680 research outputs found
External characteristic analysis and stator parameter optimization for a torque converter
The performance of a flattened hydraulic torque
converter is optimized with orthogonal experiment
and response surface method, considering
parameters of its stator blade, defined with nonuniform
rotational B-splines. The optimization
model, with maximum of the stalling torque ratio as
an objective, is determined through an external
characteristic statistical analysis under the new
European Driving Cycle condition. The
optimization results show that the stall torque ratio
is increased by 10.83%, while the highest efficiency
is above 84%
Microalgal diversity enhances water purification efficiency in experimental microcosms
The losses of biodiversity have impaired functioning and provision of ecosystem services, and the relationship between biodiversity and ecosystem functioning has emerged as a central issue in environmental sciences. However, the majority of relevant studies are conducted in terrestrial ecosystems, and they focus predominantly on the relationship between community diversity and biomass production of terrestrial vegetation. At present, water eutrophication represents an increasingly serious problem worldwide, and the use of aquatic organisms for improving water quality represents a promising approach. However, more focus is placed on the selection of certain aquatic organisms with good performance, but neglects the effects of biodiversity in the process of water purification and the underlying mechanisms. In the present study, five microalgal species commonly found in freshwater ecosystems were used to assembly experimental microcosms with varying microalgal richness and composition. We analyzed the relationship between microalgal diversity and nitrogen removal efficiency based on mixed-effect models, and further explored the underlying mechanism of microalgal diversity in the process of water quality improvement. The results showed that with an increase in microalgal diversity, nitrogen removal efficiency of microalgal communities also increased. A further analysis of the impacts of microalgal diversity showed that the complementarity effect increased while the selection effect decreased with an increase in microalgal diversity. Meanwhile, there was a significantly positive relationship between microalgal diversity and the total abundance of microalgae. On the one hand, the present study clearly demonstrates two positive diversity-ecosystem functioning relationships. On the other hand, the present study also reveals the underlying mechanism by which microalgal diversity influences nitrogen removal efficiency, namely, high-diversity microalgal communities could use limiting nutrients such as nitrogen in a more efficient and complementary manner (e.g., stronger complementarity effect in high-diversity communities), convert them into higher aggregate community properties (e.g., higher total abundance of microalge in high-diversity communities), and thus exhibit higher purification capacity (e.g., higher nitrogen removal efficiency in high-diversity communities). Under the scenario that global ecosystems are experiencing high rates of anthropogenic nutrient inputs, the use of diverse microalgal species with proper management may help provide a promising approach for improving water quality
Effective field theory with resonant P-wave interaction
A new effective field theory has been developed to describe shallow -wave
resonances using nonlocal, momentum-dependent two-body potentials. This
approach is expected to facilitate many-body calculations and has been
demonstrated to converge and to be renormalizable in perturbative calculations
at subleading orders. The theory has been applied to the neutron-alpha system,
with good agreement found between its predictions and a phase-shift analysis of
neutron-alpha elastic scattering. In the three-body system consisting of two
neutrons and an alpha particle, the nonlocal potential in this framework has
been found to recover the same qualitative features as previously shown with
energy-dependent formulations.Comment: 17 pages, 4 figure
Finite-Time Robust H
Singular systems arise in a great deal of domains of engineering and can be used to solve problems which are more difficult and more extensive than regular systems to solve. Therefore, in this paper, the definition of finite-time robust H∞ control for uncertain linear continuous-time singular systems is presented. The problem we address is to design a robust state feedback controller which can deal with the singular system with time-varying norm-bounded exogenous disturbance, such that the singular system is finite-time robust bounded (FTRB) with disturbance attenuation γ. Sufficient conditions for the existence of solutions to this problem are obtained in terms of linear matrix equalities (LMIs). When these LMIs are feasible, the desired robust controller is given. A detailed solving method is proposed for the restricted linear matrix inequalities. Finally, examples are given to show the validity of the methodology
A Beam-Steering Reflectarray Antenna with Arbitrary Linear-Polarization Reconfiguration
This work presents a beam-steering reflectarray antenna capable of achieving
arbitrary linear polarization (LP) reconfiguration. It utilizes a dual-circular
polarization (CP) reconfigurable reflectarray, along with an LP feed horn, to
synthesize a LP beam by combining two reflected CP beams in the same direction.
The LP states can be dynamically adjusted by tuning the phase constants of the
array, which correspondingly modify the wave phases. Experimental validation of
the proposed polarization synthesis concept is conducted using a 1616
dual-CP 1-bit reconfigurable reflectarray operating at 16.8 GHz. This
reflectarray generates reconfigurable LP waves with polarization states of
LP(0), LP(45), LP(90) and LP(135). Furthermore,
it demonstrates the capability to perform beam scanning, allowing for versatile
beam manipulation. The application of this polarization-reconfigurable
beam-steering reflectarray is pertinent to beam alignment and polarization
synchronization in various wireless communication scenarios, including
satellite communication and mobile communication
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