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Abstract Background Nonalcoholic fatty liver disease (NAFLD) has developed as a leading public wellness challenge as a result of changes in dietary patterns. Unfortunately, there is still a lack of effective pharmacotherapy methods for NAFLD. Wang’s empirical formula (WSF) has demonstrated considerable clinical efficacy in treating metabolic disorders for years. Nevertheless, the protective effect of WSF against NAFLD and its underlying mechanism remains poorly understood. Methods The NAFLD model was established using a 17-week high-sucrose and high-fat (HSHF) diet with 32 ICR mice. In assessing the therapeutic efficacy of WSF on NAFLD, we detected changes in body weight, viscera weight, biomarkers of glycolipid metabolism in serum and liver, transaminase levels and histopathology of liver with H&E and Oil Red O staining after oral administration. The chemical components in WSF were extensively identified and gathered utilizing the HPLC-Q-TOF/MS system, database mining from HMDB, MassBank, and TCMSP databases, alongside literature searches from CNKI, Wanfang and VIP databases. The forecast of network pharmacology approach was then utilized to investigate the probable mechanisms by which WSF improves NAFLD based on the performance of prospective target identification and pathway enrichment analysis. Besides, molecular docking was also conducted for the verification of combination activities between active components of WSF and core proteins related to NAFLD. In final, validation experiments of obtained pathways were conducted through ELISA, immunohistochemistry (IHC), and western blot (WB) analysis. Results Pharmacodynamic outcomes indicated that WSF intervention effectively mitigated obesity, fat accumulation in organs, lipid metabolism disorders, abnormal transaminase levels and liver pathology injury in NAFLD mice (P

In response to the problem of limited performance and low spectral efficiency in complex multipath environments of traditional direct sequence spread spectrum communication, a cyclic prefix (CP) block transmission structure spread spectrum system with a time-frequency hybrid direct sequence spread spectrum receiver structure was proposed.The system adopted maximum ratio combination (MRC) in the frequency domain to achieve equalization and de-spreading processes simultaneously, while achieving optimal reception performance and omitting the IFFT process to reduce computational complexity significantly.On this basis, it was proposed to replace the m-sequence with the constant amplitude zero auto correlation (CAZAC) sequence as the spread spectrum sequence, which significantly improved the system performance without increasing computational complexity.Finally, a high-speed spread spectrum communication method based on cyclic code shift keying (CCSK) was proposed to solve the problems of low spectrum utilization efficiency and limited transmission rate in traditional direct sequence spread spectrum.By utilizing the property of Fourier transform time-domain cyclic shift, a low implementation complexity CCSK decoding method was designed, which reduced the multiplication number required for CCSK de-spreading by O(N2) reduced to O (Nlog N), greatly reducing resource consume.The simulation results show that compared to existing direct sequence spread spectrum methods, the proposed method achieves approximately 3 dB gain in both Gaussian and complex multipath channel environments.

Background: Physical weakness and cardiovascular risk increase significantly with age, but the underlying biological mechanisms remain largely unknown. This study aims to reveal the causal effect of circulating metabolites on frailty, sarcopenia and vascular aging related traits and diseases through a two-sample Mendelian Randomization (MR) analysis.Methods: Exposures were 486 metabolites analyzed in a genome-wide association study (GWAS), while outcomes included frailty, sarcopenia, arterial stiffness, atherosclerosis, peripheral vascular disease (PAD) and aortic aneurysm. Primary causal estimates were calculated using the inverse-variance weighted (IVW) method. Methods including MR Egger, weighted median, Q-test, and leave-one-out analysis were used for the sensitive analysis.Results: A total of 125 suggestive causative associations between metabolites and outcomes were identified. Seven strong causal links were ultimately identified between six metabolites (kynurenine, pentadecanoate (15:0), 1-arachidonoylglycerophosphocholine, androsterone sulfate, glycine and mannose) and three diseases (sarcopenia, PAD and atherosclerosis). Besides, metabolic pathway analysis identified 13 significant metabolic pathways in 6 age-related diseases. Furthermore, the metabolite-gene interaction networks were constructed.Conclusion: Our research suggested new evidence of the relationship between identified metabolites and 6 age-related diseases, which may hold promise as valuable biomarkers.

Purpose According to international guidelines, selective lymph node dissection can be performed on patients with early-stage endometrial cancer. However, some patients at early stage have already occurred lymph node metastasis at the time of diagnosis. This study was aimed to find a method to predict the risk of lymph node metastasis in this part of patient. Methods We collected data from 571 patients as training cohort and 351 patients as validation cohort for this study. Then we performed univariate and multivariate analyses to confirm the correlation of frequently used factors and lymph node metastasis. Combined analysis of four commonly indicators (ERα, PR, P53 and Ki67) from pathological parameter sources was mainly carried out, and the combined ratio is defined as (ERα + PR)/(Ki67 + P53). Then the accuracy of the combined ratio and other factors in prediction were compared by AUC value. Also, the optimal truncation value was searched. Finally, patients followed up for more than two years were divided into groups by the threshold value, and their difference in survival was explored. Results This study showed that CA125, grade, LVSI, ERα, PR, P53, Ki67 have statistical significance (P-value

ABSTRACTOur purpose is to investigate the relationship between the microbiota of patients' tongue coating microbiota and the severity of COVID-19, and to identify the severity of COVID-19 patients' condition as early as possible. The participants were categorized into three groups: healthy controls (Con group) consisting of 37 individuals, patients with mild to moderate symptoms (M group) comprising 49 individuals, and patients with severe and critical symptoms (S-C group) consisting of 44 individuals. We collected oral swabs from all participants and performed 16S rRNA gene sequencing to analyze the microbiome. The α and β diversity differences were assessed respectively. Additionally, we employed the Linear Discriminant Analysis Effect Size (LEfSe) analysis to evaluate taxonomic differences among the three groups. Our findings revealed a significantly higher richness of tongue coating microbiota in both the S-C group and M group compared to the Con group. When compared with Con group, decreased Prevotella, Neisseria, Fusobacterium and Alloprevotella, and over-expressed Streptococcus and Rothia in M and S-C group were identified. LEfSe analysis indicated a greater abundance of Pseudomonas, Acinetbacter, Lactobacillus, Corynebacterium, Rothia in S-C group. Our study suggests a potential association between tongue coating microbiome and the severity of COVID-19 patients.

Abstract Zinc oxide nanorods have been extensively studied for the specific killing of breast cancer (BC) cells, and their killing mechanism and anticancer effects have been initially demonstrated. However, systematic studies at the single‐cell level are still necessary to explore cellular functions in detail. In this work, a hydrothermal method was used to synthesize zinc oxide nanorod arrays (ZnO NRs). Their effect on BC cells was demonstrated at single‐cell resolution for the first time through microfluidic chips and a single‐cell analysis platform. The inhibitory effects of ZnO NRs were observed. First, ZnO NRs suppressed cell proliferation and migration abilities. Moreover, Interferon‐γ, Tumor Necrosis Factor‐α, and Granzyme B in BC cells turned out to be antitumor instead of tumorigenic under ZnO NRs stimulation. Furthermore, ZnO NRs inhibition altered cellular functions and thus weakened intercellular and intercluster correlations. More importantly, MDA‐MB‐231 cells (strongly metastatic) showed much greater resistance to ZnO NRs than MCF‐7 cells (nonmetastatic). The experiments complemented the findings at the single‐cell level and provided a more comprehensive consideration of the potential risks and applications of ZnO NRs in breast cancer therapy, which is of great importance for biomedical research on nanomaterials.

Background Endometrial cancer stem-like cells (ECSCs) have been proven to be responsible for recurrence, metastasis, and drug-resistance in patients with endometrial cancer. The HIPPO pathway has been shown to play an important role in the development and maintenance of stemness in a variety of tumors. While there was less research about its function in ECSCs. The aim of this study was to explore the role of YAP1, a core molecular of HIPPO pathway, in the stemness of endometrial cancer and to reveal its influence on prognosis. Methods We collected specimens and clinical data from 774 patients with endometrial cancer to analyze the correlation between YAP1 expression and prognosis. We then examined the expression of YAP1 in ECSCs and EC cell lines (Ishikawa; HEC1-A) in vitro experiments. Changes in the stemness of cell lines were detected after YAP1 silencing by siRNA. Finally, high-throughput sequencing was used to predict the potential molecular interactions and mechanisms of YAP1’s effect on stemness. Result Down-regulation of YAP1 significantly suppresses the stemness of EC cell lines. High expression of YAP1 leads to poor prognosis in EC by regulation of stemness. Conclusion YAP1 plays an important role in the prognosis of patients with EC by regulation of stemness.

To solve the performance limitation of direct sequence spread spectrum system in complex multipath environment, an adaptive anti-jamming spread spectrum framework that organically combines single carrier frequency domain equalization (SCFDE) and direct sequence spread spectrum (DSSS) technologies was proposed.The frequency multipath fading was overcame by frequency domain equalization, and the transmission rates and high reliability was reconfigured by deploying variable spread factors.Moreover, the inherent fast Fourier transform process was made full use at the receiver to realize the adjoint detection and analysis of interference intensity, interference type and other information, etc.Then, the frequency domain bearing point online was optimized and selected to improve the adaptability to the interference, especially blocking interference.The simulation results show that the proposed direct spread spectrum waveform based on SCFDE has good communication performance in both Gaussian and multipath environments, and the notch of some frequency bands has little impact on the communication performance, which verifies the effectiveness of anti-jamming by adaptive optimizing information frequency domain bearers.

ObjectiveThe aim of this study is to explore the consistency of P53 immunohistochemical expression between preoperative biopsy and final pathology in endometrial cancer (EC), and to predict the prognosis of patients based on the 4-tier P53 expression and classic clinicopathological parameters.MethodsThe medical data of patients with stage I-III EC who received preoperative biopsy and initial surgical treatment in two medical centers was retrospectively collected. The consistency of P53 immunohistochemistry expression between preoperative biopsy and final pathology was compared using Cohen’s kappa coefficient and Sankey diagram, then 4-tier P53 expression was defined (P53wt/P53wt, P53abn/P53wt, P53wt/P53abn, and P53abn/P53abn). Univariate and multivariate Cox regression analysis was used to determine the correlation between 4-tier P53 expression and the prognosis of patients. On this basis, the nomogram models were established to predict the prognosis of patients by combining 4-layer P53 expression and classic clinicopathological parameters, then risk stratification was performed on patients.ResultsA total of 1186 patients were ultimately included in this study through inclusion and exclusion criteria. Overall, the consistency of P53 expression between preoperative biopsy and final pathology was 83.8%, with a kappa coefficient of 0.624. ROC curve suggested that the AUC of 4-tier P53 expression to predict the prognosis of patients was better than AUC of P53 expression in preoperative biopsy or final pathology alone. Univariate and multivariate Cox regression analysis suggested that 4-tier P53 expression was an independent influencing factor for recurrence and death. On this basis, the nomogram models based on 4-tier P53 expression and classical clinicopathological factors were successfully established. ROC curve suggested that the AUC (AUC for recurrence and death was 0.856 and 0.838, respectively) of the models was superior to the single 4-tier P53 expression or the single classical clinicopathological parameters, which could provide a better risk stratification for patients.ConclusionThe expression of P53 immunohistochemistry had relatively good consistency between preoperative biopsy and final pathology of EC. Due to the discrepancy of P53 immunohistochemistry between preoperative biopsy and final pathology, the prognosis of patients can be better evaluated based on the 4-layer P53 expression and classic clinical pathological parameters.

Background and objectives This study aimed to investigate the impact of intermediate-risk factors (IRFs) on the prognosis of stage I-II cervical cancer (CC) patients, and evaluate the necessity of adjuvant treatment based on investigation. Methods Medical records of 976 negative high-risk factors’ CC patients were retrospectively reviewed. Clinicopathologic characteristics and adjuctive therapy were analyzed using Kaplan–Meier analysis and log-rank tests to identify significant factors. The multivariate Cox proportional hazards regression analysis was performed to identify the independent prognostic factors. Results For patients with none, single and multiple IRFs, the 3-year recurrence-free survival rates were 97.8%, 86.3%, and 68.0% respectively (p

Abstract Background Colorectal adenomas (CRAs) are precancerous lesions of the large intestine presenting as colorectal polyps. At present, the conventional treatment methods for CRA mainly include high-frequency electrocoagulation and electroexcision, biopsy forceps polypectomy, cauterization by laser and microwave, and other endoscopic interventions. The principal advantages conferred by these treatment strategies include less trauma, quick postoperative recovery, and simplicity to perform. However, the higher recurrence rates and insignificant improvement of postoperative symptoms after endoscopic surgery are considerable drawbacks to this approach. Besides, there is currently no effective pharmacotherapy to prevent the recurrence of CRA. Jianpi Lishi Jiedu (JLJ) granules are a form of traditional Chinese medicine (TCM) used to manage postoperative patients with CRA, which has shown a certain degree of efficacy in clinical practice. However, its effectiveness and safety profile have not been convincingly evaluated. The purpose of this study is to evaluate the clinical efficacy and safety profile of JLJ granules in the management of postoperative patients with CRA and to observe the recurrence rate of adenoma in these patients. Methods A randomized, double-blind, and placebo-controlled clinical trial is performed in this study. A total of 80 postoperative patients with CRA will be randomly classified into the Jianpi Lishi Jiedu granules group or the placebo control group. Patients in both groups shall receive 3 months of intervention, after which medical follow-up and safety evaluation will be performed for all of the patients. The primary outcome is the recurrence rate of adenomas within 12 months. The secondary outcomes are the cardinal TCM symptom scores, minor TCM symptom scores, Bristol Stool Scale, efficacy of TCM symptoms, safety indicators, and blinding assessment. Discussion In this study, the impact on the recurrence of adenomas and the efficacy and safety of JLJ granules in terms of improving the clinical symptoms of postoperative patients with CRA will be evaluated. Trial registration Trial registration Chinese Clinical Trial Registry ChiCTR 2100044297. Registered on March 16, 2021

Background: The influence of the number of removed lymph nodes (RLNs) on patients with early-stage cervical cancer (ESCC) is still questionable. The objective of this study was to explore the prognostic value of RLNs on ESCC patients. Methods: A retrospective study was performed including all ESCC patients who underwent radical surgery from January 2016 to December 2018. Cox regression analysis was performed to verify the correlation between the number of RLNs and the prognosis (recurrence-free survival [RFS], disease-specific survival [DSS]) of ESCC. According to the guidelines, all the patients were divided into high-risk and non-high-risk groups. The optimal cut-off values of RLNs were determined by receiver operating characteristic curve analysis and Youden index and further the prognostic value of them was explored. Results: A total 1101 patients were enrolled. The number of RLNs was an independent prognostic influence factor of the prognosis of ESCC ( P < .001 for RFS, P < .001 for DSS). The optimal cut-off values of RLNs (40 in the high-risk group and 23 in the non-high-risk group) were significantly associated with the prognosis of ESCC, in the high-risk group ( P < .001 for RFS, P = .002 for DSS) and non-high-risk group ( P < .001 for RFS, P < .001 for DSS), respectively. Conclusions: More extensive lymph node dissection (RLNs ⩾ 40) could benefit the high-risk ESCC patients. However, in the non-high-risk group, moderate lymph node dissection (RLNs ≈23) could also benefit them and may reduce the incidence of related complications. Those findings may help to determine the scope of lymph node dissection in ESCC patients before operation.

Background: Estrogen receptors (ER) and progesterone receptors (PR) have important prognostic value in endometrial cancer, but there is no recognized positive immunohistochemical threshold for predicting the recurrence of early low-risk endometrial cancer. The purpose of this study was to clarify the optimal positive thresholds of the immunohistochemical parameters the ER and PR in early low-risk endometrial cancer. Methods: A total of 332 patients with stage IA endometrial cancer were enrolled from the First Affiliated Hospital of Chongqing Medical University and People’s Hospital of Sha ping ba District in Chongqing between January 2013 and December 2018. First, univariate and multivariate Cox regression analyses were used to analyze the correlation between various clinical factors and the prognosis of early low-risk endometrial cancer. Then, the receiver operating characteristic curve (ROC curve) and Youden index were used to determine the positive thresholds of ER and PR. Results: The positive thresholds of ER and PR for predicting the recurrence of early low-risk endometrial cancer were 12% and 8%, respectively. Multivariate analysis showed that ER ( P = 0.004), PR ( P = 0.026), and p53 ( P = 0.021) were risk factors for the prognosis of patients with early low-risk endometrial cancer. The recurrence-free survival and the overall survival in the low ER group and PR group were much lower than those in the high ER group and PR group ( P

As one of the key technologies in 5th generation mobile networks, device-to-device (D2D) communication technology can significantly improve spectrum utilization, throughput and energy efficiency as well as reduce congestion in the networks. However, due to the spectrum sharing between D2D users (DUs) and cellular users (CUs), it may also cause serious interferences. In this paper, we adopt appropriate stochastic geometric tools to model and analyze the mutual interferences, based on which the coverage probabilities of different users are derived to evaluate the network performance. Specifically, we model the locations of CUs as a Poisson point process (PPP), while the locations of DUs are modelled as a Poisson hole process (PHP), which is driven by the PPP of CUs' locations due to the exclusion between the positions of CUs and DUs. Furthermore, the approximated expressions of user coverage probabilities are obtained by two methods, which are consistent with the simulation results. The first method is to dissolve the hole, and the second method is to approximate the PHP through a thinned PPP. In addition, the user ergodic data rates and the sum data rate of the networks are also derived through the second approach. The impacts of key parameters (such as the density of DUs and the size of the warning radius) on the ergodic rates and sum data rate are analyzed.

BackgroundLymph node metastasis (LNM) is a critical unfavorable prognostic factor in endometrial cancer (EC). At present, models involving molecular indicators that accurately predict LNM are still uncommon. We addressed this gap by developing nomograms to individualize the risk of LNM in EC and to identify a low-risk group for LNM.MethodsIn all, 776 patients who underwent comprehensive surgical staging with pelvic lymphadenectomy at the First Affiliated Hospital of Chongqing Medical University were divided into a training cohort (used for building the model) and a validation cohort (used for validating the model) according to a predefined ratio of 7:3. Logistics regression analysis was used in the training cohort to screen out predictors related to LNM, after which a nomogram was developed to predict LNM in patients with EC. A calibration curve and consistency index (C-index) were used to estimate the performance of the model. A receiver operating characteristic (ROC) curve and Youden index were used to determine the optimal threshold of the risk probability of LNM predicted by the model proposed in this study. Then, the prediction performance of different models and their discrimination abilities for identifying low-risk patients were compared.ResultLNM occurred in 87 and 42 patients in the training and validation cohorts, respectively. Multivariate logistic regression analysis showed that histological grade (P=0.022), myometrial invasion (P=0.002), lymphovascular space invasion (LVSI) (P=0.001), serum CA125 (P=0.008), Ki67 (P=0.012), estrogen receptor (ER) (0.009), and P53 (P=0.003) were associated with LNM; a nomogram was then successfully established on this basis. The internal and external calibration curves showed that the model fits well, and the C-index showed that the prediction accuracy of the model proposed in this study was better than that of the other models (the C-index of the training and validation cohorts was 0.90 and 0.91, respectively). The optimal threshold of the risk probability of LNM predicted by the model was 0.18. Based on this threshold, the model showed good discrimination for identifying low-risk patients.ConclusionCombining molecular indicators based on classical clinical parameters can predict LNM of patients with EC more accurately. The nomogram proposed in this study showed good discrimination for identifying low-risk patients with LNM.

Background: Reproductive outcomes after fresh in vitro fertilization/intracytoplasmic sperm injection–embryo transfer (IVF/ICSI–ET) cycles are diverse in infertile women with a history of ovarian cystectomy for endometriomas. We aimed to develop a logistic regression model based on patients' characteristics including number of embryos transferred and stimulation protocols to predict the live birth rate in fresh IVF/ICSI–ET cycles for such patients.Methods: We recruited 513 infertile women with a history of ovarian cystectomy for endometriomas who underwent their first fresh ET with different stimulation protocols following IVF/ICSI cycles in our unit from January 2014 to December 2018. One or two embryo are implanted. Clinical and laboratory parameters potentially affecting the live birth rate following fresh ET cycles were analyzed. Univariable and multivariable analyses were performed to assess the relationship between predictive factors and live birth rate.Results: The overall live birth rate was 240/513 (46.8%). Multivariable modified Poisson regression models showed that two factors were significantly lowers the probability of live birth: female age ≥ 5 years (aOR 0.603; 95% CI 0.389–0.933; P = 0.023); BMI range 21–24.99 kg/m2 compared with BMI 7 (aOR 1.591; 95% CI 1.075–2.353; P = 0.020); two embryos transferred (aOR 1.607; 95% CI 1.089–2.372; P = 0.017).Conclusions: For these infertile women who had undergone ovarian cystectomy for endometriosis, female age 7, and two embryos transferred might achieve better clinical fresh IVF/ICSI–ET outcomes. BMI

ObjectivesTo evaluate the effect of dyslipidemia on the incidence of moderate and severe Ovarian hyperstimulation syndrome (OHSS) in the duration of assisted reproduction technique (ART).MethodsThe study included 233 moderate and severe OHSS patients who received hospitalization after in-vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) cycles to avoid severe complications. They were divided into dyslipidemia group and normal lipid metabolism group to evaluate whether dyslipidemia contributes to the development of severe OHSS. Subgroup analysis was set to avoid deviation including the freeze-all group and fresh embryo transfer (ET) group according to whether the eligible women chose fresh embryo transfer immediately after their IVF or ICSI cycles. The main outcome measures included the incidence of moderate OHSS and severe OHSS, total gonadotropin dose, number of oocytes retrieved, age and body mass index (BMI). In the ET groups, the rate of pregnancy is also included for analysis.ResultsIn the freeze-all group, lipid metabolism was ultimately identified as the factor affecting the morbidity of severe OHSS and the ones with dyslipidemia were more likely to develop to severe OHSS (P < 0.05), while the incidence of severe OHSS among the ET groups had no statistical significance (P > 0.05).ConclusionThe findings of this study suggested that dyslipidemia might contribute to the development of OHSS, especially for those patients who chose the cryopreservation of all embryos. It is essential to consider the risk of OHSS in patients with dyslipidemia although they required cryopreservation of all embryos.

In this paper, we provide a comprehensive performance analysis of simultaneous wireless information and power transfer (SWIPT) for cognitive relay networks with different relay schemes. In the considered system, the energy-constrained secondary transmitter harvests the energy from the primary signal and then employs the harvested energy to forward the primary signal along with the secondary signal simultaneously. To improve the spectral efficiency, we propose a novel cooperative spectrum sharing protocol with dynamic time-slot allocation based on energy harvesting, namely, dynamic time-power-based cooperative spectrum sharing protocol. Considering the delay-limited transmission mode, we analytically derive the exact closed-form expressions of outage probabilities and achievable throughput for both the primary and secondary networks with amplify-and-forward and decode-and-forward relaying schemes, respectively. More importantly, different from the existing works, we take into account the power outage probability at the energy-constrained secondary transmitter to better match the reality. Finally, the numerical results are provided to evaluate the effect of different key parameters on the system performance, which demonstrate that the dynamic cooperative spectrum sharing protocol improves the outage performance compared with the uniform time-slot allocation scheme.

In this paper, we propose an optimization problem of joint spectrum resource matching, power allocation and transmission time duration in energy harvesting (EH) aided device-to-device (D2D) communications underlying cellular network. Particularly, to increase the spectral efficiency (SE), multiple D2D links are permitted to multiplex the same resource block (RB) of cellular user (CU), and multiple cellular RBs are allowed to be reused by one D2D link. Taking into account the Quality of Service (QoS) of cellular users and the harvested energy of D2D links, our objective is to maximize the sum SE of D2D communications. Specifically, the joint problem is a mixed-integer nonlinear programming problem, which has been proved to be NP-hard. In view of this observation, a novel match-based resource allocation algorithm is designed, which contains two key sub-methods with a progressive relationship. First, a many-to-many matching game with externalities is developed, which produces spectrum reusing during each iteration. Second, on the basis of the spectrum matching, a resource allocation algorithm is presented by employing the Lagrange multiplier and Bisection search method. Finally, comprehensive simulation results are provided to demonstrate the performance of the proposed algorithm with different network parameter settings. Numerical results validate that the proposed algorithm can achieve near-optimal performance and significantly outperform the other matching strategies in aspects of SE.

In this paper, we analyze the anti-eavesdropping and anti-jamming performance of D2D communications with a full-duplex active eavesdropper (FAE). We consider the scenario that when the FAE intrudes the D2D underlaying cellular networks, it can passively wiretap confidential messages in D2D communications and actively jam all legitimate links. A hierarchical and heterogeneous power control mechanism with multiple D2D user equipments (DUEs) and one cellular user equipment (CUE) is proposed to combat the intelligent FAE. Moreover, a multi-tier Stackelberg game is formulated to model the complex interaction among them and the existence of Stackelberg equilibrium (SE) is proved. The best response (BR)-based hierarchical power control algorithm with perfect information and a robust learning method with imperfect information are proposed to obtain SE. The numerical results illustrate the convergence of the two proposed hierarchical power control algorithms, which are also compared with the random selection algorithm (RSA).

This paper investigates the physical layer security (PLS) for the transmission of confidential information over satellite communication systems under unified framework. The generalized shadowed-Rician (SR) fading is utilized to model the satellite channel, and multiple legitimate users are served to cooperatively receive the broadcast signal with a cluster of unauthorized eavesdroppers. In particular, the channel estimation error (CEE) is considered for both the legitimate user and eavesdropping links. Based on the practical channel modeling, we derive the closed-form expressions for the probability of strictly positive secrecy capacity (PSPSC), secrecy outage probability (SOP), and average secrecy capacity (ASC) of the considered satellite communication system in the presence of imperfect channel estimation (ICE), which can provide efficient methods to evaluate the impacts of various propagation parameters on the secrecy performance. In order to obtain further insights into the key parameters on the secrecy performance at high signal-to-noise ratios (SNRs), the asymptotic expressions of the SOP and ASC are also derived. Monte Carlo simulation results are provided to verify the correctness of our performance analysis.

In this paper, we design a new collaboration interference (CI) transmission scheme for overlay cognitive full-duplex wireless wiretap networks, where a full-duplex secondary user utilizes the licensed spectrum to transmit the secondary information and uses the secondary signal as a special noise to help and protect the secure transmission of primary information in the presence of multiple passive eavesdroppers, simultaneously. Specifically, the full-duplex secondary user firstly uses the joint transmit antenna selection/maximal ratio combining (TAS/MRC) scheme to transmit the secondary information and receive the primary information at the same time. Then, the full-duplex secondary user utilizes a new interactive zero forcing beamforming (IZFB) algorithm to transmit the primary and secondary information without mutual interference simultaneously. For comprehensively analyzing the secure performance of the primary transmission, two eavesdropping modes, i.e., non-colluding eavesdropping (NCE) and colluding eavesdropping (CE) are considered. Based on the two modes, we derived the exact and asymptotic closed-form expressions for secrecy outage probability (SOP) of the primary transmission. Furthermore, the effective throughput of secondary transmission is also derived. The results demonstrate that the proposed CI-based transmission scheme can simultaneously improve the secrecy performance of primary transmission and throughput of secondary transmission, and can further achieve better spectrum-and-energy efficiency than traditional overlay transmission.

In this article, we investigate the impact of hardware impairments (HIs) on the performance of non-orthogonal multiple access (NOMA) based integrated satellite-terrestrial relay networks (ISTRNs). Particularly, we obtain the novel closed-form expression for the outage probability (OP) of the considered NOMA-based ISTRNs with HIs. Furthermore, to get further insights of the effect of HIs on the considered system in high signal-to-noise ratios (SNRs) scenario, the asymptotic expression for the OP is also obtained, which provides an efficient way to evaluate the system performance, and effective quantification of different parameters on the system performance. Furthermore, we study the energy efficiency (EE) of the considered system and obtain interesting findings when NOMA scheme is applied. At last, numerical Monte Carlo (MC) results are given to verify the correctness of the theoretical results.

In this paper, we investigate the secrecy performance of wireless powered communication networks (WPCNs) faced by multiple passive eavesdroppers, where the full-duplex (FD) receiver utilizes the harvested energy to send the artificial jamming for enhancing the secrecy performance. Moreover, we adopt a practical maximal ratio transmission (MRT) scheme at the transmitter taking into account the impact of imperfect CSI to try to improve the transmission efficiency of the considered system. Specifically, in order to evaluate the proposed scheme, three important performance metrics, namely, connect outage probability (COP), secrecy outage probability (SOP), and secrecy throughput are adopted in this paper. Concretely, the exact and asymptotic expressions for COP, SOP, and secrecy throughput were derived to effectively analyze the impact of key parameters on the system performance more comprehensively. Through the simulation analysis, we can find that the proposed energy harvesting-based FD-aid jamming (EHFDJ) scheme can achieve better secrecy performance than the reduced half-duplex non-jamming (HDNJ) scheme under a relatively small self-interference.

In this paper, we investigate the secrecy performance of dual-hop decode-and-forward cognitive relay networks taking into account the channel correlation between the main and wiretapping channels. For the enhancement of the secrecy performance, a generalized relay selection scheme is utilized, where the kth strongest relay node is selected based on the main channel. In order to analyze the impact of key parameters on the secrecy performance, we first derive the exact closed-form expression for secrecy outage probability (SOP) of the considered networks. Moreover, to extract deep insights, the asymptotic approximation for SOP in high main-to-eavesdropper ratio (MER) regime is also provided. Our theoretical results as well as simulations demonstrate that: 1) the channel correlation does not affect the achievable secrecy diversity order, but has a positive impact on the secrecy coding gain in high MER regime; 2) the secrecy diversity order is decided by the generalized selection coefficient and the number of relays that can successfully decode the information transmitted from the secondary transmitter; and 3) the total amount of relays cannot influence the secrecy diversity order directly, but has a significant impact on the secrecy coding gain.

In this paper, we investigate the secrecy performance of dual-hop randomize-and-forward (RaF) cognitive relay multi-channel wiretap networks over correlated fading channels, in which the eavesdropper can wiretap the information from source and relays simultaneously. Specifically, in order to enhance the secrecy performance, we introduce two cooperation diversity schemes: 1) traditional partial relay selection (TPRS), where an optimal relay is selected to receive-and-forward the information based on the channel quality between the source and relays and 2) decoding threshold-aided optimal relay selection (DTaORS), where an optimal relay is selected from the threshold-based relay set based on the channel quality between the relays and destination. For these criteria, we analyze the secrecy performance of two cooperation diversity schemes by deriving the exact and asymptotic expressions for the secrecy outage probability of cognitive relay wiretap networks over correlated fading channels. From the results, we conclude that: 1) even though the channel correlation does not influence the secrecy diversity order, it is beneficial to the secrecy coding gain in high main-to-eavesdropper ratio regime; 2) DTaORS with an appropriate decoding rate can achieve better secrecy performance than TPRS. However, affected by the multi-channel wiretap, both of DTaORS and TPRS can not increase the secrecy diversity order any more, which is always equal to 1; and 3) the secrecy performance with a RaF scheme is better than that with a decode-and-forward scheme in multichannel wiretap scenario.

In this paper, we investigate the impacts of joint relay selection and user scheduling scheme on the physical layer security for hybrid satellite-terrestrial relay systems, where multiple terrestrial relays, multiple terrestrial users, and multiple illegitimate eavesdroppers are considered in the network. To strengthen the system security against wiretapping attack, we present a joint opportunistic relay selection and the threshold based user scheduling scheme to balance the system performance and implementation complexity. Furthermore, two representative eavesdropping cases are considered, i.e., the Case I, colluding case: the eavesdroppers cooperate with each other and wiretap the information together, and the Case II, non-colluding case: the best eavesdropper will be chosen to wiretap the information channel. Besides, we derive the closed-form expressions for the average secrecy capacity based on the proposed relay selection and user scheduling scheme in the presence of two eavesdropping cases. To get more insights at high signal-to-noise ratios, the asymptotic expressions for the average secrecy capacity are also derived under two cases, from which we can get the effect of different parameters on the system performance conveniently. At last, analytical results are validated through comparison with the Monte Carlo simulations.

In this paper, we investigate the performance of three transmit antenna selection (TAS) schemes for an energy harvesting decode-and-forward relay cooperative network. In the network, the energy-limited relay first harvests the energy from the received signal with the power-splitting scheme, and then utilizes the harvested energy to forward the received signal to the destination. Specifically, exact analytical expressions for the outage probability of the considered network with three TAS schemes are derived for evaluating the impact of key parameters on the outage performance. In order to deeply extract insights, we further present tractable asymptotic outage probabilities for three TAS schemes to characterize the diversity order and coding gain in high signal-to-noise ratio regimes, respectively. In addition, we also analyze the impact of feedback delays on the performance of the optimal TAS scheme, which is quantified by the reduction of diversity order and coding gain. Numerical results sustained by Monte Carlo simulations demonstrate that: 1) the second suboptimal TAS schemes achieve a comparable performance as the optimal TAS scheme with the reduced implementation cost; 2) the relay location has a great impact on the outage performance and the optimal power-splitting ratio; and 3) the feedback delay plays a critical role in determining the diversity order achieved by the considered system.

In this paper, we investigate the energy-efficient secure uplink transmission for the wireless powered Internet of Things (IoT), where one energy-constrained source and multiple energy-constrained relays harvest energy from multiple power beacons (PBs) in the presence of a passive eavesdropper. To perform energy-efficient secure communications, we consider three relay selection schemes with the best PB selected by the source, i.e., the best relay is selected randomly, the best relay is selected by the source, and the best relay is selected by the best PB (BRBP), respectively. For each scheme, the exact closed-form expressions of power outage probability (POP), secrecy outage probability (SOP), and secure energy efficiency (SEE) are derived over the Rayleigh fading channel. Furthermore, we formulate the SEE maximization problem under the transmit power constraint to optimize the transmit power in PBs and the time-switching factor. Considering the resource limitation for IoT devices, we adopt a low-complexity Dinkelbach algorithm combined with Brent's method to solve this multi-parameter fractional optimization problem. Simulation results demonstrate that the BRBP scheme achieves the best SOP performance and either increasing the number of PBs or decreasing the threshold of POP can significantly improve the SEE of the considered system.

In this paper, we present a comprehensive secrecy performance analysis of wireless powered communication networks with multiple eavesdroppers, where an energy-limited information source with multiple antennas harvests the radio frequency energy from a dedicated power beacon (PB) before transmission. To exploit the benefits of multiple antennas at source, two popular multi-antenna transmission schemes, i.e., maximal ratio transmission and transmit antenna selection, are investigated for two intercepting ways at Eves, i.e., non-colluding and colluding scenarios, respectively. Specifically, adopting the time-switching protocol at PB, we derive exact closed-form expressions of the secrecy outage probability and the average secrecy rate for both two transmission schemes taking into account the outdated channel state information. Furthermore, in order to deeply extract insights on the system design, we further present tractable asymptotic secrecy outage probability and ergodic secrecy capacity at high signal-to-noise ratio regimes, which easily enable us to obtain the secrecy diversity order and coding gain of two transmission schemes, respectively. From our analysis, several important concluding remarks are obtained as follows: 1) full secrecy diversity order can be achieved by both two transmission schemes with no feedback delay, however, it reduces to one in the presence of feedback delay; 2) as the number of eavesdroppers increases, the secrecy performance gap between non-colluding and colluding scenarios becomes large; and 3) maximal ratio transmission (MRT) scheme always outperforms transmit antenna selection (TAS) scheme with no feedback delay. However, TAS scheme achieves a similar performance as MRT scheme or even better in moderate and even serious feedback delay conditions.

We investigate the worst-case robust secure precoding design for simultaneous wireless information and power transfer in multiple-input-multiple-output wiretap system, which consists of one transmitter, one information receiver, and one energy receiver. By treating the ER as potential eavesdropper, we aim to maximize the worst-case secrecy rate by designing the transmit precoding matrix. This is a typical non-convex optimal design while the channel state information uncertainties make this problem harder to handle, thus we propose a new method to obtain the solution. Specifically, instead of approximating the logarithmic determinant as a trace, we propose to linearize the two log-det terms. After linearization, epigraph reformulation is used to deal with the bounded channel uncertainties. Then, an alternating optimization method is utilized to solve the reformulated problem. After obtaining the precoding matrix, we derive the worst-case secrecy rate by solving another optimal problem with respect to the channel uncertainty. Numerical results validate the performance of our proposed design.

Abstract This paper investigates the secrecy performance of amplify-and-forward (AF)-relaying cooperative cognitive radio networks (CCRNs) over Rayleigh-fading channels. Specifically, we consider practical passive eavesdropping scenarios, where the channel state information of the eavesdropper’s link is not available at the secondary transmitter. In order to avoid interfering with the primary receiver and enhance the secrecy performance, collaborative distributed beamforming is adopted at the secondary relays. Closed-form and asymptotic expressions for the secrecy outage probability of CCRNs in the presence of single and multiple non-colluding eavesdroppers are derived. The asymptotic analysis reveals that the achievable secrecy diversity order of collaborative distributed beamforming with M AF relays is M−1 regardless of the number of eavesdroppers. In addition, simulations are conducted to validate the accuracy of our analytical results.

In this paper, we investigate the effect of hardware impairments on the performance of dual-hop amplify-and-forward (AF)/decode-and-forward (DF) multiple relaying networks using switch-and-examine combining with post-selection (SECps) scheduling scheme in shadowed-Rician (SR) channel. Moreover, we consider a more general network, where the hard impairments are both considered at source, relays, and destination. Specifically, to decrease the high-implementation cost, the SECps scheme is adopted to choose an appropriate relay. To evaluate the performance of the considered system, we derive the novel closed-form expression of the outage probability for the AF and DF protocol, respectively. We also derive the asymptotic outage probability results at high SNRs for the DF protocol, which provides a fast way to evaluate the impact of hardware impairments on the dual-hop relay networks in the SR channel. In addition, simulation results are given to validate the correctness of the analytical results.

In this paper, we investigate the physical layer security for amplify-and-forward relay networks with simultaneous wireless information and power transfer. Specifically, by considering the dual-functional desired receiver, which is capable of decoding information and energy harvesting (EH), and assuming that only imperfect eavesdroppers' channel state information can be attained, we propose a joint robust cooperative beamforming, artificial noise, and power splitting scheme. We formulate the relay power minimization problem under both the secrecy rate constraint and the EH constraint, which is non-convex and hard to tackle. To tackle this problem, we propose a two-level optimization approach, which involves 1-D search and the semi-definite relaxation. In addition, we testify that the SDR can obtain the rank-one optimal solution. Simulation results show that the proposed robust scheme achieves better secrecy performance than other schemes.

In this paper, we investigate the secure transmission of wireless relaying systems with multidestinations and an eavesdropper (Eve) in Nakagami-m fading channels. To protect the confidential message from leaking to the Eve, an intentional interference is sent from a selected destination. We propose two jammer selection schemes under two typical communication scenarios: the channel state information (CSI) of the Eve is unknown, where ajammer is selected based on the CSI between the selected legitimate receiver and the other destination users and the CSI of the Eve is available, where a jammer is selected based on the CSI between the Eve and the other destination users. To assess the performance of the two proposed schemes, we first derive the exact closed-form expressions of intercept probability and outage probability to evaluate the security and the reliability of the system, respectively. In addition, to evaluate the security and reliability as a whole, we propose a new definition of the security-reliability tradeoff, which allows us to easily optimize the power allocation and improve the performance. Finally, simulation results are provided to verify the availability of the proposed schemes.

In this paper, we design a novel architecture of distributed satellite cluster network (DSCN). In order to achieve a good trade-off between the energy consumption and the total capacity, we investigate the joint downlink power and time-slot allocation problem, taking into account the limitation of resource, collaborative coverage of multi-satellite, and dynamism, which is proved to be a Pareto optimization and NP-hard problem. Different from the existing 1-D multi-objective optimization algorithm (1D-MOA) based on meta-heuristics, such as immune clonal algorithm (ICA), we propose an improved 2-D dynamic immune clonal algorithm (TDICA) to search the solution space for approaching the Pareto front. From simulation results, several important concluding remarks are obtained as follows: 1) the proposed TDICA can obtain more non-dominated solutions in each iteration with better accuracy than existing algorithms; 2) with inter-satellite resource optimization, the total capacity can be improved; 3) compared with 1D-MOAs, the 2D-MOA can save more energy and achieve higher total capacity; d) MOAs can be transferred into multiple single-objective optimization algorithms (SOAs) under certain conditions.

A fully hydraulic variable valve system based on spark-ignition engine BJ486EQ is introduced in this article, which can provide fully variable valve lifts, valve timing, and valve opening duration. A simulation model of fully hydraulic variable valve system is established, which is verified through experimental intake valve lift and hydraulic pressure. It is found that pressure fluctuation in hydraulic system of fully hydraulic variable valve system becomes greater with the increase in engine speed, which even leads to “lift distortion.” The cam profile of fully hydraulic variable valve system and the structure of the throttling valve which is used to reduce valve seating speed are optimized by simulation. The lift distortion and rebound do not occur in the optimized fully hydraulic variable valve system, which is indicated by the results of simulation and experiments when the engine speed is 5000 r/min, and valve seating characteristics become stable and soft.

We investigate the secrecy outage performance of spectrum sharing multiple-input multiple-output networks using generalized transmit antenna selection with maximal ratio combining over Nakagami-m channels. In particular, the outdated channel state information is considered at the process of antenna selection due to feedback delay. Considering a practical passive eavesdropper scenario, we derive the exact and asymptotic closed-form expressions of secrecy outage probability, which enable us to evaluate the secrecy performance with high efficiency and present a new design insight into the impact of key parameters on the secrecy performance. In addition, the analytical results demonstrate that the achievable secrecy diversity order is only determined by the parameters of the secondary network, while other parameters related to primary or eavesdropper's channels have a significantly impact on the secrecy coding gain.

In this paper, we introduce transmit antenna selection/maximal-ratio combining (TAS/MRC) scheme in dual-hop randomize-and-forward (RaF) cognitive multiple-input multiple-output (MIMO) wiretap networks with outdated channel state information (CSI). In this network, the secondary transmitter adopts the TAS scheme to choose the antenna with the maximal received signal-to-noise ratio (SNR), while the secondary receiver and the eavesdropper adopt the MRC scheme to combine the received signals. To thoroughly assess the secrecy performance achieved by the TAS/MRC scheme and the impact of outdated CSI on the secrecy performance, we derive a new closed-form expression for the secrecy outage probability of dual-hop RaF cognitive MIMO wiretap networks. In order to achieve more insights on the application of TAS/MRC scheme, we further present tractable asymptotic secrecy outage probability at high SNR regimes under two distinct scenarios. From our analysis, several important concluding remarks are obtained as follows: 1) the RaF relaying strategy achieves better secrecy performance than that of the decode-and-forward relaying strategy for dual-hop cognitive MIMO wiretap networks; 2) outdated CSI decreases the secrecy diversity gain of the TAS/MRC scheme from NR min (NA, NB) to (NR, NB) ; and 3) although TAS/MRC scheme cannot attain full secrecy diversity gain for the considered system with outdated CSI, it still can achieve an extra secrecy coding gain compared with the random antenna selection/MRC scheme.

A novel threshold‐based scheduling scheme for multiuser downlink wiretap networks is addressed, which consist of a base station (BS), multiple legitimate users and multiple eavesdroppers. Particularly, the active scenario is concentrated, where BS has access to the channel state information for the eavesdropper's channel. In doing so, new exact and asymptotic closed‐form expressions for the ergodic secrecy capacity are derived for multiuser downlink networks using switch‐and‐examine combining with post‐selection scheduling at legitimate users and maximum ratio combining at the eavesdroppers. Moreover, the high signal‐to‐noise ratio slope and power offset are also given to explicitly characterise the impact of main link and wiretap link on the ergodic secrecy capacity. Simulation results show the effect of key parameters such as the number of legitimate users and eavesdroppers, switching threshold on the secrecy performance of the considered wiretap network.

Space information networks are proposed to broaden the observation area and realize continuous information acquisition using satellites and high-altitude platform stations. Space information networks are able to enhance detection and transmission capabilities compared to the current single Earth observation satellite. The satellite–terrestrial network is an important component of the space information networks. Hence, the major contribution of this article is to propose a new transmitted link selection scheme in a satellite–terrestrial network. Switch-and-stay combining scheme is used by destination to have a trade-off between the complexity and efficiency. The satellite, terrestrial relays, and destination user are influenced by hardware impairments, respectively. The closed-form expressions for the outage probability and throughput are derived. In order to analyze the system performance at high signal-to-noise rate, the asymptotic expressions for the system performance are also derived to give a special view on the impact of hardware impairments on the considered network. What is more, numerical results are derived to verify the correctness of our analytical results.

In wireless sensor networks, sensor nodes are deployed to collect data and deliver the sensed information to a base station in a wireless manner. Due to the broadcast nature of wireless sensor communications, relay-sensor-based secure transmission remains a challenging issue. This article proposes a joint cooperative beamforming and jamming scheme in the relay wireless sensor networks, where the switching strategy from cooperative beamforming to cooperative jamming is applied to weaken the signal-to-interference-plus-noise ratio of the eavesdropper when the decoding threshold is not triggered. In particular, based on Charnes–Cooper transformation and S-procedure, semi-definite programming is constructed to solve the robust cooperative beamforming and jamming with a low implementation complexity, respectively. Additionally, we adopt the global power constraints in semi-definite programming to take full exploitation of the power at relay sensor. Finally, simulation results demonstrate the superiority of the proposed scheme in comparison with the traditional decode-and-forward robust scheme and the non-robust scheme.

This paper investigates the joint impact of channel estimation errors (CEEs) and hardware impairments (HIs) on the performance of a cognitive satellite-terrestrial relay network (CSTRN), where the terrestrial and satellite links are considered following Rayleigh fading and shadowed Rician (SR) fading distributions, respectively. Besides, the terrestrial relay is working in half-duplex decode-and-forward (DF) mode. By employing a general and practical model to account for both the CEEs and HIs at each link, the end-to-end signal-to-noise-plus-distortion-and-error ratio (SNDER) is first obtained for the CSTRN. Then, closed-form expressions for the outage probability (OP) and throughput of the CSTRN are obtained, which allows us to demonstrate the aggregate impact of CEEs and HIs. In order to gain insightful findings, we further elaborate on the asymptotic OP and throughput at the high signal-to-noise-ratio (SNR) condition and quantitatively determine the fundamental performance ceiling. Finally, Monte Carlo (MC) computer simulations are provided to verify the correctness of the analytical results. Besides, with representative numerical analysis’s help, interesting findings are presented.

In this paper, we investigate the secure transmission in wireless sensor networks (WSNs) consisting of one multiple-antenna base station (BS), multiple single-antenna legitimate users, one single-antenna eavesdropper and one multiple-antenna cooperative jammer. In an effort to reduce the scheduling complexity and extend the battery lifetime of the sensor nodes, the switch-and-stay combining (SSC) scheduling scheme is exploited over the sensor nodes. Meanwhile, transmit antenna selection (TAS) is employed at the BS and cooperative jamming (CJ) is adopted at the jammer node, aiming at achieving a satisfactory secrecy performance. Moreover, depending on whether the jammer node has the global channel state information (CSI) of both the legitimate channel and the eavesdropper’s channel, it explores a zero-forcing beamforming (ZFB) scheme or a null-space artificial noise (NAN) scheme to confound the eavesdropper while avoiding the interference to the legitimate user. Building on this, we propose two novel hybrid secure transmission schemes, termed TAS-SSC-ZFB and TAS-SSC-NAN, for WSNs. We then derive the exact closed-form expressions for the secrecy outage probability and the effective secrecy throughput of both schemes to characterize the secrecy performance. Using these closed-form expressions, we further determine the optimal switching threshold and obtain the optimal power allocation factor between the BS and jammer node for both schemes to minimize the secrecy outage probability, while the optimal secrecy rate is decided to maximize the effective secrecy throughput for both schemes. Numerical results are provided to verify the theoretical analysis and illustrate the impact of key system parameters on the secrecy performance.