523 research outputs found
The Frame and The Blueprint
Using drawing as a tool to explore the relationship of architecture and the body, current work extends the horizontal line into spaces to map how we can transform our gaze. This in turn asks how we might adopt methods which activate spaces as memory and use these spaces as a repository for works that activate a culture specific to drawing edges
On the Relative Effect of Underwater Optical Turbulence in Different Channel Conditions
This paper presents a simulation framework for modelling optical underwater turbulence in conjunction with absorption and scattering. Using this technique, the channel is evaluated in two ways: the turbulent statistics in different channel conditions; and the stationary channel characteristics. The turbulent statistics observed from the simulation show that the relative impact of turbulence on a received signal is lower in a highly scattering channel, showing an in-built resilience of these channels. Received intensity distributions are presented, showing that the commonly used Log-Normal fading model provides a good description of the fluctuations in received optical power due to the effect of turbulence. When considering stationary channel characteristics, the effect of turbulence induced scattering is shown to cause and increase both spatial and temporal spreading at the receiver plane. The impact of turbulence - as measured using this new modelling framework - on the channel capacity is equally investigated to provide context to the implications of the channel modelling findings on underwater optical wireless communications link performance
Effects of Turbulence Induced Scattering on Underwater Optical Wireless Communications
This paper presents a comprehensive description of the relative effect of
optical underwater turbulence in combination with absorption and scattering.
Turbulence induced scattering is shown to cause and increase both spatial and
temporal spreading at the receiver plane. It is also demonstrated that the
relative impact of turbulence on a received signal is lower in a highly
scattering channel. Received intensity distributions are presented confirming
that fluctuations in received power from this method follow the commonly used
Log-Normal fading model. The impact of turbulence induced scattering on maximum
achievable data rate in the underwater channel is investigated.Comment: 9 pages, 10 figures and 3 table
Effects of Fusion between Tactile and Proprioceptive Inputs on Tactile Perception
Tactile perception is typically considered the result of cortical interpretation of afferent signals from a network of mechanical sensors underneath the skin. Yet, tactile illusion studies suggest that tactile perception can be elicited without afferent signals from mechanoceptors. Therefore, the extent that tactile perception arises from isomorphic mapping of tactile afferents onto the somatosensory cortex remains controversial. We tested whether isomorphic mapping of tactile afferent fibers onto the cortex leads directly to tactile perception by examining whether it is independent from proprioceptive input by evaluating the impact of different hand postures on the perception of a tactile illusion across fingertips. Using the Cutaneous Rabbit Effect, a well studied illusion evoking the perception that a stimulus occurs at a location where none has been delivered, we found that hand posture has a significant effect on the perception of the illusion across the fingertips. This finding emphasizes that tactile perception arises from integration of perceived mechanical and proprioceptive input and not purely from tactile interaction with the external environment
Recommended from our members
Public Health in the Developing World: Tackling Vector-Borne Diseases
One of the most pressing policy issues of the modern era is how to improve public health in the world’s poorest regions. Of particular concern are those diseases spread by mosquitos: the World Health Organisation estimates a total of 96 million cases of dengue and, in 2017 alone, 219 million cases of malaria. Policies targeting such vector-borne diseases (VBDs) represent nothing new. However, there seems to be a continuing inability to move the agenda from one of disease reduction to eradication: clearly, current policy initiatives are not proving effective enough. This report aims to tackle this issue by outlining the problems associated with current policies and how they can be addressed through epidemiological innovation, with need to not only improve the efficacy of such policies, but also their cost-effectiveness and sustainability. Two innovative policies will be presented: that of manipulating the urban environment to reduce mosquito habitat and of harnessing predation pressure to better regulate mosquito populations
Underwater optical wireless communications in turbulent conditions: from simulation to experimentation
Underwater optical wireless communication (UOWC) is a technology that aims to apply high speed optical wireless communication (OWC) techniques to the underwater channel. UOWC has the potential to provide high speed links over relatively short distances as part of a hybrid underwater network, along with radio frequency (RF) and underwater acoustic communications (UAC) technologies. However, there are some difficulties involved in developing a reliable UOWC link, namely, the complexity of the channel. The main focus throughout this thesis is to develop a greater understanding of the effects of the UOWC channel, especially underwater turbulence. This understanding is developed from basic theory through to simulation and experimental studies in order to gain a holistic understanding of turbulence in the UOWC channel.
This thesis first presents a method of modelling optical underwater turbulence through simulation that allows it to be examined in conjunction with absorption and scattering. In a stationary channel, this turbulence induced scattering is shown to cause and increase both spatial and temporal spreading at the receiver plane. It is also demonstrated using the technique presented that the relative impact of turbulence on a received signal is lower in a highly scattering channel, showing an in-built resilience of these channels. Received intensity distributions are presented confirming that fluctuations in received power from this method follow the commonly used Log-Normal fading model. The impact of turbulence - as measured using this new modelling framework - on link performance, in terms of maximum achievable data rate and bit error rate is equally investigated.
Following that, experimental studies comparing both the relative impact of turbulence induced scattering on coherent and non-coherent light propagating through water and the relative impact of turbulence in different water conditions are presented. It is shown that the scintillation index increases with increasing temperature inhomogeneity in the underwater channel. These results indicate that a light beam from a non-coherent source has a greater resilience to temperature inhomogeneity induced turbulence effect in an underwater channel. These results will help researchers in simulating realistic channel conditions when modelling a light emitting diode (LED) based intensity modulation with direct detection (IM/DD) UOWC link.
Finally, a comparison of different modulation schemes in still and turbulent water conditions is presented. Using an underwater channel emulator, it is shown that pulse position modulation (PPM) and subcarrier intensity modulation (SIM) have an inherent resilience to turbulence induced fading with SIM achieving higher data rates under all conditions. The signal processing technique termed pair-wise coding (PWC) is applied to SIM in underwater optical wireless communications for the first time. The performance of PWC is compared with the, state-of-the-art, bit and power loading optimisation algorithm. Using PWC, a maximum data rate of 5.2 Gbps is achieved in still water conditions
Recommended from our members
Spatial consequences of bridging the saccadic gap
We report six experiments suggesting that conscious perception is actively redrafted to take account of events both before and after the event that is reported. When observers saccade to a stationary object they overestimate its duration, as if the brain were filling in the saccadic gap with the post-saccadic image. We first demonstrate that this illusion holds for moving objects, implying that the perception of time, velocity, and distance traveled become discrepant. We then show that this discrepancy is partially resolved up to 500 ms after a saccade: the perceived offset position of a post-saccadic moving stimulus shows a greater forward mislocalization when pursued after a saccade than during pursuit alone. These data are consistent with the idea that the temporal bias is resolved by the subsequent spatial adjustment to provide a percept that is coherent in its gist but inconsistent in its detail
- …