GROWTH OF SEMI-ELLIPTICAL SURFACE CRACKS IN FERRITIC STEEL PLATES UNDER CYCLIC THERMAL SHOCK LOADING

Abstract— Investigations of crack growth under thermal fatigue loading are presented. The experiments were performed with a ferritic reactor pressure vessel steel. A plate, containing a semi-elliptical surface crack is heated up to a homogeneous temperature and cyclically cooled down by a jet of cold water. On the basis of linear elastic fracture mechanics, stress-intensity factors are calculated with the weight function method. The prediction of crack growth under thermal fatigue loading using data from standard specimens is compared with the experimental result.     

The value of the greenbelt in Vienna: a spatial hedonic analysis

The Annals of Regional Science - This paper employs the hedonic price method to examine whether the implicit value of the greenbelt is capitalized into apartment prices in the city of Vienna,...     

Effectiveness of powered hospital bed movers for reducing physiological strain and back muscle activation

Battery powered bed movers are becoming increasingly common within the hospital setting. The use of powered bed movers is believed to result in reduced physical efforts required by health care workers, which may be associated with a decreased risk of occupation related injuries. However, little work has been conducted assessing how powered bed movers impact on levels of physiological strain and muscle activation for the user. The muscular efforts associated with moving hospital beds using three different methods; powered StaminaLift Bed Mover (PBM1), powered Gzunda Bed Mover (PBM2) and manual pushing were measured on six male subjects. Fourteen muscles were assessed moving a weighted hospital bed along a standardized route in an Australian hospital environment. Trunk inclination and upper spine acceleration were also quantified. Powered bed movers exhibited significantly lower muscle activation levels than manual pushing for the majority of muscles. When using the PBM1, users adopted a more upright posture which was maintained while performing different tasks (e.g. turning a corner, entering a lift), while trunk inclination varied considerably for manual pushing and the PBM2. The reduction in lower back muscular activation levels may result in lower incidence of lower back injury.     

Temperature control of the water gas shift reaction in microstructured reactors

Microchannel reactors offer unique possibilities for temperature control of chemical reactions due to the strong coupling of channel and wall temperatures. This may be applied to all chemical reactions which require a certain temperature profile to achieve an optimum yield. For the reformation of hydrocarbons for fuel cell applications a low CO concentration of the product gas is desired. In conventional systems, this is achieved by sequentially processing the reformate through a high and low temperature water gas shift reactor because increased temperature enlarges the reaction rate while lower temperature shifts the equilibrium to the desired small CO concentrations. However, for every gas composition arising during the reaction process an optimum temperature exists at which the reaction rate is highest. We will demonstrate that this optimum temperature profile to a good approximation can be achieved in a single step WGS reactor by controlling the temperature via cooling gas flowing in counter current to the reformate. Furthermore, the effect of water addition (steam injection) is analysed for a conventional two-step adiabatic reactor system and the possible size reduction in an integrated heat-exchanger reactor under comparable conditions is validated. Finally, the effect of diffusion limitations at various channel dimensions is investigated applying a two-dimensional model which allows a trade-off between pressure drop or respective reactor size and performance when dimensioning a real system in future.     

Economic application of virtual commissioning to mechatronic production systems

The interaction of heterogenous control hard and software plays a key role in enabling mechatronic production systems to become flexible and agile systems. Nevertheless, control software engineering still tends to be the last step within the development process. To a large extent it is carried out during the commissioning phase of the production ramp-up. On the first hand this leads to a loss of time and quality as well as to a loss of reputation and future orders on the second hand. A method that is referred to as Virtual Commissioning tries to overcome this situation. The aim is to enable control software engineering to, both take over the initiative in system design and to perform important activities earlier in the design process of production equipment. In this paper, the technological and economical scalability of Virtual Commissioning is analyzed. Based on the analysis, a technical concept for a scalable simulation environment is presented. The paper concludes with a new method for the economic application of Virtual Commissioning.     

Indentation Behavior of Soda-Lime Silica Glass, Fused Silica, and Single-Crystal Quartz at Liquid Nitrogen Temperature

In an attempt to elucidate the processes involved in the formation of indentation impressions, Vickers hardness measurements have been made on soda-lime silica glass, fused silica, and crystalline quartz indented at room temperature and 77 K. The hardness of all three materials increases by a factor of ∼2.5 on cooling to liquid nitrogen temperature. High-magnification SEM photographs revealed that the deformation and cracking patterns of the glasses changed strikingly: no shear lines were observed within the indentations, and ring cracking occurred instead of radial/median cracking. In addition, cracking occurs at much higher loads than at room temperature. The hardness results have been explained in terms of volume flow (densification) rather than shear flow (viscous or plastic) for the glasses at low temperature. The quartz crystal, on the other hand, deformed plastically at both room temperature and 77 K. Cracking differences result from changes in both flow and water activity     

Determination of Bridging Stresses in Reinforced Al2O3

The determination of bridging stresses by evaluation of crack opening profiles is outlined for a whisker-reinforced alumina. The application of the fracture mechanics weight function procedure results in an integral equation between bridging stresses and crack opening displacements. Its solution provides the bridging stress relation.     

New oxygen evolution anodes for metal electrowinning: investigation of local physicochemical processes on composite electrodes with conductive atomic force microscopy and scanning electrochemical microscopy

Atomic force microscopy (AFM), conductive atomic force microscopy (CAFM) in air, and scanning electrochemcial microscopy (SECM) in 2 M H₂SO₄ have been used to investigate model composite electrodes obtained by pressing sieved MnO₂ particles into a Pb matrix. These model electrodes shall resemble new composite electrodes produced by coldspraying and currently being tested for Zn electrowinning. CAFM showed a very uneven distribution of the current path through the matrix electrode with the highest currents measured at the MnO₂/Pb domain boundary. SECM images in the substrate-generation/tip-collection mode in vertical and horizontal planes could show spatial concentration distribution of H⁺, O₂ and H₂O₂ that could be evaluated qualitatively despite interfering turbulent convection due to raising gas bubbles. There is a concentration overvoltage due to deviations of the H⁺ and O₂ concentration close to the surface from the bulk value. It amounts to about 40–50 mV for both compounds. H₂O₂ is formed as an intermediate and is consumed at the MnO₂ catalyst particles.     

Simultaneous Estradiol and Levonorgestrel Transdermal Delivery from a 7-day Patch: In Vitro and In Vivo Drug Deliveries of Three Formulations

ABSTRACT

A new drug-in-adhesive transdermal patch was developed to deliver both estradiol and levonorgestrel through the skin over a 7-day period, but at different rates. This report elucidates the in vitro and in vivo biopharmaceutical studies that were necessary during the development of this product. Three test patches had to be manufactured, all delivering estradiol at the same rate, but delivering levonorgestrel at three different rates so that a levonorgestrel dose response could be studied in the clinic. An in vitro hairless mouse skin model (HMS) using modified Franz diffusion cells was used to select the test products delivering levonorgestrel in the order of 1:2:3. HMS experiments also demonstrated that the presence of estradiol did not affect the flux of levonorgestrel. Two in vivo studies in postmenopausal women showed that at steady state (four weeks of once-weekly dosing) the three test products all delivered estradiol at comparable rates. Similarly, the levonorgestrel deliveries for the three test products were in the order expected. The target fluxes of both drugs were achieved in these three test products by varying the drug loads and patch size. That this approach was successful is evidence of the value of using the HMS penetration experiments in transdermal product development and should provide useful insights for other formulations having to develop complex systems. One of the test products is now marketed as Climara Pro^TM.