84 research outputs found
Online Network Slicing for Real Time Applications in Large-scale Satellite Networks
In this work, we investigate resource allocation strategy for real time
communication (RTC) over satellite networks with virtual network functions.
Enhanced by inter-satellite links (ISLs), in-orbit computing and network
virtualization technologies, large-scale satellite networks promise global
coverage at low-latency and high-bandwidth for RTC applications with
diversified functions. However, realizing RTC with specific function
requirements using intermittent ISLs, requires efficient routing methods with
fast response times. We identify that such a routing problem over time-varying
graph can be formulated as an integer linear programming problem. The branch
and bound method incurs time
complexity, where is the number of nodes, and
is the number of links during time interval . By
adopting a k-shortest path-based algorithm, the theoretical worst case
complexity becomes .
Although it runs fast in most cases, its solution can be sub-optimal and may
not be found, resulting in compromised acceptance ratio in practice. To
overcome this, we further design a graph-based algorithm by exploiting the
special structure of the solution space, which can obtain the optimal solution
in polynomial time with a computational complexity of
. Simulations conducted on starlink constellation with
thousands of satellites corroborate the effectiveness of the proposed
algorithm.Comment: Accepted to appear in IEEE ICC 202
Translational and rotational dynamical heterogeneities in granular systems
We use X-ray tomography to investigate the translational and rotational
dynamical heterogeneities of a three dimensional hard ellipsoids granular
packing driven by oscillatory shear. We find that particles which translate
quickly form clusters with a size distribution given by a power-law with an
exponent that is independent of the strain amplitude. Identical behavior is
found for particles that are translating slowly, rotating quickly, or rotating
slowly. The geometrical properties of these four different types of clusters
are the same as those of random clusters. Different cluster types are
considerably correlated/anticorrelated, indicating a significant coupling
between translational and rotational degrees of freedom. Surprisingly these
clusters are formed already at time scales that are much shorter than the
relaxation time, in stark contrast to the behavior found in
glass-forming systems.Comment: 9 page
Structural and Topological Nature of Plasticity in Sheared Granular Materials
Upon mechanical loading, granular materials yield and undergo plastic
deformation. The nature of plastic deformation is essential for the development
of the macroscopic constitutive models and the understanding of shear band
formation. However, we still do not fully understand the microscopic nature of
plastic deformation in disordered granular materials. Here we used synchrotron
X-ray tomography technique to track the structural evolutions of
three-dimensional granular materials under shear. We establish that highly
distorted coplanar tetrahedra are the structural defects responsible for
microscopic plasticity in disordered granular packings. The elementary plastic
events occur through flip events which correspond to a neighbor switching
process among these coplanar tetrahedra (or equivalently as the rotation motion
of 4-ring disclinations). These events are discrete in space and possess
specific orientations with the principal stress direction.Comment: 26 pages, 11 figures, 2 tables, to be published in Nature
Communication
Biomineralization of a calcifying ureolytic bacterium Microbacterium sp. GM-1
Background: Biomineralization is a significant process performed by
living organisms in which minerals are produced through the hardening
of biological tissues. Herein, we focus on calcium carbonate
precipitation, as part of biomineralization, to be used in applications
for environmental protection, material technology, and other fields. A
strain GM-1, Microbacterium sp. GM-1, isolated from active sludge,
was investigated for its ability to produce urease and induce calcium
carbonate precipitation in a metabolic process. Results: It was
discovered that Microbacterium sp. GM-1 resisted high concentrations of
urea up to 60 g/L. In order to optimize the calcification process of
Microbacterium sp. GM-1, the concentrations of Ni2+ and urea, pH value,
and culture time were analyzed through orthogonal tests. The favored
calcite precipitation culture conditions were as follows: the
concentration of Ni2+ and urea were 50 \u3bcM and 60 g/L,
respectively, pH of 10, and culture time of 96 h. Using X-ray
diffraction analysis, the calcium carbonate polymorphs produced by
Microbacterium sp. GM-1 were proven to be mainly calcite. Conclusions:
The results of this research provide evidence that Microbacterium sp.
GM-1 can biologically induce calcification and suggest that strain GM-1
may play a potential role in the synthesis of new biominerals and in
bioremediation or biorecovery
Prediction of potential evapotranspiration using temperature-based heuristic approaches
The potential or reference evapotranspiration (ET0) is considered as one of the fundamental variables for irrigation management, agricultural planning, and modeling different hydrological pr?Cesses, and therefore, its accurate prediction is highly essential. The study validates the feasibility of new temperature based heuristic models (i.e., group method of data handling neural network (GMDHNN), multivariate adaptive regression spline (MARS), and M5 model tree (M5Tree)) for estimating monthly ET0. The outcomes of the newly developed models are compared with empirical formulations including Hargreaves-Samani (HS), calibrated HS, and Stephens-Stewart (SS) models based on mean absolute error (MAE), root mean square error (RMSE), and Nash-Sutcliffe efficiency. Monthly maximum and minimum temperatures (Tmax and Tmin) observed at two stations in Turkey are utilized as inputs for model development. In the applications, three data division scenarios are utilized and the effect of periodicity component (PC) on models’ accuracies are also examined. By importing PC into the model inputs, the RMSE accuracy of GMDHNN, MARS, and M5Tree models increased by 1.4%, 8%, and 6% in one station, respectively. The GMDHNN model with periodic input provides a superior performance to the other alternatives in both stations. The recommended model reduced the average error of MARS, M5Tree, HS, CHS, and SS models with respect to RMSE by 3.7–6.4%, 10.7–3.9%, 76–75%, 10–35%, and 0.8–17% in estimating monthly ET0, respectively. The HS model provides the worst accuracy while the calibrated version significantly improves its accuracy. The GMDHNN, MARS, M5Tree, SS, and CHS models are also compared in estimating monthly mean ET0. The GMDHNN generally gave the best accuracy while the CHS provides considerably over/under-estimations. The study indicated that the only one data splitting scenario may mislead the modeler and for better validation of the heuristic methods, more data splitting scenarios should be applied
Risk Analysis of Reservoir Flood Routing Calculation Based on Inflow Forecast Uncertainty
Possible risks in reservoir flood control and regulation cannot be objectively assessed by deterministic flood forecasts, resulting in the probability of reservoir failure. We demonstrated a risk analysis of reservoir flood routing calculation accounting for inflow forecast uncertainty in a sub-basin of Huaihe River, China. The Xinanjiang model was used to provide deterministic flood forecasts, and was combined with the Hydrologic Uncertainty Processor (HUP) to quantify reservoir inflow uncertainty in the probability density function (PDF) form. Furthermore, the PDFs of reservoir water level (RWL) and the risk rate of RWL exceeding a defined safety control level could be obtained. Results suggested that the median forecast (50th percentiles) of HUP showed better agreement with observed inflows than the Xinanjiang model did in terms of the performance measures of flood process, peak, and volume. In addition, most observations (77.2%) were bracketed by the uncertainty band of 90% confidence interval, with some small exceptions of high flows. Results proved that this framework of risk analysis could provide not only the deterministic forecasts of inflow and RWL, but also the fundamental uncertainty information (e.g., 90% confidence band) for the reservoir flood routing calculation
Overexpression of MicroRNA-30b Improves Adenovirus-Mediated p53 Cancer Gene Therapy for Laryngeal Carcinoma
MicroRNAs play important roles in laryngeal carcinoma and other cancers. However, the expression of microRNAs in paracancerous tissue has been studied less. Here, using laser capture microdissection (LCM), we detected the expression of microRNAs in paracancerous tissues. Among all down-regulated microRNAs in the center area of tumor tissues, only miR-30b expression was significantly reduced in paracancerous tissues compared to surgical margins. Therefore, to further investigate the effect of miR-30b on laryngeal carcinoma, we stably overexpressed miR-30b in laryngeal carcinoma cell line HEp-2 cells. It was found that although there was no significant difference in cell viability between miR-30b overexpressed cells and control HEp-2 cells, p53 expression was obviously enhanced in miR-30b overexpressed cells. Whether miR-30b could improve the anti-tumor effect of adenovirus-p53 (Ad-p53) in laryngeal carcinoma and other cancer cell lines was also evaluated. It was found that in miR-30b overexpressed HEp-2 cells, p53-mediated tumor cell apoptosis was obviously increased both in vitro and in vivo. MDM2-p53 interaction might be involved in miR-30b-mediated anti-tumor effect. Together, results suggested that miR-30b could modulate p53 pathway and enhance p53 gene therapy-induced apoptosis in laryngeal carcinoma, which could provide a novel microRNA target in tumor therapy
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