There has been intense foundational research in complex technical systems (CTSs) over the last half century. These systems are exemplified by advanced mechatronics systems, embedded control systems, real-time systems, agent-based smart systems, distributed software systems, internet of things systems, and cyber-physical systems. The objective of this paper is to offer an initial cataloguing of the various research domains and to identify the major research issues. The paper has an ontological flavour, because it concentrates on what research has been and is being done, rather than on why and how research is done. The underpinning study has been done in three stages: (i) intuition-driven exploration of a reference set of related academic publications, (ii) evidence-based specification of a categorization of the domains and subdomains of research, and (iii) refinement and validation of the proposed classification based on a control set of related academic publications. The proposed reasoning model identifies three categories of research domains. The ‘intellectualizations’ category includes research domains such as: (i) philosophy, (ii) ontology, and (iii) epistemology of CTSs. The research domains included in the ‘realizations’ category are: (iv) methodology, and (v) creation of CTSs. The domains considered in the ‘influences’ category are: (vi) manifestations, and (vii) axiology of CTSs. Based on the proposed reasoning model a landscape of foundational research in CTSs is proposed for public debate. Our follow-up study focuses on the extension of the proposed classification to other families of complex engineered systems such as sociotechnical systems and social ecosystems.

Knowledge based engineering (KBE) as a design method helps formulate a comprehensive knowledge base as a virtual prototype which includes design intent, requirements, rationale, and logic along with geometric information, which can then be utilised for representing the product design process, and to achieve complex design automation. One of the identified shortcomings in the field of design process automation using KBE as a holistic approach is a suitable neutral representation technique of a process model with well-defined syntax, axioms, and semantics for it to be shared across multiple platforms and to enable interoperability. To achieve design process automation, two steps are very important. First, a modelling method should be able to informally capture all critical aspects of a process to enable design automation. Second, the informal model should be able to be mapped onto a formal representation technique in a system, which will then enable automation by running a query through this representation. This paper discusses all the critical aspects in the form of design decomposition features and narrows down informal modelling approaches based on the criteria formulated for design automation from the literature. Formal representation techniques are discussed with the help of an example to ensure correct mapping of the informal model to a formal representation. The next steps of this research would be recommendation of the formal representation techniques of the informal model based on the discussion in this paper and for future work that will enable process automation.

This paper investigates the problem of parallel disassembly with the consideration of fuzziness. A novel approach is proposed based on optimized dispatching for parallel disassembly in which disassembly time is characterized by the fuzzy sets due to inevitable uncertainties. The proposed approach consists of three parts: in the first part, the fuzzy time-based dispatching disassembly process model is established; in the second part, the boundary conditions of the fuzzy time and the disassembly are derived, and the components’ disassembly order and available stations are encoded together to find the optimal disassembly path; in the final part, the approach is optimized by using genetic algorithm (GA) to minimize the total time and cost, and the solution is compared with other algorithms. Finally, a case study for a hydraulic press disassembly is presented to verify the effectiveness and feasibility of the proposed approach.

The indeterminacy evaluation is an effective method for system identification; it can predict the mechanical behaviors of flexible structures in the primary design. However, the conventional indeterminacy evaluation based solely on geometry and topology has neglected the influence of material properties on mechanical behavior and the contribution of each component to the total indeterminacy. To address these issues, a distributed indeterminacy evaluation taking account of the effect of component stiffness was carried out with a view to providing reasonable interpretations and feasible applications for two concepts, i.e., the distributed static indeterminacy (DSI) and the distributed kinematic indeterminacy (DKI). A unified method for the DSI is proposed, and a comparative analysis between this and an existing method revealed that the proposed method has a wider range of applicability and is essentially identical in the kinematically determinate case. It can be concluded that since the DSI is representative of symmetric properties, a simple but efficient grouping criterion can be established which can improve the efficiency of the specific force finding method entitled double singular value decomposition (DSVD). On the other side, an evaluable method for the DKI is proposed suggesting that DKI is a useful indicator for the assessment of nodal mobility and can provide a feasible solution to the form transforming study.

Triaxial compression tests were carried out on red sandstone samples which had been previously subjected to heat treatments at 20, 200, 400, and 600 °C to study the change in properties and mechanical characteristics of the rock and the permeability (gas) evolution. Results show that: (1) the color of the sandstone changes from gray to brownish red with incremental change of temperature; (2) the strength of the rock increases with heat treatments from 20 to 200 °C and decreases with heat treatments from 200 to 600 °C, while the permeability of the rock after the heat treatments changes in the opposite trend; (3) from 20 to 200 °C, the primary pores and cracks close gradually, which results in the strength and elastic modulus increasing and permeability of the rock after the heat treatment decreasing; from 200 to 600 °C, the degradation of the sandstone causes the fall in strength and elastic modulus, and the rise in strain corresponding to the peak stress and permeability of the rock after the heat treatment; (4) the permeability in a stress-strain process varies with the evolution of cracks; (5) when the heating temperature is beyond 800 °C, the sandstone is seriously thermally damaged.

In this study, air accumulation at the top of a long-term-high-lift motionless siphon hose due to air dissolution and diffusion is studied. Many factors can induce air accumulation in siphon hoses during dry seasons. In this study, effects of the unavoidable factors, such as air diffusion and dissolved-air release, are investigated. Based on experimental observations and theoretical analysis, the following results are obtained: (1) pressure decrease in high-lift siphon hoses will cause release of supersaturated air and induce a maximum 1.5 m long air column at the top of the siphon hose; (2) temperature increase will cause a maximum 0.55 m long air column; (3) air diffusion from water will lead to a less than 0.01 mm increment of the air column per day, which is considered to be negligible compared with that induced by air release due to pressure and temperature variations. Results indicate that high-lift siphon drainage can also be effectively used in arid districts. During siphon drainage design, at least 2.05 m long space to the safety level should be left for underground water rise, or the outlet should be kept 4.1 m lower than the inlet to guarantee that the released air will be gathered in the descending hoses.