Sensor device, configuration

Logs represent host by three different keys, a host name, a host IP address, and a host MAC address. The name is either fully qualified or a simple machine name, depending on the information source. This type of information is often provided by host-based information sources, or by devices configured to do on-the-fly reverse DNS mapping. An IP address is often provided by network-based IDS sensors and other network equipments. Finally, MAC addresses are provided by low-level networking devices such as wireless access points and switches, when specific network or wireless attacks are detected. All three keys are frequently found in event logs. 

The first practical problem to be addressed is the fabrication of acoustic-wave sensor devices. While some devices are commercially available (see Appendix D), a researcher may need a unique device in order to investigate some previously unexplored aspect of AW sensors and their interactions with their environment. It is therefore quite valuable to understand basic device configurations, fundamental design principles, the different properties of the range of materials that can serve as device substrates, fabrication practices, and coating technologies. These issues are addressed in Section 6.2. 

Thaditionally, solid-state gas sensors have a two-electrode configuration, where the gas sensing material is located between two metal electrodes, and a third metal electrode, which is usually platinum, is used for the heating of the sensor device. There are numerous methods by which such sensors can be realized. Figure 3.5 shows traditional gas sensor-electrode geometries.To make measurements on a semiconductor gas sensing material it is possible to use a compressed sintered or unsintered pellet with metal contacts on each face. 

Piezoelectrie effect allows transduction of electrical energy into acoustic energy and vice versa [7]. This is exploited to realize a variety of device configurations on piezoelectric crystals for sensor applications. An acoustic wave device in general... 

A variety of transducer configurations that has been employed in photometric sensor devices fall into two sensor types extrinsic sensors and intrinsic sensors. While in the former sensor type the optical fiber merely acts as a light guide, conveying the optical information between the optical source and the chemical transducer and between the chemical transducer and the detector, in the latter sensor type the optical fiber, probably in some modified form, would become a part of the transducer. 

Gonzalo-Ruiz et al. (2009) developed novel and fast disposable screen-printed sensor devices capable of quantifying chloride in sweat, thus being a suitable tool for the early detection of cystic fibrosis (CF). The method relies on the direct measurement of chloride on the skin by a four-electrode configuration (ie, anode and cathode electrodes for sweat generation WE and RE for potentiometric measurements). 

Acoustic Wave Sensors. Another emerging physical transduction technique involves the use of acoustic waves to detect the accumulation of species in or on a chemically sensitive film. This technique originated with the use of quartz resonators excited into thickness-shear resonance to monitor vacuum deposition of metals (11). The device is operated in an oscillator configuration. Changes in resonant frequency are simply related to the areal mass density accumulated on the crystal face. These sensors, often referred to as quartz crystal microbalances (QCMs), have been coated with chemically sensitive films to produce gas and vapor detectors (12), and have been operated in solution as Hquid-phase microbalances (13). A dual QCM that has one smooth surface and one textured surface can be used to measure both the density and viscosity of many Hquids in real time (14). 

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