Search

The Jiangmen Underground Neutrino Observatory (JUNO) is a multi-purpose experiment, under construction in southeast China, that is designed to determine the neutrino mass ordering and precisely measure neutrino oscillation parameters. Monte Carlo simulation plays an important role for JUNO detector design, detector commissioning, offline data processing, and physics processing. The JUNO experiment has the world's largest liquid scintillator detector instrumented with many thousands of PMTs. The broad energy range of interest, long lifetime, and the large scale present data processing challenges across all areas. This paper describes the JUNO simulation software, highlighting the challenges of JUNO simulation and solutions to meet these challenges, including such issues as support for time-correlated analysis, event mixing, event correlation and handling the simulation of many millions of optical photons. [ABSTRACT FROM AUTHOR]

It is critical to construct an accurate optical model of photomultiplier tubes (PMTs) in many applications to describe the angular and spectral responses of the photon detection efficiency (PDE) of the PMTs in their working media. In this study, we propose a new PMT optical model to describe both light interactions with the PMT window and optical processes inside PMTs with reasonable accuracy based on the optics theory and a GEANT4-based simulation toolkit. The proposed model builds a relationship between the PDE and the underlying processes that the PDE relies on. This model also provides a tool to transform the PDE measured in one working medium (like air) to the PDE in other media (like water, liquid scintillator, etc). Using two 20 ″ MCP-PMTs and one 20 ″ dynode PMT, we demonstrate a complete procedure to obtain the key parameters used in the model from experimental data, such as the optical properties of the antireflective coating and photocathode of the three PMTs. The proposed model can effectively reproduce the angular responses of the quantum efficiency of PMTs, even though an ideally uniform photocathode is assumed in the model. Interestingly, the proposed model predicts a similar level (20–30%) of light yield excess observed in the experimental data of many liquid scintillator-based neutrino detectors, compared with that predicted at the stage of detector design. However, this excess has never been explained, and the proposed PMT model provides a good explanation for it, which highlights the imperfections of PMT models used in their detector simulations. [ABSTRACT FROM AUTHOR]

The classical geodesics of timelike particles in Schwarzschild spacetime is analyzed according to the particle starting radius r, velocity v and angle α against the radial outward direction in the reference frame of an local static observer. The region of escape, bound and capture orbits in the parameter space of (r , v , α) are solved using the three cases of the effective potential. It is found that generally for radius smaller than 4M or velocity larger than c / 2 there will be no bound orbits. While for fixed radius larger than 4M (or velocity smaller than c / 2 ), as velocity (or radius) increase from zero (or 2M), the particle is always captured until a critical value v crit 1 (or r crit 1 ) when the bound orbit start to appear around α = π / 2 between a double-napped cone structure. As the velocity (or radius) increases to another critical value v crit 2 (or r crit 2 ) then the bound directions and escape directions in the outward cone become escape directions, leaving only the inward cone separating the capture and bound directions. The angle of this cone will increase to its asymptotic value as velocity (or radius) increases to its asymptotic value. The implication of these results in shadow of black holes formed by massive particles, in black hole accretion and in spacecraft navigation is briefly discussed. [ABSTRACT FROM AUTHOR]

In the version of this article initially published, there was only one author marked as corresponding author. Since Ziyan Deng and Guofu Cao have almost equal contributions to the development of the JUNO simulation software, so making both Ziyan Deng and Guofu Cao as the corresponding authors can correctly reflect the contributions in this work. [Extracted from the article]

Together with the big datamovement,many organizations collect their own big data and build distinctive applications. In order to provide smart services upon big data, massive variable data should be well linked and organized to form Data Ocean, which specially emphasizes the deep exploration of the relationships among unstructured data to support smart services. Currently, almost all of these applications have to deal with unstructured data by integrating various analysis and search techniques upon massive storage and processing infrastructure at the application level, which greatly increase the difficulty and cost of application development. This paper presents D-Ocean, an unstructured data management system for data ocean environment. D-Ocean has an open and scalable architecture, which consists of a core platform, pluggable components and auxiliary tools. It exploits a unified storage framework to store data in different kinds of data stores, integrates batch and incremental processing mechanisms to process unstructured data, and provides a combined search engine to conduct compound queries. Furthermore, a so-called RAISE process modeling is proposed to support the whole process of Repository, Analysis, Index, Search and Environment modeling, which can greatly simplify application development. The experiments and use cases in production demonstrate the efficiency and usability of D-Ocean. [ABSTRACT FROM AUTHOR]

The MapReduce framework has become the de facto standard for big data processing due to its attractive features and abilities. One is that it automatically parallelizes a job into multiple tasks and transparently handles task execution on a large cluster of commodity machines. The increasing heterogeneity of distributed environments may result in a few straggling tasks, which prolong job completion. Speculative execution is proposed to mitigate stragglers. However, the existing speculative execution mechanism could not work efficiently as many speculative tasks are still slower than their original tasks. In this paper, we explore an approach to increase the efficiency of speculative execution, and further improve MapReduce performance. We propose the Partial Speculative Execution (PSE) strategy to make speculative tasks start from the checkpoint. By leveraging the checkpoint of original tasks, PSE can eliminate the costs of re-reading, re-copying, and re-computing the processed data. We implement PSE in Hadoop, and evaluate its performance in terms of job completion time and the efficiency of speculative execution under several kinds of classical workloads. Experimental results show that, in heterogeneous environments with stragglers, PSE completes jobs 56 % faster than that with no speculation and 12 % faster than that with LATE, an improved speculative execution algorithm. In addition, on average PSE can improve the efficiency of speculative execution by 24 % compared to LATE. [ABSTRACT FROM AUTHOR]

Abstract. The optimal k-restricted 2-factor problem consists of finding, in a complete undirected graph K[sub n] a minimum cost 2-factor (subgraph having degree 2 at every node) with all components having more than k nodes. The problem is a relaxation of the well-known symmetric travelling salesman problem, and is equivalent to it when n/2 Is less than or equal to k Is less than or equal to n - 1. We study the k-restricted 2-factor polytope. We present a large class of valid inequalities, called bipartition inequalities, and describe some of their properties; some of these results are new even for the travelling salesman polytope. For the case k = 3, the triangle-free 2-factor polytope, we derive a necessary and sufficient condition for such inequalities to be facet inducing. [ABSTRACT FROM AUTHOR]

The permutahedron of a poset is the convex hull of all incidence vectors of linear extensions. For the case of N-sparse posets in which any five elements induce at most one N we give a characterization of the permutahedron in terms of linear inequalities. This yields an LP-solution for minimizing the weighted mean completion time for jobs with unit processing times and N-sparse precedence constraints. We close with an extension of our approach to arbitrary processing times. [ABSTRACT FROM AUTHOR]

We introduce a projective approach for studying symmetric travelling salesman polytopes (STSPs). The symmetric travelling salesman polytope STSP( V) (resp., Hamiltonian path polytope HP( V)) is the convex hull of incidence vectors of all Hamiltonian cycles (resp., paths) on the complete undirected graph with node set V. For any node h ∉ V, HP( V) is a projection of STSP( V ⋃ { h}). We show that HP( V) and STSP( V ⋃ { h}) are isomorphic, and HP( V) is of full dimension minus one. By this projective approach, we obtain general clique-lifting results, all based on simple conditions, for deriving large new classes of STSP facets. These results apply to all known non-trivial STSP facets, and generalize clique-lifting results of Maurras (1975), Grötschel and Padberg (1979) and Naddef and Rinaldi (1988). [ABSTRACT FROM AUTHOR]

Self-supported Fe3N-Co2N nanoarray with high electric conductivity and large surface area was prepared for growth of MIPs and further constructing a sensitive and stable electrochemical sensor. For the evaluation of its performance, Fe3N-Co2N is used as sensing electrode material, and AMP is used as template molecule to construct the MIP electrochemical sensor. Under the optimized conditions, the developed MIPs electrochemical sensor detects AMP with a low detection limit of 3.65 × 10−10 mol L−1 and shows outstanding reproducibility and stability. When the MIPs electrochemical sensor was applied to detect AMP in milk samples via standard addition method, the recovery within 97.06–102.43% with RSD of 1.05–2.11% was obtained. The fabrication of MIPs electrochemical sensor is highly promising for sensitive and selective electrochemical measurement and food safety testing. This work can provide theoretical guidance for truly challenging problems. [ABSTRACT FROM AUTHOR]

The existence and stability of circular orbits (CO) in static and spherically symmetric (SSS) spacetime are important because of their practical and potential usefulness. In this paper, using the fixed point method, we first prove a necessary and sufficient condition on the metric function for the existence of timelike COs in SSS spacetimes. After analyzing the asymptotic behavior of the metric, we then show that asymptotic flat SSS spacetime that corresponds to a negative Newtonian potential at large r will always allow the existence of CO. The stability of the CO in a general SSS spacetime is then studied using the Lyapunov exponent method. Two sufficient conditions on the (in)stability of the COs are obtained. For null geodesics, a sufficient condition on the metric function for the (in)stability of null CO is also obtained. We then illustrate one powerful application of these results by showing that three SSS spacetimes whose metric function is not completely known will allow the existence of timelike and/or null COs. We also used our results to assert the existence and (in)stabilities of a number of known SSS metrics. [ABSTRACT FROM AUTHOR]

In this work, a novel label-free electrochemical immunosensor was developed for the quantitative detection of alpha fetoprotein (AFP). Multifunctionalized graphene nanocomposites (TB-Au-Fe3O4-rGO) were applied to modify the electrode to achieve the amplification of electrochemical signal. TB-Au-Fe3O4-rGO includes the advantages of graphene, ferroferric oxide nanoparticles (Fe3O4 NPs), gold nanoparticles (Au NPs) and toluidine blue (TB). As a kind of redox probe, TB can produce the electrochemical signal. Graphene owns large specific surface area, high electrical conductivity and good adsorption property to load a large number of TB. Fe3O4 NPs have good electrocatalytic performance towards the redox of TB. Au NPs have good biocompatibility to capture the antibodies. Due to the good electrochemical performance of TB-Au-Fe3O4-rGO, the effective and sensitive detection of AFP was achieved by the designed electrochemical immunosensor. Under optimal conditions, the designed immunosensor exhibited a wide linear range from 1.0 × 10−5 ng/mL to 10.0 ng/mL with a low detection limit of 2.7 fg/mL for AFP. It also displayed good electrochemical performance including good reproducibility, selectivity and stability, which would provide potential applications in the clinical diagnosis of other tumor markers. [ABSTRACT FROM AUTHOR]