9,754 research outputs found
Workplace Wellness Programs: Are They Part of the Answer to the U.S.’s Growing Healthcare Crisis?
[Excerpt] Of the $2.8 trillion that the United States has spent on healthcare in recent years, the majority of it (75%) is spent treating chronic disease. Chronic disease is “a long-standing condition that can be controlled but not cured… It is the leading cause of death and disability in the U.S., which is 1.7 million lives each year.” To make matters worse, chronic disease indicators in the U.S. have been on the increase recently. And, even though chronic disease is commonly thought to be more prevalent among the elderly, in the past 10 years, it has increased by 25% among working-age adults. The cost of chronic disease to the U.S. economy far exceeds the money and resources spent to treat it. In fact, a study by the Milken Institute found that the indirect costs of chronic diseases (such as missed days from work) are higher than the direct costs to treat them. Furthermore, a study by PricewaterhouseCoopers found that these indirect costs are four times higher for individuals with chronic disease than for those without them. Therefore, chronic disease is strongly affecting employers’ increasing healthcare expenditure. A joint study by Tower Watson and the National Business Group on Health found that 67% of employers identified employee’s poor health habits as one of their top three challenges to maintain affordable health coverage
First gravitational lensing mass estimate of a damped Lyman-alpha galaxy at z=2.2
We present the first lensing total mass estimate of a galaxy, at redshift
2.207, that acts as a gravitational deflector and damped Lyman-alpha absorber
on the background QSO SDSS J1135-0010, at redshift 2.888. The remarkably small
projected distance, or impact parameter, between the lens and the source has
been estimated to be 0.8 +/- 0.1 kpc in a recent work. By exploiting the Sloan
Digital Sky Survey database, we establish a likely lensing magnification signal
in the photometry of the QSO. This is determined to be 2.2 mag brighter (or 8
times more luminous) than the median QSO at comparable redshifts. We describe
the total mass distribution of the lens galaxy with a one-component singular
isothermal sphere model and contrast the values of the observed and
model-predicted magnification factors. For the former, we use conservatively
the photometric data of the 95% of the available distant QSO population. We
estimate that the values of the lens effective velocity dispersion and
two-dimensional total mass, projected within a cylinder with radius equal to
the impact parameter, are included between 60 and 170 km/s and 2.1 x 10^9 and
1.8 x 10^10 M_Sun, respectively. We conclude by remarking that analyses of this
kind are crucial to exploring the relation between the luminous and dark matter
components of galaxies in the high-redshift Universe.Comment: 5 pages, 3 figures, accepted by MNRA
On the Initial Mass Function and tilt of the Fundamental Plane of massive early-type galaxies
We investigate the most plausible stellar Initial Mass Function (IMF) and the
main origin of the tilt of the Fundamental Plane (FP) for old, massive
early-type galaxies. We consider a sample of 13 bright galaxies of the Coma
cluster and combine our results with those obtained from a sample of 57 lens
galaxies in the same luminous mass range. We estimate the luminous mass and
stellar mass-to-light ratio values of the sample galaxies by fitting their SDSS
multi-band photometry with composite stellar population models computed with
different dust-free, solar-metallicity templates and IMFs. We compare these
measurements and those derived from two-component orbit-based dynamical
modelling. The photometric and dynamical luminous mass estimates of the
galaxies in our sample are consistent, within the errors, if a Salpeter IMF is
adopted. On the contrary, with a Kroupa or Chabrier IMF the two luminous mass
diagnostics differ at a more than 4 \sigma level. For the massive Coma
galaxies, their stellar mass-to-light ratio scales with luminous mass as the
corresponding effective quantities are observed to scale on the FP. This
indicates that the tilt of the FP is primarily caused by stellar population
properties. We conclude that old, massive lens and non-lens early-type galaxies
obey the same luminous and dynamical scaling relations, favour a Salpeter IMF,
and suggest a stellar population origin for the tilt of the FP. The validity of
these results for samples of early-type galaxies with different age and mass
properties still remains to be tested.Comment: 5 pages, 2 figures, accepted by MNRA
Dark matter-rich early-type galaxies in the CASSOWARY 5 strong lensing system
We study the strong gravitational lensing system number 5 identified by the
CASSOWARY survey. In this system, a source at redshift 1.069 is lensed into
four detected images by two early-type galaxies at redshift 0.388. The observed
positions of the multiple images are well reproduced by a model in which the
total mass distribution of the deflector is described in terms of two singular
isothermal sphere profiles. By modelling the lens galaxy spectral energy
distributions, we measure the lens luminous masses and stellar mass-to-light
ratios. These values are used to disentangle the luminous and dark matter
components in the vicinity of the multiple images. We estimate that the dark
over total mass ratio projected within a cylinder centred on the primary lens
and with a radius of 12.6 kpc is 0.8 +/- 0.1. We contrast these measurements
with the typical values found at similar distances (in units of the effective
radius) in isolated lens galaxies and show that the amount of dark matter
present in these lens galaxies is almost a factor four larger than in field
lens galaxies with comparable luminous masses. Data and models are therefore
consistent with interpreting the lens of this system as a galaxy group. We
infer that the overdense environment and dark matter concentration in these
galaxies must have affected the assembly of the lens luminous mass components.
We conclude that further multi-diagnostics analyses on the internal properties
of galaxy groups have the potential of providing us a unique insight into the
complex baryonic and dark-matter physics interplay that rules the formation of
cosmological structures.Comment: 9 pages, 6 figures; accepted for publication in MNRA
Monitoraggio delle acque di fondo del Bus de la Genziana (Pian Cansiglio, Nord-Est Italia)
In this paper we present the results of groundwater monitoring of the Bus de la Genziana (Cansiglio,
North-Eastern Italy). It is a cave 587 m deep and about 7 km long with a siphon hanging in the bottom. For the
fi rst time a diver instrument was installed here from March 2013 to December 2014 to discover the underground
hydrodynamics.
The level has been raised with a pattern of impulsive average of 4-5 meters with a few millimeters of rain: it
has reached 27 meters in one event and twice it has exceeded 50 meters with heavy rainfall lasting for several
days. A direct relationship is between tiltmeters recording (installed here at 25 m deep) and water level
in the siphon.
Observing the conductivity and the temperature, before the events of fl ood, the conductivity values (EC,
at 25\ub0C) were an average of 215 and 260 \u3bcS/cm, while the parameter fell between 150 \u3bcS/cm and 190 \u3bcS/cm
when the karstic system fi lls. On the contrary the temperature changes a little bit: the variations are sometimes
near the error measurement of the instrument with 0.04 to 0.3\ub0 C, minimum values 7.48\ub0 C and maximum value
8.34\ub0 C. These parameters show that the place can be affected by mixing of new infi ltration water, which is however very fast as a trigger, as less outfl ow. This type of dynamic helps us to understand that the underground
water circuits are highly conductive, as confi rmed by tiltmeters signal, and enrich the knowledge of the Cansiglio
complex hydrogeology.
Prospects for the future are to continue monitoring by installing a diver instrument also in the Abisso del Col
della Rizza, a cave near Genziana, 800 m deep, in order to understand better the underground hydrodynamics,
which are much more complex than they look
Automatic Landing System for Civil Unmanned Aerial System
In spite of a number of potentially valuable civil UAS applications The International Regulations prohibit UAS from operating in the National Air Space. Maybe the primary reasons are safety concerns. In fact their ability to respond to emergent situations involving the loss of contact between the aircraft and the ground station poses a serious problem. Therefore, to an efficient safe insertion of UAS in the Civil Air Transport System one important element is their ability to perform automatic landing afterwards the failure.
Moreover, the mathematical model of ground effect is usually neither included in the model of the aircraft during takeoff and landing nor in the design requirements of the control system Usually two different mathematical models of the aircraft are used during landing: the first Out the Ground Effect (OGE) and the second In Ground Effect (IGE).
The objective of this paper is to design a longitudinal automatic landing system taking ground effect into account. The designed control system will be tested and implemented on board by using the Preceptor N3 Ultrapup aircraft. In fact, such aircraft is used as technological demonstrator of new control navigation and guidance algorithms in the context of \u201cResearch Project of National Interest\u201d (PRIN 2008) by Universities of Bologna, Palermo, Ferrara and the Second University of Naples.
First of all, a general mathematical model of the studied aircraft is built to obtain non \u2013 linear analytical equations for aerodynamic coefficients both Out of Ground Effect and In Ground Effect conditions. According to previous researches, aerodynamic characteristics of the aircraft , have been modelled by means of hyperbolic equations in the whole flight envelope. So it is possible to use a single model during the whole landing phase taking into account the actual ground effect.
To overcome the difficulties due to the use of nonlinear models of the aircraft in ground effect for designing the controller, the control system has been designed using the following approach:
\uf02d The Landing flight path has been divided into two segments: the descending path for aircraft altitudes h > b (OGE) and the flare for h <= b ( IGE);
\uf02d The flare manoeuvre starts for h = b;
\uf02d An acceptable number of linear models has been obtained by means of linearization of the original nonlinear model in various flight conditions;
\uf02d A modified gain scheduling approach has been employed for the synthesis of the controller. It is made by six PID and by a supervisor. This one, by using the actual flight altitude, schedules the set of gains to be inserted online, depending on the real flight condition.
Several tests have been carried out by means of simulation, in Matlab Simulink environment. The obtained results show a good accuracy of the control system for trajectory tracking in ground proximity.
Further developments of the present research will be the extension of the designed control system to the take-off phase.
Afterwards the aircraft model will be improved by evaluating both lateral stability derivatives variations In Ground Effect and the bank angle derivatives (\uf066\uf020derivatives). The present methodology will be employed to design a Lateral Automatic Landing System.
The obtained results could be used later on, with the purpose to realize a fully autonomous UAS
Flight Control Research Laboratory Unmanned Aerial System flying in turbulent air: an algorithm for parameter identification from flight data
This work addresses the identification of the dynamics of the research aircraft FCRL (Flight
Control Research Laboratory) used for the Italian National Research Project PRIN2008 accounting
for atmospheric turbulence.
The subject vehicle is an unpressurized 2 seats, 427 kg maximum take of weight aircraft. It
features a non retractable, tailwheel, landing gear and a powerplant made up of reciprocating
engine capable of developing 60 HP, with a 60 inches diameter, two bladed, fixed pitch., tractor
propeller. The aircraft stall speed is 41.6 kts, therefore it is capable of speeds up to about 115 kts
(Sea level) and it will be cleared for altitudes up to 10.000 ft. The studied aircraft is equipped with a
research avionic system composed by sensors and computers and their relative power supply
subsystem. In particular the Sensors subsystem consists of :
\uf02d Inertial Measurement Unit (three axis accelerometers and gyros)
\uf02d Magnetometer (three axis)
\uf02d Air Data Boom (static and total pressure port, vane sense for angle of attack and
sideslip)
\uf02d GPS Receiver and Antenna
\uf02d Linear Potentiometers (Aileron, Elevator, Rudder and Throttle Command)
\uf02d RPM (Hall Effect Gear Tooth Sensor)
\uf02d Outside air temperature Sensor
A nonlinear mathematical model of the subject aircraft longitudinal dynamics, has been tuned up
through semi empirical methods, numerical simulations and ground tests.
To taking into account the atmospheric turbulence the identification problem addressed in this
work is solved by using the Filter error method approach .In this case, the mathematical model is
given by the stochastic equations:
\uf028 \uf029 \uf028 \uf028 \uf029 \uf028 \uf029 \uf028 \uf029 \uf029
\uf028 \uf029 \uf028 \uf028 \uf029 \uf028 \uf029 \uf029
\uf028 \uf029 \uf028 \uf029 \uf028 \uf029
\uf028 \uf029 0 0
, , ,
, ,
x t f x t u t w t
y t h x t u t
z k y k v k
x t x
\uf071
\uf071
\uf03d
\uf03d
\uf03d \uf02b
\uf03d
(1)
where x is the state vector, u is the control input vector, f and h are dimensional general nonlinear
vector functions, \uf071\uf020\uf020contains the unknown system parameters, z is the measurement vector ,w is the
process noise and v(k) is the measurement noise. The presence of nonmeasurable process noise
requires a suitable state estimator to propagate the states. To take into account model nonlinearities
in the present paper an Extended Kalman Filter has been implemented as the estimation algorithm
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