Managing complexity of control software through concurrency

In this thesis, we are concerned with the development of concurrent software for embedded systems. The emphasis is on the development of control software. Embedded systems are concurrent systems whereby hardware and software communicate with the concurrent world. Concurrency is essential, which cannot be ignored. It requires a proper handling to avoid pathological problems (e.g. deadlock and livelock) and performance penalties (e.g. starvation and priority conflicts). Multithreading, as such, leads to sources of complexity in concurrent software. This complexity is considered frightening, because it complicates the software designs and the resulting code. Moreover, this paradigm complicates the understanding of the behaviour of concurrent software. A paradigm with a precise understanding of concurrency is essential. In this thesis, a methodology is proposed that comprises a paradigm of fundamental aspects of concurrency

Bioengineering models of cell signaling

Strategies for rationally manipulating cell behavior in cell-based technologies and molecular therapeutics and understanding effects of environmental agents on physiological systems may be derived from a mechanistic understanding of underlying signaling mechanisms that regulate cell functions. Three crucial attributes of signal transduction necessitate modeling approaches for analyzing these systems: an ever-expanding plethora of signaling molecules and interactions, a highly interconnected biochemical scheme, and concurrent biophysical regulation. Because signal flow is tightly regulated with positive and negative feedbacks and is bidirectional with commands traveling both from outside-in and inside-out, dynamic models that couple biophysical and biochemical elements are required to consider information processing both during transient and steady-state conditions. Unique mathematical frameworks will be needed to obtain an integrated perspective on these complex systems, which operate over wide length and time scales. These may involve a two-level hierarchical approach wherein the overall signaling network is modeled in terms of effective "circuit" or "algorithm" modules, and then each module is correspondingly modeled with more detailed incorporation of its actual underlying biochemical/biophysical molecular interactions

A Faster-Than Relation for Semi-Markov Decision Processes

When modeling concurrent or cyber-physical systems, non-functional requirements such as time are important to consider. In order to improve the timing aspects of a model, it is necessary to have some notion of what it means for a process to be faster than another, which can guide the stepwise refinement of the model. To this end we study a faster-than relation for semi-Markov decision processes and compare it to standard notions for relating systems. We consider the compositional aspects of this relation, and show that the faster-than relation is not a precongruence with respect to parallel composition, hence giving rise to so-called parallel timing anomalies. We take the first steps toward understanding this problem by identifying decidable conditions sufficient to avoid parallel timing anomalies in the absence of non-determinism.Comment: In Proceedings QAPL 2019, arXiv:2001.0616

Integrated product relationships management : a model to enable concurrent product design and assembly sequence planning

The paper describes a novel approach to product relationships management in the context of concurrent engineering and product lifecycle management (PLM). Current industrial practices in product data management and manufacturing process management systems require better efficiency, flexibility, and sensitivity in managing product information at various levels of abstraction throughout its lifecycle. The aim of the proposed work is to manage vital yet complex and inherent product relationship information to enable concurrent product design and assembly sequence planning. Indeed, the definition of the product with its assembly sequence requires the management and the understanding of the numerous product relationships, ensuring consistency between the product and its components. This main objective stresses the relational design paradigm by focusing on product relationships along its lifecycle. This paper gives the detailed description of the background and models which highlight the need for a more efficient PLM approach. The proposed theoretical approach is then described in detail. A separate paper will focus on the implementation of the proposed approach in a PLM-based application, and an in-depth case study to evaluate the implementation of the novel approach will also be given

Development of a concurrent engineering tutorial as part of the “ESA_Lab@” initiative

As part of the “ESA_Lab@" initiative, a Concurrent Engineering facility has been constructed at the Mechanical Engineering department of Technical University Darmstadt. Concurrent Engineering is a well-proven concept for designing complex space systems and missions in the pre-phase 0/A mission phase. The Concurrent Engineering methodology and processes are enabled by a multidisciplinary team and specific infrastructure in terms of both hardware and software, which generate an effective and time efficient design management system. The university’s “Concurrent Engineering Lab” provides an environment for both researchers and students to explore and apply the Concurrent Engineering approach in areas such as (model-based) systems engineering, Industry 4.0/ Space 4.0, and space traffic management. Furthermore, collaboration with the European Space Operations Centre – also located in Darmstadt – regarding the application of Concurrent Engineering for Ground Segment & Operations has been started. The first addition to the university’s curriculum centered around the Concurrent Engineering Lab will be a “Concurrent Engineering Tutorial”, an opportunity to introduce the Concurrent Engineering methods and tools via hands-on experience to students of the newly established master’s degree program “Aerospace Engineering”. “Tutorials” are elective block courses of the degree program which offer practical learning experiences in many different fields, awarding 4 credit points upon successful completion. Building on the lectures "Fundamentals of Space Systems" and "Space Systems and Space Operations", the week-long “Concurrent Engineering Tutorial” will challenge students to use their acquired knowledge to develop a preliminary design for a predefined CubeSat mission. This Tutorial will not only provide a closer understanding of the individual subsystems of the space segment of a mission, the Concurrent Engineering process and the relevant software “COMET” by RHEA Group but will also create a synergy with a student association of the university, as one of their projects is the development of a CubeSat. This paper describes the background and approach to the development of the Tutorial, in particular the structure of the re-usable model architecture in “COMET”, which was specifically derived and implemented for this purpose and validated via a pilot stud

Temporal Control of the TGF-β Signaling Network by Mouse ESC MicroRNA Targets of Different Affinities.

Although microRNAs (miRNAs) function in the control of embryonic stem cell (ESC) pluripotency, a systems-level understanding is still being developed. Through the analysis of progressive Argonaute (Ago)-miRNA depletion and rescue, including stable Ago knockout mouse ESCs, we uncover transforming growth factor beta (TGF-β) pathway activation as a direct and early response to ESC miRNA reduction. Mechanistically, we link the derepression of weaker miRNA targets, including TGF-β receptor 1 (Tgfbr1), to the sensitive TGF-β pathway activation. In contrast, stronger miRNA targets impart a more robust repression, which dampens concurrent transcriptional activation. We verify such dampened induction for TGF-β antagonist Lefty. We find that TGF-β pathway activation contributes to the G1 cell-cycle accumulation of miRNA-deficient ESCs. We propose that miRNA target affinity is a determinant of the temporal response to miRNA changes, which enables the coordination of gene network responses

Visualization of Concurrent Computations: Doctor of Science Dissertation Proposal

Visualization, defined as the graphical representation of symbolic objects and processes, is recognized as an important tool to aid human understanding. This is particularly true in the area of program visualization, which uses images to illustrate the execution of programs. This proposal describes research to investigate the visualization of concurrent computations. The research has two major goals: the development of a model of visualization suitable for concurrent computations, and the development of methodology for constructing visualizations. The proposed visualization model treats visualization as a function from the state of the computation to an image. This differs significantly from the approach used by existing (single-process) visualization systems, but seems highly suitable for concurrent computations. The proposed methodology uses the concepts of program correctness to identify the key properties of a computation and suggest methods of visualizing these properties