2,745 research outputs found
Flow driven by a torsionally-oscillating shrouded endwall disk
No full textA study is made of time-dependent flow of a viscous fluid driven by an oscillating shrouded disk in finite geometry. Numerical solutions to the Navier-Stokes equations are obtained for the flow in a cylindrical cavity with its upper endwall disk executing torsional oscillation at a velocity Omega cos lambda t. Details of the three-component velocity field are examined at high Reynolds number. The value of the nondimensional amplitude of disk oscillation, epsilon = Omega/lambda encompasses a range up to epsilon greater than or similar to 0 (1). The numerical results for the azimuthal flow for epsilon much less than 1 are consistent with the predictions of the earlier analytical model. The azimuthal flow is largely confined to the Stokes layer thickness. The analytical predictions of the meridional flow, based on a straightforward expansion technique, display discrepancies from the numerical results. The steady meridional streaming at finite values of epsilon is exhibited. The qualitative patterns of meridional steady streaming are verified by laboratory flow visualizations. The explicit effect of Re on the overall flow character is scrutinized. The numerical data are processed to describe the behavior of the torque coefficient at the oscillating disk
Augmentation of convective heat transfer by a torsionally-oscillating endwall disk
No full textAn investigation is made of fluid flow and heat transfer characteristics in a vertically-mounted circular cylinder. Motions are generated by the top endwall disk, which oscillates about the central axis with rotation rate Omega = epsilon lambda cos(lambda t). The temperature of the top disk is higher than that of the bottom disk, producing a stable stratification of Brunt-Vaisala frequency N. Numerical solutions are acquired to the time-dependent Navier-Stokes equations. Comprehensive velocity and temperature data are obtained, which illustrate salient features of quasi-steady periodic flows. As the stratification increases, the steady meridional streaming is confined to a narrow region close to the top disk. Resonance is identified at particular values of (N/lambda), when the system is excited at correct natural frequencies. An elementary inviscid analysis indicates the modes of inertial-gravity oscillations, and the present numerical data are in close agreement with the inviscid results. The amplitudes of fluctuating parts of meridional flow and of Nusselt number display distinctive peaks under resonance conditions. Details of evolutions of fluctuating velocities and temperatures are scrutinized to offer physical explanations for resonance. (C) 1998 Elsevier Science Ltd
Use of an Adaptive Window in PID-plus Bang-Bang Control : A Motor Control Experiment
No full textPID-type controllers have been widely used in many industrial applications. Regulation properties of those can be improved through the addition of the Bang-Bang action. In spite of the potentials of this PID-plus Bang-Bang controller, their regulation properties are still limited if a fixed window limit is used in selection of a control action between PID and Bang-Bang action. Thus, this paper proposes an approach to improving regulation properties. Our approach changes window limits adaptable to plant dynamics by use of a Gradient Based Prediction Model. We experimented our control scheme with a DC servo-motor system. It has been shown through experiment that our control scheme outperformed than existing one in terms of overshoot, rise time and settling time.The authors would like to thank reviewers. Their helpful comments enalble us to improve the quality of this paper
The LIM and SH3 domain protein family: structural proteins or signal transducers or both?
No full textLIM and SH3 Protein 1 (LASP-1) was initially identified from a cDNA library of metastatic axillary lymph nodes (MLN) more than a decade ago. It was found to be overexpressed in human breast and ovarian cancer and became the first member of a newly defined LIM-protein subfamily of the nebulin group characterized by the combined presence of LIM and SH3 domains. LASP2, a novel LASP1-related gene was first identified and characterized in silico. Subsequently it proved to be a splice variant of the Nebulin gene and therefore was also termed LIM/nebulette. LASP-1 and -2 are highly conserved in their LIM, nebulin-like and SH3 domains but differ significantly at their linker regions. Both proteins are ubiquitously expressed and involved in cytoskeletal architecture, especially in the organization of focal adhesions. Here we present the first systematic review to summarize all relevant data concerning their domain organization, expression profiles, regulating factors and function. We compile evidence that both, LASP-1 and LASP-2, are important during early embryo- and fetogenesis and are highly expressed in the central nervous system of the adult. However, only LASP-1 seems to participate significantly in neuronal differentiation and plays an important functional role in migration and proliferation of certain cancer cells while the role of LASP-2 is more structural. The increased expression of LASP-1 in breast tumours correlates with high rates of nodal-metastasis and refers to a possible relevance as a prognostic marker
Assessment of the sea-ice carbon pump: insights from a three-dimensional ocean-sea-ice biogeochemical model (NEMO-LIM-PISCES)
No full textThe role of sea ice in the carbon cycle is minimally represented in current Earth System Models (ESMs). Among potentially important flaws, mentioned by several authors and generally overlooked during ESM design, is the link between sea-ice growth and melt and oceanic dissolved inorganic carbon (DIC) and total alkalinity (TA). Here we investigate whether this link is indeed an important feature of the marine carbon cycle misrepresented in ESMs. We use an ocean general circulation model (NEMO-LIM-PISCES) with sea-ice and marine carbon cycle components, forced by atmospheric reanalyses, adding a first-order representation of DIC and TA storage and release in/from sea ice. Our results suggest that DIC rejection during sea-ice growth releases several hundred Tg C yr−1 to the surface ocean, of which 3 precipitation but also ice-atmosphere CO2 fluxes and net community production) increasing the TA/DIC ratio in sea-ice modified ocean-atmosphere CO2 fluxes by a few Tg C yr−1 in the sea-ice zone, with specific hemispheric effects: DIC content of the Arctic basin decreased but DIC content of the Southern Ocean increased. For the global ocean, DIC content increased by 4 Tg C yr−1 or 2 Pg C after 500 years of model run. The simulated numbers are generally small compared to the present-day global ocean annual CO2 sink (2.6 ± 0.5 Pg C yr−1). However, sea-ice carbon processes seem important at regional scales as they act significantly on DIC redistribution within and outside polar basins. The efficiency of carbon export to depth depends on the representation of surface-subsurface exchanges and their relationship with sea ice, and could differ substantially if a higher resolution or different ocean model were used
Evaluation of the first automated thyroglobulin assay
No full textThe aim of this study was to investigate technical and analytical performance of the first automated thyroglobulin (Tg) assay (DPC-Immulite(R); Diagnostic Products Corporation, Los Angeles, USA). In imprecision studies using several human serum pools ranging from 21 to 58 replicates, a coefficient of variation of 9.0 % was obtained at a mean Tg concentration of 0.84 ng/ml and of 6.1 % at a Tg concentration of 62.1 ng/ml. In a method comparison with a non-automated assay (BRAHMS LUMItest Tg(R), BRAHMS, Berlin, Germany) using 383 sera of 303 patients with thyroid carcinoma, regression analysis according to Passing and Bablock yielded in the following equation: Immulite Tg=1.6 x BRAHMS Tg - 0.1 ng/ml (Pearson's r=0.979). Sera obtained from 59 patients with thyroid carcinoma enabled comparative follow-up studies; in all cases qualitative agreement was found with regard to increase or decrease of serum Tg; in eight cases, however, Tg was detected with the Immulite assay but not with the BRAHMS assay. Further follow-up proved the presence of thyroid tissue in these patients. From these and further methodological data (dilution linearity, interference studies, carry-over study, high-dose hook properties, and short report time) it is concluded that the DPC-Immulite Tg assay meets the requirements of routine diagnostic use
Bulk viscosity in F(T, TG) gravity
No full textThe present paper is devoted to exploring the effect of bulk viscosity in the context of F(T, TG) gravity. We consider a time-dependent viscosity model with a particular expression of Hubble parameter. We evaluate viscous effective equation of state parameter for three well-known F(T, TG) models. The behavior of the accelerated expanding universe is explored graphically through the viscous equation of state parameter. This parameter indicates the phantom-dominated era as well as crosses the phantom divide line for all three models. We conclude that the universe shows a transition from quintessence to phantom region in the presence of bulk viscosity.The presentation of the authors' names and (or) special characters in the title of the pdf file of the accepted manuscript may differ slightly from what is displayed on the item page. The information in the pdf file of the accepted manuscript reflects the original submission by the author
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