摘要：A series of novel pleuromutilin derivatives with 4H-pyran-4-one and pyridin-4-one substitution in the C-14 side chain have been designed and synthesized. In vitro antibacterial activity evaluation showed that most of the derivatives exhibited potent antibacterial activity against drug resistant Gram-positive strains. Compounds 12 a, 12 d, and 28 are the most active derivatives in this series, displaying activity comparable to that of retapamulin and BC-3781. As the metabolic stability of this series is not satisfactory, further modifications are going on to improve their pharmacokinetic profile.

摘要：呼叫接纳控制作为异构网络系统资源管理的重要部分,直接影响整个网络资源使用的有效性,因此在异构网络环境下设计一个合理有效的接纳控制策略至关重要.考虑了异构网络中的呼叫接入问题,根据各类服务的带宽需求以及提供的利润差异,针对其随机分布的特性,建立连续时间Markov分析模型,提出一种基于缓存的呼叫接入控制算法,并采取迭代策略对算法进行优化.仿真实验验证了算法的有效性,最终的控制策略是系统长期平均利润最大化的最优策略.

摘要：流量均衡是为了避免网络拥塞而作为流量工程中的路由优化目标提出来的,由于数据中心网络的流量特性,使得传统IP网络的流量工程方法不一定适合.为此,本文在SDN(Software Defined Network)的框架下,提出了一种基于链路关键度的自适应负载均衡流量工程方法:DraLCD(Dynamic Routing Algorithm based on Link Critical Degree).该方法通过对全局视图的网络管控,并充分利用了网络中存在的冗余路径,在完成细粒度流量均衡的同时,能够降低控制器的计算开销以及与交换机之间的通信开销,最终完成路由优化的目标.最后,基于DraLCD设计的原型系统,通过在Mininet仿真平台中部署并进行仿真实验,与现有的等开销多路径路由算法ECMP(Equal-Cost MultiPath)以及GFF(Global First Fit)路由算法相比较,能够明显地提升网络性能.

摘要：本文在一定假设的基础上,详细分析了移动通信卫星姿态不稳定对其覆盖性能的影响,从而为星座方案的设计、星上稳定度要求等提供了一个重要的参考依据。

摘要：在分析传统的链路——状态算法的基础上,提出了一种优化的卫星通信星际路由算法。该算法能够找出任意两颗卫星间通信的最佳路径集合,同时能够在链路质量容许的情况下,尽量避免通信链路切换的发生,从而较大地提高了系统性能。

摘要：海面物联网在海洋观测、海域监测等应用中发挥着重要作用.复杂动态海洋环境造成海洋网络链路状态、链路质量的时变特征,且其给海面物联网带来了严峻挑战,为此,将物理层自适应数据速率、媒体访问控制(MAC)层载波侦听多址接入与网络层机会路由联合进行跨层设计,提出速率自适应海面物联网跨层传输协议,通过3次握手机制机会性选择最佳转发结点并基于动态信噪比实现传输速率实时自适应调整,旨在提高动态复杂海洋环境下海面物联网的稳健性.陆地和湖上试验结果表明,所提协议在数据包交付率、能耗与时延方面性能优异,可为复杂动态海洋环境中海面物联网数据的高效传输提供重要的技术途径.

摘要：In order to achieve the functional requirements of multi-moving state, a new autonomous underwater vehicle(AUV) provided with the functions such as the submarine vectorial thrust, landing on the sea bottom, wheel driving on the ground and crawling on the ground was designed. Then five new theories and methods were proposed about the motion mechanism of the AUV such as vectorial thruster technology, design of a new wheel propeller, kinematics and dynamics, navigation control and the ambient flow field in complex sea conditions, which can all conquer conventional technique shortages and predict the multi-moving state performance under wave disturbance. The theoretical research can realize the results such as a vectorial transmission shaft with the characteristics of spatial deflexion and continual circumgyratetion, parameterized design of the new wheel propeller with preferable open-water performance and intensity characteristics satisfying multi-moving state requirements, motion computation and kinetic analysis of AUV's arbitrary postures under wave disturbance, a second-order sliding mode controller with double-loop structure based on dynamic boundary layer that ensures AUV's trajectory high-precision tracking performance under wave disturbance, fast and exact prediction of the ambient flow field characteristics and the interaction mechanism between AUV hull and wheel propellers. The elaborate data obtained from the theoretical research can provide an important theoretical guidance and technical support for the manufacture of experimental prototype.

摘要：城市产业和人口的快速聚集导致空气污染物排放量不断增加,区域性大气污染问题突出,特别是在工业园区。为明确苏南地区典型细颗粒物(PM_(2.5))污染特征和来源,笔者以苏州高新区2022年12月一次连续性污染过程为例,利用PM_(2.5)组分特征进行污染成因和来源解析。结果表明:(1)PM_(2.5)浓度与温度、湿度、风速和风向等气象因素呈显著相关,低风速、高相对湿度的气象条件有利于细颗粒物吸湿增长以及污染气团长时间停留。(2)从行业来源贡献比来看,二次生成对细颗粒物的贡献占比(62%)高于一次排放占比(38%)。一次排放源中工艺过程源(12%)、移动源(9%)以及燃煤、生物质等燃烧源(7%)贡献比较高。(3)从区域传输贡献来看,冬季PM_(2.5)主要受苏州市外传输(67.4%±15.5%)、苏州市内传输(20.5%±7.89%)和本地生成(12.1%±5.53%)影响。研究结果可为划定不同大气污染物的重点防治区域和制定联合防治行动计划提供依据,也可为环境质量管理与美丽城市生态建设提供科学支撑。

摘要：Peer-to-peer (P2P) technology provides a cost-effective and scalable way to distribute video data. However, high heterogeneity of the P2P network, which rises not only from heterogeneous link capacity between peers but also from dynamic variation of available bandwidth, brings forward great challenge to video streaming. To attack this problem, an adaptive scheme based on rate-distortion optimization (RDO) is proposed in this paper. While low complexity RDO based frame dropping is exploited to shape bitrate into available bandwidth in peers, the streamed bitstream is dynamically switched among multiple available versions in an RDO way by the streaming server. Simulation results show that the proposed scheme based on RDO achieves great gain in overall perceived quality over simple heuristic schemes.

摘要：燃油压力调节阀是船舶动力系统的重要组成部件,主要用于稳定供油系统的燃油压力,减小系统压力波动对燃机的影响。基于现代船舶航程远、体量大的特点,设计了一种适用于大流量燃油系统的压力调节阀,分析了其工作原理,研究了调节阀内的燃油流动模型,通过数值仿真分析了内部流场,搭建了一套基于实际供油系统的试验系统,对两种不同工况的系统参数进行了试验。结果表明,所设计的燃油压力调节阀结构合理,使用该阀后,系统流量、压力、响应时间符合燃机使用要求。