4,268 research outputs found
A Semiblind Two-Way Training Method for Discriminatory Channel Estimation in MIMO Systems
Discriminatory channel estimation (DCE) is a recently developed strategy to
enlarge the performance difference between a legitimate receiver (LR) and an
unauthorized receiver (UR) in a multiple-input multiple-output (MIMO) wireless
system. Specifically, it makes use of properly designed training signals to
degrade channel estimation at the UR which in turn limits the UR's
eavesdropping capability during data transmission. In this paper, we propose a
new two-way training scheme for DCE through exploiting a whitening-rotation
(WR) based semiblind method. To characterize the performance of DCE, a
closed-form expression of the normalized mean squared error (NMSE) of the
channel estimation is derived for both the LR and the UR. Furthermore, the
developed analytical results on NMSE are utilized to perform optimal power
allocation between the training signal and artificial noise (AN). The
advantages of our proposed DCE scheme are two folds: 1) compared to the
existing DCE scheme based on the linear minimum mean square error (LMMSE)
channel estimator, the proposed scheme adopts a semiblind approach and achieves
better DCE performance; 2) the proposed scheme is robust against active
eavesdropping with the pilot contamination attack, whereas the existing scheme
fails under such an attack.Comment: accepted for publication in IEEE Transactions on Communication
Management of mother-to-child transmission of hepatitis B virus: Propositions and challenges
AbstractChronic hepatitis B virus (HBV) infection due to mother-to-child transmission (MTCT) during perinatal period remains an important global health problem. Despite standard passive–active immunoprophylaxis with hepatitis B immunoglobulin (HBIG) and hepatitis B vaccine in neonates, up to 9% of newborns still acquire HBV infection, especially these from hepatitis B e antigen (HBeAg) positive mothers. Management of HBV infection in pregnancy still need to draw careful attention because of some controversial aspects, including the failure of passive-active immunoprophylaxis in a fraction of newborns, the effect and necessity of periodical hepatitis B immunoglobulin (HBIG) injection to the mothers, the safety of antiviral prophylaxis with nucleoside/nucleotide analogs, the benefit of different delivery ways, and the safety of breastfeeding. In this review, we highlight these unsettled issues of preventive strategies in perinatal period, and we further aim to provide an optimal approach to the management of preventing MTCT of HBV infection
The juxtamembrane and carboxy-terminal domains of Arabidopsis PRK2 are critical for ROP-induced growth in pollen tubes.
Polarized growth of pollen tubes is a critical step for successful reproduction in angiosperms and is controlled by ROP GTPases. Spatiotemporal activation of ROP (Rho GTPases of plants) necessitates a complex and sophisticated regulatory system, in which guanine nucleotide exchange factors (RopGEFs) are key components. It was previously shown that a leucine-rich repeat receptor-like kinase, Arabidopsis pollen receptor kinase 2 (AtPRK2), interacted with RopGEF12 for its membrane recruitment. However, the mechanisms underlying AtPRK2-mediated ROP activation in vivo are yet to be defined. It is reported here that over-expression of AtPRK2 induced tube bulging that was accompanied by the ectopic localization of ROP-GTP and the ectopic distribution of actin microfilaments. Tube depolarization was also induced by a potentially kinase-dead mutant, AtPRK2K366R, suggesting that the over-expression effect of AtPRK2 did not require its kinase activity. By contrast, deletions of non-catalytic domains in AtPRK2, i.e. the juxtamembrane (JM) and carboxy-terminal (CT) domains, abolished its ability to affect tube polarization. Notably, AtPRK2K366R retained the ability to interact with RopGEF12, whereas AtPRK2 truncations of these non-catalytic domains did not. Lastly, it has been shown that the JM and CT domains of AtPRK2 were not only critical for its interaction with RopGEF12 but also critical for its distribution at the plasma membrane. These results thus provide further insight into pollen receptor kinase-mediated ROP activation during pollen tube growth
Skipped Feature Pyramid Network with Grid Anchor for Object Detection
CNN-based object detection methods have achieved significant progress in
recent years. The classic structures of CNNs produce pyramid-like feature maps
due to the pooling or other re-scale operations. The feature maps in different
levels of the feature pyramid are used to detect objects with different scales.
For more accurate object detection, the highest-level feature, which has the
lowest resolution and contains the strongest semantics, is up-scaled and
connected with the lower-level features to enhance the semantics in the
lower-level features. However, the classic mode of feature connection combines
the feature of lower-level with all the features above it, which may result in
semantics degradation. In this paper, we propose a skipped connection to obtain
stronger semantics at each level of the feature pyramid. In our method, the
lower-level feature only connects with the feature at the highest level, making
it more reasonable that each level is responsible for detecting objects with
fixed scales. In addition, we simplify the generation of anchor for bounding
box regression, which can further improve the accuracy of object detection. The
experiments on the MS COCO and Wider Face demonstrate that our method
outperforms the state-of-the-art methods
Multimodal ChatGPT for Medical Applications: an Experimental Study of GPT-4V
In this paper, we critically evaluate the capabilities of the
state-of-the-art multimodal large language model, i.e., GPT-4 with Vision
(GPT-4V), on Visual Question Answering (VQA) task. Our experiments thoroughly
assess GPT-4V's proficiency in answering questions paired with images using
both pathology and radiology datasets from 11 modalities (e.g. Microscopy,
Dermoscopy, X-ray, CT, etc.) and fifteen objects of interests (brain, liver,
lung, etc.). Our datasets encompass a comprehensive range of medical inquiries,
including sixteen distinct question types. Throughout our evaluations, we
devised textual prompts for GPT-4V, directing it to synergize visual and
textual information. The experiments with accuracy score conclude that the
current version of GPT-4V is not recommended for real-world diagnostics due to
its unreliable and suboptimal accuracy in responding to diagnostic medical
questions. In addition, we delineate seven unique facets of GPT-4V's behavior
in medical VQA, highlighting its constraints within this complex arena. The
complete details of our evaluation cases are accessible at
https://github.com/ZhilingYan/GPT4V-Medical-Report
A Data Driven Method for Multi-step Prediction of Ship Roll Motion in High Sea States
Ship roll motion in high sea states has large amplitudes and nonlinear
dynamics, and its prediction is significant for operability, safety, and
survivability. This paper presents a novel data-driven methodology to provide a
multi-step prediction of ship roll motions in high sea states. A hybrid neural
network is proposed that combines long short-term memory (LSTM) and
convolutional neural network (CNN) in parallel. The motivation is to extract
the nonlinear dynamic characteristics and the hydrodynamic memory information
through the advantage of CNN and LSTM, respectively. For the feature selection,
the time histories of motion states and wave heights are selected to involve
sufficient information. Taken a scaled KCS as the study object, the ship
motions in sea state 7 irregular long-crested waves are simulated and used for
the validation. The results show that at least one period of roll motion can be
accurately predicted. Compared with the single LSTM and CNN methods, the
proposed method has better performance in predicting the amplitude of roll
angles. Besides, the comparison results also demonstrate that selecting motion
states and wave heights as feature space improves the prediction accuracy,
verifying the effectiveness of the proposed method
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