数控线切割机床加工精度的提高与实现

电火花线切割机床对零件的加工精度(主要指加工的形状精度和位置精度)与机床固有的结构设计精度和精度保持性也有一定的直接关系。此外,工件本身的材料特性及其热处理后材料内部的应力状态等也对零件加工精度有一定的影响。为了提高零件的加工精度在SCX-75型和DK7725-1A型数控线切割切床上,采用了多次切割工艺,为减小零件变形而在热处理前进行了预加工。实验研究结果表明:该方法可以提高零件加工精度。     

鄂尔多斯市煤田火区科学规范治理的探索与实践

通过对内蒙古自治区鄂尔多斯市煤(井)田火区的成功治理和深入探索,研究归纳出了火区治理的技术措施及工作经验,为类似资源型地区和煤炭企业治理自然发火危害提供了借鉴。     

The third-generation-mobile (3G) policy and deployment in China: Current status, challenges, and prospects

Since the inception of telecom reform in 1994, structural reform has been a main thread surrounding the course of the development of China's telecommunications industry. In structuring the 2008 reform and the 2009 3G rollout China's government adopted a relatively balanced approach in the hope of creating level-playing-field in 3G era. Nevertheless, due to the presence of substantial switching costs, substitution effects from the present technology mode, that is, 2.5G, the absence of killer applications, among other technological and institutional factors, China may not have a realistic 3G era before moving toward 4G and beyond. At the bare minimum, currently there is a lacking of either adequate technological-push or demand-pull for a full-scale 3G commercialization—there is no sign that this situation will change in the near term. Triggered by recent initiatives of market convergence between the telecommunications, Internet, and cable, a renewed circle of market, and regulatory reform is probably necessary to cast a sounder industry basis for a timing migration toward the next-generation-networks (NGNs). The timing migration toward 4G (and beyond) may provide a chance for a late-mover nation like China to leapfrog its western counterparts in leading the industry in the era of NGNs. To this end, China is confronted with a challenge in re-examining its industry policy as well as technological strategies for a sustainable development in the era of NGNs. This study offers heuristic analysis and insights on the above issues based on archival documents and interviews. While implications are suggested for China's circumstances, the Chinese experiences may also be considered by other countries and investors when it comes to 3G (and beyond) policies, regulations, deployments, and evolutions.