Sparse L1-norm-based linear discriminant analysis

Linear discriminant analysis (LDA) is a well-known feature extraction method, which has been widely used for many pattern recognition problems. However, the objective function of conventional LDA is based on L2-norm, which makes LDA sensitive to outliers. Besides, the basis vectors learned by conventional LDA are dense and it is often hard to explain the extracted features. In this paper, we propose a novel sparse L1-norm-based linear discriminant analysis (SLDA-L1) which not only replaces L2-norm in conventional LDA with L1-norm, but also use the elastic net to regularize the basis vectors. Then L1-norm used in SLDA-L1 is for both robust and sparse modelling simultaneously. We also propose an efficient iterative algorithm to solve SLDA-L1 which is theoretically shown to arrive at a locally maximal point. Experiment results on some image databases demonstrate the effectiveness of the proposed method.     

Promising electroplating solution for facile fabrication of Cu quantum point contacts

In this article,we report on the fabrication and transport measurements of Cu quantum point contacts prepared by a novel,electrochemically assisted mechanically controllable break junction (EC-MCBJ) method.By employing photolithography and wet-etching processes,suspended electrode pairs were patterned and fabricated successfully on Si microchips.Rather than adopting an acid Cu electroplating solution,a novel alkaline electroplating solution was developed and utilized to establish Cu nanocontacts between electrode pairs.Typically,the widths of the as-fabricated Cu nanocontacts were found to be smaller than 18 nm.A large number of Cu quantum point contacts were then produced and characterized by a home-built MCBJ setup.In addition to the conventional histogram,where peaks tend to decrease in amplitude with increasing conductance,an anomalous type of conductance histogram,exhibiting different peak amplitudes,was observed.Through statistical analysis of the maximum allowable bending of the Si microchips,and theoretical calculations,we demonstrated that our alkaline Cu electroplating solution affords Cu nanocontacts that are compatible with subsequent MCBJ operations,which is essential for the fabrication of Cu quantum point contacts.As sophisticated e-beam lithography is not required,the EC-MCBJ method is fast,simple,and cost-effective.Moreover,it is likely to be suitable for the fabrication and characterization of quantum point contacts of various metals from their respective electroplating solutions.     

航空机匣工件车削加工变形预测及切削参数优化研究

以航空机匣工件某车削工序为对象,结合切削过程力学仿真及有限元分析方法,实现了其车削加工过程中加工变形量的预测。然后,以背吃刀量为设计变量,以加工效率为目标函数、以加工变形量为约束条件进行了车削加工切削参数优化研究,采用整数规划优化方法,通过改变走刀次数及合理分配每次走刀的背吃刀量,减少了加工变形量、提高了切削效率,实现了航空机匣工件的高效切削。     

预应力混凝土连续梁桥挂篮法施工质量控制

预应力混凝土连续梁桥结构体系因其变形小、结构刚度好、伸缩缝少、行车平顺舒适、养护简单和抗震能力强等优点被广泛应用。悬臂浇筑预应力混凝土连续梁桥作为无支架施工,有利于通航河流建桥、深山峡谷建桥和城市立交建桥,且悬臂施工(挂篮施工)的受力接近于成桥后的结构受力。文章结合某大桥工程实例,着重阐述预应力混凝土连续梁桥挂篮法的施工工艺和质量控制。     

管道工程在市政道路给排水的设计和施工

随着科学技术的不断发展以及经济的持续繁荣,城市建设逐渐成为各国家以及各城市比较关注的内容,而城市的排水管道在城市建设中也是属于一项不可或缺的基础工作,是确保人类正常生活以及城市道路畅通的市政基本设施。市政道路的设计与施工在市政工程中占有非常大的比重,市政道路的给排水管理的施工工艺以及设计也对市政的道路有着一定的影响,它也影响了市政道路工作的整体质量。本文主要对市政道路的给排水管道工程的施工技术以及设计展开相关的探讨。     

基于动力子空间的信号迭代降噪方法

重构相空间是通过修正动力轨道来降噪的前提和基础。针对传统相空间重构方法在实际应用中嵌入维数和嵌入延迟难于准确、客观估计的问题，采用模型最小描述长度准则确定最佳的嵌入窗口，据此重构相空间并采用动力子空间法进行迭代降噪计算。数值仿真试验证明该方法在有限长非线性信号降噪处理中是有效的，特别在信噪比较低时，信噪比增益可达到10dB左右。     

电子束辐照烟气净化技术的研究和应用设想

简述了电子束法脱除火力发电厂烟气中的污染源技术的发展和现状,介绍了电子束烟气净化技术中的重要参数与ＳＯ２与ＮＯＸ脱除率的关系。根据预研究的结果,目前正就这一技术的实际应用进行初步的概念设计和可行性研究。     

四川盆地元坝地区上三叠统须家河组三段致密砂岩气甜点类型与分布

通过岩心观察、薄片鉴定、测井分析等方法,结合其他地球物理技术,对四川盆地元坝地区上三叠统须家河组三段致密砂岩储层特征进行了研究,结合研究区气井产能特征及主控因素分析,归纳了气藏的甜点类型和成因,并对甜点的分布进行了预测。研究结果表明：(1)元坝地区须三段砂岩类型多样,其中中粗粒钙质岩屑砂岩和细砾岩为优质储层;裂缝类型多样,以低角度剪切缝和成岩收缩缝为主。(2)研究区须三段气藏发育中粗粒钙质岩屑砂岩型和细砾岩型等两大类甜点,结合裂缝特征,可进一步细分为六小类;各类甜点的地质特征、测试方式和试采特征均存在差异。(3)甜点的形成主要受沉积、成岩和构造作用控制,中粗粒钙质岩屑砂岩和细砾岩多分布于三角洲平原和前缘亚相界线附近的分流河道;差异重结晶是砾缘缝形成的原因;构造活动产生的断层和地层挠曲控制了裂缝的分布。(4)中粗粒钙质岩屑砂岩和细砾岩均表现为低GR、低CNL、中—高Rd、中等AC值的特征,优质储层的横波阻抗和μρ（μ为剪切模量,ρ为密度）均表现为中—高值,中粗粒钙质岩屑砂岩孔隙型、细砾岩和穿砾缝叠加型甜点呈条带状广泛分布,其他4类甜点零星分布。     

Prediction of dynamic cutting force and regenerative chatter stability in inserted cutters milling

Currently, the modeling of cutting process mainly focuses on two aspects: one is the setup of the universal cutting force model that can be adapted to a broader cutting condition; the other is the setup of the exact cutting force model that can accurately reflect a true cutting process. However, there is little research on the prediction of chatter stablity in milling. Based on the generalized mathematical model of inserted cutters introduced by ENGIN, an improved geometrical, mechanical and dynamic model for the vast variety of inserted cutters widely used in engineering applications is presented, in which the average directional cutting force coefficients are obtained by means of a numerical approach, thus leading to an analytical determination of stability lobes diagram (SLD) on the axial depth of cut. A new kind of SLD on the radial depth of cut is also created to satisfy the special requirement of inserted cutter milling. The corresponding algorithms used for predicting cutting forces, vibrations, dimensional surface finish and stability lobes in inserted cutter milling under different cutting conditions are put forward. Thereafter, a dynamic simulation module of inserted cutter milling is implemented by using hybrid program of Matlab with Visual Basic. Verification tests are conducted on a vertical machine center for Aluminum alloy LC4 by using two different types of inserted cutters, and the effectiveness of the model and the algorithm is verified by the good agreement of simulation result with that of cutting tests under different cutting conditions. The proposed model can predict the cutting process accurately under a variety of cutting conditions, and a high efficient and chatter-free milling operation can be achieved by a cutting condition optimization in industry applications.     

圆角铣削颤振稳定域建模与仿真研究

为避免在圆角铣削加工中产生颤振,建立考虑再生作用的圆角铣削动力学模型,推导其平均方向力系数计算公式。鉴于圆角铣削时主轴转速通常远大于圆角处的进给角速度,两者的平均方向力系数近似相等。因此,经典直线铣削颤振稳定域解析模型适用于圆角铣削,前提是需要用最大径向啮合角代替名义径向啮合角进行仿真。根据铣刀与工件的啮合情况,将圆角铣削分为均匀切宽圆角铣削和非均匀圆角切宽铣削两类,并分别推导出其最大径向啮合角计算公式。在动力学建模基础上开发圆角铣削颤振稳定域仿真模块,仿真结果得到了切削试验的验证,为圆角铣削切削参数的选择提供了一条有效途径。