36,355 research outputs found
Methods and models for analyzing and controlling the safety in operations of autonomous marine systems
No full textAutonomous marine systems (AMS), such as autonomous underwater vehicles (AUVs), and unmanned surface vehicles (USVs) have evolved over the past decades. Maritime autonomous surface ships (MASS) are gradually being developed and commissioned. AMS are applied in different types of industries and research. Examples include the application of USVs or AUVs for ocean monitoring, and the development of MASS for future cargo and personnel transportation.
In these operations, AMS can help reduce the risk of personnel exposure to harsh environments, reduce the operational costs, and improve the efficiency and performance of the human operators. However, compared to conventional marine systems, new types of failure might be introduced to AMS operations due to unforeseen interdependencies in the system design, dynamic operating environments, maintenance challenges, insufficient situation awareness and decision-making from human operators, etc. Also, AMS functions are constantly being improved, and the operations of AMS are becoming more complex and advanced. The safety issues of these systems have become even more critical. Techniques for analyzing and controlling the safety of AMS operations are therefore required.
The overall aim of this PhD project is to develop methods and models for analyzing and controlling safety in operations of AMS. It is refined into the following three research objectives that are addressed in five research articles:
• Identify and analyze hazards and hazardous events in the operation of autonomous marine systems and evaluate the applicability of relevant methods as a basis for online risk modeling of autonomous marine systems.
• Analyze the dynamic changes in the operating environment and system status, and model their impacts on the safe operation.
• Propose a general method for developing online risk models for autonomous marine systems and operations, supporting risk-based control.
The work presented here reviews the existing methods and models and identifies the main research challenges and gaps with respect to the above research objectives. The research presented in the thesis addressed some of these issues. The main contributions of this thesis are summarized as follows:
• Investigation of the potential hazards/ hazardous events during the operation with multiple AMS and how these hazards/ hazardous events may affect the safe and reliable operations of AMS. The results highlight the importance of considering unsafe interactions in hazard identification or risk assessment in AMS operations.
• Comprehensive hazard identification works with a number of potential hazards/ hazardous events that may affect the safe operation of an under-ice AUV operation through various methods. The results contribute research and practical implications for improved engineering design and operational procedures to enhance the safety and robustness of future AMS operations in the Arctic.
• Identification of a list of evaluation criteria for online risk models for AMS and comprehensive evaluation of the applicability of several existing methods for online risk modeling of AMS. The evaluation results contribute to an appropriate first step towards a general framework for online risk modeling for AMS.
• Proposal for a dynamic risk analysis method to determine the dynamic changes in the operating environment and assess the environmental impact on the safe operation of AMS.
• Proposal for a novel dynamic maintenance planning method for AMS that addresses challenges in maintenance planning, including the high consequence of system shutdown, limited and irregular maintenance opportunities, and various dependencies among components.
• Proposal for a general framework for the online risk modeling of AMS to enhance the intelligence of the AMS, its situation awareness, and decision-making. The proposed framework addresses several challenges in developing online risk modeling, e.g., evidence uncertainty.
• Proposal for a two-level strategy to develop a supervisory risk control (SRC) system for AMS operations based on the developed online risk model. The SRC system can improve the intelligence of AMS by enabling its risk-based control.
In conclusion, the research and findings presented in the thesis provide researchers and practitioners in the field with a comprehensive overview of safety issues in AMS operations, and novel methods and models for analyzing and handling these. The proposed methods and models are expected to improve the safety of future AMS operations
Physical Modeling of Evaporative Emission Control System in Gasoline Fueled Automobiles: a Review
No full textFuel evaporative emission from a vehicle fuel tank have long been known to be an important source of pollution, and international regulation on automotive Volatile Organic Compounds (VOC) are becoming increasingly stringent every year, because of their eects on human health and environment. The most cost-eective solution for limiting the release of VOC to the environment is their adsorption by activated carbon through an evaporative canister device that is integrated in the vehicle fuel system. Analysis and development of these systems requires an in-depth study of the evaporation and the adsorption/desorption processes. Many theoretical and experimental studies have been performed during the years, and several physical models have been developed. This paper presents a state-of-the-art review of these studies, speci-cally focusing on the mathematical modeling of the evaporation phenomena and its application for describing real conditions, along with several fuel adsorption and desorption (purging) models of carbon canisters. A knowledge of the evaporation phenomena and adsorption/desorption process can lead to a better canister
design and purging strategies, in order to match the vehicle emission regulations that are being adopted worldwide, in a view of sustainable mobility
Influence of Processing and Stabilizer Selection on Microstructure, Stability and Rheology of Emulsion-Based Semisolid Formulations
No full textBackground/Objectives: Emulsion-based semisolid formulations are important delivery systems for many applications, including pharmaceuticals, cosmetics and food. The manufacturing process for such formulations typically involves a series of heating, cooling, mixing and emulsification steps. Stabilizing agents are usually included in such formulations, as emulsions are intrinsically unstable and are prone to various destabilization mechanisms. Precise control of each processing parameter and the selection of an appropriate stabilizing agent are essential for delivering products with long-term stability and the desired properties. In this study, the effects of emulsification temperature and the selection of the stabilizing agent on key product attributes were investigated to enable improved design and optimization of both the formulation and manufacturing process. Methods: Model emulsion systems containing propylene glycol (PG) as the dispersed phase and mineral oil as the continuous phase were prepared at different emulsification temperatures to cover both pre-crystallization and post-crystallization regimes. Three stabilizing agents, namely mono-and-diglyceride (MDG), neat monoglyceride (MG) and neat diglyceride (DG), were studied. Their crystallization behavior was first examined to determine crystallization temperatures and crystal morphologies. The resulting emulsion samples were then characterized in terms of their microstructure, physical stability and rheological properties. Results: The emulsions prepared under post-crystallization conditions exhibited better physical stability, higher rheological parameters (crossover stress and viscosity) and a more rigid microstructure compared to those formed under pre-crystallization conditions, regardless of the stabilizer used. Rheological properties were found to corelate well with physical stability. In the pre-crystallization regime, poor stability could partially be mitigated by lowering the emulsification temperature. MG was generally more effective than DG in stabilizing the emulsions and led to higher rheological properties, despite both crystallizing into the same polymorph within the system. This difference in performance was attributed to variations in the crystal morphology and spatial distribution within the emulsion. Notably, the MG-stabilized emulsions also displayed a self-hardening effect during storage. Conclusions: The selection of the appropriate stabilizing agents and processing conditions tailored to the specific system is critical for the successful manufacture of emulsion-based semisolid products with an optimized performance
Special issue: Process safety in times of a pandemic
No full textGreen Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Safety and Security Scienc
Distributed human computation framework for linked data co-reference resolution
No full textDistributed Human Computation (DHC) is a technique used to solve computational problems by incorporating the collaborative effort of a large number of humans. It is also a solution to AI-complete problems such as natural language processing. The Semantic Web with its root in AI is envisioned to be a decentralised world-wide information space for sharing machine-readable data with minimal integration costs. There are many research problems in the Semantic Web that are considered as AI-complete problems. An example is co-reference resolution, which involves determining whether different URIs refer to the same entity. This is considered to be a significant hurdle to overcome in the realisation of large-scale Semantic Web applications. In this paper, we propose a framework for building a DHC system on top of the Linked Data Cloud to solve various computational problems. To demonstrate the concept, we are focusing on handling the co-reference resolution in the Semantic Web when integrating distributed datasets. The traditional way to solve this problem is to design machine-learning algorithms. However, they are often computationally expensive, error-prone and do not scale. We designed a DHC system named iamResearcher, which solves the scientific publication author identity co-reference problem when integrating distributed bibliographic datasets. In our system, we aggregated 6 million bibliographic data from various publication repositories. Users can sign up to the system to audit and align their own publications, thus solving the co-reference problem in a distributed manner. The aggregated results are published to the Linked Data Cloud
Intersystem soft handover for converged DVB-H and UMTS networks
No full textDigital video broadcasting for handhelds (DVB-H) is the standard for broadcasting Internet Protocol (IP) data services to mobile portable devices. To provide interactive services for DVB-H, the Universal Mobile Telecommunications System (UMTS) can be used as a terrestrial interaction channel for the unidirectional DVB-H network. The converged DVB-H and UMTS network can be used to address the congestion problems due to the limited multimedia channel accesses of the UMTS network. In the converged network, intersystem soft handover between DVB-H and UMTS is needed for an optimum radio resource allocation, which reduces network operation cost while providing the required quality of service. This paper deals with the intersystem soft handover between DVB-H and UMTS in such a converged network. The converged network structure is presented. A novel soft handover scheme is proposed and evaluated. After considering the network operation cost, the performance tradeoff between the network quality of service and the network operation cost for the intersystem soft handover in the converged network is modeled using a stochastic tree and analyzed using a numerical simulation. The results show that the proposed algorithm is feasible and has the potential to be used for implementation in the real environment
Beyond interfaces: A usability study of Chinese journal databases
No full textA presentation at the Council on East Asian Libraries (CEAL) annual meeting in Boston, MA on March 21, 2007
Rose Galaida and the Central China Relief Records, 1946: Discovery, Investigation, and Implications
No full textThe materials in the Central China Relief Records (CCRR) collection provide a window to the experiences of Rose Galaida in Hubei. The collection consists of about 100 documents totaling over 300 pages (excluding duplicate copies) and 5 photographs.Peer reviewedPublished in the Journal of East Asian Libraries and available from the journal at: https://scholarsarchive.byu.edu/jeal/vol2011/iss153/
Breaking New Ground in East Asia Library History
No full textReview of Peter X. Zhou. Collecting Asia: East Asian Libraries in North America (2010).Published in H-Net Reviews in the Humanities and Social Sciences and available at: http://www.h-net.org/reviews/showrev.php?id=32231March 201
One step preparation of pure tau-MnAl phase with high magnetization using strip casting method
No full textFerromagnetic phase of Mn-Al exhibits great potential in the rare-earth free permanent magnetic materials due to its high magnetocrystalline anisotropy, high magnetization, high Curie temperature and low cost. In this work, the strip casting technique was applied to prepare MnAl magnetic phase. X-ray diffraction and energy dispersive X-ray analyses indicate that the as-prepared Mn54Al46 strip sample consists of pure tau-MnAl magnetic phase. It is found that the composition of Mn54Al46 is suitable to prepare tau-MnAl phase during the strip casting process. The Mn54Al46 strip sample synthesized through the strip casting exhibits a fairly high magnetization of 114 emu/g under a field of 5 T, while the coercivity of iHc = 2.8 kOe, magnetization of M-5T = 63.9 emu/g at room temperature can be obtained for Mn54Al46 powder sample. This preparation method can produce a large amount of tau-phase MnAl alloy and promote mass industrialized production. (C) 2017 Author(s)
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