Rectangular Array Research Articles

Computational Investigation on Natural Convection Heat Transfer in Vertical Plate Fin Arrays

Objectives: To perform computational studies on different combinations of plate fin arrays of different shapes for studying their performance in natural convection heat transfer. To compare the heat transfer performance of uniform notched fins with hybrid notched fins and also performance of normal notched fins with inverted notched fins. Methods: SolidWorks Flow Simulation software is used for the present computational studies. Three types of vertical plate fin arrays viz. plain rectangular fin, rectangular fin with square notch and rectangular fin with semi-circular notch are used with their seven combinations. These fin array combinations are: plain rectangular, rectangular square notched, rectangular semi-circular notched, rectangular inverted square notched, rectangular inverted semi-circular notched, hybrid rectangular square-semi-circular notched and hybrid rectangular inverted square-semi-circular notched. Findings: The highest average heat transfer coefficient of 7.82 W/m2K is found to be for inverted hybrid square-semicircular notched fin array. This value of heat transfer coefficient is about 8% higher than compared to that with plain rectangular plate fin array (7.25 W/m2K) subjected to same operating conditions. Average heat transfer coefficients for inverted plate fin array combinations are high as compared with the non-inverted combinations. Also, hybrid plate fin arrays, whether inverted or not, show higher heat transfer coefficient values as compared with uniform notched fin arrays. Novelty : Seven types of plate fin array combinations are studied computationally. SolidWorks Flow Simulation software is used very effectively for this 3D CFD analysis. The behaviour of fluid i.e. air during natural convection flow is studied using air flow velocity trajectories. Surface contours are effectively used for studying variation in surface temperature and heat transfer coefficient at all locations of fin arrays. Keywords Natural convection, plate fin array, heat transfer coefficient, CFD, heat transfer enhancement

Rancang Bangun Antena Mikrostrip Pattch Rectangular Array 4x1 pada Frekuensi 1800 MHz-2300 MHz

4G network is a technology that is currently being developed, known as LTE or 4G. An antenna microstrip for 4G technology is used in this paper. The antenna designed to resonate at a frequency of 1800 MHz-2300 MHz. The antenna design will use FR-4 for its substrate which functions as a dielectric for the antenna. The design is done using the help of CST Studio Suite 2014 software and NI AWR Design Environment v.12 to get the desired antenna characteristics through simulation. From our research we obtained the antenna characteristics such as return loss, VSWR (Voltage Standing Wave Ratio), gain, and bandwidth. In this research, a 4×1 patch rectangular microstrip array antenna has been designed and built that works at a frequency of 2.05 GHz for 4G technology. The antenna design uses the FR-4 for its substrate which functions as a dielectric for the antenna. The design is carried out with the help of CST Studio Suite software to obtain the desired antenna characteristics through simulation. From the research results obtained antenna characteristics such as return loss of -25.225 dB. VSWR (Voltage Standing Wave Ratio) of 1.15, the gain of 3.1 dBi, and bandwidth of 500 MHz with a 4×1 rectangular array antenna design.

Sparsity-based DOA Estimation of 2-D Rectangular Array in the Presence of Gain and Phase Uncertainty

Sparsity-based DOA Estimation of 2-D Rectangular Array in the Presence of Gain and Phase Uncertainty

A modified approach to determine the six cardiac bidomain conductivities

Accurate values for the six cardiac bidomain conductivities are crucial for meaningful computational studies of conduction in cardiac tissue, and are yet to be determined by experimental means. Although previous studies have proposed an approach using a multi-electrode array to measure potentials, from which the conductivities can be determined, it has been found that the conductivities cannot be retrieved consistently when the noise in the potentials varies. This paper presents a protocol, which not only has been shown to retrieve the conductivities to a reasonable accuracy, but does so under the presence of a more appropriate additive Gaussian noise model, while using fewer computational resources. Through repetitions of the protocol, a comparison of two pre-fabricated 128 electrode arrays, one array with a square arrangement of electrodes and the other with a rectangular arrangement, was made against a 75-electrode array proposed in previous studies. Results indicated that the two pre-fabricated arrays were generally more capable of obtaining the cardiac conductivities to a higher degree of accuracy than the 75-electrode array. The 128-electrode rectangular array was orientated such that the length of the array first ran along the direction of the fibres, then was reorientated such that the length of the array ran perpendicular to the direction of the fibres. The 128-electrode rectangular array, when orientated in this manner, was more capable of retrieving the conductivities than the remainder of the arrays tested, and thus we suggest this arrangement be used during experimental trials.

Channel Measurement for Multiple Frequency Bands in Subway Tunnel Scenario

In next-generation radio communication systems, the use of higher frequency bands and the massive multiple-input-multiple-output (MIMO) systems has turned into hot research topics because they have the potential to increase network capacity significantly by exploiting the available narrowband and broadband spectrums. Therefore, the narrowband channel measurements are executed at the following five potential frequency bands, including 2.6 GHz, 3.5 GHz, 5.6 GHz, 10 GHz, and 28 GHz in the Shanghai subway tunnel environment in order to fulfill the latest standards of fifth generation (5G). Moreover, in the broadband channel measurements, the center frequency is 3.5 GHz and 5.6 GHz and the bandwidth is considered as 160 MHz, respectively. At the transmitter (Tx) side, a uniform rectangular antenna array composed of 32 elements is fixed on the platform near the tunnel walls. The receiver (Rx) is equipped with a uniform cylindrical antenna array consisting of 64 elements, which is set on a trolley along the track. Based on the acquired massive MIMO channel impulse responses, delay spread, angle spread, eigenvalue and channel capacity are analyzed. The results reveal that the multipath delay in the tunnel scenario is quite short, the delay spread and angle spread drop rapidly as the distance between Tx and Rx increases and the channel matrix gradually becomes serious. This research provides a reference for the deployment of future 5G systems in the subway tunnel.

A preliminary study on two-dimensional grid-free compressive beamforming for arbitrary planar array geometries.

The two-dimensional (2D) grid-free compressive beamforming based on atomic norm minimization is a promising solution for estimating the source direction-of-arrival and quantifying the source strength. However, the existing method is limited to measuring with rectangular grid arrays. To overcome this limitation, a 2D grid-free compressive beamforming strategy for arbitrary planar array geometries is proposed, where the microphone pressure is transformed into a representation of 2D Fourier series expansion. The term truncation method of Fourier series polynomials is established. The effectiveness and feasibility of the proposed method in the acoustic source identification are preliminarily verified by an experimental case, and topics worthy of further study are discussed based on the numerical simulations.

Focal characteristics of partially coherent rectangular array beams focused by a bifocal lens system

The propagation characteristics of rectangular array beams through a bifocal lens system have been studied, including irradiance distribution and focal shift. By using Collins formula and diffraction integral, the analytical expressions for irradiance distributions of the array beams have been derived. The results show that the irradiance distributions exhibit diversified variations due to the different focal length in two directions, and the changes of the irradiance distributions for the correlated and uncorrelated superposition array beam are different. There are usually two maxima of the axial irradiance on propagation. The focal shifts demonstrate that the axial maximum irradiance near the larger focal distance is displaced toward the lens system when the Fresnel number is smaller. The focal shift results from the competition of the two irradiance maxima, which can lead to a permutation of the focal points. This work would be useful for the practical design and use of the bifocal lens in focusing array beams.

4D Automotive Radar Sensing for Autonomous Vehicles: A Sparsity-Oriented Approach

We propose a high-resolution imaging radar system to enable high-fidelity four-dimensional (4D) sensing for autonomous driving, i.e., range, Doppler, azimuth, and elevation, through a joint sparsity design in frequency spectrum and array configurations. To accommodate a high number of automotive radars operating at the same frequency band while avoiding mutual interference, random sparse step-frequency waveform (RSSFW) is proposed to synthesize a large effective bandwidth to achieve high range resolution profiles. To mitigate high range sidelobes in RSSFW radars, optimal weights are designed to minimize the peak sidelobe level such that targets with a relatively small radar cross section are detectable without introducing high probability of false alarm. We extend the RSSFW concept to multi-input multi-output (MIMO) radar by applying phase codes along slow time to synthesize a two-dimensional (2D) sparse array with hundreds of virtual array elements to enable high-resolution direction finding in both azimuth and elevation. The 2D sparse array acts as a sub-Nyquist sampler of the corresponding uniform rectangular array (URA) with half-wavelength interelement spacing, and the corresponding URA response is recovered by completing a low-rank block Hankel matrix. Consequently, the high sidelobes in the azimuth and elevation spectra are greatly suppressed so that weak targets can be reliably detected. The proposed imaging radar provides point clouds with a resolution comparable to LiDAR but with a much lower cost. Numerical simulations are conducted to demonstrate the performance of the proposed 4D imaging radar system with joint sparsity in frequency spectrum and antenna arrays.

Obtaining Performance Similar to Rectangular Planar Antenna Using Crossed Arrays with Smaller Number of Elements

Conventional rectangular planar arrays with fully filled elements are practically very complicated especially for large arrays. They usually occupy a large space. Thus, any reduction in the space and the number of the array elements is highly desirable in many applications. In this paper, the authors present a novel technique for obtaining a performance similar to that of the conventional rectangular planar antenna using two orthogonal crossed arrays with a smaller number of elements. The proposed technique consists of redesigning the amplitude element excitations of only two crossed arrays using either deterministic or optimization algorithms. Simulation results are shown to prove the proposed idea.

Space-Constrained Arrays for Massive MIMO

We analyse the behavior of a massive multi-user MIMO (MU-MIMO) system comprising a base station (BS) equipped with one of five antenna topologies whose spatial apertures are either unconstrained, or space-constrained. We derive the normalized mean interference (NMI) with a ray-based channel model, as a metric for topology comparison. Using an existing derivation for a horizontal uniform rectangular array (HURA), we provide closed-form NMI equations for a uniform linear array (ULA) and uniform circular array (UCirA). We then derive the same for a vertical URA (VURA) and uniform cylindrical array (UCylA). Results for the often-considered unconstrained case confirm the prior understanding that topologies with wider azimuth footprints aid performance. However, in the constrained case, performance is dictated by the angular resolution of the topology, particularly in elevation. We confirm the behavioral patterns predicted by the NMI by observing the same patterns in the signal-to-interference-and-noise-ratio (SINR) with minimum mean-squared error (MMSE) processing.

Refractive index sensor based on dual side-coupled rectangular resonators and nanorods array for medical applications

Refractive index sensor based on dual side-coupled rectangular resonators and nanorods array for medical applications

Solution of Two-Dimensional Stokes Flow With Elliptical Coordinates and Its Application to Permeability of Porous Media

AbstractIn this paper, analytical developments of the biharmonic equation representing two-dimensional Stokes flow are performed with elliptical coordinates. It is found that the streamfunction is expressed with series expansions based on Gegenbauer polynomials of first and second kinds with order one Cn1 and Dn1 for n natural integer number. Application to an elliptical fiber enclosed in an elliptical boundary with uniform flow is made. It is found that a particular solution responsible of the drag must be added to the general solution. Following this, the flow through rectangular arrays of elliptical fibers is studied, and the permeability of this medium is determined as a function of porosity.

A Partial CSI Estimation Approach for Downlink FDD massive-MIMO System with Different Base Transceiver Station Topologies

Massive multiple-input multiple-output (massive-MIMO) is a promising technology for next generation wireless communications systems due to its capability to increase the data rate and meet the enormous ongoing data traffic explosion. However, in non-reciprocal channels, such as those encountered in frequency division duplex (FDD) systems, channel state information (CSI) estimation using downlink (DL) training sequence is to date very challenging issue, especially when the channel exhibits a shorter coherence time. In particular, the availability of sufficiently accurate CSI at the base transceiver station (BTS) allows an efficient precoding design in the DL transmission to be achieved, and thus, reliable communication systems can be obtained. In order to achieve the aforementioned objectives, this paper presents a feasible DL training sequence design based on a partial CSI estimation approach for an FDD massive-MIMO system with a shorter coherence time. To this end, a threshold-based approach is proposed for a suitable DL pilot selection by exploring the statistical information of the channel covariance matrix. The mean square error of the proposed design is derived, and the achievable sum rate and bit-error-rate for maximum ratio transmitter and regularized zero forcing precoding is investigated over different BTS topologies with uniform linear array and uniform rectangular array. The results show that a feasible performance in the DL FDD massive-MIMO systems can be achieved even when a large number of antenna elements are deployed by the BTS and a shorter coherence time is considered.

Research on illumination uniformity in edible mushrooms incubator with genetic algorithm

The illumination uniformity of incubators used for growing edible mushrooms has an important influence on the accuracy of extracted light formula. To design a light emitting diode (LED) array with uniform illumination, we study the influence of number of LEDs, luminous half angle and the position on the two-dimensional plane by using the genetic algorithm. Numerical results show that the illumination uniformity of optimized LED array can reach up to 97%, which is superior to those of traditional rectangular, elliptical and triangular LED arrays. Finally, simulation results obtained from TracePro software verify that accuracy of numerical calculations.

A Greedy Flee in the Direction Routing Algorithm for Data Quality Control System of 3D Seismic Sensors Array

A rectangular array of seismic nodes is called a 3D seismic sensors array which is suitable for geographic routing. However, when certain seismic nodes have no location information, using detours or other methods to detect the path will increase latency and power consumption of geographic routing. It is challenging to maintain the high performance of geographic routing in practical 3D exploration networks. This letter proposes a greedy flee in the direction routing algorithm (GFDR). According to the feature that the intersection of the connection set of nodes is not empty, GFDR can drive the packet continuously forward in a specified direction without location information when the packet records the node ID of the path. Simulation results show that as the size of the area without location information (AWLI) increases, GFDR can keep the delivery ratio above 98%, while maintaining an approximately constant packet delay without increasing the number of packet-forwarding hops. A real seismic system experiment running GFDR algorithm confirms the simulation results and demonstrates the effectiveness of GFDR.

Hybrid Beamforming for Massive MIMO Using Rectangular Antenna Array Model in 5G Wireless Networks

Fifth and future generation (5G and B5G) wireless networks aim to serve users with higher data rates and lower latency. Data traffic due to the rapid growth in communication has motivated the study of Multiple Input Multiple Output (MIMO) systems. They utilize multiple antennas in both transmitter and receiver sides. It is necessary to improve the existing technology to achieve fast and reliable communication. In this research work, a rectangular array antenna based hybrid beamforming in a massive MIMO model has been proposed to improve the spectral efficiency of the system. Thus channel capacity with small RF chains is used. To achieve the high signal strength in the main lobe, Chebyshev tapering has been used to suppress the side lobes signals. In this manner, the proposed Hybrid Beamforming for Massive Output MIMO has been realized with a small complexity and higher spectral efficiency. In this research work, the spectral efficiency of both proposed Hybrid and fully-digital beamforming with a different number of RF chains for a various number of antennas at the transmitter, the receiver side has been analyzed. From the simulation results, it has been observed that the proposed rectangular array antenna based Hybrid beamforming in a massive MIMO system reduces the computational complexity up to 99% as compared with conventional fully digital beamforming to achieve the same spectral efficiencies, which is a productive model for 5G wireless networks.

Dual-demodulation large-scope high-sensitivity refractive index sensor based on twin-core PCF.

In this paper, a refractive index (RI) sensor based on the twin-core photonic crystal fiber (TC-PCF) is presented. Introducing the rectangular array in the core area makes the PCF possible to obtain high birefringence and low confinement loss over the wavelength range from 0.6 µm to 1.7 µm. Therefore, the core region can enhance the interaction between the core mode and the filling material. We studied theoretically the evolution characteristics of the birefringence and operating wavelength corresponding to the strongest polarization point under the condition of filling the rectangular array with RI matching fluid range from 1.33 to 1.41. Simulation results reveal that the proposed TC-PCF has opposite evolutions of change rates between the B and wavelength, and the maximum RI sensing sensitivities of 1.809×10−2 B/RIU and 8 700 nm/RIU at low and high RI infill are obtained respectively, which means that the TC-PCF features of dual-parameter demodulation for the RI sensing can maintain a high refractive index sensing sensitivity within a large scope of RI ranging from 1.33 to 1.41. Compared with the results of single-parameter demodulation, it is an optimized method to improve the sensitivity of low refractive index sensors, which has great application potency in the field of biochemical sensing and detection.

Ambient seismic noise tomography to build up a 3D shear-wave velocity model

To explore the usefulness of the ambient seismic noise tomography method for characterizing the subsoil surface structure, in this study, we apply this method to contribute to geotechnical decision-making in the construction of a school building. We used a rectangular array (36x56 m) of 48-4.5 Hz vertical geophones and produce surface wave tomographies from the travel times of Rayleigh waves extracted by cross-correlation of seismic noise. We determined a final 3D Vs model using 1D models derived from the inversion of dispersion curves obtained from the tomography maps for different frequencies. The 3D model shows an excellent resolution (vertical and lateral); we observe critical velocity contrasts in the range of 2 to 15 m deep. At depths higher than 15 m, the velocity has values close to 900 m/s; however, we observe a low-velocity anomaly associated with a lava tube or crack that seems to continue under an adjacent building.

Electronic control of the antenna array direction pattern of the vertical atmospheric probing radar station

The article is considered formation and control issues of a small-element antenna array direction pattern of vertical probing radar stations for monitoring the atmosphere. The features of the vertical probing radars functioning and construction with a small-element array are presented. In the article is presented comparative analysis, which based on results of the simulation and on change nature in the direction patterns when the main beam deviates from the vertical for rectangular and annular antenna arrays.

MHD mode identification by higher order singular value decomposition of C-2W Mirnov probe data.

The C-2W device (also known as "Norman") at TAE Technologies has proven successful at generating stable, long-lived field-reversed configuration (FRC) plasmas with record temperatures. The largest Mirnov probe array in C-2W measures three components of the magnetic field just inside the vessel wall at 64 locations distributed approximately evenly in the cylindrical vessel's azimuthal and axial dimensions. This nearly rectangular array of probes creates a unique opportunity to apply higher order singular value decomposition (HOSVD) to efficiently analyze the external magnetic field data for the purposes of reconstructing the magnetohydrodynamic mode structures in the FRC. In the first application of this method for this purpose, HOSVD is shown to quickly and effectively detect and separate toroidal modes while indicating longitudinal dependence of mode phases and amplitudes, enhancing the coherence and utility of the vast quantity of data produced by this array. Analysis of the data from the entire array at once via HOSVD proves not only computationally more efficient than methods that separately analyze groups of probes at different axial locations but also leads to improved mode resolution at axial locations where these modes are weaker.