305 research outputs found
A review of development of micro-channel heat exchanger applied in air-conditioning system
AbstractMicro-channel heat exchanger(MCHX) has been increasingly applied in HVAC&R(Heating, Ventilation, and Air Conditioning & Refrigeration) field due to its higher efficiently heat transfer rate, more compact structure, lower cost. The characteristics of micro-channel heat transfer and fluid dynamics are summarized in this paper. The methods about optimizations (ie, geometry and thermodynamic performance) and the advantages and disadvantages of the MCHX are analyzed
A Class of Lie 2-Algebras in Higher-Order Courant Algebroids
Abstract In this paper, we study the relation of the algebraic properties of the higher-order Courant bracket and Dorfman bracket on the direct sum bundle for an m-dimensional smooth manifold M, and a Lie 2-algebra which is a "categorified" version of a Lie algebra. We prove that the higher-order Courant algebroids give rise to a semistrict Lie 2-algebra, and we prove that the higher-order Dorfman algebroids give rise to a hemistrict Lie 2-algebra. Consequently, there is an isomorphism from the higher-order Courant algebroids to the higher-order Dorfman algebroids as Lie 2-algebras homomorphism
Conceptual Study of a Real-Time Hybrid Simulation Framework for Monopile Offshore Wind Turbines Under Wind and Wave Loads
As an attractive renewable energy source, offshore wind plants are becoming increasingly popular for energy production. However, the performance assessment of offshore wind turbine (OWT) structure is a challenging task due to the combined wind-wave loading and difficulties in reproducing such loading conditions in laboratory. Real-time hybrid simulation (RTHS), combining physical testing and numerical simulation in real-time, offers a new venue to study the structural behavior of OWTs. It overcomes the scaling incompatibilities in OWT scaled model testing by replacing the rotor components with an actuation system, driven by an aerodynamic simulation tool running in real-time. In this study, a RTHS framework for monopile OWTs is proposed. A set of sensitivity analyses is carried out to evaluate the feasibility of this RTHS framework and determine possible tolerances on its design. By simulating different scaling laws and possible error contributors (delays and noises) in the proposed framework, the sensitivity of the OWT responses to these parameters are quantified. An example using a National Renewable Energy Lab (NREL) 5-MW reference OWT system at 1:25 scale is simulated in this study to demonstrate the proposed RTHS framework and sensitivity analyses. Three different scaling laws are considered. The sensitivity results show that the delays in the RTHS framework significantly impact the performance on the response evaluation, higher than the impact of noises. The proposed framework and sensitivity analyses presented in this study provides important information for future implementation and further development of the RTHS technology for similar marine structures
Inhibitory Effects of Peptide Lunasin in Colorectal Cancer HCT-116 Cells and Their Tumorsphere-Derived Subpopulation
The involvement of cancer stem-like cells (CSC) in the tumor pathogenesis has profound implications for cancer therapy and chemoprevention. Lunasin is a bioactive peptide from soybean and other vegetal sources with proven protective activities against cancer and other chronic diseases. The present study focused on the cytotoxic effect of peptide lunasin in colorectal cancer HCT-116 cells, both the bulk tumor and the CSC subpopulations. Lunasin inhibited the proliferation and the tumorsphere-forming capacity of HCT-116 cells. Flow cytometry results demonstrated that the inhibitory effects were related to apoptosis induction and cell cycle-arrest at G1 phase. Moreover, lunasin caused an increase in the sub-GO/G1 phase of bulk tumor cells, linked to the apoptotic events found. Immunoblotting analysis further showed that lunasin induced apoptosis through activation of caspase-3 and cleavage of PARP, and could modulate cell cycle progress through the cyclin-dependent kinase inhibitor p21. Together, these results provide new evidence on the chemopreventive activity of peptide lunasin on colorectal cancer by modulating both the parental and the tumorsphere-derived subsets of HCT-116 cells
MLA-BIN: Model-level Attention and Batch-instance Style Normalization for Domain Generalization of Federated Learning on Medical Image Segmentation
The privacy protection mechanism of federated learning (FL) offers an
effective solution for cross-center medical collaboration and data sharing. In
multi-site medical image segmentation, each medical site serves as a client of
FL, and its data naturally forms a domain. FL supplies the possibility to
improve the performance of seen domains model. However, there is a problem of
domain generalization (DG) in the actual de-ployment, that is, the performance
of the model trained by FL in unseen domains will decrease. Hence, MLA-BIN is
proposed to solve the DG of FL in this study. Specifically, the model-level
attention module (MLA) and batch-instance style normalization (BIN) block were
designed. The MLA represents the unseen domain as a linear combination of seen
domain models. The atten-tion mechanism is introduced for the weighting
coefficient to obtain the optimal coefficient ac-cording to the similarity of
inter-domain data features. MLA enables the global model to gen-eralize to
unseen domain. In the BIN block, batch normalization (BN) and instance
normalization (IN) are combined to perform the shallow layers of the
segmentation network for style normali-zation, solving the influence of
inter-domain image style differences on DG. The extensive experimental results
of two medical image seg-mentation tasks demonstrate that the proposed MLA-BIN
outperforms state-of-the-art methods.Comment: 9 pages, 8 figures, 2 table
Aberrant Brain Regional Homogeneity and Functional Connectivity of Entorhinal Cortex in Vascular Mild Cognitive Impairment: A Resting-State Functional MRI Study
The aim of this study was to investigate changes in regional homogeneity (ReHo) and the functional connectivity of the entorhinal cortex (EC) in vascular mild cognitive impairment (VaMCI) and to evaluate the relationships between such changes and neuropsychological measures in VaMCI individuals. In all, 31 patients with VaMCI and 32 normal controls (NCs) underwent rs-fMRI. Differences in whole-brain ReHo and seed-based bilateral EC functional connectivity (EC-FC) were determined. Pearson's correlation was used to evaluate the relationships between regions with significant group differences and different neuropsychological measures. Vascular mild cognitive impairment (VaMCI) patients had lower scores in Mini-mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA) and higher ones in Activity of Daily Living (ADL) (p < 0.05). Vascular mild cognitive impairment (VaMCI) individuals had significantly lower ReHo in the left cerebellum and right lentiform nucleus than NCs (P < 0.05, TFCE FWE correction). Vascular mild cognitive impairment (VaMCI) subjects showed significant decreases in the FC of the right EC in the right inferior frontal gyrus, right middle frontal gyrus, bilateral pre-central gyrus, and right post-central/superior parietal lobules (P < 0.05, TFCE FWE correction). Significant positive correlations were found between ReHo and MoCA scores for the right lentiform nucleus (r = 0.37, P < 0.05). The right post-central/superior parietal lobules showed a significant positive correlation between right EC-FC and MoCA scores (r = 0.37, P < 0.05). Patterns in ReHo and EC-FC changes in VaMCI patients and their correlations with neuropsychological measures may be a pathophysiological foundation of cognitive impairment, which may aid the early diagnosis of VaMCI
The flavor-changing single-top quark production in the littlest Higgs model with T parity at the LHC
The littlest Higgs model with discrete symmetry named "T-parity"(LHT) is an
interesting new physics model which does not suffer strong constraints from
electroweak precision data. One of the important features of the LHT model is
the existence of new source of FC interactions between the SM fermions and the
mirror fermions. These FC interactions can make significant loop-level
contributions to the couplings , and furthermore enhance the cross
sections of the FC single-top quark production processes. In this paper, we
study some FC single-top quark production processes, and
, at the LHC in the LHT model. We find that the cross sections of
these processes are strongly depended on the mirror quark masses. The processes
and have large cross sections with heavy mirror
quarks. The observation of these FC processes at the LHC is certainly the clue
of new physics, and further precise measurements of the cross scetions can
provide useful information about the free parameters in the LHT model,
specially about the mirror quark masses.Comment: 20 pages, 5 figure
Single-image based deep learning for precise atomic defects identification
Defect engineering has been profoundly employed to confer desirable
functionality to materials that pristine lattices inherently lack. Although
single atomic-resolution scanning transmission electron microscopy (STEM)
images are widely accessible for defect engineering, harnessing atomic-scale
images containing various defects through traditional image analysis methods is
hindered by random noise and human bias. Yet the rise of deep learning (DL)
offering an alternative approach, its widespread application is primarily
restricted by the need for large amounts of training data with labeled ground
truth. In this study, we propose a two-stage method to address the problems of
high annotation cost and image noise in the detection of atomic defects in
monolayer 2D materials. In the first stage, to tackle the issue of data
scarcity, we employ a two-state transformation network based on U-GAT-IT for
adding realistic noise to simulated images with pre-located ground truth
labels, thereby infinitely expanding the training dataset. In the second stage,
atomic defects in monolayer 2D materials are effectively detected with high
accuracy using U-Net models trained with the data generated in the first stage,
avoiding random noise and human bias issues. In both stages, we utilize
segmented unit-cell-level images to simplify the model's task and enhance its
accuracy. Our results demonstrate that not only sulfur vacancies, we are also
able to visualize oxygen dopants in monolayer MoS2, which are usually
overwhelmed by random background noise. As the training was based on a few
segmented unit-cell-level realistic images, this method can be readily extended
to other 2D materials. Therefore, our results outline novel ways to train the
model with minimized datasets, offering great opportunities to fully exploit
the power of machine learning (ML) applicable to a broad materials science
community
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