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257 results on '"Johnson D. M."'

1. Reducing False Negative Reads in RFID Data Streams Using an Adaptive Sliding-Window Approach

Author

Herman Vermaak, Johnson D. M. Kinyua, and Libe Valentine Massawe

Subjects
data filtering, data cleaning, RFID, RFID middleware, sliding-window filter, Chemical technology, TP1-1185
Abstract

Unreliability of the data streams generated by RFID readers is among the primary factors which limit the widespread adoption of the RFID technology. RFID data cleaning is, therefore, an essential task in the RFID middleware systems in order to reduce reading errors, and to allow these data streams to be used to make a correct interpretation and analysis of the physical world they are representing. In this paper we propose an adaptive sliding-window based approach called WSTD which is capable of efficiently coping with both environmental variation and tag dynamics. Our experimental results demonstrate the efficacy of the proposed approach.

Published
2012
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2. Towards weird realism in music : an investigation into composing with improvisation and found objects

Author

Johnson, D. M.

Subjects
781.3, Music
Abstract

This dissertation considers the implications of using recordings of free improvisations on world music instruments and other instruments as source material for fixed media musical compositions. Generating material in this way demanded the formulation of new working methods which inevitably impacted on the character and style of the work produced. A methodology was evolved based on aspects of the performance practice of free-jazz improvisation. The individual style of free-jazz improvisation was a major part of the syntax of the created music. This further enabled novelty in that an improvised based -style replaces the conventional Western reliance on notation and its associated compositional techniques. Rather, sound is generated spontaneously and guided only by aural monitoring of it. A fascination with the sounds of world instruments led to an exploration of the sounds of those instruments in new contexts. Instruments, both world and western classical, became treated as found objects or utilised in ‘studies in ignorance’ in the manner of Sun Ra.1 The improvised material was then manipulated using computer software and structured into fixed-media works. Gesture, texture and timbre dominate these structures rather than preconceived themes or harmonic schemes. Most of the music presented with the thesis is text based or inspired by text; this provides further structural underpinning. I wished to explore the relationship between the Weird Realist aesthetic as posited by Graham Harman in the works of H.P. Lovecraft and an analogous musical response. The separation of quality from object in Lovecraft chimed with experiences of sensory distortion when under shamanic trance and this resulted in Shamanic Incantation No. 5, the only non-text based work. A fascination with fantasy in general led to the composition of an opera in Klingon in which the text and music combine to present a series of tableaux that hint at aspects of sacred violence and the breakdown of shared values in times of war. As if to underline this point, Grodek No.4 presents a collage of disturbing materials drawn from stride jazz piano, free improvisation and expressionist sprechgesang; all of which combine in a new context to illuminate Georg Trakl’s poem on the horrors of violence. As a result of these compositional procedures a cogent sound world using improvisation and electronics was created. The influence of Weird Realism and the use of world instruments stimulated ideas about how musical material can be distorted and re-contextualised. The combination of improvisatory and ‘composed’ elements was fruitful and shows a way of working with two different types of intuition, one in real time, the other not. This suggests possibilities for further exploring the combining of different experiential modes in creative work. 1 A key recording in this respect is Sun Ra, Strange Strings, El Saturn 502, 1966, explored later in the thesis.

Published
2016

13. Discussion

Author

Dawson, M. M., Kimbrough, R. L., Mulliken, A. H., Smith, Oberlin, Bartlett, John H., Douglass, W. A., and Johnson, D. M.

Published
1912

14. Preliminary Assessment of the Precision Agriculture Landscape in Arkansas.

Author

Frimpong, S., Poncet, A. M., France, O. W., Johnson, D. M., and Slaton, N. A.

Subjects
PRECISION farming, RANGE management, SOCIAL media, FARM management, INNOVATION adoption
Abstract

Producers' approaches to precision agriculture (PA) vary widely depending on their background and unique production factors. Technology use and perceptions of benefits may also be affected by previous experiences, operation size, and level of integration into the farm management decision-making process. Investigating Arkansas stakeholder views of PA is needed to characterize the range of management practices and perceptions related to PA in Arkansas, form a common vision for PA, and inform the direction of land-grant research, extension, and teaching programs in PA. Research was conducted in 2022 to assess the perceptions of PA goals, identify educational needs, and determine drivers of technology adoption in Arkansas. A survey was developed in Qualtrics XM® to collect quantitative data from field crop farmers, crop consultants, and county extension agents. The survey was advertised at field days, production meetings, and using social platforms. Data were collected electronically using an online survey accessed through a QR code and on paper. Responses and data collected between 6 August 2022 and 1 December 2022 were cleaned and summarized. Results showed that the respondents had a proper understanding of the goals of PA despite some confusion with the PA tools available to meet the PA goals. Moreover, the respondents tended to focus more on technology integration at the operational level rather than at the decision-making level. The concerns most important to respondents were those that already affect profitability and are easy to quantify. Results also showed that decision-making regarding technology adoption is a complex process hindered by many economic and social barriers. Future research will investigate specific technology adoption dynamics and the stakeholders' approach to soil testing for the characterization of in-field variability in Arkansas. [ABSTRACT FROM AUTHOR]

Published
2023

18. Rapport, Course Technology, and Self-Regulated Learning as Predictors of Student Satisfaction in an Online Horticulture Program.

Author

Estepp, C. M., Dickson, R. W., and Johnson, D. M.

Subjects
ONLINE education, SATISFACTION, STUDENT attrition, SPRING, LEARNING
Abstract

Online courses have proliferated in higher education, which has provided greater opportunities for institutions and students. However, student attrition from online programs has been a perennial problem. One potential solution to help increase retention is to improve student satisfaction. Instructor characteristics, technology, and self-regulated learning are all variables, which could contribute to greater student satisfaction in online courses. However, little research exists regarding these variables within the context of online agriculture programs. Therefore, the purpose of this study was to determine predictors of student satisfaction in the Alliance for Cooperative Course Exchange in the Plant Sciences (ACCEPtS) program, which is an online, multi-institutional, horticulture program. Students enrolled in ACCEPtS courses during spring and fall of 2020 were surveyed to determine their perceptions regarding professor-student rapport, technology, self-regulated learning, and course satisfaction. Results showed that students had favorable perceptions regarding professorstudent rapport and technology, they mostly agreed they used self-regulated learning behaviors, and they were generally satisfied with ACCEPtS courses. Technology and professor-student rapport were significant predictors of student satisfaction; however, rapport was more robust and explained about a quarter of the unique variance in satisfaction. Rapport is an important contributor to student satisfaction in online courses, and instructors should utilize behaviors that contribute to the building of relationships. [ABSTRACT FROM AUTHOR]

Published
2022

26. Photonic integration of an optical atomic clock

Author

Newman, Z. L., Maurice, V., Drake, T. E., Stone, J. R., Briles, T. C., Spencer, D. T., Fredrick, C., Li, Q., Westly, D., Ilic, B. R., Shen, B., Suh, M. -G., Yang, K. Y., Johnson, C., Johnson, D. M. S., Hollberg, L., Vahala, K., Srinivasan, K., Diddams, S. A., Kitching, J., Papp, S. B., and Hummon, M. T

Subjects
Computer Science::Hardware Architecture, Atomic Physics (physics.atom-ph), FOS: Physical sciences, Physics::Optics, Optics (physics.optics), Physics - Optics, Physics - Atomic Physics
Abstract

Laboratory optical atomic clocks achieve remarkable accuracy (now counted to 18 digits or more), opening possibilities to explore fundamental physics and enable new measurements. However, their size and use of bulk components prevent them from being more widely adopted in applications that require precision timing. By leveraging silicon-chip photonics for integration and to reduce component size and complexity, we demonstrate a compact optical-clock architecture. Here a semiconductor laser is stabilized to an optical transition in a microfabricated rubidium vapor cell, and a pair of interlocked Kerr-microresonator frequency combs provide fully coherent optical division of the clock laser to generate an electronic 22 GHz clock signal with a fractional frequency instability of one part in 10^13. These results demonstrate key concepts of how to use silicon-chip devices in future portable and ultraprecise optical clocks., 11 pages, 4 figures

Published
2018

28. Plastid and seed morphology data support a revised infrageneric classification and an african origin of the pantropical genus Xylopia (Annonaceae)

Author

Stull, G. W., Johnson, D. M., Murray, N. A., Couvreur, Thomas, Reeger, J. E., and Roy, C. M.

Subjects
Arils, biogeography, molecular phylogeny
Abstract

The floristic treatment of Engler and Diels, published in 1901, provides the only infrageneric classification of the pantropical genus Xylopia (Annonaceae). Here we test and extend that classification using molecular and seed morphology characters. Phylogenetic relationships were reconstructed using data from four plastid regions obtained from 44 of the approximately 165 species in the genus, recovering four well-supported major clades. Seed characters were examined for these taxa, and six aril morphologies, three previously undocumented, were distinguished; we also document the presence of a sarcotesta on the seeds of many species. Molecular and seed data support recognition of five sections within the genus; one, Xylopia sect. Rugosperma, is proposed here as new. Our phylogenetic results suggest an African origin for the genus and reveal complex biogeographic patterns, likely facilitated by long-distance dispersal.

Published
2017

29. Video Homework: Completion Rates, Performance, and Student Perceptions.

Author

Hood, G. T. and Johnson, D. M.

Subjects
STUDENT attitudes, DYNAMOMETER, HOMEWORK, OHM'S law, VIDEOS, COVID-19 pandemic
Abstract

Because of the Covid-19 pandemic, the lab for ASTM 1613 - Fundamentals of Agricultural Systems was not offered in fall 2020. Thus, many students lacked the experiences necessary to understand course concepts. To partially compensate, three video homework assignments (tractor dynamometer testing, spreader calibration, and Ohm's Law) were developed and used in the course along with nine traditional paper assignments. The purpose of this study was to compare student (N = 42) completion rates, performance, and perceptions for each homework type. Completion rates were significantly (p < .05) higher for paper (90.7%) than for video homework (78.6%). However, overall scores on the video (71.3%) and paper (73.4%) homework assignments were not significantly (p = .57) different. When comparing only students completing all homework assignments, students scored significantly (p < .001) higher on the video (92.9%) than the paper (84.0%) homework. On a 1 (strongly disagree) to 5 (strongly agree) scale students agreed video homework was easier to understand (M = 3.63; SD = 0.61), preferred more video homework (M = 3.51; SD = 0.61), and learned more by doing the video homework (M = 3.49; SD = 0.59); they disagreed the video homework was too much trouble (M = 2.18; SD = 0.63). Confirming their lack of previous experiences, students disagreed they knew a lot about tractor dynamometer testing (M = 2.25; SD = 0.71), spreader calibration (M = 2.03; SD = 1.03), or Ohm's Law (M = 2.45; SD = 1.30) before completing the video homework assignments. [ABSTRACT FROM AUTHOR]

Published
2020

30. Growing pains: Maturity associated variation in injury risk in academy football.

Author

Johnson, D. M., Williams, S., Bradley, B., Sayer, S., Murray Fisher, J., and Cumming, S.

Subjects
*PREVENTION of overuse injuries, *SOCCER injury prevention, *RISK assessment, *PUBERTY, *OVERUSE injuries, *STATURE, *ODDS ratio, *SPORTS events, *CONFIDENCE intervals, *SOCCER injuries, *COMPETITION (Psychology), *DISEASE incidence, *DISEASE risk factors
Abstract

Reducing injuries to youth players is of primary importance to academies, as injuries can result in a significant loss in both training and match time, as well as, negatively affecting player development. In total, 76 talented young football players were analysed over two full competitive seasons. The injury incidence and burden for all non-contact and overuse injuries were recorded. Exposure was calculated as the total number of competitive matches hours played. Somatic maturation was estimated by expressing the current height of each player as a percentage of their predicted adult height [Roche, A. F., Tyleshevski, F., & Rogers, E. (1983). Non-invasive measurements of physical maturity in children. Research Quarterly for Exercise and Sport, 54(4), 364–371.]. The period of circa-peak height velocity (PHV) (24.5 injuries per 1000 h) was associated with a significantly higher injury incidence rate and burden compared to pre-PHV (11.5 injuries per 1000 h; RR:2.15, 95%CI:1.37–3.38, P <.001). No significant differences in injury risk between maturity timing groups were observed. The interaction effect between maturity status and maturity timing confirmed there is a risk period circa-PHV, but this was not dependent on maturity timing. The main practical application of this study is that football academies should regularly assess the maturity status of young footballers to identify those players with increased susceptibility to injury. Moreover, academies should individualise training and injury prevention strategies based on maturation. [ABSTRACT FROM AUTHOR]

Published
2020
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31. Looks

Author

Johnson, D. M.

Published
1981

40. The dynamic pipeline: homeostatic mechanisms that maintain the Integrity of xylem water transport from roots to leaves

Author

Meinzer, F. C., jean-christophe domec, Johnson, D. M., Mcculloh, K. A., Woodruff, D. R., ProdInra, Migration, United States Department of Agriculture - US Forest Service, Partenaires INRAE, Interactions Sol Plante Atmosphère (UMR ISPA), Institut National de la Recherche Agronomique (INRA)-Ecole Nationale Supérieure des Sciences Agronomiques de Bordeaux-Aquitaine (Bordeaux Sciences Agro), Duke University [Durham], and Oregon State University (OSU)

Subjects
hydraulic redistribution, [SDV] Life Sciences [q-bio], [SDE] Environmental Sciences, [SDV]Life Sciences [q-bio], [SDE]Environmental Sciences, fungi, capacitance, food and beverages, hydraulic architecture, xylem embolism
Abstract

International audience; Over the last decade, it has become increasingly apparent that the properties of the root-to-leaf hydraulic pathway in trees can quickly acclimate over short timescales. In this context, the term hydraulic architecture takes on a broader meaning, making it essential to understand how static and, above all, dynamic hydraulic properties are integrated at the organismal level. Here we discuss some key processes operating in roots, stems and leaves that act in a coordinated manner to stabilize plant hydraulic function under both non-extreme and extreme conditions such as prolonged drought. Hydraulic redistribution (HR) is often manifested as reverse flow of water in shallow roots via transport of water from deeper soil layers. By partially uncoupling root water potential from that of the surrounding dry soil and slowing the rate of soil drying, HR serves to mitigate seasonal drought-induced hydraulic dysfunction in roots and to maintain nutrient uptake, thereby extending their lifespan. Stems of many species show a high capacity for refilling of embolized xylem conduits. This is an important component of their apparent hydraulic safety margins that is likely to be related to xylem structural features that confer resistance to tension-induced embolism. Hydraulic capacitance in stems contributes to hydraulic safety margins by dampening fluctuations in xylem tension that might otherwise result in excessive embolism. Embolism-induced loss of stem xylem conductivity can be partially compensated by rapid increases in the ionic concentration of xylem sap in remaining functional conduits. In many species, leaves lose and recover a substantial fraction of their hydraulic conductance daily, suggestive of a hydraulic circuit breaker function that promotes stomatal closure to avoid excessive embolism in stems upstream. The functioning of these homeostatic processes is likely to be influenced by the drier climates that are predicted for much of the globe.

Published
2013

41. Management of invasive Allee species.

Author

Chan, D. M., Kent, C. M., and Johnson, D. M.

Subjects
BIOLOGICAL invasions, ALLEE effect, FRAGMENTED landscapes, HABITATS, DISCRETE systems, MANAGEMENT
Abstract

In this study, we use a discrete, two-patch population model of an Allee species to examine different methods in managing invasions. We first analytically examine the model to show the presence of the strong Allee effect, and then we numerically explore the model to test the effectiveness of different management strategies. As expected invasion is facilitated by lower Allee thresholds, greater carrying capacities and greater proportions of dispersers. These effects are interacting, however, and moderated by population growth rate. Using the gypsy moth as an example species, we demonstrate that the effectiveness of different invasion management strategies is context-dependent, combining complementary methods may be preferable, and the preferred strategy may differ geographically. Specifically, we find methods for restricting movement to be more effective in areas of contiguous habitat and high Allee thresholds, where methods involving mating disruptions and raising Allee thresholds are more effective in areas of high habitat fragmentation. [ABSTRACT FROM PUBLISHER]

Published
2017
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