Factors significantly associated with higher mortality for all patients combined included country income status (low-income vs high-income countries, risk ratio 2·78 [95% CI 1·88–4·11], p<0·0001; middle-income vs high-income countries, 2·11 [1·59–2·79], p<0·0001), sepsis at presentation (1·20 [1·04–1·40], p=0·016), higher American Society of Anesthesiologists (ASA) score at primary intervention (ASA 4–5 vs ASA 1–2, 1·82 [1·40–2·35], p<0·0001; ASA 3 vs ASA 1–2, 1·58, [1·30–1·92], p<0·0001]), surgical safety checklist not used (1·39 [1·02–1·90], p=0·035), and ventilation or parenteral nutrition unavailable when needed (ventilation 1·96, [1·41–2·71], p=0·0001; parenteral nutrition 1·35, [1·05–1·74], p=0·018). Administration of parenteral nutrition (0·61, [0·47–0·79], p=0·0002) and use of a peripherally inserted central catheter (0·65 [0·50–0·86], p=0·0024) or percutaneous central line (0·69 [0·48–1·00], p=0·049) were associated with lower mortality. Interpretation Unacceptable differences in mortality exist for gastrointestinal congenital anomalies between lowincome, middle-income, and high-income countries. Improving access to quality neonatal surgical care in LMICs will be vital to achieve Sustainable Development Goal 3.2 of ending preventable deaths in neonates and children younger than 5 years by 2030

Analysis of Output Voltage Harmonics of Voltage Source Inverter used PI and PID Controllers Optimized with ITAE Performance Criteria

In this article, PI and PID controllers are designed using ITAE (Integral Time Absolute Error) Performance Criteria in order to obtain the controller parameters assuring improved response at selected load. The voltage source inverter (VSI) including PI and PID controllers whose parameters are estimated by minimizing errors using ITAE performance criteria are modeled in MATLAB environment. The stability analysis of the control system will be presented. VSI controlled with the PI-ITAE and the PID-ITAE controller are simulated for various loads and the results are analyzed using FFT analysis for observing and comparing the total harmonic distortion (THD) of the output voltage. The quality of the sinusoidal waveform is more important than the quantity and in order to achieve that, we need to reduce the harmonic content in the output

Analysis of Output Voltage Harmonics of Voltage Source Inverter used PI and PID Controllers Optimized with ITAE Performance Criteria

In this article, PI and PID controllers are designed using ITAE (Integral Time Absolute Error) Performance Criteria in order to obtain the controller parameters assuring improved response at selected load. The voltage source inverter (VSI) including PI and PID controllers whose parameters are estimated by minimizing errors using ITAE performance criteria are modeled in MATLAB environment. The stability analysis of the control system will be presented. VSI controlled with the PI-ITAE and the PID-ITAE controller are simulated for various loads and the results are analyzed using FFT analysis for observing and comparing the total harmonic distortion (THD) of the output voltage. The quality of the sinusoidal waveform is more important than the quantity and in order to achieve that, we need to reduce the harmonic content in the output

Analysis of PFC and THD with the Boost Converter

Boost konvertörün diğer topolojilere üstünlüğünden dolayı bu çalışmada güç katsayısı düzeltme ve harmonik bozulmayı düşürmek için boost konvertör topolojisi kullanılmıştır. Tek fazlı ortalama akım mod kontrollü devre simülasyonu ve sonuçları MATLAB/Simulinkte yapılmış ve doğrulanmıştırIn this paper, the boost converter topology which has advantages over other converter topologies is used to correct power factor and to reduce total harmonic distortion. Single Phase average current mode controlled PFC circuit is simulated by MATLAB/Simulink simulation tool and simulation results are verified. The input current and output voltage simulation waveforms are illustrated and analyzed

Stability and Performance Analysis in an Uncertain World

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Some Results on Control Systems with Mixed Perturbations

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Stability Margin Computation for Nonlinear Systems: A Parametric Approach

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Design of Stabilizing PI and PID Controllers

In this paper, a new method for the calculation of all stabilizing PI controllers is given. The proposed method is based on plotting the stability boundary locus in the (kp, ki)-plane and then computing the stabilizing values of the parameters of a PI controller for a given control system. The technique presented does not require sweeping over the parameters and also does not need linear programming to solve a set of inequalities. Thus, it offers several important advantages over existing results obtained in this direction. The proposed method is also applied for computation of all stabilizing PI controllers for multi-input multi-output (MIMO) control systems with consideration given to two-input two-output (TITO) systems using decoupling technique. Beyond stabilization, the method is used to compute all stabilizing PI controllers which achieve user-specified gain and phase margins. Furthermore, the method is extended to tackle 3-parameters PID controllers. The limiting values of PID controller parameters which stabilize a given system are obtained in the (kp, ki)-plane for fixed values of kd and (kp, kd)-plane for fixed values of ki. However, for the case of PID controller, a grid on the derivative gain or integral gain is needed for computation of all stabilizing PID controllers. Examples are given to show the benefits of the method presented

Equity Options During the Shorting Ban of 2008

The Securities and Exchange Commission’s 2008 emergency order introduced a shorting ban of some 800 financials traded in the US. This paper provides an empirical analysis of the options market around the ban period. Using transaction level data from OPRA (The Options Price Reporting Authority), we study the options volume, spreads, pricing measures and option trade volume informativeness during the ban. We also consider the put–call parity relationship. While mostly statistically significant, economic magnitudes of our results suggest that the impact of the ban on the equity options market was likely not as dramatic as initially thought