掩埋小目标声探测技术研究

探测和识别沉底、掩埋水雷等小目标在军事上显得愈来愈迫切。在介绍掩埋小目标探测声纳现状的基础上,剖析了掩埋小目标声探测的技术难点,总结了小目标声探测技术的发展趋势,主要包括探测频率向低频发展,重点发展合成孔径探测技术,积极探索时反探测和MIMO探测方法,小目标识别技术向联合利用图像特征和散射特征的方向发展等,对沉底/掩埋小目标声探测技术研究及其声纳设计有借鉴指导意义。     

某公路隧道洞门段冒顶处置方案及效果

公路隧道出洞开挖时地层覆盖较薄,受地质、天气状况和施工方法不当的影响,容易发生隧道冒顶事件,冒顶处理既影响工程进度又增加了工程投资成本。本文结合某公路隧道右线出口冒顶事件,剖析浅埋大跨隧道冒顶事件发生原因和处理方案,为同类工程设计、施工提供参考与借鉴。     

Ride sharing with flexible participants: a metaheuristic approach for large‐scale problems

Severe traffic congestion and growing ecological consciousness have led to the rise of alternative transportation systems. Ride sharing is one such alternative in which drivers and passengers with similar time schedules and travel plans are matched. For this service to be effective, a large number of users are required to increase the probability of finding suitable travel partners. The present paper proposes a late acceptance metaheuristic to decide which users act as drivers and to construct their routes. The underlying optimization model allows passengers to walk to/from alternative pickup/drop‐off locations so as to further exploit user flexibility. A computational study quantifies the impact of different types of participant flexibility on CO₂ emissions. These insights can inform and support policymakers in organizing effective ride‐sharing systems.     

Variation in the volatile terpenoids of two industrially important basil (Ocimum basilicum L.) cultivars during plant ontogeny in two different cropping seasons from India

BACKGROUND: Two Ocimum basilicum cultivars, ‘Vikarsudha’ and ‘CIM‐Saumya’, grown in the Kumaon region of western Himalaya were evaluated for their essential oil yield and composition at different stages of plant growth during two distinct cropping seasons (spring–summer and rain–autumn). RESULTS: The highest yield of essential oil was obtained at full bloom stage in both cultivars in both cropping seasons. The essential oils obtained from different stages in two cropping seasons were analysed by capillary gas chromatography with flame ionisation detection, and gas chromatography–mass spectrometry. The major component of cultivar ‘Vikarsudha’ was methyl chavicol (84.3–94.3%), while for cultivar ‘CIM‐Saumya’ the main components were methyl chavicol (62.5–77.6%) and linalool (14.4–34.1%). CONCLUSION: This study clearly indicated that cultivar, cropping season, plant ontogeny and plant part had significant effects on the yield and quality of the essential oil of O. basilicum. Further, the amount of methyl chavicol in the cultivars grown in this region was higher than in cultivars from other parts of India. Copyright © 2011 Society of Chemical Industry     

谈供热直埋热水管道摩擦力的计算

通过对新旧规程中供热直埋热水管道摩擦力的计算分析,得出同条件下新规程单长摩擦力减小了很多,且考虑了地下水位对管道摩擦力的影响,指出摩擦力的变化直接影响到管道过渡段长度、自由端热伸长以及补偿器的选择等,其计算数据关系到管网的安全运行,具有重要的实用价值。     

LTE通信基站市电引入设计中应该考虑的问题

LTE通信基站市电引入的设计是基站建设的首要环节,直接关系到基站供电的可靠性和安全性,对通信网络的安全运行起到关键的作用。基站市电引入的设计多数由施工单位自行设计施工,造成基站市电引入方式出现较混乱的局面,不合理的设计施工会造成巨大的经济损失。做好基站市电引入设计,使市电引入方式合理化、简单化,在加大可靠性和安全性的基础上,降低投资成本,减少维护量能保障通信畅通,提高经济效益。     

人工堆山工程对周边环境影响数值模拟研究

对软土地基上的拟建堆土工程进行了有限元计算,探讨了当堆土高度较高时引起周边土体的沉降和水平位移,并通过超孔隙水压力消散时间分析堆土引起的沉降固结达到稳定所需的时间,得出了一些有参考价值的结论。     

模型参数估计法计算地下地返回导体参数频率特性

在地下地返回导体参数计算中,为降低优化算法对初值选择的依赖性和提高收敛速度,基于模型参数估计(MBPE),提出了基于频域参数逐步外推概念构造初始值的方法。以Sunde公式为基础,对隐函数形式的导体参数计算公式采用非线性优化方法求解,利用已计算的参数值推出下一个频率的近似解作为优化问题初始值,根据所得初值计算不同大地电导率接地导体参数,分析冲击电流激励下接地导体暂态响应。结果表明,当大地电导率为0.1 S/m、0.01 S/m和0.001 S/m时,土壤的分布电导均远远大于其分布电容,因此,冲击电流作用下,对于实际土壤参数,接地导体时域传输线模型中可不考虑对地电容的作用。应用MBPE方法可以避免计算导体参数时初值选择的盲目性,从而提高了计算效率并保证了算法的收敛性。     

土体塌陷范围对埋地管线影响的研究

土体塌陷是导致埋地管线破坏的重要原因之一。为分析土体塌陷时埋地管线的受力情况,通过ANSYS有限元软件,将管线模拟成四节点薄壳单元,用等效土弹簧来模拟无限长埋地管线的边界,采用均布荷载加载来模拟埋地管道上方土体的作用,分析了不同范围土体塌陷情况下埋地管道的受力特性。通过模拟分析了埋地管线的应力应变,得到了埋地管线的控制截面,可为埋地管线的设计提供一定的理论依据。     

地源热泵中央空调系统地埋管施工技术

近几年,我国地源热泵中央空调系统建设发展迅速,基本上以每年20%～25%的速度在增长,该技术具有显著节能、舒适环保、零空气污染、安全、性能稳定、清洁、使用灵活、经济有效等特点。为节约用地,地源热泵空调地埋管系统常设置在建筑物基础底板下。因此,垂直地埋管管井、地埋管、水平地埋管组成的整个地埋管系统全部位于基础底板以下。底板施工后,地埋管系统无法观察,成为永久性工程。本文重点探讨了地埋管施工技术方面的问题。