Rational cubic fourfolds in Hassett divisors

We prove that every Hassett's Noether-Lefschetz divisor of special cubic fourfolds contains a union of three codimension-two subvarieties, parametrizing rational cubic fourfolds, in the moduli space of smooth cubic fourfolds.Comment: 10 page

Classification of full exceptional collections of line bundles on three blow-ups of P3\mathbb{P}^{3}

A fullness conjecture of Kuznetsov says that if a smooth projective variety $X$ admits a full exceptional collection of line bundles of length $l$, then any exceptional collection of line bundles of length $l$ is full. In this paper, we show that this conjecture holds for $X$ as the blow-up of $\mathbb{P}^{3}$ at a point, a line, or a twisted cubic curve, i.e. any exceptional collection of line bundles of length 6 on $X$ is full. Moreover, we obtain an explicit classification of full exceptional collections of line bundles on such $X$.Comment: 28 pages. To appear in Journal of the Korean Mathematical Society, A previous version with a different title appeared as [CGP17025] at https://cgp.ibs.re.kr/archive/preprints/201

The Principle of Dong Zhongshu\u27s Omen Discourse and Wang Chong\u27s Criticism of Heaven\u27s Reprimand in the Chapter “Qian Gao”

Omen discourse, the investigation of aberrant natural disasters and miraculous celestial phenomena, provided a sophisticated ideological model that could be exploited to expostulate with the sovereign for his transgressions, and to denounce the misgovernment of the imperial bureaucracy. The first of this political model is the personification of the supreme Heaven and the elevation of Heaven’s status. From the perspective of ru 儒 (Confucians) scholars, the establishment of Heaven’s supreme authority upon the human realm and the restriction of the sovereign in power guarantee the rectification of political mistakes as well as an applicable way for ru scholars to actively participate in real politics at court. The rise of omen discourse in the Western Han dynasty 西漢 (202 BCE - 8 AD) unveils the development of a significant political theory that aimed at checking the absolute power of the sovereign through Heaven’s reprimand. However, its theoretical efficacy is questioned by Wang Chong 王充 (27 - 97 AD) in the chapter “Qian Gao” 譴告 in his monograph Balanced Argument (Lun Heng 論衡). The focal point of this paper is the intrinsic logic of Wang Chong’s arguments in his radical rejection of the philosophical ideas of the Han omen discourse. By indicating the false methodology of the principle of Heaven’s reprimand, not only had Wang Chong thoroughly repudiated the Confucian model for punishing, as well as admonishing, the sovereign’s misconduct in politics, but also he undermined the active nature of Heaven as an anthropomorphic deity, eventually reverting to the initiatives of the sages and worthies in the mundane world

Optimal generator placement in a distributed network

Since the industrial and residential huge demand for electricity, as well as higher requirements for the electricity reliability and power quality. Meanwhile, the world has been in the energy crisis, the power shortage, and a large area often experienced blackouts accident. All exposed the deficiencies of ‘centralized power’. Thus, the approaches of reducing active power loss in power systems have become increasingly important. Among them, the method of the optimal location and size of distribution generators in a distributed network is one of the most prospective approaches in the future. And it can use into practice to achieve the purpose of low-carbonate, less cost and flexible power generation power systems because install DGs at the optimal location and with optimal size in distributed network can dramatically reduce active power loss in power systems. There are several models and methods have been suggested for solving the optimal DG placement problem. This paper presents models and methods applied to solve the optimal DG placement problem, and especially propose a new approach that based on an exact solution method using the enumerative method to reduce the number of the combination by request of constraints. In this case, the proposed method firstly will be applied to the simple 6 buses system, and then applied to 14 buses real size distribution network model which is based on the 126 buses real size distribution system. It can be evaluated for active power loss reduction features by DGs installation and choose optimal location and size of distribution generation in distributed network considering actual use

Spaceborne Microwave Radiometry: Calibration, Intercalibration, and Science Applications.

Spaceborne microwave radiometry is the backbone for assimilation into numerical weather forecasts and provides important information for Earth and environment science. The extensive radiometric data must go through the process of calibration and intercalibration prior to science application. This work deals with the entire process by providing systematic methods and addressing critical challenges. These methods have been applied to NASA and JAXA’s Global Precipitation Measurement (GPM) mission and many other radiometers to make important contributions and to solve long-standing issues with coastal science applications. Specifically, it addresses four important challenges: 1) improving cold calibration with scan dependent characterization; 2) reducing the uncertainty of warm calibration; 3) deriving calibration dependence across the full range of brightness temperatures with both cold and warm calibration; and 4) investigating calibration variability and dependence on geophysical parameters. One critical challenge in science applications of radiometer data is that coastal science products from radiometers have previously been largely unavailable due to land contamination. We therefore develop methods to correct for land contamination and derive coastal science products. This thesis addresses these challenges by developing their solutions and then applying them to the GPM mission and its radiometer constellation.PhDAtmospheric, Oceanic and Space SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/120728/1/johnxun_1.pd