通讯机构:
[Shuo Cao] D;Department of Astronomy, Beijing Normal University, Beijing, China
关键词:
dark energy experiments;dark energy theory;quasars
摘要:
Recently, two classes of quasar samples were identified, which are promising as new cosmological probes extending to higher redshifts. The first sample uses the nonlinear relation between the ultraviolet and X-ray luminosities of quasars to derive luminosity distances, whereas the linear sizes of compact radio quasars in the second sample can serve as standardized rulers, providing angular-diameter distances. In this study, under the assumption of a flat universe, we refreshed the calibration of multiple measurements of high-redshift quasars (in the framework of a cosmological-model-independent method with the newest Hubble parameters data). Furthermore, we placed constraints on four models that characterize the cosmic equation of state (w). The obtained results show that: (1) the two quasar samples could provide promising complementary probes at much higher redshifts, whereas compact radio quasars perform better than ultraviolet and X-ray quasars at the current observational level; (2) strong degeneracy between the cosmic equation of state (w) and Hubble constant (H0) is revealed, which highlights the importance of independent determination of H0 from time-delay measurements of strongly lensed quasars; (3) together with other standard ruler probes, such as baryon acoustic oscillation distance measurements, the combined QSO+BAO measurements are consistent with the standard ΛCDM model at a constant equation of state w = −1; (4) ranking the cosmological models, the polynomial parametrization gives a rather good fit among the four cosmic-equation-of-state models, whereas the Jassal-Bagla-Padmanabhan (JBP) parametrization is substantially penalized by the Akaike Information Criterion and Bayesian Information Criterion.
作者机构:
[杨蕾; 徐震] School of Electric & Electronic Engineering, Wuhan Polytechnic University, Wuhan;430024, China;[张光普] College of Underwater Acoustic Engineering, Harbin Engineering University, Harbin;150001, China;[吴雷] Hubei Telecom Engineering Co. Ltd., Wuhan
通讯机构:
[Xu, Z.] S;School of Electric & Electronic Engineering, China
关键词:
海面;短波;地波;正交频分复用;自适应分配;简单分组比特分配算法;编号子载波;智慧海洋
摘要:
为探讨海面短波传输网络在"智慧海洋"工程传输层中的应用,建立了海面短波地波正交频分复用(orthog-onal frequency division multiplexing,OFDM)系统,并提出一种适用于该系统的改进自适应分配算法.改进算法以简单分组比特分配算法为基础,对信噪比计算公式进行改造,并使用改造后的信噪比指导每组子载波所用调制方式.在确定了每组子载波的调制方式后,对各组子载波进行编号处理,将子载波组中的子载波分为有用子载波与非有用子载波,数据信息利用有用子载波和有用子载波的组合模式进行传输.在海面短波地波OFDM系统中使用改进算法,系统性能接近复杂的经典Chow算法,且计算量较低.
摘要:
Feed-forward gene transcriptional regulatory networks, as a set of common signal motifs, are widely distributed in the biological systems. In this paper, the noise characteristics and propagation mechanism of various feed-forward gene transcriptional regulatory loops are investigated, including (i) coherent feed-forward loops with AND-gate, (ii) coherent feed-forward loops with OR-gate logic, and (iii) incoherent feed-forward loops with AND-gate logic. By introducing logarithmic gain coefficient and using linear noise approximation, the theoretical formulas of noise decomposition are derived and the theoretical results are verified by Gillespie simulation. From the theoretical and numerical results of noise decomposition algorithm, three general characteristics about noise transmission in these different kinds of feed-forward loops are observed. i) The two-step noise propagation of upstream factor is negative in the incoherent feed-forward loops with AND-gate logic, that is, upstream factor can indirectly suppress the noise of downstream factors. ii) The one-step propagation noise of upstream factor is non-monotonic in the coherent feed-forward loops with OR-gate logic. iii) When the branch of the feed-forward loop is negatively controlled, the total noise of the downstream factor monotonically increases for each of all feed-forward loops. These findings are robust to variations of model parameters. These observations reveal the universal rules of noise propagation in the feed-forward loops, and may contribute to our understanding of design principle of gene circuits.
作者机构:
[郝明明; 秦莉; 李艳华; 宁永强; 朱洪波; 刘云] State Key Laboratory of Luminescence and Application, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China;[李艳华] School of Electrical and Electronic Engineering, Wuhan Polytechpic University, Wuhan 430023, China;[郝明明; 朱洪波; ***] University of Chinese Academy of Sciences, Beijing 100049, China
通讯机构:
State Key Laboratory of Luminescence and Application, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, China
作者机构:
[苏毅; 张慧; 刘开培] School of Electrical Engineering, Wuhan University, Wuhan 430072, China;[仰彩霞] Department of Electrical and Information Engineering, Wuhan Polytechnic University, Wuhan 430023, China
通讯机构:
[Su, Y.] S;School of Electrical Engineering, Wuhan University, China
作者机构:
[徐正全] State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University, Wuhan 430079, China;[周龙] Department of Electric Information Engineering, Wuhan Polytechnic University, Wuhan 430023, China;[Zeng, Wu] State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University, Wuhan 430079, China<&wdkj&>Department of Electric Information Engineering, Wuhan Polytechnic University, Wuhan 430023, China
通讯机构:
State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University, China
作者机构:
[乐健; 王东旭; 刘开培; 郑雪] School of Electrical Engineering, Wuhan University, Wuhan 430072, Hubei Province, China;[仰彩霞] Department of Electrical and Information Engineering, Wuhan Polytechnic University, Wuhan 430023, Hubei Province, China
通讯机构:
School of Electrical Engineering, Wuhan University, China
作者机构:
[范吉军; Zhai C.-W.] School of Electric and Electronic Engineering, Wuhan Polytechnic University, Wuhan 430023, China;[余南辉] School of Mechanical Engineering, Wuhan Polytechnic University, Wuhan 430023, China
通讯机构:
[Fan, J.-J.] S;School of Electric and Electronic Engineering, Wuhan Polytechnic University, China
关键词:
电流变液;淀粉颗粒;速度测量;激光散斑
摘要:
利用激光散斑测量装置,观察悬浮在电流变液中的淀粉颗粒在外加直流电场下的运动情况,表明当激光穿过电流变液时可以形成散斑。利用激光散斑测速法(LSV)对不同外加电场强度和不同浓度的淀粉电流变液中颗粒的运动速度进行了测量,通过自编的互相关计算软件对散斑图像进行了分析,获得了淀粉颗粒沿电场方向和垂直于电场方向的运动速度。实验结果表明在同一电场作用下,淀粉颗粒运动速度随时间的变化呈现震荡递减的趋势;并且存在一个临界颗粒浓度和临界电场强度,当低于此临界值时,颗粒运动速度增加,反之则减小。 The velocities of particles in Electrorheological (ER) fluids were measured by laser speckle velocimetry. It was verified that laser speckles could be formed by illuminating laser beam on the starch ER fluids. The speckle patterns was recorded with high speed CCD camera, and the speckle patterns sequences with short time intervals was obtained by intercepting laser speckle video. Velocities parallel to the direction of electric field and that perpendicular to the direction of electric field were obtained by processing the two consecutive speckle patterns. The experimental results show that the velocities of particles decreases oscillatorily with time. Furthermore, there is a critical electric field and a critical sample concentration. When it is lower than this critical electric field (particle concentration), the mean particle velocity increases; otherwise, it decreased.