This work focuses on the multicell multi-user distributed massive MIMO(DM-MIMO)systems,of which each user is equipped with single antenna and the base stations(BSs)consists of distributed antenna units. We first inves...This work focuses on the multicell multi-user distributed massive MIMO(DM-MIMO)systems,of which each user is equipped with single antenna and the base stations(BSs)consists of distributed antenna units. We first investigate the arbitrary BS antenna topology scenario. The derivation indicates that in this case the achievable uplink rate of an arbitrary user in central cell depends on both the number of BS's antennas and the users' access distance to each distributed antenna unit(DAU). As a result,the performance analysis based on the derivations is difficult. To overcome this issue and achieve clearer insight,we then consider a circularly distributed BS antenna array and obtain the asymptotic uplink rate of an arbitrary user by considering the asymptotic case where the number of antennas of BSs tends to infinity. It is achieved that the asymptotic uplink rate only depends on the distance from users' position to the center of reference cell. The presented numerical results show clearly that the distributed massive MIMO systems outperform the centralized ones. Moreover,it is also achieved that the interference from the adjacent cells imposes great impact on system performance. Besides this,in numerical analysis the averageasymptotic uplink rate of a user is presented,which is free of the users' position and only depends on the radius of circular antenna arrays. It is achieved the maximum average uplink rate would be achieved when the radius of circularly distributed antenna array goes to its optimization location.展开更多
Surface recombination represents a handicap for high-efficiency solar cells. This is especially important for nanowire array solar cells, where the surface-to-volume ratio is greatly enhanced. Here, the effect of diff...Surface recombination represents a handicap for high-efficiency solar cells. This is especially important for nanowire array solar cells, where the surface-to-volume ratio is greatly enhanced. Here, the effect of different passivation materials on the effective recombination and on the device performance is experimentally analyzed. Our solar cells are large area top-down axial n-p junction silicon nanowires fabricated by means of Near-Field Phase-Shift Lithography （NF-PSL）. We report an efficiency of 9.9% for the best cell, passivated with a SiO2/SiNx stack. The impact of the presence of a surface fixed charge density at the silicon/oxide interface is studied.展开更多
Array sensing is increasingly important in the development of microcantilever(MC) sensors, and response consistency is the foundation for MC array sensing. In the present work, we investigated the response consistency...Array sensing is increasingly important in the development of microcantilever(MC) sensors, and response consistency is the foundation for MC array sensing. In the present work, we investigated the response consistency of MC array sensing. The responses of two types of commercially available MC arrays were studied under conditions of temperature change, solution replacement and biochemical molecular interaction. For the thermal response, the deflections of both arrays were found to be proportional to temperature, and the responses of the MCs in both arrays were consistent with each other. The thermal response sensitivity for each MC during temperature increase and decrease also showed good consistency. Moreover, the MC array showed good consistency for the response induced by solution replacement. Finally, we also demonstrated that the MC array had good consistency in biochemical detection, exemplified by aflatoxin antibody-anti gen binding. The good response consistency makes this technology reliable and accurate for biochemical sensing.展开更多
基金supported by the Natural Science Foundation of China under Grant 61261015 and 61561043the 973 project 2013CB329104,the Natural Science Foundation of China under Grant 61372124,61363059,and 61302100+1 种基金the projects BK2011027,the Natural Science Foundation of Gansu Province for Distinguished Young Scholars(1308RJDA007)by the Foundation Research Funds for the University of Gansu Province:‘Massive MIMO channels modeling and estimation over millimeter wave band for 5G’
文摘This work focuses on the multicell multi-user distributed massive MIMO(DM-MIMO)systems,of which each user is equipped with single antenna and the base stations(BSs)consists of distributed antenna units. We first investigate the arbitrary BS antenna topology scenario. The derivation indicates that in this case the achievable uplink rate of an arbitrary user in central cell depends on both the number of BS's antennas and the users' access distance to each distributed antenna unit(DAU). As a result,the performance analysis based on the derivations is difficult. To overcome this issue and achieve clearer insight,we then consider a circularly distributed BS antenna array and obtain the asymptotic uplink rate of an arbitrary user by considering the asymptotic case where the number of antennas of BSs tends to infinity. It is achieved that the asymptotic uplink rate only depends on the distance from users' position to the center of reference cell. The presented numerical results show clearly that the distributed massive MIMO systems outperform the centralized ones. Moreover,it is also achieved that the interference from the adjacent cells imposes great impact on system performance. Besides this,in numerical analysis the averageasymptotic uplink rate of a user is presented,which is free of the users' position and only depends on the radius of circular antenna arrays. It is achieved the maximum average uplink rate would be achieved when the radius of circularly distributed antenna array goes to its optimization location.
文摘Surface recombination represents a handicap for high-efficiency solar cells. This is especially important for nanowire array solar cells, where the surface-to-volume ratio is greatly enhanced. Here, the effect of different passivation materials on the effective recombination and on the device performance is experimentally analyzed. Our solar cells are large area top-down axial n-p junction silicon nanowires fabricated by means of Near-Field Phase-Shift Lithography （NF-PSL）. We report an efficiency of 9.9% for the best cell, passivated with a SiO2/SiNx stack. The impact of the presence of a surface fixed charge density at the silicon/oxide interface is studied.
基金supported by the National Natural Science Foundation of China(Grant No.11502265)the Fundamental Research Funds for the Central Universities(Grant No.WK2480000002)
文摘Array sensing is increasingly important in the development of microcantilever(MC) sensors, and response consistency is the foundation for MC array sensing. In the present work, we investigated the response consistency of MC array sensing. The responses of two types of commercially available MC arrays were studied under conditions of temperature change, solution replacement and biochemical molecular interaction. For the thermal response, the deflections of both arrays were found to be proportional to temperature, and the responses of the MCs in both arrays were consistent with each other. The thermal response sensitivity for each MC during temperature increase and decrease also showed good consistency. Moreover, the MC array showed good consistency for the response induced by solution replacement. Finally, we also demonstrated that the MC array had good consistency in biochemical detection, exemplified by aflatoxin antibody-anti gen binding. The good response consistency makes this technology reliable and accurate for biochemical sensing.
