3,350 research outputs found
Hidden Conformal Symmetry for Vector Field on Various Black Hole Backgrounds
Hidden conformal symmetries of scalar field on various black hole backgrounds
have been investigated for years, but whether those features holds for other
fields are still open questions. Recently, with proper assumptions, Lunin
achieves to the separation of variables for Maxwell equations on Kerr
background. In this paper, with that equation, we find that hidden conformal
symmetry appears at near region under low frequency limit. We also extended
those results to vector field on Kerr-(A)dS and Kerr-NUT-(A)dS backgrounds,
then hidden conformal symmetry also appears if we focusing on the near-horizon
region at low frequency limit.Comment: 18 pages, no figure, matches the published versio
Academic Experience, Overseas Experience and Chinese Scholars’ Propensity Towards International Collaboration
Taking the Chinese inland scholars’ co-authorships in the 10 leading international academic journals in the field of technological innovation management from 1990 to 2016 as the sample, the article empirically investigates factors which influence Chinese inland scholars’ propensity towards international collaboration with Logistic regression model. The empirical results show that Chinese inland scholars who have overseas education background show higher propensity towards international collaboration. However, both the overseas academic exchange experience and academic experience have no significant impacts on the propensity towards international collaboration. Keywords: Propensity towards international collaboration; Academic experience; Overseas experienc
Testing general relativity with TianQin: the prospect of using the inspiral signals of black hole binaries
In this paper, we carry out a systematic study of the prospect of testing
general relativity with the inspiral signals of black hole binaries that could
be detected with TianQin. The study is based on the parameterized
post-Einsteinian (ppE) waveform, so that many modified gravity theories can be
covered simultaneously. We consider black hole binaries with total masses
ranging from and ppE corrections at
post-Newtonian (PN) orders ranging from PN to PN. Compared to the
current ground-based detectors, TianQin can improve the constraints on the ppE
phase parameter by orders of magnitude. For example, the improvement at
the PN and PN orders can be about and orders of magnitude
(compared to the results from GW150914), respectively. Compared to future
ground-based detectors, such as ET, TianQin is expected to be superior below
the PN order, and for corrections above the PN order, TianQin is
still competitive near the large mass end of the low mass range . Compared to the future space-based detector
LISA, TianQin can be competitive in the lower mass end as the PN order is
increased. For example, at the PN order, LISA is always superior for
sources more massive than about , while at the PN order,
TianQin becomes competitive for sources less massive than about . We also study the scientific potentials of detector networks
involving TianQin, LISA and ET, and discuss the constraints on specific
theories such as the dynamic Chern-Simons theory and the Einstein-dilaton
Gauss-Bonnet theory
Detecting the gravitational wave memory effect with TianQin
The gravitational wave memory effect is a prediction of general relativity.
The presence of memory effect in gravitational wave signals not only provides
the chance to test an important aspect of general relativity, but also
represents a potentially non-negligible contribution to the waveform for
certain gravitational wave events. In this paper, we study the prospect of
detecting the gravitational wave memory effect directly with the planned
space-based gravitational wave detector -- TianQin. We find that during its 5
years operation, for the gravitational wave signals that could be detected by
TianQin, about signals may contain displacement memory effect with
signal-to-noise ratios (SNRs) greater than 3. This suggests that the chance for
TianQin to detect the displacement memory effect directly is low but not fully
negligible. In contrast, the chance to detect the spin memory is negligible. We
also study that in which parameter space, the memory effect is expected to be
significant in waveform modeling.Comment: 14 pages, 9 figure
A PD Law Based Fuzzy Logic Control Strategy For Simultaneous Control Of Indoor Temperature And Humidity Using A Variable Speed Direct Expansion Air Conditioner
In small to medium scale buildings located in the subtropics, such as Hong Kong, direct expansion air conditioning (DX A/C) systems are widely applied. This is because, as compared to chilled water based central air conditioning systems, DX A/C systems are compact, flexible for multi-room services, energy efficient and cost less to maintain and operate. However, traditionally, a DX A/C system is equipped with a single-speed compressor and supply air fan, and employs ON / OFF control strategy to maintain indoor air temperature only, leaving the indoor moisture content (or relative humidity) uncontrolled. With the introduction of variable speed technology, the speeds of compressor and supply air fan can be varied continuously so as to realize the simultaneous control of the indoor temperature and humidity. In this paper, the development of a novel control strategy based on PD law and fuzzy logic is reported. The compressor speed was adjusted directly according to the indoor air moisture content and supply air fan speed according to the indoor air temperature, respectively, to realize the simultaneous control of indoor air temperature and humidity. Controllability tests for the novel control strategy were carried out and the test results suggested that, although two control loops for temperature and humidity were significantly coupled, the simultaneous control of indoor temperature and humidity was achieved with respect to control accuracy and sensitivity
Tris[tris(1,10-phenanthroline-κ2 N,N′)iron(II)] dodecatungstoferrate dihydrate
The title compound, [Fe(C12H8N2)3]3[FeW12O40]·2H2O, was prepared under hydrothermal conditions. The discrete Keggin-type [FeW12O40]6− heteropolyoxoanion has threefold symmetry, with the FeII atom located on the threefold rotation axis. The central FeO4 tetrahedron in the anion shares its O atoms with four W3O13 trinuclear units, each of which is made up of three edge-shared WO6 octahedral units. The FeII atom in the complex cation, viz [Fe(phen)3]2+ (phen is 1,10-phenanthroline), shows a slightly distorted octahedral geometry defined by six N atoms from three phen ligands. The polyoxoanions pack together with the cations, with the disordered water molecules located in voids; the site occupancy factor for each water O atom is 0.33
An Efficient Process for Pretreatment of Lignocelluloses in Functional Ionic Liquids
Background and Aims. The complex structure of the lignocelluloses is the main obstacle in the conversion of lignocellulosic biomass into valuable products. Ionic liquids provide the opportunities for their efficient pretreatment for biomass. Therefore, in this work, pretreatment of corn stalk was carried out in ultrasonic-assisted ionic liquid including 1-butyl-3-methylimidazolium chloride [BMIM]Cl, 1-H-3-methylimidazolium chloride [HMIM]Cl, and 1-(1-propylsulfonic)-3-imidazolium chloride [HSO3-pMIM]Cl at 70°C for 2 h. We compared the pretreatments by ionic liquid with and without the addition of deionized water. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were employed to analyze the chemical characteristics of regenerated cellulose-rich materials. Results. [HMIM]Cl and [HSO3-pMIM]Cl were effective in lignin extraction to obtain cellulose-rich materials. FTIR analysis and SEM analysis indicated the effective lignin removal and the reduced crystallinity of cellulose-rich materials. Enzymatic hydrolysis of cellulose-rich materials was performed efficiently. High yields of reducing sugar and glucose were obtained when the corn stalk was pretreated by [HMIM]Cl and [HSO3-pMIM]Cl. Conclusions. Ionic liquids provided the ideal environment for lignin extraction and enzymatic hydrolysis of corn stalk and [HMIM]Cl and [HSO3-pMIM]Cl proved the most efficient ionic liquids. This simple and environmentally acceptable method has a great potential for the preparation of bioethanol for industrial production
Is This Spontaneous Coronary Intramural Hematoma or Fibrotic Plaque? An Inconsistent Finding Between Optical Coherent Tomography and Intravascular Ultrasound
- …