236 research outputs found
Unbalanced development characteristics and driving mechanisms of regional urban spatial form: a case study of Jiangsu Province, China
Unbalanced regional development is widespread, and the imbalance of regional development in developing countries with rapid urbanization is increasingly apparent. This threatens the sustainable development of the region. Promoting the coordinated development of the region has become a hot spot of scientific research and a major practical need. Taking 99 counties of Jiangsu Province China, a typical coastal plain region, as the basic research unit, this paper explores the unbalanced development characteristics of the regional urban spatial form using three indicators: urban spatial expansion size, development intensity, and distribution aggregation degree. Then, their driving mechanisms were evaluated using spatial autocorrelation analysis, Pearson correlation analysis, linear regression, and geographically weighted regression. Our results found that the areas with larger urban spatial expansion size and development intensity were mainly concentrated in southern Jiangsu, where there was a positive spatial correlation between them. We found no agglomeration phenomenon in urban spatial distribution aggregation degree. From the perspective of driving factors: economics was the main driving factor of urban spatial expansion size; urbanization level and urbanization quality were the main driving factors of urban spatial development intensity. Natural landform and urbanization level are the main driving factors of urban spatial distribution aggregation degree. Finally, we discussed the optimization strategy of regional coordinated development. The quality of urbanization development and regional integration should be promoted in Southern Jiangsu. The level of urbanization development should be improved relying on rapid transportation to develop along the axis in central Jiangsu. The economic size should be increased, focusing on the expansion of the urban agglomeration in northern Jiangsu. This study will enrich the perspective of research on the characteristics and mechanisms of regional urban spatial imbalance, and helps to optimize and regulate the imbalance of regional urban development from multiple perspectives
Number Fluctuation and the Fundamental Theorem of Arithmetic
We consider N bosons occupying a discrete set of single-particle quantum
states in an isolated trap. Usually, for a given excitation energy, there are
many combinations of exciting different number of particles from the ground
state, resulting in a fluctuation of the ground state population. As a counter
example, we take the quantum spectrum to be logarithms of the prime number
sequence, and using the fundamental theorem of arithmetic, find that the ground
state fluctuation vanishes exactly for all excitations. The use of the standard
canonical or grand canonical ensembles, on the other hand, gives substantial
number fluctuation for the ground state. This difference between the
microcanonical and canonical results cannot be accounted for within the
framework of equilibrium statistical mechanics.Comment: 4 pages, 4 figures. To be submitted to Phys. Rev. Let
Optical and Transport Studies of Single Molecule Tunnel junctions based on Self-Assembled Monolayers
We have fabricated a variety of novel molecular tunnel junctions based on
self-assembled-monolayers (SAM) of two-component solid-state mixtures of
molecular wires (1,4 methane benzene-dithiol; Me-BDT with two thiol anchoring
groups), and molecular insulator spacers (1-pentanethiol; PT with one thiol
anchoring group) at different concentration ratios, r of wires/spacers, which
were sandwiched between two metallic electrodes such as gold and cobalt. FTIR
spectroscopy and surface titration were used, respectively to verify the
formation of covalent bonds with the electrodes, and obtain the number of
active molecular wires in the device. The electrical transport properties of
the SAM devices were studied as a function of (i) r-value, (ii) temperatures,
and (iii) different electrodes, via the conductance and differential
conductance spectra. The measurements were used to analyze the Me-BDT density
of states near the electrode Fermi level, and the properties of the interface
barriers. We measured the Me-BDT single molecule resistance at low bias and
gold electrodes to be 6x10^9 Ohm. We also determine the energy difference, D
between the Me-BDT HOMO level and the gold Fermi level to be about 1.8 eV. In
addition we also found that the temperature dependence of the SAM devices with
r < 10^-4 is much weaker than that of the pure PT device (or r = 0), showing a
small interface barrier.Comment: 32 pages 10 fugure
Single-photon Transistors Based on the Interaction of an Emitter and Surface Plasmons
A symmetrical approach is suggested (Chang DE et al. Nat Phys 3:807, 2007) to realize a single-photon transistor, where the presence (or absence) of a single incident photon in a ‘gate’ field is sufficient to allow (prevent) the propagation of a subsequent ‘signal’ photon along the nanowire, on condition that the ‘gate’ field is symmetrically incident from both sides of an emitter simultaneously. We present a scheme for single-photon transistors based on the strong emitter-surface-plasmon interaction. In this scheme, coherent absorption of an incoming ‘gate’ photon incident along a nanotip by an emitter located near the tip of the nanotip results in a state flip in the emitter, which controls the subsequent propagation of a ‘signal’ photon in a nanowire perpendicular to the axis of the nanotip
On the Degradation of Retained Austenite in Transformation Induced Plasticity Steel
© 2020, The Minerals, Metals & Materials Society and ASM International. A transformation-induced plasticity steel was thermomechanically processed and then transformed to bainite at an isothermal transformation temperature of 723 K for 1800 seconds, which exceeds the time required for completion of the bainite transformation. The formation of lenticular-shaped carbides with a triclinic lattice and internal substructure was found after thermomechanical processing. After 16 years of storage at room temperature, the decomposition of retained austenite into pearlite was observed for the first time at this temperature
Nuclear transparency from quasielastic A(e,e'p) reactions uo to Q^2=8.1 (GeV/c)^2
The quasielastic (e,ep) reaction was studied on targets of
deuterium, carbon, and iron up to a value of momentum transfer of 8.1
(GeV/c). A nuclear transparency was determined by comparing the data to
calculations in the Plane-Wave Impulse Approximation. The dependence of the
nuclear transparency on and the mass number was investigated in a
search for the onset of the Color Transparency phenomenon. We find no evidence
for the onset of Color Transparency within our range of . A fit to the
world's nuclear transparency data reflects the energy dependence of the free
proton-nucleon cross section.Comment: 11 pages, 6 figure
Inclusive scattering data on light nuclei as a precision tool for the extraction of G_M^n
We demonstrate that refinements in the analysis of inclusive scattering data
on light nuclei enable the extraction of, generally accurate, values of the
neutron magnetic form factor G_M^n(Q^2). In particular, a recent
parametrization of ep inclusive resonance excitation enables a reliable
calculation of the inelastic background, and as a consequence a separation of
quasi-elastic and inelastic contributions. A far larger number of data points
than previously considered is now available for analysis and enables a more
reliable extraction of G_M^n from cross section and R_T data on D and He. The
achieved accuracy appears mainly limited by the present uncertainties in the
knowledge of proton form factors and by the accuracy of the data.Comment: new version with minor changes in the text and figures, added
references and 5 figure
Performance issues in optical burst/packet switching
The final publication is available at Springer via http://dx.doi.org/10.1007/978-3-642-01524-3_8This chapter summarises the activities on optical packet switching (OPS) and optical burst switching (OBS) carried out by the COST 291 partners in the last 4 years. It consists of an introduction, five sections with contributions on five different specific topics, and a final section dedicated to the conclusions. Each section contains an introductive state-of-the-art description of the specific topic and at least one contribution on that topic. The conclusions give some points on the current situation of the OPS/OBS paradigms
Supersymmetric effects on Forward Backward asymmetries of
Leptonic and semi-leptonic rare decays of B-mesons are very clean (both
theoretically and experimentally) signatures of any new physics beyond the
Standard Model (SM). More specifically the decay \btokll has been theoretically
observed to be very sensitive to new physics as the Forward Backward (FB)
asymmetry in this decay mode vanishes in the SM. Supersymmetry, however,
predicts a non-vanishing value of this asymmetry. In this work we will study
the polarized lepton pair FB asymmetry, i.e. the FB asymmetry of the lepton
when one (or both) final state lepton(s) are polarized. We will study these
asymmetries both within the SM and for Supersymmetric corrections to the SM.Comment: 18 pages, RevTeX file including 21 eps figures; version accepted for
publication in Phys. Rev. D. Some references adde
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