随机早期检测算法研究

RED消除了全局同步现象．较大地提高了物理线路的利用率，减少了对突发业务的偏见。但在有大量活跃TCP连接时，RED不能有效估计拥塞的严重性．从而降低链路利用率。针对这些问题提出了RED的改进算法。仿真表明．该算法在突发业务下能对拥塞作出更及时有效的反应．并能保证链路利用率。     

模糊随机早期检测在组播拥塞控制中的应用

现有的组播拥塞控制算法大都基于端系统进行拥塞控制,而较少讨论中间路由器的主动队列管理机制。基于模糊逻辑对网络状态的动态适应性特点,提出了基于模糊逻辑的RED算法（Fuzzy Logic-based RED,FL RED）。该算法运用于组播拥塞控制中,网络能够及时对拥塞做出准确反应,更有效地分配和利用资源。仿真结果表明,该算法比普通RED算法具有更好的TCP-友好性,并且能够将队列长度维持在一个较小值,具有更小的传输时延。     

低轨预警系统动态任务规划启发式算法

该文针对低轨预警系统任务动态规划需求,从预警传感器资源和导弹跟踪任务角度对低轨预警系统动态任务规划问题进行了形式化描述,建立了系统动态任务规划的动态约束满足问题模型。该模型包括两级优化目标跟踪精度、资源利用率、传感器切换率、松弛度综合优化指标和方案调整幅度(调整率)指标;提出了求解动态规划问题的变邻域启发式搜索算法,设计了算法的直接插入、重新分配、替换和删除邻域结构及算子。通过仿真实验验证了基于梯度优化目标的动态规划模型的合理性,并说明启发式算法能有效求解低轨预警系统动态任务规划问题。     

LDPC码加权比特翻转译码算法的低复杂度提前停止准则

近年来,针对LDPC码置信传播(BP)译码算法的提前停止准则的研究已经有了很多,但设计适合加权比特翻转(WBF)译码算法的提前停止准则却研究甚少。依据对WBF算法的全新理解方式,该文提出一种实现简单、适用性强的WBF算法提前停止准则,它能在译码的初始阶段检测绝大多数不可纠错的帧。仿真结果表明,基于提前停止准则的WBF算法在性能损失可以忽略的条件下,极大地降低迭代次数,在实现复杂度和性能之间达到了很好的折中。     

混凝土早期受冻临界强度浅谈

通过对混凝土早期受冻临界的论述 ,指出了早期受冻临界强度是保证冬期施工中混凝土工程质量的重要前提。     

哈尔滨工业大学早期建筑教育的实践教学

哈尔滨工业大学前身为中东铁路企业办学,早期建筑教育注重实践,属土木建筑领域的通才教育模式.文章对早期建筑教育创办背景、培养目标、教学内容、教学方法及专业师资构成等方面的"实践"权重做客观评介及深入思考.     

实现机床颤振早期诊断的一个新的特征量

本文通过大量试验信号的互谱分析,找出了颤振建立过程中切削力和振动加速度信号互谱的特征变化:主频带的移动及其相位差的变化.然后,基于互谱与互相关函数的关系.分析了一步互相关系数的变化与互谱上述两种特征变化的内在联系.从而可将一步互相关系数作为机床颤振早期诊断的一个特征量.试验结果表明,该特征量是有效的.     

DETECTION OF EARLY RUB-IMPACT IN ROTORS VIA HIGHER-ORDER TIME-FREQUENCY ENTROPY

Due to the calculation problem of classical methods (such as Lyapunov exponent) for chaotic behavior, a new method of identifying nonlinear dynamics with higher-order time-frequency entropy (HOTFE) based on time-frequency analysis and information theorem is proposed. Firstly, the meaning of HOTFE is defined, and then its validity is testified by numerical simulation. In the end vibration data from rotors are analyzed by HOTFE. The results demonstrate that it can indeed identify the early rub-impact chaotic behavior in rotors and also is simpler to calculate than previous methods.     

颤振征兆早期识别的模糊信息融合法

基于切削试验探讨颤振征兆早期识别的模糊信息融合方法。试验中在同一个测量区内使用了功率传感器和加速度传感器,利用模糊数学与Dempster-Shafer证据论相结合的方法对两种传感器信息进行了分析融合,对切削状态进行了描述。试验证实:利用证据理论与模糊推理相结合的信息融合方法进行颤振征兆的早期模糊识别得出的目标切削状态的隶属度介于单一征兆隶属度之间,对过于敏感的传感器,会考虑其他传感器的信息予以修正,降低其评价隶属度;对于不敏感传感器,会考虑其他传感器的信息予以补偿。这种方法弥补了最大隶属度原则的缺陷,即在模糊推理中,系统对某一状态的隶属程度实际上是由模式特征集中贡献最大的那个特征决定的,而没有用到其他特征提供的信息,这说明证据理论与模糊推理相结合的信息融合方法在进行颤振征兆早期识别时具有更高的可靠度。     

Development and evaluation of an intervention to reduce rip current related beach drowning

The objective of this research was to evaluate a campaign to improve beachgoer recognition of calm-looking rip currents, known to contribute to surf drowning. Posters, postcards, and brochures conveying the message “Don’t get sucked in by the rip” were distributed in an intervention area. Beachgoers were interviewed in this and a similar control area one year before and immediately after the intervention (respective response rates: 69.9% and 82.3%), Consenting respondents were sent follow-up questionnaires after approximately 6 months and 55% responded. In the intervention area, 28.8% of post-intervention, and 57.2% of follow-up respondents, had seen our campaign. At post-intervention, intervention respondents demonstrated improvement (relative to baseline) in intentions to swim away from a calm-looking rip, ability and confidence in identifying a rip, intention never to swim at unpatrolled beaches, and responses to being caught in a rip, compared to the control respondents. Similar improvements were observed post-intervention for respondents in the intervention area who had seen our campaign (relative to those who had not), and at 6 month follow-up for intervention respondents (relative to control respondents). The relatively brief print-based campaign was effective in warning beachgoers about calm-looking rips.