Edge computing (EC) has quickly ascended to be the de-facto standard for hosting emerging low-latency applications, as exemplified by intelligent video surveillance, Internet of Vehicles, and ...augmented reality. For EC, service function chaining is envisioned as a promising approach to configure various services in an agile, flexible, and cost-efficient manner. When running on top of geographically dispersed edge clouds, fully unleashing the benefits of service function chaining is, however, by no means trivial. In this paper, we propose an online orchestration framework for cross-edge service function chaining, which aims to maximize the holistic cost efficiency, via jointly optimizing the resource provisioning and traffic routing on-the-fly. This long-term cost minimization problem is difficult since it is NP-hard and involves future uncertain information. To simultaneously address these dual challenges, we carefully combine an online optimization technique with an approximate optimization method in a joint optimization framework, through: 1) decomposing the long-term problem into a series of one-shot fractional problem with a regularization technique and 2) rounding the fractional solution to a near-optimal integral solution with a randomized dependent scheme that preserves the solution feasibility. The resulting online algorithm achieves an outstanding performance guarantee, as verified by both rigorous theoretical analysis and extensive trace-driven simulations.
A wideband circularly polarized (CP) patch antenna with enhanced axial ratio (AR) bandwidth via co-design of feeding network is proposed in this paper. One <inline-formula> <tex-math ...notation="LaTeX">\pmb \lambda/4 </tex-math></inline-formula> resonator and one <inline-formula> <tex-math notation="LaTeX">\pmb \lambda/2 </tex-math></inline-formula> resonator are introduced and coupled in proximity to two orthogonal points of a square patch radiator to excite two orthogonal modes. These two resonators not only function as impedance matching elements to achieve equal magnitude of two orthogonal modes in a wide frequency band but also provide the required 90° phase difference. In this way, two minima in the AR response appear, resulting in extended AR bandwidth. The wideband design of the antenna is carried out based on the equivalent circuit model, where the patch radiator is treated as a conductance, inductance, and capacitance parallel resonator. In particular, the feeding network and the patch are jointly considered as a three-port network for synthesis design. By mapping the radiated far field to the magnitude and phase on the radiation conductance in the circuit model, the AR response of the antenna becomes predictable in a straightforward manner. Measured results experimentally demonstrate that the 3-dB AR bandwidth of our proposed CP patch antenna is 2.7 times that of the traditional one fed with two 90° offset lines.
To deal with increasing energy consumption in the residential sector, distributed energy resources including photovoltaic (PV), fuel cell, etc. have been paid more and more attention. In this study, ...an optimization model is developed for the PV/Fuel Cell/Battery based residential energy system. While guaranteeing reliable system operation, the model may determine the optimal running strategies with annual running cost or annual CO2 emissions as the objective function to be minimized. In addition, besides the energy flows among the equipments within the hybrid energy system, the economic information including electricity tariff and natural gas price, as well as some policy issues (e.g., buy-back price) are also accounted. As the results of the model, besides the optimal electric and thermal balances, the rational utilization forms of PV module, fuel cell and battery can be also deduced. To verify the viability of the proposed approach, a numerical example is implemented and analyzed. The optimal operating strategies are deduced and compared from different perspectives. Furthermore, the results demonstrate that the PV module mainly contributes to the environmental performance of the assumed hybrid energy system, while the battery may be beneficial from the economic viewpoint.
•An optimization model is developed for a hybrid PV/fuel cell/battery energy system.•Both economic and environmental objective functions have been considered.•The PV module mainly contributes to the environmental performance.•The battery bank may be beneficial from the economic point of view.•Both battery size and buy-back price may influence the system performances.
The effects of economic development on natural environment is explored by momentous literature, this study focuses on exploring the role of institutional quality for environmental protection in the ...selected One Belt One Road (OBOR) economies. The main goal of the paper is to find the threshold level of institutional quality that may minimize CO2 emissions in the atmosphere due to widespread industrialization and transportation. The data is selected for the panel of 33 OBOR economies over the time period of 1986-2018. The panel threshold regression technique is applied to determine the threshold level of institutional quality. The estimated results of the study reveal that 2.315 is the threshold level of institutional quality in selected partner OBOR countries. If quality of institutions is above the threshold level then CO2 emission do not contribute significantly for environmental deterioration in spite of growing industrialization and transportation and vice versa. The study emphasized to improve the institutional quality up to threshold level to get potential gains from industrialization and transportation.
A single-layer microstrip-fed patch antenna with capabilities of both bandwidth enhancement and harmonic suppression is proposed. For this purpose, a pair of λ/4 microstrip-line resonators is ...introduced and coupled in proximity to a rectangular patch. The wideband property can be obtained by making effective use of the two resonances introduced by the radiating patch and nonradiating λ/4 resonators. Different from other reported dual-resonance patch antennas, the proposed antenna does not require the electrically thick substrate, so it has attractive low-profile property. Thanks to the good features of λ/4 resonators and capacitive feeding scheme, harmonic radiating modes of the patch antenna can be significantly suppressed as highly demanded in modern highly integrated communication systems. The working principle, equivalent circuit, and design procedure are extensively described. Finally, a prototype antenna operating at 4.9 GHz is designed and fabricated. The measured results show that its bandwidth is 2.7 times wider than that of the traditional insert-fed patch counterpart, and the harmful spurious radiation from other higher order radiating modes has been effectively suppressed.
Internet of Things (IoT) have widely penetrated in different aspects of modern life and many intelligent IoT services and applications are emerging. Recently, federated learning is proposed to train ...a globally shared model by exploiting a massive amount of user-generated data samples on IoT devices while preventing data leakage. However, the device, statistical and model heterogeneities inherent in the complex IoT environments pose great challenges to traditional federated learning, making it unsuitable to be directly deployed. In this paper, we advocate a personalized federated learning framework in a cloud-edge architecture for intelligent IoT applications. To cope with the heterogeneity issues in IoT environments, we investigate emerging personalized federated learning methods which are able to mitigate the negative effects caused by heterogeneities in different aspects. With the power of edge computing, the requirements for fast-processing capacity and low latency in intelligent IoT applications can also be achieved. We finally provide a case study of IoT based human activity recognition to demonstrate the effectiveness of personalized federated learning for intelligent IoT applications.
Although spinel ferrite (MFe
O
, M = Zn, Ni, Mn, etc.) has been reported as a promising catalyst, its low photocatalytic activity under visible light greatly restricts its practical application. ...Spinel ferrite-based photocatalytic composites have exhibited improved efficiency for pollutant degradation, due to interface charge carrier mobility and structural modification. Meanwhile, due to its magnetism and stability, spinel ferrite composite can be easily recycled for long-term utilization, showing its high application potential. In this review, the recent advances in the construction and photocatalytic degradation of spinel ferrite composites are discussed, with an emphasis on the relationship between structural property and photocatalytic activity. In addition, to improve their photocatalytic application, the challenges, gaps and future research prospects are proposed.
As an emerging material, nanomaterials have attracted extensive attention due to their small size, surface effect and quantum tunneling effect, as well as potential applications in traditional ...materials, medical devices, electronic devices, coatings and other industries. Herein, the influence of nanoparticle selection, production process, grain size, and grain boundary structures on the mechanical properties of nanomaterials is introduced. The current research progress and application range of nano-materials are presented. The unique properties of nano-materials make them superior over traditional materials. Therefore, nanomaterials will have a broader application prospect in the future. Research on nanomaterials is significant for the development and application of materials science.
The plugging phenomenon near the well zone of oil injection well will seriously affect the water injection development of oil field, and then affect the exploitation of oil resources. The water ...injection development of low permeability reservoir is affected by various factors. Due to the large difference between layers and the serious interference between layers, the physical property of oil layer is relatively poor, and the water injection pressure shows a trend of increasing year by year, which has a great impact on the development of oil resources. As the oilfield development benefit is not ideal, it is necessary to take reasonable measures to reduce the pressure of water injection to ensure the effect of water injection to improve the recovery of the reservoir. At present, the technology has been mature, which can reduce the pressure of water injection and ensure the oil recovery rate. The application in several oil Wells has verified the correctness of this conclusion.
Seizing the main contradiction of fast water-bearing rebound in western block III, analyzing the reasons of fast water-bearing rebound in response to the contradiction, meanwhile, by understanding ...the mechanism of polymer oil drive and combining the development effect of three western injection and gathering blocks, finding out that the main problem of slowing down water-bearing rebound is the establishment of pressure system, and therefore the corresponding management measures at the injection and extraction ends respectively.
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