Neutron Scattering Measurements of Spatially Anisotropic Magnetic Exchange Interactions in Semiconducting K0.85Fe1.54Se2 (TN=280 K)

We use neutron scattering to study the spin excitations associated with the stripe antiferromagnetic (AFM) order in semiconducting K$_{0.85}$Fe$_{1.54}$Se$_2$ ($T_N$=$280$ K). We show that the spin wave spectra can be accurately described by an effective Heisenberg Hamiltonian with highly anisotropic in-plane couplings at $T$= $5$ K. At high temperature ($T$= $300$ K) above $T_N$, short range magnetic correlation with anisotropic correlation lengths are observed. Our results suggest that, despite the dramatic difference in the Fermi surface topology, the in-plane anisotropic magnetic couplings are a fundamental property of the iron based compounds; this implies that their antiferromagnetism may originate from local strong correlation effects rather than weak coupling Fermi surface nesting.Comment: 5 pages, 4 figure

The prevalence of insomnia in the general population in China: A meta-analysis

This is the first meta-analysis of the pooled prevalence of insomnia in the general population of China. A systematic literature search was conducted via the following databases: PubMed, PsycINFO, EMBASE and Chinese databases (China National Knowledge Interne (CNKI), WanFang Data and SinoMed). Statistical analyses were performed using the Comprehensive Meta-Analysis program. A total of 17 studies with 115,988 participants met the inclusion criteria for the analysis. The pooled prevalence of insomnia in China was 15.0% (95% Confidence interval [CI]: 12.1%-18.5%). No significant difference was found in the prevalence between genders or across time period. The pooled prevalence of insomnia in population with a mean age of 43.7 years and older (11.6%; 95% CI: 7.5%-17.6%) was significantly lower than in those with a mean age younger than 43.7 years (20.4%; 95% CI: 14.2%-28.2%). The prevalence of insomnia was significantly affected by the type of assessment tools (Q = 14.1, P = 0.001). The general population prevalence of insomnia in China is lower than those reported in Western countries but similar to those in Asian countries. Younger Chinese adults appear to suffer from more insomnia than older adults

Synchronization in output-coupled temporal Boolean networks

This paper presents an analytical study of synchronization in an array of output-coupled temporal Boolean networks. A temporal Boolean network (TBN) is a logical dynamic system developed to model Boolean networks with regulatory delays. Both state delay and output delay are considered, and these two delays are assumed to be different. By referring to the algebraic representations of logical dynamics and using the semi-tensor product of matrices, the output-coupled TBNs are firstly converted into a discrete-time algebraic evolution system, and then the relationship between the states of coupled TBNs and the initial state sequence is obtained. Then, some necessary and sufficient conditions are derived for the synchronization of an array of TBNs with an arbitrary given initial state sequence. Two numerical examples including one epigenetic model are finally given to illustrate the obtained results

Measurement and modeling of rotational core losses of soft magnetic materials used in electrical machines: A review

In many situations, for example, in the cores of a rotating electrical machine and the T-joints of multiphase transformers, the magnetic flux varies with time in terms of both magnitude and direction, i.e., the local flux density vector rotates with varying magnitude and varying speed. Therefore, it is important that the magnetic properties of the core materials under various rotational magnetizations be properly investigated, modeled, and applied in the design and analysis of electromagnetic devices with rotational flux. Drawing from the huge amount of papers published by various researchers in the past century, this paper presents an extensive survey on the measurement and modeling of rotational core losses of soft magnetic materials used in electrical machines, particularly from the view of practical engineering application. The paper aims to provide a broad picture of the historical development of measuring techniques, measuring apparatus, and practical models of rotational core losses. © 2008 IEEE

Calibration of sensing coils of a three-dimensional magnetic property tester

For electrical machines with three-dimensional (3-D) magnetic fluxes, the magnetic properties of magnetic materials under 3-D excitations should be properly determined and applied in machine design and analysis. This paper presents the construction and calibration of the H (field strength) and B (flux density) sensing coils of a 3-D magnetic property testing system, and the correction of measurement error due to the misalignment of sensing coils with excitation fields. The 3-D tester has been used to measure the magnetic properties of soft magnetic composite (SMC), a material specially developed for application of 3-D flux electrical machines. Some 3-D results have been obtained on a cubic SMC sample. The measurement errors caused by the misalignment of sensing coils and excitation fields are corrected by a rotational transformation of coordinates. © 2006 IEEE

A Flexible Privacy-preserving Framework for Singular Value Decomposition under Internet of Things Environment

The singular value decomposition (SVD) is a widely used matrix factorization tool which underlies plenty of useful applications, e.g. recommendation system, abnormal detection and data compression. Under the environment of emerging Internet of Things (IoT), there would be an increasing demand for data analysis to better human's lives and create new economic growth points. Moreover, due to the large scope of IoT, most of the data analysis work should be done in the network edge, i.e. handled by fog computing. However, the devices which provide fog computing may not be trustable while the data privacy is often the significant concern of the IoT application users. Thus, when performing SVD for data analysis purpose, the privacy of user data should be preserved. Based on the above reasons, in this paper, we propose a privacy-preserving fog computing framework for SVD computation. The security and performance analysis shows the practicability of the proposed framework. Furthermore, since different applications may utilize the result of SVD operation in different ways, three applications with different objectives are introduced to show how the framework could flexibly achieve the purposes of different applications, which indicates the flexibility of the design.Comment: 24 pages, 4 figure

Modeling of Vector Magnetic Hysteresis of Soft Magnetic Composite Material

Thanks to the unique magnetic properties, soft magnetic composite (SMC) materials and their application in electromagnetic devices have achieved significant development. The typical application example of SMC is the electrical machine with complex structure, such as claw pole and transverse flux machines, in which the magnetic field is basically rotary. To design and analyze such a device, vector magnetic properties of the core material should be properly determined, modeled and applied. This paper presents the modeling of vector magnetic hysteresis of SMC based on a Stoner-Wohlfarh (S-W) elemental operator. A phenomenological mean-field approximation is used to consider the interaction between particles. With the presented model, the magnetization processes of SMC under both alternating and rotating fluxes are numerically simulated. The simulations have been verified by experimental measurements