3,657 research outputs found
Experimental generation of an optical field with arbitrary spatial coherence properties
We describe an experimental technique to generate a quasi-monochromatic field
with any arbitrary spatial coherence properties that can be described by the
cross-spectral density function, . This is done by using a
dynamic binary amplitude grating generated by a digital micromirror device
(DMD) to rapidly alternate between a set of coherent fields, creating an
incoherent mix of modes that represent the coherent mode decomposition of the
desired . This method was then demonstrated experimentally
by interfering two plane waves and then spatially varying the coherent between
these two modes such that the interference fringe visibility was shown to vary
spatially between the two beams in an arbitrary and prescribed way.Comment: 6 pages, 5 figur
Amplification of Angular Rotations Using Weak Measurements
We present a weak measurement protocol that permits a sensitive estimation of
angular rotations based on the concept of weak-value amplification. The shift
in the state of a pointer, in both angular position and the conjugate orbital
angular momentum bases, is used to estimate angular rotations. This is done by
an amplification of both the real and imaginary parts of the weak-value of a
polarization operator that has been coupled to the pointer, which is a spatial
mode, via a spin-orbit coupling. Our experiment demonstrates the first
realization of weak-value amplification in the azimuthal degree of freedom. We
have achieved effective amplification factors as large as 100, providing a
sensitivity that is on par with more complicated methods that employ quantum
states of light or extremely large values of orbital angular momentum.Comment: 5 pages, 3 figures, contains supplementary informatio
Design zero-voltage switching DC-DC buck converter
This report proposes an integrated, high switching frequency, zero-voltage-switching
dc-dc buck converter for battery charger application. The design and analysis of dcļæ½dc buck converter with integrated inductor is presented. The converter has been
optimized to convert 12V input voltage to 5V at 1.5A maximum load current at
50MHz switching frequency. The converter has been simulated using an ORCAD
16.5 based simulation tool and result show that the switching losses using zeroļæ½voltage-switching technique is less compared to conventional buck converter
Quantum-secured imaging
We have built an imaging system that uses a photon's position or
time-of-flight information to image an object, while using the photon's
polarization for security. This ability allows us to obtain an image which is
secure against an attack in which the object being imaged intercepts and
resends the imaging photons with modified information. Popularly known as
"jamming," this type of attack is commonly directed at active imaging systems
such as radar. In order to jam our imaging system, the object must disturb the
delicate quantum state of the imaging photons, thus introducing statistical
errors that reveal its activity.Comment: 10 pages (double spaced), 5 figure
State transfer based on classical nonseparability
We present a state transfer protocol that is mathematically equivalent to
quantum teleportation, but uses classical nonseparability instead of quantum
entanglement. In our implementation we take advantage of nonseparability among
three parties: orbital angular momentum (OAM), polarization, and the radial
degrees of freedom of a beam of light. We demonstrate the transfer of arbitrary
OAM states, in the subspace spanned by any two OAM states, to the polarization
of the same beam
Multiplexing Free-Space Channels using Twisted Light
We experimentally demonstrate an interferometric protocol for multiplexing
optical states of light, with potential to become a standard element in
free-space communication schemes that utilize light endowed with orbital
angular momentum (OAM). We demonstrate multiplexing for odd and even OAM
superpositions generated using different sources. In addition, our technique
permits one to prepare either coherent superpositions or statistical mixtures
of OAM states. We employ state tomography to study the performance of this
protocol, and we demonstrate fidelities greater than 0.98.Comment: 4 pages, 3 figure
Compressive Object Tracking using Entangled Photons
We present a compressive sensing protocol that tracks a moving object by
removing static components from a scene. The implementation is carried out on a
ghost imaging scheme to minimize both the number of photons and the number of
measurements required to form a quantum image of the tracked object. This
procedure tracks an object at low light levels with fewer than 3% of the
measurements required for a raster scan, permitting us to more effectively use
the information content in each photon.Comment: 10 pages, 4 figure
The accuracy of a point-of-care test among different operators using the QBC Autoread Plus Analyzer for the measurement of a basic full blood count
Background. Major issues around the implementation of point-of-care testing (POCT) include: user type, regulatory control, ongoing quality monitoring and limited guideline adherence.59 December 2019, Print editionObjectives. To determine if there are significant differences in the results of a POC full blood count test between different levels of healthcare and non-medical ālayā users compared with laboratory users (technologists/pathologists).Methods. This article retrospectively reviews the technical evaluation database of the intensive care unit (ICU), Chris Hani Baragwanath Academic Hospital, Johannesburg, South Africa. We searched for samples analysed by doctors, clerks and laboratory personnel. A minimum number of 60 comparisons were required. Bland-Altman plots, Spearmanās correlation and Passing-Bablok fit were used to analyse the dataset.Results. There were 72 comparisons for haematocrit (Hct), 98 for white cell count (WCC) and 137 for platelets (Plt) between the clerk and laboratory personnel. The correlations were 0.91, 0.96 and 0.92, respectively. All were statistically significant. Using the Bland-Altman method, there was good agreement between results of the clerk and those of the laboratory staff, with a mean bias of 0.5% (Hct), 0.1 Ć 109/L (WCC) and 10 Ć 109/L (Plt). An insufficient number of tests were performed by medical doctors for statistical comparison.Conclusions. With appropriate training, non-medical, non-healthcare lay users are able to perform a moderately complex POCT with similar accuracy as trained laboratory professionals. The focus should shift to equipment and quality management processes rather than the medical/technical qualification of the user
Assessing the readiness of contractors in implementing low carbon construction in Penang
Global warming or climate change is becoming the main concerns of humanity as it leads to an increase in Earthās temperature and rise in the oceansā level which is due to the increase of greenhouse gasses in the atmosphere. Greenhouse gasses consists of water vapour, carbon dioxide (CO2), methane (CH4), nitrous oxide (N20), tropospheric ozone (O3) and chlorofluorocarbons (CFCs). Among the gasses, CO2 is the highest and easiest gas to measure as it is emitted from human economic activities with construction industry one of the major contributors of carbon emissions. Low carbon construction is the reduction of carbon emissions from the construction activities during construction process. For the implementation of low carbon construction in our construction industry, the contractors need to be ready and have knowledge to adopt low carbon construction industry. The purpose of this research is to determine the level of contractorsā knowledge towards low carbon construction, determining the level of readiness towards low carbon construction and proposing a checklist for the contractors towards low carbon construction in Penang. This research employed questionnaire survey to analyse the level of knowledge and readiness of the contractors on low carbon construction. As a conclusion, the implementation of low carbon practices by the contractors in Penang is good, therefore established that G7 contractors implement low carbon practices throughout their construction. However, the results and findings indicated that the average mean score on the level of readiness of contractors towards low carbon construction is 3.59. The result was perceived as moderate. Therefore, it shows that the contractors are in a moderate readiness to implement low carbon construction fully in their construction projects. A checklist was established by summarizing the highest low carbon activities from each category which were sustainable site planning and management, materials and resources, waste management, water efficiency and energy efficiency, and was perceived as good.Ā Keywords: Climate change, greenhouse gases, carbon emission, low carbon construction, contractorsā readiness
Rapid Generation of Light Beams Carrying Orbital Angular Momentum
We report a technique for encoding both amplitude and phase variations onto a
laser beam using a single digital micro-mirror device (DMD). Using this
technique, we generate Laguerre-Gaussian and vortex orbital-angular-momentum
(OAM) modes, along with modes in a set that is mutually unbiased with respect
to the OAM basis. Additionally, we have demonstrated rapid switching among the
generated modes at a speed of 4 kHz, which is much faster than the speed
regularly achieved by spatial light modulators (SLMs). The dynamic control of
both phase and amplitude of a laser beam is an enabling technology for
classical communication and quantum key distribution (QKD) systems that employ
spatial mode encoding
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