Finite p-groups all of whose non-abelian proper subgroups are generated by two elements

AbstractIn this paper, we classify the finite p-groups all of whose non-abelian proper subgroups are generated by two elements

Stability Study and Nonlinear Analysis of DC-DC Power Converters with Constant Power Loads at the Fast Timescale

Rapidly growing distributed renewable networks make an increasing demand on various types of power converters to feed different loads. Power converters with constant power load are one typical configuration that can degrade the stability of the power conversion system due to the negative impedance characteristic. This paper presents a nonlinear analysis method using the developed complete-cycle solution matrix method by transforming the original linear time-variant system into a summation of segmented linear time-invariant systems. Thus, the stability of the nonlinear system can be studied using a series of the corresponding state transition matrix and saltation matrix. As this derived matrix contains all the comprehensive information relating to the system’s stability, the influence of the constant power load to system’s fast-timescale stability in both continuous conduction mode and the discontinuous conduction mode can be fully investigated and analyzed. The phenomena of fast-timescale instability around switching frequency for power converters with a constant power load are observed and investigated numerically. Finally, experimental results have proven the analysis and verified the effectiveness of the developed method

Bench-to-bedside review: Biotrauma and modulation of the innate immune response

The innate immune network is responsible for coordinating the initial defense against potentially noxious stimuli. This complex system includes anatomical, physical and chemical barriers, effector cells and circulating molecules that direct component and system interactions. Besides the direct effects of breaching pulmonary protective barriers, cyclic stretch generated during mechanical ventilation (MV) has been implicated in the modulation of the innate immunity. Evidence from recent human trials suggests that controlling MV-forces may significantly impact outcome in acute respiratory distress syndrome. In this paper, we explore the pertinent evidence implicating biotrauma caused by cyclic MV and its effect on innate immune responses

Protection against H1N1 influenza challenge by a DNA vaccine expressing H3/H1 subtype hemagglutinin combined with MHC class II-restricted epitopes

<p>Abstract</p> <p>Background</p> <p>Multiple subtypes of avian influenza viruses have crossed the species barrier to infect humans and have the potential to cause a pandemic. Therefore, new influenza vaccines to prevent the co-existence of multiple subtypes within a host and cross-species transmission of influenza are urgently needed.</p> <p>Methods</p> <p>Here we report a multi-epitope DNA vaccine targeted towards multiple subtypes of the influenza virus. The protective hemagglutinin (HA) antigens from H5/H7/H9 subtypes were screened for MHC II class-restricted epitopes overlapping with predicted B cell epitopes. We then constructed a DNA plasmid vaccine, pV-H3-EHA-H1, based on HA antigens from human influenza H3/H1 subtypes combined with the H5/H7/H9 subtype Th/B epitope box.</p> <p>Results</p> <p>Epitope-specific IFN-γ ELISpot responses were significantly higher in the multi-epitope DNA group than in other vaccine and control groups (<it>P </it>< 0.05). The multi-epitope group significantly enhanced Th2 cell responses as determined by cytokine assays. The survival rate of mice given the multi-epitope vaccine was the highest among the vaccine groups, but it was not significantly different compared to those given single antigen expressing pV-H1HA1 vaccine and dual antigen expressing pV-H3-H1 vaccine (<it>P </it>> 0.05). No measurable virus titers were detected in the lungs of the multi-epitope immunized group. The unique multi-epitope DNA vaccine enhanced virus-specific antibody and cellular immunity as well as conferred complete protection against lethal challenge with A/New Caledonia/20/99 (H1N1) influenza strain in mice.</p> <p>Conclusions</p> <p>This approach may be a promising strategy for developing a universal influenza vaccine to prevent multiple subtypes of influenza virus and to induce long-term protective immune against cross-species transmission.</p

A switched reluctance motor torque ripple reduction strategy with deadbeat current control

This paper presents a switched reluctance motor (SRM) torque ripple reduction strategy with deadbeat current control. In this method, the SRM torque is indirectly controlled by the phase current. The deadbeat control method can predict the duty cycle of the switching signal for the next control period according to current error, and achieve an accurate current tracking. Thus, SRM torque control error can be reduced significantly. The feasibility and effectiveness of the proposed strategy have been verified in both simulation and experimental studies

A switched reluctance motor torque ripple reduction strategy with deadbeat current control and active thermal management

This paper presents a switched reluctance motor (SRM) torque ripple reduction strategy with deadbeat current control and active thermal management. In this method, the SRM torque is indirectly controlled by the phase current. A deadbeat current control method is used to improve the SRM phase current control accuracy, so that SRM torque control error can be reduced significantly. According to the online measurement of the power switching device temperature, the switching frequency will be reduced to prevent the SRM power converter from being damaged by over-temperature. The feasibility and effectiveness of the proposed strategy have been verified in both simulation and experimental studies

Hydrodynamic Response and Power Efficiency Analysis of Heaving Wave Energy Converter Integrated with Breakwater

The hydrodynamic and power capture performance of an asymmetric floating device called “Dolphin” wave energy converter (WEC) integrated with a fixed breakwater has been proposed. The operation of the floating WEC device is restricted to the vertical direction called heaving motion. In this research, the theories of heaving motion, wave energy conversion, and computational fluid dynamics (CFD) were studied. A numerical simulation of the CFD with the laminar model was conducted; namely, the effects of four different model shapes were investigated, distance effect between the WEC device and breakwater, WEC integrated with/without breakwater, and vorticity effect analysis using STAR-CCM+ software based on the viscous flow theory in the time domain. The optimal power take-off (PTO) system was considered during the numerical calculation, including the parameters of the WEC model, which were optimized to exploit a higher efficiency by analyzing the motion response in order to obtain the response amplitude operator (RAO) and capture width ratio (CWR) values. From the RAO and vortex field analysis, the RAO value of the Dolphin WEC was exhibited better than that of the other models. A vortex method was applied to verify the CFD simulation results. From the vortex simulation, it can be clearly seen that the integration of breakwater also affected the hydrodynamic performance of the WEC. The Dolphin WEC model with breakwater integration at experimental scale was built and tested in wave tank at Harbin Engineering University under various wave conditions. The breakwater was welded with the steel plate to restrict movement. The displacement sensor and linear generator were installed on top of the WEC device during the experiment. To modify the damping in the system, the heaving motion and power generation characteristics were analyzed and electrical resistance was assumed. The displacement and power in the time domain, RAO, and CWR for different wave periods and wave heights were investigated in the experiment, where the maximum motion response and power efficiency of the WEC model were 1.57 and 0.376, respectively