739 research outputs found
Topological aspect of black hole with Skyrme hair
Based on the -mapping topological current theory, we show that the
presence of the black hole leaves fractional baryon charge outside the horizon
in the Einstein-Skyrme theory. A topological current is derived from the
Einstein-Skyrme system, which corresponds to the monopoles around the black
hole. The branch process (splitting, merging and intersection) is simply
discussed during the evolution of the monopoles.Comment: 10 pages,0 figure
Valley depolarization in monolayer WSe2
We have systematically examined the circular polarization of monolayer WSe2
at different temperature, excitation energy and exciton density. The valley
depolarization in WSe2 is experimentally confirmed to be governed by the
intervalley electron-hole exchange interaction. More importantly, a
non-monotonic dependence of valley circular polarization on the excitation
power density has been observed, providing the experimental evidence for the
non-monotonic dependence of exciton intervalley scattering rate on the excited
exciton density. The physical origination of our experimental observations has
been proposed, which is in analogy to the D'yakonov-Perel' mechanism that is
operative in conventional GaAs quantum well systems. Our experimental results
are fundamentally important for well understanding the valley psudospin
relaxation in atomically thin transition metal dichalcogenides
T-spline based unifying registration procedure for free-form surface workpieces in intelligent CMM
With the development of the modern manufacturing industry, the free-form surface is widely used in various fields, and the automatic detection of a free-form surface is an important function of future intelligent three-coordinate measuring machines (CMMs). To improve the intelligence of CMMs, a new visual system is designed based on the characteristics of CMMs. A unified model of the free-form surface is proposed based on T-splines. A discretization method of the T-spline surface formula model is proposed. Under this discretization, the position and orientation of the workpiece would be recognized by point cloud registration. A high accuracy evaluation method is proposed between the measured point cloud and the T-spline surface formula. The experimental results demonstrate that the proposed method has the potential to realize the automatic detection of different free-form surfaces and improve the intelligence of CMMs
Collective magnetization dynamics in ferromagnetic (Ga,Mn)As mediated by photo-excited carriers
We present a study of photo-excited magnetization dynamics in ferromagnetic
(Ga,Mn)As films observed by time-resolved magneto-optical measurements. The
magnetization precession triggered by linearly polarized optical pulses in the
absence of an external field shows a strong dependence on photon frequency when
the photo-excitation energy approaches the band-edge of (Ga,Mn)As. This can be
understood in terms of magnetic anisotropy modulation by both laser heating of
the sample and by hole-induced non-thermal paths. Our findings provide a means
for identifying the transition of laser-triggered magnetization dynamics from
thermal to non-thermal mechanisms, a result that is of importance for ultrafast
optical spin manipulation in ferromagnetic materials via non-thermal paths.Comment: 11 pages, 9 figure
Application Research of Combined Forecasting Based on Induced Ordered Weighted Averaging Operator
Aiming at the shortcomings of traditional weighted arithmetic combination forecasting model, using the induced ordered weighted averaging operator, according to the fitting accuracy of each single forecasting method at each time point of the sample interval to endue weighted, and with the error sum of squares as criterion, we establish a new combination forecasting model, which effectively improves the precision of combination forecasting. And the resident consumption levels were predicted using the model analysis
Proton electrolyte membranes with hybrid matrix structures for assembling fuel cells
Ph.DDOCTOR OF PHILOSOPH
Distribution Planning Considering Warehousing Decisions
Modern supply chains heavily depend on warehouses for rapidly fulfilling customer demands through retail, web-based, and catalogue channels. The traditional approach that considers warehouses as cost-centers has affected the profitability of numerous supply chains. A lack of synchronization between procurement and allocation decisions causes warehouses to scramble for resources during peak times and be faced with under-utilized resources during drought times. Warehouses, however, have emerged as service-centers and it is imperative that warehousing decisions be an integral part of supply chain decisions. In this paper we propose a mixed-integer programming model to integrate warehousing decisions with those of inventory and transportation to minimize long-run distribution cost. Preliminary experiments suggest a sizeable reduction in the level and variance in the warehouse workforce requirements. A cost savings ranging between 2-6% is also realized
Waste walnut shell valorization to iron loaded biochar and its application to arsenic removal
Iron loaded biochar (ILB) was prepared from waste walnut shell by microwave pyrolysis and its application for arsenic removal was attempted. The ILB was characterized using X-ray diffraction, scanning electron microscopy and BET Surface area analyzer. The adsorption isotherm of As (V) in ILB covering a temperature range of 25 to 45 °C, as well as the kinetics of adsorption at 25 °C were experimentally generated. The adsorption isotherms were modeled using Langmuir and Freundlich isotherm models, while the kinetics of adsorption was modeled using the pseudo-first-order, pseudo-second-order kinetic models, and intra particle diffusion model. The ILB had a surface area of 418 m2 /g with iron present in the form of hematite (Fe2O3) and magnetite (Fe3O4). The arsenic adsorption isotherm matches well with Langmuir isotherm model with a monolayer adsorption capacity of 1.91 mg/g at 25 °C. The adsorption capacity of As (V) well compares with other porous adsorbents widely reported in literature, supporting its application as a cost effective adsorbent
Measuring information integration model for CAD/CMM
A CAD/CMM workpiece modeling system based on IGES file is proposed. The modeling system is implemented by using a method of labelling the tolerance items of 3D workpiece. The concept-feature face is used in the method. Firstly the CAD data of workpiece are extracted and recognized automatically. Then a workpiece model is generated, which is the integration of pure 3D geometry form with its corresponding inspection items. The principle of workpiece modeling is also presented. At last, the experiment results are shown and correctness of the model is certified
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