一种螺旋桨飞机滑流影响的极曲线确定方法

在螺旋桨飞机的试飞验证中,为确定其实际的升阻特性,通过在一般极曲线的表达式中引入拉力系数项,推导出同时适用于螺旋桨飞机巡航状态、爬升状态和下降状态的通用极曲线模型。根据一型螺旋桨飞机飞行试验数据确定该飞机通用极曲线表达式。采用该通用极曲线计算得到的巡航状态下的阻力系数与试飞值的误差在5%以内,爬升率、下降率的计算值与试飞值的误差在5%左右,计算结果的误差基本在工程计算精度的允许范围,证明该模型具有工程实用性,可用于该飞机的飞行性能数据修正和扩展计算。     

裂缝性致密砂岩气藏剩余气分布预测及开发优化建议： 以川西坳陷新场地区须家河组二段为例

裂缝性致密砂岩气藏具有储层基质致密低渗、裂缝非均质发育、气水界面不统一等特点,导致天然气资源动用程度低,气井产能差异大,开发形势整体不乐观。为明确气藏的剩余气分布规律及动用对策,以新场地区须家河组二段气藏为例,根据产能主控因素分析,形成了一套适用于裂缝性致密砂岩气藏的数值模拟技术流程,定量表征了剩余气分布特征,提出了开发优化建议。结果表明：综合考虑构造裂缝和基质砂体岩性对产能的控制作用,对动态模型采用“分井区、分砂组、分介质、分岩性”的方式精细划分流动单元,保证了数值模拟的高效和精度。剩余气分布整体在构造起伏约束下,受基质岩性、断裂裂缝和井控程度影响。建议布井潜力区应具备构造高部位、基质砂体连续、断裂裂缝发育、剩余气富集等条件,进一步根据井间干扰程度和地层能量利用率优化布井位置。     

穿越溶洞型基桩竖向极限承载力计算方法研究

在岩溶地区,若基桩下伏溶洞的顶板厚度不符合稳定性要求,需考虑基桩穿越溶洞并嵌入溶洞底板以提高基桩承载力。但是,目前尚无计算穿越溶洞型基桩竖向极限承载力的成熟方法。为此,首先通过室内试验研究穿越单层溶洞基桩在桩顶逐级加载条件下“地层-基桩-溶洞”系统的渐进破坏过程及破坏模式;然后,基于塌落拱理论建立溶洞顶板张拉破坏高度的计算方法,揭示桩身侧摩阻力的“拱效应”现象;其次,基于小应变理论和单向受压微元体平衡方程,建立桩身压屈的临界条件,提出了桩身轴向受压极限荷载的计算方法;最后,提出穿越溶洞型基桩竖向极限承载力的计算流程,并采用该方法计算某实际穿越溶洞型基桩的竖向承载力。     

承压水地层管廊基坑开挖变形特征及抗突涌稳定性分析

管廊穿越富水软弱地层时,对其安全建设产生了不容忽视的影响。为了研究富水地层管廊基坑开挖变形的稳定性,依托济南新东站开源路富水地层管廊基坑工程,分析影响基坑开挖变形的关键因素,提出基坑周边土体变形破坏影响因素的敏感性评价指标,建立基坑底板抗突涌稳定性系数及隔水层临界厚度公式。结果表明:随开挖深度和承压水头增加,水平位移具有分层现象,深层呈“月牙形”,最大变形位于基坑底部两侧下部,呈现向桩后和基坑中心靠拢趋势;地表沉降呈凹槽形,从基坑边向两侧呈先增大后减小趋势,而隆起变形越靠近基坑中心越大,施工中应注意基坑底部两侧向中间过度时出现的较大隆起值。基坑周围土体变形破坏影响因素指标敏感性大小依次为开挖深度、加固厚度和承压水头,施工时要适当采取降水措施,预留足够的隔水层厚度,加固坑底以增强其稳定性,更要适当控制基坑开挖深度;与传统法相比,考虑土体抗剪强度所计算的基坑抗突涌稳定性系数较大,隔水层临界厚度较小,与现场情况更加吻合。     

基于多层联合降噪的信号处理方法

针对旋挖钻机钻杆振动信号具有非线性、非平稳的特点,以及多源振动耦合影响,提出了一种基于多层联合信号降噪方法,对振动信号进行降噪处理。首先,采用局域均值分解(local mean decomposition, LMD),得到一系列乘积函数(product functions, PF),根据计算得出的相关系数,挑选出含噪声成分最多的PF分量,舍弃残余分量,实现第一层降噪;其次,利用小波阈值降噪(wavelet threshold denoising, WTD),对挑选分量实现了第二层降噪;最后,将WTD重构信号设为奇异值分解(singular value decomposition, SVD)的前置处理单元,实现第三层降噪。基于MATLAB仿真实验与轴承数据降噪实验,分别使用EMD-SVD、LMD-SVD两种算法对目标信号进行降噪处理,LMD-WTD-SVD方法可以提高信噪比,并对比波形图与频谱图结果表明,此方法是一种更有效的降噪方法。     

Forecasting intraday S&P 500 index returns: A functional time series approach

Financial data often take the form of a collection of curves that can be observed sequentially over time; for example, intraday stock price curves and intraday volatility curves. These curves can be viewed as a time series of functions that can be observed on equally spaced and dense grids. Owing to the so‐called curse of dimensionality, the nature of high‐dimensional data poses challenges from a statistical perspective; however, it also provides opportunities to analyze a rich source of information, so that the dynamic changes of short time intervals can be better understood. In this paper, we consider forecasting a time series of functions and propose a number of statistical methods that can be used to forecast 1‐day‐ahead intraday stock returns. As we sequentially observe new data, we also consider the use of dynamic updating in updating point and interval forecasts for achieving improved accuracy. The forecasting methods were validated through an empirical study of 5‐minute intraday S&P 500 index returns.     

爆破拆除冷却塔倾倒条件的研究

从理论上研究了定向爆破拆除冷却塔的倾倒条件,建立了结构极限弯矩和倾倒力矩的表达式。计算结果表明,当爆破切口圆心角为0.626×2π时,假设结构受压区和受拉区的钢筋和混凝土同时达到塑性状态,倾倒力矩仅为结构极限弯矩的1.09倍;若按照材料力学理论以受拉区的最大拉应力大于混凝土的抗拉强度为极限条件,则倾倒力矩为结构极限弯矩的2.91倍;若按照弹塑性理论分析,则倾倒力矩为结构极限弯矩的1.62倍。最后,文章分析了支撑部位的破坏过程。     

优秀课程建设的实践与思考

以杭工院建设优秀课程作为教学改革的突破口出发,论述了通过开展课程评估,促进优秀课程全面建设的观点．     

双低频超声辐射对碘化钾溶液碘释放量影响的研究

用碘释放分析了２４ｋＨｚ,３１ｋＨｚ超声的声化学产率随声强的关系,进而研究了由２４ｋＨｚ与３１ｋＨｚ喇叭型及２４ｋＨｚ喇叭型与３１ｋＨｚ阶梯形变幅轩组成的相向辐射系统的声化学产额．结果表明,双频辐射增强的声化学产额与辐射端面积有关,本文对此现象给出理论解释．     

Modeling and Solving a Multi-Period Inventory Fulfilling and Routing Problem for Hazardous Materials

Any potential damage may be severe once an accident occurs involving hazardous materials.It is therefore important to consider the risk factor concerning hazardous material supply chains, in order to make the best inventory routing decisions. This paper addresses the problem of hazardous material multi-period inventory routing with the assumption of a limited production capacity of a given manufacturer. The goal is to achieve the manufacturer's production plan, the retailer's supply schedule and the transportation routes within a fixed period. As the distribution of hazardous materials over a certain period is essentially a multiple travelling salesmen problem, the authors formulate a loadingdependent risk model for multiple-vehicle transportation and present an integer programming model to maximize the supply chain profit. An improved genetic algorithm considering two dimensions of chromosomes that cover the aforementioned period and supply quantity is devised to handle the integer programming model. Numerical experiments carried out demonstrate that using the proposed multiperiod joint decision-making can significantly increase the overall profit of the supply chain as compared to the use of single period decision repeatedly, while effectively reducing its risk.