Partial Channel Research Articles

On Capacity of the Writing Onto Fast Fading Dirt Channel

The Writing onto Fast Fading Dirt (WFFD) channel is investigated to study the effect of partial channel knowledge on the performance of interference pre-cancellation. The WFFD channel is the Gel’fand-Pinsker channel in which the channel output is the sum of the channel input, white Gaussian noise, and a fading-times-state term. The fading-times-state term is obtained as the product of the channel state sequence, known only at the transmitter, and a fast fading process, known only at the receiver. We consider the case of Gaussian-distributed channel states and derive an approximate characterization of capacity for different classes of fading distributions, both continuous and discrete. In particular, we prove that if the fading distribution concentrates in a sufficiently small interval, then capacity is approximately equal to the AWGN capacity times the probability of such interval. We also show that there exists a class of fading distributions for which having the transmitter treat the fading-times-state term as additional noise closely approaches capacity.

Control of spin-exchange interaction between alkali-earth-metal atoms via confinement-induced resonances in a quasi-(1+0)-dimensional system

A nuclear-spin exchange interaction exists between two ultracold fermionic alkali-earth (like) atoms in the electronic $^{1}{\rm S}_{0}$ state ($g$-state) and $^{3}{\rm P}_{0}$ state ($e$-state), and is an essential ingredient for the quantum simulation of Kondo effect. We study the control of this spin-exchange interaction for two atoms simultaneously confined in a quasi-one-dimensional (quasi-1D) tube, where the $g$-atom is freely moving in the axial direction while the $e$-atom is further localized by an additional axial trap and behaves as a quasi-zero-dimensional (quasi-0D) impurity. In this system, the two atoms experience effective-1D spin-exchange interactions in both even and odd partial wave channels, whose intensities can be controlled by the characteristic lengths of the confinements via the confinement-induced-resonances (CIRs). In current work, we go beyond that pure-1D approximation. We model the transverse and axial confinements by harmonic traps with finite characteristic lengths $a_\perp$ and $a_z$, respectively, and exactly solve the quasi-1D + quasi-0D scattering problem between these two atoms. Using the solutions we derive the effective 1D spin-exchange interaction and investigate the locations and widths of the even/odd wave CIRs for our system. It is found that when the ratio $a_z/a_\perp$ is larger, the CIRs can be induced by weaker confinements, which are easier to be realized experimentally. The comparison between our results and the recent experiment shows that the two experimentally observed resonance branches of the spin-exchange effect are due to an even-wave CIR and an odd-wave CIR, respectively. Our results are advantageous for the control and description of either the effective spin-exchange interaction or other types of interactions between ultracold atoms in quasi 1+0 dimensional systems.

Development Characteristics of Partial Discharge Channels in the Power Cable Termination

Development Characteristics of Partial Discharge Channels in the Power Cable Termination

Numerical study on a novel hyperbolic inlet header in straight-channel printed circuit heat exchanger

Printed circuit heat exchangers (PCHEs) can be used as the recuperator and condenser in the supercritical CO2 (sCO2) Brayton cycle of fast cooled reactor (FCR) systems. Most researchers focused on heat transfer improvement of the core structure in previous literatures. However, the flow non-uniformity may seriously decrease the comprehensive performance of PCHEs by increasing the pressure loss. The sCO2 temperature in partial channels may be lower than the pseudo-critical temperature due to non-uniform flow distribution. Thereby, it is possible that the condenser may deviate from the steady operating condition and work inefficiently. In this paper, the flow non-uniformity of a straight-channel PCHE condenser with four different inlet headers is analyzed. Based on the streamline profile, a novel modified hyperbolic inlet header is proposed, which can reduce the flow non-uniformity by 46% compared with the current practical manufactured model. Simultaneously, the improvement of flow uniformity by the novel inlet header may increase the overall performance by 39.5%. Furthermore, the effect of core length is also investigated, and it is found that the flow non-uniformity can be minimized by varying the core length. Additionally, the relationship between the standard deviation of flow non-uniformity and the shape factor is quantitatively investigated and analyzed. Result shows that the flow non-uniformity can be expressed as a function of the shape factor and dimensionless core length. Finally, the correlations of the thermo-hydraulic performance of the straight-channel PCHE with corrections for flow non-uniformity are proposed.

Casimir (vacuum) energy in planar QED with strong coupling

The essentially non-perturbative vacuum polarization effects, caused by an extended external supercritical Coulomb source, are explored for a planar Dirac-Coulomb (DC) system with strong coupling (similar to graphene and graphene-based heterostructures). Taking account of results, obtained in Ref. [1] for the induced charge density ρVP(r→), in the present paper the evaluation of the Casimir (vacuum) energy EVP is presented. The main result is that for a wide range of the system parameters in the overcritical region EVP turns out to be a rapidly decreasing negative function ∼−Z3∕R0 with Z, R0 being the charge and the size of the external source. By an explicit calculation the possibility for complete screening of the electrostatic reflection self-energy of the external source by such polarization effects for Z ≫ Zcr,1 is demonstrated. The dependence of the Casimir energy on the screening of the Coulomb asymptotics of the external source at some R1 > R0 is also explored in detail, and some peculiar effects in the partial channels with the lowest rotational numbers mj = ±1∕2, ±3∕2 in the screened case are also discussed.

Antenna Diversity for Downlink MIMO-NOMA Systems With Partial Channel State Information

In this letter, antenna diversity is used to improve the outage performance of downlink multiple-input multiple-output non-orthogonal multiple access systems with partial channel state information, of which the transmitter only knows the distance and channel direction information associated with each user. We analyze the ergodic rate and the outage probability of the proposed system. Moreover, we derive the closed-form expression of each user’s outage probability. Numerical results confirm the accuracy of our analysis.

Resonance states in the YcN potential model

We calculate two-body $J^{\pi}=0^{+}, 1^{+}$, and $J^{\pi}=2^{+}$ resonance states of $Y_{c}$ ($= \Lambda_{c}$, $\Sigma_{c}$, or $\Sigma_{c}^{*}$) and $N$ using the complex scaling method. We employ the $Y_{c}N$-CTNN potentials, which were proposed in our previous study, and obtain four resonances near $\Sigma_{c}N$ and $\Sigma_{c}^{*}N$ thresholds. From the analysis by the binding energies of partial channel systems, we conclude that these resonance states are Feshbach resonances. We compare the results with the $Y_{c}N$ resonance states in the heavy quark limit, where the $\Sigma_{c}N$ and $\Sigma_{c}^{*}N$ thresholds are degenerate, and find that they form two pairs of the heavy-quark doublets in agreement with the heavy quark spin symmetry.

Analytical solutions of fluid flow and heat transfer in a partial porous channel with stress jump and continuity interface conditions using LTNE model

Forced convection heat transfer is analytically performed in a channel partially filled with porous media located at two inner walls under local thermal non-equilibrium (LTNE) condition. A constant heat flux is imposed at the channel walls. The Brinkman extended Darcy model is applied in the porous region and the stress jump and continuity conditions are employed at the interface. Exact solutions are obtained for velocity, pressure drop, the fluid and solid temperatures and Nusselt number. The effects of pertinent parameters on the fluid flow and heat transfer are conducted. Furthermore, the solution for the Nusselt number is compared to that by applying the local thermal equilibrium (LTE) assumption and the validity of the LTE is examined. It is shown that by applying LTNE model for different solid to fluid effective thermal conductivity ratios (K) and Biot numbers (Bi), the variations of Nusselt number with hollow ratio include three types of curves, which are: a maximized Nusselt number occurs at a small optimum hollow ratio, Nusselt number monotonically decreases by increasing hollow ratio and a minimized Nusselt number occurs at a small hollow ratio, respectively. For high K, a small critical value of S at which the Nusselt number reaches to LTE Nusselt number occurs and it lowers with the increase of Bi number and the decrease of Darcy number; while for low K, the LTNE Nu number versus hollow ratio is almost the same with LTE Nu number and therefore the LTE is valid. The stress jump at the interface is found to have negligible effect on the Nusselt number and the pressure drop, except in a high Darcy number with a low stress jump coefficient where the calculation of pressure drop need to account for the stress jump effect at the interface and the Nusselt numbers for both LTE and LTNE models slightly differs from the case of stress continuity interface condition.

Optimal Relaying Beamforming in Multiple Access Broadcast Channel (MABC) Bidirectional Cognitive Radio Networks in Presence of Interferers

In this paper, a general cognitive radio system consisting of a set of users with different level of spectrum access including two primary transceivers and several types of secondary users is considered. It is assumed that two secondary users operate based on an underlay model at the same frequency bandwidth and at the same time as the primary users based on a multiple access broadcast channel bidirectional beamforming scheme. Other secondary users provide a relaying service to the primary users in exchange for the opportunity to send their messages towards their own destinations for a fixed portion of the communication cycle. In addition, it is assumed that some interferers are active during the communication cycle and cause interference for the network. Furthermore, it is assumed that only partial channel state information (CSI) between interferers and other nodes in the network is available. We provide a robust optimization method against imperfection on the interferers’ CSI to maximize the joint primary and secondary signal-to-interference-plus-noise-ratio with the assumption of limited available power at the secondary relays. An amplify-and-forward relaying scheme is deployed at the secondary relays and the optimal beamforming is obtained using second order convex programming method. The simulation results show the performance of the proposed beamforming method against the existence of interferers, and demonstrate the effectiveness of our robust method against uncertainty in knowledge of interferers’ CSIs.

Optimal Resource Allocation Using Support Vector Machine for Wireless Power Transfer in Cognitive Radio Networks

In this paper, we present an efficient allocation of power and channel so that power-drained primary users can harvest energy from secondary systems through wireless power transfer, and in return, the secondary system can have full access to the licensed spectrum for a certain length of time. Considering partial channel state information between primary and secondary systems, we formulate an optimization problem consisting of probabilistic constraint. By introducing a confidence level and using support vector machine, we convert the probabilistic constraint to deterministic form. We also implement a particle swarm optimization technique to solve the resource allocation optimization problem, while guaranteeing the required data rate for both primary and secondary systems. The results verify that the proposed scheme enables a higher number of primary users to efficiently harvest energy, and it also increases total primary capacity.

Outage Minimized Full-Duplex Multiantenna DF Relaying With CSI Uncertainty

Multiantenna full-duplex (FD) relaying, as a promising solution for future wireless communications, has received many attentions. In this paper, focusing on FD decode-and-forward relaying with only partial channel state information available, we are interested in the relay beamforming optimization from an outage probability minimization perspective. Due to the implicit outage probability objective function, it is rather hard to find an optimal solution directly. To overcome this obstacle, we first obtain an explicit form of the outage probability, which involves intricate Marcum Q-functions. Based on the derived objective, we find out the optimal relay receive and transmit beamforming directions, which turns out to be the maximum-ratio combining/maximum-ratio transmission strategy. Then, we rigourously prove that the optimal relay transmit power is the unique solution to a strictly quasi-concave problem and, hence, can be efficiently determined. The performance advantage of the proposed optimal design over conventional schemes is validated via simulations.

Aqueous detection of antibiotics with a Cd(II)-based metal-organic framework constructed by a tetra(1,2,4-triazole)-functionalized-bis(triphenylamine) ligand

A Cd(II)-based MOF (Cd-TTPBA-4) with sra topology is constructed by a tetra(1,2,4-triazole)-functionalized-bis(triphenylamine) ligand (TTPBA-4) showing two types of 1-D channels with partial channel walls built from columnar stacks of non-coordinated triazole-terminated arms. Particularly, it constitutes a rare example of MOF-based luminescent sensor for aqueous selective detection of NZF (nitrofurazone) and NFT (nitrofurantoin) antibiotics.

Multiple access multicarrier continuous-variable quantum key distribution

One of the most important practical realizations of the fundamentals of quantum mechanics is continuous-variable quantum key distribution (CVQKD). Here we propose the adaptive multicarrier quadrature division–multiuser quadrature allocation (AMQD–MQA) multiple access technique for continuous-variable quantum key distribution. The MQA scheme is based on the AMQD modulation, which granulates the inputs of the users into Gaussian subcarrier continuous-variables (CVs). In an AMQD–MQA multiple access scenario, the simultaneous reliable transmission of the users is handled by the dynamic allocation of the Gaussian subcarrier CVs. We propose two different settings of AMQD–MQA for multiple input-multiple output communication. We introduce a rate-selection strategy that tunes the modulation variances and allocates adaptively the quadratures of the users over the sub-channels. We also prove the rate formulas if only partial channel side information is available for the users of the sub-channel conditions. We show a technique for the compensation of a nonideal Gaussian input modulation, which allows the users to overwhelm the modulation imperfections to reach optimal capacity-achieving communication over the Gaussian sub-channels. We investigate the diversity amplification of the sub-channel transmittance coefficients and reveal that a strong diversity can be exploited by opportunistic Gaussian modulation.

Closed-Form Secrecy Outage Analysis of Cellular Downlink Systems in the Presence of Co-Channel Interference

This paper analyzes the secrecy outage probability of a cellular downlink system which consists of multiple users, one base station (BS), and one eavesdropper in the presence of co-channel interferers, where the BS transmits its signals to users which are distributed according to a Poisson point process with a fixed density, while the eavesdropper attempts to tap the transmission from the BS to the users. To enhance the transmission security against eavesdropping, we propose two multiuser scheduling schemes, namely, the partial channel state information (CSI) aided user scheduling (PCSI-US) scheme where only the CSIs of users are available without knowing the co-channel interferers’ CSIs and the full CSI aided user scheduling (FCSI-US) scheme which requires the CSIs of both users and interferers. For comparison purposes, the conventional round-robin scheduling scheme is also considered as a baseline. We derive closed-form expressions of the secrecy outage probability for the proposed PCSI-US and FCSI-US as well as conventional round-robin scheduling schemes in co-channel interference (CCI) environments. Numerical results show that the proposed FCSI-US and PCSI-US schemes outperform the conventional round-robin scheduling in terms of their secrecy outage probabilities, where FCSI-US achieves the best secrecy outage performance in CCI environments. It is also demonstrated that increasing the mean number of users has a marginal effect on the secrecy performance of conventional round-robin scheduling, which can significantly decrease the secrecy outage probabilities of PCSI-US and FCSI-US schemes. This further validates the secrecy effectiveness of the proposed user scheduling methods in terms of combating the CCI.

Power Allocation for Energy Efficiency and Secrecy of Wireless Interference Networks

Considering a multi-user interference network with an eavesdropper, this paper aims at the power allocation to optimize the worst secrecy throughput among the network links or the secure energy efficiency in terms of achieved secrecy throughput per Joule under link security requirements. Three scenarios for the access of channel state information are considered: the perfect channel state information; partial channel state information with channels from the transmitters to the eavesdropper exponentially distributed; and not perfectly known channels between the transmitters and the users with exponentially distributed errors. The paper develops various path-following procedures of low complexity and rapid convergence for the optimal power allocation. Their effectiveness and viability are illustrated through numerical examples. The power allocation schemes are shown to achieve both high secrecy throughput and energy efficiency.

Josephson oscillation and self-trapping in momentum space

A nuclear-spin exchange interaction exists between two ultracold fermionic alkali-earth (like) atoms in the electronic $^{1}{\rm S}_{0}$ state ($g$-state) and $^{3}{\rm P}_{0}$ state ($e$-state), and is an essential ingredient for the quantum simulation of Kondo effect. We study the control of this spin-exchange interaction for two atoms simultaneously confined in a quasi-one-dimensional (quasi-1D) tube, where the $g$-atom is freely moving in the axial direction while the $e$-atom is further localized by an additional axial trap and behaves as a quasi-zero-dimensional (quasi-0D) impurity. In this system, the two atoms experience effective-1D spin-exchange interactions in both even and odd partial wave channels, whose intensities can be controlled by the characteristic lengths of the confinements via the confinement-induced-resonances (CIRs). In current work, we go beyond that pure-1D approximation. We model the transverse and axial confinements by harmonic traps with finite characteristic lengths $a_\perp$ and $a_z$, respectively, and exactly solve the "quasi-1D + quasi-0D" scattering problem between these two atoms. Using the solutions we derive the effective 1D spin-exchange interaction and investigate the locations and widths of the even/odd wave CIRs for our system. It is found that when the ratio $a_z/a_\perp$ is larger, the CIRs can be induced by weaker confinements, which are easier to be realized experimentally. The comparison between our results and the recent experiment shows that the two experimentally observed resonance branches of the spin-exchange effect are due to an even-wave CIR and an odd-wave CIR, respectively. Our results are advantageous for the control and description of either the effective spin-exchange interaction or other types of interactions between ultracold atoms in quasi 1+0 dimensional systems.

Development of urogenital system in the Spix cavy: A model for studies on sexual differentiation

This study documented, for the first time, the morphological patterns of differentiation of male and female genital organs of Spix cavy (Galea spixii) using histological and ultrastructural analyses, with immuno-localization of steroidogenic enzymes, cytochromes P450 aromatase (P450arom) and 17α-hydroxylase/17, 20-lyase (P450c17), involved in the synthesis of estrogens and androgens respectively throughout fetal sexual development. Undifferentiated gonads of Spix cavy develop into ovaries in females after 25 days of gestation (DG), exhibiting P450arom immunoreactivity. After 25 DG, paramesonephric ducts develop and form oviducts, uterine horns and cranial portion of the vagina. The caudal portion of the vagina originates from the urogenital sinus, and a vaginal closure membrane is present at the end of gestation. Partial channeling of the urethra into the clitoris occurs after 40 DG, but complete channeling never occurs. A preputial meatus emerges near the tip of organ. In males, undifferentiated gonads develop into testes at 25 DG and develop immunoreactivity for P450c17, which is required for androgens synthesis and likely maintenance of mesonephric ducts. Mesonephric ducts develop subsequently, forming the epididymis and ductus deferens. The pelvic urethra develops after 25 DG with channeling into the penis occurring around 30 DG. This is the first morphological study describing the process of sexual differentiation during gestation in a hystricomorph rodent and one of the most comprehensive analyses conducted in any mammal. Male genital organ development follows the general pattern described in other domestic mammals, but does not include formation of the baculum as occurs in mice and rats. In females, clitoral development includes partial canalization by the urethra and development of a preputial meatus. Further studies are required to clarify the mechanisms involved in the differentiative processes described.

Optimal and Suboptimal Routing Based on Partial CSI in Random Ad-Hoc Networks

In this paper, we consider routing in random wireless- ad hoc -networks, where each node is equipped with a single antenna. Our analysis uses a proper model of the physical layer together with an abstraction of higher communication layers. We assume that the nodes are distributed according to a Poisson-point-process and consider routing schemes that select the next relay based on the geographical locations, the channel gains of its neighbor nodes and the statistical characterization of all other nodes. While many routing problems are formulated as optimization problems, the optimal distributed solution is rarely accessible. In this paper, we present the exact optimal solution for the scenario analyzed. The optimal routing is given as a maximization of a routing metric, which depends solely on the known partial channel state information and includes an expectation with respect to the interference statistics. The optimal routing scheme is important because it gives an upper bound on the performance of any other routing scheme. We also present sub-optimal routing schemes that only use part of the available knowledge and require much lower computational complexity. Numerical results demonstrate that the performance of the low complexity schemes is close to optimal and outperforms other tested routing schemes.

Distributed Precoder Design With Direct-Link Channel Information for Distributed Antenna Systems

In this study, we investigate distributed antenna systems (DASs) with partial channel state information (CSI). In the DAS considered here, one control unit coordinates multiple baseband units (BBUs), and each BBU with multiple distributed antennas (DAs) knows only the direct channels from its DAs to its associated users and supports them simultaneously. For fairness among users, a distributed precoder structure is designed to maximize the upper bound of the minimum user rate, under the assumption that the direct channel dominates the intra-BBU interfering links. We then propose a distributed general precoder that allows multiple BBUs to serve multiple users simultaneously. Numerical results verify that, in terms of the minimum and average achievable rates, the proposed scheme significantly outperforms an existing scheme in which each BBU supports a single user. The results also demonstrate that the proposed scheme is comparable to a full-CSI based scheme.

Spatial integration of navigation data as efficient method to improve quality of vessel traffic services support

Practical need for the integration of navigation data received by spatially-dispersed network of coast navigation stations of vessels traffic service in coastal regions has been proved. Technical supportability, potential and conceptual peculiarities of the integrated processing implementation of the abovementioned navigation data have been outlined. Perspectives of effective implementation of various well-known conceptual approaches to the development of such systems have been compared and analyzed. The functional scheme of the working automated radio system with a multi radar data processing subsystem has been developed. Its accuracy has been analyzed. The method has been offered and the experimental studies results have been cited to prove the effectiveness of the navigation data integrated processing to support the theoretical expectations. The presented data show that the current integral of the error parameter is considered to have minimal fluctuations, and the standard error shall not exceed the corresponding errors of each of the partial channels.