4,296 research outputs found
Lifting of Steel Coils in Bore-Vertical Orientation
Lifting of coils with the bore in the vertical orientation could give rise to safety issues if the coil integrity is compromised during the slitting and packing operation. Coil telescoping (whereby the inner wraps of the coil spiral out) is known to occur during lifting, which could pose as a serious threat to the safety of personnel involved. In this type of incident, the coil straps are also broken when their breaking strength is exceeded and the whole coil would unwrap itself at an elevated position. Back tension is applied to the strip while shearing wide strip into narrower slits; this allows sufficient radial pressure to be built up within the bulk of the narrow coils. Upon unloading, the radial pressures at the innermost and outermost wraps decrease to zero but the bulk of the inter-wrap pressure within the coil remains largely unchanged. The interwrap frictional forces developed within the coil enable the coil to retain its integrity under its own weight. It is found that the radial pressures developed within the slit coil play the most crucial role in providing sufficient frictional resistance to support the weight of the coil wraps during lifting with the bore in the vertical orientation. In addition, the inter-wrap pressures near the footprint of the mechanical lifting device, near the bore, have the most significant influence in preventing coil telescoping
Quantum-state filtering applied to the discrimination of Boolean functions
Quantum state filtering is a variant of the unambiguous state discrimination
problem: the states are grouped in sets and we want to determine to which
particular set a given input state belongs.The simplest case, when the N given
states are divided into two subsets and the first set consists of one state
only while the second consists of all of the remaining states, is termed
quantum state filtering. We derived previously the optimal strategy for the
case of N non-orthogonal states, {|\psi_{1} >, ..., |\psi_{N} >}, for
distinguishing |\psi_1 > from the set {|\psi_2 >, ..., |\psi_N >} and the
corresponding optimal success and failure probabilities. In a previous paper
[PRL 90, 257901 (2003)], we sketched an appplication of the results to
probabilistic quantum algorithms. Here we fill in the gaps and give the
complete derivation of the probabilstic quantum algorithm that can optimally
distinguish between two classes of Boolean functions, that of the balanced
functions and that of the biased functions. The algorithm is probabilistic, it
fails sometimes but when it does it lets us know that it did. Our approach can
be considered as a generalization of the Deutsch-Jozsa algorithm that was
developed for the discrimination of balanced and constant Boolean functions.Comment: 8 page
Helstrom Theorem by No-Signaling Condition
We prove a special case of Helstrom theorem by using no-signaling condition
in the special theory of relativity that faster-than-light communication is
impossible.Comment: Minor corrections (A reference added, discussion part deleted, typos
in equations corrected), 2 pages, RevTe
Phase-covariant cloning of coherent states
We consider the problem of phase-covariant cloning for coherent states. We
show that an experimental scheme based on ideal phase measurement and
feedforward outperforms the semiclassical procedure of ideal phase measurement
and preparation in terms of fidelity. A realistic scheme where the ideal phase
measurement is replaced with double-homodyne detection is shown to be unable to
overcome the semiclassical cloning strategy. On the other hand, such a
realistic scheme is better than semiclassical cloning based on double-homodyne
phase measurement and preparation.Comment: 6 pages, 2 figures; updated references and minor corrections; in
press on Physical Review
Minimum-error discrimination between mixed quantum states
We derive a general lower bound on the minimum-error probability for {\it
ambiguous discrimination} between arbitrary mixed quantum states with given
prior probabilities. When , this bound is precisely the well-known
Helstrom limit. Also, we give a general lower bound on the minimum-error
probability for discriminating quantum operations. Then we further analyze how
this lower bound is attainable for ambiguous discrimination of mixed quantum
states by presenting necessary and sufficient conditions related to it.
Furthermore, with a restricted condition, we work out a upper bound on the
minimum-error probability for ambiguous discrimination of mixed quantum states.
Therefore, some sufficient conditions are obtained for the minimum-error
probability attaining this bound. Finally, under the condition of the
minimum-error probability attaining this bound, we compare the minimum-error
probability for {\it ambiguously} discriminating arbitrary mixed quantum
states with the optimal failure probability for {\it unambiguously}
discriminating the same states.Comment: A further revised version, and some results have been adde
Quantum-limited force measurement with an optomechanical device
We study the detection of weak coherent forces by means of an optomechanical
device formed by a highly reflecting isolated mirror shined by an intense and
highly monochromatic laser field. Radiation pressure excites a vibrational mode
of the mirror, inducing sidebands of the incident field, which are then
measured by heterodyne detection. We determine the sensitivity of such a scheme
and show that the use of an entangled input state of the two sideband modes
improves the detection, even in the presence of damping and noise acting on the
mechanical mode.Comment: 8 pages, 4 figure
Factors Associated with Depression among University Students in Malaysia: A Cross-sectional Study
Depression is a recurrent mental health problem among younger demographics, and university students are particularly susceptible owing to stress, workload and independent living, amongst other factors. This study explores the prevalence of depression and the factors influencing depression among university students in Malaysia. This cross-sectional study involved 1,023 university students (response rate 90.4%). Depression was assessed using the Centre for Epidemiological Studies Short Depression Scale (CESD -10). Binary logistic regression was used to determine predictors of depression based on sociodemographic, physiological, lifestyle, and health characteristics. Approximately 30% of respondents experienced depression, and 4.4% of this category suffered severe depression. This study demonstrates that instances of depression were 2.52 times higher (95% CI: 1.71-3.71) in second year students compared to first year students, and 1.63 times higher (95% CI: 1.08-2.45) in students staying outside campus compared to students staying inside campus. Students from poor, not well-off, and quite well-off family background had 15.26 (95% CI: 2.77-84.88), 4.85 (95% CI: 1.01-23.34) and 5.62 times (95% CI: 1.16-27.25) higher chance for depression than wealthier students, respectively. Students with mild, moderate, and severe sleeping problems were 2.50 times (95% CI: 1.61-3.88), 3.34 times (95% CI: 2.18-5.11), and 3.66 times (95% CI: 1. 93 -6. 94) more likely to be depressed than those without sleeping problem, respectively. Students with post-traumatic stress disorder (PTSD) were 1.42 times higher (95% CI: 1.07-2.56) to suffer from depression. This study concludes that higher education institutions need to pay special attention to the mental health of those students especially those in their second year, living off campus, from lower economic backgrounds, with sleeping problem, or suffering PTSD
Unified Treatment of Heterodyne Detection: the Shapiro-Wagner and Caves Frameworks
A comparative study is performed on two heterodyne systems of photon
detectors expressed in terms of a signal annihilation operator and an image
band creation operator called Shapiro-Wagner and Caves' frame, respectively.
This approach is based on the introduction of a convenient operator
which allows a unified formulation of both cases. For the Shapiro-Wagner
scheme, where , quantum phase and amplitude
are exactly defined in the context of relative number state (RNS)
representation, while a procedure is devised to handle suitably and in a
consistent way Caves' framework, characterized by , within the approximate simultaneous measurements of
noncommuting variables. In such a case RNS phase and amplitude make sense only
approximately.Comment: 25 pages. Just very minor editorial cosmetic change
Management of Renewable Energy for a Shared Facility Controller in Smart Grid
© 2016 IEEE. This paper proposes an energy management scheme to maximize the use of solar energy in the smart grid. In this context, a shared facility controller (SFC) with a number of solar photovoltaic panels in a smart community is considered that has the capability to schedule the generated energy for consumption and trade to other entities. In particular, a mechanism is designed for the SFC to decide on the energy surplus, if there is any, that it can use to charge its battery and sell to the households and the grid based on the offered prices. In this regard, a hierarchical energy management scheme is proposed with a view to reduce the total operational cost to the SFC. The concept of a virtual cost is introduced that aids the SFC to estimate its future operational cost based on some available current information. The energy management is conducted for three different cases, and the optimal cost to the SFC is determined for each case by the theory of maxima and minima. A real-time algorithm is proposed to reach the optimal cost for all cases, and some numerical examples are provided to demonstrate the beneficial properties of the proposed scheme
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