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991.
Hatice Hande Mert 《国际能源研究杂志》2020,44(8):6583-6594
A novel shape-stabilized n-hexadecane/polyHIPE composite phase change material (PCM) was designed and thermal energy storage properties were determined. Porous carbon-based frameworks were produced by polymerization of styrene-based high internal phase emulsions (HIPEs) in existence of the surface modified montmorillonite nanoclay. The morphological and mechanical properties of the obtained polyHIPEs were investigated by scanning electron microscopy analysis and the compression test, respectively. The polyHIPE composite with the best pore morphology and the highest compression modulus was determined as a framework to prepare the form stable n-hexadecane/polyHIPE composite phase change material using the one-step impregnation method. The chemical structure and morphologic property of composite PCM was investigated by FT-IR and polarized optical microscopy analysis. Thermal stability of the form-stable PCM (FSPCM) was examined by TG analysis. The n-hexadecane fraction engaged into the carbon foam skeleton was found of as 55 wt% from TG curve. differential scanning calorimetry analysis was used for determining melting temperature and latent heat storage capacity of FSPCM and these values were determined as (26.36°C) and (143.41 J/g), respectively. The results indicated that the obtained composite material (FSPCM) has a considerable potential for low temperature (18°C-30°C) thermal energy storage applications with its thermal energy storage capacity, appropriate phase change temperatures and high thermal stability. 相似文献
992.
This paper describes the design of a guidance law used for guiding a hypersonic gliding vehicle against a ground target from a near-vertical orientation with a specified final speed and a near-zero final load factor. The guidance law consists of two terms: one is Trajectory-Shaping Guidance (TSG) used for steering the vehicle to the target from the specified orientation; the other is Final-Speed-Control Scheme (FSCS) used for controlling the vehicle to perform lateral maneuver to adjust the final speed. Further, the generalized closed form solutions of TSG are obtained from a more general linearized engagement model, where the speed of the vehicle can be an arbitrary positive function of time. By analyzing these solutions, the stability domain of the guidance coefficients is obtained such that the final load factor is zero. This domain is not affected by the change rate of the speed. Thus, according to this analysis, the proposed guidance law can achieve a near zero final load factor by properly selecting the guidance coefficients in the stability domain. 相似文献
993.
为研究机载布撒器囊式抛撒系统中气囊的抛撒性能,以初始为扁平结构的薄壁金属(304不锈钢)气囊为研究对象,采用流固耦合的方法对其膨胀抛弹过程展开数值仿真分析,得到囊内的流场特性和囊壁的应力响应,计算结果与试验吻合较好.分析了入口边界条件及气囊结构对抛撒结果的影响,计算结果表明:气囊入口直径和入口边界条件是影响子弹分离速度和过载的关键因素,装药量、入口直径越大,子弹过载越大;一定装药量下,气囊入口直径不同时,子弹存在极限分离速度;气囊初始面积对子弹分离速度影响很小(仅4%),主要影响囊内的燃气压力,初始面积越大囊压越小,有利于降低囊壁的应力值.计算结果可为气囊结构的优化设计与工程实际应用提供重要参考. 相似文献
994.
Seong Yun Cho 《ETRI Journal》2015,37(3):533-540
In wireless localization, several linear closed‐form solution (LCS) methods have been investigated as a direct result of the drawbacks that plague the existing iterative methods, such as the local minimum problem and heavy computational burden. Among the known LCS methods, both the direct solution method and the difference of squared range measurements method are considered in this paper. These LCS methods do not have any of the aforementioned problems that occur in the existing iterative methods. However, each LCS method does have its own individual error property. In this paper, a hybrid LCS method is presented to reduce these errors. The hybrid LCS method integrates the two aforementioned LCS methods by using two check points that give important information on the probability of occurrence of each LCS's individual error. The results of several Monte Carlo simulations show that the proposed method has a good performance. The solutions provided by the proposed method are accurate and reliable. The solutions do not have serious errors such as those that occur in the conventional standalone LCS and iterative methods. 相似文献
995.
Present paper proposes a new technique based on double parametric form of fuzzy numbers to solve an uncertain beam equation using Adomian decomposition method subject to unit step and impulse loads. Uncertainties appear in the initial conditions are considered in terms of triangular convex normalized fuzzy sets. Using the single parametric form viz. α-cut form of fuzzy numbers, the fuzzy beam equation is converted first to an interval based fuzzy differential equation. Next this differential equation is transformed to crisp form by applying double parametric form of fuzzy numbers. Finally the same is solved by Adomian decomposition method symbolically to obtain the uncertain bounds of the dynamic response. Obtained results are depicted in term of plots to show the efficiency and powerfulness of the present analysis. 相似文献
996.
高速切削加工技术在模具和模型制造中的应用 总被引:7,自引:0,他引:7
概括了模具和模型制造业产品几何形状越来越复杂、制造精度日益提高和交货期不断缩短的发展趋势。指出高速切削加工切削速度和进给速度高 ,能够降低切削力、工件发热温升和发生切削自激振动的可能性 ,不仅直接提高切削效率 ,缩短加工时间及降低加工成本 ,而且有利于提高加工精度和表面质量 ,可以经济地应用到模具和模型制造中 ,包括加工各种钢模、电火花加工必需的铜或石墨电极、简易模具以及各种铸型和模型。分析了高速铣削模具和模型自由表面的策略方针和根据工件材料实施粗精加工的不同方案 相似文献
997.
同步带传动失效及疲劳寿命研究 总被引:2,自引:1,他引:2
通过实验及理论分析,探讨了带的张力、带及带轮的节距差、齿形等对同步带传动的失效形式及疲劳寿命的影响,并分析了同步带产生疲劳破坏的机理. 相似文献
998.
999.
冲击作用下的载荷波形对动态应力集中系数的影响 总被引:4,自引:0,他引:4
本文从理论上证明了在一定条件下阶越波入射产生的最大应力集中系数是冲击作用下种瞬态波形入射时的极限值。有限元法计算结果不仅证实了这一结论,而且展示了在一般无理论解的情况下获得极值应力集中系数的可行性。 相似文献
1000.