This experimental study is performed to investigate heat transfer performance of a multi-heat pipe cooling device in the condition of different filling ratios (40%, 60%, 80% and 100%) and different constant heat fluxe...This experimental study is performed to investigate heat transfer performance of a multi-heat pipe cooling device in the condition of different filling ratios (40%, 60%, 80% and 100%) and different constant heat fluxes (10 - 30 W). Here, pure water (distilled water) and graphene oxide (GO)/water nanofluids are employed respectively as working fluid. GO/water nanofluids were synthesized by the modified Hummers method with 0.05%, 0.10%, 0.15%, and 0.20% volume concentrations. Multi-heat pipe is fabricated from copper;the heating and cooling sections are the same size and both are connected by four circular parallel tubes. Temperature fields and thermal resistance are measured for different filling ratio, heat fluxes and volume concentrations. The results indicated that the thermal performance of heat pipe increased with increasing the concentration of GO nanoparticles in the base fluid, while the maximum heat transfer enhancement was observed at 0.20% volume concentration. GO/water nanofluids showed lower thermal resistance compared to pure water;the optimal thermal resistance was obtained at 100% filling charge ratio with 0.20% volume concentration. Studies were also demonstrated that heat transfer coefficient of the heat pipe significantly increases with increasing the input heat flux and GO nanoparticles concentration.展开更多
工业数据库通常包含大量敏感信息,为了保护数据安全,需要对不同用户或用户组设置不同的权限。然而,由于安全访问控制过程易受冗余数据、维度差异等问题的干扰,导致控制时间较长,控制效果不理想。因此,提出区块链下工业数据库访问多级安...工业数据库通常包含大量敏感信息,为了保护数据安全,需要对不同用户或用户组设置不同的权限。然而,由于安全访问控制过程易受冗余数据、维度差异等问题的干扰,导致控制时间较长,控制效果不理想。因此,提出区块链下工业数据库访问多级安全控制算法。采用线性拟合算法填补工业数据库中的缺失值,采用局部性嵌入算法(Locally Linear Embedding,LLE)降维处理工业数据,缩减数据之间的无效规模,完成数据预处理。将处理后数据存储至区块链中,实现一级控制。利用多授权属性加密方案,实现数据的细粒度访问二级控制,完成工业数据库访问的多级安全控制。实验结果表明,所提算法的计算开销小、安全性强,且控制耗时最长仅为20ms。展开更多
文摘This experimental study is performed to investigate heat transfer performance of a multi-heat pipe cooling device in the condition of different filling ratios (40%, 60%, 80% and 100%) and different constant heat fluxes (10 - 30 W). Here, pure water (distilled water) and graphene oxide (GO)/water nanofluids are employed respectively as working fluid. GO/water nanofluids were synthesized by the modified Hummers method with 0.05%, 0.10%, 0.15%, and 0.20% volume concentrations. Multi-heat pipe is fabricated from copper;the heating and cooling sections are the same size and both are connected by four circular parallel tubes. Temperature fields and thermal resistance are measured for different filling ratio, heat fluxes and volume concentrations. The results indicated that the thermal performance of heat pipe increased with increasing the concentration of GO nanoparticles in the base fluid, while the maximum heat transfer enhancement was observed at 0.20% volume concentration. GO/water nanofluids showed lower thermal resistance compared to pure water;the optimal thermal resistance was obtained at 100% filling charge ratio with 0.20% volume concentration. Studies were also demonstrated that heat transfer coefficient of the heat pipe significantly increases with increasing the input heat flux and GO nanoparticles concentration.
文摘工业数据库通常包含大量敏感信息,为了保护数据安全,需要对不同用户或用户组设置不同的权限。然而,由于安全访问控制过程易受冗余数据、维度差异等问题的干扰,导致控制时间较长,控制效果不理想。因此,提出区块链下工业数据库访问多级安全控制算法。采用线性拟合算法填补工业数据库中的缺失值,采用局部性嵌入算法(Locally Linear Embedding,LLE)降维处理工业数据,缩减数据之间的无效规模,完成数据预处理。将处理后数据存储至区块链中,实现一级控制。利用多授权属性加密方案,实现数据的细粒度访问二级控制,完成工业数据库访问的多级安全控制。实验结果表明,所提算法的计算开销小、安全性强,且控制耗时最长仅为20ms。
