3,351 research outputs found
Case study in failure analysis of accelerated life tests (ALT) on III-V commercial triple-junction concentrator solar cells
In this work the failure analysis carried out in III-V concentrator multijunction solar cells after a temperature accelerated life test is presented. All the failures appeared have been catastrophic since all the solar cells turned into low shunt resistances. A case study in failure analysis based on characterization by optical microscope, SEM, EDX, EQE and XPS is presented in this paper, revealing metal deterioration in the bus bar and fingers as well as cracks in the semiconductor structure beneath or next to the bus bar. In fact, in regions far from the bus bar the semiconductor structure seems not to be damaged. SEM images have dismissed the presence of metal spikes inside the solar cell structure. Therefore, we think that for these particular solar cells, failures appear mainly as a consequence of a deficient electrolytic growth of the front metallization which also results in failures in the semiconductor structure close to the bus bars
Propuesta de optimizaci?n de procesos operativos para incrementar la productividad y reducir el nivel de inventario en la conversi?n vehicular
En el presente trabajo de investigaci?n no experimental se expondr? el an?lisis, diagn?stico y propuesta de soluci?n para optimizar el proceso de preparaci?n veh?cular de una de las empresas con mayor participaci?n de mercado en el sector automotriz en el Per?. El objetivo principal de esta investigaci?n es dise?ar una propuesta de mejora de procesos bajo el marco metodol?gico de Business Process Management (BPM) que busca incrementar la productividad con la cual se tendr?a un impacto directo en el nivel de inventario de veh?culos en el Centro de Distribuci?n. Se realiz? un an?lisis de todos los procesos que forman parte del ?rea de producci?n, el cual incluye la preparaci?n de veh?culos (inspecciones de calidad, conversiones a gas, etc) antes de ser despachados al cliente final (directo o por concesionario). Se estableci? un redise?o de procesos como propuesta de soluci?n que pretende aumentar la productividad. Para comprobar el nivel de impacto de la propuesta de soluci?n se ha empleado el software de simulaci?n Arena. Finalmente, se menciona la variaci?n de los indicadores determinados del modelo actual (AS IS) y despu?s de la simulaci?n obtenida con el dise?o de la propuesta de soluci?n (TO BE) obteniendo un impacto te?rico significativo
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Characterization of 19.9% Efficient CIGS Absorbers: Preprint
This paper documents the properties of the world-record-efficiency CIGS solar cell by a variety of characterization techniques, with an emphasis on identifying near-surface properties associated with the modified processing
A search for TeV gamma-ray emission from SNRs, pulsars and unidentified GeV sources in the Galactic plane in the longitude range between -2 deg and 85 deg
Using the HEGRA system of imaging atmospheric Cherenkov telescopes, one
quarter of the Galactic plane (-2 deg < l < 85 deg) was surveyed for TeV
gamma-ray emission from point sources and moderately extended sources (diameter
<= 0.8 deg). The region covered includes 86 known pulsars (PSR), 63 known
supernova remnants (SNR) and nine GeV sources, representing a significant
fraction of the known populations. No evidence for emission of TeV gamma
radiation was detected, and upper limits range from 0.15 Crab units up to
several Crab units, depending on the observation time and zenith angles
covered. The ensemble sums over selected SNR and pulsar subsamples and over the
GeV-sources yield no indication for emission from these potential sources. The
upper limit for the SNR population is at the level of 6.7% of the Crab flux and
for the pulsar ensemble at the level of 3.6% of the Crab flux.Comment: 10 pages, 5 figures, 4 tables, accepted for publication in A&
A d10 Ag(i) amine-borane σ-complex and comparison with a d8 Rh(i) analogue : Structures on the η1 to η2:η2 continuum
H3B·NMe3 σ-complexes of d8 [(L1)Rh][BArF4] and d10 [(L1)Ag][BArF4] (where L1 = 2,6-bis-[1-(2,6-diisopropylphenylimino)ethyl]pyridine) have been prepared and structurally characterised. Analysis of the molecular and electronic structures reveal important but subtle differences in the nature of the bonding in these σ-complexes, which differ only by the identity of the metal centre and the d-electron count. With Rh the amine-borane binds in an η2:η2 fashion, whereas at Ag the unsymmetrical {Ag⋯H3B·NMe3} unit suggests a structure lying between the η2:η2 and η1 extremes
Search for the standard model Higgs boson in the H to ZZ to 2l 2nu channel in pp collisions at sqrt(s) = 7 TeV
A search for the standard model Higgs boson in the H to ZZ to 2l 2nu decay
channel, where l = e or mu, in pp collisions at a center-of-mass energy of 7
TeV is presented. The data were collected at the LHC, with the CMS detector,
and correspond to an integrated luminosity of 4.6 inverse femtobarns. No
significant excess is observed above the background expectation, and upper
limits are set on the Higgs boson production cross section. The presence of the
standard model Higgs boson with a mass in the 270-440 GeV range is excluded at
95% confidence level.Comment: Submitted to JHE
Search for Doubly-Charged Higgs Boson Production at HERA
A search for the single production of doubly-charged Higgs bosons H^{\pm \pm}
in ep collisions is presented. The signal is searched for via the Higgs decays
into a high mass pair of same charge leptons, one of them being an electron.
The analysis uses up to 118 pb^{-1} of ep data collected by the H1 experiment
at HERA. No evidence for doubly-charged Higgs production is observed and mass
dependent upper limits are derived on the Yukawa couplings h_{el} of the Higgs
boson to an electron-lepton pair. Assuming that the doubly-charged Higgs only
decays into an electron and a muon via a coupling of electromagnetic strength
h_{e \mu} = \sqrt{4 \pi \alpha_{em}} = 0.3, a lower limit of 141 GeV on the
H^{\pm\pm} mass is obtained at the 95% confidence level. For a doubly-charged
Higgs decaying only into an electron and a tau and a coupling h_{e\tau} = 0.3,
masses below 112 GeV are ruled out.Comment: 15 pages, 3 figures, 1 tabl
Measurement of the t t-bar production cross section in the dilepton channel in pp collisions at sqrt(s) = 7 TeV
The t t-bar production cross section (sigma[t t-bar]) is measured in
proton-proton collisions at sqrt(s) = 7 TeV in data collected by the CMS
experiment, corresponding to an integrated luminosity of 2.3 inverse
femtobarns. The measurement is performed in events with two leptons (electrons
or muons) in the final state, at least two jets identified as jets originating
from b quarks, and the presence of an imbalance in transverse momentum. The
measured value of sigma[t t-bar] for a top-quark mass of 172.5 GeV is 161.9 +/-
2.5 (stat.) +5.1/-5.0 (syst.) +/- 3.6(lumi.) pb, consistent with the prediction
of the standard model.Comment: Replaced with published version. Included journal reference and DO
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