Fabrication and field emission performance of arrays of vacuum microdiodes containing CuO nanowire emitters grown directly on glass without a catalyst

Arrays of vacuum microelectronic sources are fabricated on a glass substrate using cupric oxide (CuO) nanowire emitters. The arrays of electron sources possess a microdiode structure, which can effectively induce field emission and control the delivery of emitted electrons to the anode in a triode-type device operation. A technique for precisely growing CuO nanowires at the centre of microcavities in an array without using a catalyst and at temperatures as low as 400°C is presented. Such a simplified fabrication procedure results in improved field emission performance from the array compared with previous vacuum microelectronic devices. Typical prototype devices have turn-on gate voltages as low as 169 V to give emission current densities of 10 μA/cm2 at the anode. The ratio of anode current to cathode current reaches ~0.85, and the maximum change in emission current density per volt is 1 μA/cm2. Electron emission from the arrays is stable and reproducible under either pulsed or direct current fields. These characteristics indicate that microgate-controlled CuO nanowire emitters may find application in practical devices.     

Applications of MEMS devices in nanosatellite

micro-electro-mechanical system(MEMS) device has the advantages of both electronic system and mechanical system.With the development of MEMS devices for satellite,it is possible to establish much lighter and smaller nanosatellites with higher performance and longer lifecycle.The power consumption of MEMS devices is usually much lower than that of traditional devices,which will greatly reduce the consumption of power.For its small size and simple architecture,MEMS devices can be easily integrated together and achieve redundancy.Launched on April 18,2004,NS-1 is a nanosatellite for science exploration and MEMS devices test.A mass of science data and images were acquired during its running.NS-1 weights less than 25 kg.It consists of several MEMS devices,including one miniature inertial measurement unit(MIMU),three micro complementary metal oxide semiconductor(CMOS)cameras,one sun sensor,three momentum wheels,and one micro magnetic sensor.By applying micro components based on MEMS technology,NS-1 has made success in the experiments of integrative design,manufacture,and MEMS devices integration.In this paper,some MEMS devices for nanosatellite and picosatellite are introduced,which have been tested on NS-1 nanosatellite or on the ground.     

Probabilistic Delay Fault Model for DVFS Circuits

Decreasing the power supply voltage in dynamic voltage frequency scaling to save power consumption may introduce extra delays in CMOS circuits, which may cause errors. This paper presents the probabilistic delay fault model (PDFM), which describes the probability of an error occurring as a function of the power supply voltage and the clock period in synchronous CMOS circuits. In a wide range of applications (graphic, video, digital filtering, etc.), errors occurring with low probability and not remaining for a long time are acceptable. For combinational circuits which have long critical paths with low probability of excitation, a performance increase is achieved with a certain rate of errors determined by the PDFM compared with the traditional design which considers the worst case. The PDFM applied to array multipliers and ripple carry adders shows the agreement of the predicted probabilities with simulated delay histograms to support the practicality of using the PDFM to select power supply voltage and clock period in dynamic voltage frequency scaling circuits with tolerable error rates.     

Enhancement of magnetoelectric properties in a surface-mount magnetoelectric device

The fabrication and properties of a novel double layered surface-mount magnetoelectric(ME) device are investigated and reported. This ME device is made up of two opposite polarized piezoelectric PZT slices bonded on the same side of a magnetostrictive material Metglas, forming a novel two PZT in-series device. ME voltage obtained from the two PZT in-series is obviously higher than that of single PZT in a magnetic field with certain value. The ME voltage coefficient(αV) of the surface-mount ME device is significantly enhanced by adjusting the thickness of Metglas: 1) At a frequency of 1 k Hz, αV of this device increases with the layer number of Metglas increased, and the maximum value of αV is about 4.25 times than the minimum; 2) At a frequency of 5 k Hz, the maximum value of αV is 458 mV /Oe, which derives from the ME device with three layers Metglas. This novel design provides an effective way to manufacture miniature and high sensitive ME devices, which makes it possible to apply ME device into integrated circuit(IC).     

A Novel Design of Power management integrated circuit with 90 plus efficiency used in AC/DC converter

Recently, resonant AC/DC converter has been accepted by the industry. However, the efficiency will be decreased at light load. So, a novel topology with critical controlling mode combined with resonant ones is proposed in this paper. The new topology can correspond to a 90 plus percent of power converting. So，a novel topology of an state of art integrated circuit, which can be used as power management circuit, has been designed based on the above new topology. A simulator which is specifically suitable for the power controller has been founded in this work and it has been used for the simulation of the novel architecture and the proposed integrated circuit.     

Interface Electric Field Confinement Effect of High-Sensitivity Lateral Ge/Si Avalanche Photodiodes

A novel lateral Ge/Si avalanche photodiode without a charge region is investigated herein using device physical simulation. High field is provided by the band-gap barrier and build-in field at the Ge/Si interface in the vertical direction. Modulating the Si mesa thickness(0-0.4 μm) and impurity concentration of the intrinsic Si substrate(1×10~(16)-4×10~(16)cm~(-3)) strengthens the electric field confinement in the substrate region and provides a high avalanche multiplication in the Si region. When the Si mesa thickness is 0.3 μm, and the impurity concentration of the Si substrate is 2×10~(16) cm~(-3), the Lateral Avalanche PhotoDiode(LAPD) exhibits a peak gain of 246 under 1.55 μm incident light power of -22.2 dBm, which increases with decreasing light intensity.     

Low-Voltage Transconductor with Wide Input Range and Large Tuning Capability

A CMOS triode transconductor was developed with common mode feedback suitable for operating in low-voltage and low-power applications.The design is based on a body-driven input stage with feedback loops to extend both the signal input range and the tuning capability.The effective transconductance of the body-driven triode stage is increased using a partial positive feedback technique which also partially solves the problem introduced by the small transconductance.This design uses the UMC 0.18 μm CMOS process.Simulations show the transconductor operated with 1 V supply voltage has less than 55 dB total harmonic distortions (THD) in the complete tuning range (0 V≤Vcont≤0.43V) for a 1 MHz 0.8 Vp-p differential input.The power consumption is 70 μW for a 0.43 V control voltage.     

Low Latency High Throughout Circular Asynchronous FIFO

This paper describes a circular first in first out （FIFO） and its protocols which have a very low latency while still maintaining high throughput. Unlike the existing serial FIFOs based on asynchronous micropipelines, this FIFO＇s cells communicate directly with the input and output ports through a common bus, which effectively eliminates the data movement from the input port to the output port, thereby reducing the latency and the power consumption. Furthermore, the latency does not increase with the number of FIFO stages. Single-track asynchronous protocols are used to simplify the FIFO controller design, with only three C-gates needed in each cell controller, which substantially reduces the area. Simulations with the TSMC 0.25 μm CMOS logic process show that the latency of the 4-stage FIFO is less than 581 ps and the throughput is higher than 2.2 GHz.     

A novel portable transmitter with 8dBm output power for wireless communication equipments

In this paper,a portable 2.42 GHz transmitter for wireless communication systems,with 8dBm output power and small size is proposed.Several novel features exist in this transmitter.First,power consumption and output are balanced by introducing a differential oscillator with input signal controlled biasing,which acts as both a carrier generator and an OOK modulator.Then,power consumption of the transmitter is reduced by the OOK modulated signal via switching the oscillator and the power amplifier at the same time.Furthermore,the area size is also reduced by a class-AB power amplifier,which uses the PCB antenna as the resonance inductance.With these features,the total chip area is reduced to 670μm×740μm(In a 0.18μm CMOS process).     

Novel high PSRR current reference based on subthreshold MOSFETs

This paper takes full advantages of the I-V transconductance characteristics of metal-oxide semiconductor field effect transistor （MOSFET） operating in the subthreshold region and the enhancement pre-regulator technique with the high gain negative feedback loop. The proposed reference circuit, designed with the SMIC 0.18 μm standard complementary metal-oxide semiconductor （CMOS） logic process technology, exhibits a stable current of about 1.701 μA with much low temperature coefficient （TC） of 2.5×10^-4μA/℃ in the temperature range of-40 to 150℃ at 1.5 V supply voltage, and also achieves a best PSRR over a broad frequency. The PSRR is about - 126 dB at DC frequency and remains -92 dB at the frequency higher 100 MHz. Moreover the proposed reference circuit operates stably at the supply voltage higher 1.2 V and has good process compatibility.     

Selectable infiltrating large hollow core photonic band-gap fiber

A selectable infiltrating large hollow core photonic band-gap fiber is fabricated with simple arc discharge technique. The offset, discharge duration, arc current and discharge times are optimized for selected sealing side air-holes but leave the central large air-hole partially open. The collapse length of the PCF is shortened by increasing the number of discharges and offset with discharge duration and arc current kept at a relatively low level. Light with the wavelength located at the photonic band-gap can still propagate while the central hollow air-hole is infiltrated with a kind of oil with refractive index of 1.30. The selectable infiltrating large hollow core photonic band-gap fiber has potential application for implementing novel lasers, sensors and tunable optoelectronic devices.     

An adaptive push-styled command and control mechanism in mobile botnets

The mobile botnet, developed from the traditional PC-based botnets, has become a practical underlying trend. In this paper, we design a mobile botnet, which exploits a novel command and control (C&C) strategy named Push-Styled C&C. It utilizes Google cloud messaging (GCM) service as the botnet channel. Compared with traditional botnet, Push-Styled C&C avoids direct communications between botmasters and bots, which makes mobile botnets more stealthy and resilient. Since mobile devices users are sensitive to battery power and traffic consumption, Push- Styled botnet also applies adaptive network connection strategy to reduce traffic consumption and cost. To prove the efficacy of our design, we implemented the prototype of Push-Style C&C in Android. The experiment results show that botnet traffic can be concealed in legal GCM traffic with low traffic cost.     

Study on temperature characteristics of organic light-emitting diodes based on tris-（8-hydroxylquinoline）-aluminum

Both single-layer and double-layer organic light-emitting devices based on tris-（8-hydroxylquino- line）-aluminum （AIq3） as emitter are fabricated by thermal vacuum deposition. The electroluminescent characteristica of these devices at various temperatures are measured, and the temperature characteristics of device performance are studied. The effect of temperature on device current conduction regime is analyzed in detail. The results show that the current-voltage （I-V） characteristics of devices are in good agreement with the theoretical prediction of trapped charge limited current （TCLC）. In addition, both the charge carrier mobility and charge carrier concentration in the organic layer increase with the rise of temperature, which results in the monotonous increase of AIq3 device current. The current conduction mechanisms of two devices at different temperatures are identical, but the exponent m in current-voltage equation changes randomly with temperature. The device luminance increases slightly and the efficiency decreases monotonously due to the aging of AIq3 luminescent properties caused by high temperature. A tiny blue shift can be observed in the electroluminescent （EL） spectra as the temperature increases, and the reduction of device monochromaticity is caused by the intrinsic characteristics of organic semiconductor energy levels.     

New hybrid encapsulation for flexible organic light-emitting devices on plastic substrates

The hybrid encapsulation for flexible organic light-emitting devices on plastic substrate was investi-gated. The hybrid encapsulation consisted of four periods of AIq3/L.iF layers as the pre-encapsulation layer and a flexible aluminum foil coated with getter as the encapsulation cap. We measured the device lifetime at a continuous constant current of 20 mA/cm2, which corresponded to an initial luminance of 2000 cd/m2. The half-luminance decay time of the encapsulated device was about 458 h. More over, the hybrid encapsulation is ultrathin and flexible, ensuring device bendability.     

Study and innovation of a flexible blade turbine, a new type of tidal current generating device

Utilization of tidal current is becoming a focus of marine energy research and development field. In this paper, a new type of tidal current power generating device which called flexible blade turbine was put forward. A scale model testing was carried out, and results show that the models performed as expected with good hydrodynamic characteristics. Based on analysis of the results, a scale model turbine with a rated power of 5kW was constructed, which was an optimal scheme of the flexible blade turbine having higher coefficient of power and power generation capacity. Sea trials were carried out in the Zhaitang Island channel to evaluate the performance of the turbine. Results show that the turbine performed well, generating the power predicted. Key words: tidal current; flexible blade turbine; coefficient of power; sea trials     

Low-Power CMOS VCO with Dual-Band Local Oscillating Signal Outputs for 5/2. 5-GHz WLAN Transceivers

The paper describes a novel low-power CMOS voltage-controlled oscillator (VCO) with dual-band local oscillating (LO) signal outputs for 5/2. 5-GHz wireless local area network (WLAN) transceivers. The VCO is based on an on-chip symmetrical spiral inductor and a differential varactor. The 2. 5-GHz quadrature LO signals are generated using the injection-locked frequency divider (ILFD) technique. The ILFD structure is similar to the VCO structure with its wide tracking range. The design tool ASITIC was used to optimize all on-chip symmetrical inductors. The power consumption was kept low with differential LC tanks and the ILFD technique. The circuit was implemented in a 0.18-fim CMOS process. Hspice and SpectreRF simulations show the proposed circuit could generate low phase noise 5/2. 5-GHz dual band LO signals with a wide tuning range. The 2. 5-GHz LO signals are quadrature with almost no phase and amplitude errors. The circuit consumes less than 5. 3mW in the tuning range with a power supply voltage of 1     

Recent developments of thermoelectric power generation

One form of energy generation that is expected to be on the rise in the next several decades is thermoelectric power generation (TEPG) which converts heat directly to electricity. Compared with other methods, TEPG possesses the salient features of being compact, light-weighted,noiseless in operation, highly reliable, free of carbon dioxide emission and radioactive substances. Low current conversion efficiency and high cost, however, are some of the disadvantages. Use of TEPG is therefore justified to hightech applications associated with aerospace, military operation,tel-communication and navigation, instrumentation of unmanned vehicles monitored from remote locations. Moreover, TEPG does not contribute to the depletion of natural resource and pollution of the environment such as climate warming that has been a concern in recent times. This work is concerned with providing an overview of the state of the art of TEPG with emphases placed on assessing its current and potential application. Pointed out are the ways to fabricate high performance thermoelectric material, a hurdle to overcome for the enhancement of TEPG device efficiency.     

Progress on the Electrolytes for Dye-sensitized Solar Cells

1 Results The development of a new type of solar cell has been promoted by public concern about pollution and energy consumption.Since the prototype of a dye-sensitized solar cell (DSC) was reported in 1991 by M.Gratzel,it has aroused intensive interest over the past decade due to its low cost and simple preparation procedure.The typical cell is a sandwiched structure consisting of a dye-sensitized TiO2 electrode,a platinized counter electrode and a filled redox couple electrolyte between the electrodes.The electrolyte plays an important role in the photoelectronic performance and long-term stability for DSCs.In this review,the progress on the electrolytes in dye-sensitized solar cells is reported.A novel concept both thermoplastic and thermosetting gel electrolytes is proposed.Based on the new electrolytes,two quasi-solid-state dye-sensitized solar cells with good photovoltaic performance and long-term stability are fabricated,which are two kinds of the most available electrolytes for DSCs in practical uses and industrialization.     

Study on the bulk wave radiation of finite-length SAW devices using FEMBEM

Based on the distributions of stress and free charge on the interface of the surface acoustic wave (SAW) device calculated with the combination of boundary element method and finite element method(FEMBEM), the power of each of the three possible bulk waves radiated by the SAW device is calculated, and their contributions to the overall input conductance are separated respectively. Moreover, the formula of angular distributions of their power radiation into the substrate is derived. Consider the effect of mass loading, the resistance density，defined as a scalar, is extended to generalized resistance densities which can be written as three 4×4 tensors and for which the formulas are derived. The bulk wave radiations for a synchronous one-port resonator on 42°Y-rotated LiTaO3 are simulated. It is found that the radiated energy by slow shear wave contributes a very high proportion to input electrical energy in some frequency range.     

Research on Precision Assembly Robot''''s Joint Torque Control Based on Current Measurement

A set of new current sensing device is used to realize joint torque control based on current measurement in a precision assembly robot's third joint. The output torque's model of the joint's brushless DC motor is founded. Disturbance factors and the compensated effect of the torque's closed loop based on current measurement are analyzed. Related simulations and experiments show that the system has good current tracking and anti-disturbances performance, which improve the force control performance of the robot in assembly.