Joseph A. C. Humphrey

Bio: Joseph A. C. Humphrey is an academic researcher from University of Virginia. The author has contributed to research in topics: Reynolds number & Laminar flow. The author has an hindex of 34, co-authored 98 publications receiving 4056 citations. Previous affiliations of Joseph A. C. Humphrey include National Sun Yat-sen University & University of California, Berkeley.

Sensors and sensing in biology and engineering

Abstract: INTRODUCTORY REMARKS Sensors and sensing: a biologist's view (F. G. Barth), Sensors and sensing: an engineer's view (H. Meixner) MECHANICAL SENSORS Waves, Sound and Vibrations How nature designs ears (A. Michelsen), How to build a microphone (P. Rasmussen), The middle and external ears of terrestrial vertebrates as mechanical and acoustic transducers (J. J Rosowski), The outer hair cell: a mechanoelectrical and electromechanical sensor/actuator (K.V. Snyder, F. Sachs, W. E. Brownell), The silicon cochlea (R. Sarpeshkar), Biologically-inspired microfabricated force and position mechano-sensors (P. Dario et al.) Force and Motion The physics of arthropod medium-flow sensitive hairs: biological models for artificial sensors (J. A. C. Humphrey, F. G. Barth, M. Reed, A. Spak), Cricket wind receptors: thermal noise for the highest sensitivity known (T. Shimozawa, J. Murakami, T. Kumagai), Arthropod cuticular hairs: tactile sensors and the refinement of stimulus transformation (F. G. Barth, H.-E. Dechant), The fish lateral line: how to detect hydrodynamic stimuli (J. Mogdans, J. Engelmann, W. Hanke, S. Krother), The blood vasculature as an adaptive system: role of mechanical sensing (T. W. Secomb, A. R. Pries), Mechanism of shear stress-induced coronary microvascular dilation (L. Kuo, T. W. Hein), A possible mechanism for sensing crop canopy ventilation (T. Farquhar, J. Zhou, H. W. Haslach Jr.) VISUAL SENSORS AND VISION From fly vision to robot vision: re-construction as a mode of discovery (N. Franceschini), Locust's looming detectors for robot sensors (F. C. Rind, R. D. Santer, J. M. Blanchard, P. F. M. J. Verschure), Retina-like sensors: motivations, technology and applications (G. Sandini, G. Metta), Computing in cortical columns: information processing in visual cortex (S. W. Zucker), Vision by graph pyramids (W.G. Kropatsch) CHEMOSENSORS AND CHEMOSENSING Mechanisms for gradient following (D.B. Dusenbery), Representation of odor information in theolfactory system: from biology to an artificial nose (J. S. Kauer, J. White), The external aerodynamics of canine olfaction (G. S. Settles, D.A. Kester, L.J. Dodson-Dreibelbis), Microcantilevers for physical, chemical, and biological sensing (T. Thundat, A. Majumdar) THE EMBEDDING OF SENSORS Embedded mechanical sensors in artificial and biological systems (P. Calvert), Active dressware: wearable kinesthetic systems (D. de Rossi, F. Lorussi, A. Mazzoldi, P. Orsini, E. P. Scilingo)

Numerical calculation of thermally driven two-dimensional unsteady laminar flow in cavities of rectangular cross section

Abstract: Numerical results are reported for thermally driven laminar flow in two-dimensional rectangular geometries with one plane, the aperture plane, removed. Finite-difference expressions are derived from a set of approximated transport equations in which large temperature and density variations are allowed but high-frequency pressure oscillations are not. The approach allows small time step limitations to be removed from the calculation procedure. A second-order accurate quadratic upstream interpolation technique is used for the finite differencing of convection terms in the transport equations, thus reducing numerical diffusion error. Parameters varied in the calculations were cavity aspect ratio and inclination angle with respect to gravity, inside wall temperature, and Grashof number. A value of Prandtl number corresponding to air was fixed (Pr = 0.73). For the conditions studied, flow and temperature fields within the cavity are determined mainly by local heat transfer events.

Thermal isolation of microchip reaction chambers for rapid non-contact DNA amplification

Abstract: This paper describes further optimization of a non-contact, infrared-mediated system for microchip DNA amplification via the polymerase chain reaction (PCR). The optimization is focused on heat transfer modeling and subsequent fabrication of thermally isolated reaction chambers in glass devices that are uniquely compatible with non-contact thermal control. With a thermal conductivity approximately an order of magnitude higher than many plastics, glass is not the obvious substrate of choice for rapid thermal cycling in microfluidic chambers, yet it is preferable in terms of optical clarity, solvent compatibility and chemical inertness. Based on predictions of a lumped capacity heat transfer analysis, it is shown here that post-bonding, patterned etching of surrounding glass from microfluidic reaction chambers provides enhancements as high as 3.6- and 7.5-fold in cooling and heating rates, respectively, over control devices with the same chamber designs. These devices are then proven functional for rapid DNA amplification via PCR, in which 25 thermal cycles are completed in only 5 min in thermally isolated PCR chambers of 270 nL volume, representing the fastest static PCR in glass devices reported to date. Amplification of the 500-base pair fragment of ?-DNA was confirmed by capillary gel electrophoresis. In addition to rapid temperature control, the fabrication scheme presented, which is compatible with standard photolithography and wet etching techniques, provides a simple alternative for general thermal management in glass microfluidic devices without metallization.

A review of materials, heat transfer and phase change problem formulation for latent heat thermal energy storage systems (LHTESS)

Abstract: This paper reviews the development of latent heat thermal energy storage systems studied detailing various phase change materials (PCMs) investigated over the last three decades, the heat transfer and enhancement techniques employed in PCMs to effectively charge and discharge latent heat energy and the formulation of the phase change problem. It also examines the geometry and configurations of PCM containers and a series of numerical and experimental tests undertaken to assess the effects of parameters such as the inlet temperature and the mass flow rate of the heat transfer fluid (HTF). It is concluded that most of the phase change problems have been carried out at temperature ranges between 0 °C and 60 °C suitable for domestic heating applications. In terms of problem formulation, the common approach has been the use of enthalpy formulation. Heat transfer in the phase change problem was previously formulated using pure conduction approach but the problem has moved to a different level of complexity with added convection in the melt being accounted for. There is no standard method (such as British Standards or EU standards) developed to test for PCMs, making it difficult for comparison to be made to assess the suitability of PCMs to particular applications. A unified platform such as British Standards, EU standards needs to be developed to ensure same or similar procedure and analysis (performance curves) to allow comparison and knowledge gained from one test to be applied to another.

Biomimetics: lessons from nature--an overview.

Abstract: Nature has developed materials, objects and processes that function from the macroscale to the nanoscale. These have gone through evolution over 3.8Gyr. The emerging field of biomimetics allows one...

Thermal conductivity enhancement of phase change materials for thermal energy storage: A review ☆

Abstract: A review of experimental/computational studies to enhance the thermal conductivity of phase change materials (PCM) that were conducted over many decades is presented. Thermal management of electronics for aeronautics and space exploration appears to be the original intended application, with later extension to storage of thermal energy for solar thermal applications. The present review will focus on studies that concern with positioning of fixed, stationary high conductivity inserts/structures. Copper, aluminum, nickel, stainless steel and carbon fiber in various forms (fins, honeycomb, wool, brush, etc.) were generally utilized as the materials of the thermal conductivity promoters. The reviewed research studies covered a variety of PCM, operating conditions, heat exchange and thermal energy storage arrangements. The energy storage vessels included isolated thermal storage units (rectangular boxes, cylindrical and annular tubes and spheres) and containers that transferred heat to a moving fluid medium passing through it. A few studies have focused on the marked role of flow regimes that are formed due to the presence of thermally unstable fluid layers that in turn give rise to greater convective mixing and thus expedited melting of PCM. In general, it can be stated that due to utilization of fixed high conductivity inserts/structures, the conducting pathways linking the hot and cold ends must be minimized.

A photolabile hydrogel for guided three-dimensional cell growth and migration.

Abstract: Tissue engineering aims to replace, repair or regenerate tissue/organ function, by delivering signalling molecules and cells on a three-dimensional (3D) biomaterials scaffold that supports cell infiltration and tissue organization. To control cell behaviour and ultimately induce structural and functional tissue formation on surfaces, planar substrates have been patterned with adhesion signals that mimic the spatial cues to guide cell attachment and function. The objective of this study is to create biochemical channels in 3D hydrogel matrices for guided axonal growth. An agarose hydrogel modified with a cysteine compound containing a sulphydryl protecting group provides a photolabile substrate that can be patterned with biochemical cues. In this transparent hydrogel we immobilized the adhesive fibronectin peptide fragment, glycine-arginine-glycine-aspartic acid-serine (GRGDS), in selected volumes of the matrix using a focused laser. We verified in vitro the guidance effects of GRGDS oligopeptide-modified channels on the 3D cell migration and neurite outgrowth. This method for immobilizing biomolecules in 3D matrices can generally be applied to any optically clear hydrogel, offering a solution to construct scaffolds with programmed spatial features for tissue engineering applications.