431 research outputs found
Singlet-triplet transitions in highly correlated nanowire quantum dots
We consider a quantum dot embedded in a three-dimensional nanowire with
tunable aspect ratio a. A configuration interaction theory is developed to
calculate the energy spectra of the finite 1D quantum dot systems charged with
two electrons in the presence of magnetic fields B along the wire axis.
Fruitful singlet-triplet transition behaviors are revealed and explained in
terms of the competing exchange interaction, correlation interaction, and spin
Zeeman energy. In the high aspect ratio regime, the singlet-triplet transitions
are shown designable by tuning the parameters a and B. The transitions also
manifest the highly correlated nature of long nanowire quantum dots.Comment: 4 pages, 4 figure
Alloys-by-design:A low-modulus titanium alloy for additively manufactured biomedical implants
The performance of many metal biomedical implants – such as fusion cages for spines – is inherently limited by the mismatch of mechanical properties between the metal and the biological bone tissue it promotes. Here, an alloy design approach is used to isolate titanium alloy compositions for biocompatibility which exhibit a modulus of elasticity lower than the Ti-6Al-4V grade commonly employed for this application. Due to the interest in alloys for personalised medicine, additive manufacturability is also considered: compositions with low cracking susceptibility and with propensity for non-planar growth are identified. An optimal alloy composition is selected for selective laser melting, and its processability and mechanical properties tested. Additive manufacturing is used to engineer an heterogeneous microstructure with outstanding combined strength and ductility. Our results confirm the suitability of novel titanium alloys for lowering the stiffness towards that needed whilst being additively manufacturable and strong
Alloys-by-design:A low-modulus titanium alloy for additively manufactured biomedical implants
The performance of many metal biomedical implants – such as fusion cages for spines – is inherently limited by the mismatch of mechanical properties between the metal and the biological bone tissue it promotes. Here, an alloy design approach is used to isolate titanium alloy compositions for biocompatibility which exhibit a modulus of elasticity lower than the Ti-6Al-4V grade commonly employed for this application. Due to the interest in alloys for personalised medicine, additive manufacturability is also considered: compositions with low cracking susceptibility and with propensity for non-planar growth are identified. An optimal alloy composition is selected for selective laser melting, and its processability and mechanical properties tested. Additive manufacturing is used to engineer an heterogeneous microstructure with outstanding combined strength and ductility. Our results confirm the suitability of novel titanium alloys for lowering the stiffness towards that needed whilst being additively manufacturable and strong
Laser powder bed fusion of high-strength and corrosion-resistant Inconel alloy 725
The development of additive manufacturing, or three-dimensional (3D) printing, technologies has produced breakthroughs in the design and manufacturing of products by enhancing design freedom and minimising manufacturing steps. In addition, the complex, unique microstructures imparted by the additive processes offer prospects of unprecedented advances to produce high-performance metal alloys for high-temperature and corrosive environments. Here, we present the first additive manufacturing of Inconel alloy 725, an advanced nickel-base superalloy that is the widely accepted gold standard material of choice for oil and gas, chemical, and marine applications. We explore the printability of Inconel alloy 725 and identify a wide processing space to build material with a crack- and near-pore-free microstructure. The conventionally heat-treated Inconel alloy 725 has an equiaxed, near-fully recrystallised microstructure containing copious twin boundaries and nano-precipitates. It also displays promising tensile properties and corrosion resistance compared to its wrought counterpart. Our work opens the door toward additive manufacturing of Inconel alloy 725 components with optimised microstructure and topology geometry for applications in harsh environments
Detection and Monitoring of Marine Pollution Using Remote Sensing Technologies
Recently, the marine habitat has been under pollution threat, which impacts many human activities as well as human life. Increasing concerns about pollution levels in the oceans and coastal regions have led to multiple approaches for measuring and mitigating marine pollution, in order to achieve sustainable marine water quality. Satellite remote sensing, covering large and remote areas, is considered useful for detecting and monitoring marine pollution. Recent developments in sensor technologies have transformed remote sensing into an effective means of monitoring marine areas. Different remote sensing platforms and sensors have their own capabilities for mapping and monitoring water pollution of different types, characteristics, and concentrations. This chapter will discuss and elaborate the merits and limitations of these remote sensing techniques for mapping oil pollutants, suspended solid concentrations, algal blooms, and floating plastic waste in marine waters
Optimal Placement of Multiple Interconnected Gateways in Heterogeneous Wireless Sensor Networks
Data c ollec ted b y sensors of ten h av e to b e rem otely d eliv ered th rou g h
m u lti- h op w ireless path s to d ata sink s c onnec ted to applic ation ser v ers for inform
ation proc essing . T h e position of th ese sink s h as a h u g e im pac t on th e q u ality
of th e spec i c W ireless S ensor N etw or k ( W S N ) . Ind eed , it m ay c reate ar ti c ial
traf c b ottlenec k s w h ic h affec t th e energ y ef c ienc y and th e W S N lifetim e. T h is
paper c onsid ers a h eterog eneou s netw or k sc enar io w h ere w ireless sensors d eliv
er d ata to inter m ed iate g atew ay s g eared w ith a d iv erse w ireless tec h nolog y
and inter c onnec ted tog eth er and to th e sink . An optim iz ation f ram ew or k b ased
on Integ er L inear P rog ram m ing (IL P ) is d ev eloped to loc ate w ireless g atew ay s
m inim iz ing th e ov erall installation c ost and th e energ y c onsu m ption in th e W S N ,
w h ile ac c ou nting for m u lti- h op c ov erag e b etw een sensors and g atew ay s, and c onnec
tiv ity am ong w ireless g atew ay s. T h e proposed IL P for m u lations are solv ed to
optim ality for m ed iu m -siz e instanc es to analy z e th e q u ality of th e d esig ned netw
or k s, and h eu r istic alg or ith m s are also proposed to tac k le larg e-sc ale h eterog eneou
s sc enar ios
Measurements of the observed cross sections for exclusive light hadrons containing at , 3.650 and 3.6648 GeV
By analyzing the data sets of 17.3, 6.5 and 1.0 pb taken,
respectively, at , 3.650 and 3.6648 GeV with the BES-II
detector at the BEPC collider, we measure the observed cross sections for
, , ,
and at the three energy
points. Based on these cross sections we set the upper limits on the observed
cross sections and the branching fractions for decay into these
final states at 90% C.L..Comment: 7 pages, 2 figure
Partial wave analysis of J/\psi \to \gamma \phi \phi
Using events collected in the BESII detector, the
radiative decay is
studied. The invariant mass distribution exhibits a near-threshold
enhancement that peaks around 2.24 GeV/.
A partial wave analysis shows that the structure is dominated by a
state () with a mass of
GeV/ and a width of GeV/. The
product branching fraction is: .Comment: 11 pages, 4 figures. corrected proof for journa
Direct Measurements of Absolute Branching Fractions for D0 and D+ Inclusive Semimuonic Decays
By analyzing about 33 data sample collected at and around 3.773
GeV with the BES-II detector at the BEPC collider, we directly measure the
branching fractions for the neutral and charged inclusive semimuonic decays
to be and , and determine the ratio of the two branching
fractions to be
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