This last database has been constituted within this study and will help validating the altimeter-based pressure signal during ETDs (section 4.2).The SLA derived from altimetry has the following formulation:SLA=Orbit?Range?��Corrections?MSS_CLS(1a)where �� Corrections = Sea State Bias + Radiometer wet tropospheric correction + Ionospheric correction + GOT2000 ocean tide + Solid earth tide + Polar tide [17,18]. The IB and dry tropospheric corrections are not applied because they are correlated to SLP:IB=?0.9948*(SLP?SLP��) in cm(1b)DryTropo=?2.227*SLP*(1+0.0026*cos(2��)) in mm [18](1c)where SLP is the atmospheric pressure (in hPa), SLP�� is the instantaneous mean of SLP over global ocean, and is the latitude. The scale factor 0.9948 is based on the empirical value [19] of the IB at mid latitudes.

Several studies have shown the zonal dependence of this coefficient, from about 0.9 cm/hPa at high latitudes to ?0.5 cm/hPa at the Equator [9], with a strong space variability due to wind effects and also to some dynamic response to pressure forcing. For the present study, the SLA fields have been computed by subtracting a Mean Sea Surface field MSS_CLS, [20]), to reduce the cross-track geoid��s errors [7,9,21].Altimeter data are usually selected using thresholds on the most relevant parameters characterizing the altimeter and radiometer measurement quality. This editing procedure thus allows the selection of useful altimeter datasets for most applications and ocean studies (altimeter Validated Database or VD).

Wireless sensor networks (WSNs) are composed of massive, small and low-cost sensor nodes deployed in a monitoring region, forming a multi-hop self-organized network system through wireless communication. The target is to cooperatively sense, collect and process the information about objects in the coverage area, and then send it to the observer for processing and analyzing. It is a system with multi-functional and low energy consumption (see [1-4]).Failed nodes may decrease the quality of service (Qos) of the entire WSN. It is important and necessary to study the fault detection methods Batimastat for nodes in WSNs for the following reasons [5-6]:Massive low-cost sensor nodes are often deployed in uncontrollable and hostile environments. Therefore, failure in sensor nodes can occur more easily than in other systems;The applications of WSNs are being widened.

WSNs are also deployed in some occasions such as monitoring of nuclear reactor where high security is required. Fault detection for sensor nodes in this specified application is of great importance;It is troublesome and not practical to manually examine whether the nodes are functioning normally;Correct information cannot be obtained by the control center because failed nodes would produce erroneous data.