422 Matching Results

Search Results

Advanced search parameters have been applied.

Effects of Self-Monitoring and Monetary Reward on Fluid Adherence among Adult Hemodialysis Patients

Description: The effects of a monetary reward and self-monitoring on reducing interdialytic weight gain (IWG) were compared for 6 hemodialysis patients in an outpatient setting. A single-subject experimental design (A-B-BC-B-BC) was used to examine each variable individually and in combination, with alternating phases to control for possible sequencing effects. Monetary reward (50 cents - $3) was administered in a titrated manner according to standardized criteria, ranging from 3 % and 4% of patients' dry weight on weekdays and weekends, respectively, to 3.5% and 4.5% for weekdays and weekends. Self-monitoring involved recording daily fluid and diet intake. Results indicated that by the end of the treatment program, the 6 participants averaged a 14% reduction in weekday IWG and a 15.45% reduction in weekend IWG; however, due to significant variability, it cannot be concluded that the reductions are treatment effects. Four out of 6 participants reduced their average IWG for both weekends and weekdays by .75 kg (1.65 lb.). The average weekend reduction for these 4 participants was .85 kg (1.87 lbs.) while the average weekday reduction was .65 kg (1.43 lb.). All 6 participants showed reductions in weekday IWG that averaged .53 kg (1.17 lb.). However, only 2 participants demonstrated IWG reductions that could be attributable to either of the 2 treatment variables. The standardized dry weight criterion for assessing fluid adherence may have posed excessively stringent demands on participants, as only 1 of the 6 participants actually met the criterion. Future research should address the role of nonspecific treatment factors, as well as patient characteristics and responsivity to particular treatment components in an effort to identify those factors responsible for behavior change in this population.
Date: December 2000
Creator: Sonnier, Bridget L.
Partner: UNT Libraries

A Comparison of Two Methods of Listening and Reading Training in an Eighth Grade Language Arts Program

Description: The purpose of this study was to compare the effects of two methods of listening and reading instruction when used in the language arts programs at the eighth-grade level as related to listening, reading, study skills, and English achievement. Two groups were studied; one was an experimental group receiving programed material present by the Listen and Read Program and a control group receiving instruction through the regular classroom program.
Date: August 1963
Creator: Kraner, Robert Eugene, 1933-
Partner: UNT Libraries

Operation of an Optical Klystron with Small Dispersion

Description: The IR Upgrade design at Jefferson Lab uses an optical klystron in order to enhance the flexibility of the free-electron laser system and to match the efficiency to the energy recovery lattice. Most optical klystrons operate with a strong dispersion section [1]. The IR upgrade design requires operation with a dispersion of only a few periods in order to allow the full range of efficiency of the FEL to be explored. This paper will study the details of an optical klystron in this small dispersion limit. The peak gain vs. dispersion section strength has an oscillatory behavior, suggesting that the dispersion section strength should be adjusted in unit steps rather than continuously. The gain vs. the effective number of periods is calculated and found to be, on average, in good agreement with theory. Finally, some comments on the relative merits of using an optical klystron or a uniform wiggler in a high power FEL will be presented.
Date: September 1, 2002
Creator: Benson, Stephen V.
Partner: UNT Libraries Government Documents Department

Information Gain Based Dimensionality Selection for Classifying Text Documents

Description: Selecting the optimal dimensions for various knowledge extraction applications is an essential component of data mining. Dimensionality selection techniques are utilized in classification applications to increase the classification accuracy and reduce the computational complexity. In text classification, where the dimensionality of the dataset is extremely high, dimensionality selection is even more important. This paper presents a novel, genetic algorithm based methodology, for dimensionality selection in text mining applications that utilizes information gain. The presented methodology uses information gain of each dimension to change the mutation probability of chromosomes dynamically. Since the information gain is calculated a priori, the computational complexity is not affected. The presented method was tested on a specific text classification problem and compared with conventional genetic algorithm based dimensionality selection. The results show an improvement of 3% in the true positives and 1.6% in the true negatives over conventional dimensionality selection methods.
Date: June 1, 2013
Creator: Wijayasekara, Dumidu; Manic, Milos & McQueen, Miles
Partner: UNT Libraries Government Documents Department

Pick-up ion energization at the termination shock

Description: One-dimensional hybrid simulations are used to investigate how pickup ions are energized at the perpendicular termination shock. Contrary to previous models based on pickup ion energy gain by repeated crossings of the shock front (shock surfing) or due to a reforming shock front, the present simulations show that pickup ion energy gain involves a gyro-phasedependent interaction with the inhomogeneous motional electric field at the shock. The process operates at all relative concentrations of pickup ion density.
Date: January 1, 2009
Creator: Gary, S Peter; Winske, Dan; Wu, Pin & Schwadron, N A
Partner: UNT Libraries Government Documents Department

Measuring solar reflectance Part II: Review of practical methods

Description: A companion article explored how solar reflectance varies with surface orientation and solar position, and found that clear sky air mass 1 global horizontal (AM1GH) solar reflectance is a preferred quantity for estimating solar heat gain. In this study we show that AM1GH solar reflectance R{sub g,0} can be accurately measured with a pyranometer, a solar spectrophotometer, or an updated edition of the Solar Spectrum Reflectometer (version 6). Of primary concern are errors that result from variations in the spectral and angular distributions of incident sunlight. Neglecting shadow, background and instrument errors, the conventional pyranometer technique can measure R{sub g,0} to within 0.01 for surface slopes up to 5:12 [23{sup o}], and to within 0.02 for surface slopes up to 12:12 [45{sup o}]. An alternative pyranometer method minimizes shadow errors and can be used to measure R{sub g,0} of a surface as small as 1 m in diameter. The accuracy with which it can measure R{sub g,0} is otherwise comparable to that of the conventional pyranometer technique. A solar spectrophotometer can be used to determine R*{sub g,0}, a solar reflectance computed by averaging solar spectral reflectance weighted with AM1GH solar spectral irradiance. Neglecting instrument errors, R*{sub g,0} matches R{sub g,0} to within 0.006. The air mass 1.5 solar reflectance measured with version 5 of the Solar Spectrum Reflectometer can differ from R*{sub g,0} by as much as 0.08, but the AM1GH output of version 6 of this instrument matches R*{sub g,0} to within about 0.01.
Date: May 14, 2010
Creator: Levinson, Ronnen; Akbari, Hashem & Berdahl, Paul
Partner: UNT Libraries Government Documents Department

Analysis of Laser Acceleration in a Semi-infinite Space as Inverse Transition Radiation

Description: This article calculates the energy gain of a single relativistic electron interacting with a single gaussian beam that is terminated by a metallic reflector at normal incidence by two different methods: the electric field integral along the path of the electron, and the overlap integral of the transition radiation pattern from the conductive foil with the laser beam. It is shown that for this instance the two calculation methods yield the same expression for the expected energy change of the electron.
Date: October 26, 2005
Creator: Plettner, T.
Partner: UNT Libraries Government Documents Department

Theory of gain in group-III nitride lasers

Description: A microscopic theory of gain in a group-III nitride quantum well laser is presented. The approach, which treats carrier correlations at the level of quantum kinetic theory, gives a consistent account of plasma and excitonic effects in an inhomogeneously broadened system.
Date: June 1, 1997
Creator: Chow, W.W.; Wright, A.F. & Girndt, A.
Partner: UNT Libraries Government Documents Department

Development of an ultra cold neutron source at MLNSC

Description: Ultra Cold Neutrons (UCN) can be produced at spallation sources using a variety of techniques. To date the technique used has been to Bragg scatter and Doppler shift cold neutrons into UCN from a moving crystal. This is particularly applicable to short-pulse spallation sources. We are presently constructing a UCN source at LANSCE using this method. In addition, large gains in UCN density should be possible using cryogenic UCN sources. Research is under way at Gatchina to demonstrate technical feasibility of a frozen deuterium source. If successful, a source of this type could be implemented at future spallation sources, such as the long pulse source being planned at Los Alamos, with a UCN density that may be two orders of magnitude higher than that presently available at reactors.
Date: September 1, 1996
Creator: Seestrom, S.J.; Bowles, T.J.; Hill, R.; Greene, G.L. & Morris, C.L.
Partner: UNT Libraries Government Documents Department

Klystron beam-bunching lecture

Description: Electron beam current modulation in a klystron is the key phenomenon that accounts for klystron gain and rf power generation. Current modulation results from the beams` interaction with the rf fields in a cavity, and in turn is responsible for driving modulation in the next rf cavity. To understand the impact of the current modulation in a klystron, we have to understand both the mechanism leading to the generation of the current modulation and the interaction of a current-modulated electron beam with an rf cavity. The cavity interaction is subtle, because the fields in the cavity modify the bunching of the beam within the cavity itself (usually very dramatically). We will establish the necessary formalism to understand klystron bunching phenomena which can be used to describe rf accelerator cavity/beam interactions. This formalism is strictly steady-state; no transient behavior will be considered. In particular, we will discuss the following: general description of klystron operation; beam harmonic current; how beam velocity modulation induced by an rf cavity leads to current modulation in both the ballistic and space-charge dominated regimes; use of Ramo`s theorem to define the power transfer between a bunched electron beam and the cavity; general cavity model with external coupling (including an external generator if needed), used to describe the input cavity, idler cavities, and the output cavity, including the definition of beam loaded-cavity impedance. Although all these are conceptually straight-forward, they represent a fair amount of physics, and to derive some elements of the formalism from first principles requires excessive steps. Our approach will be to present a self-consistent set of equations to provide a mechanism that leads to a quantifiable description of klystron behavior; derivations for moderately complex formulas will be outlined, and a relatively complex derivation of the self-consistent set of equations can be found in the ...
Date: October 1, 1996
Creator: Carlsten, B.
Partner: UNT Libraries Government Documents Department