An approximation to the Heidler Function with an analytical integral for engineering applications using lightning currents

A dissertation submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering in the Lightning and EMC Research Group School of Electrical and Information Engineering September 2015The work presented contributes to research in lightning protection simulations and focuses on approximating the Heidler function with an analytical integral and hence a frequency domain representation. The integral of lightning current models is required in the analysis of lightning events including the induced effects and frequency analyses of lightning strikes. Previous work in this area has produced very specific forms of the Heidler function that are used to represent lightning current waveshapes. This work however focuses on a generic solution with parameters that can be modified to produce any lightning current waveshape that is required. In the research presented, such an approximation is obtained. This function has an analytical solution to the integral and hence can be completely represented in the frequency domain. This allows for a true representation of Maxwell’s equations for Electromagnetic (EM) fields and for an analytical frequency domain analysis. It has parameters that can be changed to obtain different waveshapes (10/350, 0.25/100, etc.). The characteristics of the approximation are compared with those of the Heidler function to ascertain whether or not the function is applicable for use with the lightning protection standard (IEC 62305-1). It is shown that the approximation does represent the same characteristics as those of the Heidler function and hence can be used in IEC 62305-1 standardised applications. This represents a valuable contribution to engineers working in the field of lightning protection, specifically simulation models.MT201

Blockage reduction to increase the efficiency of slurry application.

End of Project ReportDiscussions with farmers using band and injection slurry spreaders suggested that the rate of breakdown due to blockages, in these machines, was approximately one per day. This report shows how the use of an intake filter and a modified distributor on a band spreader can reduce this problem. A set of obstacles was assembled on the basis of information from farmers and from literature. Ten classes of obstacles were selected, at random, and between size limits. Two prototype filters, a commercial filter and an open pipe were tested while drawing slurry from an open tank to a tanker. During each test, obstacles were thrown into the slurry stream. Obstacles retained by the filter were counted afterwards. A second filter trial was organised to test the tendency of filters to clog. Obstacle tests with 3 prototype distributors and a control were conducted in a similar manner to the first filter trial but, in this case, preliminary tests were conducted in water and final tests in slurry. The initial tests identified the best prototype. This was then compared to the control distributor using slurry. The open pipe allowed 80% of obstacles to pass while the filters allowed only 4 – 19% through. The new filters offered no improvement over the commercial unit. Filters required 16 hours agitation but the open pipe required 4 hours or less. The best prototype had the same diameter as the control but had an obstacle trap attached at the side. In a test using obstacles and slurry, the control was obstructed by 56% of the obstacles while the prototype allowed only 21% to cause a blockage. Flow through the prototype was initially too large. Slowing down the rotor in the distributor and restricting the outlet from the obstacle trap with a single long pipe, connected to two nozzles, controlled the flow. The results of the filter and distributor trials were combined. Of the seventy obstacles dropped above the filter, six passed through. Four of these caused blockages in the control distributor, but only one became stuck in the prototype. The blockage rate in the distributor and nozzles was significantly reduced compared to the original unit

Effects of Deuterium on Chlamydomonas reinhardtii

In order to develop software tools to monitor rates of total protein turnover in plants, attempts were made to maximally label all the proteins in vivo. Our study focused on the use of the stable isotope of hydrogen, deuterium, to label proteins of C. reinhardtii. The goal of this study was to determine the effect of the label on algal growth. C. reinhardtii is a unicellular green algae that is heterotrophic, photoautotrophic and mixotrophic. The results showed that increasing concentrations of deuterium in the algal growth medium had a negative effect on the growth of the algae. These preliminary results indicated that other stable isotopes such as Nitrogen-15 and Carbon-13 should be assayed to see if, contrary to deuterium, they allow normal growth of the algae

15N Effects on Chlamydomonas Reinhardtii

Non-radioactive isotopic labeling has become a regular technique for efficiently labeling a wide range of macromolecules. The overall goal for this project was to develop a method of globally measuring plant protein turnover rates. In order to do so, an isotopic labeled environment that does not induce stress had to be used. The objective of this particular segment of research was to develop a 15N-labeled Tris-Acetate-Phosphate (TAP) media in which Chlamydomonas reinhardtii can successfully grow without eliciting stressed physiological responses. Our results illustrate that we have successfully developed 15N-labeled TAP that does not stress Chlamydomonas reinhardtii

Fun Versus Meaningful Video Game Experiences: A Qualitative Analysis of User Responses

Emerging research on video games has suggested that feelings of both enjoyment and meaningfulness can be elicited from gameplay. Studies have shown enjoyment and meaningfulness evaluations to be associated with discrete elements of video games (ratings of gameplay and narrative, respectively), but have relied on closed-end data analysis. The current study analyzed participants’ open-ended reviews of either their “most fun” or “most meaningful” video game experience (N = 575, randomly assigned to either condition). Results demonstrated that “fun” games were explained in terms of gameplay mechanics, and “meaningful” games were explained in terms of connections with players and in-game characters

The Digital Age: Reminder and Confirmation Preference in Blood Donation

Introduction: It is widely accepted that individuals are more likely to comply and follow through with responsibilities when reminded and asked to confirm their commitments. With the American Red Cross’ access to fast and affordable communication and this notion in mind, there is potential to develop new recruitment strategies and better methods of ensuring blood donation commitments. In particular, understanding modes of communication with the donor population can have significant implications: avoiding loss of follow up, improving donor experience, and ensuring appropriate use of resources and staff; therefore, the American Red Cross is interested in understanding demographic differences among those who prefer different modes of communication for blood donor appointment reminders and confirmations.https://scholarworks.uvm.edu/comphp_gallery/1223/thumbnail.jp

Copper-Catalyzed Decarboxylative Trifluoromethylation of Allylic Bromodifluoroacetates

The development of new synthetic fluorination reactions has important implications in medicinal, agricultural and materials chemistries. Given the prevalence and accessibility of alcohols, methods to convert alcohols to trifluoromethanes are desirable. However, this transformation typically requires four-step processes, specialty chemicals, and/or stoichiometric metals to access the trifluoromethyl-containing product. A two-step copper-catalyzed decarboxylative protocol for converting allylic alcohols to trifluoromethanes is reported. Preliminary mechanistic studies distinguish this reaction from previously reported Cu-mediated reactions

Direct LiDAR-Inertial Odometry: Lightweight LIO with Continuous-Time Motion Correction

Aggressive motions from agile flights or traversing irregular terrain induce motion distortion in LiDAR scans that can degrade state estimation and mapping. Some methods exist to mitigate this effect, but they are still too simplistic or computationally costly for resource-constrained mobile robots. To this end, this paper presents Direct LiDAR-Inertial Odometry (DLIO), a lightweight LiDAR-inertial odometry algorithm with a new coarse-to-fine approach in constructing continuous-time trajectories for precise motion correction. The key to our method lies in the construction of a set of analytical equations which are parameterized solely by time, enabling fast and parallelizable point-wise deskewing. This method is feasible only because of the strong convergence properties in our novel nonlinear geometric observer, which provides provably correct state estimates for initializing the sensitive IMU integration step. Moreover, by simultaneously performing motion correction and prior generation, and by directly registering each scan to the map and bypassing scan-to-scan, DLIO's condensed architecture is nearly 20% more computationally efficient than the current state-of-the-art with a 12% increase in accuracy. We demonstrate DLIO's superior localization accuracy, map quality, and lower computational overhead as compared to four state-of-the-art algorithms through extensive tests using multiple public benchmark and self-collected datasets

Video games as meaningful entertainment experiences

We conducted an experiment to examine individuals’ perceptions of enjoyable and meaningful video games and the game characteristics and dimensions of need satisfaction associated with enjoyment and appreciation. Participants (N = 512) were randomly assigned to 1 of 2 groups that asked them to recall a game that they found either particularly fun or particularly meaningful, and to then rate their perceptions of the game that they recalled. Enjoyment was high for both groups, though appreciation was higher in the meaningful- than fun-game condition. Further, enjoyment was most strongly associated with gameplay characteristics and satisfaction of needs related to competency and autonomy, whereas appreciation was most strongly associated with story characteristics and satisfaction of needs related to insight and relatedness

Copper-Catalyzed Decarboxylative Trifluoromethylation of Propargyl Bromodifluoroacetates

The development of efficient methods for accessing fluorinated functional groups is desirable. Herein, we report a two-step method that utilizes catalytic Cu for the decarboxylative trifluoromethylation of propargyl bromodifluoroacetates. This protocol affords a mixture of propargyl trifluoromethanes and trifluoromethyl allenes