This letter proposes a method to enhance satellite communication security based on high-dimensional spatiotemporal chaos. It separates information into two parts and processes both parts simultaneously using a single 2D spatiotemporal chaotic signal matrix. One part is mapped to the spatial-domain index value as Chaos Shift Keying (CSK), and another part is spread spectrum (SS) using a sequence generated by the spatiotemporal chaotic time-domain array determined by the index value. At the receiver, the spatiotemporal chaotic matrix is reconstructed to demodulate the spatial index and then despread the chaotic sequence. CSK and SS using one spatiotemporal chaos can simplify the transmitting and receiving process. And the theoretical analysis and simulation results show that the method proposed in this letter can improve the security performance while reducing the bit error rate.

To address the challenge of secure transmission over open channels such as satellite communications, this paper proposes a Spatiotemporal Chaotic Spread Dimension Shift Keying (SCSDK) security communication method incorporating Artificial Noise (AN). This method constructs a two-dimensional spatiotemporal chaotic matrix to map grouped information bits onto spatial dimension index selection and temporal dimension sequence spreading. Innovatively, unselected chaotic sequences are transmitted as "natural" artificial noise synchronized with the signal, achieving enhanced security without requiring additional hardware. At the receiver, the chaotic matrix is reconstructed using synchronization information. Following the removal of artificial noise, information demodulation is achieved via correlation detection. Simulation results demonstrate that, compared with conventional Direct Sequence Spread Spectrum (DSSS) schemes, this method increases the eavesdropper's Probability of Demodulation Error (PDE) by approximately 67 times while maintaining legitimate user communication quality, boosting the system's secrecy capacity by about 32.9%. This study provides an efficient and practical physical layer security solution for power-constrained satellite communication systems.

Spatiotemporal chaos with high complexity is often used in the design of low probability of intercept signals, and DS/FH(Direct-Sequence/Frequency-Hopped Spread-Spectrum) hybrid communication has strong anti-jamming ability. The combination of spatiotemporal chaos with DS/FH spread sequence is very suitable for anti-interference and anti-interception communications. But the acquisition problem of spatiotemporal chaos DS/FH sequence is an important factor to restrict its practical application. In this paper, a feasible acquisition scheme for spatiotemporal chaos is put forward that can acquire direct spread spectrum sequence and frequency hopping sequence simultaneously based on a drive-response synchronization algorithm. The simulation results show that the scheme has a faster convergence speed, good capability to resist intercept, and it is easy to be implemented with low resource consumption, which has a broad application prospect.

Satellite communications with seamless global coverage play an indispensable role in modern communications. However, the openness of the satellite transmission channel makes the signals susceptible to unauthorized interception, which poses a serious security risk, especially in the field of national defense and military applications. There is a critical demand for highly reliable covert communication systems. This paper, based on the architecture of multi-satellite cooperative, multi-antenna user terminals from the covert communication theory, investigates the covert performance of satellite-based covert communication systems in a multi-satellite cooperative framework. Integrating theoretical derivations with simulation-based analyses, this study provides research results with significant reference value for satellite covert communication engineering applications.

The Janus structure of carbonized polymer dots (CPDs) is characterized by an independent yet interdependent core and shell structure, potentially enabling them to function as a self-ratiometric photoluminescence (PL) sensor. However, to our best knowledge, the current lacking understanding and development of the Janus structure of CPDs lead to the unfortunate loss of its position as PL sensors that could have supported life analysis to some extent. Therefore, it is crucial to comprehensively explore the structural characteristics of CPDs and furtherly develop its potential as self-ratiometric sensors. Herein, green and red double-emitting CPDs has been rationally designed and synthesized, incorporating a distinct core-shell structure to create a self-ratiometric sensor for hypochlorite (ClO−). Leveraging the low toxicity and high-water solubility of CPDs, we have successfully achieved exogenous and endogenous ClO− sensing in cells. This approach offers a novel strategy for developing CPDs-based sensors and sets the stage for a more in-depth exploration of the Janus structure of CPDs.

In this paper, the user selection problem is investigated in the multi-user satellite multiple-input multiple-output (MIMO) downlink, which includes a multi-beam geostationary earth orbit (GEO) satellite in space and multiple terrestrial users on the ground. Considering that the number of users is much larger than that of beams or feeds, user selection should be performed so that multiple users can be served successively in different time slots. In order to meet the quality of service (QoS) requirements of users and maximize the system sum rate, three user selection algorithms are proposed: greedy user selection (GUS) algorithm, add swap user selection (AS) algorithm, and random add swap user selection (RAS) algorithm. Among the three algorithms, only the “add” operation is adopted in the GUS algorithm, both the “add”, and “swap” operations are considered in the AS algorithm. On this basis, heuristic search and “random swap” operation are introduced and the RAS algorithm is obtained. The complexity of the above three algorithms is analyzed analytically and the RAS algorithm is found to have the highest complexity. Besides, the performance of the three algorithms is analyzed and compared through simulations, where the random user selection (RUS) algorithm is taken as a benchmark. Numerical results show that the system sum rate and energy efficiency are greatly improved by the proposed algorithms and the RAS algorithm has the best performance.

The objective of this research was to examine the influence of nonuniform NAPL distribution and hydraulic-conductivity heterogeneity on the retention and transport of PFAS. Two-dimensional flow cell experiments were conducted to investigate the impact of NAPL configuration on PFOS retention. Two simplified NAPL configurations were used, one with decane present as residual and the other with greater-than-residual (pool) NAPL saturation. The measured and predicted retardation factors were 1.7 and 1.6 for the residual-NAPL flow cell. The fractions of retention associated with solid-phase sorption, NAPL-water interfacial adsorption, and NAPL absorption were 0.56, 0.43, and 0.1, respectively. The measured retardation factor was 1.4 for the pool-NAPL flow cell. Notably, the predicted retardation factor assuming no contribution from NAPL-water interfacial adsorption was 1.5. Comparison of the two values indicates a minimal contribution of NAPL-water interfacial adsorption to transport, which is attributed to the impact of by-pass flow effects that limited contact of PFOS with the NAPL present within the pool. Mathematical-model simulations were conducted to examine the impact of heterogeneity on PFOS transport in model NAPL-contaminated heterogeneous source zones. The results demonstrated that the impact of NAPL-water interface adsorption on PFAS transport in NAPL-contaminated source zones can be influenced by the magnitude of hydraulic-conductivity heterogeneity.

军事卫星通信系统课程是军校本科学员的首次任职专业课,对照教育部提出的"金课"建设标准,结合军队院校课程为战教战的要求,提出面向"四性一度"的军事卫星通信系统"金课"建设方案.围绕课程教学目标制定、课程教学内容优化、教学模式设计、课程资源建设与课程考核机制等方面进行具体阐述,该课程建设聚焦课程教学铸魂性和为战性军事人才培养要求,着重强调课程的高阶性、创新性、挑战度,可为面向特定岗位任职的专业课程建设提供借鉴.

Carbonized polymer dots (CPDs) have attracted great interestasa nanomaterial in biomedical applications, especially in imaging andphotodynamic therapy (PDT). However, CPDs with an aggregation-inducedeffect for type I PDT has been rarely reported. In this work, N,N & PRIME;-dimethylurea and citric acidwere used as precursors to prepare CPDs (YCPDs) with aggregation-inducedeffect in one pot by the solvothermal method. The YCPDs have a yellowemission of 550 nm and a high quantum yield of 68%, which lays a solidfoundation for cell imaging. In addition, YCPDs can produce O-& BULL;(2) (-) under white light irradiation andobtain (OH)-O-& BULL; through electron transfer or hydrogenatom abstraction. In vitro results show that YCPDs possess great cytocompatibilitybut exert severe cytotoxicity to HeLa cells with only 2% of cell viabilitywhen exposed to ultralow-power-intensity (2.5 mW/cm(2)) lightirradiation. Therefore, YCPDs, as a promising type I PDT nanomaterial,have a great potential for cancer therapy.

针对军校学生课业多、训练多、任务多,可利用的课余时间少且零碎的现状,为提高"军事卫星通信系统"课程的教学效果,以课程第四教学单元"信道资源规划与分配"为例,分别从课前在线课程设计、课中线下课程设计及课后教学评价设计3个方面进行线上线下混合式教学模式研究,探索适合军校学生学习的教学模式,使学生能够真正掌握理论知识,并将其运用到后续课程"军事卫星通信设备"中,为打造符合军校特点的混合式教学模式提供参考.

A novel modified rice husk (MRH) has been prepared for removing cationic dyes in both single system and binary system. SEM-EDS, FT-IR, XRD and XPS were used to characterize the physical and chemical properties of MRH. It showed that the maximum adsorption capacity of MRH for methyl violet (MV) and malachite green (MG) in single system was 154.49 and 996.97 mg g-1, while in binary system was 530.94 and 408.58 mg g-1, respectively. The experimental results showed that the pseudo-second-order kinetic model was better to describe the kinetic behavior of MV and MG adsorption. By using double layer adsorption model, we found that the nD for MV adsorption were 2.52, 2.65 and 3.34 at 298, 308 and 318 K, respectively, and the nD for MG adsorption were 4.59, 4.85 and 4.30, respectively. These results illustrated that multiple dye molecules were adsorbed on one adsorption site in non-parallel direction, indicating that the adsorption of dyes is multi-molecular mechanism. Furthermore, synergistic and antagonistic adsorption might be existed simultaneously in binary system. In summary, MRH has been shown well adsorption properties and reusability and our finding might provide a new idea for developing low-cost, efficient and reusable adsorbent to remove dyes from wastewater.

Waste utilization is not only the protection of the environment and the practice of green chemistry, but also one of the ways to develop new materials. Herein, we report two biomass carbon dots which prepared from bee pollen waste by one-step hydrothermal method. The new two carbon dots were used in sensing, cell imaging and plant growth regulation. The differences in the structure and properties of the two carbon dots were evaluated by TEM, XPS, TG and various spectroscopic methods. Both two carbon dots contain abundant functional groups, polyatomic doping, excellent water solubility and stable photoluminescence. Due to these good properties, we have demonstrated its versatile applications in Fe3+ sensing, cell imaging and plant growth regulation. It shows sensitive and specific Fe3+ responsiveness and good biocompatibility. This research provides a green and simple method for the recycling and reuse of bee pollen waste, and also provides a reference for the application of biomass carbon dots.

为全面提升高校本科教育质量水平,教育部要求各高校淘汰"水课"、打造"金课",合理提升课程的深度、难度和挑战度.通过将科研实践与教育教学深度融合,提出一种科研嵌入式教学模式,并基于此模式,以"卫星通信"课程为例,从教学准备、教学实施和教学评价3个方面对符合"金课"要求的教学设计进行了探讨,为打造"金课"提供了参考思路.

This paper presents the design of a compact dual-band bandpass filter (DB-BPF) with flexible passband frequencies and sharp skirt. A pair of stub loaded stepped-impedance resonators (SL-SIRs) together with two different tri-section stepped-impedance resonators (TS-SIRs) constitute this DB-BPF. The low impedance sections of two SL-SIRs and one TS-SIR are realized by ring structure, on the one hand to acquire two independent resonant modes of SL-SIRs, and on the other hand to let the harmonic mode of TS-SIR be away from the upper passband. The cross coupling, the canceling effect of mixed electric and magnetic coupling (MEMC), and the virtual ground introduce the TZs, resulting in the sharp skirt property of proposed DB-BPF. Step-to-step design process is given to guide the DB-BPF design. As an example, a 0.9 / 1.8 GHz DB-BPF is designed and fabricated. The fabricated sharp skirts DB-BPF has a compact size of 0.079 lambda(g) x 0.193 lambda(g), low passband loss of 0.84 / 0.98 dB and high band-to-band rejection of better than 40.6 dB.

Considering the spatial possibility of opportunistic spectrum sharing, sensing-based spectrum sharing method ws applied in the satellite-terrestrial network.The sensing-throughput tradeoff problem was studied, and the throughput is a concave function of the sensing duration was proved.In order to further improved the satellite uplink throughput, the multi-slots sensing method and the cooperative sensing method were proposed.Computer simulations showed that the optimal sensing duration could maximized the uplink throughput, and the multi-slot sensing method or the cooperative sensing method could further improved the throughput of satellite network.

目的 了解江苏省疾病预防控制中心艾滋病自愿咨询检测门诊(voluntary counseling and testing,VCT)男男同性性行为人群(men who have sex with men,MSM)人类免疫缺陷病毒(human immunodefi-ciency virus,HIV)感染趋势及相关影响因素,为评价艾滋病防控效果及制定防治策略提供依据.方法 2013-2018年,招募年龄≥16岁,在过去1年与男性发生过肛交或口交性行为,知情同意并自愿参与本调查的MSM,分析HIV感染的影响因素.结果 2013-2018年共调查MSM 6976人,HIV感染率、梅毒抗体阳性率和合并感染率均呈上升趋势,差异有统计学意义(P＜0.05).多因素logistic回归分析显示,最近6个月与同性发生无保护肛交性行为(OR=1.58,95％CI:1.31～1.92)、最近6个月与异性发生无保护性行为(OR=0.65,95％ CI:0.43～0.81)、最近6个月未接受过艾滋病检测(OR=2.30,95％CI:1.90～ 2.79)、梅毒感染(OR=2.23,95％CI:1.82～2.74)为HIV感染的影响因素.结论 20132018年VCT门诊MSM HIV感染呈上升趋势,应加强对该人群的行为干预,加大安全套使用的宣传,制定针对性的艾滋病防治措施.

This paper presents a K-band high-gain Class-A power amplifier (PA) with the two-way combining approach in GSMC 130-nm radio frequency (RF) complementary metal oxide semiconductor (RF CMOS). At the input, a slow-wave transmission-line transformer (S-TLT) matching network is proposed for simultaneously realizing the impedance transformation and the single-ended RF signal to differential conversion. Transmission-line transformers (TLTs) are employed between the stages for coupling and inter-stage matching. To improve the output power and efficiency, the placing and routing of the transistor layout are considered carefully for power stages to reduce the interconnecting and overlapping parasitics significantly. The PA has been fabricated and achieved good matching at 25 GHz, power gain of 17.8 dB, saturated output power of 14.9 dBm, output 1-dB compression point of 12.4 dBm, and power added efficiency of 13.7% at a supply voltage of 1.5 V.

目的 了解离异/丧偶男男性行为者(MSM)人类免疫缺陷病毒(HIV)、梅毒感染现状,分析其人口学及性行为相关特征.方法 采用滚雪球抽样法招募2018年1月至2019年12月江苏省疾病预防控制中心自愿咨询检测(VCT)门诊收取的MSM作为研究对象.采用问卷调查收集相关信息,采集其静脉血进行HIV和梅毒抗体检测.结果 共完成合格问卷调查1458人,其中离异/丧偶66人(4.53％).离异/丧偶MSM的HIV感染率为24.24％,HIV合并梅毒现症感染率为3.03％,均高于其他婚姻状况,差异具有统计学意义(P<0.05).≥40岁、大专及以上文化程度以及自我认同为同性恋性取向的离异/丧偶发生率较高,差异具有统计学意义(P<0.05).离异/丧偶MSM最近6个月与同性发生肛交性行为时每次都用安全套的占33.33％,最近6个月中最近1次与同性固定性伴发生肛交性行为时使用安全套的占56.82％.78.79％知道国家有免费艾滋病检测政策,53.03％最近1年没有做过HIV检测,差异具有统计学意义(P<0.05).结论 离异/丧偶MSM年龄较大,文化程度较高,艾滋病高危行为明显,是艾滋病防控的重点人群.

如何科学、有效地整合科研实践和教学这两种基本活动,是高校人才培养和教师队伍建设中亟须解决的问题.对目前高校教育科研实践与教学活动的现状进行了分析,总结了当前二者相互结合与转化的形式和特点,提出科研实践嵌入式教学模式.从教学准备、教学实施及评价机制3个方面对提出的教学模式进行了探讨,为高等教育提高教师综合能力、进一步培养创新型人才提供了新的发展思路.