Caching popular multimedia content is a promising way to unleash the ultimate potential of wireless networks. In this paper, we propose and analyze cache-based content delivery in a three-tier ...heterogeneous network (HetNet), where base stations (BSs), relays, and device-to-device (D2D) pairs are included. We advocate proactively caching popular content in the relays and parts of the users with caching ability when the network is off-peak. The cached content can be reused for frequent access to offload the cellular network traffic. The node locations are first modeled as mutually independent Poisson point processes (PPPs) and the corresponding content access protocol is developed. The average ergodic rate and outage probability in the downlink are then analyzed theoretically. We further derive the throughput and the delay based on the multiclass processor-sharing queue model and the continuous-time Markov process. According to the critical condition of the steady state in the HetNet, the maximum traffic load and the global throughput gain are investigated. Moreover, impacts of some key network characteristics, e.g., the heterogeneity of multimedia contents, node densities, and the limited caching capacities, on the system performance are elaborated on to provide valuable insight.
In this paper, we study the probabilistic caching for an N-tier wireless heterogeneous network (HetNet) using stochastic geometry. A general and tractable expression of the successful delivery ...probability (SDP) is first derived. We then optimize the caching probabilities for maximizing the SDP in the high signal-to-noise ratio regime. The problem is proved to be convex and solved efficiently. We next establish an interesting connection between N-tier HetNets and single-tier networks. Unlike the single-tier network where the optimal performance only depends on the cache size, the optimal performance of N-tier HetNets depends also on the base station (BS) densities. The performance upper bound is, however, determined by an equivalent single-tier network. We further show that with uniform caching probabilities regardless of content popularities, to achieve a target SDP, the BS density of a tier can be reduced by increasing the cache size of the tier when the cache size is larger than a threshold; otherwise, the BS density and BS cache size can be increased simultaneously. It is also found analytically that the BS density of a tier is inverse to the BS cache size of the same tier and is linear to BS cache sizes of other tiers.
► We propose an interval cross efficiency matrix. ► We extend the traditional DEA cross efficiency to a SMAA-based technique. ► The decision-maker does not need to select aggressive or benevolent ...strategy. ► Uniform and Normal distribution are assumed to represent the weight distribution.
Cross efficiency method is an extension of data envelopment analysis (DEA), and has been widely used for ranking performance of decision making units (DMUs). To eliminate the non-uniqueness of cross efficiency scores, the aggressive and benevolent strategies have been proposed as secondary goals to determine the unique cross efficiency score. The current paper aims to propose an alternative strategy which does not consider the preference of the decision maker in choosing aggressive or benevolent strategy. Instead, the paper considers all possible weight sets in weight space when computing the cross efficiency and each DMU is given an interval cross efficiency. By using the stochastic multicriteria acceptability analysis (SMAA-2) method, all DMUs in the interval cross efficiency matrix (CEM) could be fully ranked according to the acceptability indices. A numerical example about efficiency evaluation to seven academic departments in a university is illustrated.
This paper studies the optimal pricing strategy of a hotel that establishes an online distribution channel through cooperation with an online travel agency (OTA). The OTA promotes the hotel and sells ...hotel rooms through its website and receives commission from the hotel for rooms sold. Through a sequence game model, this paper derives the optimal decision on the unit commission of the hotel and the optimal response of the OTA to that commission. The paper notes management implications, including (1) occupancy rate of a hotel before opening online marketing is an important metric for securing cooperation with an OTA; that is, a hotel with lower occupancy rates is more inclined to cooperate with an OTA to achieve an improvement in profits; and (2) a hotel is inclined to establish an online channel through an OTA with many online customers and/or few listed hotels.
•Study the pricing game with OTAs when hotels open online marketing channel.•Propose a game model to describe the channel competition between hotels and OTAs.•Find the optimal pricing policy for hotels to maximize the profit.•Give suggestions for hotels how to choose appropriate online partners.
Visibly transparent solar harvesting surfaces are an exciting new approach to harvesting solar energy around buildings and mobile electronics to improve their efficiency and autonomy without ...impacting their appearance. The recent demonstration of ultraviolet (UV) and near‐infrared (NIR) selective light harvesters have enabled transparent luminescent solar concentrators (LSCs) that boast unparalleled scalability, flexibility, aesthetic quality, and affordability. Consequently, the question of the efficiency limits has emerged in these new systems. In this perspective, the theoretical efficiency limits of these concentrator systems are reviewed and practical considerations are outlined to approach these limits. For UV and UV/NIR selective harvesting single‐junction transparent LSCs are constrained thermodynamically to 21%, which increases to over 35% in fully transparent multipanel devices with light trapping. In deriving these limits, key material and engineering challenges are identified to fully optimize transparent solar concentrators that can push them towards commercial reality.
Transparent luminescent solar concentrators provide new routes to deploy solar energy over large areas without affecting the overall aesthetic quality. These new solar technologies are enabled by selectively harvesting ultraviolet or infrared parts of the solar spectrum. In this report, these systems are reviewed in the context of idealized configurations, efficiency limits, scalability, and properties of enabling classes of materials.
Monitoring and maintaining the health of wind turbine blades has long been one of the challenges facing the global wind energy industry. Detecting damage to a wind turbine blade is important for ...planning blade repair, avoiding aggravated blade damage, and extending the sustainability of blade operation. This paper firstly introduces the existing wind turbine blade detection methods and reviews the research progress and trends of monitoring of wind turbine composite blades based on acoustic signals. Compared with other blade damage detection technologies, acoustic emission (AE) signal detection technology has the advantage of time lead. It presents the potential to detect leaf damage by detecting the presence of cracks and growth failures and can also be used to determine the location of leaf damage sources. The detection technology based on the blade aerodynamic noise signal has the potential of blade damage detection, as well as the advantages of convenient sensor installation and real-time and remote signal acquisition. Therefore, this paper focuses on the review and analysis of wind power blade structural integrity detection and damage source location technology based on acoustic signals, as well as the automatic detection and classification method of wind power blade failure mechanisms combined with machine learning algorithm. In addition to providing a reference for understanding wind power health detection methods based on AE signals and aerodynamic noise signals, this paper also points out the development trend and prospects of blade damage detection technology. It has important reference value for the practical application of non-destructive, remote, and real-time monitoring of wind power blades.
Two enantiomeric hydrohelicenes containing a hydroxyl group and a π-conjugated nonplanar structure are assembled at the air/water interface. These molecules are found to form spreading films with ...well-defined surface pressure–area isotherms. Upon transferring the spreading film onto the mica surface, porous nanostructures are observed. The spreading film can be transferred onto solid substrates by the Langmuir–Schaefer (LS) method and the transferred LS films display optical activity as revealed by the circular dichroism (CD) spectra. The P- and M-hydrohelicene enantiomers showed mirrored CD spectra, suggesting that the chirality of the LS films was controlled by molecular chirality. When these molecules are spread on the aqueous solution containing metal ions such as Ag+, Cu2+, and Zn2+, a clear twisted ring nanostructure, which is similar to the Möbius strip, is observed. It is suggested that the interaction between the hydroxyl groups of helicenes and metal ions induced such a ring nanostructure.
The impoundment of the Three Gorges Reservoir (TGR) has changed water-sand transport regime, with inevitable effects on phosphorus transport behavior in the TGR. In this study, we measured phosphorus ...fractions in water and suspended particles transported from upstream rivers of the TGR (the Yangtze River, the Jialing River and the Wu River) to reservoir inner region over the full operation schedule of the TGR. The aim was to determine how phosphorus fractions in water and particulate phases varied in response to natural hydrological processes and reservoir operations. The results showed that total phosphorus concentration (TP) in water in the TGR inner region was 0.17±0.05mg/L, which was lower than that in the Yangtze River (0.21±0.04mg/L) and the Wu River (0.23±0.03mg/L), but higher than that in the Jialing River (0.12±0.07mg/L). In the TGR inner region, there was no clear trend of total dissolved phosphorus (TDP), but total particulate phosphorus (TPP) showed a decreasing trend from tail area to head area because of particle deposition along the TGR mainstream. In addition, the concentrations of TPP in water and particulate phosphorus in a unit mass of suspended particles (PP) in the TGR inner region were higher in October 2014 and January 2015 (the impounding period and high water level period) than that in July 2015 (the low water level period). The temporal variations of PP and TPP concentrations in the TGR may be linked to the change of particle size distribution of suspended particles in the TGR. The particle size tended to be finer due to large-size particle deposition under stable hydrodynamic conditions in the process of TGR impoundment, resulting in high adsorption capacities of phosphorus in suspended particles. The results implied that phosphorus temporal variations in the TGR could exert different impacts on water quality in the TGR tributaries.
A simplified model showing effects of upstream river inputs and reservoir operation on phosphorus temporal variations in the TGR. Display omitted
•Phosphorus fractions in water-particulate phases were observed over the full scheduled operations.•Phosphorus fraction concentrations showed significantly spatial-temporal variations in the TGR.•The differences of upstream river inputs affected phosphorus fraction allocation in the TGR.•Upstream river inputs and reservoir operation affected phosphorus temporal variations in the TGR.
The rapid spread of coronavirus SARS-CoV-2 greatly threatens global public health but no prophylactic vaccine is available. Here, we report the generation of a replication-incompetent recombinant ...serotype 5 adenovirus, Ad5-S-nb2, carrying a codon-optimized gene encoding Spike protein (S). In mice and rhesus macaques, intramuscular injection with Ad5-S-nb2 elicits systemic S-specific antibody and cell-mediated immune (CMI) responses. Intranasal inoculation elicits both systemic and pulmonary antibody responses but weaker CMI response. At 30 days after a single vaccination with Ad5-S-nb2 either intramuscularly or intranasally, macaques are protected against SARS-CoV-2 challenge. A subsequent challenge reveals that macaques vaccinated with a 10-fold lower vaccine dosage (1 × 10
viral particles) are also protected, demonstrating the effectiveness of Ad5-S-nb2 and the possibility of offering more vaccine dosages within a shorter timeframe. Thus, Ad5-S-nb2 is a promising candidate vaccine and warrants further clinical evaluation.
PDF
