Sensor nets

Keywords chemical sensors biosensors CWA BWA sensor nets wireless ad-hoc networks. 

Atlantic Rainforest Sensor Net Research. In 2009, Microsoft Research collaborated with researchers from The Johns Hopkins University, the Universi-dade de Sao Paolo, the Fundagao de Amparo a Pes-quisa do Estatdo de Sao Paulo (FAPESP), and the Instituto Nacional de Pesquisas Espaciais (INPE, the Brazilian National Institute for Space Research) to collect data about the microecology of the Serra do Mar rainforest located in the southeast corner of Brazil. To collect the data, a grid of hundreds of wireless sensors collected 18 million data points over... 

Serra, P.A., Puggioni, G., Bazzu, G., Caha, G., MigheH, R., Rocchitta, G., 2010. Design and Construction of a Distrihuted Sensor NET for Biotelemetric Monitoring of Brain Energetic Metabolism Using Microsensors and Biosensors. Intech, Italy, 241—260. 

The capture velocity of a hood is defined as the air velocity created by the hood at the point of contaminant generation. The hood must generate a capture velocity sufficient to overcome opposing air currents and transport the contaminant to the hood. For enclosing hoods, capture velocity is the velocity at the hood opening. In this case, the velocity must be sufficient to keep the contaminant in the hood. In practice, hood shape and the influence of crossdrafts on the measured capture velocity have to be considered. All three velocity components should be measured and used to calculate the magnitude and direction of the total velocity. Other methods used, not as good as the previous one, are to measure the velocity with a directional velocity sensor towards the hood or to measure the net velocity by an omnidirectional velocity sensor. In the last method the main airflow direction should be viewed and evaluated by means of a smoke test (see Sections 10.2.1 and 10.2.2.1). 

The measurement cycle of the sensor begins with a pulse of cathodic current i that induces a net flux J of cations in the direction of the membrane phase. Assuming for... 

An oxygen sensor signals whether the exhaust entering the converter is "rich" (net reducing) or "lean" (net oxidizing). 

Multi-static radar is usually combined with the net-centric approach to data exchange. All sensor sites have to be connected by high-throughput, self-configuring data links. The data links should also provide a very stable clock to make all processing coherent, and very accurate time data to synchronize all events in the distributed system. 

Among potentiometric enzyme sensors, the urea enzyme electrode is the oldest (and the most important). The original version consisted of an enzyme layer immobilized in a polyacrylamide hydrophilic gel and fixed in a nylon netting attached to a Beckman 39137 glass electrode, sensitive to the alkali metal and NHj ions [19, 2A Because of the poor selectivity of this glass electrode, later versions contained a nonactin electrode [20,22] (cf. p. 187) and especially an ammonia gas probe [25] (cf. p. 72). This type of urea electrode is suitable for the determination of urea in blood and serum, at concentrations from 5 to 0.05 mM. Figure 8.2 shows the dependence of the electrode response... 

Clearly, a mass-related signal will be obtained only if the species-sensor interaction results in a net change of mass of the chemically selective layer attached to the device. Thus, an equilibrium binding will yield a measurable signal. On the... 

The mixed potential accounts for a large portion of reported artifacts in the unorthodox potentiometric sensors, particularly biosensors, and can be rightfully called evil potential . The physical origin of such artifacts can be illustrated using a simple example. Let us assume that a multiple electron transfer takes place simultaneously at the interface of a lump of Zn immersed in dilute HC1. Because this metal is not externally connected the net current is zero. The redox reactions taking place are as follows. 

Different complications arise if the selective layer is a solid-state ionic conductor. At such an interface, a net electrochemical reaction, governed by Faraday s law, takes place and the mass transport of the electroactive ionic species within the contact region and formation of a depletion layer must be considered. In general, when the response of the sensor depends on the chemical modulation of the contact resistance by one of the above mechanisms it will be a strongly nonlinear function of concentration. Furthermore, because Rc is always dependent on the applied voltage, the optimization of the response must be done by examining the voltage-current characteristics of the contact. 

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