2,316 research outputs found
Stock portfolio selection using learning-to-rank algorithms with news sentiment
In this study, we apply learning-to-rank algorithms to design trading strategies
using relative performance of a group of stocks based on investors' sentiment
toward these stocks. We show that learning-to-rank algorithms are effective in
producing reliable rankings of the best and the worst performing stocks based
on investors' sentiment. More specifically, we use the sentiment shock and trend
indicators introduced in the previous studies, and we design stock selection rules
of holding long positions of the top 25% stocks and short positions of the bottom
25% stocks according to rankings produced by learning-to-rank algorithms.
We then apply two learning-to-rank algorithms, ListNet and RankNet, in stock
selection processes and test long-only and long-short portfolio selection strategies
using 10 years of market and news sentiment data. Through backtesting of
these strategies from 2006 to 2014, we demonstrate that our portfolio strategies
produce risk-adjusted returns superior to the S&P500 index return, the hedge
fund industry average performance - HFRIEMN, and some sentiment-based approaches
without learning-to-rank algorithm during the same period
Controlling Entanglement Dynamics by Choosing Appropriate Ratio between Cavity-Fiber Coupling and Atom-Cavity Coupling
The entanglement characteristics including the so-called sudden death effect
between two identical two-level atoms trapped in two separate cavities
connected by an optical fiber are studied. The results show that the time
evolution of entanglement is sensitive not only to the degree of entanglement
of the initial state but also to the ratio between cavity-fiber coupling () and
atom-cavity coupling (). This means that the entanglement dynamics can be
controlled by choosing specific v and g.Comment: 14pages, 3figures, conferenc
The effects of local voids and imperfections of surrounding rock on the performance of existing tunnel lining
Local voids and imperfections may exist around the tunnel due to reasons such as inadequate back infill behind the lining, insufficient local lining thickness, ground water erosion, and other imperfect construction related activities. Such local voids and imperfections generally will lead to local contact loss and discontinuity in the ground-lining interaction. This paper evaluates the effect of local voids and imperfections developing around the tunnel vault area on the mechanical performance of tunnel lining. Based on field investigation results, a series of voids and imperfections with different geometries are defined to reflect cases resulting from different causes. Numerical parametric analyses were performed to investigate how those voids and imperfections influence the internal force and the safety factor of the lining, and the reinforced concrete lining were modelled with the smeared crack model to examine the development of cracking directions and patterns. Furthermore, the numerical approach was verified by comparing with field investigations and measurements. This study aims to investigate the most unsafe situation due to local voids and imperfections around the tunnel, and the modelled cracking feature shows a way to preliminary evaluate the possible local voids and imperfections behind tunnel lining based on field observation
Finite Temperature Many-Body Theory with the Lipkin Model
We have compared exact numerical results for the Lipkin model at finite
temperature with Hartree-Fock theory and with the results of including in
addition the ring diagrams. In the simplest version of the Lipkin model the
Hartree-Fock approach shows a ``phase transition" which is absent in the exact
results. For more realistic cases, Hartree-Fock provides a very good
approximation and a modest improvement is obtained by adding the ring diagrams.Comment: 17 pages, NUC-MINN-93/16-T (4 figures obtainable by fax from the
authors
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Mixed experiences and perceptions of psychological treatment for chronic pain in Singapore: Skepticism, ambivalence, satisfaction and potential
There is little research in Southeast Asia focusing on patientsâ experiences of seeking psychological treatment for chronic pain.
Objective: This study aims to understand the experiences of patients seeking psychological treatment for chronic pain in this region.
Setting: Outpatient pain clinic at a tertiary hospital in Singapore.
Subjects: People with experiences of attending psychological treatment for chronic pain, including some who were not receiving this type of treatment.
Study design and methods: Fifteen inductive semi-structured interviews were conducted to explore patientsâ experiences regarding psychological treatment for their chronic pain. Thematic analysis was then applied.
Results: Three main themes were identified: âExpectations and Realities of Health Professionalsâ, âPatientsâ Attitudes and Beliefsâ and âPractical and Social Factors.â From the patientsâ perspectives, an empathetic health professional who was willing to listen contributed to a positive treatment seeking experience. Patients felt that health professionalsâ lack of knowledge about appropriate treatment contributed to their frustration. Patients could not understand how psychological treatment was related to pain treatment and queried why they were âpaying just to talkâ. On the other hand, their experiences were quite positive, and they found psychological treatments helpful when they participated in them.
Conclusion: Education for both patients and health professionals unfamiliar with psychological treatments for pain may improve access to these treatments
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Healthcare Professionalsâ Perceptions of Psychological Treatment for Chronic Pain in Singapore: Challenges, Barriers and the Way Forward
Purpose: There are very few studies on healthcare providersâ experiences of delivering treatment for chronic pain in a Southeast Asian setting. The aims of this study are to understand the experiences of professionals delivering treatment for people with chronic pain in Singapore and identify possible barriers to psychological treatment for this condition within the broader experiences of these professionals. Method: Healthcare professionals with at least one year experience treating chronic pain were recruited and purposefully sampled. Fifteen inductive semi-structured interviews were conducted to explore healthcare professionalsâ experiences of treating people with chronic pain. Interviews were transcribed verbatim and analysed using thematic analysis. Results: Four main themes were identified: âSystem Barriersâ, âCore Beliefs and management of Chronic Painâ, âEngaging Patients in treatmentââ, and âCreating Awareness for Chronic Pain Management.â Professionals trained in a multidisciplinary approach to pain management were seen as rare. Professionals who could refer patients for psychological treatment do not refer due to costs, and their perception that patients may lack understanding of such a treatment. Conclusion: Reducing barriers in the access to psychological treatment in settings like Singapore will require a multifaceted approach
Lattice Boltzmann modeling of dendritic growth in forced and natural convection
AbstractA two-dimensional (2D) coupled model is developed for the simulation of dendritic growth during alloy solidification in the presence of forced and natural convection. Instead of conventional continuum-based NavierâStokes (NS) solvers, the present model adopts a kinetic-based lattice Boltzmann method (LBM), which describes flow dynamics by the evolution of distribution functions of moving pseudo-particles, for the numerical computations of flow dynamics as well as thermal and solutal transport. The dendritic growth is modeled using a solutal equilibrium approach previously proposed by Zhu and Stefanescu (ZS), in which the evolution of the solid/liquid interface is driven by the difference between the local equilibrium composition and the local actual liquid composition. The local equilibrium composition is calculated from the local temperature and curvature. The local temperature and actual liquid composition, controlled by both diffusion and convection, are obtained by solving the LB equations using the lattice BhatnagarâGrossâKrook (LBGK) scheme. Detailed model validation is performed by comparing the simulations with analytical predictions, which demonstrates the quantitative capability of the proposed model. Furthermore, the convective dendritic growth features predicted by the present model are compared with those obtained from the ZhuâStefanescu and NavierâStokes (ZSâNS) model, in which the fluid flow is calculated using an NS solver. It is found that the evolution of the solid fraction of dendritic growth calculated by both models coincides well. However, the present model has the significant advantages of numerical stability and computational efficiency for the simulation of dendritic growth with melt convection
Study on Shrinkage Properties of Repairing Mortar Modified by Basalt Fiber
In order to study the shrinkage properties of modified repairing mortar, an orthogonal experiment with four factors and three levels were proceeded. Nine specimens with four factors, i.e., silica powder, sodium silicate, basalt fiber and a U-type expansive agent, were used to measure the length change ratio. The results show that the shrinkage value of modified repairing mortars have been greatly reduced. Compared with the control specimen without any additives, the shrinkage value of the modified repairing mortar with the silica powder of 3 %, the sodium silicate of 1.0 %, the basalt fiber of 0.2 % and the U-type expansive agent of 10 % at 60d drops by 42.5%. Based on experimental results, the shrinkage prediction model of modified repairing mortar has been established. The model can be used to predict the shrinkage value of the modified repairing mortar with similar compositions
Third Bose Fugacity Coefficient in One Dimension, as a Function of Asymptotic Quantities
In one of the very few exact quantum mechanical calculations of fugacity
coefficients, Dodd and Gibbs (\textit{J. Math.Phys}.,\textbf{15}, 41 (1974))
obtained and for a one dimensional Bose gas, subject to
repulsive delta-function interactions, by direct integration of the wave
functions. For , we have shown (\textit{Mol. Phys}.,\textbf{103}, 1301
(2005)) that Dodd and Gibbs' result can be obtained from a phase shift
formalism, if one also includes the contribution of oscillating terms, usually
contributing only in 1 dimension. Now, we develop an exact expression for
(where is the free particle fugacity coefficient)
in terms of sums and differences of 3-body eigenphase shifts. Further, we show
that if we obtain these eigenphase shifts in a distorted-Born approximation,
then, to first order, we reproduce the leading low temperature behaviour,
obtained from an expansion of the two-fold integral of Dodd and Gibbs. The
contributions of the oscillating terms cancel. The formalism that we propose is
not limited to one dimension, but seeks to provide a general method to obtain
virial coefficients, fugacity coefficients, in terms of asymptotic quantities.
The exact one dimensional results allow us to confirm the validity of our
approach in this domain.Comment: 29 page
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