Nanoscale cutting using self-excited microcantilever

The application of self-excitation is proposed to improve the efficiency of the nanoscale cutting procedure based on use of a microcantilever in atomic force microscopy. The microcantilever shape is redesigned so that it can be used to produce vibration amplitudes with sufficient magnitudes to enable the excitation force applied by an actuator to be transferred efficiently to the tip of the microcantilever for the cutting process. A diamond abrasive that is set on the tip is also fabricated using a focused ion beam technique to improve the cutting effect. The natural frequency of the microcantilever is modulated based on the pressing load. Under conventional external excitation conditions, to maintain the microcantilever in its resonant state, it is necessary to vary the excitation frequency in accordance with the modulation. In this study, rather than using external excitation, the self-excitation cutting method is proposed to overcome this difficulty. The self-excited oscillation is produced by appropriate setting of the phase difference between the deflection signal of the microcantilever and the feedback signal for the actuator. In addition, it is demonstrated experimentally that the change in the phase difference enables us to control the amplitude of the self-excitation. As a result, control of the cutting depth is achieved via changes in the phase difference.

Manipulation of Time- and Frequency-Domain Dynamics by Magnon-Magnon Coupling in Synthetic Antiferromagnets

Magnons (the quanta of spin waves) could be used to encode information in beyond Moore computing applications. In this study, the magnon coupling between acoustic mode and optic mode in synthetic antiferromagnets (SAFs) is investigated by micromagnetic simulations. For a symmetrical SAF system, the time-evolution magnetizations of the two ferromagnetic layers oscillate in-phase at the acoustic mode and out-of-phase at the optic mode, showing an obvious crossing point in their antiferromagnetic resonance spectra. However, the symmetry breaking in an asymmetrical SAF system by the thickness difference, can induce an anti-crossing gap between the two frequency branches of resonance modes and thereby a strong magnon-magnon coupling appears between the resonance modes. The magnon coupling induced a hybridized resonance mode and its phase difference varies with the coupling strength. The maximum coupling occurs at the bias magnetic field at which the two ferromagnetic layers oscillate with a 90° phase difference. Besides, we show how the resonance modes in SAFs change from the in-phase state to the out-of-phase state by slightly tuning the magnon-magnon coupling strength. Our work provides a clear physical picture for the understanding of magnon-magnon coupling in a SAF system and may provide an opportunity to handle the magnon interaction in synthetic antiferromagnetic spintronics.

5G Millimeter-Wave Beamforming System using Substrate Integrated Waveguide

Beamforming is a key element of 5G that uses advanced antenna technologies to focus a wireless signal to a defined direction. Butler Matrix (BM) as a beamforming network is used to control the beam direction by utilizing the amplitude and the output phase. A particular technique for designing BM is through substrate integrated waveguide (SIW), which is used to realize the bilateral edge wall vias where the waveguide mode propagates through to support the current flow and reduce the loss of surface wave. Unlike conventional BM, the proposed design requires only hybrid couplers and phase shifter without any crossover. In this BM structure, the SIW hybrid coupler is designed, with two phase shifters of -90°, and one phase shifter of -180° to control the amplitude and phase shifting. This results in an optimized transmission amplitude and output phase difference. The BM also circumvents any crossover, to provide minimal losses. The hybrid coupler exhibits Sii and Sij characteristics at 28 GHz, with values of -27.35 dB for return loss, -3.9 dB for insertion loss, -3.2 dB for coupling, and -26.54 dB for the isolation. In the BM design, high transmission efficiency is observed where the return loss is less than -10 dB, while minimal transmission amplitudes are obtained within the values of ‒6 ± 3 dB. The three-port BM is designed using SIW with minimal loss and the phase difference at each respective output port of the BM shows values of 0°, -120°, and 120°. The three consecutive beams with the gains of 11.1 dBi for port 1 excitation, 9.06 dBi for port 2 excitation and 10.4 dBi for port 3 excitation is achieved when the antenna array is fed to the BM, and each of the radiated beams has beam angles of 0, -27 and 27 degrees.

Stability and synchronous characteristics of a two exciters vibration system considering material motion

Nowadays, two exciters vibration system played an indispensable role in a majority of machinery and devices, such as vibratory feeder, vibrating screen, vibration conveyer, vibrating crusher, and so on. The stability of the system and the synchronous characteristics of two exciters are affected by material motion. However, those effects of material on two exciters vibration system were studied very little. Based on the special background, a mechanical model that two exciters vibration system considering material motion is proposed. Firstly, the system's dynamic equations are solved by using Lagrange principle and Newton's second law. Then, the motion stability of the system when material with different mass move on the vibrating body is analyzed by [Formula: see text] mapping and numerical simulation methods, and the motion forms of the material are also studied. Meanwhile, the frequency responses of the vibrating body are analyzed. Finally, the influence of material on the phase difference of the two exciters is revealed. It can be concluded that with the mass ratio of the material to the vibrating body increasing, the system's motion evolves from stable periodic motion to chaotic state, the synchronization ability of two exciters decline, and the unpredictability of abrupt change about the phase difference increases. Further, the uncertainties of both the abrupt change of phase difference and the collision location affect each other and eventually lead to the instability of the system.

Comparison of Interleaving Methods of Parallel Connected Three-Level Bi-Directional Converters

The voltage and current ripples in the three-level bi-directional converter (TLBC) can be reduced by an interleaving technique that controls a phase difference between the modules of power converter. On the other hand, the inductor current ripple in TLBC is increased due to the circulating current between the modules. In this paper, the effects of two interleaving methods on a two-phase TLBC, Z-type and N-type, are investigated and compared. In particular, capacitor current ripple, and voltage ripple are compared by two interleaving methods verified through Powersim (PSIM) simulation.

Manipulating vector solitons with super-sech pulse shapes

Theoretical simulations about manipulating vector solitons with super-sech pulse shapes are conducted based on an optical fiber system in this manuscript. By changing temporal pulses’ parameters when orthogonally polarized pulses have the same or different input central wavelengths, output modes in orthogonal directions will demonstrate different properties. When input orthogonal modes have the same central wavelength, “2+2” pseudo-high-order vector soliton can be generated when time delay is changed. While under the condition of different central wavelengths, orthogonal pulses with multiple peaks accompanied with two wavelengths can be achieved through varying projection angle, time delay or phase difference. Our simulations are helpful to the study of optical soliton dynamics in optical fiber system.

Structure and properties of summer monsoon stationary B,"Operational use of Ozone over .southern Asia: an observational study

A study of ten-year (1976-1985) mean July climatology of southern Asia and adjoining ocean areas confirms the presence of a well-defined stationary wave, believed to be due mainly to land-sea thermal contrast over the region, in the fields of several meteorological variables. The wave extends laterally over about 10 degrees of latitude with maximum intensity along about 20° N and vertically from surface to about 300 hPa. Its zonal wavelength is about 2000-2500 km and its amplitude in the field of zonal anomaly of temperature and meridional component of wind is 1 oC and 4ms-l respectively. The trough-ridge system of the wave appears to tilt eastward with height from surface to about 700 hPa and westward aloft up to about 300 hPa, while the warmest-coldest anomaly system appears to tilt eastward all the way from surface to about 300 hPa. A phase difference appears to exist between the geopotential and the temperature fields in both the lower and the upper tropospheres. The aforesaid zonal-vertical tilt of the monsoon trough and phase difference between the geopotential and the temperature fields appears to be compatible, through thermal advection, With a direct conversion of eddy available potential energy into eddy kinetic energy via a west-east (clockwise) overturning with warm air rising in the west and cold air sinking in the east in the case of the eastward-tilting lower-tropospheric trough and an east-west (anti-clockwise) overturning with warm air rising in the east and cold air sinking in the west in the case of the westward-tilting middle and upper-tropospheric trough, An enhancement of the thermal advection and hence the vertical circulation may occasionally lead to development of the trough into a I(JW or depression. However, the question of development of the trough and physical factors, which may contribute to such development, needs to be examined by further study.

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.