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Applying Beamforming to LTE Base Station for Reducing Interference Impact and Saving Frequency
Yan-Ming Cheng,Ye Wang,Il-Kyoo Lee,Zhen-Xiong Zhou 보안공학연구지원센터 2016 International Journal of Multimedia and Ubiquitous Vol.11 No.6
This paper assumes that Long Term Evolution (LTE) will be deployed in TV White Spaces (TVWSs). Beamforming is a technology that is applied to an LTE base station (BS) for reducing interference impact of LTE on DTV. A simulation method based on Monte Carlo is proposed to evaluate the interference probability in DTV receivers in the case of interference impact of LTE BS on DTV receiver. As per simulation results, the interference impact of LTE BS on DTV receiver is efficiently mitigated and the guard band remarkably reduced when LTE BS uses beamforming.
Subcarrier Intensity Modulation-Spatial Modulation for Optical Wireless Communications
Yan Cheng(정암),Seung-Hoon Hwang(황승훈) 한국통신학회 2013 韓國通信學會論文誌 Vol.38 No.12(통신이론)
In this paper, we propose a novel modulation that combines the spatial modulation (SM) with the subcarrier intensity-modulation (SIM) for optical wireless communications. The performance of SIM-SM scheme is compared to a conventional SIM by computer simulation. For the spectral efficiency (SE) of 2bits/s/Hz, the performance gain about 2dB is achieved. As the SE increases to 3bit or 4bits/s/Hz, the Eb/N0 gain becomes about 5dB. It is shown the attenuation for the SIM is more serious than the SIM-SM according to increasing the number of the subcarriers.
Rock mechanics and wellbore stability in Dongfang 1-1 Gas Field in South China Sea
Yan, Chuanliang,Deng, Jingen,Cheng, Yuanfang,Yan, Xinjiang,Yuan, Junliang,Deng, Fucheng Techno-Press 2017 Geomechanics & engineering Vol.12 No.3
Thermal effect has great influence on wellbore stability in Dongfang 1-1 (DF 1-1) gas field, a reservoir with high-temperature and high-pressure. In order to analyze the wellbore stability in DF1-1 gas field, the variation of temperature field after drilling was analyzed. In addition, the effect of temperature changing on formation strength and the thermal expansion coefficients of formation were tested. On this basis, a wellbore stability model considering thermal effect was developed and the thermal effect on fracture pressure and collapse pressure was analyzed. One of the main challenges in this gas field is the decreasing temperature of the wellbore will reduce fracture pressure substantially, resulting in the drilling fluid leakage. If the drilling fluid density was reduced, kick or blowout may happen. Therefore, the key of safe drilling in DF1-1 gas field is to predict the fracture pressure accurately.
Applicability Analysis of Microseismic Technology in Tunnel Water Inrush Monitoring
Yan-hao Chen,Shuai Cheng,Li-Ping Li,Jun-yan Yang,Hong-liang Liu,Wen-feng Tu 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.7
Water inrush disaster is one of the most serious geological disasters in tunnel construction. There are still some problems in the existing researches, such as the activity information of surrounding rock is difficult to obtain, the mechanism of water inrush disaster is unclear, the correlation between water inrush disaster and microseismic (MS) information is missing, which have caused the water inrush disaster to be passively controlled. Combining with the practical experience of tunnel engineering, the application problems of MS technology in tunnel engineering is summarized, which provides ideas for monitoring of surrounding rock activity. The formation mechanism of water inrush disaster caused by rock mass fracturing and filling medium instability has been revealed. The MS characteristics of the water inrush channel in different water inrush disasters have also been revealed. The MS response characteristics of water inrush and rockburst disasters are compared, which provides guidance for the improvement of MS monitoring technology and the analysis of effective MS information. The compression failure test of limestone under saturated and natural conditions is carried out. The results show that the presence of water weakens the ability of rock to store energy. The acoustic emission (AE) phenomenon is weaker in the process of saturated limestone failure, which increases the difficulty of AE monitoring. The number of AE events of natural limestone and saturated limestone shows a slow increase to a sudden increase in the process stress loading, which can be regarded as an important precursor of rock failure.