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• Cyclic thermodynamic perfection decreases by 20.3 % when prototype's speed increases from 6000 rpm to 10,800 rpm. • Prototype's vane and roller separate by 0.38 mm at 10,800 rpm. • Double-valve structure decreases over-compression loss by 45.0 % at 10,800 rpm. • Double-valve alleviates separation by 10.5 %. With the trend towards miniaturization of rotary compressors, increasing the speed of compressors and improving performance at high speed have become important research directions. Simultaneously, due to the need for refrigerants with low global warming potential (GWP), R290 has become an important alternative to hydrofluorocarbons (HFCs). Under the same compressor structure size, meeting the cooling/heating demands with R290 necessitates higher operating speed owing to its lower cooling capacity per unit volume. In this paper, the performance loss distribution of an ultra-high-speed R290 rotary compressor has been studied theoretically and experimentally, and the accuracy of theoretical calculation was verified through experiments. According to the calculation, the primary factor influencing the performance of the ultra-high-speed rotary compressor is over-compression loss. Consequently, corresponding solutions to improve the performance of the ultra-high-speed compressor were proposed. The internal parameters of the compressor were measured, thereby validating the conclusions and assessing the efficacy of the proposed solutions. Finally, the structure parameters were further optimized, which was also verified by experiments. It is found that the double-valve structure can effectively reduce the over-compression loss. When operating at 10,800 rpm under the ASHRAE T1, compared with the prototype, the compressor with double-valve structure can reduce the over-compression loss by 45.0 %, and increase the cyclic thermodynamic perfection by 7.85 %. [ABSTRACT FROM AUTHOR]

Ultra-high-speed data communication receivers (Rxs) conventionally require analog digital converters (ADCs) with high sampling rates which have design challenges in terms of adequate resolution and power. This leads to ultra-high-speed Rxs utilising expensive and bulky high-speed oscilloscopes which are extremely inefficient for demodulation, in terms of power and size. Designing energy-efficient mixed-signal and baseband units for ultra-high speed, Rxs requires a paradigm approach, which is detailed in this paper, that circumvents the use of power hungry ADCs by employing low-power analog processing. The low-power analog Rx employs direct-demodulation with RF correlation using low-power comparators. The Rx is able to support multiple modulations with the highest modulation of 16-QAM reported so far for direct-demodulation with RF correlation. Simulations using Matlab, Simulink R2020a Ⓡ indicate sufficient symbol-error rate (SER) performance at a symbol rate of 8 GS/s for the 71 GHz Urban Micro Cell and 140 GHz indoor channels. Power analysis undertaken with current analog, hybrid and digital beamforming approaches requiring ADCs indicates considerable power savings. This novel approach can be adopted for ultra-high-speed Rxs envisaged for beyond fifth generation (B5G)/sixth generation (6G)/ terahertz (THz) communication without power-hungry ADCs, leading to a low-power integrated design solution.

The convenience and usability of portable consumer electronics that require a motor, such as vacuum cleaners and hair dryers, will be greatly improved if both ac and dc two-input power sources can be used. The dc input power is mostly composed of a dc battery, and single-phase voltage is used as ac input power. A converter system capable of converting ac and dc voltage with control technology is required to supply the voltage for motor driving to apply both ac and dc input to the product. Because a limited number of batteries are used to decrease the weight and size of portable products, a system such as a dc converter is necessary to supply the voltage required to operate the motor and to keep the voltage fluctuation according to the usage time constant. When ac power is used in the product, a voltage drop system that can step down the ac voltage to supply voltage to the dc link is necessary to supply the voltage required to operate the motor to the dc-link. In addition, it is important to reduce the size of the system through ultra-high-speed motor operation by increasing the rotation speed because portable consumer electronics that include a motor drive should be light and portable. This paper proposed a system that can supply a stable dc-link voltage required for ultra-high-speed motor control by applying a phase control method to the ac input side and a dc boost converter to the dc input side. Furthermore, the 1-shunt sensorless method was applied to the inverter for ultra-high-speed motor design and ultra-high-speed motor control system that contributes to product miniaturization and material cost reduction, experimental verification. The ultra-high-speed motor driving evaluation under ac and dc input power conditions and the conversion to dc power input when ac power interrupt occurs were performed to more stably verify the system according to the input power change. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to acquire sealing properties of supercritical CO2 (S-CO2) T-groove seal under ultra-high-speed conditions by thermo-elastohydrodynamic lubrication (TEHL) analysis. Design/methodology/approach: Considering the choked flow effect, the finite difference method is applied to solve the gas state equation, Reynolds equation and energy equation. The temperature, pressure and viscosity distributions of the lubricating film are analyzed, and sealing characteristics is also obtained. Findings: The face distortions induced by increasing rotational speed leads to the convergent face seal gap. When the linear velocity of rotation exceeds 400 m/s, the maximum temperature difference of the sealing film is approximately 140 K, and the viscosity of CO2 is altered by 17.80%. Near the critical temperature point of CO2, while the seal temperature increases by 50 K, the opening force of the T-groove non-contact seal enhances by 20% and the leakage rate declines by 80%. Originality/value: The TEHL characteristics of the T-groove non-contact seal are numerically analyzed under ultra-high-speed, considering the real gas effect and choked flow effect. In the supercritical conditions, the influence of rotational speed, seal temperature, seal pressure and film thickness on sealing performance and face distortions is analyzed. [ABSTRACT FROM AUTHOR]

This paper proposes technical guidelines, modelling, and control of an ultra-high-speed-switched reluctance motor- generator for automotive turbo-charged assistance and energy recovery. Creation of an ideal model using electromagnetic finite element analysis and conducting a low cost/ low scale experiment is proposed. The first objective focuses on the transient simulation process. The second objective focuses on an investigation of the proposed control criteria. The modelling and analysis of a "Switched Reluctance Motor" (SRM) is an initial task for the selection of the coupled mover. Two controllers are selected for the experiment which consists of a generally low-cost solution and an optimized development board for prototyping optimization. The low-cost control solution is implemented with an Arduino Uno and an assortment of relays configured into an asymmetrical half bridge. The second controller is the "Digilent Zed Board Zynq-7000 ARM/FPGA SoC Development Board" (Zed board). ANSYS 2D, 3D modelling, data simulation for the stator and rotor are implemented. Current, voltage, and flux for all phases waveforms are included. Rotor dynamic simulation, machine transient simulations, and some other characteristics are depicted through 3D figures. [ABSTRACT FROM AUTHOR]

The theoretical temporal resolution limit tT of a silicon photodiode (Si PD) is 11.1 ps. We call “super temporal resolution” the temporal resolution that is shorter than that limit. To achieve this resolution, Germanium is selected as a candidate material for the photodiode (Ge PD) for visible light since the absorption coefficient of Ge for the wavelength is several tens of times higher than that of Si, allowing a very thin PD. On the other hand, the saturation drift velocity of electrons in Ge is about 2/3 of that in Si. The ratio suggests an ultra-short propagation time of electrons in the Ge PD. However, the diffusion coefficient of electrons in Ge is four times higher than that of Si. Therefore, Monte Carlo simulations were applied to analyze the temporal resolution of the Ge PD. The estimated theoretical temporal resolution limit is 0.26 ps, while the practical limit is 1.41 ps. To achieve a super temporal resolution better than 11.1 ps, the driver circuit must operate at least 100 GHz. It is thus proposed to develop, at first, a short-wavelength infrared (SWIR) ultra-high-speed image sensor with a thicker and wider Ge PD, and then gradually decrease the size along with the progress of the driver circuits.

Machining deformation of thin-walled bearing rings is difficult to avoid during traditional processing, resulting in an adverse impact on residual stress. Ultra-high-speed centrifugal grinding as a new method may be applied to control finished surface’s residual stress of bearing ring. This paper proposes an ultra-high-speed centrifugal grinding approach for bearing ring. First, a 3D prestress model for bearing ring in the action of inertia and magnetic force was derived by space stress solution to reveal the relationship between prestress and rotating speed. Then, several experiments of prestress and grinding temperature were conducted respectively on ultra-high-speed grinder by using prestress clamping device and clip-on thermocouple temperature sensor. Finally, residual stress, grinding force, surface morphology, grinding temperature, and surface roughness were investigated. A case study shows that circumferential prestress and axial prestress are proportional to the square of palstance. The superficial circumferential prestress, contrary to superficial axial prestress, is tensile stress, which is at least 20 times larger than the axial one. The influence of magnetic force on workpiece prestress is negligible in high rotation speed. Experimental results show that residual tensile stress decreases with increasing prestress, whereas prestress has little impact on grinding force. Moreover, a large prestress produces a deep grinding dent on the finished surface. It is also found that the maximum grinding temperature of the Salomon curve gradually shifts to the lower right with increasing workpiece speed. Low grinding temperature may be achieved in the case of high wheel speed and workpiece speed. [ABSTRACT FROM AUTHOR]

Ultra-high-speed, ultra-large-capacity and ultra-long-haul（3U）optical transmission as a new mode of communication can greatly promote the next generation of optical internet and broadband mobile communication network development and technological progress, therefore 3U has become the focus of international high-tech intellectual property and competition ground. Starting from the background and significance of 3U research, the three scientific problems in 3U were given, and the architecture, basic theory and key technology of 3U optical transmission were introduced. Finally, the verification platform was introduced together with the important experiments completed on the platform, as well as the industrial application of the innovative achievements.

Ultra-high-speed, ultra-large-capacity and ultra-long-haul (3U) are the forever pursuit of optical communication. As a new mode of optical communication, 3U transmission can greatly promote next generation optical internet and broadband mobile communication network development and technological progress, therefore it has become the focus of international high-tech intellectual property competition ground. This paper introduces the scientific problems, key technologies and important achievements in 3U transmission research. [ABSTRACT FROM AUTHOR]

The cutting performance, failure types, and mechanisms of the graded nano-composite ceramic tools were investigated during dry face milling of Inconel 718. In these tests, round ceramic inserts were used at cutting speeds ranging from 500 to 1,100 m/min. The structures of the chips, cutting forces, and surface roughness were also examined. Failure surfaces of the tools were characterized by scanning electron microscopy. The results showed that the graded tool possessed a self-sharpening characteristic and exhibited higher cutting performance compared with the homogeneous ones, as a result of its enhanced mechanical properties, higher abrasive wear, and fracture resistance. The failure mechanisms of the tools involved chipping, flaking, notch wear, abrasive wear, and adhesive wear. The mechanisms responsible for the higher cutting performance of the graded tools were inferred to be the formation of compressive residual stress in the surface layer induced by the graded compositional structure. [ABSTRACT FROM AUTHOR]

Abstract: An ultra-high-speed and very high sensitivity video camera is developed. The highest frame rate reaches 16,000,000 frames per second (16Mfps). The full well capacity is 22,000e − at frame rates up to 4Mfps, and 8000e − at 16Mfps. The pixel count is 165,072 (362×456) pixels. The total number of consecutive frames is 117, which can be doubled to 234 by interlaced imaging operation. The sensitivity is less than 10photons/pixel. [Copyright &y& Elsevier]

This paper presents the development of an ultra-high-speed permanent magnet synchronous motor (PMSM) that produces output shaft power of 2000 W at 200 000 rpm with around 90% efficiency. Due to the guaranteed open-loop stability over the full operating speed range, the developed motor system is compact and low cost since it can avoid the design complexity of a closed-loop controller. This paper introduces the collaborative design approach of the motor system in order to ensure both performance requirements and stability over the full operating speed range. The actual implementation of the motor system is then discussed. Finally, computer simulation and experimental results are provided to validate the proposed design and its effectiveness. [ABSTRACT FROM AUTHOR]

The theoretical temporal resolution limit t T of a silicon photodiode (Si PD) is 11.1 ps. We call "super temporal resolution" the temporal resolution that is shorter than that limit. To achieve this resolution, Germanium is selected as a candidate material for the photodiode (Ge PD) for visible light since the absorption coefficient of Ge for the wavelength is several tens of times higher than that of Si, allowing a very thin PD. On the other hand, the saturation drift velocity of electrons in Ge is about 2/3 of that in Si. The ratio suggests an ultra-short propagation time of electrons in the Ge PD. However, the diffusion coefficient of electrons in Ge is four times higher than that of Si. Therefore, Monte Carlo simulations were applied to analyze the temporal resolution of the Ge PD. The estimated theoretical temporal resolution limit is 0.26 ps, while the practical limit is 1.41 ps. To achieve a super temporal resolution better than 11.1 ps, the driver circuit must operate at least 100 GHz. It is thus proposed to develop, at first, a short-wavelength infrared (SWIR) ultra-high-speed image sensor with a thicker and wider Ge PD, and then gradually decrease the size along with the progress of the driver circuits. [ABSTRACT FROM AUTHOR]