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Yun Fan,Xuan Tang,Shaohan Wang,Bin Chen 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.10
Various sets of heat treatments are applied on 7075 alloy in this study in order to reduce the treatment time and yet stillachieve the similar mechanical property as the traditional T6 tempered alloy. The main parameters like solid solution treatmenttime, single aging temperature, as well as first aging duration in double aging treatment, first aging temperature andsecond aging temperature are studied and valued by hardness test. The double aging treatment at 125 °C for 60 min andthen at 165 °C for 130 min is compared with traditional single aging treatment by using advanced Cs-corrected high-angleannular dark field scanning-transmission electron microscopy (HAADF-STEM). The precipitates and dispersoids found inthose two corresponding samples are mainly Cr-containing large dispersoids, a few η particles and large quantity of fineprecipitates like η′. The similarity of precipitates in them can well support the approximate hardness level of the doubleaged and single aged samples.
Enhanced solar photocatalytic activity of Er3+:YAlO3-loaded BiPO4 composite
Yunfan zhang,Rengaraj Selvaraj,Mika Sillanpaa,김영훈,Cheuk Wai Tai 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.24 No.-
Er3+:YAlO3 loaded BiPO4 were successfully synthesized by a simple heat treatment approach in order to enhance the photocatalytic efficiency of BiPO4. Comparing with the simple substance of BiPO4, the composite system showed the better efficiency on photodegradation of Methlyene Blue (MB) solution under a simulated solar light irradiation. The relationship between loading amount and degradation rate was also investigated. It is found that the optimal loading amount of Er3+:YAlO3 is 7 wt%. The recycling test of selected sample was carried out to study the stability of the Er3+:YAlO3 loaded BiPO4 system. The composite materials were finally characterized by field-emission scanning electron microscopy (SEM), X-ray diffraction (XRD) and UV–visible diffuse reflectance spectroscopy (UV–vis DRS). Based on the findings a possible mechanism has been proposed. The existence of luminescence agent (Er3+-doped YAlO3) and the occurrence of upconversion luminescence process have been related with the enhanced photodegradation of MB over composite system.
( Hongtao Zhang ),( Zihua Yang ),( Yunfan Ye ) 한국인터넷정보학회 2016 KSII Transactions on Internet and Information Syst Vol.10 No.11
Femtocells are envisioned as a key solution to embrace the ever-increasing high data rate and thus are extensively deployed. However, the dense and random deployments of femtocell access points (FAPs) induce severe intercell inference that in turn may degrade the performance of spectral efficiency. Hence, unrestrained proliferation of FAPs may not acquire a net throughput gain. Besides, given that numerous FAPs deployed in ultra-dense networks (UDNs) lead to significant energy consumption, the amount of FAPs deployed is worthy of more considerations. Nevertheless, little existing works present an analytical result regarding the optimal FAP density for a given User Equipment (UE) density. This paper explores the realistic scenario of randomly distributed FAPs in UDN and derives the coverage probability via Stochastic Geometry. From the analytical results, coverage probability is strictly increasing as the FAP-to-UE ratio increases, yet the growing rate of coverage probability decreases as the ratio grows. Therefore, we can consider a specific FAP-to-UE ratio as the point where further increasing the ratio is not cost-effective with regards to the requirements of communication systems. To reach the optimal FAP density, we can deploy FAPs in line with peak traffic and randomly switch off FAPs to keep the optimal ratio during off-peak hours. Furthermore, considering the unbalanced nature of traffic demands in the temporal and spatial domain, dynamically and carefully choosing the locations of active FAPs would provide advantages over randomization. Besides, with a huge FAP density in UDN, we have more potential choices for the locations of active FAPs and this adds to the demand for a strategic sleeping policy.
Shear Performance of Short Channel Connectors in a Steel-UHPC Composite Deck
Qiu Zhao,Yang Du,Yunfan Peng,Chen Xu,Guanming Huang 한국강구조학회 2020 International Journal of Steel Structures Vol.20 No.1
The steel-ultra high performance concrete (UHPC) composite deck has been increasingly concerned for the fatigue damage ameliorations on the steel bridge deck and the pavement. The UHPC plate in the composite deck featured by the favorable tensile performance and small thickness helps achieving a light self-weight. However, it results to a limited short space for the shear connector to transfer the interlayer shear force. Therefore, this study proposed a kind of short steel channel-section connector for the composite deck with a thin UHPC plate, and investigated its mechanical behavior through push-out tests and parametric FEM analysis. The test results showed the deformation of the channel connector during the loading process generally included the elastic, elastic–plastic, and plastic stages, and the shear fracture of channel connector dominated in the failure mode. The shear stiff ness of the specimen with embedded reinforcement was increased by 39%, but had little infl uence on the shear capacity. On the other side, the parametric analysis told that the shear strength of connector increased signifi cantly as the connector height increased from 50 to 80 mm. Nevertheless, the connector arrangement direction was a sensitive factor to the uplift resistance of the connector.