161,607 research outputs found
A radial mode ultrasonic horn for the inactivation of <i>Escherichia coli</i> K12
Tuned cylindrical radial mode ultrasonic horns offer advantages over ultrasonic probes in the design of flow-through devices for bacterial inactivation. This study presents a comparison of the effectiveness of a radial horn and probe in the inactivation of Escherichia coli K12. The radial horn is designed using finite element analysis and the predicted modal parameters are validated using experimental modal analysis. A validated finite element model of the probe is also presented. Visual studies of the cavitation fields produced by the radial horn and probe are carried out using luminol and also backlighting to demonstrate the advantages of radial horns in producing a more focused cavitation field with widely dispersed streamers. Microbiological studies show that, for the same power density, better inactivation of E. coli K12 is achieved using the radial horn and, also, the radial horn offers greater achievable power density resulting in further improvements in bacterial inactivation. The radial horn is shown to be more effective than the probe device and offers opportunities to design in-line flow-through devices for processing applications
The Impact of Flow in an EEG-based Brain Computer Interface
Major issues in Brain Computer Interfaces (BCIs) include low usability and
poor user performance. This paper tackles them by ensuring the users to be in a
state of immersion, control and motivation, called state of flow. Indeed, in
various disciplines, being in the state of flow was shown to improve
performances and learning. Hence, we intended to draw BCI users in a flow state
to improve both their subjective experience and their performances. In a Motor
Imagery BCI game, we manipulated flow in two ways: 1) by adapting the task
difficulty and 2) by using background music. Results showed that the difficulty
adaptation induced a higher flow state, however music had no effect. There was
a positive correlation between subjective flow scores and offline performance,
although the flow factors had no effect (adaptation) or negative effect (music)
on online performance. Overall, favouring the flow state seems a promising
approach for enhancing users' satisfaction, although its complexity requires
more thorough investigations
A Review of Smart Materials in Tactile Actuators for Information Delivery
As the largest organ in the human body, the skin provides the important
sensory channel for humans to receive external stimulations based on touch. By
the information perceived through touch, people can feel and guess the
properties of objects, like weight, temperature, textures, and motion, etc. In
fact, those properties are nerve stimuli to our brain received by different
kinds of receptors in the skin. Mechanical, electrical, and thermal stimuli can
stimulate these receptors and cause different information to be conveyed
through the nerves. Technologies for actuators to provide mechanical,
electrical or thermal stimuli have been developed. These include static or
vibrational actuation, electrostatic stimulation, focused ultrasound, and more.
Smart materials, such as piezoelectric materials, carbon nanotubes, and shape
memory alloys, play important roles in providing actuation for tactile
sensation. This paper aims to review the background biological knowledge of
human tactile sensing, to give an understanding of how we sense and interact
with the world through the sense of touch, as well as the conventional and
state-of-the-art technologies of tactile actuators for tactile feedback
delivery
Why Information Matters: A Foundation for Resilience
Embracing Change: The Critical Role of Information, a research project by the Internews' Center for Innovation & Learning, supported by the Rockefeller Foundation, combines Internews' longstanding effort to highlight the important role ofinformation with Rockefeller's groundbreaking work on resilience. The project focuses on three major aspects:- Building knowledge around the role of information in empowering communities to understand and adapt to different types of change: slow onset, long-term, and rapid onset / disruptive;- Identifying strategies and techniques for strengthening information ecosystems to support behavioral adaptation to disruptive change; and- Disseminating knowledge and principles to individuals, communities, the private sector, policymakers, and other partners so that they can incorporate healthy information ecosystems as a core element of their social resilience strategies
Towards Scalable Beaconing in VANETs
Beaconing is envisioned to build a cooperative awareness in future intelligent vehicles, from which many ITS applications can draw their inputs. The problem of scalability has received ample attention over the past years and is primarily approached using power control methods. We reason power control alone will not be sufficient if we are to meet application requirements; the rate at which beacons are generated must also be controlled. Ultimately, adaptive approaches based on actual channel and traffic state can tune MAC and beaconing properties to optimal values in the dynamic VANET environment
Numerical approximation of phase field based shape and topology optimization for fluids
We consider the problem of finding optimal shapes of fluid domains. The fluid
obeys the Navier--Stokes equations. Inside a holdall container we use a phase
field approach using diffuse interfaces to describe the domain of free flow. We
formulate a corresponding optimization problem where flow outside the fluid
domain is penalized. The resulting formulation of the shape optimization
problem is shown to be well-posed, hence there exists a minimizer, and first
order optimality conditions are derived.
For the numerical realization we introduce a mass conserving gradient flow
and obtain a Cahn--Hilliard type system, which is integrated numerically using
the finite element method. An adaptive concept using reliable, residual based
error estimation is exploited for the resolution of the spatial mesh.
The overall concept is numerically investigated and comparison values are
provided
Rectenna thermal model development
Deploying rectennas in space requires adapting existing designs developed for terrestrial applications to the space environment. One of the major issues in doing so is to understand the thermal performance of existing designs in the space environment. Toward that end, a 3D rectenna thermal model has been developed, which involves analyzing shorted rectenna elements and finite size rectenna element arrays. A shorted rectenna element is a single element whose ends are connected together by a material of negligible thermal resistance. A shorted element is a good approximation to a central element of a large array. This model has been applied to Brown's 2.45 GHz rectenna design. Results indicate that Brown's rectenna requires redesign or some means of enhancing the heat dissipation in order for the diode temperature to be maintained below 200 C above an output power density of 620 W/sq.m. The model developed in this paper is very general and can be used for the analysis and design of any type of rectenna design of any frequency
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