In this study, a new experimental design, which has the advantage of estimating simultaneously the three components of the thermal conductivity tensor and the specific heat of orthotropic polymer ...composite materials, is presented. Furthermore, no sample instrumentation is required, reducing substantially the global experimental procedure duration. The measurement technique consists in dissipating a known heat flux thanks to a home-designed thin heater, composed by two distinct heating elements and sandwiched between two cylindrical samples. The heater is also used as measurement instrument since micro-thermocouples are incorporated inside. The parameter estimation is performed by solving an inverse heat conduction problem. The method has been validated on a sample with known properties. The thermal properties of a unidirectional carbon-fiber composite have been then characterized. The results, obtained from a two-step estimation strategy are in good agreement with those determined within the framework of round-robin test.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
A thermal, rheological and mechanical material characterization of an aeronautic epoxy resin from commercial prepreg is reported in this article. The kinetic of the crosslinking reaction of the resin ...is characterized and modeled. The specific heat, the glass transition temperature, the thermal expansion coefficients, the chemical shrinkage coefficients and the thermo-mechanical properties have been investigated as a function of temperature and degree of cure. Dynamic mechanical measurements are used to determine the gel point. Finally, the residual stresses developed during the curing process are calculated using a finite element simulation, taking into account the material properties evolutions according to proposed models. The results highlight the importance of the characterization accuracy and the associated models.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
This paper examines the wind induced forces and moments experienced by a high sided lorry. Full-scale measurements are combined with wind tunnel and CFD simulations in order to gain an insight into ...the flow field around the vehicle. Differences and similarities between the three techniques are noted. It is shown that the rolling moment coefficient obtained from full-scale measurements and CFD simulations agree consistently across a wide range of yaw angles. With respect to the side force coefficient, good agreement between the wind tunnel and full-scale data are achieved. Pressure distributions over selected sections of the lorry reveal that despite good agreement with the overall forces, the localised pressure field can be significantly different.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
•Fishermen were key players in a collaborative research on pelagic species monitoring.•Sporadic surveys in key areas are relevant to monitor anchovy recruitment arrivals.•Fishermen can collect ...acoustic and biological data to monitor small pelagic stocks.
Anchovy and sardine are small pelagic species occupying similar geographic areas in the Bay of Biscay (North-East Atlantic). Their biomass is strongly dependent on recruitment, making the annual assessment of TAC (Total Allowable Catch) a risky strategy due to uncertainty in predicting the magnitude of recruitment. Monitoring these resources more often and throughout their life cycle could allow management strategies to be adjusted based on observations which indicate the level of recruitment. In order to achieve a more frequent monitoring, an innovative data collection strategy involving a partnership between fishermen and scientists, was developed in 2009 and 2010 called “pilot sentinel surveys”. This paper details the partnership, the information such a partnership can provide and how it can be useful for adaptively managing such resources. The method was based on short surveys undertaken by commercial vessels several times per year, in two spatially limited “key areas” known to be potential recruitment habitats. Acoustic surveys and fishing operations enabling biological sampling, were combined in each key area. Only one scientist was on board and an ad hoc sampling strategy was adopted during each survey by the Captain–Scientist team depending on the local conditions. This partnership allowed scientists to benefit from fishermen’s experience and therefore adopt a sampling strategy which was optimized in time and space. The sentinel survey data were complemented with data collected during annual spring acoustic surveys carried out by the research vessel (RV) Thalassa. The RV was accompanied by commercial vessels allowing additional fishing operations and acoustic echo interpretation to be performed. This experiment showed that the sentinel observations in limited areas cannot provide reliable abundance indices, but are adequate to provide significant biological information on the seasonal progress of the life cycle of each species, such as growth, timing of in-coming recruitment and migration pattern. In addition, these “pilot sentinel surveys” significantly improved the mutual understanding between fishermen and scientists.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Semi-crystalline polymers are materials whose behavior during their cooling is difficult to model because of the strong coupling between the crystallization, heat transfer, pressure and shear. Thanks ...to two original apparatus we study solidification of such a polymer without shear. Firstly the comparison between experimental results and a numerical model will permit to validate crystallization kinetic for cooling rate reachable by DSC. The second experiment makes it possible to analyze solidification for high cooling rate, corresponding to some manufacturing processes. It appears that crystallization has an influence on the thermal contact resistance.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The knowledge of thermal properties of orthotropic layered composite materials is very important in the aeronautics industry. They can be measured with a dedicated apparatus but numerical ...computations develop strongly. It is well known that the microstructure has a strong impact on the calculation of the effective properties of these heterogeneous materials. The representative volume element (RVE) is then a crucial input to predict reliable results. In composites, fibre distribution often exhibits fibre-rich and fibre-poor regions. In this contribution, we first investigated a quantitative characterization of the microstructure using optical images and spatial descriptors. They give rise to microstructural features but also anisotropy. In a second time, we defined the RVEs of this microstructure for statistical parameters and effective thermal conductivities.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
One anastomosis gastric bypass (OAGB) is increasingly used in the treatment of morbid obesity. However, the efficacy and safety outcomes of this procedure remain debated. We report the results of a ...randomised trial (YOMEGA) comparing the outcomes of OAGB versus standard Roux-en-Y gastric bypass (RYGB).
This prospective, multicentre, randomised non-inferiority trial, was held in nine obesity centres in France. Patients were eligible for inclusion if their body-mass index (BMI) was 40 kg/m2 or higher, or 35 kg/m2 or higher with the presence of at least one comorbidity (type 2 diabetes, high blood pressure, obstructive sleep apnoea, dyslipidaemia, or arthritis), and were aged 18–65 years. Key exclusion criteria were a history of oesophagitis, Barrett's oesophagus, severe gastro-oesophageal reflux disease resistant to proton-pump inhibitors, and previous bariatric surgery. Participants were randomly assigned (1:1) to OAGB or RYGB, stratified by centre with blocks of variable size; the study was open-label, with no masking required. RYGB consisted of a 150 cm alimentary limb and a 50 cm biliary limb and OAGB of a single gastrojejunal anastomosis with a 200 cm biliopancreatic limb. The primary endpoint was percentage excess BMI loss at 2 years. The primary endpoint was assessed in the per-protocol population and safety was assessed in all randomised participants. This study is registered with ClinicalTrials.gov, number NCT02139813, and is now completed.
From May 13, 2014, to March 2, 2016, of 261 patients screened for eligibility, 253 (97%) were randomly assigned to OAGB (n=129) or RYGB (n=124). Five patients did not undergo their assigned surgery, and after undergoing their surgery 14 were excluded from the per-protocol analysis (seven due to pregnancy, two deaths, one withdrawal, and four revisions from OAGB to RYGB) In the per-protocol population (n=117 OAGB, n=117 RYGB), mean age was 43·5 years (SD 10·8), mean BMI was 43·9 kg/m2 (SD 5·6), 176 (75%) of 234 participants were female, and 58 (27%) of 211 with available data had type 2 diabetes. After 2 years, mean percentage excess BMI loss was −87·9% (SD 23·6) in the OAGB group and −85·8% (SD 23·1) in the RYGB group, confirming non-inferiority of OAGB (mean difference −3·3%, 95% CI −9·1 to 2·6). 66 serious adverse events associated with surgery were reported (24 in the RYGB group vs 42 in the OAGB group; p=0·042), of which nine (21·4%) in the OAGB group were nutritional complications versus none in the RYGB group (p=0·0034).
OAGB is not inferior to RYGB regarding weight loss and metabolic improvement at 2 years. Higher incidences of diarrhoea, steatorrhoea, and nutritional adverse events were observed with a 200 cm biliopancreatic limb OAGB, suggesting a malabsorptive effect.
French Ministry of Health.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Plastics are materials which show important volume variations when they undergo temperature changes. During the injection molding process, polymer parts may shrink and so become unstuck from the mold ...walls. It drives then to the apparition of air gaps which may modify both the shape of the part and its cooling time. The cooling of such a polymer part is studied, taking into account key parameters such as thermal contact resistances, residual stresses, or PvT diagram. The results of the numerical simulation, using a coupled thermomechanical approach, are compared to experiments that are led in parallel.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
An instrumented injection mould was designed to determine the crystallization kinetics of semi-crystalline polymers and short fibre reinforced bulk composites. This set-up is an interesting ...alternative to other characterization devices since it is more representative of injection process conditions, and bulk samples are more suitable for studying reinforced polymers.
We developed a methodology to estimate the Nakamura kinetic function K(T) by solving an inverse 1D heat conduction problem coupled to the kinetic equation. Estimated parameters are obtained in a temperature range which depends on the cooling rate. We first validated the experimental approach with a well characterized isotactic polypropylene. Then, we used this setup to determine the kinetic function of a technical polymer (poly m-xylylene adipamide–MXD6), for which the crystallization is complex since it contains nucleating agents. Our results are compared with a literature empirical model and with those obtained by DSC.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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