Amaryllis Audenaert

Consequences of deltoid muscle elongation on deltoid muscle performance: a computerised study

BACKGROUND The deltoid muscle plays an important role in normal shoulder function. Knowledge of the position of the glenohumeral rotational centre and of the deltoid muscle length is essential to understand optimal placement of a total shoulder prosthesis. OBJECTIVE This study is designed to analyse the effect of deltoid muscle elongation on shoulder joint function. DESIGN A three-dimensional model of the glenohumeral joint with deltoid muscle analysis in the scapular plane. METHODS A geometrical three-dimensional ball-and-socket model of the shoulder joint was developed. From dry bones, the position of the origins and insertions of the three parts of the deltoid muscle relative to the calculated centre of rotation of the humeral head was defined. The position and the direction of the muscle force working lines relative to this humeral centre were calculated using former measurements and CT-data of the deltoid. Muscle length-tension data were applied to obtain angle-force relationships. The model was used to calculate the angle-force relationships, the moment arm and the moment of the deltoid muscle components for successive arm elevation angles in the scapular plane. These data were compared to those of a theoretical situation assuming a 10% elongation of the muscle. RESULTS Muscle angle-force curves show a more favourable slope after moderate (10%) deltoid muscle elongation. Elongating the muscle by changing the distance between the humeral rotation point and the deltoid insertion along the humeral axis does not affect moment arms. The moments of the deltoid muscle forces themselves, however, seem more adapted to elevation in the scapular plane. The deltoid maximal moment exceeds the arm-weight moment by about 40% instead of being approximately equal, and that the maximum is situated around 100 degrees of elevation. CONCLUSIONS From a biomechanical point of view, stretching the deltoid muscle by 10% seems to result in a significantly more favourable position in case of shoulder elevation at 90 degrees of abduction in the scapular plane in a centred glenohumeral joint. RELEVANCE This model suggests that a 10% elongation of the deltoid muscle, the most important shoulder abductor, improves its ability to elevate the arm. If properly implemented, this observation can be very important in the treatment and early rehabilitation of rotator-cuff-insufficient shoulders treated by a specific total shoulder replacement design.

Global optimization method for combined spherical-cylindrical wrapping in musculoskeletal upper limb modelling

In musculoskeletal modelling, many muscles cannot be represented as straight lines from origin to insertion because the bony and musculotendinous morphology of neighboring structures causes them to wrap. The majority of these passive structures can be adequately described as simple geometric shapes such as spheres and cylinders. Techniques for describing smooth muscle paths around multiple obstacles have been developed for modelling use. Until now obstacle-set methods have combined the path of single structures. This does not analytically define the shortest smooth path around multiple objects. When a sphere is included in a multiple-object wrapping algorithm, muscle paths around that sphere are restricted to a bundle of planes containing the sphere center. This assumed restriction can compromise the iterative process for finding the true shortest muscle path that satisfies all restrictions of a smooth path. This can cause model instability. The new method involves the determination of the shortest smooth muscle path in a spherical and cylindrical wrapping algorithm. A typical example is musculoskeletal modelling of the upper limb, where the muscle fibers have to wrap over this combination of obstacles.

Chemical plant innovative safety investments decision-support methodology

INTRODUCTION This article examines the extent to which investing in safety during the creation of a new chemical installation proves profitable. METHOD The authors propose a management supporting cost-benefit model that identifies and evaluates investments in safety within a chemical company. This innovative model differentiates between serious accidents and less serious accidents, thus providing an authentic image of prevention-related costs and benefits. In classic cost-benefit analyses, which do not make such differentiations, only a rudimentary image of potential profitability resulting from investments in safety is obtained. RESULTS The resulting management conclusions that can be drawn from such classical analyses are of a very limited nature. The proposed model, however, is applied to a real case study and the proposed investments in safety at an appointed chemical installation are weighed against the estimated hypothetical benefits resulting from the preventive measures to be installed at the installation. CONCLUSION In the case-study carried out in question, it would appear that the proposed prevention investments are justified. IMPACT ON INDUSTRY Such an economic exercise may be very important to chemical corporations trying to (further) improve their safety investments.

Making evacuation decisions by using a discrete-time approximation methodology.

This article further elaborates the findings by Reniers et al. in 2007 and 2008. A discrete-time approximation is presented to determine the severity of a major accident threat triggering immediate evacuation and its expected resulting costs. By implementing the proposed mathematical model, precautionary evacuation decision problems can be tackled in a realistic way, i.e., allowing for major accident threats with limited duration. Furthermore, the model is moulded into a working procedure which was used to develop software to solve the suggested algorithms. A case-study is provided and the results obtained by application of the methodology are discussed. Using a (realistic) discrete-time approximation computer simulation, we found that ignoring option characteristics may produce suboptimal intervention decisions in shutdown settings.

Identifying marginal suppliers of construction materials: consistent modeling and sensitivity analysis on a Belgian case

PurposeThe identification of marginal suppliers is a key element of consequential LCA. This study investigates how systematically the identification of marginal suppliers can be performed across different products, while maintaining consistent modeling choices. Some products relevant for the Belgian construction sector are taken as a case study.MethodsTo gain insight in the current practice of identifying marginal suppliers, 30 recent studies have been reviewed. Based on the findings of the review, a method was proposed to identify geographical market boundaries from trade data and sensitive suppliers from production data. Both retrospective and prospective approaches to anticipate the future effect of a change in demand were taken into account. The method was applied to compute both a retrospective and a prospective marginal supplier’s mix per product. Finally, the effect of the modeling choices on the size of geographical market boundaries and marginal mixes was estimated via regression analysis.Results and discussionThe forecasts and marginal mixes obtained matched with those from the existing literature, although clear differences in results are observed between the retrospective and prospective approach. Deviations from default assumptions in LCA were observed as well, such as large regional geographical markets for cement and aggregates instead of local ones. The statistical sensitivity analysis showed that identifying geographical market boundaries has the largest effect on the final marginal mix and that these markets are relative stable over time.ConclusionsThe proposed method and corresponding sensitivity analysis is an attempt to gain insight into the effect of modeling choices in the context of the identification of marginal suppliers for consequential LCA. It can in principle be applied to any product for which trade and production data are available. The proposed method helps to identify marginal mixes on a consistent and transparent way, to improve the robustness of the results in future consequential LCAs.

Empirical validation of a real options theory based method for optimizing evacuation decisions within chemical plants

This article empirically assesses and validates a methodology to make evacuation decisions in case of major fire accidents in chemical clusters. In this paper, a number of empirical results are presented, processed and discussed with respect to the implications and management of evacuation decisions in chemical companies. It has been shown in this article that in realistic industrial settings, suboptimal interventions may result in case the prospect to obtain additional information at later stages of the decision process is ignored. Empirical results also show that implications of interventions, as well as the required time and workforce to complete particular shutdown activities, may be very different from one company to another. Therefore, to be optimal from an economic viewpoint, it is essential that precautionary evacuation decisions are tailor-made per company.

Defining the shortest path in wrapping algorithms for musculoskeletal modeling

In musculoskeletal modeling, many muscles cannot be represented as straight lines from origin to insertion because the bony and musculotendinous morphology of neighboring structures causes them to wrap. Most of these passive structures can adequately be described as simple geometric shapes like spheres and cylinders. A technique for describing smooth muscle paths around multiple obstacles has been developed for modeling use. Until now obstacle-set methods have combined the path of single structures. This does not analytically define the shortest path around multiple objects (Charlton and Johnson, 2001). In this study a method is presented to select the shortest muscle path between origin and insertion from all possible smooth paths between these two points. As an example for multiple obstacle wrapping the deltoid muscle was chosen.

Vleeshuis Museum: Antwerp (Belgium)

Understanding the indoor building microclimate means also verifying how the building interacts with the outdoor microclimate and how homogeneous this interaction is inside the building. As the hygrothermal dynamics influence both building users’ thermal comfort and state of conservation of movable heritage, it is essential, especially in historic buildings and museums, to combine both indoor building microclimate diagnosis and certification in an iterative process.

Buildings’ Indoor Microclimate Quality (IMQ): Assessment and Certification

Ensuring satisfactory indoor climate quality is a fundamental aspect of building management for both newly constructed and existing buildings. Moreover, as indoor microclimate quality (IMQ) plays a driving role in building energy consumptions and movable heritage preservation, its assessment and certification are fundamental in order to allow building control and optimization. In historic buildings, museums, or where indoor climate requirements should simultaneously satisfy people comfort and movable heritage safety, it is essential to propose assessment and certification methodologies capable of capturing the multidimensional nature of this management problem. Currently, a framework for guiding during IMQ assessment and certification, especially when different microclimate needs coexist, still lacks; this makes often the certification process inconsistent and arbitrary. In this contribution, after an overview on the collection microclimate management evolution, the critical aspects of the methodology to be taken into account during IMQ assessment and certification are discussed. Finally, an IMQ certification model is introduced.

Chemical Industrial Areas and their Dynamic Danger Behaviour

Chemical industrial areas or so-called chemical clusters consist of various companies situated next to each other. Such areas are composed of hundreds of chemical installations exhibiting danger to a certain degree for initiating or continuing knock-on effects. In this paper, a methodology to model such clusters as networks and to investigate their dynamic danger behaviour is proposed. This original approach leads to a tentative strategy to optimally protect chemical industrial areas against security risks.