Incomplete Cancellation Research Articles

Analysis of Optimal Diversity Combining with Imperfect Channel State Information for Cooperative Jamming-Aided Internet of Things Security

Cooperative jamming (CJ) combined with single-input multiple-output (SIMO) technology can effectively improve the security and reliability of Internet of Things (IoT) systems. However, imperfect main channel state information (CSI) leads to incomplete CJ cancellation, which degrades the performance after combining. In this paper, by considering channel estimation errors and residual CJ at each receiving antenna, the residual CJ power after jamming suppression is analyzed, and the optimal combining coefficient for maximizing the signal-to-jamming-noise ratio (SJNR) is derived. The output SJNR of optimal diversity combining is given, and the achievable secrecy rate is analyzed on this basis. The theoretical and simulation results verify the combined effect of channel estimation errors and residual CJ on the combining performance. Moreover, it is worth noting that the combining performance is closely related to the spatial correlation of residual CJ.

Design of Heart-Shaped Current Sensor Based on Incomplete Magnetic Cancellation

Design of Heart-Shaped Current Sensor Based on Incomplete Magnetic Cancellation

Optical activity and transport in twisted bilayer graphene: Spatial dispersion effects

This study investigates the mechanisms driving optical activity and quantum transport in twisted bilayer graphene systems. We demonstrate that optical activity results from spatial dispersion, making it inadequate to consider the system purely two-dimensional. Therefore, we utilize the transfer matrix method to describe the propagation of electromagnetic waves through multilayer systems, which is compatible with our treatment of spatial dispersion. Using an effective continuum model, we analyze the formation of electron states in the bilayer systems and the correlation of transverse and longitudinal motions of electrons in the two graphene layers. The chiral structure of the atomic lattices results in a finite drag component of the optical conductivity tensor due to incomplete cancellation of these correlations. We show the decisive role of this drag component for optical activity by analyzing the circular dichroism spectrum of the system. Additionally, we calculate the dc conductivity, which shows that the twisted bilayer graphene supports a quantum conductivity value proportional to ${e}^{2}/h$ at the intrinsic Fermi energy.

Joint Secure Transceiver Design for an Untrusted MIMO Relay Assisted Over-the-Air Computation Networks With Perfect and Imperfect CSI

In this paper, we investigate the physical layer security of an untrusted relay assisted over-the-air computation (AirComp) network, where each node is equipped with multiple antennas and the relay is operated in an amplify-and-forward mode. The relay receives the data from each sensor and sends them to the access point (AP) in the first and second time slot, respectively. The AP applies artificial noise (AN) to protect the aggregation of sensors’ data from being wiretapped by the untrusted relay in the first time slot. In particular, we are interested in minimizing the computation distortion measured by the mean-squared error (MSE) via jointly optimizing beamforming matrices at all nodes, subject to the MSE constraint at the relay and individual power constraints at the AP, the relay and each sensor. In the case of the perfect channel state information (CSI), we convert the nonconvex MSE minimization problem into a difference-of-convex (DC) form and propose a constrained concave-convex procedure that can obtain a local minimum to solve the DC problem. We also generalize the framework to an imperfect CSI case where the additional interference term due to incomplete interference cancellation is considered, and the nonconvex robust MSE minimization problem is solved by a proposed inexact block coordinate descent algorithm. Numerical results are presented to show the effectiveness of our proposed schemes.

Smart Trip Prediction Model for Metro Traffic Control Using Data Mining Techniques

In the urban rail transportation industry, collecting various data, including the number of trips, the number of fleet breakdowns, the number of breakdowns of railway lines, etc., contributes significantly to future planning and optimization of resources and costs. We are faced with big data analysis due to the daily production of large volumes of data in the urban rail transport industry. This study aims to find a trip prediction model for Tehran Metro to do trip decision-making. This paper provides a brief introduction to knowledge discovery from failure databases and presents the data mining methodology. The relevancy of data mining for a trip prediction model will be depicted. In this sense, considering the relevance of data collected on the metro control center and intelligent trip prediction, this paper presents a functional architecture of a predictive trip model using data mining techniques. Data Mining will identify behavior patterns, allowing a more accurate early detection of faults in the daily operation. This research has investigated three situations, including delayed trips, incomplete trips, and canceled trips, using actual data recorded over the past four years, including non-programmed failures and their impact on trips. A model with more than 90% (90.48%) accuracy suggests a trip status forecast on this line. Also, the research has used Rapid Miner software and the Decision tree technique in data mining and its rules. Also, the kappa index of 0.792 is calculated for the validation model. Therefore, the proposed model enables the prediction of three types of incomplete traffic, delayed trips, and cancellation of trips due to emergency failure at the time of the operation of the Tehran Metro.

Unusual ferrimagnetism in CaFe2O4

Incomplete cancellation of collinear antiparallel spins gives rise to ferrimagnetism. Even if the oppositely polarized spins are owing to the equal number of a single magnetic element having the same valence state, in principle, a ferrimagnetic state can still arise from the crystallographic inequivalence of the host ions. However, experimental identification of such a state as ``ferrimagnetic'' is not straightforward because of the often tiny magnitude expected for $M$ and the requirement for a sophisticated technique to differentiate similar magnetic sites. We report a synchrotron-based resonant x-ray investigation at the Fe ${L}_{2,3}$ edges on an epitaxial film of $\mathrm{Ca}{\mathrm{Fe}}_{2}{\mathrm{O}}_{4}$, which exhibits two magnetic phases with similar energies. We find that while one phase of $\mathrm{Ca}{\mathrm{Fe}}_{2}{\mathrm{O}}_{4}$ is antiferromagnetic, the other one is ferrimagnetic with an antiparallel arrangement of an equal number of spins between two distinct crystallographic sites with very similar local coordination environments. Our results further indicate two distinct origins of an overall minute $M$; one is intrinsic, from distinct ${\mathrm{Fe}}^{3+}$ sites, and the other one is extrinsic, arising from defective ${\mathrm{Fe}}^{2+}$ likely forming weakly coupled ferrimagnetic clusters. These two origins are uncorrelated and have very different coercive fields. Hence, this work provides a direct experimental demonstration of ferrimagnetism solely due to crystallographic inequivalence of the ${\mathrm{Fe}}^{3+}$ as the origin of the weak $M$ of $\mathrm{Ca}{\mathrm{Fe}}_{2}{\mathrm{O}}_{4}$.

Dual-energy tissue cancellation in mammography for improved detection of microcalcifications and neoplasms: A phantom study

Dual-energy mammography and the tissue-cancellation algorithm were applied to the problem of enhancing the detectability of calcifications and lesions in cluttered mammogram background. A multicomponent (plexiglass (PMMA), polypropylene (PP), water) tissue-equivalent breast phantom and a standard full-field digital mammography system operating in two of its standard operating modes (26 kVp, 40 mAs, Mo/Mo and 49 kVp, 6.3 mAs, Rh/Rh target/filter) were used. We studied to what extent the contrast between the tissue substitutes can be eliminated depending on the difference in their attenuation properties, and whether the obtained level of contrast cancellation is sufficient to unambiguously discriminate microcalcifications and inserts from the background.Mixed results were obtained. It was shown that the tissue-cancellation method can provide nearly perfect elimination of the background clutter (17-fold decrease in standard deviation) for homogeneous materials with close attenuation properties (PMMA and water) while increasing the contrast of a third material (PP, 1.7 times increase in contrast-to-noise ratio), thus facilitating its detection and delineation.However, canceling the contrast between materials with more different attenuation properties (PP and water) does not simultaneously lead to any significant enhancement of the contrast of a third material (PMMA), if its attenuation properties are close to those of either PP or water. Moreover, intrinsic inhomogeneity of the phantom constituents becomes important as it results in incomplete contrast cancellation and preservation of visually significant background clutter. Although contrast cancellation increased the signal-to-noise ratio of microcalcifications by about 33%, the relative contrast calcifications—background​ can diminish, making it possible for the remaining clutter to obscure the microcalcifications.

Hybrid protocol for wireless-powered untrusted relay networks with imperfect channel reciprocity

This work investigates the security issue of the energy-constrained untrusted relay network with imperfect channel reciprocity, where the relay without the built-in power supply can only scavenge energy from radio-frequency signals radiated by the source and destination. A hybrid power-splitting (PS)- and time-switching (TS)-based relaying (HPTR) protocol is presented to improve the degraded secrecy performance due to the incomplete self-interference cancellation at the destination. To evaluate the secrecy throughput (ST) of the studied system, the analytical expression of the secrecy outage probability under the delay-limited transmission mode and the closed-form lower bound of the ergodic secrecy capacity under delay-tolerant transmission mode are derived. Both linear and nonlinear models for the energy harvester at the relay are compared. The optimal PS and TS ratios are evaluated numerically. The theoretical derivations are validated by numerical results, revealing that the residual jamming has a negative effect on the secrecy performance of untrusted relay networks, which can be alleviated by the HPTR protocol. Besides, we compare the ST performance of the HPTR protocol with that of the PS and TS relaying schemes, and the results show that the HPTR protocol outperforms both PS and TS relaying protocols in terms of the ST.

Ocean glider flight in the presence of surface waves

AbstractAutonomous, buoyancy-driven ocean gliders are increasingly used as a platform for the measurement of turbulence microstructure. In the processing of such measurements, there is a sensitive (quartic) dependence of the turbulence dissipation rate, ϵ, on the speed of flow past the sensors, or alternatively, the speed of the glider through the ocean water column. The mechanics of glider flight is therefore examined by extending previous flight models to account for the effects of ocean surface waves. It is found that due to the relatively small buoyancy changes used to drive gliders, the surface wave-induced motion, superimposed onto the steady-state motion, follows to a good approximation the motion of the wave orbitals. Errors expected in measuring ϵ at the ocean near-surface due to wave-induced relative velocities are generally less than 10%. However, pressure perturbations associated with the wave motion can be significant when using the glider-measured pressure signal to infer the glider vertical velocity. This effect of surface waves is only present in the shallow water regime, and can also affect glider depth measurements. It arises from an incomplete cancellation of the wave-induced pressure perturbation with the hydrostatic component due to vertical glider displacements, whereas for deep-water waves this cancellation is complete.

Pilot-Assisted SIMO-NOMA Signal Detection With Learnable Successive Interference Cancellation

In this letter, we propose a pilot-assisted receiver scheme based on learnable successive interference cancellation (PA-LSIC) for uplink single-input multiple-output (SIMO) non-orthogonal multiple access (NOMA) systems. The PA-LSIC combines the successive interference cancellation (SIC) structure with the model-driven deep learning network. Considering the noise impact of channel estimation and the incomplete detection and cancellation in SIC process, we introduce some new parameters, such as noise cancellation factor and interference cancellation factor, which are optimized by using the back-propagation algorithm and random gradient descent algorithm. Numerical results show that the PA-LSIC has superior bit error rate (BER) performance and lower complexity during training and implementation.

Mitigation of Imperfect Successive Interference Cancellation and Wavelet‐Based Nonorthogonal Multiple Access in the 5G Multiuser Downlink Network

The fourth Industrial Revolution is expected to lead to an era of technological innovation and digitization that would require connectivity by the users, anywhere and anytime. The fifth generation of wireless communication systems and the technologies therein are being explored to cater to high connectivity needs that encompass high data rates, very low latencies, energy‐efficient systems, etc. A multiuser environment is anticipated that would require multiple access techniques, such as Nonorthogonal Multiple Access (NOMA). The user data in the power domain NOMA is superimposed, at the transmitter base station, which is in turn subjected to Successive Interference Cancellation at the user end. In the multiuser downlink, the desired user’s signal is subjected to imperfect SIC due to incomplete cancellation of the undesired user’s signal. Pulse‐shaping of NOMA symbols using wavelet transform is proposed to mitigate the multiuser interference due to imperfect SIC. Closed‐form symbol error rate (SER) expression is derived for the wavelet NOMA system for a three‐user scenario. Analytical results show that wavelet transform pulse‐shaped NOMA performs better compared to Fourier transform pulse‐shaped NOMA symbols in mitigating SIC and thereby minimize the residual error due to imperfect SIC.

Effect of stress interactions on anisotropic P‐SV‐wave dispersion and attenuation for closely spaced cracks in saturated porous media

ABSTRACTGenerally, local stress induced by individual crack hardly disturbs their neighbours for small crack densities, which, however, could not be neglected as the crack density increases. The disturbance becomes rather complex in saturated porous rocks due to the wave‐induced diffusion of fluid pressures. The problem is addressed in this study by the comparison of two solutions: the analytical solution without stress interactions and the numerical method with stress interactions. The resultant difference of effective properties can be used to estimate the effect of stress interactions quantitatively. Numerical experiments demonstrate that the spatial distribution pattern of cracks strongly affects stress interactions. For regularly distributed cracks, the resulting stress interaction (shielding or amplification) shows strong anisotropy, depending on the arrangement and density of cracks. It has an important role in the estimation of effective anisotropic parameters as well as the incident‐angle‐dependency of P‐ and SV‐wave velocities. Contrarily, randomly distributed cracks with a relative small crack density generally lead to a strong cancellation of stress interactions across cracks, where both the numerical and analytical solutions show a good agreement for the estimation of effective parameters. However, for a higher crack density, the incomplete cancellation of stress interactions is expected, exhibiting an incidence‐angle dependency, slightly affecting effective parameters, and differentiating the numerical and analytical solutions.

Suppressing migration image artifacts using a support vector machine method

Reverse time migration (RTM) can produce high-quality images of complex subsurface structures when using seismic data acquired by a reasonably dense data acquisition geometry. However, RTM produces significant image artifacts when using data from a sparse data acquisition geometry because of incomplete cancellation of migration “smiles.” These artifacts obscure migration images of actual geology, leading to possible misidentification of important geologic features of interest. A specularity filter based on the semblance equation is commonly used in the dip-angle angle-domain common image gather (ADCIG) to preserve signals while suppressing image artifacts. In dip-angle ADCIG, the signals are assumed to have higher semblance scores because they are horizontally more coherent than the artifacts. However, this assumption fails when the image artifacts are severe. We have developed a new approach to suppressing migration image artifacts using a support vector machine (SVM) method. We first develop multiple criteria to distinguish between the signals and artifacts in the dip-angle ADCIG, rather than using only the semblance criterion. We then calculate the weights using a supervised SVM method. The weights approach one for valid signal points, and approach zero for artifact points. Finally, we apply the weights to the dip-angle ADCIG to preserve the effective signals and suppress the image artifacts. We verify the effectiveness of our method, denoted as SVM filtering, using numerical tests on synthetic and field data to produce migration images with improved signal-to-noise ratios and reduced aliasing artifacts.

On the performance of roadside unit-assisted energy harvesting full-duplex amplify-and-forward vehicle-to-vehicle relay systems

This paper considers the performance of a full-duplex (FD) vehicle-to-vehicle (V2V) relay system where the relay uses amplify-and-forward (AF) protocol and harvests the energy from the radio frequency (RF) signals transmitted by source. Unlike previous reports, we investigate the case that both relay and destination are moving vehicles. Therefore, the channel between source and relay is Rayleigh fading while the channel between relay and destination is cascade (double) Raleigh fading. In addition, both fixed and variable gains are used at the FD relay. Based on mathematical analysis, we successfully derive the exact closed-form expressions of the outage probability (OP) and symbol error probability (SEP) to evaluate the system performance. Monte-Carlo simulations are exploited to demonstrate the correctness of all derived mathematical expressions. Numerical results clearly indicate that the OP and SEP performance of the considered energy harvesting (EH)-FD-V2V relay system with variable gain is much better than that with fixed gain. Moreover, the OP and SEP performance are strongly impacted by residual self-interference (RSI) due to the incomplete noise cancellation during the FD transmission. Besides the RSI, the OP and SEP performance is greatly reduced because of the cascade Rayleigh fading. We also observe that there is an optimal EH time duration to minimize the OP and SEP and this optimal value is different for fixed and variable gains. Therefore, from the transmission power of source and the type of gains used at FD relay, we can choose a suitable time EH time duration to get the best system performance.

Mean field theory and Monte Carlo simulation of phase transitions and magnetic properties of a tridimensional Fe7S8 compound

The structural, electronic and magnetic properties of Fe7S8 material have been studied within the framework of the ab initio calculations, the mean field approximation (MFA) and Monte Carlo simulation (MCS). Our study shows that two forms of the iron atoms, Fe2+ with spin S = 2, and Fe3+ with spin = 5/2 are the most probable configurations. A mixed Ising model with ferromagnetic spin coupling between Fe2+ and Fe3+ ions and between Fe3+ and Fe3+ ions, and with antiferromagnetic spin coupling between Fe2+ ions of adjacent layers has been used to study the magnetic properties of this compound. We demonstrated that the magnetic phase transition can be either of the first or of the second order, depending on the value of the exchange interaction and crystal field. The presence of vacancies in every second iron layer leads to incomplete cancellation of magnetic moments, hence to the emergence of the ferrimagnetism. Anomalies in the magnetization behavior have been found and compared with the experimental results.

Sudakov suppression of the Balitsky-Kovchegov kernel

To sum high-energy leading logarithms in a consistent way, one has to impose the strong ordering in both projectile rapidity and dense target rapidity simultaneously, which results in a kinematically improved Balitsky-Kovchegov (BK) equation. We find that beyond this strong ordering region, the important sub-leading double logarithms arise at high order due to the incomplete cancellation between real corrections and virtual corrections in a t-channel calculation. Based on this observation, we further argue that these double logarithms are the Sudakov type ones, and thus can be resummed into an exponential leading to a Sudakov suppressed BK equation.

Ferrimagnetic cluster formation due to oxygen vacancies inCaFe2O4−δ

${\mathrm{CaFe}}_{2}{\mathrm{O}}_{4}$ possesses an intriguing crystal structure characterized by the presence of ${\mathrm{FeO}}_{6}$ octahedra that share both edges and corners, and featuring zigzag Fe chains that are assembled in a honeycomb tube network. The nominal ${\mathrm{CaFe}}_{2}{\mathrm{O}}_{4}$ has been identified to show a long-range antiferromagnetic spin ordering of N\'eel temperature ${T}_{N}\phantom{\rule{4pt}{0ex}}\ensuremath{\sim}184$ K. From dc and ac magnetic susceptibility measurements on both polycrystalline and single-crystal samples, a random distribution of ferrimagnetically ordered clusters of Fe spins is proposed to exist in the oxygen deficient ${\mathrm{CaFe}}_{2}{\mathrm{O}}_{4\ensuremath{-}\ensuremath{\delta}}$. The ferrimagnetic ordering is proposed, coming from the oxygen vacancy-induced ${\mathrm{Fe}}^{3+}$ to ${\mathrm{Fe}}^{2+}$ conversion for the antiferromagnetically coupled spins of ${\mathrm{Fe}}^{2+}$ ions in the low-spin state and the ${\mathrm{Fe}}^{3+}$ ions in the high-spin state, which leads to an incomplete cancellation of staggered magnetization below ${T}_{N}$. Current model reasonably explains the inconsistencies found in the literature regarding the persistent ferromagnetic component for ${\mathrm{CaFe}}_{2}{\mathrm{O}}_{4}$, having a confirmed antiferromagnetic long-range spin ordering from neutron diffraction studies. We calculate the antiferromagnetic spin structure and the parameters of a Heisenberg Hamiltonian via spin-polarized density functional theory, obtaining results that are consistent, to a very high degree, with our experimental results for ac and dc magnetic susceptibility.

Revealing giant internal magnetic fields due to spin fluctuations in magnetically doped colloidal nanocrystals.

Strong quantum confinement in semiconductors can compress the wavefunctions of band electrons and holes to nanometre-scale volumes, significantly enhancing interactions between themselves and individual dopants. In magnetically doped semiconductors, where paramagnetic dopants (such as Mn(2+), Co(2+) and so on) couple to band carriers via strong sp-d spin exchange, giant magneto-optical effects can therefore be realized in confined geometries using few or even single impurity spins. Importantly, however, thermodynamic spin fluctuations become increasingly relevant in this few-spin limit. In nanoscale volumes, the statistical fluctuations of N spins are expected to generate giant effective magnetic fields Beff, which should dramatically impact carrier spin dynamics, even in the absence of any applied field. Here we directly and unambiguously reveal the large Beff that exist in Mn(2+)-doped CdSe colloidal nanocrystals using ultrafast optical spectroscopy. At zero applied magnetic field, extremely rapid (300-600 GHz) spin precession of photoinjected electrons is observed, indicating Beff ∼ 15 -30 T for electrons. Precession frequencies exceed 2 THz in applied magnetic fields. These signals arise from electron precession about the random fields due to statistically incomplete cancellation of the embedded Mn(2+) moments, thereby revealing the initial coherent dynamics of magnetic polaron formation, and highlighting the importance of magnetization fluctuations on carrier spin dynamics in nanomaterials.

Joint pre-processing co-channel interference cancellation for single user MIMO

In general, multiplexing and diversity gains of single user MIMO systems are restricted by min(M,N) where M, N denote the number of antenna elements at a transmitter and receiver, respectively. In order to increase the multiplexing/diversity gains and improve the performance of single user MIMO systems, a joint pre-processing co-channel interference cancellation (JPCIC) method is proposed. The JPCIC is analyzed in both the perfect and the imperfect channel state information. The dependence of channel capacity on the number of antenna elements in every subset, the number of subsets, transmit powers and channel estimation errors is discussed. As theoretical calculation result, the channel capacity increases when the multiplexing/diversity gains and/or the transmit power increase in a certain channel model whether the channel estimation error is absent or present. Compared to the conventional zero-forcing method, the channel capacity of JPCIC is considerably higher because of higher multiplexing/diversity gains, however, it is less robust and decreased more rapidly due to incomplete cancellation of interference terms when the channel estimation error increases. There is a trade-off between the channel capacity and the complexity of system, however, according to quick development in circuit techniques and miniaturization of devices, the JPCIC is expected to be an attractive technology for MIMO system.

α-attractors: Planck, LHC and dark energy

We develop four-parameter supergravity models of inflation and dark energy, constrained so that $$ \frac{\delta \rho }{\rho } $$ , n s and the cosmological constant Λ take their known observable values, but where the mass of gravitino m 3/2 and the tensor-to-scalar ratio r are free parameters. We focus on generalized cosmological α-attractor models, with logarithmic Kahler potentials, a nilpotent goldstino and spontaneously broken supersymmetry at the de Sitter minimum. The future data on B-modes will specify the parameter α, measuring the geometry of the Kahler manifold. The string landscape idea for dark energy is supported in these models via an incomplete cancellation of the universal positive goldstino and negative gravitino contribution. The scale of SUSY breaking M related to the mass of gravitino in our models is a controllable parameter, independent on the scale of inflation, it will be constrained by LHC data and future collider Energy-frontier experiments.