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In this work, GHz and THz complex dielectric spectra of a polyethylene glycol dimethyl ether (2000 g/mol) aqueous solution were studied. The reorientation relaxation of water in this kind of macro-amphiphilic molecule solution can be well described by three Debye models, including under-coordinated water, bulk-like water [water molecules in a tetrahedral hydrogen bond network (bulk water) and bulk water molecules affected by hydrophobic groups], and slow hydrating water (water molecules donating hydrogen bonds to hydrophilic ether groups). The reorientation relaxation timescales of bulk-like water and slow hydration water both show increases with concentration from 9.8 to 26.7 ps and from 46.9 to 100.1 ps, respectively. By estimating the ratios of the dipole moment of slow hydration water to the dipole moment of bulk-like water, we calculated the experimental Kirkwood factors of bulk-like and slow hydrating water. The experimental Kirkwood factor of bulk-like water increased from 3.17 to 3.44 with concentrations, while the experimental Kirkwood factor of slow hydrating water roughly remained constant at 4.13 from concentrations of 15%–60%. The estimated water molecule numbers of three water components around monomers also confirm our sorting for water components.

Over the past decade, extensive efforts have been made in the study of droplet impact, especially on stationary surfaces, owing to its direct applications in thermal cooling, self-cleaning, and power generation. However, many practical applications, such as ultrasonic cleaning, aerosolized drug delivery, and vibration-assisted welding, involve the direct interaction of droplets with vibrating surfaces, on which droplets undergo spreading and retraction. Distinct from stationary surfaces where the retraction behaviors, such as the retraction velocity and rate, are mainly governed by the surface wettability and droplet inertia, the retraction behaviors on vibrating surfaces become complicated due to the vibration velocity, which dictates the outcomes of droplet impact, such as the pinning, bouncing, gyrating, and jetting. Here, we revealed the synergistic effect of droplet inertia and vibration velocity on droplet retraction. We found that the droplet retraction behaviors on both stationary and vibrating surfaces could be characterized by a universal scaling law, allowing us to analyze and predict the maximum droplet retraction velocities. Moreover, we found that the maximum retraction rate increased with the maximum spreading radius at low Weber numbers. We demonstrated that the droplet retraction dynamics at both low Weber numbers and high Weber numbers could be unified into one integrated model, which indicates the decisive role of the maximum droplet spreading in droplet retraction dynamics.

Superconducting flywheels have potential application value in aerospace field, and its suspension time is a key factor. Alternating Current (AC) loss associated with rotation is an important parameter that affects the suspension time, so it is very important to study how to reduce the AC loss. Recently, a method of preparing YBa2Cu3O7−x (YBCO) high-temperature superconducting flywheels by Direct-Ink-Writing (DIW) 3D printing was developed. In this paper, the circular hole superconducting flywheel prepared by this method is optimized by the idea of structural optimization. Based on the finite element method, the AC loss before and after optimization is calculated and analyzed. It is found that the elliptical holes make the superconducting flywheel have lower AC loss than circular holes, with a reduction of 58.49%. Then, the YBCO superconducting flywheel with an optimized elliptical structure was prepared by the DIW 3D printing method. The magnetic levitation experiment found that the levitation time of the optimized superconducting flywheel was increased to 162 s compared with the previous 120 s under the same conditions, and the optimized structure had a higher levitation mass ratio. It provides theoretical and experimental support for reducing the AC loss of superconductors by applying the idea of structural optimization design in engineering practice.

A reproducible, quasi-stationary edge localized mode (ELM)-suppressed scenario was obtained over a wide range of plasma parameters by continuous injection of boron (B) powder into an upper-single null discharge in the experimental advanced superconducting tokamak [Sun et al., Nucl. Fusion 61, 014002 (2021)]. This powder-induced ELM-absent regime is associated with an edge harmonic mode (EHM) that provides continuous particle exhaust to maintain constant density without confinement degradation and impurity accumulation, the latter of which is often observed in ELM-free regimes. A flow rate threshold of B powder injection, leading to a threshold intensity of the EHM, is necessary for full ELM suppression. The fundamental harmonic of the EHM exhibits a toroidal mode number n = 1. The mode is observable in the entire poloidal cross section with a peak near the upper X-point in an upper-single null configuration. The EHM spans radially across the pedestal and scrape-off layer, peaking inside the separatrix. The EHM appears to be insensitive to q95, heating power, plasma toroidal rotation, and pedestal collisionality.

In saturated Ohmic confinement regime of the experimental advanced superconducting tokamak, significant changes in the relative electron temperature fluctuations T e / T ¯ e, measured by a correlation electron cyclotron emission system, have been observed. It was found that T e / T ¯ e is strongly dependent on the normalized electron temperature and density gradient, R / L T e = R ∇ T e / T e and R / L n e = R ∇ n e / n e. T e / T ¯ e stay at a high level when R / L T e is within the range of 17 − 25 and R / L n e is within the range of 4 − 6. It has been also observed that the energy confinement degradation is correlated with the increase in electron temperature fluctuations. The linear stability analysis results show that the electron temperature fluctuations are mainly attributed to the ion temperature gradient modes.

Synergistic effects between two frequencies of lower hybrid (LH) waves—operating at 2.45 and 4.6 GHz—were observed in experiment on EAST for the first time. At low density ( n e , lin ≈ 2.0 × 1 0 19 m − 3), simultaneous injection of a 65/35 mix of 2.45/4.6 GHz power achieved an lower hybrid current drive efficiency that was 25% higher than what should be expected from the linear combination of the two sources. The experiment was interpreted with time-dependent simulations, using the equilibrium and transport solver TRANSP, coupled with the ray-tracing code GENRAY and the Fokker–Planck solver CQL3D. For each discharge, profiles of current and hard x-rays from simulation and measurement agree within uncertainties. An examination of the electron distribution function indicates that the LH synergy is supported by the increased width of the LH resonance plateau in the simultaneous injection case compared to independent injection.

With a newly installed 5-channel W-band Doppler reflectometer (DR) in EAST tokamak, many interesting coherence modes and turbulences have been observed. In this paper, the tearing mode (TM), a novel inter-edge localized mode (ELM) electromagnetic mode, and the eigenmode geodesic acoustic mode (GAM) accompanied by a broadband quasi-coherent mode (QCM) during H-mode stage have been reported. The TM could be directly observed in both density fluctuation and perpendicular velocity fluctuation at the DR channel localized in the magnetic island region; moreover, many high-order TM frequency harmonics, dual turbulence peaks inside and outside the island separatrix, and strong flow shear across the island separatrix could also be observed. A high-frequency ( ∼ 230 kHz) electromagnetic mode (toroidal mode number n = 1) could be identified. The mode is generated dozens of milliseconds before the ELM crash and may affect the ELM dynamic process. The eigenmode GAM excited during the H-mode stage is generated near the top of the density pedestal and then propagates radially inward with a radial wavenumber of about 1 cm − 1. A broadband QCM with a frequency range of 20 – 100 kHz is always accompanied by eigenmode GAM and nonlinearly coupled with both GAM and the background turbulence from the bispectrum analysis. All these results convince the validity of the Doppler reflectometer in multi-scale measurement from the mesoscale to microscale.

A third generation flowing liquid lithium (FLiLi) limiter with a substrate made of TZM, an alloy with >99% Mo, was fabricated by conventional manufacturing techniques. TZM has a high corrosion resistance, a high sputtering threshold, and a good wettability to Li, as compared to stainless steel (SS), which had been used as an FLiLi substrate surface in 2014 and 2016. The third generation FLiLi was inserted into the edge in EAST H-mode plasmas in an upper single-null configuration with an ion grad-B drift toward the upper divertor with a limiter temperature of 330–380 °C and an auxiliary heating power of about 2–8 MW. Analysis has shown that by using TZM FLiLi, fuel particle recycling continuously decreased and near-complete edge localized mode elimination was achieved in H-mode plasmas with RF-only heating. The main impurities during the initial FLiLi discharges were Mo, Fe, and W resulting from strong plasma interaction at the Mo plate side, the SS collector, and the upper W divertor. Plasma stored energy increased by about 10 kJ in subsequent FLiLi discharges due to decreased impurity radiation. Engineering analysis shows a uniform lithium flow with an ∼80% Li coverage ratio on the limiter surface, similar to the second FLiLi, even though only one of two J × B pumps was functioning. Despite technical difficulties, the FLiLi gen.3 improved the overall plasma performance, providing support for flowing liquid Li plasma facing component applications in present and future devices.

This paper proposes a piezoelectric actuator based on the parasitic motion principle which overcomes the disadvantage that piezoelectric actuators designed by the parasitic motion principle always sacrifice reverse directional performance for improving forward directional performance. The parasitic motion principle based piezoelectric actuator can use two flexible mechanisms to achieve bidirectional motion, but more assembly errors will be introduced. Therefore, the proposed actuator is designed to output bidirectional motion through one flexible mechanism. To this end, two mounting slots with high flexibility are specially designed for improving output displacement. The working principle and design process are elaborated, and experiments are conducted to prove the feasibility of the proposed actuator. The fabricated prototype can achieve a maximum velocity of 1.563 mm/s and 1.054 mm/s, a displacement resolution of 5.8 µm and 6 µm, an operating bandwidth of 1600 Hz and 1200 Hz, and a vertical load capacity larger than 500 g in forward and reverse directions.

Correlations between the edge fluctuations and the pedestal evolution during the relatively large edge localized mode (ELM) cycles at high pedestal normalized electron collisionality ( ν e , ped * > 1) on the EAST tokamak are investigated. Not only the edge electrostatic coherent mode (ECM, ∼50 kHz) and the low frequency magnetic coherent mode (MCM, ∼32 kHz) but also a high frequency electromagnetic mode (HFM, >150 kHz) are observed to be coexisting between ELMs. After the ELM crash, the pedestal electron temperature recovered faster than the pedestal electron density. It is found that the saturation of the ECM coincides more with the saturation of the pedestal electron density, while the saturation of the HFM and MCM coincides more with the saturation of the pedestal electron temperature. In addition, the characteristics of the electromagnetic fluctuations (the HFM and MCM) are studied in detail: the HFM propagates in the electron diamagnetic drift direction in the laboratory frame with an average poloidal wave number of k ¯ θ HFM ≈ 0.17 cm − 1, while the MCM propagates in the ion diamagnetic drift direction in the laboratory frame with k ¯ θ MCM ≈ 0.12 cm − 1 and the toroidal mode number of n = 1. Furthermore, both the HFM and MCM have inward average radial wave numbers of k ¯ R HFM ≈ 0.13 cm − 1 and k ¯ R MCM ≈ 4.64 cm − 1. The bispectral analysis shows that the HFM and MCM have strong nonlinear interactions. The HFM is clearly observed on both low and high field side Mirnov coils, which might suggest a feature beyond a ballooning type instability, e.g., the kinetic ballooning mode. These studies may contribute to a better understanding of the pedestal evolution.

TBM (Full face rock tunnel boring machine) is a large tunnel excavation lining complete equipment which has been widely used in many practical fields. The main components of TBM rock breaking are the disc cutters. Due to the harsh working environment of TBM, such as high temperature (400°C), wear, etc., the consumption of disc cutters is extremely high. Two welding methods used to repair cutters of TBM were analyzed in this paper: shielded metal arc welding (SMAW) and flux cored arc welding (FCAW). The microstructure at RT was investigated, the hardness, indentation modulus and wear resistance from RT to 400°C were also investigated. The results showed that the microstructure of FCAW hardfacing layers was finer. In the tests, the FCAW hardfacing layers showed better hardness and elastic modulus, both parameters reduced with increasing temperature. The FCAW hardfacing layers processed higher wear resistance from RT to 400°C. A thick oxide layer was observed, and it was partially removed when the temperature reached 400°C, and it has a certain protective effect on the worn surface. Therefore, the FCAW hardfacing layers are considered as a good choice due to the better mechanical performance from RT to 400°C.

We report the development of gallium arsenide (GaAs) films grown on V-groove patterned (001) silicon (Si) by metalorganic chemical vapor deposition. This technique can provide an advanced virtual substrate platform for photonic integrated circuits on Si. A low defect density of 9.1 × 106 cm−2 was achieved with the aspect ratio trapping capability of the V-grooved Si and dislocation filtering approaches including thermal cycle annealing and dislocation filter layers. The efficiencies of these dislocation reduction methods are quantified by statistical electron channeling contrast imaging characterization. Meanwhile, different sets of dislocation filtering layers are evaluated and optimized. To further demonstrate the suitability of GaAs on the V-grooved Si technique for Si-based photonic devices, especially for the appealing 1.3 μm quantum dot (QD) lasers, a 7-layer indium arsenide QD structure was grown on both GaAs-on-V-grooved Si and native GaAs substrates. The same photoluminescence intensity and full-width at half-maximum values were observed for both structures. The optimization methodology in this work therefore offers a feasible approach to realize high quality III–V materials on Si for large-scale integration.

A miniature piezoelectric-driven fatigue device with three degrees of freedom is developed. The device integrates two fatigue testing functions, including uniaxial tensile fatigue and tensile-bending combined loading modes. The synchronous tensile-bending loading principle is described, which is applicable for calculating the vector displacements along two orthogonal directions and investigating the anisotropic fatigue properties. Regarding the combined loading mode, maximum load/displacement amplitudes for tensile and bending vector components that could be achieved are 16.9 N/22.8 µm and 3.3 N/5.6 µm, respectively. Based on tensile and tensile-bending combined fatigue loading modes, the displacement responses and fatigue lives at loading frequencies ranging from 1 Hz to 100 Hz are valuated experimentally to indicate the validation.

A modularized cryogenic indentation apparatus was designed and created to study the deformation mechanisms and mechanical properties of materials at low temperatures. The indentation process is actuated by piezoelectric stack and flexure hinge, and the entire mechanical module is kept inside the vacuum chamber to prevent the occurrence of ice. Numerous issues including the effects of the application of cooling module and processes to diminish the temperature effect on the indentation tip were addressed. Several influential factors during temperature indentation were discussed. Tests on calibration specimen demonstrated the feasibility of the apparatus. Monocrystalline silicon and copper were tested using the current apparatus at temperatures ranging from room temperature to 150 K to show its main functions and usability.

This paper presents a lever-type stick-slip piezoelectric actuator based on the lever amplification principle. The proposed actuator can achieve large strokes, high velocity, and bidirectional actuation with a single piezoelectric stack. The finite element simulation of the lever-type flexible hinge is performed, and the designed prototype is tested. When the voltage is 100 Vp-p, the maximum forward velocity is 7.69 mm/s under the symmetry of 20%. The maximum reverse velocity is 7.12 mm/s under the symmetry of 80%. The maximum forward and reverse displacement deviation within 10 cycles is 0.88 μm, and the maximum load can reach 105 g.

Based on different damage forms of various contact forms to bone, the mechanical response and mechanism were investigated by nanoindentation under different sharpness contact forms. For the purpose of simulating the different sharpness contact forms, two kinds of indenters were used in experiments and finite elements simulations. Through nanoindentation experiments, it was concluded that the residual depth of sharp indenter was bigger than that of blunt indenter with small penetration depth. However, the contrary law was obtained with bigger penetration depth. There was a turning point of transition from blunt tendency to sharp tendency. By calculation, it was concluded that the sharper the indenter was, the bigger the proportion of plastic energy in total energy was. Basically, results of finite elements simulation could correspond with the experimental conclusions. By the observation of FE-SEM, the surface of cortical bone compressed was more seriously directly below the blunt indenter than the lateral face. For the berkovich indenter, the surface of indentation compressed was less directly below the indenter, but seriously on three lateral faces. This research may provide some new references to the studies of bone fracture mechanism in different load patterns in the initial press-in stage and offer new explanation for bone trauma diagnosis in clinical treatment and criminal investigation.

Functional materials represented by ferromagnetics and ferroelectrics are widely used in advanced sensor and precision actuation due to their special characterization under coupling interactions of complex loads and external physical fields. However, the conventional devices for material characterization can only provide a limited type of loads and physical fields and cannot simulate the actual service conditions of materials. A multi-field coupling instrument for characterization has been designed and implemented to overcome this barrier and measure the comprehensive physical properties under complex service conditions. The testing forms include tension, compression, bending, torsion, and fatigue in mechanical loads, as well as different external physical fields, including electric, magnetic, and thermal fields. In order to offer a variety of information to reveal mechanical damage or deformation forms, a series of measurement methods at the microscale are integrated with the instrument including an indentation unit and in situ microimaging module. Finally, several coupling experiments which cover all the loading and measurement functions of the instrument have been implemented. The results illustrate the functions and characteristics of the instrument and then reveal the variety in mechanical and electromagnetic properties of the piezoelectric transducer ceramic, TbDyFe alloy, and carbon fiber reinforced polymer under coupling conditions.

Graphene-based materials (GMs) are promising antibacterial agents which provide an alternative route to treat pathogenic bacteria with resistance to conventional antibiotics. To further improve their antibacterial activity, many methods have been developed to functionalize the GMs with chemicals. However, the application of additional chemicals may pose potential risks to the environment and human being. Herein, a radio-frequency-driven inductively coupled non-thermal hydrogen plasma was used to treat and reduce graphene oxide (GO) without using any other chemicals, and we found that the plasma-reduced GO (prGO) is with significantly higher bactericidal activity against Escherichia coli. The mechanism of the increased antibacterial activity of prGO is due to that plasma processing breaks down the GO sheets into smaller layers with more rough surface defects, which can thus induce more destructive membrane damages to the bacteria. This work sets another good example, showing that plasma processing is a gre...

We report direct growth of 1550-nm InGaAsP multi-quantum-well (MQW) structures in densely packed, smooth, highly crystalline, and millimeter-long InP nanoridges grown by metalorganic chemical vapor deposition on silicon-on-insulator (SOI) substrates. Aspect-ratio-trapping and selective area growth techniques were combined with a two-step growth process to obtain good material quality as revealed by photoluminescence, scanning electronic microscopy, and high-resolution X-ray diffraction characterization. Transmission electron microscopy images revealed sharp MQW/InP interfaces as well as thickness variation of the MQW layer. This was confirmed by atom probe tomography analysis, which also suggests homogenous incorporation of the various III-V elements of the MQW structure. This approach is suitable for the integration of InP-based nanoridges in the SOI platform for new classes of ultra-compact, low-power, nano-electronic, and photonic devices for future tele- and data-communications applications.

In our study, an elevated-temperature depth-sensing instrumented indentation apparatus was designed and developed to investigate thermo-mechanical response of thermal barrier coatings (TBCs). A furnace was used to heat the test region up to 1600 °C and a heat protection design was proposed to protect electronic devices from high temperature environment. Load was applied by a precise loading motor and a piezoelectric actuator in high (0-440 N) and low (0-40 N) load ranges, respectively. A loading shielding scheme was designed to protect the low load sensor during the high loading process. In order to obtain reliable test data, the as-developed apparatus was calibrated at room and elevated temperatures. It is found that the developed apparatus was suitable to obtain the intended data. After that, two typical TBCs were tested from 600 to 1500 °C, and the load-depth curves were presented to show the main functions and usability of the measuring system.

Because the out circumferential lamellae have a special protective effect on the cortical bone, it is very important to understand the variations of the mechanical property of the out circumferential lamellae in cortical bone. For the purpose, the elasticity modulus and hardness of out circumferential lamellae in cortical bone were investigated in two orthogonal planes by nanoindentation, and the comparisons were made for both elasticity modulus and hardness between the two orthogonal planes. From the experiments, the decreasing trend was discovered for elasticity modulus from inside to outside in the transverse plane and ruleless variations tendency was presented in the longitudinal plane. The hardness presented the same variations in two orthogonal planes with elasticity modulus in respective plane. In the same layer, the elasticity modulus in the transverse plane was higher than that in the longitudinal plane, and the difference values between them turned to be smaller. In contrast, the hardness in the longitudinal plane was higher than that in the transverse plane in all the layers. From the heterogeneity and the microstructure of the material, the influence factors were discussed. A soft to hard structure model was put forward, and the coordinating protection mechanism of buffer and support was described. Investigation of variations of mechanical properties of out circumferential lamellae in cortical bone can provide some new understanding in researches of fracture of bone, interface load effect and design of bone graft.

The smooth impact drive mechanism (SIDM) actuator is traditionally excited by a saw-tooth wave, but it requires large input voltages for high-speed operation and load capacity. To improve the output characteristic of the SIDM operating at low input voltage, a novel driving method based on ultrasonic friction reduction technology is proposed in this paper. A micro-amplitude sinusoidal signal with high frequency is applied to the rapid deformation stage of the traditional saw-tooth wave. The proposed driving method can be realized by a composite waveform that includes a driving wave (D-wave) and a friction regulation wave (FR-wave). The driving principle enables lower input voltage to be used in normal operation, and the principle of the proposed driving method is analyzed. A prototype of the SIDM is fabricated, and its experimental system is established. The tested results indicate that the actuator has suitable velocity and load characteristics while operating at lower input voltage, and the load capacity of the actuator is 2.4 times that of an actuator excited by a traditional saw-tooth driving wave.

The water confined in nanotubes has been extensively studied, because of the potential usages in drug delivery and desalination. The radial distribution of the dielectric constant parallel along the nanotube axis was obtained by molecular dynamics simulations in a carbon nanotube and a nanotube with a very small van der Waals potential. The confined water was divided into two parts, the middle part water and the hydration water. In both cases, the hydrogen bond orientation of the middle water is isotropic, while the hydrogen bonds in hydration layers are apt to parallel along the nanotube axis. Therefore, the hydration water has higher dipole correlations increasing the dielectric constant along the nanotube axis.

The microdefects of structure frequently act as the source to generate initial cracks and lead to the fracture failure. Study on the deformation behaviors of embedded defects would be conducive to better understand the failure mechanisms of structural materials. Micro-indentation technique was applied to prepare the initial indentations as embedded surface defects at the gauge length section and central section of a cross-shaped AZ31B magnesium alloy specimen. A novel in situ biaxial tensile device was developed to apply the synchronous biaxial loads. Via the observation by an optical microscope with three-dimensional imaging and measurement functions, the changing laws of the indentation topographies under uniaxial and biaxial tensile loads were discussed. Compared with the gauge length section, the increasing trend of the indentation length of the central section was relatively flat, and the decreasing trend of the indentation depth was more significant. The changes of indentation topographies were explained by the Poisson effect, and the significant plastic tensile stress has led to the releasing of the residual stress around the indentation location and also promoted the planarization of the pileup.

A teeter-totter effect of terahertz (THz) resonant modes in C-shaped complementary split-ring resonators (CSRRs) is observed. The dual resonant mode transmission enhancement was investigated using THz time-domain spectroscopy. The intensity of the lower-frequency resonance modes increases monotonically with the CSSR gap width, which is accompanied by a monotonic decrease in the intensity of the higher-frequency resonance modes. The origin of the dual resonant modes is numerically explained by the electromagnetic energy density distribution and surface current analysis. The inductive-capacitive resonance dominates the lower frequency mode, while the dipole oscillation dominates the higher frequency mode. By tuning the gap of the CSRR, an equilibrant transmittance of above dual resonance modes can be designed. This teeter-totter effect promises a possible application of CSSRs as potential dual-bandpass filters in the THz-region.

A series of simulations of chemical mechanical polishing (CMP) were conducted to investigate the contact force between abrasive particles and specimens by using the finite element method (FEM). In this paper, a micro-contact model, which only involves the mechanical interactions, was set up to simulate the polishing process by changing the processing parameters, including the downward pressure, abrasive size, and polishing speed. Simulation results show that the contact force becomes larger when the downward pressure increases. In addition, when the downward pressure and abrasive size increase, the fluctuation of the contact force becomes large, whereas it declines with decreases in the polishing speed. In addition, corresponding CMP experiments were done to investigate the material removal rate (MRR) and polished average roughness (Ra) under different simulation conditions. Through the establishment of the contact force properties in the simulation and the MRR and Ra in the CMP experiment, qualitative research has been done on the relationship between the contact force in the simulation and experimental results. Experimental results indicate that the MRR and surface roughness are influenced by the contact force. A high MRR can be obtained by a large contact force and dramatic fluctuations can lead to poor surface-finish quality. The investigation contributes to obtaining higher polishing efficiency and lower surface roughness through optimization of the polishing parameters.

A dual-servo nanopositioning stage for high-accuracy rotary motion is presented in this article. A piezoelectric actuator is employed to achieve both the coarse motion and fine motion. By the coarse motion and fine motion, the designed dual-servo nanopositioning stage can obtain large-range rotary motion and high resolution simultaneously. The configuration and motion principle of the dual-servo nanopositioning stage were illustrated and discussed. A prototype was fabricated to test the working performance and the results demonstrate that the maximum speed of the presented dual-servo nanopositioning stage is 32,000 μrad/s and the rotary resolution is about 1.54 μrad. The working performance confirms the feasibility of the dual-servo nanopositioning stage.

Electromagnetic materials have been widely employed in micro-functional devices. Using multi-field nanoindentation technique, we have investigated the local deformation behavior of various electromagnetic materials in the form of bulk materials, foils, and thin films under electric or magnetic field. Based on dimensional analysis and experimental data, a field tunable scaling relationship among hardness, reduced contact elastic modulus, and indentation work has been found. Furthermore, a method to determine the hardness and reduced modulus of electromagnetic materials is proposed, which avoids the error from estimating the indentation contact area. This work is meaningful for the characterization of mechanical properties and design of devices made of electromagnetic materials.

This paper reports a spaser based on Fano resonance of a plasmonic nanostructure consisting of a rod and concentric square ring-disk structure coated with a layer of gain media. The amplification of the dark quadrupolar mode at the Fano resonance wavelength causes the spaser with a high Purcell factor of 3.24 × 107, a high signal to noise ratio of 4.4 × 106, and a lower threshold of 0.02086. These significant optical properties are attributed to the greatly enhanced spontaneous emission and depressed radiation loss supported by the strong localized dark mode at the Fano resonance wavelength.

As one of the candidate ion sources for a planned project, the High Intensity heavy-ion Accelerator Facility, a laser ion source has been being intensively studied at the Institute of Modern Physics in the past two years. The charge state distributions of ions produced by irradiating a pulsed 3 J/8 ns Nd:YAG laser on solid targets of a wide range of elements (C, Al, Ti, Ni, Ag, Ta, and Pb) were measured with an electrostatic ion analyzer spectrometer, which indicates that highly charged ions could be generated from low-to-medium mass elements with the present laser system, while the charge state distributions for high mass elements were relatively low. The shot-to-shot stability of ion pulses was monitored with a Faraday cup for carbon target. The fluctuations within ±2.5% for the peak current and total charge and ±6% for pulse duration were demonstrated with the present setup of the laser ion source, the suppression of which is still possible.

Understanding the behaviors of the material removal mechanism of ultra-precision polishing process has been a critical issue of generating well-formed surface. In order to make clear the abrasive self-rotation effects on material removal at the atomic level, a three-dimensional molecular dynamics (MD) model is conducted to study the mechanics of ultra-precision polishing on single-crystal copper with a diamond abrasive and the effects of abrasive self-rotation velocity and direction. Morse potential energy function and EAM potential energy function are applied to model the copper/diamond and copper/copper interactions, respectively. The simulation results show that the deformation mechanism of single-crystal copper is due to the formation and movement of dislocations in the specimen. In addition, with the increasing of abrasive self-rotation velocity, the deformation mechanism falls from cutting to plowing regimes. The abrasive self-rotation velocity and direction have effects on the morphology and quality of the specimen surface, distribution and evolution of defects under the surface of the specimen. Also, the interatomic force between abrasive and specimen is studied to account for the effects of different polishing conditions.

Effect of gas puffing from electron-side and ion-side on lower hybrid wave (LHW)-plasma is investigated in experimental advanced superconductive tokamak for the first time. Experimental results with different gas flow rates show that electron density at the grill is higher in the case of gas puffing from electron-side; consequently, a lower reflection coefficient is observed, suggesting better effect of puffing from electron-side on LHW-plasma. The difference in edge density between electron- and ion-side cases suggests that local ionization of puffed gas plays a dominant role in affecting the density at the grill due to different movement direction of ionized electrons and that part of gas has been locally ionized near the gas pipe before diffusing into the grill region. Such difference could be enlarged and important in ITER due to the improvement of plasma parameters and LHW power.

This paper presents a novel piezo-driven rotary actuator based on the parasitic motion principle. Output performances of the rotary actuator were tested and discussed. Experiment results indicate that using only one piezoelectric actuator and simple sawtooth wave control, the rotary actuator reaches the rotation velocity of about 20,097 μrad/s when the driving voltage is 100 V and the driving frequency is 90 Hz. The actuator can rotate stably with the minimum resolution of 0.7 μrad. This paper verifies feasibility of the parasitic motion principle for applications of rotary actuators, providing new design ideas for precision piezoelectric rotary actuators.

In this paper, friction between the Cube-Corner indenter and the sample surface of a Zr-based bulk metallic glass (BMG) was analyzed and discussed by the experimental method, the theoretical method and the finite element simulation. Linear residua are observed on the surface of the indenter for the first time, which gives the direct evidence that strong interaction processes exist between the indenter surface and the sample surface because of strong friction and local high contact press. A simplified model was developed to correct the penetration load with the consideration of friction. Effects of friction on the penetration load-depth curves, plastic flow, surface deformation and residual stress distribution of the sample with different friction coefficients were investigated by the finite element simulation.

A three-dimensional molecular dynamics (MD) simulation is conducted to investigate the material removal mechanism of monocrystalline silicon by mechanical polishing at atomistic scale with diamond abrasives. By monitoring relative positions of atoms in the monocrystalline silicon specimen, the microstructure transformation of monocrystalline silicon is clearly identified and analyzed. The phase transformation is accomplished under extreme conditions with high temperature and huge hydrostatic pressure, and as a result the silicon microstructure transforms from the four-coordinated diamond cubic structure (Si-I) to the six-coordinated body-centered tetragonal structure (β-silicon). The values of local pressure and temperature are consistent with previous experimental results. In addition, the force between the diamond abrasive and specimen indicates the occurrence of phase transformation in the specimen. The potential energy of each atom is also calculated, which provides us an effective approach to analyze the energy variation of atoms in the mechanism of material deformation and the formation of machined surface after ultra-precision polishing.

In situ nanomechanical tests provide a unique insight into mechanical behaviors of materials, such as fracture onset and crack propagation, shear band formation and so on. This paper presents a novel in situ nanoindentation device with dimensions of 103mm×74mm×60mm. Integrating the stepper motor, the piezoelectric actuator and the flexure hinge, the device can realize coarse adjustment of the specimen and precision loading and unloading of the indenter automatically. A novel indenter holder was designed to guarantee that the indenter penetrates into and withdraws from the specimen surface vertically. Closed-loop control of the indentation process was established to solve the problem of nonlinearity of the piezoelectric actuator and to enrich the loading modes. The in situ indentation test of Indium Phosphide (InP) inside the scanning electron microscope (SEM) was carried out and the experimental result indicates the feasibility of the developed device.

Terahertz waves, electromagnetic radiation in the spectral region commonly defined between 0.3 and 10THz, allow innovative sensing and imaging techniques that can provide spectroscopic information unavailable at other wavelengths. However, simultaneously intense, broadband, and coherent spectroscopic measurement remains challenging. We report spectrometry using gases ionized by femtosecond pulses to generate and sense broadband terahertz pulses. Using a coherent heterodyne technique, the measurements span the “terahertz gap” with ⩾10% of the maximum signal from 0.3to10THz. This spectrometer, using a recycled optical probe beam and coherent detection, offers a high field strength and time-resolved measurement.

We present the design and performance of an active mechanical noise cancellation scanning tunneling microscope (STM). This system features two key parts: a "twin-tip" scanner and an active mechanical noise cancellation algorithm. The twin-tip scanner functions as two independent STMs which share nearly the same mechanical transfer function, allowing both STMs to sense nearly identical background mechanical noise. Based on an adaptive digital signal processing technique, the active mechanical noise cancellation algorithm applies the noise sensed by the first STM to concurrently cancel the noise in the second STM and hence allows the second STM to acquire spectroscopy with a significantly improved signal to noise ratio. This system demonstrates long-term stability of the tip-sample tunnel junction and improved spectroscopy measurement in a mechanically noisy environment.

This article reviews the development of ion sources for materials processing and the progress of commercial product of ion sources in China. The various ion-beam processing and the relative needs to ion sources are mentioned and discussed, such as ion sources with ion implantation, plasma immersion ion implantation, ion-beam-assisted deposition, ion-beam deposition, and so on. The states of progress for different kinds of ion sources specially for electron cyclotron resonance∕microwave, metal vapor vacuum arc, radio frequency (rf) ion source, end-Hall ion source, and cluster ion source, are given and discussed.

To study the injection of additional electrons from an external electron gun into the plasma of a Penning ionization gauge (PIG) ion source, a test bench for the external electron-beam enhancement of the PIG (E-PIG) ion source was set up. A source magnet assembly was built to satisfy the request for magnetic field configuration of the E-PIG ion source. Numerical calculations have been done to optimize the magnetic field configuration so as to fit the primary electrons to be fed into the PIG discharge chamber along the spreading magnetic field lines. Many possible methods for improving the performance and stability of the PIG ion source have been used in the E-PIG ion source, including the use of multicrystal LaB6 cathode and optimized axial magnetic field. This article presents a detailed design of the E-PIG ion source. Substantial enhancement of ion charge state is expected to be observed which demonstrates that the E-PIG is a viable alternative to other much more costly and difficult to operate devices for the production of intense ion beams of higher charge state.