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191.
192.
我是 1990年 8月毕业于上海工程技术大学到英雄金笔厂工作的 ,从事笔类设计至今已有 12个年头了。从一个只有理论知识、冲劲十足的大学生 ,逐渐成熟稳健起来 ,现在担任企业的研究所所长 ,主要负责设计工作 ,其间确有许多体验值得回顾。在刚进厂的那段时间里 ,我在成品车间里摸爬滚打 ,熟悉产品的各道生产工序 ,为今后的工作打基础。我并不象有些大学生认为进车间实习只是过过场子 ,而是决心扎扎实实地去学一些实在的东西 ,虚心向各道生产工序的老师傅请教 ,从模具开制到成品装配 ,不厌其烦 ,凡有工作都动手 ,为的是把上上下下的工艺摸透彻。… 相似文献
193.
针对改善催化裂化反应微环境研制开发的DCA - 112催化裂化抑焦剂 ,具有抑制生焦、改善产品分布、应用流程简单、加注方便等特点 ,经中石化长炼分公司 1Mt/a重油催化装置工业应用表明 ,在相近的工艺条件下 ,掺渣比提高 4 13个质量百分点 ,总液收提高 1 0 2个质量百分点。 相似文献
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Yueqi Zhong 《Computer aided design》2006,38(10):1062-1073
This paper introduces a new method of generating 2D flat patterns from a 3D triangulated surface by opening the bending configuration of each winged triangle pair. The flattening can be divided into four steps. First, a 3D triangulated surface is modeled with a mass-spring system that simulates the surface deformation during the flattening. Second, an unwrapping force field is built to drive the mass-spring system to a developable configuration through the numerical integration. Third, a velocity redistribution procedure is initiated to average velocity variances among the particles. Finally, the mass-spring system is forced to collide with a plane, and the final 2D pattern is generated after all the winged triangle pairs are spread onto the colliding plane. To retain the size and area of the original 3D surface, a strain control mechanism is introduced to keep the springs from over-elongation or over-shrinkage at each time step. 相似文献
197.
1 Introduction Owing to the effect of crosswind, initial disturbance and the deviation of engine parameters.etc in the initial aviation, variable rolling velocity aerocraft will produce attitude angle deviation (AAD) in the ideal orientations. It must control the attitude of the aerocraft, accordingly, AAD of aerocraft can be amended.Angle stabilization control system is used for the attitude control of rolling aerocraft by this paper. This control system is generally located in the control… 相似文献
198.
Sodium sulfonate‐terminated dendritic poly(ester‐amine) (SPEA) was synthesized by sulfonation of acrylic double bond‐terminated dendritic poly(ester‐amine) (APEA) with sodium hydrogen sulfite (NaHSO3) in mixture of diglycol and 2‐butanone under normal pressure. The structure of SPEA was characterized by IR, 1H‐NMR, and elemental analysis. SPEA was water‐soluble. 1.0–40.0% (mass) SPEA aqueous solutions appeared as dilatant fluid. When pH value varied from 1.5 to 12.0, the viscosity of 1–5% (mass) SPEA aqueous solutions changed very small, and the electric conductivity almost kept stable within pH 3.0–10.0. The relationship between the viscosity and the concentration of SPEA water solutions was similar to that of NaCl water solutions. The surface tension of SPEA water solutions was lower than that of polyethylene glycol 2000 water solutions with the same concentration. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
199.
If a low weight percentage of crude fine fillers can improve properties of polymer materials directly without complicated chemical treatment process involved, it will be significant for many industrial applications. Our previous study indicated that a kind of Cancun natural sand could be an effective filler material for polymer composites. In this current work, the epoxy composites reinforced by this kind of natural sand particles were prepared and thermal and mechanical properties of the composites containing up to 5 wt % of the sand particles were characterized. Results showed that the highest flexural strength appears in the epoxy composite containing 1 wt % sand particles. A damage model was used to interpret the flexural properties, which showed an acceptable agreement with the experimental results. The glass transition temperature, high temperature storage modulus, and dimensional stability of the sand/epoxy composites monotonically increased with the addition of the sand particles. The sand particle/epoxy composites also displayed a noticeable enhancement in thermal conductivity. Theoretical analysis showed that in addition to conduction, other heat transport mechanisms played roles in the improved heat transmission through the composites. As a natural porous micron-scale material, Cancun sand has the potential for applications in cost-effective composites with enhanced mechanical and thermal properties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
200.
The effect of current stressing on the reliability of 63Sn37Pb solder joints with Cu pads was investigated at temperatures
of −5 °C and 125 °C up to 600 h. The samples were stressed with 3 A current (6.0 × 102 A/cm2 in the solder joint with diameter of 800 μm and 1.7 × 104 A/cm2 in the Cu trace with cross section area of 35 × 500 μm). The temperatures of the samples and interfacial reaction within
the solder joints were examined. The microstructural change of the solder joints aged at 125 °C without current flow was also
evaluated for comparison. It was confirmed that the current flow could cause the temperature of solder joints to rise rapidly
and remarkably due to accumulation of massive Joule heat generated by the Cu trace. The solder joints stressed at 125 °C with
3 A current had an extensive growth of Cu6Sn5 and Cu3Sn intermetallic compounds (IMC) at both top and bottom solder-to-pad interfaces. It was a direct result of accelerated aging
rather than an electromigration or thermomigration effect in this experiment. The kinetic is believed to be bulk diffusion
controlled solid-state reaction, irrespective of the electron flow direction. When stressed at −5 °C with 3 A current, no
significant change in microstructure and composition of the solder joints had occurred due to a very low diffusivity of the
atoms as most Joule heat was eliminated at low temperature. The IMC evolution of the solder joints aged at 125 °C exhibited
a subparabolic growth behavior, which is presumed to be a combined mechanism of grain boundary diffusion and bulk diffusion.
This is mainly ascribed to the retardant effect against the diffusion course by the sufficiently thick IMC layer that was
initially formed during the reflow soldering. 相似文献