4,660 research outputs found
Quantum measurement of hyperfine interaction in nitrogen-vacancy center
We propose an efficient quantum measurement protocol for the hyperfine
interaction between the electron spin and the N nuclear spin of a
diamond nitrogen-vacancy center. In this protocol, a sequence of quantum
operations of successively increasing duration is utilized to estimate the
hyperfine interaction with successively higher precision approaching the
quantum metrology limit. This protocol does not need the preparation of the
nuclear spin state. In the presence of realistic operation errors and electron
spin decoherence, the overall precision of our protocol still surpasses the
standard quantum limit
Embedded Solitons in Lagrangian and Semi-Lagrangian Systems
We develop the technique of the variational approximation for solitons in two
directions. First, one may have a physical model which does not admit the usual
Lagrangian representation, as some terms can be discarded for various reasons.
For instance, the second-harmonic-generation (SHG) model considered here, which
includes the Kerr nonlinearity, lacks the usual Lagrangian representation if
one ignores the Kerr nonlinearity of the second harmonic, as compared to that
of the fundamental. However, we show that, with a natural modification, one may
still apply the variational approximation (VA) to those seemingly flawed
systems as efficiently as it applies to their fully Lagrangian counterparts. We
call such models, that do not admit the usual Lagrangian representation,
\textit{semi-Lagrangian} systems. Second, we show that, upon adding an
infinitesimal tail that does not vanish at infinity, to a usual soliton ansatz,
one can obtain an analytical criterion which (within the framework of VA) gives
a condition for finding \textit{embedded solitons}, i.e., isolated truly
localized solutions existing inside the continuous spectrum of the radiation
modes. The criterion takes a form of orthogonality of the radiation mode in the
infinite tail to the soliton core. To test the criterion, we have applied it to
both the semi-Lagrangian truncated version of the SHG model and to the same
model in its full form. In the former case, the criterion (combined with VA for
the soliton proper) yields an \emph{exact} solution for the embedded soliton.
In the latter case, the criterion selects the embedded soliton with a relative
error .Comment: 10 pages, 1 figur
EFFECTS OF AL(2)O(3) NANOPARTICLES DEPOSITION ON CRITICAL HEAT FLUX OF R-123 IN FLOW BOILING HEAT TRANSFER
In this study, R-123 flow boiling experiments were carried out to investigate the effects of nanoparticle deposition on heater surfaces on flow critical heat flux (CHF) and boiling heat transfer. It is known that CHF enhancement by nanoparticles results from porous structures that are very similar to layers of Chalk River unidentified deposit formed on nuclear fuel rod surfaces during the reactor operation period. Although previous studies have investigated the surface effects through surface modifications, most studies are limited to pool boiling conditions, and therefore, the effects of porous surfaces on flow boiling heat transfer are still unclear. In addition, there have been only few reports on suppression of wetting for decoupled approaches of reasoning. In this study, bare and Al2O3 nanoparticle-coated surfaces were prepared for the study experiments. The CHF of each surface was measured with different mass fluxes of 1,600 kg/m(2)s, 1,800 kg/m(2)s, 2,100 kg/m(2)s, 2,400 kg/m(2)s, and 2,600 kg/m(2)s. The nanoparticle-coated tube showed CHF enhancement up to 17% at a mass flux of 2,400 kg/m(2)s compared with the bare tube. The factors for CHF enhancement are related to the enhanced rewetting process derived from capillary action through porous structures built-up by nanoparticles while suppressing relative wettability effects between two sample surfaces as a highly wettable R-123 refrigerant was used as a working fluid. Copyright (C) 2015, Published by Elsevier Korea LLC on behalf of Korean Nuclear Societyclose0
Identification technique of misalignment-rubbing coupling fault in dual-disk rotor system supported by rolling bearing
For the diagnosis of misalignment-rubbing coupling fault of rotor-rolling bearing system caused by misalignment fault, the mechanical model and finite element model of dual-disc rotor system with misalignment-rubbing coupling fault were established based on the nonlinear finite element method, rolling bearing force, equivalent misalignment torque and contact theory in this paper. And then its accuracy was validated by related experiment. According to research on dynamic characteristics of the rotor system with different rubbing stiffness, misalignment angles and rotation rates, it was found that the misalignment-rubbing coupling fault is often characterized by rubbing fault, and that double frequency appeared early, and that peak value increased rapidly. It could be used as a theoretical basis for diagnosing misalignment-rubbing coupling fault of rotor-rolling bearing system
Customizing General-Purpose Foundation Models for Medical Report Generation
Medical caption prediction which can be regarded as a task of medical report
generation (MRG), requires the automatic generation of coherent and accurate
captions for the given medical images. However, the scarcity of labelled
medical image-report pairs presents great challenges in the development of deep
and large-scale neural networks capable of harnessing the potential artificial
general intelligence power like large language models (LLMs). In this work, we
propose customizing off-the-shelf general-purpose large-scale pre-trained
models, i.e., foundation models (FMs), in computer vision and natural language
processing with a specific focus on medical report generation. Specifically,
following BLIP-2, a state-of-the-art vision-language pre-training approach, we
introduce our encoder-decoder-based MRG model. This model utilizes a
lightweight query Transformer to connect two FMs: the giant vision Transformer
EVA-ViT-g and a bilingual LLM trained to align with human intentions (referred
to as ChatGLM-6B). Furthermore, we conduct ablative experiments on the
trainable components of the model to identify the crucial factors for effective
transfer learning. Our findings demonstrate that unfreezing EVA-ViT-g to learn
medical image representations, followed by parameter-efficient training of
ChatGLM-6B to capture the writing styles of medical reports, is essential for
achieving optimal results. Our best attempt (PCLmed Team) achieved the 4th and
the 2nd, respectively, out of 13 participating teams, based on the BERTScore
and ROUGE-1 metrics, in the ImageCLEFmedical Caption 2023 Caption Prediction
Task competition.Comment: 14 pages, 3 figure
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