355 research outputs found
Peningkatan Hasil Belajar Matematika melalui Model Problem Based Learning Berbantu Media Puzzle di Sekolah Dasar
The purpose of this research is to improve results of learning mathematic using Problem Based Learning model which helped with puzzle to 5th grade students of SD Negeri Sidorejo Lor 01 Salatiga.The type of this research is Class Action Research (CAR) with a spiral model from C. Kemmis & Mc. Taggart includes planning, implementing actions and observations, and reflection. The research subjects were 5th grade students of SD Negeri Sidorejo Lor 1 Salatiga, totaling 36 students. Data collection techniques using test techniques in the form of evaluation and non-test questions in the form of observation and documentation.The results were evidenced by the average value of mathematics learning outcomes of 5th grade students in pre-cycle was 66.08 with 47.2% learning completeness increased in the first cycle to 76.38 with a completeness percentage of 77.8%. In second cycle it became 86.8 with the percentage of completeness reaching 100% of 36 students. Thus it can be concluded that the learning mathematic using Problem Based Learning model which helped with puzzle can improve results of learning mathematic to 5th grade students of SD Negeri Sidorejo Lor 01 Salatiga
A Keplerian gaseous disk around the B0 star R Mon
We present high-angular resolution observations of the circumstellar disk
around the massive Herbig Be star R Mon (M~8 Msun) in the continuum at 2.7mm
and 1.3mm and the CO 1->0 and 2->1 rotational lines. Based on the new 1.3mm
continuum image we estimate a disk mass (gas+dust) of 0.007 Msun and an outer
radius of <150 AU. Our CO images are consistent with the existence of a
Keplerian rotating gaseous disk around this star. Up to our knowledge, this is
the most clear evidence for the existence of Keplerian disks around massive
stars reported thus far. The mass and physical characteristics of this disk are
similar to thoseof the more evolved T Tauri stars and indicate a shorter
timescale for the evolution and dispersal of circumstellar disks around massive
stars which lose most of their mass before the star becomes visible.Comment: 5 page
Structure preserving schemes for mean-field equations of collective behavior
In this paper we consider the development of numerical schemes for mean-field
equations describing the collective behavior of a large group of interacting
agents. The schemes are based on a generalization of the classical Chang-Cooper
approach and are capable to preserve the main structural properties of the
systems, namely nonnegativity of the solution, physical conservation laws,
entropy dissipation and stationary solutions. In particular, the methods here
derived are second order accurate in transient regimes whereas they can reach
arbitrary accuracy asymptotically for large times. Several examples are
reported to show the generality of the approach.Comment: Proceedings of the XVI International Conference on Hyperbolic
Problem
The dusty disk around VV Ser
We have carried out observations at millimeter and centimeter wavelengths
towards VV Ser using the Plateau de Bure Interferometer and the Very Large
Array. This allows us to compute the SED from near infrared to centimeter
wavelengths. The modeling of the full SED has provided insight into the dust
properties and a more accurate value of the disk mass.
The mass of dust in the disk around VV Ser is found to be about 4 10^(-5)
Msun, i.e. 400 times larger than previous estimates. Moreoever, the SED can
only be accounted for assuming dust stratification in the vertical direction
across the disk. The existence of small grains (0.25--1 micron) in the disk
surface is required to explain the emission at near- and mid-infrared
wavelengths. The fluxes measured at millimeter wavelengths imply that the dust
grains in the midplane have grown up to very large sizes, at least to some
centimeters.Comment: To appear in Ap
Pengelompokan Tim Pengembang Berdasarkan Kriteria Perilaku Manusia dalam Kolaborasi Pengembangan Perangkat Lunak
Teknologi informasi merupakan bidang yang berkembang cukup pesat di akhir dekade ini. Hal tersebut ditandai dengan meningkatnya kebutuhan akan teknologi informasi. Salah satu bagian dari proyek teknologi informasi yang berkembang cukup pesat adalah proyek pengembangan perangkat lunak yang mempunyai ketidakpastian tinggi dengan tingkat kesuksesan yang rendah. Kualitas dan kecepatan proyek perangkat lunak sangat tergantung pada faktor sumber daya manusia. Tujuan penelitian ini adalah untuk mengembangkan sebuah strategi dan kriteria dengan mengelompokkan perilaku tim pengembang sehingga metode kolaborasi yang akan dilakukan dapat disesuaikan dengan susunan tim yang terlibat dalam pengembangan perangkat lunak. Pengelompokan perilaku programmer dalam kolaborasi tim pengembang perangkat lunak dilakukan dengan menggunakan analisis kluster dengan melihat lima variabel, yaitu usia, gender, interaksi dan komunikasi, kondisi psikologis, dan pemrosesan informasi. Pengujian diambil dari 35 programmer yang berasal dari industri perangkat lunak yang terdapat di Bandung dengan menyebar kuisioner pada tim pengembang secara online maupun offline. Hasil pengolahan data dengan software SPSS menunjukkan bahwa terdapat tiga kluster perilaku programmer dalam kolaborasi tim pengembangan perangkat lunak. Dengan diketahuinya pengelompokan perilaku programmer diharapkan tim pengembang yang dibentuk dapat menghasilkan perangkat lunak dengan kualitas yang lebih baik
Massive young disks around Herbig Ae stars
Herbig Ae stars (HAe) are the precursors of Vega-type systems and, therefore,
crucial objects in planet formation studies. Thus far, only a few disks
associated with HAe stars have been studied using millimetre interferometers.
Our aim is to determine the dust evolution and the lifetime of the disks
associated with Herbig Ae stars. We imaged the continuum emission at 3 mm and
1.3 mm of the Herbig Ae/Be stars BD+61154, RR Tau, VY Mon and LkHa 198 using
the Plateau de Bure Interferometer (PdBI). These stars are in the upper end of
the stellar mass range of the Herbig Ae stars (stellar mass greater than 3
solar masses). Our measurements were used to complete the Spectral Energy
Distribution (SED). The modelling of the SED, in particular the FIR-mm part,
allow us to determine the masses and dust properties of these disks. We
detected the disks associated with BD+61154, RR Tau and VY Mon with disk masses
of 0.35 Msun, 0.05 Msun and 0.40 Msun respectively. The disk around LkHa 198
was not detected with an upper limit to the disk mass of 0.004 Msun. We
detected, however, the disks associated with the younger stellar objects LkHa
198--IR and LkHa 198-mm that are located in the vicinity of LkHa 198. The
fitting of the mm part of the SED reveal that the grains in the mid-plane of
the disks around BD+61154, RR Tau and VY Mon have sizes of 1--1000 microns.
Therefore, grains have not grown to centimetre sizes in these disks yet. These
massive (M>3 Msun) and young (about 1 Myr) HAe stars are surrounded by massive
(>0.04 Msun) disks with grains of micron-millimetre sizes. Although grain
growth is proceeding in these disks, their evolutionary stage is prior to the
formation of planetesimals. These disks are less evolved than those detected
around T Tauri and Herbig Be stars
Dissecting an intermediate-mass (IM) protostar: Chemical differentiation in IC1396N
We have carried out high-angular resolution (1.4") observations in the
continuum at 3.1mm and in the N2H+ 1-0, CH3CN 5_k-4_k and 13CS 2-1 lines using
the Plateau de Bure Interferometer (PdBI) towards the intermediate mass (IM)
protostar IRAS21391+5802 (IC1396N). In addition, we have merged the PdBI images
with previous BIMA (continuum data at 1.2mm and 3.1mm) and single-dish (N2H+
1-0) data to have a comprehensive description of the region. The combination of
our data with BIMA and 30m data show that the bipolar outflow associated has
completely eroded the initial molecular globule. The 1.2mm and 3.1mm continuum
emissions are extended along the outflow axis tracing the warm walls of the
biconical cavity. Most of the molecular gas, however, is located in an
elongated feature in the direction perpendicular to the outflow. A strong
chemical differentiation is detected across the molecular toroid, with the N2H+
1-0 emission absent in the inner region.This chemical differentiation can be
understood in terms of the different gas kinetic temperature. The
[CH3CN]/[N2H+] ratio increases by 5 orders of magnitude with gas temperature,
for temperatures between 20K and 100K. The CH3CN abundance towards IRAM 2A, the
most massive protostellar core, is similar to that found in hot corinos and
lower than that expected towards IM and high mass hot cores. This could
indicate that IRAM 2A is a low mass or at most Herbig Ae star (IRAM 2A) instead
of the precursor of a massive Be star. Alternatively, the low CH3CN abundance
could also be the consequence of IRAM 2A being a Class 0/I transition object
which has already formed a small photodissociation region (PDR).Comment: accepted A&
Componente del insaponificable del aceite de oliva con polaridad comprendida entre el escualeno y los alcoholes triterpénicos
In the unsaponifiable matter of refined olive oils and, frequently, virgin olive oils of bad quality, a new compound with polarity between those of squalene and triterpenic alcohols was isolated.
Mass spectrometry of this compound and of their hydrogenated and; sililated derivatives, demonstrated that the compound was a long chain alcohol having 426 of molecular weight, polyisoprenic structure similar to that of squalene, and the hydroxyl group attached at the C-2 carbon atom.Se ha estudiado y determinado la estructura de un compuesto, de polaridad comprendida entre el escualeno y los alcoholes triterpénicos, que se encuentra en el insaponificable de los aceites de oliva refinados y en muchas ocasiones en el de los vírgenes, sobre todo en los de baja calidad.
La espectrometría de masas del mismo y, de sus derivados hidrogenado y sililado, ha puesto de manifiesto que se trata de un alcohol triterpénico lineal, de peso molecular 426, con el esqueleto similar al del escualeno y con el grupo hidroxilo en posición 2
Investigation of a relationship between twin-disc wear rates and the slipping contact area on R260 grade rail
Twin-disc tests present some limitations for wheel-rail wear characterization such as the obtained contact patch
and the error for very low creepages. In this work, creepage phenomena are investigated ranging from 0.12% to
2.45%. To improve the fitting of experimental tests with the theoretical adhesion curve, a modification of the
FASTSIM algorithm is proposed. A linear correlation has been found between wear and the slip area including the
non-linear zone. Normalized weight losses and wear rates are similar for all tested creepages. Applying this
relationship, identified for delaminative wear by surface and metallographic characterization, it is possible to
calculate wear for low creepages at wheel-rail contact from twin-disc tests, which should be close to the satu-
ration of the friction coefficient
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