Dynamic Stability of the Coupled Pontoon-Ocean Turbine-Floater Platform-Rope System under Harmonic Wave Excitation and Steady Ocean Current

This research proposes a mooring design which keeps the turbine ocean current, static, balanced, and fixed at a predetermined depth under water, to ensure that the ocean current generator can effectively use current to generate electricity, and that the water pressure remains adequate value before critical pressure damage occurs. In this design, the turbine generator, which withstands the force of ocean currents, is mounted in front of a floating platform by ropes, and the platform is anchored to the deep seabed with light-weight high-strength PE ropes. In addition, a pontoon is connected to the ocean current generator with a rope. The balance is reached by the ocean current generator weight, floating pontoon, and the tension of the ropes which are connected between the generator and floating platform. Therefore, both horizontal and vertical forces become static and the depth can be determined by the length of the rope. Because the floating platform and pontoons on the water surface are significantly affected by waves, the two devices subjected to the wave exciting forces are further affected by the movement of the platform, pontoons, turbines, and the tensions of the ropes. Among them, the exciting forces depend on the operating volume of the two devices. Moreover, there is a phase difference between the floating platform and the pontoon under the action of the waves. In this study, the linear elastic model is used to simulate the motion equation of the overall mooring system. A theoretical solution of the static and dynamic stability analysis of the mooring system is proposed. The dynamic behaviors of the turbine, the floating platform, the pontoon, and the tension of the rope under the effects of waves and ocean currents are investigated. The study found the relationship of the phase difference and the direction difference of waves and ocean currents, the wavelength, and the length of the rope between the carrier and the turbine. It was found that the phase difference has a great influence on the dynamic behaviors of the system. The length of the rope can be adjusted to avoid resonance and reduce the rope tension. In addition, a buffer spring can be used to reduce the dynamic tension of the rope significantly to ensure the safety and life of the rope.

A pulse current generator for dense plasma focus

A pulse current generator applied in a type of high-yield intense pulsed neutron source, the Dense Plasma Focus (DPF), is designed and developed in this paper. There are three key components in this generator. Each group of capacitors and switches is integrative to meet the DPF's requirements of low circuit inductance. A coaxial multi-channel switch is developed to solve the problems of the switch inductance, the jitter and the electrode erosion. A kind of sectorial plate transmission line is adopted to transfer the high pulse current from the capacitors to the DPF. The following technical parameters of the generator were achieved on dummy load: output current amplitude of ∼560 kA when primary capacitors are charged with 22 kV.

Characterization of an X-ray Source Generated by a Portable Low-Current X-Pinch

An X-pinch scheme of a low-current generator (45 kA, 50 ns rise time) is characterized as a potential efficient source of soft X-rays. The X-pinch target consists of wires of 5 μm in diameter—made from either tungsten (W) or gold (Au)-plated W—loaded at two angles of 55° and 98° between the crossed wires. Time-resolved soft X-ray emission measurements are performed to provide a secure correlation with the optical probing results. A reconstruction of the actual photodiode current profile procedure was adopted, capable of overcoming the limits of the slow rising and falling times due to the “slow” response of the diodes and the noise. The pure and Au-plated W deliver an average X-ray yield, which depends only on the angle of the crossed wires, and is measured to be ~50 mJ and ~70 mJ for the 98° and 55° crossed wire angles, respectively. An additional experimental setup was developed to characterize the X-pinch as a source of X-rays with energy higher than ~6 keV, via time-integrated measurements. The X-ray emission spectrum was found to have an upper limit at 13 keV for the Au-plated W configuration at 55°. The portable tabletop X-pinch proved to be ideal for use in X-ray radiography applications, such as the detection of interior defects in biological samples.

Results of studies of the direct current generator of low-temperature nitrogen-propane plasma

The effect of propane-butane addition to the plasma-forming gas on the state of cathodes with inserts made from lanthanated tungsten and hafnium is investigated. With a small propane addition (1%), the restorative effect of the insert material is noted, and the propane consumption has an upper limit when it is introduced together with the plasma-forming gas (no more than ∼ 73% of the plasma-forming gas consumption), below which the arc stability is not disturbed.

Macro-Modeling for N-Type Feedback Field-Effect Transistor for Circuit Simulation

In this study, we propose an improved macro-model of an N-type feedback field-effect transistor (NFBFET) and compare it with a previous macro-model for circuit simulation. The macro-model of the NFBFET is configured into two parts. One is a charge integrator circuit and the other is a current generator circuit. The charge integrator circuit consisted of one N-type metal-oxide-semiconductor field-effect transistor (NMOSFET), one capacitor, and one resistor. This circuit implements the charging characteristics of NFBFET, which occur in the channel region. For the previous model, the current generator circuit consisted of one ideal switch and one resistor. The previous current generator circuit could implement IDS-VGS characteristics but could not accurately implement IDS-VDS characteristics. To solve this problem, we connected a physics-based diode model with an ideal switch in series to the current generator circuit. The parameters of the NMOSFET and diode used in this proposed model were fitted from TCAD data of the NFBFET, divided into two parts. The proposed model implements not only the IDS-VGS characteristics but also the IDS-VDS characteristics. A hybrid inverter and an integrate and fire (I&F) circuit for a spiking neural network, which consisted of NMOSFETs and an NFBFET, were simulated using the circuit simulator to verify a validation of the proposed NFBFET macro-model.

МОДЕЛЮВАННЯ ПРОЦЕСУ ВЗАЄМОДІЇ ІМПУЛЬСНОГО СТРУМЕНЯ ІЗ ЗАГОТОВКОЮ ПРИ ЕЛЕКТРОГІДРАВЛІЧНОМУ НА-ВАНТАЖЕННІ

The eg-stamping of thin-leaf-sized parts has shown its technical and economic efficiency, including the ability to receive parts of ultrahon-thread accuracy. At the same time, the workpieces are loaded on the eg-presses of large intensive energy (up to 500 kJ), which have the possibility of space-time loading control. Such management is carried out using multi-terminated discharge blocks in which dozens of discharge cavities are combined into one. The controlled parameters can be the electrical parameters of tens of discharge circuits of the current pulse generator, the volume and step of the arrangement of the discharge cavities, their height to the workpiece, as well as the sequence of discharges in time (simultaneous or with a shift in the time of EG-discharges in adjacent discharge cavities). The choice of rational ranges of these parameters is impossible without numerical simulation of processes occurring in the discharge volume of the entire block.In the simulation, the processes of heat power is comprehensively considered with the EG-discharge, the formation and propagation of the vapor-gas bubble, which generates a flooded stream of liquid, and deforming the supple billet when exposed to such a jet.The results of numerical experiments in the LS-DYNA environment using the ALE method with the EG-discharge in a single bit (submersible) chamber, in two and three neighboring conditions with different variable conditions are set: the distance from the discharge zone to the workpiece (discharge distance) and the displacement of the time of two and three discharges in the adjacent discharges. As compared parameters were selected: movement of the billet and their speed, the distribution of deformations on the surface of the workpiece and the work of deformation. The adequacy of the model of the real process is shown. An energy-efficient energy-generating cell is proposed for generating EG-discharges from a multi-mounted pulse current generator.