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Direct drive wave energy conversion (DD-WEC) is a typical low-speed long-stroke application. Harvesting wave energy presents enormous challenges, because wave energy naturally exists in the form of extremely low speed, high force, or torque motion. However, the frequency of flux linkage in field-modulated machine can be increased by the magnetic gear effect, and the output voltage and power density can also be effectively enhanced. In this paper, based on the field modulated principle, a field-modulated transverse flux linear generator (FM-TFLG) is proposed. Different combinations of permanent magnet number, slot number and translator number are selected and their performances are compared and analyzed. Results show that the electric frequency is enhanced as the modulation ratio increases. Compared with 18/12/17 (permanent magnet number/slot number/translator number) topology, 12/12/11 FM-TFLG has advantages of lower thrust ripple and total harmonic distortion (THD) of back-EMF, higher thrust/power density and efficiency. The proposed 12/12/11 FM-TFLG is a good candidate for DD-WEC.

Wave energy has great prospect among many forms of marine renewable energy for its high density and storage. This paper proposes an underwater direct drive wave energy converter (UDDWEC), which is composed of a submerged point absorbing buoy and a linear-rotating axial flux permanent magnetic generator (LR-AFPMG). In addition, a maximum energy capture control strategy, resonance control, is derived for UDDWEC, based on small amplitude oscillation and hydrodynamic analysis. The proposed control strategy assumes the availability of sea condition such as wave height and period. This control strategy has three main characteristics. Firstly, this control strategy is derived based on hydrodynamic analysis of the submerged point absorber. Added mass, radiation damping and other hydrodynamic parameters are obtained to participate in UDDWEC dynamic model. Secondly, a LR-AFPMG is applied as power take-off device to realize energy conversion, which can improve the power density. Thirdly, small amplitude oscillation can be changed into long stroke rotary motion through the LR-AFPMG. The reliability and effectiveness of the proposed control strategy are assessed at various operation conditions for a heaving system and the validity for the UDDWEC is verified.

Recently, linear generators have been implemented in direct drive wave energy conversion (DD-WEC), thus simplifying the structure and improving system efficiency. Since DD-WEC is a typical low-speed application, linear generators with multi-pole design all encounter problems such as low power density and low efficiency. Similar to the magnetically geared machine, field-modulated permanent magnet transverse flux linear generator (FM-PMTFLG) has been a suitable candidate for DD-WEC, due to the high power density capability ensured by the ‘magnetic gear effect’. However, for solely PM excited generators, there is a tradeoff between high power density and wide speed operation. Hence, field-modulated hybrid-excitation permanent magnet transverse flux linear generator (FM-HE-PMTFLG) is proposed. In order to improve the thrust performance, the partitioned staggered translator (PST) topology is introduced. The simulation results show that PST topology can achieve better thrust performance than partitioned translator (PT) counterpart. Compared with PT topology, PST topology reduces the magnetic flux leakage and has advantages of higher thrust density, less thrust ripple, higher flux linkage and better total harmonic distortion (THD) of back-EMF.

Direct drive wave energy conversion (DDWEC) device ignoring intermediate transmission mechanism can simplify the structure and improve the efficiency. Usually, linear generator used in DDWEC need a low-speed design for low-frequency wave condition. However, the linear-rotating axial flux permanent magnet generator (AFPMG) proposed in this paper combines the merits of magnetic lead screw (MLS) and axial flux generator to convert the low-frequency reciprocating wave motion into high-speed rotating motion to generate power. Four similar configurations (12s10p, 12s11p, 12s13p and 12s14p) are detailed. The results show the output voltage and power density of the power generation system can be improved in this topology and 12s13p configuration can be a decent candidate for DDWEC.

A novel hybrid excitation axial flux permanent magnet generation (HE-AFPMG) is proposed to improve the electromagnetic performance of conventional axial flux permanent magnet generation and suite the demands of direct drive wave energy conversion. Firstly, the configuration of the HE-AFPMG is introduced. Then operation principle based on open-circuit field distribution and qualitative analysis of field modulation are following. Finally, the electromagnetic performances under no-load and load conditions are analyzed. Meanwhile, the influence of the application of electric excitation on generator is also investigated. It verifies the validity of generator and confirms the excellent field-regulation capability. According to the results, it is proved that the addition of electric excitation field can not only reduce the harmonic component of back EMF, but also broaden the range of load torque.

The outbreak of the novel coronavirus has resulted in significant morbidity and mortality in the affected 210 countries with 2.4 million people infected and over 163 thousand deaths. The COVID-19 spike protein is effective at binding to human cells, but this COVID-19 backbone differed substantially from other, already known coronaviruses and mostly resembled viruses found in bats and pangolins. To help predict possible dynamics of COVID-19 as well as ways to contain it, this paper develops a mathematical model for the disease, which includes two different infectious routes. The model’s predictions are fitted to data from the outbreak in New York State from the first reported case from March 01, 2020 to April 19, 2020. The containment time and the severity of the outbreaks depend crucially on the contact coefficients and the isolation rate constant. When randomness is added to the model coefficients, the simulations show that the model is sensitive to the scaled contact rate among people and to the isolation rate. The model is analyzed using stability theory for ordinary differential equations and indicates that when using only isolation for control and advising self-recovery, the endemic steady state is locally stable and attractive. After reaching the peak of COVID-19 on April 14, 2020, new infections by the virus would slow down, particularly from the beginning of May at New York State if people keep the isolation. Numerical simulations with parameters estimated from New York State illustrate the analytical results and the model behavior, which may have important implications for the disease containment in other cities. Indeed, the model highlights the importance of isolation of infected individuals and advising self-recovery may be used to assess other control measures. The model is general and may be used to analyze outbreaks in other states of the United States and other countries.

Polymers carrying a polymerizable end group, generally known as macromonomers, have frequently been utilized for the synthesis of graft copolymers (1)(2). When a polymer contains polymerizable groups at both chain ends, -a bis-macromonomer-, polymerization or copolymerization leads to the corresponding networks or segmented copolymer networks respectively. The physicochemical properties of the latter may be expected to be the result of a combination of the properties of segmented polymers at the one hand and of polymer networks at the other. For example, it should be interesting to investigate the morphology of such compounds if they are build up of two incompatible chain segments. The theory of the segmented copolymers would predict a phase separation, the morphology of which is determined by the relative lengths of the two constituting polymers. However, in the network form, phase separation is inhibited due to the restricted chain mobilities and therefore a compatibilization of two incompatible polymers may be expected. As a consequence, new materials with formerly unreachable physicochemical properties could arise.