Search

In this work, we demonstrate that an organometallic perovskite (OP) single crystal for effective photodetection can be grown on a gold (Au)-decorated substrate using liquid phase epitaxy. The covered gold could both control the shape of the epitaxial layer and act as its electrodes. An MAPbCl3 single crystal and an MAPbBr1.5Cl1.5 single crystal were used as the substrate and the epitaxial layer, respectively. The device, with an Au-perovskite-Au structure, can be fully characterized. Due to the high-quality epitaxial layer, the maximum external quantum efficiency (EQE) value is over 60% under the voltage of −20 V. In addition, the response speed can reach 200 and 500 ns (ns) rise and fall, respectively. Our work provides an effective and promising method to fabricate efficient perovskite-based photodetectors.

Although epitaxial growth is the fundamental method to realize lattice matched heterojunctions in electronics manufacturing, large-scale epitaxial single crystal layers based on solution-processing...

Global atmospheric nitrogen deposition significantly affects the nutrient cycling and C–N–P stoichiometry in ecosystems. Herein, a global meta-analysis was conducted based on 898 pairwise observations to analyze the impact of nitrogen addition on plant-soil-enzyme C–N–P stoichiometry and microbial nutrient limitation in different ecosystem types (cropland, grassland, and forest), nitrogen addition intensity (0–5, 5–10, and >10 g N m−2 yr−1) and duration (0–5, 5–10, and >10yr). Results showed that nitrogen addition significantly decreased plant C:N (shoot: 16.5%, root: 27.1%, litter: 16.5%), soil C:N (5.9%), enzyme C:P (1.2%), and enzyme N:P (5.1%), whereas significantly increased soil C:P (4.9%), enzyme C:N (7.1%), vector angle (4.4%), vector length (3.9%), and plant N:P (shoot: 24.1%, root: 23.8%, and litter: 13.5%). Furthermore, nitrogen addition mainly affected the enzyme C:N and vector length in grasslands. Additionally, the changes in C:N in plants, soil, and enzymes, and vector angle and length were higher at nitrogen addition intensity of >10 g N m−2 yr−1. The changes in C:N and C:P in plant and soil were higher at nitrogen addition duration of >10 yr. Finally, the N:P in shoot, soil and enzyme, and vector angle were strongly correlated with mean annual precipitation (MAP). In conclusion, nitrogen addition significantly reduced the C:N ratio in plants and soil and increased plant N:P, and microbial C and P limitation. These effects vary with the ecosystem type, MAP, and nitrogen addition intensity and duration. The results improve our understanding of the plant-soil-microbial nutrient cycling processes in terrestrial ecosystems under global nitrogen deposition.

The great improvements in both satellite and terrestrial networks have motivated the academic and industrial communities to rethink their integration. As a result, there is an increasing interest in new-generation hybrid satellite-terrestrial networks, where sufficient flexibility should be enabled to deploy customized SFCs to satisfy the growing diversity of user needs. However, it is still challenging to achieve such a nice vision, since many key issues remain unaddressed comprehensively such as framework design, communication procedures and resource optimization. Therefore, in this article, we focus on how to efficiently deploy customized SFCs at terrestrial- satellite hybrid cloud networks. In particular, we first propose an elastic framework used for SFC deployment at clouds, and second propose an efficient SFC mapping approach for improvement of system resource utilization. Finally, we verify the proposed framework at a proof-ofconcept prototype via a number of use cases, and evaluate the proposed mapping approach through extensive simulations based on a realworld topology. Related experimental and simulation results have confirmed the feasibility and benefits of our proposed framework and mapping approach.

Organometallic perovskites MAPbX3 (MA = CH3NH3 and X = I, Br or Cl) are considered as potential materials for X-ray and gamma ray detection due to its high Z atom, large mobility-lifetime product and growth from solution. However, perovskites with one kind halide own numbers of free charges and yielded unbearable noise current. In this work, we grow perovskite single crystals (PSC) with different halide ratio and find the MAPbBr2.5Cl0.5 PSC shows outstanding performance in electric properties. Through energy dispersive X-ray spectrum, vacancy and excess of Pb is thought as the main cause of free charges. The atomic ratio between halide and Pb as 3 in MAPbBr2.5Cl0.5 PSC and its large resistivity 5.6 × 108 Ω cm and 160 cm2 V−1 s−1 high mobility are measured. Thanks to the smaller noise current, higher electric field could be established for higher charges collect efficiency. As a result, compared with pristine perovskite single crystals, improved X-ray detection performance is demonstrated. This work provides useful information to achieve high performance X-ray detectors based on organometallic perovskites.

Solution-processed organic-inorganic pero-vskites MAPbX3 (MA = CH3NH3 and X = Cl, Br, and I) have been emerged as potential material for photodetection. Especially photodiodes based on perovskites have shown low dark current and high gain. However, intrinsic perovskites require functional layers to establish photodiodes and these functional layers’ small charges mobility and high traps density make photodiodes based on perovskites low response speed. Here, we directly grow homojunctions based on perovskite single crystals (PSCs) during the crystallization process. The pristine PSCs act as p-type donor and epitaxial growth layer with Se doping act as n-type acceptor. With simple structure Au- homojunctions- Au, our photodiodes could work under a large reverse voltage bias range from 0 to 200 V with low noise and result wide dynamic range and high response speed. Using applied voltage to control the width of depletion layer, we achieve enhanced photodetection in near-band photo detection. Our work provides useful information in solution-processed devices design.

The genetic improvement of nitrogen use efficiency (NUE) of crops is vital for grain productivity and sustainable agriculture. However, the regulatory mechanism of NUE remains largely elusive. Here, we report that the rice Grain number, plant height, and heading date7 (Ghd7) gene genetically acts upstream of ABC1 REPRESSOR1 (ARE1), a negative regulator of NUE, to positively regulate nitrogen utilization. As a transcriptional repressor, Ghd7 directly binds to two Evening Element-like motifs in the promoter and intron 1 of ARE1, likely in a cooperative manner, to repress its expression. Ghd7 and ARE1 display diurnal expression patterns in an inverse oscillation manner, mirroring a regulatory scheme based on these two loci. Analysis of a panel of 2656 rice varieties suggests that the elite alleles of Ghd7 and ARE1 have undergone diversifying selection during breeding. Moreover, the allelic distribution of Ghd7 and ARE1 is associated with the soil nitrogen deposition rate in East Asia and South Asia. Remarkably, the combination of the Ghd7 and ARE1 elite alleles substantially improves NUE and yield performance under nitrogen-limiting conditions. Collectively, these results define a Ghd7-ARE1-based regulatory mechanism of nitrogen utilization, providing useful targets for genetic improvement of rice NUE.

With the emergence of hierarchical service function chaining (hSFC), Internet providers are able to offer more flexible and scalable network functions for various user requirements via collaborations of datacenters situated at different geographical locations. However, considering scalability, how to cope with the controller placement in multiple domains of hSFC is still challenging, as corresponding signaling interactions are complicated and heavy. Thus, in this paper, we propose a binary practical swarm optimization (BPSO)-based algorithm to minimize signaling costs among hierarchical controllers through a reasonable placement. Particularly, we first formulate the hSFC controller placement problem as an integer programming model. Then, we propose a heuristic placement algorithm (BPSO-HPA) to approximate the optimal solution, along with a greedy-based placement algorithm (G-HPA) as a benchmark. Finally, we evaluate the performance of the proposed algorithms with extensive simulations, and the results prove that the proposed BPSO-based algorithm is able to approach the results derived from the optimization model with less running time, and outperform the G-HPA algorithm.

It is observed that the Internet has been slowly "fragmented" into Many Networks (ManyNets) due to both technical and commercial evolutions. The interconnection among those networks is a challenge due to their incompatible addressing mechanisms. Furthermore, emerging applications like Augmented Reality and Virtual Reality (AR/VR), holographic communications, etc. rise new requirements to the network and involve innumerable physical and virtual objects, which require more efficient and customized network services. Current Internet Protocol (IP) that aims to connect regional academic and military networks was invented half a century ago. The original IP design philosophy like fixed address length, binding machines to specific locations, and others are not sufficient anymore to tackle those challenges.In this paper, we propose a novel framework for future Internet protocol, called NEW IP, to tackle aforementioned challenges and fulfill the requirements of future applications. NEW IP inherently enables variable-length and multi-semantic network addresses, and user-definable networking. Besides the NEW IP framework, a few use cases will be illustrated to highlight the benefits it brings.

It's promising to use Software-Defined Networking (SDN) and Network Functions Virtualization (NFV) to integrate satellite and terrestrial networks. To construct network service function chains in such a multi-domain environment, we propose a horizontal-based Multi-domain Service Function Chaining (Md-SFC) orchestration framework. In this framework, multi-domain orchestrators can coordinate with each other to guarantee the end-to-end service quality. Intra-domain orchestrators also coordinate SDN controllers and NFV management components to implement intra-domain service function chains. Based on this, we further propose a heuristic SFC mapping algorithm with a cooperative inter-domain path calculation method to map service function chains to infrastructures. In this method, master multi-domain orchestrator and intra-domain orchestrators coordinate to select proper inter-domain links. We compare the cooperative method with a naive uncooperative way that domains' topology information is provided to the master multi-domain orchestrator and it calculates the shortest inter-domain path between intra-domain service function chains directly. Simulation results demonstrate that our solution is feasible. It is able to construct end-to-end performance guaranteed service function chain by horizontal-based cooperation. The cooperative inter-domain path calculation method decreases the mapping load for the master orchestrator and gets the same end-to-end performance.

To meet the urgent security demands, 5G aims to deploy virtualized and programmable security services and defense potential threats in real time. With the development of network function virtualization and software-defined networking, security functions can be dynamically and flexibly chained to cope with many types of malicious attacks. Although there are a number of studies on security function chaining for the 5G, they primarily focus on the security function composition, rather than rule enforcement. In fact, the misconfiguration of rules for security functions is notably common because of the security function diversity and rule heterogeneity that causes many unexpected and serious problems. Therefore, in this paper, we propose a priority-based anomaly-free mechanism with defined security rule anomalies. To avoid misconfiguration, we also propose and implement a simply configured rule management framework with anomaly resolution. With extensive performance evaluations, we show the availability and efficiency of our proposed mechanism to resolve security rule anomalies.

In multi-layer satellite-terrestrial network, Contact Graph Routing (CGR) uses the contact information among satellites to compute routes. However, due to the resource constraints in satellites, it is extravagant to configure lots of the potential contacts into contact plans. What's more, a huge contact plan makes the computing more complex, which further increases computing time. As a result, how to design an efficient contact plan becomes crucial for multi-layer satellite network, which usually has a large scaled topology. In this paper, we propose a distributed contact plan design scheme for multi-layer satellite network by dividing a large contact plan into several partial parts. Meanwhile, a duration based inter-layer contact selection algorithm is proposed to handle contacts disruption problem. The performance of the proposed design was evaluated on our Identifier/Locator split based satellite-terrestrial network testbed with 79 simulation nodes. Experiments showed that the proposed design is able to reduce the data delivery delay.

As satellite networks have played an indispensable role in many fields, how to integrate them with terrestrial networks (e.g., the Internet) has attracted significant attention in academia. However, it is challenging to efficiently build such an integrated network, since terrestrial networks are facing a number of serious problems, and since they do not provide good support for heterogeneous network convergence. In this article, we propose a flexible network architecture, HetNet, for efficient integration of heterogeneous satellite-terrestrial networks. Specifically, the HetNet synthesizes Locator/ID split and Information-Centric Networking to establish a general network architecture. In this way, it is able to achieve heterogeneous network convergence, routing scalability alleviation, mobility support, traffic engineering, and efficient content delivery. Moreover, the HetNet can further improve its network elasticity by using the techniques of Software-Defined Networking and Network Functions Virtualization. In addition, to evaluate the HetNet performance, we build a proof-of-concept prototype system and conduct extensive experiments. The results confirm the feasibility of the HetNet and its advantages.

When selecting security Service Function Chaining (SFC) for network defense, operators usually take security performance, service quality, deployment cost, and network function diversity into consideration, formulating as a multi-objective optimization problem. However, as applications, users, and data volumes grow massively in networks, traditional mathematical approaches cannot be applied to online security SFC selections due to high execution time and uncertainty of network conditions. Thus, in this paper, we utilize reinforcement learning, specifically, the Q-learning algorithm to automatically choose proper security SFC for various requirements. Particularly, we design a reward function to make a tradeoff among different objectives and modify the standard ∊-greedy based exploration to pick out multiple ranked actions for diversified network defense. We compare the Q-learning with mathematical optimization-based approaches, which are assumed to know network state changes in advance. The training and testing results show that the Q-learning based approach can capture changes of network conditions and make a tradeoff among different objectives.

The great improvements in both satellite and terrestrial networks have motivated the academic and industrial communities to rethink their integration. As a result, there is an increasing interest on how to combine broadband satellite networks with the clean-slate terrestrial ones, especially with clouds leveraging SDN (Software-Defined Networking) and NFV (Network Functions Virtualization) techniques, for better network openness, flexibility, elasticity and controllability. In this way, customized SFCs (Service Function Chaining) can be deployed at terrestrial and satellite ground segment clouds on demand, significantly reducing OPEX and CAPEX (Operational and Capital Expense). Nevertheless, how to efficiently leverage cloud substrate resources and deploy required SFCs is still challenging, as many issues such as system cost and revenue are involved. Therefore, in this paper, we focus on SFC mappings at SDN/NFV-based terrestrial and satellite ground clouds, and propose a related approach that considers both SF (Service Function) multiplexing and SFC merging, aiming to improve resource utilization efficiency of underlying substrate networks. Extensive simulations are performed and numerical results have verified benefits of the proposed SFC mapping approach.

The areca (Areca catechu L.) nut kernel (ANK) is a good potential protein source for its high protein content of 9.89–14.62 g/100 g and a high yield of around 300,000 tons per year in China. However, utilization of the areca nut kernel is limited. To expand the usage of ANK in pharmaceutical or foods industries, areca nut kernel globulin was extracted and angiotensin-I converting enzyme (ACE) inhibition peptides were prepared and identified using gel chromatography, reversed phase HPLC separation, UPLC-ESI-MS/MS analysis and in silico screening. Finally, a novel ACE-inhibitory heptapeptide (Ala–Pro–Lys–Ile–Glu–Glu–Val) was identified and chemically synthesized. The combination pattern between APKIEEV and ACE, and the inhibition kinetics, antihypertensive effect and endothlein-1 inhibition activity of APKIEEV were studied. The results of the molecular docking demonstrated that APKIEEV could bind to four active sites (not the key active sites) of ACE via short hydrogen bonds and demonstrated high ACE-inhibitory activity (IC50: 550.41 μmol/L). Moreover, APKIEEV exhibited a significantly lowering effect on both the systolic blood pressure and diastolic blood pressure of spontaneously hypertensive rats, and had considerable suppression ability on intracellular endothelin-1. These results highlight the potential usage of APKIEEV as ingredients of antihypertensive drugs or functional foods.

Semiconductors grown by the solution-processed method have shown low-cost, facile fabrication process and comparable performance. However, there are many reasons why it is difficult to achieve high quality films. For example, lattice constant mismatch is one of the problems when photovoltaic devices made of organ metallic perovskites. In this work, MAPbBr3 ( M A = C H 3 N H 3 + ) perovskites single crystals grown on the surface of MAPbBr2.5Cl0.5 perovskites single crystals via liquid epitaxial growth method is demonstrated. It is found that when the lattice constants of the two perovskite single crystals are matched, another crystal can be grown on the surface of one crystal by epitaxial growth. The whole epitaxy growth process does not require high heating temperature and long heating time. X-ray diffraction method is used to prove the lattice plane of the substrate and the epitaxial grown layer. A scanning electron microscope is used to measure the thickness of the epitaxial layer. Compared with perovskite-based photodetectors without epitaxial growth layer, perovskite-based photodetectors with epitaxial growth layer have lower dark current density and higher optical responsibility.

With the increasing global mobile traffic, there is a trend to deploy network services at mobile edge clouds. Benefiting from the techniques of Network Function Virtualization and Software-Defined Networking, service function chains are enabled to compose a series of required network functions dynamically. As a consequence, most of common-used and IT-based mobile network services can be deployed at MEC cloud networks under the 5G context, remarkably reducing user latency and network traffic. However, as resources in cloud networks are limited, it is challenging to promote the system utilization with guaranteed user experience. Thus, in this paper, we formulate the allocation problem of service functions in MECs as an Semi-Markov Decision Process model and present a value iteration algorithm to find the optimized solution, aiming to increase request acceptance rate. Additionally, we discuss the parameter settings of the proposed scheme under different cases to find higher rewards.

Software Defined Satellite Network (SDSN) is a novel framework which brings Software Defined Network (SDN) technologies in the satellite networks. It has great potential to achieve effective and flexible management in the satellite networks. However, the frequent handovers will lead to an increase in the flow table size in SDSN. Due to the limited flow table space, a lot of flows will be dropped if the flow table is full during the handover. This is a burning issue to be solved for mobility management in SDSN. In this paper, we propose a heuristic Timeout Strategy-based Mobility Management algorithm for SDSN, named TSMM. TSMM aims to reduce the drop-flows during handover by considering two key points, the limited flow table space and satellite link handover. We implement TSMM mechanism and conduct contrast experiments. The experimental results verify the good performance in terms of transmission quality, an 8.2%-9.9% decrease in drop-flow rate, and a 6.9%–11.18% decrease in flow table size during the handover.

Mobile-Edge Computing (MEC) is a novel and sustainable network architecture that enables energy conservation with cloud computing and network services offloading at the edge of mobile cellular networks. However, how to efficiently manage various real-time changing security functions is an essential issue which hinders the future MEC development. To address this problem, we propose a fuzzy security service chaining approach for MEC. In particular, a new architecture is designed to decouple the required security functions with the physical resources. Based on this, we present a security proxy to support compatibility to traditional security functions. Furthermore, to find the optimal order of the required security functions, we establish a fuzzy inference system (FIS) based mechanism to achieve multiple optimal objectives. Much work has been done to implement a prototype, which is used to analyze the performance by comparing with a widely used method. The results prove that the proposed FIS mechanism achieves an improved performance in terms of Inverted Generational Distance (IGD) values and execution time with respect to the compared solution.