Controlling Variables Research Articles

Properties of Hamiltonian in free final multitime problems

"In single-time autonomous optimal control problems, the Hamiltonian is constant on optimal evolution. In addition, if the final time is free, the optimal Hamiltonian vanishes on the hole interval of evolution. The purpose of this paper is to extend some of these results to the case of multitime optimal control. The original results include: anti-trace problem, weak and strong multitime maximum principles, multitime-invariant systems and change rate of Hamiltonian, the variational derivative of volume integral, necessary conditions for a free final multitime expressed with the Hamiltonian tensor that replaces the energy-momentum tensor, change of variables in multitime optimal control, conversion of free final multitime problems to problems over fixed interval."

Modeling and Reconstruction of State Variables for Low-Level Control of Soft Pneumatic Actuators.

To further advance closed-loop control for soft robotics, suitable sensor and modeling strategies have to be investigated. Although there are many flexible and soft sensors available, the integration into the actuator and the use in a control loop is still challenging. Therefore, a state-space model for closed-loop low-level control of a fiber-reinforced actuator using pressure and orientation measurement is investigated. To do so, the integration of an inertial measurement unit and geometric modeling of actuator is presented. The piecewise constant curvature approach is used to describe the actuator’s shape and deformation variables. For low-level control, the chamber’s lengths are reconstructed from bending angles with a geometrical model and the identified material characteristics. For parameter identification and model validation, data from a camera tracking system is analyzed. Then, a closed-loop control of pressure and chambers’ length of the actuator is investigated. It will be shown, that the reconstruction model is suitable for estimating the state variables of the actuator. In addition, the use of the inertial measurement unit will demonstrate a cost-effective and compact sensor for soft pneumatic actuators.

Variability of mackerel fish catch and remotely-sensed biophysical controls in the eastern Pemba Channel

Advances in satellite remote sensing of environmental perturbations have become important in understanding variations of ocean productivity and small pelagic fish catches. This marine resource is vital for coastal populations dependent on artisanal fishing for their income and food security, such as in coastal East Africa. In this region, the eastern Pemba Channel (Tanzania) represents a hotspot area, for a variety of marine species including small pelagics and coral reef associated species. This study examines the links between mackerel fish catch, one of the important small pelagic fish for direct consumption in the region, and changes in environmental oceanographic parameters over the period 2012–2018. The fisheries catch data is a rare local dataset, consisting of daily mackerel landings (from 2012 onwards) and supplemented by qualitative information on the mackerel fishery obtained through interviews with local stakeholders. The physical factors influencing phytoplankton biomass, and in turn, mackerel fisheries yield is investigated, using remotely-sensed chlorophyll-a (Chl-a) and Sea Surface Temperature (SST), together with Mixed Layer Depth (MLD) data from the high-resolution ocean model NEMO. We show that seasonal variations in mackerel landings are positively (negatively) correlated with Chl-a (SST) with a 1-month time lag (i.e., biophysical factors change first, mackerel stocks follow one month later). On the eastern side of the Pemba Channel, cooler SST and higher Chl-a are observed during the Southeast monsoon accompanied by increased mackerel landings, suggestive of enhanced productivity. Interannually, these relationships remain valid both for monthly and annual means, which confirms the close link between the variations of mackerel and biophysical conditions. Analysis of the Chl-a and MLD anomalies, relative to the mean, reveals that the phytoplankton blooms observed on the eastern side of the Pemba Channel, during the Southeast monsoon, are likely due to the deepening of the mixed layer, which tends to entrain cold and nutrient rich waters from greater depths to the surface. We conclude that upper ocean mixing contributes to the observed enhanced productivity along with other environmental factors. Additionally, we show how our results can be applied in the management of the mackerel resource in the Pemba Channel.

Pengaruh Electronic Money, Gaya Hidup Dan Pengendalian Diri Terhadap Perilaku Konsumsi Islam

This study was aimed to reveal the impact of electronic money, lifestyle and self control towards Islamic consumption behaviour pattern of Y and Z generation in Surabaya. The behaviour pattern of Islamic consumption was measured by 6 basic principles of consumption in Islam. Descriptive quantitative was applied as the research method. This study took 150 respondents as the research sample by using the formula of Malhotra. The data was collected by using questionnaire along with purposive sampling method and guttman scales. Then, probit regression analysis using the application of Stata 14 was occupied as the data analysis. It was resulted that the variable of electronic money had a marginal effect value of -9,5% so that the probability was not correspond to the Islamic consumption behaviour pattern whereas the variable of life style had a value of -9% which meant that the probability was not correspond to Islamic consumption behaviour pattern and the variable of self control indicated a value of 17% so that the probability matched with Islamic consumption behaviour pattern

In-process path replanning and online layer height control through deposition arc current for gas metal arc based additive manufacturing

Wire Arc Additive Manufacturing (WAAM) is recently receiving increasing attention as it offers a way to produce parts on a meter scale with high deposition rates and low production and capital costs. A major challenge in WAAM is the inherently variable layer height, which causes geometric inaccuracies in the final product. This paper proposes an on-line layer height control and in-process toolpath replanning for Gas Metal Arc (GMA) WAAM system, which enables better geometric accuracy when depositing tall shell parts. Deposition arc current and voltage were considered as control variables for layer height control. Arc current proved to be a more suitable control variable due to its higher sensitivity and higher correlation with changes in the contact tip to work distance. Different types of layer height controllers were developed and evaluated by depositing 30-layer high thin walls. Additionally, a re-slice algorithm was developed and implemented in the system controller. It compares the deposited section of the part to the CAD model after each layer has been built. The algorithm replans (re-slices) the toolpath to ensure better geometric accuracy of the finished part when the deviation exceeds the maximum allowable threshold. A 160 mm high case study part was manufactured and 3D scanned to demonstrate the novelty of the developed system. Results show that the layer height control keeps distance between the welding torch and the part surface during the deposition. Re-slice control, combined with layer height control, enables the manufacture of parts with correct final geometry.

Beat-to-beat blood pressure variability in patients with obstructive sleep apnea.

Cardiovascular comorbidities in obstructive sleep apnea (OSA) are difficult to treat, perhaps due to autonomic dysfunction. We assessed beat-to-beat blood pressure (BP) variability (BPV) in OSA while considering other markers derived from electrocardiogram and continuous BP signals. We studied 66 participants (33 participants with OSA: respiratory event index [mean ± SEM]: 21.1 ± 2.7 events/h; 12 females, aged 51.5 ± 2.4 years; body mass index: 32.8 ± 1.4 kg/m²; 33 healthy controls: 20 females; aged 45.3 ± 2.4 years; body mass index: 26.3 ± 0.7 kg/m²). We collected 5-minute resting noninvasive beat-to-beat BP and electrocardiogram values. From BP, we derived systolic, diastolic, and mean BP values, and calculated variability as standard deviations (systolic BPV, diastolic BPV, BPV). We also calculated diastole-to-systole time (time to peak). From the electrocardiogram, we derived QRS markers and calculated heart rate and heart rate variability. We performed a multivariate analysis of variance based on sex and group (OSA vs control), with Bonferroni-corrected post hoc comparisons (P ≤ .05) between groups. We calculated correlations of BPV with biological variables. Multivariate analysis of variance showed effects of diastolic BPV and BPV in OSA; post hoc comparisons revealed high diastolic BPV and BPV only in female participants with OSA vs controls. QRS duration was higher in OSA, with post hoc comparisons showing the effect only in males. BPV correlated positively with heart rate variability in controls but not in participants with OSA. BPV correlated positively with time to peak in females with OSA and OSA combined, whereas there was no BPV-time-to-peak correlation in healthy participants. The findings show sex-specific autonomic dysfunction reflected in beat-to-beat BP in OSA. The higher BPV may reflect poor baroreflex control or vascular damage in OSA, which are potential precursors to cardiovascular complications.

Particulate aggregation through a modulated annular one-dimensional acoustic field at resonant frequencies

The visualization and analysis of a novel acoustic-particulate system is the objective of this study. The system is composed of rice-husk fired smoke particulates (36.7nm–840μm) and one annular resonant circular-tube waveguide contrarily coupled with two sound sources. The collective interaction behavior process of smoke particulates in an inhomogeneous acoustic field is displayed during an experiment and a simulation. The result shows that the aggregation and fragmentation of particles under a change in resonant frequencies and sound pressure amplitude is extremely complex. This complex process consists of dynamically tuning the particle characteristics to attain stripes shaped like thin-films/umbrellas and clusters with volume-change/fragmentation. The balanced modulation of the acoustic radiation force and secondary radiation force to alter the particle characteristics (size and stack density) is verified to be the control mechanism of the particle system. The intermediate variable of the process control is the acoustic contrast factor (Ф) related to the physical characteristics of the growing particulates. The value plus-minus alternation of Ф results in different particulate processes. This study can enhance the application of aerodynamic acoustic-particulate-fluid systems for environment protection, energy fuel conversion, and industrial production.

Comprehensive analysis of immunoglobulin and clinical variables identifies functional linkages and diagnostic indicators associated with Behcet\u2019s disease patients receiving immunomodulatory treatment

BackgroundBehcet’s disease (BD) is a relapsing systemic vascular autoimmune/inflammatory disease. Despite much effort to investigate BD, there are virtually no unique laboratory markers identified to help in the diagnosis of BD, and the pathogenesis is largely unknown. The aim of this work is to explore interactions between different clinical variables by correlation analysis to determine associations between the functional linkages of different paired variables and potential diagnostic biomarkers of BD.MethodsWe measured the immunoglobulin proteome (IgG, IgG1–4, IgA, IgA1–2) and 29 clinical variables in 66 healthy controls and 63 patients with BD. We performed a comprehensive clinical variable linkage analysis and defined the physiological, pathological and pharmacological linkages based on the correlations of all variables in healthy controls and BD patients without and with immunomodulatory therapy. We further calculated relative changes between variables derived from comprehensive linkage analysis for better indications in the clinic. The potential indicators were validated in a validation set with 76 patients with BD, 30 healthy controls, 18 patients with Takayasu arteritis and 18 patients with ANCA-associated vasculitis.ResultsIn this study, the variables identified were found to act in synergy rather than alone in BD patients under physiological, pathological and pharmacological conditions. Immunity and inflammation can be suppressed by corticosteroids and immunosuppressants, and integrative analysis of granulocytes, platelets and related variables is likely to provide a more comprehensive understanding of disease activity, thrombotic potential and ultimately potential tissue damage. We determined that total protein/mean corpuscular hemoglobin and total protein/mean corpuscular hemoglobin levels, total protein/mean corpuscular volume, and plateletcrit/monocyte counts were significantly increased in BD compared with controls (P < 0.05, in both the discovery and validation sets), which helped in distinguishing BD patients from healthy and vasculitis controls. Chronic anemia in BD combined with increased total protein contributed to higher levels of these biomarkers, and the interactions between platelets and monocytes may be linked to vascular involvement.ConclusionsAll these results demonstrate the utility of our approach in elucidating the pathogenesis and in identifying novel biomarkers for autoimmune diseases in the future.

Optimal Perturbations of Systems with Delayed Independent Variables for Control of Dynamics of Infectious Diseases Based on Multicomponent Actions

In this paper, we apply optimal perturbations to control mathematical models of infectious diseases expressed as systems of nonlinear differential equations with delayed independent variables. We develop the method for calculation of perturbations of the initial state of a dynamical system with delayed independent variable producing maximal amplification in the given local norm taking into account weights of perturbation components. For the model of experimental virus infection, we construct optimal perturbation for two types of stationary states, with low or high viral load, corresponding to different variants of chronic virus infection flow.

A Multi-level Longitudinal Model of Risk Factors for Generalized and Separation Anxiety Symptoms in a Community Sample of 6-year-olds.

The current longitudinal study examined the relations between variables in four domains-contextual (SES, family conflict, stress), parent (caretaker depression), parenting (support hostility, autonomy granting), and child (negative affect, effortful control, sensory regulation, attachment)-and both the presence of generalized and separation anxiety symptoms at age 6in a community sample of 796 children and the change in these anxiety symptoms from ages 4 to 6. Anxiety was highly stable over time. Specific results revealed both direct and indirect pathways between age 4 and age 5 variables, and age 6 anxiety. Caretaker depression and the child variables of attachment, effortful control, negative affect, and sensory regulation were directly related to anxiety symptoms at age 6. Contextual variables (SES) at age 4 were indirectly related to age 6 anxiety through parent depression at age 5. Parent depression was indirectly related to age 6 anxiety through age 5 child negative affect. Child negative affect at age 4 was indirectly related to age 6 anxiety through age 5 effortful control and age 4 effortful control was indirectly related to age 6 anxiety through age 5 negative affect. With the exception of attachment, there was a reduction in the impact of other variables when initial levels of anxiety symptoms were included in the model. Implications of results for early intervention and further study are discussed.

Torque Ripple Reduction Method for Permanent Magnet Synchronous Machine Drives With Novel Harmonic Current Control

Torque ripple reduction has become an active research area for permanent magnet synchronous machine (PMSM) drives. This paper presents a novel torque ripple reduction method based on harmonic current control. In the proposed method, the optimal harmonic current solution based on the torque ripple model with minimum stator resistive loss is derived in the rotor reference frame (RRF). The optimal harmonic currents are injected by the proposed harmonic current controller (HCC), wherein the magnitude of harmonic currents are defined as controller variables. To estimate the harmonic currents, the proposed method also utilizes the least mean square (LMS) based adaptive filter (AF), wherein the coefficients are defined as feedback to the proposed HCC. The proposed methodology is demonstrated using both simulations and experiments and is verified to reduce torque ripples of PMSM drives over a wide range of speeds.

Survival Analysis of 3 Different Age Groups and Prognostic Factors among 402 Patients with Skeletal High-Grade Osteosarcoma. Real World Data from a Single Tertiary Sarcoma Center.

Simple SummaryAge is one of many prognostic factors for overall survival in patients with skeletal osteosarcoma. This retrospective study provides an overview of survival in patients with high-grade osteosarcoma in different age groups. It shows prognostic variables for survival and local control among the overall cohort. In this study, in which 402 patients with skeletal high-grade osteosarcoma were included, poor survival was associated with increasing age. Age groups, tumor size, poor histopathological response, distant metastasis at presentation, and local recurrence were independent prognostic factors associated to overall survival and event-free survival. Differences in outcome among different age groups can be partially explained by patient characteristics and treatment characteristics.Age is a known prognostic factor for many sarcoma subtypes, however in the literature there are limited data on the different risk profiles of different age groups for osteosarcoma survival. This study aims to provide an overview of survival in patients with high-grade osteosarcoma in different age groups and prognostic variables for survival and local control among the entire cohort. In this single center retrospective cohort study, 402 patients with skeletal high-grade osteosarcoma were diagnosed and treated with curative intent between 1978 and 2017 at the Leiden University Medical Center (LUMC). Prognostic factors for survival were analyzed using a Cox proportional hazard model. In this study poor overall survival (OS) and event-free survival (EFS) were associated with increasing age. Age groups, tumor size, poor histopathological response, distant metastasis (DM) at presentation and local recurrence (LR) were important independent prognostic factors influencing OS and EFS. Differences in outcome among different age groups can be partially explained by patient and treatment characteristics.

Characteristic Analysis and Indexing of Multimachine Transient Stabilization Using Virtual Synchronous Generator Control

As distributed power sources via grid-connected inverters equipped with functions to support system stabilization are being rapidly introduced, individual systems are becoming more complex, making the quantification and evaluation of the stabilizing functions difficult. Therefore, to introduce distributed power sources and achieve stable system operation, a system should be reduced to a necessary but sufficient size in order to enable the quantification of its behavior supported by transient theory. In this study, a system in which multiple distributed power supplies equipped with virtual synchronous generator control are connected is contracted to a two-machine system: a main power supply and all other power supplies. The mechanical torque of each power supply is mathematically decomposed into inertia, damping, synchronization torques, and the governor effect. The system frequency deviations determined by these elements are quantitatively indexed using MATLAB/Simulink. The quantification index displayed in three-dimensioned graphs illustrates the relationships between the various equipment constants of the main power supply, the control variables of the grid-connected inverter control, and the transient time series. Moreover, a stability analysis is performed in both the time and frequency domains.

Effect of Internal Control on Performance of Cooperatives in Nigeria: A Case Study of CSM Cooperative Society Abuja, Nigeria

This paper examined the impact of internal control on operational performance in CSM Cooperative Society. Cooperatives have become a good source of affordable finance for both low and medium income group all over the world. As critically important as cooperatives are to the growth and development of Nigeria vide the provision of funds for business and investment hence employment, they may not survive in the long term if they are not properly managed. The presence of an effective and efficient internal control system will go a long way in aiding the cooperatives to manage their operations well. The study investigated internal control impact on performance of cooperatives in Abuja. The target population was the Executive Management Committee, Senior Management, Senior and Junior staff of CSM Cooperative, Abuja, Nigeria. Survey method was employed, and questionnaires were distributed to all the categories of employees identified. Multiple-Linear Regression was used to analyze the data collected vide a 5 point Likert-scale questionnaire. The study revealed that the relationship between internal control (monitoring, control environment, control activities) and performance of cooperatives is not significant. It was recommended that cooperatives should ensure that they seek for and implement measures that increase profitability in addition to instituting a good and functioning system of internal control. The study also recommended that future research should add the two variables of internal control not covered in this research and also use a sample number of cooperatives in Abuja.

A scenario-based approach for translating strategic perspectives into input variables for production planning and control

Deriving conclusions for manufacturing systems from strategically planned external scenarios can be difficult, as external developments are not usually directly linked to manufacturing systems. Understanding production planning, scheduling, and control as a filter for external developments helps to make scenario-based planning more tangible. The presented approach aims to identify external scenarios and translate those into input variables for manufacturing systems to provide a systematic and transparent starting point for risk management and change processes. Therefore, strategic planning methods become interconnected with a receptor model for the operation of manufacturing systems.

Proportional-Integral-Derivative and Linear Quadratic Regulator Control of Direct Current Motor Position using Multi-Turn Based on LabView

This study accommodates the industry needs in monitoring a control system on a DC motor using LabView. The servomotor, which is usually used for position control, was replaced in this study with a DC motor coupled with a multi-turn potentiometer sensor. The use of DC motors was carried out to reduce actuator prices while maintaining control objectives. The control method used is in the form of Proportional – Integral - Derivative (PID) and optimal control which are then compared with the output. PID tuning is done using the Root Locus method. Meanwhile, for optimal control using the Linear Quadratic Regulation (LQR) approach. Testing was done by looking at the results of direct implementation of the DC motor plant hardware through observations using LabView. By using the right zero variables in the PID control, the best performance is obtained until it can track references. Too large a zero value will result in even greater Steady State Error. The results of optimal control using different Q variables did not provide a significant change. The SSE value shows the same result. The results show that the optimal control can track the reference with lower settling time and overshoot than the PID control. However, the two control methods still produce relatively small Steady State Error.

Multifractal Analysis of Heart Rate Variability by Applying Wavelet Transform Modulas Maxima Method

The analysis of heart rate variability is based on the intervals between the successive heartbeats and thanks to it information about the functional state of the person can be obtained and the dynamics of its change can be traced. The nonlinear dynamics methods provide additional, prognostic information about the patient's health, complementing traditional analyses and are considered potentially promising tools for assessing heart rate variability. In this article, studies have been carried out to identify the mono- and multifractal properties of two groups of people: healthy controls and patients with arrhythmia using Wavelet Transform Modulas Maxima Method. The obtained results from the studies show that for healthy subjects the multifractal spectrum is broader than the spectrum of patients with arrhythmia. The value of the Hurst exponent is lower in healthy controls, and in patients with arrhythmia this parameter tends to one. For the healthy subjects, the scaling exponent showed nonlinear behaviour, while for patients with arrhythmia it was linear. This indicates that heart rate variability in healthy controls has multifractal behaviour while patients with arrhythmia have monofractal behaviour. The finding may be useful in diagnosing subjects with cardiovascular disease, as well as in predicting future diseases, as the heart rate variability changes at the slightest deviation in the health status of subjects before the onset of relevant signs of the disease.

Adaptive Control System for Biogas Power Plant Using Model Predictive Control

This paper presents an adaptive control system using model predictive control for a biogas-fueled power system. The control scheme is derived from an anaerobic digestion model that includes the concentration of biodegradable volatile solid in the reactor, the concentration of volatile solid in influent, the concentration of acidogens, and the concentration of methanogens. All these concentrations are the state variables of model predictive control. The whole biogas-fueled power system has been modeled, implemented, and tested in MATLAB/Simulink environment. To validate the performance of the proposed controller, different operation conditions are studied and analyzed. The simulation results prove the effectiveness and the applicability of the proposed control system under different operating conditions.

Distributed Sliding Mode Observer-Based Secondary Control for DC Microgrids Under Cyber-Attacks

The conventional distributed secondary control is widely adopted for distributed energy resources (DERs) in DC microgrids to achieve bus voltage restorations and output current/power sharing. However, when the DER systems are under cyber-attacks, the control variables of the conventional distributed secondary control will deviate from the nominal parameters and the stability of entire DC microgrids may not be guaranteed anymore. To this end, a distributed sliding mode observer (DSMO)-based secondary control is proposed in this paper. Based on local and neighboring measurements, the DSMO initially detects the false signals. Then, the estimated false signals are compensated by the control variables of the secondary control to eliminate the adverse impact. The stability of DSMO is verified by the convergence of the state variables. Both simulation and experimental results have validated that the proposed DSMO-based secondary control can effectively regulate the DER systems to track the bus voltage references and the desired output current/power under various types of cyber-attacks.

THE INFLUENCE OF PLANNED BEHAVIOUR THEORY AND KNOWLEDGE TOWARDS THE WAQIF INTENTION IN CONTRIBUTING WAQF

Waqf performance, as part of Islamic social finance is determined by, among others, willingness of society to donate their assets into waqf. Ability to understand determinants of the willingness may contribute to more optimum waqf assets accumulation and management. This study aims to investigate the effect of attitudes, subjective norms, perceived behavioral control, and knowledge in influencing the willingness of waqif to donate through the Airlangga University Social Fund Management Center (PUSPAS). This research is a quantitative study using multiple regression analysis. Data for this study is obtained from 98 respondents. The study results imply that there was no significant simultaneous influence in the variables of attitudes, subjective norms, behavioral control, and knowledge of waqif willingness to represent in PUSPAS. The attitude and knowledge variables are variables that have a significant influence partially. In contrast, the subjective norm variables and behavioral control have a partially insignificant impact on the intention of waqf to represent.