Microwave active resonator band-pass filters in various mmic technologies

In this article, two topologies of L-C parallel active resonators are presented. These circuits are realized in MMIC technology, using three transistors which could be MESFET, hemt or HBT. The survey of these resonators shows the possibility, by controling the values of a resistor and/or a capacitor, on the one hand, to tune the resonance frequency of these circuits, and on the other hand, to cancel out their losses so as to obtain negative conductance. Compact, lossless and narrow-band filters are then implemented using previous active resonators. To date, the use of mesfet technology has reduced the synthesis of such active filters in S-band and at X-band low frequencies. Now, however, hemt and HBT technologies allow the extension of their implementation to the whole X-band. This survey is illustrated by the simulated response of a 10 GHz filter with a 500 MHz 3 dB bandwidth. The mmic technology is a 0.2 μm hemt one. The simulated performances of this filter achieve a mean transmission gain of 0. 5 dB, with a reflection loss higher than 10 dB at 10 GHz,     

Synthesis and molecular weights of metal poly(ethyl methacrylates). IV

Summary Ethyl methacrylate colloids were obtained by codeposition at 77 K of the monomer with several metals such as: Au, Ag, Cu, Pd, Zn, Cd, Al, Ga, In, Ge, Sn, Sb and Bi. The colloids were polymerized with different amounts of initiator (AIBN) at 62°C and a wide range of viscosity average molecular weights (Mv; 10⁴–10⁶) were obtained depending upon the metal used. The metal colloid concentrations and stability are reported. The thermal stability, morphology and metal composition are also described. The polymers are stable even at 300°C and the metal content is ranging from 0.10 to 3.67%.     

A Direct Solver for 2D Non-Stationary Boltzmann-Poisson Systems for Semiconductor Devices: A MESFET Simulation by WENO-Boltzmann Schemes

We present preliminary results of a high order WENO scheme applied to deterministic computations for two dimensional formulation of the transients for the Boltzmann-Poisson system describing electron transport in semiconductor devices. The collisional term models optical-phonon interactions which become dominant under strong energetic conditions corresponding to nanoscale active regions under applied bias. We treat the Boltzmann Transport equation in a spherical coordinate system for the wave-vector space. The problem is three dimensional in the wave-vector space and two dimensional in the physical space, plus the time variable driving to steady states. The new formulation avoids the singularity due to the spherical coordinate system.     

Isolation and identification of Vibrio genus microorganisms in the Quibu River

The Quibú River sewages were studied during 9 weeks, in order to isolate and characterize Vibrio genus microorganisms. Twenty Moore's hyssops were placed 2 or 3 times a week on the banks of the river, where each of them was kept in a passive capture stay for 24 hours. In all the hyssops placed, Vibrio cholerae non-01 were isolated.     

Dispersion in finlines on semiconductor and the S-parameters of a step discontinuity

The Transverse Transmission Line method is used for the characterization of bilateral and unilateral finlines on a semiconductor substrate and in conjunction with the modal method, for the calculation of the scattering parameters due to a step discontinuity on a unilateral finline with a lossless dielectric substrate. Numerical results of the effective dielectric constant, attenuation constant and characteristic impedance for the bilateral and unilateral finlines on semiconductor substrates, and results of scattering parameters of a step discontinuity for unilateral finline, are presented.     

Frictional Response of PTFE Sliding Bearings at High Frequencies

Dynamic tests were done on polytetrafluoroethylene (PTFE) sliding bridge bearings to evaluate their frictional characteristics at frequencies above 1 Hz. High frequency seismic responses of PTFE bearings are expected to occur in bridge structures in eastern North America, where the estimated ground motion is well above 1 Hz. Three different PTFE-steel interfaces were tested at frequencies ranging from 0.02 Hz to 5 Hz, with displacement amplitudes of up to ±70 mm and under confining pressures ranging from 5 MPa to 45 MPa. The experimental results showed a significant initial transient frictional response at frequencies above 1 Hz before the dynamic, steady-state, frictional behavior was achieved. This transient response is characterized by an initial high static coefficient of friction that slowly decreases to a dynamic steady-state coefficient of friction after several response cycles. Modifications to an existing mathematical friction model are proposed to take into account this initial transient frictional response.     

Cure kinetics of a diglycidyl ether of bisphenol a epoxy network (n = 0) with isophorone diamine

The study of the cure reaction of a diglycidyl ether of bisphenol A epoxy network with isophorone diamine is interesting for evaluating the industrial behavior of this material. The total enthalpy of reaction, the glass‐transition temperature, and the partial enthalpies at different curing temperatures have been determined with differential scanning calorimetry in dynamic and isothermal modes. With these experimental data, the degree of conversion and the reaction rate have been obtained. A kinetic model introduces the mechanisms occurring during an epoxy chemical cure reaction. A modification of the kinetic model accounting for the influence of the diffusion of the reactive groups at high conversions is used. A thermodynamic study has allowed the calculation of the enthalpy, entropy, and Gibbs free energy. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Neural network model of prepulse inhibition.

The authors introduce a real-time model of acoustic prepulse inhibition (PPI) and facilitation (PPF) in animals and humans. The model incorporates excitatory and facilitatory pathways activated by the positive value of changes in noise level in the environment and an inhibitory pathway activated by the absolute value of changes in noise level. Whereas excitation and facilitation are exponential functions, inhibition is a linear function of the input noise expressed in decibels. The model describes many properties of PPI and PPF that include, among others, their dependency on prepulse intensity and duration, duration of the lead interval, and changes in background noise. The model also describes how specific brain lesions enhance the strength of the startle response and impair PPI. Finally, the model correctly predicts how PPI depends on pulse intensity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Halstenbek体育场

这个庞大的椭圆型平面建筑与通常的矩形平面大跨度支撑结构形成鲜明的对比.在这座“软空间”内不存在任何边角,所有的边界融入在一条无尽的弧线中.这种“软空间”感更因一个沿整个建筑周边建造的混凝土底座变得尤为明显,它不光是建筑物的基础,还提供了可利用的空间,如衣帽间、设备间、管道间等.在地下4m处,就地采用了地热资源,可节省50%的能源.覆盖整个场地的玻璃屋顶施工技术要求复杂,采用的都是新型高科技产品.玻璃网架圆屋顶必须能承受温度的变化、强风及积雪的重量.带有横向支撑系统的屋面结构由屋顶材料和钢杆件组成.彩色玻璃和横向可调节的遮阳系统将阳光产生的眩光降低到最小程度.当白天举行比赛时,场内不需要任何人工照明.