Risk-Based Decision Support Model for the Optimal Operation of a Smart Energy Distribution Company for Enabling Emerging Resources

In this paper, a risk-based decision support model is developed for a smart energy distribution company, enabling emerging resources like renewable energy sources, electric vehicles and demand response programs in a holistic approach. Because of the inherent uncertainties of these emerging resources, the conditional value-at-risk (CVaR) method is adopted to restrict the distribution company’s risk. A risk aversion parameter sensitivity analysis is also provided on the optimal operation of the smart energy distribution company. The proposed model is thoroughly tested on a 15-bus distribution grid system, and the numerical results prove the effectiveness of the model in risk management

Structural and mechanical characterisation of the peri-prosthetic tissue surrounding loosened hip prostheses. An explorative study

Optimising joint reconstruction management in arthritis and bone tumour patient

Effect of moderate increasing exercice on the mechanical balance of the knee joint in young rats

Purpose: It is hypothesized that the amount, duration and magnitude of mechanical loading are important factors that maintain the cartilage tissue in physiological condition. The underlying subchondral bone attached to the cartilage tissue and the cartilage-bone interface are influenced by the mechanical loading as well. In this study, we aimed to investigate adaptation of the rat knee joint to the mechanical demands. For this purpose, we applied load in the form of exercise using a moderate-intensity increasing running protocol. A series of analyses was performed to elucidate the response of cartilage and bone to this physical activity. Methods: Male Wistar rats (Charles River, Germany) with an age of 8 weeks were placed in 2 groups: a moderate running group that runs for 8 weeks with a slowly increasing running velocity - from 10 m/min for 10 min, up to 20 m/min for 1 hour (n = 10), and a control group without running (n = 10). Running takes place on a 5 lane motorized rodent treadmill (LE-8700; Panlab Harvard Apparatus). At starting point and after 8 weeks cartilage qPCR, micro-CT, histology and plasma FIB 3-2 (Artialis) was performed. Results: A total 24 km running within 8 weeks of this running protocol illustrates chondrocyte sensitivity and cartilage response to the mechanical loading (Fig. 1). At the end of the experiment, aggrecan was 1.55-fold up-regulated while MMP-2 was 2.38-fold down-regulated (P < 0.05) (Fig. 1A). The histological appearance of the chondrocytes also showed load-dependency, with more hypercellularity and hypertrophy in the running group (Fig. 1B). FIB3-2 as a plasma biomarker, interacts with the tissue inhibitor of metalloproteinase 3 (TIMP-3) and the elevated amount of FIB3-2 is expected in osteoarthritis samples. FIB3-2 is also known to be cleaved by several MMPs family including MMP-2. FIB3-2 levels dropped in the running group (from 52.7 ± 13.2 nM to 30.2 ± 8.4 nM) as compared to the control group (45.3 ± 15.0 nM to 33.3 ± 9.7 nM) (Fig. 1C). MicroCT analysis revealed an enhancement in bone response as a result of early moderate physical training where epiphysis bone parameters in the running group including thickness and bone volume fraction of subchondral bone tibia plateau as well as trabecular bone mass significantly increased compared with control animals (Fig. 2). Conclusions: Gradual increase of running up to a moderate level to 1120 m/h for one hour enhances aggrecan expression, reduces catabolic enzymatic activity of MMP-2 as well as increases subchondral bone thickness in the epiphysis area and leads to hypercellularity and hypertrophy of the chondrocytes. Conclusively, a moderate exercise program can significantly influence both bone remodeling and cartilage tissue adaptation

Non-enzymatic cross-linking of collagen type II fibrils is tuned via osmolality switch

An important aspect in cartilage ageing is accumulation of advanced glycation end products (AGEs) after exposure to sugars. Advanced glycation results in cross-links formation between the collagen fibrils in articular cartilage, hampering their flexibility and making cartilage more brittle. In the current study, we investigate whether collagen cross-linking after exposure to sugars depends on the stretching condition of the collagen fibrils. Healthy equine cartilage specimens were exposed to l-threose sugar and placed in hypo-, iso-, or hyper-osmolal conditions that expanded or shrank the tissue and changed the 3D conformation of collagen fibrils. We applied micro-indentation tests, contrast enhanced micro-computed tomography, biochemical measurement of pentosidine cross-links, and cartilage surface color analysis to assess the effects of advanced glycation cross-linking under these different conditions. Swelling of extracellular matrix due to hypo-osmolality made cartilage less susceptible to advanced glycation, namely, the increase in effective Young's modulus was approximately 80% lower in hypo-osmolality compared to hyper-osmolality and pentosidine content per collagen was 47% lower. These results indicate that healthy levels of glycosaminoglycans not only keep cartilage stiffness at appropriate levels by swelling and pre-stressed collagen fibrils, but also protect collagen fibrils from adverse effects of advanced glycation. These findings highlight the fact that collagen fibrils and therefore cartilage can be protected from further advanced glycation ("ageing") by maintaining the joint environment at sufficiently low osmolality. Understanding of mechanochemistry of collagen fibrils provided here might evoke potential ageing prohibiting strategies against cartilage deterioration. © 2018 The Authors. Journal of Orthopaedic Research Published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society. J Orthop Res

Micro- and nano-mechanics of osteoarthritic cartilage : The effects of tonicity and disease severity

The present study aims to discover the contribution of glycosaminoglycans (GAGs) and collagen fibers to the mechanical properties of the osteoarthritic (OA) cartilage tissue. We used nanoindentation experiments to understand the mechanical behavior of mild and severe osteoarthritic cartilage at micro- and nano-scale at different swelling conditions. Contrast enhanced micro-computed tomography (EPIC-μCT) was used to confirm that mild OA specimens had significantly higher GAGs content compared to severe OA specimens. In micro-scale, the semi-equilibrium modulus of mild OA specimens significantly dropped after immersion in a hypertonic solution and at nano-scale, the histograms of the measured elastic modulus revealed three to four components. Comparing the peaks with those observed for healthy cartilage in a previous study indicated that the first and third peaks represent the mechanical properties of GAGs and the collagen network. The third peak shows considerably stiffer elastic modulus for mild OA samples as compared to the severe OA samples in isotonic conditions. Furthermore, this peak clearly dropped when the tonicity increased, indicating the loss of collagen (pre-) stress in the shrunk specimen. Our observations support the association of the third peak with the collagen network. However, our results did not provide any direct evidence to support the association of the first peak with GAGs. For severe OA specimens, the peak associated with the collagen network did not drop when the tonicity increased, indicating a change in the response of OA cartilage to hypertonicity, likely collagen damage, as the disease progresses to its latest stages

Non-enzymatic cross-linking of collagen type II fibrils is tuned via osmolality switch

An important aspect in cartilage ageing is accumulation of advanced glycation end products (AGEs) after exposure to sugars. Advanced glycation results in cross-links formation between the collagen fibrils in articular cartilage, hampering their flexibility and making cartilage more brittle. In the current study, we investigate whether collagen cross-linking after exposure to sugars depends on the stretching condition of the collagen fibrils. Healthy equine cartilage specimens were exposed to l-threose sugar and placed in hypo-, iso-, or hyper-osmolal conditions that expanded or shrank the tissue and changed the 3D conformation of collagen fibrils. We applied micro-indentation tests, contrast enhanced micro-computed tomography, biochemical measurement of pentosidine cross-links, and cartilage surface color analysis to assess the effects of advanced glycation cross-linking under these different conditions. Swelling of extracellular matrix due to hypo-osmolality made cartilage less susceptible to advanced glycation, namely, the increase in effective Young's modulus was approximately 80% lower in hypo-osmolality compared to hyper-osmolality and pentosidine content per collagen was 47% lower. These results indicate that healthy levels of glycosaminoglycans not only keep cartilage stiffness at appropriate levels by swelling and pre-stressed collagen fibrils, but also protect collagen fibrils from adverse effects of advanced glycation. These findings highlight the fact that collagen fibrils and therefore cartilage can be protected from further advanced glycation ("ageing") by maintaining the joint environment at sufficiently low osmolality. Understanding of mechanochemistry of collagen fibrils provided here might evoke potential ageing prohibiting strategies against cartilage deterioration.Biomaterials & Tissue Biomechanic

Decentralized multi-robot encirclement of a 3D target with guaranteed collision avoidance

International audienceWe present a control framework for achieving encirclement of a target moving in 3D using a multi-robot system. Three variations of a basic control strategy are proposed for different versions of the en-circlement problem, and their effectiveness is formally established. An extension ensuring maintenance of a safe inter-robot distance is also discussed. The proposed framework is fully decentralized and only requires local communication among robots; in particular, each robot locally estimates all the relevant global quantities. We validate the proposed strategy through simulations on kinematic point robots and quadrotor UAVs, as well as experiments on differential-drive wheeled mobile robots