Efficiency enhancements of a Monte Carlo beamlet based treatment planning process: implementation and parameter study.

OBJECTIVE The computational effort to perform beamlet calculation, plan optimization and final dose calculation of a treatment planning process (TPP) generating intensity modulated treatment plans is enormous, especially if Monte Carlo (MC) simulations are used for dose calculation. The goal of this work is to improve the computational efficiency of a fully MC based TPP for static and dynamic photon, electron and mixed photon-electron treatment techniques by implementing multiple methods and studying the influence of their parameters. APPROACH A framework is implemented calculating MC beamlets efficiently in parallel on each available CPU core. The user can specify the desired statistical uncertainty of the beamlets, a fractional sparse dose threshold to save beamlets in a sparse format and minimal distances to the PTV surface from which 2x2x2=8 (medium) or even 4x4x4=64 (large) voxels are merged. The compromise between final plan quality and computational efficiency of beamlet calculation and optimization is studied for several parameter values to find a reasonable trade-off. For this purpose, four clinical and one academic case are considered with different treatment techniques. MAIN RESULTS Setting the statistical uncertainty to 5% (photon beamlets) and 15% (electron beamlets), the fractional sparse dose threshold relative to the maximal beamlet dose to 0.1% and minimal distances for medium and large voxels to the PTV to 1 cm and 2 cm, respectively, does not lead to substantial degradation in final plan quality. Only OAR sparing is slightly degraded. Furthermore, computation times are reduced by about 58% (photon beamlets), 88% (electron beamlets) and 96% (optimization) compared to using 2.5% (photon beamlets) and 5% (electron beamlets) statistical uncertainty and no sparse format nor voxel merging. SIGNIFICANCE Several methods are implemented improving computational efficiency of beamlet calculation and plan optimization of a fully MC based TPP without substantial degradation in final plan quality

Effects of Solids Retention Time and Feeding Frequency on Performance and Pathogen Fate in Semi-continuous Mesophilic Anaerobic Digesters

Anaerobic digestion is a biochemical process in which organic carbon is biodegraded in an oxygen free environment through a microbial consortium. Engineered biological systems used for resource recovery often utilize anaerobic digestion to treat anthropogenic organic wastes by reclaiming the carbon as energy (methane gas) and a soil amendment (biosolids). Small-scale, or household, semi-continuous anaerobic digesters have been used in developed and developing countries for many decades to produce biogas from human and livestock waste, which is used for heating, lighting, and cooking. This application has been shown to improve the quality of life of the user. Although there is great potential for small-scale semi-continuous anaerobic digestion to provide much needed resource recovery functions and quality of life improvements in future development, the manner in which these systems are operated could lead to unintended consequences on human health because human waste often contains resistant pathogens. This paradigm is best demonstrated by soil-transmitted helminths that are known to be highly resilient in mesophilic anaerobic digestion environments and endemic to many developing countries. The idea that soil-transmitted helminths survive mesophilic anaerobic digestion is exacerbated when the biosolids from the digesters are land applied as a soil-amendment because this process fits perfectly into the lifecycle of soil-transmitted helminths that need soil environments to develop into infective larva. This research was divided into three sections to investigate the fate of human pathogens during semi-continuous anaerobic digestion and investigate techniques to enhance their removal. The sections were: 1) an examination into the fate (embryonation, development, inactivation, destruction) of Ascaris suum ova during mesophilic semi-continuous anaerobic digestion, with an emphasis on increased inactivation, 2) an investigation into the performance (volatile solids (VS) removal, E. coli and Salmonella destruction, methane production) of semi-continuous mesophilic anaerobic digesters and the effect of variations to solids retention time (SRT) and feeding frequency, and 3) development and application of mathematical models for pathogen inactivation kinetics and typical semi-continuous reactor residence time distributions to predict the removal efficiency of Ascaris suum ova during semi-continuous anaerobic digestion under different operating conditions. Results of these studies showed that during semi-continuous mesophilic anaerobic digestion variations in feeding frequency did not impact the fate of Ascaris suum ova or Salmonella; however it was observed that better removal of E. coli and higher methane production was achieved at the longer feeding interval (weekly). Additional results indicated that embryonated ova were destroyed faster than unembryonated ova under the experimental conditions, which suggests a potential mechanism to enhance removal of this common pathogen. Since an increased feeding interval proved to be beneficial for digester performance our findings suggest that wastes containing Ascaris suum ova could be stored in an aerated environment, for a period of time that does not negatively impact resource recovery, to lengthen the time between feedings and promote ova embryonation and ensuing destruction during digestion. Modeling results indicate that under mesophilic conditions (35oC) the ova of Ascaris suum could survive for 22 days and will not be completely removed from the effluent under typical feeding frequencies and average SRT were examined. Therefore, the use of anaerobic digestion as a resource recovery technology where soil-transmitted helminths proliferate should be applied with extra operational safeguards or be included as one step of several in a small-scale treatment train

Technical and Economic Assessment of Adobe as the Primary Building Material On the Water Yield of a Single Basin Solar Still

It is estimated that only one percent of global freshwater is available to humans, with nearly three billion people living in water scarce conditions. Populations living in impoverished settings are particularly vulnerable to water related illnesses, with approximately 2.2 million people dying each year from to waterborne illnesses. This research uses modeling and field studies to assess the quantity, quality, and economics of distillate produced for drinking water from a brackish water source using two single-sloped, single-basin distillation reactors. The reactors were constructed from adobe and concrete in an arid rural community in San Luis Potosí, Mexico and tested from August to October. The cost of one adobe reactor with an evaporative area of 0.65 m2 is 430 pesos, whereas the same size reactor made from concrete costs 630 pesos. Results show that desalination reactors made from adobe produce 848 mL/m2-day and reactors made from concrete produce 979 mL/m2-day of distillate, while similar reactors made from other materials are estimated to produce over 2,100 mL/m2-day under similar meteorological conditions. These volumes represent approximately 10 percent of drinking water needs of a local family with typical water use habits. The concentrations of total dissolved solids in the source water decreased from 1,102 mg/L to 40.3 mg/L over the study\u27s duration for a removal of 96% which is comparable to current desalination systems (97%). Results suggest that over 90% of a household\u27s drinking water demand could be satisfied (91%) if a network of thirteen distillation reactors were constructed and maintained for ten years when compared to purchasing water from private water vendors

Does an open-ended design project increase creativity in engineering students?

© 2017 IEEE. Many schools are incorporating project-based interdisciplinary exercises into their engineering curriculum in order to develop the qualitative and quantitative skills simultaneously. It has been shown that introducing design in a freshman engineering course has a positive impact on retention, stimulates interest in engineering and enhances communication, teaming and time management skills. But can design also improve creativity? Or, to be more specific, would an open-ended design project improve creativity in engineering students? In the fall of 2015, an innovative design project was used in a first-year engineering course at Michigan Technological University. Students were given the task to develop a prototype of a new product or an improvement on an existing product. While some of the tasks were defined throughout the semester, the product they created was completely up to the team. It was thought that the open-ended nature of the project and the product itself being new or innovative would help improve their creativity. Students completing this project were given a 55 question pre- and post-assessment. This assessment included several measures of general creativity and entrepreneurial intentions: Oreg\u27s Resistance to Change Scale (RTC), the Curiosity and Exploration Inventory (CEI), and the Zampetakis & Moustakis Scale (Z & M Scale). This paper focuses on the development and evaluation of this open-ended design project for first-year engineering students and the results of the various measures of creativity

Supplemental Instruction in a First-Year Engineering Course: A study from the Learning with Academic Partners (LEAP) Program

This innovative practice full paper reviews the formation and effects of the LEarning with Academic Partners (LEAP) program at Michigan Technological University in the first two years of operation. The LEAP Program combines the job requirements of a traditional Teaching Assistant (TA) with those of a Supplemental Instruction (SI) Leader. While each program has their benefits, to date, no one has evaluated the effects of a combined program such as the one established at Michigan Tech. To determine these effects, we focused our analysis on measuring course performance and student attitudes of student groups in a second semester first-year engineering course, ENG1102 - Engineering Modeling and Design: Spring 2017 (no LEAP), Spring 2017 (no LEAP/pilot LEAP with optional attendance), and 2018 (LEAP with mandatory attendance)

Work in Progress: Student Perception of Instructional Staff’s Knowledge, Skills and Attitudes and its Impact on Their Performance

This work in progress paper aims to evaluate the relationship between first year engineering students’ perception of instructor competency and their individual performance. Students will be given surveys to evaluate their perception of both the student (teaching assistant) and faculty instructor’s competency and enthusiasm to be teaching the course in which they are enrolled. It is predicted as the student perception of their instructors drops, there will be a correlated grade decline as well. A recent change in curriculum in a first year engineering fundamentals class was implemented and there has been pushback from both students and faculty. The fundamental question of “Is this person qualified enough to teach this material?” seems to be at the heart of the debate. Some faculty question whether or not students who have recently completed the course are qualified enough to be able to help teach the subject matter. Others argue it offers current students a more relaxed environment, therefore promoting learning and increasing content retention. This work aims to evaluate the relationship between student perception of instructors’, both student (teaching assistant) and faculty, competency and enthusiasm and their performance in the class. To obtain the students perception of their instructors, both student and faculty, the same survey will be given at 3 time points throughout the semester: (1) the first day of classes, effectively obtaining a first impression response, (2) halfway through the semester, around the first exam and after they had a chance to get to know their instructors further, and (3) at the end of the course before the final exam. To motivate students to complete the survey an incentive of 5 extra points was/will be given for each survey completed. In the survey, there will be a section for comments for students to qualify their answers should they feel the need. After the results of the survey are collected, the responses [n ≤ 240] – which were on a scale of 1 (low) to 10 (high) – will be correlated with individual student’s grades. Trends will be observed and preliminary conclusions will be drawn

Modeling Inactivation of Highly Persistent Pathogens in Household-Scale Semi-Continuous Anaerobic Digesters

© Copyright 2016, Mary Ann Liebert, Inc. 2016. Household-scale anaerobic digesters (ADs) are used to stabilize and recover energy from organic wastes generated by rural agricultural communities. These systems are typically operated under ambient conditions and fed intermittently; however, use of ADs in this manner may not be sufficient to inactivate prominent human pathogens such as Ascaris spp. In this study, a mathematical model was developed to describe and predict inactivation of Ascaris suum in household-scale semi-continuous ADs. The model was based on the segregated flow model, which combines the following: (1) an expression for the residence time distribution of semi-continuous reactors in terms of feeding interval (FI) and solids retention time (SRT) and (2) an expression for A. suum inactivation in a batch reactor. Three mathematical expressions for pathogen inactivation in batch reactors are presented based on results of laboratory experiments. The segregated flow model predicted that, under mesophilic conditions (35°C), pathogen inactivation was weakly dependent on FI (61% inactivation when FI = 2 days, 64% when FI = 7 days) but strongly dependent on SRT (40% inactivation when SRT = 15 days, 73% when SRT = 45 days). Comparison of segregated flow model results using different pathogen inactivation expressions suggested that a sudden-die-off model offered a conservative approach when detailed laboratory data are not available. Near 100% removal of A. suum can be achieved when the FI exceeds the time required for complete inactivation under ambient conditions. This result identified a potential design and operational strategy for small-scale ADs that are operated in areas afflicted with neglected tropical diseases, such as soil-transmitted helminths

Engaging Students in Synchronous, Remote, or Hybrid First-Year Engineering Courses

The emergence and rapid spread of COVID-19 changed the face of education. At our University, planning for the Fall 2020 semester started well before the end of the 2019-20 academic year. For the Fall 2020 semester, faculty at our university had the option to teach in various modalities according to what fit their personal and course needs. The options included online (asynchronous materials completed with time and place flexibility), remote (synchronous, scheduled meetings that students can attend virtually), or hybrid (classes that have face-to-face meeting times, but offer students opportunities to complete most activities virtually and/or remotely). Restrictions placed on class size with physical distancing measures limited the number of students who could attend a given class session face-to-face. In the first-year program at our University, we value an active, collaborative learning environment; an environment that would be difficult to implement asynchronously. Throughout the summer, the faculty in our department expanded our knowledge of online learning and teaching in this modality. All faculty took classes in online teaching over the summer. Additionally, some faculty completed courses on creating accessible course content. All were engaged in the planning for an interactive, collaborative fall experience for first-year students that could be offered in a synchronous remote or hybrid environment. In a normal face-to-face setting, our first-year engineering courses meet three times a week: two 110-minute studio sessions led by a faculty member with support from five LEarning with Academic Partners (LEAP) Leaders and one 50-minute (LEAP) session led by their LEAP Leader. The studio sessions are fully flipped, where students watch videos, complete reading assignments, and submit a short assignment before attending class. During class they have a short quiz over the preparation materials and then they spend the majority of the session applying what they learned by working through problem sets together in a team of three to four students while getting support from their team, their LEAP Leader, and their faculty member. There are up to 120 students in the studio session and one LEAP Leader per 24 students. During studio sessions the LEAP leaders monitor and guide their students through the in-class assignments. The LEAP sessions are active collaborative sessions designed and facilitated by their LEAP Leader to review the most difficult content covered in class that week. In Fall 2020, the studio sessions were offered in a remote or hybrid environment with up to 20 students per LEAP Leader. All LEAP Sessions were offered remotely. Despite the shift to a remote or hybrid modality, we wanted our first-year students to still experience an active, collaborative learning environment. In this paper, we focus on discussing the steps we have taken to maintain and/or improve the connection between students and the engagement with the course materials. Data from Fall 2019 will be used to compare our results from Fall 2020