Lobe Width Research Articles

Singular Value Decomposition-Based Generalized Side Lobe Canceller Beamforming Method for Ultrasound Imaging

In the previous studies, eigenspace-based minimum variance (ESBMV) algorithms were proposed, however, the quality of the algorithm will degrade in low signal to noise occasions. In this study, a singular value decomposition generalized side lobe canceller (SVD-GSC) beamforming method based on the GSC is proposed. The sample covariance matrix is eigendecomposed, and a kind of further SVD is introduced to establish the noise space and the signal space, respectively. After that, the weighting vectors acquired by GSC are projected into the left singular space of the desired signal space. The performance of the proposed method is investigated by both of the simulation and experimental data. And the sound velocity error is also investigated in this paper. The imaging quality of point targets are measured by the [Formula: see text][Formula: see text]dB main lobe width and the peak side lobe (PSL). The contrast ratio (CR) is introduced to describe the quality of cyst phantom. Both the point targets and cyst phantom simulation show that the proposed SVD-GSC performs better in terms of spatial resolution, PSL and CR. Furthermore, the proposed method has a stronger robustness than the traditional GSC.

Two new species of feather mites (Acarina: Psoroptidia) from the Oriental Magpie-Robin, Copsychus saularis (Passeriformes: Muscicapidae)

Two new feather mite species from the bird host Copsychus saularis (Linnaeus) collected in Indonesia (Kalimantan) are described: Dolichodectes latilobus n. sp. (Proctophyllodidae, Pterodectinae), and Trouessartia saularis n. sp. (Trouessartiidae). The new species, Dolichodectes latilobus, has the following distinctive characters: in males, the opisthosomal lobes are widened in the posterior half; the opisthoventral shields are fused, forming a single shield that covers ventrally the posterior quarter of the body; legs I have longitudinal crest-like processes ; and setae ra on these legs are spiculiform. In females of D. latilobus, the posterior margin of the hysteronotal shield has a deep median invagination, and epimerites II extend to the level of the anterior margin of epigynum. The males of T. saularis have the adanal apodemes with two narrow lateral membranes, and the females have the terminal cleft width smaller than the opisthosomal lobe width, and the collar of the spermatheca cover 1/2 from the length of secondary spermaduct.

An Improved Adaptive Received Beamforming for Nested Frequency Offset and Nested Array FDA-MIMO Radar.

For the conventional FDA-MIMO (frequency diversity array multiple-input-multiple-output) Radar with uniform frequency offset and uniform linear array, the DOFs (degrees of freedom) of the adaptive beamformer are limited by the number of elements. A better performance—for example, a better suppression for strong interferences and a more desirable trade-off between the main lobe and side lobe—can be achieved with a greater number of DOFs. In order to obtain larger DOFs, this paper researches the signal model of the FDA-MIMO Radar with nested frequency offset and nested array, then proposes an improved adaptive beamforming method that uses the augmented matrix instead of the covariance matrix to calculate the optimum weight vectors and can be used to improve the output performances of FDA-MIMO Radar with the same element number or reduce the element number while maintain the approximate output performances such as the received beampattern, the main lobe width, side lobe depths and the output SINR (signal-to-interference-noise ratio). The effectiveness of the proposed scheme is verified by simulations.

A novel ultra‐wideband antipodal Vivaldi antenna with trapezoidal dielectric substrate

AbstractAn ultra‐wideband Vivaldi antenna is designed in this article, its frequency band is 3.3–40 GHz. Based on the traditional antipodal Vivaldi antenna, a trapezoidal dielectric substrate is loaded in the direction of major axis, which not only eliminates the antenna gain peak shifting problem, but also improves the directional radiation performance. The dimension of the antenna is 57.5 mm × 60.7 mm. The substrate of the antenna is Rogers RO4003C with relative dielectric constant (ɛr) of 3.38, loss tangent of 0.0027, and thickness of 0.508 mm. The simulation and measured results show that bandwidth of the antenna is 3.3–40 GHz, and it also has many advantages such as good radiation direction, high gain, narrow main lobe width, and low cross‐polarization ratio.

Multicarrier SAR Image Reconstruction Using Integrated MUSIC-LSE Algorithm

In synthetic aperture radar (SAR) applications, high-resolution images and effective estimation processes are vital for the reconstruction of any targets. This can be achieved by using multicarrier waveforms such as orthogonal frequency division multiplexing (OFDM) with the help of appropriate signal processing algorithms. However, the quality of the reconstructed image degrades in low signal-to-noise ratio (SNR) environments during SAR data acquisition. In this paper, an integrated multiple signal classification (MUSIC) assisted least square estimation (LSE) algorithm (MUSIC-LSE) is proposed to enhance the quality of the reconstructed SAR image in a low-SNR environment. Simulation results measured and evaluated the quality of the reconstructed image using three performance indicators of root-mean-square-error, main lobe width and cumulative side lobe levels. These indicators are also used to investigate the effect of OFDM subcarrier selection on the reconstructed image for a different number of subcarriers. Experimental validation of the approach is carried out using two steel pipes to image and detect the curvature of the steel pipes. The results show that the proposed MUSIC-LSE approach produces better-reconstructed images compared with the existing linear frequency modulated (LFM) chirp and OFDM-LSE approaches in low-SNR (−10 dB) environments and enables the radar to distinguish and detect the curvature of the pipes even below the radar range and cross-range resolution.

Blueprint for Large-Scale Silicon Optical Phased Array Using Electro-Optical Micro-Ring Pixels

We propose a modularized architecture of a large-scale optical phased array (OPA) on a silicon on insulator (SOI) platform, using electro-optical (EO) pixels. Each pixel contains a directional coupler, a micro-ring phase shifter, and a grating optical antenna, on a compact configuration of area 50 μm × 50 μm, with optical and electrical interconnections. Moreover, we present an exemplary blueprint of an OPA consisting of 32 × 32 EO pixels, which sets the width of the main lobe as 0.04° × 0.04° and the field of view as 1.78°. By applying an over-coupled condition, the modulation efficiency and the accompanying intensity modulation are balanced, thus, the OPA performance is not severely degraded. The discussion on the fabrication tolerance shows that the proposed architecture is robust and feasible regarding the state-of-the-art fabrication process, and the performance of the main lobe width and field of view can be further optimized by a larger system size and smaller pixel size. Furthermore, the complexity of interconnections linearly depends on the number of rows and columns, making it highly scalable.

Actual deviation correction based on weight improvement for 10-unit Dolph–Chebyshev array antennas

In order to achieve higher gains and lower side lobe in antenna design, array antenna is conventionally adopted. Besides, Chebyshev polynomial amplitude ratio is widely employed in the design, and it optimizes the main and side lobes under specific main lobe width and side lobe level. However, the actual product can be easily affected by machining error and the antenna material property, which change along with the frequency. The influence is evident at millimeter waves level owing to the short wave length. In micro-strip antenna applications, the test frequency for key parameters of high-frequency base material is limited by 10 GHz, while the parameters have no explicit definition at higher frequency. Therefore, a large mismatch between the design and actual product may exist when the frequency reaches 77 GHz or higher. In this paper, a weighting method is proposed to compensate parameters of the base material and machining error. Based on this method, simulation result of the design is revised to match tested result of actual product.

Printing anisotropic appearance with magnetic flakes

The ability to fabricate surfaces with fine control over bidirectional reflectance (BRDF) is a long-standing goal in appearance research, with applications in product design and manufacturing. We propose a technique that embeds magnetic flakes in a photo-cured resin, allowing the orientation distribution of those flakes to be controlled at printing time using a magnetic field. We show that time-varying magnetic fields allow us to control off-specular lobe direction, anisotropy, and lobe width, while using multiple spatial masks displayed by a UV projector allows for spatial variation. We demonstrate optical effects including bump maps: fat surfaces with spatially-varying specular lobe direction.

Investigation of Non-linear Chirp Coding for Improved Second Harmonic Pulse Compression

Non-linear frequency-modulated (NLFM) chirp coding was investigated to improve the pulse compression of the second harmonic chirp signal by reducing the range side lobe level. The problem of spectral overlap between the fundamental component and second harmonic component (SHC) was also investigated. Therefore, two methods were proposed: method I for the non-overlap condition and method II with the pulse inversion technique for the overlap harmonic condition. In both methods, the performance of the NLFM chirp was compared with that of the reference LFM chirp signals. Experiments were performed using a 2.25 MHz transducer mounted coaxially at a distance of 5 cm with a 1 mm hydrophone in a water tank, and the peak negative pressure of 300 kPa was set at the receiver. Both simulations and experimental results revealed that the peak side lobe level (PSL) of the compressed SHC of the NLFM chirp was improved by at least 13 dB in method I and 5 dB in method II when compared with the PSL of LFM chirps. Similarly, the integrated side lobe level (ISL) of the compressed SHC of the NLFM chirp was improved by at least 8 dB when compared with the ISL of LFM chirps. In both methods, the axial main lobe width of the compressed NLFM chirp was comparable to that of the LFM signals. The signal-to-noise ratio of the SHC of NLFM was improved by as much as 0.8 dB, when compared with the SHC of the LFM signal having the same energy level. The results also revealed the robustness of the NLFM chirp under a frequency-dependent attenuation of 0.5 dB/cm·MHz up to a penetration depth of 5 cm and a Doppler shift up to 12 kHz.

Curvas de crescimento de plantas de mandioca submetidas a doses de potássio

Potassium is considered nutrient extracted over cassava. Thus, its low availability in the soil affects plant growth, reflecting the expansion of cultivated area and productivity of crops potassium deficient. The objective of this present work was to establish growth curves of plants cassava cultivar Aciolina submitted to five doses of potassium, grown in Roraima savannah environment. The experimental design was in blocks at random in scheme of split plots, with four replications. Five doses of potassium (0, 30, 60, 120 and 240 kg ha-1 K2O) were randomized in the plots and evaluation times (150, 210, 270 and 360 days after planting - DAP) in the subplots. The variables evaluated: stem diameter, height of first ramification, plant height and leaf characteristics. The height growth of cv. Aciolina occurred at all levels of fertilization with potash, indicating that the low content of K restricts the growth of the plant height. The components of growth of the cassava plant, stem diameter, height of the first ramification and plant height are positively affected by increasing doses of potassium up to 240 kg ha-1. The width of the sheet, the number of lobes and the relationship between the length of the central lobe width of the central lobe are not affected by the potassium.

A study of the properties of twin radio arms of FR-II extragalactic radio sources within z ≤ 1 $z\le1$

We carried out a comparative analysis on the properties the two arms (the longer arm and the shorter arm) on a sample of 98 FR-II radio galaxies comprising of 15 quasars, 11 broad-line radio galaxies, 57 narrow line radio galaxies and 15 low excitation radio galaxies within $z\le1$ . Our result indicates that in general, the arm lengths (lobe linear sizes) and luminosity, jets (lengths and luminosities), hotspots (sizes and luminosities), of the longer arm are larger than those of the shorter arm, while the lobe width and polarization of the shorter arm are larger than those of the longer arm. The differences are more in quasars, broad-line radio galaxies than in the narrow-line radio galaxies and low excitation radio galaxies. Our result generally indicates that beaming plays a role in the structure of more powerful radio sources while environmental factors seems more important in the structure and dynamics of the less powerful radio sources.

2-D Ultrasound Sparse Arrays Multidepth Radiation Optimization Using Simulated Annealing and Spiral-Array Inspired Energy Functions.

Full matrix arrays are excellent tools for 3-D ultrasound imaging, but the required number of active elements is too high to be individually controlled by an equal number of scanner channels. The number of active elements is significantly reduced by the sparse array techniques, but the position of the remaining elements must be carefully optimized. This issue is faced here by introducing novel energy functions in the simulated annealing (SA) algorithm. At each iteration step of the optimization process, one element is freely translated and the associated radiated pattern is simulated. To control the pressure field behavior at multiple depths, three energy functions inspired by the pressure field radiated by a Blackman-tapered spiral array are introduced. Such energy functions aim at limiting the main lobe width while lowering the side lobe and grating lobe levels at multiple depths. Numerical optimization results illustrate the influence of the number of iterations, pressure measurement points, and depths, as well as the influence of the energy function definition on the optimized layout. It is also shown that performance close to or even better than the one provided by a spiral array, here assumed as reference, may be obtained. The finite-time convergence properties of SA allow the duration of the optimization process to be set in advance.

Strong direct path interference suppression based on spatial filtering

Strong direct path interference suppression is one of the problems to be solved in AUVs' cluster system which has the advantages of concealment, precision, anti-jamming capability and function distance. In order to estimate the target direction，3 methods of beamforming，including covariance matrix taper(CMT) condition，null-constrained condition and second-order cone programing(SOCP) constraint condition, are used to restrain direct path interference suppression separately in this paper. Comparing the 3 methods with simulation, SOCP gives the weights taking main lobe response, sidelobe level, depth, and width of zeros into consideration; null-constrained condition has a smaller amount of calculate and better anti-interference ability. But when the array disturbance exists, all the methods' performances are not good. Then, an improved algorithm is proposed to improve the tolerance of array disturbances.

English

This study was conducted to evaluate the growth and yield stability of cassava mosaic disease (CMD) resistant breeding populations clones against early drought. Field trials were planted using 200 CMD resistant clones and 7 local landraces in a randomised complete block design with 3 replicates at the International Institute of Tropical Agriculture (IITA) station, Sendusu in Namulonge (Central Uganda) during the second rains of 2006 (2006B) and the first rains of 2007 (2007A). The 2007A crop suffered from drought stress in the first 4 months after planting (MAP). Data were taken on the leaf lobe length and width at 6 MAP and plant height at 12 MAP. Harvest was done at 12 MAP during which the number of storage roots per plant and storage root yield were recorded. Data were analysed using the Mann-Whitney U test to compare crop performance between the 2 seasons. The 2006B crop had significantly (P<0.01) longer leaf lobes, taller plant heights, higher number of storage roots per plant and higher storage root yield than the 2007A crop. There was no significant difference in the leaf lobe width. In this experiment, it was observed that the CMD resistant breeding clones were susceptible to early drought and thus it was recommended that selections should be done for higher water use efficiency. Key words: Abscisic acid, Manihot esculenta Crantz, Stomatal conductance, water use efficiency, Uganda.

Rhizocorallium hamatum (Fischer-Ooster 1858), a Zoophycos-like trace fossil from deep-sea Cretaceous-Neogene sediments

Rhizocorallium hamatum (Fischer-Ooster 1858) is a trace fossil of the Zoophycos group, which is distinguished by its mostly horizontal, branched spreite lobes. It has so far, been ascribed mainly to Zoophycos, but the latter should be limited to forms having helical whorls, which are absent in R. hamatum. It has also been ascribed to Phycosiphon, which, however, shows J-shaped spreite lobes, while the lobes of R. hamatum are U-shaped. R. hamatum is very similar to R. commune var. irregulare, but the latter displays a distinctly wider marginal tunnel with respect to lobe width. R. hamatum occurs from the Turonian to Eocene, possibly from the Hauterivian to Oligocene, but mostly from Maastrichtian to Palaeocene, deep sea, mainly turbiditic sediments rich in marl. The tracemaker, probably a ‘worm’-like invertebrate, ingested an organic-rich mud of the background sediment and relocated it into the middle to deep tiers within the underlying turbiditic marl, mostly in form of faecal pellets packed within the spreite lobes, for further use as a food resource. This way of feeding was a response to food deficiency on the deep-sea floor.

An analytical filter design method for guided wave phased arrays

This paper presents an analytical method for designing a spatial filter that processes the data from an array of two-dimensional guided wave transducers. An inverse problem is defined where the spatial filter coefficients are determined in such a way that a prescribed beam shape, i.e., a desired array output is best approximated in the least-squares sense. Taking advantage of the 2π-periodicity of the generated wave field, Fourier-series representation is used to derive closed-form expressions for the constituting matrix elements. Special cases in which the desired array output is an ideal delta function and a gate function are considered in a more explicit way. Numerical simulations are performed to examine the performance of the filters designed by the proposed method. It is shown that the proposed filters can significantly improve the beam quality in general. Most notable is that the proposed method does not compromise between the main lobe width and the sidelobe levels; i.e. a narrow main lobe and low sidelobes are simultaneously achieved. It is also shown that the proposed filter can compensate the effects of nonuniform directivity and sensitivity of array elements by explicitly taking these into account in the formulation. From an example of detecting two separate targets, how much the angular resolution can be improved as compared to the conventional delay-and-sum filter is quantitatively illustrated. Lamb wave based imaging of localized defects in an elastic plate using a circular array is also presented as an example of practical applications.

Piecewise LFM waveform for MIMO radar

To separate the received signals in a multiple-input multiple-output (MIMO) radar, the transmitted signals should be orthogonal or have a low cross-correlation level. Some other properties, such as low autocorrelation sidelobes, high range resolution, and good Doppler tolerance are also desired. However, they are difficult to achieve simultaneously. In general, an improved criterion is at the cost of another degraded one. In this paper, we propose a piecewise linear frequency modulation (PLFM) waveform for the MIMO radar. The transmitted signals are pulse trains, including diversified subpulses, which are divided into three segments with controllable durations and bandwidths. The duration sequence of the second segment is obtained by the genetic algorithm to optimize the cross correlation. Theoretical analyses and numerical results are presented to illustrate the properties of the proposed PLFM waveform. Compared with the polyphase coding and the discrete frequency coding waveforms, the PLFM waveform has a lower cross-correlation level and higher degrees of freedom. The relationship of the bandwidths among different segments can be used to adjust the sidelobe peak and the main lobe width of the autocorrelation function.

Synthetic transmit aperture focusing using optimal sparse receive array for reducing computational complexity

Synthetic transmit aperture focusing (STAF) has the problem of high computational complexity. An STAF scheme with greatly reduced computational complexity by using an optimal periodic sparse receive array (SRA) is proposed. An analytic method to design optimal SRAs that provide minimum main lobe width and grating lobe levels for a given number of active receive elements is also suggested. The experiment results show that the proposed STAF method can reduce computational complexity by up to 66.67% compared with conventional STAF.

Phaeophyscia esslingeri sp. nov. (Physciaceae, lichen-forming Ascomycota) – a new lichen species from Eastern Asia, with a world-wide key to the hairy species of the genus

Phaeophyscia esslingeri, a new species for science, is described from South Korea, Eastern Asia, compared with closely related taxa and illustrated with photographs. It is similar to Phaeophyscia hirtella, but diff ers by larger and light grey thallus, wider lobes, apothecia without a corona of dark rhizines around the base, shorter cortical hairs, and wider ascospores. Status of the hairy taxa of the genus Phaeophyscia from Eastern Asia is discussed. A world-wide key to hairy species of the genus Phaeophyscia is also included.

A new feather mite of the genus Trouessartia Canestrini 1899 (Acariformes: Trouessartiidae) from the Seychelles magpie-robin, Copsychus sechellarum (Passeriformes: Muscicapidae).

A new feather mite species, Trouessartia sechellarum sp. n. (Astigmata: Analgoidea: Trouessartiidae), is described from the Seychelles magpie-robin Copsychus sechellarum (Passeriformes: Muscicapidae), an endangered endemic passerine bird inhabiting the Seychelles Islands. The most clear features distinguishing this mite from the related species, T. microfolia Gaud, 1952, are as follows: in both sexes, setae c2 do not exceed 30 μm and are subequal in length to setae c3 and sRIII; in males, the hysteronotal shield is completely split into the prohysteronotal and lobar parts by a narrow groove, and the terminal lamellae are attenuate apically; in females, the median part of the hysteronotal shield bears numerous ovate lacunae, the terminal cleft width is approximately equal to the opisthosomal lobe width, and the collar of the spermathecal head is smooth.