Compressive sensing based sparse antenna array design for directional modulation

Directional modulation (DM) can be achieved based on uniform linear arrays where the maximum spacing between adjacent antennas is half-wavelength of the frequency of interest in order to avoid spatial aliasing. To exploit the additional degrees of freedom provided in the spatial domain, sparse antenna arrays can be employed for more effective DM. In this study, the spare array design problem in the context of DM is formulated from the viewpoint of compressive sensing (CS), so that it can be solved using standard convex optimisation toolboxes in the CS area. In detail, a common set of active antennas needs to be found for all modulation symbols generating a response close to the desired one. The key to the solution is to realise that group sparsity has to be employed, as a common antenna set cannot be guaranteed if the antenna locations are optimised for each modulation symbol individually. Moreover, two practical scenarios are considered for the proposed design: robust design with model errors and design with practical non-zero-sized antennas, and corresponding solutions are found by modifying the proposed standard solution

Numerical simulation of stress wave interaction in short-delay blasting with a single free surface

It is generally believed that stress wave superposition does occur and plays an important role in cutting blasting with a single free surface, in which explosive columns of several blast holes with short spacing are simultaneously initiated. However, considering the large scatter of pyrotechnic delay detonators that are used in most underground metal mines in China, the existence of stress wave superposition and the influence of this effect on rock fragmentation are questionable. In the present study, the stress wave interaction in short-delay blasting with a single free surface was studied through the use of the LS-DYNA code. Stress waves induced by two blast holes blasting with different delays were compared with the single blast hole case, and the effects of delay time, detonating location and spacing on stress wave superposition were investigated. The numerical results showed that for blast holes with a 1 m spacing, stress wave interaction only occurs when the delay time is 0 ms and does not occur for blasting with delays of more than 1 ms. An increase in the duration of a stress wave via optimizing the detonation location does not improve the stress wave interaction. For a 1 ms delay, stress wave superposition only occurs when the spacing is more than 4 m, which is a rare case in practice. The results indicated that the occurrence of stress wave superposition for blasting with a single free surface is strictly limited to conditions that would be difficult to achieve under the existing delay accuracy of detonators. Therefore, it is unrealistic to improve fragmentation via the stress wave interaction in field blasting. Furthermore, the numerical results of the stress wave interaction also show that there would be a great potential to reduce the hazardous vibrations induced by short-delay blasting by using electronic detonators with better control of delays in an order of several milliseconds

Quaternion-valued single-phase model for three-phase power system

In this work, a quaternion-valued model is proposed in lieu of the Clarke's α, β transformation to convert three-phase quantities to a hypercomplex single-phase signal. The concatenated signal can be used for harmonic distortion detection in three-phase power systems. In particular, the proposed model maps all the harmonic frequencies into frequencies in the quaternion domain, while the Clarke's transformation-based methods will fail to detect the zero sequence voltages. Based on the quaternion-valued model, the Fourier transform, the minimum variance distortionless response (MVDR) algorithm and the multiple signal classification (MUSIC) algorithm are presented as examples to detect harmonic distortion. Simulations are provided to demonstrate the potentials of this new modeling method

A method to separate temperature and precipitation signals encoded in tree-ring widths for the western Tien Shan Mountains, northwest China

Separating temperature and precipitation signals encoded in tree rings is a complicated issue. Here, we present a separation method by combining two tree-ring width chronologies of Schrenk's spruce (Picea schrenkiana) from the upper and lower timberlines in the western Tien Shan Mountains, northwest China. Correlation analyses show that both chronologies correlate positively with precipitation. However, temperature correlates positively with the chronology from the upper timberline, while negatively with the chronology from the lower timberline. This suggests that the two chronologies contain similar precipitation information but opposite temperature signals. In light of this, we calculated the average and difference of the two chronologies, and found that each of them has a much stronger correlation with precipitation or temperature alone. Finally, we reconstructed local precipitation and temperature variations over the past 201 years by using the average and difference of the two chronologies. The two reconstructions do not have a significant correlation, but they have significant positive and negative relationships on the high- and low-frequency band, respectively.postprin

Locked Temporary Vascular Shunt for Wartime Vascular Injuries

IntroductionTo reduce the ischaemia time of injured limbs in wartime, temporary vascular shunts (TVS) are commonly used. However, TVS are stabilized at the ends of the injured vessels using manual suture ties, the risk of dislodgement is high, and tightening manual suture ties is too time consuming.Technical summaryLocked temporary vascular shunts (LTVS) were designed, and each was composed of a silicone tube with a threaded outer surface and smooth inner surface in addition to two nylon buckle switches. The buckle switches were used to stabilize the silicone tube of the LTVS with respect to the vessel walls. This job was performed with two manual suture ties with the current TVS. The mean bursting pressure value of the veins shunted with the LTVS was 114.3% higher than that of the veins shunted with the TVS (0.045 ± 0.008 MPa vs. 0.021 ± 0.012 MPa; p = .00). Although the mean shunting time of the LTVS was reduced by 60.4% compared with that of the TVS (138.89 ± 18.22 seconds vs. 350.48 ± 52.20 seconds; p = .00), there was no significant difference in the patency times between the two types of devices (8.20 ± 9.01 hour vs. 8.40 ± 8.85 hour; p = .98).ConclusionThe LTVS, which was designed to treat wartime vascular injuries, might be safer and more efficient than the current TVS

Climate–growth relationships of Schrenk spruce (Picea schrenkiana) along an altitudinal gradient in the western Tianshan mountains, northwest China

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Molecular cloning and characterization of two genes - PHKG2 and IRAK4 from black-boned sheep (Ovis aries)

The complete coding sequences of two sheep genes-PHKG2 and IRAK4 were amplified using the rapid amplification of cDNA ends (RACE) method based on three sheep expressed sequence tags whose translated amino acids contain the mitochondrial carrier domain. The sequence analyses of these two genes revealed that the sheep PHKG2 gene encodes a protein of 406 amino acids which has high homology with the phosphorylase kinase, gamma 2 protein of five species: Cattle (99%), human (96%), mouse (92%), rat (91%) and chicken (63%). The sheep IRAK4 gene encodes a protein of 456 amino acids which has high homology with the interleukin-1 receptor-associated kinase 4 protein of six species: Cattle (94%), pig (88%), human (87%), mouse (79%), rat (79%) and chicken (54%). The tissue transcription profile analyses indicated that the Black-boned sheep PHKG2 and IRAK4 genes are generally but differentially expressed in the detected tissues including spleen, muscle, skin, kidney, lung, liver, heart, fat and small intestine. These data serve as a foundation for further insight into these two genes.Key words: Black-boned sheep, PHKG2 and IRAK4, tissue transcription profile

Multiple Avalanche Processes in Acoustic Emission Spectroscopy: Multibranching of the Energy−Amplitude Scaling

Several physical processes can conspire to generate avalanches in materials. Such processes include avalanche mechanisms like dislocation movements, friction processes by pinning magnetic domain walls, moving dislocation tangles, hole collapse in porous materials, collisions of ferroelectric and ferroelastic domain boundaries, kinks in interfaces, and many more. Known methods to distinguish between these species which allow the physical identification of multiavalanche processes are reviewed. A new approach where the scaling relationship between the avalanche energies E and amplitudes A is considered is then described. Avalanches with single mechanisms scale experimentally as E = SiAi2. The energy E reflects the duration D of the avalanche and A(t), the temporal amplitude. The scaling prefactor S depends explicitly on the duration of the avalanche and on details of the avalanche profiles. It is reported that S is not a universal constant but assumes different values depending on the avalanche mechanism. If avalanches coincide, they can still show multivalued scaling between E and A with different S-values for each branch. Examples for this multibranching effect in low-Ni 316L stainless steel, 316L stainless steel, polycrystalline Ni, TC21 titanium alloy, and a Fe40Mn40Co10Cr10 high-entropy alloy are shown

Three-Dimensional Wind Profile Prediction with Trinion-Valued Adaptive Algorithms

The problem of three-dimensional (3-D) wind profile prediction is addressed based a trinion wind model, which inherently reckons the coupling of the three perpendicular components of a wind field. The augmented trinion statistics are developed and employed to enhance the prediction performance due to its full exploitation of the second-order statistics. The proposed trinion domain processing can be regarded as a more compact version of the existing quaternion-valued approach, with a lower computational complexity. Simulations based on recorded wind data are provided to demonstrate the effectiveness of the proposed methods

Fractal dynamics analysis of the VHF radiation pulses during initial breakdown process of lightning

Author name used in this publication: Chen, Mingli.Author name used in this publication: Du, Yaping.2009-2010 > Academic research: refereed > Publication in refereed journalVersion of RecordRGCPolyU 512908EPublishe