317 research outputs found
Cargo compartment fire extinguishing system
In all large passenger transport airplanes, halon fire bottles are used to extinguish fire in the cargo compartments.
Halon as a fire-extinguishing agent, contributes to the destruction of stratospheric ozone in the atmosphere and it
is banned in many countries. FAA considers halon 1301 as an effective firefighting agent due to its low toxicity and
noncorrosive properties but because it damages the ozone layer, it has been phased out of production. However,
it is still widely used on commercial aircraft until a suitable replacement is found. In this paper we will present an
alternative approach to using halon 1301 as a fire fighting paradigm. In the proposed method, nitrogen is first
extracted from the atmosphere by using the onboard air separator module it is then cooled, and pressurized into the
cargo compartments to suppress any fire. Several methodologies can be used to increase the flow rate from the air
separator module, to extinguish fire in cargo compartment
Fuel leak detection on large transport airplanes
Fuel leakage has the risk of being ignited by external ignition sources, and therefore it is important to detect
any fuel leakage before the departure of the aircraft. Currently, there are no fuel leak detection systems installed
on commercial aircrafts, to detect fuel tank leakage, while only a small number of more recent aircraft, have a fuel
monitoring system, that generates a fuel leak-warning message in cockpit in the case of fuel imbalance between the
tanks. The approach proposed in this paper requires the fuel vent ports on the wings to be replaced with fuel vent
valves, which can be controlled to be in open or close position. The fuel vent valve will be in close position, when
certain conditions are fulfilled (all the related fuel valves closed, pumps not operating, etc.), the fuel tank ullage area
is then pressurized to 4 psi and the rate of change of the pressure is measured over a period. Several experiments
have been conducted and, the result show that a continuous fuel leak of one liter per minute can be detected. Further
experiments show that if the fuel tank is pressurized to higher pressures, a fuel leak can be detected sooner
Nearly Supersymmetric Dark Atoms
Theories of dark matter that support bound states are an intriguing
possibility for the identity of the missing mass of the Universe. This article
proposes a class of models of supersymmetric composite dark matter where the
interactions with the Standard Model communicate supersymmetry breaking to the
dark sector. In these models supersymmetry breaking can be treated as a
perturbation on the spectrum of bound states. Using a general formalism, the
spectrum with leading supersymmetry effects is computed without specifying the
details of the binding dynamics. The interactions of the composite states with
the Standard Model are computed and several benchmark models are described.
General features of non-relativistic supersymmetric bound states are
emphasized.Comment: 39 pages, 2 figure
Governance gaps in eradicating forced labor: from global to domestic supply chains
A growing body of scholarship analyzes the emergence and resilience of forced labor in developing countries within global value chains (GVCs). However, little is known about how forced labor arises within domestic supply chains concentrated within national borders, producing products for domestic consumption. We conduct one of the first studies of forced labor in domestic supply chains, through a cross-industry comparison of the regulatory gaps surrounding forced labor in the United Kingdom. We find that understanding the dynamics of forced labor in domestic supply chains requires us to conceptually modify the GVC framework to understand similarities and differences across these contexts. We conclude that addressing the governance gaps that surround forced labor will require scholars and policymakers to carefully refine their thinking about how we might design operative governance that effectively engages with local variation
Confronting the business models of modern slavery
Despite growing attention from companies and regulators looking to eradicate modern slavery, we know little about how slavery works from a business perspective. We address this gap by empirically examining innovations in the business models of modern slavery, focusing on how the business models of slavery in advanced economies have evolved since slavery was legally abolished. While continuities exist, novel business models have emerged based on new actors, activities, and linkages. We categorize these as four innovative models per actors involved (producer/intermediary) and how value is created and captured (revenue generation/cost reduction), and discuss implications for research, policy, and practice
Composite Inelastic Dark Matter
Peaking consistently in June for nearly eleven years, the annual modulation
signal reported by DAMA/NaI and DAMA/LIBRA offers strong evidence for the
identity of dark matter. DAMA's signal strongly suggest that dark matter
inelastically scatters into an excited state split by O(100 keV). We propose
that DAMA is observing hyperfine transitions of a composite dark matter
particle. As an example, we consider a meson of a QCD-like sector, built out of
constituent fermions whose spin-spin interactions break the degeneracy of the
ground state. An axially coupled U(1) gauge boson that mixes kinetically with
hypercharge induces inelastic hyperfine transitions of the meson dark matter
that can explain the DAMA signal.Comment: 5 pages (two-column), 1 figure, revised version, references adde
Differences in proliferation rate between CADASIL and control vascular smooth muscle cells are related to increased TGF beta expression
Cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a familial fatal progressive degenerative disorder. One of the pathological hallmarks of CADASIL is a dramatic reduction of vascular smooth muscle cells (VSMCs) in cerebral arteries. Using VSMCs from the vasculature of the human umbilical cord, placenta and cerebrum of CADASIL patients, we found that CADASIL VSMCs had a lower proliferation rate compared to control VSMCs. Exposure of control VSMCs and endothelial cells (ECs) to media derived from CADASIL VSMCs lowered the proliferation rate of all cells examined. By quantitative RT-PCR analysis, we observed increased Transforming growth factor-beta (TGF beta) gene expression in CADASIL VSMCs. Adding TGF beta-neutralizing antibody restored the proliferation rate of CADASIL VSMCs. We assessed proliferation differences in the presence or absence of TGF beta-neutralizing antibody in ECs co-cultured with VSMCs. ECs co-cultured with CADASIL VSMCs exhibited a lower proliferation rate than those co-cultured with control VSMCs, and neutralization of TGF beta normalized the proliferation rate of ECs co-cultured with CADASIL VSMCs. We suggest that increased TGF beta expression in CADASIL VSMCs is involved in the reduced VSMC proliferation in CADASIL and may play a role in situ in altered proliferation of neighbouring cells in the vasculature.Peer reviewe
Joint Source and Relay Optimization for Parallel MIMO Relay Networks
In this article, we study the optimal structure of the source precoding matrix and the relay amplifying matrices for multiple-input multiple-output (MIMO) relay communication systems with parallel relay nodes. Two types of receivers are considered at the destination node: (1) The linear minimal mean-squared error (MMSE) receiver; (2) The nonlinear decision feedback equalizer based on the minimal MSE criterion. We show that for both receiver schemes, the optimal source precoding matrix and the optimal relay amplifying matrices have a beamforming structure. Using such optimal structure, joint source and relay power loading algorithms are developed to minimize the MSE of the signal waveform estimation at the destination. Compared with existing algorithms for parallel MIMO relay networks, the proposed joint source and relay beamforming algorithms have significant improvement in the system bit-error-rate performance
Interspecific Hybridization Yields Strategy for South Pacific Filariasis Vector Elimination
Lymphatic filariasis (LF) is a global health problem, with over 120 million people affected annually. The current LF elimination program is focused on administering anti-filarial drugs to the entire at-risk population via annual mass drug administration (MDA). While the MDA program is proving effective in many areas, other areas may require augmentative measures such as vector control. An example of the latter is provided by some regions of the South Pacific where Aedes polynesiensis is the primary vector. Here, we describe a novel vector control approach based upon naturally occurring Wolbachia bacterial infections. Wolbachia are endosymbiotic intracellular bacteria that cause a form of sterility known as cytoplasmic incompatibility. We show that introgression crosses with mosquitoes that are infected with a different Wolbachia type results in an A. polynesiensis strain (designated ‘CP’) that is incompatible with naturally infected mosquitoes. No difference in mating competitiveness is observed between CP males and wild type males in laboratory assays. The results support continued development of the strategy as a tool to improve public health
Fano resonances in plasmonic core-shell particles and the Purcell effect
Despite a long history, light scattering by particles with size comparable
with the light wavelength still unveils surprising optical phenomena, and many
of them are related to the Fano effect. Originally described in the context of
atomic physics, the Fano resonance in light scattering arises from the
interference between a narrow subradiant mode and a spectrally broad radiation
line. Here, we present an overview of Fano resonances in coated spherical
scatterers within the framework of the Lorenz-Mie theory. We briefly introduce
the concept of conventional and unconventional Fano resonances in light
scattering. These resonances are associated with the interference between
electromagnetic modes excited in the particle with different or the same
multipole moment, respectively. In addition, we investigate the modification of
the spontaneous-emission rate of an optical emitter at the presence of a
plasmonic nanoshell. This modification of decay rate due to electromagnetic
environment is referred to as the Purcell effect. We analytically show that the
Purcell factor related to a dipole emitter oriented orthogonal or tangential to
the spherical surface can exhibit Fano or Lorentzian line shapes in the near
field, respectively.Comment: 28 pages, 10 figures; invited book chapter to appear in "Fano
Resonances in Optics and Microwaves: Physics and Application", Springer
Series in Optical Sciences (2018), edited by E. O. Kamenetskii, A. Sadreev,
and A. Miroshnichenk
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