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Conceptualization and design of intellectualized, socialized, and personalized cyber-physical systems (CPSs) need integration of existing knowledge across the involved disciplines, as well as exploration and synthesis of novel knowledge beyond disciplinary boundaries. The latter needs a combined use of interdisciplinary, multidisciplinary, and transdisciplinary research. Supradisciplinary research has emerged as a new doctrine of combining these research approaches from epistemological, methodological, and procedural perspectives. However, no methodology can be found in the literature that could facilitate the practical execution of supradisciplinary research programs. This position paper proposes a conceptual framework that can be used as a blueprint for operationalization of such undertakings. The framework rests on six generic pillars: (i) problematics, (ii) infrastructure, (iii) method, (iv) stakeholders, (v) operations, and (vi) knowledge. It specifies the major concerns that have to be taken into consideration in a systematic manner in developing executional scenarios for supradisciplinary research. The framework facilitates (i) management of research organization tasks, (ii) joint formation of shared research infrastructure, (ii) setting up concrete research program, (iii) academic partnering and public stakeholder involvement, (iv) process flow management and capacity/competence allocation, (v) a holistic knowledge synthesis, assessment, and consolidation, and (vi) development of tools supporting the preparation and execution of large-scale supradisciplinary research. In its current form, it does not cover the specific societal and personal issues of a successful organization of the inquiry at individual researchers, research teams, and research community levels. A community-based follow-up research may focus on the practical application and testing of the framework in concrete cases—a task that an individual researcher cannot address.

Mathematical modelling of the shape-forming process of multi-layer multi-bead parts dealing with (i) a single layer, (ii) inclination angles and (iii) various slopes, is carried out. In the layers-overlapping model, material shortage areas are generated at the edges of layers. To solve the problem, the deposition amount of beads at the edges of the second and above layers should be modified, in association with the parameters applied to fabricate the slope. Various basic inclined components were deposited to validate the proposed mathematical formulation. Findings from the basic experiments were: (i) depositing additional material to compensate for the material shortage areas is necessary for realizing the designed geometries of the layers, (ii) depositing the bead at the layer edges alongside an already-deposited neighboring bead enables a better shape-forming in the case of negative slopes and (iii) the deposition order of beads in a layer has little influence on the shape formation of positive slopes. A complex part was also fabricated as a case study to validate the model and findings in the real-life context. Practical issues with regard to using the model and the solutions to the issues were discussed.

Nautical traffic management in The Netherlands is shifting from local traffic control to corridor traffic management. Current traffic management systems do not sufficiently support operators in perceptual and cognitive process to interpret and understand the large amounts of information needed for corridor traffic management. Newly developed user interface concepts aim to overcome deficiencies of current interface designs that insufficiently support situation awareness assessment. The effects of these new user interfaces, however, are insufficiently known due to the intricate relations between situation awareness, task performance, and workload. The objective of this study is to evaluate the effects of the three previously developed user interface concepts on operators’ situation awareness, task performance, and workload to gain better insights into the benefits and limitations of the user interface design concepts. The effects were tested in a simulator environment. The results show that user interface features of an integrated user interface allowed operators to apply more effective information processing, which resulted in better task performance. Features of a context-dependent adaptable user interface triggered proactive behavior of operators, which resulted in better task performance for tasks in which operators require insight into future activities of the elements in the environment.

Robotic wire and arc additive manufacturing (WAAM) systems are required to provide predictable and efficient operations to fabricate solid metallic parts with high morphological fidelity and geometric accuracy. Since the metallic parts are fabricated based on a layer-by-layer principle, the interactions between the neighboring beads and layers strongly influence the geometric accuracy of the fabricated part. The layers-overlapping process has been studied and a traditional layers-overlapping model (T-LOM) has been published in the literature. This paper proposes a layers-overlapping strategy (LOS), based on which a revised layers-overlapping model (R-LOM) was proposed for the fabrication of multi-layer multi-bead (MLMB) components with homogeneous layers. A mathematical model for layers-overlapping is presented, which considers the material shortage areas at the edges of the layers. This is important since the material shortage areas result in a situation that the component width is smaller than the expected value. In addition, they will be accumulated when multiple layers are overlapped through normal unidirectional parallel (NUP) paths. The proposed LOS addresses two aspects: (i) the deposition amount of the first bead and the last bead in the lap layers should be increased and (ii) the deposition position of the first bead and the last bead in the lap layers should be moved towards the edges with a given offset distance. Validation experiments were designed and conducted to test the proposed concepts and models. The experimental results indicated that (i) the R-LOM enables the MLMB components to achieve the expected width and (ii) for components deposited with NUP paths, the R-LOM eliminates the effect of accumulation of material shortage areas on the first bead and increases the surface flatness.

Wire and arc additive manufacturing (WAAM) is a competitive technology for fabricating metallic parts with complex structure and geometry. It enables the fabrication of multi-layer multi-bead (MLMB) parts. The basis of planning the deposition paths is the beads overlapping model (BOM). The existing overlapping models consider only the geometric area of adjacent beads, but ignore the spreading of the melted weld beads. The objective of the research was to develop an enhanced BOM (E.BOM) for WAAM, which takes the spreading of the weld beads into consideration. A deposited bead spreads to the already deposited neighboring bead and as a consequence, its center point deviates from the center point of the fed (to be melted) wire. Experiments were designed to explore the relationships between the geometries of the beads, and the offset distance between the center of a weld bead and the center of the fed wire. An artificial neural network was used to predict the offset distance of a certain weld bead based on the results of the experiments. In addition, a reasoning algorithm was implemented to calculate the optimal distance between the centers of adjacent deposition paths in order to achieve a planned center distance between adjacent beads. This enables the control of the actual center distance of the adjacent beads according to an expected value. The E.BOM has been tested by validation experiments. On the one hand, it improves the surface flatness of layers of MLMB parts produced by WAAM. On the other hand, it prevents formation of defects inside the parts.

Smart cyber-physical systems (S-CPSs) are complex engineered systems empowered by cyber-physical computing and equipped with the capability of reasoning, learning, adapting, and evolving. As an outcome of data-driven dynamic computing, reasoning capabilities, and the run-time obtained own knowledge, nonlinear and emergent behavior of S-CPSs whilst in operation is an open issue, not experienced in the case of conventional technical systems. This paper analyzes the technical issues of run-time operation and emergent behavior of S-CPSs, reviews the current understanding and state of advancement in designing S-CPSs for run-time, explores the paradox, and issues of designing for run-time adaptation, and synthesizes some general principles that can be taken into consideration when addressing the challenges, first of all, in the context of advanced manufacturing systems. This paper introduces four levels of CPSs according to reasoning capabilities and adaptation freedom of systems, and recognizes the paradox that a system with a higher level of freedom requires a higher level of self-control and resource management according to the overall objective of operation. Specific and common design principles are presented and critically assessed for each advancement level of CPSs. The principles synthesized by the authors provide only a partial fulfillment of the generic need. The planned future research addresses these issues and proposes (largely implementation and application independent) genuine principles for system developers.

An approach to repairing surface defects of metal parts is proposed, which includes a combined application of (i) groove machining, (ii) wire and arc additive manufacturing (WAAM), and (iii) finishing machining. The completed analysis revealed that (i) the inclination angle of the groove to be machined is strongly influenced by the manufacturing parameters of the WAAM process, and (ii) the WAAM process models designed for fabricating parts on a flat substrate are not appropriate for filling grooves. To overcome these issues, this research investigated the range of variation of the proper inclination angle of the groove. A mathematical model was developed to determine the manufacturing parameters of WAAM that result in a proper filling of the groove. The effectiveness of the proposed fundamentals was investigated in a case study. The experimental results showed that using the proposed approach and the chosen manufacturing parameters resulted in a complete filling of the machined groove. The fabrication error of the main part of the repaired region before the finishing machining was less than 0.3 mm, while the ‘buy-to-fly’ ratio of the deposited material was 92.1%. The proposed approach for morphological repair lends itself to a computer-aided automatic part repair process.

As a novel computational approach, ubiquitous computing was emerging at the beginning of the 1980s and has reached a rather mature level by now. It assumes that computing can be available anywhere, anytime and in any context due to technological developments, social demands and calm implementations. Over the years, the opportunities of this computing paradigm have been explored and the benefits have been exploited successfully in many application fields. This survey paper addresses ubiquitous computing from the perspective of enabling computer aided design. The specific objectives of the reported survey are to: (i) give an overall account of the current status of ubiquitous computing and technologies, (ii) cast light on how ubiquitous computing has influenced the development of CAD systems, tools, and methods, and (iii) critically investigate future development opportunities of ubiquitous computing enabled computer aided design. First, the paper discusses the principles and typical technologies of ubiquitous computing. Then, the development and spectrum of the so-called standard computer aided design tasks are analyzed from a computational point of view. Afterwards, the already implemented design enabling functionalities are discussed and some additional functional possibilities are considered. The literature provides evidence that ubiquitous computing has not managed to revolutionize the methodologies or the systems of computer aided design so far, though many researchers intensively studied the affordances and the application possibilities of ubiquitous technologies. One reason is that ubiquitous computing technologies had in the last two decades to compete with other kinds of computational technologies, such as high-capacity computing, high-speed networking, immersive virtual reality, knowledge ontologies, smart software agents, mobile communication, etc., which had a much stronger influence on the development of computer aided design methods and systems. In combination with the rather conservative and conventionalist industrial practice of CAD system development and application, this may explain why the ubiquitous computing revolution remained weak in computer aided design. The literature clearly indicates that application of ubiquitous technologies did not lead to radically new functionalities that could have been exploited by the concerned industries. Consequently, it seems to be possible that computer aided design simply steps over the paradigm of ubiquitous computing and expects new functionalities from the emerging new computing paradigms, such as brain-computer interfacing, cyber-physical computing, biological computing, or quantum computing. An overall account of the status of ubiquitous computing and technologies in CAD.Penetration of ubiquitous computing remained insignificant in most applications.Application of ubiquitous technologies did not lead to radically new functionalities.Computer aided design steps over the paradigm of ubiquitous computing.New CAD functionalities expected from the emerging new computer paradigms.

There has been an increase in the amount and complexity of traffic on Dutch inland waterways. Traffic management shifted from local traffic control to corridor traffic management. Due to these changes, operators in nautical traffic management centers experience difficulty to gain and maintain sufficient situation awareness. In our previous research, three groups of deficiencies of current situation awareness support have been identified. To overcome these deficiencies, a theoretical framework for information engineering user interface concepts was developed and used for designing three interface concepts. A coherent, an integrated and a context-dependent adaptable user interface were designed and implemented as testable prototypes. To support the process of information engineering, we combined user-centered design techniques with the formalism of set theory, directed graphs and semantic networks. From a methodological point of view, these proved to be useful both in conceptualization and implementation of the concepts. The usability of these concepts was tested in a simulator environment. The results show that the implemented prototypes represent an important improvement compared to the traditional interface solutions currently used by nautical traffic management operators. However, it was recognized that the coherent user interface implementation still suffered from a number of deficiencies. The context-dependent adaptable user interface was evaluated most positively.

This paper presents an analysis scheme which aims to support asystematic study of required situation awareness (RSA). This scheme supportsidentification of deficiencies of support for situation awareness (SA).Information needs are goal and task dependent and can be defined usingexisting cognitive task analysis (CTA) methods. RSA, however, is a subset ofinformation needs and depends on the interaction between goals, tasks, systemfactors and individual factors. The analysis scheme has helped to identify thatthe current methods to define RSA do not support a distinction betweeninformation needs and RSA. The scheme was trialled in a nautical trafficmanagement context as an extension to existing CTA methods. The researchactivities necessary to study RSA and to identify deficiencies of current supportfor SA in nautical traffic management context were applied. The study showedthat the research set-up designed through application of the analysis schemehelped to define RSA, and that RSA is considerably context and operatordependent. Future research will focus on the potential for context-awareadaptable interface solutions to allow for RSA dependent informationvisualisation.

There are many real-life processes whose smart control requires processing context information. Though processing time-varied context information is addressed in the literature, domain-independent solutions for reasoning about time-varying process scenarios are scarce. This paper proposes a method for dynamic context computation concerning spatial and attributive information. Context is interpreted as a body of information dynamically created by a pattern of entities and relationships over a history of situations. Time is conceived as a causative force capable of changing situations and acting on people and objects. The invariant and variant spatial information is captured by a two-dimensional spatial feature representation matrix (SFR-matrix). The time-dependent changes in the context information are computed based on a dynamic context information (DCI) management hyper-matrix. This humble but powerful representation lends itself to a quasi-real time computing and is able to provide information about foreseeable happenings over multiple situations. Based on this, the reasoning mechanism proposed in this paper is able to provide informative instructions for users who needed to be informed in a dynamically changing situation. This paper uses the practical case of evacuation of a building in fire both as an explorative case for conceptualization of the functionality of the computational mechanism and as a demonstrative and testing application. Our intention is to use the dynamic context computation mechanism as a kernel component of a reasoning platform for informing cyber-physical systems (I-CPSs). Our future research will address the issue of context information management for multiple interrelated spaces.

The use of virtual prototypes in product development has been proliferating rapidly in the last two decades. New computational methods and tools have been developed to generate virtual prototypes for various engineering analysis, simulation and optimization tasks. Virtual prototypes can represent several aspects of products, including among others; geometric and structural properties, physical operations and behavior, and production, use and maintenance processes. The development of methods and tools is continuously expanding towards new application domains and users are getting more and more involved in testing virtual prototypes of products. Numerical computations are getting more accurate and reliable. Through the analyses and simulations of virtual prototypes, design engineers are now able to ensure that a product will possess exactly the desired functions, properties, behaviour, quality and cost. In the hope of new opportunities, multi-disciplinary, transdisciplinary and trans-domain knowledge transformation has become one of the central topics of scientific research in virtual prototyping. Typical examples of multiand transdomain knowledge transformation are based on: (i) generalization of methods (e.g., design of computer experiments), (ii) introduction of novel technologies to enable simulation of complex physical phenomena (e.g., multiple contact in ropes), (iii) development of multi-physics solvers that facilitate the analysis of multi-faceted systems, and (iv) integration of interactive virtual testing of concepts into the product validation processes. In the field of computer-aided engineering analysis and simulation, multi-disciplinary transformation of knowledge involves the following activities: (1) identification of opportunities for integration of knowledge of multiple disciplines, (2) exporting knowledge among various mono-disciplinary applications, and (3) combining monodisciplinary knowledge to enable multi-disciplinary simulation and optimization. It has to be noted that the mono-disciplinary analysis and simulation methods are also further refined. The new methods and tools allow us to model, simulate and optimize the operations of complex engineering systems, such as internal combustion engines, industrial process plants, multi-product packaging systems, smart robotic systems, etc. In this Special Issue, we provide examples of multi-, and trans-disciplinary and trans-domain knowledge and numerical computation technology transfer in the field of engineering analysis and simulation, in addition to presenting results of the efforts towards enhancing mono-disciplinary analysis and simulation approaches. Furthermore, we intend to show that the methods and tools proposed by the contributing authors are not only significant from an academic point of view, but are also valuable for the industrial practice. The selected papers cover a wide range of application fields, indicating the importance of multi-domain knowledge enrichment and transfer. Originally, the papers were presented at the Ninth International Symposium on Tools and Methods of Competitive Engineering (TMCE 2010), that was held in Ancona, Italy, from 12 until 16 April, 2010. The TMCE 2010 Symposium was jointly organized by the Universita Politecnica delle Marche, Italy, and the Delft University of Technology, the Netherlands. The papers have been thematically arranged in this special issue. The first five papers are representative examples of knowledge enrichment. They focus on monoZ. Rusak (&) I. Horvath Delft University of Technology, Delft, The Netherlands e-mail: Z.Rusak@tudelft.nl

Product design is a highly involved, often ill-defined, complex and iterative process, and the needs and specifications of the required artifact get more refined only as the design process moves toward its goal. An effective computer support tool that helps the designer make better-informed decisions requires efficient knowledge representation schemes. In today's world, there is a virtual explosion in the amount of raw data available to the designer, and knowledge representation is critical in order to sift through this data and make sense of it. In addition, the need to stay competitive has shrunk product development time through the use of simultaneous and collaborative design processes, which depend on effective transfer of knowledge between teams. Finally, the awareness that decisions made early in the design process have a higher impact in terms of energy, cost, and sustainability, has resulted in the need to project knowledge typically required in the later stages of design to the earlier stages. Research in design rationale systems, product families, systems engineering, and ontology engineering has sought to capture knowledge from earlier product design decisions, from the breakdown of product functions and associated physical features, and from customer requirements and feedback reports. VR (Virtual reality) systems and multidisciplinary modeling have enabled the simulation of scenarios in the manufacture, assembly, and use of the product. This has helped capture vital knowledge from these stages of the product life and use it in design validation and testing. While there have been considerable and significant developments in knowledge capture and representation in product design, it is useful to sometimes review our position in the area, study the evolution of research in product design, and from past and current trends, try and foresee future developments. The goal of this paper is thus to review both our understanding of the field and the support tools that exist for the purpose, and identify the trends and possible directions research can evolve in the future.

This article presents a new methodology that enables designers to include in simulations not only the physics aspects of artifact behavior, but also human actions. The motivation for this research came from the fact that none of the conventional approaches to engineering simulations includes manipulative control of products by users as foreseen by designers. By implementing control over physics simulations, changes in parameters can be introduced that alter the course of the simulated process. As a means to do this, we propose to use scenario bundles, with which designers can operationalize their conjectures of how human users interact with products as a series of interconnected simulations. For the imaginary use process described in a scenario bundle, the designer can specify various product designs, user characteristics, and environments, which may in each case lead to different concatenations of simulation actions. The proposal facilitates the exploration of possible mismatches and anomalies in use processes. In this article, we describe the theoretical fundamentals and the overall concept of the proposed methodology, as well as its realization as a proof-of-concept implementation. This implementation can be used as a tool to specify scenario bundles and to perform controlled simulations of human-product interaction. The use of the tool is demonstrated through a practical example. Although the implementation has proven to be successful in terms of executing scenario bundles, two bottlenecks need further attention: (i) devising stable algorithms for large deformations in physical interaction simulation and (ii) incorporation of already existing algorithms for simulation of low-level human motion control.

Ball-end milling tools have been widely used in machining of complex freeform surfaces. The precision and efficiency of ball-end milling process can be improved by an accurate modeling of the tools, the tools' paths and the machining conditions. However, only rough geometric models have been applied so far, which do not consider the machining conditions and the physical changes. To achieve the best results, an accurate modeling of the cutting edge and the physical behavior of the entire cutter is needed. This paper proposes an articulated model that enumerates both the geometric characteristics and the physical effects acting on the cutting edge-segment of a ball-end milling cutter. The model considers the deformations caused by the milling forces, vibration, spindle eccentricity, together with thermal deformation and wear of the cutter. The mathematical description of the behavior has been transferred into a computational model. The pilot implementation has been tested in a practical application. The first findings show that the proposed theoretical model and implementation provide sufficiently precise information about the behavior of the cutter in virtual simulations; hence it can be the basis of a fully fledged and more efficient planning of milling processes.

This paper summarizes the results of an empirical study concerning the use of hand motions as one of the input mechanisms of a multi-modal interface of computer aided conceptual design systems for initial shape design of consumer durables. A hand motion language (HML) has been developed and used in designed experiments to describe simple, compound and hybrid shapes. The subjects were asked to reconstruct the presented shapes by sketching on paper. Comprehension of the hand motion language has been evaluated in terms of fidelity and efficiency. The results clearly indicate the potentials of a HML in shape conceptualization. In addition, the experiments revealed several new issues related to the application of the hand motion language in a multi-modal interface.

The communication of design model data between participants of an engineering team is a fundamental subprocess in concur rent engineering (CE). The problems encountered in data transfer are abundant. It is understood that data transfer should be enhanced to ward knowledge transfer. Although it is possible to define what knowledge transfer is in general terms, it is crucial to specify it at the subprocess level; only then loss-less data communication can be implemented in practice. We, therefore, need to specify the conditions for successful data transfer subprocesses. In this paper we investigate which conditions are specific for CE. They are then formulated using the finite automaton formalism. From these conditions it can be concluded which measures should be taken in order to avoid data exchange problems and hence to support knowledge sharing. Examples are provided and an outlook to further applications is discussed.

Research in computer support to industrial design typically involves much experimentation. Proposals for new modeling methods are commonly evaluated using pilot software implementations. The experimentation tends to be lengthy and therefore expensive. We propose a faster way to evaluate the functionality of design tools. This evaluation method, called abstract prototyping, can be used in a very early stage of the development of a computer tool, prior to any software implementation. The evaluation focuses on how potential users appreciate new modeling functions by simulating their basic properties. The method aims at decreasing the risk of building a useless tool. We have applied abstract prototyping to make a selection among different candidate shape modeling techniques. The method proved to be feasible, fast and inexpensive

This paper reports on the theretical fundamentals of a novel modeling approach that follows the singularity theory rather than the continuity theory. The singularity oriented modeling is very useful in Certain applications, e.g. in form-giving and styling, rapid prototyping and shape generation based on gestural devices. The authors refer to this novel description technique as natural shape representation (N-rep). The key modeling entities are shape singularities of various order, structures formed by their arrangements, and natural surfaces. A shape singularity is an observable discontinuity of the boundary of an object that is featured by specific tangency and curvature characteristics. Besides the formal definition of singularities, the paper deals with their structural properties. A natural surface has been defined as a compound geometric entity that, as a domain of a boundary, obeys some specific continuity and finiteness conditions. The N-rep data scheme extends the conventional B-rep scheme with higher level constructs. The paper describes an application of the theory for shape generation by gestural device.

This paper presents a design approach to create gestural user interfaces for 3D modelling software tools. Our approach consists of a set of design methods and tools, which: 1) support understanding the user needs; 2) provide means for exploring affordances of 3D modelling systems, tracking technologies, and natural user interfaces; 3) facilitate generation and evaluation of interface ideas; 4) support implementation and validation of gestural UI concepts. The proposed approach has been tested in a case study, in which a hand gesture interface for Autodesk Maya has been build and tested with novice users. The results of the experiment showed that the gestural interface can be as efficient as the conventional mouse and keyboard in terms of tasks performed; and it can result in efficient learning curve while it provides access to all features of Maya.

Since driving in haste influences traffic safety negatively, we try to identify its indicators automatically. At studying driving in haste in a driving simulator, the major issue is how to reproduce it and how to keep drivers in this state. We assumed that it could be replicated by driving under time pressure. Unfortunately, the literature did not discuss how to apply time pressure in the above context. Therefore, we applied time shortage in combination with various forms of motivation (competition, reward, etc.) as a replacement in a driving simulator. The effects of the different motivations were evaluated and compared in various laboratory settings. Our observation was that the applied forms of motivation did not result in significant difference. We concluded that the novelty of being in a driving simulator and imposing time shortage on task execution could jointly create a kind of haste situation, but it cannot be heavily influenced by the tested motivations.

This paper introduces the idea of extending quality assurance efforts in the processes of development of computer aided design (CAD) software systems to include formal review or testing of underlying engineering principles, theories, methods, or physical phenomena. It stems from the principle of disembodiment of CAD software systems and incorporates elements of existing well-established methodologies such as participatory design, extreme programming, and spiral software development. Under this approach, ideas’ generation, theories’ selection or creation, methods’ development, algorithms’ design, and pilot prototype implementation are the intermediate tasks in the early stages of the process of development of CAD software. Theories, methods, algorithms, and pilot prototypes are the deliverables of these tasks. Each task involves stepwise translation of requirements into a respective deliverable. Application experiences have shown that this procedure enlarges the scope of requirements’ acquisition and quality assurance of CAD software.

This paper describes a new approach to identify freeform shape patterns in measured point data, to extract them and to fit their parameters. The method is based on direct matching of parameterized shape templates to digitized points. For a given class of feature, the optimal pose and the optimal intrinsic feature parameters are determined relative to the point data at hand. Although this principle has been used in digital image processing and also for fitting of prismatic features, it has rarely been applied in 3D to freeform features. Yet, several engineering applications may profit from improved feature fitting. The motivation of our investigation is the supporting of shape modeling using precedent designs available in the form of physical parts. We aim at an extension to what is generally known as reverse engineering. However, the proposed technique can also be used to extract feature parameters from imported CAD models. This paper addresses computational aspects of the method and presents the algorithms, implementation tests and numerical results.

In several application fields, large sized, free-form objects of various soft materials are widely used. Available layered prototyping technologies cannot be applied for fabrication of these kinds of objects due to size limitations. The authors have developed a novel approach of layered manufacturing that is the most appropriate for physical concept modeling. This paper presents the algorithms for geometrically-based modeling of the profile curve of the flexible blade tool. It also describes the algorithm for direct slicing of the CAD model. The second part of the paper deals with the algorithms for slicing, tool positioning and tool path calculation. On the front surfaces of the layers G2, quasi G1 continuity can be implemented at the transition from one layer to another. In the circumferential direction G0 continuity exists.