The springback behavior has been revealed to affect the dimensional accuracy of sheet metal products significantly in the forming process. As the forming scale decreases to micro/meso level, the ...deformation behavior of sheet metals has been reported to be different from that at the macro level due to the so-called size effect. This study thus aims to investigate and characterize the springback behavior of sheet metals affected by the size effect at micro/meso scale. The copper specimens with different thicknesses and grain sizes were employed in the uniaxial tensile, nano-indentation and micro hardness tests to analyze the size effect on the material elastic/plastic deformation behavior at first. The flow stress, yield strength and hardness are revealed to decrease with the increase of grain size. Following that the bending experiments with three different punch angles were performed. The effects of both feature and grain sizes on the springback angle were investigated. The springback angle is found to decrease with the punch angle, the grain size, the ratio of thickness to grain size (t/d) and the reduction of thickness. To dig the fundamental mechanism behind the size-effect affected springback behavior, a composite model based on the surface layer theory was employed to describe the constitutive plastic deformation of material with different grain size and thicknesses. The model was further applied in the finite element (FE) simulations of bending process. Based on the experimental and FE results of sheet metals at micro/meso scale bending process, the interactive effect of feature and grain sizes is revealed to be critical in microforming processes. As a preliminary work, the flow stress reduction described by the composite model is found to be able to characterize the global springback behavior during the micro bending test.
•Geodetic data and model reveal transient mass changes in Greenland.•NW Greenland exhibited different change patterns than the rest subregions.•Precipitation anomalies were opposite in signs in east ...& west Greenland.•Atmospheric circulation anomalies may cause most of the transient mass changes.
Much of the research to understand the ice mass changes of Greenland ice sheet (GrIS) has focused on detecting linear rates and accelerations at decadal or longer periods. The transient (short-term, non-secular) mass changes show large variability, and if not properly accounted for, can introduce significant biases into estimates of long-term ice mass loss rates and accelerations. Despite the growing number of geodetic observations, in terms of spatial coverage, types of observables, and the extent of the time series, studies of the transient mass changes over GrIS are lacking. To address this limitation, we apply multi-channel singular spectral analysis to the Gravity Recovery and Climate Experiment (GRACE) mass concentrations (mascon), surface mass balance (SMB) model output, and ice discharge data, to determine the transient mass changes over Greenland over the decade (2007 to 2017). The goal of this analysis is to elucidate the spatio-temporal variability of the ice mass change. For the entire GrIS, both the mascon and SMB transient mass changes are characterized by a sustained mass gain from late 2007 to early 2010, a sustained mass loss from early 2010 to early 2013, and a mass gain from early 2013 to mid-2015. Global Positioning System sites deployed along the coast of Greenland showed uplift from early 2010 to early 2013 and subsidence from early 2013 to 2015, consistent with the corresponding ice mass loss and gain of the entire GrIS. The peak-to-peak amplitude of the transient mass change was estimated to be −294 ± 27 Gt from GRACE mascons and -252 ± 16 Gt from the SMB where the latter value includes the effect of ice discharge. The transient mass change due to ice discharge accounted for less than 10% of the total transient mass change. Our regional assessment reveals that the central-west, southwest, northeast, and southeast regions display similar time-varying patterns as we found for the entire GrIS, but the north and northwest regions show different patterns. Atmospheric circulation anomalies as measured by the Greenland Blocking Index (GBI) are able to explain most of these transient anomalies. More specifically, high-GBI-associated high temperature was one of the main reasons for the transient mass loss of the entire GrIS during 2010-2012 while low GBI can explain the transient mass gain during 2013-2015. Contrasting behaviors of precipitation anomalies in east and west Greenland under abnormally high or low GBI conditions may explain the different patterns of the transient mass change in the northwest and the rest of Greenland.
Imaging guided ablation therapy has been applied in both biomedical research and clinical trials and turned out to be one of the most promising approaches for cancer treatment. Herein, the ...multifunctional nanocapsules were fabricated through loading perfluorooctylbromide (PFOB) and superparamagnetic iron oxide nanoparticles (SPIOs) into poly(lactic acid) (PLA) nanocapsules (NCs), followed by the formation of PEGylated gold nanoshell on the surface. The resulting multi-component NCs were proved to be able to act as nanotheranostic agent to achieve successful bimodal ultrasound (US)/magnetic resonance imaging (MRI) guided photothermal ablation in human tumor xenograft models non-invasively. Such a single theranostic agent with the combination of real-time US and high-resolution MR imaging would be of great value to offer more comprehensive diagnostic information and dynamics of disease progression for the accurate location of therapeutic focusing spot in the targeted tumor tissue, showing great potential as an effective nanoplatform for contrast imaging guided photothermal therapy.
The Global Positioning System (GPS) and Gravity Recovery and Climate Experiment (GRACE) provide important geodetic datasets to study glacial mass change. Applying the multichannel singular spectral ...analysis to the GPS-measured vertical and horizonal crustal displacement and GRACE-derived vertical displacement near Jakobshavn Isbræ (JI) in western Greenland from 2007 to 2017, we reconstruct the short-term loading displacements due to ice mass changes. Both the vertical and east displacements show strong seasonal variability. They also reveal three episodes of transient displacements: downward and eastward motion from late 2007 to around 2010, sustained upward and westward motion from 2010 to early 2013, and downward and eastward motion till late 2016. We also forward model the seasonal and transient displacements caused by surface mass balance (SMB) and glacier dynamics. Our model agrees well with the geodetic observations and provides quantitative insights into the contribution from SMB and ice dynamics to the ice mass changes. We find that SMB is the dominant contributor to the seasonal and transient displacements at three out of four GPS sites (AASI, ILUL, and QEQE). While, at the fourth GPS site (KAGA) that is closest to the glacier, the contributions to the transient displacements from SMB and glacier dynamics are comparable. The forward modeling also suggests that the dynamic mass change in the JI catchment underwent strong seasonal variations and these variations correlated more with the seasonal retreat and advance of the calving front than with the changes of glacial velocities. Our altimetry results reveal that the frontal portion of JI catchment lost 34 Gt in 2012 and this loss of ice declined to only 11 Gt in 2016 due to widespread thickening along the main flowline.
•Geodetic data reveal short-term ice mass changes near Jakobshavn Isbræ (JI).•JI underwent three episodes of transient mass changes from 2007 to 2017.•SMB is the dominant contributor to the bedrock's transient displacements.•Ice discharge and calving contributed differently to dynamical ice mass changes.•Altimetry data first reveal the widespread thickening along JI's main flowline.
A Bayesian deep learning (DL) scheme is proposed for simultaneous inverse design and uncertainty qualification (UQ) for frequency-selective rasorber (FSR) with switchable and tunable (S/T) abilities. ...The inversely designed FSR could work in single/two passband modes with bilateral absorption bands, where the tunable passband is controlled by varactor diodes, and the number of passbands is switched by elaborately designed bias lines. Further, the constraints of resonance are embedded into the inverse-design process based on the equivalent circuit model (ECM). In the uncertainty quantification process, both data uncertainty and model uncertainty of predicted S-parameters are modeled by the Bayesian neural network (BNN), whose effectiveness is verified by the correlation coefficient between true error and predicted uncertainty. At last, the inversely designed FSR sample is manufactured and measured, where the electromagnetic (EM) responses including S-parameters and absorption bands verify the accuracy and efficiency of the proposed method.
Flexibly and actively updating expectations based on feedback is crucial for navigating daily life. Previous research has shown that people with schizophrenia (PSZ) have difficulty adjusting their ...expectations. However, there are studies suggesting otherwise. To explore this further, we used a novel trial-based expectation updating paradigm called attribute amnesia. In the task, the participants needed to report the location of a target stimulus among distractors in pre-surprise trials. In the surprise trial, they were unexpectedly asked to report the identity of the target before reporting its location. Afterward, control trials were conducted whereby the participants were asked the same questions as in the surprise trial. Notably, the surprise trial and control trials were nearly identical, except that the participants expected to be asked about identity information in the control trials but not in the surprise trial. Thus, an improvement in identity reporting accuracy in the control trials in comparison with the surprise trial indicated active updating of expectations. In the current study, a total of 63 PSZ and 60 healthy control subjects (HCS) were enrolled. We found that both the PSZ and the HCS were unable to report information that they had fully attended to (i.e., identity) in the surprise trial. However, both groups showed a significant improvement in reporting identity information even in the first control trial. Critically, there was no significant difference in the magnitude of improvement between the two groups. The current findings indicate that PSZ have the ability to update their expectations as quickly and flexibly as HCS, at least in the context of the current task. The possible factors that might contribute to the discrepancy regarding expectation updating are discussed.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Study Design:
Retrospective study.
Objective:
Current studies suggested that the posterior cervical deep muscles should be preserved during the atlantoaxial posterior approach. This study aimed to ...modify the conventional temporary posterior fixation by preserving the semispinalis cervicis and to evaluate the radiographic and clinical outcomes compared with the conventional technique.
Methods:
Applied anatomical and imaging study were assessed prior to the clinical studies. Thirty patients with odontoid fracture were enrolled. 12 patients underwent modified operation with preservation of semispinalis cervicis (Group P-SSC), and 18 patients underwent conventional approach with detachment of the semispinalis cervicis (Group D-SSC) as controls. Clinical and radiological assessments were evaluated postoperatively, including activities of daily living (ADL), axial symptom scoring system (Ass), cervical range of motion (ROM), and the average atrophy rate of muscles.
Results:
All patients experienced fracture healed within 10 months after temporary fixation. At early follow-up, ADL accompanying extension and flexion were significantly different between the two groups. The Ass scores in the Group P-SSC were constantly higher than that in Group D-SSC. Flexion-Extension ROM in Group P-SSC was significantly larger than that of Group D-SSC. The average atrophy rate at the C3 and C5 level in Group P-SSC was 7.62±3.38% and 7.55±3.89%, repectivcly, while 15.67±5.97% and 8.56±4.76% in Group D-SSC, respectively. Significant differences in the atrophy rate were found between groups at C3 level.
Conclusions:
Compared with the conventional technique, the modified surgical technique with preservation of semispinalis cervicis was effective in improving axial symptoms, decreasing the atrophy rate of muscles, and increasing the cervical ROM.
Lithium sulfide (Li2S) is an attractive cathode material for lithium–sulfur batteries due to its matching with the lithium‐metal‐free anode, but limited by its preparation and processing difficulty, ...low electronic conductivity, and high dissolution of polysulfide intermediates. Herein, a novel, low‐cost, and scalable method (termed as inverse fabrication route) is proposed to directly prepare Li2S‐based electrodes. This methodology uniformly anchors in situ generated Li2S nanocrystals with a controllable size of 5–10 nm on the woven carbon fibers (WCF) substrate to fabricate a spatial conductive network structure, which provides continuous high‐speed pathways for electron/ion transport. Furthermore, Li2S nanocrystals are encapsulated into a nitrogen/fluorine (N/F) codoped carbon framework to directly fabricate a spatial structure of Li2S‐nanocrystals @ doped‐carbon/WCF (Li2S @ DC/WCF) composite cathode. N/F codoped carbon yields certain catalytic effects on the electrochemical redox reaction for lithium–sulfur batteries, and N‐containing groups in carbon lead to a strong chemical interaction with Li2S/lithium polysulfides, thus improving the electrochemical reaction kinetics and suppressing the polysulfide shuttle. Hence, the as‐prepared Li2S @ DC/WCF composite cathode exhibits a high discharge capacity of 913 mA h g−1 at 0.2C, and the discharge capacity remains at 98% even after 200 cycles at 1C, corresponding to an average capacity decay of 0.01% cycle−1.
A spatial structure of Li2S‐nanocrystals@doped‐carbon/woven carbon fiber composite cathode is constructed by a novel inverse fabrication strategy. The structure provides high‐speed pathways for electron/ion transport, the N/F codoped carbon yields certain catalytic effects, and the N‐containing groups lead to a strong chemical interaction with lithium polysulfides, thus improving the electrochemical kinetics and suppressing the polysulfide shuttle to enhance the electrochemical performance.
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