1,451 research outputs found
Expert System for Development Diagnosing Disease with Hepatitis Using Wamp
Expert systems are computer-based system that usesknowledge, facts and reasoning techniques in solving problemsusually only be solved by an expert in a particular field. Systemexperts to provide added value in technology to assist in handlingera of increasingly sophisticated information.Expert System produces output in the form of disease possiblehepatitis based on symptoms suffered by the user. This system alsomanampilkan amount of trust against the possibility of disease symptomskidney suffered by the user. The value of these beliefs isresults of calculations using the method-Factor Certainly.This expert system is designed with the view that considering the ease inin pengoprasiannya.Bibliography : (xiv + 93 + 33 Appendix
Expert System Development for Diagnose Disease Hepatitis Using Wamp 2003
Sistem pakar adalah sistem berbasis komputer yang menggunakan pengetahuan,fakta, dan tehnik penalaran dalam memecahkan masalah yang biasanya hanyadapat dipecahkan oleh seorang pakar dalam bidang tertentu. Sistem pakarmemberikan nilai tambah pada teknologi untuk membantu dalam menangani erainformasi yang semakin canggih. Sistem Pakar ini menghasilkan keluaranberupa kemungkinan penyakit hepatitis yang diderita berdasarkan gejala yangdirasakan oleh user. Sistem ini juga manampilkan besarnya kepercayaan gejalatersebut terhadap kemungkinan penyakit ginjal yang diderita oleh user.Besarnya nilai kepercayaan tersebut merupakan hasil perhitungan denganmenggunakan metode Certainly-Factor. Sistem pakar ini dirancang dengantampilan yang memperhatikan kemudahan di dalam pengoprasiannya
Reconstructing the potentials for the quintessence and tachyon dark energy, from the holographic principle
We propose an holographic quintessence and tachyon models of dark energy. The
correspondence between the quintessence and tachyon energy densities with the
holographic density, allows the reconstruction of the potentials and the
dynamics for the quintessence and tachyon fields, in flat FRW background. The
proposed infrared cut-off for the holographic energy density works for two
cases of the constant : for we reconstructed the holographic
quintessence model in the region before the crossing for the EoS
parameter. The cosmological dynamics for was also reconstructed for
the holographic quintessence and tachyon models.Comment: 21 pages, 18 figures, 2 table
Quantum effects, soft singularities and the fate of the universe in a braneworld cosmology
We examine a class of braneworld models in which the expanding universe
encounters a "quiescent" future singularity. At a quiescent singularity, the
energy density and pressure of the cosmic fluid as well as the Hubble parameter
remain finite while all derivatives of the Hubble parameter diverge (i.e.,
, , etc. ). Since the Kretschmann invariant
diverges () at the singularity, one expects
quantum effects to play an important role as the quiescent singularity is
approached. We explore the effects of vacuum polarization due to massless
conformally coupled fields near the singularity and show that these can either
cause the universe to recollapse or, else, lead to a softer singularity at
which , , and remain finite while {\dddot H} and
higher derivatives of the Hubble parameter diverge. An important aspect of the
quiescent singularity is that it is encountered in regions of low density,
which has obvious implications for a universe consisting of a cosmic web of
high and low density regions -- superclusters and voids. In addition to vacuum
polarization, the effects of quantum particle production of non-conformal
fields are also likely to be important. A preliminary examination shows that
intense particle production can lead to an accelerating universe whose Hubble
parameter shows oscillations about a constant value.Comment: 19 pages, 3 figures, text slightly improved and references added.
Accepted for publication in Classical and Quantum Gravit
Probing Cosmic Acceleration Beyond the Equation of State: Distinguishing between Dark Energy and Modified Gravity Models
If general relativity is the correct theory of physics on large scales, then
there is a differential equation that relates the Hubble expansion function,
inferred from measurements of angular diameter distance and luminosity
distance, to the growth rate of large scale structure. For a dark energy fluid
without couplings or an unusual sound speed, deviations from this consistency
relationship could be the signature of modified gravity on cosmological scales.
We propose a procedure based on this consistency relation in order to
distinguish between some dark energy models and modified gravity models. The
procedure uses different combinations of cosmological observations and is able
to find inconsistencies when present. As an example, we apply the procedure to
a universe described by a recently proposed 5-dimensional modified gravity
model. We show that this leads to an inconsistency within the dark energy
parameter space detectable by future experiments.Comment: 8 pages, 7 figures; expanded paper; matches PRD accepted version;
corrected growth rate formula; main results and conclusion unchange
Quintessential Inflation on the Brane and the Relic Gravity Wave Background
Quintessential inflation describes a scenario in which both inflation and
dark energy (quintessence) are described by the same scalar field. In
conventional braneworld models of quintessential inflation gravitational
particle production is used to reheat the universe. This reheating mechanism is
very inefficient and results in an excessive production of gravity waves which
violate nucleosynthesis constraints and invalidate the model. We describe a new
method of realizing quintessential inflation on the brane in which inflation is
followed by `instant preheating' (Felder, Kofman & Linde 1999). The larger
reheating temperature in this model results in a smaller amplitude of relic
gravity waves which is consistent with nucleosynthesis bounds. The relic
gravity wave background has a `blue' spectrum at high frequencies and is a
generic byproduct of successful quintessential inflation on the brane.Comment: 9 pages, 5 eps figures. Discussion and one eps figure summarizing the
GB correction to steep brane world inflation added, typos corrected and
references added; final version to appear in PR
Quantum vacuum effects as generalized f(R) gravity. Application to stars
It is assumed that, for weak spacetime curvature, the main gravitational
effect of the quantum vacuum stress-energy corresponds to adding two terms to
the Einstein-Hilbert action, proportional to the square of the curvature scalar
and to the contraction of two Ricci tensors, respectively. It is shown that
compatibility with terrestrial and solar systems observaction implies that the
square roorts of the coefficients of these terms should be either a few
millimeters or a few hundred meters. It is shown that the vacuum contribution
increase the stability of white dwarfs.Comment: GEneralizes and improves previous versio
Delicate f(R) gravity models with disappearing cosmological constant and observational constraints on the model parameters
We study the theory of gravity using metric approach. In particular we
investigate the recently proposed model by Hu-Sawicki, Appleby Battye and
Starobinsky. In this model, the cosmological constant is zero in flat space
time. The model passes both the Solar system and the laboratory tests. But the
model parameters need to be fine tuned to avoid the finite time singularity
recently pointed in the literature. We check the concordance of this model with
the and baryon acoustic oscillation data. We find that the model
resembles the CDM at high redshift. However, for some parameter values
there are variations in the expansion history of the universe at low redshift.Comment: 16 pages and 9 figures, typos corrected, few references and minor
clarifications added, revised version to appera in PR
Linearized gravity on the Randall-Sundrum two-brane background with curvature terms in the action for the branes
We study gravitational perturbations in the Randall-Sundrum two-brane
background with scalar-curvature terms in the action for the branes, allowing
for positive as well as negative bulk gravitational constant. In the zero-mode
approximation, we derive the linearized gravitational equations, which have the
same form as in the original Randall-Sundrum model but with different
expressions for the effective physical constants. We develop a generic method
for finding tachyonic modes in the theory, which, in the model under
consideration, may exist only if the bulk gravitational constant is negative.
In this case, if both brane gravitational constants are nonzero, the theory
contains one or two tachyonic mass eigenvalues in the gravitational sector. If
one of the brane gravitational constants is set to zero, then either a single
tachyonic mass eigenvalue is present or tachyonic modes are totally absent
depending on the relation between the nonzero brane gravitational constant and
brane separation. In the case of negative bulk gravitational constant, the
massive gravitational modes have ghost-like character, while the massless
gravitational mode is not a ghost in the case where tachyons are absent.Comment: 23 pages, revtex, published versio
Can the Chaplygin gas be a plausible model for dark energy?
In this note two cosmological models representing the flat Friedmann Universe
filled with a Chaplygin fluid, with or without dust, are analyzed in terms of
the recently proposed "statefinder" parameters. Trajectories of both models in
the parameter plane are shown to be significantly different w.r.t. "quiessence"
and "tracker" models. The generalized Chaplygin gas model with an equation of
state of the form is also analyzed in terms of the
statefinder parameters.Comment: 6 pages, 2 figure
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