With the integration of advanced computing and communication technologies, smart grid is considered as the next-generation power system, which promises self healing, resilience, sustainability, and ...efficiency to the energy critical infrastructure. The smart grid innovation brings enormous challenges and initiatives across both industry and academia, in which the security issue emerges to be a critical concern. In this paper, we present a survey of recent security advances in smart grid, by a data driven approach. Compared with existing related works, our survey is centered around the security vulnerabilities and solutions within the entire lifecycle of smart grid data, which are systematically decomposed into four sequential stages: 1) data generation; 2) data acquisition; 3) data storage; and 4) data processing. Moreover, we further review the security analytics in smart grid, which employs data analytics to ensure smart grid security. Finally, an effort to shed light on potential future research concludes this paper.
Ultrafine PdAg nanoparticles (NPs) are successfully immobilized on zirconia/porous carbon/reduced graphene oxide (ZrO2/C/rGO) nanocomposite derived from metal organic framework/graphene oxide. ...Monodispersed PdAg NPs (diameter ≤2.5 nm) can be facilely anchored on the ZrO2/C/rGO and the aggregation of metal NPs can be avoided utmostly. By virtue of the synergistic effect between metal NPs and support, the resulting PdAg@ZrO2/C/rGO exhibits excellent activity (turnover frequency, 4500 h−1 at 333 K) for the dehydrogenation of formic acid. As an effective strategy, it provides an opportunity to immobilize ultrafine metal NPs on metal oxide/porous carbon/reduced graphene oxide, which has tremendous application prospects in various catalytic fields.
A superior support, namely ZrO2/C/rGO derived from metal–organic framework/graphene oxide, to immobilize ultrafine PdAg nanoparticles (NPs) (diameter ≤ 2.5 nm) is reported. By virtue of the synergistic effect between metal NPs and support, the resulting PdAg@ZrO2/C/rGO nanocatalyst shows extremely high catalytic performance (turnover frequency, 4500 h−1) for the dehydrogenation of formic acid.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The real-time electrical market operations in smart grid require reliable and accurate data from state estimation. However, state estimation is vulnerable to data integrity attacks, in which ...strategically manipulated meter measurements can bypass the conventional bad data detection and introduce errors. As a result, it becomes more likely for the attackers to control real-time electrical market through manipulations of meter measurements. In this paper, we first reveal the intrinsic relations between data integrity attacks and real-time electrical market operations, and explicitly characterize their complex interactions as a process simulator. Then a simulation-based global optimization problem is formulated from which attackers could maximize financial incentives through constructed data integrity attacks. More importantly, a novel systematic online attack construction strategy is proposed, such that attackers can launch the desired attacks only by the real-time data streams of meter measurements and no power network topology or parameter information is needed. A corresponding online defense strategy is also presented to detect and identify the malicious measurements without extra meter hardware investments. Finally, we evaluate the performance of the proposed attacking strategies and countermeasure through numerical simulations in IEEE test systems with both synthetic and real data from the New York Independent System Operator.
Excavation in close proximity to the existing shield tunnel often leads to impacts on the stability of tunnel. However, interventions committed to mitigate the impacts may not be effective in ...preventing tunnel movement and/or deformation from occurring. This study presents a case history where two shield tunnels pass between two excavation pits belonging to the east square of the existing Zhengzhou East High Speed Rail (HSR) station. The centre down-top pit retained using a series of bored piles and three rows of tieback is first excavated in each excavation pit, followed by the periphery top-down pit retained by the diaphragm wall. The tunnels measured cumulative uplift and lateral deformation being equal to 22.9 mm and 77.9 mm, respectively, as the two excavations reached the final depth of 19.3 m. The tunnels also observed ballast separation, lining crack, and joint leakage. The contribution from each of the construction stages to the tunnel uplift and deformation is analysed. The effectiveness of the rectifications adopted is assessed and the lessons learnt are summarised preventing future similar incident from reoccurring.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Abstract
The Large High Altitude Air Shower Observatory (LHAASO) (Fig. 1) is located at Mt. Haizi (4410 m a.s.l., 600 g/cm
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, 29° 21’ 27.56” N, 100° 08’ 19.66” E) in Daocheng, Sichuan province, P.R. ...China. LHAASO consists of 1.3 km
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array (KM2A) of electromagnetic particle detectors (ED) and muon detectors (MD), a water Cherenkov detector array (WCDA) with a total active area of 78,000 m
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, 18 wide field-of-view air Cherenkov telescopes (WFCTA) and a newly proposed electron-neutron detector array (ENDA) covering 10,000 m
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. Each detector is synchronized with all the other through a clock synchronization network based on the White Rabbit protocol. The observatory includes an IT center which comprises the data acquisition system and trigger system, the data analysis facility. In this Chapter, all the above-mentioned components of LHAASO as well as infrastructure are described.
Future smart grid (SG) has been considered a complex and advanced power system, where energy consumers are connected not only to the traditional energy retailers (e.g., the utility companies), but ...also to some local energy networks for bidirectional energy trading opportunities. This paper aims to investigate a hybrid energy trading market that is comprised of an external utility company and a local trading market managed by a local trading center (LTC). The existence of local energy market provides new opportunities for the energy consumers and the distributed energy sellers to perform the local energy trading in a cooperative manner such that they all can benefit. This paper first quantifies the respective benefits of the energy consumers and the sellers from the local trading and then investigates how they can optimize their benefits by controlling their energy scheduling in response to the LTC's pricing. Two different types of the LTC are considered: 1) the nonprofit-oriented LTC, which solely aims at benefiting the energy consumers and the sellers; and 2) the profit-oriented LTC, which aims at maximizing its own profit while guaranteeing the required benefit for each consumer and seller. For each type of the LTC, the optimal trading problem is formulated and the associated algorithm is further proposed to efficiently find the LTC's optimal price, as well as the optimal energy scheduling for each consumer and seller. Numerical results are provided to validate the benefits of the hybrid energy trading market and the performance of the proposed algorithms.
This study demonstrates the first athermal polysilicon Mach-Zehnder interferometer (MZI) based on strip and subwavelength grating waveguides in commercialized bulk CMOS without any process ...modification. As-fabricated MZI exhibits a temperature sensitivity of ±4 pm/°C over 1500~1600 nm wavelength range with a slope of -0.055 pm/°C/nm. This wavelength filtering device is therefore immune from the temperature gradient issue arising from the nearby electronic circuits, thus is promising for practical on-chip optical interconnect and sensor applications in bulk CMOS.
In this paper, we investigate the cooperative resource sharing and pricing for the licensed Primary User (PU) and Cognitive Radio Networks (CRNs), where the PU jointly determines how to share its ...under-utilized radio resource with Secondary Users (SUs) and how to charge the SUs accordingly. Meanwhile, the SUs jointly determine how to utilize the shared radio resource from the PU and their preferred payments. Since both the PU and SUs expect to benefit from cooperation, we model their interactions as a Nash bargaining problem. Viewing the nonconvexity of bargaining problem, we first propose a two-step procedure to solve it efficiently. The two-step procedure explores the connection between the bargaining problem and its associated social optimization problem, and thus turns the original nonconvex bargaining problem into two consecutive convex optimization problems. We then propose two efficient algorithms, each with guaranteed convergence, to solve these two problems, respectively. Numerical results show that our proposed two-step procedure achieves the optimality of the bargaining problem with significantly reduced computational complexity. Also, our joint resource sharing and pricing scheme guarantees that each SU and PU can positively benefit from the cooperative bargaining, and the benefit is fairly allocated among them.
WiFi connections are vulnerable to simulated attacks from rogue access points (APs) or devices whose SSID and/or MAC/IP address are the same as legitimate devices. This kind of attack is difficult to ...counter with traditional network security mechanisms. In this article, we propose a new security mechanism that uses environment-independent features extracted from channel state information (CSI) to detect and identify rogue WiFi devices or APs, and reject their connections. We find that due to the <inline-formula> <tex-math notation="LaTeX">I/Q </tex-math></inline-formula> imbalance and imperfect oscillator of each WiFi network card (NIC), the nonlinear phase error of different subcarriers will vary with the NIC. Through our experimental verification, this cross-subcarrier phase feature is invariant to the location and the environment. We deploy systems on two platforms that can extract constant phase errors from the constantly changing CSI in less than 1 s, which is at least <inline-formula> <tex-math notation="LaTeX">8 \times </tex-math></inline-formula> faster than that of the state-of-the-art solution. Extensive experiments on commercial routers and end devices in different scenarios show that based on the Industrial Platform Computer (IPC) platform, where only nonencrypted rogue connections can be detected, the detection accuracy rate reaches 96%, and the false alarm rate is less than 2%. Based on the ASUS router platform (a commercial WiFi router), WiFi channels and smart device types are not restricted, which greatly improved universality, and the accuracy of device connection detection can even reach more than 99%. We improve a device-type identification method based on the communication traffic features of the device when connected to WiFi. Experiments show that even if there are multiple similar devices from the same manufacturer, the accuracy of device-type detection exceeds 99%.
Due to the low cost and ease of deployment, wireless sensor networks (WSNs) are emerging as sensing paradigms that the structural engineering field has begun to consider as substitutes for ...traditional tethered structural health monitoring (SHM) systems. Different from other applications of WSNs such as environmental monitoring, SHM applications are much more data intensive and it is not feasible to stream the raw data back to the server due to the severe bandwidth and energy limitations of low-power sensor networks. In-network processing is a promising approach to address this problem but designing distributed versions for the sophisticated SHM algorithms is much more challenging because SHM algorithms are computationally intensive, and involve data-level collaboration of multiple sensors. In this paper, we select a classical SHM algorithm: the eigen-system realization algorithm (ERA), and propose a few distributed ERAs suitable for WSNs. In particular, we first design a method to incrementally calculate the ERA and then propose three schemes upon which the incremental ERA can be carried out along an Hamiltonian path, along a path in the minimum connected dominating set (MCDS) and along the shortest path tree (SPT). The efficacy of these schemes are demonstrated and compared through both simulation experiment. We believe the proposed schemes can also serve as a guideline when applying WSNs for other applications like SHM which are also data-intensive and involve sophisticated signal processing of collected information.
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