89 research outputs found
Establishing Confidence in Safety Assessment Evidence
No full textWith the increased complexity and higher safety commitment of modern safety–critical systems, safety assessment models of these systems are increasingly complicated and obscure. In practice, however, there is insufficient guidance on how to improve the understanding and evaluation of these models, while they are often used as important items of evidence in safety cases. This significantly threatens the confidence we can have in the soundness of safety cases.
In this thesis, a coherent, structured approach to establishing confidence in safety assessment evidence is developed. Firstly, a means for the structured documentation of the core data elements of safety assessment models is defined, to support the development of both primary safety arguments and confidence arguments. Secondly, a model of evidence is developed to support the interfacing of safety assessment evidence with safety arguments. Thirdly, a
structured cross-model inconsistency analysis method is proposed as a means of scrutinizing potentially inadequate models. Finally, an expanded argument construction process is established to add rigour to safety case development, and a number of argument patterns are designed to guide and inspire structured justification of the adequacy of safety assessment models as evidence for safety critical systems.
The evaluation of the approach is carried out primarily through examples and cases studies. It is demonstrated that the approach is feasible and the confidence issue in safety assessment evidence is addressed more explicitly and more rigorously by using the approach
Do safety cases have a role in aircraft certification?
No full textAbstractSafety cases, as a means of demonstrating system safety, have been increasingly used as the basis for system assurance, especially in safety or mission-critical systems in fields such as offshore installation, railway operations, nuclear plants, and air traffic control. Despite the increased adoption of safety cases in the aforementioned areas, the usage of safety arguments is still limited in the certification of a civil aircraft design. This paper provides 1) a brief overview of the key regulations and guidelines in support of aero-system certification especially at the development stage; 2) a review of the history, the essence, and the practice of safety cases; 3) an analysis of the role of processes and safety arguments in aircraft certification; and 4) recommendations on the future work in terms of further application of safety cases in aircraft certification
Magnetically Driven Muco-Inert Janus Nanovehicles for Enhanced Mucus Penetration and Cellular Uptake
No full textOne of the main challenges of transmucosal drug delivery is that of enabling particles and molecules to move across the mucosal barrier of the mucosal epithelial surface. Inspired by nanovehicles and mucus-penetrating nanoparticles, a magnetically driven, mucus-inert Janus-type nanovehicle (Janus-MMSN-pCB) was fabricated by coating the zwitterionic polymer poly(carboxybetaine methacrylate) (pCB) on the mesoporous silica nanorod, which was grown on one side of superparamagnetic Fe3O4 nanoparticle using the sol–gel method. X-ray diffraction, transmission electron microscopy, vibrating sample magnetometry, and Fourier infrared spectroscopy were used to characterize the structure and morphology of the nanovehicles, proving the success of each synthesis step. The in vitro cell viability assessment of these composites using Calu-3 cell lines indicates that the nanovehicles are biocompatible in nature. Furthermore, the multiparticle tracking, Transwell® system, and cell imaging experimental results demonstrate that both the modification of pCB and the application of a magnetic field effectively accelerated the diffusion of the nanovehicles in the mucus and improved the endocytosis through Calu-3. The favorable cell uptake performance of Janus-MMSN-pCB in mucus systems with/without magnetic driving proves its potential role in the diagnosis, treatment, and imaging of mucosal-related diseases
Implications from protein uptake kinetics onto dextran-grafted Sepharose FF coupled with ion exchange and affinity ligands
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Cooperative Maneuvering Mathematical Modeling for Multi-Tugs Towing a Ship in the Port Environment
No full textThe towing operation of multi-tug-assisted ship navigation mainly relies on the experience of the captain, and there is no set of effective operation methods. Therefore, it is difficult to achieve accurate assisted navigation when multiple tugboats work in coordination. The calculation method of maneuverability of the towing system with multi-tug-assisted navigation is proposed in this paper. In view of the complexity of multi-tug-assisted large ship maneuvering, this article focuses on solving the problems of force analysis and maneuvering modeling between the multi-tug and ship systems. Firstly, a maneuvering mathematic model for towing ships is established, and the hydrodynamic force of the hull, rope force of the tugs, and force of wind interference are analyzed. The thrust and moment of the ducted azimuthal propeller are calculated, and the mathematical model of the tug’s cable tension is discussed. Then, the fourth-order Runge–Kutta method is used to solve the differential equations of the maneuvering motion of the ships and each tug. Based on the ship-towing process by multiple tugs, a multi-tug-assisted ship towing simulation platform was built by using the Visual Studio development tool. Finally, on the simulation platform, multi-tug longitudinal-towing-simulation experiments at different speeds were carried out, and the simulation of turning towing maneuvers under the influence of wind was done. The simulation results showed that as the towing speed increases, the initial towing speed fluctuates greatly. There is a significant drift effect on the ships by the wind force. And the wind will cause a fluctuation in the tug’s rope force. The simulation of the multi-tugs towing a ship entering the port was carried out in the port environment. The results showed that the multi-tug towing system and simulation platform may be used for the safety training of the tug’s crew
A Reply to “Comments on “A New Elliptical Model for Device-Free Localization””
No full textRecently, a comment paper on “A New Elliptical Model for Device-Free Localization” (Sensors 2016, 16, 577) has been presented, and the authors have provided a modified model. However, there are still some misunderstandings. In this reply, we further explain the proposed elliptical model in (Sensors 2016, 16, 577) to make it more understandable
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