一种超声速气体冲击射流噪声的屏蔽抑制方法

根据对冲击射流离散频率噪声产生的反馈机理的认识，提出了一种能够有效地破坏反馈环的形成，从而抑制冲击射流离散频率噪声的喷嘴屏蔽方法。这种方法是通过阻隔反馈声波使其不能到达喷嘴唇口、同时屏蔽物不与射流接触来实现降噪的目的，实验结果表明，对于合适的屏蔽罩参数，正常降噪效果达5dB以上。分析表明这种降噪方法对射流冲击平板的推力和除尘除水效率的提高有帮助。     

科研工作中科技情报检索的作用--浅谈应用国际联机情报检索的体会

科技情报检索是科研工作中的重要环节,也是科研成果评价的必要手段.课题研究必须了解国内外发展动态,进行可行性和经济效益分析.本文通过国际联机情报检索的两个应用实例,阐明了情报检索不仅提高了科研工作效率,而且在课题研究的方法、深度和广度、最终结果方面都能得到很大益处.     

抽出式通风煤巷掘进过程中粉尘浓度分布规律的数值模拟

根据气固两相流理论，针对矿井掘进工作面的特点，采用计算流体力学的离散相模型（DPM）对掘进工作面通风过程中粉尘浓度进行数值模拟，总结抽出式通风掘进巷道中粉尘浓度的沿程分布及变化规律。     

Evaluating the Quality of Citizen‐Scientist Data on Pollinator Communities

Abstract: Concerns about pollinator declines have grown in recent years, yet the ability to detect changes in abundance, taxonomic richness, and composition of pollinator communities is hampered severely by the lack of data over space and time. Citizen scientists may be able to extend the spatial and temporal extent of pollinator monitoring programs. We developed a citizen‐science monitoring protocol in which we trained 13 citizen scientists to observe and classify floral visitors at the resolution of orders or super families (e.g., bee, wasp, fly) and at finer resolution within bees (superfamily Apoidea) only. We evaluated the protocol by comparing data collected simultaneously at 17 sites by citizen scientists (observational data set) and by professionals (specimen‐based data set). The sites differed with respect to the presence and age of hedgerows planted to improve habitat quality for pollinators. We found significant, positive correlations among the two data sets for higher level taxonomic composition, honey bee (Apis mellifera) abundance, non‐Apis bee abundance, bee richness, and bee community similarity. Results for both data sets also showed similar trends (or lack thereof) in these metrics among sites differing in the presence and age of hedgerows. Nevertheless, citizen scientists did not observe approximately half of the bee groups collected by professional scientists at the same sites. Thus, the utility of citizen‐science observational data may be restricted to detection of community‐level changes in abundance, richness, or similarity over space and time, and citizen‐science observations may not reliably reflect the abundance or frequency of occurrence of specific pollinator species or groups.     

ABC算法优化SVR的磨损故障预测模型

目的为了提高故障预测的精度,针对支持向量回归SVR(Support vector machine for regression,SVR)参数选择困难的问题,提出一种采用人工蜂群(artificial bee colony,ABC)算法优化支持向量回归(SVR)的故障预测模型(ABC-SVR)。方法该模型先对样本数据进行重构,然后将故障预测误差(适应度)作为优化目标,通过ABC算法寻优找到最优的SVR参数,建立故障预测模型。最后通过实例仿真验证模型的优越性。结果采用ABC算法优化的SVR故障预测模型进行时间序列预测,能够较好地跟踪发动机滑油金属元素浓度的变化过程,并且能够提前2个取样时间预测异常情况的出现。结论 ABC-SVR模型有效解决了SVR参数选择难题,能够更加准确地表现故障变化规律,提高了故障预测精度。     

模糊控制技术在污水处理中的应用

针对污水处理过程中采用传统的流量程序控制和时间程序控制的不足,提出了一种基于单片机的模糊控制方法。该方法以污水流量、溶解氧(DO)浓度和污泥回流比为主要被控对象,以DO浓度为主要控制参数,通过离散计算和在线查表的模糊推理方法可得到最佳的风机转速,使污水处理生化池内DO浓度保持在最佳状态,同时还通过控制曲线展示了当输入污水流量发生扰动时对DO浓度的控制精度,使污水处理质量保持稳定。通过实际应用表明,该控制方法不但能确保出口净化水水质达标,还可以节约15%的电能。     

Experience,but not distance,influences the recruitment precision in the stingless bee <Emphasis Type="Italic">Scaptotrigona mexicana</Emphasis>

Recruitment precision, i.e. the proportion of recruits that reach an advertised food source, is a crucial adaptation of social bees to their environment. Studies with honeybees showed that recruitment precision is not a fixed feature, but it may be enhanced by factors like experience and distance. However, little is known regarding the recruitment precision of stingless bees. Hence, in this study, we examined the effects of experience and spatial distance on the precision of the food communication system of the stingless bee Scaptotrigona mexicana. We conducted the experiments by training bees to a three-dimensional artificial patch at several distances from the colony. We recorded the choices of individual recruited foragers, either being newcomers (foragers without experience with the advertised food source) or experienced (foragers that had previously visited the feeder). We found that the average precision of newcomers (95.6 ± 2.61%) was significantly higher than that of experienced bees (80.2 ± 1.12%). While this might seem counter-intuitive on first sight, this “loss” of precision can be explained by the tendency of experienced recruits to explore nearby areas to find new rewarding food sources after they had initially learned the exact location of the food source. Increasing the distance from the colony had no significant effect on the precision of the foraging bees. Thus, our data show that experience, but not the distance of the food source, affected the patch precision of S. mexicana foragers.     

基于人工蜂群算法与BP神经网络的水质评价模型

针对BP网络水质评价模型的不足,引入人工蜂群(ABC)算法,将求解BP神经网络各层权值、阀值的过程转化为蜜蜂寻找最佳蜜源的过程,提出了一种新的结合人工蜂群算法的BP网络水质评价方法(ABC-BP)。并以2000—2006年渭河监测断面的10组实测数据作为测试样本对其水质进行了评价,实验结果表明该方法得到的水质评价结果准确,并具有很强的稳定性和鲁棒性。     

交通系统智能决策的算法研究

遗传算法是近年来迅速发展起来的一种全新的随机搜索与优化算法，但由于其自身固有的缺陷，通常优化过程的收敛速度较慢，局部搜索能力不足，而且算法稳定性较差。而蚁群算法广泛应用在旅行商问题计算中，目前是较好的求解最短路由问题的算法之一。就其自身来说有很多优点，如正反馈性、鲁棒性和智能性，但是在寻优过程中容易陷入局部最佳的缺点。针对上述情况，将遗产算法与蚁群算法相结合，用于实际交通系统寻找最优路径的问题中，并定义了目标函数，以路径可靠性和路径长度为优化目标，寻找最合适的救灾路线。最后通过实际计算结果的对比验证，说明了该方法的有效性。     

车辆事故紧急呼救技术发展综述

综述了车辆事故紧急呼救技术的原理,从车辆事故检测识别技术、移动车辆定位技术、无线通信技术和地理信息系统几方面概述车辆事故紧急呼救技术的研究内容。进一步介绍车辆事故紧急呼救技术的国内外研究和应用现状,并从车辆事故识别技术、地图匹配及组合导航、集群通信及通信网络几方面总结并指出车辆事故紧急呼救技术的关键技术和难点。展望了车辆事故紧急呼救技术的发展趋势,并就我国发展车辆事故呼救技术的可行性和发展方向进行探讨。