Study on Effect of Product Liability to Inherent Safety

AbstractMany industry accidents and product liability problems occur in China in recent years. The safety of products not only influents public daily life, also affects industrial production. Product safety concept reflects the attitude of people to product safety, and is reflected in product liability system. The influences of different product liability system to the status of inherent safety were studied based on the analysis of the doctrine of liability fixation in different technology development period. It can be seen that there were still many problems in the product liability acts such as the standard and identification of product defects, compensation liability, which were not beneficial to improve the industry safety though strict liability has been accepted in our country. Therefore, product liability system should be improved, and the method of design defect determination should be established. At the same time, carrying out the risk evaluation of the products, increasing the amount and scope of compensation are also important to realize the product safety and industrial inherent safety

Reliable geocasting for random-access underwater acoustic sensor networks

a b s t r a c t Reliable data delivery for underwater acoustic sensor networks is a major concern in applications such as surveillance, data collection, navigation, and ocean monitoring. Geocasting is a crucial communication primitive needed to support these applications, which consists in transmitting one or multiple consecutive data packets -all carrying an atomic message -to nodes located in a certain geographic region. In this article, two versions of a distributed, reliable, and efficient underwater geocasting solution (based on different degrees of neighbor information) are proposed for underwater networks whose acoustic modems use random-access Medium Access Control (MAC) protocols. By jointly considering the position uncertainty of nodes as well as the MAC and routing functionalities, packet transmissions are prioritized and scheduled so to maximize link reliability while limiting the end-to-end geocasting delay. Moreover, a simple yet effective timer-based mechanism is designed to limit the number of transmissions by selecting only a subset of neighbors for packet forwarding. Performance is evaluated and compared via thorough simulations against existing geocasting solutions tuned for the underwater environment that were originally designed for terrestrial wireless networks

Trajectory-Aware Communication Solution for Underwater Gliders Using WHOI Micro-Modems

Abstract—The predictable trajectory of underwater gliders can be used in geographic routing protocols. Factors such as drifting and localization errors cause uncertainty when estimating a glider’s trajectory. Existing geographic routing protocols in underwater networks generally assume the positions of the nodes are accurately determined by neglecting position uncertainty. In this paper, a paradigm-changing geographic routing protocol that relies on a statistical approach to model position uncertainty is proposed. Our routing protocol is combined with practical cross-layer optimization to minimize energy consumption. Our solution’s performance is tested and compared with existing solutions using a real-time testbed emulation that uses underwater acoustic modems. I

Inter-glider underwater communication and coordination for ocean monitoring and coastal tactical surveillance

In order to achieve efficient and cost-effective sensing of the vast under-sampled 3D aquatic volume, intelligent adaptive sampling strategies involving teams of Autonomous Underwater Vehicles (AUVs) endowed with underwater wireless communication capabilities become essential. These autonomous vehicles should coordinate and steer through the region of interest, and cooperatively sense and transmit multimedia data to onshore stations for real-time data processing and analysis. Because of the propagation limitations of Radio Frequency (RF) and optical waves, the typical wireless physical-layer communication technology in underwater networks, for distances above a hundred of meters, relies on acoustic waves. Due to the stringent constraints of the underwater acoustic channels, as of today existing works on underwater acoustic communications are mostly focused on enabling delay-tolerant low-bandwidth applications tailored for measuring only scalar physical phenomena. Hence, it is necessary to design solutions for reliable, high data-rate multimedia underwater acoustic communications and to seamlessly integrate the control and communication of AUVs. In this dissertation, I propose solutions to improve the performance of inter-vehicle acoustic communication and coordination among AUVs. In particular, these solutions are based on underwater gliders and can be extended to other classes of AUVs following predictable trajectories. Due to the inaccessibility of Global Positioning System (GPS) signal underwater, location estimates of a node may be inaccurate. Inaccuracies in models for deriving position estimates, self-localization errors, and drifting due to ocean currents, however, cause uncertainty when estimating an AUV's position. In this dissertation, I first propose a statistical model to estimate an AUV's position and its associated position uncertainty. Then, the position uncertainty under the influence of ocean currents is further predicted using the Unscented Kalman Filter. Based on this model, in order to optimize the inter-vehicle communications, I propose a delay-tolerant networking solution exploiting the predictability of AUV trajectories and the directional radiation pattern of transducers, a reliable geocasting solution for AUVs with high position uncertainty, and an under-ice localization solution that can minimize localization uncertainty and communication overhead. Based on these underwater communication techniques, I also propose efficient team-formation and -steering algorithms for underwater gliders in order to take measurements in space and time from the under-sampled vast ocean. Team formation and steering algorithms relying on underwater acoustic communications are proposed to enable glider swarming that is robust against ocean currents and acoustic channel impairments. These algorithms use real underwater acoustic modems and are combined with realistic underwater communication models. Additionally, novel bio-inspired underwater acoustic communication techniques are also proposed to improve the coordination performance. I also designed and implemented an underwater network emulator using WHOI Micro-Modems, and the performance of the proposed solutions is evaluated using this emulator as well as software simulations. Communication protocols were also implemented on acoustic modems and tested in ocean experiments.Ph. D.Includes bibliographical referencesIncludes vitaby Baozhi Che

Development of a large bore superconducting magnet with narrow liquid helium channels

A large bore NbTi superconducting magnet is designed, manufactured and tested. The superconducting magnet has an inner diameter of 460 mm, outer diameter of 600 mm and height of 540 mm. The magnet is dry wound using rectangular and round superconducting wires with their dimensions of 1.3 times 2.0 mm and Oslash1.3 mm respectively. In order to improve helium cooling effect, narrow liquid helium channels are set between adjacent layers. The magnet can generate 4 T central magnetic field at the designed operating current of 305 A. The magnet has been tested in a compact cryostat. Experimental results show that the superconducting magnet reached the designed magnetic performance. Details of the magnet design, fabrication and test are described in this paper

QUO VADIS: QoS-aware Underwater Optimization Framework for Inter-vehicle Communication using Acoustic Directional Transducers

Abstract—Underwater acoustic communications consume a significant amount of energy due to the high transmission power (10−50 W) and long data packet transmission times (0.1−1 s). Mobile Autonomous Underwater Vehicles (AUVs) can conserve energy by waiting for the ‘best ’ network topology configuration, e.g., a favorable alignment, before starting to communicate. Due to the frequency-selective underwater acoustic ambient noise and high medium power absorption – which increases exponentially with distance – a shorter distance between AUVs translates into a lower transmission loss and a higher available bandwidth. By leveraging the predictability of AUV trajectories, a novel solution is proposed that optimizes communications by delaying packet transmissions in order to wait for a favorable network topology (thus trading end-to-end delay for energy and/or throughput). In addition, the solution proposed – which is implemented and compared with other solutions using an emulator that integrates underwater acoustic WHOI Micro-Modems – exploits the frequency-dependent radiation pattern of underwater acoustic transducers to reduce communication energy consumption by adjusting the transducer directivity on-the-fly. I