摘要：This study first investigated cracks on the surface of an actual steel strip. Formulating the Anand model in ANSYS software, we then simulated the stress field in the molten pool of type 304 stainless steel during the twin-roll casting process. Parameters affecting the stress distribution in the molten pool were analyzed in detail and optimized. After twin-roll casting, a large number of transgranular and intergranular cracks resided on the surface of the thin steel strip, and followed a tortuous path. In the molten pool, stress was enhanced at the exit and at the roller contact positions. The stress at the exit decreased with increasing casting speed and pouring temperature. To ensure high quality of the fabricated strips, the casting speed and pouring temperature should be controlled above 0.7 m/s and 1520℃, respectively.

摘要：Hourglass is remarkably aroused in ring rolling simulation with reduced integration element because of violent ring vibration and small contact area of ring with forming rollers. Hourglass energy can be reduced by improving mesh density. Combined approach of artificial damping and artificial stiffness can control the hourglass. A ring with rectangular section is simulated with the weight factor of artificial stiffness resistance set to 0.2. The artificial damping hourglass control coefficient is set to 0.1, and the artificial stiffness hourglass control coefficient is set to 0.001. The ratio of hourglass energy to internal energy is reduced to 2.5 percent. Compared with axial spread width test, the effectiveness of hourglass control in ring rolling simulation is verified.

摘要：采用4点弯曲试验方法对常温养护超高性能混凝土的弯曲性能进行了试验研究,并在试验结果的基础上讨论了适于超高性能混凝土UHPC弯曲性能的评价方法.试验结果表明,UHPC没有明显的初裂点,但有明显的"挠度硬化"行为.结合不同钢纤维掺量下UHPC荷载-挠度关系曲线,分析总结了三种国外常用的弯曲性能评价方法(ASTM C1018法、JSCE SF4法和ASTM C1609法)的优点和不足.通过比较分析,ASTM C1609规定的不同挠度及其对应的弯曲强度给予了UHPC结构设计更为准确的指标,能满足UHPC结构设计的多种需求.

摘要：针对仍普遍存在的超、特高压电磁环网,结合省级电网的实例总结了电磁环网的不同发展形态和结构,认为电磁环网的主要风险在于潮流转移和控制,并提出了衡量电磁环网强弱和风险的耦合度指标。在网络结构优化和加强方面,认为强耦合的弱电磁环应优先加强上级电网,弱耦合的强电磁环应优先考虑短路控制和简化结构,多级电磁环应尽快解耦等,分析了电磁环网的典型分片方案。鉴于超、特高压电磁环网将长期存在,阐述了电磁环网单一和连锁跳闸后实用化的潮流转移控制方法,特别是针对大功率、强耦合型电磁环网提出了一种严重故障后快速切除联络元件的非常规稳定控制措施,以实现解耦控制、均衡潮流,有效提升过渡期电网的稳定水平和输电能力。在实际电网中的多个应用实例表明其效果良好。

摘要：在低压漏失油井中采用氮气泡沫冲砂作业,可以减少冲砂液漏失,有效将地层出砂携带到地面,在井底形成负压或低压循环,激励产层,这是恢复油井产能的一项有效工艺技术。根据能量方程、质量守恒方程和动量守恒方程,建立了泡沫流体在井筒内流动的温度、压力分布的数学模型以及相应的边界条件和约束条件,给出了求解思路和计算程序。开发了泡沫冲砂设计软件,模拟计算了井筒条件下泡沫流体密度以及泡沫流体压力变化,优化气/液比、地面施工压力等施工参数,同时开展了连续泡沫流体冲砂技术研究,配套连续冲砂井口装置和工艺管柱,现场试验15井次,满足最低地层压力系数在0.5情况下循环冲砂要求,实现了不停泵连续冲砂210 m作业目的,最大程度保护了油气层,使施工安全性、环保性以及施工效率明显提高。

摘要：Bone defects have serious economic and clinical impacts;however,despite improvements in bone defect management,the range of clinical outcomes remains limited.A variety of biomaterials have been used to treat complex bone ***,final bone repair outcomes may be adversely affected by poor osteogenic capacity and risk of ***,therapeutic methods are required that reduce bacterial contamination and increase the use of osteogenic ***,we report the preparation of poly(lactic acid-coglycolic acid)(PLGA)microspheres coloaded with magnesium(Mg^(2+))and gallium(Ga^(3+))ions(Mg-Ga@PLGA),which can fill irregular bone defects and show good *** in vitro testing,Mg-Ga@PLGA not only showed a synergistic effect on promoting osteogenic differentiation but also inhibited osteoclastic ***,we found that Mg-Ga@PLGA demonstrated an antibacterial *** in vivo testing,Mg Ga@PLGA exhibited strong in situ osteogenic *** conclusion,Mg-Ga@PLGA has good potential for treating bone defects at risk of infection.

摘要：以6 m3轨行式混凝土搅拌车为例,介绍了搅拌车结构组成。利用Solid Works软件建立了搅拌筒的结构模型,借助ANSYS软件对搅拌筒进行应力和变形分析,结果显示:搅拌筒的结构不能满足材料的强度和刚度要求。通过结构优化,最大应力减少了大约24%,实现了延长搅拌筒使用寿命的目的。通过目标驱动优化,获得了筒体厚度、载荷与最大等效应力最小值之间的关系。

摘要：针对红外连续变焦系统受温度影响导致变焦曲线变化、调焦补偿复杂等问题,分析了温度变化时系统各组件的相互关系,提出一种新的无热化方法,通过变倍组和补偿组的局部无热化设计,使系统仅通过变倍组和补偿组的线性平移就能对温度影响进行补偿,变焦曲线不需改变,降低了调焦机构的控制难度。采用该方法设计了12倍中波红外连续变焦系统,通过局部无热化设计,仅通过一组变焦曲线以及随温度的线性平移,实现在25~300 mm焦距范围、-45~50℃的全温度范围在30 lp/mm的MTF在0.3左右,接近衍射极限水平。具有连续变焦、高变倍比、变焦曲线无热化、分辨率高、结构简单、控制系统简化等优点。

摘要：模拟仿真分析是描述、解释突发事件形成机理,提升人类应对突发事件决策能力的重要方法。为政府及相关部门仿真分析提供可实施的模式,本文从概念设计、系统设计和应用设计三个层面,依次综述了面向突发事件的仿真模型构建过程。概念设计说明了情景从描述、构建到演化的整个过程;系统设计对比了现有的仿真分析方法与平台,描述了仿真建模与评估过程;应用设计分别论述仿真模型在三类突发事件中的应用状况。最后指出当前仿真分析过程中存在的挑战。

摘要：运用文献资料法、实地考察法、专家访谈法、逻辑分析等方法,调查了湛江东海岛人龙舞、海岛及工业园发展的现实状况,着重探讨了创建湛江东海岛人龙舞、海岛及工业三位一体的旅游园区的可行性和路径模式.研究认为:共处一地的本土民俗文化气息浓郁的人龙舞、先天优越滨海休闲圣地的东海岛、装备制造及现代企业文化引领的工业区,它们有着核心资源吸引、出行便利、市场和政府共同看好等因素,形成了创建三位一体旅游园区集聚发展的理想地带.由于资源、资本、智力和市场及政府的叠加作用,可促成观光旅游型、休闲度假型、文体创意型、装备制造型等旅游产业集聚发展模式.