2,497 research outputs found
Gravitational Effects of Rotating Bodies
We study two type effects of gravitational field on mechanical gyroscopes
(i.e. rotating extended bodies). The first depends on special relativity and
equivalence principle. The second is related to the coupling (i.e. a new force)
between the spins of mechanical gyroscopes, which would violate the equivalent
principle. In order to give a theoretical prediction to the second we suggest a
spin-spin coupling model for two mechanical gyroscopes. An upper limit on the
coupling strength is then determined by using the observed perihelion
precession of the planet's orbits in solar system. We also give predictions
violating the equivalence principle for free-fall gyroscopes .Comment: LaTex, 6 page
A Schwarz lemma for weakly K\"ahler-Finsler manifolds
In this paper, we first establish several theorems about the estimation of
distance function on real and strongly convex complex Finsler manifolds and
then obtain a Schwarz lemma from a strongly convex weakly K\"ahler-Finsler
manifold into a strongly pseudoconvex complex Finsler manifold. As
applications, we prove that a holomorphic mapping from a strongly convex weakly
K\"ahler-Finsler manifold into a strongly pseudoconvex complex Finsler manifold
is necessary constant under an extra condition. In particular, we prove that a
holomorphic mapping from a complex Minkowski space into a strongly pseudoconvex
complex Finsler manifold such that its holomorphic sectional curvature is
bounded from above by a negative constant is necessary constant
Boost Integrated Push-Pull Rectifier with Power Factor Correction and Output Voltage Regulation using a New Digital Control Technique
An integrated converter is a synthesized converter based on the overall system integration, which is simplified by the system objective and can implement the system functions similar to the discrete converters. An integrated converter consists of converter sets; each converter set has a special function defined by the designer. A family of DC/DC Boost based integrated rectifiers with two active switches can be derived by the integration concept. In this paper, Boost + Push-Pull integrated converter is introduced and derived. To regulate the output voltage and shape the input current, a new simple digital control method is applied. In contrast to the conventional analog control methods, the principal idea of this new digital control algorithm is to use real-time analysis and estimate the required on time of the switches based on the value of the output voltage, input inductor current, and input voltage. The high capacitor voltage stress caused by the compatibility of the integration can be reduced by two methods. Pulse regulation control method is used to control this converter. Simulation results are presented
A New Estimative Current Mode Control Technique for DC-DC Converters Operating in Discontinuous Conduction Mode
A new digital control technique for power converters operating in discontinuous conduction mode (DCM) is introduced and applied to a boost converter. In contrast to the conventional analogue control methods, the principal idea of this new control scheme is to use real-time analysis and estimate the required on-time of the switch based on the dynamic of the system. The proposed control algorithm can easily be programmed in a digital signal processor (DSP). This novel technique is applicable to any converter operating in DCM including power factor correctors (PFC). However, this work mainly focuses on the boost topology. In this paper, the main mathematical concept of the new control algorithm is introduced, as well as the robustness investigation of the proposed method, simulation, and experimental results
Topological Crystalline Insulators with Rotation Anomaly
Based on first-principles calculations and symmetry-based indicator analysis,
we find a class of topological crystalline insulators (TCIs) with
rotation anomaly in a family of Zintl compounds, including
,
and
. The nontrivial band topology
protected by coexistence of rotation symmetry and time-reversal symmetry
leads to two surface Dirac cones at generic momenta on both top and bottom
surfaces perpendicular to the rotation axis. In addition, ()-dimensional
helical hinge states are also protected along the hinge formed by two side
surfaces parallel with the rotation axis. We develop a method based on Wilson
loop technique to prove the existence of these surface Dirac cones due to
anomaly and precisely locate them as demonstrated in studying these TCIs. The
helical hinge states are also calculated. Finally, we show that external strain
can be used to tune topological phase transitions among TCIs, strong Z
topological insulators and trivial insulators.Comment: 10 pages, 10 figure
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