Design automation with the characteristics properties model and the property driven design for redesign

This paper presents a framework consisting of a mathematical model and an algorithm for representation, analysis and exploration of the design space in redesign problems. The framework develops and extends the existing formalism of the Characteristics Properties Model (CPM) and Property Driven Design (PDD). A platform independent quantitative model based on formal log-ic is presented to map the characteristics and properties, as well as the relations and dependencies between them, along with solution conditions. The model is based on generalization of existing mathematical design models and is support-ed by the development of an algorithm enabling property driven design. The re-sulting framework offers a rich and flexible syntax and vocabulary along with a mathematical and computational tool applicable to mechanical product design

Set-based design of mechanical systems with design robustness integrated

This paper presents a method for parameter design of mechanical products based on a set-based approach. Set-based concurrent engineering emphasises on designing in a multi-stakeholder environment with concurrent involvement of the stakeholders in the design process. It also encourages flexibility in design through communication in terms of ranges instead of fixed point values and subsequent alternative solutions resulting from intersection of these ranges. These alternative solutions can then be refined and selected according to the designers’ preferences and clients’ needs. This paper presents a model and tools for integrated flexible design that take into account the manufacturing variations as well as the design objectives for finding inherently robust solutions using QCSP transformation through interval analysis. In order to demonstrate the approach, an example of design of rigid flange coupling with a variable number of bolts and a choice of bolts from ISO M standard has been resolved and demonstrated

Tolerance analysis approach based on the classification of uncertainty (aleatory / epistemic)

Uncertainty is ubiquitous in tolerance analysis problem. This paper deals with tolerance analysis formulation, more particularly, with the uncertainty which is necessary to take into account into the foundation of this formulation. It presents: a brief view of the uncertainty classification: Aleatory uncertainty comes from the inherent uncertain nature and phenomena, and epistemic uncertainty comes from the lack of knowledge, a formulation of the tolerance analysis problem based on this classification, its development: Aleatory uncertainty is modeled by probability distributions while epistemic uncertainty is modeled by intervals; Monte Carlo simulation is employed for probabilistic analysis while nonlinear optimization is used for interval analysis.“AHTOLA” project (ANR-11- MONU-013

A statistical tolerance analysis approach for over-constrained mechanism based on optimization and Monte Carlo simulation

Tolerancing decisions can profoundly impact the quality and cost of the mechanism. To evaluate the impact of tolerance on mechanism quality, designers need to simulate the influences of tolerances with respect to the functional requirements. This paper proposes a mathematical formulation of tolerance analysis which integrates the notion of quantifier: ‘‘For all acceptable deviations (deviations which are inside tolerances), there exists a gap configuration such as the assembly requirements and the behavior constraints are verified’’ & ‘‘For all acceptable deviations (deviations which are inside tolerances), and for all admissible gap configurations, the assembly and functional requirements and the behavior constraints are verified’’. The quantifiers provide a univocal expression of the condition corresponding to a geometrical product requirement. This opens a wide area for research in tolerance analysis. To solve the mechanical problem, an approach based on optimization is proposed. Monte Carlo simulation is implemented for the statistical analysis. The proposed approach is tested on an over-constrained mechanism

Outcome Comparison of Endoscopic (Endonasal Trans-Sphenoidal) Repairs of CSS Leak vs. Transcranial Approach

Objective:   To compare the effectiveness of Endoscopic (Endonasal transsphenoidal) repair of CSF leak with transcranial approach in terms of post-operative complications like infection, recurrence and hospital stay. Material and Methods:  The comparative experimental randomized study was conducted in the Department of Neurosurgery Unit I, PGMI, Lahore General Hospital, Lahore. After approval from ethical committee this study was carried out in our unit. 40 subjects with the history of CSF leak were randomly divided into two groups; one was treated with endonasal trans-sphenoidal repair and another was treated with trans-cranial approach, the subjects were followed up for 1 year. Detailed history, neurological examination, preoperative CT and MRI scans were performed in all patients. Results:  The mean age of patients with CSF leak was 25.58 ± 14.38 years. Among the patients, 17 were females and 23 were male. The mean age of the female was 31.70 ± 14.29 years. The mean age of the male was 21.04 ± 12.95. The recurrence was observed in 2 (10%) of the patients treated with endoscopic technique and 1 (5%) of the patients treated with trans-cranial approach. Those patients were successfully repaired in a second operation. Overall success rate was 92.5%. One patient (2.50%) among the trans-cranial approach develops infection which was treated successfully. Conclusion:  The endoscopic repair of CSF leak is both safe and effective and should be considered as the standard procedure of choice in most of the cases

Terrorist bombings: Medical response in a developing country

Objective: To evaluate the process of transport and immediate Emergency Department (ER) management of mass casualties following the recent bomb blasts in Karachi and review in detail the medical response and management of victims undertaken in these two incidents. Methods: Eyewitness accounts of the victims, medical personnel and newspaper clippings were used to understand and identify difficulties faced during the rescue process. Data regarding presenting injuries and their outcomes was also collected from all victims presenting to the emergency department at Aga Khan University Hospital. Results: Seventy nine individuals died and over 250 victims were injured in the two incidents. All victims and dead bodies were shifted to the nearest public sector hospital overwhelming the health care facility. Subsequently all victims were evacuated to private sector hospitals creating similar difficulties. Over half of the victims presenting at the emergency department had minor injuries and did not require admission. Most patients requiring admission needed orthopaedic intervention. Conclusion: A comprehensive disaster plan with a centralized command and control system is required for the city of Karachi, involving all stake holders including charity ambulance services, security agencies, and trauma management facilities. Training courses and exercises for health care personnel should also be made mandatory to achieve professional excellence

A statistical tolerance analysis approach for over-constrained mechanism based on optimization and Monte Carlo simulation

Tolerancing decisions can profoundly impact the quality and cost of the mechanism. To evaluate the impact of tolerance on mechanism quality, designers need to simulate the influences of tolerances with respect to the functional requirements. This paper proposes a mathematical formulation of tolerance analysis which integrates the notion of quantifier: ‘‘For all acceptable deviations (deviations which are inside tolerances), there exists a gap configuration such as the assembly requirements and the behavior constraints are verified’’ & ‘‘For all acceptable deviations (deviations which are inside tolerances), and for all admissible gap configurations, the assembly and functional requirements and the behavior constraints are verified’’. The quantifiers provide a univocal expression of the condition corresponding to a geometrical product requirement. This opens a wide area for research in tolerance analysis. To solve the mechanical problem, an approach based on optimization is proposed. Monte Carlo simulation is implemented for the statistical analysis. The proposed approach is tested on an over-constrained mechanism

Management of product characteristics uncertainty based on Formal Logic and Characteristics Properties Model

Uncertainty in product characteristics is ubiquitous in any engineering system at all the stages of product life-cycle. Considering uncertainty from different sources during the product design phase is critical to its reliable performance. This paper presents a framework integrating the uncertainty propagation through different product characteristics and its effect on product properties. The framework consists of three main parts: a descriptive model based on formal logic and characteristics properties model; a mathematical implementation through set theory and probabilistic approach; and an algorithm for design space evaluation and tolerancing. The application of framework is demonstrated through an industrial case study