The varying population density leads to imbalanced utilization rate of satellites. To ensure an intelligent engineering of traffic over satellite networks, a distributed routing scheme for single-layered satellite network, load balancing routing protocol based on mobile agent (LBRP-MA) is proposed. For LBRP-MA, mobile agents explore route by migrating autonomously. Upon arriving at destination, mobile agents migrate back. On each intermediate satellite, mobile agents evaluate path cost considering satellite geographical position as well as inter-satellite link (ISL) cost, and finally take ISL congestion index into account to update routing tables. Through simulations on the Courier-like constellation, the proposed approach is shown to achieve guaranteed end-to-end delay bound and decrease packet loss ratio with better throughput, which is especially suitable for data transferring in case of high traffic load. Moreover, results of the complexity analysis demonstrate that LBRP-MA can have low onboard signaling, storage and computation requirements. Furthermore, issues of LBRP-MA such as ISL congestion index and cost modification factor are discussed. 相似文献
Continuous biaxially textured CdTe films were grown on biaxial CaF2 buffer layers. The CaF2 nanorods were grown by oblique angle vapor deposition and possessed a {111} 〈121〉 biaxial texture. The CdTe film was deposited
by metal organic chemical vapor deposition (MOCVD). Film morphology and the CdTe/CaF2 interface were studied by scanning electron microscopy and transmission electron microscopy. Characterization showed that
small CdTe grains formed initially from the CaF2 surfaces. These small grains then merged into large columnar grains during growth. Analysis revealed that the crystalline
orientation of the CdTe film followed the biaxial texture of the CaF2 nanorods. 相似文献
An ideal craniofacial bone repair graft shall not only focus on the repair ability but also the regeneration of natural architecture with occlusal loads-related function restoration. However, such functional bone tissue engineering scaffold has rarely been reported. Herein, a hierarchical 3D graft is proposed for rebuilding craniofacial bone with both natural structure and healthy biofunction reconstruction. Inspired by the bone healing process, an organic–inorganic nanoink with ultrasmall calcium phosphate oligomers and bone morphogenetic protein-2 incorporated is developed for spatiotemporal guidance of new bone. Based on such homogeneous nanoink, a biomimetic graft, including a cortical layer containing Haversian system, and a cancellous layer featured with triply periodic minimum surface macrostructures, is fabricated via projection-based 3D printing method, and the layers are loaded with distinct concentrations of bioactive factors for regenerating new bone with gradient density. The graft exhibits excellent osteogenic and angiogenic potential in vitro, and accelerates revascularization and reconstructs neo-bone with original morphology in vivo. Benefiting from such natural architecture, loading force is widely transferred with reduced stress concentration around the inserted dental implant. Taken from native physiochemical and structural cues, this wstudy provides a novel strategy for functional tissue engineering through designing function-oriented biomaterials. 相似文献
5G network is an inevitable trend in the development of mobile communications. Mobile cloud computing is a more promising technology for 5G networks. This paper proposes a hierarchical distributed cloud service network model, which is composed of three layers: “access cloud + distributed micro cloud + core cloud”. On the basis of access to the cloud, a distributed micro cloud system is deployed to migrate the service capabilities of the remote core cloud server to the local area. This paper proposes a task offloading assignment algorithm in a small cell cloud scenario. This algorithm establishes a SCC (Small Cell Cloud) based on the channel quality between small cells and the remaining available computing resources, and allocates the load to each small cell in the SCC according to the channel quality and the remaining available computing resources. Simulation results show that this solution can improve the utilization of wireless and computing resources in the small cell cloud computing scenario, and improve the user QoE (Quality of Experience). In order to make the system operate normally under heavy load, this paper proposes a feedback adaptive random access strategy based on the adaptive random access model. This can ensure that the throughput rate does not decrease under heavy load conditions, and at the same time, the average access delay of the existing system is reduced. When the arrival rate of user requests gradually increases, the throughput rate of RA-RACH access will continue to decrease due to collisions until it approaches below 0.1. In the state where the number of users is low and the load is lighter, both RA-RACH, AC-RACH, and FC-RACH have a higher access success rate. But as the load continues to increase, RA-RACH will quickly drop to 0.
Exploring efficient electrocatalysts for oxygen evolution reaction (OER) is an urgent need to advance the development of sustainable energy conversion. Though defect engineering is considered an effective strategy to regulate catalyst activity for enhanced OER performance, the controllable synthesis of defective oxides electrocatalysts remains challenging. Here, oxygen defects are introduced into NiCo2O4 nanorods by an electrochemical lithiation strategy. By tuning in situ lithiation potentials, the concentration of oxygen defects and the corresponding catalytic activity can be feasibly regulated. In addition, the relationship between the changes in the defect density and electronic structure and the lithiation cut-off voltages is revealed. The results show that NiCo2O4 nanorods undertook intercalation and two-step conversion reaction, in which the lithiation-induced conversion reaction gives rise to a CoO@NiO-based structure with higher defect density and lower oxidation states. As a result, the defective CoO@NiO-based catalyst exhibits exceptional OER activity with an overpotential of 270 mV at 10 mA cm−2, which is about 74 mV below the pristine nanomaterials. This research proposes a novel strategy to explore high-performance catalysts with structural stability and defect control. 相似文献
AlGaN-based ultraviolet-B light-emitting diodes (UVB-LEDs) exhibit great potential in phototherapy, vitamin D3 synthesis promotion, plant growth regulation, and so on. However, subjected to the excess compressive strain induced by the large lattice mismatch between multiple quantum wells (MQWs) and AlN, UVB-LEDs that simultaneously satisfy the requirements of high light output power (LOP), low working voltage, and excellent stability are rarely reported. Here, a substrate-dominated strain-modulation strategy is proposed. By precisely manipulating the strain in AlN grown on nano-patterned sapphire substrate (NPSS) to a slightly tensile one, the compressive strain in the following Al0.55Ga0.45N underlayer and Al0.28Ga0.72N/Al0.45Ga0.55N MQWs is successfully suppressed. As a result, an outstanding UVB-LED with a peak wavelength at 303.6 nm is achieved. The 20 × 20 mil2 UVB-LED chip shows a wall-plug efficiency (WPE) of 3.27% under a forward current of 20 mA and a high LOP of 57.2 mW with an extremely low voltage of 5.87 V under a forward current of 800 mA. It is more exciting that the LOP degradation is as low as 17% after 1000 h operation under a forward current density of 75 A cm−2, showing excellent stability. The here-developed UVB-LED, with a high LOP and excellent reliability, will definitely promote the applications of AlGaN-based UVB-LEDs. 相似文献