904 resultados para GAP FILLING
Resumo:
The new intemationalization of the field of hospitality management has led to increased opportunities in the Russian Federation. At the same time, there are major challenges to be overcome. This article describes what needs to be accomplished to be successful at business in this New World Order.
Resumo:
There is currently a lack of research about the needs of vegetarians, from a practitioner or academic perspective. This paper contributes to filling this research gap, by discussing the needs of vegetarians who dine out and their current difficulties in participating in the dining experience, in the present context. Specifically, it is argued that the typology of vegetarians presented in this paper, based on their motivations to adopt the chosen diet, might prove useful for restaurants in order to understand the vegetarian guest and develop menu items and services that will better cater to their needs. Recommendations for practitioners and future research areas are presented.
Resumo:
The relationship between trade policy and productivity growth is regarded as ambiguous in the literature. This dissertation examines under what condition the relationship would be positive (or negative). Through the use of static and dynamic analysis, we find two conflicting effects (the pro-protection effect and the pro-competitive effect) that cause the relationship to be ambiguous. If there exists a productivity gap between the import-competing and foreign industries, and if the level of protection is low (high), the relationship is positive (negative). We also show that the import-competing firm responds to a change in the protection level by choosing a level of investment in innovation which yields a different rate of productivity growth. The policy implication, therefore, is that a trade-policy maker should set the trade protection at a level which induces the firm to choose the highest rate of productivity growth, and, as a result, leading the firm to close the initial productivity gap in the most efficient way. ^
Resumo:
My thesis examines fine-scale habitat use and movement patterns of age 1 Greenland cod (Gadus macrocephalus ogac) tracked using acoustic telemetry. Recent advances in tracking technologies such as GPS and acoustic telemetry have led to increasingly large and detailed datasets that present new opportunities for researchers to address fine-scale ecological questions regarding animal movement and spatial distribution. There is a growing demand for home range models that will not only work with massive quantities of autocorrelated data, but that can also exploit the added detail inherent in these high-resolution datasets. Most published home range studies use radio-telemetry or satellite data from terrestrial mammals or avian species, and most studies that evaluate the relative performance of home range models use simulated data. In Chapter 2, I used actual field-collected data from age-1 Greenland cod tracked with acoustic telemetry to evaluate the accuracy and precision of six home range models: minimum convex polygons, kernel densities with plug-in bandwidth selection and the reference bandwidth, adaptive local convex hulls, Brownian bridges, and dynamic Brownian bridges. I then applied the most appropriate model to two years (2010-2012) of tracking data collected from 82 tagged Greenland cod tracked in Newman Sound, Newfoundland, Canada, to determine diel and seasonal differences in habitat use and movement patterns (Chapter 3). Little is known of juvenile cod ecology, so resolving these relationships will provide valuable insight into activity patterns, habitat use, and predator-prey dynamics, while filling a knowledge gap regarding the use of space by age 1 Greenland cod in a coastal nursery habitat. By doing so, my thesis demonstrates an appropriate technique for modelling the spatial use of fish from acoustic telemetry data that can be applied to high-resolution, high-frequency tracking datasets collected from mobile organisms in any environment.
Resumo:
Welding is one of the most employed process for joining steel pipes. Although, manual welding is still the most used one, mechanized version and even automatized one have increased its demand. Thus, this work deals with girth welding of API 5L X65 pipes with 8” of nominal diameter and 8.0 mm thickness, beveled with V-30º narrow gap. Torch is moved by a bug carrier (mechanized welding) and further the parameters are controlled as a function of angular position (automatized welding). Welding parameters are presented for filling the joint with two-passes (root and filling/capping passes). Parameters for the root pass were extracted from previous author´s work with weldments carried out in plates, but validated in this work for pipe welding. GMAW processes were assessed with short-circuit metal transfer in both conventional and derivative modes using different technologies (RMD, STT and CMT). After the parameter determination, mechanical testing was performed for welding qualification (uniaxial tension, face and root bending, nick break, Charpy V-notch impact, microhardness and macrograph). The initially obtained results for RMD and CMT were acceptable for all testing and, in a second moment, also for the STT. However, weld beads carried out by using the conventional process failed and revealed the existence of lack of fusion, which required further parametrization. Thus, a Parameter-Variation System for Girth Welding (SVP) was designed and built to allow varying the welding parameters as a function of angular position by using an inclinometer. The parameters were set for each of the three angular positions (flat, vertical downhill and overhead). By using such equipment and approach, the conventional process with parameter variation allowed reducing the welding time for joint accomplishment of the order of 38% for the root pass and 30% for the filling/capping pass.
Resumo:
Peer reviewed
Resumo:
Peer reviewed
Resumo:
Acknowledgments This work was supported by the University of Konstanz, Germany. The first author was supported by a fellowship of the Swiss National Science Foundation (Fellowship P2ZHP1_155103).
Resumo:
This brief paper draws upon part of the findings of a HEA Sponsored evaluation of work conducted in 8 Universities across UK aimed at addressing the attainment gap between BME and White students. Following a grounded theory approach, semi-structured interviews with staff at each of the institutions were analysed and three main themes identified: Organisational Sensitivities: Language: and, Ownership. This paper provides a brief discussion of the issues identifying two areas where positive change is needed in institutional practice. The conclusion highlights the complexities of the underlying issues impacting and shaping the Attainment Gap before reaffirming the need to identify and evaluate which interventions are most likely to be transferable across the Sector so as to address the issues and thus enhance the experiences of all students.
Resumo:
This work looks at the effect on mid-gap interface state defect density estimates for In0.53Ga0.47As semiconductor capacitors when different AC voltage amplitudes are selected for a fixed voltage bias step size (100 mV) during room temperature only electrical characterization. Results are presented for Au/Ni/Al2O3/In0.53Ga0.47As/InP metal–oxide–semiconductor capacitors with (1) n-type and p-type semiconductors, (2) different Al2O3 thicknesses, (3) different In0.53Ga0.47As surface passivation concentrations of ammonium sulphide, and (4) different transfer times to the atomic layer deposition chamber after passivation treatment on the semiconductor surface—thereby demonstrating a cross-section of device characteristics. The authors set out to determine the importance of the AC voltage amplitude selection on the interface state defect density extractions and whether this selection has a combined effect with the oxide capacitance. These capacitors are prototypical of the type of gate oxide material stacks that could form equivalent metal–oxide–semiconductor field-effect transistors beyond the 32 nm technology node. The authors do not attempt to achieve the best scaled equivalent oxide thickness in this work, as our focus is on accurately extracting device properties that will allow the investigation and reduction of interface state defect densities at the high-k/III–V semiconductor interface. The operating voltage for future devices will be reduced, potentially leading to an associated reduction in the AC voltage amplitude, which will force a decrease in the signal-to-noise ratio of electrical responses and could therefore result in less accurate impedance measurements. A concern thus arises regarding the accuracy of the electrical property extractions using such impedance measurements for future devices, particularly in relation to the mid-gap interface state defect density estimated from the conductance method and from the combined high–low frequency capacitance–voltage method. The authors apply a fixed voltage step of 100 mV for all voltage sweep measurements at each AC frequency. Each of these measurements is repeated 15 times for the equidistant AC voltage amplitudes between 10 mV and 150 mV. This provides the desired AC voltage amplitude to step size ratios from 1:10 to 3:2. Our results indicate that, although the selection of the oxide capacitance is important both to the success and accuracy of the extraction method, the mid-gap interface state defect density extractions are not overly sensitive to the AC voltage amplitude employed regardless of what oxide capacitance is used in the extractions, particularly in the range from 50% below the voltage sweep step size to 50% above it. Therefore, the use of larger AC voltage amplitudes in this range to achieve a better signal-to-noise ratio during impedance measurements for future low operating voltage devices will not distort the extracted interface state defect density.
Resumo:
Empirical studies of education programs and systems, by nature, rely upon use of student outcomes that are measurable. Often, these come in the form of test scores. However, in light of growing evidence about the long-run importance of other student skills and behaviors, the time has come for a broader approach to evaluating education. This dissertation undertakes experimental, quasi-experimental, and descriptive analyses to examine social, behavioral, and health-related mechanisms of the educational process. My overarching research question is simply, which inside- and outside-the-classroom features of schools and educational interventions are most beneficial to students in the long term? Furthermore, how can we apply this evidence toward informing policy that could effectively reduce stark social, educational, and economic inequalities?
The first study of three assesses mechanisms by which the Fast Track project, a randomized intervention in the early 1990s for high-risk children in four communities (Durham, NC; Nashville, TN; rural PA; and Seattle, WA), reduced delinquency, arrests, and health and mental health service utilization in adolescence through young adulthood (ages 12-20). A decomposition of treatment effects indicates that about a third of Fast Track’s impact on later crime outcomes can be accounted for by improvements in social and self-regulation skills during childhood (ages 6-11), such as prosocial behavior, emotion regulation and problem solving. These skills proved less valuable for the prevention of mental and physical health problems.
The second study contributes new evidence on how non-instructional investments – such as increased spending on school social workers, guidance counselors, and health services – affect multiple aspects of student performance and well-being. Merging several administrative data sources spanning the 1996-2013 school years in North Carolina, I use an instrumental variables approach to estimate the extent to which local expenditure shifts affect students’ academic and behavioral outcomes. My findings indicate that exogenous increases in spending on non-instructional services not only reduce student absenteeism and disciplinary problems (important predictors of long-term outcomes) but also significantly raise student achievement, in similar magnitude to corresponding increases in instructional spending. Furthermore, subgroup analyses suggest that investments in student support personnel such as social workers, health services, and guidance counselors, in schools with concentrated low-income student populations could go a long way toward closing socioeconomic achievement gaps.
The third study examines individual pathways that lead to high school graduation or dropout. It employs a variety of machine learning techniques, including decision trees, random forests with bagging and boosting, and support vector machines, to predict student dropout using longitudinal administrative data from North Carolina. I consider a large set of predictor measures from grades three through eight including academic achievement, behavioral indicators, and background characteristics. My findings indicate that the most important predictors include eighth grade absences, math scores, and age-for-grade as well as early reading scores. Support vector classification (with a high cost parameter and low gamma parameter) predicts high school dropout with the highest overall validity in the testing dataset at 90.1 percent followed by decision trees with boosting and interaction terms at 89.5 percent.
Resumo:
We studied the optical properties of a strain-induced direct-band-gap Ge quantum well embedded in InGaAs. We showed that the band offsets depend on the electronegativity of the layer in contact with Ge, leading to different types of optical transitions in the heterostructure. When group-V atoms compose the interfaces, only electrons are confined in Ge, whereas both carriers are confined when the interface consists of group-III atoms. The different carrier confinement results in different emission dynamics behavior. This study provides a solution to obtain efficient light emission from Ge.
Resumo:
Terrestrial ecosystems, occupying more than 25% of the Earth's surface, can serve as
`biological valves' in regulating the anthropogenic emissions of atmospheric aerosol
particles and greenhouse gases (GHGs) as responses to their surrounding environments.
While the signicance of quantifying the exchange rates of GHGs and atmospheric
aerosol particles between the terrestrial biosphere and the atmosphere is
hardly questioned in many scientic elds, the progress in improving model predictability,
data interpretation or the combination of the two remains impeded by
the lack of precise framework elucidating their dynamic transport processes over a
wide range of spatiotemporal scales. The diculty in developing prognostic modeling
tools to quantify the source or sink strength of these atmospheric substances
can be further magnied by the fact that the climate system is also sensitive to the
feedback from terrestrial ecosystems forming the so-called `feedback cycle'. Hence,
the emergent need is to reduce uncertainties when assessing this complex and dynamic
feedback cycle that is necessary to support the decisions of mitigation and
adaptation policies associated with human activities (e.g., anthropogenic emission
controls and land use managements) under current and future climate regimes.
With the goal to improve the predictions for the biosphere-atmosphere exchange
of biologically active gases and atmospheric aerosol particles, the main focus of this
dissertation is on revising and up-scaling the biotic and abiotic transport processes
from leaf to canopy scales. The validity of previous modeling studies in determining
iv
the exchange rate of gases and particles is evaluated with detailed descriptions of their
limitations. Mechanistic-based modeling approaches along with empirical studies
across dierent scales are employed to rene the mathematical descriptions of surface
conductance responsible for gas and particle exchanges as commonly adopted by all
operational models. Specically, how variation in horizontal leaf area density within
the vegetated medium, leaf size and leaf microroughness impact the aerodynamic attributes
and thereby the ultrane particle collection eciency at the leaf/branch scale
is explored using wind tunnel experiments with interpretations by a porous media
model and a scaling analysis. A multi-layered and size-resolved second-order closure
model combined with particle
uxes and concentration measurements within and
above a forest is used to explore the particle transport processes within the canopy
sub-layer and the partitioning of particle deposition onto canopy medium and forest
oor. For gases, a modeling framework accounting for the leaf-level boundary layer
eects on the stomatal pathway for gas exchange is proposed and combined with sap
ux measurements in a wind tunnel to assess how leaf-level transpiration varies with
increasing wind speed. How exogenous environmental conditions and endogenous
soil-root-stem-leaf hydraulic and eco-physiological properties impact the above- and
below-ground water dynamics in the soil-plant system and shape plant responses
to droughts is assessed by a porous media model that accommodates the transient
water
ow within the plant vascular system and is coupled with the aforementioned
leaf-level gas exchange model and soil-root interaction model. It should be noted
that tackling all aspects of potential issues causing uncertainties in forecasting the
feedback cycle between terrestrial ecosystem and the climate is unrealistic in a single
dissertation but further research questions and opportunities based on the foundation
derived from this dissertation are also brie
y discussed.
Resumo:
Controlling the growth mechanism for nano-structures is one of the most critical topics in material science. In the past 10 years there has been intensive research worldwide in IIIN based nanowires for its many unique photonic and electrical properties at this scale. There are several advantages to nanostructuring III-N materials, including increased light extraction, increased device efficiency, reduction of efficiency droop, and reduction in crystallographic defect density. High defect densities that normally plague III-N materials and reduce the device efficiency are not an issue for nano-structured devices such as LEDs, due to the effective strain relaxation. Additionally regions of the light spectrum such as green and yellow, once found difficult to achieve in bulk planar LEDs, can be produced by manipulating the confinement and crystal facet growth directions of the active regions. A cheap and easily repeatable self-assembly nano-patterning technique at wafer scale was designed during this thesis for top down production of III-N nanowires. Through annealing under ammonia and N2 gas flow, the first reported dislocation defect bending was observed in III-N nanorods by in-situ transmission electron microscopy heating. By growing on these etched top down nanorods as a template, ultra-dense nanowires with apex tipped semi-polar tops were produced. The uniform spacing of 5nm between each wire is the highest reported space-filling factor at 98%. Finally by using these ultra-dense nanorods bridging the green gap of the light spectrum was possible, producing the first reported red, yellow, green light emission from a single nano-tip.