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21.
在实践教学过程中,通过加强与产业界的合作,多方位、充分地利用了产业界的资源,这对提高教师实践教学水平、培养学生工程实践能力和创新能力、优化毕业设计内容与过程起到了重要作用,迭到了提高实践教学质量的目的.  相似文献   
22.
介绍了用两相切曲面于切点处相联系的曲挠圆,推导一种利用中曲率和曲挠圆半径矢量求相对法曲率和相对短程挠率的简便方法。  相似文献   
23.
末端区域能量管理是重复使用运载器实现精确无动力水平着陆非常重要的一个飞行阶段。本文将末端区域能量管理段水平轨迹和纵向轨迹分开设计,参数化的水平轨迹设计包含3个校正圆,以实现航向、航程以及位置的精确调整;纵向轨迹采用2段二次高度-航程曲线以实现对高度和速度的控制。在此基础上,给出了水平和纵向轨迹的跟踪制导方法。仿真结果及其分析表明该轨迹设计方法可以灵活地设计末端区域能量管理段的标称轨迹,且制导方法能够实现标称轨迹的良好跟踪。  相似文献   
24.
讨论了路、堤、渠、坝边坡坡面的形成及边坡坡面等高线的作图方法 ,在建立变径圆族包络线参数方程的基础上 ,建立了锥顶沿圆柱螺旋线、水平圆弧、直线运动的常用的边坡坡面的参数方程 ,准确绘制边坡坡面的等高线、坡度线 .该数学模型为路、堤、渠、坝的边坡坡面设计提供了一种准确、方便、适用于数字化设计的数学模型 .  相似文献   
25.
We present a new rapid prototyping method designed for simple fabrication of 3D microfluidics using a maskless direct writing technique on polymer substrates. The entire process is enabled by a commercial cutter plotter with 10 μm resolution precision and high speed. A CAD design of top and bottom microstructures is directly written on a polymer substrate using a cutter plotter after setting up the suitable force. The smallest channel width of 20 μm was obtained with the minimum force and 100 μm from the maximum. Also the written depth increased linearly with force from 30 to 130 μm. Several 3D microfluidic devices are demonstrated using a maskless writing technique. The entire fabrication process from CAD layout to a final 3D device can be completed in 30 min outside the clean room facilities.  相似文献   
26.
Cutter holder is a crucial component of tunnel boring machine (TBM), whose performance evaluation and selection needs to consider many factors, which is a challenging Multiple criteria decision-making (MCDM) problem. To enhance the TBM overall construction manifestation, it is fundamental to synthetically evaluate and accurately select the most suitable cutter holder from alternatives according to the engineering requirements and geological conditions. This paper develops a hybrid fuzzy comprehensive evaluation approach for cutter holder. In this approach, the weights of criteria are determined by Fuzzy Analytic Hierarchy Process (FAHP), and the max-min linear normalization is employed to integrate the information of qualitative and quantitative indicators of alternatives. Finally, the ranking and further comparison are achieved in the form of radar chart. A case study of cutter holder selection from six alternatives is carried out to validate the proposed approach. It shows that the proposed approach is effective, reasonable, complete and easy to operate, which can be promoted to the evaluation and selection of non-standard crucial components for large mechanical engineering equipment.  相似文献   
27.
基于移动社交群,提出了一种面向群体推荐互联网内容的系统。这种面向社交群体的新精确营销模式不仅能提升营销效率,也减少了客户接触频次,提升了客户感知。  相似文献   
28.
In this paper, we explore how the combination of Information and Communication Technologies (ICT) and self‐organised study circles improves rural communities' ability to enhance their economic opportunities. We present the case study of an adult study‐circle project in the Kwale County of Kenya with the objective of providing rural communities with viable and sustainable livelihoods. Study circles can be seen as a democratic and emancipatory method for learning, where community groups regularly meet for participatory discussions to educate themselves on a variety of topics of their own interest. The main goal of the study‐circle members was to increase economic opportunities using ICT and, more specifically, to start micro‐businesses, improve production efficacy and methods, and obtain employment. Using the capability approach and affordances as theoretical lenses, our analysis of the explorative case study shows that the outcomes of the study circle were dependent on various conversion factors and facilitating conditions, such as resources, skills, socio‐cultural norms, and infrastructure. The main contributions from our work are represented by the five practical lessons learned from the study‐circle members' goals (starting micro‐businesses, product efficiency, and obtaining employment) from the self‐organised training approach (study circles) and from our theoretical approach (combining the capability approach and affordances).  相似文献   
29.
In this paper the nodes of the hexagonal grid are used as points. There are three types of neighbours on this grid, therefore neighbourhood sequences contain values 1, 2, 3. The grid is coordinatized by three coordinates in a symmetric way. Digital circles are classified based on digital distances using neighbourhood sequences. They can be triangle, hexagon, enneagon and dodecagon. Their corners and side-lengths are computed, such as their perimeters and areas. The radius of a digital disk is usually not well-defined, i.e., the same disk can have various radii according to the neighbourhood sequence used. Therefore the non-compactness ratio is used to measure the quality of approximation of the Euclidean circles. The best approximating neighbourhood sequence is presented. It is shown that the approximation can be improved using two neighbourhood sequences in parallel. Comparisons to other approximations are also shown.  相似文献   
30.
南水北调中线一期穿黄工程北岸竖井,采用圆形地下连续墙作为围护结构,地下连续墙的壁厚为1.5 m,内径为18 m,外径为21 m.分14幅进行施工,其中Ⅰ期槽7幅,Ⅱ期槽7幅.Ⅰ期槽长6.5 m,共分三铣成槽,中间一铣在地下连续墙轴线上的有效长度为0.9 m;Ⅱ期槽长2.8 m,一铣成槽.Ⅰ、Ⅱ期槽在地下连续墙轴线上搭接长度为0.4 m,采用套铣接头进行槽段连接.地下连续墙深度为76.6 m.采用双轮铣进行成槽施工,根据双轮铣的特点,改进了普通的地下连续墙的接头,使用套铣接头的形式,较好的解决了地下连续墙接头处夹泥夹砂的问题.在成槽过程中,采用优质泥浆进行护壁.  相似文献   
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