A unified PID tuning method for load frequency control (LFC) of power systems is discussed in this paper. The tuning method is based on the two-degree-of-freedom (TDF) internal model control (IMC) ...design method and a PID approximation procedure. The time-domain performance and robustness of the resulting PID controller is related to two tuning parameters, and robust tuning of the two parameters is discussed. The method is applicable to power systems with non-reheated, reheated, and hydro turbines. Simulation results show that it can indeed improve the damping of the power systems. It is shown that the method can also be used in decentralized PID tuning for multi-area power systems.
PID tuning of load frequency controllers for power systems is discussed in this paper. The tuning method is based on a two-degree-of-freedom internal model control (IMC) design method, and the ...performance of the resulting PID controller is related to two tuning parameters thus detuning is easy when necessary. Then an anti-GRC scheme is proposed to overcome the generation rate constraints. Finally, the method is extended to two-area cases.
Linear active disturbance-rejection control (LADRC) is investigated in this paper. First, it is shown that LADRC structure can be changed to a two-degree-of-freedom (TDF) internal model control (IMC) ...structure, where the nominal model for the IMC design is simply a multiple integral plant, so analysis of LADRC can be done via the IMC framework. Then it is shown that the widely adopted bandwidth-tuning method for LADRC is equivalent to tuning the two time constants of the setpoint filter and the disturbance-rejection filter in IMC. Finally, to improve the control performance of an LADRC, a general method is proposed to incorporate extra dynamics of the controlled plant in LADRC.
We had previously demonstrated the feasibility of preparing a centimeter-sized bone tissue construct by following a modular approach. In the present study, the objectives were to evaluate ...osteogenesis and tissue formation of human amniotic mesenchymal stem cells-laden CultiSpher S microcarriers during in vitro perfusion culture and after subcutaneous implantation. Microtissues were prepared in dynamic culture using spinner flasks in 28 days. In comparison with 1-week perfusion culture, microtissues became more obviously fused, demonstrating significantly higher cellularity, metabolic activity, ALP activity and calcium content while maintaining cell viability after 2-week perfusion. After subcutaneous implantation in nude mice for 6 and 12 weeks, all explants showed tight contexture, suggesting profound tissue remodeling in vivo. In addition, 12-week implantation resulted in slightly better tissue properties. However, in vitro perfusion culture time exerted great influence on the properties of corresponding explants. Degradation of microcarriers was more pronounced in the explants of 2-week perfused macrotissues compared to those of 1-week perfusion and directly implanted microtissues. Moreover, more blood vessel infiltration and bone matrix deposition with homogeneous spatial distribution were found in the explants of 2-week perfused macrotissues. Taken together, in vitro perfusion culture time is critical in engineering bone tissue replacements using such a modular approach, which holds great promise for bone regeneration.
To clarify in patients with covid-19 the recovery rate of smell and taste, proportion with persistent dysfunction of smell and taste, and prognostic factors associated with recovery of smell and ...taste.
Systematic review and meta-analysis.
PubMed, Embase, Scopus, Cochrane Library, and medRxiv from inception to 3 October 2021.
Two blinded reviewers selected observational studies of adults (≥18 years) with covid-19 related dysfunction of smell or taste. Descriptive prognosis studies with time-to-event curves and prognostic association studies of any prognostic factor were included.
Two reviewers extracted data, evaluated study bias using QUIPS, and appraised evidence quality using GRADE, following PRISMA and MOOSE reporting guidelines. Using iterative numerical algorithms, time-to-event individual patient data (IPD) were reconstructed and pooled to retrieve distribution-free summary survival curves, with recovery rates reported at 30 day intervals for participants who remained alive. To estimate the proportion with persistent smell and taste dysfunction, cure fractions from Weibull non-mixture cure models of plateaued survival curves were logit transformed and pooled in a two stage meta-analysis. Conventional aggregate data meta-analysis was performed to explore unadjusted associations of prognostic factors with recovery.
The primary outcomes were the proportions of patients remaining with smell or taste dysfunction. Secondary outcomes were the odds ratios of prognostic variables associated with recovery of smell and taste.
18 studies (3699 patients) from 4180 records were included in reconstructed IPD meta-analyses. Risk of bias was low to moderate; conclusions remained unaltered after exclusion of four high risk studies. Evidence quality was moderate to high. Based on parametric cure modelling, persistent self-reported smell and taste dysfunction could develop in an estimated 5.6% (95% confidence interval 2.7% to 11.0%, I
=70%, τ
=0.756, 95% prediction interval 0.7% to 33.5%) and 4.4% (1.2% to 14.6%, I
=67%, τ
=0.684, 95% prediction interval 0.0% to 49.0%) of patients, respectively. Sensitivity analyses suggest these could be underestimates. At 30, 60, 90, and 180 days, respectively, 74.1% (95% confidence interval 64.0% to 81.3%), 85.8% (77.6% to 90.9%), 90.0% (83.3% to 94.0%), and 95.7% (89.5% to 98.3%) of patients recovered their sense of smell (I
=0.0-77.2%, τ
=0.006-0.050) and 78.8% (70.5% to 84.7%), 87.7% (82.0% to 91.6%), 90.3% (83.5% to 94.3%), and 98.0% (92.2% to 95.5%) recovered their sense of taste (range of I
=0.0-72.1%, τ
=0.000-0.015). Women were less likely to recover their sense of smell (odds ratio 0.52, 95% confidence interval 0.37 to 0.72, seven studies, I
=20%, τ
=0.0224) and taste (0.31, 0.13 to 0.72, seven studies, I
=78%, τ
=0.5121) than men, and patients with greater initial severity of dysfunction (0.48, 0.31 to 0.73, five studies, I
=10%, τ
<0.001) or nasal congestion (0.42, 0.18 to 0.97, three studies, I
=0%, τ
<0.001) were less likely to recover their sense of smell.
A substantial proportion of patients with covid-19 might develop long lasting change in their sense of smell or taste. This could contribute to the growing burden of long covid.
PROSPERO CRD42021283922.
► A method to analyze the stability of a multi-area power system under a decentralized LFC is derived. ► It is possible to tune local LFC controller by first ignoring the tie-line power flow. ► The ...proposed method is easy to apply and good damping performance can be achieved.
Decentralized load frequency control (LFC) for multi-area power systems is studied in this paper. A method to analyze the stability of a multi-area power system under a decentralized LFC is derived by accounting the inherent structure of the multi-area power system. The method separates the local transfer matrix from the tie-line power flow network, and the impacts of the tie-line power flow network and the local load frequency controllers on the power system can be easily checked. This result makes it possible to tune the local LFC controller for each area by first ignoring the tie-line power flow network. Decentralized LFC tuning on a three-area and a four-area power system shows that the proposed method is easy to apply for multi-area power systems and good damping performance can be achieved.
Photothermal therapy (PTT) at present, following the temperature definition for conventional thermal therapy, usually keeps the temperature of lesions at 42-45 °C or even higher. Such high ...temperature kills cancer cells but also increases the damage of normal tissues near lesions through heat conduction and thus brings about more side effects and inhibits therapeutic accuracy. Here we use temperature-feedback upconversion nanoparticle combined with photothermal material for real-time monitoring of microscopic temperature in PTT. We observe that microscopic temperature of photothermal material upon illumination is high enough to kill cancer cells when the temperature of lesions is still low enough to prevent damage to normal tissue. On the basis of the above phenomenon, we further realize high spatial resolution photothermal ablation of labelled tumour with minimal damage to normal tissues in vivo. Our work points to a method for investigating photothermal properties at nanoscale, and for the development of new generation of PTT strategy.
•A nature-inspired driven approach is proposed to optimally design off-grid microgrid.•Development of a rule-based energy management scheme based on queuing theory.•The optimization problem minimizes ...energy cost and maximizes system reliability.•The proposed grasshopper optimization algorithm is compared with PSO and CSA.•The performance of the microgrid has been analysed against future uncertainties.
Off-grid electrification of remote communities using sustainable energy systems (SESs) is a requisite for realizing sustainable development goals. Nonetheless, the capacity planning of the SESs is challenging as it needs to fulfil the fluctuating demand from a long-term perspective, in addition to the intermittency and unpredictable nature of renewable energy sources (RESs). Owing to the nonlinear and non-convex nature of the capacity planning problem, an efficient technique must be employed to achieve a cost-effective system. Existing techniques are, subject to some constraints on the derivability and continuity of the objective function, prone to premature convergence, computationally demanding, follows rigorous procedures to fine-tune the algorithm parameters in different applications, and often do not offer a fair balance during the exploitation and exploration phase of the optimization process. Furthermore, the literature review indicates that researchers often do not implement and examine the energy management scheme (EMS) of a microgrid while computing for the capacity planning problem of microgrids. This paper proposes a rule-based EMS (REMS) optimized by a nature-inspired grasshopper optimization algorithm (GOA) for long-term capacity planning of a grid-independent microgrid incorporating a wind turbine, a photovoltaic, a battery (BT) bank and a diesel generator (Dgen). In which, a rule-based algorithm is used to implement an EMS to prioritize the usage of RES and coordinate the power flow of the proposed microgrid components. Subsequently, an attempt is made to explore and confirm the efficiency of the proposed REMS incorporated with GOA. The ultimate goal of the objective function is to minimize the cost of energy (COE) and the deficiency of power supply probability (DPSP). The performance of the REMS is examined via a long-term simulation study to ascertain the REMS resiliency and to ensure the operating limit of the BT storage is not violated. The result of the GOA is compared with particle swarm optimization (PSO) and a cuckoo search algorithm (CSA). The simulation results indicate that the proposed technique’s superiority is confirmed in terms of convergence to the optimal solution. The simulation results confirm that the proposed REMS has contributed to better adoption of a cleaner energy production system, as the scheme significantly reduces fuel consumption, CO2 emission and COE by 92.4%, 92.3% and 79.8%, respectively as compared to the conventional Dgen. The comparative evaluation of the algorithms shows that REMS-GOA yields a better result as it offers the least COE (objective function), at $0.3656/kW h, as compared to the REMS-CSA at $0.3662/kW h and REMS-PSO at $0.3674/kW h, for the desired DPSP of 0%. Finally, sensitivity analysis is performed to highlight the effect of uncertainties on the system inputs that may arise in the future.
We unveil an unexpected non-Hermitian phenomenon, dubbed edge burst, in non-Hermitian quantum dynamics. Specifically, in a class of non-Hermitian quantum walk in periodic lattices with open boundary ...condition, an exceptionally large portion of loss occurs at the system boundary. The physical origin of this edge burst is found to be an interplay between two unique non-Hermitian phenomena: non-Hermitian skin effect and imaginary gap closing. Furthermore, we establish a universal bulk-edge scaling relation underlying the non-Hermitian edge burst. Our predictions are experimentally accessible in various non-Hermitian systems including quantum-optical and cold-atom platforms.
Whether goal-directed fluid therapy based on dynamic predictors of fluid responsiveness (GDFTdyn) alone improves clinical outcomes in comparison with standard fluid therapy among patients undergoing ...surgery remains unclear.
PubMed, EMBASE, the Cochrane Library and ClinicalTrials.gov were searched for relevant studies. Studies comparing the effects of GDFTdyn with that of standard fluid therapy on clinical outcomes among adult patients undergoing surgery were considered eligible. Two analyses were performed separately: GDFTdyn alone versus standard fluid therapy and GDFTdyn with other optimization goals versus standard fluid therapy. The primary outcomes were short-term mortality and overall morbidity, while the secondary outcomes were serum lactate concentration, organ-specific morbidity, and length of stay in the intensive care unit (ICU) and in hospital.
We included 37 studies with 2910 patients. Although GDFTdyn alone lowered serum lactate concentration (mean difference (MD) - 0.21 mmol/L, 95% confidence interval (CI) (- 0.39, - 0.03), P = 0.02), no significant difference was found between groups in short-term mortality (odds ratio (OR) 0.85, 95% CI (0.32, 2.24), P = 0.74), overall morbidity (OR 1.03, 95% CI (0.31, 3.37), P = 0.97), organ-specific morbidity, or length of stay in the ICU and in hospital. Analysis of trials involving the combination of GDFTdyn and other optimization goals (mainly cardiac output (CO) or cardiac index (CIx)) showed a significant reduction in short-term mortality (OR 0.45, 95% CI (0.24, 0.85), P = 0.01), overall morbidity (OR 0.41, 95% CI (0.28, 0.58), P < 0.00001), serum lactate concentration (MD - 0.60 mmol/L, 95% CI (- 1.04, - 0.15), P = 0.009), cardiopulmonary complications (cardiac arrhythmia (OR 0.58, 95% CI (0.37, 0.92), P = 0.02), myocardial infarction (OR 0.35, 95% CI (0.16, 0.76), P = 0.008), heart failure/cardiovascular dysfunction (OR 0.31, 95% CI (0.14, 0.67), P = 0.003), acute lung injury/acute respiratory distress syndrome (OR 0.13, 95% CI (0.02, 0.74), P = 0.02), pneumonia (OR 0.4, 95% CI (0.24, 0.65), P = 0.0002)), length of stay in the ICU (MD - 0.77 days, 95% CI (- 1.07, - 0.46), P < 0.00001) and in hospital (MD - 1.18 days, 95% CI (- 1.90, - 0.46), P = 0.001).
It was not the optimization of fluid responsiveness by GDFTdyn alone but rather the optimization of tissue and organ perfusion by GDFTdyn and other optimization goals that benefited patients undergoing surgery. Patients managed with the combination of GDFTdyn and CO/CI goals might derive most benefit.
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