对书写工具的选择与预防近视的认识和建议

从字迹是视觉信号这个角度来说,中小学生写字时最好使用较软质的铅笔或用钢笔。如果说低头歪头写字达不到书写＂三个一＂的要求,是孩子们＂喜欢低头歪头＂,那么众多家庭从孩子小的时候就手把手地教孩子怎样握笔写字、上学后老师又是那么耐心地教学生如何正确执笔书写,反而还有如此多的学生还是很难达到书写＂三个一＂的要求呢？     

中医药科研工作者信息检索的主要方法

根据上海中医药大学教学、科研人员在中医药文献信息利用过程中经常出现的问题,提出了中医药教学、科研人员应从字词检索、古籍检索、中文期刊文献检索、外文期刊文献检索等方面着手,尽快掌握中医药文献信息检索的主要方法,获取所需的文献信息。     

Resolvent and Application of Policy Control for QoS

With the rapid increase of the Internet user and widely application of Web,the current network technology is facing great challenge. More and more multimedia operations occupy plenty of bandwidth,and result in the network congestion. Therefore,people begin to use QoS to utilize the bandwidth effectively,and ensure the transport of the emergent operation data. The paper introduces the protocols and basic components of QoS,then expatiates the conception and the basic principles of policy control QoS, moreover,emphasizes the structure model of policy control QoS and how it runs. At last,it introduces the transport process of data packets under the control of policies in a policy control QoS system,and how to make the policies in the real world.     

低温工艺条件下刀具的相变与耐磨性研究

研究了低温工艺条件下高速钢刀具显微组织中回火马氏体和残留奥氏体相变过程，即从回火马氏体中析出大量弥散的碳化物，并伴随组织的超微细化和残留奥氏体的转变，提高了刀具的耐磨性，降低了被加工零件的表面粗糙度，延长了刀具的使用寿命。     

聚晶立方氮化硼刀具的性能及其选用

聚晶立方氮化硼(PCBN)刀具已在切削加工的各个方面表现出了优异的切削性能,尤其是超硬特性被使用者所熟悉。为此,介绍了PCBN刀具的物理性能、切削性能以及常见的刀具结构形式;从刀具的几何参数、切削用量、使用条件、加工实例等几方面,论述了PCBN刀具的使用特点和要求。     

并联机床——新一代数控机床

并联机床是数控机床行业的新生代,目前尚处于起步阶段,本文简要介绍了国内外发展动态,以及面临的问题。     

Monitoring forage production for farmers’ decision making

Objective management of grazing livestock production systems needs monitoring of forage production at the managerial unit level. Our objectives were to develop a system that routinely estimates forage above-ground net primary production (ANPP) at the spatial and temporal resolution required by farmers in the Pampas of Argentina, and to facilitate adoption of the system by end users as a managerial support tool. Our approach was based on the radiation use efficiency (RUE) logic, which proposes that ANPP is determined by the amount of photosynthetically active radiation absorbed by the canopy (APAR), and the efficiency with which that energy is transformed in above-ground dry matter (radiation use efficiency, RUE). APAR is the product of incoming photosynthetically active radiation (PAR) and the fraction absorbed by the canopy (fPAR). We estimated fPAR as a non-linear function of MODIS normalized difference vegetation index (NDVI). RUE was empirically estimated for the two principal forage resources of the region, yielding the following relations: ANPP = 0.6 × APAR + 12, (R² = 0.86; p < 0.001; n = 18) for the upland sown pastures, and ANPP = 0.27 × APAR + 26, (R² = 0.74; p < 0.001; n = 18) for the lowland naturalized pastures, with ANPP in g/m²/60 days and APAR in MJ/m²/60 days. The models were able to predict independent ANPP values with acceptable accuracy. Computational procedures were automated and run in a Relational Data Base Manager System that stored and managed all the information. The system is currently monitoring 212,794 ha in 83 farms and provides monthly ANPP values for the previous month and a history of the last 6 years. The data so generated show ANPP differences between the two major forage resources, considerable variability of a given month’s ANPP among years and paddocks, and contrasting among-farm differences in the efficiency of conversion of ANPP and forage supplements into beef production. The system was well accepted by end users who utilize it mainly for making near real time decisions according to last month ANPP, and explaining results of previous production cycles by incorporating ANPP as an explicative variable. However, there were differences among farmers in the degree of utilization, apparently related to the advisor’s attitude toward this new technology. Our results indicate that (1) forage production of large extensions can be monthly monitored at the paddock level by a small laboratory with capabilities in geographic information systems, and (2) advisors and farmers apply this information to their managerial decisions.     

机床误差对螺旋锥齿轮齿形的影响规

基于螺旋锥齿轮齿面分析的数学模型,采用最优化算法和一种新的计算齿形误差的方法,计算了误差齿面与理论齿面在理论齿面法线方向的齿形误差.通过引入机床调整误差和刀具参数误差,分析了各种误差对螺旋锥齿轮齿形的影响规律,以图形的方式表示了误差齿面相对于理论齿面的偏离方向以及误差值的大小,为机床的精度设计、齿形误差的修正以及指导实际加工提供了理论依据.通过实际的磨齿加工和检测对算法以及分析结果进行了验证.     

镶嵌固体润滑剂的自润滑刀具切削温度研究

在刀具前刀面月牙洼磨损区域加工装填MoS2固体润滑剂的微孔,制备了一种镶嵌固体润滑 剂的自润滑刀具（SLT〖CD*2〗1）,并与前刀面有孔但无固体润滑剂的刀具（SLT〖CD*2〗2）以 及传统刀具（SLT〖CD*2〗3）进行切削对比试验。用TH5104红外热像仪测试了3种刀具切削45 号淬火钢的切削温度变化规律。结果表明：SLT〖CD*2〗1自润滑刀具的切削温度明显降低,比 传统刀具SLT〖CD*2〗3降低15%～20%,SLT〖CD*2〗2刀具比SLT〖CD*2〗3降低5%～10%。通过切削 温度理论分析表明,由于自润滑刀具SLT〖CD*2〗1在前刀面形成润滑膜,降低了前刀面剪切应 力以及减少了刀屑接触面积,使得切削温度显著降低。     

面向智能制造的数控机床多目标优选法研究

考虑当前制造业智能化发展趋势以及数控机床在现代制造工程领域所发挥的关键作用,提出了一种集质量功能展开(QFD)、模糊线性回归和0-1目标规划优点于一体的数控机床多目标优选法。在研究智能制造对数控机床特定要求的基础上,运用QFD考察智能制造需求与数控机床性能之间的因果关系,采用质量屋将智能制造的需求有机地融入数控机床选型中。基于模糊线性回归法确定智能制造需求与数控机床性能在质量屋中的相互关联程度,运用层次分析法计算智能制造需求指标的权重系数,并采用0-1目标规划法在众多候选数控机床中做出最佳选择。以某智能制造平台搭建过程中的数控机床多目标决策问题作为应用案例,从5台候选数控机床中挑选出综合性能最好的1台。研究表明,所提出的面向智能制造的数控机床多目标优选法具有较高的工程实用性。