Mass transfer in aerated fermentation broths in a stirred tank reactor

The volumetric mass transfer coefficients, k_La, measured in a pilot plant (0.1 m³) and an industrial (67.5 m³) fermentor during an actual fermentation process are presented. Problems related to the estimation of the phsyical properties as well as to the correlation of experimental data and to scale up procedures are discussed. Although the scale up factor was rather high, both sets of data could be represented by single correlation. Comparison of the experimental data with several available correlations demonstrated the need for pilot plant experiments and scale up procedures, since it is almost impossible to take into account all relevant system properties.     

高炉型熔渣中TiO2的活度

在1500℃下用金属Sn作熔剂,石墨作还原剂,采用“熔渣—金属Sn”化学平衡法和相图计算法,得到了高炉型熔渣中TiO_2的活度,并讨论了渣中TiO_2的活度和活度系数随其浓度变化的规律。     

Virtual approach to holonic control of the tyre-manufacturing system

Tyre manufacturers aiming to remain competitive in complex modern markets must promptly adjust to the changes within the production environment. With traditional tyre-manufacturing systems, a slow response during optimization of the manufacturing process and low-level adaptability to system disturbances is evident. The presented approach to virtual holonic control of the tyre-manufacturing system enables dynamic response in the event of new optimization demands, decrease of the impact of disturbances on system productivity and smaller future investments in the manufacturing equipment.     

Water Sorption and Diffusion in (Reduced) Graphene Oxide‐Alginate Biopolymer Nanocomposites

The water sorption and diffusion in (reduced) graphene oxide‐alginate composites of various compositions is analyzed. Water sorption of sodium alginate can be significantly reduced by the inclusion of graphene oxide sheets due to the formation of an extensive hydrogen bonding network between oxygenated groups. Crosslinking alginate with divalent metal ions and the presence of reduced graphene oxide can further improve the swelling resistance due to the strong interactions between metal ions, alginate, and filler sheets. Depending on conditions and composition, the overall water barrier properties of alginate composites improve upon (reduced) graphene oxide filling, making them attractive for moisture barrier coating applications. Water sorption kinetics in all alginate composites indicate a non‐Fickian diffusion process that can be accurately described by the Variable Surface Concentration model. In addition, the water barrier properties of sodium alginate‐graphene oxide composites can be adequately predicted using a simple model that takes the orientational order of filler sheets and their effective aspect ratio into account.

     

Voluntary pacing and energy cost of off-road cycling and running

PURPOSE: The purposes of this study were (1) to compare self-chosen speed of off-road cyclists and runners on a hilly course, (2) to compare the energy expenditure of off-road cyclists and runners on the same terrain, and (3) to describe changes in energy expenditure over the course of the exercise period. METHODS: Runners and cyclists performed three laps on a 2.75 km gravel course in a single exercise bout. The course was divided into 13 segments differing in grade and length. Position on the course and heart rate were recorded every few seconds. Speed was computed for each course segment on each lap; energy expenditure was estimated using recorded heart rates and exercise-specific maximal oxygen uptake measurements made prior to participation in the study. RESULTS: There were significant relationships between grade and speed for both runners (r = 0.64) and cyclists (r = 0.44). The differences between cyclists and runners were greatest on downhill segments. Energy expenditure rates were not significantly different for runners (71.6% VO2 peak) and cyclists (68.5% VO2 peak). CONCLUSIONS: Off-road cycling and running are comparable in energy demands. Variation in skill levels may account for the increased variability in speed among cyclists on downhill terrain.     

Tension and compression testing of single-crystalline gamma Ti-55.5 pct Al

High-quality single crystals 6 to 10 mm in diameter of γ-Ti 55.5 pct Al have been grown using the optical float zone furnace technique. These crystals have been oriented and cut into microsample tension and compression specimens with a gage area of 250×250 μm and an effective gage length of 300 μm. These specimens have been deformed using a microsample testing machine which applies loads on the order of 50 N and measures strain using an interferometric strain/displacement gage. Stress-strain curves have been obtained for four different orientations and two temperatures and as a function of the sense of the applied load. Of special interest is the availability of tensile data for the resolved shear stress. Preliminary comparison of tension and compression microsample tests indicates that the tension-compression asymmetry is negligible at 500 K. This article is based on a presentation made in the symposium “Fundamentals of Gamma Titanium Aluminides,” presented at the TMS Annual Meeting, February 10–12, 1997, Orlando, Florida, under the auspices of the ASM/MSD Flow & Fracture and Phase Transformations Committees.     

The features of sustainable Solar Hydroelectric Power Plant

This work presents the main features of the new power plant that comprises the modified reversible hydroelectric (HE) power plant operating together with the photovoltaic (PV) power plant. Such Solar Hydroelectric Power Plant (SHE) uses solar energy as the only input for production of solar and hydro energy. Thereat, water reservoir serves for daily and seasonal energy storage, thus basically solving the problem of energy storage, which is the biggest problem of wider use of solar energy. The most expensive part of SHE is the PV generator, whose optimal sizing is essential for providing energetic independence of a settlement or isolated consumer. A systematic approach that includes all relevant elements of this system has been implemented for optimal sizing of the PV power plant. The developed model was used in analysis of certain parameters of the SHE system. The results of the analysis show the system characteristics and that the proposed model describes the operation of the power plant very well. The feasibility and characteristics of the power plant were tested on electric energy supply of the island of Vis in Croatia. It has been established that the system is real, feasible and can be very successfully applied on different locations, for different consumers and can vary in size. The prerequisite for realization of such system is the construction of a modified reversible HE power plant. The presented SHE represents a permanently sustainable energy source that can continuously provide power supply to a consumer, using exclusively natural and renewable energy sources, without causing harmful effects on the environment.     

Upper limb motion analysis using haptic interface

An objective test for evaluating the functional studies of the upper limbs (UL) in patients with neurological diseases (ND) is presented. The method allows assessment of kinematic and dynamic motor abilities of UL. Our methodology is based on creating a virtual environment, using a computer display for visual information and a PHANTOM haptic interface. The haptic interface is used as a kinematic measuring device and for providing tactile feedback to the patient. In virtual environment, a labyrinth in patient's frontal plane was created at the start of each test. By moving the haptic interface control stick the patient was able to move the pointer (a ball) through the labyrinth in three dimensions and to feel the reactive forces of the wall. The new test offers a wide range of numerical and graphic results. It has so far been applied to 13 subjects with various forms of ND (e.g., Friedreich Ataxia, Parkinson's disease, Multiple Sclerosis) as well as to healthy subjects. The comparison in performance between right and left UL has been carried out in healthy subjects