Short‐term salmon price forecasting

This study establishes a benchmark for short‐term salmon price forecasting. The weekly spot price of Norwegian farmed Atlantic salmon is predicted 1–5 weeks ahead using data from 2007 to 2014. Sixteen alternative forecasting methods are considered, ranging from classical time series models to customized machine learning techniques to salmon futures prices. The best predictions are delivered by k‐nearest neighbors method for 1 week ahead; vector error correction model estimated using elastic net regularization for 2 and 3 weeks ahead; and futures prices for 4 and 5 weeks ahead. While the nominal gains in forecast accuracy over a naïve benchmark are small, the economic value of the forecasts is considerable. Using a simple trading strategy for timing the sales based on price forecasts could increase the net profit of a salmon farmer by around 7%.     

弹性需求用户平衡分配模型及其应用

对具有弹性需求的交通网络随机用户平衡分配问题进行了分析研究,将其描述为一个等价的变分不等式。最后将模型应用于拥护公交网络系统的平衡分配问题,并针对公交网络系统的特殊性,提出相应的求解算法 法。实例表明了模型的合理性和算法的有效性。     

煤层冲击倾向性试验及数值模拟

冲击地压是一种特殊的矿山动力现象,而冲击倾向性是煤岩体发生冲击地压的内在因素和必要条件.对松树镇煤矿主采煤层进行冲击倾向性试验,对冲击能量指数、弹性能量指数和动态破坏时间三个煤层冲击能量指标进行分析,得出煤层无冲击倾向性.但对开采煤层数值模拟,得出深部煤层顶部最大主应力值、顶板下沉较大,需要实施一定的防治措施.这为该矿防治冲击地压提供了科学依据.     

高弹性合金Cu-Ni-Sn的研究与发展

阐述了Cu-Ni-Sn合金依靠其良好的力学性能和环保等特点,作为一种有望替代铍青铜的新型铜基弹性合金,被广泛应用于制作各种接插件、弹簧件和开关等弹性元件.文章介绍了该合金国内外研究现状和制备工艺,分析了Ti、Si、Cr、Al、Co、Fe、In和Mn等元素对合金组织和性能的影响,指出了Cu-Ni-Sn合金未来研究的重点应集中在降低合金偏析程度、优化加工工艺和添加适当微量元素提升其性能等方面.     

螺型位错与含共焦裂纹弹性椭圆夹杂的干涉效应

研究了基体与夹杂中任意位置螺型位错与含共焦裂纹弹性椭圆夹杂的干涉问题,运用复变函数的分区全纯理论、柯西型积分、应力函数奇性主部分析方法与Rieman边值理论,将问题归结为一个初等复势函数方程的求解.获得了基体与夹杂区域复势函数的级数形式精确解,导出了裂纹尖端应力强度因子解析表达式和作用于位错的像力公式.计算结果表明:夹杂中的裂纹对于位错与夹杂的干涉具有强烈的扰动效应,它增强软夹杂对位错的吸引,减弱硬夹杂对位错的排斥,甚至将排斥转变为吸引.裂纹尖端附近的应力强度因子等值线表明,螺型位错位于裂纹尖端附近特定区域时对于裂纹扩展具有屏蔽效应.     

Design and passive analysis of a novel softness display device

Simulating the softness property of object is quite a challenge in virtual reality system. A novel softness display system was developed based on the principle of deformable length of elastic element control （DLEEC）. In the system, the equivalent stiffness of the device is adjustable, and is inversely proportional to the third power of the deformable length of elastic beam. PD position control is employed to guarantee the accurate softness display. The softness of the virtual objects in large scale can be felt with the softness display device. Compared with other haptic devices, the device is passive and exert the react force only when the operator ＂actively touch＂ the virtual objects. The stability of the softness display system was analyzed. It was theoretical proved that the system satisfied the criteria of wide impedance range ＂Z-width＂, and the performance was superior to an active system. The experimental results were presented.     

波动方程在半无穷柱体和外部区域上的空间爆破和衰减性

利用能量分析的方法,首先考虑定义在三维半无穷柱体上的波动方程,当空间变量趋于无穷时,证明其解或者指数式增长或者指数式衰减;其次,考虑定义在球面外部区域上的波动方程,证明其解随半径的二择一结果;最后,证明对于非线性弹性方程,二择性定理仍有效.     

圆环圆拱承受均匀径向荷载时弹性失稳的加权余量解

本文用加权余量法推导出圆环和圆拱在均匀径向荷载作用下,发生弹性失稳时临界荷载q_(cr)的计算公式.     

直线滚动导轨考虑滑块体弹性变形时的刚度计算

本文应用赫兹（Hertz）弹性接触变形理论,以及有限元方法,分析了直线滚动导轨考虑滑块体弹性变形时的工作机理,即物理关系和几何关系,导出了承受垂直载荷时的刚度计算方法,并通过实验验证了本计算方法的有效性.     

平面弹性中反对称载荷时裂纹问题的Fourier积分变换解法

在用Fourier积分变换解决裂纹问题的著作中,都讨论对称载荷情况下的裂纹问题.本丈利用Fourier积分变换,一些特殊积分的性质和Abel积分方程的解,便可得到平面弹性中反对称载荷裂纹问题的解.