The huge amount of data generated by the Internet of Things (IoT) devices needs the computational power and storage capacity provided by cloud, edge, and fog computing paradigms. Each of these ...computing paradigms has its own pros and cons. Cloud computing provides enhanced data storage and computing power but causes high communication latency. Edge and fog computing provide similar services with lower latency but limited capacity, capability, and coverage. A single computing paradigm cannot fulfill all the requirements of IoT devices and a federation between them is needed to extend their capacity, capability, and services. This federation is beneficial to both subscribers and providers and also reveals research issues in traffic offloading between clouds, edges, and fogs. Optimization has traditionally been used to solve the problem of traffic offloading. However, in such a complex federated system, traditional optimization cannot keep up with the strict latency requirements of decision-making, ranging from milliseconds to sub-seconds. Machine learning approaches, especially reinforcement learning, are consequently becoming popular because they could quickly solve offloading problems in dynamic environments with some unknown information. This study provides a novel federal classification between cloud, edge, and fog and presents a comprehensive research roadmap on offloading for different federated scenarios. We survey the relevant literature on the various optimization approaches used to solve this offloading problem and compare their salient features. We then provide a comprehensive survey on offloading in federated systems with machine learning approaches and the lessons learned as a result of these surveys. Finally, we outline several directions for future research and challenges that have to be faced in order to achieve such a federation.
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bstract
We bootstrap
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1
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superconformal field theories in six dimensions, by analyzing the four-point function of flavor current multiplets. Assuming
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8
flavor group, we present universal ...bounds on the central charge
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and the flavor central charge
C
J
. Based on the numerical data, we conjecture that the rank-one E-string theory saturates the universal lower bound on
C
J
, and numerically determine the spectrum of long multiplets in the rank-one E-string theory. We comment on the possibility of solving the higher-rank E-string theories by bootstrap and thereby probing M-theory on
AdS
7
×
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ℤ
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•Ni/C composite derived from Ni-metal organic framework was synthesized.•Hollow structure contributed to the electromagnetic absorption.•The optimal RL of Ni/C composite reached ...−57.25 dB.•Effective absorption bandwidth achieved 5.1 GHz with a thin thickness of 1.8 mm.
Hollow nickel/carbon (Ni/C) microsphere was synthesized by in situ pyrolysis of the Ni-based trimellitic acid framework (Ni-MOF) at argon atmosphere. The morphology of Ni-MOF precursor can be easily controlled by adjusting the volume ratio of DMF and H2O in solvothermal process. When the volume ratio of DMF: H2O is 2: 1, hollow Ni-MOF microspheres can be obtained and the corresponding Ni/C composite exhibits extremely strong electromagnetic wave absorption. The maximum reflection loss is up to −57.25 dB with the matching thickness of only 1.8 mm, while the corresponding effective absorption bandwidth (reflection loss below −10 dB) achieves 5.1 GHz. The excellent electromagnetic wave absorbing capabilities is related to the hollow structure and the synergistic effect between carbon and nickel nanoparticles. This work confirms that the as-prepared Ni/C composite with superior electromagnetic wave absorption properties is a promising candidate for lightweight electromagnetic wave absorbing materials.
A multi-omics quantitative integrative analysis of lignin biosynthesis can advance the strategic engineering of wood for timber, pulp, and biofuels. Lignin is polymerized from three monomers ...(monolignols) produced by a grid-like pathway. The pathway in wood formation of Populus trichocarpa has at least 21 genes, encoding enzymes that mediate 37 reactions on 24 metabolites, leading to lignin and affecting wood properties. We perturb these 21 pathway genes and integrate transcriptomic, proteomic, fluxomic and phenomic data from 221 lines selected from ~2000 transgenics (6-month-old). The integrative analysis estimates how changing expression of pathway gene or gene combination affects protein abundance, metabolic-flux, metabolite concentrations, and 25 wood traits, including lignin, tree-growth, density, strength, and saccharification. The analysis then predicts improvements in any of these 25 traits individually or in combinations, through engineering expression of specific monolignol genes. The analysis may lead to greater understanding of other pathways for improved growth and adaptation.
This paper presents a low-power 10-bit 50-MS/s successive approximation register (SAR) analog-to-digital converter (ADC) that uses a monotonic capacitor switching procedure. Compared to converters ...that use the conventional procedure, the average switching energy and total capacitance are reduced by about 81% and 50%, respectively. In the switching procedure, the input common-mode voltage gradually converges to ground. An improved comparator diminishes the signal-dependent offset caused by the input common-mode voltage variation. The prototype was fabricated using 0.13-¿m 1P8M CMOS technology. At a 1.2-V supply and 50 MS/s, the ADC achieves an SNDR of 57.0 dB and consumes 0.826 mW, resulting in a figure of merit (FOM) of 29 fJ/conversion-step. The ADC core occupies an active area of only 195 × 265 ¿m 2 .
Noncovalent weak interactions hydrophobic interaction and hydrogen (H)-bond play crucial roles in controlling the functions of biomolecules, and thus have been used to design artificial ...metalloproteins/metalloenzymes during the past few decades. In this review, we focus on the recent progresses in protein design by tuning the noncovalent interactions, including hydrophobic and H-bonding interactions. The topics include redesign and reuse of the heme pocket and other protein scaffolds, design of the heme protein interface, and de novo design of metalloproteins. The informations not only give insights into the metalloenzyme reaction mechanisms but also provide new reactions for future applications.
Transport-sharing systems are eco-friendly and the most promising services in smart urban environments, where the booming Internet of things (IoT) technologies play an important role in the smart ...infrastructure. Due to the imbalanced bike distribution, bikes and stalls in the docking stations could be unavailable when needed, leading to bad customer experiences. We develop a dynamic repositioning strategy for the management of bikes in this paper, which supports dispatchers to keep stations in service. Two open datasets are examined, and the exploratory data analysis presents that there is a significant difference of travel patterns between working and non-working days, where the former has an excess demand at rush hours and the latter is usually at a low demand. To evaluate the effect when the demand outstrips a station’s capacity, we propose a non-linear scaling technique to transform demand patterns and perform the clustering analysis for each of five categories obtained from the sophisticated analysis of the dataset. Our repositioning strategy is developed according to the transformed demands. Compared with the previous work, numerical simulations reveal that our strategy has a better performance for high-demand stations, and thus can substantially reduce the repositioning cost, which brings benefit to bike-sharing operators for managing the city bike system.
A mild and eco-friendly visible-light-induced decarboxylative acylation of quinoxalin-2(1
H
)-ones and α-oxo carboxylic acids with ambient air as the sole oxidant at room temperature was established. ...The reaction proceeded efficiently without any metal catalysts, strong oxidants or external-photosensitizers, ultimately reducing the generation of waste.
An eco-friendly visible-light-induced decarboxylative acylation of quinoxalin-2(1
H
)-ones and α-oxo carboxylic acids with air as the oxidant under external-photocatalyst-free conditions was established.
Vitamins are a class of essential nutrients in the body; thus, they play important roles in human health. The chemicals are involved in many physiological functions and both their lack and excess can ...put health at risk. Therefore, the establishment of methods for monitoring vitamin concentrations in different matrices is necessary. In this review, an updated overview of the main pretreatments and determination methods that have been used since 2010 is given. Ultrasonic assisted extraction, liquid⁻liquid extraction, solid phase extraction and dispersive liquid⁻liquid microextraction are the most common pretreatment methods, while the determination methods involve chromatography methods, electrophoretic methods, microbiological assays, immunoassays, biosensors and several other methods. Different pretreatments and determination methods are discussed.
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