Deep-Learning Based DOA Estimation in the Presence of Multiplicative Noise

Wireless Personal Communications - The paper addresses the narrowband direction of arrival estimation problem in the presence of multiplicative noise, namely, the local scatterers affect the...     

Oncogenic RAS genes impair erythroid differentiation of erythroleukaemia cells

RAS mutations occur frequently in acute myeloid leukaemia and myelodysplasia, suggesting a functional role for this oncogene in leukaemogenesis. We show here, for the first time, that both N-RAS and H-RAS can impair erythroid differentiation of erythroleukaemia cells induced with hexamethylene bisacetamide. Transformation by RAS allowed extended proliferation in the presence of inducer and also inhibited maturation as measured by impaired haemoglobinization and reduction in cell size. These data provide an interesting counterpoint to the effect of mutant RAS on monocytic cells, where it has a potentiating effect on differentiation and may indicate a causal link between the activation of RAS and erythroid lineage dysplasia in preleukaemia.     

Wideband radar cross section reduction using a novel design of artificial magnetic conductor structure with a triple‐layer chessboard configuration

A novel wideband three‐layer chessboard‐like structure is proposed to reduce the radar cross section (RCS) of the radar target. This configuration is composed of two artificial magnetic conductor (AMC) cells formed by two crossed ellipses with different sizes in two cells. A desired 180° ± 37° phase difference is achieved by combining these unit cells and the measured 10 dB RCS‐reduction bandwidth is extensively broadened to more than 96% (from 8.11 to 23.32 GHz, covering X, Ku, and K bands for different radars) in comparison with the other works. This characteristic is obtained by carefully adjusting the positions of all resonances using the proper sizes for the ellipses and the proper dielectric constants and thicknesses for the three layers. Although, the proposed design has three layers with the overall thickness of 2 mm, it is still thinner than most of the recent related works. This low‐profile structure is also cost‐effective due to the fact that 60% of the overall thickness is formed by an air substrate. The proposed cells are designed, simulated, and fabricated in a chessboard‐like configuration for both monostatic and bistatic RCSs. Simulations and measurements are in a good agreement, which shows the capabilities of the design.     

Chemicals from heavy oils by ZSM-5 catalysis in supercritical water: Model compound and reaction engineering

Dodecane cracking and aromatization over ZSM-5 was studied in the presence and absence of supercritical water (SCW). A group-type model was used to determine five best-fit rate constants to describe yields to aliphatics, aromatics, coke, and gases. SCW accelerated gas formation while suppressing coke formation. CO and CO₂ were formed in the presence of SCW, but not in its absence; a new, low-temperature coke gasification pathway was suggested to account for this observation. Similarly, a low-temperature alkane reforming pathway was hypothesized to explain the increased relative rate constant for production of gases in the presence of SCW compared with its absence. Additional tests and analysis indicated that these effects could not be ascribed solely to zeolite degradation in the presence of SCW, implying that water directly influences the reaction mechanism. These results provide new insights into the role(s) of water during oil cracking under supercritical conditions.     

Full-wave simulation,design and implementation of a new combination of antenna array feed network integrated in low profile microstrip technology

In this paper, a new modified combination of antenna and array feed network integrated in low thickness microstrip technology is presented. A concept similar to the concept of coherently radiating periodic structures is used to feed a 4-element antenna array. In the feed network, a new combination of Gysel-based 3 and 5 port components as power dividers/combiners is employed to propagate the power into the antenna array so that the desired Gaussian-like amplitudes and linear phase distributions can be obtained. These multi-port components are modified to design the feed network by single-layer microstrip technology without the matching and isolation circuits and through-substrate vias. Therefore, the manufacturing cost and difficulty and design complexity are reduced, considerably. Full-wave simulations of the feed network, unit cells and the final integrated antenna array are done, step by step and the results considering all possible losses are presented. To validate the designs, two prototypes, first the feed network and second the integrated module including both antenna array and feed network designed at 3.5 GHz were fabricated and measured and the S parameters (amplitude and phase) were compared with the full-wave simulations. A good agreement between the results including impedance and radiation characteristics is shown.     

The effect of design drift limit on the seismic performance of RC dual high‐rise buildings

Current building codes aim to ensure the acceptable performance of structures implicitly. Because these provisions are empirically developed for low‐ to medium‐rise buildings, their applicability to high‐rise building warrants further investigation. In this paper, the effect of design drift limit on the seismic performance of reinforced concrete dual high‐rise buildings is considered. Nine buildings are designed for 3 drift limits: the code limit (i.e., 2%), one that is lower than the code limit (i.e., 1.5%), and one that is higher than the code limit (i.e., 3%). For each drift limit, buildings of 3 heights (20, 25, and 30 stories) are designed. Finite element models are constructed in OpenSees, and incremental dynamic analysis is performed. The results are used to develop probabilistic seismic demand models, where model parameters are determined using maximum likelihood estimation to incorporate equality and censored data. Reliability analysis using probabilistic demand models is conducted to derive seismic fragility and demand hazard curves. In addition, the collapse performance of the drift limits is evaluated using the Federal Emergency Management Agency (FEMA) P695 procedure. The study results show that the design drift limit affects the building's seismic performance, and the effect depends on the performance level considered. Moreover, from a structural integrity perspective, a larger design drift limit does not induce a significantly higher risk and might yield a more cost‐effective design.     

A microstrip folded compact wideband band-pass filter with wide upper stopband

A miniaturized wideband band-pass filter with a 3-dB fractional bandwidth of 109.3% (1.53 GHz to 5.22 GHz), high out-of-band attenuation greater than 25 dB, and wide upper stopband up to 14 GHz is proposed. The design consists of a dual-composite right/left handed resonator, embedded open-circuited stub, and a pair of quarter-wavelength short-circuited stubs. These elements are coupled in the near distance to form a miniature filter with a compact occupied area of 0.21 λ _g × 0.19 λ _g (≈ 0.013 cm²). The optimized filter has multi-transmission poles in the passband, substantially improving the return loss and insertion loss characteristics. The behavior of the passband and stopband is verified against the results of a lumped element model and matrix analysis with a full-wave moment-based analysis and actual measurements. The results of this verification and a comparison with the performance of filters in other references indicate that the proposed filter is very efficient and applicable to compact microwave systems.     

Double triangular monopole‐like antenna with reconfigurable single/dual‐wideband circular polarization

A polarization and frequency reconfigurable circularly polarized (CP) antenna is proposed based on a novel bilateral switching mechanism. Two triangular monopole antennas are connected to each other in an L‐shaped form by a narrow link to produce a CP operation. In the proposed technique, 4 PIN‐diode‐based switches are designed with desired insertion loss and isolation, and only 2 DC‐voltage controllers. These switches are located on the links and the feed lines to realize a polarization reconfigurable feature including both right‐hand CP (RHCP) and left‐hand CP (LHCP) modes. Moreover, 2 CP states, a single wideband operation and a dual‐band operation, can be supported by this mechanism. In a special performance of the switches, CP reconfigurability can be obtained in a narrow‐band mode around 2.45 GHz. Two general simulations are performed based on the simple microstrip links and a diode‐circuit model. The measured results exhibit a wide overlapped bandwidth (AR < 3 dB and VSWR < 2) of 44.4% (1.63–2.56 GHz) with a peak gain of 2.88 dBi in the first state and 5.5% (1.22～1.29GHz) and 20.6% (2.12–2.61 GHz) with the peak gains of 0.52 and 3.0 dBi in the second state, respectively. A wide beamwidth is obtained more than 75°. This work is appropriate for L‐ and S‐band CP diversity applications.     

A robust method for the computation of new closed‐form Green's functions for microstrip structures

A robust approach for the computation of new closed‐form Green's functions is considered to calculate the symmetrical microstrip Green's functions. In this method, the surface‐wave poles are first extracted using a recursive contour integration method. Then, the remainder is approximated by a series of complex exponentials using the Prony's method or the generalized pencil‐of‐function method (GPOF) along the extended rooftop shaped path in k_ρ‐plane. Subsequently, an analytical identity is employed to obtain the new spatial‐domain Green's functions. It is observed that this method can evaluate the spatial‐domain Green's functions accurately and efficiently for both near and far fields. In addition, there is no erroneous results in the near‐field region when z ≠ z′ and ρ → 0. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.