Mapping piezoelectric nonlinearity in the Rayleigh regime using band excitation piezoresponse force microscopy

Band excitation piezoresponse force microscopy enables local investigation of the nonlinear piezoelectric behavior of ferroelectric thin films. However, the presence of additional nonlinearity associated with the dynamic resonant response of the tip-surface junction can complicate the study of a material's nonlinearity. Here, the relative importance of the two nonlinearity sources was examined as a function of the excitation function. It was found that in order to minimize the effects of nonlinear tip-surface interactions but achieve good signal to noise level, an optimal excitation function must be used. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3593138]

Tono-Pen determination of intraocular pressure in patients with band keratopathy or glued cornea

Aims. To evaluate the intraocular pressure (IOP) measurements in patients with band keratopathy or glued corneas obtained from affected and non-affected areas. Methods. 15 patients with band keratopathy or glued corneas were prospectively recruited. When both eyes were affected, only the right eye was analysed. Tono-Pen readings of IOP were obtained sequentially from the affected and non-affected corneal surface. Additionally, Goldmann applanation tonometry was attempted. Results. Determination of IOP with the Tono-Pen was possible in all cases, while Goldmann tonometry was not performed in three patients because of severe corneal irregularities. The average of the Tono-Pen readings obtained from the affected cornea (34.8 (SD 14.0) mmHg) was consistently and significantly higher (p <0.001) than mean IOP obtained by the Tono-Pen from the non-affected area (14.8 (4.3) mmHg). The average of Goldmann tonometry readings (14.4 (6.1) mmHg) did not differ significantly from the Tono-Pen values obtained from the non-affected corneal area (p = 0.47) but was significantly lower than the Tono-Pen measurements obtained from the affected area (p <0.001) Conclusion. In patients with band keratopathy or glued corneas determination of IOP by Tono-Pen tonometry varies from affected to non-affected area. The Tono-Pen overestimates the level of IOP when it is applied to areas with band keratopathy or with glue.

Evaluation of the performance of a multi-band antenna for On-Board applications

The performance of a multi-band antenna consisting of a microstrip patch with two U-slots is designed and tested for use in aircraft cabin wireless access points. The objective of this paper is to evaluate this antenna that covers most of the current wireless bands from 1.7GHz to 5.85GHz.A specially designed wideband probe antenna is used for characterization
of field radiated from this antenna. This measurement setup gives room for future development like human presence in the cabin, the fading effects, and the path loss between transmitter and receiver.

A SiGe Power Amplifier with Integrated BALUNs for 81-86 GHz E-Band Backhaul Applications

The design of a two-stage differential cascode power amplifier (PA) for 81-86 GHz E-band applications is presented. The PA was realised in SiGe technology with fT/fmax 170/250 GHz. A broadband transformer with efficiency higher than 79.4% from 71 GHz to 96 GHz is used as a BALUN. The PA delivers a 4.5 dBm saturated output power and exhibits a 13.4 dB gain at 83.6 GHz. The input and output return losses agree well with the design specifications.

Integrated Low-Loss Passive SiGe Power Splitter and Combiner Operating Across 78-86 GHz Band

This paper describes the design, implementation, and characterization of a new type of passive power splitting and combining structure for use in a differential four-way power-combining amplifier operating at E-band. In order to achieve lowest insertion loss, input and output coils inductances are resonated with shunt capacitances. Simple C-L-C and L-C networks are proposed in order to compensate inductive loading due to routing line that would otherwise introduce mismatch and increase loss. Across 78-86 GHz band, measured insertion loss is about 7 dB. Measured return losses are >10 dB from 73 GHz to 94 GHz at the input port and >9 dB from 60 GHz to 94 GHz at the output port. When integrated with driver and power amplifier cells, the simulated complete circuit exhibits 18.2 dB gain and 20.3 dBm saturated output power.

SiGe V Band Wide Tuning-Range VCO and Frequency Divider for Phase Locked Loop

A V-band wide tuning-range VCO and high frequency divide-by-8 frequency divider using Infineon 0.35 µm SiGe HBT process are presented in this paper. An LC impedance peaking technique is introduced in the Miller divider to increase the sensitivity and operation frequency range of the frequency divider. Two static frequency dividers implemented using current mode logic are used to realize dividing by 4 in the circuit. The wide tuning range VCO operates from 51.9 to 64.1 GHz i.e. 20.3% frequency tuning range. The measured phase noise at the frequency divider output stage is around -98.5 dBc at 1 MHz. The circuit consumes 200mW and operates from a 3.5Vdc supply, and occupies 0.6×0.8 mm2 die area.

A Compact V-band power detector

Email
Print
Request Permissions











A compact V-band active power detector using Infineon 0.35 µm SiGe HBT process (fT/fmax =170/250 GHz) is described. The total chip area is only 0.35×0.8 mm2 including all pads. This design exhibits a dynamic range larger than 20 dB over the frequency range from 55 GHz to 67 GHz. It also offers a simple and low-power application potential as an envelop detector in multi-Gbps high data rate demodulators for OOK/ASK etc.

A J-band detection of the sub-stellar mass donor in SDSS J1433+1011

We present time-resolved J-band spectroscopy of the short-period cataclysmic variable SDSS J143317.78+101123.3. We detect absorption lines from the sub-stellar donor star in this system, which contributes 38 +/- 5 per cent to the J-band light. From the relative strengths of the absorption lines in the J band, we estimate the spectral type of the donor star to be L2 +/- 1. These data are the first spectroscopic detection of a donor with a confirmed sub-stellar mass in a cataclysmic variable, and the spectral type is consistent with that expected from semi-empirical evolutionary models.

Using skew mapping, we have been able to derive an estimate for the radial velocity of the donor of K-d = 520 +/- 60 km/s. This value is consistent with, though much less precise than, predictions from mass determinations found via photometric fitting of the eclipse light curves.

Observation of an optical phonon band in situ in TiO electrochemistry:A possible indicator of strongly trapped intermediates in the O evolution reaction

This Letter reports in situ Fourier transform infrared (FTIR) spectroscopic data on thermal TiO films fabricated by heating titanium plates in air at 475, 700 and 800 °C. The films were studied in the dark and under UV-irradiation in aqueous 0.1MNaClO in the presence and absence of 0.1 M Na(OOC) and at 10, 25 and 50 °C. The film fabricated at 800 °C showed a broad feature near 1580cm under UV-irradiation that was not observed in the dark, whilst the films fabricated at lower temperatures, 475 and 700 °C, showed no such feature. This feature appears to be associated with the accumulation of surface-mobile holes at the complex, porous film-electrolyte interface and the capacity of such holes to enhance the absorption cross-section of optical phonons characteristic of the rutile crystal form at and near the surface of the TiO/electrolyte interface. © 2001 Elsevier Science B.V.

Probable z'-band Ground-based Detection of the Secondary Eclipse of WASP-19b

We present the probable ground-based detection of the secondary eclipse of the transiting exoplanet WASP-19b. The observations were made in the Sloan z'-band using the ULTRACAM triple-beam CCD camera mounted on the NTT. The measurement shows a 1±0.2mmag eclipse depth, consistent with a dayside temperature of 2900K, matching previous predictions based on H- and K-band measurements. However, since this is based on a single observation, the eclipse depth - at the moment - is not particularly well constrained, and would benefit from additional observations at similar wavelengths. Our technique for the data reduction and analysis is described, along with our approach to dealing with systematic errors associated with ground-based secondary eclipse observations.

Octavius 4D characterization for flattened and flattening filter free rotational deliveries

Purpose: In this study the Octavius detector 729 ionization chamber (IC) array with the Octavius 4D phantom was characterized for flattening filter (FF) and flattening filter free (FFF) static and rotational beams. The device was assessed for verification with FF and FFF RapidArc treatment plans.

Methods: The response of the detectors to field size, dose linearity, and dose rate were assessed for 6 MV FF beams and also 6 and 10 MV FFF beams. Dosimetric and mechanical accuracy of the detector array within the Octavius 4D rotational phantom was evaluated against measurements made using semiflex and pinpoint ionization chambers, and radiochromic film. Verification FF and FFF RapidArc plans were assessed using a gamma function with 3%/3 mm tolerances and 2%/2 mm tolerances and further analysis of these plans was undertaken using film and a second detector array with higher spatial resolution.

Results: A warm-up dose of >6 Gy was required for detector stability. Dose-rate measurements were stable across a range from 0.26 to 15 Gy/min and dose response was linear, although the device overestimated small doses compared with pinpoint ionization chamber measurements. Output factors agreed with ionization chamber measurements to within 0.6% for square fields of side between 3 and 25 cm and within 1.2% for 2 x 2 cm(2) fields. The Octavius 4D phantom was found to be consistent with measurements made with radiochromic film, where the gantry angle was found to be within 0.4. of that expected during rotational deliveries. RapidArc FF and FFF beams were found to have an accuracy of >97.9% and >90% of pixels passing 3%/3 mm and 2%/2 mm, respectively. Detector spatial resolution was observed to be a factor in determining the accurate delivery of each plan, particularly at steep dose gradients. This was confirmed using data from a second detector array with higher spatial resolution and with radiochromic film.

Conclusions: The Octavius 4D phantom with associated Octavius detector 729 ionization chamber array is a dosimetrically and mechanically stable device for pretreatment verification of FF and FFF RapidArc treatments. Further improvements may be possible through use of a detector array with higher spatial resolution (detector size and/or detector spacing). (C) 2013 American Association of Physicists in Medicine.