Nodes irregular

But if a node x 6 that is, a node is irregular with respect to on the irregular pattern, then the difference operator A can be rewritten as... 

Furthermore, in giving the approximation error at the irregular nodes as a sum... 

Remark Quite often, the Dirichlet problem is approximated by the method based on the difference approximation at the near-boundary nodes of the Laplace operator on an irregular pattern, with the use of formulae (14) instead of (16) at the nodes x G However, in some cases the difference operator so constructed does not possess several important properties intrinsic to the initial differential equation, namely, the self-adjointness and the property of having fixed sign, For this reason iterative methods are of little use in studying grid equations and will be excluded from further consideration. 

Substituting this expression into the equation A y = —/ and regarding formally the node x to be irregular in all directions x, we finally get... 

Let X G be a near-boundary and irregular node only in some direction and = (+ ) G g From the equation... 

Observe that provides a second-order approximation at the regular nodes A w — LaU = O(h ), while A m — L,yU = 0(1) at the irregular ones. 

With these, we proceed to the complete posing of problems related to y and w. The intention is to use the equation for y in the canonical form (25) in combination with expression (18) for the difference operator Aa not only at the regular nodes, but also at the irregular nodes ... 

A growing neural gas has an irregular structure. A running total is maintained of the local error at each unit, which is calculated as the absolute difference between the sample pattern and the unit weights when the unit wins the competition to match a sample pattern. Periodically, a new unit is added close to the one that has accumulated the greatest error, and the error at the neighbors to this node share their error with it. The aim is to generate a network in which the errors at all units are approximately equal. 

The electrical impulse for contraction (propagated action potential p. 136) originates in pacemaker cells of the sinoatrial node and spreads through the atria, atrioventricular (AV) node, and adjoining parts of the His-Purkinje fiber system to the ventricles (A). Irregularities of heart rhythm can interfere dangerously with cardiac pumping func-tioa... 

Tachyarrhythmias (sinus rate more than 100 per minute) are produced by a disturbances of impulse generation or of impulse conduction in the heart. Tachyarrhythmias due to disturbed impulse formation are associated with irregular and rhythmic discharge from ectopic pacemaker activity in areas of the heart other than the SA node. The characteristic of myocardial cells, which enables them to generate spontaneous depolarization, is called automaticity. 

We offer below more a detailed classification of inner nodes. With this aim, let us draw up a straight line parallel to the axis Oxa through an inner node x u>h. Its intersection with the domain G is an interval (or several intervals), whose ends are boundary nodes along the direction Oxa. The nodes from this interval can be distinguished by the approved rules. We call the nearest to the end of the interval node a near-boundary node along the direction Oxa (with respect to z0). If the distance to the boundary jh is h ha, any such node is said to be irregular with respect to xa. Let... 

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