Notes on the Epidemiology of Multiple Sclerosis,with Special Reference to Dietary Habits

A hypothesis, based primarily on the occurrence of multiple sclerosis (MS) in the Faroe Islands and supported by numerous analytical epidemiological studies, is described. It proposes that MS is caused by the interaction of a virus disease with intestinal pathology, e.g., infectious mononucleosis, and application of smoked and nitrate/nitrite-cured meat products in the diet during circumscribed time intervals. The biological mechanisms might involve a break of tolerance by an alteration of self within the central nervous system, by nitrophenylated compounds conjugated to animal tissue, in particular to proteins occurring in the central nervous system. Further research is needed.     

Mitigation of tower and out-of-plane blade vibrations of offshore monopile wind turbines by using multiple tuned mass dampers

Offshore wind turbines are vulnerable to external vibration sources such as wind and wave excitations due to the increasing size and flexibility. It is necessary to mitigate the excessive vibrations of offshore wind turbines to ensure the safety and serviceability during their operations. Some research works have been carried out to control the excessive vibrations of the tower and the in-plane vibrations of blades. Very limited study focuses on the out-of-plane vibration mitigation of blades. In the present study, a detailed finite element (FE) model of the latest NREL 5MW wind turbine is developed by using the FE code ABAQUS. The tower and blades are explicitly modelled, and the rotating of the blades is considered. Multiple tuned mass dampers (MTMDs) are proposed to be installed in the tower and each blade to simultaneously mitigate the out-of-plane vibrations of the tower and blades when the wind turbine is subjected to the combined wind and wave loadings. The effectiveness and robustness of the proposed method are systematically investigated. Numerical results show that MTMDs can effectively mitigate the out-of-plane vibrations of the tower and blades when the wind turbine is in either the operational or parked condition.     

基于线性回归和神经网络的金属陶瓷激光熔覆层形貌预测

目的研究激光熔覆关键工艺参数(激光功率、扫描速度、送粉速率)与单道熔覆层宏观形貌(宽度、高度、熔池深度)之间的数量关系,以实现对WC-Co50复合熔覆层形貌的预测,从而为牙轮钻头的修复提供参考。方法设计不同的实验参数,利用4k W光纤激光器在牙轮钻头钢15MnNi4Mo表面熔覆单道WC-Co50复合涂层。采用工业显微镜观察单道熔覆层的横截面宏观形貌,并测量其三维尺寸。在上述形貌参数的基础上,分别运用多元线性回归分析和人工神经网络方法,建立关键工艺参数与熔覆层宏观形貌之间的关系模型,并将实验结果与模型预测结果进行对比。结果总体来讲,神经网络对熔覆层形貌的预测结果更为精确,平均相对误差为5.3187%;多元线性回归分析预测的平均相对误差为6.0028%。分析表明,对熔覆层宽度的预测结果最精确,两种方法的平均相对误差仅为1.2999%;对高度及熔池深度的预测结果稍差,平均相对误差分别为8.0586%和7.6237%。结论两种预测方法都具有较高的精度,但神经网络法函数关系不明确,运算过程复杂,需要通过进一步的算法优化来提高预测精度。     

变截面涡旋盘齿面粗糙度的双预测模型

目的精确预测三段基圆变截面涡旋盘齿面粗糙度,确定合理的铣削参数,提高变截面涡旋盘齿面的加工质量。方法首先在正交试验的铣削参数条件下,用XK714数控铣床对毛坯件进行铣削加工,获得三段基圆变截面涡旋盘,用SJ-210表面粗糙度测量仪测量已加工涡旋齿侧面的粗糙度值。然后利用铣削参数和测量的粗糙度值,建立齿面粗糙度的多元回归预测模型和改进的BP神经网络预测模型及双预测模型,并验证该三种模型的精确度。最后对单一因素条件下的粗糙度进行预测、分析。结果经过计算可得,齿面粗糙度的多元回归预测模型的平均误差为1.43%,最大误差为3.09%。改进的BP神经网络预测模型的平均误差为1.33%,最大误差为3.22%。两种模型的预测平均值作为双预测模型时,预测平均误差为0.627%,最大误差为1.51%。结论齿面粗糙度的双预测模型的平均误差明显降低,同时可以避免单一预测模型产生主观预测误差。各铣削因素对粗糙度的影响程度不同,进给量fz吃刀深度ap刀具转速n侧吃刀量ae。随着进给量、吃刀深度、侧吃刀量的增加,齿面粗糙度值增加;随着刀具转速升高,齿面粗糙度值降低。     

流量喷嘴及其在实验室风量测量中的应用

根据国内外文献并结合作者数年来的实践经验,详细地叙述了当今广泛应用于实验室风量测量的多喷嘴风量测量装置的设计、风量计算和风量调节等问题。给出了该装置的设计实例。     

Job accessibility impacts of intensive and multiple land-use scenarios for the Netherlands’ Randstad Area

This paper examines job accessibility impacts of intensive and multiple land-use scenarios in the Netherlands’ Randstad Area for the period 1996–2030. The scenarios involve a heavy increase in the density and diversity of activities around railway stations. Accessibility impacts are examined using location-based accessibility measures and utility-based accessibility benefit measures within a high-resolution land-use/transport interaction modelling framework, taking into account the regional demand for economic activities and possible market responses. It is concluded that extreme concentrations of economic activities at central urban locations well served by public transport are not to be preferred over less heavy concentrations of economic activities at more locations. Heavy concentrations of new firms may firstly repel existing firms in the neighbourhood and secondly result in decreasing marginal returns of accessibility benefits for public transport users.     

对沿海城镇规划的思考

随着我国城市化进程的加快，沿海城镇的规划和建设日益被社会所关注，结合东平镇允泊湾海洋经济区可行性研究报告，提出沿海城镇规划应结合当地实际情况，在确保总体规划完整性的同时，有特色、有重点、多元化地发展。     

冬季工况多次温度循环下微型钢管桩群桩热力响应特性现场试验

能量桩技术具有支撑上部结构和浅层地热能换热器双重作用;作为一种节能减排新技术,近年来获得了一定的发展。依托微型钢管桩加固既有基础托换工程,开展冬季工况多次温度循环下微型钢管桩群桩的热力响应现场试验;实测不同间歇时长情况下桩身温度与应力等变化规律,探讨不同运行模式下的桩基换热性能系数（C_OP,coefficient of performance）。试验结果表明：文中试验条件下,桩身附加温度应力随循环次数增加而增大,且随间歇时间的延长而减小;桩基C_OP随循环次数增加而减小,且随间歇时间的延长而增大;附加拉应力未超过设计控制范围、不会导致桩体破坏。     

大跨空间网格结构在多点输入下的弹塑性地震响应分析

采用时程分析法对大跨空间网格结构分别进行了多点和一致输入下的弹塑性地震响应分析,多点输入下的相干函数模型采用著名的R.S.H arichandran模型.对两种输入方式下的结构响应进行了对比,发现两者的塑性开展规律大体一致,但多点输入下进入塑性杆件的数量明显多于一致输入,同时塑性杆件分布更加均匀.     

QC成果的模糊综合评判

本文阐述采用模糊综合评判方法 ,通过模糊变换求得综合评判矩阵 ,同时根据需要给评语集赋以权重 ,对 QC成果进行定量和客观的描述 ,并通过实例 ,分析其在 QC成果应用中的具体计算方法和应用过程。