Optimally scheduling interfering and non‐interfering cranes

This article treats the problem of scheduling multiple cranes processing jobs along a line, where cranes are divided into different groups and only cranes in the same group can interfere with each other. Such crane scheduling problems occur, for example, at indented berths or in container yards where double rail‐mounted gantry cranes stack containers such that cranes of the same size can interfere with each other but small cranes can pass underneath larger ones. We propose a novel algorithm based on Benders decomposition to solve this problem to optimality. In a computational study, it is shown that this algorithm solves small and medium‐sized instances and even many large instances within a few seconds or minutes. Moreover, it improves several best known solutions from the literature with regard to the simpler problem version with only one crane group. We also look into whether investment in more complicated crane configurations with multiple crane groups is actually worthwhile.     

关于取绝对值的函数可微性的讨论

求绝对值函数的导数是高等数学的一个难点。本文证明了一个公式,能较全面地解决绝对值函数的求导问题。     

网络撕裂法在测磁仪故障诊断中的应用

针对CCY - 1G型数字测磁仪的具体电路结构及功能 ,利用网络撕裂法对其进行故障诊断 ,实现了故障诊断快速、准确的目的     

子自仿射集的Hausdorff维数

设S1,S2 ,… ,SN 是Rn 上的N个仿射压缩映射 ,若Rn 的紧子集E满足E UNi =1 Si(E) ,则称E为子自仿射集 .作者在一定条件下得到了子自仿射集E的Hausdorff维数 .     

投资消费模型中价值函数的基本性质

在有交易费的投资消费模型下,讨论了价值函数的一些基本性质,即给出了价值函数是有限连续和非减凹函数.     

一种基于DSP的雷达/电视视频图像压缩解压缩技术

在基于多媒体DSP处理器DM642并行处理平台上,提出一种雷达、电视视频图像压缩解压缩技术系统方案。采用多尺度小波分解技术和MPEG4压缩解压缩技术,分别对采样后的雷达视频、电视及红外视频数据压缩并分发到网络,由终端接收解压缩后融合实现多层多窗口综合显示。应用该方案可以实现舰载视频传感器和显控台以及武器系统的动态组合,提高装备的使用灵活性。     

输入分机核心板的改造方案

提出关于输入分机两种电路的改造方案,即绝对值和正切函数发生器电路的工程实现方法,从而解决修理中备件替换问题．经实验证明,电路具有很高的精度,且容易实现．     

弹性轨道磁悬浮控制系统模型降阶研究

在磁悬浮控制系统中,常常忽略轨道的弹性来设计控制算法。在这种控制算法作用下,当轨道刚度较小时,系统容易产生振动。为解决该问题,可以将轨道弹性加入悬浮模型,然后设计控制算法。考虑轨道弹性之后,悬浮系统的模型会比较复杂,控制算法难以在工程实现。为此,采用Hankel范数近似法对考虑轨道弹性后的模型进行降阶,并且在降阶模型的基础上设计控制算法,解决了轨道弹性引发的系统振动问题。并且,这种方法容易在工程中实现。文章最后利用仿真结果验证了降阶方法的可行性。     

Liquid phase in-situ synthesis of LiF coated boron powder composite and performance study

Among practical metal additives, boron (B) has a high volumetric heating value, making it a promising choice as a fuel additive. Although B can theoretically yield a large amount of energy upon complete combustion, its combustion is retarded by the initial presence of B oxide, which coats the surfaces of B particle. To improve the ignition and combustion properties of B powder, LiOH and NH₄F were used as precursors to synthesize uniformly LiF-coated B composites (LiF-B) in situ. The LiF-B mixture was also prepared for comparison using a physical method. X-ray diffraction (XRD), Fourier-transform infrared (FTIR), scanning electron microscope (SEM), and energy-dispersive X-ray spectroscopy (EDS) were used to characterize the morphologies and compositions of the products. The thermal and combustion properties of the samples were characterized by thermal gravity-differential thermal gravity (TG-DTG), differential scanning calorimetry (DSC) and closed bomb experiment. The XRD, FTIR, SEM and EDS results demonstrated the successful preparation of the coated LiF-B sample. The TG-DTG and closed bomb experiment results indicated that the addition of LiF decreased the ignition temperature of B powder, and increasing its reaction efficiency. DSC results show that when LiF-B was added, the released heat of underwater explosive increased by 6727.2, 7280.4 and 3109.6 J/g at heating rates of 5, 10, and 15 °C/min, respectively. Moreover, LiF-B decreased the activation energy of secondary combustion reaction of explosive system as calculated through Kissinger's method by 28.9%, which indicated an excellent catalytic effect for the thermal decomposition of underwater explosive. The results reveal that LiF can improve the combustion efficiency of B powder, thereby increasing the total energy of explosives. The mechanical sensitivity increased slightly after adding LiF-B to the underwater explosive. Compared to the underwater explosive with added B, the mechanical sensitivity of the explosive with added LiF-B was significantly lower.     

希尔伯特-黄变换在脉冲涡流信号消噪与识别中的应用

针对传统方法无法有效识别不同尺寸细小裂纹所产生的脉冲涡流信号,提出一种基于希尔伯特-黄变换的脉冲涡流信号消噪与识别算法。对脉冲涡流信号进行集成经验模态分解并通过归一化自相关函数及其方差特性分选出含有噪声的本征模态函数;对含噪声的本征模态函数进行阈值消噪并与未做处理的本征模态函数重构成无噪声信号;对无噪声信号进行希尔伯特-黄变换并计算出希尔伯特边际谱;根据希尔伯特边际谱的差异识别出不同细小尺寸的表面与下表面裂纹。实验结果表明了所提方法的有效性,经过集成经验模态分解消噪,消除了噪声对脉冲涡流信号的干扰;而基于希尔伯特-黄变换的方法则能够有效识别出不同尺寸的裂纹。