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

To help improve the comfort of an amputee, it is important to develop artificial skin to understand the load distribution between the residual limb and the prosthetic socket for a prosthetic socket system. This paper presents an interfacial stress sensor which is capable of simultaneously measuring normal compressive stress and horizontal shear stress and is expected to create an artificial skin to understand such load distribution. A mathematical model based on regression analysis is built and an experiment is conducted to obtain the transfer function of the sensor. A significance test shows that the transfer function has a statistical significance at a significance level of 0.05 and the regression model fits the experimental data with a sample determination coefficient . The relative error is also analyzed in the end. The results show that the sensor is capable of measuring a range 0-320 kPa normal compressive stress with a relative error of 5% and a range of 0-70 kPa horizontal shear stress with a relative error of 14%.

Transfer Function of Interfacial Stress Sensor for Artificial Skin Applications

Moisture concentration was measured in a 1.5 mm thick transformer pressboard as a function of time and position during moisture diffusion process. A flexible interdigital three-wavelength sensor was used to provide the necessary information regarding pressboard dielectric properties at different depths from the sensor-pressboard interface. Results were obtained by processing the signals from the three-wavelength sensor, air humidity sensor, and thermocouple installed in the experimental chamber. Air-pressboard equilibrium curves were used to provide boundary conditions and the relative moisture level magnitude. The proposed technology has significant potential for measurement of diffusion processes in various dielectrics.

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Measurement of moisture spatial profiles in transformer pressboard

Estimation of physical properties of insulating materials may effectively be done by using nondestructive /spl omega/-k (frequency-wavelength) dielectrometry technology. Essential to this technology are pairs of interdigitated electrodes, which respond to the change in resistive and capacitive properties of the surrounding media. This paper presents both experimental and theoretical data, which helps to investigate the ability of the sensor to characterize multi-layered insulating and semi-insulating materials. Issues of precision and reliability of the measurements are discussed.

Measurement of dielectric property distributions using interdigital dielectrometry sensors

Future thermal management of microelectronics demands high heat flux removal capabilities due to rapid increases in component and heat flux densities generated from integrated circuits (ICs). Although electrospray evaporative cooling (ESEC) has been investigated as the potential package-level thermal management solution for future microelectronics, the optimal heat transfer performance of ESEC devices using a different number of nozzles has not been thoroughly investigated as a whole. This paper presents three different kinds of ESEC chambers with different spacing, in order to investigate their optimal heat transfer performances. The maximum enhancement ratio of 1.87 was achieved by the 8-nozzle 5 mm spacing ESEC chamber at the lowest heat flux. The optimal heat transfer performance for the 4-nozzle chamber is the chamber with 6 mm spacing. Both the 8-nozzle 5 mm spacing ESEC chamber and the 8-nozzle 6 mm spacing ESEC chamber achieve optimal heat transfer performance. Furthermore, although the increase in the number of electrospray nozzles of the ESEC chambers does not provide obvious improvement on the maximum achievable heat transfer enhancement ratio, the highest cooling rate is noticeably enhanced by increasing the number of electrospray nozzles of the ESEC chamber.

Optimal heat transfer performance of the microfluidic electrospray cooling devices

Fringing electric field (FEF) sensors are widely used for noninvasive measurement of material properties, such as porosity, viscosity, temperature, hardness, and degree of cure. They are also used to detect the presence of a material or estimate the concentration of a material within the test environment. No generic analytical models exist for FEF sensors. Optimization of FEF sensor design often involves complex and time-consuming finite element simulations. This paper presents a nondimensionalized parametric model to improve the design process. The effects of design parameters, such as sensor geometry and substrate material, are quantified in the model. The model parameters are determined from a three-dimensional surface fit of finite element simulation results for the most common type of sensor geometry. The variables in the model are nondimensionalized, which makes the model applicable to a wider range of sensor designs

Alexander Mamishev

Papers

Transfer Function of Interfacial Stress Sensor for Artificial Skin Applications

Measurement of moisture spatial profiles in transformer pressboard

Measurement of dielectric property distributions using interdigital dielectrometry sensors

Optimal heat transfer performance of the microfluidic electrospray cooling devices

Nondimensionalized Parametric Modeling of Fringing Electric-Field Sensors