Non-orthogonal multiple access (NOMA) is considered as a promising technology for improving the spectral efficiency in fifth-generation systems. In this correspondence, we study the benefit of NOMA ...in enhancing energy efficiency (EE) for a multiuser downlink transmission, wherein the EE is defined as the ratio of the achievable sum rate of the users to the total power consumption. Our goal is to maximize EE subject to a minimum required data rate for each user, which leads to a nonconvex fractional programming problem. To solve it, we first establish the feasible range of the transmitting power that is able to support each user's data rate requirement. Then, we propose an EE-optimal power allocation strategy that maximizes EE. Our numerical results show that NOMA has superior EE performance in comparison with conventional orthogonal multiple access.
The heterogeneous cellular network (HCN) is a promising approach to the deployment of 5G cellular networks. This paper comprehensively studies physical layer security in a multitier HCN where base ...stations (BSs), authorized users, and eavesdroppers are all randomly located. We first propose an access threshold-based secrecy mobile association policy that associates each user with the BS providing the maximum truncated average received signal power beyond a threshold. Under the proposed policy, we investigate the connection probability and secrecy probability of a randomly located user and provide tractable expressions for the two metrics. Asymptotic analysis reveals that setting a larger access threshold increases the connection probability while decreases the secrecy probability. We further evaluate the network-wide secrecy throughput and the minimum secrecy throughput per user with both connection and secrecy probability constraints. We show that introducing a properly chosen access threshold significantly enhances the secrecy throughput performance of a HCN.
In this paper, we study covert communications between a pair of legitimate transmitter-receiver against a watchful warden over slow fading channels. There coexist multiple friendly helper nodes who ...are willing to protect the covert communication from being detected by the warden. We propose an uncoordinated jammer selection scheme where those helpers whose instantaneous channel gains to the legitimate receiver fall below a pre-established selection threshold will be chosen as jammers radiating jamming signals to defeat the warden. By doing so, the detection accuracy of the warden is expected to be severely degraded while the desired covert communication is rarely affected. We then jointly design the optimal selection threshold and message transmission rate for maximizing covert throughput under the premise that the detection error of the warden exceeds a certain level. Numerical results are presented to validate our theoretical analyses. It is shown that the multi-jammer assisted covert communication outperforms the conventional single-jammer method in terms of covert throughput, and the maximal covert throughput improves significantly as the total number of helpers increases, which demonstrates the validity and superiority of our proposed scheme.
Abstract
As a newly discovered protein posttranslational modification, histone lysine crotonylation (Kcr) involved in cellular regulation and human diseases. Various proteomics technologies have been ...developed to detect Kcr sites. However, experimental approaches for identifying Kcr sites are often time-consuming and labor-intensive, which is difficult to widely popularize in large-scale species. Computational approaches are cost-effective and can be used in a high-throughput manner to generate relatively precise identification. In this study, we develop a deep learning-based method termed as Deep-Kcr for Kcr sites prediction by combining sequence-based features, physicochemical property-based features and numerical space-derived information with information gain feature selection. We investigate the performances of convolutional neural network (CNN) and five commonly used classifiers (long short-term memory network, random forest, LogitBoost, naive Bayes and logistic regression) using 10-fold cross-validation and independent set test. Results show that CNN could always display the best performance with high computational efficiency on large dataset. We also compare the Deep-Kcr with other existing tools to demonstrate the excellent predictive power and robustness of our method. Based on the proposed model, a webserver called Deep-Kcr was established and is freely accessible at http://lin-group.cn/server/Deep-Kcr.
In this article, the sliding mode control (SMC) design is studied for a class of stochastic switching systems subject to semi-Markov process via an adaptive event-triggered mechanism. Network-induced ...communication constraints, semi-Markov switching parameters, and uncertain parameters are considered in a unified framework for the SMC design. Due to the constraint of measuring transducers, the system states always appear with unmeasurable characteristic. Compared with the traditional event-triggered mechanism, the adaptive event-triggered mechanism can effectively reduce the number of triggering than the static event-triggered mechanism. During the data transmission of network communication systems, network-induced delays are characterized from the event trigger to the zero-order holder. The aim of this work is to design an appropriate SMC law based on an adaptive event-triggered communication scheme such that the resulting closed-loop system could realize stochastic stability and reduce communication burden. By introducing the stochastic semi-Markov Lyapunov functional, sojourn-time-dependent sufficient conditions are established for stochastic stability. Then, a suitable SMC law is designed such that the system state can be driven onto the specified sliding surface in a finite-time region. Finally, the simulation study on boost converter circuit model (BCCM) illustrates the effectiveness of the theoretical findings.
This article studies the observer-based output feedback control problem for a class of cyber-physical systems with periodic denial-of-service (DoS) attacks, where the attacks coexist both in the ...measurement and control channels in the network scenario. The periodic DoS attacks are characterized by a cyclic dwell-time switching strategy, such that the resulting augmented system can be converted into a class of discrete-time cyclic dwell-time switched systems including a stable subsystem and an unstable subsystem. By means of a cyclic piecewise linear Lyapunov function approach, the exponential stability and <inline-formula><tex-math notation="LaTeX">l_2</tex-math></inline-formula>-gain analysis, and observer-based controller design are carried out for the augmented discrete-time cyclic switched system. Then, the desired observer and controller gains in piecewise linear form are determined simultaneously so as to ensure that the resulting closed-loop system is exponentially stable with a prescribed <inline-formula><tex-math notation="LaTeX">\mathcal {H}_{\infty }</tex-math></inline-formula> performance index. Finally, a practical application of unmanned ground vehicles under periodic DoS attacks is provided to verify the effectiveness of the developed control approach.
High altitude retinopathy: An overview and new insights Han, Cong; Zheng, Xing-Xing; Zhang, Wen-Fang
Travel medicine and infectious disease,
March-April 2024, 2024 Mar-Apr, 2024-03-00, 20240301, 2024-03-01, Letnik:
58
Journal Article
Recenzirano
Odprti dostop
High altitude retinopathy (HAR) is a common ocular disorder that occurs on ascent to high altitude. There are many clinical symptoms, retinal vascular dilatation, retinal edema and hemorrhage are ...common. These usually do not or slightly affect vision; rarely, severe cases develop serious or permanent vision loss. At present, the research progress of HAR mainly focuses on hemodynamic changes, blood-retinal barrier damage, oxidative stress and inflammatory response. Although the related studies on HAR are limited, it shows that HAR still belongs to hypoxia, and hypobaric hypoxia plays an aggravating role in promoting the development of the disease. Various studies have demonstrated the correlation of HAR with acute mountain sickness (AMS) and high-altitude cerebral edema (HACE), so a deeper understanding of HAR is important. The slow ascent rates and ascent altitude are the key to preventing any altitude sickness. Research on traditional chinese medicine (TCM) and western medicine has been gradually carried out. Further exploration of the pathogenesis and prevention strategies of HAR will provide better guidance for doctors and high-altitude travelers.
•In recent years, high altitude retinopathy has become a hot issue, and how to prevent it needs to be paid more attention.•Studies have shown that high altitude retinopathy is related to acute mountain sickness and high altitude cerebral edema.•This paper discusses the role of changes in hemodynamics and blood-retinal barrier in high altitude retinopathy.•Finally, this paper puts forward a new direction and research idea for the future study of high altitude retinopathy.
The intercalation of potassium ions into graphite is demonstrated to be feasible, while the electrochemical performance of potassium‐ion batteries (KIBs) remains unsatisfying. More effort is needed ...to improve the specific capacity while maintaining a superior rate capability. As an attempt, nitrogen/oxygen dual‐doped hierarchical porous hard carbon (NOHPHC) is introduced as the anode in KIBs by carbonizing and acidizing the NH2‐MIL‐101(Al) precursor. Specifically, the NOHPHC electrode delivers high reversible capacities of 365 and 118 mA h g−1 at 25 and 3000 mA g−1, respectively. The capacity retention reaches 69.5% at 1050 mA g−1 for 1100 cycles. The reasons for the enhanced electrochemical performance, such as the high capacity, good cycling stability, and superior rate capability, are analyzed qualitatively and quantitatively. Quantitative analysis reveals that mixed mechanisms, including capacitance and diffusion, account for the K‐ion storage, in which the capacitance plays a more important role. Specifically, the enhanced interlayer spacing (0.39 nm) enables the intercalation of large K ions, while the high specific surface area of ≈1030 m2 g−1 and the dual‐heteroatom doping (N and O) are conducive to the reversible adsorption of K ions.
NH2‐MIL‐101(Al) templated preparation of nitrogen/oxygen dual‐doped hierarchical porous hard carbon indicates high reversible capacity, superior cycling stability, and excellent rate capability as anode materials for potassium‐ion batteries (KIBs). The present strategy opens a new avenue to design and construct novel anode materials for coming KIBs.
In this paper, we study the secure multiantenna transmission with artificial noise (AN) under imperfect channel state information (CSI) in the presence of spatially randomly distributed ...eavesdroppers. We derive the optimal solutions of the power allocation between the information signal and the AN for minimizing the secrecy outage probability (SOP) under a target secrecy rate and for maximizing the secrecy rate under an SOP constraint, respectively. Moreover, we provide an interesting insight that channel estimation error affects the optimal power allocation strategy in opposite ways for the two given objectives. When the estimation error increases, more power should be allocated to the information signal if we aim to decrease the rate-constrained SOP, whereas more power should be allocated to the AN if we aim to increase the SOP-constrained secrecy rate.
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