Dielectric resonator magnetoelectric dipole(DRMED)arrays with enhanced isolation,reduced cross-polarization,and backward radiation are proposed for base station(BS)applications.The proposed antenna comprises an elevat...Dielectric resonator magnetoelectric dipole(DRMED)arrays with enhanced isolation,reduced cross-polarization,and backward radiation are proposed for base station(BS)applications.The proposed antenna comprises an elevated dielectric resonator antenna(DRA)on a small metal plate above a sizeable common ground plane.The DRA is designed in its T Eδ11 mode,acting like a magnetic dipole.The surface current excited by the differential probes flowing on the small ground plane is equivalent to an electric dipole.Since these two equivalent dipoles are orthogonal,they have the magnetoelectric dipole characteristics with reduced backward radiation.Meanwhile,the small ground planes can be treated as decoupling structures to provide a neutralization path to cancel the original coupling path.A linearly-polarized 4-element prototype array was verified experimentally in previous work.Here,a dual-polarized DRMED antenna is presented to construct a 2-element and 4×4 array for BS applications.To investigate its MIMO performance,sophisticated multi-cell scenario simulations are carried out.By using the proposed dualpolarized DRMED array,the cellular system capacityis improved by 118.6%compared to a conventional DRA array.This significant MIMO system improvement is mainly due to the reduced backward radiation and,therefore,reduced inter-cell interferences.Measurements align well with the simulations.展开更多
V0405 Dra is a W UMa-type binary star.Based on the TESS data,we have conducted an orbital period study and performed a light curve analysis for the system.The orbital period study reveals that the O-C curve for V0405 ...V0405 Dra is a W UMa-type binary star.Based on the TESS data,we have conducted an orbital period study and performed a light curve analysis for the system.The orbital period study reveals that the O-C curve for V0405 Dra exhibits secular decrease at an extremely high rate of d P/dt=-2.71×10^(-6)day year^(-1),along with periodic variations characterized by an amplitude of A_(3)=0.0032 day and a period of P_(3)=1.413 years.The orbital periodic change is possibly due to the light-travel time effect resulting from an additional third body in the system,for which we estimate a minimum mass of M_(3)=0.77M_(⊙).By employing the 2013 version of the Wilson-Devinney(W-D)method to synthesize a light curve,we derived photometric solutions indicating that V0405 Dra is a new deep(f=68.7%)and low-mass ratio(q=0.175)contact binary.The fast decrease in its orbital period is likely caused by mass transfer from the more massive primary star to the less massive secondary star,or due to angular momentum loss.With further mass transfer and loss of angular momentum,the binary will gradually evolve into a tighter contact configuration,eventually leading to a merger into a single star,following the evolutionary paths suggested for such deep and low mass ratio contact binaries.展开更多
DRA 基因属 BoLA 家族Ⅱ类基因，编码Ⅱ类抗原分子的α链，其第2外显子编码的抗原结合区在抗原呈递中发挥重要作用。以天祝白牦牛、大通牦牛、甘南牦牛和普通牛为研究对象，利用 PCR-SSCP 的方法对 BoLA-DRA 基因第2外显子及第2内含子...DRA 基因属 BoLA 家族Ⅱ类基因，编码Ⅱ类抗原分子的α链，其第2外显子编码的抗原结合区在抗原呈递中发挥重要作用。以天祝白牦牛、大通牦牛、甘南牦牛和普通牛为研究对象，利用 PCR-SSCP 的方法对 BoLA-DRA 基因第2外显子及第2内含子多态性进行了检测。结果表明，DRA 基因第2外显子区检测到197位 T ＞C 和116位 G ＞A 突变，对应 A、B 和 C 3种等位基因，PIC 值为0．249～0．424，为中度多态。第2内含子区发现1个 A ＞G、1个 T ＞C突变和1个 C ＞T 突变，对应 a、b、c 和 d 4种等位基因，PIC 值为0．389～0．515，为中度及高度多态。聚类分析表明，牦牛 DRA 基因第2外显子区碱基序列与普通牛以及山羊的同源性最高，系统进化情况与它们亲缘关系远近一致。展开更多
详细介绍了移动多媒体广播（China Mobile Multimedia Broadcasting,CMMB）的含义、发展历程、系统架构和核心技术,以及现代远程教育新的发展趋势——移动学习（mobile-Learning）的含义和特点。对于将移动多媒体广播技术用于移动学习...详细介绍了移动多媒体广播（China Mobile Multimedia Broadcasting,CMMB）的含义、发展历程、系统架构和核心技术,以及现代远程教育新的发展趋势——移动学习（mobile-Learning）的含义和特点。对于将移动多媒体广播技术用于移动学习的优势进行了初步的分析。展开更多
基金supported by the National Key Research and Development Program of China under Grant 2020YFA0709800.
文摘Dielectric resonator magnetoelectric dipole(DRMED)arrays with enhanced isolation,reduced cross-polarization,and backward radiation are proposed for base station(BS)applications.The proposed antenna comprises an elevated dielectric resonator antenna(DRA)on a small metal plate above a sizeable common ground plane.The DRA is designed in its T Eδ11 mode,acting like a magnetic dipole.The surface current excited by the differential probes flowing on the small ground plane is equivalent to an electric dipole.Since these two equivalent dipoles are orthogonal,they have the magnetoelectric dipole characteristics with reduced backward radiation.Meanwhile,the small ground planes can be treated as decoupling structures to provide a neutralization path to cancel the original coupling path.A linearly-polarized 4-element prototype array was verified experimentally in previous work.Here,a dual-polarized DRMED antenna is presented to construct a 2-element and 4×4 array for BS applications.To investigate its MIMO performance,sophisticated multi-cell scenario simulations are carried out.By using the proposed dualpolarized DRMED array,the cellular system capacityis improved by 118.6%compared to a conventional DRA array.This significant MIMO system improvement is mainly due to the reduced backward radiation and,therefore,reduced inter-cell interferences.Measurements align well with the simulations.
基金supported by the Joint Research Fund in Astronomy(grant No.U1631108)under a cooperative agreement between the National Natural Science Foundation of China(NSFC)the Chinese Academy of Sciences(CAS)the Chinese National Natural Science Foundation of China(NSFC,grant No.12103030)。
文摘V0405 Dra is a W UMa-type binary star.Based on the TESS data,we have conducted an orbital period study and performed a light curve analysis for the system.The orbital period study reveals that the O-C curve for V0405 Dra exhibits secular decrease at an extremely high rate of d P/dt=-2.71×10^(-6)day year^(-1),along with periodic variations characterized by an amplitude of A_(3)=0.0032 day and a period of P_(3)=1.413 years.The orbital periodic change is possibly due to the light-travel time effect resulting from an additional third body in the system,for which we estimate a minimum mass of M_(3)=0.77M_(⊙).By employing the 2013 version of the Wilson-Devinney(W-D)method to synthesize a light curve,we derived photometric solutions indicating that V0405 Dra is a new deep(f=68.7%)and low-mass ratio(q=0.175)contact binary.The fast decrease in its orbital period is likely caused by mass transfer from the more massive primary star to the less massive secondary star,or due to angular momentum loss.With further mass transfer and loss of angular momentum,the binary will gradually evolve into a tighter contact configuration,eventually leading to a merger into a single star,following the evolutionary paths suggested for such deep and low mass ratio contact binaries.
文摘DRA 基因属 BoLA 家族Ⅱ类基因，编码Ⅱ类抗原分子的α链，其第2外显子编码的抗原结合区在抗原呈递中发挥重要作用。以天祝白牦牛、大通牦牛、甘南牦牛和普通牛为研究对象，利用 PCR-SSCP 的方法对 BoLA-DRA 基因第2外显子及第2内含子多态性进行了检测。结果表明，DRA 基因第2外显子区检测到197位 T ＞C 和116位 G ＞A 突变，对应 A、B 和 C 3种等位基因，PIC 值为0．249～0．424，为中度多态。第2内含子区发现1个 A ＞G、1个 T ＞C突变和1个 C ＞T 突变，对应 a、b、c 和 d 4种等位基因，PIC 值为0．389～0．515，为中度及高度多态。聚类分析表明，牦牛 DRA 基因第2外显子区碱基序列与普通牛以及山羊的同源性最高，系统进化情况与它们亲缘关系远近一致。
