One-bath dyeing of poly(ethylene terephthalate)/cotton blends with alkali-clearable azo disperse dyes containing a fluorosulphonyl group

Monoazo disperse dyes containing a fluorosulphonyl group, based on 4-amino-4'-fluorosulphonylazobenzene derivatives, were dyed on poly(ethylene terephthalate)/cotton blends and their dyeing and fastness properties investigated. A one-bath dyeing method was used, as these dyes can be alkali cleared in the same bath. In particular, the cross-staining of cotton was studied in order to assess their suitability for the one-bath dyeing of poly(ethylene terephthalate)/cotton blends.     

ZnSe heteroepitaxy on GaAs (110) substrate

ZnSe heteroepitaxial layers have been grown on GaAs (100), (110) on axis, and (110) 6° miscut substrates by molecular beam epitaxy. ZnSe on GaAs (110) shows smooth and featureless spectra from Rutherford backscattering channeling measurements taken along major crystalline directions, whereas ZnSe on GaAs (100) without pre-growth treatments exhibit large interface disorder in channeling spectra. ZnSe films grown on GaAs (110) on axis show facet formation over a wide range of growth conditions. The use of (110) 6° miscut substrates is shown to suppress facet formation; and under the correct growth conditions, facet-free surfaces are achieved. Etch pit density measurements give dislocation densities for ZnSe epitaxial layers grown on GaAs (100), (110) on axis, and (110) 6° miscut substrates of 10⁷/cm², 3 × 10⁵/cm² and 5 × 10⁴/cm², respectively. These results suggest that with further improvements to ZnSe growth on GaAs (110)-off substrates it may be possible to fabricate defect free ZnSe based laser devices.     

Aeroacoustic tonal noise prediction of open cavity flows involving feedback

 A new hydrodynamic/acoustic splitting method isemployed to predict aeroacoustic tonal noise of self-sustained oscillatory flows over the open cavity at low Mach numbers. Acoustic field is computed using a sixth-order compact scheme and a fourth-order Runge–Kutta method, with acoustic sources obtained from the unsteady incompressible Navier–Stokes calculation. First, numerical accuracy of the present splitting method is assessed for the aeolian tone generated by Karman vortex shedding from a circular cylinder at Re _D = 200 and M _∞ = 0.3. A direct comparison was made with solutions of direct acoustic numerical simulation (DaNS) and Curle's acoustic analogy. The fundamental mode characteristics of the cavity flows at (i) Re_δ* = 850 and M _∞ = 0.077 and (ii) Re_δ* = 1620 and M _∞ = 0.147 are examined by the present method, verifying the solution with the experimentally measured sound pressure level (SPL) spectra. A dual tone characteristic observed in experiment (Henderson 2000) for case (i) is also confirmed computationally by the present method. Received: 15 April 2002 / Accepted: 5 March 2003 The authors wish to express gratitude to Prof. Henderson at the Kettering University for kindly providing the experimental data. This work was partially supported by the Korea Science and Engineering Foundation (1999-1-305-001-5).     

A miniature 2.1-GHz low loss microstrip filter with independent electric and magnetic coupling

A miniature planar two-pole microstrip filter with independent electric and magnetic coupling has been developed at 2.1 GHz. The independent coupling allows separate control of two transmission zeroes and result in a sharp filter skirt. The two-pole filter occupies an area of 6.6/spl times/4.6 mm/sup 2/ (30 mm/sup 2/) on an /spl epsi//sub r/=10.2 substrate, and shows a 5% bandwidth (100 MHz) and an insertion loss of 1.4 dB. The filter unloaded Q is 150 at 2.1 GHz which is much better than compatible filters done in LTCC technology.     

Hybrid symbol- and bit-based source-controlled channel decoding for MELP speech parameters

A joint source channel coding (JSCC) scheme which exploits bit-level correlation as well as symbol-level correlation efficiently in a source-controlled channel decoding (SCCD) process is proposed and applied to the mixed-excitation linear prediction (MELP) parameters of speech. A modified BCJR algorithm is also proposed for use in the SCCD algorithm. Simulation results show that our proposed scheme performs better than other redundancy-based JSCC schemes such as bit-based SCCD, soft-bit speech decoding (SBSD) and iterative source-channel decoding.     

Wide-scan spherical-lens antennas for automotive radars

A new approach to wide scan-angle antennas at millimeter-wave frequencies is introduced with special focus on ease of manufacturing and reliability. The system is composed of planar feed antennas (tapered-slot antennas), which are positioned around a homogeneous spherical Teflon lens. Beam scanning can be achieved by switching between the antenna elements. The spherical-lens system is analyzed through a combined ray-optics/diffraction method. It is found that a maximum efficiency of 50%-55% can be achieved using Teflon, Rexolite, or quartz lenses. The efficiency includes taper, spillover, and reflection loss. Calculations also indicate that the maximum lens diameter is 30-40 λ₀, which results in a maximum directivity of 39.5-42 dB. Measurements done on a single-element feed and a 5-cm Teflon lens agree very well with theory and result in a 3-dB beamwidth of 5.5° and better than -20-dB sidelobe levels at 77 GHz. Absolute gain measurements show a system efficiency of 46%-48% (including dielectric loss). A 23- and 33-element antenna array with a scan angle of ±90° and a -3.5- and -6-dB crossover, respectively, in the far-field patterns was also demonstrated. The 23-element array resulted in virtually no gain loss over the entire 90° scan angle. This represents, to our knowledge, the first wide scan-angle antenna at millimeter-wave frequencies     

94 GHz integrated horn monopulse antennas

A monolithic azimuthal monopulse antenna for 94-GHz applications has been developed. The structure consists of a single dipole suspended in one plane of an integrated horn cavity to obtain the sum pattern, and an antiparallel pair of dipoles suspended in a different plane of the same horn cavity to achieve the difference pattern. Pattern measurements of microwave models and on the millimeter-wave antennas show good agreement with theory and exhibit symmetry with a sharp -30-dB null at broadside for the difference antenna. Microwave model measurements show input impedances close to 50 Ω, with greater than -25-dB isolation between sum and difference antennas across a 10% bandwidth     

A DC-contact MEMS shunt switch

This paper presents the design, fabrication, and performance of a metal-to-metal contact micro-electro-mechanical (MEMS) shunt switch. The switch is composed of a fixed-fixed metal beam with two pull-down electrodes and a central DC-contact area. The switch is placed in an in-line configuration in a coplanar waveguide transmission line. This topology results in a compact DC-contact shunt switch and high isolation at 0.1-18 GHz. The isolation at MM-wave frequencies is limited by the inductance to ground and is -20 dB at 18 GHz. The application areas are in wireless communications and high-isolation switching networks for satellite systems