5,134 research outputs found
Economics and operation of alternating-current and direct-current systems; a comparative study
This item was digitized by the Internet Archive. Thesis (M.B.A.)--Boston Universityhttps://archive.org/details/economicsoperati00lun
Estimation of the Composition of Three Component Liquid Mixtures
While carrying out research on the extraction of oil from soybeans using mixtures of various solvents, it was quite often necessary to know the composition of a mixture of liquids containing three components. A search of the literature for ways of obtaining the composition of such mixtures by the use of physical constants revealed a very convenient method employing a combination of density and refractive index. Before this method can be used, however, solutions covering the entire ternary system must be made up accurately, their refractive indices and densities taken and plotted in such a manner that the composition of solutions of constant refractive index and solutions of constant specific gravity can be determined. Finally a triangular diagram must be constructed showing the lines of constant refractive index and constant specific gravity as related to the composition (1, 2)
Simple Vortex States in Films of Type-I Ginzburg-Landau Superconductor
Sufficiently thin films of type-I superconductor in a perpendicular magnetic
field exhibit a triangular vortex lattice, while thick films develop an
intermediate state. To elucidate what happens between these two regimes,
precise numerical calculations have been made within Ginzburg-Landau theory at
and 0.25 for a variety of vortex lattice structures with one flux
quantum per unit cell. The phase diagram in the space of mean induction and
film thickness includes a narrow wedge in which a square lattice is stable,
surrounded by the domain of stability of the triangular lattice at thinner
films/lower fields and, on the other side, rectangular lattices with
continuously varying aspect ratio. The vortex lattice has an anomalously small
shear modulus within and close to the square lattice phase.Comment: 21 pages, 6 figure
Solvent Extraction of Soybean Oil by Mixtures of Trichloroethylene and Ethyl Alcohol
Various solvents have been used for extracting vegetable oils such as soybean oil. Certain petroleum fractions are widely used commercially. They have the advantage of low cost, but the disadvantage of being highly flammable and their vapors being explosive in a wide range of mixture with air. Certain of the chlorinated hydrocarbons are excellent solvents but have had only limited use because of high cost and lack of suitable processing methods and equipment. Process and equipment for the use of trichloroethylene, one of these chlorinated hydrocarbons, have been developed in Engineering Experiment Station Laboratory, Iowa State College. Trichloroethylene is a colorless liquid boiling at 86.7°C. with a specific gravity of 1.46 at 25°C. It is an excellent solvent for soybean oil, is non-flammable, and of a toxicity of the order of the usual petroleum fractions. Various alcohols such as ethanol and methanol have had limited application
Capacitated Center Problems with Two-Sided Bounds and Outliers
In recent years, the capacitated center problems have attracted a lot of
research interest. Given a set of vertices , we want to find a subset of
vertices , called centers, such that the maximum cluster radius is
minimized. Moreover, each center in should satisfy some capacity
constraint, which could be an upper or lower bound on the number of vertices it
can serve. Capacitated -center problems with one-sided bounds (upper or
lower) have been well studied in previous work, and a constant factor
approximation was obtained.
We are the first to study the capacitated center problem with both capacity
lower and upper bounds (with or without outliers). We assume each vertex has a
uniform lower bound and a non-uniform upper bound. For the case of opening
exactly centers, we note that a generalization of a recent LP approach can
achieve constant factor approximation algorithms for our problems. Our main
contribution is a simple combinatorial algorithm for the case where there is no
cardinality constraint on the number of open centers. Our combinatorial
algorithm is simpler and achieves better constant approximation factor compared
to the LP approach
The nonlinear time-dependent response of isotactic polypropylene
Tensile creep tests, tensile relaxation tests and a tensile test with a
constant rate of strain are performed on injection-molded isotactic
polypropylene at room temperature in the vicinity of the yield point. A
constitutive model is derived for the time-dependent behavior of
semi-crystalline polymers. A polymer is treated as an equivalent network of
chains bridged by permanent junctions. The network is modelled as an ensemble
of passive meso-regions (with affine nodes) and active meso-domains (where
junctions slip with respect to their positions in the bulk medium with various
rates). The distribution of activation energies for sliding in active
meso-regions is described by a random energy model. Adjustable parameters in
the stress--strain relations are found by fitting experimental data. It is
demonstrated that the concentration of active meso-domains monotonically grows
with strain, whereas the average potential energy for sliding of junctions and
the standard deviation of activation energies suffer substantial drops at the
yield point. With reference to the concept of dual population of crystalline
lamellae, these changes in material parameters are attributed to transition
from breakage of subsidiary (thin) lamellae in the sub-yield region to
fragmentation of primary (thick) lamellae in the post-yield region of
deformation.Comment: 29 pages, 12 figure
Predictors of growth kinetics and outcomes in small renal masses (SRM ≤4 cm in size):Tayside Active Surveillance Cohort (TASC) Study
Objective: To determine outcomes of small renal masses (≤4 cm) on active surveillance and explore factors which can influence their growth.Patients and Methods: Two hundred twenty six patients between January 2007 and December 2014 were analysed using cross-linked methodology of healthcare data and independent review. Cancer specific and non-specific survival were the primary outcomes. Growth kinetics, factors influencing growth and need for interventions were secondary outcomes.Results: 101 (64.4%) solid and 4 (5.9%) cystic SRMs showed growth. 43 (19.02%) of SRMs required treatment interventions. Seven patients (7/158; 4.4%) died due to renal cancer at a median follow-up of 21.7 (SD 10.6, min 6-42) months, all in solid category. Independent review of serial radiological imaging of these seven cases showed two patients had subtle metastatic disease at the initial presentation, and 5 of the 7 did not adhere to recommended imaging regime. 33 (33/158; 20.8%) died due to other causes including non-renal cancers (14/158; 8.8%). Multivariate analyses showed that lower eGFR at baseline, co-morbidities and tumour location were independently associated with growth in size.Conclusions: A higher cancer-specific mortality was seen in the present study compared to the reported literature. Independent critical review of imaging of cases with poor outcome underscored the importance of adherence to a robust protocol including follow up. Comorbid conditions had a significant impact on growth and overall survival of patients with SRMs.</p
The Relationship between Therapeutic Alliance and Service User Satisfaction in Mental Health Inpatient Wards and Crisis House Alternatives: A Cross-Sectional Study
Background
Poor service user experiences are often reported on mental health inpatient wards. Crisis houses are an alternative, but evidence is limited. This paper investigates therapeutic alliances in acute wards and crisis houses, exploring how far stronger therapeutic alliance may underlie greater client satisfaction in crisis houses.
Methods and Findings
Mixed methods were used. In the quantitative component, 108 crisis house and 247 acute ward service users responded to measures of satisfaction, therapeutic relationships, informal peer support, recovery and negative events experienced during the admission. Linear regressions were conducted to estimate the association between service setting and measures, and to model the factors associated with satisfaction. Qualitative interviews exploring therapeutic alliances were conducted with service users and staff in each setting and analysed thematically.
Results
We found that therapeutic alliances, service user satisfaction and informal peer support were greater in crisis houses than on acute wards, whilst self-rated recovery and numbers of negative events were lower. Adjusted multivariable analyses suggest that therapeutic relationships, informal peer support and negative experiences related to staff may be important factors in accounting for greater satisfaction in crisis houses. Qualitative results suggest factors that influence therapeutic alliances include service user perceptions of basic human qualities such as kindness and empathy in staff and, at service level, the extent of loss of liberty and autonomy.
Conclusions and Implications
We found that service users experience better therapeutic relationships and higher satisfaction in crisis houses compared to acute wards, although we cannot exclude the possibility that differences in service user characteristics contribute to this. This finding provides some support for the expansion of crisis house provision. Further research is needed to investigate why acute ward service users experience a lack of compassion and humanity from ward staff and how this could be changed
Theory and design of InGaAsBi mid-infrared semiconductor lasers: type-I quantum wells for emission beyond 3 m on InP substrates
We present a theoretical analysis and optimisation of the properties and
performance of mid-infrared semiconductor lasers based on the dilute bismide
alloy InGaAsBi, grown on conventional (001) InP
substrates. The ability to independently vary the epitaxial strain and emission
wavelength in this quaternary alloy provides significant scope for band
structure engineering. Our calculations demonstrate that structures based on
compressively strained InGaAsBi quantum wells (QWs)
can readily achieve emission wavelengths in the 3 -- 5 m range, and that
these QWs have large type-I band offsets. As such, these structures have the
potential to overcome a number of limitations commonly associated with this
application-rich but technologically challenging wavelength range. By
considering structures having (i) fixed QW thickness and variable strain, and
(ii) fixed strain and variable QW thickness, we quantify key trends in the
properties and performance as functions of the alloy composition, structural
properties, and emission wavelength, and on this basis identify routes towards
the realisation of optimised devices for practical applications. Our analysis
suggests that simple laser structures -- incorporating
InGaAsBi QWs and unstrained ternary
InGaAs barriers -- which are compatible with established
epitaxial growth, provide a route to realising InP-based mid-infrared diode
lasers.Comment: Submitted versio
- …