Adaptive mutual synchronization of a CFT robot system

I n this report an adaptation mechanism for linear friction parameters is developed in order to achieve mutual synchronization for one direction of the CFT robot system. In particular, a mutual synchronization scheme is extended with an adaptation mechanism for the linear friction parameters in order to improve the performance. A stability analysis is made to develop the adaptation mechanism. During simulations the behaviour and performance of the adaptive mutual synchronization scheme is assessed. Finally the adaptive mutual synchronization scheme is tested oii the C i T rotjot sfsteiii iii the K T laboiat~iy at the Eindhoven Uni\versity of Technology. The experiments illustrate that it is possible to achieve adaptive mutual synchronization, but a part of the interconnections between the robots are lost and restrictions are given to the weighting factor in the synchronization error. However it is seen that the performance of the scheme has made an enormous improvement

Piston / Cylinder Interface Of Axial Piston Machines – Effect Of Piston Micro-Surface Shaping

Axial piston machines are widely used in current industries such as aerospace, agriculture, automotive, heavy machinery, military, etc. Thus new cost-effective and highly efficient designs with better performance and reliability are needed. These new, high efficient pumps and motors will also aid in new applications such as hybrid hydrostatic transmissions and displacement controlled actuation. The aim of this work is to study how to reduce the energy dissipation (increase efficiency) while also improving the load carrying ability of the fluid film between the piston and the cylinder through surface shaping of the piston over a wide range of operating conditions. The impacts of this study also include the utilization of modern manufacturing technologies as low tolerances are necessary such that this could affect the overall efficiency of the machine drastically. This study could also open up ways to use water as a lubricating fluid in order to significantly reduce costs. In doing so, a comprehensive understanding of the phenomena occurring between the piston and cylinder will also be achieved in order to find a balance between the viscous friction of the fluid, while reducing any contact occurring, and the leakage. In order to verify the code used in this surface shaping study, a comprehensive study was conducted on the baseline and then compared to measurements

Vorming van percolaatwater en uitspoeling van nutriënten bij composthopen van bloembollenafval

Op een vijftal bloembollenbedrijven in Noord-Holland zijn gegevens verzameld over het composteren van bloembollenafvallen, over de wijze van uitvoering van het composteringsproces, over de vorming daarbij van percolaatwater en over het gehalte aan nutriënten (N, P en K) in dit percolaatwater. Achterliggend doel was een beeld te krijgen van de mogelijke belasting van de bodem door nutriënten. Het droge-stofgehalte van de bloembollenafvallen bedroeg in alle gevallen meer dan 30%

Phosphoinositide-3-kinase/akt - Dependent Signaling is Required for Maintenance of [Ca\u3csup\u3e2+\u3c/sup\u3e]\u3csub\u3eI,\u3c/sub\u3eI\u3csub\u3eCa\u3c/sub\u3e, and Ca\u3csup\u3e2+\u3c/sup\u3e Transients in HL-1 Cardiomyocytes

The phosphoinositide 3-kinases (PI3K/Akt) dependent signaling pathway plays an important role in cardiac function, specifically cardiac contractility. We have reported that sepsis decreases myocardial Akt activation, which correlates with cardiac dysfunction in sepsis. We also reported that preventing sepsis induced changes in myocardial Akt activation ameliorates cardiovascular dysfunction. In this study we investigated the role of PI3K/Akt on cardiomyocyte function by examining the role of PI3K/Akt-dependent signaling on [Ca 2+]i, Ca2+ transients and membrane Ca2+ current, ICa, in cultured murine HL-1 cardiomyocytes. LY294002 (120 μM), a specific PI3K inhibitor, dramatically decreased HL-1 [Ca 2+]i, Ca2+ transients and ICa. We also examined the effect of PI3K isoform specific inhibitors, i.e. α (PI3-kinase α inhibitor 2; 28 nM); ? (TGX-221; 100 nM) and γ (AS-252424; 100 nM), to determine the contribution of specific isoforms to HL-1 [Ca 2+]i regulation. Pharmacologic inhibition of each of the individual PI3K isoforms significantly decreased [Ca2+]i, and inhibited Ca 2+ transients. Triciribine (120 μM), which inhibits AKT downstream of the PI3K pathway, also inhibited [Ca2+]i, and Ca 2+ transients and ICa. We conclude that the PI3K/Akt pathway is required for normal maintenance of [Ca2+]i in HL-1 cardiomyocytes. Thus, myocardial PI3K/Akt-PKB signaling sustains [Ca 2+]i required for excitation-contraction coupling in cardiomyoctyes

Performing SELEX experiments in silico

Theoretical Physic

Deformability and collision-induced reorientation enhance cell topotaxis in dense microenvironments

In vivo, cells navigate through complex environments filled with obstacles. Recently, the term 'topotaxis' has been introduced for navigation along topographic cues such as obstacle density gradients. Experimental and mathematical efforts have analyzed topotaxis of single cells in pillared grids with pillar density gradients. A previous model based on active Brownian particles has shown that ABPs perform topotaxis, i.e., drift towards lower pillar densities, due to decreased effective persistence lengths at high pillars densities. The ABP model predicted topotactic drifts of up to 1% of the instantaneous speed, whereas drifts of up to 5% have been observed experimentally. We hypothesized that the discrepancy between the ABP and the experimental observations could be in 1) cell deformability, and 2) more complex cell-pillar interactions. Here, we introduce a more detailed model of topotaxis, based on the Cellular Potts model. To model persistent cells we use the Act model, which mimicks actin-polymerization driven motility, and a hybrid CPM-ABP model. Model parameters were fitted to simulate the experimentally found motion of D. discoideum on a flat surface. For starved D. discoideum, both CPM variants predict topotactic drifts closer to the experimental results than the previous ABP model, due to a larger decrease in persistence length. Furthermore, the Act model outperformed the hybrid model in terms of topotactic efficiency, as it shows a larger reduction in effective persistence time in dense pillar grids. Also pillar adhesion can slow down cells and decrease topotaxis. For slow and less persistent vegetative D. discoideum cells, both CPMs predicted a similar small topotactic drift. We conclude that deformable cell volume results in higher topotactic drift compared to ABPs, and that feedback of cell-pillar collisions on cell persistence increases drift only in highly persistent cells

Output feedback tracking of ships

Abstract-In this brief, we consider output feedback tracking of ships with position and orientation measurements only. Ship dynamics are highly nonlinear, and for tracking control, as opposed to dynamic positioning, these nonlinearities have to be taken into account in the control design. We propose an observer-controller scheme which takes into account the complete ship dynamics, including Coriolis and centripetal forces and nonlinear damping, and results in a semi-globally uniformly stable closed-loop system. Furthermore, a gain tuning procedure for the observer-controller scheme is developed. Experimental results are presented where the observer-controller scheme is implemented onboard a Froude scaled 1:70 model supply ship. The experimentally obtained results are compared with simulation results under ideal conditions and both support the theoretical results on semi-global exponential stability of the closed-loop system

Ultraviolet-Visible (UV-Vis) Spectroscopy

Ultraviolet-Visible (UV-Vis) spectroscopy is a versatile and powerful analytical method, which allows to investigate a wide variety of catalysts in both the liquid-phase and solid-state and their interfaces at elevated temperatures and pressures. In the case of solid catalysts, they can be studied in the form of powders (e.g., in diffuse reflectance mode) and as thin wafers (in transmission mode), and when combined with a microscope even in the form of catalyst bodies (e.g., extrudates) and single crystals. In the past two decades, UV-Vis spectroscopy has been increasingly used under in situ and operando conditions to shed light on/gain insight in the working principles of heterogeneous catalysts, homogeneous catalysts, electrocatalysts, as well as photocatalysts. One of the advantages of this method is that it can simultaneously measure, e.g., the electronic transitions of organic molecules (mainly via their n → π* and π → π* transitions) and transition metal oxides or ions (via their d-d and charge transfer transitions). Unfortunately, absorption bands in the UV-Vis range are often broad and overlapping and hence their interpretations are not always trivial. Advanced theoretical calculations are required to provide a proper foundation of their interpretation, while, e.g., chemometrics can help prevent biased analysis when many (time-resolved) spectra are collected. Finally, UV-Vis spectroscopy is often combined with other analytical methods to provide complementary information. Examples include X-ray absorption spectroscopy and diffraction, next to vibrational spectroscopy (i.e., infrared and Raman) and magnetic resonance (i.e., electron spin resonance and nuclear magnetic resonance) methods. The above-described scientific and instrumental developments will be illustrated by using a selection of showcase examples, covering the different areas of catalysis. The chapter concludes with some main observations as well as some future developments on what might become possible in the not-too-distant future