Thermal Effects and RF Power Handling of DC～5GHz MEMS Switch

A DC to 5GHz series MEMS switch is designed and fabricated for wireless communication applications,and thermal effect and power handling of the series switch are discussed.The switch is made on glass substrate,and gold platinum contact is used to get a stable and little insert loss.From DC to 5GHz,0 6dB insertion loss,30dB isolation,and 30μs delay are demonstrated.Thermal effect of the switch is tested in 85℃ and -55℃ atmosphere separately.From DC to 4GHz,the insert loss of the switch increases 0 2dB in 85℃ and 0 4dB in -55℃,while the isolation holds the same value as that in room temperature.To measure the power handling capability of the switch,we applied a continuous RF power increasing from 10dBm to 35 1dBm with the step of 1 0dBm across the switch at 4GHz.The switch keeps working and shows a decrease of the insert loss for 0 1～0 6dB.The maximum continuous power handling (35 1dBm,about 3 24W) is higer than the reported value of shunt switch (about 420mW),which implies series switches have much better power handling capability.

A Study on the Static Characteristics of Typical Composite High Speed On-Off Valves

Natural properties of high speed on-off valves can be described through their on-off behavior and spool movement (static and oscillating) characteristics. High speed on-off valves can be combined with actuators in systems into four typical types of composite valves whose static characteristics are related not only to the structures of the single valves and the composite ones, but also to the PWM control modes. It is proved that the composite valves have similar features as those of servo valves. The nonlinear specific properties of single valves composited can be completely compensated by the suitable PWM control modes.

化工

日本合成可“开关”的荧光蛋白质，生物配方柴油技术研制成功。

Structure optimization and flow field simulation of plate type high speed on-off valve

There is a relatively complex flow state inside the high speed on-off valve,which often produces low pressure area and oil reflux in the high-speed opening and closing process of the spool,causing cavitation and vortex and other phenomena.These phenomena will affect the stability of the internal flow field of the plate valve and the flow characteristics of the high speed on-off valve.Aiming at the problems of small flow rate and instability of internal flow field,a new spool structure was designed.The flow field models of two-hole and three-hole plate spools with different openings were established,and software ANSYS Workbench was chosen to mesh the model.The standard k−εturbulence model was selected for numerical simulation using FLUENT software.The pressure distribution and velocity distribution under the same pressure and different opening degree were obtained.The structure and parameters of the optimization model were also obtained.The stability analysis of flow field under different pressure was carried out.The results demonstrate that the three-hole spool has a similar flow field change with the two-hole spool,but it does not create a low pressure zone,and the three-hole spool can work stably at 2 MPa or less.This method improves the appearance of low pressure area and oil backflow in the process of high speed opening and closing of spool.The stability of flow field and the flow rate of high speed switch valve are improved.Finally,the products designed in this paper are compared with existing hydraulic valve products.The results show that the three-hole plate type high speed on-off valve designed in this paper maintains the stability of the internal flow field under the condition of 200 Hz and large opening degree,and realizes the increase of flow rate.

Enhancing Reliability via Checkpointing in Cloud Computing Systems

Cloud computing is becoming an important solution for providing scalable computing resources via Internet. Because there are tens of thousands of nodes in data center, the probability of server failures is nontrivial. Therefore, it is a critical challenge to guarantee the service reliability. Fault-tolerance strategies, such as checkpoint, are commonly employed. Because of the failure of the edge switches, the checkpoint image may become inaccessible. Therefore, current checkpoint-based fault tolerance method cannot achieve the best effect. In this paper, we propose an optimal checkpoint method with edge switch failure-aware. The edge switch failure-aware checkpoint method includes two algorithms. The first algorithm employs the data center topology and communication characteristic for checkpoint image storage server selection. The second algorithm employs the checkpoint image storage characteristic as well as the data center topology to select the recovery server. Simulation experiments are performed to demonstrate the effectiveness of the proposed method.

Current Limiting Characteristic Analysis of Magnetic-controlled Switcher Type Fault Current Limiter

A novel magnetic-controlled switcher type fault current limiter (FCL) based on the topology of the saturated iron core high temperature superconducting FCL is proposed. The magnetic field distribution of the FCL iron core is analyzed by FEA software ANSYS. The current limiting characteristic is investigated by both 3-D field-circuit coupled simulation and Matlab. The experiments on the 220 V/50 A test model show that the FCL can limit the fault current swiftly and effectively,and the FCL has the advantages of simple and reliable structure, flexible control strategy. The simulation and experimental results prove that the theoretical expectation and current limiting performance is satisfactory for practical use.

Research on the Influence Factors and Struction of University Teachers Leader-Member Exchange

The leader - member exchange theory is one of the leading and the hot topic in recent years of the study of Western leaders. Structural studies of LMX factors have important theoretical and practical value in college teachers. In this paper, the ＂impact factor structure of university teachers LMX Questionnaire＂ for four universities 808 subjects was investigated. By exploratory factor analysis and confirmatory factor analysis, it found that the structure of university teachers LMX factors includes five dimensions： values, attitudes up, personality characteristics, switching behavior, objective situations. The questionnaire has good reliability and validity.

Hf_(0.5)Zr_(0.5)O_(2)-based ferroelectric memristor with multilevel storage potential and artificial synaptic plasticity

Memristors are designed to mimic the brain’s integrated functions of storage and computing,thus breaking through the von Neumann framework.However,the formation and breaking of the conductive filament inside a conventional memristor is unstable,which makes it difficult to realistically mimic the function of a biological synapse.This problem has become a main factor that hinders memristor applications.The ferroelectric memristor overcomes the shortcomings of the traditional memristor because its resistance variation depends on the polarization direction of the ferroelectric thin film.In this work,an Au/Hf0.5Zr0.5O2/p+-Si ferroelectric memristor is proposed,which is capable of achieving resistive switching characteristics.In particular,the proposed device realizes the stable characteristics of multilevel storage,which possesses the potential to be applied to multi-level storage.Through polarization,the resistance of the proposed memristor can be gradually modulated by flipping the ferroelectric domains.Additionally,a plurality of resistance states can be obtained in bidirectional continuous reversibility,which is similar to the changes in synaptic weights.Furthermore,the proposed memristor is able to successfully mimic biological synaptic functions such as long-term depression,long-term potentiation,paired-pulse facilitation,and spike-timing-dependent plasticity.Consequently,it constitutes a promising candidate for a breakthrough in the von Neumann framework.

Subthermionic field-effect transistors with sub-5 nm gate lengths based on van der Waals ferroelectric heterostructures

Overcoming the sub-5 nm gate length limit and decreasing the power dissipation are two main objects in the electronics research field. Besides advanced engineering techniques, considering new material systems may be helpful. Here, we demonstrate two-dimensional(2D) subthermionic field-effect transistors(FETs) with sub-5 nm gate lengths based on ferroelectric(FE) van der Waals heterostructures(vdWHs).The FE vd WHs are composed of graphene, MoS2, and CuInP2S6 acting as 2D contacts, channels, and ferroelectric dielectric layers, respectively. We first show that the as-fabricated long-channel device exhibits nearly hysteresis-free subthermionic switching over three orders of magnitude of drain current at room temperature. Further, we fabricate short-channel subthermionic FETs using metallic carbon nanotubes as effective gate terminals. A typical device shows subthermionic switching over five-to-six orders of magnitude of drain current with a minimum subthreshold swing of 6.1 mV/dec at room temperature. Our results indicate that 2D materials system is promising for advanced highly-integrated energy-efficient electronic devices.

Conductive metallic filaments dominate in hybrid perovskite-based memory devices

Organic-inorganic hybrid perovskites (OHPs) are well-known as light-absorbing materials in solar cells and have recently attracted considerable attention for the applications in resistive switching memory. Previous studies have shown that ions can migrate to form a conductive channel in perovskites under an external voltage. However, the exact resistance mechanism for Ag or halogens which dominate the resistive behavior is still controversial. Here, we demonstrate a resistive switching memory device based on Ag/FA0.83MA0.17Pb(I0.82Br0.18)3/fluorine doped tin oxide (FTO). The migration of Ag cations and halide anions is demonstrated by energy dispersive X-ray spectroscopy (EDS) after the SET process (positive voltage on Ag). By comparing the I-V behavior of the Au-based devices, it is clear that the conductive channel formed by Ag is the main factor of the switching characteristics for Ag-based devices. Meanwhile, by controlling the appropriate SET voltage, two kinds of resistance characteristics of the analog switch and threshold switch can be realized in the Ag-based device. As a result, it may be possible to implement both data storage and neuromorphic computing in a single device.

Van der Waals contact between 2D magnetic VSe_(2)and transition metals and demonstration of high-performance spin-field-effect transistors

This study used density functional theory and the quantum transport method to investigate the interfacial coupling and spin transport of transition metals(TMs)with a Fe,Co,and Ni/2H-VSe_(2)hybrid nanostructure.Because the indirect coupling of TM-Se-V led to an obvious reduction of the magnetic moment and the disappearance of the half-metal characteristics of 2H-VSe_(2),the expected spin-filtering effect of individual TMs and 2H-VSe_(2)deteriorated at the contact region.Nevertheless,all the TM/2H-VSe_(2)-based dual-probe devices exhibited an interesting bias-dependent spin-injection efficiency with a maximum output spin-polarized current of 666 mA mm-1 in Co/2H-VSe_(2).The proposed TM/2H-VSe_(2)-based spin-field-effect transistor demonstrated outstanding performance.The Ni/2H-VSe_(2)-based transistor achieved a maximum output spin-polarized current of 3117 m A mm-1 and demonstrated a good switching characteristic of 106 mV dec-1.Importantly,all transistors achieved a widely tunable scale of spin-extraction efficiency ranging consistently between 96%and-92%with gate bias.These results indicate a promising candidate for use in high-performance spintronic devices.

Resistive-switching tunability with size-dependent all-inorganic zero-dimensional tetrahedrite quantum dots

All-inorganic zero-dimensional(0D)tetrahedrite(Cu12Sb4S13,CAS)quantum dots(QDs)have attracted extensive attention due to their excellent optical properties,bandgap tunability,and carrier mobility.In this paper,various sized CAS QDs(5.1,6.7,and 7.9 nm)are applied as a switching layer with the structure F:Sn O2(FTO)/CAS QDs/Au,and in doing so,the nonvolatile resistive-switching behavior of electronics based on CAS QDs is reported.The SET/RESET voltage tunability with size dependency is observed for memory devices based on CAS QDs for the first time.Results suggest that differently sized CAS QDs result in different band structures and the regulation of the SET/RESET voltage occurs simply and effectively due to the uniform size of the CAS QDs.Moreover,the presented memory devices have reliable bipolar resistive-switching properties,a resistance(ON/OFF)ratio larger than 104,high reproducibility,and good data retention ability.After 1.4×10^6s of stability testing and 104cycles of quick read tests,the change rate of the ON/OFF ratio is smaller than 0.1%.Furthermore,resistiveswitching stability can be improved by ensuring a uniform particle size for the CAS QDs.The theoretical calculations suggest that the space-charge-limited currents(SCLCs),which are functioned by Cu 3d,Cu 3p and S 3p to act as electron selftrapping centers due to their quantum confinement and form conduction pathways under an electric field,are responsible for the resistive-switching effect.This paper demonstrates that CAS QDs are promising as a novel resistive-switching material in memory devices and can be used to facilitate the application of next-generation nonvolatile memory.

Bias Current Influence on the Characteristic of the Magnetic-controlled Switcher Type Fault Current Limiter

A novel magnetic-controlled switcher type fault current limiter （FCL） for high voltage electric network is presented. The current limiting principle of the FCL and the bias current influence on the characteristic of the FCL axe discussed. The experiments on the 220 V/50 A test model show that the FCL can limit the fault current swiftly and effectively. Under the normal state, the bias current adjustment can change the FCL voltage loss; under the fault state, the steady fault current can be easily adjusted to the preset level by bias current regulating. The experimental result is in accordance with the principle analysis and the FCL has the advantages of flexible control strategy and simple and reliable structure.

Reversible optical control of the metal-insulator transition across the epitaxial heterointerface of a VO_(2)/Nb:TiO_(2) junction

Optical control of exotic properties in strongly correlated electron materials is very attractive owing to their potential applications in optical and electronic devices.Herein,we demonstrate a vertical heterojunction made of a correlated electron oxide thin film VO_(2) and a conductive 0.05 wt% Nb-doped TiO_(2) single crystal,whose metal-insulator transition(MIT)across the nanoscale heterointerface can be efficiently modulated by visible light irradiation.The magnitude of the MIT decreases from ~350 in the dark state to ~7 in the illuminated state,obeying a power law with respect to the light power density.The junction resistance is switched in a reversible and synchronous manner by turning light on and off.The optical tunability of it is also exponentially proportional to the light power density,and a 320-fold on/off ratio is achieved with an irradiance of 65.6 mW cm^(-2) below the MIT temperature.While the VO_(2) thin film is metallic above the MIT temperature,the optical tunability is remarkably weakened,with a one-fold change remaining under light illumination.These results are co-attributed to a net reduction(~15 meV)in the apparent barrier height and the photocarrier-injection-induced metallization of the VO_(2) heterointerface through a photovoltaic effect,which is induced by deep defect level transition upon the visible light irradiance at low temperature.Additionally,the optical tunability is minimal,resulting from the quite weak modulation of the already metallic band structure in the Schottky-type junction above the MIT temperature.This work enables a remotely optical scheme to manipulate the MIT,implying potential uncooled photodetection and photoswitch applications.

A nonlinear optical loop mirror-based linear cavity switchable multi-wavelength erbium-doped fiber laser

A nonlinear optical loop mirror(NOLM)-based linear cavity switchable multi-wavelength erbium-doped fiber(EDF) laser is proposed and experimentally demonstrated.Due to the characteristics of the intensity-dependent transmissivity,the NOLM can effectively mitigate the mode competition of the homogenous broadening gain medium,so that the multi-wavelength lasing can be achieved at room temperature.By adjusting the states of the polarization controllers(PCs),the number of the lasing wavelengths in the proposed laser can be adjusted flexibly from 11 to 13 with a wavelength spacing of 0.4 nm around the wavelength of 1 530 nm.