A hysteretic multiscale formulation for nonlinear dynamic analysis of composite materials

This article has been made available through the Brunel Open Access Publishing Fund.A new multiscale finite element formulation is presented for nonlinear dynamic analysis of heterogeneous structures. The proposed multiscale approach utilizes the hysteretic finite element method to model the microstructure. Using the proposed computational scheme, the micro-basis functions, that are used to map the microdisplacement components to the coarse mesh, are only evaluated once and remain constant throughout the analysis procedure. This is accomplished by treating inelasticity at the micro-elemental level through properly defined hysteretic evolution equations. Two types of imposed boundary conditions are considered for the derivation of the multiscale basis functions, namely the linear and periodic boundary conditions. The validity of the proposed formulation as well as its computational efficiency are verified through illustrative numerical experiments

Time-average and asymptotically optimal flow control policies in networks with multiple transmitters

We consider M transmitting stations sending packets to a single receiver over a slotted time-multiplexed link. For each phase consisting of T consecutive slots, the receiver dynamically allocates these slots among the M transmitters. Our objective is to characterize policies that minimize the long-term average of the total number of messages awaiting service at the M transmitters. We establish necessary and sufficient conditions on the arrival processes at the transmitters for the existence of finite cost time-average policies; it is not enough that the average arrival rate is strictly less than the slot capacity. We construct a pure strategy that attains a finite average cost under these conditions. This in turn leads to the existence of an optimal time-average pure policy for each phase length T , and to upper and lower bounds on the cost this policy achieves. Furthermore, we show that such an optimal time-average policy has the same properties as those of optimal discounted policies investigated by the authors in a previous paper. Finally, we prove that in the absence of costs accrued by messages within the phase, there exists a policy such that the time-average cost tends toward zero as the phase length T →∞.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44208/1/10479_2005_Article_BF02025184.pd

Alloimmunisation during pregnancy in Greece: need for nationwide HDFN prevention programme

Aim/ObjectivesTo access the incidence and specificity of maternal red blood cells alloimmunisation and its relevant clinical impact in Greece. BackgroundThe rate of alloimmunisation in pregnant women in Greece is unknown. Materials/MethodsWe performed a 4-year study in two tertiary hospitals in Greece. Demographics, transfusion and obstetric history were analysed. Maternal alloimmunisation was detected with indirect anti-globulin test. ResultsWe investigated 4368 pregnant women. Of which 3292 (75<bold>37</bold>%) were Greek and 1076 (24<bold>63</bold>%) were migrants. In 39 alloimmunised women, 41 alloantibodies were detected (0<bold>89</bold>%). The incidence of alloimmunisation was 0<bold>66</bold>% (22/3292) in Greeks and 1<bold>76</bold>% (17/1076) in migrants (P=0<bold>01</bold>). Anti-D was the most frequent alloantibody (0<bold>18</bold>%). Anti-D was more frequent in migrants; 5<bold>76</bold>% compared to 0<bold>56</bold>% in Greek RhD negative women (P=0<bold>002</bold>). Other antibody specificities in declining frequency rank were anti-K, anti-E, anti-Lea, anti-M, anti-c, anti-Ce, anti-Jka, anti-Jkb and anti-C. Primiparae vs para >2 and past history of blood transfusion were significantly associated with alloimmunisation during pregnancy (P=0<bold>0088</bold>, P<0<bold>0001</bold>, respectively). ConclusionsOur results depict differences in the delivery of health care between migrants and Greek women, as well as the heterogeneity in practices for the prevention of haemolytic disease of foetus and newborn in Greece and highlight the need for the implementation of nationwide guidelines