The prevalence of Internet of Things (IoTs) allows heterogeneous embedded smart devices to collaboratively provide intelligent services with or without human intervention. While leveraging the large-scale IoT-based applications like Smart Gird and Smart Cities, IoT also incurs more concerns on privacy and security. Among the top security challenges that IoTs face is that access authorization is critical in resource and information protection over IoTs. Traditional access control approaches, like Access Control Lists (ACL), Role-based Access Control (RBAC) and Attribute-based Access Control (ABAC), are not able to provide a scalable, manageable and efficient mechanisms to meet requirement of IoT systems. The extraordinary large number of nodes, heterogeneity as well as dynamicity, necessitate more fine-grained, lightweight mechanisms for IoT devices. In this paper, a federated capability-based access control (FedCAC) framework is proposed to enable an effective access control processes to devices, services and information in large scale IoT systems. The federated capability delegation mechanism, based on a propagation tree, is illustrated for access permission propagation. An identity-based capability token management strategy is presented, which involves registering, propagation and revocation of the access authorization. Through delegating centralized authorization decision-making policy to local domain delegator, the access authorization process is locally conducted on the service provider that integrates situational awareness (SAW) and customized contextual conditions. Implemented and tested on both resources-constrained devices, like smart sensors and Raspberry PI, and non-resource-constrained devices, like laptops and smart phones, our experimental results demonstrate the feasibility of the proposed FedCAC approach to offer a scalable, lightweight and fine-grained access control solution to IoT systems connected to a system network.
Real-time information fusion based on WAMI (Wide-Area Motion Imagery), FMV (Full Motion Video), and Text data is highly desired for many mission critical emergency or security applications. Cloud Computing has been considered promising to achieve big data integration from multi-modal sources. In many mission critical tasks, however, powerful Cloud technology cannot satisfy the tight latency tolerance as the servers are allocated far from the sensing platform, actually there is no guaranteed connection in the emergency situations. Therefore, data processing, information fusion, and decision making are required to be executed on-site (i.e., near the data collection). Fog Computing, a recently proposed extension and complement for Cloud Computing, enables computing on-site without outsourcing jobs to a remote Cloud. In this work, we have investigated the feasibility of processing streaming WAMI in the Fog for real-time, online, uninterrupted target tracking. Using a single target tracking algorithm, we studied the performance of a Fog Computing prototype. The experimental results are very encouraging that validated the eﬀectiveness of our Fog approach to achieve real-time frame rates.
Space situational awareness (SSA) and defense space control capabilities are top priorities for groups that own or operate man-made spacecraft. Also, with the growing amount of space debris, there is an increase in demand for contextual understanding that necessitates the capability of collecting and processing a vast amount sensor data. Cloud computing, which features scalable and flexible storage and computing services, has been recognized as an ideal candidate that can meet the large data contextual challenges as needed by SSA. Cloud computing consists of physical service providers and middleware virtual machines together with infrastructure, platform, and software as service (IaaS, PaaS, SaaS) models. However, the typical Virtual Machine (VM) abstraction is on a per operating systems basis, which is at too low-level and limits the flexibility of a mission application architecture. In responding to this technical challenge, a novel adaptive process based cloud infrastructure for SSA applications is proposed in this paper. In addition, the details for the design rationale and a prototype is further examined. The SSA Cloud (SSAC) conceptual capability will potentially support space situation monitoring and tracking, object identification, and threat assessment. Lastly, the benefits of a more granular and flexible cloud computing resources allocation are illustrated for data processing and implementation considerations within a representative SSA system environment. We show that the container-based virtualization performs better than hypervisor-based virtualization technology in an SSA scenario.
The need for a global collaborating space situational awareness (SSA) network, including radars, optical and other sensors for communication and surveillance, has become a top priority for most countries who own or operate man-made space-crafts. Such a SSA system requires vast storage, powerful computing capacity and the ability to serve hundreds of thousands of users to access the same database. These requirements make traditional distributed networking system insufficient. Cloud computing, which features scalable and elastic storage and computing services, has been recognized as an ideal candidate that can meet the challenges of SSA systems' requirements. In this paper, we propose a Cloud-based information fusion system for SSA and examine a prototype that serves space tracking algorithms. We discuss the benefits of using Cloud Computing as an alternative for data processing and storage and explore details of Cloud implementation for a representative SSA system environment.
For a novel method of characterize stress of concrete structure by measuring embedded ceramic disc, we establish a model of a piezoelectric ceramic disc under the situation mentioned above, and then the relationships between the complex coefficients and the equivalent circuit parameters are obtained. Derived from the piezoelectric equations with complex coefficients, the dissipation factors are related to the equivalent circuit parameters. Experimental results show that there are linear relationships between most of the equivalent parameters and the loadings applied on the concrete structure. The mechanisms of the results are discussed by use of the theory of moving domain walls and point defects. The results also support the method of estimating the stress by measuring the value of equivalent circuit parameters of piezoelectric ceramic.
In order to meet the demand for miniaturization and excellent performances of antennas to send and receive the wireless signals, in this paper a novel Photonic Band Gap (PBG) structure of a two-dimensional square lattice array etched on one side of silicon wafer is proposed as the grounds of a microstrip patch antenna. An analysis of the performance of a patch antenna with a PBG ground has been carried out, then two rectangle MEMS microstrip antennas with a conventional and a PBG ground respectively, are designed, while the alternating direction implicit finite-difference time-domain (ADI-FDTD) is adopted to perform time simulations of Gaussian pulse propagation in the microstrip antennas, as a result of the versatile method, the frequency-dependent scattering parameters and input impedance could be derived. An important reduction of the surface waves in the PBG antenna has been observed in the simulations, which consequently leads to an improvement of the antenna efficiency and bandwidth. Subsequently, the MEMS PBG antenna is micromachined and measured, and the simulation characteristics are verified by the measured curves of the MEMS PBG antenna. The measured peak return loss of PBG patch antenna is -21dB at 5.36GHz, and the bandwidth of 8.5%, which is three times wider than that of the conventional patch, therefore the gain and the bandwidth are enhanced by means of PBG process.
In order to measure laser-produced plasma x-ray in the 1.33-2.46-nm region, an elliptical crystal spectrograph has been designed and fabricated. The potassium acid phthalate (KAP) crystal with a 2d spacing of 2.663 nm is used as the x-ray dispersive element, it is elliptically bent and glued on a rustless-steel substrate with a 0.9586 eccentricity and a 1350-mm focal distance. The spectrograph is equipped with an x-ray charge-coupled device (CCD) camera for recording the space-resolved spectrum on one port, and an x-ray streak camera for recording the time-resolved spectrum on another port. The first testing experiment was carried out on the XG-2 target chamber, the experimental results demonstrate that the spectral resolution is about 640 for this spectrograph.
A novel elliptical crystal spectrometer has been designed and manufactured to diagnose pulsed plasmas x-ray. The light path is designed according to the elliptical focusing property. The spectrometer is composed of the elliptical x-ray analyzer, the alignment devices, the vacuum system, the ports of the spectral detectors for x-ray CCD camera and x-ray streak camara, the supporting base, and the adapting flange to the target chamber. The target-shooting experiment was performed at the XG-Π and SGΠlaser facilities for testing the spectrometer. The optical system, optoelectronic machinery system, experimental results are discussed in this paper.
For applying micro/nano technologies and Micro-Electro-Mechanical System (MEMS) technologies in the Radio Frequency (RF) field to manufacture miniature microstrip antennas. A novel MEMS dual-band patch antenna designed using slot-loaded and short-circuited size-reduction techniques is presented in this paper. By controlling the short-plane width, the two resonant frequencies, f10 and f30, can be significantly reduced and the frequency ratio (f30/f10) is tunable in the range 1.7~2.3. The Haar-Wavelet-Based multiresolution time domain (H-MRTD) with compactly supported scaling function for a full three-dimensional (3-D) wave to Yee's staggered cell is used for modeling and analyzing the antenna for the first time. Associated with practical model, an uniaxial perfectly matched layer (UPML) absorbing boundary conditions was developed, In addition , extending the mathematical formulae to an inhomogenous media. Numerical simulation results are compared with those using the conventional 3-D finite-difference time-domain (FDTD) method and measured. It has been demonstrated that, with this technique, space discretization with only a few cells per wavelength gives accurate results, leading to a reduction of both memory requirement and computation time.
The accuracy of intensity modulation optical fiber sensors worsens greatly due to disturbances such as temperature fluctuation. This paper reports a novel m X n network compensation technique which can be simultaneously applied to many fiber sensors to minimize the degradation. We demonstrate a m X n network (m, n are integers and greater than 1) can compensate (m-1)(n-1) sensors at one time. Further analysis indicates that a m X n compensation network can be looked as the combination of (m- 1)(n-1) four-node networks or three-node networks depending on its structure. Furthermore, its compensation potential is similar to elementary single-sensor networks.