Ricci flow on K\"ahler-Einstein manifolds

In our previous paper math.DG/0010008, we develop some new techniques in attacking the convergence problems for the K\"ahler Ricci flow. The one of main ideas is to find a set of new functionals on curvature tensors such that the Ricci flow is the gradient like flow of these functionals. We successfully find such functionals in case of Kaehler manifolds. On K\"ahler-Einstein manifold with positive scalar curvature, if the initial metric has positive bisectional curvature, we prove that these functionals have a uniform lower bound, via the effective use of Tian's inequality. Consequently, we prove the following theorem: Let $M$ be a K\"ahler-Einstein manifold with positive scalar curvature. If the initial metric has nonnegative bisectional curvature and positive at least at one point, then the K\"ahler Ricci flow will converge exponentially fast to a K\"ahler-Einstein metric with constant bisectional curvature. Such a result holds for K\"ahler-Einstein orbifolds.Comment: 49 pages. This is a revised version. Sections 4 and 5 are simplified and streamline

Universal Quantum Degeneracy Point for Superconducting Qubits

The quantum degeneracy point approach [D. Vion et al., Science 296, 886 (2002)] effectively protects superconducting qubits from low-frequency noise that couples with the qubits as transverse noise. However, low-frequency noise in superconducting qubits can originate from various mechanisms and can couple with the qubits either as transverse or as longitudinal noise. Here, we present a quantum circuit containing a universal quantum degeneracy point that protects an encoded qubit from arbitrary low-frequency noise. We further show that universal quantum logic gates can be performed on the encoded qubit with high gate fidelity. The proposed scheme is robust against small parameter spreads due to fabrication errors in the superconducting qubits.Comment: 7 pages, 4 figure

Effect factors of part-load performance for various Organic Rankine cycles using in engine waste heat recovery

The Organic Rankine Cycle (ORC) is regarded as one of the most promising waste heat recovery technologies for electricity generation engines. Since the engine usually operates under different working conditions, it is important to research the part-load performance of the ORC. In order to reveal the effect factors of part-load performance, four different forms of ORCs are compared in the study with dynamic math models established in SIMULINK. They are the ORC applying low temperature working fluid R245fa with a medium heat transfer cycle, the ORCs with high temperature working fluid toluene heated directly by exhaust condensing at low pressure and high pressure, and the double-stage ORC. It is regarded that the more slowly the system output power decreases, the better part-load performance it has. Based on a comparison among the four systems, the effects of evaporating pressure, condensing condition, working fluid, and system structure on part-load performance are revealed in the work. Further, it is found that the system which best matches with the heat source not only performs well under the design conditions, but also has excellent part-load performance

Constrained structure of ancient Chinese poetry facilitates speech content grouping

Ancient Chinese poetry is constituted by structured language that deviates from ordinary language usage [1, 2]; its poetic genres impose unique combinatory constraints on linguistic elements [3]. How does the constrained poetic structure facilitate speech segmentation when common linguistic [4, 5, 6, 7, 8] and statistical cues [5, 9] are unreliable to listeners in poems? We generated artificial Jueju, which arguably has the most constrained structure in ancient Chinese poetry, and presented each poem twice as an isochronous sequence of syllables to native Mandarin speakers while conducting magnetoencephalography (MEG) recording. We found that listeners deployed their prior knowledge of Jueju to build the line structure and to establish the conceptual flow of Jueju. Unprecedentedly, we found a phase precession phenomenon indicating predictive processes of speech segmentation—the neural phase advanced faster after listeners acquired knowledge of incoming speech. The statistical co-occurrence of monosyllabic words in Jueju negatively correlated with speech segmentation, which provides an alternative perspective on how statistical cues facilitate speech segmentation. Our findings suggest that constrained poetic structures serve as a temporal map for listeners to group speech contents and to predict incoming speech signals. Listeners can parse speech streams by using not only grammatical and statistical cues but also their prior knowledge of the form of language

A study of the problems associated with Dalangdian reservoir, China

There are over 2,300 lakes over 1 km2 in China (total area 80 000 km2). In addition there are approximately 87 000 reservoirs with a storage capacity of 413 billion m3. These form the main supply of drinking water as well as water for industrial and agricultural production and aquaculture. Because of a lack of understanding of the frailty of lake ecosystems and poor environmental awareness, human activities have greatly affected freshwater systems. This article focuses on the problems of one water supply reservoir, Dalangdian Reservoir, and considers options for improving its management. Dalangdian Reservoir is described and occurrence of algal genera given. The authors conclude with remarks on the future of the Dalangdian Reservoir

Network domains in social networking sites: expectations, meanings, and social capital

This paper examines why the use of social networking sites (SNSs) leads to different results in cultivating bridging and bonding social capital for different groups of people. Based on in-depth interviews of forty-five university students in Hong Kong, I find that Mainland Chinese students studying in Hong Kong actively use SNSs for seeking practical information about offline matters, and they obtain substantial enacted support from other Mainland students of the same university through SNS use. As a result, they accumulate both bridging and bonding social capital. Local Hong Kong students, however, use SNSs mainly for social information seeking and are only able to accrue limited bridging social capital through SNS use. Drawing on the theory of network domains, I argue that the different offline network structures in which students are located—namely, homogeneous and closed networks versus heterogeneous and open networks—explain this difference. Students with closed offline networks have defined expectations of online ties; they think of their online activities as practical and leading to real changes in their status among peers. Those with open networks have indefinite expectations of their online audience; thus, they interpret online activities differently, thinking of them as recreational, and they are playful in their online behaviour. These different outcomes of online activities consequently lead to diverse results in social capital accrual.postprin

Space and Personal Contacts: Cross-Group Interaction between Mainland and Local University Students in Hong Kong

Despite sharing physical space which supports contact with out-group members and institutional arrangements that encourage cross-group interaction, many university students still congregate within their own groups. To explain this phenomenon, this study examines the micro-level social processes that prevent or facilitate intergroup interaction. A qualitative study of Mainland Chinese and local university students in Hong Kong reveals that students lack opportunities for mutually engaging experiences across multiple points in time due to fragmented daily living space, defended interpersonal space, and politicized online space, which contribute to the absence of cross-group interactions. Cross-group friendships depend on external forces to remove inhibitions, which then allow emotional bonding. This study contributes to the understanding of cross-group interaction by pointing out the importance of daily routine activities and mutually engaging experiences in influencing cross-group interaction among students.postprin