Mixed Sensitivity Research Articles

Evaluating the sensitivity of jurisdictional heterogeneity and jurisdictional mixing in national level HIV prevention analyses: context of the U.S. ending the HIV epidemic plan

BackgroundThe U.S. Ending the HIV epidemic (EHE) plan aims to reduce annual HIV incidence by 90% by 2030, by first focusing interventions on 57 regions (EHE jurisdictions) that contributed to more than 50% of annual HIV diagnoses. Mathematical models that project HIV incidence evaluate the impact of interventions and inform intervention decisions. However, current models are either national level, which do not consider jurisdictional heterogeneity, or independent jurisdiction-specific, which do not consider cross jurisdictional interactions. Data suggests that a significant proportion of persons have sexual partnerships outside their own jurisdiction. However, the sensitivity of these jurisdictional interactions on model outcomes and intervention decisions hasn’t been studied.MethodsWe developed an ordinary differential equations based compartmental model to generate national-level projections of HIV in the U.S., through dynamic simulations of 96 epidemiological sub-models representing 54 EHE and 42 non-EHE jurisdictions. A Bernoulli equation modeled HIV-transmissions using a mixing matrix to simulate sexual partnerships within and outside jurisdictions. To evaluate sensitivity of jurisdictional interactions on model outputs, we analyzed 16 scenarios, combinations of a) proportion of sexual partnerships mixing outside jurisdiction: no-mixing, low-level-mixing-within-state, high-level-mixing-within-state, or high-level-mixing-within-and-outside-state; b) jurisdictional heterogeneity in care and demographics: homogenous or heterogeneous; and c) intervention assumptions for 2019–2030: baseline or EHE-plan (diagnose, treat, and prevent).ResultsChange in incidence in mixing compared to no-mixing scenarios varied by EHE and non-EHE jurisdictions and aggregation-level. When assuming jurisdictional heterogeneity and baseline-intervention, the change in aggregated incidence ranged from − 2 to 0% for EHE and 5 to 21% for non-EHE, but within each jurisdiction it ranged from − 31 to 46% for EHE and − 18 to 109% for non-EHE. Thus, incidence estimates were sensitive to jurisdictional mixing more at the jurisdictional level. As a result, jurisdiction-specific HIV-testing intervals inferred from the model to achieve the EHE-plan were also sensitive, e.g., when no-mixing scenarios suggested testing every 1 year (or 3 years), the three mixing-levels suggested testing every 0.8 to 1.2 years, 0.6 to 1.5 years, and 0.6 to 1.5 years, respectively (or 2.6 to 3.5 years, 2 to 4.8 years, and 2.2 to 4.1 years, respectively). Similar patterns were observed when assuming jurisdictional homogeneity, however, change in incidence in mixing compared to no-mixing scenarios were high even in aggregated incidence.ConclusionsAccounting jurisdictional mixing and heterogeneity could improve model-based analyses.

Design of IoT-oriented demand side management model in microgrid via improved metaheuristic framework

The amplified use of power applications by customers is a rising concern in the energy field every day, which leads to an imbalanced ratio of supply and demand. The integration of renewable energy sources and increasing greenhouse gas emission leads to power demand and affects the climate. Shortage of power supply is the major issue in remote areas, to rectify this issue microgrids have become the best solution. Demand side management (DSM) is a very important means for avoiding major deficits from the supply side and improving energy efficiency (EE). The development in the management of energy mainly focuses on minimizing the entire cost of electricity with no limitation in the utilization part and instead, it chooses to lessen the power utilization at peak hours. This paper intends to introduce a sophisticated DSM and controlling scheme for an Efficient Energy Management system (EMS) in Smart Microgrids (SMG). Initially, an optimal cost-efficient EMS operation is established depending on Modified Cat Swarm Algorithm (M-CSA) model and is augmented via time-of-use pricing (ToU) theory. Subsequently, the SMG frequency and voltage are optimally controlled via an improved PID-based Mixed Sensitivity H-infinity (PID-MSH∞) model while functioning in islanded mode. Thus, the developed approach exploits the massive IoT (Internet of Things) aptitudes for ensuring a secure and economic operation of SMG. The energy cost value of the proposed method is 8138.9 which is 33.67%, 37.94%, 35.42%, and 32.27% superior than the traditional approaches such as CSA, IDE, GA and JA. Thus, several analyses are used to demonstrate the created approach's superiority.

Specific Lipid Studies in Complex Membranes by Solid-State NMR Spectroscopy.

Specific interactions with phospholipids are often critical for the function of proteins or drugs, but studying these interactions at high resolution remains difficult, especially in complex membranes that mimic biological conditions. In principle, molecular interactions with phospholipids could be directly probed by solid-state NMR (ssNMR). However, due to the challenge to detect specific lipids in mixed liposomes and limited spectral sensitivity, ssNMR studies of specific lipids in complex membranes are scarce. Here, by using purified biological 13 C,15 N-labeled phospholipids, we show that we can selectively detect traces of specific lipids in complex membranes. In combination with 1 H-detected ssNMR, we show that our approach provides unprecedented high-resolution insights into the mechanisms of drugs that target specific lipids. This broadly applicable approach opens new opportunities for the molecular characterization of specific lipid interactions with proteins or drugs in complex fluid membranes.

Selective sensitization strategy for high-performance panchromatic dye-sensitized solar cells incorporated with ruthenium-based double dyes

To facilitate the assembly of high-performance panchromatic dye-sensitized solar cells (DSSCs), it is important to determine the selection and sensitization of dyes in photoelectrodes. This paper reports the fabrication of panchromatic DSSCs comprising freestanding and fixed TiO2 thin films (TFs). These TFs constitute a bilayered photoelectrode coated with ruthenium-based double dyes. In addition, we systematically examine the effect of the separated sensitization of double dyes on DSSC performance. The UV–vis spectroscope measurements reveal that the ruthenium-based dyes exhibit light-absorbance values in the order of C106 > N719 > N749. The results of the separated sensitization of C106 (bottom layer)/N719 (top layer) dyes reveal a maximum efficiency of 8.10 %. Correspondingly, the separated sensitization of N749/N719 dyes yields a poor PCE of 5.85 %. In addition, the mixed sensitization of the double dyes (i.e., C106 + N719, C106 + N749, and N719 + N749) is found to demonstrate poor DSSC performance compared to the corresponding separated sensitization (i.e., C016/N719, C106/N749, and N719/N749). This can be attributed to the occurrence of negative interactions between mixed dyes. Therefore, to improve the panchromatic DSSC performance, it is suggested that dyes with high and low light-absorbance values be sensitized on the bottom and top layers, respectively.

Robust composite control design of drag-free satellite with Kalman filter-based extended state observer for disturbance reduction

For future space-based gravitational wave detectors, drag-free control is one of the core technologies to achieve ambitious ultra-quiet-stable requirements. Generally, the high performance of such a drag-free satellite is severely limited by the intrinsic nonlinearities, various noise and limited bandwidth. To overcome these limitations, a dual-loop drag-free control scheme with the merits of simple structure and tuning method is proposed. First, a special combination of Kalman filter (KF) and extended state observer (ESO) is applied in the inner-loop to perform disturbance reduction. The KF serves as noise filtration, while the ESO accepts the filtered measurement signals to achieve better online reconstruction of states and lumped disturbances. Then, GS/T mixed sensitivity H∞ controllers are adopted in the outer-loop to stabilize the test masses in the cage center. The controllers are tuned based on the sensitivity function and complementary sensitivity function specifications to enhance robustness. Finally, a simulation considering various disturbance models is built to test the effectiveness of the control system. A comparison between three types of controllers reveals the advantages of the proposed method in terms of the disturbance attenuation and control performance.

Illustrative Application of the nth-Order Comprehensive Adjoint Sensitivity Analysis Methodology for Nonlinear Systems to the Nordheim–Fuchs Reactor Dynamics/Safety Model

The application of the recently developed “nth-order comprehensive sensitivity analysis methodology for nonlinear systems” (abbreviated as “nth-CASAM-N”) has been previously illustrated on paradigm nonlinear space-dependent problems. To complement these illustrative applications, this work illustrates the application of the nth-CASAM-N to a paradigm nonlinear time-dependent model chosen from the field of reactor dynamics/safety, namely the well-known Nordheim–Fuchs model. This phenomenological model describes a short-time self-limiting power transient in a nuclear reactor system having a negative temperature coefficient in which a large amount of reactivity is suddenly inserted, either intentionally or by accident. This model is sufficiently complex to demonstrate all the important features of applying the nth-CASAM-N methodology yet admits exact closed-form solutions for the energy released in the transient, which is the most important system response. All of the expressions of the first- and second-level adjoint functions and, subsequently, the first- and second-order sensitivities of the released energy to the model’s parameters are obtained analytically in closed form. The principles underlying the application of the 3rd-CASAM-N methodology for the computation of the third-order sensitivities are demonstrated for both mixed and unmixed second-order sensitivities. For the Nordheim–Fuchs model, a single adjoint computation suffices to obtain the six 1st-order sensitivities, while two adjoint computations suffice to obtain all of the 36 second-order sensitivities (of which 21 are distinct). This illustrative example demonstrates that the number of (large-scale) adjoint computations increases at most linearly within the nth-CASAM-N methodology, as opposed to the exponential increase in the parameter-dimensional space which occurs when applying conventional statistical and/or finite difference schemes to compute higher-order sensitivities. For very large and complex models, the nth-CASAM-N is the only practical methodology for computing response sensitivities comprehensively and accurately, overcoming the curse of dimensionality in sensitivity analysis of nonlinear systems.

Servo Control of Drive-Trains Incorporating Magnetic Couplings

This article presents a high performance and low-cost design methodology for the servo control of magnetic drive-trains (MDTs) operating in direct drive mode. For the first time, this article considers using sensitivity peaks to analyze the robustness and stability of MDT control systems. Initially, through analysis of a dynamic model, the key spring characteristic parameters with respect to operating points, are developed. It is also shown that a wider dynamic performance envelope can be achieved by linearizing the MDT model at around 60 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\%$</tex-math></inline-formula> –80 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\%$</tex-math></inline-formula> of the maximum coupling torque, as opposed to traditional linearization under zero torque conditions. Subsequently, this article exploits the spring characteristics for a design methodology based on the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\text{H}_\infty$</tex-math></inline-formula> mixed sensitivity approach to determine suitable control parameters. Following this, the maximum exogenous load-torque disturbance and speed reference that will not induce pole-slipping can be determined. Finally, preferential position reference profiles and optimal gains for position controllers are given to prevent demand-induced speed oscillations. The proposed methodologies are validated through simulation and experimental studies.

Accelerated synthesis of Li(Ni0.8Co0.1Mn0.1)O2 cathode materials using flame-assisted spray pyrolysis and additives

Nickel-rich cathode materials are promising in lithium-ion battery applications because of their high energy density and low material cost. Unfortunately, reducing the synthesis cost of nickel-rich cathode materials is challenging because of the time-consuming and energy-intensive calcination. Therefore, the current work aims to explore strategies for significantly reducing the calcination time of nickel-rich cathode material Li(Ni0.8Co0.1Mn0.1)O2 (NCM811). We used a flame-assisted spray pyrolysis method to synthesize samples with and without using low-cost urea as an additive. Both in situ thermal X-ray diffraction (XRD) and ex situ XRD revealed that urea addition weakened the sensitivity of crystallization and cation mixing to calcination conditions. As a result, with only 20 min of calcination at 875 °C and without any preheating and ramping steps, the NCM811 sample showed an ordered layered structure and comparable electrochemical performance to those with long-time calcination. Moreover, the current work demonstrated that the shortened post calcination was benefited from lithium-embedded particles that likely improved the uniformity of lithium distribution in as-synthesized powder. Therefore, carefully designing initial lithium distribution in particles prior to calcination could also be a useful strategy for other synthesis methods to shorten high-temperature calcination steps, leading to significant reductions in energy consumption and fabrication cost.

Influence of Air Voids and Aggregates Composition on Moisture Damage Sensitivity of Bituminous Mixes

Influence of Air Voids and Aggregates Composition on Moisture Damage Sensitivity of Bituminous Mixes

Robust fuzzy gain scheduling power control of a generation IV nuclear reactor

Gen-IV nuclear reactors are deemed to actively participate in the load following operations in order to meet the ever increasing energy demands. Robust fuzzy gain scheduling is proposed in this work as an advanced and efficient control strategy for the power cycling of the BREST design of lead cooled fast reactors (LFR). To this end, a reasonably accurate coupled thermo-neutronic simulator is developed at first. System identification techniques are employed thereafter to extract a multi-model set at various operating levels relying on the data obtained from this simulator. Uncertainties incurred as a result of the statistically based identification schemes are moreover accounted for using a narrow band (99%) confidence level for the determined model parameters. A set of robust controllers are contrived through a mixed sensitivity analysis framework and are blended afterwards by way of a fuzzy inference mechanism to appropriately schedule this regulation practice with the reactor power level. Certain load following scenarios are finally examined wherein the closed loop system exhibits an efficient and quite feasible control attempt.

TRPV4 mutations causing mixed neuropathy and skeletal phenotypes result in severe gain of function.

ObjectiveDistinct dominant mutations in the calcium‐permeable ion channel TRPV4 (transient receptor potential vanilloid 4) typically cause nonoverlapping diseases of either the neuromuscular or skeletal systems. However, accumulating evidence suggests that some patients develop mixed phenotypes that include elements of both neuromuscular and skeletal disease. We sought to define the genetic and clinical features of these patients.MethodsWe report a 2‐year‐old with a novel R616G mutation in TRPV4 with a severe neuropathy phenotype and bilateral vocal cord paralysis. Interestingly, a different substitution at the same residue, R616Q, has been reported in families with isolated skeletal dysplasia. To gain insight into clinical features and potential genetic determinants of mixed phenotypes, we perform in‐depth analysis of previously reported patients along with functional and structural assessment of selected mutations.ResultsWe describe a wide range of neuromuscular and skeletal manifestations and highlight specific mutations that are more frequently associated with overlap syndromes. We find that mutations causing severe, mixed phenotypes have an earlier age of onset and result in more marked elevations of intracellular calcium, increased cytotoxicity, and reduced sensitivity to TRPV4 antagonism. Structural analysis of the two mutations with the most dramatic gain of ion channel function suggests that these mutants likely cause constitutive channel opening through disruption of the TRPV4 S5 transmembrane domain.InterpretationThese findings demonstrate that the degree of baseline calcium elevation correlates with development of mixed phenotypes and sensitivity to pharmacologic channel inhibition, observations that will be critical for the design of future clinical trials for TRPV4 channelopathies.

Effects of CO2 and Ocean Mixing on Miocene and Pliocene Temperature Gradients

AbstractCenozoic climate changes have been linked to tectonic activity and variations in atmospheric CO2 concentrations. Here, we present Miocene and Pliocene sensitivity experiments performed with the climate model COSMOS. The experiments contain changes with respect to paleogeography, ocean gateway configuration, and atmospheric CO2 concentrations, as well as a range of vertical mixing coefficients in the ocean. For the mid‐Miocene, we show that the impact of ocean mixing on surface temperature is comparable to the effect of the possible range in reconstructed CO2 concentrations. In combination with stronger vertical mixing, relatively moderate CO2 concentrations of 450 ppmv enable global‐mean surface, deep‐water, and meridional temperature characteristics representative of mid‐Miocene Climatic Optimum (MMCO) reconstructions. The Miocene climate shows a reduced meridional temperature gradient and reduced seasonality. In the case of enhanced mixing, surface and deep ocean temperatures show significant warming of up to 5–10°C and an Arctic temperature anomaly of &gt;12°C. In the Pliocene simulations, the impact of vertical mixing and CO2 is less important for the deep ocean, which we interpret as a different sensitivity dependence on the background state and mixed layer dynamics. We find a significant reduction in surface albedo and effective emissivity for either a high level of atmospheric CO2 or increased vertical mixing. Our mixing sensitivity experiments provide a warm deep ocean via ocean heat uptake. We propose that the mixing hypothesis can be tested by reconstructions of the thermocline and seasonal paleoclimate data indicating a lower seasonality relative to today.

Surface wave mitigation in a copper converter via H∞ mixed sensitivity control

In this paper, a robust control strategy for surface wave mitigation in copper converters is presented. In copper converters, the purification of copper is carried out by injection of air into the molten bath through lateral tuyeres. The constant rate of air injection produces undesirable oscillation and splashing of the bath in the surface diminishing the lifetime of the internal cover. An H∞ mixed sensitivity approach is proposed to robustly control the air injection rate in order to eliminate the modes of oscillation in the surface even in the case when uncertainty in the parameters of the model and noise in the measurements are present. The effectiveness of the proposed approach is shown by simulations and by comparison with a non-robust LQG control strategy.

Flexible Joint Robotic Manipulator Performance Improvement Using Mixed Synthesis Technique

The flexible joint robot is gaining more popularity in research and development because of its light weight and numerous applications. The major problems of the flexible joint robotic manipulator are poor tracking performance and instability. This work aims at improving the tracking performance and stability of the flexible joint robot based on the tracking error, damping time, overshoot and stability margins of the flexible joint model. To achieve this, a mixed synthesis method was applied. The mixed sensitivity synthesis is a robust control technique which uses adjustable weights to design a robust controller model which improves the performance and stability of a plant through loop shaping. From the results, the flexible joint model recorded damping time of infinity which is very high, gain margin of 22.8dB and very low phase margin of 3.21e-12deg. This means that the flexible joint model suffers from poor performance and it is unstable. The mixed synthesis controlled flexible joint model recorded low damping time of 0.993seconds, overshoot of 0%, tracking error of 0.0214dB, gain margin of 24.9dB and phase margin of 86.9degrees. This means that the mixed sensitivity synthesis controlled FJR achieved improved tracking performance and robust stability. The mixed synthesis control technique maintained negligible changes in damping time, tracking error and stability margins when the joint flexibility coefficient of the joint was varied to verify the robustness of the system. The work concludes that the flexible joint tracking performance and stability improvement was achieved using mixed sensitivity synthesis.

A novel method for optimal robust PID design based on mixed sensitivity closed loop shaping and convex programming

In industry, the PID controller remains ubiquitous. Its design is typically tackled from classical design methods which do not properly take into account model uncertainty. Robustness is therefore typically a major issue with classically tuned PID controllers. This in turn results in PID controllers that are ‘detuned’ experimentally by an operator in order to avoid these robustness issues. A more generic method is hence required for tuning robust PID controllers.This paper proposes a novel method to enforce a PID (classic and higher order PID) architecture in the mixed sensitivity controller synthesis problem (which is the basis for the mixed sensitivity H∞ design), based on sequential convex second order programming with guaranteed convergence to a stationary point of the optimization problem.Numerical validation of the proposed method is presented by means of some toy problems illustrating the flexibility and practicality of the proposed method. The resulting PID controllers are compared with classical H∞ controllers illustrating the viability of the method to synthesise robust PID controllers based on H∞ controller design specification.

Robust Control Design for Kaplan Turbine

The paper presents the dynamic model of a Kaplan turbine coupled to a DC generator, which is part of the H112D didactic system. A robust controller is designed using two different techniques: H ∞ mixed sensitivity and Quantitative feedback Theory (QFT). The robustness of the controller was analysed with three indicators: analysis of parameter uncertainties, transient response given a variable reference signal and robustness against disturbances.

Additive Mixed Sensitivity Design of PID Controllers for Continuous-Time System with Uncertain Time-Delay

This paper presents an algorithm for all achievable coefficients of Proportional Integral Derivative (PID) controllers in an integral-derivative plane that stabilizes and satisfies additive mixed sensitivity constraint with an uncertain time delay for a continuous-time system. This algorithm solves the singularity problem of designing PID controllers in the integral and derivative plane and estimates achievable ranges of proportional gain of the PID controllers. A numerical cascaded ball and beam with unity feedback control of an SRV-DC motor and uncertain communication time delays in the system process demonstrate the application of this methodology. In this application, the additive weight bounds the additive errors for the cascaded ball and beam and the closed-loop SRV-DC motor system transfer function with the internal communication time delays

Frequency Separation Control for Drag-Free Satellite With Frequency-Domain Constraints

For a drag-free satellite, one core technology required to achieve the mission requirements is drag-free control. The purpose of control is to offset the interference such as sunlight pressure, gravitational gradients of Earth and Moon, nonspherical perturbation, etc. Currently, the drag-free controller design is mainly aimed at the full frequency band. This will inevitably mix the control signal into the scientific measurement signal, thereby interfering with the processing of scientific data. Besides, the control at the full frequency band will increase fuel consumption. To solve the above problems, this article presented the controller design method for a drag-free satellite with scientific measurement constraints, which covers motion model establishing, coordinate axis decomposition, frequency separation control strategy formulation, H∞ mixed sensitivity controller design, controller stability analysis, and performance results.

외란과 모델 불확실성이 존재하는 가변속 냉동시스템의 강인제어를 위한 H-infinity 제어기 설계

This paper describes the design of H-infinity controller for robust control of a variable speed refrigeration system. The suggested controller can ensure robustness against disturbance and model uncertainty by minimizing H-infinity norm of the transfer function from exogenous input to performance output and applying the small gain theorem. In particular, the controller was designed to simultaneously reduce the effects of disturbance and model uncertainty by formalizing these problems as a mixed sensitivity problem. In addition, an integrator was included to the controller to prevent the occurrence of steady state error. The validity of the proposed controller was demonstrated by computer simulations and real experiments. Moreover, the effectiveness of the proposed controller was confirmed by comparing its performance to the PI controller, which was tested under the same experimental conditions as the H-infinity controller.

A novel multivariable nonlinear robust control design for turbofan engines

Traditional steady-state control methods are applied to turbofan engines operating in the small region near certain operating conditions, which need to switch controllers for operating in the large region and then may lead to instability and performance degradation of the closed-loop system. In this paper, a novel multivariable nonlinear robust control method for turbofan engines is proposed to improve the control performance within the large region. To enlarge the controllable region, a polynomial state-space model describes the nonlinear characteristics of turbofan engines. Based on the analysis of the closed-loop control system, by using the Lyapunov function theorems, a polynomial robust controller is designed to ensure the stability and desired nonlinear control performance of turbofan engines. Compared with the classical PI, mixed sensitivity, and H∞ control, simulation results show that the proposed method has better transient responses, disturbance rejection, and other control performance for the turbofan engine within the large region.