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Objective: To investigate the correlation between ultrasonic measurements of swallowing movement parameters and aggravation of swallowing dysfunction in patients with chronic obstructive pulmonary disease (COPD). Methods: COPD patients with swallowing dysfunction (n = 120) and COPD patients with normal swallowing function (n = 100) treated in our hospital between January 2020 and January 2023 were included in observation and control groups, respectively. The correlation between ultrasonic measurements of swallowing movement parameters and COPD with swallowing dysfunction was analyzed. The observation group was divided into mild and severe groups according to their Gugging Swallowing Screen (GUSS) scores. The correlation between ultrasonic measurements of swallowing movement parameters and COPD exacerbation combined with swallowing dysfunction was analyzed. Results: In the observation group, Hyoid muscle thickness, hyoid bone displacement, geniohyoid muscle movement distance, HLAS, and CSR were lower compared to the control group, negatively associated with COPD‐related swallowing issues. Conversely, geniohyoid muscle movement time and minimum hyohyoid distance (NHLA) were higher in the observation group, positively correlated with COPD‐related swallowing dysfunction. In COPD patients with swallowing problems, the severe group exhibited lower values for lingual muscle thickness, hyoid bone displacement, geniohyoid muscle movement distance, HLAS, and CSR compared to the mild group, while geniohyoid muscle movement time and NHLA were higher in the severe group. Receiver operating characteristic (ROC) curves were created, indicating the promising diagnostic utility of these parameters for assessing the presence and severity of swallowing dysfunction in COPD patients. Conclusion: The ultrasonic measurement of swallowing motion parameters can effectively assess swallowing dysfunction in COPD patients. [ABSTRACT FROM AUTHOR]

The high flammability of vinyl ester resin (VE) significantly limits its widespread application in the fields of electronics and aerospace. A new phosphorus-based flame retardant 6,6'-(1-phenylethane-1,2 diyl) bis (dibenzo[c,e][1,2]oxaphosphinine 6-oxide) (PBDOO), was synthesized using 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and acetophenone. The synthesized PBDOO was further incorporated with VE to form the VE/PBDOO composites, which displayed an improved flame retardancy with higher thermal stability. The structure of PBDOO was investigated using Fourier transformed infrared spectrometry (FTIR) and nuclear magnetic resonances (NMR). The thermal stability and flame retardancy of VE/PBDOO composites were investigated by thermogravimetric analysis (TGA), vertical burn test (UL-94), limiting oxygen index (LOI), and cone calorimetry. The impacts of PBDOO weight percentage (wt%) on the flame-retardant properties of the formed VE/PBDOO composites were also examined. When applying 15 wt% PBDOO, the formed VE composites can meet the UL-94 V-0 rating with a high LOI value of 31.5%. The peak heat release rate (PHRR) and the total heat release (THR) of VE loaded 15 wt% of PBDOO decreased by 76.71% and 40.63%, respectively, compared with that of untreated VE. In addition, the flame-retardant mechanism of PBDOO was proposed by analyzing pyrolysis behavior and residual carbon of VE/PBDOO composites. This work is expected to provide an efficient method to enhance the fire safety of VE. [ABSTRACT FROM AUTHOR]

To expand the application scope of prestressed carbon fiber-reinforced polymer (CFRP) cables in civil engineering, the ultimate tensile strength of these cables was tested and evaluated under bending conditions. First, the study analyzed the tensile failure mechanism of CFRP cables under bending conditions based on elastic bending analysis theory. Thereafter, the ultimate stress state of individual tendons and cables was derived and a calculation model for the tensile strength of bent CFRP cables was established. Second, 14 sets of test conditions were created for CFRP cables under bending angles of 20–40° and bending radii of 1.5–3 m. Then, bending tensile tests were conducted to evaluate the effects of the above factors on the ultimate tensile strength, and the correctness of the computational model was verified using experiments. Finally, the ultimate performance of CFRP cables was theoretically predicted using the established model. The results showed that the cable bending tensile strength was associated with the radius r, tensile strength f, and elastic modulus E of the reinforced material and the bending radius R, but was not correlated with the interface buffer material or the bending angle of the steering system. Moreover, the flexural tensile residual strength was only affected by R/r and E/f. When E/f involved conventional material parameters, the residual strength increased nonlinearly with increased R/r. When R/r ≥ 600, the residual strength reached more than 80%. Therefore, R/r at 600 could be used as the design basis for a safe critical radius. [ABSTRACT FROM AUTHOR]

Two-dimensional materials have a wide range of applications in many aspects due to their unique properties. Here we carry out a detailed structural search and design of the BP2 using the first principles method, and find a new PMM2 sheet. The analysis of the phonon dispersive curves shows that the 2D PMM2 is dynamic stable. The study of molecular dynamics shows that the 2D PMM2 can be stable under high temperature, even at 600 K. Most importantly, when a suitable strain is applied, the structure can exhibit other electronic properties such as direct band gap semiconductor. In addition, the small strain can tune the band gap value of the PMM2 structure to around 1.4 eV, which is very close to the ideal band gap of solar materials. Therefore, the 2D PMM2 may have potential applications in the field of photovoltaic materials. [ABSTRACT FROM AUTHOR]

PP/EPDM (TPV) is a common thermoplastic elastomer with excellent performance and a wide range of uses. Polyhedral oligomeric silsesquioxane (POSS) with its own functional organic group (OV-POSS) was used to improve the combustion performance of TPV systems. 1 wt%, 3 wt% and 5wt% OV-POSS were added to TPV respectively, and their mechanical properties and thermal stability were tested. The results showed that the TPV mechanics performance of OV-POSS was slightly reduced, but the thermal stability was improved. Cone test results showed a 53% reduction in the heat release rate of TPV containing 5wt% OV-POSS compared with TPV without adding OV-POSS. The release of CO and CO2 also decreased significantly, and the amount of carbon formation increased from 1.1% to 14.8%. As can be seen from TG-IR analysis, the addition of OV-POSS slows down the thermal decomposition process of hydrocarbons. OV-POSS was added to improve flame-retardant properties and reduces fire risk of TPV. [ABSTRACT FROM AUTHOR]

With the continuous development of microgrids (MGs), a hybrid structure consisting of single-phase MGs and three-phase MGs has been widely promoted. When each submicrogrid (SMG) pursues its economic benefit, it can easily cause a three-phase power unbalance for a grid-connected three/single-phase hybrid multimicrogrid (MMG). To address this problem, an optimization model based on the multileader and multifollower game theory is proposed for a grid-connected three/single-phase hybrid MMG in this paper. In the proposed optimization model, the three-phase unbalance constraints are integrated into the utility functions of the leaders and followers to reduce the impact of the unbalance constraints on the benefits of the participants. The performance of the proposed optimization model is verified by a series of tests. The test results show that the proposed optimization model can effectively reduce the three-phase power unbalance factor of the system and improve the profit of the three/single-phase hybrid MMG. [ABSTRACT FROM AUTHOR]

With the proliferation of distributed generation in distribution networks, quickly and smoothly converting to a state of regional autonomy in the case of distribution network failure is one of the main challenges for the stable operation of a multimicrogrid (MMG). To address the aforementioned problem, this paper proposes coordinated control of the passive transition from grid-connected to islanded operation for a three/single-phase hybrid MMG. Under the premise of fully considering the constraints on the tie-line transfer power undertaken by the master power supply (MPS), the following two scenarios regarding safety and emergency are formulated: 1) when the output power of the MPS is in the safe range, the proposed strategy coordinates the energy storage (ES) in each submicrogrid (SMG) to achieve power balance; 2) when the output power is in the emergency range, this paper proposes a three-phase balance method based on a bubble sort to realize the combination optimization of the single-phase source-load-storage (SLS) and a fast power regulation method based on implicit enumeration for the SLS to reduce the tie-line transfer power, which could prevent failure of the mode transition from power overload. The test results verify the effectiveness and feasibility of the proposed coordination strategy. [ABSTRACT FROM AUTHOR]

As the penetration of photovoltaic (PV) generation increases, there is a growing operational demand on PV systems to participate in microgrid frequency regulation. It is expected that future distribution systems will consist of multiple microgrid clusters. However, interconnecting PV microgrids may lead to system interactions and instability. To date, no research work has been done to analyze the dynamic behavior and enhance the stability of microgrid clusters considering the dynamics of the PV primary sources and dc links. To fill this gap, this paper presents comprehensive modeling, analysis, and stabilization of PV-based multiple microgrid clusters. A detailed small-signal model for PV-based microgrid clusters considering local adaptive dynamic droop control mechanism of the voltage-source PV system is developed. The complete dynamic model is then used to access and compare the dynamic characteristics of the single microgrid and interconnected microgrids. In order to enhance system stability of the PV microgrid clusters, a tie-line flow and stabilization strategy is proposed to suppress the introduced interarea and local oscillations. Robustly selecting of the key control parameters is transformed to a multiobjective optimization problem which is solved by genetic algorithm. The proposed damping controller can effectively damp the power oscillations and provide robust control performance under variable operating conditions. Theoretical analysis, simulation results under various scenarios are presented to verify the effectiveness of the proposed scheme. [ABSTRACT FROM AUTHOR]

Summary: With the increasing amount and type of connected microgrids in the near‐term future power networks, how to optimize the operation of multimicrogrids efficiently and reliably has become essential for taking full advantage of the complex systems. In this paper, a multitimescale coordinated optimization strategy for hybrid three‐phase/single‐phase multimicrogrids is proposed. The multitimescale strategy is implemented for day‐ahead economic optimization on a long‐time scale and real‐time tracking optimization on a short‐time scale. With the consideration of the economy of microgrids and three‐phase unbalance constraints in multimicrogrids, a strategy of collecting‐distributing fuzzy modified adaptive particle swarm economic optimization is introduced. In this day‐ahead strategy, a bilayer rolling optimizing structure is designed, where the lower layer conducts economic optimization at all time slots and the upper layer balances the tie‐line power at each time slot based on the results obtained from the lower layer. On this basis, by taking a day‐ahead optimized tie‐line power as baseline values, the real‐time power of energy storage systems is obtained by adopting an improved nondominated sorting genetic algorithm, which achieves distributed real‐time optimization for the multimicrogrid. Simulation results verify that the proposed strategy is feasible. [ABSTRACT FROM AUTHOR]

With the fast proliferation of microgrids integrated into the power grid, several nearby microgrids with common benefit have been coupled to be multi‐microgrids (MMGs), which is a significant stage for developing the smart grid. A suitable control structure and corresponding control device need to be proposed for the MMGs operating efficiently. However, mostly micrgrid control devices are still restricted to the single microgrid and have limited application without the common design. The authors develop control devices with a prodigious popularisation value for the MMGs based on the hierarchical control structure. According to the proposed four‐layer control architecture (scheduling layer, central control layer, integrated terminal layer and bottom layer), the hardware and software design suitable for the MMGs control devices and its multi‐time scale communication architecture has been presented. Furthermore, the appearance design and interface exploitation were introduced as well. Experimental results are provided to demonstrate the validity of the proposed MMGs control structure and devices, which could contribute to the large‐scale application of MMGs control devices and provide a reference for other MMGs projects. [ABSTRACT FROM AUTHOR]

In this paper, a novel type of voltage control strategy based on internal model robust and compound control is proposed for three/single-phase hybrid multimicrogrid, which is composed of two parts, feedforward control and internal model robust feedback control. Feedforward control is mainly used to improve the dynamic response and reduce the steady-state error of the system. The objective of the internal model robust feedback control system is to achieve the optimization of control performance, robustness, and the ability to suppress disturbances of the whole system. In order to achieve the goal, the design of the internal model robust feedback controller is transformed into solving a convex optimization problem with linear matrix inequality constraints and linear objective functions. The proposed voltage control strategy is verified by a variety of experimental tests. The experimental results show that the controller can get better voltage output characteristics and robustness in dealing with micro-source output power fluctuations, loads abrupt change or nonlinear loads and unbalanced loads. [ABSTRACT FROM PUBLISHER]

The V/f control adopted by the master power supply has problems of slow dynamic response, poor anti‐interference ability in response to micro‐source output power fluctuations and loads abrupt change. Aiming at problems of the output voltage mentioned above, an improved V/f control strategy based on compound control is proposed in this study. The improved V/f control strategy is composed of two parts, feedforward compensation and robust feedback control. The design of the feedforward compensator is realised by the method of approximate full compensation. The design of the robust feedback controller is transformed into solving a convex optimisation problem with linear matrix inequality constraints and linear objective functions. The designed V/f control strategy is verified by a variety of comparative tests. Test comparisons show that the controller can get better voltage output characteristics, dynamic characteristics and robustness in response to micro‐source output power fluctuations, loads abrupt change or non‐linear loads and unbalanced loads. [ABSTRACT FROM AUTHOR]

In this paper, an islanded medium-voltage (MV) microgrid placed in Dongao Island is presented, which integrates renewable-energy-based distributed generations (DGs), energy storage system (ESS), and local loads. In an isolated microgrid without connection to the main grid to support the frequency, it is more complex to control and manage. Thus, in order to maintain the frequency stability in multiple time scales, a hierarchical control strategy is proposed. The proposed control architecture divides the system frequency in three zones: (A) stable zone, (B) precautionary zone, and (C) emergency zone. In this way, dynamic stability control that copes with disturbances in short-time scale is implemented by microgrid central controller within Zone B and Zone C. Meanwhile, steady-state stability control to solve the peaks and valleys problem of loads and DGs in long-time scale is executed by the microgrid energy management system within Zone A. Furthermore, based on the developed complete small-signal state-space model, sensitivity analysis of the eigenvalues is conducted in order to reveal the dynamic stability margin of the MV microgrid, and to identify the proper range of the control parameters of Zone B. Theoretical analysis, time-domain simulation, and field test results under various conditions and scenarios in the Dongao Island microgrid are presented to prove the validity of the introduced control strategy. [ABSTRACT FROM AUTHOR]

Cyanobacterial collected from eutrophic freshwater lakes constituted intractable waste with a rich algae biomass content. Supercritical water gasification (SCWG) was proposed to treat the cyanobacterial and to produce hydrogen for energy. The H2yield reached 2.92 mol/kg at reaction conditions of 500 °C, 30 min and 22 MPa; this yield accounted for 26% of the total gaseous products. Abundant ammonia and dissolved reactive phosphorous were concentrated in the liquid product, which could be recovered and used as a liquid fertilizer. Solid residue, which accounted only for about 1% of the wet weight, was mainly composed of coke and ash. The efficiency of H2production was better than that from other biomass, because of the abundant organic matter in cyanobacterial. Thus, cyanobacterial are an ideal biomass feedstock for H2production from SCWG. [ABSTRACT FROM PUBLISHER]

Secondary dewatering of dewatered sludge is imperative to make conventional drying and incineration of sludge more economically feasible. In this study, a secondary dewatering of dewatered sludge with selected solvents (i.e. acetone and ethanol) followed by vacuum filtration and nature drying was investigated to achieve in-depth dewatering. After the entire secondary dewatering process, the sludge was shown to be odourless and the organic matter content was greatly retained. Increased mean particle size of sludge after solvent contact improved solid–liquid separation. With an acetone/sludge ratio of 3:1 (mL:g) in solvent contact and subsequent nature drying at ambient temperature after 24 h, the moisture content of sludge can be reduced to a level less than 20%. It is found that the polysaccharides were mainly precipitated by acetone, whereas the release ratios of protein and DNA were increased significantly as the added acetone volumes were elevated. During nature drying, accumulated evaporation rates of the sludge after solvent contact were 5–6 times higher than original dewatered sludge. Furthermore, sludge after acetone contact had better nature drying performance than ethanol. The two-stage dewatering involves solvent contact dewatering and solvent enhanced evaporation dewatering. Through selecting an appropriate solvent/sludge ratio as well as economical solvents and minimizing the solvent loss in a closed-pilot system, this dewatering process can be competitive in industrial applications. Therefore, this solvent-aided secondary dewatering is an energy-saving technology for effective in-depth dewatering of dewatered sludge and subsequent sludge utilization. [ABSTRACT FROM PUBLISHER]

Abstract: Colony formation of Microcystis plays a significant role in Microcystis blooms. Calcium (Ca) and magnesium (Mg) are important nutrient elements during algae growth. In this study, the influences of Ca and Mg concentrations on extracellular polysaccharides (EPS) content and colony formation of Microcystis were investigated, and then the effects of EPS content and specific growth rate on colony formation were discussed. The results showed that Ca had a direct observable influence on the colony formation of Microcystis; however, Mg was not obvious. More specifically, when Ca concentration was lower than 20 mg•L-1, the Microcystis was dominated by single cells, when the concentration was over 20 mg•L-1, Microcystis colonies were found and took up more than 50%, and the size of colony was increased with the increasing Ca concentration. Moreover, it showed that the mean size of Microcystis had significant correlation with EPS content, and lower specific growth rate was in favor of colony formation. [Copyright &y& Elsevier]