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A systematic review of software development cost estimation studies
This paper aims to provide a basis for the improvement of software estimation research through a systematic review of previous work. The review identifies 304 software cost estimation papers in 76 journals and classifies the papers according to research topic, estimation approach, research approach, study context and data set. A web-based library of these cost estimation papers is provided to ease the identification of relevant estimation research results. The review results combined with other knowledge provide support for recommendations for future software cost estimation research, including: 1) Increase the breadth of the search for relevant studies, 2) Search manually for relevant papers within a carefully selected set of journals when completeness is essential, 3) Conduct more studies on estimation methods commonly used by the software industry, and, 4) Increase the awareness of how properties of the data sets impact the results when evaluating estimation methods
Physics-informed Neural Networks for Solving Inverse Problems of Nonlinear Biot's Equations: Batch Training
In biomedical engineering, earthquake prediction, and underground energy
harvesting, it is crucial to indirectly estimate the physical properties of
porous media since the direct measurement of those are usually
impractical/prohibitive. Here we apply the physics-informed neural networks to
solve the inverse problem with regard to the nonlinear Biot's equations.
Specifically, we consider batch training and explore the effect of different
batch sizes. The results show that training with small batch sizes, i.e., a few
examples per batch, provides better approximations (lower percentage error) of
the physical parameters than using large batches or the full batch. The
increased accuracy of the physical parameters, comes at the cost of longer
training time. Specifically, we find the size should not be too small since a
very small batch size requires a very long training time without a
corresponding improvement in estimation accuracy. We find that a batch size of
8 or 32 is a good compromise, which is also robust to additive noise in the
data. The learning rate also plays an important role and should be used as a
hyperparameter.Comment: arXiv admin note: text overlap with arXiv:2002.0823
The scaling relations of early--type galaxies in clusters I. Surface photometry in seven nearby clusters
This is the first paper of a series investigating the scaling relations of
early-type galaxies in clusters. Here we illustrate the multi-band imagery and
the image reduction and calibration procedures relative to the whole sample of
22 clusters at 0.05 < z < 0.25. We also present the detailed surface photometry
of 312 early-type galaxies in 7 clusters in the first redshift bin,
z~0.025-0.075. We give for each galaxy the complete set of luminosity and
geometrical profiles, and and a number of global, photometric and morphological
parameters. They have been evaluated taking into account the effects of seeing.
Internal consistency checks and comparisons with data in the literature confirm
the quality of our analysis. These data, together with the spectroscopic ones
presented in the second paper of the series, will provide the local calibration
of the scaling relations.Comment: 36 pages, 13 figures, 7 tables, accepted for publication in A&
Cultivar and Year-to-Year Variation of Phytosterol Content in Rye (Secale cereale L.)
Intake of phytosterols (and -stanols) has been shown to decrease the level of low-density lipoprotein cholesterol and thus protect against development of cardiovascular diseases. Therefore, studies on the cultivar and year-to-year variation in phytosterol content in rye grains have been performed. The phytosterol content and composition of different rye cultivars, grown under identical conditions on the same field in three consecutive years, were analyzed. Both cultivar and year-to-year variation in sterol content were statistically significant (p < 0.0001). The total sterol content varied from 1007 ± 21 mg/kg in the highest yielding cultivar, Tsulpan 3, to 761 ± 10 mg/kg in the lowest yielding cultivar (Amando in the 1999 harvest). Because the meteorological conditions varied substantially between the different years, it was possible to deduce the impact of varying weather conditions on phytosterol content in the different cultivars. The studied cultivars had all the lowest phytosterol contents in the dry and warm harvest season of 1999. Although there were statistically significant cultivar and year-to-year variations in the sterol composition (p < 0.0001), these were only between 2 and 4% of the total sterol content
An estimating equations approach to fitting latent exposure models with longitudinal health outcomes
The analysis of data arising from environmental health studies which collect
a large number of measures of exposure can benefit from using latent variable
models to summarize exposure information. However, difficulties with estimation
of model parameters may arise since existing fitting procedures for linear
latent variable models require correctly specified residual variance structures
for unbiased estimation of regression parameters quantifying the association
between (latent) exposure and health outcomes. We propose an estimating
equations approach for latent exposure models with longitudinal health outcomes
which is robust to misspecification of the outcome variance. We show that
compared to maximum likelihood, the loss of efficiency of the proposed method
is relatively small when the model is correctly specified. The proposed
equations formalize the ad-hoc regression on factor scores procedure, and
generalize regression calibration. We propose two weighting schemes for the
equations, and compare their efficiency. We apply this method to a study of the
effects of in-utero lead exposure on child development.Comment: Published in at http://dx.doi.org/10.1214/08-AOAS226 the Annals of
Applied Statistics (http://www.imstat.org/aoas/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Subarcsecond resolution observations of warm water towards three deeply embedded low-mass protostars
Water is present during all stages of star formation: as ice in the cold
outer parts of protostellar envelopes and dense inner regions of circumstellar
disks, and as gas in the envelopes close to the protostars, in the upper layers
of circumstellar disks and in regions of powerful outflows and shocks. In this
paper we probe the mechanism regulating the warm gas-phase water abundance in
the innermost hundred AU of deeply embedded (Class~0) low-mass protostars, and
investigate its chemical relationship to other molecular species during these
stages. Millimeter wavelength thermal emission from the para-H2-18O
3(1,3)-2(2,0) (Eu=203.7 K) line is imaged at high angular resolution (0.75";
190 AU) with the IRAM Plateau de Bure Interferometer towards the deeply
embedded low-mass protostars NGC 1333-IRAS2A and NGC 1333-IRAS4A. Compact
H2-18O emission is detected towards IRAS2A and one of the components in the
IRAS4A binary; in addition CH3OCH3, C2H5CN, and SO2 are detected. Extended
water emission is seen towards IRAS2A, possibly associated with the outflow.
The detections in all systems suggests that the presence of water on <100 AU
scales is a common phenomenon in embedded protostars. We present a scenario in
which the origin of the emission from warm water is in a flattened disk-like
structure dominated by inward motions rather than rotation. The gas-phase water
abundance varies between the sources, but is generally much lower than a
canonical abundance of 10^-4, suggesting that most water (>96 %) is frozen out
on dust grains at these scales. The derived abundances of CH3OCH3 and SO2
relative to H2-18O are comparable for all sources pointing towards similar
chemical processes at work. In contrast, the C2H5CN abundance relative to
H2-18O is significantly lower in IRAS2A, which could be due to different
chemistry in the sources.Comment: 12 pages, 9 figure
On C*-algebras generated by pairs of q-commuting isometries
We consider the C*-algebras O_2^q and A_2^q generated, respectively, by
isometries s_1, s_2 satisfying the relation s_1^* s_2 = q s_2 s_1^* with |q| <
1 (the deformed Cuntz relation), and by isometries s_1, s_2 satisfying the
relation s_2 s_1 = q s_1 s_2 with |q| = 1. We show that O_2^q is isomorphic to
the Cuntz-Toeplitz C*-algebra O_2^0 for any |q| < 1. We further prove that
A_2^{q_1} is isomorphic to A_2^{q_2} if and only if either q_1 = q_2 or q_1 =
complex conjugate of q_2. In the second part of our paper, we discuss the
complexity of the representation theory of A_2^q. We show that A_2^q is *-wild
for any q in the circle |q| = 1, and hence that A_2^q is not nuclear for any q
in the circle.Comment: 18 pages, LaTeX2e "article" document class; submitted. V2 clarifies
the relationships between the various deformation systems treate
Disk and Envelope Structure in Class 0 Protostars: I. The Resolved Massive Disk in Serpens FIRS 1
We present the first results of a program to characterize the disk and
envelope structure of typical Class 0 protostars in nearby low-mass star
forming regions. We use Spitzer IRS mid-infrared spectra, high resolution CARMA
230 GHz continuum imaging, and 2-D radiative transfer models to constrain the
envelope structure, as well as the size and mass of the circum-protostellar
disk in Serpens FIRS 1. The primary envelope parameters (centrifugal radius,
outer radius, outflow opening angle, and inclination) are well constrained by
the spectral energy distribution (SED), including Spitzer IRAC and MIPS
photometry, IRS spectra, and 1.1 mm Bolocam photometry. These together with the
excellent uv-coverage (4.5-500 klam) of multiple antenna configurations with
CARMA allow for a robust separation of the envelope and a resolved disk. The
SED of Serpens FIRS 1 is best fit by an envelope with the density profile of a
rotating, collapsing spheroid with an inner (centrifugal) radius of
approximately 600 AU, and the millimeter data by a large resolved disk with
Mdisk~1.0 Msun and Rdisk~300 AU. These results suggest that large, massive
disks can be present early in the main accretion phase. Results for the larger,
unbiased sample of Class~0 sources in the Perseus, Serpens, and Ophiuchus
molecular clouds are needed to determine if relatively massive disks are
typical in the Class 0 stage.Comment: Comments: 13 pages, 8 figures, 3 tables; accepted for publication in
the Ap
C18O (3-2) observations of the Cometary Globule CG 12: a cold core and a C18O hot spot
The feasibility of observing the C18O (3-2) spectral line in cold clouds with
the APEX telescope has been tested. As the line at 329.330 GHz lies in the wing
of a strong atmospheric H2O absorption it can be observed only at high altitude
observatories. Using the three lowest rotational levels instead of only two
helps to narrow down the physical properties of dark clouds and globules. The
centres of two C18O maxima in the high latitude low mass star forming region CG
12 were mapped in C18O (3-2) and the data were analyzed together with spectral
line data from the SEST. The T_MB(3-2)/T_MB(2-1) ratio in the northern C18O
maximum, CG 12 N, is 0.8, and in the southern maximum, CG 12 S, ~2. CG 12 N is
modelled as a 120'' diameter (0.4pc) cold core with a mass of 27 Msun. A small
size maximum with a narrow, 0.8 kms-1, C18O (3-2) spectral line with a peak
temperature of T_MB ~11 K was detected in CG 12 S. This maximum is modelled as
a 60'' to 80'' diameter (~0.2pc) hot (80 K < Tex < 200 K) ~1.6 Msun clump. The
source lies on the axis of a highly collimated bipolar molecular outflow near
its driving source. This is the first detection of such a compact, warm object
in a low mass star forming region.Comment: APEX A&A special issue, accepte
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