Stability of Parallel Queueing Systems with Coupled Service Rates

This paper considers a parallel system of queues fed by independent arrival streams, where the service rate of each queue depends on the number of customers in all of the queues. Necessary and sufficient conditions for the stability of the system are derived, based on stochastic monotonicity and marginal drift properties of multiclass birth and death processes. These conditions yield a sharp characterization of stability for systems where the service rate of each queue is decreasing in the number of customers in other queues, and has uniform limits as the queue lengths tend to infinity. The results are illustrated with applications where the stability region may be nonconvex.     

Smoothing methodology for predicting regional averages in multi-source forest inventory

The paper examines alternative non-parametric estimation methods or smoothing methods in the context of the Finnish multi-source forest inventory. It uses satellite images in addition to field data to produce forest variable predictions for regions ranging from the single pixel level up to the national level. With the help of the bias-variance decomposition, the influence of the smoothing parameters on prediction accuracy is considered when the smoother's pixel-level predictions are averaged in order to produce predictions for larger areas. A novel variation of cross-validation, called region-wise cross-validation, is proposed for selecting the smoothing parameters. Experimental results are presented using local linear ridge regression (LLRR), which is a variant of the better known local linear regression method.     

In vitro and in vivo studies of creatine monohydrate supplementation to Duroc and Landrace pigs

Duroc and Landrace pigs as well as primary myotubes from these breeds were used to investigate mechanisms behind differences in their response to creatine monohydrate (CMH). Pigs were supplemented with 0, 12.5, 25 or 50g CMH/d for 5 days (n=10 per treatment and breed). Plasma levels of creatine increased dose-dependently in both breeds, while muscle-creatine phosphate content increased only in the Duroc pigs. (1)H NMR metabolic profiling showed a tendency towards clustering according to CMH supplementation only among Duroc pigs, revealing a stronger response compared to Landrace pigs. The abundance of insulin-like growth factor I and myostatin mRNA was decreased by CMH supplementation while that of type 1 IGF-receptor and creatine transporter was unaffected. Protein synthesis, increased in the myotubes from both breeds, indicating protein accretion, but no effect was observed on the mRNA abundance of IGF-I, type 1 IGF-receptor, myostatin or the creatine transporter in myotubes.     

Effect of Shot Peening Parameters to Residual Stress Profiles and Barkhausen Noise

The production of gear components includes numerous manufacturing operations which are carried out to ensure proper surface characteristics of components to deal with wear and fatigue. Surface shot peening is one way to increase the compressive residual stresses on the surface and thus ensure better wear and fatigue resistance. An experimental plan for shot peening was conducted to produce samples with varying surface characteristics. Residual stress profile and Barkhausen noise measurements were carried out for the samples. The objective of the study was to evaluate the interactions between the shot peening parameters studied, the residual stress profiles and the Barkhausen noise measurements. A multivariable regression analysis was applied for the task. Some remarkable correlations were found between the shot peening parameters, residual stress profile and Barkhausen noise features. The most important finding was that when the shot peening intensity was high enough, over 0.5 mmA, it dominated the shot peening coverage density parameter and thus no correlations could be gained. On the other hand, if the intensity parameter was lower than the limit of 0.5 mmA, the correlation between residual stress and Barkhausen noise measurements was remarkable. This means that the surface Barkhausen noise measurements could be used for the evaluation of the stress gradient in the shot peening process.     

Electrochemical reaction rates in a dye-sensitised solar cell—the iodide/tri-iodide redox system

The electrochemical reaction rate of the redox couple iodide/tri-iodide in acetonitrile is characterised by impedance spectroscopy. Different electrode materials relevant for the function of dye-sensitised solar cells (DSSC) are investigated. Preferably, the reaction with the iodide/tri-iodide couple should be fast at the counter electrode, i.e. this electrode must have a high catalytic activity towards the redox couple, and the same reaction must be slow on the photo electrode.The catalytic activity is investigated for platinum, poly(3,4-ethylenedioxythiophene) (PEDOT), polypyrrole (PPy), and polyaniline (PANI)—all deposited onto fluorine-doped tin oxide (FTO) glass. Both Pt and PEDOT are found to have sufficiently high catalytic activities for practical use as counter electrodes in DSSC. The reaction resistance on FTO and anatase confirmed the beneficial effect of a compact anatase layer on top of the FTO glass in lowering the tri-iodide reduction rate.     

Pentanol as co-surfactant in polypyrrole actuators

Conducting polymers have been investigated for the use as active component in polymer actuators. Addition of 1-pentanol as co-surfactant to the polymerisation solution is shown to increase the reversible linear strain that can be achieved with polypyrrole films doped with dodecyl benzene sulfonate (PPy-DBS). When such films are prepared without pentanol, the length change between the oxidised and the reduced state is 2.5%. If pentanol is added to the synthesis solution in concentrations above 2.4 vol%, a linear extension of 5.6% was measured at a constant load of 0.6 MPa. The morphology of the film is changed considerable upon pentanol addition, although electrochemical quartz crystal microbalance measurements indicate that pentanol is only incorporated in the polymer to a small extent. The mechanical properties, conductivity and doping level of PPy-DBS films show little or no changes with the addition of pentanol. The use of pentanol as co-surfactant during polymerisation will, therefore, be beneficial for the use of PPy-DBS as active component material in polymer actuators.     

Stretching DNA in polymer nanochannels fabricated by thermal imprint in PMMA

We present results regarding the fast and inexpensive fabrication of polymer biochips for investigating the statics and dynamics of DNA confined in nanochannels. The biochips have been fabricated by means of nanoimprint lithography (NIL) in low molecular weight polymethyl methacrylate (PMMA) using a 4?inch diameter two-level hybrid stamp. The fluidic structures were sealed using thermal polymer fusion bonding. The stamp has nanometer-?and micrometer-sized protrusions defined in a thermally grown SiO(2) layer and the sol-gel process derived duromeric hybrid polymer Ormocomp, respectively. The stamp is compatible with molecular vapor deposition (MVD), used for applying a durable chlorosilane based antistiction coating, and allows for imprint up to a temperature of 270?°C. The extension of YOYO-1 stained T4 GT7 bacteriophage DNA inside the PMMA nanochannels has been experimentally investigated using epi-fluorescence microscopy. The measured average extension length amounts to 20% of the full contour length with a standard deviation of 4%. These results are in good agreement with results obtained by stretching DNA in conventional fused silica nanochannels.