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This study was an investigation into the effects of repetition on a listening comprehension test for second language learners. Repetition has been previously examined in a cursory way, usually as a secondary question to a primary treatment. Additionally, the method of repetition was limited to one way and to one treatment condition; therefore, it is not clear how different methods of repetition have influenced the results. To date, there are few studies on the influence of repetition on listening comprehension tests in English as a Foreign Language (EFL) situations. The purpose of this study was to examine four methods of repetition on listening comprehension with Japanese learners of English. In addition, the effect of repetition method on proficiency level, question type, and question difficulty was also examined. The participants were 2,041 students attending a private university in Tokyo, Japan. They experienced five conditions: non-repetition, immediate repetition, delayed repetition theory, delayed repetition A, and delayed repetition B. The participants listened to 12 passages under one of the five randomized conditions, and then answered five questions in one of three question types: true-false, multiple-choice, or short-answer. Additionally, the test included questions intended to measure two levels of comprehension, specific details and inference. Finally, the participants were divided into two listening proficiency levels based on the Global Test of English Communication. The results indicated that the type of repetition had an effect on listening comprehension. Overall, both proficiency groups in the delayed repetition conditions had higher comprehension scores. In addition, the delayed repetition conditions were better for all question types (true-false, multiple-choice, and short-answer) with each proficiency group responding equally well. Finally, the delayed repetition conditions reduced the range of question difficulty, especially when participants were allowed to preview questions. The theoretical implications of this study are that comprehension scores are affected by the strength of memory trace, focus of attention, and activated memory. The pedagogical implications are that delayed repetition is useful in the classroom because it not only improves comprehension scores on tests, but also reinforces material learned across several activities, and incorporates recycling into the curriculum design. The results will help test-makers consider new avenues to testing, teachers to incorporate delayed repetition into classroom activities, and administrators to incorporate delayed repetition into the curriculum. / CITE/Language Arts

The spacing effect is one of the most remarkable and reliable phenomenon to emerge from the experimental research in learning and memory. In fact, over the past 100 years it has been demonstrated with a wide range of learning paradigms, materials, and participants. Not surprisingly, several researchers have outlined suggestions for its application to the classroom (e.g., Demspter, 1988; Rohrer & Pashler, 2007). However, while it is important that educational practices are grounded in research, it is equally important that researchers consider established teaching practices when formulating experiments. This point is especially pertinent to the research on the spacing effect because despite its 100 year history, there are relatively few ecologically valid demonstrations of its effect. The primary purpose of this study was to examine the congruence between teaching practices with respect to repetition and the timing of repetitions, and research methodologies used in studies of the spacing effect. Specifically, the research objectives of this study were to investigate teachers': 1) self-reported use and opinion of repetition as a teaching strategy, 2) self-reported preferences and beliefs regarding massed versus distributed methods of teaching, and 3) self-reported beliefs about the ecological validity of massed versus distributed teaching methods. Data for this study were gathered from 303 US teachers who completed a self-report web-based survey. While results revealed that teachers reported to use repetition in their classrooms, reported reasons for using repetition varied by grade level taught. With respect to the timing of repetitions, results indicated that teachers are knowledgeable of the benefits to memory of spaced repetitions. Interestingly, principles of the spacing effect were often reported as impractical to use in the classroom, and massed methods of teaching were overwhelmingly viewed as more ecologically valid. Results suggest the that breakdown between the research on the spacing effect and educational practice may not stem from lack of knowledge on part of the teachers, but rather from a lack of congruence between teaching practices and research methodologies. Important implications for researchers seeking to conduct ecologically valid demonstrations of the spacing effect are discussed. / Educational Psychology

Yes / Laboratory experiments are presented to investigate the effect of different piggyback pipeline configurations on the morphology of local scour under wave conditions. Scour depth and width around the pipelines under regular and irregular waves are measured and analyzed for a range of pipeline and wave conditions; such as the spacing between two pipes (G), gap between the main pipe and seabed (e), pipe diameter (D), wave height (H) and period (T). Experimental results reveal that both the scour depth and width around piggyback pipeline is much larger than those around single pipe under the same wave conditions. Scour depth increases with the increase of the Keulegan-Carpenter (KC) number and decreases with increase of G and e. When e exceeds 0.5D, scour depth tends to approach 0.When spacing G is greater than 0.4D, the destabilization from small pipe to large one is greatly reduced, resulting in scour depth around piggyback pipeline being close to that around single pipe. Similar to scour depth, scour width broadens with the increase of KC number increasing and decreases with the increase of G. Experiments also show that the effect of e on scour depth is greater than that of G under the same test conditions, while their impact on scour width is opposite. Furthermore, scour width under irregular waves is extended slightly compared with regular wave for otherwise the identical conditions. / National Natural Science Foundation (No. 51279189).

This study investigates the wake shading effect in wind farms, focusing on turbine spacing, horizontal rotor tilt (yaw angle), wind speed, and power production. With the global population increasing, the demand for energy continues to rise, emphasizing the importance of renewable energy sources like wind power. In wind farms, where multiple turbines operate together, the wake effect resulting from one turbine's influence on wind flow for others significantly impacts their power production. This research is focused around Jädraås Wind Power Park in Sweden, using a scaled model of a section of this park in a controlled environment to conduct a detailed analysis. Utilizing both experimental setups in a wind tunnel and numerical simulations for visualization, the study explores the dynamics of wake interactions among turbines and proposes to mitigate their adverse effects.Through the experiments conducted in the wind tunnel, the results demonstrate significant wakeinduced power losses at downstream turbines. The yaw adjustment mechanism of the upstream turbine is used so as to see how it has affected the power output of downstream turbine. The results also indicate significant reductions in power production as a function of turbine spacing. Specifically, the maximum reduction in power output, influenced by the presence of two upstream turbines, occurred at closer spacings between them: a decrease of 66% at 2.08D (2.08 Rotor Diameters between the downstream and the nearest upstream turbine) and 45% at 4.15D. Conversely, at broader spacings of 7.29D and 8.3D, the reductions were more moderate, a decrease of 28% and 18%, respectively. These findings underscore the critical influence of spatial arrangement on the wake-induced power losses within wind farms.Through an investigation of two purposely positioned upstream and downstream turbines at 4D meter of spacing, the optimal yaw angle for maximum combined power generation has been predicted using sinusoidal fitting, the results indicated that at yaw angle range of ±11° of theupstream turbine rotor, a maximum combined power output has been observed. Hence, a sophisticated optimization mechanism should be employed in an operating wind farm so as tolower wake effects.

This thesis presents the results of testing to determine if spacing between bolts in a multiple-bolt, single-shear connection subjected to natural hazard loading affects seven strength and serviceability parameters: maximum load, failure load, E.E.P. yield load, 5% offset load, elastic stiffness, E.E.P. energy, and ductility ratio. This research also determines if a statistical difference exists between previously published research for 4D spacing as compared to results produced by this research for five alternate spacings: 8D, 7D, 6D, 5D, and 3D. Finally, this research determines which of the spacings examined: 8D, 7D, 6D, 5D, 3D; produced the most optimal results for each examined strength and serviceability parameter where optimization is based on economy and performance. Three connection configurations with five different spacings between bolts were subjected to reverse cyclic loading for a total of one hundred and fifty tests. The reverse cyclic protocol was based on recommendations by the Consortium of Universities for Research in Earthquake Engineering (CUREE) for testing woodframe structures. The same connection configurations were also subjected to monotonic loading for an additional forty-five tests. Results of this research can be used to evaluate the current design recommendation presented in the National Design Specification (NDS) for Wood Construction (AF&PA, 2001) of spacing bolts at four times the bolt diameter (4D) to determine if a different spacing should be recommended for natural hazard loading conditions. / Master of Science

The United States share of the exported flue-cured tobacco market has decreased over the last decade as other countries have increased production of improved quality tobacco. Such tobacco is available at a substantially lower price than U. S. tobacco and thus desirable for the manufacture of less expensive discount cigarettes. Although world consumption of American style cigarettes is increasing, demand is not sufficient to maintain current production levels of premium quality U. S. flue-cured tobacco. Production systems that increase yields of suitable quality tobacco for discount cigarette manufacture without increasing production costs would allow tobacco to be offered competitively on the world market while maintaining current income. A study of ten management systems was conducted evaluating the influence of plant spacing, topping height, and harvest method on yield and quality of flue-cured tobacco. Leaf populations of 538,000/ha harvested once-over resulted in a 6.5%, 11.0%, 6.0%, and 13.5% increase in yield, value, price, and grade index, respectively, compared to the standard treatment. An expert panel showed no preference among systems and judged all systems acceptable in quality. A study conducted as a randomized complete block in a split plot arrangement evaluated the influence of row spacing and plant spacing on the yield and quality of flue-cured tobacco harvested once-over. Yield, value, and grade index increased while price per kg was unchanged as plant population increased. Flue-cured tobacco harvested in a single harvest produced cured leaf of acceptable quality; however, increased leaf populations are required to maintain acceptable yields. / Master of Science

Wake vortices pose a threat to a following aircraft, because they can induce a roll and compromise the safety of everyone on board. Caused by a difference in pressure between the upper and the lower part of the wings, these invisible flows of air are a major hazard and have to be avoided by separating the aircraft at considerable distances. One of the known constraints in airport capacity for both departure and arrival operations is the large headway resulting from the wake spacing separation criteria. Reducing wake vortex separations to a safe level between successive aircraft can increase capacity in the National Airspace System (NAS) with corresponding savings in delay times. One of the main goals of the Wake Encounter Model (WEM) described in this thesis is to assess the outcome from future reduced separation criteria in the NAS. The model has been used to test probable encounters in today's operations, and can also be used to test NextGen scenarios, such as Close Parallel Approaches and reduced in-trail separation flights. This thesis presents model enhancements to account for aircraft turning maneuvers, giving the wake a more realistic shape. Three major airspaces, New York, Southern California and Atlanta, were analyzed using the original and the enhanced WEM to determine if the enhanced model better represents the conditions in today's operations. Additionally, some analysis on the wake lateral travel for closely spaced runways is presented in this thesis. Finally, some extension tools for post -analysis, such as animation tool and various graphs depicting the interactions between wake pairs were developed. / Master of Science

High resolution earth observation from geostationary orbit offers several advantages compared to traditional low earth orbit systems. Among the advantages are decreased time to scan the visible geo-disk and the ability to stare at a particular event. The following work is concerned with the design of a reflector antenna configuration for passive remote sensing and suitable for use on a geostationary platform; however, the resultant configuration is not limited to this application. The specific goal is the design of a reflector antenna configuration capable of precision beam scanning over a range of several degrees in all directions while minimizing vibration and inertial torque such as to have minimal effect on the other instruments sharing the platform. Desirable characteristics of such a reflector configuration are: a stationary feed consisting of a single element or a small array; simple reflector motions; and high primary aperture utilization for all scan directions (high illumination efficiency). This dissertation documents the development of a novel tri-reflector antenna configuration which addresses the design goals outlined above. The reflector configuration has been named the conjugate tri-reflector. The conjugate tri-reflector consists of a parabolic primary reflector an elliptical secondary reflector and a shaped tertiary reflector. Beam scanning is performed entirely by motion of the relatively small tertiary reflector. The proposed reflector configuration offers substantial improvement in scan performance compared to that achieved by feed displacement with a prime focus parabolic reflector and has a much higher aperture efficiency than comparable spherical reflector configurations. / Ph. D.

Mathematical methods of assessing the spatial autocorrelation associated with individual tree characteristics in forest stands were identified. These measures were used to investigate the spatial autocorrelation of discrete tree characteristics including the species, product, and defect classifications. With the exception of the species classification, none of the discrete tree characteristics examined showed any evidence of significant (α = 0.05) levels of spatial autocorrelation in loblolly pine stands. The significant autocorrelation of the species classification was probably due to past stand history or microsite variability rather than overall stand conditions such as age, density, or percent pine. The relationship between the level of spatial autocorrelation associated with basal area and several descriptive stand characteristics was also examined. No strong relationships were identified but trends were noticed between the autocorrelation measures and measures of stand competition such as basal area and crown competition factor. The measures of spatial association indicate positive autocorrelation between the characteristics of neighboring trees at very low levels of competition with the autocorrelation becoming increasingly negative as competition increases. At extremely high levels of competition, the spatial autocorrelation measures become positive again, reflecting the stagnated condition of the stand. Methods were developed, using the measures of spatial autocorrelation, to assign characteristics to individual trees in computer generated stands. These methods, applicable for discrete or continuous characteristics; assign the characteristics to individual trees depending on the spatial location of the individual tree and the locations and characteristics of its neighbors. / Ph. D.