检索结果-南通市图书馆

Channel Knowledge Map(CKM)-Assisted Multi-UAV Wireless Network:CKM Construction and UAV Placement

在线全文

学校读者我要写书评

暂无评论

Journal of Communications and Information Networks 2023年第3期8卷 256-270页

作者： Haoyun li Peiming li gaoyuan Cheng Jie Xu Junting Chen Yong Zeng School of Science and Engineering and the Future Network of Intelligence Institute(FNii)the Chinese University of Hong KongShenzhenShenzhen 518172China National Mobile Communications Research Laboratory and Frontiers Science Center for Mobile Information Communication and Security the Southeast UniversityNanjing 210096the Purple Mountain LaboratoriesNanjing 211111China

Channel knowledge map(CKM)has recently emerged as a viable new solution to facilitate the placement and trajectory optimization for unmanned aerial vehicle(UAV)communications,by exploiting the siteand location-specific radio propagation *** paper investigates a CKM-assisted multi-UAV wireless network,by focusing on the construction and utilization of CKMs for multi-UAV placement ***,we consider the CKM construction problem when data measurements for only a limited number of points are *** this end,we exploit a data-driven interpolation technique,namely the Kriging method,to construct CKMs to characterize the signal propagation ***,we study the multi-UAV placement optimization problem by utilizing the constructed CKMs,in which the multiple UAVs aim to optimize their placement locations to maximize the weighted sum rate with their respectively associated ground base stations(GBSs).However,the weighted sum rate function based on the CKMs is generally non-differentiable,which renders the conventional optimization techniques relying on function derivatives *** tackle this issue,we propose a novel iterative algorithm based on derivative-free optimization,in which a series of quadratic functions are iteratively constructed to approximate the objective function under a set of interpolation conditions,and accordingly,the UAVs’placement locations are updated by maximizing the approximate function subject to a trust region ***,numerical results are presented to validate the performance of the proposed *** is shown that the Kriging method can construct accurate CKMs for ***,the proposed derivative-free placement optimization design based on the Kriging-constructed CKMs achieves a weighted sum rate that is close to the optimal exhaustive search design based on ground-truth CKMs,but with much lower implementation *** addition,the proposed design is shown to significant

关键词： UAV communications CKM CKM construction UAV placement derivative-free optimization

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

冬季降温对潢川金桂叶肉细胞超微结构的影响

北华大学学报（自然科学版） 2020年第1期21卷 93-98页

作者：尤扬宋帆宋凯曹红霞李小果李高远齐玉杰河南科技学院园艺园林学院河南新乡453003 郑州森林公园河南郑州450003

研究冬季降温对潢川金桂叶肉细胞超微结构的影响以及叶肉细胞组织结构的变化规律.以自然降温条件下的潢川金桂叶片为试材,用HITACHI-HT7700型透射电子显微镜观察不同自然温度下潢川金桂叶肉细胞组织结构变化.结果显示:常温下,细胞壁和... 详细信息

研究冬季降温对潢川金桂叶肉细胞超微结构的影响以及叶肉细胞组织结构的变化规律.以自然降温条件下的潢川金桂叶片为试材,用HITACHI-HT7700型透射电子显微镜观察不同自然温度下潢川金桂叶肉细胞组织结构变化.结果显示:常温下,细胞壁和细胞质膜结构完整,中央大液泡已形成,叶绿体、线粒体形态完整;0℃时,细胞壁和细胞核形状结构完整,液泡空间被挤压,叶绿体出现肿胀现象,线粒体和嗜锇体明显增多;-4℃时,叶绿体肿胀加剧,线粒体变化不明显;-10℃时,发生质壁分离现象,并且细胞结构解体破碎.观察可知:冬季降温对潢川金桂叶肉细胞有一定影响且不同温度对细胞器的影响程度也不同,温度低于-10℃将不适于潢川金桂生长,因此,将温度控制在-10℃以上有利于植物生长.

关键词：潢川金桂冬季降温超微结构

在线全文

学校读者我要写书评

暂无评论

微生物降解石油烃的代谢机制及研究进展

环境工程 2023年第2期41卷 234-246页

作者：胡梦杰钟磊蔡晓鲜卿晋武孙于茹栗高源阮海华陈冠益天津商业大学天津300134 天津大学天津300072 污染场地安全修复技术国家工程实验室北京建工环境修复股份有限公司北京100015

石油烃类污染物是复杂的有机化合物,对生态环境和公众健康具有较大危害。目前微生物技术已成为修复石油烃污染环境的主要方法,微生物可利用目标污染物作为碳源,通过一系列的酶催化对其进行代谢降解。研究了微生物降解石油烃的代谢机制,... 详细信息

石油烃类污染物是复杂的有机化合物,对生态环境和公众健康具有较大危害。目前微生物技术已成为修复石油烃污染环境的主要方法,微生物可利用目标污染物作为碳源,通过一系列的酶催化对其进行代谢降解。研究了微生物降解石油烃的代谢机制,可通过合理设计降解途径中关键步骤的酶,降低限制因素对石油烃微生物降解的影响,提高限速步骤的反应速度,从而提高对石油烃的降解率,以更好地应用于石油烃污染场地的修复。通过梳理总结石油烃的主要组成和结构、代谢途径、功能基因和关键酶种类,以及组学和合成生物学技术在石油烃降解代谢机制研究中的应用现状,为进一步优化提升微生物修复技术在石油烃污染领域的应用前景提供参考。

关键词：石油烃微生物降解降解机制功能基因酶组学技术

健康青年男性进驻更高海拔地区急性高原病分析

在线全文

学校读者我要写书评

暂无评论

西北国防医学杂志 2018年第6期39卷 360-364页

作者：李相俊李平史连胜刘书友王秀亮姜俊杰马长青李高元解放军22医院心肺内科青海格尔木816099 陆军军医大学新桥医院心内科全军心血管病研究所解放军22医院医务处

目的:分析健康青年男性急进更高海拔地区急性高原病(acute mountain sickness,AMS)的发病特点及规律。方法:选取2017-04~06世居平原移居海拔2 815m地区非藏族健康青年男性196例,乘驾重型卡车从海拔2 815m地区急进到海拔4 547m地区,根据... 详细信息

目的:分析健康青年男性急进更高海拔地区急性高原病(acute mountain sickness,AMS)的发病特点及规律。方法:选取2017-04~06世居平原移居海拔2 815m地区非藏族健康青年男性196例,乘驾重型卡车从海拔2 815m地区急进到海拔4 547m地区,根据受试对象是否发生AMS,分为AMS组和非AMS组。收集人口学资料(身高、体质量、年龄、吸烟史、饮酒史、预服用红景天药物史),填写路易斯湖评分(lake louise scale,LLS)量表,分析高海拔地区AMS的发病特点。结果:海拔3 540 m、4 547 m地区AMS组与非AMS组的体质量指数(BMI)、年龄、吸烟史、饮酒史、预服用红景天药物史等资料比较,均无显著性差异(P>0.05);海拔3 540m地区的头痛发生率为34.69%、头晕(眩晕)发生率为46.94%、胃肠道症状发生率为24.49%、睡眠困难发生率为65.31%、疲劳(虚弱)发生率为67.35%,均显著低于海拔4 547m地区的63.27%、69.39%、42.86%、77.55%及73.47%,差异有统计学意义(P<0.05);海拔3 540m地区AMS患病率为32.65%,其中轻度AMS患病率为16.33%,重度AMS患病率为16.33%;海拔4 547m地区AMS患病率为57.14%,其中轻度AMS患病率为18.37%,重度AMS患病率为38.78%,海拔4 547m地区AMS患病率高于海拔3 540m地区(P<0.05)。结论:移居高原的非藏族健康青年男性急进更高海拔地区后,AMS的发生可能与BMI、年龄、吸烟、饮酒、预服用红景天无关;进驻海拔高度越高,头痛、头晕(眩晕)、胃肠道、睡眠困难、疲劳(虚弱)发生率越高,可为早期诊治AMS提供理论依据。

关键词：高原急性高原病青年男性

A New Hybrid Hierarchical Parallel Algorithm to Enhance the Performance of Large-Scale Structural Analysis Based on Heterogeneous Multicore Clusters

在线全文

学校读者我要写书评

暂无评论

Computer Modeling in Engineering & Sciences 2023年第7期136卷 135-155页

作者： gaoyuan Yu Yunfeng Lou Hang Dong Junjie li Xianlong Jin School of Mechanical Engineering Shanghai Jiao Tong UniversityShanghai200240China Aerospace System Engineering Shanghai Shanghai201108China School of Aerospace Mechanical and Mechatronic EngineeringUniversity of SydneySydneyNSW2006Australia

Heterogeneous multicore clusters are becoming more popular for high-performance computing due to their great computing power and cost-to-performance effectiveness ***,parallel efficiency degradation is still a problem in large-scale structural analysis based on heterogeneousmulticore *** solve it,a hybrid hierarchical parallel algorithm(HHPA)is proposed on the basis of the conventional domain decomposition algorithm(CDDA)and the parallel sparse *** this new algorithm,a three-layer parallelization of the computational procedure is introduced to enable the separation of the communication of inter-nodes,heterogeneous-core-groups(HCGs)and inside-heterogeneous-core-groups through mapping computing tasks to various hardware *** approach can not only achieve load balancing at different layers efficiently but can also improve the communication rate significantly through hierarchical ***,the proposed hybrid parallel approach in this article can reduce the interface equation size and further reduce the solution time,which can make up for the shortcoming of growing communication overheads with the increase of interface equation size when employing ***,the distributed sparse storage of a large amount of data is introduced to improve memory *** solving benchmark instances on the Shenwei-Taihuzhiguang supercomputer,the results show that the proposed method can obtain higher speedup and parallel efficiency compared with CDDA and more superior extensibility of parallel partition compared with the two-level parallel computing algorithm(TPCA).

关键词： Heterogeneous multicore hybrid parallel finite element analysis domain decomposition

A Multilevel Hierarchical Parallel Algorithm for Large-Scale Finite Element Modal Analysis

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Computers, Materials & Continua 2023年第9期76卷 2795-2816页

作者： gaoyuan Yu Yunfeng Lou Hang Dong Junjie li Xianlong Jin School of Mechanical Engineering Shanghai Jiao Tong UniversityShanghai200240China Department of Structural System Aerospace System Engineering ShanghaiShanghai201108China School of Aerospace Mechanical and Mechatronic EngineeringThe University of SydneySydneyNSW 2006Australia

The strict and high-standard requirements for the safety and stability ofmajor engineering systems make it a tough challenge for large-scale finite element modal *** the same time,realizing the systematic analysis of the entire large structure of these engineering systems is extremely meaningful in *** article proposes a multilevel hierarchical parallel algorithm for large-scale finite element modal analysis to reduce the parallel computational efficiency loss when using heterogeneous multicore distributed storage computers in solving large-scale finite element modal *** on two-level partitioning and four-transformation strategies,the proposed algorithm not only improves the memory access rate through the sparsely distributed storage of a large amount of data but also reduces the solution time by reducing the scale of the generalized characteristic equation(GCEs).Moreover,a multilevel hierarchical parallelization approach is introduced during the computational procedure to enable the separation of the communication of inter-nodes,intra-nodes,heterogeneous core groups(HCGs),and inside HCGs through mapping computing tasks to various hardware *** method can efficiently achieve load balancing at different layers and significantly improve the communication rate through hierarchical ***,it can enhance the efficiency of parallel computing of large-scale finite element modal analysis by fully exploiting the architecture characteristics of heterogeneous multicore ***,typical numerical experiments were used to validate the correctness and efficiency of the *** a parallel modal analysis example of the cross-river tunnel with over ten million degrees of freedom(DOFs)was performed,and ten-thousand core processors were applied to verify the feasibility of the algorithm.

关键词： Heterogeneous multicore multilevel hierarchical parallel load balancing large-scale modal analysis

Ultrahigh electrostrain with excellent fatigue resistance in textured Nb^(5+)-doped(Bi_(0.5)Na_(0.5))TiO3-based piezoceramics

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Advanced Ceramics 2023年第3期12卷 487-497页

作者： lixiang Lai Zhihao Zhao Shuo Tian Bao Ou gaoyuan liang Bin li Yejing Dai School of Materials Sun Yat-sen UniversityShenzhen 518107China

(Bi_(0.5)Na_(0.5))TiO_(3)(BNT)-based lead-free piezoceramics exhibit excellent electric field-induced strain(electrostrain)properties,but often suffer from large hysteresis and poor fatigue resistance,which strongly limit their ***,textured Nb5+-doped 0.8(Bi_(0.5)Na_(0.5))TiO_(3)–0.2(Bi_(0.5)K_(0.5))TiO_(3)(0.8BNT–0.2BKT)ceramics with a high degree of texturing(~80%)were prepared by the reactive template grain growth(RTGG)method using Bi4Ti3O12 as a *** the combination of donor doping in the B-site and the RTGG method,the electrostrain performance achieves a significant enhancement.A high electrostrain of 0.65%and a piezoelectric coefficient(*33 d)of 1083 pm/V with reduced hysteresis at an electric field of 6 kV/mm are *** electrostrain performance degradation is observed after unipolar electric field loading of 10^(5)cycles,showing excellent fatigue *** results indicate that the texturing BNT-based lead-free piezoceramics by the RTGG method is a useful approach to developing eco-friendly actuators.

关键词： (Bi_(0.5)Na_(0.5))TiO_(3)(BNT)-based ceramics donor doping electrostrain textured ceramics

一期末段可弯硬性输尿管肾镜钬激光肾盂旁囊肿切开引流术的疗效分析

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

中华泌尿外科杂志 2019年第8期40卷 574-577页

作者：杨国胜牛得草张涛王炳卫钟瑞伦刘百川李高远陈波特蒋廷森邱晓拂李环辉刘跃加罗友华广东省第二人民医院泌尿外科广东省第二人民医院泌尿外科微创激光中心广州 510317

目的探讨一期末段可弯硬性输尿管肾镜钬激光一期肾盂旁囊肿切开引流术的安全性和有效性。方法回顾性分析2016年2月至2018年8月广东省第二人民医院收治的26例肾盂旁囊肿患者的临床资料。男15例,女11例;年龄32~68岁,平均53.5岁。体检发现7... 详细信息

目的探讨一期末段可弯硬性输尿管肾镜钬激光一期肾盂旁囊肿切开引流术的安全性和有效性。方法回顾性分析2016年2月至2018年8月广东省第二人民医院收治的26例肾盂旁囊肿患者的临床资料。男15例,女11例;年龄32~68岁,平均53.5岁。体检发现7例;腰腹部酸胀不适19例,其中2例有肉眼血尿;1例合并2型糖尿病,3例合并高血压。单侧单发肾盂旁囊肿24例,双侧单发肾盂旁囊肿2例;26例中一侧单发肾盂旁囊肿伴对侧单纯肾囊肿4例,一侧单发肾盂旁囊肿伴同侧肾结石2例。囊肿最大径为3.4~5.6 cm,平均4.8 cm。26例均全麻下行末段可弯硬性输尿管肾镜钬激光肾盂旁囊肿切开引流术,直视下经尿道置入末段可弯硬性输尿管肾镜(如不能直接上镜,则放置双J管1~2周后再行处理),观察输尿管情况,以及集合系统与肾盂旁囊肿的解剖关系。用200 μm钬激光光纤向集合系统微凸起的囊壁开窗引流,开窗直径1.5~2.0 cm,使囊腔和集合系统交通,留置双J管引流。分析一期手术患者的手术时间、住院时间、手术出血量,及术后并发症、临床症状缓解情况。结果26例一期上镜23例,上镜成功率88.5%。3例一期上镜未成功者,留置双J管2周后,行二期手术。23例一期手术患者单侧肾盂旁囊肿处理时间11~25 min,平均17.2 min。无术中出血病例,术中、术后均无严重并发症。术后随访3~30个月,平均17.0个月,22例囊肿消失,1例囊肿较术前缩小>1/2,未见囊肿复发,其中19例有腰痛患者术后腰痛症状均消失,3例高血压患者血压恢复正常,2例血尿消失。2例合并同侧肾结石患者术后3个月复查CT未见结石残留。患者未出现囊肿复发、感染、血肿、癌变等。结论一期末段可弯硬性输尿管肾镜钬激光肾盂旁囊肿切开引流术创伤小、并发症少、疗效确切,手术安全、有效。

关键词：囊肿肾盂旁输尿管肾镜,末段可弯钬激光

基于SMA-Elman的IGBT寿命预测研究

在线全文

学校读者我要写书评

暂无评论

微电子学与计算机 2023年第3期40卷 117-124页

作者：周昂帕孜来·马合木提李高原赵智强刘行行新疆大学电气工程学院新疆乌鲁木齐830017

绝缘栅双极晶体管(insulated gate bipolar transistor,IGBT)作为功率变换器的重要组成部分,其剩余使用寿命的预测极为重要.针对IGBT的剩余使用寿命问题,提出了利用黏菌优化算法(slime mould algorithm,SMA)优化Elman神经网络实现权值... 详细信息

绝缘栅双极晶体管(insulated gate bipolar transistor,IGBT)作为功率变换器的重要组成部分,其剩余使用寿命的预测极为重要.针对IGBT的剩余使用寿命问题,提出了利用黏菌优化算法(slime mould algorithm,SMA)优化Elman神经网络实现权值和阈值的自适应选择,并将其用于IGBT的寿命预测.首先,对NASA研究中心老化试验数据集中的栅射极关断电压尖峰峰值进行平滑处理.其次,对处理后的数据进行时域特征提取.再次,用核主成分分析(kernel principle component analysis,KPCA)进行优选降维。最后,利用SMA-Elman神经网络模型实现IGBT的寿命预测.结果表明,提出的SMA-Elman神经网络模型相比Elman、BP神经网络及SVR模型具有更优的性能,均方误差为0.021%,均方根误差为0.014,拟合度为0.998,可以更好地实现IGBT剩余使用寿命的预测.

关键词：绝缘栅双极晶体管寿命预测黏菌优化算法 Elman神经网络时域特征