55 research outputs found
A new fault diagnosis method using deep belief network and compressive sensing
Compressive sensing provides a new idea for machinery monitoring, which greatly reduces the burden on data transmission. After that, the compressed signal will be used for fault diagnosis by feature extraction and fault classification. However, traditional fault diagnosis heavily depends on the prior knowledge and requires a signal reconstruction which will cost great time consumption. For this problem, a deep belief network (DBN) is used here for fault detection directly on compressed signal. This is the first time DBN is combined with the compressive sensing. The PCA analysis shows that DBN has successfully separated different features. The DBN method which is tested on compressed gearbox signal, achieves 92.5Â % accuracy for 25Â % compressed signal. We compare the DBN on both compressed and reconstructed signal, and find that the DBN using compressed signal not only achieves better accuracies, but also costs less time when compression ratio is less than 0.35. Moreover, the results have been compared with other classification methods
Blind Inpainting with Object-aware Discrimination for Artificial Marker Removal
Medical images often contain artificial markers added by doctors, which can
negatively affect the accuracy of AI-based diagnosis. To address this issue and
recover the missing visual contents, inpainting techniques are highly needed.
However, existing inpainting methods require manual mask input, limiting their
application scenarios. In this paper, we introduce a novel blind inpainting
method that automatically completes visual contents without specifying masks
for target areas in an image. Our proposed model includes a mask-free
reconstruction network and an object-aware discriminator. The reconstruction
network consists of two branches that predict the corrupted regions with
artificial markers and simultaneously recover the missing visual contents. The
object-aware discriminator relies on the powerful recognition capabilities of
the dense object detector to ensure that the markers of reconstructed images
cannot be detected in any local regions. As a result, the reconstructed image
can be close to the clean one as much as possible. Our proposed method is
evaluated on different medical image datasets, covering multiple imaging
modalities such as ultrasound (US), magnetic resonance imaging (MRI), and
electron microscopy (EM), demonstrating that our method is effective and robust
against various unknown missing region patterns
Direct imaging of a zero-field target skyrmion and its polarity switch in a chiral magnetic nanodisk
A target skyrmion is a flux-closed spin texture that has two-fold degeneracy
and is promising as a binary state in next generation universal memories.
Although its formation in nanopatterned chiral magnets has been predicted, its
observation has remained challenging. Here, we use off-axis electron holography
to record images of target skyrmions in a 160-nm-diameter nanodisk of the
chiral magnet FeGe. We compare experimental measurements with numerical
simulations, demonstrate switching between two stable degenerate target
skyrmion ground states that have opposite polarities and rotation senses and
discuss the observed switching mechanism.Comment: 18 pages, 4 figure
Edge-Mediated Skyrmion Chain and Its Collective Dynamics in a Confined Geometry
The emergence of a topologically nontrivial vortex-like magnetic structure,
the magnetic skyrmion, has launched new concepts for memory devices. There,
extensive studies have theoretically demonstrated the ability to encode
information bits by using a chain of skyrmions in one-dimensional nanostripes.
Here, we report the first experimental observation of the skyrmion chain in
FeGe nanostripes by using high resolution Lorentz transmission electron
microscopy. Under an applied field normal to the nanostripes plane, we observe
that the helical ground states with distorted edge spins would evolves into
individual skyrmions, which assemble in the form of chain at low field and move
collectively into the center of nanostripes at elevated field. Such skyrmion
chain survives even as the width of nanostripe is much larger than the single
skyrmion size. These discovery demonstrates new way of skyrmion formation
through the edge effect, and might, in the long term, shed light on the
applications.Comment: 7 pages, 3 figure
Electrical Probing of Field-Driven Cascading Quantized Transitions of Skyrmion Cluster States in MnSi Nanowires
Magnetic skyrmions are topologically stable whirlpool-like spin textures that
offer great promise as information carriers for future ultra-dense memory and
logic devices1-4. To enable such applications, particular attention has been
focused on the skyrmions properties in highly confined geometry such as one
dimensional nanowires5-8. Hitherto it is still experimentally unclear what
happens when the width of the nanowire is comparable to that of a single
skyrmion. Here we report the experimental demonstration of such scheme, where
magnetic field-driven skyrmion cluster (SC) states with small numbers of
skyrmions were demonstrated to exist on the cross-sections of ultra-narrow
single-crystal MnSi nanowires (NWs) with diameters, comparable to the skyrmion
lattice constant (18 nm). In contrast to the skyrmion lattice in bulk MnSi
samples, the skyrmion clusters lead to anomalous magnetoresistance (MR)
behavior measured under magnetic field parallel to the NW long axis, where
quantized jumps in MR are observed and directly associated with the change of
the skyrmion number in the cluster, which is supported by Monte Carlo
simulations. These jumps show the key difference between the clustering and
crystalline states of skyrmions, and lay a solid foundation to realize
skyrmion-based memory devices that the number of skyrmions can be counted via
conventional electrical measurements
Vision meets mmWave Radar: 3D Object Perception Benchmark for Autonomous Driving
Sensor fusion is crucial for an accurate and robust perception system on
autonomous vehicles. Most existing datasets and perception solutions focus on
fusing cameras and LiDAR. However, the collaboration between camera and radar
is significantly under-exploited. The incorporation of rich semantic
information from the camera, and reliable 3D information from the radar can
potentially achieve an efficient, cheap, and portable solution for 3D object
perception tasks. It can also be robust to different lighting or all-weather
driving scenarios due to the capability of mmWave radars. In this paper, we
introduce the CRUW3D dataset, including 66K synchronized and well-calibrated
camera, radar, and LiDAR frames in various driving scenarios. Unlike other
large-scale autonomous driving datasets, our radar data is in the format of
radio frequency (RF) tensors that contain not only 3D location information but
also spatio-temporal semantic information. This kind of radar format can enable
machine learning models to generate more reliable object perception results
after interacting and fusing the information or features between the camera and
radar
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Porous Pyrene Organic Cage with Unusual Absorption Bathochromic-Shift Enables Visible Light Photocatalysis
We have constructed a novel porous pyrene-based organic cage, PyTC1, through the condensation reaction of cyclohexanediamine with 5,5′-(pyrene-1,6-diyl)diisophthalaldehyde. Single-crystal X-ray diffraction analysis reveals the effective intercage C–H...π interaction between cyclohexanediimine and pyrene segments. Such a soft intercage C–H...π interaction, rather than a classic J-aggregate with slipped π–π-stacking configuration, induced an unusual bathochromic shift of pyrene-based chromophore absorption from an ultraviolet region of PyTC1 in solution to the visible light region of PyTC1 in solid-state. This enabled heterogeneous visible light photocatalysis of aerobic hydroxylation of benzeneboronic acid derivatives. To the best of our knowledge, this is the first report that represents an absorption bathochromic shift caused by C–H...π interaction. Such phenomenon could endow visible-light-driven photocatalysis that originally could only be achieved using UV light with the same chromophore.
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Reliability-Based Opportunistic Maintenance Modeling for Multi-Component Systems with Economic Dependence under Base Warranty
Maintenance usually plays a key role in controlling a multi-component production system within normal operations. Furthermore, the failure of components in the production system will also cause large economic losses for users due to the shutdown. Meanwhile, manufacturers of the production system will be confronted with the challenges of the warranty cost. Therefore, it is of great significance to optimize the maintenance strategy to reduce the downtime and warranty cost of the system. Opportunistic maintenance (OM) is a quite important solution to reduce the maintenance cost and improve the system performance. This paper studies the OM problem for multi-component systems with economic dependence under base warranty (BW). The irregular imperfect preventive maintenance (PM) is performed to reduce the failure rate of components at a certain PM reliability threshold. Moreover, the OM optimization model is developed to minimize the maintenance cost under the optimal OM reliability threshold of each component. A simulated annealing (SA) algorithm is proposed to determine the optimal maintenance cost of the system and the optimal OM threshold under BW. Finally, a numerical example of a belt conveyor drive device in a port is introduced to demonstrate the feasibility and advantages of the proposed model in maintenance cost optimization
Exfoliation of amorphous phthalocyanine conjugated polymers into ultrathin nanosheets for highly efficient oxygen reduction
It is a significant challenge to develop a high-efficiency synthetic methodology to access fully conjugated 2D conjugated polymer (CP)/covalent organic framework (COF) nanosheets (NSs) that have great application potential for electronics and energy. Herein, we report the exfoliation of a series of amorphous ethynyl-linked phthalocyanine (Pc) CPs (MPc-CPs, M = Fe, Co, Fe0.5Co0.5) into ultrathin MPc-CP NSs. Random coupling between the four regioisomers (with D4h, D2h, C2v and Cs symmetry) of the two tetra-β-substituted phthalocyanine precursors endows the resulting phthalocyanine conjugated polymers MPc-CPs with intrinsic structural defects and a disordered framework on individual layers. This in turn induces a diminished interlayer overlapping and a weakened interlayer π–π stacking interaction, facilitating the possible exfoliation of MPc-CPs into ultrathin 2D NSs with a yield of over 50%. The direction observation by transmission electron microscopy (TEM) and atomic force microscopy (AFM) demonstrates that the ultrathin MPc-CP NSs possess a smooth surface with a uniform thickness of 1–3 nm and a lateral size of hundreds of nanometers. The as-prepared bimetallic Fe0.5Co0.5Pc-CP NSs were further used to fabricate a heterostructure Fe0.5Co0.5Pc-CP NS@G with graphene NSs as an oxygen reduction reaction (ORR) catalyst, which exhibits an onset potential of 1006 mV and a half-wave potential of 927 mV in 0.1 M KOH, representing one of the best values in an alkaline medium. Moreover, the excellent ORR activity of the exfoliated tetrapyrrole-based conjugated NSs hybridized with graphene has also been demonstrated by a Zn–air battery device, showing an open circuit voltage of 1.34 V and a peak power density of ca. 180 mW cm−2
Overexpression of a new stress-repressive gene OsDSR2 encoding a protein with a DUF966 domain increases salt and simulated drought stress sensitivities and reduces ABA sensitivity in rice
National "973" Pre-research Program of China [2012CB126312]; National Program of Transgenic Variety Development of China [2011ZX08001-001]Overexpression of a new stress-repressive gene OsDSR2 in rice resulted in enhanced sensitivity to ABA-dependent salt and simulated drought stresses by downregulating the expression of multiple stress-responsive genes. Domain of Unknown Function 966 (DUF966) gene family was found in the protein family database, which consisted of seven genes in rice. The proteins encoded by these genes contained one or two highly conserved DUF966 domains. The available data of public microarray databases implied that these genes might play crucial roles in plant response to abiotic stresses. In this study, a member of the DUF966 gene family, DUF966-stress repressive gene 2 in Oryza sativa (OsDSR2, Loc_Os01g62200), was cloned and its role in rice responding to salt and simulated drought stresses was functionally characterized. OsDSR2 was expressed mainly in nodes of stems and leaf blades from rice. Expression profile analysis of adversity showed that OsDSR2 had different transcriptional responses to salt, drought, cold, heat and oxidative (H2O2) stresses, as well as abscisic acid (ABA), methyl jasmonate, salicylic acid, gibberellin acid and auxin treatments. Transient expression demonstrated that OsDSR2 was localized in the membrane and nucleus. Overexpression of OsDSR2 could increase salt and simulated drought (polyethyleneglycol)-stress sensitivities in rice by downregulating the expression of ABA- and stress-responsive genes including OsNCED4, SNAC1, OsbZIP23, P5CS, Oslea3 and rab16C. Furthermore, OsDSR2-overexpressing plants showed reduced ABA sensitivity during the post-germination stage. These results suggested that OsDSR2 negatively regulated rice response to salt and simulated drought stresses as well as ABA signaling, which provided some useful data for understanding the functional roles of DUF966 family genes in abiotic stress responses in plants
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