Control performance and energy saving of multi-level pressure switching control system based on independent metering control

Aiming at the problem of large energy consumption in hydraulic control system with large load and variable working conditions, based on the multi-level pressure switching control system(MPSCS), a multi-level pressure switching control system based on independent metering control is proposed combined with the independent metering control technology. The configuration principle of the system is given, the mathematical model of this system is established, and the control strategy of the system under 4 different working quadrants is put forward. Finally, the control performance and energy saving characteristics of the system are tested. The test results show that the switching of high and low pressure power supply has a certain effect on the response of step position and ramp position under impedance working condition. The displacement curves show slow climbing or abrupt change of ramp position, and the position accuracy is less than 1 mm. The multi-level pressure switching control system based on independent metering control can recover and store energy under the transcendence working conditions. The control accuracy is about 1 mm, and the energy recovery rate is about 70%～80%.     

Ultrafast polarization optical switch constructed from one-dimensional photonic crystal and its performance analysis

All-optical switch with the ultrafast optical switching rate is a key device in the next generation optical network. In this article, we propose a polarization switch with ps switching time, which is constructed from one-dimensional resonant photonic crystal （1D RPC）. The model of switch operating at 1.5 μm is established based on the optical stark effect （OSE）. We calculate the performance indices of the switch and the influences of errors of periods and refractive index on the performance characteristics.     

Synchronization control for electro-hydraulic dual-cylinder system based on force/position switching

If the rigidity of a mechanism is stiff enough, the position synchronous error of the two cylinders driving one degree-of-freedom （DOF） of the mechanism may be less than the resolution of position sensors. To handle this synchronization problem this paper proposes a force/position switching scheme, which partitions the two cylinders into a master cylinder and a slave cylinder. The master cylinder is always position tracking controlled by a second-order sliding mode controller and the slave cylinder is integrated with a force tracking controller which is a first order sliding mode controller. When the position tracking error is less than a given value, the slave cylinder switches to be force controlled. Two synchronization control methods are presented based on the switching scheme： the master - master ＋ force/position switching control and the master - slave ＋ force/position switching control. Simulations show that the formance compared with two given proposed synchronization control position-based control methods. methods can get a better per-     

Generalized Low-Density Parity-Check Coding Scheme with Partial-Band Jamming

In this study, a class of Generalized Low-Density Parity-Check （GLDPC） codes is designed for data transmission over a Partial-Band Jamming （PBJ） environment. The GLDPC codes are constructed by replacing parity-check code constraints with those of nonsystematic Bose-Chaudhuri-Hocquenghem （BCH）, referred to as Low-Density Parity-Check （LDPC）-BCH codes. The rate of an LDPC-BCH code is adjusted by selecting the transmission length of the nonsystematic BCH code, and a low-complexity decoding algorithm based on message- passing is presented that employs A Posteriori Probability （APP） fast BCH transform for decoding the BCH check nodes at each decoding iteration. Simulation results show that the LDPC-BCH codes with a code rate of 1/8.5 have a bit error rate performance of 1 x10-8 at signal-noise-ratios of -6.97 dB, -4.63 dB, and 2.48 dB when the fractions of the band jammed are 30%, 50%, and 70%, respectively.     

A novel lambda negative-resistance transistor in the 0.5 μm standard CMOS process

A novel negative-resistance transistor (NRT) with a Lambda shaped I-V characteristic is demonstrated in the 0.5 μm standard CMOS process. To save on the number of component devices, this device does not use standard device models provided by CMOS processes, but changes a MOSFET and a BJT into a single device by fabricating them in the same n-well, with a p-type base layer as the MOSFET’s substrate. The NRT has a low valley current of -6.82 nA and a very high peak-to-valley current ratio of 3591. The peak current of the device is -24.49 μA which is low enough to reduce the power consumption of the deivce, and the average value of its negative resistance is about 32 kΩ. Unlike most negative-resistance devices which have been fabricated on compound semiconductor substrates in recent years, this novel NRT is based on a silicon substrate, compatible with mainstream CMOS technology. Our NRT dramatically reduces the number of devices, minimizing the area of the chip, has a low power consumption and thus a further reduction in cost.     

Enhanced conversion efficiency of Yb2＋-Yb3＋-codoped glass as spectral converter for photovoltaic application

We propose a kind of Yb2＋-Yb3＋-codoped glass, which is used as spectral converter layer to adjust AM1.5 solar spectrum for a better match with silicon bandgap. The energy-level rate equations and power transmission equations are established to analyze the down-conversional effect of the codoped glass on solar spectrum. The numerical results show that with proper doping concentration and thickness the glass layer may improve conversion efficiency by about 12 %. Moreover, we also apply the modified spectrum as excitation source of solar cell in a simulation platform, and reveal that there is about 15 % improvement in practical cells.     

Purity of SiC powders fabricated by coat-mix

Silicon carbide powders were synthesized by the coat-mix process, with phenolic resin and silicon powders as starting materials. The effects of synthetic conditions, including sintering temperature and the molar ratio of resin-derived carbon to silicon on the composition and the purity of the resultant powders were investigated. The results show that a higher sintering temperature and an appropriate molar ratio of resin-derived carbon to silicon are favorable for producing high purity silicon carbide powders. It is found that the silicon carbide content increases slightly with increasing the sintering temperature during the solid-solid reaction. The temperature gradient plays an important role on this trend. When the sintering temperature is raised up to 1500℃, the formation of silicon earbide is based on the liquid-solid reaction, and high purity (99.8wt%) silicon carbide powders can easily be obtained. It can also be found that the optimum molar ratio of resin-derived carbon to silicon is 1:1.     

Theoretical analysis and simulation of InP-based uni-traveling-carrier photodetector

In this paper the photocurrent response of InP-based uniotraveling-carrier photodetectors （UTC-PDs） is analyzed using the drift-diffusion approach. Based on the theoretical analysis, an InP/InGaAs UTC-PD is modeled utilizing a numerical device simulator （ATLAS）, and the physics of the device＇s operation and its performance as a function of biasing and power level are simulated. The simulation results indicate that the linear dynamic range is up to 60 mW, the f-3 dB is about 40 GHz and the full-width at half-maximum （FWHM） of the current pulse is 28 ps with 10 mW optical power injection for an optimized structure UTC-PD.     

Design and Implementation of a Bootstrap Trust Chain

The chain of trust in bootstrap process is the basis of whole system trust in the trusted computing group （TCG） definition. This paper presents a design and implementation of a bootstrap trust chain in PC based on the Windows and today＇s commodity hardware, merely depends on availability of an embedded security module （ESM）. ESM and security enhanced BIOS is the root of trust, PMBR （Pre-MBR） checks the integrity of boot data and Windows kernel, which is a checking agent stored in ESM. In the end, the paper analyzed the mathematic expression of the chain of trust and the runtime performance compared with the common booring process. The trust chain bootstrap greatly strengthens the security of personal computer system, and affects the runtime performance with only adding about 12% booting time.     

Proton Exchange Membranes for Fuel Cells Challenges and Recent Developments

The current technology of proton exchange membrane fuel cells （PEMFC） is based on perfluorosulfonic acid （PFSA） membranes （e. g. Nation ） as electrolyte. It operates on pure hydrogen and oxygen/air at typically 80℃ with high power density and long-term durability. For the membranes to be conductive, a minimum threshold of absorbed water molecules is about 6 to 7 mole per sulfonic site. The highest conductivity is only obtained under fully hydrated conductions, i.e. 21 - 22 mole water per sulfonic acid site. In other words, the proton conductivity is achieved by the locally liquid-like hydrophilic domain of the nanostructure. This strong dependence of conductivity on the water content in membranes limits the operational temperature of PEMFC below 100 ℃.     

Study on Support Vector Machine Based on 1-Norm

The model of optimization problem for Support Vector Machine（SVM） is provided, which based on the definitions of the dual norm and the distance between a point and its projection onto a given plane. The model of improved Support Vector Machine based on 1-norm （1 - SVM） is provided from the optimization problem, yet it is a discrete programming. With the smoothing technique and optimality knowledge, the discrete programming is changed into a continuous programming. Experimental results show that the algorithm is easy to implement and this method can select and suppress the problem features more efficiently.Illustrative examples show that the 1 - SVM deal with the linear or nonlinear classification well.     

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.     

Robust Controller Design of a Class of Uncertain Switched Fuzzy Systems with Delays

The robust control problem for a class of uncertain switched fuzzy systems with delays is investigated. Firstly,the model of the switched fuzzy system is presented and the parallel distributed compensation（ PDC） technology is employed to design fuzzy controllers. Then, based on the convex combination method, a sufficient condition for robust stabilization in terms of linear matrix inequalities（ LMIs） is obtained and a switching law is presented.Meanwhile,the Lyapunov-Krasovskii functional is taken to deal with time varying delays. Moreover,an algorithm is applied to finding a solution for a group of convex combination coefficient. Finally,a numerical example is given to demonstrate the effectiveness of the proposed method.     

Photovoltaic properties of MEH-PPV/TiO2 nanocomposites

Photovoltaic properties of photodiodes based on nano-TiO2 and poly[2-methoxy,5-（2＇-ethlhexyloxy）-p-phenylenevinylene] （MEH-PPV） composites are investigated. By comparing composite devices with the same weight of TiO2 （nanoparticles and nanotubes）：MEH-PPV, it was found that the device with TiO2 nanotubes exhibited better performance. By further optimizing the weight radio of TiO2 nanotubes： MEH-PPV, we gained the device with a short circuit current density of 9.27μA/cm^2 with a light intensity of 16.7mW/cm^2 at the 500 nm wavelength, the highest open-circuit voltage of 1.1V, and a photosensitivity of 332 at reverse bias of -0.6V. The photosensitivity is improved by a factor of 33 compared with the undoped MEH-PPV device.     

An electrical-filtered optical heterodyne technique for tuning speed measurement of DBR lasers

A new scheme based on the electrical-filtered optical heterodyne technique is proposed for measuring the tuning speed of tunable distributed Bragg reflector (DBR) lasers. In this scheme, a 10 GHz high-pass electrical filter is used and the wavelength switching time of a tunable DBR laser for different tuning frequencies corresponding exactly to different delay lines is measured. The switching time is measured to be nearly 300 ns and can be improved by reducing the equivalent resistance-capacitance (RC) time constant of the device. The distribution of the beat signal of the DBR laser in the time domain is also obtained, and is a good match with the waveforms measured using an optical filter.     

Study on high efficient electric discharge milling of silicon carbide ceramic with high resistivity

A new method which employs a group pulse power supply for electric discharge milling of the silicon carbide ceramic with the resistivity of 500 Ω·cm is presented. Due to the good machining stability and high pulse utilization, the material removal rate （MRR） can reach 72.9 mm^3/min. The effects of high-frequency pulse duration, high-frequency pulse interval, peak voltage, peak current, polarity, rotate speed and group frequency on the process performance have been investigated. Also the EDMed surface microstructure is examined with a scanning electron microscope （SEM）, an X-ray diffraction （XRD）, an energy dispersive spectrometer （EDS） and a micro hardness tester. The results show that the conditions of smaller high-frequency pulse duration and pulse interval, higher peak voltage and peak current, and positive tool polarity are suitable for machining the SiC ceramic. The optimal rotate speed is 1090 r/min and the preferable group frequency is 730 Hz. In addition, there is a small quantity of iron on machined surface when machining with steel electrode. The average grain size of the EDMed surface is smaller than that of the unprocessed, and the micro hardness of machined surface is superior to that of the unprocessed.     

Micro-Friction and Adhesion Measurements for Si Wafer and TiB2 Thin Film

An apparatus was specifically developed for micro-friction and adhesion measurements. The force measurement range is 10-2000 μN with a horizontal speed of 10-400 μm/s . The apparatus was tested us-ing a 0.7-mm diameter steel ball as the upper specimen to measure the micro friction and adhesion behav-iour of a Si (100) wafer and a TiB2 film. The effects of rest time, speed, and load were studied. The results show that the maximum static and sliding friction forces of both the Si (100) wafer and the TiB2 film increase with the load. At low speeds, the influence of speed on the friction force is significant. The adhesion forces of the Si (100) wafer and the TiB2 film increase with rest time, reaching stable values after about 3000 s. The TiB2 film has significantly less adhesion and micro friction forces than the Si (100) wafer.     

Data Integration Strategy for Database Grids Based on P2P Framework

The differences between the data integration of a dynamic database grid （DBG） and that of a distributed database system are analyzed, and three kinds of data integration strategies are given on the background of DBG based on Peer to Peer （P2P） framework, including the centralized data integration （CDI） strategy, the distributed data integration （DDI） strategy and the filter-based data integration （FDDI） strategy. CDI calls all the database grid services （DGSs） at a single node, DDI disperses the DGSs to multiple nodes, while FDDI schedules the data integration nodes based on filtering the keywords returned from DGSs. The performance of these three integration strategies are compared with and analyzed by simulation experiments. FDDI is more evident for filtering the keywords with data redundancy increasing. Through the reduction of large amount of data transportation, it effectively shortens the executing time for the task and improves its efficiency.     

Analysis of Multi-Channel and Slotted Random Multi-Access Protocol with Two-Dimensional Probability for Ad Hoc Network

A higher quality of service （QoS） is provided for ad hoc networks through a multi-channel and slotted random multi-access （MSRM） protocol with two-dimensional probability. For this protocol, the system time is slotted into a time slot with high channel utilization realized by the choice of two parameters p1 and p2, and the channel load equilibrium. The protocol analyzes the throughput of the MSRM protocol for a load equilibrium state and the throughput based on priority. Simulations agree with the theoretical analysis. The simulations also show that the slotted-time system is better than the continuous-time system.     

Direct electrochemistry and electrocatalysis of horseradish peroxidase in MnO2 nanosheet film

A novel material MnO2 nanosheet has been used as the support matrix for the immobilization of horseradish peroxidase （HRP）. HRP entrapped in MnO2 nanosheet film exhibits facile direct electron transfer with the electron transfer rate constant of 6.86 s^-1. The HRP/MnO2 nanosheet film gives a reversible redox couple with the apparent formal peak potential （E^0＇） of -0.315 V （vs. Ag/AgCl） in pH 6.5 phosphate buffer solution （PBS）. The formal potential E^0＇ of HRP shifts linearly with pH with a slope of -53.75 mV.pH^-1, denoting that an electron transfer accompanies single-proton transportation. The immobilized HRP shows an electrocatslytic activity to the reduction of H2O2. The response time of the biosensor for H2O2 is less than 3 s, and the detection limit is 0.21 μmol · L^-1 based on signal/noise = 3.