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We propose a framework based on the use of a set of beampattern shaping constraints. The proposed beamformer possesses not only adaptive interference-rejection ability and robustness against large steering direction errors, but also direct sidelobe control. It contains a new weighing ratio that can automatically control the relative proportions of interference-rejection and sidelobe suppression in different scenarios, without ambiguity. Unlike other beamformers, the proposed beamformer is robust against strong moving interferences, requiring only a coarse estimation of their directions-of-arrival. The generic framework encompasses different optimization strategies for specific application problems. Index Terms--Adaptive arrays, array signal processing, robustness.

The magnetic properties of Nd[sub 60-x]Y[sub x]Fe[sub 30]Al[sub 10] (x = 0, 10, 30) melt-spun ribbons were studied. The ribbons contain two amorphous magnetic phases characterized by their Curie temperature T[sub C1] and T[sub C2]. The Y atoms may be unevenly distributed in the two magnetic phases. The Y atoms prefer to substitute Nd in the low T[sub C1] phase. Thermo-history effects are found in the thermomagnetic curves for field-cooled and zero-field-cooled samples. The bifurcation temperature T[sub b] decreases with Y addition, suggesting a decrease of the anisotropy energy and the coercivity. The room-temperature coercivity and remanence ratio also strongly decrease with Y addition. The apparent coercivity μ[sub 0]H[sub C] for x = 0 first increases with decreasing temperature, reaching a maximum at about 60 K, near the Curie temperature of the T[sub C1] phase, then strongly decreases in the two-magnetic phase region. The coercivity mechanism is assumed as domain-wall pinning effect. [ABSTRACT FROM AUTHOR]

The amorphous alloys Nd[sub 40]Fe[sub 40]Co[sub 5]Al[sub 8]B[sub 7], Nd[sub 57]Fe[sub 20]Co[sub 5]Al[sub 10]B[sub 8], and Nd[sub 57]Fe[sub 20]Cu[sub 5]Al[sub 10]B[sub 8] were prepared by copper mold casting, melt spinning, and mechanical alloying. Despite their similar x-ray diffraction patterns, samples display different magnetic and thermal behavior correlated with the method of preparation. The fully amorphous melt-spun ribbons exhibit relatively soft magnetic properties with coercivities approx. 40 kA/m at room temperature and a Curie temperature (T[sub C])approx. 474 K. Apparently only the mold-cast cylinders of 3 mm diameter show hard magnetic behavior with a coercivity in the range of 258–270 kA/m (depending on composition) and have approximately the same T[sub C] as that of the melt-spun ribbons. An additional magnetic transition at 585 K due to the presence of Nd[sub 2]Fe[sub 14]B phase in the case of Nd[sub 40]Fe[sub 40]Co[sub 5]Al[sub 8]B[sub 7] cast rod has been observed. Heat treatment above crystallization temperature in as-cast Nd[sub 57]Fe[sub 20]Co[sub 5]Al[sub 10]B[sub 8] and Nd[sub 57]Fe[sub 20]Cu[sub 5]Al[sub 10]B[sub 8] samples destroys the hard magnetic properties. In contrast, mechanically alloyed amorphous samples are soft magnetic with maximum coercivity up to 11 kA/m but show an entirely different T[sub C]approx. 680–740 K, which is rather characteristic of an Fe solid solution. The magnetic properties are discussed in terms of different local atomic environment and cluster sizes in amorphous samples prepared by different methods. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Network structure determination is an important issue in pattern classification based on a probabilistic neural network. In this study, a supervised network structure determination algorithm is proposed. The proposed algorithm consists of two parts and runs in an iterative way. The first part identifies an appropriate smoothing parameter using a genetic algorithm, while the second part determines suitable pattern layer neurons using a forward regression orthogonal algorithm. The proposed algorithm is capable of offering a fairly small network structure with satisfactory classification accuracy. Index Terms--Genetic algorithms, orthogonal algorithm, pattern classification, probabilistic neural network (PNN).

A closed-form conditional probability density function (pdf) of the Nakagami-faded-interference-to-signal power ratio, given the exact location of the tagged mobile, is derived for integer values of Nakagami fade parameter m. The conditional pdf, whose coefficients can be computed efficiently in a recursive manner, significantly reduces the computational complexity of forward-link bit error rate (BER) evaluation of a direct-sequence code-division multiple-access (DS-CDMA) cellular system over a fading channel. BER curves reveal that the performance improvement of increasing m is not significant for m [is greater than] 4. Performance results for noninteger values of m can be estimated using the linear interpolation technique. With the derived BER expressions, a more realistic cellular model that takes into account the effects of nonidentical m and path-loss exponent is proposed and analyzed. By substituting appropriate values of m, the BER performance for a class of fading distributions such as Rayleigh and Ricean fading can he evaluated or approximated. In particular, Nakagami approximation may be treated as a tight lower bound to the corresponding mathematically involved Ricean case. Index Terms--Combined PDF approach, DS-CDMA, Nakagami fading channels, performance analysis.

We report a real-time method to determine the size, i.e. diameter, and refractive index of single gold nanoparticles using an optofluidic chip, which consists of a quasi-Bessel beam optical chromatography. The tightly focused (~ 0.5 μm) quasi-Bessel beam with low divergence (NA ~ 0.04) was used to trap sub-100 nm gold nanoparticles within a long trapping distance of 140 μm. In the experiment, 60 to 100 nm gold nanoparticles were separated efficiently with at least 18 μm. The diameter and refractive index (real and imaginary) of single gold nanoparticles were measured at high resolutions with respect to the trapping distance, i.e. 0.36 nm/μm, 0.003/μm and 0.0016/μm, respectively. [ABSTRACT FROM AUTHOR]