When two nodes are close enough (i e , smaller than a threshold D

When two nodes are close enough (i.e., smaller than a threshold Dth), the force is in repulsive pattern, which intends to separate them; When two nodes are far from each other (i.e., larger than the threshold Dth), the force becomes attractive pattern, which draws them closer. As once can see, the repulsive force is to make sensors sufficiently scarce, avoiding redundant coverage by the dense deployment of sensor nodes; while the attractive force is to keep a certain density of the nodes, avoiding blind areas.The threshold Dth is used to control the sensor density, which is determined by the users, e.g., according to the required sensing probability of the applications. Usually it ranges between [3r,2r].

More specifically, the force exerted on Node i by Node j in the network (denoted by Fij��) is given by Equation (1):Fij��={Wa(dij?Dth),��ijifdij>Dth0ifdij=DthWrdij?1,��ij+��ifdij), is then calculated by adding all forces contributed by the nodes in the network.Fi��=��j=1,j��inFij��,(2)where n denotes the number of mobile sensor nodes in the given ROI. The orientation of Fi?.gif” border=”0″ alt=”i” title=”"/> is determined by the angle of the summation of all the force vectors exerted on Si.Once Fi?.gif” border=”0″ alt=”i” title=”"/> and its orientation is determined, the sensor moves to its new location under the total external force, in order to maximize the coverage area in ROI.

2.3. Analysis of Virtual Force AlgorithmBy analyzing the forces between sensor nodes in VFA as given by Equations (1)-(2), we find that there always exists attractive force whenever the distance between two sensors is often more than threshold Dth. However, this may result in several problems, as elaborated below.VFA cannot always guarantee that the distance between sensors is reached at threshold Dth;As shown in Figure Drug_discovery 1(a), assuming sensor nodes S1, S2, S3 are located on the vertices of an equilateral triangle, when optimized coverage of ROI is achieved by using VFA. Zhang has demonstrated in [18] that in this case it ensures that not only ROI is fully covered, but also the over
In 1661 Dutch physicist and astronomer Christian Huygens invented the U tube manometer, which was a modification of Torricelli’s barometer for determining gas pressure differences.

Although the manometer is one of the earliest pressure measuring instruments, it is still widely used because of inherent accuracy and simplicity of operation. It is an important device used for measuring low pressure differences and gauge pressures by balancing the pressure against the weight of a column of fluid on laboratory and industrial scale [1].

Leave a Reply

Your email address will not be published. Required fields are marked *

*

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>