A design exploration method for resolving parameter coupling in engineering change propagation

A process simulation based method for scheduling product design change propagation

Computer integrated design systems will require an improved understanding of the engineering design process, including formalized notions of (1) the structure of the process, (2) the design tasks that need to be performed, and (3) the information required to carry out these tasks. An organizational model for the structural engineering design process, termed themultilevel selection-development (MSD) model, has been outlined in a recent paper. The current paper continues development of the MSD model by providing more detailed descriptions of the specific design tasks that must be carried out. The MSD model is briefly reviewed, and a simple example is presented. The design tasks are then classified and described.

Due to the complicated dependencies among design tasks, design changes in a design task can cause changes to many other tasks, which may cost a lot of time and resources to completely resolve them. Therefore, optimal scheduling of design change propagations is required to reduce the total process time. This article presents an integrated approach for scheduling design changes in the complex product development process by combining simulation of change propagations with optimization algorithms. The process model is built using “And/or” graphs, which can take the logic relationships among design tasks into the process model. Genetic algorithm is applied to the change process model to find the optimal propagation likelihood for each optional propagation path in order to obtain the shortest process run time. The approach is incorporated into the process-oriented computer-aided product design system, and two design changes occurring in the motorcycle engine design process, namely an initiated and an emergent design changes, are used to test the approach. The initiated design change case shows the integrated approach can find the optimal solution more efficiently than the Monte Carlo simulation method, while the emergent change case demonstrates the approach can timely find the optimal solution to the change especially when designers are pressed for delivery of their achievements.

Associations management and change propagation in the CAD assembly

Design processes are characterised by uncertainty and iteration, making them difficult to plan and manage. These characteristics are incorporated into an original model in which information flow is simulated explicitly such that the dynamic complexity of design processes with interdependent tasks is captured. This is accomplished through the linkage of information exchange to the work done during each design task, the availability of resources, and the techniques used to manage the product development (PD) process. The model generates rework due to iteration and failure in design reviews according to the ability of tasks to reduce the uncertainty of design information. The model is applied to the investigation of coordination and its effects on process behaviour under various conditions. Coordination mechanisms are studied through the choice of input parameters that influence the degree of overlapping of tasks, the allocation of resources that process information, the delay of communication of information, and the interval of communication between tasks. Findings uncover the mechanisms that drive the pace of progress during engineering design processes and highlight strategies that reduce span time in complex PD.

Deploying radio frequency identification (RFID) devices or applying robust production control policy can both reduce the negative impact of inventory inaccuracy. In this paper, we investigate the problem of optimally deploying RFID devices in a multistage production system with inventory inaccuracy and robust control policy. We first model the multiple-stage production system as a Markov decision process model, in which the decision of deploying RFID devices is included. After that, an integer programming model is constructed for optimally deploying RFID device problem. Meanwhile, we propose a robust production control strategy by employing the policy iteration and the decomposition/coordination techniques, and a heuristic algorithm is proposed to solve the integer programming model. Finally, numerical experiments are conducted to examine the performance of the proposed optimal RFID deployment approach. We discover that when RFID is deployed at a certain workstation (i.e., production equipment), the benefits of deploying RFID devices can transfer to the upstream and downstream stages (i.e., reduce the production cost of both upstream and downstream stages). Furthermore, numerical experiments reveal that the deploying RFID devices evenly among all the stages of the production system will generate a better performance.

An engineering change (EC) is an alteration made to a system that has been released following a system design process. EC propagation is a series of ECs occurring due to dependencies among components of a product. ECs can consume up to 50% of the overall engineering efforts during the development of a complex system. Therefore, EC propagation prediction received considerable attention in past decades as the product development industries started to suffer from the negative impacts of change propagation. This paper evaluates the current approaches to EC propagation prediction and presents a dynamic Bayesian networks (DBNs) approach to estimate change propagation risk (CPR) as well as a novel approach to estimate EC durations. Literature research shows that although some studies have used design structure matrices to estimate CPR and the total redesign duration (TRD) due to change propagation, an approach that allows iteration while accounting for the conjunction of all impacts has not been explored. This paper aims to fill the gaps for calculating CPR using DBN and evaluating change propagation paths from a Split-and task outcome logic, which accounts for the conjunction of all component relationships. This paper compares the proposed method results with the existing CPR and engineering change duration estimation methods using a real-world dataset from a U.S. Navy shipbuilding program. The results indicate that the CPR can be calculated using the proposed method without the shortcomings of the existing method and the accuracy for estimating engineering change durations is increased.

In prototyping complex systems, concept iterations often reach a point where incremental modifications to one part in a complex system can produce unexpected, cascading changes in the rest of the system. This phenomenon can require time-consuming and expensive corrections, particularly when physical prototypes are involved — as was the situation in the case study presented here. A design tool, the Design Structure Matrix (DSM), is commonly used to predict change propagation in complex designs. Using several examples, this paper illustrates situations where conventional DSMs fail to predict change propagation in the prototypes created during a robotic inspection system design project, due to complex interactions and system design constraints. The case study discussed here, a robotic inspection system for a nuclear waste storage cask, included interactions not easily captured in a conventional DSM. It was these interactions that interfered with the use of this tool to predict design change propagation. The paper then presents a method that was conceived to manage such changes; a way of modifying conventional DSMs to include design constraints and components. The case study examples show that the resulting technique, called the C+C DSM method, would have better predicted mid-development change propagation in the prototyping process.

Product design change propagation in automotive supply chain considering product life cycle

The biotechnological production of organic compounds using renewable carbon sources is an approach consistent with sustainable development and green technologies. The development of these processes requires refinement of both the upstream stage, including the selection of microorganisms and the use of waste raw materials, and the downstream stage. The fermentation broth contains not only the main product but also unreacted substrates and by-products. The paper presents computer simulations that analyse the possibility of using esterification for the separation of lactic acid from acetic acid. The standard distillation approach does not allow for a high degree of separation, but a distillation step is possible for esters of both acids. As a result, high-purity ethyl lactate is obtained and, by introducing a hydrolysis step, pure lactic acid. The issue was analysed using Chemcad software with the UNIFAC thermodynamic model.

This study aimed to investigate grade-7 students’ negotiation during the engineering design process regarding the students’ status of argumentation training. The participants were 33 students studying at a public urban middle school in Turkey. They worked in small groups on four engineering design tasks about electricity and light. Data were collected through small group audio recordings, student worksheets, and the observation. The data were analyzed by using content analysis. The results indicated that negotiation patterns were similar across all groups. However, differences were found between the group that received argumentation training and the one that did not receive in terms of proposing ideas for material design, using justifications when in agreement with others, counter proposing and acquiring information for better planning and altering the design, and critiquing for design advantages and disadvantages.

A non-negligible part of the noise emitted from aero-engines is due to combustion. The relative importance of this source is even expected to increase with the next generations of engines where both fan and jet noise are reduced with such technologies as chevrons, micro-jets or highly-swept and leaned composite blades. In his PhD. dissertation, Candel showed that the noise due to combustion in aero-engines could have two different origins: (a) the well-known direct combustion noise, which is directly generated by the unsteady combustion, and transmitted and reflected through the upstream (compressor) and downstream (turbine) turbo-machinery stages; and (b) an additional source of noise, the indirect combustion noise. The latter comes from the conversion of entropy spots generated by the combustion into acoustic waves when they accelerate in the downstream turbine stages. Candel showed that this source could be important and explain the observed excess noise. More recently, Leyko et al. developed scaling laws from a simplified one-dimensional (1-D) model of combustor, which showed that the indirect combustion noise could even be ten times as important as the direct one. For both direct and indirect noise sources, the downstream turbo-machinery is involved in the transmission and generation of the combustion noise. Thus, the acoustic behavior of the turbine blade rows must be known to evaluate the noise due to combustion at the engine outlet. More specifically, the transfer functions of the turbo-machinery stages for the waves involved in the combustion process (acoustic, entropy and vortical) must be calculated. Several analytical and semi-analytical approaches have been proposed for 2-D flows to deal with the propagation of acoustic waves and vortices through turbo-machinery stages. Muir 5 delt with the case of the actuator disk theory which assumed a 2-D configuration with an infinitely thin blade row, and used classical conservation laws to establish relations between upstream and downstream flow. Kaji and Okazaki 7 proposed the semi-disk actuator theory assuming in a first step that the spacing between the blades was infinitely thin but the chord-length was finite. A second step 7 proposed a model with a finite chord-length and a finite spacing between blades. For both cases, the equations were solved numerically. Many other models are available for such 2-D problems. Recently Posson and Roger proposed a three-dimensional rectilinear cascade model both for generation and transmission losses based on Glegg’s response, which also accounted for cascade effects and finite chord, but neglected flow deviation (flat plates

Environmental decision making in multi-stakeholder contexts: applicability of life cycle thinking in development planning and implementation

Process Optimization

Safety is the most important concern in the construction industry, and construction workers’ attention allocation is closely associated with their hazard recognition and safety behaviors. The recent emergence of eye-tracking techniques allows researchers in construction safety to further investigate construction workers’ visual attention allocation during hazard recognition. The existing eye-tracking studies in construction safety need to be comprehensively understood, to provide practical suggestions for future research and on-site safety management. This study aims to summarize previous studies on the application of eye-tracking techniques to the construction safety context through a systematic literature review. The literature search and study selection process included 22 eligible studies. Content analysis was then carried out from participant selection, device selection, task design, area of interest determination, feature extraction, data analysis, and main findings. Major limitations of the existing studies are identified, and recommendations for future research in theoretical development, experiment improvement, and data analysis method advancement are proposed to address these limitations. Even though the application of eye-tracking techniques in construction safety research is still in its early stage, it is worth future continuous attention because relevant discoveries would be of great significance to hazard control and safety management in the construction industry.