Resilient Data Collection in Smart Grid

Sensors and measurement devices are widely deployed in Smart Grid (SG) to monitor the health of the system. However, these devices are subject to damage and attack so that they cannot deliver sensing data to the control center. In tree-based data collection schemes, a relay failure can further lead to unresponsiveness of all the devices in its sub-tree. In this paper, we study the resiliency issue in collecting data from SG measurement devices. We first design a protocol that guarantees successful data collection from all non-faulty devices in a backup-enabled tree structure. Then, we formulate the tree construction problem to optimize data collection time. Since the formulated problem is NP-hard, we propose a heuristic algorithm to solve it. We evaluate our algorithm using a real utility network topology. The experiment results show that our algorithm performs well in large scale networks.CREDCOpe

Chandra and HST Observations of the Supersoft ULX in NGC 247: Candidate for Standard Disk Emission

We report on multiwavelength observations of the supersoft ultraluminous X-ray source (ULX) in NGC 247 made with the Chandra X-ray Observatory and Hubble Space Telescope (HST). We aligned the X-ray and optical images using three objects present on both and identified a unique, point-like optical counterpart to the ULX. The X-ray to optical spectrum is well fitted with an irradiated disk model if the extinction measured for Cepheids in NGC 247 is used. Assuming only Galactic extinction, then the spectrum can be modeled as a standard thin accretion disk. Either result leads to the conclusion that a disk interpretation of the X-ray spectrum is valid, thus the source may be in the X-ray thermal state and contain an intermediate mass black hole of at least 600 solar masses. In contrast to other supersoft ULXs which are transient and exhibit a luminosity temperature relation inconsistent with a disk interpretation of the X-ray emission, the NGC 247 ULX has a relatively steady flux and all available X-ray data are consistent with emission from a disk in the thermal state.Comment: 9 pages, 5 figures, accepted for publication in Ap

Case-Based Reasoning of Man-Made Geohazards Induced by Rainfall on Transportation Systems

Due to global warming and environmental change, disastrous natural events have increased in scale and impact, e.g., Typhoon Morakot, in 2009 and 2011 Tōhoku earthquake and resulting tsunami in Japan. Hazard management is becoming increasingly important, making it a necessity to manage risk and fully understand critical scenarios. For example, the National Infrastructure Protection Plan of the United States emphasizes on lessons learned from past disasters. In this chapter, several selected cases of accidents caused by man-made geohazards in Taiwan are studied

trans-Di-μ-carbonyl-bis­{carbon­yl[η5-2,3,4,5-tetra­methyl-1-(2-thien­yl)cyclo­penta­dien­yl]ruthenium(I)}(Ru—Ru)

The title compound, [Ru2(C13H15S)2(CO)4], is a centrosymmetric binuclear metal–carbonyl complex containing an Ru—Ru single bond [2.7511 (8) Å]. Each RuI atom is coordinated by two bridging carbonyl ligands, one terminal carbonyl ligand and one η5-cyclo­penta­dienyl group. The complex has a trans conformation and the two cyclo­penta­dienyl ring planes are parallel. The crystal structure involves weak C—H⋯O hydrogen bonds

trans-Di-μ-carbonyl-bis­{carbon­yl[η5-2,3,4,5-tetra­methyl-1-(5-methyl-2-fur­yl)cyclo­penta­dien­yl]ruthenium(I)}(Ru—Ru)

In the crystal structure of the title compound, [Ru2(C14H17O)2(CO)4], each RuI atom is connected to one end-on and two bridging carbonyl groups and one cyclo­penta­dienyl ring. The two Ru atoms are connected into binuclear complexes via two bridging carbonyl groups, forming four-membered rings which are located on centres of inversion. The Ru—Ru distance of 2.7483 (11) Å corresponds to a single bond. The two carbonyl groups in these binuclear complexes are trans-oriented

Resilient Data Collection in Refinery Sensor Networks Under Large Scale Failures

Wireless sensors and measurement devices are widely deployed in oil and gas refineries to monitor the health of the pipes. These sensors are deployed along the pipes in an open area and thus are subject to large scale failures due to cyber-physical attacks and hazardous environments. In this paper, we study the resilience issues in collecting data from a dense and large scale set of sensors deployed over the physical refinery pipe network. We construct a multi-tree sensor mesh network over the refinery sensors for data collection. The reporting messages within one of the trees, while passing along the tree, are protected by a secret key shared among all sensors on the tree. Our construction aims to minimize the data collection time and ensures that the information leakage probability of the secret key is bounded. To tolerate large scale failures, we present a distributed self-healing protocol, which enables a tree node to discover a secondary path when its parent fails. The simulation result shows that the self-healing protocol tolerates large scale failures with high probability and has small overhead in data collection time.Ope

The Geomorphometry of Rainfall-Induced Landslides in Taiwan Obtained by Airborne Lidar and Digital Photography

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