SST effect on the pre-monsoon intraseasonal oscillation over the South China Sea based on atmospheric-coupled GCM comparison

The role of sea surface temperature(SST)variability in the pre-monsoonal(April to July)intraseasonal oscillation(ISO)over the South China Sea(SCS)is investigated using the Community Earth System Model Version 2(CESM2).An Atmospheric Model Intercomparison Project(AMIP)simulation forced by daily sea surface temperatures(SSTs)derived from a parallel coupled general circulation model(CGCM)run was compared with observations and the mother coupled simulation.In the coupled model,the SST warming leads the peak convection about 1/4 period as in observations.The paralell uncoupled model fails to simulate this phase relationship,implying the importance of air-sea coupling in reproducing realistic ISO.Due to the near-quadrature phase relationship between SST and precipitation ISOs during the ISO events,it is difficult to distinguish the active/passive role of SST from observations alone.Significant correlation in intraseasonal precipitation between the daily SST-forced AMIP and mother CGCM runs indicates that SST plays a role in driving the atmospheric ISO.

一种新的基于封装的区分服务多播方案QoSAMDD

笔者旨在设计一种性能优越的基于区分服务框架的QoS多播方案，支持组内成员数可扩展，允许成员动态的加／V离开．文中提出一种新的基于封装的区分服务多播方案QoSAMDD，增加了控制多播分组复制和选路的IP扩展首部树结构封装域，并在新成员加入时引入了延时T，避免带宽不足时频繁申请加入．经理论分析，QoSAMDD代价不超过基于边界类方案，且灵敏度更高；完全解决了被忽略的预留子树问题，且支持组大小可扩展．通过仿真实验与基于边界类方案的优秀代表EBM方案进行比较，QoSAMDD在吞吐量和与TCP流的公平性等方面表现更好．

移动节点间安全关联管理方案设计

在IETF的IKEv2方案中,离线移动后的安全关联(SA)更新过程中可能存在无法通信的情况,而MOBIKE方案的SA更新效率低,且无法抵御恶意反射攻击。为此,通过改进SA的建立过程,减少移动节点的SA重协商次数,采取安全关联与移动节点家乡地址相关联的方法,提出一种安全管理方案。分析结果表明,与MOBIKE方案相比,该方案可以在离线移动情况下确保安全关联的更新,并具有更高的切换效率和安全性。

Ad Hoc网络路由协议研究及其性能比较

介绍和分析了当前Ad Hoc网络中的主要路由协议算法,在Linux下使用网络仿真软件NS2评价Ad Hoc路由协议中的距离矢量路由协议、临时排序路由算法、动态源路由协议和Ad Hoc按需距离矢量路由协议,编写了用于仿真实现的脚本程序,并对仿真结果进行了分析比较和性能评价,由此得出不同协议的特性及其适用范围。

料位控制测量的无线网络在NS2中的模拟

文中主要对料位控制测量无线网络ZigBee的星形拓扑在模拟软件NS2中的实现进行了研究。实现对ZigBee星形拓扑在模拟环境中的数据传输分析。并对ZigBee无线技术和NS2模拟软件各自做了介绍。最后,利用分析工具对NS2软件模拟结果文件进行分析。从而实现在2.4GHz频段上,对无线网络ZigBee的星形拓扑中各个网络参数的分析。模拟结果显示整个网络数据吞吐量和数据正确传输率满足要求,ZigBee无线网络星形拓扑可以应用于料位控制测量。

LICOM3.0海洋模式中太平洋北赤道逆流的模拟偏差分析

本文用CORE-IAF(Coordinated Ocean-ice Reference Experiments–Interannual Forcing)外强迫场分别强迫LICOM3(LASG/IAP Climate System Ocean Model Version 3)和POP2(Parallel Ocean Program version 2)两个海洋模式,并分析了这两个模式中太平洋北赤道逆流(NECC)的模拟结果。我们发现LICOM3和POP2模拟的NECC强度均弱于实测,这和Sun et al.(2019)的研究结果一致,也进一步证明了海洋模式中NECC偏弱是CORE-IAF外强迫场造成的,海表风应力及对应的风应力旋度是海洋模式准确模拟NECC的最主要因子。同时,我们也分析了NECC的模拟在动力机制上的差别,这里的动力强迫项包括风应力项、平流项和余项。我们发现模式的外强迫场虽然相同,但是两个模式中各动力强迫项(风应力项、平流项和余项)对NECC模拟的影响并不完全相同。

概率转发的AODV路由协议的改进

按需距离矢量路由协议(AODV)在寻找路由时是通过洪泛法发送路由请求(RREQ)实现的。洪泛法能较好地找到所需的路由,但时延较大,产生了许多不必要的重传,易造成广播风暴。针对AODV路由协议,提出了一种基于概率转发的机制。这种机制根据邻居节点的个数,选用不同的概率转发RREQ。NS2仿真模拟结果表明,该方法可以降低时延,提高吞吐量,提高分组投递率。

分层分布网络管理系统的研究与设计

本文在分析了背景和网管的现状之后,比较并确定了海军C^3I系统的分层分布网管的解决方案,建立了分层分布网管的模型,并提出了利用当前较流行的网管平台SunNet Manager(SNM)的API来构造中间管理者的实现途径。

扩展NS2的移动Agent仿真方法研究

在分析NS2仿真移动Agent的过程的基础上,通过扩展NS2中Packet结构,注册新的协议头并定义TCP的子类SCDTcp,解决了NS2上真实数据传输以及在TCP缓冲限制下的动态链接维护问题。设计了一个验证实例并在仿真平台上进行实验,实验结果表明所提出的扩展NS2设计可以有效地完成以上功能。

无线传感器网络快速组网机制的改进

无线网络的入网连接时延过长,在要求快速组网的场合下应用不理想。对IEEE802.15.4无线传感器网络的协议进行了改进,NS2仿真结果证明,与原协议标准相比,分别将入网连接的两个步骤时延缩短了90%和80%左右,改进效果非常明显,使得无线网络能够应用到实时监测场合。

基于改进YOLOv4的工件表面缺陷检测方法

针对将深度学习用于工件检测环境中计算资源受限的问题,提出了一种基于改进YOLOv4的工件表面缺陷检测方法。首先,使用轻量化网络模型MobileNetV2替换YOLOv4原有的主干特征提取网络,并使用深度可分离卷积替换掉YOLOv4中使用的3×3标准卷积,大幅减小模型的参数规模,提升模型的检测速度;其次,提出一种图像预处理方法,在输入检测网络前定位并裁取出图像中工件的区域;最后,由于YOLOv4已有的Mosaic数据增强方法在自制VOC数据集上表现不佳,引入一种新的数据增强方法以防止训练过程产生过拟合现象。实验结果表明,该方法对工件缺陷的检测精度达到90.63%,检测速度为每秒34.56帧,相较于原始YOLOv4模型,模型规模减小82.1%,检测精度提升了2%,检测速度提升了150%;与SSD和FasterR-CNN等模型相比较,该模型在检测速度和检测精度上有着出色的综合表现,能够针对工件银面缺陷进行高效的检测。

A new algorithm for wireless sensor network based on NS-2

Considering wireless sensor network characteristics,this paper uses network simulator,version2(NS-2)algorithm to improve Ad hoc on-demand distance vector(AODV)routing algorithm,so that it can be applied to wireless sensor networks.After studying AODV routing protocol,a new algorithm called Must is brought up.This paper introduces the background and algorithm theory of Must,and discusses the details about how to implement Must algorithm.At last,using network simulator(NS-2),the performance of Must is evaluated and compared with that of AODV.Simulation results show that the network using Must algorithm has perfect performance.

Impact of biliary complications on quality of life in live-donor liver transplant recipients

BACKGROUND Despite significant advancements in liver transplantation(LT)surgical procedures and perioperative care,post-LT biliary complications(BCs)remain a significant source of morbidity,mortality,and graft failure.In addition,data are conflicting regarding the health-related quality of life(HRQoL)of LT recipients.Thus,the success of LT should be considered in terms of both the survival and recovery of HRQoL.AIM To assess the impact of BCs on the HRQoL of live-donor LT recipients(LDLT-Rs).METHODS We retrospectively analysed data for 25 LDLT-Rs who developed BCs post-LT between January 2011 and December 2016 at our institution.The Short Form 12 version 2(SF 12v2)health survey was used to assess their HRQoL.We also included 25 LDLT-Rs without any post-LT complications as a control group.RESULTS The scores for HRQoL of LDLT-Rs who developed BCs were significantly higher than the norm-based scores in the domains of physical functioning(P=0.003),role-physical(P<0.001),bodily pain(P=0.003),general health(P=0.004),social functioning(P=0.005),role-emotional(P<0.001),and mental health(P<0.001).No significant difference between the two groups regarding vitality was detected(P=1.000).The LDLT-Rs with BCs had significantly lower scores than LDLT-Rs without BCs in all HRQoL domains(P<0.001)and the mental(P<0.001)and physical(P=0.0002)component summary scores.CONCLUSION The development of BCs in LDLT-Rs causes a lower range of improvement in HRQoL.

车速对车载自组网络性能的影响分析与研究

作为智能网联汽车关键技术之一,对车载自组网(VANET,Vehicular Ad Hoc Networks)的分析与优化一直是研究难点。文章分析了车载自组网的主要特点,基于NS2(Network Simulator,version2)仿真平台,根据车辆最大移动速度变化,分别从车辆行驶纵向与侧向出发,针对DSDV、DSR及AODV三种路由协议,分析车速对VANET性能的影响。仿真结果表明:在汽车行驶侧向上,AODV性能优于其他两种协议;在汽车行驶纵向上,在一定速度内,DSR性能最优。

Why Are Arctic Sea Ice Concentration in September and Its Interannual Variability Well Predicted over the Barents–East Siberian Seas by CFSv2?

To further understand the prediction skill for the interannual variability of the sea ice concentration(SIC)in specific regions of the Arctic,this paper evaluates the NCEP Climate Forecast System version 2(CFSv2),in predicting the autumn SIC and its interannual variability over the Barents–East Siberian Seas(BES).It is found that CFSv2 presents much better prediction skill for the September SIC over BES than the Arctic as a whole at 1–6-month leads,and high prediction skill for the interannual variability of the SIC over BES is displayed at 1–2-month leads after removing the linear trend.CFSv2 can reasonably reproduce the relationship between the SIC over BES in September and such factors as the surface air temperature(SAT),200-hPa geopotential height,sea surface temperature(SST),and North Atlantic Oscillation.In addition,it is found that the prescribed SIC initial condition in August as an input to CFSv2 is also essential.Therefore,the above atmospheric and oceanic factors,as well as an accurate initial condition of SIC,all contribute to a high prediction skill for SIC over BES in September.Based on a statistical prediction method,the contributions from individual predictability sources are further identified.The high prediction skill of CFSv2 for the interannual variability of SIC over BES is largely attributable to its accurate predictions of the SAT and SST,as well as a better initial condition of SIC.

华北平原冬小麦生长期典型农田热、碳通量特征与过程模拟

以位山试验站典型农田为对象,利用位山站2005-10-10～2006-06-10日的实验观测数据,探讨了冬小麦整个生长期农田的热、碳通量特征,并运用SiB2(simple biosphere model Version2)模型对热、碳通量进行了模拟分析,结果表明,农田的热、碳通量在冬小麦生长过程中表现出明显的日变化,这些通量的最大值基本出现在正午前后;热、碳通量的日际变化也较明显,其中净辐射与潜热通量在冬小麦不同生长期表现为:越冬期<拔节抽穗期<灌浆成熟期;感热通量表现为:拔节抽穗期<灌浆成熟期<越冬期;而CO2通量为:越冬期<灌浆成熟期<拔节抽穗期.对以上通量及地表温度的模拟表明,SiB2模型能较好地模拟冬小麦生长期中农田热、碳通量及地表温度,净辐射、潜热通量、感热通量、CO2通量与地表温度的模拟值与观测值的一致性较好,线性相关系数R2分别达0.985、0.637、0.481、0.725、0.499与0.877,其中感热通量与CO2通量模拟偏差较大.另外,按冬小麦生长期分阶段对农田以上分量模拟结果表明,SiB2模型在冬小麦拔节抽穗期模拟效果最好,并发现模型对叶面积指数敏感.

Prostate Cancer Detection with Multiparametric Magnetic Resonance Imaging： Prostate Imaging Reporting and Data System Version 1 versus Version 2

Background：Prostate Imaging Reporting and Data System （PI-RADS） is a globally acceptable standardization for multiparametric magnetic resonance imaging （mp-MRI） in prostate cancer （PCa） diagnosis.The American College of Radiology revised the PI-RADS to address the limitations of version 1 in December 2014.This study aimed to determine whether the PI-RADS version 2 （PI-RADS v2） scoring system improves the diagnostic accuracy of mp-MRI of the prostate compared with PI-RADS v1.Methods：This retrospective study was approved by the institutional review board.A total of 401 consecutive patients,with clinically suspicious Pca undergoing 3.0 T mp-MRI （T2-weighted imaging ＋ diffusion-weighted imaging ＋ DCE） before transrectal ultrasound-guided biopsy between June 2013 and July 2015,were included in the study.All patients were scored using the 5-point PI-RADS scoring system based on either PI-RADS v1 or v2.Receiver operating characteristics were calculated for statistical analysis.Sensitivity,specificity,and diagnostic accuracy were compared using McNemar＇s test.Results：Pca was present in 150 of 401 （37.41%） patients.When we pooled data from both peripheral zone （PZ） and transition zone （TZ）,the areas under the curve were 0.889 for PI-RADS v1 and 0.942 for v2 （P =0.0001）.Maximal accuracy was achieved with a score threshold of 4.At this threshold,in the PZ,similar sensitivity,specificity,and accuracy were achieved with v 1 and v2 （all P 〉 0.05）.In the TZ,sensitivity was higher for v2 than for v1 （96.36% vs.76.36%,P =0.003）,specificity was similar for v2 and v1 （90.24% vs.84.15%,P =0.227）,and accuracy was higher for v2 than for v1 （92.70% vs.81.02%,P =0.002）.Conclusions：Both v1 and v2 showed good diagnostic performance for the detection of Pca.However,in the TZ,the performance was better with v2 than with v1.

Applicability Assessment of the 1998–2018 CLDAS Multi-Source Precipitation Fusion Dataset over China

Traditional hourly rain gauges and automatic weather stations rarely measure solid precipitation, except for those stations with weighing-type precipitation sensors. Microwave remote sensing has only a low ability to retrieve solid precipitation. In addition, there are no long-term, high-quality precipitation data in China that can be used to drive land surface models. To address these issues, in the China Meteorological Administration(CMA) Land Data Assimilation System(CLDAS), we blended the Climate Prediction Center(CPC) morphing technique(CMORPH) and Modern-Era Retrospective analysis for Research and Applications version 2(MERRA2) precipitation datasets with observed temperature and precipitation data on various temporal scales using multigrid variational analysis and temporal downscaling to produce a multi-source precipitation fusion dataset for China(CLDAS-Prcp). This dataset covers all of China at a resolution of 6.25 km at hourly intervals from 1998 to 2018. We performed dependent and independent evaluations of the CLDAS-Prcp dataset from the perspectives of seasonal total precipitation and land surface model simulation. Our results show that the CLDAS-Prcp dataset represents reasonably the spatial distribution of precipitation in China. The dependent evaluation indicates that the CLDAS-Prcp performs better than the MERRA2 precipitation, CMORPH precipitation, Global Land Data Assimilation System version 2(GLDAS-V2.1) precipitation,and CLDAS-V2.0 winter precipitation, as compared to the meteorological observational precipitation. The independent evaluation indicates that the CLDAS-Prcp dataset performs better than the Global Precipitation Measurement(GPM) precipitation dataset and is similar to the CLDAS-V2.0 summer precipitation dataset based on the hydrological observational precipitation. The simulated soil moisture content driven by CLDAS-Prcp is slightly better than that driven by the CLDAS-V2.0 precipitation, whereas the snow depth simulation driven by CLDAS-Prcp is much better than that driven by the CLDAS-V2.0 precipitation. This is because the CLDAS-Prcp data have included solid precipitation. Overall, the CLDAS-Prcp dataset can meet the needs of land surface and hydrological modeling studies.