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In a fuel cell system, the performance of the ejector is limited when it operates under off-design conditions. To improve the performance of the ejector under all operating conditions in the fuel cell system, this study employs a multi-response optimization approach to optimize the structural parameters of the ejector. The optimization objectives are the entrainment ratio under low-power and high-power operating conditions, with the optimization variables including the mixing tube diameter (Dm), primary nozzle exit position (Lnxp), and mixing tube length (Lm). A quadratic polynomial model is proposed to correlate the key structural parameters of the ejector with the entrainment ratio using the response surface methodology based on the Box-Behnken design. The optimal structural parameters of the ejector are obtained using the desirability function approach. The results demonstrate that this optimization approach significantly improves the ejector performance under off-design conditions while the performance remains essentially unchanged under high-power operating conditions. [ABSTRACT FROM AUTHOR]

The failure rates of phase 3 trials are high. Incorrect sample size due to uncertainty of effect size could be a critical contributing factor. Adaptive sequential design (ASD), which may include one or more sample size re-estimations (SSR), has been a popular approach for dealing with such uncertainties. The operating characteristics (OCs) of ASD, including the unconditional power and mean sample size, can be substantially affected by many factors, including the planned sample size, the interim analysis schedule and choice of critical boundaries and rules for interim analysis. We propose a systematic, comprehensive strategy which uses iterative simulations to investigate the operating characteristics of adaptive designs and help achieve adequate unconditional power and cost-effective mean sample size if the effect size is in a pre-identified range. [ABSTRACT FROM AUTHOR]

Single-arm phase II trials are very common in oncology. A fixed sample trial may lack sufficient power if the true efficacy is less than the assumed one. Adaptive designs have been proposed in the literature. We propose a Simon’s design based, adaptive sequential design. Simon’s design is the most used fixed sample design for single-arm phase II oncology trials. A prominent feature of Simon’s design is that it minimizes the sample size when there is no clinically meaningful efficacy. We identify Simon’s trial as a special group sequential design. Established methods for sample size re-estimation (SSR) can be readily applied to Simon’s design. Simulations show that simply adding SSR to Simon’s design may still not provide desirable power. We propose some expansions to Simon’s design. The expanded design with SSR can provide even more power. [ABSTRACT FROM AUTHOR]

This study presents a novel observer-based fuzzy control for chaotic systems (CSs). A class of CSs with unmeasurable states, unknown input constraints and unknown dynamics is taken to account. A generalised type-2 (GT2) fuzzy logic system (FLS) is formulated to approximate the uncertainties. The parameters of GT2-FLS are adjusted through the tuning rules that are extracted from robustness investigation. The proposed method is applied on CSs and it is demonstrated that the suggested observer and control system result in good performance in versus of disturbances, uncertainties, unknown and time-varying input nonlinearities, unmeasurable states and noisy faults. Comparison with other type of fuzzy systems demonstrates that the proposed GT2-FLS based controller is more effective. [ABSTRACT FROM AUTHOR]

A centrifugal pump whose open impeller was made of polycarbonate was adopted to explore the influence of different concentrations of slender fiber particles on the external characteristics of the pump and to obtain the motional characteristics of the particles in the channels of the impeller. The external characteristics of the pump were used to determine the performance of the pump. A high-speed photographic system was used to analyze the motion of fiber particles in the channels of the impeller. Changes in the head and efficiency of the pump and changes in the distribution of fiber particles in impeller channels were obtained under different concentrations of fiber particles and different flow rates of fiber suspensions. The head associated with the transport of a fiber suspension whose mass concentration of fiber particles was 0.15% and the head associated with the transport of a fiber suspension whose mass concentration of fiber particles was 0.30% did not differ greatly from the head associated with the transport of clean water. However, compared to the transport of clean water, the transport of the fiber suspensions improved the efficiency of the pump. When the pump transported the fiber suspension whose mass concentration of fiber particles was 0.30%, on average, the efficiency of the pump increased by 8.49%. When the flow rates of the fiber suspensions increased, the uniformity of the distribution of the particles increased. When entering the impeller, a small number of fiber particles showed rotating and flapping motions. However, the motions gradually disappeared as the particles left the impeller. At a constant radius (i.e., 75% and 95% radius, respectively), the velocity profile increased gradually when the mass concentration of fiber particles increased from 0.1% to 0.15%. It is manifest that fiber suspension undergoes less flow loss as the mass concentration of fiber particles increases. [ABSTRACT FROM AUTHOR]

This paper presents studies on a robust adaptive output feedback stabilisation for a class of nonlinear systems, which is subjected to parametric uncertainties and disturbances. The disturbances are considered to be general, i.e. both the matched and unmatched ones are present. A novel robust adaptive control is developed for this problem. A technique is employed to avoid the difficulty in handling the nonlinear gain functions associated with the disturbances. For this, a new Lemma is obtained to handle the nonlinear functions that simplify the controller derivation steps. The unknown parameters and disturbances are tackled by deriving the tuning functions using a backstepping design. Finally, simulation is carried out to validate and show the effectiveness of the proposed robust controller. [ABSTRACT FROM AUTHOR]

Evidence about the effect of age at menarche (AAM) on blood pressure (BP) has largely been drawn from studies in developed countries. Studies in developing countries are expanding recently but have not been summarised. To systematically explore the association between AAM and BP and the potential modifiers in developing countries. We searched PubMed, Embase, and Web of Science for publications until March 2022. A random-effects model was used to calculate the pooled relative risk (RR) with 95% confidence interval (CI). Twenty studies were eligible. In studies with participants' mean age at BP assessment <55 years, women in the oldest group as compared with the middle or the youngest group of AAM had a higher risk of hypertension in those studies without adjustment for confounders (RR 1.79, 95% CI 1.41–2.28, I2=97.0%), those with adjustment for confounders excluding adiposity (1.25,1.04–1.51, I2=84.8%), and those with adjustment for confounders including adiposity (1.38,1.03–1.86, I2=91.8%). In studies with participants' mean age at BP assessment ≥55 years, no significant differences were found for studies without adjustment for confounders (RR 1.07, 95% CI 0.78–1.47, I2=90.3%), studies with adjustment for confounders excluding adiposity (0.85, 0.78–0.92, I2=12.3%), or studies with adjustment for confounders including adiposity (0.95, 0.80–1.11, I2=45.5%). A similar association was observed between AAM and baseline systolic BP and diabolic BP. Late menarche was associated with a higher risk of BP and this association was modified by age and adiposity in developing countries. [ABSTRACT FROM AUTHOR]

The (FeCoNi)86Ti7Al7 multi-principal-element alloy with a dual heterogeneous microstructure was successfully fabricated by selective laser melting, exhibiting an excellent combination of strength (ultimate tensile strength, 1085.2 ± 23.2 MPa) and ductility (30.5 ± 2.6%). It is evidenced that the joint effects of the hetero-deformation induced hardening from grains with heterogeneous geometrically necessary dislocations densities, in-situ formed B2 phase, and the coherent precipitation hardening from in-situ formed nano L12 phase were responsible for the strength. This work sheds light on the feasibility of simplifying the production of multi-mechanism strengthened alloys within one step and paves a new avenue to produce high-performance complex-shaped components. (FeCoNi)86Ti7Al7 multi-principal-element alloy exhibiting heterogeneity on the grains structure and in-situ precipitation was successfully fabricated by selective laser melting. It shows both good tensile strength and ductility. [ABSTRACT FROM AUTHOR]

A simple dynamic positioning (DP) system has been developed for the scaled model of a novel twin-lift decommissioning operation. Such a decommissioning solution involves the two semi-submerged vessels transporting the topside to another vessel. And it requires the synchronised motion of the two topside-carried vessels at a low speed, under the environmental disturbances. In order to ensure efficiency and safety, model tests with a scaling factor of 1:37 have been carried out in the wave tank. The DP system in the experiment consists of a 3-Degree of Freedom (3DoF) motion equation, a Proportional–Integral–Derivative (PID) controller and a thrust allocation algorithm. This paper investigates the motion response of each vessel under the random wave and constant wind of different angles, to assess the low-speed manoeuvring performance. It is found that the given control scenarios allow the twin-lift decommissioning system to yield good motion performance under operational conditions. [ABSTRACT FROM AUTHOR]