The boundary layer equations for plane, incompressible, and steady flow are 

$$\matrix{ {u{{\partial u} \over {\partial x}} + v{{\partial u} \over {\partial y}} = - {1 \over \varrho }{{\partial p} \over {\partial x}} + v{{{\partial ^2}u} \over {\partial {y^2}}},} \cr {0 = {{\partial p} \over {\partial y}},} \cr {{{\partial u} \over {\partial x}} + {{\partial v} \over {\partial y}} = 0.} \cr }$$

Boundary Layer Theory

Sensor networks with battery-powered nodes can seldom simultaneously meet the design goals of lifetime, cost, sensing reliability and sensing and transmission coverage. Energy-harvesting, converting ambient energy to electrical energy, has emerged as an alternative to power sensor nodes. By exploiting recharge opportunities and tuning performance parameters based on current and expected energy levels, energy harvesting sensor nodes have the potential to address the conflicting design goals of lifetime and performance. This paper surveys various aspects of energy harvesting sensor systems- architecture, energy sources and storage technologies and examples of harvesting-based nodes and applications. The study also discusses the implications of recharge opportunities on sensor node operation and design of sensor network solutions.

Energy Harvesting Sensor Nodes: Survey and Implications

This book, written by two major figures in adaptive control, provides a wealth of material for researchers, practitioners, and students. While some researchers in adaptive control may note the absence of a particular topic, the book‘s scope represents a high-gain instrument. It can be used by designers of control systems to enhance their work through the information on many new theoretical developments, and can be used by mathematical control theory specialists to adapt their research to practical needs. The book is strongly recommended to anyone interested in adaptive control.

Adaptive Control

Energy harvesting generators are attractive as inexhaustible replacements for batteries in low-power wireless electronic devices and have received increasing research interest in recent years. Ambient motion is one of the main sources of energy for harvesting, and a wide range of motion-powered energy harvesters have been proposed or demonstrated, particularly at the microscale. This paper reviews the principles and state-of-art in motion-driven miniature energy harvesters and discusses trends, suitable applications, and possible future developments.

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Energy Harvesting From Human and Machine Motion for Wireless Electronic Devices

Wireless power technology offers the promise of cutting the last cord, allowing users to seamlessly recharge mobile devices as easily as data are transmitted through the air. Initial work on the use of magnetically coupled resonators for this purpose has shown promising results. We present new analysis that yields critical insight into the design of practical systems, including the introduction of key figures of merit that can be used to compare systems with vastly different geometries and operating conditions. A circuit model is presented along with a derivation of key system concepts, such as frequency splitting, the maximum operating distance (critical coupling), and the behavior of the system as it becomes undercoupled. This theoretical model is validated against measured data and shows an excellent average coefficient of determination of 0.9875. An adaptive frequency tuning technique is demonstrated, which compensates for efficiency variations encountered when the transmitter-to-receiver distance and/or orientation are varied. The method demonstrated in this paper allows a fixed-load receiver to be moved to nearly any position and/or orientation within the range of the transmitter and still achieve a near-constant efficiency of over 70% for a range of 0-70 cm.

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Analysis, Experimental Results, and Range Adaptation of Magnetically Coupled Resonators for Wireless Power Transfer

Interdigital dielectrometry technology provides means for non-destructive measurement of various physical properties in the bulk of insulating materials. Results of continuing work on the refinement of this technology are presented. A close match of theoretical results and experimental values is achieved with a sensor designed to minimize non-ideal effects. Optimization of the sensor design and parameter estimation algorithms is performed by studying the influence of various geometric parameters on the sensor's response.

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Influence of geometric parameters on characteristics of an interdigital dielectrometry sensor

Interdigital frequency-wavenumber dielectrometry can be used for measurement of dielectric properties of insulating materials. It is not always possible to adequately model distributed circuit parameters of the sensor structure. Even in cases when the forward problem can be solved, that is, the distribution of electric field can be calculated using numerical techniques, it may not be suitable for the solution of the inverse problem due to the high sensitivity of the parameter estimation algorithms to variations in circuit and material parameters as well as nonideality in the models due to finite size of the sensor, fringing field effects, and lead effects. This paper particularly shows the advantage of changing the function of the conducting plane beneath the interdigital electrode structure from a ground plane to a guard electrode that follows the sensing electrode voltage. The techniques presented in this paper build a bridge between idealized models of interdigital structures and real measurements. Employment of such techniques allows experimental calibration of the sensor, verification of the intermediate steps in the process of development of parameter estimation algorithms, and provide data necessary for improvement of experimental arrangements.

Techniques for semi-empirical characterization of material and sensor properties in interdigital dielectrometry

Diabetes is a global epidemic that impacts millions of people every year. Enhanced dietary assessment techniques are critical for maintaining a healthy life for a diabetic patient. Moreover, hospitals must monitor their diabetic patients' food intake to prescribe a certain amount of insulin. Malnutrition significantly increases patient mortality, the duration of the hospital stay, and, ultimately, medical costs. Currently, hospitals are not fully equipped to measure and track a patient's nutritional intake, and the existing solutions require an extensive user input, which introduces a lot of human errors causing endocrinologists to overlook the measurement. This paper presents DietSensor, a wearable three-dimensional (3D) measurement system, which uses an over the counter 3D camera to assist the hospital personnel with measuring a patient's nutritional intake. The structured environment of the hospital provides the opportunity to have access to the total nutritional data of any meal prepared in the kitchen as a cloud database. DietSensor uses the 3D scans and correlates them with the hospital kitchen database to calculate the exact consumed nutrition by the patient. The system was tested on twelve volunteers with no prior background or familiarity with the system. The overall calculated nutrition from the DietSensor phone application was compared with the outputs from the 24-h dietary recall (24HR) web application and MyFitnessPal phone application. The average absolute error on the collected data was 73%, 51%, and 33% for the 24HR, MyFitnessPal, and DietSensor systems, respectively.

DietSensor: Automatic Dietary Intake Measurement Using Mobile 3D Scanning Sensor for Diabetic Patients.

In a new measurement technique, impedance spectroscopy is used with fringing electric field sensors to measure the concentration of moisture, fiber, and titanium dioxide in pulp. This method can be integrated into a paper machine without disrupting the manufacturing process because the measurements are taken without contacting the pulp. Experimental results show consistent accuracy is when the moisture concentration is from 94% to 86% and the concentration of other constituents in the pulp is between 0% and 7%. The calibration procedure can be implemented with only a few experimental data points. Application: By accurately measuring the pulp moisture at the wet end of the paper machine, papermakers can exercise more precise control over the early stages of paper production. VOL. 4: NO. 2 TAPPI JOURNAL 23 24 TAPPI JOURNAL FEBRUARY 2005 PROCESS CONTROL EXPERIMENTAL SETUP The experiments were designed to emulate the operating conditions in a paper machine. In the wet end, the pulp is prepared so that the fibers form a homogeneous suspension in water.The moisture content of the pulp is above 98% at this stage of the manufacturing process. The pulp loses most of its moisture on the wire as a result of the vibrations from the rollers and the pressure differential caused by the aerofoils.By the end of the wire section, the pulp forms a paper web with a moisture content of about 70%. Our purpose was to measure the moisture content of the pulp while it is on the wire. Figure 2 is a photograph of the e x p e r i m e n t a l setup.The pulp was placed in the acrylic tray, and the sensor was placed beneath it.The sensor used was an interdigital sensor with a spatial periodicity of 40 mm, a finger length of 160 mm, and a penetration depth of 7 mm. A guard plane was placed underneath the sensor electrodes to shield it from external electric fields. Measured quantities of paper fiber, titanium dioxide, and water were mixed in a commercial blender.The pulp was cooled to 25°C and placed in the sensor tray.The geometry of the sensor and the electrical connections are shown in Fig. 3. The RCL meter generates 1 volt sinusoidal AC voltage in the frequency range of 50 Hz to 100 kHz. At each frequency, the meter calculates the effective impedance between the two channels by computing the magnitude of attenuation and phase shift between the input voltage and the loop current. This general-purpose instrument is good for studying the relative effects of different additives. In the future, this type of measurement could be made with multi-channel, custom-built circuits to gather data at more than one measurement point. The measurements were made at frequencies in the range of 200 Hz to 100 kHz. Ten sets of measurements were taken at each frequency and were averaged to reduce the noise. All sources of noise were assumed to have zero mean distribution. EXPERIMENTAL RESULTS Experiments were conducted to characterize the response of the sensor to the variation in moisture in a pulp consisting of water, titanium dioxide, and fiber. The titanium dioxide content of the pulp was varied from 0% to 7% in steps of 1%, and the moisture content was varied from 94% to 86%, as shown in Table I. Twenty-one electrical parameters, not all of which were independent, were measured or derived from measurements for each pulp sample at every frequency. Here, we consider only four parameters—the capacitance, the magnitude of complex admittance, the conductance, and the phase. Figure 4 shows the seven-dimensional scatter plot of the measurements of pulp samples with 0–7% TiO 2 at 100 kHz.The plot shows the variation of electrical parameters such as capacitance, admittance, conductance, and phase. It also shows the percentage concentrations of titanium dioxide, moisture, and fiber in the pulp with respect to each other. Each of these parameters is plotted against every other parameter in one of the rows of the scatter plot. For example, the first row shows the variation of capacitance against admittance, phase, conductance, and the percentage composition of the constituents of the pulp. The main advantage of representing the data this way is that the underlying correlations among measured parameters become explicit, and data trends in the experiment become more apparent. For example, in the data shown in Fig. 4, the data points at 92% and 93% moisture content are noisy. Figure 5 shows the five-dimensional scatter plot of the measurements of a pulp sample with 4% titanium dioxide, 89.28% moisture, and 6.72% fiber concentration at frequencies from 900 Hz to 100 kHz. The scatter plots in row and column (4, 5), (4, 6), and (4, 7) of Fig. 4 and (4, 5) of Fig. 5 show the dependence of conductance on the titanium dioxide I. Composition of the pulp samples. Sample TiO2, Moisture, Fiber, no. % % % 1 0 93.00 7.00 2 1 92.07 6.93 3 2 91.14 6.86 4 3 90.21 6.79 5 4 89.28 6.72 6 5 88.35 6.65 7 6 87.42 6.58 8 7 86.49 6.51 1. A fringing field dielectrometry sensor can be visualized as a parallel plate capacitor (a) with electrodes that open (b) to provide one-sided access (c) to the material being tested. 2. Photograph of the experimental

Measuring moisture, fiber, and titanium dioxide in pulp with impedance spectroscope

Due to the current trend of increasing component densities and decreasing form factors for microelectronics, greater heat intensities are generated across smaller surface areas, exceeding the current cooling capabilities of conventional cooling technologies. Air cooling technologies still play an important role in overall thermal management strategy. Among air cooling technologies, electrohydrodynamics (EHD)-based air movers, also known as electrostatic fluid accelerators (EFAs) or ionic wind pumps, have been considered one of the most advanced air cooling devices due to their superior features, such as the elimination of moving parts and high energy efficiency. EFAs use Coulomb forces between charged molecules as the driving force to push bulk air to generate airflow. In contrast to conventional rotary fans, EFAs significantly reduce acoustic noise and increase energy efficiency due to the elimination of moving components. Therefore, further development of EFAs will enable their widespread adoption and effective use of EFAs. This investigation presents guidelines for the optimization of a wire-rod EFA device, in terms of the number of electrodes and the applied voltage at the corona electrodes. These guidelines are carried out by using the statistical method, analysis of variance (ANOVA), to analyze the numerical data. The results indicate that the air velocity at the channel outlet is not proportional to the number of electrodes. Obtaining a maximum air velocity requires a thoughtful multistep optimization procedure, in which several geometrical and material property parameters are considered.

Alexander Mamishev

Papers

Influence of geometric parameters on characteristics of an interdigital dielectrometry sensor

Techniques for semi-empirical characterization of material and sensor properties in interdigital dielectrometry

DietSensor: Automatic Dietary Intake Measurement Using Mobile 3D Scanning Sensor for Diabetic Patients.

Measuring moisture, fiber, and titanium dioxide in pulp with impedance spectroscope

Optimization of wire-rod electrostatic fluid accelerators