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- 저자 : Jiangtao He (검색결과 3 건)
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Fabrication of W-Cu Alloy via Combustion Synthesis Infiltration Under an Ultra-Gravity Field
Yuepeng Song,Qian Li,Jiangtao Li,Gang He,Yixiang Chen,김형섭 대한금속·재료학회 2014 METALS AND MATERIALS International Vol.20 No.6
Tungsten copper alloy with a tungsten concentrate of 70 vol% was prepared by self-propagating hightemperaturesynthesis in an ultra-gravity field. The phase structures and components of the W-Cu alloyfabricated via this approach were the same as those via traditional sintering methods. The temperature andstress distributions during this process were simulated using a new scheme of the finite element method. The results indicated that nonequilibrium crystallization conditions can be created for combustion synthesisinfiltration in an ultra-gravity field by the rapid infiltration of the liquid copper product into the tungstencompact at high temperature and low viscosity. The cooling rate can be above 100,000 K/s and high stresses intungsten (~5 GPa) and copper (~2.6 GPa) were developed, which passivates the tungsten particle surface,resulting in easy sintering and densifying the W-Cu alloy. The reliability of the simulation was verified throughtemperature measurement and investigation of the microstructure. The W-Cu composite-formation mechanismwas also analyzed and discussed with the simulation results.
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Monitoring the Deterioration of Masonry Relics at a UNESCO World Heritage Site
Yang Wu,Qiang Li,Hanbing Tong,Zhang He,Jiangtao Qu,Bingjian Zhang 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.8
Since 2015, six typical masonry cultural relics around the China’s UNESCO World Heritage Site - the West Lake Cultural Landscape of Hangzhou have been systematically monitored from three aspects: deterioration patterns, physical and mechanical properties, and the changes of the micro-environment, using non-destructive testing equipment like optical microscope, ultrasonic pulse wave, Schmidt hammer, surface roughness tester, thermo-hygrometers, rain gauges, air quality monitors and so on. High-throughput sequencing technology had also been used to study distribution and diversity of microorganisms on the surface of masonry. Results show that the deterioration of relics can be reflected by their physical and mechanical properties, comprehensive evaluation of the heritage’s health state can be made through long-term continuous monitoring. It also found that different deterioration pattern will occur with different types of materials or in different preservation conditions, marble artifacts which completely exposed outdoors tends to significant degradation in just five years due to temperature fluctuations and acid rain. Besides, Microorganisms’ growth and propagation correlate positively with environmental conditions. As a case study, this paper described in detail the whole process of monitoring the deterioration of masonry relics at a UNESCO World Heritage sites, which may provide some references for researchers in similar fields.
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Jia Zhang,Jun Wu,Zehao Chen,Ze Chen,Jipeng Gan,Jiangtao He,Bangyu Wang 한국인터넷정보학회 2022 KSII Transactions on Internet and Information Syst Vol.16 No.4
In order to meet the rapid development of the unmanned aerial vehicle (UAV) communication needs, cooperative spectrum sensing (CSS) helps to identify unused spectrum for the primary users (PU). However, multi-UAV mode (MUM) requires the large communication resource in a cognitive UAV network, resulting in a severe decline of spectrum efficiency (SE) and energy efficiency (EE) and increase of energy consumption (EC). On this account, we extend the traditional 2D spectrum space to 3D spectrum space for the UAV network scenario and enable UAVs to proceed with spectrum sensing behaviors in this paper, and propose a novel multi-slot mode (MSM), in which the sensing slot is divided into multiple mini-slots within a UAV. Then, the CSS process is developed into a composite hypothesis testing problem. Furthermore, to improve SE and EE and reduce EC, we use the sequential detection to make a global decision about the PU channel status. Based on this, we also consider a truncation scenario of the sequential detection under the sensing delay constraint, and further derive a closed-form performance expression, in terms of the CSS performance and cooperative efficiency. At last, the simulation results verify that the performance and cooperative efficiency of MSM outperforms that of the traditional MUM in a low EC.
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