High Power Conditions Research Articles

Crosslinked PAES-based sandwich-structured polymer nanocomposites with covalently strengthened interface towards high-temperature capacitive energy storage

As a key material for capacitors, high-performance polymer dielectric films still exhibit the problem of low energy storage density, which cannot meet the requirements of high-power and high-temperature conditions. Here, a sandwich-structured composite film with inner layer doped TiO2-BCB (titanium dioxide – benzocyclobutene) and outer layer doped BN-BCB (boron nitride – benzocyclobutene) nanoparticles was prepared, which exhibits reduced dielectric loss, leakage current and enhanced dielectric constant (ε) and breakdown strength (Eb). Diels-Alder reaction and radical polymerization reactions are utilized to form the entire cross-linked sandwich structure. Moreover, the thermal-induced crosslinked structure replaces the traditional multilayer structure established by Van der Waals forces, thus improving the dielectric and mechanical qualities of the film. Specifically, the sandwich structure composites achieved a large discharge energy density (4.0 J/cm3) and high charge-discharge efficiency (84%) at 150 °C and 450 MV/m, and the dielectric dissipation factor is less than 0.005. These results demonstrated that designing a cross-linked network in multilayer nanocomposite structure is a feasible method to improve the high-temperature energy storage performance of these films.

Improvement of YX42° Cut LiTaO3 SAW Filters with Optical Proximity Effect Correction Method.

Due to the influence of the optical proximity effect (OPE), it is easy for a pattern of photoresistance to be inconsistent with a design pattern, thus damaging the performance of a SAW resonator. To solve this problem, this paper proposes an optimization method for SAW filters based on optical proximity correction (OPC). This method can avoid the tip discharge problem of SAW filters by suppressing the problem of rounding and shrinking of dummy electrode and electrode tail caused by OPE. This method increases the quality factor (Q) of the SAW resonator and thus decreases the insertion loss of the SAW filter. The filter increases the bandwidth by 1.8 MHz at -1.5 dB after applying the OPC method. Additionally, it improves the stability of the filter under high power conditions.

A New Family of Reconfigurable Waveguide Filters and Diplexers for High-Power Applications

In this paper, we discuss how the use of the recently developed modified tuning pin (MTP) can be extended to the design of filters and diplexers implemented in rectangular waveguide, that can be reconfigured in a number of discrete states, and that can be used in high-power payloads. As an application example, the design of two reconfigurable filters and a reconfigurable diplexer is fully described. The high-power behavior of these components (in particular, with respect to corona and multipaction effects) is also studied in detail, in order to demonstrate that the structures that we discuss can operate correctly under high-power conditions. Furthermore, comparisons between simulations and measurements of several prototypes are also included, showing an excellent agreement between simulated and experimental data, thereby fully validating both the design approach and the filter reconfiguration strategy.

Material Wear Calculation of Braking Surface under High-Power Braking Conditions

The wear phenomenon of the braking surface of a high-power disc brake under emergency braking conditions is analyzed in this paper. Considering the classical Archard wear model, including the influence of the braking load, speed, and friction coefficient on the braking surface, the wear model of the brake disc surface is established to obtain the wear depth and distribution. It is essential to investigate the wear mechanism of the brake disc surface, and the evolution of wear laws is revealed under different braking parameters. The results have shown that the brake disc surface wear is constantly accumulating. The large load, the high speed, and the large friction coefficient would aggravate the surface wear area. It is expected that the wear study of the brake disc surface can guide the design of the disc brake.

Evaluation of the resection efficiency and safety of an enhanced power plasma generator using cadaveric intervertebral discs.

Plasma energy has been used to provide minimally invasive interventional treatment for spinal problems. However, this procedure has been used for limited indications mainly because of its small resection range. To overcome this problem, we designed the enhanced power plasma device. This device seeks to maximize the resection area by modifying the electrode arrangement and enhancing the maximum electric power. The purpose of this study is to assess the efficiency and safety of this newly designed plasma generator, a device for percutaneous disc decompression. We performed an intradiscal procedure on 7 fresh human cadaver lumbar spine specimens using the enhanced power plasma under C-arm fluoroscopic guidance at various voltages. As a result, the volume of the removed area was proportional to the applied magnitude of the electric power level. In particular, under the high-power level condition after 500s treatment, nearly the entire nucleus pulposus was eliminated. The generated plasma density also tends to grow along with the given electric power. The highest level of temperature rise did not exceed the level that would lead to degeneration in the collagen tissue of the intervertebral disc. Histopathologic examination also demonstrated that there was no thermal damage to the surrounding neural tissues. In conclusion, we speculate that the concepts of this newly designed enhanced plasma generator could be applied to remove huge disc materials without thermal or structural damage to the adjacent target tissues in future spine clinics.

Influence of small ground surface on plasma property in an inductively-coupled plasma with floating liner

Currently, the components of semiconductor processing chamber are coated with oxides to avoid metal contamination. As a result, electrical ground is hidden from the plasma. In this study, we experimentally investigate the effect of small ground surfaces in an inductively-coupled plasma (ICP) generated in an electrically floating liner. Peak-to-peak and DC voltages at a biasing stage and a floating liner are measured as a function of stage peak-to-peak voltage for various ICP powers and the ground surface areas. The results show that the stage and liner voltages vary with changing ground surface area due to a change in sheath thickness. The analytical plasma potentials, calculated from the experimental values are compared with the simulation results, show good agreement. It is suggested that under low biased voltage and high ICP power conditions, such as in the atomic layer etching process, the small ground surface affects the potential structure in the chamber.

Influence of the Refrigerant on the Performance of a Heat Pump with Gas Bearings

Heat pumps have become a potential technology for future thermal management systems in space. However, conventional heat pumps lubricated with oil are currently unfeasible due to the difficulty separating oil in microgravity environments. The oil-refrigerant mixture reduces the heat transfer capacity of heat exchangers, and insufficient separation can damage the compressor. This paper proposes a new heat pump with gas bearings (HPGB) that combines a centrifugal compressor with externally pressurized gas bearings to solve lubrication problems. A numerical model is established to compare performance of the HPGB system with different refrigerants. The results show that the coefficient of performance (COP) of the HPGB system is slightly smaller than those of conventional heat pumps, but higher than those of heat pumps with the impact of an oil concentration of 5%, when evaporator power is 30 kW. The HPGB system is more suitable for high-power conditions because of the higher COP. Ammonia is the best choice for the HPGB system under high-power conditions (above 80 kW). R134a is the best choice under middle-power conditions (from 25 kW up to 80 kW). R1234yf is more suitable with the maximum COP of 2.88 under low-power conditions (below 25 kW).

Effect of Pre-Existing Micro-Defects on Cutting Force and Machined Surface Quality Involved in the Ball-End Milling Repairing of Flawed KDP Crystal Surfaces

When serving in extremely high-power laser conditions, KH2PO4 (KDP) surfaces are susceptible to incur laser damage points (also known as defects). Using micro-ball end milling cutters to repair and remove the pre-existing damage points on the flawed KDP crystal surface is the most effective method to control the growth of laser damage points on KDP crystal surfaces and prolong their service life. However, there are various forms of micro-defects (such as pits, scratches and brittle fractures) around the laser damage points on KDP crystal surfaces which possess remarkable effects on the micro-milling repair process and consequently deteriorate the repair quality. In this work, combined with nano-indentation experiments, elastic-plastic mechanics and fracture mechanics theory, a constitutive model considering the anisotropic property of KDP crystals and a three-dimensional (3D) finite element model (FEM) were established to simulate the cutting force and surface topography involved in the ball-end milling repairing of flawed KDP crystal surfaces. Besides, the micro-milling experiments were conducted to evaluate the change of cutting force and machined surface quality in the presence of micro-defects with various feed rates. The results show that micro-defects would induce the fluctuation of cutting force and a change of the undeformed cutting thickness (UCT) in the process of repairing the damage points on the crystal surface, which would lead to the brittle-ductile transition (BDT) and affect the machined surface quality. The machined surface quality was found to be deteriorated by the pre-existing micro-defects when the UCT was small (the UCT was less than 375 nm). On the contrary, brittle mode cutting in the local area can be transformed into ductile mode cutting, resulting in an improvement of repaired surface quality that is exhibited by the cutting force and microtopography. This work has great theoretical significance and engineering practical value for the promotion and application of micro-milling repairing technology in the practical manufacturing and operation of KDP optics applied to high-power laser systems.

Simultaneous electrical and thermal rectification in a monolayer lateral heterojunction.

Efficient waste heat dissipation has become increasingly challenging as transistor size has decreased to nanometers. As governed by universal Umklapp phonon scattering, the thermal conductivity of semiconductors decreases at higher temperatures and causes heat transfer deterioration under high-power conditions. In this study, we realized simultaneous electrical and thermal rectification (TR) in a monolayer MoSe2-WSe2 lateral heterostructure. The atomically thin MoSe2-WSe2 heterojunction forms an electrical diode with a high ON/OFF ratio up to 104. Meanwhile, a preferred heat dissipation channel was formed from MoSe2 to WSe2 in the ON state of the heterojunction diode at high bias voltage with a TR factor as high as 96%. Higher thermal conductivity was achieved at higher temperatures owing to the TR effect caused by the local temperature gradient. Furthermore, the TR factor could be regulated from maximum to zero by rotating the angle of the monolayer heterojunction interface. This result opens a path for designing novel nanoelectronic devices with enhanced thermal dissipation.

Fabrication and Mathematical Modeling of the Brushless Doubly Fed Induction Generator-Based Wind Electric Conversion System

Electricity generation with minimal environmental pollution is required for the world’s sustainable future, and wind electric generation is one of them. Brushless doubly fed induction generator (BDFIG), which derives from cascade induction machine technology, has grown in popularity as a wind electric generator due to advantages over doubly fed induction generator (DFIG) and permanent magnet synchronous generator (PMSG) such as the absence of slip rings and brushes and high-cost permanent magnets. Wind energy research is critical for any country’s economic development and long-term sustainability. As a result, an experimental setup in a laboratory is required to replicate the behaviour of a wind turbine in the steady state. This study discusses the emulation of wind turbine characteristics in the laboratory using a prototype of a separately excited DC motor mechanically coupled to a brushless doubly fed induction generator (BDFIG). The wind turbine emulator-brushless doubly fed induction machine (WTE-BDFIM) prototype was tested in the laboratory under high power and low wind speed conditions. As a result, the simulation of the same hardware configuration in MATLAB was performed to investigate the overall performance of the BDFIM-based WECS. To determine the equivalent circuit parameters of the BDFIM, which are required for simulation, tests were performed on a prototype of 3.5 kW, 2/6 pole, 400 V, star/delta-star, and BDFIM in two modes, namely, the simple induction mode and the cascade induction mode. Based on the BDFIM parameters, a MATLAB Simulink model of a BDFIG-based wind electric conversion system (WECS) is created and its performance is investigated. Results of both hardware and simulation show that BDFIG can be used as the wind electric generator over a wider speed range compared to that of DFIG, an important feature that is required to get maximum power extraction from the wind turbine.

Electrothermal Coupling Model With Distributed Heat Sources for Junction Temperature Calculation During Surges

High junction temperature is usually the main factor leading to device failures in high-power working conditions, such as surges or avalanches. It is of great significance to obtain the junction temperature quickly and accurately. Direct measurement of junction temperature is inconvenient, and usually indirect electrical measurement combined with model calculation is used. An electrothermal coupling junction temperature calculation model with distributed heat sources is proposed in this article. This model can accurately and quickly predict the device behavior during the surge process, as well as the voltage drop and temperature changes of each part of the device, without actually performing surge tests. This article describes the theoretical basis and calculation principles of the model. By taking a commercial SiC merged PiN Schottky diode as an example, this article also explains the details of the establishment of the electrical and thermal characteristic models of the device, as well as the calculation steps of the junction temperature by the thermal coupling model. The calculated device voltage drop curve of the device is in good agreement with the measured ones, and the calculated junction temperature curve is more consistent with the device failure mechanism than the one by the traditional RC thermal circuit model.

High power conditioning of RF couplers for the BISOL Linac

Two coaxial couplers have been successfully designed and fabricated by Peking University for the BISOL (Beijing Isotope-Separation-On-Line neutron-rich beam facility). These devices use double-cylinder ceramic windows for the lower-frequency couplers. To reduce expenses, they were designed to transmit RF power for the HWR cavities at a level of 20 kW at 162.5 MHz and for the QWR cavities at between 1–5​ kW at 81.25 MHz. RF conditioning and long-time testing are necessary steps to verify the couplers’ performance before installation. This paper describes the process and method of high-power conditioning. We completed the high-power conditioning of the couplers at the design power of 20 kW in the continuous wave mode. The devices were tested at room temperature for about 24 h. The results showed that the double-cylinder-window couplers have excellent performance.

I am entitled to it! Social power and context modulate disadvantageous inequity aversion

Previous research consistently indicated that social power influences one's fairness consideration. However, it is unclear how social power and context jointly affect inequity aversion and whether these processes would be manifested in brain activities. In this study, participants were randomly assigned into either high or low power condition and then took part in a modified ultimatum game (UG) as responders in both gain and loss contexts, with their event-related potentials (ERPs) recorded. Behavioral results showed that powerful participants were more likely to reject unfair offers in both contexts compared with powerless ones. In addition, powerful participants showed a more negative feedback-related negativity (FRN) loss-win difference wave (d-FRN) upon presentation of proposed offers compared with powerless participants only in the gain context. Interestingly, in a later time window, differences of P300 responses to proposed offers were modulated by social power in both gain and loss contexts. These results suggested that powerful people were more sensitive to fairness levels and FRN may manifest fairness consideration in a gain context, but not in a loss context. Meanwhile, P300 is sensitive to fairness considerations in both gain and loss contexts.

Ultrafast laser micromachining of hard carbon/fumed silica anodes for high-performance sodium-ion capacitors

The slow sodium-ion storage kinetics of battery-type electrodes limits the performance of sodium-ion capacitors (SICs) operating under high-power conditions. In this study, ultrafast laser micromachining was utilized to accelerate the sodium-ion storage kinetics of hard carbon/fumed silica (HC/f-SiO2) anodes. The ablation process involving an ultrafast femtosecond laser source enabled three-dimensional microstructuring of hot-short HC/f-SiO2 anodes with minimal photothermal damage. The microporous structure of the HC/f-SiO2 anodes facilitated the electrolyte wetting of the active materials as well as the diffusion-limited supply of sodium-ions from the bulk electrolytes. The microstructured HC/f-SiO2 anode exhibited a sodium-ion storage capacity of 370 mAh g−1, which was higher than those of unstructured HC/f-SiO2 anodes of comparable mass (298 mAh g−1) or thickness (248 mAh g−1). In addition, the rate capability of the microstructured HC/f-SiO2 anode was superior to that of the unstructured samples. Comparative full-cell tests with oxidized single-walled carbon nanotube cathodes confirmed that micromachining of the HC/f-SiO2 anode was crucial for improving the performance of the SIC full cells. This study demonstrates that ultrafast laser micromachining of HC/f-SiO2 electrodes is a facile and reliable strategy for the development of high-performance SICs.

Flexible Aluminum-Air Battery Based on Ionic Liquid-Gel Polymer Electrolyte.

There is an urgent demand to develop high-performance flexible batteries for a wide range of contemporary emerging fields, including flexible electronics, wearable sensors, and implantable medical devices. However, the inherent safety and stability issues of traditional organic liquid-based electrolytes make their application in flexible batteries unsatisfactory. Therefore, exploring gel electrolytes with superior ionic conductivity and safety is considered to be the key to the development of flexible batteries. In this paper, two types of high-quality ionic liquid-based gel polymer electrolyte membranes (PVDF-ILs) are created by a conventional solution-casting method, which are further integrated into flexible aluminum-air batteries to guide the interface and process research, and the related discharge properties of two ionic liquid-based electrolyte membrane (PVDF-[C4mpyr]Cl, PVDF-[BMIM]Cl) in different bending states are discussed. The results show that PVDF-ILs have a rich pore structure and interwoven skeleton network, leading to relatively high ionic conductivity (2.97 × 10-3 S cm-1). Moreover, two types of batteries can meet the needs of flexibility, although there is a slight loss of power density under various bending conditions. In general, a PVDF-[C4mpyr]Cl-based flexible aluminum-air battery is suitable for the working conditions of high power and low bending angle, while the PVDF-[BMIM]Cl-based flexible aluminum-air battery is favored for microwatt low-power devices with high flexibility requirements.

An Interleaved Two Switch Soft-Switching Forward PWM Power Converter with Current Doubler Rectifier

Forward converters have been broadly used in the power supply industry due to their simplicity, worthy efficiency, and low cost. A novel prototype soft-switched zero-voltage and zero-current ZVZC PWM DC-DC power converter with low voltage/current stresses is introduced for telecommunication power feeding in this paper. A new two-switch interleaved forward converter circuit is introduced to minimalize current circulation with no supplementary auxiliary snubber circuits. This converter circuit includes some outstanding benefits such as reduced components, improved efficiency, high power density and economic circuit configurations for high power conditioning applications. The simple operation principle is demonstrated on the basis of steady-state analysis. Furthermore, the effective feasibility of the proposed circuit topology is evaluated and verified practically for a 500 W–100 kHz prototype breadboard. The operation principle and steady-state characteristics are demonstrated from a theoretical point of view. To verify the practical effectiveness of the proposed power converter, a 500 W–100 kHz prototype converter using ultrafast IGBTs is implemented for a distributed telecommunication energy plant. The studied soft-switching converter is evaluated in comparison with the previously-proposed PWM converters in terms of voltage, current stresses, and operating efficiency.

For Powerholders ‘More is More’: Power Shapes Judgments of Logically Equivalent Comparative Statements

Human judgments are inherently comparative. Recently, a so-called more-less asymmetry in comparative communication has been demonstrated: ‘more than’ comparisons are preferred to corresponding ‘less than’ comparisons. Here we show that a ubiquitous social-structural factor – social power – shapes biases in such comparisons. Powerholders, relative to powerless individuals, liked more, agreed more with and considered more likely to be true ‘more than’ compared to ‘less than’ statements. This was true despite the fact that the differently formulated statements were logically equivalent. In Study 1 (<em>N</em> = 153), induced high power (vs. control or low power) led to believing that ‘more than’ statements were more likely to be true. In Studies 2A/B (<em>N</em> = 449) the judgments of participants in high power conditions were more favorable when comparisons were made using ‘more than’ comparisons. This was also the case in a pilot study (<em>N</em> = 149) in which individual differences in chronic sense of power were assessed. These findings suggest that powerholders’ decisions based on comparative information are especially prone to the more-less judgmental bias resulting in asymmetry. They are in line with approaches positing that power increases and lack of power decreases reliance on subjective experiences, including – but not limited to – ease of information processing and the use of fast and frugal strategies in judgment and decision-making.

Hardening of (Ba0.5Na0.5)0.85Ba0.15TiO3 lead-free piezoelectric ceramics by adding (Bi0.5Na0.5)MnO3

The hardening of (Bi0.5Na0.5)0.85Ba0.15TiO3 (BNBT15) piezoelectric ceramics was investigated by adding raw materials with Bi0.5Na0.5MnO3 (BNM). BNBT15-BNM exhibited a single phase of BNBT15. BNM acts as a sintering aid for BNBT15 to produce domain pinning, and produces tetragonality based on BaTiO3 for increased stability. BNBT15-BNM hardens piezoelectric material with low Mn content, increasing the coercive field and mechanical quality factor. The mechanical quality factor of BNBT15-BNM (0.75 wt%) exceeded 1200. In high-power conditions, BNBT15-BNM (0.75 wt%) exhibited a vibration velocity twice that of hard-PZT. The quality factor gradually decreased with a high vibration velocity. The equivalent stiffness slightly decreased with strain, and the mechanical nonlinearity was much less than that of hard-PZT. BNBT15-BNM (0.75 wt%) has superior high-power properties, and is expected to be a candidate material for use in lead-free piezoelectric ceramics in high-power applications.

Highly photostable fluorescent probes for multi-color and super-resolution imaging of cell organelles

High-performance microscopy with organelle-targeting fluorescent probes has been an indispensable bioimaging tool for cell biology. Confocal or super-resolution imaging often requires highly magnified and/or longitudinal scanning conditions, necessitating the advent of photostable fluorophores. Herein, we report novel organelle-targeting fluorescent probes derived from a highly photostable fluorophoric skeleton, i.e., 1,5-naphthyridine-2,6-dione (NTD). With organelle-specific derivatization and π-conjugation extention, we developed NTD-based molecular probes with blue-to-red fluorescence tunability and intracellular organelle selectivity for staining, as well as minimal cytotoxicity, which allowed us to demonstrate intracellular differentiation of lysosomes and mitochondria by multi-color confocal imaging. Under the condition of longitudinal microscopic examination, these new probes showed excellent photostability of fluorescent signals as opposed to the rapid photobleaching of commercial trackers. By virtue of these beneficial properties, the NTD-based probes were successfully applied to super-resolution cell imaging by enduring the high-power illumination conditions of sub-diffraction microscopic techniques including stimulated emission depletion (STED) and structured illumination microscopy (SIM).

Role of NBI fuelling in contributing to density peaking between the ICRH and NBI identity plasmas on JET

Density peaking has been studied between an ICRH and NBI identity plasma in JET. The comparison shows that 8 MW of NBI heating/fueling increases the density peaking by a factor of two, being R/L n = 0.45 for the ICRH pulse and R/L n = 0.93 for the NBI one averaged radially over ρ tor = 0.4, 0.8. The dimensionless profiles of q, ρ *, υ *, β n and T i/T e ≈ 1 were matched within 5% difference except in the central part of the plasma (ρ tor < 0.3). The difference in the curvature pinch (same q-profile) and thermo-pinch (T i = T e) between the ICRH and NBI discharges is virtually zero. Both the gyro-kinetic simulations and integrated modelling strongly support the experimental result where the NBI fuelling is the main contributor to the density peaking for this identity pair. It is to be noted here that the integrated modeling does not reproduce the measured electron density profiles, but approximately reproduces the difference in the density profiles between the ICRH and NBI discharge. Based on these modelling results and the analyses, the differences between the two pulses in impurities, fast ions (FIs), toroidal rotation and radiation do not cause any such changes in the background transport that would invalidate the experimental result where the NBI fuelling is the main contributor to the density peaking. This result of R/L n increasing by a factor of 2 per 8 MW of NBI power is valid for the ion temperature gradient dominated low power H-mode plasmas. However, some of the physics processes influencing particle transport, like rotation, turbulence and FI content scale with power, and therefore, the simple scaling on the role of the NBI fuelling in JET is not necessarily the same under higher power conditions or in larger devices.