Space station experiment definition: Long-term cryogenic fluid storage

The conceptual design of a space station Technology Development Mission (TDM) experiment to demonstrate and evaluate cryogenic fluid storage and transfer technologies is presented. The experiment will be deployed on the initial operational capability (IOC) space station for a four-year duration. It is modular in design, consisting of three phases to test the following technologies: passive thermal technologies (phase 1), fluid transfer (phase 2), and active refrigeration (phase 3). Use of existing hardware was a primary consideration throughout the design effort. A conceptual design of the experiment was completed, including configuration sketches, system schematics, equipment specifications, and space station resources and interface requirements. These requirements were entered into the NASA Space Station Mission Data Base. A program plan was developed defining a twelve-year development and flight plan. Program cost estimates are given

Demonstrating that Medical Devices Satisfy User Related Safety Requirements

One way of contributing to a demonstration that a medical device is acceptably safe is to show that the device satisfies a set of requirements known to mitigate hazards. This paper describes experience using formal techniques to model an IV infusion device and to prove that the modelled device captures a set of requirements. The requirements chosen for the study are based on a draft proposal developed by the US Food and Drug Administration (FDA). A major contributor to device related errors are (user) interaction errors. For this reason the chosen models and requirements focus on user interface related issues.FEDER - Federación Española de Enfermedades Raras(000062)This work has been funded by the EPSRC research grant EP/G059063/1: CHI+MED (Computer–Human Interaction for Medical Devices). J. C. Campos was funded by project NORTE-07-0124-FEDER-00006

Scaling Hierarchical N-body Simulations on GPU Clusters

Abstract — This paper focuses on the use of GPGPU-based clus-ters for hierarchical N-body simulations. Whereas the behavior of these hierarchical methods has been studied in the past on CPU-based architectures, we investigate key performance issues in the context of clusters of GPUs. These include kernel orga-nization and efficiency, the balance between tree traversal and force computation work, grain size selection through the tuning of offloaded work request sizes, and the reduction of sequential bottlenecks. The effects of various application parameters are studied and experiments done to quantify gains in performance. Our studies are carried out in the context of a production-quality parallel cosmological simulator called ChaNGa. We highlight the re-engineering of the application to make it more suitable for GPU-based environments. Finally, we present performance results from experiments on the NCSA Lincoln GPU cluster, including a note on GPU use in multistepped simulations

Generic safety requirements for developing safe insulin pump software

Background: The authors previously introduced a highly abstract generic insulin infusion pump (GIIP) model that identified common features and hazards shared by most insulin pumps on the market. The aim of this article is to extend our previous work on the GIIP model by articulating safety requirements that address the identified GIIP hazards. These safety requirements can be validated by manufacturers, and may ultimately serve as a safety reference for insulin pump software. Together, these two publications can serve as a basis for discussing insulin pump safety in the diabetes community. Method: In our previous work, we established a generic insulin pump architecture that abstracts functions common to many insulin pumps currently on the market and near-future pump designs. We then carried out a preliminary hazard analysis based on this architecture that included consultations with many domain experts. Further consultation with domain experts resulted in the safety requirements used in the modeling work presented in this article. Results: Generic safety requirements for the GIIP model are presented, as appropriate, in parameterized format to accommodate clinical practices or specific insulin pump criteria important to safe device performance. Conclusion: We believe that there is considerable value in having the diabetes, academic, and manufacturing communities consider and discuss these generic safety requirements. We hope that the communities will extend and revise them, make them more representative and comprehensive, experiment with them, and use them as a means for assessing the safety of insulin pump software designs. One potential use of these requirements is to integrate them into model-based engineering (MBE) software development methods. We believe, based on our experiences, that implementing safety requirements using MBE methods holds promise in reducing design/implementation flaws in insulin pump development and evolutionary processes, therefore improving overall safety of insulin pump software

Architecture reconstruction and analysis of medical device software

New research is underway at the FDA to investigate the benefits of integrating architecture analysis into safety evaluations of medical-device software. Due to the complexity in setting up testing environments for such software, the FDA is unable to conduct large-scale safety testing; instead, it must rely on other techniques to build an argument for whether the software is safe or not. The architecture analysis approach, formalized using relational algebra, is based on reconstructing abstract, yet precise, architectural views from source code to help build such arguments about safety. This paper discusses the use of the formal approach to analyze the Computer-Assisted Resuscitation Algorithm (CARA) software, which controls an infusion pump designed to provide automated assistance for transfusing blood. The results suggest that a) architecture analysis offers many insights related to software quality in general and testability (i.e., the ease of testing) and its impact on safety in particular, and b) architectural analysis results can be used to help configure static analysis tools to improve their performance for verifying safety properties

Laser beam melting for tooling applications - new perspectives for resource-efficient metal forming and die casting processes

Applying additive manufacturing technologies in the tooling sector is reaching a new level with Laser Beam Melting, since this technology allows layer-by-layer manufacturing of completely dense tool and die inserts in standard high-alloyed tool steel. The technology is now ready to go beyond applications in low impact processes like plastic injection moulding and enters metal working process applications like metal forming and die casting. The potential of additive manufacturing for added value in tooling applications has now been investigated for various metal working processes. The paper presents results of research and pilot application projects to apply laser beam melting to manufacture tooling for metal forming and aluminium die casting. The paper describes the shortcomings of conventional cooling channels in metal working tools and the resulting inadequate cooling effect in critical areas. The paper shows how innovative cooling systems can be implemented in metal working dies through laser beam melted die inserts. Cooling of specific die areas has been realized by placing specially designed cooling channels very close to the die cavity, targeting shorter cycle times, structural and dimensional quality improvements of manufactured metal parts and a reduction of energy consumption for cooling and idle times of forming presses and die casting machines. The paper will present the achieved results for both metal working applications and point out the general potential of additive manufacturing in tooling

Model-based development of the Generic PCA infusion pump user interface prototype in PVS

Abstract. A realistic user interface is rigorously developed for the US Food and Drug Administration (FDA) Generic Patient Controlled Analgesia (GPCA) pump prototype. The GPCA pump prototype is intended as a realistic workbench for trialling development methods and techniques for improving the safety of such devices. A model-based approach based on the use of formal methods is illustrated and implemented within the Prototype Verification System (PVS) verification system. The user interface behaviour is formally specified as an executable PVS model. The specification is verified with the PVS theorem prover against relevant safety requirements provided by the FDA for the GPCA pump. The same specification is automatically translated into executable code through the PVS code generator, and hence a high fidelity prototype is then developed that incorporates the generated executable code

How to assure correctness and safety of medical software: the hemodialysis machine case study

Medical devices are nowadaysmore and more software dependent, and software malfunctioning can lead to injuries or death for patients. Several standards have been proposed for the development and the validation of medical devices, but they establish general guidelines on the use of common software engineering activities without any indication regarding methods and techniques to assure safety and reliability. This paper takes advantage of the Hemodialysis machine case study to present a formal development process supporting most of the engineering activities required by the standards, and provides rigorous approaches for system validation and verification. The process is based on the Abstract State Machine formal method and its model refinement principle