Number Of Stable Points Research Articles

Depletion Interactions at Interfaces Induced by Ferromagnetic Colloidal Polymers.

The pair-interaction force profiles for two non-magnetic colloids immersed in a suspension of ferromagnetic colloidal polymers are investigated via Langevin simulations. A quasi-two-dimensional approach is taken to study the interface case and a range of colloidal size ratios (non-magnetic:magnetic) from 6:1 up to 20:1 have been considered in this work. Simulations show that when compared with non-magnetic suspensions, the magnetic polymers strongly modify the depletion force profiles leading to strongly oscillatory behavior. Larger polymer densities and size ratios increase the range of the depletion forces, and in general, also their strength; the force barrier peaks at short distances show more complex behavior. As the length of the ferromagnetic polymers increases, the force profiles become more regular, and stable points with their corresponding attraction basins develop. The number of stable points and the distance at which they occur can be tuned through the modification of the field strength H and the angle θ formed by the field and the imaginary axis joining the centers of the two non-magnetic colloids. When not constrained, the net forces acting on the two colloids tend to align them with the field till θ=0∘. At this angle, the force profiles turn out to be purely attractive, and therefore, these systems could be used as a funneling tool to form long linear arrays of non-magnetic particles. Torsional forces peak at θ=45∘ and have minimums at θ=0∘ as well as θ=90∘ which is an unstable orientation as slight deviations will evolve towards θ→0∘. Nonetheless, results suggest that the θ=90∘ orientation could be easily stabilized in several ways. In such a case, the stable points that the radial force profiles exhibit for this orthogonal orientation to the field could be used to control the distance between the two large colloids: their position and number can be controlled via H. Therefore, suspensions made of ferromagnetic colloidal polymers can be also useful in the creation of magnetic colloidal tweezers or ratchets. A qualitative explanation of all the observed phenomena can be provided in terms of how the geometrical constraints and the external field modify the conformations of the ferromagnetic polymers near the two large particles, and in turn, how both factors combine to create unbalanced Kelvin forces that oscillate in strength with the distance between the two non-magnetic colloids.

Deep feature regression (DFR) for 3D vessel segmentation

The structural information of coronary arteries has important clinical value for quantitative diagnosis and treatment of coronary artery disease. In this study, a deep feature regression (DFR) method based on a convolutional regression network (CRN) and a stable point clustering mechanism for 3D vessel segmentation is proposed. First, the vessel model is constructed by a vessel section generator and a series of deviation parameter estimators. The generator provides 2D images for the training and prediction processes, while the estimators calculate pose parameters of an input vessel section. Second, estimators are trained by a series of CRNs, in which deep vessel features are automatically learned from 600 000 sample images. Third, we propose a stable point clustering mechanism that evaluates the reliability of the CRN estimation through iterative regression of vessel parameters. This mechanism eliminates the outliers, thereby increasing tracking robustness. Finally, we present a vessel segmentation algorithm using trained deviation parameter estimators. And, the termination criteria are designed based on both the number of stable points and an intensity constraint. The proposed method is evaluated on a public coronary artery data set. The average overlapping ratio and error are 97.5% and 0.27 mm, respectively. A quantitative test on a public cerebral artery data set demonstrates that the proposed DFR method tracks the vessel centerline with high accuracy, for which the average error is less than 0.33 mm.

Multistable circuit using Λ‐shaped negative resistance devices and its application to frequency divider

AbstractNew voltage‐controlled negative resistance devices, Λ‐shaped negative resistance devices, are combined with Zener diodes and resistors to form a unit circuit. These unit circuits are connected in parallel to create circuit configurations that cannot be realized by previous voltage‐controlled negative resistance devices. This circuit exhibits multipeak characteristics and realizes a multistable circuit and a frequency dividerIn previous multipeak characteristics, the current peak increases with the voltage. In the present multipeak characteristics, the current peak can be set independetly. A multistable circuit has been constructed with the present structure, analyzed, and its characteristics found. The voltage of the stable point can be varied independently and the number of stable points can be varied with the gate voltage of the Λ‐shaped three‐terminal negative resistance device. When the multistable circuit is used for construction of a frequencey divider, the reset circuit can also be made simply with the Λ‐shaped negative resistance device. In addition to the 1/n divider, an arbitrary rational ratio divider can be fabricated by addition of a feedback loop.