377 research outputs found
(E)-1-Bromo-4-(2-nitroÂprop-1-enÂyl)benzene
The title compound, C9H8BrNO2, which was synthesized by the condensation of 4-bromoÂbenzaldehyde with nitroÂethane, possesses a trans configuration. The dihedral angle between the benzene ring and the mean plane of the double bond is 7.31â
(3)°. The crystal structure is stabilized by short interÂmolecular BrâŻO contacts [3.168â
(4)â
Ă
]
Sparticle spectrum and dark matter in type I string theory with an intermediate scale
The supersymmetric particle spectrum is calculated in type I string theories
formulated as orientifold compactifications of type IIB string theory. A string
scale at an intermediate value of GeV is assumed and extra
vector-like matter states are introduced to allow unification of gauge coupling
constants to occur at this scale. The qualitative features of the spectrum are
compared with Calabi-Yau compactification of the weakly coupled heterotic
string and with the eleven dimensional supergravity limit of -theory. Some
striking differences are observed. Assuming that the lightest neutralino
provides the dark matter in the universe, further constraints on the sparticle
spectrum are obtained. Direct detection rates for dark matter are estimated.Comment: LaTeX file (10 pages+10 figures), improved references, v3: typos
fixed, accepted for publication in Physics Letters
Supersymmetric Pati-Salam Models from Intersecting D6-branes: A Road to the Standard Model
We provide a systematic construction of three-family N=1 supersymmetric
Pati-Salam models from Type IIA orientifolds on \IT^6/(\IZ_2\times \IZ_2)
with intersecting D6-branes. All the gauge symmetry factors arise from the stacks of D6-branes with U(n) gauge
symmetries, while the ``hidden sector'' is specified by branes,
parallel with the orientifold planes or their images. The
Pati-Salam gauge symmetry can be broken down to the via D6-brane splittings, and
further down to the Standard Model via D- and F-flatness preserving Higgs
mechanism from massless open string states in a N=2 subsector. The models also
possess at least two confining hidden gauge sectors, where gaugino condensation
can in turn trigger supersymmetry breaking and (some) moduli stabilization. The
systematic search yields 11 inequivalent models: 8 models with less than 9
Standard model Higgs doublet-pairs and 1 model with only 2 Standard Model Higgs
doublet-pairs, 2 models possess at the string scale the gauge coupling
unification of and , and all the models possess additional
exotic matters. We also make preliminary comments on phenomenological
implications of these models.Comment: RevTeX4, 48 pages, 18 tables, typos fixed, added comments on
confinement of massless chiral exotics, accepted for publication in Nucl.
Phys.
An Iterated Greedy Algorithm for a Parallel Machine Scheduling Problem with Re-entrant and Group Processing Features
This research paper addresses a novel parallel machine scheduling problem with re-entrant and group processing features, specifically motivated by the hot milling process in the modern steel manufacturing industry. The objective is to minimize the makespan. As no existing literature exists on this problem, the paper begins by analyzing the key characteristics of the problem. Subsequently, a mixed integer linear programming model is formulated. To tackle the problem, an improved iterated greedy algorithm (IGA) is proposed. The IGA incorporates a problem-specific heuristic to construct the initial solution. Additionally, it incorporates an effective destruction and reconstruction procedure. Furthermore, an acceptance rule is developed to prevent the IGA from getting stuck in local optima. The proposed approach is evaluated through computational experiments. The results demonstrate that the proposed IGA outperforms three state-of-the-art meta-heuristics, highlighting its high effectiveness. Overall, this research contributes to the understanding and solution of the parallel machine scheduling problem with re-entrant and group processing features in the context of the hot milling process. The proposed algorithm provides insights for practical applications in the steel manufacturing industry
Can we distinguish SUSY breaking terms between weakly and strongly coupled heterotic string theories ?
We study soft SUSY breaking terms in heterotic M-theory. We show that both
weakly and strongly coupled heterotic string models lead to the same relations
of soft SUSY breaking terms, and , up to .Comment: 11 pages, late
Integrating the Symmetry Image and Improved Sparse Representation for Railway Fastener Classification and Defect Recognition
The detection of fastener defects is an important task for ensuring the safety of railway traffic. The earlier automatic inspection systems based on computer vision can detect effectively the completely missing fasteners, but they have weaker ability to recognize the partially worn ones. In this paper, we propose a method for detecting both partly worn and completely missing fasteners, the proposed algorithm exploits the first and second symmetry sample of original testing fastener image and integrates them for improved representation-based fastener recognition. This scheme is simple and computationally efficient. The underlying rationales of the scheme are as follows: First, the new virtual symmetrical images really reflect some possible appearance of the fastener; then the integration of two judgments of the symmetrical sample for fastener recognition can somewhat overcome the misclassification problem. Second, the improved sparse representation method discarding the training samples that are âfarâ from the test sample and uses a small number of samples that are ânearâ to the test sample to represent the test sample, so as to perform classification and it is able to reduce the side-effect of the error identification problem of the original fastener image. The experimental results show that the proposed method outperforms state-of-the-art fastener recognition methods
Quasi-Supersymmetric Unification from Intersecting D6-Branes on Type IIA Orientifolds
We construct three quasi-supersymmetric GUT models with symmetry
and gauge coupling unification from intersecting D6-branes on Type IIA
orientifolds. The Standard Model fermions and Higgs doublets can be embedded
into the bifundamental representations in these models, and there is no any
other unnecessary massless representation. Especially in Model I with gauge
group , we just have three-family SM fermions and three pairs of Higgs
particles. The gauge symmetry in these models can be broken down to the
Standard Model gauge symmetry by introducing light open string states. And 1
TeV scale supersymmetry breaking soft masses imply the reasonable intermediate
string scale.Comment: Latex, 14 pages, typos fixed, version to appear in PL
D6-brane Splitting on Type IIA Orientifolds
We study the open-string moduli of supersymmetric D6-branes, addressing both
the string and field theory aspects of D6-brane splitting on Type IIA
orientifolds induced by open-string moduli Higgsing (i.e., their obtaining
VEVs). Specifically, we focus on the Z_2 x Z_2 orientifolds and address the
symmetry breaking pattern for D6-branes parallel with the orientifold 6-planes
as well as those positioned at angles. We demonstrate that the string theory
results, i.e., D6-brane splitting and relocating in internal space, are in one
to one correspondence with the field theory results associated with the
Higgsing of moduli in the antisymmetric representation of Sp(2N) gauge symmetry
(for branes parallel with orientifold planes) or adjoint representation of U(N)
(for branes at general angles). In particular, the moduli Higgsing in the
open-string sector results in the change of the gauge structure of D6-branes
and thus changes the chiral spectrum and family number as well. As a
by-product, we provide the new examples of the supersymmetric Standard-like
models with the electroweak sector arising from Sp(2N)_L x Sp(2N)_R gauge
symmetry; and one four-family example is free of chiral Standard Model exotics.Comment: 44 pages, 7 figures; The anomaly-free models in Subsections 4.2 and
4.3 presented, references added, typos fixe
CofiFab: Coarse-to-fine fabrication of large 3D objects
This paper presents CofiFab, a coarse-to-fine 3D fabrication solution, which combines 3D printing and 2D laser cutting for cost-effective fabrication of large objects at lower cost and higher speed. Our key approach is to first build coarse internal base structures within the given 3D object using laser-cutting, and then attach thin 3D-printed parts, as an external shell, onto the base to recover the fine surface details. CofiFab achieves this with three novel algorithmic components. First, we formulate an optimization model to compute fabricatable polyhedrons of maximized volume, as the geometry of the internal base. Second, we devise a new interlocking scheme to tightly connect laser-cut parts into a strong internal base, by iteratively building a network of nonorthogonal interlocking joints and locking parts around polyhedral corners. Lastly, we also optimize the partitioning of the external object shell into 3D-printable parts, while saving support material and avoiding overhangs. These components also consider aesthetics, stability and balancing in addition to cost saving. As a result, CofiFab can efficiently produce large objects by assembly. To evaluate its effectiveness, we fabricate objects of varying shapes and sizes, where CofiFab significantly improves compared to previous methods
M-theory dark matter
The phenomenological implications of the eleven dimensional limit of
-theory (strongly coupled ) are investigated. In particular
we calculate the supersymmetric particle spectrum subject to constraints of
correct electroweak symmetry breaking and the requirement that the lightest
supersymmetric particle provides the dark matter of the universe. We also
calculate direct detection event rates of the lightest neutralino relevant for
non-baryonic dark matter experiments. The modulation effect, due to Earth's
annual motion is also calculated.Comment: LaTeX file, 30 pages including 12 figures;v2 typos fixed and
references adde
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