Using the Natural Scenes’ Edges for Assessing Image Quality Blindly and Efficiently

Two real blind/no-reference (NR) image quality assessment (IQA) algorithms in the spatial domain are developed. To measure image quality, the introduced approach uses an unprecedented concept for gathering a set of novel features based on edges of natural scenes. The enhanced sensitivity of the human eye to the information carried by edge and contour of an image supports this claim. The effectiveness of the proposed technique in quantifying image quality has been studied. The gathered features are formed using both Weibull distribution statistics and two sharpness functions to devise two separate NR IQA algorithms. The presented algorithms do not need training on databases of human judgments or even prior knowledge about expected distortions, so they are real NR IQA algorithms. In contrast to the most general no-reference IQA, the model used for this study is generic and has been created in such a way that it is not specified to any particular distortion type. When testing the proposed algorithms on LIVE database, experiments show that they correlate well with subjective opinion scores. They also show that the introduced methods significantly outperform the popular full-reference peak signal-to-noise ratio (PSNR) and the structural similarity (SSIM) methods. Besides they outperform the recently developed NR natural image quality evaluator (NIQE) model

Unsupervised SAR Image Segmentation Based on a Hierarchical TMF Model in the Discrete Wavelet Domain for Sea Area Detection

Unsupervised synthetic aperture radar (SAR) image segmentation is a fundamental preliminary processing step required for sea area detection in military applications. The purpose of this step is to classify large image areas into different segments to assist with identification of the sea area and the ship target within the image. The recently proposed triplet Markov field (TMF) model has been successfully used for segmentation of nonstationary SAR images. This letter presents a hierarchical TMF model in the discrete wavelet domain of unsupervised SAR image segmentation for sea area detection, which we have named the wavelet hierarchical TMF (WHTMF) model. The WHTMF model can precisely capture the global and local image characteristics in the two-pass computation of posterior distribution. The multiscale likelihood and the multiscale energy function are constructed to capture the intrascale and intrascale dependencies in a random field (X,U). To model the SAR data related to radar backscattering sources, the Gaussian distribution is utilized. The effectiveness of the proposed model for SAR image segmentation is evaluated using synthesized and real SAR data

Power Control for Device-to-Device Communication with a Hybrid Relay Mode in Unequal Transmission Slots

Device-to-device (D2D) pairs are allowed to reuse the spectrum of cellular users who are in a good quality channel state with underlaying cellular network. However, cellular users usually suffer a poor performance in term of achievable rate when they are in a cell edge or in deep fading. To solve this problem, a hybrid relay-aided D2D communication scheme with a two-antenna infrastructure and using two unequal transmission slots is proposed in this paper. Different from the pure half-duplex and full-duplex D2D relay work, the hybrid-duplex relay mode that we propose enables the D2D relay to receive and transmit signals at the same time in the first time slot. Thus, it is similar to the full-duplex which could increase the spectrum efficiency. In addition, in the second time slot, the D2D relay will forward only the cellular user’s signals, thus avoiding the transmission of mixed signals which would deteriorate the system performance, similarly to the half-duplex mode. Moreover, by bringing in a slot splitting factor, the relay node in our hybrid-duplex mode is set to guarantee the matching of the transmission rate in two hops. We formulate the problem of maximizing the D2D transmission rate while guaranteeing in priority the minimum rate for the cellular user. By using the method of rate matching and linear programming, we deduce the expression of the slot splitting factor as well as the optimal power allocation for the base station and D2D relay, while guaranteeing the minimum rate requirement for the cellular user in a close form. The simulation results show that the proposed relay-based hybrid-duplex D2D scheme outperforms the existing half-duplex and full-duplex relay-based D2D communication schemes in term of achievable rate

DOA and Polarization Estimation Using an Electromagnetic Vector Sensor Uniform Circular Array Based on the ESPRIT Algorithm

In array signal processing systems, the direction of arrival (DOA) and polarization of signals based on uniform linear or rectangular sensor arrays are generally obtained by rotational invariance techniques (ESPRIT). However, since the ESPRIT algorithm relies on the rotational invariant structure of the received data, it cannot be applied to electromagnetic vector sensor arrays (EVSAs) featuring uniform circular patterns. To overcome this limitation, a fourth-order cumulant-based ESPRIT algorithm is proposed in this paper, for joint estimation of DOA and polarization based on a uniform circular EVSA. The proposed algorithm utilizes the fourth-order cumulant to obtain a virtual extended array of a uniform circular EVSA, from which the pairs of rotation invariant sub-arrays are obtained. The ESPRIT algorithm and parameter pair matching are then utilized to estimate the DOA and polarization of the incident signals. The closed-form parameter estimation algorithm can effectively reduce the computational complexity of the joint estimation, which has been demonstrated by numerical simulations

Analysis of Maneuvering Targets with Complex Motions by Two-Dimensional Product Modified Lv’s Distribution for Quadratic Frequency Modulation Signals

For targets with complex motion, such as ships fluctuating with oceanic waves and high maneuvering airplanes, azimuth echo signals can be modeled as multicomponent quadratic frequency modulation (QFM) signals after migration compensation and phase adjustment. For the QFM signal model, the chirp rate (CR) and the quadratic chirp rate (QCR) are two important physical quantities, which need to be estimated. For multicomponent QFM signals, the cross terms create a challenge for detection, which needs to be addressed. In this paper, by employing a novel multi-scale parametric symmetric self-correlation function (PSSF) and modified scaled Fourier transform (mSFT), an effective parameter estimation algorithm is proposed—referred to as the Two-Dimensional product modified Lv’s distribution (2D-PMLVD)—for QFM signals. The 2D-PMLVD is simple and can be easily implemented by using fast Fourier transform (FFT) and complex multiplication. These measures are analyzed in the paper, including the principle, the cross term, anti-noise performance, and computational complexity. Compared to the other three representative methods, the 2D-PMLVD can achieve better anti-noise performance. The 2D-PMLVD, which is free of searching and has no identifiability problems, is more suitable for multicomponent situations. Through several simulations and analyses, the effectiveness of the proposed estimation algorithm is verified

Defect-regulated charge carrier dynamics in two-dimensional ZnO/MoS2 heterostructure

Van der Waals ZnO/MoS2 heterostructure has been experimentally demonstrated as one of the potential candidates for photocatalyst, however, the charge carrier dynamics upon photoexcitation still remains unclear. By using nonadiabatic molecular dynamics simulations, we mainly focus on the influences of interfacial point defects on photogenerated charge separation in the ZnO/MoS2. The results reveal that oxygen vacancy in ZnO layer can induce a higher hole transfer efficiency compared to the pristine ZnO/MoS2, which attributes to the enhanced nonadiabatic coupling, originating from an out-of-plane vibration mode of S atoms, a decreased energy gap for intralayer hole transfer and stronger energy state oscillation. Alternatively, S vacancy in MoS2 introducing additional energy states in the band gap of ZnO/MoS2, serves as charge carrier recombination channels, and significantly reduces charge carrier lifetime, while doping O atom in S vacancy can compensate this effect. This study provides helpful guidance to design functional devices for solar energy photovoltaic conversion, based on two-dimensional ZnO/MoS2 heterostructures

Polynomial Phase Estimation Based on Adaptive Short-Time Fourier Transform

Polynomial phase signals (PPSs) have numerous applications in many fields including radar, sonar, geophysics, and radio communication systems. Therefore, estimation of PPS coefficients is very important. In this paper, a novel approach for PPS parameters estimation based on adaptive short-time Fourier transform (ASTFT), called the PPS-ASTFT estimator, is proposed. Using the PPS-ASTFT estimator, both one-dimensional and multi-dimensional searches and error propagation problems, which widely exist in PPSs field, are avoided. In the proposed algorithm, the instantaneous frequency (IF) is estimated by S-transform (ST), which can preserve information on signal phase and provide a variable resolution similar to the wavelet transform (WT). The width of the ASTFT analysis window is equal to the local stationary length, which is measured by the instantaneous frequency gradient (IFG). The IFG is calculated by the principal component analysis (PCA), which is robust to the noise. Moreover, to improve estimation accuracy, a refinement strategy is presented to estimate signal parameters. Since the PPS-ASTFT avoids parameter search, the proposed algorithm can be computed in a reasonable amount of time. The estimation performance, computational cost, and implementation of the PPS-ASTFT are also analyzed. The conducted numerical simulations support our theoretical results and demonstrate an excellent statistical performance of the proposed algorithm

Allicin Alleviates Reticuloendotheliosis Virus-Induced Immunosuppression via ERK/Mitogen-Activated Protein Kinase Pathway in Specific Pathogen-Free Chickens

Reticuloendotheliosis virus (REV), a gammaretrovirus in the Retroviridae family, causes an immunosuppressive, oncogenic, and runting–stunting syndrome in multiple avian hosts. Allicin, the main effective component of garlic, has a broad spectrum of pharmacological properties. The hypothesis that allicin could relieve REV-induced immune dysfunction was investigated in vivo and in vitro in the present study. The results showed that dietary allicin supplementation ameliorated REV-induced dysplasia and immune dysfunction in REV-infected chickens. Compared with the control groups, REV infection promoted the expression of inflammatory cytokines including interleukin (IL)-1β, IL-6, IL-10, interferon (IFN)-γ, and tumor necrosis factor-α (TNF-α), whereas, allicin reversed these changes induced by REV infection. The decreased levels of IFN-α, IFN-β, and IL-2 were observed in REV-infected chickens, which were significantly improved by allicin. Allicin suppressed the REV-induced high expression of toll-like receptors (TLRs) as well as melanoma differentiation-associated gene 5 (MDA5) and the activation of mitogen-activated protein kinase (MAPK) and the nuclear factor kappa B p65. REV stimulated the phosphorylation of JNK, ERK, and p38, the downstream key signaling molecules of MAPK pathway, while allicin retarded the augmented phosphorylation level induced by REV infection. The decreased phosphorylation level of ERK was associated with REV replication, suggesting that ERK signaling is involved in REV replication, and allicin can alleviate the REV-induced immune dysfunction by inhibiting the activation of ERK. In addition, REV infection induced oxidative damage in thymus and spleen, whereas allicin treatment significantly decreased the oxidative stress induced by REV infection, suggesting that the antioxidant effect of allicin should be at least partially responsible for the harmful effect of REV infection. In conclusion, the findings suggest that allicin alleviates the inflammation and oxidative damage caused by REV infection and exerts the potential anti-REV effect by blocking the ERK/MAPK pathway