Common Base Four-Finger InGaAs/InP Double Heterojunction Bipolar Transistor with Maximum Oscillation Frequency 535 GHz

A common base four-finger InOaAs/InP double heterojunction bipolar transistor with 535 OHz fmax by using the 0.5 μm emitter technology is fabricated. Multi-finger design is used to increase the input current. Common base configuration is compared with common emitter configuration, and shows a smaller K factor at high frequency span, indicating a larger breakpoint frequency of maximum stable gain/maximum available gain （MSG/MAG） and thus a higher gain near the cut-off frequency, which is useful in THz amplifier design.

Influence of Oscillation Frequency of a Sieve on the Screening Process for a Conical Sieve with Oscillatory Circular Motion

Removal of foreign bodies from seed mixtures, or their calibration for use as planting material, as well as fraction classification of granular materials requires screening surfaces with vibratory motion. This paper presents some aspects on the working process of a sieve, made of perforated sheet and having an outer conical surface with oscillatory circular motion （alternative） on the horizontal. Results are presented for some experimental researches on the movement of material on the sieve, for various kinematical parameters of the sieve （amplitude and oscillation frequency）. A conical sieve, suspended at the upper and lower in three points, was tested for screening of rapeseeds in order to estimate the influence of oscillation frequency on the screening process. Curves were drawn for separation intensity on the sieve generating line, and by regression analysis with normal distribution law were determined the equation coefficients and the correlation with experimental data. Movement of material on the sieve and its working process, in general, was appreciated by means of the peak position of distribution curve depending on the oscillation frequency of the sieve, considering that the normal distribution law correlates very well the data obtained by experiments.

Radio frequency transistors based on ultra-high purity semiconducting carbon nanotubes with superior extrinsic maximum oscillation frequency

In this paper, we report polyfluorene-separated ultra-high purity semiconducting carbon nanotube radio frequency transistors with a self-aligned T-shape gate structure. Because of the ultra-high semiconducting tube purity and self-aligned T-shape gate structure, these transistors showed an excellent direct current and radio frequency performance. In regard to the direct current characteristics, these transistors showed a transconductance up to 40μS/μm and an excellent current saturation behavior with an output resistance greater than 200 kΩ·μm. In terms of the radio frequency characteristics, an extrinsic maximum oscillation frequency （fmax） of 19 GHz was achieved, which is a record among all kinds of carbon nanotube transistors, and an extrinsic current gain cut-off frequency （fT） of 22 GHz was achieved, which is the highest among transistors based on carbon nanotube networks. Our results take the radio frequency performance of carbon nanotube transistors to a new level and can further accelerate the application of carbon nanotubes for future radio frequency electronics.

Influence of oscillator phase on oscillation frequency and sensitivity of an electrode-separated piezoelectric sensor

Theoretical consideration was proposed for the influences of the oscillator phase on the response nature of an electrode-separated piezoelectric sensor (ESPS) to liquid properties and verified experimentally. For the oscillators with different phases, the oscillation frequency of the ESPS may increase, maintain nearly constant or decrease with increasing conductivity in low conductivity solutions. The sensitivity of response to density and viscosity increases slightly with increasing oscillator phase. The response to permittivity depends hardly on the oscillator phase. In addition, the dependence of the oscillation frequency of the ESPS on the supply voltage of the oscillator was explained. The ESPS was used to determine atropine sulfate with a detection limit of 1.6x10(-7) mol/L.

The Seasonal Climate and Low Frequency Oscillation in the Simulated Mid-Holocene Megathermal Climate

The mid—Holocene climate about 6000 years ago was simulated by using the atmospheric general circulation model. The orbital parameters for 6 ka BP (before present) were prescribed and other forcing factors were set in the modern conditions. Results show that the large—scale climate change in the African—Asian monsoon areas during the summer—time is strongly compared to the present climate, while the changes in other seasons and regions are generally weak. The results also revealed the change of the low frequency oscillation in the atmosphere. Key words Seasonal climate - Low frequency oscillation - Mid—Holocene This research was jointly supported by the National Natural Science Foundation of China (NSFC) key project “ Variation of Paleo—environment over East Asia and Its Dynamic Relation with the Global Change” under contract 49894170 and the NSFC project “ Coupling of the AGCM with an Biome Model and the Simulation on the Mid-Holocene Climate” under contract 49975018.

Dust Storms in North China in 2002: A Case Study of the Low Frequency Oscillation

The low frequency oscillation in both hemispheres and its possible role in the dust weather storm events over North China in 2002 are analyzed as a case study. Results show that the Aleutian Low is linked with the Circumpolar Vortex in the Southern Hemisphere on a 30-60-day oscillation, with a weak Circumpolar Vortex tending to deepen the Aleutian Low which may be helpful for the generation of dust storm events. The possible mechanism behind this is the inter-hemispheric interaction of the mean meridional circulation, with the major variability over East Asia. The zonal mean westerly wind at high latitudes of the Southern Hemisphere in the upper level troposphere may lead that of the Northern Hemisphere, which then impacts the local circulation in the Northern Hemisphere. Thus, the low frequency oscillation teleconnection is one possible linkage in the coupling between the Southern Hemisphere circulation and dust events over North China. However, the interannual variation of the low frequency oscillation is unclear.

Low Frequency Oscillations of the Heat Distribution in the Global Upper Ocean Layers

The heat distributions in the upper layers of the ocean have been studied and some important low frequency oscillations （LFOs） are already found and quantified by using various characteristic factors. In this paper, the ‘heat center＇ of a sea area is defined with a simple method. Then the temperature data set of the upper layer of the global ocean （from surface down to 400 m, 1955-2003） is analyzed to detect the possible LFOs. Not only some zonal LFOs, which were reported early, but also some strong LFOs of the vertical and meridional heat distribution, which might imply some physical sense, are detected. It should be noted that the similar vertical oscillation pattern can be found in the Pacific Ocean, Atlantic Ocean and Indian Ocean. Results from some preliminary studies show that the vertical LFO might be caused by the solar irradiance anomalies. This study may help reveal some unknown dynamical processes in the global oceans and may also benefit other related studies.

The low frequency oscillations of the sea surface temperature in the Equatorial Eastern Pacific and El Nino formation

-In this paper the variations of the sea surface temperature anomalies (SSTA) in the Equatorial Eastern Pacific are analysed. The results show that there are two peaks in the spectrum. One is the low frequency oscillation with a period of 3 - 5 years, and the other is the quasi-biennial oscillation. The former shows a westward migration in the warm episode of SSTA and the latter has the opposite trend. The El Nino events will be formed while the two frquency bands are in phase in the warming stage of SSTA in the Equatorial Eastern Pacific

A Disturbance Source Location Method on the Low Frequency Oscillation With Time-varying Steady-state Points

The low frequency oscillation is a serious threat to security and stability of a power grid.How to locate the disturbance source accurately is an important issue to low frequency oscillation disposal.Existing methods have poor adaptability to the low frequency oscillation with time-varying steady-state points because of the limitations in the location criterion derivation.A disturbance source location method on a low frequency oscillation with good generality is presented in the paper.Firstly,the reasons why the steady-state points are time-varying on a low frequency oscillation are analyzed.Then,based on the energy function construction form,the branch transmission energy is decomposed into state energy,reciprocating energy and dissipation energy by mathematical derivation.The flow direction of the dissipation energy shows the source and destination of the disturbance energy,and the specific location of a disturbance source can be identified according to its flow direction.Meanwhile,to meet the needs of energy calculation,a recognition method on the electrical quantities steady-state points is also presented by using the cubic spline interpolation.Simulation results show the correctness of the derivation and analysis on energy structure in the paper,and the disturbance source can be located accurately according to the dissipation energy.

Physical modeling of direct current and radio frequency characteristics for In P-based InAlAs/InGaAs HEMTs

Direct current（DC） and radio frequency（RF） performances of InP-based high electron mobility transistors（HEMTs）are investigated by Sentaurus TCAD. The physical models including hydrodynamic transport model, Shockley–Read–Hall recombination, Auger recombination, radiative recombination, density gradient model and high field-dependent mobility are used to characterize the devices. The simulated results and measured results about DC and RF performances are compared, showing that they are well matched. However, the slight differences in channel current and pinch-off voltage may be accounted for by the surface defects resulting from oxidized InAlAs material in the gate-recess region. Moreover,the simulated frequency characteristics can be extrapolated beyond the test equipment limitation of 40 GHz, which gives a more accurate maximum oscillation frequency( f;) of 385 GHz.

Improvement on Frequency Performance of SOI SiGe HBT

Based on the advantages of SOI technology, the frequency performance of SiGe HBT with SOI structure has been simulated. Compared with bulk SiGe HBT, the results show that the buried oxide layer （BOX） can reduce collector-base capacitance CCB with the maximum value 89.3%, substrate-base capacitance CSB with 94. 6%, and the maximum oscillation frequency is improved by 2.7. The SOl structure improves the frequency performance of SiGe HBT, which is adaptable to high-speed and high power applications.

Low-Frequency Reciprocating Fretting Wear Testing System Design and Experiment Research

The fretting wear is resulted from different or same sample's surfaces by the small variationand leads to mechanism failures. The main factors consist of the variation of normal load and oscillation frequencies,among which surface topography of different materials are the main factors to the problems of the fretting wear.Therefore,a novel low-frequency reciprocating fretting wear test system is designed upon the principle of Friction coefficient measurement. Four metal and non-metallic samples are measured under various normal load and oscillation frequencies to obtain the instantaneous friction coefficient in the repeat experiments. In fact,the experimental results show that Co F curves of different samples with the increase of the normal load are the similar exponential decay or parabolic shapes,which are consistent with the literatures to verify the rational design and reliable-operation of the system under the conditions of different frequencies.

THE NORTH-SOUTH ANTI-PHASE DISTRIBUTION OF RAINFALL IN MEIYU PERIODS AND ITS RELATIONSHIP WITH QUASI-BIWEEKLY OSCILLATION IN THE ATMOSPHERE

Based on the daily rainfall datasets from 740 stations in China from 1954 to 2005 and the NCEP/NCAR reanalysis data, the relationship between the north-south anti-phase distribution(APD) of rainfall during Meiyu periods and the Quasi-Biweekly Oscillation(QBWO) in the atmosphere was analyzed. Diagnostic results are as follows:(1) there was significant north-south oscillation of Meiyu rainfall during the 16 years from 1954 to 2005. Since the 1990 s, the APD enhanced significantly and showed 2- and 4-6-year period. In the region with more rainfall, the QBWO was always more active.(2) The APD of Meiyu and north-south movements of precipitation in eastern China belong to the same phase.(3) The 10-25 day filtered water vapor flux could spread to the area north of 30°N in 1991. The divergence of the water vapor flux which propagated from middle- and higher- latitudes to the of Yangtze-Huaihe River Basins(YHRB) was significant in 1991, but the latitudes that the water vapor flux could reach were further southward and there was no southward propagation of divergence in 1993.(4) The locations of Western Pacific Subtropical High(WPSH) and 10-25 day anti-cyclone, which modulated WPSH's advancement in and out of the South China Sea, were relatively northward in 1991. Furthermore, the vertical circulation showed north-south deviation between 1991 and 1993, just as other elements of the circulation did.

A 37 mJ,100 Hz,high energy single frequency oscillator

Ways on energy enhancement for single frequency oscillator are reported in this paper.By quantitative analysis on gain and loss coefficients for each cavity mode with inserted etalons,a 37 mJ,100 Hz high energy single-frequency Nd:YAG oscillator is obtained.The pulse energy is promoted by enhancement of nearly 7 times for a single frequency oscillator reported.The result proves that this method does help for energy enhancement.It has attractive potential for high energy single frequency oscillator design,especially on condition of intensive side pumped or long cavity laser,where strong competitors exist and are hard to be suppressed.

Low frequency acoustic properties of bilayer membrane acoustic metamaterial with magnetic oscillator

A bilayer membrane acoustic metamaterial was proposed to overcome the influence of the mass law on traditional acoustic materials and obtain a lightweight thin-layer structure that can effectively isolate low frequency noise. The finite element analysis（FEA） results agree well with the experimental results.It is proved that the sound transmission losses（STLs） of the proposed structures are higher than those of same surface density acoustic materials. The introduction of the magnetic mass block is different from the traditional design method, in which only a passive mass block is fixed on the membrane. The magnetic force will cause tension in the membrane, increase membrane prestress, and improve overall structural stiffness. The effects of the geometry size on the STLs are discussed in detail. The kind of method presented in this paper can provide a new means for engineering noise control.

Oscillations of an Inviscid Encapsulated Drop

The problem relating to the small-amplitude free capillary oscillations of an encapsulated spherical drop is solved theoretically in the framework of asymptotic methods.Liquids are supposed to be inviscid and immiscible.The formulas derived are presented for different parameters of the inner and outer liquids,including densities,thickness of the outer liquid layer,and the surface and interfacial tension coefficients.The frequencies of oscillation of the encapsulated drop are studied in relation to several“modes”which can effectively be determined in experiments by photo and video analysis.The results are presented in terms of oscillation frequencies reported as a function of the mode number,the spherical layer thickness and the relation between the(surface and interfacial)tension coefficients.It is revealed that the influence of the liquids’parameters(and related variations)on the drop oscillation changes dramatically depending on whether oscillations are“in-phase”or“out-of-phase”.Frequencies for“in-phase”type oscillations can be correlated with linear functions of the shell thickness and the relative values of interfacial tension coefficient whereas the analogous dependencies for the“out-of-phase”type oscillation are essentially non-linear.

The Dynamical Influence of Land－Sea Contrast and Sea Surface Temperature on Intraseasonal Oscillation in Tropical Atmosphere

An equatorial β-plane model which includes realistic non-uniform land-sea contrast and the underlying surface temperature distribution is used to simulate the 30-60 day oscillation (LFO) processes in tropical atmosphere, with emphasis on its longitude-dependent evolution and convective seesaw between Indian and the western Pacific oceans.The model simulated the twice-amplification of the disturbances over indian and the western Pacific oceans while they are travelling eastward.It reproduced the dipole structure caused by the out-of-phase oscillation of the active centres in these two areas and the periodical transition between the phases of LFO.It is suggested that the convective seesaw is the result of interaction of the internal dynamics of tropical atmosphere with the zonally non-uniform thermal forcing from underlying surface.The convective activities are suppressed over indonesia maritime continents whilst they are favoured over the Indian Ocean and western Pacific warm waters, so there formed two active oscillation centres. The feedback of convection with large-scale flow slows down the propagation of disturbances when they are intensifying over these two areas, therefore they manifest a kind of quasi-stationary component to favor the 'dipole' structure. Whereas the disturbances weaken and speed up over the eastern Pacific cold water region due to the interaction of sensible heating and evaporation with perturbational wind. Therefore the two major centers just show out-of-phase oscillation during one cycle around the latitudinal belt.By introducing the SST anomalies in El Nino and La Nina years into the surface temperature,we also show that they have significant influence on LFO processes. In an anomalously warm year, the LFO disturbances dissipate more slowly over the central-eastern Pacific region and can travel further eastward; whilst in an anomalously cold year,the opposite is true.

Variable Frequency Harmonic Oscillator in an Electromagnetic Field

The invariant, propagator, and wavefunction for a variable frequency harmonic oscillator in an electromagnetic field are obtained by making a specific coordinate transformation and by using the method of phase space path integral method. The probability amplitudes for a dissipative harmonic oscillator in the time varying electric field are obtained.

Frequency Performance of Ring Oscillators Based on a-IGZO Thin-Film Transistors

Ring oscillators based on indium gallium zinc oxide thin film transistors are fabricated on glass substrates. The oscillator circuit consists of seven delay stages and an output buffer inverter. The element inverter exhibits a voltage gain higher than -6 V/V and a wide output swing close to 85% of the full swing range. The dynamic performance of the ring oscillators is evaluated as a function of supply voltage and at different gate lengths. A maximum oscillation frequency of 0.88MHz is obtained for a supply voltage of 50V, corresponding to a propagation delay of less than 85 ns/stage.

In_(0.53)Ga_(0.47)As/In_(0.52)Al_(0.48)As HEMTs with f_(max) of 183GHz

By epitaxial layer structure design and key fabrication process optimization,a lattice-matched InP-based In0.53Ga0.47 As-In0.52Al0.48As HEMT with an ultra high maximum oscillation frequency （fmax） of 183GHz was fab- ricated. The fmax is the highest value for HEMTs in China. Also, the devices are reported, including the device structure, the fabrication process, and the DC and RF performances.