385 research outputs found
Four new earthworms of the genus Amynthas (Oligochaeta: Megascolecidae) from Mount Emei, Sichuan Province, China
No full textSun, Jing, Jiang, Jibao, Hu, Feng, Qiu, Jiangping (2016): Four new earthworms of the genus Amynthas (Oligochaeta: Megascolecidae) from Mount Emei, Sichuan Province, China. Journal of Natural History 50: 2499-2513, DOI: 10.1080/00222933.2016.1193649, URL: http://dx.doi.org/10.1080/00222933.2016.119364
Generating chaos for a class of linear switching control systems: a hybrid approach
No full textAbstract not available.Yuping Zhang, Peng Shi, Hong Zhu, Jiangping Hu, Yong Zen
Chaotification of a class of linear switching systems based on a Shilnikov criterion
No full textAvailable online 10 June 2017Abstract not availableYuping Zhang, Peng Shi, Cheng-Chew Lim, Hong Zhu, Jiangping Hu, Yong Zen
sj-docx-1-tct-10.1177_15330338241249690 - Supplemental material for A Single-Arm Multi-Center Phase II Clinical Trial of Cadonilimab (anti-PD-1/CTLA-4) in Combination with or without Conventional Second-Line Treatment for Patients with Extensive Stage Small Cell Lung Cancer
No full textSupplemental material, sj-docx-1-tct-10.1177_15330338241249690 for A Single-Arm Multi-Center Phase II Clinical Trial of Cadonilimab (anti-PD-1/CTLA-4) in Combination with or without Conventional Second-Line Treatment for Patients with Extensive Stage Small Cell Lung Cancer by Can Chen, Minjun Chen, Yuju Bai, Yajun Li, Jie Peng, Biao Yao, Jiangping Feng, Jian-Guo Zhou and Hu Ma in Technology in Cancer Research & Treatment</p
Fabrication and characterization of integrated silicon nanowire electromechanical systems
No full textThis research addresses the design and implementation of nanoelectromechanical systems (NEMS) based on silicon nanowires. As the counterpart of MEMS in the nanosale regime, NEMS have the potential to reach higher frequencies, larger quality factors, higher mass sensitivities and lower powers. Two fabrication approaches, both compatible with CMOS processing, have been introduced: bottom-up and top-down. In the bottom-up approach, silicon nanowires are synthesized using a Vapor-Liquid-Solid (VLS) process. The silicon nanowires synthesized by VLS process with large diameters tend to grow along a \u3c111\u3e orientation with a hexagonal cross section. Due to nanofabrication process variance and defects, however, the VLS silicon nanowires often show irregular hexagonal cross sections. This phenomenon leads to resonant mode splitting near the natural frequency of the nanowire observed by laser vibrometery. Due to high resistance of VLS silicon nanowire resonators, however, electrostatic measurement of resonance above the thermoelectrical noise floor is not possible. In light of such limitation, silicon nanowire resonators based on SOI wafers are prepared using the top-down technique. In the top-down approach, silicon nanowires are prepared based on silicon-on-insulator (SOI) with dual gate structure using e-beam lithography. The mechanical resonance is electrostatically excited and detected by the use of the mixing technique. Both in-plane and out-of-plane vibration modes are observed. The peak frequency of the silicon nanowire resonators can be tuned both upward and downward due to the combination of tension hardening effects and capacitive softening effects by the dual gate design. Nonlinear tuning has also been investigated on the top-down silicon nanowire resonators. Hysteresis in the resonant response has been observed by sweeping the excitation frequency up and down, which shows the onset of nonlinearity. The ability of simultaneously tuning the peak frequency both downward (softening) using the d.c voltage on the gate and upward (hardening) using the a.c. voltage on the drain has been demonstrated. To the author\u27s knowledge, the research is the first demonstration of electrostatically transduced silicon nanoresonators based on SOI technology. This technique could be a promising solution to the integration of future on-chip NEMS resonators and paves the way for future nanoelectromechanical circuits
The theory of the high temperature superconductors
No full textThe purpose of this thesis is the theoretical study of the high temperature superconductors. Among many high temperature superconducting materials, the study is focused on the cuprates and the recently discovered iron-based superconductors (oxypnictides). High temperature superconductor theory has been one of the frontiers in condensed matter physics in the two decades since its discovery. We do not focus on the mechanism of how the superconductivity arises in these materials. Rather, we pay more attention to the several characteristic features in the high temperature superconductors. Contrary to the conventional low transition temperature superconductors, the high temperature superconductors are strongly correlated electronic systems in which many types of low energy orders are present. These orders compete with the superconductivity. Furthermore, the high temperature superconductors reveal a non-trivial pairing symmetry, and to identify this symmetry is the goal of a significant number of ongoing research projects. In this thesis, first, we study the physics of the universal phenomena in cuprates from the point of view of the competing order. To this purpose, we propose a new order to understand the physics in the disordered states and at the temperature above Tc, and review the general characters of this order, emphasizing the symmetry and order wave-vectors. Second, we investigate the symmetry of the superconducting order and its relation to the magnetic properties of the iron-based superconductors
Iron based superconductors: Models and properties
No full textDiscovered in 2008, the Iron based Superconductors (FeSCs) have added yet another avenue for researchers to explore and understand the riddle of High Temperature Superconductivity. With the highest obtained T c of ∼ 56 K in bulk and ∼ 65K in thin films, FeSCs stand only second to the Cuprate Superconductors which were discovered about twenty five years ago. So far, the process of uncovering the pairing mechanism and pairing symmetry remains the central quest of most theorists trying to understand a High Temperature Superconductor(HTSC). While a symmetry protected nodal d– wave pairing has been firmly established for the Cuprates, no such consenses has been reached for the FeSCs, and a complete picture regarding the pairing mechanism is still lacking in either of the two. In this work, we begin by briefly reporting the current experimental status in FeSCs, review some of the existing and newly proposed theoretical models for FeSCs which include LDA and effective tight binding models describing the kinematics and pairing symmetry, deduce properties and consequences of these models, and finally provide a comparison with experimental data which support or refute their key features
The Mechanism for High Temperature Superconductivity
No full textThe emergence of FeSC drives the physics community to hot debate, bringing more confusion and new opportunities to the research in high temperature superconductivity. We start with the conventional theory and its hint for high temperature superconductors. The hopping and exchange interaction for the effective model are derived. From the effective exchange, an unification theory for the magnetism in FeSC is explored. Specially, the spin wave theory and its Higgs mode are studied in detail, as an interpretation of the observed gapped excitation. The latest theory to unify the high Tc problem is given and the possible candidates for new class of HTSC are predicted. We wish this work ultimately to push the theory of HTSC to a new stage. Besides, the energy saving mechanism and some other miscellaneous topics are attached as a completion of this thesis
Quantifying and tuning entanglement for quantum systems
No full textA 2D Ising model with transverse field on a triangular lattice is studied using exact diagonalization. The quantum entanglement of the system is quantified by the entanglement of formation. The ground state property of the system is studied and the quantified entanglement is shown to be closely related to the ground state wavefunction while the singularity in the entanglement as a function of the transverse field is a reasonable indicator of the quantum phase transition. In order to tune the entanglement, one can either include an impurity in the otherwise homogeneous system whose strength is tunable, or one can vary the external transverse field as a tuner. The latter kind of tuning involves complicated dynamical properties of the system. From the study of the dynamics on a comparatively smaller system, we provide ways to tune the entanglement without triggering any decoherence. The finite temperature effect is also discussed. Besides showing above physical results, the realization of the trace-minimization method in our system is provided; the scalability of such method to larger systems is argued
Magnetism in iron-based superconductors and their parent compounds
No full textIn this dissertation, I study the magnetism of iron-based superconductors and their parent compounds using local spin models. The study is focused on two major types of iron-based superconductors: the iron-pnictides and iron-chalcogenides. A 3D Heisenberg model on a layered lattice with nearest neighbor, next nearest neighbor and inter-layer exchanges (the J 1- J2- Jz model) is argued to have captured the qualitative features of the phase diagrams of the 1111-family and 122-family iron-pnictides. In an analysis, an emergent Ising degree of freedom named the nematic field is found stabilized by quantum fluctuation and plays a key role in explaining the separation of lattice distortion transition and Neel order transition. A modifiedJ1- J2 model, i.e., the J1- J2- J3 model is shown to exhibit magnetic ground state consistent with experiments on the 11-family of iron-chalcogenides. In the recently discovered 122-family of iron-chalcogenides, the J1- J2- J 3 model explains the magnetic structure in the vacancy ordered compounds A0.8Fe1.6Se2, but also suggests a magnetic origin of the vacancy ordering. Besides producing phase diagrams, the local spin models also give predictions on dynamic properties such as dynamic spin susceptibility. They are studied using spin wave theory for the magnetically ordered states. The results are compared with recent neutron experiments on various materials in iron-pnictides and iron-chalcogenides. Inhomogeneity in the spin models is also studied. It is found that a small concentration of static spin vacancies in a frustrated 2D model ( J1- J2 model) can drive the ground state from collinear antiferromagnet to anticollinear antiferromagnet through a quantum phase transition
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