368 research outputs found
Single Photon Transport through an Atomic Chain Coupled to a One-dimensional Nanophotonic Waveguide
We study the dynamics of a single photon pulse travels through a linear
atomic chain coupled to a one-dimensional (1D) single mode photonic waveguide.
We derive a time-dependent dynamical theory for this collective many-body
system which allows us to study the real time evolution of the photon transport
and the atomic excitations. Our analytical result is consistent with previous
numerical calculations when there is only one atom. For an atomic chain, the
collective interaction between the atoms mediated by the waveguide mode can
significantly change the dynamics of the system. The reflectivity of a photon
can be tuned by changing the ratio of coupling strength and the photon
linewidth or by changing the number of atoms in the chain. The reflectivity of
a single photon pulse with finite bandwidth can even approach . The
spectrum of the reflected and transmitted photon can also be significantly
different from the single atom case. Many interesting physical phenomena can
occur in this system such as the photonic bandgap effects, quantum entanglement
generation, Fano-like interference, and superradiant effects. For engineering,
this system may serve as a single photon frequency filter, single photon
modulation and may find important applications in quantum information
Risk Intelligence: Making Profit from Uncertainty in Data Processing System
In extreme scale data processing systems, fault tolerance is an essential and indispensable part. Proactive fault tolerance scheme (such as the speculative execution in MapReduce framework) is introduced to dramatically improve the response time of job executions when the failure becomes a norm rather than an exception. Efficient proactive fault tolerance schemes require precise knowledge on the task executions, which has been an open challenge for decades. To well address the issue, in this paper we design and implement RiskI, a profile-based prediction algorithm in conjunction with a riskaware task assignment algorithm, to accelerate task executions, taking the uncertainty nature of tasks into account. Our design demonstrates that the nature uncertainty brings not only great challenges, but also new opportunities. With a careful design, we can benefit from such uncertainties. We implement the idea in Hadoop 0.21.0 systems and the experimental results show that, compared with the traditional LATE algorithm, the response time can be improved by 46% with the same system throughput
Structure and control of self-sustained target waves in excitable small-world networks
Small-world networks describe many important practical systems among which
neural networks consisting of excitable nodes are the most typical ones. In
this paper we study self-sustained oscillations of target waves in excitable
small-world networks. A novel dominant phase-advanced driving (DPAD) method,
which is generally applicable for analyzing all oscillatory complex networks
consisting of nonoscillatory nodes, is proposed to reveal the self-organized
structures supporting this type of oscillations. The DPAD method explicitly
explores the oscillation sources and wave propagation paths of the systems,
which are otherwise deeply hidden in the complicated patterns of randomly
distributed target groups. Based on the understanding of the self-organized
structure, the oscillatory patterns can be controlled with extremely high
efficiency.Comment: 16 pages 5 figure
Supplier Empowerment: Moderating the Casual Relationship between Supplier Modularity Practices and Build-to-order Supply Chain Capabilities
Psychological empowerment attracts researchers in theory building, measurements, and applications at the individual and team levels. Based on social dilemma theory and resource dependency theory, this study proposes a research model to explore (1) the relationship between supplier modularity practices and build-to-order supply chain (BOSC) capabilities, (2) the role of supplier empowerment in moderating the relationship between supplier modularity practices and BOSC capabilities, and (3) the direct impact of supplier empowerment on BOSC capabilities in a supply chain context. The model is tested with 208 responses from automotive suppliers in North America and in China
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Doping-free complementary WSe2 circuit via van der Waals metal integration.
Two-dimensional (2D) semiconductors have attracted considerable attention for the development of ultra-thin body transistors. However, the polarity control of 2D transistors and the achievement of complementary logic functions remain critical challenges. Here, we report a doping-free strategy to modulate the polarity of WSe2 transistors using same contact metal but different integration methods. By applying low-energy van der Waals integration of Au electrodes, we observed robust and optimized p-type transistor behavior, which is in great contrast to the transistors fabricated on the same WSe2 flake using conventional deposited Au contacts with pronounced n-type characteristics. With the ability to switch majority carrier type and to achieve optimized contact for both electrons and holes, a doping-free logic inverter is demonstrated with higher voltage gain of 340, at the bias voltage of 5.5 V. Furthermore, the simple polarity control strategy is extended for realizing more complex logic functions such as NAND and NOR
Spatial-Temporal Imaging of Anisotropic Photocarrier Dynamics in Black Phosphorus
As an emerging single elemental layered material with a low symmetry in-plane
crystal lattice, black phosphorus (BP) has attracted significant research
interest owing to its unique electronic and optoelectronic properties,
including its widely tunable bandgap, polarization dependent photoresponse and
highly anisotropic in-plane charge transport. Despite extensive study of the
steady-state charge transport in BP, there has not been direct characterization
and visualization of the hot carriers dynamics in BP immediately after
photoexcitation, which is crucial to understanding the performance of BP-based
optoelectronic devices. Here we use the newly developed scanning ultrafast
electron microscopy (SUEM) to directly visualize the motion of photo-excited
hot carriers on the surface of BP in both space and time. We observe highly
anisotropic in-plane diffusion of hot holes, with a 15-times higher diffusivity
along the armchair (x-) direction than that along the zigzag (y-) direction.
Our results provide direct evidence of anisotropic hot carrier transport in BP
and demonstrate the capability of SUEM to resolve ultrafast hot carrier
dynamics in layered two-dimensional materials.Comment: 21 pages, 6 figure
Adapting Offline Speech Translation Models for Streaming with Future-Aware Distillation and Inference
A popular approach to streaming speech translation is to employ a single
offline model with a \textit{wait-} policy to support different latency
requirements, which is simpler than training multiple online models with
different latency constraints. However, there is a mismatch problem in using a
model trained with complete utterances for streaming inference with partial
input. We demonstrate that speech representations extracted at the end of a
streaming input are significantly different from those extracted from a
complete utterance. To address this issue, we propose a new approach called
Future-Aware Streaming Translation (FAST) that adapts an offline ST model for
streaming input. FAST includes a Future-Aware Inference (FAI) strategy that
incorporates future context through a trainable masked embedding, and a
Future-Aware Distillation (FAD) framework that transfers future context from an
approximation of full speech to streaming input. Our experiments on the MuST-C
EnDe, EnEs, and EnFr benchmarks show that FAST achieves better trade-offs
between translation quality and latency than strong baselines. Extensive
analyses suggest that our methods effectively alleviate the aforementioned
mismatch problem between offline training and online inference.Comment: work in progres
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