Jamming Assisted Covert Wireless Communication in Multi-Channel Systems

This paper investigates the jammerassisted multi-channel covert wireless communication(CWC)by exploiting the randomness of sub-channel selection to confuse the warden.In particular,we propose two sub-channel selection transmission schemes,named random sub-channel selection(RSS)scheme and maximum sub-channel selection(MSS)scheme,to enhance communication covertness.For each proposed scheme,we first derive closed-form expressions of the transmission outage probability(TOP),the average effective rate,and the minimum average detection error probability(DEP).Then,the average effective covert rate(ECR)is maximized by jointly optimizing the transmit power at the transmitter and the number of sub-channels.Numerical results show that there is an optimal value of the number of sub-channels that maximizes the average ECR.We also find that to achieve the maximum average ECR,a larger number of subchannels are needed facing a stricter covertness constraint.

A novel multi-channel porous structure facilitating mass transport towards highly efficient alkaline water electrolysis

An advantageous porous architecture of electrodes is pivotal in significantly enhancing alkaline water electrolysis(AWE)efficiency by optimizing the mass transport mechanisms.This effect becomes even more pronounced when aiming to achieve elevated current densities.Herein,we employed a rapid and scalable laser texturing process to craft novel multi-channel porous electrodes.Particularly,the obtained electrodes exhibit the lowest Tafel slope of 79 mV dec^(-1)(HER)and 49 mV dec^(-1)(OER).As anticipated,the alkaline electrolyzer(AEL)cell incorporating multi-channel porous electrodes(NP-LT30)exhibited a remarkable improvement in cell efficiency,with voltage drops(from 2.28 to 1.97 V)exceeding 300 mV under 1 A cm^(-1),compared to conventional perforated Ni plate electrodes.This enhancement mainly stemmed from the employed multi-channel porous structure,facilitating mass transport and bubble dynamics through an innovative convection mode,surpassing the traditional convection mode.Furthermore,the NP-LT30-based AEL cell demonstrated exceptional durability for 300 h under 1.0 A cm^(-2).This study underscores the capability of the novel multi-channel porous electrodes to expedite mass transport in practical AWE applications.

Design of Cold-Junction Compensation and Disconnection Detection Circuits of Various Thermocouples and Implementation of Multi-Channel Interfaces Using Them-A Secondary Publication

Cold-junction compensation(CJC)and disconnection detection circuit design of various thermocouples(TC)and multi-channel TC interface circuits were designed.The CJC and disconnection detection circuit consists of a CJC semiconductor device,an instrumentation amplifier(IA),two resistors,and a diode for disconnection detection.Based on the basic circuit,a multi-channel interface circuit was also implemented.The CJC was implemented using compensation semiconductor and IA,and disconnection detection was detected by using two resistors and a diode so that IA input voltage became-0.42 V.As a result of the experiment using R-type TC,the error of the designed circuit was reduced from 0.14 mV to 3μV after CJC in the temperature range of 0°C to 1400°C.In addition,it was confirmed that the output voltage of IA was saturated from 88 mV to-14.2 V when TC was disconnected from normal.The output voltage of the designed circuit was 0 V to 10 V in the temperature range of 0°C to 1400°C.The results of the 4-channel interface experiment using R-type TC were almost identical to the CJC and disconnection detection results for each channel.The implemented multi-channel interface has a feature that can be applied equally to E,J,K,T,R,and S-type TCs by changing the terminals of CJC semiconductor devices and adjusting the IA gain.

Multi-channel terahertz focused beam generator based on shared-aperture metasurface

Most of existing metasurfaces usually have limited channel behavior,which seriouslyhinders their development and application.In this paper,we propose a multi-channel terahertz focused beam generator based on shared-aperture metasurface,and the generator consists of a top square metal strip,a middle layer of silica and a metal bottom plate.By changing the position and size of the shared-aperture array,the designed metasurface can generate any number of multi-channel focusing beams at different predicted positions.In addition,the energy intensity of focusing beams can be controlled.The full-wave simulation results show that the metasurface achieves four-channel vortex focused beam generation with different topological charges,and five-,six-,eight-channel focused beam generation with different energy intensities at a frequency of 1 THz,which are in good agreement with the theoretically calculated predictions.This work can provide a new idea for designing the terahertz multichannel devices.

Fast pre-stack multi-channel inversion constrained by seismic reflection features

Classical multi-channel technology can significantly reduce the pre-stack seismic inversion uncertainty, especially for complex geology such as high dipping structures. However, due to the consideration of complex structure or reflection features, the existing multi-channel inversion methods have to adopt the highly time-consuming strategy of arranging seismic data trace-by-trace, limiting its wide application in pre-stack inversion. A fast pre-stack multi-channel inversion constrained by seismic reflection features has been proposed to address this issue. The key to our method is to re-characterize the reflection features to directly constrain the pre-stack inversion through a Hadamard product operator without rearranging the seismic data. The seismic reflection features can reflect the distribution of the stratum reflection interface, and we obtained them from the post-stack profile by searching the shortest local Euclidean distance between adjacent seismic traces. Instead of directly constructing a large-size reflection features constraint operator advocated by the conventional methods, through decomposing the reflection features along the vertical and horizontal direction at a particular sampling point, we have constructed a computationally well-behaved constraint operator represented by the vertical and horizontal partial derivatives. Based on the Alternating Direction Method of Multipliers (ADMM) optimization, we have derived a fast algorithm for solving the objective function, including Hadamard product operators. Compared with the conventional reflection features constrained inversion, the proposed method is more efficient and accurate, proved on the Overthrust model and a field data set.

Opportunistic Routing with Multi-Channel Cooperative Neighbour Discovery

Due to the scattered nature of the network,data transmission in a dis-tributed Mobile Ad-hoc Network(MANET)consumes more energy resources(ER)than in a centralized network,resulting in a shorter network lifespan(NL).As a result,we build an Enhanced Opportunistic Routing(EORP)protocol architecture in order to address the issues raised before.This proposed routing protocol goal is to manage the routing cost by employing power,load,and delay to manage the routing energy consumption based on theflooding of control pack-ets from the target node.According to the goal of the proposed protocol techni-que,it is possible to manage the routing cost by applying power,load,and delay.The proposed technique also manage the routing energy consumption based on theflooding of control packets from the destination node in order to reduce the routing cost.Control packet exchange between the target and all the nodes,on the other hand,is capable of having an influence on the overall efficiency of the system.The EORP protocol and the Multi-channel Cooperative Neighbour Discovery(MCCND)protocol have been designed to detect the cooperative adja-cent nodes for each node in the routing route as part of the routing path discovery process,which occurs during control packet transmission.While control packet transmission is taking place during the routing path discovery process,the EORP protocol and the Multi-channel Cooperative Neighbour Discovery(MCCND)protocol have been designed to detect the cooperative adjacent nodes for each node in the routing.Also included is a simulation of these protocols in order to evaluate their performance across a wide range of packet speeds using Constant Bit Rate(CBR).When the packet rate of the CBR is 20 packets per second,the results reveal that the EORP-MCCND is 0.6 s quicker than the state-of-the-art protocols,according to thefindings.Assuming that the CBR packet rate is 20 packets per second,the EORP-MCCND achieves 0.6 s of End 2 End Delay,0.05 s of Routing Overhead Delay,120 s of Network Lifetime,and 20 J of Energy Consumption efficiency,which is much better than that of the state-of-the-art protocols.

首次复治菌阳肺结核合并糖尿病患者血清IAP、25(OH)D水平及对疗效的预测价值

目的探讨首次复治菌阳肺结核(TB)合并糖尿病(DM)患者血清免疫抑制酸性蛋白(IAP)、25-羟基维生素D[25(OH)D]表达变化及2者对治疗疗效的预测价值。方法选取本院2019年1月至2022年4月首次复治菌阳TB合并DM患者48例为实验组,另选同期单纯TB患者48例为对照组。测定并比较两组患者治疗前后血清IAP、25(OH)D水平;多因素Logistic回归分析影响菌阳TB合并DM患者痰菌阴转的可能因素;受试者工作特征(ROC)曲线评估IAP、25(OH)D对患者痰菌未转阴的预测价值。结果实验组痰菌阴转患者31例(64.58%)显著低于对照组痰菌阴转患者40例(83.33%)。治疗2个月后,实验组、对照组血清IAP均显著降低,25(OH)D水平均显著升高(P<0.05);且治疗2个月后实验组血清IAP水平显著低于对照组,25(OH)D水平显著高于对照组(P<0.05)。多因素Logistic回归分析显示,IAP高水平是首次复治菌阳TB合并DM患者痰菌未阴转的危险因素(P<0.05),25(OH)D高水平是首次复治菌阳TB合并DM患者痰菌未阴转的保护因素(P<0.05)。ROC曲线显示,IAP预测痰菌未阴转的AUC为0.719,25(OH)D预测痰菌未阴转的AUC为0.791,2者联合预测痰菌未阴转的AUC为0.871,明显高于2者单独诊断(Z_(联合vs IAP)=2.605、P=0.009;Z_(联合vs 25(OH)D)=2.408、P=0.016),且灵敏度、特异性分别为78.46%、82.86%。结论首次复治菌阳TB合并DM患者经治疗后血清IAP水平降低、25(OH)D水平升高,2者联合对菌阳TB合并DM患者痰菌未阴转具有一定预测价值。

1990—2020年波曲流域冰川冰湖时空变化及其对气候变化的响应

基于Landsat TM/ETM+/OLI遥感影像和数字高程模型(DEM)数据,结合比值阈值法与目视解译提取了1990—2020年波曲流域冰川边界,同时利用归一化水体指数与目视解译提取波曲流域冰湖数据,分析近30 a波曲流域冰川冰湖空间分布与变化特征以及母冰川-冰湖相对位置变化关系,探究波曲流域冰川冰湖协同演化及其与气候变化的响应关系。结果表明:(1)1990—2020年波曲流域冰川加速退缩,尤其是近10 a来冰川加速退缩趋势更为显著;波曲流域冰川主要分布在海拔5500~6100 m范围内,规模上看,大规模(≥10 km^(2))冰川数量保持稳定,小规模(≤0.5 km^(2))冰川数量呈增加趋势。(2)近30 a波曲流域冰湖数量、面积均不断增加,冰湖面积扩张率为74.24%;冰湖主要分布在海拔4900~5300 m之间,大冰湖(≥0.07 km^(2))面积不断扩张;小冰湖(≤0.03 km^(2))数量增加显著。(3)与母冰川相连冰湖是最重要的冰湖扩张类型,该类型冰湖面积增长量占总冰湖增量的72.08%。(4)近30 a波曲流域气温缓慢上升,降水量总体略微下降。气温上升和降水量下降是造成冰川退缩重要因素,同时冰川融水促进冰湖扩张。通过波曲流域冰川-冰湖分布面积、变化特征及其协同演化关系的探究为流域冰川面积变化趋势和冰湖溃决灾害的预测及防治提供数据支撑。

利福平联合复方新诺明对复治涂片阳性肺结核炎性因子的影响

目的分析利福平联合复方新诺明辅助治疗对复治涂片阳性肺结核患者疗效和血清炎性因子水平的影响。方法将2017年5月—2022年8月我院收治80例复治涂片阳性肺结核患者使用随机信封法分为观察组及对照组各40例。对照组采用利福平治疗,观察组采用利福平联合复方新诺明辅助治疗;治疗后对患者临床疗效、复发率及痰菌阴转率进行评估,并检测治疗前后血清炎性因子水平。结果治疗后观察组病灶吸收率90.00%高于对照组77.50%,空洞缩小率95.00%高于对照组82.50%,差异均具有统计学意义(均P<0.05);观察组复发率2.50%低于对照组15.00%,痰菌阴转率97.50%高于对照组80.00%,差异均具有统计学意义(均P<0.05);观察组治愈率95.00%高于对照组85.00%,差异具有统计学意义(P<0.05)。治疗后观察组血中白细胞介素-37(IL-37)、触珠蛋白(HP)、骨桥蛋白(OPN)水平均下降,观察组3种因子水平分别为(4.63±0.83)pg·mL^(-1)、(810.38±31.64)μg·mL^(-1)、(189.19±20.74)pg·mL^(-1)低于对照组的(6.33±0.91)pg·mL^(-1)、(1283.73±101.67)μg·mL^(-1)、(456.28±45.92)pg·mL^(-1),差异均具有统计学意义(均P<0.05)。结论利福平联合复方新诺明对复治涂片阳性肺结核患者后有助于提高临床疗效,改善血液中IL-37、HP、OPN水平。

不同剂量异烟肼抗结核化疗方案对药物敏感复治肺结核的疗效

目的探讨药物敏感复治肺结核患者应用不同剂量异烟肼抗结核化疗方案治疗的效果及安全性。方法选取收治的对药物敏感的复治肺结核患者97例,按照随机抽样的方式将其分为标准组(n=48)和高剂量组(n=49),标准组依据国家统一的常规剂量(异烟肼0.3 g·d^(−1))给药,高剂量组根据患者体质量决定用药量,≥70 kg者异烟肼剂量为0.5 g·d^(−1),<70 kg者为0.4 g·d^(−1),疗程为8个月。比较2组患者治疗结束后X线摄影显示肺部病灶吸收情况的变化;痰菌阴转情况;血清细胞因子水平变化[白细胞介素-18(interleukin-18,IL-18)、γ干扰素(interferon-γ,IFN-γ)、肿瘤坏死因子-α(tumor necrosis factor-α,TNF-α)、白细胞介素-10(interleukin-10,IL-10)]、生活质量[肺癌生活质量评估量表(functional assessment of cancer therapylung,FACT-L)]评分以及不良反应情况。结果高剂量组病灶吸收率为87.76%,明显高于标准组的70.83%(P<0.05);治疗第1个月和第2个月,2组患者痰液转阴率比较差异无统计学意义,治疗第4个月和第8个月高剂量组患者痰菌转阴率显著高于标准组(P<0.05);治疗8个月后,2组患者血清IL-18、IFN-γ、TNF-α及IL-10水平均显著低于治疗前,且高剂量组显著低于标准组(P<0.05);2组患者FACT-L评分均显著高于治疗前,且高剂量组高于标准组(P<0.05);高剂量组不良发应发生率(18.37%)与标准组(16.67%)比较差异无统计学意义。结论对药物敏感复治肺结核采用高剂量异烟肼治疗疗效较好,能有效增强患者肺部病灶吸收,加快空洞闭合,痰液尽早恢复阴性,血清中的炎症因子水平降低,从而提高生活质量,且无明显不良反应。

Development of multi-channel observation and inversion for IP electrical sounding method

In order to improve the exploration effect of deep non-ferrous mineral resources, multi-channel observation methods for induced polarization （IP） electrical sounding data and their inversion imaging technology are studied. First of all, four multi-channel observation methods are developed based on conventional IP electrical method, namely three-electrode and four-electrode arrays of unilateral and bilateral current transmitting. Then the maximum smoothness constrained inversion method of the least squares sense for IP electrical sounding data is proposed, and the inversion software is programmed. Finally, the simulation and inversion results of geo-electrical model for the proposed observation methods are analyzed. And the comparison results show that three-electrode array of bilateral current transmitting gives the best result, but the intensity in field work is larger than others; unilateral three-electrode and four-electrode arrays give the better results. Taking detection results and convenience of field exploration work into consideration, these two methods are more suitable for practical application; bilateral observation method of four-electrode array is not suitable for the detection of the steep ore bodies.

Design of multi-channel data acquisition system based on LabVIEW and NI PXI-5105

A data acquisition system based on LabVIEW and NI PXI-5105 is presented for multi-channel data acquisition. It can realize the functions of parameter setting, data acquisition and storage, waveform display and data analysis using LabVIEW and NI-SCOPE device driver. The advantages of the system are that the setting is convenient, the operation is easy, the interface is friendly and the functions are practical. The experiment results show that the system has good stability and high reliability and is a powerful tool for multi-channel data acquisition.

海洋型冰川表碛与退缩区土壤微生物群落特征——以阿扎冰川和米堆冰川为例

以藏东南阿扎冰川和米堆冰川为研究区,采用细菌16S rRNA基因扩增子测序和真菌ITS测序技术,研究了冰川表碛与退缩区不同植被演替阶段土壤中微生物群落特征及土壤化学性质影响.结果表明,两条冰川表碛与退缩区土壤中共发现细菌门38个,其中Proteobacteria(40%)、Actinobacteriota(23%)、Bacteroidota(14%)为优势群,共发现真菌门7个,Basidiomycota(47%)和Ascomycota(45%)为优势群.阿扎和米堆冰川表碛中Patescibacteria、RCP2-54、Bacteroidota、Gemmatimonadota和Acidobacteriota的菌群丰度存在显著差异,米堆冰川表碛和退缩区土壤中微生物群落结构和丰度存在显著差异(P<0.05),而退缩区三个演替阶段之间的群落结构差异不显著.适应极端环境的微生物群落在表碛中丰度最高,而随着演替进程参与植物定殖或与植物共生的微生物群落丰度与多样性显著增加,微生物群落的α多样性上升,NMDS模型也逐渐接近重叠,群落结构在植被演替后期逐渐趋于稳定,.除全钾外,养分含量在两条冰川表碛中均较低,随着植被演替土壤pH值逐渐降低而养分逐渐增加,演替后期显著高于前两阶段.表碛中的微生物群落与pH值和全钾显著正相关(P<0.05),而退缩区土壤中则与速效钾、硝酸盐氮、全磷、可溶性有机碳显著正相关(P<0.05),并以磷限制为主.

农田退水生态削减净化技术研究进展

针对农田退水产生的来源和农田退水污染的特点,综述可选用治理农田退水的国内外源头管控措施及生态净化技术的应用场景。经过多年发展应用,源头管控措施可以在源头削减退水量及退水污染负荷,是控制退水的关键策略。生态处理技术因其生态效益、建设成本等方面的优势成为农村地区可选的最佳退水处理方法。对现有面源污染治理模式进行总结,提供一种农田退水生态逐级截留净化的治理思路,对农田退水处理技术的未来发展方向进行展望并为农田退水未来治理提供参考。

下分层停采线外延后回撤通道顶板预裂卸压研究

分层开采时,当上分层已经回采完毕,为了对下分层尽量多回收煤炭资源,需要下分层安全通过上分层停采线后,继续向前外延回采。为了避免下分层外延的末采期间发生矿压灾害,需保证下分层的采空区顶板能够及时冒落。因而提出了工作面外延末采时伪斜调整渐进式通过上分层停采线,此外在上覆顶板采用水力压裂超前预裂的方式,对坚硬厚层砂岩弱化卸压。结果表明:下分层在安全通过上分层停产线后又安全外延回采了70 m,多回收煤炭资源近3万t;采用水力压裂对下分层外延后的顶板致裂卸压后,顶板厚层砂岩能够及时垮落,垮落的周期来压步距小于15 m,未发生矿压灾害,保证了安全生产。

青藏高原海螺沟冰川退缩区原生演替序列优势乔木氮磷化学计量及重吸收特征研究

以海螺沟冰川退缩区原生演替序列为对象,研究各演替阶段优势乔木氮(N)、磷(P)化学计量及重吸收效率特征。结果表明:优势乔木鲜叶及凋落叶N、P浓度随演替下降,且鲜叶的N∶P在整个演替序列中总体小于14,表明该演替序列优势乔木的生长主要受N元素限制;优势乔木N、P的重吸收效率在演替中期最高,表明植物较高的生长速率会增加其对养分的吸收利用效率;优势乔木N、P的重吸收效率与其生长速率呈正相关关系,而与土壤的N、P储量呈负相关关系,说明树木生长速率(需求)和土壤养分状况(供给)共同调节植物对养分的吸收模式;优势乔木N重吸收效率与其鲜叶N∶P呈正相关关系,表明植物对N的重吸收过程对维持其体内N∶P的平衡有着重要意义。研究结果有助于深入认识原生演替过程中植被对养分的利用机制,可为植被恢复提供理论依据。

植物多样性与物种组成随原生演替进程的变化规律——以贡嘎山冰川退缩区为例

研究原生演替过程中植物多样性与物种组成的演变规律有助于解析植物群落的演替动态与构建机制。以冰川退缩区原生演替序列上7个演替阶段(S1~S7)的植物群落为研究对象,于2022年开展群落调查工作,结合α、β多样性两方面,分析其乔木层、灌木层、草本层植物多样性和物种组成的变化规律。结果显示:(1)本次调查在海螺沟冰川退缩区原生演替序列中记录到植物共41科66属100种,其中单(寡)种属居多,初步反映了本研究区植物物种组成的复杂性和多样性;(2)原生演替序列上,各层植物的优势种组成在不同演替阶段差异明显,出现明显的更替;(3)随着演替的进行,乔木层和灌木层的多项α多样性指数均呈“单峰型”响应格局,演替初期上升,达到峰值后缓慢下降;(4)不同生活型植物在演替序列上的β多样性差异明显,物种周转在物种组成变化中起主要作用,其中草本层的周转程度最高,为92.16%,而灌木层的周转程度最低,为58.01%;(5)冰川退缩区植物群落的主林层(乔木层)主要经历了先锋群落、落叶阔叶林、针阔混交林、顶级针叶林4个演替阶段。研究结果可为原生演替过程中植物群落的构建机制提供参考。

国民党军队撤离新疆始末研究

1949年夏,人民解放军第一野战军向西北五省国统区发起“大进军”,随着陕、甘、宁、青四省解放,孤悬塞外的新疆局势亦风起云涌:一方面,对国民党当局失去信心的美国政府希冀经营新疆为抵御共产主义阵营南下印度之最后堡垒,故对新疆采取种种渗透和颠覆活动;另一方面,国民党军方高层或认为与中共仍未决胜负,遂打起“内调”新疆驻军参战的算盘。新疆的十万驻军不仅是可以支援战局的机动力量,也是在险恶的外部环境下保全领土的关键因素。在“保全国土”与“戡平内乱”的纠结中,国民党决策部门与地方军政当局就新疆驻军及国民党上层派驻新疆人员何去何从的问题展开了一系列争论,最后作出“起义”和“撤退”两种相对和平的选择,这也为新疆的和平解放创造了条件。

气候变化背景下沿海城市有管理撤退的适应策略与挑战

近年来,气候变化带来的各种极端灾害事件严重冲击了沿海地区的安全稳定和可持续发展,如何适应气候变化的不利影响成为备受关注的议题。沿海气候变化的适应手段经历了从结构性保护到非结构性保护再到有管理撤退的认知转变。然而,当前对有管理撤退的挑战和对策还缺乏系统分析。该文首先回顾了有管理撤退的基本概念演变,指出撤退作为其他适应策略失败后的补救措施,以自发性和区域性管理为主,并概述了各国有管理撤退的实践现状;其次,讨论了当前有管理撤退面临的问题和发展趋势,如土地矛盾和撤退投资回报率、撤退公平性、文化遗产与社会和感情属性、政府管理和政治风险等;第三,聚焦我国有管理撤退的现状问题和未来研究方向,指出有管理撤退研究在中国仍处于起步阶段,缺乏完整的理论体系和实践,未来需要对概念、撤退阈值和行动规划、政策框架和相关影响进一步分析。前瞻性地对有管理撤退进行研究,可为沿海地区采取积极有效的气候适应行动,实现长期有效的灾害风险治理提供科学依据。

基于多源遥感解译的洞庭湖区自然湖岸线演变过程研究

伴随泥沙淤积、水库运行、湖区围垦、岸线侵占和破坏等自然和人为因素的影响,洞庭湖区湖岸线已发生显著的改变,但是目前仍缺少遥感解译揭示其演变过程。利用1986-2022年多源遥感影像,通过归一化差异植被指数、最大值合成法以及大津法和目视解译相结合的阈值划分方法,识别并提取东洞庭湖、南洞庭湖和目平湖的植被带范围,进而分析洞庭湖区湖岸线的演变规律。通过栅格计算得到湖泊每年(相比于上年)植被带扩张和萎缩的面积,以及1986、1990、2000、2010和2020年植被带变化的空间分布。结果表明,洞庭湖区自然湖岸线呈现普遍扩张的趋势,并且不同位置在不同时期扩张和萎缩面积的占比不尽相同。东洞庭湖、南洞庭湖和目平湖的自然岸线所围水域面积分别缩减144.84、191.42和80.48 km~2,缩减率分别为27.83%、39.20%和48.26%。藕池河东支尾闾汇入东洞庭湖内,通过数字岸线分析系统对其自然岸线进行统计分析,结果表明:藕池河东支尾闾的自然岸线平均每年扩张距离为45 m,净岸线移动最大和最小距离分别为3281和386.93 m,线性回归的决定系数为0.68。总体而言,泥沙冲淤和水位变化是洞庭湖自然岸线变化的主要原因,人类采砂活动在局部区域造成了洞庭湖自然岸线的萎缩。